Water Journal May - June 2000 by australianwater

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Volume 27 No 3 May/ June 2000 Journal of t he Australian Water Association

Editorial Board F R Bishop, Chairman B N Andmon, P Draayers, W J Dulfer, G Finl.iy,on , G A I Jokier, M Kirk. B L1bz,1, M Muntisov, N Orr, P Nadebau111, J D Parker, M Pascoe, A J Priestley. J P.. issman. F Roddick. E A Swinton

CONTENTS

·, Water is a refereed journal. This symbol indicates tha t a paper has been refereed.

Submissions Submissions should be made to E A (Bob) Swinton, Features Editor (see below for details).

General Editor P et er Stirling PO Box 84, H ampton Vic 3 188 Tel (03) 9555 7377 Fax (03) 9555 7599

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

4 Pleasant View Crcs, Wheelers Hill Vic 3150 Tel/Fax (03) 9560 4752 Email: swintonb@c03 I .aonc.net.au

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Water (ISSN 0310 · 0367) is published in January, March , May, July, September and November.

Australian Water Association Inc AR.BN 054 253 066

Federal President Allen G ale

Executive Director C hris Davis

AWA ·1"'>

INDUSTRY

Subscriptions Water is sem to all AW A 111e111bers six times a year. It is also available via subscription for SSO a year.

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PEOPLE

WATER The Need for a New ICM Model ..................... .............. ........................... .... L Bou!Jy ·, Cryptosporidium and Campylobacter in Drinking Water Supplies Part 1: Estimation of Numbers Present .. .. .. .. ... ... .. .. .. .. .. .. .. . .. .. .. .. .. .. ... .. . .. .. .. .. . Part 2: Estimating the Incidence of Infection and Illness .. .. ... .. .. .. . .. . . . . .. . .. .. P Nadebaum, K Walsh and D D eere Small Water and Wastewater Systems .. .. . .. .. .. .. .. . .. .. . .. .. .. .. . .. ... ... .. .. .. .. . .. .. .. Report by M Leake

36 44

WASTEWATER ·, Effluent Irrigation of Sugar Cane - Who Pays, Who Gains? .. ... .. . .. .. 46 EA Gardn er, LE Brennan, SN Lisson and AM Vieritz

AUSTRALIAN WATER ASSOCIATION

Australian Water Association (AW A) assum es no responsibility for opinions or statements of facts expressed by contributors or advertisers. Edito1ials do not necessarily represent official AW A policy. Advertisements are included as an infonnation se,vice to readers and are reviewed before publication to ensure relevance to the water environ111cnt and objectives of AW A. All material in Wnrer is copyright and should not be reproduced wholly or in part w ithout the written permission of the General Editor.

VIEW

Interview: Jeff Wright .. .. .. .. .. .... .. .. ..... .. .. .. .. .. ... .... .. . .. .... .. . .. .... .. .. . .. .. ...... .. .. ... .. .. .. 5 Stockholm Junior Water Prize ................................. .. ......... .. ............ .......... 10 R eport by R. Curti n Young Water Scientists 2000 ............. ................... .. ........ .. ........ .. ................ 15 Report by EA (Bob) Swinton The World Water Congress .. .. .. .. .. .. .. ... ... .. . .. .. .. .. .. .. .. .. .. .. ... .... ... .. .. .. .. ... ... .. .. . .. . 18 R.eport by EA (Bob) Swinton Enviro 2000 Sparked with Energy and Enthusiasm ...... .. .. .. ..................... 23 R.eport by D H ope

Ill...

The Australian Urban Water Industry - Where Does it Sit? .. .................... 8 D Evans

Features Editor EA (B ob) Swinton

POINT

ENVIRONMENT •, Australian Water Resources Assessment - 2000 .. ... .. .. ... .. .. ... .. .. ... .. .. 52 WS McDo nald, C L Cre igh ton , PD Erlanger BUSINESS ·, Regulatory Standards for Water Outages - A Pipe Dream? .. .... .. ... . 58 K Young

DEPARTMENTS Aquaphemera .. ... .... .. .. .. ... ...... .. .. .. ... ........ .. .. .. .. ... .. ..... .. .. ... .. .. .. .. ... .. .... .. .. .. .. .. ... .... . 2 Book Reviews ... ............................... .. .... .... ....... .. ....... .. ....... .. ......... .... .... .......... 62 Membership ... .. .. .... ..... ...... ... ..... ......... ............................................................... 63 Meetings ..... ... ........... .. ............................... ....... .. ....... .. ...... .. .......... .. .. ....... ...... .. 64 OUR COVER: The rnviro11111cntally da111aging i111pact of land clearing is starkly cvide11f in the cover photograph of a property near Bcve11dale i11 the Upper Lachla11 Catch111e11t area in southern central Ne11, South Wales. Re111oving the vegetation has triggered heavy erosio11 throughout this localised sub-catch111eut, a prob/c111 which has been co111poun ded by the rising saline waler table ,vhich has killed the trees. Photograph cou rtesy of Ke/ La11gfield of the NSW Department of Land and Water Co11servatio11.

FROM

THE

PRESIDENT

The Education Unit I was very pl eased wh en , at our last Fede ra l Counc il meeting, a proposal from Rod Lehmann (Directo r, Water Po li cy and Technology), to establish a National Water Education Uni t, was adopted. AWA has dabbl ed in e du ca tion up to now, producing th e Teach er's Resource CD, taking pa rt in the Canbe rra ex hibition for National Scie nce Week, and runni ng the Stockholm Junior Water Prize in Australia . Each of those initiatives has been worthy in its own right, but the sum total has not made a great deal of diffe rence to water education for Australians. Th e Apri l decision marks a sea change. It has m any of its roots in Queensland. Our Qu eensland I3ranch, under the energetic and enthusiastic leadership of Jenifer Simpson, has been working on a suite of water in formation resources (funded by the N atural H eritage Trust and due for release about now). Th e same l3ranc h un de rtook to produce an interactive display about water, so housing the proposed Educa tion Unit in the sam e Brisbane office makes good se nse. W e have noticed over the years that an erstwhile national network among water educators, which probably hit a high spot with a Âˇworkshop in Fremantle in 94, has gone th e way of many good initiatives in th e face of managerial ism - starvation - because it is a net cost to o rganisations . M any AW A members, though, have noti ced that making decision s abou t water in Australia (big and small) is bedevilled by th e fact that many aspects of water and o ur erratic rainfall are not understood by the community. The only way to counter that ongoing problem is to ensure that good, impartial information abo ut water is made available to the general public, users and, most important, children. Fragmented efforts by individual organisations to assemble and deliver information resources arc doomed to failu re, fo r all except th e most well-resourced enterprises. A collaborati ve effort, using shared resources, is the o nly way to succeed. Our recent name change seems to have increased our chan ces of success; as the broad-based, Water Association , our credibility is hi gher th an it was as AWW A, beari ng urban and 'dirty water' overtones. P otential partn ers are thus quite ple ntiful and the prospect of wo rkin g together with th e massive W aterw atch netwo rk is reall y quite excitin g . The In stitu tion of Engineers Australia is another potential partner, with w hom we have lo ng ties and many co111mon m embers. I particu larly like th is project because it will help to achieve two goals that I identifi ed for my term as Presiden t of AW A 2

WATER MAY/JUNE 2000

Allen Gale

workin g 111ore collaborati vely w ith other groups an d increasin g the profile of AWA. Undoubtedly, a successful education network is going to de111and and create a lot of co llabora ti on . Given th e vacuum in the area, there is no prospect of co111peti tio11, nor vvould it make sense. We'll have to w ork hand-i n-glove with a wide range of stake holders, from teacher's associa tion s and education departments, through to governments and all the other waterrela ted associations and research establishments. At the same tim e, A WA's presence as a facil itator of water education , and our branding on many of the resources, wi ll make m any more people aware of t he Assoc iation and its goals. W ho knows together w e may bring about some good results on the natio nal water front. Of course, an initiative like this takes vision. Clearly several of our members have vision, as the Queensland initiatives have demonstrated. It also takes partnerships and th ere seem to be good candidates for those. Money is needed, of course, and as [ write we are searching for fundin g sources that can und erwrite the first year of operatio n, unti l the Unit becomes selfsustaining. Finally, however, it needs a passionate, energeti c and entrepreneurial teacher who can take up the challenge, run the Unit, create the national network among edu cators and make it all happen. As soon as funds have hit the risk thresho ld, we w ill be out searching for that key person and , 1 hope we can say in five yea rs tim e, the rest will have been history.

Allen. Gale

Aquaphemera Which nation uses th e m ost water per head of population? T he answer to this qu estion is fraught w ith probl ems of definition, reliability and availabi lity of data. However, it emerged at the World Wate r Conference in M elbourne that Australia is a likely candidate as th e 'biggest' user. Australian average annual data on wa t e r use h as not be e n seriously assessed since the ea rly J980s, but despite this appall ing lac k of data the pattern of use is undispute d. C lose to 80% of nationa l water us e is in the agricultural sector, overw helmingly dominated by irrigation. T h e use of the remainder is approxi m ately equally di vided betwe e n t h e d omes ti c a n d commerc ial / industrial sect ors. Spatially, som e 60% o f to tal nationa l wate r use is in th e Murray Darling Basin (MBD) and approximately half of that water is appli ed to pasture. Thus, of total average annual water use in Australia som e 30% is used to water grass in the MDB , and that excl udes crops such as lu cerne! I am loathe to add to these global compa risons but it is very likely that Australia uses a larger proportion of its water to irrigate grass t h an any other nation . Australia may be the 'biggest' water user per h ead but it is certainly not o ne of the 'best' users. Notwithstanding the lack of a good data base, most of the irrigation of pasture in the MBD still employs fl ood irrigation techn iqu es, long since abandon ed in many Third World co u ntries. These are ineffici ent in terms of quantity and have adverse effects on the salinity of soils and waters. Austral ia' s wate r r es ourc e problems are those of quality not quantity . What is ur gen tly required is better managem ent. Compe tition policy will e nsure that water w ill be diverted from those irrigators w ho still us e ineffi c i e nt and wasteful techniques to higher value uses. Happily , water for drinking and domestic use w ill never be a major limiting factor in t h e 'l ucky country'.

Dingle Smith

WATER

CRYPTOSPOR/0/UM AND CAMPYLOBACTER IN DRINKING WATER SUPPLIES Part 1: Estimation of Numbers Present P R Nadebaum, K Walsh and D Deere Abstract As pa rt of a C oo pe rative R esearch Centre fo r Water Q uali ty and Treatm ent Program 1 (H ealth Ri sk Assessment) P roj ect, m on itorin g data obta ined by Australian water au thoriti es relating to Cryptosporidi11111 and Camp ylobacter in drinki ng wate r supplies w e re re viewed and assessed co de te rmin e how t he in fo rmation shou ld be in te rp ret ed. Th e monitoring data usual ly consisted of " non detect" resul ts, w ith th e occasio nal po siti ve r esu lt, and c an be hi g h ly variable. Ofte n t he mon itoring info rmation w ill pertain only to the so urce wa ter b efo re treatm ent, and key informatio n such as th e infectivity of the organisms to humans is unlikely co be available. Because o f these facto rs, pa thoge n monito1ing data sho uld be viewed in ce1111s of providing an indicatio n of the presence of co ntamination and the general m agn itude o f the nu mbers of organ isms that are likely to be present, rather than precise results. It is impo rtant to apply j udgm ent w hen interpreting the results, particularly as co w heth er o rganism s detected are likely to be viable and infective. P art 1 of chis paper o utlines the fa c tors in volved in estim ating the nu m bers o f organisms present . Part 2 o u tlin es how information o n the numbers of o rganisms presen t ca n be used to determin e

bo rn e o utbreaks o f gastro enteritis (T e uni s

the level of risk w ith regard to in fectio n and illness in th e com mu n ity.

et al, 1997; Lun d, 1996) .

Introduction Cryptosp orirl i11111 (protoz o a) and Ca111pylobacter (bacteria) arc pathogeni c m icro organism s associated w ith gastroenteritis. T hese o rgan ism s can be t ransmitted via a num ber o f ro u tes, incl uding th e co nsumpti o n of co ntam inate d w ater. Concentrations of Cryptosporidi11111 and Ca111pylobacter approac hing the li m its of detec tio n of curre nt analytica l m e thods have bee n reported co result in water-

:l?

~ ~ ~

;; z

0 C

~ ~ ~ Al

Cryptosporidium oocysts stained using a fluorescein-conjugated monoclonal antibody.

All warm blooded animal species arc pro ba b ly capab le of becoming in fec ted b y o n e o r m o re stra i ns o f t h ese pathogens, alth ough the stra ins infec ting an ima l species are not necessarily in fe ctio us to h umans. N ot surprisin gly th en , mo ni to rin g resul ts sho w t hat t h ese m icro o rga nisms are peri odically fo und in wate r suppl ies in Australia. Beca use of the ir o cc urre nce and significa nce, t hey have bee n sel ected for th is stud y fo r the pu rposes of illustrating issues relate d to th e in te rpretatio n of m o nito ring results for th e tw o classes of o rganisms, p rotozoa and bac teria. At the present time there is great un certainty regard ing the relatio n sh ip between m o nitoring results fo r o rgan isms in drinki ng w ater and the health o f the consun1er populatio n. Clear guidance is no t available for vvater authorities concen1in g the interpretation of m onitoring results and the appropriate correspondi ng ac tio n required to m.i nimise the likel.ihood of po tential illness in the comm unity . [n order to improve under~tan<lin g o f the significance of Au stralian pathogen monitoring data fo r w ate r supplies an d to w ork cowa rds ac hieving a co nsensus p ositio n o n how the risk of illn ess associCryp tosporirl i 11111 a nd a ce d w i th WATER M AY / JUNE 2000

WATER

Table 1: Summary of tests used by water suppliers (1991-1998). Type of test

Observation Counts or P/ A

Detects genus

Detects species

Indication of viability

What must be assumed to have been in the sample to give a positive result

Historical frequency of use of use scale of 1-5

Campy/obacter

Growth in broth

P/ A

Yes

•

1 viable Campylobacter

Growth in broth followed by genus level DNA PCR

P/A

Yes

•

1 viable Campylobacter

Growth in broth followed by DNA PCR for speciation

P/A

Yes

• •

1 viable Campylobacter 1 viable Campy/obacter the species identified

***** ** *

Cryptosporid/um

Microscopic examination of antibody (IF) labelled oocysts (with or without f low cytometry)

Counts

Yes

•

the count of Cryptosporidium oocysts (dead or alive)

Microscopic examination of antibody (IF) labelled oocysts followed by FISH

Counts

Yes

•

the co unt of Cryptosporidium oocysts (dead or alive) the count of oocysts that are both viable and C. parvum.

•

rtPC R of oocysts purified from water

P/ A

Ca111pylobacter should be estimated, a review of the assumptions underl ying th e estimation of risk has bee n carri ed o ut unde r a proj ect with th e C R C for Wa te r Quality and T reatm e nt. R epo rts we re prepared on th is work, and these were internati o nally p eer rev iew ed during the Cryptosporidi,1111 i11 vf/a ter con fe rence in M elbourn e (1998) (An o n , 1998) . Thi s p ap e r summari se s t h e 6ndings of this work , and su ggests how wate r supply m onitoring info rm ation fo r Cryptosporidi11111 and Ca111p ylobacter ma y be interpre ted. It is hoped that this paper will clarify som e of th e issues, and will assist the Australian water industry in th e process o f gainin g a co nsensus o n inte rpreting the risk of su ch o rganisms.

Interpreting Monitoring Data Determine the Numbers of Pathogens Present in Water Occurrence of Microorganisms in Water C ryptospo ridi11111 and Ca 111p ylobacter occ ur as di screte orga nisms o r as clump s in water. T hey occur o nly o ccasio nally, and w heth e r they are d e tec ted b y m oni toring depe nds o n w h ether th e taking o f water sa mples co incide w ith the presence of o rganism s in that particular water sa mpl e. In thi s respect they are d iffere nt from substan ces w hi ch are uniforml y distributed in the water, suc h as colo ur, turbidity or dissolved salts.

WATER MAY/ JUNE 2000

Yes

1 viable C. parvum oocyst

W hat types o f da ta are typically obtained by Australian water autho rities? In orde r to cha racterise th e nature of c urre nt mo ni t o ring data , samplin g programs and m on itorin g resul ts fo r Cryptosporidi11111 and Ca111p ylobacter we re obtain ed fo r th is stud y fro m som e o f the major urban wate r authorities within Australia. T h is provided direct informa tio n o n th e type o f data th at is actually obtained by Australian water authori ties. A summary of the information is sho wn in T able 1. In the maj o rity of cases, sampl es o f raw wa te r were taken fro m eithe r reservoir o r river locations, a nd anal yse d by a l ab o ra tor y fo r patho ge n s. The a n alyt ica l m e t hods provided results that we re recorded as eithe r Presence/ Abse nce (P / A) or as count data. M ost o f th e results were recorded as " none de tected" . Mu ch of th e C ryptosporidi,m, data received was co unt data, althou gh the proportion of P / A data had increased in rece nt years du e to the development of the reverse transcriptase P C R (rtPC R) me thod o f viability testin g. Althou gh the laboratori es unde rtaking th e analyses were usually NAT A accredited fo r som e tests, th is accreditation did not extend to the sp ecific analyses fo r Cryptosporidiu111 and Campylobacter w here such accreditatio n is still being developed at th e time o f w riting.

Th e

da ta

se t

**** *

** suppli e d

for

Cryprosporidi11m (typically 10 or 100 L samp le volume) and Ca111pylobacter (2 L samp le volum e) were largely take n as single samples in isolation at one dilutio n , though repli cates were obtained for a few locati o ns. Samples we re typically taken o n a weekly or monthly basis with many of the organisatio ns perform ing o ne-off surveys at geographi cally distinct sites. R esul ts o f thi s typ e lac k statistical stre ngth. H o we ver, to o bta in statisti cally vali d results would require mu ch greater sa mpl e numbe rs, and this b ec om es prohibitive in cost. It ca n be concl ud ed that ve ry few microorganism monitorin g programs will be sufficient to c haracterise th e occurre nce of organisms in statisti cal te rms. What can be concluded regarding the density of organisms that are present in the water, given certain presence/ absence (P/ A) monitoring results? Presence/absence data can be e valuated using the Most P robabl e Number (MPN) me th od. T his me thod of estimation can be used to give the m ost likely density o f microorganisms (d) and the upper and lower lin1its of th e confiden ce inte rval for th e d e nsity . Su c h a n approac h assumes that th e data originates fro m a larger data set that can be described by a P oisson distribution. T his assumption has been widely criticised

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WATER

Table 2: Estimated pathogen density (d) for presence/absence data Type of Sample

Monitoring Regime

1 sa mple

Observed Result

Annual

Estimated Range of Pathogen Density (d)

-ve +ve

$ 3.7 ~

0.2

4 samples

Quarterly

All -ve 2 +ve All +ve

$ 0.9 $ 3.2

12 sam ples

Monthly

Al l -ve 6 +ve All +ve

$ 0 .3 $ 1.8

52 sam ples

Weekly

Al l -ve 22 +ve All +ve

$ 0.07 $ 0 .6

0.5

1 .3

2. 7

1. 97.5% confidence limit ford; density=number of organisms per volume of sample used for analysis.

