Wednesday, November 20, 2013

E-version of my book "Your first guide to water quality monitoring in Singapore" is out!

In case some of you are not aware, you can download a free (yes, free!) e-version of my book "Your first guide to water quality monitoring in Singapore" at PUB's website.

[Added by author on 6 April 2016]
Due to new security requirements for government websites by IDA, the above link to PUB no longer works and I have no idea whether it will be reinstated in the future.

[Added by author in Oct 2016]
If you would like to have an electronic copy, please join my mailing list here. Once your subscription has been confirmed, you will be offered the option to download a copy.

[Extracted from PUB's website when it was still available]
Water Quality Monitoring in Singapore
Authored by Kwok Chen Ko, in collaboration with PUB – Singapore’s national water agency, "Your First Guide to Water Quality Monitoring in Singapore" allows teachers and students to explore water quality monitoring with minimum academic theory. The key topics covered include:

  • The most critical water quality parameters to monitor.
  • How to design a robust water quality monitoring programme for a chosen water body.
  • Common problems encountered and how to avoid them.
Chen Ko is currently an Environmental Science lecturer from Singapore Polytechnic. The book is made possible by the FairPrice Water Education Fund


Saturday, August 17, 2013

Help! My rainwater harvesting system (RWHS) is not working (well)!

Further to my earlier posts on rainwater harvesting (RWH), I thought I should also present some possible problems faced by the rainwater harvester lest the reader thinks that rainwater harvesting is a big bed of roses. Nevertheless, I stand by my proposition that RWH is the best source of domestic water in rural/developing countries as long as you are living in a sub-Saharan climate.

These pointers are based by my experiences gained from my RWH projects so they are by no means exhaustive. But then again, RWH is not rocket science. As long as you exercise some common sense, do some basic research and you are on your way. Teething problems? Of course you will have them but nothing even close to life-and-death or that cannot be solved with hard work and ingenuity. "Improvise, adapt, overcome" If this motto is good enough for the US Marines, it is good enough for us.

Back to my pointers.

  1. A first flush diverter (FFD), roof washer or whatever-you-call-it is mandatory. It is basically a device to divert, filter or remove the first batch of rainwater from your roof - also the dirtiest part of the rain. Some people advise the first 5/10/15/(put your favourite number here) minutes of rain to be removed. Anyway, we tested the water quality from our FFD vs. the rainwater collected throughout the entire duration of the rain and no surprise, the FFD turned up significantly dirtier for almost all the water quality (WQ) parameters.

    Moral of the story: don't skim on your FFD/roof washer. Remember the old adage - penny wise, pound foolish.
  2. We tested out about 14 WQ parameters e.g. pH, conductivity, turbidity, nitrate, chloride, coliform, E. coli, hardness, alkalinity on rainwater itself, FFD water, final treated rainwater and compare them against PUB WQ from their water treatment works (no longer available on PUB's website but you can refer to their drinking WQ report for 2012) The parameter for final treated water that half the time did not meet PUB's guidelines is pH. Acceptable range is 6.5 - 9.5 while we got an average of 6.6 with a few data points below 6.5.

    No big deal actually for drinking (no, we didn't drink the rainwater though) but a small consideration for washing of metal parts e.g. car. Corrosion could be enhanced by acidic waters.
  3. Like the FFD, a vital piece of equipment is the strainer at the top of the downpipe (joining the gutter to the tank). If you place your RWHS in a well vegetated area like we did (in a garden), you will get lots of leaves, twigs and unidentified stuff trapped there in rainy Singapore. Clean it regularly or you will find your system clogged up or worse, a hot bed for mosquito breeding.
  4. Treat your rainwater treatment train (filters, UV plus whatever purification device) like your car - check them, clean them and change them when necessary.

    Case in point. UV disinfection is simple to install and use. No chemicals are needed. Just plug into a power source and presto. Right? No really... you  have to check the UV lamp regularly for fouling and clean it if fouled. A fouled lamp does not disinfect well. Ultimately, the lamp will gradually lose its intensity and you have to change it... remember pennies and pounds.
Good luck, folks!

Figure: The PVC portion jutting down from the tee forms the FFD

Wednesday, August 14, 2013

New publication on water quality monitoring in tropical ponds

This just came out hot from the press, published by CUGE (Centre for urban greenery and ecology). I am one of the contributors.

