__MAIN_TEXT__

Page 1

ISSN 0310- 0367

I

Official Journal of the

rA•~i i;M •ti!: l\¼ii 3;W :1 11

l\1*iiffii=t;f!~i-i•X!Jt£iit•1~1 Vol. 12, No. 3, September 1985- $3.00 Registered by Australia Post -

publication no. VBP 1394


FEDERAL PRESIDENT R. Ll oyd , G.H . & 0 ., GPO Box 668, Bri sbane 4001 .

FEDERAL SECRETARY F. J . Cart er, Box A23 2 P.O . Sydney Sth ., 2001.

FEDERAL TREASURER J . D. M o lloy, C/- M.M.B.W. · 625 Lt . Co llin s St ., Me lbourn e, 3000.

BRANCH SECRETARIES Canberra, A.C.T . Dr. L. A . Nagy, 8 Belco nne n W ay, Page, A .C .T . 2614. (062 54 1222)

water Official Journal

AUSTRALIAN WATER AND WASTEWATER ASSOCIATION

Vol. 12, No. 3, September 1985

CONTENTS

New South Wal es C. Davis, G.H . & D. P/L, P.O. Box 39, Rai lway Square 2000 (02 690 7070)

Vi ctoria J. Park, Water Tra in ing Ce nt re, P.O. Box 409, . We rr ibee, 3030. (74 1 5844)

Qu ee nsland D. Mackay, P.O. Box 412, West End 41 01. (07 44 3766)

South Au st ralia A. Glatz, State Water Laboratories, E. & W .S. Private Mail Bag , Sali sb ury , 5108. (259 03 19)

Western Au stralia Dr B. Kavanagh , Wate r Auth . of W .A. , PO Box 100, Leedervil le 6007 (09) 420 2452

Tas mani a G. Nolan , G.P.O . Box 78A Hobart , 700 1. (002 28 0234)

Northern Territory M. Lukin , P.O. Box 37283 Win nellie, N.T. 5789.

EDITORIAL & SUBSCRIPTION CORRE SPONDENCE G. R. Goffin, 7 Mossman Dr. , Eaglemont 3084 03 459 4346

Viewpoint- Timothy Smyth, Director GH & D, President NSW Branch A WWA . .. ... ...... ... ....... .

5

Association News, Views and Comments ............ .. .... . . . ... .

6

Strategic Plan for AWWA-A Perception -F. R. Bishop . ............ . ....... . ..................... .

10

Calendar 1985-86 .. . .... . . . . ... . .. . . ... .. . .. ............... . . .

11

Report-Seminar on Desalination, Adelaide -Correspondent Neil Palmer . ....... . .. . ..... . .... . ..... . . .

13

Development of a Beach Pollution Index for Sydney Coastal Beaches -N. R. Achuthan, J. D. Brown, J. D. Court and D. D. Low

14

Cowra Water Treatment Plant, Uprating Augmentation -S. M. H. Jones ... .... .. . .... . ..... . .. . ... .. . ........ . .. .

21

Book Review ..... . .. ... .. .. .. .. ... ......... .. ...... . ...... ,. . .

25

Advanced Sewage Treatment for Western Sydney -8. Walters . . .... . ... . .... . ... .. ........ .. .. ... , ....... .

27

Computer Controlled Diversion Scheme - Georges River Catchment, Sydney -P. J. Fisher . . .... .... . ..... . .... . ... . .. .... ... .. ...... .

32

Conferences - Courses - Technical Interests . . . . . . . . . . . . . . . . . . . . .

37

People - Plant - Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

39

COVER PICTURE The Nepean River 11 km downstream of Penrith . Under low to medium flow conditions, the river is eutroptic. This is caused primarily by discharge of effluents from sewage treatment works, re sulting in the elevation of nitrogen and phosphorus concentration s. The photograph shows excess ive growth s of aquatic plants - Duckweed, Azolla and Hydrodic tyon - in the river. Th ese growth s have been the cause of much public complaint and have resulted in the NSW State Pollution Control Commission imposing nutrient controls on the discharge of treated se wage to the river and its trubutaries . The paper in this issue 'Advanced Sewage Treatm ent for Western Sydney' by B. Walters of the Sydn ey Metropolitan Water, Sewerage and Drainage Board, provides details of the nutrient controls now being installed at some of the sewage treatment works discharging to the Hawkesbury-Nepean River System. Cover picture -

donated by State Pollution Co ntrol Co mm issio n, New So uth Wates.

Th e sta temen ts made or opinions expressed in 'Wa ter' do not necessa ril y reflect the vie ws of th e Austra lian Water an d Was tewater Association, its Co un cil or co mmittees.

W AT E R Sep tember, 1985

I


ASSOC/A TION

ing water supply and sewerage technical officers in Papua New Guinea . Both members gave the meeting an interesting and valuable perception of work in South East Asian countries . Programme

Friday, September 27: The Branch's annual guest night will be held at the Institution of Engineers, 11 Bagot Street, North Adelaide. This year's speaker will be Mr. Michael Bowering, S.A. Deputy Crown Solicitor, and the meeting will commence with a buffet tea at 7.00 p.m. All members and their wives or partners are welcome to this event. Friday, October 25: Vic Neverauskas from the State Water Laboratory, Bolivar, will give an address entitled 'The Impact of Port Adelaide Sewage Treatment Works on the Marine Environment'. Thursday, November 28: An afternoon meeting will be held at 2.00 p.m. in the State Convention Centre, Flinders Street, Adelaide for the visit of Professor M. B. Pescod, Head of the Civil Engineering Department of the University of Newcastle-upon-Tyne in the U.K . Professor Pescod is a world renowned

NEWS

VIEWS

authority on environmental engineering, and will address the meeting on the subject 'Hazardous Waste Disposal'. New Members

The Branch Commmittee is pleased to welcome Roxby Management Services as a sustaining members. The firms nominated contact officer is Bill Rymill who, among other things, is responsible for the water supply and treatment facilities for the Olympic Dam venture. The Branch also extends a warm welcome to Brenton Browning of Abtech Environmental Services, Phil Hine, Scientific Officer, E. & W . S. Department (members) and Jim Jones, Technical Officer from E. & W. S. (associate member) .

STATE NEWS The new Coober Pedy water supply system was officially opened on July 7, 1985 by the Hon. Jack Wright, Deputy Premier. Member Roger Stokes, whose firm designed the scheme and supervised its construction, reported that consumers in Coober Pedy now have a reticulated water supply for the first

COMMENT

time. Water is metered and a computerised accounting system sends out bills monthly, with water price being $4.10 per kilolitre. The desalination plant converts brackish groundwater (TDS 4500 mg/ L) to potable water currently with TDS of 300 mg/ L. Construction is underway for a $ I. 9 million water supply scheme for Coffin Bay on Eyre Peninusula. Funded partly by the Commonwealth as a Community Employment Project, the scheme is being designed and supervised by the E. & W. S. Department and should be completed before Christmas. The State Water Laboratory is currently involved in a research programme to investigate removal of organics from water supplies, using magnetic based resins. the research, partly funded by the Commonwealth, is being carried out by members Don Bursill, Phil Hine and Jim Morran and a pilot plant has been set up at Hope Valley to evaluate the cost of the process. It is reported that dramatic reductions in chemical requirements for subsequent flocculations, filtration, pH adjustment and disinfection can be achieved in addition to benefits in filtered water quality (e.g. lower trihalomethane concentration by precursor reduction) .

WATER COMMISSION FOR THE TERRITORY? The NT Government announced in July the decision to investigate the possibility of the Territory having a statutory water authority along the lines of the NT Electricity Commission. The Chief Minister, Mr Ian Tuxworth, has selected the Deputy Under-Treasurer and Chairman of the Territory Insurance Office, Mr Phil Temple, to head the study which is expected to be completed before the end of the year. Mr Tuxworth said that the Grants Commission had expressed concern in its last two reports about the way water and sewerage costs were recovered in the NT. It suggested that these public utilities should be accounted for separately. The Chief Minister said one of Mr Temple's first tasks would be to investigate the costs incurred in providing water and sewerage services to various Northern Territory communities and the extent to which 'user-pays' cost recovery principles operate. Mr Temple would also advise on whether new legislation should be brought down to establish an appropriate water authority . If such an authority is found necessary he will recommend ways in which it could incorporate existing areas of Government with some involvement in water matters. Responsibility for water and sewerage functions is currently distributed among the four Divisions in three Departments as follows: Ground and surface water resource investigation and monitoring.

Water Resources Division, Department of Mines and Energy.

Planning, operation and maintenance of systems, and revenue collection.

Water Division, Department of Transport and Works .

Design and construction of systems.

Public Works Division, Department of Transport and Works.

Plumbing inspection.

Planning and Building Division, Department of Lands.

Establishing a water authority embracing the who!; Territory will involve some difficult issues. Not the least being the sparse and disproportionate population distribution . The Territory is 1.4 times the size of NSW but has one twenty-fifth the population. Almost half the 140,000 Territory population is in Darwin, one quarter in the main towns of Alice Springs, Katherine, Tennant Creek and Nhulunbuy, and the remaining quarter widely scattered in some 50 remote Aboriginal communities. With the exception of Darwin, Katherine and several small communities, all water supplies are from bores and Darwin and Katherine supplies are supplemented from bores. Consequently, operating costs are generally higher than for gravitated catchment supplies. The main towns and almost all remote Aboriginal communities have sewerage reticulation and disposal systems. Water and sewerage rates are levied in the main towns. Recently the Government decided to introduce per capita charges for essential services to Aboriginal communities to improve the level of cost recovery . The NT Electricity Commission, mentioned as a model for a new water authority, has since its formation in 1978, progressively taken over power supplies throughout the Territory. The most recent transfers were the 50 or so Aboriginal communities which passed to the Commmission last year. Previously, community power supplies were constructed and operated by the Department of Transport and Works with funding being provided by the Department of Community Development. The Territory Government is to be applauded for making the move to review the fragmented structure of its water administration. Those in the industry see it as an advance towards improvement in efficiency, consolidation of expertise, and provision of a more cost effective service to consumers. RICHARD MARKS, President NT Branch WATER September, 1985

9


Strategic Plan for AWWA

A Perception

F. R. Bishop - Nov. 1984

The Federal Executive asks that members foward comment and suggestions to the Federal Secretary, Sydney 1. INTRODUCTION It is considered that any organization which has a change in leadership every one or two years needs some guidance in its ·policy. A medium term strategic plan to cover four to five years ahead could be considered desirable.

2. GOALS OF THE ASSOCIATION • disseminate technological advances in industry; • publis h technological information; • sponsor conferences, symposia; • inform the public and government; • encourage education, training and research; • maintain international links. Management and economic issues are largely absent from A WW A goals - and shou ld be included.

3. ORGANIZATION The Association is a federation of State Branches, and there has been little change in the organizational structure since I 962. Recognizing there is li mited Association membership (2,000) and consequently income, consideration needs to be given to whether the level of service meets Association objectives. The Association, with its limited funding, attempts to achieve a national status and outlook by the following: (a) Two Council Meetings per year. (b) Both Federal Councill ors from each State Branch attend together with Federal Officers. (c) The Exec utive (President, Vice President, Past Pres ident, Secretary, Assistant Secretary and Treasurer) meet four times per year to take action on business arising between meet ings. (d) A part time office manager has been operative since February, 1984, to reduce the load on the honorary secretaries and expedite routine administration matters. (e) Communication is achieved by the Journal 'Water' - four issues per year, with a paid part time editor. Some States have monthly newsletters prepared by vo luntary labour. (f) Biennial conferences, workshops and seminars with a large vo luntary labour component from members are conducted. Professional paid assistance is becoming increasingly necessary, but that cost can be built into the registration fee . (g) Standing Committees At the Federal Council Meeting in November, 1979, endorsement was given to the establishment of a number of StanIO WATER September, 1985

ding Comm ittees to faci litate management of the Association. The objectives of the Standing Committees were: - to enable the conduct of in-depth studies on areas of management and to provide an ongoing assessment. - to advise the President and Council on any matters of topical signficance and on the future role and management of the Association. - to facilitate the work of Counci l and the conduct of Council Meetings. - to achieve a greater invo lvement of members in work of the Association. The Standing Committees were reviewed in a Report prepared by Mr. D. J. Lane in 1982 and presented to Council on November 5, 1982.

4. DUTIES OF ST ANDING COMMITTEES The Standing Committees have made positive contributions to the Association and have certainly accelerated investigations and studies that, if undertaken by indiv iduals, would have extended the time frame considerably. The following comments are made on the various Standing Committees: 4.1 Executive Committee

Effective in decision making on key matters between Council Meetings and in programming for Council consideration. The Executive meets four times per year. The Executive should continue as is. 4.2 Standing Committee on Science and Technology A number of initiatives have been taken and several sumissions made to the Senate and various Federal Government Committees of Enquiry. These have been well received. There has been a lack of direct approach by Governments to the Association (and S&T Committee) and an improvement in this can only achieved by publicity coupled with the professional standing that such bodies as the Institution of Engineers Australia, Royal Australian Chemical Institute, ASTEC etc . receive from the Government. It is believed that the S&T Committee can add to the prestige of the Association but improved marketing of the Association and its learned society - unbiased technical advice role, is necessary. 4.3 Committee on Budget and Finance

This Committee does not meet as a group but provides a valuable link on financial matters between Federal Counci l and State Branches. The service provided by the Federal

Treas urer in preparing budgets and progressively mon itoring performance, along with collating State performance, · is an important service. No change is considered necessary, but one Term of Reference is to prepare a three year financial plan. It is believed this aspect should be examined - see later. 4.4 Committee on Future Policy and Planning

This is a very important Committee as far as the Association is concerned . T he Committee has responded well to several tasks. The role of the Association must be under continual scrutiny in the years ahead. The role of this Committee has two key components: 'Policy' - goals, changes in characteristics of A WW A, membership, affiliations in Australia and overseas. 'Planning' - a medium term strategic plan (say 3-5 years ahead should be produced and integrated with a financial plan). In fact, two separate committees would be a possibility. 4.5 Committee on Publicity and Education

T his Comm ittee has played a major part in the Aims and Objectives brochure and the draft 21st Annual Report. ' Education of the public, schools, universities and government on key issues has not proceeded very far for a number of reasons including economtc ones. The scope of this Committee may need revision with a view to playing a more leading role. 4.6 Committee on Membership Services

This is an important group, recommend ing what service is needed for members, students and associates. The principa l recommendation appears to be better communication by the Journal and Branch newsletters. Needs in the future must be considered part of any strategic plann ing process. 4.7 Committee on Administration

This Committee has been active and while work load is reducing, there wi ll be ass ignments from time to time . Continuation of the Committee is desirable. 4.8 Committee on Legislation and Government

Difficulty was encountered by one Committee collecting legislation from all States and reviewing it. It would appear that new legislation vital to the water industry will be first noted by the State Branch or ACT Branch for federa l legislation - and can thus


be acted on or referred to Federal Council (or Executive) for action . The Committee should be disbanded. 4.9 Committee on Conferences

The main ac hievement of thi s Committee have been the calendar of national and international conferences (an ongoing task), . A WW A Conference timetable a nd Guidelines on Summer Schools and Conventions. Through no fault of the Committee, it has not undertake n one of the Terms of Reference - 'to undertake the co-ordination of A WW A conferences'. Thus fa r the responsibility seems to pass from Federal Co uncil to the State Organizing Committee. Recognizing that convention planning has been well done by State Branches, the documentation appears to be one facet which is left wanting after the effort of running a convention . Modification of the Terms of Reference is desirable and perhaps nomination of this Committee to co-ordinate and provide liaison for conferences for Federal Council with the State Organizing Committee. 4.10 Committee on External Relations

Much of the work (actually done by Executive) has related to li aison and closer working relations with the Institution of Engineers. Currently, in spite of cordia l relations, there does not appear to be the opportunity fo r closer interaction. The demise of the A WCC a nd parallel operation of the Australian Committee of IA WPRC has not resulted in increased workload. External relations are an important aspect, and some amalgamation with WPCF and other committees is desirable. 4.11 Committee on Relations to WPCF

This has operated well, with action being taken by A. P ettigrew (Director), and now R. F. Lloyd. 4.12 Committee on Relations with IWSA

This function was undertaken by the Executive. At present interaction is minimal. In view of our involvement/contact/ membership with: IA WPRC, IWSA , American A WW A, IWE&S (UK), IWPC (UK) and NZWS&DA as well as our firmer ties with WPCF, it is considered that one single Committee to look at 'external relations' could be advantageous. Budgets for interaction could be set with some uniformity in approach. 4.13 Journal Committee

This has well and truly met its Terms of Reference and is one of the best sources of comm unication with members, potential members a nd others. Meets objectives fully, could be improved by increasing from four to six issues/year but would require more income and effort. A decision to increase income can only be achieved by taking over publishing (and advertising) from Appita. It would require significantly increased labour, time and costs to that provided now by G. R. Goffin (Editor).

