Sunday, January 28, 2007

Poll Vaulted

The Queensland Government have decided to scrap the $10 million water recycling poll. The Courier Mail has the full story.

Premier Beattie’s explanation for the decision is that "the reality is there is no choice". He said "I wanted to put this decision to the people but the reality is that sometimes a leader has to just go ahead and do what needs to be done."

Deputy Premier Anna Bligh said the dry summer meant the "luxury of giving the people an option had disappeared". She said “not only is it increasingly inevitable that we will have to use purified water as soon as the pipe is available but we may have to use it for quite a long time...What is the point of offering people a vote on something that is not optional?"

Beattie said that his decision had also been influenced by growing cross-party acceptance of indirect potable reuse as a viable solution for the region.

Brisbane's Acting Mayor David Hinchliffe confirmed support for today’s decision on ABC News. “Frankly I don't think the Government has got any alternative - we are in a dire situation,” he said.

My personal opinion on polls like the one that had been proposed is made clear in my earlier post titled Ask a Stoopid Question. However, I was not alone in considering such a poll to be either counter-productive or a waste of time or money. Queensland Democrats Senator Andrew Bartlett called for the poll to be axed just a few days ago.

Chris Griffith from the Courier Mail posted a blog titled ‘Scrap the Water Referendum’ in November last year. He wrote “As we will certainly need recycled water to survive in south-east Queensland, there is little point holding a referendum on the subject”. While a number of interesting responses were posted, few of them directly addressed the issue of whether the poll was appropriate. Most argued passionately either for or against potable water recycling, or else for or against Wendy of Toowoomba.

Chris posted another blog when the poll date was announced at the start of December. By this time, many commentators began to call the poll a waste of time and money. Rod R of Toowoomba did so on the basis that politicians “were elected to the position of power to make hard discissions”. Elizabeth from Toowoomba agreed, urging governments to “PLEASE govern as you were elected to do, and save the taxpayer much needed monies for other projects, or use the money saved for our water”. Allan of Gold Coast pointed out that “tenders are already being let for the construction of the pipeline required to take the recycled water to the dam”. He argued that the purpose of the poll was simply to make us “feel like we are part of the process”.

Terry Nilsson of Redcliffe saw a much more sinister motivation for the poll. He wrote that “the only reason the State GOV. are going to the polls on drinking water is to leave them NOT at fault for your health or for your planned children, as in defects. If you vote this yes or no, you have no compensation claim against the GOV. because you had your say”.

I notice that ‘Scoop’ even had the foresight to ask the question that would later be answered “If drinking recycled sewage water is completely safe, as Beattie and his Australian Water Association friends tell us, why not make it 100pc?”

I think the mere threat of a poll did have one obvious and very significant advantage. It got us all talking about water. I suspect that the vast majority of residents of South East Queensland know something about water recycling that they didn’t know three months ago. This does not mean that they necessarily support the idea, but at least people are beginning to recognise that it is a realistic proposal.

But still, the process of making information available in the lead up to the poll had really barely begun. Discussion papers were to be produced and community forums were to be held. I sincerely hope that the QLD Government continue to see the value of these activities, regardless of the need to persuade people on how to vote at a poll.

…Oh and I also wish they’d stop talking about Armageddon. The situation is indeed serious, but hopefully good governance may prevent it from causing the world to come to an end.

Mr Beattie and Ms Bligh will hold a press conference shortly after midday today at which details of the decision will be announced. If anything significant transpires, I’ll add an update later.

Saturday, January 27, 2007

Tim Flannery - Australian of the Year

Professor Tim Flannery was announced yesterday as 2007 Australian of the Year. Flannery is an internationally acclaimed palaeontologist and climate scientist. He is also the author of number of popular books including The Future Eaters and The Weather Makers.

Flannery’s views on climate change and on nuclear energy are well known. Less so, his views on recycled water. A few comments in today’s Daily Telegraph bring us up to speed...

