Thursday, May 28, 2009

San Diego Update

As many readers of this blog would be aware, the City of San Diego has been toying with the idea of indirect potable water recycling for at least a decade now. However, as the city generally credited with having popularised the term ‘toilet to tap’, it may be no surprise that negative public perception has been a major obstacle.

I came across an excellent article today in the San Diego News Network. It’s a fairly solid article providing a good current perspective on the situation. It’s worth reading if –like me- you’re interested in this kind of stuff... and if you’re not, you’re really reading the wrong blog site!

Overcoming the stigma of ‘toilet-to-tap’ water

From water officials to academics, and private business experts, all agree that the reuse of water for drinking is safe, affordable and necessary. But what about the yuk factor?

By E.A. Barrera, SDNN
San Diego News Network
Wednesday, May 27, 2009

Water resource specialist Chris Reilly would often take his sixth grade students to waterways - streams, ponds, estuaries - when he was a teacher for the Boulder Creek YMCA in Santa Cruz. A 1985 graduate of Cal Poly San Luis Obispo and a future water resource specialist with the San Diego County Water Authority, he would take the kids on field trips to discuss nature, water and the life-cycle of all living things on the planet.

“I would have them look at the life in the water and think about the water they were playing in or drinking,” said Reilly, who spent 12 years with the San Diego County Water Authority and now serves Northern California’s Indian Valley as Water Master for the California Department of Water Resources. “I would remind them that the water they were studying was the same water the dinosaurs had once drank and lived on. All water is recycled and the same water that was around 5 million years ago is still with us. There is no such thing as new water.”

With the city of San Diego declaring a Level 2 drought alert and Gov. Arnold Schwarzenegger issuing a water shortage emergency, water specialists like Reilly feel it is critical communities across the state develop as many water retention, conservation and reserve capabilities as possible.

“We can’t afford to take anything off the table and that includes indirect potable reuse water that is very safe when the proper filtration systems are in place,” Reilly said.

For almost two decades, San Diego has debated the use of Indirect Potable Reuse (IPR) water as a source of replenishing the reservoirs in the city and county for its drinking supply. From water officials at the San Diego County Water Authority (SDCWA) and the local water districts within the county, to academics, and private business experts, all agree that the reuse of water for drinking is safe, affordable and necessary.

But buttressing this argument is the “yuk factor” associated with the concept of drinking treated sewage water, and the belief by many that trying to blend sewage water into the drinking supply is a recipe for disease and a public health disaster. The term “toilet-to-tap” has become the rallying cry for opponents to IPR, who include San Diego Mayor Jerry Sanders.

“Mayor Sanders is concerned with the public’s perception of indirect potable reuse and feels there are other priorities which the city should focus on - mainly in the area of conservation of water,” said Bill Harris, deputy press secretary to Sanders.

In San Diego County, water is delivered and collected through three primary sources: The Sacramento/San Joaquin River, the Colorado River, and the many reservoirs built within the region. But more than 80 percent of the county’s water comes from the Colorado River, with less than 15 percent collected through local sources. According to the Southern California Metropolitan Water District (MWD), most water supplies in Southern California begin as snowmelt or rainfall that flows into rivers. However, 75 percent of that runoff occurs in the northern parts of the state, while the majority of California’s population lives in the south.

In order to bring that water supply down to residents in Southern California, the water is carried through aqueducts that are several hundred miles long. Whether from the Colorado River - that has a point of origin just north of Colorado’s Grand Lake in the Rocky Mountains - or snow melt and rain runoff transported south via aqueduct, MWD notes both federal and state rules protect the drinking water along its journey.

Under Title 22 of the California Code of Regulations, water safety is monitored and regulated so that it will be safe before coming in human contact. Several agencies - including the U.S. Environmental Protection Agency, the State Water Resources Control Board, the California Department of Health Services, and of course, the Metropolitan Water District of Southern California - keep an eye on water, even before it reaches a treatment plant.

Nevertheless, millions of people also make use of the river water and other sources, fueling the complaint by IPR advocates that there is something inherently cleaner about water originating from these sources over supplies already being used.

“There seems to be a myth that water coming down the Colorado is ‘pure Rocky Mountain spring water.’ In fact, nothing could be further from the truth,” said San Diego State University professor Phillip Pryde in 2004.

Pryde, who served as chairman of the San Diego County Water Authority’s Reclamation Committee, noted that water from the Colorado River passed through several towns and cities on its way to San Diego.

“Tens of thousands of recreational users of the river make direct use of it for ‘fast, fast relief’ while floating down it or swimming in it (as do, in some cases, their pets),” he said. “A portion of this water goes directly into our drinking water plants without prior treatment. It may be argued that it’s highly diluted, if that makes people feel better, but it still contains untreated human wastes.”

The process for treatment of water involves a multi-phase filtration system broken down into nine steps.

During the first two steps, the water passes through various screens and sedimentation, including beds of anthracite coal, which removes most suspended solids from the water. According to experts familiar with the process, the water at this point is safe for irrigation and other non-drinking uses.

After these initial steps, the water is sent through a treatment called “microfiltration” which further filters out any remaining solids. Water is then run through a procedure called reverse osmosis, which pumps the water through special membranes whose pores are so small, only water molecules or something smaller are said to be able to pass. During a 1998 debate on the topic, the SDCWA issued a pamphlet describing the differences in size between water molecules and other molecules, by claiming that if a water molecule were the size of a tennis ball, a virus would be the size of a semi-truck, a bacteria the size of a pyramid, and a protozoa the size of a volcano. The SDCWA further stated that even the molecules of microscopic metals and other inorganic compounds, as well as organic compounds, would be too large to pass through the Reverse Osmosis membrane.

After the Reverse Osmosis procedure, the water is further cleaned by introducing Ion Exchange, which reduces nitrate concentrations to negligible levels, much as a water softener works. Then Ozone, a disinfectant, is released into the water for further cleansing.

In the next phase, the recycled water is blended into the surface water reservoirs of San Diego, where it is mixed with the raw water supply. From the reservoir, the water is once again run through the normal filtration process before being distributed to the general public.

“The re-purified water is cleaner than the water that comes out of the tap,” Reilly said. “Then that water is blended in with the reservoirs and run through the normal filtration process, so that nobody should be worried about the safety of that water.”

Former Ramona Municipal Water Water Disrict manager Tom Brammell agreed.

“Personally, drinking recycled water is OK with me,” Brammell said. The filtration and dilution make the water extremely clean.”

San Diego River at Alpine County supervisor Bill Horn, an avocado rancher, said re-purified water was so clean he often had to add components into the mix before using it for his crops.

