Water Journal June 1974

·

I 1ssN 0310-03671

Official Journal of the fflll-i i iM • tl1 ~ l'.Wi i #I iE ~I•) W/!J.i i =1ro1' i :t iE-i-i•ItJ ,!i i [I]~ I

IVOL. 1 NO. 2

- JUNE 1974- Price $1.00

I

r I EDITORIAL COMMITTEE Chairman: C. D. Parker Committee:

G. R. Gollin F. R. Bishop Joan Pawling A. G. Longstaff Hon. Editor:

A.H. Truman Publisher: John G.Craig

BRANCH CORRESPONDENTS A.C.T.: A. Macoun, cl· Dept. of Works, Phillip,

wale

1,ss" 03•HJ61 I Official Journal of the IAOSf:RALIAN WATER_Af@

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CONTENTS Editorial - 'Biennial Convention '74'

7

Advanced Waste Water Treatment - David M. Philp

8

A.W.W.A. Sixth Federal Convention

16

A Point of View - Symposium '74

20

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, c/-E. & W. S.

G.P.O. Box 1751, Adelaide, 5001.

W.A.:

B. S. Sanders, 39 Kalinda Drive, City Beach, 601 5.

TASMANIA: D. A. Walters, Box 94A, G.P .0., Hobart,

7001.

Editorial Correspondence: Hon. Editor,

A. H. Truman, _ c/- Davy-Ashmore Pty. Ltd., P.O. Box 4709, Melbourne, 3001.

Or to State Correspondents.

Advertising Enquiries:

Applications of total organic Carbon Measurement and correlations with oxygen demand parameters 21 - N. H. Pilkington and E. A. Swinton Association News

25

New Products - Projects

26

Calendar of Events ..

27

FRONT COVER The large aeration por:ids for the biological treatment of waste process water recently commissioned at the Petrie · (Queensland) paperboard mill of Australian Paper Manufacturers Limited. Four large floating aerators re-condition the water before its release to the North Pine River. A.P.M."s water treatment installation at Petrie is similar to those at Maryvale Mill, in Gippsland, Victoria, where the aeration ponds cover an area of 12.5 hectares and the water is purified before release to the Latrobe River, also at Broadford Mill, Victoria, where a system of contour channel irrigation precedes a series of three aeration ponds for clarification and reoxygenation of the process water before its release to Sunday Creek. At A.P.M."s mills else where the story is the same - maximum possible recycling of water within the plant and purification of the used water before it is released.

John Craig, 'Water' Box 175, Nunawading, 3131.

Phone: 874 2133.

Continued on Page 7

• FRONT COVERS OF SUITABLE MATERIAL ARE AVAILABLE FREE OF CHARGE EXCEPT FOR MECHANICAL COLOUR SEPARATION WHERE NEEDED. ENQUIRIES TO JOHN CRAIG (SEE COLUMN LEFT).

ADVANCED WASTE WATER TREATMENT David M. Philp B.E. (Hon.) Sydney, M.I.E. Aust.* The term advanced waste water treatment is used in this paper in the broadest sense to cover all process systems for the removal of oxygen demanding substances, suspended solids, bacteria and biostimulants to achieve a waste water effluent and solids disposal which minimises their impact on the environment.

With the development of large inland cities waste water effluents could become a significant portion of the river flows during dry periods, as is the case with Canberra and the ,Murrumbidgee River. The capability of these cities to add significant quantities of pollutants such as oxygen demanding substances and biostimulants, (i.e.) nitrogen and phosphorus, to the river systems could result in deterioration of water quality in the down stream sections of the rivers.

Even in river systems where waste water will not significantly reduce dissolved oxygen levels or cause increases in bacterial pollution the wide range of river flows will cause significant variations in biostimulant concentrations increasing the stress on the ecological systems of the river.

While biostimulants from waste water is not the only source, the cont_inuous nature of this input must make it more significant than the more intermittant inputs from urban and rural run-off given that both were equal in .load. However this will be dependant on the individual situation.

Impoundments, constructed to control river flows and to Two basic approaches can be made to the problem of increase utilisation of limited water resources, are more senadvanced waste water treatment. sitive to biostimulation than flowing river systems. The potential source of biostimulants from large cities, if allowed to enter these impoundments could result in a major quality {i) Tertiary Treatment deterioration of these resources limiting or significantly · In this process additional treatment is under.Jaken using increasing the cost of water utilisation. This will be particueffluent from conventional treatment processes or seconlarly so for public water supplies and recreational uses which dary effluent. will increase in demand with the development of inland cities. (ii) Advanced Waste Water Treatment The interaction between nitrogen and phosphorus and the In this case advanced waste water treatment is conenvironment is not completely understood despite the sidered in its strictest sense where a multipurpose func- amount of knowled_ge which is available. Research is required tion is achieved from the individual process units. under Australian conditions to more fully understand and In many ca_ses where secondary treatment facilities already control the problem of eutrophication, however while there is exist nutrient removal from secondary effluents will be evidence to suggest that eutrophication can be controlled by utilised. However the tendancy in the future wilt be to con- limiting either nitrogen and phosphorus, and a suggestion struct combined facilities due to the lower capital cost. At that a balance be maintained between these.substances, both Lower Molonglo economic comparisons indicated the com- should be limited in effluents disposed in areas where bined facility provided the lowest capital cost solution when eutrophication is likely to cause difficulties. In any case compared with other types of facilities. These comparisons nitrogen in the river receiving water should be limited to 10 mg/! to provide a suitable raw water quality for publ_ic water will be discuss·ed later in the paper. supplies. In the case of the Lower Molonglo Plant facilities Investigation work carried out in the U.S. by the Environ- are being provided for the limitation of both phosphorus and · mental Protection Agency and other groups suggest that in nitrogen as required. general the provision of separate facilities for phosphorus With the development of large inland cities the need for removal on secondary effluent will increase the capital cost of advariced waste water treatment facilities will increase and treatment over that of the combined system. will be necessary if the effect of this development on the In addition the operating cost with phosphorus removal is environment is to be minimised. higher where recarbonation is required. Recarbonation is almost always required where treatment of secondary effluent CANBERRA is undertaken-.

Canberra is a major inland city with a current population of some 180,000 persons. Its present growth ra:te is such that its Australia is a dry continent with rainfalls less than any other population is doubling every 7 to 8 years. With this growth it continent in the world. Rainfall is for the most part seasonal is expected that Canberra will reach the present size of Perth and erratic. Australia lacks the high mountain ranges of other by 1990 or the present size of Brisbane by 1993. qontinents and in consequence has no permanent snowfields.

