Water Journal June 1984

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I ISSN 0310- 0367 I Official Journal of the

Vol. 11, No. 2, June 1984-$2.50 Registered by Austra lia Post -

publication no. VBP 1394

FEDERAL PRESIDENT F. Bishop, Scott & Furphy , 390 St . Kilda Rd. , Albert Park, 3004

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


Officia.Journal of the - ~A~u=s=T=RA-,-Lc-,1-:-A:--:-N WATER AND WASTE WATER ASSOCIATION

Vol. 11, No. 2 June 1984


625 Lt . Collins St. , Melbourne, 3000 .

BRANCH SECRETARIES Canberra, A.C.T. J. E. Dymke, 4 Story St. , Curtin , 2605. Office 062 (54 1222)

New South Wales D. Russe ll , Camp Scott & Furphy , 781 Pacific Highway , Chats wood 2067. (02 412 2688)

Victoria J. Park , S.R .W.S.C. Operator Training Centre, P.O. Box 409 , Werribee, 3030. (741 5844)

Queensland D. Mackay, P.O. Box 412, West End 4101. (07 44 3766)

South Australia A. Glatz, State Water Laboratories , E. & W.S. Private Mail Bag , Sali sbury, 5108 . (259 0319)

Western Australia R. Loo, 455 Beach Rd ., Carine , 6020. (09 447 6550)

Tasmania G. Nolan , G.P.O. Box 78A Hobart , 7001 . (002 28 0234)

CONTENTS Viewpoint . ... ... . . .... ... ... ................ ..... .. .


Association News, Views and Comment ........ .. .. .... .


Deepening Urban Wetlands: an Assessment of Water Quality in Four Wetlands on the Swan Coastal Plain, Western Australia -P. Newman and L. Hart ... . . . ... .. ........ ...... .


The Peel-Harvey Estuarine System-Review of Study Progress -P. B. Birch, J. 0. Gabrielson and E. P. Hodgkin


Technical Interests ... .. . . .. .......... ....... ....... . .


Predicted Oxygen Transfer CharacteristicsRiser Pipes at Wastewater Pumping Stations -Keith Cadee .... .... ......... .... ............. .


Oxygen Dissolving Facilities-the Munster Pumping Station -K. Cadee, T. E. Long and R. E. Wain ... . ....... ... .


The Asian Institute of Technology-a Unique Organisation - T. L. Jude/I .......... ...... ........ . . . .... .... .


Plant and Equipment .... . . . .. . ..... . ... .. .. . . ....... .


Northern Territory G. Sleeman , P.O. Box 37283 Winnellie, N.T. 5789. (089 81 5772)

EDITORIAL & SUBSCRIPTION CORRESPONDENCE G. R. Goffin , 7 Mossman Dr. , Eaglemont 3084 03 459 4346

COVER The Metropolitan Water Authority in Perth has installed one of the largest oxygen dissolvers of its type in the world in the Southern Perth suburb of Munster. The GIG Vito x II dissolver located at the Munster Pumping Station, oxygenates wastewater for Sulphide control before discharging to the Woodman Point Treatment Plant. The installation is part of the Authority 's programme for serving the growing southern sewerage system . This involves expanding the wastewater conveyance, treatment and disposal fac ilities associated with the Woodman Point Wastewater Treatment Plants.

ADVERTISING Miss Ann Sykes , Appita, 191 Roya l Parade, Parkville 3052. 03 347 2377

The statements made or opinions expressed in ' Water' do not necessarily reflect the views of the Australian Water and Wastewater Association, its Council or committees. WAT ER June, 1984



Deepening Urban Wetlands: An Assessment -o f Water Quality Four Wetlands on the Swan Coastal Plain Western Australia P. Newman and L. Hart


Four wetlands on the Swan Coasta l Plain near Perth in Western Australia were monitored for water qua lity and changes in algae population to determine if any significant difference could be ascribed to the depth of the wetland. Murdoch Swamp, which had been deepened some 40 years previously, was compared with two shall ow lak es, North and Bibra Lakes , and another nearby swamp, Bibra Swamp . The results show significant differences in water quality characteristics with Murdoch Swamp being slight ly acid, relatively low in nutrients, particularly phosphorus , and generally very stab le. T he other wetlands, particu larly North and Bibra Lakes , are much less stab le, being characterised by alkaline waters of very high nutrient content. The shallow wetlands are highly eutrophic and are regularly subj ect to extens ive blue green algae blooms. The deepening may minimise the potential for blue green algae growt h ensur ing a longer period of sub-optimal water temperature, and through shallow sediments reducing pH and phosphate levels. The results suggest that deepening of wetlands such as these may have several beneficial effects on water quality especially in reducing the extent of blue green algae blooms. INTRODUCTION

Wetlands face a range of potentially damaging changes in an urban context. A series of shallow groundwater wetlands on the Swan coastal plain in Perth, Western Australia are threatened by: • Hydrologic changes due to urbanisation and a nearby groundwater scheme, • water qua lity changes due to urban storm water drainage and potentially deteriorating groundwater inputs, and • increased recreational pressures. The wetlands are an important summer refuge for waterfowl, being frequented by some 56 species when inland water areas dry up (Newman et al 1976). In recent years drought has ca used most of the shallow wetlands to dry out in summer, raising the question whether deepening of some or all of these wetlands should be attempted. Many of the wetlands experience algae blooms for much of the year, especially of the blue green variety. These cause problems due to odour, toxicity to some water fowl and raise pub lic health questions (Department of Conservation & Environment 1977). The apparent advantages of deepening include: • A permanent summer water source is availab le as refuge for waterfowl and the wet land is improved aesthetically for summer recreation. • Groundwater extraction co uld lower regional groundwater levels without affecting the deepened wetlands. • Bottom sediments often have economic value (in this case peat and diatomaceous earth) which may offset the cost of dredging. The uncertainty in such a scheme is whether the water quality would he improved (especially with regard to blue green algae) and whether there would be any deleterious biological changes. Other studies overseas have mostly suggested positive resu lts for deepening of shallow or damaged lakes, though not always (Maugh 1979). This paper reports a study designed to examine the potential effects of deepening some lakes on the Swan coastal plain with an emphasis

Dr. Peter Newman is Senior Lecturer in Environmental Science al Murdoch University, Western Australia. Lesley Hart is Technical Officer, Environmental Science, Melbourne State College, Victoria. 12

WATER June, /984

on water quality change. The stud y compares severa l similar wetlands, one of which had been deepened some 40 years previousl y. The long length of time since deepening took place is considered an advantage as it has allowed sufficient time for the system to have settled down and re-established biological processes in a rea/jo nable state of equi librium. From an ecologica l perspecti ve there are a number of unresolved questions about the relation of deepening to successional patterns of these Swan coastal plain wetlands . As the wetlands a re sha llow they can rapidly reach a stage of complete in-fill with peat and have extensive growths of aq uati c macrophytes and terrest rial vegetation. However, because the region is fire-based ecosystem, it appears probable that the wetland is eventually regenerated by fire burning out the peat layer during summer when th e water table is lowered. This process has been observed and wetlands in each of these stages are apparent in the chain of wetland s assoc iated with those in the study (Newman et al, 1976). It has been post ulated that deepening may be an artificial way of accelerating the regeneration of an aging urban wetla nd (Riggert 1976, 1966) in the same way that peat bogs in North America are deepened to reverse their success ion by the use of explosives (Mosby 1963) . If this were so then a deepened wetland could be expected to show improved water quality characteristics (ie less eutrophic), with less extremes obvious in the physico-chemical and biological parameters and with fewer algal blooms, especially of the deleterious blue-green variety. METHODS OF STUDY 1. CHOICE OF WETLANDS

The wetlands chosen for study are shown in Figure I and their important physical characteristics are li sted in Table I. North and Bibra Lakes were chosen for study as they are becoming increasingl y important urban recreation centres and are also va luable waterfowl refuges. The question of dredging has been rai sed it\ connection wit h both of these quite large lakes, though most frequently with Bi bra Lake which is slightly shallower and has partially dried out every summer from 1978-8 1. Murdoch Swamp was chosen because it had been deepened previously and was immediately adjacent to North and Bibra Lakes. Bibra Swamp is a nearby small wetland, lik e Murdoch Swamp, which has not been deepened; this swamp dries out every summer. It was thus poss ible to compare the seasonal water quality and algal changes of these four wetlands to see if any significant difference could be ascribed to the depth of the wetland, taking in to account the size of the water body. All other external factors were co nsidered to be essentially constant as: • the immediate vegetation (mainly native species with some pastureland) surrounding the wetlands are similar (see Figure I). • Geologicall y they are part of the same wetland chain which li es on an interdunal depress ion between two sand types and are fed by the same groundwater source (Seddon 1972, Newman et al 1976). • Land use patterns around the lakes are similar (mostly passive recreation) tho ugh Bibra Lakes has had sanitary landfill on its western and southern fringes. Although samples of sediments were not co llected from all parts of the lakes, they were found in all cases to be peat, consisting of around 30 per cent organic matter, with the remaining sediment being mostly siliceous material. Occasional patches of diatomaceous earth have been located beneath the peat in North and Bibra Lakes. A major difference between the wetlands is that Murdoch was deepened in the late 1930s by some two metres so that it could be a permanent water source in fire control and hence it not only has deeper water but also shallower sediments.




The primary aim of the field work was to establish seasonal changes in water quality for each of the wetlands. The following physical and chemica l parameters were exam ined ; dissolved oxygen (Beckman Field Oxygen Analyser), p H (pye Unicam Model 293 pH meter), temperature, turbidity Hach Turbidimeter Model 2100A), conductivity Electronic Instruments Ltd-Type MC3), dissolved orthophosphate (Techn icon Auto Analyser II manifold No 116-D047-01), nitrate-nitrogen and nitrite nitrogen (Technicon Auto Analyser manifold No ll6-D049-01) and ammonia nitrogen (Technicon Auto Analyser manifold No 116-D 186-01). Ch lorophyll-a was determined using the membrane filter technique (APHA I 975) to give an indication of phytoplankton biomass and the dominant algae present were determined by microscopic examination. Qualitative observations of in vertebrate li fe were also made. The water quality parameters were studied weekly from 24.2.78 to 27 .9. 78 . The wetlands were studied again weekly for three month periods at various other times of the year from 1979 to 1981. In a ll , each wetland was sampled over 100 times and, as no sign ificant differences were found in the data over the extended periods, the data presented for analysis is just for the intensive seven month period in 1978. Samples were taken at approximately the sa me tim e of day from several different points around the wetlands. To further characterise the lakes a series of 24-hour studies were conducted with samples taken every hour in order to determine diurnal water quality flu ctuations.





The range, standard deviation a nd mean values for the water quali ty parameters in the four wetlands a re presented in Tab les 2a and 2b. The weekly results for the main parameters in each wetland were grap hed as were the results of the diurnal studi es conducted on North Lake and M urd och Swamp. Space li mitations prevent inclusion of t he graphs with this paper. The a lgal species found in the wetlands are presented in Table 3 with the dominant species in each case being highlighted. After each algal bloom there was a rapid growt h in zoo plankton, mostly Daphnia sp though there were also Copepoda (Calanoid sp) and Ostracods present. This pattern was found in all the wetlands except for Murdoch Swamp which does not have Daphnia present. Other insect life found in a ll wetlands include backswimmers (Notonectidae), water boatmen (Co/eoptera), water strider (Gerridae), water beetles (order Coleoptera) and water spiders and mites (Arachnida) . Nort h Lake, Bibra Lake and Murdpch Swamp have populations of the Long-necked Tortoise (Chelodina longicollis) with Murdoch Swamp having a population of a t least 30.




.!'. ~






al;J ti. 0

..J l;J



a ~









· Area of Water ' (ha) Depth of Water' (m) Volume of Water' (m') Depth of Sediment• (m)


The results indicate sign ificant differences in water quality between the deepened Murdoch Swamp and the other wetlands. Each parameter is examined briefly below and an assessment is made of how water quality changes affect the algal life.

