Water Journal March 1974

I1ssN 0310 °367 I Official Journal of the Mll-i i iM • tl1 ~ l'M) i 3iW ~ I•l

'1½·1-~-r•IIJ mi c,1 ~ I V.¼1-ii=l!4'4)i3iL-

IVOL.1 N0.1- MARCH 1974 . - - _Price $1-00 ]_

FEDERAL COUNCIL President: Vice-President: Councillors:

T. L. Judell (N.S.W.) H. McFie (Tasmania) M. Flynn (N .S.W.) G. Goffin (Victoria) C. D. Parker (Victoria) D. J. Lane (S.A.) R. C. Williams (S.A.) W. G. Volk (Qld.) A. Pettigrew (Old.) F. C. Speldewinde (A.C.T.) G. Evans (A.C.T.) D. Montgomery (W.A.) B. S. Sanders (W.A.) D. R. Walters (Tas.) Hon. Secretary/ Treasurer: R. F. Goldfinch

EDITORIAL COMMITTEE FOR 'WATER' Chairman: Committee:

C. D. Parker G. R. Goffin F. R. Bishop Joan Powling A. G. Longstaff G. B. Frecker

BRANCH CORRESPONDENTS A.C.T.:

A. Macoun,

cl - Dept. of Works, Phillip, 2606 N.S.W.:

M. Dureau, Envirotech Australia Pty. Ltd., 1 Frederick Street, Artarmon.

VICTORIA:

A. G. Longstaff, Gutteridge Haskins & Davey, 380 Lonsdale Street, Melbourne, 3000.

QUEENSLAND:

L. C. Smith, 24 Byambee Street, Kenmore, 4069.

S.A.:

R. C. Clisby, 31 The Common, Beaumont, 5066.

W.A.:

B. S. Sanders, 39 Kalinda Drive, City Beach, 6015.

TASMANIA:

D. R. Walters, Box 94A. G.P.O., Hobart, 7001 .

CONTENTS Branch News 2&3 3 Presidents Message . .

Business News . .

16 Water Treatment Studies for Metropolitan Adelaide - R. C. Williams 9-10-11 Odour Control in Wastewater Treatment Plants - J. J . Ryan 13-14-15-16 Distinctive Characteristics of Australian Inland Waters - W. D. Williams 17-18-19 Editorial Correspondence : Hon. Editor, A. H. Truman, c/ - Davy-Ashmore Pty. Ltd., P.O. Box 4709, Melbourne, 3001 Or to State Correspondents.

Advertising Enquiries : John Craig, 'Water' Box 175, Nunawading, 3131.

Phone : 874 2133

FRONT COVER The M elbourne and M etropol itan Board o f Work 's $71 million South-eastern Purificat ion Plant is on e of th e most modern in the world .

Th e Plant is an essent ial part o f the Sout h-eastern Sewerage Syst e m wh ich will comme nce operatio n in lat e 1974. The first stage capacity of t he plant is 6 4 million gallons a day and it will serve a population of approximately 900 ,000 in 175 square mi les or almost one-third of the Board 's area o f sewerage respons ibility.

Humes L imited supplied over 3,000 precast or prestressed concrete plenum units, tie beams, wal kway units, Y beams and single T units. Plast iline P.V. C. sheet for t he protection of insit u concrete struct ures. and 66 " diameter Humespun Plasti line pipes to the project.

Humes sub-contracted to Lewis Construction Co. Pty. Ltd. and Fluor A ust. Pty. Ltd.

-

5 1,111 111111111111 11111111111 1111 11111111111111 1111111111111111 111111111111111 1111111111111111 11111111111111 111111111111 1111 11111111111111 111111111117

1

WATER TREATMENT STUDIES FOR METROPOLITAN ADELAIDE Mr. R. C. Williams, B.Sc., A.S:A.S.M., M.I.E. (Aust.)

INTRODUCTION

For many years the quality of the water supplies of Metropolitan Adelaide has been subject to criticism by local and interstate residents and authorities on account of the physical characteristics of the supplies.

A review of water quality characteristics extending back for ten years indicates that while the supplies are satisfactory as far as chemical and radiological characteristics are concerned and hardness levels are tolerable, they are well below recognised world standards in respect to physical characteristics. Acceptable bacteriological standards are being maintained with increasing difficulty by the adoption of higher levels of chlorination of the raw water. Some secondary chlorination within the reticulated system has been found necessary during the past few years.

Metropolitan Adelaide's main water resources are the Mount Lofty Ranges Watershed and the River Murray. Governmental approved water pollution control policies are now being applied in these areas to control residential, industrial, agricultural and animal husbandry activities and to maintain raw water quality at present day levels. By some world standards however these qualities are no longer acceptable.

Treatment by municipal works will supply water to meet these World Health standards and provide many benefits to the community. These benefits include clear sparkling water, free from tastes and odours, enhanced efficiency of chlorination, elimination of consumers complaints from staining and sediment as at present, attraction of industries requiring high quality process water.

..