(Haas and H e lle r, 1988) bu t no bette r m ethod w ith gene rn l app licability has been pu t forwa rd. It is not possible to de term ine the freq ue ncy d istri bu tion o f m icroorganisms in a wate r body using onl y P / A data and th us co nfi rm w het her th e Poisson distributio n o r so me o th er distrib u tio n is app li ca b le. C onfirm a tion of t h e frequ ency d istributio n fo r a partic ular w ate r body requ ires count data. T able 2 illustrates the co nclusio ns t hat can be drawn regarding th e density o f mi c roorgan isms present fr om typi cal

P / A data o b ta i n e d in m on itori n g programs . Th ese esti mates are based o n 97 .5% co nfid ence lim its for d assu ming that the data follo ws a Poisson distribution, the pathogen density is constant between monitoring pe riods and the recovery effi ciency was 100%. These resul ts show, for exam ple , th at for a quarterly sampli ng program invo lving fo ur lO L samp les for w hich all results we re repo rted as "non- de tect", although the most probable density o f orga n isms is mu ch less than o ne per 10 L, it is o nly possible to say with a leve l

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WATER MAY / JUNE 2000

Neville Ward, Ron Edwards & Dr Peter Nadebaum (03) 9272 6666 Peter Zemek (07) 3233 1611 NEWCASTLE

Ian Gregson (02) 4929 3255 NSW

David Russell, Dr Ian Garrard (02) 9412 9999 OLD

Stephen Trainor (07) 3233 1611 VIC

Don Vincent, Dr Jeff Bazelmans, Mike Juleff, Dr Wayne Drew (03) 9272 6666 WA

Scott Bird (08) 9220 9300 SA

Paul Lindon (08) 8271 2322

of co n fid e nce o f 95%, th at th e density is less than 0. 9 organisms pe r 10 L. Even th en , t his assum es perfec t mi xing and ·100% sampling e fficacy. What can be concluded regarding the density of organisms present in the water, given certain count data from a monitoring program? When assessin g the significan ce o f m o nito rin g data, it is impo rtant to co nsider bo th th e proportion o f sampl es w h ich have organ isms p resent, and th e nu mbe r o f o rga nisms present in those samp les w hi c h t est po siti ve . For examp le, th e risk to a cons um er can be di ffe rent if in drinking o ne glass of wate r each day ove r a year, each glass of wate r contained one o rganism , compa red w ith the case whe re only on e glass con tained 365 organisms. Th e bes t way of charact e r isi n g thi s is t o dete r m in e t h e freq uen cy di stribu ti on w hic h describes th e occ u rre n ce o f orga ni sm s, an d w hethe r the pathoge ns are distributed uniforml y througho ut the water body, or wh ethe r they are present in clusters (term ed he terogene ity). Pathogen de nsi ties in drin king w ater can vary w ith both lo cati on and time for any given water body (Ga le, 1996; H aas and L<..o se, 1996) . An acceptabl e fi t was fo un d be twee n t h e oc cu rre n ce o f Cryptosporidi11111 oocysts and th e Poisso n d ist ribu ti on in re latively clean wa ters that m ay be co nsistent w ith dri nking water (Haas and R ose 1996), bu t others fo un d t he negati ve b ino mia l distri bu tion to provide a better fit (Teunis el nl, 1997; M edem a et nl, 1995). So me in vesti gators suggest that, in general, the P oisson di strib uti o n m ay ass u m e to o littl e he teroge neity when deali ng w ith mi crobial pat h oge ns (Coc h ran 1950; EI Sharwaa ri et nl 1981 ; H aas an d H e lle r 1988 ; G ale 1996). C ou nt data, if sufficient in numb er, ca n be a n alyse d to d e term i ne th e frequ e ncy distributio n that describes th e occurrence of the o rga nisms, bu t this usuall y will requ ire a mu ch larger data set tha n is ava ilable from most pathoge n m onitoring stud ies. In the case of th e data obtained from th e Au stralia n water authori ties, th e majority o f the data w ere no n- detect results or P / A data, and it was no t possible to determin e th e u nde rlying freque ncy distribu tions from such limite d data.

T he signi ficance o f the extent of clustering depends on : • W he th er th e likeliho od o f infection is highly depende n t on th e num be rs o f orga n isms in ges te d . Fo r a particular de nsity of o rga nisms, a un iform dist ribu tion of organism s m aximises th e c hance

WATER

that at least som e o rganisms w ill be ingeste d. This w iLI increase th e risk of infection if ingestion Observed Count Estimate for d of o nl y o n e o r t w o 1 < 5.4 orga n is m s c an c au s e in fec tion , but ma y 5 < 10.8 redu ce th e risk if th e 25 < 33.4 probability of in fe cti on is 50 < 59.6 very lo w w ith such lo w 100 < 110 doses. • Whe th er the m easure of interest is the m ost probable (eg mean) risk of infection o r an upper estimate (cg a statistical uppe r confid ence limit o f the m ean). C lustering results in more highl y variable data, and the uppe r con fid e nce limit m ay be mu ch hi gher (our estimates based on Monte C arlo simu lation suggest m o re than a fa c tor of 10) than if the data is un iform . W e suggest that wh ere the end point is a no n- life threatening illn ess and the data is variabl e, th e n the most probabl e (m ean) risk of in fectio n is m o re appro priate than upper estimates o f th e risk. This diminishes th e se nsitivity of th e risk estimate to data variability and the se lection of th e fre qu ency distri bution.

Table 3: Estimated pathogen density ( d) for count data

T able 3 illustrates the co nclu sio ns that can be drawn regarding th e de nsity of mi croorganisms prese nt, from typi cal cou n t data obtained in m o nitori ng programs. Th ese estimates are based o n 97.5% confide nce li mits ford assuming that the o rgan isms are uniformly di stri buted (ie they foll o w a P oisson di stribu ti o n) and the pathogen de nsity is con stant between m o nitoring pe riods. This shows that th ere is a consid erable range fo r d w he n on ly a few o rganism s are detected. If the organisms occurred in clusters, then th e ran ge w o uld be greate r. How should the recovery efficiency of the analytical method be taken into account?

C urre nt analytical m ethods do no t acc urately estimate the num bers o f organisms, and it is necessary to know the recove ry e ffi cie ncy o f the analytical m ethods to determi ne the density of o rgan ism s present. l f th e re cove ry effi ciency is say x%, th en the most like ly den sity is the measured de nsity/(x/ I 00) . R ecovery e ffi c ie ncy is usually dete rmined by means of spike experim ents w here a sample of stoc k suspension containin g a known numb er of Cryµt osµoridi11111 oocysts and/ or Ct1111pylobacrer ce lls is added to wate r and th en enumerated in the sam e way as th e samples from the wa ter bod y. The rati o o f path ogens de tected to path oge ns seeded (spiked) in a kno wn vo lum e is th e n used as the perce ntage recovei-y e ffi cie ncy . In th e case of th e data available fro m t he water authoriti es for th is study, th e rec ove ry effici ency was alm ost neve r repo rted. The recovery effi cie ncy achi eved in practice ca n va ry w idely, and at best w ould be within th e ran ge o f 25- 100%, although m uc h lowe r recoveries o f less than 0.1 % can occur. Because of this variability, path ogen monitorin g data sho uld be vi ewed in terms of providing an ind ication o f co ntamin ati o n rath er than prec ise results. Th e moni tori ng programs review e d did not include indepe ndent c hecking o f the labo ratories (eg by circ ulating spiked sampl es), and it is o nl y now that w ater autho rities and NATA are establishing this p rocedure . Initial wo rk suggests th at th e reliability of individua l resul ts is poor, and obta111111g good substantiatio n of results is diffic ult. M o re compl ex, statistical approaches for estimating m ethod recovery e ffi cie ncies have been proposed. Fo r exa mple , where th e recovery fo r C ryptosporidi11111 varies between each data set or trial, w ith eac h o rga nism in a seeded sampl e having a parti cu-

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Jar probability of being re covered (Teunis et al, 1995). This approach requires a large amount of data that is generally unavailable, and is considered to be inappropriate for general use within the water industry unless knowledge of such information is critical. How can viability and infectivity be taken into account?

When estimating the pathogen density, it is important to recognise that not every organism detected by analysis may be alive (viable) or capable of initiating infection (infective) within that host (host specificity) (T eunis et al, 1995). T he viability of oocysts can vary within different hosts and within the environment as a result of un favou rable conditions (Bukhari and Smith, 1997). Cryptosporidium is widespread in mammals, although transmission to humans is onJy well documented for organisms from other humans, cattle and sheep. The infective dose varies with different strains of the same major subtype (eg volunteer studies on three strains of Type 2 (DuPont, 1995; Okhuysen et al, 1999)) and the very low human infectious dose seen with the TAMU strain shows that at least some cattle-grown oocyst strains can very efficiently infect humans (Okhuysen et al, 1999). As analytical m ethods improve, a large number of different strains are being recognised. The following factors are important when interpreting monitoring information: (a) lnfectivity The infectiv ity of pathogens for humans is not routinely m easurable, although in vivo cell culture assays and animal models do exist. In the USA new methods are now being applied to assess the viability and infectivity of oocysts (LeChevallier, 2000). Some strains are likely to vary in their potency and infectivity for humans due to environmental conditions. In general, a measure of infectivity w ill rely on the analytical m ethods being able to identify the particular species and genotypes present, and trials having been carried out on similar genotypes to characterise infectivity. It can be concluded that in most situations within the Australian water industry involving routine monitoring, it is unlikely that reliable in fectivity data will be available. (b) Viability In the case of Campylobacter, the analytical m ethods used in most cases rely on cultivation of the organisms, and thus provide direct confirmation that the o rganisms are viable.

WATER MAY/JU NE 2000

In th e case o f C ryptospo ridium, methods are available to indica te viability although the most commonly used m ethod based on microscopic inspection does not provide confirmation of viability (although th e analyst may be able to distinguish whether the intracellular structure of an oocyst is consistent with a viable organism). In m ost cases, it can be expected that water authoriti es will not be able to confirm the viability of detected oocysts. In the future, reliable m easurement of viabili ty may be possible. At present it is probably better to talk only in terms of organisms having properties consistent with being viable or non-viable. In the case of th e data obtained from the Australian water authorities for this study, information o n viability and infectivity was not spec ifically recorded, though it is possible that the analyst may have taken viability into account during reporting. Where viabili ty and infectivity are not reported, there are various options for accou nting for these effec ts: • Take a precautionary approach and assume that all organisms reported are viable and potentially infective. • Co mmissio n advance d analyses to d eter min e wh e th e r the ge notyp es present are those that are more likely to be associated with infective organisms and apply an infecti vity factor. • Assign an "infectivity factor" based on the likely infectivity, taking into account whether pathogens are likely to have o ri ginated from humans o r animals associated with a potentially high or low level of infec tivity. The absence of water borne disease or the absence of unusually high levels of infection in the communi ty associated with the specific organisms over m any years may also provide confidence that the presence of infective organisms is at a low level. • Assign a "viability facto r" based on the likely viability, taking into account the time for the organisms to reach the point of ingestion from the point at which they were m easu red, and th e environmental situati on and likelihoo d that this would have led to a loss of viability. Adopting a precautionary approach (that is, assuming all organ isms are viable and infec tive to humans) is the safest approach , but is likely to grossly overestimate the risk of infection by up to several orders of m agnitude except where very fres h human sewage or agricultural animal wastes are the source. It is important that method development efforts continue in their present direction to increase viabil-

ity sensitivity, and to obtain a better understanding of species and infectivity. Consideration should be given to assigning infectivity and viability factors when assessing m onitoring data. How should the decrease in numbers of organisms in the supply system and by water treatment be taken into account?

In drinkin g water supplies, monitoring of treated water fo r organisms will usually not provide a usefu l and statistically valid measure of organism numbers, because the occurrence of o rganisms will be very infrequent and at low numbers. Instead, if assurance is to be achi eved that the numbers of organisms are suitably low, then it can be expected to be m ore useful to m onitor the water prior to treatment and estimate the reductions that ca n be expected to occur through the various water supply system operatio ns based, for example, on particle count reduction. Substantial reductions in the densities of organisms can occur, for example, in natural waters, in long detention time storages, coagulation and settlement, filtration, and disinfection. Each treatment will reduce the density of pathogens and the resu ltant health risk to consun'lers. For example: • D etention in lakes/dams or within river systems can reduce the numbers of viable pathogens by several orders of magnitude. However, to use this information in risk assessment there is a need for quantitative data on the survival of pathogens in natural waters, their association with organic matter, behaviour during the process of sedimentation and effects of solar irradiance on viabili ty. Another factor is the possibility of shortcircuiting of incoming polluted water. Such information is available and its amount is in creasi ng. However, to apply new and existing information to indi vidual systems, the fate and transport of particles and o rganisms needs to be understood at a reasonable level of detail. • C oagulation, settlement and filtratio n can effect several orders of magnitude reduction in pathogen numbers. This is dependent on the treatment steps and their efficiency of operation. Chlorination may achieve substantial reductio n of cert ai n mi croorgani sms su c h as Campylobacter bu t can be expected to be relatively ineffective fo r Cryptosporidium . Recent studies have indicated that UV can achieve a substantial reduction in the infectivity o f Cryptosporidium oocys ts (Malley, 2000). Nominal allowances can be used to give a first approximation for the reduction of mi c roorgan ism s ach ieved

Ai IE R

through these processes. Measurements to confirm the reduction can be justified where there is significant contamination of the source water and reliance is placed on the efficiency of the storage and treatment steps. This can provide a basis for predicting the risk reduction able to be achieved from treatment barriers and has been described briefly by Tcunis ct al (1997), Gale (1996) and in more detail by CMPS&F (1998).

Conclusions There is considerable uncertainty in interpreting monitoring results for pathogens such as Cryptosporidi11111 and Ca111pylobactcr. Key factors are: • Monitoring information often consists of "non detect" results, with the occasional positive result. It is unlikely that sufficient results will be obtained to have statistical rigour. • The recovery efficiency of analytical methods can be highly variable, and the reliability of individual monitoring results is likely to be poor. Obtaining good subst;111tiation of results is difficult. • Monitoring information will often pertain only to the source water before treatment, and the presence of organisms in water supplied to consumers will need to be inferred from the source water quality and the likely efficiency of removal of treatment systc111s. • Monitoring programs applied routinely by water authorities are unlikely to provide good information on the species and strains of the organisms present, and whether they arc likely to give rise to infections in humans. In the absence of such information, the source of the contamination and whether it is likely to be associated with human infection may be the best indicator of viability and infectivity. Because of these factors, pathogen monitoring data should be viewed in terms of providing an indication of the presence of contamination and the general magnitude of the numbers of organisms that are likely to be present, rather than precise results. It is important to apply judgment when interpreting the results, particularly as to whether organisms detected are likely to be viable and infective. In Part 2 of this paper it is discussed how the monitoring results can be used to estimate the incidence of infection and illness in the community.

References Anon {1998) Cryptospm'idi11111 in Water. A Consensus Conference. Cooperative Research Centre for \Vater Quality and Treatment. ISBN ! 87(1616 00 8.

Uuklmi, Z. and Smith, 1-1.V. (1997) C1yptosporidirnn parvum: oocysts excretio11 and viability patterns in experi1rn.·ntally infected bmbs. Epidc111iol. li1/l'ct. ! 19: 105-108. CMPS&:F (1998) Tre.mne1it Require111e11b fix Australian Waters. Report to the Department of Primary Industry and Energy under the Landcare Progr.im. Cochran, W.G. (1950) Estimation of bacteria! densities by means of the "most probable number". Bfomclrics 6, 105-116 Du Pont, 1-1.L., Chappell, C.L., Sterling, C.R .. Okhuysen, P.C., Rose,J.B. andJ.ikubowski, W. (1995) The Infoctivity of Cryptosporidium parvum in Healthy Volunteers. Nc11, E11.~lmul Jnm111/ (?f Mcdid11c. 332, 855-859. EI-Sharwaari, A.H., Esterby, S.R and Dutka, BJ. (1981) llacterial density in water determined by Poisson or neg.Hive binomial distributions. Applied mu/ E1111inlll//U'1ttal Microbiofogy 41, 107-116. Gale, P. (19%) Developments in microbiologic;1] risk assessment models for drinking water - a short n.·view.Jo11ma/ 1:fApplied Bactcriofogy 81, 403-410. Hrns, C.N. and Rose,J.B. (19%) Distribution of Cryptosporidium oocysts in a water supply. Water Rcscard1 30, 225 !-2254. Haas, C.N. and Heller, U. (1988) Test of the validity of the Poisson assumption for analysis of most-probable-number results. Applied a11d E1w/r()11111mtal Mimibiol(t~Y 54, 2996-3002. LeChevallier, M. (2000) Challenges to Maintaining and Improving Microbial

Water Quality. />we. E1wir()2000, April, Sydney, Australian Water Association. Lund, V. (1996) Evaluation of E. C()fi as an Indicator for the Presence of Cm11pylobactcr Jej1111i and Ynsi11ia h'111cn1colilica in Chlorinated and Untreated Oligotrophic Lake Water Waler R..csmrd1 30, 1528-153-L Malley. J. (2000) The Emerging Role of UV Disinfection for Drinking Water Treatment in North America. Proc. E111'im2000, April. Sydney, Australian Water Association. Medema, GJ., Tt·Lmis, P.F.M., Gornik, V., Havebar, A.H. and Exner, M. (1995) Estimation of the Cryptosp()r/diw11 infection risk via drinking water. Ill: Protozoa, Parasites and Water. Betts, W.13., Casemore, D., Fricker, C., Smith, H. and Watkins, J (eds.) The Royal Society of Chemistry. pp 53-5(1, Okhuyscn, P.C., Chappell, C.L., Crabb, J.H., Sterling, C.R. and DuPont, H.L. (!999) Virulence of three distinct Cryptosporidi11111 p11r1'11111 isolates for healthy adults. "f11cjo11mol (?f b!f1.'Cti011s Diseases 180, ! 275-128 ! . Teunis P.F.M, Havclaar, A.H. and Medema, G.H. (!995) A Literature Survey on the Assessment of Microbiological Risk for Drinking Water. Report No. 73-1-301006, RIVM, 13ilthoven, NL Teunis, P.F.M., Medt·ma, G.H. and Havdaar, A.H. (1997) Assessmt·nt of the risk of infection by Cryptosp()ridi11111 or Gillrdia in drinking w.itt·r from a surface water source. IV<1ta RtS('(//'dl 31, 1333-1346.

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CRYPTOSPORIDIUM AND CAMPYLOBACTER IN DRINKING WATER SUPPLIES Part 2: Estimating the Incidence of Infection and Illness P R Nadebaum, K Walsh and D Deere Abstract

What volume of water is consumed?

