某Cr（Ⅵ）污染场地修复的PRB反应材料及结构设计研究

渗透反应格栅(permeable reactive barrier,PRB)在国外被广泛应用于场地尺度的地下水污染修复,因其无须外源动力、不占地面空间、运行成本低等优势在国内受到广泛关注。不同场地水文地质条件、污染物类型、污染羽分布具有差异性,前期场地调查、反应材料的筛选、反应墙尺寸结构的设计对于PRB的有效运行至关重要。本文以PRB修复河南某Cr(Ⅵ)污染场地为例,详细阐述场地调查、材料筛选、材料反应参数确定、PRB结构优化等方面的研究过程及成果,可为后续PRB修复技术的应用提供参考。研究结果表明:PRB修复技术适用于该场地,铸铁与活性炭混合材料为最佳修复材料;反应门长40m(反应材料厚2m,上下游分别为2m厚砾石层),东西两侧隔水墙长为60m的U型漏斗门系统型PRB,可有效捕获并修复污染羽,工程成本远低于连续反应墙式PRB,为该场地修复最优PRB结构类型。     

中试尺度下可渗透反应墙位置优化模拟——以铬污染地下水场地为例

可渗透反应墙（PRB）是一种高效的地下水污染原位修复技术。不同水文地质条件下，污染场地墙体位置布设合理性影响其修复效果，而利用地下水数值模拟可实现墙体位置优化。文章以某Cr6+污染地下水场地为例，基于Visual Modflow建立了研究区平面二维稳定流数值模型，并通过模型检验。根据墙体的设计尺寸（长20 m×宽2 m×深12 m）及填充材料的渗透系数（80 m/d），利用所建模型分别计算了4种布设方案（墙体尺寸大小和填充材料渗透系数相同，布设位置不同）下墙体的捕获区宽度、粒子滞留时间和通过墙体的Cr6+通量。结果表明:4种布设方案模拟的滞留时间和捕获区宽度取值差异性不大，变异系数小于2%；Cr6+通量差别较大，变异系数高达76.32%，主要由地下水中Cr6+浓度空间分布不均引起。对比分析4种方案的各评价指标，方案2求得的捕获区宽度为21.9 m，粒子滞留时间为4.1 d，Cr6+去除量可达127.7 mg/d，可作为最佳布设方案。本研究建立的地下水流数值模型符合场地实际情况，可有效评估PRB截获污染羽的范围和去除目标污染物的能力，为铬渣类污染场地PRB原位修复工程设计与实施提供技术支撑和参考依据。     

污染地下水原位处理PRB技术研究进展

系统介绍了一种新型地下水污染治理技术,PRB（可渗透反应墙）技术。阐述了PRB的类型、活性材料的选取、反应机理、PRB的构建、应用实例以及存在问题等。并展望了其今后还需深入研究的方向。认为其是一种非常有发展前景的环境污染修复技术。这将为在我国开展该方法的研究和应用打下基础。     

铬污染地下水的PRB反应介质筛选及修复试验

通过实验研究筛选出一种经济可行的用于修复Cr(Ⅵ)污染地下水的PRB反应介质。实验以Cr(Ⅵ)污染地下水为研究对象,选用MB、Fe0、粉煤灰和活性炭4种材料进行PRB介质筛选的静态实验,选取处理效果好且经济的MB作为PRB反应介质进行动态修复实验。结果表明:以MB作为PRB反应介质可以使Cr(Ⅵ)的质量浓度从0.50 mg/L降低到0.05 mg/L以下,达到地下水水质Ⅲ类标准;且MB具有吸附量大、固液分离容易、无解吸、无二次污染等优点。以MB作为PRB反应介质修复Cr(Ⅵ)污染的地下水是可行的。     

矿物介质材料在渗透反应格栅技术中的应用研究进展

渗透反应格栅(Permeable Reactive Barrier, PRB)技术是一种有效、实用的地下水原位修复技术,反应介质材料是PRB技术的核心。鉴于传统铁基介质材料在PRB运行中存在易氧化、堵塞的问题,本文围绕3大类典型矿物材料(含铁矿物、孔道/层状结构矿物和磷灰石),结合其晶体结构特点,介绍了它们作为PRB介质材料的原理及应用研究进展,并进一步讨论了目前相关研究的局限及未来发展的重点方向。     

