Water Journal May 2008

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Journal of the Australian Water Association

Volume 35 No 3 May 2008

OPINION AND INDUSTRY NEWS OPINION Water Availability and Cost DBarnes, President, AWA Alphabet Soup TMollenkopf, CE, AWA My Point of View Elizabeth Nosworthy, Choir, Queensland Water Commission 2008 International Year of Sanitation Nick Apostolidis, Director, GH D Obituary - Peter Cullen CROSSCURRENT National, International, States, Industry, People in the News AWA NEWS

20

NATIONAL SPECIALIST NETWORKS

26

YOUNG WATER PROFESSIONALS

30

AWA EVENTS CALENDAR

32

AWA MEMBERSHIP NEWS

32

4

s 6 10 12 14

PROFESSIONAL DEVELOPMENT AWA MASTER CLASSES

34

CONFERENCE REPORTS

36

CAPACITY DEVELOPMENT

GLeslie, WSAA

46

Report by EA(Bob) Swinton

S2

TMatthews, GFender

S8

WRobinson, TFerrero, DSweeting

68

Compiled by EA (Bob) Swinton

78

GVKorshin, CWKChow, MDrikos

83

GPymon, AForster-Knight

88

TJ Hurse, POchre

94

TECHNICAL FEATURES (I·,I indicates the paper has been refereed ) TRENCHLESS TECHNOLOGY The ASTT Conference Trenchless Technology in Sydney Water's Priority Sewerage Program Four sewerage schemes completed, with capital cost S230M Upper Blue Mountains Sewerage Scheme A world-first, pushing capabilities for a 2.4 km bore Ovoid Sewer Rehabilitation Two innovative rehabilitation techniques DISINFECTION [l] Real Time Monitoring of Disinfection By-products Using Differential UV Spectroscopy The difference in UV spectra between pre- and post-chlorination SCADA Hydroshare Internet-based automatic monitoring ODOUR MANAGEMENT ~ The Lost Art of Sewer Ventilation Predicting the performance of a sewer ventilation system is complex

WATER BUSINESS NEW PRODUCTS AND BUSINESS INFORMATION - SPECIAL FEATURE: INSTRUMENTATION ADVERTISERS' INDEX

99 112

OUR COVER The big HDD rig at Parsley Bay, drilling under thf Hawkesbury estuary to Dangar Island. One ofa number ofsuccessf11/ applications of trenchless technology by Sydney Water. See article on page 58. Photo courtesy ofSydney Water.

Journal of the Australian Water Association

Water

MAY 2008 1

~ AWA CONTACT DETAILS

•

..........

41/IIUU.Ui

w,.nt

'Promoting the sustainable management ofwater'

POSTAL ADDRESS PO Box 388, ARTARMON NSW 1570

EMAIL info@awa.asn.au WEBSITE www.awa.asn.au PRESIDENT David Barnes - president@awa.asn.au

CHIEF EXECUTIVE Tom Mollenkopf - cbeer@awa.asn.au

Journal of the Australian Water Association ISSN 0310-0367

Volume 35 No 3 May 2008

AWA WATER JOURNAL MISSION STATEMENT 'To provide a print ;ournol that interests and informs on water molters, Australian and international, covering technological, environmental, economic and social aspects, and to provide a repository of useful refereed papers.'

CHIEF OPERATIONS OFFICER Ian Jarman - ijarman@awa.asn.au

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DISCLAIMER Austra lian 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 AWA . To seek permission to reproduce Water Journal material email your req uest to: enyers@awa.osn.au

2 MAY 2008

Water

PUBLISH DATES Water Journal is published eight times per year: February, March, May, June, August, September, November and December.

EDITORIAL BOARD Chair: Frank RBishop Dr Bruce Anderson, HLA-Enviro Consultants; Terry Anderson,Consultant SEWL; Greg Finlayson, GHD; Dr Brian Labza, Vic Health; Professor Felicity Roddick, RMIT University; Mike Muntisov, GHD; David Power, Beca Consultants; Dr Ashok Sharma, CSIRO; and Bob Swinton, Technical Editor.

EDITORIAL SUBMISSIONS Water Journal invites editorial submissions for: Technical Papers and topical articles, Opinion, News, New Products and Business Information.

Acceptance of editorial submissions is subject to editorial board discretion.

Email your submissions to one of the following three categories: 1. TECHNICAL PAPERS AND FEATURES Bob Swinton, Technical Editor, Water Journal: bswinton@bigpond.net.au AND journal@awa.asn.au Papers of 3000-4000 words (allowing for graphics); or topical stories of up to 2,000 words. relating to all areas of the water cycle and water business.

Submissions ore tabled at monthly editorial board meetings and where appropriate are assigned to referees. Referee comments will be forwarded to the principal author for further action. See box on page 4 for more details.

2. OPINION, INDUSTRY NEWS, PROFESSIONAL DEVELOPMENT Edie Nyers, enyers@awa.asn.au Articles of 1000 words or less 3. WATER BUSINESS Brian Rault, National Sales & Advertising Manager, Hallmark Editions brion.roult@halledit.com.ou Water Business updates readers on new products and associated business news within the water sector.

ADVERTISING Brian Rault, National Sales & Advertising Manager, Hallmark Editions Tel: 61 3 8534 5014 (direct), 61 3 8534 5000 {switch), brion.rault@holledit.com.ou Advertisements ore included as an information service to readers and ore reviewed before publication to ensure relevance to the water environment and objectives of AWA. PURCHASING WATER JOURNAL Single issues available @ $12.50 plus postage and handling; email dwiesner@owa.asn.au BACK ISSUES Water Journal bock issues ore available to AWA members at www.awa.osn.au PUBLISHER Hallmark Editions, PO Box 84, Hampton, Victoria 3188 Tel: 61 3 8534 5000 Fax: 61 3 9530 8911 Email: hallmark.editions@halledit.com.ou

Journal of the Australian Water Association

SKILLS SHORTAGES IN THE URBAN WATER INDUSTRY G Leslie This short article is based on the WSAA Occasional Paper 21 Background

14%

Water Services Association of Australia (WSM) is the peak body of the Australian urban water industry and has offices in Melbourne and Sydney. Its 30 members and 31 associate members provide water and wastewater services to approximately 16 million Australians and many of Australia's largest industrial and commercial enterprises.

WSM was formed in 1995 to provide a forum for debate on issues of importance to the urban water industry and to be a focal point for commun icating the industry's views. WSM provides a national focus for the provision of information on the urban water industry for all interested parties. The Association aims to encourage industry cooperation to improve the water industry's productivity and performance and to ensure the regulatory environment adequately serves the community interest.

In keepi ng with its purpose the WSM Board considered the topic of addressing the skills shortage in the urban water industry as one of the highest priorities to be addressed by the Associatio n in the 2007/08 Business Plan.

As a result the consultant Infohrm Pry Led, based in Queensland, was commissioned to conduct stage 1 of a 2 stage project.

Stage One of the project used both qualitative and quantitative survey techniques to better understand the extent of the skills shortage in the urban water industry. T his survey work also explored the skills needs of the industry in the future and, in the context of current skill shortages in the industry, the gaps between the skills available and the skills required.

Stage Two will explore how the industry can cake the outputs from Stage One to assist it in workforce planning and how chis challenge could be taken in a holistic manner. T he Australian Water Association will cake responsibility for the next stage of the project and manage it to its ul timate conclusion. WSM will remain closely aligned and committed to the project.

46 MAY 2008 Water

- -----10.7%

12%

9.4%

10% 8% 6%

6.u~10

-----~

13.3%

7 .3%

6.3%

4% 2% 0%

L-

2009

Scenario 1=

2017

2012

nd (:dieted chang: _ -

scenario 2 demand (Unplanned change)

Figure 1. Estimated Increase In Total Staff.

Discussion The approximate head count of all the WSM members that provide water and sewerage services is 19,500 fu ll-time equivalents. D ata was received fro m companies to a total of 1 1,300 employees, i.e. over 50% of all WSM M embers and qualifying Associates employees.

The data captured gives us a current state of play and the likely future needs of WSM members given two scenarios.

Scenario 1 is a predicted change scenario and reflects business and workforce implications that have been identified in each member's strategic business planning.

Scenario 2 is an unplanned change scenario where a number of extra variables are introduced. These relate to climate change, water pricing, the regulatory framework etc.

Current State of Play The Infohrm Group consults exclusively in the field of planning, measuring and reporting on human capital in organisations and established the Infohrm Benchmarking and reporting program in Australia in 1992. M uch of the workforce comparison data is taken from this benchmarking program.

Demographic profile The age d istribution of WSM members is more pronounced in the over 45 years age

Journal of the Australian Water Association

grouping than in the median age distribution of the general working population. 49.2% of the population is over 45 years old compared to 40.2% in the 2007 Info hrm benchmark.

WSM members have signifi cantly more tenure than the working population as 25% of WSM members' staff have greater than 20 years experience with the one organisation. This compares with an insignificant number in the general working population. The average retirement age is 62.5 years.

The gender balance is 73%/27% in favour of males. Members employ 93.4% full-rime staff and 6.6% part-time staff.

The principal job fam ilies are, Business Support (39%), Water Industry Operators (18%), Professional Engineers (13%) and Managers 10% .

Water Industry O perators include Construction and Maintenance workers (59%), Plant Operators Waste Water (25%) and Plant Operator Water (16%) .

Of the Professional Engineers, 70% are C ivil Engineers, 12% are Environmental Engineers and 8% are Process/Chemical Engineers.

Skills profile The skills profile of the Urban Water Industry indicates that the Industry Knowledge and T echnical skills are generally adequate and there are programs

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in place to manage rhe current businesses.

In rhe area of people and business skills there are identified deficiencies in leadership in rhe Mechanical, Electrical and Environmental Engineers, Strategic Thinking and Business planning ar Environmental Engineer and Environmental Para Professional (Scientific level).

12% will have chosen another career path therefore leaving the water industry all together. The rest will leave their current positions but are expected to have different jobs or be promoted within the water industry (refer Figure 2).

100% 90% 80% 70% 60% 50%

These fi gures do not rake into consideration the anticipated growth in demand.

10I

40%

71 The future demands are many. In 30% Industry Knowledge there will be a Gap Analysis requirement for skills or training in 20% Coupled with anricipared plant operating processes, water retirements and leakage, the gap 10% quality standards and environmental between supply and demand sustainability. Technical skills will 0% widens quite significantly. The 2017 Current 2009 2012 have to be further developed in most likely combination is Environmental Engineering, 0 Net Suoolv • R1tsion,11ioM. Chum D Reslanation!I • Leakaoft D Ret1Mment11 Scenario 1 with a 20% leakage developments in technology and over 10 years. If chis is rhe case science and process technology. There then the predicted gap in all job Figure 2.

Estimated Progress of Current Employees. is a need to build relationships and roles char will leave the water cultural awareness, and project industry by 2009 will be 16% management skills across all growing ro 44.3% in 2017, as disciplines of engineering. Managers will is a lack of employee exit data with regard shown in Figure 3. need ro develop better strategic thinking to leakage and so 20 % was chosen as the When combined with the industry churn and business planning skills. 'best guess' drawn from industry figures the expected requirement for staff in experience.

Future Projections to 2017 2009 will be 31% growing to 9 1.3% by The labour supply data used the most 2017.

Demand likely Scenario and again assumes a 20% Outcomes Labour demand has been forecasred in leakage. Sydney Water represents Figure 1 using the 2 scenarios described approximately 16% of the survey Clearly the report demonstrates that there earlier: population and has a significantly lower is a skills shortage in the urban water resignation and retirement rare rhan the • Scenario 1 - Predicted change forecasts industry. rest of rhe population (about 4%). so rhar by rhe end of 2009, there will be a In terms of rhe percentage requirement Therefore for the purposes of the likely demand of 6.3% in staff levels, by job role of staff required to be replaced following,Sydney Water data has been growing to 7.3% by 2017 from current over the next 10 years, ten roles are the excluded. levels. most critical, as shown in Table I. The survey, as shown in Figure 2, • Scenario 2 - would have a demand of The workforce skills requirement indicates that by December 2009, 25% of 10.7% ro 13.3% in 2017. between now and December 2009 indicates current staff will have left their current role rhar 25% of all existing staff will have to be Supply in the water industry, by 2012 rhar number replaced. In terms of pure numbers of staff On the supply side a 20% leakage has been grows to 51% and by 2017, 84% will have that will be required the following table factored in. The leakage is defined as left their current employment. However ir represents the top 10 J ob Families. people who leave the water industry to join should be no red that by 2017, 25% of the a different career path, (e.g. mining) . There surveyed population will have retired and

Table 1. The Ten M ost C ritica l Job Roles.

20%

13.3%

1c~o--=--=- =-~-=- ~::~::~:•

0

9.4% ~--------1]~/c_-7C: 6.0% - - - - - - --fi!:.3%• - -

10%

Job Role

7.3%

0%

Professional Chemists

107% 96%

Mechanical Engineer

80%

Electrical Engineers

-10% -10% -20%

Environmental Paraprofessional (Scientific)

-19% -30% -37%

-40% 2009

....... Scenario 1 demand (Predicted change)

2012

2017

- - Scenario 2 demand (Unplanned change)

Supply (20% leakage+ retirements)

Civil Paraprofessional Plant Operator - Waste W ater Environmental Paraprofessional (Engineering) Microbiologist M echanical Paraprofessional

Figure 3. Predicted Gap Between Supply and Demand.

48 MAY 2008

Water

Journal of the Australian Water Association

Most Likely Gap by 2017

Electrical Tradesperson

64.3% 63% 61% 57% 47% 47% 47%

Table 2 Job Families

Most Likely Gap by 2017

Business Support Paraprofessional

1,792

Business Support Professional

1,284

Construction & Ma intenance - Water

863

Civil Engineer

822

Mechan ical Tradesperson

638

Plant Operator - Waste Water

537 528 427 278 207

Operational Manager Civil Pa raprofessional Plant Operator - W ater Corporate Manager

Issues There is no doubt chat che survey reveals chat there is a shore term need fo r a range o f job roles and chat some areas are more critical than ochers. The p rincipal issue is chat in the shore term there will be a great demand o n water uciliries to recruit and retain staff.

25% of WSM member's staff have over 20 years tenure with their respective o rganisations and it is likely char all of these will reti re within rhe next 10 years. This highlights the potential for knowledge loss co rhe ind ust ry. Of particular concern will be the loss of Plant Operators in Water and Waste Water. Many regional water utilities have aging infrastructure rhac is operating within its environmental compliance levels mainly due to the knowledge of the staff char operate chem. Knowledge retention, mentoring of new staff and inter-company secondments muse be a pare of any overall skills management plan.

While the anticipated overall forecas ced turnover to 2017 is at present 84% of current staff, the issue will be char 37% of chose staff will be lose to the water industry.

Based o n these fig ures a replenishment requirement of 44.3% in new staff to the water industry will be needed. On current WSM Members staff numbers chat would equate to 8,638 people. Even by December 2009, rhe requ irement is likely to be 3,120. le should be remembered chat the data p resented here represents the major urban water urilicies. I r does nor include regional water u tilit ies, the irrigation secror, local governmen t sector (storm water ere), rhe construction industry associated with rhe water ind ustry or environ mental consultancies. In reality the requirement for staff in the water industry could be 2 or 3 rimes h igher rhan rhe data presented in chis paper.

T he Australian Water Association is currently working to begin the task of raking a whole of water indust ry approach to addressing the skills shortages.

This is not a small cask and will require the participation and commitment from all o rganisations and individuals char participate in chis o ne of the most viral of industries.

The Author Grant Leslie is Program Manager, Water Services Association of Australia, 0 2 9290 3655, gran r. leslie@wsaa.asn.au

THE ASTT CONFERENCE MARCH 2008 Report by EA (Bob) Swinton Reticulation means pipes, pipes, pipes, and the business is growing for a number of reasons. One is the rapid expansion of potable water supply and sewerage reticulation as che population increases, second, the vital need to reduce leakage and third, the increasing emphasis on recycling, fourth, new sewerage connections to central treatment plants to protect the environment, and last but not least, the need to check and where necessary, rehabilitate old sewers, some of them, in our inner suburbs, over 100 years old. Add to these the upgrading of old irrigation channel systems.

Most pipes are still laid in open cut, but increasing numbers of projects are raking advantage of the relatively new and rapidly developing techniques of horizontal directional drilling (HDD) and microtunnelling. Bur 'rrenchless technology' also covers high-tech CCTV inspections, in situ repairs and rel ining, and the 7th National Conference of the Australian Society of Trenchless Technology (ASTf) focused half the papers on such asset management topics.

T he conference was held in Sydney's Bicentennial (Olympic ) Park, a very pleasant venue, with the exhibition expanded far beyond the capacity of the conference centre, into not only a huge marquee, but also a series of smaller marquees in order to cope with the 60 companies keen to exhibit. ASTT was fi rst formed at a conference in 1990, when the business was still a novelty. However it pleased this reporter to see the Pezzimenti Laserbore booth. I saw it for the firs t time nearly twenty years previously at an AWA conference in Perth. Gilbert and Aurelio were probably the first to introduce HDD to Australia. Gilbert told me he would never forget the Perch conference. He and his brother finish ed a drilling project in Melbourne, cleaned and packed their gear onto a truck and drove non-stop across the Nullarbor, arriving in Perth to display it the day the exhibition opened.

Menno Henneveld, President of ASTT, in his opening address, said that back in 1990, the business in Australia probably totalled some $20M a year. Now it is commonplace, though still in novative, and totals over $1000 M per year. Of the 350 delegates and exhibitors he welcomed a 52 MAY 2008

water

Investigation, evaluation of concepts

Influence on costs

--1

Contractor

-costs Project phase Conceptual engineering

Delailed engineering

Execution of works

Figure 1. Stages of a project and potential for cost saving.

dozen from overseas. (Australia has hosted two international TT conferences, the last being in Brisbane in 2006, reported in Water February 2007).

T he keynote address was from James Thomson, from UK, who performed his first pipe-j acking project in the Barbados in 1958, and introduced the concept to Australia in 1970. He reviewed the history of tunnelling for water supply, from tunnels built in Oman some 5000 years ago, through to the Romans, rhen, 1700 years later, the impact of the industrial revolution. Brunel built his fa mous tunnel under the Thames using a rectangular shield, but the first true technology dates froml901 , when the Price Mechanical Shield, the first T BM, was developed.

Sewers were installed by cunnels, but since the face was excavated by pick and shovel, the minimum diameter was 2 metres, and the work was extremely hazardous.

Pipe-jacking started in 1958, and has steadily become more and more sophisticated, with significant inputs from Japan, Germany and USA. The main applications for jacked pipes are fo r gravity sewers, though the original application, for crossings of roads, railways or rivers, still remains a large market.

In his keynote and in a later paper he stressed the importance of allowing more budget for the conceptual stage. Extending this budget from, say 2% to 3%, could save millions, as illustrated in Figure 1.

T his has been hammered home by experienced engineers for all construction projects but is even more important for underground work where the relative

Journal of the Australian Water Association

unknowns of geology and water cable predominate. A client's accountants are driven by che shore-term, but requiring an engi neer to actually quantify how much saving he will obtain by investing more money at the conceptual stage is impossible.

For underground work, risk is higher than for most engineering. Proper risk allocarion is viral, and management of risk should be based on identification and evaluation, not on the lawyers setting out to pass the buck to the ocher parties.

Many fea r chat designing a sewer scheme using micro-tunnelling may expose engineers to additional liability. Some local government clients feel chat restricting che number of contractors able to bid will expose them to public criticism, and conventional trenching allows any number, even che inexperienced, to bid. (It is unlikely chat even the client would apply these cri teria to che choice of a heart surgeon).

T he choice of crenchless over conventional open-cue is increasi ngly being driven by che externalities. A recent UK WIR report estimates chat the social cost of open-cue is some three times the accual contract price, and another 10% could be added for third party damages. T he carbon foo tprint is also beginning co be recogn ised.

An analysis of a recent contract in Berlin noted chat TT had reduced the number of truckloads through the city by 148,000.