Title: Guidelines on Water Quality Assessment and Management for Tropical Ponds

"Guidelines on Water Quality Monitoring for Tropical Ponds sets out recommended standards for pond water quality for key parameters with reference to empirical measurements from 59 ponds across Singapore. It explains how to use water quality monitoring results to diagnose water quality concerns, and outlines a range of associated management strategies for addressing water quality issues in tropical ponds."

This guide is basically for tropical freshwater ponds. And it is geared towards assessing and managing the problem of eutrophication in ponds. No surprise since eutrophication happens to be the dominant problem in Singapore ponds with most under the jurisdiction of Nparks.
Of particular usefulness is a set of water quality guidelines e.g. salinity, pH, turbidity, total nitrogen, total phosphorus with qualitative and quantitative limits. This provides a useful benchmark for pond managers to determine the health of their ponds.
This guide discusses several management strategies to deal with eutrophication e.g. chemical treatment, wetlands, dredging, filtration.

Overall, it is a great introduction to the world of pond water quality, especially for  park managers who are familiar with plants and landscaping and clueless about water quality.

Monday, August 12, 2013

Do we actually have our own drinking water standards?

Perhaps not well known but Singapore has its own set of drinking water standards. This may be a result of the frequent mention of WHO as the sacrosanct authority on water quality (WQ) by the our authorities when it comes to drinking water. (Of course, our OWN standards are based on WHO standards with some modifications.)

Here goes:

WHO, IWA (International Water Association) webpage, NEA webpage
The above basically covers about 100 WQ parameters and their limits in drinking water. PUB has published their drinking water quality reports (2011 is no longer available online, 2012) based on testing for these parameters.
2. Code of Practice on Piped Drinking Water Sampling and Safety Plans

Essentially speaking, anyone who wants to dabble in his drinking water ought to go through these 2 documents to understand what is going on besides knowing how to turn on the tap and have water coming.

Wednesday, August 07, 2013

More recognition to grey water recycling!

Grey water (1, 2, 3) recycling has always been a less glamorous cousin to rainwater harvesting. After all, rainwater is clean water for drinking, bathing, cooking... all important processes for our health and well-being, while grey water is wastewater best kept out of sight and mind... as long as someone else is taking care of its disposal.

News update: Water is water is water (no typo here) by whatever name. The only difference lies in the "impurities" in the water, hence giving rise to black water (toilet bowl), grey water (sink, laundry, bath), yellow water (urine only), dark grey water (kitchen sink, diapers laundry). All water is intricately connected in the water cycle - both natural and human. In other words, rainwater or any other "clean" water can come from grey water. Therefore, it pays to conserve (read recycle) and handle your grey water properly.

It is therefore great news when I see that PUB has added a section on the guidelines of grey water recycling in Singapore.

1. Alternate sources of water
On this page, rainwater and grey water are officially recognised as alternative sources of water, not just at the national level or at the residential/individual level. I have written about rainwater harvesting in an earlier post.

2. The document itself

Some highlights
  1. It goes without saying - no potable use. But irrigation and general washing are also forbidden. Why then do you recycle grey water???

    Well.... it can only be used for toilet flushing and as cooling tower make-up water.

    Personally, depending on your treatment process, grey water can even be made potable. Even with simple treatment, its water quality can be made adequate for general washing and irrigation.
  2. As for rainwater harvesting, grey water recycling must follow PUB's standards for fittings and code of practice for water services, as well as NEA's standards for prevention of mosquito breeding.
  3. Raw grey water should not be stored for more than 24 hours. This IS reasonable as any time longer will lead to anaerobic conditions and foul odours.
  4. Treated grey water should not be retained for more than 72 hours. This DEPENDS on the type of treatment. If the final water quality is that of drinking water, I am sure the duration can be stretched.
  5. Incidentally, there is no mention of WHAT type of treatment process you should use... Instead, whatever treatment must produce a water conforming to the water quality guidelines (listing the various water quality parameter and their limits) given in this document. This is immensely useful as previously, there were no such guidelines.
  6. And also very useful is the schedule for water sampling and monitoring e.g. testing for E. coli and coliform should be done monthly.

 Figure: PUB guidelines for treated grey water quality

Figure: PUB sampling regime for treated grey water

Source of the above 2 figures: PUB document (

In conclusion, I believe we are on the right track on publishing such standards for grey water in terms of its water quality and testing schedule. I hope more developers and individuals will take up the challenge to implement grey water recycling on a residential or building scale.