Sewage answer to water crisis

The Daily Telegraph
By Luke McIlveen
January 27, 2007

AUSTRALIANS must face up to the inevitability of using water recycled from sewage to wash, bathe and drink, the head of Prime Minister John Howard's new water task force warned yesterday.

Senator Bill Heffernan told The Saturday Daily Telegraph: "There is plenty of science available today that recycled water can be made more sterile than our rivers and streams. If this dry spell continues, there will come a time when some areas will have to inject recycled water into the drinking supply."

His message – backed by Australian of the Year environmental scientist Tim Flannery – will re-ignite the debate on whether drinking treated effluent is the only solution to the water crisis.

Senator Heffernan – heading a task force to address the crisis – said: "We shouldn't be using A-grade drinking water to water The Domain – at the very least you should be using recycled water for that."

With the Government launching its $10 billion plan this week to tackle drought in the bush, the pressure will now shift to the cities to help overcome the crisis, with recycled water increasingly being seen as the only option.

Dr Flannery claimed all Australians should be drinking recycled water, taking the lead from countries such as Singapore. "All water is recycled ultimately anyway. There's been no new water on the planet since the dinosaurs," he said.

Dr Flannery warned major residential areas could run out of water.

"The cities are on the cusp. Places like the Central Coast are in a pretty bad way," he said.

Mr Howard appeared to endorse drinking recycled water yesterday.

"I think Australians will accept that. I'm certain we will accept that very readily provided the thing is done in a very scientific fashion," he said.

Senator Heffernan called for a campaign to dispel the myths about recycled water.

He said a referendum on recycled water in the Queensland town of Toowoomba last year had failed because people had "played politics".

While the Toowoomba referendum was a setback for recycled water advocates, recent surveys have found a majority support it.

A Newspoll in December found 70 per cent of people would not object to drinking recycled sewage.

Sydney Olympic Park water and energy manager Andrzej Listowski has been running the facility on recycled sewage since 2000.

"The quality of the water is fantastic, it's just as pure as ordinary drinking water but we don't use it for drinking because of the public opposition to it," he said yesterday.

The water system at Olympic Park and in the nearby suburb of Newington uses recycled sewage for toilets, washing clothes, airconditioners and irrigation.

Tuesday, January 23, 2007

Potable Recycling in Colorado

I don’t usually re-post articles straight from newspapers here. However, I thought some readers might find this one from the Denver Post interesting.

Notable is the fact that the city planners, the water authorities and the Colorado Department of Public Health and Environment are all keen to promote what we would call an ‘unplanned’ or ‘incidental’ potable water recycling scheme. In Australia, some State Governments would play it down or pretend not to notice. Some community members call it ‘bad practice’ and would have you believe that US agencies are opposed to it.

Tapping used water
By Jeremy P. Meyer
Denver Post, 23 January 2007.

The city of Aurora is working on a $754 million project to extract water from the South Platte River, treat it and pipe it to customers - a process that will increase Aurora's water supply by 20 percent.

Snowmelt running down mountainsides and into reservoirs has been Aurora's main source of drinking water - as it has been for other Front Range cities.

In three years, residents of the Denver metro area's second-largest municipality will get recycled water out of their taps.

The city's $754 million Prairie Waters Project will draw South Platte River water downstream from the Denver Metro Wastewater Reclamation District's plant.

The river water will be sent through sand and charcoal filters, treated with chemicals and zapped with ultraviolet light.

"This is the wave of the future," said Glenn Bodnar, drinking-water specialist for the Colorado Department of Public Health and Environment.

"The way Colorado is growing and the finite amount of pure water we have, water systems are going to be looking for additional sources of drinking water," Bodnar said. "Aurora is leading the charge."

The water will be pulled from the river near Brighton, sent 34 miles south to Aurora, treated in the 40-day, six-step process, and ultimately blended with the mountain water.

Prairie Waters was created when the city faced the risk of running out of water in 2003 after a persistent drought.

Lack of snowfall and rain in the mountains left Aurora's reservoirs with only a couple of months' supply as the summer season approached.

