垃圾填埋场渗沥液击穿防渗系统的指示污染物研究

Investigation of indicating pollutant for landfill leachate breaking through anti-seepage system

中国垃圾填埋场渗沥液中的污染物种类繁多,成分复杂,污染物击穿填埋场防渗系统,造成地下水以及土壤污染已成为填埋场环境安全问题中最为关注的问题之一。目前以什么标准判断击穿,以何种污染物作为指示污染物计算击穿时间并评价防渗系统的防污性能尚不明确。针对这一问题,以中国6个典型填埋场内代表性污染物的平均浓度为初始浓度,以中国相关环境标准中规定的各类污染物极限浓度作为污染浓度,建立污染物在复合防渗系统中的一维对流–弥散有限元模型。通过计算各类污染物在填埋场防渗系统中的击穿规律和击穿时间发现,相比重金属和持久性有机污染物,有机污染物(COD)最早击穿防渗系统,有机污染物(COD)可作为判定击穿的指示污染物,击穿HDPE土工膜单层和双层复合垫层的时间分别为84.2 a和122.6 a;而击穿时间主要受污染物的初始浓度、规定的污染浓度和污染物的迁移弥散参数共同影响。这一结果可为填埋场防渗系统击穿时间的计算和防污性能的评价提供参考。

The leachate of the landfills in China consists of different pollutants and has complex composition. Breaking through anti-seepage system and contaminating the underground water and soil by pollutants have become the concern of environmental safety for landfills. However, the criteria of breakthrough and the indicating pollutant used to calculate the time of breakthrough and evaluate the performance of the anti-seepage system are not clear. To solve this problem, based on the concentration of average pollutants in six typical landfills in China and the limit concentrations for different pollutants in environmental standards, one-dimensional advection-dispersion finite element models are established. Compared with heavy metals and persistent organic pollutants（POPs）, COD breaks through the anti-seepage system first, and it can be regarded as the indicating pollutant to determine the breakthrough time. The time of breaking through the single and double HDPE composite liners is 84.2 years and 122.6 years. The breakthrough time is influenced by the initial pollutant concentration, limit pollutant concentration and parameters of pollutant migration together. The results can be a reference for calculating the breakthrough time and evaluating the performance of the anti-seepage system.