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.)

Tuesday, November 30, 2010

Are our streams dying?

First, it was Ngee Ann Stream - formerly natural (or "naturalised") stream surrounded by beautiful secondary forests was cleared and replaced by a canalised version. (See former posts - 1, 2, 3)

Now, development or rather its effects have come to my favourite tributary leading to Sungei Ulu Pandan. On 2 visits to this tributary as part of my field trip for my course on Freshwater Quality and Biodiversity, it was badly polluted by an ugly layer of black oil floating on the surface. On the first trip, the only living macroinvertebrates (bugs) we could find were a couple of blood worms. The second trip proved to be much worse with ZERO bugs and this time, besides the black oily film, there was also a strong petrochemical smell, presumably from the oil. Most of the adjacent vegetation have also been stained by the oil. I am skeptical that the stream can survive the ordeal.

Where could this oil have come from? Further upstream was some road construction works and even further up, a golf course was being extensively cleared. Were they the culprits? Possible but no way to tell without further investigation.

There goes another educational site. It was already small to start with though we could still find dragonflies, damselflies, snails easily then. We even found the odd freshwater eel sometimes. Now, I will have to crack my head to look for another viable alternative.

I happened to see this recent article: Stormwater Runoff Disrupts Urban Stream Life. This study in Seattle basically says that stormwater carries many pollutants from the land into water bodies, killing or driving off aquatic life. Though nothing new, it reminds us of the interconnectivity between human activities and nature and especially the relationship between land use and water.

At first sight, land and water appear separated and independent but never forget that water in stream does not just come from upstream, it comes from a much wider land area known as the watershed. Anything bad going down in the watershed can eventually find its way into the stream and even the sea. I heard of this interesting remark that "we all live downstream", meaning our (or human) actions will often come back to haunt us, whether for good or bad depending on what the said actions were.
Figure: Black oily stuff floating down from upstream. Though the aquatic plants managed to block off the bulk of it, the oil inevitably trickled downstream to kill off the bugs in the stream.

Figure: Another view of the oil

Friday, November 19, 2010

Do we really need water filters 2?

Here is a follow-up to the previous post.

Thanks very much for your very detailed explanations.

Just wonder, since "New Water" is quite pure and will be gradually added to our reservoir, how can consumers be protected from any harmful effect that it might bring about ?  Is water filter one of the solutions ?  Any other ways ?

I would not worry about any harmful effects from Newater. Newater is produced by treating the effluent from water reclamation plants using microfiltration, reverse osmosis and UV disinfection. Most (but not all of course) impurities e.g. salts, metals, organic compounds, would have been removed. This is probably already very close to pure water. Anyway, we are not drinking Newater straight unless you have accumulated cartons of Newater and drink exclusively from them. As you pointed out, Newater is mixed in a small percentage with reservoir water so I will worry more about other sources of contaminants.

I missed out a point in the previous post. The water from the water works is routinely tested and compared against WHO (World Health Organisation) drinking water guidelines. Let's assume that the WHO guidelines are adequate safeguards of the water's suitability for drinking, does this mean that water from the tap should be good to drink? Perhaps not because most of the testing and sampling are done right at the output from the water works. The water from the water works then has to flow through a complicated distribution network before reaching your home.

How many of us routinely test the water from our taps? Is there leakage along the way between the water water and our tap? Could the water have come into contact with sewage which may have also leaked from sewage lines? Or perhaps other contaminants have entered the cracks in the lines? What about the pipes and fixtures themselves? Lead, copper, zinc from old pipes could have gone into the water as the pipes corrode. All these scenarios can be real.

Is there other info that might help consumers in their cost benefit analysis as water filters incur recurring cost.

Our drinking water and sanitary standards are considered quite impressive compared to many countries. We do not have epidemics of cholera, typhoid or dysentry as seen in some developing countries or cases of severe heavy metal poisoning that turns whole villages into a public health nightmare. Therefore, most of our concerns are on potential or unconfirmed long term health effects e.g. chlorine, fluoride (update: check out Fluoride Action Network for arguments against fluoridation). This of course makes a quantitative analysis of costs and benefits difficult. For example, how do you quantify the cost of a cancer that may or may not manifest in 30 years time? I suppose the best we can do is a qualitative analysis. Is the risk of cancer (in 30 years time) worth the $300 you spend per year in water filters? Or perhaps is that $300 worth the peace of mind you get from filtering your drinking water? Obviously different people will have different opinions here.

Also, Is there any independent studies being conducted on the water filters and do they really live up to what they had claimed ?

