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Volume 36 No 7 NOVEMBER 2009

AWA JOURNAL OF THE AUSTRALIAN WATER ASSOCIATION


Water loss is a US$14 billion problem.

WaterGEMS"' - delive r s active leakage control, pressure management strategies and improves the speed and quality of repairs . HAMMERÂŽ- reduces breakages caused by high pressure transients. BentleyÂŽ Water - identifies aging infrastructure and enables remediation planning strategies.


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Journal of the Au~ral;an Water AssoclaUon ISSN 0310-0367 Volume 36 No 7 November 2009

contents REGULAR FEATURES From the AWA President

4

Delivering Infrastructure Projects P Robinson

From the AWA Chief Executive Ask Not What Your Association Can Do For You... T Mollenkopf

My Point of View

B Grear

Crosscurrent

Sensors to Protect Marine and Freshwater Ecosystems see page 19

5 6 10

Aquaphemera

R Knee 12

Industry News

18

AWA News

20

Events Calendar

26

FEATURE REPORTS Innovation Key to Success for Singapore's Changi Water Reclamation Plant Dr Glen Daigger, Senior Vice President and Chief Technology Officer, CH2M The Changi NEWater Plant: Another Innovative Design William Yong, Director of Black & Veatch's client services for the South Asia Pacific region New Centre for Desalination Australia's New National Centre of Excellence in Desalination (NCED) Prepare Now to Comply with Queensland Water Quality Legislation Tom Belgrave, Group Manager, Business Solutions, MWH Algal Biofuels - Alchemy of the 21st Century Sejla Alimanovic and John Poon, CH2M HILL AWA CONTACT DETAILS Australian Water Association ABN 78 096 035 773 Level 6, 655 Pacific Hwy, PO Box 222, St Leonards NSW 1590 Tel: +61 2 9436 0055 Fax: +61 2 9436 0155 Email: info@awa.asn.au Web: www.awa.asn.au DISCLAIMER Australian Water Association assumes no responsibility for opinion or statements of facts expressed by contributors or advertisers. COPYRIGHT AWA Water Journal is subject to copyright and may not be reproduced in any format without written permission of the AWA. To seek permission to reproduce Water Journal materials, send your request to media@awa.asn.au WATER JOURNAL MISSION STATEMENT 'To provide a journal that interests and informs on water matters, Australian and international, covering technological, environmental, economic and social aspects, and to provide a repository of useful refereed papers. ' PUBLISH DATES Water Journal is published eight times per year: February, April, May, June, August, September, November and December. EDITORIAL BOARD Chair: Frank R Bishop; Dr Bruce Anderson, AECOM; Dr Terry Anderson, Consultant SEWL; Michael Chapman, GHD; Robert Ford, Central Highlands Water (rtd); Anthony Gibson, Ecowise; Dr Brian Labza, Vic Health; Dr Robbert van Oorschot, GHD; John Poon, CH2M Hill; David Power, BEGA Consultants; Professor Felicity Roddick, RMIT University; Dr Ashok Sharma, CSIRO; and EA (Bob) Swinton, Technical Editor. EDITORIAL SUBMISSIONS Water Journal welcomes editorial submissions for technical and topical articles, news, opinion pieces, business

28 32 34

36 38 The Changi NEWater Plant - see page 32

information and letters to the editor. Acceptance of editorial submissions is at the discretion of the editor and editorial board. • Technical Papers and Features Bob Swinton, Technical Editor, Water Journal- bswinton@bigpond.net.au AND journal@awa.asn.au Papers 3,000-4,000 words and graphics; or topical articles of up to 2,000 words relating to all areas of the water cycle and water business. Submissions are tabled at monthly editorial board meetings and where appropriate are assigned referees. Referee comments will be forwarded to the principal author for further action. Authors should be mindful that Water Journal is published in a 3 column 'magazine' format rather than the full-page format of Word documents. Graphics should be set up so that they will still be clearly legible when reduced to two-column size (about 12cm wide). Tables and figures need to be numbered with the appropriate reference in the text e.g. see Figure 1, not just placed in the text with a (see below) reference as they may end up anywhere on the page when typeset. • Industry News, Opinion pieces and Media Releases Edie Nyers, Editor, Water Journal - journal@awa.asn.au • Water Business and Product News Brian Raul!, National Sales and Advertising Manager, Hallmark Editions - brian.rault@halledit.com.au

ADVERTISING Advertisements are included as an information service to readers and are reviewed before publication to ensure relevance to the water sector and objectives of the AWA. Brian Raul!, National Sales and Advertising Manager, Hallmark Editions - brian.rault@halledit.com.au Tel: +61 3 8534 5014 AWA BOOKSHOP Copies of Water Journal, including back issues, are available from the AWA Bookshop for $12.50 plus postage and handling. Email: bookshop@awa.asn.au PUBLISHER Hallmark Editions, POBox 84, Hampton, Vic 3188 Tel: 61 3 8534 5000 Fax: 61 3 9530 8911 Email: hallmark.editions@halledit.com.au

OUR COVER Singapore PUB has been one of the most progressive authorities in the world, and the recent opening of the Changi Water Reclamation Plant (see page 28) and virtually simultaneously the Changi NEWater Plant, built on top of it (see page 32), is another milestone. Our cover picture shows an operator about to install a Siemens-Memcor MF module in the latter plant.

water

NOVEMBER 2009 1


wat er

Journal of !he Australian Wale, Association ISSN 0310-0367

Odour Control at Melbourne's Western Treatment Plant - see page 40

TECHNICAL FEATURES

Volume 36 No 7 November 2009

contents

Biofuels and Water Treatment by Growing Algae in Wastewater - see page 92

(Uill INDICATES THE PAPER HAS BEEN REFEREED)

ODOUR MANAGEMENT

[i]

Odour Control at Melbourne's Western Treatment Plant

J Cesca, A McDonald, N J R Kraakman, I Malpas

40

N J R Kraakman

52

A Hurlimann

60

Upgrades at the Metropolitan Syracuse WWTP, New York - Part 2 Phosphorus Removal GHook, T Carpenter, N Hatala, B Munn, K George, RCopithorn Pilot testing to full-scale operation

68

Three years of successful operation despite higher H2S inflows

Developments in Odour Control for the Wastewater Industry Reliability is the key to success in odour control management

[ii

Recycled Water: Perceptions of Colour and Odour

A survey at the Mawson Lakes dual pipe system WASTEWATER TREATMENT

DESALINATION

[I]

Concentrate Treatment Using Wetlands

Developments in Australia and California

[II

J Kepke, J Bays, J Lozier

75

CL Marti

83

T Mannhardt. I Cameron

87

J Li

92

D W Evans

97

Saline Effluent Discharges: Dynamical Behaviour Studies

The effluent from the Perth desalination plant does not enter the deep waters

Coal Seam Gas Water: Viability and Treatment CSG water is not simple or without risk for supplier or end user ALGAL BIOFUELS

[I]

Biofuels and Water Treatment by Growing Algae in Wastewater

Unique opportunities for water authorities ASSET MANAGEMENT

Towards Uniform Standards for Engineering Thermoplastics Correct materials and design are critical to successful tank construction WATER BUSINESS

New Products and Business Information. Feature: Pumps

112

Advertisers' Index 2 NOVEMBER 2009

99

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feature article

Innovation Key to Success for Singapore's Changi Water Reclamation Plant Dr Glen Daigger, Senior Vice President and Chief Technology Officer, CH2M HILL Innovative. Gigantic. Underground. Sustainable. Only a few of the words used to describe Singapore's Changi Water Reclamation Plant (CWRP) at its June 2009 grand opening celebrations at the Singapore International Water Week, with Prime Minister of Singapore Mr Lee Hsien Loong officially opening the facility. Part of Singapore's Deep Tunnel Sewerage System (DTSS), the CWRP and overall sewerage system represents one of the largest used water ('wastewater') collection and treatment projects ever undertaken worldwide. This innovative and comprehensive system, managed by PUB, Singapore's national water agency, will help meet the increasing demands from Singapore's strong population growth, industrialisation , and continued urbanisation. The DTSS program collects all used water from the island nation, replacing more than 130 pumping stations and six treatment plants. CH2M HILL, in joint venture with Parsons Brinckerhof, managed and integrated the planning , design, and construction of the DTSS, which involved concurrent management of six design-build contracts with more than 1,500 workers.

Single Treatment Source and Small Footprint Frees Up Precious Land for Redevelopment The CWRP is the cornerstone treatment component, and replaces th ree existing water reclamation plants. It is a state-ofthe-art, compact, and covered used water treatment facility designed to handle 800 MUd and expandable to an ultimate 2,400 MUd. It required the management of twelve construction contracts and seven major equipment procurement/installation contracts encompassing more than 4,500 construction workers. CH2M HILL provided the design, construction engineering, management, inspection, and startup services. At the end of 2008, the CWRP was fully commissioned, completing Phase 1 of the overall DTSS program. Th is milestone paves the way towards Singapore's goals of cleaner waters around the island, a healthier environment for its citizens, and enhancing the country's reputation as a global water high-tech centre. The CWRP is producing product water of quality suitable for reuse, will help improve water quality in the shallow waters around Singapore through its advanced solids processing and outfall systems, and improve sewerage system operations overall. Constructing the CWRP on the island's eastern edge on reclaimed land freed up much valued land currently occupied in central Singapore by other reclamation plants and pumping stations.

Mr Lee Hsien Loong, Prime Minister of Singapore and Dr Glen Daigger during the CWRP grand opening at Singapore International Water Week.

aesthetic, marine environment and functional goals. Local architects led the way in designing the landscapes using native plants. The CWRP is significant on a global scale for many reasons: • It is a grassroot s facility, incorporating current design and operations concepts and building on PUB's experience in operating its existing six water reclamation plants • The ultimate facility is huge, but much of it is underground and designed to be easily expandable in phases • Significant site constraints necessitated placing most of the liquid treatment process underground and using compact process tank configurations such as step-feed activated sludge and two-level, stacked primary and secondary clarifiers • Stringent odour and noise criteria defined the design and construction of the plant • Influent is conveyed through the newly constructed deep tunnel system to the CWRP. To address some of the challenges listed above, the process train (Figure 1) consists of: • Coarse screening and influent pumping • Preliminary treatment by fine screening, vortex removal, and grease removal • Primary treatment

Innovation in Design and Construction The CWRP was designed for a 100-year lifecycle, has mitigated noise and air emission impacts to satisfy Singapore environmental regulations, as well as meeting goals of a small footprint, odour control, aesthetic appearance and multi-modal use. Double-covered liquids treatment removes tanks from sight and provides space for rooftop development featuring light industry including a 227 MUd NEWater® Plant. Materials, fin ishes, fenestration, and landscaping were designed to meet

28 NOVEMBER 2009 water

Figure 1. Process Flow Diagram.

feature articles


feature article

Changi WRP Features: Top Left - Completed Solids Digesters; Top Right - Influent Pump Station Discharge Header and Isolation Valve; Bottom Left - Influent Pump Station and Discharge Pipework; Bottom Right - Solids Process Building Exterior.

• Activated sludge using the anoxic step feed process with secondary clarification

and associated Solids Handling Facilities in early February 2007, and the Liquid Module Biological process in early 2008.

• Pri mary sludge degritti ng; primary and waste activated sludge (WAS) t hickening using centrifuges

The CWRP initially received secondary treat ed effluent from exist ing plants, and moved towards a combination of raw used wat er (sewage) and secondary treat ed effluent with the decommissioning of one wat er reclamation plant in February 2008 and the phasing in of biological processes.

• Anaerobic digestion in cyli nder digesters • Dewatering sludge using centrifuges followed by thermal drying, using biogas. Anoxic step feed was selected to minim ise tank volume, contro l activated sludge settling characteristics, and recover alkalinity to minimise pH depression with nitrification. A compact configuration was selected using rectangular tanks and two-st orey stacked primary and secondary clarifiers. CH2M HILL has 250 professionals in its int ernational headquarters in Singapore and formed a cohesive t eam of consultants and subconsultants from Singapore and other cou ntries to work closely with PUB and other agencies.

Three Phase Commissioning Results in Excellent Performance Outcomes The plant was commissioned in three phases - the Influent Pumping Station and Deep Tunnel system was commissioned in the third quarter 2005, Liquid Module 1 Biological process

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The plant has been loaded to above its nominal design capacity and has demonstrated the ability to perform well up to and above its nominally rated capacity. Excellent performance has been achieved, including five-day biochemical oxygen demand (BOD5) and total suspended solids (TSS) performance within specification, along with partial nitrification and denitrification. Sludge settleability has been excellent. The anoxic step feed process has provided stable treatment and avoided significant pH depression; sludge volume index (SVI) values averaged 105 mUg and were consistently below 150 mUg.

Sustainable Design Solutions Offer Energy and Labour Savings The CWRP offers many energy- and labour-saving features including automated monitoring and control using advanced

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water NOVEMBER 2009 29


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feature article advantages of 3-D design were multiplied with the addition of an attached database that contained a large amount of information about every plant element. For construction, the database provided exact specifications and quantities for materials and equipment, saving many hours of checking and verification work. During plant operation, personnel can also access the information on every piece of equipment, including its size, material, manufacturer, age, maintenance and repair records.

Completion of Phase 1 of Master Plan Just the Beginning

Figure 2. 3-D Design Cross Section. computer technology, making it one of the world's most advanced and integrated water reclamation plant control systems. The plant uses biogas produced from the anaerobic sludge digestion process to operate the thermal drying process. This is a key feature that reduces the volume of sludge going to the landfi ll as land is precious in Singapore.

The DTSS and CWRP are only part of the master plan to reach Singapore's goals of cleaner waters around the island, a healthier environment for its citizens, and enhancing t he country's reputation as a global water tech nology hub. Other projects including the PU B's five landmark NEWater plants, an extensive public education program, and the long-term Active, Beautiful, Clean (ABC) Waters program, are helping to complete the vision. Adapted from an original article that ran in the June 2008 issue of World Water and Environmental Engineering.

The design for the liquid process module roof structure incorporated the Changi NEWaterÂŽ plant being constructed on top of the module, reducing the required footprint for the combined plants and minimising the pipelines used for conveyi ng secondary treated effluent to t he plant. NEWaterÂŽ will be supplied for commercial and industrial use.

3-D Design Improved Design, Tendering, and Construction Management CH2M HILL designed the CWRP using an advanced 3-D model with an attached database to improve the tendering and construction management. During design and construction, engineers and builders viewed computer images of 3-D plant drawings to fully understand how it would be built and operated (Figure 2). The project team checked the design for interferences to be corrected and for features req uiring construction t echniques. The many

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water NOVEMBER 2009

31


feature article

The Changi NEWater Plant: Another Innovative Design By William Yong, Director of Black & Veatch's client services for the South Asia Pacific region Solving Land Use Problems Stage 1 of the Changi NEWater Plant (SCNP) in Singapore started commercial operations on July 31st 2009. Black & Veatch provided full design engineering for the plant along with construction support and commissioning services. The design of the SCNP minimised land use and construction costs by placing the main NEWater facilities on the roof of the Changi Water Reclamation Plant (CWRP). The treated used water from the CWRP is pumped directly to the SCNP as feedwater, minimising the extent of pipework for conveyance. The plant is owned by Sembcorp Industries, contracted by PUB, Singapore's National Water Agency, to supply NEWater, or high-quality recycled water as it is branded in Singapore, mainly to high-t ech industry. Stage 1 of the plant supplies 69 MUd, and when Stage 2 is completed next year, SNCP will become one of the largest recycled water plants in the world, capable of producing a total of 228 MUd of NEWater Sembcorp was awarded the project in January 2008 and has an agreement to supply PUB with NEWater for the next 25 years. SNCP relies on advanced wat er treatment process steps, which include micro-filtration membranes, reverse osmosis membranes and ultraviolet disinfection to produce NEWater. To ensu re that the plant stayed on the fast-track schedu le Black & Veatch had 120 professionals from their integrated global workforce working on the plant.

Technical Notes: • Ultimate capacity of 228 MLD. • The Sembcorp Changi NEWater Plant is Singapore's fifth and largest NEWater plant • Together, the five NEWater plants will satisfy 30 per cent of Singapore's current water needs by 2010 • Because the plant is constructed on an innovative "plant-onplant" design it covers a smaller land area. Total area of the plant is 12,300 m2

Siemens MF modules. Photo courtesy Sembcorp.

• Special care had to be taken during the construction process to prevent damage to the existing roof structure and to allow continuous operation of the Changi Water Reclamation Plant. • NEWater storage tanks are sited on reclaimed land which required greater bored piling depth due to the presence of marine clay • SNCP receives treated used water from PU B's Changi Water Reclamation Plant, which is designed to collect about half of Singapore's total used water. Specialist features have been built in to ensure reliable and flexible operations.

The Partners Black & Veatch is a leading global engineering, consulting and construction company specialising in infrastructure development in energy, water, telecommunications, management consulting, federal and environmental markets. With US$3.2 billion in revenue, the employee-owned company has more than 100 offices worldwide and has completed projects in more than 100 countries on six continents. Sembcorp Industries is a leading utilities and marine group. The Group provides centralised utilities, energy and water to industrial and other customers in Singapore, the United Kingdom, Asia and the Middle East. Sembcorp has total assets of more than S$9 billion and employs more than 7,000 employees. For more information about NEWater, please visit www.pub.gov.sg/NEWater

Toray RO membrane stacks. Photo courtesy Sembcorp.

32 NOVEMBER 2009 water

Process Area. Photo courtesy Sembcorp.

feature articles


feature article

New Centre for Desalination Murdoch University was recently appointed the Administering Organisation of Australia's new National Centre of Excellence in Desalination (NCED). Murdoch will receive $20 million from the Federal Government over five years to host the Centre, with an additional contribution of up to $5 million from the Western Australian Government. The funding honours an election commitment by the federal and state governments to boost research into desalination.

The WA-based Centre , located at Murdoch's Rockingham campus, will bring t ogether the country's leading desalination and water science research organisations, Australian universities, industry and international partners. A world-class desalination test-bed and pilot scale research facility will also be developed at the Rockingham campus, to allow researchers and industry to performance t est novel and improved desalination technologies and processes at pilot scale, and allow industry to validate commercial products, integrate currently deployed technology and evaluate potential technology options. Th e Centre wi ll adopt a hub-and-spoke model of national engagement leveraging capability and expertise around the nation. The Centre's mission is to advance science to lower the carbon footprint of t he desalination technologies, improve efficiency and to optimise those technologies for Australia's unique circumstances. Scientists across the county will work to develop new technologies w ith widespread application for the benefit of all Australians. Professor David Doepel, from Murdoch 's Research Inst itute for Resources Technology, has been appointed Interim CEO of the Centre. Mr Doepel previously served as a Principal Policy Adviser to the Hon. Alan Carpenter, Premier of Western Australia. Prior to that engagement he was the Regional Director for the Americas, based in Los Angeles, for the Western Australian Trade and Investment Office. In that role he was responsible for the State Government's strategic marketing efforts on behalf of industry in the Americas. In both positions Mr Doepel was a powerful advocate for Australian technology, creativity and innovation.

34 NOVEMBER 2009 water

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National Centre of Excellence in Desalination Professor Doepel said the Centre wou ld work closely wit h industry and commercialisation partners. He has recently returned from a to ur of the United States and South-East Asia, meeting w ith venture capitalists and industry to explore commercialisati on opportunities and partnerships. "Water security for Australians is one of the most important areas of policy and research ," he said. "With its diverse rainfall patterns and climates, Australia will need a range of technology and behavioral and cultural solutions to ensure water for all." Professor Doepel said the extremes of our climate and relatively hig h energy costs with a high reliance on carbon-intensive energy sources presented some sign ificant chal lenges for securing water for industry, agriculture and residential use. " It's clear that for much of Australia's grow ing population, relying on rainfall alone will not deliver long-term water security. "If historic trends, which point to red uced precipitation for much of Australia's southern populations are a guide, then the water situation for southern Australia in 1O years ' time will be even more challenging. The commitment to large-scale desalination projects for major metropolitan regions, coupled with significant programs aimed at per capita reduction, can provide water security."

Professor Doepel said the new Centre aimed to deliver desalinated water that had a lower energy footprint , a lower carbon footprint and a reduced environmental impact. "Renewable energy can be used to desalinate water. Research has already been done in th is area and the Centre will be exploring further options as the research program develops." The Cen tre is cu rrently undertaking the development of a Technology Roadmap for desalination research in Australia. This roadmap will act as a framework for the activities of the Centre over its life. It is anticipated that the tec hnology roadmap will be continuously updated by the Centre management on an annual basis to take into account any new developments relevant to national needs. The outcomes of the roadmap include: • Provision of strategic recommendations on how best t o allocate NCED R&D investments. • Identification of candidate critical technologies or gaps in technology performance requirements to meet near, medium and long t erm performance t argets. • Identification of ways to leverage NCED R&D investments through coordination of activities with key need sectors and academic and industry partners. The Desalination Technology Roadmap is anticipated to be complete by December 2009. The Centre is currently consulting research and industry stakeholders in the development of the Roadmap. For more information on the Centre go to www.desalination.edu.au

feature articles


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feature article

Prepare Now to Comply with Queensland Water Quality Legislation Tom Belgrove, Group Manager, Business Solutions, MWH detailed reports on drinking water quality for the 2009 calendar year. This dat a will allow the Office to determine current water quality and performance and identify any areas that need additional investigations or support.

In 2003, the Victorian Government helped elevate the topic of water quality in Australia by introducing the Safe Drinking Water Act. Queensland's Water Supply Safety and Reliability Act (the Act) introduced in July 2008 is now also focusing attention, and efforts, toward improving quality and standards. The Queensland Act, which was initiated as part of a push toward improving Queensland's water quality management and compliance with Australian Drinking Water Guidelines, requires water service providers to prepare drinking water quality management plans and wi ll be phased in from July 2011 to 2013, dependent upon the size of the service provider. The larger providers wi ll have the shortest amount of time to prepare and there is much work to be done in order to achieve the targets. The community and elected representative expect ation is that water supplied to communities be safe for all St ate residents, regardless of location. In a sign of the legislation's importance, the St ate Government established the Office of Water Supply Regulation within the Department of Envi ronment & Resource Management which has, as one of its key duties, the review and approval of drinking water quality management plans of the 80 to 90 water service providers around the State.

The Approach This legislat ion affords water service providers an occasion to develop a plan, or plans, to help ensure water of the highest quality is provided to residents for years to come. To take fu ll advantage of this opportunity, there are a few recommendations that should be kept top of mind:

Tom Belgrove has 30 years of experience in various roles within local government and water utilities. He currently leads a team of strategic consultants who partner with public and private organisations to evaluate and improve business performance through the efficient management of people, assets, resources and budgets. Throughout Tom's career, he has held a number of leadership positions within the industry, including President of the AWA OLD Branch and a member of AWA's National Board of Directors.

The Requirements According to the requirements under t he Act, it is not a simple one-to-one equation that wi ll call for each wat er service provider to prepare a single drinking water management plan for its given jurisdictions. While there are only about 80 to 90 providers around the State, some will need to prepare plans for multiple schemes, which may result in as many as 300 to 400 plans being implemented. For example, water service providers in councils such as Toowoomba Regional Council or Somerset Regional Council, w hich serve multiple towns with their own independent water supplies, wi ll need to prepare separate water management plans for each. It is only in circumstances where these supplies are integrated that one overarching plan can be applied. Suddenly the deadlines - 201 1 for large utilities, 2012 for medium utilities and 2013 for small utilities - do not appear so far away, particularly when many councils do not have the resources or specialist skills available to develop even one plan in-house. And while taki ng a phased approach provides smaller organisations, wh ich generally have less funds available to support work such as t his, the most time to achieve fu ll compliance, the Office of Water Supply Regulation has request ed that all providers (regardless of size) contribute

36 NOVEMBER 2009 water

Assess you r situation. Given the t ime and cost implications of this legislation, it is important that water service providers quickly determine whether they have the capacity to prepare plans that are compliant, effective and manageable. Ask for help. Management plans as detailed in the legislation will need to be reviewed by independent auditors. Providers are therefore recommended to include specialists in the early evaluation stages where appropriate to avoid being subject to significant reworks to obtain approvals. Try to make sure the people you use in these early stages have an understanding of the reg ulations and water supply network operations.