As part of a Cooperative R esearch Centre for Water Quality and Treatm ent Program 1 (H ealth Risk Assessment) Project , monitoring data obtained by Australian water authorities relating to Cryp tosporidi1m1 and Campylobacter were reviewed and assessed to determine how the information should be interpreted. In Part 1 of this paper it was discussed how monitori ng data can be interpreted to determine the numbe rs of organisms present in dri nkin g water. In this part, the significa nce of these organism s in drinkin g water with respect to in fec tion and illness in the community is discussed. The analysis supports the position that low levels of Cryptosporidi111n and Campylobacter in source waters are unlikely to give rise to rates o f infec ti on w hi ch wou ld be detectable in th e community, but that in the treated water suppli ed to co nsumers that the numbers of viable and infective organisms should be vety low . The most cost effective and reliable m eans of managing the risk to human health from microbial pa thogens will be to provide assurance th rough appropriate source water m anageme nt and treatment , rather than us ing routin e treated wate r monitoring fo r pathogens as the control m easure.

The incidence of infection will be depe ndent on the extent of consumption of unboiled water, and th e number of organisms prese nt in this water. T he most commo n assumption for ri sk assessment purposes is that the vo lume of water consumed is 2 L per day (bo iled and unboiled) (eg NHMRC, 1996) . Co nsumption of0.25 L per day has been used in the N etherlands for risk assessm ent (T eunis et al, 1997). A M elbo urn e study indi cated that the average dai ly consumption of unboiled tap water was 0 .58L (CMPS &F, 1998), and we cons ider this value to be more reasonable than 2 L per day. In prac ti ce, co nsu mption w ill vary, and on an individua l cons umer basis will range from. zero to greater than 2 L per day. Th is va riation can be taken into accou nt sta t istically, if t h e frequency distri bution of consu mptio n is known. T he da ily consu mption o f unb o il ed drinkin g wa t er in th e Melbourn e study was fou nd to foll ow a normal distribution (CMPS&F, 1998), w ith zero values included so that nil consumptio n leads to a nil risk fo r a person for that day. Takin g these factors into accou nt will inc rease the range of risk levels, but w ill not change the mean risk level to the population. We suggest that such statisti cal refinement is not w arranted unless upper co nfidence limits are the r equired assess m ent n1easure.

Introduction After the densities of viable and infective pathogens in the water supplied to consumers have been estimated, their significance with respect to the health of the general population can be assessed. The potential for the consumption of water containing pathogens to give rise to illness is usually described mathematically by the "dose-response" relationship . Th e dose-respo nse relationship relates the rate of infection to th e number of organisms ingested, which in turn is dep endent on the volume of water consumed and the density of organisms in the water. 36

WATER MAY /JU NE 2000

What Dose-Response Relationship should be assumed?

T he dose-response relationship relates the rate of infection to the number of organisms ingested. T he relationship is determined from experimental trials in w hich the rate of infection arising from ingestion of known numbers of organisms has been m easured. There is limited experimental data fro m which dose-response relationships ca n be developed . T here is general

consensus that the most relevant data is that of Black et al (1988) for Campylobacta (strain A3249) and DuPont et al (1995), and more recently, O khuysen et al (1999), for Cryptosporidi1uÂˇ11 panmm. T he percentage incidence of infection vs th e number of organisms ingested in these studies is sho w n in Figure 1A and 1B. T his illustrates a key issue : how sho uld the data be extrap o lated to predict the incidence of infectio n when ingesti on of on ly one or a few organ isms occurs, as applies in the consu mption of drinking water? M ost investigato rs extrapolate the data assuming the data fo llo w certain freque ncy distributions. These are simply mathem atical extrapolations, and do not necessarily take into account the variation that might occ ur in practice (eg whether there could be a threshold dose below which infectio n will not occur). Figure 1A and lB indicate th e importance of plotting the data to better un derstand what i s in volved : â&#x20AC;˘ In the case of Carn.pylobacter j ejuni, the data suggest a uniform relationship between the percentage of persons infected and log(dose). Extrapolatio n of the data (assuming a beta-Poisson distribution with values of 0.0919 and 0.7 1 for the alph a and beta parameters, respectively) suggests that there is an appreciable risk o f infection even if only one organism is ingested. While this is a good statistical fit, it is not necessarily mech anistically sound and upper and lower bounds have been included to accou nt for the unce rtainly. â&#x20AC;˘ In the case of Cryptosporidium parvum it can be seen from Figure lB there is surprisingly good agreement in the results of ingestion trials with three different stra ins (DuPont, 1995; Okhuysen et al, 1999), and we ha ve included indica tive upper and lower bou nds to account fo r uncertainty in extrap olating the data. The lower bound curve is that which has been proposed

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This T able shows that th e risk to the pop ulation is h ighest if the organism s are un iformly distributed rath e r than being prese nt in clusters. l n the case of Cryptosporidi11111, th e risk of infec tion is very lo w w he n ingestio n of on ly one or two organism s occurs. For Ca111pylobacter, the risk of in fe c tion is relatively high when ingestion o f on ly o ne o r two o rganism s occ urs. Th e incidence of infection ca n b e estimated by the following equ atio n:

(H aas et al, 1996) as a good fi t to the D uP o n t data (assu m in g an exp one ntial distribution with a valu e o f 238 for the parame ter K) suggests a relatively low risk of in fectio n (P = 0 .004) if o n ly one organ ism is ingested . While the latte r result has been widely quo ted , Figure l B indicates that the expone ntial d istribu tion may be inappropriate and its use may unde resti mate th e risk. T hese results suggest th at mo dels based on the actual mech anism and li kelihood o f infec tion may pro vide a more valid basis fo r extrapo latio n than simple statistical cu rve fitting. In general, ca utio n is required in interpre ting th e data , as the data are limited and can be in fl uenced by o nly small varia tions in th e numbe rs of persons i n fected during the stu di es. T he implications of th e data can be und erstoo d b y con side ri ng th e case wh ere l 000 perso ns consu m e 1000 organism s, but th ese are in gested either as 1 organism p er perso n , 10 organisms by 100 persons, o r 1000 organ ism s by 1 perso n. T he estimated risk correspo nding to th e dose- response c u rves 111 Figu re 1A and B is show n in Table 4 .

Incidence of infection = 1 - (1 - P)"'. (1) ~ NxP for values of NxP << 1 (2) where N = the number of exposure events, and P = probabi lity of infection from each expos ure event.

T h e ann ual inciden ce of infectio n esti mated fro m these eq uations has been p lotted in Figu re 2, by making the fo llo w ing assumptions: • Th e probability o f a viable and in fective organ ism bein g presen t in wate r consumed o n any o ne day is dete rmined from monitoring data (ie the de nsity of orga nisms as organisms/ L); • t h e av e r age q u a n t ity of w at e r

Figure 1A. Campylobacter jejuni dose response study

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0.1 L-----~.._______._...______ _ ..._____......__ _...__, 10 100 1000 10000 Number of Oocysts

WATER MAY/ JUNE 2000

consumed each day is 0.58 L/ day; • the probab ility of in fection for in gestion o f a single viable and in fe ctive o rgan ism is gi ve n by Figures 1A an d 1B. Figure 2 and equatio ns 1 and 2 can be used to de termine the risk of illness fro m mon itori ng informatio n. If, for exampl e, mo nito ring suggests that water contains on average 1 viable and infec ti ve organism per lO L, the n: • if th is o ccurred for only a short time (say 5 days) the n fro m Equation 1 the risk of in fec tion to individua l consu m ers would be low and in the order of ·1% (0 .6% fo r C. panm111and 3% for C. j~j1111i); • if this cond iti on persisted over a year then fro m Figure 2 th ere would be a h igh probabi lity (greater than 50%) that co nsu me rs wo uld beco me in fe cted at some tim e d uri ng the year. As a check of these relatio nships, a M o nte Ca rl o analysis was ca rri ed o u t (CM PS&F, 1998). This analysis was based on the expe rime ntal dose- respo nse data refe rred to above (B lac k et al (1988) fo r Ca111pylobacter and DuPo nt et al (1995) fo r Cryptosporidil1111). Valu es of the alpha and beta paramete rs for th e d istr i bu ti o n for b e ta- P oi ss on Ca111pylobacter jej 1111i (H aas, 1983), and the expo ne ntial parame ter K fo r C. pan;11111 (T e unis et al 1997) were ge nerated and the n applied to esti mate th e probabili ty o f in fecti o n. T he analysis ind ica ted that the more de tailed M onte C arlo method gave sim ilar estimates for the mean risk, but that th e estimates are dep e nde nt on the me th od use d to extrapolate the dose-respon se data. What are the important assumptions underlying these estimates?

Th is me thod of estimation of the probability o f in fec tion relies on the va lidity of t he exp e rim e ntal d oseresponse da ta. Key assu mptions unde rl yin g the use o f this data are: • The dose response data can be extrapolated to predict in fec tion at low doses o f 1 or 2 organism s. • T he experimental data relates to a particular stra in and genotype, and a sel ected subset o f the human popu lation. No allowa nce has bee n made for vari atio ns in the probability of in fec tio n based on the virulence of th e path ogen , or the h ealth, age and immuno-compete ncy of the host, although th ese are fac tors that ca n i nflu ence the probability o f infectio n (So bsey er al, 1993) . N o allowance has bee n made fo r immun ity, and it is assum ed th at on ce in fec ted , an individual will be no less likely to become infec ted a second tim e than the first. T his is a conserva tive

WATER

jejuni, resp ec tiv e ly .

assumption but is supported by data from previous studies (Okhu ysen et al, 1995). The effe c t of previou s exposure and the resulti ng immunity ga ined appears to be in reduc ing the severity o f ill ness rath er in than reducin g th e probability of in fecti o n.

W ith r e feren ce t o Figure 2, this corresponds to t he occu rre nce of organisms with a mean density o f 0 .2/100 L and 0 .002/2 L for C. parvurn and C. jejuni, respectively.

Of the persons infected, how many are likely to have symptoms of the infection, and what rate of infection is likely to be detected in surveillance programs?

What can we infer about the numbers of organisms detected in a monitoring program and the need for management action?

Based on th e feed ing studies carri ed out by DuPo nt et al (1995) and Black et al (1988), a signi fi cant pe rce ntage (b ut not all) o f those infec te d will exhibit symptom s of the in fec tion (eg 61 % for C. parv11111, and 24% for C. jej11111). Typically the overa ll annual rate of gastro enteritis in the co mmunity is in the orde r of 50-70%, less than 1% of infection s are no tified to hea lth authorities, and of these, 2% and 5% may be fo r C. panm111 a n d C. j ej11ni res p e ctiv e ly (P adig li o n e a nd Fa irl ey, 1998). In pra c ti ce, th ese figur es va ry g rea tl y accordin g to region. Associatin g infection w ith the concen trations of organisms in water is diffi cult with traditional e pide miol ogical te c hniqu es . If it is assum ed that a do ubling of th e notifi cati on of a parti cular illn ess would be req uired befo re it wou ld be detectab le, th e n th is wo u ld correspo nd to a n increased rate of infection in the co mmu nity of l % and 2.5% for C. par,;11111 and C.

Figure 2: Predicted annual incidence of infection. Annual incidence was expressed as a percentage of the population infected per year estimated from Figure 1A and B.

C 0

u .!!!

.s 0

.,u

~ 'O ·o

1.0%

.!: 'iii ::,

Cryptosporidium parvum

-, ----------

C C <(

' '

0.01%+---'---"-.........~-~................."-"'+- - ' -.........~-'-'t-0.0001 0.001 O.D1

0.00001 It is no t possibl e to dete rmin e the acceptable o r target levels of organi sm s in drinking water, as there has not ye t been agreem ent with regard to the acceptable level of infection in the co mmun ity. There are several possible approaches fo r setting suc h targets. For exa m.pie , targe ts co uld be set on th e basis of: • Cost of illness to the community: Ifwe assume that on average th ere is o ne lost work day p er case of infection in t he commun ity and the va lue of wages lost and medi cal costs equ al $ 150 pe r case of in fec tion , and the cost of water treatm e nt is $30 pe r pe rso n per year, then to minimise th e ove ra ll cost to th e commun ity , water treatment should be provided

Table 4: Case Example: Risk of Infection of 1000 persons from 1000 organisms Number of persons likely to be infected ( estimated from Figures 1A and 1B). Cryptosporidium pa rvum

Dose Scenario

1000 persons each ingest 1 organism

Campy/obacter Jejuni

Number of persons likely to be infected

Overall Risk of Infection

0.02

1 00

0.1

0.01

0.02

0.004

0.003

0.001

0.5

0.0005

Number of persons Overall Risk likely to be infected of Infection

100 persons each ingest 10 organ isms , 900 persons ingest nil organisms 10 persons each ingest 100 organisms , 990 persons ingest nil organ isms 1 person ingests 1000 organisms, 999 persons ingest nil organisms

~ ' - ' -........""i

0.1

Mean density (d) of Organisms per L

if the annual rate of infection exceeds 2000 per 10,000 persons. T his would equate to m ea n densities of organ isms of 5/100 Land 0.02/ 2 L for C. parvum and C. jejuni, respectively. If the costs of infecti o n and illn ess in the comm.unity are hig he r than assumed above , then the corresponding target de nsities would reduce. • Levels of illness that are detecta ble ab ove the general backgro und of illn ess in th e c ommuni ty: As indicated above, th is correspo nds to the occurren ce of organisms w ith a 1nean de nsity of 0.2/100 L and 0.002/ 2 L for C. parvum and C. jejuni, respectively. • A n o m inate d target level for predi cted in fectio n or illness: An an n ual rate of infection of 1 in 10,000 is being discussed in the USA and the N e therlands; this would correspon d to mean d e n s i ti es of organisms of 0.002/ 100 L and 0.00001/2 L, for C. parvum and C. jej11n.i respectively. T hese comparisons indi cate: • In order to e nsure that illness w ill not be detected in the commun ity, o rganism s shou ld not be at numbe rs which can be de tecte d in treated water by the u sual analytical m ethods, unless the orga nism s are not associated with infection in humans (eg are strains wh ic h are not assoc iated w ith human infection, or are not viable) . • The target levels being discussed in th e USA and the Netherlands correspond to levels of detec tion that are mu ch lower than can be detected in the communi ty, and correspo nd to densities of o rganism s which are much lower than can be determined through m onitoring o f the WATER MAY/ JUNE 2000

WATER

treated water, and wou ld no t appear to be j ustifi ed in term s of cost to the commu n ity. T he inferred levels o f treatme nt for differen t source water qualities are listed in Table 5. T h is table indicates that C. jej1111i requires a hi gher leve l of treatmen t than C. p11n111111 1 reflecting the h igh er rate of infec tio n indicated in Fi gure 1B for C. jej11 11i w ith low n u mbe rs of organisms ingested. C. jej1111i is more easil y rem oved by c hlo rination than C. parvum , and this is taken into accou n t in the treatme nt require me nts infe rred in T able 5 . Rece nt studies (Malley, 2000) have shown that U V can redu ce th e in fec tivity of Cryptosporidi,1111 oocysts and th is may improve the e ffectiveness of disinfection .

Conclusions There is considerable uncertainty in i n terpreting monitorin g re sults for pathogens such as Cryptosporidi11111 and C11111pylo&acter. M o nitoring information often con sists of " non detect" res ults, with the occas iona l positive resul t . Ofte n the monitori ng information will pertain o nly to the source w ate r befo re treatment. K ey fac tors in the interpretation of m o nitoring informatio n include : • Th e reliability and recovery of the an al ytical methods. • T he species and st rains of the organisms present, and whether th ey are likely to give rise to infections in humans. [n th e absence of the ability to measure this, th e sou rce of the contam ination and w hethe r it is likely to be associated w ith human infec tion may be the best

indicator of viability and in fec tivity . • T he likelihood that low doses of organisms (eg o ne or two) w ill give rise to in fec tion . • The acceptable level of illness in the co mmu n ity and the objectives fo r mana ge m ent of pathogens in wate r supplies. These have not yet been agreed in Australia. T he analysis suggests that: • T he objectives for mana geme nt of pathogens in water supplies need to be defin ed. Adoption of target risk levels being discussed in th e USA and Europe wo uld in fe r chat the numbers of organisms present should be red uced to very low levels, well below our ability to m easure directly. Achieving such levels w ill requ ire a high level of treatment and substantial cost to the community.

Table 5: Inferred Levels of Treatment Required for Various Source Water Qualities (with respect to measured numbers of Cryptosporidium and Campy/obacter only) Source Water Quality (numbers of organisms . f erred f rom mon1"t on.ng 111 annual basis

Inferred Level of Treatment1 (Reduction In Numbers of Organisms) Required To Meet Target Target: Overall cost to the community is minimised

Target: No illness detected In the community

Target: Annual Risk of Infection less than 1 in 10,000

None req uired None requi red Disinfection only

None required S 1 log Disinfection on ly

s 2 log s 3 log Ret ention in reservoir, di sinfection, and reduction in distribution system may be adequate

None required S 1 log Disinfection only

S 1 log s 2 log Retention in reservoir, di sinfection, and reduction in dist ribution system may be adequate

s 3 log s 4 log Retention in reservoir, effective disinfect ion, and reduction in distri bution system may be adequate; if disinfection has low effectiveness then fi ltration wi ll be necessary.

;:: 1 log ;:: 2 log Retention in reservoir, disinfection, and reduction in distribution system may be adequate

;:: 2 log ;:: 3 log Filtration and disinfection

;:: 4 log ;:: 5 log High efficiency filtration and disinfection

Excellent Source Water

Infrequent detection at low nu mbers, organisms detected unlikely to be infective* C. parvum $ 1 per 10 0 L C. jej uni s 0 .1 per 2 L * infectivity < 0.1 that in Figure 1.

Good Source Water Infrequent detection at low numbers , organisms detected like ly t o be infective C. paNum s 1 per 100 L C. jejuni s 0.1 per 2 L

Poor Source Water Frequent detect ion, organisms detected likely to be infective C. paNum ;:: 10 per 100 L C. jejuni ;:: 1 per 2 L

Note: 1.Treat ment for Cryptosporidium and Campylobacter only. Treatment may be necessary for ot her water quality parameters. Treatment refers to reduction in numbers of viable organisms that will take place between the source and the point of use (includes loss in reservoir, treatment system, and distribution system). For cases where organisms are likely to be infectious it is assumed that Figure 1A and 1B dose-response curves apply.

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• Occasional detection of organisms in low numbers in source water (prior to treatment) indicates caution is required. Th e numbers of organisms will reduce through normal supply syste m processes. Simple chlo ri nation may be an adequate leve l of treatment where the source water is of excellent quality and organism s are unlikely to be infective to humans. • Frequen t detection of organisms in source waters indicates reliable treatment (filtration + disinfection) is required, parti c ul arly where th e org ani sm s detected are likely to ca use infectio n in humans such as those organisms associated with other human s, ca ttle and sheep. • Organisms should not be detected in water supp li ed to consume rs. l f o rganisms are detected , then othe r factors p ertaining to the water supply shoul d be examined to determine wheth er the analysis is reliable and representative and

whether the organisms are like ly to be of the type t hat will be infectious to humans . • Because the numbers of organisms in water supplied to consumers sh ould be very lo w, monitoring to achieve statistically valid results w ill be prohibitive in cost. If organisms arc detected, it is likely to be difficult to de term ine th eir significa n ce . The mo st cost effective and reliable m ea ns of mana ging th e risk to human h ealth fr om microbial path ogens will be to provide ass u rance through appropr ia te so urce wa t e r management and tre atm ent , rath er than us ing routin e treated water monitori n g for pathoge ns as th e control m eas ure . Beca use t he results of in fec tion are generally not life threate ning and t here is considerable uncertainty in the risk estimates and a high level of variability in the analytical methods, we su ggest that:

• measures of risk shou ld be based on th e most probable estimate (eg the m ean) rather than statistically estimated upper confidence limits for the mean; and • the estimation of risk shou ld be based on simple methods tlut do not obscure the relationships involved.