The most widely used standards I have come across are the NSF/ANSI (National Sanitary Foundation International/ American National Standards Insitute) standards. (Other countries e.g. Japan also have their own standards for water filters. Ditto for other organisations such as USEPA and American Red Cross which certify/approve various water treatment units though some of these units are for outdoors use. Update to the update: USEPA DOES NOT test or approve filters. It apparently registers filters though.) NSF/ANSI 42 applies to improvement of aesthetic effects in drinking water using a filter while NSF/ANSI 53 applies to mitigation of health effects from contaminants in drinking water. Water filters can be certified under either or both of these standards though if you are more concerned about your health, NSF/ANSI 53 will be more useful.

However, even if a water filter is certified under these standards, do check the kind of water quality parameters it is tested against. One filter may lay claim to reduction of turbidity and bacteria while another may be certified to reduce only iron and hydrogen sulphide. These are the fine points most consumers will miss out. (Even the sales staff may not be knowledgeable enough.) Make sure you know what contaminants you are concerned about and check whether your water filter is certified to remove those contaminants.

To complicate things a bit more, these standards can apply to the filter component (cartridge or element) itself or the whole system (filter housing + cartridge). Even though a filter element is certified, if the housing has a leakage, the filtered water can be cross contaminated by the inflow. If possible, get a filter that is certified as a whole system and not just the cartridge itself.
(Update by author: The current NSF/ANSI standard apparently does certify the system itself to be structurally sound and does not add anything harmful into the water.)

On a final note, an uncertified filter does not necessarily means that it performs poorly. Remember, certification costs money and that cost will certainly be reflected in the price of the filter.

By the way, may I know which is the Doulton gravity filter you are referring to as they had quite a few models ?

The model that I have is the stainless steel gravity filter, STS-S-ATC ( which uses the ATC Super Sterasyl filter element ( It is the smallest model available here (I have seen a smaller one sold overseas though) so if you have a big family, it may not be enough. Also note that the ATC Super Sterasyl filter element is designed to remove microbes, particulates, metals, organics, chlorine etc. It is very versatile but that comes at a price (monetary and otherwise). Besides the higher price, its filtration capacity is reduced compared to the other filter elements from Doulton. If you are chiefly concerned about chlorine, you can consider getting the STS-SS10 ( instead.

I personally advocate getting a gravity filter because of its beauty in operating without electricity and water pressure. However, it can be a pain to keep scooping water into the filter and pouring out the filtrate from the lower chamber. If you find this too painful, you can consider getting a counter-top (model: HCP-Single) or under-sink (model: HIP-Single) housing incorporating the Supercarb filter element (or candle as they call it) ( (Their webpage shows the above models fixed with their Ultracarb filter element which is higher end. I suppose if you ask for the Supercarb, the price should be lower.)

Thanks & Regards.

Monday, November 15, 2010

Do we really need water filters?

I got an enquiry about water filters and their necessity. I have posted my reply below. (As a side note, I am currently working on a project to determine the effectiveness of water filters in reducing contaminants in our tap water.)


 I was searching for water filters and happened to see your blog

I had a few queries and hope that you could comment or advise :

 May I know whether the tap water/new water in Singapore is safe to be consumed directly without boiling ?

The tap water in Singapore has its quality benchmarked against World Health Organisation (WHO) drinking water guidelines. Its water quality meets and sometimes even surpasses the requirements given by WHO. From this perspective, yes, tap water in SG can be consumed directly.

As for boiling, it is most effective at killing microorganisms in the water. Boiling can prevent you from getting a case of food poisoning or diarrhea if the water is contaminated by pathogens. However, boiling is not good at removing chemical contaminants such as heavy metals, organic compounds or even chlorine if they are present in the water.

 I heard from salesman selling water filters that tap water contain chlorine which is not suitable to be boiled as it may produce trihalomethanes (THMs) which may cause cancer over long period of usage. 

Yes, our tap water contains chlorine for its ability to prevent the growth of microorganisms in the water. But the concentration is still within the limits given under the WHO guidelines.

Yes, chlorine can form trihalomethanes (THM) under the right conditions. First, you will need organic compounds in the water to react with chlorine to form THM. Usually the organic matter content in our tap water is too insignificant to form any THM. Our tap water is normally slightly acidic (< 7) so THM, if any, will form very slowly as they favour a high (alkaline) pH.

To be fair, the most well known member of THM, chloroform, is (only) a confirmed animal carcinogen with unknown relevance to humans. (Of course, I will rather not take my chances with ingesting chloroform.) The other members of THM are much less studied regarding their toxicity effects.