(a) Design criteria for each unit of plant (bl The most effective and economic plant layouts (c) Unit plant performances under varying raw water conditions

(d) Most effective chemicals for use in treatment of the Adelaide Water Supply The pilot plant was constructed adjacent to the Terminal Storage of the Mannum-Adelaide Pipeline and has been operating continuously for four'¡ years.

Raw water can be drawn from the Mannum-Adelaide Pipeline or Terminal Storage itself.

LABORATORY

A small laboratory is operated adjacent to and in conjunction with the pilot plant. Equipment includes a six head multispeed laboratory flocculator for comparative flocculation and settling tests, turbidimeter, colorimeter pH meter, conductivity meter and associated equipment necessary for effective control.

MIXING AND FLOCCULATION TANKS

The main plant incorporates rapid mixer and flocculation tanks with a maximum throughput of about 63 gpm. Chemical solutions (coagulant, soda ash and coagulant aids) are made up in batches in mechanically stirred dissolving tanks and then fed into the rapid mixer using adjustable dosing pumps. By varying the flow of water the detention time in the mixing tank can be varied between 1O and 90 seconds. A variable speed mixer (500 ~ 2000 rpm) has been provided.

While the technology for water treatment facilities has been available, for some time it was considered in 1967, that it would be sound practice to operate a pilot plant to study 'treatability' of Adelaide raw water supplies and evaluate various methods of treatment.

Standard filter alum is the best coagulant in all cases, the dose varying from 50 to 70 ppm depending on the exact nature of the raw water. pH adjustment simultaneously with alum dosing has not been found beneficial.

Research and testing have continued uninterrupted for 4 years and from these studies, criteria have been derived to provide a sound basis for economic design.

These design parameters have been used in the investigations and preparation of proposals for the first water treatment works at Hope Valley.

Coagulant aids including activated silica and several polyelectrolytes have been examined and slight

TREATMENT PROCESS

Some conventional water treatment processes such as Screening, Rapid Chemical Mixing Coagulation and Flocculation, Sedimentation, Filtration Disinfection and Fluoridation are required in whole or part to achieve the necessary water quality.

The response of a particular raw water to the various processes is related to its physical and chemical properties and to the climatic conditions under which the treatment is performed.

PILOT PLANT STUDIES

Pilot plant studies into all processes being considered have been carried out to determine:

improvements have been noticed in some instances.

FLOCCULATION

A pipe connects the mixing tank to the flocculation tank with provision for bleeding off some of the flow to permit control of detention time in the flocculation tank. Detention times of 16 minutes and over can be achieved. The tank is divided into 4 bays with baffles between each bay to minimise short circuiting. Each bay has a set of paddles which can be operated at speeds between 4 and 15 rpm.

Flocculation tests have been carried out in the pilot plant on Mannum-Adelaide and Torrens (Millbrook) waters with similar results. Both waters flocculated readily with the right detention times, paddles speeds, water temperatures and alum dosage. It has been found that the maximum detention time necessary for good flocculation is about 20 minutes.

9

Cont. from page 9

SEDIMENTATION Horizontal Flow

A sedimentation tank of the rectangular horizontal flow type has been installed. Flow to this unit can be varied by means of a metered bleed on the inlet pipe.

The tank is designed to operate at flows between 1 O and 57 gpm corresponding to detention times of 200 to 50 minutes and surface loadings of 260 to 1490 gpd per sq. ft.

Tests have been aimed at finding the maximum overflow rates which will give a settled water turbidity of about 5 Jackson turbidity units. Because of viscosity changes in water with variation of temperature, sedimentation efficiency is very temperature sensitive as shown below: Overflow Rates (gpd/sq. ft.)

Temperature 0 c 1400 25 1170 20 960 13 ¡ Sludge concentration varies from solids content of 1.4 per cent after one day retention to 2A per cent after about seven days retention in the sedimentation tanks.

Distribution characteristics of the inlet conditions

have proved very critical if optimum performance is to be obtained from the settling basin. Uneven distribution will result in short circuiting along the basin with resultant high levels of turbidity in the settled water and consequential additional solids load to the filters.

Design practice has been to adopt horizontal openings in the baffle walls between the flocculators and the settling basin. Approximately 30 per cent openings in these walls has proved effective in maintaining floe

formation.

Solids Contact Clarifier A small conical bottom solids contact clarifier 6 ft. in diameter has been installed. Water from the mixer or flocculator can be fed to the tank at rates up to 41 gpm corresponding to a surface load of 2,100 gpd per sq. ft. On one side a slurry weir between the hopper is provided, the height of the slurry weir between the hopper and the upflow section being <1diustable.

Coagulated water enters at the bottom via a central vertical pipe and turbulent mixing occurs. It then flows upwards through the suspended slurry blanket and over the circumferential weir. The clarified water may be passed to the rapid sand filters or directed to waste.

This unit has proved to be very sensitive to changes in. operation and varied in its efficiency. Flocculation was found necessary after rapid mixing with the best surface loading rates being found by establishing a rate which gave a stable floe blanket in the clarifier.

