Water Journal December 1987

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DECEMBER 1987 JOURNAL OF THE AUSTRALIAN WATER AND WASTEWATER ASSOCIATIONEXECUTIVE DIRECTOR P. Hughes Box A232 Sydney South 2000 (02) 269 6814FEDERAL PRESIDENT M. Dureau , Kent Inst rumen ts P/L P.O. Bo x 333, Caringbah 2229 (02) 525 28 11 .waterISSN 0310-0367Off icial Journal AUSTRALIAN WATER AND WASTEWATER ASSOCIATIONVol. 14, No. 4, December 1987FEDERAL SECRETARY G. Cawston Box A232 P.O. Sydney Sth., 2000. (02) 269 6157FEDERAL TREASURER J . D. Molloy, Cl- M.M .B.W. 625 Lt . Collins St ., Me lbourn e, 3000. (03) 615 5991BRANCH SECRETARIES Canberra, A.C .T. M. Sharpin , Willing & Part ., . P.O. Bo x 170, Curlin, A.C.T. 2605. (062) 815 811CONTENTS Viewpoint .... ....... .... . .. .. ..... . .............. . . . ....... .5Association News, Views and Comments . ............ .. ... . ..... .6Environmental Effect of Canal Estates in Australia -P. M. Nuttal and 8. J. Richardson . ........................ .14The Dirty Dollar and How it's Laundered -J. G. Parker and B. J. Lyons . ... ... ....................... .18Setting Priorities for R & D in the Water Sector -Dr Peter Nadebaum for the A WWA23National Water Research Seminar Canberra-September 1987 -Dr P. R. Nadebaum . ............ . . ...... ............. . .. .25Polyelectrolyte in Sludge Conditioning Use of Rheology for Control - T. R. Bridle and C. K. Hertle . ...... . .............. ........ .27IA WPRC News . ... ... .. ............................ ... ...... .28Towards Affordable and Effective Water Treatment -A. G. Strom and J. A. Crockett30The Quality of Water is not Strained - J. R. L. Forsyth ... . ............ . ..... .. . .. ...... .. ..... .34Water Quality Management in Victoria -R. A. Graham and R. G. Peck . .............. .. ............ .4()Book Reviews ... .. .... ..... .... .. . . ........ .... .. . ... ....... .44People & Company News ............. . ....................... .46Products • Plant • Equipment .......... ... .......... .. ......... .47New South Wa les Mrs S. Tonki n-Hill , Sinclair Knight & Part. 1 Chandu s St. , St . Leonards, 2065, (02) 436 7166Victoria J . Park, Water Training Centre, P.O. Box 409, Werribee, 3030. (03) 741 6844Queensland D. Mackay , P.O. Box 41 2, We st End 4101. (07) 844 3766)South Australia R. Town se nd, State Water Laboratories, E. & W.S. Private Mail Bag , Salisbury, 5108. (08) 259 0316Western Australia Mr K. Cadee , Wat er Aulh. of W.A. , P.O. Box 100, Leedervill e 6007 (09) 420 2457Tasman ia G. Nolan , G.P.O . Box 78A, Hobart 7001 (002) 44 0600Northern Territory P. Abbey, P.O. Box 37283 Winnellie, N.T. 5789. (089) 89 7290EDITOR IAL & SUBSCR IPTION CORRESPONDENCE G. R. Goffln , 7 Moss man Dr., Eaglemont 3084 03 459 4346COVER PICTURE The newly constructed Bank-note Printing Works of the Reserve Bank.at Craigieburn on the northern outskirts of Melbourne ,which involved a unique and complex waste-disposal problem. WSL Consultants Pty Ltd of Melbourne performed the necessary investigations and designed the requisite treatment plant which is constructed partly ins ide the building and partly externally, at a capital cost of $1.5 m. The investigation, process design and monitoring of the operating plant are described in this issue, pages 18-20. Front cover donated by WSL Consultants Pty Ltd.The statements made or opinions expressed in 'Water' do not necessarily re flect the views of th e Australian Water and Wa stewa ter Association, its Council or co mm ittees.Environmental Effect of Canal Estates in Australia P. M. Nuttall and B. J. Richardson ABSTRACT Canal estate development in Australia has created over 200 artificial waterways throughout Western Australia, New South Wales, Victoria and Queensland. Construction began in the subtropics during the 'fifties' as a means of extending the limited water frontage available for real estate development. However, canals almost invariably exhibit problems with water quality, biology or hydraulics, not only in the water channels but also within the parent water body. This paper reviews the environmental effects already experienced in canal estate developments in Australia.INTRODUCTION Canal estates were introduced to Australia during the mid-l 950s with the intention of extending the limited area of tidal waterfront land available for residential development. The first of these artificial waterways was constructed on the Nerang River in Queensland's Gold Coast. Since 1960, residential canals in Australia have proliferated rapidly. In the eastern sub-tropical region alone there are now over 200 completed developments with major canal systems at Southport and Mooloolaba. At least 45 residential tidal canals have been developed in New South Wales, with the majority situated in the northern sub-tropical zone and built in the 1970s. A number are still under construction or are incomplete. In Western Australia, construction of residential canal estates has been limited to the Peel-Harvey inlet. In Victoria there are a number of developments, under construction and proposed, located around Port Phillip Bay and in the Gippsland Lakes. Although these developments differ in the nature of the waterbodies on which they are built, all have a common design feature of providing private residences adjacent to a tidal waterway with space for private boat moorings, ramps or jetties . The main channels most commonly branch into closed-end canals, although an increasing number of estates are designed as flow-through with access to open seas, estuary or bay through two or more openings.Mr. Peter M. Nuttall, B.Sc.