On the other hand, even disregarding THM, chlorine can be toxic in other ways - by itself or reacting with other chemical compounds IF its concentration in water is high enough. I have heard of water treatment companies in other countries dumping large doses of chlorine to disinfect their tap water and in the process, causing health problems in their consumers e.g. tumours, miscarriages. However, the chlorine in our tap water is definitely much lower (again according to WHO guidelines) as we routinely test it as part of our students' training.

 If that is the case, does it mean that we need to buy water filters in order get rid of the  chlorine before boiling the tap water for making hot beverages ?

Just like issues on food and medicine, water is surrounded by much controversy, especially on the health effects of its components, whether for good or bad. Chlorine in water is no exception. I can't say for certain that chlorine is completely harmless. This is complicated by the fact the health effects are usually only seen in the long term. Performing unbiased studies on human health for the long term (25, 50 years) will be difficult so no one can be sure what the long term effects are.

My thought is if you are worried and you can spare the budget (remember, filters are consummables and require constant changes), do go ahead and get yourself a good filter to reduce the chlorine content in tap water.

 May I know what are the impurities that are still present in the tap water/new water and what are the suitable filter to address them ?

Despite its clear appearance, our tap water contains lots of impurities. (Try googling for "PUB tap water quality".) Water of high purity (Newater by itself is quite pure though) is normally used in microelectronics/wafer fabrication, medical applications, pharmaceutical manufacture. (Actually, high purity water is considered "agressive" and may be bad for health. Oh boy, another can of worms here.)

One impurity of notoriety is fluoride. Our tap water is intentionally fluoridated (addition of fluoride) to fight against tooth decay. However, studies (again inconclusive) have shown that fluoride can be bad for health (arthritis, mutagenicity etc.) and unlike decades ago, we are already getting enough fluoride from our food and toothpaste. Do we still need fluoridation then? Like chlorine, may factors come into play in determining whether fluoride really does exert those negative effects e.g. concentration, time frame. And like chlorine, if you are worried, you should get a filter to reduce fluoride.  (Update: check out Fluoride Action Network for arguments against fluoridation)

I saw "arkwater" filter being mentioned, is it advisable to get it to remove the impurities present like chlorine ?

I believe that the Doulton gravity filter (get the high-end one) from Arkwater is a very good overall filter to remove many contaminants in water - microorganisms, heavy metals, organic compounds, fluoride, chlorine. This is especially critical for disaster or emergency relief when you do not have a clean source of water. Being a gravity filter, it does not need pressure (e.g. water mains) or electricity (what if your power is down). In addition, the filter can handle thousands of gallons of water before needing a replacement. Even if your intention to remove (or reduce) contaminants of unconfirmed health effects as in your case, the filter should still perform beautifully. (I must stress that I am in no way affiliated to Arkwater and derive no benefits from their sales.)

Figure: Doulton (aka British Berkefeld) fluoride removal filter cartridge. You will need this additional cartridge to remove fluoride as the others cannot remove this controversial compound.

Figure: Doulton (aka British Berkefeld) ceramic filter cartridge - the ATC Super Sterasyl model - the highest end for their line of gravity filter cartridges. It contains activated carbon to remove chlorine and organic compounds. Also inside is a metals removal medum.

Figure: Shell of the Doulton filter. The top compartment holds the filter cartridge and accepts raw water. Raw water filters through the cartridge by gravity and you get clean water in the bottom compartment.

At the end of the day, what I am trying to say is beware of sales tactics based on fear only with little or no truth. I am not saying that you should not get a good filter for your domestic use. But if you do, your decision should be based on sound judgement of facts or at least probabilities after weighing the costs and benefits sufficiently.

 Thanks & Regards.


Monday, October 25, 2010

Outdoor Education Conference (27 Oct 2010)

For those of you heading to this conference (walk-in registration is still available), you may be interested to know that I am presenting 2 sessions on 27 Oct 2010 (Wed).

Details for the concurrent sessions are as follows.


Water Quality Monitoring as a Tool for Environmental Education27 Oct09:00am-11:00amMr Kwok Chen Ko Singapore Polytechnic, SingaporeB08-09

Water Quality Monitoring as a Tool for Environmental Education27 Oct11:30am-12:30pmMr Kwok Chen Ko Singapore Polytechnic, SingaporeB08-09

1. Appreciate the importance of water quality to the health of the environment

2. Understand how several fundamental water quality parameters interact with aquatic life
3. Recognise the potential and challenges to water quality monitoring in Singapore

Target audience
Teachers/ Practitioners/ Coordinators of outdoor education programmes

Brief Description of SessionBesides the usual classroom talk on water quality monitoring, we will go through some of the instruments used in the field via a demonstration.
1. What is water quality
2. The basic water quality parameters
3. Measuring these parameters in the field
4. Challenges to water quality monitoring in Singapore
5. Resources for water quality monitoring

Sunday, October 10, 2010

Is Pasir Ris water really unsafe?