5. ANALYSIS OF STANDING COMMITTEES It is considered that the Standing Committees serve a useful positive fun ction in the Federal Co uncil Organizational Structure. Some modification of Committees and their Terms of Reference cou ld be considered. If the Association decides to upgrade its serv ices, then strategic and financial planning will assume increasing importance, and in fact will be vital.

6. THE FUTURE Federal Council (representing Association members) will have to make a decision to: (a) continue as at present; or (b) upgrade its services. A survey of members th rough the Journal may be a su itab le app roach . If (a) is accepted, then present subscription level will be adeq uate (subject to indexing for inflation) . It is unlikely that the AWWA will rise to become a national leader for the water industry and may in fact decline in influence. If (b) is proposed then it will be necessary to decide on medium term objectives and this will necessitate production of: • strategic plan • finan cial plan • marketing plan The level of ' upgrade' and consequently, increased participation in communication with governments and the general public will be reflected in the need for more income. There are three optio ns (or a combination thereof): (a) increase members' subscription rates (b) campaign for more members (c) campaign fo r more Sustaining Members (and increase minimum rate) . Option (c) will undoubtedly increase income the most. Undoubtedly, upgrading the Association, would be best achi eved by appointing a full time (or part time) professionally qualified person with experience in the water industry as Executive Director of the Association. He would be able to undertake Executive duties presently completely done by honorary officers (Mess rs. J. Carter and G. Dooley) and part time office manager (J. Sears). The presence of an Executive Di rector would enable contact with Ministers and Senior Government officials to be achi eved and maintai ned . The cost would not stop at the Director who would require office support. A report several years ago by the Policy and Planning Committee high lighted the significant costs.

CALENDAR 1985-86 October 6-11, Kansas City, USA

WPCF National Conference and Exposi tion. October 9-10, Winston-Salem, USA

International Symposium on Management of Hazardous Chemical Waste Sites. October 14-18, Manjing, China

Symposium on the Analysis of Extraordinary Flood Events October 14-25, A dana , Turkey

Seminar on Applications of Isotopes and Nuclear Techniques in Hydrology in Arid and Semi-arid Lands. October 18 , Sydney, Australia

Water and Rural Industry, WRFA. October 21-25, Tucson, USA

Nineteenth International Symposium on Remote Sensing of the Environment. October 22-25, Maroochydore, Queensland

Fourth Australian Soil Conservation Conference. October 23-25, Brisbane, Queensland

Concrete Confere nce . October 23-25 , Ann Arbor, USA

Fift h Remote Sensing Symposium. November 4-8, Kuala Lumpur, Malaysia

First Asian Water Technology Ex hibiti on and Conference. November 5-7, Nice ~ France

Internal and External Protection of Pipes Sixth International Conference. November 9-14, Atlanta, USA

Water a nd Human Health . N ovember 11-14, Sao Paulo, Brazil

International Symposium on Water Resources Management in Metropolitan Regions. N ovember 13, Sydney, Australia

Seminar, Participation in Asian Proj ects, AWWA. November 13-16, Nevado, USA

7. CONCLUSION The Association is in a changing environment a nd it must retain a flexible approach else it will slip into a comfortable club with no achievements. This paper is not comprehensive but is intended to stimulate views of Federal Councillors. It is suggested that individual Co uncillors should di scuss with their Branch Committees and respond to the Federal Executive by February, I 986.

Irrigation, Drainage and Flood Control. N ovember 17-21, Fresno, USA

Third International Drip/ trickle Irrigation Congress. November 17-23, Bermuda

Second World Desalination Congress and Exhibition. November 20-22, Paris, France

Nitrates in Water (WHO, IA WPRC). WATER September, 1985

11


1986

CALENDAR (Continued)

May 15-16, Madeira, Portugal

Seventh European Conf~ence on Environmental Protection.

January 5-9, Calcutta, India

Water and Sanitation at Mid-decade.

May 28-30, Paris, France

November 27-29, Singapore

Management of Watet and Sanitation Networks.

Biotech '85.

January 26-30, Cocoa Beach, USA

December 2-5, Hong Kong

Geotechnical Applications of Remote Sensing Transmission .

Polmet '85 Co nference Urban Areas.

February 24-27, Monaco

Ecology and Environmental Quality.

Mediterranean Water Technology Exh ibition and Conference.

June 10-13, Bournemouth, UK

June, Jerusalem, Israel

Pollution in

December 4-5, London, UK

Symposium - Impact of Fina ncial Constraints on Level of Service in Water Industry.

March 27-28, Florida, USA

Water Quality Modelling in the Inland Natural Env ironment.

Sixth International Symposium on Environmental Pollution.

July 2-10, Budapest, Hungary

Second IAHS Scientific Assemb ly.

December 7-11, Texas, USA

Water Quality Technology Conference.

April 9-11, Dubrovnik, Yugoslavia

December 8-13, Kentucky, USA

International Symposium on Comparison of Urban Drainage Models with Real Catchment Data .

Surface Mining, Hydrology, Sedimentology and Reclamation. International Seminar on Environmental Impact Assessment of Water Resources Projects.

13th Biennial International Conference, IAWPRC. August 24-30, Canberra, Australia

April 9-11, London, UK December 12-14, Roorkee, USA

August 17-22, Rio de Janeiro, Brazil

· Sediments Down-Under.

Measuring Techniques for Hydraulic P henomena.

September 7-10, Minneapolis, USA

Distribution System Symposi um .

April 14-18, Adelaide, Australia

Engineering Conference, IE Aust. December 16-17, Illinois, USA

Fifith International Symposium on Agricultural Wastes.

April 22-25, Ostend, Belgium

December 16-20, Manila, Philippines

May 11-16, Brisbane, Australia

Regional Workshop on Salt Water Infusion in Large Coastal Cities.

International Conference Systems Under Stress.

SITIAINISIEINIS

September 8-15, Carlovy Vary, Czechoslovakia

Fourth World Filtration Congress.

Nineteenth Congress, International Association of Hydrologists.

Groundwater

September 22-24, Hanover, W. Germany

Pressure Surges.

introduce the .....

NEW ISCO MODEL 2700 WASTEWATER SAMPLER Specifically engineered for reliability

• • •

Totally sealed construction with keypad control Continuous memory to maintain sampler settings Corrosion resistant materials and a new plastic pump that promotes longer tubing life

Unsurpassed versatility in controls

• •

• •

Six modes of operation including sequential time, sequentia l flow, composite time, composite flow, nonuniform time interval, and sequential flow composite True composite sampling with user selection of the number of samples to be taken, indication of the number collected, and a fail-safe float shutoff to prevent accidental overflow Wide time or flow settability Simple, self-prompting controller setup

SITIAINISIEINIS 12

WATER September, 1985

Melbourne Sydney Brisbane Adelaide Perth

544 8022 750 7444 52 5141 212 5700 446 9455


Report

Seminar on Desalination Adelaide -

June 1985

Correspondent - Neil Palmer Walkerville Town Hall near the City of Adelaide was the venue for the SA Branch's Seminar on Desalination held on June 28, 1985. A total of 115 delegates attended from a wide diversity of Government, industry and consultant backgrounds with a significant number of interstate visitors, revealing a widespread interest in desalination .

OPENING SA Branch President Peter Norman welcomed delegates and introduced the SA Minister of Mines and Energy, the Hon Ron Payne MP, who officially opened the seminar. Mr Payne commended the Association for its initiative in arranging the seminar, pointing out that more than half of the underground water resources in South Australia had a salinity of 7000 mg/ L or more and required some form of desalination for it to be useful for potable water or irrigation. Mr Payne mentioned successful applications of desalination in the State on a commercial or municipal scale, but chall enged delegates to consider the need for small scale units which do not need mains electricity for isolated communities and fami li es throughout the arid areas of the State.

FIRST SESSION: THEORY AND WORLDWIDE TRENDS The keynote address was given by Professor Chris Fell of the School of Chem ical Engineering and Industrial Chemistry, University of NSW. Professor Fell 's address was lively and entertaining, and covered the subject 'Desalination Processes and Theory'. He brought delegates up to date on the various processes currently available commercially with explanations and comment upon advantages and disadvantages. Professor Fell also outlined a new process (membrane distilation) which has attracted considerable interest overseas, especially in Europe and adivised that commercial prototype units are already availab le. A second presentation in this theoretical session of the Seminar was given by Ian Fergus, Sales Manager, Membra~e Systems, from Permutit. Ian spoke on 'Trends and Applications in Membrane Desalination Systems', outlining recent advances in membrane technology. Ian also covered case histories of some large scale overseas reverse osmosis plants and outlined selection criteria for different types of membranes currently on the market. Factors pertinent to the choice between reverse osmosis and electrodialysis reversal were presented in Ian's written paper along with common operating problems which influence process selection .

Left to right: Peter Norman (Branch Pres.), Hon. Ron Payne MP, Minister of Mines and Energy, Prof. Chris Fell (Uni. of NSW), Bob Jones (Seminar Organiser).

multistage flash distillation) in commercial or industrial installations at Coober Pedy, Leigh Creek, Roxby Downs and Moomba in South Australia. Mike Makestas, Investigating Engineer from the E & WS Department related early experiences with desalination at Coober Pedy including solar stills and tubular reverse osmosis. Roger Stokes (R Stokes and Associates) followed with an address on the design, construction and commissioning of the new Coober Pedy water supply reverse osmosis plant which was supervised by his firm . Charles Steer (Chemist-Technical Services) from the Electricity Trust of SA outlined operating experiences with reverse osmosis equipment installed to supply potable water to the relocated coal mining town of Leigh Creek. Bill Rymill (Senior Project Engineer, Roxby Management Services) followed with a slide presentation on the Roxby Downs mining venture and the electrodialysis reversal plant used to desalinate Great Artesian Basin water for the town and mine pilot plants. Allen Gower from Santos completed the case studies with a presentation on operating experience with multittage flash evaporators which are used to supply up to 1.3 ML per day of distilled water for the Moomba gas processing plant. In closing the seminar before supper, Peter Norman expressed appreciation to all the speakers and the session chairmen Ralph Wood and B?b Jones . He also paid tribute to the work of the organising committee (Bob Jones, Chairman; Mike Makestas and Neil Palmer) for their efforts in arranging the seminar). Summarising, the seminar provided a valuable exchange of information between designers, manufacturers and operators of desalination equipment. A complete set of sem inar papers is available and can be obtained for $20 (includes postage) from the Secretary A WW A (SA Branch), State Water Laboratory, Private Bag, Salisbury 5108. Telephone (08) 259 0211.

PAPERS OF THIS SEMINAR NOW AVAILABLE

The seminar in session.

SECOND SESSION: CASE STUDIES Case studies were presented of the design and operation of three desalination processes (reverse osmosis, electrodialysis reversal and

This comprehensive set of notes includes a theoretical introduction and up-to-date operating and cost data.

Apply to A. Glatz, State Water Laboratory, Private Bag, Salisbury 5108 (08) 259 0211. Price: $20 Aust. plus postage overseas. WATER September, 1985

13


Development of a Beach Pollution Ind.ex for Sydney Coastal Beaches N . R. Achuthan, J. D. Brown , J. D. Court and D . D . Low ABSTRACT

WARRlEWOOD OUTFALL

At Sydney coastal beaches, the levels of visual sewage pollution indicato rs and faec al coliform densities were monitored during the swimming seasons o f 1984-85 . The relatio nships between these indicato rs of pollution are investigated . Further , a Beach Pollution Index (BP I) based only on visual indicators has been developed . A BPI would classify the severit y o f polluti on as nil , low, medium o r high.

I

1. INTRODUCTION T he purpose of developing a Beach Polluti on Index (BPI) is to give users of Sydney beaches a n indication of the pollution levels occurring on a daily basis. Altho ugh there is already a public awareness of the lin k between the major shoreline discharges of sewage at North H ead , Bo ndi , and Malabar (Figure !) , and the res_ultant pollution of Sydney beaches, a BPI would qualify and quantify the relationship . Like the Sydney Air P ollution Index (SP!) , the BP I would be a single number based on the severity of representative visual indicators of pollution . The BPI co uld be calculated daily fo r each of Sydney's coastal beaches and reported as nil , lo w, med ium , or high polluti o n.

'------ NORTH HEAD OUTFALL

/

BONDI OUTFALL

2. INDICATORS OF BEACH POLLUTION Historically, the con cept of beach pollution has been related to an assumed link between faeca l contaminatio n 6f bathing waters and public health . This assumption was based on the theory, th at during recreation , a wide variety of pathogeni c micro-organisms of faeca l origin could be transmitted to humans through contact with water conta minated by sewage . Unfortunately, methods for determinin g th e presence o f these micro-organi sms were, and are still, not suitable for the routine examination of recreatio nal waters. Th e faecal coliform test , on the other hand, was and is relatively simple . As a result , the faeca l coliform density in beac h waters was adopted as the standard meas ure of beach pollutio n on an average basis both in Australi a and overseas. Although statistical res ults from the faecal

The A uth ors are all with the State Pollution Control Commission (SPCC), New South Wales, Dr. Narasimaha Achuthan as a Scientific Of f icer; M r. Jeff Brown is the Senior Scientist Wa ter Branch (Water Technical Services); M r. John Court is Chief (Water Division) and Mr. Derek Low is an Engineer (Clean Waters Branch). 14

WATER September, 1985

'----- MALABAR OUTFALL

BOTANY BAY

.__ CRONULLA OUTFALL

Figure I. Locations of major Sydney coastal beaches and sewage outfalls.

coliform test (American Public H ealth .\ssociation 1975) a re use ful as indicators of ,age contamination , there are a number of

problems related to the use of this test. The fir st problem is the time lag between sampling and the availability of results. C urrently this


lag is around 24 hours. Reasoner et al. ( 1979) proposed a modified procedure for faecal co li form test reducing the tim e lag to around seven hours. Added to this is the travelling time between the collection point and the laboratory. The second problem is the timedependent variabilit y of the waters being samp led. Un li ke swimm ing pools and other impounded bodies of water such as lakes and reservoirs, coastal waters are continually moving due to the effects of tides, wind s, and ocea n currents. As a result, there is often little or no correlation between results of samples coll ected one day, or even one hour, and the next. Thus bacterial pollution of beaches is normally expressed in terms of statistical means (State Pollution Control Commission [SPCC] 1976). The third problem is that conflicting evidence was obtained when researchers attempted to correlate the concentration of faeca l co li form s and other such bacterial indicators with pathogens (SPCC 1979). Furthermore, studies by The British Committee on Bathing Beach Contamination (Moore 1959) concluded that bathing in sewage-polluted sea water carries only a low risk to health , even on beaches that are aesthetically very un satisfactory, and therefore considered that it was unn ecessary to introduce a bacterial standard for recreational swimming beaches. More recently, The Coastal Pollution Research Comm ittee of the Water Pollution Research Laboratory (Department of the Environment [U .K. ] 1974) recommended that the following aesthetic requirements for bathing beaches should apply: (i) No faecal solids, or other material clearly of sewage origin, stranded on the beach or visible in the water near the shore. (ii) No noticeable turbidity or di scolouration of the water near the shore. (iii) No perceptible smell due to sewage in a reas accessible to the public. (iv) Any sewage slick formed shou ld be in offensive. Further studies by Moore (1975) found that there was no evidence to show that the incidence of minor illness is higher for bathers than for non -bathers. The public aversion to bathing in diluted sewage effluent is neverth eless very real, despite the lack of conv incing scientific evidence of a health risk at the levels of pollution usually encountered in Syd ney.

BEACH NO . I

DAY

MJNTH

rn 3

2

[I] Wll.O SPEED

[ I "]

5

'

IS

$:

.

16

[IJ

CO'\ ING FRCl'l

KNOTS

'

8

[I] [IJ

WIND DIRECTION

13

T!r-E ( 24

YEM 7

6

.....

HR CLOCK) II

10

I I I

12

I

I

(ff SHOOE WAVE DIRECTI ON

'

17

,rt"

18

[IJ

CCl'l! NG FRCl'l

$

W AVE f£ 1GHT

" o

NO . Cf PERSONS AT THE BEACH

• .o

CLOUD COVER 21

22

23

I I I

= THAN 5 = = 50 THAN 50 =

NOT PRESENT

5

TO

r-ol<E

SEWAGE ODOUR IN THE AIR NOT PRESENT SLI GHT ODOUR M)D, ODOUR STRONG ODOUR

10

25

26

27

I I I

l

1%

2 3

Q.

