AWWA ACE93172

The Town of North Kingstown, Rhode Island, experienced an outbreak of total and fecal coliform in the non-disinfected groundwater system. The most probable cause appears to be the transport of bacterial contaminants to a supply well from a nearby surface water and subsequent bacterial colonization with the distribution system biofilm. Chlorination disinfection alone was not completely effective for inactivation of biofilm organisms. Increasing the distribution system pH to 8.3 effectively inhibited biofilm growth. This case study describes the various investigations which were undertaken to identify the most likely cause of the outbreak and bring the system back into compliance with the Total Coliform Rule.