污泥屏障渗透性及重金属阻截效果试验研究

Permeability and heavy metal retardation of sewage sludge barrier

目前,废弃物处置场渗滤液中的重金属污染物只能依靠极低渗透性的水力屏障来控制,还不存在利用化学场专门拦截重金属污染物的反应型屏障。在有机结合生活污泥的低渗透性与丰富的有机质和厌氧微生物特性的基础上,提出"污泥屏障"的构想。研究利用柔性壁渗透仪测量不同有效应力作用下生活污泥试样的渗透系数,并对渗出液的化学性质进行了监测,验证污泥屏障的可行性。试验结果表明:随着有效应力的增大,污泥试样干密度提高,渗透系数的对数值随孔隙比的减小线性降低。试样内部微生物厌氧呼吸形成的生物膜和无机物沉淀以及黏土颗粒双电层厚度的增大,也是污泥渗透系数降低的原因,污泥渗透系数仅为9 110 c m s数量级。另外,污泥强烈吸附能力及厌氧微生物呼吸作用形成的中-弱碱性还原环境,对渗透液中的Zn和Cd都起到了很好的拦截作用。

At present,heavy metal pollution in the leachate of waste disposal site only can be controlled by hydraulic barrier of extremely low permeability.The chemical field of the barrier has never been used for the retardation of heavy metal pollution.A conception of ＂sewage sludge barrier＂ is proposed based on the integration of low permeability with plentiful organic matter and anaerobe contained in the sewage sludge.To investigate the feasibility of the sewage sludge barrier,the flexible wall permeameter is used in this study to measure hydraulic conductivity of sewage sludge under different effective stresses;and the chemical properties of the effluent are monitored.Test results show that with the increase in effective stress,the dry density increases and the logarithm of hydraulic conductivity decreases linearly with decrease in void ratio.The formation of biofilm and inorganic precipitates with the anaerobic respiration,and the increase of the thickness of diffuse double layer of the clay particle within sewage sludge specimens are also responsible for the decrease in hydraulic conductivity.Hydraulic conductivity of sewage sludge as low as 9 1 10 c m s,combined with strong adsorption and neutral to weak alkaline reducing conditions induced by the anaerobic respiration,makes the heavy metals of Zn and Cd retarded effectively.