Water Journal December 1994 by australianwater

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AUSTRALIAN WATER & WASTEWATER ASSOCIATION

Volume 21, No 6 December 1994 Editor EA (Bob) Swinton

CONTENTS

Editorial Correspondence 4 Pleasant View Crescent Glen Waverley Vic 3150 Tel/Fax (03) 560 4752

ASSOCIATION NEWS From the Federal President From the Executive Director Association Meetings

2 4

MY POINT OF VIEW Where Now with Cities and our Environment

Dr G Allison

FEATURES Phosphate - Removing Microbes - New Insights on their Ecology P L Bond, L L Blackall, J Keller Struvite Precipitation in WWPTS: Causes and Solutions D G Chirmuley Oxygen Transfer Coefficient - Relative Humidity Relationship

21 24

M Sivakumar, C Shiau Pumping Sewage Dowhill

LD Mott Forumlating Ecology Water Quality Guidelines

I Lawrence, W Maher, P Liston, A Wade Pulp and Paper Industry Wastewaters

P Donlon

REPORTS BNR2

EA Swinton The SA Environment Protection Authority and Water

Advertising Sales & Administration Margaret Bates Tel (02) 413 1288 Fax (02) 413 1047 A\V/'il,IA Federal Office Level 2, 44 Hampden Road Artarmon NSW 2064

Editorial Board FR Bishop, Chairman B N Anderson, G Cawston, M R Chapman P Draayers, W J Dulfer, GA Holder M Muntisov, P Nadebaum, JD Parker A J Priestley, J Rissman

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P Thomas

DEPARTMENTS Industry News International Affiliates Products Books Meetings

Australian Water & Wastewater Inc

8 9 39 39

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Richard Marks

Federal President Executive Director Chris Davis

OUR COVER Nutrient Removal Retrofit. West Wodonga WWTP was commi ssioned in 1986 as an extended aeration oxidation ditch with rotating brush aerators. It was later required to reduce phosphorus to 2 mg/L for discharge to the River Murray, as well as augmenting from 15,000 to 45,000 then to 75,000ep, including the week- day loads from two major food processing factorie s, which dominate the normal domestic load. This was accomplished without increasing the size of the ditch by building anoxic and anaerobic tanks alongside the ditch, fitting the necessary recycle systems and installing extra aeration by fin e bubble diffusers (ref Oorschott & Crockett, Water June 1994). Our photograph shows the overhead air plenum, with the completely sound- proof blower house in the background . Currently a prefermentation tank, designed by CSIRO , is being installed to ensure adequate readily biodegradable feed even at the weekends and during factory shut- downs. The plant was visited during the BNR2 Conference. Photo by Ross Graphics, courtesy of Wodonga City Council

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RESEARCH

PHOSPHATE- REMOVING MICROBES - NEW INSIGHTS ON THEIR ECOLOGY PL Bond) LL Blackall*,J Keller Abstract This paper covers general aspects of biological phosphorus removal, followed by a review of classical microbiological methods. Some new microbiological terms and some novel methods are introduced. Results of the microbial ecology of phosphate-removing activated sludge obtained with these new methods are presented and compared with those from other laboratories. Our conclusion is that the numerical dominance of Acinetobacter in phosphateremoving actiyated sludge as determined from culture-dependent methods is overemphasised and that the ~Proteobacteria are the numerically dominant microbial community in activated sludge.

Introduction Improvement in the operation and design of EBPR plants requires information about the metabolism of the bacteria responsible for phosphate removal. Some of the biochemical characteristics of EBPR have been obtained empirically by experiments with activated sludge. For example, readily biodegradable COD is known to be required for phosphate removal but specific detail of the microbial metabolic transformations that result in phosphate removal are virtually unknown. However, a number of researchers have implicated bacteria from the genus Acinetobacter in EBPR.

Classical Microbiological Methods Microbiologists have up to the present studied sludge by classical methods. These include sample collection (eg of mixed liquor) and transport of the sample to the laboratory under some preservation regime (eg chilling). The sample is homogenised to disrupt the floes and then diluted in a liquid . These dilutions are spread onto some agar solidified complex growth medium in a petri dish and incubated. Temperatures and times of incubation can vary considerably - eg 18-32Â°C and 1-5 days. Typically within a day or so, a range of bacterial colonies can be seen on the surface of the agar media. The colonies can be enumerated and the bacteria comprising them can be identified. WATER DECEMBER 1994

Often, but not always, a particular colony type on the growth medium is very common and dominates over the other colony types. One conclusion that can be drawn from this is that the dominant colony type is comprised of bacteria that predominated in the sample. With phosphate removal and Acinetobacter, this has often been the case. Indeed in one particular laboratory-scale activated sludge plant operated by Wentzel et al (1988), 90% of the isolated and identified organisms were Acinetobacter. However, because the selective pressures placed on the microbial community are so different in the laboratory from those in the natural situation, the proportions of microorganisms that are able to compete and grow on the agar may well bear little resemblance to those in the original sample. The nutrients (carbon, nitrogen, phosphorus and so on), the temperature, the aeration status and other physicochemical conditions will all differ dramatically between the laboratory and the reactors in EBPR plants. The fluctuations of all the variables will also differ. This is demonstrated by the example of the bacterium Nocardia pinensis, which can easily be seen and identified microscopically because of its distinctive morphology. It often comprises more than 50% of the microbial biomass in foams on the surface of activated sludge plants . However, if conventional laboratory procedures of sample dilution and plating are employed to isolate it, no colonies of N. pinensis will result. It cannot compete with the heterotrophs that were present in the sample, which grow more rapidly under the laboraory conditions. Similarly, Escherichia coli is a commonly used public health indicator organism in the monitoring of the liquid effluent from activated sludge plants since it may indicate a possible risk. Specific selective pressures have to be employed in the isolation strategy to ensure that if E. coli is present, even in very low numbers, it will be able to grow and be enumerated. We have some information about autotrophic nitrifiers. We know that they use CO 2 as carbon source, NH/ -N or N0 2- N as an energy source, and that they grow very slowly. We can and do employ 'isolation strategies based upon our know!-

edge of their physiological attributes. Of course, although, we may be successful in isolating nitrifiers, we will almost certainly not be isolating all the autotrophic nitrifiers present in the original sample. For research purposes the isolation of bulking and foaming filamentous bacteria into pure cultures is also very important, because their physiological attributes can be ascertained - Âľ max, Ks for oxygen and carbon, and substrate uptake and storage ability. This data can then be compared with those for typical floe forming bacteria that are likewise studied in pure culture. Consequently, outcomes of competitions between floe formers and filaments can be accurately determined (Blackall et al, 1991; van Niekerk et al, 1987 ) . This information can be used in the design and operation of selectors for filament control. Therefore, although classical microbiological culture-dependent techniques are very important and useful (eg in determining public health risks, in selector operation, and ifl nitrification kinetics determination); for microbial community structure analyses, they are of limited use. We really cannot tell the proportions and dominance of microbial groups by employing culture-dependent methods . Each method that we do employ is intrinsically "selective" . Furthermore, cultivation- dependent methods are limited to only a small fraction (< 1%) of the cells present since we can only grow that number (Trebesius et al, 1994). New methods are being developed in a number of laboratories, but to understand them, a knowledge of the terminology is required.

New Terms The new terms are important in the understanding of the novel methods. 16S rRNA gene. This is a gene or small part of the bacterial chromosome. For all intents and purposes, it is a "molecule" that all bacterial cells contain. Indeed, all living cells contain an rRNA of one sort or another. rRNA is important in

* CRC - Waste Management & Pollution Control Ltd, Department of Microbiology, The University of Queensland, Brisbane 4072 17

protein synthesis and therefore in cell survival (Figure 1). Phylogeny .This is the grouping of living things according to their evolutionary relationships. The universal phylogenetic tree of life on Earth is shown in Figure 2. Since the rRNAs are important in cell survival and all biological cells have them, they have been found to be markers of evolution. The "family tree" in Figure 2 was prepared by comparing rRNAs from a wide range of living things. Eucarya contain the animals, plants, fungi, and protists. Under the heading Bacteria are the microorganisms such as Nocardia pinensis, Escherichia coli, the autotrophic nitrifiers, the cyanobacteria and so on. The Archaea are a group of microorganisms that are found in extreme environments extremes of temp erature, salinity, and extreme anaerobiosis. Wastewater personnel will be familiar with the organisms that produce methane - the methanogens. These are members of the Archaea (ie the most primitive forms of life). Now if we focus on the Bacteria (the major group of microorganisms in activated sludge), it can be seen that this Domain can be subdivided (see Figure 3). Proteobacteria. This is one major lin e of evolutio nary descent in the Bacterial domain. It contains many of the Gram negative bacteria . This is furth er subdivided into major groups - the a, p, y and 8 (actually there are also now two more subdivisions of the Proteobacteria). For example, many ammonia-oxidising bacteria (eg Nitrosococcus) and Zoogloea are in the P subgrou p, Escherichia coli, Aeromonas, Moraxella and Acinetobacter are in the y subgroup and anaerobic sulfatereducing bacteria are in the 8 subgroup. In the Bacterial domain, there are at least 10 other lines of descent of Gram negative bacteria - one is shown in Figure 3 - the flavobacteria . There is al so one line of descent containing all the Gram positive bacteria - see Figure 3. Probe. Many wastewater personnel are familiar with dissolved oxygen and pH probes. They are large physical things that yo u can see and pick up. However, a probe, in the chemical or biological sense, is a mol ecule having a strong chemical interaction only with a specific target and having a means of being detected (via a "reporter") so that we can see when the probe ha s interacted. For exampl e, we have a biological probe that is specific for Acinetobacter. This probe is based upon l 6S rRNA information and strongly interacts with the ribosomes insi de bacterial cells - see Figure 1. The ribosomes are the specific target for the probe. A fluorescent molecule is one example of a reporter that is used to detect this specific interaction. The fluor esce nt mole cul e is coval ently 18

Table 1. Soluble phosphate concentration in the influenf and effluent from two lab scale SER reactors Reactor

InfluentP04

mg/I

16S rRNA gene,

Rtbo,ome, conta1n1ng . _ . . . . , . . - - - - - - 16SrRNA

Effluent P0 4

mg/I

SERI

1.5

SBR2

Genomic DNA

Figure 1. A bacterial cell - showing the genetic DNA and ribosomes

Eucarya

Proteobacteria 0 y

,. ,.

Figure 2. Universal phylogenetic tree three domains

Figure 3. Enlargement of the domain Bacteria to show some lines of descent including the Proteobacteria

Mixed liquor with bacteria

l~llll

Obtain rRNA from each bacterial cell

"Read" the books in the rRNA library (i. e., analyse rRNA)

Put rRNA into "books" in the "rRNA library " Each "book" represents information from one bacteri al cell in the original sample Compare data from library with that available on publicly accessible databases-> group the information from your library Y-Proteobacteri a ~-Proteobacteria

Flavobacterium _ _ _ _ _ _ _ _....., Noca rdia . . , . . - - - - - - - - --"'-.

EvolutionaryÂˇ lines of descent can be detennined for x, y, and z from library. Identification in some cases e.g., w - Nocardia

z is related to Acinetobacter; y is related to 'Zoogloea; x appears to have no close relatives in the family tree presented.

Figure 4. Outline of steps involved in preparing and analysing a library WATER DECEMBER 1994

Buchan , 1983

Cultured

Lotter, 1985

Other

Brodisch, 1985 Kerdachi et al. , 1987 Wentzel et al. , 1988 Cloete & Stey n, 1987 Hirai shi era/. , 1990 Wagner et al. , 1994

Fluorescent Antibody -

Quinone profile

Bio lorr ical orobe

Percent

Figure 5. Enumeration of Acineobacter in phosphate removing sludge

Percent 90 ~ - - - - - - - - - - - - , 80

o. Proteobacteri a

y Proteobacteria

Acinetobacter

Cytophaga/Flavobacterium

Actinomycete phenotype Gram positives

Proteobacteria

20 10

A Identification of growth on agar

Biological Probe

Figure 6. Community structure of phosphate removing sludge (Wagner et al.,1994) Percent

40 35 30 25 20 15 10 5 0

Sludge probed Wagner eta/., 1994

a Proteobacteria

PProteobacteria

SBRl library

l:i:::i:I Cytophaga/Flavobacrerium ~

i;:;;:J YProteobacteria

Actinomycete phenotype Gram positives

i..l Clostridium phenotype Gram positives 1111111111

c:::::J 6 Proteobacteria

Planctomycetaceae

~ Unidentified

Figure 7. 16SrRNA analysis of EBPR and rwn-EBPR plants

WATER DECEMBER 1994

SBR2 library

attached to the biological probe. If a fluorescent molecule is employed as the reporter, we can observe the probe-target interaction by observing a mixture of the sample and the probe by epifluorescent microscopy. The sample could be mixed liquor containing Acinetobacter. This allows us to observe the fluorescence and we can actually see and perhaps quantitate the fluorescing bacterial ce ll s of Acinetobacter. If no Acinetobacter cells are present in the sample , there will be no probe target and no cells will be fluorescent.

Novel Methods These methods are not based on the ability to grow the bacteria. They rely on analysis of the 16S rRNA gene and this information is useful because different bacteria have different 16S rRNA genes. The rRNAs contain diagno stic regions which are of identical composition in the molecules of closely related organisms and different in the rRNAs from all other organisms. Therefore, the 16S rRNA gene of Escherichia coli is different from that of Nocardia pinensis and different from that of Acinetobacter. However, the 16S rRNA gene of Nocardia pinensis is very similar to that of Nocardia amarae. There are basical1y two ways to analyse th e 16S rRNA genes from a bacterial community. The first is prepare b'iological probes from the 16S rRNA information as outlined above. The seco nd invo lves preparing a library ot the 16S rRNA gene information and is the method employed in our laboratory. A library is prepared when we take the 16S rRNA gene from each bacterial cell in the sample (eg mixed liquor). For the purposes of this paper, we will use the analogy of the regular library that you are familiar with - ie the one with books in it. Now presume that the 16S rRNAÂˇgene from each bacterium in the microbial community is placed into a "book" and then each "book" placed into a library. We now have to read each book in the library ie obtain the 16S rRNA gene information from each book. This information is compared with rRNA information from a wide range of bacteria. From this data analysis, we know what sorts of bacteria were in the original community (mixe d liquor) and how many of each. Because there are milli ons of books in the lib rary from any microbial community, it is logistically impossible to read all of them. Therefore, a random representative number of books are read. The information from the 16S rRNA library can be ,compared with 16S rRNA information from a range of bacteria and a phylogenetic tre e prepared (Figure 4).

