Bioassay procedures for predicting coliform bacterial growth in drinking water

The degradation of water quality, due to the growth of coliform organisms, is an area of concern for many water utilities. Currently the nutrient status of drinking water is difficult to measure and can only be defined in relative terms. To date, the procedures developed for determining the amount of biodegradable material present in potable water have utilized heterotrophic bacteria as bioassay seed organisms.; The purpose of this research was the development of a procedure which utilized coliform bacteria as the bioassay organisms for determining the ability of the water to support and promote growth of coliform bacteria. This procedure was compared with a standard assimilable organic carbon (AOC) bioassay. A variety of water types collected from different stages of treatment and from different geographical areas were analyzed. The results of these analyses were also compared with standard water quality parameters.; The coliform bioassay procedure was shown to have the sensitivity required for the detection of nutrient substances in drinking water. The nutrient status of the water, based upon the coliform bioassay, did not correlate with any of the normally measured water quality parameters. The coliform growth response significantly, but only very weakly, correlated with levels of AOC. In general, the coliform growth response increased with increasing levels of AOC. Differences were seen between the coliform growth response and various treatment types, with significantly higher responses being associated with waters which had been exposed to ozonation. The proposed coliform bioassay procedure provides a viable method for ascertaining the biological stability of drinking water supplies.