Water Journal December 1984

Page 1

I ISSN 0310- 0367 I Official Journal of the

fA•~i i ;b1 • M~ lw£i i =i ;E, ~II] WA1--ii=l\!Mi=i;f!~$i•X!lrtiit•1~1 Vol. 11, No. 4, December 1984-$2.50 Registered by Australia Post -


publication no. VBP 1394

FEDERAL PR ESI DENT F. Bishop, Scott & Furphy, 390 St . Kil da Rd., Albert Park , 3004

FEDERAL SECRETARY F. J. Carter, Box A232 P.O. Sydney 5th ., 2001 .



Offi ci al Journal

Cl- M.M.B.W.


625 Lt . Co ll ins St. , Melbourne, 3000.

Vol. 11 , No. 4, December 1984

BRAN C H SEC RETARIES Canberra, A.C.T. Dr. L. A. Nagy , 8 Belconnan Way, Page , A.C.T. 2614 . (062 54 1222)

New South Wales C. Davis , G.H. & D. P/L, P.O. Box 219, Neutral Bay Jun ct. 2089 (02 908 2399)

Vi ct oria J. Park, S.R.W.S.C. Operator Trai ni ng Cen tre, P.O. Box 409, Werribee , 3030. (741 5844)

Qu eens land D. Mackay , P.O. Box 412, Wes t End 410 1. (07 44 3766)

South Au strali a A. Glatz, State Wa ter Laboratories , E. & W.S. Private Mail Bag , Salisbu ry, 5108. (259 0319)

Weste rn Australi a P. Jack , Govt . Chem . Lab s 30 Plain St. 6000

Tas mani a G. Nolan , G.P.O. Bo x 78A Hobart , 7001 . (002 28 0234)

North ern Te rritory G. Clark , P.O. Box 37283 W innel lie , N.T. 5789.

EDI TORIA L & SUBSC RI PTION CO RR ESPON DENCE G. R. Goffin , 7 Mossman Dr., Eag lemont 3084 03 459 4346

CONTENTS Viewpoint - Dr. John Paterson, Director General, Department of Water Resources, Victoria . . . . . . .. . . . . . .... .. . .


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


Limiting Factors for Land Treatment of Cheese Factory Waste in the Mount Gambier Area, South Australia -G. Schrale, P. C. Smith and A. J. Emmett . .. . . . . ....... , . . , ..


Book Reviews . .. . ... . . . ... ........ . . .. . . . . . . . ... .... .. ... . . . .


National Seminar, Adelaide -The Changing Management Needs of the Australian Water Supply and Sewerage Industry . ...... .. . . .. .


Automatic Process Control for Large Wastewater Treatment Plants -K. Barr . . .. ..... ..... .. . .. . .. .. . . .. . . .. . .. .. . . .. .


Synthetic Rubber Factory in South Africa-Efflu ent Treatment I. 8. Law .. . ... . . .. . . .. . ... . . . . . .... . .. ... . ...... . ... . ... .


Trends in Sewage Treatment - the Future for Vic toria - J. A. Crockett .... ...... . ... ... ... .. . . , .. .. . .... . .. .. . . .


, .. ..... .. . .... . . . . .... ... .... . .. . ... . . . . .. . . . . .. . ...


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


Tech nical Inte rests ...... . . . . ... . . . .. . ... .. .. .. ... .. .. , .... .. .



Plant and Equipment

COVER PICTURE This cheese factory near Mo unt Gambier in South Austra lia produces large vo lum es of whey which have to be disposed of wi th out po llu tin g the 'lim es tone' aqui fe r. In the past the whey was discharged un derground throug h a dra inage well. Now a trave lling irrigator spreads the surp lus whey on to pasture. To ensure safety and effectiveness, the effects on the pasture, soils and groundwater qua lity were monitored by an interdisciplinary group from the Government Departments of Engineering & Water Supply, Mines & Energy and Agriculture. The pa s ture growth is greatly stimu lated by the wastewater irrigation. The land is grazed and twice a year is either cut for silage or for hay. Gradua lly en larging the area of irrigation allowed the nitrogen app lication rate to be matched to the pa s tu re 's rate of uptake when adjacent landholders re alised th e benefi ts in increasing pa sture produc tion . This project is one of a number of joint studies by private indu stry and South Australian Government Department s with the aim of preventing groundwater pollution and of utilising agricultural was tes. Front cover donated by the Departmen t of Agriculture, Sou th Australia.

The sta tements made or opinions expressed in 'Wa ter' do not necessarily reflect the views of the Aus tralian Wa ter and ~astewater Associa tion , its Council or committees.

WATER December, 1984


ASSOCIATION NEWS VIEWS AND COMMENTS PRESIDENT'S MESSAGE It has been my privilege to report to Members in this column during my two years as Federal President. At the November Federal Council Meeting I handed over to Robert Lloyd (Queensland Branch) and I am confident that the Association will go forward and progress under his able direction and dedication to the Association. I have been most appreciative of the wholehearted support from Federal Councillors and officers and last but not least the Federal Executive which, during my term, included Robert Lloyd, Doug Lane, Allan Pettigrew, together with officers John Carter, Graeme Dooley, Jim Greer and later John Molloy and office manager Judy Sears. Over the last two years, the Association has fulfilled its role in arranging conferences so as to provide a forum in Australia for the interchange of multi-disciplinary knowledge for the water industry as evidenced by the 10th Federal Convention in Sydney, the Specialist Conference on the Water Regime in Mining held in Darwin, the 5th Summer School in Canberra and the recent Seminar on Management of the Water Industry. The success - and all have been successful - lies in the vast amount of enthusiastic help received from many Branch Members of the Association - without that help there would not be the high standard conferences that are expected of the A WWA, which are equal, even better than some of the overseas co nferences. The Adelaide Seminar and the 5th Summer School has reflected the Association's concern for key management issues as well as technological iss ues. The participation by top executives of all major organisations in the recent and very success ful Adelaide Seminar shou ld underline the depth of expertise and the interest of top-level industry personnel in the Association. Hopefully this may register with the Federal Government who may seek impartial professional advice from the Association in the future before framing policies that impact on the water industry. Members will have received the Programme and Regist ration Brochure for the I Ith Federal Convention in Melbourne in April-May, 1985, and can be assured of a high quality technical programme and an entertaining socia l programme. The International Conference is jointly sponsored by the Water Pollution Control Federation and will meet that high standards of past events.

FRANK BISHOP Federal President


WATER December, 1984


INTERNATIONAL AND FEDERAL CONVENTION '85 Melbourne, April 28-May 3 This will be a unique event in the Association's history, the combination of our 11th Federal Convention and an International Convention in conjunction with the Water Pollution Control Federation as co-sponsors.

With no campaigns, debates, media coverage or vituperation, not even any marching girls (pity!) Frank Bishop (left) stepped down from the office of President of the Association at the Federal Council Meeting on November 21 and Bob Lloyd (right) of G. H. & D. Brisbane became our new President, Vice-President is Mike Dureau of Kent Instruments. Frank becomes Immediate Past President with two meritorious years behind him in the Association's most demanding office. Bob and Mike both have record s of lengt hy and hardworking service in the Branch and Council spheres and are well known to the membership. Under their gu idance the continued momentum of the Association is assured. Congratulations to all three.

AUTHORS SECRETARIES CORRESPONDENTS PLEASE NOTE! Technical papers and similar submi ssions for publication in 'Water' should be in a form suitable for appraisal and, if accepted for editing and printing . To assist and achieve the desirable standard of submissions , 'Adv ice to Authors' is available from the Editor of 'Water' direct or through Branch Correspondents. The' Advice' gives gu idance as to typing requirements (single spaced texts are not acceptable) , the preparation of diagrams and graphs, the conventions to be adopted and the use, format and punctuation of references. Perusal and attention to 'Advice to Authors' will avoid unnecessary correction and, in many cases, the complete re-drafting of papers, graphs and diagrams with consequent time delays and potential irritations.

The Convention coincides with Victoria' s 150th Birthday celebrations in November with some 3000 separate function s planned for the following 12 month s and providing a happy combination with the Convention programme of soc ial events and tours. Melbourne is 'dressed up' for the occasion and offers a further incentive to joining the Convention. All the techn ical papers are to hand , including over 20 from overseas Authors and process ing is we ll under way. Standards are high, as expected and the range of interests is extensive, see the not ice on page 4. Regi stration applications are already being received , attracting the 'early bird ' di scount s on fees and ensuring accei,tance for events having a limitation on numbers. Delegates are expected from all states and the overseas contingent will include visitors from South Africta, New Zealand, USA, Japan, Netherlands, Sweden, UK, Singapore, Hong Kong, China, Indonesia and Papua New Guinea . A most comprehensive Second Announcement and Registration Brochure has been widely circu lated and furt her copies are availab le from GPO Box 358F, Melbourne, Vic. 3001, Australia. Telex NEIL AA3294. Ph. (03) 63 1574. Regi stration closure date is March I, 1985. Later registration will in cur a penalty fee. This is the most significant event on the 1985 A WW A calendar - be there!

NATIONAL SEMINAR MANAGEMENT IN THE WATER INDUSTRY The Adelaide Seminar of Nov. 22-23 achieved a high point in technical content, presentation and participation. Attracted by the subject matter and the impressive speaker array, 170 registrant s from all states spent a rewarding two days upon

Limiting Factors for Land Treatment of Cheese Factory Waste in the Mount Gambier Area, South Australia G. Schrale, P. C. Smith and A. J. Emmett ABSTRACT Since June 1976, diluted water from a cheese factory has been spray irrigated on nearby pasture land . The waste water applied each year is a mixture of 17 mL of whey, 50 mL of wash water and 100 mL of groundwater to dilute the waste to a salinity of 2 000 mg L-•. The objective of the six year study was to determine limiting factors for land treatment of cheese factory wastes by monitoring the effects on herbage, soil and groundwater. Three drainage lysimeters were installed in 1979 and operated over three years. On average, 7 000 kg of salt ha-•yr-' were applied and effectively leached through the soil profile. About 600 kg ha-•yr-• of nitrogen were applied on the treatment area. On the highland, between 350 to 400 kg N ha-•yr-• was utilized by grazing and cutting the pasture. In the lowland area the nitrogen removal was 230 kg N ha-•yr-• . The excess to plant uptake of nitrogen was leached mainly as nitrate. All the excess of phosphorous was fixed in the soil. Only 5 per cent of the 700 kg ha-•yr-• of potassium app lied was leached beyond three metres . Degradation of groundwater quality occurred over the years of waste irrigation at the excessive application rates. The nitrogen application is a major limiting factor for land treatment of cheese factory waste. It can be expected that a nitrogen application rate greater than the maximum plant uptake rate gives increased nitrate leaching and the vegetation may become toxic to grazing stock. Another limitation of whey irrigation is that salt applied to land with permeable soils will eventually reach the water table despite some removal by plant uptake. The ultimate impact of land treatment on groundwater quality can be determined by monitoring wells not only in the waste irrigation area but also in the down gradient direction .

INTRODUCTION In the Lower South East of South Australia agricultural and industrial waste were previously discharged directly into the karstic limestone aquifer via sink holes and wells; this resulted in point source pollution (Ward 1941, Barnes 1952, McPharlin 1983). Underground disposal of untreated waste is now prohibited under the S.A. Water Resources Act, 1976-1982 (hereafter the Act). The only significant town, Mount Gambier, is solely dependent upon groundwater for its reticulated water supply and thus the discharge of wastes threatened the town water supply. The cheese factory at Mil-lei is located about 7 km upgradient from this town of 20 000 inhabitants. For more than 40 years the factory wastes were discharged underground through a nearby drainage well. The extent of the groundwater contamination downstream has been reported by Smith and Schrale (1982). Over the years it became necessary to relocate the factory water supply wells at increasing distances from the disposal site. Ultimately an expensive supply well had to be constructed to the 100 m deep confined aquifer (Barnett 1976). After the introduction of the Act, the management of the cheese factory selected land treatment as an alternative method of waste disposal. Land application of whey is rather unique. Elsewhere in the world, large volumes of whey are used as stock feed or processed for the food industry. However, in this area the quantities of whey are too small to make reprocessing economical. Land treatment is a process whereby the soil acts as a biochemical filter; organic matter is broken

Dr. Gerrit Schrale is Senior Research Officer (Irrigation) with the Department of Agriculture, South Australia. Mr. Peter Smith is Senior Geologist with the South Australian Department of Mines and Energy. Mr. Andrew Emmett is Regional Chemist of the Engineering and Water Supply Department in Mt. Gambier. 10 WATER December, 1984


l G. Schrale

P. C. Smith

A. J. Emmett

down by soil micro organisms; nutrients are made available for re-use by plants; and salts are transmitted through the soil profile (Klinger and Schrale, I 984). There needs to be sufficient leaching to avoid a salt build up in the soil. Some leaching of nutrients, particularly nitrate is unavoidable. Land treatment of waste is only successful when plant and animal health at the site and the quality of the regional groundwater resources remain within tolerate limits. The objective of this study was to determine limiting factors for land treatment of cheese factory wastes by monitoring the effects of herbage, soil and groundwater.

METHODS AND MATERIALS Irrigation Area and Facilities The average rainfall at Mount Gambier is about 750 mm yr-• and pan evaporation is about I 500 mm yr-•. Rainfall exceeds pasture water use between April and September. The thin, permeable soils have a limited water retention capacity. Allison and Hughes (1978) found that the groundwater recharge under pasture in this area is 200 mm yr-• . The bulk of the waste is produced during the winter months, thus the waste irrigation is super-imposed on the natural recharge. The land treatment site consists of highland and relatively flat lowland. The highland comprises Soil Units I to 3 and the lowland Soil Unit 4 as described in Barnett et al., 1977 (See Figure l). Soil Unit I has a sandy loam surface texture over clay underlain at about I .5 m by a coarse textured calcareous sandstone. Soil Unit 2 is a deep sand profile (up to JO m) of moderate undulation. Soil Unit 3 consists of shallow red clayey soi ls over calcareous sandstone and is of restricted occurrence. Soil Unit 4 is composed of sandy loam up to I m underlain by bluish-grey, low permeable clay, which is usually waterlogged in winter. At the site, groundwater is at depths varying between I and 12 m; its salinity is about 450 mg L'. The whey and wash down water leaving the factory are initially screened and diluted with contaminated groundwater to a salinity of about 2 000 mg V'. The wastewater is then sprayed onto 40 ha of land with a travelling irrigator which is operated from hydrants on a high pressure main running underground through the centre of the irrigation area. Most paddocks were sod sown with a mixture of perennial rye grass (Lolium perenne L.), demeter fescue (Festuca arundinacea Schreb. cv demeter) and a small quantity of lucerne (Medicago saliva L.). In winter the pastures were either grazed with cattle or forage harvested and were usually cut for hay in summer. Some proportions of the land were cropped with potatoes, sweetcorn, sunflower, oats and barley. In June I 979 three lysimeters were installed to study the water, nutrient and salt balance at the treatment area. The lysimeters are 2 m diameter steel tanks installed into carefully excavated pits. The soil was carefully removed in layers on the basis of soil stratigraphy and temporarily stockpiled. The tanks were back filled with the soil in the original sequence, structure and state of compaction. Soil processes and biological activity occur mainly in the top I m of the soil profile.


were subdivided into 500 mm sections which were analysed for macro nutrients and the major inorganic ions. Where possible, herbage samples were taken at the,ame time of soil sampling and ana lysed as for the soils. The weight of the forage and hay was estimated at the time of removal. The nutrients removed by grazing were not accurately determined; the number of grazing days were recorded and the weight gain over the grazing period was estimated .