Results While some authors are convinced that 19

Acinetobacter is the microorganism of relevance in EBPR, reports of other bacteria being important in the story are numerous. Results pertaining to Acinetobacter from pho sphate-removing acti vated sludges are presented in Figure 5, which demon strate s why the importance of Acinetobacter in this process is being questioned. The question then is, what is responsible? Wagner et al (1994) prepared biological probes for some of the different groupings of the domain Bacteria: a-Proteobacteria, P-Proteobacteria, y-Proteobacteria, the Flavobacterium/-Cytophaga evolutionary line of descent, Acinetobacter and the Actinomycete phenotype Gram positive bacteria. They also had a biological probe whose target was any member of the domain Bacteria. Samples of mixed liquor from an EBPR plant were obtained. They used the probes to quantify the different groupings of Bacteria. The y then employed classical microbiological methods and quantified the bacteria that were able to grow on the agar plate and produce colonies. Figure 6 shows the comparisons. Clearly, the proportions of bacteria in the ecosystem are dramatically different. The dominance of Acinetobacter and the yProteobacteria is over-emphasised when culture-dependent techniqu es are employe d. The P-Proteobacteria and Actinomycete phenotype Gram positives are dominant when the biological probe is used. In our laboratory we decided to prepare libraries with 16S rRNA information from two sources. One was from mixed liquor from a laboratory-scale, sequencing batch reactor (SBR) EBPR plant and one was from mixed liquor from a laboratoryscale, SBR non-EBPR plant. The effluent phosphate levels in the two lab scale plants are given in Table 1. We wanted to compare the microbial community structure in the two systems. If we found group(s) present in the EBPR plant that were absent from the non-EBPR plant, they could be the ones res pon sible for phosphate removal. The libraries show some similarities with the results of Wagner et al (1994) as shown in Figure 7. There are a couple of difference s. Wagner's probes detected slightly more y-Proteobacteria than the libraries, and the number of Gram positive bacteria was greater when the probe was employed. The similarities were the low occurrence of y-Proteobacteria (this is the subgroup containing Acinetobacter), and high numbers of P-Proteobacteria. Since there were no bi ologi cal prob es to the Planctomycetaceae, the probes were not useful for highlighting this microbiologica ll y unu sual group. They comprised approximately 12% of the bacterial community in SBRl and 6% in SBR2 in the library approach . There were different 20

subgroupings in the P-Proteobacte.ria between SBRl and SBR2 (data not shown) - this is possibly where the good EBPR bacteria are. Both Wagner et al (1994) and Hiraishi & Morishima (1990) suggest focussing on Gram positive bacteria for good EBPR. Our libraries did not concur with this conclusion.

Conclusions and Future Work The major conclusions from this paper are:• the library approach to studying the microbial ecology of activated sludge has been used and the results largely concur with those from a study employing biological probes. • a wide range of bacteria not previously studied are numerically dominant in activated sludge • subgroupings of the P-Proteobacteria in the EBPR plant differ from those in the non-EBPR plant • Acinetobacter were not a prominent group in the microbial community structure of either EBPR sludge or non- EBPR sludge. Future work in thi s experiment includes "reading more of the books in the library" to cover more to the total number in the library, phylogenetically analysing the complete dataset, and determination of the organisms that differ between the EBPR and non-EBPR microbial community. The rRNA data will be used to generate a biological probe for detection of the target organisms in situ . We will then attempt to isolate these bacteria. A numb er of isolation strategi es could be employed such as micromanipulation or deduction of "selective" protocols based upon the target organisms nearest neighbours' physiological attributes. Once pure cultures of the putative EBPR bacteria have been obtained, th e bioch emi ca l mechani sm for phosphate accumulation will be studied . Finally, this information will be used to design more efficient EBPR plants, to alleviate failures in the current EBPR plants and to assist with the accurate modelling of EBPR processes.

Acknowledgements Dr Philip Hugenholtz is thanked for great assistance wi th data analysis and Elizabeth Mi.inch is also thanked for expertly operating the sequencing batch reactors from which th e slud ge was obtained for microbial community structure analyses. The work is funded by the CRC for Waste Management and Pollution Control Limited, a centre established and supported under the Australian Government's Cooperative Research Centres Program.

References Blackall , LL, Tand oi, V & Jenkin s, D (1991 ) .

Con tinu ous ultur e studi es with Nocardia amarae from activated sludge and their implications for Nocardia foaming control. Research Journal WPCF63, 44- 50. Brodisch, KE U (1985 ). Inte raction of different groups of micro-organisms in biological phosphate removal. WST 17, 89-97. Buchan, L (1983). Possible biological mechanism of phosphorus removal WST1 5, 87- 103. Cloete, T E & Steyn, P L (1987). A combined fluorescent antibody- membrane filter technique for enum erating Acinetobacter in activate d sludge. In Biological Phosphate Removal from W'a stewaters, pp . 335-338. Edited by R Ramadori. Pergamon Press: Oxford. Hiraishi, A & Morishima, Y (1990). Capacity for polyphospha!e accumulati on of predominant bacteria in activated sludge showing enhanced phosphate removal. Jnl of Fermentation and Bioengineering 69, 368-371. Kerdachi, D A & Healey, K J (1987) . The reliability of co ld perchloric acid extraction to ass ess metal- bound phosphates. In Biological Phosphate Removal from Wastewaters, pp 339-342. Edited by R Ramadori. Pergamon Press: Oxford. Lotter, L H (1985). The role of bacterial phosphate metabolism in enhanced phosphorus removal from the activated sludge process. WST 17, 127-138. Trebesius, K, Amann, R, Ludwig, W, Miihlegger, K & Schleifer, K-H (1994). Identification of whole fixed bacterial cells with nonradioactive 23S rRNA-targeted pol ynucleotide probes. Applied and Environmental Microbiology 60, 3228-3235. van Niekerk, A M, Jenkin s, D & Richard, M D (1987 ). The co mp etiti ve grow th of Zoogloea ramigera and Type 021 in activated sludge and pure culture - A model fo r low F:M bulking. ]WPCF 59, 262-268. Wagner, M, Erhart\ R, Manz, W, Amann , R, Lemmer, H, Wedi, D & Schleifer, K-H (1994). Development of an rRNA- targeted oligonu cleo tide pro be specific for th e genu s Acinetobacter and its application for in situ monitoring in activated sl ud ge. Applied and Environmental Microbiology 60, 792-800. Wentzel, M C, Loewenthal, R E, Ekama, G A & Marais, G V (1988). Enhanced polyphosphate organism cultures in activated sludge systems Part 1: Enhanced culture development. Water SA 14, 81-92.

Authors Philip Bond is currently undertaking a PhD at the University of Queensland on the microbiology of phosphate- removal from wastewater. He has a BSc (Hons) from the University of Melbourne and is a researcher with the CRC Waste Management & Pollution Control Ltd. Linda Blackall is a Lecturer in Environmental Microbiology at the University of Queensland . Her research activities revolve around elucidating complex microbial communities such as those in wastewater treatment processes. She is a member of the Centre for Bacterial Diversity and Identification. Jiirg Keller is a Senior Lecturer in the 1 Department of Chemic al Engineering at the University of Que ensland and the Project Leader of "Improved Design and Operation of Biological Wastewater Treatment Processes", a project in the CRC Wa ste Management & Pollution Control Ltd.

WATER DECEMBER 1994

Acinetobacter is the microorganism of relevance in EBPR, reports of other bacteria being important in the story are numerous. Results pertaining to Acinetobacter from pho sphate-remo ving activated sludges are presented in Figure 5, which demonstrates why the importance of Acinetobacter in this process is being questioned. The question then is, what is responsible? Wagner et al ( 1994) prepared biological probes for some of the different groupings of the domain Bacteria: a-Proteobacteria, P-Proteobacteria, y-Proteobacteria, the Flavobacterium/-Cytophaga evolutionary line of descent, Acinetobacter and the Actinomycete phenotype Gram po sitive bacteria. They also had a biological probe who se target was any member of the domain Bacteria. Samples of mixed liquor from an EBPR plant were obtained. They used the probes to quantify the different groupings of Bacteria. They then employed classical microbiological methods and quantified the bacteria that were able to grow on the agar plate and produce colonies. Figure 6 shows the comparisons. Clearly, the proportions of bacteria in the ecosystem are dramatically different. The dominance of Acinetobacter and the yProteobacteria is over-emphasised when culture-dependent techniques are employed . The P-Proteobacteria and Actinomycete phenotype Gram positives are dominant when the biological probe is used. In our laboratory we decided to prepare libraries with l 6S rRNA information from two sources. One was from mixed liquor from a laboratory-scale, sequencing batch reactor (SBR) EBPR plant and one was from mixed liquor from a laboratoryscale, SBR non-EBPR plant. The effluent phosphate levels in the two lab scale plants are given in Table 1. We wanted to compare the microbial community structure in the two systems. If we found group(s) present in the EBPR plant that were absent from the non-EBPR plant, they could be the ones re spon sible for pho sphate removal. The libraries show some similarities with the results of Wagner et al (1994) as shown in Figure 7. There are a couple of differences. Wagner's probes detected slightly more y-Proteobacteria than the libraries, and the number of Gram positive bacteria was greater when the probe was employed. The similarities were the low occurrence of y-Proteobacteria (this is the subgroup containing Acinetobacter), and high numbers of P-Proteobacteria. Since there were no biological probes to the Planctomycetaceae , the probes were not useful for highlighting this microbiologica ll y unu sual group. They comprised approximately 12% of the bacterial community in SBRl and 6% in SBR2 in the library approach . There were different 20

Conclusions and Future Work The major conclusions from this paper are:• the library approach to studying the microbial ecology of activated sludge has been used and the results largely concur with those from a study employing biological probes. • a wide range of bacteria not previously studied are numerically dominant in activated sludge • subgroupings of the P-Proteobacteria in the EBPR plant differ from those in the non-EBPR plant • Acinetobacter were not a prominent group in the microbial community structure of either EBPR sludge or non- EBPR sludge. Futur e work in thi s experiment includes "reading more of the books in the library" to cover more to the total number in the library, phylogenetically analysing the complete dataset, and determination of the organisms that differ between the EBPR and non-EBPR microbial community. The rRNA data will be used to generate a biological probe for detection of the target organisms in situ. We will then attempt to isolate these bacteria. A number of isolation strat egie s could be employed such as micromanipulation or deduction of "selective" protocols based upon the target organisms nearest neighbours' physiological attributes. Once pure cultures of the putative EBPR bacteria have bee n obtained, the biochemical mechanism for phosphate accumulation will be studied. Finally, this information will be used to design more efficient EBPR plants, to alleviate failures in the current EBPR plants and to assist with the accurate modelling of EBPR processes.

Acknowledgements Dr Philip Hugenholtz is thanked for great assistance with data analysi s and Elizabeth Munch is also thanked for expertly operating the sequencing batch reactors from which the slud ge was obtained for microbial community structure analyses. The work is funded by the CRC for Waste Management and Pollution Control Limited, a centre established and supported under the Australian Government's Cooperative Re se arch Centres Program.

References Blackall , LL, T and oi, V & Jenkins, D (199 1) .

Co ntinu ous ~ ltur e studi es with No ca rdia amarae from activated sludge and their implications for Nocardia foa ming control. Research Journal WPCF63 , 44- 50. Brodisch, KE U (1985 ). Interaction of different groups of micro-organisms in biological phosphate removal. WST 17, 89-97. Buchan, L (1983). Possible biological mechanism of phosphorus removal WST 15, 87- 103. Cloete, TE & Steyn, PL (1987). A combined fluorescent antibody- membrane filter technique for enumerating Aci11etobaccer in activated sludge . In Biological Phosphate Removal from Wa stewaters, pp. 335-338. Ed ited by R Ramadori . Pergamon Press: Oxford. Hiraishi , A & Morishim a, Y (1990). Capacity for polyphosphate accumulation of predominant bacteria in activated sludge showing enhanced phosphate removal. Jnl of Fennentation and Bioengineering 69, 368-371. Kerdachi, D A & Healey, K J (1987). The reliability of cold perchl ori c acid extraction to assess metal- bound phosphates. In Biological Phosphate Removal from Wastewaters, pp 339-342. Edited by R Ramadori. Pergamon Press: Oxford. Lotter, L H (1985). The role of bacterial phosphate metabolism in enhanced phosphorus removal from the ac ti vated sludge process. WST 17, 127- 138. Trebesius, K, Amann, R, Ludwig, W, Muhlegger, K & Schleifer, K-H ( 1994) . Id entifi ca ti on of whole fixed bacterial cells with nonradi oactive 23S rRNA-targeted polynucle otide probes. Applied and Environmental Microbiology 60, 3228-3235. va n Niekerk, A M, Jenkin s, D & Richard , M D (1987) . The competi tive grow th of Zoogloea ramigera and Type 021 N in ac tivated sludge and pure culture - A model for low F:M bulking. ]WPCF 59, 262-268. Wagner, M, Erha ~t , R, Manz , W, Amann, R, Lemmer, H, Wedi, D & Schleifer, K-H (1994). Development of an rRNA- targete d oli go nu cleotide probe specific fo r the ge nu s Aci11etobaccer and its application for in situ monitoring in ac ti va ted slud ge. Applied and Environmental Microbiology 60, 792-800. Wentzel, M C, Loewenthal, R E, Ekama, G A & Marais, G V (1988). Enhanced polyphosphate organism cultures in activated sludge systems Part 1: Enhanced culture development. Water SA 14, 81-92.

