Friday, December 14, 2018

Use of Reverse Osmosis (RO) Filters in Developing Countries?

Dear Chen Ko

May I know what is your opinion on filters using the RO process? Will the result be water that is too “pure”, extracting both harmful components but removing beneficial minerals as well?

Specifically, I just received a 2nd hand filter, the Elken Bio Pure Narisia S250 which uses RO - however, they are distributed by a MLM company, so am somewhat skeptical of bringing this to use in developing countries (e.g. Vietnam, Thailand).

Locals have told me the water infrastructure has problems in their piping (metals) and water sources contaminated (industrial pollution). One would not drink tap water, unless boiled. Even then, it has its risks after boiling. Was wondering if you could share some light on such a filter's practicality there.

Thank you, and wishing you a good week ahead.

Warmest regards


Hi Thomas,

You did not mention whether you are bringing the Elken unit to Thailand, Vietnam for short term or permanently. Or are you going to be carrying it around with you from SG to other countries and back?

A few thoughts…

1.       To me, the logistics of packing such a unit to various countries do not sound appealing, especially on a short term basis. Hooking up the unit to the piping and making sure there is electricity (you have consistent electricity there, don’t you?) can be a hassle.

Getting replacement parts (e.g. filter cartridges) in your foreign country may also present a challenge, especially if they do not last long.

2.       You may want to read my article “3 Critical Questions to Choosing Your Water Filter” for a better understanding of selecting the right water filter.

3.       In short, there are 3 major considerations.

a.       Based on your water source, what contaminants do you expect to find in your raw water? You cited metals and industrial pollution. You may want to find out more (possibly from the local authorities and reports) and be more specific.

b.      Are the contaminants in the raw water of concern? Are their concentrations in water of concern? You may refer to the WHO drinking water guidelines for these answers.

c.       And most importantly, can your chosen water filter remove those contaminants of concern or at least reduce their concentrations to safe limits? I have checked up the Elken website and could not find your particular model. And for the other models, I can hardly find any documentation to their contaminant removal efficacy.

You may want to contact the company directly on whether it has any official documentation, preferably scientifically tested by an accredited laboratory on the performance of your water filter. The documentation should state clearly that the water filter can handle your contaminants of concern.

Of course, the gold standard is for the filter to be certified under NSF/ANSI 58 which pertains to RO treatment units. I don’t seem to find such certification mentioned on the Elken’s website so the chances of certification should be low.

To be honest, a well designed and built RO unit can remove (or at least reduce) a lot of water contaminants. The question is: is yours well designed and built? Being sold through an MLM structure, I am sceptical of the amount of development and testing that goes into your water filter since most of its costs go towards paying the hierarchy of marketers.

4.       As for your first concern on the purity of RO water: if I am going to use the filter on foreign water of questionable quality, I will be a lot more worried about the contaminants in the water and whether my filter can effectively remove/reduce them.

But let’s say you only use your RO unit in good, old SG, will the purity of the product be harmful? It seems that the main issue of very pure water (provided your unit is well designed and built) is its ability to leach stuff out of its containers or piping. Therefore, my suggestion is as much as possible, store such pure water in glass containers for minimum leaching. If you find glass too heavy or fragile, then stainless steel is next best. Obviously, use only food grade materials.

Figure: For serious filtration of raw water of questionable quality, I will bring my Doulton along. My version is a bit bulky but it can serve a family easily. It also comes in a smaller size. Similar and perhaps even better is Big Berkey. Both are well recognised and documented water filters that do not need electricity to work.

Friday, November 30, 2018

Implications of water quality on coffee

Thanks to Jeremy for reminding me about the importance of water quality on coffee. Indeed, I have mentioned before that water quality affects beverage quality - think coffee, tea, coca cola etc. - posts 1, 2. People like Starbucks and Coffee Bean not just for their ambience and branding. These coffee joints sell good coffee using quality coffee powder/beans plus that very critical yet often unseen ingredient - water of consistently good quality.

Figure: My favourite kind of beverage - tea with milk aka teh in SG parlance. How often do we consider that water quality can affect the taste of this ubiquitous beverage?