Consider future regulatory expectations. Ensure the plans developed are not unnecessarily complex develop them in a manner t hat suits your current state and can be adhered to now and also down the track as regulations change. There is considerable risk for non-compl iance to the legislat ion. Not having a plan in place by t he required deadline may lead to penalties, and supplying water that is not fit for purpose wi ll result in even harsher consequences. The legislation does include maximum fines of up to 3000 penalty units (equating to $300,000, as at September 2009). While these penalties are harsh enough, the broader implications of a service provider's reputation within the community is a key long term risk.

About MWH Headquartered in Broomfield Colorado, MWH is a private, employee-owned firm with approximately 7,000 employees worldwide. We provide water, wastewater, energy, natural resource, program management, consulting and construction services t o indust rial, municipal and government clients in the Americas, Europe, Middle East, India, Asia and the Pacific Rim. MWH has operat ed in Australia since 1907 and currently employs more than 500 employees throughout the country. For more information about MWH, please visit the company's website at www.mwhglobal.com.

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Australia's Peak Environment and Sustainability Event

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feature article

ALGAL BIOFUELS ALCHEMY OF THE 21ST CENTURY By Sejla Alimanovic and John Poon, CH2M HILL The Persian Empire's interpretation of alchemy was the achievement of ultimate wisdom and immortality. In practice, alchemy was about turning common substances into gold. The post-industrialised world has redefined this however - where inorganic chemistry is well understood and people are living well beyond their means in the western world. Turning water into renewable oils is the new alchemy - and in theory should be able to supplement demand for transportation and st ationary energy in order to create a more sust ainable future. In theory, it could be the answer we've been looking for. The onslaught of climate change related impacts in the last five years have driven researchers to find alternatives to replace non-renewable energy and fuels all around the world. From wind, solar, tidal , and geothermal to compost toilets and stormwater harvesting, there's one catch: to be applicable, affordable, competitive on the market, efficient and sustainable, this new technology must slot into the current infrastructure. The solution has to be innovative and iPOD cool , yet simple enough to avoid the 'inconvenience' of behavioural change possibly the most complicated aspect of curbing run-atEway climate change - and minimise the way that this 'new fuel' is created , transported and used. The 'new fuel' must provide an energy source on a large scale, but should have a small ecological and structural footprint - including a minimal water footprint. As suggested by Mike Hightower of Sandia National Laboratories of Albuquerque at the ReUse Conference held in Brisbane this year, there is an obvious and vital interconnectedness between energy production, distribution and use, and water. It is not possible t o have one without the ot her - to create energy, water of higher quality is typically requ ired, and to treat, distribute and use water one must have energy. So what is the answer? How can populat ions in the developed world continue to live beyond sustainable means, and how can populations in the undeveloped world strive to raise their quality of life without becoming leading per capita polluters like Australians? As Bryan Walsh recently reported in the 2009 January issue of Time, algal biofuels are gaining increasing interest from major investors - and quite often from reputable global corporations whose sole interest are fuels, such as General Motors. Walsh highlights the research in the USA that is clearing the pathway for algal biofuels to enter the competitive energy market. But - th is technology is not new - the idea of using ethanol based fuels for combustion engines was a vision back in 1908 when Henry Ford's first Model T car left the assembly line, as reported by Suzanne Bohan for Mercury

38 NOVEMBER 2009 water

News earlier th is year. The vision entailed the establishment of a market for ethanol, the growth and development of crops for fuel , and moving away from non-renewable fuel sources. This vision t emporarily faded into the background due to limitations on alcohol production within the US, but regained momentum in the early to mid 1970's in an effort to remove America's dependence on the Middle East for oil. Plant based fuels were only available from corn and sugarcane in the early days as the plants' sugars are simple to ferment in order to produce the desired product - known as t he first generation of biofuels. Another fuel was biodiesel produced by the chemical transformation of plant oils extracted from corn, soy and oi l palm. The negative impact on global food supplies has been the major challenge for mass biodiesel production around the world and therefore has lost momentum. This has not deterred the search for the answer to the water-energy nexus however, but has driven scientists around the world who have rapidly developed the second generation - algal biofuels. Algae are defined as a group of aquatic, photosynthetic organisms ranging from unicellular to multicellular forms and generally possess chlorophyll but lack true roots, stems, and leaves characteristic of terrestrial plants. Photosynthetic microorganisms, generally referred to as microalgae, represent a complex and diverse array of life forms that vary greatly in their metabolic capabilities, environmental adaptations and morphology. The alchemic characteristic of these organisms is their ability to produce oils in the form of diglycerides and triglycerides - similar to that of the first generation biofuels which can be used as an alternative for fuel production. There are strains of algae whose oil content can vary between 15 and 77 per cent of the dry weight of the algae, and some that can double their biomass in as little as 24 to 48 hours. To do this, the algae require carbon dioxide, water and sunlight - a feat unachievable by the first generation of terrestrial plants. Compared to corn - which can produce about 3,360 Uha/year - algae can produce 56,093 Uha/year of ethanol as has recently been proven by American company Algenol. There is hope that biotechnology wi ll assist scientists at Novozyme, a research facility in the US, t o directly evolve enzymes within the algae cell in order to improve its ability to break down cell ulose. Despite the positive direction that algal biofuel research has taken, and the promise of a better tomorrow for humans and the respective ecosystems, there are some significant challenges to overcome before they can become competitive on the global market.

feature articles


feature article The general scientific and ethical challenges associated with algal biofuel production are: • Water consumption for production - to produce a meaningful volume of algae and to process algae for ethanol production req uires water. In Australia, water supply and security has been the primary environmental concern since the drought began 12 years ago. Securing a water source for production of algal biofuels will either mean removing water supplies from other processes, or finding an alt ernative source - a significant challenge in itself. • Space required to meet Australian/global demands - the construction of ponds which are big enough to produce the volume of fuel needed is limited by the space available in the agriculture industry. The development and construction of such ponds wou ld t ake away from food crops - which are also significantly increasing in demand. • Funding for research to find an algae which is high in oil production, i.e. t hat can break down cellulose quick enough - the funding for cu rrent research is typically from private sources, with little support from government bodies, especially in Australia. • Algae that can digest cellulose and spit out ethanol in one step - the challenge for scientists is t o find or develop a type of algae which can digest cellulose and produce ethanol in one step, increasing the possible yield.

The challenges from the engineering aspect include: • Designing of ponds - to produce a large volume of algae, a shallow pond of water is required, and to create a large enough ponds the water becomes deeper due to the required hydraulics. This is a significant challenge to designers and can have significant impacts on cost. • Recovery and extraction of oils. • Polluters - there is potential for the pollution of the algal ponds due to a number of external and environmental influences such as wind, other algae, plants, animals. • Using current water and wastewater treatment faci lities for harvest ing of algae - this is mostly a transportation and space challenge. There is no question t hat the human race is facing one of the biggest challenges in history - finding a fuel that wi ll allow us to survive on this planet beyond the 21st century. We might just have to settle with the idea that there is no one answer rather a collaboration of answers depending on the application. There is no ultimate elixir to life on Earth, but there are a number of opportunities wit hin reach that will increase our chances of survival, one of which is algal biofuels. The challenge lies in finding a sustainable method for producing useful vol umes of t his 'new fuel' and in doing so, realise the dreams of our modern day alchemist s.

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odour management

L1]

ref ereed paper

ODOUR CONTROL AT MELBOURNE'S WESTERN TREATMENT PLANT J Cesca, A McDonald, N J R Kraakman, I Malpas sewage is delivered to the plant via the Western Trunk Sewer (WTS). Manhole 1 (MH1 ) is located within the plant boundary an d educts 126,000m 3/h of air extracted from the WTS for corrosion control in the upstream sewer. Prior to the installation of the Odour Control Facility (OCF) in 2006, air from the WTS was vented to atmosphere via this 30m stack. Its approximate location is show n in Figure 1.

Abstract Melbourne Water installed the largest biotrickli ng filter syst em in the southern hemisphere at the Western Treatment Plant (WTP) in 2006, treating 126,000m3 /h of odorous air from the Western Trunk Sewer (WTS) which conveys over half of Melbourne's sewage to the WTP.

Extensive Process Proving I t Trials conducted on-site found J that the multi-stage biotrickling Due to Melbourne Water's filter system exceeded its "no odour" policy and a design performanc e proposed residential COCOROC requi rements. In more recent ,,,. development on the northeast times hydrogen su lphide of the site, the OCF corner concentration has increased to reduce was installed by about 50% from original odorous emissions from the design requirements due to extracted air. increased sewage Figure 1. Approximate Location of OCF at MH1 . concentration and travel time This paper presents a case resulting from water study on the implementation of The odour control facility has proved conservation activities. Despite t his Biotrickling Filter (BTF) technology to to be robust and has coped well with increase in hydrogen sulphide loading, control H2S and odour based on the altered process conditions and req uires the installation still meet s or exceeds its results of the Proc ess Proving Trial and minimal maintenance. original performance requirements. subsequent test ing after ongoing

I

l

Introduction

Three years of successful operation despite higher H~ inflows.

operation.

The Western Treatment Plant (WTP) is located at Werri bee, an outer suburb of Melbourne in Victoria and treats approxi mat ely 54% of Melbourne's sewage, averaging 450ML per day. Raw

Equipment Selection BTF technology was det ermined to be the most appropriate for this site due to the high H2S load as well as a number of

Table 1. Key Design Parameters.

water

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Parameter

Air Flow at 20°C Air Temperature,•c Air Relative Humidity, % H2S Concentration, ppm, Absolute Peak H2S, ppm, Odour Concentration, OU

Influent Condition

126,000

Effluent Condition

Nm 3/hr•

15 - 35

60- 100 6- 27

:s os·

45.9

6,000 - 76,000

:S 2000· ..

*Normal cubic metres per hour, based on ideal gas flow at a temperature of 20°c and pressure of 1 atmosphere. •• To apply to at least 99.5% of all HzS readings, measured as the average of any ten consecutive readings taken at two minute intervals. ••• Readings shall be measured in accordance with the procedures as specified in the Australian Standard AS4323.3.

technical features


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odour management

[El

refereed paper

other economic, social and environmental considerations. The BTF system with a multi-stage tower design, including structured inert media, is guaranteed for 20 years, leading to much lower operating costs in comparison to conventional biofilters. It also has a significantly smaller footprint. Although the capital cost of BTFs was about double that of a comparable chemical scrubber installation, but they did not require expensive chemicals for treatment. Based on the estimated H2S load, the payback period for the extra capital cost was less than three years. BTFs are also a more sustainable alternative as they only require water and a small amount of nutrient for effective treat ment. For this installation all the nutrients required were available in the secondary effluent used for irrigation. Additionally, they do not rely on chemical removal of contaminants, and do not create hazardous waste streams.

Key Design Parameters Extensive sampling and dispersion modelling was used to develop the key design parameters listed in Table 1. These criteria also form the basis of the OCF performance testing requirements. The OCF compri ses 10 biotowers (PURSPRING™) designed by Bioway Technologies Australia Pty Ltd and constructed by a joint venture between United Group Infrastructure and Bioway Technologies Australia (Figure 2). The primary control system philosophy of the OCF is to provide the ability to operate the plant unmanned and automatically under normal operation,

Figure 2. The Odour Control Facility at Werribee. with supervisory control provided from the Main Operator Control Room via the existing SCADA System.

Process Proving Methodology This section describes the methodology of the analysis and the equipment used for the measurements during the Process Proving Trial. The Process Proving Trial was undertaken during the period from 27 November to 26 December 2006. The air sampling t ook place over a four (4) week period, with odour samples taken at six (6) day intervals to capture different daily trends. Five (5) inlet and outlet odour samples were taken on each day resulting in a total of ten (10) inlet and ten (10) outlet odour samples.

Continuous inlet and outlet H2S measurements were also taken throughout this period as well as number of other operational parameters as outl ined below. Pl ant airflow was determined by measuring the air velocit y using a pitot tube in the discharge stack. The airflow distribution through the 10 bio-towers was measured by 10 differential pressure transmitters (Endress & Hauser, type Deltabar S) installed before and after the air outlet of each biot ower. The total pressure drop across the Odour Control Facility was measured using differential pressure transm itters (Endress & Hauser, type Delt abar S) installed in the ductwork before and after the OCF.

Odour Control and Gas Purification

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42 NOVEMBER 2009 water

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technical features


~ refereed paper

odour management Table 2. Operating Parameters of Odour Control Facility.

Day

Date

Sampling Session

Time start sampling

No. Towers

INLET (OU)

Range

Parameter Water Consumed" (Uh)

Table 3. Odour Analysis Results. OUTLET (OU)

Removal Efficiency (%)

30 Nov

Morning

10:26am

10

23000

480

4,800-6,500

30 Nov

Morning

11:25am

10

21000

610

97.1

2.5

30 Nov

Afternoon

13:13pm

10

19000

860

95.5

30 Nov

Afternoon

14:19pm

10

18000

590

96.7

9:20am

10

22000

170

99.2

10:29am

10

22000

190

99.1

Nutrient Consumed (L)

1

97.9

Upper: 7.9 - 8.1 Lower: 1.9-2.2

2

6 Dec

Morning

2

6 Dec

Morning

Temperature (°C) and Relative Humidity (%) of OCF

22.1 - 28.1°C 73- 93%

2

6 Dec

Afternoon

14:14pm

10

33000

320

2

6 Dec

Afternoon

15:32pm

10

60000

480

99 99.2

Temperature (°C} and Relative Humidity (%) of OCF during Process Trial

11 - 32°c 23-60%

Process Water pH

Pressure Drop in bio-towers (incl dampers) {Pa)

700 - 800Pa

" During the Process Proving Trial, potable water was only used during one period, totalling only 3.5% of total water usage.

An online H2 S transmitter (Drager, type Polytron 7000 H2S detector) and an H2 S datalogger (Odalog, type 0-200ppmv) at the inlet sampling ports measured inlet foul air H2 S concentrations to the OCF. Outlet treated air H2 S concentrations from the OCF were measured by an on line H2 S transmitter (Honeywell, type MDA Model SPM "Chemcassette" analyser), and an H2 S datalogger (Odalog, type 0-2ppmv) installed at the outlet sampling ports. Odour c oncentrations were measured by collecting bag samples and analysing them in the NATA registered laboratory EML in accordance with the requirements of the AS/NZS method 4323.3.2001. This standard is the Australian equivalent of the internat ional standard method EN13725. Samples from the inlet and o utlet airstream were taken sim ultaneously. Volati le Organic Compound (VOC) concentrations were analysed in laboratories using Gas ChromatographyMass Spectrometry methods for hydrocarbon and sulphur compounds using the bag samples collected for odour concentration analysis. The on ly compound detected above the detection limit was methane (between 1.1 and 9.6mg/m 3) so no additional reporting of voe is provided in this paper. Air temperatures and humidity were measured twice daily. Temperature was measured using a calibrated temperature probe. Humidity was determined by measuring the wet bulb and dry bulb temperature and using the Mollier diagram to establish relative humidity.

44 NOVEMBER 2009 water

3

12 Dec

Morning

11:07am

10

23000

540

97.7

3

12 Dec

Afternoon

14:45pm

10

46000

1100

97.6

3 4

12 Dec

Afternoon

15:45pm

10

57000

1900

96.7

18 Dec

Morning

9:28am

10

40000

430

98.9

4 4 4

18 Dec

Morning

10:29am

10

ND**

170

ND**

18 Dec

Afternoon

13:lOpm

10

29000

320

98.9

18 Dec

Afternoon

14:20pm

10

55000

380

99.3

Notes:**Not determined due to broken sample bag

Acclimatisation of Odour Control Facility Biotower #1

the Process Proving Trial are summarised in Table 2.

One of the OCF biotowers (Biotower #1) was repaired d ue to a small leak 9 days prior to commencement of the Process Proving Trial, with start-up of Bi otower #1 on ly occurring 6 days prior to the trial start.

Class C recycled wat er is used for irrigation and requires no additional nutrients. The recycled water nutrient content is in this case sufficient for the catalyst (main ly bacteria) of this process.

A start-up period of approximately 8 weeks is usually required to ensure ful l acclimatisation of the OCF towers. This means that Biotower #1 was tested with only partial acclimatisation. The airflow through Biotower #1 was initially restricted and gradually increased over 4 weeks in 25% increments to reach the 100% design value. During the first 4 weeks of the Process Proving Trial, as Biotower #1 was sti ll starting up, the conseq uential extra air was distributed to the other nine towers. However, Biotower #1 was operated in normal operating mode together with the ot her 9 towers during sampling days. Additional air samples were also collected on three of the four sampling days to analyse the expected odour concentration with only 9 biotowers in operation. This was done by closing the damper to Biotower #1 once sampling of conditions under normal operation (10 towers) had been completed. Approximately 5 minutes after closi ng the damper, sampling of the outlet airstream began.

System Operation During Trial The operating cond itions for the main process parameters of t he OCF d uring

Several process upsets and process changes d uring t he Process Proving Trial were also recorded, which included the following: • A power fai lure of approximately 8 hours prior to the Process Proving Trial due to storm damage; • Recycle water supply fai lure between December 10 to 12, requiring t he use of potable water and additional nutrients; • Measures to improve fan air delivery caused airflow to increase to approximately 18% higher than its design f low. Of note is that despite these changes to the process, no significant effect to the H2S and odour removal efficiencies were observed.

Results Airflow The design airflow through each Odour Control Facility Biotower was 12,600m3/hr. During the Trial the airflow through Biotower #1 was increased from 32% in t he first week to 97% in t he last week. The airflow through the other Biotowers (Biotower #2 to Biotower #10) varied between 98% and 112% during the Process Proving Trial. The total airflow through all operational towers

tee n1cal features


odour management

~ refereed paper

was measured at 140,000m3/ hr, which is about 11 % higher than design.

Table 4. Odour Analysis Results.

Olfactometry analysis

Day

Results from the olfactometry analysis of the OCF are presented in Table 3. The results from the olfactometry analysis when one biotower was taken offline (only nine 9 out of the ten biotowers) are presented in Table 4. The inlet and outlet odour concentrations of all measurements for the OCF during normal operation (10 biotowers) are summarised in Figure 3. Resu lts of samples unable to be determined due to errors were excluded from the analysis. The inlet and outlet odour concentrations of all measurements for the OCF for one biotower out of service (only 9 towers in operation) are summarised in Figure 4. These samples were taken on three of the four sampling days, and undertaken as only 9 biotowers were fully acclimatised during the Process Proving Trial as described previously. A summary of the odour conce ntrations observed under both operating conditions are presented in Table 5. As apparent f rom Table 5, the Odour OCF installed at MH1 WTP had consistently good removal efficiencies between 95.5% to 99.2% regardless of the odour levels of the incom ing air for normal operation. The odour removal efficiency when one biotower was taken out of service (only 9 biotowers in operation) was also noted to be consistently good, with removal efficiencies between 94.2% and 99.3%.

Date

Sampling Session

Time start sampling

No. Towers

30-Nov

Afternoon

13:37pm

9

19000*

1100*

30-Nov

Afternoon

14:43pm

9

18000*

720*

96.0

2

6-Dec

Afternoon

14:52pm

9

33000*

380*

98.8

Outlet concentrations lower than t he detection limit of 50 ppbv were not detected and instead logged as 1 ppbv for the online analysers. Of note is that the Honeywell and Drager transducers were cali brated on 13 December and 19 December respectively after the Drager Transducer showed consistently lower results than the Odalog. Calibration of the Drager transducer with a 25 ppmv

46 NOVEMBER 2009 water

OUTLET (DU)

Removal Efficiency (%) 94.2

2

6-Dec

Afternoon

16:02pm

9

60000*

420*

99.3

4

18-Dec

Morning

10:49am

9

ND**

360*

ND**

4

18-Dec

Afternoon

14:46pm

9

55100*

630*

98.9

Notes:• Inlet samples were taken just prior to outlet sampling, with outlet sampllng starting approximately 5 minutes after inlet sampllng stopped **Not determined due to broken sample bag

Table 5. Summary of odour concentrations observed at the Odour Control Facility. Parameter

Normal Operation (10 biotowers)

One biotower out of service (9 biotowers)

18,000 - 60,000

18,000 - 60,000

170-1 ,900

360 -1 ,100

95.5% - 99.2%

94.2% - 99.3%

98.5%

98.3%

Inlet odour (OU) Outlet odour (OU) Odour removal efficiency (%) Average odour removal (%}

Table 6. Summary of H2S observations at the Odour Control Facility. Parameter

Online Transducers

Odalogger

Inlet H2S (ppm,}

0.1 - 16.9* (Drager)

0-41

Outlet H2S (ppm,)

:s 0.050 (Honeywell)

0- 0.080

~ 99.1%

99.1%- 99.9%

H2S removal efficiency (%)

f

70,000

-

§_ .t!

= INLET (OU) -

Olm.ET (OU) ....... Remowl Eflclency (%)

110

-·--,j·lr-....... •

i .,,.___.,...__._..,.......--...,--.,.,._.....,..-.,.--·---,·--·--·......

100 • 90 80

g

40,000

• 70 60

.i

30,000

50

20,000

40 30

60,000 50.000

i

C

::, ~ 0

c3

20

10,000 80

g

~

w iii

~

., Di:

10

0

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ .,~ .,~ .,~ .,~ 'o0 'o0 'o0 'o0 .,_'1,0 .,_'1,0 .,_'1,0 .,_'1,0 .,_' b0 .,_'b<:) .,_'b0

Hydrogen sulphide {H 2S) concentrations H2S concentrations were analysed and logged online using the automatic online H2 S analysers, with the results of the Process Proving Trial shown in Figure 5 for measurements using the online transducer, and Figure 6 for measurements using Odalog.

INLET (DU)

Sampling Oates

Figure 3. All Odour Sampling Concentration Data for Normal Operation.

70,000 60,000

~ -~ ::,

50,000

T

• • • • -. -.- - _-

1

-_-_=__

'N-LE_T'.~0 ,.,--U -) -- -:--:0:-U-TLET_ (..,. O~r-)-----::-: - Rom :-:owl= E~::cl~enc -=y-· (-%-)

-:---·-=· : : : : --~ i~~

- t ~g 80 ,. 70

40,000

C

). 60

-

30,000 .... - --

c3

20,000

:, 0

,.

I

I

r ··------------- --------- ----

,!!!

ie

-, 50

~

r40 ------~ 30

~

~

I- 20

10,000

1

1100

.j._..1!!:!!:aJ..- -~

720

_J,,-J- ~_

380

Jo...i...;.:.:...~

420

_L-ii...:.:.~

-

630

..L.....L.--

1

O

0

Sampling Oates

Figure 4. Odour sampling concentration data for only nine biotowers in operation.

technical features


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odour management H2S span gas showed a measured reading of only 14.9 ppmv. This highlighted that the inlet H2S reading prior to 19 December were most likely reading low by a factor of about 1.68. Even after calibration the Drager transducer still measured lower readings than the Odalog, which was calibrated prior the testing period .

[!I

Table 7. Design Specification and Results of process Proving Trial. Design Specifications

Parameter

< 2000*

Outlet Odour Concentration (OU) average and range

96%

Odour Removal Efficiency (%) Inlet H2S Concentration, (ppmv)average and range

From Table 6, the OCF is also found to exceed its original design performance requirements with respect to H2 S removal efficiency.

H2S Removal Efficiency (%)

During the Process Proving Trial, the OCF was operated in a stable manner without major upsets. The upsets that were experienced prior to or during the Process Proving Trial did not influence the operating efficiency of the Odour Control Facility. The weather conditions d id not change much during the Process Proving Trial. During the sampling days, the ambient temperature ranged from 17-32°C and the relative humidity ranged from 23-60%. The inlet odour concentration ranged from 18,00060,000 OU and the inlet H2S concentration ranged between approximately 0-40 ppmv. A summary of the operating parameters during the trial is provided in Table 2.

Process Proving Trial Results

29,950

6,000-76,000

Inlet Odour Concentration (OU)

A summary of the H2S result observations are shown in Table 6.

Other operating and performance information

refereed paper

6- 45.9 < 0.5**

Outlet H2S Concentration, (ppmv) average and range

18,000-60,000 460 170-1,900 98.5% 0- 41.3 0.010 0- 0.080 99.6%

99.5%

* Readings shall be measured in accordance with the procedures as specified in the Australian Standard

•• To apply to at least 99.5% of all HzS readings, measured as the average of any ten consecutive readings taken at two minute Intervals.

service, the required odour and H2S removal efficiencies were achieved.

Tests on the odour and H2 S removal efficiency of the OCF for situations where one biotower is offline have been conduct ed. The result s indicate that even when one biotower is out of

The Process Proving Trials found that the biotrickling filter well exceeded its performance requirements.