Authors Philip Bond is currently undertaking a PhD at the University of Queensland on the microbiology of phosphate- removal from wastewater. He has a BSc (Hons) from the University of Melbourne and is a re se archer with the CRC Waste Management & Pollution Control Ltd. Linda Blackall is a Lecturer in Environmental Microbiology at the University of Queensland. Her research activities revolve around elucidating complex microbial communities such as those in wastewater treatment processes. She is a member of the Centre for Bacterial Diversity and Identification. Jiirg Keller is a Senior Lecturer in the Department of Chemical Engineering at the University of Queensland and the Project Leader of "Improved Design and Operation of Biological Wastewater Treatment Processes", a project in the CRC Waste Management & Pollution Control Ltd. WATER DECEMBER 1994

TECHNICAL NOTE

STRUVITE PRECIPITATION IN WWTPS: CAUSES AND SOLUTIONS ~ D G Chirmuley * Abstract Stru vit e (magnesium ammonium phosphate) precipitation is a recognised probl em in sludge handling systems at wastewater treatment plants around the world, which is likely to increase with the current trend toward biological nutrient removal. The paper presents an overview of causes and solutions and suggests steps that should be taken to locate and alleviate this problem.

Introduction Rawn et al ( 19 58) while stud yin g sludge digestion in 1939, found white crystalline deposits, identified as magnesium ammonium phosphate (also known as guanite or struvite), in a supernatant pipeline. Since then a number of WWTPs have reported its occurrence, eg Hyperion (Borderging 19 72), Oakland (Snoeyink and Jenkins 1980), a piggery wastewater treatment plant in Western Australia (Webb and Ho 1992) and many major WWTPs in Australia. Formation of struvite is accentuated in BNR plants where extra pho sphoru s is tak en up by the sludge. In the anaerobic digester the phosphorus is released into the water phase. Struvite deposits are hard and, once formed , difficult to di slodge. The se depo sits can cause damage to pumping equipment and almost totally block sludge pipes, resulting in costly maintenance and repairs, and disruptions to the operations of the plant. Borgerding reported that at the Hyperion treatment plant, struvite depo sits reduced the diameter of the pump suction line to the digester from 12 inches (300 mm) to 6 inches (150 mm). At the same plant in another instance the Hazen- William's coefficient "C" of the sludge pipeline downstream of the digester decreased from 85 to 31 "in a matter of months" (ie increasing the friction loss by 750 percent). He reported that water jets at a pressure of 300 psi (2,068 kN per m2) directed at deposits failed to remove them. The three ions which form struvite (magnesium, ammonium and phosphate) · WATER DECEMBER 1994

are present in all waters and wastewaters. In some instances, magnesium can enter the sewers due to seawater intrusion as at Southeast Water Pollution Control Plant in San Francisco (Pitt et al 1992) These ions can be present in supersaturated concentrations in anaerobic digester sludge and supernatant, sludge centrifuge centrate and sludge filter filtrate, and will precipitate under the right conditions. Struvite is a valuable plant fertiliser because it contains a high percentage of readily available plant nutrients, and also because of its low solubility and "nonburning" prop erty. Salutsky et al 1972, showed that up to 90% of the phosphate in digester supernatant can be precipitated as struvite and other insoluble phosphates.

Properties of Struvite Magnesium ammonium phosphate hexahydrate (MgNH 4PO 4.6Hz0), or struvite, as it is more commonly called, is a white crystalline powder having a specific gravity of 1. 7. Struvite precipitates can occur either as large single crystals, very small crystals, large curds or a gelatinous mass. Struvite has a low solubility in water of about 160 mg per litre at 25°C (struvite solubility product, ksp = 10-13 .1 ) . It is highly soluble at acidic pH and highly insoluble at alkaline pH. Its solubility is enhanced by salts of strong acids and weak bases. Experimental work has shown that high pH and high soluble phosphorus concentrations are the key factors which result in struvite formation. Rawn et al (1958) have suggested that struvite crystals are formed in sludge pipelines under flow conditions which lead to a release of CO2 from the sludge and subsequent increase of pH. Experimental work carried out by sc ienti sts at Metropolitan Water Reclamation District of Greater Chicago (Prakasam and Jain, 1993) suggests that soluble phosphorus levels greater than 50 mg per litre are necessary for pr ec ipitation as st ruvi te . Precipitation will also depend on the con-

centrations of magnesium, ammonium and pH. Thus, except in soft- water areas, precipitation in the anaerobic digester is likely, particularly for BNR plants.

Case Histories Case histories of two treatment plants illustrate the different situations in which struvite precipitation occurs. The Hyperion Treatment Plant, which is the largest of the four wastewater treatment plant s se rving the City of Lo s Angeles, treats a daily dry weather wastewa ter flow of nearly 1,400 ML/d in an activated sludge plant using high purity oxygen. At the plant, the primary sludge and waste activated sludge (WAS) are mixed in a 80:20 mixture and digested in a two- stl ge process. After digestion the biosolids are beneficially used. The effluent from the plant is dispersed approximately 8 km off-shore at a depth of 60 m. During the digestion process the phosphorus in the biomass is released and combines with magnesium and ammonium ions present, forming struvite . Any struvite carried over from th e primary digester then precipitates in the underflow line of the secondary digester. It is speculated that this occurs due to pH effects (resulting from release of CO2 from solution), and/or it may be due to vibration from sludge screens. The York River (Virginia) Wastewater Treatment Plant (WTP) was modified in 1988 to operate as a biological nutrient removal plant using the Virginia Initiative Plant (VIP) process (Daigger, 1990). · At the plant the anaerobically- digested sludge is dewatered in a belt filter and the filtrate which is rich in soluble nitrogen and phosphorus is returned to the primary influent. The primary diges ted sludge therefore contains high concentrations of phosphorus (6-8% phosphorus - volatile suspended solids basis) and high NH/

* Urban Water Resources Centre, University of

South Australia, The Levels SA 5095

levels. These are responsible for struvite formation in the digester.

Causes of Struvite Precipitation In addition to the high reactive ion concentrations, Borgerding gives four other factors that may be responsible either singly or in combination for producing suitable conditions for struvite precipitation. • Surface to Volume Ratio. In sludge storage units such as the digesters, the surface area to volume ratio is small, whereas in sludge supernatant pipelines it is large. Therefore a pipeline provides proportionately larger surface areas than a digester on which nucleation and crystallisation can occur. Furthermore, during the times of no flow (i.e. no sludge or supernatant withdrawal) the conditions are ideal for the settlement of formed struvite. • Condition of Interior Surface of Pipewalls. Rough pipelines provide better nucleation surfaces (joints in the pipes also serve the same purpose). Tests carried out at the Hyperion plant showed that of the pipes tested , PVC pipes had the least growth, and cast iron the thickest growth. • Increase in Energy. Vibrations and gentle stirring have been found to aid the formation of precipitates in supersaturated solutions . Experiments show that if NH 4OH and NH 4Cl are added to solutions containing MgHPO 4, the crystalline deposit of struvite is formed slowly, but stirring with a glass rod, ie energy addition to the system, promotes crystallisation. Scratching the wall of the beaker creates vibrations which nucleate crystal formation. At wastewater treatment plants, vibrations occurring in centrifuges, pumps etc, cause struvite to precipitate at these locations. For example, at the Stickney Water Reclamation Plant (Chicago, USA) a struvite precipitation problem appeared after change- over from low- speed to highspeed centrifuges for dewatering the sludge (Prakasham and Jain 1993). • Pres sure Changes in Pipelines. Localised pressure decreases occur at bends in pipelines, pump suction lines, venturis, etc causing the release of dissolved CO 2 at these locations which in turn raises the pH. Struvite is highly insoluble at alkaline pH and therefore precipitates occur at these locations.

Precipitation Control Techniques Since the main factors leading to struvite formation and precipitation are high concentrations of soluble phosphorus, and high pH, all struvite formation and precipi ta ti on control/elimination strategies should involve lowering soluble-P levels and lowering pH in the digested sludge or 22

the digester supernatant. At the Hyperion Treatment plant, the struvite precipitation problem was alleviat- · ed by diluting the digested sludge with the secondary effluent in a volume ratio of3: 1. This prevented super-saturation and subsequent crystallisation of struvite. Furthermore, addition of an extra volume of water to the sludge pipeline increased the velocity of flow creating an increased scouring effect in the pipeline. At the Oakland plant, where dilution of the sludge could not be practised and where it was not possible to keep carbon dioxide in solution in the supernatant, the struvite problem was solved by adding a polyacrylamide crystal inhibitor at doses of 10-20 mg per litre. Precipitation of phosphorus as another compound can be used to control struvite formation. Ferric chloride (FeC13), can be used and it also lowers pH. It is either added to the wastewater flow or to the digesting sludge. The target is to reduce soluble-P concentration to less than 50 mg per litre and the pH to less than 7.2 (Pitt et al 1992) At the Stickney plant (Chicago, USA), the sludge feed to the centrifuge is dosed with 36.4 kg FeC13 per dry tonne of sludge to achieve adequate phosphorus precipitation. At the Metropolitan plant experiments indicated that a dose of 150 mg per litre of FeC1 3 to the centrate would prevent struvite precipitation (Prakasham and Jain,1993). The main problems associated with the use of FeC1 3 are its cost coupled with the costs associated with experimental work to predict its dosage. Pitt et al (1992) provide a rational method for determining the FeC1 3 dosage to achieve undersaturation of struvite, and suggest that experiments must be conducted to accurately determine the dosage. On the other hand Snoeyink and Jenkins (1980) state that the solution to struvite problem lies in consideration of the solubility product, and empirical solutions should not be relied upon. The action of carbon dioxide (CO2) is different from that of iron salts, in that it only lowers the pH. It is available at a WWTP, being a by-product of the anaerobic digestion process. However, it needs separation from the digester gas . Use of ferric chloride is favoured because the availability of carbon dioxide is dependent upon vagaries of the digestion process, and hence cannot be relied upon.

Theoretical Struvite Formation Potential (TSFP} As stated in the previous section, using FeC1 3 as a means of controlling struvite precipitation is reliable though costly. Furthermore, before a treatment plant operator decides to use FeC1 3 it will be

necessary to dete4.mine if the sludge or the supernatant has a struvite formation potential. Snoeyink and Jenkins (1980) and Stumm and Morgan (1981 ) have applied a conditional solubility product to estimate the theoretical struvite formation potential (TSFP) . This concept can be used to estimate the struvite formation potential (SFP) at a wastewater treatment plant and its seasonal variability. The solubility of struvite is not, theoretically, a simple calculation of solubility product Ksp = [Mg] [NHJ [POJ f (Mg) f(NHJ f(PO 4) where f is the simple activity coefficient, because, for example the ions exist in solution in a number of forms : Mg+2, MgOH· 1 NH4• 1, NH3 PO/ , HPO/, H2PO/., H3 PO 4 the proportions being dependent on pH, so that the activities of the ions are reduced, thus appearing to increase the solubility. The conditional solubility product (Ps) is a simplified concept, which ignores the side- reactions. Such simplification gives a range of values which are appropriate only for given experimental conditions. Using standard physical chemistry, curves of Ps against pH can be developed for various ionic strength and temperatures. Stumm and Morgan (1981) found it convenient to represent the activities of the individual components as a function of pH, combining the three to yield a curve of Ps showing a minimum solubility at pH 10.7. Snoeyink and Jenkins ( 19 80) also brought in the effect of ionic strength on activities in their calculations, where log f=Az 2 [µ/1+µ- 0.2] A= ion- size parameter, z the charge of the species Empirically, u= 1.6 x 1Q·5 x conductivity (u mho/cm) Thus the TSFP is a function not only of the three components but also of pH, temperature and ionic strength. Both authors state that a theoretical struvite formation potential (TSFP) will exist only if the ion product [Mg] [NH4] [PO 4] exceeds the calculated value of the conditional solubility product by at least one order of magnitude. The knowledge of TSFP at a wastewater treatment plant will indicate to the operators where and when struvite scaling could occur and the operation of the plant could be altered to avoid it. It will also reveal any seasonal variations and thu s save chemical usage. Therefore, for a plant faced with a struvite precipitation problem, a program as outlined in the next section should be implemented to monitor its TSFP.

TSFP Monitoring Programme WATER DECEMBER 1994

The objectives of this program are : 1) to receive quick feedback regarding possible struvite precipitation sites; 2) to obtain information about variability ofTSFP; 3) to obtain cost savings from lower use of additives for control of precipitation; 4) to produce TSFP curves. The analytical program involves collecting daily random samples of digester influent, filter process/centrifuge influent and filtrate/centrate and analysing for soluble magnesium, soluble phosphorus, soluble ammonium, pH, conductivity (microsiemens per cm), temperature and alkalinity (the latter if a polymer is to be added to improve dewaterability of the sludge) .

Conclusion Struvite scaling of pipes and equipment is predicted to increase with the trend towards biological nutrient removal (BNR) treatment. There is a need, therefore, for an understanding of this problem if costly repairs and disruptions to the plant are to be avoided, and determination of a theoretical struvite formation potential is the first step towards its solution.

1996 Churchill Fellowships for overseas study The Churchill Trust invites applications from Australians , of , 8 years and over from all walks of life who wish to be considered for a Churchill Fellowship to undertake, during 1996, an overseas study project that will enhance their

usefulness to the Australian community.

