Succession of bacterial biofilm communities following removal of chloramine from a full-scale drinking water distribution system

Abstract Monochloramine is used to regulate microbial regrowth in drinking water distribution systems (DWDS) but produces carcinogenic disinfection byproducts and constitutes a source of energy for nitrifying bacteria. This study followed biofilm-dispersed communities full-scale DWDS distributing ultrafiltered over three years, before after removal monochloramine. Communities were described using flow cytometry amplicon sequencing, including full-length 16S rRNA gene sequencing. Removal monochloramine increased total cell counts by up 440%. Increased abundance heterotrophic bacteria was emergence the predatory Bdellovibrio , community potentially metabolizing small organic compounds replaced core community. No Mycobacterium or Legionella observed. Co-occurrence analysis identified network Nitrosomonas Nitrospira Sphingomonas Hyphomicrobium suggesting that supported this biofilm While some species expanded into changed niche, no immediate biological risk consumers indicated within DWDS.