As a follow-up to the news update on the fecal bacteria laden water of Pasir Ris, this news may throw more questions (instead of light) on the issue of poor water quality at Pasir Ris.

First, a quick summary. A press release from NEA (Sep 2010) stated that the water at Pasir Ris Beach is unsafe due to the off-specs level of Enterococcus (a bacteria) in the water. Enterococcus is supposed to indicate the level of fecal contamination. More Enterococcus of course means more fecal contamination, implying a higher possibility of the presence of human pathogens.

Why don't we analyse the water directly for the pathogens? There are simply too many pathogens to test for so going down this route will easily lead to a logistical nightmare. Therefore, we stick to an indicator organism, something that is strongly linked to humans. Since Enterococcus (supposedly) comes from the human gut, its presence is (supposedly) sufficient to prove the contamination of the water by humans.

Going back a bit backwards in the history of water quality testing, the title of indicator organism for fecal contamination used by held by a group of bacteria known as coliforms. Not surprisingly, coliforms are also found in the human gut and its presence used to conclude the presence of human contamination. Unfortunately, coliforms are also found in other animals and soil. Some years back, Enterococcus has taken over this position as it was found to produce a better correlation to many human pathogens found in sewage. (Opps, the summary seems a bit longer than I initially thought.)

Ok, enough of summarising. Check these out:
1. Evaluation of Chemical, Molecular, and Traditional Markers of Fecal Contamination in an Effluent Dominated Urban Stream

2. How To Define "Safe" Water? Water Pollution: Southern California study highlights the limits of bacteria used as fecal indicators

The study basically argues that even Enterococcus is not a good enough indicator for fecal contamination in water. Why? Because it can also be found naturally in the river bed (in the study). In fact, it can actually grow in the river bed under favourable conditions i.e. good nutrient availability. Therefore, a bacterial count using Enterococcus tends to be overestimated with regards to the actual fecal contamination. (Granted, the study took place in fresh water and not seawater. But being such a versatile creature, Enterococcus can tolerate a wide range of conditions - pH, temperature, salinity, presence/absence of oxygen so it will not be surprising to find it thriving nicely in seawater.)

Is the water at Pasir Ris safe then? Your guess is as good as mine.

However, the study did recommend a substitutre for Enterococcus - something known as human-specific HF183 Bacteroides. This bacteria is supposedly (?) found only in the human gut. Testing for the presence of its genetic material will provide an accurate (?) picture of the amount of fecal contamination in water.

Will it really work?

Me? I will wait for the next piece of study to throw a spanner into this theory :-)

Friday, October 08, 2010

Digging around at Pandan Reservoir

I managed to steal some rare spare time to tag along with a NUS team and JH for a biodiversity survey of the floating wetlands at Pandan Reservoir.
What floating wetlands?!? If you have been observant enough, Pandan Reservoir and Lower Seletar Reservoirs have several bunches of plants floating right in the water. No, they are not aquatic weeds that suddenly grow up from the reservoir bed. They were deliberately placed there as an experiment(?) to improve the water quality. (Check out my previous post on how plants can clean up water.)

Figure: One of the floating wetlands at Pandan Reservoir. Notice that the plants on the wetland are different from those on the shore.

These floating wetlands are actually made of a floating plastic matrix above which a layer of coconut husks is embedded. The plants are allowed to extend their roots through these 2 layers.

Will they float away? No. Short of an extreme weather event, each wetland is anchored to the bed by rocks.

These floating wetlands dotted the northern shore of Pandan Reservoir. Are they effective in improving the water quality? My opinion is there are probably too few of such wetlands to make a difference to the reservoir as a whole. (Did I say that this was just an experiment?) Any change in water quality is probably localised and restricted to the immediate vicinity of the wetland. You will likely need a series of these wetlands to ring the entire reservoir. Maybe add another ring or two.

Figure: By the way, we had the luxury of sitting in a PUB motorboat as we passed by several floating wetlands

Next question - do bugs (macroinvertebrates) live under these wetlands? If so, what kind of bugs? These are interesting questions as my usual bug surveys were performed in running water (e.g. stream) or stationary water (e.g. pond). In the substrate of a floating wetland?!? No one knows...

Figure: Digging and scrapping and sweeping through the underside of a floating wetland

Figure: Voila! You can see a Marble Goby (top left) and a shrimp (bottom right) clearly here.