References Borgerd in g, J (1972 ). "Pho sphate Depo sits in Digestion Systems" ]WPCF, Vol 4 (5) pp 813819. Chirmuley, D (199 3). "S tru vi te Precipitation Control", A report to Madison Metropolitan Sewerage District, (unpublished). Daigger, G T (1990). "Full- scale and Pilot- scale Exper ience with the VIP Proce ss", 1st Australian Conference on BNR, July 8-12, 1990, Bendigo, Australia. Masters, G M (19 74). "Introduction to Environmental Science and Technology", John Wiley & Sons, New York. Prakasham , TB S and Jain , J S (MWRDGC, Chicago, USA) Personal Communication, June 1993. Pitt, P et al (I 992). "Struvite Control Using Ferric Chloride at the Southeast Water Pollution Co ntrol Plant, San Francisco", Re search Symposia Proceedings, Vol 1, 65th Annual Conference, WEF, New Orleans, September 2024, 1992. Rawn, AM et al, as quoted in Kappe, SE (1958). "Dige ster Supernatant: Problem s, Characteristics and Treatment", JWPCF, Vol 30 (7), pp 937- 952. Salutsky, ML et al (1972). "Ultimate Disposal of Phosphat e from Wastewater by Recovery as Fertiliser", Effluent & Water Treatment Journal, Vol 12 (10), pp 509-519 Sen, D, Virginia Re se arch Station, Personal Communication, May 1993. Snoeyink, V Land Jenkin s, D (1980), "Water Chemistry", John Wiley and Sons, New York. Stumm, W and Morgan, J J "Aquatic Chemistry", John Wiley and Sons, New York, 198 1. Webb, K M and Ho , G E ( 1992 ). " Struvite Solubility and Its Applicat ion to a Piggery Effluent Problem", Wat Sci, Tech , Vol 26 (911 ), pp 2229- 2232.

STRUVIT!: THE FERTILISER Chirmuley's paper discusses the potential for precipitation and crystallisation of struvite in WWTPs, which, when it deposits in the wrong places, is a considerable nuisance. However, struvite does have some redeeming features as mentioned by the author. Its use as a fertiliser has been proposed by numerous authors (eg Bridger G L et al, 1962, "Metal ammonium phosphates as fertilisers" Agriculture and Food Chemistry, Vol 10, 3). It has slow-release properties and, because It does not cause burning of roots and leaves, can be applied in high doses. The rate of availability can be controlled by its granularity. It is currently being used for horticulture and other intensive agricultural industries in the USA and Europe. Thus the nuisance could be turned into an advantage if the crystallisation of struvite could be controlled and harnessed as an effective tool for removing high levels of N and P from various industrial and wastewater streams. The CSIRO Division of Chemicals and Polymers and the RMIT Department of Chemistry are collaborating to develop a procedure to identify which effluents could be a profitable source of struvite, for example, filtrates from the filter- pressing of anaerobic sludges from BNR plants and effluents from abbattoirs.

Water Reticulation Network Models

No prescribed qualifications are required , merit being the primary test, whether based on past achievements

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TECHNICAL NOTE

OXYGEN TRANSFER COEFFICIENT RELATIVE HUMIDITY RELATIONSHIP

Abstract In wastewater treatment, aeration or oxygen transfer is an indispensable process. Hence, correct estimation of the amount of the oxygen transferred into a · body of water is essential for design. The oxygen transfer coefficient (KLa) is generally related to temperature, bubble diameter, superficial velocity, liquid density and viscosity for diffu sed aeration system. However, laboratory tests conducted at the University of Wollongong indicate that relative humidity (Rh¾) also has an effect on oxygen transfer coefficient. It has been found that the minimum value of KLa (20°C) occurs at 100 % relative humidity and that the oxygen transfer coefficient increases with decerease in relative humidity

Experimental Methods A bubble aeration tank was used to conduct laboratory experiments. The tests were conducted inside a small temperature-controlled fog room (2.52 m W x 3.64 m H x 3.88 m L) equipped with an air conditioner and a humidifier controlled by a Honeywell humidity controller unit. A Hanna HI 8564 portable thermohygrometer was used to monitor the air temperature and relative humidity. The diameter and height of the aeration tank was 288 mm and 370 mm respectively and was filled to 300 mm with tap water. An immersible heating element was used to ·maintain water temperature at close to 20°C. A coarse bubble diffuser was immersed at the bottom of the tank. A polarographic oxygen electrode (YSI 5730 DO probe) was connected to a DO meter (YSI 59 DO meter) to monitor changes in DO and water temperature, and calibrated before each test. The membrane and KC! solution of the DO probe were changed for each run. The meter was connected to a portable computer and DO, water temperature, Rh¾ and air temperature were recorded at 30 sec intervals. Aeration data was measured using a non- steady- state method. The water was first deoxygenated by adding sodium sulfite based on stoichiometric calculation, using cobalt chloride as the catalyst. A new batch of water was used each time to

M Sivakumar) * C Shiau avoid ion accumulation. Due to the limitation in the experimental set up, the relative humidity was selected to range between 45 % to 85 % in steps of about 10%. A series of experimental runs was conducted with air flow rate varying from 1.8 Umin to 8.2 Umin. The procedure for a typical run was as follows: 1. set a selected air flow rate 2. set the Rh¾ to selected value 3. perform aeration until the water was 90% saturated 4. increase Rh¾ 5. perform aeration 6. repeat steps 2 to 5 up to an Rh¾ of approximately 85%.

if'C

avJ

Rh% lT'C

avg!KLa 20

· · · ~···!'·· -~~-g· ·r~~t~~:·· 11~··· ·ii:40·-r·23_3o·r·2i:oo··:·i£93 . )j:_9_9J ~~:~·9··!'-ii)_9_J·i~.s.9. . ?:3-?9..:.4s.5.9._j_ }~:J.9.. :..12.49 23.80_) 65.4Q) 22_.30 ) 12.12 .2.1}9i.71:~9..L~~A0 I 11.38 24.40 I 85.10 )22.60 ) 10.68

Table 1 :Experimental conditions and KLa(20) for run 4.

After finishing such a run, the water tank was refilled with fresh tap water. A second air flow rate would then be set and another run performed. The dissolved oxygen concentration versus time data were truncated to within 10 - 90% of the saturation concentration and the ASCE nonlinear regression method was used to obtain the reaeration coefficient and converted to KLa(20°C).

Results and Discussion Results of the variation of KLa(20) and Rh¾ are shown in Table 1 for run 4. It is seen that as Rh ¾ increases, KLa(20) decreases at a rate of 1 percent for every 3 percent increase in relative humidity. This observed phenomenon may be due to a number of reasons bu,t could be attributed to the partial pressure of oxygen at the airwater interface in the dynamic conditions of the surface film. Based on..,the observation of experimental data, equation 1 has been suggested and is further illustrated in Figure 1. Kla(Rh) ,. Kla(Rh,ooi=(101-Rh)

(1)

where KLa (Rh) = oxygen transfer coefficient at 20°C and a given relative humidity Rh¾, KLa (Rh 100) = oxygen transfer coefficient at 20°C and 100% relative humidity, and~ is a coefficient= 0.12.

Conclusion

ln(lOl-Rh) Figure 1: ln (KLa) versus ln(JOJ-

Rh).

The influence of humidity on reaeration coefficient was investigated. Experimental evidence shows that oxygen transfer coefficient KLa decreases with increase in relative humidity and the relationship between KLa and Rh¾ appears to be log linear. An equation has been suggested which could be used to correct the relative humidity effect on KLa. The value of KLa (Rh 100) can be used as a standard value for relative humidity correction just as KLa(20°C) is used for temperature correction. This observation may have significant application in water and wastewater treatment practice. * Department of Civil and Mining Engineering, University of Wollongong , Wollongong NSW 2522.

WATER DECEMBER 1994

TECHNOLOGY

PUMPING SEWAGE DOWNHILL LDMott* Abstract Traditionally, sewerage sys tems, whereever possible, operate solely by gravity. Pumping is adopted as a last resort and then only as a distinctly separate component of the system. There appear to have been few applications of peak flow "pump boosting" of gravity sewerage syste ms , either as an integrated function within new systems or for low-cost retrofitting to existing overloaded sewerage infrastructure. This paper ~ets out the rationale for wider consideration of such systems by showing four wide-ranging examples which displa y considerable advantages. Advantages that have, and can be realised, include reduction of both initial capital and net-present-value costs and avoidance (or at least a major reduction) during construction of environmental disturbance and social disruption. In addition, both sulphide generation potential and excess surcharge to the environment are reduced in operation, and greater flexibility to adapt to varied future system flows is achieved. One example set out in this paper, the Breakwater pump boosted gravity system at Geelong, recently received a "Highly Commended" in the 1993 IEAu st Engineering Excellence Awards and "The Award of Special Merit" in the 199 3 ACEA Exce llence Awards. The ACEA award is the highest given and it is the first time that it has been given in the civil, or any, category since 1989.

Background Sewerage systems are subject to widely varying hydraulic loads and have a potential for sulphide generation. Hydraulic load variations occur on a diurnal basis and during and following wet weather. Typically, peak dry weather flow (PDWF) is about twice average dry weather flow (ADWF). Peak wet weather flow (PWWF) varie s from abo ut 3.5 time s ADWF to 14 times ADWF, depending primarily on the age, construction and operational quality of the particular sewerage scheme. The duration of the higher wet weather flows is typically much less than 5% of the total time, and often less than 1% of the total. Sulphide generation potenWATER DECEMBER 1994

tial depend s on many factors, including sewage age, oxygen uptake from surfaces open to atmosphere, and the presence of anaerobic wall slimes. Considerable judgement is required for system design to minimise capital costs, operating costs, and sulphide emissions, as the design criteria are often either conflicting, not well established or cannot be accurately predicted. Compromises are invariably necessary. For example: • While grading of a major trunk outfall to achieve sediment transport is essential, steeper grading to achieve slime shearing velocities is not always practical, • Both population and design per capita hydraulic loading on systems varies with system age. In a new system the connected population and per capita peak hydraulic loads in most cases are fractions of the ultimate population and hydraulic loading. • Long-term population and de sign hydraulic per capita loadings on sys tems must be considered at best "a prediction" and are not known with any certainty.

Concept Traditional engineering approaches, since the development of separate sewerage systems in the 19th century, have aimed to tran sport all sewage flow s by gravity "down-hill" if possible. Pumping is adopted as the last option and then only for raising all flows "uphill. " The "pump boo sted " concept , as described in this paper, differs in the case of down-hill flo ws . Dry weather flo ws (which occur for more than 95 percent of the time) flow by gravity and peak flows

are handled by booster pumping. During gravity operation, slime shearing or even self cleansing velocities need not be attained in the discharge pipelines. However, much higher velocities, sufficient for slime shearing (and perhaps higher than 2.5 to 3.5 mis) can be achieve d during pump operation. This is possible because there is : a) less likelihood of water hammer due to the favourab le downhill pipeline profile and the ability to automatically revert to gravity operation. Further, in "low- head" pressure boosting cases, the use of an open discharge tower buffers the effects of pump starting and stopping; b) little concern about operating costs from the increased pumping head, as pumping only lasts for a sbort time. Pump controls are se t to operate pumps on a once per day basis during dry weather to "exercise" the pumps, to scour se dimei!t and to shear slimes from th e "pump boosted" gravity main. During wet weather the pumps operate "on demand" as a normal pump station. Thus power cost, usually a most significant operating cost of a pump station, is minor. In a new system, significant economies are achievable by the reduced di scharge pipe size, perhaps as much as half the diameter of a normal system. New pipe materials such as HDPE and Hobas are preferred because of their corrosion resistance, lo wer friction factors , and long radius bends that all reduce losses at the higher maximum operating velocities. The life of an existing system (which is structurally sound, but hydraulically overloaded during peak flow periods), can be extended by low head pressuri sation. If required , a polyethylene liner could be used to increase the possible level of pressurizing without jeopardising the structural integrity of the pipe or the joints. This either saves the costs and environmental and social disruption of complete replacement, or significantlJ extends the service life of the pipeline. Peak flow pump boosting is possible for any gravity system such as a gravity * GHD Pry Ltd, 300 Lonsdale St Melbourne

outfall, trunk sewer, tunnel , inverted syphon, ocean outfall, aqueduct or combination of systems. Four projects incorporating "pump boosted " gravity systems that di spla y th e co nsid era bl e advantages referred to above are described below.

Longwarry Pressure/Gravity Outfall Longwarry is a small town about 80 km east of Melbourne. Design of the sewerage sys tem was undertak en for th e Mornington Peninsula and District Water Board (now Melbourne Water). Longwarry's existing population is about 600 with a future projection to 1500 . Connection to the system of two smaller neighbouring towns, Bunyip and Garfield, will increase future sewage flows from the town system. Ultimate loading from these three township s could reach more than 7500 equivalent population. The topography is relatively flat , with an average fall of about 1 in 800 to the south. The town's sewage gravitates (or is pump ed) to a main pump station and thence, via an outfall system, to the wastewater purification plant located about 4.5 km to the south of the town. Options considered for this outfall system included: Option 1 Single Stage Rising Main. A single stage rising main of 450 mm dia . with an initial capital cost of $1.SM Option 2 Two Stage Rising Main.A first stage rising main of 300 mm dia. at an initial capital cost of $1.0M and a second 300 mm dia. stage after a minimum of 10 years Option 3 Gravity Outfall. Convetional single stage 600 mm dia. gravity outfall and low lift pump station with an initial capital cost of $2.4M Option 4 Pump Boosted Pressure/Gravity Outfall. A 300 mm dia. pump boosted pressure/gravity outfall at an initial capital cost of $1.0M, with second stage addition of high head "peak flow" pumps to the pump station after a minimum of ten years Ne tt pr ese nt va lu es (whi ch includ e costs of later stages and annual costs for operation, power and sulphide control over the next 50 years) are shown on Figure 1. Both Option 2 (conventional two-stage rising main) and Option 4 (pump boosted pressure/ gravity outfall) have the lowest initial capital costs of about $1.0M. Ho wever Option 4, th e pump boo sted pressure/gravity outfall, also presented significant nett present value cost savings over conventional alternatives. The Mornington Peninsula and District Water Board (now Melbourne Water) therefore adopted this option. The pre ssure/gravity outfall sys tem comprising a pump station and a 300 mm dia . uPVC pipeline has been constructed by Melbourne Water. The pump station ·

ha s provision for four pumps wi th two "low-flow low-head" pumps installed initially and two "high-head high-capacity" peak flo w pumps install ed lat er when increase d loading dictates. The general arra nge ment is sho wn on Figure 2 . Commissioning awaits completion of the wastewater purification plant currently under construction.