Hydraulic

and

temperature

variations

can

cause

'boiling¡ of the sludge blanket and carry over of floe becomes difficult to control with the result that satisfactory sedimentation may result with overflow rates varying over a range of 1 500 - 21 00 gpd/ sq. ft.

Tube Settler Clarifier A small tube settler unit has also been installed. The actual clarifier compartment is 2 ft. 6 in. square and

10

contains plastic modules forming 2 in. square tubes at 60 degree to the horizontal. The depth of the modules . is 21 in. Chemically dosed and flocculated water enters a chamber on one side, flows down, then up through the module tubes and is then decanted over the offtake weirs. Floe settling in the tubes rolls down and falls into the sludge hopper at the base of the unit.

Sludge is withdrawn at intervals from the bottom of the hopper. The clarified water may be passed to the filters or directed to waste.

Results indicate that an increase of 3.5 times the loading in a horizontal flow basin can be achieved, i.e.

5,500 gallons per day per sq. ft. The evaluation of many factors, will be needed before a final decision is made on the use of these units. ,, Adequate sludge removal facilities must be provided for this type of unit.

FILTERS Four filters have been provided designed to filter up to 8 gpm per sq. ft. Each consists of a perspex tube between 7 and 8 ft. high, filters A, B and C being 8-in. square and filter D being circular with an area of 1 sq. ft. Each has a metered inlet at the top and an outlet fitted with a rate of flow controller at the bottom.

Backwash and air scour facilities for rates of up to 20.5 gpm per sq. ft. and 4.5 cubic feet per minute per sq. ft., respectively, have been provided. Head loss gauges indicate when backwashing should be in'itiated.

Specification for Filter Media

SAND Depth (in.)

Effective Size (mm)

12 0.45 Uniformity Coefficient 1.50

ANTHRACITE Depth (in.I

18 1.0 1.40

Effective Size {mm) Uniformity Coefficient

All filters have 9 in. of graded gravel under their media beds, filter A was originally set up as an upward flow filter with 4 ft. 6 in. of sand (effective size 0.45 mm). After sufficient tests of the upward flow principle had been completed the unit was converted to the conventional downflow type. Filter D was installed later in the testing programme and was designed to allow testing of the various types of commercially available underdrain nozzles. In addition piezometers were installed at various depths in the filter to enable head loss studies to be made.

Currently tests are proceeding with the packed as under: B C Mixed Media 18 in.

Anthracite 18 in.

12 in. Sand E = 0.45 Anthracite (coarse) 9ln. Sand E = 0.55 U = 1.50 U = 1.50 9 in. Graded 3 in.

IIlmenite Sand Grave!

3 in. Garnet 9 in. Graded Gravel Gravel 9in. Graded Gravel

A 54 in. Sand

filters

D 18 in.

Anthracite 12in. Sand

E =0.45 U = 1.50 9 in. Graded Grave\

At this stage no comparative figures are available on respective filter performances.

Cont. from page 1O

CHEMICAL DOSING

All filters have produced water less than 1 JTU at flow rates up to 8 gpm per sq. ft. Filter runs in excess ¡ of 30 hours have been obtained with settled water turbidities of 3 JTU. Head loss under these operating conditions has been approximately 10-ft. The dual media filter produced high quality water with longer filter runs than single media beds. Generally length of filter run was governed by head loss and not deterioration in filter water quality.

Cleaning of the filters was best accomplished with the use of air scour followed by high velocity backwash. Savings of 50 per cent usage of backwash water proved possible using air scour methods.

Further considerations given in design of the various water treatment works have been: SLUDGE DISPOSAL

Provision has been made in design for increasing the solids content of the sludges by sedimentation and selected chemicals. Sludge disposal will be achieved in many cases by discharging into the sewerage system. Alternative storage using lagoons will be adopted where necessary.

Aluminium sulphate filter (Alum) will be used for chemical coagulation of turbidity and colour in the raw wa¡ter.

Activated Carbon will be used when necessary, for the removal of tastes and odours.

Polyelectrolytes will be used, as filter aids.

Lime will be used to adjust the pH of the treated water to acceptable levels.

SUMMARY

Design Criteria based on maximum weekly flow for Water Treatment Units.

Unit ....... 25 Rapid Mixer Detention Time (seconds).. ....... 20 Flocculator Detention Time (minutes) Sedimentation Tank Overflow Rate (gpd per sq. ft.) 900 Filters Flow Rate........ . ............... 3.5 Based on these studies eight water treatment plants are proposed to serve Adelaide, with the first plant at Hope Valley in 1974.

SIXTH FEDERAL A.W.W.A. CONVENTION, MELBOURNE APRIL 30 -MAY 3, 1974

"MAN AND WATER" An in-depth study of the wise use and re-use of our water resources. To be held at the Convention Centre, Exhibition Buildings, Melbourne.

The keynote speaker will be Professor Eckenfelder of Vanderbilt University and the programme includes speakers from U.S.A., Great Britain, SouthEast Asia, as well as from various Australian states.

For programme and late registration particulars, contact your State Secretary.