Aurora Water director Peter Binney, who had been in the job for a year, said he never wanted to go through that kind of a crisis again.

"You don't want to be running a large water system with that kind of vulnerability," Binney said.

(Click to enlarge)

Deals with farmers were arranged for their water rights, and the city looked at 54 plans to get more water to the city.

Prairie Waters - the first large-scale water-reuse project in Colorado and the state's first big water project in 40 years - became the No. 1 choice.

"It's really setting up a water machine that is as close to a perpetual-motion machine as you can get," Binney said.

While the system of diverting mountain water to the Front Range has allowed eastern Colorado to prosper, it also has pitted the Western Slope against the Front Range, farmers against city dwellers, and water managers against environmentalists.

The reuse approach of Prairie Waters, some say, is one way to broker peace in the water wars.

"It's an approach no one has taken in Colorado," said Aurora Mayor Ed Tauer. "We've spent in this state decades fighting about water."

Environmental groups are still scrutinizing Prairie Waters but have given their initial approval.

"This is a progressive way to meet new water needs," said Bart Miller, water program manager for Western Resource Advocates. "We're very encouraged because of what it's not doing - another transmountain diversion."

The project is slated to be completed in 2010, boosting the city's water supply by 20 percent.

The city's 300,000 customers are already picking up the tab, paying an average of 12 percent more on their bills this year and an additional 12 percent next year.

Tap fees have risen from $6,711 per home to $16,641. Aurora also plans to sell bonds later this year for the project.

"The one downside is the project will be expensive," Tauer said. "But it will be cheaper to do it now than in 20 years."

In drought years, junior water users downstream - particularly farmers and others with wells - may be forced to leave fields fallow if Aurora uses all of its 10,000 acre-feet in the Prairie Waters system, Binney said. An acre-foot, which is the amount of water that would cover one acre to a depth of one foot, is generally believed to be enough to serve the needs of two families of four for a year.

The quality of the drinking water will also remain a challenge.

"The water that they will begin with will be of lesser quality than what we divert or what Aurora diverts," said Chips Barry, manager of Denver Water, the state's largest water company. "Now, it hasn't been through someone else's kidneys. They will have to do more advanced treatment than if it were pure snowmelt."

That is the reason Aurora is using a six-step process, when only two steps are needed to meet state and federal drinking- water standards, city officials say.

The goal is to make the reused water indistinguishable from the current supply.

Aurora's water currently has a total dissolved-solids concentration of 200 parts per million.

Officials want Prairie Waters to produce water with a maximum of 400 parts per million TDS concentration - which they say cannot be detected.

"They are setting a precedent," said Bodnar. "If cities want to continue to grow, and people are still looking for water to serve those additional folks, we're going to have to be creative. This sets the bar."

Saturday, January 20, 2007

Health Studies of Indirect Potable Reuse

Just before Christmas, I was asked to write a report for the Local Government Association of Queensland. They wanted the report for their members (Queensland councillors and mayors) to assist them in assessing the safety of indirect potable recycling schemes. You can download a copy from the LGAQ website.

To prepare the report, I enlisted the assistance of my colleague, David Roser. David has much experience in undertaking risk assessments for many types of water-related projects. He also has a background in microbiology, so he knows a lot more about pathogenic organisms than I do (which wouldn’t be hard!). My background is in chemistry, so of course, that’s where I predominantly contributed.

We did make some effort to write the report in fairly plain language so that it would be widely accessible. However, I admit that we probably failed at this and much of it is rather technical. Still, I don’t think its unreadable and you don’t need a PhD in water sciences to pick up the major points.

I expect that some people will have decided to criticise the report before they have even read it. Furthermore, its very easy to throw stones from behind the protective cover of an anonymous pseudonym. Of course, people are welcome to use the comments section of this post to do this. However, it would be wonderful if a few people were genuinely interested enough in this topic to want to engage in a rational discussion. I am certainly willing to discuss it further. In some of the case-studies, I don’t have much more information than what is presented, however, I will try to answer any questions and provide any further details that I can.