Natually, there is much more to be done. E.g. I am impressed when habitats use plants not only to clean up grey water but also to provide edibles for their inhabitants. Bananas can be clearly seen in my previous posts (12) illustrating this concept in an Earthship.

Figure: Bananas, anyone? (Source:

Tuesday, August 06, 2013

More power to rainwater harvesting in Singapore!

Hi folks,

It has been a long while (Mar 2004 till now to be exact) since Dr Tan Cheng Bock (Singapore presidential candidate in 2011) advocated water conservation by implementing a rainwater collection tank to water his garden despite the illegal nature of such an act before that time. See Straits Times article below (dated 16 Mar 2004).

Source: Straits Times 16 Mar 2004

Before 2004, collection of rainwater was forbidden except for the use of pails in residences. Building a rainwater tank was strictly a no-no. Rationale: rainwater was a property of PUB acting in the best interests of the nation in water conservation and rainwater collection via the canals and drains that ultimately flow into reservoirs (technically, only two-thirds of the land area here is available for rainwater catchment so not all rainwater is channelled into reservoirs). Yes, you are expected to let the government handle YOUR water needs. What a mentality...

Since then, even though not widely known, rainwater harvesting has been legalised for households as long your rainwater storage tank is no bigger than 5x2x2m (or you will have to pay a levy for wastewater treatment) and your rainwater is for non-potable uses. Institutions and companies will have to apply for a permit if they want to implement rainwater harvesting. Still, many got their permits e.g. Changi Airport (1, 2), Nanyang Polytechnic, Poh Ern Shih Temple.

But now, it is official!

Details are now more clearly spelled in PUB's website:

1. Alternate sources of water
This page also includes grey water recycling (I will cover this in a separate post) which is now officially recognised too! How exciting!

Some highlights:
  • Owner/developer/QP/PE can submit an application to PUB for rainwater harvesting.
  • Please note that rainwater is only (and still) for non-potable use.

More details can be found in this document.

Some highlights:
  • Not surprisingly, rainwater harvesting equipment has to comply with the Code of practice for water services and the fittings must follow the standards under PUB.
  • What are your non-potable options in the use of rainwater?
    • general washing
    • toilet flushing
    • irrigation
    • Sorry, no bathing and washing of hands... (and I though that rainwater is supposed to be good for your hair)
  • Excess rainwater should be allowed to overflow into drains which of course goes back to becoming the property of PUB.
  • Don't forget the other governmental big brother, NEA. Your rainwater system also has to comply with NEA's guidelines, especially concerning mosquito breeding.
      • Guess what... gutters are now allowed (though "discouraged") for rainwater harvesting provided they follow the guidelines given here.
      • The same rainwater is not supposed to remain for more than 7 days in the storage tank (translated as residence time to the engineer reading this).
3. Drainage handbook
A big document - 82 pages. More for further info and background.

My take
Well and good. People should have a role in conserving and utilising this precious resource. No doubt, centralised rainwater harvesting by PUB is indeed useful. However, the people need to be allowed more freedom for initiative to take care of themselves and the environment.

Personally speaking, rainwater is really clean water. The possible contaminants will be dust and dissolved gases and whatever that adds into the water by the collection system e.g. bird droppings, dead insects. After some minimal treatment, rainwater is certainly potable. As mentioned in a previous post, I strongly suggest rainwater as compared to other sources for consumption rural/developing communities overseas.

Figure: Source: Straits Times c2003. Rubbish choked water in Muara Baru, north Jakarta. I don't know about you but I prefer to get my water from the rain rather than from surface water like this. 

Tuesday, July 30, 2013

Appreciating our City in a Garden - NParks 50 years of Greening Singapore Music Video

Just helping Nparks to promote their music video here since I have collaborated with them on numerous occasions.
"To commemorate 50 years of Greening Singapore, NParks produced a music video to reach out to more Singaporeans to appreciate our City in a Garden. Local singer-songwriter Lorraine Tan specially composed a song to mark this signicant milestone and there are special appearances by popular Youtube personalities Dr Jiajia & Big Bro, Ch 8 TV actress Paige Chua (who volunteered to film this), as well as our lovely otters and hornbills J. "

Friday, July 12, 2013

Water testing strips: a quick and easy way to monitor water quality

To most people unfamiliar with water quality monitoring (WQM) techniques, testing your water may sound like a frightening proposition, filled with scientific jargons, chemical names and strange equipment.

