KARACHI, Aug 20: The water supplied by the Karachi Water and Sewerage Board (KWSB) is faecally polluted and contains high percentage of potential human pathogens, a study recently carried out by a group of scientists at the University of Karachi revealed.
The study was aimed at determining the level of bacterial contamination in water supplied by the KWSB, said Prof Dr Shahana Urooj Kazmi, chairperson of the KU department of microbiology, who supervised the study.
The water samples were collected from Gulshan-i-Iqbal, Nazimabad, Gulistan-i-Jauher, Liaqatabad, Gulshan-i-Hadeed, Federal B. Area and other locations.
She said all water samples were tested for presence of normal faecal organisms, e. coli, as indicator of faecal pollution.
It was stated that the e.coli count of water supplies was the most reliable test for routine quality control and to determine whether the water was bacteriologically safe for drinking.
Dr Shahana said most of the samples examined were found to be faecally polluted and contained high percentage of potential human pathogens.
She said since the KWSB was supplying contaminated water or the water got contaminated by mixing with leaking sewage, the alternatives left are to either boil or filter the cloudy and possibly contaminated water for drinking.
Unfortunately, she remarked, many filters have to be changed regularly, because silt in water tends to block the pores where bacteria, especially pseudomonas, thrive and multiply. Filters using ultraviolet light are also relatively ineffective depending on the degree of suspended particles present. Boiling, then, is logically the safest bet for us.
She said it is an efficient mean of physical disinfection. But boiling for how long is the main question. Boiling for ten minutes, she said, is considered to be adequate for inactivating all faecal pathogens.
Dr Shahana said since proteins were denatured at 60 degrees Centigrade, except for heat-resistant enzymes, a temperature of 80 degrees for 5-10 minutes is required to essentially kill all vegetative forms of bacteria, yeasts and molds, and inactivate nearly all viruses.
Boiling would kill almost all infective agents in a matter of minutes; among viruses that people were till recently worried about and that can be spread
by faecal-oral route was HAV (Hepatitis-A virus), which has now been shown to be destroyed by boiling for five minutes.
Bacterial endospores, however, are among the most heat- resistant forms of life known, requiring longer boiling times, but B anthracis (causative agent of Anthrax) is also susceptible and gets inactivated in 2-15 minutes at 100 degrees.
Dr Shahana emphasized that the city not only faces inadequate water supply, but the intermittent turning on of the pumps, which drags organisms from sewage leaks in the vicinity, adds to the misadventure of drinking a murky, odorous glass of drinking water.
She said every year, with the advent of the monsoon season, Karachiites are forced to drink turbid water with faecal microbial flora. “During the last two months, we have been supplied with water that has the appearance of diluted milk.”
The emergency wards of various public-sector hospitals reported a sharp rise in cases of intestinal problems, with a considerable number of infants in particular, presenting with acute diarrhoea and dehydration. — APP