11

ODOUR CONTROL IN WASTEWATER TREATMENT PLANTS

By J. J. RYAN - A.S.T.C., F.I.E. Aust.* •Associate - Gutteridge, Haskins & Davey Pty. Ltd.

Before considering the control of odours· in .a sewerage scheme it is

necessary to consider their formation and source.

ODOUR PRODUCTION

Fresh sewage in all cases contains some dissolved oxygen and the bacteria present utilise this oxygen in degrading the unstable organic matter present. The gaseous by-products of these bacteria's metabolism are mainly stable inoffensive gases such as CO 2 • When all the oxygen has been used however, and the sewage becomes stale anaerobic bacteria take over and utilize chemically combined oxygen, e.g. oxygen in sulphates.

The by-products of anaerobic decomposition. and in particular the acid digestion phase, include a large number of very odorous gases, predominantly hydrogen ·sulphide but also including lndole Skatole and the Mercaptan group.

The threshold odour levels of these gases vary subjectively but are generally of the order of 1 part in 107 for hydrogen sulphide with lower concentrations for the lndole Skatole and Mercaptan groups.

SOURCES OF ODOUR

With adequate flow velocity and good ventilation, domestic sewage carried in the majority of gravity sewers will arrive at the wastewater treatment plant .in a reasonably fresh and odourless condition. A variety of trade wastes can cause problems but should be pre-treated before discharge.

Once pumping stations and the "'associated rising mains are insert-

ed into the sewerage system, the detention time for sewage within the system will usually increase and the probability of odour problems likewise be increased.

Tr.is latter type of system is common in Queensland, particularly in flat coastal areas and these factors together with higher sewage temperatures, leads to a more ready production of odorous gases.

If the gravity system is properly designed and well maintained, in most circumstances the sewage should still be fresh when it reaches the first pumping station.

Anaerobic decomposition could well commence before the waste is pumped and short detention times are therefore important. Within the rising main the gases formed by anaerobic decomposition remain in solution under pressure but once

the wastes are discharged to atmosphere, either at the head of a gravity sewer or at the treatment plant itself, the gases will come out of solution and are discharged to atmosphere.

CONTROL OF ODOURS

Odour control takes two forms: 1. Limiting the generation of hydrogen sulphide and the other odorous gases - i.e. the prevention phase; or 2. Removal or neutralization of the gases once formed i.e. the cure.

PREVENTION

The ideal prevention is the design of a sewerage system in which the wastes remain fresh until they are discharged at the treatment plant. Ideals are rarely attainable in practice and it is a fortunate plant Operator or maintenance Engineer who does not face some odour problems at the plant inlet.

The two principal methods of preventing or limiting the formation of hydrogen sulphide are chlorination and aeration of the sewage as it is discharged to the rising main at the pump station.

Chlorination is widely used at pumping stations, the chlorine introduced into the sewage acting in two ways. Firstly it destroys a major proportion of the bacteria present in the sewage, including those responsible for the production of odorous gases. Secondly it reacts directly with hydrogen

sulphide to precipitate free sulphur.

The amount of chlorine needed depends on the degree of septicity, i.e. the concentration of hydrogen sulphide. For relatively fresh sewage, doses of four to six parts per million are usually required to keep the hydrogen sulphide level below 1 part per million. 0nce the sewage has gone septic however the dosage rate may have to be very much larger, in the range of 20 to 60 parts per million.

The addition of compressed air to the rising main at the pump station has also been used to a limited extent with some success. Several examples of this system are operating in Queensland and are understood to be performing quite satisfactorily. The oxygen from the air induced into the rising main oxidises hydrogen sulphide present and also prevents the multiplication of anaerobic bacteria while the oxygen lasts in the rising main. The method has definite cost advantages in both equipment and running costs when compared -with chlorination.

One disadvantage of this system is that air takes up space in the rising main and consequently affects the hydraulic performance of the main. For long rising mains

large quantities of air would be required and, as can be imagined, a continually rising main from the pump station to the point of discharge would be necessary unless the air is to be injected at numerous points along the rising main.

In undulating country there is a possibility of · odorous air being released at air valves and the odour problem might then be transferred from the point of discharge to various other points along the main. This would of course be more difficult to control.

Regular cleaning of slime from sewers and rising mains by means

of swabbing will help considerably in the reduction of sulphide build up.

Thjs paper was presented to the Queensland Branch of the Australian Water and Wastewater Association on 11 July, 1973.

13

Cont. from page 13

BIOFILTER

CURE If the production of hydrogen sulphide and other odorous gases in the collection system cannot be prevented, means must be found to control them whether they occur at the pumping station, a point of discharge from a rising main to a gravity sewer or at the treatment plant itself.

Plastic Media~.

/,

Numerous methods for the control and/or removal of odour have been employed, and include: 1. Disposal of gases through a high vent 2. Passing gases up through a biological filter 3. Passing gases through soil beds 4. Adsorption 5. Combustion 6. Masking of sewer gases 7. Scrubbing of sewer gases.

