Microbial contamination of groundwater in Chennai, India

Full text: A survey of groundwater quality in Chennai, Tamilnadu, India showed that some drinking water wells were consistently contaminated with bacteria. The aim of this study was to identify susceptible wells and if possible to provide remedial measures. During 2003 the Chennai city recorded poor rainfall (738 mm as against the normal 1267 mm). The third lowest recorded in the past 100 years, which in turn might have influenced the groundwater table. The study carried out during late 2003 and early 2004 assessed the microbial quality of groundwater collected from bore-wells whose depth ranged between 22 ft and 60 ft. in a densely populated area of Chennai. To assess the microbial load, indicator parameters, viz. heterotrophic plate count, total coliform count, faecal coliform count and faecal streptococci count were studied. Overall, faecal coliform counts were higher than faecal streptococci count. This indicates that the source of contamination may be from human origin. The highest load of faecal coliform load was 1000 organisms/100 ml. Bacterial indicators are distributed throughout North Chennai but their distribution was not uniform. The rainfall during the sampling period was meagre. This study shows that the groundwater quality deteriorated rapidly when contaminated by bacterial populations. Apart from poor rainfall, improper method of sanitation may also boost bacterial contamination. (author)