1%

GREASE ON BEACH: NO . PARTI CLES IN 5 M SECTI ON LE SS

D0

= 10 TO 100 = = 100 TO 500 MORE THAN 500 = LESS THAN

M

FRACTI ON Cf BEACH POP ULATl ON IN THE W ATER

2,

20

28

D D 2 " D

0 l

JS

3

ll

D = = = 2 D = D 0 l 3

38

45

GREASE ON BEACH : Ml\X IMLM SIZE IN 5 M SECTION

5

TO

5

MM DIA ,

M'l DIA ,

50

MM DI A.

32

TURBID !TY PEYOND ERE.AKERS WATER CLEAR SLI GHTLY CQOURED M'.lD, Ca..OURED VER Y CQ OURED

EARLy f'ORNI NG BEACH f'1AI NTENANCE = 0 WAS MANUALLY CLEANED = l NOT DETERMINABLE

50

l'ORE THAN

WAS NOT CLEANED

WAS ME CHANI CALLY RAKED

36

NOT PRE SENT LESS THAN

L] = 0 = 1 D = 2 " = 3 D

= 2 = 3

D "

D D"

= = = =

0 l

2 3

D " D . D

f'1ATERI fil Cf SEWAGE OR IG IN ON BEACH NO . PIECES IN 5 M SECTION = 0 NOT PRESENT LESS THAN 5 = l 5 TO 50 = 2 MORE THAN 50 = 3 f'1ATER1/ll Cf SEWAGE OR IGIN IN W ATER NOT PRESENT LI GHT CONCENTRATI ON M'.lDERATE HEAVY

= 0 = l = 2 = 3

30

D D " D [] " D " D 37

.

NAr-E Cf OBSERVER: ADDITION.Al CO'M:NTS:

1

I F SAMPLES WERE COL LECTE O FOR BACTERIOLOGICAL OR CHEMICAL ANALYSIS PLEASE TICK BOX AND COMPLE TE REVERSE SIDE

"

D

Table 1. SPCC Beach Pollution Survey Sheet

As a result of these problems, there has been a move in recent years away from using bacterial tests as direct and immediate measure of beach pollution. Both the SPCC arid the Department of Health have recommended the use of visual indicators and aesthetic judgement in making day-to-day decisions about closure of beaches in bath ing waters.

manly include the extent of grease and debris on the beach, and the presence of floating scum and turbidity in the water. At Manly, a very popular beach near the North Head Outfall, beach inspectors and health surveyors have been carrying out beach pollution surveys for a number of years. Parameters observed incl ude ev idence of grease, faecal, and plastic or rubber materials on the beach, the frothiness of the water, and sewage smell in the air, as well as wind direction and res ults of bacterial examination .

Thus , in Sydney, some of th e counci ls of coastal municipalities and shires now post signs on beaches warning of visible sewage pollution. The decision to post a sign is usually based on subjective evaluation of beach and water cond itions by a coun cil beach inspector on a daily basis. Factors considered vary from inspector to inspector, but com-

The SPCC decided to move to the development of relevant daily BPI to introduce a degree of quantification and consistency in the semi-subjective judgements of visual indicators now being made. It is not claimed that such an index has any direct relation to a health risk. It wou ld be a quantification of visual indicators.

3. DEVELOPMENT OF SPCC BEACH POLLUTION SURVEY Beach pollu tion data collected by Manly Council between March 1981 and April 1982 were analysed to determine whet her or not there were any correlations between indicators of pollution, faeca l coliform densities and wind directions. The analyses showed that, for Manly beaches, there was statistical evidence of structural relationships between faecal coli form densiti es, wind directions, and visual pollution indicators. As a result, the SPCC designed a beach pollution survey which relied almost solely on visual pollution indi cators. Table 1 shows the survey sheet. Before its design, discussions were held with officers of the beach side counci ls of Warringah, Man ly, Waverley, Randwick and Sutherland to seek assistance and provide instructions on the WATER September, 1985

15 /


method of data collection to be followed by council health surveyors and/ or beach inspectors during the surveys. T he first half of the survey sheet provided a record of relevant meteorological and oceanographic conditions, and the beach population at the time of the survey. The second half of the survey sheet was for recording parameters which provide an ind ication of the extent of sewage pollution. These included the number of grease particles on the beach the maximum size of grease particles, the number of pieces of material of sewage origin on the beach, the presence of sewage odour in the air, the degree of turbidity beyond breakers, the presence of material of sewage origin in the water, and whether or not the observed section of the beach had been previously cleaned or raked. The levels of these parameters were coded from O to 3 as explained in the survey sheet. The parameters were observed in randomly chosen five metre sections of the northern, central and southern zones of the beach . The reverse side of the . survey sheet was used for recording results of bacterial and oil and grease analysis on water and sand samples, if collected. Beach pollution surveys were conducted from January 1984 to April 1984 and from December 1984 to April 1985 . Council beach inspectors, health surveyors, and officers of the Metropolitan Water Sewerage & Drainage Board (MWS&DB) and the SPCC were involved in the data collection . Figure I shows the Sydney coastal beaches under study together with the locations of the sewage outfalls.

4. RESULTS OF SPCC BEACH POLLUTION SURVEY 1984 The beach pollution survey of 1984 was conducted at 21 Sydney coastal beaches. In total, 2212 survey sheets were completed (Table 2).

TABLE 2. SYDNEY'.S COASTAL BEACHES INCLUDED IN 1984 SURVEY Beach Number 1 2 3 4

5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 16

Beach Name

Warriewood Turimetta North Narrabeen Collaroy Long Reef Dee Why South Curl Curl Freshwater (Harbord) Queenscliff North Steyne South Steyne Fairy Bower Shelly Beach Bondi Tamarama Bronte Clovelly Coogee Maroubra Long Bay Wanda

WATER September, 1985

Noof Survey Sheets Completed 26 21 173 132 164 165 158 147 48 30 35 39 32 190 138 193 88 108 227 22 76

•• II

w l!1

a:

18

I-

z w u

71

0:

w

Q.

w >

81

... ,. a: I-

...J

w

0:

w

...

41

>

I-

a:

38

...J :::, J:

:::,

u

28

N

"

fl

w

~

=

• ! ~ ~ ? BEACH NUMBER

!

~

!

~

m

~

N

LEGEND. GREASE ON BEACH: NUMBER PARTICLES PER 5 METRE SECTION Level 0 (Not present) .. . Leve l 2 (5 to 50) --Leve l I (Less than 5) + + + Leve l 3 (More than 50) x x x

Figure 2. Grease -

4.1 Visible Sewage Pollution The occurrence pattern of the visual pollution indicators, grease on the beach, materials of sewage origin on the beach , turbidity beyond breakers and materials of sewage origin in the water were analysed at the three (north, centre and south) zones of

occurrence pattern.

each beach. There was no significant difference between these distributions for each of the visual pollution indicators, therefore, for each visual pollution indicator, the three distributors were combined to form one by taking the maximum of the three observed zonal values in each survey sheet.

••

.

w l!1 a:

Ill

I-

z w u

71

II!:

w

Q.

w

....::,. Ia:

81

,.

...J

w 0:

w

...

48

>

I-

a:

38

_J

1:::

::l J:

:::, 21

u

...,

Ill

• N

~

~

m

~

• ! : ~ ~ BEACH NUMBER

?

~

!

~

LEGEND. MATERIALS OF SEWAGE ORIG IN ON BEACHES : NUMBER OF PART ICLES PER 5 METRE SECTION Level 0 (Not present) .. . Level 2 (5 to 50) --Level I (Less than 5) + + + Level 3 (More than 50) x x x

Figure 3. Distribution -

sewage material on beach.

!

~

~

N


,.

Severity of visib le sewage pollution on Sydney's ocean beaches seems to depend significantly on the proximity of the beach to a major sewage outfall. Figures 2 and 3 show the occurrence pattern of grease and materials of sewage origin on beach, respectively , for the 21 beaches assessed during the survey . Higher levels of all visual indicators were more frequently observed at South Curl Curl, Freshwater, Tamarama, Clovelly and Maroubra beaches. Lower levels occurred at Warriewood, North Narrabeen, Collaroy, Bronte, Long Bay and Wanda. Moderate levels of visual pollution indicators were observed at the remaining beaches. It should be noted that only 20-30 survey sheets were completed for some of the beaches (Table 2) .

w ~

. .

!zw

11

le

II

~

w >

1-4

I-

a: .J ~

L,J

~

-..........

/////////

.........

-

,.

.... . ....

1

Mean Minimum 16th Percentile 25th Percentile 50th Percentile 75th Percentile 84th Percentile 90th Percentile 95th Percentile 99th Percentile Maximum

476 10 39 70 170 260 470 840 930 3800 5400

Grease levels I 2 3290 10 20 90 180 410 440 920 4700 4700 4800

404 30 44 60 130 540 580 830 1100 1100 2300

+++++++++

1 ::::::::: ...... ...

..... ....

.........

......... 41

.........

1

1

j , ...... . .

·········. ,!i ........ 1 ...... . ..

......... .......... ......... +++++++++

++++++m

....... ..

'! ' ' ' " " ' " II

,......... I

1::::::::: 1 , ..... . . .

:... .... .. 1 ....... ..

~

.. .. ..... .... .... .

f " ' " '"''' ,

....... .. ,i ....... .. j ....... ..

I ", .... ..

,... .... .. ! , ....... . ,....... ..

II

,

.. ....... 1

.........

.. .. ' . . . '

1 ....... ..

.

I

LEVELS OF GREASE

"

LEGEND. FAECAL COLIFORM COLONIES PER 100 mL , (0 lO 100 ... (500 to 1000) X X X (100 to 200) + + + (1000 to 7000) Ill (200 to 500) ---

Figure 4. Faecal coliform occurrence pattern.

5. DEVELOPMENT OF THE BEACH POLLUTION INDEX (BPI) An ideal BPI would be one based on the concentration of some constituent of sewage. Unfortunately, apart from the bacterial methods discussed above, there are no known indicators which can be rapidly determined in-'situ. However, the Commission has been investigating a technique which makes use of inherent fluorescent properties of sewage discharged from the Sydney outfalls. Preliminary results of this work were encouraging. In the absence of established and rapidly determined chemical measures of sewage pollution, it appeared that a BPI could be developed based solely on visual parameters. The BPI concept is related to public perception of pollution, namely aesthetics. This is an adequate basis for a BPI considering its

Mean Faecal Coliform Densities (organisms/ JOO mL)

Maximal Faecal Coliform Densities (organisms / JOO mL)

0

......... ......... ......... +++++++++

TABLE 3. PERCENTILE VALUES OF FAECAL COLIFORM DENSITIES FOR VARIOUS GREASE LEVELS Percentile Values

/Ill/Ill/

r--+++++++++

+++++++++

--·/////////

-- ......... /I'll/I/II

r---

.J ::J J: :J II u

When bacterial testing was undertaken co un cils collected three distinct water samples, one from each zone, for analysis of · faeca l coliforms. Samples were collected for 108 survey sheets during the study period . In order to understand the behviour of the average and the worst case occurrences of faecal coliform densities, the mean and maximum densities of the three samples reported in each survey sheet were statistically analysed . The relationship between faeca l coliform densities and visual indicators was complex and a single mathematical relationship between these two parameters could not be obtained. Table 3 shows the percentile values of mean and maximum faeca l coliform densities for various levels of grease. High faecal coliform densities were observed more frequently when high levels of grease were detected. During the study period, the MWS&DB completed 276 survey sheets and implemented one faecal coliform analysis per sheet. Figure 4 shows the relationship between faecal coliform densities and various levels of grease. Again, high levels of faecal coliform densities occurred more frequently when high levels of grease were detected. This type of relationship was common to all the visual pollution indicators.

/////////

/I/Ill/I/

>

4.2 Relationship between Faecal Coliform Densities and Visual Indicators

--

Ill/I/II/

1-4

I-

a:

-

//I/Ill/I

3 4242 70 80 270 3400

5600 7300 8000 8000 8000 12000

0 34 1 10 20 37 97 174 260 397 690 3400 3567

Grease levels I 2 1411 6 13

50 100 270 404 863 4067 4067 17367

293 17 30 44 77 387

506 510 733 733 1833

3 2673 43 60 203 2200 3640 3866 6433 6433 6433 8000

purpose as a guide to day to day pollution. A relationship between faecal coliform densities and visual parameters would be desirable but is not a n essential requirement. About 15 different indices were considered as mathematical functions of the four visual indicators under study. The indices were compared using scatter diagratns between the index and faecal coliform densities. All of the indices produced correlation coefficients less than 0.6. After careful consideration, the following index havit1g a correlation coefficient of 0.55 was proposed as the BPI for use during the coming summer season . BPI = 11+12-1 Where II = {(G+l)'(MB+l)'(T+l)' (MWT+ 1)}' 1 ' 0 and 12 = Maximum {G, MB, T, MWT}. and G: Code for number of grease particles on beach. MB: Code for materials of sewage origin on beach. T: Code for turbidity beyond breakers. MWT: Code for materials of sewage origin in water. (For details of these codes refer to Table I. Note that, G, MB, T and MWT can take values 0, I , 2, or 3.) Portion II of' the index represents the weighted geometric mean of the visual pollution indicators G, MB, T and MWT. These factors have a weighting of 5, 2, 2 and I, respectively. The weighting resulted from a practical judgement as to the significance of robustness of the ind icators for beach pollution. In computing I I, the levels of the visual indicators were increased by one (i.e. 1.0 was WATER September, 1985

17


1118

TABLE 4. CLASSIFICATION OF BPI

Oto > 1 to >2 to >4 to

Nil Low Medium High

1 2 4 6

added to the ratings) to avoid the occurrence of zero values. A subsequent correction (by subtraction of one) is made in computing the BPI. Portion 12 of the index quantifies the worst level of visual pollution among the four indicators. The performance of 11-1 as an index, by itself, was not as favourable as the proposed BPI which includes the 12 component. In this way the possible error introduced by visuall y under-estimating a highly weighted indi cator (say G) and so reducing the va lue of II, wou ld be offset by the value of 12 not being reduced correspondingly, since the chance of an observer simultaneously making this error in all the four indicators is very low. This assumes that there is some degree of correlation among the indicators, wh ich was in fact observed. Levels of pollution were classified as nil, low, medium and high using the BPI, as shown in Table 4. Figure 5 shows the occurrence pattern of faecal co liform densities for various levels of beach pollution as clssified above, for data obtained by .the MWS&DB .

6. FINALISATION OF BPI METHODS AND PROCEDURES Prior to the 1985/ 86 swimming season, a number of modifications will be made to survey parameters to further refine BPI observations and calculations . Firstly, the grease term in the BPI formula will include a size factor based on an estimate of the average diameter of grease particles. As a result, the value of the calculated BPI will more accurately reflect public perception of the severity of beach pollution due to sewage grease . Secondly, the parameters 'sewage odour in the air' and 'turbidity beyond the breakers' will be omitted from the survey sheet. Analyses of results from the previous two swimming seasons have indicated that these parameters cannot be reliably and accurately assessed and observed levels are not always representative of actual beach pollution levels. However, these two indicators will be

NUIUII IIU NI

XlUDUOlUX

Pollution Levels

BPI Value

-- -

.........

H

w

l'f

~

811

711

li:

lOtXXXXXIOt

•••x•••••

xxxxxxxxx

---

8B

+++++++++

-

511

..J

~

411

> 1-4 ~

3B

l:

211

w

•iuxuxxx UXXlOIXJCX

••010.:xxx XXXJUUCXXIII

(l_

~ 1-4

xxx1n11nnnr

--.......... +++++++++

:::::::::1

::J

u

111

~

~ LEVELS Ot POLLUTION AS PER BPI LEGEND. FAECAL CO LIFORM COLON IES PER JOO mL (0 to (()(). (500 to l000) X X X ( 100 to 200) + + + (l000 to 7000) /// (200 to 500) ---

Figure 5. Faecal coliform patterns at various BPl's.

replaced by indicators related to the severity of pollution due to materials of stormwater origin. The relative va lues of these indicators could be determined following an assessment of the impact of stormwater pollution on bathing water quality. Finally, for purposes of BPI calculations, observations should be restricted to three randomly selected sites within the flagged area, that portion of the beach most frequented by beach users. These modifications will shorten the time required for carrying out surveys.

