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Volume 27 No 4 July/August 2000 Journal of the Australian Water Associat ion

Editorial Board F R Bishop, Chairman B N Anderson, P Draayers, W J Dulfer, G Finlayson, G A Holder, M Kirk, B Labza, M Muntisov, N Orr, P Nadebaum, J D Parker, M Pascoe, AJ Priestley, ] R.issman, F ls.oddick, EA Swinton

, Water is a refereed journal. This sym b ol ind icates that a paper has been refereed.

CONTENTS

Submissions Submissions sho uld be made to E A (1306) Swinton, Features Editor (see below for details).

General Editor

From the Federal President .......................... ....... ... ....................................... 2 From the Executive Director ................ ....... ........... .............. .... ..................... 4

Peter Stirling PO Box 84, 1-lampton Vic 3 I88 T cl (03) 9530 8900 Fax (03) 9530 8911

Features Editor EA (Bob) Swinton 4 P leasant View C res, Wheelers Hill Vic 3150 T el/Fax (03) 9560 4752 Email : bswinton@bigpond.net .au

AWA Head Office PO 13ox 388, Artarmon, NSW 1570 Tel +612 94 131288 Email: info@awa.asn.au

Water Advertising & Production Hallmark Editions PO Box 84, Hampton, Vic 3188 Level I, 99 Bay Street, Brighton, Vic 3 I 86 Tel (03) 9530 8900 Fax (03) 9530 89 11 Email: hallmark@ h alledit.com.au

Advertising coordination: Fiona Second Graphic design: Mitzi Mann

Water (ISSN 0310 · 0367)

INDUSTRY

Interview: Graeme Dooley ................. .. ... ..... ........ ....... .. ........... ........................ 7 MY

