Page 1


Volume 29 No 5 August 2002 Journal of th e Australi an Wat er Assoc iati on

Editorial Board F R Bishop, Chairman B N Anderson, R Considine, W J Dulfer, G Finke, G Finlayson , G A Holder, B Labza, M Munri sov, P Nadebaum, J D Parker, J R..issman, F Roddi c k, G R.yan, S Gray ~ Water is a refe reed journal. Th is sym bol indi cates th at a pape r has been refereed.

CONTENTS

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[I] CLEANING UP A WATER SUPPLY SYSTEM

Iron/manganese problems solved by permanganate/lime P Mosse, K Bugden

41

AUSTRALIAN WATER ASSOCIATION

Australian Water Association (A WA} assumes no responsibility for opinions or statements of facts expressed by contributors or advertisers. Editorials do not necessarily represen t official AW A policy. Advertisements are in cluded as an

MECHANICAL DESTRATIFICATION FOR RESERVOIR MANAGEMENT Aslow speed impeller and draft tube proves cheaper than air bubbles P Morgan, S L Elliott

AWA

Bar ry N o rman

:; ON-LINE MONITORING OF RESERVOIRS FOR RISK M~NAGEMENT Application of HACCP to water storages

FOREST RESEARCH Runoff from logging tracks: Water yield from plantations in China G Sheridan, J Morris

WASTEWATER 43

~

SEWAGE DISCHARGES IN THE GREAT BARRIER REEF REGION Areview of the facilities of the island resorts J Waterhouse, J Johnson

ENVIRONMENT SO 111 THERMOTOLERANT COLIFORM BLOOMS: WHAT IS THEIR SIGNIFICANCE? Abloom is not necessarily sewage-related D Page, R Leeming, I Lawrence, C Magyar, 0 B Horsburgh, T P Sritharan

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OUR COVER: Lake Burley Griffin in Canberra was closed for recreational contact in early 2001 du e to a colifonn bloon,. Th e necessity for the closure is questioned in the paper by Page et al on. page 50. Photo by Seve11tyeight.com.a11, courtesy ofA cte1vAGL. WATER AUGUST 2002

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,WATER

llJ

ON-LINE MONITORING OF RESERVOIRS FOR RISK MANAGEMENT J D Brookes, D M Lewis, L G Linden, M D Burch Abstract Th e Australian wa ter indu stry is mo vin g to adopt a risk-based approach to th e management of w ater q uality. This . approach requires a detailed assessm ent of the entire system from catchm ent to reservoirs, treatment and distribution to identify " Critical Control Points" , which by definition, require both continu o us monitoring and are also process steps that are amenable to intervention or correcti ve action to prevent a downstream problem. Reservoirs have a role in the system as both a so urce and a barrier to hazards, and knowledge of how these hazards behave is criti cal if they are to be effectively managed. This paper describes a case study

of ho w the understanding of wa ter quality processes and the time-scales ove r which they occur in a reservoir, can be combined wi th on-line monitoring for hazard precli ction and early detection. The hazards considered are cyanobacterial g ro w th , pat h o ge n c ontamination associated with intruding inflows, and iron and man gan es e rege n e ra tion from sediments during stratifica tion.

Introduction There is a trend within the Australian w ater industry to adopt a risk-based approac h to the managem ent of water quality. A model example of this approach is the draft NHMRC " Framework fo r

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Management of Drinking Water Quality" released in May 2001 (M cRae et al. , 2001). T h e implicit intention of the framework is to shift the fo cus for water quality managem ent away from "e nd prod uct testing" or compliance monitoring to overall quality assurance management of the system. The framework approac h extends from the catchment to th e c u sto m e r tap an d r equir es sys te m know ledge and understanding. T here is a similar philosophy within the H ACC P (" Hazard Analysis and Critical Control Points") ma nagem ent system developed fo r the food industry . Aspects ofHACCP are also being considered for incorporation into w ater quality managem ent systems (D eere and D avison, 1998; Gray and Morain, 2000). These framewo rks incorporate th e principles of both multiple barriers for hazard interception and management, and " Critical Control Points" (C CP's) to enhance security in the supply sys tem . Within the context of the cliscussion of the barrier approach , there has been debate abo ut the role of reservoirs. In some cases the reservoir provides a detention- time barrier for the progress of contaminants such as pathogens, turbidity or pesticides from the catchment to the off-take or treatment plant. However, it is possible for contaminants to be ca rri ed by intruding flo ws rapidly and directly from inlet to outlet thro ugh the reservoir, ie shortcircuiting. This transfer can be significantly fa ster than expected, based on a nominal retention tim e fo r turnover of the w holevolume. Also , in the case of other w ater quality problems , such as those ca used by cyano bacterial growth and iron and manganese, the reservoir may be a source of haza rds rather than a barrier. Wi thin th e HA C CP sys tem th e " Critical Control Points", by definition, require both continuo us monitoring and are also process steps that are amenable to interve ntion o r corrective ac tion to prevent a downstream problem. T he aim is to control hazards as close as possible to their source (D eere and D avison, 1998). In the case of a reservoir as a compon ent of the water supply system , a potential


WATER

Sediment Concentration

·--F_--

J

Nutrient Concentration

Inflow Volume

_L ___

1.J_~'

~

Inflow Temperature

f

d

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7

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0

Hypohmnet1c [ -··

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' Nutnents

Hypolimnet1c Oxygen Depletion

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-

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L

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Metals

- --- ;,

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Depth Distnbut1on i....., of Pathogens

CCP is the off-take, w here intervention could consist of se lec tion of di ffe re nt depths to take water, or choosing not to take water if the q uality is suffi ciently compromised. The usefulness of a CCP at the reservoir outlet dep ends upo n cl1e speed with which the haza rd can be detected and assessed for pro-active intervention . This paper describes a case study of how the understanding of water quality processes and the time-scales over which they o ccu r in a reservoir, can be combined with on-line monitoring for hazard prediction and early d e t ec tion. Th e ha za rd s considered are cya nobacterial gro w th, patho ge n contamination of intruding flow s , a nd non a nd manga nese generated from sediments durin g stratifi cation.

Reservoir Processes, Hydrodyn, mics and Time-Scales of Hazard Development

An essential component of a risk-based manage ment • --. framework for water quality Cyanobactenal Metal Concentration at 1Pathogen Concentration Concentration at Offtake Offtake at Offtake is the requirement for a high level of knowledge and 'I' u nd e r s tanding of th e ~ Cyanobacterial Risk Metal Risk particular system in question. _ _P_a_t_h_o_g_e_ n_R_i_s_ k_ ~ t To develop this requires the assessment of historical inforFigure 1. Conceptu al model of factors contributing to cya nobacterial, met al or pathogen hazards. mation to identify haza rds, and to understand how they co uld evolve into risks in that system . In reservoirs, it is important to understand both the processes that control the Diumal Surface Layer hazards, and the time- scales over which they occur. A conceptual model which describ es the developmen t of three types of hazards ~ Diurna!Thf - - I -_ocline cyanobacteria, pathogens, and soluble metals (Fe & Mn) in a reservoir is given in Figure 1. An important issue in designing a monitoring program for each of these haza rds is that they :tvietalimnion evolve at different time-scales . Cyanobacterial Seasonal Thermocline growth occ urs within the surface layers and consequently is strongly influ enced by changes in the depth of the surface mixed layer and Hypolimnion meteorolo gical conditions, which ra n change on a scale of minutes to days. Solu ble metal c~ ~ ~ ~ : : l . ~ ~ ; r , ~ ~ ~ ~ ~ ~ ~+ """'°~'~l:..---:i release from sediments is dependent upon the sediment oxygen demand and the reducing state of the hypolimnion. Consequently the ha za rd Figure 2. Tem perat ure profile showing relevant terminology (adapted from develops over a scale of weeks to months. Mon ism ith et al., 1990) .-

-

-

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WATER AUGUST 2002

21


WATER

Table 1. Sensors deployed on meteoro logical stations at Myponga Reservoir. Sensor

Depth

Water temperature

Betatherm thermistor

15 depths through water column

Wind speed and direction

Climatron ics WM-111

2 m above water

Air temp and relative humidity

Vaisa la 0yj Model HMP-45A

Mounted on raft

Solar radiation

Shortwave (300-3000 nm) Middleton EP09 vl.3 Upwelling and downwel ling longwave (0 .3-60 Âľm ) Middleton CNl-R vl.2.3

Mounted on raft

Redox potential

Greenspan

30m

Locat ion

Parameter

Myponga Reservoir

Myponga River

Temperature

Betatherm thermistor

Flow

Gas bubbler at V-notch weir

so me of the haza rds ca n develop at timecatchment, as well as kno wledge of the Pathogen challenges are usually "events" w hich are associated with creek inflow scales that are shorter than the sa mpling nutrient status and stratification behaviour interval. The keys to developing an of the reservoir. The on-lin e monitoring and flood events and consequently the enhanced monitoring system for real-tim e considered here consists of automatic flow time-scale of haza rd development is haza rd detection are firstly an underga uging on in fl ow strea ms, hi gh from hours to days . standing of the reservoir hydrodynamics, reso lution thermi stor ch ains in th e T he dynamic nature of the water reservoir, and redox probes susp ended at and secondly, integrating the required onquali ty processes co nsidered h ere is line physical and chemical data and depth , adj ace nt to the bottom sediments. overlain and dri ve n by the hydrodyna mic ro utine data with an understanding of the T he monitoring is combined with detailed pro cesses operating in the reservoir. ecological, chemical and physical processes knowledge of reservoir processes for each That is, the dynamic heating and cooling (ie algal grow th , metal ch e mi stry , haza rd (Figure 3) to carry o ut th e of the wa ter column, which is influ enced situ ation and risk assessment. In its most pathogen mo ve m ent). A process flow by solar radiation, wind spe ed and chart of these steps is give n in Figure 3 . adva nced form this monitoring co uld be direction, and inflow events. The best Examples linked to 'state of the art' hydrodyna mic of backgro und historical system known hydrodynamic process in reserknowledge wo uld include an underand ecological model to provide extra voirs w hich affects many chemical and decision support by predictive modelling s t a n din g of seaso n al h y dr o lo gy, biological processes is th ermal stratifiknowledge of sources of pathogens in the of stratification, algal growth and metal cation, w here reservoirs are divid ed into reso lubili sa tion. T hi s discrete laye rs separated approac h is not considered by sh arp gradi e nts in here. However an example of d ens it y (tem p e ratur e System Knowledge such a sophisticated model is a nd / or co ndu c ti v it y) His torical knowledge of DYRESM-CAEDYM & reservoir catchmen t (Figure 2). To describe behaviour developed by the Centre for these laye rs the termiW ater R esearch in W estern nology of Monismith et al. Au s tr a li a ( http: // (1990) is adopted in this On-Line Monitoring www. uwa.cwr. edu. au/ ). Routine Monitoring paper but see Imberger and Temperature profiles, Algae, pathogens, metals, - weekly inflows, redox/OO P atterson (1990) for a On-line Monitoring r ev i ew of ph ys ical On-lin e monitoring 111 limnology. The essential reservoi rs is not wi d e ly point to recognise from an prac ti se d, in contras t to Hazard Identification analysis of hydrodynamic monitoring and automation of processes in reservoirs is wate r tr ea tm e nt p l ant that the scale of change for processes. T his is not du e to density laye r formation , Situation Assessment Hydrodynamic/ the lack of either instrumenBased on process knowledge internal wave gen eration Ecological Models & understanding of tation or technology, as the - Dynamic feedback to and ve rtical and lateral hydrodynamics, chemis try, support decisions ecology sensors and telemetry required tr a nsport i s rapid are identical to other industrial (Imb e rge r, 1999) a nd pro cess monitorin g, but va riabl e, a nd th ese Risk Assessment & because the real- time inforpro cesses dri ve th e Management m ation from co ntinuou s c h e mi cal pro cesses on Intervention monitoring of reservoir stratsimilar short-term scales. ificatio n or stream flow has Reservoir Outlet: A conventional routine - Selection of offtake depth not been regarded as useful in monitorin g pro g r am Critical Control Point - Isolate offtake Treatment Plant: operational decision making. usually provides weekly - Process enhancement The issue is one of knowledge or monthly data on the to interpret and apply the physical, ch e mi cal and biological status of the Figure 3. Conceptual framework for monitoring for hazard and risk information for intelligent assessment in reservoirs. reservoir. But as indicated management.

t

22

WATER AUGUST 2002


WATER

allow decisions regarding sampling to be targeted to a ceitain pait of the hydrograph, once the particular system is understood .

Australia

How Hazards Behave in Reservoirs - our understanding of the processes for cyanobacteria, iron and manganese, and pathogens

(!)

0

15

30 45

60

75 km

So uthe rn Ocean

Figure 4. Myponga reservoir location.

Reservoirs The instrumentatio n req uired for onlin e mo nitoring in reservoirs ca n va ry in so phi stica tion de pen d ing upon th e requirements for information and budget co nstraints. The simplest monitorin g system consists of a string of thermistors suspend ed at va riou s depths in the reservoir combined with a meteorological station including sensors for wind speed and direction, air tern.perature and relative humidity. T he num ber, resolution and depth distribution of the thermistors, w hich influences th e cost, depends upon the intended long-term use of the data; high resolution data is required for physical modelling work. Short- and long-wave solar radiation sho uld also be recorded to ma xim ise the val ue of the data for analysis and modelling in the fuwr e. Dissolved oxygen (DO) sensors deployed near the surface and in the hypoli mnion indicate the oxic/ anoxic status at depth and adjacent to the sediments, which determines whether release of io ns (Fe, M n , P , N) from sediments is likely . N ew rob ust DO sensors are now available, w hich ca n be deployed for long p eriods w itho ut

main tenance . Alternatively, a redox prob e can b e dep l oyed in t h e hypolimnion to indica te the redu cing potential of the hypolinmetic water. All of these instruments can be deployed from either an anchored bu oy or raft, and can be solar- powered with communica tion by radio o r mobile ph one, depending on location and site cove rage. The se nso rs deployed at M ypon ga R eservoir in this study are listed in T able 1.

Creek or River Inflow Although in flow to many Australian reservoirs is measured, much of this data is unavailable by telemetry and the magnitude offlood events and the potential risk associated w ith these is often not known until som etime after the event. It is important to record water temperature in conj unction w ith flo w, as this indicates the density of a the water mass in a significant inflow event. This can be used to estimate the depth at which the flow will intrude into the reservoir, and determine w hether it will mix or become a shortcircuiting intrusion front. Inflow volume and temperature data available on-line can

\ll)ponga Rhcr

Study Site The study site for these examples is M yponga R eservo ir, located on the Fl eurieu P eninsula , So uth Australia (S 35°21' 14" E 138° 25' 49", Figure 4). The reservoir is part of the water supply sys te m for so uth ern m e tropol itan Adelaide, and the growing coastal towns from Victor Harbour to Goolwa. The reservoir has a water . filtration plant employing DAF, which has a capacity of 50 ML d- 1• T he reservoir has a capa city of 26,800 ML, a m aximum depth of 36 111 and is fed by M yponga R iver, which drai ns 78 km2 of the 124 km 2 catchment and receives a mean ann ual rainfall of750 mm. During the su mm er mont h s M yponga reservoir is artific ially destratified by an ae rato r delivering air at a rate of 120 L s- 1 and two surface mo unted m echanical mixers (B urch et al., 2000) . The reservo ir has two m eteorological stations with th ennistor chains one of w hich is located in the main basin (M et 1) and the other in a long na rrow side-arm (Met 2) of the reservoir (Figure 5) . Creek flow and temperature are also measured in M yponga River.

Cyanobacteria

Dam \\all Outler

®

Knowledge of how haza rds behave in reservoirs is critical if they are to be effectively managed. T hree case stu dies demonstrate how on- line monitoring, and knowledge of processes and timescales ca n be used to assess the risks to wa ter quality posed by cyanobac terial growth, iron and manganese and contaminants associated with a winter in-flow event .

l

~-

The risk to water quality from

LCGEl'. D 1·9

-

Sam pling locat ions

Aerator

Meteoro logical stati on ®

Surfocc mixer

500

111

Figure 5. Sampling location s and met eoro logical station including thermi stor chain s at Myponga Reservoir.

cyanobacteria arises firs tly from tas te and odo ur compounds, which are problematic at low cell concentrations (Bowmer et al., 1992) and secondly from toxins w hich become problematic at high e r biomass (Chorus & Bartram, 1999). T here are three pre-requisites for cyanobacterial growth: adequ ate light, adequate nutri ent supply, and an in ocu lum from w hi ch t h e WATER AUGUST 2 00 2

23


WATER

25

-T100 mm -

24

u. "~ "'

e'.

23

T3_0m

-

TS_Om

-

T10_0m

-

T20_0m

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T30 _0m

22

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21

C.