The National Capital Development Commission is responsiThe run-off from rainfall is low, with the Murray-D/:1,rling river system having a run-off of approximately 3 per cent and most ble for the development and construction of Canberra. The inland river systems having a run-off of less than 1 per cent. administration of the· A.C.T. is the responsibility of the DepartRiver and stream flows are highly variable with near no flow ment of the Capital Territory which delegates certain responsibilities including the operation and maintenance of conditions during drought periods being a regular feature. the Water Supply and Sewerage facilities to the Department In consequence river systems,_ particularly in Australia, of Housing & Construction. The Department of Housing & offer only a limited sink into which waste water effluents can Construction also assists the National Capital Development be disposed. This contrasts sharply with the situation -for Commision in planning, design a11d construction of water coastal cities where significantly higher dilutions of waste supply and sewerage facilities for the National Capita!. water effluents in ocean waters are available.

Canberra is being developed as a number ·of town areas

* David M. Philp, Supervising Engineer Sewerage and Treatment, Major Development Section, Department of Housing and Construction, Canberra, A.C.T. 8

each with a population of approximately 100,000 persons.

Three town areas have been developed so far, these being Canberra, Woden-Weston Creek and Belconnen with a fourth area under development at Tuggeranong.

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Waste water from these areas is currently being treated at three major treatment facilities: 1. Weston Creek Sewage Treatment Works This plant is capable of treating wastes from a population of 135,000 to 140,000 persons. After screening and primary sedimentation the plant is divided into two separate processes, one consisting of low rate trickling filters and humus tanks, the other consisting of high rate trickling filters and an activated sludge plant. Sludge disposal is by anaerobic digestion with the digested sludge being pumped some 8 kilometres from the plant to sludge lagoons. Effluent from the plant is disposed direct to Weston Creek just upstream of the Molonglo River.

2. Belconnen Water Pollution Control Centre Designed for a population of 50,000 persons it provides screening, primary sedimentation, activated sludge treatment with tertiary lagoons for bacteria removal. Effluent from the plant is discharged to the Ginninderra Creek.

Sludge disposal is by anaerobic digestion and lagoon disposal.

CANBERRA

SEWERAGE

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Sewage Flows at Weston Creek Sewage Treatment Works 1972 Parameter Raw Sewage Final Effluent B.0.D. 213mg/l 16 mg/I Suspended Solids 193 mg/I 16 mg/I · Ammonia 38 mg/I 37 mg/I Nitrate Nil 3.4 mg/I Phosphate 26 mg/I 18.2 mg/I The average flow was 36.8 MI/D (8.10 MGD) at Weston Creek S.T.W. During this period the plant served a population of approximately 123,000 persons plus a flow of R.68 MI/D (0.59 MGD) from the Fyshwick Sewage Treatment Works.

In 1972 the flow from the Belconnen Plant was 41.8 MI/D (0.92 MGD).

The Weston Creek S.T.W. site is limited in area and is not considered suitable for expansion beyond the current design population of 136,000 persons. A new treatment plant is required by 1976 to handle sewage from the Canberra and Woden-Weston Creek areas and the new .,diStrict of Tuggeranong. Initial development in Tuggeranong is to be treated by a temporary oxidation ditch type sewage treatment works.

Effluent from the Weston Creek S.T.W .. flows down the Molonglo River to the Murrumbidgee River. The Molonglo River rises on the Great Dividing Range to the east of Canberra. It is fed by two main rivers, the Molonglo and the Oueanbeyan Rivers. The Molonglo River passes through the old mining town of Captains Flat and seepage and run off from the old mine workings results in significant quantities of zinc being carried down to Lake Burley Griffin. The Molonglo River enteres the A.C.T. near Queanbeyan.

In 1964 the Scrivener Dam was constructed to form Lake Burley Griffin, a .major water feature in the centre of Canberra. This dam has resulted in a reduction of flow in the Molonglo River below the dam during dry 'periods. At times the only flow in this section of the river is effluent from the Weston Creek Plant.

Water quality analyses of this part of the river indicate a reduction of dissolved oxygen of up to 50 per cent of saturation ·with £. coli counts being well above limits set by the American Water Quality Criteria Committee for body contact sports. The Lower portion of this river flows through undeveloped country with the area near the plant being generally inaccessible to the public.

Effluent from the Belconnen Plant flows down the Ginninderra Creek which rises in the northern part of the A.C.T. Flows in the creek vary over a wide range and during dry periods the main flow in the creek is due to effluent from the plant. During these dry periods the creek contains high concentrations of free floating algae.

The Ginninderra Creek crosses into N.S.W. just below the plant and flows into the Murrumbidgee River.

The Murrumbidgee River rises in the Kosciusko National Park and flows via the Tantagara Reservoir to the A.C.T. through lands which are primarily used for cattle and sheep grazing. Upstream.o.f the Molonglo River within the A.C.T. the river is used and accepted for body contact sports with facilities being provided for picnicking; the water is clean and of acceptable qu,ality. No nuisance algal growths have been EXISllNG TRUNK SEWERS - reported in this section of the river even during drought conPROP05ED TRUNK SEWERS - - S.T.W.• SEWAGE lREATMENl WORKS ditions. Phosphorous levels are generally less than 0.01 mg/I W,P.CC,•WATER POLLUTION CONTROL CENTRE with 0.02 mg/I being rarely exceeded. The nitrogen content W.Q.CC.•WATER QUALITY CONTROL CEITTRE is generally less than 0.2 mg/I with 0.5 mg/I being exceeded on very few occasions.

3. Fyshwick Sewage Treatment Works However below the junction with the Molonglo River high The design population for this plant is 20,000 persons. It concentrations of nitrogen 8.nd phosphorus have been detectprovides screening, primary sedimentation. trickling filters, ed and concentrations are showing a general increase comand tertiary lagoons for bacteria removal SI udge is patible with the growth of population in Canberra. Levels of anaerobically digested with disposal on drying beds. phosphorus during the spring 1972 reached an average of Effluent from the plant is disp6sed into sewers in the b.43 mg/I with concentrations of 1.4 mg/I being achieved in Weston Creek S.T.W. catchment.

Summer 1972-73.

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Inspections of the river have shown a predominance of long filimentous algae atached to the rocks in the river bed with large mats of algae consisting of Cladophora and Hydrodicton occurring during drought periods. Rocks along the river are covered with dried algae during the dry periods causing unpleasant odours. The bacterial quality of the river does not meet the requirments set down by the U.S. Department of Interior Water Quality Criteria Committee for body contact Sports. The poor bacterial quality can be attributed to waste waters discharged from the Weston Creek Sewage Treatment Works. The nitrogen and phosphorous concentrations correllate well with the quantities of these substances discharged in waste water effluents.