AR.BN 054 253 066

Federal President Allen Gale

Executive Director C hris Davis

AWA ·;re> lit.._

~~~

AUSTRALIAN WATER ASSOCIATION

Australian Water Association (A WA) assumes no responsibility for opinions o r statements of facts expressed by co ntributo rs or advertisers. Editorials do not necessarily represent official AW A policy. Advertisem ents are included as an information service to readers and are reviewed before publication to ensure relevance to the water environment and objectives of AW A. All material in Warer is copyright and sh ould not be reproduced wholly or in part without the written permission of the General Editor.

Subscriptions ~Vater is sent to all AW A membe rs six times a year. It is al~o available via subscription.

Visit the

POINT

OF

VIEW

The Safety of Water is Not Absolute ..... .... ...................... ...... ..................... 10 By P R Nadebaum WATER , Improved Management of Drinking Water Quality ............. .............. 12 P R Nadeba um , L M Adlem, A J Baker, M R C hapman, S R.izak ·-l] Artificial Destratification: Evidence for Improved Water Quality .... .. ...... 18 J Brookes, M Burch, P Tarrant [ ·,I Circulation, Destratification, Mixing and Aeration: Why and How? .. .. ... .. .. .. . .. .. .. .. ... .. ... .. .. ... .. ... .. .. .. .. .. .. ..... .. . . ..... .. . .. .. .. . .. .. .. .. ........ 24 BK Kirke

is published in Jan uary, March , May, J u ly, September and November.

Australian Water Association Inc

PEOPLE

WASTEWATER [ ·l Oil and Grease Removal in Brisbane's Activated Sludge Plants .... 31

D Brooker, E v. Muench, K Barr

ENVIRONMENT ·l.] The Murray-Darling Cap - Sharing a Natural Resource ...... .. .............. 37 A F C lose, A J McLeod

· l Recent Behaviour of the River Murray Mouth .... ... ............................. 43 DJ Walker

BUSINESS Arrangements for Setting Drinking Water Standards ... ... ................... ... 49 DEPARTMENTS Aquaphemera .. ..... .. .. .. ..... .. .. ....... .. .. .. ......... .. .. .. .. .. ........... .. .. ....... .. .. .. ..... .. .. .. ..... .. . 4 International Affiliates ..... .. ....... .... .... ... ... ................. ................ .... ....... .. ... ....... 5 Membership ... ......... ...... ...................... ........... ... ............. .. ......... .. .. .. .................. 55 Meetings ......................................................................... ... ... .... ........................ 56 OUR COVER: The regrrlation of drinking wafer qrrality is a co11tentious issue, with the legitimacy ofg11ideli11es versus standards under review. Cover photo is ef tire Research North elevated tank, capacity 380kL, wlriclr supplies a bushland residential area on the outer northeastern fringe of Melborrnr e. The steel stn-rctrrre is about 30 metres high and is a prominent local landmark. Plroto courtes y of Depart/1/ent of Hu/I/all Services, Victoria .


FROM

THE

PRESIDENT

THE NEED FOR A WATER INDUSTRY FORUM T he wate r industry, in all its guises, is vulnerable to sudden political moves at state or federal level in A ustralia. I make that assertion beca use of the degree to which we are fragmented , b etween jurisdictions and within those jurisdictions. Of cou rse, there are organ isations that look after th e interests of segm ents of the industry: WSAA (the Water Services Association of Australia) is the body that represents the 21 largest water authorities across the cou ntry; w hil e ANCID (the National Comm ittee on Irrigation an d Drainage) p erforms a similar role fo r irrigation age ncies, bu t in a more diverse structu re. T he three most populous states, though (NSW, Vi ctoria and Quee nsland) all have multiple organisa tions in vo lve d with water services and deli very, u rban and rural. Ensuri ng that they act coherently and wi th broad industry and community interest in mind is very difficu lt. Although AW A is the largest single wate r organi sa ti on , with 4,000 m embers, we are still not capab le, at least in the short term, of representing all water interests effectively. That is why th e re is a ro und of negotiatio ns under way to bring together the main , national water players: ANCID, AWA, WSAA and the !AA (Irrigation Associa ti on of Australia) in a single, loose affiliatio n to bring som e coordination to the water advocacy and policy scen e. As I w rite, the name of that group has not bee n cem ented , but something like Australian W ater Indu stry Forum is the sort o f name likely to eme rge. It seem s likely that collaboration across a broad spectrum of water associations, like this one , will allow for genu in ely representative vie ws to b e put, and for gove rnme nts to be receptive to the strength of the constituencies. [ h ope we can forge this allian ce and create the Forum . At the sam e tin1e as we need a crossindustry coalition , we also need to engage wate r industry leadership be tter. Clearly, WSAA and ANCID, by th eir nature, effectively bring CEOs to the table, but A WA has not been as successful in that regard. To red ress that deficiency, I have arranged for a survey of a sample of CEOs across the country to be carried out by AWA leadership. That will be concluded by th e end o f J uly and th e resu lts should give us a much better grasp of what top man agem e nt in water thinks about issu es, and about AWA. 2

WATER JULY/ AUGUST 2000

Allen Gale

1 believe we can use those results, and the collaboration w ith peer organisations, to make AW A move into a more influe ntial mode and truly deliver our mission of promoting r espon sibl e managem e nt and conservation of water and the related e nvironment. Another Demonstration of the Quality of the Australian Water Industry

At the time of w riting, I have just returned from the annual con fere nce of our sister organisa tion, th e Ame rican Water Works Association, in D en ver, Colorado. 1 was impressed by the size and scope of th e event and the developme nts in wa ter supply practice in the USA. I can1e away, though , confident that Australian water supply is in good hands and holding its own on the wo rld stage. The percepti on of the USA often is that e verything is " big". This is not th e case in the water industry. There are abo u ts 170,000 water suppli ers, with o ver 160,00'0 serving less than 3300 people . Even the large suppliers, on average, serve only about 60,000 p eople . Th us the industry is extremely fra gm ented , and I beli eve it suffers in that there are limitatio ns on tech n ical expertise in many orga nizations and fi nancial clout is limited. T he situation is analogous to that in Victoria prior to refo rm in the 1990's that co nsolidated more than 300 water and sewerage authorities to 15. Our USA counterparts could be nefit greatly by studying the water reform that has taken place in Australia over the last 10 years. Comments made to me were that this would be diffic ult to achieve as a State Gove rn or , or a F e d e r al

Co ngressma n or Senator would upset many people if suc h a refo rm was to be introdu ced. P ri vatisation is at an uncertain stage in the U SA, with many of the people I spoke to expressing n ervousness as to how they should go about tackl ing the issu e of possible " takeover" by a USA or fore ign "giant". I b elieve that we in Australia have m oved well b eyond this and , on th e w hole, have a good balance between ownership of community facilities an d optimization of performance of these facilities. T echnically I believe that we in Australia can hold our heads high. Microfiltration was talked of very mu ch as th e emerging technology and it was good to be able to re mind whoever would listen that this was a technology developed in Australia. A paper was presented by the Water Corporati on of Western Australia on the first full -scal e application of the MlEX proc ess, which is anothe r Australian developm e nt by Orica. W e in Australia can be confident that our industry is of wo rld class standard.

Allen Gale

water Contributions Wanted The Water j ourn al welcomes the submission of papers equivalent to 3,0005,000 words (allowing fo r graphics) relating to all areas of the water cycle to be published in the Water, Wastewater, Environment and Business sections of the journal. You may email a draft copy with figures and low resolution graphics (e.g. jpeg) to Features Editor, Bob Swinton, at e m ail bswi n to n @ bi gpo n d .n et.a u. Following his assessment of suitability, high resolution gra phics sho uld be emailed or mailed on disk (pi:ints suitable fo r scanning are also accep table) to 4 Pleasant View Cres, Wheelers Hill, Vic 3150. Topical stories of up to 2,000 words may also be accepted.

Graphics: Colour or black & white photo-graphs and illustrations can be sent either as transparencies or prints, or as high res scans (300dpi) as tiff or eps files on a 100 MB Zip disk.


INTERVIEW

state governments haven ' t con verted one of th eir governm ent uti lities into a signifi cant private sector entity. The model f adm ire is probably AGL, a long standin g regu lated utility, albeit in gas , w hi ch has flo u rished and d ev e lo p e d its busi n ess w h e n t h e competitive forces of a fre e and open market have existed. It has acquired significant interest in electricity and long distance gas pipelin es both in Australia and New Zealand and has other inte rests in other parts of the world. Now there's no reason w hy a large water uti lity couldn't enj oy the sa me growth , no t only in its home area and with in th e Aust ralian and N ew Zealand area b u t also in Asia.

R od: ls the dividend paid by govem111e111 water authorities lo the go11en1r11enl reasonable? Graeme: I'd say, no, i t's not. I don 't th ink that the publi c needs to pay more fo r water. What I do feel, howeve r, is that the reve nu e that is ea rn ed needs to be applied to the long-term fun ctio n of the wate r uti lity itself. State Treasuries ha ve lo n g e njoyed th e ben efit of in creased revenu e fro m ga mbling and

dividends from th eir electri city and water u tilities, and it has given everyon e a false sense of co mfort that water utiliti es in parti cular have been able to susta i n th eir bu siness e ve n t houg h they' ve paid a dividend to treasuries. I t h i n k th a t is s h or t sig ht e d . Th e Institution of En gineers' report on the degradation of o ur nation 's infrastru ctu re has, correctly, ide ntified that grossly insufficient funds have been applied to the renewal of assets to sustain their pe rformance in perpetuity. Th is was the proble m that occ urred in th e UK where a large asset stock was a!Jowed to run down very dramatically. The estimate in the mi d S0's was that 50 billio n pounds would be needed to bring th e infrastructu re up to the standard that was required fo r both drinking water and e nvironmental discharge. Th at 50 billion pounds was just not in the publi c purse and th e privatised utilities fu nded it through equity fro m shareho ld ers and raising debt but applying far greater levels of efficiency. T his in evitabl y leads to two conclu sions fo r Au stral ia, one, chat the i nlbstru ctu re w ill continue to degrade or

seco ndl y so me alternate m eans of funding be found such as pushing the utilities in to the private sector, in som e way like the Common wealth Bank , QANTAS or th e Victorian electricity privatization models.

Rod: Well thanks very 11111ch, Graem e, is there 1111y other co111111ent you would like to 111ake before we close t/1e i11te1view? Graeme: l wo uld have predicted at the beginning of the nine ties that on e o r two o f the big uti lities would end up in so me form of pri vate sector combination . l suspect that the governme nts of both political pe rs uasions are probably go in g to re treat from wate r un ti l electricity is well and tru ly bedded do w n. M y only personal problem is that I wou ld have liked to be part of it and l think that given that it's likely to be mo re th an a decade away l m ight we ll be re tired and miss ou t on all the exciting acti on. But I'd have to say that the last te n years w ith the e mergence of private water co mpanies has bee n a most interestin g ex peri ence and continues to be an exceedingly in te resting part of pro fess ional wate r practice .

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9


MY

POINT

OF

VIEW

THE SAFETY OF WATER IS NOT ABSOLUTE Peter Nadebaum The Australian water industry is at an important point in its history with respect to the managem ent of drinking water quality. The industry has been well served by guidelin es for drinking water quality p ubli s h e d by NHMRC and ARMCANZ, and by the World H ealth Organisation. U ntil th e past few yea rs these ha ve bee n used for guidance purposes rather than as standards req uiring absolute compliance . However, with the increasing level of regulation and corporatisation, a shift is occurring in which the gu ideline values are being used as absolute m easures of performa nce . The reality is that drinking water is a highly complex mixture of inorganic and organic compounds and living organisms, and the concentration s of these vary widely with time. Water supply systems are fa r fro m steril e, and it is through understandin g and managin g the potential avenues by which problem mi croorganisms can enter the supply system that an acceptable level o f water quality is achieved. Previously we had only very crude m easures of w hat is present in water and, as our ability to detect the presence of problem organisms improves, we are faced with the possibility of having to treat to h igher and higher standards, possibly beyond that w hich represents a sensible balance with respect to cost and benefit for our community. A deca de ago the en vironmental agencies in Austra lia fa ced a similar problem with toxicants such as dioxins, and took the approach o f effectively setting a " performance-based" approach to regulating contaminant concentrations. W ith respect to protecting human health , their approach has been to specify the desired level of protec tion (in terms of what is deem ed to be acceptable levels of effects on human health) and to publish a co nservative set of guidelin e concentrations for contaminants in soil and grou ndwater for various uses w ith the objecti ve that these should be met unless a more detailed assess1nent can show that the risk meets th e performance criterion . H ence, in the environmenta l arena

10

WATER JULY/A UGUST 2000

have been afforda ble and may not have occu rred at all. The Australian drinking water guidelin es have some provision for varyi ng from guidance valu es in th e case of total coliforms. However, to date where water au tho riti es hav e varie d from th e published va lues this has been on an informal basis and with a sense that the publishe d valu es sh o ul d rea ll y be complied with.

Dr Nadeba11111,a chemical e11gineer, is the National Manager, Environmental Management, for EJ?iS Consulting Australia (previously CMPS&F). He has some 25 years experience in 1JJater treatment a11d environmental control. H e sits on the Board of tire Co-operative Research Centre for Water Quality and Treat111e11t, and has been active over many years i11 A WA. Dr Nadebm1111is particularly recognised i11 AHstmlia and New Zeala11d with regard to the 111a11age111ent ef risk associated u1it/1 water quality and water supply syste111s and the selectio11 and optimal applicatio11 of u,atcr treatme11t tec/r110/ogies. contaminant concentrations very much high er than the published guideline va lues can be (and often are) accepted by showing through more detailed analysis that the contamination in fact does not pose a concern to human health or the environment. Th is approach is inherently flexibl e beca use new knowledge can be ¡ in corporated into the decision m'aking process immediately it comes to hand, and does not have to pass through a regulatory acceptance process. This approa ch is w idely recognised as saving the Au st ralian c ommun it y enormous sum s of m oney in avoidin g unn ecessary expenditure on cl ean ing up contamination in th e environment. This approach has also had a major improvement in the qu ality of ou r environment , through allow ing affordable clean-up approaches to be adopted. If clean up had been requ ired to be much more stringent and costly, clean up ma y not

It has been stated that our abili ty to m easure constituents in water and their effects is insufficient to set performance objectives for drinking water. H owever, our ability to m easure such things is rapidly improving. Further, we do not necessarily need to rely on direct m easures of organisms and constituents, as is being recognised with th e introduction of HACCP into the fie ld of water management. It can be noted that the limitations in measurement which applied in the en vironmental field a decade ago were not judged to be a suffici ent reason to not adopt a performance-based approach. The recent Productivity Commission this study (summarised elsewhere in issue) discusses, inter alia, these aspects and remarks:

"A ustralia-wide, the 1-trban water sector faces the prospect ef having to make latge investments in treatment technologies, because ef an increase in the scope and stringency of water quality standards. Given the magnitude of potential costs and the importance of public health objectives, it is timely to explore how higher standards are developed, how risks are analysed, and how decisions are taken to implement higher sta11dards". "There is a need to ensure that health risks from contaminants are addressed i11 the most effective way across all possible sorirces, including those from hazards other tha11 water. Above all, there is a need fo r a well-i,iformed public debate about ho1.11 safe drinking water should be and consultation on how much consurners are prepared to pay for grea ter safety".


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IMPROVED MANAGEMENT OF DRINKING WATER QUALITY P R Nadebaum, L M Adlem, A J Baker, M R Chapman, S Rizak Abstract The A ustrali an wa ter i ndu stry is adopting a risk managem e nt approach to water quality managem ent. T he basis fo r adopting a fo rmal approac h is discussed , an d th e framework currently b eing consid ered is outli ned. M ost water au th orities are choosing to build o n and improve their e xi sting ma nagem ent system s by in corp o rating the requirem en ts for effecti ve drinki n g w a te r quality manageme nt for the w h ole of their w ater supply system s, w h ich m ay extend fro m catch ment to tap. R isk man age m e nt prin c i p l es a r e be i n g adopted, draw ing on the principles o f Hazard Analysis and Criti cal Co ntrol P o ints (H ACCP) a nd AS/NZS43 60 (R isk Manageme nt). T his w o rk gene rally in volves a " gap an alysis" to identify whe re existi ng m ana ge m e n t sys tem s n eed to be improved, a co m preh e nsive p rogram to ide ntify w here w ater quality proble ms can arise, and the developme nt and implem en tation of app ropriate plans and p rocedures to avoid and m anage these problems.

Introduction The r e is in creasing inte rn ational recognition that monitoring of drinking w ater for co mpliance w ith numerical health limits is not su ffi cie nt to gu aran tee the qu ality an d sa fety of our w ater supplies. Th is creates a need for mo re effective dri nking w ater quality practices tha t pro vid e o n go ing ass urance o f reliable an d safe drinking water supplies. The threat to Sydn ey's water supply in 1998 highli ghted the n eed for a more system ati c means of man aging drinking water quali ty for the protec tion of public health. T h e m ost effe c tive way to do this is th rou gh the adoption of an approach that en compasses all steps in w ate r productio n fro m catchm en t to tap w ith an emphasis o n the identifi ca tio n of poss ibl e w ate r qu ali ty pro ble m s in a dvan ce an d t h e ir preve n tion an d managem e nt, rather than reac tion w he n proble ms do arise. This approach is essentiall y o n e of risk managem e nt. This paper discusses th e need fo r a for m al approa c h to d rinking wa te r

12

WATER JULY /AUGUST 2000

quali ty managem ent, the fo rm that a fram ework can take, and issues that can arise, draw ing fro m the experiences of the authors in assisting maj or Australian urban water authorities in improving the ir drinking water quality m anagement syste ms.

Terminology

• "risk m anagem ent" is the system atic eval uation of the water supply system (eg from catch me nt to tap), the identification of hazards and hazardous events, th e assessm e nt of risks (the likelihood of occurrence of th ese hazards and their severity), and the developme nt of strategies to manage these risks.

Do Water Authorities Need a

The application of risk manageme n t Formal System? in troduces terminology which can vary dependi ng on the source of the m ethodIm plem en tation of form al manageology. In the con text of drinking w ater m ent systems are becoming increasingly quali ty managem e nt, we defin e: comm.on in the water industry as an e ffec tive m eans of assuring product and • " hazards" as those w a te r qu ality service qu ali ty. Variou s management param e ters w hi ch, if certain levels are fram ewo rks an d standards are u sed exceeded, w ill give rise to unacceptable q u a li t y. Fo r examp le , w at e r w ithin the industry, suc h as ISO 9001 Cryptosporidium is a wa ter quali ty hazard (Q u a li t y Sys te m s), I SO 1 4 00 1 and , if present at numbers of oocysts per (Enviro nmental M anagem ent System s), vo lume o f wate r ab ove a c ertain level, can pose a co n cer n w i th regard to public "TODAYS' TECHNOLOGY PROTECTING TOMORROWS' ENVIRONMENr' health. • "ri sk " as a fu nction o f t he likeli hood that a hazard will occur, and the seve rity of the effect of the hazard . For exam ple , th e risk ass o c ia te d w i t h Cryptosporidi11m is a fun ction of the li ke lih oo d th a t • High quality effluent Cryptosporidium discharge o o cys ts w ill b e • Low Maintenance pr ese nt at numbe rs w hic h • Uses no water for flushing are o f c on cern , • Government approved and the severity in all states of effect (ie the • Patent Pending numb ers of Worldwide persons like ly to • 6 to 150 person be ill, the extent units available of t h e suppl y syst em affec ted , and the resultant FreeCall 1800 069 805 co n cern that t he www.gough.com.au identificati on will Agents in all states. result in).

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ISO 18000 (Occupational H ealth and Safe ty), AS/NZS 4360 (Risk Manage me nt) and H azard Analysis C ritical C ontrol Point (HA CC P) m ethod olo gy as used by th e food ind u stry. Most wate r auth orities have adop ted va rio us e le m ents of q uality manageme nt syste ms in th eir busin ess. H owever, the exte nt of appl icati o n o f th ese va ries w ith eac h authority and can range from an in fo rmal managem ent system to a certified quality managem e nt syste m. At prese nt, son1e water authorities arc ce rtified to ISO 9001 or ISO 900 2 (Qu ality Systems), and a growin g numbe r arc al so ce rtifie d to ISO 14001. So me w ate r authorities are also pu rsuing HACC P ce rtification. Existin g quali ty manage me nt fram ew o rks are usuall y ind epe nde nt of any specific indu stry and pro vide ge ne ric require me nts fo r organi sations und ertaking a wide range o f ac tivities. Th erefore, th e ir guida nce is often " gene ral purpose" in nature and do cs not specifi call y address all of the issu es that must be con sidered for effective drinking water qua li ty m anagement. A q uality managem ent syste m may, for exam ple , cover a n um ber o f busi ness areas su ch as fina nc ial m anage ment, design o f treatment syste ms, maintenan ce o f syste ms, and e nvironm ental compliance. Drinking water qual ity manage m ent, however, requires consideration of several uniqu e and diffi cult c hallenges which existing managem ent fram eworks arc often defic ient in or are not suffic ientl y compre hensive in addressing. Fo r example, key require ments arc an in - depth know ledge o f the water supply system , as well as th e identifi cation of haz ards and the specifi c m easures to control hazards emphasisin g th ose el em ents that can be m o nitored in real tim e, and the docum entati o n co de mo nstrate that th e contro l processes chat govern drin ki ng wate r quality and safety arc implem ented appropriately and fun ction ing effectively. Drinkin g water qual ity manage ment must also address a num ber of other facto rs that have the abili ty to affect drink in g water quality eith er directl y or indirec tl y including employee trai n ing and aw aren ess , e ffective com mu nications, and the ongoing com m itm ent to continua lly improve the managem ent of water quality. T herefo re it is im po rtant for water au tho ri ties to care ful ly revie w their manageme nt systems to ensure that th e y comply w ith th e require me nts fo r good drin ki ng wate r quali ty manage ment. Ensuring that th ere is a good system in place offe rs a number o f benefits, in that it: • protects pub li c health by assuring safer drinkin g water for co n su mers, and i ncreases trust and confide nce in w ater authori ties by de mon strati ng commitme nt to q uality m anagem ent; • e n sures that potential wate r quality problems are identi fi e d in advance and are properly managed; • pla ces more emphasis on preventio n rath er than corrective actio n, leadi ng to mo re satisfactory and often mo re cost-effective solu ti ons; • defines responsibiliti es o f various age ncies and stakeholde rs in volved in the supply of drink ing w ate r; and • provides an effec ti ve framew ork for communi catio n w ith th e public, e mplo yees and stakehold ers.

What Form Should a Framework Take? A s part o f its Publi c H ealth R isk A ssessm e nt Program , th e Cooperative R esearc h C e ntre fo r W ater Quality and Tre atm ent (CRCWQT) has developed a dra ft Fra111e111ork for Dri11ki11g Water Quality Ma11age111ent to assist water autho ri ti es a nd stakeholde rs in addressin g th e key co nsid erations

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that gove rn drinking water quali ty and safety from catchment to tap. T he framework was deri ved by supplem enti ng the information o n prevent ive system managem en t already provided in the c urrent Austra lian D rin ki ng Wa ter Gu ideli nes w ith principles of quality management, i ncl ud ing th ose espoused by HA CCP , AS/NZS 4360, ISO 14001 and ISO 9001. Beca use of the w ide variety of water su ppl y systems across Australia , and the varying institu tiona l a rra n ge m e nts (catchment b oard s, contractors, who lesale/retail, etc) , the framework is necessaril y generic and allows for a flex ibl e and progressive implementatio n. T h e seco nd rou nd of the roll ing revi ew p rocess fo r t h e A u st ralian Dri n ki n g Wa te r G ui de lin es h as co mmenced, and is to include a review of the drin king water quality managem ent advice provided i n the G uideli nes. To this end, the C R C p roj ect on th e develop men t of a wate r quali ty mana gem e n t fram ewo rk is co ntin u in g in conj un ction w ith the N ational Health a n d M e d ica l R esea r c h Co u n c il (NHM R C) and severa l water autho rities across Austra lia to further re fi ne the fra mework and iden ti fy issues in its applicatio n . T he fina l fram ework will t h en b e i nc lu de d in t h e r ev ised G ui delines. Table 1 lists the m ain elements of the framework; the full fram ework includes a descriptio n of w h at eac h c le m e nt

