Chemical and bacteriological monitoring of drinking water from an urbanised water catchment drainage basin

The Linggi river drainage basin in Negeri Sembilan, Malaysia supplies water to the whole of Port Dickson district and meets 50% of the Seremban district needs. The Linggi River, the main tributary, passes through the highly urbanised and densely populated Seremban district while the water treatment plant is located 16 km downstream. In 1979 the USEPA declared the river unsuitable as a source of raw water whereas the WHO classified it as being heavily polluted requiring more extensive and effective treatment. In order to meet the WHO drinking water standards, an ozonation system was installed in the conventional water treatment plant. The objective of ozonation is for the control and removal of organic micropollutants and other deleterious matters. This study investigated the concentrations and distribution of organic micropollutants, heavy metals, and bacteriological counts in water samples collected from within the catchment and the treated water. The effectiveness of the ozonation system was also studied. The total level of phenolic water pollutants in the catchment was generally found to be very much higher than the maximum recommended level of 2.0 mu gl(-1). The extensive treatment process carried out at the plant was very effective in reducing the levels of total phenols in the treated water to less than 1.0 mu gl(-1) However the process was not efficient enough to reduce the levels of some heavy metals as required by the standards, for examples Cd and Pb were still three times higher than the standards of 5 mu gl(-1) and 0.05 mgl(-1) respectively. For bacteriological study, coliform group of bacteria, Salmonelia, faecal streptococci and injured coliform were monitored in the raw and treated water. The raw water contained coliforms about 1000 times higher than the required standard for raw water, but after the secondary treatment by ozonation coliform bacteria were absent, however a small number of Salmonella was still present occasionally. The study also showed that restructuring of the district and relocating of some commercial activities along the river banks to other areas carried out over the last five years has improved the general quality of the river water.