Horn’s board colleague - Pam Slater-Price said it was important the region look at every option for sources of water.

“We definitely have to do it. We no longer have the luxury of not using Indirect Potable Reuse water and in fact are already doing it,” said Slater-Price. “People have the conception of water coming from the Colorado River or other natural sources as pristine and they may be repulsed by the thought of sewage water being reused for drinking. But when you understand that all water is reused and the system of treatment in place cleans the water so thoroughly that it is cleaner than when it comes out of the tap, then you realize it is something we can do and is necessary.”

Yet worries about the health of the water persist and memories of the 1993 cryptosporidium outbreak in Milwaukee fuel continued fears about what can happen when sewage water is mixed into a drinking water supply. Cryptosporidium is a virus which passes through the intestines of animals, mostly cattle, and exits through their fecal matter. It can cause severe stomach flu-like symptoms, such as diarrhea, nausea, vomiting, fatigue and low grade fever. The disease is particularly susceptible to waterborne delivery.

In healthy persons, the infection can last up to two weeks, according to Dr. William R. Mac Kenzie in a 1994 article for the New England Journal of Medicine. But in people with weak immune systems, such as the elderly, babies and those diagnosed with other illnesses such as the HIV virus, cryptosporidium infection can be deadly. During the Milwaukee outbreak, 50 cryptosporidium-associated deaths were reported, according to the Wisconsin Bureau of Public Health. The outbreak resulted from flooding which overwhelmed the Milwaukee sewage system.

“A heavy snowfall followed by spring flooding and a heavy storm contributed to sending record amounts of overflow from the Milwaukee Harbor into Lake Michigan,” Mac Kenzie wrote. “This caused sewer overflows and a sewage bypass which created an overworked waste water treatment plant system and sent the cryptosporidium virus into the water.”

San Diego does not suffer flooding problems from heavy snow and ice, but other natural disasters do occur, including wildfires and even the occasional earthquake. But, Reilly said, what happened in Milwaukee resulted from older technology that has been improved in the last 15 years.

“That outbreak was a result of mechanical failures within the treatment plant and it is always possible mechanical devices will break and some portion of the treatment process will fail. But there are so many backup systems and safety procedures in place, that you have to trust they will work in the case of a natural disaster,” he said.

Mike Espiritu, the former water quality superintendent with the Helix Water District, shares Reilly’s view. During San Diego’s debate over reusable water a decade ago, Espiritu said that what happened in Milwaukee would not happen in San Diego.

“Milwaukee was an aberration. They were ill-prepared. Every one of their multiple barrier systems broke down. San Diego’s system is much better. The safeguards we have in San Diego would prevent such an accident,” he said in 1998.

Slater -Price said that before she ever voted on a system for using IPR water, she would discuss the safety conditions with all available water experts and would tour the treatment plants, making sure health safeguards were in place.

Yet the term “Toilet-to-Tap” persists and registers in the public arena very easily. Originating from Gerald Silver, an angry Encino homeowner’s association president who used the phrase in 1995 during a debate over IPR in Los Angeles, the phrase quickly became the term most opponents used to refer to the idea of IPR.

In San Diego, when the plan was put to public review in 1998, angry protestors including then city councilmember George Stevens, assemblymember Howard Wayne, and former San Diego city councilmember Bruce Henderson used the term to state their opposition to IPR.

Bernie Rhinerson, who served as chair of the SDCWA in 2003, said inflammatory language such as phrases like “toilet-to-tap” were more for political purposes than scientific ones.

“It’s used because the public is still against it,” he said. But all the science I’ve read says (IPR) is a viable source of potable water. Diversity of water supplies has to be at the center of our commitment to provide enough water for residents.”

During an October 2007 water conservation summit held at the University of San Diego, mayor Sanders spoke to a large collection of academics, engineers and other water experts. While he supported their efforts on conservation and the use of non-drinking recycled water for agriculture and landscapes, his opposition to IPR created frustration with many of the other speakers.

Among them was James Stayer, Division Manager for the PBS&J West Water/Wastewater Group, which is based in Carlsbad. The firm works on water and water reuse projects tin California, Nevada and Arizona. Stayer blamed both politicians and the media for the continued use of the term toilet-to-tap.

“This is a drought proof water supply and the media is to blame for creating this image of toilet to tap. It does not allow any room for meaningful discussion of the subject,” said Stayer.

But Slater-Price, in assessing why an idea that so many agree works well is still not in use after more than a decade of debate, said the blame for the lack of support among the public was universal.

“There are a lot of people living with ignorance on this subject and it is not just politicians. We have not done a good job of explaining this, but neither have those in academia and professional circles. A lot of them were way ahead of the public on this topic and they don’t seem to understand that. It is incumbent on all of us who care about this and want to see IPR put in place to do a better job educating people why it is needed.”

Friday, May 08, 2009

Western Corridor Mothballed

The following article is from today’s Courier Mail newspaper.

It is following up on the Queensland Government’s decision to delay adding recycled water from the Western Corridor Recycled Water Project to drinking water supplies until those supplies dip below 40% of capacity. The projection here is that that figure will not be reached until December 2010 at the earliest. A few apparent pieces of missing information seem to be:

Who’s projection is this? The Queensland Water Commission? The Courier Mail? Someone else?

Are there plans to actually produce and productively use the remaining 120 megalitres per day of recycled water?

Water Recycling Pipeline in Mothballs
The Courier-Mail
Craig Johnstone

May 08, 2009 12:00am

A 16km pipeline of recycled water is ready to pump the liquid the final 100m into southeast Queensland's drinking supply but that may never happen.

The pipeline leading to Wivenhoe Dam, the main source of the region's drinking water, has been built, tested and commissioned as part of the Bligh Government's $2.4 billion Western Corridor recycled water project.

But the pipeline, meant to carry purified recycled water from Lowood to the dam, was effectively mothballed as soon as it was built due to the Government's decision to put recycled water into the drinking supply only as a last resort.

Completed before the Government backflipped on its recycled water policy last November, the pipeline was still commissioned, with the operator, Watersecure, testing it for leaks and signal faults.

The 1.2m-diameter pipe is now full of recycled water, ready to deliver it down a 100m cascade into the dam.

Premier Anna Bligh last November reversed her position on putting recycled water into the region's drinking water.

After insisting for months during the region's drought that there was no other option than to top up southeast Queensland's then shrinking dam system with recycled water, she announced the Government would only use it as a last resort.