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20 19 18 31/12/99

07/01 /00

21/01 /00

14/01/00

28/01 /00

04/02/00

Date

Figure 6. Temperature profil e at Myponga Reservoir.

-5.0

y

~\

22 /01 /00

15 /0 1/0 0

8/01 /00

1/01 /00 0.0

VII u \J'An.f\J V'V ~~

29 /01 /00

5/02 /00

~ ~

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· 10.0

.§. .c

0. .,

-15 .0

0

-20.0 -2 5.0 -3 0 .0

Figure 7. Diurna l surface layer, defined as the sha ll owest depth at which the temperature difference between two adjacent therm istors is 0.05°C or greater.

limited . Species such as J\llicrocystis aeruginosa and Anabaena circinalis have maximal growth rates w hen they experience a daily light dose of photosynthetically active radiation (PAR: 400-70011111) of approximately 7 mol photons m-2 d- 1 (R eynolds, 1997) . T his occurs w hen the diurnal thermocline is approximately the same depth as the eupho ric depth (ass uming short wave radiation is 1000 Wm-2) . W hen a suitable physical environment is established, w hich is a crucial prerequi site, a nutri ent supply and an inoculum are required for a cyanobacterial pop ulation to develop. T hese factors sh ould be determined in the ro utine monitoring program, whereas the dynamic physical environ m ent of stratification

population can propaga te. There is a good degree of co nceptual understanding of how these operate and interact in a quantitative way to determine the relative risk of significa nt growth or bloom formation . A key charac teristic of planktonic cyanobacteria is their buoyancy, w hich enables them to float during periods oflow turbulence when other species tend to sink below the diurnal thermocline (Figure 2) . The depth of the diurnal thermocline changes in response to w ind mixing, air · temperature and consequ ently on warm, calm nights a shallow diurnal thermocline persists. As the diurnal chermocline deepens th e phytoplankton are mixed deeper and sp end more time out of the euphoric zone and may b ecom e li ght

Table 2. Anabaena circinalis concentrations (ce ll s mL·1 ) at five locations at Myponga Reservo ir. (-) sign ifies that A. circina/is was not detected in a 1ml, 10x concentrated sample. Location

1 4 5 6 7

24

21/12/99

29/12/99

4/01/00

10/1/00

18/1/00

25/1/00

4

9

43

3891 2186 146 1470 448

45 2 12 30 8

2

29 163 459 WATER AUGUST 2002

and mixing can best be assessed by on-line temperature profiling. Although cyanobacteria are often perceived as a symptom of eutrophication, the paradox is that they do not require high concentratio ns of nutrients to reach relatively high biomass . Concentrations of phosphorus less than 0.0 1 m g L- 1 filterable reactive phosphorus (FRP) are considered to be growth limiting (Sas, 1989) and 0. 1 mg L-1 soluble inorganic nitrogen is considered the minimum co ncentration to m ai ntain growth during th e growing seaso n (Reynolds, 1992) . Higher co ncentrations wo uld support rapid growth with higher fin al biomass.

Cyanobacterial population development - January 2000 M yponga Reservoir is generally a wellmi xe d storage and cya nob ac t e rial co n ce ntrations ar e generally low. However, during summer the physical co nditions can b eco me suitable for Anabaena circinalis to grow rapidly . This filam entous species is a significant odour and som etimes toxin produ cer. In early January 2000 the reservoir was well mixed. Howeve r over a two week period, between January 7 andJanua1y 21, there was significant heating of the smface water (Figure 6) T his was detected and recorded quite clearly by the thermistor chain deployed at M etl. T his resulted in the fo rmation of p ersistent stratifica tion and the diurnal surface mixed layer, calculated afte r Sherman et al. (2000), remained shallow (Figure 7) . Cyanoba cteria were not entrained deep into the w ater column each night and could immediately begin grow quite rapidly each day. Coupled with these physical conditions, the other pre-requisites for growth , light and nutrients, were known to be ideal. The euphoric depth in J anua1y was 3.6111 (kd= 1.22) and nutrient concentrations we re suffic iently high to support both a rapid growth rate and a hi gh yield (a mmonia - 0.027 mg L- 1, filterable reactive phosphorus - 0.038 mg L- 1, total phosphorus - 0.05 1 m g L- 1, total Kjelda hl nitrogen - 0.98 mg L-1, nitrate and nitrite - 0.131 mg L-1) . Presumably Anabaena circinalis was present und er w ell -mix ed condi tions in early December and was detected at low numbers late in D ecember (Table 2) . As the water column became stratified the growth of A . circinalis accelerated and by 10 Janua1y 4000, reached the highest concentration of 3891 cells mL-1 . T he m ean growth rate between 4 Janua1y and 10 Janua1y was 0.36 day- 1 and cell concentrations we re high enough to present a geosmin threat to the treatment plant.


WATER

to operate artificial destratification 0 .8 systems to minimise release of solu ble 0.6 0 .6 m etals. 0.4 0 .4 The ability to use m easurem ents ~0 0.2 ~ 0 .2 of redox potential in the reservoir for 0 Mn ·' ?:. 0 ?:. 0 predi ction of soluble m etal release 0. 0. 2 cc F e* cc ·0 .2 depends upon understanding the 0 ·0 .2 0 chemistl)' of the pro cess in the ....::,: .::,:.... FeCO , -0.4 -0 .4 MnCO , sediments. Ferrous ions are released e.cc e.cc Fe (OH), · 0 .6 -0 .6 ::. :a readily from sediments w hen the Fe · 0 .8 ·0 .8 redox potential declines to about 200 10 2 8 12 14 6 14 10 12 2 4 6 8 m V (Figure Sa) , while resolubilisation pH pH ofMn 2 + fro m the sediment occurs at redox potentials in th e order of 400 Figure Sb. Distribution of manganese Figure Sa. Distribution of iron species with rn V at neutral pH (Figure 86). In species with respect to pH and redox res pect to pH and redox potentia l. more alkalin e environments, such as potential. (Modified from Wetzel. , 2001 (Modified from Wetzel. , 2001 and Stumm lake sediments, iron and manganese and Stumm and Morgan, 1996). arid Morgan, 1996). require a lower redox potential to remain soluble. Release of manganese stratification can be readily observed with In this case the A.circinalis population o n- line m o nitoring of temperature, iron was controlled with a chemical algicide on therefor e precedes iron , and manganese 11 Janu ary 2000 . It can be seen that the will remain soluble if the m,-ygen saturation and manganese can then be managed by 1 on-line temperature information could be is less than abo ut 50% (-4 mg L- ; W etzel, varying the off-take depth or adjusting 200 1). used to predict and follow the onset of the water treatment accordingly . Withdrawal Iron has a taste threshold of 0.3 mg L-1 from the epilimnion or m etalimnion may " hi gh - risk" conditions for growth of A. circinalis in this rese rvoir. The under- in wate r and becomes obj ectionable avoid the elevated hypolimnetic concen1 trations, however rapid mixing or 'overturn' standing of the processes allows us to above 3 mg L- (NHMRC/ ARMCANZ, of the storage will distribute the ions identify periods when cyanobacteria may 1996) . Soluble manga nese concentrati ons 1 througho ut the wa ter-column and m ay prese nt a threa t and the appropriate greater than 0.1 mg L- are considered problematic althou gh concentrations as deliver poor qu ality wa ter to the plant. m ana gem ent strategy can be implelow as 0.05 mg L-1 can cause 'dirty water' U sing on-line monitoring, coupled w ith m ented . problem s and require oxidation in the routine analysis, the overturn event can be Iron and Manganese treatment plant. Many op erators aim to readily observed and the risk associated with Excessive iron and manganese 111 keep soluble Mn as low as 0.01-0.02 mg manganese and iron can be minimised by 1 source water can lead to discoloured water L- to avoid subsequ ent problem s in the the timely introdu ction of appropriate distribution system. trea tment in the plant. at customer taps if these ions are not The seasonal increase in iron and oxidised and fl occulated in the treatment Iron and Manganese - Summer, pro cess . Moderate co ncentrations of m a n ga n ese c on ce ntr ation s in th e 2000 soluble iron and manganese entering the hypolimnion occurs during stratified periods distribution system can also be problematic w hen the hypolimnion (Figure 2) is effecAt M yponga R eservoir the release of as they may be accumulated by bio-films tively separated from the atmosphere. iron and manganese from the sediment is which dislodge during periods of high flo w Brookes et al. (2000) identified a cmTelation controlled by artificial destratification, between the duration of persistent stratifiand co mpromise wa ter quality . however, iron and manganese concentrations tend to increase progressively at depth The period in w hich high iron and cation (temperature difference between manganese concentrations in source wa ter 1Om and 30111 > 1°C) and the maximum during autumn, even though thermal stratcan become problematic is generally iron and m anga n ese con ce ntrations ification is weak. In the summer of 2000 , th e monitoring data from the raw wa ter wee ks to months. This is because the m easured through summer. P ersistent intake to the treatment plant development of ano xic sh ows there was an up ward con dition s ab ove th e 0 .1200 tre nd in the manga n ese sediments depends upon conce ntration from earl y th e se dim e nt o xyge n 2 0.1000 January 2000 to April 2000 demand, and the degree of "' (Fi gure 9). Th e on-lin e oxygenation and circu~ 0.0800 m eas ur e m e nt of r e do x lation in the overlying "' 0.0600 C: adJacent to the sediment in water. C onditions leading 200 0.0400 the reservoir for the same to metal resolubilisation "' C: 150 ~ period give n in the sam e :::E can be detected early with 0.0200 +-- - - -- - - - , , . - - - - - - - - - - - 1 100 ~ 50 figure show a corresponding on-line monitoring of 0.0000 +-~- ~-~~-~~-~-~~-~--+ 0 steady decrease . There is redox potential. This then 0 0 0 0 0 0 0 0 0 0 "'~ 0c:: 0c:: 0c:: 9 0 .00 9 9 9 9 inadequate data tp develop a allows an early approu .0 .0 C. C. C1l ,"' ,"' ,"' u. u.C1l u.C1l ::;;;;; ::;;;;; 0 < < strong correlation between priate response such as J, J, J, ..;. ..;. ..;. J, J, ..;. ..;. <O ~ these two m easurem ents, 0 C\J 0 C\J 0 0 C\J tr ea tm e nt b y pr eDate altho ugh the trend is obvious oxidation at the plant. and the process link is well Alternatively, monitoring Figure 9. Manganese concentrations at the raw water inlet tap and und erstood. It is usually of dissolved oxygen onredox potential measured in the main basin adjacent to the impractical to collect samples line can allow for decisions sediment at Myponga reservoir. 0.8

(1)

. . (1)

)(

FMn7

(1)

~

~

WATER AUGUST 2002

25


WATER

17

G ~

300

16 250 ::;-

;

15

"'

14

~

13

150 > -;;;

12

0

~

~ 200

~

Creek Temp (degC)

-

Met 1 Temp 0.1m

0

-

Met 1 Temp 25m

-

Met 2 Temp 0.1m

-

Met 2 Temp 15m

-

Creek Da i~ Tot (ML)

~

~

~

~

-

E

100 ;

a. E 11 ~

~

...

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10

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Figure 10. Temperature at the surface and bottom at Met stations 1 and 2 in Myponga Reservoir and daily total creek inflow and temperature recorded in Myponga Creek.

for laboratory analysis for m etals more frequently then weekly. In addition it takes at least several days for the laboratory analyses to be completed. On-line redox m onitoring, by contrast, can give very early wa rning of potential release of metals from the sediments allowing timely intervention by the trea tment plant operators.

Pathogens Incidents within Australia such as the Sydney C ryptosporidium / Giardia episode (M cClellan , 199 8) have prompted many water authoriti es to ta ke renewed interest in catchment issues . These have often focussed on increased monitoring to detect contaminating pathogens (often at very low numbers) , rath er than addressing the cause or the risk of pathogens entering the plant. R o utine m o nitoring requires a signifi ca nt and costly inves tment to determine the presence and concentration of pathogens . T his m o nitoring w ould be more effective if the fa te and transp ort of pathogens in the storage were kno wn and sa mpling could be adjusted accordingly. Altho ugh o ur present knowledge in this ·area is limited, there is sufficient info rmation to apply som e general principles to allow for the use of on-line monitoring. On- line monitoring of flo w can detect short-circuiting and allow early wa rning of th e risk of pathogens travelling rapidly through a reservoir to the treatment plant. T he phenom enon of rapid sho rtcircuiting by flood flows in a large rese rvo ir h as b ee n illu strat e d for Burragorang R eservoir, N SW (Dr. J ose R om ero , pers com.m.). A combination of hydrod y n ami c data and m o d ellin g indicated that a flood wa ter intrusion from a fl ood in 1997 tra velled 50 km throu gh the reservoir within eight days (see: http :www . cw r. uw a. edu .au / - ro m ero / burrago rang/ elcom_caedym / elcad_sims. html).

26

WATER AUGUST 2002

As flood waters such as this intrude into reservoirs there is a chance that pathogens carried by the intrusion w ill reach the offtak e a n d tr ea tm e nt p l a nt b efo r e m o nito ring res ults are ava ilable o n contaminant levels. R eal time monitoring of these inflow and intrusion events w ould grea tly assist in risk assess m ent and managem ent of th e transpo rt of a range of contaminants including pathogens throu gh a reservoir

Inflow Events at Myponga Significant rainfall in September, 1999 in th e catchment of M yponga R eservoir led to a minor flo od flow into the R ese rvo ir. Thi s inflo w eve nt was monito red in the reservoir at th e time using an Acoustic D oppler Velocity Probe (ADV). On September 22, 1999 at 10. 20 am the inflow intrusion w as detected at M et station 2 in the side arm of the reservoir. The inflow intruded at betwee n 11 and 13111 and had a m ean velocity of 0.047 ms-1 . Based on the ga uge h ei g ht o f th e r ese rv oir , a nd th e m orphology of the reservoir at this site, the width of the intrusion w as estimated to be 10111. The w ater temperature at M et sta ti o n 2 (s id e arm) at 10: 20 am , Septemb er 22 1999 was 13 .31°C at 10111 and 13.2°C at 12.5111. In the main basin (met station 1) the temperatures we re similar, 13.32°C and 13.24°C at 10m and 12 .5111 respectively . T hese m easurem ents of wa ter temp erature ac ross the basin indi cated that the inflow w ould continu e to intrude into the main basin at between 11 and 13 m. As the fro nt of the intrusion continu ed to spread laterally throu ghout the basin its velocity wo uld decrease . T o illustrate the potential wo rst case for a short-circuiting flow event, it was possible to estimate the progress of the inflow by the fo llowing calculatio n: ass uming a m aximum fl ow rate (0 .047 m s- 1) and

minimum route distance betwee n infl ow and o utflow (5040111) then the minimum transport time throu gh the sto rage wo uld be approximately 30 hours. An inflow can also be detected using thermistor data if there is a temp erature difference betwee n th e inflow ing creek and the reservoir. A small flood w ith a peak daily total flow of 240 ML was recorded at M ypo nga C reek on M ay 18, 2001 (Figure 10). T he temperature of the intruding creek water during the elevated flow ranged betwee n 9.5-10.6°C. T he intruding fl ow was detected as a departure from isothermal conditio ns and cooling at depth. The intrusio n was detected at m eteorological statio n 2, in the side arm, (Figure 8) at 17:10 on M ay 17 and at meteorological station 1, in the main basin 1.3km away, at 4: 00 on May 18 . This equates to a velocity of 0.041 ms-1. The velocity of the intrusio n calculated fr om the th ermistor data is similar to the separate inflow recorded w ith the ADV . C urrently most m o nitoring programs sample fo r pathogens in the inflowing creek and at the surface of the reservoir. D etection of pathogens in reservoirs could be enhanced if it were coupled to on-line monito ring. C reek 'sampling co uld be m odified to target particular regions of the hydrograph and reservoir sampling could be modified to obtain samples from within the intrusion , w hich potentially present the greatest risk to the treatment plant. The potential difference in time-scales between pathogen detection and risk to treatment plant requires a m odel of creek flo w pathogen risk, including seasonal va riation . The magnitude of creek flow and potential pathogen risk, due to low vegetation cove r in the catchment or calving season, can be used to constru ct a conceptual model for scaling wa ter treatment fo r pathogen contamination rather than relying solely on pathogen detection.

Conclusion On-line monitoring of reservoir wa ter temp erature, creek inflow and hypolimnetic dissolved mryge n or redox potential can readily be integrated into the w ater treatment process to improve the efficiency of treatment for potable wa ter. The conceptual models illustrated in this paper are prelimina1y and represent a framework for developing integratedr reservoir and treatment plant operating strategies . To generate the best risk manage ment strategy incorporating on-line m onitoring the following conceptu al fram ework sho uld be applied. • R eview historical data


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• Identify hazards to water quality and threats to treatment plant • D <; ploy on-line monitoring • Continue routine analysis of nutrients, cya nobacteria and pathogen • D eterni.ine hydrodynamic features which lead to hazard generation • Develop conceptual model for predicting risk and treatment response, given the prevailing and predicted hydrodynamics.