7. ACKNOWLEDGEMENTS The authors express their appreciation to the officers of the various Councils, Metropolitan Water, Sewerage & Drainage Board and State Polution Control Commission for their enthusiastic co-operation in the data collection stage of the study. Special thanks are to the members of the Inter Branch Committee of the Commiss ion for their effective guidance during the study .

THE

8. REFERENCES American Public Health Association (1975). 'Standard Methods for the Examination of Water and Wastewater'. 14th ed . (American Public Health Association, Inc., New York). Department of th e Environment (1974). Report of Coastal Pollution Research Committee of the Water Pollution Research Laboratory, Department of the Environment, London, Her Majesty's Stationery Office . , MOORE , B. (1959). Sewage Co ntamination of Coastal Bathing Waters in England and Wales. Journal of Hygiene, Vol. 57: 435-472. MOORE , B. (1975). The Case Against Microbial Standards for Brhing Beaches ' Discharge of Sewage from Sea Outfalls' . (Pergamon Press, Great Britain). REASONER, D. J. , BLANNON , J. C. and GELDREICH, E. E. (1979). Rapid Seven-Hour Faecal Coliform Test. Applied and Environmental Microbiology, Vol. 38(2), 229-236. State Pollution Control Commission (1979). Health Aspects of Faecal Contamination-Environmental Control Study of Botany Bay- BBS 4, State Pollution Control Commission, Sydney. State Pollution Control Commission (1976). Design Criteria for Ocean Discharge, Environmental Design G uide WP- 1, State Pollution Control Commission, Sydney,

AUTHORS

i

All the Authors are with the State Pollution Control Commission, New South Wales

l Dr Narasimaha Acuthan Scientific Officer 18

WATER September, 1985

Jeff Brown-Senior Scientist Wa ter Branch

John Court-Chief Water Division

Derek Low-Engineer Clean Waters Branch


COWRA WATER TREATMENT PLANT UPRATING AUGMENTATION S. M. H. Jones ABSTRACT

• 1939: T he original plant, comprising five grav ity sand filters, building, chemi cal To meet the growing water demands of the Cowra township and handling, storage and dosing equipment, surrounds, cons ulting engineers Rankine & Hill were engaged in 1980 and reservoir . to evaluate the various options for upgrading the overall water supp ly system . In conjunction with consultants Judell, Platt, Thomas & • 1959: Construction of five extra sand filters, with an extens ion to the filter s. M. H . Jones Associates, various a lternatives were investigated for doub ling the building . treated water output from the exist ing capacity of 684 ml/ hr to 1340 • 1966: Construction of a separate flocculation tankage and two ml/ hr, principally: horizontal sedimentation basins (flocculation paddles and travelling • De-commissioni ng the existing plant and building a new plant of bridge sludge scrapers). 1340 ml/hr total capacity on another site. • Maintaining the plant in service at existing capacity, including • I 979 : Modification of one filter for trial purposes, incorporating a new nozzle/ lateral filter floor and Mixed Media filter . substantial revamping and maintenance work, and building a new plant of 656 ml/hr capacity on anot her site. In recent years, the plant was unable to meet the township water • Upgrading and uprating the existing plant to 1340 ml/ hr output demand during the summer months. Also, the quality of water from capacity. the sedimentation basins has been poor, largely due to the floccu lation During the period of evaluation of commerciall y available tankage being separate fr om the two settling basins resulting in floe technologies, NEI John Thompson (Australia) was requested in 1982 breakup during transfer via channels a nd weirs to the inlet of the to assess and report on the technical feasibility and economics of ap- basins . The plant as a whole required substantial revamping to plying high performance tube settlement and high rate filtration pro- upgrade it to current standards . cesses to uprati ng ex isting treatment plant. Of the alternatives considered, econom ic evaluation favoured plant uprating utilising this technology and the report recommendations were adopted as the basis UPRATING PHILOSOPHY A radical augmentation of the whole plant was required to uprate for the final Treatment Plant augmentation.

R.W. INLET

FM. TANK(1)

FILTERS(10)

SEDIMENTATION BASINS(2)

e/W HEAD TANK

AIR

T.W. TO RESERVOIRS

8/W

HOLDING TANK

1-------------<:J--------------------l

CHEMICAL DOSING FL , NaOH CL. PAC NaOH POLY CL.

Figure 1. Cowra WTP flow diagram .

Open Tenders were invited in November 1984, NE! John Thompson was the successful tenderer for the project and design and constru ction phases are now well advanced . The augmentation involves a number of other unique features, and this paper details the overall uprating philosophy and design parameters associated with each aspect of the process.

INTRODUCTION The existing treatment plant was built in a number of stages, as follows:

Stephen Jones is Project Manager with NE! John Thompson (Australia) Water Treatment Division, N.S. W.

existing faci lities and double the plant capacity. Figure 1 shows the simpli fied flow diagram, and Tab le 1 provides a summary of the principal process design parameters. The fo llowing summarises the work involved in the uprating: • Installation of new raw water pipe main, with flow metering. • Installation of a Flash Mixing Tank . • De-commissioning the separate flocculation tank, and installation of new flocc ulation compartments to the inlet end of each sed imentation basin (this involves reversing the flow direction through the basins). • Installation of settling tube modules in the settling section of the basins, with associated baffling, finger weirs, a nd new submerged sludge scraper mechanisms. WATER September, 1985

21


TABLE 1. SUMMARY OF MAIN PLANT DESIGN PARAMETERS Plant Capacity

-Existing Output (m'/ hr) -Uprated Output (m'/hr) -Plant Design Flow (m'/ hr)

684 · 1340 1400

Treated Water Quality

- Colour Max ( 0 Hazen) -Turbidity Max (NTU) - Iron Max (mg/ L) -pH -Aluminium Max (mg/ L)

5 1.0 0.1 7.0 to 8.5 0.2

Flash Mixing Tank

- Number Compartments - Detention/ Compartment (sec) - Max G, 3rd Compartment (sec-') Flocculation - Volume (m' ) - Detention (min) - Max G (sec-') - Power Input (Watt)

3

20 500 Comp. 1 Comp . 2 Comp . 3 Comp . 4 117 117 32 32 10 10 2.7 2.7 100 50 14 9 11 70 293 6

Sedimentation

- Number Basins - Flow/ Basin (m' / hr) - Overall Sedimentation Area (m' ) - Settling Tube Area (m ') -Tube Surface Loading (m/ hr) -Launders/ Basin

2 700 196 147 4.9 3

Filtration

- Number Filters - Total Filter Area (m' ) - Average Filtration Rate (m/ hr) - Filter Backwash Rate (m/ hr) -Filter Air Scour Rate (m/ hr)

10 I 38 I0.2 45 40

• Installation of new settled water pipe main to filter building. • Upgrading of all 10 filters, with new nozzle/ lateral underdrain systems (suitab le for air scour as well as washwater), and installation of Mixed Media filter media to replace the existing sand media. • Addition of air blower and associated system to facilitate filt er air scour (previously only backwash water used). • Installation of new filter gallery pipework and pneumatically actuated buttefly va lves, to accommodate increased flow and remote operation of valves. • New control cubicles at the filter gallery, facilitat ing electric switch operation of the pneumatically actuated filter valu es. • Filtered water outlet Chemical Dosing Tank (modified). • Backwash Holding Tank, pumps, and pipework (new) . • Sludge Pumping Tank, pumps, and pipework (new). • Completely new bulk liquid chemical storage, metering, and injection systems for sodium hydroxide, polyaluminium chloride (PAC), polymer, chlori ne, and fluoride (reconditioned and automated). • Civil wo rks, comprising two new buildings for control and chlorination, bulk chemical bund area, earthworks, roadworks, underground process piping and drainage, fencing, and new concrete structures associated with tankages, channels, and plant modifications listed above. • Electrical and control equipment, comprising switchboards, motor control centres, distribution boards, wiring, area lighting, and field instrumentation.

FLASH MIXING TANK The new Flash Mixing Tank comprises three compartments, each of approximately 20 seconds detention time. The first compartment provides hydraulic mixing of ch lorine and sodium hydroxide dosed solutions, the second provides mechnical mixing of polyaluminium chloride, a nd the third mechanica l mixing of polymer. Recycled filter backwash is also returned to the second compartment . Flexibility is provided to vary dosing points if required to optimise 22

WATER Seprember, 1985

coagulation . The impeller type mixers are provided with variable speed drives, and have the capability of generating a maximum velocity sheer gradient (G) of 500 sec-•.

BASIN FLOCCULATION SECTION Flow from the Flash Mixing Tank is split equally to the existing basins, via a new inlet dividing channel, and is distributed evenly across each basin by a series of holes drilled in the base of the inlet channel. The inlet/ out let channels and basin structures were ex isting, but the flow direction had to be reversed, to locate the sludge hopper at the outlet end below the settling tubes and to permit the new flocculation compartments being located at the front end of the modified basin . This arrangement was also more compatible with the location of the flash mixing tank, new ch lorination building and associated equipment. The flocculation section comprises four compartments in series, with 25 minutes total detention time and occupies fhe first one-third of the basin . This arrangement provides 'tapered' flocculation, where the energy input to successive stages is progressively reduced, thereby reducing the velocity shear gradient as the floe particles grow in size and are increasingly fragile. The first two compartments incorporate mechanical flocculation, and the final two compartments utilise hydraulic flocculation. The compartments were formed in the basins by new partition walls. Compartment 1: This compartment utilises a reel type paddle design, comprising six arms and 12 blades, mounted horizontally across the basin, with two separate reels on a common drive shaft. The paddle drive unit is mounted above the water beside the basin, operating the shaft by chain and sprocket drive connection . The drive unit speed may be adjusted remotely by variable frequency controller. The paddle is designed to impart a maximum G of 100 sec-' in the compartment, of 10 minutes detention time. Flow enters the compartment near the surface from the inlet channel, and exits to the second compartment via the underflow skirt of the first partition . Compartment 2: This compartment is identical to the first compartment, having the same 10 minutes detention and identical paddle design but the maximum paddle G will be 50 sec· 1 and it is expected that a lower operating G will be maintained by operating the paddle at lower speed. Compartment 3: Flow enters this compartment via a series of square inlet holes in the upper half of the partition inlet wall. A total of 26 hol es in three staggered rows generate a low hole velocity (to minimise floe shear), whi ch imparts a kiQ,etic energy input to the compartment of 6.1 watts. Compartment detention is 2.7 minutes, with a resultant G of 14 sec· 1 from this hydraulic flocculation stage . Compartment 4: Flow enters this compartment via 42 square holes in five staggered rows in the inlet partition wall (holes offset from the preceeding wall). Hole velocity is further reduced to minimise floe shear, yielding a kinetic energy input to the compartment of 2.7 watts. Compartment detention time of 2.7 minutes is identical to Compartment 3, and the resultant G is 9 sec· • from this hydraulic flocculation stage. The fina l partition wall comprises 43 holes in five staggered rows (holes offset from preceeding wall) , with hole velocity reduced finally to 0.06 m/ sec. This wall adds a degree of final flocculation immediately downstream, and serves to distribute the flow entering the sedimentation section of the basin.

TUBE SEDIMENTATION BASIN Flocculated water enters the basin sedimentation section , and flows horizontally to the 60° settling tube section, which occupies the end 52 per cent of total basin area. The partially baffled open area of basin between the flocculation and settling tube sections assists in dissipating energy currents and stabilising the flow before entering the tube settlement section. Heavier floe particles, and those entering at a low level · near the basin floor, will settle out naturally in this region. Lighter floe particles will travel further down the basin, some settling naturally to the basin floor beneath the tube section, with the remainder lighter floe particles travelling upwards into the tube module bank. Shallow depth settling occurs on the 60° inclined tubes, and


clarified water exits t he top of the tube bank , located 700 mm below the surface. Three sta inless steel V- notch laund ers , extending t he full length of the tube section , provide uni form sur face co llectio n of clarified water in each basin . Floe settling in the tube m od ules agglo m-. erates to form a denser sludge wh ich slid es off t he 60° inclined tubes and settles to the basin floor . The effect ive tube upflow ratin g is 4.9 m/ hr (a ll ow ing for loss of settling t ube area due to wall bla nking effects). The act ua l area covered b y t ubes is 147 m' , giving an apparent tube upflow rating of 4.76 m/ hr. Tube modu les are supported undernea th by ta ll ow wood bea ms, which are supported from the side walls a nd the three overhead steel beams. The tube modules a re placed at rightangles to the direction of flow to prevent circu lati ng currents.

Theory of Tube Settlement Figure 2 shows the velocity vectors for particles settling in a co nve ntional horizontal basin , having liquid forwa rd flow velocit y, V,, a nd critical particle settling velocity Vp. The inflow is eve nl y distributed over the basin height, H, the basin havi ng width , W, and lengt h L . For a particle to be removed from th e li qu id ph ase it mu st settle to the floor of t he basin within the tim e of liquid travel a long the length of the basin i.e. : [!] H / Vp s LIV, Ex pressing V, in term s of Q , the total basin flowrate, divided by basin cross-sect io n area (H x W), gives V, = Q / (H X W) Substituting in equat io n [!] gives: Vp :2: Q/ A where A is the bas in area (L x W). Hence , for a pa rticle to be removed, its settling ve locity must be eq ua l to or greate r than the bas in surface loading rate (Q I A), a nd is independent of the depth of the bas in (assumin g that the forwa rd velocity is not hi gh eno ugh to sco ur settled sludge back into the water flow). Particles have a slower sett ling velocity than Vp = Q/ A, say Vp' , will be removed o nly in the proportion Vp' / Vp, equi va lent to the particles enteri ng the basin at a lower depth i.e . less th an (Vp' / Vp)H from the basin floor. For those slower settling particles entering above this point, they co uld be co ll ected if sha llow depth ho rizonta l settling trays we re stac ked verti call y at close intervals over the full depth of the basin end wall.

t ubes, each approx imately 605 mm long, with success ive tube rows a lt erna ting in direction of inclin at ion to create a ~igid criss-crossing module struct ure (Fig. 4). T he rigid structure enab les t he tube modu les to be fabr icated from ABS plastic, th e standard mod ul e d im ensio ns being 3. 7 m lo ng x 0.75 m wide x 0. 53 m deep. One of the virtues of sectioning of the inclined pla tes into tubes is that it prevents sideways circulati ng currents which can result across a n inclin ed pla te. The tube modules a re placed below the surface, across the full width, and at the o utlet end portion of t he basin . Flow enters the modules. from und erneath, a nd at this slope, the flo w pa ttern within the tubes (laminar , with Rey nolds numbers usua ll y less than 500) resemb les tha t of an upflow clarifier rather than th a t of a hori zon ta l flow system. The sett lin g modules are self-cleaning - sludge which sett les on the upper tube faces slides down the tubes, particles co llide and stick together resulting in the larger agglomerated sludge particles leav ing the bottom of th e tubes and being able to settle against the velocity of infl owing water.

L

z Figure 3. Settling tube module st> ltling velocity vectors.