The Queensland Water Commission has recommended that the Government consider adding purified recycled water to the drinking supply when dam storage levels drop to 40 per cent.

On current estimates, this will not happen until December, 2010, even if the region suffers a repeat of its worst rainfall period on record.

The Swanbank and Tarong power stations remain the only consumers of purified recycled water despite the Government spending $2.4 billion on the western corridor project.

The project is designed to produce up to 232 megalitres of recycled water a day but is currently only delivering an average of just over 112 megalitres a day to the two power station companies, with no new customers for its product in the offing.

A spokesman for Watersecure said the pipeline, which has been specifically built to supply recycled water to the dam, had been "dry and wet commissioned", but no recycled water was released into the dam during any testing.

Thursday, April 30, 2009

Californian IPR wins Engineering Award

As many readers of this blog will know, the largest planned indirect potable water recycling (IPR) scheme in the world is the Groundwater Replenishment (GWR) System in Orange County, California.

I was interested to read this morning of the GWR winning the “Grand Conceptor Award” in this year’s American Council of Engineering Companies (ACEC) Engineering Excellence award competition.

A quick Google search reveals plenty of previous “Grand Conceptor Award” winners, but still I may have to establish an award for anyone who can tell me what a “Grand Conceptor” is. I have still not quite learnt how to speak American…

Groundwater Replenishment System Wins ACEC Award
Water World, 29th April, 2009

CAMBRIDGE, Massachusetts, April 29, 2009 — The 70 mgd Orange County Groundwater Replenishment (GWR) System, designed by the engineering firm CDM, recently won the Grand Conceptor Award in the 2009 American Council of Engineering Companies (ACEC) Engineering Excellence award competition. This groundbreaking $480 million project, which converts highly treated wastewater into an indirect potable water source, officially went online on January 25, 2008. The award was formally presented to CDM at the official ACEC awards gala on April 28, 2009.

Orange County Water District and Orange County Sanitation District hired CDM to design a solution that would meet an increased demand for potable water while minimizing the impact of extended area droughts. The expandable GWR System treats effluent with a multi-barrier approach — microfiltration for pretreatment, reverse osmosis for purification, and ultraviolet light for disinfection — removing bacteria, emerging contaminants, chemicals, and viruses.

Following treatment, the purified water is injected into an underground seawater barrier or percolated into aquifers before becoming part of the drinking water supply for the county's residents. This solution takes advantage of water that was formerly discharged into the ocean, helping to protect the environment and providing a new water source for the county.

As part of the project, CDM also designed supporting chemical systems, buildings, an electrical substation, three water pumping stations, more than 13 miles of transport pipeline, 3 miles of barrier pipelines, and 16 injection wells on eight different sites. CDM provided bidding support and construction services, operations and maintenance services, and assisted with operator training and facility startup.

This pioneering advanced water purification and groundwater replenishment system helps drought-proof Orange County while providing safe, potable water to a growing population in an environmentally friendly and energy-efficient way.

Monday, April 13, 2009

Drugs in Fish

Sometimes you can wind up on the front page of the Canberra Times just by answering a phone call from a journalist...

There was a very interesting research paper published recently in the journal Environmental Toxicology and Chemistry. The details (for anyone interested) are:

A. J. Ramirez et al (2009). "Occurrence of pharmaceuticals and personal care products (PPCPs) in fish: Results of a national pilot study in the U.S." Environmental Toxicology and Chemistry DOI: 10.1897/08-561.1.

The paper describes how “a national pilot study was initiated in the USA to assess the accumulation of pharmaceuticals and personal care products in fish sampled from five effluent-dominated rivers that receive direct discharge from wastewater treatment facilities in Chicago, IL, Dallas, TX, Orlando, FL, Phoenix, AZ, and West Chester, PA”.

For some years now, scientists have been reporting the presence of pharmaceuticals in waters receiving effluents from wastewater (sewage) treatment plants. So it is not terribly surprising to now learn that some of those chemicals are bio-accumulated and can be measured in the tissue of fish swimming in effluent-receiving waters.

Anyway, I received a call from the Canberra Times to ask whether such a situation could occur in Australia. I pointed out that it certainly could, but that we have not yet done sufficient research to know the extent of any impacts to Australian wildlife. The next thing I know, I’m on the front page of the Canberra Times with an old file photograph from 2005!

Chemical sewage causes fish to flounder
By Ewa Kretowicz
Canberra Times
6 April 2009

It's enough to make a fish gasp. Australian scientists fear that Canberra's sewage treatment plant could be filling the Murrumbidgee's fish with prescription drugs like Prozac.

Fish swimming below the Lower Molonglo Water Quality Control Centre could be high on a mixture of uppers and downers after American studies found fish from five US rivers were tainted with traces of medications and common chemicals, which are not removed by water purification.

Chemical contaminants in water expert Dr Stuart Khan said Canberra effluent was treated then released back in to the Murrumbidgee.

''[Canberra] would be an obvious place to look for high concentrations of pharmaceuticals in rivers and therefore potential concentrations accumulating to fish as reported in this study,'' Dr Khan said.

The common antihistamine diphenhydramine (Benadryl), an anticonvulsant and two antidepressants were among the seven types of pharmaceuticals found in the tissue and livers of fish from waterways in or near Chicago, Dallas, Philadelphia, Phoenix and Orlando.

In Australia, as in America, federal standards exist for treated waste- water, but they do not address pharmaceuticals or most personal care products, and little is known about the effects they have on the environment and wildlife.

Actew's Ross Knee said Canberra's water treatment plant did not specifically target pharmaceuticals.

''In Australia it's never been identified as an issue ... we tested our effluent for over 200 parameters recently and it included a lot of organics and pharmaceuticals, pesticides and herbicides, a lot were below detection limit but all were within the drinking guidelines.''

Dr Khan is urging a national water survey to investigate and resource poor quality waste water discharged into river environments.

He said Australia's largest cities, like Sydney and Melbourne discharged effluent into the ocean, but lower inflow into our rivers could be compounding the problem.

The results of the US study were very concerning.

''We know these are biologically active chemicals and they are designed to have effects on the human body.''

He said no conclusion about the effects of exposure to very low concentrations of pharmaceuticals not prescribed to the person had been reached. '

'I would say the consensus would be that there is no evidence of ill effects of those chemicals but there is certainly widespread concern

That there are cancer-producing chemicals accumulating in biological organisms is certainly a concern for its own sake for the health of the ecosystem and if they become part of the food source for humans then I think there are obvious implications there as well for exposure to those chemicals.''