Murdoch Swamp

North Lake

Bibra Lake

Bibra Swamp

1.3 1.5-2.5 1400

15.6 0.5-1.5 284 000

60 .2 0.3-1.3 72 1 600

0.2 0-0.5 300






I. The area was taken from the average winter water mark which is clearly defined by fringing vegetation. 2. The sed iment surface of the wetlands is almost uniformly flat and hence the depth of water is consistent over most of the water body. The depth is shown as the average year 's range. 3. Volume was calculated using the depth of average winter water. 4. The peat layer is mostly around 0.5 metre deep apart from Murdoch Swamp.

Tempera ture

All four wetlands showed sim ilar seasona l temperature fluctuations with the shallower water bodies, Bibra Lake and Bibra Swamp being generally a li tt le warmer as air temperatures began to rise. Murdoch Swamp is severa l degrees cooler for a number of months in the latter half of the year. It is possible that this temperature difference is a signifi cant factor in determi ning development of blue green algal blooms (see later discuss ion). The diurnal stud y showed that Murdoch Swamp is not subject to extremes in temperature in its daily cycle, as well as over a seasonal cycle. Acidity

Murdoch Swamp is significantly more acidic than the other wetlands, particµlar ly the lakes, which are a lkaline for most of the year. Th e pH in Murdoch Swamp is more like the pH of the gro und water in the area (average 5.6, Binnie, 1976). This may be partly attributable to its shallower sediments which may not be as effective in filtering o ut the humic acid s in the gro und water as th ey pass into the swamp. The pine forests that have surro unded Murdoch Swamp in recent years may also have been a factor in this acidity and the shallow sediments could contain less material that can act as a buffer to the low pH groundwater as it enters. Th is difference of nea rly 2 pH units between the wetlands co uld also be of sig nificance in controlling blue green algal blooms and other life in the wetland . WATER June, /984



Water Temperature


Dissolved Oxygen mgl L

Turbidity NTU

Total Dissolved Salts mgl L


Murdoch Swamp

Range Std. Dev. Mean

11.9-32.0 5.8 20.2

4.2-7.8 I.I 6.0

3.9-11.5 1.9 8.7

0.4-3 .0 0.8 1.3

360-960 190 683

North Lake

Range Std. Dev. Mean

11.9-31.1 5.2 20.3

6.8-10.2 0.9 8.0

5.3-14.3 2.3 9.0

0.8-25.0 5.2 4.0

390-2000 495 951

Bibra Lake

Range Std. Dev . Mean

11.8-32. 7 4.6 18.2

6.6-9.3 0.8 7.7

4.1-26.0 5.8 IO.I

1.3-63.0 14.3 9.0

1195-17250 4288 3310

Bibra Swamp

Range Std. Dev. Mean

11.4-34.4 4.7 19.0

6.3-9 .8 1.1 7.4

6.2-16.7 3.2

0.4-15.0 3.2 2.8

226,-1095 179 374


NOTE: Total Dissolved Salts are conductivity readings converted to equivalent as NaCl at 28°C.


Chlorophyll-a (mg l m')

Nitrate (mg N I L)

Nitrite (mg N I L)

Ammonia (mg N I L)

Orthophosphate (mg P04I L)

Murdoch Swamp

Range Std. Dev. Mean

0-19.6 3.9 3.4

0.34-1.30 0.25 0.69

0.01-0.49 0. 10 0.04

< 0.1 -0.64 0.16 0.10

0.02-0 .24 0.06 0.10

North Lake

Range Std. Dev. Mean

0.7-146 .9 40.1 27.7

0.30-1.22 0.27 0.76

0.01-0.65 0.20 0.09

< 0.1 -0.80 0.35 0.35

0.05-0.96 0.26 0.26

Bibra Lake

Range Std. Dev . Mean

1.2-2893 .4 940.5 506.2

0.37-2.26 0.53 1.13

0.01-1.10 0.23 0.14

< 0.1 -2.50 0.75 0.85

0.12-5. 60 1.20 1.92

Bibra Swamp

Range Std. Dev. Mean

0.8-6 14.5 138.7 61.3

0.36-2.03 0.49 0.87

0.01-0.49 0.14 0.08

< 0.1 -0.85 0.25 0.23

o. i4-1.76 0.45 0.99 ~


Location Murdoch Swamp North Lake

Franceia sp. (September) Ankistrodesmus sp . Scenedesmus (quadricauda) (March) Pediastrum sp. Chlamydomonas sp. (July) Volvox (aureus)• (September)

Bibra Lake

Chlamydomonas sp . (July) Oedogonium• sp. Spirogyra • sp. (August-October) - attached to reeds

Bibra Swamp

Scenedesmus (quadricauda) Tetraedron sp. (March) Volvox (aureus)• Oocystis sp. (March, May) Spirogyra• sp. Oedogonium• sp. (August)

• Indicates dominant algae present. 14

WATER June; 1984

Baciflariophyceae (Yellow-Brown Algae)

Euglenophyceae (Euglenoids)

Myxophyceae (Blue Green Algae)

Euglena sp. (March) Fragilaria sp. Pinnularia sp. (March, July)

Euglena sp . (March)

Anabaena (spiroides)* Microcystis sp. (March, October)

Navicula sp. (October)

Anabaena (spiroides) Microcystic sp. (March , June)

Diatoma sp. Pinnularia sp. Cyclotefla sp. Navicula sp. (March) Fragilaria (August)

Trachelomonas sp. Phacus sp. (March)

Dissolved Oxy_gen (D 0)

Larger variations in DO were found, especially in Bibra Lake during the time when blue green algae were dominant. All the mean values a re above saturated oxygen levels, though all these readings were take n in the ear ly afternoon when dissolved oxygen levels are most likely at thei r peak . The diurnal readings show a significant variat ion in dissolved oxygen in North Lake, which ranges between 4 and 11 mg/ L. These large changes are attributable to the dominant blue green algal bloom. By co mparison, conditions in Murdoch Swamp were much more stab le, wit h dissolved oxygen ranging only between 9 a nd 11 mg/ L. TABLE 4. TROPHIC STATUS AND CHLOROPHYLL-A (after St. John et al 1976) Trophic Starus

Ch lorophyll (mgl m')

Wetland (mean values of chlorophyll-a)


Bibra Lake (506) Bibra Swamp (61) North Lake (28)



Murdoch Swamp(3)




Ch lorophyll-a

The mean va lues and ranges of chlorophyll -a reflect the dominance of algal blooms in North Lake, Bibra Swamp and Bibra Lake with Murdoc h Swamp showing considerably lower va lues. The bloom of green a lgae in Bibra Lake in August a nd in North Lake in September was a floatin g filamentous mat that was very extensive but did not influence the chlorophyll-a read in gs as t he water samples were collected from just below the water su rface. Murdoch Swamp did not show any sign of an alga l bloom whi lst the other three wetlands have continued to show consistent extensive blooms other than in the winter months. In terms of trophic status, St John et al (1976) suggest the class ification as in Tab le 4, which wo uld lead to Murdoch Swa mp being considered mildly mesotrop hi c and the other wetlands all highl y eutrophic. Turbidity

Turbidity relates to chlorophyll-a in alm ost every case, indicating t he extent to whi ch the water quality is dominated by the algal blooms whi ch occ ur. Total Dissolved Salts

There is considerab le variation in salt content in the four wetlands which can be explained in terms of their depth and size. Bibra Lake is by far the saltiest a nd thi s is most probably due to the fact that it frequently dries out, a nd since it covers an exclus ive area there is a large build-up of salt in the water and sediments as it evaporates. Nort h Lake has not completely d ried out since records have been kept (I 928). By comparison Murdoch and Bibra swamps, being quite small , are strongly influenced by rainfall. The higher salinity levels in Bibra Lake did not seem to restrict the growth of algal li fe as Bibra Lake and Nort h Lake experienced very similar types of blooms. Nutrients

The relationship between nutrients and algal growth can be seen in a total sense from Tab le 2b and also in the weekly monitoring curves. Murdoch Swamp is lower in nutrients, especially orthophosphate, co mpared to the ot her wet lands. However, nitrate levels are similarly high in Murdoc h Swamp and North Lake. T he mai n nitrate so urce appears to be from the ground water (values of 0.1-1.0 mg/ L) have been found by Bishaw (1980) in shallow bores on the Swan coastal plain. Also, although nitrat e can be cycled between sed im ent s a nd water, there is a biological mecha nism for its complete removal from the sy tern (denitrification). By comparison, phosphate builds up in the sedi ment s and can be re leased at any tim e, part icu la rly under anaerobic cond iti ons. Therefore, one wou ld expect th e sediments of Murdoch Swamp to give ri se to a lower orthophosphate concentrati on in th e water, though a comparable nitrate level is quite possible.

Weekly monitoring is not suitable enough to show whether a particular nutrient triggered off an algal bloom. However , it is possible to see in most of the monitoring profiles that: • During a bloom there is generally a drop in orthophosphate wh ich then increases after the bloom begins to fa de; this may be due to uptake of phosphates by the algae in their growt h stages and subsequent release upon decay . Also, blue greens are known to store levels of phosphate which can be released suddenly when the algae begin to die (Foree et al 1979). • There is often a build-up of ammon ia after a bloom, presumably due to t he breakdown of organic matter which releases ammonia as the first nitrogen decomposition product. • Nitrate seems to be slowly building up throughout the wetter months (July-September) in North Lake and Murdoch Swamp which is consistent with the notion of nitrate being main ly groundwater-derived rather than being from the sediments. In Bibra Swamp and Bibra Lake, whi ch are dominated by algal blooms, nitrate fluctuates wildly, building up to a peak between the algal blooms. The nutrient results as apparent from graphs and shown in Table 2b clearly illustrate that apart from Murdoch Swamp there are very large variations in nutrient levels, especially in the two most shallow wetlands and by comparison with wetlands overseas these nutrient levels are all ext remely high . Only Murdoc h Swamp can be considered less than eutrophic on th e basis of its nutrient levels (Table 5). TABLE 5. TROPHIC ST A TUS AND NUTRIENT LEVELS (after St. John et al, 1976) Total N (mg N I L)

Total P (mg PI L)




0.03 -1.0

Bibra Lake (2. 12 mg N/ L, 0.63 mg P/ L)* Bibra Swamp (1. 18 mg N/ L, 0.32 mg P/ L) North Lake (1.20 mg N/ L, 0.09 mg P/ L)




Murdoch Swamp (0.83 mg N/ L, 0.03 mg P/ L)




Trophic Status

• Nutrient levels in wetlands are totals of inorganic N and P but do not include organic N and P, hence they are underestimates. Algal Life


As previously d iscussed, the three shallow wetlands experienced a number of algal blooms during the study period, including several blue green blooms in the two lakes. Murdoch Swamp was free of any obvio us bloom and the on ly algae found were not blue green. The ecology of blue-green algae has been well st udi ed a nd their growth has been found to depend on : _ • A temperature range of 18-22° C (Hutchin son 1957). • A pH range greater than 8 with an optimum of IO (Gerloff et al , 1952), or no less than 6 (Round 1973). • Nutrient levels exceeding 0.01 mg/ L of phosphorus or 0.2-0 .3 mg/ L of nitrogen (many blue greens are also nitrogen fixers) and micro nutrient avail ab ility especially sod ium (Vollenweider 197 1 and Round 1973). Th is information can be used to interpret the presence or absence of blue green blooms. In North Lake, as soon as the temperature fell below 20°C in April, the blue green bloom died and just as the st ud y finished the temperature was picking up again to th is level (a blue green bloom was subsequently observed in October). The same pattern is ev ident in Bibra Lake, though when the temperature increased there was a green alga l bloom, perhaps because the pH was too low for a blue green. The green algal bloom was subsequently replaced by a blue gree n bloom in late summer. The green alga l blooms in Bibra Swamp seem also to be controlled by temperature as both occurred when the optimal 20°C was reached and died off when the temperature was below this. The pH at thi s time was also a little low for blue greens. Alth ough temperature conditi o ns are important in controllin g a lgal blooms , temperature alone is not the on ly controlling factor which showed in the data for Murdoch Swamp which had high WATER June. /984


enough temperature for algal blooms in March and May and late September but did not show a ny signs of algal growth. This may have been due to eithe r low nutrien ts, especially orthophosphate, and/ or low pH (u sually below 6). Also, in Murdoch Swamp the optimal temperature for algal growth was not reached for so me two months later than the other wetlands. A ll wetlands in the area are high in sodium (Hart 1978), so this parti cular mi cronutrient is not expected to be a limiting factor on algal growth . The factors relating to the development of algal blooms (especially blue greens) a nd their relationship to the dredging question can now be postulated. The depth of water in a wet land is a significant factor in the control of temperature whereby sha ll ow wetland s can reach optimum levels for algal growt h mu ch quicker. In addition, the dept h of sediments can influence both pH and phosphate levels, such that where sediments are sha llow there is more co ntrol over rapid alga l growth , especially blue greens. A further relationship between algal blooms and dredging may also be possible: Kappers (I 976) found that spores and fragments of blu e greens can remain viable in the sed iment and when conditions in the water improve these can seed an algal bloom . A dredged lake may have these 'seeds' removed. Murdoch Swamp has been shown to have considerabl y better water quality, probably because it has been deepened. At the same time, though a full biologica l survey as in Collett et al (198 1) has not been done, all the major zoo plankton and aquatic insects were present in th·e swamp that were fou nd in the other wetlands, as well as the thriving population of long-necked tortoise . Because of the nutrient a nd pH differences as well as the variation in sediment thick ness, there probably is some loss of biological activity in the bent hic layer with impli cat ions fo r higher organisms including bird life which could be further examined . CONCLUSION

