填埋垃圾初始含水率对渗滤液产量的影响及修正渗滤液产量计算公式

我国填埋场设计阶段,渗滤液产量计算结果往往偏小.参照山谷型填埋场,建立了一个长400 m,宽500 m的水量平衡计算模型,模型中垃圾体高50 m,分5个填埋阶段,每阶段填高10 m,用时2 a,共填埋10 a.利用该模型,分阶段计算填埋垃圾初始含水率对渗滤液来源组成和总产量的影响.渗滤液总产量由降雨入渗量和垃圾自身渗滤液产量组成,初始含水率越高,垃圾自身渗滤液产量和渗滤液总产量越大,垃圾自身渗滤液产量所占渗滤液总产量的比例也越高.当填埋垃圾初始含水率分别为27%、40%、50%和60%时,日平均渗滤液总产量分别为272、583、823和1 063 m3.d-1,垃圾自身渗滤液产量分别为-144、168、408和647 m3.d-1.垃圾初始含水率高于50%时,自身渗滤液产量占渗滤液总产量的比例超过50%,成为渗滤液总产量的主要部分.目前中国规范中采用的渗滤液产量计算方法,未考虑垃圾自身渗滤液产量,当填埋垃圾初始含水率较高时,计算结果偏小.基于上述水量平衡分析结果,进一步提出了包括垃圾自身渗滤液产量的修正计算公式,并通过2个大型中国南方填埋场的现场实测数据进行了验证.

Impacts of Initial Moisture Content of MSW Waste on Leachate Generation and Modified Formula for Predicting Leachate Generation

The amount of leachate generation rate in MSW landfills is often underestimated during design phase in China. A water balance model of a valley landfill, whose size is 400 m long, 500 m wide and 50 m thick, is created to investigate the influences of initial moisture content of waste on source and production of leachate. The 50 m thick waste mass is assumed to be 5 layers. Each layer is 10 m thick with a filling period of 2 years. The leachate mainly comes from precipitation and from squeezed pore water of waste. It is found that higher initial moisture content of waste leads to higher amounts of squeezed leachate and total leachate generation rate, and also results in a high ratio of squeezed leachate to total leachate generation rate. For the cases that the initial moisture contents of waste are 27%, 40%, 50%, and 60%, the amounts of total leachate generation rate are 272, 583, 823 and 1063 m³·d^-1, respectively, and the amounts of squeezed leachate are -144, 168, 408, and 647 m³·d^-1, respectively. It is also found that when the initial moisture content of waste is greater than 50%, the squeezed leachate becomes the primary source of total leachate generation rate. However, the formula for predicting leachate generation rate used in the national code could not consider the contribution of squeezed leachate, this may cause a significant underestimation of leachate generation rate for the case having a high initial moisture content of waste. Based on the water balance analyses, a modified formula for predicting leachate generation rate, which includes the contribution of squeezed leachate is proposed. It is verified by consideration of the operational practices of two large-scale landfills in southern China.