Strathfieldsaye Staged Pump Boosted Syphon Strathfieldsaye is a small township of some 1500 population located about 11 km east of Bendigo, Victoria. The town's ult imat e planned population is so me 10,000 by the year 2020, but the actual growth rate may not be as high. It was propo se d to discharge th e sewage 11 km to the Co liban Region Water Authority's system. This requires pumping across two large hills and through the small community of Junortoun (ultimately 1500 population) in the intervening valley. Low initial loading, combined with pumping requirements and the long distances, make the control of sulphide particularly important for this system. The four outfall system options considered for connecting Strathfieldsaye were: Option 1 Single Stage Pump & Gravity System. Co nve ntional single stage pump/gravity systems at an initial estimated capital cost of $3 .0 M. The systems would comprise 300 mm dia. rising mains, 375 mm dia. gravity sewers and two conventional high head pump stations at Strathfieldsaye and Junortoun Option 2 Two Stage Pump & Gravity System. As for (1) above , but with twin 200 mm dia. rising mains constructed in stages at an initial capital cost estimate of $2.5 M Option 3 Single Stage Pump & Pump Boosted Gravity Syphon System. A single stage pump/pump boosted gravity syphon system at an initial capital cost estimate of $2.6 M. As for (1) exce pt a 280 mm dia . HDPE "pump boosted" gravity syphon across th e Junortoun valley with a small pump station at Junortoun to serve the local catchment discharging to the syphon. Option 4 Two Stage Pump & Pump Boosted Gravity Syphon System. As for (3) above, but with twin 200 mm dia. stage constructed rising main s from Strathfieldsaye and with the pump boosted syphon acting as pump/gravity system during the first stage. At the second stage, the Junortoun Pump Station converts to a local stati on only di sc hargi ng di rec t to th e syphon main. The initial capital cost estimate is $2.4 M. This option is shown diagrammatically in Figure 3. A SO-year nett present value cost comparison of the four options is set out in Figure 4.below. The nett present valu es

include capital, costs of later stages and annual costs of operation, power and sulphide control over a 50 year period. Option 4 incorporating staged implementation of a pump boosted gravity system presented cost savings over conventional alternatives, both in terms of initial capital costs and nett pr ese nt The Authority adopted this option. The first stage of this system was successfully commissioned in August 1993. The Junortoun pump station general arrangement showing the stage 1 flow path is shown on Figµre 5.

Breakwater Pump Boosted Gravity System Geelong, Victoria's second largest city, is served by a flat-graded gravity outfall sewer to the Black Rock treatment facility on Bass Strait. Sewage from about half the 150 000 population gravitates to this outfall sewer via an 80 year old 1295 x 910 mm rei nforce d concrete ovoid branch sewer. This branch sewer forms a major element in Barwon Water (BW) (formerly Geelong and District Water Board) sewerage system. The lower 3000 m section of the ovoid sewer is flat graded at 1 in 2500 and included a 750 metre long aqueduct cross ing of th e Barwon River at Breakwater. The aqueduct, also 80 years

N p V

s M

DJSCOUl'IT RATE(¾)

- -

-+-

Option I Option 3

-a-' Option 2 -X-

Opt ion 4

Figure 1 Longwarry Outfall Options

Figure 2 Longwarry Pump Station -

Peak Flow Path WATER DECEMBER 1994

old, is of major engineering heritage value. However, it was constructed using reinforced concrete trusses and is in poor structural condition because of serious deterioration of the concrete. An alternative sewer crossing to this National Trust registered structure was required urgently. Future hydraulic loading for design purposes was difficult to determine, but 1600 U s was adopted by the BW based on planning proj ections. Staged replacement of the sewe r is part of the BW forward planning strategy. The replacement of the aqueduct comprised the first stage. The four main aqueduct replacement options considered were: Option 1 Aqueduct. A new aqueduct consisting of a bridge structure with a mm 1600 dia. cement lined mild steel pipeline. A cable-stayed structure was found to be the most economical aqueduct structure . Initial capital cost estimates were $6.5 M. Option 2 Pump Station. A conventional pump station comprising a gravity trunk sewer under the river with a direct re lift to the downstream outfall sewer . Initial capital cost estimates were $8. M. Option 3 Air Cushion Sewer. An "air cushion" sewer (a lo w le vel pressur e/gravity sewer in which flo w depths are controlled by air pressure variation to mimic normal gravity flow condi-

tions). Initial capital cost estimates were $6.8M. Option 4 Pump Boosted Gravity System. A pump boosted gravity system comprising a peak flow "pump boosting" station, and a 750 mm dia. and 900 mm dia. HDPE syphon pair. Initial capital cost estimates were $3.9 M. The pump station would also "pump boost" peak flows in the existing downstream section of the ovoid sewer, thereby increasing its capacity by about 50% and achieving cost savings due to the deferment and size reduction of this section. Figure 6 shows the system profile and operating hydraulic grade lines of this option. (Note particularly "pump boosting" of the downstream sewer occurs only during extreme peak flow conditions, whereas "pump boo sting" of the new syphon occurs during both typical and extreme peak flow conditions). Nett present value costs for the four options that include costs of later stages and all annual costs (including allowances for operation, power and sulphide control) over a 50 yea r period are shown on Figure 7. Option 4, a pump boosted gravity system, had both initial and nett present value cost savings, and therefore was adopted by the BW. The system was successfully commissioned in November 1992 at a final cost

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WATER DECEMBER 1994

Figure 5 Junortoun Pump Station - First Stage Flow Path ·

of$4.2 M. Figure 8 sets out the general arrangement of the pump statio n. The station incorporates a discharge tower and a service tower containing wet well access, control room, staff amenities, a future generator room and di scharge tower acc ess. Pumps are standard Flygt CP 3500 units (apart from a modified "straight through" pedestal). All average "dry weather" flows are passed by gravity while typical peak flows (i.e. peak dry weather and/or smaller storm flo ws) are handled by one pump operation. Two or more pumps in parallel pass the extreme peak flows (i.e infrequent large peak wet weather flows). The detailed design of the pump station itself will be the subj ect of a paper to be published later.

Geelong Gravity Outfall Sewer The 11 km outfall sewer from Marshall to the treatment facilities at Black Rock comprises 10.5 km of 1670 mm dia. plastilined RRJ Reinforced Concrete pipeline. This pipeline replaced the original reinforced concrete ovoid sewer in the late 1960s and the pipe is reportedly in good condition. However, with the growth of the city of Geelong, the outfall is now operating close to its hydraulic limit during storm events. Therefore BW is considering options for either upgrading the outfall capacity or relieving increased loading as part of its ongoing capital works program. Duplication of the outfall would be the conventional approach. However, initial capital costs are hi gh, around $18 M. Also, environment disturbance and social disruption during construction would be unavoidable. One of several alternatives being considered by BW is lo w- head pump boosting. The outfall was originally designed in the early 19 60s for conventional gravity operation using plastilined reinforced concrete pipes. However, advice given by the pipe manufacturer indicates that both the pipes and joints have a hydrostatic intern&! de sign tes t pre ss ur e of nin e metres. Therefore, subject to a detailed condition assessment of the in-situ pipes, low-head peak flow pump boosting may provide an economical means to increase capacity and avoid maj or disruption during construction. Further, to pro gressive ly increase capacity as loading increases, pump boosting could be increased in stages to achieve a 90% increase with a maximum six metre boost (Refer Figure 9). If a second pump station is added later , around 120 % increase can be achieved with a six metre boost at each pump station (refer Figure 10). Initial capital costs for the first pump station will be low, estimated at about $3 M. This cost includes allowances for investigation and provision of additional measures, 27

such as bolt-do wn manhol e covers to accommodate short term pressure operation slightly above natural surface in some isolated locations. Also, as the existing outfall sewer is flat-graded (1 in 2750), pump boosting would improve scouring velocities so that the costs of sulphide suppression measures and periodic physical scouring measures are reduced or eliminated. These operating cost savings tend to balance increased costs

of pump station operation and any necessary increased pipe condition monitoring. The low initia l capital costs of thi s alternative, combined with the ability to stage increase in pace with development (and therefore keep capital cost expenditure in pace with development) will result in lower nett present value costs (possibly more than 50% lower) when compared to the conventional approach of outfall duplication.

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Therefore, Joor-hea d pump boosting provides a cost-effective alternative, among others, to conventional dupli cation for consideration by BW when and if upgrading is required". Low head pump boo sting therefore provides another cost-effective alternative to conventional duplication.

Conclusions Peak fl ow boosting of both new and existing gravity sewerage systems potentially offers many advantages over "all gravity" and "conventiol).al combined pump/gravity" systems. The advantages of this innovative approach can include: • reduction in both capital costs (particularly initial capital costs) and nett present value costs; • operational cost reduction (particularly power costs and costs to suppress sulphide generation); • reduced excess surcharge to the environment and sulphide generation potential; • flexibility to accommodate varied future hydraulic loading; • minimum environmental disturbance and social disruption during construction. While the pump stations may involve some additional layout co mpl exity and therefore increased design input, simple operation using standard industry components and control systems can be achieved with careful design. New pipe materials such as HDPE, Hobas and uPVC lend themselves to use in pressure/~ravity pipelin es. Their elastic properties tend to reduce water hammer and the reduced frict ion losses of their smooth bores, less joints and ultra long radius bends enable higher velocities under pumping. This allows smaller pipeline sizes to be adopted. The above fo ur examples also show that benefits can be achieved in both small and large systems. Similar benefits could also be possible for many gravity systems whether they be gravity outfalls, trunk sewers, tunnels, inverted syphons, ocean outfalls, aqueducts or combinations of sys-

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terns. Pump boosting can be adopted in a new system or in the rejuvenation of an existing under-capacity infrastructure pipeline that is structurally sound.

References GHD Report - Basis of Design, Longwarry Collection System fo Mornington Peninsula District Water Board - May 1990. GHD Report - Function Design Report Township of Strathfieldsaye Sewerage Outfall System for Bendigo Water Board - March 1992. GHD Reports for Barwon Water: Preliminary Design Report on River Crossing Options - February 1990. Detailed Design Report - Replacement of Ovoid Sewer Breakwater - June 199 1. Co mmi ssioning Report on Breakwater Pump Boosted Syphon - March 1993. Technical Notes on Inn ova tive Sewer Rehabilitatio n and Augmentation Options February 1993.

Acknowledgements The Author wishes to thank the clientsMelbourne Water Corporation, Coliban Region Water Authority and Barwon WATER DECEMBER 1994

Water - for: a) involving the Author through GHD as a part of their project team; b) the co-operation and support of their Branches and their individual staff members; c) their willingness to adopt such an innovative concept which greatly differed from both standard industry practice and original expectations; and d) their permission for publication of this paper.

Author Lindsay Mott is a Principal Design Engineer with Guueridge Haskins and Davey Pty. Ltd, Consulting Engineers. For 28 years he has been involved with concept development, strategy development, detail design, construction and operation of sewerage systems. Lindsay has specialised in new and innovative approaches to design. He graduated from Monash University with a Bachelor of Civil Engineering (Honours) in 1966.

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ENVIRONMENT

FORMULATING ECOLOGICAL WATER QUALITY GUIDELINES I Lawrence*, W Maher) P Liston) A Wade Introduction Water quality guideline s pro vide a benchmark for assessing acceptability of water for a given end point use or environmental value . Because the guidelines represent desirable ambient conditions, or provide scope for development of local guidelines, considerable innovation is required on behalf of land and water managers to put them into practice. The guidelines have often mistakenly been described as standards. Since our understanding of aquatic ecosystems is far from perfect the question of setting standards , for example formulating point source licensing discharge standards, is a complex process and must accommodate an appreciation of the full range of catchment impacts, natural and anthropogenic, that impact on the quality of receiving waters. This paper reflects our experience in developing local water quality guidelines, based on the Australian guidelines, and indicates how these are being applied to manage waters of the Australian Capital Territory.

Origins of Water Quality Guidelines Prior to release of the Australian Water Quality Quidelines for Fresh and Marine Waters, several other groups had published water quality guidelines, but these were really only known to regulators and the well-informed of the water industry. The best known of these guidelines were the Victorian Environment Protection Authority's Recommended Water Quality Criteria (19 83 ), A Compilation of Australian Water Quality Criteria (Hart, 1974 ), and the Western Australian Environment Protection Authority's Water quality criteria for marine and estuarine waters of Western Australia (1981 ). Recently released Australian Water Quality Guidelines for Fresh and Marine Waters (Australian and New Zealand Environment and Conservation Council, 1992) have created active debate, both in environmental circles and across a wide range of water dependent industries. A recent seminar, Reconciling industrial rural and urban waste water disposal with

URBAN

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Figure 1 Locality Map 30

Australian water quality guidelines (Nov 31-Dec 1, 1992), raised many practical concerns about how to identify land and water management practices which would enable ambient guidelines' benchmark levels to be achieved (Baker; Bell; Court; Lawrence; Smalls; Wright) . Put another way, there has been general uncertainty as to whether the Australian water quality guidelines can be implemented and whether the National Water Quality Management Strategy can achit ve its stated objectives of improved water and land management practice (Burton 1993).