Due to the very short period leading up to the South East Queensland water recycling poll, we were provided with very little time to prepare this report and we both spent much of our Christmas break working on it (sob, sob). I tell you this, only so that you might be generous enough to forgive the few typos and sloppy sentences that I have since noticed lurking within.

The executive summary is copied below. Feedback, as always, is encouraged.

Risk Assessment and Health Effects Studies of Indirect Potable Reuse Schemes

Executive Summary

Planned potable reuse of municipal wastewater refers to the purposeful augmentation of a potable water supply (surface water or groundwater) with highly treated reclaimed water derived from conventionally treated municipal effluents. In ‘indirect’ potable reuse schemes, the mix of reclaimed and traditional source waters receives additional treatment prior to distribution to customers.

Municipal wastewaters contain a complex mixture of chemicals and microbiological organisms. As a result, they pose particular challenges for assuring the safety of their use as sources of potable water. These challenges have been addressed by the incorporation of Advanced Water Treatment (AWT) processes that provide a level of treatment that is not normally used in either existing sewage treatment plants currently discharging into Australia’s rivers and oceans or drinking water treatment plants currently operating on water abstracted from Australia’s rivers or dams.

Planned indirect potable recycling schemes have been implemented and assessed in terms of their human safety in the USA since the 1960s. A number of major case studies are presented in this report including:

• Montebello Forebay Groundwater Recharge Project (California)
• Potomac Estuary Experimental Water Treatment Plant (Washington DC)
• Denver Direct Potable Reuse Demonstration Project (Colorado)
• San Diego Total Resources Recovery Project (California)
• Tampa Water Resource Recovery Project (Florida)
• Singapore Water Reclamation Study “The NEWater Study”

The planned indirect potable recycling schemes provided different levels of advanced water treatment, ranging from simple filtration and disinfection in the early studies conducted on the Montebello Forebay, through to granular activated carbon (GAC), reverse osmosis (RO) and ozonation used in schemes located in Colorado and Florida. Notwithstanding this, the health-effects studies from each project are extremely encouraging in terms of the potential safety of planned potable water recycling in Australian cities. In spite of comprehensive investigations, no clear deleterious effects have been identified. Furthermore, waters treated in preparation for recycling were routinely shown to be of equal or greater quality than traditional potable water sources. This applies to both microbial and chemical water quality. Risks associated with indirect potable reuse (while never zero) are successively decreased with increasing levels of treatment.

Specific conclusions from this study are:

1. Despite more than forty years experience, no clear deleterious health effects from planned indirect potable recycling schemes have been observed.

2. As judged by potable water standards the microbial and chemical quality of water intended for indirect potable recycling is generally very high even before its release into the natural environment and further drinking-water treatment.

3. Advanced treatment processes such as reverse osmosis and advanced oxidation are highly effective barriers to recently identified chemicals of concern such as the pharmaceutically active steroidal hormones and molecules like NDMA and 1,4-dioxane which can be difficult to remove from water using traditional treatment processes.

4. Unplanned, or incidental, indirect potable water recycling is common in many developed countries including Australia. The manner and extent to which water is unintentionally indirectly used for potable purposes is distinguishable from planned indirect potable recycling schemes primarily by lower levels of treatment involved and less stringent approaches to water quality monitoring and risk management. Therefore, it should be acknowledged that the level of stringency applied to planned indirect potable water recycling schemes is well beyond that which is common international practice and already occurs in water supplies in Sydney, Brisbane and Melbourne.

5. Treated municipal wastewaters are complex sources of potable drinking water and differ from natural source waters in several major fashions. For example, the range of potential contaminants in municipal wastewaters is significantly greater than in well protected environmental waters. Furthermore, concentrations of chemical and microbial contaminants can fluctuate during events which may be difficult to detect by conventional monitoring (e.g. as a result of gastrointestinal illness in the community). Accordingly, there is a need for the application of more comprehensive risk management regimes to protect human health than may normally be applied for traditional water sources.

