Effect of domestic pipe materials on microbiological safety of drinking water: Different biofilm formation and chlorination resistance for diverse pipe materials

Microbial biofilms that develop in pipe walls can pollute domestic water systems. Understanding biofilm for-mation and its chlorine resistance in domestic pipe materials will help reduce the possibility of microbial pollution. This study investigates microbial biofilm formation and chlorine resistance in three representative domestic pipes: polypropylene random (PPR), stainless steel (SS), and copper. Biofilm formation determined using crystal violet staining, heterotrophic plate count, and adenosine triphosphate, and extracellular polymeric substance (EPS) content of several typical bacteria were determined before and after disinfection in the different pipe materials. Bacteria in PPR pipes develop significantly more biofilm biomass than in the two metal pipes. EPS content was highest in copper pipe, while lowest biofilm biomass and EPS contents was displayed in SS pipe. The bacteria with more biofilm biomass in three pipe materials appeared to be different. Bacterial chlorine resistance did not differ significantly between the three pipe materials. The chlorine resistance of the same single-species biofilm appeared to vary in the pipe materials, and it was influenced by physiological state of bacterial cells, such as EPS. The data reveal the significant effects of domestic pipe materials on biofilm properties, which mean the possibility of microbial pollution is different.