RAPID DETECTION OF FECAL-COLIFORMS IN SEWAGE USING A COLORIMETRIC ASSAY OF BETA-D-GALACTOSIDASE

A rapid colorimetric method has been developed for the detection of faecal coliforms in sewage. The method is based on the hydrolysis of o-nitrophenyl-beta-D-galactopyranoside by the bacterial enzyme beta-D-galactosidase and detection of liberated o-nitrophenol. Enzyme activity correlated well with numbers of faecal coliforms determined by conventional membrane filtration over a range of bacterial concentrations. A lower limit of 10(3) faecal coliforms per mi could be detected within 60 min. It is proposed that the method, which is amenable to automation, may be used asa surrogate for monitoring faecal coliform concentrations in sewage and a variety of effluents with a view to providing an early-warning indicator of sewage contamination or leakage.