Some New Approaches to Formulating Guidelines In 1989, the ACT Water Policy Plan was released . The Plan included an inventory of the Australian Capital Territory water resources. Water uses and ecological values were also identified and are similar to those in Australian guidelines (Table 1). A notable divergence of Australian Capital Territory philosophy from the national guidelines is the recognition of the inseparability of the intrinsic values of waters (for example ecosystem maintenance) and their inevitable use as receiving waters. The reality is that all waters, marine, stream, lake and ground water systems, are impacted by human activity, and that such receiving water use must be recognised; the need is to identify means of minimising the impacts of point source and diffuse discharges. Also specified in the Water Policy Plan, as in the Australian guidelines, were sets of water quality guidelines for each identified water use . Subsequentt to the release of the Water Policy Plan a more comprehensive Territory Plan, incorporating water resource planning, was produced . Simultaneously the water quality guidelines * Office of the Environment PO Box 1119 Tuggeranong 2902

WATER DECEMBER 1994

were reviewed at a conceptual and practical level. Initially, a set of wa.ter quality indicators (physical, biological, chemical) was identified that allowed the suitability of the water for a given use or ecological value to be assessed. The indicators chosen were also sensitive to catchment based pollution loading and have the capability of identifying present and future water quality problems. Once appropriate indicators had been selected, it was necessary to establish water quality and ecological guideline levels for these indicators that would maintain the different water uses and ecological values. Australian Capital Territory guidelines emphasise the need to provide: • adequate protection of water uses and ecological values under local conditions; • quantitative rather than qualitative assessment, so they can be used for monitoring trends in water quality spatially and over time; and • consistency with Australian Water Quality Guidelines for Fresh and Marine Waters. In the past, guidelines have focussed on setting levels or ranges of water quality indicators that are not to be exceeded. The new guidelines that are being implemented in the Australian Capital Territory contain several nov el features. In cluded in Australian Capital Territory guidelines are: • primary water quality guidelines, reflecting Australian guidelines (Australian and New Zealand Conservation and Environment Council, 1992, and National Health and Medical Research Council Australian Water Re source s Council, 1993); and include the recognition that a single set of guidelines may not always be appropriate to protect diverse ecosystems; • secondary downstream guidelines for: • estimating sustainable loads of ecosystem modifying substances such as nutrients and sediments; • detecting and measuring contaminants in sediments; and • monitoring changes in biota. These secondary guidelines have been introduced to bridge the gap between prescribing ambient water quality guidelines, the main thrust of the Australian guidelines, and indicators to protect and manage aquatic ecosystems.

Primary Water Quality Guidelines Primary water quality guideline s are values that must be achieved to maintain a particular water use. A range of mechanisms may be used to maintain water quality, including legislation, planning, development practices and management techniques. Primary water quality guidelines are based on previously published water quality criteria. The United States Environment Protection Agency (USEPA) defines a criterion as: WATER DECEMBER 1994

Table 1 Water values ACT Water Policy Plan

Australian water quality guidelines for fresh and marine waters

Potable water supply Recreation Irrigation; stock water supply Discharge zones and drains Conservation of ecosystems; scientific study and education

Drinking water supply Recreation and aesthetics Agricultural water Industrial water Ecosystem protection

Table 2 Ecosystem classification in the Australian Capital ten-itory Catchment terrain/land use Sub-alpine Forested mountain slopes Rural catchments Urban catchments

Streams

Wetlands

Ponds and lakes

Fens/bogs Alpine ponds and lakes Streams Seepage zones adjacent to streams Rivers Floodplain Stream billabongs, farm dams Streams, drains Wetlands Storm detention ponds and recreational lakes

Reservoirs -------------Water supply reservoirs Water supply reservoirs

Table 3 Supplementary ecosystem guidelines adapted to protect diverse water habitats Indicator

Rural Urban streams and lakes and rivers ponds Acidity (pH) 6- 9 6.5 - 9 Cadmium (µg/L) 0.8 0.8 Chlorophyll a (µg/L) < 10 Dissolved oxygen (mg/L) >4 >4 Lead (µg/L) 2 2 Nickel (pg/L) 65 65 Suspended solids (mg/L) 25 25 Total phosphorus (µg/L) 100 100 Turbidity (NTU) < 10 < 30

Urbans drains and streams 6-9 0.8 >6 2 65 25 100 < 10

Urban wetlands

Forested' mountain reservoirs

Rural reservoirs

6- 9 0.8 < 10 >4 2 65 25 190 < 30

6.5 - 9 0.2 <2 >6

6-9 0.2 <5 >4

25 12 .5 40 < 10

25 25 100 < 30

. Table 4 Downstream loading guidelines for sediment Loading criteria

Sediment load guideline value

Sediment load ) (kg/y/river reach

Murrumbidgee River from site 213 to site 990 I Murrumbidgee River from site 9901 to site 9903 Murrumbidgee River from site 9903 to site 209 Murrumbidgee River from site 209 to site 208 Murrumbidgee River from site 208 to site 207 Murrumbidgee River from site 207 to site 205 Murrumbidgee River from site 205 to site 204 Murrumbidgee River from site 204 to site 20 I Molonglo River from site 609 to site 606 Molonglo River from site 606 to site 60 I Molonglo River from site 413 to site 407 Molonglo River from site 407 to site 40 I Paddy's River from site 834 to confluence with Cotter River Ginninderra Creek from Lake Ginninderra to Murrumbidgee River

Total phosphorus for major lakes (kg/y)

Lake Tuggeranong Lake Burley Griffin Lake Ginninderra Lake Burrinjuck (Murrumbidgee Arm)

600 8600 300 83200

Biochemical oxygen demand for major lakes(kg/y)

Lake Tuggeranong Lake Burley Griffin Lake Ginninderra Lake Burrinjuck (Murrumbidgee Arm)

5600 51200 8400 110600

88,000 166,000 133,000 57,000 101,000 66,000 124,000 228,000 39,000 19,000 20,000 25,000 4800 9800

Table 5 Phosphorus loading guidelines (kgly) Loading criteria

Sediment load guideline value

Total phosphorus for major lakes (kg/y)

Lake Tuggeranong Lake Burley Griffin Lake Ginninderra Lake Burrinjuck (Murrumbidgee Arm)

600 8600 300 83200

Table 6 Biodegradable organic carbon loading guidelines Loading criteria

Sediment load guideline value (kg/y)

Biochemical oxygen demand for major lakes

Lake Tuggeranong Lake Burley Griffin Lake Ginninderra Lake Burrinjuck (Murrumbidgee Arm)

5600 51200 8400 110600

Table 7 Sediment contaminant guidelines Sediment contaminants Sediment load guideline value

Pesticides Heavy metals * Polycyclic aromatic hydrocarbons (PAH)

A sediment total pesticide concentration more than two standard deviations higher than the long term mean. Sediment heavy metal concentrations more than two standard deviations higher than the long term mean. A sediment PAH concentration more than two standard deviations higher than the long term mean.

*Arsenic, cadmium, copper, lead, nickel, mercury, selenium, and zinc

Table 8 Biological water quality guidelines Biological guideline value

Water quality at a site will be considered to be impaired if species richness is more than twenty per cent lower than at an appropriate reference site. Water quality at a site will be considered to be impaired if there is a significant difference in ecosystem community structure from that at the reference site, as judged by Hocutt's procedure or another appropriate statistical technique.

"A de signated concentration of a constituent that when not exceeded will protect an organism, an aquatic community or prescribed water use or quality with an adequate degree of safety. " To protect ecosystems, a single set of water quality guidelines for toxicants, for example heavy metals and pesticides, based on Australian and overseas data and similar to Australian Water Quality Guidelines for Fresh and Marine Waters (Australian and New Zealand Environment and Conservation Council, 1992) is regarded as entirely appropriate. Th e Canadian approach (Canadian Council of Resource and Environment Mini sters, 1987 and update s) to establishing toxicant water quality guid elin es, base d on the lowest published, that is, well established, observable effect level on biota, has been adopted in both the Australian and the Australian Capital Territory guidelines; this approach ha s been adopted in prefer ence to the United States Environmental Protection Agency (1985 ) approach that requires stringent application of lethal toxicity criteria (LC50, that is fifty per cent lethal concentration tests). The USEPA approach does not guarantee protection of all organisms at all stages of their life cycle and does not address the probl ems of subl ethal effects such as reduced fecundity or physiological behaviour changes. Hence, direct application of Australian Water Quality Guidelines to local water bodies is not always possible. For example, water quality appropriate for the protection of a sub-alpine fen , or lowland saline lake, 32

will be quite different from that necessary to protect a mountain stream. Nutrient loadings necessary to sustain the highly productive and diverse wetland ecosystems would cause major problems if applied to the open wa ter bodies of the lake s. Determination of environmental value s and water quality guidelines appropriate to lakes, rivers and streams appropriate to local conditions is required. The ecology of local waters is a reflection of the adaptation of community composition and structure to the highly variable climate, flow regime, turbidity (and salinity in the case of lowland lakes and stream s) of riv er systems of inland Australia. The ecology of these systems has adapted to extremes of salinity, temperature, oxygen, and suspended solids. Prior to urbanisation, riverine systems in the Australian Capital Territory were ephemeral, with flora and fauna adapted to such conditions. This flow regime was exacerbated by substantial clearing of land and grazing back in the l 870's. Following urbanisation, a number of rivers and streams have experienced sustained flow (even through drought periods) and have had high nutrient loadings. In response to these changes in hydrology and nutrient regimes, diverse and productive wetlands and riverine ecosystems have evolved. In addition, wetlands, ponds and lakes have been constructed in natural channels as landscape, recreation and pollution control features. These ecosystems are highly valued by the local community. For example, the wetlands at the upper

end of Lake Bu rjey Griffin and Lake Ginninderra are highly valued by the Canberra community as bird sanctuaries. Yet these ecosystems are dependent on high loadings of organic material and nutrients, typical of urban storm water, to sustain their productivity and biodiversity. The community tends not to differentiate between the value of these urban wetlands, and the natural wetlands occurring in the river floodplains, despite their highly modified character. The example outlined above highlights the dilemma faced in classifying modified stream systems, since comparison with natural ecosystems is not valid. Indeed, few streams in Australia remain in anything like their original condition. Consequently, planning and management of modified systems are the norm rather than the exception. An extensive body of water quality and biota monitoring data has been collected over more than twenty years and this information has been interpreted to gain an understandin g of water bodies in the Australian Capital Territory. The information has been used to formulate water quality guidelines that are more appropriate to local conditions (Maher, Liston, Wade, Moore, Cullen, and Norris,1993). An aquatic ecosystem classification system has been developed which: â&#x20AC;˘ categorises systems in terms of their habitat, stream flow , and water quality characteristics; â&#x20AC;˘ recognises the need for a system of universal application, providing opportunities for comparison with like systems in other regions; and â&#x20AC;˘ provides a practical categorisation of biota that permits assessment of sustainability. Catchment terrain and land uses are the principle determinants of both stream morphology characteristics and constituents of flow, and hence provide a sensible basis for classifying aquatic ecosystems. Within each of the se catchment types, there is a range of water body categories that can be identified based on flow characteristics, namely streams, wetlands, ponds, lakes, and reservoirs. Such a classification system is shown in the Table 2. This system of classification closely parallels the approaches adopted in numerous water quality and ecology studies undertaken in the region over the last fifteen years including ACT Region Water Quality Study (Department of Construction and Binnie International, 1978); Waters of the 8 anberra Region (N ational Capital Development Commission, 1981 ); Aquatic Resources of the ACT (Hogg and Wicks, 1989) and Ecological Resources of the ACT (Hogg, 1990). Where possible specific ecosystem guidelines have been developed to protect WATER DECEMBER 1994

diverse water habitats (Table 3). These guidelines have been expanded as local knowledge has improved. The approach also closely parallels the system adopted in The Environmental Conditions of Victorian Streams (Department of Water Resources Victoria, 1990).

Secondary Water Quality Guidelines Secondary guidelines values are levels which, if exceeded, will require an investigation of the cause to allow appropriate management action to be taken. Secondary guidelines apply to variables known to indicate ecosystem impact or degradation, but for which there is insufficient understanding to warrant inclusion as primary guidelines. Examples are downstream loading guidelines and sedi ment contaminant guidelines. In the event of exceedance of these guidelines, measures to remediate or control the sources of pollution will be required to ensure that uses or ecological values are not compromised.

Downstream Loading Guidelines

Vollenweider model (Upper Murrumbidgee River Catchment Coordinating Committee, 1993), which links the annual phosphorus load of a lake to water column phosphorus concentration and hence to chlorophyll-a concentration. Biodegradable organic carbon loading guidelines were based on the recognition that when sediments become depleted in oxygen (less than 1 mg/L 0 2), significant release of phosphorus to the water column occurs. The breakdown of organic carbon is seen as the critical component in depletion of sediment oxygen levels (Maher and DeVries, 1993) and biodegradable organic carbon loading guidelines have been developed to minimise phosphorus release from se dim ents (Table 6) . These guidelines were based upon the rate at which bottom waters can be reoxygenated by diffusion under still conditions. Organic carbon loading, as measured by the biochemical oxygen demand (BOD 5) test, was then set at a level not exceeding this rate of reoxygenation. Downstream loading guidelines measure the dynamic loading of water bodies over a finite time frame, typically reflecting seasonal or annual change.