However, the bulk of HDD and microcunnelling is done on a smaller scale and papers illustrated the benefits for customer connections in suburban side streets.

A major facto r in such urban environments, before drilling, is knowing

technical teatures

what else is there beneath the roadway and there were many devices on display using geo-magnetics and ground-penetrating radar.

Professor Ian Moore, of Q ueens University, Canada, still speaking with a distinct Aussie accent, gave an erudite presentation on che modes of collapse of concrete sewers. Leakage creates voids in the surrounding ground, and underground pressure, the unsupported pipe distorts into an ellipse, and cracks along the spring line.

The question is, when the sewer is relined, how will the lining, conforming to the distorted shape of the host pipe, stand up to the continued forces, and he employed both structural analysis and full-scale experiments to assist its design.

Paul N icholas, of the Robbins Company, outlined the fu ll gamut of trenchless technology which is being employed in the Western Corridor and Southern Regional projects in SE Q ueensland. Over 300 km of pipeline and over 100 trench less crossings are involved.

The majority of the pipelines will be constructed by open-cut, parallel to roads and railways, but crossing of roads, railways and some rivers will be completed using pipe-jacking and some HOD. He reviewed the various methods: auger bo ring, microtunnell ing, tunnel boring and HOD .

Figure 2. The pipe thruster in action, w ith the bori ng machine, ahead of the pipeline, about to commence drilling. to the cutter. To steer an SBU-M, the operator utilises a laser and high-pressure articulation cylinders which are adj usted every 3-6m. They are suitable for hard rock and mixed ground above the water table, or below the water table if permeability is limited.

The use of the SBU-A and SBU-M in Q ueensland is a first in Australia, and where applicable they are proving to be, overall , 30-50% cheaper than microtunnell ing.

Auger boring machines are adequate for soils, sands and gravels with little water pressure, for ho rizontal d rives less than 150 min length. The larger man-entry tunnel-boring machines have been cutting harder and harder rock as manufacture rs have gained knowledge of cutter tech nology.

Micro-tunnelling systems are the most commonly used in Australia. They are the most techno logically advanced and h ighest costing, and suit unstable ground below the water table. Very long, accurate, complex drives with curves are possible. Practical limits for transport of the pipes themselves limit them to less than 3 m in d iameter.

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Small boring units (SBU) incorporate 50 years of hard rock cutting technology. They cut a diameter slightly larger than the casing, and required the development of smaller cutters, which enable bores of 290 mm down to 165 mm. Steering is accomplished by manually adjustable stabiliser pads. If accurately adjusted for the first 6-9 m of the drive the SBU-A will normally maintain direction in rock to a high degree of accuracy.

For long tunnels, the torque requirement to drive both the cutter and the auger which removes the spoil eventually becomes too high. A motorised unit, SBU-M, provides separate electrical or hydraulic power d irect

Perhaps the most recent innovation is the d irect pipe system engineered by the Hamburg-based engineering fi rm, de la Motte & Partner. M ichael Lubberger of Herrenknecht outlined its simplicity. The required length of pipeline is welded and supported on rollers behind the launch pit.

A microcunnelling machine is mounted in front of the pipeline and the pipe thruster clamps the pipeline on the outside so chat both together are pushed, stroke-wise at 5m intervals, into the ground. Figure 2

•

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www.citywater.com.au Journal of the Australian Water Association

water

MAY 2008 53

illustrates the thruster in action. The runnel is drilled slightly overdiameter and benconice slurry is used so chat the friction on the pipe is relatively minor. The direct installation of the pipeline allows for continuous drill-hole support preventing hole collapse.

Upon arrival in che target shaft, only the microcunneller and the connection pipes have co be disassembled; the installation of the produce pipeline in the ground is already completed. Feed and slurry lines as well as control, data and power cables are led through the pipeline on special roller assemblies; they can easily be removed from the pipeline using a rope winch.

The system made its debut in a crossing of the Rhine near Worms in September 2007. A 1200 mm casing was pushed beneath the river for 464 m and will carry a 600 mm water pipe and various power and communication ducts. On average, a 90 m long pipe section was jacked per day; with average thrust forces of only 70 to 80c, nearly all of which was delivered co the boring face. The system is not restricted to steel pipes, PE pipes have also been installed.

A keynote address by Stephen Loneragan, Managing Director of HDD in the A J Lucas Group, speculated on the future fo r accurate long-distance drilling. He extrapolated his talk from the slide he presented at the International Conference in November 2006, and showed just how fast the ab ility of the industry was developing.

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In 1990 the first truly directional rig in Australia drove 180 m accurately. In 2007 the Blue Mountains project fo r Sydney Water drove 2400 m co intersect with an existing sewer 70m below the surface. From 450 mm being regarded as big, there are now 1.4 m diameter pipes being pulled into drilled holes.

T he length of a drive is determined by friction on the drill seem and by the danger of buckling as it transmits the torque co the drill bit.

Friction as well as pressure balance was previously controlled just by adding benconice to the mud, but nowadays it involves high-tech fluid engineering, adjusting the rheology and density of the mud system by on-sire laboratory cescs, and using additives such as hollow glass spheres co adjust density. He noted chat for a 1000 m drive, it would cake three hours for the mud to travel from the drill bit co the surface fo r analysis.

For long drives, buckling is minimised by the slider system, which shifts the torque fu rther down. Locking-up can be avoided by ' rocking and rolling'. High performance wedge threads on the pipe sering transmit four times the conventional torque without jamming or unscrewing on the reverse twist.

Drill-bit location technology is being driven by the demands of the oil and gas industries, and now for the coal-seam gas fields, where multiple laterals from a main hole are accurately located into narrow seams. Directional accuracy depends on new geo- magnecics for locating the position and depth of the drill head, and by rotary steering systems a long way ahead of (and more expensive than) the chisel bit.

More and more, operator judgement is being improved by computer control. It is not unusual for an oil drill to travel 10-11 km whereas in HDD we have only achieved a quarter of chis length, albeit with different criteria. For big projects logging of the rig's parameters can be transmitted by satellite in real-time back co head-office for instant supervision and control.

He concluded by saying chat with such high technology the contract method of lump-sum tender was our-of-dace. The designer and the drill engineer muse work together in the co ncept phase, to develop creative answers for a proj ect. He made a plea chat consultants and designers should not be afraid to adopt new technologies, but not co rely on the salesman, ensure chat there is good engineering back-up.

In the asset management stream, Lance H orlyck, sewer assessment consultant, asked the question "do we really know what we don' t know?" leading into a discussion of the capabilities of CCTV for

54 MAY 2008

Water

Journal of the Australian W ater Association

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technical features

trenchless technology inspection, and the subsequent assessment of whether, or when, action must be taken, underlining chat 'criticality' of effect was a dominant facto r. He note that sheer age was not the significant criterion. Pipeline collapse is never a steady deterioration, it is nearly always triggered by an event.

CCTV tractors were highly featured in the exhibition, and Barry Holloway of the Water Corporation and Steve Apeldorn of Project Max, NZ gave thorough reviews of the techniques which can be used, and the difficulties of interpretation, particularly for the various types of pipe and sewer which have been installed over the years. Barry noted the use of sonar on a tractor for inspection below the water line. Steve noted the technique for assessing the deformation of both rigid and flexible pipes. A ring oflaser light is projected onto the inner surface of the pipe and photographed, then compared with the original circular profile. He mentioned a new (and expensive) CCTV camera, Panoramo, from Germany, by IBAK, (who were the first in CCTV field 60 years ago).

As it tracks at 0.35 m/sec through pipeline or sewer, 360° stereo photos are taken by xenon flash. All data is downloaded continuously onto a computer and can be examined live, or re-examined, zoomed, unrolled, measured, in

the comfort of the office. Veolia Network Services have purchased one and Sydney Water is to run a trial later this year.

Once the condition has been assessed comes the decision, whether, when and how to rehabilitate. Numerous techniques for CIPP were on display in the exhibition and Scott Pearson of Insicuform o uclined their new iPlus Infusion cube. Ir requires a smaller amount of equipment, a smaller footprint and being steam-cured uses only 2% of the water and 50% of the energy chat traditional hoc water curing would use.

Interflow demonstrated spiral relining, similar to RibLoc, fo r small diameter pipes, and a sl ick technique for sealing lateral connections.

A 'next generation' rapid-setting polymeric spray lining, Copon Hycoce 169HB, has been developed by 3M E.Wood in UK for water mains with corrosion or localised damage. l e is applied by a spray head, with a minimum thickness of 3mm.

Initial setting rime is one minute and the pipeline can be returned to service in an hour. Tests by Bradford University show char it confers structural strength and could extend pipe life by 50 years. IT has been used by numerous authorities since 2004.

CLM T renchless will be the first certified

licensee for the delivery of the spray lining system in Australia.

For repair of corroded water service connections to residences, Utility Services offers InnaTube. Made of PET it is readily threaded into the cleaned pipe, softened by hot water, then expanded into a tight fie by 5.5 bar pressure, all in one to three hours.

Since 2004 it has been extensively used by Melbourne's retailers, and the company is preparing for trials in USA. Three papers trialling tech nologies for rehabilitation of the very old brick-lined ovoid sewers in our inner cities were very interesting, and are summarised in a separate article in this issue. Two papers summarising Sydney Water's experience in applying trenchless technology to their Priority Sewerage Program are also published in this issue.

Various case studies of trenchless technology, both large and small diameter, each had lessons for other pracci cioners and are contained in the Conference CD. Limited numbers of the CD, with the 35 papers, are available from the conference o rganisers, Great Southern Press, GPO Box 4967, Melbourne 200 1 (who publish the official ASTT journal, Trenchless Australia) The cost is $99 including GST and mailing, email query@gs-press.com.au.

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56 MAY 2008

water

Journal of the Australian Water Association

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technical features

trenchless technology

TRENCHLESS TECHNOLOGY IN SYDNEY WATER'SPRIORITY SEWERAGE PROGRAM T Matthews, G Fender Abstract In the course of the Priority Sewerage Program (PS P) Sydney Water Corporation (SWC) is using a five-partner alliance to construct back-log sewerage in environmentally sensitive areas. This paper describes how the use of crenchless technologies has allowed rhe Alliance to achieve ou tstanding outcomes in the program objectives and summarises fou r schemes completed to dace.

Introduction Sydney Water Corporation provides sewerage services to more than four million customers in the Sydney, Illawarra and Blue Mountains regions. I n September 2002, SWC engaged in an alliance with external compan ies comprising Mon tgo mery Watson Harza, John Holland, U nited Group and Manidis Robercs to deliver the remainder of Stage 1 of the Priority Sewerage Program.

I n order for the program delivered by the Alliance co be considered a success, che following objectives had to be achieved: • Safety - no harm to chose delivering or affected by che program • Schedule - meet all targets and milestones on time without compromising ocher objectives • Cose - NOT TO exceed cost targets across program and projects whilst d elivering o utstanding resulcs • Environment - gen uine and demonstrated sensitivity to be integrated into the delivery of all p roject activities • Community - live the "customer first" approach through consultation and responsiveness • Quality - fir for purpose and righ t the first time.

The Alliance Sydney Water has been servicing what was known as "backlog sewerage" for several decades and as its own engineering base declined, it was recognised chat there was a This is an edited version of a presentation co the 7th ASTT Trenchless Technology Conference, Sydney, March 2008.

58 MAY 2008 Water

need to either resource-up or adopt new methods of delivering projects. In mid to lace 20 02, a number of common problems were identified in the delivery process, such as: • Cose-per-property of the schemes delivered was increasing • Cycle time and upfront costs to deliver the schemes from concept to completion were becoming significan tly greater. The processes of environmental assessment, consulcacion, sub mission of documentation and approval had been known to cake four or more years.

• Sewerage work, i.e. inserting infrastructure into a b uilc up environment, was most invasive for customers

• Ir was difficult to develop a safe working culrure with contractors who had an itinerant workforce with liccle or no experience in sewering established communities.

• The lessons learnt were nor transferred from one scheme to the next, unless it was by the same contractor. There was discon tinuicy in staffing.

• U nreasonable allocation of risk between SWC (as client) and contractors had ensured chat both parries took defensive positions to achieve an outcome, so stifling collaboration and innovation.

SWC opted to do two th ings, the first being to develop knowledge and capab ility in alternative sewerage technologies and the second was use a "pure-alliance" delivery method for the remainder of Stage 1, based on previous alliancing experience. We found chat when you bring people with the righ t capabilities and attitudes together into a collabo rative environment where their interests are aligned, there is almost no challenge chat cannot be overcome.

Specifically SWC chose to use an alliance because: • It would enable better, more informed strategic decisions to be made about the program on aspects such as : - allocat ion of resources and priorities across the various schemes - consistency of standards across the program - consistency in dealing with the community

Journal of the Australian Water Association

- purchasi ng/procurement policies/ procedures - an interface with on-going Sydney Water operations personnel

• An all iance could achieve the kind of breakthroughs char would be needed co exceed the stated program objectives.

• The lessons learned in the early schemes could be incorporated into the lacer schemes • Professional liaison with che community would significantly enhance Sydney Water's stand ing with chose affected by che program.

• T he people on the Integrated Program Team, including Sydney Water personnel, were more likely co acquire new skills, derive great jo b satisfact ion and develop relationships chat would endure beyond the program.

• An alliance p rovided the basis fo r a seamless solution to handle the transition from planning through design to delivery and handover, without rhe usual contractual interfaces. It also solved a staffing and logistics issue for SWC. The Alliance Partners with SWC are Montgomery Warson Harza, (design engineers) Joh n Holland (construct ion), United Group (Mand E design and installation) and Manidis Roberts (Commu nity Consultation and environ mental).

In summary, servicing unsewered co mmu nities has required careful planning to identify and adopt the most appropriate system design chat results in the lowest life cycle cost. An alliance provides che greatest confidence of a best value outcome for Sydney Water, the commun ity and o cher stakeholders.

Pressure Sewers and HOD Running concurrently with the above initiative, SWC investigated a number of alternative technologies for providing sewerage to developed and built up areas, with the outcome chat pressure sewerage

Four sewerage schemes completed, with capital cost$230M

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was the most promising available technology.

After calling for expressions of interest from the marketplace, a Strategic Supply and Services Agreement (SSSA) was signed with a consortium that could provide proven equipment, with backup in terms of system design, training and ongoing service.

At that rime there was no Australian Standard or Water Services Association of Australia (WSM) Code of Practice for Pressure Sewerage Systems (PSS), so SWC's engineers prepared a series of "Interim Guidelines" fo r reticulation networks and for on-property equipment, which enabled the Alliance to commence work on its first scheme at Northern Towns, without delay.

Concept design of the networks and guidance in preparing property works, known as "H omeplans", was provided through SWC's SSSA contract, which was the start of the "learning" process for the Alliance and for SWC in rhe practical application of PSS. Looking back to early 2003, it is doubtful that the Northern Towns sewerage scheme co uld have been delivered effectively using PSS in any other contractual arrangement than through the flex ible and collaborative environment of an alliance.

While pressure sewerage has emerged as a cost-effective solution to backlog areas that were hitherto difficult to service, it has also been one of the drivers that has made trenchless methods attractive for reticulation delivery of pressure networks. Prior to this, the constraints of line and level for gravity works ruled out horizontal directional drilling in many instances.

T here are many pressure sewerage schemes now being constructed in metropolitan and non-metropolitan urban communities across Australia. Pressure sewerage requires the installation of a collection tank and grinder pump on each eligible property, allowing macerated sewage to be pumped through a lateral into a reticulated sewer pressure main and thence to an existing system, or to a treatment plant.

mm minimum, and the main reticulation is run in street frontages like a water main, generally down one side of the street.

This enables main runs of pipe and laterals into properties to be directionally drilled using relatively small track-mounted or truck-mounted rigs. However, for the schemes chat are described below, there was also the need for some quite long bores to be undertaken linking catchments by rising main or by inverted siphon in d ifficu lt terrain. There were also a number of creek and waterway crossings to be done.

The remainder of this paper will discuss some of the types of trenchless technology used in each of the schemes within the Program, citi ng the four completed schemes and the reasons fo r selecting the method employed. On all the schemes, a combination of both conventional and trenchless methods was used to best fit the situation.

Case Studies The Northern Towns The N orthern Towns scheme is actually located south of Sydney, about 24 km from Wollongong and includes the villages of Coalcliff, Stanwell Park, Stanwell T ops and Orford.

One of the principal reasons fo r abandoning gravity sewerage system was the presence of slip zones in Coalcliff. G ravity sewers might de-stabilise roads and steep terrain, should the restored trenches act as stormwater ducts during wet weather.

The other reason was chat Sydney Water wanted all sewage to be pumped to Cronulla Sewage T reatment Plant (STP) via a transfer system at H elensburgh that had limited additional capacity. Any system that had the potential for substantial increase in wet weather flows was unacceptable.

Consequently the Alliance decided to utilise pressure sewerage.

A considerable amount of the street reticulation and laterals into properties in all of the villages except Stanwell Tops, was executed by small HDD rigs, which typically installed pipelines in 200+ metre runs.

Because construction of pressure sewerage most often occurs in existing developed areas, where ground conditions permit, the water industry has adopted installation by trenchless methods to minimise disruption to the community and reduce spoil generation and restoration costs.

There were 11 incidences of "frac-our" of drilling mud, because of flaws in the strata and the shallow depth at which we were drilling. But in the main this was all manageable and lessons were learned on this scheme, to the benefit of later schemes.

This has been possible because the pressure lines are generally of small diameter (40 to 250 mm ID) HDPE material, not subject to being laid on grade like a gravity sewer, can be of shallow depth 450 to 600

Construction of the transfer main along the road from Stanwell Park to Orford was considered to be difficulc and costly due to the terrain, narrowness of the road system and constraints by local authorities. T hus, it

60 MAY 2008

Water

Journal of the Australian Water Association

was decided to install a rising main through the old disused Orford Railway Tunnel, which was constructed as a brick arch structure in about 1884, 1.47 km long.

However, because the tunnel was listed under the Heritage Act 1977 (NSW) and covered by one of the EIA Conditions of Approval, the Rail Safety Act 1992 (NSW), governed this work and we were not permitted to simply lay a pipe through rhe tunnel on cradles, nor fasten a pipe to the tunnel walls.

Various options were investigated to use this route, including excavation of the tunnel floor and open cut installation, however chis might lead to a runnel collapse. Initially, the method of pipe placement proposed was to directionally drill beneath the floo r of the tunnel from each end and to meet in the middle.

H owever, this was subsequently changed to drill from one direction to avoid working within the tunnel.

T he fl oor of the tunnel was mostly eroded sandstone with a central brick and sandstone block-covered drainage channel, over which ballast had originally been laid to bed the rail lines which had been removed in 1920. But over time, because the tunnel sloped at a grade of about 1 in 40 from Orford down to Stanwell Park, it became a d rainage track for seepage and surface flows, resulting in a build up of material at the Scanwell Park end up to two metres deep that had to be cleared to permit access.

Within 200 m of the southern end, at some stage around 1943, army demolition work had taken place (apparently to test the ability of the runnel to act as a storage area for military ordinance). To enable the tunnel to be opened up at a lacer date, chis damaged section was subsequently rectified by the internal construction of a reinforced concrete box culvert 3.2 m wide by 2.3 m high over a 13 m length.

In the event, a drill rig was set up at the lower Stanwell Park end of the tunnel, and in one drive the 250 mm diameter pilot hole was drilled a distance of 1,800 metres from one end of the tunnel to the other, and then beyond this to pass diagonally under the rail line, rising to emerge adjacent to the site of transfer pumping station SPS792. The bore was then back reamed to 375 mm diameter before a 225 mm ID SDR 11 PE 100 HDPE line was butt welded together in 450 m lengths at the upstream (Orford) end and pulled back through the bore as one operation. After installation the liner pipe was pressure tested before being connected up to the rest of the system.

