Saturday, June 28, 2014

Rainwater harvesting in HDB flats? Check out Treelodge @ Punggol

I had the privilege of given a tour of Treelodge @ Punggol by HDB staff some time back. The tour includes a sneak review of the various green implements on the rooftop (normally locked from the public) of this housing development.

Of particular interest to me is the rainwater harvesting system. Some highlights:
  1. Rainwater is harvested from the rooftop, treated and channelled into storage tanks at the top level.
  2. Grating is installed at inlets on the rooftop to remove large contaminants e.g. leaves, litter
  3. The system is designed to make use of gravity to minimise pumping.
  4. A first flush system is used to remove the first portion of each rainfall event. (As mentioned in my previous posts (1, 2), a first flush device or system is absolutely essential to remove the initial and dirtiest portion of rainwater.)
  5. The treatment of rainwater involves something called DPA system or technology.
    • "proprietary technology which harness on the works of Hydrocavitation, where liquid is subject to forces of fluctuating pressures within the enclaves of its cavitational chamber, is a chemical-free water treatment process.
    • DPA system is effective in controlling pH levels, increasing dissolved oxygen and significantly reducing bacterial and algae growth in the water."
    • Installed by a company called Sif Eco Engineering Asia. Tried to visit its website at but ended up at a page under construction so I don't know anything more about this company. 
  6. Not surprisingly, the treated rainwater is only used for:
    • Washing of staircases, void decks, corridors
    • Irrigation
  7. Obviously, potable use of the treated water is out of the question. Neither is it used for toilet flushing.
  8. No mention of how successful the system is but I don't think there are any problems. Rainwater is one of the cleanest forms of water.
Figure: Garden beds on the rooftop. Nice touch. Cool the top levels?

Figure: Experimental wind turbine. In Singapore, you have to go high for wind turbines to capture the energy of the stronger winds.

Figure: Photovoltaic (PV) panels on the rooftop to provide extra juice to power consumption in the common areas

Figure: Explanatory panel on the rainwater harvesting system. Unfortunately, this panel is on the rooftop so the public normally does not read it. Not sure if there are similar panels in the accessible areas.

Figure: Notice the grating inlet fixed into the floor (rooftop). It is designed to filter off the gross (in size) contaminants in the rainwater. Also, notice the small white pipes jutting out of the garden beds. The plants probably help to clean up the rainwater a bit before channelling it to the inlet.

Figure: Treelodge @ Punggol

Sunday, June 22, 2014

Advice on purchasing water testing kit for JCU Singapore

I found your blog online whilst looking for water testing equipment. I hope you don't mind me contacting you! 

I am a sessional lecturer at JCU Singapore and teach a first year subject called Environmental Processes and Global Change. It is essentially an introductory amalgam of geography and ecology. I take my students on at least two field trips (and a 3rd if we have time and the weather is kind to us!) Last year, for one trip, we went around the corner to Bishan Park to do a number of activities, including water quality testing. The kit I used was borrowed from (removed by blog owner) and was really far too basic for our needs (although none of the students had ever done ANY field work before so it was still fun). I would like to order a kit for the department (we don't have one yet), preferably one that has a number of options and could be used for other subjects (e.g., marine science, aquaculture etc). 

Do you know of a brand / local supplier you could recommend? Ideally it would be robust (come in a lightweight case) and give accurate enough data to compare DO, pH, salinity, temp etc between locations. I have found a kit online from a company based at Ubi Ave (, but would appreciate any recommendations or advice before I go any further!

It would be nice to touch base with you anyway, as it seems we may be teaching similar subjects.

Kind Regards,

Hi M,

Glad to see that you bring your students for field trips. I always believe that our students don't go out of their classroom enough. There are of course logistics and safety to be concerned with but something suitable can usually arranged.

Previously, I minimise mentioning about companies, brands and models as I don't want to be seen to be endorsing them. However, there had been many requests from my readers to recommend vendors and equipment to them, whether for water filtration, water quality monitoring (WQM) or water engineering. I realise that I am doing a disservice to you by withholding such information.