450

20

e

.e,: 0 :;:;

No major failures or process upsets were recorded during the Process Proving Trial, w ith stable operation recorded. Minor process upsets experienced prior to or during the Process Proving Trial itself did not influence the operating efficiency of the OCF. No major change in the weather conditions were observed during the Process Proving Trial, with ambient temperatures ranging from 17 to 32°C and relative humidity between 23 to 60% during sampling days.

48 NOVEMBER 2009 water

0

I;,:

~

300

,: Cl)

u

Cl)

u ,:

,: 0

250 10

0

(.)

(.)

rn

200

rn

i

i

to-

150

to-

w !:

w

..J

..J

to-

100

::> 0

50 0

0 -

A summary of the OCF performance in comparison to the original design specifications are presented in Table 7.

Q

.e,:

350

15

It can be concluded that during the Process Proving Trial the OCF had been runni ng according to design specifications.

Conclusion from Performance Trial

1

400

Q

Tlmo (days }

-+- Inlet H2S~oncentratlon (ppmv) Online Transducer

_.,_ Outlet H2S-concentratlon (ppbv) Online Tr.ansd ucer

Figure 5. H2S Concentration measured with online transducers (Drager for inlet concentrations and Honeywell for outlet concentration).

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Figure 6. H2S concentrations measured with calibrated Odalogs at inlet and outlets.

technical features


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~ refereed paper

odour management Subsequent Operating Performance

Table 8. Summary of odour concentrations observed at the Odour Control Facility. Date

Odour Concentration {OU)

Inlet odour (OU)

20 Oct 06

23,000 & 24,000

Outlet odour (OU)

20 Oct 06

1,600 & 3,300

Inlet odour (OU)

12 Feb 07

40,000 & 35,000

Outlet odour (OU)

12 Feb 07

2,000 &1,800

Parameter

As part of ongoing performance monitoring, MW have conducted periodic odour sampling on the inlet and outlet of the OCF. The monitoring was undertaken without any proc ess optimisation which would further improve the results. Environmental Testing Consultants undertook all the sampling and testing and the result s are shown in Table 8. All the resu lts apart from one on October 20 demonstrated similar performance to that experienced during the Process Proving Trial. This result cou ld be an anomaly associated with the testing which is not unusual. In more recent times, drought and reduced water usage as a resu lt of water restrictions and improved trade waste management have seen both liquid and gas phase su lphide levels increase by about 50%. Hydrogen su lphide levels of

93% & 87%

Odour removal efficiency (%)

95%

Odour removal efficiency (%)

up to 64.5 ppmv were recorded in February 2008 on the inlet to the Odour Control Facility which was consistent with a measured increase in dissolved sulphide levels from about 3.5 mg/L to about 7 mg/L. Outlet hydrogen sulphide levels continue to be less than 50 ppbv.

on Class C recycled water and req uires no additional nutrients. The odour control facility has proved to be robust and has coped well with altered process cond itions, and requires minimal operator attention and maintenance.

Conclusions

Thanks t o Melbourne Water and Bioway Technologies for providing the results for th is paper.

After more than 3 years of operation the Odour Control Facility still meets or exceeds its performance requirements. This is despite th e increase in sewer hydrogen sulphide levels since its design. The faci lity operates effectively

1\camtek T o!dtng.logy fty Ltq

Acknowledgment

The Authors

Josef Cesca (email josef.cesca@ ch2m.com.au) is the ANZ Regional Technology Manager for CH2M HILL. He was responsible for the initial designs and technology selection for this project and was assisted by Amy McDonald.

B.L. Camtek Technology Ply Ltd. I'\ a leading Australian engineering company committed to the development and Implementation of a~vated-carbon filters . This field Is limitless In Its applications Some areas covered Include larg..scale ramoval ol noxious gases, punflcaUon of chemicallycontaminated water, air punf,calion fo, use ,n reactions, the filtration of gases from reaction vessels and sewage plants. The unique systems and equipment that have been designed and developed by the company, (and are continuing to be designed), are affective, efficient, and environmentally friendly.

Bart (N J R ) Kraakman (email b.kraakman@bioway.com) is the Technical Director of Bioway Technologies P/ L. Imogen Malpas is currently responsible for the operation of the facility for Melbourne Water.

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50 NOVEMBER 2009 wat er

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technical features


odour management

DEVELOPMENTS IN ODOUR CONTROL FOR THE WASTEWATER INDUSTRY N J R Kraakman Abstract

Percentage of Time Odour Concentration Exceeded

It has never been an easy task predicting odour nuisance from wastewat er treatment facil ities nor treating odours effectively with predictable costs. With the availability of more objective tools to quantify odours and the use of more reliable and more cost effective treatment methods, odour nuisance problems from wast ewater facilities can now be controlled more simply and predictably, using advanced biological systems. It can make life much easier for plant managers and operators.

Introduction In climates like Australia odour problems are exacerbated by elevat ed temperatures. The often relatively flat coastal terrain with high population densities and long rising sewer mains leads to a relatively high risk of odour problems. The sandy soil which is often present also increases t he risks of odour problems due to the intrusion of sulphaterich seawater. (Sharma et al, 2008). Wastewater treatment plants built many years ago outside of residential areas, are now often hemmed in by residential developments. Wastewater collection syst ems have often been extended over the years resulti ng in greater odour emissions as a result of the septic co nditions created in these extended sewage collection systems. Municipalities and water corporations are constantly searching for cost efficient and community friend ly methods of dealing wit h odours emitted from wastewater collection systems and wastewater treatment plants. Traditionally, odour control methods, while fairly effective, involved chemical ad d ition to the sewer, chemical scrubbers and activated carbon filtration which com e with high operating costs and requ ire operator attention. Preferred odour control methods are chemical free, wit h low predictable operation costs, minimal maintenance and easy to operate.

52 NOVEMBER 2009 wat er

1000

100

10

Hour, per Yoar Odour Concentration Excoodod

Figure 1. Acceptable odour concentrations from wastewater facilities in relation to the time of exposure (Wallis and Cadee, 2008).

Developments in Odour Management Odour management at wast ewater collection and treatment facilities used to be largely reactive responding to complaints from people living near the faci lity. Solving the odour nuisance was not easy, because of the lack of objective useful methods to quantify the problem. This has changed over the recent years as many countries have adopted a practice of dealing with odours from sewage treatment works based on the prediction of odour concentrations using modelling with validation against odour com plaints. Odour impact risks analysis is now commonly performed and is often required prior to building new or upgrading existing facil ities. Predicting odour nuisance is not always an easy task. Just because an odour is detectable does not automatically mean it may be classified as a nuisance. Although odour nuisance can be characterised in

Reliability is the key to success in odour control management.

many ways, the most commonly used measure is odour concentration. The odour concentration is expressed in odour units (ou), which represents the number of times that the odorous air needs to be diluted with odour free air so that it is just at the threshold of detection by a panel of trained odour assessors under conditions set by the AS/NS 4323.3, which is based on European CEN methodology. The acceptable level of odour concentration by a recept or is dependent on the character of the odour, but always related to the time of exposure to the odour. The acceptable level of odours typical from wastewater facilities can be expected to be close to those proposed by Wallis and Cadee (2008) as shown in Figure 1. Fewer hours of exposure will increase the acceptable levels of the odour. Risk analysis including predicting odour concentrations is now usually part of an odour management plan for the sewage treatment facility design and urban planning. As fewer hours of exposure will decrease odour nuisance, a more reliable and efficient odour treatment facility will

tee h n i ca I features


odour management increase the acceptable odour concentration off-site.

Developments in Odour Treatment Containment of the odours is important in preventing unwanted odour emissions. Many types of covers for the different processes at the wastewater treatment facil ity have been improved over the last ten years. This can reduced the amount of foul air extraction required to ensure negative pressure under covers and prevent or reduce the volume of fugitive odour releases from these covered sources. Maintaining negative pressure where access for inspection and maintenance is required will be more difficult to achieve and th us higher ventilat ion rates must be adopted for these. Different techno logies for odour control are used ; among the most com mon are chemical-physical methods like chemical dosing or scrubbing, adsorption using activated carbon and biological methods. With uncertain energy prices, more advanced biological systems are of increased interest due to their low operating costs and their improved reliability. Hardly any resources are required for operation and no waste is normally generated, which makes biological air treatment usually a 'green' technology with a lower carbon footprint.

Developments in Biological Odour Treatment Biological systems are increasingly applied to solve problems of polluted air emissions in different industries. Over

POLLIITAl'IT CONCF.NTRA110N

GAS PHASE

Figure 2. Pollutant concentration profile in biological odour treatment system for a compound that is mass transfer limited (A) and biological reaction limited (B1 and B2). The biological reaction limited can be dependent on the pollutant concentration (zero order kinetics; B1) or independent on the pollutant concentration (first order kinetics; B2). recent years, much progress has been made in areas such as microbiology, process modelling, reactor design and reactor-operation. Experiences with biological odour control at wastewater facilities ranging from hot climate condition like Australia and the Middle East to colder climate conditions like North Europe and Canada have all led to increases in both efficiency and reliability. Biological waste gas treatment systems convert a mixture of pollutants from the air into wat er, carbon dioxide and salts. Micro-organisms, primarily bacteria, are the catalyst of this process. The overall process in a system can be

divided in two phases: the mass transfer of the pollutants from the foul air to the micro-organisms, and the biological degradation of the pollutants (see Figure 2). The combination of different physical, chemical and biological mechanisms results in a relatively com plex system. Fundamental parameters including mass transfer, absorption of t he different pollutants and degradation kinetics in the biofilm, as well as airflow and water distribution are often difficult to quantify. Much progress has been made in understanding the fundamental aspects, which are necessary for design and operations. Still much of the current design work, on both sizing and operations, is based on empirical

wat er NOVEMBER 2009 53


odour management experience. Models have been greatly improved but are still not always applicable, especially for the treatment of compound mixtures and varying concentrations. Various reactor configurations have been developed for different applications. The different biological techniques are tradit ionally classified as biofilters, biotrickling filters and bioscrubbers. In the wastewater industry, biotrickling filter type systems are now the most common, but are often also referred to as bioscrubbers. The conventional biofilters using organic or partly organic media are applied less frequently as they face important design limitations and operating stability problems. The air stream from, for example, wastewater normally contains hydrogen sulphide, which is oxidised to su lphuric acid in a biofilter system. Sulphuric acid accumu lates in the media as it is difficult to wash with water, red ucing the overall odour removal efficiencies over time. Also, the air streams are not always com pletely saturated with water, which leads to partial drying out of the media, especially in the inlet (usually bottom) part of the biofilter. Moisture conditions

are critical in a biofilter and a drop in moisture as result of uneven irrigation or no prehumidification w ill result in a reduction of odour removal efficiency. Over- irrigation can also result in premature media decomposition and increased in backpressure and power use. The design and operational limitations of conventional biofilters including the requirement of media replacement are solved w ith the development of more advanced biological air treatment systems. In the more advanced biological odour treatment reactors the media change-out or cleaning is no longer required, since inert preferable structured support material for the micro-organisms is used as well as the control of co nditions for the biological process is improved. Although the more advanced systems requi re higher investment cost, the operational costs are greatly reduced, since up to 40% of the operational cost of a conventional biological system is typically related to the media change-out. The most important process parameters for biological odour co ntrol in the wastewater industry are a wet

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54 NOVEMBER 2009 water

environment and optimal conditions (e.g. pH, nutrients) for the different microorganisms. The inlet odorous airstream provides an ongoing source for oxygen and energy (the odorous compou nds) for the biological process. Odour control in the wastewater industry is specific for the following reasons: â&#x20AC;˘ The air contains a mixture of compounds, which requires a mix of different micro-organisms for its removal in order to achieve high efficiencies or low outlet concentrations. â&#x20AC;˘ Reliability is important t o minimise operator interference as in many situations the odour treatment equipment has to operate unstaffed, for example at lift stations and small wastewater treatment facilities.

Odours from Wastewater are a Mixture of Compounds Odorous air streams from wastewater processes contain a mixture of many com pounds. These various compounds usually have very different chemical properties as can be seen from, for example, their water solubility and their biodegradabi lity. To degrade all odorous com pounds an optimal mix of microorganisms is required. Micro-organisms differ from each other in their capacities to obtain their energy, carbon and nutrients. Micro-organisms also differ in their ability to form a good biofilm structure, their growth-rate, their affinity for compounds, their degradation capacity, and their nutrient requirements. Unfortunately the optimal environmental conditions for the micro-organisms also differ. Therefore due to the many different compou nds in the air stream, a mix of micro-organisms is required and different environmental cond itions are preferred in the biological odour treatment system. When an air stream contains multiple c ompounds, it can be expected that the removal of many of the compounds is affected by the presence of other compounds. In the situation that a bioreact or system is removing two or more compounds, the metabolic activity in a micro- organism may involve the mechanism of induction, inhibition and sometimes co-metabolism. Induction refers here to the process that initiates the production of enzymes that catalyse the biodegradation in the cell. Inhibition involves the toxicity effect of certain compounds on the metabolic activity of

technical features


odour management Maintaining Optimal Conditions

Table 1. Examples of volatile reduced sulphur compounds (WEF, 2004). Molecular Weight

Odour Threshold (ppbv)

H-S-H

34

CHrSH

48 62 62 74 76

0.47 1.1 0.1 0.19

Pollutant

Formula

Hydrogensulphide Methylmercaptan Dimethylsulphide

CH3-S-CH3

Ethylmercaptan

CH3-CH2-SH

Allylmercaptan

CH2=CH-CHrSH

Propylmercaptan

CHrCH 2-CHrSH

Crotylmercaptan

CHrCH=CH-CHrSH

Dlmethyldisulphide

CHrS-S-CH3

Amylmercaptan

CHdCH2lJ-CHrSH

Benzylmercaptan

C5H5-CH2 -SH

104 124

Biological odour treatment reactor at wastewater collection and wastewat er treatment plants often deal with many odorous compounds, among them mixtures of volatile reduced sulphur compounds, like H2S and mercaptans, which are important because of their very low odour threshold (see Table 1 ). Although different micro-organisms are known for the degradation of volatile reduced sulphur compounds, the treatment of an air stream cont aining

mixtures of reduced sulphur compounds remains challenging for two main reasons. Firstly, the energy yieldi ng process of H2S oxidation is higher and thus preferred over the oxidation of other reduced sulphur compounds. Secondly, the degradation of many of these sulphur compou nds is only possible with high efficiencies at neutral pH, whi le a degradation product from sulphur compounds is su lphuric acid which reduces the pH. Different types of organisms require different environmental conditions including the absence of easily degradable compounds and are, therefore, preferably separated in different layers of the reactor. Polishing with, for example, activated carbon is now often applied to obtain low outlet odour concentrations, but is normally not necessary when the biological odour treatment system is designed well. The elimination of activated carbon polishing reduces complexity and the risk of unpredictable operating costs involved with the change-out and the disposal of the activated carbon.

90

1

o

20

30

40

ea

ea

0.029 1 0.3 0.19

90 94

the micro-organisms and co-metaboli sm is the (partial) conversion of certain compounds by enzymes that are induced by other compounds. The mechanism for micro-organisms to ensure that the organism uses the more readi ly catabolisable carbon and energy source is called catabolite repression. One consequence of catabolite repression can be that if more compounds are present at the same time, the metabolism of a certain compound is resumed only after another compound causing catabolite repression is used first (so-cal led diauxic growth). Therefore it is often a necessity in a biological system that certain compounds are removed first, before other compounds can be removed.

o

0.05 0.075

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Figure 3a and 3b. Examples of gas distribution in a reactor expressed in seconds of different media at different gas velocities. (Kraakman, 2008). 56 NOVEMBER 2009 water

The reactor size and shape and the config uration of the internal carrier (media) for the micro-organisms directly influences the removal capacity of the biological system and wi ll impact important design parameters such as mass-transfer rat e, bact erial degradation capacity, water holding capacity and pressure loss. Often underestimated is the influence of the reactor and media configuration on the air flow characteristics through the biological gas treatment system. When high removal efficiencies are required (>99%), all the air has to be treated effectively. In order to treat the air effectively, all the air needs to stay in the reactor for a minimum period of time to exchange the compounds to the catalysts in the biofilm on the media. An optimum air distribution in the reactor is required and preferably moves the air through the reactor as a plug-flow. Preferential air streams or partial bypasses of the air should be avoided at all times. In present theoretical models describing the degradation of gas components in biological filters, air flow is described as a plug-flow, but this theory seems to be oversimplified as illustrated in Figure 3a and 3b showing examples of real gas distribution in typical media. The air flow behaviour has considerable effect on the maximum achievable outlet concentrations and thus overall cleaning efficiency (Kraakman, 2008). A reactor with one layer of randomly packed media is likely to be subject to sub- optimal air distribution through the media after a period of operating time. Pre-engineered structured media can prevent this. Structured media also makes the operation more determined by design rather than chance. The media used should be inert and not subject to blocking, fouling, erosion or corrosion causing, for example, shrinking of the media or preferential airstreams through the media. The method by which water is added to the reactor is important as water not only prevents the biofilm layer in the biological system from drying out, but also serves as a supplier of nutrients for the micro-organisms in addition to removing the degradation product, sulphuric acid. Water can be recircu lated over the media or can be added to the top of the media and then,

technical features


odour management after passing through the media, be directly removed from the bottom of the system. Minimising water use in the reactor can have benefits. First, a thinner wat er film can be maintained on the biofilm layer, which is often preferred to minimise the resistance for mass transfer of the pollutants from the gas phase to the m icro-organisms. Secondly the thinner water film on the med ia results in a larger void vol ume in the media. A larger void vol ume is better as the pollutant airstream wi ll be in contact with the biofilm longer, resulting in a longer so-called actual residence time. The actual gas residence time is a better design parameter than the often used

theoretical empty bed gas residence time (Theoretical EBRT) as it represents the real time in seconds that the air is in cont act with the biofilm. Theoretical EBRT = media volume (m3 ) air flow (m3 sec- 1) (sec)

/

Actual RT = media volume (m3) x void fraction (%)/airflow (m 3 sec-1) (sec)

Optimising Reliability Equipment should preferably be simple and reliable to operate. Quantification of the robustness of a biological air purification system wou ld be helpful to designers and operators. Robustness can be defined to reflect the ability of the

biological syst em to deal with fluctuations and operational upsets. Robustness may be quantified by determining the risk of negative effects on the biological system for each possible upset, multiplying by the frequency of the upset, and summing over all possible upsets. The risk of negative effects on a biological system (R) can be defined as:

R = I (p x E)

p = the probability of occurrence of an upset E = the negative effect of the upset

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odour management cleaning is no longer required and the reliability greatly improved.

The negative effect of the upset (E) can be expressed as the loss of the removal efficiency (%), the loss of the total removal (kg/day or kg/year), or the impact on the people living near the installation (e.g. the number of occurrences during w hich the concentration of t he emitted air stream exceeded t he allowed odour threshold in t he neighbourhood). The m icrobiological community in a biological treatment system will face fluctuations related to the process upstream as a result of continuous or discontinuous processes, irregularly unplanned shut dow ns, planned maintenance shut-downs and diurnal fluctuations. There may also be fluctuations related to the operation of the system, for example, associated with loss of control of power, water or nutrient su pply. Examples of quantification of robustness of full-scale biological waste gas treatment systems are illustrated elsewhere (Kraakman, 2003 and 2004).

With the use of more objective tools to quantify odours combined with the use of more reliable cost effective treatment met hods, odour emissions from wastewater facilities can now be controlled more simply and predictably.

The Author

Bart (N J R ) Kraakman is Technical Director, Bioway Technologies Aust ralia Pty Ltd, and works part t ime at the Delft Technical University in The Netherlands. Email b.kraakman@bioway.com.

References A multi-layered biological odour treatment installation treating 126,000 m3/h of odorous air (Cesca et al, 2009).

Microbial responses to stress conditions are interesting and important to quantify. Biological air treat ment systems using mixed microbial cultures as inoculum are self-optimising w ith species becoming dominant that are most competitive under the environmental conditions in t he system. Unfortunately this self-optimising adaptation process seems to be relatively slow and is likely to take months or longer. On the other hand, different applications and tests showed that a biological system can deal w ith spikes. Experiences also show a biological system can handle very well the diurnal occurring peaks typical for odour emissions from wastewater processes. When temporary reduced rem oval efficiencies are noticed, it's often the first day after many days of wet weather when t he relatively low concentrations reduce the (enzyme) activity of the microorganisms over a couple of days. Recovery to full activity is fast and is normally a matter of minutes or hours to maximum of one day. It's important that t he robustness is quantified and the risks are understood, so that extra measures can be taken if necessary to reduce the risks to obtain

58 NOVEMBER 2009 water

an odour t reatment system t hat is predictable in operational costs and is operator friendly.

Conclusions In climates like Australia odour problems are exacerbated by the high temperatures and the relatively flat and densely populated areas along the coast. Odour management at wastewat er collection and treatment facilities use to be mainly based on reacting to odour complaints from people living in residences nearby the odorous facilities. Solving t he odour problem was not easy, because of a lack of useful objective methods. This has changed over t he recent years as now the practice used for dealing with odours from sewage treatment works is based on the prediction of odours using modelling with validation against odour complaints. Odour control methods are preferred t hat are chemical free, have low and pred ictable operational costs, relatively maintenance free and easy to operate. The development of more advanced biological systems solved the design and operational limitations with conventional biological odour treatment systems including the requirement of internal media replacement. In the more advanced biological odour treat ment systems the media change-out or

Cesca, J., A. Mc Donald, N.J.R. Kraakman, I. Malpas (2009). Odour Control at Melbourne's Western Treatment Plant Water, 36 No 7 (this issue)

Kraakman, N.J.R. (2003) Full-scale biolog ical treatment of industrial CSr emissions at extreme conditions; The robustness of a biological system and its risks to the waste gas purification. Environmental Engineering, Vol 22 No 2, 79-86. Kraakman, N.J. R. (2004) H2 S and Odor Control at Wastewater Col lection Systems: An Onsite Study on the Robustness of a Biological Treatment. Poster presented at the USC-CSC-TRG International conference on biofiltration. Santa Monica, October 20-22, 2004 Kraakman, N.J.R. (2008) Multi-layered bioreactors: the new standard in managing odors. Design considerations, implementation issues and operating experiences. Proc. WEF/A&WMA-Odor and Air Emissions Specialty Conference, Phoenix. Apri l 6-9, 2008. Sharma, K., D.W. de Hass, S. Corrie, K. O'Halloran, J. Keller and Z Yuan. (2008) Predicting hydrogen suldife from sewers: a new model. Water. March 2008: 132137. Wall is, I., K. Cadee. (2008) Odour exposure criteria and odour modelling in Western Australia. Water. March 2008: 144-1 48. Water Environmental Federation. (2004). Control of odour and emissions from wastewater treatment plants. Manual of Practice No. 25. Alexandria, Virginia.

technical features


odour management

~ refereed paper

RECYCLED WATER: PERCEPTIONS OF COLOUR AND ODOUR A Hurlimann Abstract This paper reports results from a study conducted in 2007 regarding the Mawson Lakes dual water supply system. The paper reports residents' experience of recycled water, use of recycled water, and their perception of aesthetic attributes of recycled water (colour and odour). The majority of survey respondents use the dual water supply system for its intended purpose. The study found than 49% of respondents perceived a colour, and 28% perceived an odour was present in the recycled water. Despite this perception of colour and odour, a high level of satisfaction with the recycled water system was conveyed by survey respondents.

