Laboratory reactors operated under conditions relevant for drinking water distribution systems were used to examine the impact of support surface, chloramine residual, biodegradable organic matter (BOM) concentration, shear, and temperature on the growth of heterotrophic microorganisms. In terms of both heterotrophic bacterial growth-supporting and corrosion characteristics, mild steel and stainless steel/polycarbonate substrata bracket metallic pipe materials, such as ductile iron. Results of gradually increasing disinfectant dosage studies suggest that a 0.5 mg/L free or combined chlorine residual on polycarbonate surfaces, and 0.5 mg/L free chlorine or 2.0 mg/L combined chlorine residual on ductile iron substrata would be needed to reduce biofilm HPC numbers to approximately 103 CFU/cm2. Regression analysis suggests low or very low correlation between biofilm and suspended HPC numbers.