Table 1. Framework for Drinki ng Water Qu alit y Management Commitment to Drinking Water Quality Management

System Monitoring (Verification)

Operational Monitoring

Water Quality Policy

Compliance Monitoring

Multi-Agency Involvement

Investigative and Research Monitoring

Requirements and Objectives Assessment of the Drinking Water System

System Analysis

Consumer Satisfaction Health Surveillance Participation Reliability of Data

Hazard Identification and Risk Assessment Incident and Emergency Response Water Quality Performance Investigation Preventive Strategies for Drinking Water Quality Management (Planning/ Identification)

Preventive Strategies Improvement Plan Programs for Drinking Water Quality Management (Implementation)

Catchment Management Program Intake/ Reservoir Management Program Treatment Plant Operation Program Service Reservoir and Distribut ion System Program Maintenance Program

Corrective Action Incident and Emergency Response Research and Development Employee Awareness and Training Community Involvement and Awareness

Community Consultation Communication and Reporting Documentation and Reporting

Documentation and Records Management Reporting Performance Evaluation and Continual Improvement

Drinking Water Quality Performance Evaluation Drinking Water Quality Management Audit

includes, together w ith explanatory notes. T he framework provides guidance that will assist water autho rities in developing a comprehensive preventive strategy for managing drinking water quality, from catch m ent to tap. T his approach emphasises good operational practices and the

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perfo rmance of barri e rs (such as reservoir aeratio n , fi ltratio n and/or chl orina tion), rat h er t ha n relyin g on compli a nce monitorin g of the wate r supplied co customers. By m easuring indicators of performa nce (such as aerator power and pressure, turbid ity reductio n , o r C.t va lues fo r disinfectant), there is potential to reduce the difficulties, uncertainty, cost and reliance of treated wa ter monitoring for the protection of public health.

Issues in the Development and Application of a System The framework in T able 1 is inte nded to be fl ex ible to accom mo date the w ide

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ran ge of diffe rences in water supply systems and the varying circu mstan ces of water au thorities. Th e ele m ents shou ld no t be regarded as exha usti ve or prescriptive, and are in tended co provide gui da nce on the key considerations in the effec tive manage ment of drinking water qu ality fr om catch ment to tap. T he indicated requirem e nts can be satisfied in a number of ways and a manageme nt system can take a variety of forms. Th ese ca n ra nge fro m develop ing a selfstanding syste m , th rou gh to ex panding an existin g ma na ge m e nt syste m to i nclude the required elements. Eac h could lead to certi fication by a qu ality manageme n t agency.


WATER

Th e opti on of developing a self-sta ndin g system focused so lely on drin ki ng water qua lity m anagement can be ~een as analogo us to adopting an environmental management syste m fo r enviro n mental issues. T his approach wou ld e n sure there is a strong and visible e mphasis on d rinking water quality management, and can also serve as an effective framework for communication w ith the public. The framewo rk presented in Table I ou tl ines one possible stru cture fo r a mana ge m ent syste m. In practice this ca n be ex pected to vary with eac h water authority, reflecting indi vidual circu msta nces . Th e option of expanding an existing m an age111en t syste m to includ e th e indi cated clements for water quality m anagement recognises that m any water auth o riti es ha ve al r ead y deve loped qu ality mana ge 111e nt syste m s for clements o f the ir business, for exa mple ISO 900 I and ISO 1400 I, and they m ay des ire to incorporate the impo rtant additional fun cti o ns required for dri nk ing water qu ali ty m a nage me nt into their existin g sysce111 rath er than deve lop a nevv se lf sta ndi ng syste m. Because t he fram ework for drinkin g water q uality m anage m e nt was derived usin g qual ity management prin cipl es that are reflected in th e various manage m e nt fram ewo rks com111 o nl y used in the water industry, it shou ld be easil y aligned and integrate d w ith m anage me nt syste m s likely to be fou nd in w ate r auth oriti es. Th e fra m ework pro vides a checkl ist against wh ic h an existing managem e nt system can be compared to e n sure that all necessary clements of drinki ng wate r qua li t y man agem ent arc in cluded. 1.n Australia , all of the m aj o r urban water authorities in Au stralia have em barked on a process of imp rove m ent of th e ir drinking water quality ma nagement system s. W e have bee n in volved in ass isting a num ber of chem in this process, and th is has generally in vo lved a review of th e ir ex ist ing m anagem ent system s to determi ne where improve me nt can tak e place, and how this mi g ht be best e ffe cted o n a case by case basis. While in all cases a ce ntral o bj ec tive has been to ach ieve effective management of drinking water qua li ty, so m e water autho riti es arc wo rkin g cowards integratin g drinking water qua lity management w ith other busin ess m anagement requirements into an overall busin ess managemen t sys te m . For exampl e, consid eration is be ing give n to quality manage m e nt, asset man age m e nt, environmental ma n age me nt, occupational health and safety management, as we ll as drin ki ng water q uality 111anagcm ent. T he decision as to the fo rm of the drin king water quality m a nagem e nt sys te m w hi ch should be adopted by a water au ch a rity depends o n the n eeds and philosoph y of the o rgan isati o n . Factors involved in th is decision may include co n siderat io n of t he range of w ate r supply sys tem s i nvolved, th e managem ent systems already in place, and the desi re for certifi ca tion for external q uality assurance purposes. If certi fi cation is an important co nsideration , th en water autho rities m ay choose to direct their attentio n to those fram eworks and system s w ith establish ed accredi tation. External auditin g provides the forma l ass urance that the m anagement system elem e nts are in place and that the processes influ enc ing quality arc reliably ca rried o ut. Of t he above opti o ns , only t he ISO and HACCP fra m ewo r ks have a well -established basis for ce rtification. H owever, if the re is a hi gh degree of consensus among the wa ter industry and regulato ry au thori ti es, th en it would be possible for an industry-wide commitm ent to be pursu ed. Similar initi atives have been developed in ocher industries,

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such as Responsible Care which started in Canada as a voluntary initiative of the chemicals industry to improve the performance of operations and to increase community involvement and awareness. In just over ten years, this program has become a major success internationally and is now an in itiative of the c hem ica ls industry in 40 co untri es .

Identifying Gaps in an Existing System T he initial step in impl ementing a syste m is to assess the existing management systems against the requ irem e nts for effective drinking wate r quality management, suc h as those outlined in Table 1 , and to identify w here gaps may be present. This is then followed by pl anning and impl ementing appropriate systems to fi ll these gaps. Th is "gap analysis" should be undertaken systematically and include the identification of where existing syste ms arc not working efficiently, and w here th e necessa ry linkages and chain of responsibilities are not in pla ce. Our experie nce in assisting a number of the major Austra lian water authorities in undertakin g gap an alyses of their management systems aga inst th e requirem ents of Table 1 has indicated that, in general: • Man y of the c lemen ts needed fo r th e effe ctive management of drinking water quality will a lr eady be in place. H owever, ex isting practices may not be sufficiently developed or comprehensive to fully ad dress the range of dri nking water quality issues that can arise, nor be sufficiently visible to ensure that all employees know and un derstand the entire system. • Th e most commonly encou ntered and important gaps are hazard identifi ca tio n , risk assessment, and risk management. While water authorities will be aw;ire of many of the risk issues, man aging risk wi ll often not have been approached systematically a nd compre hensive ly . Improvem ent ca n involve, for example, developing an understanding of the water supply system in its entirety, identification of how wa ter qua li ty problems may arise, assessment of these problems, and developing appropriate methods to provide contro l. This correspo nds to the "Aspects and Impacts" assessment of an Environmental Management System, and can be ac hieved by implementing the principles of 1-!ACCP or a more generic risk managemen t approach such as AS/NZS 4360 . 16

WATER JULY/AUGUST 2000

• Other comm only encountered gaps w here improvement may be indicated include, for example: defining a policy with respect to drinking water qual ity; defin ing and strengthening management and staff accountabilities and responsib iliti es; defining responsibilities of external suppliers (such as a bulk water provider or a catc hment management authority); providing clear performance objectives, plans and procedures for critical activities; improvin g staff training and awareness; and providing a systema tic program of audit and management review.

Identifying Potential Water Quality Problems The process of analysing water supply system s to id entify ex isting and potential water quality problems and assess risks shou ld be approached system atica ll y. It needs to take into account: • direct experience and observati ons fo r the water supply system of interest, and what is known from other systems and the scie ntific literature; • the sources of water quality problems and the ra nge of water quality parameters, such as taste and odou r, appearan ce (colour and turbidity), as well as health related indicators, that can be associated with each even t; and • the likelih ood, severity and significance of the possible excu rsion s in water quality parameters both at the point at wh ich they occ ur, and downstream at the point of consumption after controls have been applied. A workshop approach is an effective and efficient way of undertaking th is process o f analysis. The workshop wi ll typ ically involve operations and ma intenance staff for the va rious supply system clements (catchment, reservoir, treatment syste m , distribution system), water quality manager and sc ientists, water treatment engin eer, and may includ e representatives of othe r stakeholde rs such as the health department. It is desirable that the workshop be run by a fac ilitator experienced in such workshops who understands the application of risk management to water supply systems. An assessmen t of the drinking water supply system using this approach will result in the identification of numerous items which give rise, or have the potential to give rise, to wa t er quality problems. When a situation that can give rise to a sign ifi cant water quality problem has been identified, management strategics and preventive measures can then be planned to prevent or control th e h azard, thereby minimising

its risk. The leve l of preventive action planned to control a hazard shou ld be proportional to the associated risk. The application of HACCP principles and concepts such as Control Points, C riti cal Limits, and Control Plans can be used to provide objective evidence that water quality risks arc properly mana ged. Applying HACCP principles w ill lead to preparing plans, programs and procedu res whic h detai l the specific operational procedures and the requirements for effective impl ementation fo r catchment man agem en t programs, treatment plants, distribution systems , maintenan ce, etc. Where these are presently not available, this may simply require documentation of procedures that are already known to operators and staff.

Conclusions The Austral ian water indu stry is adopting a risk mana geme nt approach to wate r quality management. Water au t horities arc improving their ex istin g management systems by incorporating the requirements for effective drin king water quality management for th e w hole of th e water supply system, from catchment to tap. Risk management prin cipl es arc being adopted, drawing on th e principles of Hazard Analysis and Critical Co n trol Points ( HA CC P) and AS/NZS4360 ( Risk Management). This work genera ll y in volves a "gap ana lysis" to identify where existi ng m anage m ent syste ms ne ed to b e improved, a comprehensive program to identify how water qual ity problems can ari se, and the developme nt and implementation o f appropriate p lans and procedures to prevent and manage th ese problems.

Authors Dr Peter Nadebaum (e mail nadeba u 111 p@mcl.egisconsult.com. au) (Nati o nal Manager, E n vironmental Management), Lisa Adlem (Se nior Environmental Engineer), Dr Alison Baker (Man ager, Water Qu a lity, Internati onal) and Michael Chapman (Pr in cip al, W ater Quality and Treatment) are all w ith Egis Consulting Austra lia. Samantha Rizak is an E n v ir onmen t a l Scientist at the Depa r tment of Epidemiolo gy and Preventive Medicine, Monash University. Both organisa tions are partners in the Coopera tive Research Centre for Water Quality and Treatment.


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Abstract

Introduction

Thermal stratifi cation is a common feature of the physical environment at M yponga Reservoir, Sou th Australia. T he rmal stratificati o n effectively iso lates the hypolim nion from th e atmosphere resu lting in low dissolved oxyge n an d resolubili sa ti o n of iron and mangan ese from sediments. The co ncen tra tion of iron and manganese in the hypo limnion was correlated w ith th e durat ion of t herm al stratifi cation. A bubble plum e aerator was d e ployed in 1994 to induce mix in g, oxyge nate th e hypolim nion and decrease the flux of iron and manganese from the rese r vo i r sedim ents . Th e artificial dcstratifier has de creased the mean iron concen tration at 30 m from 0.7 1 m g L- 1 in 1986 to 0 .345 m g L- 1 in 1996. T he mean concentration of manganese at 30 111 has decreased from 0 .41 m g L- 1 in 1986 to 0.052 mg L- 1 in I 996 . Conc en trations are now consistently below drinking water guid e lin es . Keywords: Thermal strati ficat ion, iron , mangan ese, artifi cia l d estratifi catio11.

Ve rtical thermal stratificatio n is a co mmon fea tu re of many lakes and reservo irs w hich develops as seasons progress from sprin g to summer and as so lar in put increases and heats the surface layer. T hi s creates a temperature and d ensity gradient w hi ch sepa rates the warmer surface layer from the deeper, cooler hypolimnion. The rmal stratifi cation resists vertical m ixing li miting the transfer o f water a n d disso lved

18

WATER JU LY /AUGUST 2000

substa nces between the surfa ce and t he hypoli mn ion. P rolonged therm al stratifi cation isolates the hypoli m n ion from t h e atmosph ere a nd leads to seaso nal deoxygenation o f th e hy p ol imni on Wh e n th e h y p o limnion beco m es deple ted in oxygen the redox potential dec reases promoting th e resolubilisation of und es irable substan ces, such as iron, manganese and phosphorus, from th e reservo ir sediments. T h e a moun t of iron in solution depends primaril y on pH, redox paten-

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Figure 1. Myponga Reservoir is located on t he Fleurieu Peninsula, South Australia.


WATER

sign ifi ca ntly in creases the cost of water treatm ent. Artifi c ial destracifi catio n has been used exte nsively in reservo irs to reduce iron and m anganese co ncen t rations in t h e so ur ce wa te r (eg Ram a n a n d Arbu ckl e, 1989) . Artific ial des trati fi cat ion is m os t ofte n achieved u sing bu bble plume aerators. Bubble pl u m e ae rators opera te by entra inin g water w ith fin e air bu bbles, w hich m ixes and pro p agates an intrusion ge n e rating c irc ulation and in creasing th e exc hange o f wa ter between th e shall ow and de epe r laye rs. T he inc reased c irculatio n redu ces the differences i n tem pera tu re, oxygen and n utrie nts betwee n th e sur face and h ypo limni on. Oxygen levels in the hypol imnion arc therefore in c reased.

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Myponga R ese rvo ir is located on th e Fleurieu P enin sula , So u t h Austra lia (Fi gu re I , S 35' 21' 14", E 138' 25' 49"). T he reservo ir has a capacity of 26800 ML , maximum depth of 36 111 and the district receives a m ean an nu al rainfall of750 111111. T he catc hm ent area is 124 km 2 and is primarily improved pasture for dairyi n g, be ef and hay produc tion , although th e re arc isolated patch es of re mnant native vegetation. A bubble plume aerator was deplo yed in the rese rvo ir in 1994 and is o pera ted betwee n October and Apri l each yea r b ased on routin e t e mp erat ure and dissolved oxygen pro fi les. The aerator

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cial and temp erature. Ferrous ions arc released readily from sed iments whe n redox poten tials decline co about 200 mV , howeve r, rcsolub ili sa ti o n of Mn 2 + from th e sediment occu rs at re dox potentials in the order o f 400 111 V at ne utral pH (Stu mm and M orga n , 1996; Wetz e l, 1983 ). In m ore alka l ine environm ents, suc h as lake sedim e nts, iron and m angan ese requ ire a lower re dox pote n tia l to re m a in so lu b le . Re l ease of m a n ganese ther e fo r e p recedes that o f iron, and man ganese w ill rema in so luble i f th e oxygen saturation is less th a n ab ou t 50% (W e tzel, 1983) . If not rem oved by an ox idationprec ipitation pro cess, so lubl e iron and manganese re prese nt a sign ificant water qua l ity pro bl e m as t h ey b eco m e oxid ised by chl orine or air in the d istribu ti o n system and ca use dirty w ater at ' t h e tap'. R emoval of so luble iron and man ganese in wate r filtration plants ca n

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~

c',

~

c',

c',

(")

<')

q>

>-

Date Figure 4. Soluble iron concentration at the surface and at 30m depth at Myponga Reservoir.

WATER JULY/ AUGUST 2000

19


WATER

Table 1. Duration of persistent thermal stratification (temperature difference between 10m and 30m > l "C) and the maximum iron and manganese concentrations measured at 30m in Myponga Reservoir.

undertake n by Bulk Water Division , SA Water and c h emical dete rmina tions performed at th e Austral ian Water Qual i ty Ce n tre, Bo li va r , South Australia w ho also mai nta in the historica l wate r q uali ty database .

co nsists of a 300 m diffuser li ne deli verin g air at a rate of 120 L s- 1•

Methods Water temperature was measured weekly at a location near the dam wa ll adjacent to t h e offta k e site. Temperature and disso lved oxyge n were measured at the surface, 10 111 , 20 111, and 30 111 using a Yellow Sp rings Instrume nts p robe. Iron and manganese concentrations were determined from monthly sam pl es collected at the surface and 30 111 from the same location . The sa mpling location is approximately 20 111 from the aerator line wh ich, whe n opera tiona l , induces considerably mixing at this site. T he monitoring is

~:; Cl

0.15 1.8 0.31 0.15 0.97 1.23 0 .88 0.24 0.47 0.49 0.05 0.09 0.07

0.33 2.55 0.79 0.84 1.39 2.84 1.36 0.63 1.00 1.00 0.56 0.39 0.58

119 224 133 119 247 218 161 241 161 175 105 28 0

1984/85 1985/86 1986/87 1987/88 1988/89 1989/90 1990/91 1991/92 1992/93 1993/94 1994/95 1995/96 1 996/97

Maximum soluble manganese concentration {mg L·1 )

Maximum soluble iron concentration {mg L·1 )

Number of days where temperature difference between 10m and 30 m >1°C

Year

Results Thermal stratification Seasonal tern pera ture stra ti fication was evident at Myponga Reservo ir during summ er from 1984 until 1994. Since deploy1nent of the aerator in 1994 isothermal cond iti ons have b ee n maintained at the sam pli ng si te (Figure 2). H owever, surface layer heating is ev ide nt at oth er sites in the reservoi r outside of the immediate bu bb le p lume

2

-

1.6

Surface 30m

§. GI

Ill GI 1.2

C

~

Cl

C

~

0.8

E GI

:a:::,

0.4

0

(/)

0

~C:

"' <;>

~

.....

C:

::,

::,

7

7

7

7

::,

0

::,

0

0

<;> C:

0

~

iv'

~

C'}

a,

i~

....

C'}

~

l

i

-a;

¼

l

C'}

0C'}

0C'}

0C'}

g

~

ai

~

~

~

C'}

N

~

~

~

"' ~

~ iv'

~ a,

N

.....

l

~

d, N

Date

Figure 5. Soluble manganese concentration at the surface and at 30m depth in Myponga .

20

WATER JULY/AUG UST 2000

wh ic h is consisten t with other reservoirs where bubble plume aerators are ope ratin g (Visser et al., 1994; She rman et al. , 1999). Dissolved Oxygen Dissolved oxygen data was available from 1992 to 1997. During the summer of 1992/93 and 1993/94 th e d issolved oxygen co ncentra tion at 30 m was significan tly lowe r th an at th e surface (Figure 3). D issolved oxygen concentrations were be low 4 mg L- 1 for extended periods during 1992/93 and 1993/94 wh ic h provided conditions favourable for mangan ese reso lu bilisatio n. Since aerator operation in 1994 the dissolved oxyge n concentration at 30 111 has been maintai n ed above 4 mg L- 1_ Iron and Manganese Prior to 1994 the con centration of iron at 30 m depth was co n sistentl y highe r th an the su rfa ce co ncentrations d u ring summ er and autu mn (Figure 4). This coi nc ides w ith the p eri ods of extrem e tempe rature stratification and low d isso l ved oxyg e n 111 th e hypolimnion . Solubl e iro n at 30 m depth reac hed a maxi m um concentration o f 2.84 mg L- 1 in March 1990. T he vertical gra d ie nt in iron co n centration has dec reased since deployment of the bubble p l u m e aerator The mean conce ntration of iron at 30 111 has decreased from 0.71 mg L- 1 i n 1986 to 0.345 111g L- 1 in 1996, and the large flux events have been eli111inated. Manganese concentrations at 30 m have responded to destra tifi cation in a si milar manner to iron (Figure 5) . T he m ea n conce ntration of man ga nese at 30 1 111 was 0.4 1 mg L- in 1986 and redu ced to 0 .052 mg L- 1 in 1996 due to destratification . T he high yea rl y m ean in 1986 ,vas signifi cantly ele vated because of the flux from sed iments du ri ng summer and au tu mn where the 111axi111u m concen tration was approximately 1.8 mg L- 1• T hese large fl ux eve nts observed prior to 1994 have been reduced by operatio n of the destratifier. The co n cen tration of iron a n d man ga nese in the hypoli rnnion depends upon the rate of fl ux fr om se dim e nt and the duration of stratifi cation. Once the h y p ol imnion b ecomes anoxi c the conditions suitable to maintain iron and man ganese in the soluble form will persist whilst there is littl e mixing and the h ypo limni on remains separa ted from the atmosphere . To allow a co mpariso n between years the duration o f strati fic ati on was quantifi ed as number of days per year Qu ly/Jun e)


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WATER

w h e re th e t e mp e rature difference between 10 m and 30 m was greater than 1°C . M easu rements were generally taken in the morning, however, the tem.perature diffe rence between 10 m and 30 m w as selected as the best indicato r of persistent stratification as this avoids confounding effects due to diurnal surface heati ng, and time of sa mpling. There was a temperature difference of greater tha n 1 °C for 224 days in the year 1985/86 wh ic h gave rise to maximu m iron and manganese concentrations of 2.55 mg L- 1, 1.8 m g L- 1, respe ctively (T able 1). In the year 1995/96 there was on ly 28 days where therm al strati ficatio n between 1 Om and 30111 occurred and consequen tly the maximum iron and mangan ese concentrations were low, 0.386 m g L- 1 and 0087 mg L- 1, respectively. The yearly maximum concentration of iron at 30111 was significa ntl y co rrelated with the duration of strati fication (Spearman no n-parametric correlatio n, r,=O. 73 28, P=0.0044). The max imum manganese co ncen tration was also significa ntl y correlated with th e duration of stratifi cation (S p ear man non-parame tri c correlation r,=0.8303, P=0.0004). The yearly maximum manga nese co ncentrati on corre lat e d w ith the yea rl y m ax i mum ir on co nc e ntrati o n s (Spearman non-param etric correlation r,=0 .9133, P <0.0001) indicating that manganese resolubilisati on coincided with iron resolubilisation.

1996). Th e bubble plume aerator at Myponga ha s b een s u ccessfu l at m ainta ining manganese conce ntratio ns below this level. M anganese wou ld not be considered a health threat unless the concen tration exceeded 0.5 mgL- 1, a level which has not been realised since aerator operatio n .

References Aust ralian D rin king Water Gu idelines ( 1992) . N ational H ea lt h and M edical Research Council. Raman, R.. K. and Arbuckle, B. R. (1989) . Long-term Destratification in an Illinois Lake. Joumal of tl,e A111erica11 Water Works Associatio11. 81: 66-7 1 Sherman , B. S., Whittington , J. and Oliver, rt. L. (2000). T h e impact of destracification on water quality in Chaffey Dam. , Proc . Kinneret Symposium on Limnology and Lake Management 2000+. A rcl,iv fiir H ydrobiologie (in press) Stumm, W. and Morgan, J. J. (1996). Aquatic C/1e111istry: cl,e111ical equilibria mid rates i11 11atural waters. Th ird edition . John Wiley and Sons, New York. Visser, P. M ., lbeli ngs, 13., van der Veer, B., Koedoods, J . and Mur, L. ( I 996). Artificial mixing prevents nuisance bl ooms of the cyanobacterium Microcystis in Lake Nie uwe Meer, the Net herlands. Fres/111mter Biology. 36: 435-450.

Wetzel (1983). L/111110/ogy. Second Edition. C BS Coll ege Publish ing, Philadelphia.

Authors Dr Justin Brookes is a R esearch Scientist in volved in a large interdisciplinary study at the CRC for Water Quality an d Treatment, examining the use of mec han ical mixers and aerato rs to dest racify reservo irs and co n trol cyanobacteria. CRC for Water Quality and T reatmen t, PMB 3, Sali sbury, SA, 51 OS.P h . (08) 8 259 0222 e- m ai l justin.brookes@sawater.sa .gov .au Michael Burch is Projec t Leader for t h e CRC for Water Quality and T reatment proj ect " Artificial M ix ing fo r D estratifi cation and Co n tro l of Cya nobacteri al Growth in Reservoirs". H e is also the ARMCANZ National Algal Manager. Ph. (08) 8259 0352. email mi ke. burch@sawater. sa.gov.a u Peter Tarrant is M anager W ater Q uali ty, Bulk Water Division of the South Austra lian Water Corporation. Peter has 20 years ex peri ence in water supply e ngin eering and water qu ali ty m anageme nt with SA W ater. Ph.: (08) 8207 134 l , e- m ail: p et e r. tarran t@ saw ater. sa .gov .au.

