Permeable Reactive Barriers for In-Situ Treatment of Arsenic-Contaminated Groundwater

摘要

Many areas around the world are under increasing pressure to protect local inhabitants from arsenic in groundwater. Arsenic (As) is a toxic metal that commonly occurs in groundwater as a result of natural processes and anthropogenic activities. Laboratory and field research has shown that permeable reactive barriers (PRBs) containing a variety of materials can treat As contaminated groundwater. Since 2002 we have been evaluating the performance of several PRBs installed at industrial sites in Canada and USA for the treatment of As-contaminated groundwater. The sites where these PRBs are located include a mine tailings facility, fertilizer and chemical manufacturing sites, a thermal-electric power generation facility and an electrical trans- mission site. The reactive material in these PRBs includes mixtures based on zero valent iron (ZVI) filings with or without an organic carbon (OC) source such as wood chips or compost or alternatively, basic oxygen furnace slag (BOFS). Removal of As to below drinking water limits (currently 0.05 mg/L Canada; 0.01 mg/L mandate in USA effective January 23, 2006) has been observed in all of these PRBs. The PRBs range from test scale a few meters long to 600 m long. Although the reactive materials in each PRB (except BOFS) are similar, there is significant diversity in the groundwater geochemistry and flow conditions encountered by each of the PRBs. Despite this diversity, groundwater geochemical monitoring at these sites indicates that two or more years after installation, removal of As is still occurring in all of the PRBs, and there is no indication that the level of treatment is diminishing.