In September, 1971, the Senate Standing Committee on Social Environment undertook an enquiry into Canberra's Sewage effluents and concluded that effluents from Canberra did have an effect on the bacterial quality of the Murrumbidgee River but this was acceptable in relation to the current use of the water (i.e.) pastoral and water oriented sports downstream in Burrinjuck Dam. This committee recommended that joint management by the Commonwealth and the State of New South Wales should be established for the Murrumbidgee River Basin and that under joint management suitable water quality and waste disposal standards should be determined and maintained. In conjunction with the Health Commission of N.S.W. water quality studies are to be Undertaken on the Murrumbidgee River and Burrinjuck Reservoirs with intensive short term studies being undertaken to examine specific effects in detail.

10

PREOICTEO

MONTHLY

HUCTUATlOH IN

BIOSTIMULANT CONCENTRATIONS MURRUMBI06EE mYER

The Burrenjuck Reservoir On the Murrumbidgee River is located some 40 km downstream of the Molonglo River.

In 1970 the aerial survey indicated the presence of algal blooms despite unusually heavy spring rains. At the same time Tantangara Reservoir upstream of the A.C.T. was completely free of algal blooms. Again in the summer of 1971/72 an aerial inspection was undertaken indicating the presence of algal blooms extending through a significant portion of the reservoir.

The Water Conservation and Irrigation Commission of N.S.W. have undertaken monitoring of water qua)ity within the reservoir. Their monitoring in 1972 at 3 sampling points indicated total phosphorus concentrations in the order of 0.03 mg/I with maximums reaching 0.08 mg/I in the upper waters of the reservoir. Waters. near the bottom of the reservoir average 0.05 mg/I of total phospho·rous with maximum concentrations of 0.24 mg/I. Nitrate concentrations averaged 0.16 mg/1 with maximums reaching 0.34 mg/I for surface waters while bottom waters average 0.32 mg/I with maximums of 0, 72 mg/I. Algal analyses have shown the presence of Anacystis cyanea.

The three graphs (above) indicate the expected trends in nitrogen and phosphorous concentrations in Murrumbidgee River and Burrinjuck Reservoir. Tentative standards for the maximum concentrations of phosphorous and nitrogen have been adopted,

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In the first stage waste water will be delivered to the plant via a major trunk sewer down the Lower Molonglo ·valley.

This trunk sewer will have a diameter of 2,590 mm with a capacity of approximately 12,300 Jps. A contract was let to Johri Hollands Holdings Ltd., in the amount of $7.2 million for the construction of the trunk sewer. A contract for the supply of pipes had previously been let to Humes Pty. Ltd., for $2 million.

It should be pointed out that the aim is not to prevent growth of algae but to limit the occurrence of nuisance growths which interfere with the functional use of the river and reservoir.

The Molonglo Valley trunk sewer will collect waste water Potential recreation sites exist on the Murrumbidgee River below the Molonglo River however these sites have not been from the existing Canberra and Woden-Weston Creek Outfall developed due to the recognised contamination of the river sewers and a new sewer tunnel from the Tuggeranong catchby effluents from Canberra's sewage treatment works. After ment. The Tuggeranong sewer tunnel consists of a 1900 mm completion of the Lower Molonglo Plant there will be no res- diameter tunnel 9.14 km long with a capacity of 4,540 lps. triction on the development of these recreation areas for The tunnel due for completion in 1975 is being constructed

by Pearson Bridge-Group Engineering Joint Venture for $6.3 swimming, picnicking and hiking.

The Burrinjuck Reservoir is approximately 80 km by road million. ·, from Canberra and is a popular water recreation area. The The Lower Molonglo Plant has been design·ed' with allowdemand for recreational facilities in this area is increasing with the growth of population in Canberra. The reservoir has ances for future changes in the characteristics of Canberra's a number of beaches, inlets and protected waters which are waste water. considered ideal for fishing, picnicking, hiking, water skiing The basic design allownces for the plant are set out in the and swimming. Protection of water quality of this reservoir is table below. The loadings allow for future increases and the therefore of interest to the residents of Canberra.

Canberra is rapidly approaching the stage where its existing actual population which can be handled by the first stage with recreational areas will be overloaded. Experieqce in other the current loadings is significantly higher than shown in the areas has shown that overloading of the·se facilities leads to design allowances table: rapid deterioration.

Alternative water oriented recreation facilities are limited.

Design Loadings Final Development Initial Development 1,005,000 persons Lake George is subject to wide fluctuations in level making it Population 269,000 persons 17,000 I/ ha/ day unreliable as a major recreation site. Ocean beaches are Trade wastes 17,000 I/ha/day approximately 160 km from Canberra and therefore of limited Peak to average dry weather flow use to the residents of the A.C.T. 1.5 1.5 The development of the Murrumbidgee River below the Wet weather 2.2,500 I/ha/day 22,500 I/ha/day Molonglo River -for water recreation and maintenance of the Infiltration Burrinjuck Reservoir in a satisfactory condition is of sig- Average nificant value to the residents of the A.C.T. and surrounding dry weather flow 436MI/D 109 MI/D areas. peak Wet weather flow 1709 MI/D 545 MI/D THE LOWER MOLONGLO WATER QUALITY CONTROL CENTRE

The Department of Housing and co·nstruction, through its consultant Caldwell Connell Engineers, is undertaking the design of an advanced waste water treatment facility at Lower Molonglo for the National Capital Development Commission.

To meet the need for additional treatment facilities with the rapid growth of Canberra's population investigation studies have shown that the construction of a treatment plant at Lower Molonglo was the most satisfactory solution. In adopting nutrient removal facilities for Lower Molonglo consideration was given to the present and future high concentrations of nitrogen and phosphorus in the Murrumbidgee River, the existing quality of the Murrumbidgee River and Burrinjuck Reservoir and information obtained in experiences overseas.

It was recognised that extended and detailed studies of the Murrumbidgee River and Burrinjuck Reservoir would be required to establish quality and nutrient standards necessary for the Murrumbidgee River Basin as compared with the standards set elsewhere.

The Lower Molonglo Water Quality Control Centre is to be located on a site near the junction of the Molonglo and Murrumbidgee Rivers where it is capable of commanding three major catchments in the A.C.T. These are the: (i) Molonglo River Catchment {ii) Murrumbidgee River Catchment

{iii) Ginninderra Creek Catchment The plant is being planned for four possible stages for a notional population of up to one million people. The first stage of the plant is being designed for an average dry weather flow of 109 MI/D.