H

L'-----~ 1-1 L

Figure 2 . Horizontal sedimentation basin settling velocity vectors. The concept of shallow depth sedimentation, whil st a ppreciated since the turn of the century, has not until the last two decades been implemented successfully due to lack of suita bl e simple methods of removing sludge from a multiple of closely stacked horizon tal t rays . Backfl ushing with filter was hwater has has been practised on small package plants but was not pract ica l for large basins. A compromise solution was achieved by inclining the settling plates at the a ngle of 60 ° and rather than using plates, the tube settler module co ncept was develo ped in which the plates are sectioned off by vertical dividing sheets at 50 mm spacings , the inclin ed plates a lso being 50 mm a pa rt. Thi s provided a netwo rk of 50 mm incli ned square

Vertical dividin shee t s Figure 4. 60° se ttlin g tube module. Fig . 3 sho ws the velocity vecto rs for particles entering a nd set tling o n an inclined tube module. A particle entering a tube module on ly has to settle across the direct io n of flow, a maximum di stance of 50 mm , before bei ng collected on the tube sur face and velocit ies through t he tubes ca n be ve ry much higher than conven tional upflow basins . The formu la rela ting critical pa rticle settli ng velocity (Vp) to the vertica l (upflow sur face loading) com po nent of ve locity (Vu) in a tube settler (Ba rnes et. al, 198 1) is: Vu

= V:

[

½sin 20 + 2 ]

It can be seen th at th e optimum a ngle 0 for settling is 45 ° but the selected a ngle of 60° is necessary to ensure sludge slides from the tubes without a ny accumulation o r clogging. Substitution of t he tube module dimensions and a ngle (L = 605 mm , S = 50 mm, 0 = 60 °) demonstrates th at the eq ui valent tube module upflow can be, WATER September, / 985

23.


theoretically, a factor of six times the critical particle settling velocity, different density media, as follows: Vp. In practice however, tube module ratings of typically two to three Anthracite (ES 1.0 to 1.1 mm) = 42(lmm times conventional upflow ratings are achievable due to other limiting Silica Sand (ES 0.5 to 0. 55 mm) = 230mm factors such as sludge scouring when sliding against the flow within Garnet Sand (ES 0.25 to 0.3 mm) = 115mm the inclined tubes, now ideal flow variations within the basins, and in · Total Depth = 765 mm particular , the ability of the agglomerated sludge to settle against the The larger anthracite granules, with lowest density (SO = 1.55), inlet upflow at the point of discharge from the underside of the tube have a lower settling velocity than the intermediate sized sand particles modules . Once the settling sludge is clear of the tube modules in a (SO = 2.6), which in turn have a lower settling velocity than the horizontal basin, the settling is more across the direction of flow, finest, yet densest (SO = 4.1), garnet granules. Accordingly, when enabling higher tube ratings to be achieved with horizontal basins than backwashed , the anthracite particles are graded to the top of the bed, with fully upflow basins. with silica sand in the middle, and garnet sand at the bottom yielding the desired grading from top to bottom of course to fine granules Sludge Removal respectively. Furthermore, the required degree of intermixing is The old travelling bridge sludge scrapers were made redundant and achieved at the interfaces of the diferent media layers, to avoid any a new scraper mechanism was provided in each basin to scrape settled sharp size transitions between layers which can cause interface sludge to the outlet sludge hopper . The original design concept assumed a single chain-flight scraper mechanism would be employed but suspended solids buildup and localised higher headloss within portions of the bed . the 10.8 m basin width substantially exceeded the maximum widths for commercially available single chain-flight mechanisms , necessitating two scrapers per tank, operated.by common or independent shafts and drive units. Hence, the scraper design was changed to the more simple submerged sludge scraper bogie. The bogie wheels ride on rails fixed to the basin floor and the bogie is driven up and down the sedimentation floor section, with sludge blade down in the forward direction to push sludge to the hopper and up (horizontal blade) in the reverse direction. The bogie is driven by a continuous stainless steel cable operated by a drive unit located above water level on a platform at the outlet end of the basin . Automatic pinch valves are installed in the sludge pumping tank, to provide timer controlled sludge wasting from the basin hoppers. The sludge is then withdrawn via pumps to the sludge lagoons.

TOP

~-

E E

DUAL•.

[_

0

-r

i=

a..

u.J

Cl

FILTERS Clarified water is fed via a new 600 mm diameter pipemain and new filter gallery inlet pipework, to the existing bank of 10 gravity filters. The upgrading of the filters entails: • Removing existing old underdrain system, and installing new nozzle/ lateral filter floors, suitable for both air scour and backwash water. • Installation of high rate Mixed Media filter media, to replace the existing sand media. • Provision of filter backwash control cubicles at the filter gallery for manual switch operation of the new filter automatic valves. • Provision of an air blower and associated pipework and controls to facilitate filter air scour. • Provision of new backwash water holding tank, and pumps (duty and standby) to fully recycle washwater back to the Flash Mixing Tank. The suspended matter in the recycled washwater provides added nuclei for aiding flocculaton and promoting a denser faster settling floe . The backwash system, comprising head tank above the filter building and distribution pipework and valves to each filter, was assessed as adequate for the modified filters and simply required new automatic butterfly valves.

Principles of Mixed Media Mixed Media filter beds are designed to achieve the ideal filter arrangement with the largest grains at the top of the bed, progressively diminishing down the bed to the finest grains at the bottom. This ideal arrangment enables in-depth filtration, with particulate matter being able to penetrate deeper in to the bed through the larger granular spaces in the upper sections, achieving greater solids holding capacity per unit volume of bed . Furthermore, fine particles which penetrate deeper into the bed are ultimately filtered more efficiently by the finer granules at the bottom, yielding consistently high quality filter ed water. The deficiency of a conventional sand filter is that, after upflow backwashing, the bed is graded from the finest particles on top to the largest at the bottom . Accordingly, downflow filtration results in filtration only in the uppermost layers. Suspended particles penetrating through the top layers have a higher probability of passing. right through the bed, resulting in poorer quality filtered water emanating from the sand filter, and poor overall solids holding capacity. Mixed Media achieves the ideal grading by utilising three layers of 24

WATER September, 1985

a::

u.J f-

....J

LL

• • • ••

1•0mm GRAIN SIZE

E E

ll'l

BOTTOM~ 2·0mm

Figure 5. Comparison of filter media.

Fig. 5 shows media grading sizes as a function of bed depth for sand, dual and Mixed Media filter beds. By using Mixed Media: higher filtration rates can be maintained , longer filtration runs can be achieved and better filtered water quality can be obtained. The average service filtration rate for the uprated Cowra filters will be 10.2 m/ hr, which is fairly co nservative for Mixed Media operation. Whilst garnet is expensive relative to silica sand, and anthracite is also more expensive than sand, the layer of garnet is relatively thin and uniformity coefficients for the Mixed Media layers are not nearly as tight as monograde sand. Hence, the Mixed Media screening reject is less than say a 1.0 mm monograde sand and uniformity coefficient of 1.25, which has a reject of the order of three to four times the product , making large quantities of monograde sand very expensive.

Declining Rate Filtration Another rather unique feature of the augmentation is the use of declining rate filtration, a method which requires no filter system i.e. no level, flow, or flow splitting controls. The filter bank shares a common headloss from inlet to outlet, with common top water level and filter outlet channel level. The operating level difference is a function of the total filter system resistance, yet the flow to each filter is a function of the individual filter resistance. Accordingly, the main inflow to the filter bank is distributed to all the


on-line filt ers, proportioned in relation to the specific headloss of each fi lter at that instant. The system resistance of a filter is dominated by the filter media head loss and will progressively increase as the filter fou ls. Hence, each · filter will return to service after backwashing with its lowest resistance, and hence highest serv ice flow, and t his flow will progressively decline over the period of the filter run. A limit stop is provided on each filter outlet valve to prevent flow through a clean filter at the start of a service run. With a bank of IO filters therefore, each filter will be a t a different degree of fouling depending on its duration in service and each filter will be passing a different flo wrate. By a dopting a uniform interval between each filter backwash a nd organising the filt ers so that they are washed in the same sequence each day, the filters then a ll experience basically the same filtering cycle and maintain their relativity to each other. Operator management of the filters involves taking off filters at approx imately uniform intervals for backwashing, each time taking off the filter which has been in service longest. The operating water level on the wh ole bank of filters can be varied by adopting a different filter cycle duration for all the filters i.e. if the level is desired to be lower, shorter filter runs will be adopted with shorter backwashing intervals between success ive fi lters. The level decl ines in this insta nce as the total system resistance is less due to the filter s being less fou led from shorter filter runs. The particula r virtue of this method , apart from the absence of a ny sophisticated control equipment , is that it ena bles the cleanest a nd therefore most efficient filters to share the largest percentage of the flo w. As filter fo uling develops with d uration in service, the flow progressively declines, thereby reducing floe shear from the filter media and enabling the more fouled filters to remain in service for a longer period before reaching significant turbidity breakthrough.

CHEMICAL DOSING During the initia l period of design development, coagulation and flocculation jar tests were performed by Judell Platt & Thomas on the raw water, testing a comprehensive range of coagula nts and floccula nts, followed by operational plant test runs . T his resu lted in the decision to de-commi ssion the existing dosing equipment comprising a lum and soda ash feeders. These feeders were under capacity and nearing the end of their practical life a nd the jars tests indicated other coagulants were more suitable a nd required different bulk storage, hand li ng and injection facilities. T he existing feeders will be kept on standby. New faci lities, including a bulk liqu id storage area, new ch lorination building, etc, were provided to handle the final range of chemicals, as follows: • Polyaluminium Chloride (PAC): two fibreglass bulk liquid storage tanks, located in the chemical bund, with new duty and standby metering pumps and associated equipment to dose the PAC solution to the fl ash mixing tank. • Sodium Hydroxide: two steel bulk liquid storage tanks, located in the chemical bund, with two metering pumps a nd associated equipment, one delivering NaOH solution to the flash metering tank for coagulation pH adjustment and the other delivering solution to the C hemical Dosing Tank for post pH correction.

BOOK REVIEWS OPERATING THE ACTIVATED SLUDGE PROCESS K. J. Hartley Publisher, G.H. & D . , 87 Wickham Terr., Brisbane 4000. Price $20.85 mailed. (! 17 pages) In a mpli fication of the short review appearing in the June issue, the purpose of this book is to provide a practical guide on plant operation and to contribute to better operation by encouraging the operator's feel

• Polyelectrolyte: storage and handling room within the chlorination building, comprising storage for bagged or liquiif'drum polymer, a solution preparation batch tank with motorised stirrer, polymer eductor, etc. and final metering pump to dose liquid polymer solution to the flash mixing tank. • Chlorine: faci lities with the Ch lorine Building comprise storage a nd handling of 6 one tonne liquid chlorine cylinders and two chlorinators, one delivering chlorine solutions for pre-dosing at the flash mixing tank and the other for post-dosing of filtered water a t the chemical dosing tank. • Fluoride: the existing fluoridator is to be reused, with revamping to increase dosing capacity (speed a djustment) a nd provision of automatic dosing in proportion to plant flow rate.

CONCLUSION T he use of high performance technology, in particular settling tubes a nd Mixed Media, provided a proven and cost effective means of doubling the capacity of the Cowra Water Treatment Plant. This augmentation requ ired a major and more comprehensive plant modification than any other previous uprating using this technology, yet the capital cost of the project was substantia lly less than a fully new plant option. The value of the main contract, to provide a plant of 32 MLD capacity was $ 1. 8 million , a nd th e work entailed extensive modifications and new plant for virtually every stage of the process to upgrade the whole faci lity to 1985 standards. The modifications used to the best advantage were the existing main site structures, i.e. sedimentation basins, filters shells, and the original building. A ll new mechanical and electrical plant, pipework, valves, etc., were provided for the new chemical dosing bulk storage, flash mixing, flocculation, sedimentation, filtration, and sludge handling and disposal faci lities. A lso forming part of the contract was the provision of new buildings, concrete tankage, major supply and gravity mains, bulk storage bunds, roadworks, drainage, demolition of some old existing structures, etc. Whilst a ll options must be considered when evalua ting an increase in treated water output capacity, past history confirms that where an uprating method is technically feas ible it will a lso offer the lowest capital cost option. Most upratings utili sing settling tubes and/or Mixed Media, are much less complex than the Cowra instance a nd accordingly the cost of the uprating is much less. A lso, it will be appreciated from this paper that in an uprating it is not simply a inatter of adding tubes to a clarifier basin or replacing the filter sand with Mixed Media. A full technical appraisal of the whole proc;ess is required involving assessment of other units e.g. flash mixing, flocculation, and the increased hydraulics, within as well as betw~en, each unit of the process.

REFERENCES BARNES, D., BLISS, P. J., GOULD, B. W., and VALLENTINE, H. R. (1981). 'Water and Wastewater Engineering Systems', Pitman Books Ltd., Bath, U.K.

for his plant and the lifting of performance goals. T he emphasis is on understanding of process b eh av iour an d simpli city of operation. Mathem atics have been kept to a minimum a nd information is presented in graphical form as far as practicable. Chapters cover: Fundamentals, T he Aeration Basin, T he C larifier , Sludge Volume Index, Control of Sludge Age, Control of Aeration, Control of Sludge Recycle, Operating Problems, Alkalinity and pH, T uning, Monitoring, The Intermittent Process and Startup. The Author , in comment, points out that,

the purpose of t he book is not to argue the case for COD in place of BOD (in fact neither parameter is particularly useful for practical pla nt optimisation) but to provide a practical guide on pla nt operation, written specifically with that objective. T he text includes 51 figures a nd is supplemented by a troubleshooting guide a glossary and references to 56 publications from the technical literature.

Editor

WATER September, 1985 25

.I


ADVANCED SEWAGE TREATMENT FOR WESTERN SYDNEY B. Walters I. ABSTRACT Deteriorating water quality within the Hawkesbury/ Nepean River, as a resu lt of the urban expansion of Sydney, will require greater contro l of nutrient inputs. The Metropo litan Water Sewerage and Drainage Board, as the authority responsib le for operation of most of the sewage treatment plants in the catchment, has been involved in a number of studies into biological and chemical methods of nutrient control. As a result, and in consu ltation with the NSW State Pollution Control Commission, a nutrient contro l policy has been adopted for implementation at existing treatment plants over the next four years .

expected to intensify in the future . By the year 2000 it is anticipated that the EP served by sewerage within the catchment will be about 900 000 (Table 1).

4. WATER QUALITY 4.1 Point and Diffuse Sources of Nutrients Because of the increased urbanisation of

growth during subsequent low flow periods. During the period 1978- 1981 the NSW State Pollution Contro l Comm ission (SPCC) carried out a water quality B. Walters control survey of the Hawkesbury/ Nepean River downstream of Camden (SPCC, 1983).

2. INTRODUCTION Due to the proximity of the City of Sydney to the Pacific Ocean most of the sewerage systems developed to serve its three million inhabitants have been based on disposal to the sea. Whilst ocean di sposal will remain the principal means of sewage effluent disposal in Sydney, the environmental significance of inland systems will increase substantiall y in the future in response to the urban expansion of Sydney westwards. In particular, the waters of the Hawkesbury/ Nepean River and some of its tributaries will come under increasing stress.

TA SMAN

3. SEW AGE TREATMENT IN THE HA WKESBURY / NEPEAN BASIN Although the catchment of the Hawkesbury/ Nepean River extends well beyond the Sydney region, that portion of major concern as regards water quality occurs more or less immediately to the west of metropolitan Sydney (Fig . 1). Within this area the Metropolitan Water Sewerage and Drainage Board (MWS&DB) operates 22 sewage treatment plants serving about 300 000 eq uivalent persons (EP). In addition, two other plants are operated by local government authorities and serve a total of about 70 000 EP . There are also a number of smaller privately operated installations. The principal treatment plants within that area of the Hawkesbury/ Nepean basin depicted in Fig. 1 are listed in the Appendix. All treatment plants provide at least secondary treatment and most also provide tertiary treatment by means of oxidation ponds or filtration. During the 1970s development within the catchment increased considerably and this is

Mr. Brian Wa lters is a Public Health Manager in the Sewerage Planning and Investigation Sub-Branch of the Metropolitan Water and Sewerage and Drainage Board, Sydney.

SEA

~

MENANGLE , 0

7\,0.

~\

Sewered area.December 1984 <;. Ezisting Sewage Treatment Plants;• MWSDB; •Council \ Proposed Sewage Treatment Plants;o MWSDB;o Council \. --.._ / Treatment Plant code · see Appendix /

7 Scale

Figure I. Principal sewage treatment plants in the Hawkesbury-Nepean Basin near Sydney.

the Hawkesbury/ Nepean catchment, and extensive agriculture, eutrophic conditions in the river waters have occured with increasing frequency in recent years. Nutrient enrichment has resulted in periodic appearance of algal blooms and in some areas, surface coverings of floating aquatic plants such as Duckweed (Lemna minor) and Azolla (A zol/a sp.). The relative importance of point and diffuse sources of nutrients is a complex issue. During prolonged dry periods point source discharges from sewage treatment works dominate. Diffuse nutrient inputs occur during wet weather but they may contribute to the eutrophication problem for a much longer period . Inputs arising from small to moderate storms for example, may not be completely flushed from the river system and thus they may become available for plant

TABLE I. EQUIVALENT POPULATION PROVIDED WITH SEWERAGE IN THE SYDNEY AREA System

Equivalent Population•

Ocean Outfalls

Dec 1984

Estimated 2000

3 869 000

4 965 000

Hawkesbury/ Nepean - MWS&DB - Council

298 000 73 000

753 000 122 000

Other Inland

143 000

Totalt

4 383 000§

-t 5 840 000

• Equivalent population (EP) includes 1he res idential population served by a treatm ent plant plu s an allowance to cater for the sewage contribution from commercial and indu strial sources. t Figures do not include minor in stallations operated by bodi es oth er than MWS&DB and local governm ent. i System 1ransferred to ocean outfa ll. § Residential population served approx . 3 100 000.