棕地地下水污染修复技术筛选方法研究——以某废弃化工厂污染场地为例

科学合理的地下水污染修复技术筛选方法对于有效修复受污染地下水体、节约修复工程成本、保护地下水资源、维护生态系统安全和人体健康具有重要意义。以某化工厂遗址早期排污渗坑为目标污染源,在结合水文地质勘查和地下水人体健康风险评价的基础上确定场地受污染地下水修复目标污染物,根据污染物迁移性、降解性、人体健康风险等指标及抽出处理、化学修复、生物修复、渗透反应格栅等地下水污染修复技术特点,使用偏好顺序结构评估法(PROMETHEE)进行修复技术筛选。结果显示,该场地地下水中主要污染物为1,2-二氯乙烷、1,4-二氯苯等有机污染物,其中1,2-二氯乙烷在呼吸吸入条件下的最大致癌风险达9.54×10-7。化学清除、监测自然衰减等四项技术适用于该场地地下水1,2-二氯乙烷修复,化学清除法综合排序分值最高,而在成本优先控制条件下,监测自然衰减技术更为适宜。研究对于我国场地地下水污染调查评估及修复工作具有积极的参考意义。     

铬污染土壤和地下水的修复技术研究进展

上海20世纪70年代含铬废水排放量大,其中六价铬毒性大、溶解度高、迁移性强,极易随水淋溶污染地下水系统。开展高效、经济的土壤和地下水中铬污染修复方法的研究,具有重要的现实意义。本文系统地综述了铬污染场地修复技术现状,包括还原稳定、渗透反应墙、电动修复、生物修复等,重点探讨了上海地区污染深度大于4m的低渗透性的铬污染场地电动反应墙联合修复技术的发展趋势。     

青海海晏海北化工厂地下水Cr(Ⅵ)污染机理及治理方案

为研究青海省海晏县海北化工厂地下水Cr(Ⅵ)污染治理方案,在深入分析青海省海北化工厂一带环境水文地质条件、历年地下水及地表水环境Cr(Ⅵ)监测资料、地下水Cr(Ⅵ)点状污染源现状规模、污染羽空间展布特征以及地下水污染途径等的基础上,分析了海北化工厂地下水Cr(Ⅵ)污染地下水污染机理。基于此,从保护水环境的角度,经多方案比选,推荐可渗透反应墙(PRB)技术为修复治理海北化工厂Cr(Ⅵ)污染地下水的最佳方案。     

PRB技术在地下水污染修复中的研究进展

在综合分析可渗透反应墙（PRB）修复污染技术基础上,提出了存在问题及发展趋势,进而理出需通过深入研究,提高修复系统性能及其可行途径。预计在不远的将来,PRB处理工艺的持续性也同样会有大幅度改进和发展。     

岩溶型尾矿库渗滤液重金属污染防治技术研究进展

文章通过对岩溶型尾矿库渗滤液重金属污染防治技术相关方法进行研究,结果表明可渗透反应墙(PRB)处理污染地下水具有初期建设投资低、可以根据所要处理的污染物质灵活选择、运行期不需要能量供给而且处理设施不会占用宝贵的土地资源等显著优点,是岩溶型尾矿渗滤液治理方面最具发展前景的方法之一。     

Clamshell excavation of a permeable reactive barrier

Nowadays, permeable reactive barriers (PRB) are one of the most widespread techniques for the remediation of contaminated aquifers. Over the past 10 years, the use of iron-based PRBs has evolved from innovative to accepted standard practice for the treatment of a variety of groundwater contaminants (ITRC in: Permeable reactive barriers: lessons learned/new directions. The Interstate Technology and Regulatory Council, Permeable Reactive Barriers Team 2005). Although, a variety of excavation methods have been developed, backhoe excavators are often used for the construction of PRBs. The aim of this study is to describe the emplacement of a full-scale PRB and the benefits deriving from the use of a crawler crane equipped with a hydraulic grab (also known as clamshell excavator) in the excavation phases. The studied PRB was designed to remediate a chlorinated hydrocarbons plume at an old industrial landfill site, in Avigliana, near the city of Torino, in Italy. The continuous reactive barrier was designed to be 120 m long, 13 m deep, and 0.6 m thick. The installation of the barrier was accomplished using a clamshell for the excavation of the trench and a guar-gum slurry to support the walls. The performance of this technique was outstanding and allowed the installation of the PRB in 7 days. The degree of precision of the excavation was very high because of the intrinsic characteristics of this excavation tool and of the use of a concrete curb to guide the hydraulic grab. Moreover, the adopted technique permitted a saving of bioslurry thus minimizing the amount of biocide required.     