6. A range of new methods for risk assessment have been introduced worldwide to better and more quantitatively assess microbial and chemical risks associated with drinking water generally. These are applicable to indirect potable recycling and their application in this context is already underway especially in the USA.

While studies undertaken overseas bode well for the safety of recycled water generally, exactly how effectively these studies can be translated to potential Australian schemes is less clear. Water sources will differ and water treatment processes will differ. Furthermore, environmental barriers (surface water or groundwater environments) may differ significantly from scheme-to-scheme. Therefore, in order to ensure the full protection of public health, a comprehensive health assessment should be undertaken specifically for any planned Australian scheme. Australian health risk assessment guidelines such as those published by the enHealth Council provide guidance on how such risk assessments should be undertaken. More specific guidance is anticipated in Phase 2 of the National Guidelines for Water Recycling which is undergoing development during 2007.

The full report is available from the LGAQ website.

Saturday, January 13, 2007

Membrane Rejection Diagram

Back in May last year, I published a blog post titled The Mechanisms of Chemical Removal by Reverse Osmosis. That post explained that there are three main mechanisms that may act to prevent a chemical contaminant from passing through a reverse osmosis or nanofiltration membrane:

1. Size exclusion
2. Hydrophobic adsorption
3. Electrostatic repulsion

I’d like to examine this topic in a little more detail and to do so, I will introduce something known as a ‘membrane rejection diagram’. Some of this post uses some unavoidable scientific terminology...I apologise for that but don’t worry: you don’t need to be familiar with every single term in order to gain an understanding of the general concept presented.

Chris Bellona is a PhD student working with Associate Professor Jörg Drewes at the Colorado School of Mines. Bellona has spent his PhD studies closely examining which chemicals are able to pass through different membranes and which ones are rejected by the membranes. By understanding the three rejection mechanisms listed above, Bellona was able to categorise different chemicals according to their chemical properties that would determine how effectively they would be rejected by a specific membrane. The important molecular properties identified by Bellona are:

Molecular size: The size of a molecule is often approximated by reference to its molecular weight (MW), but can be more accurately described in terms of its molecular diameter and molecular width (MWd).

Electrostatic properties: The electrical charge of a molecule is related to how acidic it is. This is commonly described by an acid dissociation constant (pKa) and its relationship to the overall acidity of the water (pH).

Polarity or hydrophobicity: The ‘polarity’ of a molecule determines whether it is generally very soluble in water or would prefer to partition to non-water phases. Molecules that tend to partition away from water are said to be ‘hydrophobic’. The degree of hydrophobicity is commonly described by an ‘octanol-water partitioning coefficient’ (Log Kow).

The most fundamental of the rejection mechanisms is size exclusion. This is a sieving process for which molecular size or geometry prevents large molecules from passing through the dense molecular structure presented by the active surface of the membrane. Depending on the particular membrane being used, size exclusion is believed to be the dominant retention mechanism for relatively large molecules such as surfactants, hormones, most pharmaceuticals, proteins and other molecules with MW greater than 200 atomic mass units.

However, commercial membranes vary in terms of their ability to reject molecules by size exclusion. Their ability to do so is often described by the membrane’s Molecular Weight Cut-Off (MWCO). This is the manufacture's rating of the membrane's ability to reject an uncharged dextran (sugar) based on molecular weight. Membranes with a low MWCO are commonly referred to as ‘tight’ membranes compared to those with a higher MWCO, referred to as ‘loose’ membranes.

Experiments with looser membranes (nanofiltration, ultrafiltration and microfiltration), have revealed that under some conditions, some chemicals are prevented from permeating the membrane due largely to adsorption to the membrane surface. This adsorption is believed to be due to hydrophobic interactions between relatively non-polar molecules and membranes. Such adsorptive removal may be less reliable than removal based purely on size exclusion since variations in solution pH lead to variations in hydrophobicity, and possible saturation of adsorption sites may limit total adsorption capacity if the membranes are not routinely cleaned.