Lysimeters The vegetation on the lysimeters was kept (as far as possible) representative of the surrounding paddock. The depth of the waste irrigation on the lysimeter was measured with rain gauges placed on its periphery. The drainage eater was pumped out weekly, sampled monthly for complete analyses and weekly for pH, Total Dissolved Solids (TDS) and nitrate.

Groundwater Levels Inner a nd outer observations well networks were estab lished. The inner network holes were drilled for this investigation whilst the outer network wells were selected from private wells. The inner network was monitored monthly and the outer network three monthly .

Groundwater Quality Since early 1976 the wells have been sampled at three monthly intervals using a submersib le pump. Water samples were collected after 30 minutes of pumping at a set depth of about 4 to 5 m below water level. All samples were analysed using Standard Methods for water analysis at the State Water Laboratories.




400 Metres



Ly• lm•t•r site Soll / herbage samp l e site


Sandy l oam / c l ay

Groundwater level observation well


Daap sa nd

0 124

Gr oundwater quality obHrvatlon wa ll


C lay/ ca l c::. sandstone


Sandy loam / g l ay clay


--60 ......


Water table contour (m A.H.D.) - Aprll 1976 Water tabla contour (m A.H.D.) - May 1982



Figure 1. Locality plan and site details. Therefore, Lysimeters 1 and 4 are 2 m deep and Lysimeter 2 was install ed to 3 m in the deep sandy profi le. The locations of the lysimeters are shown in Figure I. The numbers used to identify the lysimeters correspond with the paddock numbers at the time of installation.

Monitoring Programme

Wastewater Production The daily volume of surplus whey was calculated from the number of cheese vats used and the volume of whey collected by pig farmers. The volume of wash down water was measured in a co llection tank and gro undwater used for dilution was metered.

Wastewater Irrigation The depth of wastewater applied was calculated from th e recorded hours of irrigation from eac h hydrant.

Wastewater Loading The nutrient load of the wastewater was found to vary co nsiderably during the day. A compos ite sampler was installed in November 1977 for an accurate determ ination of the wastewater composition. Since that time a total of 32 composite samples were analysed ; each consisti ng of su b-samples taken at hourly intervals during daily operation.

Soil and Herbage T he nine (9) sites chosen for soil and herbage sampling are shown in Figure 1. T he sampling was carried out at three monthly intervals from December 1975 to September 1982. The two metre long cores

Volume of Waste Production The yearly pattern of whey production was consistent over the period of investigation. Production usually commences by late April and peaks during the spring months, thereafter decreases and is usually terminated by late January . The wash water is in general up to three times the volume of whey. The chemical load of the wash water is considerably less but forms the major portion of the load of irrigation water in summer. Each year bout 17 mL of whey and 50 mL of wash water, generated from cheese making and other activities, are mi xed with 100 mL of gro undwater before irrigation. As an indirect resu lt of'the waste water mixing and monitoring, it was discovered that up to 5 tonnes yr-• of cheese can be easily recovered by screening the wastes before irrigation.

Chemical Load of Irrigation Water The chemical analyses of 32 composite waste samples were categorised according to monthly whey production rate. The results in Table 1 show that the pH of the irrigation water is between 4 and 5 for most of the year despite dilution. The total nitrogen (NT) loading in Table I was highest in the 'medium' production season whilst potassium, phosphorous and chloride loading in the water was highest in the peak production period. These figures reflect not only the portion of the whey to be disposed by irrigation but also probable variation in the relative volumes of the constituents . During the period of no whey production the nutrient load is reduced to less than 50 per cent. The total chemical load of the waste water pumped is about 350 tonnes yr-• of dissolved salts which includes 33 tonnes of main ly organic nitrogen, 13 tonnes of phosphorous and 45 tonnes of potassium. Most of this is applied to the 40 ha, but in recent years about 30 per cent is irrigated onto adjacent land .

Soil analyses As a typical example of the variation in the nutrient levels in the so ils the chemical analyses of the major nutrients for Site I are plotted against time in Figure 2. The total soil nitrogen level has only risen slightly since waste irrigation commenced six years ago. Schrale and Magarey ( I 979) showed that the ammonia concentration in the top soil fell drastically after commencement of irrigation. This is probably due to the increased availabi lity of organic carbon as a micro-b iological energy source. Although the resu lts are not presented here, the ammonia level in the WATER December, 1984











February March April

January May June

July August December

September October November

9 4.8 2 000 164 50 165 45 700

13 3.8 2 200 252 83 215 29 730


No. of Samples pH TDS (mg L"') NT (mg L"') PT (mg L"') K (mg V') so;- (mg L- ') C J·(mgL"')

Herbage analyses

5.9 I 700 70 52 155 60 760

8 4.1

2 200 208 110 438 30 I 220

The NT content in the herbage has risen from I o 2 per cent before waste irrigation to about 3 to 5 per cent of dry matter (DM) content. The high nitrogen values in the pasture during summer coincide with the high nitrate levels in the soi l. The analyses show that the nitratenitrogen (NO,-N) levels in late summer are near 0.34 per cent of DM content, which is the limit above which nitrate toxicity in grazing cattle can occur. (Harris and Rhodes, 1969). The concentration of phosphorous has increased three to five fold. However the increased levels are considered not to be detrimental to plant growth . Similarly, potassium has risen from about 1 to 3.5 per cent of DM content. High potassium levels may interfere with micro-nutrient (e.g. zinc and manganese) uptake of plants but deficiencies were not detected from the ana lysis. I I



3 000

soi l peaks during winter when the bulk of the waste is appli ed. The ammonia level decreases sharply in summer when it is transformed into nitrate by the high micro-biological activity. A gradual build up of (plant availab le) phosphorous occurred only in the 0.5 m top layer over the period of application (See Figure 2). The electrochemical exchange of potassium occurs mainly in the top 0.5 metres. In the sandy profiles however, the potassium accumulation extends to greater depth; no major potassium leaching has yet occurred. The following soil chemical results are briefly summarized. The soi l TDS and chloride levels show a distinct pattern of build up from late spr ing to summer and leaching occurs as the wetting front moves through the profile in the following winter. Despite irrigation of waste with a pH of about 4.5 the soil pH in the initially slightly acid top soil has graduall y become more alkaline. The pH in the sub-soil strata has a lso risen from neutral to slightly alkaline.


(IN) '



~18 000 I




t2 500









( I N)



u ::;









79 000 I



76 000


"'> ~



~ zw


Cl 0









50 - 100 cm

Irrigation commenced



............ ,., ..... ,_ ...... ,

______, ,,,' ,............. _.., ,.,,,-- ...............




w Cl



Irrigation commenced

>< w

200 'g

100 - 150 cm




...w 100 Ill ...





0.2 Irrigation commenced






. P (ppm)





-' :, :I :,












Figure 3. Cumulative nutrient and salt application/removal for Lysimeter 2 with time.

Lysimeters 100




WATER December, /984

The results (not presented here) show that the quantity of nutrients removed from the treatment area by grazing cattle is sma ll relative to that associated with hay production. The forage and hay production was on average eight tonnes DM ha·•yr·•. This land use resulted in a nutrient removal of about 300 kg N ha-•yr- •, 30 kg P ha·•yc' and 200 kg K ha· 1 yr· 1 • From the results of nutrient removal by other crops grown, it is concluded that pasture offers - by far - the greatest potential for nutrient removal when it is frequently cut for si lage or hay .


150 - 200 cm

1 1976






YEAR Figure 2. Total Nitrogen, (plant available) Phosphorous and exchangeable Potassium concentrations in the soil profile at sampling site 1 with time. 12



0 (.)




:::; C w

iJ 000










e ! "...w <(





100 ~


...z ...c3 w -, "~

p 500

0 200

,,_K (ppm)


s u

...0 ...





-' :, :I

E -'


z 100

"' ::l






"'!::; C "'



"'CC 1 000






! 0.2

;12 000 r.n

2 000




. z


i15 000 ;





0 :I


,-- ---

As an example, the total quantities of salt and (major) nutrients applied by irrigation and removed with the drainage water from lysimeter 2 are plotted against time in Figure 3. The cumu lative amount of salt app li ed is 10 times greater than the cumu lative nitrogen and potassium loading. The quantity of salt transmitted through the 3 m profile slightly less to that applied. The sma ll quantity of salt stored over the three years is calcu lated to be about 1 000 kg ha-• (Lawson and Klingberg, 1984). It is anticipated that in the long term the quantity applied will be equa l to that removed as a new equi librium becomes estab lished.


NOTE; For 1:1catlon of ;bs.,...,atlon wall s GAM 112 and 124 ... Figure 1.


Nutrient Leaching (percentage of total applied)

Soil Unit Description

Nitrogen sandy loam











over clay , over

sands10ne (at 1.5 m)







(deep) fine sand





sandy loam over clay, shallow water table




The mean application rate for nitrogen is about 600 kg N ha-•yr-•; at this relatively high rate the nitrate leaching from lysimeter 2 is substantial, 250 kgNO,-N ha-•yr-•. All the phosphorous excess to plant uptake (about 200 kg ha-•yr-') is fixed in the soil profi le. About 95 per cent of the 700 kg ha-•yr- 1 of the potassium applied on lysimeter 2 was either used by the pasture or chemicall y bound in the soil profile. · The nutrient leaching from the 3 m deep lysimeter profiles is expressed in Table 2 as a percentage of the total quantity applied. No phosphorous was leached; about 5 per cent of the potassium applied was transmitted beyond 3 metres. These results confirm the above trends indicated by the soi l sampling results. The nitrate leaching however was quite substantial, in particular from Soi l Unit 4, where the water tab le is shall ow . Between ~O and 60 per cent of the 600 kg ha-•yr-• of organ ic nitrogen was leached mainly as nitrate. These results imply that under this land use the nitrogen removal at the highland (Soil Units l and 2) is about 400 kg N ha-•yr-• and 230 kg N ha-•yr-• at the low lying land.

Groundwater In this hydrogeological environment no mounding occurred un der the irrigation area (See Figure 1). It is estimated that the groundwater movement is 50 m yr-• in a SSW direction, which is diagonally across the land disposal area. The results show that groundwater quality in the observation wells has been affected by the leaching of nutrients and sa lt. For example, the TDS and NO,-N results for observation well GAM 124 within the irri gat ion area are compared with those for well GAM 112 not yet affected by waste irrigation (see Figure 4). The salinit y and nitrate concentrations in GAM 124 increased considerably with time . After three years the concentrations stabilized. Subsequent variations reflect seasonal groundwater recharge containing nutrient and salt. The TDS and nitrate concentrations fluctuate in phase and peak in early to mid summer when the recharge to the water table has terminated . T he change in groundwater quality , and the variab les affecting it are summ arised in Table 3. There has been a substantial increase in nitrate concentration with time whilst the increases for phosphorous and potassium are relatively small. This behaviour was expected from the lysimeter results.



Figure 4. Change in groundwater quality with time.

The positions of the wells in relation to the boundaries of the irrigation area and the regional groundwater flow direction was used to calculate the flow path length i.e. the distance over which groundwater has received leachate from the waste irrigation area. It can be seen from Table 3 that the cha nges in TDS and nitrate are greatly dependent upon the flow path length . The increase in TDS consists mainly of chloride, sodium and calcium.

DISCUSSION The mass balance of nutrien ts and salts for this land application system is schematically presented in Figure 5. On average, the waste irrigation was 350 mm yr- ' ; this resulted in a salt loading rate of 7 000 kg ha-•yr- 1 • All three soil types were capab le of transmitting the applied salt and thus soil salinisation is unlikely to occur. Assuming that the waste irrigation increases the natural groundwater recharge of 200 mm yr-• proportionally, then the salinity of the recharge water will be 1250 mg L-• (about 2.5 times ambient salinity). The mean application of nitrogen on the lysimeters was 600 kg N ha-•yr- 1 • The nitrogen rem oval by microb10logical breakdown and plant uptake from the soil ranged from 350 to 400 kg 1:-1 ha-•yr-• at the highland and was 230 kg N ha-•yr-' on the lowland, where the water table is within 1 m of the surface in winter. The water table effect is greater than the soil characteristics in determining nitrogen attenuation processes . Lawson a nd Klingberg (1984) claim that the wet conditions in the soil and consequent ly lower soif temperatures in winter may decrease microbiological activity . The nitrogen removal from highland pastures by cutting and carting away for silage and hay was estimated to be 300 kg N ha-•yr-•. This estimate, combined with the lysimeter results, suggest that the nitrogen release to the atmosphere by vo latilisation (i.e. ammonia release from animal excretions) and de-nitrification (nitrogen gas produced by soil micro-o rganisms) is 50 to 100 kg N ha-•yr- ' under the agricultural use of the irrigated highland . Despite high application rate the soil nitrogen has not increased (see Figure 2); the nitrogen applied in water was transformed into nitrate


GAM 11 2 124 131 147 149 197* l98t l99t

Cumulative depth of Waste Applied (mm) 0 2830 3360 2570 2570 2780 1660 1660

Soil Unit No .


2 2 2 3 4

Flowpath length (m)



0 460 70 600 70 600 10 600

+ 70 +535 0 +285 + 75 + 580 + 50 +430


• Results from GAM I97 matched to resu lts from GAM I 35 in I 976. t Results from GAM 198 matched to results from GAM I 54 in 1976.

Concentration In crease (mg L-') over the monitoring period

1.2 +21.3 - 0.2 + 14.0 + 2.2 + 26.0 - 2.8 +24.0







-0.01 - 0 .01 - 0.05 - 0 .04 - 0.01

+ 8 + 86 - 3 +66 + 8

0 +7 - I +3 0

+ 14 +84 + 6 +52 + 9

+0. 1 +3 .5 + 0.3 + 0.8 +0.6

+3 +9 +4 +3 +2

+ 11 +237 + 2 + 119 + 28 +22 1 + 45 + 172

t Results fron; GAM 199 matched to results from GAM 151 , 152, 153 in I 976. § Na + K values are over period 1977-1982 as analysis in 1976 was by difference for Na + K i.e. gave a combined figure. WATER December, 1984


in the following summer and then leached from the root zone in the subsequent wi nt er. It is apparent that the soil / plant system can transmit the excess nitrogen as nitrate to the water table. The res ults of the soi l analysis indi cate that potassium and phosphorous, surplus to plant uptake retained mainly in the soi l pro'. file. Only a small fraction was leached by the drainage water as show n in Table 2. The drainage water reaching the water table is mixed with the ambient groundwater which moves at a rate of about 50 m yr-• diagonally across the irrigation area (see Figure I). The measured cha nges in groundwater quality are determined by both the quality of the recharge water and the length of the flow path under the irrigation site. Therefore it is imperative that the well s are monitored not on ly within the treatment area but a lso in the down gradient direction. Data from the down gradient holes will then indicate cumulat ive effect of the degraded quality of groundwater recharge. The result s of the lysi meter invest igation indicate that at an average annual application rate of 600 kg N ha-•yr-•; up to 400 kg N ha- •yr-• was utilised by plant growth or released at the highland. In contrast, only 230 kg N ha-•yr-• were utilised on the lowland areas. This does not impl y that nitrate leaching wi ll not occur if the waste irrigation rates are reduced to the levels of plant utilisation cited above. Groundwater monitoring showed that the two limiting factor s are : the sa lt transmission a nd nitrate leaching. In add iti on the flow path length and the dimensions and orientation of th e disposa l area with respect to the groundwater flow direct ion wi ll ultim ately determine the change in down grad ient gro und water quali ty . The width a nd concentration in the pollution plume, and therefore the impact of waste water irrigation wou ld be reduced by having the longitudinal axis of the application area perpendicu lar to the groundwater flow direction.