Fortunately, there is a quick and easy way to test your water without sending your water samples to a commercial lab which can bite off a chunk of your budget and take time from submitting your samples and receiving your data.

If you have been holding your breath, here is your answer - water testing strips. The instructions look simple to follow. No messy and hazardous chemicals to handle. No heating and special sample preparation needed. Most strips simply require you to dip them into your water sample, take out and wait for some time (typically a minute or so) to the colour to develop. Match the resultant colour against a colour chart and viola! Instant water quality data. (The longest time I waited was about 10 minutes for the chloride test. I have not used the bacteria strips but most still need the typical incubation time e.g. 48h.) If this sounds like your DIY urine glucose testing strips, you are absolutely right.

On-site tests can be done with these guys with no lag time that can allow reactions to interfere with your results.

There are various suppliers for these strips but the one I tried came from Hach - a well recognised company for water analysis. There are strips for pH, hardness, alkalinity, iron, copper, ammonia, nitrate, phosphate, chlorine, chloride and even arsenic and bacteria. But in case we get too carried away with the WQ parameters that can be tested with these strips, keep in mind that WHO drinking water guidelines have about 200 parameters so there are still many parameters not available for testing on strip.

Another limitation of strips is the precision of your results. It may only give you a range of say, 0-5, 5-15, 15-30 ppm (parts per million). For the strips testing for bacteria, the result is a simple present or absent. Sometimes that is not good enough to tell you whether the water is safe, tolerable or plain dangerous. And for research purposes, you need a more definite figure to plot your trends or perform your statistical analysis.

Nevertheless, if you keep in mind their limitations, water testing strips are a great (quick and easy) method to test your water. Use them for preliminary tests or perhaps as screening tools to check if further and more precise analyses are necessary.

Figure: Water testing strips normally come in bottles like these. This make them extremely mobile - no bulky equipment and chemical containers to cramp the space in your travel bag. Each bottle usually has a colour chart on it exterior. Notice the colour chart on the leftmost bottle.
Figure: 5-in-1 testing strip. Each coloured square tests for a separate WQ parameter.

Sunday, March 31, 2013

Kampung Temasek

I have the privilege of being invited to Kampung Temasek (KT) located in Johor, Malaysia (near Ulu Tiram). It is designed to be an outdoors learning centre, open to school activities and corporate workshops.

On my part, I am checking it out as a potential location for my school's outdoor activities and a potential site for green projects. It turned out that they are looking at implementing a rainwater harvesting programme for their visiting groups. Currently, their huts are harvesting rainwater for toilet flushing but more can be done, especially when large groups go over and these large groups cannot fit into the huts. Also, rainwater can be used for more applications than just toilet flushing e.g. washing of dishes and hands. Naturally, washing of hands and dishes will require a better water quality compared to toilet flushing and irrigation so a treatment train will probably be needed. Of particular potential is their main hall which can be modified into a giant rainwater collection device.

Figure: 2 of the 6(?) huts. Notice the raised above ground architecture for ventilation and avoidance of floods. Also, check out the solar panel on the roof of the hut on the left. Unfortunately, solar power is limited due to the heavy cloud cover in the tropics. Rainwater is harvested for toilet flushing in each hut but in my excitement, photographing this unit has simply slipped my mind. (Side note: KT is still tied in to the grid and water supply for the area. Sanitation is provided by septic tank.)

Figure: The main hall with nice sloping roofs. Great for rainwater harvesting. We may not even need all 4 sides!

Figure: The kampung style of lighting

Figure: The eutrophic pond where students do their confidence jump together with ducks and geese

Figure: Our highlight of the day. 1 of 2 banana plants we transplanted to a location we believe to be more suitable than the original one. Partial shade, raised ground, soil is well drained yet still moist

Figure: A not so green practice. Solid waste is disposed by burning on site. Without municipal solid waste collection, this is a common practice in rural parts of Malaysia. A partial solution will be to compost the biodegradable waste, producing compost for the vegetable on site. But this idea MUST BE sold to the local caretakers on its merits in contrast to the extra work of composting vs. burning.

