Abstract:
Waterborne diseases are now known to be caused by several microorganisms;
mainly by bacteria and parasitic protozoa. In recent years, several outbreaks of
Crytosporidium spp. waterborne transmission have been reported from several parts of
the world. In Thailand even though the drinking water, supplied by 4 water treatment
plants in Bangkok, is known to be clean and safe to drink after being passed through
the water distribution system, enteric bacteria and parasitic protozoa e.g.
Cryptosporidium spp. have never been surveyed in the drinking water collected from
the water supply pipeline at primary schools in area of Bangkok. This study was
designed to investigate the quality of drinking water in terms of the waterborne
microbe and the microbiological contaminations. In addition, the physical and
chemical qualities were also determined. Drinking water collected from 50 districts in
Bangkok, comprising 54 schools was investigated.
Using centrifugation and acid-fast staining method, no Cryptosporidium
oocysts were found in any of the raw water or tap water samples but they were
observed in 7.4% (4/54) of the drinking water from the 54 schools with a mean of 0.74
oocyst per litre. Sources of oocyst contamination could not be identified in this study.
Thus, contamination of oocyst into the drinking water might have occurred after water
treatment process.
Total coliforms, Escherichia coli, Salmonella spp., Clostridium perfringens,
and Yersinia enterocolitica were found in each of the 4 raw water samples but not in
drinking water. No microbiological contaminations were found in tap water.
Cadmium, cyanide, and phenols were not detected in the raw, tap, and drinking water
samples from any of the 4 water treatment plants. The highest lead (3.50 μg/L) and
zinc (0.244 mg/L) contents were found in drinking water samples from Mahasawat
and Samsen respectively, however, the values were lower than the maximum
acceptable level for drinking water standards.