No so clear in the figure include: backswimmers (many!), unknown zooplankton (?) (many!), copepods, chironomids (your wriggling blood worms), a few damsel flies, dragonfly nymph exoskeletons (surprisingly, no live nymphs though we can see adult dragonflies happily scuttling through the air), chironomid eggs and pupa cases, mayflies (!). Looks like the biodiversity in these floating wetlands ain't so bad.

Figure: No, this is not part of the wetland survey. Actually, this is the primary task of the NUS team - deploying sampling traps in the reservoir to find out what kind of bugs can be lured into them.

Figure: On the way back, we stopped by this odd looking contraption floating in the middle of the reservoir. (Actually, it a buoy housing sensors though no one in the team knows what kind of sensors.) Of course, data from the sensors are transmitted telemetrically to some receiver on shore. Everything is this package is powered by solar energy as evident by the solar panels. See a previous post on descriptions of a similar setup. Oh, we didn't stop here just to admire this blue box. The NUS team actually wanted to catch some spider specimens here as a healthy population of spiders seems to be thriving on this buoy in the middle of nowhere.

Saturday, September 18, 2010

How to reduce flooding in Singapore? Harvest more rainwater!

Harvesting of rainwater may sound foreign to most of us even though this term is commonly used in other countries. It simply means collection and storage of rainwater. It may be on an individual, residential, community or even national basis.

Actually, Singapore has been harvesting rainwater for a long time on a national basis. From PUB's webpage, two-thirds of the land area here is available for rainwater catchment (Yes, right, "catchment" is more commonly used here).

Is so much of our area covered by reservoirs? NO! It means that land (residential, industrial, recreational, waste etc.) is used to funnel all that rainwater into reservoirs. For example, rainwater falls on rooftops, flows into drains which lead into canals, ultimately joining up with a reservoir. Because of the flash floods in June, everyone now knows that Orchard Road is part of the catchment area for the Marina Reservoir. Talk about practical environmental education.

Indeed a very clever system to alleviate the shortage of water in this densely populated island. However, it suffers from a few drawbacks.

One, in times of heavy rainfall, no way will the reservoirs be able to hold so much water. The natural thing to do is to drain the excess into the sea. (E.g. the Marina Barrage is well touted to be able to do this in the event of heavy rains.) This of course means a waste of fresh water. AND IF the excess CANNOT be drained (e.g. blockage of some water way), flooding will result. In the (good?) old days when Singapore is still a tropical jungle, most rainwater will be soaked up by the vegetation and soil. But with the increase of built-up area, we no longer have such a luxury. Most rainwater will flow over the ground surface straight into drains and canals or perhaps accumulate in some low lying area as a flood.

Another challenge of open reservoirs like ours is the loss of water through evaporation. In the dry months, the water level in the reservoirs drops not only because of the lack of rainfall but also through the above mentioned loss.

This article predicts that the rainwater harvesting (RWH) markets in Europe and India are set to experience high growth rates in the coming years due to a rising fresh water shortage. More RWH systems will be installed at the residential, commercial and industrial levels.

Guess what? This is nothing new in Singapore! Changi Airport has such a system. Nanyang Polytechnic has one too. The airport is reported to satisfy one-third of its water demands in this manner, saving $390 000 per year. Such water is normally collected on the roof-top and undergoes minimal treatment for non-portable use e.g. toilet flushing, firefighting drills, watering of plants.

Imagine... if we have more of such systems, not only will our reservoirs be less stressed in times of heavy rain, there will also be less loss of precious fresh water through evaporation.

If your interest has been piqued, how do you set up a RWH system. SIF Technologies is selling a "chemical free RWH system". Chemicals are sometimes added in conventional water storage to discourage microbial growth. (Chlorine in PUB water does this job.) In the case of SIF, they are using a proprietary non-chemical means to do the same thing.

But RWH can be simple and cheap. Consider this 3rd world method of RWH. However, remember to always discard the first 10min of so of rainwater as it may contain pollutants from the air or your roof-top.

Figure: using a tin roof to collect rainwater (Water for Life, Hesperian Foundation)

Figure: My own version of a RWH system for use in a high-rise flat from a project several years back. (Naturally, we can't have every household in a HDB block harvesting rainwater. I suspect only the top floors will get any significant amount. The other concern is not to have a high-rise RWH system becoming killer litter.)

Oh, before you rush out to install a RWH system, here is an extract from Singapore Law.


Prohibition on extraction of water
No person shall, without the approval of the Board (PUB), construct any works for taking or intercepting water from any place or sea, within the territorial limits of Singapore.