Underlying the adoption of concentrations as the quantitative measure of water Sediment Contaminants quality is the assumption that concentraMany contaminants including persistion directly determines the impact of con- tent pesticides and heavy metals are rapidly taminants on organisms. While this is valid partitioned to sediments. Because of the in the case of toxicants, many runoff condiscrete nature of sampling for water qualistituents accumulate in rivers and lakes ty indicators, intermittent pollution events and the detrimental impacts on aquatic may not be recorded. Such contaminants ecosystems are dependent upon the load, may have profound and lasting impacts on not the concentration. In recognition of aquatic ecosystems during their brief time cumulative loading effects, downstream in the water column. In addition, accumuloading guidelines have been introduced for sediment, phosphorus and biodegrad- lations of these contaminants in sediments can have major impacts on sediment infauable organic matter (Tables 4, 5 and 6). na and associated aquatic biota. Sediment loading guidelines are based Guidelines for contaminants in sedion the potential smothering effect of sediments (Table 7) are proposed to assist in ment on benthic macroinvertebrate communities. These guidelines were developed the management of water bodie s. by assuming that greater than two millime- Monitoring would be carried out on a time ters of sediment of grain size smaller than basis determined by deposition rate s. 200 millimeters will produce a significant Additional sampling would be undertaken impact on stream fauna (Hogg and Norris, if there were evidence of adverse impacts 1988; Marchant, 1989). Permissible sedion an aquatic ecosystem, for example a fish ment loads were developed by partitioning kill, where there was no obvious cause. Sediment contaminant guidelines major rivers into sections 10-20 kilometers (cumulative loading guidelines) are potenlong delineated by tributarie s that are tially useful in the context of: potential sources of sediment. Permissible sediment loads were calculated based on a • monitoring current intermittent polludeposition of no more than one millimeter tion episodes and long past events where of se diment per year. Phosphorus and the chances for detecting pollution in the biodegradable organic carbon loading main water body are unlikely; guidelines have been introduced because of • detecting low level build-up of persistent the potential of external and internal toxicants that partition to stream and lake sources of phosphorus to trigger unwanted sediments; and • assessing potential for remobilisation of algal blooms in lakes. Permis sible phosphorus loads for sediment components, for example phosAustralian Capital Territory lakes from phorus and heavy metals, under eventexternal sources, for example river inflow driven conditions such as scouring or high (Table 5), were calculated using the · organic loading of bottom waters. WATER DECEMBER 1994

Changes ill Biota Physical and chemical indicators of water quality are only surrogate measures of the health of ecosystems (Maher and Norris, 1990). Even if clear links between physical and chemical measurements and biological impact are established, because of the discrete nature of sampling for physical and chemical indicators, intermittent or episodic pollution events may be over looked. Furthermore, the impacts of physical or chemical constituents that are not m_easured or where effects are not known, will not be taken into account. The monitoring of changes in aquatic macroinvertebrates has been introduced as a measure of aquatic ecosystem health. Biological guidelines have been developed (Table 8) based on: • changes in community structure; defined as the relative and absolute abundance of taxa comprising the community; and • changes in species richness, defined as the number of species in a community or within a site. From previous studies of impacted ecosystems in the Australian Capital Territory, fauna! groups that are sensitive to changes in stream or lake conditions have been identified . Although the responses of these fauna! groups to impact are not yet understoo d well enough to establish absolute guidelines, they provide a useful focus for investigation of changes in community structure and species richness. A <;,tiange in species richness of twenty per cent has been adopted to indicate unacceptable ecosystem degradation as this represents a compromise between adequate sensitivity and practicality. For changes in community structure the ordination procedure of Hocutt (1975) was specified to identify significant changes and trends in community structure. Changes in biota have the attractive potential to monitor ecosystem changes. Such biological stress or community structure (ecosystem) change indicators: • measure biological change, such as community structure or species diversity, as outlined in the Review of ACT Water Quality and Ecological Guidelines (Maher et al, 1993); • reflect changed organism behaviour related to water pollution, that is hard to detect by classical monitoring, such as detection of deformities and physiological changes; and • provide a tool for community hands-on assessment of impacts of changing water quality.

Conclusion Water quality management practice is currently undergoing a renaissance. The approaches being adopted to rehabilitating and protecting our va luable water resources have seen the emergence of: 33

• total catchment management practice which recognises the integrating impact of land management and storm and waste water discharges on water quality; and • increasing community ownership of land and water quality problems that recognises the human dimensions and considerable resources required to change water quality. Assessing acceptable loadings of ecologically modifying sub stanc es such as nutrients, and the use of sediment guideline s and observab le biological impact guidelines are seen as providing a more certain and tangible indication of water quality problems than classical concentration criteria.

References In: Reconci ling Industri al, Rural and Urban Wastewa ter Disposal with Austr alian \'ilater Quality Guid eline s (1992 ). (Wade A, ed .) Austra li an Academy of Science, Canberra Baker H. Industry responses to guidelines Bell C J. Achieving water quality outcomes Court J. Translating water quality guidelines into effluent requirements Hart BT, Angehern C, Campbell I C, Jones M J The role of the Australian guidelines in protect ing ecosystem health. Lawrence I. Catchment water quality management strategy. Smalls I. Use of guidelines for water resources management. Wright H. Concerns about how gui delines are applied. Aus tral ian an d New Zealan d Conservation and Environment Council (1992). Australian Water

Quality Guidelines for Fresh and Marine Waters. Burton, J. (1993) in 'Water quality', Crosscurrent, 4 (6) 1.

Canadian Council of Re source and Environment Ministers (1987 and updates) . Canadian Water Quality Guidelines, Inl and-Waters Directorate, Ottawa, Canada. Department of Water Resources Victoria (1990). The Environmental Conditions of Victorian Streams. Victorian Department of Water Resources. Environment Protec tion Authority, Department of Conservation and Environment (1981 ). Water Quality Criteria for Marine and Estuarine Waters of Western Australia, Bulletin No 103, Apri l 198 1, 57 pp, Hart, B.T. (1974). A Co mpilation of Au strali an Water Qua lit y Crit eria . Australian Water Resources Council Technical Paper Numb er 7.A.G.P.S.Canberra. Hocutt, C.H. (1975). Assessment of a watershed macroinvertebrate community. Water Resources Bulletin, 11 , 620-835. Hogg, D. McC. (1990) . The Ecological Resources of the ACT: a review of recent information. Report to the Nat ional Capit al Deve lopment Commission, 69 pp. Hogg, D. McC. and Wicks, B.A. (1989). The Aquatic Ecological Resources of the ACT. Report to the National Capital Development Commission, 36 pp. Hogg, I.D. and Norris, R.N. (1988). Murrumbidgee River water quality: performance monitoring. Rep ort to the Nati onal Capital Development Commission, 68pp. Maher, W, Liston, P, Wade, A, Moore, J, Cullen P, and Norris R (1993). Review of A.C.T. Water Qualit y and Ecological Guideline s. Wate r Research Centre, University of Canberra, 76 pp. Maher, W.A., and DeVries, M. (1993). Release of phosphorus fro m oxygenated estua rin e sediments. Chemical Geology (in press) .

Marchant, R. (1989).~hanges in the benthic inverte brate communities of the Thomson River, south eastern Au stralia , after dam co nstruction. Regulated Rivers 4, 79-89. National Capital Development Commission (198 1). Waters of the Canberra Region. Technical paper 30. National Capital Development Commission. National Health and Medical Research Council Australian Wate r Resources Council (1993 ). Draft Australian Drinking Water Guidelines. United States Environme nt al Protec ti on Age ncy (1985 ). Guidelines for Deriving Nu merical Nationa l Water Quality Criteria for the Protection of Aquatic Organisms and their Uses. Office of Re sea rch and De ve lopm ent , US Environmental Protection Agency, Washington, D.C. Upper Murrumbidgee River Catchment Coordinating Co mmi ttee (1993 ). Regional Wa ter Quality St udy of th e Upp er Murrumbidgee Ri ver Catchment. A report fo r the ACT and SubRegion Planning Committee and the Upper Catchment Coordinating Committee, 56 pp. Victorian Environment Protection Authority (1983) Recommended Wate r Quality Criteri a, fir st edition. Publication: 165, May 1983, 253 pp.

Authors Ian Lawrence is principal of the Environmental Planning and Assesment Section of the A CT Planning Authority. Dr. Peter Liston is an Environmental Planner, and Dr. Alan Wade was, at the time, the Assistant Manager of the Water Section in the Office of the Environment, A CT. Dr. Bill Maher is an environmental chemist in the Cooperative Research Centre for Freshwater Ecology, University of Canberra.

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WATER DECEMBER 1994

SEMINAR

THE SOUTH AUSTRALIAN ENVIRONMENT PROTECTIOI AUTHORITY AND WATER Report by Phil Thomas The South Australian Branch held a seminar titled " The EPA and Water" in September 1994. The Seminar was timely because of the imminent proclamation of the Environment Protection Act in South Australia and it was opened by the Minister for the Environment and Natural Resources, David Wotton. The keynote address was given by Professor David Shearman , President of the Conservation Council of South Australia. In a very interesting and stimulating address he expressed his philosophy that we should be thinking in ecological and not environmental terms. He then gave several examples of links between human health and the environment including the classical work undertaken by John Snow in England in the 1850' s. Concerns were specificall y expressed about the use of chlorine, catchment management, the proliferation of blue- green algae and sick seagrass environments. Professor Shearman urged greater community involvement in environmental maters but felt that people in the water industry were constrained by government policy and those in priva te industry by shareholders. Chris Bell, Deputy Director Policy from EPA Victoria, outlined his thoughts on the ye t to be formed National Environment Protection Council (NEPC) and its relationship with another national initiative, the National Water Quality Management Strategy (NWQMS ). The components of the current NWQMS strategy were discussed p.articularly the formation of various guidelines. Chris then explained how the Intergovernmental Agreement on the Environment (IGAE) provide s for the establishment of the NEPC. The IGAE will ensure consistency across Australia in terms of protection from air, water and soil pollution and from noise . In relation to water, NEPC may establish measures for ambient marine, estuarine and freshwater quality. These may include standards, goals, guidelines and protocols. The preparation of such measures will generally not be undertaken by the NEPC permanent staff but by outside expertise. The Executive Director of the Office of the EPA (S.A.), Rob Thomas , gave an address on the culture of the Authority WATER DECEMBER 1994

emphasising the cooperative and collaborative mechanisms between government and industry that are now used to achieve env ironm ental impro ve ment s. Rob explained the main features of the EPA Act including the concept of general environmental duty, the use of single integrated licences, codes of practices and environmental audits. He discussed the makeup of an advisory forum which will act as a community consultative group and a six member body to oversee the administration of the Act. The EPA will be guided by the precautionary principle and by taking a conservative line in the assessment of the impacts of discharges on the environment. Data presented showed that the EPA is small by Australian standards and that the burgeoning environmental industry will be encouraged to expand in South Australia. Vic Ne verauskas , Manager Aquaculture and Environment wi th Primary Industries, South Australia, gave a number of examples where environmental harm has been caused to marine environment s by various activities such as wastewater effluent discharges, stormwater runoff, ballast water, oil spills and fishing activities including aquaculture, oyster and tuna farming. Results of such pollutional activities were highlighted by some interesting slides showing seagrass degradation in Gulf St Vincent adjacent to effluent discharges, man grove losses and algal blooms. Interestingly, a large release of 35 tonnes of halogenated organics released from Lake Bonney in 1989 produced a spectacular visual plume over an area of 55 square kilometres but apparently no contamination of either sediment or biota. Licensing, monitoring and performance evaluation as it pertains to the EPA (S.A.) was explained by Bob McLennan, Manager of the Monitoring and Wastewater Branch of the EPA. It is expected that there will be almost 2000 licences issued in the first year after the Act is proclaim ed. Attached to each licence will be a set of conditions generally relevant to the environmental impact of the waste discharge and in some cases an agreed Environmental Improvement Program (EIP). The estimated average fee of $1 000 is less than that charged in other states principally due to lower monitoring requirements. As indicated by Rob

Thomas the EPA wi ll operate on t notion of "self regulation". A number competitive advantages may flow fro companies adopting bes t enviro nme practice leading, for example, to : accreditation with the propo se d IS 14000 standard. The EPA will encoura export industries in particular to achie an accredited environment manageme sys tem. Monitoring requirements w include the licensee providing details their expense of types, quantities and qu: ity of waste and the impact on the enviro ment. The EPA will be responsible f deciding whether the ambient enviro ment is improving or deteriorating. i increasing emphasis is being placed < biological monitoring and an EPA pr gram incorporating ambient monitori1 programs for both air and water will I finali sed shortly. An interesting aspect stormwater monitoring will be the use frogs as audible indicators of pollution. Peter Gross a Senior Environmen1 Engineer with Sinclair Knight Merz gave pre se ntation on Environment Improvement Programs (EIP). An EIP ii document that sets a future direc tic along an agreed path to achieve a goal improve d environmental performanc Peter explained the methodology requin for an EIP including elements such as ba data, environmental audits, cleaner pr duction and consultation of stakeholde1 The latter item is important because of tl need to consult widely including not on management and employees but also cor. munity groups and individuals sharing ti same environment as the facility bei1 assessed. Having compiled all availab information some extra monitoring may 1 required to fill in the gaps. It is then tin to develop measures for environment improvement by a number of mechanisn in cluding brainstorming sess ions ar workshops followed by preliminary optic analysis and shortlisting before detail< consideration of short li ste d option Finally appropriate management systen are put into pla'ce including aspects sue as monitoring, reporting, reviewing ar modifying. Complementing Peter Gross w: Graham Brown from Graham A Bro\! & Associates (Sydney) who discussed em ronmental audits which are becoming i

essential part of the management program for resource (including water) projects. Graham went through legislative requirements particularly concentrating on penalties for non- compliance and explaining terms such as strict liability offences, civil offences, notices, orders and restriction of activities. A relatively recent phenomenon is the issue of environmental liabilities particularly as it applies to contaminated land and consequential reduction in the value of the land. This becomes important when clean up costs are considered. Environmental audits are becoming an important tool in the resource management industry in Australia and it can be shown to have many benefits if carried out in the correct way. In South Australia the holder of an Authorisation is required to comply with the requirements of an audit and compliance if the holder has on one or more occasions contravened the conditions of the Authorisation. Dr David Blackburn, Senior Environmental Scientist with Kinhill Engineers, gave a presentation on environÂˇmental modelling and monitoring systems for receiving waters, particularly marine environments. David examined the limitations of the conventional approach to marine ecological studies of using fixed transects and quadrants. He discussed the important role of nitrogen as the limiting

nutrient in marine environments before moving on to explain the many advantages of using remote sensing devices, Geographic Information Systems and numerical models. Changes in the areas of major marine communities within the Bolivar WWTP outfall region were shown to be significant with losses of seagrasses and increases in mangroves and bare sand areas. Recent studies of this outfall have integrated remote sensing and field surveys with numerical modelling. Detailed comparisons were made between the cost effectiveness of field based programs and those using digital image analysis of aerial photography. The use of the latter technique results in very significant cost savings. The final two presentations were concerned with environmental improvement programs. Dr Tim Gamon , Managing Director of Acer Wargon Chapman (SA), explained the wastewater quality improvement strategy being implemented at Pasminco Metals-BHAS lead smelter at Port Pirie, the world's largest. Tim gave details of the staged approach to reduce heavy metal concentrations in effluent flowing into Spencer Gulf and therefore subject to condition s outlined in the Guidelines for Licensing Discharges to the Marine Environment (1993). Methods used included greater re-use of effluent,

containment of spillages and sedimentation pond upgrade . Results have been encouraging to date with significant reductions in lead, selenium, iron, arsenic and copper. Further improvements will be outlined in a Wastewater Management Plan which will be submitted to EPA in 1995 and will identify the projects needing to be implemented over the next five years. Jerry Brown, Supervising Engineer Wastewater Treatment, Engineering and Water Suppl y Department, gave an overview of the strategic management plan devised for the disposal/re-use of effluent water from metropolitan Adelaide's wastewater treatment plants. Licences issued under the Marine Environment Protection Act require that, by March 2001, marine discharges should not result in environmental harm. Consequently, improvement programs have been developed to meet this licence condition at the Bolivar, Christies Beach, Glenelg and Port Adelaide plants. Essentially there are two approaches available, one is to reduce the nutrient levels with continued discharge, the other is to encourage land based reuse. Jerry then detailed the costings and environmen ta! benefits for the se two approaches. Options include use of woodlots, dual reticulation, groundwater recharge, wetlands and process variations including chemical and biological nutrient removal.

