压力对填埋垃圾产甲烷的影响研究

Effect of compression on methane production from landfilled municipal solid waste

压实作用被认为是影响填埋垃圾降解过程的一个重要因素,实验通过自制的压缩降解模拟填埋反应器装置,研究了阶梯增加式压力21k Pa→42 k Pa→84 k Pa(分别在垃圾填埋后的第75、103和131 d时施加)对填埋垃圾产甲烷这一资源化重要阶段的影响,包括产气特性、渗滤液性质及固体沉降等的变化.21 k Pa和42 k Pa分别恒定了4周,垃圾最后在84 k Pa恒定压力下降解,实验总共持续了170 d.结果表明,在初始21k Pa的压力作用下,由于接种物跟垃圾接触面积的增大,甲烷日产量从第75 d的1.85 L·d-1增加到了第76 d的2.95 L·d-1,产甲烷速率提高了59.82%,42 k Pa和84 k Pa时均有所增加,但增加程度均不明显.压力还使砾石层上部积留了一定水位高度的渗滤液,渗滤液的COD和含氮量在压力作用下都有了暂时的升高.压实作用还令垃圾体产生了较大的沉降,但压力进一步增大并没有使垃圾继续发生较多的沉降.实验结果有助于更好地了解压力对填埋垃圾降解过程的影响.

In this study,the impact of compression on methanogenic degradation of municipal solid waste（ MSW） was investigated using a simulated landfill bioreactor equipped with a hydraulic compaction device. Three pressure loads,21,42,and 84 k Pa,were applied by one to another. The first pressure load was applied on day 75 and maintained for about 4 weeks,and then 42 k Pa was applied for another 4 weeks,and lastly 84 k Pa was used. The results showed that methane production rate was improved by the compaction of MSW. When the first pressure load was applied,daily methane generation rate increased up to 59.82% temporally from 1.85 L·d-1（ 75thday） to 2.95 L·d-1（ 76thday）. It was thought that MSW compaction increased the contact areas between methanogenic and acidogenic sites of MSW lumps. However,the increases of methane generation rate by applying higher pressure loads（ 42 k Pa and 84 k Pa） were insignificant. The compression resulted in leachate ponded on upper layer gravel,and COD and nitrogen concentrations of leachate also temporally increased. MSW settlement occurred considerably due to the compaction. However the settlement variation by increasing pressure load was small. The research results demonstrate the positive effect of compaction on MSW decomposition in methanogenic phase. The findings in this study can improve understanding of MSW degradation under compacted conditions.