TOWERS

I

I

l . S.

l

~

"" Ii I

~

II

II

1I COLLECTION I1 il ____ J1

II

, _ _ _ _ _ =._J

I

II SUMP

11

l!:::_-~_::::::--::::.j

ELEVATION

PART SECTION

HIGH VENT

Use of high vents for gas disposal has been extensively used with mixed success.

In built-up areas discharge should be at a height of 2.5 times the height of any nearby building and 30 feet above the highest adjacent building. In any case the vent should be 50-60 feet high.

Velocities are usually limited to 1,800 f.p.m. within the stack bore to limit noise, but increased to at least 3,000 f.p.m. at the exit nozzle to reduce the chance of the gases being caught in a down-draught.

When down-drag occurs, disposal is a real problem since hydrogen sulphide is heavier than air.

Particular attention must be paid to corrosion protection and stainless steel is currently preferred for any permanent installation although involving high initial cost.

BIOLOGICAL FILTEA

The removal of odours by passing the foul air through biologic a I filters has been tried experimentally at a number of plants. As far as is known the method was pioneered by Mr Hicks of the Auckland Regional Authority, at the Manukau Sewage Treatment Plant, and consists basically 14

/

FIGURE

I.

OOOUROUS AIR PRIMARY EFFLUENT

PLAN of collecting the foul air and discharging it upwards through a filter bed of either conventional stone or plastic media, on which a biological growth has been promoted by the application of primary settled sewage effluent (sometimes with secondary effluent added).

The Thia-bacillus bacteria in the biological growth on the filter oxidises the sulphides in the air stream to sulphates. This system is shown diagrammatically in Figure 1.

Since May 1972 the Author has been associated with a pilot scheme at the Redcliffe

Wastewater Treatment Plant to investigate, under local conditions, the effectiveness of this method of treatment.

A 650 c.f.m. fan withdraws foul air from the existing pre-aeration chamber situated at the head of the plant. This air is then directed through an above ground collapsible polythene circular duct, to the under drainage system of one of the existing conventional stone trickling filters. Short circuiting of the foul air is prevented by a polythene sheet covering around the outlet channel of the filter.

The threshold odour level concentration for hydrogen sulphide is too low for practical quantitative tests but the qualitative opinion of plant operators and nearby residents is favourable.

Over a test period of 1O months not one complaint has been received from surrounding residents although frequent complaints had been received previously.

It has been concluded that this method of odour control has been successful and a biofilter tower incorporating plastic media is proposed as part of the plant augmentation.

solution in the filter, with the possibility of later release in subsequent stages, are still proceeding but there is definite indication that the sulphide level in the filter effluent is less than in the influent whilst sulphates are correspondingly somewhat higher. The indication is that the sulphides are being oxidized to sulphates as expected.

cause is oxygen starvation.

To ensure nitrification the BOD loading will be less than 1 lb BOD, per cubic yard per day. Irrigation rate will be in excess of 30 gallons per hour per square foot of media plan area. The filter will be sized to take 40 c.f.m. of foul air per square foot with media height approximately 16 feet. Operating costs for a plant serving an equivalent population of 25,000 persons are estimated to be of the order of ~5.50 per day.

Chemical tests to check that the sulphide is not being taken into

SOIL BED

Reduction of filter efficiency was noted during the trials. Although this was first thought to be due to sulphide poisoning of the zooglea, fu"rther experimentation (still proceeding) indicates that the

ODOUR CONTROL SOIL BED ODOUROUS AIR

{'

IN

Odour control by passing the foul air up through soil beds has been successfully employed in the USA for some years. The air is forced up through a bed of moist loam where soil micro-organisms extract hydrogen sulphide from the air.

At a flow of 0.35 cu. ft. per minute per sq. ft. of soil surface, sulphide gas concentrations of 15 mg/I have been reduced to an imperceptible level using a depth of loam of 32". The effectiveness of the soil beds apparently does not diminish markedly over a period:

SPRINKLER

LOAM

~t ;··;

gr,_·•·_·.•_.•

PERFORATE AIR PIPE

P, V, C.

SECTION

FIGURE 2

ADSORPTION

Odour removal by adsorption has been widely employed in fields other than sanitary engineering with activated carbon frequently used as the adsorptive medium.

Studies in the USA have shown however that there are several limitations in the use of activated carbon.

Only small concentrations of hydrogen sulphide can be present in the air because of the possibility of a fire or explosion occurring due to heat being liberated by the activated carbon during the removal process. The heat is produced by chemical reaction between the hydrogen sulphide and the activated carbon. Generally the size of filters structures is quite large and whilst this form of odour control has been used in the USA on a number of smaller installations it is not generally considered to be a desirable or economic means of odour control for sewerage schemes.

COMBUSTION

Odours can be destroyed by combustion at temperatures in the order of 1300°F but it is generally economical to do this only in large plants where the heating units can be operated at th0 higher teiTiperatures required.