References 13lack, l~.E ., Levine, M.M., C lements, M.L., High cs, T. P. and B laser, M.J. ( 1988) Experimental Ca111py/obartcr j~j1111i infect ion in humans. Journal o f Infectious Diseases

157, 472-479. CM PS&F ( 1998) Treatment Requirements fo r Australian Waters. R cport to the Department of Primary Industry ,rnd Energy under the Landcan, Program. Du Po nt, H.L. , C happell, C.L., Sterling, C. 11... , Okhuysen. P .C., l~ ose, J.B. an d Jakubowski. W. (1995) The lnfectivity of C ryp to.<poridi111J1 pr1n111111 in H ealthy Volunteers. Nf111 E11gla11djo11mal '!{iV!ediri11I'. 332, 855-859. Haas, C.N. (1983) Estimation of risk due to low doses of microorganisms: A comparison of

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alt<:rnaciw n1ethodologies. A111e,-irn11 )011mnl of' Epid1•111iology 118: 573582. Haas, C.N .. C rockett, C.S., R ose,J. 13., Gerba, C. P. and Fazil , A.M. ( 1996) Assessing the risk posed by oocysts in dri nking water. ) 0111·1,n/ A W WA: Sept 13 1- 136. M alley, J. (2000) The Emerging Role of UV Disinfect ion fo r Drinking Water Treatment in North America . Pror. E1111iro2000, April , Sydney, Australian W ate r Association. N ational Health and Medical l'l..esearch Council ( I 996) Australian D rinking Water Guiddines. Comrnomvealch of Australia 1996. !SUN () (,+2 24+63 + Okhuysen, P. C., C happell. C. L., Sterling, C. R ., Jakubowsk i, W. and Du Po nt, H . L. (1995) Susceptibili ty and serologi c response of healthy adul ts co n:infection wi th Cryprosporidi,1111 p11r,111111. /11/'ccric>11 m,d /1111111111iry 66, ++ 1-++3. Okhuysen, P.C., C happell, C. L., C rabb,J.H .. Ste rling, C. R. and DuPont, H .L. ( 1999) Virulence of three distinct Crypto.;poridi11111 pmv11111 isolates for healthy adults. TIil' ) 011mnl ,!( !1!fccri()l1s Diseases 180, 1275- 1281. Padiglione, A and Fairley, C. K. ( 1998) Early cktection of outbreaks of waterborne gastroe nteritis. Wnil'I'. N ov: I I- 15. l"l..ynne, F. and Dart, P. ( 1998) Microbial Health H azards Associated with Emuent l"l..cusc. Urb1111 vJ/,111·r R escard, Assori11rio11 of' A11stmlin. l'l..esearch l"l..eport No. I++. !SUN I 876088 47 8 . Sobsey, M.I) .. Dufo ur, A.P .. Gerba, C .P. , LeChcv:illier, M.W. and Payment. P . (1993) Using a conceprnal framework for assessing risk to health from microbes in drinking water.)0111·1111/ A !VIVA March:++- 48. T e unis, P.F.M ., M edema, G .1-1. and H avclaa r, A.H. (1997) Assessme nt of the risk of infection by Cryprosporidi11111 or Ci11rdi,1in drinking water from a surf.1ce water source. vJ/111,•r Resc11rrl, 31 , 1333-1 346.

Authors Peter Nadebaum and Kathryn Walsh arc with Eg is Consulti ng Au strali a, and Daniel Deere is w ith South East Water Ltd.

CALL FOR PAPERS Water Recycling Conference To mark Water Week 2000, the A WA Australian Water Recycling Fornm w ill ho ld th e 1st Australian Water R ecycling Conference in Adelaide, South Australia, on '19-20 O ctober 2000. T he Conference will be an opportuni ty to learn about the latest and best water recycling developments in Australia. Richard Marks is the Conference Coordinato r, and he ca n be contacted o n 08 8343 8633. Day o ne comprises a water reuse environmental health workshop followed by a tour of landmark wa ter recycl ing projects such as the 20,000 ML/a Virg inia Pipeline Scheme, residential water recycling and aquifer storage and recovery. Day two comprises presentatio ns of papers on the themes of sustainable water cycle management, management of hea lth issues, resource differentiation and beneficial uses, reuse planning and risk management, role of reuse in environmental managem ent, irrigation and on-site reuse projects, advanced recycling proj ects, econo mics, finan cing and pricing. Mr Keith Israel, General Manager of the M onterey R egio nal Water Po lluti on Control Agency and leader of the M onterey County W ater R ecycling Scheme is the be keynote speaker. We in vite you to contribute a paper and join us in Adelaide fo r Water R ecycling Australia. Abstracts of not more than 250 words are invited on the subjects listed above. The initial call for papers closed on 15 May but abstracts received by 27 May will be considered o n the understanding that selected authors undertake to provide the completed eight page paper by -+ Augmt 2000. Fo rward abstracts to the conference managers, H artley Management Group P ty Ltd, Adelaide via email at wra2000@ hartleymgt. com.au. Contact Lo uise Carnell 08 8363 4399 for the abstract forma t.

WATER MAY/ JUNE 2000

WATER

SMALL WATER AND WASTEWATER SYSTEMS An International Symposium, Phoenix, Arizona, January 2000 Reported by M Leake This Symposium and T ech nology Expo for small water and wastewater system s was o rganised by the NSF International and the American Rural Water Res ea rc h and Ed u ca t io n Foundation and ran fo r th ree days with over 100 technical sessions in three d iffe re nt streams . Topi cs cover ed inclu ded Innovative Drinking Water Technologies: Membranes and Filtration: Disinfection: Innovative Wastewater

WATER MAY / JU NE 2000

Trea tment: Analysis and Monitoring: Decentralised /Onsite Systems: Operations: Distrib11tion and Resources : System Management: R egulatory and Compliance Tools: ETV Prog rams: Assistance and Assemnent and International Issues. T he co nference was well attended with over 550 delegates and more than 50 exhibitors. It offered mu ch with its focus o n small community wate r systems both from the papers presented

and the exhibitors present. T here was a c omp re h e ns ive cov erage of m an y aspects of small water systems including technical requirem ents and operation of system.s, regulatory approaches an d issues, management considerations and options, and reviews of successes and fail ures of currently operating sm all systems. A key point to note is that the US EPA defines a small co mmuni ty as one that has a po pulation of less than 10,000, however, many papers covered issues fo r co nsiderably small er communities. Man y of the issues that w ere covered are relevant to Australia, w ithin the general them e of 'What can be done to cost-effe ctively co mply with increasingly stringent regulati ons for small town drinking water and wastewater systems'. Surprisingly there was only a handful of delegates from outside North America . The conference offered a forum fo r the mu tua l transfer of technolo gies and ideas fo r sm all system s, and we in Australia need to take advantage of these technologies. A key initiative of the US E PA and NSF is the Environm.ental Tech nology Verification (ETV) pilot program on Package Drinking Water Systems. It aims to bring a greater number of regulated small communities in the US into compliance with the Safe Drinking Water Act by conducting trials to validate the claims m ade by suppliers of package w at er treat m e nt sys t ems. Although the US E PA does not go as fa r as to endorse a product it provides a means for third party evaluation of systems that would not be feas ible for man y small water au thorities, lo cal governments and suppliers. Since the ETV p rogram is op era ted by the Federal EPA it is automatically valid for all the oth er states in USA, w hich reduces the required investment by

WATER

suppliers for certifi cation, approval a nd verifica tion. T he ETV program is also actively in vo lved w ith approvals organ isations from Eu rope and C anada, all ow ing th e veri fi ca tion pro cess to c ross inte rnational boundaries and he nce facilitate a quic ker up-take of n ew and inno vati ve tec hnologies. B y redu cin g th is repetitive and poten tially exp ensive qualify in g and verifyi ng process, there sh ould be a redu ction in the costs of these sys tem s availabl e to the e nd user. Many pape rs discussed improvements in commo n processes eg. a better fil ter, che mica l reagent or process train, but with a foc us on how they addressed the issues specifi c to small drinki ng water and wastewa te r syste ms. There was also a significa nt emphasis on redu cing the complexity of sol utio ns for these small systems eg. a solar-powered pond aeration system to redu ce odo urs on overloaded lagoon syste ms, and incorporatin g an anaerobi c solids digestio n pit withi n a lagoon design to reduce odours. Th e con fe rence, and obvi ously the soc ial events, provided an idea l clearinghouse scenario fac ilitating netwo rking and transfer of ideas focussi ng on small systems. M y co mpa ny, Earth Systems P ty Ltd, was represented with a booth hi ghlighting our portabl e N e u traMill treatmen t system w hi ch we deve loped to disp ense alum and lime ove r storage lagoons (' W ater' M ay/June 1998). W e arc curre ntl y in vestigating the possibility of arran gin g a verifica tion mechan ism with in Au stralia unde r th e ETV p rogram as a m eans of improving access to th e North Am erican market . Ne il H ea ley, Area Manager, Gou lburn Va lley Water, presented an update of our 1998 paper inco rporating so me recent resu lts, illustrating how he was able to provide fi ve small towns (population arou nd 500 each) with water sa tisfying W H O guidelin es for a tota l ca pital ou tl ay of less th an $50,000. Both th e booth and th e paper attracted mu ch interest , and we have a ne twork of contac ts across the USA. I stron gly reco mmend tha t o pera tors, e ngin eers and manage rs wi th small co mmun ities co nsider the option of attending the next con fere n ce in 2001 . For man y the cost will be not mu ch more than attend ing th e AW A confere nce. W e too often tend to try and reinvent the w heel w hen it is not necessary and the conferen ce is an id eal way fo r the rap id transfer of tec hnology fo r sm all drinki ng water and waste wa ter systems. Fo r information on the E TV program, visit www. info@ns f.org, for a copy of proceedings email in fo@nsf.org. (A summary of the more innovative technologies was presented by Neil H ealey to the recent AWWOA Workshop in Daylesford, Vic . Neil than ks AWOOA for fi nancial assistance towards attending the Am eri can conference) .

The Author Micha el

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E A Gardner, L E Brennan, S N Lisson and A M Vieritz Key Words: Emuent, reuse, irrigation, econ o mi cs, mo dell ing, SUGAR.COST

Abstract Sewage effluent gene r a ti on 111 Quee nsland coastal sugar towns has th e potential to increase ca ne yield by over 700,000 t/year, if it is used fo r irrigation. T his paper d isc usses the biop hysica l performance standards requ ired for re use sc hem es, w hic h in clude freq ue ncy of eilluen t spillage in wet weather and reli ability o f irrigatio n suppl y in dry weathe r. Examp les are give n usin g ou tput from th e APS IM-Sugarcan e and MED LI crop growth / h ydrology m odels. Th e economics of effl u e nt reuse schem es is assessed usin g the fi nancial sp reads h eet m o d e l S U GAR.COST wh ich uses a comb ination of defa ult va lu es and sc h em e sp ecific da ta . A worked example is pro vided fo r a reuse scheme in so u thern Queensland, illustrating its eco nom ic viability unde r curre nt fu nd ing arrangem ents, and the pote ntial fo r gaining a larger share of the savings to Local Authorities by deferring sew age trea t ment plant up grade to tertiary treatm ent standards. Overall the m ethodology deve loped is logica l, tran sparen t and re producible allmNing an informed debate between all sta keholders in a reuse sc hem e.

WATER MAY/ JUNE 2000

Introduction Quee nsland sugar towns produ ce over 60,000 M L o f seco ndary trea ted sewage emu en t eac h year (Bryant er al. 1994) w hi ch if used for irrigation, has th e pote ntial to produce over 700,000 tonn es of extra sugar can e each year (assuming 1 ML of irrigation prod u ces 12 ton nes ca ne; K ingston 1994). With th e in c reas in g pr ess ur e b y t h e Enviro n menta l Protection Authority on local authori ties to e ithe r upgrade the qu ality of th e ir sewa ge e fflu ent to tertiary stan dards (a ca pital intensive optio n - H artl ey & K e lle r 199 7) or cease its discha rge to rivers and estu aries, there is an oppo rtunity for co mmu n ities in rural areas to turn thi s problem into a win/win situation, by reusing seco nd ary treated e fflu e nt for crop irrigation. T his option is partic ularly attractive in sugar towns w h ere t h e close ly settled n atu re of th e indu st ry p resen t m odest pumping di stances (eg. < 20 km) and the high w ater consumptio n of can e e nsures modest to h igh irrigation demands in eve n tropica l N o r t h Queensla nd (Rob e rtson et al .1 997) . M o reover because sugar is a processed product involving high temp eratures in its man ufacture, the health risks from in gesting e fflu e nt irriga ted sugar are m inusc ule co mpared w ith the risks from

say eillue nt irrigati on of salad crops that are eate n raw (Gardne r el al. 1998) . T he re are a number of major issues associ ated wi th the safe , environme ntall y sustainable re use of sewage e mu e nt, and these include h uman health risks, irrigation schemes hydrology and economic asp ects. Human health risks asso c iated with the micro biological quality o f e m uent, and the method of e fflu ent application have be e n disc usse d elsew here (R ynne et al. 1998, Vi eritz et al. 1998a). The hydrology of irrigation schemes is on e of th e key issues that dete rmine e nvironmen tal sustainability. The successful operation of e illue nt reuse sche m es depends largely on ge tting the correct co mbin ation of wet weather storage volum e (ML) and irrigation area (hectares) for a gi ven em ue nt produ cti on (M L/year) to e nsure a low fr eq uency o f po nd o vertopping, and a high re liability o f e fflu ent irriga tion suppl y. Th ese p e rform a n ce c riteria mu st al so b e ach ieved at th e lowest practica l cost. In th is paper we present a bri ef o verview of th e design tools available for th e irrigation- agro nomy compo n ents and apply th ese too ls to a case study taken fro m south east Queensland . The economic aspec ts of e ffiuent irrigation often gen e rates th e mo st debate as both th e eilluent produce r (a local au thority) and th e potential e illuent

WASTEWATER

consumer (e .g . ca ne fa rmers) be lieve th ey are eac h doing th e othe r a m ajo r favou r. And the recipie nt of this fa vo ur sho uld bear the m aj or cost of the irrigation scheme!! If we now introd uce the concept of co mmunity savings by deferrin g expensive sewage treatment plant (ST P) u pgrade to tertiary leve ls, and a mi x of su b sidi es from lo ca l and co mmonw ea lth au t horiti es for ST P upgrade o r reuse sc heme constru ction , id entifyin g fai r partitioning of costs and benefits becomes very co mpl ex. To assist in this important commu nity indu stry and environmental debate, we have developed the sp reads heet model SUGA R. COST to pe rfo rm fi nancial eva lu a tion of effl u ent irrigation by comparin g the benefits to loca l auth o rities in deferrin g sewage treatment plant upgrade and su bsidising effluent irrigation sc hem es vs the benefi ts and cost to sugar ca ne growers in investing in efflucn t irrigation infrast ru ct ur e . Th e m ethodology developed is logical, transparent and reprod ucible allowing an inform ed debate between all the sta keholders in a re use sc he me (i ncluding the State Governm ent) . In th is pape r we describe th e struc ture ofS UCARCOST, the input data required and illustrate its app lication to a sugar reuse sc heme 111 so utheast coasta l Queensland.

Irrigation Hydrology Design Tools Daily time step bioph ysical mode ls are proving invaluable in providi ng good estimates of irrigation de mand , taking into acco unt the interaction between c limate, crop g ro wth and so il ty pe. Irri gation demand alo ng w ith wet weather storage vo lum e are central to the success o r failure of an cffiuc nt irri gation scheme of given e fflu ent supp ly. T he irrigation demand - crop yield response predictions for reuse sc hem es in vo lv in g s u ga r c ane in d i ffere n t locatio ns have been calculate d using the physiologically soph isti cated, daily t im e ste p crop growth model A PS IM Sugarcan e (Keat ing et al. 1999) . Th e m ajo r ad vantage of APSIM Sugar is its ability to incorporate the effects o f suga r cane agronomy such as plant vs ratoon ca n e; pre harvest d ryin g down period, and so il nutrition etc o n can opy develo pm ent, and hence the amount and timing of irrigation requirements, and translate this into a predicted irrigated sugar yield. Th e interaction bet wee n effluent supply, effiuent storage, crop demand and climate vari ability was captured by adding into APSIM Su ga rcane t h e lagoon water balance algorithm s from

Table 1 . Average (40 year) predicted cane fresh weight for dryland and irrigated production, seasonal and effective rainfall, irrigation demand, crop water use figures for fully irrigated production.

Dryland Cane fresh we ight (t/ha) Irrigated Cane fresh weight (t/ha) Average rainfall (mm)

Ingham

1 06 171

100

126

177 2037

183 1734 628 1980 493 1120

2028 712

Effective rainfall (mm) Average Class A pan evap (mm) Average irrigation demand(mm) Crop water use (mm)

Cairns

2130 602 1314

th e e fflu ent disposal m odel MEDLI (Gardner el al. 1996) . Tab le I shows the average resul ts fo r a 40 yea r simulation run under dryland and fully irri gated co ndi t ions for a ran ge of sugar tow ns alo ng coastal Australia. Pred icted irrigation dema nd varies from 470 mm /year to 780 mm/year, yet the va riation is not always expl ai ned by rain foll. Apart from the substantial annual irrigation d e mand for a ll lo ca tion s (includin g Ca irn s) the modellin g has id enti fied so m e no n intuiti ve resul ts su ch as the similar irri gati on demand for Mackay (490m m /yr) and Crafton (470 mm / year) which has 700 111111 less rain per year, but similar potential crop water use (about I I 00 mm /year). One o f the ma in reasons fo r the hi g h yield/ low irrigation demand at Mackay is its (re lative ly) small vapour pressure deficit (wh ich AP SIM uses to sca le the Water Use Effic ie n cy facto r w hi c h con ve rts biomass into water use). In terms o f m axi m ising wate r use to mini m ise the area of irrigated ca ne, In g ham is the prefe rred locatio n (780 mm / y r irri gat ion demand) c lo se ly

741 2180 781 1522

Mackay M aryborough

Grafton

95 174 1 117 655 1640 707

110 162 1050 654

1362

1038

1650 474

fol lowed by Mary boroug h (7"10 111111/ yea r) . Once the pote ntial irrigation demand for a sc hem e is de te rmin ed it must be combin ed w ith irrigatio n area and wet weathe r storage to predict h ydrological behaviou r. Fig ure 1 shows t he effec t of various area-vo lum e combinations o n ovcrtopping vo lum es for a 2900 ML/ year effl uen t reuse sc hem e in south east Q uee nslan d, usin g 20 years of climate data. As the irrigati o n area in creases from 120 ha to 270 ha there is a sharp decline in overtopp ing volume fo r a ll wet weath e r storage volumes ( I 00 to 900 M L). T hi s effect is far m o re important than the re du ction in overtoppi ng volum e w ith increased sto rage volumes, for an y of the chosen irri gat io n are as (120 ha to 700 ha). A s this ovcrtoppi n g vo lume is seco ndary trea ted sewage effi uent, a discharge li cence has to be negot iated w ith the EPA o n the basis of volum e per yea r (eg I 0% of e fflu ent prod uction) or freq ue ncy of overtoppin g (cg fi ve events per ten yea rs) . Th is will be a location spec ifi c negotiati o n depending o n the

OVERFLOW VOLUME (ML)

2000 1800 1600 1400

1200 1000 800 600

Figure 1: Ave rage (20 year) predicted annual overflow volumes (ML) for various combinations of irrigation area (120, 270, 540, 700 ha) and storage volumes (100, 200, 500, 700 and 900 ML). Effluent supply is 2900 ML/year. WATER MAY/ JUNE 2000

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south east Queensland which fa lls within the volume-a rea bounds show n in Figu res 1 and 2.