Just some of the medications and chemicals found from among the 36 tested for were the cholesterol drug gemfibrozil (Lopid), which researchers say had never before been found in wild fish; diltiazem (Cardizem), a medication that helps control high blood pressure; carbamazepine (Tegretol), a drug used for epilepsy and bipolar disorder; and norfluoxetine, an active ingredient in the antidepressant fluoxetine (Prozac).

Monday, March 23, 2009

Water Quality Data for Western Corridor

The first interim water quality data for the Queensland Western Corridor Recycled Water Project (WCRWP) were released this month.

The full report and an evaluation of it by the Expert Advisory Panel are available from the website of the Queensland Water Commission.

The interim report presents final water quality data (presumably after the advanced oxidation and lime stabilisation) from the advanced water treatment plant at Bundamba. These cover the three-month period of plant validation and verification from 22 May to 25 August 2008 and all subsequent results during normal operation up to December 2008 (an additional four months).

I recommend that interested people download and read the actual interim report. But for those who may care, my own personal comments and interpretation are as follows:

Scope of the water quality analysis

On the range of chemical and microbial contaminants monitored, I think the report is very comprehensive and by far exceeds any water quality monitoring program that I have seen previously from anywhere in the world.

I’m not sure whether the intention is to sustain this level of monitoring. But if that can be done, it will provide a valuable source of knowledge to improve risk assessment and planning for many future advanced water treatment processes.

My only real disappointment with the way that the data are reported is the failure to include analytical detection limits for measurements that were below the analytical detection limit. To report data simply as ‘not detected’ (ND) provides very little information unless the detection limit is known to the reader. From the way that the data are presented, it is clear in all cases that ‘ND’ means that the concentration was less than the Public Health Regulation Standard, but it would be helpful to have some indication of how much less it may have been.

While I understand that this is a summary report (and it is intended to be highly readable to a wide audience), it would also be helpful to have some additional statistical description of the water quality parameters. In some cases, means and standard deviations may have been determinable (where there were sufficient data). In others, the data may have been well presentable as a cumulative probability distribution or other similar means of description.

It would also be helpful to know the concentrations of the chemical constituents earlier in the treatment process. This would allow an assessment to be made regarding the treatment performance of the various treatment ‘barriers’. Such information is useful to give an indication that the individual treatment processes are doing what they are expected to do and thus to properly validate the ‘multiple barrier’ concept.

Physical characteristics

It is a little difficult to interpret the physical parameters without an explicit description of the water sampling location. However, I presume that the water has undergone final stabilisation, which involves the addition of ‘hardness’ (calcium ions) and alkalinity (bicarbonate ions). This explains the relatively high pH (7.5 – 7.8) and total dissolved solids (110 – 170 mg/L) that would both otherwise be expected to be lower directly after reverse osmosis and advanced oxidation treatment.

The stabilisation process is important since ultrapure water is quite ‘aggressive’ and leads to corrosion of pipes. This has the effect of picking up other (less desirable) dissolved substances along the way.

Inorganic compounds

Sixteen cations and four anions were monitored. Of these, the heavy metal cadmium, was observed to exceed the Public Health Regulation Standard on one occasion at the beginning of the validation process. A concentration of 0.0023 mg/L was recorded, compared to a standard of 0.002 mg/L. The explanation given in the report is that cadmium is found is small quantities in the lime that is used for stabilisation and that imprecise lime dosing led to the presence of the dissolved cadmium. This has now been corrected and no such exceedence was again identified following the validation phase or during the operational phase.

Disinfection byproducts

The advanced water treatment process includes a number of disinfection steps, which normally (almost certainly) lead to some formation of disinfection byproducts. The key disinfection processes that may lead to byproducts include chloramination prior to microfiltration, UV/H2O2 advanced oxidation and final chlorination.

The monitoring program included three types of disinfection byproducts. These were inorganic byproducts (bromate and chlorite), organic byproducts (trihalomethanes and haloacetic acids), and nitrosamines (NDMA and NDEA).

One exceedance of bromate (0.04 mg/L compared to standard of 0.02 mg/L) was reported and this was explained to have been the result of a short-term excessive chlorine dose. Corrective action was undertaken on the chlorine dosing system and no further incidences of bromate exceedance have been observed.

Three exceedances for bromodichloromethane reflect the difficulties in regularly complying with the relatively stringent standard of 6 ug/L. There are many drinking water supplies throughout the world that would rarely comply with this standard. From what I understand from the interim report, this standard was introduced in July 2008, after the validation period for the advanced water treatment plant had commenced. As a result, plant operations were adjusted in order to comply with the standard and since then, all subsequent results have been in compliance.

While the NDMA results are technically not an exceedance of Public Health Regulation Standard, the maximum concentration was reported to be 10 ng/L, which is precisely equal to the Standard. In this case, it would certainly be helpful to have a more detailed description of the NDMA concentration distribution. For example, was it commonly within 10% of the Standard, or was this a single aberrant outlier? This is important to help understand the likelihood of exceeding the Standard during future operations (as well as for understanding overall long-term exposure).


Eight well-known steroidal hormones were monitored. These included four estrogens (17-alpha-ethynylestradiol, 17-beta-estradiol, estriol and estrone), three androgens (androsterone, etiocholanolone and testosterone) and one progestin (norgestrel).

Many people will be more interested in the results for hormones than I am. In my opinion, the fact that none of the hormones could be detected was inevitable given the source water quality and the nature of the advanced treatment processes.

The issue of risks associated with hormones in advanced water recycling schemes has been severely exaggerated by certain politicians who apparently don’t mind looking foolish for the sake of whipping up a little hysteria.

Nonetheless, the results for the hormones provide a useful illustration of my earlier comment regarding detection limits. The Public Health Regulation Standard for 17-alpha-ethinylestradiol is given as 1.5 ng/L. Depending on the analytical method used, it is quite likely that this value is very close to detection limit. Thus it would be helpful to have an indication of how far below the standard we can be confident of being.

Other organic chemicals

None of the five chemicals presented in this category were reported to have exceeded the Public Health Regulation Standard on any occasion. Those chemicals for which actual numbers (as opposed to ‘ND’) were reported indicate that a very significant gap exists between the standard and actual measured concentrations.

Microbiological water quality

Results for Escheria coli and clostridium perfringens spores indicate excellent disinfection of bacteria across the multiple barrier system. The more difficult micro-organisms to manage are viruses. The non-detection of somatic coliphages is an indication of good control of viruses, but the two exceedances for F-RNA phages do raise the eyebrows.