SPECIALISING IN ENVIRONMENTAL SERVICES ENVIRONMENTAL GROUP

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The bubble plume aerator deployed in M y p o n ga R ese r vo ir ha s bee n successfu l at reduc ing the conce ntratio n of iro n and m an ga nese ions which in crease treatment costs and contribute to "dirty water' problems du ri ng distribu tion . According to th e Australian Drinking Water Gu idelines (1996) the conc entration of iron in d rinkin g water should not exceed 0.3 mgL- 1• T hi s guideline is based upon the concentration at wh ic h iron precipitates fro m solution and the caste th reshold. Prio r to th e installatio n of a destratifier at Myponga R ese rvo ir the solubl e iron concentration frequen tl y exceeded the gu ideli n e . H owever, since ae ra t o r ope ration the iron concentration is ma intain ed closer to the gu ide line concentration . Based o n aesthetic conside ratio ns the concen tration o f m anga nese in drinking water should n ot exceed 0.1 mgL- 1 (Australian Drinking Water Guideli nes,

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22

WATER JULY / AUGUST 2000

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~

WATER

CIRCULATION, DESTRATIFICATION, MIXING AND AERATION: WHY AND HOW? BK Kirke Abstract Som e storages benefit fro m circulation du ring summer. This pro cess results in mix ing, destratifi cation and aerati on. B enefits may include reduction o r eliminatio n of cyan o bacteria (blu e gree n algae), reducti on of phospho rus and metals in solution, eliminatio n of taste and odour problems and fish ki lls, extensio n o f fish habitats and elimination of autumn turno ver and th e associated water quality probl ems, although circu la tion do es not al ways solve all of these problems. Mixing may b e achieved by m eans of eithe r bubble plu m es or m ec han ical circula tors. This arti cle explains how these two alte rnati ve methods o f mi xing work, th eir advantages and disadvantages, and cites some evide nce of th eir effec tiven ess and limitations. Keywords: Aeratio n; bubbl e plum es; circulation ; cyanobacteria; destratifi cation; dissolved oxyge n; impell er; mi xing

Introduction Wh en naturally flo wing rivers are dammed to provide water for domestic, industrial and agricultural use or for hydro-electric power, the natura l m ixi ng and aeration processes associated with flow are stopped and large static water bodi es are created. This does not generally cause problems in winter when the water surface becomes cooler than the lower levels and natural convection keeps th e water colum n mixed. Due to convectio n th e whole water column remains essentially uniform in temperature and oxygen ated by downward movem ent of oxygen- rich surface water. But in su mmer this natural convection is reduced and re-aeration fr om the atmosphere occurs only in the top fe w metres of the water column , w hich are mixed by wind shear. B elow thi s le vel, d ecompositio n of o rganic m at erial gradu ally d e p le t es DO (di ss o lve d oxygen) so that the lower levels of the water body become stagnant, anoxic and effectively dead except for anaerobic bacterial activity. Fig.1 shows a typical correlation betwee n thermal stratifi ca-

24

WATER JULY/A UGUST 2000

tio n, depleted DO and high ma ngan ese and iron at de pth in summer. In contrast , typical winter pro fil es show uniform temperature, uniform high DO and lo w manganese and iron . U nless artifi cial mixing is introdu ced in summer to mimic the natural convection that occurs in winter , several problem s may result , and these are discussed below.

Water quality problems related to stratification and oxygen depletion 1. Fish suffer in creasing distress and re duc e d growth rat es as t h e DO (dissol ve d o x yg e n) c o n ce n tration decreases below a certain level, th e actual level varying with species. For exampl e Tu cker and Steeby (1995) refer to th e use of emergen cy aeration in catfish ponds when DO levels drop belo w 2 to 3 mg/ 1. 2. C old water with low DO released from the lower levels of a dam can upset fish migratio n patterns downstream (see for example Mobley et al, 1995, Greene et al, 1997) . T his effect can be overcome by vertical mixing so that the water at lower levels in the da m is of similar temperature and DO concentration to surface water.

As an alternative, surface water can be pumped or ducted to the intake . 3. In th e absence o f oxygen, a chemi cally redu cing en vironment results in anaerobi c de co mp osition of o rga nic material, w hich can cause odour and taste problems. AJso metals such as manganese and iro n from the botto m sediments go into solution in a redu cin g environment (Fig.1) . This may ca use clogging o f pipes and aesthetic problems, and in extreme cases, health problems. Con versely, by maintaining an oxidizing environment these problems can ge nerall y b e avoided . 4. It is gen erally accepte d (see for example Oliver et al. , 1998) that reduced mixing offers some adva ntage to bloomfo r min g cy an o ba cteria (co mmonly known as " blu e gree n algae"). This m ay b e du e to se ve ral fac tors including increased availability of phosphorus in th e anoxi c lower levels and the ability of cyanobacteria to m ove from th e su rface where they can photosynth esize to the lower levels w here th ey can get nutri ents. So me sp ecies of cya no bac teria becom e toxic and present a hazard to human and animal health under certain conditions, and if a bloom occurs, the water b ecomes unusable . Thermal stratification, Little Nerang Dam

Dissolved manganese, Little Nerang Dam

26

0.6

24

-summer -winter

'a, E 0.4

.,ci, 22

c

O 20

ci:

::!:

i

"'--

(.J

E 18

0.2

~

16

""'-

1-summerl I-winter I

14

6

0

9

12

15

18

0

3

6

depth, m

-winter I

/

I

/

6

9

'a,

8

E

6

60

18

+,.-=,._---------~ -summer -winter

4

2

0

3

15

12

10

/

'"1-summerl

0

12

Dissolved oxygen profile, Little Nerang Dam

Dissolved iron, Little Nerang Dam

/

9 depth, m

12

15

18

0

0

depth, m

3

6

12 9 depth, m

15

18

Figure 1 . Typical temperatu re and DO profiles in winter and summer. Strat ification

and low DO correlate with high manganese and iron.


WATER

above, c irc ulati o n Bubble plumes and exc han ge of T he co nventio11,1l m<:thod of de,traLw ater sh ou ld be ific atio n is co release air bubbles near th e maintained between bo tto m o f t h e sto rage , w hic h ri se the surface an d the beca use of their buoyancy, entraining leve ls. l owe r w ate r fro m th e low e r levels in th e C irculati on has tw o process. T h is relative ly rapid upward main benefits: fl ow o f entrained bottom water wi LI tend 1. D estratifi ca tion. to mi x w ith th e surrounding w ater as it Approximately goes. It ma y detrain if the density gradiuni fo rm te mperae nt is strong, the reby creating three ture and de nsity is circulatio n ce!Js (Fig. 2a), w ith little maintain ed, so the re imm edi ate effect o n stratifi catio n. If is littl e te ndency fo r eno ugh energy is put into th e syste m , au t um n turn ove r turbule n t mi xing w ill wea ken th e stratiand associated w ate r fication to th e po int w he re th e cold , qual ity p robl ems. de nse botto m wa ter reac hes th e surface. 2. " Aeration ." Howeve r th is is a slow and ineffi cie nt Adequate le vels of way to ac hieve exchange betwee n top Figure 2a. Bottom water detrains at a st rong thermocline. DO are maintained and bo ttom. Plunging f low sets up two c ircu lation loops above thermocline. th e t h ro ughout T he wa ter e ntrained by a bubble c olumn. w ate r T he re are nu mero us refe re nces in the plum e may reac h the su rface directly in C ontrary to popular belief, bubble plumes lite rature to reductions in algal blo oms a weakly stratifi ed w ate r body (Fi g. 26), add only a small amount of oxygen to the and/ or me tals in soluti o n co rrespo nding th e re b y a c hi ev i n g b o ttom to to p water (T o lland, 1977, Smith et al., 1982). co n atural or artifi cial destratification . Sec exchan ge. But w h en th e nutrient- ri ch Thus most of th e oxygen must come fo r e xample R.id lcy (1966), Irw in (1966), botto m water do cs reach the surface, it from th e atmosph e re, and the effectiveToe cz (198 1), Durns (1994), Daldorph w ill ma ke th e nu tri ents more readily ness o f bubble plum es in maintai n in g D O ( 19 98), J ones and Pop lawski (1998), available to cyan obac te ria. l t w ill then on their abili ty co ach ieve verti depends W h ittingcon et al (1998), Smith and tend to plunge below th e surfa ce as it cal exchange of water between the surface H o lJands (1999), C he ng ( 1999), LAS w ill still be more de nse th an the surfa ce and the rest o f the water co lumn. Inte rn ation al (2000) . Fu rthe r, it has been wate r despite so me mi xing w ith w armer Al th ou g h d es tra t i fic at ion a nd fo un d at C haffey D am in N ew So uth wate r on th e w ay up. Because of chis "aeration " are signifi cant for diffe rent W a les th at at leas t on e sp ec ies o f mi xin g, it w ill be less de nse than the reaso ns, as explain ed above, th e two u ndisturbed bo ttom w ater, so it w iLI then cya n o bac te ri a, A 11abae11a circi11alis, is very p rocesses tend to occ ur sim ultaneo usly se n s iti ve t o lo w li g h t c o ndition s sprea d o ut at its ne utral density level and the term s are often used inte r(Fig. 26). Where sal inity is lo w o r (S he rm an , 1996). If the surface layer of c han geab ly . The real aim s of both un ifo rm , th is w ill co inc ide wit h th e w ate r in w hich th e algae bloom can be "aerati o n " and " dcstratifi ca tion " are thc rm ocline, but w he re th ere arc signi fco nti nuo usly re moved from the surface ac hieved by maintainin g an adequate rate icant diffe re nces in salini ty with depth, as and pumped to a level be lo w th e phocic of exc ha nge of w ate r bet w een cop and in M ypo nga R eservoir, chis ma y not be zon e at a suftic ic nc rate, this may have bottom . Mixin g can be regarded as a bythe case. the e ffect o f suppressing blooms. produ ct o f exchan ge, and is not necesAs it plun ges it w ill e ntrain so me I n the absence o f al gal bloo ms or sa ry except co preven t re-stratification warm , oxygen- rich surface wate r and bac te rial contami nation , w ater dra w n o ff whe n the re is a signiffr o m th e o xygen - ri c h surface layer ica nt d e nsity diffe rgenerally presents few proble ms. But it is ence between top and no t always possible to draw o ff only chi s bo tto m. surface w ate r. Th e intakes on som e dams Whe n th ere is a are deep enough co draw o ff anox ic reduc tio n in natural wa te r unde r normal summ e r conditio ns, convectio n , artifi cial and even w hen intakes are near th e mea ns ma y be used to surface, anoxic water can be brou ght co mimi c n a tur a l the surface by two mec hanisms: co nv ec ti on. Thi s 1. Autumn turno ver, w he n the surface artifi c ial c irc ulati o n beco m es cooler and more de nse tha n t he ma y be achieved in lo wer leve ls a nd c onv ec tion sta rts eith er o f two ways: sudd enl y. bubbl e plum es or 2. Seiching, or w ind-ind uced oscillati on mec ha n ica l ae rators. of th e interface between the de nser, In o rder to assess th eir cool er low er laye r and the warm er, less relati ve effectiven ess, dense upper laye r. it is useful to examine carefull y how each o f Artificial circulation, mixing, th es e m e th ods destratification and aeration achi eves th e aim o f Figure 2b. Plunging flow and intrus ion of mixed , T o min imi ze all o f th e probl ems listed vertica l exchange . intermediate densit y at thermocline. WATER JULY/AUGUST 2000

25


WATER

pull it downwards, but only as far as its neutral density level. At best, a bubble plume moves the warm, oxygen-rich surface water downwards indirectly and only very slowly. Smith et al (1982) give the following expression relating ,Nater raised Qw, air flow rate Q, and depth H of injection of air (in SI units): Qw!Q 113 = 0.16(H + 0.07) 513 Which simplifies to

QW

= 0 .l 6Q1 13 H5;3

for H >> 1 m. This equation predicts that an air flow of 120 1/s from 30 111 depth in Myponga Reservoir would entrain about 22.5 1113 /s of water in the absence of a density gradient . This is based on a point source and a line of diffusers along a pipe is lik ely to produce more flow for the same power. For example Sherman (1996) has estimated a flow of 40 m 3 ls for the 100 kW compressor at Chaffey Dam. At fu ll supply level the surface area of Myponga reservoir is 280 Ha (Suter and Kilmore, 1990). Thus the surface area could be in the order of 100 Ha (106 1112 ) in late summer when the water level is low and algal blooms tend to be at their worst. Assuming a volumetric flow of 401113Is, the average rate velocity of water displaced downwards would then be abo ut 4x10-5 mis. T his is about 4 orders of magnitude lower than the downward velocity produ ced by an impeller and may be too low to entrain algal cells at the surface.

Mechanical impellers A less well-known method of circulating and exchanging water between the surfa ce and the lower leve ls is by pumping the water using a 111.echanical impeller. This was done as early as 1966 (Irwin et al, 1966, Ridley et al, 1966) using conventional pumps and pipes, and was found to be effective but expensive d ue to the la rge amount of power needed to pump very large amou nts of water at velocities of about 2 to 2.5 m is. In the 1970s Garton pi oneered the concept of large, low speed impell ers mounted under pontoons, pump ing vertically downwards at velocities less than l m is (Garton and Rice, 1976, Garton, 1981a, 1981 6). By reducing the flow velocity by a factor of about 3, Garton improved the energy efficiency by a factor of about 10 and made m echanical impell ers a potentially viable approach for circulating significant sized storages. Garton's Sm diameter impeller, mounted under a pontoon and driven by a 5.3 kW motor, pumped at a cla imed rate of about 15 1113 Is. This unit made a significant impact on an 80,000 M L 26

WATER JULY / AUGUST 2000

storage but did not completely destratify it. Two manufacturers, ITT Flygt and Lig h t ni n, now manufactu re open impellers based on Garton's concept. More recently Griffith University Sc hool of Engineering and WEARS (W at er Engi n eering and Re searc h Solutions Pty Ltd, a Gold Coast based company) have demonstrated an impeller in a low cost draft tube. B ecause it does not rely on the momentum of a jet for vertical exchange, this arrangement permits even lower flow velocities than Garton used, while at the same time forcing vertical exchange at least to the depth of the draft tu be and reducing the risk of re-suspending bottom sediments (Fig.3) . T he fu rther improvement in energy effi cien cy possible with a p roperly designed draft tube opened up the possibility of circulating larger storages, and also of using solar powered impellers in smaller storages and in the upper reaches of larger dams, which are often algal " hot spots." In summer 1995-6 a Griffith University solar powered prototype with a low cost 1.8 m diameter, 10111 deep draft tube (Fig.4) pumped 900 1/s using only 100 W of electrical power, confirming earlier predictions and model measurements (Kirke and Elgezawy, 1997). A lm diameter fibreglass draft tube was trialled by Kilmore in Myponga Dam in SA in the late 1980s. Bu t it was not u ntil Griffi t h University and WEARS demonstrated low cost draft tubes made of flexible materials that the draft tube co ncept was proven to be practicable on a large scale. Fig.5 shows a 5 m diameter impeller and entry cone, with draft tube removed, designed and built by WEARS. This u nit uses a 3 kW

motor and requires only a power cable from the shore. It was designed to destratify the 8,000 ML Little Nerang Dam in SE Qld. Fig.6 shows the shed containi ng two 37 kW compress ors which were formerly used to destratify the Little Nerang Dam.

Expected advantages of pumping downwards In recent years open impellers or "mixers" have been placed at various depths and in various orientations (see fo r example Suter and Kilmore , 1990, Banks and Banens, 1993). Pumping downwards from the su rface, which can easily be done by impellers but not by bubble plumes, appears to have two key advantages over other arrangements: 1.Water is drawn radially inwards at the surface, albeit very slowly at distances of the order of hundreds of metres from the impeller. This movement is likely to be less than that produ ced by wind effects at the surface. H owever drogue measurements in Little N erang Dam suggest that there is a general trend in flow over time towards the impeller, at least up to a distance of 200 m at a depth of 1 m . Thus it is hoped that the warm surface layer where cyanobacteria tend to bloom w ill be skimmed off, in a manner analogous to a swimming pool skimmer box, and pumped down to a level below the photic zone. It is hoped that this w ill upse t algal me tabolism. This is in contrast to the very slow downward movement of surface water caused by a bubble plume, and the energy-intensive, random movement created by tu rbulent horizontal j ets. 2. Oxygen is transported down to the anoxic water in the lower levels, rather

A. Open impeller

B. Impeller with draft tube 8. solar heat

gain l'

7. wind shear ,.

Figure 3. Open impeller and impeller with draft tube: Fast downward flow from surface due to impeller, displacing bottom water very slowly upwards.


WATER

Figure 4 . Low cost 1.8 m diamet er draft tube fo r solar powered impeller being lifted int o Little Nerang Dam, 1995.

tha n the oth er w ay aro und , so ph osp horus and me tals can be expected to be oxidised and to se ttle o u t of the wate r col u mn at a lowe r le vel, and thus have less impa ct o n the wate r co lumn.

Energy efficiency B ubb le p lu m e sys t e m s ca n b e desi gned so that they are capable o f des t ratifying sto rages . H oweve r t he ene rgy cost o f destratification is likely to be m uch high er fo r a compressed air sys te m than for a su rface mou nted, vertically o rie nt ed m e c ha ni ca l im p e lle r , sim p ly because the latter does w hat needs to b e done in th e most d irec t, effi c ie nt wa y know n . For exa m p le the flow rate produced by t he 100 kW compresso r in C h affey dam has been estimate d at 40 111 3 /s, i.e . the fl ow rate is abou t 0 .4 m 3 /s per kW. Flygt imp ellers achieve abo ut 1 1113 /s/ kW , i. e. they are abo ut 2 .5 times more e nergy efficie nt than bu bbl e plu m es in terms o f wate r pu mped per kW o f power used. H owever Suter and K ilm o re (1990) fou nd that th ree Flygt imp ell ers drawing 9 .3 kW and pum pi ng a b o u t 9 m 3 / s pro vid e d "e qui va le nt m ix in g characte ristics" to th e 100 kW compresso r at M ypon ga. Th is makes th e m abo ut 11 time s more e ne rgy e ffic ient and suggests that their m ode o f mix ing was more effe c tive pe r uni t flo w than th e c ompresse d a ir syste m. C u rre ntly install ed W E A RS im pellers are about twice as e nergy effi cient as Flygt mixers in terms of discharge pe r kW , and experime ntal imp ell e rs being develop ed at G ri ffi t h Uni versity are several tim es mo re e ffi cient again. M o re resea rch is needed to assess w he th er the d raft tube arrangement co nfers furt her advantages in te rm s of e ffectiveness of circ ulation.

Does circulation work? M cAu liffe and R.osic h (1990) report that compressed air system s have had some success in reducing undesirable algal species in a little o ver 50% of cases, and have reduced manganese, iro n o r sulphi des in 69% of cases. In rece nt years m echanical im pelle rs have bee n used in several tria ls in Australia and elsewhere. Al t ho ugh t he re have n ot ye t b ee n e nough imp ell e r installatio ns to e nable fair co m parati ve costings to be do n e be tween impe lle rs and the well-establi sh ed bubb le plu m e m et ho d , so me im pell er trials have yie lded e ncou raging results. For exampl e: 1. T he re are several refere n ces in the literature to reductions in alga l b lo oms and / or me tals in solution correspo nd ing to destrati ficatio n by mec hanical m eans (see fo r exa mple R idley et al, 1966, Irw in el al, 1966, T oe tz, 1981). 2. A US- based company cites a large

numbe r of case studies o ver a period o f 24 years in w hich their small capacity mechanica l circ ulators are claimed to have solved proble ms of algae, taste, odou r and me tals in solution (LA S Inte rnati onal, 2000) . 3. An op en Flygt impe lle r install ed in Manly Dam near Sydn ey ten years ago appears to have significantly redu ced algal bloo ms (C he ng, 1999) . 4. Sooley Dam nea r Goulburn su ffe red fre qu en t BGA bloo ms until a Flygt impell er was install ed in 1998 (Smith and H o llands, 1999) . There were no BGA blo om s in summe r 1998-9, and altho ugh th e re w as a bloom in spring 1999 it was less severe than previous bloom s and w as appare ntl y caused by a sudde n in flo w of nu trie nt- ri ch run o ff fo ll owing heavy rain. N o am ou nt of circ ulation coul d be expec te d to prevent suc h an event. Th e o nly ways to deal w ith nutrie nt- ric h in flo w wou ld be eith er im pro ved ca tc hme nt managem ent to reduce the nutrie nts and/ or the peak flows, o r else to trap the sedim ent-rich w ater near th e po ints of entry to th e dam and all ow it to settl e. 5.Timor Dam nea r C oonabarabran su ffered fre que nt algal blooms until a WEARS im pelle r was installed th e re in N ove mbe r 1999 . Since the n it has bee n free o f cya nobacte ria (Fig.7), and cou nts of other algal spe cies have also d ropped signifi cantly. Although it is too soon to draw fi rm concl usions abou t the lo ng-term success o f most of these trials, indications are defini te ly positive . T here is ampl e evidence that destratifi cation o ften , if no t always, has a be nefi cial effect on me tals and algal bloom s, and the argume nts cited abo ve in fa vou r of im pelle rs suggest th at fu rther t rials are wa rranted. In cases whe re aim s

Figure 5. 5 m diamet er impeller and entry cone with draft tu be removed. WATER JULY/ AUGUST 2000

27


WATER

Figure 6. Shed containing two 37 kW compressors which we re formerly used to dest ratify the Little Nerang Dam.

of anoxic bottom sediments that no amount of mixing can prevent blooms (see fo r exa mple Gachter and W ehrli , 1998) . In such cases the only solution w ould appear to be either to remove these bottom sediments by dredging, or to immo bilise them by chemi cal treatm ent or by depositin g an imp ermeable layer over them . Improved methods of dredging, w hich d o not re -su sp end botto m sedin1ents, are being investi gated. 5 . Large inflows of nutrient- ric h water. As m enti oned abo ve in the case ofSooley Dam , large inflo ws of nutrientrich water ca n tempo rarily create the righ t co nditio ns fo r a bloom. Increasing vegetation in the catchment can reduce the pea k discharge, redu ce erosion and resulting tu rbidity, and fi lter th e incomin g wate r. But thi s is a lon g- term

ha ve not been achieved , the reasons are exc han ge b etween the surface and lower o ften obvious. Some of these reasons are layers. This may make sense in a shallow dam w here horizontal flow may produ ce discussed below . enough vertical mixing to destratify the 1. Inadequate flow rate. In som e trials th e flow capacity of impellers has been storage. But th e inadequate. Fo r example th e single Flygt logic is hard to Cyanobacteria, Timor Dam, 1997-2000 (circulator impeller used in Avon dam and reported fo llow in a deep installed 3 Nov 1999) by Banks and Banens (1993) was clearly dam , where verti120000 exc han ge inadequate fo r th e size o f storage. R idl ey c a I be 100000 et al (1966) fou nd th at a fl ow rate of 2% s hould I of the storage capa city per day was maximised. E 80000 adequate to prevent stratifi catio n in two 3. Penetration. ] 60000 stora ges in th e T h am es Vall ey in J ust as important Q) 0 40000 England . Garto n and Rice (1 976) fo und as th e volumetric .. ,1 that an open impelJer with a flow equiv- flo w rate is th e 20000 _...__ alent to 1.6'Ÿ, o f the storage volume per need to penetrate .-....I 0 day did not completely destratify Lake the full depth of 5-May-98 25-Jan-98 16-Mar-98 6-Dec-97 28-Aug-97 17-0ct-97 Arbuckl e (80,000 ML), but th is may have t he st ora ge. T o been du e to lack of penetration o f the j et achi eve adequate 60000 rath er than inadequa te flow rate. Timor depth of circulaDam (1200 ML has been destratified ti on , at least o ne using a 2. 5 m diameter W EARS impell er o f three condi40000 with an estimated flow of about 1. 5 111 3 /s, tio ns must be met: E i. e. about 10% per day. ~ (i) Pumping must ] Q) Under Austra lian summ er conditions start b efor e th e (J 20000 it may be necessary to provide twice the storage stratifi es in sprin g and mu st flow used by Ridley et al, i.e. 4% per day, \,_ or about 1 111 3/ s per 2000 ML. On th is b e suffi cient to 0 bas is Av on D a m wo uld re quire a prev e n t , rath e r 27-Sep-98 16-Nov-98 5-Jan-99 24-Feb-99 15-Apr-99 4-Jun-99 discharge of about 80 m 3 /s, no t th e than break down, 3 stratifi catio n, or 3 m /s pro vided b y a single Flygt impeller. (ii) An o p e n j e t 20000 Base d on th e above fi gures, it would must have a high be reasonable to exp ec t that Myponga e nou gh ve rtic al dam , with a capacity of about 30,000 m om entum to ML, w ould requ ire a flow o f about co mp o n e nt pen etrate to th e 15 3 /s. Thus the 9 111 3 /s provided by 3 Q) Flygt impellers (Suter and Kilmore, ¡1990) required depth, o r 0 wo ul d probably have be en less than (iii)A d raft tu b e adequate, even if they had been o riented must be used to verti cally or near ve rtica ll y. force flow to the 0 2. Flat orientation of jet. Impellers required depth. 27 -Sep-99 16-Nov-99 5-Jan-00 24-Feb-00 14-Apr-00 3-Jun-00 have sometimes been o ri ented with their 4. Eutrophi c axes n ear ho ri zontal, so most of the storages . Some Figure 7. Algal counts in Timor Dam showing elimination of kinetic en ergy imparted to the water by eutrophi c storages the impell ers was dissipated in horizontal con t ain su c h a cyanobacteria since inst allation of impeller in early November circulation rath er than in useful vertical large acc umulation 1999.

/ vi

~ JV\.

1

28

WATER JULY /AUGUST 2000

\


AT iE R

solution, and in the interim it may be possible to place a permeable barrier across the upper reaches of the storage where the offending inflow occurs, to promote settlement of sediment before it reaches the main basin.

