黄土性土壤对垃圾渗滤液的净化作用

Purification effect and mechanism of loessial soil to leachate

【目的】研究黄土性土壤对垃圾渗滤液的净化作用,为黄土地区垃圾填埋场渗滤液的污染控制,以及填埋场覆盖层的选材及厚度设计等提供参考依据。【方法】分别采集耕层(0～25cm)、犁底层(25～60cm)、黏化层(60～120cm)和钙积层(120～175cm)土壤,按不同液土比(体积(mL)质量(g)比,下同;5∶1,10∶1,20∶1,30∶1)加入垃圾渗滤液,采用静态和动态吸附试验,研究不同土层土壤对垃圾渗滤液中COD、NH4+-N的吸附特征及COD去除率随时间的变化规律。【结果】耕层、黏化层、钙积层土壤在振荡4h、犁底层土壤在振荡2h时,对垃圾渗滤液中COD的吸附量达到最大;犁底层、黏化层、钙积层土壤在振荡2h、耕层土壤在振荡1h时,对垃圾渗滤液中NH4+-N的吸附量达到最大;随着液土比的增大,不同土层(除犁底层外)土壤对渗滤液COD、NH4+-N的吸附量逐渐增加。【结论】黄土性土壤对垃圾渗滤液中的COD吸附净化可分为全吸附阶段、部分吸附阶段和基本饱和阶段。综合分析不同土层对垃圾渗滤液中COD、NH4+-N的吸附净化作用,填埋场覆盖层应选择耕层及黏化层土壤,覆盖层厚度以100cm为宜。

【Objective】 The study was to provide information about materials selection and depth design of cover in waste landfill,and to leachate pollution control in loessial area by studying purification of loessial soil.【Method】 Collecting soil samples in cultivated horizon（0-25 cm）,plow pan（25-60 cm）,argillic horizon（60-120 cm） and calcic horizon（120-175 cm）,adding leachate in terms of different ratios of solvent to soil（Vloume（mL） to mass（g） ratio,the same with below;5∶1,10∶1,20∶1,30∶1） by static and dynamic adsorption experiments,adsorption characteristics of COD and NH＋4-N in different layer loessial soil,and changes of COD removal rate are researched.【Result】 The results show that adsorption amounts of cultivated horizon,argillic horizon and calcic horizon to COD in leachate reach the maximum amounts,which are 100,80,60 mg/g,respectively when oscillation time is 4 h.Those of plow pan,argillic horizon and calcic horizon to NH＋4-N in leachate reach the maximum amounts,which are 13.76,13.24,10.76 mg/g,respectively,when oscillation time is 2 h.But the maximum adsorption amounts of cultivated horizon to NH＋4-N is 26.12 mg/g when oscillation time is 1 h.With the increase of ratio of solvent to soil,the adsorption amounts of different layer soil to COD and NH＋4-N are increased gradually（except plow pan）.【Conclusion】 The purification of loessial soil to COD divides into three stages which are complete adsorption,partial adsorption and saturation adsorption.Considering purification of different soil layers,cultivated horizon and argillic horizon should be selected as materials of cover in waste landfill,and cover depth is 100 cm properly.