Drinking water quality at resettlement areas in Chongqing, 2014—2018

Objective To investigate and analyze the quality of drinking water in resettlement areas in Chongqing from 2014 to 2018, find potential safety hazards, and ensure the drinking water safety of the local population.

Methods From 2014 to 2018, water samples of finished water and tap water were collected twice a year in the wet season (August-September) and dry season (February-March) in15 centralized water supplies at 6 districts and counties in Chongqing. The water samples were tested and evaluated according to the Standard Examination Method for Drinking Water(GB/T 5750-2006) and the Standard for Drinking Water Quality(GB 5749-2006).

Results From 2014 to 2018, 205 water samples were collected from resettlement areas of 6 districts and counties in Chongqing, with 134 samples qualified, and the overall qualified rate was 65.37%. The qualified rates of finished water and tap water in 5 years were 66.67% and 63.92%, respectively. The qualified rates of water samples in wet season and dry season were 59.80%(61/102)and 70.87%(73/103), respectively. There was no significant difference in the qualified rate of water samples at different sampling time(χ²=2.77, P>0.05).The qualified rates of water samples from centralized water supply units and small centralized water supply units were 67.91%(91/134)和60.56%(43/71), respectively. There was no significant difference in the qualified rate of water samples at different sampling time(χ²=1.11, P>0.05). Unqualified indicators mainly include chlorate, total coliform, chlorite, total bacterial count, chloroform, Thermotolerant coliforms and Escherichia coli and the quaulified rates were 60.00%, 80.49%, 81.25%, 90.24%, 92.41% and 92.63%, respectively.

Conclusion The potential water quality safety hazards were water-borne diseases and disinfection by-products caused by drinking water disinfection in resettlement areas of six counties and districts in Chongqing.In the future, it is necessary to strengthen the disinfection of drinking water, focus on the indicators of microbiol indices, disinfectant indices, disinfection by-products and turbidity, oxygen consumption and mercury, and appropriately increase the monitoring frequency of these indices in order to prevent the outbreak of water-borne diseases.