Are impellers and draft tubes practicable and economical on a large scale? Garton and Rice (1976) showed that impellers up to Sm diameter are practicable, and units up to this size are now available commercially. Carton's conclusion after testing his Sm prototype in an 80,000 ML storage was that he should have built an 8.5 111 diameter impeller. Wind turbines up to 30 m diameter and more arc now in production, and wind turbine rotors arc structurally and mechanically similar to impellers, so there seems no technical reason why much larger impellers could not be built and installed. However sizes larger than Sm diameter become difficult to install, and work is now in progress at Griffith University, in collaboration with WEARS, to assess the feasibility of using the draft tube as a diffuser. For example a Sm diameter impeller could pump at a velocity of 1 mis and then the velocity could be reduced through a diffuser to an economical exit velocity of say 0.3 mis, \Vith the velocity head converted back to pressure head. Discharge would then increase from 6 m.1/s to 20 m 3 /s but the power required per unit discharge would not increase. Assuming the 1 111 3 /s/2000 ML rule of thumb proposed above proves to be about right, this would mean that a 40,000 ML storage could be circulated using a single Sm diameter surface-mounted impeller and draft tube. The power consumption would be around 10 kW or less, and the cost should not be much over S 100,000 installed.

Acknowledgements The initial work on this project was funded by Griffith University research grants. Gold Coast Water has provided support in kind. Dr Bradford Sherman of CS!RO, Dr Mike Burch of the CRCWQT and numerous others have provided useful information and feedback. Mr Steve Elliott of WEARS, without whom the Griffith University work could not have borne fruit, continues to "make it happen."

References Banks, G., and 13anens, B. (1993). A11 Assessment (?f the .1foo11 R.escn1oir Propeller Trail, 1Hard1-May 1993. Australian Water Technologies, Sydney Water Board, Science and Environment Report No.93/66, Augmt. Burns, F.L. (1994). Case Study: Blue-green Alga! Control in Australia by Y car-round Automatic Aeration. Lll~c a11d R.cscmoir Ma11a,i!CIIIC11t 10(1), 61-67. North American Lake Management Society. Cheng, D. (1999). An ecolot,'lcal approach for the control ofbluc green algal bloom. Bl11e green a{i!ae should m¡11er be sce11. Wollondilly Phosphorus Action Campaign Forum, Gou!burn, NSW, 30 Apr 1 May, pp. 53-60. Daldorph, P.W.G. (1998). Management and treatment of algae in lowland reservoirs in Eastern England. Wal. Sci. Tech. 37/2, 57-63. Gachtcr, R.. and Wehrli, B. (1998). Ten years of artificial mixing and oxygenation: no effect on the internal phosphorus loading of two cutrophic lakes. Ew. Scic11aâ&#x20AC;˘ mu/ Tccl11wfo.i!)' 32/23, 3659-3665. Garton,]. E. (1981a).Jcts and Destrntification of Reservoirs. In l3urns, F.L. and Powling, IJ. (Eds) Destratijim1io11 .?f Lakes a11d


ATER

R..esl'rvoirs to l111pro11e M/atcr Q11ality, Aust. Water Res. Council Conference, Series No 2, Australian Government Publishing Service, pp.187-200. Garton, J.E. (1981 b) Destratification Experiments to Determine Design Factors for the Garton Pump. Dcstratij/Catfo11 of fokes a11d reservoirs lo improw water quality. Aust. Water Res. Council Conference, Series No 2, Australian Government Publishing Service, pp.354-375. Garton,J.E. and Rice, C.E. (1976). J111pro1Ji11g Ilic Q11alit)' of VVata R..cll•ases from La~rze R.ese1voirs by Mea11s of a Lar._rzc Dia111etcr P11111p. Oklahoma Water Resources Research Institute, Report OKLA C-5228. Greene, G.R., Rogers, J.G., Romney, JS., Marsden, T.J., Gehrke, P.C. and Harris,J.H. (1997). Rehabilitating Dammed Environments - Options for a High Fishway at Tallowa Dam. Aust. Nat. C()IIIIJlittee 011 Lm;i.;c Da111sll!1st. qf E11_1;s. Amr. Sc111i11ar 011 Dams a11d the Emdrmt/1/l'ltl. Sydney, 27 June. Irwin, H. W., Symons, J- M. and Robeck, G. G. (l 966): Impoundment De-stratification by Mechanical Pumping. J. Sa11iMry E11_1;. Div., Proc ASCE, Dec., 21-40. Jones, G.J. and Poplawski, W. (1998). Understanding and management of cyanobacterial blooms in sub-tropical reservoin; of Queensland, Australia. Wal. Sd. Tech. 37/2, 161-168. Kirke, B.I<. and Elgezawy, A.S. (1997). Design

and Model Tests for an Efficient Mechanical Circulator/Aerator for Lakes and Reservoirs. Water Research 31(6), 1283-1290. LAS International (2000). www.lasinternational.com. Promotional Material, LAS International Pty Ltd, Bismarck, ND, USA. McAulitTe, T.F. and Rosich, R.S. (1990). The triumphs and tribulations of artificial mixing in Australian water bodies. /,Vara, Aug., pp.22-23. Mobley, M, Tyson, W., Webb,J- and Brock, G. {1995). Surface water pumps to improve dissolved oxygen content of bydropower releases. TVale11M11cr '95. July 25-28, San Francisco, Cal. Tech paper 95-2. Oliver, R.L., Recs, C.M., Grace, M.R., Hart, 13.T., Caitcheon, G. and Olley, J- (l998). Cyanobacterial Blooms in the Darling River. Water 25(3), 18-19. Ridley,J.E., Cooley, P. and Steel,J.A. (1966). Control of Thermal Stratification in Thames Valley Reservoir, Pmc. S<ic. for Water Treatme/11 mu! Exm11i11atio11, 15(14), 225-244. Sherman, 13. (1996). CRC for Freshwater Ecology/CSIRO Centre for Environmental Mechanics, Cmberra. Pas. Comm. Smith, A., and Hollands, M. (1999). The experiences of blue green algae blooms. Blue ,1;rcc11 a{\;ac sho11ld never be scc11. Wollondilly Phosphorus Action Campaign Forum, Gou!burn, NSW, 30 Apr - 1 May, ppl-6. Smith, J.M., Goossens, L.H.J. and van Doorn, M. (1982). Mixing of ponds with bubble 1

plumes. Pr()c 4th European Cmlj: 011 1Hixi11g, Noordwijkerhout, Netherlands, April 27-29, pp.71-80. Suter, P.G., and Kilmore, G. (1990). Mechanical Mixers: An Alternative Destratification Technique, Myponga Reservoir, South Australia, TVatl'I', February, 32-35. Toetz, D.W. (1981). Effects of whole lake mixing on water quality and phytoplankton. Water Research 15, 1205-1210. Tolland, H.G. (1977). Dcs1ratijicatfo11/Aemtfo11 in Rescn1oirs. Water Research Centre, Medmenham Laboratory/Stevenage Laboratory, UK, Technical Report TR 50. Tucker, C.S. and Steeby,J-A. (1995). Daytime mechanical water circulation of channel catfish ponds. Aquawltural E1~1;i1/Cerii(I; 14, 1527. Whittington,]., Sherman, 13.S. and Oliver, R.L. (1998). Blue Green algae and Artificial Destratification. W11ta 25(3), 15-17.

Author Dr Brian Kirke is a Senior Lecturer at the School of Engineering, Griffith University, Gold Coast Campus, PMB 50, Gold Coast Mail Centre, Queensland 9726, Australia. Tel 07 5594 8672 Fax 07 5594 8065 email B.Kirkc@mailbox.gu.cdu.au

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WATER JULY/AUGUST 2000


~

WASTEWATER

Abstract

results and develop a better understanding of TOG rem ova l in activated sludge Two wastewater treatm ent plan ts plants, regular testing of TOG levels was o perated by Brisban e Water have lice nce in itiated in Septem ber 1999 at Lu ggage requirem en ts to reduce the total oil and grease (TOG) concentration in the eillu- Point, Oxley Creek, Gibso n Island and ent to less than 10 mg/ I. An analysis of Waco ] Wastewater Treatmen t Plan ts. oil and grease in the wastewater revealed W h ilst Gibson Is land and W aco ! that the ave rage co ncen tration of T OG WWTP's have no li cence requirements fo r T OG, they were inc luded in the in the raw sewage in B risbane varied study beca use they are pu rpose-bu ilt b e tw ee n 50 and 80 m g/ L. nitrogen removal plants which may have Approximately 50% of this oiJ and grease a superior TOG removal performance. is r e moved in the primary sedimentation An analysis of these results has been tanks. T he co ncentration is furthe r ca rried o ut to determ ine the effecti veness reduced to approximately 7-8 mg/ L o f o il and grease removal at these four du ring secondary trea tment. activated sludge plan ts. The problem exists that the TOG co n centration in the eill uent periodically Background to Oil and Grease in spikes above 10 mg/ L to values up to 30 Wastewater Treatment mg/ L. Th ere appea rs that there is little Oil and grease enters the sewers and that can be don e to impro ve TOG wastewater treatmen t plan ts in a variety re m.oval in ac tivated sludge plants and of fo rms. It can be cl assified as either ens ure that the oil and grease licence is polar or no n-polar. Polar oi l and grease m e t , unless cap ital is spent on n ew is generally biodegradable. It originates process un its. from animals and vegetables and may Keywords: Total o il and grease, TOG, include waxes, oi ls, soaps and fatty acids. was tewa ter treatment, activated sludge. Non p ol ar oil and grease is l ess

Introduction Two wastewater treatm en t plan ts operated by Brisba ne Water loca ted at Luggage Point and Oxley C reek ha ve licen ce requirements to maintain a total oil and grease (T OG) co ncentration below 10 mg/L in the eilluen t. This li ce nce needs to be met biann ually. In order to maintai n a database of

b iod eg radabl e, or igina t i n g from petroleu m hydrocarbo ns (APHA, 1998) . Oil and grease is gen eralJy immiscible in water. H owever, it may also be present in wastewater in the emu lsifi ed form where it is held in suspension. Emulsificatio n can occur due to elevated te mperatures, the presence of detergents, enzymatic action and mec hanical shearing (APHA , 1998) .

T he lice nce limit for oil and grease emissio ns is set at 10 mg/L by both the Queensland and the New South Wales EP A. This li mit is intended to correspond to a concentration wh ere the eilluent is visually free of o il and grease. New legislation under development in New South W ales will result in oil and grease being assessable pollutants for load based licensing. Specific limits are yet to be set.

Testing Methods for TOG Th e current method used by Brisbane Water's Scien ti fi c and Analytica l Services laboratory (SAS) to determine the oil and grease co ncentration of a sa mple is the Soxh let Extraction Method (A PHA , 1998) . Soluble metall ic soaps are fi rst acidifi ed to form a hydrol yzed product . Any oils and solid or viscous grease present in the sam ple is separated by fi ltration. The sa mple is then dissolved in an n- hexane solvent and extracted in a Sox hl e t appa ra t us. T h e so lve nt is removed by evaporatio n at 103°C. T he residue is then weighed to determ ine the oil and grease content. In addition to oil and grease other compounds including fa tty acids, waxes, soaps, organ ic dyes and any other compound that is soluble in nhexane will be recorded in the T OG result. O il and grease can therefore be defined as any material recovered as a substa nce in the solven t n- hexane. T h e c u rr e nt NATA (N ation al Acc r e d ited Test ing Assoc iatio n ) approved detection limit for SAS is 10 WATER JULY / AUGUST 2000

31


WASTEWATER

Table 1. Description of WWTPs used in TOG investigat ion Luggage Point

Gibson Island

Oxley Creek

Wacol

Conventional Activated Sludge

Conventional Activated Sludge

Extended Aeration

ADWF (M L/ day)

153

55

43

5.3

Primary Clarifiers

Yes

Yes

No

No

Bioreactor HRT at ADWF (hours)

10

6

21

51

Bioreactor SRT (days)

13

5.4

14

30

Scum Removal on Final Settling Tanks

No

No

Yes

Yes

being upgraded for N Removal

bei ng upgraded for N Removal

Yes

Yes

Treatment Process

Ca pable of N Removal

Primary Effluent

Table 2. Influent TOG concentration Luggage Point

Oxley Creek

Gibson Island

Wacol

51 ± 1

59 ± 3

82 ± 3

60 ± 2

Minimum (mg/ L)

35.7

30 .4

4 2 .8

40.0

Maximum (mg/L)

86.4

95.5

1 21.1

89 .1

13.7

19.0

16.1

11.7

23

33

26

Mean (mg/ L}*

Std Deviation No. of Samples

* Mean

44

values given with a 9596 confidence interval.

m g/ L. SAS are currentl y conducting testing to gain N ATA approval fo r a detec tion limit of 5 mg/L.

Influent and Effluent TOG Results TO G data was co llected fro m Lu ggage Point, Oxley Creek, Gibson Island and W acol WWTP's by weekly 24- hour com pos it e sa m ples over the pe ri od September 1999 to April 2000 . T able 1 outlines the characteristics of eac h of the treatment plants in the in vestigati o n. Plant Influent

A summary o f th e oil and grease concentratio n in the influent is presented in Table 2. T chobanoglous and Bu rto n (199 1) give the fo llowing typi cal valu es for T O G concentra tion in th e influent: • W eak: 50 mg/L • M edium: 100 mg/L • Stron g: 150 mg/L The results show that the infl uent T OG concentrations at the fo ur WWT P's are in

treatm en t plants can fl uctuate significan tly fro m one week to the next. T hese fl uctuations m ay be a result of flu ctuating oil and grease levels entering the sewer an d the effect of dilutio n by rainwater infiltration . Seaso nal fluc tuations in the level of oil and grease from trade waste sources are expected . Th ese seasonal flu ctuatio ns inclu de increased production leading up to the C hristmas pe ri od. T here is insufficien t historical data however to evalua te the significance of seasonal influences o n T O G concentratio ns. Luggage Point and O xley C reek treatm ent plants include pri m ary clarifiers in the trea tment pro cess. T he primary clarifi ers include surface skimming scum collection and removal systems. T he q uali ty o f th e p ri ma ry e fflu e nt i s summarised in Table 3. Figu res 1 and 2 indicate that in general the amount of T O G in th e primary effluent is proportio nal to th e TOG in the influ ent. At both plants the p rimary eilluent T OG concen tration is approxima tely half that of th e influ ent. T he prim ary settling tanks therefore play a significan t role in th e re moval o f oil and grease at Ox ley C r ee k a nd Lu ggage P o i n t WWTP's. This TOG rem oval is li kely to occur via a combination of the scum

the weak to medium range. O n average Gibson Island WWTP receives a T OG con centration o f 82 m g/L, with peaks in excess o f 120 mg/L. Lu ggage Po in t WWTP receives an ave rage co ncentrati o n of only 51 n1g/L. Th e high T O G loading on Gibson Island can be 80 exp la ined in part by the 70 large number of industries in its catc hment t hat r e le ase oil an d grease to the se wers. 30 These include M eadow 20 Lea, Ingham , Smiths 10 and N a tio na l Hid es P ro du cts. Th ese fo u r -+-tnfluet'\t - e- Pnm.aty Effluent indu stries c ontribut e approxim ately 15% to Figure 1. TOG concentration in influent, primary effluent 20% of Gibson Island's and fin al efflu ent at Luggage Point WWTP. in fl ue n t T O G ma ss 100 load. 90 The T OG concen90 t rat io n e n ter in g th e 70

,.

Table 3. Primary effl uent TOG concentration Luggage Point

Oxley Creek

24 ± 1

27 ± 1

Minimum (mg/L)

12.5

11.3

Maximum (mg/ L)

48.5

47.3

9 .6

7 .4

Mean (mg/ L)*

Std Deviation

23 No. of Samples * Mean values given with a 9596 confidence interval.

32

WATER JULY / AUGUST 2000

23

J\

\.......- ~ ,......... \

\/ i

10 0

. ...

'.'. _,•. ...------~ \'. /

\

L..::::!...21.::::...~-.....\<:C:::::....:.......::i.- ~ --..::::::::..:_ ~ _~

0 l·S...99

28·Feb-OO

31-0ct•99 -+-1nnuon1

-•

Primllry Effluent

28·Apt-00

_._ Flnal Eltlueot

Figure 2. TOG con centration in influent, primary effluent and f inal effluent at Oxley Creek WWTP.


WASTEWATER

BIOBLOCI(

Table 4. Final effluent TOG data Luggage Point

Oxley Creek

6.8 ± 0.3 0.9 Maximum (mg/L) 30.6 Std Deviation 5.7 No. of Samples 23 % Removal from Influent 87% No. of Exceedances+ 4 Mean (mg/L) *

Minimum (mg/ L)

* Mean

Stage 1&2

Stage 3&4

7.8 ± 0.3 0 .6 16.6 4.3 23 87% 5

6.7 ± 0.3 0.1 15.6 4.5 23 89% 5

Gibson Island

Wacol

6.9 ± 0.3 1.6 16.6 4.3 23 91% 4

7.2 ± 0.3 1.2 22.9 4.8 26 88% 5

values given with a 95% confidence interval.

+ These are "unofficial " exceedances of licence within survey period (TOG

> 10 mg/ L). They are "unofficial" since licence limit only has to be met biannually for two predetermined sampling dates.

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co llection systems and re moval w ith the raw sludge.

A lth ough the average fin al effi ue nt con ce ntration is approximately equal fo r alJ fo ur plants it can flu ctuate significantl y Final Effluent be tween sa mples. T he flu ctu ati ons of T OG in th e influe nt and fin al effiu e nt A ll fo ur plants surveyed, on average, ap pea r unrelated . T his may be a result o f rem ove oil and grease to a con centration the hydrauli c detention tim e w ithin th e of approxi mately 7 to 8 mg/L (Table 4). plant (th e 24- hou r composite samples are It is important to note that Gibson Isla nd take n durin g th e sa me 24 ho ur pe riod for WWTP, with a high infl ue nt T OG in fl ue nt and efflu e nt samples) . co n centration and no primary settling For th e period sampled, the concen tratanks has an effiu ent conce ntration similar ti on of TOG in the effiu ent of Stage 3&4 to Lu ggage Point WWTP w hic h re moves at Oxley C reek WWTP is sli ghtly lower half its oil and grease during primary treatthan for Stages 1&2. Zeobte is added to me nt and rece ives low in fl uent T OG . Stage 3&4 to increase the scttleability o f Fi nal effi uent results fo r all fo ur WWTP's the sludge but is not added to Stage 1&2. are shown in Fi gures ·1 to 4. "ZELfl occ" T he process may also have 130 . - - - - - - - - - - - - - - - - -- - - - , a slight positive effect 120 11 0 on T OG re mova l. 100 T able 4 also shows 90 th at dur in g th e 80 10 moni toring program , ~ 60 all four plan ts 50 occasio nally had fin al 40 30 effiuent TOG concen20 trations in excess of 10 the lice nce limit of 10 --"- --"'' - - -- - ' ' - ~ - - - ' 0 '--- " " =- - - --=----Ol ·Sop-99 31-0ct-99 28-Feb-OO mg/L (approximately ,.._lnffuent 20% o f sa mpl es) . There is therefore a Figure 3. TOG concentration in influent and effluent at risk tha t O xley C reek Gibson Island WWTP. and Lu ggage P o int may have licence no n90 compliance inciden ts 80 at th eir next " official" 70 biannual TOG testing.

t

Relation of TOG to Other Parameters

30 20 10

01 -Sep-99

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28-Feb-OO

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Figure 4. TOG concentrati on in influent and efflu ent at Wacol WWTP.

Attempted correlation of influent TOG and influent COD concentrations

Figure 5 shows a co mpari so n of th e infl ue nt TOG to the

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Figure 5. 'Correlation ' of influent TOG with influent COD concentrations.

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Figure 6. 'Correlation' of influent TOG and influent BOD

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influ ent COD concentration. The plot includes results from all four treatment plants involved in the study. There appears to be no correlation between the influent TOG and influent COD concentration fo r the four plants. There was also no correlation for individual plants (results not shown here).

Of course, they meet the m ost stringent of international approval standards. The STRAUB name is synonymous with high

Attempted correlation of influent TOG with influent BOD concentration

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Figu re 6 shows a comparison between TOG and BOD concentration in th e influent for all fo ur plants. There does not appear to be a correlation between influent T OG and influ ent BOD concentration for these four plants.

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Attempted correlation of effluent TOG with effluent BOD concentration

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Figure 7 shows that there is no correlation between the TOG and BOD concentration in the effiuent. This indicates that for the plants tested the total oil and grease is not a major co mponent of the fina l effiuent BOD.

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Typical grease removal systems involve the use of flotation to separate the oil and grease from water and water soluble compounds. The results from Luggage Point and Oxley Creek wastewater treatment plants indicate that the o il and grease is being removed in 2 stages. These two stages are: 1. Approximately 50% of the oil and grease is removed during primary treatment. The probable mechanisms are: a) In the primary clarifiers a portion of the oil and grease is separated from. the water and floats to the surface. This is collected via the scum removal system. b)Small portions of the fa ts and oils coat surfaces and settle with the grit and raw sludge (T chobanoglous and Burton, 1991).


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

,. ,.

.

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o'---- ---------------~ ,. ,o 0

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"

Effluent TOG (mgll)

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Figure 7. 'Correlation ' of effluent TOG with effluent BOD concentration.

1 . The second stage of oil and grease re moval occurs durin g the aero bic treatment and fin al clarifi cation . Three m echanisms are likel y to co ntribute to th e o il and grease re moval here. a) Th e o il and grease is digested by bac te ria during th e aerobic treatm ent process. b) A small portion of the fa ts and oils coats surfaces and is re 1noved with the waste ac tiva ted sludge. c) A portion o f the T OG is rem oved via the fi nal clarifiers. N o te that Luggage Point and Oxley C reek WWTP's have no scum re mo val faciliti es on the fi nal clarifiers. With o ut sc um ren10val th e oil and grease wi ll not be re mo ved via flo tation in the final settlin g tanks. Options for improving oil and grease removal

Th ere is a range of techniqu es avai lable for the re mova l of oil and grease from was tewate r. Th ese techniques include grease traps, dissolved air flo tatio n , bio logi cal treatment, c he m ica l treatme nt, centrifuges and filtration. Bio logical trea tm e nt is an important m echani sm at Lu ggage P o int, O xley C ree k, Gibso n Island and W aco] WWTP's fo r oil and grease re m oval th ro ugh th e ac tivated sludge pro cess. A literature review was carried ou t in the area of oil and grease re moval. The on ly information found relating co bio logica l trea tme nt o f oil and grease was an article by C apps et n/. ( 1993) desc ribing oil and grease re moval in o il refin e ry wastewater treatme nt. It is suggested that biolo gica l oxidatio n syste ms beco me troubl e-pro ne at o il and grease influ ent co n centratio ns greate r than 50 mg/ L (but this will depend on the type of TOG prese nt) . Capps et n/. (1993) indica tes that th e removal o f oil and grease can be best op timised by limiting shock loads of pH , salinity and toxic contamin ants to th e system . As th e operators of th e trea tm ent pl ants ha ve no cont rol o ve r th e make up o f the wastewate r e nte ring th e pl ant this is not a practica l optio n fo r optimisin g oil and grease rem o val. There is a large amoun t of literatllre describing no nbiological tec hniqu es fo r the re moval o f TOG from industrial w as t ewaters with high con ce ntrations ofTO G . Th ese include ultr a filtratio n (R eed el al. , 1997), dissolved air flotatio n (C apps, et al., 1993) and po lym er addition (Zhu , ¡1997) . These tec h niqu es are effective at redu cing o il and grease co ncentrati o n s over 1000 mg/L. They are no t effective however at red u cin g o il and grease conce n trati ons below 10 m g/L. Gibson Island WWTP is an exceptionally welJ- performing was tewater treatme nt plant w ith respect to nitrogen removal. le o ft en achi eves total nitroge n in the efllu ent of less than 1 mg/ L but still struggles to re move aJI oil and grease. Th e eillue nt T O G con centration at Gibso n Island WWTP is approximatel y equal to that o f Oxley C ree k WWTP, a 30% ove rloaded plant that has fa il ed its long term 80th percentile WATER JULY/AU GU ST 2000

35


WASTEWATER

BOD licence for the 1999/2000 licence period. This indicates that no significant improvement in TOG removal can be attained by optimising plant performan ce. An alternative option to reduce oil and grease concentration in th e efiluent of wastewater treatment plants is to limit the oil and grease released to the sewers as trade waste . The results from Luggage Point, Oxley Creek, Gibso n Island and Waco! WWTP's indicate that thi s may have a limited effect on redu cing o il and grease in the efiluent. Luggage Point WWTP, on average, receives 30 mg/ L less oil and grease in the influ ent than Gibson Island WWTP. Both plants have similar eilluent TOG conce ntrations. Therefore, th ere is no evidence that a reduction in th e o il and grease in the influent w ill result in a reduced TOG co ncentration in the efiluent.

Conclusions

3. Investigate the contributions of oil and grease from industry with the possibility of imposin g tighter restrictions. 4. Liaise with other water authorities on the issue of TOG licence limits and TOG removal. 5. In itiate di sc us s ion wit h th e Queensland EPA concerning th e basis for the current TOG li cence limits. W e hop e that this paper may spark disc ussions amongst wastewa ter treatm ent profess ionals and believe that further work is requi red to answer th e following qu estions: • What are the typical influent and effluent TOG concentrations at other WWTP 's in Australia? • What are th e TOG effiuent lice nce requirements around Australia? • W hat ca n be don e to improve TOG remova l in activated sludge plants? • What is th e effect of TOG on the environment? The authors would appreciate any comments or information from others on these issues.

frui tful discussions in relation to TOG analysis techniqu es.

References APHA, AWWA and WPCF (1998) Sta11dard Methods 20th ed. (Am erican Public Health Association , USA). Capps, R, Matelli, G and Bradford, M (1993) R educe oil and grease content in wastewater, Hydrorarbo11 Processi11g, 72 (6), pp. 103110. Reed, B, Lin, W, Dunn , C, Carriere, P and R oark, C ( 1997) Treatment of an oil / grease wastewater using ultrafiltration: PilotScak results, Separatio11 Scie11ce all(/ Tec/1110/o,~y, 32 (9), pp 1493- 1511. Tchobanoglous, C and Burton, F.L (199 1) W astewater E11gi11eeri11g 3rd ed., (McGraw H ill, N ew York) Zhu, X, Reed, 13, Lin, W, Carriere, P, and Roark, G (1997) Investigation of emulsified oil wastewater treatment with polymers. Separatio11 Srie11ce a11d Tecl,110/o,~y, 32 (13), pp. 2173-2187.

Authors

David Brooker, Dr Elisabeth von TOG was m easured m the influent and efil uen t at Luggage Point, Oxley Muench and Keith Barr are process Creek, G ibson Isla n d and Wa col engineers with Brisban e Water, 240 WWTP's during September 1999 to Donaldson Rd. , Rocklea, Q ld 4106. April 2000 . R esults from th e TOG Acknowledgements David Brooke r' s e-ma il address 1s 111oi1ito ring program indi cate that the T he authors th ank Julie McLellan fo r poe3bw@brisbane.qld.gov. au average concen tration of o il and grease in the efilu ent is approximately 7-8 mg/ L. However, it p eriodica lly exceeds th e 10 mg/ L required by th e efflu ent li cence requirements, and no trends could be identified in the data to predict We make wireless alternatives to when an exceedance is likely to occu r. Effluent concentration appears to be cabling. Radio licence exempt gizmos independe nt of the influent TOG for tipping bucket rain gauges, 4-20 mA co ncentration and th e type of activated current loop, automatic meter reading sludge treatm ent process, and no sign ifi& remote control/monitoring. ca nt correlation could be found betwee n either influent COD or BOD w ith influent TOG , nor between effl uent BOD with effluent TOG concentration. When primary clarifiers are used in the treatment process, approxima tely 50% of the oil and grease is rem oved fro m the wastewater before it enters the secondary trea tment stage, but two extended aeration plants did not employ such clarifiers, yet gave similar results . To develop a greater understanding of oil and grease in wastewater further investigation is required. This wi!J involve: 1.Maintain a reg ul ar monitoring program for the influ ent and effiuent total oi l and grease conce ntration at Luggage Point, Oxley C reek, Gibson Island and Waco! to continue to build the database of TOG concentrations and enable seasonal effects to be assessed. 2. Investigate methods for increasing the Ph 02 4579 6365 Fax 02 4579 6942 removal of total oil and grease with in the Web www.acay.com.au/-kmclean treatment plants.

