awmc wr challenges-1

8/8/2019 Awmc Wr Challenges-1

1/36

The Challenges of Water RecyclingTechnical and Environmental Horizons

January 2007

Compiled byJeff Foley

Damien BatstoneJurg Keller

Advanced Wastewater Management CentreThe University of Queensland

Brisbane QLD 4072Australia

www.awmc.uq.edu.au

Advanced WastewaterManagement Centre


2/36


3/36

iiiWater Recycling in AustraliaAWMC Position Paper

5. Examples of Water Recycling Schemes 29

6. Conclusions and Comments 32 7. References 33

Table IndexTable 1 Annual Water Reuse by State in 2004/05 5

Table 2 Potential Risks Associated with Using Recycled Water 6

Table 3 On-line Water Quality Measures 13

Table 4 Indicative Log Removal of Viruses by Various Treatments 15

Table 5 International Water Recycling Schemes 29 Table 6 Australian Water Recycling Schemes 30

Figure IndexFigure 1 Average Annual Rainfall in Australia 1

Figure 2 Rainfall Deficiency 2005/06 2

Figure 3 Inflows to Perth Surface Water Dams 3

Figure 4 Urban Water Use in Australias 22 Largest Cities 4

Figure 6 Generalised Wastewater Treatment Processes forEffluent Reuse 9

Figure 7 Distribution of Particles Size and Application of MembraneTechnologies 10


4/36

1Water Recycling in AustraliaAWMC Position Paper

1. Introduction

1.1 The Drivers for Water Recycling

Australia is a wet country. Even in the drought-affected years of 2004/05, our continentreceived 2,789,424 gigalitres (GL) of rainfall enough to fill Sydney Harbour almost 5,000times 1 (Trewin, 2006). With only a relatively small population of 20 million people, we receivedenough rainfall to be able to provide each person with approximately 130 megalitres (ML) ofwater for the year.

Unfortunately, Australias rainfall is not distributed evenly spatially or temporally and theextent of run-off into our rivers and lakes is pitiful. In 2004/05 only 8.7% of rainfall made it intoour surface water bodies (Trewin, 2006). As Figure 1 shows, most of Australias rainfall and

runoff occurs in the sparely populated drainage divisions of Australias north-east coast, theGulf of Carpentaria and the Timor Sea. Our major population centres of south-eastQueensland, greater Sydney, greater Melbourne, Adelaide and Perth sit precariously on theedge of good rainfall zones. In our major agricultural production zone of the Murray-DarlingBasin, only 6.2% of rainfall is collected as run-off (Radcliffe, 2004).

Figure 1 Average Annual Rainfall in Australia

The variability of Australias climate is well-known and oft-lamented. In times past, thisvariability has been combated by the provision of large water storages for our populationcentres. This has led to Australia having the highest level of water storage capacity per capitain the world (4 ML per person) (DAFF, 2004). It has also meant that we have been able tolead a relatively water-unconstrained lifestyle for many generations. In fact, Australia has the

1 A survey of Port Jackson in 2004 by the NSW Marine Authority estimated the volume at high tide to be 562,000 ML.


5/36


3rd highest per capita consumption of water amongst OECD countries, after Canada and theUnited States (Radcliffe, 2004). Despite this abundance of storage infrastructure, we are all

well aware of the water shortages facing most cities and regional centres across Australia. Asof June 2005, Australias 501 largest dams were only at an average of 47% of capacity(Trewin, 2006), with storages in some centres being much lower. At the end of November2006, the dam storage levels in Australias major cities were:

Brisbane 24.9%; Sydney 38.6%;

Adelaide 57.0%; Melbourne 41.7%;

Perth 29.5%; Canberra 42.6%; and

Darwin approx. 85%; Hobart 91%.

(Water Services Association of Australia, 2006)

In recent times, the coalescence of many different pressures population growth, increasingurbanisation, drought, reduced run-off has placed major strains on these existing waterstorages. Figure 2 below shows how severely the drought has impacted our major populationcentres of south-east Queensland, southern Australia and the south-west coast of WesternAustralia. In Perth, the trend in surface water inflows has dropped so alarmingly over the pastcentury (Figure 3), that the dams nestled in the Darling Scarp now only collect one-third of theflows from earlier in the century (Cadee, 2006).

Figure 2 Rainfall Deficiency 2005/06


6/36


Figure 3 Inflows to Perth Surface Water Dams

Political opportunism in many jurisdictions over the decades has also colluded to minimise theextent of investment in meeting these growing water supply demands. This combination offactors has now pushed the water issue firmly into the political spotlight. It is within thisenviro-socio-political climate that water recycling has emerged as one of the potentialsolutions for long-term sustainable water supply.

1.2 The Uses, Reasons and Risks of Recycling Water

Historically, all of the water supplied through an urban water scheme has been of potable ordrinking quality. This classic case of conservative engineering design has been an enormouspublic health success. Clearly though, not all water uses require this very high standard ofwater quality. Therefore, there are two broad areas in which recycled water can be applied toprovide a net saving in water consumption:

Substitution for potable water in applications that do not require potable water quality i.e.irrigation, sports ovals, horticultural fields, dust suppression, toilet flushing etc.; and

Treatment and recycling back into the potable water supply either directly or indirectly.

It is the first of these areas non-potable reuse that has already been exploited most widelyand still holds the most potential for water savings. Figures published by the Water ServicesAssociation of Australia shows that supply to non-potable applications in commerce, industry,fire fighting and irrigation of parks and gardens accounts for 28% of all water supplied (Figure4). The largest urban water consumers are residences (59%), but of the volume of watersupplied to each house, typically 40% is used in the non-potable applications of toilet flushing,laundry and garden irrigation (Figure 4). In the final analysis, only around 1% of drinking wateris actually used for drinking (National Health and Medical Research Council and Council,

2004). Clearly, the scope for recycled water in non-potable applications is large.


7/36


Residential Water Consumption

Gardens, 20.1%

Toilet, 11.8%

Kitchen, 3.0%

Bathroom, 15.3%

Laundry, 8.9%

Urban Water Consumption

Residential, 59.1%

Industrial / Commercial, 21.2%

Meter Errors, 2.4%System Losses,10.7%

Local Govt / Parks / Fire Fighting, 6.7%

Figure 4 Urban Water Use in Australias 22 Largest Cities

(Radcliffe, 2004)

However, as water supply pressures continue to bite, the implementation of planned potablereuse is being considered more often. The recent Toowoomba public vote, the planning beingundertaken by Goulbourn City Council and the south-east Queensland plebiscite on indirectpotable reuse in March 2007, are just the most recent examples.

Whilst the water saving benefits afforded by recycling are obvious, there are also many othergood reasons for planned and unplanned reuse (National Coordinator for Recycled WaterDevelopment in Horticulture, 2005):

Reduce nutrient and contaminant loads to waterways;

Recovery/recycling of nutrients back to agricultural land, and minimisation of chemicalfertilisers;

Reduce stress on groundwater aquifers and surface water catchments;

Provide an additional water source for fire fighting;

Provide environmental flows and wetlands maintenance; and Improve water supply security for both potable and non-potable uses.

With so many benefits, it is not surprising that water recycling is already widely practised inAustralia. In 2004/05, we recycled a total of 424,615 ML of water, with 49% of this being donein the urban environment (Trewin, 2006). Many small towns throughout Australia alreadyrecycle 100% of their wastewater (National Coordinator for Recycled Water Development inHorticulture, 2005). In many cases, this is unplanned, with the wastewater discharge from onetown being a significant percentage of the water supply source for the next town downstream.An excellent example of this is the Lower Molonglo Water Quality Control Centre in Canberra,which discharges to the Molonglo River, then the Murrumbidgee River and Burrinjuck Dam. At


8/36


times, this tertiary treated wastewater from Canberra provides up to 100% of river flow(National Coordinator for Recycled Water Development in Horticulture, 2005).

