Evaluation of a rapid method for E coli and thermotolerant coliforms in recreational waters

The management of recreational beaches based on the standard methods for E coli or thermotolerant coliforms can present a challenge to public health o fficials. Typically there is a 30-48h delay between sample collection and a vailability of results. Bacteriological water quality can change significan tly during this period. During 1995 and 1996, a rapid method, based on the production of glucoronidase by E coli or galactosidase by thermotolerant co liforms, was developed to shorten this delay. During the summer of 1997, th e rapid method was compared to the standard membrane filtration technique f or E coli. Using 563 comparisons, the correlation for E coli detected by th e rapid method and membrane filtration yielded a r(2)=0.89. The percent agr eement between the methods based on the number of times both provided resul ts above or below the provincial objectives of 100 E coli/100mL was 84.6%. Similar results were obtained for 1,168 comparisons of thermotolerant colif orm data. Using the rapid method, results for samples collected in the morn ing are available by the afternoon of the same day. The rapid method not on ly allows for the prompt closure of beaches but also maximises the times wh en the beaches are open. (C) 1998 Published by Elsevier Science Ltd on beha lf of the IAWQ. All rights reserved.