TDS: 7 000 N: 600 P: 220 K: 700

N: 50 - 100

Accumulation in the soil profile

Haymaking and grazing

TDS : 500 N: Nil P: 185 K: 425

TDS : 500 N: 300 P: 35 K : 250

Leachate TDS: 6 000 N: 200 - 370 ( soil & vegetation dependent) P: Nil K: 25 (ultimate ly will breakthroug h)




UNITS : kg ha- 1 year - 1

CONCLUSIONS At this site with its permeable, sandy soi ls and moderate (winter) rainfall it is possible to leach the 7 000 kg ha-•yr-• of salt appli ed with the waste. Nitrogen app licatio n averaged 600 kg N ha-•yr-• . The storage, uptake and release of ni trogen in the plant/soil ecosystem was in the range of 350 to 400 kg N ha- •yr-• on a duplex soi l underlain at about 1.5 m by limestone. A sim ilar valu e was obtained for a deep, sandy profile. However, this was o nly 230 kg N ha-•yr-• for a clayey soi l with a water tab le fluctuating between I and 2 m of ground surface. All of the 650 kg ha-• of phosphoro us applied over the three yea rs of lys im ete r monitoring was eit her utilized by plant uptake, or stored at shallo w depth in the so il profile. Of the 2 000 kg ha-• of potassium applied over the three years only 5 per cent was leached beyond 3 metres. The potassium retention in the soi l is a cation exchange process. The downward moving front of potassium saturation has reached greater depth than that of phosphorous fixat ion . Ultimately potassium will breakthrough to the water table. The nutrient concentrat ion s in the herbage have increased steeply and show a marked flu ct uat ion from a summ er high to a winter low. The nitrate-nitrogen level in the grass in su mmer at some of the nine sampling sites is approach ing the toxic level for grazing catt le. Waste water application at these excessive rates led to degradation of groundwater quality which was reduced by a gradual doublin g of the 40 ha irrigation area, after adj ace nt farmers were convinced of th e benefits of waste irrigation for increased pasture production. It was found that nitrogen rate app lication is the major limiting factor both with respect to toxicity of the herbage for stock grazing and nitrate leaching. The other li mitation of whey irrigation is that sa lt applied to land with permeable soi ls will eventually reach the water table despite some removal by plant uptake. Increased sa lt transm issio n through the unsaturated zone will occur in any area where agricu ltura l wastes are di sposed onto land . It is essential to monitor th e gro undwater quality not only within the waste irrigation but also in the down gradient direction to determine the ultimate impact of land treatment. It is therefore concluded that for the siting of any land treatment area, the fo llowing factors have to be taken in to account : the quality of leachate, th e rate and direction of gro undwater movement, the distance of down gradient extraction a nd th e permissible degradation of the groundwater quality. 14

WATER December, 1984

Figure 5. Sc hematic mass balance -

salt and nutrients.

ACKNOWLEDGEMENTS The authors wish to express their appreciation to the permanent heads of the Department o f Agriculture, Mi nes and Energy and Engineer ing and Water Suppl y an d to the Management of Kraft Foods Ltd . for permission to publish this wor k. In addit ion thanks go to our co lleagues who have provided in valuable discussion and to the members of the South East Water Resources Co-ordin at ing Committee for the benefit bf their expertise. Finally, the co-operation and assista nce of the Manager and Farm Officers of Kraft 's Mil-lei factory is ac knowledged with th ank s.

REFERENCES ALLISON, G. B. and HUGHES, M. W. (1978). The use of environmental chloride and tritium to estimate total recharge to an unconfined aquifer. Aust. J. Soil. Res. Vol. 16: 181 - 195. BARNES, T. A. (1952) . Mil-lei Cheese Factory - Pollution of the Water Suppl y. S. Aust. Dept. Mines Rept. Bk 33/ 84 (un pub .). BARNETT, S. R. (1 976). Knight Group Aqu ifier Test - Kraft Foods, Mil-lei, S .A. Dept. Mines Rept. Bk. 76/55 (unpu b.). BARNETT, S. R. , ARMSTRONG, D. W. and EMMETT, W. (1977). Disposal of Effluent at Kraft Cheese Factory, Mil-lel , Mt. Gambier Progress Rept. No. I S. Aust. Dept. Mines Rept. Bk 77/ 21 (unpub.). HARRIS , D. J. and RHODES, H . A. (1969). Nitrate and nitrate poison ing in catt le in Victoria. Aust. Vet. J. Vol. 45: 590-591. KLINGBERG, C . M. a nd SCHRALE, G. (1984) . G uidelines for Land Application of E fflu ent from Intensive A nimal Enterprises and Related Industries. AWRC Project 80/ 134 , Department o f Nat ional Resources and Energy, Canberra (in press). LAWSON, J. S. and KLINGBERG, C. M. ( 1984). The Effects on Soil and Drainage Water of Land Application of Waste from a Cheese Factory near Mt. Gambier, South Australia . Technical Report, South Australian Department of Agric ultu re. (in p ress). McPHARLIN, D. (1983). Kongorong Resisti vity Survey. S. Aust. Dept. of Mines and Energy Rep!. Bk 82/ 49 (unpub .). SCHRALE, G. and MAGAREY , A. A. (1979). Determining Criteria for Land Treatment of Wastewater from a Cheese Factory near Mt. Gambier, South Australia. Proceedings of Groundwater Pollution Conference, A WRC Reb. 1979, Aust. Gov. Publ. Service pp 437-453. SM ITH, P. C. and SCH RALE, G. (1982). Proposed rehabilitation of an aquifer contaminated with cheese factory wastes. A WWA J ournal, Water, Vol. 9: 12 1- 124. WARD, L. K. (194 1). Report of lnnammable gas at Kalangadoo Cheese Factory . S. Aust. Dept. Mines Rept. Bk. 17/ 287 (unpub .).

BOOK REVIEWS DEVELOPMENT IN HYDRAULIC ENGINEERINGEdited by P . Novak Applied Science Publishers London and New York, 1984, 242 pages. $5 1 in Aust.

This is the second in a se ri es of books intended by the publi sher to be an up-to-date state-of-the-art series on hydrauli c engineerin g design . T he 242 pages contain contributions from six auth ors in both Europe and the United States. Th e ear lier chapters di scuss vibration of stru ctures and aeration of water flow with a strong theoretica l and computational bias. The latter chapters a re more orientated to problems encountered in the design of large hydraulic structures. The authors are mainly engaged in the des ign and/or testing structures and have illu strated the text with man y examp les drawn from around the world. Written to give a comprehensive review of a specialised subj ect to practicing engineers, the book would also be of interest to advanced students. Th ere is a trend to larger hydrauli c st ructures, e.g. 23 of the 25 highest dams in the world have been constructed since 1960. The larger flows and higher velocities which result from this trend give ri se to greater possibilities of damage arising from vibration , cavitation within these structures. It is often the details which can cause these major problems. This book in quoting actual examples and resulting so lutions, provides a bridge between the theoretical and practica l aspects of the subject. That the work is up-to-date is illustrated by the fact that it deals with th e design of aeration slots in hi gh dam spillways . Aeration slots were included very late in the design of Thom son Dam spillway which , at the time of this review is still und er construction. Published by Elsevier Appl ied Science Publishers Ltd , the review copy was obtained from their Barking, England Office . R.PAYNE METHODS OF SEAWATER ANALYSIS, 2ND EDITIONEdited by K. Grasshoff, M. Ehrhardt and K. Kremling Ver lag Chemie, Weinheim, 1983. OM 140 - approximately A$60 . 419 pages.

This book cou ld be more accurately described as a Discussion of Selected Methods for Sea Water Analysis. The authors do not set out to prese nt the methods in a cook book fashio n , such as the American Pub li c Health Assoc iation Standard Method s or Strickland and Parsons' Handbook of Sea Water Analys is, both of wh ich are presented in a form su itab le for reference at the bench. Rather , the methods are discussed, in a highly informative and practi ca l fashion, and it is often left to the reader to decide which approach to adopt, especiall y in the case of sample preservation. The writers provide more back ground and di scuss ion than is usua l for methods prese nted in this form. Descriptions of the in-

di vidual steps of the analytical method are provided , however, these assu me a basic knowledge of analytical techniques and would need to be expanded to form a step by step method for the anal yst to follow. Diagrams or clear descriptions of any apparatus are given where necessary. A rather basic sec tion on errors due to sampling and ana lysis is included , together with precision estimates for each of the method s. The a uthors are cl early experts in their res pective field s and have thoroughly researched each of the methods . However, the choice of indi vidual methods does re flect their personal prejudices and back ground, such as the use of complexo metric titrations for calcium and magnesium . The book 's European origin is apparent here, not only in the selection of methods but also in its strict ad herence to SI units and rigorous nomenclature, unfamiliar to many analysts. Although of considerable interest to ana lytical chemists working in the fresh water field, it is probably only marine chem ists who would refer to the vo lume suffi ciently often to justify its cost. R. W. BANNISTER K. 1. MARSHALL SEPTIC TANK SYSTEMSJohn H. Timothy Minneberger Butterworth 's Publishers-Ann Arbor Science Book , 1984, two volumes $80 .

Volume I, of 14 chapters, deals with the subsurface disposal of septic tank effluents, and consists of 220 pages plu s an additional 18 pages which cover items such as details of the author's backgro und , a prologue, and contents page. Major topics covered include soil percolation tests; assim il ation and the sizing of disposa l field s; site evaluation; and public health concerns. Vo lum e II deals exclusively with Septic Tanks. It consists of only 123 pages plus the prologue and background information contained in Vo lume I. Major topics covered are the remova l of suspended solids, nitrogen, oxygen, and disease-ca using orga nisms; stratification and settling; sludge and scum their characeristi cs and production ; and gas production . The credentials of the author are impressive. Dr. Winneberger was sponsored by the USA Federal Housing Admininstration to carry out research on septic tank s and effluent disposa l at the Sanitary Engineering Research Laboratories of th e University of California. After eight years research (and many publications) he then became a full time consultant as we ll as (for a short period to gain a complete viewpoint of his subject) a contractor. The result is a book which contains a wealth of practical information clearly very re levant to Austra lian situations . Although each vo lume is described as a consultants handbook, the material is particularly essential reading for all Australian authorities concerned wit h septic tank effluent. Dr. Winneberge r (to the initial surpri se of the rev iewer) makes many criti cisms of both the USA Public Health Service Manual of Septic Tank Practice and the USA Environmental Design Manu al of Onsite

Wastewater treat ment. The cnt1c1 sm s , although severe, are alw31ÂĽs supported by reasoned a rguments. Perhaps th e greatest concentration of criticism against the practices recommended in these USA official manuals is contained in Chapter 9 of Volume I where many fallacious gu idelines are li sted and discussed. Some coverage of the politics of septic ta nks in the USA is also included . The most outspoken of ma ny pertinent comments is th e final sentence in the chapter on percolation rates (Vol. I) ' Doubtless inadequate septic-tank regulations have needlessly divested many people of property rights'. It is rare indeed to find vo lum es written with such complete a uthority which are both academically pleasing and immensely practical. It is regrettable tha~ the cost of this outstanding material is $80 . Neither of the volumes is large so they co uld easily have been combined into one book at less expense. G .A.HOLDE R LAND CAPABILITY FOR SEPTIC TANK EFFLUENT ABSORPTION FIELDS 1. Brouwey and R. M. Bugeja Aus tr a li an Water Resources Co un ci l Technical Paper No. 80. The Australian Government Publishing Service, P.O . Box 858, Canberra 2601. Two parts in a sin gle volume, 344 pages.

Part A (1 87 pages) reports the results of monitoring studi es carri ed o ut on effluent s from pairs of sept ic installations in four differe nt locat ions (Lara, Bacc hus Marsh, Don cas ter-Temp lestowe and Mt. Macedon) in th e Melbourne area chosen to evaluate the effect of different soi l types . Other factors such as the variations in climate, especially ra in fa ll, topograph y, and vegetation are also discussed. A formula for , calculat ing th e necessary trench lengt h for disposal of septic tank efflu ent is developed with comparisons using the proposed new formula and the meth ods recommended by the USA EPA and the Hea lth Co mmi s\ion of Victoria. A major findin g was that the con tribution to effl uent disposal of evapot ranspirat ion is not adequ ately allowed for in the present septic-tank guidelin es for Victoria. Part B (157 pages) reviews research and regu lat ion s for on-site wastewater disposal. Co mpariso ns are made between the approaches adopted in our states and between Australi a and overseas countries with a major emph asis on regul at ions in the U.S.A. Perhaps the most import ant of many important points brought out is that th e site-rating systems used by most authorities (including Victorian) contain in co nsistencies which should be elimin ated and that a change to a system similar to that used in the state of Maine (U.S.A.), where each sit e is ¡assessed on its merit (pages 294-298) has much to reco mm end it. The authors are to be congratulat ed on producing an excellent and timely work co ntainin g much useful data of parti cular relevance to Aust ralian situations. It is not possible to adequately su mmarise all the valuable co nclu sion s and recommendations contained in th e thi s rev iew. T he publi cation is strongly recommended.

G.A.HOLDER WATER December, 1984




The changing Management Needs of the Introduced by Chairman Peter Norman, Austra lian Water Supp ly and Sewerage In - John Todd Chairman of the S.A. Branch of dustry was the theme of this seminar held in the Institution provided the official opening, Adelaide over November 22 and 23 and paying tribute to the engineers of yesterday organ ised jointly by the South Australian and today and to the co-operation between Branches of the Association and the Institu- the Association and the Institu tion. tion of Engineers (Aust.). The Keynote speaker Duane Georgeson, The success of the event, 170 registrants Assistant General Manager (Water) City of from all States, evidences the timeli ness and Los Angeles, Department of Water and appeal of the theme, the calibre of the battery Sewer, then delivered an excellent and well of top level speakers assembled and the presented paper 'Management of Aging forethought and organising ability of Chair- Assets in the United States' which is reviewed man Peter Norman and his Committee, Brian later. Maquire, David Pearce, Bob Clisby, Lyn Sanders, John Langford, Kim Lim and Bruce Brook. The venue, Hotel Oberoi provided very good facilities and comfortable conditions untroubled by the size of the audience except for catering arrangements which suffered. Programming and timing were excellent and the momentum of activities and audience participation were maintained over the two days with a welcome break for the Seminar Dinner on the first night. Formalities were commendably brief from the official 'Opening' to the 'Closure' which was preceded by a Summary delivered expertly by Past President Frank Bishop who is now well practised in th is role. The assembly of papers was not distributed to participants until after the closure - by intent. The ' fors' and 'againsts' this approach seemed to be even ly balanced - it certain ly results in au- Chairman Pet• r Norman of A WW A starts dience concentration upon the speaker and tile ball rolling. eliminates the time-honoured speaker quanIn tk ''0llowing session a panel discussion dary - has the audience or has it not read his prov,c' · opportunity for Messrs. Lewi s, paper? From the Keynote address by Duane lnger~o,1 ,u ld Dr. Craw ford to outline the imGeorgeson and the following panel session of pact of ' " 'winds o f change' upon their Messrs. Lewis, Ingersoll and Dr. Crawford , organi~, .Jns and the consequent dramatic presentation and discussion were frank and change, -1 philosophy , structure, corporative informative to a most marked degree, depart- managrl7ent and establishment. mental reticence more or less normal in this These two sessions established the pattern area, was absent and the value of the exercise and the theme fo r the remainder of the technic,, sessions which are scanned in the accordingly enhanced. The message dominant in most presenta- overvie ,elow. The inar Dinner provided an opportions, whilst not new, was conveyed with great emphasis -- the halcyon days of ever- tun ity hairman Peter Norman to present increasing capital expenditure are in the past, to th e" 1bly the newly elected President of the management needs and action s for the the As,, tion, Bob Lloyd of G. H. & D. future are in the areas of conservation and Brisbat Bob became President at the optimum usage of assets and resources, effi- Federal uncil Meeting earlier in the week ciency, the fin ing down and restructuring of and so r, .. de his maiden Presidential speech. organisations and communications with and He stressed the multi-disciplinary nature of education of the end target - the consumer. the Association, the much appreciated sup·It may or may not be significant that the con- port given to A WW A by the major sumer, as such was not represented at the Author ities and the desirability of widening membership acceptance to include those sem inar. The Seminar was most succsessful in con- disciplines differing from the strictly science tent and in presentation and provided a great based and now playing such an important deal of valuable information for authorit ies part in management as evidence in the conand management, both large and sma ll , for tent and proceedings of the seminar. the problems venti lated and discussed are John Todd followed Bob Lloyd with comcommon throughout the industry, only the ment on the role of the Institution in this degree varies. The assembled papers provide changing world and warning of the imbalance a most useful commentary upon the industry in Australia between the training of scientists in the current climate and warrant a wide and engineers and the predominance of the market. former. He appealed for greater appreciation 16

WATER December, 1984

John Todd, IE Aust. declares the Seminar open.

of the engineer, greater support of R. & D., more dynamic thinking by engineers and more politi cal involvement. Chairman Peter Norman took the opportunity for sincere thank s for support received from the Sydney Board, the Melbourne MMBW and the E & WS of South Australia and Director Keit h Lewis, also the financial contr ibuti ons of Humes Limited and Adelaide Brighton Cement. He spoke warmly of his Committee confreres, · employees and organisations, the hard work of John Todd's Secretary and the assistance of Session Chairmen.

