Friday, July 07, 2017

Slides from Talk at Bishan Public Library: Finding safe drinking water overseas

About a month back, I gave a talk at Bishan Public Library on Finding Safe Drinking Water Overseas. The turnout was encouraging and the audience asked several useful questions. It was heartening to know that we do have people concerned about water quality in our midst.

Anyway, there had been requests for me to release my slides for public consumption so here they are. If somehow, you have missed the talk or you happened to be there but would like to recheck some parts of the talk, click on this link. (You will need to opt in though, even if you had joined the mailing list previously.)

Figure: Thanks to Victor for taking this photo of me during the talk

Friday, June 16, 2017

Does Singapore have marine water quality standards like Malaysia?

Hi Chen,

First at all, my name is Aizat and I am a technician from Malaysia. I have come through your blog: , and I think you can answer my question regarding Singapore coastal water quality. I would like to ask is there any classes or threshold limit for Singapore water quality parameters? For example, in Malaysia, we have Marine Water Quality - , that define water usage and parameter for coastal area.

Thank You 

Hi Aizat,

Thanks for the link to Malaysia's marine water quality.

As for Singapore:
"Coastal water samples are analysed for metals, total organic carbon, and other physical, chemical and bacteriological parameters."
The above are under NEA (National Environment Agency). Nope, no mention of the exact parameters measured or their threshold concentrations

Perhaps, the closest to publicly available water quality guidelines will be WHO Guidelines (2003) for recreational water quality. But this only applies to certain beaches in Singapore, again under jurisdiction of NEA.
"Singapore adopts the World Health Organisation (WHO) Guidelines (2003) for recreational water quality at our beaches and fresh water bodies. 
The guidelines are used to assess the suitability of a recreational beach or fresh water body for primary contact activities (e.g. swimming, skiing and wakeboarding) where:
  1. the whole body or the face and trunk are frequently immersed; or
  2. it is likely that some water will be swallowed.
Activities such as canoeing, dragon boating, kayaking are not primary contact activities.
The parameters used to assess the water quality are as follows:
For recreational beaches:
  1. 95% of the time, the Enterococcus counts should be less than or equal to 200 counts per 100 millilitres of water;
  2. Susceptibility of the location to faecal influence;
  3. Only beaches classified as 'Good' and above will be considered suitable for primary contact activities.
Water Quality of Singapore's Recreational Beaches in 2016
NEA conducts weekly sampling of water quality from the seven (7) recreational beaches listed below:
    • Sentosa Island Beaches (Siloso beach, Palawan beach, Tanjong beach)
    • Seletar Island Beach
    • Sembawang Park Beach
    • Changi Beach
    • East Coast Park Beach
    • Pasir Ris Beach
    • Punggol Beach
All the popular recreational beaches monitored by NEA are assessed to be suitable for primary contact activities as they are graded 'Good'. These seven beaches continue to meet the WHO water quality guidelines for recreational use."

Our Maritime and Port Authority (MPA) administers the Prevention of Pollution of the Sea Act but it is more of a prescription for stakeholders to avoid marine pollution. Again, no mention of actual water quality parameters and threshold values.

Therefore, I am afraid I do not have the answers you want. Assuming NEA still does its coastal water sampling and testing (no reason to assume otherwise), I believe they ought to have certain standards to adhere to. Regrettably, these are not shared in the public domain.

Updated by author on 16/6/17:


Thanks to an  update from Aizat, the water quality parameters monitored by NEA (not PUB! PUB is into water supply and wastewater management) along Singapore's coastal areas may be obtained from NEA


Figure: (Source: NEA) Locations of Non-Catchment and Seawater Sampling Points

Interestingly, NEA already has an automated and continuous water quality monitoring system in place along our coasts.



A real-time, continuous water quality monitoring system for the coastal waters of Singapore was fully commissioned in 2014. The system comprises 8 buoy-based monitoring stations with sensors for key water quality parameters. The locations of the stations are in Chart 5.11. Data from the stations is transmitted real-time to an Operational Management System (OMS) which processes and manages the data. The OMS also incorporates water quality models for forecasting water quality and to predict, backtrack and identify pollution sources and determine coastal areas affected by oil or chemical spill incidents.



Figure: (Source: NEA) Monitoring Locations and Water Quality Parameters Measured in real time

Unfortunately, we can't find any threshold values linked to the parameters given in the figure above.