Table 1 Annual Water Reuse by State in 2004/05

Region Wastewater (ML/yr) Reuse (ML/yr) % Reuse

Qld 309,558 51,582 16.7

NSW 633,516 193,866 30.6

ACT 27,293 2,189 8.0

Vic 384,992 130,574 33.9

Tas 57,603 4,858 8.4SA 84,315 22,186 26.3

WA 124,054 17,508 14.1

NT 12,903 1,852 14.4

Australia 1,634,234 424,615 26.0

(Trewin, 2006)

The use of recycled water, whether planned or unplanned, poses many risks. Hence, waterauthorities have long recognised that any strategy that brings recycled water closer to directhuman contact must be designed to assure public health (Radcliffe, 2004). Table 2 highlightssome the risks that must be managed in a recycled water scheme. Some of these risks arealso associated with traditional potable water delivery, but it is fair to say that the frequency ofexposure is likely to be increased with the use of recycled water. Recognising and managingthese risks is critical to the successful implementation of recycled water schemes.

This paper does not aim to discuss each of these risks specifically. The reader is referred tothe abovementioned references for further details.

Recognising the added risks associated with water recycling, it is clear that the future

sustainable supply of water to our ever growing urban centres will require recycled water tobe an intentional part of our water supply mix. Whilst there do exist many other options forexpanding the base of water sources new dams, groundwater, desalination, urbanstormwater harvesting, trading of agricultural water entitlements water recycling will be apart of the mix, well before the arrival of Armageddon.

Furthermore, whilst water recycling can take many forms, this paper focuses mainly on theissues associated with the recycling of domestic wastewater (i.e. sewage, greywater,blackwater) for reuse in potable and non-potable applications at any scale.


9/36


Table 2 Potential Risks Associated with Using Recycled Water

PathogenRisks

PhysicalRisks

ChemicalRisks

RadiologicalRisks

EnvironmentalRisks

Bacteria

Viruses

Protozoa

Helminths

Cyano-bacteria

Colour

Taste

Appearance

Manganese

Nitrate

Agriculturalchemicals

Chlorine

Fluoride

Traces oflead, copper

Industrialchemicals PAHs

Endocrinedisruptingcompounds

Naturallyoccurring radium,uranium

Salinity

Sodicity

Sodium

Chloride

Nitrogen

Phosphorus

ChlorineResiduals

HydraulicLoading

Boron

Surfactants

(Radcliffe, 2004), (National Coordinator for Recycled Water Development in Horticulture,

2005)

1.3 Community Support and Acceptance

The issue of community support and acceptance for water recycling schemes is perhaps oneof the biggest challenges facing its widespread implementation. There are many examples ofrecycling projects, both in Australia and overseas, that have failed due to adverse publicityand a lack of community support. The No vote in Toowoomba is only the most recentexample.

At the AWMC, we recognise that the psychology of community support for water recyclingschemes is an extremely important area of practice and research. However, we are notqualified to comment any further, except to recognise the CSIRO research (Po et al. , 2004)that indicates the following factors have a significant bearing on peoples attitudes to recycledwater use:

Disgust or a Yuck factor;

Perceptions of risk associated with using recycled water;

The specific uses of recycled water, and particularly how close the water use comes topersonal contact or ingestion;

The sources of water to be recycled;

The issue of choice;

Trust in the authorities and scientific knowledge;


10/36


Attitudes towards the environment;

Environmental justice issues;

The cost of recycled water; and

Socio-demographic factors.

1.4 Outline of Paper

In the face of urban Australias on-going plight for increased water supply security, it is clearthat the treatment of domestic wastewater for reuse in potable and non-potable applicationswill become increasingly prevalent. This paper aims to discuss only the scientific and

technical challenges involved in recycling of domestic wastewater. These issues arepresented within the context of three horizons.

In the first horizon, we review the challenges that we have already addressed as a technicalcommunity. These are the problems that have already been conquered, both in theory and inpractice.

In the second horizon, we address the problems that are currently plaguing water recyclingprojects and for which we may have the answer. These are the problems that we understandwell, that we think we have solutions for, but are yet to be properly implement in full-scalepractice.

In the third horizon, we ponder the problems for which we yet have no answer. We alsospeculate on the potential for future and dramatically different technologies from those weroutinely implement today. These are the areas of research interest.


11/36


2. Horizon One: The Problems Weve ConqueredIn this section, we briefly review the issues and technologies that are currently well-understood and well-applied in the water recycling industry. It is important to recognise herethat water recycling is not a new phenomenon. The first direct potable recycling scheme wasimplemented over 40 years ago in Windhoek, Namibia. We are currently using the 6 th or 7 th generation of water recycling technology (including about the 3 rd generation of membrane based technology). So this horizon mainly relates to those key technologies biological,adsorption and membranes that provide us with the capability of returning domesticwastewater back to pure water. We also consider the mature state of risk managementpractices for water recycling projects in Australia. And finally, we discuss two of the easierresidual products from the water recycling treatment processes solids and inorganics.

2.1 Biological Technologies

In 2004/05, Australias sewerage service providers treateda total of 1,634,234 ML of wastewater (Trewin, 2006). Atleast 75% of this wastewater is treated to a secondary ortertiary standard and hence would be suitable for sometype of water recycling application.

In Australia, every secondary and tertiary wastewatertreatment plant employs some type of biological technologyfor the removal of organics, solids and nutrients. Thetheory, design, implementation and operation of thesebiological treatment facilities is well known and wellunderstood throughout the water industry.

Examples of these well-known biological technologies are:

Lagoon systems (anaerobic, facultative, mechanicallyaerated, maturation);

Trickling filters;

Rotating Biological Contactors;

Activated sludge plants; Biological Nutrient Removal (BNR) plants:

o Modified Ludzack-Ettinger (MLE) process;

o Oxidation Ditch;

o 4-stage or 5-stage compartmentalised processes.

Notwithstanding that there are still significant active research areas in the field of biologicalwastewater treatment, we do not consider that this field presents any impediment to thedelivery of water recycling projects.

Tertiary34.1%

Secondary42.8%

Primary23.1%

No Treatment0.0%

Figure 5Wastewater Discharge by TreatmentLevel Trewin, 2006


12/36


An example of a generalised water recycling process is shown below. This figure illustratesthe central role that biological processes play in the primary, secondary and (in some cases)

tertiary treatment stages.

Figure 6 Generalised Wastewater Treatment Processes for Effluent Reuse

(Radcliffe, 2004)

2.2 Adsorption Technologies

The illustration of a generalised water recycling process in Figure 6 above shows that rolethat adsorption processes can play in the tertiary treatment stage. Granular Activated Carbon(GAC) and Biological Activated Carbon (BAC) processes are usually employed on asecondary effluent for enhanced solids, organics and metals removal.

The theory, design, implementation and operation of these units are well-known and well-understood. As such, the use of adsorption technologies does not represent any obstacle tothe implementation of water recycling projects.


13/36


2.3 Membrane Technologies

The use of membrane technologies for the tertiary treatment of wastewater has becomeincreasingly popular in recent times, as both construction and operating costs havedecreased. The operating range of membrane processes is illustrated in Figure 7 below.There are currently many examples of water recycling processes in Australia that employ acombination of micro- or ultrafiltration as a pre-treatment stage to reverse osmosis (seesection 5).

Figure 7 Distribution of Particles Size and Application of Membrane Technologies

(Radcliffe, 2004)

There still remain some significant issues with the on-going operation and maintenance ofmembrane facilities, and these will be discussed in Horizons 2 and 3. However, in general thetheory, design and implementation of membrane processes is well-understood. The reliabilityand cost-effectiveness of membrane technology make it an increasingly popular tertiarytreatment selection for water recycling projects.


14/36


2.4 Risk Management

The perception of risks associated with using recycled water is one of the key factors found toinfluence public opinion and support for water recycling schemes (Po et al. , 2004).Governments, water suppliers and engineers have long recognised risk management asbeing of critical importance and hence have developed very good risk managementguidelines.