KEYNOTE ADDRESS Duane L. Georgeson

Keynote Speaker Duane Georgeson in action.

In 'Management of Agin g Assets in the United States' Duane Georgeson painted a picture of neglect and deterioration of public 'infrastructure' as a result of continuing reduction in expendit ure on maintenance and replacement over decades but with results, at least in water supply, not as traumatic as

NATIONAL WATER MANAGEMENT SEMINAR-ADELAIDE some forecasts would indicate. The causes are many, including changing life style effects, population and industry changes, inflation, diversion of available finance to other social areas and emphasis on capital projects rather than maintenance. Estimate of the 20 year needs of the water and wastewater industries vary greatly but are in many billions of dollars. In many communities the potential for future development is limited by the deficiencies of their water and wastewater systems a limitation unreali ed. The solutions are long term and the most important emerging are long term financial control and the move to self-servicing with the requisite increase in direct community charges in contrast to reliance upon Federal financial assistance. The corollary to this is the estab li shment of rating systems providing funding from local sources. Community education is a vita l factor and realisation that the onus for rectification of the problem rests squarely upon the community.

PAPERS-OVERVIEW All papers and au th ors are listed in detail and seq uence on page 19 of th is issue. In the 'Panel' session on the Semester theme, Keith Lewis of the E. & W .S. Department traversed the changes from the boom of the mid '70s to the present, the downturn and call for public 'accountabi li ty' and the resulting self examination by the Department. Future needs were determined, programmes estab li shed and implemented involving, re-organisation with management changes, a three-tiered planning structure, policy and performance review, regionalisation and changes to management information systems. In co ncludin g he expressed concern that the pendulum swi ng involved may have been detrimental to the technical aspects. Peter Crawford aptly described the Water Industry as suffering 'cultural shock'. He outlined the changing needs to be met social, economic and philosophical in genera l and by the Sydney Board. In that organisation radica l re-organisation is proceeding with emphasis upon regionalisation and altered approach to management. Demand Management and Risk Management figure in the considerations. The Melbourne Board's operations were outlined by Russell Ingersoll ¡and the need for re-thinking to meet the diminution of uncommitted water resources, the dramatic changes in economics, public accountability demands and community expectations. Extensive reorganisation now in hand will reduce the decision making leve ls and give a leaner establishment. Recent experience supports the belief that a water conservation ethic can be developed, reducing demands. General discussion and questions to the panel ranged over economics, R. & D., restrictions, re-use, public participation and educat ion, day-labour vs contract and the econom ics of design.

Keith Lewis summed up: water and sewerage is developed for the benefit of all, the principles are common to all authorities and changes should be seen as 'fun' and be innovative. John Paterson presented a most comprehensive review of the historical and current aspects of water legislation and legal ities, with all its complications and state variatio ns and terminated with comment on pricing and its role in resource management. The Commonwealth view of the current situation of the industry was put by Alex Manderson with references to the recent New Water Policy and programme, he identified the key elements and stressed the necessity for better management in the industry. Various aspects of the Commonwealth programme were outlined associated with the changing management needs. The industry must concern itself with the efficient distribution of existing resources and realism in the industry outlook is essential. John Langford's theme was drought and demand management, the Melbourne experience with restrictions and public education, the rationale of 'risk' and probability approaches to demand limitations. Ken Aubrey traversed the capital expenditure/ work force scene of the Sydney Board and the effects of capital expenditure reaction. The objectives of conta ining rate increases and of achiev ing largely self financing of capital works have been attained. He discussed industrial relations, labour organisation and staff aspects of a contracting (as distinct from expanding) establishment and the importance of care and patience to staff morale and to industrial relations. The profligate spendi ng and indebtedness of Governments was highlighted by Neil Killmier who offered pertinent comments on capital works programmes and their review and the opportunities for savings in operating costs, with suggest ions as to their achievement. The extensive changes now being implemented in W.A. with the creation of a State Authority were described by Bob Hillman. The objective has been the merging of metropolitan and country activities of the Metropolitan Authority and the PWD with proper regard to effects upon morale in both organisations. Bill Webber on 'Water Management for Smaller Communities' traversed the Queensland scene and the problems arising in water supply and sewerage and the challenges presented by reduced Government assista nce, high interest, deterioration of assets and poor staffing in small communities. Corporate Planning and its advantages in a period of change was expertly covered by John Shepherd. He outli ned strategic planning concepts and application in the pub lic sector embracing innovation and risk taking, measures of performance, accountabi lity, the dilemma of competing dema nds on Government and the problems and desirability of true costing of services and of charging for such. Duane Georgeson returned to the rostrum

with three case studies of Aging Assets in the U.S.A. with systems suffering lack of finance and deterioration. Corrective measures include community educatio n, major reorganisation, rate increases towards self financing, rationalisation of servicing. This paper was supported by a panel discussion with Bill Hazel of the M.W.S. & D. Bd and Harry Hicks of the E.W. & S. presenting a most interesting session on asset management. Performance measurement techniques of the M.M.B.W. was well covered by Bill Robertson, long practised in the private sector, it is an urgent need in the industry. He traversed the basics, corporate context and techniques. The picture of the E. & W .S . response to the changing scene was further amplified by Don Alexander who described the organisation changes, altered approach to management, the strategic plan and the committee systems developed. In the fina l paper, Brian Lloyd stressed the importance of human resources and was critica l of the performance of civil engineers in the industry in slowness of response to the changes now recognised, changes requiring a move from a static structure to a system view. Manpower and education are the crucial issues to be met in the coming decades.


Frank Bishop sums up.

Upon conclusion of his summary of the Seminar content, Past President Frank Bishop expressed the appreciation of Federal Council and of the Registrants of the efforts of the Organising Committee under Chairman Norman, The A.W.W.A . Branch Committee, the I.E. Aust. and the E. & W.S. Department and its officers. Mike Dureau, the newly elected Federal Vice President supported the expression of appreciation and presented Chairman Peter Norman with a remembrance token to provide a tangible reminder. WATER December, 1984



The In gerso ll -Le wis-Crawford Panel in actio n .

Presentatio n to C ha irm a n Peter Norm a n (right) by V. Presiden t Michael Dureau.



WATER December, 1984

1984 I ~

SEMINAR PAPERS AND AUTHORS Management of Aging Assets in the United States

Statewide Management of the Water Industry in Western Au stralia

D . L. Georgeso n - Asst. Gen . M a nager (W a ter) Dept. o f W a ter a nd P owe r , Los Ange les

R. M . Hillm a n - C ha irm a n , Water A utho ri ty, Western A ust ra li a.

Changing Management Needs of the Au stralian Water Supply and Sewerage Industry

Water Management for Small Communities - Taking Stock W. A. Webber - Ass t. Directo r , E ng. & Tec hni ca l Services, Dept. Loca l Governm en t , Q ' la nd .

K. W. Lew is (left) -

Dir. General a nd E ng.- in- C hi e f, E . & W .S. Dept. , Sth. A ust. D r . P . J. C rawford (ce ntre) - Gen . M a nager, M .W .S. & D . Bd. R. J . In ge rsoll (right) - Gen . Man age r , M .M . B.W. , Melbo urn e.

Corporate Planning as a Tool for Guiding Organisations Through Change K. J . Sheph erd - Director T echnica l Se rvices, E. & W .S. Dep t., S. Au st.

The Management of Aging Assets Three U .S . Case Studies A State Level View of Water Management Systems

D . L. Georgeson a nd J . D. Po wers Dept. of W a ter a nd P ower, Los A ngeles.

Dr . J. R . P a tterson - Di recto r Genera l, Dept. o f W a ter Resources, Victo ri a.

Water Resources Management and the National Interest A. Ma nderson - Fi rst . Asst . Secretary, W a ter a nd Deve lo pm ent Di vision , Dep t. of Resou rces a nd E nergy, Ca nberra .

Community Perceptions and Expectations of the Water Industry Dr. K. J. La ng ford - Actg . Ma nager, W a ter Supp ly H ead work s a nd Distributi o n , M .M .B.W ., Mel bo urn e.

The Implications of Diminishing Capital Works Programmes K. G. Aubrey - Director of Develo pm ent, M.W .S . & D.Bd ., Sydn ey.

The Financial Dilemma - The Mismatch Between Revenue and Cost A . N . Killmi er - Directo r , Admini strati on a nd Finan ce, E. & W .S . Dept. , S. Au st.

Performance Measurement Techniques W. J. Ro bertson - Dej)'. Dir. E ngin ee rin g (Systems O pera ti o ns) , M.M .B.W ., Melbo urn e .


Managing the Performance of a Water Supply and Sewerage U ndertaking D. J . Al exander - Dep. Dir . Genera l, E . & W. S. Dept. , S. A ust.

Education , Training and Manpower Planning B. E . Lloyd -

Engin ee ring Co nsul ta nt , Mel bo urn e.

Bound sets of Seminar Papers are now available

Appl y: Hon. Secretary, S. A. Branch of A WW A , State Water Laboratory, E & WS Dept. , Private Mail Bag, Salisbury 5108 . Pri ce: $20 Au st. per set plus postage - $5 sur face m a il wit hin Austra li a, elsew here ac tual cost.

WATER D ecember, 1984


Automatic Process Control for Large Wastewater Treatment Plants K. Barr 1.0 INTRODUCTION

For major cities, eco nomies of sca le dictate that large wastewater treatment plant s will have significant cost advantages over a greater number of sma ll er treatment plants. As well as these economies in terms of capita l costs, more efficient operation is usuall y poss ible at large treatment works which represent considerable savings in operation costs compared with those costs for small works. To enab le optimum process co ntrol at large wastewater treatment plants a reliable automat ic process control system capa ble of sequence and modulating control is required. In recent times the activated slud ge process has been favoured over trickling filter s for large plants mainly due to savings in land area. However, the more inten se activated sludge process requires more sophisticated mechanical and electrical equipment which in turn require a high er level of monitoring and contro l. ¡2.0 TYPES OF CONTROL REQUIRED

The two types of co ntrol required at any large process plant are modu lating and sequence contro l. Modu lating contro l is usually achieved by local analogue controllers and consists of the adj ustment of a physical item (often a valve) to maintain a process variable (often a flow rate) at a desired va lu e. Sequence contro l is usua ll y required for the st art up or shut down of a major plant item (e.g. a blower or centrifuge) where certain logical operat ion s must be performed in the correct sequence wit h appropriate time delays to effect a satisfactory and safe start up or shut down of the plant item. Sequence contro ll ers can be so lid state/ relay systems of software based seque nce co ntrol systems by programmable logic controllers (P .L.C.). Remote process mon itoring of ana logue va lues and digital states is usually required in addit ion to the control functions . Typical ana logue va lues wou ld be sludge flow s, di gester temperatures and disso lved oxygen concentrat ions. It is often necessary for these va lu es to be tran smitted to a central control station for data loggin g. Remote indication of digital events is usually associated with alarms (e.g. lo w lu be oil flow, high sludge blanket level). 3.0 AUTOMATIC CONTROL SYSTEMS 3.1 Conventional Systems A simple co nventiona l system may compr ise loca l analogue controls and instrumentation, so lid state/ relay sequ ence co ntrol systems a nd loca l alarm annunciato rs. This system can o nl y be converted into a remote centralised contro l system by physical hardwiring from the field units to a centra l control room . A typical contro l room for this sys tem would have hundreds of indi cators, recorders, indi vidual swit ches and push buttons around the walls or on the co ntrol desk. With this system every control loop operates independent ly and it is difficult to obtain a satisfactory overview of a large system and impossib le to apply an integrated control strategy to the comp lete process . 3.2 Computer Based Systems

These systems contai n a large process computer wh ich performs direct digital contro l of the process usually via some type of shared commu nication link (telemetry or digital encoded seria l data transmission system). Here all control is peformed by a remote intelligent device. The centra l control room wou ld normally contain vi sual di splay uni ts for indications, alarm an nunci a tion and mimic diagrams as well as a multi-purpose keyboard for contro l initiation. Thi s centra lised operation makes sophi st icated integrated co ntrol avail able . Main disadvantages of th is type of system a re the com plex software structures required and the extremely time-consumin g efforts

Keirh Barr is Process Engineer ar rhe Luggage Point WWTP of rhe Brisbane Ciry Council. 22

WATER December, 1984

at all stages (design, programming, commissioning, maintenance and extension) . Also since the whol e process is dependent on the computer, an uninterrupted power suppl y and perhaps a spare computer may be required for the desired reliability to be achi eved.


K. Barr

3.3 Distributed Control Systems

These systems contain local int ellige nt analogue and sequence control devices which interface directly with the process, accepting analogue plant stat us a nd alarm inputs . T hese local contro ll ers perform modulating and seq uence contro l si milarl y to the conventional sys tem, however, they exchange information to a hi gher level system to enab le data logging and supervisory functions associated with integrated co ntrol w be carried out. The comm uni cat ion li nk between the local stations and the central control room is usuall y some type of telemetry data tran smi ss ion system as for the computer based control system . Visual di splay unit based indi cation, alarm annunciation, mimic diagrams and keyboard cont rol initiation from the central co ntrol room are also part of thi s sys tem. Here the contro l is performed by a uto nomous local co ntrollers wit h loca l controller override being performed from the central contro l room to enable an integrated co ntrol strategy to be achieved. Th is system has increased reliab il ity over direct digita l contro l as loca l co ntrol conti nues if the hi gher level contro l system fa ils . 4.0 APPLICATIONS FOR AUTOMATIC PROCESS CONTROL 4.1 Screening

The fir st contro l function required is for standby screens to be brought into serv ice a utomatically. This may be dpne by a control loop between the measured flow into the plant (e.g. from a flume) a nd the number of screens required for a particu lar flow velocity . The screen raking cycl e would also be con troll ed for operation on a particular time cycle which may be related to flow rate. T he normal cycle of raking may be int errup ted by additional' raking cycl es in itiated by the head loss through the screen exceed ing a pre-set val ue. Automatic systems can also be used for di sposa l of the screenings. A typical system wou ld be for the screen ings to d ischa rge onto a belt conveyo r which deposits them into a hopper for dewatering a nd in cinerat ion. This type of sequence co ntro l can eas il y be achieved by simple relay systems and the extra expense of in sta ll ing a programmable logic co ntroller is probab ly not wa rrant ed because once t he contro l system is establ ished it is unlik ely to be changed. 4.2 Grit Removal and Pre-aeration

Horizonta l velocity contro ll ed grit remova l is not normally employed at large plants because of the cost of constr uction of parabol ic channels and the large head losses through the contro l device downstream of the channel. Spiral flow aerated grit removal is commo nl y used. A co ntrol system is required to suppl y the correct a mount of air to mainta in the desired particle velocity . A simple system wou ld be to supp ly a constant air volume to prov ide correct spiral flow velocity for the average dr y weather sewage flow. However, after havi ng determ ined t he optimum spiral velocity for grit separation a contro l system may be adopted whi ch modulates air flo ws proportionall y wit h sewage flow to allow ma ximu m grit depos ition at low flows as well as wet weather flow s. A si mple co ntro l loop could be used to provide the minimum air req uired for pre-aerat ion . A modulating control system would be required to supply air to grit and pre-aeration cha nnels. The adjustments of air flow related to sewage fl ows would be determined by the higher level computer which has access to flow data. Also a simple seq uence controller may -be employed for automatic collect ion, separation and disposal of the grit.