Unlike a coca cola factory or even a commercial café, most of us mortals would not bother to purchase the filtration equipment necessary to produce water of consistently good quality. The next question is: what do you mean by good quality water? As I always maintain, water quality must be tied to the purpose of the water. Tap water of course has relatively stringent requirements (at least in developed countries). In SG, we generally follow WHO drinking water guidelines.

But what about coffee? How does one define water quality guidelines for coffee (or tea or coca cola for that matter)? Obviously, the guidelines (if there are any) must be above and beyond those of drinking water.

For example,
Figure: SCAA/SCAE (Specialty Coffee Association of America/ SCA of Europe) guidelines in water quality for coffee making
A few points to keep in mind:
  1. Coffee quality in terms of taste and smell are obviously subjective. Therefore, such subjectivity extends to the water quality requirements as well.
  2. How comprehensive are the above guidelines? I see only 8 parameters. WHO has about 200 parameters in its drinking water guidelines. How would other WQ parameters (e.g. fluoride, metals) affect the quality of coffee?
  3. For us in SG, how well does our tap water compare against the above values? Let's take a look.

  1. Odour - unobjectionable. No issues here.
  2. Colour < 5 Hazen units. Should not be an issue here.
  3. Total chlorine 1.70-2.80mg/L. Hmmm... possible issue since our tap water MUST HAVE a certain amount of residual chlorine.
  4. TDS (total dissolved solids) 74-269mg/L. More or less falls within the SCAA guidelines.
  5. Total hardness 27-221mg/L as CaCO3. This of course includes calcium and other forms of hardness so we can't tell for sure. But if your tap water happens to be near the higher end of the range, you may have a problem as compared to the SCAA guidelines for calcium hardness.
  6. Total alkalinity 6-40mg/L as CaCO3. If your tap water is near the lower end, you may have too little alkalinity to neutralise the acidity in your coffee. But then again, it depends on how acidic you like your coffee.
  7. pH 7.8-8.3. Compared to the SCAA guidelines, is our tap water too alkaline for coffee?
  8. No value given in the report as it is not a priority pollutant for drinking water.
Finally, our tap water quality cuts across a range of values though it should still stay within specs. With so many different sources of water (various water treatment plants and reservoirs with and without desalted water mixed in), it is no surprise that the actual water quality parameters can change from time to time and area to area.

Therefore, if you are really serious about producing consistently good quality coffee, you need good quality filtration equipment to treat your tap water (in addition to other good quality ingredients of course). I leave the cost/benefit analysis up to you to evaluate.

Figure: Everpure water filter kit for coffee brewers. Only for illustration purposes. Not an endorsement or recommendation.

Wednesday, November 28, 2018

The one device you can't do without for serious water sampling

I am of course talking about the depth sampler. If you want to collect a water sample at a given depth, you simply need this standard piece of equipment. Depending on the length of your rope, it can easily go down to 100 feet and beyond.

You can suspend this guy from a surface craft (e.g. kayak, motor boat) or a bridge overlooking the water body of interest. Once you have reached the desired depth as indicated on the marking on the rope, you release the messenger (a metal weight) which rushes down along the rope towards the sampling bottle. Upon hitting the bottle's "trigger", the 2 ends snap shut like a fish trap to enclose your water sample within the bottle.

Purchase Considerations

  1. Alpha (aka van Dorn) vs. beta (Kemmerer). Alpha samplers are not recommended for chemical analysis (trace metals and organics) of the water sample due to possible cross contamination (mercury, phosphorus) from the materials in its construction (seals & closure tube). For chemical analysis, one is advised to use a beta sampler.
  2. PVC vs. acrylic. Whether alpha or beta, the bottle body can be either made of PVC or acrylic. PVC is opaque but durable while acrylic is clear and less durable. If you need to see the contents within the sampling bottle, by all means, go for acrylic.
  3. Horizontal vs. vertical. A horizonal sampler means the sampling bottle descends into the water parallel to the bed. Water enters from both sides of the bottle. This is useful for sampling at the thermocline, other stratification levels or just above the bottom sediment. A vertical sampler on the other hand descends with its body perpendicular to the bed. Water flow is not restricted during descent, making it desirable for collecting plankton and suspended sediments.
Figure: Lowering the depth sampler into the water body of interest. In this case, we were using the alpha, horizontal, acrylic version.