Some modern reverse osmosis membranes have been designed with chemical functional groups attached to the membrane surface. These functional groups can be negatively charged, thus they repel molecules that are also negatively charged away from the membrane. They are designed to do this since it requires much less energy to reject molecules by this mechanism than it would to rely on size-exclusion alone.

By considering the combination of the properties of a particular contaminant (MW, pKa, Log Kow, MWidth), the water solution (pH) and the particular membrane (MWCO, surface charge), general rejection behaviour can be estimated by the following rejection diagram developed by Bellona and Drewes. Click on the image to enlarge for a better view.

Some time ago, I went to the trouble of setting up an Excel spreadsheet that allows me to enter the properties of a membrane and a molecule and determine which of the above ten rejection categories the molecule should fall into (call me a geek, I can take it). I ran a large number of chemicals through the spreadsheet and the results were very pleasing. I found that the predicted behaviours matched reported experimental observations very well.

For example, the rejection diagram predicted that the pharmaceuticals acetylsalicylic acid (aspirin), clofibric acid, diclofenac, gemfibrozil, ibuprofen, ketoprofen, naproxen, and propyphenazone would all fall into category 10 for a membrane with MWCO 100. This predicted very high rejection is consistent with published experimental observations. Alternatively, some compounds such as 1,4-dioxane, 1,2-dichloroethane, dichloromethane and nitrosodimethylamine (NDMA) fell into category 3 indicating that they were predicted to be poorly rejected. Again this is very consistent with observed behaviour and (in the case of 1,4-dioxane and NDMA) precisely the reason that advanced oxidation was added to indirect potable water recycling schemes in California.

Of course, back in the real world things are not quite as simple as this neat rejection diagram suggests. Other important factors that contribute to rejection include the type of spacer material used to form the membrane feed channels and the system operating conditions including pressure, flow rate of water across the membrane and precise water chemistry. For this reason rejection data determined in simple lab scale experiments should be interpreted cautiously before drawing conclusions on full scale plant performance because the conditions under which the membranes operate will be different.

During normal operation, membranes are prone to fouling by the build-up of precipitated chemicals retained by them or by the growth of biomass. Fouling can lead to significant changes in membrane surface properties and thus in the way in which the membranes interact with water and dissolved contaminants. In many cases, fouling is regarded as a hindrance since it decreases membrane porosity and thus requires elevated pressures to maintain the flow of water across the membrane.

However, recent investigations reveal that fouling can also lead to improved rejection of many solutes. This observation is believed to be due to a number of factors including partial pore-blocking (thus effectively reducing the MWCO). Other factors may include increased negative surface charge leading to increased electrostatic rejection of ionic species; and increased adsorptive capacity for hydrophobic chemicals.

Most previous studies reporting relationships between physical-chemical properties of solutes and membrane interactions have been conducted using unfouled ‘virgin’ membranes and thus their conclusions are unlikely to be quantitatively transferable to full-scale systems subjected to long-term operation. Indeed, many such studies were used in the derivation of the rejection diagram by Bellona and this must be seen as a limitation to its current usefulness.

More details regarding Bellona’s membrane rejection diagram can be found in the following publication:

Bellona, C., Drewes, J. E., Xu, P. and Amy, G. (2004) Factors affecting the rejection of organic solutes during NF/RO treatment--a literature review. Water Research, Volume 38, Issue 12, Pages 2795-2809.

Sunday, January 07, 2007

Potable Reuse Plans for Perth

Planned indirect potable water recycling is likely to play a key role in securing future water supplies for the city of Perth. South Western Australia’s geography is somewhat different to that of the eastern states and this has a significant impact on the way water resources are managed in and around Perth. This has been the case for traditional water provision and would also be so for potable water recycling. Most significantly, a major potable recycling scheme would almost certainly involve a process know as managed aquifer recharge (MAR).