4.3 Pri mary Sed imentation

Some large plants have power generation facilities, utilising biogas generated from the sludges removed from the plant. Therefore the collection a nd remova l of the maximum amounts of sludge is important. for improved treatment levels and in terms of the cost benefit gained from the extra biogas produced. Rectangular tanks are normally used for large plants main ly due to economies in land use. A sequence contro l system is usually adopted for scraping and des ludging primary tanks. A typical automatic cycle for rectangular tanks would be as follows. The travelling bridge scraper moves from the park pos ition at t he outlet end of the tanks and scrapes sludge along the tank floor and scum along the water surface. The scraper stops at the inlet of the tank and side concentrators move the sludge into hoppers o n the tank floor and scum into a sight box usuall y directly above the sludge hopper. After a pre-set dwell time to allow the sludge to consolidate in the hopper the main scraper and side scrapers will return to their park positions. After sludge consolidation, telescop ing va lves are lowered to discharge sludge hydrostatica ll y into the sight boxes. Sludge from the sight boxes discharges to a wet well for transfer to sludge digesters. The time of the sludge drawoff may be time contro lled or density controlled whereby a signal from a density meter that the sludge has become too thin will cause the telescoping valves to raise and end the drawoff. Here the many sequent ial operations are best controlled by a software based contro ll ed P.L.C. as many of the operating variab les e.g. park time at outlet end of tank, dwell time, time for drawoff, number of fu ll or partial scrapes per day, may be changed to improve tank performance. 4.4 Bio logical Treatme nt 4.4.1 Tricklin g Filters

The main advantage of automatic contro l for the operation of trickling filters would be the control of the recirculation ratio such that the mini m um flow fo r wetting of the media is always adequate. Having determ ined by expe ri mentation the minium flow rate to prevent drying of the biomass film an automatic control loop would enable the recircu lation ratio to be increased during low flows and reduced during times of peak in fl ows. For a large plant this will reduce pump ing costs as well as achieving better process control. 4.4.2 Activated Sludge

The basic phi losophy for efficient operation of an activated sludge process is to maintain a constant level of dissolved oxygen in the aeratio n reactors to provide optimum conditions of growth for the aerobic purifyi ng bacteria. It is also necessary to contro l the numbers of bacteria and normally a fixed population level is maintained in the aeration tanks by control of activated sludge return and wasting rates. Disso lved oxygen co nt ro l invo lves varying the oxygen input to compensate for variat ion in oxygen demand due to changes in organic strength of sewage such that a pre-determined level of D.O. is always main tained . For surface aeration systems dissolved oxygen concentration is increased by increasing the speed of the rotating aerators or by immersing the aerator lower into the tank. Often the effect of lowering the aerator is achieved by raising the liquid level of the aeration ta nk by weir cont ro l. For diffused air systems more oxygen is disso lved by increasing the speed of the blowers or by increasing the air flow to the suction side of the blower for constant speed blowers. He re a modu lating contro l loop is required wit h input from a d isso lved oxygen ana lyser and output to t he oxygen co ntrol device (e .g. weir, blower motor speed). Sequence control systems are also employed for the start-up and shut-down event sequences for large ' blowers. Control of return sludge rates is necessary to ensure that sludge is being removed from the final settling tanks at a sufficient rate to prevent acc umu lation and washou t . Also un less strict symmetry ex ists, control is often required to ensure an even feed of return sludge into the aeration tanks so that the same level of activated sludge solids can be ma intained in each tank. The level of sol ids is held constant by ma ni pulation of the slu dge wasti ng rate to matc h the slu dge synthesis rate of micro-organ isms. Th is can be achieved by selecting a sludge age value (calcu lation of so lids retention time is explained below). So li ds ca n be co ntro lled via the inpu t from a turbidity meter but in pract ice devices have been too insensitive and unab le to manage normal solids variation during a day.

Modulating contro l systems are required for operation of valves and penstocks for return and waste sludge flow control. Associated with biological process control is the waste sludge disposal facility. Centrifuges and dissolved air flotation units are most commonly used at large plants. Modulating control systems enable machine adjustments for variation in feed sludge characteristics. For biological process control, high level computations are useful to enable finer control of the process. Some examples of advanced control functions are included below. (i) Automatic variation of return sludge recycle rate with the sewage flow. The high level computer reads the sewage flow continuously and determines the total return sludge rate required to maintain the recycle rate at a fixed percentage of the sewage flow rate. This system allows a constant sludge blanket to be maintained in the secondary clarifiers as well as maintaining constant densities of M.L.S.S. and R .S.S.S. during the daily fluctuations in sewage flow. (ii) On-line determination of solids retention time for waste sludge control. The equation for determining S.R.T. S .R.T. = (M.L .S.S. x Aerator Vo lume)/ (R.S .S.S. x Waste Rate) is solved by the computer to enable on-line and instantaneous determinat ion of S.R.T. without any chemical analysis results. This program uses the instantaneous value of waste rate with the constant aerator volume and determines the M.L.S.S ./ R.S.S.S. ratio by a mass balance for the secondary clarification system and therefore S.R.T . can be determined. A contro l loop can then be established to maintain a constant S.R.T. consistent with the biological regime. (iii) On-line determination of oxygen uptake rate (OUR). T he equation for oxygen absorption rate in mg L- 1 h- 1 R = aKLa (/3C ,-C) can be solved on-line by the computer. The mass transfer coefficient KLa for the particular aerat ion system is determined from performance data for a measured air flow. Saturation oxygen concentration C, is calculated for a measured aeration tank temperature. Alpha c, and beta (3 are constants specific to the type of wastewater and are determ ined separately by experimental work. C is the average measured dissolved oxygen concentration of the aearation tank . This on-line determination of OUR allows more accurate monitoring of the state of respirat ion (activity) of the bio logical popu lation. 4.5 Sludge Digestion

Process co ntrol for anaerobic d igestion involves maintai ni ng the mixed digester contents at an average tera-perature of 35 ° C or 55 °C for mesophilic or thermophilic digestion respectively using internal or external heat exchangers. T he energy for water heating is usually provided by a sludge gas fired boiler or waste from the power generation plant. Considerable time is required to raise the temperature of a cold digester to the optimum temperature, once attained a simple control system can be employed to ma intai n this temperature . For a d igester operating at design temperature the main heat losses are due to radiation and make up heat is required to match these losses as well as to raise the temperature of the feed sludge. A typical sequence control system for external heat exchangers would operate as follows. Upon commencement of raw sludge feeding, a recircu lating sludge pump starts and mixes heated sludge with the raw sludge before feedi ng the heat exchanger. A temperature sensor mounted on the suction side of the heat exchanger will sense when the target digester temperature has been reached and the recircu la ti ng pump and the hot water supply to the heat exchangers wi ll be stopped. If the average digester contents fall below design temperature the recircu lating pump will operate and pump sludge through the heat exchange to raise the digester contents to design temperature. Efficient heating of digesters is dependent on the effectiveness of the installed mixing system. Gas recirculation systems are commonly used for large digesters to maximise the distribution of feed sludge, ensure adeq uate biologica l contact and provide heat dispersion over the whole digester volume. Software based sequence control is not essential and many simple relay systems are successfu l. However, for a plant with power genera-



Synthetic Rubber Factory in South Africa Effluent Treatment I. B. Law SYNOPSIS

Th e background to, and the design of, the effluent plan t at Karbochem 's synt hetic rubber factory in Newcastle are discussed. Flexibility in the design was essential in order to meet varying and unknown influent chara cteri stics . Co mm iss ion ing ex per iences together with rece nt resu lts are presented . The Author was, unti l February 1983 , a director of the consulting engineerin g firm Meirin g and Partners Inc . in Pretoria, South A fri ca and was res ponsib le for the design and commiss ioning of th e effluent treatment facili ties . 1.0 INTRODUCTIO N

Karbochem' s Afprene Project , a $350 milli o n synth etic rubber factory in Newcastle, South Africa, produces three types of synthetic rubbers; polybutadi ene (PBR), styrene- butadi ene (SBR) a nd po lyisoprene (PIR). The PBR / SBR process invo lves the catalytic solution polymerisation of the monomers butadiene a nd styrene according to well proven America n tec hno logy. The processes in vo lved in th e produ ct ion of PJR are based on various proven European technologies with acetylene, generated from carb ide , and acetone being the major raw materials. T hough there are ma ny synthetic rubber plants in the wo rld, thi s one at Newcastle is uniq ue in that all the fe edstocks are coa l based, as is shown in Figure I which shows a bloc flow diagram of the Factory. Once on line the factory wi ll be capable of producing som e 36 000 tpa of a mix of various grades of PBR and SBR and 45 000 tpa of polyisoprene . The first phase of th e project - th e PBR/ SBR plant and its associated utiliti es was success fu ll y commi ssioned in June 1982 and the PIR plant was commissioned in August this year but a seriou s wa ter short age prompted it being shut-down after a short period of operation. Detai led engineering of the effluent treatment pla nt began in January/ February 1981 and co nstruction activities began in June 198 1. The plant was commissioned in June 1982 in time for the di scharges from the PBR/ SBR plant and it s related utilities .

handling various influent qualities and yet produce a treated effluent of a quality at a ll tim es accepta ble to th e environm ental authorities. It was decid ed that th e efflu ent plant should be ph ased, with Ph ase I compr ising those unit operations and processes required to enab le a fina l treated efflu ent with a quality acceptab le to the DEA, to be prod uced when all areas of the project a re in producti on. Phase 2 would involve installing such I. Law faci liti es as required to produce a treated effluent th at may be readil y reused in the factory - thereby approaching the zero effl uent discharge concept. It was envisaged that th ere would be a one to two year interval between phases. Th e design of the effluent plant was di scussed with the DEA and a disc harge permi t was gran ted subj ect to review in two yea rs by wh ich time all phases of the project would be on-line and the fin al effluent quality co uld be readily assessed .

3.0 NATU RE OF THE DISCHARGES Th e fa ctor y compri ses nin e speci fi c areas of production and it was decided ear ly in the project design that the di scharges from the vario us areas wou ld be segregated with the segregation based on the nature of con tamination. Th ere are thus fi ve separate sewer system s (or five effluent







T he project site is in a water se nsitive area with the result that the So uth Africa n Department of E nvironm ental Affairs (DEA) insisted that the quality of effluent discharged to a near by creek should comply with their STY RENE / BUTAOIENE General Standards for Discharge. RUBBER Negotiat ions were entered into with the Department as it was considered that a relaxation of the COD and TDS standards would be required. A decision was also taken at thi s stage that treated effl uent wou ld, at sometime in the futur e, be returned to the factory for reuse. T he design of the effl uent plant was complicated by the fact that there is no simi lar proj ect anywhere else in the world from which the likely quality of project di scharges could be gauged. T he treatment fac ilities had therefore to be fl ex ib le, capable of

Ian Law is a Senior Associate with Camp Scott Furphy Ply . Lid. , Consulting Engineers, Sydney. Th is paper was presented lo the NSW Branch of the Association in October, 1983. 24

WATER December, 1984





Figure 1. Flow diagram of factory. categories): sa nitary sewage, clea n sto rmwater , co ntaminated storm water , process effluent a nd minera lised efflu ent. The first two categories a re self explanatory and the last three are further discussed below: 3.1 Contaminated Stormwater

T hi s discharge arises from stormwater run-off from those areas that are open to th e elements and on which chemical sp ill age can occur such as th e Tank Farm, railcar off-loading, etc . The co nta minant load of this discharge should decrease the longer a storm pers ists and thi s forms the basis for the des ign of th e contamin ated stormwate r treatment facilities.

Boiler blowdown, cooling tower blowdown and some unreturned condensate from the SBR / PBR plant are also routed to the contaminated stormwater sewer. 3.2 Process Effluent The process effluent comprises those discharges that contain organic contaminants in addition to a relatively low inorganic presence. Examples of the expected organic contaminants are isoprene, acetylene, hexane, acetone, butadiene, adsorber oil and nitrosophenyl-hydroxylamine. As most of these contaminants are vo latile it is likely that a degree of load reduction (and safety hazard creation) would occur through str ipping at points of excess ive turbulence. Suspended solids in the form of rubber crumb and si lt and inorganic contaminants resulting from the use of catalysts and acids could also be expected. The pH of the effluent is expected to be in the 3.8 to 4.0 range when the PIR plant is in production, otherwise approximately 6.5. Table l summarises the estimated process effluent quality when a ll the areas are in production. TABLE 1. ESTIMATED QUALITY OF PROCESS EFFLUENT pH COD BOD TDS TN as N TP as P Na+ Ai 3 + Zn 2 + Ti4 +

c1 Oils etc.

3.8-4.0 850 mg/ L 270

fluent to the Newcastle Municipal treatment plant, the studies involved activated sludge treatment of the PIR effluent in admixture with sanitary sewage - in a 40:60 proportion. The studies confirmed that the effl uent could be readily treated in admixture with a san itary sewage but that the activated sludge did not settle as readily as one from purely sanitary sewage. This poor settleab ility was attributed to a fine precipitate of titanium hydroxide that accumulated in the MLSS - especially at long SRT values - until it interfered with sett lement. Experience elsewhere has shown that sy nthetic rubber plant wastes may be satisfactori ly treated by biological mean s. However the rates of biological degradation of suc h wastes are much slower than for a pure sanitary sewage and a greater contact time is required between the waste and the biota to achieve a sim ilarly hi gh degree of treatment. This prolonged contact time requirement is inconsistent with the use of conventional trickling filters and an activated sludge system operating with a long SRT (Solids Retention Time) and a long HRT (Hydraulic Retention Time) would be preferred. As the Municipal plant to which it was intended to pump the effluent is of the trickling filter type, it was decided after discussions with the Newcastle personnel that the process effluent should be treated on the Afprene sit e using the activated sludge process. The sanitary sewage flow generated on the site amounts to some 5-7 per cent of the process effluent flow. It was decided that as th ere was no real benefit - from a nutrient balance viewpoint - in treating the two flows together, the san itary sewage should be pumped away to the Municipal plant.