Gross Solids

0.0112M'/MI 1.22M 3 /day

0.0112M 3 /MI 4.90 3 /day

0.0096M 3/MI 5M 3 /day

0.0094M 3 /MI 16M 3 /day

2.5 mg/I 50 mg/I

3.5 mg/I 75 mg/I

0.086 kg/cap/day 26,300 kg/day 4.15 kg/ha/day 3,360 kg/ day

0.1 kg/cap/day 110,600 kg/day 4.15 kg/ha/day 10,100 kg/day

0.077 kg/cap/day 20,700 kg/ day 3.8 kg/ha/day 3,100 kg/ day 211 mg/I

0.091 kg/cap/day 91,000 kg/day 3.8 kg/ha/day 9,300 kg/day 230 mg/I

0.014 kg/ cap/ day 3,800 kg/day

0.026 kg/cap/day 15,200 kg/day

Grit

Floatable Materials

Floatables Hexane extractable Susp'ended Solids

Domestic wastes Trade wastes Oxygen Demanding Substances (BOD,)

Domestic Wastes Trade wastes Av. Concentration Toxic Substances

Ammonia Biostimulants

Nitrogen as N phosphorus as P

0.024 kg/ cap/ day 0.026 kg/cap/day 26,200 kg/day 6,400 kg/day 0.0045 kg/cap/day 0.0055 kg/cap/day 5,500 kg/day 1,200 kg/ day

Surface Active Agents

as MBAS

0.0018 kg/cap/day 485 kg/day

0.002 kg/cap/day 2,000 kg/day 11

The plant site for the Lower Molonglo Plant is subject to some limitations due to the nature of the terrain and poses a number of difficulties. Because of this, in 1970 the National Capital Development Commission undertook an environmental study of the area extending along the Murrumbidgee and Molonglo Rivers. It was concluded that a natural reserve should be established in the area around the plant with initial development upstream of the junction and later development downstream after the plant had been completed.

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The main requirement of the reserve is that restoration of the existing flora be undertaken to approach as close as possible the area's natural state with recreation facilities being provided at suitable locations. The study recommended that the plant should not dominate the site or alter the character of the area.

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It was neccesary to consider the following factors: (al No obvious sign of waste water effluent such as floatables, suspended solids, algal growth or detergent foams;

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(bl No odours which can be linked with the plant: (c) No requirement for danger signs such as "No Swimming" associated with effluent from the plant; (d) Access roads to the treatment plant and facilities for visitors to the plant should be separate from those required for the recreation area.

The plant should not be obvious from the access roads to the recreation area and from within the recreation area itself.

This last factor imposes limitations on the area of the site which can be developed restricting the plant to the upper part of the- site.

4 5 CONCENTRATION

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ASSUMPTIONS:

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NO NUTRIENT REMOVAL PROCESS OCCUR\NG IN THE TREATMENT OR RIVER SYSTEMS 2 TOTAL VOLUME OF THE RESERVOIR UTILISED ANNUALLY. 3. NO ACCUMULATION OF NUTRIENTS IN THE RE SE AVIOR BEYOND A YEAR. 4. NUTRIENT COMPLETELY MIXED WITH THE RESERVOIR CONTENTS.

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BIOSTI MU LANT CONCENTRATIONS BURRINJUCK

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The plant site is located on a ridge near the confluent of the two rivers with steep gullies on either side of the plant.

The fall down the plant site is approximately 60 m.

The plant site is to be landscaped using native trees and shrubs with a minimum of specially grassed areas so that the plant will blend in with its natural surroundings.

The plant has been designed to be an attractive place to work and good facilities will be provided to encourage pride 12

in the plant and .in the service of water pollution control.

The raw waste water will enter the plant at an enclosed screen room and will be screened by one of three bar screens with automatic controlled removal of screenings. The screenings will be fed to disintegrators and will then be delivered to the solids handling system. The screens are designed for the maximum flow from the trunk sewer.

Flows in excess of the maximum design flow of the plant of 545 Ml/day would

only result from the catastrophic entry of surface water into the trunk sewer.

Overflow facilities are provided downstream of the screens to bypass flows in excess of the design maximum direct to the Molonglo River. Chlorination facilities are provided on this bypass.

The screen room ventilation system is fitted with a hypochlorite scrubber unit, to treat air from the Molonglo Valley sewer as well as the screen room. Prior to screening, facilities are available for addition of chlorine to the raw waste water for odour control.

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After the screening and overflow by-pass facilities lime will be added to raise the pH to II - 11.5. Hydraulic mixing of the lime will be used via an hydraulic jump with a flow measuring flume being provided downstream of these facilities.

The hydraulic capacity below the Overflow by-pass will be maximum design flow or 5 times average dry weather flow.

Further overflo°w by-pass facilities are provided down stream of the primary sedimentation tanks to limit the flow to the nitrifying aeration tanks to 3 times average dry weather flow.

This overflow will be fed to the screened waste water overflow system upstream of the chlorination facilities.

The waste water is then fed to the combined flocculation and grit removal chambers. Flocculation and grit removal is carried out using air from coarse bubble diffusers. Grit , removed from the chambers is then pumped to the solids handling system. Two chambers will be provided in the first stage.

The degritted waste water is then fed via aerated channels to four horizontal sedimentation tanks. The tanks will be equipped with chain and flight sludge scrapers and screw cross collectors. Scum will be removed with water sprays and rotary helical skimmers. Sludge and scum will be pumped to the solids handling system using pumps located in a gallery b9tween the grit chambers and the sedimentation tanks.

Sludge pumps are also provided to recirculate lime sludge to the flocculation chambers to maintain the optimum suspended solids concentration for flocculation.

The primary effluent is then collected through submerged fibreglass pipes with the tank water level being automatically controlled by throttling butterfly valves in the discharge channel.

Primary effluent is then fed to four biological nitrification tanks to convert ammonia to nitrate and to oxidise organic

MODEL OF LOWER MOLONGLO W.Q.C.C. material. Each tank consists of eight cells in series with a·0.6 m drop at the discharge end of each cell. The§,e drops will provide additional aeration of the mixed liquor, reducing operating costs but no allowance has been made for thiS aeration in the design of the aeration blower unit. The aeration of the mixed liquor is to be controlled automatically to a pre set dissolved oxygen concentration using dissolved oxygen probes and adjustable inlet vanes on the blower units.

The return nitrified sludge is to be mixed with the incoming flow to the nitrification tanks. Waste nitrified sludge will be pumped to the grit removal chambers for removal in the primary sedimentation tanks. Aeration air will be provided by three 900 kw aeration blower units located in a blower building upstream of the nitrification tanks. Air will be ihtroduced to the tanks via flat fine bubble porous plates set in special precast plenum units in the base of the tanks. The porous plates are arranged in a uniform pattern over the base of the tanks.

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The mixed liquor is collected in a channel across the ends of the tanks and is delivered to the final clarifiers.

Clarification is carried out in five circular clarifiers. The mixed liquor will be introduced to the centre of the tanks through a baffled inlet structure and effluent removed in concentric launders. Sludge is continually removed via a rotary scraper fitted with sludge removal pipes located along the scraper unit. The sludge is removed from the clarifier units through the centre column.

