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Episodes of nitrification outbreak have been reported in many chloraminatedwater distribution systems (CWDSs), and water quality deterioration often results in suchsystems. One major culprit behind this phenomenon has been believed to be the growth ofnitrifying microorganisms in biofilms in the CWDSs. This indicates that commonly usedmonochloramine (NHsub2/subCl) residuals have not been effectively inactivating biofilmmicroorganisms in CWDSs. In the process of inactivation against embedded cells in biofilms,NHsub2/subCl must first penetrate through the biofilm matrix and then attack its targets.Understanding of the penetration process is critical to evaluating the effectiveness of NHsub2/subCl ininactivating biofilm microorganisms. Based on a newly developed microelectrode suitable forNHsub2/subCl measurement, this research studied the penetration process of NHsub2/subCl in drinking waterbiofilms as well as the impacts of substratum materials on this process.Biofilms were developed in an annular reactor installed with 3 typesof 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 systemwas used as the seed for inoculation as well as the continuous feed of the reactor. Conditions ofslow-flow sections in distribution systems were simulated with respect to shear force and flowrate. Filtered air was dispersed into the feed tank to ensure an aerobic condition in the reactor. Includes figure.

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Edition: Vol. - No. Published: 11/01/2008 Number of Pages: 2File Size: 1 file , 710 KB