MASKING

In recent years general plant odours have sometimes been controlled by masking or counteracting the offensive odour with other One installation has deodorised odours calculated either to provide air from a pumping station success- a less unpleasant over-riding smell fully for a period of three years, or, due to the interference of the using a greenhouse to maintain soil added aroma, to lower the temperatures in the range of 25° threshold level of the gases. There to 30°C, but in our climate soil tem- are several proprietary chemical peratures would usually be in this lines on the market and costs are range without protection. quite high. This method is not in Facilities need to be provided for the author's opinion, a proper watering and promoting a grass and method of odour control and its plant growth on the soil bed, which usefulness yvould appear to be reshelps to maintain the porosity of tricted to' providing temporary the bed. Details of a typical soil bed odour alleviation during particular operations or pending installation installation are shown in Figure 2. of one of the foul air control This method represents a cheap systems described. and simple method of odour control. Such an installation has SCRUBBING been installed in the Elanora TreatScrubbing of sewer gases is ment Plant on the Gold Coast and somewhat similar in principle to the will shortly be put into service. biofilter tower with the exception

15

that the oxidation of sulphides to feature. Indicative all-up operating sulphates is carried out by the use cost for this means of control is in of hypochlorite or other oxidising the order of 20c per 1,000 c.f.m. of .solution. ·foul air treated, per part per million The tower consists of a scrubbing of hydrogen sulphide, per day of column packed with ceramic rings operation. Cost of ventilation or plastic media through which the system is not included. hypochlorite solution is passed.

The foul air is blown counter-flow One example of this system is a through the packed tower and test plant installed by the Sydney oxidised by contact with the Water Board at one of the major hypochlorite. The spent solution is syphon crossings of Sydney Harbour which reduces the concollected at the base of the tower, centration of H'S in the air stream re-generated by means of elect I r II d from in excess of 3 p.p.m. to an ro y 1c ce s an re-cycled through imperceptible level. the system.

This system could for example, be installed quite readily in a CONCLUSION The paper has referred principalreasonable sized sewage· pump station superstructure. Due to its ly to control of odours at the inlet higher running costs it is generally to the treatment plant where it can consioered less economical for use be reasonably agreed that most of at treatment plants where the the odour problems arise. If volume of foul air is quite high but sewage is in reasonably good conpatented hypochlorite re-genera- dition prior to primary and....;. secon: .;_ lion systems may improve this dary treatment and plant

housekeeping is conscientiously carried out odours from primary settling tanks, biological filters, digesters and sludge drying beds should normally be at acceptable levels. If this is not the case and odours persist, the only available measure for control is to cover the offending units and evacuate the foul air for treatment by one of the means previously discussed in this paper.

It is noted that one of the most helpful devices at a treatment plant, once the odour is.. under. control, would be a recordin'g wind gauge providing a continuous record of wind direction. Plant operators and sewerage maintenance Engineers would then have a ready defence against many regular complainants who attribute any odour to the treatment plant even when, as is often the case, the wind is blowing in the opposite direction.

__ ______ ___

BUSINESS NEWS ANALYTICAL TECHNIQUES AND INSTRUMENTATION An ultrasonic flowmeter which will directly measure total flow rates in rivers has been developed by the Water Resources Board and the Atomic Energy Research Establishment in Harwell, England. The equipment offers no obstruction to the river flow and operates automatically and continuously. Measurements are made at preselected intervals, normally every 15 minutes, and the result is displayed locally in numerical form and then transferred to eight-hole punched paper tape in computer-compatible form. Water level is also measured as part of the sequence by a resistance level gauge and again displayed in numerical form; readings are not affected by the condition of the year.

Ultrasonics, 11(5):195-196, September

1973. 0281.

$2 MILL .. WASTE WATER TREATMENT PLANT

gravity through a common flume into a wet well, the sewage is divided into two separate treatment trains. The first process component in each train is an Ecodyne Reactivator clarifier which uses lime to precipitate phosphates as calcium phosphate. After clarifier retention of four hours, effluent pH is lowered from 11 to 8.5 before entering four ecodyne Graver Monoscour filters (two filters handle each section of the stream). The dual media filters reduce inorganic and organic suspended solids to 3-5 ppm in filtered effluent. After filtration, the effluent is- pumped to a filtered water holding tank that regulates any surges occurring in the system.

From the holding tank, water is pumped to six carbon adsorption tanks, three on each stream, for removal of dissolved organics·. The effluent then enters a secondary set of four Ecodyne Monoscour filters to remove fine solids, flow$ to another holding tank and then into an ion exchange vessel for ammonia removal. Effluent from the ion exchange system, the last treatment step, is discharged from the plant with less than one ppm ammonia nitrogen.

A two-million-dollar advanced wastewater treatment plant at Rosemount, Minnesota is nearing completion under the supervision of the Sewer Board System. The plant is designed for a 600,000-gpd average capacity with sizeable expansion possible.

Technology, 1973. 0294.

Raw sewage enters the plant through a one-inch bar screen that removes large objects and trash. After flowing by

Problems are bread and butter for The Hazardous Materials Service (Harwe!I-U.K.). The problems cover a

16

Environmental

Science

7(9):804-805,

and

September

ANONYMOUS CHEMICALS

staggering range.

