Water: avoiding contamination

Published Aug 10, 2012 02:31am

RECENTLY five deaths have been reported in Karachi, after being tested positive for naegleria fowleri.

According to the US Centres of Disease Control and Prevention, naegleria is a microscopic thermotolerant amoeba that can cause severe infection of the brain. The amoeba is commonly found in warm freshwater and soil. Only one species (type) of naegleria infects people: naegleria fowleri.

It infects people by entering the body through the nose. This occurs when people go for swimming in warm freshwater, or in swimming pools in which water is inadequately chlorinated.

A person cannot be infected with naegleria fowleri by drinking contaminated water. Naegleria fowleri is not found in salt water, like the ocean.

The Naegleria fowleri ameba causes primary amebic meningoencephalitis (PAM) when it travels up the nose to the brain and destroys the brain tissue. PAM is a fatal infection. It cannot be spread from one person to another.

In case of Karachi, the most probable cause could be the ablution, performed before saying prayers. While performing ablution, Muslims are required to put water inside the nose, roughly halfway up. This would then suggest that the water supplied by the KWSB is contaminated.

To prevent the infection, the water should be distilled, sterilised, boiled, or filtered, using a filter with an absolute pore size of one micron or smaller. It will not be possible for mosques to provide such type of water for ablution, nor can ablution be performed without putting water in the nose. The responsibility, therefore, falls on the KWSB to supply properly treated water.

According to an ADB (2004) publication, ‘Water in Asian Countries,’ KWSB provides low consumer satisfaction. The loss of water due to leakages is 30 per cent. High loss of water due to leakages suggests that the water distribution system in Karachi is in bad shape. The resulting recontamination of drinking water may be causing the current episodes of infection. The KWSB should note that if the turbidity in water is greater than five ntu, the disinfection process will not work, even if there is free residual chlorine.

This is because microorganisms enclave themselves within the turbid particles, where disinfectant cannot reach them. The residual chlorine levels in the water distribution system at the farthest end of the supply network should be 0.5 milligrams per liter. The KWSB must conduct water quality tests regularly.

The acidity (pH) of the water has a significant effect on the efficiency of chlorine as a disinfectant. The pH level should be between 7.2 and 6.8. Water temperatures also impact disinfection. In general, the effectiveness of disinfection increases as temperature increase.

The KWSB should also note that disinfection byproducts are formed when disinfectants used in water treatment plants react with natural organic matter (i.e., decaying vegetation) present in the source water. This is common in case of the Indus river.

Different disinfectants produce different types or amounts of disinfection byproducts. One such byproduct is trihalomethanes (THMs). THMs (chloroform, bromoform) are cancer-causing. This requires source or catchment protection. Source protection (protection of raw water sources) provide safety in, and risk-free water supply systems.

F. H. MUGHAL Karachi


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