Each Australian state has its own environmental and water-related legislation which ultimatelycontrols the implementation of water recycling projects. However, most States also publishwater recycling guidelines such as the Queensland Water Recycling Guidelines (Environmental Protection Agency, 2005) and the South Australian Reclaimed Water Guidelines Treated Effluent (DHS, 1999) to provide further guidance on the design andimplementation of recycled water schemes. In November 2006, the Federal Governmentthrough the Natural Resource Management Ministerial Council, Environment Protection andHeritage Council and Australian Health Ministers Conference released the Australian Guidelines for Water Recycling: Managing Health and Environmental Risks (Phase 1) (NRMMC et al. , 2006). These guidelines provide a 12-element framework for themanagement of recycled water quality and use:

1. Commitment to responsible use and management of recycled water quality, includingengagement with stakeholders such as the community;

2. Assessment of the recycled water system, including hazard identification and riskassessment;

3. Preventative measures for recycled water management, including the identification ofcritical control points and implementation of multiple barriers;

4. Operational procedures and process control;

5. Verification of recycled water quality and environmental performance;

6. Protocols for management of incidents and emergencies;

7. Operator, contractor and end user awareness and training;

8. Community involvement and awareness;

9. Validation, research and development;

10. Documentation and reporting;11. Evaluation and audit;

12. Review and continuous improvement.

The level of risk which is considered acceptable for recycling projects is the same, if not betterthan that used for drinking water treatment and reticulation (National Coordinator for RecycledWater Development in Horticulture, 2005). With such strong legislation and guidelines at boththe State and Federal level, we consider that risk management is a well-defined, well-understood and well-addressed issue for water recycling projects.


15/36


2.5 Inorganic and Solids Residuals

The generalised water recycling treatment process in Figure 6 above illustrates that whilst wecan produce clean recycled water from domestic wastewater, we also produce a significantquantity of inorganic and solid residual products.

Solids residuals from biological treatment processes typically undergo some furtherprocessing for stabilisation, degradation and dewatering. Processes such as anaerobic oraerobic digestion, lime stabilisation, lagoon stockpiling and mechanical dewatering are allwell-established within the wastewater industry.

Whilst it is again recognised that there still remains significant research activity in the area ofsolids treatment, the practices on the ground are well-understood and successful. As such,the handling of solids residuals represents no barrier to water recycling projects.

In the tertiary treatment processes for fine suspended solids, colloids and dissolved saltremoval, another inorganic residual product must be handled. Again, the technologies forstabilising and dewatering this by-product are already widely applied.

In Horizon 3, we will discuss further the issue of downstream management of readilydissolvable salts once they are recovered from a recycled water stream.


16/36


17/36


Method Measures Application

Electrochemical pH and redox Identify key problems orinterferences with specificprocesses

Varying (electrochem,colourimetric,scanning)

Nutrients (N and P) Water quality measures

Absorbance turbidity, colour Water quality measures, can beused to control specificprocesses.

Oxidative total organics, TOC, COD Water quality measure, totalorganic content.

The measures given in Table 3 do not measure specific properties, such as Xenobioticorganic compounds, specific toxic elements, microbes (viruses and bacteria), and qualitiessuch as odour and flavour.

Newer methods need to be developed to address these important measures. In particular, ageneralised measure is needed that provides rapid feedback of water quality, to indicateproblems during operation. These should be able to reflect many of the lumped propertiesgiven above. Newer methods, often based on spectroscopy, are very effective in this regard.These include:

Light spectroscopy (emission and absorption) can be used in visible and non-visiblespectrums to detect a wide range inorganic and organic molecules;

Mass spectroscopy to determine the molecular mass and potentially identify individualcompounds;

Redox and pH titration, to produce a spectrum of ion-active and reactive compounds; and

Redox and pH titration, to produce a spectrum of ion-active and reactive compounds

Normally, these methods would be used against a known standard to determine specific

concentrations. In this case, the sampled spectrum is continuously compared against abackground spectrum of good water. Significant deviations from this water to either aknown, or unknown state is a basis for immediate intervention.

3.2 Virus Removal

There are more than 100 types of viruses known to exist in human waste, with many possiblepathways for exposure airborne, waterborne, soil, dermal and food ingestion. They are alsohighly infectious and relatively persistent, making them probably the biggest pathogenichealth risk in the use of recycled water. Inhaling even one adenovirus may be sufficient toinfect 50% of subjects exposed (Radcliffe, 2004).

Consequently, the Australian Guidelines for Water Recycling (NRMMC et al. , 2006) require avery high level of virus reduction in the generation of recycled water. For example, to use


18/36


recycled water for irrigating commercial food crops, such as lettuce, a 6 log reduction ie. a 10 6 fold reduction (based on rotavirus) is recommended. This guideline is calculated from a

health-based risk assessment to reduce the potential health effects to less than 10 -6 DALY2 per person per year.

In order to guarantee this level of virus removal, a treatment process must adopt a multiplebarrier approach. This ensures that if one stage of the treatment train fails, there is sufficientredundancy within the remaining treatment processes to meet the required end water qualitytargets.

We already know that many processes can achieve a level of virus removal. However, as isclearly evident in Table 4, there is a wide range of virus removals reported for differenttechnologies. In practice, this leads to a highly precautionary approach in the design andimplementation of recycled water treatment processes.

Table 4 Indicative Log Removal of Viruses by Various Treatments

Region Virus Removal

(inc. adeno-, rota- and enteroviruses)

Primary Treatment 0.0 0.1

Secondary Treatment 0.5 2.0

Dual Media Filtration, with Coagulation 0.5 3.0

Membrane Filtration 2.5 >6.0Reverse Osmosis >6.0

Lagoon Storage 1.0 4.0

Chlorination 1.0 3.0

Ozonation 3.0 6.0

UV Light >1.0 adenovirus

>3.0 enterovirus, hepatitis A

Wetlands N/A

(NRMMC et al. , 2006)

Our knowledge of viruses, their transportation in the water supply system and the effects theycan have upon our health is voluminous. Our theory and practical experience with effectivevirus removal is growing rapidly. As we continue to move towards this horizon, we anticipatethat our expanding body of practical experience will help to refine the expectations of virusremoval for each of the treatment processes listed in Table 4. As this happens, it may bepossible to streamline our treatment processes, minimising the extent of over-design withoutcompromising on the protection of public health.

2 DALY Disability Affected Life Years


19/36


3.3 Inorganic Fouling - Precipitation

Precipitation is a process in which compounds (inorganic and organic) exceed their solubilitylimit (become supersaturated), and start to form solid compounds. Major precipitationreactions are as follows:

Ionic precipitation; a number of ionic compounds combine to form an inert solid precipitate.The driving force for precipitation is the concentration product of the different ionicsubstrates.

Molecular precipitation; a dissolved compound, normally a solid at room temperature,exceeds its solubility limit. The driving force is the concentration of the dissolvedcompound.

The first is more common, and the main management target, but the second is starting to beidentified as an important issue. The main problem is in reverse osmosis membrane systems,as by their nature, they concentrate specific (larger) molecules on the retentate side. Thesecompounds exceed their solubility limit and form precipitates. Precipitation can either formdirectly on the membrane (scaling), within pipes, or as particles in solution. While the lattersituation is preferred, all can be managed to some degree:

Membrane scaling is normally avoided by use of non-polar membrane surfaces, whichmake the membrane less attractive as a precipitation site.

If precipitate particles are well above the membrane pore size, they will primarilyaccumulate in the retentate side, and be removed in the concentrate stream. If they are onthe order of the membrane pore size (manly for microfiltration), they will block the poresdirectly and cause fouling.

Fouling by ionic precipitates is managed by chemical cleaning, which changes the pH(normally to low pH), such that most compounds are re-solubilised.

Molecular precipitation is difficult to manage, since a chemical clean is often not possible(for inorganic compounds). Normally, ultra-pure water (permeate) must be used to re-solubilise the compounds. Examples of molecular precipitants are silica and other inertmetals.