The interim report describes how these results were further investigated and states:

“On balance, it is concluded that these two detections were the result of the analytical method used and did not indicate the presence of bacteriophages in the purified recycled water.

In line with the findings of the investigations, the following corrective actions have been implemented:
  • duplicate samples are being taken, to provide greater certainty of results;
  • the number and frequency of water quality tests will be increased where an initial positive result is returned; and
  • changes have been made to the sampling and analysis process.

“False” positives will continue to be reported even if duplicate analyses return a negative result. Continuous monitoring, plant shut down controls, and additional water quality testing are part of the ongoing plant operation and form part of the robust risk identification and mitigation practices.

I’d suggest keeping a close eye on this parameter in order to improve our understanding of both the analytical reliability and the nature of its removal/inactivation by the various individual barriers of the advanced treatment processes.

Additional PCR testing for a range of specific viruses (rotavirus, astrovirus, noroviruses, adenovirus, enteroviruses, hepatitis A and reovirus) provides some assurance of the absence of these highly pathogenic organisms.

Herbicides, pesticides and phenols

Thirty five herbicides, pesticides and phenols were monitored, but none of then exceeded the relevant Public Health Regulation Standard. Without reported detection limits, it is difficult to interpret how low expected concentrations may be for most of these contaminants.

I would be interested to compare this result with current water quality in Lake Wivenhoe…

Pharmaceuticals and personal care products

Fifty five pharmaceuticals and personal care products were monitored, but again, none of them exceeded the relevant Public Health Regulation Standard.

Some of these results would be particularly useful to relate to concentrations prior to individual treatment processes. Some, such as caffeine and salicylic acid can provide a very good indication of reverse osmosis treatment performance and thus it is useful to monitor their removal (even if they are well below Public Health Regulation Standards).


No exceedance of radioactivity was observed.

QWC Expert Advisory Panel comments

The Interim Water Quality Report is preceded by a letter of assessment by the QWC Expert Advisory Panel. The letter states that:

“Based on the testing results in the report, the commissioning of the Western Corridor Recycled Water Project is proceeding well, providing confidence it is capable of consistently producing purified recycled water that is safe to be used to supplement Wivenhoe Dam.

The results indicate that the treatment process barriers are effective in controlling water quality hazards and reliably producing purified recycled water suitable for release into Wivenhoe Dam. No exceedances of the water quality standards have been measured in this testing data after normal operations commenced.”

I agree with this assessment. However, I'd like to see some more raw data, purely for the purpose of trying to draw some further information and insights from it.

I think it is very important not to get carried away with monitoring end-point water quality. In my opinion, much more important information can be gleaned by carefully observing individual treatment processes and ensuring that they are each operating effectively. This is the whole basis of the multiple-barrier treatment philosophy. Without closely monitoring each individual barrier, it is not possible to have confidence that if one barrier fails, then another will provide the necessary redundancy to ensure safety.

I’m not suggesting that suitable multiple-barrier monitoring is not being undertaken, -I presume that it probably is. However, I’d like to raise awareness that this is the type of data that we should really all be interested in, -rather than just long tables of ‘non-detects’… more on that topic soon!

Tuesday, March 17, 2009

A note from Meredith Jayne

I received the below note from a reader by the name of Meredith Jayne. At the end of her note, Meredith states "Since everyone is entitled to an opinion, I would appreciate my comments being posted on your website".

I am happy to post Meredith’s views here since the person most likely to sue myself for libel in this case is myself.

Its clear that Meredith is opposed to indirect potable water recycling...and I don’t think she likes me very much either! She is, of course, entitled to express both views.

But for the record, I reject the suggestion that I have "vested financial interests in the recycled sewage scheme". Nor have I "been highly paid by the Government to provide data that support their views on recycled sewage". I consider myself to be an independent and ethical researcher with high standards for scientific integrity, openness and transparency.

Meredith's Message...

Khan, (Chief sewer sipper and propaganda minister.) Something stinks in Queensland and it's not just the sewerage. Government and corporate greed is driving the water crises. The Government is hooked on using waste to raise revenue and is just using the public drinking water supplies as cash cows (and a cheap means of disposal), failing for decades to invest in new water infrastructure and failing to maintain existing infrastructure. Government greed counts more to making profit from the sale and production of recycled sewage than the safety and health of the consuming public. The assets of the people are being exploited by the Government. Health concerns are not a priority of this greedy Government, profiteering is. After the name change and marketing was put in place the next step in the sewerage shenanigans was to hire industry friendly scientists. The Government hired their own 'independant experts'to defend and promote their recycled sewage product who were bought in various ways to manipulate and shape science. The Government set out to build a body of science around the notion that hazardous highly toxic, industrial and hospital diseased wastes are rendered harmless by simply passing the material through a sieve. The public is too smart too believe that nonsense. The Government and their propaganda hit men have used every opportunity to discredit emminent scientists and dismiss information associated with consuming recycled sewage. Because it is clear and odorless recycled sewage is being fraudently marketed as a safe user friendly product without revealing that it is full of highly toxic chemicals and diseases. The Government routinely runs massive multi million dollar advertising campaigns, complete with graphic images to warn smokers of the dangers, yet strangely enough the public has not received any warnings or informtion on the same, (plus many more) cancer causing agents being discharged to the sewerage system--our new drinking source. What was once viewed as a nuisance and a liability is now being recast as a valuable resource. The Government has decided on recycled sewage as they just love a good project that will splash lots of tax-payer money around. The arrogant, lying, self serving, contemptuous Bligh Government and their science-for-hire know-it-alls as well as their spin doctor friends in the media have insisted that recycled sewage is 'safe'to drink and is not a threat to human health, with no supporting evidence to back their absurd claims they have continually given the public their assurances in regards to it's so called 'safety'. We were once told that asbestos was safe, too, with no threat to human health. Australia now has the highest rate of mesothelioma in the world. The Government also once recognised that working with recycled sewage was an occupational health hazard, then approved it's use for drinking purposes. If they all believed in the so called 'safety'of their recycled sewage product so much why did the Bligh Government find it necessary to introduce a new law that absolves themslves as well as the water service providers and operators in the event of any health problems arising from consuming recycled sewage? They cannot be sued, do not have to pay compensation and therefore are not accountable to the people. The onus is on the public. This is just another demonstration of utter contempt that this greedy, self serving Government has for the people they are being paid well to represent. The claims that recycled sewage is done all over the world is absolute rubbish. The announcement of the introduction of the Governments bizzare recycled sewage experiment made major world news headlines, a good indication no other country in the world deliberately adds recycled sewage to their drinking water supplies, One of the many lawyer firms representing the Government has said that recycled sewage is a new product and that the effects on humans and the environment of it's long term use is not fully known. The act further recognises the need to offer some form of protection from the potentially huge liability that water industry players could be subjected to through the use of recycled sewage. Does'nt sound too safe, now does it Khan? If it was so safe there would not be the need to introduce a new law that protects the Government, water service providers and operators from law suits. The Government and the cash strapped water researchers as well as their spin doctor friends in the the media have gone to great lengths to promote recycled sewage and to conceal information on the tens of thousands of highly toxic chemicals which are being allowed to be routinely dumped into the sewerage. No information on the drug resistant diseases or the health risks or consequences of drinking from a highly contaminated source. Since recycled sewage is an extremely high risk area the public is entitled to all relevant information that has the potential to cause serious illness and death. The Government has no right to withhold that vital information. The Government has ignored public health concerns while the so called 'yuck factor' has been exploited for all it's worth. We all know the (shonky) polls have been designed to elicit answers favourable to the governments cause. It is a well known fact that the vast majority of the public is strongly opposed to being poisoned. Get off your soap box Khan and stop grandstanding. You have no doubt been highly paid by the Government to provide data that support their views on recycled sewage. I am considering becoming a researcher too. All I need to do is plagiarise and falsify data, just like you Khan. You can stop the pretence now. I think most people would be well aware that you and Paul Greenfield to name a few have vested financial interests in the recycled sewage scheme. By the way Khan, for your information Bligh did in fact say that the public will be drinking 100 percent recycled sewage. That information was contained in reports tabled in parliament. The media news sources as we all know, especially the trashy tabloid, the Courier mail work only in the best interests of the Government and are being handsomely paid to support the Governments views on recycled sewage. They will not publish anything negative they view as having the potential to de-rail the Governments bizzare recycled sewage scheme. Since everyone is entitled to an opinion , I would appreciate my comments being posted on your website.