The Harwell teams may be called out to cope with unidentified drums washed up on a beach, or with spillage of some anonymous chemical from a tanker.

In their plant at Harwell they may be dealing with wastes as unusual as millions of contraceptive pills withdrawn from the market because of their high content of hormone oestrogen, now unacceptable, or tons of contaminated insecticide.

Things they find can border on the bizarre. At a tin-smelting factory in the north of England, being demolished under their guidance, they discovered strange stalactites near the base of a chimney, that proved to be almost pure arsen1c.

In two years, their computer will have stored perhaps the most comprehensive mass of information in the field, and will have collated and referenced it so that the use of keywords will bring it pouring out of tht computer on cal!.

The computer will a!so help with instant difficulties such as identification.

Labels of possibly dangerous materials can be ripped in accidents. If, all that is left on a label is two or three letters, they can be fed into the computer which will then print out the names of materials containing the letters in any .combination. This is a quick narrowingdown method that coutd be vital in an emergency.

DISTINCTIVE CHARACTERISTICS OF AUSTRALIAN INLAND WATERS

by W. D. Williams*

In the past there has been a general lack of appreciation among water and waste-water engineers not only of the distinctive physical and che.mical characteristics of Australian inland waters but also of the plants and animals which inhabit them. It is important for us to recognize these particular features for, by so doing, we shall come to realize that in many cases where limnological principles need to be applied to particular aspects of water management, we are unable to apply the theories and concepts of limnologists working in the northern hemisphere and from where, to date, the bulk of research on aquatic ecosystems has been carried out. In this article the.biological, physical and chemical features of our inland waters will first be outlined and then followed by a discussion of some of the problems which confront Australian limnologists working here with a concern for local problems.

BIOLOGICAL FEATURES Fauna A most important point is that much of the fauna of Australian inland waters is endemic which means that these animals are confined to Australia either exclusively or else not wellrepresented elsewhere. Also certain ecological niches are occupied by faunal groups not usually associated elsewhere with such niches, and some cosmopolitan groups are absent altogether, such as the crustacean Asellus (water louse) which is of direct interest to water pollution biologists in Europe.

The native fish of our inland waters also possess unique characteristics. None of the freshwater forms of northern hemisphere fish, the salmonids (trout), cyprinids (carp), or the percids (perch), reached our waters by natural means and, while there are some 130 endemic freshwater forms in Australia, only two of which can be said to be primarily freshwater in origin.

All others show a close evolutionary relationship with marine forms which indicates that the vast majority came from the sea in relatively recent times. The native fish have an extremely low diversity by comparison with fish fauna of other countries. 路 Bearing these facts in mind it is clear that much overseas research using freshwater fauna as a means of assessing the degree and nature of

water pollution is inapplicable for Australian studies. At the same time however this does not mean that our own fauna cannot be used as such an index, providing the necessary ecological studies are carried out in advance.

We must first of all learn more about the taxonomy and ecology of the biota of uppolluted waters and then examine the ways in which various kinds of pollution exert their effect.

Heterotrophy of streams A second distinctive feature of Australian inland waters relates to the nature of the energy input to streams. It appears that a maior source of energy for streams comes from fallen leaf material which, in the northern hemisphere, is strictly seasonal on account of the deciduous trees. In Australia, where our native trees are evergreen, the input is more evenly distributed throughout the year and could reasonably be expected to exert some effect on the fauna. It certainly seems from work done to date that the life cycles of certairi insects are less precisely timed than in northern hemisphere streams and also that the biotic diversity in our streams is decreased.

PHYSICAL FEATURES Among the physical features which distinguish Australian inland waters are the thermal characteristics of lakes and reservoirs. All large bodies of water tend to stratify vertically with a seasonal pattern which depends on their geographic location. In Australia the typical pattern is monomictic, i.e. one 'overturn' which occurs in winter, whereas in northern hemisphere lakes the pattern is dimictic with two periods of 'overturn路, one in spring after the ice melts and the other in fall.

Polymictic lakes which never stratify or have no persistent stratification, theoretically occur only in the tropics. However such lakes are quite common here in the temperate regions of the Tasmanian central plateau and western Victoria.

These features are of direct interest to water management as the circulation and concentration of available nutrients are often associated closely with the thermal patterns and care must

*From a talk delivered to the A.W.W.A. Victorian Branch, 24th May, 1973 by W. D. Williams, Department of Zoology, Monash

umvers1 路 路,Y-

Cont. on page 18

17

Cont. from page 17

therefore be taken when overseas work is consulted in relation to Australian problems.

River discharge values fluctuate widely in Australia both seasonally and over the long term. As a direct result of this unreliability it has been necessary to build more impoundments for river management than would appear necessary in relation to mean discharge values. Before such structures were built the fluctuations in stream flow would have been considerable.

