Abstract:

Objective: To learn the status of microbial contamination of central water supply in the rural areas of Henan province,and to analysis the influencing factors of water microbial in order to provide basis for making the policy of drinking water safety improvement.Methods: During 2011-2014,the water sampling of central water supply in eight cities (counties) in Xinxiang city of Henan province were selected and the hygiene condition investigation (water source type,water period type,water supply scale,seasonal,local area,and disinfection) was performed.According to the Drinking Water Standard Test Method (GB/T5750-2006),the microorganisms in factory water and tap water were detected,including the total number of colonie,total coliform count,thermotolerant coliform bacteria and Escherichia coli (E.coli).The influencing factors of total number of colonies exceeding the standards were detected by Logistic regression analysis.The influencing factors of total number of colonies and total coliform count were detected by Poisson regression analysis.Results: There were 824,820,526,and 636 water samples in each year during 2011-2014.The most source of supply water was deep water(90%).The samples of drinking water without any treatment accounted for 70.6%. The qualified rates of total number of colonies were 76.0%,75.5%,66.5%,and 72.6%,respectively,and the qualified rates of coliform count were 97.3%,94.9%,99.6%,and 94.3%,respectively.The exceeding standard rates of total number of colonies of disinfected central water supply were lower than those of central water supply without disinfection (P<0.05) during 2011-2014.The exceeding standard rates of total number of colonies of tap water were higher than those of produced water during 2012-2014 (P<0.05).The exceeding standard rates of total number of colonies in medium water supply engineering (100-1 000 t) were lower than those in large(≥ 1 000 t) and small (<100 t) water supply engineerings in 2013 and 2014 (P<0.05).The Logistic regression analysis results showed that the unqualified rate of total number of colonies in wet season was higher than that in dry season (χ²=12.31,P<0.001).The disinfection could reduce the unqualified rate of total number of colonies (χ²=85.32,P<0.001).The unqualified rates of total number of colonies in the engineering for the purpose of removing fluoride and resolving bitter salt water were lower (χ²=34.44,P<0.001;χ²=39.44,P<0.001). The Poisson regression analysis results showed that wet season (χ²=6 972.75,P<0.001),without disinfection (χ²=5 415.46,P<0.001),tap water (χ²=97.64,P<0.001),long operating time (χ²=26.57,P<0.001),low water supply capacity (χ²=4 502.57,P<0.001),the engineering for the purpose of removing fluoride and resolving bitter salt water (χ²=6 226.68,P<0.001;χ²=13 441.50,P<0.001) increased the total number of colonies. The number of E.coli in samples of central water supply was lower in 100-1 000 t of water supply engineerings (χ²=802.18,P<0.001) and the engineering for the purpose of removing fluoride and resolving bitter salt water (χ²=2 711.88,P<0.001;χ²=1 470.91,P<0.001).The number of E.coli in samples of central water supply was higher in the water of wet season (χ²=16 583.10,P<0.001),the water without disinfection (χ²=276.34,P<0.001),tap water (χ²=1 205.26,P<0.001) and the water with long operating time (χ²=3 220.58,P<0.001).Conclusion: The ratio of disinfection of central water supply in the rural areas of Henan provice is low,the qualified rate of colonies is not high,and the qualified rate of total coliform count was high.The microbial contamination in central supply water in the rural areas is influenced by water period type,disinfection,water sample type,operating time,water supply capacity,and purpose of water supply engineering.

Key words: microorganism, health monitoring, rural areas, Thermotolerant Coliform bacteria, total coliforms, central water supply