Meredith Jayne.

Thursday, March 12, 2009

Fluorescence for monitoring recycled water

Four years ago I had an idea for a potential new application for monitoring recycled water systems. The idea was to use fluorescence spectroscopy to try to distinguish different ‘types’ of waters such as drinking water, secondary treated municipal sewage, reverse-osmosis treated water, etc. I had two main applications in mind:

1. to be able to detect ‘cross connections’ in dual reticulation (purple pipe) non-potable water recycling systems with the adjacent potable water supply.

2. to allow real-time ‘on line’ monitoring of reverse osmosis treatment performance with increased sensitivity compared to current techniques.

So during 2005-2006 I made a lot of phone calls and sent a lot of emails to water companies. I managed to secure the support of eight major Australian water companies with a keen interest in (potable and/or non-potable recycled water). These were:

Gold Coast Water (QLD)
City West Water Ltd. (Vic)
Melbourne Water (Vic)
South East Water Ltd. (Vic)
Sydney Olympic Park Authority (NSW)
Sydney Water Corporation (NSW)
Water Corporation (WA)
Yarra Valley Water Ltd. (Vic)

This strong industry support gave me the bargaining power to be able to apply for an Australian Research Council (ARC) Linkage Projects Grant. To do this, I recruited a few co-researchers to build a strong research team. These were Prof Richard Stuetz (UNSW), Dr Michael Storey (Sydney Water) and Prof Andy Baker (University of Birmingham). I went all the way to Birmingham to meet Andy and ask him to participate since he is the world expert on fluorescence analysis of freshwater samples.

Our first application was in 2006, but this was not successful so we had another shot at it in 2007. On the second application we were awarded the grant for a three year research project which began at the end of 2007.

In addition to the necessary equipment and consumables, the grant allowed us to hire a full time post-doctoral researcher as well as a second part-time researcher. It also included two PhD scholarships. The full-time post-doc, Rita Henderson came from Cranfield University in the UK and now manages the project on a day-to-day basis. The part-time researcher is Dr Kate Murphy (from UNSW). The PhD scholarships have been awarded to Adam Hambly (from University of Sydney) and Sachin Singh (from University of South Pacific).

During the last year, Rita, Adam and Sachin have been undertaking intensive research with water samples collected from some of the above listed water companies. This work is on-going and no results have yet been published (apart from a few conference papers).

However, the first major paper from the project was recently published (Henderson, et al., 2009). This is a review of previous literature assessing, as best as we could, the question of whether fluorescence has the potential to be used as a monitoring tool for recycled water. It presents what we consider to be the evidence for why it does, as well as highlighting some of the areas that require further investigation. You can read the abstract of the paper by clicking on the image below.

I’m really keen on this project (and really proud of the team we have assembled and the progress made so far), so I hope to be able to report some exciting updates during the next two years.


Henderson, R. K., Baker, A., Hambly, A., Murphy, K. R., Stuetz, R. M. and Khan, S. J. (2009) Fluorescence as a potential monitoring tool for recycled water systems: a review. Water Research. Vol 43, Issue 4, Pages 863-881. (available here).

Gold Coast Water also have a short description of this project on their website.

Monday, March 02, 2009

Matt Laffan

My cousin, my playmate, my childhood, my best friend, my confidante, my co-conspirator, my accomplice, my flatmate, my teacher, my inspiration, my awe, my idol.

I just can’t say how much I’m gonna miss ya.

Richard Matthew Laffan
11 September, 1970 - 1 March, 2009.

Matt Laffan
Matt's website

News and Obits:
ABC Radio News, 2 March 2009
The Australian 2, March 2009
The International Herald Tribune, 2 March 2009
Accessibility.Com, 2 March 2009
The Sydney Morning Herald, 3 March 2009
The Daily Telegraph, 3 March 2009
HeavensGame.Com, 3 March 2009
Intenational Rugby News, 3 March 2009
USA Today

Some blogs:
The Chipolata
Pure and Applied
Cafe Grendel
Dreams in Colour

Some history:
Coffs Harbour Advocate, 31 October 2008
Enough Rope, 15 March 2004
Australian Story Reunion, 21 June 2004
Australian Story, 26 April 2001

Oh, and the water recycling connection? Matt’s policy from his run for Sydney Lord Mayor in 2004, as reported in the Sydney Morning Herald:

Matt Laffan, independent Laffan, a lawyer with the NSW Department of Public Prosecutions, would convene a meeting to develop a planning strategy for the city for the next decade. He would establish council-funded precinct committees with a diverse membership.

Laffan wants a new land-rating system to provide landowners with incentives if they achieve environmental sustainability. He would also push for recycled water for every home. Sydney Harbour foreshore land should be protected. Street lighting would be improved, council patrols of parks and retail areas increased and the graffiti program upgraded.