Two variable speed vertical turbine pumps are located at each clarifier for the return nitrified sludge. As the clarifiers are set at different levels this arrangement minimises pumping costs.

Dentrification is carried out in fixed growth reactors. The columns consist of completely enclosed rectangular concrete tanks containing approximately 5.8 m of plastic tower packing media. The nitrified effluent is distributed to the media through a fixed trough system and splash plates. The denitrified effluent is then fed to the effluent filters.

Methanol is fed into the influent to the tower and will be controlled by a nitrate probe.

Filtration is to be carried out on dual media rapid filters.

The media will consist Of 1060 mm of anthracite coal and 450 mm of sand. The four filters will be fitted with a concrete channel and nozzle under drain system with an air-water back wash facility. The pipe gallery will be located across the ends of ¡the filters containing all major pipework, air backwash system, rate controllers and associated instrumentation. The backwash pumps, air blowers, plant water pumps and associated equipment are located in the filter pump building.

The effluent from the filters is discharged to the chlorine contact tanks located below the filter structure. The final effluent is then discharged to the Molonglo River. Facilities for dechlorination with sodium sulphite will be provided to remove the toxic effects of chlorine when necessary. Chlorine for disinfection of the final effluent, raw water waste for

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odour control and overflow disinfection will be provided from one of two fifteen tonne chlorine tanks.The liquid chlorine will be fed through an evaporator and distributed at subatmospheric pressure to the points of application. The equipment for chlorination will be located in the maintenance building and will be completely isolated from other areas for safety. â&#x20AC;˘ The solids handling system consists of two major compo_nents, the centrtifuges and the furnaces. The equipment will be housed in the screening-incinerator building along with the lime storage and feeding equipment. The building will also house the scum thickeners and the grit washing and dewatering equipment. Two furnaces will be provided, one for burning sludge and the other for lime reclamation.

Scum and grit are dewatered and fed directly to the sludge furnace. Sludge removed from the primary sedimentation tanks is delivered to a classification centrifuge where the heavier calcium carbonate sludge is removed as a cake.

The cake is fed to the recalcining furnace where it is converted to calcium oxide for reuse. The centrate is fed to a balance tank where it is mixed with the screenings. The thickener under flow is fed to the clarification centrifuges and then to the sludge furnace. Ash from the sludge furnace is to be disposed in land fill. Gas emission from the furnaces will be treated with after burners, dry cyclones and wet scrubber units. Exhaust gases from the furnaces is expected to contain light dust particles of calcium hydroxyapatite. The carbon dioxide in the discharge gas will lower the pH of the scrubber water redissolving these particles. This low pH, phosphorous containing, waste will be returned to either the grit chambers or nitrification tanks. The feed to the nitrification tanks will help to lower the pH of the flow to these tanks and provide additional phosphorous for biological activity in the tanks.

The feed will be controlled to minimise leakage of phosphorous through the plant. The effluent quality from the

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plant is to be monitored using an auto analyser to give a constant record of effluent quality.

Odour control at the plant will consist of the collection of air from the sludge handling equipment.and the trunk sewer, the. grit-flocculator chambers, the primary sedimentation tanks inlet and outlet channels and the nitrification tank settled waste water" channels. The air will be deodorised at three hyj:)ochlorite air treatment units.

Process control instrumenation and power supply operations will be carried out at one of the three field control centres for the screening - incinerator complex, the primary sedimentation tanks, nitrification facilities and final clarifier systems, and the filter and final chlorination facilities. In addition all processes are supervised, monitored and logged at the Supervisory Monitoring Centre in the maintenance building. Instrumentation will be basically electronic with $ome pneumatic instruments. Analog control is provided at the Field Control Centres, all alarms and most measurable variables are transmitted to the Supervisory Monitoring Centre for logging on a digital data processor.

Dual 11 KV power supply is to be provided for the plant with a generator as a back up facility against complete power blackouts.

Five major buildings will be provided at the plant: 1. Administration building containing offices, ,,lecture room and laboratory. The building will serve as the administrative centre for the plant.

Filtration and Disinfection System

2 No (4 half filters) 7.24 m 32 m 1.51 m 4.11/s/m' 12.651/s/m' 1 No 50 minutes

Dual media filters width length bed depth filtration rate at 3 x A.D.W.F. backwash rate Chlorine Contact Tanks detention time at A.D.W.F. chlorine dosage Prechlorination - Postchlorination - Bypass chlorinators capacity

10 mg/I 5 mg/I 15 mg/I 3 No 3630 kg/day

Solids Disposal and Lime Recovery

solids disposal - primary - waste activated sludge Sludge centrifuges Classification centrifuge solids -- cake - centrate Clarification centrifuges feed solids -cake - centrate 2. Maintenance Building containing staff amenities, Multiple hearth furnacei workshops, offices, mechanical equipment room and diameter of hearths chlorination building.

No. of hearths rated capacity 3. S~reening - Incinerator Building.

83,600 kg/<day 6,400 kg/ day 5 No feed 8% solids 55% solids 4% solids

4% solids 15% solids

1% solids 2 No

6.7 m 9 Sludge burning duty 32 tonne of dry solids/day recalcinati'on dutY 108 4. Blower Building for the aeration blowers and generator. tonne dry solids/day.

5. Filter control Building.

The plant is designed to give the following effluent standSome basic design data for the treatment plant first stage is ard: (a) Substantially free of settleable solids or floatable solids, as follows: turbidity, colour and odour; (b) BOD 5 and suspended solids concentrations both less Primary Solids Separation than 5 mg/I. ' 230 mg/I Lime dosage as Calcium Oxide (c) Free of toxic substances; 30 mg/I Iron Chloride dosage as Fe Cl3 (d) Median fecal coliforms concentration of less than 50 per 2 No F/oculator-grit removal tanks 100 ml; 20 minutes detention time at A.D.W.F. (el A nitrogen concentration of less than 2 mgA and a 4 No Sedimentation tanks phosphorous concentration less than 0.15 mg/I; Overflow rate at A.D.W.F. 35,7001/m'/day (f) Detergent concentrations of less than 0.5 mg/I M.B.AS. Detention time at A.D.W.F. 108 minutes Acknowledgements Hydraulic capacity each 182 Ml/day This information was presented as a paper by Mr. D. A BOD 5 removal 70% Stockdill, Assistant Director, Major Development Section, 80% Suspended Solids removal Department of Housing and Construction, Canberra at the Nitrification-Dentrification System

Nitrification tanks Volume Assumed mixed liquor suspended solids¡ Loading lbs BOD,/day/lbs MLSS detention time at A.D.W.F. aeration blowers Dentrification Columns area total volume of media methanol feed at A.D.W.F. 10 Final Clarifiers diameter overflow rate at 3 x A.D.W.F.

