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 fa ecal coliforms in sewage. The method is based on the hydrolysis of o-n itrophenyl-beta-D-galactopyranoside by the bacterial enzyme beta-D-gal actosidase and detection of liberated o-nitrophenol. Enzyme activity c orrelated well with numbers of faecal coliforms determined by conventi onal membrane filtration over a range of bacterial concentrations. A l ower limit of 10(3) faecal coliforms per mi could be detected within 6 0 min. It is proposed that the method, which is amenable to automation , may be used asa surrogate for monitoring faecal coliform concentrati ons in sewage and a variety of effluents with a view to providing an e arly-warning indicator of sewage contamination or leakage.