But first my caveat: throughout my blog, any recommendation of companies, brands, models is purely based on my experience and knowledge. Unless stated explicitly, I am in no way affiliated to them and derive no benefits from recommending them.

You may want to read my book "Your first guide to water quality monitoring in Singapore" for a description of the WQM equipment that I have used. It is available online free at PUB's website.

There are actually many distributors of many brands of water testing equipment in Singapore but the following are the few I have worked with and feel comfortable enough to recommend.
  1. Most of the equipment comes from the brand, Aqualytic. Local distributor is Quantum Technologies Global Pte Ltd.
  2. The Hach series of products (including test strips) is also very good as it is a very established supplier in the area of water testing. Local distributor is Fluke South East Asia Pte Ltd.
  3. The YSI brand is also very reputable and their products are usually designed tough for field work. One distributor is Spectra-Teknik.
I am not sure about bksna as I have never used their equipment before or heard any reviews about them. Still, you can go ahead to check out their specs and prices and compare to the others above.

Good luck!

Saturday, June 21, 2014

Water quality of wetlands - Sengkang Floating Wetland

My name is J, and I am an undergraduate studying Environmental Studies in NUS. I will be starting on my honors thesis with my professor Dr. L this coming semester, and it is based on water quality monitoring at constructed wetlands-Sengkang Floatingwetland and Lorong Halus wetland. I have been reading your blog, and it has a lot of wonderful information very useful to me. I am still in the midst of my research before I start fieldwork, and I would like to ask you a few questions.

1. What are the parameters that you have measured in these wetlands before, and is it possible for me to obtain the data of these parameters? Considering the fact that I will be conducting some tests, a comparison with previous records of your data would be very useful.

2. Also, have you done a dissolved carbon analysis of the waters in Singapore/pCO2 analysis?

Thank you very much Sir!


Hi J,

Glad that you like my posts. And I am happy to see that you are doing some field work at Sengkang Floating Wetland and Lorong Halus Wetland. I feel that not enough is being done to monitor the water quality in our water bodies.

1) I have not done any monitoring at Lorong Halus.

As for Sengkang Floating Wetland, I have conducted a workshop for teachers (1, 2) there in collaboration with PUB. No data was officially documented as that was a training workshop rather than a scientific monitoring session. But I have dug up a photo of the white board when the participants presented their results. See if you can make sense of it.

Figure: Results of water quality monitoring workshop at Sengkang Floating Wetland (11 Nov 2011)
2) No, I have not a dissolved carbon/ pCO2 analysis. My choice of parameters in water bodies is determined more by the demands of a healthy ecology. (Naturally, if I am working with drinking water or wastewater, the demands and thus parameters will be different.) In my opinion, dissolved carbon/ pCO2 are indirect parameters when it comes to water ecology as they reflect the interactions of water and geology more.  There are already so many parameters to monitor. No need to complicate matters or use up more resources unnecessarily :-)
Good luck!

Friday, June 20, 2014

More questions on the British Berkefeld (BB) (Doulton/ Berkey) Water Filter

I'm not really knowledgeable about water. I'm wondering if you could give your opinion about some question I have.

1) Do you use this filter at home or another filter? If another kind, why?

2) I'm thinking of getting a small one for myself as I don't think the water I get from the tap (even though I boil it) is healthy. Do you have any thoughts on that? I'm sure using the filter would ensure the water is better right than just drinking boiled tap water in Singapore right?

3) There are so many other kinds of filters or water products, etc. - Kangen that gives alkaline water, Diamond, etc. How do you think the Berkefeld compares to the rest?

Also, if I get the Berkefeld, I heard some people say that I should get the arsenic and flouride filter too. I think that was from people in America getting the Berkey brand (according to you, both are the same right?) Are those additional filters necessary and available from Arkwater?


Hi J,

Sorry for the delay in replying.

You may want to check out my previous posts on water filters/purifiers as I have touched in depth on the answers to some of your questions. In particular, please read the post on "Testing your drinking water - the whys and why nots".

