The potential for biofilm growth in water distribution systems

Biofilms on pipe walls in water distribution systems are composed of bacter ia in a polymeric matrix, which can lead to chlorine demand, coliform growt h, pipe corrosion and water taste and odour problems. The majority of previ ous studies have been laboratory or pilot plant based and few results are a vailable for field conditions. In this study, field observations of biofilm were made using biofilm potential monitors. The monitor results were compa red with pipe samples taken from the distribution system and with laborator y pipe reactors. An empirical equation quantified the inhibitory effects of free chlorine and decrease of temperature on biofilm growth. With water ha ving total organic carbon concentrations in the range 1.5-3.9 mg/l, a free chlorine residual of 0.2 mg/l was needed to reduce biofilm concentration to below 50 pg ATP/cm(2). Pipe material influenced biofilm activity far less than chlorine with mean biofilm activity being ranked in the order glass (1 36 pg ATP/cm(2)) < cement (212 pg ATP/cm(2)) < MDPE (302 pg ATP/cm(2)) < PV C (509 pg ATP/cm(2)). (C) 2001 Elsevier Science Ltd. All rights reserved.