Introduction The use of recycled water has been increasing in many areas of Australia over t he past decade. One component of the success of recycled water initiatives will be the community's willingness to use the recycled water for the intended purposes. A number of recycled water projects have fai led due to negative community perceptions (Hurlimann and McKay 2004). Given recycled water intended for non-potable use may have different characteri stics to potable water, it is important to understand how the community perceives these attributes. For example, will a higher salt content of recycled water impact consumer use of recycled water on gardens? Will the presence of a colour and odour impact the uptake of recycled water use for outdoor cleaning? Both internationally and locally there is a lack of research conducted with communities that are actually using recycled water. Bruvold and Ongerth (197 4) suggested there may not be any difference between hypothetical attitudes to recycled water use and attitudes based on experience. They compared attitudes between members of the USA public who had experienced recycled water use (n=479) and those who had no experience with recycled wat er use (n=493). Attitudes were compared for 25 uses of recycled water, and no significant

60 NOVEMBER 2009 water

difference was found , However, other literature indicates that there is not necessarily a relationship between attitudes and behaviour (Fishbein and Ajzen 1975; LaPiere 1934; Schuman and Johnson 1976). A survey of office workers in Japan who use recycled water for toilet flushing found they perceived the presence of odour (Yamagata et al. 2002). The study did not report if this had any impact on respondents' use of the recycled water (e.g. if the presence of recycled water made them avoid using the toilets). Albrechtsen (2002) undertook a pilot study in Denmark which investigated community responses to the use of rainwater and greywater for toilet flushing. Several respondents complained about bad smell. This resulted in the closure of one pilot treatment plant. In Australia, Marks et al. (2002) surveyed 20 residents from the New Haven Estate in Adelaide where recycled water is used for non potable purposes. A number of respondents identified occasional problems with recycled water use for toilet flushing, including occasional odour, a murky co lour and sediment. In an earlier survey conducted in 2004 at Mawson Lakes in South Australia, attitudes to the aesthetic attributes of recycled water: colour, odour and salt were investigated using the conjoint analysis methodology (Hurlimann and McKay 2007). The st udy found that for garden watering having 'low salt levels' was the most important attribute, for clothes washing 'colourless' was the most important attribute, and for toilet flushing a 'low price' was the most important attribute. Respondents were found to be willing to pay for improvements to the quality of recycled water. The amount they were w illing to pay varied depending on use and the attribute in question. The study found respondents were wi lling to pay $0.04/kL to reduce salt levels of the recyc led water use for garden watering. The study

A survey at the Mawson Lakes dual pipe system.

did not investigate how the presence of these attributes may impact an individual's use of recycled water.

The Study Location The results reported in this paper are part of a long-term study of the Mawson Lakes community in Adelaide, South Australia and their attitudes to the use of recycled water (see Hurlimann 2008 for further information about Mawson Lakes and the long-term study). The suburb has a purpose-built dual wat er supply system which delivers a combination of Class A recycled water and renovated stormwater for non-potable purposes including toi let flushing, garden watering and car wash ing. Recycled water officially commenced delivery though the dual pipe network in April 2005. This long term study of community attitudes to recycled water at Mawson Lakes involved fou r telephone surveys: two prior to recycled water use commencing (2003 n=136 and 2004 n=136) and two post recycled water use commencing (2005 n=162 and 2007 n=269). The third survey was conducted only 8 weeks after recycled water use had commenced. During these eight weeks the water flowing through the recycled water pipes varied in composition: at times fully potable water and at other times a combination of treated wastewater and potable water.

Research Method For the fourth survey, which is the focus of this paper, a total of 269 Mawson Lakes households were randomly surveyed over the telephone by professional interviewers during the months of June and July 2007. The interviewers used computer assisted telephone interviewing (CATI), as per the first three surveys. The households were randomly selected from a phone list of 704 Mawson Lakes households (due to privacy laws, these phone numbers were obt ained from marketing company). At the time of survey there were approximately 2860 households occupied at Mawson Lakes, wh ich gives the results a precision level of Âą 6%, where the confidence level is 95% and P = 0.5. The interviews took an average of

technical features


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Jl 1111 ,.,1,1,


odour management 27 minutes to complete. Information collected in the survey included: use of recycled water; experience of recycled water use (including the presence of the attributes colour and odour); responses t o a series of attitude and perception statements; and demographic information.

~ refereed paper

Table 1. Recycled water use rates, Mawson Lakes 2007. Recycled water use

Results The respondents consisted of an even distribution of gender (female: n= 134, and male: n=135). Most of the respondents were aged between 31-50 years of age (44%), lived in 1-2 person households (50%), and had a high school and/or other certificate (49%).

Number (%) of respondents who use 259 (96.3%)

3(1.1%)

260 (96.7%)

8 (3.0%)

1 (0.4%)

Car washing

212 (78.8%)

51 (19.0%}

6(1.1%) 9 (3.3%}

Clothes washing

13 (4.8%}

247 (91.8%)

Drinking

4 (1.5%}

263 (97.8%)

2 (0.7%}

Cooking

2 (0.7%)

264 (98.1%)

3(1.1%)

Showering

4 (1.5%}

262 (97.4%}

3(1.1%)

Recycled water characteristic

Yes N(%)

Are you happy with the pressure?*

C

Cloudy water

C

·c

-0

E

Chemicals

CJ3

2005

2007

2005

2007

2005

2007

32 (20)

26 (9)

1 (1)

2 (1)

128 (79)

241 (90)

84 (52)

106 (40)

37 (33)

104 (40)

41 (25)

59 (20)

Does it have an odour at times?

32 (20)

76 (28)

124 (76)

188 (70)

6 (4)

5 (2)

Does it have a colour at times?**

43 (27)

132 (49)

11 7 (72)

135 (50)

2 {1}

2 (1)

water disconnected, and six respondents indicated they live in a townhouse/u nit which does not have a garden. Respo ndents were also asked if they use recycled wat er for purposes beyond those included in the survey. A total of 221 (82%) respondents said that they do not. Twelve (5%) respondents did not know, and 36 (13%) respondents listed other uses. These 36 responses included : nine who use recycled water to clean outdoor areas, and three respondents st ated each of the following: cleaning inside; in water features; in fish ponds; pet drinking water; to wash pets; and to fill children's wading pools. The uses indicated by these respondents show that t hey are using recycled water

I

I

I

I

I

03 -

I

I

0

,I: ~

~ '6

si

al

l J ~

Taste E ) 3

]6

Other

10

There are guidelines

13

Quality

I

I 127

Odour

I

Colour

0

I 147 10

15

20

25

30

35

40

45

Number of respondents

Figure 1. How recycled water differs from drinking water, Mawson Lakes 2007. 62 NOVEMBER 2009 water

Don't know/refused N(%)

Does recycled water differ from drinking water in any way?**

Psychological tJ2

i01

No N(%)

Significance level: • = 0.01 level; •• = 0.001 level

For toi let fl ushing two respondents indicated that they have had the recycled wat er turned off (disconnected) and the other indicated that they are not sure if the recycled water is connected as they are living in a town house. With regards to garden watering, two respondents again indicated t hey had the recycled

:;.

7 (2.6%)

Toilet flushing

Table 2. Perceived recycled water characteristics at Mawson Lakes - comparison between 2005 and 2007.

Respondents were asked whether they ever use recycled water for seven purposes. These included those permitted by the South Australian Reclaimed Water Guidelines (Department of Human Services et al. 1999) and ad ditionally some uses not permitted by the Guidelines. Results are displayed in Table 1. As can be seen, a number of respondents use recycled water beyond the uses allowed by the guidelines. Notably, four respondents indicated they have drunk recycled water, four that they have showered with recycled water, and two that they have cooked with recycled water. Th irteen respondents indicated they use recycled water for clothes washing.

Algae build up 0 2

Number (%) don't know/refused

Garden watering

Stated use of recycled water

s

Number (%) of respondents who don't use

50

for uses beyond whic h are permitted by the Guidelines, and communicated in brochures regarding recycled water use. Use of recycled water beyond guidelines also occurred in Leidsche Rijn Utrecht, a suburb in t he Netherlands with a dual water supply system where 15% or people indicated that they used the nonpotable water to fill children 's wading pools (Source Water and Sanitation News 2003). A cross contamination in this system led to all dual water supply systems being banned in the Netherlands (Cooperative Research Centre for Water Quality and Treatment 2003).

Recycled water characteristics Respondents were asked a series of questions about recycled water characteristics such as pressure, colour and odour. These questions and results can be seen in Table 2. The results indicate that the majority of respondents were happy with the pressure of the recycled water, with on ly 10% of respondents expressing they were not happy. Poor pressure was a major concern expressed by respondents in previous surveys at Mawson Lakes and indicates that the situation has improved. This is verified by statistical analysis (ANOVA) wh ich indicated a significant increase in satisfaction with pressure in 2007. Recycled water is typically run through dual water supply systems at a lower pressure than potable water, as one safeguard against cross contamination.

technical features


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odour management A total of 106 respondents (40%) indicated that they perceived recycled water was different from drinking water. Statistical tests indicate this was a significantly higher proportion of respondents than in 2005. These respondents were asked how it differs from recycled water. Responses to this question were coded into categories and are displayed in Figure 1. The majority of responses to the question of how recycled water differs from drinking water related to aesthetic attributes including colour/sediments and odour. This relates directly to subsequent survey questions which specifically asked respondents if recycled water had an odour or colour at times. A total of 28% of respondents said recycled water did have an odour and 49% said it did have a colour (see Table 2). Statistical analysis indicates that a significantly larger proportion of 2007 survey respondents perceive the recycled water has a colour, in comparison to 2005. Respondents who indicated recycled water had colour or odour were asked to give detail of the odour and colour. Those responses were coded into categories and the results are displayed in Figures 2 and 3. These figures provide detailed information of the colour and odour experienced by respondents. With regard to odour, the majority of comments related to the recycled water having a stagnant/stale smell. Respondents mentioned this was most notable in the bathroom. Some comments made by respondents are found below: "It has a slight odour in toilet and extra staining - particularly if not used for a while" "It stains the toilet and sometimes has an odour"

C 0

"' ~ .,,lg

Wetlands I creek / swampy

Sewerage ,._..=

Associated with toilets

'-"-';....;.---.J6

,-:.....;;..;...._""" 5

Dirty I Muddy

2

10

0

C

0

~ ~

Cloudy

i

8

"The water smells bad sometimes in the toilet" With regard to colour, the majority of respondents commented that the recycled water had a brown appearance, especially in the toilet bowl. Respondents were then asked to rate how satisfied they were with recycled water at present on a scale of 0-10 where 0 = not at all satisfied and 10 = extremely satisfied. Despite the aesthetic characteristics mentioned above, the mean for this question was 8.6, indicating a high degree of satisfaction. This was a significant increase in satisfaction since the 2005 survey (the mean in 2005 was 7.5, with a significant difference at the 0.01 level). To test whether the perceived presence of colour or odour in recycled water had an impact on satisfaction with recycled water, a chi square analysis was undertaken. The results showed that a higher proportion of those respondents

,,________. I 16

,...........-=........~

19

Yellow , __ _ _ _ _ _.._....... 22

0

10

20

30

40

50

60

70

Numbor of respondonts

Figure 3. Details of recycled water 'colour' experienced by some Mawson Lakes residents 2007.

64 NOVEMBER 2009 water

25

Figure 2. Details of recycled water 'odour' experienced by some Mawson Lakes residents

6

Other .....,._ _ _ _ _ _~

20

2007.

Darker

Grey

15

Number of respondents

who perceived the recycled water has a 'swampy odour at times' indicated they were not satisfied with t he recycled water (Chi square = 9.36, 1df, sig = 0.05). Additionally, a higher proportion of those respondents who perceived the recycled water has a 'colour at times' indicated they were not satisfied with the recycled water (Chi square = 6.8, 1df, sig = 0.05). Only a very small number of respondents do not use recycled water for toilet flushing or garden watering (see Table 1). All respondents who indicated t hey did not use recycled water (or answered 'not applicable') for toilet flushing and on the garden were asked why t hey did not use it. Three respondents provided information about why they did not flush their toilet with recycled water, with two indicating they had had the recycled water d isconnected , and one did not know if it was connected. Eight respondents provided information about why they did not use recycled water on the garden, with two indicating they had had the recycled water disconnected, four indicated they did not have a garden, and one said there is no need to water their garden. Thus on ly two respondents refused to use recycled water, a very small proportion of the total population. The final question relating to recycled water use experience asked respondents if they had any comments they wanted to make about the recycled water and whether or not it had met their expectations. These responses were coded into categories and can be found in Figure 4. The results indicate that the majority of respondents thought the recycled water had met or exceeded their expectations (169, 73% of val id responses). A total of 62 (25%)

technical features


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odour management respondents said it did not meet their expectations and the major reason related to the recycled water being more expensive than anticipated. A limitation of the results reported in this paper is that they rely on respondents' honesty in stating their use of recycled water and their perceptions of its quality. It would be beneficial in future to study (with the use of smart meters) actual consumption of recycled water for various purposes. Further research with other communities using recycled water for non-potable purposes would be beneficial. It would additionally be beneficial to measure how satisfaction with and use of recycled water change in relation to water quality parameters, and to establish threshold levels of acceptance of aesthetic attributes of recycled water. In a paper regarding marketing aspects of recycled water, Dolnicar and Saunders (2006) provide a detailed review of research conducted into community acceptance of recycled water use. The authors posit that more insight is needed into actual use and behaviour regarding recycled water, rather than hypothetical evaluations by respondents.

Conclusion This paper has reported the Mawson Lakes' community's use and experience with recycled water for non-potable purposes. Most respondents use recycled water for the purposes intended through the dual water supply system. A small number of respondents indicated they have used recycled water beyond the uses specified by the guidelines (i.e. for drinking, showering, clothes washing and children 's wading pools) . This indicates that despite a detailed communication plan, a small number of people still use recycled water inappropriately at times. Overall 73% of respondents indicated that recycled water had met their expectations. For those who disagreed, the main reason stated was that the recycled water was too expensive. With regards to aesthetics attributes of recycled water, 49% of respondents perceived a colour, and 28% perceived an odour was present in the recycled water. Despite this satisfaction with recycled water was high, and the use of recycled water at Mawson Lakes did not appear to alter because of these perceptions. This indicates that some level of colour and odour is acceptable to the community for nonpotable uses of recycled water at Mawson Lakes.

66 NOVEMBER 2009 water

Ha-,ng no water restrictions Is great

04

I

Should be ex tended to other suburt>s / uses Good / great

I No comment

iE

I

Other

E

j18 ·1119 ·119 •23

I

I

I

Fine / OK

I

Its too expensise

I

I I I

I

8

Did not meet expectations

refereed paper

I

~8

I

· 130 I

32

-.

Met expectations

0

10

20

30

40

50

60

70

77

80

Number of respondents

Figure 4. How recycled water has / has not met respondent expectations, Mawson Lakes 2007.

Acknowledgments This research was funded by the Cooperative Research Centre for Water Quality and Treatment, the full results are published in CRCWQT Research Report Number 56 (2008). The author would like to acknowledge the following people and organisations for their support of this research: Mr Chris Maries from SA Water, Dr Stan Salagaras from Delfin Lend Lease Ltd, Professor Jennifer McKay from the University of South Australia, Ms Kirsty Willis from the Ehrenberg Bass Institute, and the survey participants.

The Author

Dolnicar, S., and Saunders, C. (2006). "Recycled water for consumer markets a marketing research review and agenda" Desalination, 187(1-3), 203-214. Fishbein, M., and Ajzen, I. (1 975). Belief, Attitude, Intention, and Behavio ur: An Introduction to Theory and Research,

Reading, Massachusetts: AddisonWesley. Hurlimann, A. (2008). Community Attitudes to Recycled Water Use and Urban Australian Case Study - Part 2, Adelaide:

Cooperative Research Centre for Water Quality and Treatment Hurlimann, A. , and McKay, J. (2004). "Attitudes to Reclaimed Water for Domestic Use: Part 2. Trust." Water, Journal of the Australian Water Association, 31 (5), 40-45.

Hurlimann, A., and McKay, J. (2007). "Urban Australians using recycled water for domestic non-potable use-An evaluation of the attributes price, saltiness, colour and odour using conjoint analysis " Journal of Environmental Management,

Dr Anna Hurlimann is a Senior Lecturer in Urban Planning at the University of Melbourne Australia. Email: anna.hurlimann@unimelb.edu.au; Phone: +61 3 8344 6976; Fax: +61 3 8344 5532.

References Albrechtsen, H. J. (2002). "Microbiological investigations of rainwater and graywater collected for toilet flushing." Water Science and Technology, 46(6-7), 311316. Bruvold, W. H., and Ongerth, H.J. (1974). "Public Use and Evaluation of Reclaimed Water." Journal of the American Water Works Association, 66(5), 294-297. Cooperative Research Centre for Water Quality and Treatment. (2003 ). "Health Stream News Items: Netherlands Bans Dual Supplies ". City: Cooperative Research Centre for Water Quality and Treatment.

83(1 ), 93-104 LaPiere, R. T. (1934). "Attitudes vs Actions." Social Forces, 13, 321-333. Marks, J., Cromar, N. , Fallowfield, H. , Oemcke, D., and Zadoroznyi, M. (2002). "Community Experience and Perceptions of Water Reuse" 3rd World Water Congress of the International Water Association. City: International Water Association: Melbourne. Schuman, H., and Johnson, M. P. (1976). "Attitudes and Behaviour." Annual Review of Sociology, 2, 161 -207. Source Water and Sanitation News. (2003). "Netherlands: government bans largescale dual water systems." Source Water and Sanitation News, 8 September (3536). Yamagata, H., Ogoshi, M., Suzuki, Y., Ozaki, M., and Asano, T. "On-Site Water Recycling Systems in Japan." Presented at World Water Congress, Melbourne.

technical features


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wastewater treatment

UPGRADES AT THE METROPOLITAN SYRACUSE WWTP, NEW YORK Part 2 Phosphorus Removal G Hook, T Carpenter, N Hatala, B Munn, K George, R Copithorn Abstract The County of Onondaga, New York, was required to upgrade the performance of their Syracuse Metropolitan Wastewater Treatment Plant to reduce pollution in Onondaga Lake. Two papers cover pilot plant trials, design of full-scale plant, construction, commissioning and lessons learnt for both ammonia oxidation and phosphorus removal (precipitation and filtration). Part 1 (Water, September 2009) deals with nitrification to oxidise ammonia (but with no deliberate denitrification) to achieve less than 1.2 mg/L NH 3 in summer, and 2.4 mg/L NH3 in winter with sewage temperatures as low as 8°C. This paper (Part 2) deals with achieving high efficiency precipitation and filtration to achieve a stringent limit of 0.02 mg/L P, since phosphorus had been determined as the critical factor in the lake ecology.

Introduction Onondaga Lake, located in Central New York State within the City of Syracuse limits, had the dubious distinction of being one of the most polluted lakes in the U.S. In 1998, Onondaga County signed an amended Consent Judgment {ACJ) with the State requiring $380 million worth of projects to increase the level of treatment at the 318,MUd (84 mgd) Metropolitan Syracuse Wastewater Treatment Plant (Metro Plant). With a total construction cost of approximately $130 million, these facilities were focused on achieving some of the strictest nutrient discharge limits in the country in accordance with the timetable presented in Table 1. The project had to confront several challenging design constraints including: • The existing site was tightly constrained with little available space • Poor soil cond itions requiring the installation of all structures and piping on pile supports

68 NOVEMBER 2009 water

Table 1. Mandated Discharge Limits. Parameter

Stage I mass load

Stage II (mg/I)

Stage Ill (mg/I)

1.2

Ammonia (NH 3) Jul 1-Sept 30

4000 kg/d

2.0

Oct 1-Jun 30

6000 kg/d

4.0

2.4

Existing limit

May 1, 2004

Dec. 1, 2012

Deadline Phosphorus (TP) Deadline

180 kg/d

0.12

0.02

Existing limit

April 1, 2006

Dec. 1, 2012

Table 2. Testing Conditions. DensaDeg

Actiflo

Ferric Chloride Dose (mg/L)

25

25

Polymer Dose (mg/L)

0.5

0.5

Hydraulic Loading Rate (m 3/m 2 per day)

528

1,760

• Peak wet-weather flows were very high (greater than 240 mgd or 908MUd ), i.e. > 3X, but sustained (3-5 days) • Influent wastewater temperatures in the winter were low • An aggressive timetable mandated by the consent judgment. This project was completed by Environmental Engineering Associates, a partnership of Stearns and Wheler/ GHD, Blasland, Buck & Lee and O'Brien & Gere.

Existing Wastewater Treatment Plant As more fully described in Part 1, the Metropolitan Syracuse Sewage Treatment Plant (Metro) is a 318 MUd conventional facility. Hydraulic capacity through secondary and tertiary treatment systems is provided for treatment of wastewater flows up to 450 MUd. Storm events during both the wet season and dry season can produce peak flows in excess of 900 MUd. Flow to secondary treatment facilities is

Pilot testing to full-scale operation.

limited to the maximum of 450 MUd. However, the duration of the peak causes adverse impacts on operations. Dry weather peaks are generally shortterm (3 to 5 hours) and do not adversely impact performance, as solids washed out of the aeration tanks are captured in the secondary clarifiers. However, during the wet season, storm events are often accompanied by snowmelt, which can cause peak flows to be sustained for 3 to 5 days. During these sustained peak flow events, solids carryover occurs degrading the quality of secondary effluent. CBOD 5 and TSS concentrations in the secondary effluent can reach 50 mg/L and 80 mg/L, respectively. Wastewater temperatures vary from a low of 8°C to a high of 23°C. Low temperatures are the result of snowmelt and can occur anytime from January through March and often occur in combination with sustained high flow conditions.

Phosphorus Removal The severe space constraints of the site eliminated consideration of conventional tech nologies to achieve the strict discharge limits. Consequently several more innovative technologies were

technical features


considered and pilot-scale studies were completed in order to develop appropriate design criteria and demonstrate reliable performance. The work was completed in two phases; Phase 1 addressed the Stage II limits (0.12 mg/L TP) while Phase 2 focused in the Stage Ill limits (0.02 mg/L TP).

Phase 1 Pilot Test Results The objective of Phase 1 was to demonstrate that selected high-rate flocculated settling (HRFS) technologies are able to meet or exceed the proposed Stage II TP limit of 0.12 mg/I, and to develop design and operating criteria to support regulatory approval of the process as an element of plans and specifications for construction. HRFS systems marketed by Kruger (ACTIFLO) and lnfilco Degremont (DensaDeg) were tested to achieve the Stage II 0.12 mg/I TP limit. The results demonstrated that both the DensaDeg and Actiflo technologies were capable of achieving TP effluent concentrations below the Stage II requirement of 0.12 mg/L. These results were achieved under the conditions listed in Table 2. Each of the t echnologies were also tested under high flow conditions, high coag ulant dose, and with two units operated in ser ies. On the basis of all testing, both the DensaDeg and Actiflo technologies were selected for final design.

Full Scale Project Since both the DensaDeg and Actiflo technologies differ significantly, the design req uirements are also significantly different. Thus, two different designs would be required for a conditional design/bid/build process. Instead, a process procurement step was undertaken as a means of competitively bidding each of these technologies. This was accomplished through completion of preliminary designs for each technology, bidding of equipment costs and vendor services, and comparison of capital (equipment and construction) and operating costs to identify the lowest evaluated bid cost. The Kruger Actiflo process had the lowest evaluat ed bid amount of $21.8 versus $24.1 million and was selected as the technology for final design. The ACTIFLO process is a high performance, compact clarification system using microsand enhanced flocculation and settling. A coagulant (ferric chloride) is added to the wastewater in a separate coag ulation tank. The coagulated wastewater then enters a second tank called the injection tank , where microsand (80 to 120 micron) and polymer are added. The microsand provides a large contact area and acts as a ballast therefore accelerating the settling of the floes. The destabilised suspended solids bind to the microsand particles by polymer bridges. In the third tank, the maturation t ank, the particles agglomerate and grow into high-density floes known as microsand ballasted floes, which settle quickly to the bottom of the settling tank. The efficiency of settling is further increased by the use of the lamella tubes. The solids/microsand mixture collected at the bottom of the tube settler is pumped to hydrocyclones where the sludge is separated from the microsand by the centrifugal force of the vortex action. The recovered clean microsand is then recycled to the injection tank whereas the separated solids are continuously discharged.

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Phase 2 Pilot Test Results The objective of Phase 2 was to evaluate additional technologies to determine the feasibility of achieving the proposed Stage Ill TP limit of 0.02 mg/I. The plan for Phase 2

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wastewater treatment of the advanced phosphorus demonstration program included sideby-side testing of different tertiary wastewater filtration technologies using effluent from one of the two HRFS pilot units (ACTIFLO and DensaDeg) tested during Phase 1. The ACTIFLO pilot was selected based on its larger capacity and ability to supply treated water in the amounts required for the Phase 2 testi ng. Given the lack of historical data on low-level phosphorus removal, the project team was interested in testing as many different types of technologies as possible which included the following:

Single Stage Pilots to Follow HRFS • DynaSand single media, deep bed, upflow, continuous backwash • Memcor membrane microfiltration, with membrane modules • HydroClear single media, shallow bed, downflow, intermittent backwash and air pulse • Tetra single media, deep bed, downflow, intermittent backwash . • ABW dual media, shallow bed, downflow, intermittent backwash.