IRRIGATION DEMAND MET(%)

Economic Analysis using SUGARCOST - its structure and assumptions

100

90 80 70

60 Âˇ 50

A120 A270 A540

V700

V900

Figure 2: Average (20 year) predicted applied irrigation expressed as a

percent age of the irrigation demand under fully irrigat ed conditions for combinations of irrigation area (120, 270, 540 & 700ha) and storage volume (100, 200, 500 , 700 & 900M L) for a 2900 ML/year effluent supply. assimilative capacity an d en vironmental sensitivity of the receiving environment. Most of the coastal sewage treatm ent plants in Queensland discharge into tidal rivers, whilst most of the e fflu e nt volum e is di sc harged into rive r mouths or estuaries (Bryant et al. 1994). Figure 2 shows the effect of irrigation area and w et w eath er stora ge volume on the reliability of irri gation supp ly, defined as the percen tage of irrigation d emand m et fo r unrestricted water supply (average irrigation demand for this location is 700 mm/year). T his is the hydrauli c performance criterion which is of most interest to farmers. T he irrigation reliabi lity percen tage encapsulates the effect of year to yea r varia tion in effective rainfall , w here in dry years, there is insuffici ent efflu ent volume to completely supp ly th e above average ir rigati on d em and , des pite w ithdrawals from th e wet weath er storage of e fflu ent ca rried over from previou s (abo ve average) rainfall yea rs. The major sensitivity is to irrigation area with a substantial redu ction in reliability as the area increases from 270 ha to 540 ha. T he initial gain in the reliability of supply with increasing sto rage size for a given irrigation area can be attribute d to a substantial decline in overflow (or wet weather spillage) Figure 1. Eventually th e storage gets to a size w h e r e overflow losses are minimal, and irri gation reliab ility is 1. The pump/pipeline cost calculator supplied with Sugarcost has been developed by FSA Environmental P/ L.

WATER MAY/JUNE 2000

primari ly restricted by the supply of effluent. A similar calculation ca n be presented for cane yield response, but because of the strongly coupled nexus between water use and yield in the APSIM model, the form of respo nse is very similar to that in Figure 2. It is clea r that th ere is a co nvergence between low overtoppi ng volum e and high irrigation reliability as wet weather storage volume increases, but a divergence between these two outcomes as irrigation area in creases. Mu ltiple runs using optimisation tec hniqu es in models such as MEDU (Gardner et al. 1996) can establish an area - volume domain where both irrigation reliability (eg 80%) and spi ll volume (eg 10%) criteria are fulfilled and then identify a generic minimum cost area - volume con1.bination, (Vieritz et al. 19986) but this fac ility is no t available in the APSIM Sugarca ne model. We do not believe that this is a severe limitation for this pap er as th e main objective of Figures 1 and 2 is to demonstrate the nature of th e interaction betwee n storage volumeirri ga ti o n ar ea on overtoppi n g behaviour and irrigation reliability. For complete scheme designs, calculating the frequency of overtopping (e .g. 1 event per 10 years or 5 events p er lO years or the volume of precau tionary discharge from storage) is often required by regulatory authorities., and this w ill require a more rigorous analysis than shown in Figure 1. Later in the tex t we will use SUGARCOST to describe the economic aspec ts of a 700 ML - 740 ha reuse schem e under constru ction in

SUGARCOST can be used to assess th e costs and benefits o f suga rcane effiue nt irrigation sc hem es by inserting appropriate values for many user-defin ed bi o l og ical , physi ca l and financial variables. Although equ ipped with a large set of default data, most of th e variables sho uld be user- defi ned because many costs are highly specific to th e scheme bein g examined. Operators of SUGARCOST should th erefo re have basic design information of the proposed scheme. Similarly, while SUGARCOST can be used to analyse the profitability of irrigated efflu ent schemes stand alon e, it should be used in conjunction with APSTM and MEDLI to obtain data on th e yield respo nse to applied irrigation rates associated with various storage volume / irri gation area combinations. T he basic structure of SUGARCOST is a series of linked Mi crosoft Excel Spreadsheets containing data for effiuent storage and di stribution, STP upgrading options, on-farm costs, and financial eva luations. Fea tures of th ese are discussed below. 'STP to Farm ' Infrastructure Costs Th e "STP to Fann " section of SUGARCOST calculates capita l and operating costs associated with pumping efflu en t from the STP to a storage near the cane area to be irriga ted, and pumping effiuent from the storage via a network of pi pelines to the cane fa rms as requ ired. It is assumed that these costs, p r in cipall y assoc iat ed with sto ra ge co nstru ction, p umps and distribution pipelin e, are incurred by the local authority unless otherwise specified by the user. In this section of SUGARCOST, provisio n has been made for the user to nominate alternative sources of funding fo r the infrastructure, including government subsidies and co ntributio ns to the schem e from cane growers. Costs fo r storage pond co nstruction depend on the volume of th e efflu ent storage. The storage requirem ent is d eter min e d fr o m the biophysical modelling using APSIM (and MEDLI) accordin g to percent effiu ent reuse and freq uency of overtopping criteria and crop water use. The costs of building a storage pond is rep resented by a default value, or a built in calculator' , however users may elect to enter their own estimate of storage construction cost ($/ ML). Likewise, for pump and pipe

WASTEWATER

costs, S UGAR.C O ST users ma y enter th eir ow n estimate o f pump and pipelin e costs or use the built- in calculator ' w hich estimates pump/ pipe cost fro m a set of user-defined physical specifications incl uding pipeline distance, static lift, flow rate, p ressure and hou rs o f p ump operation. An nual sc heme maintenance costs are estimated as percentages o f capital cos ts, wh ilst pump o perating costs are calculated in th e add- in pu mp/p ipeline calculator. O ther costs such as land acqu isition, environmental mo nito ring, applicatio n fees fo r lice nce and o ngoing annual lice nce fees can be estimated by the user and inpu t in to the spreadsheet. Cane production

Th e "Ca n e Pro du ct io n " s h ee t co mpares th e cos ts and be nefi ts of effi ue n t- irri gate d ca n e pro du c ti o n w ith th ose ass oc iated wi t h drylan d ca n e prod u ctio n. Th e user is requ ired to e nt e r d e ta ils ab o ut t h e irri ga ti o n sc h em e, in cludin g the wh o le sc hem e irrigated area, the n umber of fa rms in sc h em e, irrigatio n appli ed (ML/ ha), the can e yi elds fo r irri gated an d dry land prod uctio n , and the type of irri ga tio n sys tem install ed . 1rrigation capital costs can be specifi ed as either being incu rred in fu ll at th e time o f p urchase or expressed as an ann uity, w hich represents an an nual repaym ent o n borrowed fu nds. Th e sprea dsh eet also acc ounts fo r fi xe d ove rhead costs (e.g insuran ce, registratio ns) and va riable productio n costs or "cash costs" (eg fertil iser, crop chemica ls, fue l and lu brican ts). Additional costs assoc iated w it h op erating irriga t io n e quipm e nt are sp ec ifi e d separate ly. Th ese in clud e electri city fo r p umps, repairs and maintenance fo r irrigatio n equipm ent, and hire o f additio nal labour. The additio nal harvesting cost in curred as a result of higher yields is calcu lated in the spreadsheet. Grower contribu tio ns to sc heme capital costs and/ or ope rating costs are carried over from the lin ked "STP to farm " spreadsheet and added into the assessm ent o f cane produ ction costs. G ross in com e fo r bo th irrigated and dryland production is calculated , based on the can e paym en t formula. Th e sugar price and ccs fo r irrigated and dryland ca n e prod u ctio n a r e u se r-d e fi n e d va riables. T he spreadsheet calculates net profi t before in terest and tax per fa rm . In a later section , the sensitivity of th e calcu lation to sugar yield and price is explored (T able 4).

STP upgrade

The decisio n to set up an efilu ent irrigatio n scheme w iU be influ enced not on ly by the potential profi tab ili ty of using eillu ent fo r irrigatio n, but also o n th e com parative profitability (o r n et co sts) of al te rn ative reuse options. T ertiary sewage trea tm ent involves a high level of nu trient remo val and is an alte rn ativ e to e fflu e nt ir r iga t i o n . SUG AR.. C O ST co nducts fin ancial evaluatio n fo r three STP upgrade o p tions to tertiary trea tment: • Upgradi ng activated sludge p lant to reduce N by biological tream1en t and P by chemi ca l treatment. • Upgrad ing activated sludge p lant to redu ce N and P by b io logica l treatm ent. • Insta ll ing a n ew BN R. (Biologica l N u tri ent R.. emova l) plant (bio P and bio N) . T he cost o f upgrad ing STPs was obtained from a n umber o f so urces (Ken Hartl ey 1998 and pers. com. , Geoff Ham ilton , Gold Coast C ity Co u ncil, pers. co m. , So nja Ko marows ki , R edland Shire C ou ncil, pers. co mm). Estimates o f capita l and annual o peratin g an d ma in tenance costs are provided for a range of upgrade optio ns in SUGAR.C O ST. T he costs to upgrade ST Ps depend on the type o f plant and equi pm ent alrea dy in operatio n, the vo lume of e ffiu ent t reated , th e n utrie n t co n ce n tratio n prese nt after secondary treatmen t and the target leve l o f nutrient after tertiary treatment. Beca use so many variables affect th e costs, the va lues calcula ted in th e sprea dsheet sho uld be used o nly as a guide. Financial performance Annu al cash flows and net prese nt values (N PVs) are calculated fo r both the Local Au tho rity incurred costs (co veri ng th e inves tm en t in irriga tio n schem e in frastructu re), the o n- fa rm costs, and the benefits o f using eilluent fo r irrigati on . Fo r the N P V calculations, only the add itional cash fl o ws directly related to the reticulation o f eilluen t fo r producers (lo cal au tho rities) and consum ers (cane growers) have bee n incl uded in the m odel. Likewise, only additional costs involved in the alternative upgrading o ptio ns are considered. T he spreadsheet is currently configured fo r a 'base case' of d ryland cane productio n. H owever , altern ative base cases, m ch as farm with existi ng irrigation e qu ip m ent an d a limited supply of irrigation water may be co nsidered. From the local authority's perspective, the 'base case' in SUGAR COST is discharge of seco ndary treated

efflu ent to waterways using existing STP treatment. A discounted cash flow approach over a 20 year perio d can be generated fo r two capital payment optio ns: a) use of own funds for up- front purchase of capital b) use o f bo rrowed fu nds repaid o ver the fu ll life o f the proj ect. The discountin g procedu re captures th e opportuni ty cost o ver time that is assoc iated w ith the resources tied up in the pu rchase. A key assu mptio n in the curren t vers io n o f the sp rea dsheet is that th e costs and benefi ts remain constant o ve r th e li fe of the proj ect. T h is mea ns that un it prices an d costs m ove in lin e with ch anges in the rate of inflatio n, and th at th ere is no yield or sugar price variab ility from yea r to year. Economic analysis - Case study

Th e sa m e case stu dy of a south ern Qu ee n sland r e gio na l s u g a r t o wn described in Figures 1 and 2 was also used to exp lo re the retu rns (and savin gs) to co u ncil and cane growers by co mmissio n ing a reuse schem e, thereby defe rring STP upgrade . T he assu mptions w e used w ere taken fro m the scheme design unde rtaken by an engineeri ng consu ltant. Effluent Vo lume

2,920 ML/ year

Storage Volume

700 M L

Irrigation Area

7 40 ha

Number of Farms Dryland Yield Irrigat ion Yield Irrigation Applied Pipeli ne length (to storage)

14 80 t;h a 120 t / h a 3 ML/ ha/ year 6.6 km

Pipeline length (from storage to farm) 6 km State Government Subsi dy

50%

C ompared with the m odelled ou tput, the existing sc heme design has a muc h large r irrigatio n area (740 ha vs 270 h a) and a considerably smaller irriga tion app li cation (3 ML/ha /yr vs 7 M L/ha / year). Whilst the volu m e-area combinatio n c ho se n by th e sc h e m e con sul tants minimises overtopping volu me (Figu re 1) th e resulting lower amo un t and reliability o f irrigatio n supply (Figure 2) h as m ean t that th e irrigated yields we used were adj usted do w nwa rds to 120 to nn es ca ne/ha (vs l 74 t/ha predicted - Table 1). The sugarcane produ ction econ o mics are based on a represen tative farm for the so uth ern Q u eensland ca ne p ro duc tio n regio n . T ypical productio n costs for the rep resen ta tive farms were sourced from Ca n egrowers (199 7) and AB ARE (1997) . R evenue fro m cane sales was calculated using a suga r price of $320/t WATER MAY / JUNE 2000

WASTEWATER

and a ccs (commercial cane sugar) of 12. Capital and op erating costs fo r a winch irrigation system were included. It was assu m ed that the representative cane fa rm did not have an existing irrigation reticulation system. It is assumed that local authorities and consortium of growers participating in the sche1ne have negotiated a costsharing arrangement that involves cane growers contributing to the infrastructure capi tal and operating costs associated with deliverin g eilluent from the central storage to the farms. For this case study, this comprises a con tri bution to the cap ital cost of the scheme collected through a $10/ML levy over 20 years. In add ition, growers also full y pay for the operating and maintenance costs of the sch eme through a $/ML paym ent. The loca l authority is eligible to claim a State Governm en t (Department of Local Govern m ent and Plannin g) subsidy of 50% contribution towards the capital costs of the irrigati on schem e. A 40% subsidy can also be claimed towards the cost of upgrading an STP from secondary to tertiary treatment, which will allow conti nuing discharge of eilluent to water bodies . Table 2 shows the additional annual costs and benefits to local authorities and growers from in vestment in an efflu ent irrigation scheme. An nual costs and benefits have been incorporated in to a d iscounted cash flow analysis to estimate the va lue of th e investment over a 20 year period. N et present values were calculated using a 7% and 10% discount rate (Table 3) . Grower benefits On the basis of this case study, investment in effluent reuse fo r irrigation is worth whi le fo r a can egrowe r. T h e additional annual profi t (before interest and tax) compared w ith dryland production is approximately $17 000 (i. e. $49,900- $32,900 Table 2). Over 20 years, the net present va lue for a 7% discount rate is $205 000 per farm (Table 3). Th e combined NPV for the 14 farms in the schem e amou nts to $2.87 mi llion net benefit (Tabl e 3). T hese numbers, as expected, reduce fo r a 10% race but the returns are still very favourable. NPV is highly se nsitive to changed sugar pric es and y i eld in c r eases attribu tabl e to eillue nt irrigation (Table 4). With a projected yield increase of 40t/ha, NPV is 2.5 times higher if the sugar price obtained increases from $270/ t to $370/t. H owever, the investm ent in effluent irrigation from the growers point of view would not be

WATER MAY/JUNE 2000

Table 2. Additional annual costs and benefits to local authorities and growers associated with investment in an effluent irrigation scheme. Benefits per year

Costs per year

Local Authority

$29,200 - grower contribution to scheme collected t hrough $10/ML levy.

$1.485m - capital cost after 50% State Govt. subsidy (once off)

Individual cane grower

$49,918 - revenue from additional cane product ion of 40 tjha.

$32,975 comprising: - $8,136 (annuity for 15 years only) capital costs irrigation equipment Âˇ $14,800 add itional harvesting costs Âˇ $10,039 irrigation O&M costs - $4,013 total contributions to scheme infrastructure and operating costs

worth while if a below-expected yield increase of only 20t/ ha was achieved, combined with a $270/ t sugar price over the in vestment period (T able 4). The sensitivity analysis is pertin ent in the current period of low sugar prices being experienced by the sugar industry. The sensiti vity analysis highlights th e importance of considering long term informa tion abou t s uga r ca n e yie ld s and comm.odity prices because they have such a significan t impact on the financial viability of th e investment. Council - effluent irrigation vs STP upgrade

From the loca l au thority view, investment in an eilluen t irrigation scheme appears n1.ore economically attractive than replacing the STP with a tertiary treatm ent BNR plant. W hile neither option generates a positive NPV (Table 3), if faced with having to make a choice between th e two options, the local authority would be better off by $11.4 million at a 7% discount rate by deferring STP upgrade and investing in an effl uent irrigation sc hem e (Table 3) . The savings reduce to $10.3 m illion when a 10% discount rate is assumed. Effiuent re-use sc hem es can cl early benefit both loca l auth orities and cane growe rs. SUGARCOST presents an opportunity fo r both parties to n egotiate for a share of these savings.

An important compone nt of this financial analysis is regu latory permission to di scharge secondary treated effl uen t into waterways during extended periods of wet weather. In wet coastal climates it may onl y be practical to reuse say 8085% of annua l efflu e nt production, because the wet weather storage acts as net rainfa ll accumulator (i .e. rainfall input exceeds evaporation losses). H ence increas ing storage size actually increases the volume of effluent required fo r reuse/ disposa l. The NSW EPA (1995) rec ognises this issue to some extent and allows the average freq uency of overtopping to inc rease as the nutri ent and BOD concentration of the eilluent decreases. T his approach is also consistent with their load based licensing philosophy. A corollary to this approach is precautionary discharge which is co ntrolled efflu ent discharge into receivin g waters that are made only under set conditions which include the effluent discharge rate, the river flow rate and storage level in the wet weather storage (Pettit and Murtagh 1999). The objecti ve is to achieve a minimum (effluent) dilution rate in the of at least 70 in the river. Other site specific criteria can apply, suc h as faecal colifo rm concentration .. Allowable faecal coliform levels of th e discharge is usually strict with a count of less than 200 cfu/100 ml on a 95

Table 3. Discounted net benefits over 20 years, at 7% discount rate, associated with two effluent management options and the effluent irrigated sugar cane production for both individual farms and all farms in the scheme . The numbers in brackets were calculated using a 10% discount rate. Council option 1 : Effluent reuse scheme

Council option 2 : STP upgrade*

-$1,1 54,001

-$12,572,392

$205,003

$2,870,043

(-$1,211,544)

(-$11,536,605)

($153,357)

($2,146,994)

* 30,000 EP Plant.