I do have one question though - how effective is this online continuous monitoring system in reducing the damage from phytoplankton events on fish farms along the Johor Straits, especially in the Pasir Ris area?

Tuesday, June 13, 2017

Rainwater and river water: collection, treatment and storage

Dear Mr Chen Ko


My name is Thomas, and I am looking to work on a small-scale implementation for a water storage and filtration pipeline. I would like to seek your advice on the following as I deemed them requiring a more informed opinion than just a simple google search. Please excuse me if terminologies used are inaccurate or the context is too generic - I would definitely like to understand more about the practicalities and improve if possible.


This pipeline is a proof of concept to collect rainwater and river water, treating them separately, then mixing it (via manual carry), then storing it in a tank (preferably steel) for later or immediate treatment. The treated water will placed in a separate tank for distribution by tap to pail/smaller storage tanks to be given to the rest of the community or other usages. These will then be boiled on their if used for consumption, otherwise for bathing/watering plants.


1. Natural means to treat water/water tank. The temporary storage tank could hold the aggregated water for a week up to a month - and I think some bacteria could fester, and even if it was already clean, some might stick on to the inner tank surface. I attended some talk which spoke of possibility of using Hydrilla to clear the water, and some other plants/organic (aka cleansing biotopes) material which could dissuade bacteria growth or absorb other harmful things. An use case is cleaning the inner tank itself. This sounded too good to be true from the onset, but I do see some use for the Hydrilla to clear the water before UV treatment. May I know if such methods have been tried before, and whether it would be feasible to focus on this area?


2. Scaling up UV disinfection. I read one of your posts stating the UV Pen (i.e. Steripen:  drops in effectiveness if there are still particles above a certain size as bacteria could hide behind them and the light cannot reach them. What about the feasibility of a slightly larger version of the UV pen, to ensure more thorough disinfection? The idea is to shine multiple pens inside the tank, or have a larger UV light do this job. Does the cost increase a lot for such an implementation?


3. Water quality measurement. Taking measurements of water quality (e.g. pool test, turbidity). It seems infeasible to keep sending water samples from this pipeline for testing. And instead of doing a pool test manually each time, what are your thoughts on integrating some sensors to collect this data electronically? 


The assumption is that rain water is cleanest - but mixing with river water introduces some issues, so there is need to check for:

i) E-coli

ii) Heavy metals

iii) Chlorine, Fluoride, Nitrates.


Would you know reliable vendors and quote estimates that can detect these in one? I have done an Internet-of-things module in school, and sensors seemed quite cheap - I might be wrong regarding these specific set of measurements though, thus my question.


Many thanks for reading this, and wishing you a good week ahead!


Warmest regards




Hi Thomas,


Do you have a particular location in mind to implement this project? it sounds like a developing country!


You also did not mention the size of the community you are serving.


1.       Are you collecting rainwater from the roof or from the ground?

2.       If it is from the roof, it is more efficient to have each individual household handle its own collection unless you have a really big community building (e.g. church, hall) to collect it.

3.       You are indeed right to point out that rainwater is clean so I don't see the logic in mixing it with river water.

4.       Even if the location you have in mind does not have adequate rainwater, it is not economical to mix it with river water.

5.       It is easier to have separate treatment trains for rainwater and river water. And perhaps release treated rainwater (treatment should be minimal anyway) for consumption and treated river water for washing/flushing/irrigation.

6.       Phytoremediation has been documented to be effective in cleaning up water. I remembered Hydrilla used too though I can't recall its effectiveness off my head. A few issues to keep in mind though

7.       Most phytoremediation work was to clean up wastewater which means the treated water was not to drinking standard.

8.       Phytoremediation is typically used to remove organic pollutants, nutrients, certain heavy metals. It may reduce the pathogen population in the process but this is usually NOT the reason for phytoremediation. In fact, the process may introduce bacteria of its own into the water. (Admittedly, these introduced bacteria are probably not pathogenic.)

9.       The Steripen (1, 2) is designed for personal UV treatment of water. Instead of using multiple Steripens, you would be better served with the correct sizing of the UV treatment unit. This of course depends on the community size you are serving.

10.   Don't forget the need for electricity (which may not be easily available in your location) if you are installing a large scale UV unit.

11.   And you are right, clarity of water is VERY important for UV to work effectively. Turbidity of less than 1 NTU is ideal.

12.   The technology of Online measurement of water quality parameters has always been progressing in the water industry.

