污水处理厂苯系物暴露风险评价及控制对策

Exposure Risk Assessment and Control Countermeasures of Benzene Series in Sewage Treatment Plant

对污水处理厂6个处理单元逸散出的苯系物进行了采集和分析,研究了苯、甲苯和二甲苯在不同季节和不同处理单元的浓度变化规律,并对夏季逸散出的苯系物的致癌和非致癌风险进行了评价,提出了苯系物等挥发性物质的控制对策。结果表明:3种苯系物的气相浓度由高到底均为夏>春>秋>冬。夏季初沉池散逸的苯、甲苯、二甲苯最多,气相浓度分别为83、99和172μg/m3。苯系物在春、秋和冬季的平均浓度为其夏季浓度的97.6%、94.0%和87.7%。苯系物对人体以致癌风险为主,长期工作在污水处理厂处理单元附近的工作人员存在轻微的致癌风险。通过减少污水紊流、优化污泥回流过程、采用合理的曝气方式、减少暴露年限和对处理单元加盖密封等方法可以从源头减少苯系物等挥发性物质的逸散。

Benzene series from six treatment umts m sewage u^a~,,,~,,, e alyzed. The variation characteristics of benzene, toluene and xylene in different seasons and different treatment units were investigated. The carcinogenic risk of the benzene series escaped in summer was e- valuated and the control countermeasures for volatile substances were put forward. The results showed that the mass concentrations of 3 benzene series in the gas phase were different during four seasons, and the concentrations in summer were all highest, followed by spring, autumn and winter. In summer, the gas phase concentrations of benzene, toluene and xylene escaped from primary settler were highest with thevalues of 83 μg/m3, 99 μg/m3 and 172 μg/m3. The average concentrations of the benzene series in spring, autumn and winter were respectively 97.6%, 94.0% and 87.7% of those in summer. According to the risk assessment, benzene series had the major carcinogenic risk to human body. If the staffs contin- ued to work for a long time in or near the sewage treatment plant, there was a slight carcinogenic risk. The volatilization of benzene series could be reduced by reducing sewage turbulence, optimizing sludge return process, using reasonable aeration way, reducing exposed fixed number of year and sealing treat- ment units.