Effluent irrig cane (per farm)

Effluent lrrig cane (whole scheme)

WASTEWATER

percen tile basis (P ettit and Murtagh 1999). In NSW the EPA (P. Ma rczan pe rs. co m m .) wi ll also re quire eill uent that is disc harged e ith er co ntinuously or above a certa in frequ ency, to m ee t e illue nt discharge criteria. Th ese cri teria arc determ in ed on a case by case basis ta ki ng into account the water q uality objectives fo r t he receiving wate r and the requ irem ents of Th e Protectio11 cf the E1wiro11111e111 Opernlio11s A ct 1997. For exa mple, in inla nd waterways cmuent w ill often be requ ired ca n designate the rece iving river as "sensiti ve waters" and requ ire the eillu ent to have nutrie nt levels of N::; 10 mg/L a nd P ::; 0.3 mg/ L, 90% of the tim e . In th is case tertiary trea tm en t of the emu ent w ill almost certain ly be req uired, an d co u ld re m ovi n g som e of t h e econom ic be ne fi t to co un cil of deferrin g ST P upgrade (T ab le 3 - Co u nci l Option 2) . Howeve r, in NSW in centives are also provided in t he form of up to a I 00% reductio n in the po llu ta nt load co mponent of lice nce fees for that portion of th e e ffiu ent that is reused. T h is approach has enco uraged a st ro ng m ove towa rds effiuent re use in m ajor co un try tow ns such as A lbu ry, M udgec, Na rrab ri and Arm idale (P. Marcza n pers. co m m .. ). l t wo u ld be most iron ic if regu latory ini tiatives to protec t water q uality encou raged the disposa l of tertiary treate d cffiuen t befo re market fo rces, d riven by wate r reform initi ati ves, fu ll y recognise d the econo mi c ben efits of reusi ng trea ted emucnt as an irrigation water so urce. In Q uee nsland , the EPA advises (L. Bevis pers. co111.m.) that the di scharge of seco nda ry t reated efflue n t fr o m sewage trea tm en t works to waterways , in cl udi n g wet we at h er releases, arc negotiated on a case by case basis in accordance w ith t he requ irem ents of the

E1/l)iro11111e11tnl Protectio11 Policy ( vVnte1) 1997 (E PP Water). C le arl y SUGA R. COS T h as t h e potential to in flu ence gove rnme nt policy to increase t he ec o no m ic attractiven ess of sustainabl e re use options pa rtic ularl y as it is a more preferre d disposal o ption than re leases to surface waters, and in li ne with the phi losophy of the EPP Wate r

Conclusion T he , ugar indmtry i, we ll placed to use sewage effluent as an irrigatio n so urce and increase ca ne yields by over 700,000 tonnes per year. SUGAR.COST demonstrates that even under curre nt cost sharing arrangemen ts w it h local

Table 4 . Net Present Values for one cane fa rm for three sugar prices ($270/ t, $320/ t , and $370/ t) and two projected yield increases attributable to effluent irrigat ion (20t/ ha and 40t/ha) Addit ional Yield tjha

$270/ t

$320/ t

$370 / t

20 (poor)

- $ 37 1 80

$5 960

$49 1 00

40 (e xpected )

$118 723

$20 5 0 0 3

$291 283

au thorities, emue nc irrigation is li kely to be economica ll y (and soc ially) worthwhile. T he m od el has also identifie d th e potential for cmue nt irrigators to gain a share of t he savi ngs ca ptu red by u rban rate payers from defe rring th e upgrade of ST P s to tertiary s ta n dard s. Thi s economic argu m ent di sappears however if Loca l Au th o rities a rc forced into tertiary trea tm ent by regu la tory or ocher types of co mmu nity pressu res w itho ut othe r ince nti ves be ing in place. A remaining cha ll enge fo r the sugar ind ustry is to ensure that secondary trea ted cffiu en t can be irrigated w it ho u t enda ngering t he h ealth of farm ers, th eir fa milies o r th e pu blic at la rge. T his wi ll req u ire a combinatio n of good em u ent di sinfection pra ctices and care in the m et hod of em uc11t application (e .g. spra y 11s fu rrow vs d rip) (Gardn er et al. 1998 , l'tyn ne et nl. 1998) .

References AI3A ls.E ( 1997) . Australian Farm Surveys Repo rt 1997 , Ca nberra. 13rya nt, A .. G ardne r, E.A. and 13cavers, P. 1) . ( 1994) . Generation and land disposal of sewage effluent in Queensland: a survey of c urre nt prac t ice . QDP I P ubli cation Q 9-1034. pp. 2-1. Canegrowers ( 1997) . C anegrowing costs and returns in the 13undaberg district 1996. Loca l district newsktter. Gardner, E .A., C hinivasagam. N., R ao , A., Vie ritz, A., 131acb ll, P. , R yn ne . F., Thomas, Is.., Klieve, A. , Ulaney. 13 ., Green, P. and Barry, G. ('I 998). Quantifying the Healt h Risk of Spray Irrigating Treated Sewage Effiuenr. P rese nted at W ate rtcc h '98, A WW A. 13risbane. April 1998 . Ga rdner , E.A., Vieritz. A. , Atzen i, M .. 13eecham, R... Littleboy, M ., C asey, IC Sharma , P. , Farley, T .. Da v is, Is.., McG raha m , E., and Dillon P. ( 1996). MEDLI: A compu ter based design model for sustainable ef1-luent disposal from intensive rural industries using land irrigation. In: ' Land Application of Wastes in Australia and N ew Zealand: ls.escarch and Practise' (Eds. P.J. Polglase and W.M. T unningley). pp. 11-1- 12-1. Proctoedings I-Ith Land Treatment Collective M eeting, Canberra, 30 SeptemberI October. H artl ey, K.J. ( 1998). The cost of Australian 13NR plants. Water. Jan/Feb. pp.20-22 . Keat ing, B.A., R obercson. M .j. , Muchow, R .C. and H uth, N.I. (1999). Modelling sugarcane production systems I: Description and valida-

tion of the sugarcane module. Field Crops Researc h, 6 1: 253-271. Keller, J. and Hartley, K.J. ( 1997). Biological Nutrient R emoval - Present Status and Future D irections. Water. September/ October, 1997. Kingston, G. ( 1994) . Be nchmarking yield of sugarcane fro m est imate of crop water use.

Prorel'dit(es of tlie A ,wmlia11 Sorie1y Ca11e Ter/111vlo,~is1s 16. 201-209.

of S11.~ar

N SW Environment Protection Auth o rity ( I 995) . !)raft guidelines for the utilisation of tr<:ated effiucnt by irrigation. Pettit. Is.. and Murtagh, J. (I 999) . R.euse from the fa rme rs viewpoint - how to q uantify th e be n efits . A WW A R.egio nal Co nferen ce 1999, Albury N SW pp.1 -7. ls.ynn e, F.G., i)arc, P.J.. Gardner, E.A. and Vieri tz, A.M. ( 1998) . Effiuent reuse c urre nt practice and presentation of a reuse "decisio n tree". Watertech '98, A WW A, 13risbane, April 1998. n..obcrtson, M .J. , lnman- 13ambe r. N .G. and Muchow, ls..C. ( 1997). Opportunities fo r improving the use of limi ted water by the suga rcane crop. In Keating 13A and Wi lson J ls. (eds), Intensive sugarca ne product ion: M eeting the C halle nges 13eyond 2000, C AU International, Wallingford, pp. 287-304. Vieritz, A.M.. Gardner, E.A. , Ulac kall, J>., C hinivasaga m , N. and Ayotte. K. (1998a). Quantifying health risk from e Alue nt irrigation using the ME l)LI modd. 6th NSW ls.e cyc kd Wat e r Seminar, Sydney, November 1998, pp. 35-41. Vieritz, A.M. , Gardner, E.A., Littleboy. M .. Atzeni , M.G., Ueecham , R .E., Casey, K.D ., Farley, T., D avis, J.ls.. , Sharma, P. K. , G ahan , E.J. and l)i llo n, P.J. ( 19986) . M EDLI - A model fo r designing sustainable irriga tion syste m s fo r th e r e u se of effluent .

l.:1wirm1111ÂŁÂˇ111al Bm~(,rs <!f' Soil 1\l/a11,wc111e111. 1998 National Soil Science Confere nce, 13risbane, 27-29 April 1998 .

Authors Ted Gardner is a Prin c ipal Scien tist wit h th e Q uee nsland D epartme nt of Natura l R esourc es at l ndooroop ill y, Bri sban e . E mai l: ga rd n e t@ dnr.q l d. gov.au . Dr Lisa Brennan and Dr Shaun Lisson are a Ag ric u ltural Systems Econom ist and Crop and Soil m odeller with CS IRO , Divisio n of Tropi ca l Agric ultu re in Brisban e and T ownsv ill c (respec tiv e ly) . Alison Vieritz is a n Environmental m ode ll e r w i th th e Qu ee n sla nd Dep a rtm e nt of Natural R esou ces at lndooroopilly. The fi rst th ree authors are asso ciated wit h t he C R C fo r Sustainable Sugar Production w hi c h spo nsored this study . WATER MAY/JUNE 2000

ENVIRONMENT

Ill

AUSTRALIAN WATER RESOURCES ASSESSMENT - 2000 W S McDonald, C L Creighton, P D Erlanger* Abstract Th e Nat i ona l Land and Wate r Resources Audit's (Aud it) terms of reference require a National Water R esource Assessmen t to be und ertaken. T his assessm en t is th e fourth water resourc e assessment undertaken in Australia o ver the last 40 years. Th e most recent assessm en t bei n g th e " 1985 R ev iew o f Australia's Water R eso urces and W ater Use" (R eview 85) conducted under the au sp ices of th e Au stra lian W at e r Resources Council. The focus of th e Audit 's wa ter resource assessmen t is to co llate data and make it available in readily accessible *This paper was presented at the World Water Congress, Melbourne.

format and to provide information on th e status and trend in water resou rce use and availabili ty. This assess ment is being done in the co ntext of water resource manage ment activities of the States and Territo ries. Options fo r mana gem ent activities, resou rce development and protection wi ll also be explored - recognising that natural resource managem ent inclu des biop hysical, social, econo mic and politica l di m ensions. This paper ou tlines the Audit's W ater Availability Theme cu rrently bein g undertaken by the Audit in partn ersh ip with Austra lia's State and Territory agencies . After a W orkshop in Jul y, the fi nal report shou ld be available on the web-site by August.

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Introduction · The Audit Th e Natio n al Land and Water R esources Audit w ill fos ter mo re rigorou s na tu ral reso urce m a na gement dec ision makin g by collatin g and makin g readily availabl e data on Australia 's land , vegetation and water resources. The Audit is tasked with providing a nation wide assess m ent o f Australi a's land , vegeta ti o n a nd water re so urces to support sustainable developm ent now and in the future. The Au dit's Strategic Plan ide ntifies fo urteen key chall enges facing natural reso urce man age men t in Australia . T he

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ENVIRONMENT priori ty natural reso u rce man age m en t iss ues have been group ed into seve n the mes: w ate r availability; dryland salin ity; vege tation; ra nge lands m o nitoring; agric u ltu ral produ ctivity and su stainabil ity; capacity to imp lem ent c han ge and ecosys te m hea lth. Th e key fo c us fo r these Aud it the mes is to place th e statu s and trend in resou rce co nditi o n in the c onte x t o f c urr e nt m ana ge ment respo nse and to ide n tify options fo r re m edial actio n , res ource devel opmen t a nd prote c tion - rec ogni sin g tha t natural resou rce managemen t incl ud es bi o p h ys ic al , soc ia l a nd economi c compo n en ts. T he Aud it w ill be driven by th e concept o f best available knowledge a nd it w il l be tasked o ver three yea rs, w ith a total resource available of $30 million . It will pu t in place an Au straliaw ide decision- makin g system for natu ral resource m anage me nt and to repo rt on key issues fac in g Au stralia so th at in ves tm e nt m ay be b e tt e r tar ge t e d. Particu la rl y, th e Audit is tasked to prov ide data , a nal ys is a n d apprai sal w h ic h fa c ilita te impro ve d d ec isionm aki ng on land , vege tatio n and natural resource mana ge me nt by bu il din g an Australia-wide information base . The Audi t sho uld me et natural res ourc e nee ds in th e areas of po li cy assess me nt and deve lopm e nt, in vestme nt dec isio ns, evaluatio n of progra m and poli cy perfo rman ce and direct reso u rce mana ge me nt, partic ularl y by Governme nt. T he primary focu s of the Audit will be on the needs o f C om m o nwealth and State age nc ies. The G ove rnme nt recogni ses that th e Aud it w ill also have value for Lo ca l Go ve rnme nt, rural industries, com mun ity groups, and a range o f oth er g ove rnm e nt a nd non -g o ve rnm e nt organisation s. Wh ere poss ible, the Audit wi ll pro vide data to assist plann ing at the catc hment and regi o nal le vel. Seve ra l c hara cte ristics differentiate the Audit fr om previo us resource in ve ntory exercises. T hese include requ ireme nts to report holistically o n bioph ysica l, social and economic fac tors releva nt to natu ral resou rce manage me nt and to link resource cond itio n and tre nd w ith resource manage m ent prac tice . The Audit w ill also explo re a nd report o n n a t u r a l r eso u r ce m a n age m e n t rem edi al optio ns and ide ntify opportunities to d eve lo p a nd impl em e nt a n a tio nal reso urce da ta m an ageme nt infrastruc tu re.

Water Resource Assessments Review 85 (DP!E, 1987) still serves as the o nly co mprehe nsive source of water resource availability and use da ta across

Australia's major groundwater resources: abstraction during 1983/84 (G L)

0.0 - 0.5 0.5 - 1.5 1.5 - 2.5 2.5 - 5.0 5.0 - 10.0 10.0 - 15.0 15.0 - 23.0 23.0 - 43.0 43.0 - 79.0 79.0 - 322.0

(data from Australian Water Resources Council 1985 Review ofAustralia's Water Resources and Water Use.)

Figure 1 - Major groundwater resources - Water Review 1985 Au strali a (e.g. gro und water abstractio n , see Fi gure 1). H owever, the use fuln ess and re levance of this pote ntially va luable inform a ti o n have bee n ma rgi nali sed beca use it has not been kept up to date. Fac tors co n tr ibuti n g to th is have include d wate r resou rce de ve lopments; e me rgent iss ues suc h as environm ent flow requirem e nts and provision s; institu tio nal and water reso urce manage m ent c h an ges su c h as t h e C oun c il for Australian Gove rnm e nts (COAG) W ate r R eform agenda. It has bee n estim ated that gross wate r supplied has increased by approximately 25% betwee n 1983-84 and 1995-96. Increase in wa ter use can be attributed to signifi cant in creases in irri gated agri culture wh ich accounts for approx imate ly 70% of natio nal water use . Assessm ents show th at 60-70% of th e additio nal w ater is sou rced fro m pri vate di ve rsion s, grou nd wate r, unregulated strea ms and fa rm dams wh ile th e re maind er co mes fro m the con ve nti onal surfa ce water diversio ns . lnteresti ngly, urban centres have sho w n eithe r low increases or absolute decreases in w ater consumpti on o ver th e sam e p eriod (AATSC/ lEA,

1999) . Th e A ud it's W a t e r Ava il a bilit y Th em e ac ti vities wilJ characterise eac h of Australia's surface wa ter and groundwater resource syste ms in terms of water ava ilabi lity, use (the 1996/ 97 fin ancial year has been selected as th e baseline year for the A udit), alJocation and manage-

m ent regime . O n th e basis of th is charact e r isati o n , eac h Surfa ce Water M a n age m e nt Are a (SWMA ) a n d Ground w at e r M.an age m e nt Arc a (GWMA) is to be categorised accordin g to the degree of water resou rce co mmi tm ent , taking account o f co nsumptive and enviro nm ental w ater requirem en ts to th e exte nt that these are alread y defined. Th e Audit's Ecosystem H ealth them e wi ll bu il d on th e water quali ty and w aterwa ys condition work bein g undertake n thro ugh State and T errito r y agency monitoring programs, and the N a t ion a l Ri ve r H ea lth P ro g ra m 's AUSR fVA S compo ne nt to dev e lop furt he r th e cond itio n and trend o f o u r w ate r res o urces fr o m a n ecolo gic al pe rspe ctive.

Issues in the Development of a National Water Resource Assessment The key issues facin g Australia 's wate r resou rce managers were ca nvassed as part o f a needs analysis undertaken at the inception o f th e Audit. From the nee ds an alysis it beca me evident at early stage that the Audit wou ld not be able to co ver all issues or answ er alJ qu estions over its 3 yea r operatio nal life and limited budge t . The Audit is heavily reliant on the u se of ex1st1ng data, partnerships w ith t h e key cli ents and stakeho lders of th e Audit, in partic ular, th e State and T errito ry agencies. T o maintain relevance and credibility th e Audit th em e w ork pla ns WATER MAY/ JU NE 2000

ENVIRONMENT

ha ve bee n design ed to tackle the highest priority issues and do those well. This is in prefe rence to sprea din g the reso urces thinly across a broader range of issues. The key questions raised w hich are directly rel evan t to water availability and qual ity are summ arised belo w . Surface water availability, allocation, use and efficiency of use

• What is the curre nt degree of com mitment of rivers and streams by use? • H ow can we e nsure that allocation processes promote equ i table and economical ly e ffi c ie nt use within susta inability limits' • W he re and when do co nflicts occur b e t ween al loca tion s and demands, between allocations and environmen tal needs, and between usage and en viron me n tal needs? • H ovv is th e c urrent water refo rm agenda c hanging use' • What is the in-stream demand and va lu e for water fo r recreational and oth er uses? • Where are water qua lity and water reuse co nsiderations influenc ing use' Sustainability of surface water use including environmental flows

• Wh at is the e n vironmental status of o ur rivers? What allocations arc provided to ens ure river hea lth' • H ow do we best define environme ntal req uire m e nts for diffe ring ri ve r system s covering quantity, timing and othe r attributes relating to ecological processes? • H ow wou ld allo cati ons and restri ction on use, if an y, need to be c han ged to deliver sustainability'

Infrastructure and investment

• W here do opportu nities for urban and ru ral wate r infrastru ctu re developm e nt occur so that resource use is optim ised and issues of land ca pability, water resource management, socioeconom ic and environmental he ritage are covered? • W here is the existing water infrastructure viable ; w here can it be made more viabl e; and where is the cost of maintenance, harvestin g and supply greater than the total return s fro m t he w ater suppli ed by that in frastructure' • Where do sign ificant opportuniti es to ac hieve water use effi cie nc ies and/ or e n vironmental imp rovement t h rough capital investm ent, improved management of infrastructure or oth er m echanism s occur? • H ow wi ll populati on c hanges affect the demand for water and availab ility for rural and other extensive uses' The Audit's national water resou rce assessment will ch aracterise eac h of Australia 's surface water and grou ndwater systems in terms of water ava ilabili ty, use, allocation and manageme nt regime . On the basis of this characterisation each catchment is to be categorised accordin g to the degree of water resou rce commitment and m anage ment responses, taking acco unt o f consumptive and e nvironmental water requirem e nts. A broad assessme nt o f future system de mands and potential fo r development will also be unde rtaken. Manage me nt acti ons for Au stralia's water resou rces wi ll be identified in the context of the Commonwea lt h of Austral ian Governments (COAG) Water Reform and Ecolo gical Sustainable Development objectives. In combination w ith other

Groundwater availability against sustainability limits - demand, allocation and efficiency of use

• .H ow can susta inabil ity be defined for grou nd water? • What is the influence of gro undwater use on groundwate r quality' • Where do mi smatc hes occu r between groundwater availability, allocation and de mand? • H ow are c hanges in surface water allo cation policies changing grou ndwater use and de man d' • H ow do we ensure total water cycle management, given t h e impact of in c reased su rfa ce and gro u n dwater demand? • R ecog ni si n g the d i ve r gence i n approach and manage me nt arrangem ents between States, how can we develop consiste ncy in data collectio n?

