Microbiological Methods for Safety Testing of Drinking Water Directly Reclaimed from Wastewater

Abstract

The following results were obtained in research on microbiological methods for assessment of the safety of drinking water directly reclaimed from wastewater: Studies on a wide variety of pathogenic micro-organisms revealed that the safety of the water could reliably be monitored by practical indicators such as standard plate counts, coliform bacteria, coliphages and acid-fast bacteria. A convenient plate incorporation modification of the Ames Salmonella mutagenicity assay proved suitable for routine quality surveillance of potentially mutagenic and carcinogenic compounds; results were confirmed by comparative tests using a hamster embryonic cell transformation assay in which sensitivity was increased by preparing growth media from test water. Screening for toxic activity was reliably done by assays based on interference with the multiplication of Pseudomonas putida, the cloning efficiency of BGM, HeLa and mouse lymphoma cell lines, and activity of the enzyme urease. A commercial limulus amoebocyte lysate assay proved a reliable and sensitive method for the detection of endotoxins. Correlation with results obtained in sophisticated chemical analyses, as well as long-term epidemiological studies on consumers, confirmed that, subject to the maintenance of certain operational conditions, the safety of directly reclaimed drinking water could reliably be monitored by relatively simple, inexpensive and rapid microbiological tests and bioassays.