This study has suggested that the dee peni ng of a shallo w wetla nd in the Swan coastal plain of Western Australia may have the followin g effects. It may: • Dampen the fluctuations in temperature on a daily and seasonal basis and hence reduce the potential period the lake is in an optimal condition for a blue green a lgal bloom. • Lower the pH and hence make blue green algal growth difficult. • Reduce the nutrient levels, especially phosphate, thus res tri cting a lgal growth . • Reduce the extent of algal blooms by remov ing a lgal spores present in the sed iment. T he absence of extensive a lgal blooms wo uld appear to considerably reduce flu ctuations in most water quality parameters such as disso lved oxygen , chlorophyll-a, turbidity and nutrients. Also, the deeper water wou ld result in a smaller proportion of the lake evaporating and hence the total disso lved salts level shou ld be lower. Added to these water quality factors the wetland is likely to be much more attracti ve for recreation a nd should be more usefu l for waterfow l, especially when compared to a lake that has dried out. However, it would be important to keep a range of water levels and habitats for di ffere nt species and hence uni for m dredging should not be advised. For th e large lakes, Bibra and North Lake, it may be sufficient to deepen them in a wide channel on their western side (nearest developed recreational areas) thus improving the water quality in the warmer periods when they normally have almost dried out and yet leaving the lake essent ially the sa me when it is full in winter time and too cold for extensive a lgal bloo ms to occur. As urbanisation is likely to increase the flow of nutrients into these wetlands, thu s furth er accelerating eutrophication, it would appear that the strategy of deepening urban wetlands may become increasingly necessary as a tool for improving wet la nd water qual ity on the Swan coastal plain.

REFERENCES APH A (1976), 'Standard Methods for Examination of Water and Wastewater'. 14th Edition, AP H A, Washington . BINNIE AN D PARTNERS (Australia) (1976) . Perth groundwater recharge study, Metropolitan Water Suppl y Sewerage & Drainage Board, Perth. BISH AW, M. ( 1980) , Preliminary observations on nutrient inputs from external sources, and turbidity at Emu Lak e, Honours Thesis, Murdoch University. 16

WATER June, /984

CO LLETT , L. C., COL LI NS , A. J ., G IBB S, P. J ., a nd WEST, R. J . (198 1). Shallow dredging as a strategy for th e contro l of sub li 1toral macrop hytes : A case stud y in Tuggerah Lakes, New Sout h Wa les . Aust. J. !#ar. Freshwater Res. 32: 563-7 I. Department of Conservation a nd E nvironment (1977) , Report of the algae odour control working group. Department of Conserva tion and Environment, Perth. FORREE, E.G ., J EWELL , W. J. a nd McCARTY , P. L. ( 1970) . The extent of nitrogen and p hospho rus regene rat ion from decomposing algae. Proc of 5th Int Conf. on Wat,er Pollution Research , Cali fo rni a . GE RLOFF, G. C., FITZGERA LD , G . P ., and SKOOG , F. (1952). The mineral nutrition of microcystis aeruginosa. American Journal of Botany 39: 26-32. H ART , L. A. (1978) , Wet la nd Ecosystems: A stud y of several Swan Coastal Plain wet land s, with impl ications fo r management. Honou rs T hesis, Murdoch University . H UTC HI NSON, G. E. ( 1957). 'A Treatise on Limnology'. Vol. I a nd 9, J ohn Wi ley & So ns, New York . KAPPERS , F. I. ( 1976). Presence of blue green algae in sediments of Lake Brielle. In Go lterma n, H . L. (ed), ' Interact ion between sed im ent s and water ' . Proc. of In ternational Symposium . Amsterdam , Sept. 6-10, pp 382-386. MARTIN , R. (1980) . H ydrogeochemica l stud y of an unconfined aquife r in the vicinity of Perth, Western Australia . Ph.D. Thesis, Dept of Geo logy , Un ive rsity of Western A ustra li a . MAUGH, T. H . ( 1979), Restoring damaged lakes, Sciences 203 : 425-427. MOSBY, H. S. (ed) ( 1963). ' Wildlife ln vestiga tional Techniques' . Wildlife Society, Washington DC . NEWMAN, P . et al ( 1976). The Cock burn Wetlands St udy. For Nat ional Estate and Town of Cockbu rn . RIGGERT , T . L. ( 1966) . Wetlands of the Swan Coastal Plain. Fisheries Wi ldlife , Perth. R IGGERT , T . L. (1976). Herdsma n Lake Concept Plan . Metropol it an Regional Planning Authority , Perth. ROUND, F. E. (1973) , 'The Biology of the Algae' , Edward Arnold Ltd ., London . SE DDO N, G. (1 972), 'Sense of P lace', University of W .A . Press, Perth. ST. JOHN , B. G. , CARMAC K, E . C., DALEY, R. J. , GRAY, C. B. J ., a nd PHARO, C. H . ( 1976), The Limnology of Kamloops Lake. B.C., Envi ronment , Canada. VOLLENWEIDER , R. A. (197 1), Scientific fundame nt als of th e Eutroph icatio n of Lakes and Flowing Waters, wit h particular reference to Nit rogen and Phosphorus as factors in E utrophication. O rgan ization for Economic Co-operatio n a nd Development, Paris.


Notice to Applicants Application forms are available from Branch Secretaries (addresses on page 1 this issue) and should be completed and returned to the appropriate secretary.

Membersh ip is in four categories: • Members hip - quali fications su itab le for membersh ip of the In st itution of Engineers (Aust.) or eq uivalent qual ifications of sim il ar profes s ional organ isat ions . Fees $25 p.a. Experience in the water and/or • Associate wastewater industry without formal qual if ications . Fees $25 p.a. • Student. Fees $5 p.a. • Sustaini ng Member - an organisation or firm involved in the water and wastewater industry, wishi ng to support and further the aims of the Association . Fees $100 p.a .

Fees are plus state levies where app licable.


A report on thi s st udy iss ued December I 980 showed that the eutrophic condition of the estuary resulted from the great increase in input of phosph orus to the estuary over the last three decades, 80 per ce nt of it being derived from agricultural drainage on the coastal plain. Since then the study has concentrated on two aspects : the factors mediating massive blooms of the blue-green a lga Nodu laria and recycling phosphorus through the estuarine sedim ents to it; identifyin g fert ili zer phosphorus flow paths through the various so il types and devising appropriate agronomic measu res to reduce loss of phosphorus to drainage . INTRODUCTION

This study began in 1976 beca use of the excessive growth of green algae in Peel In let, a large shall ow coasta l lagoon 60 km so uth of -Perth, Western Austra lia (Fig. !). Masses of algae accumu late on the ·s hores fouling what had been clean sand y beaches in the I 950s. The problem is a meliorated by raking the rotting algae into piles, cart ing it away and dumping it, at a cu rrent cost of $80 000 a year. More recently dense blooms of a microscopic blue-green a lgae (Nodularia spumigena) have exacerbated the problem, principally in Harvey Estuary. Phase I of the study was directed primarily to determining the cause of the problem an d the research report, published in December 1980 (W .A. Department of Conservation and Environment Report No 9), clearly identified this as being the abundance of plant nutrients entering the estuary from agricultural drainage. Phosphoru s espec ially had increased greatly as the result of th e application of superp hosp hate to phosphoru s deficient so ils of the coas tal plain catchment over the previous 30 years. A subseque nt report to the State Government recommended: (i) Continued research to determine how best to reduce the amount of phosphorus available to algae in the est uary. (ii) Improved measures to ameliorate the algal problem until there is effective reduction in available nutrients. (iii) That a ll new developments near the estuary shou ld be deep sewered. Phase 2 of the study is directed mainly towards determining ho w best to reduce the input of phosphorus from agricultural drainage. However, a number of other management measures have also been exam ined . THE NATURE OF THE PROBLEM ·

The estuary is only about 2 m deep and has wide ma rginal shallows. Daily tidal range is negligible, but longer period (5-15 days) variation in water level ensures co nsiderable exchange between estuary and ocean. Rainfall and river flow are strongly seasonal, with river flow being mainl y in winter. In co nseq uence the salinit y range is ex treme, from fresh to 500,60. Since the late 1960s macroscopi c green algae have been abundant throughout Peel Inl et. They accumulate in the shallows where they begin to decay and are driven onshore by wind and waves. The rotting argae give off hydrogen sulphide which is offensive to residents on the northern and western shores of the Inl et. Green algae ha ve given little trouble in Harvey Est ua ry, but since the summer of 1980-81 there have been massive blooms of the bluegreen alga Nodularia spumigena. _Thi s drifts into Peel Inlet and ac-

Dr. P. B. Birch is Senior Environmental Officer with the Department of Conservation and Environment, Western Australia. Mr. J . 0. Gabrielson is a Research Officer wirh the Department of Soil Science and Plant N utrition, Universiry of Western Ausrralia. Dr. E. P. Hodgkin is the Research Co-ordinator for the Pee/Harvey Estuarine Sysrem, Departmen t of Conservation and Environment.

DIMENSIONS Rivers Serpentine Murray Harvey Agri. Drains

Catchment Area km' 1000 7000

600 400

Depth 2m Inlet Channel 5 km x 700 m Peel 75 km' 60 x 1o•m• Harvey 56 m' 56 x 1o•m•



Figure 1. Map of the Peel-Harvey estuary . cu mulates on th e western beaches where, it decomposes rapidly. Residents have had to abandon their homes because of noxious gases evo lved and there have been fish and crab deaths, attributed to anoxic conditions resu lting from decaying algae. The study has shown unequivocally that phosphorus is the plant nutrient in shortest supply and hence limits algal growt h much of the time. There has been an enormous increase in the amount entering the est uary since the early I 950s and the estimated input from coastal plain drainage was 130 tonnes in I 98 I. Phosphprus losses are: to the ocean, estimated at less than half the present input; in algae removed, less than 2 per cent of input; with the balance retained in the sediments . In such a sha ll ow water body as the Peel-Harvey system the sediments can play a vital role in storage and remineraii zing pla nt nutrients, thus making possible a high productivity at times when there is little or no external nutrient supply . Although there is a large store of phosphorus in the sed iments this only becomes available at rates sufficient to support algal blooms under anoxic conditions. These occur either as the result of strat ificat ion of the water body or from decomposition of organic matter (BOD). WATER June, 1984


The riverine input of nutrients in winter initiates diatom blooms which, on death and decomposition, add to the available phosphate in the surface sediment. This occurs in the photic zone and the benthic green algae which abound in Peel Inlet are well placed to assimilate phosphorus released by remineralisat ion at the sediment-water interface. In recent years, the more turbid water of Harvey Estuary appears to have favoured Nodularia which starts to grow rapidly in September-October using phosphorus recycled from the surface sediment. .