4 No 4990 m 3 each 2000 mg/I 0.18 4.4 hours 3 No 8 No 120 m2 each 5,572 m3 10,700 kg/day 5 No 36.6 m 66,550 I/m'/day

Conference of Engineers Representing Authorities Controlling Water Supply and Sewerage Undertakings serving cities and towns of Australia held in Newcastle 20th to 24th Se ptember, 1973.

The author expresses his appreciation to Mr. M. A. Cornell the Project Manager for the Lower Molonglo Water Quality Control Centre for his technical assistance and to the National Capital Development Commission and Department of Housing and Construction for their approval to. publish this paper.

Author's Comment

The original pa.per presented at the conference has been amended to include the latest design information on the Lower Molonglo Plant as at November, 1973, and has been converted to the metric system of units. References overleaf

EDITOR'S NOTE: This article is the first of two by this author, concerning the Lower Molonglo Water Quality Control Centre. The record will be published in the next issue.

15

REFERENCES 1. National Capital Development Commission, Design Report on Lower Molonglo Water Quality Control Centre, prepared·

by Caldwell Connell Engineers. April,

1971.

2. Commonwealth Department of Works, Revisions to Design Report Lower Molonglo WatE)r Quality Control Centre, prepared by Caldwell Connell Engineers.

May, 1972.

3. National Capital Development Commission, Lower Molonglo Water Pollution Control Centre, Environmental Study Richard W. Gray. September, 1970.

4. Canberra - Strategy for City Growth and Waste Water Quality Control, F. C. Speldewinde. Institute of Engineers Conference, Perth. 1973.

5. Advances in Waste Water treatment in Melbourne, South Eastern System, R. C. Aberley and A. W. Bird. Water and

.sewage Works. November, 1972.

6. Full Scale Testing of Water Reclaimation ·System, G. A Norskotte, D. G. Niles, D. S. Parker and D. H. Caldwell. 45th Annual Conference Water Pollution Control Federation Atlanta, Georgia. October. 1972.

7. Sludge Disposal. by R. C. Aberley, A.W.W.A. Summer School. February, 1973. ' 8. Nitrogen and Phosphorus Removal from Waste Water Parts 1 and 2 by Adnan Shindala, Wat.er and Sewage Works.

June-July, 1972.

9. Chemistry of Nitrogen and Phosphorus in Water Committee Report Jour.

'A.W.W.A.' February, 1970.

10. Biological Dentrification, Paper by J. L Barnard National Institute for Water Research, South Africa.

11. Phosphorus Removal by Luxury Uptake

by M. C. Mulbarger, D. G. Shifflett, M. C. Murphy and D. D. Huffman, Jour.

W.P.C.F. August, 1971.

12. Design-Operation Interactions at Large Treatment Plants. Water Research, Vol. 6.

April-May, 1972.

13. Phosphorus Removal - Environmental Protection Agency, U.S.A. Process Design Manual. October, 1971.

14. Water Pollution in Australia - Report from the Senate Select Committee on Water Pollution. 1970.

15. Nutrients and Eutrophication - Special Symposia. The limiting Nutrient Controversy American Society of Limnology and Oceanography. February, 1971.

16.. Advanced Waste Water Treatment, R. L. Culp and G. L. Culp. Van Nostrand Reinhold Environmental Engineering Series, 1971.

17. Nitrogen Removal from Municipal Waste Water by Columnar Denitrification, Smith, Masse, Feige and Kamphake. Environmental Science and Technology, Vol. 6, No. 3. March, 1972.

18. Nitrate Removal by Ion Exchange. Evans, Jour. W.P.C.F. April, 1973.

16

THE NEW A.W.W.A. SIXTH FEI MAN AND WATER was the theme of the Association's sixth Biennial Convention held from April 30th to May 4th, 1974 at Melbourne's Exhibitions Buildings; a most imposing building constructed in the late 1870's and now classified 'A' by the National Trust.

E Seer

T atter seen the sobE

The Convention sought to explore all, aspects of its chosen topic from conservation of water to complete recycling of waste water, and attracted a registration of 335 delegates accomp·anied by 93 ladies, with all States being well represented as the following table indicates:

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900(

Whic

E Delegates Ladies

VIC

N.S.W.

OLD

S.A.

TAS

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W.A.

167

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N.Z.-2, Malaysia-1, N.G. -

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Registration and accommodation was arranged by the Victorian Water Commission and as full co-operation was obtained from the Motels involved the affairs of most delegates could be easily arranged. However, late registrations produced the usual chaos.

The Convention was opened by the Hon. W. A. Borthwick, Victorian State Minister for Conservation. The Minister welcomed all delegates and overseas speakers and in his opening remarks expressed pride in the way in which Australia's expertise and technology was keeping abreast with that which exists overseas. He went on to say that a few years ago the risk of eutrophicatiori of Port Phillip Bay had led to a decision to convey treated sewage effluent of high quality for disposal in Bass Strait, the wisdom of which decision, although not generally well receiVed initially, would undoubtedly be appreciated by future generations.

Prof. Eckenfelder of Vanderbilt University, Nashville, Tennessee, U.S.A. then gave an entertaining address in which he explained the role of "bugs" in sewage disposal. His grass-roots approach to the subject kept the ladies amused and gB.ve all present a primer course in sewage treatment by biological means couched in refreshing phraseology. · The Convention Committee set out to combine Australian knowledge with overSeas experience in the technical sessions and succeeded in achieving a most rewarding combination. Papers and presentation by Australian authors were of great interest and high standard. They were complemented by contributions from visiting experts of international standing, including: Prof. W. Eckenfelder, Mr. J. D. Parkhurst (Pres. W.P.C.F.), and Dr. B. Bell of the USA; Dr. B. Gustaffson of Sweden, Dr. A. Downing and Dr. A. Coleman of the U.K. and Dr. G. Mohanrao of India.

In particular, the Paper by Dr. Mohanrao - "Problems of Wastewater Control in India" - provided a marked contrast to the accounts of the high-powered technical advances in technology, by setting out the many and fundamental problems a country such as India has to overcome in the water and wastewater field.

The keynote address was delivered by Professor Eckenfelder and was titled "Progress towards Complete Recycling of Wastewater". His informative, objective and often witty narrative served to form a solid tou·ndation for the ensuing three days of technical sessions.

The introduction of_a Forum session provided a most successful innovation at a Technical Convention of this nature. 'Effluent Quality Standards - have we reached the practical limit - or passed it?' - was the topic introduced and discussed by members of the panel comprising Professor Eckenfelder, U.S.A., Dr. Mohanrao, India, Dr. Downing, U.K., Mr. Parkhurst. U.S.A., and Professor Shap.iro, U.S.A. (now in Victoria with the Westernport Study Authority). This subject proved to be most provocative and stimulated the audience into lively and constructive participation. It is hoped that selected sections of the discussion will be printed and circulated during the coming months.