He has also pledged a major focus on public transport development. Laffan will direct preferences to the Democrats followed by the Greens.

Sunday, February 01, 2009

Sewage Treatment Plant by Night

I’ve just returned from an interesting field trip at the Old Bar sewage treatment plant (STP) not far from Taree on the mid-coast of NSW.

One of our research group’s PhD students, ‘Nhat’ is investigating the fate of some antibiotic drugs during biological sewage treatment processes. In doing so, he is comparing how well the drugs are removed during conventional activated sludge treatment with removal by an experimental membrane bioreactor.

Old Bar STP is operated by MidCoast Water, with whom we have an on-going research relationship. So in order to characterise the performance of the STP and simultaneously obtain some useful data for Nhat’s project, we decided to undertake a ‘diurnal investigation’ of the plant.

This means that we monitored the performance of the STP in removing a wide range of chemical contaminants (mainly pharmaceuticals, hormones and pesticides) over a 24-hour period. This can be a useful step in characterizing an STP since a number of factors can change over this diurnal period.

For example, the flow of water into the plant changes according to community sleeping habits. We see a peek flow around 7-8am when people are showering and another later in the evening for bath-time and dishwashing. We have also previously observed that the concentration (and the ‘load’) of pharmaceuticals in sewage changes over 24 hours, presumably as a consequence of factors such as when particular drugs are taken, the rate of metabolism and when people go to the toilet.

We collected samples from the influent to the STP every two hours and samples from the effluents of the activated sludge process and the membrane bioreactor every other hour. Since we were sampling in triplicate, this meant that we had to collect, filter and extract over 100 samples during the 24 hour period.

It will probably take a month to analyse the samples and process the data, so we won’t have any results until then. However, I took the opportunity to take some slightly unusual ‘sewage treatment plant by night’ photographs, which I thought I’d like to share... Who would have guessed that an STP could look so pretty by night!?

Nhat with our equiptment

Solid phase extraction in the lab

Hard at work...of course!

Our 5-star accomodation

Activated sludge by night #1

Activated sludge by night #2

Activated sludge by night #3

Sampling the untreated sewage influent at 2am

Secondary clarifier at night

The ultraviolet (UV) disinfection system glows by night

Secondary clarifer at dawn

Mission accomplished!

Tuesday, January 27, 2009

Cashing in on the Scare Campaign

I recall discussing recycled water scare campaigns on this blog a couple of years ago. So I was interested to read this article from a Queensland local newspaper. It seems there’s money to be made from playing on people’s fears...

Should I really be surprised?

Water Wise see Beyond Sales Pitch
By Christopher O’Leary
South West News
29 January, 2009.

SOUTHWEST: Door-to-door water purifier salesmen are reported to have told residents that they were risking diseases including cancer by drinking town water.

The salesmen were reported in Gailes, Goodna, Springfield, Collingwood Park and Redbank Plains, claiming the area’s water was recycled.

Eight people complained to Ipswich City Councillor Paul Tully’s (Div 2) office about the traders, who were trying to sell water purifiers and coolers by direct debit from residents’ bank accounts.

Cr Tully said at least two people signed up and one complained to the Office of Fair Trading after trying to contact the company behind the products to cancel the sale. Fair Trading officers are now investigating reports in Ipswich.

This month foul-smelling, dirty-tasting water flowed through southwest taps due to an algae outbreak at Mt Crosby Weir.

Gailes resident Julie Fullarton said two people from the sales group said the local water was recycled, and from Toowoomba.

“I said we don’t get Toowoomba water, then my husband Howard shut the door on them,’’ she said.

Goodna resident Maryanne Reynolds was frightened when one salesman named “David” arrived at her door last week.

She said “David” showed her a picture of a woman’s breasts that were covered in blisters.

He told Ms Reynolds the blisters were a symptom of breast cancer, which she could develop from drinking tap water.

“I was frightened,’’ she said.

“I was horrified to look at it even as a nurse.

“Imagine if they showed that to someone who had breast cancer.”

“David” provided Ms Reynolds with his phone number but refused to talk when the News contacted him on Friday.

The company believed to employ the salespeople declined repeated requests for comment about the complaints.

According to the Queensland Water Commission, purified recycled water will only be introduced into Wivenhoe Dam when South-East Queensland’s combined dam levels reach the 40 per cent trigger level.

Queensland Health maintains that water fluoridation has been endorsed by the World Health Organisation and poses no known health risks.

It has also been endorsed by the Australian Medical Association and American Academy of Pediatrics.

Traders caught breaching the 1989 Fair Trading Act faced fines of up to $54,000, and $270,000 for companies.

Thursday, January 08, 2009

Upper Occoquan Reservoir

The Upper Occoquan reservoir in Virginia, USA is a commonly cited example of indirect potable water reuse. An excellent description of the scheme was reported in the newspaper ‘The Voice of San Diego’ this week.

As previously reported on this blog, the City of San Diego has been considering the development of a potable water reuse scheme for a number of years. Thus this article was written to provide a practical example of how water can be safely recycled as a drinking water supply. The example applies equally to Australian cities considering potable water recycling.

I’d be interested to know your thoughts on how the Upper Occoquan scheme compares with the Western Corridor Recycled Water Project currently under development in South East Queensland.

Purified sewage flows down a spillway into a tributary of the Occoquan Reservoir in Northern Virginia. Photo: Rob Davis

Where Water Reuse Isn't a Dirty Word
By Rob Davis
Voice of San Diego
January 7, 2009.

Wednesday, Jan. 7, 2009 | Centreville, Va. -- Tucked behind evergreens, down a long lane in an otherwise anonymous stretch of this Washington, D.C. suburb south of Dulles International Airport, sits a facility that provides San Diego with the best evidence that it's safe to fill drinking water reservoirs with purified sewage.

Here, a treatment plant has been purifying sewage and dumping the clean water into the Occoquan Reservoir, a source of drinking water for 1 million residents of Northern Virginia's densely populated suburbs in Fairfax and Prince William counties.

And they've been doing it 30 years.

The sewage arrives here at the Millard H. Robbins Jr. Water Reclamation Plant from the toilets of 275,000 nearby residents. A day-and-a-half later, after being disinfected and stripped of its contaminants, it washes down a wide concrete spillway into Bull Run, the Occoquan Reservoir tributary made famous by its Civil War battles.