WATER MAY / JUNE 2000

Audit act i v iti es, parti cu la r l y the Ecosystem H ea lt h (catchment/river /est uarin e ecosystems) Theme, a report card fo r each of Au stra lia's ca tchm e nts w ill be prepared.

The Assessment Framework T he maj o r co mpo nents and co ncepts that form the basis for the Aud it's water r esource ass ess m e nt a rc presented be low. Geographic Reporting Framework

R ev iew 85 compil ed surface water and gro undwater resou rce information for 245 rive r basins in Australia, and then aggre ga ted in to 77 region s and 12 drainag e d i v ision s . Groundwater Pro v in ces we re bro ad ly defined a geograph ic framework as pa rt of Review 85. From a management perspec ti ve these regions have no real valu e. T he Audit 's assess m e nt w ill report b y Austra lia's grou nd wa te r and sur face managemen t areas t h at have been defined by the relevant State or Territory water resource m anagement agency(s). In so me cases these w ill coin cide w ith the Austral ian Water R esources Council (A WRC) basin bo undari es - the A WRC basin has been set as the 1111111111um repo rting unit fo r the Audit. Resource concepts

R eview 85 intro du ced a number of reso urce co ncepts (Be rg man , 1989) . T hese co n cepts we re deve loped throu gh ex ten sive con sultatio n and debate wi th the water r esource management community . There still re mains a high degree of ow nership (adoption) and und erstanding of these concepts. To a large exten t th ese conce pts wi ll be carried forwa rd in to th e current assess-

System Yield 100%

•• I I I

Mean An nual Flow Divertible Yield

I I

Non-diverti ble Resource

Environm ental Flow Req's

Sustainable Yield

Spare Water

Developed Yield

Deve loped Usage Developed Usage

Figure 2. Conceptual Fra m ework for Catego rising Water Resource Systems

ENVIRONMENT

100

Total Resource

•

Environmental Provision

•

Spare Water Actual Use

System Category

Figure 3 . Conceptual Framework for Categorising Water Resource Systems ment. Brie fl y, the resou rce co ncepts were: • Total w ater resource - th e vo lum e o f wa ter present in the e nviron m ent , measured as mean annual run off fo r surface water, and mea n annu al recharge fo r groundwa ter • D ivertibl e resou rce - th e portion of ru noff and rech arge w hi ch can be developed for use . • Developed resource - the portio n of the dive rtible resou rce w hi ch has been develope d fo r use. • Resource utilisation - a measu re of the portion o f the developed resou rce w hich is actually used. • Major and minor resource - the distin ctio n be tween maj o r and m inor resource in th e Audit's assess ment has been d ropped . Add itio nal resource co ncepts to be used in th e Audit's water resource assessment are outlin ed below. Critical period

Fo r the pu rpose of categorising the

wate r resource systems, the te rm critical p eriod has bee n introduced . T he criti cal pe riod is th at period ove r w hic h the de mands on the reso urce resu.lt in the greatest stress on the system , inclusive of e n viro n me n ta l n ee ds. M ea n an nua l flo ws alo ne, altho ugh useful, can be mislead ing as o fte n m uch o f th e to tal flo w occu rs over a very small period o f ti me and the rest of the year can be made up of low flo ws or even no flow at all. M any strea ms only fl o w fo r short pe riods e very few yea rs. Th e critica l period con cept has bee n introdu ced into th is aud it to m ake allo w an ces for these factors and is de fi ned as t he period in wh ich total de mand and/ o r e nviro nme ntal co nsiderati o ns are most li mited . T here are th ree t ypes o f Su rface W ater M anage ment Areas (SWM A): 1. Areas that are unregulated. Th e critical period he re w ould be the peri od w hich li m its the oppo rtu nity for use and / or the enviro nment th e m ost and expec ted to range from o ne day to several w eeks.

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WATER MAY/ JUNE 2000

ENVIRONMENT

2. Areas that have small storages with no carry over. These areas would have a critical period that is a fun ctio n of the drawdown time of th e storage. It is expected that these areas w ould have critical peri ods of 1 to 8 months. 3. Areas with large storages and carry over. The critical period for th ese areas wil l be determin ed by th e time it takes to run th e storage from fu ll to empty. This will often exceed on e year but fo r th e purposes o f this audit total resource, divertible reso urc e and developed reso urce should b e determ ined for a maximum period of o n e year. It is understood tha t the critica l period in any SWM A wi ll vary dep ending on the reach under consideration and the issue un der co nsidera tion. So m e sp ec ies of plants and animals may have criti cal peri ods that are very sho rt (e ven less than a day at certain times of yea r) and oth ers m ay have ve ry lo ng pe riods when the righ t amount o f flo w is desirab le or even essential for species survival. For this audit, the cri tical p eriod should be set using a pragmatic fram ework that is based on the m ost important issu es in the SWMA as determined by the water age ncies. Sust ainable Yield

Th e "Sustainable Yield" is a concept preferred o ver more valueladen judgem ent- based con cepts such as ecol ogicall y su stain ab le y ield . T his preference is based on reco gnitio n that wa t e r res ource use and allo ca tion dec isio ns are the result o f a com plex se t of interacting param eters and trade-offs mad e in th e con text o f environmental, economic and political decisions. Fo r this w ater resource assessm en t the su st aina b le y ield m e thod and th e accuracy o f its determination wiJl be defi ned b y th e State an d T errito ry age ncies and recorded on a system by system basis. Environmental Flow Requirements

Environme ntal flow allo ca tio ns and m ethods used fo r determining environmenta l fJo w r equire m ents w il l b e collated as part of the Audit, however , no n ew assessments of e nviro nm ental flow requirem ents w ill be undertaken . Resource System Characterisation and Assessment

A simple conceptual model has b een adopted to pro vide a summary of the status of each of Australia's surfa ce w ater and grou ndwater systems. It is re cog-

WATER MAY/ JUNE 2000

WATER QUALITY A collateral paper on th e Australiawide Water Quality Assessm en t was prese nte d at th e World Wat er Congress by Jonas Ball, Sinclair Knight Merz, and Belinda Hack, Australian State of th e E n vironm ent Section, Environment Australia. Th e outcomes of the assessm ent are to be included in the 200 1 Australian State of the E nviron111ent R eport and in National Land and Water Resources Audit's (NLWRA) r es o u r c e ma ppi ng o u tputs a nd reports. The major proj ect tasks included assessin g the exceedance of key water quality variables against management objectives or gu idelines, and determining the significance and magnitude of any trends in salini ty ,

nised that this model o ver sin1pli fi es th e all o catio n of water to the environment as it is not a percentage of fl ow or total quan tity so much as a dynamic flow regime . H o w ever account is taken of this dim ension by th e introduction o f th e con cept of "su sta inable yield " . Figure 2 shows fo ur co mpo n ents: • Actual water use - the porti on of water use for consumptive purposes • Environmental provision - reflects the allocation to enviro nmenta l and no n -co nsumptive uses. • "Spare water" - th e water remaining in th e system to be used by consumptive uses • Sustainable Yield - the ran ge and upper limit o ve r which consumptive reso urce use is co nsid ered unsustain abl e or u ndesirable. The mo del is simply based o n the degree of commitmen t o f the avail able reso urce but has built-in flexibility to tak e accou n t of the system -sp ecific valu e judge ments that are a part o f rou tine wa ter use an d allo c ation d ec ision making. Fi gu re 3 shows th e appli cation of the ca tegorisatio n fram ework. In summary, Category 4 systems are over co mmitted in w ater all oca tion and use terms - insuffic ient p rovisio n has been made for en vironmental and nonconsumpti ve uses, managem ent intervention and in fo rmation requirem en ts are su bstantial - it is a claw back; C ategory 3 systems are close to their developmen t limit and requ ire a high level of manage m ent inputs. R eso u rce info rmation and monitoring is vital for

nitrogen and phosphorus co ncentrations. A framework methodology was developed which allowed State and T er ritory agencies to use their own management objectiv es/ guidelin es and trend assessment techniqu es, but produ ce d outputs w hi c h wer e c omparable betwe en States and T erritories. This project high lights a successful coop era tive partne rship b etw een Environme n t A ustralia , NL WRA , key State and T erritory stakeholders and private industry and h as fostered ow n e r ship of th e methodology, process and results. It has provided an important framework and base for futur e national water quali ty assessm ents.

these system s. Catego ry 2 systems are mod erately developed , management and reso urce in formatio n requirement is moderate. C ate gory 1 systems have low levels o f resource use, direct managem ent interventi o ns and informati o n requirem ent is low. Th e determinatio n of th e exact threshold of acceptable use tightens as the resource demand and pressure increases. T his infers a rampin g up of both management and info rmatio n needs. Consequ ently empha sis w ill be p u t on gathering more d etailed data for C ategory 3 and 4 systems.

Water Resource and Assessment Process and Outputs Assessment Process

Th e Audit's natio nal water reso urce assess me nt wil l charac teri se eac h of Australia 's surface water and grou ndwater systems in term s o f water availability, use, allocation and m anagement regime. On th e basis of this characterisatio n each ca tchm ent is to be categorised accordin g to the degree o f water resource commitment and m anageme nt respo nses, takin g account of consumptive and enviro n mental water requirements. A broad assessm ent of future system demands and potential fo r develo pment will also be undertaken. Managem ent actions fo r Au stralia 's w ater resources will be id entifi ed in the context of the C OAG Water R eform and E colo gical Sustainable D evelopm ent objectives. Assessment Outputs

Th e

Audit' s

National

W a t er

ENVIRONMENT

R esou rce Assessment will prepare a numbe r of information produc ts, data manage me nt capabiliti es and protocols. Figure 4 outlines th e produc ts and delivery fram ework fo r th e Australi an W ate r R esources Assessm e nt 2000 . T he ac tivities of the wate r resource assessme nt w ill: • facilitate a consiste nt and comparable approa ch to water resource assessme nt, • u nd ertake an analysis of data and in form ation fo r eac h surface w ate r area an d g rou nd water m anage m e nt unit inc luding:

1. biophysical statu s and tre nd of w ate r reso u rces - ava ilability and environm ental flo w requirem ents 2 .ec onomi c - val u e th e be n e fits accrui ng from th e use of w ater 3. reso urce manage me nt - quantify c urrent allocation and describe alJocatio n m ec hanisms; and likely future mana geme nt responses and allocation m ec hanisms • id entify the informatio n gaps • assess th e e ffi cacy of the c urrent monito rin g n e tworks a n d id e ntify changes (if an y) in syste m design/ impl em e ntatio n re q uire d to de li ve r the required data a n d info rmation e .g . d ensity/ di stribu ti o n of m o nitoring sites; a ttribut es m eas ure d ; fre qu e n c y o f measurem e nt; acc ura cy; data compi lation , data a nalysis and reporting • identify data managem e nt requirements to maintain and pro gressive ly upgrade and make access ibl e informa tion on Austral ia's su rfa ce and gro u ndwater resources; • ide ntify optio ns for Commonwealth and State/Territory age ncies (and othe r Industry and C ommun ity groups) to address data and informatio n gaps; and • link w a te r qu a ntity an d quality monitoring with land use pa ttern and productivity .

Conclusions Conclusio ns draw n fro m th e data re qu ire me nts analysis and proj ect activity to date, identify that Australia needs to: • ado p t co nsist e nt and comparabl e approac hes to water resource assessm ent and monitoring, includin g, data coll ecti on , sample d esign, units of m easurem ent, data analysis, data storage and managem ent system s; • link w ater qu a ntity a nd q u ality m o nitoring w ith land use patte rn and pra ctices, p roviding an integrated basis fo r recommendation s and managem en t actio n at the catc hment scale;

• maintain and progressively upgrade and make accessible information on Australia 's surface and gro un dwate r resou rces; and • develop m etho ds that use h yd rological and re lated data to assess c hange in catchment pr ocesses, r ec omm e nd re m edial ac tio ns and predict the implications o f ca tchme nt use optio ns. By th e end of Ju ne 2000 the database w ill have been com pl e ted. A Workshop to chec k the R eport will be h eld on Jul y 5th . w ith seni or officials fro m all th e States and T erritories, pl us o ther key pe rsonne l. T he key fi ndi ngs will i ncl ud e long-term arrangem en ts to o rganise the capac ity to report o n wate r resources statu s in th e future . Au s tralia 's Wat e r R eso ur ce Assess ment w ill be comple ted at the end of July 2000 , and w ilJ be available fro m th e A ud it ' s atlas web s it e a t www.nl wra .gov .au / atla s. E x t e ns ive backgrou nd information is available via th e Audit's hom e page www.nlwra. gov.a u .

Acknowledgments W e are grateful to Fereal Addicott

(Sinclair Knight Merz, M elbo urn e) a n d Erwin W einmann (M o nash University, Departme nt o f Civil E ngin eering) for the ir input into th e refin em ent of t h e A udi t's resource concepts and the te xt o f this paper.

References AATSC/IEA (1999) Water and the Australian Econo m y. Joint st udy proj ec t of th e Au stra lia n Acade m y of Tec hn o logical Sc i e n ces a n d E n g in ee rin g a nd the Insti tuti on of Engineers Australia . . 13e rg man , I D (1989) A nati onal water resource inventory fo r th e I 990's. Ci11i/ Colle.f!e Technical Report M ay 5. 5pp. D epartment of Primary Industries and Energy (1987) 1985 R.eview of Australia's W a ter l"l..esources and Wate r Use . Australian W ater R esources C ouncil. Volumes 1 and 2.

The authors Warwick

McDonald 1s th e Direc tor a nd Colin Creighton th e Exec utive D irector of the N ational Land and W ater R.esou rces Audit (GPO Box 2 1 82, Ca n be rra , 2601 ). Peter Erlanger is a Seni or C o nsultant with Si nc lair Kni ght M er z, M elbo urne . Te c hni ca l

Environmental and Water Industry Specialists • • • • •

asset management water and wastewater technology risk management infrastructure planning strategic partnership

Contact Andrew Osborne or Peter Everist Tel 03 9694 1200 Fax 03 9694 1211 Web www. fisherstewart.com .au Engineers • Surveyors • Project Managers • Planners • Environmental Co nsultants

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WATER MAY/ JUNE 2000

BUSINESS

REGULATORY STANDARDS FOR WATER OUTAGES A PIPE DREAM? K Young standard. A later foc us of th is paper will b e th e se tting o f c ustome r se rvi ce standards . With resp ect to minimising life cycle costs fo r a parti cular pip e ele men t, th e fo ll owin g key dec isiom (amo ng oth ers) need to be made. • When is th e o p timum tim e fo r replacem ent or re hab ilitation of the asset, given a c urrent probabili ty of failu re, fut ure likeli hood of failure, consequ e nce of fai lure and cost of re placemen t/ re habilitation? • When is co nditio n moni toring o f an asset worthwhile' • For w hich assets should an o rganisation have o peration al contingency plans in place? (docume nted respome procedu res to mini mi se the impact of asset failu re?)

Keywords R.egulati on , D ep rec iation, Water main , Economi c Life, R.isk, Customer Service Standa rds

Introduction Water authoriti es are capital intensive particularly w ith respect to network assets (water distrib u tion/retic ulation pipes and sewer mains). Given the c urrent age o f the pi pelines and the uncertainty about the li fe o f pipelines un der va ry in g co n ditions, th e re is concern that water authorities may have to cope w ith escalating pipe failu res and increasing capital expendi ture. In the face of this, the re is also concern that custom er im pacts will in crease in line with a foc us o n commercial/operation and a lack o f co mpetiti on in natural monopolies. This is exacerbated by a lack of kn ow le d ge o n the i n, pa c t of custom ers th rough water ou tages. Water authorities need to respond to these concerns. T he Ame ri can Water Works Association R esearc h Foundati on (A WW ARF) co mmissioned a research project in 1998 to investigate the fi nancial implicatio ns of various water main replacement strategies. H unte r Wate r (HWC) and Brisbane Water Corporati on (BWC) were selected by the Water Services Association o f Australia (WSAA) to t ak e part in thi s proj ec t. R e pr ese nt a ti ves fr o m twel ve (1 2) American water authorities and two (2) Ca nadian water authoriti es also parti cipated in this exercise . Australia can make a strong contribution to this research because of the substantial data which has been collected o n pipe type, fai lu re and re placement and our progress with asset m anagement/risk policies. In addition, there has been a stron g foc us on customer services in Austra lia whic h has resulted in a valuable data set on the impact of water m ain failures on customers, such as the number o f hours per year customers are w ithout water (WSAA facts, 1999) .

WATER MAY/ JU NE 2000

This paper covers Australian in pu t to the project fo cusing on an asset management approach and discusses pote ntial regu lato ry impacts on th e decis ion m aking process.

Risk Management

Asset Management of Watermains

Risk theory provides the appropriate framewo rk to assist in decision m aki ng. Formal risk manage m e n t req u ires a quantitative approa ch to risk assessment. T he magnitude of risk ca n be defined by

Asset M an agement can be defin ed as th e minimisation of an asset's li fe cycle costs while m eeting a custom er service

I 1...---+- ------i-. I I I I I I I I \ I I I \

I I I I I

MANAGEMENT APPROACH

vs ASSET RISK PROFILE

l \

I CO"\TROLLED

ope~ate to fa lure, repl ce/ reha~llltate If pr jected fall\are costs lustlfy \

Increasing Risk$ pa

EACTIVE \

\ ,

\ \

' ' ........ ........ .....

