Fate of faecal coliform bacteria in a waste water retention reservoir containing Lemna gibba L.

The comparative survival of total and faecal coliform bacteria was studied in a stable waste-water retention reservoir. The surface of the water reservoir was covered with a macrophyte, Lemna gibba L. Sets of dialysis sacs were suspended in an exposed site to the sun light, while other sets of sacs were suspended beneath the thick green film of L. gibba; where sunlight is almost absent. Total coliform bacteria regrow in sun and in sacs unexposed to sun, while faecal coliform cells exposed to sunlight disappeared with a decay rate 0.1768 h−1. Interestingly, faecal coliform in sacs suspended under the L. gibba green film did not decline during the period of the experiment.