The issue of inorganic precipitation and fouling was placed under Horizon 2, becausealthough there are good management strategies available, the problem is difficult to predict,causes greatly increased operation costs, and increases financial and operation risk tomanagement. Many compounds and their interactions are still being identified (e.g., silica co-precipitation with calcium), and research is needed to produce better management practices,and identify more potentially detrimental compounds. Issues related to unidentifiedcompounds, and especially molecular precipitants should probably be placed under Horizon3. As inorganic fouling can have a direct and major impact on the operational performanceand costs, it is likely that this will be heavily addressed over the next 10 years, as moremembrane systems are implemented.


20/36


3.4 Process Integrity / Security for Biological Systems

It is essential that systems for recycled water have a metric to indicate gross process failure,with a related stop to prevent product contamination. Membrane systems can use pressuredrop across the system to indicate process failure; a decrease below a critical limit willindicate gross failure (though a minimal increase may allow contamination without alarm).Another option for RO members is the TDS (total dissolved solids) level as measured byconductivity; a rapid rise indicates that the membrane has been breached.

Biological/chemical purification systems use a range of metrics, including turbidity, colour, andTDS, but because the system is primarily a treatment rather than a barrier system, all areindicative of process performance, and less as measures of integrity. Indeed, biologicalsystems vary more in product characteristics, and active operation is needed to produce goodproduct. A poorly operated biological process will produce poor, or dangerous product, whilea poorly operated membrane process will produce good product inefficiently.

Currently existing measurement methods allow to operate biological/chemical processes well,however, the measurements are often not directly linked to control actions, thereby limitingthe actual capacity to ensure product quality and security. Again, both measurement andcontrol technologies are currently available, the main limitation is their effectiveimplementation in full-scale processes. While it is likely that most future recycling projects willinvolve membrane separation as a major barrier system, the provision of consistent and goodquality bio/chemical process effluent as feed to the membrane stage will likely put additionalemphasis on the overall process optimisation to ensure good systems integrity.

3.5 Endocrine Disrupting Chemicals (EDCs) and Pharmaceuticals andPersonal Care Products (PPCP)

One of the key issues for the general public in the recycled water debate is the potential forcertain chemicals to cause adverse effects on human health, even at very low concentrations.The focus of this concern is usually on pharmaceutical and personal care product chemicals,steroid hormones, oestrogenic compounds, and others that may interfere with the humanendocrine system. The endocrine (or hormonal) system regulates human functions such assexual development, growth and reproduction (Radcliffe, 2004). In recent years, there hasbeen some evidence that such chemicals can cause disruption to the endocrine systems andcan affect hormonal control of development in aquatic organisms and wildlife (Ying et al. ,

2004).

The concentration of EDCs and PPCPs in treated wastewater effluent is in the order ofmicrograms (10 -6 g) or even nanograms (10 -9 g) per litre (Ying et al. , 2004), which is manyorders of magnitude lower than the concentrations likely to have adverse health effects onhumans. The epidemiological studies to date indicate that low-level environmental exposureto endocrine disrupting chemicals does not cause harm to human health (Radcliffe, 2004;Ying et al. , 2004).

Significant research efforts have recently been focused on this area. Beside the studies onthe human health impact in water recycling situations mentioned above, several investigationshave focused on the effectiveness of existing and novel treatment processes. In particular, alarge EU project (POSEIDON, 2005) has determined the effect of a wide range of treatmentprocesses on a number of EDCs and PPCPs. It was found that biological wastewater


21/36


treatment plants with more than 8-10 days aerobic sludge age (solids retention time, SRT) arequite effective at removing many of the studied compounds. Such conditions are commonly

used in modern nutrient removal processes and therefore a significant removal of many ofthese compounds can be expected. Furthermore, activated carbon, ultra- and nanofiltrationmembrane and advanced oxidation (eg. ozone, UV/H 2O2) processes were also found to bevery effective at removing these compounds to very low levels. Surprisingly, many naturalprocesses occurring in lakes and during soil infiltration (eg. river bank filtration) also seemvery effective at removing both EDCs and PPCPs from the water. Similar, supporting resultshave also been obtained in a study commissioned by CSIRO (Ying et al. , 2004).

It must be noted however, that research in this area is on-going. At present, there is limited in-depth information available on the transformation, fate and activity of EDCs and PPCPs intreated wastewater. .Although our knowledge in this area is still growing, it appears likely that

even current discharge levels have no adverse impacts in humans, however there may wellbe a ecological impact on the receiving waterways, particularly if membrane concentrates aredischarged untreated. Given the effectiveness of the proposed and implemented waterrecycling processes, the levels in purified water are extremely low (usually not detectableeven with most sensitive methods) and are therefore of no concern to human health.

3.6 Dissolved Organic Residuals

Although current (biological) wastewater treatment plants are very effective at removingdissolved organics from the wastewater, this is largely limited to the biodegradablecompounds. Some additional removal is achieved by adsorption of largely hydrophobic

compounds on the biosolids (sludge) which are then removed with the excess sludge from theprocess.

Some dissolved organic compounds remain in the effluent, which is often referred to as inertsoluble organics (typically measured as COD) or dissolved organic carbon (DOC). InertCOD levels of 40-100 mg/L (corresponding to around 15-40 mg/L DOC) are often present inplant effluents. This consists of a wide range of natural and synthetic compounds at very lowconcentrations, some likely even produced by the biomass itself.

Most of these compounds are effectively removed by nanofiltration or RO membraneprocesses, but again then appear in concentrated form in the reject streams of suchprocesses. The effective destruction of such residuals is clearly a Horizon Two issue.Advanced oxidation and adsorption processes are clearly able to remove or destroy suchcompounds, however, the capital and operating costs are very significant. Combinations ofchemical and biological processes might offer some more cost-effective solutions, but theseare yet to be fully developed and competitively demonstrated in actual full-scale operations.

3.7 Energy Consumption and Greenhouse Gas Emissions

The topic of energy consumption and the associated greenhouse gas emissions is not uniqueto the water recycling debate. This issue could well be placed on the second horizon of manycurrent technical and political discussions.

As a starting point, it is important to recognise and acknowledge the very sensibleengineering design of existing potable water supply systems. In most cases, early water


22/36


supply engineers made optimum use of gravity to ensure a reliable and cheap method ofsupplying water to our taps. Consequently, most of our water supply infrastructure also flows

down the hill. Our reservoirs are typically located high in the hills and our sewage treatmentplants on the lowlands, near the ocean or creek discharges. So for many recycled waterschemes, it may be necessary to turn the water around and return it back to the heights fromwhich it came. So whilst we may indeed solve the problem of water supply, we are alsocontributing to another problem by increasing (non-renewable) energy consumption, and theassociated problem of increased greenhouse gas emissions. We are simply trading water forenergy.

This paper does not intend to contribute to the debate about the potential impacts of climatechange on society as a whole, or more specifically on changing rainfall patterns. It isinteresting to consider though that one mooted cause for our current drought and water

supply shortage is enhanced climate change. Our response to this water shortage crisis is toemploy energy intensive water supply solutions, such as recycling and desalination (e.g.South East Queensland, Sydney, NSW central coast, and others), thereby contributing furtherto the greenhouse gas emissions and climate changing conditions that cause the problem inthe first place. The irony should not be missed.

A typical biological nutrient removal sewage treatment plant may operate at an energyefficiency of approximately 420 kWh per ML (Radcliffe, 2004). Adding the typical recycledwater treatment processes of microfiltration and reverse osmosis potentially adds another 930kWh per ML (Radcliffe, 2004). The recycled water must then also be returned to the proposedusers. This will clearly vary significantly, depending on the scope of the scheme and the

topography of the area. As an example however, the Western Corridor Recycled WaterScheme under construction in south-east Queensland proposes to pump up to 100 ML/d ofrecycled water via a 200 km pipeline from the Bundamba treatment plant in Ipswich toCaboonbah at the top of the Wivenhoe Dam a static lift of approximately 45m. Thisenormous pumping task is likely to add at least a further 550 kWh/ML in energy consumption.This figure is similar to Singapores NEWater scheme, which is reported to operate at 700 900 kWh per ML (Radcliffe, 2004).