Sunday, March 24, 2013

Overseas community service (OCS)/ Youth expedition project (YEP) part 3: Are there still more things to check if my water is safe?

This post follows from 2 previous posts.
  1. Overseas community service (OCS)/ Youth expedition project (YEP) part 1: Is that water safe?
  2. Overseas community service (OCS)/ Youth expedition project (YEP) part 2: How do I know if that water is safe?
So you have checked out your watershed and everything looks ok. No industries, agriculture or villages around. Are we home and dry?

NO! We have not checked out the history or to be more exact, the geographical history of the watershed! Find out what the area used to be...

2. Historical geography

Example 1: Mining
Mining (granite, coal, metals etc.) can especially be nasty to health and environment even after closing down for years. Digging deep into the earth can release toxic substances (lead, radiological compounds, heavy metals etc.) found underground into water once the mine fills up with water after closure. Not surprisingly, mining can also impact groundwater quality so those looking at using well water do take note as well.

Or sometimes, the mining operation itself left hazardous waste which remains uncleared after closure.

Google "toxic legacy of mining" and you can find tonnes of examples. Here are a couple.
    Australia - copper and gold mining can create a leachate with hazardous levels of copper, manganese and zinc.
    France - uranium mining - "accumulation of radioactive metals in sediments and plants of rivers, ponds, and lakes by contamination around former mine sites has also been found to have high enough contamination to be considered “radioactive waste”"
And a common example is acid mine drainage in which sulfide ore from underground turns into sulfuric acid upon reaching the ground surface (chemistry is involved). This can be quite serious as it can turn water very acidic - pH of 1 or less.

Example 2: Agriculture
Depending on the type of agriculture, you can find different pollutants in the soil or sediment. And these pollutants may subsequently leach into the adjacent water bodies. If the pollutant load in the soil/sediment is heavy, the leaching can occur over a long period of years. Short of dredging the entire load of sediment or bulldozing the whole lot of earth, the problem can only be treated symptomatically without eradicating it source. (See a potential case study in a previous post - How to get rid of your seemingly unstoppable pond algae at Sungei Buloh.)

If we are talking about crop land or plantations, there is a likelihood of pesticides and fertiliser residues in the soil/sediment. On the other hand, animal farms will likely introduce animal waste (which is also a source of nutrients) into the soil/sediment. Nutrients/fertilisers are especially good at promoting eutrophication in water bodies while pesticides can be toxic to the ecology and us.

Most of you probably knows that Sungei Buloh used to be house prawn and fish farms in its mangroves before being converted into the wetland reserve we know together. However, do you know that it used to house pig farms too? (Wetland forest of Sungei Buloh mangroves) Has all the pig waste been cleared from the area? If not, can this be a source of nutrients leaching from the soil/sediment into the current mangrove area and causing eutrophication?

Example 3: Estuaries
In simple terms, an estuary is the intersection between a river and the sea. It can be in the form of a swamp, bay, delta etc. Not only does it accumulate (depending on the tidal and hydrological conditions) stuff from the river (think about oil, pesticides, heavy metals), it can also receive pollutants from shipping (ballast, waste, cargo overboard), especially along a busy shipping channel or near a port.

The port and upstream factories may not be there anymore but the pollants remaint in the sediment, possibly for a long time of decades and slowly releasing its toxic load of heavy metals and persistent organics (including dioxins, PCBs (polychlorinated biphenyls), -cides (pesticides, insecticides, herbicides)). BUT if someone decides to dredge the sediment (perhaps to keep the channel deep for shipping), you may see the serious problem of a massive dosing of pollutants into the water. Morale of the story: don't disturb the sediment unless you intend to remove the whole chunk as a long term solution.

Incidentally, heavy metals or persistent organics can show up in bottom feeders such as shellfish (mussels, clams etc.). They accumulate the substances as they wade through the sediments for food. Of course, what this means is they are potential bioindicators - indicating the health of the environment without doing a chemical analysis first.

The other more serious implication is if the locals feed on these bottom feeders, they may very well be intoxicating themselves.
Figure: 1969 topo map of the area around Ngee Ann Stream. Notice that the old railway track splits into 2 lines near the Bukit Timah station. Old maps are a good source of information on the geographical history of the area. Another source is old aerial photographs.

Figure: Google Earth view of the same Ngee Ann Stream (imagery data 2009, 2010). Some roads and waterways remain after all these years.

