FACTORS AFFECTING BIOFILM ACCUMULATION IN MODEL DISTRIBUTION SYSTEMS

Annular reactors fed with synthetic or actual water were used to examine the effects of chlorine or monochloramine, easily biodegradable organic matter(BOM),flow velocity(shear stress),pipe material and temperature on biofilm accumulation as measured by biofilm heterotrophic plate count(HPC)values. Under the conditions studied,the disinfectant residual was the most important factor for biofiolm accumulation. In the abscence of a BOM supplement,temperature appeared to have almost no effect,whereas shear appeared to be important. In the presence of a BOM supplement,temperature was important at lower shear stress, altough shear conditions themselves had little effect. The condition leading to the highest levels of biofilm HPCs was a high level of easily degradable BOM combined with the abscence of a disinfectant.