__ --- --

CONDITION MONITOR .cehab~tate/ replace prior to failure or

llPERATIONAUONTUIGE.!"CY PLAN

---

CONSEQUENCE OF FAILURE $

Figure 1. Risk distri bution of water main fai lures

BUSINESS

multiplying the dollar consequences of an event and the probability of occurring in a given period of time. If risk cost is plotted against its two components (probability ;rnd comequencc), the shape of the lines of equal risk arc hyperbolic as shown by Figure I (adapted from Buckland I 999). The consequences of a failure include both direct costs (break repair costs, restoration) and indirect costs (customer disruption costs, traflic disruption costs, community/ media outrage). In Hunter Water Corporation's case, risk based procedures/policies have been put in place and as a start a full detailed analysis of our top I 00 high consequence or "critical" assets has been undertaken. This requires best available estimates of asset physical life (based on soils, age, material, location etc), condition assessment costs, conseque1ices of failure (direct costs plus an estimate of community costs) and possible improvements through rezoning, replacement/ rehabilitation or simple capital cost improvements through say, insertion of additional stop or reflux valves (to limit customer impacts). Our experience is that these analyses arc time-consuming and cannot be automated. As shown by Figure I, this asset risk type falls in the right hand side of the risk profile. While this detailed analysis could be undertaken for all 4,000km of Hunter Water's water mains (at high costs), it is important to note that most water main failures are higher probability, low consequence events such as the small diameter water main failures which effect around 40 homes (if the customer is at home and not asleep!). Around 90% to 95% of Hunter Water Corporation's water mains fall in this category and a controlled reactive maintenance approach is adopted. For these assets, failure is allowed to occur until failure frequency reaches an economic trigger level where it is more economic to replace or rehabilitate ;1 main than it is to allow continuing failure costs to occur. While direct costs dominate these small diameter assets, an allowance is also made for community impacts. Controlled reactive assets have the greatest potential for an automated replacement/rehabilitation support system using a GIS.

Given that a rigorous controlled reactive maintenance analysis has been put in place and detailed risk assessment of high consequence assets, data can be collected over a number of years on capital/rec111Tent costs. Statistical modelling of pipe life can be undertaken providing long-term estimates for planned (including replacement/ rehabilitation) and unplanned expenditure (including repair costs). Long term financial modelling based on this analysis can form the basis of future price changes (if rapid deterioration of assets is indicated, prices will need to rise to maintain a customer standard). It is speculated that in the longer term, increases in prices may change community opinion on the appropriateness of customer service standards and a trade-off could occur between increases in prices and movemL'llt to higher customer service standards.

Regulatory Influences It is often found that regulatory decisions can result in non-optimal life cycle costs. This can be by limiting capital or setting a tight customer service standard. This standard may have been put in place based on perceived poor system performance, or to lock into historic service levels, or as a regulator's assessment of what is reasonable. From the author's viewpoint what has been lacking in the industry is an ability to assess whether an existing customer service standard represents good value to the community. Service standards, once set, are locked in and only move to a higher level. Other authors have reviewed the regulatory role and the need for standards to be set for monopolies which do not face competition and consumer choice. An assessment of those concerns (in life cycle terms) should start with a private company focus. Regulators fear that a private or commercialised company will focus on profit and look at minimising lifr cycle costs based only on their direct costs (repair and replacement/ rehabilitation costs). Interestingly, a company would not just allow repairs to escalate, but would choose to operate at the lowest level of financial cost (which corresponds to ;1 set level of service (Fs) (see Figure 2). Regulators would argue (correctly) that the inconvenience costs to the customers have not been

Great Opportunity. Great lifestyle. Programme Manager, Wastewater Treatment South West Region Bunbury, Western Australia

The Company: As one of the largest businesses in Western Australia, the Water Corporation provides water, sewerage, drainage and irrigation services co 1.7 million customers in urban, rural and remote centres across all of the State. Our South West Region has an annual capital works program exceeding $l00m per annum. A significant proportion is aimed at upgrading the current wastewater systems which include 26 wastewater plants. BNR technology and a range of complex efOuent disposal systems. Exciting and rewarding opportunities exist for a professional person co join our progressive organisation providing a challenging future in the area of wastewater treatment, bioâ&#x20AC;˘soHds management and effluent re-use. The wastewater systems are in an environmentally sensitive and rapid growth area of Western Australia. There are challenges in the efficient management of complex treatment and disposal systems and in balancing environmental needs with the Corporation's business objectives. The Region is currently seeking EMS accreditation leading towards world best practice as pan of its commitment co the environment.

The Opportunity: This position pmvides an exciting opportunity to play a key leadership role in ensuring issues relating to wastewater treatment, efOuent disposal and biosolids management are addressed through the provision of a centre of expertise in process management, treatment plane operation. and key input into asset creation projects. The successful appHcanc will have a tertiary qualification in civil engineering or equivalent. and substantial experience in wastewater treatment and conveyance systems. To be successful in this challenging role, applicants must be results orientated, and have high level leadership competencies with proven experience in influencing and motivating ochers. In addition, a strong commercial focus and considerable investigative and interpersonal communication skills arc required.

The Location: The position is located at Bunbuiy, a progressive regional city. about 160 kilometres south of the capital. Perth. Situated on the coast, it is within easy reach of surfing beaches, forests and wine growing districts for which the region is famous. International studies have concluded that the living conditions in Bunbury are amongst the best in the world. For further details and to forward your confidential application, a current resume and a detailed a statement as to how you could contribute to our wastewater program, please contact Patricia Paterson, Human Resources Branch, PO Box 100, lccdcrvil!e WA 6902, or email patrida.pacerson@watcrcorporation.corn.au by 4pm Friday 9 June 2000. For technical enquiries about the position please contact Mr Peter Newhouse, Manager, Asset Management, South West Region, Bunbury on (08) 9791 0415.

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taken into account and Fs may be unacceptable . Th ere is a clear need fo r indirect costs to be taken into account. As noted, wh en failure of a water main occu rs, th ese wo u ld in clude, amon g o t he r th in gs, t he in co n ven ie nce co sts to customers for water outages and traffic disruptions. H owever, what is often overlooked is the inconvenience costs to customers through replacem ent of a main (water o utages, plus traffic disrupti o n, plus loss oflocal amen ity) . Dialogue w ith c u st o m e r s on ind irec t co s ts p rod uc es n ew total community or econ o mic cu rves as show n by Figure 3 . (AWW AIU Project 6207 will tackle the issu e of community costs in 2000). From an economic viewpo int, the assessment of community costs leads to increased capital expenditure and a higher and more appropriate level of service. This p rocess provides the framework fo r rational discussio n with regulators on a proposed (or existing standard). If a regulated higher level of customer service (R s) is in place, the cost curves presented by Figure 3 indicate spending o f unnecessary community funds (Re-E e) are being mandated. T his may also apply where limits on capital spending, or a maximum. number of breaks per year are in place. It is also important to note that Figure 3 indicates that regulated service levels may resu lt in lower economic life of assets and higher deprec iation levels for the organ isati on . Given that a water authority integrates community costs in its decision m akin g p rocesses, what th en is the role fo r regulation?

What Role for Regulation? In an idea l world a water autho ri ty would inc orporate co m munity costs into its asset m anagem ent processes and regulators wo u ld pe ri o di call y audit th ese cos ts. As p rice is related to customer standards a regulator, as part of an audit, ma y also requ ire eviden ce that key c ost e lem ents (ie . repai rs, replacem ent, rehabilitation) are bein g effi cientl y d eliv er ed (th ro u gh , say, b enchmarkin g studies) and th at n ew rep lacemen t materi als / construction tec hniqu es are b ein g used (where th ese lead to lower life cycl e costs) . If all of this is in place a simple m easurable custo m er serv ice standard co uld be se t as an o u tput m easure. This form o f ligh t-h anded regula tio n sho uld be base d o n regulators " talkin g softly but carrying a big stick" . Rogue auth orities could face a m ove from output re gu latio n to input regulatio n w ith frequ ent auditing o f processes.

WATER MAY/JU NE 2000

Fs"" Flnandal Level ofServlce Fez Flna nclal Level of Cost

t;:;

Fs POOR

WATER DISCONTINUITY LEVEL OF SERVICE

EXCELLENT

Figure 2. Minimising Water Main Financial Life Cycle Costs What is th e best simpl e o utput measure? A review o f different n1.easures in place throu ghout Australia and overseas indicates a diversity of indicators with no sin gle perfo rmance indicator being ideal. Examples include the follo wing: â&#x20AC;˘ R esponse standards ie in 95% of cases

respond on site within one ho ur (th is encourages first co ntact o n-site no t n ecessarily rectificatio n of service w hi ch may be more important to custo mers) . â&#x20AC;˘ A limit on the number of water outages per customer per year. Th is needs to be carefull y assessed (as shown by Figure 3),

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to ensure community funds are we!J spent. In additi on this indicator lacks a severity assessment (a 20 ho ur outage rates the same as a 10 minute o utage) . • A limit of the total maxim um number of breaks per year, or a limi t o n capital expenditure. Again these Jim.its need to be assessed to ensure community fu nds are well spent. Placin g a lim it o n total number of brea ks may also e ncourage autho1ities to focus on small diameter breaks and igno re large catastrophic failures. • A c umu lative wa te r di sco n ti n u it y measure (ie . no more t han 8% o f cusrom ers sho uld be out of w ate r for m o re than 5 hours per year and a re bate will be paid if c u m u lative o utages exceed 24 hours). Whil e t his cumu lative indicator encourages au thorities to look at breaks across their entire risk spectru m its effects may be diluted in h ig h grow t h systems (where additio n of new non fa ilin g pipes may m as k actu al pe rformance in older areas) . Furth e r debate is req uired in the industry o n appropriate custom er se rvice sta ndards.

Conclusion R egul atory standards set on a n arbitra1y basis can impose unn ecessa ry co mmun ity costs . An asset managem ent/ risk manage m ent framework is proposed w hich incorporates all costs, both direct and i ndi rect, in the decision m aking process. By including commu nity costs, water authorities can m inimise life cycle costs for an asset set w hile ensuring the im pact of asset failure o n customers are fai rl y assessed. While significa nt tools are ava ilable to assist in the asset managem ent framework proposed, more research is required in the area of va luing customer impacts and determ.in ing t he physical life of assets (through und erstanding the impacts of soil type, material, pressure, locatio n e tc on pi pe fa ilu re). In addition , further ind ustry debate is requi red on appropriate performance ind icators fo r water outages, not to allow comparability, but as a simple o utput m easure designed for each water autho rity. It is specu lated that this process could a!Jow custom er trade offs between increases in prices and higher standards o f service .

References Young K and Belz P (1999) A Whole of Life Approach t o Manageme nt of Water Mains.

/81/1 A WWA Federal Co1we1rrio11. R obinson R , Anderson K and M eiers S (1996) Risk and Reliability. A11 /11rrod11ctory Texr -

Risk a11d R eliabiliry Associates Pty Ltd. Saunders I, Constantine G and Miller R (1998) .Burst M ain Data Analysis. R eport N11111ber

Fs z Flnanclal l evel of Service Fez Financial Level or cost Es z Eco nomic l evel of Service Ee• Economic Leve l of Cost

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...z

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------Fs Es POOR HIGH LOW

... ... ...

WATER DISCONTI NUITY LEVEL OF SERVICE

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DEPRECIATION

" " "

EXCELLENT LOW HIGH

Figure 3. Minimising Wat er Main Economic life Cycle Costs WSAAfa cts '99. T1,e A11stm/ini, Urbn11 Water

/11d11stry l3 uck land P ( 1999) Asset M anagement - An Economic Approach. 18th A WWA federal

Co111mrtio11.

Secreta ry a n d M a na ge r Co rp o ra t e Plann ing and Governm ent R egulatio n for H unter W ater Corporation with a spe ci al i nt e r est in

The Author

reg ulatory / asset

m anagem en t issues. H is e-mai l add ress

Kevin Young 1s th e Compa n y

is you ngk@ hunterwate r. co m .au

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CMIS 98-106. Water Services Association of Australia (1999)

WATER MAY/ JU NE 2000

BOOK CRC for Catchment Hydrology: Industry Reports This series of reports maintains the standard of excellence of previous reports. Th ey are crisp ly w ritten, easy to read , well illustrated, and ;1bove alJ , practical. 99/14. December 1999. G Mitchell, R Mein, T McMahon. The Reuse Potential of Ur /Ja11 Stormwater aud Wastewater. RRP $25. This repo rt summarises Project C 2 w hi ch included studies of litter, detention basins, a snu ll urban pond, and the water quality in differe nt urban streams. Above all it deals with th e feasibility of reusing sto rm wate1Âˇ to reduce the demand on potable water suppli es in Australian cities. 98/7 /2 Sept. 1999. T Wong, P Breen, N Son1es, S Lloyd. Ma 11agi11g Urban Stormwater 11si11g Co nstru cted Wetlands. RRP $20. Storm water treatmen t using wetlands involves a co mbination of physical , chemical and biological processes. and their d esign m ust in volve in tegratio n of hydro logical, h ydraulics and botani ca l co nsiderations. This repo rt summarises the results o f a j o int program w ith the C R C for Freshwater Eco logy. 98/5 June 1998. P Hill, R Mein, L Siriwardena. /-fo11, M11r/1 Rai1!fall Bcw111cs R.1111-,ff? Loss Morlclli11g.for Floor/ Esri11iatio11. RRP $20 . This report conce11trates on the derivation of new loss parameters, from empirical analysis of a large co ll ated d ata base. It d evelo ps a new loss model for realtime flood fore casting, of immediate use to practitioners. 99/11 November 1999. J Croke, P W allbrink, P Fogarty, P Hairsine , S Mackler, B McCormack, J Brophy. Managiug Sedime11t Sources aud Moveme11t ill Forests. RRP $25. This research o n erosion o n unsealed roads, tracks, effect of drainage etc. has been collated to provide u p- co - date information 0 11 m ana g in g sediment processes to protect w ater quality in forested catchments,. 99/5 April 1999. M Gilfedder. L Connell, J Knight. Irrigation Bay Salt Export and Salinity Ma11ageme11t. RRP $20. An extensive fiel d prog ram has mon itored run -off and solute processes in high water table irrigatio n areas, kading to quantification of the export of salt from irrigation bays into the d rainage network of the Barr C reek in N o rthern Victoria . This " industry report" is more accessible to prac titioners than the acade mic th eses on chis subject. Available from the CRC CH, email: virginia. verelli@eng.monash.edu .au - EA (Bo/J) Swinto11

Wastewater Treatment Systems. Modelling, Diagnosis and Control by G 11staf O lsso11 and Bo/J Newell. I WA P11blishi11g ISBN 1900222159 RRP-TBA R ecently the community and environ-

WATER MAY/ JUNE 2000

REVIEWS

m ent protection watchdogs have demanded improvements in the quality of treated waters fina lly retu rned to the environment and levels of residual pollutants have been wound ever lower. E ngineers and o perators of wastewater treatment plants traditionally have used both aerobic (oxygen consuming) and anaerobic o rganisms to assist in the reprocessing and "cleaning" o f this used water. They have been lookin g to place added emphasis on o pti mising plant performance by improving the efficiency of use of natu ral organ isms. The process is ca lled biological nutrient removal and many tradi tional WWTP are being upg raded to achieve these goals. J;Vas frltl{l fff Treat111e111 Syste/1/s . J\llorlclli11,1Z, Dia,e11osis a,,r/ Control by Gustaf O lsson and l3ob Newell is a fa ctual and logica l text fro m IW A Publishin g in UK. It fiUs a gap in this area and explains clearl y how plant o perators and engineers can model and control the operation of the l3NR process to im prove o perational efficiency for their pla nt. Mathematical formula e are also introd uced simply so that th ey appea r nonthreatening to those less com fortab le with numbers and equations particularl y as th ey relate to biological reactions, breakdown processes, kinetic, v:iriablc hyd ra ulic cond itions. Detection of a problem , definition or diagnosis and management arc addressed including examples such as an abnormally slow fl ow rate, slowness in recogn ising problem situatio ns, equipment fai lures. For chose more comfortable w ith a co mputer, there is also a coll ection of MATlAI3 progra m s and fun cti ons that are m entio ned throughout the book. T he MATLAB programs and WWT toolbox that a cc ompan y t h e b ook can b e downloaded free o f charge fro m th e !WA Pu blishing website. h ttp: //www. iwap.co . uk/ books/books. hem IWA Publishing is a new so urce for AW A l3 ookshop and the publications selected, like chis book , are tec hnically derailed but clearly laid out an d practical in o ri en tatio n. - D. Weisner (A WA Bookshop)

Toxic Cyanobacteria in Water. A Guide to their public health consequences, monitoring and management. Edited by Ingrid Chorus and Jami e Ba tram. Published by WHO . Availa/Jlefrom AWA Bookshop $69.95 p/11s P&H.

Tiixic Cya11obacteria in W ater is o ne of a series of guidebooks concerning water quality issues published on behalf of th e W H O. T he list of contributing auth ors is impressive and includes many of the better known researchers in the field. As well as notable international contributors such as Professors Wayne Carmichael and Geoff Codd, a nu mber o f Austra lian scientists contributed to the preparation of the book. This contributio n reflects the prevalence and

significance of cyanobacteria in Australia. Und ersta nding o f the pu blic health significance of toxic cyanobacteria is :i d eveloping field w hich still contaim large inform:ition gaps. There is also a shortage o f good reference materi al. The strength of the guidebook is that it pro vides a welcome and needed compilatio n o f present knowled ge with an emphasis 0 11 practical issues related to occurrence, potential impacts and management of cya no bacteria in water resou rces. There are excellent chapters o n cyanoba cterial tox ins, cya nobacteria in the e n viro nm e nt , h uman h e al th aspects, preventative measures, remedial ac ti on, mon itoring and testing. Fo r suppliers of drinking water, the chapter on rem edi al action includes a compre hensive review of co ntro l measures that can be applied in reservoi rs or in water treatment plants. Case studies including a number from Australia arc used throughout th e gui debook co illustrate points and ma ny useful summary tables ha ve bee n provided. There arc some faul ts. Gui dance on "alert levels" is heavi ly weighted toward Microcystis and microcystin. To an extent th is is understandable as microcystin LR is the on ly tox in for wh ich W H O has prod uced a guidel in e val ue. H owever, not enough consideration is given to ocher tox i c cy a nobac ce ri a p art i c ul a rl y in discussing response protocols. In addition , risk assess m ent related to recrea tiona l exposure is no t handled well. Three guideline levels are suggested, 20,000 cells/ ml for low probabiliti es of adverse health effe cts, 100,000 ce lls/m l for a moderate p robability of adverse health risks and the prese nce o f scums as an indicator of a high risk of adverse hea lth effects. The supporting arguments for th ese numbers is curio us and uncon vincing. Fo r example, it is stated that the 20,000 cell / ml fi gure is based on the study of P ilotto et al ( I 997). H owever, as discussed earlier in the g uidebook, thi s study suggested chat th ere could be an in creased risk o f illness w hen cell numbers exceed 5,000 cells/mL. There is a comprehensive an d detail ed d iscussion of risk- managem ent strategies inc luding preven tion, impleme ntati o n , response protocols and treatment but the informatio n is spread over at least four chapters and could have been better organised. Little in the way of linkage is provided to draw the va rious aspects into a cohesive man age m ent structure. This probab ly reflects the nature of the guidebook in that chapters were prepared by separate groups. Despite these criticisms th ere is great d eal to recommend about the guidebook. le is an invalu able reference that should be a first choice for managers or regulators of water resou rces and chose concern ed with the treatment and supply of drinking w ater. - D C unliffe. D.H.S. S.A.