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WATER JU LY / AUGUST 2000


II

ENVIRONMENT

THE MURRAY-DARLING CAP SHARING A NATURAL RESOURCE

-

A F Close, A J McLeod Abstract Queensland

managem ent of the Basin's natura l resou rces.

The Murray- Da rl ing Basi n cove rs most of inland so uthWater Storage and Water eastern Australia. In J une 1995 an Use in the Murray-Darling audit of water use in the MurrayBasin Da rl ing Basin was presented to the South Austral/a Figure 2 demonstrates t h e Murray-Darli ng Basin Ministerial grow th in sto rage ca pa c ity Cou ncil. The audi t reveal ed chat throughout the Murray-Da rli ng development in the Basin to that Basin from 1920 to the presen t . time had reduced th e median ~ DEi.AiDE Govern ment-financed headwo rks annual flow to the sea to 21 % of .JJ storages were all for the primary th e natural flows. Th e audit also c,, purpose of water supply for irrig ashowed that average water use had tion. A period of rapid expa nsion inc reased 8% in the previous six is evident between 1950 and 1980 years and that if no action were with storage capacity exceeding taken , a further 15% growth was Figure 1: The Murray-Darling Basin mea n natural annual outflow of likely. Co un cil dec ided that a th e Basin by 1960. From l 980 balance n eede d to be stru ck expansion has levelled off, sin ce b e tw ee n co n s umptive and instream uses of water in th e Mu rray- ment into the huge inland areas of most of the availab le good dam sites h ad Darling Basin. It instituted a process that Australia, away from th e upland regio ns bee n utilised, along with the almost led to the Cap on water use in the Basin of the south-east Basin and the wette r complete abi li ty to ca pture the water fro m the wetter eastern part of the Basi n. bei ng fo rmally agreed in July 1997. In coastal fringe. The fo ur States, Q ueensland, N ew The total storage capa city througho u t most of the Basin , the Cap aims to prevent growth in water use beyond that South Wales, Victoria and South Australia , the Basin, including that in private water associa ted w ith the level of development along with the Australian Capital T etTitory storages, is shown from 1988. This shows and manage men t rules that existed in and the Commonwealth make a total of a con tinued rise in storage to the present 1993/94. This paper describes, and puts six Governments that have an interest in day, which is m ost notable in the no rth into context, the introduction of a Cap the Basin. Since inigatio n commenced in of th e Basin (Queensland and north e rn on water diversions from the ri ver system the Basin more than on e hundred years New South Wales). of the Murray- Darli ng Basin. ago there has been competition for water Figure 2 also shows the trend in Keywords: Murray-Darli ng Basin , The between the States, a n d und e r th e annual diversio ns, w hi ch is highly correCap, water dive rsions, wate r sharing, Au stra lian Constitution the State lated w ith the storage capacity . Governments retain sustainability , public policy. considerable power Introduction <0,000 over the use of the The Murray-Darling Basin (Figure 1) land and the water in 35.000 covers 1.06 n,jJJion square kilometres o r the Basin and that -TocatBuln ao-..m-sw,.. 30,000 approximately one-seventh of th e total power is defended -(GI.I area of Australia. It includes muc h of the v igorou sl y against :; 2S.OOO country's best fa rm land and nearly two e n c roa c hm e nt b y !2. million peop le. Outside th e B as in both ~ 20,000 the 3 another million pe op le are hea vi ly Commonwealth 0 > 15,000 dependent on its water. Use of the Government and the Basin's water resources has made possible other States. 10,000 the expa nsio n of agricultural developIn 1988 the Murray-Darling T ins paper 1s an edited version of one presented B asi n Commission 11MO 1. . . 1920 11130 "'"" 1970 1980 1890 2000 to an international audience at the World water was fo rmed to faciliCongress, March 2000, and deserves being Figure 2: Storage capacity and diversions in the Murraytate interstate republished here. cooperation on the Darling Basin versus time. WATER JULY/AU GUST 2000

37


ENVIRONMENT

Bas in " (Klund er, 19 93) . (Figure 3) . B y 1994, water consu mptio n Minister Klunder supported in th e Basin had reached approxim ately an emerging view that 11,000 GL per year. In the northern 12000 "there be no further regula- pa rts of t he Basin , the p ercen tage tion and diversion arrangeincreases were very much greater, largely 5 10000 m ents which wou ld exacer- as a result o f the expa nsion of the cotton !:2. .§ 8000 b ate deteriorating flo w industry, though large increases were also ~ regimes" throu ghout th e experienced in other areas . 6000 B asi n . In response th e Amo ng other things, the levels of ~C Ministerial Council directed ,i 4000 water d iversion h ave signifi ca ntl y that a report be prepa red on reduced flows in th e lower reaches of the 2000 the of water diversions form River Murra y. U nder 1994 levels of the river syste m of the Murray-Darljng Basin. T his develop ment, median annual flows from 1920 1930 1~0 1950 1960 1970 1980 1990 2000 2010 2020 Year report, "An Audit of Figure 3 . Growth in Water Use in Murray-Darling Water Use in Basin . the M urray"·ooo Diversions have grown continually Da rli n g B asin" was since the 1870s but th e rate of growth pub li shed by th e increas ed sharp ly in th e 1950s and 1960s. Ministerial Council in June For exam ple, water extractions in the 1995 (MDBMC, 1995). Basin more than tripled in the 50 years T he Audit confirmed ...--··· S.000 to 1994. This development of the Basin's increasing levels of diver···-················· water resources received active govern - sions and the consequ ent ,oo 10 ro 90 m ent and broad co mmunity suppo rt decline in ri ver health. Pe,cenl~· of YN rs That Flow ll IAH ThMI Vafu. th roughou t most of this period. From 1988 to 1994, water consumption in th e Basin Figure 4. Fl ow duration curve for t he mouth of t he The Audit of Water Use in the increased by 8% overall River Murray. 14000

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B y the ea rly 1990s it had beco me clear that the rivers of the MurrayDa rling Basin were under stress, w ith a realisation that there was a finite amount of water in the Basin. A need to strike a ba lance b e t ween co nsu mptiv e and instrea m uses of the water was identi fied and it was clear that any further increase in extractio n would effect the security of supply to other users. T h e highest forum for in terstate cooperation o n the managem en t of the natural reso urces of the Basin is th e M u rray-Da rlin g Basin M i nisterial Cou nc il (th e "Ministerial Cou ncil") . Th e Ministerial Council consists of the ministers responsible for land, water and environmental resources in each o f the Com m onwealth, New South Wales, South Australia, Victoria, Queensland and Au st ralian Capit al T e rritory Governments . Being a political forum, the Ministerial Council has the power to make decisio ns fo r the Basin as a whole. R esolutions of the Council require a un an imo u s vo t e. This m ea n s th at decisions taken by the Council represent a consensus of Government opinio n and policy across the Basin. In J u ne 1993, South Australian Minister Klunder presented a paper tO the M urray-Darling Basin Ministerial C ouncil entitled "The Changing D emands for Surface Water in the Murray-Darling 38

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20,000 - - - - - - - - - - - - - - - -- -- - - ~

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Figure 5. Water diversions in the Murray-Darling Basin and the co rresponding limit pl aced on diversions by the water allocation system s.

the Basin to th e sea are on ly 2 1% of those that wou ld have occ urred under natural co nd iti o ns (Fi gure 4) . T he reduction in flow has affected most no tably the small to m ediu m size flood events. T he frequ ency of th ese eve nts has been substantially reduced and many o f them are completely harvested . On e co nsequence is that th e lower reaches o f th e Murra y now expe rien ce severe drought- like £lows in over 60% of years co m pared wi th 5% of yea rs u n der natural conditio ns (Figure 4). Th e Audi t also exa m ined the scope fo r dive rsio ns to grow fu rther under th e water a!Jocatio n system that existed at th at time. T he existing system had evo lved at a time when water managers were trying to encou rage deve lopm ent of the Basin 's water resou rces. As such, th e system ratio ned water d uring periods o f shortage bu t was not effective fo r c ontro ll in g di v ersio n d u rin g n o n d rought cond itions. In the fi ve years before the Audit, o nly 63% o f the water that was permitted to be used was used, leavin g co nsiderabl e scope for further increases in co nsumption, w ithout any cha nge in entitlemen ts. Th e Audit fo u nd that if all existing water entitl ements were fu!Jy developed th e average diversions wou ld increase by a further 15%. Such an increase in diversion would reduce security of suppl y for existing irrigators. Increased diversions would m ean that th e level of reserves held in the storages would be lower than is cu rre ntl y th e case . U n d e r this scenari o, water su ppli es for existing irrigators would have becom e less secure and river h ealth problem s would have been exace rbated.

The Cap on Diversions In response to the issues raised by the Aud it, t h e M u r ray -D a rlin g Bas in

M in isterial C oun cil at its Ju n e 1995 meeti ng dec ided to introdu ce an interim Cap o n di versio ns o f water from th e Basin. T h is was later con fi rmed as a pe rmanent Cap effective fro m 1 Ju ly 1997. This was seen as an essential first step in establishi ng managem ent systems to achieve h ealthy ri vers and sustain able consum ptive uses. In o th er words, th e Co u n cil de ter m ined that a ba lan ce needed to be struck between th e significa nt econo m ic and social benefits that have been obtain ed fro m the developm ent o f the Basin's wa ter resou rces on the one hand, and the environ mental uses of water in th e rivers on th e oth er. The M inisterial C ou ncil agreed that: The Cap be defi ned as "Th e volume of wa ter that would have been diverted under 1993/94 levels of development. In unregulated rivers this Cap may be expressed as an end-of- vall ey fl ow regime." This has been the way th e C ap has been applied , with sma ll variations, in N ew South Wal es, Victoria and South Australia (wh o b etwee n th em extract 95% o f th e water diverted in the Basin). In Q u een slan d an d th e Au st rali an Capital T erri tory (total of 5% o f Basin diversio ns), the fi nal details of the Cap are yet to be determ ined. Di version at 1993/ 94 levels of development does no t mean the volum e o f wa ter that was used in 1993/ 94. R ather, the C ap in an y year is the volum e of water that would have been used w ith th e in fras tru c ture (pu mps, d am s, chann els, areas developed for irriga tion , managemen t rules, etc.) that existed in 1993/ 94, assuming similar climatic and hydrologic conditions to those experienced in the year in questio n. For example, to establish the Cap target in the 1999/ 2000 water yea r, compmer m odels are used to calcula te the diversion that would have occurred under the WATER JULY/ AUGUST 2000

39


ENVIRONMENT

climati c se q u e n ce expe rie n ce d in 1999/2000 assuming 1993/94 managem ent rules and infrastructure still existed. T hus, the C ap p rovides scope fo r greater water use in certain years and lo wer use in other years. The Cap itself does no t attempt to reduce Basin diversions, m e r ely p re vent the m fro m increasing. N ew developments are possible under the Cap provided that the water for them is obtained by improving water use effi ciency or by purchasing water from existing developments.

Implementation of the Cap The C ap is a fundamental piece of public policy in the natural resource arena . It effectively defines the environm ent 's share o f the water in the Basin as well as defining much more rigorously the shares of the individual Australian States that com prise th e Basin. By stating that the quantum of water available for consumptive use has now been full y committed, it foc uses attention on water trade and water use efficiencies as the

40

WATER JULY/ AUGUST 20 00

on ly source of water for future develo pmen t. It is expected that this will accelerate the movement toward higher valu e crops and red uce accession of irrigatio n water to the grou ndwater. These accessions are a majo r threat to the sustainability o f irrigatio n in th e Basin since th e area o f land w here the ¡watertable is less than two m etres below th e surface is contin ualJ y expanding and the groundwater salini ty in much o f the Basin is very high. The task of implemen ting the C ap is large, complex and politicalJy chall engin g. By agree ing to th e Cap , the Ministerial C ouncil has effectively established a new framework fo r w ater sharing in the Basin. T his will require considerable changes to the way the water allocatio n system is mana ged across the Basin, bo th within States and between th em. The m ost fundamen tal task is to modi fy the water allocation system . The procedures that the States have developed to alloca te water to the

individual wa ter use rs evolved at a tim e w hen the States we re trying to encou rage economi c development of the water resource. As a conseq uence, practices have de veloped such as declaratio n of o ff- all ocation (addi t io nal access to "surplus" river flows) and the all owance fo r under usage by dozers and sleepers (th ose licence-ho lde rs w ho use li ttle o r no ne o f their en titlem ent) which are difficu lt to change. T he combination of the sleepers, the C ap and enh anced w ater trade resul ts in som e irrigators seeing th eir access to wa ter bein g redu ced through the tighteni ng of the allocation system despite the fact that the Cap will no t reduce total water use . This tightening o f the allocatio n system to deal with this issue could have been expected witho ut th e dec ision to Cap di versio ns. The C ap , however, has made this process more obvio us. Figure 5 shows the actual diversion since 1984 and, where available, the total water allocated across the MurrayDarli ng Basin fo r th is same period. T he differe nce between the amount of water made available in the water managemen t practi ces leading up to 1994 compa red to actual use is clearly dem o nstrated in this figure. In the five years to 1994, 160% of the water actually diverted was mad e available fo r irrigatio n . Since 1994, th is ratio bas reduced to 130% which indica tes the extent of the ti gh tenin g of th e allo cati o n system since this time . Th is tightening of the allocation system is one of the key too ls used th roughout the Basin to ensu re water use remains within the Cap. W hile progress is evident in the tightening of the a!Jocation syste m, it may be too early to determine whether the Cap has been effective in curtailing fur ther growth in diversions. T he highest ever use of water in the Basin was recorded in the 1997 water year and , fro m inspection of Figure 5, it may be possible to concl ude that diversions continue to trend upwards. Prior to the com pletio n of the necessary compu ter simulatio n m odels that can account for climatic fac to rs it is difficu lt to ascertain whether there has been a growth in diversions over the last few years o r the high diversion levels recorded are a pro duct of the climati c sequence experienced in the Basin. The tightening of the allocation system does, however, give wa t er managers greater control over water use as Cap targets are refined with the fu rth er deve lop m ent of co mp uter simulation models. T he tim e scale in Figu re 5 extends to 2010 indicating diversions and alloca-


ENVIRONMENT

It is expected that this review wi!J see furth e r e nha n ce m ent of cr e dibl e, explainable and repeatable me thodologies for de termi ning Cap compliance.

The Cap in Context Boundless Plains to Share

Figure 6. Sir Rona ld East st radd les the River Murray near Swan Hill in March

1923. ti o ns in the Murray-Darli ng Basin wi ll conti nue to be m onitored close ly over the com ing years. Assum in g average cl im atic conditions over the co ming decade, an updated version of this figure in 20 10 will provide a sin gular assessment of the success of the Cap on di versio ns. T he imple me ntation of the Cap is not yet com plete throughou t the Basin. 1mportan t tasks that arc bein g addressed and will need to be completed before the Cap is fu ll y impleme nted in clude: • improving the mo nitoring and reporting on all fo rms of wa ter use; • establishing clear defin itions of w hat constitutes a water use; and • the deve lop ment and approva l of the comp uter mode ls wh ich will be used at the end of each yea r to define the climate-adjusted 1993/94 developm ent Cap water use target for the year just e nd ed. Also, as part of the ori ginal decision by the Ministerial Council to introduce the Cap, a m ajor review of the operation of the Cap is taking place throughout 2000. This is a review of the operation of the Cap, not the Cap itself, and is seeki ng to identify suggestio ns fo r the more effective future operation o f the Cap through investigations in each of the following areas: • the ecological sustainability of rivers; • econo mic and social impacts; • equ ity issues; and • implementation and co mp liance issues.

The large size and relatively sm a!J population of Austral ia has foste red a sense of the boundless ness of its natu ral resou rces since th e ea rly days of the establishm en t of the British colo nial adm inistration at Sydney in 1788. T o this day the Australian national an them , Advance Australia Fair, penn ed in the 1800s, talks of " bou ndless plains to share". B y th e 1990s, however, the de teriorating health o f the river system of the Basin had m ade it very clear that development of the Basin was indeed bo und ed. In deciding to pl ace a Ca p on d iversions, it was recognised that the limitl ess expl o itatio n o f the natural resources of Au strali a is som ething upon whic h Australians cou ld no longer rely. Sir Ronald East (1899 - 1994) of Victoria The high ly variable hydrology of the Au stralian co ntin e nt made it clea r in the very ea rly days that th ere was a need to bui ld water "co nse rvation " storages for irrigation. Pre-eminent in th e history of the d eve lo pm e nt o f irr iga t ion in t h e Murray-Darlin g Basin is Sir Ronald East (1899 - 1994) . Sir Ronald was an e n g in ee r , t he n Co mmiss ioner and C hairman of the State Ri vers and Water Supp ly Comm ission ofVi cto ria over th e period 1922 to 1965. There is no m ore icon ic image in th e history of th e developm ent of Australia's irrigation industry than the p hotograph of Sir R o na ld straddlin g the Rive r Murra y n ear Swan Hill in Ma rch 1923 (Figure 6) . T his is a photograph that provid ed e ndorse m e nt to the dam builders e ngaged in a period of rapid deve lopm e nt of th e wa te r sto rages throughout th e Basin (a SO-fold increase in storage Basin-wid e in the subsequent 60 yea rs) and o n e that can continue to cause concern in the irrigation community. If A ustralia 's " mighties t" ri ver co uld cease to flow, surely there was a need for major storages to protect the irrigation industry?

Figure 6 is generally co nsidered to be evidence of how low natural flows could get in the R iver Murray. H owever there were already sign ifi ca nt irri gation extractions (approximately 1,000 GL/yr) upstream of this poi n t by 1923. A

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41


ENVIRONMENT

simu lated natural fl ow seq uence for the Ri ver Murray indicates that w ithout u pstream irrigation diversions th e flow on th e day of th is p hotograph would have b een approximately 2,000 M L/ d (25 m 3 /s) . On a h uman scale this wou ld ha ve placed Sir R o nald in wate r 0.7 111 deep in a rive r 30- 40 111 wide w ith a velocity above 1 m /s . Wh ile th e variabil ity o f Australia's h ydrology is unquestioned, Fig ure 6 would be be tte r thoug ht of as an early example of the prepa redness of extracti ve users to harvest the available water to the po int o f d rying u p th e river downstream. Sir Ronald was som eo ne w ho dealt w ith the chall e nges of his day th rough imagination , c re ativity , courage and long- te rm commitm ent. It is interesting to conside r ho w Sir Ronald would have app li e d th e sam e qua litie s to t h e ch alle nges w e are n ow fo cing.

Reasonable Use T he Co nstitutio n of Au stralia, w hich came into e ffec t in 1901 upon the federation of the Australian States, contains the following clause: 100 . Th e C o111111 011 wealth shall not, by an y law or regulation of trade or co mmerce, abridge th e right of a State or of th e residents th erein to th e reasonable use of th e waters of rivers for conservatio n or irrigation . Rather tha n leave th e States with th e abso l u t e sove r ei g nty ov e r wa t e r resources they had enjoyed to 190 I, th e frame rs o f th e Au stralian C onstitution introdu ce d th e con ce pt of th e " reasonable use" as an upper limi t to the irrigation extractio n of an y on e State . It is inte res ting t o n o te that t h e word " reasonable " was added to chis clause, fu ndam entally alte rin g its e ffect, at th e insisten ce o f a Mr Dow ner, a de lega te at th e C onstituti o n Co nventio n o f 18 98 from Sou th Australia - the downstream Sta te in th e Murray- Da rlin g Basin (Conne ll , 1999). Th e Australian Constitu tio n ca n thus lead us to ask: is o ur current use o f the water resources of the Murray-Darling Basin reaso nable? W ays is w h ich this q uestio n can b e conside red are from: • an agricultu ral p erspecti ve; • a river health perspecti ve ; • a sustainabilcy perspective; and • an inte r-generatio nal eq uity perspecti ve. Clearly the defini tion of "reasonable use" c hanges with time . Perhaps o ur curren t u nde rstandin g of " reasonable

42

WATER JULY/AUGUST 2000

use" is the level at which the Cap on diversions is set. It is important to note, ho w ever, that there is no g uarantee that w e will see a halt to environm e ntal d e t e r io ratio n und e r th e Ca p . Th e curre nt level for th e Ca p on diversio ns is just the leve l that existed at the time it was decided that a lim it neede d to be intro du ced. Indee d Wh ittington and Hillman (199 9) repo rt that "som e of Australia's leading sci entists have argu ed that setting the C ap at the cu rre nt level of diversio ns will no t stop the river deteriorating. They arg ue that the rivers are already seriously overdevelop ed and the onl y hope is to significantl y redu ce d iversions from their present levels". The Future

The work sti ll require d to fully imp lem e nt that C ap can be exp ec ted to take p lace in an atmosphere of em erging acceptan ce of the bene fits of t he C ap to the sernrity o f supply to ex istin g irrigators and reduced environme ntal impa cts. This paper has described th e Cap as it is curre ntly u nderstood and imple m e nted. Poss ibilities fo r furth e r elabo rations in the manage ment o f the water resources of t he Basin over the comin g decades are e xplored in Bl ack m ore (1999). In 1995, th e Murray-D arlin g l3asin was the first inter-j urisdictional rive r system w here it is k nown th at such a limit had been introduced in an atte mpt to stri ke a balan ce between in stream and con sump tive uses o f the available w ater resources. Since this tim e, a similar arran ge m ent has be en introduced in the Tarim Basin o f western China in the fo rm o f " w ater use quotas " which cover bo th su rface and groundwater use (T arim Basin Water R eso urces C om missio n , 1997). More exa mpl es of caps on diversio ns are likely to appear as diversions from vario us river system s approach , or exceed , sustainabl e levels.

Conclusion Against a backdrop of over 100 years of active de velopm e nt, the C ap o n wa te r diversio ns from the river system of the Murray-D arli ng Basin is now recogni sed as a la ndmark de c isio n in n atural resource manage m e nt. The introdu ction of this Basin- wide limit to the extractions fro m a river syste m is a first step to strikin g a balance between instrea m and co nsumpt ive uses , bu t there is still mu ch to do in its implem entation . This w ork can be expected to take place in an atmosphe re of e m e rging acceptance of its be n efits.

References Blackmore, DJ. ( 1999). The Murray-Darl ing Basin Cap on Diversions - policy and practice for the new millennium. National Water Conference, Sydney, 15- 16 June. 12 pp. Connell , D. (1 999) . The Corowa R.iver Murray Wa ter Co nserva tion Con fe rence 19 0 2. Murray- Darli ng Basi n Com mission, Canberra. 28 pp. Klunder, J. (I 993) . The Changing Demands for Surface Water in the Murray-Darl ing Basin. Address to the M urray-Darli ng Basin Ministerial C ouncil Meeting 12 - 25 June 1993 by the South Australian Min istt:r Ho n. J. Klu nder MP, Melbourne. 4 pp. MD13MC (Murray- Darl ing Basin Ministerial Council), ( 1995) . An Audit of Water Use in the Murray-Darling Basin. Murray-Darling Basin Ministerial Council, Canberra, 40 pp. Murray- Darlin g Basin Commission web page ,v,v,,v .n1dbc.gov.au

Tarim Basin Water l"l...esources Commission (1997) . R.egulations on Tarim R.iver Basin Water Management. Tarim l"l...ivcr Ilasin (China) . Final Dra ft, November. 7 pp. Wh ittin gto n J. , and Hillman T. ( 1999) . Sustain abl e l"l... ive rs: T he Ca p and Environmental Flows. Cooperative R.esearch Centre for Freshwater Ecology, Canberra, 13 pp.

Authors Andy Close BE ( H o ns ) ME (Ad elaid e) G .Dip .BA (SA IT) is th e Manager of the W ater Po licy Sectio n of the Murra y-D arlin g B asin C ommission (MDBC) . H e has been w ith th e MDBC, and its predecessor the Ri ver Murray C om mission , sin ce 1984 and has been responsibl e for th e deve lopm ent of th e m o delli ng tools for the Ri ver Murray and th e develo pment and analysis of w ater po licy, including th e C ap , for th e Murray-D arling Basin. Tony Mcleod BE ( H o n s) P hD (M elbo urne) is a me mbe r of the W ater Poli cy Section o f t he Murray-Darling Basin Commission. Since j o ining the MDB C in 1998 he has been in vo lved in the impl em entatio n of th e Cap o n di versio ns throug ho ut the Basin. H e is also the project m anager o f the 2000 fiv eyear R eview o f th e Operatio n of th e C ap . Email: to ny.mcleod@ mdbc.gov.au . W e b Page fo r the Murray-D arling Basin C omm ission: www.mdbc.gov .au