(Hons.), M.Sc., M.I. Biol. is Research Biologist for the Dandenong Valley Authority and is presently completing a Ph.D. through Deakin University on the environmental effects of canal estates in Victoria. He has many years experience in pollution control studies and in the field of environmental management. Dr. Bruce J. Richardson, Dip. Tchg., B.Sc.(Hons), Ph.D., is Lecturer in Microbiology in the Division of Biological and Health Sciences at Deakin University, Geelong, Victoria. His research interests include the use of living organisms as monitors of environmental contamination. He has been particularly involved in monitoring polychlorinated biphenyl (PCB) contamination in the Australian environment. Loss of mudflats and alteration in the tidal prism, was caused by dredge-and-fill operations for canal estates on Brisbane Waters, N.S.W. The area was an important feeding ground for waders which have decreased in both numbers and diversity since development began in the early 1970s. A comparable situation could result from the second stage of the Waterside Mandurah estates under construction on the Peel-Harvey inlet, south of Perth, where the loss of mudflat!!; would drastically alter the invertebrate food base for trans-equatorial migratory waders.LOSS OF COAST AL RESOURCES Canals are invariably built in low-lying, unprepossessing areas associated with estuarine mudflats or sand beds, coastal wetlands, saltmarsh-mangrove and ti-tree communities or shallow, saline lagoons (Figure 1). As a result of this there has been increasing . concern expressed over the effects of such developments on the coastal environment. In New South Wales, for example, many estuaries and wetlands have been damaged through the effects of dredging and reclamation as a result of indiscriminate or ill-planned developments (Middleton et al., 1984). Pointless destruction of mangroves was done by the now aborted construction of the Wandering Star canal project at Yamba. Mangrove and marsh plants, along with seagrass, are vital to estuary life. Each square metre of mangrove forest contributes an average 1 kg a year of organic matter to the food chain that supports most of the species sought after by commercial fishermen. Studies by Ellway and Heger! (1972) showed that dredging on the Tweed River at Coolangatta accounted for the loss of 11 fish species from the estuary. This, and a rapid decline in the total numbers of other fish species, was primarily the result of smothering by silt from the dredging of small aquatic animals eaten by the fish. About 600Jo of the commercial fish species in the total New South Wales catch are dependent on estuarine habitats at some stage in their lifecycle (Pollard, 1976) and the Australian oyster industry, currently undergoing rapid expansion is conducted in and wholly reliant on closed coastal waters. 14WATER December, 1987V Figure 1. Location of completed tidal canal estates in Australia (each circle represents 1 or more developments).WATER MOVEMENT IN CANALS Because of hydraulic problems experienced with many tidal canals constructed elsewhere in the world, attention has been focused in Australia on circulation and exchange of canal water with the parent water-body. In engineering evaluations, it has been common practice to attribute water renewal in residentialcanals to tidal currents and tide-induced m1X1ng. However, in closed-end canals greater than an arbitrary 5 km in length most water replacement comes from radiation induced density chang~s or wind-induced movement. This is particularly so where the tidal range is so weak as to be ineffective as a flu shing mechanism , for example in ca nal estates under constru ctio n on the Gippsland Lakes, Victoria. Wind-induced move ment of wa ter is substantially restricted by house constru ction and fences alongside water channels and the growth of pla nted trees in gard ens even where canal widths are greater than th e ge neral minimum of 45 metres (Figure 2) . Weak circulation also res ul ts from stratification with less dense freshwater runoff sitting on top of saltwater and restricting density-induced move ment to the surface layers. Stratification may persist for severa l wee ks causing oxyge n depletion below the stratified water.FLOODING Canal developments are often sited in flo od-plains which are subj ect to peri odic floodin g. Filling to above flo od levels do es not necessarily