Figure: Photograph from The Straits Times, depicting the floods in 1978 and men rescuing their pigs. More importantly, it tells you that Woodlands, Braddell Road, Potong Pasir to Changi used to be a "farm belt". Such old news are another source of information.
Figure: Quarry lake on Pulau Ubin. Disused after the granite quarry has closed. How does such a mining activity affect the water quality?

Sunday, March 17, 2013

Overseas community service (OCS)/ Youth expedition project (YEP) part 2: How do I know if that water is safe?

For those working in developing countries:
In case you are still not sold on the idea of drinking from rainwater based on my previous post (Overseas community service (OCS)/ Youth expedition project (YEP) part 1: Is that water safe?), read on. Incidentally, some communities do not want to drink rainwater because of tradition and culture. They have drinking from surface water (ponds, rivers, lakes) since the time they were born, they do not see other sources of water as viable. Depending on the situation, you may not want to fight an uphill battle to suddently switch their drinking habits to a rainwater source. Perhaps, you may be better off convincing them of implementing some treatment method.

I have been consulted by organisations which want to operate in developing countries and know more about the safety of their drinking water. An approach similar to the one below may be used.

1. Geography
If you are collecting surface water, know what is upstream. (This was covered in the previous OCS/YEP post but I will add some more information here.) Residences, villages, resorts, tourist attractions or heaven forbid, industries and agriculture upstream should light up a big red flag with a buzzing alarm... Drink the raw water at your own BIG risk.

But knowing the land use should extend to more than just along the waterways. Know your watershed! (In Singapore, we call it catchment basin or drainage area instead.) Your watershed is basically the land area acting as a big umbrella to catch and convey the rain to your water point. It includes the forests, parks, carparks, roads, other built up areas for the rain to flow over before reaching your water collection point. Naturally, any substance (e.g. litter, oil, animal droppings, soil, minerals) on the ground surface is fair game for the rainwater to pick up as it flows to your water point.

So you say that your river does not flow past any industry but if your watershed has a leather tannery or beer brewery, their waste chemicals may find their way into your river (and your mouth if you are drinking from the river).

Traditionally, we use topographical maps to delineate the watershed. In simple terms, water always flows from high to low points. Join up all the high points surrounding your water collection point and you have set the boundaries for the funnel into which water flows. (You may refer to Georgia Adopt-a-stream file here for a better description of the process. In fact, I strongly recommend that website as it contains a lot of useful information for water quality monitoring.)

However in current times, computer software and GIS (geographical information system) are used to calculate the watershed.

Of course, you may not have a topographical map. (Some countries consider this a state secret. Even in Singapore, it is not easy to get one.) Much less the digital map for your area of interest. Then the next best method will be to check out the areas adjacent to the waterway upstream of your water point. An area 1-2 km from your waterway will be a good start. Same as before, check out the landuse patterns in these areas. Does anything stick out like a sore thumb?

Figure: Sample topographical map. Useful to delineate your watershed if you don't get overwhelmed by the amount of details in the map. It also tells you quite a bit on the landuse in your watershed.

Figure: Students' rendition (sketch) of the landuse patterns around Ngee Ann Stream

To be continued...

Sunday, March 10, 2013

What water filter does the military use?

This piece of news jumped at my attention immediately, partly because of the connection to the U.S. Military. Items used by them (military specifications or milspec) are usually quite good and certainly up to the rigours of combat and heavy outdoors use.

Water Purifier Meets Requirements of US Military Small Unit Tests (28 Feb 2013)

Figure: Seldon Technologies WaterBox™ 300 MIL ( Look closely at the left compartment and you will see 3 filters (within seemingly conventional housing) with labels (jack up your magnification to see clearly). R to L: some sort of pleated sediment filter; some sort of depth filter (melt blown?) to remove smaller sediments and protect the main filter; the main filter and the star of the show - a nanofilter made into a mesh of carbon nanotubes hence giving rise to nanometer sized pores (

I have extracted some of its highlights from

  • Setup time is under five minutes
  • Requires no maintenance, no chemicals, and no heat to operate
  • No waste water is generated as a result of the purification process
  • Removes bacteria, viruses, Cryptosporidium, and Giardia to USEPA drinking water standards: 99.9999% of bacteria, 99.99% of viruses, and 99.9% of cysts
  • Reduces sediments, chlorine, total organic carbons, bad taste, and odors
  • Reduces chemicals and many harmful heavy metals (e.g., mercury and lead)
  • Self-priming system can pump from any water source with up to 4.3 meters (14 feet) of lift
  • Patented Nanomesh technology for high-performance contaminant removal

