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Authors
Affiliations
1 Department of Environmental Science, Bangalore University, Bangalore-560 056, Karnataka, IN
Source
Nature Environment and Pollution Technology, Vol 8, No 3 (2009), Pagination: 497-501
Abstract
Tanks in and around urban areas of Bangalore receive considerable amount of sewage, which has caused a severe and persistent microbial pollution. The main objective of this study was to measure level of faecal contamination in Madiwala lake using different techniques of E. coli estimation. Results show that the golden green colonies of coliforms with metallic sheen showed a luxuriant growth at 35°C with M-Endo Agar (M1106) at incubation time of 24-48 hrs. The growth of both E. coli and Enterobacter aerogens using M-Endo Agar plate was also luxuriant at 35°C temperature. But E. aerogens colonies were pink and mucoid while that of E. coli varied from pink to rose-red with metallic sheen. The confirmatory test using Agar M-392 confirmed the presence of Enterococcus fecalis in yellow colour colonies at luxuriant growth of 35°C temperature. The presumptive test results of different volumes of the lake samples after 24 and 48 hours using lauryl tryptose broth indicated significant colour change, gas production, and turbidity. Confirmed results showed gas production in brilliant green using lactose bile broth at 37°C in 48 hrs. The completed result with EMB agar inoculated with positively confirmed test tube incubated at for 24 hrs at 35°C showed greenish metallic sheen colonies while the coliform colonies inoculated on Nutrient Agar slant and a broth tube incubated for 48 hrs at 35°C showed growth as observed on slant with gas production in the broth tube. Moreover, Gram staining results showed Gram negative with sporing rods in the tested samples. The MPN Index of the lake sample was found to be 38/100mL. Water is generally considered safe for drinking if it contains fewer than 4 coliforms/100 mL. It is also considered safe if it contains less than 2 Enterococcus bacteria colonies/100mL of a sample. These observations indicate that environmental status of Madiwala lake with respect to microbial pollution is continuing to deteriorate.
Keywords
Madiwala Lake, Water Quality, Faecal Contamination, E. coli, Enterococcus fecalis, Enterobacter aerogens.
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