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technical features

trenchless technology Jamberoo The village of Jamberoo is located in land from Bomba (south of Wollongong) in a q uiec rural valley setting, and comprises close to 400 residences with a main street containing the local bowling club, golf club, schools, hotel and a shopping centre. This environment caused the ream to decide on a pressure sewerage system.

Lessons had been learnt about the application of HDD for street mains and laterals into p roperties with the outcome that equipment was able to be set up at locations to minimise residents affected, and any one sec up was usually completed within rwo days. T h is minimised any nuisance impacts of noise and access.

Within properties, either a vertical soil auger or a coring bucket was used on a small rubber tracked excavator for the holding tank installation, as an alternative to backhoe or rock hammer. Beyond che built up area, the long discharge main from the village centre to the pumping station was installed by a mix of open trench and directional drilling, with H DD being used for creek crossings or where ch ere were iterns of significant heritage value.

Mulgoa, Wallacia and Silverdale This scheme provided a gravity sewerage service to three villages, which are linked by five sewage pu mping stations with long rising mains to transfer sewage fro m gravity catchments in Mulgoa, Wallacia and Silverdale, and from the old Warragamba SIP, which was later decommissioned.

One feature of chis scheme is chat it was che fi rst time that SWC adopted a modified standard fo r gravity sewerage to reduce infiltration by che use of plastic manholes, inspection shafts where human access was not required, and solvent jointed UPVC junctions and pipeline joints where possible.

Before the scheme commenced, SWC had geocech surveys conducted on all through routes for transfer mains and at all proposed sewage pumping station (SPS) sites, so that the methods of construction for individual and key pares of the work could be decided prior to target cost preparation.

In some cases trench less tech nology is the correct solu tion, in others it is not. For this scheme the majority of the gravity reticulation was delivered using conventional methods because of the nature of grou nd conditions, ease of access and the fact chat it required accurate placement of pipes to line and level. However there were two significant H OD bores undertaken, the effluent discharge line from the new treatment plane in Wallacia to the Warragamba River and che rising main from

62

MAY 2008

Water

che pumping station at the old Warragamba STP to the new plant. For this an ADWF of 4.5 Lis but PWWF of 35 Lis required DN250 SDRl 1 PElO0.

Several routes and construction methods for the rising main were investigated. These routes were: • Directional bore to balance rank or to cleared transmission easement: These options were variations o n the option ultimately adop ted, and both required much longer bores at a significant additional cost.

The option to drill direct to the balance tan k was the most direct horizontal alignment, however it passed directly beneath a farm dam and carried the slight risk of d raining this dam. • Two directional bores connecting at Megarricy's Creek Road above Megarrity's Creek: This option would have provided an operational facility to scour the rising main, a positive for Sydney Water operations.

However the option carried with it significant environmen tal and construction risk. For the bores to surface at Megarricy's Creek Road, there was a significant additional risk of leaking d rill fluids to the creek and the receiving Warragamba River.

Megarricy's Creek is usually dry with a rough terrain creating difficulty fo r drill fluid containment. Also, constructio n works being carried out by the Scace Department of Commerce for the Sydney Catchment Authority at the base of Megarricy's Creek would have caused significant logistical interference. • Trench down Megarricy's Creek Road and bore to the new SIP: This option would significantly d isturb Megarrity's Creek Road and the works by the Department of Commerce as well as create additional environmental risk asso ciated with open excavating as opposed to drilling.

In addition to this, the roadway had just been resurfaced and was known to contain a number of live water mains and underground power supply cables to a major water pumping station at che end of the road. Excavation of the roadway in rock berween the services, electrical pits and stormwater crossings would have been both difficult and expensive.

A tender was sought for drilling of the rising main. Three renderers suggested methods and one was selected wh ich minimised environmental impact and work required at river level.

T he first 170 m was open excavated at minimum depth through a small section of scrub along a cleared transmission easement, including the power supply to the proposed pump station. A 350 mm diameter bore was driven for a total of 900 m to run well

Journal of the Australian Water Association

under Megarrity's Creek (three 300 m lengths of the PE pipe were prepared, then pulled in, joining each section). The final 180 m was by open excavation along a crack within SWC's property, to a balance tank at the inlet to the new SI P. During the drive the contractor shutdown operations fo r six calendar days during the Easter long weekend. When che contractor attempted to restart the works he was unable to rotate the drill seem, the head being stuck at a distance of 682 m, and 57 m below surface level. Finally, after a three month period of trying to move the drill string the problem was identified. It appeared that che drill ing flu ids, which had previously been under p ressure, were relieved during the shutdown period and migrated back into the bore, encasing the head and drill sering.

After several weeks of flushing with water, and a re-evaluation of the specific gravity of the d rilling fl uid used, the head and string was loosened and che drilling con tinued.

Despite the delay of the bore, the scheme was completed on rime.

Brooklyn and Danger Island This sewerage scheme (BDI) whilst servicing che villages of Brooklyn (on the mainland) and Dangar Island (Figure 1) is part of a regional scheme which will also treat sewage from che Gosford City Council areas of Mooney Mooney and Cheero Point north of the Hawkesbury River, as well as picking up the NSW Department of Aging, Disability and Home Care (DADHC) hospital and nursing quarters at Peat Island.

Original plans for the BDI part of the scheme were for a gravity system with low lying sewers on water frontages, and a total of 13 sewage pumping stations to convey sewage to a treatment plant at the O ld Dairy site in Brooklyn.

T he system chat has just been commissioned in Brooklyn is a pressure sewerage system, with no sewage pumping stations, which conveys macerated sewage to a scare-of-the-art membrane bioreactor treatment plant at che Old Dairy site.

Street reticulation In keeping with usual practice, SWC had u ndertaken geocech nical studies for the main reticulation through routes and for the crossing to Dangar Island p rior to target cost preparation. It was found chat along the road reserves in Brooklyn where the reticulation mains would be laid there was a mixture of fill, some cobbles and clay.

Along Brooklyn Road a vehicle-mounted ground penetrating radar (GPR) field system, manufactured by the American company Geophysical Survey Systems, Inc., with an antenna freque ncy of 400 MHz,

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technical features

trenchless technology Dangar Island

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4

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Figure 1. Brooklyn and Dangar Island Sew erage Scheme. was used for rhe georechnical investigation.

The antenna was operated to one side of the roadway at approximately 4 km/hr.

For the minor side streets and on Dangar Island, a pushcart (Noggin Smart Cart) GPR system with an antenna frequency of 259 MHz at walking pace, was used. In both cases, there was a signal penetration depth of two to three metres. Location of the route features was given by DGPS in order to provide a longitudinal GPR profile, which was scaled to position and to depth assuming an average radar velocity within the subsurface materials of 0.1 metres per nanosecond.

In addition to chis, a series of I 6 bore logs were taken along the line of the survey for correlation purposes. In general, the GPR images showed variable conditions ranging from shallow rock at less than 1.5 m depth to no rock in evidence within several metres to surface level, areas of overburden ranging from coarse fi ll with a soil matrix and signifi cant gravel and cobble content, to very coarse fill with boulders to alluvium and colluvi um with coarse gravel, cobbles and boulders, and to finer grained soil with isolated boulders.

On Dangar Island, the conditions were similar, except that there was more rock at shallower depth below surface.

The variable subsurface conditions, most probably created by formation of rhe roadways, rhe sometimes shallow depth to rock and the p resence of cobbles and boulders, were difficult for HDD. Despite some early attempts being made over a twoweek period to use HDD from the STP sire

64

MAY 2008

Water

along Brooklyn Road, the nature of the subsurface conditions d efeated char initiative. As a result, the majority of the reticulation was installed by open trench, with HDD only being used for laterals under the road and into properties.

As the village of Brooklyn is only serviced by a narrow two lane road, any work along this access was subject to carefully worked traffic control, same day restoration and small machinery.

To add to this difficulty, the road was also rhe route for the main fibre optic cables to Newcastle, which were crossed a total of 96 times in a distance of about 4 km. The challenge of avoiding damage to the fibre optic cables resulted in site crews u tilising rhe services of contract underground service locators and becoming very fam iliar with rhe use of vacuum excavation as a tool to locate key services.

We were fortunate nor to damage any of the fibre optics. Unfortunately, we did b reak one of SWC's water mains where a car rear axle and other substantial parts buried beneath the main road misled our pipe locators, near what turned our to be an old cou ncil rubbish dump. This main was then repaired.

Bore between Parsley Bay and Dangar Island The major application of rrenchless technology was the connection pipe between Dangar Island and the mainland at Parsley Bay. Early investigations had ruled our jetting a trench in rhe silt laden floor of rhe river as

Journal of the Australian Water Association

there was a history of silt bed migration towards the downstream end of the estuary, which had caused Brooklyn Harbour to become so shallow as to restrict entry of any deep draft vessels unless periodic dredging occurred. There was concern char any pipe laid within a potentially moving silt bed would be fractured over a period of rime.

The ocher factor was char the Department of Primary Industry (Fisheries) wished to protect seagrass beds in the area between the island and rhe mainland, and would nor permit any open trench methods to be used at rhe rime of seeking p roject approval.

Added to which ir would have been almost impossible to contain the silt plume originating from any dredging operation in the tidal estuary.

So rhe p referred option char we investigated was a deep bore in bedrock from Parsley Bay to the island. The georechnical studies included a marine reflection study to identify the bedrock profile, an underwater seismic refraction study near each foreshore for about 250 m; a vertical borehole to 80 m deep at Parsely Bay end of the proposed bore; and surface fea ture mapping at the launch site and along the road at the exit sire on rhe island.

Seismic studies of rhe strata between Parsley Bay and the island showed competent rock underlying a 30 m deep bed of mud and silt, through which it was rhoughr a bore could be d rilled from the mainland end . To avoid problems with the bore emerging on rhe elevated and nearest roadway on the island, it was decided to d rill further under the high point of rhe

island and exit in low lying open space adjacent to Grantham Parade. This added a further 300 m to the length of the bore, caking ic to a cocal length of 1,3 15 m.

The design of the reticulation and pressure sewerage system on the island was tailored to suit the head capability of the property grinder pumps and included a fl ushing regime with downstream control at the mainland end, to promote velocities in the pipeline which would ensure scouring of any deposits. The selected liner pipe was 89 mm inside diameter PE 100 SDR 7.4 HDPE. As the liner pipe was quite small in diameter (125 mm OD) it was possible co drill a 250 mm diameter pilot hole from the mainland to rhe island at a rare of I 00 to 120 m per day, taking into account the fact rhac rhe drilling bit teeth had to be renewed three rimes during the process. The DD - 660 Drill Rig was larger than required to do the job and had a torque capacity of 120 kNm and push/pull capacity of 330 tonne. le completed rhe drilling work in a cwo-week continuous period (Figure 2).

Whilst the drilling work proceeded, 12 metre lengths of PE pipe were shipped to the island by barge, strung out along the peripheral roadways of the island, butt welded together and progressively de-beaded, then placed on roller supports along the island roads before being pulled back as one long snake to the mainland by the HDD rig at Parsley Bay. The pull back cycle was achieved in one working day, only being limited by how quickly che operators could unscrew and remove the rods from the rig (Figure 3).

To summarise, on the BDI scheme, trenchless methods were used for drilling laterals in to properties from the main road system and in parts of Hawkesbury Avenue where steep grades and rock would have made conventional methods difficult, time consuming and coscly. Excavation to locate services was also undertaken by vacuum eductor truck, and in general small auger machines under bored concrete driveways.

The main use of HDD was for rhe crossing to Dangar Island, which was conducted with little impact on the local residents, but it did generate considerable interest with che local community, which was supportive of our efforts throughout the project.

Upper Blue Mountains Servicing of the Upper Blue Mountains is another of che PSP Alliance schemes being delivered at present, which has broken new

Figure 2. Drill string emerging at Dangar Island.

ground in terms of che lengths drilled by HDD to link the systems up to the Blue Mountains sewerage tunnel at North Kacoomba. Ir is reported in Robinson et al, chis issue.

Conclusion Over a six year period, the PSP Alliance has delivered fo ur sewerage schemes to a capital cost of $230 million and is currently in the process of delivering a further three schemes for Sydney Water utilising rrenchless technology ranging from HDD, through micro-tunnelling to pipe jacking, pipe cracking and auger boring, with vacuum extractive excavation fo r non-destructive location of underground services.

Bue to put chis into perspective, the use of trenchless methods augments rather than replaces conventional methods of excavatio n and inscallacion, and chis situation has been accelerated by che progressive cake up of pressure sewerage technologies, rather than conventional gravity systems, for difficult-to-service areas.

On all schemes delivered, a combination of both conventional and trenchless methods is used to best fie rhe situation, and chis is determined to a great extent upfront on a project at the cime of escimacing, which under the Alliance delivery method, is not done without considerable environmental, community, survey, geotechnical and pre-design investigation to ensure chat target costs truly reflect the final cost to the clien c.

Trenchless methods come into their own where factors such as restricted working access, contaminated ground conditions, sensitive environments, built up areas and public amenity are important considerations, which would significancly impact on the cost of delivery by conventional means.

The Authors

Figure 3. Pulling back the HDPE pipe from Dangar Island to Brooklyn .

66 MAY 2008

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Journal of the Australian Water Association

Trevor Matthews is Project Development Manager for rhe SWC Priority Sewerage Program, email: T revor.Marthews@ sydneywarer.com.au. Gerald Fender at the rime of the works, was rhe PSP Alliance Program Manager. Gerald has since moved to John Holland as the NSW Water Operations Manager, and retains an interest in the PSP Program as the John Holland Alliance Leadership Team member.

UPPER BLUE MOUNTAINS SEWERAGE SCHEME W Robinson, T Ferrero, D Sweeting Abstract In September 2002, Sydney Water Corporation engaged in an alliance with MWH, John Holland, United Group and Manidis Roberts ro deliver Stage 1 of the Priority Sewerage Program (PSP). The latest project is the Upper Blue Mountains Sewerage Scheme.

This paper describes how trenchless technology, includ ing two very long HDD bores in environmentally sensitive areas, was adopted co overcome the project's challenges.

Introduction The Upper Blue Mountains area is located approximately 110 km west of Sydney. The three townships included in the scheme are Medlow Bath, Blackheach and Mount Victoria, which border the Blue Mountains National Park. The Greater Blue Mountains were listed as a World Heritage Area in N ovember 2000.

Due co the great significance of the area, che scheme needed co meet the following prime objectives: • Minimise che potential for environmental impacts.

• Meet pollution reduction program targets.

• Reduce levels of nutrients and pathogens discharged co the drinking water catchment.

• I mprove water quality further downstream of the Upper Blue Mountains.

• Deliver a commitment co provide improved sewerage services co the townships by 2008.

In order co meet these objectives and che expectations of the various stakeholders, the scheme comprises the fo llowing elements: • A 23 km pressure sewerage and gravity transfer main from Mount Victoria co North Kacoomba linking the U pper Blue Mountains sewerage system co the existing Blue Mountains Sewerage Tunnel at North Katoomba.

This is an edited version of a presentation to the 7th ASTT Trenchless Technology Conference, Sydney, March 2008.

68 MAY 2008

water

• Construction of 45 km of reticulation network, both pressure sewerage systems (PSS) and gravity, co service properties in che three townships.

• Construction of five below ground sewage pumping stations.

• Decommissioning of existing sewage pumping stations and sewage treatment planes at Mount Victoria and Blackheath.

Once the scope was defined, Sydney Water's PSP Alliance began developing the derailed design and che target out-turn cost (TOC), and sought stakeholder approvals.

Approval was granted for construction co commence in December 2006.

One of the most challenging sections of the scheme involved the construction of the sewer transfer main connecting the Upper Blue Mountains townships of Medlow Bach, Blackheath and Mount Victoria co che existing Blue Mountains Sewerage Tunnel at North Kacoomba.

• Sewer pipe amplifications required as a consequence of the increased flows from new infrastructure installed on che scheme.

To overcome the complex challenges at Cascade Dam and Mount Boyce, AJ Lucas was engaged as the sub-alliance partner co deliver the main horizontal directional drilling for che scheme, comprising twin 2.4 km HDD bores at the Cascade Dam and a 1.4 km HDD bore under M ount Boyce at Mount Victoria.

Ocher companies involved in delivering infrastructure using trenchless technology included: • Pezzimenti Laser Bore - Transfer Main micro bores • Codmah Pty Led - HDD for pressure and on-property reticulation systems • CLM Trenchless - sewer pipe amplifications utilising pipe bursting • Construction Infrastructure - HDD Rising Mains.

The main challenges for the transfer main system included the following:

Update

• Undertaking 2.4 km twin horizontal d irectional d rill (HDD) bores (650mm &325mm) under the Cascades Dam, the main water supply for the Blue Mountains situated within the Blue Mountains National Park and water catchment area.

The key infrastructure is completed and ready for commissioning. The reticulation is due for completion by lace 2008, well ahead of the committed completion dace of mid 2009. The coca! cost of the scheme is approximately $120 million.

• Undertaking 1.4 km HDD bore (500mm) under Mount Boyce at Mount Victoria, due to safety iss ues associated with trenching within the western freigh t line rail corridor.

Scheme Overview

• Undertaking four 560 mm laser guided micro bores under the Great Western Highway and Western freight line rail corridor.

There were also challenges for che reciculacion system, including: • Installation of pressure reticulation highdensity polyethylene (HDPE) type pipes 40 mm co 250 mm in size across che three townships co minimise community restoration impacts, and issues with restricted access that could not be overcome by conventional trenching.

• HDD for 470 mm and 350 mm rising mains alongside protected hanging swamps and inclines greater than 30 degrees, which were unable co be trenched.

Journal of the Australian Water Association

Key management issues in delivering the scheme Key issues that needed to be managed carefully included the approvals process, environment, safety, quality, community and external stakeholder communicatio ns, time and cost.

Approvals Previously the project was proposed as a "treat and discharge locally" solution with substantial planning work already completed. However, the world heritage listing of the surrounding area resulted in chis changing co a "transfer down the mountain" option with decommissioning of

A world-first, pushing capabilities for a 2.4 km bore.

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trenchless technology undertaken by che Alliance have achieved an outstanding level of safety and quality outcomes. Construction to dace is approximately 70% complete and all key infrastructure undertaken by crenchless methods has been pressure tested and has passed with no defects.

local treatment plants and treatment of wastewater at the Winmalee Sewage Treatment Plane. Thus various approvals and further planning were necessary for the project to proceed.

T his process was carried out by Sydney Water and involved rigorous planning meetings with various stakeholders to address their issues and concerns. The approvals required included access and easement agreements as well as agreements to pro ceed and endorsements. Stakeholders included the Sydney Catchment Authority, National Parks and Wildlife Service (NPWS), Rai!Corp, Roads and Traffic Authority (RTA), Commonwealth Department of Environment and Heritage (DEH) and NSW Department of Environment and C limate Change (DECC) . The approval process was fu rther delayed due to the need for a State Environmental Planning Policy No 58 amendment.

The use of trenchless technology allowed the concerns of these stakeholders ro be successfully addressed, and approvals were achieved well ahead of construction work proceeding with no delays to che work program.

Various high risk activities have also been undertaken on the scheme including deep excavations for the pumping stations, work on numerous work fronts across the three townships, connection of che HOD transfer main to the existing Blue Mountains Sewerage T unnel at North Katoomba (approximately ?Om below ground level) and an array of subcontract work with large mobile machinery operating in close proximity to che public. All these activities required rigorous planning and implementation. Some work was also undertaken 24 hours a day, seven days per week due to the technical risk of working standard hours.

Figure 1. Aerial View of Cascade Dam.

Environment In addition to the proximity of the work to the Blue Mountains World H eritage Area and the water catchment for the Blue Mountains, the environmental issues to be managed included areas of heritage and cultural significance, regionally significant communities, and a unique ecological community protected by Commonwealth Legislation.

Environmental impacts chat had to be carefully managed included achieving noise levels within background levels and the management of spoil and ground water during the work. The Blue Mountains area has many natural springs and hanging swamps protected as an endangered ecological community under Commonwealch Legislation.

There are also various early European heritage structures in the Upper Blue Mountains, which required vibration and d ilapidation monitoring during che works.