References Bowmer, K. H. , Padova n, A. , Oli ver, R. L. , Korth , W . and Ganf, G . G. (1992) . Physiology of geosmin produ ction by A11abae11a circi11alis isolated from the Murrumbidgee Ri ver, Au stralia. Water Scie11ce an.d Tec/1110/ogy. 25: 259-267. Burch, M. D. , Brookes, J. D., Tarrant, P. and Dellaverde, P. (2000). Mi xi ng it up with blue-green algae. Water. 27(2): 21-22 . Brookes, J. , Burch, M . and Tarrant, P. (2000) . Artificial D escratification: · Evidence for impro ved water quality. Water. 27(4) : 18-22. C horus I and Bartram J, Editors (1999) Toxi c Cyanobacceria in Water. A Guide co their Public H ealth Consequences, Monitorin g and Management. 416p. E&FN Spon, London. D eere, D . and Davison, A. (1998) . Safe drinking water: Are food guidelines the answer? Water Nov. 21-24 Gray and Morain, (2000) . HACCP Appli cation co Brisbane Water. Water Jan. 41-42. lmberger, J. and Patterson, J. C. (1990) . Physical Linmology. Advances in Applied Mechanics. 27: 303-473. Imberger, J. (1999). FhLx paths in a stratified lake: A revi ew. In J. Im berger (Ed). Ph ysical Processes in Lakes a11.d R eservoirs. AGU. Washington, D C. McClellan, P. (1998) Sydney Water Inquity. Final R eport. New So uth Wales Premiers D ept. ISBN: 0 7313 30763 0. (http :/ / www. premiers. nsw.gov.au and follow links co Publications, th ence to Sydney Water Inqui ry). McR ae, B. , Callan, P. , C unliffe, D. , Riza k, S. Bursill, D. and Neller,A. (200 1). D evelopm ent of the framework for manage ment of drinking water quality . Water. June 37-41. Monismich , S. G. , lmberger, J. and Moriso n, M . L. (1990). Convective motions in the sid earm of a small rese rvoir. Li111nology a11.d Ocea11ography. 35: 1676-1702 . HMRC/ ARM CA Z, (1996). Australian Drinking Water Guidelin es. National H ealth and Medical R esearch Council . Agricultural and R eso urce Management Co uncil of Australia and New Zealand. Canberra , Australia. Reyno lds, C. S. (1992). Eutrophi cation and th e management of planktoni c algae: what VolJenvei der couldn 't cell us. In J. G. Jones & D. W. Sutcliffe (Eds.), E11trophication: R esea rch and Application to Water Supply. Ambleside, U.K.: Freshwater Biological Association. R eynolds, C . S. (1997). Vegetation Processes in the Pelagic: A M odel for Ecosystem Theory. 0 . Kinne. (Ed). Excellence in Ecology Seri es. Ecology Institute, Oldendorf/Luhe, Germany. R o m e ro, J. http: www.cw r.uw a.e du . a u / -rom e ro / burragorang/ elcom_caedym/ elcad_sims. htmJ Sherman, B. S., Whittington, ]. and Oliver, R .L. (2000) . The impact of destratifica tion on wa ter quality in C haffey Dam. Archi11 fur Hydrobiologie. Spec. Issues Advance Limnol. 55: 15-29 . Sas, H. (1989). Lake restorati on by redu ction of nutri ent loading: Expectations, Experiences, Extrapolations. Sanke Augustin : Academia Verlag Richarz. Wetzel, R.G. (200 1). Linmology. Third Edition. Academic Press. USA.

The Authors Dr Justin D. Brookes is a Research Scientist, David M. Lewis is a PhD candidate , and Leon G. Linden is a Research Scientist, all involved in the CRC for Water Q uality and Treatment Project "Artificial Mixing for Destratification and Control of Cyanobacterial Growth in Reservoirs " . Michael D. Burch is Project Leader and is also the ARMCANZ National Algal Manager. CRC for Water Quality and Treatment, PMB 3 , Salisbury, SA , 5108. Tel: (08) 8259 0222, email: j ustin.brookes@sawater.sa. gov .au


m

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MECHANICAL DESTRATIFICATION FOR RESERVOIR MANAGEMENT: AN AUSTRALIAN INNOVATION P Morgan, S L Elliott Abstract

O ver the pas t 40 yea rs attempts to artificially destrati fy T h e low-ve loc ity, hi g h 100 darns and reservoirs have been efficiency mechanical destratifimade with limited success . cation system, with flexible draft 80 Adaptatio ns of mec hani cal tub e, d evelop ed by Wa ter impellers were made w here E n gin ee ring A nd R esea rch 60 little was known of flow ra te Solutions Pty Limited (WEARS) has demonstrated in a number of requi re ments, j et velocities, ::i2 40 applications the benefits of the optimum location and direction SMDl-5 system , both for oxygenation of and operating protocols. 20 benthic layers to reduce dissoBubble Plume Bubble plume systems, with lution of iron and manganese, either an air curtain or point 0 and fo r the control of algal 100 200 400 ae ration have been used in 0 500 300 bloo ms by pumping the surface Australia and overseas. These Capacity ML X1000 laye rs dow n into light-limiting compressed air destratifica tion zones. systems consume high energy Figure1. Power requirements of SMDl-5, and compressor (about 100kW in a typical driven Bubb le Plume destratification methods, versus Introduction mediu m size dam) H owever, storage capacity. Bubble Plume data compiled from actua l A rtifi cial d es tratifi ca ti on M cAuliffe and R osich (1990) install ations . [Chichester Dam NSW, Bundanoon NSW, involves mixing the water body rep orted th at bubble plu me Suma Park NSW and others, (Data from Blackman 2001)]. to dissipate thermal laye rs, with sys tem s h ave h ad limited the aim of ac hieving a unifo rm success in redu cing undesirable • metals such as manganese (Mn) and Iro n temperature and oxygen gradient over the algal species in a little over 50% of cases, depth of the storage. T he benefits are: (Fe) are oxidized out of the wa ter. and have redu ced manganese, iro n or • autumn turno ver is eliminated and sulphides in only 69% of cases. Blackman, • fish habitat in the reservoir is improved therefore anoxic and toxic water is (200 1) reported that only 53% of • cold water with low DO released from prevented from mixing throu gh the compressed air systems were successful to the lower levels of a dam, w hich can upset water column. some extent and only 11 % of da m fi sh migrati on patterns downstrea m • water drawn off is of more uniform managers reported that they were fully (M obley et al, 199 5, Greene et al, 1997), quality and therefore potentially easier to satisfied with the success of the system in ·is minimized . treat. their dam. M any bubble plume installa• ecological balance of a degraded storage tions stand idle since their ability to solve • blue-green algae is controlled and the the problem has not been realised, and is restored. use of ch emicals or PAC eliminated . Power requirements vs storage capacity

= . 1 <I)

Figure 3. SMDl-2 .5 installation at the CS Energy Swanbank power station reservoir.

30

WATER AUGUST 2002


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in ve1y large storages greater than 100,000ML. Th e system incorporates variable speed drives w ith sma rt programmable electronics WEARS Typical Air Diffuser enabling impell er speed to be set and controlled so 4 No of units 1 A New Development flow rates match storage kW Powe r 12 100 An Australian-owned capacities th us eliminating 30 40 Flow m3 / s company; WEARS, has in unn ecessa r y pow e r 2.5 0.4 m 3 / s per kW Efficiency recent yea rs developed consumption. On ce a Pontoon Dam fl oor Location and i nt e rn a tio n a ll y uniform thermal profile has Yes No Draft Tube patented a large Surfa ce been established, static head Mounted Destratification due to the density gradient annual $15 ,704 * Power cost $87,360 ** Impeller system, or SMD I,is redu ced to almost zero (*) Operating continuously. (**) Operating 2/ 3 of the year. _specifically designed for and so the required power reservoir destratification, is redu ced even further. that is currentl y achieving Energy Requirement Figure 1 compares the power inputs of a 100% success rate in terms of: a typical bubble plu me system with those T h e sm all mode l, SMD I-2.5, 1s • increased efficiency compared w ith of an SMD I for various volumes of powe red by a 1.1KW electric motor and traditional aeration systems, storage. The reason for the dramatic is capable of destrat.ifying a storage • improved raw water quality thereby difference in energy requirements is the volume of up to 4,200ML, the larger reducing treatment costs , and exploitation of the principles of hydraulics SMDI-5 with a 4KW motor will destratify • minimizing the reservoir managers risk and fluid dynamics in the liquid phase and a storage of approximately 18,S00ML. of toxic algal blooms. Outstanding results in larger reservoirs of the elimination of the inefficiency of air compress10n. This new technology uses a low over 30,S00ML have been achieved energy (4-SkW) mechanical circulation A prel.im.ina1y design and scoping study wi th the close-coupled SMDI-5 and the system that efficiently and effectively (Elliott 1997) compared operating costs opportunity now exists to solve problem s moves water through the thermocline; i. e. the thermal barrier between smface water and bottom water thereby artificially destratifying the whole of the storage . Unlike traditional aeration systems that attempt to raise anoxic bottom water from the hypolimnion, often loaded with dissolved metals, such as reduced iron (Fe) and manganese (Mn) as well nutrients, to mix w ith the water high in dissolved o>..'Ygen (DO) at the surface, the WEARS system moves DO saturated smface water Dynamic modelling for design to the hypolimne tic bo ttom region w here and analysis of stormwater high biological oxyge n demand (BOD) and high chemical oxygen demand and wastewater projects (COD) occur. By removing the surface layer and directing fl ow to the hypolimhas just ~etic bottom layers the: (i) rate of transfer of oxygen at the surface interface become easier! is increased, (ii) nett DO distribution throug h o ut th e w h o le storage is maximized, and (iii) nutrients (which feed algal blooms) are not brought to the surface and made available for algal growth at the euphotic zo ne. Top-down circulation is desirable in the control of Cyanobacteria or Blue Green Algae . The surface layer, w here algae breed, is sucked in and discharged More information: below the euphotic zo ne. The algae are thereby transported through turbulent sa les@xpsoftwa re. com. au flow , subject to an instantaneous pressure change and light-limited, . Th.is creates an www.xpsoftware.com .au en vironment that is unfavo urable for the ce ll growth and th e li fe cy cle of Cyanoba cteria is disrupted. their operating costs are high . Thus th e only viable alternati ve was seen to be exp ensive treatment of the poor quality raw water at the treatment plant.

Table 1. Cost comparison of the WEARS system with air diffuser for Ch affey Dam (1997 ). Since thi s study t he effi ciency of the SMDI has been greatly increased by an improved im pelle r des ign and furth er ca pital and operati onal cost savings have bee n rea li sed.

M2000vB notice the difference.

Ph: 02 6253 1844 WATER AUGUST 2002

31


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of artifi cial des tratifi ca ti o n m ethods prop osed fo r C haffey D am near T am w orth N SW and is summarized in T able 1. This study was carried out prior to th e n ew hy drod ynami c tap ered- tw isted ca rb o n- fibr e blade profile that was developed in 2001, but still demo ns trated that th e me th o d h ad t h e po tential to use only 12% of the p owe r of co mpr esse d a1r systems.

2000 .) reported a 5% increase in plant efficiency and removal of the risks to staff from toxic Blu e Green Algae contac t.

Blua·Gct@O AIAI@ Counts 120000 110000

-

100000

97/98 S umm e r 98/99 summ er

...... 99/00 summ er 90000

i

Algal Control

80000

Res ults foll owing installations of the recently developed SMDI-2. 5, and the SMDI-5, J soooo show that they have not o nly i •oooo exceeded desired outco mes in 30000 ii> both thermal and ch emical 20000 d es tratifi ca ti o n , but h ave 10000 of--+~- ,._.....,...,._f.-+,_....,.....,_..,..::.,.,.,..:::.-,.___.,__ perfo rmed exceptio nally well Capital Costs 111 th e co ntro l o f ·10000 Cyanobac teria . A repo rt o n Based o n a reservoir of about the installatio n of a SMD I-2 .5 Figure 4 . Blue gree n alga l counts in Timor Dam, for summer 16,000ML the capital expenin the Timor D arn (2,000 ML) between 1997-2000. periods diture wo uld be about $170,000 in ce ntral NSW indi ca tes for a full y installed sys tem successfully Blu e Green Al gal including consultancy, design Iron and Manganese co ntrol. T ighe (2000) . fees and remo te m o nitoring system. For T he most recentl y co mpleted proj ect Blu e green algal counts, w hich had a reservoir of abo ut 5, 000ML the capital (late June 2002), fo r the Hunter W ater been historically high, are now continually expense wo uld be abo ut $75,000 for a Co rp oratio n, was instaJl ed to overcom e basic unit. low (Figure 4) . Since the WEARS high soluble manganese concentration. In system was installed there have been no this instance the o riginal bubble plume Horizontal Distribution of significant blu e green algal bl oo ms, and system was achieving satisfa cto ry raw Dissolved Oxygen Cya no ba cteria has been held at near zero w ater quality results, ho wever a cost counts since 1999, apart from an identifi ed W arm , oxygen- rich surfa ce wa ter ben efit analysis fav oured the W EARS ' 'washin' event, where 1001nm of rainfall pumped do wnwa rds by a mixe r w ill mix SMDI system w hich uses o nly -8.5% of period occµrr ed in the upstream in a 24hr to some extent w ith cooler, lower DO the power during peak season , w ith the catchment and a rapid increase in cell wa ter near the bottom of th e jet. It will estimated pay-bac k period being approxnumbers occurred. H owever within a few then find its neutral bu oya ncy level and imately 4 yea rs days the count was again near zero due fl ow radially outwards as an intru sive C onsequently the bubble plume system to the impact of the SMDI system . gravity current, thereby transferring DO was decommissioned and a close-coupled A saving in excess of$25,000 each year horizontally. T here is ve1y little turbulence SMDI-5 system installed in the 22, S00ML and therefore ve1y little mixi ng bet\;veen has bee n realised by eliminating th e use C hichester Dam. It currently draws 4of powdered ac tiva ted carbon (PAC) laye rs beyond the immediate vicinity SkW of electrical power. w hich was previously used to ove rcome (approx 180 111 radi us) of a bubble An SMD I- 2.5 , (Fig 3) unit was tas te and odo ur problems associated w ith plume, and the same should be tru e of a installed by CS Energy in Swanbank Dam, algal blooms. Tighe (2001 ). m ec hanical mixe r. Thu s it ca n be their primary storage for plant cooling wa ter , to remo ve th e probl em of expected that a single mixer will have an Exp e rime ntal sys te ms, usin g the m anganese build- up in the power plant 01iginal prototype impeller blade designed effect o n the DO profile as well as the cooling to wer. M cAlpine (pers comm, and installed by WEARS at Myponga and temperature profile of the w hole storage . ! 10000

i!

§ 60000

. i

0

T

OCT

OCT

NOV

IOV

DEC

DEC

DEC

JAN

JAN

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8

26

7

24

6

22

5

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0

3

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2 1 0

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en

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Depth (m ) Figure 5. Temperature gradient before and after a WEARS Close Coupled SMD l-5 system was installed at Cooby Dam .

32

4

0

---- 30/10/01 Before

14

10

Cl E

E 18

16

WATER AUGUST 2002

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t.1.AA

MAR

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:§: 20 ~

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-1

----- 30/10/01 Before 14/11 /01 After - a - 15/01 /02 After

...

M

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...

,-..

,-.. Depth (m )

Figure 6. Dissolved oxygen gradient before and after a WEARS Close Coupled SMDl-5 system was insta lled at Cooby Dam .


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PERSEVERANCE DAM DO Gradient

PERSEVERANCE DAM Tern~ Gradient

'

- + - 23/10/01 Before

- + - 23/10/01 Before ---- 12/02 /02 After 30/4/02 After 14/05/02 After

28 26 24 22 ~ 20 C. E 18 Cl) I- 16 14 12 10

8 . . - - - - - - - - - a - 12/02/02 After 30/4/02 After 14/05/02 After

7

6

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Figure 7. Temperature grad ient before and after a WEARS Close Coupled SMDl-5 system was instal led at Perseverance Dam .

H appy Valley SA, have also shown a positive effect in controlling B GA even tho ugh these early systems produ ced less than half of the mass flow rate of the comm ercial uni ts currently available. Since switching on at M yponga in 1998, the incidence of copper sulphate dosing has been reduced from an average of 4 times per year to only one (Mr. Bob C uthbert, Sto rage m anage r. pers . comm .