The Murra y -Darling Basi n Commission has released two reports on Environmental Flows (' Scientific Panel ' and 'Barrages'). They w ill be used co develop an environmental fl ow pl a n that will go t o th e Ministe rial Council in March 2001. Both documen ts can be downloaded from http: / / www.mdb c .gov.a u / MediaRel/


II

ENVIRONMENT

Abstract A sig nifi ca nt red u ct io n in water Sow in g over the barra ges and out to sea in rece nt yea rs has led to the situ ati o n w here the mouth of the Ri ve r Murra y is beco min g increasingly congested with sa nd. T h is is restri ctin g tidal flu shin g of the Coo ro ng, and navigat io n i n the area, but has th e pote ntial for much g reate r harm if total mouth c losu res beco m e m o re frequent. The present study has foc ussed on using re lationships be tween river fl ow and m outh restri cti o n to d ete rmin e opt i mum st ra t eg ies for man aging the m o uth if add itio nal flows cou ld to be mad e available. It has been fou nd that a uniform in crease in flow th roug ho ut the year is more effective at preventing clogging of the m o uth th an an annual flu sh in g fl ow. Key Words: River Murray, Coorong, tidal inlets

Introduction R ecent concerns about the state of the River Murray mouth (Figure 1) have renewed inte rest in its behaviour, and its role as th e downstre am co ntrol of Austra lia 's maj or river system.. For much o f 1999 the m outh was observed to move steadily towards a tota l closure as excess sed iment buil t up inside the mouth area , restricting tidal flows , water excha nge and navigation.

The Murray-Darli ng bas in is a n important agric ultural area , based largely on irrigation. The basi n in cl ud es 42% of the country's co m merc ial farming ente rprises, 47% of irrigated ho ldings and is responsible for over 40% of the coun try's ag ric ul tural produ ction (P owe ll , 1999) . The valu e o f primary produ ction in the Murra y-Darlin g basin was estim ated at S10 billio n per annu m (M cP hail and Y ou ng, 1992) . To ach ieve this leve l of production the extracti on of water for irriga tion alo ng the length of the river has inc reased to the po int th at for a signifi ca nt po rti o n o f t he tim e little water is actualJy fl ow ing o ut to sea. Low flows and thei r effects, however, are n ot a recent phenomeno n . The pla n to co nstru c t the series of locks and weirs that are now an integral part of th e river system was formul ate d and put into action aft er th e drought of 1914 w he n the river had shrunk to a series of pools (DE HAA , 1999). In the 1930s low ri ver fl ows led to salt water intrusions in to Lakes Alexandrina and Albert. A series of barrages were completed in 1940 to assist in k ee pin g the lowe r lakes fresh (DE HAA, 1999) . W hat has changed is the freq uency at whic h the low flow events occur. Accord ing to Cu ll en (1999), over 80% of the median flow at the mouth of t h e Murray is now removed for irrigation and oth er uses, and drought conditions occur one year

in two rat her t han the o ne in twenty unde r natural conditions. Prev io us wo rk by a num ber o f resea rche rs (W alker, 1990; Walker & J essup , 1992; Fri c k el al. , 1996; Elford et al., in press) has resulted in a descripti o n of the size of the mouth in terms o f a num ber of facto rs suc h as rive r fl ow, o nsh ore wi nds and the barrages in o pe ration. Th e m odelling was d o n e in te rms of a syste ms approach where relatio n-

Figure 3. Location of the Murray mouth in relation to the lower lakes (Alexandrina and Albert) and Th e Coorong. WATER JULY/AUGUST 2000

43


ENVIRONMENT

River flows Transfer Function

New Mouth State

Onshore wind

Barrages in Use

Figure 2. Schematic of syst ems approach to modelling the River Murray mouth .

ships were developed based on measured data rather than the physics of the processes. A system diagram for th e mouth is shown in Figure 2. The aim of the present study was to apply previously determined relationships between mouth opening and ri ver flows to evaluate strategies for improving the m outh opening.

Study Site The River Murray mouth is loca ted near Goolwa in So uth Australia (Figure 3). The mouth has altered its position on the coast, and intermittently deposited and rem oved signifi cant vo lu mes of sed iment on the landward side for all its observed history . Since the 1830s th e position of th e mouth has varied w ithin a range of approximately 1400 m etres. During this time the size of th e mouth has varied from being several hundred m etres wide during heavy flood flows to a situ a t ion w h e r e i t was cl osed completely at low tides in April 1981. In the last two decades concern has fo cussed on the buildup of sediment inside the m outh and th e effect this may have on tidal fl ush ing and the ecology of the Coorong. Harvey (1988) lists the m ajor issues associated with closure as: recreation and tourism , th e fishin g industry that operates in the Cooro ng (and is responsible for 12% of th e state's catch (Sinclair, 1998)), the potential for floodi ng and the possible deterioration of water quality. The C oorong's significance in en vironmental terms has been r ecog niz ed in tha t it 1s a listed RAMSAR site. In April 1981, after a lo ng period without any flo w over the barrages there was a complete closure of the mouth. T he mouth was re-opened with heavy excavation equipment, with the timing designed to coincide with reaso nable river flows that were able to flush large quantiti es o f th e sediment from the m outh. D espite the flushi ng there was a

44

WATER JULY/AUGUST 2000

subsequent near closure during 1983. T he mouth, at the time of the closure in 1981 , is shown in Figure 4. It is evident that the blockage involved not just a plug of sand in the mouth , but an ex tensive area of sand banks that had built up over the p receding months. The present situ ation at the mouth, as shown in Figure 5, is similar to that of 1981 with the exception that the mouth is currently in a position several hundred metres to the west (left) , and would appear to ha ve taken in more sand.

Figure 1. Aerial photograph of River Murray mouth looking south (date not known). River flow to the mouth is split into the Goolwa Channel (bottom of picture), Mundoo Channel (left) and the Tauwitchere Channel (top).

Morphological Processes From the time of European settlem ent a buildup of sediment inside the mouth in the form of a flood tidal delta and extensive areas of shoals had been observed (Bourman and Harvey, 1983) . Bird Island (shown top of Figure 5) has built up in the period since 1949 wh en, according to Bourman and Harvey (1983), the flood ti de deltaic sedim ents had stabilized sufficiently to suppo rt a few shrubs. By 1956 the deposits were stable enough to survive the river's largest h istoric flood. Given the micro-tidal conditions and the domination o f wave energy o n the coast the large fl ood tidal delta is expected (H ayes, 1991). The tendency fo r inlets in this situatio n to close periodi cally has bee n observed in many seasonally open inlets (Ranasinghe et al., 1999). The river flow has been important in flushing sediments from the area but the increasing river diversions have stea dily re du ced t h ese flows. For example, H arvey (1 988) fo u nd that since the barrages were constructed there had been twenty p eriods of 100 days or more where there had been no flo w over the barrages and out to sea. The likelihood of these sorts of low flow events is increasing and has been estimated to occ ur as frequently as one every six to eight years. Figure 5 also shows that as th e

Figure 4. River Murray mouth in April 1981 showing full blockage at the mouth and restriction of water exchange between the Goolwa (left) and Tauwitchere (right) Channels. Th e red arrow marks a reference point for the mouth position.

Figure 5. Th e River Murray mouth, taken on February 29, 2000. The red arrow marks the reference point shown in Figure 4.


ENVIRONMENT

sediment builds up inside the mouth the ab ility of the tidal flows to reach the Goolwa and T au w itc he re C hannels would be reduced. It is this feat ure of the sediment buildup and the resultant tidal restriction that has been used to make an estimate of the state of the m outh . The buildup of sediment is important fo r a number of reasons. It results in a much redu ced tidal prism (volu me of water entering and exiting the m ou th on each tidal cycle) and also reduces the natural tidal flushing of th e Coorong and Goolwa C hann els.

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Analysis of Tidal Data and Mouth Restriction Th e River Murray mo uth has been th e subj ect of investigation and study since th e days of colonisation in the 1830s. According to Thomson (1975) th e ini tial interest was related to th e possibility o f constru cti ng a harbour at th e mouth , or a chan nel through to Goolwa, to serve the Murray Va lley. One of the proble ms w ith attempting to describe the size of the m ou th is the lack of data fro m the area. Whil e the re have been a number of surveys of the mo uth regio n the area does not lend itself to easy m easurement. T o overcom e the problem of lac k of specifi c details o f sedim ent bu ildup Walker (1990) u se d the tide data collec ted from Victor Harbou r (outside the mouth), the G oolwa Barrage (inside th e m o uth ) and t h e Tauw icc h e re Barrage (inside the m ou th) co de te rmine a n e ffe ct i ve m o uth opening. Th e reasoning beh in d th is c hoi ce was chat the sediment buildup in th e mouth would act to restrict the free flow of tidal waters from the ocean into the c hannels leading to the barrages. An y restriction wou ld be reflected in a reduced tidal amplitude at the barrage locations. The m easure used was relative tidal amplitude (R ), where this was defined: Ei11 side (1) R = Eo111side w here E = tidal ene rgy at locati on inside and outside the mouth. B ased o n thi s, R sh o u ld vary between O (complete closure leading to no tides inside m o uth) to 1 (compl ete opening leading to full transmi ssion of tides to barrages). Spectral an alysis was carried out cha t all owed th e tid al energy to be determined. In chis way it was possibl e to specify a n effective openin g w ithout the need to ha ve the mou th surveyed on a regular basis. An attempt was made to relate th e relative

Figure 6 . Re lative tidal amplitudes at the Murray mouth. The effect of mouth restrictions is seen as a reduction in the size of the tide inside the mouth compared to that outside.

was w ritten: = 0 .734 R.,_1 + 0.000 132 F,_2 (2) w here R., = relative tidal amplitude in month t; Ft = flow over barrages in CL in m o nt h t; (F,_2 = flow two months previously).

tidal amplitud e to ph ysical cha racteristi cs of the m outh suc h as th e width or a n estimated area of the main c hann el, bu t insuffi cien t data were available to allow a reliabl e rela tions hip to be d etermin ed . Th e relati ve tidal energy fo r Goolwa a nd Tau witchere fo r part of 1998 is shown in Fi gure 6 . Two points ca n be made regarding the resul ts: • the Goo lwa C hann el tends to be less restri cted than the T auwitchere C hannel and transmit more of the tidal signal; • the re appears to be a trend fo r decreasing tran smi ssio n of tidal signal fo r this part o f 1998 indi catin g in creasin g sediment bu il dup at the Murray mouth . Wa lker (1990) was able to explain mu ch of the variation in tidal transmi ssion in te rms o f th e monthl y ri ver flo w. T he relationship fo r relati ve tidal amplitude, based o n data fro m ·1981 -1 985 and developed using Tim e Series Analysis,

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The accuracy of Equati on 2 has been veri fied by ru nning one m o nth fo recasts on the relative mouth openin g from 1990 to l 998 . In additio n to the one m onth forecas ts a more severe test was p e rform ed w h ere th e relati ve tida l amplitude was forec ast based on ly o n the initial opening and the predicted barrage flows. The resu lts for Goo lwa are shown in Figure 7 . Th e agreeme nt is not as good as th e one m onth predictions but still gives a reaso nable long-term predicti on of the mouth be haviour. In these predi ction s it was necessary to ha ve estimates of the fl ow over the barrages. T hese were obtain ed from the

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WATERJULY/AUGUST2000

45


ENVIRONMENT

Murray-Darli n g Basin Commissi on using a computer program MURKEY that simulates flow and salinity in the ri ver. The fl ow over t h e barrage estimates are highly sensitive to the observed water level in the lower lakes, but are the best estimate that is ava ilable. Analysis of the predicted flow over the barrages fo r the last thirty years indicates a gradual decrease. Given the dependence of the mouth opening on the flows this is of concern. T ide data were avai lable for the Goolwa Barrage from 3 1st August 1976 to 12th October 1998 and for th e Tauwitchere Barrage from 6th M ay 1983 until 6th October 1998. These data were used to determ ine th e long-term trends in tidal co nveyance w here the semi-diurn al tidal componen ts were selected using sp ectral analys is. T h e situation for T auwitchere is shown in Figure 8 together with a linear trend line that was fitted to the data. Despite the variations over the last fi fteen to twenty years sim ilar analysis on the Goolwa C ha nnel indicates that it is rema ining esse ntially constan t in its ability to pass the tidal flows. This is perhaps not su rprising since the channel is used for much of the discharge from the lakes and represents an effici ent chann el to the ocean. In the case of Tauwitchere it appears that the chan nel is bei ng affected in the long-term by a consistent bu ildup in sediment inside the mouth and the ability of the chan nel to pass tidal flows is slowly being reduced. This is of serio u s concern given that the Tauwitchere channel is the gateway to the Coorong.

Flow Requirements and Management Options It is clear from the preceding sections that there is a problem developing at the R iver Murray mou th. River flows are decreasing. This is leading to increased sedimentation w hich is in turn restricting flow through the mouth, and silting up the main channel to the Coorong. Us in g riv e r flows predicted b y MDBC and Equation 2 it is possible to predict the relative mouth opening at the Goolwa barrage. T his is shown in Figure 9. The closure in 1981 and the near closure in 1983 are shown to be predicted with the graph dropping to show virtually zero tidal transmission. Also shown are a number of other times when it was predicted that the mouth would be near to closure . By selecting a nominal closu re level (R ~ 0.05) it 1s

46

WATER JULY/ AUGUST 2000

O.D7 0.06

'j

0.05

.s>- 0.04 f:?'

~ 0.03

LJ.J

0.02 0.01 0 (\J (') LO <O I'C1> 0 0 co co co ~ ~ co ~ C1> ;;; ;;; C1> ~ ;:::: C'5 ~ ,- ~ a, i:15 C\l a5 ,C\l 0 i:15 0 0 0 0 0 0 0 ~ ;:::: ;:::: ;:::: a, ;;; ii; ;:::: ~ (\J ~ i:15 i:15 (\J N ~ i:15 (\J

&3

i:15 0

--

i

ig ~

(\J

LO

LO

C1> C1> ~ C\l 0,- i:15 0

~

0

I'-

~

0

I'C1>

a, 0

a, 0 0 C\l (') (\J

~ i:15

0

~

Figure 8. Tid al amplitude at Tauwitchere based on data from Tauwitchere Barrage .

possible to determine the number of months where near closure woul d be predicted. In the sim ulation shown the figure predicted is 58 mo nths . If additional flows co ul d be made available for discharge from th e barrages they could be provided in a number of different ways. T wo such options have been evaluated, the firs t where th e flow was spread evenly throughout the year, and the second where a fl ushing flow was provided in a single month. T he results, in terms of the predicted number of months where the mouth wo ul d be essen tially closed, are shown in Figure 10. It is evident that the provision of additional flows on a monthly basis provides a better solution particularly when the annu al supplement exceeds 360 GL/year. To put the figures in to perspective Harvey (1988) quotes an opinion that a flow of 20 GL/ day for a month (total of

600 GL) should be sufficient to flush the mouth clear of sediment. T he simulatio n suggests that a better use of the water wou ld be to spread it over the total year.

Summary and Conclusions A study of the River Murray mouth has been undertaken in vesti gatin g the recent behaviour of the mouth in terms of the effect that sediment buildup has had on tida l fl ows in the Goolwa C hannel and at the head of th e Coorong (as recorded at Tauwitchere barrage). It has been shown that the tidal flows to the Coorong are decreasin g and this has major environmental issues for the area . Using previously determined relati onships between river flow and m outh restriction th e stu dy has evaluated options for reducing the likelihood of future m ou th restrictions and closures. Numerical simulations, using predicted river flow data , have shown that a steady flow over the barrages is superior to an

1.2 ~ - - - -- - - - - - - - - - - - - - - - - - - - ~ C, C

¡c

8.

0

0.8

.c

s

~

0.6

-ÂŤi~ Q)

a:

"closure"

le-.el

Figure 9. Predicted mouth opening based on present situation. A nominal level where tidal influence is reduced to R :'.5: 0.05 has been selected to indicate mouth closure.


ENVIRONMENT

70 60 ~

::,

U)

[ ...... Monthly Supplement] --Annual Supplement

50

0

0

.s::;

:5 40 0

E

0 30 U)

.s::;

c0 20

~

10 0 0

120

240

360

480

600

720

840

960

1080

1200

Walker, D .j. (1990) T he 11..ole of River Flows in the Behavio ur of the Mun-ay Mouth. South

Additional annual flow (GL)

Figure 10. Predicted effect on the number of closures of the mouth if additional flows are available and made on a month ly basis or as a single flushing flow once a year.

annual flushin g flow if the same volu me of water is used in eac h case.

Acknowledgements Th e fl ow data used in th is study we re suppli ed qui c kl y and e ffi c ie ntly by Mr And y C lose of th e Mu rray-D arl ing Basi n Comm ission. The tid e data were s uppl ie d b y T h e D e partm e n t of Env iro nm en t, H eritage an d Abo riginal A ffa irs. Than ks to the review e rs w ho p r ov id e d v alu a bl e co mm e n ts a nd suggestio ns o n the first draft of this pap er.

References 13ou nm n, 13. and Harvey, N. (1983) T he M urra y M o u t h Flood Ti d a l D elta . A ustralian Geogra pher, I 5(6), 403-406 C ull en, P. (1999) W ater a nd the Emerging P o lit ica l Im peratives . Water Resea rc h F ounda t ion of A u stra li a , R.es e arc h R eport. DE HAA (1999) South Australia. In: A Century of W a ter R.eso urces Development in Austrnlia (Ed. W . B oughton), Institution of Engineers Australia, 110-14 1 E lford, C.J.; Frick, 11...A.; Rij nks, D . and B o urman, R .P. (in press) A Control Model for the Mouth of the River Murray, South A ust ral ia. In te rn ation a l J o urn a l o f Environmental and Po llutio n . Fric k , 11...A.; Bourman, R . P. a nd Lucic, D. ( 1996) T ow ards a C o ntro l Model for the M urray M o uth. Environmental M odelling a nd Assessment ( I), 37-44 Harvey, N. (1988) C oastal Management Issues for the M outh of the l"l..iver Murray, South Australia. Coastal M anagement, Vo l. 16, 139-149 H ayes, M. O. (1991) Geomorp hology and Sedimentation Patterns o f Tidal Inlets: A R eview. In : Coastal Sedimen ts '91, (Ed. N .C. Kraus; K.J. G ingeric h and D .L. Kriebel), ASCE Proceedings of a Specialty Confe re nce on Quantitative Approach es to Coastal Sediment Processes, Vol. 2, 13431 355

Bough to n), ln sti rnti o n of Engi n eers Australia, 201-215 Ranasm ghe, R . and Pam aratc h,, C . (! 999) The Seasonal Closure of Tidal In lets: W ilson Inlet - A Case Study. Coastal Engineering, 37 , 37- 56 R iver M urray Catchment Water Management B oard (undated) Managing t he M urray. Inform atio n N ewsletter Sincla ir, D . (1998) Lakes & Coorong Fishers Lead by Example. Environment SA, Vo l. 7, No. 2, 31 T homson, R .M . (1975) The Geomorp hology of the M urray Valley in South Australia. Thesis for M .A. , Th e Uni versi ty of Adelaide.

M c Pha il , l.R. and Young, E. M. (1 992) Water fo r th e Environm ent in the Murray-Darling B as i n. Wate r A llo ca t ion fo r t h e Environ m ent, Proceedings of Internat io nal Sem inar and W o rkshop. (Eds. J .J. Pigram and B.P. H oope r), 19 1- 21 0 Powell, J.M. ( 1999) Mur ray-Darl ing 13asin. In: A Cent ur y of W ate r R eso u rce s D eve lo pm en t in A u st r al ia ( Ed. W .

Australian Geographical J o urnal, 90, 50-65 Walker, D .j. and Jessup, A. ( I 992) Analysis o f the Dynamic A 9spects of the R iver M urray Mouth, South Aust ralia. J o urnal of C oastal R esearch , 8(1), 71 - 76

Author DJ Walker is w ith th e Centre for Appli e d M o d e llin g 1n Wat e r Engineering, at the Depa rtm e11t of C ivil & E n viro nme n tal En gin ee rin g, The Un iversity of Ade laide .

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The Australian Environment Directory Hallmark Editions, publishers of Environment Business newsletter and The Green Guide, have released a significant new reference and resource publication, The Australian Environment Directory. This new 424-page Directory gives a comprehensive overview of the entire environment sector at Federal and State levels, allowing readers to quickly identify which departments, agencies, sections and units have particular responsibilities and roles such as greenhouse abatement, biodiversity and environment protection. Branches and divisions are listed as well as the support programs and funding opportunities they manage, providing a unique insight into the management structure of the departments and agencies. This allows the right contact person to be quickly and easily identified. In each State and Territory Chapter, details are included of programs run by government departments and EPAs. These range from waste minimisation and greenhouse reduction through to air quality, catchment management, land, coastal and marine management. Local Government environmental bodies, and the nongovernment environmental organisations are described in detail. The major environmental programs in the Federal and State sphere are linked back to the relevant departments and agencies allowing readers to clearly locate the source of the program. Identifying the funding sources available

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ARRANGEMENTS FOR SETTING DRINKING WATER STANDARDS The P roduc tivity Commiss ion's International Benchmark in g Report, Arrange111e11ts for Setti11g Drinking Water Sta11dards was released on 14 April 2000. T his study forms part of a continuing program of research benchmarking the p erformance o f economic infrastructure industries. Earlier studies have fo cused on information about outcomes, such as prices and productivity. This study of the water sector, however, compares regulatory processes for the development and enforcement of quality standards, in Australia and overseas, against accepted best practice principles. The following article is an edited summary of the Overview of this vital report. Readers are advised to consult the whole report, which can be purchased from Ausinfo shops in all capital cities, RRP $21.95 (plus CST). The phone-shop number is 13 24 47. T h e report is also accessible on the web site: www.pc.gov.au/ research/ b enchmrk/ drinkw/finalreport/index.html or scroll from www.pc .gov.au The other chapter headings are: • Introdu ction, and study scope • R eview of the drinking water sector, history, current concerns, technologies, economics • R egulatory practices and institutions • Setting parameter values Monitoring and enforcem ent • Systems management, cost recovery, risk commu nication • O verarching issues. The Appendices compare th e situations in all Australian States and Territories, and the bench mark situations in seven overseas coun tries.

Overview Australia-wide , the urban wate r secto r faces the prospect of ha ving to make large investments in treatment techno logies, because of an in crease in the scope and strin gency of wa ter quality standards. Given the magnitude o f po tential co sts and th e importance o f pu blic health obj ec tives, it is tim ely to explore how higher standards are developed, how risks are analysed, and how decisions are take n to impl ement higher standards. This study was undertaken fo llowing co nsultations with a number o f ju risdictions. Benchmarking approach and scope

Re g ul a t o r y ar r an g e m e nt s a nd processes fo r establishing and enforcing drinking water standards in Australian jurisd ictions were co mpared w ith those in Canada, France, N ew Z ealand , th e UK and US. Th e p u rp ose was to co 1npare regulatory processes - n o t sta n d ards, or the gap between standard requirem ents and ac tual water quality or public health o utcomes, fo r w hich data are not generally obtainabl e. Information

was collec ted o n t he orga ni sations involved in developing, promulgating and enfo rcing drinkin g water standards. T he informatio n includes details o f these organisatio ns' responsibilities, processes and accoun tabilities. Differences were examined against best prac tice regulation makin g and enfor ce ment. Wid ely accepted criteria for determi ning best practice were used. Ther e was n o atte mpt made to de velop an ideal Au stralian regulatory model. In any event, there is insufficient in fo rmation to do so and it is unlikely that a single model w ould suit all jurisdi ctions and circumstances. Best practi ce principles T he followin g principles are widel y recognised by Australian governments as best practice in gove rnm e n t admini stration and regulation making. (From ORR 1998, Audit Office of NSW 1997). • Cl early defined objectives. • Avoidan ce of sha red responsibility . • Transparent pro cesses. • Adequate communication and co nsultatio n for community acceptance

• Clearly defin ed regulato ry objectives • Id entification of regu latory alternatives. • Benefit- cost assessment of all proposals. (resources may be wasted in developing and complying w ith a regulation that does no t achi eve its intended purpose). • Flexibility (Regulations sho uld fo cus on o utcomes that are co nsistent with the regulatory objectives, bur should be sufficientl y flexible to allow different mea ns o f compliance that are cos t effective) . Background: Drinking water guidelines and standards

Drin king water quality guidelines and standards are set for microbiological , chemical and radiologica l contaminants, as well as physical characteristics such as odo ur, taste and clarity. Guidelines and standards establish quantitative limits or values fo r individual drinking water contaminants. In the case o f chemi cals, these values generall y rep rese nt th e concentration o f a co ntaminant that w ould no t resul t in any significant risk to health if consumed over a life tim e. H owever, no t all indi viduals bene fit equ ally, as some groups, particularly those who are immun o- compromised , require higher quality dri nking water t h an o th e rs in th e com munit y . Guidelines and standards are promulga ted b y th e N atio nal H ealth and M edi cal Research Co uncil (N HMRC) and Stare and T errito ry governments respectively. • Guidelines are non - enforceable , with discretionary compliance. Th ey may be adopted as goals to be achieved o ver tim e.