Figure: After retrieving the depth sampler, the water sample was drained into a suitable container.

Saturday, June 16, 2018

Water quality workshop for water filtration company

The regular followers of my blog should realise that most of my workshops are geared towards schools, whether for teachers of students. I have recently conducted one in collaboration with Singapore Red Cross and Lifelong Learning Council though.

But this time round, I organise a water quality workshop for a water filtration system company. Interestingly, the attendees were staff from sales & marketing, admin, installation and management. Quite a mix of job functions and technical background! Challenging for a trainer but nothing I have not seen before.

Regardless, the rules of pedagogy still apply. A trainer or facilitator should always present materials of use and interest to the audience. In a chemistry class, chemical equations of reactions in water are ubiquitous but to a sales staff (and his customer), the same equations become Greek and frankly of little use.

And whether in a chemistry class, public workshop or private workshop for a client company, it always bring satisfaction to a trainer when he sees his learners motivated to know more and keen to try out the newly acquired skills. In that sense, trainers (and learners) are perhaps not that different despite the differences in subject matter, background and current levels of knowledge and skills.

Figure: A practical session in water quality testing within the company's premises. No, those participants looking outside the window were not admiring the scenery. They were using the colour comparator (not visible) which needs a good souce of lighting e.g. daylight.

Wednesday, June 13, 2018

Worried about lead? Here's a simple test

Lead in tap water was mentioned in some of my earlier posts - 1, 2. Essentially, SG tap water is relatively safe when it comes to lead. "Unless you happen to live in a really old building which still retains its leaded pipes over the decades... and unless somehow your building falls under the radar of the extensive sampling and monitoring programme... then maybe you should be worried."

Nevertheless, I had a concerned reader contacting me about his worry of lead in tap water because he bought a water faucet over the net from Taobao. Apparently, he read (only after buying the faucet) about lead being used in fabrication of the faucet. With online shopping becoming more common now, who even knows much about the product one bought? Where are the parts from? Are they certified safe? Are the accreditation standards different from SG?

But I hear you say that it is SO convenient to buy online. Indeed it is. I too buy lots of stuff online...

Anyway, back to lead...

In another post, I recommended this product to test for lead in water painlessly.
PurTest DIY Lead Water Testing Kit. USD16.95
I chanced upon another similar product but of a different supplier on Amazon and got 2 tests for SGD33, inclusive of delivery.

Figure: Test kit for lead from USA. About as foolproof as a test kit can be.
Figure: The testing materials are all packed in a foil package. Open it only when you are ready to test your water.

Figure: A workshop participant residing in the Havelock area was concerned about lead in her tap water as her building was really old, say 40 years or older. An aliquot of her tap water was placed in the plastic container (part of the test kit) before dipping the test strip inside and waiting for 10min.
Figure: Just like a pregnancy test kit! The pattern of the 2 lines - 1 faint, 1 dark, indicate a negative result. As usual, such a test only tells you YES or NO or in this case, whether the lead level has exceeded the safety level. Do keep in mind that this test kit is designed for USA with a safety level of 15ppb (parts per billion) whereas SG follows WHO standards which stipulate a safety level of 10ppb. Nevertheless, I am not going to get a stressed up over a difference of 5ppb. If the lead level is safe enough for USA, it is good enough for me. Still, doing the test 1 or 2 more times and getting a negative will improve my confidence in the water's safety.

Saturday, June 09, 2018

No good place for field work? Finally settled on a new location...

I recently conducted water quality monitoring (WQM) workshop for teachers in a secondary school. Naturally, field work is part of the workshop's curriculum. However, I experienced a knotty issue in finding a suitable location in good old SG.

Here are some of the potential sites and why they were not selected.

Figure: Alexandra Canal - much of this upstream portion was fenced up and under construction
Figure: Alexandra Canal further downstream. Highly inaccessible with a a few metres down from ground level. No way I am climbing down there.