Research so far has shown that the condition of the estuary will not improve until the amount of phosphorus avai lable to plant life is substantially reduced. Beyond that it is not possible -to predict its future with any certainty, there are too many unknown factors e.g. the variabi li ty of rainfall and river flow, the use of agricu ltural fertilizers, the abi lity of both the coastal plain soils and the estuarine sediments to store and release phosphorus. Over the last four years the input of phosphorus has been proportional to river flow and the intensity of Nodularia blooms, as measured by chloroph yll concentration, have been roughly proportional to phosphorus inpu t (Fig. 2b), though the bloom of I 982 was more extensive than expected on the basis of phosphorus load. All were years of average or below average rainfa ll. In 1973 and 1974 rain. fall was well above average and, on the evidence of Figure 2a, presumabl y so also was phosphorus loading. However, there were no reports of Nodularia blooms, though there is indirect evidence from pH record s that there were moderate blooms in those years. These observations suggest that there has been a progressive increase in the amount of phosphorus available for Nodu/aria growth from Harvey Estuary sediments. Blooms of blue-green algae such as Nodu laria clearly are unacceptable and our first objective must be to prevent their recurrence. There was no bloom in 1979 when river flow and phosphorus input were at their lowest during the study . At a first approximation then phosphorus input needs to be brought back to the I 979 level (67 tonnes) which means halving the 1981 input. However , this is not necessarily the only approach to management. The phosphorus flow diagram (Fig. 3) gives a simple picture of phosphorus flow through the coastal plain - estuary ecosystem and suggests how flow to nuisance algae can be reduced or interrupted at a number of points. Some of these are discussed below.






g " ::,

• 1981





z z

z z



y = 12 X • 38, r = 0.93



1982 •


• 1980

g "


1978 •



IC 1982












y = 0.39X + 1.93, r "' 0.99













Q. J


...0" ...

...0" ... 0


0 0



2(a). In relations to river flow.


I mg /L)

2(b). In relation to load of chloroph yl in estuary waters during Nodularia blooms, regress ion lin e for 1978-81. (1980 phosphorus load est imat ed from river flow).

Chlorophyl data supplied by Waterways Commission, W.A. a nd R. J. Lukatelich, Centre for Water Research , Universit y of W .A.

Figure 2. Phosphorus loadin g to Harvey Estuary .

range of doses tested and the reactions were nearly complete after 15 minutes in both cases (Fig . 4). A lthough both chem icals show potential for removing phosphate from drainage water, they require considerable attention to dose rates to maintain efficiency without resulting in pH problems. Also the resulting floe might need to be removed to avoid re-release of phosphate in the estuary, or aesthetic problems. PHOSPHATIC FERTILI ZERS APPLI ED TO L AND





Engineering solutions to the problem, such as diverting drainage water direct to the sea, or significantly increasing marine flushing, are lik ely to be costly and have a long lead time before they are effective, moreover they may result in undesirable changes to the estuarine ecosystem . Nevertheless they must be and are being investigated by the Public Works Department of Western Australia. At one stage it was suggested that removing the nutrient-enriched top 10 cm of estuarine . sediment wou ld substantia lly reduce the amount of phosphorus available to algae. The practical problems of dredging and disposing of this semi-liquid material from such a large area sufficiently rapidly to be effective are formidable . Moreover as indicated above it is probable that, while there is a large store of phosphorus in the sediment, release to algae is dependent indirectly on the input of sufficient phosphorus from drainage.










. A preliminary stud y has been made of the potential for chemical removal of phosphate from Harvey River water. Iron , aluminium and calcium ions can precipitate phosphate and are used in advanced wastewater treatment processes . In thi s sort of application initial and even final phosphate concentrations are in mg/ Las opposed td typical concentrations in the Harvey River of 200-500 ug/ L. Because of the imprecisely understood mechani sms of phosphate remova l by these ions, it is not possible to predict accurately removal efficiencies or optimal dosages to be used. Varying concentrations of ferric nitrate, alum (Al,[SO.l,) and limestone were investigated as precipitating agents in our system. All three displayed the abi lity to remove significant amounts of soluble reactive phosphate from solution . Reductions of up to 94 per cent and 98 per cent for Fe>• and AP· respectively were achieved within the 18

WATER June, 1984



D Figure 3. Phosphorus flow paths in the coasta l plain/ estuary ecosystem. Shaded boxes potential management measures.






• ~









\ \

_g o.



~ 20

\ '---

-- --- ---


,,,0 10







Concentration of Fe,• ( - - )or A P• ( - - ) (mg/I )

Fi gure 4 . Removal of solubl e reacti ve phosph o ru s from ri ve r water by iron and aluminium.

Exp.eriments using lim estone, eit her as a coarse gravel or sa nd size, showed a mu ch slower rate o f phosph ate remova l a nd the adsorbti ve capacity was too low for it to be of practical va lue on the scale requ ired . A furth er problem with the use of chemi cals results from the extremely seasonal nat ure of river flow. Treat ment methods wo ul d have to treat large vo lumes in a short time or, alternati vely, la rge holding bas ins would have to be buil t, both are very costly proced ures. T he use of algicid es to ameliorate the problem is a lso being co nsidered , but · thi s will requi re careful investigation if un for seen side effects are to be avoided beca use o f possible toxicity to oth er organi sms, especially fi sh. Moreover, it wo uld leave most o f th e phosph oru s to accu mulate in the sed iments. H A RVESTING A LGA E

Recently a weed harvester has operated to co llect algae fro m water 0.5 to 1. 5 m deep and thi s has been successfu l in largely preventing the accumulati on of algae on beac hes near housing sett lements, thu s greatl y mitigat ing the nu isance. H owever, this does nothing to attack the cause of the problem by reducing the amount o f ph osphorus available to a lgae. CATCHM EN T MAN AGEM ENT

T he eutrophic co ndition o f th e estu ary is caused by inefficient use of phosphorus on sandy agricultura l catchments. T herefore, the preferred solution is to alleviate this conditi on by using ph osphoru s more effi cientl y, thereby so lving two problems at once at li ttle cost and minimal disturba nce to the estuari ne ecosystem . In I 981 fa rm ers applied about 500 tonnes o f ph osph oru s (as superphosphate) to the coastal pla in catchment of H arvey Estuary, at a cost of $450 000. Of this, 110 tonnes fo und its way into th e estuary, a loss to far mers of $ 100 000. thi s was equi va lent to fe rtilizing the water at approx im ately 18 kg/ ha, the same rate as that appli ed by fa rmers to th eir paddocks. Clearly it wi ll be advantageo us both to fa rm ers and to the est ua ry to reduce this loss substanti ally. H ow to achieve this reduction is th e ma in focus of o ur Ph ase 2 catchment studi es. Fo ll ow ing th e fi ndings of Ph ase I , a pil ot scale study was made in 1981 to pinpoint th e major sources of phosp horus within th e catchment o f Harvey Estuary fro m the various soil types (Fig. 5). The results are summari sed in Table l . T hese show a strong relati onship between phos phoru s export and the domina nt soil category within the catchment, but not wi th fert ili zer application rates. T he catchment with predominantly deep grey sands, the Meredith drain catchment, had the highest ex port rate (1. 9 kg/ ha); this was fo llowed by the predomin antly sand over cl ay catchment o f the May fi elds drain (1. 3 kg/ ha) . Signi ficant ly lower export rates (0 .4-0.6 kg/ ha) were recorded fo r the other three d rai ns which included mainl y clay and loams within their catchm ents. Table 2 shows th at sa ndy-surfaced soils are the most important sources of phosphoru s for the es tuary, proba bly accounti ng for about 75 per cent of the total load and this fi nding was con fi rm ed by more extensive sampling in 1982 . They have poor ability to absorb phosphorus and leaching losses are high. Up to one-t hird of the phospho rus applied in the Meredith drain catchment appeared in dra inage water (Table 1). T his represents a serious agronomic problem as well as causing eutroph ication , and mea ns th at emphasis needs to be placed on determining how these leaching losses can be redu ced.


~, \


Figure 5 . Major soil categories on the co as tal plain catchment of th e Peel-H arvey estu ary. WATER June, 1984


TABLE 1: TOTAL PHOSPHORUS LOADINGS FROM HARVEY RIVER AND AGRICULTURAL DRAINS WITHI CATCHMENT DURING WINTER, JUNE - SEPTEMBER 1981 Carchmen1 Harvey River (mouth) Harvey River (mid) Ma yfield Drain Meredith Drain Waroona Drain Logue Brook Dr. Samson Brook - North Drain

Area (km')

Flow (JO"m')

P Cone. (mg/ LJ

540 240 97 52 49 56 17

240 130 30 9 18 12

0 .36 0.26 0.36 I.I 0.12 0. 16 0 .20



% of Catchment

Export Rare (kg/ ha)•

21 28 23 28

1.9 1.3 0.5 0.5

Deep Grey Sands Sand over Clay Loams and C lays Otherst

% of P Load 39 36 II 14

75 25


This ass umes the export rates for so il types as estimated from the subcatchments a s in Table I. t These so ils include mostl y foothills and hills soi ls of the Darling Scarp and are likely to adsorb phosphate similarly to loams and clays. Therefore an export rate of phosphorus equal to that of the loams and clays has been assumed , although this is likely to be an o ver estimate since about half of the hills a rea is forested.

Work in 1982 has focu ssed on thi s problem . Fertili ze r trials using slow releasing phosphatic ferti li zers such as lim e-reverted superphosphate made by reactin g orginary s uperphosphate with li me . Thi s convert s water solub le mono-calcium phosph a te (80 per cent of th e phosphorus fraction in superphosphate) into citrate so lu ble , di calcium phosphate. These tri a ls gave en couragin g res ult s. Lim ereverted superphosph a te gave about th e same yield as ordinary super-

BRANCH NEWS CONTINUED On 29th March, Doug Gannon of En vironmenta l Engineering, addressed a s pecial meeting on developments in fibre reinforced pla stic pipes for water a nd sewerage work s . The presentation arou sed considerabl e interest because of the po tential for use of the material for la rge sewers with integra l manholes in corrosive situations and a lso for large diam eter press ure main s wh ere the light wei ght fac ili tates co nstruction a nd reduces frei ght costs. Digby Habel, Assistant C hief Inspector of Dan gero us Good s, Department of Mines and Energy, addressed the Apri l meetin g on issues in vo lved in the tran sport, storage, use and di sposa l of ha za rdou s material s . Members were enlight ened on the critical aspects of the world-w ide problem being caused by t he ever increasing use cif hazardou s chemica ls and t-he cr e at i on of h a zardo u s wa s te s . Developments in controllin g legislation in the Territory and ot her States were present ed . Frank Dileo of Ionics In c. spoke to a group of members in Ali ce Sprin gs on desalinat ion , with particular emp hasis on elcctrodia lisis. Ionics supplied a nd in stalled a I M L/ day unit wh ich has been operat ing since last yea r at Yulara Vi ll age near Ayres Rock. TERRITORY TITBIT For som e years it has been realized that bore supplies to remote coa stal communities in the Territory are aggress ive. Fourteen com 20

WATER June, 1984

P Exported (kg/ ha) (Tonnes) 94 39 12 IO 2.6 2.4 I.I

1.7 1.7 1.3 1. 9 0 .53 0.43 0 .65


P A pplied (kg/ ha)

Dominant Soil Type

7.2 8.2 II 6 8.4 7.3 15

Mi xed Mixed Sa nd O ver Clay Deep Grey Sand C lays, Loams C la ys, Loams C lays, Loams

phosphate in th e first year, but with reduced leaching losses from the surface 10 cm of soil compared to plot s fertili zed with norm a l superphosphate . In another project , soil fertilit y leve ls were measured on about half the farm s (95) in th e Harvey and Mayfield catchm ent s . Phosphorus levels in th ese soils indica ted th a t, des pite leaching losses, rese rves ha d built up over th e years and that most farmer s cou ld safel y reduce phosphorus a ppli cation ra tes by 50 per cent or more . This was es pecia ll y true of th e sand over clay soils . An inten sive a gricultural extension campaign is now under wa y to persuade farmer s to reduce appli cation rates a nd to use lim e-reverted superphOSiJhate where phophorus is still required. It is not yet clear how rapidly these measures will be effective in reducing the load of p hosphorus to the est uary and resea rch planned for the winter of 1983 aims to measure loss of phosphorus to drainage in relat ion to cha nged fertilizer practices . This wi ll be done both on large natural catchments and small experimental catchments where water and phosphoru s movement through the soil can be monitored more preci sely in relation to fertili zer a pplication or the lack of it. ACKNOWLEDGEMENTS The authors wish to thank fellow workers in the Peel-Harvey estuarine system study for helpful di scuss ions and provision of data . This work has been funded by the Department of Conservation and Environment, Western A ustrali a .