13.   I am not sure what sensors you have seen to be cheap (probably temperature, conductivity, pH) but the rest of the sensors are not cheap and most of the water quality parameters are not available as sensors.

14.   Many WQ parameters require certain sample preparation and chemical reaction, possibly involving heating. These cannot be duplicated by a sensor alone and will require a full suite of automation to accomplish, involving chemical reservoirs, precise sampling, mixing and heating of accurate amounts of chemicals. And you still need a detector which may not be common off-the-shelf kind.

15.   Heavy metals is a big group of very different elements e.g. cadmium, nickel, lead so they cannot be measured together as a single parameter. You have to know exactly which one to measure. And oh, they cannot be measured simply by a sensor alone.

16.   And testing for E. coli typically involves incubation - anyone with 1-2 days to spare?

17.   Having said all the above, yes, I will still recommend that you install the sensors for the cheap tests - temperature, pH, electrical conductivity as they can indicate problems if they are out of specs.

Hope the above are not overwhelming.


Good luck!


Figure: Hydrilla in the wild - Ngee Ann Stream which I have not visited for a long time

Friday, May 05, 2017

Talk at Bishan Public Library: Finding safe drinking water overseas

The link is now ready! Please click on "Register here!" above to register.
You are required to key in your NRIC. Due to a bug in NLB's system, you can't enter alphabets even though the NRIC field requires 9 letters. Therefore, you can add any 2 extra digits as a walk-around to the bug.

Monday, May 01, 2017

Workshop: Desalination for the future: opportunities and challenges

Figure: Tuaspring Desalination Plant - Singapore's newest and largest
desalination plant as of now

Desalination for the future: opportunities and challenges link

Date and Time

Wed 21 February June 2017
09:00 – 17:00 SGT
To be confirmed


By now, most of us in Singapore would have heard of seawater desalination - its promise of reliable fresh water independent of the whims of climate change or those of a neighbouring country but also its exorbitant costs which necessitates a 30% price hike in tap water.

Desalination is however more than just that. It presents opportunities to those in the right industries providing products, services and training. On the flip side, it also presents challenges in terms of costs, energy needs and environmental conservation. Meanwhile, advances in technology hold the promise of improving desalination many fold in the future.

Join water educator, Chen Ko, for an action packed one-day workshop focused on the opportunities and challenges in seawater desalination.
  1. The morning will kick off with a classroom discussion of the technologies, equipment and issues in desalination.
  2. Chen Ko is a firm believer of blending theory and practice so after lunch, the participants will get to visit a real life seawater desalination plant (Tuaspring) to experience for themselves just how everything works together.
  3. The workshop will close off with a debrief of the day's activities, especially touching on the learning points for all participants.
Participants are guaranteed to walk away with a deeper understanding of what desalination is all about and how it can fit into your work.

  • Overview
  • Water quality monitoring of feed and product
  • Pretreatment of seawater
  • Membrane operations and maintenance
  • Post-treatment of product
  • Disposal issues of unwanted "products"
  • Future of desalination

Anyone with a deep seated interest about the opportunities, challenges and future of desalination, whether you are a teacher/trainer, water contractor, water equipment sales staff, water testing team or simply a concerned member of the public.

Wednesday, April 26, 2017

Armed for bear: My favourite portable water filters configuration

For today's post, let's move away from serious talk such as national water supply and dive back into water filters.

When I am outside of good old SG where the water (tap or otherwise) cannot be relied upon to be safe (biologically at least), I trust my health on the water treatment that has never failed me (yet) - good old boiling. Boiling is great against microbes and parasites! For good measure, I prefer to get a rolling boil for 3min though some literature quote that 1min is enough.

But let's face it - boiling requires a good source of fuel (e.g. finding dry wood can be a pain after a heavy downpour in the middle of the jungle) and a big enough pot (typically metallic which can another pain to carry along in the bush). This is not to mention that you have wait... for the boiled water to cool down before drinking.

Therefore in cases for which the above conditions do not apply (e.g. no fuel, no pot, need to drink now), I rely on a handy package to treat my water.
  1. I have already introduced the Sawyer Mini filter before. What's not to like about it? It is small and versatile, removes most bacteria and parasites (99.99999% and 99.9999%, respectively) and super high capacity (100 000 gallons!).
  2. To squeeze even more performance out of my Mini, I hook it up to a Platypus Gravityworks Carbon element. Containing granular activated carbon (GAC), it is good to remove odours and taste due to organic compounds and chlorine.