Heard about what a great place Berlayar Creek was. Finally took some time to check its suitability for field work.
Figure: Berlayar Creek is a nice mangrove stream leading to the sea. But it is not accessible without going through some serious mud and probably getting stuck. It sounds fun but may not be so appropriate for a group new to WQM and not used to bashing through the wild. In addition, I am not in favour of disturbing the ecology there by getting a group of humans fumbling through the place.
West Coast Park is another nice place that I have been visiting for years, either for WQM or biodiversity survey. Accessible, safe yet natural enough. What's not to like about it?

Figure: Photo of West Coast Park taken a few years back. Guess what? This nice brackish water body is now fenced off for renovation! I don't have a photo of it now though.
Ngee Ann Stream - one of my favourite locations of all time! Regrettably, I haven't been there for years and the last time I went, there were construction and development in one of the last bastions of nature in SG.

Regrettably again, I did not take any photos but unbelievably, the first part of Ngee Ann Stream (just opposite Ngee Ann Polytechnic) was hopelessly overgrown with vegetation! Without some heavy bashing or getting one wet in the stream itself, it was pretty impassable. Another dead end to finding a place for field work!


a place further than normally I would go with a big group....

Kallang River @ Bishan-Ang Mo Kio Park

The river itself is mostly accessible. Toilets and shelters nearby. No need for bashing through. Some mud is unavoidable but not a problem. (Hey, this is field work, remember?)

Amazingly, there are even designated water sampling points!!! Stone paths leading down to the water edge clear of vegetation. Sounds too good to be true. (Read to the end of this post for an unforseen problem - something no recce would have uncovered.)

Figure: Bishan-AMK Park. This spot is not a designated WQM station but it is easy enough to access by the bank. Alternatively, a depth sampler can be released on the bridge to sample water right in the middle of the river.

Figure: Depth sampler. Quite bulky to carry around in its casing but immensely useful for sampling water from a bridge, jetty or in a boat. The yellow reel holds a rope which is marked along its length to measure the depth the sampling cylinder is submerged.
Figure: 1 of the designated sampling spot in Bishan-AMK Park. Paved stones leading down to the water edge.
Figure: WQM is not just for students. Teacher have to get their hands wet and dirty too. Testing the water sample for nutrients, hardness and other WQ parameters. The shade from this shelter was a bonus.
If you have been reading this far, you deserve to know a problem we encountered when we did the actual field work. (I assume you did not jump straight to the end here just to find out.) 

While we were thick in the middle of WQM by the water's edge, a security staff (Gosh, we have Cisco security in parks now!) came up to chase us off because Lower Peirce Reservoir was upstream of us and it was going to open its dam to release water into Kallang River. For our own safety, we have to climb up the slope beyond the safety markers which were some distance away from the water.

Too bad but safety always come first. We did manage to collect some water samples for further testing under the shade of shelters so it was not a total loss for us.

Sunday, May 27, 2018

Workshop Review: Applying Water Quality and Filtration (supported by LearnSG Seed Fund & Singapore Red Cross)

Applying Water Quality and filtration!

Groups and individuals had a great time on 13 and 20 May 2018 at Red Cross House, learning about the water quality parameters critical to drinking water, how to test if the water is safe and some methods to produce safe drinking water.

The workshop was not merely a theoretical classroom lesson as participants got to interact with the facilitator and other participants, discussing about their uncertainties and fears regarding safe drinking water. The workshop ended with a hands-on session in which participants had the opportunity to dirty their hands (gloves actually) testing several critical water quality parameters in water samples.

Figure: Hands-on session with apparatus and materials laid out on the benches

Figure: When using a colour comparator, make sure you hold it at a light source (ideally the sky) for a good reading
Figure: Hands-on session with instruments and chemical reagents
Figure: Nitrate test - User was holding a test strip and comparing its colour. In the background was another test kit requiring the addition of chemical reagents.
Figure: Using a colour comparator to test for ammonia. Holding it to the sky gives a good reading of the ammonia level in the water sample
Figure: Thanks to the support Singapore Red Cross, we had this comfortable and conducive environment for our workshop.