munities plus num erou s out station s are invo lved. Recent ly, fo ll owing incidents of high

water use and report s of plumbing corrod ing out so rapid ly that hou ses could not be main tained in habitable condit ions, A ustralian Min e ral D e velopment L a boratori es (AM DEL) of Q ueen sla nd were com mi ss io ned by the Department of Transport a nd Work s to investigate the problem. T he Consultant concluded tha t fai lu res are occurring on a massive scale to an extent unknown elsewhere in Au stral ia, and that the hi gh fa ilure rate of copper pipe, brass fittin gs and hot water sys tem s is a res ult of the co rrosiveness of the soft , acidi c bore waters . Acidity of the suppli es generall y ranges from pH4 to 6, TDS less than 50 mg/ L and Total Hardness less than 5 mg/ L. Extremely rapid internal attack of copper pipes is occurrin g by acidic erosion corrosion support ed by cuproso lvency. Pipes afflicted look as though shot by a scatter gun. Dezin cification fa ilure of brass fitting s is also occur ring rapid ly. Darwin is not subject to the prob lem as it has a surface suppl y with minor supplem entation from bores whic h are non-aggress ive . Con sideration is bein g given to overcoming the problem by eit her in sta ll ation of neutrali zation treatment plant s or changin g to corrosion res istant plum bi ng. Neutra liza tion plants are not favoured be cau se of maintenan ce difficu lti es associated with remoteness of th e location s whi ch are often isolat ed for month s during

the Wet, th e general non- a vailabi li ty of suitabl y skill ed operators, and the hi gh cost of rearrangin g multiple so urce supplies for sin gle station dosin g. C hanging to corrosion resistant plum bing appears to be the m~re pra ctical solution. In this regard con sid eration is being given to reinforced plastic tappin g saddl es with dezincificat ion (DR) ferrule co cks, PVC se rv ice pipes and DR brass taps, from ma in to building. Within buildin gs PVC for cold water ru ns and polybutyle ne (PB) for hot (or both hot and cold) wat er run s in accordance with th recentl y iss ued Au stralian Standard for PB is bein g con sid ered . Corrosion res istant sola r collectors and hot water tank s are a lso bein g inves tigated . A further contribution to th e Journal will be made when a special plumbing code has been implem ented a nd res ults o f fie ld performance known.

CHANGING YOUR ADDRESS? WHY NOT CONFIDE IN US? Advi se your Branch Secretary or the Editor.

Predicted Oxygen Transfer Characteristics Riser Pipes at Wastewater Pumping Stations Keith Cadee ABSTRACT The use of oxygen to control septicity in wastewater pressure mains has been wide ly used for many years . The oxygen is most commonly introduced into the ri ser pipe at the pumping station, downstream of the pumps. In this st ud y a computer model was used to in vestigate the oxygen dissolving characteristics of riser pipes. The effects of initial bubble diameter, alpha factor , initial pressure, d issolved oxygen concentration and riser hei ght were investigated . Although riser pipes are effective oxygen transfer devices, the mode l predicts comparatively low transfer effi cien cies in most circum sta nces. This demonstrates the importance of the di ssolving character istics of the pressure mains in the successfu l app li cation of oxygen injection for septi city co ntro l. I. INTRODUCTION Oxygen inj ection into the riser pipe at wastewater pumping stat ions has been used for many years to control septicity. The oxygen disso lved into the wastewater in this way maintains aerob ic conditions in the pressure main. This prevents the formation of many of the odorous by-products of anaerobic decompos ition. In addition, the oxidizing environment destroys ma ny of the odorous compounds which may have already formed. Despite the widespread and effective use of this technique, no information on the dissolving characteristics of riser pipes appears to have been publi shed . However, some work in related field s has been published. Speece et al. ( 1970) modelled th e oxygen transfer from small oxygen bubbles used to oxygenate deep, stratified reservoirs , whi le Motarjemi a nd Jameson (1978) have in vestigated th e oxygen transfer from small bubbles of air and oxygen in qu iescent water. The oxygen dissolving characteristics of U-tube dissolvers has been studied and modelled by a number of researchers including Speece er al. ( 1980) and Bilstad a nd Lightfoot (I 980). Although a number of important inferences on the oxygen di ssolving characteristics of riser pipes may be drawn from these publi shed studies, there is a need to specifically model riser pipes. Th is paper describes a co mputer model whi, h has been developed for predicting the oxygen d issolving characteristics of riser pipes. The model has then bee n used to investigate the factors influ enci ng oxygen transfer. 2. DETAILS OF THE COMPUTER MODEL The rate of mass transfer between gaseous

Mr Keith Codee is Wastewater Treatment Engineer, Metropolitan Water Authority, Perth, Western Australia.

a nd liquid phases in the riser pipe may be described by, dm dt

= KLA(Cs- C)


dm dt KL


rate of mass transfer, g/s

liquid phase mass tran sfer coefficient, mis A total su rface area of gas/ liquid interface, m 2 C, saturation concentration of the gas in liquid, mg/ L C concentration of the gas in liquid, mg/ L By finite approx imat ion, l',M = KLA (C,- C) l',t (2) For this study, l',t was taken as 0.1 seconds. The saturation concentration of the gas in liquid may be calcu lated from C, = H Xp (3) where H Henry's constant, mg/ L per 2 N/ m abso lu te Xp partial pressure of the gas, N/ m 2 abso lute For small bubbles the effects of surface tension increases t he pressure inside the bubb le -


P, = PL + 4 where



PL =

o d,


pressure inside bubble, Ni m' absolute press ure in liqu id, N/ m 2 absolute surface tension, Ni m bubble diameter, m

Hence, Cs = HP, X; (5) where X; = mole fractio n of the gas in the bubble. The number of bubbles and hence the bubble surface area was calculated from the oxygen fl ow rate (adjusted to the press ure at the injection point) and the initial bubb le diameter . The model ass umes no bubble coalescence occurred in the rise r pipe. The model calcu lated the mass of oxygen and nitrogen transferred during the time interval L\.t. T he sum of the liq uid ve locity and the bubble rise velocity was then used to calculate the incremental volume through which the bubbles travelled during the time L\.t. T his in cremental vo lume was then used to calculate the changes in dissolved oxygen and nitrogen concentrations resulting from mass of oxygen and nitrogen transferred. The new gas vo lum e, partia l pressures, bubble diameter, bubb le surface area and saturatio n concentrations were then calcu lated for the next time interval. This process was repeated for the full height of the ri ser.

4g(sL-s,)d, ] ½ (6) 3CdsL where V, bubble rise ve locity, mi s sg gas density, kg/ m' Cd = drag coefficient Sime s L is approximately 1000 times sg for oxygen and water the rise velocity may be calcu lated from


v. =



gd~ ½ (7) 3Cd Very small bubbles behave as rigid spheres (Re <0.3) and Stoke's Law may be applied. C


(8) Re where Re = Reynolds Number Larger bubbles do not behave as rigid spheres and the relationship between drag coeffic ient and Reynolds number has been determ ined by Haberman and Morton (1953) for air a nd tap water. The predictions of the Haberman and Morto n relationsh ip used in the model are shown on Figure I together with the original meas urements of Haberman and Morton (1956) and the measurements of Motarjemi (I 976). The predicted ri se velocities are generally sli ghtly lower than the measured velocities shown , but are believed to be appropriate for wastewater.

3.2 Mass Transfer Coefficient, KL The mass transfer coefficient K L for oxygen transfer to tap water at 20°C has been measured by a number of researchers and their published resu lts are summarised on Figure 2. The measurem ents ex hi bit co nsiderable scatter although a salisfactory relationship between KL and bubble diameter was derived from the data for use in the model. For bubb le diameters greater than 2.2 mm, Hi gbie' s equation for free ly circulating bubbles was used , Higbie (I 935). Sh 1.1 3 Pe½ (9) where Sh Pe

KL d, Sherwood number -- n;:-

Peele! numb er

= dn~'


DL diffusion coefficient, m'/ s At bubble diameters less than 2.2 mm , no such theoretical equations fit th e data sufficiently well to be used . The empirica l relation ship used in the model is shown on Figure 2. The value of KL for nitroge n has been ass umed to be 1. 16 19 times the corresponding KL for oxygen . This con flict s with the values calculated from so me of the pub lished values of the diffusion coefficients. However, this relationship is supported by t he measurements of Bilstad and Lightfoot ( 1980) taken during their investigat ion of U-tube dissolvers.

3.1 Bubble Rise Velocity

3.3 Overall Mass Transfer Coefficient, KLA

The bubble velocity may be calculated from

Values of KLA ca lculated from the reported values of KL presented on Figure 2, WATER June, 1984



· ~------~-------~---------,---------~ ---- - ---,







0 .3








' "f

.5 ~ 0






..,... ...



... /





.; <



., •

.,. .,

., .,•


. ~

1 ~

. • ., . •.. ~·. •

•• •••••

•• • • •


1 0 , - - - ~ - - - -- -, - - - - - - - - - -, - -- - - - - - - ~













• •

Fig. 2. Reported Values of Mass Transfer Coeficients for Oxygen Transfer to Tap· Water at 20°C. (After Barnhart 119691 and Motarjemi and Jameson [19781) . •

., .,



Fig. I. Bubble Rise Velocities at 20°C.

• • ., •




•... •









o . 1 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __


_ _ _ _ _ _ _ __



1. 0 BUBBL E AG E (S EC . )


Fig. 3. Overall Mass Transfer Coefficients Calculated from Figure 2.

Fig. 4. Effect of Bubble Age on Mass Transfer Coefficient (Using the data from Pasveer (19551).



together with the prediction s of the model, are shown in Fi gure 3. The model predi cts a maximum value of K, at a bubble diameter of 1. 2 mm. For bubble diameters greater than 1.2 mm , the value of K,A d ec reases with increasing bubbl e dia meter. At bubble diameters less than 1.2 mm , K, A initiall y decreases with decreasin g bubble diameter then becomes independent of bubble size at diameters less than 0.4 mm. This illu strates the importance of achi eving small diameter bubbles if the overall mass trans fer coefficient is to be maximi sed. Howeve r , the model clearly shows that there is no benefit in achieving ve ry small diameter bubbles substa ntia ll y less than 1.2 mm in diameter. Although the gross surface area of these very small bubbles is very hi gh , this is more than outweighed by the reduction in the mass transfer coe fficient K, . 3.4 Effect of Bubble Age on Mass Transfer Coefficient The mass coe fficient does no t solely depend on the diameter of the gas bubble. It is a lso a function of the age of the bubble. As the age of th e bubble in creases, K, decrea ses . This may be illustrated using the data reported by Pasveer (1955). The average bubble age has been calculated from the column height and average rise velocity. To normali ze the results from different bubble size experiments, the values of K, at time t have been divided by the value of K, at IO seco nds as determined by linear interpolation of the data. The values of K,(t) / K,(l 0) versus average bubble age are shown in Figure 4. Thi s ph enomena explains some of the variabi li ty in the measurements shown on Figure 2 . The relationship betwee n K, and bubble diameter used in the model is bel ieved to be appropri ate for bubble ages of 5 to IO seconds. In cases where the bubble age is a ppreci ably greater than this, so me reduction in the va lue of K, should be made.

3.5 Alpha Factor Th e alpha facto r is the ratio of the rate of oxyge n trans fer in wastewater to the rate in clean water. The presence of surface act ive agents in wastewater retards mass transfer between t he bubble and wastewater and a lpha is ge nerally less than 1.0 for bubble processes. Most measurements of alpha have been made in mi xed liquor as part of the invest igation of aeration processes for the activated sludge process. However, some measurements in untreated wastewater have been made. Kessner and Ribbius (I 935) determined a lpha to be 0.20 for sterili zed wastewater while Holroyd a nd Parker ( 1952) found a lpha factors as low as 0.50 in the presence of hi gh surfactant concentra tions (20-100 mg/ L). Baars (I 955) measured alpha factors rangi ng from 0.9 to 0.4 for non ionic surfactants in the range 4 to 10 mg/ L respecti ve ly. The addition of antifoaming agents furth er reduced these alpha factors to 0.8 and 0.35. Lister and Boon (1973) reported alpha factors as low as 0.3 when wastewater is fir st mixed with return sludge in an aeration tank.