CHEMICAL FEATURES There are a variety of chemical compositions in Australian waters which do not conform to the 'standard composition concept' of other countries ('calcium carbonate'). An average chemical composition for our waters would be a 'sodium chloride' type. As a reflection of the general aridity of Australia and the hydrological regime of many drainage basins the Total Dissolved Solids (TDS) concentrations in natural standing waters on the mainland are usually higher than those found elsewhere and the proportion of saline to fresh standing water bodies is also higher.

The concentrations of plant nutrients such as nitrogen and phosphorus in south-eastern Australian standing waters have been found, from limited data, to be higher th.an those levels, proposed by northern hemisphere workers, which are not to be exceeded if eutrophication (the process of becoming enriched) is to be avoided.

Some eutrophic lakes in Europe have P04-P values as low as 0.02 mg/I, whereas the average value encountered for different salinities here ranged from 0.14 to 0.58 mg/I in one study.

These values are not only higher than proposed critical values but also appear to be higher than most absolute values recorded elsewhere.

These apparently high concentrations may perh,.1ps be correlated with the relatively high concentrations of total salts in our lakes, but they may also be a result of the widespread agricultural use of phosphatic fertilizer.

Australian lakes with high nutrient concentrations, although displaying most of the diagnostic features of eutrophic lakes, usually lack the more marked nuisance characteristics of north-temperate eutrophic lakes. For example excessive growths of water-weeds is not a common feature of Australian natural lakes, probably because of the increased salinities and the static conditions found in most lakes.

18

PROBLEMS Many ecological problems are faced by limnologists studying Australian inland waters on account of the distinctive characteristics outlined above.

1. Locality or habitat Basic ecological data for our inland aquatic environment is extremely sparse and it is clear that any study of running waters will provide no mere repetition of results gained elsewhere. With regard to lakes, it appears from some recent results that the bottom-dwelling communities of aquatic insects (in this particular case the Chironomidae) do not fit into the cla!isical and generalized scheme proposed by several European limnologists. said to be applicable to both hemispheres.

Australian underground waters, both interstitial subsurface waters and underground cave systems, have been poorly studied but they promise to yield interesting and exciting biological information. Springs too, such as the mound springs of the arid inland of Australia. and other thermal and non-thermal types, have yet to be studied biologically despite the fact that much of Australia is underlain by aquifers including the Great Artesian Basin, said to be the world's largest.

Inland salt lakes, whilst not confined to Australia, do seem to span the whole spectrum of salinity, are homogeneous in chemical composition and range from ephemeral to permanent.

2. Specific groups of organisms

Little is known of the ecology of most groups of organisms living in Australian inland waters though it may be mentioned that groups of high regional interest are increasingly being studied by overseas visitors who build a reputation on our fauna while we ignore it!

The ecology of our native fish is poorly known whilst paradoxically that of the introduced fish is much better known, although such knowledge includes little which is related to the interaction between the two.

The phytoplankton (algae) seem to offer fewer problems of regional interest but likewise have been little studied.

3. Chemical problems The source of the salt in our inland waters is of great regional interest and, although there is a Cont. on page 19

great deal of evidence that a substantial proportion is derived from marine sources (i.e. cyclic salts), this evidence is mainly circumstantial and there are several criticisms of this theory which should be considered.

Plant nutrient concentrations must be examined more thoroughly to see whether they are really as high as the preliminary data suggest, and if so, why? Also, are they so important as limiting factors in lakes here as elsewhere? For many of the more inaccessible Australian lakes we know nothing of their water chemistry apart from the fact that it is potable, brackish or salty!

4. Applied problems Relatively few applied limnological investigations have been undertaken to date in Australia and the reasons for this do not include an absence of applied problems. Examples here are of the extent to which introduced fish interact wit·h and affect other aquatic life and the environment in general. The effect of Cyprinu·s carpio (European carp) springs to mind. Some maintain that the species is responsible for great physical disturbance to aquatic habitats because of its feeding habits which could cause increased turbidity; others argue that Australian rivers are naturally turbid.

Other exotic biota such as the water hyacinth, Eichhornia crassipes, and the water fern. Salvinia auriculata, whose introduction may have important consequences, have also been little studied against the total limnological background. Both are highly pestiferous outside their native South America, both occur in Australia and should be considered as potential pests in such tropical impoundments as the Ord. To summarize finally, an attempt has been made to show that whilst many Australian engineering problems are cosmopolitan in character, the same cannot be said with regard to Australian ecological problems.

• The Editor would be pleased to receive Technical Articles,

WATER AND WASTE WATER •

Chlorination & pH Control Systems

•

Chemical Metering Pumps

•

Flow Meters Magnetic (PVC) Variable Area Positive Displacement

•

Level Indies.tors

•

Rotary Glandless and Centrifugal Plastic Pumps

•

Valves (Automatic) Level Pressure Flow Control

Association News, Business News, for future publications, A.W.W.A. members please send copy to your Branch Correspondent, otherwise to the editor. Addresses on page 1.

All copy should be accompanied by a letter slating author's consent to publish and freedom from any prior publishing rights.

ACROMET PTY. LTD. P.O. Box 491, Clayton, Vic. Tel.: 547 3077 Sydney. Tel.: 982 8055

19