Monday, August 28, 2017

Public Utilities Board (PUB) drinking water guidelines vs. National Environment Agency (NEA) effluent discharge standards

Hi, thanks for your effort in educating readers about water quality in Singapore.

I was looking at the water quality  table of values published by NEA ( and PUB ( and noticed that temperature is measured in controlled watercourse such as canals, ponds and rivers but not measured in drinking water. Conversely, turbidity is measured in drinking water but not in controlled watercourse. Is there a reason for this differentiation, please? 

Also, may I have a e-version copy of your book "Your first guide to water quality monitoring in Singapore" please? 

Thanks and regards



I am not from NEA or PUB so I am not privy to their rationale.


However, I can make a guess…



The drinking water from the water treatment plant (under purview of PUB) exits at more or less ambient temperature. Ditto as it flows the piping network to your home. Therefore, it is pointless to measure temperature for drinking water.


In contrast, discharge of wastewater into sewers/water course/controlled water course (under purview of NEA) comes from industry. Depending on the type of industry, the temperature can vary quite a lot from ambient. In the case of sewers, the temperature can affect downstream wastewater treatment operations. In the case of water course/controlled water course, the temperature of the water can affect aquatic life.




Turbidity is important for drinking water (PUB) as turbid water is obvious to the human eye and no one appreciates drinking turbid water. This includes victims of disasters. Therefore, one of the major parameters to check in water treatment in disaster relief is, you guess it, turbidity!


In the water world, turbidity is roughly correlated with total suspended solids (TSS) but unlike turbidity, TSS can an actual amount in mass of the solids in your water. This is probably what NEA prefers when it set up its effluent discharge standards.



You may sign up in my mailing list to get a free copy of my ebook, Your first guide to water quality monitoring in Singapore.

Good luck!

Figure: Turbidity in water can be obvious to the human eye above a certain level. From left to right: 1, 10, 100, 1000 NTU

Saturday, August 26, 2017

Chlorine in water and water filters to get rid of it

Dear Mr Chen,

I have been reading the articles on your website. Thanks for the many info that you have provided.

Just wondering whether our Singapore tap water is still good enough to drink straight from the tap at this point of time. Is chlorine a health concern, should we at least remove it from the water before consuming it. I'm now looking for a water filtration system.

Your advice on this would be appreciated. 

Thank you


Dear Jennifer,
I am glad that you find my information helpful.
  1. As far as WHO drinking water guidelines go, yes, our tap water is well within their standards and is safe to drink straight.
  2. I have discussed about chlorine in a previous post. In a nutshell, the chances of suffering adverse effects from the chlorine in Singapore's tap water are very low. In fact, your chances of suffering from diarrhea due to contamination from improper food handling and poor hygiene are significantly higher.
  3. However, keep in mind that WHO drinking water guidelines are not omnipotent (see my earlier post). No doubt the guideline values (GV) are designed to be conservative but they are still partly derived with inherent uncertainties. For example, long term health effects e.g. cancer of ingesting small quantities of a chemical continuously are rather hard to determine experimentally so GVs are derived from mathematical models.

    To cut a long story short, you do have a right to be concerned though the degree of risk you are exposed to in drinking this water cannot be quantified easily.
  4. Aesthetic concern. I will the first to admit that I am not a fan of drinking water chlorinated by "chlorine tablets" or powder. It tastes too much like swimming pool water to justify me drinking it for more than a few days.

    When I compare the taste of our tap water with bottled distilled water, I do detect a difference but nothing like the "swimming pool" water above. Perhaps I am the lucky one as I know of people who are more sensitive to the taste of chlorine in our tap water. And if you are one of them, by all means, do something about it.
  5. At the end of the day, I guess it comes down to whether the concern about drinking our chlorinated water is affecting you adversely. If so and if you can afford the cost of a filter (plus the cost and time for replacements), please go ahead to get one. If nothing else, the peace of mind is well worth it!
  6. If your concern is only about chlorine, I suggest getting a good (i.e. ideally with NSF/ANSI certification to remove chlorine. Refer to 1, 2, 3 for more info) filter incorporating activated carbon.
  7. One recommendation is either a countertop or undersink filter housing from Arkwater incorporating the Ultracarb filter element which can remove chlorine and quite a few other contaminants. (Let me reiterate that I do not derive any benefit from the sales of Arkwater.)  Obviously, there are many other brands and models that can do the same thing so feel free to look around.
Figure: Arkwater's countertop model. Stainless steel. The Ultracarb filter element is housed inside.

Figure: Arkwater's undersink model. Stainless steel. The Ultracarb filter element is housed inside

Figure: P&G PUR satchet contains a chlorine compound and a coagulant. Made in Singapore! Pretty effective but the taste is simply unforgettable and not something to be taken over long term