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 (http://www.arkwater.com/stainless.html) which uses the ATC Super Sterasyl filter element (http://www.arkwater.com/ceramiccandles.html). 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 (http://www.arkwater.com/stainless.html) 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) (http://www.arkwater.com/residential.html). (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.