Before I go further, let me reemphasise that throughout my blog, any recommendation of companies, brands, models is purely based on my experience and knowledge. Unless stated explicitly, I am in no way affiliated to them and derive no benefits from recommending them.)

Now, to answer your questions:

1) No, I don't regularly use any sort of filter at home. Most of the filters mentioned in my blog are part of my academic endeavours (aka projects). The exceptions are the small portable ones e.g. Katadyn Mini for my personal use outdoors. (Hey, even if the virgin jungle streams are supposed to be free of pollutants, I very much prefer to at least boil or filter the stream water. Nevertheless I have drunk straight from the stream without ill effects. Not something I recommend but it has been done.)

Oh, back to your question... Despite the shortcomings of the WHO drinking water guidelines and the controversies surrounding chlorination and fluoridation of drinking water, I still believe PUB is doing a good job of ensuring safe drinking water in Singapore. Not taking things at face value, I have done various tests on tap water over the years. Though nowhere as extensively done as PUB (I frankly don't have the resources that it has), the results generally agree with the claims by PUB on compliance to or even surpassing WHO guidelines.

Then why am I talking about the BB filter at all? Because, it is a valuable item to have around during emergencies when the quality of your water supply is suspect. That is, if you have any water coming out of your tap at all. Check out the disasters in Chile, Haiti, Pakistan, New Zealand and I am sure in many other countries too on the status of their water supply after a bad dose of earthquake, storm or flood.

And for those who venture to developing countries to do OCS (overseas community service), a BB filter is invaluable in areas with unknown water quality unless you enjoy bottled water for 2 weeks or more.

2) Again, please read my earlier posts on water filters/purifiers. In short, Singapore tap water is already very clean so a water filter will find itself hard pressed to clean the tap water further. Any removal of contaminants will likely be marginal. Unless you are prepared to go a big step up to the next level of water distillers, reverse osmosis (RO) or air-to-water devices. These machines are generally expensive at the outset and also in terms of the power they suck up. RO involves the replacement of the RO membrane modules which are not exactly cheap, partly because most of them are proprietary for your particular make and model. 

However, having said the above, psychology is a powerful factor to consider. If you feel that a water filter can ensure your good health, do go ahead to install one. Furthermore, many health issues regarding drinking water are controversial. Heck, who knows, some of them may be proven right in the future. E.g. chemical X is indeed bad for your health... you mean you have consuming it all your life... oppps.

Ultimately, what I am saying is if you indeed make a purchase, know why you are doing so. It should not be based on blind fear or unsubstantiated rumours or worse, unscrupulous sales tactics by a water filter supplier.

Think about the "whys" in buying a water filter. Are you worried about a particular chemical(s)? If so, is it at a significant level in your tap water? If it is, can your filter really remove it effectively? Not sure? How about this: before your buy, ask the supplier to let you run a real water sample through the filter and send the input and output samples to a certified lab for testing of that particular chemical? I am not sure if the supplier will agree but it is worth a try.

3) I shall not comment much on alkaline water at this point except to say that I prefer to remove contaminants from water rather than try to add something (alkali) (a contaminant?) into my drinking water. Something which is still controversial in its health claims and that complicates matters unnecessarily.

4) Arsenic is not a problem in Singapore. It is a big and dangerous problem when groundwater (well water) is used e.g. Bangladesh and parts of USA.

Fluoride in water is still a controversial topic. You can find out more about fluorosis in Internet. I believe the fluoride removal element from Arkwater needs to be connected to your pressurised water supply (i.e. tap) to work. It doesn't work well with gravity flow. Something to take note of if you decide to get it.

Good luck!

Figure: BB filter big enough for a family. There are smaller and bigger versions too.

Figure: My Katadyn Mini. Small and handy. Useful for the outdoors. Has a capacity of 7000 litres per filter element. Unfortunately, it can only remove particles and microbes of bacterial size and above. Not so effective against viruses and chemicals.

Figure: Inside a BB filter housing - 3 filter elements (or candles) to allow a reasonable throughput for a family