Abstract

Drinking water systems supplied by untreated groundwater were examined to determine whether coliform or heterotrophic plate count bacteria are capable of growing. Filterable bacteria were present in 42% of the 46 groundwater sources examined by using nonselective media (R2A and full strength m-HPC agars). Pseudomonads were the most frequently identified group of filterable bacteria detected. Flavobacterium, Alcaligenes, Acinetobacter and Achromobacter isolates were also identified. Total coliforms were recovered only from six samples taken from wells near the wastewater lagoon, following filtration through 0.45-µm-pore-size membrane filters by using selective M-Endo LES agar or mT7 agar. In addition, none of the isolates identified from nonselective media were coliforms. Similarly, neither total coliforms nor specifically Escherichia coli were detected in these filtrates when Colilert P/A medium was used.

Key words: ground water, contamination, Flavobacterium, Alcaligenes, Acinetobacter, Achromobacter, Escherichia coli.