城市污水处理厂污泥化学组分与重金属元素形态分布研究

采用现场调查采样及室内分析的方法,研究了无锡芦村污水处理厂污水处理过程中污泥的化学组分和重金属元素的形态分布。结果表明,污水处理厂污水处理过程中的初沉污泥、消化污泥、生化污泥和二沉污泥总体呈高有机质、高氮磷、低K、高微量营养元素,具有良好的农用价值。但污泥中的重金属元素A s超过国家标准,限制了污泥的农用。重金属元素总量分布研究表明污水处理过程中重金属元素沉积到污泥中没有显著的差异。连续提取研究表明,不同的重金属元素的形态分布差异较大,因而其潜在的迁移性和植物毒性明显不同。A s、Ni、Zn的有效态含量的百分率在30%以上,潜在的迁移性和植物毒性最值得关注。污泥的消化无害化处理可以改变污泥中重金属元素的形态,但不能降低污泥中的重金属元素的含量。建议在污水处理过程中适当运用废水处理技术,改变重金属元素沉积方式,从而降低污泥处置成本,并提高污泥资源的利用效率。

Chemical Components and Heavy Metals in Sludge from Wastewater Treatment Plant

With rapid increase of sewage treatment plants,the disposal and environmental impact of municipal sludge have been receiving more and more attention.Sewage sludge was collected from Lucun wastewater treatment plant,Wuxi,and the chemical components and heavy metals by a sequential extraction in sludge were investigated in the present study.We found that all had high organic carbon contents,high contents of N,P and trace elements,and the sludge may be regarded as organic fertilizer.However,As content was beyond the state control standard of municipal sludge for agricultural application and this limited their agricultural application.There was no significant difference in the sedimentation of heavy metals during the wastewater treatment process.The results obtained by the sequential extraction procedure indicated that there was significant difference in the fraction of heavy metals,so the movability and phyto-toxicity of heavy metals also varied greatly.Among them,the percentages of available fraction of As,Ni,Zn were over30%,so their movability and phyto-toxicity was the highest.Non-hazardous treatment of municipal sludge could change the fraction of the metals contents,but may not be able to reduce their contents in municipal sludge.It is suggested that some treatment techniques be taken to change the sedimentation of heavy metals during the wastewater treatment process to reduce the disposal cost and increase the resource utilization efficiency of municipal sludge.