WATER September, 1985

27


That study coincided with one of the most severe droughts recorded in south eastern Australia . Under these conditions mean total phosphorus and mean total nitrogen loads of 2.7 kg.ct-• and 27 .2 kg.ct-•, respectively, were recorded at Penrith weir . These values represent background loads transported by the river at a location upstream of the major point source discharges. During the study the average daily contributions of nutrients to the river system from all point so urces were approximately 950 kg .ct- • and 3500 kg.ct-• total phosphorus and total nitrogen, respectively. During wet weather, nutrient loads transported by the river may be several orders of magnitude higher than the mean values recorded at Penrith weir during the SPCC studies. For example, two storm flow events monitored at Penrith over three consecutive days in February and July 1984 yielded average phosphorus loads of 3500 kg.ct-• and 9400 kg.ct· • respectively (Heath et al, 1985) . Neither of those storms completely flushed the river sys tem by extending the saline wedge · to Broken Bay.

4.2 Limiting Nutrient Another complex iss ue concerns the nitrogen to phosphorus ratio within waters receiving sewage effluent discharges. If this ratio is excessively low , nitrogen would tend to be the nutrient limiting plant growth. Low ratios, then, would favour growth of those organisms able to assimilate nitrogen directly from the atmosphere (nitrogen 'fixers'). In this category are certain 'blue-green' algae, organisms which are undesirable for several reasons including toxicity effects and their implication in taste and odour problems in water supplies. In its study, the SPCC considered that a N:P ratio in the range 9: I to 17: I was desirable at which level 'balanced' aquatic plant growth would occur. Based on low N:P ratios observed in the river and the results of algal growth potential studies, the Commission concluded that nitrogen was the nutrient limiting plant growth in the Hawkesbury/ Nepean system. Whilst a reduction in the nitrogen concentration of sewage effl uent would be expected to make nitrogen even more limiting and thus control the growth of most plants, this was not contemplated by the Commission as an initial control measure due to the possibility of stimulating growth of blue green algae. Rather, it was recommended that phosphorus control be implemented initially to make phosphorus the limiting nutrient. A degree of nitrogen removal was also recommended as a lower priority action.

4.3 Effects of Ammonia The biological conversion of ammonia to nitrate (nitrification) is an oxygen demanding process and can lead to depleted oxygen levels in receiving waters. Furthermore, ammonia can be directly toxic to aquatic life . In South and Eastern Creeks, the tributaries which received the highest sewage effluent flows, little assimilation of nutrients occurs. Accordingly, the nutrient load is transported undiminished to the mainstream. The SPCC report speculates that the high ammonia concentration in the tributary waters may be 28

WATER September, 1985

responsible for this. Recently the two largest treatment plants in western Sydney (at Quakers Hill and St. Marys) have been modified to achieve ' inplant' nitrification. This is part of an ongoing programme being undertaken by the MWS&DB for all its major inland treatment plants.

4.4 Nutrient Control Strategy As a result of its st udies, the SPCC recommended a nutrient control strategy to be phased in at existing larger treatment plants over the next four years (SPCC, 1985), with nitrification being the top priority action, followed progressively by phosphorus and then nitrogen control. Probable effluent nutrient requirements are given in Table 2 for medium to large treatment plants . In regard to nitrogen removal, the Commission has recommended an average effluent nitrogen concentration of 15 mg/L for plants discharging int o particular tributaries. This is the reason for the range of values given in Table 2. TABLE 2. PROBABLE NUTRIENT LIMITATIONS Item

Ammonia -50 percentile -90 percentile

Effluent Concentration (mg I L)

2

Total Phosphorus -90 percentile Total Nitrogen - mean, dry weather

5-30 (see text)

4.5 Ongoing Water Quality Studies Wh ile the recommendations of the SPCC study have been generally accepted by the sewage treatment a uthoriti es, there remain some areas where further research is needed. In particular , the concept of 'balanced' aquatic growth is not universally accepted. There is evidence, for example, that the N:P ratio in receiving waters may need to be as high as 30: I to discourage the growth of blue green algae (Smith, 1982). If such high values are substantiated by further research, the degrees of nitrogen and phosphorus removal prov ided at treatment plants may need to be reassessed. The fate of wet weather nutrient inputs also requires further study. Point source nutrient control is undoubtedly the logical first step in a nutrient control strategy. Bearing in mind, however, that wet weather nutrient inputs to receiving waters may not be flushed out of the system, it would be quite absurd to spend vast sums in removing nutrients at treatment plants only to permit perhaps greater amounts to enter sensitive areas from diffuse sources. The SPCC has recommended that policies for control of urban runoff be implemented (SPCC, 1985).

5. POINT SOURCE NUTRIENT CONTROL 5.1 Nitrification During biological nitrification two groups

of micro-organisms sequentially oxidise ammonia to nitrate under aer~bic conditions . Nitrifying organisms (Nilrosomonas, particularly) have growth rates much less than that of the mixed group of heterotrophic organisms present in conventional activated sludge systems designed for oxidation of organic matter only. The solids retention time (SRT) adopted in these cases is usually so low that nitrifying organisms are 'washed out ' of the process. In addition the oxygen supplied to such systems is usually on ly sufficient for oxidation of organic matter so that nitrifying organisms cannot grow effectively unless the treatment plant is underloaded. In 1978 the MWS&DB engaged Un isearch Ltd., to under take plant scale studies at the Castle Hill treatment plant ,to confi rm design criteria for nitrification. This followed a literature survey which indicated that nitrification was feasible at the Board's activated sludge treatment plants. The studies proceeded until the end of 1981 (Bliss et al, 1981) and the following principal recommendations were made. • Design SRT (winter) - 12.5 days at a safety factor of 2.5. • Maximum peak/average flow ratio - 1.5. • Norn. Hydraulic retention time (HRT) 10.9 hours at settled sewage BOD of 200 mg/ L and MLSS of 2500 mg/ L. • Oxygen requirements - 13.6 kg.h-'ML- 1 at settled sewage BOD of 200 mg/ L and ammonia concentration of 30 mg/ L. These results were, more or less, as anticipated by the literature survey. The oxygen requirement is about 60-70 per cent greater than that required for oxidation of organic matter only and the HRT is some 35 to 50 per cent greater. Increasing the mixed liquor concentration to between 3500 mg/ L and 4000 mg/ L would overcome the ,need for an increased HRT but this would also increase solids loading on secondary clarifiers . The maximum peak / average ratio of 1.5 is required to prevent breakthrough of ammonia in the effluent atd suggests that flow equalisation be considered .

5.2 Denitrification Denitrification (the reduction of nitrate to gaseous nitrogen products) is carried out by a broad range of the organisms present in activated sludge. To do this, nitrate (or nitrite) replaces free oxygen in the respiratory process of the organisms. As free oxygen will always be used in preference to oxidised nitrogen, anoxic conditions are necessary (i.e. no free oxygen). The trend in recent years has been to 'predenitrification' systems in which nitrified mixed liquor is recycled to an anoxic zone preceeding the normal aerated zone of an activated sludge system. This permits utilization of organic matter present in the sewage for organism growth rather than relying on an external source such as methanol. Pre-denitrification systems have been found to produce effective results if the TKN/COD ratio of the incoming sewage is less than about 0.10 . At higher values the amount of nitrogen to be removed is too great in · relation to the organic matter available for organism growth and only partial denitrification occurs .


However, by modification of sewage characteristics to increase the fraction of readi ly bi odegradab le materia l (RBCOD) , good denitrification ca n be achieved at apparently unfavourable TKN/ COD ratios. RBCOD represents that fraction of the orga nic matter which is read ily absorbed into organisms and may be abo ut 250Jo of the total. By increasing the RBCOD fraction of the influent the efficiency of the anox ic oxidation of organic matter is improved . Methods that have been used to increase RBCOD will be discussed later as they are also relevent to bio logical phosphorus removal. Fo llowing on from the nitrification invest igation a pilot plant denitrification study was set up at the Castle Hill trea tm ent plant. This study was also co-ord inated fo r the MWS& DB by Un isearch Ltd. T he pilot plant comprised six 200 litre reactors in series followed by a clarifier. The reactors were arranged such that they could be operated either aerob ica ll y or a noxically. In this way the relative proportions of the unaerated a nd aerated sludge masses could be varied. Internal recycle of mixed liquor could also be varied between different reactors and step feed ing of influent settled sewage could be carried out. T he stud y confirmed tha t the most efficient denitrification was promoted when nitrate and mixed liquor were brought into anoxic contact at the point whe re the max imum amount of organic matter was available i. e. a ' pre-denitrification ' system or one in which feed is split between an initial anoxic zone and a subsequent anoxic zone further downstream. Overall , results have been variable as mi ght be expected since a large number of di ffe rent process configurations have been examined. The highest removal of total nitrogen has been of the order of 70 per cent. A contributing factor to the variab le results is believed to be the nature of the sewage at Castle Hill which appears to co ntain insuffi cient organic matter for consistently reliable denitr ification. Modificat ion of sewage characteristics was not attempted although this will be done durin g current work into biological phosphorus removal in which the same pilot plant and sewage source are being used .

5.3 Chemical Precipitation of Phosphorus Phosphorus precipitation using metal ions such as aluminium or iron is a well estab lished proced ure. It is widely used in North America and in parts of Europe . The capita l cost of chem ical dosing equipment is quite low . However, signficant cost may ari se from the co ntinuing cost of chemicals and the cost of treatment of the additi onal sludge produced. In the Sydney area, a cheap source of ferrous chloride is ava il able as a component of waste pickle liquor . This material , as supplied by IC!, contains approximately 10 per cent iron. Because of the ready availability of pickle liquor, a pla nt scale trial was carried out during 1983 to determ ine the fo llowing criteria (Nguyen and Lim , 1985): • op timum dose rate

• optimum dosing point • effect on sludge production The results from the study indicated that an effluent phosphorus limit of I mg/ L co uld be ach ieved by a pickle liqu or dose of a bout 300 mg/ L . Slu dge mass increased by 55 per cent but the increase in sludge volume was onl y about 15 per cent. An addi tiona l benefit of pickle liquor dosing was a decrease in th e amount of Nocardia scum formed on the aeration tank s (Heath and Chan , 1985) .

5.4 Biological Phosphorus Removal Over the past decade biolo g ica l phosphoru s remova l has been the subj ect of considerable research, pa rticular ly in South Africa. It is now generally accepted that, for effi cient biological phosp horus removal to occur, the mixed liquor mu st be subjected to a period under anaerobic conditions fo llowed by a n aerobic per iod . Note that in thi s context the ter m 'anaerobic' implies lack of both free oxygen a nd oxidised nitrogen. In order to ex plain th e bi o logical phosphorus removal ph enomeno n , the hypothes is depicted in sim plified for m in Fig . 2 has been proposed (Marais et al, 1983) . T he important feat ures a re: • The organ isms whi ch carry out phosphorus r e lease / uptak e are predominantly Acinetobacter species wh ich favo ur volat ile fatty acids (VFA) as substrate. • VFA may comprise part of the sewage inflo w and can also be produced under anaerobic conditions by some of the mixed heterotrophic organ isms in mixed liquor. • Acinetobacter species are predominantly aerobic and cannot grow under a naerobic conditions. The hypothesis suggests that they can ta ke up and store food within the cells under anaerobic conditions thus ma king food unavailable for other organi sms. • Under subsequent aerobic conditions, the Acinetobacter species utilise the stored food for growth without competition from other organisms. The anaerob ic/ aerobic condi tions thus cause the Acinetobacter species to proliferate. • The presence of ni trate renders the anaerobic zone a noxic. In such circum stances the organisms which produce

VFA under anaerob ic conditions switch to a more effi cient meta1"olism thu s reducing the amount of food favo ured by the Acinetobacter species with a conseq uent reduction in phosphorus release/ uptake. • In practi cal situations, phosphorus is removed from the sys tem by wasting of aerob ic mixed liqu or (i.e . at the stage that phosphorus is bound up with the sludge) . • Phosphorus uptake has been observed under anoxic conditions, suggesting that organisms other than the aerobic Acinetobacter may be involved. Modificatio n of influent sewage characteristics to increase the RBCOD fraction in the form of VFA, ca n substantially improve both denitrificat ion and biological phosphorus removal (Barnard 1984, Osborne and Nicholls, I 985) . Met hods which have been suggested include: • Addition to the inflow of sludge from anaerob ic digesters operated in the aci d phase. • Recirculation of raw sludge around a primary sedimentation ta nk to provide ferm entation and elutriation of VFA into the feed to the biologica l reactor. T he advantages of biological phosphorus removal in compar isio n with chemical precipitation are the low operating costs, even though supplementary chemical addi tion may be needed at times to ensure compliance with effluent phosphorus limitations. As noted previously biological phosphorus removal is being studied at the Cas tle Hill pilot plant. Results are expected to be available during 1986. The MWS&DB is also particularly intere sted in pro spects for biologica l phosp horu s remo va l in intermittently decanted systems. Encouraging results have been achieved at bench scale in the USA (Manning and Irvine, 1985) and pilot plant work is proposed in Australia by the CS IRO. The Board will be a joint sponso r of this research. Plant scale stu~ies are also being considered at one of the Board's intermittently decanted systems. If feasib le, this project will examine mea ns of modifying the operati ng cycle of this type of plant such that the fe rmentation products favo ured by phosphorus

ANAEROBIC ENVIRONMENTAL CONDIT ION S

AEROBIC / ANOXIC

So lubl e Phosphoru s P-relea se

MI CRO-ORGAN ISMS

Phosphorus acc umul ating organi sm s

SUB STRATE / PROD UCTS 'Readily bi odegra dabl e COD "Vo latil e folly acids

Figure 2. Biological phosphorus release uptake . WATER September, 1985

29


accumulating organisms are produced.

7. IMPLEMENTATION OF NUTRIENT CONTROL

Specialist advice for the conceptual design of a biological nitrogen and phosphorus removal plant at Rouse Hill was sought from Camp Scott Furphy consulting engineers. A decision was subsequently taken to proceed with detailed design of the plant shown schematically in Fig. 3 for an initial equivalent population of 25 000. A feature of the new plant will be a prefermentation stage in which a portion of the inflow will be diverted to a small sedimentation tank incorporating sludge recycle to promote formation of VFA. The anaerobic/anoxic/aerobic reactor will be designed for a total nominal detention time of 22 hours and a solids retention time of 25 days. Another feature of the plant will be a premix section at the inlet to the anaerobic zone where return sludge and incoming sewage are brought into intimate contact. The aim of this feature is to promote a high initial food to micro-organism ratio, a condition which has been associated (under aerobic conditions) with improved sludge settleability by preferential selection of non-filam entous organisms (Lee et al, 1982). This is in line with work being carried out in South Africa although it is not certain that the premix zone will be effective under anaerobic conditions.

6. OTHER METHODS OF NUTRIENT CONTROL

The incremental capital cost of nutrient control facilities within the Hawkesbury/NeIn addition to 'in-plant' nutrient control, a pean basin by the year 2000 is expected to be number of other strategies have been con- of the order of $40M to $60M depending on sidered for the Hawkesbury/ Nepean basin. the degree of additional sludge treatment facilities needed for plants where chemical These include : • Transfer of sewage flow s to ocean outfalls. precipitation of phosphorus is employed. • Flushing of nutrients by releases from Operating costs for individual treatment potable water storages (e.g. Warragamba •plants may be between $3 and $6 per head annually. This represents an increase of 15 to 30 Dam). per cent in the operating cost of a tertiary • Agricultural reuse. • Nutrient uptake by aquatic macrophytes treatment plant. (large aquatic plants). Of these, the fir st two have been largely 7.1 Penrith City Council discounted on economic grounds. The potenA new 25 000 EP biological phosphorus tial for resuse and for nutrient uptake by removal plant was commissioned by Penrith macrophytes is bei ng actively studied . City Council in late 1984. This is the first full scale plant of this type in Australia and has 6.1 Reuse been desc ribed previously in ' Water' The potential for large scale agricultural (Crockett, 1984). Phosphorus removal during the initial six reuse in the Hawkesbury/ Nepean basin is limited due to the scarcity of large areas of to eight month s of operation was only 55 per · suitable la nd within reasonable di stances of cent. Although chemical dosing facilities sewage treatment pla nts. The potential for have been provided for the removal of reuse by industry is also limited as most larger residual phosphorus these were not used durindustries are located in areas served by ocean ing the intial process optimisation period. Nitrification/denitrification performance has outfall sewerage systems. The most likely application of agricultural been satisfactory. reuse is at the Camden Park Estate, southwest of Sydney . The area under state ownerOISsot.VEO AR ship is some 1600 ha , not all of which is FLOATATION EMERGENCY TH!CKENING SLUDGE suitable for irrigation . The existing West ) LAGOON Camden treatment plant and the future I Menangle pla nt are reasonably close to the :~i1\ Estate (Fig. I) . I A feasibility study into the application of reuse at the Estate is being co-ordinated by I I the MWS&DB and involves representatives of Agricultural , Planning, Health , Water I ~ Reso urces and Pollution Control authorities.