~

Figure 8. Dissolved oxygen gradient before and after a WEARS Close Coupled SMD l-5 system was installed at Perseverance Dam .

1999) which rep rese n ts a savin g of $120,000 in copper sulphate dosing, at a cost of abo ut $1/ kg applied.

The Toowoomba City Project In Toowoomba , o n Qu eensland 's D arling D owns, regular algal blooms at the city's three wa ter supply dams resulted in the T oowoomba City Council reassessing

its strategies and ability to deal effectively with an o rganic contamination event . Council's current response plan for algae o utbreaks is multilevel, in that it involves both management of the storages by source substitution between the three storages and treatment by chlorination. T oowoomba's wa ter supply is sourced fro m an aquifer under the city and surface wa ter storages.

~ Allanris Water Management

Atlantis Eco Paver 1st Stage Stops 100% of gross pollutants from entering the system , while infi ltrating water at 20 l/sec/m 2 .

Atlantis EcoSoil 2nd Stage Captures , treats and filters nutrients and biologicaly brakes down toxic elements.


WATER

CLARRIE HALL DAM Tern~ Grad ient

CLARRIE HALL DAM DO Grad ient 14

-+- 4/02/02 Before -a- 11/03/02 After

12 10

-&-- 15/05/02 After

Cl 8

E 0 C

6 4 2 0

30 28 26 24 ~ 22 Q. 20 E Q) 18 I16 14

-+- 4/02/02 Before -a- 11/03 /02 After

12

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10

<:)

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b<

'o

'o

'<:)

,'1-

,b<

,<o

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'1,<:)

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Figure 10. Te mpe rature gradie nt before a nd afte r a WEARS

S MD l-5 syste m was ins ta lled at Cla rrie Ha ll Da m. The surfa ce sto ra ges, Lakes Cooby, Perseverance and Cressbrook, provide up to 85% of requ irements. When a storage reaches algal alert levelthree (the highest alert level), the storage is taken off line and an alternative supply is selected. If other storages are simultaneously in alert level conditions, a decision is mad e to take water from the lowest risk storage and to treat it using chl orine. T his response plan is limited and there is the possibility that all three water sto rages might b e impa cted simultaneously by either levelthree algae co unts , to xicity, metals in solution or taste and odour compo unds.

the incidences ofBGA outbreaks. Council felt that th e WEARS system was the best way to do that. (Dinsey 2002) .

Description of the work In Ma y 2001 , the Council accep ted a proposal submitted by WEARS for the design , manufacture, installation and con1111issioni ng oflow-energy m echanical syste ms for Lake Coo by and Lake

Council's eventual decision to install the WEARS system was influenced largely by the long-term benefits of destratification and the energy savings associated with that system . It

34

WATER AUGUST 2002

'o

'<:)

,'1-

,b<

,<o

,<o

'1,<:)

Figure 11. Di sso lved oxygen grad ie nt befo re a nd after a WEARS S MDl-5 syste m was in sta ll ed at Clarrie Hall Da m.

Design and installation of the traditional type destratification system, using bubble plum e technology, was estimated to cost $200,000 per storage, with annual operating (power) costs .approximately $20,000 $30,000. An al ternati ve technique wo uld be to install a PAC faci li ty, at the Water Treatment plant, with the high cost of the activated carbon and the ancillary equipment and pro cess required.

was not j ust a case of avoiding one or two BGA contamination events, but a case of eli minating

'o

Depth (m)

Dept h (m )

Figure 9. One of th e WEAR S S MD l-5s, to be co upled with a nothe r, be ing pre pa red fo r in sta llatio n at Cooby Da m for th e Toowoomba City Council.

Perseverance. The units incorporate large diameter axial flow imp ellers located approximately two metres below the wa ter surface. The imp ellers rotate at a constant, relatively low speed, depending on flo w requirem ent. To achieve the anticipated design flo w rates of between 10,000 and 15 ,000 litres per second, the installations at both storages comprise two units attached by a walkway, w ith the two contra-rotating imp ell ers eac h driven by 4KW motors. Co u n cil adopted t his n ew strategy, instead of the PAC dosing p l ant at Mt Kynoch or a compressor type system, for several reasons. These included: • mu ch lower power requirements of the WEARS reservoir systems resulting in about only 810% of the operating costs in terms of electrical energy; • an ability to use the systems in larger, deeper water storages; • control of algal toxins and other wa ter quality problems at th e source rather than by treatment of downstream contaminated wa ter at the PAC dosing plant; • water supplied to consumers between the water storages and the water treatment plant does not have to be treated independently; To account for a stronger temp e ratur e gradient u nd e r Australian summer conditions, the design for the Cooby system was based on a flow rate of 12 cubic metr es per second and t h e Perseverance system on a flow rate of 14 cubic m etres per second. T he units are designed to operate 24 hours per day all yea r ro und.


WATER

The dissolved OJ\.'Ygen gradients and mperature gradients for Cooby and Perseverance Dams respectively, clearly demonstrate the effect of the system in breaking the thermal and chemical strata. Figures 5,6, 7 and 8 are derived from data collected by Toowoomba C iry Co uncil's laboratory, co u rt esy of M r. Alan Kleinschmidt, Lab Manager. The system was installed late in 2001 in each of these Dams and since this tim e raw water piped to the Mt Kyno ck T reatment plant has been grea tly improved.

Tweed Shire Clarrie Hall Dam in the Tweed Shire in northern New So uth Wales had a single SMD I-5 installed early in 2002 . Given the dissolved oxygen and temperature gradient results shown in Figs 10 and 11 , the indications are that improved raw wa ter quality and cost savings will be realised, as with all installations to date.

problems associated with water storages such as : autumn turnover, metals in solution, eutrophication, Blue Green Algal blooms, all of w hich contribute to problems of taste, odour and quality, along w ith downstream cold ,,va te r pollution or downstream cold water discharge, general raw water qualiry and reservoir ecological health. Problems that have traditionally been expensi ve to overcome in terms of ongoing costs and capital expense are now available to both large and small reservoir management authorities .

The Authors

Conclusion

Phill Morgan is the R esearch and Production Engineer, Stephen Elliott is t h e Pri n cipal E n gine e r for Wate r Engineering & R esea rch Solution Pry Limited, consulting and development engineers to the water ind ust1y. T el: 61 7 5521 0834 , Emai l: wears @ wears.com.au.

Water management authorities are becoming increasingly more aware that the WEARS system is the most economic operational tool available to deal with

Blackman, A. (2001 ). S11rvey - Australian R eservoir D es trat!fication . Th e Co mp etiti ve Options, Market R esearch. Gold Coast, January

References

Burns, F. (2002) A utomatic Aeration. of Slr allow Wastewa ter Storage. Wate r. 29 No .3 pp 4546.

C uthbert, R (1 999). SA W ater, R eservoir mana ger. Pers. comm. Dinsey, G (2002). R eport to T oowoomba City Coun cil Elli ott, S. (1997) . Preli111i11ary Design & Scopi11g St11dy, C haffey Dam. Proposed CS IRO joint project. Gree ne, G. R. , R ogers, J.G ., Romney, J. S., Marsden, T.J. , Gehrke" P. C. and Harris, J.H. (1997) . R elinbilitari11g Dam111ed E11viro11111e11ts - Optiomfor a Higlr Fislrway at Tal/0111a D a111. Aust. Na t. Committee On Large Dams/ Inst. of Engs. Aust. Seminar on Dams and th e Environment. Sydney, 27 June. M cAlp ine, B. (2000) Plant Ma11ager CS E11ergy, Pers comm .. M cAuliffe, T.F. and Rosich, R.S. (1990) . Th e triumphs and tribulations of nrt!ficial mix i11g i11 Australian water bodies. Water 17, 4 pp. 22-23 . Mobley, M , T yson, W ., Webb, J. and Brock, G. (1995) . Surface water pumps to improve dissolved oxygen co11tent of hydropower releases . Waterpower '95. July 25-28, Sa n Fra ncisco, Cal. T ech paper 95-2. T ighe K (2000). R eport to Co un cil, Binnaway, NSW, Ma rch T ighe K. ( 2001). D irector of T echn ical Service Coonabarabran, Timor Dam, NSW , Pers co nun.

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WATER AUGU ST 2 002

35


m

WATER

CLEANING UP A WATER SUPPLY SYSTEM P Mosse, K Bugden Abstract Sale in Eastern Victoria has a long history of dirty wa ter complaints. Studies showed that although iron and manganese levels in the wa ter supplied to customers ¡ were w ithin the Australian Drinking Water G uidelines, it was necessary to further reduce these levels to reduce the incidence of dirty water complaints . A trial using an unconventional chemical dosing system of potassium permanganate w ith lime to pH 7.5, with no further coagulant, gave excellent filt er run times and reduced levels of iron and m anganese. There has been a sustained long-term reduction in fo1mal dirty water complaints since the dosing was introdu ced in August 2000 .

Introduction The C ity of Sale, situ ated at the head of the Gippsland Lakes in Victoria , has a history of wa ter supply problems dating back to the mid 1800 's (Synan 1988). Initially, raw water was taken from the Thomson Ri ver, but this source becam e progressively polluted from goldmining, pig farming and slaughter yard operations. In 1880, after more than 20 years of debate, a bore was sunk, but the gro und water was sulphurous and corrosive to the early cast iron reticulation system. In 1888, the supply reverted to the still polluted T homson River and , in 1935, a filtration plant was built. This plant was augmented

0 .45 0.4

4 - - - - - - - - - - - - - - - - - - - - - 1 1 1 - - - - - - - - - --1

0.35

m

f

O.3 - + - - - - - - - - - - - - - - - - - - - - 1 0 .25 0.2

-+--------------

0 .15

0.1

-+--------------

0.05

0 Effluent Mn

Influent Mn

Influent Fe

Effluent Fe

Figure 1. Leve ls of iron and manganese in the water entering and leaving the WTP. The figures for the water entering the plant are for samples takel'l after the aeration towers . Co loured bars represent data for weekly samples for the period October 2000 to July 2001.

as the C ity grew until 1965 w hen colour, tas te and odour problems, associated with effiu ent from the milk fac tories ap proximately 30 km upstream , became insurmountable. On C hristmas D ay 1970, after a period of over 80 years, Sale returned to a gro und wa ter source for its raw water supply.

The data in the Table indicates that there are ve ry subtle differences in the water quality from the different bores. The raw wate r has a pH of around 5.6 and a TDS of aro und 200 mg/ L.

The W ater Treatment Plant (WTP) supplies a current population of 13,366 and consists of two cascade aeration towers Water Quality for the removal of hydrogen sulfide and partial oxidation of iron and manganese. Water is draw n va riously from six bores. Typical raw water quality for some Lime and alum are added in a mixing of the bores is shown in Table 1. chamb er and the chemically treated wa ter then flo ws through a flo ccuTable 1. Raw water quality. Data is for the period 1995 to 2001 and is derived from l a tion tank an d th ence to a quarterly samples except for turbidity, wh ich is sampled month ly. Data are means and sedimentation tank. The clarified standard deviations. wa ter passes through three dual Bore 5 Bore 6 Bore 2 Bore 3 Bore 1 media rapid gravity filters and is disinfec ted with gaseous chlorine. 24 (5) 24 (7) 24 (3) 28 (5) 24 (2) Alkalinity (mg/L) The majority of the sulfides are 0 .90 (1 .23) 2.07 (3 .99) 2.25 (3 .82) 3.94 (5 .59) 1.02 (1.03) Turbid ity removed in the aeration towers, pH (NTU)

Colour (PtCo) Iron (mg/L) Manganese (mg/L)

36

6

5

5

5

5

0.39 (0 .60)

0.55 (0.45)

0.25 (0.14)

0.32 (0.16)

0.99 (2.43)

0.052 (0.005)

0 .059 (0.018)

0 .051 (0.003)

0.055 (0.006)

0 .059 (0 .016)

WATER AUGUST 2002

increases from about 5.8 to 7.2, and the iron is reduced to around 0.2 m g/L. There is little reduction in manganese. Iron and manganese levels entering the plant after the aeration towers are


WATER

shown in Fi gure 1. Typically the influent manganese and iron levels are aro und 0 .06 mg/ L and 0.2 mg/ L respecti vely.

Dirty Water Complaints The township has a long hi tory of dirty wa ter complaints, and those from 1996 to 2000 are included in Eigure 6.

Sale Complaints (Manganese) 2 .---- - - - - - - - -

J

Cl

.ยง.

j

1.5 1

0.5 0 ~ - , - - -,........-L-jLL-~.J..A.-.1.,-J.l--J,.- -J_.J

Figure 2 . Leve ls of manganese in water samples co llected from dirty water co mplaint sites ove r th e pe ri od Dece mber 1999 to August 2000.

expect dirty wa t er com p l aints w ith manganese levels as low as 0.02 mg/ L A program was initiated to test wa ter from hou seholds in Sale complainin g of dirty water. The sa mple was taken as close to th e time of .lihe complaint as possible. T his occurred for a period of8 months from December 1999 to August 2000. A total of 45 samples were analysed for Fe, Mn , C u and Al . R esults for Fe and Mn are sho w n in Figure 2 and 3.

Early inves ti gations Sale Complaints (Iron) of the dirty wa ter 1 p ro bl em included a Figures 4 and 5 show 0 .8 comparison of the levels clearly that in contras t to 0 .6 of iron, manganese and 0.4 the regular reticul ati o n al uminium in Sale with sa mples, these dirty 'Nater 0 .2 those from other major sa mples regularly exceeded 0 towns supp l ie d b y desirable levels of iron and Gippsland Water where manga ne e. It is likely that dirty water complaints som e of the samples that were less conm1on. The returned a satisfactory level levels for Sale were all we re in fac t sampled after Figure 3 . Leve ls of iron in wate r samples coll ected from di rty water less than the Australian the immediate event had complaint sites over t he period December 1999 to August 2000 . Drinking Water passed, so th e d a t a G uid elin e (ADWG) presented here may underair sco ured in M ay and J une 1997, valu es and are wi thin the range fo und at estimate the extent of the problem. September and October 1999 (in part) and all Gippsland W ater towns (Table 2). The There was clearly a need to reduce the again in J uly 2000 (in part). Although manganese levels are however at the upper level of Fe and Mn in the water supplied difficu lt to ga uge there was no sustained end of the range for all the tow ns. The to Sale. Based on discussions w ithin the overa ll impro ve m ent base d on th e iron level are generally low, with the Australian Water Industry a targe t level number of dirty wa ter complaints (Figure exception of M orwell, and Sale one of the of0.01 mg/ L was set for manganese and 6) . lowest. T he aluminium results in the 0.1 mg/ L for iron. Table also sho w low levels in the Sale Dirty water complaints persisted reticulation. T he results in Table 2 are Trials Discussions with other authorities ave raged data co ll ec ted from sites Potassium p ermanga nate has been within Australia (notably Hunter Water throughout the reticulation and as such used extensively for the removal of iron and Gold Coast C ity Council) suggested may not reflect dirty wa ter events. and manganese from potable wa ter. A that the ADWG guideline levels may be Based on th ese res ults completed in series of jar tests we re undertake n to too high and that W ater Authorities could 1998, Gippsland W ater felt the source of determine th e best trea tment the problem lay elsewhere. regime for the Sale water. Gippsland W ater contrac ted The reticulation system Table 2. Iron, manganese and aluminium leve ls in water the services of Aluminates P/ L had a large number of cast supp lied to larger towns by Gipps land Water, for th e peri od 1992 to 1998. Data is de rived from t he qu arte rly reti cul at ion to carry out the initial j ar iron fittings that showed signs sample. The site va ries from qua rter to qu arte r. Dat a are testing. This decision was of corrosion, so a program mea ns and standard deviat ions . taken to fac ilitate th e perforwas initiated to remove these m ance of th e large number of w h erever p oss ibl e . This Reticulation Fe (mg/ I) Mn (mg/I) Al (mg/ I) tests required in the ea rly produced so m e localised 0.042 (0.014) 0.06 (0 .03) 0 .08 (0.03) Sale stages of the proJect. impr ove m e nt s in th e 0 .08 (0.04) 0.041 (0.041) 0. 12 (0 .12) Maffra immediate region w here the Th e i nitia l t es tin g 0.038 (0.019) 0.42 (0.44) Trara lgon 0.15 (0.17) fittings were removed but no suggested 20 ppm(v) of a 1% 0.033 (0.024) 0 .18 (0.06) 0.15 (0.12) Moe ge neral improve m ent . An solution of potassium perman0.035 (0.023) 0.32 (0 .73) 0 .16 (0 .10) Morwell ganate (i. e. 0.2 mg/ L KmnO 4) air-scouring program was also 0 .029 (0.025) 0.31 (0 .20) Warragul 0.10 (0.04) gave the best removal of both initiated and the system was WATER AUG UST 2002

37


WATER

iron and manganese, using both iron and aluminium coagulants. Some improvem ent in the removal Average FIiter was achieved with the addition of Run Time (min) lime to achieve a pH of around 8.5. Since equipment for prechlona rination w as alrea dy installed at the WTP, the optio n of using 800 chlorine as an oxidant was also trialled. At the dose nee ded to 2480 ac hi eve some r e m ova l of m a n ga n ese, a s tr o n g and unacceptable chlorine odour was present in the wa ter. For this reason the use of chlorine was rej ec ted. A plant trial using potassiu m permanganate, alum and lime was co ndu cted. The o ptimum do se for p o tassium permanganate was fo und to be 35 ppm(v) of a 1% solution. This contrasted to the j ar test optimum of 20 ppm (v) . The difference was partly attributed to th e poor mixing in the mixing tank. Good m anga n ese removal and acceptable aluminium residuals were obtained at a pH of 7.3 . However the main problem w ith the new trea tment regime was the filter run- time. The alum dose was increased initially r.o assist with fl oe fo rmatio n and m anga nese rem oval, however filter run times (see Table 3) we re redu ced and manganese breakthro ugh coincided with both turbidi ty and aluminium breakthro ugh .

