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.


report$s said...

Going to disclose how much you were paid for the report?

stinks said...

Seen the Brisbane testing facility photos in the Sunday Mail?

W.F. Blog said...

Hi Stuart, I read it twice but haven't studied it.

I'm disappointed in the age of the studies you look at and surprised that with the amount being spent on R&D for membrane technology that there are not parallel amounts being spent on tox/epi studies.

You don't exactly tie yourself to the mast on this with the disclaimer and the last two paragraphs which rather suport the Toowoomba view about ongoing testing and non-potable uses first.

Windhoek deserved a better review but the tests are probably too ghastly.

It probably raises more questions than it answers for the layman.

I'll give it a more thorough review in another place but it could carry the headline "Khan warns of sewage water risks." ;-)

Stuart Khan said...

Hello Report$s,

If you’re going to cast aspersions by implying that we would allow financial incentives to influence a scientific review, you could at least be courageous enough to take responsibility for the suggestion by putting your name to it. I’m normally quite happy to allow anonymous comments, but it becomes moderately pathetic when you engage in a personal attack.

David and I did not receive any extra remuneration for this report. We were paid our normal salary from our normal employer. Our employer (UNSW) billed the LGAQ for our time and services (and overheads). I don’t think I’m at liberty to disclose the precise amount, but can tell you that it was a pittance compared to commercial rates for this type of research.

Stuart Khan said...

Yes Stinks,

I did see those reports and I was very glad to hear BCC Cr Jane Prentice confirm that funding for a new lab was already in next years budget. Needless to say, I support calls for more spending on water quality analysis and research in Australia.

Stuart Khan said...

Thanks for the feedback W.F.,

Yes, I tend to agree with you and I also think more funding on toxicological studies is warranted. Maybe also the epidemiologic studies, but I think they are likely to be less conclusive.

I’m afraid the disclaimer is standard and appears on all of our reports (or at least, its supposed to). But yes, I am naturally cautious and certainly not going to come out saying ‘recycled water is safe no matter how poorly you manage it’. Is that what you expected?

Indeed, I do support your calls for some significant water quality testing and hope that you can see that I have said so rather loudly.

I’m not so sure about Windhoek. The environmental and social conditions are significantly different to Brisbane. Part of the problem is that gastro-intestinal diseases are highly endemic in Namibia, regardless of whether people live in areas receiving recycled water or not. So its really very difficult to try to observe any epidemiologic ‘signal’ above the ‘noise’.

Your alternative headline is not too bad, but I think that most people know instinctively that water sourced from treated effluent carries risks. The important thing is to take those risks seriously so that we can manage them safely and reliably.

desal boy said...

I look forward to reading the report. Stuart, you may recall an earlier point I made on the proposed Sydney desal plant being environmentally friendly. Iemma claims to be going to use only renewable energy to power it. Current problem is there's not enough renewable energy in NSW but they could always expand capacity I guess.

Stuart Khan said...

Thanks for the update Desal Boy,

Yes, I did see those reports. I think there’s an important distinction between using an energy-efficient system and simply off-setting huge amounts of energy use by purchasing renewable energy credits. I would prefer to see renewable energy used to reduce our greenhouse emissions (rather than simply off-set new emissions). Still, off-setting is indeed better than not off-setting.

If I am not mistaken, I think the problem was that there is not enough renewable energy credits available in the whole of Australia…not just NSW. Expanding capacity sounds like a good idea and it would be productive to provide incentives for industry to do so (or for a completely radicle idea: simply build something themselves).

desal boy said...

I agree that renewable energy is better than renewable energy credits. Credits do not really force industry to be more environmentally friendly - as long as they can buy credits from somewhere. I guess there's a price limit beyond which it makes more sense to conserve/switch energy sources.

I'm not sure the people of NSW would think it credible to use a coal fired desal (or recycling) plant and then buy a million trees for the Amazon and call it eco-friendly for us.

Jaun said...


Studies, but where is the long term affects on the environment and human health. How can a study on this subject be conclusive, when in hasn't been tested in real life.

Besides, we don't need another element destroying this country further; we already have farmers clearing massive areas of forest, resulting in lower rainfall (Google Earth and prove this point. Massive land clearing resulting in lower rainfall, this is a fact for most of the over farmed areas.

How about you go about replanting of our forests, instead of worrying about recycled water, after all trees and forests help produce the climate for rain. No seems to care about destroying our country, and people like you want to add to it.

IMO, Beattie needs sacking, and so does everyone else who thinks recycled sewerage is the only solution to a drought. Yes, we can’t control the weather, but we do contribute to its development, and tree clearing has destroyed it.

You go ahead with your studies, it’ us PEOPLE who have the last say, and this continued debate is only proving we have an incompetent government in power. This needs to change.

Stuart Khan said...

Thanks for taking the time to read the report Jaun. I do appreciate it.