  • Capacity: up to 30,000 liters (8,000 gallons), depending on water quality
  • Flow rate: 1.89 liters (0.5 gallons) per minute
  • Weight: 78 pounds (31.8 kg)
  • Power source: 12VDC, 24VDC, 115VAC 60-Hz, or 230VAC 50-Hz

Looks good. Their Nanomesh technology is a form of nanofiltration. In simple terms, it can filter off particles down to nanometers in size, meaning most microbes and many types of molecules and ions (the big ones). NOTE that it is not designed to filter off sodium chloride which is the salt in seawater so it is not for desalination.

It can accept DC and AC from the more common voltages. BUT it still needs electricity basically to run the pump (top left on the right compartment). Meaning that in a grid down situation that you and I are likely to face in an emergency, this thingy will just sit pretty there. On the other hand, I believe, Seldon Technologies has a version that works on manual pumping. (Check out my previous posts on an alternative water filter for emergencies: Do we really need water filters 2?, Do we really need water filters?, Introducing the British Berkefeld filter - something you can count on when the chips are down)

Weight of 31.8kg is not exactly a walk in the park to carry around so plan on having a helper or a trolley if you want to move it around much. Capacity of up to 30000L (before replacement of the main filter?) is pretty impressive, considering that a person needs 2L per day for purely survival mode (no sweating and jumping around). A flowrate of 1.89L/min is quite decent for a small group, similar to a squad of Navy Seals or Special Forces that this filter is designed for.

Sunday, March 03, 2013

PUB drinking water quality report 2011

Readers interested in our drinking water quality may want to check out this report on tap water quality in 2011.
It compares our tap water values against WHO drinking water guidelines and indicates whether there is compliance. Not surprisingly, all those parameters that have a corresponding WHO drinking water standard show compliance.

Let's see... it contains data on 1 microbiological parameter, 2 physico-chemical parameters, 3 radiological parameters and 90 chemical parameters! Wow, that makes almost a hundred water quality parameters which is a big improvement from the 21 parameters (20 physical/chemical + 1 microbiological) from another PUB water treatment webpage comparing the waters from various water treatment plants. Astute readers will course notice that some of the parameters from the water treatment webpage are not included in the water quality report e.g. pH, conductivity, taste, odour, total alkalinity, total hardness, total dissolved solids. Nevertheless, such a report is very useful for citizens who want to know more about our tap water quality - beyond the common yes/no statement that the water is drinkable and follows WHO standards.

However, the statisticians out there may be disappointed to learn that no other details on the testing regime are given.
  1. How many samples were tested?
  2. From where? Water treatment plant, tap, distribution network, storage tank?
  3. How frequent were the samples collected? Any specific dates?
  4. Which testing lab(s) were involved?
  5. Were other parameters tested? (My personal belief is more testing had been done than what is reported.) Did they clear the standards?
Despite the lack on information on the above points, I am glad that such a report is available to the public. It goes a long way to educating the public on such a vital resource as water. And I think this is the current trend our society is following. The end user becomes more educated and hence wants to find out more about the resources he is using in order to make an informed decision in synch with his beliefs. Hopefully, this will lead to a more sustainable future.

Figure: Students learning about water quality testing in SP

Thursday, February 28, 2013

Question about Lorong Halus

Hello Chen Ko

My name is B and I came across your blog ( while trying to find out more about the health risks of running in the possibly leachate-containing mud trails near Lorong Halus landfill (I browsed your blog and I realise this might not be your area of expertise but I would appreciate any insight at all :-) ).

I live near to Sungei Serangoon and have recently started running at and exploring the area around Lorong Halus (it's an awesomely beautiful area with lots of wildlife - and I share your love of nature and I'm also concerned about how successful these new wetlands will be - the undeveloped east bank carries so much more biodiversity than the developed west bank which is Punggol Promenade and HDB flats).