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TECHNOLOGY PULP AND PAPER INDUSTRY WASTEWATERS Report by Peter Donlon Industry Background The pulp and paper industry has historically used huge amounts of water and has consequently generated similar volumes of wastewater. In addition, the use of process treatment chemicals such as chlorine, primarily in the bleach plant, has generated organochlorine compounds including chlorophenols and dioxins. These discharges have been a major reason for concerns abo ut the environmental performance of the industry and peaked with the abandoning of the proposed Wesleyvale Pulp Mill in Tasmania. The Industry, both in Australia and overseas has reacted to these concerns by sometimes radical changes to bleaching technologies, including chemicals used and the installation of processes essentially designed to remove organic matter which may react with chlorine compounds. Understanding of wastewater treatment and means to assess environmental impact has also progressed. The Federal Government has reacted to these concerns by preparing guidelines on effluent quality and appropriate monitoring requirements for any new Bleached Eucalypt Kraft Mill (BEKM) to be constructed in Australia. In addition, the Government has provided money to be overseen by the Nationa l Pulp Mills Research Program to facilitate research on various aspects of the pulp mill industry, including chemical analytical methods, BEK effluent composition, pulping processes, bleaching, effluent treatment, bioassays, mesocosms, biomarkers, monitoring programs design, effluent dispersal and risk assessment. This research is necessary as eucalypts used for BEKM are not widely used as a source of wood overseas and consequently not all research carried out overseas is directly applicab le to Australia.

brown stock without washing, prior to ch lorinati on (Mini-O Process) in the bleaching process, has significantly reduced absorbable organo halide (AOX) emissions and has successfully reduced AOX leve ls to less than 0.75 kg/ADT (Cook et al 1990). Further reductions in AOX were demonstrated in the laboratory by use of extended cooking or oxygen delignification fo llowed by a combined chlorination/alkaline extraction stage of the total pulp slurry. No washing is carried out between the chlorination and extraction stages. (Cook, 1992) Increasing substitution of elemental chlorine with chlorine dioxide has also minimised AOX. These modifications have also contributed to eliminating dioxins from the effluent . CSIRO research has demonstrated that high quality and high brightness pulp can be produced from eucalypts by substitution of elemental chlorine with 100% chlorine dioxide, producing effluent well below the Commonwealth guideline AOX level of 1 kg / air dried tonne pulp (Nelson, 1993). Oxygen derived chemicals such as ozone are also being investigated for use as a chlorine replacement using eucalypts. Pilot scale success overseas using ozone and hydrogen peroxide has led to the construction of a number of commercial mills using this technology for non eucalypt wood stocks (Co lodette et al. 1994). Interest in the use of high pressure and temperature hydrogen peroxide bleaching processes is also increasing. A benefit of replacing chlorine in the bleach plant with oxygen based chemicals is the possibility that effluent free processes may be feasible, alth ough a significant amount of further work is required to resolve all problems associated with this approach.

Effluent Composition Bleaching Processes and Organochlorine Emissions High quality paper generally requires the use of the Bleached Kraft Process. The challenge has been to continue to achieve this quality while altering the bleaching and other processes to reduce possible environmental effects. Research carried out at Australian Paper was implemented in a 140,000 tonne/per year mill. It demonstrated the use of alkaline oxidation of the WATER DECEMBER 1994

At the recent TAPP! environmental conference, there was continued concern about the chlorinated organics, including dioxins, despite obvious improvements in bleaching processes. This appears to be more a result of the new United States EPA regulations on AOX and dioxins, rather than a greater und erstanding of whether these compounds are causing damage to the environment. The compounds generated by the use of elemental

chlorine with high residual lignin in bleac plants include the chlorinated phenolic. catecols, guiacols, syringols, dioxins an furans, chlorinated resin acids and a grou of unidentified chlorinated organic corn pounds encompassed by the AOX w parameter. Improved bleaching processe as described above have virtually eliminat ed dioxins and substantially reduced quan tities of these other compounds . Mill using chlorine dioxide as a bleachin, chemical were found to produce high level of chlorate, which has been shown to b, particularly damaging to brown alga1 (Sodergren A. 1992) . Of particular interest in Scandinavi; was the discovery that 3,4,5 trichloroguiacol has been found in widespread areas oJ the Baltic Sea and is associated with bleach plant discharges. None is found in non pol1u ted sites (Sodergren A. 1992). In Australia, 2-chlorosyringaldehyde has been identified as the major chlorinated phenol when pulps are bleached with 100% chlorine dioxide in the laboratory (Wallis et al. 1993) . Interestingly, levels of chlorinated phenols, including 2-chlorosyringaldehyde and 3,4,5 trichloroguiacol are barely detectable in the wastewater from the Maryvale Mill Q. Jelbart pers comm) and are non-detectable in the effluent after anaerobic and aerobic treatment in Gippsland Water's Dutson Treatment System.

Effluent Treatment Traditional effluent treatment from pulp and paper mills has usually consisted of aerated lagoons with retention ranging from a few days to up to a month. Focus in the United States and Canada has been to improve effluent treatment whereas until recently Scandinavia has focused on improved bleaching technologies as well as physico-chemical treatment. In Australia effluent treatment ranges from primary to extended secondary. Most systems have been designed to remove suspended solids and COD, however with the discovery of organochlorine compounds in mill effluent, much recent work has focused on organochlorine reduction. High colour has also been of concern. Various forms of flocculation and settling processes has been used on mill effluent. Alum was shown to reduce AOX by 50-70% and reduce chronic toxicity levels 37

in softwood pulp effluent, however no effect was seen on individual chlorinated organics (Barton et al 1992). Other testing using alum has found only marginal reductions in AOX and chlorinated phenolics (Radian Corporation 1991 ). Other processes including membrane technology have al so been tried. However these processes are often expensive and results variable. Recent work carried out und er the National Pulp Mills Research Program by CSIRO, Gipp sland Water and the University of New South Wales has shown clear benefits in the use of biological anaerobic, anoxic and aerobic systems. Under anaerobic conditions, 63 % of organochlorines were shown to degrade, while 41% degradation could be achieved under aerobic conditions. Both are substantially biological processes as under sterile conditions only 11 % reduction was seen. (Duncan et al. 1994). Using intermittently decanted aerated reactors variable AOX reduction was seen (less than 20%) (Boyden et al. 1994) . These studies showed that up to 69 % of COD was removed while acute toxicity as measured by photoluminescent bacteria (Microtox) was also minimised. As a modern bleaching sequence presently uses chlorine dioxide rather than molecular chlorine , by-products of this process are important. Chlorate, a known toxic compound to marine algae, can be generated in high levels if chlorine dioxide is used in the bleaching process. The above studies also showed that chlorate can be substantially reduced by biological processes. Intermittently decanted aerated reactors were able to reduce chlorate by 67%. Anaerobic treatment was able to reduce chlorate by 90%, while aerobic treatments were not as effective. These results clearly suggest that mills using chlorine dioxide bleaching processes should incorporate an anaerobic treatment process step.

Environmental Effects Environmental effects relating to pulp mills have been extensively reviewed in the past (Sodergren 1992, Huggett 1990). Effects are dependent on the quality of the effluent, the method of discharge and the receiving water environment. They range from no detectable impact to widespread contamination of regional water bodies. The most comprehensive studies being performed in Australia relate to marine discharges from the Australian Paper Maryvale Mill. These studies have been described (Donlon et al 1994) and results will be reported in the future. They include multi-tiered toxicity assessment, bioaccumulation, sediment and water quality, macroinvertebrate community analysis, fish tainting and biomarker assessment. Associated with environmental impact 38

is the need for effective dilution to minimise local effects. An oceanographic model has been developed for Australian Coastal Waters and is capable of predicting effluent concentrations in the receiving waters of a pulp mill discharge. The model ha s been test ed using predicted and observed sewage concentrations in an area of Bass Strait north or Devonport in Tasmania (Fandry et al 1994).

Environmental Monitoring A major focus on environmental monitoring for pulp mills in Australia has been bioassa ys. These types of assays are believed to more closely assess potential changes in the biota of ecosystems, than traditional chemical assessment of abiotic compartments. A suite of standard bioassays using local species of marine phytoplankton, macroalgae, and fish larvae have been developed recently (S tauber et al 1994). These sensitive early life cycle or growth rate bioassays have been designed to provide rapid feedback (days) compared to conventional chronic bioassays using adult fish (weeks or months) . Developments have also taken place using me socosms in Western Australia Oacoby et al 1994). Mesocosms are medium-sized enclosed experimental ecosystems and can be used to assess complex interactions of effluent with the ecosystem. Re sea rch on biomarkers using the mixed function oxidase group of li ve r enzymes is being carried out on sand flathead and spikey globefish exposed to pulp mill effluent (Holdway et al. 1993) These tests are aimed at assessing chronic environmental effects by monitoring the normal enzymatic and biochemical responses of adult fish to sub-lethal chemical stresses.

Conclusions Research in Australia relating to pulp mill s ha s bee n sp urred on by th e Wesleyvale debate. Many of the results, particularly of the Natio nal Pulp Mills Research Program, will satisfy environmental regulators and Government that the means exists to adequately assess proposals for new pulp mills. However the research has also provided many tools that are just as relevant to state of the art waste treatment, environmental monitoring and assessment for a broader range of effluents produced by industry and sewage treatment plants.

References Barton D, Hall T , Drake E. Bou squet T . Physicochemi cal Treatment of Bleach Plant Filtrates and Final Effluents for the Reduction of Chl orina ted Organic Com pound s. TAPP/ E11viro11111emal Conference 1992. Boyden B, Sun D, Schul z T. Aerobic Biological Reduction of COD, Chlorate and Toxicity in Eucalypt Bleachery Effluent. Pro ceedings of 48th APP/TA Annual Gen eral Conference, Melboume 1994. Colodette J, Singh U, Ghosh A, Dhasmana B, Singh R. Development of a New Bleaching System Based on the Use of Oxygen Derived Chemicals. TAPP! Enviro11111emal Conference 1994. Cook R, Eagle A and Gough G. Cost Effective AOX Reduction. Ozjigen Delignification Symposiu111, Toronto. TAPP! Press I 990. Cook R. - A Bleaching Process for Minimising AOX Discharges. TAPP! Environmental Conference. 1992. Donlon P, Mosse P - The Latrobe Valley Ocean Outfa ll A Co mmunit y Mediated So lution . Water June 1994 Duncan A, Thia B, Jelbart J, Donlon P. Anaerobic Aero bi c Treatment of Pulp Mill Effluent. Proceedings of 48th APP/TA Annual General Conference, Melboume 1994 Fandry C, Walker S. Oceanographic Studies Relevant co Siting a New Bleached Kraft Eucalypt Pulp Mill. Proceedings of 48th APP/TA Annual General Conference, Melboume 1994 Holdwa y D. , Brennan S, Brumley C, Ahokas J. Development of Standardised Methods for Using Li ve r MFO Enzymes in Sand Flathead and Spikey Globefish as Biomarkers of the Marine Exposure to Bleached Eucalypt Kraft Effluents. Proceedings of 47rh APPITA Annual General Conference, Rotonwa. April 1993 Huggett R, Mehrle P, Dickso n K, Hartung R, McLeay D, Oil<ari A, Sprague J. (Scientific Panel on Pulping Efflu ents in the Aquatic Environment) Pulping Effluents in the Aquatic Environment. Presemed ar rhe Conference and U7orkstlop 011 Toxicology and Monitoring Melboume. 1990. Jacoby C, Ward T. Roles of Mesocosms in the Pulp and Paper Indu stry. Proceedings of 48rh APPITA Annual General Conference, Melboume 1994 Nelson P, Chin W, Grover S. Bleaching of Eucalypt Kraft Pulps from an Environmental Point of View. Proceedings of 47th APPITA Annual General Conference, Rotonwa. April 1993 Radian Corporation. Bench Scale Dioxin Treatability Stud y for Pulp and Paper Wastewaters Preliminary Test Data. USEPA Contract No 68-CO-0003 1991. Sodergren A. - Bleached Pulp Mill Effl uen ts, Composition, Fate and Effects in the Baltic Sea. Swedish Environ mental Protection Agency Report No 404 7, I 992) Stauber J, Gunth orpe L, Deavin J, Munday B, Ahsanulah M. Application of New Marine Bioassays for Assessing the Toxicity of Bleached Eucal ypt Kraft Mill Effluents (BEKME). Proceedings of 48ih APPITA Annual General Conference, Melboume 1994 Wallis A., Smith T. and Wearne R. - Determination of Chl orinated Phenol s in Effluent from Bleached Eucalyp t Kraft Mi lls. pp National Pulp Mills Resea rch Progra111 Tech11ical Report No2. 1993.

Acknowledgments Many thanks to Brian Bolto for providing the "stimulus" to prepare this brief review and the members of the IA WQ Specialist Group on Pulp and Paper Wastewaters and the National Pulp Mills Research Program who sent information on their work.

Author Peter Donlon works for Gippsland Water

and is the Coordinator of the IA WQ Specialist Group on Pulp and Paper Indu stry Wastewater Treatment and Environmental Effects. WATER DECEMBER 1994