Sewers induce changes in the chemical characteristics, bacterial communities, and pathogen distribution of sewage and greywater

Sewers may affect the characteristics and bacterial communities of wastewater, and need be studied as they may impact treatment facilities and recycling operations. In this study, the wastewater characteristics and bacterial communities from the inflow and outflow of two sewers (sewage and greywater) were analyzed. The chemical oxygen demand was significantly reduced in the sewage and greywater sewer and the greywater sewer generated less sulfide and methane. Proteobacteria, Bacteroidetes, and Firmicutes as the major phyla in sewage and greywater and sewer biofilms. Sewer conveyance caused changes in the distribution and community interaction of suspended bacteria. Greywater contained abundant water-related pathogenic bacteria (WPB) and some WPB (e.g. Aeromonas, Klebsiella and Shigella) number in greywater were not lower than sewage. Sewers could increase the number of Shigella in sewage and decrease the number of Acinetobacter in greywater. Further treatment or disinfection of greywater collected by sewers was necessary and directly reuse of greywater without treatment should be avoided.