Table 3. Comparison of final treated water qu ality for different treatment regi mes tri alled in the Sa le WTP pl ant. Data are indicative on ly. (na - no data ava il able) Turbidity (NTU)

Aluminium (mg/ L)

Manganese (mg/ L)

Iron (mg/ L)

Raw Water

0.10

0.043

0.064

0.214

Alum, Lime and Ch lorine

na

na

0.03 - 0.04

na

Alum , Lime and Potassium Permanganate

0 .05

0.075

0.003

0 .005

Lime and Potassium Permanganate

0 .06

0.05

0.002

0.005

0.06 0.05 0.04

::J' Cl

-

E 0 .03 Q)

L1.

0 .02 0.01 0

Figure 4. Iron levels in water sam pl ed weekly from the 8 sample sites . Coloured bars represent data for weekly samples coll ected over t he period October 2000 to Ju ly 2001 .

0 .06 0 .05

...,_

-t

0 .04 0.03

C

:E

0 .02 0 .01

0

Figure 5. Manga nese leve ls in water sampled weekly from th e 8 sample sites. Coloured bars re present data for weekly samples co ll ected over t he period October 2000 to July 2001.

38

WATER AUGUST 2002

J enkins et al 1984 reported a dose dependent remo val of m anganese by calcium ions (dosed as lim e) across a filter system in the absence of other coagulants. Additional j ar tests were carried out using potassium permanganate and lime without a coagulant. These produced excellent results; however the resultant pH of about 8.2 raised som e concerns for disinfection effi ciency. The j ar testing indicated manganese levels less than 0.01 m g/ L could be achieved w ith a permanganate dose of20 ppm(v) (as a 1% solution) and a pH of around 8.2 . When trialled in the plant, in the absence of alum, the optimum dose of potassium permanganate was again fo und to be 35 ppm(v) (as a 1% solution) (ie. 0.35 m g/ L KMnO 4) w ith sufficient lime to maintain the pH at 7.5 . Higher pH levels, althou gh resulting in slightly , . lower manganese levels, compromised disinfec tion effi ciency, so a target pH of 7.5 was set. A summary of the plant trials is provided in Table 3.


WATER

25 20 -

V,

C:

15

-

E 0

10

-

ca C.

I

\ I

I

t

t

(.)

5 0

-

~

n

-

n

-

-

~n

nn

~

~n

n

f--

~~

nn

n

n

n nn

nn

J FIV A IV J JlA s:c NC J FIMAIIV J JA 8iOINC J Fllv AM J J AIE c :r-- DJ F rv AIIV J J lA sp 1\ C J FIVA rv J JlAlsc N C JjF!rv Aitv J JA IE

1996

1997

1998

1999

2000

2001

Figure 6. Dirty water complaints received by Gippsland Water for the City of Sa le since 1996. The larger dark arrow indicates the commencement of the alte red treatment regime at the WTP . The smaller arrows indicate when air scouring was carried out. A small area of the town was also air scoured in July 2000.

The target levels fo r both manganese and iron were readily ac hieved using potassium perman ganate as oxidant. In contrast chlorine was not able to achieve the req ui red removal.

Eight sites were selected within the system. These sites were chosen to represent the entire reticulatio n system and included sites in the general areas w here dirty water complaints were

prevalent. Sites were sampled weekly over the period October 2000 to July 2001. The results are presented in Figure 5 and 6 and clearly sh ow that th e low manganese levels leaving the plant have

Aluminium residuals were slightly elevated w h en alum was u se d as coagulant. The most interesting operati onal consequence of the treatment was the effect on filter run times. Th e run-time, using alum as coagulant, was abo ut 800 minutes under optimum dosing condi tions. When alum dosing was removed , it was fo und that the filter run time was increased to aro und 40 ho urs w itho ut turbidity or manganese breakthrough. T he actual breakthrough point was not determined under these conditions as the fil ter was only in operation for about 8 hours a day. T he 40 ho ur run time therefore equated to roughly 5 days operati on. For other reaso ns this was conside red inappropria te and filters backwashed every second day . T his equates to a total filter run time of around 16 ho urs in w inter and aro und 30 ho urs in summer.

Distribution System Results Figure 1 shows the results of plant performance over a period of 9 months. Treated wate r averaged 0.001 m g/ L manganese and 0.004 mg/ L iron . A monitoring program was established to monitor the impact of the changes at the WTP on the reticulati on system. WATER AUGUST 2002

39


WATER

been maintained througho ut the reticulation system ; however there has been som e va riable elevatio n in the iron levels. This was m ore marked fo r som e of the sites than o thers. T he interesting observa tion is that the relative va riation has been largely retain ed ove r the sampling period. There is a rou gh correlation b etween the level of iron and the distance from the WTP . Altho ugh the iron levels are higher than those in the wa ter leaving the treatment plant, the levels are all w ell below the target level of 0.1 m g/ L. These results also suggest that the deterioration in water quality is unlikely to be biofilm derived, since, if this we re the case, one might expect occasional higher levels of both manganese and iron. The fac t that only iron is elevated is strongly suggestive of an inorganic source, most likely reticulation fittings them selves . Figure 6 shows the number of formal dirty wa ter complaints received by Gippsland W ater since 1996 . The total numbers are not high; ho weve r they are likely to ve ry mu ch underestimate the dissatisfaction with the water, because only a relatively small proportion of concerned customers take the step to ac tually register a formal complaint. Figure 6 howeve r shows very clearly that since the change in treatment process at the WTP , there has been a significant decrease in the number of dirty w ater complaints. Since the altered chemical trea tment regim e was introdu ced to the WTP in August 2000 there have been less than 5 complaints per month for 13 m onths. Prior to this the longest peri od with less than 5 complaint per m o nth was for 5 months in 1998 . Since August 2000 there have been 3 m onths w ith zero dirty water complaints. There is also some anecdotal evidence of an improvem ent in the taste of the wa ter.

Conclusions

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40

WATER AUGUST 2002

For more information or a brochure, contact Philmac on (08) 8300 9200 or check our website. www.philmac.com.au

The m odifi cati ons to the treatment process at the Sale WTP have redu ced the levels of iron and manganese in the wa ter supplied to the distribution system. These redu ced levels have ac hieved a reduction in fo rmal dirty wa ter complaints received by Gippsland W ater.

Acknowledgements The autho rs thank Trevor Martin , the op erator of the Sale W ater Treatment Plant, fo r his assistance during these trials.

References Jenkins S R , Benefi eld L, Keal M J and Peacock R S (1984) Effecti ve manganese removal using li me as additive. J A WW A 76, 82-86. Sandeman C. (1991) C ity of Sale Water T reatment Process. Paper presented to the 54th Water Indusny Engineers and O perators Co nfe rence. Synan P. (1988) Precious Wa ter. 100 years of reti culated supply in Sale. Paper prepared for the Bicentenary Celebrati ons. Published by th e City of Sale.

The Authors Dr Peter Mosse (m ossep@ gippswater. com.au) was the W ater Treatment M anage r at Gippsland W ater, and is currently operating as a consultant in water and wastewater treatment (phone 0428 941 013) for both Gippsland Water and other clients. Kelly Bugden (kbu gden@aluminates. net) is a Chemical E ngineer w ith Aluminates C hemical Industries, P .O. Box 3020 Gippsland M ail Centre, Vic 3842 .


WATER

FOREST RESEARCH G Sheridan, J Morris Quality of Catchment Water

landscape, and in particular the quality of streams. Tracks Victoria's Forest Science have a principal function but Centre is performing new th ey are also small bu t research on the impa ct of important ater catchments. runoff water from unsealed However, they contribute fores t roads, w hich sho uld sediment far o u t of lead to th e d es i g n and proportion to the relatively management of forest roads to sm all area they occupy. red uce sediment inp ut to fo rest streams. T he research is currently focused in Gippsland's Upper ¡ Unsealed roads are known Tyers River wa ter supply to be the maj or source of such catchment. Data collection is pollution, but little is known being car ri e d o ut b y about the scale of the problem monitoring run-off from or how best to manage roads road sections using turbidity to protect water quality. Initial prob es and manual sampling research has foc used on newly (Figure 1) to quantify inconstru cted roads and stream Figure 1. Unsealed roads produce dirty runoff water that pollutes stream impacts at the local cross in gs, w hil e future streams , impacting on stream eco logy and drinking water quality. and catchment scale. Figure research will focus on methods 1 demonstrates the problem, to improve water quality from Figure 2 shows Dr. Gary the effective environmental management mo re established roads and crossings. Sheridan, the Principal Scientist in charge The next revision of the Code of of forest tracks , with the Triple Bottom of the program, monitoring water quality. Line shifting to management of the forest Forest Practices will almost certainly cover

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WATER

Figure 2. Field installation measuring pollutant loads from a dirt road during rainfall. Impact of plantations on water resources

Tree plantations are a major growth industry in both Australia and similar climates w orld w ide, for both salinity control and wood harvesting. Howeve r, they impact on wa ter reso urces, eith er gro undwa ter or run-off, to the detriment of other users. C R CRCH and CSIRO are investigating such impacts through models such as MAY A , with useful results. T he Victorian Forest Science Centre was co mmissioned by the Australian Ce ntre for International Agri cultural R esearch (ACIAR), in 1999, for a four yea r, one million dollar, proj ect in the

Figure 3. Jim Morris (with the hat) with the Chinese team members

and local authority representatives monitoring stream flow.

Leizhou Peninsula, southern China, to apply Australian know-how and models, and to draw up a m eaningful economic analysis of plantation managem ent options, including costs and benefits of hydrological impacts.. T ypically, both in C hina and Australia , farmers are expressing con cern abo ut the impact of for estry on wa ter resources for agri culture. The fourth and final yea r of the proj ect is planned to operate a comprehensive technology transfer program to ensure that the findin gs rapidly reach a wide research and operational audience . T his includes training of Chinese personnel in the 3 PG

growth model and hydrologic models which, although already very effe ctive, are still subj ect to current research in Australia.

The Authors Dr Gary Sheridan and Dr Jim Morris are Princip al Research Scientists w ith th e Fores t Scie n ce Centre w hi ch is an allian ce including the Vi ctorian Gover nment 's D epartment of Natural R eso ur ces and Envi ronm e nt a nd M elbourn e Uni ve rsity . Contact Gary Sh eridan and Jim Morris, Tel (03) 9450 8 6 0 0 , e m a il : G a r y . s h e r i d a 11 @ nr e.v i c . gov.au, Jim.Morri s@ nre. v1c. gov. au 0

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SEWAGE DISCHARGES IN THE GREAT BARRIER REEF REGION J Waterhouse, J Johnson Abstract There are 28 islands with resort, residenti al or research stati o n fa ciliti es in the Grea t Barrier R eef World H eritage Area . W hilst these islands alJ ba ve f ac ili t i es for th e manage m ent of sewage, six island resorts are permitted to have o utfa lls th at discharge efflu ent direccly into the wa ters of th e Great Barri er R ee f Marine Park. A review 111 2000/ 200 1 indicated that 16 fa ciliti es di sc h argin g in or adjacent to the Great Barrier R eef World H erita ge Area wo uld n eed upgrading to m eet th e sta ndard s fo r sewage managem ent, and tw o fa ciliti es that have m arine outfalls w ould need significant improvem ents to m eet the Autho rity's tertiary treatment policy requirement by a deadline of March 2002.

Introduction

l

Wei Tropics Coas t

Proserpine

Fitz roy

I

Boyne Burnett

100

200

T he discharge of excessive am o unts of human waste co Figure 1. Great Barrier Reef Catchment Area . coastal areas is one of the m ost w id esprea d glob al pollution probl em s fa cin g n ear-sh ore R eef M arine Park Authori ty (GBRMPA) e n v ironm e nts. Sew age di sc h a rges has limited jurisdiction in this regard , contribute a very small proportion of the unless sewage is discharged direccly into overall polJutant load co the Great Barrier the GBRMP. R eef W orld H eritage Area (GBRWHA), In 199 1 GBRMPA develop ed the ho wever, these inputs may be significant Sewage Discharges fro m Marine Ou ifalls into on a local scale. In the Great Barrier R eef the Great Ba rrier Reef M arine Park policy (GBR) catchment (Figure 1), the majority paper (the Policy), w hich was impleof sewage effl uent from coastal setclements m ented in 1991 and updated in 1993 to is discha rged to wa terways of the GBR includ e a sew age E n v ironm e nt al catchment, w ith a small proportion of Manage m ent C harge . This Policy refers island resorts discharging directly into th e directly co sewage discharged into th e G re at B a rr i e r R eef M arin e P a rk GBRMP and w as developed for o.-isting (GBRMP) . Seve ral coa stal sewage island outfalls, especially those requiring treatment facilities serving major populaGBRMP A p ermi ssio n . Th e Poli cy tions reuse a proportio n of secondaty required that efflu ent discharges meet treated efflu ent for land irrigation. tertiary or tertia1y equivalent standards of Sewage treatment plants in Queensland treatment by 1 J anuary 1996. T ertia1y w ith a capacity greater than 21 equivalent equ ivalent treatment is w hen the total persons are licensed by the Environmental volum e of marine discharge is only 5% of Protection Agency (EPA). Smaller systems seconda1y treated efflu ent produ ced with are regulated by th e D epartm ent of the remainder used for land irrigation . N atural R esources and Mines (DNRM), T ertiary treatment is the use of nutrient and local government. T he Great Barrier stripping treatment plants, for example,

w here nitrogen is remo ved by denitrification and phospho ru s remo ved by precipitation into the sludge. A furth er issue was in regard to th e placem ent of o utfalls in a loca tion and depth that enhan ce d di sp ersal of w astewater w hil e minimising any potential impac ts on the m arine environment. Op e rator s w ho h eld a Mar i n e P a rk p e rmit for disc harge of sewage from treatment fa cilities were give n until 1 Jan ua1y 1996 to modify their efflu ent quali ty and o ucfaJJ position co meet these new standards. By 1 Januaty 1996, 9 op erato rs had upgraded their sewage trea tment plants to the required standards and several op erators changed from an ocean outfall to land disposal as a result of the P oli cy . Fo ur operators had not complied by 1 January 1996 and were given a further 12 months to comply. By mid 1997, only 2 operators we r e n o t c on s i s t e ntl y complying w ith GBRMPA's standards. On 5 D ece mb er 1997, GBRMP A agreed to extend the du e date for implementation of tertia1y treatment or equi valent tertiaty treatment standard to 30 June 1998 . Anoth er m echanism used to improve efflu ent quality and redu ce the impa cts from sewage on th e GBRMP w as the application of different Environmental Management Charges (EM C) for different levels of discharge , sec ondary created efflu ent incurring a greater EM C than tertiaty treated efflu ent. The second phase of the P olicy required that operators upgrade their STP to tertiaty treatment standard by 1 M arch 2002, as defin ed in R egulation 74(3) of the G reat Barrier R eef l\llarin e Park R egulations. There are currently 6 island resorts with M arine Park , p ermits for sewage discharge outfa11s remaining in the GBRMP (Figure 2) . Fo ur of these are issued to island resorts in the Whitsunday Island Gro up; Daydream Island, South Molle Island , H amilton Island and Hayman Island in the Central Section of WATER AUGUST 2002

43


WASTEWATER

th e GBRMP. The o ther res orts are Gree n Island R esort located off C airns in the Cairns Section of the GBRMP , and Great Keppel Island R eso rt lo cated east of Y eppoon in the Mackay/ Capricorn Bunker Section of the GBRMP. GBRMPA and Q ueensland authorities are also w orking to gether to set efflu ent quality standa rds, based on the kno w n impacts of increased nutrient levels, fo r aquaculture discharges . T hi s rece nt development includ es mo re strin ge nt environmental requirem ents fo r eilluent discharged into 0 150 th e GBRMP an d it is Ki lometres intended that in the future Figure 2. Location of marine outfa ll s in the GBRMP . these discharge levels are standardised fo r all discharges into the GBRWHA, such as aquaculture, sewage and industrial eillu ent. fa cilities w ithin the GBRWHA. T he intention of the review w as to obtain an O ve r the period September 1999 to updated status report of the implemenJu n e 2000 , GBRMPA condu cted a tation of the Policy, and to determin e the review of the island sewage treatm ent

The Embassy of Italy Office of the Scientific Attache In collaboration with:

Effects of Sewage Discharges on the Marine Environment

The Commonwealth Department of Education Science and Training, University of Canberra Universita di Siena, dip G. Sarfatti CSIRO, Centre for Advanced Analytical Chemistry CRC for Freshwater Ecology

CAnorn.~A .....,

Present: Ecotoxicological Tools for Environmental Management 4 · S November 2002 University of Canberra, Canberra Topics will include:

- .,,

Remediation of Contaminated Sites Environmental Legislation Global issues - Antarctica VI European Framework Technology transfer - Knowledge brokering

Bioavailability Bioindicators Biomarkers Bioassays

Contacts: Bill Maher +61 (02) 6201 2S31 Alessandra lero, email: events@scientific.ambitalia.org.au www .scientific.ambitalia.org.au /science/ ecotox

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WATER AUGUST 2 002

likelihood of compliance with th e Policy req uirem ent to apply terti ary standard fo r discharge in all instances by 1 M arch 2002 . T h e review in clud ed in sp ec tion of a majority of the fa cilities, many undertaken in conj unction with officers from EPA and the Queensland Parks and W ildlife Service (:QPWS). T he inspecti on s includ e d d e ta il e d examination of the sewage treatment plant or septic system op e ration s a nd th e land irri ga ti o n sys t e m s u se d. M eetings w ere also held w ith resort managers and maintenance staff to discuss current sewage treatment prac tices, En vironmental Management Plans and future upgrade plans. Inspection of the six island resorts with marine outfalls als o includ e d a simp l e biological survey of the habitat surrounding the sewage o utfall pipes and a general assessm ent of the conditio n of the o utfall stru ctu res . T his review follows a pap er prepared by GBRMP A in 1994 (Brodie, 199 5), whit h o utlined the status of sewage discharges in the GBRMP.

