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随着我国城市化进程加快,土壤及地下水污染问题日益突出,对人群健康、生态环境造成严重威胁,污染修复工作亟需大力推进[1]。目前,针对土壤重金属污染修复技术主要包括固定化/稳定化技术、土壤淋洗技术、电动修复技术、植物修复技术、微生物修复技术以及联合修复技术等[1-2]。其中,固定化/稳定化技术作为一种热门修复技术,常与安全填埋技术联合使用,固定化/稳定化技术修复后的重金属污染土壤,经鉴定为固体废物后可进行填埋处理。由于固废填埋渗滤液中污染物浓度高、毒性大、水量水质波动大、暴露风险大等特点[3-4],对周边地表水和地下水具有潜在威胁,渗滤液处理是固体废物安全填埋的核心问题和重要保障[5],常见的固废填埋渗滤液处理技术主要有生物处理技术、物理化学处理技术和土地处理技术[4-6]。
可渗透性反应墙 (permeable reactive barrier, PRB) 技术是一种经济、简易、高效、可持续、二次污染少的原位被动修复技术[7-10]。1998年美国环保署 (EPA) 发行《污染修复的PRB技术》手册定义该技术为:在地下安装填充有活性反应材料的墙体拦截污染羽,污染物与活性材料发生降解、吸附、沉淀、氧化还原等反应而被去除,使污染物浓度达到环境标准值[11]。近年来,PRB技术可用于修复有机、石油类、重金属类污染地下水等[12-15],已成为了国内外污染修复领域中的研究热点[16-17]。例如钱程等[18]利用PRB技术修复含有多种重金属、有机、氨氮等污染物的地下水发现均具有良好的去除效果;沈前等[19]在岳阳市桃林铅锌矿区创建了地下水PRB示范基地。国内相关研究也论证了PRB技术治理污染垃圾渗滤液的可行性和有效性。例如崔海炜等[20]对PRB技术治理垃圾渗滤液污染地下水进行了实验模拟研究,狄军贞等[21]构建三重垂直流PRB强化砂箱模型对垃圾渗滤液进行连续动态处理研究。但是,目前针对PRB技术修复固废填埋场渗滤液的研究及工程应用却鲜有报道。由于固废填埋场渗滤液性质与污染地下水、垃圾渗滤液有一定相似性,综合了垃圾渗滤液集中收集、污染羽小,以及污染地下水的污染类型稳定、有机质含量少等特质,使得PRB技术修复固废填埋场渗滤液具备可行性、且预计修复效果良好。
本研究以固废填埋场渗滤液为研究对象,通过PRB反应介质筛选,开展静态批实验和动态柱实验;同时,经PRB结构设计、工程施工及运行监测等工程实践工作,拟论证PRB技术原位处理固废填埋场渗滤液的可行性和有效性。本研究拟为PRB技术处理固废填埋场渗滤液的研究和实践提供参考,并拓宽PRB技术在环境修复领域的应用范围。
Application of permeable reactive barrier technology in treatment of solid waste landfill leachate
- Received Date: 05/09/2022
- Available Online: 26/02/2023
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Key words:
- permeable reactive barrier /
- heavy metal /
- solid waste landfill /
- leachate /
- in-situ treatment
Abstract: Percolation reactive wall (PRB) is an efficient, energy-saving, green and sustainable in-situ remediation technology, which can effectively treat landfill leachate and contaminated groundwater. Due to the similar properties of solid waste landfill leachate, PRB technology can also be applied to in-situ treatment of solid waste landfill leachate. In this study, the leachate produced by safe landfill after solidification/stabilization of heavy metal contaminated soil was taken as the research object. The PRB reaction medium was screened by preliminary investigation, static batch experiment and dynamic column experiment were used to evaluate the repair effect of reaction medium. At the same time, the feasibility of treating leachate by PRB technology was verified by engineering practice such as PRB design, construction and operation monitoring. The results show that when hematite: limestone = 2:1 and the reaction time was 12 h, the adsorption capacities of Ni, As and Sb reached 499.31 mg·kg−1, 494.32 mg·kg−1 and 18.63 mg·kg−1, respectively. When the reaction medium was used as the filling material for column experiment, the concentration of As and Sb in 0~28 d was far lower than the target value, and the concentration of Ni reached the standard within 0~14 d, and then the concentration increased sharply after 21 d to penetrate the PRB column. In this project, the above material was used to fill the permeable reactive barrier, and the PRB was integrated with leachate collection tank, the thickness of the barrier is 1.5 m. In the early stage of the project operation, after 3 months after the PRB construction, the pollutant data of the monitoring wells in the field reached the groundwater IV standard, and the pollutant data of the downstream monitoring wells had no change, so the project did not cause secondary pollution. Therefore, PRB is a feasible, effective and economical remediation technology to treat solid waste landfill leachate, and has good green sustainability and broad application prospect.