2-Stage Stand-Alone Unit Tested Without HRFS • SuperSand 2-stage, single media, deep bed, upflow, continuous backwash.

Phase 2 Pilot Unit Descriptions

DynaSand Filter The DynaSand filter, marketed by Parkson Corporation, is characterised as a contin uous backwash, upflow, deepbed granular media filter. The fi lter is equipped with an airlift pump and sand washer for continuous cleaning of the sand filter media. Dirty sand is removed from the bottom of the filter by the airlift pump and pumped to a sand washer mechanism located at the top of the filter. The sand washer mechanism provides continuous cleaning of the sand media. Clean sand is redistributed on top of the filter bed and rejects (backwash) water, containing solids removed from the filter media, is collected for treatment.

Memcor The Memcor Continuous Microfiltration System (Memcor), marketed by U.S. Filter, is a submerged membrane

wastewater treatment process. The core component of a Memcor filter is the 0.2micron porous polypropylene fibre membrane, which forms the filtration barrier. The fibres are bundled together to form a sub-module and are bound in a molded nylon netting. A group of four sub-modules are connected to a manifold to form the basic fi lter module. The filter module sits in a rectangular cell.

Hydro Clear The HydroClear sand filt er system, marketed by US Filter's Zimpro Product Group, was specifically developed for the filtration of solids from wastewater treatment plant effluent. It is a gravity filter that incorporat es a shallow bed design and the ability to periodically "pulse" the bed during the filt er cycle , in order to increase the time between backwash cycles. The influent flow is distributed throughout the ce ll and onto sand by means of a backwash/ distribution trough and splash plate assemblies. The flow then filters through the media, which consists of a 0.25m layer of fi ne sand with an effective size of approximately 0.45 mm.

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Tetra The Tetra sand filter system , marketed by Severn Trent services, is a deep-bed, dow nflow intermittent backwash sand filter. The Tetra uses a large diameter media (5 mm) to allow large f ilter rates and long filter runs between backwashes. The 1 ,8 m deep media bed sits on top of a gravel underdrain system. The pilot unit tested consisted of dual 0.4 m diameter colu m ns. A separat e feed pump was connected to each column , allowing the columns to operate independently.

ABW The Automatic Backwash Filter (ABW), marketed by lnfilco Degremont (IOI), is a travelling bridge rapid sand filter. It consists of a number of cells arranged in a row, served by a common influent chamber. A backwash pumping system capable of cleaning one cell at a time travels along a bridge system spanning the entire length of the unit. The ABW tested was a dual media filter, using an anthracite layer and a sand layer. The 2.8 m 2 filter bed provided was partitioned into cells approximately 0.3m wide. The media in each cell consisted of 0.3 m of 0.60 millimetre diameter anthracite and 0.3 m of 0.40 mm diameter sand .

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The SuperSand pilot was the on ly standalone 2-st age pilot technology tested in Phase 2. The SuperSand did not use effluent from a HRFS pilot plant as its influent, and attempted to provide treatment of water from the blend tank to the 0.02 mg/I T P limit. The system, marketed by Waterl ink Separations, consist s of two deep-beds, continuously washed, upflow sand filters connected in series. The first sand filt er (first column) had a sand size of 1.2 mm, and the second sand filter (second column) had a sand size of 0.9 mm .

MST1

Results

MST2

The SuperSand and DynaSand were both close to achieving the 0.02 mg/L TP goal. These two vendors were asked if they had any ideas that could further optimise thei r units to be able to achieve the goal.

Supplement MST1 with specific assays for Bacteroidal es by polymerase chain reaction (PCR) (presence/absence result); and Bocteroides qPCR (quantitative PCR) for human and ruminant animal sources.

Parkson Corporation , the vendor for the DynaSand filter, suggest ed that better performance might result from reduci ng the sand size in the filter. Sand with a finer grain size was available at the site, and was switched from the existing 1.2 mm sand to the finer 0.9 mm size. Wat erlink, the vendor for the SuperSand filter, requested a change in testing that involved switching from a SuperSand/SuperSand combination to an ACTIFLO/SuperSand combination. The first stage of the SuperSand system was disco nnected. The second stage had a sand size of 0.9 mm. The required piping changes were made to allow operat ion of the ACTIFLO /SuperSand co mbination . An additional 10-day testing period was run with the ACTIFLO/DynaSand and ACTIFLO/ SuperSand combinations. Each pilot was run at a hydraulic rise rat e of 160 Umin/ m, and each unit received the same ferric ch loride dose.

Chemical Determination Testing Coagulant testing on each of the technolog ies piloted yielded the recommended dosages summarised in Table 3.

Optimal Performance Testing Period Duri ng the months of August and September 2000, proc ess parameters were varied and performance monitored for each of the pilot units. Once optimal performance was established, the

Identify sites of concern using standard assays for turbidity, pH, ammonia, f . coli and Enteroco cci to rank water quality results as low, medium or high risk.

MST3 Supplement your MST2 results with specific assays for Compylobocter and Solmonello spp. and PCR assays for the Human enteric viruses (Adenovirus and Norovirus Genogroup II).

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~ ANALYTICAL SERVICES


wastewater treatment chemical and hydraulic rates presented in Table 4 were applied to the units under steady state conditions.

Operational Issues Operational issues with the technologies experienced were relatively minor and were mostly attributable to the small scale of these pilots. A summary of these issues is presented in Table 5 . One major exception however was encountered with the ABW fi lter. The ABW filter appeared to perform well during initial testing but it was soon discovered that hyd rau lic throughput was being limited by the formation of a red-coloured layer in the filter. Repeated backwashing did not restore the fi lter. After replacement of the media was completed, the layer returned and again restricted hydraulic performance. Th erefore data for the ABW fi lt er is not inclu ded.

Conclusions fro m Pilot Testing Pilot testing for advanced phosphorus removal at the Metro Syracuse Wastewater Treatment Plant concl uded that: â&#x20AC;˘ Best performance (lowest levels of total phosphorus in effluent) was obtained with the membrane fi lter

Table 3. Coagulants and dosages used in tests: Technology

Coagulants tested

Coagulant of choice

DynaSand Memcor (ll

FeCl3, PAC, PASS, Alum

FeCl3

20 mg/I

ACH

ACH

2.4 mg/I

HydroClear

FeCl3, PAC, Alum FeCI3, PAC, Alum FeCl3, PAC, Alum

PAC

20 mg/I

FeCl3

10 mg/I

FeCl3

20 mg/I

FeCl3, PAC

FeCl3

30 mg/I, 1o mg/I l2l

Tetra ABW

SuperSand

Selected dose

(1) U.S. Filter would only authorise use of aluminium chlorhydrate. (2) First stage and second stage doses, respectively.

Table 4. Process variables and results. Technology

Process variables

Media size

Average tp concentrations (mg/I)

Chemical dose

Hydraulic rate

20 mg/I FeCl3 2.4 mg/I ACH

152

Umin/m 2

1.2 mm

0.135

0.017

70 Umin

0.2Âľ

0.1 1

0.014

HydroClear

20 mg/I PAC

100 Umin/m2

0.45 mm

0.124

0.03

Tetra

10 mg/I FeCl 3 20 mg/I FeCl3

200 Umin/m2

5 mm

0.135

0.073

0.6 mm/0.4 mml1J

(2)

(2)

1.2 mm/0.9 mm(3l

1.09(4)

0.024

DynaSand Memcor

ABW SuperSand

30/10 mg/I FeCl3 160/73 /min/m2 (3J

Influent

Effluent

(1) 0.6 mm anthracite; 0.4 mm sand (2) Operational problems due to clogging of the filter caused loss of performance. (3) First and second stage, respectively. (4) Blend tank TP concentration.

...

~

MELBOURNE Peter Everist 03 9863 3535 peverist@wigroup.com.au

SYDNEY ADELAIDE Hugh McGinley Owen Jayne 02 8904 7504 08 8348 1687 hmcginley@wigroup.com.au ojayne@wigroup.com.au

72 NOVEMBER 2009 water

BRISBANE Graeme Anderson 07 3866 7860 ganderson@wigroup.com.au

~&t

Water Infrastructure A Tyco Company GROUP International

technical features


wastewater treatment • Good performance (effluent total phosphorus less than the 0.02 mg/I target) was obtained with the continuously backwashed fi lter technology both in series with HRFS and as a two-stage system • Replacing the media with a smaller grain size resulted in improved performance • FeCl3 dosages above 20 mg/I resu lted in pass through into the effluent followed by fou ling of t he media • Approximat ely half of the tot al phosphorus in the effluent at 0.02 mg/I is soluble (passes a 0.45 µ filter).

Commissioning HRFS System (Phosphorus Removal) The ACTIFI LO system was placed into service in January 2005. Following an initial startup period, a 30- day performance was conducted from February 2005 to March 2005. The effluent TP concentrations during this period are illustrated in the Figure 1. The results of the performance testing showed that the performance

Table 5. Operational Issues Summary. Technology

DynaSand Memcor HydroClear

Issue

Resolution

Algae Growth in Clean Well

Cover

Membrane Fouling

Chemical Clean-In-Place

Algae Growth

Cover

Tetra

Iron Pass Through

Lower Dose

ABW

Chemical/Particulate Buildup

No Solution

No Significant Issues

N/A

Supersand

requi rements for all parameters were met with the exception of TP. The actual average effluent TP concentration of 0.122 mg/L was slightly higher than the performance requirement of 0.12 mg/L. Immediat ely after the completion of t he 30-day performance test , effluent TP concentrations st arted increasing. During the period of May to June 2005, effluent TP concentration increased to a maximum of 0.3 mg/ L. During this time period, the plant staff noticed a significant bui ld-up of solids on the settling tubes. Also, the settling tubes loosened and were floating within the settling tan k. During t his period, the ult raviolet d isinfection quartz tubes were becoming fou led by iron and were causing increases in coliform counts.

Ot her observations during the post startup period included wear and failure of t he microsand fill pipe and wearing of the sand recirculation pumps. The orig inal design of the fill pipe specified stainless steel welded pipe with long rad ius elbows. Within a very short t ime period, the microsand had worn the elbows and they had to be replaced. The sand recirculation pumps were also experiencing wear in two locations: 1) t he pump discharge increaser fitt ing; and 2) t he pump casing at the mechanical seal. The project team immediately began developing a trou bleshooting program to evaluate these operational problems and to develop recommendations for

)Iran tiinr lxihrwn fail111~=Jfl1Br L(o1wmtio11al time)

oITBF numIirr off111.1m-rs

water NOVEMBER 2009 73


wastewater treatment improvements. Kruger initiated a fullscale optimisation study and a pilot-scale study. As a result of investigations and proc ess troubleshooting, t he fo ll ow ing process modifications were implemented.

INnIAL30 DAYilSTPERIOD EFFLUENTPHOSPHORUS CONCENIRA'IlONS

1- I.S ~ - - - - - - - - ~ - - - - - ~ - - - - - - -- - - ~

a. Larger Lamella Settling Tubes. 85 mm lamella tubes were installed to minimise solids build-up. Also, additional cable restraints were installed to prevent shifting of the tube bundles w ithin the tanks . b. Coagulant Dosage/ Mixer Speed/ Submergence. The optimum chem ical dose was verified to be 25 mg/ L and 0.6 mg/ L of ferric chloride and polymer. How ever , the Cou nty operations staff can increase the ferric dose to 30 or 35 mg/ L, if improved performance is necessary. The optimum m ixer speed was determined to be 100 per cent. M ixer depth was determined to be optimal at the highest elevation. c. Iron Addition Point. As an alternative to improving flow distribution or individually measuring the influent f low and continuing chemical feed t o each t rain, the poi nt of iron addition point w as relocated upst ream prior to flow splitting. Iron addition now oc curs in t he influent channel and continues to be paced on total flow d. Cleaning of Tanks. The County adopted a new routine of cleaning the settling tanks to prevent bu ild-up of so lids. Tanks are cleaned by partially draining a tank, washing the settling tubes down and pumping out solids. Tanks are monitored daily and cleaned a minim um of once every two weeks or sooner if subject to a large flow or solids loading.

vvos

2/ VOS

4/1/0 5

Figure 1. Results of 30-day Performance Test.

The results of t hese process modific ations were immediate and are illustrated in Figure 2. TP effluent conc entrations q uickly decreased to less than 0 .12 mg/ L. During the remainder of the year, the average TP concentration was less than 0.12 mg/ L.

4. Provide capability for multiple chemical feed locations. 5. Provide good mixing at eac h location. 6. Full-scale results do not always match pilot test results; incorporate fu ll-sc ale optimising processes. 7. Phosphorus test methods d iffer;

Lessons Learned Some of the key lessons learned from this experience are summarised below:

1. Microsand storage, feed , and solids recirculat ion systems must be designed for maximum abrasion resistance.

2. Consider alternate materials o r alternate pump models for solids recirculat io n pumps.

3. Chemical feed and flow spl it is very important. Provide individual f low measurement and control to each train.

choose a method corresponding with the TP range anticipated.

8. Provide an additional t reatment train to serve as a standby to faci litate required cleaning schedule.

9. Eval uate settler t ube size further to determine optimum size. 10. Inf luent TP is very important for overall process performance; verify the actual concentration and monitor for variability.

Conclusions Since completion of t he BAFs (see Part 1 paper) and HRFS systems to meet the Stage II permit limits, the water quality in Onondaga Lake has improved dramatically. The need therefore, for f urther red uctions in effluent phosphorus may not exist and the need for construction of additional processes is currently under considerat ion.

EFFLUENT PHOSPHORUS CONCENIB.ATIONS METRO S y racus e W WTP , O non daga Coun ty , NY --lnnoenl

3/ VO S

Ernucnl - -Ernuent Limi1 â&#x20AC;˘ 0. 12 ma lL(1nm,1al1vcr1&c)

The Authors

I I VV2005

4 / 1/2005

1

~~b Ll 1/V2 005

,.

10 11/2005

VV2006

Figure 2. Results of Process Modifications. 74 NOVEMBER 2009 water

4 /1/ 2006

7/1/2006

I0/1/2006

1/1/2007

Gerald Hook, Tim Carpenter, Nick Hatala, Bruce Munn and Kelvin George, are all Professional Engineers (PE) with Stearns & W heler/ GHD. Gerald (Jerry) Hook was t he engineer in charge of t he project. Rhodes (Rip) Copithorn, P.E. is the Business Group Manager Wastewater for Stearns & Wheler/ GHD, Email: rip.copithorn@ghd .com.

technical features


l

I

desalination

r efereed paper

CONCENTRATETREATMENT USING WETLANDS J Kepke, J Bays, J Lozier Abstract

..

ROC from A W T P Pilot

Recent pilot studies of wetland treatment of RO concentrate (AOC) in Brisbane, Australia, and Oxnard, California, point to the potential benefits of using wetlands for concentrate management.

I I

I

I

I

I

bark

Biobed 2 Canadian peat

"I'

"I'

.,.

I

I

I

Surface Flow Cell2

Surface Flow Cell 3

Biobed 1 Pine

I

Introduction Operators of RO plants in arid climates, particularly those inland without access to an oceanic discharge, are challenged to develop new methods of concentrate disposal. A review was recently undertaken of a range of beneficial and non-traditional uses of membrane concentrate alternatives to conventional disposal methods (Jordahl et al., 2006), including wetlands. Wetland vegetation communities along coastlines and in estuaries, and in inland waters naturally high in salts are well adapted to saline environments. Further, treatment wetlands have a proven capacity for removal of pollutants such as nutrients and metals (Kadlec and Wallace, 2008). Toxic contaminant removal, beneficial reuse, and creation of ecosystem function in riparian and aquatic ecosystems are just some of the benefits provided by treatment wetlands. In addition, wetlands consume a substantial amount of water via evapotranspiration during the warm productive months, making them useful for seasonal concentrate volume reduction in some climates. Recent pilot studies of wetland treatment of ROG in Brisbane, Australia and Oxnard, California point to the potential benefits of using wetlands for concentrate management. Table 1 sum marises the characteristics of the ROG tested.

Luggage Point, Brisbane, Australia As part of the Western Corridor Recycled Water Project, an Advanced Water Treatment Plant (AWTP) is now operated at Luggage Point near the mouth of the Brisbane River, with a final Reverse Osmosis stage. In 2008, a Pilot Scale AWTP was constructed at the Luggage Point site with an approximate product water capacity of up to 0.5 megalitres per day (MUD). A Pilot Treatment Wetland was constructed to evaluate constructed wetlands as an option to treat ROG prior to release into the Brisbane River. The project schedule was extremely compressed, with only 13 weeks available for testing.

Methods The Pilot Treatment Wetland consisted of surface-flow (SF) cells and vertical upflow ("biobed") cells comprised of an

Surface Flow Cell 1

~

.

~

organic substrate. Pipework was installed to allow the biobeds and surface flow cells to run in parallel or to be linked in series. The biobeds were designed to remove metals and other ROG contaminants anaerobically. All biobed and SF cells were constructed using cement blockwork on a concrete pad to minimise the footprint within the pilot AWTP site, as well as to allow construction with wet soil conditions. The inner surface of the blockwork was lined to reduce seepage potential. Wetland effluent was returned to the wet well pumping station at the Pilot AWTP to transfer to the inlet of the local WWTP. A total ROG flow of 0.194 Usec was provided by the Pilot AWTP. The electrical conductivity of the ROG ranged from 10,200 to 22,400 µmho/cm, and averaged 15,242 µmho/cm. Three 2 x 2 x 1.1 m vertical upflow biobed cells were constructed, each containing a 0.8-m deep layer of organic material, and with 0.3 m of freeboard . A perforated pipe manifold distributed the influent flow across the bottom of the biobeds. Each of the three biobeds contained a different organic material:Canadian peat, coconut shell mulch, and pine bark. Three identical 12 x 4 m (L x W) SF cells were installed with an operating water depth of 30 cm. Water level control was provided by two pivot pipes at the outlet of each cell. A wall

Table 1. Water Quality of ROC streams tested in pilot wetlands. Parameter Nitrate-N (mg/L) Nitrite-N (mg/L) Ammonia (mg/L)

Australia and California.

Figure 1. Layout of Luggage Point treatment wetland pilot system in parallel flow mode.

Luggage Point Recycled Water ROC

Oxnard Groundwater ROC

Oxnard Recycled Water ROC

11.8 0.73

54.4

15.8 14.8 72.4 98 4.2 11 ,850

TOG (mg/L)

Developments in

Biobed 3: Coconut shell mulch

80D5 (mg/L) TDS (mg/L)

102 10 10,800

2,350

water NOVEMBER 2009

75


desalination

~ refereed paper

with gaps was constructed at the midpoint of the cells to redistribute flow and minimise preferential flow paths/short circuiting. A deep zone was provided at the outlet to collect discharge water from the entire width of the wetland and thereby minimise preferential flow paths. A 150 mm layer of washed river sand was placed in the bottom of the SF cells and raked flat. A 150 mm layer of soil material containing common reed rhizomes was obtained from a nearby donor wetland site and was placed on top of the sand. Recognising that the short duration of the project would not allow development of the critical litter layer that largely drives treatment of many constituents, a 15 cm layer of coarsely chopped (-15 cm pieces) sugar cane mulch was added to the cells after planting to simulate an established litter layer. The pilot wetland system was operated as individual cells in parallel, i.e. all individual cel ls received the same ROC influent, as shown in Figure 1. The system design will allow operation of the cells in series in a proposed future phase. In a parallel experiment to determine the effects of the ROC water on the plant growth and health, six - 10-L buckets were planted with common reed in wetland sediment from the donor site. Two buckets were then filled with fresh water (no ROC) as a control, two with 50% fresh water and 50% ROC water, and t wo were filled with 100% ROC. Based on the volumes of the two cell types, th e biobeds were operated with a hydraulic loading rate of approximately 30 cm/d and a hydraulic retention time of approximately 2.67 days based on porosity of the peat materials. The SF cells had a hydraulic loading rate of 7.7 cm/d with a hydraulic retention time of 3.9 days assuming ideal mixing and high porosity of the cane mulch. The 7.7 cm/d hydraulic loading rate is roughly equivalent to the loading rate that would be requi red for a fullscale 20-ha SF system.

8 -+-Influent

~

5

CII

.ยง.

4

~

3

:i::

z

2

0

Figure 2. Ammonia Results for BioBeds. 8

-+-Influent

T

-tt- WeUand4

a :J'

-+- Wetland5

6

'ii,

-+- WeUand6

.ยง. ~

2

3

2

0

Figure 3. Ammonia Results for Wetlands. 41

r-------:=====------------,

<ll - -

-----

31 - 1 - - - -~ 30 -

-

---

Results

"' 21 - 1 - - - -!.

Data from April 22 -June11 2008 are considered representative of post-startup cond itions.

"!'

211

~

11 1+---,i:\-- +J.----7-t--+--l-l-l- -~ +-1--1---+I-I 10

~--~

l+-+4,.L-i-ll~l.--l-~L_~",----!m.li,...,..;~ ~ '<--1-.H

Nutrient removal Ammonia removal results are presented for the biobeds (Fig. 2) and the wetlands (Fi g. 3). Significant ammonia removal was not expected, nor observed from the biobeds given the anaerobic substrate. Short term removals of ammonia are attributable to sorption. Decreasing levels of treatment with time suggest that this capacity was exceeded with in one month, especially for peat-based Biobed 2.

Figure 4. Nitrate Results for BioBeds.

so ,----::~===::::::-------------, "5 l - - --

--1

-+-Influent

40 l-----<i---1

Ammonia removal results for the SF cells were variable from early April through much of May, however, from May 21 through the end of the study almost complet e nitrification in the surface flow treatment wetland cells was observed despite large fluctuations in influent concentrations. Nitrate removal results for the biobeds are shown in Figure 4, and for the SF in Figure 5. Although there was considerable variability in influent concentrations, there was generally a significant reduction in nitrate concentration for each of the biobeds. There was little apparent difference among the different types of media, however, there appeared to be increasing overall variability in removals toward the end of the study in conjunction w ith increasing variability of influent concentrations. Decreases in labile organic matter t o support denitrification may be a factor. Longer term data collection is required to confirm the level of variability between media types.

76 NOVEMBER 2009 water

g~ c5z z

35 30 ,___

_,_,....._--<

M ~===~tt~C=====~==Z=t=~~~==t:t~c=====j

20 TT

15 4+---i"\l---l-~ - ---,>.ii-./-----\-Hl---\-1--\-- -------1f-\-l 10 ++-+4--Al/--l::Jl-,L-jf1tc-J----'------ยฅ---l...c>....--/-----\ 5

Figure 5. Nitrate Results for Wetlands.

The SF cells also generally provided good reductions in nitrate throughout the study. In spite of the variability in the inflow concentration and the spike in nitrate following the addition of mulch (April 8). Effluent NO 3 -N concentration

technical features


WINNER Gloh.11 W.H~r Aw.,nls ' 2009 .

--

SOLUTIONS DON'T ALWAYS RAIN DOWN FROM THE SKY. WE WORK ON EVERY CONTINENT SO THAT THE SCARCITY OF WATER CAN CEASE TO BE A PROBLEM. We are a worldwide point of reference in research on water, using our techniques to successfully export to some of the most developed countries. Because we are always considering the future. And we want to keep dependence on water as a resource from conditioning our children's lives.

(faccio'1.~


des a Ii nation ranged from less than 1 mg/L (prior to the addition of the sugarcane mulch) to generally 5 mg/L or less. The average concentration of NOrN in the effluent of the wetlands cells is approximately 4. 5 mg/L. Total nitrogen results for the biobeds are shown in Figure 6. These results show that significant reductions in TN were observed for most sampling dates, despite large fluct uations in influent concentrations. Influent concentrations ranged from less than 10 mg/L to more than 45 mg/L, and effluent concentrations ranged from less than 5 mg/L to more than 15 mg/L. There was little performance difference among the materials used in the beds, suggesting that if TN is the criteria, the least cost of these media would be desirable. Longer term data may yield greater differences in performance or indications of system life-span. Total nitrogen removal in the SF was consistent, as shown in Figure 7, with effluent concentrations <10 mg/ L. There was little difference between replicate cells. Average performance improved slightly through early May and then stabilised.

