USE OF 2 FORMULATIONS OF COLILERT AND QUANTITRAY(TM) FOR ASSESSMENT OF THE BACTERIOLOGICAL QUALITY OF WATER

The use of standard Colilert (IDEXX) for the detection of coliforms an d E. coli in potable water has been studied. In a large survey, Colile rt recovered E. coli from similar numbers of samples to membrane filtr ation whilst recovery of coliforms was higher with Colilert. Further e xperiments to study the sensitivity of the two methods using pure cult ures, showed that there was no significant difference in their ability to recover E. coli. Studies on a newly developed form of Colilert (Co lilert 18) which is said to give results within 18 h showed that there was no significant difference between the two forms of the product. U se of the Colilert Is in a quantitative format using QuantiTray(TM) sh owed that the product gave similar quantitative results to membrane fi ltration, but was easier to read and was less time consuming. Subcultu re of a proportion of positive samples demonstrated that there was no need to confirm results obtained with the Colilert/QuantiTray(TM) syst em. The results of this study suggest that both formulations of Colile rt are suitable alternatives to the United Kingdom membrane filtration method for monitoring the bacteriological quality of drinking water. (C) 1997 Published by Elsevier Science Ltd.