SLUDGE

_____

:r·-·-·

:: I! i I ~~

6.2 Macrophyte Project A large-scale pilot study on aquatic macrophyte systems has been established at the Hawkesbury Agricultural College (HAC) adjacent to the Richmond sewage treatment plant. The study is a joint undertaking of the MWS&DB, HAC and CS IRO . The study , which commenced in late 1983 and will run for three years, involves the pumping of secondary effl uent through five experimental and two control trenches each 100 m long, 4 m wide and 0.5 m deep. The experimental trenches contain several different types of aquatic macrophytes (Fisher , 1985). The objectives of the study include: • Eva lu ation of the use of artificial macrophyte systems for efficient removal of sewage nutrient s. • Development of criteria for design and operation of full scale artifical macrophyte systems. • Determination of the potential of such systems for broad application in sewage and other effluent treatment and in the provision of assimilation zones for water resource protection. Hawkesbury Shire Council is also actively investigating the application of artificial wetland systems for efflu ent polishing at its Windsor treatment plant (Kinhill Stearns, 1984) . 30

WATER September, 1985

<[

lL

SLUDGE

OE WATERING

DISPOSAL

SUPPLEMENTARY CHEMICAL ADDITION

SECONOAR'!'

(HlORlNATION

EFFLUEN'T

SECNHENTATION

':t

H1xr'otiauoR 1fcvctE

I

__ _ - - - - _ _ _ _) RETURH ACTtVATEO SLUDGE

Figure 3. Rouse Hill nutrient control plant.

7.2 MWS&DB A degree of nutrient control will be required at some 15 of the 24 treatment plants expected to be operated by the MWS&DB in the Hawkesbury/ Nepean basin by the year 2000. This will be implemented at existing treatment plants generally as follows: • Continuation of the policy of providing nitrificat ion . • Control of phosphorus by chemi cal precipitation . • Provide for pre-denitrification during the warmer months of the year by making use of the spare aeration tank capacity that exists at such times because of increased biological activity. Future plants will be designed for integrated nitrogen and phosphorus control by biological means, with chemical dosing facilities being provided for removal of residual phosphorus only. The first treatment plant of this type within the Board 's system will be at Rouse Hill, north-west of Sydney.

It is not anticipated that design of the plant will be affected appreciably by results of the Castle Hill pilot plant study. The principle benefit of the study will be optimisation of the operation of the full scale plant.

8. CONCLUSION Control of point source nutrient discharges to the Hawkesbury/Nepean River is being progressively implemented by sewage treatment authorities within the Hawkesbury/ Nepean basin . Studies carried out by the MWS&DB have indicated that nutrient control (to the extent proposed by the SPCC) can be achieved at a reasonable cost.

CONTINUED ON PAGE 36


Computer Controlled Sewage Diversion S@heme Georges River Catchment, Sydney P. J. Fisher ABSTRACT The Metropolitan Water, Sewerage and Drainage Board, Sydney, is implementing a cost-effective sewage flow diversion scheme which will optimize the dry weather use of the existing capacity of a major gravity sewage submain and minimize the occurrences of sewage overflows from this submain in wet weather. In dry weather, raw sewage flows will be pumped to the submain but wet weather flows, diluted by infiltration , will be treated at a new Water Pollution Control Plant designed speci ficall y to treat storm sewage. A computer- based control system will optimise the operation of the entire flow . diversion and treatment system which incorporates two variable speed pumping stations and a physico-chemical treatment plant.

Prior to mid-1984, sewage in Orphan School Creek catchment drain to the Fairfield WPCP which provides treatment by means of biological trickling filter s and maturation ponds. Most of the effluent was pumped to the North Georges River (NOR) Submain, a major gravity sewer which drains to Malabar WPCP and some tertiary treated effluent was discharged to the adjacent Orphan School Creek under peak flow conditions. Fairfield WPCP would require amplification together with the installation of nutrient removal facilities if effluent discharge into Orphan School Creek was to continue in dry weather. The Board' s strategy to relieve both the hydraulic overloading on the Fairfield WPCP and the existing wet weather overload on the

1. INTRODUCTION Sewers are designed to provide capacity to carry peak dry weather flows plus an allowance for the increased flow in wet weather due to infiltration. High wet weather sewage flows, which can amount to many times the dry weather flow , generally occur for only a small percentage of time each year. Consequently, for most of the time the entire installed sewer capacity is not utilised. This paper describes the use of innovative flow diversion technology devi sed by the Metropolitan Water Sewerage and Drainage Board, Sydney, to optimise the flow carrying capacity of a large existing sewer and to minimise the impact of dry weather effluent di scharges to the Georges River and its tributaries. The Georges River catchment is located in the south-western region of Sydney, as shown in the locality sketch of Figure I. The upstream region of the George River basin contains three sewerage systems, with Water Pollution Control Plants (WPCPs) being located at Glenfield, Liverpool and Fairfield. Sewerage facilities in the areas to the north of the downstream section of the Georges River are provided by the sewerage system which drains to the ocean via Malabar WPCP.

NOR Submain is shown diagrammatically in Figure I . The Prospect Creek catchment drains to a sewage pumping s tation P. J. Fisher (SPS 258 shown as 419 on Figure I) which pumps raw sewage to the NOR Submain. The NOR Submain has ample capacity for dry weather flows, but infiltration during prolonged wet weather ma y cause the downstream sections of the Submain to become overloaded, resulting in overflow into the Georges River . SPS 258 is also hydraulically overloaded in wet weather. All dry weather flows from both the OrPROSPECT CREEK

i ORPHAN SCHOOL CREEK CATCHMENT

I I

LIVERPOOL WPCP

x.-~"~ 0"'~~~":,~~<,,, <v' ~c., """Q_:

LIVERPOOL

RI SING MAIN

CATCHMENT owF wwF

GRAVITY SEWER DRY WEATHER FLOW WET WEATHER FLOW

!LOCALITY SKETCH

2. FAIRFIELD SEWERAGE SCHEME 2.1 Scheme Description

PAR RAMA TT A

Fairfield is a developing area which embraces two sewerage catchments: Orphan School Creek catchment, with an area of some 3900 ha, and Prospect Creek catchment of approximately 5100 ha. Sewage flows in both catchments are steadily increasing due to the residential development occurring in the region.

Mr. Peter Fisher is a Civil Engineer in the Sewerage Planning and Investigation SubBranch of the Metropolitan Water Sewerage and Drainage Board, Sydney. 32

WATER September, 1985

MALABAR

SCALE

Figure I. Fairfield Diversion Scheme and Georges River Effluent Transfer Scheme.


phan School Creek and Prospect Creek catchments will be pumped to the NGR Submain, thus utilising the available dry weather submain capacity. In wet weather, flow 'from both these catchments will be progressively diverted from the NGR Submain in sufficient quantities to keep flow in the Submain below overflow level for all storms except those of exceptional intensity. The diverted flow will be pumped to a new Physico-chemical WPCP which is currently being constructed at Fairfield adjacent to the trickling filter WPCP. The new Plant allows the existing trickling filter Plant to be decommissioned . The Fairfield Diversion Scheme incorporates two large, variables speed sewerage pumping stations: SPS 384 serving the Orphan School Creek catchment and SPS 419 (which replaces SPS 258) serving the Prospect Creek catchment. Both these SPSs will be capable of pumping sewage to either the NGR Submain or Fairfield WPCP, or splitting the flow and pumping simultaneously to both the NGR Submain and Fairfield WPCP. ¡ Pumping capacity will be developed in two stages, as shown in Table 1. Because of the characteristics of the pumps purchased, Stage I capacity of the SPS (when operating at maximum speed) will be slightly higher than Stage 1 capacity of the WPCP. Pump speed will be limited, however, to ensure that the WPCP is not overloaded. It is anticipated that Stage 1 of the SPSs will have sufficient capacity until about the year 2000.

250 000 persons. The Fairfield catchments have an estimated combined population of 500 000 persons at full development and further Plant stages will be provided to ensure that storm treatment facilities are available at all times for the increasing population within the catchment. Flocculation and sedimentation tanks will be filled sequentially in parallel and no effluent will be allowed to flow to Orphan School Creek until all tanks are full . Thus treated storm sewage effluent from Fairfield WPCP will only be discharged to the adjacent Orphan School Creek during times of excessive rainfall, and even then, only when all available tank storage afforded by the physico-chemical Plant is utilised. The treated storm sewerage remaining in the tanks when inflow to the Plant ceases will be discharged to the NGR Submain (via SPS 384) as soon as capacity is available to receive the extra flow. The proposed solids disposal system for the WPCP will pump a mixture of chemically precipitated sludge, scum and disintegrated screenings through a 1. 7 km long rising main to the NGR Submain. Design considerations for the sludge pumping facility have been described by Cowper and Berman (1983) . Sufficient space has been provided in the Plant layout for the possible future installation of dual media filters and/ or chlorination facilities if found necessary following operational experience. The need for these facilities

TABLE 1. STAGED DEVELOPMENT OF SPS 384 AND SPS 419 SPS

Stage

Persons Served

Installed Pumping Capacity

120 000

1900 Lis to NOR Submain 2420 Lis to Fairfield WPCP

200 000

1900 Lis to NOR Submain 3770 Lis to Fairfield WPCP_

200 000

1570 Lis to NOR Submain 2750 Lis to Fairfield WPCP

300 000

2720 Lis to NOR Submain 4350 Lis to Fairfield WPCP

384 Ultimate

419 Ultimate

The diversion scheme was one of five treatment upgrading and four sewer submain amplification options investigated by the Board to alleviate the hydraulic overloading of the existing Fairfield WPCP and wet weather overloading of the NGR Submain. Analysis of the alternatives revealed that the diversion scheme was the most cost-effective option that would achieve an environmentally acceptable soiution . It is believed that the diversion scheme is the first of its type in the country and incorporates the first physico-chemical treatment plant in Australia for treating dilute wet weather sewage flows.

2.2 Description of Fairfield Physicochemical WPCP The Fairfield physico-chemical WPCP will be an entirely new primary treatment plant employing chemical precipitation to treat dilute storm sewage from the Orphan School Creek and Prospect Creek catchments. Stage 1 of the new WPCP will provide screening, alum feeding, rapid mixing, polymer dosing, flocculation and sedimentation facilities for

will be reviewed periodically . The Plant will operate only during periods of prolonged wet weather and it is estimated that ultimately the annual duration of operation will be of the order of 300 hours.

2.3 Current Status of New Scheme Civil construction of the new Fairfield WPCP is complete and electrical and mechanical installation is in progress. The plant is programmed to be commissioned in January 1986. Electrical and mechanical installation work is also currently in progress on SPS 419 and this pumping station is programmed to be commissioned in late 1985 . All construction activities on SPS 384 were completed in mid-1984 and this has allowed the Board to partially commission the pumping station and disuse the existing Fairfield WPCP .

3. GEORGES RIVER EFFLUENT TRANSFER SCHEME Tertiary treated effluent from the Glenfield and Liverpool WPCP is currently dicharged

the Georges River. The Board is now constructing a scheme to transfer the dry weather treated effluent from these WPCP to the ocean via the NGR Submain. However, during wet weather flow conditions in the NGR Submain, chlorinated tertiary effluent from Liverpool and Glenfield WPCP may be discharged to the Georges River at Georges Hall . The major components of the Effluent Transfer Scheme are shown in Figu~ 1. This scheme was identified in the Georges River Environmental Impact Statement (Caldwell Connell Engineers, 1981) as being the most cost-effective option available to improve the water quality in the Georges River. The Determining Authority's Report for the transfer scheme (M .W.S . & D. Board, 1982) recommended the implementation of the Georges River Effluent Transfer Scheme in two stages. Stage 1 will involve the transfer of effluent from Glenfield WPCP and will incorporate a sewage pumping station at Glenfield (SPS 580) and some 12 km of rising main . Effluent will be pumped by SPS 580 to the NGR Submain via an existing sewage pumping station at Georges Hall (SPS 406) . Stage 1 will eliminate the discharge of treated effluent into the freshwater section of the Georges River (i.e . upstream of the Liverpool Weir) except during widespread wet weather conditions . This stage should be commissioned by the end of this year. Stage 2 will involve the additional transfer of effluent from Liverpool WPCP to the NGR Submain and will require the construction of a sewage pumping station at Liverpool (SPS 582) and the amplification of SPS 406 and its rising main to the NGR submain. In wet weather, overflowed effluent will be discharged near SPS 406 and this will eliminate all effluent discharges directly into the estuarine section of the' Georges River upstream of the proposed Moorebank and Chipping Norton Lakes Schemes in both wet and dry weather. These . Lakes Schemes are recreational lake de'1'elopments which will be constructed on the Georges River upstream of Georges Hall (SPS 406). The target date for commissioning the second stage of the transfer scheme is late 1987. The average dry weather flow input from the Georges River Effluent Transfer scheme will initially be 650 Lis and will increase gradually to some 900 Lis by the year 2000. Implementation of the Effluent Transfer Scheme will result in a signficant water quality improvement in the Georges River by reducing the nutrient input to the river from point sources . Nutrient inputs from diffuse sources, such as agricultural and urban runoff, will continue and these would probably be sufficient to maintain aquatic weed growth in some sections of the Georges River.

4. CONTROL OF DIVERSION AND TRANSFER SCHEMES 4.1 General Description The new Fairfield WPCP will not be continuously manned and will be designed to operate automatically . The need for the Plant to come on-line will be determined from sewer flow depth and rainfall data transmitted from gauges installed in the Orphan WATER September, 1985

33


School Creek, Prospect Creek and NGR Submain catchments. A computer-based Data Acquisition and Control System (DACS) will monitor this data and automatically control flow diversion to and from the NGR Submain as well as the operation of Fairfield physico-chemical WPCP treatment facilities. The DACS consists of the following components: (i) Computer hardware and suitable control panelling (ii) Computer software which has been designed to suit the operating parameters of the scheme (iii) Primary field monitoring devices (iv) Connecting links and panels between the field devices and computer hardware (v) Control equipment which can respond to directions from the computer.

4.2 Diversion Control Strategy Flow transferred to the NGR Submain from the Georges River Effluent Transfer Scheme will be tertiary effluent currently being discharged to the Georges River in dry weather. Accordingly, in wet weather conditions when the NGR Submain has insufficient capacity to accommodate all pumped and gravity inflows, effluent from the Georges River Effluent Transfer Scheme will be diverted to the Georges River before any raw sewage jn the Fairfield catchment is diverted to the Fairfield WPCP . Only when all effluent from the Georges River Effluent Transfer Scheme has been diverted to the Georges River and there is still limited capacity in the NGR Submain, will the new Fairfield WPCP receive flow from the Fairfield catchment. This philosophy ensures that the minimum amount of treated effluent from the Fairfield physico-chemical WPCP will be discharged to Orphan School Creek . Before any flow from Fairfield catchment can be diverted to the Fairfield WPCP, inflow to the diverting SPSs (SPS 384 or 419 or both) must be in excess of twice the average dry weather flow (ADWF). The reasons for this are as follow s: (i) The physico-chemical treatment process cannot ach ieve the required effluent quality when treating undiluted raw sewage inflows. Laboratory tests performed by the Board's Scientific Services Branch have indicated that the minimum volumetric dilution rate required to ensure that WPCP inflow is amenab le to treatment is 1 part stormwater ingress to 5 parts raw sewage. To ensure that sewage is sufficiently diluted flows of less than 2 x ADWF will not be diverted to Fairfield WPCF except in an emergency. (ii) The Fairfield WPCP is designed to operate only in periods of excessive wet weather. For the Fairfield system, the Board and the NSW State Pollution Control Commission have agreed that 'wet weather' conditions in the sewers can be defined as occurring when sewage flow is in excess of 2 x ADWF. During dry weather it is possible for failure of a critical component of the diversion scheme to result in the sewage level in the wet well of SPS 384 or 419 rising excessively. To mitigate any possible overflow from the SPSs 34 WATER September, 1985

to the adjacent receiving waters, an emergency duty (initiated by high wet well level) has been provided at each SPS to allow it to pump to Fairfield WPCP in dry weather. This will provide a storage of about 12 hours (based on pumping ADWF from one SPS) before any overflow occurs.