Uiiter treatment costs can be expected to increase • Standards have th e fo rce of law, must be complied within a spec ified timeframe and are usually backed by penalti es fo r non-complian ce. • Guid e lin es ma y also diffe r fr o m standards in the way they are established, w it h no form al requirem ent for a R egulato ry Impact Statem ent.

WATER JULY/ AUGUST2000

49


BUSINESS

KEY DIFFERENCES BETWEEN COUNTRIES The benchmarking revealed that Australia, along with most of th e other countries benchmarked , is unlikely to be at best practice in the regulatory assessm ent of drinking water standards. • The Australian Guidelines are based mainly on scientific assessm en t. fn contrast, the US Environmental Protection Agency (US EPA) is required to undertake detailed benefit cost evaluation of its regulatory proposals, which it p ublishes. • Standards are promulgated in Australia using a variety of quasi- regulatory instruments, under which legal responsibilities are not always clear and rigorous assessm ent is lacking. In other countries, national legislation is the norm. • In the US and EU, standards are promulgated in national legislation. In Australia, C anada and NZ, guidelines are developed at the national level and are promulgated - sometimes as standards - at a State, provincial or local level. • T he regulations in Austra lia are not as strictly enforced as i_n France, ~he UK and US and there is often no separation between the agencies responsible for promulgation and enforcem ent. • In France, the UK and US , where private sector involvement in water supply is greater, regulators have th e legal power to impose substantial penalties for noncompliance. • Self-reporting of compliance occurs in all o f the countries studied including Australia, but test results are more closely monitored overseas.

Over the last twenty years the stri ngen cy of dri nking water standards in developed countri es, including Australia, has increased considerably and their scope has widened . This has been in response to in creasing contamination o f source water in some areas, combined w ith a greater understandin g o f the effects of m icrobiological pathogens on health. D eve lo pm en ts in the sc ien ce of detecting contam inan ts and im provem ents to technolo gy to remove them as well as an increase in co mmunity awaren ess and demand for clean er water - have also played a role.

The need for flexibility in implementation is recognised.

It is estimated that $400 mill ion is spent ann ually on wa ter treatm ent in Australia. If a higher level o f water safety is desired , costs could be exp ected to in crease. Any degradatio n of source water cau sed by human activity is also likely to result in higher treatm ent coses. Addition al trea tme nt fa cil it ies can in volve large capi tal expe nditures. Fo r exampl e, it has been estimated that up to SSOO mi lli on would be requ ired to filter all of M elbourne 's wate r. Indu stry leaders consulted by the C ommission 50

WATER JULY/AUGU ST 2000

observed that consumer confidence in the safety of Australian d rinking water has decreased, even tho ugh there is very little evidence o f deteriorating quality or

adverse health effects. (The 1998 Sydney w ater crisis is likely to have contribu ted to such loss of confidence). Broad regulatory approach

The re are signifi ca nt differen ces am.on g countri es in the approaches to se ttin g, p romul ga ting and en fo rcin g standards, refl ec ting a divergen ce in regulatory processes or philosophy. In Au stralia, a 'light- handed ' regulato ry approach has evolved, w ith water suppliers cooperating with governmen t bodies. This approach results in lo wer compliance costs by p roviding grea ter flexibility to set standards according to local circumstances, particularl y the co st of treatment. However, there may also be less certainty of compliance and less tra nsparency and accountability. The NHMRC is the expert technica l bo d y that d evelo ps Au strali a's Drinkin g W at e r Gu i del in es . Th e Guidelines include lists o f recommended maximum. values for contaminants, as well as informatio n on water quality n1.anage111ent practi ce and monitoring. Guid eli ne valu es are the m aximum reco mm e nd e d c once ntr ation o f a c onta minant de e med un li k e ly to

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produ ce an adverse health effect. The status of t h e Aust ra li an G uidelin es is o ften misu nderstood. Th e values listed in the G uidelines have no binding status . In practi ce, most suppliers try to comp ly with a version of the Guidelin es, although not necessarily the m ost recent. The N HMR.C ac knowl edged in the 1996 G uid elin es th at water qu ality improvem ent works may have to be phased in gradualJ y over a number of years. In effect, this introduces £l exibility to acco mmodate variations in the quality of source water, and the fi nancial capacity of lo cal co mmuniti es to meet the costs. Similar regional variatio ns and constraints are recognised overseas. Under Australia's Consti tution , water quality is a State and Territo ry responsibili ty. Consequently , th ose jurisdictio ns d e t e r min e whether and h ow th e Gu idelin es are to be im pl em ented. M ost j urisdictio ns, consisten t wi th the NHMR.C's approach, have viewed the G uideli nes as long term goals - to be adopted as en fo rceab le standards as qu ic kl y as poss ible. T his has led to considerable di ffere nces in regulation and wa t er qua li ty across Australia. Versions of the Australia n Gu idelines ha ve bee n adopted in som e jurisdictions as en forceabl e sta ndards without regulato ry assessment, usin g a variety of quasi-regu latory instrum ents such as operating li ce nces and m em oranda of und ersta nding (Ta ble 1). From a nationa l perspective, impleme n tation loo ks hap haza rd, bu t th e resulting varia tion in water quali ty ca n be expected to re£lect loca l circumstances and pr e fere n ces t o some extent. N evertheless, differences in the quali ty of

Table 1 . Guidelines promulgated as enforceable standards Jurisdiction

New South Wales

Victoria

Queensland

Supplier(s)

Sydney Water

NHMRC 1996

NHMRC 1996

Hunter Water

NHMRC 1994

NHMRC 1996

Wyong Shire Council

NHMRC 1 996

Gosford City Council

NHMRC 1996

Non-metropolitan suppliers

NHMRC 1997 & 1996

Melbourne Water

NHMRC 1987

City West Water

NHMRC 1987

South East Water

NHMRC 1987

Yarra Valley Water

NHMRC 1987

Non-metropolitan suppliers

WHO 1984

South East Queensland Water

NHMRC 1996

Western Australia Water Corporation South Australia

Enforceable Standard• Guidelines Achievedb

NHMRC 1987

SA Water

NHMRC 1996

United Water

NHMRC 1996

Riverland Water

NHMRC 1996

Tasmania

Suppliers of potable water

NHMRC 1996

Northern Territory

Power and Water Authority

NHMRC 1 987

Australian Capital ACT Electricity and Water

NHMRC 1996

Territory • This is the Gu ideline version that is generally adopted as a standard by governments. b

This is the Guideline version currently met by water suppliers. These are nonenforceable and t here is discretion in com pliance.

water across the co u ntry may prove to be con tentio us in th e future un less the publi c understand the reasons. In Australia and overseas, there are protocols fo r dealin g with publi c hea lth problem s once they have been de tected. These protocols provide a m echanism for addressing system fai lures. Th ey are an acknowledgment that it is un realistic and imprac ticable from a tech ni ca l and econo mi c view point to ensure that standa rds are always met. T he acceptance o f poss ible system fai lures mi ght also imply that th e co nsequ ences of the resid-

BENEFIT-COST ASSESSMENT UNDER SCIENTIFIC UNCERTAINTY • The lin k between clifferent drinking water standards and health outcom es is not well understood . T he evidence supporting such linkages is m ainly inferential, often derived from animal exp eriments at dose rates that are unlikely to be encountered by humans in drinking water supplies. • Uncertain ty provides no excuse fo r not identifying and, w here possible, evaluating the benefits and costs of standards; or con versely, for not implem enting standard values for certain contaminants. Indeed, the evaluation of the ben efits and costs with in an assessment framework can ma ke the limitations imposed by uncertainty more explicit. • That said, taking a conservative approach to ~ctting standard valu es witho ut a be n efit cost evalu ati on - through the adoption of safety factors, for exa mple m ay be necessary when knowledge about even ts and effect~ is particularly limited. • The precautionary approach to environm ental heal th management recognises tha t policy must always be of a provisional nature, pending the resu lts o ffur ther research and information. Thus, research and information should be seen as tools fo r reduci ng un certainty and improvin g decision making.

ual ri sks are not considered to be serious. T his approach mea ns that the public bears so me risk that not all drinking water hazards can be foreseen and that th ere may be (rare) fa ilures in the detecti o n and treatm ent of co ntamin ants. How standards are set

Id eall y th e processes followed to arri ve at standards (maximum leve ls of contaminants) should include sc ientifi c assessm en t, eco nom ic eva lu ation and consul tati o n. T he exte nt to wh ich all three processes are undertaken di ffers am o n g co untri es. ln Au strali a, the N HMR.C is responsible for sc ientific assessm ent and h ealth sp ecialises and practi tioners from governme nt-owned water su pply authorities throughout the country assist in the ongoing development of th e G ui deli nes. R isk assessment procedures are used to evaluate health hazards in drinking water. In doing so, the N H MR.C se ts its guidelines at levels judged to represent an 'acceptable risk '. Most countri es, including Austra lia, rely heavily o n existing assessm ents by the World H ealth Organisa tion. In contrast, th e US develops m any of its own st and ards usi n g th e co n s id e rabl e resou rces of th e US EPA. State and Territory governments do no t appear to subj ect the NHMRC's guidelines to rigorous economic assessm ent wh en adopting them as sta ndards WATER JULY/A UGU ST 2000

51


BUSINESS

NEW ZEALAND'S WATER SUPPLY GRADING PROGRAM {f rom ONZPCE, 1996) New Zealand water quality is graded by the Ministry of H ealth for the purpose of: â&#x20AC;˘ assessing w hether a pa rticular drinking water supply consistently delivers a safe w holesome product ; and â&#x20AC;˘ ensuring that co mmunities are provided with reliable information about the quality of their water supply. The grading system assesses separately the source and treatment part of the water supply system, as well as the distribution system . A two letter grading is designated, such as Aa, Cb, Ed. The capital letter (A 1, A, B, C, D or E) represents the grade of the water coming into the zone (source quality and treatment) while the lowercase letter (a, b, c, d, or e) indicates the quality of the water received at the co nsumer's tap. Both gradings are presented in the R egister of Community Drinking-Water Supplies in New Zealand, which is accessible through public libraries. The description of th e grades for source and treatment is as follows: Al Completely satisfactory, negligible level of risk, demonstrably high quality A Completely satisfactory, very low level of risk B Satisfactory - low level of risk C Marginal - moderate level of risk D Unsatisfact01y - high level of risk E Com pletely unsatisfacto1y - very high level of risk The evaluation of the distribution system uses a system of demerit marks fo r factors in the distribution of the water supply which adversely affect, or put at risk, the quality of the distributed water. The description of the distribution grading is similar to the source and treatment description and uses letters a to e, with the smallest n um ber of demerit marks receiving an 'a' grade . despite inter-govern mental agreements that this sho uld happen w ith all regulati on making. H owever, .in the US, under the more stringent regulatory approach, benefit-cost evaluation is mandated. W ithout economic evaluation o r an appreciation of risk preferences, it is difficu lt to determine the level of resources that should be devoted to water qua li ty. That said, benefit-cost analysis in this area is not stra ightforward, partl y because of scientifi c uncerta in ty c once rn ing th e relationship between standards and health outcomes Consultation helps to ensure that standards are effective and efficient. In Australia, consultation by the NHMRC is main ly with hea lth and water quality experts. Although this is true of most of the coun tries studied, the US has very con1prehensive processes that examin e both techn ical and economic issues. Consumers have the right to information about risks. Co mpared with some ove rseas co untri es, Australian co nsumers receive relatively littl e information on risks, expected changes to h eal th outcomes and costs. Consequentl y, there is no basis for communicating their preferences when guidelines or standards are developed. With greater transpa rency, water suppli ers are more effectively accountabl e fo r their p e rform an ce. Also, 52

WATER JULY/AUG UST 2000

consumers are less suscep tible to 'scare campaigns' about the safety of drinking water. New Zealand and the US we re fou nd to be leaders in providing readily understood consumer information on water quality. The NZ system of grading water quality and providing a broad indication of risks is outlined in the box. Promulgation and enforcement

The institutiona l arrangements for promulgating and enfo rcing standards differ among cou ntries. In the US , the EPA promulgates stand ar ds on a national basis, whereas in Australia and C anada, standard promulgation is the responsibility of State (and T erritory) and Provincial governments respectively. In France, the UK and US, central governmen ts retain a stron g role in regu lation, even w here enforcement fun ctio ns are devolved to State or regional levels. The opposite is tru e in Australia, New Zealand and Canada . T here is institutional fragmentation with in jurisdictions in promu lgating and enfo rcing standards in Australia. H ealth departments, w ater reso urces departments and the water supp liers are

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BUSINESS

REGULATING WATER QUALITY REQUIREMENTS IN AUSTRALIA State and I erntory governments have taken diverse approaches to comnuttmg w ater suppliers in their jurisdictions to the Australian Guidelines. In most cases, governments ha ve used quasi- regulation such as operating licences, charters, m emoranda of understanding and customer contracts. The instruments employed vary not only between States and T erritories, but also w ithin som.e j urisdictions. O ften som e combination of these instruments is employed. O ne jurisdiction (South Australia) has comm ercial contracts with the private sector, while three other jurisdictions (Queensland, ACT and NT) currently have no regulatory requirem ents in place.3 Jurisdiction

Supplier(s)

Instruments

New South Wales

Sydney Water and Hunter Water Wyong Shire Council Gosford City Council

Operating licence, memorandum of understanding, customer contract Water supplier business plan City Management Plan

Victoria

City West Water, South East Water and Yarra Valley Water Melbourne Water Non-metropolitan suppliers

Operating licence, Health (Quality of Drinking Water) Regulation 1991b, Customer contract Memorandum of understanding Memorandum of understanding

Queensland

South East Queensland Water .

No regulatory arrangements in place

South Australia

SA Water United Water Riverland Water

Charter, performance agreement Commercial contract Commercial contract

Western Australia

Water Corporation

Operating licence

Tasman ia

Suppliers of potable water

Public Health Act 1997 ¡ Guidelines for Water Quality

Northern Territory

Power and Water Authority

No regulatory arrangement in place.

Australian Capital Te rritory

ACT Electricity and Water

No regul atory arrangement in place.

s

The ACT is about to introduce a Code of Practice.

b

Regulations establish monitoring arrangements only.

all involved. T his sharing of responsibi lity poten tially lessens accountability for public health ou tcomes. Moreove r, drinking water standards are ofte n established in Australia through instrum en ts that are not scru tin ised th rough normal parliame ntary processes . An adva ntage of operating licences and m emoranda of understa nding is that they are easier, and less costl y, to cha n ge as c ir c um stan ces alt e r. H owever, there is unce rtainty about the legal force of these instruments and th e obligations that they impose. In addition, the process of 'referen cing' sta ndards in ope ratin g li ce n ces or m en1oranda of understanding does not provide for the sam e level o f transparency and accou n tabi li ty as that achi eved in countries where standards are set o ut in regul ation. Au stralia and m ost o f the other cou ntri es studied ma ke provisio n for the enforce m ent o f drinkin g wa ter sta nd a rd s. H owever, e nfor ce ment

mechanisms in the US and UK are much stri cter, and larger penalties are ap plied w hen non -complia nce occu rs. Approa c h es to m o ni tori n g and e n fo r ce m ent usual l y depend on w hether standards are backed by th e fo rce of law, and w heth er there are assoc iated age nci es respo n sible fo r e nforc eme nt. In Australia, governme nts typically rely on coopera tion between State H ea lth Departments and govern men t-ow ned wa ter suppli ers. Australian go vernm ents al so rely on se l f- r ep o r ti n g by th e indust r y . Although similar approac hes are used in the UK and the US, in Australia there do not see m to be the processes in place to scru ti ni se the information provided to the sa m e degree. Suppliers in most Australian j urisdictions, and in the benchmarked cou ntries, are required to repo rt instances where sta ndards are significantly exceeded. W hen this occurs, they are required to take ac tio n to miti gate risk. In Australia,

however, sanctions for non-co mpliance are generally not imposed and there is more scope for administrative discretion about compliance. Findings and policy issues

The benchmarking revealed that the regulato1y assessment of water quality standards does not satisfy importan t best practice criteria in most co untries, including Austra lia. An exception is the US, wh ich consults widely and has a very transparent process of rigorously assessing standards . T he overall findings and some o f the issues arisin g o ut of chis study are ou tlined in the 'Key Messages'. The benchmarking results suggest that there is scope co inject greater ri gour int o Au stralian regu lat ory processes for establishing and enfo rcing drinki ng water standards. Th is would be particularl y importa nt if there were proposals for new standards requiring substantial in vestm ent in new wa ter treatment facilities. Of partic ular importance is to assess whether th e cooperati ve approach is the m ost effec ti ve means of ac hi eving efficient outcom es. Also, whether the relati ve emphasis on o utput (maxim um leve ls of contamin an ts) and process regulation (requirements to have quality assured risk management plans) is effecti ve and efficient. 1n Australia , compliance costs are lower and there is greater flexibili ty co sec standards according co .local circumstances. H owever, there is Jess certainty about whether co mpliance has bee n ac hieved and in stitution al responsibili ties rema in unclea r compared with overseas regimes. The 'righ t' balance between specifi c regu lation and gene ral consum er protection law is also important. This is best resolved by assessin g regulatory options as part of the regula tory assessment process.

Broad community consultation is relatively limited in Australia as is risk communication. Moreover, the current approach to standards settin g in Australia, w hich appears to be predica ted on government ownership, may not be sustainable if parts of th e industry undergo further restructuring and co mmercialisation, or WATER JULY/AUGUST 2000

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even privatisation. For example, the public would be likely to expect governm ents to take a more formal approach to regulation and mon itoring with private ownersh ip. With greater p rivate sector involvement, greater specificity would also be necessary. For example, the extent to w hich som e standards are to be met over a perio d of time would have to be precisely specified to ensure enfo rceablity. Evolving technology poses new challenges

The development of new co ntam inant detection techniques and treatm ent tech nologies crea tes a number of additiona l c hall en ges. For exam ple, there is some industry conc ern that extensive training would be required to up grade co mpete n c ies of st aff to operate some new tech nologies. Also, there are understandable co m111ercial ince ntiv es for developers of new technology to push for more stringent standards that make use of their equipment. In the absence of information to assess w hether it is cost effective to increase standards, th ese pressures may be hard to resist . Institutional arrangements could be improved

A key req uirem ent of reform in this area, as in others, is to establish effective institu tional structures and appropriate objectives. The thres hold institu tional issue in Austral ia is the respective roles and responsibili ties of the NHMRC and the State standard setting b odies. R espo n sibili ty for d r ink ing water regulation is effectively shared between t he N H MR.C and th e States an d T erritories, when N HM R..C guidel ines are adopted as standards witho ut formal regulato ry assess men t. Shared responsibility makes it d iffi cult to apportion respons ibility fo r poor outcomes. T he NHMRC's role shou ld complem ent the State and Territory responsibility fo r setting w ater qu ality stand ards and administerin g public health. Specifically, o ne of the NHMR..C's objectives in developing th e Australian Gu id elines sho u ld b e to re in force State an d Territory responsibility for the rigorous assessment of standards. T he N H MRC sho uld continue to pla y an important role in pro viding scie n tific advice. Ho weve r, th e N H MRC gu ide lin es would be j ust one, albeit importan t, input in to the regulatory assessment process und e rt aken b y State and T errito ry gove rnments. 54

WATER JULY/AUGUST 2000

R egulatory authorities need to be adequately resourced to maintain their independence and have po wers that enable them to obtain information . A greater commitment of expertise and resources is lik ely to be req uired. Overseas agencies appear to allocate significa ntly 111ore resou rces than is cu rrently the case in Au stralia. For exa mple , Washington State, wi th a comparable populatio n to N SW, has 80 to 90 people em ployed in th e dri nking water program. The wa ter unit ofNSW H ealth has a staff of four. T here is a need to ensure that health risks from contaminants are addressed in the m ost effective and effic ien t way across all possible sources·, in cluding those from hazards other than water. Above all, there is a need fo r a well in form ed public debate about how safe drinking water should be and consultation o n h ow mu ch consu111ers are willing to pay fo r grea ter safety.

Key Messages • Th e study has revealed approaches to developing, and enforci ng standards, Australia and across the coun tries.

a diversity of prom ulgating both within bench marked

• In Au stral ia, as in most of th e countries examined, there is co nsid erable scope to improve these processes. In Australia, relatively little resources are e111ployed. • Apart from in th e United States, benefit-cost ana lysis is rarely used . • In the abse nce of rigorous regulatory assessm en t, it is difficult for autho riti es to fu lly justify existing standards, w hich vary across and with in jurisdictions. It is difficult to make so und decisio ns on investm ents in the face of pressures to adopt new tec hnology. • An increase in standards will requi re signifi cant add itional investment. Th e resulting costs to consumers will be relatively larger for smaller comm unities. • There is a dearth of information on the quali ty of drinking wa ter in different parts of Australia and the acco111pan ying risk levels. Such informatio n is needed fo r effective community consultation to ensu re that sta ndard s are appropriate. • D ivid ed responsibilities for wate r qu ality regu latio n ca n diminish accountab ility.

Drinking Water Research. American Waterworks Association. ISSN 1055-9140. US$50 for six iss11es. T he recen t issue, Volume 10, Numbe r 3, May / J une 2000 su mmarises the results of a study on m ethods for removing Arsenic and disposin g of residuals. The study was consequent o n the probable promulgation o f a m aximum contaminant level of 5 m icrograms per litre in J u ne. It has also been estimated that this will cost the USA some 1.3 bi ll io n do llars for g round wa t er systems, bu t this is j udged to be a proper balance against the health risks. T his may still be the most costly MCL that the US water supply community has encountered to date. Other re ports include bi ofi lm growth factors, enhanced coagu lation and eva luat ion of ozone and PEROXONE.

Wast ewater Treatment Systems. Modelling, Diagnosis and Control by G11staf O lsson a11d Bob N ewell is a fact11al a11d logical text from IWA Publishing ill UK. T h is book explains clearly ho,v plant operators and engineers can model and control the operation of the BNR process to improve operati onal efficiency for th eir plant. Mathematical form ulae arc also introduced simply so that they appear nonthreatening to those less comfortable w ith numbers and equations, particularly as they relate to bio logical reactions, breakdown p rocesses, kinetic, variable hydraulic conditions . Detection of a problem, defi nition or d iagnos is a nd m anage m ent ar e addressed including examples such as an abnorma ll y slow flow rate, slowness in recognising problem situations, equipment failures. There is also a collectio n of MATLAB programs and funct ions that are mentioned throughout the book. T he MATLAB programs and WWT toolbox that accompany the book can be downloaded free of c harge from t he lWA Website. www.iwap.co. uk/ books/ books.hrml IWA Publishing is a new source for AWA Bookshop and the publications selected, like this book , are technica lly detailed b ut clearly laid out and practical in orientation. Dr Diane Wiesner, AWA Bookshop

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Water Journal July - August 2000  

Water Journal July - August 2000