15 ~ - - - - - - ~ - - - - - - , ~ - - - - - - , ~ - - - - - - , ~ - - - - - - , RISER Dl*°'ETE~



15 . 0m


3 0 .V m




Fig. 5. Predicted Dissolved Oxygen Concentrations at Various Bubble Diameters and Alpha Factors.




"!!!z "~



10 . 0ffl









:: z


"> X



















Fig. 6. Predicted Oxygen Transfer Efficiencies for 10.0 m Riser Height at Various Dissolved Oxygen Concentrations and Initial Pressures. King (I 955) measured a lpha factor s in the range 0.27 to 0.46 for fresh wastewater still containing some diss olved oxygen and 0 . 16 to 0.19 for wastewater in whic h anaerobic condition s had been es tablished. For the conditions encountered in ri ser pipes th e alpha factor cou ld reasonably be expected to be in the ra nge 0.2 to 0.4. 4 . PREDICTIONS OF THE MODEL The factors affecting oxygen tra nsfer in the riser pipe may be illustrated by way of the following examples. 4.1 Bubble Diameter The prediction of the model at different initial bubble diamete rs are shown on Figure 5 . The optimum bubble diameter may be seen to be about 1.0 mm. This is sli ghtly lower than the value predicted from K, A considerations due to th e slightly longer contact time which resul ts from the lower rise velocity of the small bubble. The model also predicts that oxygen tran sfer is reasonably insensitive

to initia l bubble diameters within the range 0.1 to 1. 2 mm . 4.2 Alpha Factor The importance of the alpha factor on oxygen transfer is also illustrated on Figure 5. The correct selection of alpha is the si ngle most importa nt factor in predicting oxygen transfer in the riser pipe. For the followin g examples an alpha factor of 0.4 has been adopted for the purpose of illustration. 4.3 Initial Pressure At low diss olved oxygen concentration s, the oxygen transfer in the riser pipe is relatively insens iti ve to the initial pressure at the inject ion point. Thi s is illustrated in Figures 6, 7 and 8. This phenomenon results from the fact that for a pa rticular bubble diameter , the volume of ga s and hence surface area decreases as pressure increases. The reduction in surface area is compensated for by a corresponding increase in the saturation concentration. The net result is similar oxygen WATER June, 1984


transfer efficiencies regardless of initial pressure. As the dissolved oxygen concentration increases to a signifi ca nt fraction of the initial saturation concentration, initial pressu·res become more significa nt . Under these ci rcumstances, oxygen transfer increases with higher initial pressures. The effect of initial pressure is more pronounced for long risers (Figure 8) than for short riser hei ghts (Figure





> 0







."' ffi

250 l/1



::"' z






4.4 Dissolved Oxygen Concentration eo


In all cases, the oxygen transfer efficiency decreases as the dissolved oxygen concentration increases . For short ri ser heights and low dissolved oxygen concentrations the oxygen transfer efficiency is reasonably insensitive to initial press ures . This phenomenon is illustrated on Figures 6 and 7. As a consequence, the oxygen transfer ch·aracteri stics of riser heights less than about 15.0 m may be assumed to be independent of initial pressure and a function of dissolved oxygen only. This relationship holds for di sso lved oxygen concentrations less than about 35 to 50 per cent of the initial saturation concentration.














Fig. 7. Predicted Oxygen Transfer Efficiencies for 15 .0 m Riser Height at Various Dissolved Oxygen Concentrations and Initial Pressures.

For riser heights greater than about 15 m, the oxygen transfer efficiency is much more sensi tive to the di ssolved oxygen concentration as may be seen from Figure 8.



"'z ::"' z


4.5 Riser Height

" >


The oxygen transfer effic iency for an alpha factor of 0.4 and at low dissolved oxygen concentrations varies from about 15 to 30 per cent for riser heights of IO and 20 m respecti vely. At higher disso lved oxygen concentrations the oxygen transfer efficiency declines and efficiencies in the range IO to 25 per cent are predicted for most circumstances. The longer contact time afforded by increased rise r height is beneficial in achieving higher oxygen transfer effi cienci es as illustrated on Figure 9.












Fig. 8. Predicted Oxygen Transfer Efficiencies for 20.0 m Riser Height at Various Dissolved Oxygen Concentrations and Initial Pressures.




250 L/1




The following empirical equation may be used to estimate the oxygen transfer efficiency for initial bubble diameters in the range 0.1 to 1.2 mm , and low disso lved oxygen concentrations such that the transfer efficiency is independent of initia l pressure. E 5at (10) where E oxygen transfer efficiency, O'/o a alpha factor nominal liquid retention time in riser pipe, s


30 . 0m




o., 20



"'... 0:
















Fig. 9. Effect of Riser Height on Oxygen Transfer Efficiencies.


WATER June, 1984



The oxygen transfer efficiency is essentially proportional to the contact time in the riser pipe at low dissolved oxygen concentrations. As a consequence, lower liquid velocities in the riser pipe will be beneficial in achieving higher oxygen transfe r efficiencies.




4.6 Liquid Velocity

The following conclusions may be drawn from the predi ct ions of the computer model. • The riser pipe at wastewater pumping stations can be effective in dissolving oxygen although oxygen transfer efficiencies are low. Transfer efficiencies depending on riser height, dissolved oxygen concentra-


tion, initial pressure and liquid velocity. The optimum bubb le diameter for oxygen transfer is about 1.0 mm although oxygen transfer is relatively insensitive to initial bubb le diameters in the range 0. 1 to 1.2 mm. Oxygen transfer is in sensit ive to initial pressure at low oxygen dosages. At higher

dissolved oxygen concentrations, increasing initial pressure is beneficia l in achieving higher transfer efficiencies. For riser heights less than about 15.0 m, the oxygen transfer efficiency may be assumed to be independent of initial press ure and a function of the di ssolved oxygen concentration only . This relation-

ship hold s for dissolved oxygen concentrations less than about 35 per cent to 50 per cent of the initial saturation concen tration. • Oxygen transfer efficiency increases as the height of the riser increases due to the longer contact time availab le. • The oxygen transfer efficiency increases as the liquid velocity in the riser pipe decreases due to the long contact time . At low di ssolved oxygen concentrations the oxygen transfer efficiency is essentially proportional to the contact time. • The low oxygen tran sfer efficiencies predicted by the model demonstrate th e importance of the disso lving characteristics of the following pressure main in the successful application of oxygen inj ect ion for septicity control. ACKNOWLEDGEMENTS

Th e model presented in this paper was developed as part of investigations conducted by the Sewerage and Drainage Branch of the Metropolitan Water Authority, P erth. The author wishes to thank the Director of Engineering, Metropolitan Water Authority for permi ssion to publi sh this paper.

REFERENCES AIBA, S., and TODA , K. (1964). J. Gen . Appl. Microbiol. Vol. 9, p 157. BAARS, J. K. (1955). 'The effects of detergents on aeration: A photographic approach.' J. Proc. Inst. Sew . Puri/. pp 358-362. BARNHART, E. L . (1969). 'Transfer of oxygen in aqueo us solutions' . J. San it. Enging. Div. Soc. Civ. Engrs. Vol. 95, pp 645-661. BILSTAD, T. and LIGHTFOOT, E. N. (1980). ' Predicting oxygen and nitrogen absorption rates from submerged suspensions of bubbles.' Prog. Wat. Tech . Vol. 12, Toronto pp 23-25. COPPOCK, P. D. and MEIKLEJOHN, G. T . (1951) . Trans. Inst. Chem. Engrs. Vol. 29, p 75 . HABERMAN , W. L. and MORTON, R. K. ( 1953). 'Ex perimental stud y of the motion of gas bubbles in various liquids. David Taylor Model Basin, Navy Dept., Report 802. HABERMAN , W. L. and MORTON, R. K. (1956) . Trans. Am. Soc. Civ. Engrs. Vol. 121, p 227-250. HIGBIE, R. (1935). 'The rate of absorption of pure gas into a still liquid during short periods of exposure'. Trans. A m. Inst. Chem. Engineers. Vol. 31, p 365. HOLROYD, A. and PARKER, H . B. (1 952) . ' Invest igations of the dynamics of ae ration'. J. Inst. Sew. Puri/. p 280-297 . KESSENER, H . J. N. H. and RIBBI US, F. J. (1935) . 'Practical activated sludge research. J. Proc. Inst. Sew. Puri/. p 50-66.

KING, H . R. (1955). 'Mechanics of oxygen abso rp-

tion in spiral flow aeration tanks, II. Experimental work.' Sewerage Industrial Wastes. Vol. 27, No. 9, pp 1007- 1026. LISTER , A. R. and BOON , A.G. (1973) . 'Aeration in deep tanks: An evaluation of a fine bubble diffused-air system '. J. Inst. Sew. Purif. p 3-18. MOTARJEMI, M. (1976). 'The optimum bubble size for mass transfer in a stationary liquid. MSc. Report , Imperial College, University of London. MOTARJEMI, M . and JAMESON , G. J . (1978) . 'Effect of bubble size on oxygen utilization in ae ration process' in 'New Processes of Wastewater Treatment and Recovery.' (Edited by Mattock, G.), Ellis Horwood Ltd . PASVEER, A. (1955). 'Research on activated sludge, VI. Oxygenation of water with air bubbles.' Sewage and Industrial Wastes. Vol. 27, No. 10, pp 1130-1146. PHILPOIT , Cited in Barnhart (1969). SPEECE, R. E. RAYYAN, F. and MURFEE, G . (1970) . 'Alternative considerations in the oxygenation of reservoir disc harges and rivers.' In 'Advances in Water Quality Improvements'. (Edited by Gloyna, E. F. and Eckenfelder, W. W. Jr.) . pp 342-36 1, University of Texas Press. SPEECE, R. E., GALLAGHER, D. , KRICK, C. and THOMSON , R. (1980). ' Pilot performance of deep U-tubes.' Prog. Wat. Tech ., Vol. 12, Toronto, pp 359-407.

CALENDAR 1984-85 July 15-20, Cambridge, U.K. Int. Co nference on Ion Exchange.

September 5-7, Queensland , Australia Sixth Austra li an Biotechnology Conference.

July 25-Aug. 6, Urbana, Ill. U.S.A. Stochastic H ydra ulics and Safety of H ydra uli c Systems.

September 10-13 , Glasgow, Scot land Inst. of Water Pollution Co ntrol , Annual Co nferen ce and Ex hibition.

August 13-16, Washington D .C., U.S.A. 20th American Water Resources Con ference . August 15, Washington D.C., U.S.A. Annual A.W.R.A. Symposium. August 23-24, Canberra, Australia Sympos ium on the Ecology of Bio logical In vasions. August 26-31, San Diego, U.S.A. Future of Water Re-use. August 27-30, Glasgow, Scotland Int. Assoc. for H ydrau li c Research- 1984 Symposium. August 27-Sep. 7, Adelaide , Sth. Austra lia Aust. Minera l Foundation Eighth Groundwater School. September 1, Brussels, Belgium Inter-U ni ve rsit y Postgraduate program in H ydrology.

September 10-14 , Stockholm, Sweden Int. Symposium on Balances of C hemical Substa nces in Water. Se ptember 12-14, Copenhagen, Denmark Degradat io n, Retention a nd Disposa l of Pollutants. September 15-16, Cardiff, Wales Biological Monitoring in Groundwater. September 17-20, Amsterdam, Net herland s 12th Internationa l Conference on Water Pollution Research a nd Control, IA WPRC. September 17-20, Amsterdam, Netherlands AQUATECH '83 - International W a ter Technology Exhibition. September 19-22 , Canberra, Australia Australian Pump Manufacturers' Association Co nference.

September 25-26, Ca nberra, Aust. Nat iona l Conference on Conservation a nd th e Economy. September 29-30, Canberra, Aust. Managing the Murray. September 30-Oct. 5, New Orleans, U.S.A. WPCF Conference.


October 15-17, Bangkok , Tha iland 1st International Conference on Rural Water Syste ms. October 29-November 2, Monastie, Tunisia 13th Int. Water Supply Co ngress & Exhibition.