Ocher environmental issues included che management of drilling fluids during the work and its disposal.

The work was also required to be undertaken in urban areas in the three townships and during certain times of the year, large numbers of tourists visit the Blue Mountains area. As such, traffic

70

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management became a major requirement, as well as restoration of areas d isturbed by che work. Trenchless methods were adopted to minimise restoration impacts across the scheme.

Community and external stakeholder communications A key fo cus of the scheme was to ensure the DECC, RailCorp, Blue Mountains C ity Council and the residents of che three townships were consulted and kept informed to maintain their continued commitment to che proj ect.

C ommunity consultation started in the early planning stages and was continued through to the design and construction phases. Individual meetings were held with affected property owners to help chem prepare for construction. It was critical chat chis process was undertaken, as a lot of the work was carried out on private property.

Consultation was also undertaken with the surrounding residents at the proposed drilling site at Medlow Bath to ensure chat they were not impacted by the need for 24 hour drilling. The drilling was completed with no noise complaints from the surrounding residents.

Safety and Quality Safety and quality management is of paramount importance to Sydney W ater and its PSP Alliance. Vario us schemes

Journal of the Australian Water Association

To date, the scheme has completed over 400,000 contractor man-hours in 16 months and only two M edical Treated Injuries and one Lose Time Injury have been recorded for che scheme.

HDD Technology and Challenges Due to the complexity and limitations of che construction methods chat could be adopted on the scheme, trenchless technology was utilised for critical elements to ensure delivery of the scheme to meet Sydney Water's Operating Licence requirements and stakeholder commitments. Other conventional methods , such as open trenching were not suitable due co safety, environmental, community, technical, time and cost constraints .

Cascade Dam HDD The work for the Cascade D am HOD consisted of two bores, each approximately 2.4 km long starting from M edlow Bach and finishing ac the Blue Mountains Sewerage Tunnel at North Katoomba, 70 m below ground (Refer to Figures 1 to 3).

T he design of these bores evolved over two years. Initially the design called for cwo bores drilled end to end at the roe of the Upper C ascades Dam. One bore was to be drilled up to Medlow Bach with the rig then turned around and a second bore drilled down to the Blue M ountains Sewerage Tunnel at North Katoomba. This plan was developed due to the face a 2.4 km

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single shoe bore was considered well outside acceptable risk parameters.

During the design development and planning stage, and with the involvement of the sub-alliance partner AJ Lucas, the possibility of drilling a 660mm bore 2.4 km long became a real alcernacive. Additional geocechnical invescigacion and analysis, hydraulic design and stakeholder consultation was required co allow chis alternative alignment co be constructed.

The alignment of the H DD for the Cascade Dam drill, shown in Figure 2, commenced in Medlow Bach and followed a route through che Cascade drinking water catchment, che main water supply catchment for che Blue Mountains. Due co geocechnical requirements and potential frac-ou cs to che surface of drilling fluids, the HDD alignment passed at a depth of approximately 40 metres below the toe of the existing Upper Cascade Dam. The alignment continued through co intersect che existing Blue Mountains sewerage tunnel ac a depth of approximately 70 m below ground, with a one-metre wide target window within che tunnel. The vertical profile is illustrated in Figure 3.

To undertake the drilling, an American Auger Dl 100 was used. Maximum drilling races of approximately 200 m/day were achieved and che project cook just over five months co complete, with sub-alliance parrner AJ Lucas working 24 hours a day in sometimes extreme weather conditions co complete che 2.4 km long duty and contingency bores.

The HOD project commenced on 5 March 2007 and finished on 28 J uly 2007.

The breakthrough of the 2.4 km bore into che Kacoomba Tunnel on 12 May 200 7 signalled che success of the longest HOD bore of its type in Australia.

Some of the hurdles chat were successfully addressed included:

Figure 2. Cascade Dam HDD Alignment (Plan).

• Carryi ng drill cuccings 2.4 km in a 660 mm bore.

• Achieving weight co bit for the HOD bore over 2 km.

• Ensuring drill fluid would not escape che bore (frac-out).

• Negating survey cool wire line failu re over 1,800 m in length.

• Installing produce pipes for both large HDD bores: - Floating the 450 mm HOPE pipe 2400 m, with an installation load of 12.5 con for 180 con DN450 pipe.

- Floating the 225 mm HOPE pipe 2400 m, with an installation load of 1.8 con co install 45 con of DN225 pipe.

• Undertaking 24 hours a day, 7 days a week works with no community impacts.

• Undertaking drilling under the main Blue Mountains' water supply without any impacts or incidents.

Profile View of Hole 2 - DN450

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72

MAY 2008

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Journal of the Australian Water Association

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The drilling work encountered mulciple iron scone bands dipping in the same direction as the direction of che bore, which meant che steerer was conscancly adjusting che steering parameters co prevent che driller over-steering through che hard bands into the soft bands.

The driller maintained his ability co direct the bore wichouc coo much difficulty.

However, ic did cake its coll on the drill sering and maintaining hard banding on the pipe was a constant critical path cask.

A key expectation of all parties was co ensure chat no frac-out of bentonice occurred, considering that che drilling works were being undertaken across a National Park and under the main water supply for the Blue Mountains.

In order co ensure chat frac-ouc did nor occur, frac plots were undertaken and proved co be a useful cool. The annular p ressure cracked well against che model.

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Significant factors in overcoming the above challenges were the structure of the Alliance and how all parties including external stakeholders were involved throughout the whole process from initial planning approvals, development of the TOC and the successful implementation of che work.

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The added benefit of real time logging of che annular pressure was chat che driller could see chat swabbing the bore created more pressure than the drilling and che swabbing speed could be adjusted co prevent over-pressurising the bore.

The overall project was a success and a world first due co the technology, constraints and challenges involved. The main learnings and achievements of the project included:

• The Alliance principles were a major contributing factor to the success of rhe project. There was no "battening down of rhe hatches" when problems did occur and problems and possible solutions were openly discussed to overcome rhe challenges. Traditional contracting delivery methods may nor have produced rhe same success.

• Understanding the risk and applying effective mitigation measures and involving all parries during this process.

• Use of historical data and experience to underpin design and delivery.

• Accuracy of engineering models and assumptions proven in the field.

• Managi ng rhe work with a successful outcome withi n a National Park and drill ing under rhe main water supply for rhe Blue Mountains.

• Achieving outstanding successful delivery in the areas of community, enviro nmental and safety.

• Floating of rhe pipe into the bore at rhis length created a new world record.

Underpinning experience with sound engineering, based on reliable data and rhe active involvement of all rhe All iance partners was fundamental in achieving this successful ou rcome.

Mount Boyce HDD

Figure 4 . HDD Cascade Dam - Installation HDPE pipe at night. designed and agreed. Georechnical investigation was undertaken to confirm char this route and the bore were possible.

The overall length of rhe bore was 1.4 km long at a grade of 2½% with a hole diameter of 500 mm. Figure 5 shows rhe path raken.

forward ream the bore to a diameter of 500mm. The proximity of rhe gas and water mains to the exit point meant that conventional reaming would have involved accepting a higher level of risk and add itional co ntrols would have been req uired.

The rig sire was sp lit in two to reduce the area to be cleared to support rhe work. T he drilling rig was sicuaced in one area and the power pack and mud handling system in another area to minimise the impact on vegerario n. The site required the rig to be fla t on the ground as the inclination of the bore was at 2½% in an upward direction.

Reaming the bore proved to be quite challenging and presented a number of technical difficulties to overcome incl uding:

A section of the main transfer pipeline over Mount Boyce was intended to fo llow rhe rail corridor. H owever, during rhe preliminary design some challenges were identified such as rhe potential risk arising from utilising conventional excavation techniques alongside rhe existing rail line in very unstable ground.

T his bore was relatively straight-forward, with rhe mai n criteria being rhar the bore had to be on grade and could nor interfere with gas or water mains located approximately 4 m from the exit point.

A HDD bore under Mount Boyce at Mount Victoria was seen as a solution to negate rhis risk and a drill path was

The pi lot hole advanced quickly in soft ground, however rhis was a concern in that the methodology relied on being able to

Figure 5. The Mount Boyce alignment.

74

MAY 2008

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Journal of the Australian Water Association

• Approvals from RailCorp prior to commencing drill ing work had to be sought.

• Continual ground water inflows at a rare of ap prox 4 to 5 1/s.

• Extreme weather conditions, rain and 4°C at night.

• Ground condi tions and keepi ng the hole open during drilling and pipe installation, as ground condi tions were much softer rhan th e georechnical bore logs indicated.

• Working with in and alongside live rail line.

technical teatures

• Drilling under an existi ng high-pressure gas main.

• Managing the works on a 24 hou r, seven day a week basis.

Although there were numerous challenges and unforeseen conditions, the drill was completed successfully, within the original TOC and on time.

HDD for pressure sewerage reticulation system A pressure sewerage system (PSS) requires the installation of an underground collection tank and grinder pump on the property to be serviced. The macerated sewage is then pumped via a service lin e into a reticulation line that services an area or township. The reticulation lines and service lines consist of HDPE pipe ranging in size from 40 mm to 250 mm ID PE 100PN l 6 (SRRII). The reticulation network also has ancillary items such as air valves, stop valves, boundary kits and flush ing points as required for operation and maintenance of the system. The benefit of a pressure system is that the sewer network does not have to b e laid at grade, un like gravity systems, and chis main benefit provides installation cost savings, flexibility in p ipe routes and greater potential to utilise HDD. HD D technology was the preferred method fo r installing PSS infrastructure and was successfully adop ted in previous sch emes such as ch e N orchern Illawarra Towns, Belimbla Park, Jambero o, Brooklyn and Dangar Island . HDD was used in che Upper Blue Mountains Sewerage Sch eme to install che main reticulation lines and service lines to the properties.

Figure 6. HDD reticulation work at Blackheath. requirements. HDD reduced chis cost substantially.

• I mpacts of wee weather. HDD works continued during wet weather, when trenching works were halted. The Blue Mountains is known for extended periods of wee weather.

• Various major roads, rail and creek crossings to be undertaken. Conventional crenching was not possible and HDD proved very successful in these circumstances.

• Access restrictions into residents' properties. Existence of concrete driveways, dwellings, structures and property boundaries at rimes made trenching impossible.

• Noise issues with rock b reaking near residential properties.

Approximately 70% of the PSS network was installed using HDD. HDD was fou nd to be the p referred construction method due to che fo llowing issues:

• Pocen cial impacts on heritage structures.

H DD resulted in minimal vibration impacts where works were undertaken near heritage structures.

• High restoration coses d ue to road restoration requirements and environ mental

In che early days of che construction works for the PSS network, problems were

experienced with ironstone bands, gas services laid at very shallow depths and disposal/handling of drilling mud. All these issues were overcome. Potholing for che ironstone bands and gas services was undertaken to ensure optimal drilling depths and lengths were achieved. A transfer facility was established at the Blackheach sire compound where the drill ing fluids were mixed with trenching spoil. This material was then reused across the sch eme.

The HDD work for the pressu re system was delivered by cwo rigs (both D 24 Vermeer HDD). App roximate production races of 100 - 150 m/day were achieved for each rig, dependent on the size and length of the drill (refer to Figure 6).

For the work in private property, production rates of three services lines a day of approx 30 - 40 m were achieved, and included the set-up and demobilisation for each property. To date, the entire pressure sewerage reticulation infrastructure is in place with ap proximately 26 km of the PSS n etwork installed using HDD technology.

NEW ELECTROFUSION SEWER SADDLE. FASTER FIT. ~=c_cc-=-~=-===----====~f~U~L~LY. SEALED. NO LEAKS.

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Journal of the Australian Water Association

Water

MAY 2008 7 5

technical features

trenchless technology Micro bores - transfer main

Pipe amplifications - reticulation

As part of the Upper Blue Mountains Sewerage Scheme, four micro laser-guided bores were undertaken for the transfer main.

Micro bores were adopted over conventional trenching as the transfer main at these locations crossed the Great Western Railway Line and Great Western Highway.

Due to increased flows into the existing sewerage network at Blackheath , various pares of the existing network required amplification.

T he bores consisted of using a laser-guided microboring machine with a boring diameter of 560 mm and which achieved in hard rock lengths of up to 90 m. On completion of the bores a DN560 PElO0 SDRl 1 PN 16 pipe was installed and fully grouted .

To undertake the bores, approval was required from Rai!Corp and the RTA as the bores crossed under their infrastructure.

Overall , approvals required 12 months of investigations and negotiations with the relevant authorities. On completion of the negotiations, the work only cook 4 months to complete.

There were specific challenges in undertaking these bores, which included the following: • Work had to be carried out near heritage structures. Vibration control was critical and micro boring allowed low vibration limits co be achieved.

• RailCorp specified settlement monitoring and vibration limits on their infrastructure. No settlement occu rred due to the work and vibration levels were achieved.

• Maintaining the hole open during the boring work.

Geotechnical investigation identified that sound rock was at depths of approx 4 - 6 m. The hydraulic design of the pipeline was optimised to meet this depth so chat boring work posed no risk of collapse under the rail line.

,i IMCD ·--

76 MAY

2008

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Journal of the Australian Water Association

One of the major pipe amplifications required was along the Blackheach Golf Course. Approximately 30 0 m of existing sewer had to be amplified from 225 mm co 300 mm. This amplification was undertaken by pipe bursting as it allowed the specific challenges and constraints to be overcome successfully.

The challenges and constraints included: • Pipe bursting along the existing fairway at Blackheath Golf Course.

• Various house service lines connected co the new amplification and so there was a need co maintain the house service during the works.

• Minimising restoration impact to the Blackheath Golf Course fairway.

• Minimising impact (noise) to properties adjoining the golf course fairway.

• Allowi ng the existing network co operate d uring the works.

The detail review of methodologies found that conventional trenching would not overcome the challenges involved in the work but would create greater risks. The option of pipe bursting/cracking was adopted fo r chis amplificat ion and p roved quite successful. Ocher amplifications on the scheme are planned and this technology is to be adopted again.

technical features

In considering the option of utilising crenchless technology on a project, a cost versus benefit analysis is necessary, and chis was undertaken for all options described in this paper. le is also imperative char early investigation work such as geocechnical, detailed design, commu n ity consultation and stakeholder management are undertaken so chat the benefits of utilising crenchless technology over convention al trenching can be realised.

From the case studies described, where crenchless technology was adopted on ch is scheme, all areas and challenges were overcome and the costs were with in the project's target out-turn cost.

The 2. 4 km bore ended 3 m from the existing Blue Mountains Sewerage Tunnel at North Katoomba. The final transition from Tunnel to bore was created by stitch drilling the perimeter w ith a 200 mm core barrel.

HDD - sewage pumping station rising mains and gravity lines Two of the p umping stations to b e constructed, SPS767 and SPS769, had incoming gravity lines and exiting rising mains.

Conventional trench ing would not be possible d ue to the following challenges:

T renchless technology methods have proven to be successful on the Upper Blue Mountai ns Sewerage Scheme as well as ocher Pri ority Sewerage Program schemes. As che industry and clients understand its potential, crench less techn ology will be utilised more often to meet technical, safety, environmental, community and stakeholder challenges in che future.

The Authors Wayne Robinson is che Sydney Water Project Manager for the Upper Blue Mountains Sewerage Scheme, wayne. robinson@ sydneywacer.com.au; Tino Ferrero is the Upper Blue Mountains PSP All iance Project Manager and works for John H olland Water; Daniel Sweeting was the PSP Sub-Alliance Project Manager for the Cascade project for AJ Lucas.

• The risi ng main and gravity sewers at SPS769 pass near a hanging swamp, which is protected by Commonweal ch Legislation.

• Boch pumping stations are situated at the bottom of a hill with sewer lines traversing slopes greater than 30 degrees in inclination.

• The rising main and gravity p ipes at SPS767 pass under a flowing creek , which flows into the Blue Mountai ns National Parle • The rising main and gravity sewer at SPS767 pass under a bushwalking crack chat was required to remain open during the work.

The Ditch Witch 30/20 AT successfully installed four 100 to 120 metre bores, 350 mm and 470 mm.

Drill ing was conducted in an uphi ll direction, captu ring the d rill ing fl uids at the pumping station excavation site. This ensured that the return of fluid s was ach ieved and the potential of frac-ouc to the environment was min imised. On completion of the back reams, the H DPE pipes were welded at the cop of the drive and pulled down cowards to the pumping station using the H DD rig.

After installation, the pipes were tested and fu lly grouted .

Conclusion Over the lase 14 months, various types of trenchless technology have been adopted co overcome the challenges for the scheme with successful outcomes. The challenges chat were overcome included technical, safety, environmental, community and stakeholder requirements.

The crenchless technology adopted as described in chis paper included horizontal directio nal drills, both large and small diameter, and in one case for the Cascade Dam crossing, undertaking a world first by pushing the capabilities of the technology. Other crenchless methods included microboring and pipe bursting, which also ach ieved the desired outcomes.

Journal of the Australian Water Association

Water

MAY 2008 77

technical features

trenchless technology

OVOID SEWER REHABILITATION Compiled by E A (Bob) Swinton This article has been compiled by the Editor from three papers presented at the 7th Trenchless Technology Conference, Sydney 2008, with the cooperation of the authors.

History W h en the new sewers were designed for Londo n in the last half of the 1800s, oviform shaped sewers were determined to be the best cross-section for the larger "combined " sewers. The rationale was to have a narrow invert so that a reasonable self-cleansing velocity was attained even at low flow. As flow increased, the upper 'circular' profile provid ed capacity. They were usually co nstructed of brick and mortar, and later in un-rei nforced concrete.

FIG. 4,-Ynin Sewe1¡, Southampton.

Over time, the "self cleaning" Figure l : Egg sha ped sewers circa 1910. characteristics of the egg shaped pipe proved to be as effective as rhe This article covers Sydney Water's engineers had projected and the oviform experience in the rehabili tation of both shape was used ex tensively in early sewer non-man entry sewers and large man-entry construction not only in Europe but in roams.

Australia as well . Ir is no real surp rise to find chat, though 100 years old, they still Non-Man Entry represent a critical component of the sewer Robert Loncar and Sudipta Basu of network and are most often found in Sydney Water Corporation described the densely populated areas of the centre and design process d eveloped to ensure ad equate inner suburbs. strength fo r the re-lined sewer.

By 1940 the design had been completely Sydney Water has over 100 kilometres of superseded by large-diameter spun concrete such oviform sewers. Dimensions vary in pipes. H owever, many kilometres of the old height and width from 380mm x 250mm to ovoid sewers are still in use. Over a hundred 1800mm x 1200mm. The shapes also vary years of use has taken its toll, and widely. Some are more circular in shape, replacement and/or rehabilitation is while others are oval shaped with relatively increasingly necessary. flat sides.

In the early 1980s, Sydney Water adopted CIPP lining to rehabilitate nonman entry ovifo rm sewers. Between 1980 and 1982, an estimated six (6) projects totalling 1.8 kms were rehabilitated using this method. The line sizes varied from 384mm x 256mm to 1066mm x 711mm. Sydney Water and che lining contractors of the rime had a number of issues to address. Such issues included rhe design method to determine liner thickness, material selection an d installation and curing methods to achieve the required stiffness and strength.

Equipped with a better understanding of che curing process and new design method, more oviforms were subsequen tly lin ed in che mid 1980s. However, overall results were still mixed, with some defective work requiring removal. Possible causes for rhe defective work were lack of understanding of design issues, inexperience in application of relatively new technology and q uality of materials.

Lacer in 1996, Kensington sub-main, a deep 990mm x 660mm sewer in watercharged ground was successfully rehabilitated. P revious unsu ccessful attempts to line this main appeared to have been caused by inadequate management of groundwater.

A recent su rvey of some successful works of rhe mid 80s has shown that the liners are h olding well after 24 years. However, there are signs of surface deterioration and wrinkling. Wrinkles are mostly on the thin inner surface coating layer. Localised resin loss has also been observed which is readily identifiable at liner stitching locations.