Therefore, it can bee seen that the implementation of a recycled water scheme can increasethe energy consumption of wastewater treatment and disposal by 300-400% or more,depending on the circumstances.

The issue of energy consumption with recycled water treatment and transport needs to berecognised as a significant drawback, when compared against more traditional methods ofwater delivery under gravity. There are advantages and disadvantages for recycled waterschemes. Unfortunately, crisis-mode responses to severe water shortages may lead to someof the disadvantages being ignored.

The theory of energy efficiency and greenhouse gas emissions is well established. Thechallenge for the industry is to ensure that the delivery of recycled water does not come at theunacceptable cost of other environmental damage. The decision of the Western AustralianWater Corporation to power their new Desalination Plant by renewable wind power isrecognition that the water supply debate cannot be divorced from the greenhouse gas

emissions / climate change debate. Unfortunately, many other authorities and jurisdictions areyet to make this connection.


23/36


3.8 Recycled Water Pricing

The reported cost of producing recycled water is highly variable, with schemes in Australiaranging from $1.45 to $4.00 per kilolitre of Class A recycled water (Radcliffe, 2004). This widerange in costs is due to many reasons, not least of which is the lack of transparency inassessing the true cost of water supply systems. Clearly though, site-specific factors witheach scheme will weigh heavily in the analysis of the water production cost.

Therefore, it is not surprising that the price of recycled water is also highly variable, withAustralian values ranging from $0.07 to $0.83 per kilolitre of Class A recycled water(Radcliffe, 2004). Compare this with a typical potable water supply cost of $1.00 per kilolitre;or $3,300 per kilolitre of bottled water! ($2.00 for 600mL bottle). There are many drivers forwater authorities in setting the price of recycled water. Typically, the most important of thesereasons is providing an incentive for uptake of the recycled water (Radcliffe, 2004). A pricedifferential between recycled and potable water offers an incentive for users to change theirwater use habits. However, a low water price may encourage excessive usage, thereby partlydefeating the purpose of the recycled water application in the first place.

The price of recycled water is also clearly affected by market demand and the willingness ofusers to pay. Radcliffe (2004), citing earlier work by Mills and Asano (1998), identifies 16elements that should be considered in surveying the potential market for recycled water:

Specific potential uses of recycled water; Water quality needs;

Location of users; Recent historical and future quantityneeds;

Timing of needs (seasonal, dailyvariations);

Present source and cost of water;

Water pressure needs; Reliability needs;

Future land use trends that couldpreclude recycled water use;

What is the current status and schedulefor scheme development;

To what extent is the user likely to want todispose of residual recycled water afteruse;

Identification of on-site treatment orplumbing retrofit needed to acceptrecycled water;

An indication of the potential users

willingness to pay;

When would users be willing to start taking

recycled water; Internal capital investment and operating

and maintenance costs for on-sitefacilities to accept recycled water;

Needed monetary savings on recycledwater to recover site costs or desired pay-back period and rate of return on capital.

Clearly, the issue of recycled water price is complicated. It is made even more so if authoritiesattempt, as they should do under the CoAG water reform principles, to capture the cost ofexternalities in the production of recycled water (Radcliffe, 2004). In some schemes theremay also exist some confusion over ownership of the recycled water, mainly since it was

previously considered as a waste product with no value (National Coordinator for RecycledWater Development in Horticulture, 2005). This was the case when the Toowoomba City


24/36


Council investigated the sale of its recycled water to the nearby Millmerran Power Station forcooling water. Previously, the effluent had been disposed to Gowrie Creek where it was

subsequently withdrawn, free of charge, by downstream farmers on the Darling Downs forirrigation.

The pricing of recycled water will continue to be a challenge for scheme operators. The manycompeting factors, such as market demand, consumers willingness to pay, operators costrecovery and capturing of externalities, suggest that there is unlikely to ever be a universallyaccepted value of recycled water. Into the future, authorities will continually need to considerthese factors and attempt to offer what is collectively viewed as a fair price for their recycledwater.

3.9 System Optimisation

Australian coastal environments, particularly estuaries, bays or the Great Barrier Reef lagoon,are very sensitive to nitrogen. This leads to very strict limits, with many licenses requiring atotal nitrogen concentration below 5 mg/L or as low as 3 mg/L (as 50%iles). Given thecommonly found organic nitrogen concentration of 1-2 mg/L, the inorganic nitrogen(ammonium plus nitrate) level has to be of close to zero. Removal of the last 10 mg/Linorganic nitrogen (from 10 mg/L to 0 mg/L) requires a disproportional amount of energy, andmay require addition of carbon (likely methanol, from non-renewable sources, or ethanol).Removal of this residual (oxidised) nitrogen in activated sludge treatment plants is relativelyinefficient, as much of the carbon source is either directly oxidised, or oxidised aftertransformation to biomass. However, for effluent discharge to sensitive aquatic environments

this approach is often taken.If the final effluent is no longer discharged but used as feedstock for water recycling, theoverall system optimisation changes considerably. A membrane-based water recyclingprocess will concentrate the pollutants in a brine stream, which can be further treated prior todischarge (or alternative disposal). This allows treatment of a much lower hydraulic load withhigher concentrations, which will likely improve the efficiency of the pollutant removal, whilestill reducing the overall discharge load.

In terms of nitrogen, it may therefore be possible to relax the effluent discharge limits in theupstream plant (to reduce energy input and chemical addition), and remove the remainingnitrogen instead through a membrane separation and brine treatment system. Removal ofconcentrated nitrogen in a dedicated brine treatment system is more effective, since carbonadded can be used more effectively in a dedicated denitrification stage. Especially if adedicated post-aeration denitrification stage is used, carbon requirements can be reducedsubstantially.

However, depending on the separation efficiency of the RO membrane, it may be necessaryto change the form of nitrogen supplied in the feed flow. Certain RO membranes seem lessefficient at nitrate removal, while in other situations the membranes seem to be morepermeable for ammonium (likely as ammonia gas). This is an area where some goodbackground knowledge is available, but needs to be specifically tailored to particularapplications.

This is therefore a typical Horizon Two topic, since much of the knowledge and tools toaddress these issues are available but they need implementation on an individual basis.


25/36


Given the known and potential cost and environmental benefits, this area of overall systemsintegration and optimisation is well worth considering as a major objective in the design and

operation of water recycling schemes.


26/36


4. Horizon Three: The Frontier Problems for

Water RecyclingAt Horizon Three, we come to the currently unsolved problems for water recycling. These arethe issues that, whilst not slowing the rate of implementation of water recycling schemes,need yet to be resolved. We also speculate about the possibility of some future technologiesfor water recycling, beyond the current preferred choice of membranes. In this area, wefreewheel the possibilities of nanotubes, electrostatic separation and bipolar membranes.

These are topics of longer-term research projects for organisations such as the AWMC.

4.1 Virus Testing and Analysis

The presence of viruses in recycled water has already been identified as the greatestmicrobiological risk to human health. The processes of formal risk identification andmanagement are firmly established in the various State guidelines and the Australian Guidelines for Water Recycling (NRMMC et al., 2006) . The methods for virus removal areemerging on Horizon Two and are becoming increasingly well-established in practice.However, the final and critical step of monitoring through virus detection remains on the edgeof our theoretical and practical knowledge. Virus detection in relatively clean water requiresthree general steps (American Public Health Association et al. , 1998):

1. Collecting a representative sample;

2. Concentrating the viruses in the sample; and3. Identifying and estimating quantities of the concentrated viruses.

However, there are several inherent problems associated with virus analysis (American PublicHealth Association et al. , 1998):

The small size of viruses (20 100nm in diameter) makes them difficult to detect;

In recycled water, there are likely very low numbers of viruses;

Viruses are inherently unstable biological entities;

The various dissolved and suspended materials in the water may interfere with virus

detection; and There are limitations with the present methods of virus estimation and identification.