A project supported by the LearnSG Seed Fund:

Every Day, A Learning Day

Also supported by
Singapore Red Cross

Wednesday, April 04, 2018

Workshop: Applying Water Quality and Filtration (supported by Lifelong Learning Council & Singapore Red Cross)

Figure: SETA water filtration unit for use in humanitarian assitance/ disaster relief
Date: 13 May 2018 (Sun) / 20 May 2018 (Sun)
[The 2 sessions are similar so you only need to sign up for one unless you feel like you need a revision.]
Time: 1 - 5p.m.
Venue: Red Cross House, 15 Penang Lane
No. of places for each session: 40 pax
Workshop Description
Water quality is a constant challenge for disaster relief and developmental work in developing countries. You may find sufficient water sources but how do you know whether the water is drinkable? When the lives and welfare of your beneficiaries are dependent on your judgement, it is imperative you make the right decision.
Often, the staff or volunteer responsible for such work is in need of useful and concise information on water quality and filtration to act effectively in the field.
At the end of this workshop, the learner should be able to:
  1. Identify critical water quality parameters to consider in the provision of drinking water
  2. Decide on the water contaminants of significance
  3. Apply the correct type of water filtration (if any) in the provision of drinking water
This workshop emphasises hands-on work by the learners in literature search and water quality testing.

Figure: Chemical testing of water quality

A project supported by the LearnSG Seed Fund:
Every Day, A Learning Day

Also supported by
Singapore Red Cross

Wednesday, March 28, 2018

What good is testing for ORP (oxidation reduction potential)?

Personally, I hardly have a need to test for ORP (oxidation reduction potential). But recently, a supplier mentioned this water quality paramter in our discussion so I thought of writing a bit about it.

It is supposed to measure the redox (reduction-oxidation) state of a water sample. Usually in units of mV, it indicates whether the water is more likely to support oxidation (positive values of ORP) or reduction (negative values of ORP).

For those unfamiliar with chemistry, a very simple (perhaps overly so) explanation: oxidation is the process of chemical compounds reacting with oxygen (think combustion) while reduction happens when chemical compounds lose oxygen to become something else. (Yes, I know this explanation is woefully inadequate but it will have to do for this post. If anyone is inclined to find out more, please feel free to search for through the numerous chemistry websites.)

An alternative perspective through a biological lens:
  1. positive potential means the water is in an aerobic state
  2. negative potential indicates an anaerobic state
This can obviously apply to natural waters and wastewater treatment. In wastewater treatment, ORP can be easily and continuously monitored for feedback and control. But in the case of natural waters, I prefer to simply test for dissolved oxygen (DO) level if I am interested in how aerobic or anaerobic it is. I like DO being a direct measure of an important chemical species (i.e. oxygen) which directly affects aquatic organisms and biochemical processes.

Technically, an ORP probe is a circuit containing a reference electrode (immersed in a reference electrolyte) and an indicating electrode (immersed in the water sample). A salt bridge links the reference electrolyte and the water sample, allowing flow of ions but not mixing. The other ends of the 2 electrodes are linked to a voltmeter which shows the potential difference between the 2 electrodes - this is the ORP reading. Relatively simple and cheap, it can provide continuous monitoring in process control.

  1. Unlike DO or pH, ORP does not measure any specific chemical species since it reflects the various reactions occuring on the indicating electrode to produce a "mixed potential". This gives rise to a "black box" effect - you have an output but you have no idea what processes are involved.
  2. The "black box" effect becomes an impediment to interpreting ORP values across different water systems. Actually, they probably make no sense beyond a very broad qualitative kind of conclusion. The ideal use of ORP is to make comparisons within the same system in which it can indicate a disturbance in the process.
  3. Being an electrode system, the ORP can suffer from polarisation and poisoning of the indicator electrode surface, further affecting the accuracy of the reading.
Uses of ORP
  1. Chemical disinfection seems to have found a use for ORP as it can give an idea of the disinfectant strength. Chemistry tech talk: most chemical disinfectants (ozone, chlorine, chloramine etc.) are oxidising agents (chemicals that promote oxidation) so the greater the disinfectant concentration, the more positive the ORP value. Nevetheless, it is a good idea to correlate the ORP to other tests that measure the actual chemical species e.g. ozone.
  2. With the craze in alkaline water, hydrogen water etc. in recent years, it seems customary to measure the ORP to showcase the water's "anti-oxidant" properties. Of course, in this case, the more negative value, the stronger its anti-oxidant power. The health benefits are controversial and you can read a bit more in a previous post.
Figure: My ORP meter. Simple to measure but hardly used

