AWWA WQTC69435

Episodes of nitrification outbreak have been reported in many chloraminated water distribution systems (CWDSs), and water quality deterioration often results in such systems. One major culprit behind this phenomenon has been believed to be the growth of nitrifying microorganisms in biofilms in the CWDSs. This indicates that commonly used monochloramine (NH₂Cl) residuals have not been effectively inactivating biofilm microorganisms in CWDSs. In the process of inactivation against embedded cells in biofilms, NH₂Cl must first penetrate through the biofilm matrix and then attack its targets. Understanding of the penetration process is critical to evaluating the effectiveness of NH₂Cl in inactivating biofilm microorganisms. Based on a newly developed microelectrode suitable for NH₂Cl measurement, this research studied the penetration process of NH₂Cl in drinking water biofilms as well as the impacts of substratum materials on this process. Biofilms were developed in an annular reactor installed with 3 types of removable slides made from polyvinyl-chloride (PVC), polycarbonate (PC) and concrete. Flushed wash water sampled during repair work of water mains in a water distribution system was used as the seed for inoculation as well as the continuous feed of the reactor. Conditions of slow-flow sections in distribution systems were simulated with respect to shear force and flow rate. Filtered air was dispersed into the feed tank to ensure an aerobic condition in the reactor. Includes figure.