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.