Dual pipe rehabilitation Due to rhe mixed success with CIPP lining, Sydney Water had experimented with dual pipe rehab ilitation of oviform sewers. A smaller d iameter pipe was installed in rhe invert and a larger pipe above. Once installed, voids were grouted to provide restraint and uniform supp ort

Two innovative rehabilitation techniques.

Figure 2. CCTV Inspection of Haberfield Sewer.

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technical features

Whilst initially no operational issues were reported, with ti me, blockages, siltation and ocher operational problems began to emerge, primarily due to the choking of the lower smaller pipe. As a result, frequent cleaning was required. Calculations also showed that some 20-30% of peak capacity was lose.

An urgent problem In 2006 two sections of oviform sewer at Haberfield and Drummoyne were identified as requiring urgent repair.

Haberfield is a relatively shallow unreinforced concrete sewer of size 838 x 597mm. The sewer is located in a built up area with a 90 degree bend in align ment under the roadway. Amongst other defects, CCTV inspection revealed that two secrions of the bend had badly corroded or we re co mpletely missing (Figure 2) .

D rummoyne is a deep unreinforced co ncrete oviform sewer of size 533 x 406 mm. The sewer was laid parrly in trench bu r mostly in rock runnel. CCTV revealed defects including extensive surface corrosion wi ch substantial loss of wall thickness at some locations.

Mindfu l of past experiences with dual pipe rehabilitation, Sydney Water looked to ocher renewal/rehabilitation options.

On review it appeared char whereas alternative processes would nor be able to be mobilised in time, current conventional CI PP oviform lining system met all the criteria and was immediately available. With experience gained over recent years, a nu mber of enhancements had been made to materials and work methods leading to greater quality assurance and confidence.

These enhancements include: • Changes in resin tech nology fo r improved cu n ng.

• Better understanding of curing process to achieve higher lining density.

• Better understanding and manipulation of felt resin systems ro achieve desired properties.

• Beerer work practices.

Typically a CIPP liner comprises polyester felt/resi n type materials, with claimed long term flexural modulus and strength values of 1250 MPa and 20 MPa respectively.

Liner design methods Design methods applicable to CIPP lining systems were investigated for non-man entry oviform sewers requiring rehabilitation. The problem, simply scared, is chat the relatively flat sides between the invert and the upper circular section are weaker than a complete circular section (Figure 3).

The critical design problem is that the "straight8 side of the oviform offers much less resistance to buckling than a "circular' lining

External - ~a:. water pressure

Width of lining = w "straight'' section = 2/3 h critical length / = w or 2/3 h (whichever is greater)

Figure 3. Stre sses o n a n ovoid liner.

Currently, Sydney Water classifies sewers ro be rehabilitated into two co ndition categories, namely 'i ntact' and 'deteriorated'.

Intact sewers are considered capable of withstanding soil overburden and traffic loads in the long term. Liners for such sewers are designed solely for hydrostatic loading caused by a water cable above the pipe. T he Type 11 method described in the WRc Sewer Rehabilitation Manual is che most widely accepted design method for so called 'intact' sewers and is favoured by Sydney Water. Ocher methods include equivalent circular diameter, fi nite element modelling (FEM) and a recenrly developed analytical method by Thepot. Comparison of the above methods fo r a given design scenario reveals the WRc method ro be che most conservative.

Conversely, the long term capacity of deteriorated sewers is uncertain and as such, the liner muse be designed to bear the fu ll soi l overburden and traffic loads. T here are no standard or universally accepted design methods available. Although methods such as simplification to an equivalent circular diameter or more comprehensive finite element methods are available, there is no standard procedure or accepted guidance for their use to provide consistent and reliable results.

The future In order to overcome liner thickness limitations and increase range of applicability, a number of measures need to be explored for the CIPP method. These include: • Development of more sophisticated or refined design methods.

• Formulation of higher stiffness an d strength of materials.

• Refi nement of installation and curing methods.

• Felt reinforcement.

• Restraint of liner at the critical 'straight' length.

• Modification of ovifo rm geometry (e.g. reduction of straight length by infilling and reshaping invert).

Ir may be argued char until che above issues are addressed, higher surveillance should be undertaken such char non-man entry oviform sewers can be rehabilitated prior to reaching a 'deteriorated' scare.

Currenrly variations in fel t composition are being trialled using glass and carbon fibre reinforcements. Resin technologies are also improving. Alternate CIPP materials such as high strength GRP, cured using ultraviolet light methods have been successfully cried overseas.

Installation Th e actual rehabilitation work of the Drummoyne and Haberfield sewers was carried out by Kembla Wacertech P/L. Alan Sutton, Engineering & Overseas Manager, described the CIPP system which was developed in discussions between cl ient and con tractor to design structural linings to satisfy external load condi tions. The installation work was undertaken at night during restricted hours and involved large scale sewer bypass and traffic control sec ups. Special customer, safety and environmental plans were established.

Kembla's Enviroliner system is a resinimpregnated flexible rube which is inverted into che existing conduit by use of hydrostatic pressure. T he rube is cured ro a hardened scare while held in intimate contact rhus caking the shape of the host

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trenchless technology pipe b ut not relying on any bond for its structural strength.

There were numerous meetings between Kembla and SWC design staff to determine the appropriate design criteria to be applied and hence what thickness of lining would be necessary to satisfy the performance criteria of buckling, strength, deflection and min imum liner thickness.

Haberfield: This sewer is only at a shallow depth and if the sewer pipe could be considered as "intact" then the design thickness required was 16 mm for the 760 x 600 mm section , equivalent to a 70 0 mm liner. A total of 95 m was to be treated.

However, there was serious deterioration in the 90 bend, only 300 mm beneath a busy road. As conventional CIPP lining could not cater for traffic loadings alone, it was decided to encase the bend locally with reinforced concrete. Prior to encasement, however, the entire oviform sewer length was lined using conventional CIPP methods.

T he critical aspect was how to provide an ' intact' pipe at the deteriorated 90 degree bend and chis was successfully accomplished. Once the lining had hardened, the bend could be exposed without the need to bypass the flow, and the CIPP liner p rovided the formwork for the concrete pour.

Figure 4. Feed ing the impregnated liner into the ma nhole. project p resented a very difficult bypass situation.

The dry weather design flow capacity had ro be 165 Lisee and because of a rising main in the vicinity the only feasible route to bypass the flow was up one side of the road, across and then down to the discharge chamber.

Drummoyne Project T he total length of sewer ro be lined was 332m with an ovoid section of 533mm x 406mm, which correlates to a 450mm d iameter lining. D ue ro the nature of defects and original co nstruction of the sewer in a rock tun nel, the cond ition was assessed as 'intact' for design p urposes, bur the 13m depth was a problem, with the W Rc manual requiring a design thickness of over 22mm. However Kembla considered the maximum liner thickness which could be confidently installed in this d iameter as 18 mm . After consideration of the local topography ch is was accep ted as capable o f withstanding the anticipated long-term hydrostatic load.

While a logistical nightmare, the flow management strategy proved effective and efficient in bypassing the existing sewer flow for the duration o f all site activities without a single environmental incident, and the lay-flat hose could be readily dismantled.

Lining Installation Because of their non-standard size, the linings were specially manufactured at an ISO 9001 accredited faci lity in the UK which supplies CIPP linings worldwide.

Mixing and impregnation of the resin was carried o ut at Kembla's CIPP factory in Newcastle.

Two linings of 250m and 82m were to be installed from an intermediate launching manhole of 7m depth . Receiving manholes depths were 3.2m and l.9m.deep.

Whereas providing pumped bypass fo r the Haberfield p roject was relatively easy, the Drummoyne 80 MAY 2008

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Considerations were given to d irectional drilling under the road bur chis was co st p rohibitive. Consequently a 400mm wide x 500mm deep trench was dug and 2 x 200mm lay-flat hose lengths were laid within the trench. A Lampe Plug was installed on the oviform pipe and two silenced diesel pumps employed at nigh t during low fl ow conditions. The bypass operation included maintaining balance of pump flows d uring h igh and low conditions, fuelling of pu mps, maintenance of pumps and in the event of breakdown the engagement of stand by pumps and repair of the duty p ump.

Figure 5. Before a nd a fter.

Journal of the Australian Water Association

T he impregnated linings were stacked into a refrigerated truck for transport to site. If kept cold, the impregnated linings have a considerable shelf life which p rovides a contingency against unfo reseen events such as wet weather.

technical features

services providing derails of road closures, including copies of RTA approved traffic plans.

_il_u?hlf_JL Figure 6. Interlocki ng of ad jacent strips.

Because of rhe weight of rhe liner a crane was used to lift ir from inside the trailer into position (Figure 4).

The head of water or air pressure inside rhe turned back section of lining provides the pressure to invert rhe lining into rhe oviform Th is internal pressure is maintained at all rimes so rhar rhe lining is held right against rhe pipe wall. Once the lining reaches the far end hot water or steam is circu lated inside the lining while the internal pressure is maintained until the lining is fully cured in place. Given the thickness of 18mm and the egg shape chis particular installation at Drummoyne was one of the most difficult ever undertaken in Australia. The 250m length had a total weight of 8.7 tonnes and was successfully installed over one night which high lights the speed and efficiency of this type of li ning system.

Figu re 5 compares rhe 'before' and 'after' conditions.

Arrangements were made for standby accommodation should ir be required by residents due to excessive noise. The Kembla Customer Relations Officer was on sire at Drummoyne throughout rhe night work activity. Residents were advised of this prior to work commencing to give them a sense of assurance that there was someone on hand who was aware of their situation and who could provide assistance should rhey need ir. When rhe work was completed ar both Drummoyne and Haberfield rhe Customer Relations officer visited all residents (those who were home) and commercial cusromers, ro advise chat work had been completed and to thank them personally for their patience during rhis rime.

Many advised rhar there had been no disruption to their life and routines ar all, to be expected of course since rrenchless technology was used rather than dig up and replace.

Mon-Entry Sewers Although CIPP had proved practical for the non-man entry sewers, the larger sewer at Ashfield demanded a different technique. John Monro, Technical Support Manager of lnrerflow, described rhe development of Interli ne Pro, by modify ing the Australiandeveloped Roraloc liner to make it suitable for use in an ovoid shaped sewer.

The Western Branch Main Sewer was constructed in the late 1890s, servicing Sydney's inner-west suburbs. Ir was hand-built with bricks and mortar, and is roughly 2 m high and in places over 20 m below ground level. Despite over 100 years of continuous use

Customer Relations Customer relations was a key focus and a meeting was held at the early planning srage with the SWC Communications Team to confirm roles and responsibil ities. A door knock/letter drop advising of rhe work to be ca rried our gave 48 hours notice to residents and 7 days fo r commercial customers and notices were sent to local pol ice (traffic office), fire brigade and ambu lance

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Figure 7. The Rotaloc machine in action.

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trenchless technology The latter was chosen since it would be consistent quality, i.e. nor relying on workmanship for a sprayed coating in difficult conditions, rhe preparation of rhe deteriorated surface was nor critical and it had srrucrural strength, even for the flat side surface. None-rhe-less, ir was planned ro install drainage scrips between rhe PVC and rhe hose pipe ro relieve groundwater pressure. A further criterion was char flow could nor be by-passed, so that work had to proceed in a live sewer during low-flow nigh r hours.

Figure 8. Trial replica.

it is still structurally sound, with repairs having been done when necessary.

However, in 2008, rhe large Liverpool ro Ashfield pipeline will be connected ro ir, so SWC called for renders ro ensure chat it had rhe capacity to cope with the extra flow.

Inspection revealed char rhe invert was in good condi tion, bur corrosion was evident in some places above the water line.

One technique suggested was rhe application of acid-res isting coating, rhe ocher the installation of a 'partial' PVC liner ro be applied only above rhe waterline.

Roraloc is readily applied ro circular sewers. An extruded PVC strip, some 91 mm wide, is fed down a manhole to a Figure 9. The Design. machine wh ich moves along inside rhe deteriorated pipeline in rerlocking the edges of the Grouting was required behind the liner. strip as it rorates.(Figure 6). The Following these trials, a contract was let for machine can vary its diameter during this a 1.4 km run. T he work rook place at operation so the liner can be made to night, from existing manholes as deep as 38 closely contact the pipe wall. metres (Figure I 0).

However, the challenge of applying it ro The lower edges were cur by air-operated an ovoid shape required pilot testing so a saw and bolts applied. Lessons were learned full scale replica was built. The Roraloc on-the-job and an average rate of 40 m in a machine was mounted on a steel universal nigh r's work was achieved. All cools were beam and the lining applied in the standard pulled out as each morning's flow manner, as a cylinder. The lining was then increased. The results were so successful sawn just below the ADWF water line, on char the contract was extended for an both sides, and the lower edges bolted back addi tional section. ro the sewer wall, closed by a stainless steel The project was completed ahead of strip (Figures 8, 9). schedule despite periods of wet weather. Ir offers a new option for lining large ovoids and has been named Interline-Pro. Ir gained the 2008 ASTI Project of the Year Award in the Rehabilitation category.

Conclusion The cooperation between the client and the two contractors has led to two successful innovative rehabilitation techn iques, part of rhe spectrum of rrenchless technologies.

The Original Authors Robert Loncar is Senior Engineer and Sudipta Basu is Principal Engineer,

Figure 10. A job successfully completed.

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Sydney Water, email: Robert.Loncar@ sydneywarer.com.au; Alan Sutton is Engineering and Overseas Manager, Kembla Warerrech P/L, email: alans@kemblawaterrech.com.au; John Monro is Technical Support Manager, Inrerflow Pry Limi ted, email: jmonro@inrerflow.com.au

refereed paper

REAL TIME MONITORING OF DISINFECTION BY-PRODUCTS USING DIFFERENTIAL UV SPECTROSCOPY G V Korshin, C W K Chow, M Drikas Abstract Th is paper describes rhe principles of absorption spectroscopy, defines differential spectroscopy and ill ustrates how chis technique can be employed to crack the formation of chlorinated disinfection byproducts (D BP). T his prov ides a concept fo r real rime monitoring of DBP using two on-line UV spectrometers which is being explored in Australia.

Introduction T he primary task of drinking water quality managers is to ensure supply of safe and high quality potable water. It is agreed chat disinfection is rhe key process. The use of disinfection by chlorine can ensure the sup ply of microbiologically safe water co customers bur at rhe same rime ir bri ngs another important topic into discussion; chat of the presence and effect of disinfection by-products (D BPs).

C hlorine effectively controls practically all infectious microorganisms (except Giardia and Cryptosporidium), and for chat reason it is the most freq uently used disinfectant worldwide. However, reactions between chlorine and natural organic matter (NOM), present in all surface waters, cause potentially harmful disinfection by-prod ucts (D BPs) to form (Krasner et al. 1989, Arora et al. 1997, Black et al. 1996, Singeret al. 1995).

In the late 1970s, the USEPA set an in terim maximum contaminant level (MCL) for coral trihalomerhanes, T HMs, (the sum of chloroform, bromodichloromerhane, dibromochloromerhane, and bromoform) of 0. 10 mg/Las an annual average, appl icable to community water systems se rving at least 10,000 people. In December 1998, the USEPA promulgated the Interim Enhanced Surface Water Treatment Rule and The Stage I Disinfectants and Disinfection Byproducts (D/DBP) Rule. T he Stage I D/DBP Rule lowered rhe MCL fo r total THMs co 0.080 mg/L and established an MCL for haloacecic acids (HAAS , the sum of mono-,

di- and trichloroacetic acids, denoted as MCM, D CM and TCM, respectively, and mono- and dibromoaceric acids) ar 0.060 mg/ L (USEPA 1998). The Stage I D/DBP rule applies to all commu nities and systems providing disi nfected water.

In Australia, guideline values for DBP species in the Australian Drinking Water Guidelines (ADWG) incl ude the sum of four T HMs, three haloaceric acids (MCM, DCM and TCM) and chloral hydrate.

Condi tions specific ro Australia such as long to extremely long conveyance pipes, high NOM and/or bromide concentrations fo und in many sources and high temperatures often require char high chlorine doses be used ro maintain a residual throughout the distribution system. These conditions are conducive to increased yields and rapid formation of DBPs. T hus, achieving a good balance between protecting public health via maintaining a proper level of disinfectant residual and yet meeting req ui rements set by the DBP guidelines represents a challenge to Australian water suppliers.

To suppress the fo rmation of DBPs, reactive fractio ns of NOM can be removed by coagulation or adsorption. There are limits to how much NOM can be removed by these and related methods. O nce an economically feasible limit of NOM removal is reached, further improvement of DBP control depends on how rapidly operators can adjust chlorine dose in response to shore- and long-term variations of water quali ty parameters in order to maintain both a desired level of chlorine residual and suppress DBP formation as much as possible.

The precision and timeliness of such measures depend critically on the quality and representativeness of data on chlorine residual and DBP concentrations at representative points in a distribution system. While instruments for on-line measurements of chlorine residual are available chose fo r DBPs are not currently available. Complete rel iance on laboratory measurements of DBP in samples taken in

rhe field and processed elsewhere is of limited use compared to on-line monitoring and optimisation.

The use of UV absorbance spectroscopy fo r various surrogate measurements has been discussed previously (Edzwald et al 1985; Chow et al., 2007) . The combined advantages of simple instrumentation, rapid measurement and on-line capability make chis technique a preferred monitoring cool for process optimisation. In chis paper, we will discuss applications of UV absorbance spectroscopy for on- line monitoring of DBP formation. Basic relevant concepts and facts are presented in the sections chat follow.

UV Spectroscopy for DBP prediction Conventional absorbance spectroscopy

The goal of absorbance spectroscopy is to determine how much light is absorbed by a sample of water. Mathematically, rhe abso rbance at any wavelength (A) is denoted as A1,. and defined as the logarithm of the ratio of intensities of light entering the cell (11,._ 0) and chat leaving it (h): ( 1)

h_o and h values and, correspondingly, A ), can be measured with high precis ion

using reasonably simple equipment. In addition to its precision, absorbance spectroscopy has ocher advantages. T hese include unlimited time resolution char allows tracking short-term changes of water quality. Second, on-line absorbance measurements do not require any reagents to be injected in rhe water and/or disposed of. Third, absorbance equipment tends to be robust; chis and reagen rless operation of such equipment result in low mai ntenance coses. Finally, absorbance measurements can be automated and integrated into

The difference in UV spectra between preand post-chlorination.

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technical features refereed paper

existing supervisory control and data acquisition (SCADA) systems.

In all waters, measured A,. values comprise contributions of true absorbance associated with soluble species, and light scattering caused by colloidal particles. In ware rs wi rh low levels of these particles, or when light scattering caused by them has been accounted for using an appropriate algorithms (Langergraber et al. 2004; Van der Broeke et al. 2006), the corrected A,. value is defined by the length of the optical cell (l,,u) used for the measurements, concentrations of light-absorbing species (c;) present in a water sample, and their molar absorption coefficients (E,._;) that reflect how strongly these species interact with light at any given wavelength:

(2)

0.14

......

0.12

E

0.10

II) (J

0.08

';'

.e.

C

ca

...

.0 0

0.06

.0 c(

0.04

1/)

0.02 0.00 250

275

300

325

Disinfection by-products and differential absorbance spectroscopy The utility of conventional absorbance for measurements of nitrate, NOM and chlorine species (Langergraber et al. 2004; Van der Broeke et al. 2006) notwithstanding, on-line water quality monitoring using UV absorption spectroscopy presents complex challenges that are associated with the need to detect and quanti fy trace-level organic species that

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375

400

Figure 1. UV absorbance spectra of chlorinated Judy Reservoir raw water.

Cl 2/D0C =3, Reaction time 5 minutes to 168 hours, pH 7.

0.075 168 hr.

0.08

48hr

The length of the optical cell varies between 1 and 10 cm in most applications.