In dry weather, that purified sewage spends three months meandering and mixing in the sprawling tree-lined reservoir, making its way 17 miles downstream to a dam, where a local water provider draws it out, treats it to be safe for human consumption -- it picks up contaminants along the way from urban runoff -- and pipes it to homes.

The facility's existence directly counters one of the talking points Mayor Jerry Sanders has frequently recited as a reason for objecting to the City Council's plan to recycle sewage as a drinking water source. Sanders has claimed that San Diego would be the first municipality anywhere to pipe purified sewage into a drinking water reservoir. He made that claim in October and again in December when articulating his opposition to the council's $11.8 million pilot study of recycled sewage.

"I want to make it very clear," Sanders said at a Dec. 4 press conference. "No one else has done what we're being asked to do. People confuse us with Orange County, people confuse it with a lot of other places. No one else has ever talked about putting recycled water into a reservoir and then using it for drinking water. That's what we'll be doing testing on to see if that can even work."

In Northern Virginia, that conversation happened in the 1970s. And the region found that recycling sewage is effective and safe, said Charles Boepple, executive director of the Upper Occoquan Service Authority, which operates the sewage recycling facility.

"We have been doing exactly what San Diego is exploring for 30 years," Boepple said.

Bill Harris, a Sanders spokesman, said the mayor was referencing San Diego's place as the first in California to use recycled sewage to fill a drinking water reservoir.

"If you add the two words -- in California -- it becomes perfectly relevant," Harris said. "That's the background understanding of what we're up against. We've always had to talk about getting approval from [the state Department of Health Services].We will clarify it from this point forward and make certain those two words get added."

Sanders' opposition could be softening. Bruce Reznik, executive director of San Diego Coastkeeper, a sewage recycling supporter, said he is optimistic the mayor will support the concept once the city's pilot study advances. The U.S. Environmental Protection Agency recently urged San Diego to develop a long-range plan for reusing sewage; Coastkeeper is negotiating with the city about that plan.

San Diego would be the first in California to fill a drinking water reservoir with recycled sewage. The city has frequently been contrasted with Orange County, which moved forward with the technology without being tripped up by the polarizing toilet-to-tap label that ended San Diego's 1990s recycling effort. While San Diego and Orange County would use a similar purification method, it's more appropriate to compare San Diego's concept with what Virginians decided was acceptable back in the mid-1970s.

In Orange County, which began recycling sewage last year, the purified sewage filters into the ground and winds up in an underground aquifer. It stays at least six months, mixing with the water that naturally fills the basin, before getting sucked out, treated and, ultimately, swallowed again.

In Virginia, the purified sewage goes straight from the plant into the reservoir. San Diego is studying the same idea: Pumping straight into the San Vicente Reservoir.

Virginia turned to recycled sewage in the 1970s as a way to improve water quality in the Occoquan Reservoir. In the late 1960s, gooey algae began growing in the reservoir. Too many nutrients were feeding the water, the result of 11 small sewage-treatment plants that dumped partly treated sewage there.

Officials needed a solution to the bad color and gross taste that residents got from the reservoir water. Those residents were already drinking partially treated sewage; with state approval those smaller plants were closed and an improved sewage purification plant was opened. Officials had debated other less-desirable alternatives: Limiting housing growth or pumping the treated sewage outside the area. But water is a precious resource even in Northern Virginia, which averages 41 inches of rainfall annually (San Diego averages 10 inches but imports most of its drinking water). Ultimately, they settled on purified sewage.

"Some fairly bold thinkers said: I think this resource is too valuable," Boepple said. "You can help supply the population increase with water because you're reclaiming. Otherwise this region would have a tough time."

The plant offers a double benefit. It provided needed sewer service to residents at the same time helping meet the water demands of Northern Virginia's exploding population. Since opening in 1978, the plant has expanded three times. A 2005 upgrade brought the treatment capacity to 54 million gallons a day -- just more than the planned Carlsbad desalination plant would produce.

"This has been a monumental success," said Tom Grizzard, director of the Occoquan Watershed Monitoring Laboratory, an independent agency that studies the reservoir's water quality. "When you develop a supply, the cardinal rule is to go to the water of the highest quality. It's the highest quality available. It's better than natural drainage in every respect."

While the plant's 30-year success has attracted visitors from 70 countries, no other localities in the United States dump purified sewage in their drinking water reservoirs. Boepple blames the "yuck factor" -- the visceral reaction people have to the idea of drinking sewer water.

"The focus needs to be on the science and what we've achieved," Boepple said. "If they separate the irrational fears, they'll see it's a viable alternative for water-short areas."

On a typical day, about 5 percent of the Occoquan Reservoir's flow comes from the sewage recycling facility. Boepple said the facility has provided as much as 80 percent of the reservoir's flows during prolonged drought. The rest comes from rainfall. In a watershed filled with cattle farms, homes, roads and agriculture, that rainfall is dirtier than the recycled sewage -- it washes contaminants such as cow manure, brake dust and herbicides into the reservoir. The sewage plant's water is so clean it actually gets dirtier as it mixes in.

The facility has spilled raw sewage into the reservoir during storms. Boepple said early 2003 was the most recent problematic time. Heavy spring rains and a contractor's failure to complete an expansion on time led to a sewage spill that totaled several hundred thousand gallons, he said.

Sewage recycling in San Diego wouldn't be subjected to that same problem. If heavy rains were overpowering the system, the flow could be diverted to the existing sewage plant at Point Loma. San Diego would have the luxury of filling the San Vicente Reservoir only when conditions were right. The city estimates it could create enough water to supply 52,000 homes for a year.

San Diego's recycling system would also include an additional safeguard that the Virginia facility doesn't: Reverse osmosis membranes. With that, sewage is forced through thin membranes with holes so small that water molecules are about the only things that get through. It's the same technology used to desalinate seawater and stops just about everything. (The handful of chemicals it doesn't stop is destroyed in a final disinfection stage.) The technology wasn't commonly available when the Virginia facility opened.

The Virginia plant also offers evidence that sewage could be recycled for less than Sanders has estimated. The Orange County sewage recycling facility produces water for $850 an acre foot (enough to supply two families for a year). Grants and subsidies cut the cost to about $550 an acre foot, close to the price of pumping in imported water from the Colorado River and Sacramento Delta, San Diego's two main sources.

The Upper Occoquan facility produces water for about $700 an acre foot. That figure, which does not include past construction costs, is borne by sewage customers, who pay about $40 a month.

Sanders has estimated that San Diego's cost to recycle sewage may be as high as $1,882 per acre foot. Those figures, originally drafted in 2006, are being revised as part of the city's ongoing sewage recycling pilot study.