However, I believe the law has been relaxed for residential installation provided the storage tank is less than a size of 5x2x2m. Anyting bigger will require a water-borne fee to be paid. But if you are planning a system for your company or school, you still have to go through the bureaucracy for permission. One last point, check out the guidelines for collection of rainwater at NEA.

(Update: Rainwater Harvesting Seen as Solution for Drought and Flood Control: In Kenyan cities like Nairobi, rainwater harvesting is seen as a solution to multiple problems.)

Wednesday, September 15, 2010

Water resources from Loughborough University

Loughborough University's Water, Engineering and Development Centre (WEDC) has a new knowledge base where 150 books, over 1700 conference papers and hundreds of other knowledge outputs are available for download FOC if you register.

Topics range from water supply, sanitation, emergencies/disasters, lessons from floods and many more.

Tuesday, September 14, 2010

Revisiting Pasir Ris

Thanks to Ria for her post on Pasir Ris water quality deteriorating due to the high concentration of enterococcus bacteria in the water.

An explanation of the situation from NEA press release (7 Sep 2010)
"According to results from a study released by NEA in 2009 during the last annual assessment of water quality at beaches, Pasir Ris beach’s water quality is affected by various possible sources, including minor leakage from older sewers, moored vessels, animals, as well as discharges from small-scale Sewage Treatment Plants (STPs) that presently serve the more remote areas in Pasir Ris. The low water currents in the concave part of Pasir Ris beach are not effective in diluting and dispersing the discharges."

I do not have the answers to most of the whys and hows in this issue. Instead, I will pose a few more questions. (Does this complicate the issue further?)

Fish farms in the vicinity
  1. I believe the staff on these farms dispose of their bodily waste directly into the sea straight without treatment so yes, this can be a source of the E. bacterium. (Anyone care to refute the part on direct disposal?)
  2. Fish waste is another issue altogether. Yes, they may decompose and cause the dissolved oxygen level to plummet but enterococcus??? Not likely as the bacteria normally comes from humans.
Aging sewage treatment plants (STP) in Changi and Tampines
  1. Can anyone throw some light on these plants? Where are they? Industrial (probably)? What kind of industry? What is in the sewage - human, animal or industrial waste?
  2. Doesn't sewage go into the PUB sewers?
  3. Why are they allowed to discharge unhealthy effluent into our waterways? Any discharge into a watercourse must be approved by NEA under the trade effluent regulations of Environmental Protection and Management Act.

    Unfortunately, under the same regulations, there is no mention on the limit of coliform, enterococcus or even bacteria for a discharge.

    The closest will be BOD5 (biochemical oxygen demand for 5 days) under the regulations. (In simple terms, BOD5 is a measure of the biodegradable substances e.g. faeces, urine, food in the water.)

    "The 5-day Biochemical Oxygen Demand at 20° Celsius (referred to in this paragraph as BOD) and the Chemical Oxygen Demand (referred to in this paragraph as COD) of any trade effluent analysed in accordance with regulation 11 shall not be in proportions greater than those set out below:
    (a) 50 milligrams per litre of BOD and 100 milligrams per litre of COD where the trade effluent is discharged into a watercourse other than a controlled watercourse"
    I assume the waterways which lead to the sea off Pasir Ris are non-controlled watercourse since they do not go into a reservoir. Still, 50mg/L of BOD5 is easily exceeded by normal domestic sewage (100 - 300mg/L). (Agricultural or food wastewater may go into the thousands in terms of BOD5.)

    How efficient are these STP in treating sewage i.e. percent reduction in BOD5? Did anyone check whether their discharges exceed the limits set out in the trade effluent regulations?

    Nevertheless, it is entirely possible that the discharge can pass the BOD5 test but yet contains enough human waste to give a high enterococcus count in the sea.
Sembawang Park

The water quality off Sembawang Park (also given in the same report) seems fine. Being located along the Johor Straits as is Pasir Ris Park, I imagine the seawater dispersion there is as dismal. Perhaps, the smaller number of fish farms and the lack of aging STPs and leaking sewers do make a difference.

Friday, September 10, 2010

Introducing the British Berkefeld filter - something you can count on when the chips are down

The latest earthquake in New Zealand (Christchurch and surrounding area, 4 Sep 2010, 4:35a.m. Saturday, 7.1 magnitude) got me thinking about the supply of water again but this time round it prompted me to pen it down. (Long post as follows)

If you have been following this year's (2010) natural disasters - earthquakes in Haiti, Chile; flood in Pakistan, public water supply has always been a fragile creature. Infrastructure can be destroyed, piping and storage tanks can be broken.