可渗透反应墙处理垃圾渗滤液的实验研究

文章以垃圾渗滤液为研究对象,分别用铁粉、改性膨润土、活性炭及其混合物为反应介质,设计4种不同介质配比的PRB反应器进行实验研究。结果表明,PRB对垃圾渗滤液有较好的处理效果,其中,以还原铁粉、改性膨润土为介质的反应器,对氨氮的去除效率最大为97.58%,以还原铁粉、活性炭为介质的反应器对COD的去除效率为84.87%,对总磷的去除效率最大为80%。     

混合PRB介质处理渗滤液污染地下水的可行性研究

反应介质的选择是可渗透反应墙(PRB)系统原位处理污染地下水的一个关键问题。本实验采用两种混合介质A(陶粒与活性炭的混合物)和B(沸石与活性炭的混合物),对修复被渗滤液污染的地下水的可行性进行了研究。结果表明,混合介质A和B对CODCr的平均去除率分别达到了71.8%和63.4%;对NH4 的平均去除率分别为13.5%和58.7%;对重金属的去除,反应介质B则优于A。因此,PRB反应介质的选择要根据污染物的性质而定。     

Long-term performance evaluation of zero-valent iron amended permeable reactive barriers for groundwater remediation – A mechanistic approach

Permeable reactive barriers (PRBs) are used for groundwater remediation at contaminated sites worldwide. This technology has been efficient at appropriate sites for treating organic and inorganic contaminants using zero-valent iron (ZVI) as a reductant and as a reactive material. Continued development of the technology over the years suggests that a robust understanding of PRB performance and the mechanisms involved is still lacking. Conflicting information in the scientific literature downplays the critical role of ZVI corrosion in the remediation of various organic and inorganic pollutants. Additionally, there is a lack of information on how different mechanisms act in tandem to affect ZVI-groundwater systems through time. In this review paper, we describe the underlying mechanisms of PRB performance and remove isolated misconceptions. We discuss the primary mechanisms of ZVI transformation and aging in PRBs and the role of iron corrosion products. We review numerous sites to reinforce our understanding of the interactions between groundwater contaminants and ZVI and the authigenic minerals that form within PRBs. Our findings show that ZVI corrosion products and mineral precipitates play critical roles in the long-term performance of PRBs by influencing the reactivity of ZVI. Pore occlusion by mineral precipitates occurs at the influent side of PRBs and is enhanced by dissolved oxygen and groundwater rich in dissolved solids and high alkalinity, which negatively impacts hydraulic conductivity, allowing contaminants to potentially bypass the treatment zone. Further development of site characterization tools and models is needed to support effective PRB designs for groundwater remediation.     

Large-diameter,non-pumped wells filled with reactive media for groundwater remediation

A groundwater flow and contaminant transport model was used to simulate arrays of non-pumped wells with reactive media for remediating contaminated groundwater. Each array featured a minimum number of wells, with identical diameter, capable of removing a contaminant plume within a hypothetical site. Simulated well diameters ranged from 0.25 m (similar to typical remediation wells) to 1.25 m (similar to large-diameter, bucket-augered wells). Both arrays occupied a linear transect located approximately 5 m downgradient of the front of a polluted enclave and oriented 90° to the hydraulic gradient. The minimum smallest diameter array contained 23 wells, whereas the minimum largest diameter array contained only four wells. Results of this study suggest that bucket-augering technology, adapted to install non-pumped wells with reactive media, may be an effective alternative for remediating contaminated groundwater in some environments.     

Permeable Reactive Barrier for Groundwater Pollution Remediation: An Review

As an in situ, simple and passive technology, Permeable Reactive Barrier (PRB) is becoming widely used in groundwater remediation. Based on its definition and development process, the development of PRB can be divided into two stages: The traditional zero-valent iron PRB before 2000 and the PRB composed of novel mixed media after 2000. With the rapid worsening of groundwater pollution, the increasing application of PRB and the rapid development of materials science, the development of PRB technology in future will be mainly focused on the investigation of mixed and novel media, the design of mixed PRBs, the combination of PRB technology with other remediation technology, and the long term monitoring and management of PRB projects.     

开封市垃圾场污染物运移模拟与控制

在对开封市某典型垃圾场进行野外调查的基础上,应用Visual Modflow建立了该垃圾场污染场地的水流和溶质运移耦合模型并进行数值模拟预测,预测了20年后该污染场地垃圾渗滤液污染羽运移范围、途径及方式等特点。模拟了应用防渗墙和抽水井两种方式控制地下水污染的措施和方案,并利用计算机模型对污染控制的效果进行了模拟分析。模拟结果表明,模拟初期污染羽覆盖了3个抽水井,污染羽前缘距离村庄688 m。模拟20年后污染羽已经覆盖了7个抽水井,其中浓度超标井有3口,污染羽前缘距离村庄605 m。建议在加强污染物监测的同时协助开展其他的污染控制措施,进一步控制污染羽的扩散。