Approximately 60% of the water supplied to Perth is sourced from groundwater. Sandy areas or porous rocks which contain significant amounts of underground water are called aquifers. In some locations there can be numerous aquifers at different depths separated by impervious rock. The upper-most aquifer is known as the ‘shallow aquifer’ or ‘unconfined aquifer’ and its upper surface is the water table.

The water table tends to follow the topography of the ground surface, -rising where the ground gets higher and dropping in lower areas. As a result, groundwater ‘mounds’ tend to develop in comparatively higher areas. Where this happens, there is a slow horizontal flow of water outwards from the mounds under the influence of gravity. The horizontal flow rate is typically only 10 to 100 metres per year.

The city of Perth sits on what is known as the Swan Coastal Plain. The unconfined aquifer directly below it is known as the Superficial aquifer and is on average about 50 metres thick. The Superficial aquifer has two important mounds. These are the Gnangara mound to the north of Perth and the smaller Jandkot mound to the south. Below the Superficial aquifer there are a number of confined aquifers, the largest of which are the Leederville, which is typically several hundred metres thick, and the Yarragadee, which in many areas is more than a kilometre thick.

The Leederville aquifer is an important drinking-water source for Perth. The Superficial aquifer has also been an important water source for many decades and it is very common for Perth households to extract water directly from it for garden and lawn watering. The exploitation of this groundwater is rapidly approaching sustainable limits in some areas, causing the water table to drop markedly.

Managed aquifer recharge refers to the process of adding a water source such as recycled water to depleted aquifers under controlled conditions. Water can be added to an unconfined aquifer by passive infiltration from a pond (or ‘basin’) or by pumping it along a shallow pervious pipe or gravel trench known as an infiltration gallery. In either case, the water infiltrates down through the soil to the aquifer. Recharging a confined aquifer normally requires pressurised pumping through an injection well.

The organisation that manages Perth’s water resources is Water Corporation. They have signalled that they see managed aquifer recharge as a means of potentially supplying around 27 gigalitres per year of public drinking water injected via the Gnangara mound by 2015. The source water would be advanced-treated recycled water from Beenyup Wastewater Treatment Plant. It would then be transported via a (roughly 40 km) pipeline to a nature reserve further north of Perth. At various points en route, water would be injected into the confined Leederville aquifer or infiltrated into the Superficial aquifer.

The image below is a conceptual diagram of such a scheme showing a recycled water pipeline from Beenyup. The red crosses show possible injection points for the Leederville aquifer and the red squares show possible infiltration sites for the Superficial aquifer. Click on the image and magnify it for a better view.

Potential Perth MAR Scheme by 2015

However, before committing to the hundreds of millions of dollars needed to build such as scheme, Water Corporation have elected to begin by the construction of a smaller trial, through which annually 1.5 gigalitres of recycled water would be injected into the Leederville aquifer at Beenyup. Before injection, the treated effluents would be upgraded to potable standard by advanced treatment including microfiltration, reverse osmosis, and advanced oxidation (probably UV). The water will then be injected to a depth of around 200 metres. Water Corporation have predicted that this water would then take a minimum of 50 years before reaching drinking-water production bores more than three kilometres away.

Detailed monitoring of water quality will be undertaken prior to injection into the aquifer and also via a number of extraction wells as the water moves horizontally away from the Gnangara mound. The monitoring program is intended to be undertaken over a period of three years.

As well as demonstrating the technical feasibility, an important aspect of the trial project is to enhance community confidence in potable recycling by managed aquifer recharge. This week, the West Australian newspaper ran a front page story with the large-font headline 'The plan for us to drink treated sewage' (Warnie doesn’t look too impressed with the idea!). Personally, if I were the paper’s editor, I would have left out the word 'treated' for an even more alarmist headline. But more importantly, the accompanying article did give a good description of the proposed scheme and the role that it is expected to play as a component of future water supplies. As we have all seen, communication and the provision of accurate information to the community must be key components of planning for potable water recycling schemes.

I think this is an exciting trial which heralds a new dimension to sustainable water management in Australia. What do you think?