In Pakistan, the deluge caused natural sources of water (e.g. wells, springs, streams) to be contaminated with whatever the flood water carried - human and animal waste, pathogens from corpses and carcasses, pesticides from farms, heavy metals from industry. In the short term though, it was the water borne diseases that caused the most problems - diarrhea, dysentry, cholera, typhoid etc. The breakdown of sanitation and water supply led to a nightmare for public health (probably nowhere near top notch even before the flood).

Bottled water naturally became a valuable commoditity as seen in Chile when it became one of the top looted items (together with bread and candles). I imagine the same would have occurred in Haiti if there was enough bottled water to go around to be looted.

Being a developed country, New Zealand was spared from serious looting (some still took place according to the news) or outbreaks of water borne diseases. Heck, no one was killed by the quake as according to some experts, the strict building codes to quake-proof its structures have helped. (Compare against 230 000 killed in the Haiti quake.) Nevertheless, the sewage pipes were broken in the quake, allowing sewage to mix into the drinking water supply which probably probably suffered from broken piping too.

Consequently, residents in affected areas were asked to boil their tap water for drinking. I am thinking: these people are lucky (despite the quake and all). They still have electricity or/and gas. Imagine... if you have no gas, no electricity and only sewage infused tap water, how are you going to boil your water?

Imagine some more.... the NZ scenario (without the gas and electricity) happens right here in good old SG (assuming we survive the quake), do you have a wood burning stove and charcoal at home? How about a camp stove with extra gas tanks? The lucky ones will be those NOT using piped gas. The years of effort to heft around those gas cylinders would have been worth it.

Do you have Aquatabs on hand? Bleach? Do you know how much to add into water? Personally, these are not my favourite choices because of strong chlorine taste and many health controversies of overchlorination. By the way, if you opt for bleach, only use the straight ones without extra ingredients e.g. scent.

Boiling is good if you can do it but it only removes the bugs and not all the other nasty stuff (pesticides, metals) in the water. Imagine having a Pakistani scenario here. I will boil my water before running it through a good filter.

I personally recommend the British Berkefeld (or Doulton) gravity filter. (In America, it is sold under the name of Berkey.) No water pressure, no electricity needed. Simply pour your water through the top and collect clean water at the bottom. The key element in the setup is the filter candle with the ATC SuperSterasyl being the best. It has a ceramic outer shell impregnated with silver. The ceramic physically remove microbes and particulate matter from the water while the silver suppresses bacterial growth. The water next enters a granular activated carbon core containing a metal ion removal medium (works by ion exchange, I believe) to eliminate many organic compounds (e.g. pesticides), chlorine and metals (e.g. lead, cadmium).

Figure: The external setup of the British Berkefeld stainless steel gravity filter minus the faucet which should be attached near the bottom. It is certainly not small (this is already the smallest stainless steel model) so it should be used for the family or small group at a static location.

Figure: Opening the lid reveals 3 holes for fixing a filter candle each

Figure: The heart of the filter system - ATC SuperSterasyl filter candle. Notice the white ceramic exterior. Water enters through the ceramic and filtered water leaves through the black nozzle on the right.

Figure: The top portion is removable for fixing the filter candles. Filtered water goes into the bottom portion for dispensing via a faucet.

Having one of these filters will certainly add a great degree of water security to any family. And if you are involved in overseas community projects, keeping one with you serves as insurance, especially if you are not sure of the water quality or source of your drinking water.

This line of filters may be procured locally from Arkwater. Of course, I am in no way affiliated with the company except for purchasing these filters from them.

Thursday, September 09, 2010

Sembcorp water technology prize (Sec 2 - JC2)

Just saw the poster below even though my colleagues have mentioned to me that they are involved in the competition. More details are found on PUB's webpage here. If you are considering to participate, the deadline is 18 Sep 2010.

Apparently, there is this push into membrane technology as the solution to getting clean water. Membrane technology is certainly cheaper and more energy efficient compared to traditional distillation. Theoretically, it can remove almost any impurity (salt, organic compound) in water. A membrane is basically a filter with very tiny pores. Depending on the specifications, some are small enough to block off microbes while others can block off even dissolved ions like sodium and chloride, allowing only water molecules to pass through. Seawater and heavily contaminated water can be made into potable water.

Naturally, pushing water through such tiny pores requires lots of pressure (and energy) so using membrane to purify water (e.g. reverse osmosis) is by no means cheap but prices seem to be dropping all the time.