It is pre-selected for an on-l ine absorbance instrument; rhe choice of rhe cell length is important because coo low or too high (,/1 values will result either in the loss of the measurements' sensitivity, or precision, or both. For a constant fuu, several species common in drinking water have values of the product of la11E,.c that is high enough for these species to be reliably detected by absorbance spectroscopy. These include nitrate, which absorbs strongly in the range of !l.<230 nm, chlorine and chloramine, whose absorbance is affected by the pH where chlorine at pH>7 has a reasonably incense band with a maximum close to 300 nm, and, last not least, NOM (Korshin et al. 2002) . The absorbance ofNOM is defi ned by its concentration and also by its intrinsic properties such as the abundance of non-activated and especially activated phenolic groups. The latter groups, wh ich are active in interactions with chlorine, contribute overwhelmingly co the absorbance of surface waters at wavelengths > 250 nm (Korshin et al. 1997; Chin et al.

1994). Carboxylic, carbonyl and other functionalities typical for NOM do not absorb light in chat region but contribute to the absorbance at 11.<230 nm.

350

Wavelength (nm)

'e

o.oo 0.05 ~

.!::!..

N 0.03

cf

0.02

<j

0.00 0

0.000 250

275

300

325

350

375

400

Wavelength (nm)

Figure 2. Differen tia l spectra of chlorinated Judy Reservoir water at varying reaction times. Cl2/DOC = 3 , pH 7.

have concentrations ranging from < 1 ng/L to >100 Âľg/L. These species include DBPs, algal roxins, residuals of pharmaceutical and personal care products, and other concaminancs of concern. Conventional abso rbance spectroscopy is severely li mited in its ability co detect these compounds because most of them, notably THMs and HAAs, do not have any absorbance bands.

Some compounds of interest have absorbance bands (e.g. nitrosamines), but their concentrations are coo low co produce a ( ,11E,.c product that would be meaningful enough fo r absorbance measurements.

These limitations can be circumvented if a su rrogate absorbance parameter whose behaviour reflects that of a compound of interest can be fou nd. Because the generation of DBPs is inherently linked co the transformations of NOM, monitoring fo r these species offers such an opportunity.

Indeed, interactions of NOM with chlorine involve predominantly light-absorbing, or chromophoric, activated phenolic functional groups (Boyce and Horn ig 1983; Larson and Weber 1994). Interactions of chlorine with these groups may not account

Journol of the Austrolian Water Association

fo r the entire amount and complexity of released DBPs, but the role of chromophoric groups in the generation of HAAs and T HMs is overwhelmingly important in virtually all cases.

Thus, the amount ofTHMs and HAAs is expected to increase as the concentration of the light-absorbing groups in NOM decreases because chlo rination causes these groups co break down and cleave DBPs. Th is means that one needs ro compare the absorbance of water before chlo rination and at any moment after chlorine has been added (Korshin et al. 1998). The difference of absorbances associated with NOM chlori nation is accord ingly referred co as "differen tial absorbance" or M,., which is computed as shown below:

Mjt)= A.(O)-A;_(t)

(3)

where A,.(t) and A,.(0) are the absorbances of NOM at wavelength 11. after reaction rime t and prior co chlorination, respectively.

Properties of the differential spectra of NOM and their relationsh ips with the

technical features refereed paper

formation and speciacion of DBPs can be illustrated by the data for chlorinated Judy Reservoir water. This site is located in Skagit County, Washingcon, USA and supplies water co rhe city of Mc.Vernon, Washi ngcon, USA (130 km north of Seaccle). The D OC of che water varies between 3 and 4.5 mg/L, and the average SUVA2s4 value is 3.3 Lmg· 1m· 1. The concentration of bromide in che water is <0.02 mg/L, and the pH of the fi nished water is 7.2 co 7.5. Although currencly chis treatment plane util ises chloramine as che secondary disinfectant, we will d iscuss here data obtained for Judy Reservoir water created with chlorine (Korshin et al. 2002).

A typical sec of conventional absorbance spec era for Judy Reservoir warer chlorinated using a fixed initial dose of chlorine but varying reaction times is shown in Figure I (residual chlorine was quenched wirh sulfite in these experiments). The data demonstrate char chlorination is associated with a decrease of absorbance ar all wavelengths >240 nm, but rhe spectra are all featureless, other than a trend of decreasing absorbance with increasing wavelength.

D iffe rential spectra rhac were calculated using equation (3) and rhe conventional spectra shown in Figure 1 are represented in Figure 2. They exhibit features that are practically universal co the d ifferential absorbance spectra of most types of NOM (Korshin et al. 2004). Specifically, che maximum in the differential absorbance spectrum is in rhe range of wavelengths from 263 co 273 nm, independent of che reaction time, pH, disinfectant dose, and disinfectant type. The peak in che differential spectrum is broad, with rhe differential absorbance values between 263 and 273 nm differing by only 1 to 3%.

Correlations between the intensity of the differential absorption spectrometry (DAS) signal and rhe formation of DBPs will be examined at the wavelength of 272 nm.

Differential absorbance values chat correspond co chis wavelength will be denoted henceforth as M 272. The insert in Figure 2 shows chat che value of M 272 increases very rapidly afrer the scare of chlorination bur for reaction times above 24 hours it tends to be nearly stable.

Si multaneous analyses of DBP release (Figure 3). show chat che kinetics ofTHM, chloral hydrate (CH) and HAA release are similar co chat of M 272 (Figure 2 inset).

Namely, the concentrations of these species increase monoconically with rime In all cases, significant concentrations of individual DBPs are formed within 5 co 10 minutes of chlorination. The reaction continues co be relatively rapid during fi rsr

150

::J' c, 120 2: C:

.~

~C:

90

c.,

60

Q)

C:

0 c., 0..

m

30

0

40

80 Reaction Time (hours)

120

160

Figure 3. Formation of DBPs in chlorinated Judy Reservoir raw water as a function of reaction time, pH 7.

180

::i Cl 150 2: C:

•

oCHCl3, pH 7 • CHCl3, pH 8

0 :;: 120

-e C:

a,

90

u

C:

0

60

u

30

u..,

J: 0

0 0.00

0.01

0.02 0.03 -M272 (cm- 1)

0.04

0.05

Figure 4. Relationship between chloroform formation and differential absorbance at 272 nm. Chlorinated Judy Reservo ir water.

36

::i Cl 2:

oCH, pH 7

27

•CH, pH 8

C:

0

:;:

~ 18 C:

a, (.)

C:

8

9

J:

u

0 0.00

0.01

0.02 -M212

0.03 (cm- 1)

0.04

0.05

Figure 5. Formation of chloral hydrate as a function of the differential absorbance at 272 nm. Chlorinated Judy Reservoir water.

2 co 4 hours of reaction, afrer which ir slows considerably.

The correlarions of DBP formation with 272 are much simpler than the correspo nding DBP versus ri me relationships, as demonstrated by rhe dara for the formation of chloroform (CHC1 3) at pH 7 and 8 (Figure 4). T hey do nor exhibit rhe continuous curvature seen when rhe same DBP data are plorred as a fun ction of

M

rime. Rather, rhe CHC13 versus M 272 relarionship is virtually linear for M 272 values exceeding a threshold value M;;;s'""d which is approximately 0.015 cm· 1 for Judy Reservoir warer. Recent studies indicate char conditions in which IU,12 < M;;;"""" correspond co the initial phase of chlorine reaction during which lircle DBP is formed (Korshin et al. 2007). Chlorine doses and reaction times chat exist for most drinking

Journal of the Australian Water Association

Water

MAY 2008 85

refereed paper

waters cause corresponding M 272 values to A .d thr,s/told , exceed the ='112 value, and resulnng THM vs. M 272 correlations are likely to be almost linear in most practically important situations.

::J' 12 C) C:

The data presented above demonstrate that differential absorbance spectroscopy can be utilised to determine concentrations of DBPs on-line, once relationships between changes of absorbance caused by NOM chlorination and attendant release of DBPs are established. The daca also show that differential absorbance spectroscopy can be utilised to monitor the formation of all chlorinated DBPs of interest fo r the Australian Drinking Water Guidelines.

On-line DBP monitoring using differential spectroscopy le needs to be recognised that, in contrast to experiments that are carried out in laboratory conditions where in this case M1- values can be determined using a single instrument, monitoring DBP formation in 86 MAY 2008

Water

9

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Similar results can be observed for CH (Figure 5) and chloroacetic acids (Figure 6).

For mono-chloroacetic acid (MCAA), the relationship follows the familiar pattern that noticeable concentrations of MCAA can be detected only when M 272 exceeds a threshold value (Figure 6A). The concentrations of di-chloroacetic acid (DCAA) formed were almost an order of magnitude higher than those of MCAA, reaching maximum values near 100 µg/L (Figure 6B). The concentrations of trichloroacetic acid (TCAA) form ed in chlorinated Judy Reservoir water were higher than chose of DCAA, with values up to approximately 150 µg/L at pH 7 (Figure 6C).

The concentrations of CHC13, MCAA, DCAA and TCAA and M 272 values are linearly correlated at both pHs examined in this study. In contrast, the relationship between CH and differential absorbance is markedly non-linear (Figure 5), with CH concentrations increasing at higher M 272 values. This feature of CH fo rmation has been observed for most water qualities, and it appears to correspond to a formation mechanism for chis compound that is different from that ofTHMs and HAAs (Korshin et al. 2007). Effects of pH on DBP vs. M 272 correlations can also be estimated based on the data presented in Figure 4 to Figure 6. In accord with the literature data (Arora et al. 1997; Singer et al. l 995; Diehl et al. 2000), yields of chloroform increase with the pH, while those ofTCAA decrease. The formation of CH, MCAA, and DCAA do not appear to be noticeably affected by pH variations.

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- AA 272 (cm- 1) Figure 6 Formation of (A) MCAA, (B) DCM and (C) TCAA as a function of the differential absorbance al 272 nm . Chlorinated Judy Reservoir waler. drinking water distribution systems requires at least two UV absorbance spectrometers.

One of them needs to be positioned before the introduction of chlorine in the treatment sequence, while the ocher can be located in any place in the distribution system (Figure 7). If necessary, more than one absorbance spectrometer can be installed in the system to monitor DBP formation at sires chat are deemed important for the overall monitoring program.

The concept of monitoring DBP using differential spectroscopy has been discussed with the Australian water industry in lace 2007 during an extended visit by Professor

Journal of the Australian Water Association

Gregory Korshin to Australia between September and November 2007. Several water utilities have shown great interest in developing this new concept of DBP monitoring as a real-rime monitoring technique. Several case studies have been planned as pare of a project in the Measurement Program of the CRC for Water Quality and Treatment.

Conclusions Providing a safe and high qual ity drinking water can prove challenging for operators.

The use of UV spectroscopy is becoming a popular tool to assist operators due co the simplicity of the technique, its broad

technical features refereed paper

applicability and particularly the availability of on-line instrumentation. This paper has provided an overview of using d ifferential spectroscopy, utilising rwo or more instru ments, ro moni ror DBPs and has demonstrated its successful application for waters in the US. To establish this useful technique as an operational cool, several "proof of concept" case srudies ro apply this techniq ue in che field for real-rime DBP monitoring have been proposed for 2008 with the support of a number of Australian water utilities.

Acknowledgments The financial support of rhe CRC for Water Quality and Treatment (CRCWQ &T), International Centre of Excellence in Water Resources Management (ICE WaRM), American Water Works Association Research Fo undatio n (AwwaRF) is gratefully acknowledged .

The Authors Gregory Korshin (email korshin@ u.washingron.edu) is a p rofessor ar rhe Department of C ivil and Environmental Engineering, U niversity of Washington, Seacrle, WA, USA. Christopher Chow (email: C hris.Chow@sawacer.com.au)is a Project Leader withi n the CRC fo r Water Quality and T reatment and Senior Research Scientist, Water Trearmenr unit, Australian Water Q uality Centre, Private Mail Bag 3, Salisbu ry, Sou ch Australia, 5 108, Australia. Mary Drikas (email: Mary.D rikas@sawacer.com.au) is the Program Leader, Water Treatment Technology, CRC for Water Q uality and Treatment and rhe Principal C hemise, Water T reatment unit, Australian Water Q uality Centre.

References Arora H.; LeChevallier, M.; Dixon, K.L. (1997) DBP occurrence survey. J. Amer. Water Works Assoc. 89 (6) 60-68.

Black, B.D.; Harrington, G.W.; Singer. P.C. (1996) Reducing cancer risks by improving organ ic carbon removal. J. Amer. \~alt'r Works Assoc. 88 (6) 40-52.

Chlorine injection Abs.unit

Abs.unit

Water treatment unit

A,i(O)

Ai 1)) '

.-----------,

'

:_ ______________ ~ M=,\.(0)¡A,_(1)

'' '' ' '

r------------------:'

Figure 7. Conceptual scheme of differential absorbance measurements in a drinking water distribution system.

Boyce, S.D.; H ornig, J.F. ( 1983) Reaction pathways of trihalomethane fo rmation from the halogenation of dihydroxyaromatic model compounds for humic acid. Env. Sci. Technol. 17 (I) 202-21 1.

Chin, Y. P.; Aiken, G.; O 'Loughlin, E. (1994) Molecular weight, polydispersiry and spectroscopic properties of aquatic humic substances. Env. Sci. Technol. 28 (11) I 8531858.

Chow, C.; Dexter, R.; Sutherland-Stacey, L.; Fitzgerald, F.; Fabris, R.; D rikas, M.; Holmes, M.; Kaeding, U. (2007) Multiwavelengt h UV/Vis spectrometry in drinking water quality management, AWA Water journal 34(4) 63-66.

Diehl, A.C.; Speitel, G.E.; Symons, J. M.; Krasner, S.W.; Hwang, C.J. ; Barrett, S.E. (2000) DBP formation during chloramination. J. Amer. Water Works Assoc.

92 (6) 76-90.

Edzwald, J .K. ; Becker, W.C.; Wartier, K.L. (I 985) Surrogate parameters for monitoring organic mat ter and THM precursors.}.

Amer. Water Works Assoc. 77 (4) 122-132.

Korshin, G.V.; Benjamin, M.M.; Chang, H .S.; Gallard , H. (2007) Examination ofNOM chlorination reactions by conventional and stop-flow differential absorbance spectroscopy. Env. Sci. Technol 4 1 (8) 2776278 1 Korshin, G .V.; Benjamin, M.M.; Chang, H.S. (2004) Modeling Disinfection By-P roduces Formation Kinetics: Mechanistic and Spectroscopic Approaches. AWWA Research Foundation and American Water \~orks, Denver, CO Korshin, G.V.; Benjamin, M.M.; Hemingway, O.; Wu, W . (2002) Development of Differential UV Spectroscopy for O n-line DBP Monitoring. AWWA Research Foundation and American Water Works Association, Denver, CO

Korshin, G.V.; Benjamin, M.M; Li, C.W. (1998) Principles and appl ications of differential UV spectroscopy for monitoring and predicting the formation of disinfection by-produces.}. Amer. Water Works Association 90 (8) 88- 100.

Korshin, G.V.; Li, C.W.; Benjamin, M.M. (1997) Monitoring the properties of natural organic matter th rough UV spectroscopy.

Evaluation of a consistent theory. Water Research 31 (7) 1787-1795.

Krasner, S.W.; McGuire, M.J.; Jacangelo, J.C.; Parania, N.L.; Reagan, K.M.; Aieta, E.M. (1998) T he occurrence of disinfection byproducts in US drinking water./ Amer.

Water Works Assoc. 81 (8) 41-53.

Langergraber, G.; Gupta, J.K.; Press!, A.; Hofsraedter, F.; Letti, W.; Weingartner, A.; Fleischmann, N. (2004) O n-line monitoring for control of a pilot-scale sequencing batch reactor using a submersible UV/VIS spectrometer. Water Sci. Technology 50 (IO) 73-80.

Larson, R.A.; Weber, E.J . (1994) Reaction

Mechanisms in Environmemal Organic Chemistry. Lewis Publishers, Boca Raton, F L Singer, P.C.; Obolensky, A.; G reiner, A. (1995) DBPs in chlorinated North Carolina drinking waters J. Amer. Water Works Assoc.

87 ( 10) 83-92.

USEPA 1998 National Interim Primary Drinking

\Vater Regulations; Disinfectants and Disinfection By-products Rule. Final Rule Federal Register. U nited States Government Printing Office, Washington, DC, pp.

69390-69476.

Van der Broeke, J.; Landergraber, G.; Weingardner, A. (2006) On-line and in situ UV/Vis spectroscopy for multi-parameter measurements: a brief review.

Spectroscopy/Europe I 8 (4) I 5- 18.

Journal of the Australian Water Association

water

MAY 2008 87

technical features

scad a

HYDROSHARE G Pyman, A Forster-Knight Abstract 'us' - Utility Services, an alliance between Melbourne's South Ease Water (SEW), T hiess Services and Siemens have combined several technologies and applications into one powerful managemen t cool, Hydroshare. Think of SCADA, GIS, G PS, mobile computing, Personal D igital Assistant (PDA) data collection, video surveillance and mobile phone network data communications all rolled up into an internee enabled package.

Internal and external customer requirements for agile, elegant, economical and flexible solutions co problems involving smart loggi ng of data, timely and relevant reporting, asset and vehicle locations, and security have been mer with chis application.

Figure 1. Atta chment of d ata-lo gger and tran smitter to a w ater meter .

Background Across most of Australia, people are experiencing the effects of severe drought, with water storages at all time lows.

Managing and reducing water consumption is therefore high on the public agenda and a priority for individuals, businesses and governments.

Among che most critical issues affecting our ability co save water is the lack of precise, reliable data co help each of us understand our consumption, identify wastage, leaks an d opportunities co save water, and monitor our own performance.

This applies co ocher utili ty (gas, electricity) consumption as well.

H ydrographics cl ients are demanding timely web based access co data (e.g. water quality, river and scream flows and levels, ground water measurements) which had been hitherto gathered by site visits or old dial-up telemetry methods. Information abou t rhe sires, their location, when lase visited, together with photographs, are also requirements of these organisations.

locations. Having considerable experience and expertise in chis area, 'us' - U riliry Services is beginning co exploit the lacesr communication networks for security and operational needs.

T he solution for all of chis resides in the internet based application Hydroshare.

The Application Thiess Services H ydrographics customers had long been asking fo r a cool char would provide web based data, in real or "near real" rime. Manual data collection was relatively expensive and rhe provisio n of data co rhe customer cook several days at best. Telemetry using land lines in the more remote rural regions was nor proving

In addition co OHS benefits from using Geographical Positioning Systems (GPS) on vehicles, works management is grearly enhanced using chis cool.

88 MAY 2008 Water

South Ease Water were assisting large industrial customers implementing water saving programs including leak detection schemes. Key co these programs was measuring of consumption and validating the effectiveness of the solutions.

Siemens had been involved in rhe development of a produce wh ich was compatible with their range of flowmere rs as well as any ocher transmitter which had pulse outputs and were trialling chem with South Ease Water.

In lace 2005, 'us' - Utility Services SCADA engineers got together with rhe Hydrographics ream, the SEW water leak derecrion group and Siemens co design a web based, automatic monitoring system which mer all the needs of these users. The result was Hydroshare. le is an innovative, powerful and easy to use cool, designed for industrial and commercial users, chat provides chis information in a simple, precise way.

3G communications networks are opening up new opportunities for viable real time video images from critical

Internet-based automatic monitoring.

sufficien rly reliable and the presentation of information using these legacy systems was sub-standard.

Figure 2. Accessi ng data on-line.

Journal of the Australian Water Association

H ydroShare works by logging data from the transmitter (water meter, chlorine residual analyser, electricity power meter etc) (Figurel) using a new generation

technical features

of smart data loggers and translating ic in real-rime, co easy-co-understand trends and tables, on clients' own computers.

Leak of 82 kL per week detected and fixed

A key feature of HydroShare is chat data is accessed through a simple internet connection, on any web sire (Figure 2).

That means char anyone, wich authorised access, can see it - no special hardware or software is needed. Users can share the data with as many of their people as they wish, at ch e same time. In addition, water auchoricies and other relevant organisations can also view che same data ac che same rime co help identify, analyse and resolve any use or quality issues. Simply, H ydroShare allows data to be accessed from any computer via the internee anywhere in the world.

