FIGURE 2.

Relative abundance of bacterial community in the DWTS bulk water and sand biofilm at the phylum level (A) and genus level (B). Sequences that could not be classified into any known phylum or genus are assigned as unclassified bacteria. The rare species with relative abundance <0.1% are assigned to others. A1–A3: raw water; B1–B3: flocculation tank effluent; C1–C3: sedimentation tank effluent; D1–D3: quartz sand; E1–E3: sand filter effluent; F1–F3: chlorine-disinfected water; G1–G3: tap water. Three samples were taken from each sampling site.