兰州市城市污水处理厂污泥中重金属形态分布特征与潜在生态风险评价

通过现场调查采样及室内分析,研究了兰州市七里河安宁污水处理厂和雁儿湾污水处理厂污泥中重金属的形态分布特征,并对其进行了潜在生态风险评价。结果表明,污泥总体呈高有机质、高全N和有效P、高微量营养元素,且Cu、Zn、Cd、Pb、Ni5种重金属的含量均低于污泥农用控制标准,具有很好的农用价值。污泥中Zn、Cd、Pb主要以有机结合态和残渣态存在,而Cu、Ni可交换态所占比例较高,分别为14.95%和14.41%,不稳定态所占比例分别为41.12%和31.04%,表现出较高的生物活性和可利用性。七里河和雁儿湾污泥中重金属的潜在生态风险属于低度风险;Cd、Cu是污泥中重金属潜在生态风险的主要贡献者,在污泥处理处置时应引起高度重视。

Fractionation and Environmental Assessment of Heavy Metals in the Sludge from Lanzhou Municipal Wastewater Treatment Plants,China

Municipal sludge samples were collected from Qilihe Anning and Yanerwan wastewater treatment plants,Lanzhou,China.Fractionation of heavy metals was analyzed by a sequential extraction,and their potential ecological risks were evaluated by Hakanson method in sludge.There were high organic matter,high contents of total N,availability P and trace elements in the sludge.Meanwhile,the total contents of Cu,Zn,Cd,Pb,and Ni were all less than the Chinese sewage sludge criteria for agricultural use（soil pH≥6.5）,and the sludge might be regarded as organic fertilizer.Zn,Cd and Pb existed mainly in the forms of organometallic compounds and residues.The proportions of stable form of Zn,Cd and Pb were 87.96%,81.86% and 92.70%,respectively.But the proportions of exchangeable form of Cu and Ni both were more than 14%,and the proportions of unstable form of Cu and Ni were 41.12% and 31.04%.The bioavailability of Cu and Ni was considerably high.According to the potential ecological risk index,the average integrated index of heavy metals was 85.268 and 44.171 in the sludge of two selected wastewater treatment plants,and it was therefore concluded that the sludge had slight potential ecological risk.However,the single potential ecological risk index of Cd and Cu was 53.534 and 8.779,which revealed that the main pollution factor was Cd and Cu.The high index of Cd and Cu implied its high ecological risk,which should be emphasized as controlling,handing with and recycling use of municipal sludge.