Metal removal Metals were sampled seven times between Apri l 2 and June 10. Significant removals (50 per cent or more) were noted in the biobeds for B, Cu, Cr, and Mo. In the wetland cells, significant removals were noted for Cu, Pb, Mo, and Zn. Net increases were observed in the biobeds for Al, Pb, Ni, and Zn. Net increases in concentration in the wetlands were observed for As, Al, Cd, and Mg. Net increases in metals are attributed to leachin g of metals from the peat materials in the biobeds and from soil media and/or cane mulch added to the SF cells. These net increases would decrease over time, but the duration is unknown.

Bucket test As noted earlier, common reed rhizomes were planted in small buckets to determine plant response to varying mixes of freshwater and ROC. This was in response to the observation that the wetland vegetation once transferred to the treatment wetland cells showed signs of stress initially, fol lowed by emergence of new growth over time. In the bucket test, all three treatments (freshwater, 50% ROC/50% freshwater, and 100% ROC) initially showed some signs of plant stress mimicking what was observed in the wetland cells. Within two weeks, however, new shoots were observed in all three treatments, indicating that neither the ROC or the mulch were likely the primary cause of plant stress and the limited shooting seen in the pilot system, but rather the rapid increase to the full normal operating water level shortly after transplanting. A greater number of new shoots, however, were observed in the freshwater control and 50/50 buckets as compared to the 100% ROC.

~ refereed paper

IO

..•••• i ..••

-+- Influ ent •

BioBed1

-w- BioBed2 ......- BloBed3

z

J ,.

20

~

10

Figure 6. Total Nitrogen Results for BioBeds.

i

...IO .,.--:::========,--------------, ••

z

!

,. i r - - - \ - - - - - , , " - - - - - - - - --

----'rt'---1

10

Figure 7. Total Nitrogen Results for Wetlands. study provided an initial indication of performance and data would need t o be collected over a longer period to better understand steady stat e system performance. However, these results are promising and consideration of wetlands and/ or biobeds for ROC treatment is justified.

Oxnard, California, USA

Summary

The City of Oxnard in Ventura County California investigated the feasibility of wetland reuse of ROC as part of the City's Groundwater Recovery Enhancement and Treatment (GREAT) Program. This program is developing alternative water supplies by combining wast ewater recycling and reuse; groundwater injection, storage, and recovery; and groundwater desalination for water supply solutions to the Oxnard region (Bays et al., 2008). The GREAT Program includes construction of two treatment plants: the "Desalter" to remove salts and minerals from brackish groundwater for potable use, and the "Advanced Water Purification Facility", or AWP F, to remove nutrients, salts, minerals, and ot her contaminants from secondary effluent from the City's WWTP for reuse, incl uding agricultural irrigation, groundwater recharge, and municipal and industrial uses.

Significant reductions were observed for NO3 -N, TN and some metals in both biobeds and SF cells, and t hese were the major constituents of concern. Further testing would determine if either the biobed or the wetland alone could provide the required water improvement potential. If equal in removal efficiency, then the most cost-effective (capital , O&M) could be constructed. The study confirmed that common reed wi ll grow in 100% ROC with a conductivity of more than 15,000 µmho/cm, and send new shoots, though at a reduced rate com pared to less saline water. The biobeds provided some removal of some metals, especially B, Cu, Cr, and Mo, but net increases in Al, Pb, Ni, and Zn were found. This short-term

ROC to be generated by these treatment plants will be disposed of through the Oxnard WWTP deep ocean outfall. A conceptual alternative to ocean disposal could be the use of membrane concentrate as a water source to create or restore brackish or salt marsh wetlands, if fou nd to be compatible with the local environment. If feasible, membrane concentrate could be used for beneficial creation of new c oastal marshes or for enhancing flow to existing marshes. To address the feasibility of this concept, the City decided early in the Program that a pilot study would be necessary to provide preliminary design criteria and a tangible proof of concept. Mesocosm-scale pilot studies were conducted on ROC derived from groundwater

78 NOVEMBER 2009 water

technical features


desalination

, refereed paper

8). Pilot testing conducted from 2003 through May 2006 consisted of supplying the tanks with 95-284 Ud from a storage t ank filled weekly with concentrate trucked from the nearby Brackish Water Reclamation Demonstration Facility operated by the Port Hueneme Water Authority.

Figure 8. Initial configuration of Oxnard Pilot Wetlands Membrane Concentrate Study. from 2003-2006 and on ROC derived from reclaimed water from 2008-2009.

Methods The Oxnard Pilot Wetlands Project addressed the sustainability of wetland communities hydrat ed by ROC, the removal of conservative (i.e. inorganic ions, trace metals) and nonconservative (i.e. nutrients) constituents, and the effect of the wetlands on ROC toxicity.

Of the wetland types selected, the marsh and SAV cells represent the major brackish water plant communities known to exist withi n the existing Ormond Beach wetlands. The SSF and VF cells t est two wetland technologies that offer potential for reduction of water quality parameters of greatest concern to plant life and wetland wildlife, such as boron and selenium, while significantly minimising potential contact with wildlife. These types of wetlands represent natural "end-of-pipe" treatment systems that could further buffer or polish water that is discharged from the membrane treatment facil ity before its application to a wetland restoration site. In the second phase of groundwater ROC testing , six of the tanks were re-pl umbed as two series, or trai ns, of three cells each. Train 1 consisted of VF, SSF, and SAV cell s to provide the least potential exposure of concentrate to wildlife. Train 2 consisted of VF, SFH M, and SFLM cells to approximate the varied plant communities of a natural salt marsh. The VF cells were placed first to maximise anaerobic treatment. Testing was cond ucted on the two treatment trains over a 6-month period from September 2004 through March 2005. Hydraulic loading data for the different periods are summarised in Table 3.

Three phases of pilot testing of groundwater ROC were conducted: 1) Construct ion, operation, and testing of pilot wetland mesocosms from June 2003 - May 2004 to demonstrate the safety and potential beneficial use of ROC for wetlands rest oration (CH2M HILL 2003, 2004); 2) Testing on re-configured pi lot wetland mesocosms from September 2004 - March 2005 to assess the treatment effect iveness of an optimised series of pi lot wetlands mesocosms (CH2M HILL, 2005). 3) Final sampling of the mesocosms in July 2006 to quantify the distribution and accumulation of salts (CH2M HI LL, 2007). A single phase of pilot testing of reclaimed water ROC was conducted from August 2008 - June 2009 using a portable subsurface flow constructed wet land developed by Mobile Environmental Systems (Irvine CA).

Groundwater ROC Testing 2003-2006 The Pilot Wetlands research platform for testing groundwaterderived ROC consisted of twelve one-cubic meter wetland tank mesocosms constructed from agricultural fruit storage bins comprising two replicat es of six wetland types (Table 2; Figure

Table 2. Oxnard Mesocosm Characteristics. Type

Surface flow high marsh (SFHM) Surface flow low marsh (SFHM) Horizontal subsurface flow (HSSF) Peat-based vertical upflow (VUF) Submerged aquatic vegetation (SAV) Saltgrass evaporation (SE)

& Depth (cm)

Water Depth (cm)

30 soil 30 soil 60 gravel

10 45 -1 0

20 cm peat on 45 cm gravel

saturated

30 soil 45 soil

30 saturated

Media Type

water NOVEMBER 2009

79


~ refereed paper

desalination Table 3. Mesocosm Flow Summary. HLR in (cm/d)

HLR out (cm/d)

HRT (d)

1.19 0.79

0.04 0.19 0 0.83 0.55

88 30 62 19 32

8.8 8.4 12.6

2.4

Oct - Nov 2003

SAV

SFHM 1.58 SFLM 1.35 SSF VF 1.3 Treatment Train 1: Jan - Feb 2005 VF 16.3 SSF 8.8 SAV 8.4 Treatment Train 2: Jan - Feb 2005 VF SFHM SFLM

18.1 10.8 10.2

10.8 10.3 8.8

1.9 6.3

Figure 9. Portable Subsurface Flow Constructed Wetland (Mobile Environmental Solutions, MES).

2.1

Results

2.6 6.5

Groundwater ROC Testing 2003-2006

Reclaimed Water ROC Testing 2008-2009 The portable MES wetland was set up at the Oxnard WWTP (Figure 9). Installation was completed in August 2008. While the fi nal components of the MF/ RO pilot system were being install ed, the MES wetland plant and bact erial co mmunities were gradually acclimated to the TDS levels in the MF/RO concentrate. The MES wetland had a solar panel array that powered a small pump. The wetland was initially fi lled with secondary effluent which was recycled through the wetland for the first week. Over the next three weeks sea salt was added to the wetland to attain a TDS of 5 g/ L and finally 11 g/L. During this time the water continuously recycled through the wetland at a rate of 1.9 Umin. While the wetland was in the acclimation mode, the rest of the test site was assembled including the influent and effluent lines to and from the wetland. All components of the study were operational by the end of September, 2008. Initially, the MES wetland was loaded at t he relatively high rate of 1 Umin, yielding a hydraulic loading rate of 12.9 cm/ d and a theoretical residence time of 2.5 d. From late September 2008 to late January 2009 there were a number of occasions where the MF/ RO system shut down. By late January 2009 most of the operational issues were resolved and the inflow to the wetlands was halved to 0.5 U min. The HLR became 6.45 cm/d with a HRT of 5 d. During this time there was no aeration of MF/RO concentrate and there was no addition of sodium bisulfite to inactivate the free and combined ch lorine.

Table 4. Comparison of Concentration and Mass Reduction for Selected Parameters. Nutrient

Metal

Salt

Units mg/L mg/L

N03 54.4 9.5

%

83%

Se 0.022 0.007 67%

Fe 0.30 0.05 82%

TDS 2350 2695 -15%

Mass loading

g/m2/yr

246

Mass out MR MR %

g/m2/yr g/m2/yr

9 237

0.10 0.01 0.09

1.36 0.05 1.31

10616 2548 8068

%

96%

93%

96%

76%

Parameter Influent Effluent CR %

80 NOVEMBER 2009 water

Plant species survival Within 11 months of planting, all mesocosms had achieved more than 100% cover by native brackish marsh species, all of the plant species installed in t he mesocosms had survived, and height measurements indicated a normal range of growth ranging from 30 cm for low ground cover species to over 3 m for bulrush (CH2M HILL 2004). This trend in dominance by native brackish marsh species continued through the final phase of testing with normal to above-average biomass development compared to other marshes.

Nutrient and metal removal Throughout th e study, significant concentration reductions were measured in NO3-N, TP, and most metals in all wetland types. Nitrate was reduced from 54 mg/ L to < 10 mg/L by the low marsh and vertical flow wetlands, presumably through their greater extent of anaerobic habitat. The two treatment trains reduced NOr N at higher hydraulic loading rates to <4 mg/L. Concentrations of TP decreased by 50% from 0.2 to 0.1 mg/L through the wetlands in the original testing and >90% from >0.9 mg/ L to 0.03-0.09 mg/ L in the two treatment trains (CH2M HILL 2005). Chemical oxygen demand (COD) generally increased through the system as the water came in contact w ith biomass and soil. Eight metals (Ag, Be, Cd, Pb, Hg, Mn, Ni, and Zn) varied within quantitation limits and showed no c onsistent trend. Four metals (Al, Cr, Th, V) exhibited slight concentration increases, presumably related to soil leaching. The remaining six metals (As, Ba, Cu, Fe, Se, Sb) showed variabl e decreases in one or both testing phase. Se was red uced from 22 µg / L to 7.3 µg / L by the VF wetland and variably by the other systems and from 12 µg/ L to 6-9 µg / L in the two treatment trains, and fro m 19 µg/L to 3-6 µg / L in the remaining bins.

Inorganic parameter removal With the exception of the SAV syst em, inorganic parameters (hardness, Ca, Mg, K, Na, B, SO4, CL, F, alkalinity, specific conductance and TDS) generally increased in concentration throug h the Pilot wetlands. For example, average TDS for nonSAV wetlands increased 15% from 4,560 mg/L to 5,222 mg/L and 17% for Train 2 (without SAV) from 4,200 mg/ L to 4,900 mg/L. In contrast, TDS in the SAV mesocosms decreased by 27%. The difference in performance between the SAV tanks and treatment series, and the other wetlands, is attributable to the

technical features


~ refere e d pap e r

desalination

open aspect and the dense growth of pondweed in the tank. As the submerged plants grow, unshaded by other plants, they consume free CO2 for photosynthesis and shift the hydrogen ion equilibrium to alkaline conditions. Th is increases the pH, creating conditions appropriate for precipitation of calcium carbonate, which can also co-precipitate calcium phosphate and calcium sulfate. Even with the slight increase, all of the parameters measured tended to show significant mass removal through the Pilot wetlands in response to water loss through plant transpiration. Table 4 compares the average concentration and mass reductions for nitrate, seleni um, iron and TDS for the vertical upflow cells in the first testing phase. Concentrations of N0 3N, Se and Fe decreased by 67-83% and mass decreased by 93-96%. In contrast, TDS increased by 15% from 2350 to 2695 mg/ L, presumably through evaporative concentration of solids, but the overall mass of TDS decreased by 76% because of the significant evapotranspiration of flow . Similar red uctions in mass were calculated for all other parameters.

Toxicity reduction Water column conc entrations of parameters with known ecotoxicological properties were reviewed and compared to available benchmarks. Of the metals analysed, only copper and selenium were measured at levels in the concentrate that exceeded toxicity thresholds. Inflow concentrations of Cu (26.7 µg/ L) and Se (22.3 µg/ L) were great er than their respective guidance thresholds of 12 µg/ L and 5 µg/ L (NOAA, 1999). Copper concentrations were reduced t o detection levels in all types while the VF and SSF wetlands consistently reduced Se to 5-7 µg/ L. Whole effluent toxicity studies were performed using mysid shrimp (Mysidopsis bahia) and topsmelt (Atherinops affinis) on t he concentrate and on the effl uent of the individual

41~. Mr=rs~~~-

mesocosms and the treatment trains. Chronic 7-day whole effluent testing in both phases of testi ng showed that the concentrate and the wetland effluents were not toxic to mysid shrimp. Using an IC50, an estimate of the effluent concentration that causes 50 per cent red uction in growth or reproduction, the concentrate IC50 ranged from 82-97% , indicating that the concentrate would have little or no chronic effect on mysid survival. Mysid shrimp IC50 growth and survival values from the wetland discharges ranged from >100% for SAV and SSF, indicating that the concentration wou ld have to be greater than tested t o have a significant effect on mysid survival, to 80-97% for SFH M, and 81.5-86% for SFLM. Topsmelt chron ic IC50 values were all >100%, meaning that the co ncentrate would have to be a higher strength than that tested to reduce growth and survival by 50% . Results from the treatment trains showed mysid sh rimp survival IC50 values that showed the effluent from the treatment trains was substantially less toxic than the inflow concentrate. All wetland effluent samples had IC50 values at 100 %, except for one sample of 98% for Trai n 2. Mysid shrimp IC50 values were all > 100% and showed no chronic effect for the concentrate and none for the effluents from both treatment train series. All of the topsmelt IC50 values were >100%. As with the acute tests, t opsmelt growth and survivorship was not adversely affected by the concentrate.

Reclaimed Water ROC Testing 2008-2009 Plant species survival Plant survival and growth was assessed during an initial stud y and at the concl usion of the experiment. As a first step toward meeting the study objectives, it was considered prudent to determine if bulrush co uld tolerate the high levels of TDS and ammonium in the RO concentrate. At no point in time

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water NOVEMBER 2009 81


desalination

[

1

Table 5. Performance of the Pilot Wetland System for Selected Parameters. RO Concentrate; or Wetland Influent (median)

Wetland Effluent (median)

Per cent Change in median

Nitrate-N (mg/L)

15.8

4.6

71 %

Nitrite-N (mg/L)

14.8

5.2

69%

TDC (mg/L)

72.4

58.2

20%

Ammonia (mg/L}

98

126

-29%

80D 5 (mg/L)

4.2

6.4

-51 %

TDS (mg/L)

11,850

14,900

-26%

Parameter

,

A total of six samples collected weekly were analysed.

refereed pape r

Table 6. Mass Reduction of the Pilot Wetland System for Selected Parameters Parameter

Value (g/d)

% Change

Total Dissolved Solids ROC

85,320

WE

79,668

7%

Ammonia-N ROC

702

WE

674

4%

Nitrate-N ROC

113

WE

25

78%

Orthophosphate as P throughout the experiment were indications of stress evident, including tip browning, shoot necrosis, s hoot pi gment loss , or other indications of plant mo rtality or injury . The bulrush t hrived and grew t hroughout all cond itions.

ROC

68

WE

71

ROC

521

WE

311

Water quality

Total Selenium

Data were co ll ected from January 20 to March 5 2009. Table 5 summarises the analytical results.

ROC

216

WE

123

Median concentrations of TDS increased by 26 % t hrough evapoconcentration caused by p lant upt ake and t ranspiration. Average f low through the wetland decreased from 7.3 m 3/ d to 5 .6 m 3/d over t he estimated 5-day HRT. A proportional increase in ammonia reflects the anaerob ic root zone environment with limit ed nitrification . For these reasons, t hough, nitrate and nitrite decreased by approximately 70% through denitrification. BOD concentrations increased slightly, possibly attributable to the transformation of carbonaceous compounds from more labile forms. Mass balance analysis of the pilot wetland showed a consistent reduction in total mass of salts, nutrients, an d metals t hrough t he processes affecting concentrations of key parameters combined wit h the net red uction of 23 % in f low t hrough the wetland by plant evapotranspirat ion (Table 6).

Conclusion Treatment wet lands have been tested for decades for treat ment of conventional wastewater pollutants, but have o nly rec ent ly been t est ed on an experimental scale for ROC t reatment. Results of pilot studies reviewed in t his paper show t hat treatment wetlands red uce the concentrations of a number of constituents in ROC suc h as nut rients, metals and some inorganic ions. In terms of salinity, under some conditions wetlands may reduce mass load ings but not concentrat ion (i.e. TDS). The potential for wetlands treatment of ROC should also be viewed in a b road context of pot ential environmental benefits, such as t he potential for wildlife habitat, volume red uction, and the restoration and/or creation of salt marshes.

The Authors

-4%

Total Organic Carbon 40%

43%

WE =wetland effluent.

Tec hno logy, respect ively, with CH2M HILL based in t he USA. Email: Jacquelin e.Kepke@CH2M .com.

References Bays, J., N. Wall, and K. Ortega. 2004. First-year Results of the Oxnard Membrane Concentrate Pilot Wetlands. Poster presented at 2004 American Membrane Technology Association, San Antonio, TX. Bays, J. , P. Frank, and K. Ortega. 2005. "Preliminary Results of the Oxnard Membrane Concentrate Pilot Wetlands Study" . Proc. Water Quality Technology Conference, American Water Works Association. Denver, CO. Bays, J., P. Frank, and K. Ortega. 2008. "Oxnard's Membrane Concentrate Pilot Wetlands Project". WateReuse Association 12th Annual Water Reuse & Desalination Research Conference. The Westin Tabor Center Denver, Colorado. CH2M HILL. 2009. City of Oxnard Advanced Water Purification Facility (AWPF) Pilot Wetlands Study Report. Report for the City of Oxnard, June 2009. Chakraborti, R. , Lozier, J., Witwer, M., Bays, J. Erdal. U., Vorissis, M., and Ortega, K. 2009. "Pilot Study on the Performance of Reverse Osmosis, Microfiltration and Wetlands Concentrate Treatment of Wastewater with High Fouling Potential. " WEFTEC, Orlando, Florida. Jordahl et al. 2006. Beneficial and Non-traditional Use of Membrane Concentrate. WateReuse Foundation Project 02-006b-01 . Alexandria, VA: 2006. Kadlec, R.H. and R.L. Knight. 1996. Treatment Wetlands. Boca Raton, FL: CRC Press/ Lewis Publishers. Kadlec, R. H. and S. Wallace. 2008. Treatment Wetlands. 2nd Ed. CRC Press. Boca Raton, FL. 1016 pp.

Jackie Kepke, Jim Bays, Jim Lozier are Global Technology Leader for Water Portfolio Management, Princi pal Scientist for Nat ural Treat ment Systems, and Fellow for Membrane

82 NOVEMBER 2009 water

Knight , R. L. , W. E. Walton, G. F. O'Meara, W. K. Reisen, and R. Wass. 2003. " Strategies for effective mosquito control in constructed treatment wetlands." 21 :4-5.

technical features


~ refereed p a per

desalination

SALINE EFFLUENT DISCHARGES: DYNAMICAL BEHAVIOUR STUDIES CL Marti Abstract The Perth Seawater Desalination Plant (PSDP) with a capacity of 125 MUd is the first in a procession of large projects in Australia. The Centre for Water Research (CWR) at The University of Western Australia undertook a thorough study in 2006-7 to determine the dynamical behaviour of the saline effluent released by the PSDP in Cockburn Sound. As a part of the study, two detailed field experiments were conducted with dye release tests in December 2006 and Apri l 2007 to provide information on the dilution characteristics of the saline plume under calm conditions and further data to validate a 3D numerical model. The results of these two field experiments are presented and discussed.

Introduction

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374

376

378

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384

386

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Figure 1. Cockburn Sound bathymetry (colour is depth in metres), showing the locations of the PSDP outfall and the LDS station. Note the shipping channels dredged in the shallow eastern bank, running initially East-West (Stirling Channel), and then North and North-East (Calista Channel). The exit of Stirling Channel is considered the point where the bathymetry drops rapidly to greater than 15 metres at the western end of Stirling Channel.

The Perth Seawater Desalination Plant (PSDP), locat ed on the eastern shore of Cockburn Sound, a coastal embayment 40 km south of Perth, Western Australia (Figure 1) started supplying water in November 2006. The plant was designed to produce an average of 125 MUd of potable water per day via reverse osmosis providing on average 17% of Perth's water needs. The desalination process is approximately 42% efficient , thus the hypersaline discharge retu rned to the Sound is estimated to have a salinity of approximately 65 psu (practical salinity units), with the salinity of the ambient receiving waters being approximately 36 psu. The saline discharge enters the Sound th rough a diffuser, designed to nominally reduce the salinity to 1 psu above ambient concentrations within 50 metres of the diffuser, i.e. a dilution fact or of greater than 45.

The Experiments Two field experiments were conducted to provide information on the dilution characteristics of the saline plume under calm conditions and further data to

validate a 3D numerical model over short timescales. The first experiment was conducted in December 2006 where the saline effluent discharge was 50% of full capacity, and the second experiment in April 2007 where the saline effluent discharge was 83% of full capacity. The effectiveness of the diffuser in mixing the saline effluent with the background waters of Cockburn Sound is a function of flow rate, with the lowest dilution occurring at low flow rates (Wallis 2006). Therefore, the worst case conditions (t hat is, the leastdiluted plume) will occur under low flow rates and calm cond itions, which was exactly the conditions under which the field experiments were conducted (Okely et al. 2007).

Each experiment incl uded the deployment of a Lake Diagnostic System (LOS) over several months, consisting of a meteorological station and thermistor cha in (Figure 1), the opportunistic deployment of a high resolution profile (F-probe) (lmberger and Head 1994) to measure temperature, conductivity, pH,

The effluent from the Perth desalination plant does not enter the deep waters.

Figure 2. View of Rhodamine WT at the water surface during the second experiment in April 2007. Photo taken on April 26, 2007 at 10.55 am.

water NOVEMBER 2009 83


l,l

desalination dissolved oxygen, turbidity and fl uorescence over several days in December 2006 and April 2007, and the release of Rhodamine WT dye, added to the PSDP discharge over approximately a 20 minute period (Figure 2), at concentration of 3889 µg/L and 4432 µg/L for the 2006 and 2007 experiments respectively. This dye was traced with the F-probe for three days to determine the dilution of a single parcel of water released f rom the diffuser, with dilution determined by dividing the released Rhodamine WT concentration (prior to the diffuser) by the measured Rhodamine WT concentration, as the background co ncentration of dye was zero. Note that all dissolved material present in that parcel of water, salt included, wi ll dilute with the background concentration at the same rate. The non- zero background concentration of salt is irrelevant, as the dye test is a direct indicator of the effectiveness of the diffuser and any dilution greater than 45 indicates the diffuser is performing as expected. Numerical modelling was conducted in conjunction with the field experiments to validate the 3D model over short timescales (Okely et al. 2007).

ref ereed p a pe r

SALINITY (psu)

., .,

0

., .,

• 1•

i o..

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5

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8

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FIELD 2006-12-19 06:0S-07:29

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SALINITY (psu) FIELD 2007-04-2611 :50-14:40 0

i

5

..<::

o..