To overcome the difficulties associated with the direct detection of viruses, surrogates orproxy indicators are often used for on-line operational monitoring. For example, turbiditymeasurements (or particle counters) can be used to determine filtration plant performanceand can be a surrogate for removal of Cryptosporidium, Giardia and viruses (NRMMC et al. ,2006).

The use of proxy indicators is not sufficient however to properly validate and verify theperformance of a recycled water scheme. As noted earlier, there are over 100 types of virus

known to exist in human waste. The practical difficulty is therefore to choose which virus(es)is the most appropriate to monitor. Of the enteric viruses, there is no single one that


27/36


represents an ideal reference pathogen (NRMMC et al. , 2006). The following notes are takendirectly from the Australian Guidelines for Water Recycling :

Rotaviruses are a good candidate for risk assessment because they pose a major threat ofviral gastroenteritis worldwide, they have a relatively high infectivity compared with otherwaterborne viruses and a doseresponse model has been established (Havelaar andMelse, 2003).

Noroviruses, though causing less severe disease, have been shown to be the mostprevalent cause of viral gastroenteritis in developed regions (Lopmam et al , 2003), but atpresent there is no published doseresponse model for norovirus. However, althoughrotaviruses and noroviruses have the highest pathogenicity of candidate viruses and arelikely to be present in high numbers in human waste, there are no suitable cell-culturemethods and little data on prevalence of viable viruses in sources of recycled water.

Reoviruses, enteroviruses and adenoviruses are culturable, and there are Australian andinternational data for numbers of these viruses in sewage, but infection rates are lower. Ofthese three viruses, adenoviruses have been detected in the highest numbers, and theyappear to be the most resistant to removal or disinfection (WHO, 2004; Gerba et al , 2002;unpublished data SA Department of Health). Australian adenovirus data (from the VirginiaPipeline Scheme in South Australia) have been compared with published polymerasechain reaction (PCR) data for rotavirus and norovirus, adjusted to consider infectivity(Lodder and Roda-Husman, 2005). The comparison indicates that prevalence of the threeviruses in sewage could be similar.

Given these considerations, the Australian Guidelines for Water Recycling settle on anamalgam of rotavirus and adenovirus, using doseresponse data for rotaviruses andoccurrence data for adenovirus, as the preferred reference pathogen.

Agreeing on a national reference for virus removal is a significant advance in this challengingissue of virus testing and analysis. However, there is presently only one Australian laboratorywith the appropriate NATA accreditation for the assessment of the virological condition ofwaters, including effluents. Only the Sydney Water Analytical and Field Services Laboratorycan provide NATA-accredited determination of enteric viruses in water, using cell culture andpolymerase chain reaction (NATA, 2005).

Therefore, given the inherent challenges associated with virus detection, the difficulty in

selecting an appropriate reference or indicator virus and the distinct lack of laboratoryservices, the issue of virus testing and analysis remains on the far horizon of our technicalknowledge and experience.

4.2 Organic Fouling

It may be surprising to find this topic in the Horizon Three section given the large amount ofresearch and application work done in this field. However, we still consider that there is alarge degree of uncertainty in the predictability and prevention of organic fouling for variousmembrane systems.

Organic fouling refers to the attachment of organic compounds on membrane surfaces,leading to the eventual blocking of membrane pores and reduced fluxes through the


28/36


membranes. These compounds are considered to be mainly macromolecules and colloidal orparticulate organics, but could include whole bacteria and their associated products

(extracellular polymeric substances, EPS). These attached compounds can typically not beremoved by simple backwashing but requires chemical cleaning with acids and/or alkalis, aswell as disinfectants.

However, some of the fouling does seem to be irreversible, eventually reducing the flux evenafter chemical cleaning. This impact, as well as other factors, will ultimately requirereplacement of the membrane module, which is still one of the main operational costs of suchsystems. Hence it would be highly beneficial if the (irreversible) fouling could be reducedconsiderably and hence the useful membrane life extended beyond the currently typical lifeexpectancy of 4-6 years.

4.3 Inorganic FoulingIt is quite possible that the irreversible fouling mentioned in the previous section is due to thecombination and/or interaction of organic and inorganic compounds. This is thought to beparticularly the case for molecular precipitation (see Section 3.3 above) as this is difficult toremove by the usual chemical cleaning procedures. However, there is to our knowledge atthis stage still a major research need existing in relation to the inorganic and organic foulingaspects.

The prevention of inorganic fouling through anti-scalants is fairly well developed, but couldlikely also benefit from an improved understanding of the precipitation processes andinteractions with different ionic and neutral compounds in the water. As previously mentioned,the deposition of silicates poses one of the major challenges in this respect, particularly dueto some unexpected and as yet unexplained interactions with common cations (Ca, Mg) andanions (CO 3, Cl, NO 3) present in the feed water.

4.4 Impact of Residual Organics on Ecological Systems

It may be argued that the waste streams from water recycling discharge the same amount ofresidual organics as is currently the case, just in higher concentrations. However, this may, ormay not, have a significant effect on the local environment where these discharges occur,depending also on the long-term dilution factor in the area. For example, the currentdischarge of a wastewater treatment plant may contribute a major fraction to the overall flowto a particular waterway, hence providing a level of dilution of the discharged (and otherwisecontributed) pollutants in this aquatic system. If now 90% of the water is recycled, but the totalpollutant load remains the same, the impact on the local aquatic environment may be verydetrimental.

Many of these natural processes, including the impact and breakdown of dissolved organicnitrogen (see following section) in the receiving waterways are poorly understood at present.Based on this lack of knowledge, sometimes unnecessary (and potentially environmentallymore detrimental) steps are being taken in an attempt to minimise or avoid the discharge ofsuch residuals to certain waterways. The construction and operation of a separateconcentrate discharge pipeline from inland plants is a case in point where this solution mightwell cause overall more environmental harm than having a local discharge. But without


29/36


reasonable knowledge on the impact of this discharge on the local aquatic environment it isimpossible to determine the optimal solution in such a case.

4.5 Organic Nitrogen Removal

Dissolved organic nitrogen (DON) represents typically 1-3 mgN / L (generally 20%-80% oftotal) effluent nitrogen in a nutrient removal wastewater treatment plant. It is generallycomplex organic material, though with relatively small molecule sizes (99.5% of dissolved salts and up to 97% of mostdissolved organics (Radcliffe, 2004). However, the salt is not eliminated, just concentrated in

the concentrate (brine) stream from the membrane system.


30/36


For coastal recycled water schemes, disposal of a highly saline waste stream may notpresent a serious problem. Suitable design and management of a coastal outfall should

prevent serious ecological damage from high salt concentrations, particularly since theywould likely still be considerably lower than seawater salinity. However, for inland schemesthe solution is not so clear. The problem of inland salinity is clearly illustrated by the plight ofthe Murray-Darling Basin and the quality of drinking water in Adelaide.

For inland areas, the most common solution for dealing with saline residual streams is to useevaporation basins, similar to those used at Noora and Stockyard Plains as part of theMurray-Darling Basin salt interception scheme. Such an approach requires a large, relativelyimpermeable and unused site to allow effective evaporation. It may then be possible to makecommercial use of the harvested salt, although there is no guarantee of this, and it isgenerally a very low value commodity (Radcliffe, 2004). The accumulation of the harvested

salt also poses a further risk in that it may infiltrate into surrounding aquifers or be re-solubilised in heavy rain and washed back into the creeks/rivers in a highly toxic shock load.

Unfortunately, there is an abundance of salt in inland Australia, so it is unlikely that this wasteproduct of recycled water treatment processes will ever be valued as a highly useful resource.Therefore, unless new technological solutions or management controls are introduced, it islikely to remain as an unpleasant waste product and high environmental risk.