Other challenges. Membrane fouling is a major problem. After some time, contaminants accumlate on the surface of the membrane till it can no longer function efficiently. It is time to either clean the membrane or replace it entirely. To prolong the operating life of a membrane, it is essential to have good pretreatment. In other words, you need to have many steps before the actual membrane itself to filter off increasingly smaller contaminants. Imagine having several filters of decreasing mesh size so that the final filter will not be stressed by a big load of contaminants.

Of course, this sort of setup comes with controls and maintenance operated by skilled personnel. Though there are now remote control interfaces, allowing a treatment unit in say, Africa to be controlled by a technician in America, you still need boots on the ground to attend to certain maintenance tasks. Therefore, this technology is still not so useful for rural areas without the presence of skilled personnel. Very often, even with skilled personnel present, the local population may not be able to operate the treatment unit once these personnel leave.

But for Singapore, sure, no problem. Membrane technology is the way to go!

Wednesday, September 08, 2010

A quick update for the past months

I would like to convince myself (and you) that my packed work schedule has prevented me from posting anything since the end of May. I know it is a shame but I am also sure that inertia has played a large part - not having posted for so long propagates the said behaviour :-)

In part to prove that I am really "busy" and to update you on the past activities, here is a summary of my "work".

June - July
Conducted "Freshwater quality and biodiversity" course for Crescent Girls, Henderson Sec Sch, Clementi Woods SS, Queensway SS. It was back to a tributary (sort of a naturalised drain) of Sg Ulu Pandan for more water quality testing and bug hunting.

Figure: The group hunt (for bugs)

Figure: Don't forget the water quality parameters

Figure: Sorting out the spoils of the hunt

Figure: A rare find - freshwater eel - too small for unagi though

Figure: The common Dragonfly nymphs though perhaps not so commonly seen by the students

Conducted a round of 6-day intensive AEM (advanced elective module) "Water quality and pollution".

Figure: On first sight, nothing wrong with the scene. But if you look closely enough, lots of people are looking down on their pants and shoes. This is what happens when you venture out in the wilderness in the rain and through knee high vegetation. All manner of creepy-crawlies are out their homes, latching on to the hapless passer-by (i.e. us).

Figure: Part of Ngee Ann Stream. Looks like another canal except that this used to be a natural stream with thick secondary forest on both edges. See next figure.

Figure: The same part of Ngee Ann Stream as the figure above but a year back. Note the vegetation stretching right to the edge of the secondary forest stream

Figure: An unusual find - a catfish struggling against the current in the "canalised" Ngee Ann Stream. Why was it doing so? I have no idea. Perhaps it should have just flowed along with the tide of change as what the rest of the stream did when it gave way to "development".

Figure: Due to the earlier heavy rain (what else is new in Singapore?), the whole canal was flooded, preventing the students from sampling the water (too dangerous).

Figure: The same part of the canal as the figure above but in drier times and more than a year back.

Figure: I simply can't resist putting in this routine group photo. Must show that the participants are in good spirits, right?

Singapore International Water Festival (27 Jun 2010)
Once again, I was roped in to organise the event "Amazing Greenviron Challenge" - an environmental quiz of sorts with indoor and outdoor components at the Marina Barrage. Weather was terrible in the morning so the outdoor part has to be moved indoors. (Right, rain was indeed heavy in June, giving rise to the shocking floods in downtown Singapore.)

Figure: Only 1 photo to show you here - the super group photo with organisers, student helpers and participants.

(Are we not done with the summary yet??? Afraid not... Did I mention that I had a tight schedule then?)

Water Quality Monitoring (WQM) (19 Jun 2010)
Amidst the tight schedule, I managed to sneak in a round of WQM with Team Seagrass at Chek Jawa.

Figure: On this rare sunny June morning, my students prepared their equipment for WQM.

To top it off, I attended the 4-day Wilderness Medical First Responder (WMFR) Course by OBS (Outward Bound Singapore) on Pulau Ubin. More on this in a later post.

Figure: WMFR participants and our dummies

WQM at Pasir Ris
Ah yes, the problematic kid on the block with regards to water quality - Pasir Ris Beach. (The latest advisory on its "fair" water quality is found here.) We checked out this notorious locale on this rainy July morning. Perhaps unknown to most people, this stretch of sand hosts 2 significant patches of seagrasses even though they are not monitored by Team Seagrass. (Some of the Team's members do however check out the seagrasses here in their own capacity.) And since there are seagrasses here, my team will of course be interested in the WQ.

Figure: 1 patch of seagrasses near Sg Loyang

Figure: The 2nd patch of seagrasses near Sg Tampines. I was told that there is a smaller patch further west near the end of Pasir Ris Park. We did not check this one out though.