Effect of outdoor pipe materials and community-intrinsic properties on biofilm formation and chlorine resistance: Black sheep or team leader

Abstract

Community-intrinsic properties affect the function and composition of microbial community, and understanding of the microbial community-intrinsic properties in different pipe materials of drinking water distribution systems can help to prevent microbial pollution more reasonably and efficiently. This study investigated the biofilm formation and chlorine resistance of multi-species biofilms in two representative outdoor pipe materials (polyethylene (PE) and cast iron pipe). The results showed that cast iron pipes have higher biofilm biomass but lower biofilm activity than PE pipes. The different growth environments of the two pipe materials resulted in diverse microbial community-intrinsic properties and affected multi-species biofilm formation. The microbial communities without Sphingomonas or Acidovorax in cast iron pipe exhibited higher biofilm biomass, when compared with those in PE pipe. In contrast, the microbial community without Bacillus in PE pipe presented higher biofilm biomass, when compared with those in cast iron pipe. Extracellular polymeric substance (EPS) and corrosion products protected bacteria from chlorination. Although community-intrinsic properties helped bacteria resist chlorination, the same microbial community exhibited diverse chlorine resistance in different pipe materials owing to different community-intrinsic properties. While the chlorine resistance of microbial community without Bacillus was low in PE pipe, that in cast iron pipe was better owing to high corrosion degree. Multi-species biofilm without Sphingomonas or Acidovorax presented higher biofilm biomass, but lower EPS content and corrosion products in cast iron pipe, resulting in low chlorine resistance. In summary, this study revealed that outdoor pipe materials could affect microbial community-intrinsic properties, which in turn could influence biofilm characteristics, and provided unique insights for ensuring drinking water safety.