Wednesday, December 22, 2010

Singapore wastewater reuse

Dear Sir,

I am currently looking for information regarding wastewater reusing in Singapore.

Basically, I am looking for the Singaporean regulatory framework as far as reuse of wastewater is concerned, to answer this very specific question : which recycled water quality for which use (agricultural, domestic, urban uses…) ?

I have found your blog very interesting and I wonder if you could help me to find the information I need or to advice me where I could find it.

This would be extremely helpful.

I really thank you for your diligence.

Yours sincerely,

Dear N,

As mentioned in an earlier post, Singapore is a small country so almost all its water needs and wastewater (domestic) handling services are provided by a single government agency,  PUB (Public Utilities Board). Again, due to the country's size, reuse of domestic wastewater is limited to the production of NEWater and industrial water by none other than PUB. NEWater is a highly purified water suitable for high-end electronics manufacturing (and drinking of course) but also used to supplement our reservoir water. Industrial water is non-potable and only used by chemical industries in Jurong Island.

The water quality of NEWater is partially given here (I am sure many more other tests on NEWater have been performed though their results are not publicised). Water quality for industrial water is even harder to find. You probably have to approach PUB for more answers.

Good luck.

Tuesday, December 21, 2010

Water filters in Singapore

Dear Mr Kwok,

I happened to read your blog and I was wondering if you could help me with my project, "Study on the Effect of Poorly Maintained Water Filters on Water Quality". You mentioned that you did a project on the effectiveness of water filters, could you share the research paper/report with me? I will definitely acknowledge the source under my report so not to worry.

I have a few questions to ask as well:
1. Do you have any opinions/comments/inputs with regards to my project title?
2. Why would people still buy water filters although our tap water is well within WHO standards?
3. What is the major cause why these tend to be poorly maintained (because they forget to change, it is costly to change, do not know they have to change[perhaps the people who sell the filters to them did not mention it explicitly], etc?)
4. What kind of water filters are being sold in Singapore and which are the ones that are more likely to be poorly maintained?

I would certainly very much appreciate it if you could help me out.

Thank you very much!
Best regards,

Hi R,

More information about water filters may be found in my earlier posts.
My project on testing the effectiveness of water filters is still on-going so I am not able to share the results with you at the moment. If all goes well, it should finish by Feb 2011 and I will post the results on this blog.

Your project will certainly be useful and of interest to consumers of water filters as this is a poorly researched topic with even less publicity on the results from the few studies on said topic.

I suppose that your project pertains to the Singapore context which is rather unique compared to most parts of the world. Becuase of our small size, water supply is controlled, regulated and provided by a single agency, PUB (with the exception of some islands). In this aspect, I believe that PUB has done a good job of providing safe and affordable drinking water to the populace. In Singapore, you don't see epidemics of water borne diseases or people suffering from dehydration. This of course presents a unique market for water filters. People are not worried about pathogens like Giardia, Cryptosporidium or Salmonella in their tap water. (Despite this fact, most people still boil their water here.)

As you ask, why are people buying water even though our tap water is well within WHO standards? I am afraid you will have to conduct a consumer survey to find the real answer(s) but I shall offer my perspective here.