Unfortunately, it was not part of our brief to investigate the possible effects of the use of recycled water on the environment (only health). However, I am aware of quite a lot of work that has been done and agree that this would be a useful topic to address in a later post.

I hear your concerns regarding long term studies on humans. The Montebello Forebay scheme (Los Angeles) described in the report has been operating since 1962 and that is really where the longest controlled epidemiological studies have been undertaken.

The many toxicological bioassays and live animal studies described in the report were designed to assist in the identification of long-term human effects (exactly the same way as we use the exactly the same studies to identify long-term human effects of new pharmaceuticals). However, I agree that they are not themselves long-term human studies. I would be interested to know the type of study that you would design to address this. Do you think it is realistic?

I agree with your comments regarding land clearing. I had no idea that you were such an old tree hugger ;-)

Anonymous said...

I agree with Jaun- more trees = more rain, common sence, but I have known that since I was a young kid! I tried going to the site to read our report in full, but some weird browser error, I read everything on this page though..... why are there no numbers, measurments etc of exactly what is in the recycled water? I heard that you cannot take the pharmacuitical drugs, hormones etc out of water, is this true for all possible ways of filtration? if you cannot take out ALL of the pharmacuitical, hormones, prions (yes from criutzfieljakob disease) (mind my spelling I know it sux) and chemicals, as well as pesticides, etc you get my piont. if you CANNOT get these to be ZERO on a piece of paper (legitimatly using REAL scientific research not just what the government Wants us to think) then obviously injesting all of this lovely chemical cocktail would do harm not good! well DUH! it does not take a genious to work that out now does it? if this ""drinking shitty water"" comes in I will be buying my bottled water, and wont be giving this crap to myself or my family, not even my dog! BUT if all this rubbish can be filtered out of the water 100% thats another story... why cant all the possible filtration methods be used all at once, going from each of the different ways of filtering, right down to the final filtering through special plants that take out all the heavy metals etc and other pollutants (saw that one on the ABC) but then there is the dirty word involved (money) the government is looking for the cheapest easiest way of doing things, which would meen in essence that they would use a pretty shitty way of purifying the shit water now wouldnt they? besides the fact that they had plenty of time to set up desalinsation plants, or put pipes in from way up north to way down south to get all that water thats up there, but it hasnt happened, honestly why are there imputant morons in piwer that like to turn a blind eye to problems while filling up thier back pockets with the tax payes money thinking that all their problems will just ""dissapear"" Beazly is an idiot, I wouldnt trust him with a urine sample, and I dont see him drinking this recycled water! you knwo what? it would be great if there was this corruptable disintergration ray, that only turned all the dirty lieing corruptable people in power to dust, leavign the good truth telling ones, and if all the wages of these politionas were taken way down to the average paying job, not 5 million a year for this and that, then you would get more honest people in. There should have been steps in years ago, many years ago for desalination and pipe lines etc, then we wouldnt need to be having this huge talk on drinking poo water. 100% pure with nothing in it, or else theres gunna be huge HUGE heath problems for all! it would most likly manifest in more cancers in the long run, amoung many other things, unless it is 100% pure. dont settle for 80% dont even settle for 99% its 100% or bust!

Anonymous said...

ahu! its me again! I went to
and here is a paragraph....
""...Adverse health effects from recycled water could appear only if it were ingested in large quantities over an extended period of time. That is why it is not intended for drinking. ...""

Stuart Khan said...

G’day Anonymous,

Thanks for your extended comment…you have given me lots of issues to address!

I also noticed that the LGAQ site was not working this morning. However it seems to be now, so I suggest try again and you should be able to grab a copy of the report. The reason that there are no numbers and measurements in the above post is because that is just the executive summary. I can assure you that there are plenty of numbers in the actual report. If these don’t satisfy your numerical desires, references to all of the original studies are provided.

Advanced water treatment processes are indeed able to remove all of the chemicals that you listed down to below any concentration that can be measured. However, it is important to realise that providing pure H2O without any other molecules is not the purpose of any water treatment process. Neither you, nor I have ever drunk a glass of pure H2O without any other molecules. It is practically impossible to provide such a thing and also impossible to verify it. Advanced treated recycled water is about the closest thing to it that either of us are ever likely to drink. The purpose of drinking water treatment is to provide water that is fully protective of human health.

Once you have read the report, you will be aware that the quality of recycled water is routinely equal to or better than traditional drinking water sources. If you disagree with this finding, I’ll be happy to discuss it further.

Your doubts regarding the willingness of governments to use the best available technology is unfounded. The combination of treatment processes intended for use in Brisbane is the most effective and most reliable in the world. You can’t be expected to know this since I don’t think many details have been released. However, I am sure that they will be soon and I’ll be happy to address any issues that arise when they are. I have already provided a considerable amount of fundamental detail regarding reverse osmosis and ultraviolet treatment on this blog.

I’m not sure who you are referring to as ‘Beazly’. If this is a reference to the ex-federal opposition leader Kim Beasley (?), then I don’t think you need to worry. He is unlikely to be responsible for managing any water recycling scheme in South East Queensland. I like your idea of a ‘corruptible disintegration ray’.