4.7 Source Control / Identification

Sewer discharge (or trade waste) standards are commonly applied in most large cities andmunicipalities. The have been primarily driven by two aspects, (1) the protection of thewastewater collection and treatment assets and their operation; and (2) the dischargerequirements of the treated effluent. However, with this effluent becoming the feedstock to thewater recycling process, the objectives of the source control in sewers change considerably.

Since water recycling plants introduce a range of new process technologies (particularlymembranes) to the overall treatment train, the major additional concerns are relating tocompounds that might have an acute or chronic effect on these processes. They can eithercause operational problems such as fouling, impact on the membrane life expectancy, or maynot be effectively removed in the treatment train. However, it is at present largely unknownwhich compounds may be of particular concern, especially in relation to industrial chemicalsused for cleaning or in production processes.

In addition to the lack of identification of these compounds, the often very intermittent, butconcentrated discharge of such chemicals can also cause specific problems. They maycreate infrequent and non-reproducible operating problems that are difficult to identify andhence control.

There is limited knowledge on the detection and prevention of such discharges and currentlythere appears to be no understanding of the likely compounds that should be monitored infuture. Close and open collaboration between trade waste dischargers (and their chemicalsuppliers), the urban water utilities and the recycled plant operators will be required todevelop updated trade waste standards that consider the needs of all parties involved. Thisneeds to be based on good technical/scientific information on the impact of the relevantcompounds being targeted.


31/36


4.8 Nanotubes in Membranes

The largest expense, and environmental impact from membrane purification of domesticeffluent is the electricity use; on the order of 1-2000 kWh/ML. This is largely related(inversely) to permeability of the membrane. Producing membranes with better poreconsistency and higher permeability may offer drastic reductions in this electricity cost.

Carbon nanotube membranes employ nanotubes (defined molecular tube assemblies)approximately 6 water molecules wide, placed in an impermeable matrix (Holt et al. , 2006).

These have been found to have water permeabilities 100 times that of polycarbonatemembranes. They would be expected to have relatively low permeability of water, as thenanotubes are very hydrophobic. However, this decreases molecular interactions, and allowsthe water to flow through the tube. While this is exciting research, selectivity (apart from the

molecular level) needs to be investigated, and no work at all has been done on water withother compounds added. It therefore remains firmly in Horizon 3, with a probable timeline of10+ years to application.

4.9 Electrostatic Separation / Bipolar Membranes

Electrostatic systems are used to drive improved performance, with less fouling thanconventional systems. They are specifically orientated towards systems with a relatively highsalinity. An example process (from GE) uses anion and cation selective membranes, togetherwith an applied electrical driving force to produce a clear centrate stream, and a very highsalinity concentrate stream. While the technologies are relatively well developed, there has so

far been little application to main stream wastewater purification. The major limitations at thisstage are likely the costs and the practical applicability of the bipolar membranes, as well asthe operating costs.


32/36


5. Examples of Water Recycling SchemesAs a final chapter, we present several examples of water recycling schemes that have alreadybeen implemented, both here in Australia and around the world. Non-potable water recyclinghas an excellent and well-documented performance track record, which to-date has featuredno documented health problems, strong public acceptance and good regulatory compliance.The majority of these projects provided tertiary treatment followed by disinfection becausethat provided for the needs of any unrestricted urban use .

Of course, there are also many examples of unplanned or incidental indirect potable reusealready occurring in many parts of the world (Radcliffe, 2004). These are typically urbancentres on the downstream end of a river system, such as:

New Orleans on the Mississippi River (e.g. downstream of Minneapolis); London on the River Thames (e.g. downstream of Oxford and Reading);

Numerous cities on the Rhine River (e.g. Strasbourg, Mainz, Bonn, Cologne, Rotterdam);

Osaka on Yodo River (e.g. downstream of Kyoto); and

Adelaide on the Darling/Murrumbidgee/Murray River system (e.g. downstream ofCanberra).

Presented below in Table 5 and Table 6 are just a few examples of planned recycled waterschemes around the world and in Australia. For a more extensive list and further details, thereader is referred to the review published by the Australian Academy of Technical Sciencesand Engineering (Radcliffe, 2004).

Table 5 International Water Recycling Schemes

Location Description

Los AngelesCounty,California, USA

Surface-spreading of secondary effluent (dual media filtration +chlorination) into the Whittier Narrows Groundwater basin since 1962.Potable water is subsequently withdrawn. Estimated that 23% ofpotable water is indirectly recycled water.

Orange CountyWater District,California, USA

OCWD has operated Water Factory 21 since 1976, using limeclarification, air stripping and re-carbonation, filtration, carbonadsorption, RO and disinfection of secondary effluent. Recycled wateris used for groundwater replenishment and to avoid seawater intrusioninto the aquifer. Up to 5% of the recycled water may return to thepotable water supply from the basin.

St Petersburg,Florida, USA

Dual distribution system uses highly treated recycled water forirrigating 8000 homes, 46 schools, 66 parks and 6 golf courses. It hasbeen operating since 1977.

Orlando, Florida,USA

Walt Disney World Resort Complex uses recycled water for irrigating 5golf courses, highway medians, a water park and tree farm.


33/36



Upper Occoquan,Virginia, USA The Upper Occoquan Sewage Authority uses recycled water forindirect potable supply via the Occoquan Reservoir, starting from1978. In droughts, up to 90% of water is from the recycled water.Treatment is by secondary treatment, lime, clarification, re-carbonation, sand filtration, GAC, ion exchange and chlorination.

Windhoek,Namibia

Windhoek has low rainfall, high evaporation and a limited catchment. Ithas exploited all surface water resources within 500km, has maximumgroundwater utilisation, demand management in place and nowdepends on direct recycled potable water supply. Treatment consistsof secondary treatment, pre-ozonation, DAF, sand filtration, ozonation,GAC, UF and chlorination.

Singapore The NEWater plant produces recycled water from secondary effluent.Treatment is by micro-screening, MF/RO, plus UV irradiation. Mostrecycled water is supplied to high technology industries. Small portionreturned to water supply reservoir.

Yokohama,Japan

Yokohama International Stadium uses recycled water as a heatsource for heat pumps, toilet flushing, sprinklers and artificial streamsin surrounding landscaped parks.

Osaka, Japan Osaka has a target of 100% water recycling by 2030. The NagisaPlant already produces recycled water for landscape irrigation and asa heat exchange source for district air conditioning, for fire mains andtoilet flushing.

Wulpen, Belgium The Wulpen STP in Belgium recycles 2.5 GL of domestic wastewater.It is treated by MF/RO, stored in an aquifer for 1-2 months, and thenused for water supply augmentation.

Israel In 1994 20% of Israels water supply came from recycled water, withthe aim of 100% recycling by 2010. The Dan Region project provides95 GL/annum of secondary effluent from Tel Aviv to recharge acoastal aquifer for further treatment and storage. Water is thenpumped from aquifer to irrigation areas.

(Radcliffe, 2004)

Table 6 Australian Water Recycling Schemes


Rouse Hill,Sydney, NSW

Australias first direct non-potable reuse scheme. A 4.4 ML/d treatmentplant ozonation, MF and super-chlorination serves 12,000 homesvia a third pipe.

Illawarra, NSW Illawarra Wastewater Strategy provides 20 ML/d of recycled waterby an MF/RO process on secondary effluent. The recycled water is

mainly used by BlueScope steel in place of potable water for non-potable water applications.


34/36



Sydney OlympicPark, NSW Sydney Olympic Park Authority / Newington integrated sewagetreatment and stormwater collection undergoes advanced tertiarytreatment, with water returned for non-potable purposes (e.g. irrigationof parklands and playing fields). A dual reticulation system is alsoimplemented in the adjacent suburb of Newington.

Shoalhaven,NSW

Shoalhaven Waters Recycled Water Management Scheme (REMS)provides 2GL/yr of effluent from four interconnected STPs in 2003.The recycled water is provided fee of charge to dairy farms, allowingthem to convert from dry land to irrigated dairying.