'

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l insp ing

APPLICATION OF TOTAL ORGANIC CARBON MEASUREMENTS AND CORRELATIONS WITH OXYGEN DEMAND PARAMETERS * N. H. PILKINGTON and E. A. SWINTON INTRODUCTION

mination of volatile organic carbon, and both instruments can be so operated that soluble organic, volatile and non-volatile The organic pollution of water and wastewater streams has organic and inorganic carbon can be determined by appropritraditionally been determined by time consuming ate treatment of the sample. measurement of biochemical oxygen demand (BOD) or chemical oxygen demand (COD). The possibility of direct EFFLUENT QUALITY PARAMETERS determination of organic content by means of Total Organic Carbon {TOC) measurement has long been recognised, but BOD and COD since the known wet methods of (TOC) analysis were just as BOD and COD are well established as bas·;~ wastewater time consuming, this approach has had little impact until parameters but both are subject to shortcomings. The major recently. disadvantage of BOD for effluent control is that it normally Within the last decade however, commercial instruR requires five days to complete the test. By the time the result mentation has been developed for the rapid determination of is available the situation will have changed. this basic water parameter and is now available in Australia.

BOD is not basically an absolute parameter. Originally it This paper is written to bring this important technique and some of its applications to the attention of Australian chem- was an attempt to simulate conditions in a receiving stream to ists, engineers and consultants and to discuss the limitations be able to gauge the oxygen depletion effect of wastes that involved in establishing correlations between TOC and BOD may be discharged to that stream. Since uncontrollable or COD. Some results obtained on Australian domestic waters factors such as sunlight, temperature, turbulence and the bioare also presented. This is not to say that TOC is a logical population affect oxygen level in natural waters, the replacement for BOD 5 as a primary standard for water quality test conditions must be arbitrarily chosen. The standard five day test at 20°C was chosen largely with English, river condimeasurement. tons in mind (the average time taken to reach the sea being five days), it also has the effect of minimizing the effects of INSTRUMENTS AVAILABLE FOR THE nitnfying organisms. Other specifications could be more DETERMINATION OF TOC appropriate in Australia.

Commercial TOC analyzers have developed along two lines There are variables which may influence the actual and representatives of each are available in Australia. The Beckmant Model 915 TOC Analyzer is based upon combus- measurement of BOD. Sample pretreatment (e.g. pH adjusttion and Infra Red detection of the liberated carbon dioxide 1 : ment, removal of residual chlorine. removal of oxygen superthe Dohrmann-t DC-50 TOC Analyzer depends on combustion saturation), the use and acclimation of seed material and the followed by reduction of the carbon dioxide to methane, presence of toxins all introduce unce·rtainties. In some cases which is measured by a Flame Ionisation Detector. 2 '3 Both the result obtained may everi depend on the dilution used methods have been demonstrated to be specific and quantita- when measuring it. Further, organic compourids are not all tive for organic carbon and are acceptable to the United equally biodegradable.

States E.P.A. 4 as test procedures for the analysis of pollutants The COD test has also been arbitrarily standardized and, so in water. far as stream pollution is concerned, it is more artificial than tMention of trade names is for purposes of identification and does BOD in that the sample is chemically oxidized. Precautions not imply endorsement by the C,S.I.R.O. may be necessary to prevent interference from chloride and The analysis time is approximatelY five minutes per sample other inorganic reductants (e.g. ferrous iron, nitrite, sulphide, for each instrument and both utilize micro-litre samples. In sulphite and thiosu!phate) and the use of catalysts (e.g. silver the normal mode of operation, the Beckman instrument sulphate to oxidize straight chain aliphatics) may be required. measures organic carbon by the difference between Total Organic compounds also vary in their susceptibility to Carbon and Inorganic Carbon determined on two successive chemical oxidation under the conditions of the test. Thus difinjections of the same sample whereas the Dohrmann unit ferent oxidants (e.g. permanganate or dichromate) give difmeasures TOC directly on a single injection of a pre-acidified ferent values. sample.

T.O.C. TOC analyzers are expensive, but experience with a The advantages of TOC are that it is absolute, precise and Beckman analyzer in these laboratories has shown it to be a rapidly determined. Organic carbon content is a fundamental very reliable instrument. Over a period of nine months, some water parameter and is not determined by an arbitrclrily stan1,250 samples have been analyzed with no more than simple dardized procedure. With the combustion catalysts now availroutine maintenance carried out by the operator. Similar able, TOC is quantitative and free from interferences. Operexperiences have been reported for the Dohrmann analyzer, ator error {e.g. reproducible operation of a microlitre syringe) including one 5 by the United States E.P.A. and sampling techniques {e.g. adequate homogenization of Whilst these instruments are primarily designed to measure suspensions) are the limiting factors to reproducibility. The total organic carbon, they can be more versatile. The normal TOC analysis requires only 5 minutes per sample compared mode of operation of the Dohrmann includes separate deter- with 2 • 3 hours for COD and 5 days for BOD.

* To whom correspondence should be addressed at C.S.I.R.O., Division of Chemical Technology, 69 Yarra Bank Road, South Melbourne, Victoria, 3205.

19

APPLICATIONS OF TOC ANALYZERS The range of applications of TOC is, of course, limited only by the condition that the water or waste water contains, or might contain, organic carbon. One of the most important uses of organic carbon analyzers is the monitoring of effluent quality. This may be required for two reasons, the first being to determine compliance with discharge regulations. The standards of most Australian authorities are currently expressed in terms of the familiar BOD and COD but TOC is already acceptable in some States provided the results are correlated to these parameters.

In Victoria, for example. parallel tests of BOD (and/or COD) and TOC must first be carried out and then rechecked from time to time. 6 It is likely that as the use of TOC analyzers becomes more common and the significance of the results becomes more familiar, acceptance of TOC as a parameter in its own right will follow.

The second purpose for effluent monitoring is to prevent loss of product or raw materials. The financial value of early detection, not only in terms of product loss but also in terms of infringement of antipollution regulations, are obvious. The rapid feedback of results enables TOC to be particularly applicable to process control and monitoring. TOC is already t1sed by Environment Protection bodies, by water authorities to monitor supplies and by sewerage authorities to monitor process efficiency and effluent quality. Just as sewage treatment plants are now designed and operated and charges calculated on a BOD or COD basis, this could equally well be done via TOC.

~0 Straight line of best fit by linear regression analysb,

0 0

0

No. of points 16 Correlation coeff. 0,989

aoo

;:, 200

] 0 0

100

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Industrial users in Australia already include petroleum refineries, petrochemicals, mineral processing and pulp and

T

Figure 2.

