Bench scale investigations of bacterial regrowth in drinking water distribution systems

Laboratory reactors operated under conditions relevant for drinking water d istribution systems were used to examine the impact of support surface, chl oramine 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 characteristic s, mild steel and stainless steel/polycarbonate substrata bracket metallic pipe materials, such as ductile iron. Results of gradually increasing disin fectant dosage studies suggest that a 0.5 mg/L free or combined chlorine re sidual on polycarbonate surfaces, and 0.5 mg/L free chlorine or 2.0 mg/L co mbined chlorine residual on ductile iron substrata would be needed to reduc e biofilm HPC numbers to approximately 10(3) CFU/cm(2). Regression analysis suggests low or very low correlation between biofilm and suspended HPC num bers. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.