Now, regarding your second post... This is a classic old scare campaign tactic (see point #9 from ‘How to Run a Successful Scare Campaign’). The ‘recycled water’ from the website you refer to is simply tertiary treated sewage used for irrigation. It is not intended for drinking and not treated to a standard anywhere near what we would expect for potable water recycling.

Anonymous said...

There seems to be a fair amount of info that shows it's pretty safe to drink recycled water if it's done right. My concern is the adequacey of quality control to ensure infrastructure is built to standard, and the adequacey of checks and balances for monitoring ongoing operations. This is where the science stops and the "people" issues start, including inadequate resourcing of government authorities, labour and material scarcity for construction, incompetent project management expertise in government, unrealistic deadlines leading to shortcutting etc etc all come into play. Loading a whole heap of infrastructure projects onto the table at the same time only compounds all these risks. Good luck to the Qldr's, hopefully their government will be open and transparent enough to come clean on all this.

Stuart Khan said...

Hello Anonymous,

Of course, your point is correct and indisputable. Furthermore, it applies equally to most aspects of human safety including food safety, aeronautical safety, workplace safety, etc. Just because something can technically be done very well, doesn’t necessarily mean that it will be.

For this reason we do need to maintain a high degree of vigilance to ensure that Governments do follow appropriate internationally established protocols and do put the necessary checks and balances in place. I agree that if a job is done badly, then the risks increase.

AJ said...

Stuart, read the report. Found it informative and will follow-up reading some of the references you site.
I have two questions:
1) A big sticking point in the recycled water debate is system/technology reliability. People are uncomfortable with statements like "operational nearly 100 per cent of the time".
Do you know of a reclaimed water treatment plant that has experienced problems with achieving water quality targets?
2)pg 10, bullet point 2 "viruses can not reproduce in the natural environment". What is the natural environment?
Thanks,can't believe you have a day job as well!

Stuart Khan said...

Hi AJ,

Thanks for the feedback and your questions.

Regarding your first question, I’d first like to be sure that we are referring to the same document. I recently made a few revisions to the “Health Studies and Risk Assessment” report. These were mainly correcting a few typos, but I also added a more detailed section (Section 5) on “System Reliability”. If your report is 45 pages, you have the old version. The new version is 48 pages and the links above now point to it.

The statement about “operational nearly 100 per cent of the time” refers to a “Critical Component Analysis”. This type of analysis is undertaken to examine the down-time for components of an engineered scheme. Its purpose is not only to identify failures that may lead to public health risks, but also as a means of ensuring that a plant is operational as consistently as possible for the purpose of optimising production. For example, a bottle manufacturing plant may undertake such an analysis to ensure that they can manufacture as many bottles as required to meet production targets.

All equipment at all plants requires maintenance. Some of this is planned preventative maintenance and some of it will always be unplanned maintenance for repairs. Every water treatment plant in the world deals with these issues and they do so by ensuring that certain components or modules can be taken off-line for maintenance. Where that is not possible, production must cease.

The plant that was examined in this study was a pilot plant which was not required for supplying any water supply, so there may not have been a need to provide the full ability to continue production while undertaking maintenance. It is included in our review primarily because it demonstrates the value of collecting component performance data and the insights that this can provide to understanding system reliability.

I know of a couple of Australian plants that have had difficulties meeting their anticipated water production. One of the earliest Australian dual-reticulation plants went through quite a number of design modifications (including changing the treatment processes) during its first five years of operation. I guess that comes with the territory of being a pioneer. I also know of an Australian advanced water treatment plant (supplying non-potable recycled water for industry) that had some difficulties with membrane lifespan. The membranes were being ‘fouled’ or ‘clogged’ much more quickly than they normally should have been and thus were requiring replacement more often than they should have. Such issues tend to be addressed fairly quickly since they represent additional costs to the operators. However, they have no impact on final water quality.

The study quoted in our report noted that “the analysis confirmed statistically that observed plant equipment failures do not tend to cause a significant interruption to the operation of the overall plant”. This is significant because it means that you can then determine the water quality variation in terms of normal (expected) operational variation.

The issue of viruses not being able to reproduce “in the natural environment” is simply referring to the fact that viruses require a host organism to reproduce. So in this context, “the natural environment” could also be extended to mean engineered lakes etc. If you are suggesting that host organisms (humans and other animals) are part of the natural environment, then I accept your point!

Suzanne said...

This is a great discussion. I am writing a paper for my water quality class on this very topic. Thank you Stuart for this blogg and for your efforts to clearly communicate the issues.

I'm all for "toilet to tap" as we call it in San Diego. I would actually rather drink advanced treated water straight rather than pumping it back into the water supply only to have to treat it again. Seems like a waste of energy to me.

I don't think people realize that there is risk associated with drinking water that is not reclaimed as well as risk in drinking bottled water.

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