2023年北京市某区洪涝灾害后农村自备井微生物污染应急监测分析

Emergency monitoring and analysis of microbial contamination of rural self-provided wells after flood disaster in a district of Beijing

目的了解北京市某区23·7洪涝灾害后农村自备井微生物污染情况,落实“快”“准”针对性防制措施,确保饮用水卫生安全。方法洪涝灾害发生后立即对19个乡镇街道的226个村存在供水能力的247口农村自备井饮用水进行应急普查。经过恢复重建,随机抽样选取45口自备井抽查。本文采用描述性流行病学方法对与介水疾病密切相关的总大肠菌群和大肠埃希菌两种致病微生物指示指标的监测结果进行分析。结果应急监测结果显示,247口农村自备井总大肠菌群和大肠埃希菌两种致病微生物指示指标综合评价超标率达68.42%,超标率分别为67.21%和35.22%。重度、中度和轻度受灾地区自备井两种致病微生物指示指标超标率比较,差异无统计学意义(χ^(2)=0.781,P=0.677)。根据定量分析,严重受灾地区末梢水总大肠菌群检出情况最严重,最大概率数(MPN)中位数(M)和四分位数(P_(25),P_(75))为62.85(1.00,200.50)/100 mL,大肠埃希菌MPN M(P_(25),P_(75))为1.00(0.00,5.85)/100 mL。不同受灾地区末梢水总大肠菌群(Kruskal-Wallis检验,H=7.892,P=0.019)和大肠埃希菌(Kruskal-Wallis检验,H=6.023,P=0.049)指标检测量差异有统计学意义。经两两比较,主要是重度和轻度地区末梢水(总大肠菌群调整后,P=0.015,大肠埃希菌调整后P=0.045)污染情况比较,差异有统计学意义。恢复重建后,抽样监测自备井超标3口(6.67%),均位于严重受灾地区;出厂水和末梢水均超标3件,为总大肠菌群超标,大肠埃希菌合格。恢复重建后较应急监测合格率明显上升,应急处置前后自备井(χ^(2)=59.968,P<0.001)、出厂水(χ^(2)=37.257,P<0.001)和末梢水(χ^(2)=40.008,P<0.001)两种致病微生物指示指标综合评价超标率差异均有统计学意义。结论“23·7”暴雨历时长、总量达、强度高,导致重度、中度、轻度三类不同受灾地区均出现不同程度普遍性的生物污染;其中重度受灾地区污染程度更重;落实各项干预措施后效果显著,水质合格率大幅度提升。应急监测有助于对其他地区灾后自备井饮用水管理工作提供参考。

Objective To assess the microbial contamination of rural self-provided wells after 23·7 flood disaster in a district of Beijing,and implement targeted prevention and control measures to ensure drinking water sanitation and safety.Methods Immediately after the flood disaster occurred,A comprehensive inspection was conducted on 247 rural self-supplied wells for drinking water in 226 villages across 19 townships and streets where there was a possibility of water supply capacity.After restoration and reconstruction,45 self-provided wells were randomly selected for random inspection.In this paper,descriptive epidemiological method were used to analyze two indicators of pathogenic microorganisms,total coliforms and Escherichia coli,which were closely related to waterborne diseases.Results The overall exceedance of the two pathogenic microorganism indicators in the comprehensive evaluation of 247 rural self-provided wells was 68.42%,the exceedance rates of the total coliforms and Escherichia coli were 67.21%and 35.22%,respectively.There was no significant difference in the exceedance rate of two pathogenic microorganism indicators in severe,moderate and mild disaster areas(χ^(2)=0.781,P=0.677).Quantitative analysis showed that the load of total coliforms in the tap water of severely affected areas was the highest,with MPN median and interquartile range of 62.85(1.00,200.50)/100 mL,and that was 1.00(0.00,5.85)/100 mL for Escherichia coli.There were statistical significants in the detection amount of total coliforms(Kruskal-Wallis test,H=7.892,P=0.019)and Escherichia coli(Kruskal-Wallis,test H=6.023,P=0.049)in tap water across different disaster areas.Pairwise comparisons revealed statistically significant differences in tap water contamination between severe and mild areas(adjusted P=0.015 for total coliforms and adjusted P=0.045 for Escherichia coli).After reconstruction,3 wells(6.67%)exceeded the standard,all located in severely affected areas.Both finished water and tap water exceeded the standard in 3 cases,with total coliforms exceeding the standard while the Escherichia coli index remained within the standard.The qualified rate was significantly higher than that of emergency monitoring.After emergency disposal,there were statistically significant differences in the overstandard rates of two indicators of pathogenic microorganisms:the well(χ^(2)=59.968,P<0.001),finished water(χ^(2)=37.257,P<0.001)and tap water(χ^(2)=40.008,P<0.001).Conclusions The“23·7”rainstorm was prolonged,with high total rainfall and intensity,leading to varying degrees of widespread biological contamination across severe,moderate,and mild disaster areas.Among these,the pollution level in the heavily affected areas is more serious.After the implementation of various intervention measures,the effect was remarkable,and the qualified rate of water quality is greatly improved.Emergency monitoring provides valuable references for the management of potable water from self-provided wells in other areas after disasters.