affect fl ood capaci ty, providing adequate fl oodways are retained . Ho wever , ma ny Australian canal estates are on river mouths where land obstru ction to water passage increases the potential for flooding du ring storms. Kawa na Waters is built on the mou th of the Moo loolah River on the Sunshine Coas t where rainfa ll is aro und 250 cm a year. Risk of floodin g is increased by the removal of catchment vegetation which would normall y retard storm water runoff enterin g the river . Predi ctions of global warm ing and relative changes in rainfall and in the sea level of at least 0.2- 1.4 metres by the next decade must increase the hazard of fl ooding fo r the majority o f canal estates around the A ustralian coastline.GROUNDWATER CHANGES>I(J¡o.J UJ50 .. ..>' â&#x20AC;˘Cz==0 9.IX.86D26.IX.8614. X .86OPEN WATERCanal estate development can alter gro und water reso urces by influencing the mo vement of phreatic water or by dim inishing bore water supplies through overuse by residents. A superficial aquife r underlying coastal Wes tern A ustralia was drawn on by established residents using pri vate bo res, mostly fo r gard en irrigation , even though a reticulated water supp ly was availab le. Subsequent dewatering fo r canal estate constru ction in the area fo llowed by intensifi ed demands upon the aquifer by the increasing number of households fro m canal developments is believed to have caused an undesirable shift in the saltwaterfreshwater interface . It was recommended that the EPA should advise residents that continuing supplies o f ground wa ter could not be guaranteed and that furth er drawing on the aqu ife r was undesirable.j:::;:::j TIDAL C ANALS WATER QUALITY Figure 2. Wind velocity at water surface level in develo ping canals (o pen water) and mature canal estates.The Yunderup canals in Wes tern Austra lia exhibi t mar ked stratification during January and July res ulting in a 5007o oxygen sag in layered water (B rindley, 1984) . Flushing is so poor at Yunderup that for ced circulation has been suggested as a remedy fo r stagnation problems. A t other times of the yea r radiant heat penetrates to the bottom layers o f stratified water which in turn become heated and reach a higher temperature than the surface layers. T his solar pond phenomenon has also been observed in canal estates at P atterson La kes, Victoria (Nuttall , 1987). In Queensland , stratification is generally not a prob lem in canals of minimum depth (2 m below chart datum) although hypoxia has been recorded in some deeper canals and there are some reports of a noxia combined with a thermocline-halocline in deep canals of small tidal range .TIDAL FLUSHING Increasing the num ber o f turns of canals, creating islands and obstru ctions such as bridge abutments and flo odwater barriers reta rds water flo w. In suffi cient tidal exchange contributes to stag nation in many of the backwa ter canals on the Tweed Rive r where the long lead channel res ults in poor mixing. Detention periods in canal estates on the Nerang and Mooloolah Rivers vary fr om 36 h to about 1 month . Moss (1 982) notes that deep water deoxygenation can be significant at the upper ends o f extensive canal systems on the Ne rang River. In some Queensland canals there is intentional red uction of tidal influ ence . At Bribie Gardens the mean tidal ra nge of 2 m is redu ced to a tenth to fac ilitate boat mooring by gates across the canal entrance. Residential canals increase the volume and velocity of water to the parent water-body at ebb and fl ood tides, altering esta blished flow and circulatio n patterns. T he tidal vo lu me of the Nerang Rive r has been increased by two th irds because of canal development, resulting in excessive tidal velocities in the canals and estuary. A single open ing to the Patterson Lakes tidal canals south o f Melbourne is being duplicated at a cost of $1.2 million to allevia te boat nav igati on difficulties throu gh the entrance caused by high water velocity fr o m continuing canal construction .Water quality in canal estates not only depends upon the configuration and dimension of channels, on the quality o f th e parent water- body and on the tida l range but als,o on biological and physiochemical processes whic h go on in the canals and on the nature a nd fre quency of envi ronmental stress which might occur . Weak circula tion or insufficient tidal exchange in closed-end canals periodi cally leads to substa ndird water quali ty characterised by defi cient oxygen levels and blooms of algae. Algal res pi ration at night , decompositio n o f dead algae and the breakdown of orga nic matter within the sediments contributes to increased oxygen depletion in the wate rways . Sediments which become anoxic during summer in th e Murray Lakes and Windslee canal estates, Wes tern Australia, are the res ult of poor flu shing and water mo vement combined with high nutrient levels entering from the Mur ray River (Lukatelich and McComb , 1983) . If marin e