Canberra, ACT The Lower Molonglo Water Quality Control Centre provides tertiarytreated water to surrounding golf courses and vineyards. Anyremaining water is discharged to the Molonglo River, which then flowsto the Murrumbidgee River and Burrinjuck Dam. So effectively thisprovides for 100% water reuse.

Aurora, EppingNorth, VIC

The Aurora development at Epping North incorporates a third pipesystem for non-potable use at 9000 dwellings, with recycled waterprovided from its own STP.

Melbourne, VIC The Eastern Irrigation Scheme Initially supplying recycled water fromMelbournes Eastern Treatment Plant to Sandhurst Golf Club, withfuture third pipe residential development, and extension toagricultural customers.

Luggage Point,

Brisbane, QLD

$18 million plant commissioned in October 2000. It provides 10-12

ML/d of tertiary treated (fine screening, MF, RO and final chemistrycorrection) water to the nearby BP Refinery for boiler feedwater andemergency fire-fighting supply.

Wide Bay, QLD The Wide Bay Water irrigation schemes provide recycled water for400ha sugar cane, 60ha native pastures, 60ha native woodland, turffarm, golf course, sports field and airport. In 2004, WBW wasachieving 75% reuse, and aiming for 100% by 2007.

Caboolture, QLD The Caboolture Water Reclamation Plant is a 10 ML/d advancedtertiary treatment plant biofilm (MBBR) denitrification with methanoldosing), pre-ozonation, flash mix coagulation, DAFF, ozonation, BAC,ozonation. However, due to public opposition, the majority of recycled

water is still disposed to Caboolture River.Virginia, SA Virginia Recycled Water Irrigation Scheme provides Class A water

from Adelaides Bolivar STP (activated sludge + DAFF) to horticulturalfarms north of Adelaide.

Mawson Lakes,SA

The Mawson Lakes residential development includes a dual supplysystem for recycled water in non-potable uses. Recycled water issourced from the Bolivar STP and on-site stormwater throughengineered wetlands.

Kwinana, Perth,WA

The Kwinana Industrial Area Water Recycling Project provides 5GL/yrof recycled water to nearby heavy industries. Similar to the earlierLuggage Point treatment plant, it uses MF/RO technology.

(Radcliffe, 2004), (Hopkins and Barr, 2002)


35/36


6. Conclusions and CommentsA quick glimpse at this paper would give the impression that since the sections for Horizons 2and 3 are twice the size of the Horizon 1, the remaining problems are of far greater magnitudethan those solved. In fact, it demonstrates the maxim that solving the big problems exposes amyriad of smaller issues, and provides a number of new opportunities. It is also evident thatthere are research opportunities in almost every area of applied and fundamental science andengineering and we have barely addressed economic issues and not even touched on thesocial aspects.

The Horizon system offers some valuable classification of research needs and opportunities:

Horizon 2 problems mainly represent short term applied research topics, with immediate

benefits, achieving implemented solutions over a 1-3 year range. These are the type ofprojects that industry have been most interested in and are currently being investigated tosome degree.

Horizon 3 problems represent longer term, more fundamental research projects, as thereexist serious questions regarding either the scientific understanding, or the road to deliveryof solutions. Given the risk-reward ratio of these research issues, joint government-industry funding is likely required to address them. They will also need close collaborationbetween different scientific/technical disciplines and progressive water industry partners.

Given the wide range of challenges outlined above, there will be a need for different keyresearch and industry groups to focus on specific aspects. In Australia, we have a range ofwell recognised expertise in areas such as micropollutants, virus removal and detection, riskassessment, membrane processes, and ecological impact of pollutants. The rapidly growingindustry needs will help to further develop and expand Australian expertise in these areas.

From our perspective at the Advanced Wastewater Management Centre, we intend to focuson topics related to our major research expertise in biological and chemical processes and inoverall system optimisation and control engineering. Therefore, our main emphasis is ontopics in Horizons 2 and 3 relating to pollutant characteristics and control, concentratetreatment including inorganic and organic fouling and overall system integration andoptimisation. Significant progress has already been made on a number of aspects and will be

reported separately in future.Overall, there will be a significant need for R&D activities in many areas relating to waterrecycling. Given the rapid and widespread introduction of this concept in Australia, and therelative lack of expertise and experience in most other parts of the world, this providesexcellent opportunities to not only establish leading research expertise in this field, but alsodevelop strong industry know-how and experience that is applicable in many situationsworldwide.


36/36

7. ReferencesAmerican Public Health Association, American Water Works Association, and Water Environment Foundation. (1998)

Standard Methods for the Examination of Water and Wastewater , 20th edition. American Public HealthAssociation, Washington DC.

Bowyer, J. (2004). The ecological significance of dissolved organic nitrogen from wastewater treatment plant effluents . University of Queensland, Brisbane.

Cadee, K. (2006). Security through Diversity - The Water Crisis: Fact or Fiction? Water Corporation, Perth.

DAFF. (2004). http://www.affa.gov.au/content/output.cfm?ObjectID=F283DB44-6641-4723-8D4CC6B45E49F3A0 ,accessed 14/12/06.

DHS. (1999). South Australian Reclaimed Water Guidelines Treated Effluent Department of Human Services,Adelaide.

Dwyer, J. (2006) Unpublished results, AWMC.

Environmental Protection Agency. (2005). Queensland Water Recycling Guidelines . Queensland Government,Brisbane.

Holt, J. K., Park, H. G., W ang, Y. M., Stadermann, M., Artyukhin, A. B., Grigoropoulos, C. P., Noy, A., and Bakajin, O.(2006) Fast mass transport through sub-2-nanometer carbon nanotubes. Science 312 (5776), 1034-1037.

Hopkins, L., and Barr, K. (2002) Operating a Water Reclamation Plant to Convert Sewage Effluent to High Quality Water for Industrial Reuse . in IWA 3rd World Water Congress, Melbourne.

NATA. (2005). http://www.nata.asn.au/index.cfm?objectid=91A6633A-65B1-96AB-7EAF2879B94B08C3&parentCategory=Biological%20Testing/Sewage/virological&categoryLevel=4 ,accessed 19/12/2006.

National Coordinator for Recycled Water Development in Horticulture. (2005). Water Recycling in Australia . Land &Water Australia, Horticulture Australia Ltd, Arris Pty Ltd, Department of Primary Industries Victoria, CRC for

Irrigation Futures.

National Health and Medical Research Council, and Council, N. R. M. M. (2004). Water Made Clear: A consumer guide to accompany the Australian Drinking Water Guidelines 2004 . Australian Government, Canberra.

NRMMC, EPHC, and AHMC. (2006). Australian Guidelines for Water Recycling: Managing Health and Environmental Risks . National Resource Management Ministerial Council, Environment Protection and Heritage Council,Australian Health Ministers' Conference, Canberra.

Patel, M. V., Leslie, G., Yanguba, J., Pirbazari, M., and Ersever, I. (2001). Ch. 30: Options for treatment and disposalof residuals. in S. J. Duranceau, editor. Membrane Practices for Water Treatment . American Water WorksAssociation, New York.

Po, M., Kaercher, J., and Nancarrow, B. (2004). Literature review of factors influencing public perceptions of water reuse . CSIRO Land and Water, Melbourne.

POSEIDON. (2005). http://poseidon.bafg.de/servlet/is/2888/ , accessed 21/1/07.Radcliffe, J. C. (2004). Water Recycling in Australia . Australian Academy of Technological Sciences and Engineering,

Parkville.

Trewin, D. (2006). Water Account: Australia 2004-05 . Australian Bureau of Statistics, Canberra.

Water Services Association of Australia. (2006). http://www.wsaa.asn.au/download/2006/DecRestrictions.doc ,accessed 12/1/07.

Ying, G., Kookana, R., and Waite, T. D. (2004). Endocrine Disrupting Chemicals and Pharmaceuticals and Personal Care Products in Reclaimed Water in Australia . CSIRO Land and Water, Adelaide.

awmc wr challenges-1

Documents