Wednesday, November 05, 2008

Singapore drinks recycled water too

An article in The Australian today points out the fact that Singaporeans are drinking recycled “sewage” too. That fact in itself may not seem remarkable since there is treated effluent in most water supplies of most large cities.

However, what is more interesting in Singapore is the high level of treatment used (including reverse osmosis and UV disinfection). This has made the water highly suited for a number of applications including Singapore’s considerable electronic chip manufacturing industry. Only a very small proportion is then left over to recharge public drinking water reservoirs with (to provide about 1 per cent of the island's total potable water supply).

We have looked at the situation in Singapore a few times previously on this blog. One of the most interesting aspects for me was the 'NEWater Study' that was undertaken to investigate the health effects of using highly treated recycled water as a drinking water supply.



An Expert Panel was formed in 1999 to oversee the NEWater Study. This Expert Panel was comprised of both local and overseas members with expertise in human health and toxicology, microbiology, engineering, water technology, epidemiology, water quality and environmental chemistry.

A pilot scale (10 ML/day) advanced water treatment plant, known as the NEWater Factory was constructed and commenced operation in 2000. The NEWater Factory received water from the Bedok Sewage Treatment Works, which produced secondary treated effluent. The technologies employed at the NEWater Factory included microfiltration, reverse osmosis and ultraviolet radiation.

An extensive water quality sampling and monitoring program was devised for approximately 190 physical, chemical and microbiological parameters. Samples were tested from the plant feedwater, individual treatment module effluents, final produced NEWater, as well as untreated and treated traditional drinking-water supplies. Overall, almost 20,000 test results from seven sampling locations, including over 4,500 for NEWater were measured between November 1999-April 2002. The physical, chemical and microbiological data for NEWater were shown to be well within current (2002) US EPA and World Health Organization guidelines for drinking-water quality.

The health effects study was conducted with two components. A mice study was undertaken to assess long-term chronic toxicity and carcinogenicity, while a fish study was undertaken to assess toxic and estrogenic effects. In these studies, NEWater was compared with untreated reservoir water.

A sensitive mouse strain (B6C3F1) was used for the mice study. This strain is widely used for conducting long-term health effects studies of new pharmaceuticals. Groups of mice were fed 150-fold and 500-fold concentrates of NEWater and untreated reservoir water over a period of two years. The testing was undertaken with culls at 3, 12 and 24 months. At the time of publication of the expert review panel findings, the 3 and 12 month results were available and these indicated that exposure to concentrated NEWater did not cause any tissue abnormalities or health effects. The 24-month results were due to be completed in October 2002, but as far I know, remain unpublished. I would really like to see these if anyone is able to dig them up.

Fish studies were undertaken in accordance with a recommendation from a recent US National Research Council report. The purpose was to assess long-term chronic toxicity as well as the estrogenic potential (reproductive and developmental). The orange-red strain of the Japanese medaka fish (Oryzias latipes) was selected for the study due to the availability of an extensive biological database for this species.

The fish testing was conducted over a 12-month period with two generations of fish. The NEWater tests were initially undertaken during 2001 and both generations showed no evidence of carcinogenic or estrogenic effects from exposure to NEWater. The fish study was repeated in 2003 (due to some design deficiencies of the aquarium system, fish husbandry issues and weaknesses in the original study protocol) and confirmed the findings of no estrogenic or carcinogenic effects.

I don’t think that these types of live animal studies are necessarily justifiable for the South East Queensland scheme. However, it would be extremely helpful to see some of the existing data to confirm excellent performance of the advanced water treatment barriers.

4 comments:

Daqtaoge (newoneone@yahoo.com) said...

Hi Stuart,

I would like to point out that although the testing regime in Singapore appears to have been stringent and well thought out, the political climate here did not allow for public consultation and debate.

In fact, I see that the Australian system is much better. If you can convince Collignon and not only Collignon, you have a case. Otherwise you will split your society, which is far worse.

There can be doubts about Singapore, because many issues were never brought out and openly discussed, due to fear of financial bankruptcy by the leaders or public ridicule. The government here is ultimately the paymaster of many and we do not have the financial freedom nor muscle nor society nor government social security to speak as we choose.

Looking at your scientific arguments, if I had known prior to what they were about to politically announce via a Prime Minister drinking at the tennis court session then, I would have also objected as I do now. But I would have voiced my opinion before the all powerful government had made their decision and hopefully allowed them to let me think through and bring up exhaustively all issues. The decision has a commercial smack to it most probably from the manufacturers of the RO system membranes rushing this membrane goldmine of theirs at our health expense. I would expect constant membrane replacement and when oil prices go up, they cannot contain the price which is passed on to us, take it or leave it.

