干旱区污水处理厂污泥资源化风险评价

Risk Assessment of Sludge Recycling in Wastewater Treatment Plants in Arid Areas

为探讨干旱区污水处理厂的污泥养分和重金属质量比季节性变化规律,并评价其环境风险,自2019年9月—2020年9月在中卫市某污水处理厂共采集了7次生活污泥样品,按照国家标准测定污泥中养分含量、5种重金属及其他指标。结果表明,污泥中有机质的质量分数,全氮、全磷、全钾的质量比,pH和含水率的平均值分别为63.9%、30 g/kg、300 mg/kg、5.79 g/kg、6.9和88.2%。磷质量比季节性变化明显,表现为秋季最高,冬季最低,这与人类生活习性相关。5种重金属质量比均低于《农用污泥污染物控制标准》(GB 4284—2018)限值,重金属铬季节性变化较为明显,呈春季最高,秋季最低。重金属内梅罗综合污染指数和综合因子潜在生态风险指数的评价结果为轻度污染和低危害风险。

To explore the seasonal variation pattern of the nutrients and heavy metals mass ratios in wastewater treatment plants in arid areas and assess their environmental risks,a total of seven domestic sludge samplings are collected from September2019 to September 2020 at a wastewater treatment plant in Zhongwei City,and the nutrient content,five heavy metals and other indicators in them are determined according to national standards.The results show that the mean values of mass fraction of organic matte,mass ratio of total nitrogen,mass ratio of total phosphorus,mass ratio of total potassium,pH and water content of the the seven sludge samples are 63.9%,30 g/kg,300 mg/kg,5.79 g/kg,6.9 and 88.2%,respectively.The seasonal variation of phosphorus mass ratio is obvious,showing the highest in autumn and the lowest in winter,which is related to living habits.The contents of five heavy metals are lower than the limits of the Control Standards for Agricultural Sludge Pollutants(GB 4284—2018).The seasonal variation of heavy metal chromium is obvious,showing the highest in spring and the lowest in autumn.The evaluation results of heavy metal Nemero composite index and composite factor potential ecological risk index are mild pollution and low hazard risk.