100 O

c

(mg/l)

COD vs TOG , Pri.rnary Clarified SC!wage

paper manufacturers. Overseas users also include the food, rubber, soap and plastics industries.

100

TOC is also a valuable research tool. It has been used in these laboratories to monitor coagulation experiments for the treatment of cattle, chicken and pig effluents' and a!so to measure carbon absorption isotherms. Research applications elsewhere include the measurement of carbon material balance in a biological sewage treatment plant 7 and the determination of the biodegradability of organic compounds.8

80

a

•

COD

o

•

800

6.

• TOC

Specifically, the authors have used TOC to monitor process efficiency of a pilot plant for the physico-chemical treatment of domestic sewage. 9 Since one of the primary aims of sewage treatment is the removal of organic compounds, TOC is particularly relevant for such monitoring. Typical removal efficiencies measured by TOC, BOD and COD are shown in Figure 1.

20

Pr1mar)' Clarified Influent

rigure 1.

20

After

"'""

Clarifier

After Iron Clarifier

After Sand filter and chlorination

After Carbon Adsorption

Removal Efficiencies of Physico-Chemical Sewage Tl'eatment Process

The authors have also used TOC for rapid detection of plant upsets such as loss of a floe blanket or breakthrough of a carbon column. Whilst ample time for correction is usually available in the case of the slow steady-state processes used in conventional biological treatment plants, this is not always so in PCT plants. The rapid feedback of TOC data also permits monitoring of the effects of the rapid changes in sewage composition which always occur. 9 '0 CORRELATION OF TOC WITH BOD AND COD Until TOC is accepted by Environmental authorities as a basic parameter in its own right, TOC results will frequently have to be interpreted in terms of BOD or COD. Correlations are often possible, but they are entirely empirical, and due regard must be paid to the following limitations:

1. Types of Organic Compounds Present Oxygen demand and organic carbon are fundamentally different parameters. Neither BOD, COD nor TOC is a measure of the total concentration of organic compounds; the value found for each will be influenced tly the types of compounds present. Each organic compound possesses a characteristic carbon content and theoretical oxygen requirement per unit weight and a characteristic degree of biodegradability or susceptibility to chemical oxidation. Thus the less variable the overall composition of a waste, the better the possibility of establishing a correlation between TOC and BOD or COD. This applies particularly in cases where heteroelements such as hydrogen, nitrogen or sulphur contribute to the BOD or COD as these, of course, are not included in a TOC measurement.

2. Precision of each type of analysis.

No empirical correlation can be better than the analyses upon which it is based. Because of the relative number of variables involved, the precision of TOC is better than that of COD which, in turn, is better than BOD. TOC, therefore, usually correlates better with COD than BOD. This has been confirmed by our own studies and many other experiences, including those of Schaffer et al. 7 , reported in the literature.

Notwithstanding such limitations, in practice reasonable correlations can be obtained for specific cases. An example of a typical COD:TOC correlation study is shbwn in Figure 2, in which the dichromate-COD value is plotted against TOC for a primary clarified domestic sewage. Similar straight line correlations were obtained at other sampling points of the CSIRO-PCT pilot plant, but the line of best fit is different for each point. This occurs because different types of organic compounds remain after each unit operation.

In conjunction with the Melbourne Metropolitan Board of Works, correlation studies have also been carried out between BOD and TOC on sewage samples from a number of treatment plants throughout the Melbourne area. In these tests, the degrees of fit were not as good as those obtained for the COD study reported above. The results also showed: 1. The ratio BOD/fOC for the raw sewage is different at each plant, even though they all treat essentially domestic sewage.

2. As treatment proceeds, the BOD/fOC ratio decreases.

3. The correlations are not as good towards the end of the process.

Different BOD/TOC ratios for the raw $ewage at each plant are not unexpected since the types of compounds in sewage depend on its sources and its age. The values of the BOD/TOC ratios for the raw sewage were in the range 1.32.1, which is similar to ranges previously reported. 7 ' 11 As the biological treatment processes proceed, the relative amount and variability of the residual non-biodegradable organics increases. Hence the BOD/TOC ratio decreases and becomes more variable i.e. correlations are poorer. Further difficulty arises in establishing correlations near the end of the processes because the range of values encountered becomes more limited and the points become centred in one region of the graph. The BOD's in the final effluents also tend ¡ to be more erratic than the TOC, probably as a result of the uncertainties in measuring BOD at low levels.

SUMMARY TOC is a rapid, specific and precise method which complements the BOD and COD tests for the determination of organic pollution loading. Although there is no fundamental relationship between TOC and BOD or COD, empirical correlations may be established in most cases. Separate correlation studies are necessary for each sampling point and

due regard to the limitations involved should be exercised when using TOC analyses to estimate BOD or COD values.

However, the potential of TOC is not being fully realised when the results are used in this way. TOC may be used without reference to other techniques for process control and for effluent quality monitoring. TOC analyzers are also valuable research tools.

ACKNOWLEDGEMENTS The co-operation of personnel at the M.M.B.W. South Melbourne Laboratory in supplying routine samples and BOD data and the technical assistance of N. J. Anderson and C. T. Chin is acknowledged. Valuable discussions have been held with L. 0. Kolarik.

REFERENCES

1. C. E. Van Hall and V. A. Stenger, Anal. Chem., 39 503507 (1967).

2. R. A. Dobbs, R. H. Wise and R. B. Dean, ibid., 39 12551258 (1967).

3. F. R. Cropper and D. M. Heineky, Analyst (London), 94 484-489 (1969), and earlier papers in the same series.

4. U.S. Federal Register, 38 (199) 28758-28760 (1973).

5. R. L. Booth, U.S. E.P.A., Report 513-684-2900, cited in Newsletter No. 15, Oct. ¡1972, Analytical Quality Control Laboratory, National Environmental Research Centre, Cincinnati, Ohio 45268.

6. M. Hussein, E.P.A. of Victoria. Privat~ communication.

7. R. B. Schaffer, C. E. Van Hall, G. N. McDermott, D. Barth, V. A. Stenger, S. J. Sebaster and S. H. Griggs, J. Wat. Pollut. Contr. Fed., 371545-1966 (1965).

8. J. C. Buzzell Jr., C. H. Thompson and D. W. Ryckman, Reported in Chem. and Eng. News, 47 (51, Dec. 8) 42-43 (1969).

9. L. 0. Kolarik, J. P. K. Peeler, N. H. Pilkington and E. A. Swinton, Australian Water and Wastewater Association, 6th Federal Convention, Melbourne, 1974. pp. 345-359.

10. Metcalf and Eddy, Wastewater Engineering: Collection, Treatment and Disposal, McGraw-Hill, 1972. p. 233.

11. R. H. Blackmore and D. Voshel, Water and Sewage Works, 114 398-401 (1967).

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