填埋场原位注气好氧稳定化工程中的全域优先流效应

Field-scale preferential flow effect in landfill in-situ gas injection aerobic stabilization project

填埋场原位好氧稳定化技术是加速填埋场稳定化的重要技术。现有评估方法集中于对稳定化进程进行评估,而缺少对注气流量空间分布的估算与评价。通过分析浙江省温州市某简易填埋场好氧注气稳定化工程运行期间堆体内氧气、甲烷、二氧化碳原位监测数据,揭示了工程运行期间填埋气浓度存在时空分布不均的特征,提出利用气体浓度在线监测数据估算注气流量分布的方法,发现好氧稳定化的全域优先流效应。结果表明:1)堆体内氧气、二氧化碳、甲烷存在较高的空间异质性,氧气浓度与甲烷、二氧化碳浓度呈显著负相关。2)该填埋场注气稳定化过程中,流量最小的23%面积区域仅通过总流量的1.3%,90%的区域通过流量为总流量的47%,余下10%面积通过总流量的53%,不均匀性的基尼系数达0.594,存在严重的全域优先流效应。堆体渗流性质差异是造成该问题的原因,注气不均可能导致注气效率下降、温室气体排放量增加、能耗增加。提出在稳定化工程开展前、进行中、监测保障阶段的措施建议,可根据气体渗透系数开展分区分时注气。

Landfill in-situ aerobic stabilization is a crucial technology for accelerating the stabilization of landfills.Existing evaluation methods focus on assessing the stabilization process but lack estimation and evaluation of the spatial distribution of gas injection flow rate.By analyzing the on-site monitoring data of oxygen,methane,and carbon dioxide from an aerobic stabilization project at a basic landfill in Wenzhou,Zhejiang Province,uneven spatial and temporal distributions of gas concentrations within the landfill pile during the operation period were revealed.A method to estimate the gas flow distribution using real-time gas concentration data was proposed to uncover the field-scale preferential flow effect of landfill aerobic stabilization.The results showed:(1) Spatial heterogeneity was observed in the distribution of oxygen,methane,and carbon dioxide within the landfill pile.Oxygen levels were significantly negatively correlated with methane and carbon dioxide levels.(2) During the landfill aerobic stabilization process,23% of the total area with the lowest flow rate had a flow rate accounting for merely 1.3% of the total flow,whereas 90% of the area contributed to 47% of the total flow.The remaining 10% of the area accounted for 53% of the total flow,resulting in an unevenness represented by a Gini coefficient of 0.594,indicating a severe field-scale preferential flow effect.The study suggested that differences in the permeability properties of the landfill body were the cause of this issue.Uneven aeration could lead to a reduction in aeration efficiency and an increase in greenhouse gas emissions and energy consumption.Measures and suggestions were proposed for the pre-operation,operation,and monitoring and maintenance phases of the stabilization project,recommending zonal and temporal gas injection based on the gas permeability coefficient.