8

10 15 20 2

0

3

4 Distance (km)

5

6

7

8

Figure 3. Transect of measured salinity along the main shipping channel on December 19, 2009 (upper panel) and April 26, 2007 (lower panel). respectively in the region of the shipping channel closest to the diffuser. The salinity and vertical thickness of the layer decreases away from the diffuser both north and south along the length of the shipping channels, becoming more diluted with distance from the diffuser. Off-shelf the layer become very thin (less than 1 m in height) and was barely discernable 1 km from the Stirling exit (<0.2 ppt).

Plume Characteristics The behaviour of the saline effluent plume is demonstrated in Figure 3 for both field experiments conducted in December 2006 and April 2007 respectively. The measurements indicated that the bottom salinity in an approximately 3 km vicinity (i .e. - 1.5km along the channel in either direction) of the diffuser is 0.2 psu to 0.8 psu greater than the background salinity of 36.5 psu. The saltier bottom layer extends down-slope from the diffuser and forms a layer of height 1.5 m and 3 m in December 2006 and April 2007

so- - - - - - - - - - ~ - - - ; : ; : 7 ; ; : ; : :Dec ::::=2008 ::;:;::::;i ••

35

15 10

Figure 4. Histogram of saline effluent layer heights in profiles made off shelf from the Stirling Channel exit. Data are separated according to each field experiment.

Within 500m of the exit of Stirling Channel, 45% of the profiles measured detected no saline effluent plume, and for an additional 38% of profiles the saline effluent plume was less than 1 m

Bottom TRACER (ug L- 1)

Surface TRACER (ug L- 1) FIELD 2006-12-19 09:19-11 :17

Af>t:2007

FIELD

th ick (Figure 4) and less than 0.6 kg m·3 above the background density (i.e. 2.2%). This is with in the range of naturally occurring density differences in the Sound (D'Adamo 2002).

Dilution of Saline Effluent

6438 6437 .5

6437.5

6437

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10.0 8.0

6 .0 Z

6436.5

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::::i:

::::i:

5

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t-

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2.0

6435.5

6435.5 6435'--....,_- ~ - - ~ 383 384 385 UTM E(km)

0.0

6435'--....,_-~_ ___, 385 383 384 UTM E(km)

Figure 5. Surface and bottom Rhodamine WT concentrations measured in the nearshore vicinity of the diffuser on December 19 2006 during the dye release experiment.

84 NOVEMBER 2009 water

Figure 5 shows surface and bottom Rhodamine WT measurements from all profiles made in the vicinity of the desalination diffuser during the dye release experiment on 19 December 2006. The released concentration was 3889 µg/L and concentrations of greater than 9 µg/L were detected during the profiler circuit 100 m from the diffuser. During the 200 m circuit, the dye plume was intercepted south, south-east and shoreward of the diffuser, and concentrations were less than 8 µg/L. Intensive near- shore profiling on 21

technical features


[ ~ refereed paper

December 2006 (Figure 6) showed concentrations of up to 0.7 µg/ L in t he deepest parts of the region surrounding the diffuser. Dilution of the saline effluent w as examined in t he f iel d exp eriments via Rhodamine WT d ye tracing . The design dilutio n of the diffuser was 45 t imes, meaning that 1 lit re of hypersalin e effluent (approximatel y 65 psu) will be diluted with 45 L of background seawat er (approximately 36 psu) w ithin 50 metres of the diffuser, res ulting in a dilute plume of salinity approximat ely 36.6 psu or 0.6 ps u above background .

desalination

I

Surface TRACER (ug L- 1) FIELD 2006-12-21 07 :52- 12:09

Bottom TRACER (ug L- 1 ) FIELD

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=>

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~

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0.8

6436 0.4

6435.5

6435.5

0.0

5435~~--- - ~ 383 384 385 UTM E(km)

6435 - - - - - -383 384 385 UTM E (km)

Figure 6. Surface and bottom Rhodamine WT concentrations measured in the nearshore vicinity of the diffuser on December 21 2006.

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desalination This dilution of the initial dye plume was traced for both field experiments for 3 days and the range of dilutions is presented in Figure 7. The field measurements indicated t hat within 36 hours of the release the saline effluent was diluted more than 1000 times with t he background salinity.

, refereed paper

a)

10000

.§ 1000 '.2 0

Discussion The resu lts from the field experiments have lead to a detailed understanding of the dynamics and dilution characteristics of the saline effluent plume under calm cond iti ons. The saline effluent from the p lant leaves the diffuser verticall y, forming a s ignificantly diluted plume in the vic inity of t he diffuser. The negative buoyancy of the sal ine effluent causes t he plume to plunge to t he sea floor w here it spreads laterally following the depth contou rs of the Sound until it intersects the dredged shipping channels, where it is present as a semi-permanent feat ure (dependent on wi nd conditions) approximately 2-3 metres above the bed. Once in the shipping channels the plume moves both to t he north and south under gravity.

Conclusions Measurements made during tw o experiments at the exit of Stirling Channel under very calm (worst-case) conditions indicate the plume w as undetectable 45% of the time, and between O and 1.0 m t hick 33% of the t ime. In all cases the plume was undetectable approximately 500 m from the exit of Stirling Channel, even for the cases where t he plume was more t han 1m thick at the exit. Th ere is therefore no possibility of a sal ine plume from the desalination saline effluent entering the deep waters of Cockburn Sound (> 1Om) and sufficiently prolonging stratification such that dissolved oxygen is drawn down to low levels, as discussed by Lu keti na and Christie (2008).

Acknowledgments This work was funded by the Water Corporation of Western Australia. The field experiments would not have been successful without the effort of J. lmberger, J. Antenucci , P. Okely, G. Attwater and C. Lam from the Centre for Water Research at The University of Western Australia. This article represents Centre for Water Research reference 2320 CM.

86 NOVEMBER 2009 water

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0

6440

0

6435

- -- ~- - - - ~ - - - _ _ _ _ J 28 29 27 Apr 2007

6434 ' - - - - - - - - - - ' 380 382 384 (km)

Figure 7. Dilution of the saline effluent during the a) December 2006 and b) April 2007 experiments. The right panel shows the location of the field samples relative to the bathymetry in the east of Cockburn Sound in the vicinity of the shipping channel, with the red square indicating the location of the diffuser.

The Author

Dr Clelia Luisa Marti is a Research Associate managing the Flagship Field Programme at t he Centre for Water Research , The University of Western Australia, email: marti@cwr.uwa.edu.au.

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References D'Adamo, N. 2002. Exchange and mixing in Cockburn Sound, Western Australia: a seasonally stratified, micro-tidal, semienclosed coastal embayment. PhD Thesis, Dept. Civil Engineering, University of Canterbury, Christchurch, New Zealand. lmberger, J. and Head, R. 1994. Measurement of turbulent properties in a natural system. In Fundamental and Advancements in Hydraulic Measurements and Experimentation. Hydraulics Division, ASCE. Luketina, D., and Christie, S. 2008. Monitoring of the Perth SWRO Brine outfall. Water, 35(8): 72-74. Okely, P.N., Antenucci, J. P. , lmberger, J . and Marti, C. L. 2007. Field investigations into the impact of the Perth Seawater Desalination Plant discharge on Cockburn Sound - Final Report. Report prepared for Water Corporation. Centre for Water Research, University of Western Australia. WP2150PO, 102 pp. Wallis, I. 2006. Perth Seawater Desalination Plant Peer review of diffuser design proposed by MDJV. Prepared by Consulting Environ mental Engineers for the Water Corporation. 11 pp.

technical features


desalination

COAL SEAM GAS WATER: VIABILITY AND TREATMENT T Mannhardt, I Cameron Abstract This paper explores the prevalence and treatment of coal seam gas (CSG) water in the agriculturally rich and droughtprone Surat Basin, Queensland. Water extracted from CSG wells varies in quality and is significantly different in composition across wells and areas of extraction. This makes it difficult to predict water quality in storage locations and thus adapt the treatment required. The typical treatment process is desalination - with particular attention to a reverse osmosis design with a twostage array having conservative flux rates for the membrane elements. This approach will provide enough redundancy in the design to handle raw water supplies peaks.

Typical lined evaporation pond for disposal of brine concentrate.

Introduction The recent exploration and development of coal seam gas (CSG) reserves in the Surat Basin has led to unique opportunities for the use of brackish water which is a by-product of the CSG extraction process, as outlined by Oldridge and Whatman (2009). The region where the gas extraction is most prevalent is in the Surat Basin which encompasses the Darling Downs, approximately 300 kilometres west of Brisbane in Queensland. The region is rich in agriculture and has in recent years suffered from sustained drought conditions, which have gravely affected the prosperity of these rural communities.

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desalination The CSG wat er liberated from the wells is at its greatest volume during the initial phase of t he gas well 's life. Over the life of the well the liberated water volume declines as CSG is extracted. The volumes of water that are likely to be produced are estimated to be 30,000 ML per annum to 80,000 MUa over a 20 to 25 year period, depending on CSG production to meet liquefied natural gas export t argets.

Current CSG Water Disposal and Users At present the disposal of CSG water is via evaporation ponds - large constructed storages for the purpose of evaporating vast quantities of water located within the vicinity of CSG extraction wells. These ponds are serviced by a network of pipelines w hich convey the water for disposal. The long term viability of creating enough lined evaporation ponds to service the water extracted from the wells is doubtful, and the Queensland Government has legislated to discontinue their use as a primary means

of disposal. (DIP, 2008) CSG producers are exploring alternative means of reuse and disposal. Such alternatives as ground reinjection of the CSG water are available but immediate solutions to disposal of the water will involve a treatment process. A number of potential uses for treated CSG water exist. These include irrigation for agriculture, industrial users such as power stations, mines and municipal users supplementing water supplies. However, all these require significant treatment before the water could be reused - the exception is water used for coal washing in mines; however, this will be limited by the tolerance of materials exposed to elevated levels of salinity contained within coal wash plants.

Water Quality Water extracted from the CSG wel ls is highly variable in quality and significantly different bet ween wells and areas of extraction. This results in the difficulty of predicting the water quality in storage dams as samples are from multiple water sources from different wells.

CSG water has a physical water quality wh ich varies significantly in terms of turbidity and suspended solids (SS). Levels of SS can be present at 1,500 mg/L. This may be the result of well drilling operations and is anticipated to decrease over the life of the gas well. CSG water also contains saturated gases and hydrocarbon contaminants at various levels depending on the well source being an issue for treatment. The pH of CSG water can vary from 7.8 - 9.6 with a total alkalinity in the range of 9001,600 mg/I, typically after extraction . However the variability of alkalinity may be impacted by the cyclic effect of evaporation in storage dams over a lengthy period of time. The water extracted from the CSG well is best described as brackish, having a total dissolved solids (TDS) of 1,500 to 12,000 mg/L. This is typical of ground waters throughout inland Australia. These brackish waters are predominately comprised of sodium chloride (NaCl). All the typical trace elements are present, with levels of Alum inium, Iron, Silica, Barium, Calci um, Magnesium and Fluoride being the most variable.

Process Treatment -

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Lecturers in Water Supply and Sewerage Reticulation Design

Expression s of interest are invited for suitably qualified and experienced practitioners to deliver lectures on the design of water supply and sewerage reticulation systems to water industry engineers and technical offi cers.

These positions are casual and would be suitable for persons previously in the water industry or retired from practice. Applicants will need to demonstrate experience and proficiency in design. Courses are delivered over 3 days using prepared material. Courses can be programmed to suit available times. Where required City West Water will provide assistance and training to certificate 4 level in teaching to the successful applicants. Recently retired people with experience in water and sewer design may also wish to apply. Opportunities currently exist for delivery of the courses in Melbourne and Sydney and may be extended to other capital cities throughout Australia.

For further information contact Ross Carruthers via email at: rcarruthers@citywestwater.com.au

Written applications should be addressed to: Manager Standards and Design City West Water - Locked bag 350, Sunshine 3020 Vic

88 NOVEMBER 2009 water

It is essential to reduce to a low level the variable suspended solids (SS) load in CSG water prior to desalination. The SS load can be reduced via an appropriately designed reservoir located upstream of a treatment process to allow sufficient settling time. A nominal retention time is also beneficial to reduce the presence of saturated gases withi n CSG water as gas liberation rates increase when the water is exposed to the atmosphere. The design of the pre-treatment process for CSG wat er is likely to incorporate a solid-liq uid separation step throug h a clarification process of adding coagulant and flocculant. Appropriate selection of the combi nation of coagulant/flocculants to be used must be undertaken with screening work and the variability of pH of the water will challenge this selection. The periodic removal of the sludge generated from the clarification process will need to undergo further dewatering and ultimate disposal. Any design examining the treatment of CSG water must factor in the potential for the feed water to increase or vary in concentration, caused by the cyclic effect of evaporation in the upstream storage reservoir and/or changes in salinity from new wells.

technical features


Pre-treatment of CSG water is vital for this water to be suitable as feed water for reverse osmosis (RO) treatment. Ideally RO feed water requires an SDI <3 (silt density index). A fundamental challenge for any designer of the pre-treatment process is the unknown variability of t he water quality. This will be based on the selection, most likely of either micro or ultra filtration which can be installed in a submerged or pressurised variant. Again a conservative approach to flux rates will give the best operational outcome and performance.

I) ENGINEERING PLASTIC PRODUCTS

The treatment process available for CSG is typically desalination, via RO. Developing a process train of equipment for the treatment of CSG water req uires particular attention to a RO design with a two-stage array having conservative flux rates for the membrane elements. This approach will provide enough redundancy within the design to handle sufficient peaks given the likely variable water quality. The difficulty for the RO system is the presence of scaleforming species on a membrane surface which in turn dictates the level of recovery that the RO syst em can achieve. Fluctuations in Fluoride, Silica, Barium, Sulphate and Calcium in the presence of each other and in a soluble form have long been troublesome for RO designers. Although treatable through use of specific anti-sealants and membrane selection, these issues compl icate the ongoing operation of such systems. In addition to the challenges of the variable levels of suspended solids,. biological activity can be present and will need to be addressed in combi nation with a selected pre-treatment process prior to RO treatment. The biological activity can be overcome by pre-treatment disinfection such as chlorination/ dechlorination and a robust cleaning regime of a selected pre-treatment system like micro or ultra filtration. Post-treatment of the water from the RO syst em may also be necessary, depending on the final water quality required. Water producers may need to stabilise the water by correcting the alkalinity, depending on the aggressiveness of the water. The degree, to which this is required, depends on the RO design, which will be most likely focused on achieving the highest level of recovery possible. A typical process stream is illustrated in Figure 1.

Weighing up the Costs The volumes of water likely to be produced within the Surat Basin region are substantial - as is the need for robust treatment processes. The core driver is to replace the present means of disposal via conventional evaporation ponds, given the surface area required to achieve the necessary evaporation rates for volumes in the order of 200-300 MUd range. Large-scale, brackish water reverse osmosis plants (80150 MUd) are an obvious solution , provided the level of recovery can be achieved (> 75%). The great est challenge from a treatment perspective is to increase the level of recovery without substantial increases in operational costs for such plants. Innovative designs for specific pretreatment processes, which selectively remove the troublesome cations/anions which limit t he recovery is one such solution.

• Sedimentation Systems • Sprockets and Flights • Wear and Return Shoes • Wear Strips • Scrubbers • Chain and Chain Attachments (720 and H78 Series) • Centreless Screw Conveyor Linings (with wear indicators) • Gear to Drive Drum Filters • SG Iron Sprockets (720 and H78 series

--

However, in utilising RO as a technology for disposal of CSG, it will only ever be solving a part of the problem.

water NOVEMBER 2009 89


desalination UflMF MElf&AANt fk.TIV.TIOH PLM'T I STRAINER.

lSTAGEROSmEM

PACKED TowtR

AEAATOA.

FILTRATE SIOIW)(

TANI<

""'""" TANKS

OID USER

TO EVAPOAATION P~OI BACKWASH TREATMENT PAOCtSS RO CONCENTRATE ITOAAOt:TANI<

Figure 1. Typical process schematic (Duty/standby configuration). Waste streams produced from a clarification, pre-treatment and RO process will require disposal, wit h reinjecti on or evaporation ponds the

likely solution There is a strong likelihood that any such RO in st allation would need to be c omplemented by a nearby power

station to provide the necessary power req uirements and would need to be delivered in parallel with the RO inst allation.

Infrastructure issues

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90 NOVEMBER 2009 water

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Given the amount of CSG water produced from a large-scale RO plant and its relati vely isolat ed locat ion , identifying an end user for such w ater becom es an issue. Given the cost of treatm ent the region is limited by few users capable of taking such volumes of water and/or accepti ng the price, reflective of how much it cost t o produce. There are a number of infrastructure issues associat ed with delivering such a large-scale RO plant to faci litate the disposal of CSG water. In the cont ext of a centralised RO plant, where the delivery of raw wat er is t o be t reated, the logistics of moving extracted water from the wel l heads to the treatment location presents challenges . The potential geographic spread and the anticipat ed production life-span of the wells makes it difficult to determine an appropriate site for a large scale RO plant. In conjunct ion to delivering t he water to a viable enduser within a close proximity, the supply and delivery of the water via a network of pipelines increases the cost of the water. From an operational perspect ive for an RO plant the continu ity of raw water supply is a critical issue. Producers of CSG water need to have

technical features


desalination certainty throug h supply agreements with their customers (end-users). Equally, customers of CSG -treated waters need to have a guaranteed supply. The infrastructure m ust include contingency measures for the storage of water during those periods when either cannot supply or take water respectively.

water required at an agreed q uality and price. To facil itate such a water supply scheme wou ld involve a legal agreement between the supplier and end-user which takes into account variable wat er quality and availability.

Conclusion

For this to succeed requires a cu lture of cooperation between a proposed upstream supplier of bu lk water and the end -user. Given t he operat ional responsibilit ies of such a plant being critical for the gas producer and the end-user, bot h need provisions in place to take or deliver water t o a balancing storage so to mitigate risk.

CSG water treatment is not simple and not witho ut process risk. Due to t he variability of bot h CSG water quality and q uantity t here is a need for a robust treatment process, which includes operatio nal flexibility. The issues associated wit h brine management and disposal of brines and solids from t he treatment process require close invest igation.

Community Issues

The Authors

The Surat Basin is a large region with a sparsely spread population of rural commu nities and townships. The recent CSG explorat ion work has crossed much of the reg ion's farm land and brought with it a sign ificant boost to local employment. Potential disruptions in the region may result from continued CSG extraction and the su pply and distribution of water to/from a RO plant. Access to corridors for pipelines through critical routes wi ll come with the potential for objection and delay for delivery of such projects. A focus on community engagement and consultat ion will again be critical for risk mitigat ion.

Thomas Mannhardt is a Water & Process Engineer in the Brisbane office of Parsons Brinckerhoff. involved wit h various projects involving the assessment and design of t reatment processes for CSG water utilising membrane technolog ies, for supply of water for Power Stations and domestic uses.

Constraints and Challenges There are many const raint s to delivering sustai nable, beneficial reuse of CSG water in t he Surat Basin . These are const raints which must be overcome to manage t he large vol umes of water from CSG extraction. A f undamental challenge is reaching agreement on the water quality and vol ume to be supplied t o any end-user. Prod uct water quality impacts t he design required for treatment and operat ional cost for the RO plant by t he supplier of t he water. Reaching commercial agreement wh ich is acceptable to both parties (supplier/end-user) w ill pose as a serious constraint. The chall enge for the supplier of t reated CSG water will be the ability to identify an end-user who is prepared to accept the vol umes of

Ian Cameron is a Principal Water Engineer and has been involved in CSG water management projects since 2002, and has a high in dustry profile based on seven CSG water related confere nce presentations and his ongoing industry involvement. Email contact thro ugh: E1 Hill@pb.com.au

References Oldridge, S. and Whatman , L. (2009) 'Beneficial use of coal seam water gas' Water, June 2009. Department of Infrastructure and Planning (DI P) 8 December 2008. Article on water supply options in the Surat region (Information available at http://www.dip.qld.gov.au/ projects/ water/nathan-dam.html)


~ r ef e reed p ap e r

algal biofuels

BIOFUELS AND WATER TREATMENT BY GROWING ALGAE IN WASTEWATER Jli Abstract Research on water treatment and biofuels by growing algae in wastewater is reviewed . Two systems of growing algae, the open systems and closed systems are shown. The benefits of growing algae in waste water treatment plants are explained and it is shown that wat er authorities can make significant contributions in reduci ng greenhouse gases emission.

Table 1. Potential annual oil yield from different crops (Pienkos, 2007). Crop

Oil Yield L/ha/yr

Corn

171

Cotton

333

Soybean

456

Mustard seed

580

Sunflower

969

Rapeseed/Canola

1207

Jatropha

1919

Introduction

Oil palm

6033

As in the rest of the developed world, there has been recent activity around the development of an Australian biofuel industry to partially offset our reliance upon petrochemical sources of transport fuels and t o reduce our GHG emissions. O'Connell et al. (2007a, 2007b) examined the capacity of first generation feed stocks to supply biofuels for Australian transport requ irements. In the case that all the Australian domestic crop of sugar, molasses, wheat and coarse grains was converted into ethanol using first generation technologies, and all biodiesel inputs were used to make biodiesel we still could not replace all of Australia's requirements for transport fuel (by a long margin for diesel). A mandat e of 10% ethanol in all Australian petroleum sourced from first generation feedstocks wou ld probably lead to a requirement to import grain in drought years. O'Connell et al. (2007a, 2007b) concluded that biofuels based on fi rst generation feedstock would supply less than 10% of Australia's transport needs.

Algae (10 g/m2/day at 30% TAG)

11,400

Algae (50 g/m2/day at 50% TAG)

95,000

A potential solution to this is the development of biofuels that utilise algae. The advantages of producing biofuels from algae are that it does not require arable land and th us would not compete with food crops, some algal species can provide a much higher oil yield, their byproduct can provide value adding, and

Table 1 shows the potential oil yield from different crops as stated by Pienkos (2007). In Table 1, algae with two growth rat es and two different triacylglycerols (TAG) content are listed . The TAGs are molecules for fuel production. It can be seen t hat algae can produce nearly 80 times the oi l prod uced from canola for the same land area. Table 2 from Chisti (2007) shows that microalgae are the only viable crops to provide the US with 50% of its current transport fuels.

they can be grown, harvested and converted into liquid biofuels relatively easily.

The Potential of Oil Production from Algae Algae, and more specifical ly microalgae, are some of the simplest and oldest organisms ever to grace the planet. They are unicellular and grow and multiply through photosynthesis just like plants. Their simple structure allows them to efficiently convert solar to chemical energy. The potential to grow large quantities of microalgae quickly is when they become significant as an energy source.

So far only a fraction of microalgae have been studied in any detai l, and less than one handful have been cultured successfu lly out doors. Table 3 shows a list of algae that show reasonably high oi l cont ent. In producing biofuel from algae, high oil content is only one factor in selecting a particular species. In t erms of importance, the order of criteria in selecting an algal species inc lude: 1) environ mental tolerance; 2) growth rate; 3) maximum cell density; 4) harvestability; and 5) oil content. Micro-algae contain lipids and fatty acids as membrane components, st orage products, metabolites and sources of energy. Algal fatty acids and oi ls have a range of potential applications. Algal oils possess characterist ics similar to those of fish and vegetable oils, and can t hus

Table 2. Comparison of some sources of biodiesel (Chisti, 2007). Oil yield (L/ha)

Land area needed (M ha) •

Per cent of existing US cropping area •

172

1540

848

446

594

326

Canola

1,190

223

122

Jatropha

1,892

140

77

Coconut

2,689

99

54

Oil palm

5,950

45

24

Microalgaeb

136,900

2

1.1

Microalgaec

58,700

4.5

2.5

Crop Corn Soybean

• for meeting 50% of all transport fuel needs of United States

Unique opportunities for water authorities. 9 2 NOVEMBER 2009 water

b

70% oil (by wt) in biomass

c 30% oil (by wt)

in biomass

technical features


algal biofuels

[ ] refereed p a per

be considered as potential substitutes for t he product s of fossil o il.