600 12 Trace 55 51 Trace 64

222 Presence

It must be stressed that there was very little data available as to the magnitude of the organic pollution parameters of COD and BOD. Consequent ly, the COD va lue presented in Table l represents the calculated va lu e assum ing complet e chemical oxidation of the organic compounds reportedly present in the various effluent streams, while the BOD has been based on the calcu lated COD and on reported relative biodegradability of certain of the organic compounds. The Table shows that the process effluent could be nutrient deficient if biological treatment were to be contemplated. The process effluent flow is estimated to average some 4 ml/ day for the entire project, with a peak flow of some 60 Li see.

3.3 Mineralised Effluent The mineralised effluent comprises those discharges which are inorganically contaminated and it is estimated that the daily flow cou ld amount to some 750 m 3 /day when the entire factory is in production. Some 50-60 per cent of the mineralised effluent flow originates from one source within the Carbide/ Acetylene plant with the balance being made up by discharges from the Demin Plant, Catalyst Plant and Isoprene Plant. It was estimated that the TDS of the Iola/ mineralised effluent flow would be in the I .0- 1. 5 per cent range, with the constituents being sodium chloride, sodi um su lphate , potassium chloride, calcium carbonate, calcium sulphate, ammon ium sulphate and ammonium chloride. The pH will be greater than 9.5. 4.0 FORM OF TREATMENT

4. I Process Effluent The use of physical-chemical methods of treatment using ultrafiltration followed by RO was investigated . However, in the light of the uncertainty as to the actual process effluent composition and the likely high capital costs it was decided to utilize biological treatment methods. Treatability studies were carried out on samples of effluent from an overseas PIR plant at the University of Cape Town under the gu ida nce of Professor Marais in early I 980. As it was, at that stage, the intention to discharge the Afprene ef-

4.2 Mineralised Effluent Consideration was given to the use of solar evaporation ponds for a period of five years during which time the mineralised effluent could be both quantified and qualified. A deci sion wou ld t hen be taken as to the eventual form of treatme nt. Calculations indicated that some 40 ha of ponds would be required and that as a result of poor permeability rates the ponds would have to have a synthetic lining. The costs of such a scheme (approx $SM) which would have to be written off after five years which prompted an investigation into alternative methods of treatment, namely RO, deep well injection and mechanical evaporation. Mechanical evaporat ion followed by a crystallisation stage was found to be most economically feasible and was further investigated. Multi-effect or multi-flash evaporat ion requires high steam and cool in g water inputs with low electrical energy input while mechanical vapour recompression evaporation requires a high electrical energy input with low steam and cooling water inputs. Table 2 summari ses the utility require111ents of various different multi-effect (ME) and mechanical vapour recompressed (MVR) evaporators for a 600 ton/ day throughput. TABLE 2. SUMMARY OF UTILITY REQUIREMENTS Utility

Cooling water (m3 / hr at 25 °C) Power installed (kw) Steam (tph)

Supplier A

Supplier B





Supplier C MVR

280 140 7 .5

92 592 2.0

540 89 5.7

82 1060 2.56

150 750 1.50

The investigation confirmed that in the Afprene co ntext where electricity was avai lable while stea m and cooling water was limit ed there was definite merit in installing a mechanical vapour recompression (MVR) evaporation installation followed by a crystallization stage. An overseas visit to operational installations in the U.S.A., Belgium and Israel took place in January/February 1981 and equipment was selected in March 1981 - to be operational by Ju ly 1982. 5.0 THE EFFLUENT PLANT Figure 2 shows the flow schematic of the process effluent and contaminated stormwater treatment facilities. 5.1 Contaminated Stormwater The flow in the contaminated stor mwater sewer is directed via an AP! type oil sepa rator to a balancing lagoon from where it is pumped WATER December, /984








- --

Figure 2. Process effluent and contaminated stormwater treatment. to th e eq ua li sa ti on basin th at forms a part of the process effl uent treatment seq uence. · The AP ! unit is 33 m long by 6 m wide with a depth ranging from 2.5 mat the outlet end to 3.0 mat the inlet. The unit was designed on an upflow of 2 m/ hr at a maximum flow of 390 m 3 / hr. It is equipped with a rotating cy linder o il skimmer and the skimmed oi l is co llected in the sump adjacent to the unit, from where it is removed for disposal. In the event of a heavy rainfa ll th e flo w through the AP ! unit will increase until after a preset time period (20-30 mins) the fl ow wi ll be automat icall y diverted to a channe l at the south of the effl uent plant side.

5.2 Process Effluent •

• • •

T he process effluent is treated in the following seq uence : Qua li ty and fl ow equa lisa tion in a 1500 mJ earth lagoon, lined with a 1. 5 mm thick HOPE lining and equipped wit h two 7 .5 kW floating aerators. pH adjustment using lime to attain a pH value of 8.5-9.0 . Caust ic soda could not be used on account of the relatively hi gh sodium presence in the process effluen t . Polyelectrolyte additi on, if necessary, just after lime a ddition . C hem ical clarification (12 m dia. x 3 m SWD) with recycle of chemical sludge to the lim e reactor. Activated sludge treatment in a 4650 m3 reactor (depth 3.5 m), equipped with six 22 kW floating high speed aerators - four of which are dual speed. SRT valu es of 25-50 days have been a ll owed for (MLSS val ues 3500-6000 mg/ L). Recycle rat ios 0.5-1.5 . Fina l clarificat ion with the uni t being sized on very co nse rvative design data ( 19 m dia. x 3.5 m SWD). Fina l polishing by reed beds having a retention per iod of so me IO days and MINERALISED depth of 0.5 m. E.FFWENT

5.3 Mineralised Effl uent !"igure 3 sh ows the flow schematic of the mineralised effluent treatment faci liti es and includes: • Qua li ty and flow equalisation in two 14 000 m 3 earth lagoo ns , lin ed with a 1.5 mm thick HOP E linin g a nd equipped with a herringbone unde rdrai nage sys tem. • Neutra li sation to pH 6.8-7.5 in a two stage dosing in sta llation with int erstage sett lement. Su lphuric acid is automatica lly dosed to both stages, wh il e caustic soda is manually dosed to the fir st stage. • Eva poration and crysta lli sa ti o n . The co nd ensate (product water) is pumped to the reed bed s in ad mi xture with the treated 26

WATER December, 1984



process effluent. This was a temporary arrangement in case there was excessive organic presence in the co ndensatt but recent experience has con firm ed tha t th e qual ity is so hi gh that steps will shortl y be ta ken to route it back to the facto ry. The crysta ls are bagged and stored on site until a suitable di sposal site is estab li shed. The evapora tion in sta ll ation consists of two hori zo ntal tube , low temperat ur e Mechanical Vapour Reco mpression (MYR) co nce ntra to rs, des igned to operate either in parallel or in seri es, with t he la t ter mode being the design for the anticipated eventua l feedstock composit io n . The evaporated li quor then passes to a conventiona l forced circ ul at io n c r ys ta lli zer with fin a l crys t a l dewatering being ac h ieved throu gh a decanter-type so lid bowl cent ri fuge. Design throughput is 750 mJ / day at 1.5 per ce nt TDS.

The feed liqu or is introduced to the concentrator through nozzles above the horizontal tube bank. As the liqu or cascades down the tube bank, a port io n fla shes to va po ur sin ce th e vapo ur compressor, th rough it s sucti on, provides a press ure lower than the liquid-vapo ur equi librium p ressure of the co ncentrate film on th e tubes. The vapour generated passes th rough a demistor to the inlet of the compressor where it is compressed and di sc harged into the tubes at a press ure sli gh tl y higher than equi lib riu m pressure. The vapour conden ses in the tubes, giving up its latent heat of co nd ensatio n through the tube wa lls to the conce ntrate flo wing down on the outside , thus providing th e heat required to eva porate add ition a l co ncentrat e. Th e co ndensate in the tubes di sc harges from th e tube end s int o a trough and is piped to an internal compartment which is co nnected to the condensate pipin g outside the concentrator. The rema inder of t he fa llin g conce nt rate leaves as a concentrateslurry from the bottom of t he vessel. Non-condensib le gases (N CG) re ma inin g after co ndensation of the process vapour are co ntinuall y removed from the co ndensate com partment by a vacu um pump.

5.4 Slud ge Disposal Sludge is generated from th e chemical clarifier and from th e activated sludge system . Both slud ges are pumped to a 10 m dia. gravit y thi ckener where consolidati on occ urs, with th e thi ckened sludge (at 4-6 per cent OS) bein g tran sferred to a stirrt!d 50 m3 sludge ho lding tank which serves as a surge fo r a solid bowl, decanter type centrifuge designed for a sludge throughput of 8 m3 / hr. Facilities are provided to dose polyelectrolyte to the feed to the ce ntrifuge a nd it is expected that a 25-3 0 per ce nt OS cake will be produced when lim e is being added at the pH adjustment stage (re fer to 5.2), dropping to some I 5- 17 per ce nt OS when th e slud ge feed is







Figure 3. Mineralized effluent treatment facilities.

predominantly waste activated sludge. The cake is transferred by conveyor belt to a stockpil e just outside the building from where it is loaded into an agricultura l manure spreader and spread on an area of land in the NE corner of the overall project sit e. Centrate from the centr ifu ge is returned to the activated sludge process. Sludge production when all areas of the factory are in production is estimated as 17 ton / day (as 25 per cent OS sludge). The method of sludge disposal will be reviewed in the next couple of years. S.S Costs The overall cost of the effluent treatment faci liti es was approximately $6M, of which approximately $2.75M was associated with the mineralised effluent plant. 6.0 PLA T START-UP 6.1 Contaminated Stormwater and Process Effluent

The evaporators and crystallizer have experienced mechanical problems which in general have been speedily rectifie~ by the suppliers. Modifications to the pipework, such as routing a start-up steam line 10 the second concentrator and repositioning of in -li ne filt ers have enabled the present day mineralised effluent to be effectively handled, either with one or both of the MVR Concentrators in operation. The plant was shut-down in December 1982 when the mineralised effluent storage lagoons were empty . Table 4 shows the characteristics of mineralised effluent fed to the evaporators as well as the quality of condensate produced. TABLE 4. MINERALISED EFFLUENT CHARACTERISTICS Analysis



TDS Ca Hardness CL

4976 172




Apart from a misaligned mixer shaft and one or two other < I ss mechanical and electrical problems the equipment in sta lled has 3071 3 S04 operated as intended. 2 TOC The initi al organic load introduced into the activated sludge plant 1579 NIL a derived from the SBR / PBR plus associated utilities and is only some P04 <I IO per cent of that eventually expected. MLSS values are thus low K 40 NIL (100-200 mg/ L) and no SRT control has yet been implemented. Orthophosphoric acid is added to the influent to the act ivated sludge 7.0 ACKNOWLEDGEMENTS reactor. This paper would not be comp lete without an acknowledgement Serious problems were encountered with ash from the boiler plant of the collaboration, enthusiasm and plain hard work of the effluent which found its way via the API unit sludge pump into the chemical plant Superintendent, Mr. Gert Saayman. clarifier. The chemical and thickened sludge pumps are of the progressive cavity type and the ash serving as an excellent grinding paste, thus giving rise to accelerated and unnecessary wear. This problem K. BARR CONTINUED FROM PAGE 23 was erad icated through the construct ion of ash traps at the boiler plant. Once the ash was removed from the system, the sludge from the tion faci liti es P. L.C. contro l of sludge heating and mixing is desirable chemical clarifier consisted mainly of rubber crumb, silt, etc. and this to enable experimentation to maximise sludge gas production. material was fed via the thickener and sludge storage tank to the centrifuge over a few hours each week . A spadeable cake is produced but 4.6 Power Generation the operation of the centrifuge has sti ll to be optimised (in terms of With the decision to install power generation faci lities, a comm itspeed differenti al, etc) for this type of sludge . Tab le 3 summ a rises certain of the treated effluent characteristics ' ment follows to install an adva nced contro l and monitoring sys tem. Hundreds of digital and a nalogue alarm states need to be monitored over the last three months of 1982. and automatic control start up, shutdown, synchronisation and waste TABLE 3. EFFLUENT CHARACTERISTICS heat disposal is required. Sequence, modulating and high level computer is required for operation of a power station.' Month (1982)


pH TDS mg/ L COD mg/ L OA mg/ L SS mg/ L P04




4. 7 Tertiary Treatment

7.4 283 38 2 22 1.7

8.1 216 37

7.5 316 37 2 5 0.9

Sequence contro l may be employed for the operation of rapid sa nd filters . An automatica ll y controlled bacltwashing cycle would be initiated by a pre-determined head loss through the filter. A modulating control system would be the most economic method of controlling chlorine dosing and could be established to relate dosing to effluent flow rate. On line continuous ch lorine residual ana lysers co uld be a more efficient system of contro l.

5 18 0.9

The comm issioni ng of the PIR plant this year in creased the load (both hydraulic and organic) on the treatment plant but unfortunately the serious drought in the area curtailed the operation of the PIR plant and it was shut down shortly after start-up. Reports confirm that the treatment plant handled the increased load as intend ed although it was once 'knocked-out' through a high pH. 6.2 Mineralised Effluent The mineralised effluent has been mainly regenerant from the Demin Plant and has characteristics vast ly different from the effluent that will eventually be fed to the evaporators in that the TDS is only some 0.5 per cent and it consists mainly of sodium su lphate. Althou gh the regenerant has a pH in excess of 9.0, it s buffer capacity is far lower than wi ll be the case when the Carb id e-Acetylene plant discharges to the mineralised effluent sewers. This has resulted in the su lphuri c acid pumps having to operate at the limit of their turndown range which in turn has led to problems in maintaining the pH of the feed to the evaporators in the desired range. When it is realised that an off-spec pH value will close down the evaporators feed pump (after a time delay) it will be appreciated that th is was quite a prob lem. Hard graft by process, operating and in st rumentat ion personnel ha ve to a large extent a ll eviated the difficu lties but it is st ill an a rea that requires close surveillance.