First, from a scientific point of view, the WHO standards for drinking water are not all encompassing and do have their limitations.
  1. Under the standards, the limits for certain chemicals in water are set because that is the best our latest technology can detect. Say chemical A can only be reliably detected at 5ppb (parts per billion) using the latest and best instrument X. Therefore, 5ppm is set as the WHO standard. This of course does not mean that chemical A is harmless at 5ppm.
  2. Sometimes, chemical B may be harmful at 2ppb but because our water treatment plant can only economically reduce its concentration to 2ppb, 2ppb becomes the standard for chemical B.
  3. WHO standards set limits for about more than 100 parameters but there are easily tens of thousands of chemicals out there. Can you be sure that these chemicals are not in your water and if they are, they are harmless?
  4. The standards mostly cover single chemical substances. In many cases, mixtures of substances (e.g. heavy metals) can actually exert a synergistic effect, making the cocktail more deadly than the sum of the individual components. However, water regulators are starting to wake up to this fact and steps have been taken to categorise several substances into a single group under a single standard.
  5. To be sure, most of the toxicology studies on which a limit is set are based on animal studies. Let's say chemical C has no adverse effects on a guinea pig population at 1ppb so 1ppb is set as the standard. (This is grossly simplified for illustration purpose.) Can this 1ppb be translated to humans? This can go both ways - the value can be higher or lower in humans but nobody knows for sure.
  6. Even for those rare standards based on human studies, a large percentage of them are still short term studies. Who can be sure whether the same chemical D (supposedly safe at 3ppb for a month) will be safe if consumed for 30 years?
Science aside... (Are consumers knowledgeable enough about the science? I myself don't know much about the technical specifications in my laptop. As long as it works, I am happy.)

More than scientific facts, the most important element in sales (as any good salesman should know) is psychology. Show the consumer a high-profile example of person poisoned by lead (or substitute your least favourite chemical here) in drinking water, you will have the masses starting to show concern about their water and whether they should get a filter. This is notwithstanding the fact that the high-profile case may involve extraordinary circumstances not shared by the majority. Or more often than not, a latest piece of research may publicise that toxic chemicals are found in drinking water. Yes, this should push the panic button of many people and herd them towards the latest filter.

Don't get me wrong. I am not against water filters. But people should be rational about such purchases and should never buy based on fear or peer pressure.

3. What is the major cause why these tend to be poorly maintained (because they forget to change, it is costly to change, do not know they have to change[perhaps the people who sell the filters to them did not mention it explicitly], etc?)

Again, you will have to do a consumer survey to find out the truth. But I suspect most consumers do not keep track of their water use as conscientiously as they should. Most water filters are rated for a certain capacity (e.g. 1000 gallons of ordinary tap water) before replacement. Or perhaps you can say that most water filters not as well designed as they should as there is no meter or indicator when the 1000 gallons have passed through it. To make things simpler for the consumer, some filter suppliers have specified a timeframe instead e.g. the filter should be changed every 6 months. Again, this can be misleading as the usage of the consumer can vary. A family of 4 filtering 10 gallons of water a day is quite different from an extended family of 10 requiring 25 gallons a day. However, I have also seen some filter models incorporating an indicator that change colour when it is time to change the filter. I have not tried these models but they should be useful if they work as claimed.
4. What kind of water filters are being sold in Singapore and which are the ones that are more likely to be poorly maintained?

Unlike in certain countries, the household filters here are mostly of the point-of-use type that does its filtration at the point of discharge (tap). Not surprisingly, the low-end ones are rather popular. They may come in the form of jugs or faucet attachments. Slightly more expensive will be the counter-top and under-sink models. These filters mostly consist of a sediment sieve, an activated carbon packing and possibly a ceramic piece or plastic membrane.

The higher end ones will involve reverse osmosis (the same process used in Newater treatment). Ultraviolet units are rather rare. Ditto for distillation units and deionisation units. (I am using the term "filters" loosely here as some of the above items are strictly speaking, not filters.) In recent years, air-to-water units (e.g. Hyflux dragonfly/dolphin) have come onboard the water filter/purifier market. In my opinion though, they needlessly use energy to produce clean water and are excruciating slow to produce a decent amount of water.

Again, a consumer survey will be useful to find out the answer but I bet the more unwieldy and troublesome to change the filter, the more likely it will remain unchanged.

Monday, December 20, 2010

Phytoremediation of Wastewater

Hi Chen Ko,

Hope all is well with you. While researching on phytoremediation for wastewater, I chanced upon your blog.

Your blog has enhanced my understanding of phytoremediation and its potential in SEA. In the blog, you mentioned Earthship Biotecture. Do you happen to know the company/inventor behind this concept?

