Examination of the behaviour of Escherichia coli in biofilms established in laboratory-scale units receiving chlorinated and chloraminated water

Groundwater was treated with chlorine and chloramine to study the incorpora tion and survival of Escherichia coli in developing biofilms in laboratory- scale units. Membrane filter and standard spread plate procedure were used to enumerate coliform and heterotrophic plate count bacteria respectively. Within 96 h the adhesion of heterotrophic plate count bacteria on stainless steel coupons was obvious in all systems, with a higher number of organism s (4 log cfu cm(-2)) noted for the non-disinfected water. Attachment of E. coil added 24 h after the formation of young biofilms was obvious on stainl ess steel coupons exposed to the non-disinfected water (9 cfu cm(-2)) and c hlorinated water (2 cfu cm(-2)). A significant difference between E. coil c ounts in the non-disinfected water and chloraminated water, and the chlorin ated and chloraminated water, was found. However. the ANOVA test indicated no significant difference in E. coil counts for the non-disinfected water a nd chlorinated water. This investigation revealed the effectiveness of chlo ramine in preventing the attachment of E, coil in developing biofilm. (C), 1999 Elsevier Science Ltd. All rights reserved.