EVALUATION OF THE DISINFECTION POTENTIAL OF LOW CHLORINE CONCENTRATIONS IN TAP WATER USING IMMOBILIZED ENTEROCOCCUS-FAECIUM IN A CONTINUOUS-FLOW DEVICE

A simple continuous now device in which bacteria were immobilised on m embrane filters and flushed with tap water with free chlorine residual s of 0.05, 0.1, 0.2 and 0.4mg/L at pH 7.7 and 10 degrees C, has been u sed for disinfection experiments with faecal streptococci. A 99.99% re duction of Enterococcus faecium was observed between 3.4-5.2min (0.05m g/L), between 2.8-4.1min (0.1mg/L), between 1.7-3.1min (0.2mg/L) and b etween 0.8-2.1min (0.4mg/L). CT-products covered a range of 0.17 (0.05 mg/L, lower limit) up to 0.85mg/L/min (0.4mg/L, upper limit). The test system is suggested as a more reliable alternative to batch experimen ts when the disinfection potential of low chlorine concentrations acti ng for several minutes has to be evaluated. The system cannot be used to demonstrate exact reduction kinetics but it allows the calculation of CT values and the evaluation of the disinfection potential of chlor inated water at any point of a distribution system where initial chlor ine concentrations may have already remarkably declined. (C) 1997 IAWQ . Published by Elsevier Science Ltd.