Water Quality and Influencing Factors of Centralized Water Supplies in Rural Lanzhou in 2017

Objectives To understand the sanitary situation of centralized water supplies in Lanzhou rural areas.

Methods 188 centralized water supply projects were selected randomly and investigated in Lanzhou rural areas in 2017. Water samples of dry season and wet season were collected and water quality was analyzed.

Results Water supply treatments and disinfections were carried out in 67.0% and 50.0% of the 188 projects, respectively, and 23.9% used disinfection equipment as required. The qualified rate of 376 water samples was 54.5%. The qualified rate was lower in wet season than that in the dry season, and the qualified rate of groundwater was lower than that of the surface water (χ²=27.898, 7.143, P < 0.05). The range of qualified rate of 33 indexes were from 72.1% to 100.0%, of which total coliform bacteria was the lowest. The qualified rates of total coliform bacteria, thermotolerant coliforms, escherichia coli, and colony count in dry season were higher than those in wet season (χ²=59.317, 19.998, 23.367, 28.636, P < 0.05). The qualified rates of escherichia coli and turbidity of groundwater were higher than those of surface water, while the qualified rates of nitrate nitrogen, chloride, sulfate, soluble total solid, and total hardness were lower (χ²=7.419, 15.020, 5.212, 13.808, 23.222, 26.998, 45.599, P < 0.05).

Conclusions The main problems of the water quality of centralized water supplies in Lanzhou rural areas are microbial contamination and over-standard physical and chemical indicators. Disinfection and softening of centralized water supplies should be strengthened.