October 30-31, London , U.K. Reuse of Sewage Effluent. November 22-23, Adelaide , Sth. Australia Seminar A.W.W.A. & I. E. (Aust.)Changing Management Needs in the Industry.

1985 Feb ruary 11 -14, Melbourne, Australia 'Po lymer '85'. Internatio nal Polymer Symposium.

September 3-7 , Junkoping, Sweden Elmia Air and Wate r Conference.

September 24-25 , Antwerp, Belgium Advanced Trea tment T ec hnologies for Remova l and Disposa l of Micropollutants.

April 28-May 5, Melbourne, Australia 11th Federal Convent ion A .W.W.A .

September 5, London, England Seminar on O zone In st. o f Water Engineers & Scientists.

September 24-25, Paris, France Enhanced Biological Phosphorus Removal from Wastewater.

August 19-23, Melbourne, Australia International Congress on H ydraulic Resea rch . WATER June, 1984



Five, CIG Vitox II oxygen dissolvers have been installed as part of the septicity control facilities for the Woodman Point Wastewater Treatment Plant. The largest of these is located at the Munster Pumping Station just upstream of the treatment plant. Design details of the Munster system are discussed. Operating parameters are presented which demonstrate that the septicity control facilit ies effectively oxidi ze sulphides in the wastewater and achieve a high degree of odour control at the wastewater treatment plant. INTRODUCTION The Commonwealth Industrial Gases Limited (CIG) developed the Vitox II oxygen dissolving technology in Australia to solve severe septicity problems not treatable by existing methods . This work has positioned Australia at the forefront of septicity control technology. . The Metropolitan Water Authority of Perth has installed five CIG Vitox II oxygen dissolvers as part of septicity control facilities for the new Woodman Point Wastewater Treatment Plant. These facilities are shown schematically on Figure I. The system cons ists of four oxygen dissolvers located on pressure mains upstream of the Munster Pumping Station (P .S .) and a fifth dissolver located at the Munster P .S. Temporary prechlorination facilities have also been provided at the treatment plant which act as a backup for the oxygen systems and assist in preventing reformation of sulphides in the primary sedimentation tanks. Only a small dose of ch lorine has been required during the diurnal low flow period in the early morning hours. The total capital cost of the septicity control facilities upstream of


the Woodman Point Treatment Plant was approximately $700,000 out of a total expenditure of about $85 million for all of works associated with the redevelopment and amplification of the Woodman Point System . However, at the time of writing only three Vitox II dissolvers were operational out of the five proposed (Fig. I) - Munster, South Fremantle and Mount Pleasant. The largest of the oxygen dissolvers, and one of the largest of its type in the world, is the I 100 mm diameter dissolver located at the Munster P .S. The function of this dissolver is to: • Prevent the formation of sulphides in the pressure main between Munster Pumping Station and the treatment works. • Oxidize the residual sulphides not removed by the oxygen dissolvers located upstream of the pumping station. • Provide a residual dissolved oxygen concentration at the discharge end of the main which ass ists in preventing reformation of sulphides in the primary sedimentation tanks of the plant. PREVIOUS WORKS

During the past 20 years the Metropolitan Water Authority has conducted trials using chlorine, hydrogen peroxide and caustic soda to control septicity in its sewerage system. Although all of these chemicals were found to be effective in certain circumstances, oxygen proved to be the most cost effective option for the Woodman Point system . Experiments with the use of oxygen in Perth commenced in 1974 and a considerable amount of work has been conducted during the past IO years to understand the mechanisms of oxygen treatment and to develop effective methods of dissolving oxygen into wastewater. Different methods of dissolving oxygen were evaluated, including direct injection into riser pipes and various other types of oxygen dissolvers.





Fig. 2. Schematic of CIG Vitox II Oxygen Dissolver.

ST H. P' A E MANTl E P. S .





Fig. 1. Sc hematic of Septicity Control Facilities for the Woodman Point Sewerage System. Mr. Keith Codee is Wastewater Treatment Engineer, Metropolitan Waste Authority, Perth, Western Australia. Mr. T. E. Long is Odour Cont.-ol Officer with the Authority. Mr. R. E. Wain is with Commonwealth Industrial Gases Ltd. in Perth, Western Australia. 28

WATER Jun e, /984

The CIG Vitox II dissolver, illustrated in Figure 2, was developed by CIG for use by the Authority. The dissolver enables high dissolved oxygen concentrations to be achieved at high efficiency, thus avoiding potential gas lock ing problems. The high degree of oxygen utilization achieved, enabled a minimum oxygen consumption and was a contributing factor for selecting the Vitox II process over alternative systems. The first unit was installed in June 1979 at Spearwood on the Mt. Pleasant pressure main. This was the first time an oxygen dissolver was used for septicity control in Australia. Extensive trials were conducted on this unit and these formed a basis for design of the current Woodman Point septicity control system. MUNSTER SYSTEM

The oxygen saturation co ncentrations at 30°C for pumping and non-pumping conditions in the 915 mm diameter, 2700 m long

pressure main for the Munster P.S. to the Woodman Point plant are shown in Figure 3. The pumping rate for the Munster Pumping Station is variable within the range 400 to 1500 Li s and the detention times in the main range from I hour 14 minutes to 20 minutes during pumping periods. This large variation in flow rate of 3.75:1 was a complicati ng factor which limited the selection of suitable oxygen dissolving equipment. Previous experience with the Vitox II dissolver indicated this design could cope with large diurnal variations. The Vitox II system is normally operated with velocities in the range 0.45 to 1.20 mi s, a variation of 2.67: I. The upper limit is set to limit headloss through the di ssolver. For the Munster dissolver, the maxi mum velocity during peak flow is 1.70 mi s. The Mun ster P.S. has been designed to function correctly under these higher than normal velocities through the dissolver. The Vitox II system is capable of achieving up to about 75 per cent of the saturation oxygen co ncentration at an oxygen transfer efficiency of greater than 90 per cent. From Figure 3 it may be seen that the unit is capable of dissolving at least 53 mgl L of oxygen if required. The Munster system was designed on the basis of providing a residual dissolved oxygen concentration of 10 mgl L at the discharge end of the main to assist in the prevention of sulphide reformation in the primary sedimentation ta nks. Exper ience during the past summer indicates that a oxygen injection rate of approximately 15-20 mgl L -was adequate for sulphide control between the Munster Pumping Station and Woodman Point Treatment Plant. Sufficient capacity exists to adeq uately meet a ny expected oxygen requirements, even during the initial years of operation when intermittent operation during the early morning res ults in extended detention times. MANUFACTURE AND INSTALLATION

The overall septicity control on the Woodman Point system was designed by the MWA in conjunction with CIG. The Vitox II dissolver was selected because of the success of the prototype dissolver located on Mt Pleasant pressure mai n in controlling septicity of the Woodman Point wastewater. The Vitox II oxygen dissolving technology was licenced to the MWA by CIG . The licence agreement provides for: • Design of the dissolver • Computer simulation of the septicity control fac ilities • Technology of the dissolving mechanisms • Design of oxygen control equipment • Requirements and specifications for the oxygen supply pipework • Assistance with the commissioning of the system. The Vitox II dissolver at Munster, shown on the front cover of thi s issue has the following dimensions: Pipe diameter 1100 mm Height 7500 mm Width 6970 mm Phase Separator-diameter 2150 mm - length 6270 mm Oxygen return line diameter 200 mm SU,TIC






CHLOR INATI0!!._(10 mg/L)







"' :I' "'






g o






.... .:····· ·-:

. ·~' •.


. ...'J

... ,

\ ....... ·\.;





• /, ....... ··:::·,./ '...

.: ,/ .,. , . -,, ~---------"'-'-~,...:..,...._,,'\.___,~~...:_---:':-:"-:-::C_:c--=_ - - - '--._, PLANT INLET



2 100


5-1 - 84

0900 6- 1 -84

TIME (hrs)

Fig. 4. Typica l Sulphide Concentrations -

January 1984.

The dissolver was fabricated by the Metropolitan Water Authority at its Shenton P ark Workshops. The MW A designed and constructed the Munster Pumping Station and also installed all of the pumping and oxygen equipment. The installation, periodical inspections and all ma intenance associated with the oxygen storage vessel is conducted by CIG . The liquid oxygen storage vessel (VIE 15000) shown in Figure 4 has a liquid capacity of 13420 L. The dimensions of the vessel are, height 7035 mm and diameter 2285 mm. This vessel has a maximum working pressure of 1900 kPa. RESULTS The Munster oxygen dissolver was comm issioned in May 1983. The other oxygen dissolving faci lities upstream of the pumping station were progressively commissioned during the following 12 months. The septicity control facilities are achi eving all design expectations and are producing essentially sulphide-free wastewater at the Woodman Point Wastewater Treatment Plant. Typical results during Janu ary 1984 are shown on Figure 4. Under prevailing conditions at that time, the oxygen disso lving faci lities upstream of the Munster Pumping Stations were capable of controlling su lphide effects with sewage entering the pumping station having sulphide concentrations ranging from 5 to 2 mgl L with typical concentration of abo ut 2 mgl L. With the introduction of oxygen at the Munster Pumping Station, these sulph ide concentrations were reduced ~ negligible amounts at the inlet of the treatment plant as may be seen from Figure 4. T he oxygen dissolving facility is also capable of achievi ng significant dissolved oxygen concentrations at the plant inlet as may be seen from Figure 5. This dissolved oxygen, in com bination with the addition of about 10 mglL of chlorine during the early morning hours, effectively controls reformation of sulphides in the primary sedimentation tanks to acceptable levels. The operating costs for the septicity control system in January I 984 were:

::; 5

10 0

"'E -



w ">- 3 )(

0 2

--- -- - --


w :; 1 0



Fig. 3. Munster - Woodman Point Pressure Main Oxygen Saturation Concentrations at 30°C.







5 - 1-84


0900 6-1-84

TIME (hr s )

Fig. 5. Typical Dissolved Oxygen Concentrations - January 1984. WATER June, /984


Oxygen (including delivery a nd tank rental) Additional power consumption Chlori ne

$295 / day $35/ day $135 / day


$465/ day

The current costs are sli ghtly hi gher as neither the Injector dissolver nor the Westfield di sso lver were operating in Jan uary. However , a reduction is expected in ch lorine consumption resulting in lower cos ts when the remaining two oxygen disso lvers are commissioned. This operating cost may also be expressed at $0 .009/ kL of wastewater treated. SUMMARY The use of CIG Vitox I I oxygen dissolving equipment as part of sep-

ticity control facil ities for the Woodman Point Wastewater Treatment Plant has been found to be an effective method odo~r control. These faci li ties which have been developed as a resu lt of a co-operative effort between the Metropo li tan Water Authority and CIG now enable the Woodman Point Treatment Plant to operate without causing an odour nui sance to neighbouring residents. ACKNOWLEDGEMENTS The facilities described in this paper were designed and constructed as a result of the efforts of a number of people from both the Metropo lita n Water A uth or it y and C IG over ma ny years . Their contributions are gra tefully acknowledged. Thi s paper is published with the permiss ion of the Director of Engineering, Metropolitan Water Authority, P ert h.