There are questions like radiactivity thrown down the sewers, a simple route which we cannot talk about really for security reasons. And I am being irresponsible by bringing it up and you will be also if you continue to allow this post mentioning it to be on your blog. How do you sieve out radioactive elements which take decades to remove? It is so easy to pour down the sewer, and many alpha and beta elements have been poured down science labs anyway after the physics experiments.

You should side Collignon, bring the matter into many more decades of study. The time is not now for it, if ever. It is just too soon.

It is only ready for debate, and that is all you should really achieve. The risks are just too great.

Yet another risk is from drugs which are in urine. If it could go through the osmotic membrane of the intestines and the blood vessels into the kidneys, you want to tell me it is removed? They aren't and Collignon is proven right in his assumption that they aren't, don't you think so?

Stuart Khan said...

Hi Daqtaoge,

Thanks for your comments. I appreciate your contribution and feedback.

Honestly I don't think you need to worry too much about the "security" implications of throwing radio-isotopes down the sewers. If you did that up-stream on a large river like the Thames, Mississippi or Darling Rivers, it is true that some people may be exposed downstream. However, in a city where sewage effluents are treated by reverse osmosis, such would-be terrorists would be foiled by the fact that they must have been unaware that such treatment processes are an effective barrier to ionised elements (and conventional sewage treatment is also an effective barrier to hydrophobic non-ionised heavy elements).

There is plenty of research available showing the effectiveness of advanced water treatment processes for removing drugs (I even did a PhD on the topic). I agree that some of the mechanisms relating to advanced water treatment processes are conceptually similar to processes associated with our cell membranes (including intestines and blood vessels). However cell membranes and synthetic reverse osmosis membranes are otherwise different to each other, -both in composition and operational conditions. It doesn't necessarily follow that because drugs can be transported across cell membranes, that they can not be well rejected by reverse osmosis membranes.

Daqtaoge (newoneone@yahoo.com) said...

I am quite intrigued by this Reverse Osmosis membrane. In our generation, the science that was taught was molecular and atomic in nature.

Elements comprise of atoms and when they are bound together, they would be molecules.

The reverse osmosis membrane has some kind of atomic structure, I presume, and is patterned to allow water AND other elements the same size to go through correct me if I'm wrong.

Therefore the pore size of the RO membrane is the question and what is in between the pores as well which may be one or two atoms, maybe, and how thick?

This must be shown, but how to show? It is just so small and the equipment may not be able to show.

How do we know the pattern of it? How do we know if it will not break?

The size of water is H20, maybe clumps of H20, possibly. Then there is HCl, H2SO4, all from basic chemistry. When we touch organic chemistry, CH4, benzene. The polymer that probably is the RO membrane, trade secrets and all, I suspect it to be from oil, so some form of CHCHCHCHC etc. Arrangement? Uniformity? Quality control?

From the physical viewpoint, the RO membrane must be a very very fine sieve, and may not be totally selective when the size of the atoms are same as water, or perhaps even some other simple organic solution, such as ethanol. Both may go through.

We want to have information at the nanometre scale. Not just something from an advertising agency, or a PR house paid to support the scheme, and hiding some other information on the atomic structure of the pore size and just all the other things that will go through. Can we be informed about it or will we just wait to find out in the next generation?

Whilst drinking by politicians may be used, to me it is bad PR and very gung ho. I could firewalk too, but I just won't.

However, if Cambridge, Harvard and Yale biochemistry and medical dons would drink it, it would help PR. But would they? It doesn't help either, if the RO membrane manufacturers are going to have wild profits from it. Basic science tends to be ignored in such situations.

So, what is the size of the pore, is it uniform, and what is the size of the ions, etc, the myriad other substances that do wittingly or unwittingly, enter the sewerage system and the list of the items going through if we can get security clearance on that.

As a footnote, after 2003, some new diseases that we hear of in Singapore in the news are Chikukungya disease, Sudden cardiac deaths, Hand foot and mouth disease, and there were some cases of cholera (which had never happened before in my life in Singapore).

Daqtaoge (newoneone@yahoo.com) said...

'However cell membranes and synthetic reverse osmosis membranes are otherwise different to each other, -both in composition and operational conditions. It doesn't necessarily follow that because drugs can be transported across cell membranes, that they can not be well rejected by reverse osmosis membranes.'

Stuart,

This paragraph: it needs some elaboration. I don't think you mean that RO membranes totally reject all drugs and all by-products of drugs whether they are harmful or not. You can't possibly make such a claim and guarantee.

What happens to drugs and the by-products of drugs?

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