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 ...

Saturday, October 21, 2017

Corporate Social Responsibility (CSR) in Batam: Solving issues in water shortage

Due to ongoing business discussion, I have left out names of the parties involved and certain details that can impact business decisions.

I got a rare chance to tag along with this water company (referred to as the company) to Batam to evaluate the water issues facing a holiday resort and a couple of nearby villages. This is not your typical urban resort as it is located faraway from the island's centre.

  1. The resort was concerned about the (in)adequacies of its current water storage and treatment set-up. Though nothing adverse has happened (yet), it decided to pre-empt any problems by engaging the company to check out its set-up anyway.
  2. 2 small villages on different islands. 1 with about 20+ residents, the other with about 80+ residents. No water issues for most part of the year except when the drought comes in. This drought can last for 3-4 months, enough to run the springs and wells dry.
  3. One pre-survey suggestion thrown up was the use of rainwater harvesting. We also evaluated the feasibility of implementing RWH there.
I will not present the proposed solutions here as they are still undergoing business discussion. Instead, I will highlight some of the interesting observations during our survey.

A couple of personal observations: Perhaps due to the nature of the company's business, grey water recycling/use and sanitation were not considered as part of the solution, though in my opinion, these can be relevant factors to close the water usage loop.

Figure: Partially covered spring serving the resort's water needs. I just thought that it ought to be better covered to prevent animals from accessing it.

Figure: Water from the spring is pumped uphill to be stored in these tanks. Notice 1 line allows water to enter the tanks, the other line to transfer the water to the resort downhill by gravity.

Figure: Closer view of the water tanks. The larger ones have a capacity of about 1000L each.

Figure: Typical well serving the villages. There are several of these. Typically not covered. Clarity ranges from clear to slightly turbid

Figure: Washing and bathing using the more turbid water. Clear water is reserved for drinking.

Figure: the watering hole providing turbid water for non-potable purposes

Figure: Perhaps the villages are not as poor as what we initially thought. Common sight of solar panels and TV antennae

Figure: Nothing to do with water issues, just too nice to leave out. The sea at dawn

Figure: If there is one thing I learned, it is the importance of geography to water issues. Climate, topography, vegetation, geology affect the quantity and quality of water. View from the highest point of 1 of the islands.