Theories
In order to understand the theories, one must first understand what a carcinogen is and how carcinogens are formed.
Almost all water authorities worldwide agree that the main carcinogen found in water supplies that boost the world’s cancer rate is the famous Trihalomethane (THM).
You can log into any international health authorities’ website to look for information regarding THM or read the attached page (Attachment #1) from University Kebangsaan Malaysia’s website (www.ikm.org.my/mjc5_056_066_MdPauziAbdullah.pdf).
The report states that “chlorine posed potential health risks due to formation of carcinogenic or mutagenic halo-organic compounds as disinfection by-products such as THM.”
You may be quite confused by some of the technical words; however the following explanation may help clear some of your doubts.
THM are a group of four organic chemicals - bromoform, chloroform, dichloromethane and dibromochloromethane – that forms when chlorine, used as a disinfectant, reacts with organic matter in water.
To put it simply: Free Chlorine + Organic Matter = THM
(e.g. Decaying leaves & animal carcass)
Where:
- Free Chlorine is a poisonous gas injected into the water at the municipal treatment plant to kill bacterial.
- Organic Matter is trapped sediments (organic based), given sufficient time (more than a week) to decay and dissolved in water.
In another words, THM will not be formed if any one of the two elements is absent. On the other hand, a high Free Chlorine and Organic Matter presence in the water will result in a high level of THM.
Since there are only two elements, it is not difficult to study each element in detail.
Free Chlorine
The World Health Organisation recommends that in order to prevent secondary infection, certain amount of residue chlorine should remain in the pipe-line until it reaches consumers.
For reference, attached herewith is a copy of ‘Water Quality Standards and Frequency of Monitoring’ (Attachment #2). It is recognised and is supposed to be strictly followed by the Water Works Department of Malaysia.
It recommends that the standard readings should not be less than 0.2mg/l and 1.0mg/l for Free Chlorine and Combined Residue Chlorine respectively. One of the reasons for the much higher recommended content of Combined Chlorine as compared to Free Chlorine, is that Combined Chlorine creates fewer THM.
Now, let’s look at the actual situation. Does our tap water comply with the recommendation? The answer is a definite NO.
This can be proven instantly by simply using a field water test kit on any tap water at anytime. Popular brands of field water test kits are LOVIBOND or PALINTEST. Their DPD 1 test reagent tablet will be able to detect the presence of Free Chlorine while the DPD 3 test reagent tablet will detect the presence of Combined Chlorine. Many water authorities worldwide use similar test reagents to test for the presence of Chlorine.
I discovered this ridiculous phenomenon way back in 1993 when I tendered for a water-treatment project for Kapar Power Station in Selangor. For the purpose of system design and calculation, the consultant had to furnish the bidders with a comprehensive analysis of the raw water supply, which in this case, was the city’s tap water.
As stated in the tender document, (Attachment #3 - Water Analysis Report), Combined Chlorine was not present, while Free Chlorine was measured at 2.0 mg/l, 10 times more than the recommended level.
Sarcastically, the consultants had to cover-up our "weird demand" by preventing the result from being exposed to the other international professionals (the tender was open to international bidders), chose to put the words “in an epidemic”, next to the figures for Free Chlorine. By doing so, the consultants had assumed that we were experiencing an epidemic outbreak throughout the year. If this was true, our government would have declared an emergency due to the epidemic. Or was this situation so common that it became a non-issue?
Organic Matter
The main risk associated with the high level of Free Chlorine is if it reacts with Organic Matter to form THM.
Due to excessive rainfall, raw water in Malaysia contains little organic matter. As long as organic matter is not produced in the filtration stage, Free Chlorine, by itself, cannot produce THM.
The Municipal Water Works Department has taken various steps to ensure their sand filters remain clean at all times. By doing so, the decaying process of trapped organic sediments could not take place inside the filter thus restricting the generation of organic matter.
The operators must frequently (preferably daily) backwash the filter with specially sized high flow-rate water pumps. The backwash efficiency is further enhanced by air scouring.
Even with the presence of high Free Chlorine, the level of THM generated could still be minimized. Please refer to the report by UKM (Attachment #1).
Without the above, it is very difficult for normal home water filters to avoid generating organic matters. The end result will be horrible, when accompanied by the known high levels of Free Chlorine.