Basic Processes of Growing Algae for Biofuels Producing biofuels using algae involves two main areas of research and development: biology and engineering. Figure 1 show a schematic diagram of processes involved in producing biofuels fro m algae. Like any plant, algae require water, sun light, CO 2 and nutrients to grow. Some algae grow in sali ne water and others grow in freshwat er or brackish water. The nutrients include nitrogen, phosphates and minor minerals. The amount of nut rient requirement and t he opt imal ratios of these nutrients are species dependent. Some algae are very good at absorbing heavy metals from wastewater and have been used for wastewater treatment for such purposes. To enhance production, it is always necessary to su pply CO2 to the algal growing system since limited CO2 in the atmosphere and wat er wi ll limit algal growth. The biological aspect involves strain selection for a particular site, provision of experimental data on the tolerance range of t he selected algae to temperature, light intensity, pH level, salinity , nutrients and ability to maintain a pure culture, and

Algal

Table 3. Oil content of some microalgae. Microalga

Oil content (% dry wt)

Botryococcus braunii Ch/ore/la sp. Crypthecodinium cohnii Cylindrotheca sp. Dunaliella primolecta Jsochrysis sp. Monal/anthus salina Nannochloris sp. Nannochloropsis sp. Neochloris oleoabundans Nitzschia sp. Phaeodactylum tricornutum Schizochytrium sp. Tetraselmis sueica

25-75 28-32 20 16-37 23 25- 33 > 20 20-35 31-68 35-54 45- 47 20-30 50-77 15-23

improving the algal species genetically t o improve the productivity of oil. From a biological point of v iew, one of t he main tech nical issues seems to be t he selection of stable algae strains that can be maintained in large systems such as open ponds. An algal species dominance can be challenged by invasion from 'weed' algal strains, grazing by zooplan kton, invasion by water plants or other , often unknown, factors resulting in a pond crash. Current tech niques require the development of

gt owing

s~¡stem Harvesting system

Figure 1. Schematic diagram of a typical biofuel from algae plant (a modification from http://www.biodadi.lv/algaelink_photo_bioreactors.html).

Figure 2. A large scale raceway ponds (Spirulina Production in India, Parry Nutraceuticals Ltd., Weissman, 2007).

inoculum product ion in case the ponds are contaminated. The engineering aspect involves the design of algal growing systems (especially for large scale production), maintaining and operating the systems so that all t he parameters (temperature, light intensity, pH level, salinity, and nutrients) are w ithin their respective tolerance ranges, minimising conditions t hat cause the algal growing systems to crash, design of harvesting systems, operation of t he harvesting syst ems, oil production from algae and converting the oil to biodiesel.

Algal growing systems Algal growing systems have been developed in a number of countries for growing specific strai ns of algae for pharmaceutical chemicals (Figure 2).They would be the most important component in a system of producing biofuels from algae. The main f unction of the growing systems is to provide algae with an environment where light can be efficiently used by algae in photosynthesis. There are two main categories of algal growing systems, open systems and closed systems. The closed systems are also called photo-bioreactors. Open systems are ponds and lagoons, and are generally equipped w ith paddle wheels for mixing. The ponds wit h paddle w heels are also called raceways. Mixing in raceways provides several functions for algae growth, including: 1) reduced thermal stratificat ion compared with ponds; 2) exposure of greater amounts of algae to sunlight; 3) maintaining t he algae in suspension; and 4) providing gas exchange with ai r. Baffles are generally used for guiding flows. Conti nuous harvesting t akes place before the paddle wheel, and feeding of nutrients, CO2 and fresh culture after the padd le wheel. Figure 2 shows an example of raceway pond. Commercial raceway ponds for growing algae are generally shallow with water depth less than 30 cm in order to increase the ratio between the surfacearea and the volume of water. Because of shadi ng effects from algae, light can in general penetrate less than 5 cm below the water surface unless algal density is very low, which will result in high harvesting costs. Engineering constraints also set limits on the depth of the ponds. According to Benemann and Oswald (1996), ponds depth below 15 cm make the construction and operation of large ponds difficult (in terms of slop accuracy) and wind fetch wou ld make operations

water NOVEMBER 2009 93


~ refere e d pape r

algal biofuels problematic. Above 50 cm, t he cost of construction becomes prohibitive for many applications, as does the higher cost of harvesting (as density is an inverse function of depth). Large (>1 ha) raceway ponds would be designed to be operated at depths between 20 to 30 cm. The engineering design of t he raceway ponds requires caref ul consideration to ensure the provision of nutrients in amounts and time that do not constrain the prod uctivity of the culture, nor result in waste of nutrients. Algal dry biomass composition contains up to 46 per cent carbon (C), 1O per cent nitrogen (N) and 1 per cent phosphates (P). One kilogram of dry algal biomass utilises up to 1.7 kg carbon dioxide (CO2). Closed systems can be in various forms such as tubes, bags, and plate panels. Covered ponds and greenhouses can also be considered as closed photobioreactors. Figure 3 shows a closed system. They are common ly used for preparing inoculation quantities. The advantages of closed systems are that the ratio of surface area to vo lume for water is in general higher t han t hat in raceways ponds, it is easier to control the water temperature, the algal density is generally higher, algal harvesting is easier (due to the higher algal density and smaller water volume), and the contamination of the algal c ult ure is minimised. Li (2009) summarised t he advantages and disadvantages of the closed and open systems. There are recommendations for combin ing raceway ponds with photobioreactors to minimise the capital cost and better control of algal culture in minimising contam inat ion in raceway ponds. In a case study for Botryococcus Braunii, a slow growing algal species, Benemann and Oswald (1996) proposed a 9 stage inoculation. Huntley and Redalje (2006) used a combined system to grow Haematococcus pluvialis. They commented that "the key to success is to red uce the residence time in t he open ponds, where cultures are susceptible to contami nation ... "

Harvesting Harvest ing algae is one of the most difficult processes for biodiesel production from algae (the other is to maintain a steady high rate of algae production per unit area). This is because microalgae are small in size (between 2 Âľm to 20 Âľm) and low in concent ration (typically less than 500 ppm). The smal l size makes it d ifficult

9 4 NOVEMBER 2009 water

Figure 3. Closed photo-bioreactors from Vertigro (http://www.valcent.net/). to fi lter the algae out of t he water. The low concentration of algae means t hat t raditional harvesting techniques such as applying centrifugat ion directly will be too expensive in terms of capital and operating costs. One way to increase algal concentration in raceway ponds is to use shallow ponds less than 30 cm deep. Algae can be harvested using microscreens, centrifugation, flocculation and froth flotation. Alum and ferric chloride are chemical flocculants used to harvest algae. A commercial product called "Chitosan", commonly used for water purificat ion, can also be used as a flocculant but is far too expensive. Water t hat is more brackish o r saline requires addit ional chemical flocculants to induce flocculat ion. Harvesting by chemical flocculat ion is often too expensive for large operations. In froth flotation, the water and algae are aerated into a froth, with the algae then removed from the water. Interrupting the carbon dioxide supply to an algal system can also cause algae to flocculate on its own, w hich is called "autoflocculation". Benemann and Oswald (1996) reviewed various techn iques of microalgae harvesting and estimated the costs of using each technique. The challenge is to increase the concentration of algae from its culture, usually at less than 500 ppm, to 1-2%. According to them, it is generally simple and not too expensive to concentrate from there, by centrifugation, t o a high (> 10%) solids concentration, suitable for processing to fuels and other products or drying. Putt (2007) suggested a low-cost , energy efficient, sim p le, and fully

effective means of harvest ing fresh water micro-algae Chlorella. The harvest ing comprises two steps, namely flocculation and dewatering. Flocculation is a two step process, in which cellulose fibres are first added, via a static mixer, fo llowed by ferric nitrate , also via a static mixer. The cellulose, added at a rate of 10% of the algae weight, provides a fibrous struct ure on w hich the algae agglomerate upon addition of the ferric nitrate, yield ing a robust, fibrous floe wh ich stands up to t he dewateri ng process.

Value adding from algal residua l In large scale prod uction of biofuels from algae, residuals left over from t he production of oil need to be d isposed or reused due to its large quantity. One way of using the residual is to send it to an anaerobic digester (if one is avai lable) to generate biogas. The biogas can be used to generate electricity, provide CO2 to the algal growing system, and supply heat to the digester. Algal biomass has other potential onand off-farm uses. Althoug h it has primarily been considered as an alternative high-grade protein source in animal feed for fish, pigs, cattle and chickens, alga biomass wit h a balanced N:P ratio is a potentially valuable organic ferti liser. The algal residual can also be used for producing ethanol because of its high content of starch, although t he t echnology for produci ng ethanol from second generation biomass still needs f urther development to make it economically viable.

technical features


~ refereed paper

algal biofuels

Microalgae In Wastewater Treatment In Benemann and Ostwald (1996), it has been suggested that producing biofuels from growing algae in wastewater treatment lagoons would be a most likely path to market. In general, algae grow in lagoons by themselves (Li, 2009) and may create problems for water authorities, particu larly if the algae species growing is toxic blue-green algae. Effluent with algae (even non -toxic algae) above a certain level can not be released to the environment because it may upset the local ecological system. Microalgae can also be used for municipal and industrial wastewater treatment (Oswald, 1988). In wastewater treatment ponds, known as "oxidation ponds", microalgae provide dissolved oxygen used by bacteria to break down and oxidise wastes, thereby liberating the CO2 , phosphate, ammonia, and other nutrients used by the algae. Figure 4 from Lundquist (2007) shows the relationship between algae and bacteria in an oxidation pond. In growing algae in wastewater treatment lagoons, the algae need to be harvested since discharge of the pond effluent, containing the algae biomass results in a suspended so lids and BOD (biological oxygen demand) load in the receivi ng bodies of wat er. Th is potentially creates problems (oxygen deficits, eutrophication), unless the effluents can be greatly diluted. Species control cou ld aid in algal harvesting by choosi ng easily settable or filterable algal species (Benemann et al, 1982). It can be seen from Figure 4 that growing algae in lagoons can enhance wastewater treatment and thus lagoons of smaller capacity can be used to treat the same amount of wastewater. According to Benemann and Ostwald (1996), the usually unmanaged nature of conventional facultative oxidation ponds and their generally poor hydraulics makes such systems unpredictable in basic performance aspects such as final suspended solid concentration. Algal biomass, estimated at about 80% of the total suspended solids discharged by such systems, can vary by a factor of ten within a period of days. This variation can be caused by sudden blooms of algae, or of rotifers or other algal grazers or settling of algae. The important consequences of this high algal concentration in the effluent are: 1) it is difficult to use conventional

Reclaimed Water

Algae

Waste Water

Bacteria

Figure 4. Relationship between algae and bacteria in oxidation ponds (Lundquist, 2007).

disinfection (e.g. chlorination) because of the large amount of organic matter represented by these solids; and 2) when the algal biomass is discharged int o receiving bodies, the algae exerts a proportional oxygen demand and may upset ecosystems. Benemann and Ostwald (1996) suggested that the solution to the problems of conventional oxidation ponds - the large amount of land used, the uncontrolled nature of the waste treatment process, the difficulties of removing algal solid from the effl uents is to make the algal treatment system more intensive and predictab le. This must involve, first, better hydraulic mixing, to achieve a more uniform and predictable pond environment. Mixing by paddlewheels makes the algae below the water surface come to the top so that they are exposed to sunlight. Addition of CO2 to the pond maximises algae growth. According to Lundquist (2008), the C:N:P ratio in wastewater is in general 20:8:1, but optimal algae growth requires the ratios to be 50:8:1. Without supplementing CO 2 , the lagoon will be carbon deficient and algae growth wi ll be limited when sufficient sunlight is available. By supplementing CO 2 in the right ratios for growing algae, it is expected that the algae biomass production can be more than doubled. The second benefit of adding CO2 to the lagoon is to produce effluent with much better nutrient removal than the conventional wastewater t reatment

processes since this will have essentially complete removal of N, and at least 50%, and likely 70-80 %, reduction of P concentrations (Benemann and Ostwald, 1996). The third benefit of supplementing CO2 is that growing algae to the point of N-limitation can produce an algal biomass with high lipid content (Benemann and Tillett, 1987). Disinfection and chlorine dosing of the effluent will still be req uired to treat the wastewater after the algae have been harvested, as is the cu rrent practice in wastewater treatment. There are wastewater treatment plants that encourage the growth of algae, such as the Advanced Integrated Wastewater Pond Systems (AIWPS) proposed by Professor Wi lliam J Oswald and his coworkers at the University of California, Berkeley over the past four decades. Although AIWPS may appear to be an adapted traditional pond syst em, each AIWPS facility incorporates a series of low-cost ponds or earthwork reactors. A typical AIWPS facility consists of a minimum of four ponds in series. These are Advanced Facultative Ponds (AFP), Secondary Facultative Ponds or Algal High Rate Ponds (HAP), Algae Settling Ponds (ASP) and Maturation Ponds (Li, 2009). AIWPS's do not require sludge management; indeed t he tim~ in which sludge residues accumulate to require removal and disposal is on the order of decades. Carbon is transformed in AIWPS's through two important mechanisms: methane fermentation and biological assimilation by microalgae.

water NOVEMBER 2009 95


~ refereed p ap er

algal biofuels The conversion of waste organic solids to methane, nitrogen gas and carbon dioxide via methane fermentation and the assimilation of organ ic and inorganic carbon to algal biomass via photosynthesis provides the basis for primary, secondary, and tertiary treatment in AIWPS's.

Conclusions and Discussions Microalgae use photosynth esis to convert energy from light into chemical energy. It has been used commercially for many years to produce nutritional supplements and in aquaculture. Microalgae have great potential in meeting our demand for transport fuels and in mitigating CO2 emissions. Given the right environment in terms of temperature, light, CO 2 concentration and nutrients, algae can grow at a much faster rate than any land based crops. Some algae strains have very high oil content and can produce up to 80 times the amount of biodiesel per hectare as land based crops. These characteristics make them particularly attract ive in the current climate of global warming and fluctuating international oil prices. Two systems are currently used for growing algae, one is t he open system that utilises raceway ponds, and the other is the closed photo-bioreactor syst em. For large scale systems, raceway ponds are preferred because of their relatively low cost. Photobioreactors are in general being used for preparing inoculat ion quantities. Algae have also been used for wastewater t reatment in many places around the world. The advantages of using algae in wastewater t reatment include: 1) enhanc ing the biological process in breaking down TOC; 2) ach ieving tertiary t reatment of the wastewater; and 3) reducing the size of the lagoons. Selecting algae species w ith the right attributes (fast growth rate, tolerant to local environment, and high in lipid content) and growing them in wastewater can achieve two objectives: 1) enhancing wastewater treatment; and 2) prod ucing bio-diesel. This will provide unique opportunities for Water Authorities to make contributions in reusing the wastewater and in reducing the greenhouse gas emissions.

Microalgae Ponds for Conversion of CO2 to Biomass, Pittsburg Energy Technology.

The Author

Dr Jun-De Li is Senior Lecturer at t he School of Engineering and Science, & Institute for Sustainability and Innovation, Victoria University. Email jun-de.li@vu.edu.au. He has had 20 years experience in Fluid Mechanics, Heat and Mass Transfer.

References Benemann, J.R., Goebel, R.P ., Weissmadn, J.C., Augenstein, D.C., (1982) Microalgae as a Source of Liquid Fuels, Final Report to the US Department of Energy. Benemann, J.R. and Oswald, W. J. (1996), System and Economic Analysis of

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For information on advertising rates, please contact Brian Rault at Hallmark Editions, Tel (03) 8534 5000 or email

Acknowledgments

brian.rault@halledit.com

This project was financially supported by GWM Water and Central Highlands Water of Victoria, Aust ralia.

.au

96 NOVEMBER 2009 water

Benemann, J.R. and Tillett, D.M. (1987) Microalgae Lipid Production, Symp. Proc. Energy from Biomass and Wastes XI, ed. Klass, D., Institute of Gas Technology, Chicago, Illinois. Chisti, Y. (2007) Biodiesel from microalgae, Biotechnology Advances 25, pp.294- 306. Huntly, M. E and Redale, D. G. (2006) CO2 mitigation and renewable oil from photosynthetic microbes: a new appraisal, Mitigation and Adaptation Strategies for Global Change, Springer. Li , J.D. (2009) Biofuels from Algae growing in wastewater, Industry Report for Central Highlands Water and GWMWater, Victoria University. Lundquist, T.J. (2008) Production of Algae in Conjunction with Wastewater Treatment, AFOSR Workshop Washington, D.C. February 19-21, 2008. Nayar, S. (2008), SARDI Microalagl Feedstock Research Program, Bioenergy Australia Algae Workshop 27 March, 2008, Canberra. O'Connell, D., Batten, D., O'Connor, M., May, B.,Raison, J., Keating, B., Beer, T. , braid, A., Haritos, V., Begley, C., Poole, M., Poulton, P. , Graham, S., Dunlop, M., Grant, T., Campbell, P., Lamb, D. (2007a), Biofuels in Australia - issues and Prospects, RIRDC publication No. 07/071, Rural Industries Research and Development Corporation, Canberra, Australia. O'Connell, D., Haritos, V., Graham, S., Farine, D. , O'Connor, M. , Batten, D., May, B., Raison, J., Braid, A., Du nlop, M., Beer, T., Begley, C., Poole, M., Lamb, D. (2007b), Bioenergy, Bioproducts and Energy - A Framework for Research and Development, RIRDC publication No. 07/078, Rural Industries Research and Development Corporation, Canberra, Australia. Pienkos, P. T. (2007) The potential for biofuels from algae, Algae Biomass Summit 2007, San Francisco, CA, November 15. Putt, R. (2007) Algae as a biodiesel feedstock: a feasibility assessment, CM3 , Department of Chemical Engineering, Auburn University, USA. Vonshak, A. (1986). Laboratory techniques for the cultivation of microalgae. In: CRC Handbook of microalgal mass culture. Richmond A. (Ed.). CRC Press, Inc., Boca Raton, Florida, USA, pp 117-145. Weissman, J.C., (2007) Microalgae Biofuels - The Great Green Hope, 2007 Farm to Fuel Grants Program "A Novel Process for the Production of Biofuels and An imal Feed from Microalgae".

technical features


asset management

TOWARDS UNIFORM STANDARDS FOR ENGINEERING THERMOPLASTICS D W Evans Abstract As chemical resistant thermoplastic sheet increasingly supplants steel, stainless steel, fibreglass or similar materials in the chemical vessel, process equipment and tank building industry, correct material selection and design are critical to successful tank construction

Introduction Plastic tanks are becoming integral to many industrial processes - including water and waste water treatment- and an understanding of the technology involved in advanced thermoplastic types wi ll help optimise thei r performance. What needs to be understood at the outset is that the physical and chemical property of the plastic product is greatly dependent upon the widely varying polymer used.

Thermoplastics The main advantages of properly specified thermoplastics like polyethylene (HOPE), polypropylene (PP) and PVDF include: • Excellent chemical resistance • Predictable service - 20 years or more, depending on application • Light weight and easy to construct (butt or extrusion weldable) • Impact resistant, relatively inexpensive • Low maintenance • Very safe. However, because plastics often look the same to the untrained eye, many people new to plastics technology presume that they all function in the same way and offer similar performance over time. Th is is a fundamental mistake - and one that can not only lead to design fai lure, but, in the worst instances, profound safety issues. For example, with polyethylene the properties are primarily determined by density, molecular weight and molecular weight distribution. Higher density

Plastic tank being fabricated. (higher crystallinity) increases tensile strength, rigidity, hardness, solvent resistance and permeation to gases. With this comes a lower impact strength, transparency and stress crack resistance. Whereas increasing molecular weight increases impact and tensile strength, elongation at break and stress crack resistance. The variants in HOPE are immense, broad molecular weight distribution grades are easier to process and this is reflected in market price, but the properties required for long term serviceabil ity are not there. Organisations such as Basel! have developed processes that have given rise to so-called third generation materials, the bimodal molecular weight distribution polymers. Special process design results

Correct materials and design are critical to successful tank construction.

in a blend of short and long chained molecules optimising the opposed properties of toughness and rigidity into the one polymer. HOPE grades such as Polystone 300, a PESO style of polyethylene, are products of this bimodal technology. Further enhancements to the polymer in recent years have given rise to the PE100 grade (Polystone PG100) that is remarkable in its excellent combination of toughness and rigidity. Th is results in additional advantages of high creep resistance, high resistance to slow and rapid crack propagation, good weldabi lity and resistance to aggressive media. The situation is exactly the reverse for Low Density Polyethylene, utilised in roto-moulding. This has lower crystallinity, leading to a lower elastic modulus and hardness along with lower ultimate strength. To pass temperature and corrosion tests, stabilisation systems are also added. Why does it matter? Because knowing the physical characteristics of the plastic

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asset management Observations in the field with specialised tasks often highlight t hat the material/ technique used is sometimes not even remotely appropriate - and could lead to catastrophic failure, in the worst instance death. Upon examination knowledgeable engineering content appeared to be zero. There are numerous examples, such as sodium hypochlorite (bleach), acids and alkalis, being stored in roto-mou lded tanks which, by definition, lack the molecular length and st rength to do the job. They have indeterminate hoop strength and lack Environmental Stress Crack Resistance necessary for such applications.

Towards an Official Standard The current lack of an Australian Standard for thermoplastic tanks leaves us well short with world's best practice. involved and having a means of testing, allows you to: â&#x20AC;˘ Match the characteristics of the thermoplastic with the task they are being asked to perform, especially the chemical, its concentration and temperature with which they will come into contact, be it a chemical solution, black water, grey water, or potable water. â&#x20AC;˘ Then build the tanks to a specification - an internationally reliable standard from which you can calcu late the ideal materials to use, eliminating otherwise unforeseen safety issues and confidently predict lifespan. You can thus arrive at a known performance outcome. Why is this important? Because it is obvious that, wh ile there is wide general awareness throughout Australasia of the benefits of plastics for tank construction, there is also a considerable need for education. Knowledgeable engineers specifying tanks for applications would know, for example, that pipe grade polyethylene (PE 100 HOPE sheet) is one of the ideal materials for chem ical engineering and tank building. The material offers superior, long term strength, with exceptional weld strength, superior chemical resistance, exceptional UV stability and advanced environmental stress cracking resistance - up to 100 times better than standard HOPE. Alternatively, for inside use, or under cover applications, polypropylene (PPH) or, for sodium hypochlorite (bleach), PVC sheet shou ld be considered.

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'Dotmar EPP' is currently working with fabricators, end users and specifiers to develop an outline for an official Standard for Australia and New Zealand that reflects world's best standard, such as the British Standard BS EN 12573 and German DVS 2205. Using such a Standard involves relatively complex calculations, but this has been simplified through the 'RITA' (Roehling Integrated Tank Assist) program, introduced to Australia and New Zealand by 'Dotmar EPP' . 'RITA' incorporates 21st Century advances in thermoplastic engineering and design, now being widely adopted in Europe. The program - developed in conjunction with the Technical Approvals Institute in Germany in accordance with DVS stri ngent guidelines - streamlines calculation for design and fabrication technique, enabling maximisation of the benefits found in PE and PP, with a proven predicable method for service life under the influence of stress, corrosive chemicals and high temperature.

As an industry leader, 'Dotmar EPP' is also actively participating in the education of tank construction, especially welding, with schools for Fabricators around Australia. These incorporate practical and theoretical tests on fabrication techniques, how to weld and why to weld. Classes of up to 30 are also taught how to test to ensure a known end result, so that safety is built into their outcome. The aim is fabrication by Australian welders trained and certified to German st andards and using state-of-the-art PLC-controlled sheet weldi ng machines. Thus the target is a continuous line of quality assurance according to IS09001 that includes the resin supplier, sheet manufacturer, sheet suppli er and the fabricator with the ability to incorporate, where required, complementary metal products such as mild steel, stainless steel, aluminium or FRP to Australian structural standards, including AS3990, AS 4100, AS 1664 (aluminium) and BS4994 (FRP). But further work remains to be done. Advances towards uniform standards are increasingly important as engineering thermoplastics play an increasingly important role in enhancing the efficiency and reliabi lity of industrial, water and waste water infrastructures.

The Author David Evans (M Mgt, Dip Chem) david.evans@dotmar.com.au is Business Development Manager for thermoplastics engineering specialists, Dotmar EPP, North Ryde, NSW. He has 40 years experience in thermoplastics and related fields.

It has been designed by professional engineers utilising the standards BS EN 12573 and DVS2205 or in conjunction with advanced Finite Element Analysis techniques specifically tailored for plastics. Test results for periods exceeding 50 years are not yet available because PE, PP or PVDF have not been around that long . However, a relationship between mechanical stress and the exposure time to stress at given temperatures has been proved.

technical features

Profile for australianwater

Water Journal November 2009  

Water Journal November 2009