5. CONTROL SYSTEM HARDWARE The DACS hardware comprises an extensive field monitoring system and a centralised control system. Components of these systems are described below.

5.1 Monitoring System The efficient operation of any automatic sewage diversion control system must be based on information on the current conditions in both the contributing a nd receiving sewerage systems. A system of field monitoring devices provides the DACS with the necessary information from rain gauges, sewe r flow level gauges, sensors indicating pump speed and pump rates at the major SPSs, and status indicators for all major automatic control valves in the system. Additionally, field sensors provide data on quality of sewage inflow to Fairfield WPCP, the status of major equipment at the physicochemical Plant and the status of components of the sludge pumping system. Data from all field devices will be telemetered to the central control room at Fairfield WPCP via private lines leased from Telecom.

5.2 Centralised Control System A Westinghouse Distributed Processing Family (WDPF) computer system is being installed to monitor and control the flow diversion and transfer scheme. The WDPF system distributes data acquisition and supervisory functions into independent distributed unit modules and so eliminates the need for a host computer and its associated data bottlenecks. Every distributed unit module has continuous and automatic access to all the process information via a 2 megabit/ second data highway. This means that the WDPF system is always ready for the worst-case condition - an important consideration in the automatic control of the diversion scheme. System hardware equipment for the Fairfield DACS includes: (i) Four distributed process units (DPUs), each containing a 16 bit functional micro-processor, which preform both data acquisition and control functions of the WDPF system. One DPU hosts the flow prediction and diversion control software model which is outlined in Section 6.1. The other three DPUs control the operation of equipment at Fairfield WPCP, the major pumping stations (SPS's 384, 419, 580/582) and the valve at the Effluent Diversion Structure at Georges Hall. (ii) Three VDU / keyboard consoles for displaying process output and alarms and providing system interface with control personnel. One VDU wi ll be dedicated to displaying the status of the entire diversion system at all times and one console will incorporate an alarm

event printer. (iii) One System Controll!!r's console which provides all softwa re engineering tools and hardware dev ices required to display, program and maintain the WDPF system . (iv) Two historical storage and retrieval units to collect process data for short-term storage on a Winchester disc. Data for long term storage is transferred to magnetic tape . The DACS will be provided with a back-up power supply capable of maintaining the memory of the computer system for 24 hours following a total mains power fai lure.

6. CONTROL SYSTEM SOFTWARE A specifically written software package has been developed by the Board to provide the logic to enable the DACS to: (i) predict if an overflow from the NGR Submain is likely. (ii) control the diversion of the Glenfield / Liverpool effluent to the Georges River at Georges Hall . (iii) control the diversion of flow from SPS 384 and SPS 419 to Fairfield WPCP. (iv) efficiently operate the Fairfield physicochemical WPCP. (v) indicate when Fairfield WPCP can be shut down and control the shut down process and draining of the works. (vi) control the reintroduction of flow from SPSs 384 and 419 to the NGR Submain. (vii) control the reintroduction of Glenfield / Liverpool effluent to the NGR Submain. The software package consists of a mathematical model used to predict flows and control the flow diversion process, and the control programme for the optimisation of the operation of the Fairfield WPCP.

6.1 Flow Prediction and Diversion Control Model A mathematictlmodel has been developed to enable the DACS to predict future flow conditions in the NGR Submain and to control any necessary flow diversions required to reduce the incidence of overflow from the Submain. Figure 2 shows a flowchart indicating the operating philosophy of this mathematical model. The predictive stage of the model monitors both flow depth and rainfall in the NGR Submain and Fairfield WPCP catchments on ly. If the monitored sewe r flow depth gauge values exceed predetermined limits, an overflow is predicted and the diversion control stage of the model is initiated. Using recorded rainfall, the Antecedent Precipitation Index (AP!) is calculated for each pluviometer. The AP! is a common hydrological measure of catchment wetness (Linsley et al, 1982). Pluviometer AP! values are weighted, using the Thiessen polygon method, to derive a design AP! for the subcatchment draining to each existing NGR Submain overflow. Predetermined limits for the upper magnitude and maximum time rate of change of overflow AP Is are used to determine if an overflow is likely. Hence, sewer flow and rainfall data are tested independently to determine the likelihood of a future overflow. If the preset


the wet well of SPS 384 and in the NGR Submain are low enough to enable the contents of the tanks to be drained without unduly restarting the WPCP after only a short period off-line.

N

DOES GAUGED DATA EXCEED SET LIMITS

y NO

>------~ OVERFLOW

IS NGRS CAPACITY ADEQUATE

PREDICTED

N

DIVERT EFFLUENT FROM GEORGES RIVER EFFLUENT TRANSFER SCHEME TO GEORGES RIVER

y

IS NGRS CAPACITY ADEQUATE NOW N

IS FAIRFIELD SEWAGE DILUTE ENOUGH

N

y ...J

0

,------------'---------~

1-

DIVERT FAIRF IELD SEWAGE TO FAIRF IELD WPCP

er

z

8 ~--------~----------' z

Q (/) er u.J > i3

N

IS WET WEATHER OVER y

CAN NGRS HANDLE GEORGES RIVER

N

EFFLUENT TRANSFER SCHEME EFFLUENT y

REDIRECT GEORGES RIVER EFFLUENT TRANSFER SCHEME EFFLUENT TO NGRS

Figure 2. Flowchart for flow prediction and diversion control model.

limits in either test are exceeded an overflow is predicted and the mathematical model progresses to the diversion control stage. In this stage, the model firstly predicts the future flow conditions in critical sections of the NGR Submain. A predictive equation, derived from a historical analysis of NGR Submain flow conditions, is used to establish future flow depths. After using a rating table to convert the predicted depth to a predicted flow, the future available capacity of the Submain is calculated by making an allowance for the current inputs from the major sewage pump. ing stations (SPSs 384, 419 and 580/582). If the future available capacity of the NGR Submain to accommodate inflows from the Fairfield catchment and the Georges River Effluent Transfer Scheme is inadequate, the flow diversion processes are initiated to reduce the major inflows to the NGR Submain. In the first instance, tertiary treated effluent from the Georges River Effluent Transfer Scheme is diverted from the NGR Submain to the Georges River. The diversion structure, which is located at Georges Hall, some 10 km downstream of the Liverpool

Weir, has valve settings permitting complete, partial or no diversion of effluent to the Georges River. The DACS will automatically control the position of the valve at the effluent diversion structure. If all flow from the Georges River Effluent Transfer Scheme is being diverted to the Georges River, and gauged sewage flows in the Fairfield catchment are in excess of 2 x ADWF the DACS will begin the gradual diversion of the Fairfield diluted raw sewage from the NGR Submain to the Fairfield physico-chemical WPCP. In these circumstances, the DACS will select the required pump duty at SPSs 384 and 419 and when the NGR Submain is limited, the pump speed will also be selected by the DACS. The operation of the Fairfield WPCP will then be optimised by the DACS (Refer Section 6.2). When wet weather ceases, the DACS red irects the Fairfield sewage flow back to the NGR Submain and determines when the WPCP can be shut down. Treated sewage contained in the flocculation and sedimentation tanks of the WPCP will be drained via SPS 384 to the NGR Submain. Hence, Before the WPCP can be shut down, the software program tests to ensure that sewage levels in

6.2 Process Optimisation Model for Fairfield WPCP Apart from a general caretaking and routine maintenance gang, the new Fairfield physico-chemical WPCP is not intended to be manned. All the treatment processes of the Fairfield physico-chemical WPCP are designed to operate fully automatically. Commensurate with good engineering practice, as much stand-by equipment as necessary has been provided and in most cases fully automatic stand-by facilities have been provided. In order to maximise operational confidence in what is an inherently complicated Plant, the starting and operating hardware and software is reduced wherever possible to the simplest terms. Whenever possible, equipment is started and stopped by means of simple level control or limit switches. The DACS monitors the operational status of all process equipment and displays on the VDUs in the Fairfield WPCP Central Control Room readings from recording instruments at the WPCP, SPSs 384, 419, 580/ 582, the effluent diversion structure at Georges Hall and the catchment rainfall and sewer flow gauge network. Failure of any operatio nal device is logged on the event typewriter and an alarm sounds. Critical alarms are also monitored by separate automatic dial-out faci lities where operator call-out may be considered necessary when a failure occurs while the Plant is unmanned. The only process that the DACS has complete control over is the selection of the dose rate of alum flocculant. Extensive jar testing was undertaken by the Board's Scientific Services Branch to determine the optimum alum dose under a wide range of opearting conditions. It was found that an optimum alum dose could be achieved if a pH of 6.3 could be maintained in the alum dosed sewage. The optimum dose rate of cationic polyelectrolyte was determined by these jar tests to be 5 mg/ L. Fairfield WPCP is equ ipped with a small pilot-plant which will be used by the DACS to determine the quantity of alum dosed via a variable speed, variable stroke pump. The pilot-plant provides flocculation and sedimentation to alum dosed, de-gritted sewage. The DACS will ultimately control the speed and/or stroke of these pumps using measurements of diluted sewage inflow, pH of alum dosed, de-gritted sewage and turbidity of pilot-plant effluent. Initially, the DACS will control the dosing pump operation according to whether the WPCP is receiving inflow from either SPS 348 or SPS 419 or both. Following receipt of a small volume of degritted sewage at the pilot-plant, the DACS will control the operation of the dosing pump to maintain a set point pH in the alum dosed de-gritted sewage (i.e. pilot-point effluent) of 6.3. Additionally, allowance has been made in the DACS software for the further refineW ATER September, 1985

35


ment of alum dose based on the pilot-plant effluent when operating experience of the WPCP has been obtained. Because control of all a lum dosing equ ipment is by means of specifically developed software packages in the DACS, alteration of dose rate determination in the light of operating experience is simplified. When flow to the WPCP ceases, the DACS initiates an automatic cycle which subsequently fl ushes down all the civil structures. This is performed before the logic in the flow diversion software model gives permission for the WPCP to be drained and shut down . Cleaning and flushing of minor items of plant will be done manua lly. The DACS software also includes a maintenance schedule. Most equipment can and will be regularly and automatically exercised by the DACS . The equipment which cannot be exercised on an unmanned bas is wi ll be the subject of regu lar reminder lists from the DACS .

7. SUMMARY The Fairfield Diversion Scheme will optimise the dry weather use of an existing major grav ity sewage stibmain and minimise the occurrence of sewage overflows from the submain in wet weather. This is the first known sewage flow diversion system of its type in Austra lia and incorporates the country's first physico-chemical treatment works to treat dilute storm sewage . Both the Diversion Scheme and Georges River Effluent Transfer Scheme are currently being installed. During the initial year or so of operation, the control strategies will be closely monitored to ensure that optimum performance is provided by the computerbased control system.

8. ACKNOWLEDGEMENTS The investigation, design and implementation of the Fairfield Diversion Scheme and Georges River Effluent Transfer Scheme have involved the efforts of many people over several years. The combined efforts of these

people are gratefully acknowledged. The encouragement of the SeweN1ge Planning and Investigation Manager of the Metropolitan Water Sewerage and Drainage Board, Sydney is particularly acknowledged.

9. REFERENCES CALDWELL CONNELL ENGINEERS (198 1). 'Environmental Impact Statement: Georges River Water Quality Improvement Proposals', prepared for Metropolitan Water Sewerage and Drainage Board, Oct. 1981. COWPER, N. T. and BERMAN, M. B. (1983) . Long Distance Pumping of Sewage Sludge in the Sydney Region, Australian Water and Wastewater Association Tenth Federal Convention, Sydney, April 1983, pp , 29.1-29.13. LINSLEY, R. K., KOHLER, M. A. and PAULHUS , J. L. H. (1982). 'Hydrology for Engineers' (McGraw-Hill, New York). METROPOLITAN WATER SEWERAGE AND DRAINAGE BOARD (1982). ' Determining Authority's Report on Georges River Water Quality Improvement Proposals'.

ADV AN CED SEW AGE TREATEMENT FOR WESTERN SYDNEY - Continued from Page 30 Methods to be adopted at individual treatment plants will depend on individual circumstances. Chem ica l precipitation of phosphorus combined with partial (summer) denitrification appears to be most suited to existing plants. At new plants, however, integrated biological nitrogen and phosphorus removal seems to offer a number of advantages at little, if any, cost penalty over combined biological/chemical systems. In some situations agricultural reuse may be feasible thus reducing 'in-plant' nutrient contro l requirements. In itia l studies, however, have indicated that there will be limited economic advantage of reuse. A decision to implement such a disposal method 1 wo uld probably be based on other factors. '

9. REFERENCES BARNARD, J. L. (1984). 'Activated primary tanks for phosphate removal'; Water SA, 10, 3, 121. BLISS, P. J., BARNES, D. and WINDSCHUTTEL, B. A. (1983). 'Towards optimal design of the nitrifying activated sludge process'; Proc . 10th Fed. Conv. AWWA Sydney, 9-1 . CROCKET, J. A. (1984). 'Trends in sewage treatment - the future for Victoria'; Water, 11, 4, 28.

CHANGING YOUR ADDRESS? ENSURE RECEIPT OF YOUR JOURNAL BY TELLING US Advise your Branch Secretary or the Editor

36

WATER September, 1985

FISHER, P. (1985). ' Aquatic macrophage systems for nutrient removal'; unpublished report, MWS&DB . HEATH , C., SHAW, S. L. and SMALLS, I. C. (1985). 'Assay studies on phosphorus utilisation by algae in the Nepean Hawkesbury system'; Proc. 11th Fed . Conv. A WW A Melbourne , 524. HEATH , C. and CHAN, J. (1985). 'Laboratory and plant scale trials using pickle liquor for Nocardia control in activated sludge plants; Proc. I Ith Fed. Conv. AWWA Melbourne, 346. KINHILL STEARNS (1984). 'South Creek Wetland Study'; report prepared for Hawkesbury Shire Council. LEE, S-E., KOOPMAN, B. L., JENKINS, D. and LEW IS, R. F. (1982). 'The effect of aeration basin configuration on activated sludge bulking at low organic loading'; Wat. Sci. Tech. , 14, 6/7, 407. MANNING, J. F. and IRVINE, R. L. (1985). 'The biological removal of phosphoru s in a sequencing batch reactor'; Journal WPCF, 57, I, 87. MARA IS, GvR., LOEWENTHAL, R. E. and SIEBRITZ, I. P. (1983) - ' Review: Observations supporting phosphate removal by biologial excess uptake'; Wat . Sci. Tech. , 15, 3/ 4, 15. OSBORNE, D. W . and NICHOLLS, H . A. (1985). 'Biological nutrient removal in South Africa'; Proc. 11th Fed. Conv. AWWA Melbourne, 361. NGUYEN, T. and LIM , I. (1985). ' Phosphorus precipitation with pickle liquor at Glenfield WPCP' unpublished report, MWS&DB. SM ITH, V. H. (1982). 'Predicting the effects of eutrophication: re s pon s e s in the phytoplankton'; Proc. Symposium on the Prediction in Water Quality, Aust. Academy of Science, Canberra, 249. SPCC (I 983). 'Water quality in the Hawkesbury/ Nepean: A study and recommendations' ; State Pollution Control Commission , NSW. SPCC (1985). 'A strategy report for the management of the water quality of the Hawkesbury and Nepean Rivers'; State Pollution Control Commission , N.S.W.

SEWAGE TREATMENT PLANTS IN THE HA WKESBURY /NEPEAN CATCHMENT Equivalent Population Served (EP)

Plant

Name

Code

Hornsby Heights West Hornsby Round Corner Castle H ill Kellyville Rouse Hill Quakers Hill St. Marys Riverstone Bligh Park Windsor Richmond Nth Richmond Penrith Winmalee Nth Springwood Valley Heights Springwood Hazelbrook Wentworth Falls North Katoomba South Katoomba Black heath Mt Victoria Mt Rive rview Glenbrook Warragamba West Camden Menangle

HH WH RC CH K RH Q SM RV BP

December Estimate Year 1984 2000

Code as denoted in Fig. I .

ws RM NR p WM NS V SP HB WF NK SK BH MV MR G WG WC MA

6300 25190 10000 3300 88890 92590 3500 8000 8520 1480 65000 300 200 2200 4440 4070 3330 2960 14070 4070 370 4300 10000 2220 5930

29000 47000 8000 28000 75000 175000 191000 15000 12000 10000 8000 7000 100000 7 100 3000 3000 6000 5000 3000 15000 6000 700 6000 14000 2300 64000 35000

Profile for australianwater

Water Journal September 1985  

Water Journal September 1985