渗滤液循环对填埋气体产生量影响的实验研究

以上海市生活垃圾组成为依据,通过填埋模拟柱实验研究了不同渗滤液循环方式对新鲜垃圾填埋层填埋气体(LFG)产生的影响.渗滤液循环方式包括:原液循环、厌氧预处理后循环、好氧预处理后循环、原液与陈垃圾柱出水混合后循环.结果表明,原液循环抑制了甲烷化进程,产气速率小,产气期分散.渗滤液经适当预处理后循环均能改善LFG的各项气量指标,表现为产气速率显著提高、产气期集中(本实验条件下约1a);Qt(实际累积产气量)增加,Q有效 Qt值(甲烷浓度大于50%的填埋气体量与实际累积产气量的比值)大于0 80,Qt Qp值(实际累积产气量与计算总产气量的比值)大于0 4.但渗滤液经不同预处理后循环对LFG各项气量指标的优化效果不同,排序为厌氧预处理后循环>原液与陈垃圾柱出水混合后循环>好氧预处理后循环.优化LFG各项气量指标的关键是:①缩短填埋层进入稳定的甲烷化阶段的时间;②减少垃圾中有机物的场外去除量.而渗滤液的预处理程度和方式对这两个因素有直接影响.

Effects of leachate recirculation on landfill gas production

Based on the typical MSW composition in Shanghai, lab-scale simulated landfill columns were used to study the effects of different leachate recirculation operations on landfill gas (LFG) production. Fresh leachate, pretreated leachate (anaerobic process or aerobic process), and leachate mixture (fresh leachate and leachate from a well-decomposed landfill) were recirculated to landfill columns respectively. The results indicated that the recirculation of leachate without any pretreatment inhibited methane fermentation, while the recirculation of leachate pretreated to some extent benefited to methane fermentation, in that it greatly improved the gas production rate, cumulative gas production Q_t, the ratio of Q_(eff)/Q_t (above 0.80, Q_(eff) means production of gas with methane concentration over 50%), and the ratio of Q_t/Q_p (above 0.40, Q_p means theoretic gas production), as well as shortened the gas production period into near one year. Different leachate pretreatment leaded to different effects, the descending sequence of effectiveness was anaerobic process, mixing with leachate with well-decomposed landfill, and aerobic process. Different leachate pretreatment processes and their treatment level were regarded to influence the methane fermentation and the amount of organic matter disposed ex situ, thus changing the production and quality of LFG.