5.0 CONCLUSION Lower manning levels and improved¡ co-ordinated operation of the whole process are the principal advantages of centralised control and supervision. The centralised access to plant and process information allows sign ifi cant and related process variables to be grouped, displayed and logged in su itabl e formats. Operating events, process variab le deviation and alarms in the sequence they occurred can be logged such that an accurate analysis of process changes and plant failures can be made. Derived inputs such as efficiency of the various processes with other specialised information can be compiled and presented in a management report. Automatic process control with supervisory computer control and data coll ection is essent ial for efficient operation and control of large wastewater treatment plants. 6.0 ACKNOWLEDGEMENTS Much of t he data presented was obtained from experience at the Luggage Point Wastewater Treatment Plant. This plant is the largest wastewater treatment facility operated by the Brisbane City Counci l. Appreciation is extended to officers of the Department of Water Supply and Sewerage, particularly Mr B. P. O'Connell, Chief Engineer and Manager and Mr M. L. Lever, Manager, Luggage Point Wastewater Treatment Plant for assistance received. WATER December. 1984


TRENDS IN SEWAGE TREATMENT THE FUTURE FOR VICTORIA J. A. Crockett I. INTRODUCTION Thi s paper sets out a perso nal approach to design and operation of sewage treat ment plants and summari ses current trends, developments and needs, particularly in Victoria. Current trends are bein g hea vily innuen ced by the high cost of capital, high operating costs, increasing public awareness of water polluti on as well as increased pressure to reduce rates and charges . Everybody wants more for less . This is not always an unreasonable want and is encouraging better design and operation . The paper is divided into four major sectio ns dealing with: • plant operability and safety • secondary treatment ; with emphasis on activated sludge, nitroge n and phosphoru s removal, and lagoons • reuse • plant operation and optimisation, data aquisition and process ing Sludge treatment and di sposa l is not covered as it is a major subject on it s own. Finally some conclusions as to trends in sewage treatment particularly in country Victoria , are set out. 2. PLANT OPERABILITY AND SAFETY However experienced and knowledgeable a desig ner is, he will design into a plant several features that make it either difficult or impossible to operate, or unsa fe because a designer has to consider so many factor s in add ition to operabi lit y and safety that these two important factors do not achieve the emphasis they shou ld. In this field the water indu stry lags behind the chemical process industry which was forced by a se ries of major di sas ters to introduce formalised hazard and operability assess ments as a final step in the design process. Traditional checking of calculat ions and drawings achieves little in regard to operability and safety. The need is for an engineer with experience in both design and operation, who is thoroughly familiar with the processes in a particular plant to start-up, operate, and shut down the plant, simu late fai lures and walk a ll over th e plant - all on paper. This engineer will not be as constrained as the designer by co nsiderations of cost, site factors, alternative processes or equipment, contractua l matters or deadlines. He wi ll accord in gly be more lik ely to pick up defects . Such a procedure is not all that cost ly, an average wastewater plant (20 000 ep) could be checked over in a week's work. Design changes could cost a little more. Money spent here will avoid expensive cha nges during construction or operation, and will protect the designer and operating authorit y against damage claims. 3. SECONDARY TREATMENT 3.1 General Secondary treatment in volves the removal of the non-settleable contaminants in wastewater and di sin fection. Thi s paper does not cover primary treatment becau se its performance is never the major issue as is secondary treatment and because it is inadequate as the sole treatment process for the great majority of cases in Victoria. Seco ndary treatment really mean s biological treatment beca use chemically assisted wastewater treatment has proved expensive and is rarely justified. Over the last decade there has been an almost total move to activated sludge treatment and th e installation of biological filters is now uncommon in Au stralia. Where effluent of a high quality is not required, lagoon s remain the cheapest and most reliable form of treatment for sma ll communities . Land treatment is talked of but rarely adopted a lthou gh it cou ld we ll be appropriate in some cases. Anaerobic bio logical treatment is being app li ed to indu strial

Jona Ihon Crockell is a Chemical Engineer wilh Gu11eridge Haskins & Davey PI L, Consulling Engineers, Melbourne. 28

WATER December, 1984

wastewater. It is the only economic form or biologica l treatment prior to sewer discharge but alone will not produce the effluent quality necessary for di scharge to the env ironment. It is not possib le to cover all the above forms of treatment in this paper which will accordingly concentrate upon activated sludge, which is generally the most appropriate process in Victoria, producing the best effluent, and upon lagoons which are suitable, where 20/ 30, or better, effluent is not req uired.

J. A. Crockett

3.2 Features of a Well-Designed Activated Sludge Plant 3.2.1 Sludge Separation It is questionable whether our designs for activated sludge plants have improved since the I 930's. More people may have a better understanding of the process, but often designers are not included. The major problem with all activated slud ge plant s is the separation of the sludge from the treated wastewater. The process depends on maintaining a large population of micro-organisms within t he aeration tank to quickly metaboli se incoming biodegradab le material. To make the process work, the activated sludge mu st settle fast and the clarification system must be adequately sized. Much is known about the requirements for improved sludge settleability but designers too frequently disregard pr are unaware of this body of knowledge. (Chambers and Tomlinson I 982). The approach is often to provide a rectangular box as an aeration tank and hope for the best. Most of the methods which improve sludge settleability involve subjecting the sludge at some stage in it s travel through the aerat ion lank to surplu s concentrations of necessa ry nutrients and oxygen. Thus plug-flow, and race- track, aeration tanks give better sludges than complete-mix tank s. A small tank at the start of a complete-mix tank will provide a similar effect and should be prtvided. The reason this is so is that the fi lamentous bacteria, whi ch are the usual ca use of poor sludge settleabilit y, have a hig h surface area in relation to their vol ume compared to bacteria in den se, fa st-sett ling floes. Thus filament s get fir st bite at the available nutrient s and oxygen, and where these materials are in limited supply, insufficient wi ll be left for the floccu lant bacteria. Filaments will then predominate. Clarifiers have in the past been grossly undersized. Solids loading rather than hydraulic loading is usually the deciding factor and longavailable hindered settling theory is only now bein g successfu ll y appli ed in clarifier design and operation. Ge nerally al peak hourly flow, solid s load should not exceed about 6 kg/ m' .hr. 3.2.2 Aeration Undersizing of aerat ion systems has also been com mon and there are still several text s in common use which give misleading low oxygen requirements. It is very easy lo measure oxygen demand of activated sludge and such measurement s allow preci se design. More mu st be done to control aeration automatically. A study by USEPA some years ago showed definite energy sav in gs in plants with automatic contro l. Good control of aeration becomes essentia l where biological nutrient removal is incorporated. One sound method involves a continuous measurement of respiration rate and this is being don e on severa l plants t hrou ghout the world. As well as automatic control it is necessary, in these times of rising energy costs and decreasing availabi lity, to choose an aeration system which is energy efficient. Table I below sets out typical energy consumptions in terms of kW .hr per kg of BOD treated. The range in consumption is wide due in part to ineffi cient control,

TABLE I. RANGE IN AERATION ENERGY FOR ACTIVATED SLUDGE Plant • USA Plant s-N itrifying -Non nitrifying • Nitrifying/ denitrifyi ng plant in Vienna Mornington S.A. Fine bubble with separate aerobic digestion

kW.hr/ kg BOD Removed

0.64-1.76 3.69-3.75 0.53-0.98 1.6

• Crockett, 1979.

to inefficient aeration sys tem s, and to unwi se choice of control set point s. It is essential to a im at the lowest DO wh ich wi ll allow proper plant operation and encourage good sludge sett leability. Separation of aeration and mixing is a nother way of reducing energy use. 3.2.3 Needs and Developments

Whi lst none of the above comments represe nt any ad va nce over the last seve ra l decades in activated sludge plant design and operation, they are still not all applied in the d es ign of new plants or the upgrad ing of existing plants. T h us, the inco rporation of such features is essential if our plant s are to improve. New development s in the act ivated sludge process now bein g ap.plied include biological nutrient remova l, which is d ea lt with in the next section, and some developments in the use of oxygen for aeration dea lt wit h in the sec tion on innovative processes. 3.3 Nitrogen and Phosphorus Removal 3.3.1 General

Some of the most exciting developments in sewage treatment in the last 20 years have been in the area of nitrogen and phosphorus removal. Development has occurred in two separate directions: in North America and Nort hern Europe along the physica l/ chemical path, and in South Africa and Central Europe along the bio logical path. Australia has tended to follow North American trend s and unfortunate ly we are now fin ding, as are t he North Americans, that the biological path is far less costly. 3.3.2 N itrogen Remova l

It is doubtful we will see much more use of ion exchange, ammonia stripping and separate denitrification for nitrogen removal, except per haps where disc harge to an impoundment without much dilution is to be practiced which would require very low nitrogen limits. Singlesludge ni t ri fication a nd den itrificat io n is the simplest, cheapest and most effective nitrogen removal method available. The plant configurations in which bio logica l nitrification and denitrification can be carried out are many . However one of the simplest is an aeration tank having a "racetrack" now pattern and with separate clarifier. A "racet rack" now pattern is provided in the now common ox idation d itch and in the "Carrousel". This configuration has several advantages over tho se comprising tanks of fixed aerobic and anoxic vol ume, namely: a very large internal recycle of nitrate is provided (more than 20 times the plant innow) by the circulation around the race-track , thi s bein g necessary to ensure maximu m de nitrification. a race-track easily achieves thorough mixing and requires only about 8 watts/ kL compared to about 15 watt s/ kL in a rectangular tank. T hi s low energy m ixing a lso provides the internal recircu lation. because load on a plant varies diurnally, and becau se rates of reactio n vary seasona ll y with temperature, it is desirab le to have variable vo lumes for the aerated and anoxic zones. This is provided eas il y in a racetrack by vary in g aeration but cannot be provided in compartmented tank s. With t hese advantages it is not surprising that the racetrack tank has been the m ost co m mo n ly used co n figurat io n for new plant s in Australia in the last five years. Even with the right tank configuration, nitrogen removal will not be good if other necessa ry con diti ons are not met. Firstly it is essential to have the correct balance between BOD and nitrogen. Fortu nately the ba lance in un sett led raw sewage is normally correct but thi s mea ns that prima ry sedi men tation shou ld not be used if nitrogen removal is required.

Secondly, the supply of oxygen must be carefully co ntrolled since over-supply will reduce denitrification (denitrifiers a.ily use oxygen in nitrate when free oxygen is unavailable) and under-supply will prevent full nitrification. An aeration control system based on measuring respiration rate is the best method. The right conditions for biological nitrification and denitrification ca n be supplied in a fill and draw system but consistently good nitrogen removal is difficult. When nitrogen removal is required, primary sedi mentation is undesirable and extended aeration or separate aerobic di gestion is more appropriate than anaerobic digestion. Whilst this increases electri ca l energy consumption, this increase must be put in perspective. Firstly, sewage treatment requires about 5 watts of installed power per perso n. Th is is a minute fraction of average domestic power requirements and an even sma ller fraction of the power used by a communit y. Optimising sewage treatment energy use will therefore save little energy overall. Secondly, some well-controlled extended aeration plants require less than 5 watts per person, whereas ~ome plants with digesters ca n consume far more due to inefficient equipment and poor control. At current interest rates the econo mics of anaerobic digestion are unfavourable. Against thi s, however, must be balanced the potential energy recovery as methane (if a simple use for it, such as sludge pasteur isation, can be found) and the fact that a naerobically digested sludge is more ea il y dewatered. Finally it mu st be emphasised that if an activated sludge plant nitrifies (as most do in Australia even if this was not intended) it is probabl y economic to denitrify, even if thi s is not required for emuent quality reasons because some of the oxygen used in nitrification ca n be recovered, hence sav ing electrical energy. Furthermore, introduction of an anoxic tank for denitrification in a nitrifyi ng plant will control filaments a nd will prevent rising sludge in the clarifier. This on it s own would be sufficient justification in view of the fact that poor sludge settleability is the major reaso n for plant upsets. In fact, the tendency now is to obtain the highest quality efnuent possible from an activated sludge plant and the way to do this is to operate at a low Food to Micro-organism ratio at which nitrification is bound to occur. 3.3.3 Phosphorus Removal-Chemical or Biological?

It is certainly very simple to dose with chemicals for phosphorus remova l, particu larly with cheap waste pick le liquor from steel finishing. The Canberra plant uses lime and pickle liquor continuously. The Sydney Water Board is about to start pickle liquor dosing on a significant sca le in the Hawksbury Valley. Several other authorities around Australia whose plants discharge to inland waters are also ·• using or cons idering chemicals. Such addition of chemicals to a plant can improve effluent quality generally and fears of overload of sludge handling facilities are rarely borne out in practice. Biological phosphorus removal is however a strong contender and prerequisites for it are described below. The majority of development work on this process has taken place in South Africa but useful contributions have been made by the Americans and Israelis. Whil st argument continues on the chemistry, biochemistry and microbio logy of the process, the conditions under which biological phosphoru s uptake occurs are now fairly well understood. The key is to regular ly subject the activated sludge to a period in the absence of air and nitrate , this period being of such a length as results in about 15 to 20 per cent of the mass of sludge at any one time being so subjected. A mode l of the effect of th is anaerobic ho lding period in removing phosphorus follows although it is st ill open to question: several types of bacteria, including the common non-motile aerobic acinetobacter group, appear to have the ab ili ty to grow under anaerob ic conditions by drawing on accumulated reserves of pol yphosphate for energy. By subjecting t he sludge periodically to anaerobic conditions, such bacteria are given a competitive advantage over strictly aerobic, no nphosphate-accumulating bacteria. Thus the proportion of phosphateaccumulatio n bacteria in the activated sludge is increased resulting in more phosphorus in the waste sludge. The presence of nitrate in the anaerobic tank will allow the non-phosphate-accumulators to grow by denitrificat io n hence removi ng the competitive advantage of the phosp hate-acc umulators. To provide a fully effective anaerobic tank requires several condit ions to be met, pri ncipal among them being the complete removal of nitrate from any feed to the anaerobic tank. Equally important, is that WATER December, /984


the concentration of readily biodegradable material in the anaerobic tank be sufficiently high to allow the phosphate accumulators to grow rapidly. If this is not provided, their competitive advantage will be of no use and they will not increase. A final condition to be met is that waste sludge must be withdrawn from a part of the plant where the phosphorus-accumulators contain a maximum concentraton of phosphate. Withdrawal of mixed liquor from the aerated part is preferable although phosphorus will stay bound in the return sludge flow because there is little degradable material left. In the anaerobic tank, phosphorus is actua ll y released as a result of the metabolic process which the phosphate accumulators rely upon. It is by the withdrawal of phosphate-rich activated sludge that phosphorus is removed from the effluent. By this method it is possible to remove phosphorus down to the levels obtainable with chemicals although this is rarely achieved in practice. This is because it is difficult to meet all the conditions, particularly with some physical arrangements which have been proposed such as the well publicised "Bardenpho" process . Once removed, this phosphate rich sludge must be carefully handled. Holding in an anaerobic state for more than about four hours will result in release of phosphate to the liquid which in most cases will be returned to the plant. Gravity sludge thickening can be used but would require very careful operation. Dissolved air flotation thickening wou ld be safer. Possible sludge handling approaches when bio logical phosphorus removal is used include: irrigation of all sludge and associated liquid dissolved air flotation thickening and anaerobic digestion, the liquid fraction after digestion being irrigated or treated with chemicals to precipitate phosphorous direct dewatering of waste sludge with minimal storage time lagoon disposal or storage with chemical treatment of supernatant. Whilst some of these methods involve chemical treatment, the doses used are somewhat lower than those for full chemical phosphorous removal. Furthermore, lime can be used rather than an iron salt or alum and the stream to be treated is steady rather than variable. To ill ustrate how the conditions necessary for bio logica l phosphoro us remova l can be provided it is worth describing a full scale applicat ion at Penr ith where a biological nitrogen and phosphorus removal plant is current ly under construction. A plant layout is shown in Figure I. The plant wi ll comprise a "Carrousel" with the anaerobic tank being added along one side of it. The latter will be mixed by means of submersible mixers. Aeration of the "Carrousel" will be controlled to match oxygen input to the respiration rate by means of a microprocessor based control system into which a respirometer signal will be fed. This system should ensure complete nitrification / denitrification. Raw sewage and return sludge will be fed to the anaerobic tank and the return sludge pump station has been designed to avoid drops in level which could dissolve oxygen. Cross-connectors between the anaerobic tank and the "Carrousel" wi ll be prov ided to a ll ow later introduction of the University of Cape Town (UCT) process, shou ld nitrate be present in the return sludge. In this mode, return sludge wou ld go to the "Carrousel" and raw sewage to the anaerobic tank. A submersible mixer would be used to divert a substantia l flow from the anoxic zone of the "Carrousel" into the anaerobic tank. In summary, enough is known to design a plant capable of achieving biological phosphorus removal. However, careful operation will be required, and in this area we have some way to go. 3.4 Recent Examples of Activated Sludge Plants in Victoria

Some of the ideas outlined in the previous sections have been implemented on several new act ivated sludge plants in Victoria. At Dromana-Rosebud an aerated lagoon plant has been converted to a 15 ML/d nitrify ing and denitrifying plant by add ition of a clarifier and provision of aerated and anoxic zones in two sloping-wa ll ed, concrete lined lagoons . At Mornington a denitrification zone is to be incorporated into an existing fine-bubble nitrifying aeration tank. Anaerobic digestion and sludge dewatering is also being added to increase plant capacity to 12.6 ML/d . An intermittent activated sludge process has been implemented at Cranbourne to ultimately treat 5 ML/ d in an existing rubber lined 30