. f U i l f W... fllll((OLO<;Y

Sewage eilluent contains a number of substances that may impac t on the marine enviro nm ent . T hese inclu de organic m atte r, nutri ents, susp end ed soli ds, microorganisms (bacteria , viruses, fungi, protozoa , parasitic w orms), some of w hich may be pathogenic. T here may also be toxic trace m etals, toxic synthetic organic substances such as pesticides and solve nts; petroleum oil; detergents; biologically active drug residues such as vitamins and steroids; and litter (Brodie, 1995). In more industrialised areas, sewage can also contain elevated concentrations of heavy metals. Sewage inputs are one of th e major causes of eutroph ication and decreased dissolved 0:>,,')'gen in many coas tal areas w orldwide. Symptoms of eutrophicatio n include the developm ent of algal blooms, w hich may be toxic, anoxia in bottom waters, high concentrations of metal ions in bottom waters and sediments, fish kills and other undesirable aspects of water quality (Harris, 1995) . Or$anic enrichment via the disposal of sewage has been documented in a range of marine conm1unities, including rocky shores (FaiJ.weather, 1990; Bickford, 1996), coral reefs (Grigg, 1994), kelp for ests (Smith and Simpson , 1992), and subtidal soft bottoms (Smith


WASTEWATER

et al. , 1973; P earson & Rosenburg, 1978; O tway, 1995; H all et al., 1997) . The direct discharge of sewage also introdu ces human pathogens , w hich contaminate seafoods and diminish th e recreational attractive ness of the littoral zone. R ecent experiments at O ne Tree Island in the so uthern Great Barrier R eef h ave d e m o n str at e d th at n utri e nt enrichment may produce severe effects on corals such as redu ced reprodu ctive activity (W ard, 1997; Koop et al., 2000); redu ced coral density (Koop et al., 2000); redu ced co ral calcifica tion (S timson, 1992; Dubinsky & J okiel, 1994) and slower coral growth (Stambler et al. , 199 1). Seagrass beds are also affected by nutrient enrichment. While low levels of nutrient increases may promote seagrass grow th (for example, Green Island) at higher levels of nutrient inputs, epiphytic algal overgrow th occurs, redu cing light penetration and leading to seagrass demise (Orth & M oore, 1983; Bulthius, 1983; Ca mbrid ge & M cC omb , 1 984; N everauskas, 1987; Walker & M cComb , 1992; Short et al., 1996) . The best documented example of the effects of sewage on a coral reef is Kaneohe Bay, H awaii (Smith et al., 198 1). Sewage discharges into the Bay from the end of the Second W orld W ar to 1978 saw the waters become increasingly rich in phytoplankton (Clutter, 197 1) and reefs closest to the outfall becom e overgro w n by filter- fee ding organisms, such as sp on ges, tub e-worm s and b arn acl es (Banner, 1974) . R eefs in the centre of the Bay furth er from the outfa lls we re overgrown by the green alga Dictyosphaeria sp. (Smith et al. , 1981). After diversion of the outfalls into the ocean in 1978, the reefs have slo wly recovered (M aragos et al. , 198 5). As an enclosed bay , this study

Table 1. Qua lity of final effluent after primary, secondary and tertiary treatment. Parameter

Biologica l Oxygen Demand (mg/ L) Suspended Solids (mg/ L) Total Nitrogen (mg/L) Total Phosphorus (mg/ L) Surfactants (mg/ L)

300 300 50 10 2

200 120 45

15 20 20

9

7

2

1

is particularly relevant to the GBRWHA lagoo nal area . R esearch in C hesapeake Bay (Kemp et al., 1983) has also shown that the depletion of oxygen in coastal environments is associated with fis h kills , changes in benthic community stru cture, depressed densities of bottom fish, and altered nutrient cycling. T h e most well known occurrence of sewage discharge in the GBRMP is at Green Island, near C airns. Prolonged discharge of primaiy treated eflluent (1972 to 1992) led to abnormal and luxuriant growth of sea grass in an area near the cay w here the hydrodynamic regime ca used retention of the diluted efflu ent (van W oesik, 1989) . Since then, the system has been upgraded to tertiary treatment and the changes are being monitored. R ecent seagrass fe rtilisation experiments in Green Island, M orton Bay, W eipa, and R ottnest Island, Western Australia, all indicate that nitrogen rather than phosphorus can stimulate seagrass growth and biomass (Udy & D enniso n , 1997a; Udy & D ennison, 1997b). Udy et al. (199 9) suggest that the wa ters off Green Island are also influ enced by mainland runoff, lea ding to current existence of the seagrass beds even after improved sewage treatment.

3 marine outfalls Sewage treatment

8 land Irrigation

3 marine outfalls

9 land Irrigation

Primary (11) (settlement only)

150

Primary Treatment

Secondary Tertiary Treatment Treatment

2 2 4 <1 <1

Source: Brodie, (1995)

Tertiary (11) (nutrient removal)

11 absorption or evaporative trenches

Raw Sewage

300

Kilometres

Figure 3. Summary and Location of Island Sewage Facilities .

It

Primary

-

Secondary

Q

Tertiary

It has also been demonstrated that the secondary treated discharge from H ayman Island in the Whitsunday Group has caused localised effects on adj ace nt coral reef (Steven & va n W oesik, 199 0). The areas surveyed closest to the outfall had the lowest number of taxa, lowest net increase in coral colonies and the greatest proportion of local extinctions. T he efflu ent discha rge from the Airlie Beach settlement into Pion eer Bay is believed to have caused significant impacts on seagrass and minor increases in algal growth over hard corals in Pioneer Bay and Bo athave n B ay (FR C Coastal R esource and E nvironmental , 1999) . Other demonstrated effects of sewage discharge include: signifi cant changes to loc al fa una and flora communiti es including the bioaccumulation of trace contaminants by fish in the vicinity of inshore outfalls (Lincoln-Smith & Mann, 1989 ; M ann & Aj ani , 199 1; M cLean et al. , 199 1; Scanes, 1992); increased cove r of opportunistic green algae, Ulva lactuca and En.teromo1pha intestin.alis (Fainvea ther, 1990); elevated levels of chloro-hydrocarbon, organochlorine compound and trace metal contaminants in sediment and fish aro und outfalls (Krogh & Scanes, 1996); high rates of organic matter d ep ositio n affec ting bio ge o ch emi cal processes within sediments (Bickfo rd, 1996); changes in trace metal contamination in sediments around outfalls (Gray, 1996); eleva t ed co n ce ntration s of organochl orin es in oysters (Scan es, 1996); and changes in offshore fish and invertebrate communities, manifested as shifts in community structure and abundance (e .g. Puffe r et al. , 1982; Grigg, 1994; Otway, 1995; H all et al. , 1997), reproductive impairm ent (Hose et al. , 1989) and histopathological changes (Brown et al., 1987) . It is important to note that the impac t of sewage discharge fr om ocean outfalls is generally localised. For example, studies at Coffs H arbour, NSW, showed that impacts are restricted to w ithin approximately 300 m of the outfall fo r m ost va riables (eg . algal species ri chness, WATER AUGUST 2002

45


WASTEWATER

Table 2. Status of island sewage treatment fac ilit ies in t he GBRWHA Operation

Specifications of sewerage treatme nt fac ilities June 1994

June 2000

Cairns GBR Section

Li zard Island Resort Lizard Island Research Station

2°, LI

3°, LI

Pit toilets

CT

Double Island Resort

2°, LI

No change

Fitzroy Island Resort & Camp Ground

ST, AT

No change

Green Island Resort

3°, MO, LI , reuse

No change

Dunk Island Resort & Camp Ground

2° , LI

3°, LI

Bedarra Island Resort

2°, LI

3°, LI

Hinchinbrook Island Resort

2°, LI

No change

Palm Island Commun ity

2°, creek discharge 3°, LI

Centra l GBR Section

Orpheus Island Resort

ST, AT

No change

Orpheus Island Research Station

ST

Unsatisfactory ST

Nel ly Bay Community (Magneti c Is)

2°, LI

No change

Horseshoe Bay Community (Magnetic Is) 2°, effluent lagoon

No change

South Mo lle Island Resort

Partial 3°, MO

Partial 3°, MO, LI (100%)

Club Crocod ile Long Island Resort

2°, LI

No change

Palm Bay Hideaway Resort (Long Is)

ST

3°, LI

Paradise Bay Resort (Long Is)

ST

2°, LI

Hayman Island Resort

2°, MO , LI

2°, MO (<5%), LI

Hook Island Resort & Backpackers

Unsatisfactory ST

No change

Hamilton Island Resort & Residentia l

2°, MO (60%), LI

2°, MO (40%), LI

Li ndeman Island Club Med Resort

3° , LI

No change

Daydream Island Resort

2°, MO, LI

2°, MO , LI (100%)

Camp Island

ST

No change

Stone Island

ST

No change

Titan Island

ST

No change

Great Keppe l Island Resort

2°, MO

Partial 3°, MO , LI (100%)

Keppe l Haven Resort

2°, LI

3°, LI

Keppe l Island Holidays (YHA)

2°, LI

No change

Pumpkin Island Resort

ST, ET

No change

Brampton Island Resort

2°, LI

No change

Newry Island Resort

ST

No change

Heron Island Resort & Research Station

2°, SI

3°, SI, reuse in to ilets (20%)

One Tree Island Research Station

No fac il ities

CT

Lady Ell iot Island Resort

2° , LI

Mackay / Capricorn GBR Section

Kesw ick Island

No change Proposed 2°, LI

3° - tertiary treatment, 2" - secondary treatment, ST - septic tanks, AT - absorption trenches , CT - composting toilets, ET - Evaporation Trenches , LI - Land Irrigation, MO Marine Outfall, SI - Subsoil Injection.

changes to the structure of invertebrate communities living in kelp holdfasts) . Howeve r, the green alga Ul11a lactuca showed significantly greater cover than at reference sites for a distance of 500 m from the point of discharge (Smith, 1996). Similarly, Anderlini and Wear (1992) found chat only benthic communities within a 500 m radius of the outfall in Fitzroy Bay, Wellington, New Zealand, were affected by the disc harge. However, for sewage discharge into enclosed bays, 46

WATER AUG UST 2002

impacts may be extensive as show n in the Kaneohe Bay studies . This is particularly relevant at marine outfall sites in the GBRWHA lagoonal area that are located near sensitive environments including coral reefs and seagrass beds.

Management of Sewage Discharges This study aimed to review the current status of island sewage treatment fac ilities, effiu ent qu ality and recycling

prac tices. The level of treatment applied to the sewage from these facilities ranges from primary to tertiary. Primary treatment removes a proportion of the solids in the effiu ent, principally through the use of settlement tanks or ponds. Seconda1y treatment reduces the organic loading in the effluent and furth er removes solids through incorporation of aera tion and settlement components in the system. T ertiary treatment produces the highest quality efflu ent and in addition to seconda1y treatment processes, also removes nutrients. This may be ac hieve d throu gh ch emi cal do sing, balan ce of aeration and se ttlem ent processes, and filtration of the efflu ent. Typical efflu ent quality for these three levels of treatment is shown in Table 1. Effiuent disposal methods from the facilities include ocean discharge , evaporation and absorption tren ches , land irrigation and some reuse including toilet flushing. Twenty-eight islands we re reviewed in this study, consisting of 34 sewage treatment facilities as some islands have multiple resorts and facilities. The results are show n in Table 2 and summarised in Figure 3. Ten of the facilities have upgraded significantly since the review was undertake n in 1994. O f the 34 facilities considered, 20 were operating at tertia1y or tertiary equivalent standard and reusing a maj ority of the efflu ent on land. Eleven facilities are served by septic tank systems, which are not the preferred method of disposal in a world heritage area. Five facilities have some form of secondary or certia1y treatment, but are experiencing design difficulties and GBRMP A has been negotiating the improvem ent of these sys tem s to mee t tertiary trea tment standards. GBRMP A is currently reviewing the policy for sewage discharges into the GBRMP based on the outcomes of this review. T he policy will also be expanded to include consideration of fac ilities within the GBRWHA that do not discharge directly into the GBRMP, primarily through the encouragem ent of effiu ent reuse and the upgrade of prima1y treatment facilities . Another consideration for the policy review is the application of 'tertia1y equivalent' standard . Studies undertaken by CRC R eef (Gallagher et al., 1999) were designed to track gro undwa ter nutrients from 3 island resorts that we re irrigating seconda1y treated efflu ent. The islands, Dunk, Brampton and Great Keppel, are charac terised by loam , clay and sand soils respectively . The transfer


WASTEWATER

of nitrogen from the unsaturated zones in the profile of the irrigation areas was reduced by 85% on D u nk Island, 93% on Brampton Island and 44% on Great Keppel Island. Improved nitrogen reductions were achi eved by removal of grass clippings. This indicates that furt her investigation is required on the groundwater transfer of nutrients and the receiving environments of those islands that irrigate secondary treated efiluent, especially on sand-based islands in the GBRWHA to determine whether current effluent management practices are appropriate. GBRMPA will be liaising with EPA, who licence these irrigation areas, i:n these circumstances .

Further studies: Review coastal facilities GBRMP A has undertaken a preliminary desktop review of the coastal sewage facilities adjacent to the GBRWHA, including documentation of 42 major facilities (Figure 4) . A majority of these , 33 in total, disc harge all or a portion of the secondary treated effluent generated into waterways that drain into the GBRWHA. Thirteen facilities incorporate some degree of land irrigation (Figure 4). There are also many smaller coastal communities that still use septic tank systems with absorption or evaporative trenc h es adjacent to the GBR WHA. The extent that these communities may pose a risk to the health of inshore waters of the GBR has not been assessed, and requires further investigation. In August 2001 , GBRMPA gazetted 28 additional areas that were previously excluded from the GBRMP. These new areas incorporate three of the existing marine outfalls from maj or coastal sewage facilities . GBRMP A will be liaising with the relevant local governments and Queensland agencies to negotiate appropriate timeframes for upgrading these outfalls to tertiary standard based on a detailed assessment of these discharges. The EPA licences for these three facilities require upgrade to tertiary standard by 2008 . The EPA's State Coastal Management Plan states that in areas w here nu trients have been identified as a problem, sewage treatment works are designed and managed to enable appropriate nutrient removal for discharge of efiluent from the mainland into coastal waters by 2010.

