Evaluation of drinking water supplies by bioassays

The objective of the study was to determine the applicability of a bioassay method for determining the toxicological quality of surface water and groundwater. A core battery of bioassays (Daphnia magna, Hydra attenuata, and Lactura sativa root inhibition test) was tested on each sample. Physicochemical parameters determined consisted of pH, conductivity, total hardness, alkalinity, temperature, turbidity, dissolve oxygen (DO), total suspended solids, total dissolved solids, and chemical oxygen demand (COD). In addition, the algal test using Selenastrum capricornutum was conducted for selected water samples. The results were presented as LC sub(50), EC sub(50) or IC sub(50) values. Natural water samples produced a toxic response in 24% of cases with all three core bioassays. When all bioassays are considered, the percentage of raw samples showing toxicity with at least one bioassay increased to 60%. Based on the overall rate of responses for the core battery of tests, the Hydra attenuata test was the most sensitive, followed by Daphnia magna. Selenastrum capricornutum was also found to be an efficient and reliable bioassay for toxicity assessment.