On several trips recently I've been exploring the dirt trails that run along the east bank of Sungei Serangoon, and up and down one tributary just south of Lorong Halus Wetland (it leads up to Lorong Halus near the TPE entrance), and I've been running across what looks like leachate, especially near the green pumping stations:

1. Most commonly orange-ish puddles/mud similar to these:

2. Oily rainbow sheen on puddles/mud

3. (least common) Black fluid leaching into some puddles

There's no way to avoid these so I've been getting my feet into them, and though I don't really intend to return to those trails in future, I was concerned about how toxic these are, and I was wondering if you have any idea? (I've done some googling and found that (as per your blog as well) the common hazards are heavy metals and toxic organics - PCBs and dioxins?) These areas are not open to the public currently, but there are trails used by foreign workers who fish there (probably from the dorm at Tampines Road near Old Tampines Road).

Here's thanks in advance for any advice you can provide. :-)

Best regards and happy trails!


Hello B,

First off, here is a quote for the purpose of Lorong Halus Wetland. "Using an innovative bio-remediation system, national water agency PUB designed the Lorong Halus Wetland to collect and treat water passing through the former landfill, preventing it from flowing into Serangoon Reservoir." (1, 2)

My stance is I would not say that leachate is escaping from the landfill without rock solid proof.

Unfortunately, environmental forensics is often a complicated and expensive activity. Imagine gathering numerous soil, water and solid waste samples from many locations and testing them using sensitive AND expensive equipment in the lab. When the data come out, you still have to interpret them to build up a useful case. One method is to obtain a chemical "fingerprint" of the liquid oozing out of the earth to match that of the solid waste in the landfill. Perhaps the solid waste has a very specific pattern of chemicals (this gives you the "fingerprint") not found anywhere else in the surroundings. If you can positively detect the same patternin your liquid, voila! Then you may have a case.

But we are talking about the environment here. Many physical, chemical and biological processes (both human and natural) are occuring at the same time and these can alter your "nice" pattern of chemicals in unpredictable ways.

Or perhaps you can't find any usable "fingerprint". All is not lost. Another method involves injecting a tracer chemical into your landfill and see if it ends up somewhere else in the surroundings. Obviously, this tracer should not already be in the environment and should be easily detected. A good tracer can be radioactive for ease of detection though it may not be so friendly to the ecology. Some applications have used your familiar salt as a tracer so if your streams suddenly turns salty, you know where it comes from. Same thing here - your ecology may not like such an influx of salt much.
Even if you can afford the time and money, at the end of the day, your tonnes of data may still be inconclusive to prove that leachate is indeed escaping from a landfill. I guess this is quite similar to criminal forensics in which your evidence is based on probabilities e.g. 95% confidence level. What is not to say that the heavy metals and toxic organics in your puddle could have come from the metal processing plant a kilometre away?
In response to your observations:
  1. "Orange-ish puddles/mud" are often caused by the presence of iron. Iron from soil (especially in Singapore soils) leaches out to the surface and form precipitates (orange solids similar to rust). This process can be facilitated by iron bacteria which "eat" (the chemical term is "oxidise") the iron for energy. Iron bacteria is easily identified by a orange/brown gelatinous slime.
  2. "Oily rainbow sheen" can indeed be due to oil, especially if there is iridiscence. But it can also be caused by iron/manganese particles from the soil. A simple way to find out is to use a stick to disturb the sheen. If the sheen breaks up into pieces, it is probably iron/manganese. If the sheen swirls around and follows your stick, it is probably oil. Even if it is oil, it can be from natural sources e.g. plants, dead animals.
  3. "Black fluid leaching into some puddles" can also be from nature. Is your fluid thick and viscous like engine oil? Or is it more like tea - black/brown yet clear? Tea coloured water can simply be tannins from decaying vegetation or humic substances (also originates from vegetation) from soil.

In essence, smoking gun evidence or even probable cause is hard to come by without further investigation and chemical testing. But if you ever find mass or sudden kill of plants or animals in the area, that is certainly a cause for concern though leachate may still not be the culprit.
Figure: Iron bacteria in a stream in Chinese Garden (Apr 2011). It can be a big aesthetic problem.

Figure: Iron bacteria in a small tributary at Ngee Ann Stream (Feb 2008). Even the vegetation were coated brown.

Figure: No, this is not sand. More iron bacteria on the canal bed at Ngee Ann Stream (Feb 2008)

Figure: Oil sheen on canal bed at Ngee Ann Stream (Feb 2008). Notice the iridiscence in the sheen.