Conclusions The implementation of the Sewage

STP Treatment Tertiary 3 (nutrient removal)

$

Secondary

Tertiary

3 river outfalls

6 marine ouHal la 6 total land lrrlgatton 30 river outtalls 100

200

Kllomet,11

Figure 4. Summ ary and Location of coasta l sewage facil ities.

Barrier R eef Marine Park policy has resulted in significant and important improvements to the methods of sewage treatment in the GBRMP. However, furt her improvements to some facilities will be required in order to meet the tertiary standard effluent requirement. Recent evidence that effluent used for land irrigation can disc harge into the marine environment highligh ts the importance of all sewage facilities producing high quality efiluent, and for the phasing-out of septic systems.

Further negotiation regarding upgrading of septic tank facilities and encouraging efiluent reuse should further reduce the impac ts and improve the management of sewage inp uts into the GBRWHA. Coastal sewage facilities also have the potential to impact on the inshore areas of the GBRWHA . The prelimina1y review undertaken b y GBRMP A indicates that further investigation and negotiation of the upgrading of these facilities is required.

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Discharges from Marine Ouifalls into the Great WATER AUGUST 2 002

47


WASTEWATER

The Authors Jane Waterhou se is a Proje ct Manager in the Water Quality & Coastal D evelopment Group at GBRMPA and has been involved in the review and managem ent of sewage in the GBRMP and GBRWHA since 1998. Johanna Johnson is also a Proj ect Manage r in the Group and at the time of this review was in the Environmental Impact Management Group involved in the assessm ent of sewage discharges into th GBRMP. Great B arr i e r R eef Marine Park Authority, PO Box 1379, Townsville, Queensland , 4810 , Australia, j.johnson@ gbrmpa.gov.a u or j .waterhous e@ gbrmpa .gov.a u

References Anderlinj, V.V . and Wear, R. 1992. The effec t of sewage and namral seaso nal disturbances on benthi c macrofaunal communities in Fitzroy Bay, Welli ngton , New Zealand . Marin e Pollutio11 B11lleti11 24 (1), 21-26. Banner, A.H. 1974. Kanoehe Bay, Hawaii: Urban pollution and a coral reef ecosystem. In Proceedi11gs of the Seco11d l11 tematio11al Coral R eef Syniposi11111 , Brisbane, 2, 685-702 . Bickford, G.P. 1996. T he effects of sewage organic matter on bio geoc he1nica l processes

wi thin nud-shelf sediments offshore Sydney, Australia. Mari 11e Poll11tio11 B11lleti11 33(7-12), 168-175. Brome, J. 1995. Management of sewage ruscharges in the Great Barrier R eef M arine Park. The Sixth Pacific Congress on Marine Science and T ec hnology, PACON 1994, pp 457-465. Brown, D.A. , Bay, S.M., Greenstein, DJ. , Szalay, P., Herswhelman, G.P., Ward, C.F., Wescott, A.M. and Cross, J. . 1987 . Muni cipal wastewater contamination in the south ern California Bight: Part 2 - Cycosoli c distribution of co ntaminants and biochenucal effects in fis h li vers. 1v!ari11e E11viro11111ent R esearch 21, 131-161. Bulthius, D.A. 1983. Effects of in sim light reducti on o n de nsity and growth of the seagrass H eterozostera tas111a11ica (M artens ex Asc hers) den H artog Wes tern Port and Port Phillip Bay, Victoria, Australi a. ] 011mal of Experi111e11tal Man·11e Biology n11d Ecology 67, 91103. Cambridge, M.L. and McComb , AJ. 1984. The loss of seagrass from Cockburn Sound, Western Austra]ja_ l. The tim e course and magnimde of seagrass decline in relation to industrial development. Aquatic Bota11y 20, 229-243. Clutter, R.J. 1971. Subtle effects of pollution on inshore tropical plankton. In FAO Fisheries R eport (No . 99) , FAO, Rome, 435-439. Dubinsky, Z . and Jokiel, P.L. 1994. R atio of energy and nutri ent fluxes regulates symbiosis

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between zooxanchallae and cora ls. Pacific Sciwce 48, 313-324. Fairwea th er, P.G. 1990. Sewage and the bi ota on seashores: assessment of impact in relation to namral visibili ty. E11viro11111wtal Mo11itori11g Assessment 14, 197-2 10. FRC Coastal R eso urce and En vironmental, 1999. Pio11eer Bay E1wiro11111wta l Nlo11 itori11g Progra111. Third Mo11irori11g E11e111, May, 1999. R eport to the Whitsunday Slure Co un cil. Gallagher, M.R. , Volker, R.E. and M enzies, N.W. (1999). um erical studi es of ru trogen fl ows under effiu end rrigated lawns on island in th e Great Barrier R eef. CR R eef R esearch T ec hnj cal Report (submitted for publication). Gray, L.A. 1996. M etal concanunati on of sed iments associated with deepwater ocean sewage outfalls, Sydney, Australia. Mari11e Pollution B111/eti11 33(7-12), 182-189. Grigg, R.W. 1994. Effects of sewage discharge, fishing pressure and habitat complericy on coral ecosystems and reef fi shes in Hawai i. Mari11e Ecology Progress Series 103, 25-34. Hall,J.A., Frid, C.L.J. and Gill, M .E. 1997 . The respo nse of esmarine fi sh and benches to an in creasing discharge of sewage effiu enc. Mari11e Poll11tio11 B11lleti11 34(11 ), 527-532. H arris, G. 1995. Eutropru cation - Are Australian waters different from those overseas? ftVarer May/June, 9-12. Hose, J.E ., Cross, J. N ., Smith , S.G. and Diehl, D. 1989. R eprodu ctive impairment in fi sh inh abiting coastal environment of so uth ern California. E11 viro11111r11tal Poll11 tio11 57, 139148. Kemp, W.M., Boynton , W.R., T will ey, R.R. , Stevenson, J. C. and Means, J. C. 1983. Th e decl ine of submerged vascular plants in upper Chesapeake Ba y: summary of resu lts co ncerrung possi ble causes . Mari11 e Tech11ical Society ] 011mal 17, 78-89 . Koop, K. , Booth, D ., Broadbent, A., Brodie, J. , Bucher, D. , Capone, D. , Coll, ]. , D ennison, W. , Erdmann, M ., Harrison, P. , HoeghGuldberg, 0 ., Hutchings, P. A., Jones, G. B. , Larkum, A. W. D. , O 'Neil, J., Steven, A., T entori, E., Ward, S., Willi amso n, J. and Yellowlees, D. (2000). ENCORE: The effect of nutrient enri chment on cora l reefs. Synthesis of results and conclusions. Marin e Pol/11tion B11lleti11 42 (2), 91-120. Krogh, M. and Scanes, P. 1996. Organochlorine co mpound and trace metal co ntanunants in fish nea r Sydney's ocean outfalls. Nlarine Poll11tion Bulleti11 33(7-12), 213-225. Lincoln-S1n ith , M.P. and Mann , R .A. 1989. Bioaccu111ulation i11 11earshore 111arin.e 01;ga nisms I. State Pollution Control Conunission, Sydney. Mann , R.A. and Ajani , P. 1991 . Con ta111i11a11ts i11 Fish. Precommissio1ung Phase R eport, Volum e 11. State Pollution Co ntrol Commission, Sydn ey. Maragos, J.E., Evans, C. and Holtus, P. 1985. R eef corals in Kano ehe Bay six years after termination of sewage discharges . In Proceedings of the Fifth International Coral R eef Sy111posiu111, T aruti, French, Polynesia , 577582 . M cLean, C., Miskiwicz, A.G. and Roberts, E.A. 199 1. Effect of three primary treatment sewage outfalls on metal concentrations in the fish Cheilodactylus fu scus collected along the coast of Sydney, Australia. Marine Pollution Bulletin 22 (3), 134-140.


WASTEWATER

N everauska , V.P. 1987 . M onitorin g seagrass beds around a sewage sludge outfall in South Au stralia. Marin e Polh1 tio11 Bulleti11 18, 158164. Orth, R.J. and M oore, K.A. 1983 . C hesapea ke Bay, an unprecedented decline in submerged aq uati c vegetati on. Scie11ce 222, 51-53. Otway, N .M. 1995. Assess ing im pacts of deepwacer sewage disposal: A case study from ew South W ales, Australia. Mari11e Pol/,1tio11 B11/leri11 31(4-12), 347-354. Pearso n, T.H. and Rose nburg, R. 1978 . Ma cro benchi s successio n in relati on co organi c enrichment and pollution of th e marine environm ent. Ocea11ograp/,ic JVfori11 e Biology A111111al R eview 16, 229-31 1. Pu ffer, H .W ., Azen, S. P. and Duda , M.J. 1982. Sportfishing activity and ca tches in polluted coasta l regions of metropoli tan Los Angeles. Nor//, A111erica11 j o11r11al ef Fis/, Ma 11age111ent 1, 74-79. Sca nes, P. 1992. Inshore bioaccumulacion studies along th e Sydney coast. In Proceedi11gs of a Bioacw11111latio11 vVorks/, op. Assess111e111 of rhe Disrribll(io11, Impacrs a11d Bioacw1111-tlatio11 of Co11ta111i11a11ts i11 Aq11atic E11viro11111e11ts, ed. A.G. Miski ewicz, pp .81-92. Sca nes, P. 1996. 'Oyster Watch': Mon ito ring trace metal and orga noc hlorine concentrations in Sydney's coastal waters. Mari11e Pol/111io11 Bulletin 33(7-12), 226-238. Sho rt, F.T. , Burdi ck, D.M ., Granger, S. and

N ixo n, S.W. 1996 . Long-term decline in eelgrass, Zostera 111ari11a L., linked to increased housin g developm ent. In Seagrass Biology: Proceedi11gs of a11 illtematio11al Works/, op, eds J. Kuo, R .C . Phillips, D. I. Walker and H . Kirkman , pp. 29 1-298 . J anuary 25-29ch 1996, R ottn est Island Western Australia. Smith, K.L. , Rowe , G.T. and ichols, J.A. 1973. Benchic community respirati o n near Woods H ole sewage outfall . Est11ari11e Coasral Shelf Sciwce 1, 65-70. Snu th , S. D. A. 1996. Th e effects of domesti c sewage eilluent on marine co mmuniti es at Coffs H arbour, ew Saud, W ales, Australia. Mari11 e Pollurio11 B11/leti11 33(7-12), 309-316. Smith, S.D.A. and Simpso n, R.D. 1992. M onitoring the shallow subliccoral using the fa una of kelp (Eck lo11ia radiata) holdfas cs. Mari11 e Pol/11tio11 Bulleti11 24, 46-62 . Snuch, S.V., Kinunerer, W.J. , Laws, E.A., Brock, R .E . and Walsh, T.W . 1981. Kaneo he Bay sewage diversion expeiiment: Perspectives on ecosystem response co nutritional perturbati on . Pacific Scie,,ce 35, 279-395. Scambler, N. , Popp er, N ., Dubi nsky, Z. and Stimson , J. 1991. Effe cts of nutrient enri chment and water moti on on th e coral Pocillopora da111icor11is. Pacific Scie11ce 45 (3), 299307. Steven, A.D. and van Woesik, R . 1990. A M11ltidiscipli11ary Exa,11inatio11 of the Hay111a11 lsla11d Fl'i11gi11g R eef: I1ifl11e11ce of a Seco11dary Se1vage

Disc/, arge. R eport co th e Great Barri er R eef Marine Park Authority, Townsvill e. Stim so n, J. 1992 . Th e effect of amm on ium addition in coral growth rate. In Proceedi11gs of rhe 7t/, Intematio11al Coral R eef y111posi11111 , C11a111 1, 380. Udy, J.W. and D e111uson, W.C. 1997a. Growth and physiological responses of three seagrass species co eleva ted sediment nutrients in Moreton Bay, Auscralia. J o11r11al ef Experimewal Mari11e Biology a,1d Ecology 27, 253-277. Ud y, J.W. and D enni so n, W. C . 1997 6. Ph ysiologica l responses of seagrasses used co iden ti fy anthropoge ni c nutri ent inputs. Mari11 e a11d Freshwater Research 48, 605-614. Udy, J.W., D e111uso n, W .C., Lee Long, W .J. and McKenzie, L.J. 1999. R esponses of seagcass co nuni ents in the Grea t Barri er R eef Au strali a. Marin e Ecology Progress Seri es 185, 257-271. van Woesik, R. 1989. A Preli111i11a,y Exa111i11ario11 of the Sedi111e11.tology, R eef G rowth a11d H ydrograph y of Cree11 lsla11d. Report co th e Grea t Barrier R eef Marine Park Authority, Townsville. W ard , S. 1997. T he effe cts of elevated tutrogen and phosphorus on the reprodu ction of three species of acro porid reef corals. PhD Th es is, Southern Cross Uni ve rsity. Walker, D. I. and M cCo mb , A.J. 1992. Seagrass degradation in Australi an coastal waters. Mari11 e Pol/11tio11 B11/leti11 25(5- 8), 191-1 95 .

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ENVIRONMENT

THERMOTOLERANT COLIFORM BLOOMS: WHAT IS THEIR SIGNIFICANCE? D Page, R Leeming, I Lawrence, C Magyar, 0 B Horsburgh, T P Sritharan Abstract During March-April 2001, Lake Burley Griffin, ACT experienced an environmental " bloom" of thermotolerant coliforms (50,000 - 380,000 cfu/ 100 ml) . The bloom was caused by the extensive and rapid in-lake growth of thermotolerant coliforms, associated with the breakdown of plant (algae or macro-plants) material. The collapse in plant biomass was triggered by a combination of a drop in temperature (Autumn) and storm inflows contributing high turbidity to the lake. Monitoring ofbiomarker (faecal sterols) and conve ntional water quality indicators implied that faecal origins were most unlikely . However, the exceedance of Guideline levels necessitated the closure of all recreational activities within the lake. This highlights the importance of establi shing a risk-based assessment protocol; w herein if agreed guideline levels are exceeded, this triggers an assessment of the source (health risk) of thermotolerant coliform (environment or human faecal origin) sources, rather than an immediate assumption of a threat to human safety.

Introduction Bacteria are natural components of all ecosystems, including fresh and marine waters. Most are involved in the breakdown of organic matter and pose no threat to health . Howeve r, on occasions, pathogenic forms do enter the water systems. In March and April 2001 an unusually high thermotolerant coliform co unt was observed during routine monitoring of Lake Burley Griffin in Canberra (Figure 1).

Figure 1. Lake Burley Griffin , Canberra, ACT.

Although high coliform numbers are traditionally associated with faecal contamination of waters, this is not always the case, as this article will illustrate. Previously there have been instances of "blooms" of faecal and total coliforms in reservoirs in NSW (Mackay and Ridley 1983, Lawrence 2001). Because of high coliform counts in Lake Burley Griffin, the National Capital Authority closed the lake to all forms of recreation and commissioned ECOWISE Environmental Pty. Ltd. to conduct additional event sampling to characterise the observed thermotolerant coliform bloom. In addition to higher frequency of sampling, more depth samples were taken in order to better represent the bacterial distribution through the wa ter co lumn . T h e sampling program additionally aimed at:

Table 1. Nutrient concentrations in Lake Burley Griffin . Site West Lake Scrivener Dam East Basin Central Basin

50

1993-2000 Ammonia (mg/L)

2001 Ammonia (mg/L)

1993-2000 0rtho P (mg/L)

2001 0rtho P (mg/L)

0 .03 0 .03 0.03 0.03

0 .03 0.03 0.03 0.06

0 .007 0.007 0.007 0.008

0.005 0.003 0.003 0.007

WATER AUGUST 2002

• Monitoring further changes in water quality; • Determining w hen the lake co uld be reopened to recreational use; • Determining the cause of the bloom. In this article, the results of the incident and the lessons that can be learned are highlighted.