Best Regards

Hi I,

Glad to hear that you find my post useful. From what I know, Earthship Biotecture was founded by Michael Reynolds. The idea of an Earthship is a self-contained living environment that maximises the recycling of water - closing the loop as they call it, and minimises the wastage of energy. Food is actually a "by-product" of the recycling of water. Though it does not mean 100% self-sustaining as in a spaceship, the concept is nevertheless useful as a model for future housing.

If you are seriously interested in Earthship, you can actually sign up at the website as a volunteer to help out in the construction of their current projects. Unfortunately, there are no projects in our region as they are mostly located in the U.S.

Or if you prefer to find out more before diving head-first into the physical work, check out the 2 books by Michael Reynolds.
  1. Earthship
  2. Water from the sky
Here is a review of book #2 that I have written for my campus library in 2007.

Do you want to harvest rainwater and recycle your wastewater so that you will never have to depend on public utilities? Perhaps you simply want to reduce your rising water bills. Or perhaps you are an environmentalist at heart and feel strongly about conserving such a vital resource like water. If you have any of the above goals, this book excels in illustrating the processes of rainwater collection and recycling of both grey and black water. Detailed designs are available for the reader to immerse into the bolts and nuts from choosing the right materials to building a functional system which includes water treatment for rainwater, grey water and black water. Numerous photos and illustrations enable the reader to visualise each stage of the construction. This is however not a science book since the scientific reasons behind most designs are not well explained. The reader is advised to find out more about the science from other sources. One major shortcoming is the lack of costing details, impeding the reader from gauging how economical such a system is. Even though the author claims that the recycled water is drinkable after treatment, there is no mention of any physical, chemical or microbiological test being done. The relevant tests would have strongly validated his claims. Despite the above inadequacies, the book presents plenty of useful hands-on information that many “scientific” books lack. It should be read by anyone interested in rainwater collection and wastewater recycling.

Friday, December 03, 2010

Boil Water Advisory due to power outage in New Orleans

I recently came across this article (Boil Water Advisory In Effect For Orleans Parish East Bank) about New Orleans which was best known for its devastation by Hurricane Katrina in 2005 from a water point of view. (Yes, I know that it is well known for its Madi Gras and the Cajun influence but hey, this is a water blog.)

What caught my eye was "It's the most widespread boil-water order in New Orleans since Hurricane Katrina, affecting more than 300,000 people." Basically a 10-minute (yes, only 10 minutes) power outage at the local water treatment plant prompted city officials to declare that all tap water for drinking and cooking should be boiled for at least a minute. Bathing is fine as long as you keep your mouth shut. This advisory lasted for a day or so.

Again, I stressed that energy and water are intimately linked. Remember the Matrix Reloaded, electricity is supposed to be the system all other systems are built on. Knock it out and other systems will follow.

Of course, if the power outage lasts longer, how are you going to boil water with your electric kettle? If your gas supply is down, the stove becomes out of the question too. Therefore, it is never a bad idea to have a good water filter handy for such emergencies, if not for routine use.

Thursday, December 02, 2010

Water quality in Sungei Buloh Wetland Reserve (SBWR)

I just found my article has been published in Wetlands. It has taken a long time to reach print so I must admit the data is slightly outdated (2008).

Overall, the water quality in SBWR was either relatively unpolluted or weakly polluted. Some concerns are raised regarding the levels of
dissolved oxygen (DO), phosphorus, nitrogen (ammonia and nitrate) and Escherichia coli. Regarding that last bit about E. coli, please do not comtemplate swimming in those waters as the E. coli count was sometimes found to be above the EPA limits for primary contact activities e.g. swimming. In case you are wondering where E. coli comes from, it is found in the human gut and normally enters water via human fecal matter. I guess you can imagine the rest. (See previous post on a similar indicator microbe, Enterococcus.)