矿化垃圾中Fe(Ⅲ)还原耦合CH_4厌氧去除特性

Characteristics of Anaerobic Methane Removal Coupled to Fe(Ⅲ) Reduction in Aged Refuse

填埋场内Fe的含量极其丰富,被誉为"世界第三大铁库",同时又是重要的甲烷释放源.本研究利用Fe的变价特性,结合矿化垃圾可用作生物覆盖材料的特点,设计反应器模拟填埋场覆土层,通过添加FeCl_3研究了Fe(Ⅲ)对CH_4厌氧去除的影响及与共存电子受体NO_3^-、SO_4^(2-)之间的相互作用.结果表明,矿化垃圾中添加Fe(Ⅲ)可明显促进CH_4厌氧去除,CH_4含量随时间变化符合零级动力学,去除速率(以CH_4/干垃圾计)达1.28 mmol·(kg·d)^(-1).厌氧条件下CH_4共存时,外加Fe(Ⅲ)有利于矿化垃圾中形成活性Fe(Ⅱ),与共存电子受体NO_3^-、SO_4^(2-)还原形成耦合效应,从而加速NO_3^-、SO_4^(2-)的消耗.

Landfills are the third largest iron reservoir and one of the largest sources of methane release.Iron,as a kind of transition metal,plays a particularly important role in environmental biogeochemistry and is closely linked to the biogeochemical cycle of C,S and N.The aged refuse could be utilized as bio-cover material to improve the removal of contaminants.Therefore,this work investigated the effect of iron reduction on anaerobic removal of methane,and the interactions of ferric iron with nitrate and sulfate in the aged refuse.The columns were operated as landfill bio-covers and recirculated leachate with addition of FeCl_3 solution.In the experiment,three columns were used,two of them were used as controls（named as B1 and B3）,B1 was fed with leachate and CH_4,whereas B3 was only recirculated with leachate adding FeCl_3.The treatment B2 was fed with the above two substrates.During the operation of columns,the contents of CH_4,CO_2 and N_2in the gas,and the concentrations of NO_3^-,NO-2,NH＋4,SO_4^（2-）,Fe（Ⅲ） and Fe（Ⅱ） in the leachate and refuse were respectively determined.The results showed that adding ferric iron obviously enhanced the removal of methane in anaerobic aged refuse,the decrease of methane content with time obeyed zero-order kinetic,and the rate of methane removal（denoted as CH_4/aged refuse） reached 1.28 mmol·（kg·d）^-1.In the anaerobic condition,methane could improve the reduction of Fe（Ⅲ） to dissolved,active and bioavailable Fe（Ⅱ）.The active Fe（Ⅱ） probably coupled to the transformation of NO_3^-and SO_4^（2-）,and thus accelerated the removal of NO_3^-and SO_4^（2-）.