Wednesday, February 07, 2018

If you only want to test one drinking water parameter, this is the one... and how to do it

If you have been reading my blog, you will no doubt find that I have touched upon quite a number of water quality parameters e.g. COD (chemical oxygen demand), pH, electrical conductivity. Yet, when it comes to drinking water, the number one parameter to check is:

Bacterial count

And not just any bacteria, the favourite in the water industry seems to be E. coli though Enterococcus seems to be a strong contender. Essentially, the idea is to find an indicator microbe to "indicate" recent faecal pollution which implies possible presence of human pathogens. In addition, this microbe has to be:
  • Always present in faeces of humans 
  • Present in high numbers
  • Easy to detect by simple and inexpensive methods
  • Unable to multiply after they have left the body and entered the water supply
  • Not a pathogen itself
Obviously, no microbe can satisfy all the above criteria perfectly but E. coli (and Enterococcus) comes as close as you can get.

How to measure it?

In 1 of my previous posts - How do I test my own tap water: a DIY guide (part 2) , I recommended this product for E. coli.
Industrial Test Systems 487197 WaterWorks EZ Cult Bacteria Test. USD9.77
Thanks to Victor who provided 2 test bottles, I finally have a chance to test it out. Personally, I still find this product rather pricey, especially when you factored in the shipping costs. But as mentioned in my previous post, this product is as idiot-proof as you can get.

Anyway, with Victor's help, we set up 1 bottle to be the sample with live faecal pollution and the 2nd bottle to be the blank with deionised water.

I also took the chance to try out Aquagenx CBT (compartment bag test) specifically to quantify E. coli in MPN (most probable number). The setup is similar to the above - 1 live sample and 1 blank.

Important: WaterWorks EZ Test is qualitative - either YES or NO for the presence of coliform (and E. coli under UV light) while Aquagenx CBT is a semi-quantitative test that provides a numeral in MPN for E. coli count.

Though Aquagenx CBT allows for "incubation" at ambient temperature provided it does not fluctuate too much, we nevertheless incubate all tests in a mini-incubator that I dug out. (Personally, I find the requirement for incubation at a steady temperature e.g. 35C to be the most formidable technical challenge for anyone engaging in DIY bacterail testing, more so if under field conditions.)


Figure: Before incubation. Left - live sample, right - blank.

Figure: Preparing for incubationl Notice the leftmost bottle for live sample has already turned green, indicating the presence of coliform. And this is only at most half an hour after inoculation. The Aquagenx CBT (rightmost) is the live sample.

Figure: After 1 day of incubation. The CBT blank (white clip) still remains brownish while the CBT sample (red clip) has fully turned green, indicating E. coli and also translating to > 1000 MPN/100mL or very high risk. Unfortunately, my UV light was not working so I could not confirm the presence of E. coli in the EZ Test sample as under UV light, E. coli will display fluorescence.

Ok, that's it, folks! Hope the discussion above is helpful to those doing testing of drinking water, especially in the field. Oh, the price of Aquagenx CBT: including shipping cost --> ~USD150 for 10 tests.

Thursday, January 25, 2018

Latest from WSG - Professional conversion programme (PCP) for Utilities Engineer

Hi folks,

I have been busy with setting up this latest Professional Conversion Programme PCP for Utilities Engineer/ Assistant Engineer for WSG -

Targeted at mid-career switches into the water industry, it is open to applicants who have just secured a job with companies in or supporting the water industry.

Foundational training for common processes in the water industry will be provided by Singapore Polytechnic (SP) to all successful applicants.


Added on 31/1/18:

Here's the link to the same PCP on SP's website:

Gooey cactus guts remove arsenic and bacteria from ...