WATER December, 1984






-7 I I I I



Figure 1 -

Penrith Biological Nitrogen and Phosphorus Removal Plant.

lagoon. An intermittent activated sludge plant of the Pas veer Ditch type is being constructed at Gisborne to treat 1 ML/ d. Later expansion of this plant will be achieved by adding clarifiers . 3.5 Lagoons

Of the 100 sewage treatment plants in Victoria, almost half are lagoons, incl ud ing some large systems at Werribee, Dutso n Dow ns, Shepparton, Swan Hill, and Wangaratta. There is no doubt that in country areas lagoons are by far the cheapest way of providing sewage treatment. Capital cost is about half that of a biological filter or activated sludge plant a'nd operating cost can be negligible if mechanical aeration is not required. Lagoons can produce a reasonable quality effluent. However, since they mostly rely on algae for oxygen supply, quality varies with the season and with cycles in algal growth. Effl'Uent from lagoons is ideal where disposal by evaporation or land treatment is possib le, and it is satisfactory for discharge to surface waters in some cases. If a simple, nuisance-free and low-cost method of algae removal could be found, then lagoons wou ld see even wider use. Such a method is not ava il ab le at this stage and research in the area is less energetic than it might be. Chemical coagu lat ion is a sure but expensive method. Biological control, for examp le using Daphnia, is theoretically possible but the ecology is insufficiently understood fo r it to be controlled. Passage through rock filters or natura l gravels which cut out light and allow sedimentation will certain ly remove algae but the life must be limited and odour has been reported. Grass filtration or passage through macrophyte ponds may be successful but dense shade is necessary requiring careful planting and cropping. Lagoon designs can be improved. Primary lagoons must be relatively large and the load evenly distributed to ensure facultative operation. Recirculation from later lagoons can increase the possible load on a primary lagoon by more than 50 per cent. Depths greater than 1.5 meters seem to encourage high su lph ide levels and poor mixi ng. . Where su lphate leve ls are high, sudden loss of facu ltative operat ion can occur due to periodic rises in sulph ide which can inh ib it algal growth and increase oxygen demand. Such prob lems have been noted at Swan Hill and at Whyalla, Sout h Austral ia. Weather condit ions also have a major effect. Still conditions reduce mixing and enco urage stratification and more problems are experienced where lagoons are sheltered. Mechanical mixing using very low energy input can be used during such periods. Aerated lagoons save area at the expense of energy cost. Completely mixed aerated lagoons with short detention times of 24 to 72 hours are very effective and have been used successfully at Cranbourne a nd

In late summer, blooms of nitrogen-fixing blue-green algae regu larly occu r, and result in odo ur when their populations start to decline. There is a trend to increasing t he number of lagoons in series since this reduces short-circuiting. Three should be a minimum and five is a preferable number. Use of anaerobic lagoons is risky although their operation without excessive odour nuisance is possible. They are certainly effective and cheap. For industrial waste, we might see the use of covered anaerobic lagoons equipped with gas burners, or of anaerobic rock filters. Use of maturation lagoons for disinfection is already fairly wide and overcomes the safety and undesirable environmental effects of chlorination. Deeper maturation lagoons reduce algal growth, although at the expense of lessened UV sterilisation. Design of maturation lagoons could be improved, and shorter detention times than the present 15 to 30 days could probably provide an acceptab le standard of disinfection. A realistic assessment of the risk of transmitting enteric disease via discharge of non-disinfected efnuent would also be worthwhile. 3.6 Innovative Processes 3.6.1 The Need for Innovation

Use of novel forms of intensive biological treatment will increase as cost pressures increase. We have already seen increasing use of cheap constru ction methods, such as sloping-wa lled earth tanks, often rubber or gunite lined. These are often called temporary but in reality they have reasonably long useful lives. There should be more experimentation on existing plants which we are often keen to abandon. On biological filter plants built in the 1950s, increased recirculation, new humus tanks and recycling of humus sludge over the filters might well great ly improve effluent quality. Such modifications offer potential savings but require lengthy and expensive engineering. State support of experimental designs wou ld also encourage the desirable trend to the novel, since it would spread the certain risk of occasional failure more widely. Use of anaerobic treatment, such as anaerobic nuidised beds and the Upnow Anaerobic Sludge Blanket (UASB) (used for hot, strong industr ial wastes) is being tried for cold, dilute, domestic sewage with some success . Oxygen activated sludge has been used extensively in the USA where oxygen price is low. In Australia relatively high oxygen prices have limited its use. The advantages of using oxygen include high mass transfer efficiency, which enables the operator to run at a higher mixed liquor suspended so lids and resu lts in an overall energy efficiency simi lar to that for the best atmospheric air aeration system. The ability to run at a high mixed liquor suspended solids enables use of smaller aeration tanks which is important where there are site constraints. Use of oxygen also results in little emission from the aeration tank and therefore decreases odour production. Odour production from an aeration tank can be a problem in high rate plants operation at FM ratios above 0.5 sin ce with such FM's not all volatile organic material is degraded before it can be released to the atmosphere. The innovative Enviroshield process developed by C IG involves treatment by activated sludge in a single tank. The tank comprises a central phase separation zone to wh ich oxygenated mixer liquor is returned and an outer annular activated sludge and clarification zone. A trial of this process is being carried out for the Municipality of Clarence in Tasmania at its Rosny plant. This plant is situated on a steep rocky river bank and space for expansion is severely limited. The plant effluent requires upgrading to a 40/ 60 standard which the Enviroshield process should achieve. The plant has now been in operation for several months and activated sludge is present and most of the time effl uent is relatively clear and within the 40/ 60 specification. Whilst oxygen costs will be high, capital cost is minimal. In this case the plant was installed in and around an existing primary sedimentation tank for a cost of some $ 100 000 for 13 000 persons. Rising main and gravity sewer oxygenation is also now common and from thi s has developed the idea of in-main treatment. In N.S.W., GlC has run trials at Boulder Bay enabling a primary clarifier at the end of a series of rising mains to produce a 40/ 60 effluent. 4.0 REUSE There is scope for increased reuse in Victoria of treated effluent Dromana-Rosebud. They are less subj ect to problems than partiallymixed aerated facultative lagoons.

(reclaimed water). Reuse to date has been inhibited by lack of coordination between, and interest of, water su))i)ly and sewerage managers. The 1983 drought encouraged greater reuse. Of the total available reclaimed water resource in Victoria, 5. 7 per cent is presently reused or 31 per cent if Werribee is included (but Werribee is primari ly an example of disposal of raw sewage). About 78 GL/ annum from the Carrum plant represents the major potential for reuse. The cost of piping Carrum effluent to the Latrobe Valley, or its distribution for reuse by industry, agriculture and for aquifer recharge in the Kooweerup basin/ Mornington peninsula area wou ld on ly be marginally higher than the cost of duplicating the existing outfall . Thus a useful resource would be provided in areas where alternative suppli es would be far more costly. Reuse by industry has an important advantage over reuse for irrigation in that demand is relatively constant and therefore all wastewater can be disposed of. Whilst treated wastewater will not be of suitable quality for a ll industrial uses, the quality requ irem ents for different uses vary widely and are in any case dependent on ,vater cost and process operating costs. A major potential for reuse is for evaporative cooling in the Latrobe Valley and the technology of reuse for this purpose is well understood. In other areas, reuse for summer irrigation wi ll reduce demands on water resources and must be encouraged. The standard of plant operation must be improved to enable reuse. Also the pub li c must be educated to accept reuse as a means of reducing water rates. Water managers must recognise the potential of reuse as a means of delaying or avoiding expensive water harvesting schemes. Treated wastewater is a particularly reli able source. 5.0 PLANT OPTIMISATION

Various studies in the USA have shown that the n:Jjor reason plants fail to meet performance criteria is poor operation. Selection of better (and hence more expensive) operators, and better training are essenti al and operators must be afforded the status befitting controllers of major processing plants. Victoria leads in Australia with operator training but we still have a long way to go. Operators also need yardsticks by which to gauge plant performance. Currently designers are insulated from operators by the consultant / contractor/ authority system in Victoria. Designers don't get feedback about design deficiencies and about improvements developed by operators, or the opportunity to analyse operating data; and operators are not kept in contact with developments or guided by the often broad feel a designer has for possible effi'ciencies of various processes. Operators tend to quickly become set in their ways. As long as their plant is working well they rarely have an interest in making it work better or more efficie ntl y. For examp le, !in extended aeration plant can be operated to consume less than l kWhr per kg of BOD load. The majority of activated sludge plants consume more than this, often up to 3 kWhr/ kg BOD. We need to constantly set targets, check whether they are being met and if they are not, determine why. Operating methods also need improvement. It is on ly in recent years that operators of sma ll plants, including package plants, have been provided with basic test equipment and instruction as to how to use it. Even when such eq uipment and instruction is ava il ab le it is common for operators to slip into trial-and-error operating techniques rather than to use a scientific approach. Trial-and-error requires less mental effort and less time at a desk, but when things go wro ng, it is the slowest way to re-establish operation. The keeping of plant records is also an area where operators need to improve. Record keeping tends to be dominated by the needs of Authority accounting systems. It is very common to be to ld of power and chemicals in dollars rather than in actual quantities. Proper records require more desk work, and knowledge of the plant processes and equipment. The rewards are a better understanding, and a history which a ll ows problems to be identified and so lved with less time, worry and effort than if records are poor. To enable an operator to keep proper records, he must have a well set out operating manual, which needs regular review. Such a manual shou ld explain the theory of the process, the particular features of his plant including design loadings, and unit sizes and capacities and provide him with a fault diagnosis section set up for quick reference. It must set out a monitoring and record keeping system and a preventative mainteriance programme and include basic safety instructions and emergency procedures and include all equipment data from manuWATER December, 1984


facturers. Such a manual, while costl y, should be included with every design whether it be a new plant or modifications to an old plant. In st rumentation mu st be thought full y selected a nd placed, and provided where it s ou tput wi ll be use ful. The need for th e measurement mu st be im pressed on the operator and ·usefulness demonstrated. Onfy then wi ll t he operator have the in centive to keep it worki ng. There is a trend in the USA for companies who design and construct plants to a lso operate them as a tota l contract package. The owner meets the capital cost and pa ys an ann ual charge. Thi s development result s from press ure for cost co ntrol and for better performance of pl a nt. Des igners and operators are then part of the same orga ni sation and effic iency of design a nd operation is essential if the compa ny providin g th e service is to remain co mpetitive . No doubt there are traps in such a sys tem but it also has des irable features. The silicon chip revolution in data- process ing offers man y ad va ntages in design and operation. Designers ca n use complex design models which are improvin g at a rap id rate and plant data can be mani pulated in an in sta nt into for ms use ful to designers a nd operators. The equipment is very reliable and not ex pensive. What in hibits full use of the eq uipm ent is interfacin g with people and processes. In struments are often poorl y se lected and install ed a nd operators unaware of th e ben efits . Software tends to be provided by a third part y with no knowl edge of the process, the plant , or the operators' requirement s.

continued use of lagoons for communities of a few thou sand, but impro ve ments to their desig n a nd operatio n. Some inla nd lagoon sys tem s may be aba nd o ned or a ugmented because a solution to the problem of algae is unlik ely to be found. • th e few new in stallations will be acti vated slud ge plan ts of the racetrack ex tended aeration type. • more emp hasis on improving plant performance by: coll ecting a nd ana lys ing operat ing data in some cases using microprocessors; mod ifi cation a nd augmentation; greater attention to operator select ion a nd trainin g and improved a ut omat ic a nd ma nual control of processes. • greater reuse of efflu ent for irri gation of pub lic open space in cou ntry a reas a nd possibl y for industry. • decreased use of chlorine for disinfection a nd shorter rete ntion times in maturation lagoons as better realisa tion of chances of in fectio n are developed . • where nutri ent removal is required , biol og ica l methods which a re now we ll understood. All of these trends are desira bl e and th erefor e to be encouraged . To ensu re max imu m bene fit from expenditure, resea rch and development in some areas should be better supported a nd the profession should place mo re emphasis on co-operative information excha nge. REFERENCES


C HAMBER S. B., and TOM LI NSON, E. J. ( 1982). ' Bulki ng of Activated Sludge -

The trend s in sewage treatment in Victori a in the com ing decade are li kely to include:



Prcve n1a1i vc and Remedial Method s' Ellis H orwood for the U K WR C.

C ROCKET , J. A. ( 1979). 'Use of the Oxidation Ditch as the Aeration Stage in Maj or Activa1ed Slud ge Plant s' A W\V A 8th Feb. Convention, Surfers Paradi se.



CALENDAR 1985 January, Arizona , USA Int ernational Co ngress of !AH. January 14-July 12, Birmingham, UK Water Reso urces Technology in Develop in g Cou ntries. February 11-14, Melbourne, Australia 'Polymer '85'. Int ernational Polymer Symposium. March, Jakarta , Indonesia 1st SE Asian Water Techno logy Ex hibition and Co nferen ce . April, Yellowknife, Canada Arctic Wat er Pollution Research . April 14-27 , Newcas tle upon Tyne , London Manage ment of Hazardous Wastes a nd Diffi cult Industrial Efflue nt s. April 15-19, Melbourne, Australia Eighth Australian Sympos ium on Ana lytica l Chemi str y. April 16-18, Coventry, UK 9th Pump T ec hn ology Conference. April 16-18, London, UK Trenchless Co nstruction. April 22-28, Berlin , Germany Wasser Berlin '85. April 28-Ma} 3, Melbourne, Australia 1st International and I Ith Federa l Conventi on, A WW A. May 6-9 , Burlington , Ontario Toxicit y Testing Using Bacteria. 32

WATER December, /984

May 14-16, Sydney, Australia H ydrology and Water Resources Sympos ium.

August 23-25, Jarrahdale, W. Australia Annual Congress, Au stra li a n Society for Limnology.

May 16-17 , Salzburg, Austria 6th Europea n Conference on Env ironmental Pollution.

August 25-Sept, 5, Townsville, Queensland, Aust. Fifth Afro-Asian Reg ion al Conference and Study Tour.

June 3-7, Bangkok , Thailand G ro undwa ter and Mineral Exp loration. June 9-15, Brusse ls, Belgium 5th IWRA World Co ngress on Water Reso urces. June 10-14, Alexandria , Egy pt 3rd Interna ti o nal Sym pos ium on Industrial a nd Hazardou s Wastes. June 10-15, Libreville, Gabon 3rd Congress of African Un ion of Water Supp li ers and I WSA Regional Conference. June 22-28, Washington DC, USA A WWA Annual Co nventi on June 24-28, Lausanne, Switzerland 15th Congress on Large Dams . June 27-28, Quebec, Canada International Symposium on E nvironmental Pollution . July 7-19 , Ankara, Turkey Karst Water Resources International Symposium . August 19-23, Melbourne, Australia Intern a tional Co ngress on H ydra ulic Research.

September 4-5, Geneva, Switzerland T echni cal Con ference on the Use of Microprocessors apd Microcomputers in Opera tional H ydrology . September 8-13 , Cambridge, UK 18th Congress of !AH- H ydrology in t he Se rvice of Man . September 10-13, Leuven, Belgium 5th Internatio nal Conference on C hemi stry for Protection of t he Environmen t. September 15-20, Lake Ru sseau, Ontario International Seminar on Acidic Precipit at ion. September 17-21 , Granada Interna tional Mine Water Association Conference. October 21-25, Tuscon, USA Arid Lands Today and Tomorrow. October 22-25, Maroochydore, Queensland Fourth Australian Soil Co nservation Co nfe rence '85. Nove mber 4-8, Kuala Lumpur, Malaysia First Asia n Water Technology Exhib ition.