To transfer data, che system relies on che mobile phone com munications infrastructure.

If a network goes d own, each logging unit collects data at site, stores it (for up to 6 months) and transfers it as soon as communications are restored.

The in itial objectives for HydroShare were co:

Figure 3. Trend showing 23 days water consumption with instantaneous read ings (green and blue traces) from 2 main meters and the daily totals at a Melbourne school. co monitor, analyse and reduce cheir water usage.

from where ic is inscancly viewable on che client's web page.

H ydroshare has been scoped co allow fo r large scale deployment and rapid growth across many clients and sires, co meet growing demand.

• 10 year lithium battery capacity (and alert fun ctions when battery power is low), for reliable data capture

Features

Other features incl ude:

• Open internee-based protocols for data transfer

• Deliver the data mo re quickly to clients, the water users, and make it easy for chem to access and understand it

Building che system upon open standards and protoco ls has provided the fl exibility co choose any make or mod el of smart data logging devices. As long as a data d evice is able co transmit scored data w irelessly using internet protocols, it can be adapted co H ydroShare. This fl exibility has made it possible co use H ydroShare in a wide variety of applicat ions.

The system has been developed so chat che logging units simply emai l the compressed and encrypted data co o ur servers for collection and processing.

• Provide more d erailed data than ever before, givi ng users much greater capacity

Powerful back-end software is used to push data into che H ydroshare database,

This simplifi ed data capture considerably, mad e the system easier co

• Collect data abo ut water quality (such as water levels, turbidi ty, salin ity and cemperacure) more effi ciencly • Provide clients with useful data about real cime water consumption

• no th ird parry software, upgrades or maintenance, and so that anyone with internee (and the appropriate authority) can access the data.

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Journal of the Australian Water Association

water

MAY 2008 89

technical features

implement, and also opened up the potential for easy use overseas.

The capacity fo r clients ro create their own reports has been developed, scheduling their own leak dececrion and usage summary reports HydroShare can deliver scheduled "leak alert" reports ro the website, and can also send notification co specified mobile numbers or email addresses if there are unexpected spikes in water usage, or any technical issues with rhe system - 24/7, 365 days of the year.

Results The system is bei ng used by businesses, hospitals, parks and gardens, golf courses, and ocher organisations which are keen ro better understand - and therefore better control - their water consumptio n. Over half of the monitored sites have detected potential leaks or wastage.

A growing number of schools have adopted HydroShare. It gives staff and students an easy way co view, understand and manage data about the school's water usage,. Ways co present the data have been created so chat long term effects on water usage could be easily seen and interpreted, as well as the real time data. E.g. for schools, an innovative benchmarking system for water usage has been developed, so schools ca n benchmark against each other and be encouraged co improve their ranking.

HydroShare is also versatile enough for students co use in their curriculum studies.

Curriculum units have been developed by South East Water in which students use HydroShare as pare of their lea rning about how water is used, and how it can be consumed more efficiently.

Approximately 85 per cent of schools using the applicatio n have identified leaks.

For example, HydroShare detected a constant leak at a small primary school, which would have wasted some 600 kL of dri nking water a year, and another at a larger combined primary and secondary school that saved the school 4300 kL per annum as shown in the plot in Figure 3.

Figure 4. Wa ter, Gas, & El ectricity Consumption at a SEW site. to determine possible site leakage or unaccounted usage.

Annual leakage is estimated based on the night-rime base water flow race from 12.00am to 3.00am.

The cost of leakage is calculated based on assumption of$ J.60 per kL (this allows fo r sewerage disposal charges).

Initial results are: • H ighest leakage: 6,603 kL/year at a cost of $10,565 p.a • Average leakage per flowmeter: 1,455 kL/year or $2,328 p.a.

• Median leakage: 688 kL/year or $ 1, I O1 p.a • Total leakage identified: 49.46ML pa • i.e. Total cost co 26 schools: $79,136 pa The once-off cost of the dacaloggers, including installation, was of the order of $50,000.

A featu re we have noticed chat with schools in parcicular, the internal pipe

90 MAY 2008

Water

HydroShare is being used in diverse applications co give a comprehensive, real time understanding of actual water usage, and enable management of consumption.

Clients' experience (at hospitals, schools, factories, parks and gardens and golf courses) using H ydroShare, and seei ng an accurate visual representation of their daily, weekly and monthly water usage, has led co sign ificant water savings.

'Real rime' monitoring mea ns clients can quickly identify and address leaks and unexpected spikes in usage. Many ocher clients using Hyd roShare have introduced initiatives co reduce consumption and improve water efficie ncy.

The fact the system offers the capabi lity co share online information, through a simple internet connection, means many people can get involved in monitoring water quality and consumption , and immediately see improvements in performance.

As businesses and other organisations share real, easy-co-understand information about their use of water, and can see where it is going and what changes will be effective, they can alter their processes and water use habits to reduce day-co-day consumption. This will have a far reaching impact in helping co achieve long-term water savings.

SEW is conducting a HydroShare pilot program with 26 schools monitoring 34 flowmerers. Schools were invited co participate based on an analysis of their total site water consumption and the number of students attending the school.

(In addition, 8 schools are also participating in a pilot study in Sydney).

A HydroShare data logger has been installed at each school's main water meter(s) and consumption data is analysed

networks are often in a poor state resulting in failures at different locations at di fferent ti mes. Until the schools are able co invest in major upgrades, the Hydroshare installation will continue co identify water leaks year on year and hence repeat the savings.

Figure 5. Entering data manua lly for subsequent transmission.

Journal of the Australian Wa ter Association

HydroShare can be used for benchmarking for different sires within a

technical features

business or across business sectors, allowing quick and easy analysis of data by ind u stry type, usage type and other categories.

The system is now also being used for monitoring o f electricity and gas con sumption with che use of intrinsically safe equipment where required. This cap ability was first utilised at SEW's head office as shown in Figure 4. The top trend shows instantaneous consumption from cwo water flow meters in kL every 5 minutes (green and blue traces - blue meter not in use) and the daily rocalised fl ow in kL (yellow trace) . T he middle t rend is of instantaneous gas con su mption (green trace in cubic metres o f gas per 5 min) and the d aily gas energy co nsumption in Mega Joules. The last trend shows electricity co nsumption in kWhrs per 5 mi n ute intervals (yellow trace), hourly demand - kW (green trace) and average demand per day in kW (blue trace) .

Figure 6. Hydroshare network diagram.

• Taking measu rements and validation of measurement data.

Alternative Data Collection

• Photograp hing sires

It is not always feasible co collect data wi relessly in such a fash ion. Clients with man y hundreds o r even thousands of sires which are read monthly or even less frequently can not just ify che capital cost of installing instrumentation and loggers at each locatio n. H owever timely accurate d ata is still required.

• Synchronisation fea cure for easy transfer of data direccly into Master D atabase.

These PDA devices p rovide derai led informatio n fo r all sites in a scheduled data collectio n run and can collectively score multiple runs on che same storage device, eliminating the need of large scale paperwork. The PDA solution also offers

To faci litate chis, a Personal Digital Assistant (PDA) solutio n chat transfers data wirelessly (just as for Hydroshare) has been developed. Instead of of an instrument providing che raw data, an operator keys in the relevant reading. The PDA software has data validation rules whi ch prompt the user if a suspected incorrect figure is entered. O nce validated che u ser can synchronise the PDA with the main database over the mobile data network for subsequent disp lay o n the web via H ydroshare (F igure 6).

The solution consists of three main components: • PDA Devices provid ed co fi eld staff for accurate data capcure.

• R eports and analysis platform via the H ydro-Share program.

• Graphical rep resentation asset locat ion and feacu res • The PDA devices have been designed co assist field staff with the following: • GPS locator to assist field staff in locating sires.

• Completing site safety, sire inspection and maintenance information using specifi cally designed check.lists.

Journal of the Australian Water Association

Water

MAY 2008 91

technical features

-

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data transfer ability on demand, in turn making most recent data available for users for analysis within much reduced timeframes. The introduction of the PDA also eliminates the need of multiple devices for field staff as it offers multi device capability including mobile phone, GPS, data entry, camera, bar code scanner etc. T he devices are also enabled to provide real time data validation against historical data at the time of measurement data entry. History collected by other means over the years before H ydroshare was implemented, can be loaded into the Historian database to present the whole picture as shown in Figure 7.

Asset and Vehicle Location w.-•rOoo•Wll'••....,._ T_ • •N>fl l•T•.. Cl• teth T-, SU CCKHI f.c:,Tt,WQLOU-i,ty

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Figure 9. Locations of all the ' us' maintenance trucks at 3:20pm on March 28, 2008.

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Figure 10. Tracking of service vehicle #19 over 24 hours.

92

MAY 2008

Water

Journal of the Australian Water Association

With thousands of assets scattered across a large area, clients find it very useful to locate their assets graphically, obtain an overview of its properties and then interrogate history.

,..._.

The HydroShare - Internet Portal allows asset location and GPS vehicle tracking via the Locate 'us' module for any client Australia wide or internationally from any internet co nnection .

This tool is important tool not o nly for OH&S reasons but also for asset and fleet management as well as work dispatching tasks. The simple and secure interface allows any asset or vehicles in the client's system to be quickly and easily located.

Links can be created fro m key assets such as pumping stations and monitoring sites to provide access to consumptions and usage profiles within HydroShare.

Hyperlinks enable immediate viewing of the trend of asset history and a "Find this asset" feature is available on the trend page co enable the location of rhe asset to be displayed immediately.

Vehicles send location information received from satellites back to the Locate 'us' server using Next G, 3G, or GPRS communications. This can occur as often as is required but typically ir is done every 30 seconds whilst the vehicle is in motion.

Figure 8 shows the location of a sampling vehicle (green icon) and sample sites for water quali ty and groundwater level. The drop-down data format for the next target sampling site is ready for use.

Using Microsoft 's Virtual Earth map base, a user is able to track vehicles anywhere. For example in New Zealand, vehicles deployed on a contract in Auckland are tracked by the Locate 'us' module. H yperlinks enable immediate viewing of the trend of asset history and a

technical features

"Find this asset" feat ure is available on the trend page to enable the location of the asset to be displayed immediately (F igure 9).

ation Pla11t

Additional features like alarms for 'Duress/Emergency' can be added and also vehicle performance details, i.e. speed , service, motor data, etc are available.

The application offers the capability to replay a vehicle's movements over any period of time which can be invaluable for audit reasons or resolving customer co mplaints (F igure 10).

Future Developments Installations are about to commence using the Hydroshare network to transmit video using the latest generation video cameras over 3G com ms networks (Figure 11) . Ini tial pilots and trials are very interesting from an asset owner's perspective and with the capabilities of these latest commun ications systems, im proved security and asset moni toring at reasonable costs will fo llow.

10:00:00PM

28-Mar-08 12:00:00AM I

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12

Conclusion In summary Hydroshare is a versatile web based management tool interlinking asset and vehicle location with current and historical records of the asset or vehicle performan ce. Use of the latest data logger and communication technology is allowing economic and secure automatic collection of data which hitherto has been manually read on a much more infrequent basis. Data loss is minimised as the user is alerted immediately to equipment or communications errors where in the past a faulty manuallyinterrogated logger might have mea nt months of lost valuable information.

These technological advances are enabling users to become more efficient in operating their enterprise, make savi ngs, and augment their environmental performance.

For any of these applications hardware can be leased or purchased depending upon requirements, with the application customised fo r the particular project concerned

Figure 11 . Video monitoring of entrance to unmanned plant.

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The Authors Glenn Pyman is Manager Technology and Innovation, 'us' - Utility Services, email: glenn.pyman@usus.com.au; Andrew Forster-Knight is SCADA Manager for South East Water Ltd.

~ p-PUMPS

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THE LOST ART OF SEWER VENTILATION T J Hurse, P Ochre Many aspects of a ventilation system will, nevertheless, fall within the scope of Australian/New Zealand standards (e.g. chose relating co electrical systems, or co safe working in confined spaces).

Abstract Is sewer ventilation an art or is there some real science behind che design of ventilation systems in sewer systems? Gold Coast Water (GCW) has undertaken extensive master planning studies of the Beenleigh and Merrimac catchments in SE Queensland, resulting in a series of new works, upgrades and renewal works over the planning horizon. The Beenleigh Merrimac Pimpama (BMP) Alliance, which is currently delivering this infrastructure, identified the need co gain a better understanding of the design criteria associated with sewer ventilation. Guidance as co current ventilation practice elsewhere in Australia and co che supposed purpose of vencilacion was sought from various sources. le was found chat criteria in use in Australia for designing general vencilacion systems are based on "rules of thumb" without a solid and clearly acknowledged scientific basis. In ch is article relevant guiding documents are surveyed, che purposes served by sewer venrilacion are clearly identified, and che issues chat have co be faced when designing a ventilation system are discussed.

Opportunities for researchers are highlighted.

Introduction Within Austral ian sewerage autho rities and with in che firms specialising in sewerage system design and construction, ir is not uncommon co encounter widely differing opinions about the extent co which a sewerage system should be ventilated.

Decisions concerning the vencilacion of particular pares of the sewerage system should be taken after consideration of applicable standards, codes, and good practice guidelines, if available, or, in their absence, or where they allow flexibiliry, after an assessment of che benefits and

Sewer B

Australian codes

SewerM Figure 1. Schematic of sewers M and B and the receiving pumping station.

limitations of ventilation in that situation.

This sore of assessment presupposes chat the designers are aware of che potential benefits and limitations of ventilating sewers, and have access co design cools, i.e. procedures for quantifying che impacts of different degrees of ven cilacion. In chis article relevant guiding documents are reviewed, che purposes served by sewer ventilation are clearly identified, and existing design cools are discussed. Suggestions are offered as co che aspects of ventilation design chat could benefit from further research. The major points are illustrated with references co the vencilacion system of two trunk sewers (B and M) being co nstructed on the Gold Coast (SE Qld) by che BMP Alliance.

Derails of the sewers and their arrangement in relation co che downstream pumping station (SPS) are given in Table I and Figure I.

Relevant Guiding Documents

Aus/NZ standards Although there is an Australian/New Zealand standard chat specifies requirements for the vencilacion of sanitary plumbing and drainage fro m fixtures co a sewer (AS/NZS 3500.2:2003), there is no corresponding Australian/New Zealand standard that sci pulates how che sewerage system as a whole should be ventilated.

Table 1. Approximate characteristics of trunk sewers B and M. Sewer

Length 1km)

Number of shafts

Internal diameter of the pipe Imm)

B M

4.5

21 10

1200 900

1.2

Ultimate peak flow during wet weather IL/ s) start

end

1233 343

1788* 835

â&#x20AC;˘ ;us/ upstream of the confluence with sewer M

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Journal of the Australian Water Association

The current (2nd) edition of the Sewerage Code ofAustralia (WSA 02-2002, hereafter referred co as SCA) stipulates chat vent shafts shall be provided on branch sewers (nominally DN375 co DN600) and trunk sewers (>DN600) in urban areas where property connection sewers are not vented or where water seals (boundary craps) are in place. The BMP Alliance trunk sewers B and M serve an area in which, by and large, che property connections are vented and che use of boundary traps is min imal. The SCA stipulates ventilation for reticulation sewers (generally DNI00 co DN300) immediately upstream of syphons, ac sewage pumping stations, and at manholes where risi ng mains discharge inco a gravity sewer. T he code advises chat natural venti lation, with an alcernacing sequence of induce and educe vents in which the educe co educt interval is about 300 m, is usually adequate for ventilating branch and trunk sewers, but mechanical ventilation may be required for "some larger trunk sewers".

Notwithstanding these various stipulations, there is an acknowledgement in the com mentaries co the relevant SCA standard drawings chat "ventilation of sewers is a copical issue [ ... and .. . ] some Water Agencies do not allow the use of venting systems."

The current (2nd) edition of the Sewerage Pumping Station Code ofAustralia (WSA 04-2005) deals with che ven tilation of pumping stations (200 Lis and less) and pressure mains (ON 375 and narrower).

Manuals of practice The Hydrogen Sulphide Control Manual ( 1989) (henceforth referred co as the HSCM) is an Australian manual of practice

Predicting the performance ofa sewer ventilation system is complex.

technical features refereed paper

odour management prepared by the Technological Standing Committee on Hydrogen Sulphide Corrosion in Sewerage Works, a committee appointed by che major urban water authorities of Australia. The HSCM was intended as a reviewed and rewritten version of che internationally known manual "Control of Sulphides in Sewerage Systems" (edited by DKB Thistlechwayce, 1972) (hencefo rth referred to as the CSSS). The H SCM also drew upon che American manual Process Design Manual for Sulfide Control in Sanitary Sewerage Systems (USEPA, 1974) (henceforth referred to as the USEPA manual). Boch che CSSS and che HSCM provide guidance on ventilation praccice (and on many other aspects of the H 2S problem).

The H SCM is specifically mentioned in the SCA as the source to be consulted for further information about ventilation practice, and is the standard reference in use in Australia. The H SCM provides design guidance and ill ustrative case studies for naturally ventilated and for mechanically ventilated systems. l e identifies situations in which any ventilation should be mechanical rather than natural: these situation include places where "wastewater is always septic", "wastewater is either scale or septic and flow turbulence can't be avoided i.e. sewer drops", and "freq uent odour problems are likely co occur and odour treatment &/or stack dispersion is critical. " In view of these recommendations, only mechanical ventilation cou ld be considered fo r BMP trunk sewers B and M, as they convey sulfidic sewage through a predominantly residential area.

In the CSSS two alternative design criteria are given for general ventilation (as opposed to ventilation for the purpose of keeping the sewer wall dry) : one based on rhe air-change race and one based on the air-over-surface race. The air-change race is the volumetric rate at which air flows along the headspace between adjacent induct and educe vents, expressed in terms of the volume of chat headspace, and the range recommended was l to 4 changes per hour. The air-over-surface rate (o r "airosur") is defined in the CSSS as the volumetric rate of ventilation air flow (in c.f.m.) per square foot of sewage surface ventilated. The origins of the air-oversurface rate are obscure, being attributed in the CSSS to an unciced Australian investigation chat had concluded chat "sewer conditions probably would be satisfactory if natural ventilation resulted in about 0.05 airosurs." The two design criteria given in the CSSS have been reseated as such in the HSCM, with the

air-over-surface criterion metricized as 2.5 x 10-4 m3/m2/s. The HSCM contains a separate procedure for designing a ventilation system so as to keep the sewer walls dry (see further on). The air-oversurface rate is acknowledged in rhe HSCM to be more pertinent rhan the air-change rate, especially for corrosion control, and the use of the air-change rate is explicitly discouraged (p. 23, Monograph 6.1). A third parameter, rhe airosur divided by rhe mean speed of rhe ai r relative to rhe mean speed of the sewage surface, is advanced, diffidently it muse be said, as a more appropriate design parameter than rhe airosur. The rationale for chis claim is rhe belief that chis relative velocity "relates" to the mass transfer co-efficient for H 2S emission. We chink chat the relevance of this third parameter needs reconsideration: the resistance to H 2S desorption from sewage is thought to lie chiefly in the liquid-phase (Yongsiri et al, 2004), and even if the value of chis relative velocity were zero, the time-averaged air velocity would still be expected to change with respect to vertical distance above the sewage surface, and a predominantly turbulent airflow would not be precl uded.

The HSCM advises chat for naturally ventilated systems rhe interval between adjacent vents should be between 300 and I 000 m. A longer interval is typically achieved in mechanically ventilated sewe rs.

In a case study included in rhe HSCM as an illustration of the wall-drying benefits of mechanical ventilation it is reported that adjacent educes were sited ar intervals of between 900 and 1800 m, although some of these ventilated reaches were operated as a single ventilated reach of 4232 m for a period of about 18 months.

According to rhe CSSS the upper practical limit for the length of a mechanically ventilated reach is 10,000 to 12,000 ft.