sediments remain anoxic for long enough, hydrogen sulphide is produ ced by sulphate- redu cing bac teria which then combines with iron oxides to fo rm the blac k, anaero bic hydrotroili te and fe tid-smelling disulp hydry l iro n muds. Hydroge n sulphide and other noxio us gases can be brought to the sur face on occasions when the water becomes mixed and can cause pro blems to residents who lived beside the cana ls. Fish kills, od our and discolouration have occurred on the Neran g River estates fo llowing autumn turnover . An add ed cause o f oxygen depletion in some Q ueensland canal developments may be run off containing organic peat fro m the Wallum heath swamps which were drained and excavated fo r canal constru ction (Wes tman, 1975).POLLUTION O rganic pollution fr om septic ta nk discharges to waterways has prompted pu blic complaints a t Sylvania Wa ters, N .S. W ., Yunderu p, W .A ., Florida Gardens a nd other canal developments on the Gold Coast. A number o f Queensland canals initiall y had efflu ent entering soa kage trenches and pits which fo un d its way into canals. Highl y va riable soils may cause engineering problems if the soil is inadeq ua te as fi ll material. Fractures a nd leaks fr om sewerage lines have happened on a num ber of canal estates caused by di ffere ntial settlement of reclaimed land . Urb an run off en tering canal systems fr om road drains contributes a substantial portion of organic and inorga nic con taminants to wa terways. In some cases, provision has been made WATER December, 198 715to either divert or detain urban runoff. For example, pipe outlets are screened and drainage lines directed away from closed-end canals on Patterson Lakes canal estates, Victoria. Enrichment from the excessive application ¡ of garden fertiliser, from hydromulching during the final stage of canal development and from the release of human waste from boats and marinas appears to be common to many canal estates. Release of pollutants such as oil and petrol from boat fuelling facilities and the leaching of heavy metals from boat antifouling paint is associated with marinas located within or at the entrance to canal estates. Polycyclic aromatic hydrocarbons have been found concentrated at boat marinas on canal estates in Victoria (Nuttall, 1987). In many cases, water quality in closed-end canals proves to be inferior to the parent water-body, resulting in a fall in standards such as turbidity, suspended-solids and chlorophyll-a during ebb tides. Canals constructed on river mouths are vulnerable to catchment runoff, particularly in urbanised or industrialised areas where various biodegradable and non-degradable pollutants enter the water. Even where low flow river diversion is undertaken to protect water quality standards on canal estates (for example Dandenong Creek is diverted from the Patterson Lakes estuary developments on Port Phillip Bay) flood flows carrying a significant amount of pollutants in the first flush enter the original course of the river.A10.11.86 2m 20mA16.1.87mobile siltSEDIMENTATION On-site runoff during heavy rain or aerial fall during hot, dry winds causes silt and clay from canal construction to enter the parent water-body and other completed waterways. Stormwater runoff, particularly from developing catchments, carries large amounts of inorganic and organic particles which wash into the estuary and settle out in the slack water of canal estates (Figure 3). 198619872.0 -+--'----J'--., ..... . . . , ,J. ,. ..... . . . , ,,~fl;:::==:::::::::=.=------~1 s o <..::::::::::: , : 219751.51986119861 ,~rJj......GI1.0GIE:r: I-0.5Cl.wC0 closed-end canals estuary entrance to canals Figure 3. Water clarity in Patterson Lakes canal estates, Victoria (measured over a 16 month period using a Secchi-disc).The result is that bottom sediments in canal estates have an increased silt and clay content when compared with the parent water-body. Bottom sediments collected from McMillan Strait, Gippsland Lakes contained a higher percentage of coarse material such as sand and shell than sediments from the Riviera Harbours canals estates being developed on the strait. At times, runoff from Riviera Harbours carried a plume of turbid material into McMillan Strait which eventually settled on the coarser sediments causing a localised but measurable increase in the silt-clay fraction. There are several important environmental effects from this sedimentation pattern. Firstly, tidal canals undergo profile changes caused by the deposition of suspended solids (Figure 4). The problem is intensified by boat movement reworking and redistributing loose, unstable sediments and by the erosion of beaches by anglers using sand pumps to collect bait. Organisations who are responsible for maintaining the waterways as navigable channels usually respond to this problem with suction or mechanical dredging , even though it is accepted that this affects the ecological stability of aqu
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