Methods for observing and counting bacteria Lake Burley Griffin sampling is undertaken by boat, with routine samples being collected with a tube sampler, 5 metres in depth, w h ere depth was sufficient. Additional event samples were collected 0.3 m below the water surface by grab sampling. All samples were stored on ice during transport to the laboratory and analysed in a NATA accredited laboratory according to the APHA Standard Methods fo r the Analysis of Water and Wastewater, 20th edition. The lake is routinely monitored during the summer season at 4 si~es located near the centre of the each of the main sections of the lake at East Basin, Central Basin, West Lake and Scrivener Dam (Figure 1) . Samples were collected monthly from October to May. Water quality was assessed for a range of parameters, the


ENVIRONMENT

annual averages of nutrients being listed in Table 1. It is important to note that lake nutrient levels were similar in 200 1 to the previous seven years. Furthermore, there was a substantial decrease in some parameters (not shown), particularly oxidised nitro ge n and chlorophyll a. Event sampling for thermotolerant coliforms in the lake commenced on 20th March fo llowing the discovery of a sudden increase of these bacteria and continued until the bloom subsided in April. The decline of the thennotolerant coliform levels at the four monitored lake sites is s_how n in Figure 2 . The peak in the lake monitoring (Figure 2) on the 20th of March coincided wi th a peak in B each Watch sampling (Figure 3) . Both samples collected at the lake sites and at the beaches confirmed the presence of high thermotolerant coliform co unts throughout the Lake. The thermotolerant coliform co unts ranged from 380,000 cfu / 100 ml in East Basin, to 50,000 cfu / 100 ml in West Lake. The Beach wa tch program also revealed counts from 370,000 cfu / 100 ml at the East Basin site to 340,000 cfu / 100 ml at Black Mountain Beach In addition , samples we re analysed for the presence of Salmonella and Naegleria fowlerei; howeve r, on all occasions the results were negative . In contrast, a sample coll ected on the 21st March from the principal inlet to Lake Burley Griffin, the Molonglo Ri ver at Dairy Flat Road bridge, had thermotolerant coliforms counts of5 cfu / 100 ml , w ith the Ammonia at 0.01 m g/ L. both of w hich are wi thin the normal range exp erienced in the lake On the subse qu ent sampling run condu cted on the 23rd of March, analysis for Enterococci was also performed at the beach wa tch sites . The proportion of Enterococci contributing to th e total thermotolerant coliforms va ried from <0 .2% at Blac k Mountain Beach to 14% at Lotus Bay - West Basin . Continu ed sampling revealed the ratios of 1-2%, apart from Lotus Bay site w hich was 10%. Enterococci analysis was performed to give an indication of the potential contribution from sewage sources to the bloom. Anm10111a levels for samples taken from lake sites on the 20th March we re betwee n 0.01 - 0.04 m g/ I; within th e normal range (Table 1). The similarity of these results w ith previous yea rs indicated that it w as unlikely that the bloom was du e directly to a sewage leakage. On the 27th March an extensive sampling run was undertaken to inves-

1000000 East Lake

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5 10

20-Mar

25-Mar

04-Apr

30 -Mar

Figure 2. Thermoto lerant co liform leve ls at lake monitoring sites.

tigate potential point sources of faecal contamination to the lake. Samples were collected from 25 sites, and the results are listed in Table 2. The results presented in T able 2 we re as anticipated, howeve r, it is interesting to note the higher co unts of thermotolerant coliforms reported for som e of the stormwa ter sites . Samples were continually taken from the seven Beach Watch sites daily and the counts reduced dramatically, as show n in Figure 3. By the 26th of M arch the levels of thermotolerant coliforms we re back to background levels. In o ther studies the survival of thermo tolerant coliforms was found to have a 90% die off after 48 hours (Gabutti et al. 2000) which is consistent with the results of this inves tiga tion .

Faecal Sterols To furth er charac terise the source of the bloom, wa ter samples were analysed

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for faecal sterols The sterol of primary interest is coprostanol, w hich is a chenucal indicator of fa ecal pollution (Leeming 2000) . Coprostanol (5 ~-cholestan-3 ~ol) is the predominant sterol in a family of " fa ecal sterols" and is derived from cholesterol in the intestines of humans and a variety of other animals by microbial transformation . Faecal con ce ntrations depend on the source, diet and other environmental fa ctors. Coprostanol is always present in adult human faeces. A representative chromatogram is give n in Figure 4. Only one sample (Black Mountain B eac h) sho we d any sign at all of unambiguo us human faecal contamination. The other samples contained only traces of coprostanol in the wa ter column w hich could not be unambiguou sly determined as being derived from human or h erbi vo re faeca l co ntamination . However, the percentages of cholesterol,

Black Mountain Beach wHton P1rk · Weal •Wuton Park , eu, ·Varralum la Beach

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26-Mar

31 -Mar

Figure 3. Decline in thermotolerant co liform leve ls at beach mon itoring sites . WATER AUGUST 2002

51


ENVIRONMENT

Table 2. Nutrients and thermotolerant co liform counts at se lected sites of Lake Burley Griffin.

Discussion

The decisio n rules used by the regulator fo r closure of Lake Burley Site Site Description: Ammonia Ortho P Thermotolerant G riffin to body contact and recre(mg/L ) Number (mg/L) coliforms ation are ba sed solely on the (cfu/100 ml) thermotolerant co li form counts Molonglo River 0.01 < 0.01 1 36 exceeding the ANZECC guidelines East Basin 0 .05 < 0.01 2 2100 m edian valu e of 150 cfu / 100 ml. H ence in the absence of more Jerrabomberra Creek · Upstream of the lake 0.01 < 0.01 3 590 comprehensive decision rul es to Jerra bomberra Creek· Hind marsh Drive 4 0.02 0.01 27 assess th e tru e risks, includin g Kingston Boat Harbour 5 < 0.01 0.01 2000 assess m e nt o f e n vir o nm e nt al Bowen Park Stormwater Inlet 0.02 0.03 6 730 co mp o ne nts su ch as " in- lake 7 East Basin 0 .06 < 0.01 2300 gr o w th of ch e rm o t o l e r a nt Centra l Basin 0 .08 0.01 8 1100 coliforms", there w as little choice Nare llan Ponds 0.03 < 0.01 9 590 for the regulator but to close the Ferry Terminal 10 0.05 < 0.01 1000 lake to body contact recreational use (Law rence 2001). Acton Peninsula · East 0.04 0.01 11 960 Acton Peninsula · Point The revised Australian and N ew 12 0.03 < 0.01 1300 Zealand Guidelines fo r Fresh and 13 Acton Peninsula · West 0.01 < 0.01 940 Marine W ater Quali ty (2000) have 14 Lotus Bay Stormwater Inlet 0.02 < 0 .01 2200 moved away from this approach by West Lake 0 .02 < 0 .01 15 1100 adopting trigge r valu es, above Yarralumla Beach 0.01 < 0.01 16 1300 w hich there is a requirement of risk 17 Yarralumla Bay · Eastern 0.02 < 0.01 1300 assess m ent appropri ate to th e Yarralum la Bay · Main 0.02 < 0.01 18 1300 particular hazard . Similarly, the Western Park Beach East 0.04 19 < 0.01 2000 World H ealth Organisation, Draft Western Park Beach West 0.02 < 0.01 20 510 guidelines fo r safe recrea tio nalwa ter en viro nments: Coastal and 21 Yarramundi Reach 0.02 < 0.01 480 freshwaters (1998) guidelin es adopt 22 Scrivener Dam 0.04 < 0.01 840 a stron g " risk" based approach and 23 Sullivans Creek < 0 .01 < 0.01 690 require sa nitary surveys as an Molonglo River 24 < 0.01 0.02 100 a djun c t t o ba c t e ri o l og i c a l 25 Jerrabomberra Creek · Canberra Ave < 0.01 < 0.01 270 monito ring. They stress the importance o f assess ing the source of polluti o n in interpreting th e public campesterol , stigmasterol and 24- ethylprime ca use of elevated thermotolerant health risk significa nce of the bac terial cholesterol in the w ater column are most coliforms and w ith the absence of 5~indicator numbers. It is acknowledged that similar to the fa ecal sterol profile derived stanols like coprostanol, this points to birds bac terial indicators refl ect a mix o f fro m fresh wa ter fo wl faeces (Leeming being a prime so urce of faeca l contam.ipathogenic and no n- patho geni c bacteria na tio n (Leeming 2000) . 2000). Bird life around th e lake can be a fro m sewage, recreational activities, industri al discha rges, urban drainage and stock 116.33 and w ildlife sources . , Previously, Mackay and Ridley (1983) had noted that blo oms had occurred in both high rainfall and low rainfall periods, but te nded to follo w spring and summer " rains. They considered that relati vely high turbidity w as a fa ctor in the development of blooms. 37.52 51.82 High bac te rial co unts have been related occasio nall y to an increase of 41.67 turbidity fr o m a sto rm (EC OWISE u 48,43 44,20 E nvironmental , unpublished data) . This 48.43 " turbidi ty, w hich pro vides an input of 40,20 nutrients and ocher pollu cants adsorb ed 38.13 o nto the particl es , also pro tects th e bacteria and aids in prolonging their life. , 40 the eve nt presently under discussio n In " Tlmo(mlnute.) this was also likely to be the case . During this period there were significa nt daily Figure 4. Chromatogram of Lake Burley Griffin East Basin sample showing th e ra in falls o n the 5th February (5 5.4 mm) absence of coprostanol. The marked sterols have a similar profile to bird faeces with a predominance of cho lestero l compared to 24-ethylchol estero l (coprostano l is and the 17th M arch (22 .4 111111) 111 an the minor blip at 42.48 minutes) . oth erw ise low rainfall peri od.

.

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.

52

WATER AUGUST 2002

.


ENVIRONMENT

Lake Burley Griffin

T h e prec ursor of th e " b loom " fo ll owe d th e fo ll owin g tim elin e : Fo ll o w ing th e storm disch arge o n Februaty 5th aquatic macrophytes died off as a result of temperature drop or increase in turbidi ty w ith associated light limiting conditi ons, resulting in the release of nutri ents and dissolved organic m atter w hich suppo rted gro wth of therm otolerant coli fo rms. Lake turnover appears to have occurred in the period between 28th o f Fe bru ary and 2 0th o f M arc h . Furthermore, the storage of harves ted aquatic m ac rop hytes piled up on the foreshore, awaiting collection for disposal to landfill, have the potential to contribute leachates high in both nutrients and dissolved o rganic matter. Finally, the storm events on the 17th of M arc h p ro du ced m o re disc harges hi gh in suspended solids, nutrients and o rga nic matter to further compound the problem . The faecal sterol results indica te that the thermotolerant coliforms were no t of hu man origin , and therefore not an indicator of discharge of hu m an fa ecal material. (If the so urce of the faecal bac teria had been sewage , then it wo uld require the to tal Canberra sewage o utpu t fo r a period of 30 days to be discharged to the lake in one day to reac h the observed bacterial counts of 330,000 cfu/100 ml). T he wa ter qu ality data coll ec ted indicates th at the likely ca use of the high thermotolerant colifo rm levels was du e to in-lake bacterial grow th . T he real risks to human health fro m this level of colifo rm contaminatio n are fa r fr om cl ea r. W hen the source of the bac teria is principally fro m birds, then the risks to human health

from prima1y contac t are unclear and should be investigated for parts of the lake zoned for that purpose . T his in-lake thermo tolerant coliform grow th indicates the need to develop supplem enta ry protocols that incorporate

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the possibili ty of oth er enviro nmental fac tors as sources of elevated thermotolerant coliforms into the risk assessment of faecal pollutio n . The measurements o f thermotoleran t coli fo rms cove rs a broad range of o rganisms including non-fa ecal coliforms such as Klebsiella, a ubiquitous environmental bacterium (Ashbolt et al. 1997) w hich wo uld be potentially large contributo rs to the observed bloom. When the primary -source cannot be clearly identified, then the issues of naturally occurring blooms of faecal bacteria need to be furth er assessed. Furthermore, w hen normal mammalian gut coliforms are fou nd to be identical to environmental strains of bacteria then their applicabi li ty as a su itable indi ca tor organism com es into question. W at e r qu ali ty assess m e nt u sin g indica to r o rga nisms is based on the premise that they die off in so m e predictable way afte r exposure to the environment. In some instances, this is not the case, w orse still, if they can multiply outside their normal environment, then some reassessm ent of the basic assumptions are required . On the other hand if these bacteria differ from the normal fa ecal

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Water Recycling Asset Management Water & Wastewater Technology Catchment Management Risk Management Infrastructure Planning Strategic Partnership

200 Offices Worldwide Australia Asia Pacific Head Office 71 Queens Road Melbourne + 61385179200 www.earthtech .com

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WATER AUGUST 2002

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ENVIRONMENT

bacteria and do not behave like the indicator organisms then current decisionmaking rules for beach closure require revaluation. Finally, it sho uld be noted that in view of the significant delay between sampling and confirmed analysis of bacterial counts, bacteriological monitoring in isolation is not a p rac tical basis for day-to-day m ana ge m e nt of he alth prot ec tion (Lawrence 2001).

Conclusions The use ofthem1otolerant coliforms on its own for decision-making is insufficient; regul ators should look to a risk- based approach for manage ment of water quality. The difficulty of this situation for any regulator managing an urban lake is not the risk to health from faecal bacteria of environmental origin, but rather the possibility of mas king a ge nuine faecal pollution discharge. Other indicators, such as ammonia , alternate bacterial indica tors and faecal sterols are considered important in making an informed judgement of the true risks to public health. P ublic health protection for recreational contact is best based on m anagem ent measures such as locatio ns of swimming areas m zo nes rarely exposed to high thermo tolerant co li form numbers, the pro vision and

ma intenan ce of effec tiv e sewe ra ge co ll ec tion and removal facilities, and the notification requirements in respect to accidental spills or overflows . T he monitoring provides an indication of the adequacy of these management meas ures.

Acknowledgements The autho rs thank Dr. Btian Labza of the D epartment of Human Services, Victoria, and Dr. Melita Stevens of M e l bo u rne Wat e r for rev iewing t h e pap e r and valuable comm ents .

References Ashbolt NJ, M R Dorsch, PT Cox and B Banens (1997). Blooming E. coli, w hat do they mean? In: Coliform.s and E. coli, Problem or Solution . (Eds Kay D . and Fricker C.) T he Royal Society of C hemist1y, Cambridge, pp 78-85. ECOWISE Environmental Pcy Ltd (Scientific), Special R eport Lake Burley Griffin , April 2001. Gab utti G., De D onno A. , Bagordo F. and Montagna MT (2000) Co mparative survival of faecal coli forms and hum.an con tami nants

CYTEC

Technology A head of its TimeÂŽ

TECHNICAL SALES REPRESENTATIVE WATER TREATMENT CHEM ICALS Sydney or Melbourne based Home office operation Specialist in water and wastewater treatment te chnologies Cytec Australia Holdings Pty Ltd , a leading global supplier of specialty chemicals to a number of industries , is seeking a successful Technical Sales Representative within our Water Treatment segment. Taking ownership of thi s national business , your responsibil ities will include managing the existing client base as well as identifying and devel oping new business opportunities and areas of growth for the business throughout Australia and New Zealand . The Water Treatment Product portfolio includes flocculants , coagulants and related products. Ideally you will have a successful track record of performance in key account sales as well as Tertiary Qualifications in Chemistry or related disciplines. Specialist industry knowledge in industrial wastewater treatment technology such as liquid-solids separation, process water treatment and municipal waste is essential. As you will be required to build effective working re lationships both internally and with customers and rese llers, strong interpersonal skills are critical. Operating from a fully equipped home office, you will be provided with a generous base salary, participation in a performance based incentive scheme, fully maintained company vehicle and the opportuni ty for furt her training and development, including exposure to global operations. A great opportunity to make your mark within this specia list field . To indicate your interest forward your resume to: Human Resources Manager Cytec Australia Holdings Pty Ltd PO Box 7125 Baulkham Hills NSW 2153 Fax: 02 9659 9776 Emai l: kristine_mcmurray@as.cytec.com

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WATER AUG UST 2 002

and the use of Sraphy/oca,s a11re11s as an effective indi cator of human J:lOllution, Marin e Pol/11tio11 Bulleti11 , 40, 8, p697-700. Lawrence L (2001) R eview of reported faecal pollution of Lake Burley Griffin: R eport to the National Cap ital Authority. Lee min g R . (2000) A guide to the ana lysis of faeca l biomarkers vl. 0, R eport prepared for CRCWQ&T Project 2.2 . 1 Ma11age111ent of Pathogens i11 Source vVaters. Mackay S J & Ridl ey J P (1983) Survival and growth of Escherichia coli in Lake Burragorang, Tech11ical Papers, A11stralia11 Water & lillaste111ater A ssociatio11 Twrh Federal Co11vell(io11, 46- 1 46-12. Worl d H ealth Organisation, Draft guidelines for safe recreational- water environments: Coastal and fres hwaters 1998.

The Authors Dr Declan Page is the principal scientist, Barry Horsburgh and Carl Magyar are the chemistry business and chem istry IT managers respectively at ECOWISE Environmental Pty. Ltd . Dr. Rhys Leeming is an environmental scientist with the CSIRO Division of Marine R esearch. Ian Lawrence is a program lea der at the Coo p erative R esearch Centre for Freshwater Ecology. Thamotheram Pillai Sritharan is a senior project officer with the National Capital Estate, N ational Capital Authority. C ontac t d e tails: Dr. D ec lan Page, ECOWISE Environmental Pty . Ltd. 16a Lithgow St., (PO Box 1834) Fyshwick, ACT 2609 . T el: 02-62707650 Fax: 0262707631 E-mail: dpa ge@ec o w ise . com.au

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Water Journal August 2002  

Water Journal August 2002