Purpose of Ventilation Ventilation is usually proposed for one or more of the five reasons set out below (HSCM). Awareness of the benefits and disadvantages of ventilation is strongly influenced by experience, and experience is constrained by the role in which it is gained, as well as by the climate, rhe topography, the extent and design of the sewerage system, and the community's expectations in rhe place where char experience is gained. This should be kept in mind as a lot of sewerage infrastructure planning, design and construction in Australia is being outsourced to companies whose teams are drawn fro m all pares of Australasia and, increasingly, the world.

1. Reaeracion - to maintain rhe supply of oxygen needed to stop or delay rhe onset of septici cy 2. Wall drying - to keep the unsubmerged sewer wal ls dty, and thereby to discourage the development and/or activity of the biofilms char oxidise H 2S to corrosive sulfuric acid

3. Dilution - to flush the headspace with fresh air and thereby reduce rhe concentration of H 2S 4. Odour management - to withdraw odorous air from the sewer at defined points and thereby to manage the release of odorous air into the environment 5. Safety - to counter the development of a lethal or explosive atmosphere.

These fi ve supposed benefits of ventilation are described in more derail below, and ill ustrated with experience drawn from the BMP tru nk sewer ventilation project.

Reoerotion In regard to ventilation's role in promoting reaeracion, it is apposite to consider the views expressed in rhe HSCM about oxygen depletion, because the potential rate of reaeration will decrease if the oxygen co ntent of the sewer atmosphere decreases. The view expressed in the HSCM is chat ventilation may be required to lessen the degree of oxygen depletion in places where the free passage of air is prevented, but chat "under most sewer conditions the depletion of oxygen in the sewer air is insignificant due to both the displacement of air by the rise and fall of the liquid level and the normal downstream air movement attributable to wastewater drag. " This im plies char any more ventilation than is necessary to allow chat displacement and downstream movement of air to occur will not aid reaeracion. This should be confirmed if the sewer were very long and the sewage temperature warm. We can report char, in the case of the 4.5 km long BMP trunk sewer B, the air change race necessary to march the race of oxygen consumption in the hypothetical case where reaeration were not the race limiting seep would be about 0.04 ac/h. The air change race needed to match the actual reaeracion rate is only about 0.003 ac/h (at the ultimate average dry-weather flowrace, and a sewage temperature of 30°C).

Woll drying The corrosion-promoting role played by moisture condensation on the sewer walls is emphasised in the HSCM, and in consequence of ch is, a detailed design

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odour management procedure for avoiding condensation by means of (mechanical) ventilation is presented in that manual. The procedure is grounded in the belief that condensation will nor occur if che dewpoint temperature of the sewer air is less than the temperature of the sewer wall.

The case study provided in support of che dew-point calculation procedure concerned a mechanically ventilated 4 km stretch of a main sewer in M elbourne.

Wall-wetting became apparent after a distance of about 2 km, a result predicted by application of the design procedure to chat case. T he same procedure was applied to the case of BMP trunk sewers B and M, as a matter of interest, for it had already been decided to use non-corrodible polycrete pipes and, in the shafts, to apply suitable reinforcement covering for the exposure conditions. It was found chat even if each of the reaches of trunk sewer B were ventilated separately, the ventilation rate required to keep the walls of the sewer dry most of the day during summer would range between 0.75 m 3/s (for the shortest reach, I 06 m) and 2.75 m 3/s (for the longest reach, 250 m) .

Each is a considerable flowrate, and bearing in mind chat some of the extracted air streams would require treatment to red uce their odour before discharge, it would be impractical to rely on ventilation to protect those trunk sewers fro m corrosion throughout the year. It should be noted chat during summer the temperature of the sewage, the d ry-bulb temperature of the air, and the relative humidity of the air are approximately 30°C, 26-27°C (both at 9 am and at 3 pm) and 66-72% (at 9 am and at 3 pm), respectively. Ventilating to keep sewer walls dry is thus unlikely to be practical in warm, humid areas.

Dilution

..

The pred iction of H 2S concentrations under different ventilation scenarios is surprisingly complex, and very important, for reasons detailed further on. T he complexity is illustrated by the following two examples. If the volumetric rate at which air flows along the sewer is gradually increased, the H 2S concen tration will fa ll. As this concentration fa lls, the concentration driving force for H 2S desorptio n from the sewage to the headspace increases, and the concentration d riving force for H 2S diffusion to the wall (if any is occurring) decreases. Consequendy, the mass rate of H 2S desorption increases, and the mass rate of H 2S d iffusion to the wall decreases, although the decrease in the latter race is mitigated somewhat by the fact chat the

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increase in velocity also reduces the boundary layer thickness. The upshot of the increase in air flowrate is an increase in the mass rate of H 2S flow along and eventually o ut of the sewer, wh ich translates into a greater impact if uncreated and if discharge arrangements are unaltered (USEPA manual; CSSS).

Another approach to improving ventilation is to install more stacks, but to leave the rate at which air is extracted from the whole sewer unchanged. We considered how the installation of 1, 3 or 6 vents along the alignment of the BMP trunk sewer B, in additio n to a vent at the downstream pumping statio n, would alter the odour impact experienced as a result of the d ischarge of uncreated sewer air from the vents. We concl uded that the installation of vents along the sewer alignment would alleviate the impact in the vicinity of the receiving pumping station, bu t not sufficiendy to guarantee that the impact would meet the relevant criterion set by the EPA. Moreover, che impact of the first upstream vent might nor meet that EPA criterion. The implication of installing the extra vents was a need to treat the extracted air at two sites instead of at one site with a slighdy larger treatment unit. T he latter option is clearly preferable to the former.

Managing the release of odorous air Barometric pressu re changes, the diurnal flu ctuation in sewage level, wind- and thermally induced pressure gradients, and, to an extent, sewage drag can all provide a motive force for the sustained discharge of air from the sewers. T he intermittent discharge of odorous air caused by rapid changes in the sewage level is also problematic. The sewage level changes of most importance in this regard are chose occurring in the wee-well of the receiving pumping station, and also those that occur in and just downstream of a vented risingmain discharge manhole. The case of the wet-well illustrates the issue. As the sewage level in the wee-well rises, it aces like a piston seeking to expel the air from the wet-well at the same rate. If the air cannot escape at that rate, the headspace will become pressurised. Pressurisation should be avoided, if only because it will almost certainly cause odorous air to be forced our into the enviro nment through any gaps or weak seals. The most severe form of p ressurisation due to the piston effect can be avoided if the air is able to flow back up the sewer, e.g. if or while the sewer obvert is unsubmerged, or through a high-level connection installed expressly to allow air to be directed in to the sewer upstream. T wo means of avo id ing

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pressurisation are to extract air through the pumping station ventilation system, or to keep the level in the wet-well steady by matching the pumping rate to the rate of sewage inflow.

The pumping station that is to receive sewage from BMP trunk sewers B and M will be equipped with a mechanical extraction and odour treatment system sized for an air flowra te of I m 3 /s .

Because there are three sewage pumps, each fi tted with a variable frequency drive, sewage can be pumped at any rate between 425 and 2600 1/s. I t is therefore only if the rate of sewage flow into the wee-well is less than 425 1/s chat the level of sewage cannot be held steady, and the piston effect has to be considered.

T herefore, the maximum volumetric rate of air displacement due to sewage level rise is 425 Ifs, and at chat sewage flowrate the volumetric rate of air flow due to sewage drag is estimated to be about 745 1/s.

Thus, the combination of high-level connection, mechanical ventilation and variable pumping rate should ensure that there is no significant pressurisation of the wee-well. Had the set of pumps been designed to pump only at the peak wetweather flowrate, the air extraction and treatment system would probably have had to be sized fo r about 20 00 1/s so as to cope with the air movement caused in dry weather by the piston effect and sewage drag. This benefit of using a set of pumps that can match the run of sewer is not yet widely appreciated.

Preventing lethal or explosive atmospheres As for expectations chat ventilation will or should prevent the development of lethal or explosive atmospheres in the sewer, the HSCM advises chat "[i]t would not be viable to keep a sewerage system continuously ventilated [so as to guarantee a safe atmosphere) for the few times workmen would be required to enter it" and that "(a) ventilation system cannot be guaranteed to always provide complete protection against explosions." The USEPA manual contains very similar advice.

Design Tools In order to assess a proposed ventilation schem e, che design ream needs to predict the scheme's cost, operation and maintenance requirements, and environmental impact. In chis regard there are two distinct design need s: the first is to determine the characteristics of the extracted air stream, and the second is to predict the impact of char stream once it

technical features refereed paper

odour management has been created and discharged through a stack into the environment. T here is a desire to meet the first need through mathematical modelling, bur the current models are simplistic and the results must be judged in the light of experience. The second need can be met with a soph isticated atmospheric dispersion model, provided that the major odorant, its concentration in the discharged air, and its odour threshold or regulatory limit are all known. The issues of odorant identity in che d ischarged air and H 2S concentration in the extracted air are critical and are discussed below.

Odorant identity

Although there are certainly odorous compounds ocher than H 2S in sewer air, a strong correlation is generally observed between the odorousness of that air, and the concentration of H 2S in char air. This fact, as wel l as the causal relation between H 2S and sewer corrosion, and the fact chat H 2S concentration is easier to measure with precision than odour, all accou nt for the foc us on H 2S. The correlation between odour level and H 2S concentration does not of itself prove char H 2S is the main odorant, but the hypothesis seems likely given the observation chat the raising of the sewage pH to 8.5 un its tends to reduce the odour of sewer air considerably; chis would be unusual if the principal odorant were a mercapran or an amine, compounds char can often be detected in sewer air. In view of che foregoing it is a com mo n practice in Australia to judge the likely impact of untreated sewer air on the basis of H 2S concentration and an odour threshold of about 0.5 ppb. This procedu re was adopted to predict the likely impact of extracting and discharging untreated air from BMP trunk sewer B and the pumping station. The practising engineer needs to be aware that the chief odorant in treated sewer air may not be H 2S, This is the case with air discharged from chemical scrubbers or biological fil ters.

We have also been advised of instances where the air leaving a media filter (mixture of activated carbo n and oxidants) has, as the filter media approach exhaustion, developed an odour reminiscent of che smell of rotten meat. A better understanding of what compounds are responsible for the odour in created sewer-air may lead to the improved performance of treatment systems.

Estimating the concentration of H2S in the extracted air

O ne aspect that received some attention in the CSSS (I 972) but next to none in

___H_e_ad_sp_a_ce------------+1-ff-....,_

. parce

.. L ~

Sewage

~ /v\

. movmg

Sulfide flux

Figure 2. O ne-dimensional plug-flow concept, side and end-on views (after CSSS,

1972) . the H SCM ( 1989) is the matter of estimating the co ncentration of H 2S at a given point in the sewer headspace.

Knowledge of the concentration and the mass rate of flow of H 2S in sewer air is, in principle, critical for the design of a system to treat extracted sewer air, and is certainly necessary fo r the atmospheric dispersion modell ing assessment referred to above. The matter of predicting the H 2S co ncentration has since received fu rther attention (Matos and de Sousa, 1992) but it is only with difficulty chat che model can be used to yield an esti mate char the practising engineer can have confidence in.

One dimensional model. In the models in the CSSS and in Matos and de Sousa's paper, air is assumed to move along the headspace in accordance with the plug flow ideal, and sewage is assumed to flow along the sewer as a scream free of drops, hydraulic jumps and other major flow disturbances. The dimensions of the pi pe and the sewage scream, the composition of the sewage, and che flowrate of sewage are assumed constant with respect to rime and position. The air is assumed to move in che direction of sewage flow, and as it does so it is assumed to pick up H 2S from the sewage, and, potentially, to lose H 2S to the H 2S oxidising microbial communities on the sewer wall (see Figure 2). O n this basis, a mathematical expression relating the concentration of H 2S in the air bulk to the distance the air has travelled along the sewer is derived.

Quite apart fro m the question of the appropriateness of assuming air movement to conform to the plug flow ideal, and not to mention the limitations imposed by excluding co nsideration of major flow disturbances, there are five major obstacles to be overcome before the model can be applied.

T he firs t obstacle is the fact chat sewage scream dimensions, sewer diameter, sewage flowrate, and concentrations of dissolved H 2S in sewage do generally change with respect to position along a sewer. In che investigation undertaken for che BMP Alliance we circumvented chis obstacle by breaking the sewer up into

reaches in each of which the assumptions of uniform dimensions, flowraces and dissolved H 2S concentration held.

Determi ning what dissolved H 2S concentration to assume for each reach is the second obstacle. If the scenario to be modelled involved the existing sewage scream, che concentrations could be obtai ned through a sewage monitoring program. O n the ocher hand, if the sewage scream in the scenario under study does not yet exist, one has to predict the concentrations with another model. Such was the case fo r BMP trunk sewers B and M. Predictions of dissolved H 2S co ncentration were made using the Po meroy-Parkhurst sewage model and measured values of key characteristics (see below) of sewage similar to the sewage to flow along tru nk sewers B and M. The third obstacle to the application of che headspace model concerns the H 2S loss to the walls. The predicted val ue of H 2S concentration in the air bulk is very sensitive to the assumed value of fp, the H 2S concentration in the air immediately adjacent to the wall divided by the H 2S concentration in the air bulk. The sensitivity increases as fP approaches a value of 1, and is such chat a change in the assumed value offP fro m 0.9 to 1 might increase the predicted H 2S concentration ten fold. T he choice of a value of fP is a matter calli ng for considerable judgment and experience.

T he prediction of the air flowrate is the fourth obstacle to model application, one made particularly difficult to negotiate by virtue of che number and variability of forces potentially acting on the air, and by the river and tributary structu re of the sewer network. Notwithstanding che guidance char is available in the CSSS, in publications by Pescod & Price (1982 , 1983), in a USEPA emissions estimation manual (1994), and in recent publications

by Edwini-Bonsu and Steffler (2004, 2006), the problem of estimating flowraces is hardly routine, and the accuracy of answers will be limited by uncertainty about the degree to which air can enter the network (e.g. through

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pumping station hatches and vents, emergency overflow structures, and illegal connections).

The final obstacle is co make allowance for che variarion of all of rhe above, especially rhe dissolved H 2S concentration, wirh rime. A lor of rime and money can be spent on monitoring or modelling sewage jusr co characrerise temporal variation in sewage composirion and flowrace. The characrerisarion should enable predicrion of rhe peak concenrrarion and mass rare of flow of H 2S in any extracted sewer air, as these will be needed co establish the requirements for treatment and dispersion of char air. For the design of the ventilation system for BMP trunk sewers B and M, chis characterisation was undertaken with sewage samples taken between 4am and IO am on a weekday morning in summer, a period during which rhe temperature, BOD, and concentrations of coral and dissolved H 2S were expected co be at their respective peaks. The conservative assumption was then made chat these cond itions would prevail at all times. Es timation of the average concentration and mass rare of flow of H 2S would also be desi rable if their values had sign ifica nt implications fo r the choice and cost of treatment technology.

T he effort needed for a more comprehensive characterisation (e.g. a probabi lity distribution fun ction for the H 2S concentration) would be justified only in circu mstances where it may lead co che avoidance of large and unnecessary cost, e.g. if it were suspected char the value of the mass rare of H 2S flow char coincides with conditions of poor atmospheric dispersion is considerably lower than the peak value.

Multidimensional model. The more fu ndamental question of whether a onedimensional plug-flow model can ever provide chose designing, operating or maintaining the sewers with useful guidance about the variation of H 2S concentration along the sewer headspace still awaits an answer. Ir has been demonstrated through investigations with 3-D hydrodynamic models (Edwini-Bonsu and Steffler, 2004, 2006), through studies with laboratory-scale sewers (Pescod and Price, 1982), and by observation of real sewers (USEPA manual) chat air does not flow as a plug along a sewer, and chat che longitudinal velocity profile is very different from the plug-flow ideal, especially if sewage drag is che only moti ve force. Nevertheless, secondary circulation currents chat tend co distribute material througho ut the cross-section have been observed, and pred icted co arise. Their

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existence and predicted speed give some reason co believe char even if the actual longitudinal velocity profile is quite different fro m the plug-flow profile, a plug-flow reaction model augmented with terms co represent longitudinal dispersion and the spatially incense release of H 2S from drops and hydraulic jumps - and possibly incorporati ng temporal variations as well (i.e. being fully dynamic) - might satisfy the practising engineer's requirements for speed and accuracy.

Improvements to the plug-flow model are needed, and most urgently in respect co the procedures for ( I) estimati ng the areal rare ofH 2S release in the vicinity of drops and hydraulic jumps and (2) selecting che appropriate value offP - does fP depend on the material on rhe inside wall of the pipe?

T he long term goal should, however, be a full solution of the rime-and-spacedependent equations of momentum, hear, H2S- and water-vapour transfer, and in a dimensionless form, if at all possible, so as co facilitate the preparation of co rrelations and charts for design purposes. Defi ning the rares of the biological processes involving H 2S is expected co be a particular challenge.

Conclusion Sewer ventilation design practice varies appreciably in Australia, chiefl y because the benefits and disadva ntages of sewer ventilation depend on location, and the physical, chem ical and biological phenomena affecting the perfo rmance of a ventilation system are complex and by no means fu lly understood. There is enormous potential in ch is field fo r research institutions and sewerage engineering organisations co collaborate co their mutual advantage.

Acknowledgments The authors acknowledge the stimulating feedback provided by staff of the BMP Alliance. (The Alliance is an alliance of Gold Coast Water, T enix Alliance Pry Led, and GHD Pry Led).

The Authors Dr Timothy Hurse (email cimochy.hurse@ ghd.com.au) and Pip Ochre are both Process Engineers in the Municipal Process Service Group in the Brisbane Office of GHD Pry Led.

References Edwini-Bonsu S and Steffler PM (2004). Air flow in san itary sewer conduits due co wastewater drag: a computational fluid dynamics approach, J. Environ. Eng. Sci. 3: 33 1-342.

Edwini-Bonsu S and Steffler PM (2006).

Dynamics of air flow in sewer conduir headspace,j. Hydraul. Eng. 132(8) 79 1799.

M aros JS and de Sousa ER ( 1992) T he forecas ting of hydrogen sulphide gas buildup in sewerage collection systems, Wat. Sci. Tech. 26(3-4) 9 15-922.

Odour Impact Assessment fi"om Developments Guideline (2004). Environmental Protection Agency (Qld, Australia).

Pescod MB and Price AC ( 1982). Major factors in sewer ventilation. journal WPCF, 54(4) 385-397.

Pescod MB and Price AC ( 1981 ).

Fundamentals of sewer venrilation as applied to the T yneside sewerage scheme.

Water Pollm. Control, 80( 1) 17-33.

Hydrogen sulphide control manual - septicity, corrosion and odour control in sewerage systems ( 1989). Sanders BS and Score PH (eds .), 2 volumes, Melbourne and Merropolitan Board of Works, Melbourne, Australia. (Reprints available from Water Services Association of Australia Inc, Melbourne).

The control ofsulphides in sewerage systems ( 1972) . T hisclethwayte 0KB (ed.), Burcerworths Sydney, Australia.

Water Advertising To reach the decision-makers in the wate r field, y ou should consider advertisi ng in Wate r Journal, the official journal of Australian Water Association.

For information on advertising rates, please contact Brian Rault at Hallmark Editions, Tel (0 3) 8534 5000 or email brian.rault@halledit.com.au

Journal of the Australian Water Association

Process design manual for sulfide control in sanita,y sewerage systems ( 1974) . U .S. Environmental Protection Agency, Technology T ransfer Office, Washingron D.C., USA

Air emissions models for waste and wastewater ( 1994). U.S. Environmenral Prorccrion Agency Office of Air Q uality Plan ning and Standards, Research T riangle Park, North C arolina, USA. EPA-453/R-94-080A.

Sewerage Code ofAustralia (2002). 2nd edi tion, Warer Services Association of Ausrralia Inc, Melbourne, Ausrralia.

Yongsiri C, Vollercsen J, Rasmussen Mand Hvicved-Jacobsen T (2004) . Air-warer transfer of hydrogen sul fi de: an approach for applicarion in sewer nerworks. Water Environ Res 76(1) 81 -88 .