TO THE EDITOR QUESTIONS TO THINK ABOUT Dear Mr. Editor, Is our industry rev iewing it s few advances, .ideals, a nd aim s at a rap id enough rate? Whi lst other industries/ professio ns ap pear to be taking great strides in improvin g their technology - take the computer industry for examp le - ou r adva nces, as far as treatment processes are concerned are relat ive ly minor. We seem to be a mob of followers, not leaders capable of sta nding back and doing a serious re-a ppraisal of what the a ims of our work shou ld be. Is our aim merely to package the process to be a little more 'env ironmentally acceptable' each time or is our a im to genuinely improve th e process? Is it not true t hat our indu stry, our leaders, all judge our work by what it costs . .. not what it does? Is not the person who has a budget of $100 m to control assessed as a 's uperi o r' professional compared with the one who has only a $50 m budget? Is it not true that he with an empire of 50 professio na ls is held in hi gher esteem t han he who has 35 technician s and 15 profess ional s - irrespective of how productive or successful the 'team' or how effectively the end products function and operate? Is it no t true th at th e greater the number of people employed on a project , the greater the status of the project leader? The greater his in come? The greater hi s co mpany' s profits? (Especially if work in g at hourl y rates!) W hat then is the in cent ive for strivin g fo r greater product ivity, better team-work and sensible economies? What incentive besides personal satisfactio n? (l sn ' t personal satisfaction a very private thing - on ly you know how much true honest effort you exert). What incentive is there for saving the community money? In th e consu ltin g field, very little - it means hav in g to find more work more often! In the public sector, it mean s the lowering of one's own status whilst the professional next to yo u di scovers he can use yo ur budget savings to increase his own 'empire '! Because of a ll hi s 'unfo reseen difficultie s' the seco ndment of an extra 10 people to hi s staff is now possbile - thanks to the ' suc ker' next door, who by work in g capably a nd di lige ntl y managed to reduce the JO

WATER June, 1984

cost and hence the importan ce of his flea-b it e project. Do we persuade ourselves that our nation is improving its productivity (wh ilst silentl y work ing to increase our own emp ire)? How prevalent is li p serv ice only to national ideals? For examp le, yes, I agree its true, but I'm looking after number one first - when I've made my million o r the Ch ief, whateve r, then I' ll tell you what's best for the rest of the nation. Are we as guilty as the medica l profession of 'over-serv icin g' under the gui se of 'inves tigative engi nee ring' or 'ego trippin g' or building ourselves 'monuments' at the communities expense? Could not the majorit y of us point to ve ry large expensive wh ite elephants wo rkin g in a fashion provid ed we over- look some aspects or perhaps the manpower required to keep it functional or the annual maintenance bill? H ow can th e indu stry guard agai nst future unnecessa ry expenditure? Is this an honest way to reduce the unemployment problem? How many of o ur younger profess ionals are fru strated in their current employment knowing one man could be doing the work of two, or a less qualified person could be doing the job just as we ll or bett er? Bucking th e sys tem is often j ust not worth it - forget yo ur ideal s, they get in the way of promotion, just do as you're told, accept yo ur sa lary, be glad you have a job and relax - life is wo rth living - thi s nation has nothin g to worry about! Youn g professionals can be easil y moulded into the sys tem (especially in times of hi gh un employ ment), they need to support wives, yo un g children and mortgages the refo re it is easier to do as the boss wants it - don't question the logic or a rgue (father knows best son). Cripes, there mu st be a better universa l measure of profess iona l s uperiority than wealth or empire size! Any more waffle a long the above lin es and this journa l wi ll be subjected to abuse from many readers advisi ng than none of the above applies to them or their organizations built-in rules and regulations no doubt , pure professional minds with the communities best interests a lways paramoun t - yes, I ca n' t see

any need for imp rovement in m y own camp either, we reall y are all perfect, well you and I anyway, but someone else obviously isn't. Ot her indu stries/ professio ns appear to be takin g great strides in imp roving their techno logy and I presume the economies of the processes in vo lved, yet we seem to advance at a rate slower than the average turt le. How man y times has the ~esearch in the water and wastewater field go ne around and around in circles without a ny real apparent advance? How do we get off the merry-goround, start from scratc h a nd take a fres h look at a ll th e poss ibili t ies? It is easy to do even the imposs ible wit h plenty of mon ey, there is no ski ll associated in engineering designs that cost the earth and work. Surely the skill and thrill co mes with doin g so mething of benefit to the commu nit y for next to no cost . Idea li st ic it might be, but it is a challen ge we shou ld all take up - and any perso n that sta nds in ,he way of a im s such as t hi s shou ld be swept o ut of o ur associat ion and industry. O.K . , so so me of the above views are possib ly not quite a~curate - but can't we a ll see a bit of truth in some of the points expressed? The express ion may be lack ing but the thoughts expressed do ha ve a ring of truth don 't they? Sure ly our industry a nd our nation' s performance wi ll o n ly advance if we exam in e o u r work and our motives honest ly and cr it ica ll y? We have a n indu stry that needs to step into the 1990s with a few new hori zons . Don't we? Yours sincerel y, R. LOO -



The Asian Institute of Technology A Unique Organisation T. L. Judell The Asian Institute of Technology is an autonomous, international post-graduate in stitution establi shed in Bangkok, Thailand, to help serve the technological requirements of the people of Asia by providin g advanced education in engin eering and related sciences. Scope of Activities

stud y, hydra uli c engineering, and had a faculty of eight members seconded from France, New Zealand, United States and the United Kingdom. In November, I 967, the Inst itute became fully independent under it s present title. Its Charter, gra nted by the Royal Thai Government, accords the Institute the sta tu s of an autonomous, international insti tution and em powe rs it to award degrees and diplomas. Today the In st itute has over 570 students from 21 countries and 104 faculty and se nior staff members from 25 countries and provides students from Asian countries with the opportunity to pursue practical academic st udies, seeki ng , defining and testing alternative solutions to urgent problems found in the region.

The Inst itut e offers selec ted st udents: Academic programs leading to the Diploma of the Asian In stitute of Technology and to the deg rees of Master of E ngin eerin g, Master of Science, Doctor of Engineering and Doctor of Technical Science. Degree and Diploma programs are offered in nine academic di vision s: Agricultural and Food Engineering Computer Applications Energy Technology Environmental Engineer ing Geotechnical and Transportation Engineering Human Settlements Development Indu st rial Engi neering and Management Structural Engineering and Construction Water Resources Engineering • Research by st udents, faculty and research staff directed towards the solution of technological problems relevant to -Asia. • Special programs comprising conferences, seminars and short courses.

The language of in struction at A.I.T. is English. Students reaching the Institute come with a wide va riety of lingui stic back grounds and a considerable range of abi lities in English. Upon arrival at the Institute, the new students are given an English Readiness Test. The performance on that test is used as a basis for deciding the amount of time enrollees should study English to enable them to ca rry on their regu lar academic programs. Students might be required to take up to three term s of English, but about 50 per cent of them are who lly exempt because of adequate proficiency. These English co urses do not receive credit but grades obtained appear on official transcripts. This program is administered by the English Language Centre of the Institute.

A.LT. campus

Academic Building

The In stitute 's academic and research programs are related closely to the needs of Asia; they include the stud y of problems common to the region as well as the study of the engineering and scientifi c methods upon which the so lutions to these problems depend. Histo ry and Development of the Institute

T he concept for the developm ent of a graduate sc hoo l of engineering to serve all of South Eastern Asia was first proposed by the SouthEast Asia Treaty Organ isation (SEA TO) in I 958 and exploratory plans were drawn up in co-operation with the Colorado State University under the sponso rship of USAID. The In stitute was founded in 1959 as the SEA TO Graduate School of Engineering through a Royal Decree signed by the King of Thailand. It bega n with I 9 students from three countries: Pakistan, the Philippines and Thai land. Initially A .I.T. offered one field of

Dr. Trevor Jude/I has provided this article in acknowledgement of Australian interest in and contribution to technical development in Asia.

Language of Instruction

Area-Oriented Research

At A.I.T., research is an integral part of the educational program and research programs are designed not only to supplement the eduction of A.LT. stu dents but also to produce practical benefits for the region. The In stitute accepts research grants and co ntracts from governments or indu stries when there is expertise available at A.LT. and provided that the research problem will offer suitable topics for students thesis work. More than 50 projects are underway or have been completed by the variou s Divisions of the In stitute . Buildings and Facilities

The campus occupies a site of approximately I 60 hectares at Rangs it , 40 kilometres north of Bankok and 17 kilometres north of Don Muang Airport. A lease for the si te has been granted by the Royal Thai Government. This area forms part of a 400 hectare site, the remainder of which will be availab le for the development of WATER J une, /984


Thammasat University. Construction of the fi rst stage of the Rangsit Governm ents of Austra li a, Canada , Japan, Germany, France, campus sta rted in early 197 1 and this new campus was officia lly open- Netherlands, Thailand , United Kingdom a nd the United States are ed in February, 1973 by their Majesties the King and Queen of among the donors now making major contributiont Thailand . Prior to that, A.l. T. was located in Bangkok on the campus Another fo rm of fi nancial support is the secondment of fac ulty a nd of Chulalongkorn University. · senior administrative staff. At present almost 50 per cent of the faculThe Institute's complex of buildings and equipment , valued at over ty and senior administrators a re seconded to the Insti tute by donor $20 million , includes Administration and Academic buildings, Con- governments which provide salaries, allowances and travel costs. fere nce Centre , Regional Computer Centre, Region al Engineering Ex- Recently, donors, in addition to seconding fac ulty , provided fund s so perimental Centre, Library housing an English Language Centre, that the Institute can empl oy Asian fac ulty directly. This procedure Regional Documentation Centre, Language and Media Units and helps the Institute's cash position by decreasing the amount A .LT. must spend fro m current funds for fac ulty. staff and service buildings. Contract a nd sponsored researc h is another and increasingly imporT he academic buildings include lecture rooms, laboratories and fac ulty offices; the Conference Centre provides a 600 seat auditorium , tant source of income which is co ntributing to the operating income of simultaneous translati on faci li ties , audio-visual fac ilities, dini ng the Institute. rooms, recreational fac ilities and room accommodation for 120 perAustralia has been a consistent major donor to A.L T. Assistance in sons; the Regional Computer Centre provides the latest IBM 303/ 6 the early stages of development included fund s for general operati ng computer sys tem . It offers computer related educational programs for costs, staffing and scholarships. Currently Australi a is contributing $4 mill ion fo r the period 1982- 1985 of which $180,000 will be di rected A. l. T . and public agencies in th e region. towards the fundi ng of three specialised informatio n centres within A. I.T's Regional Documentation Centre. These centres play a major ·Academic ,Staff role in the dissemination of information in the region . At present A. LT. has over 100 faculty staff members fr om 25 counAustralia is represented on the Board of Trustees of the Institute by tries . Many are provided under secondment by their governments P rofessor D . W. George, Vice-Chancellor of the Uni vers ity of while others are paid directly by A. I. T . It is expected that in the Newcastle and by the Australian Ambassador to Thailand , both of foreseeable future governments will continue to provide about 50° per whom report regularly and favou rably on the work of the Institute. cent of the faculty requirements of the Institute. In addition to seconThe University of Wollongong is the agency through whi ch ding their own nationals so me Western Governments have recently Australian funded staff are seconded to A. LT . These staffi ng arprovided funds fo r the employment of quali fie d Asian fac ulty rangements allow tenured Australians to take up secondment at A.LT members. without loss of entitlements such as superannuation or long service The faculty-student rati o is set at I :8. leave . Financial Support and Australia 's Contribution

Financial support has, thus fa r, come from 77 governments, international organisati ons, foundations a nd individuals in the fo rms of grants for construction, equipment , seconded fac ulty, scholarships, confe rences, local funds, endow ment and operating costs. The


The Author gratefull y acknowledges info rmation prov ided by Dr. Jacques Valls and Dr. D . M. Tam of the Asian Institute of Techn ology and the Australian Assistance Bureau.




Each metre of Ring/ace contains 10-20 km of polyvinylidene chloride fibres, the increased surface area giving excellent capacity for capturing and fixing a large mass of diverse type of sludge organism. Applicable to a wide range of systems from full scale municipal and industrial plants to small packaged units.

Released by Contrec Systems, this is a highly accurate microprocessor based RATE INDICATOR which can be scaled to display rate directly in engineering units. Outstanding is the ability to filter the incoming digital signal and to display the rate in almost any format desired. Compatible with a wide range of inputs from flowmeters, incremental encoders, proximity sen sors and voltage-to frequency converters, it has a wide frequency range and 0.05% accuracy.

High BOD removal is achieved and loadings up to 1.5 kg/m 3 are possible with good tolerance to fluctuations. Ringlace is installed as a prefabricated curtain with element spacing to suit application.

The range of pressure recorders is suitable for stem-mounting, wall mouniing and portable pipeline tests. The units are compact, accurate, lightweight and sturdy and can be calibrated in all engineering units - an alternative to simple pressure gauges where records are necessary.

Information: Jastec P/L, 102 Glover St., Cremorne, 2090.

Information: Temperature Technology, P.O. Box 79, Henley Beach, S.A.5022.


WATER June, / 984

Information: Motorized Technology Int. P/L., P.O. Box 654, Ringwood, 3134 Vic.