    However, compared to the Mini, this little guy is only rated for 300L capacity, depending on the water quality so expect to replace it long before the Mini. There is also a slight increase in resistance when the 2 are connected together so be prepared to suck or squeeze harder to get drinkable water but it's nothing that cannot be overcome.

    Finally, the most important caveat... it is not designed to remove dangerous substances such as pesticides, solvents, heavy metals, radioisotopes... so if you have a reason to suspect such nasty stuff in your water, forget filtration and look for another water source.
  3. Not forgetting another nasty group of microbes - the viruses. I have posted before about the Steripen and how convenient it is. This guy can now play rear defence to polish whatever nasty bugs not removed by the Mini. Having the Mini in front also serves to remove particulates which may otherwise reduce the effectiveness of the Steripen.
  4. In actual practice, I do not place the Mini as the first man unless the water is exceedingly clear such as in an uphill jungle stream. Either I allow the water to settle first, then draw the supernatant into the Mini or I place a coffee filter before the Mini. This small and cheap accessory will prolong the life of my Mini so that it does not clog up prematurely.
  5. What I love about this setup is I can pack everything into a typical pencil case and I am ready to go. Just to restate a precaution, this setup is NOT omnipotent and does not remove chemical and radiological hazards.
Figure: The Carbon Element MUST BE fixed after the Mini to minimise unwanted bacterial growth on the GAC.

Figure: clearing up the leftover bugs with the Steripen

Friday, April 21, 2017

Relooking at the numbers of Singapore's water supply: 3 very interesting deductions (part 3 - final)

Though this is the final deduction of my 3-part series (part 1, part 2), I am planning to write a few more posts based on the discussion we had in the Future of Singapore forum on water security. For example, solutions to more effective rainwater harvesting (RWH) and another method to augment our water supply in "water scarce" SG. (But if you have read my part 1, SG definitely has no lack of rainwater.)

From  part 1
  1. Currently, our local catchment can presumably contribute 150MGD (imperial mega gallons per day) to an overall demand of 430MGD.
  2. Total demand in 2030 was interpolated to be 570MGD.

From PUB figures
  1. year 2030
    1. Contribution from Newater = 50%
    2. Contribution from desalination = 30%
  2. Year 2060
    1. Total demand is projected to be 860MGD.
    2. Contribution from Newater = 55%
    3. Contribution from desalination = 30%
Working with the numbers above
  1. 2030
    1. As in part 1, we reasonably assume that we can do without imported water (aka Johor water) and that the Newater and desalination plants are working hard at full capacity, local catchment can supply the remaining 20% of total demand.
    2. Multiplying by 570MGD, this works out to 114MGD.
  2. 2060
    1. Since we are only a year away from expiry of our water agreement with Malaysia in 2061, let's assume we are completely self-sufficient in 2060. (What are the odds of renewing the agreement? Hard to tell since it is still so far in the future.)
    2. Taking imported water out of the equation, our local catchment is left with contributing the remaining 15% of total demand.
    3. Multiplying by 860MGD, this works out to 129MGD.
  3. The trend then goes like this for our local catchment:
    150MGD (2017) --- 114MGD (2030) --- 129MGD (2060)
    Why are we seeing a decreasing contribution from our local catchment between now and the future?
    (Let's ignore the increase from 2030 to 2060 for now.)
    No doubt, I did make a couple of assumptions but I believe they are reasonable.
  4. Climate change?
    Possible. This region is modelled to have more intense rainfall but also more evaporation from a higher temperature.
  5. What is strange is according to PUB, "In the long run, our water catchment area will increase from two-thirds to 90% of Singapore’s land area. Most of this will be made up of unprotected catchments which are land where development is allowed, for example, for residential, commercial and non-pollutive industrial purposes."
    Shouldn't this translate to a greater contribution from local catchment?
    One possible explanation is the increase in catchment area is not via your typical reservoirs but through exploiting the small rivers and drains around the outskirts of SG island. This involves the use of VSP (variable salinity plant) which can desalt either brackish water (during rainy weather) or seawater (during dry weather). (References: 1, 2)

    Perhaps these VSPs are classified as desalination too? But if this is so, perhaps we should not be describing that our catchment is increasing to 90%? Still, VSPs do not explain the decrease in the contribution of our local catchment between now and the future.
  6. Something that we do not know??? If you do know, please share with the rest of us.