Immobilization of arsenic and manganese

This study investigates the effectiveness of permeable reactive barriers (PRBs) using zero valent iron (ZVI) combined with sheep manure to remove arsenic (As) and manganese (Mn) from contaminated groundwater. A column test was conducted to assess the immobilization processes of As and Mn under different conditions. The results indicate that arsenic was predominantly immobilized via sorption and co-precipitation with iron-bearing minerals, and precipitated as FeAsO4, particularly in the presence of sulfate-reducing bacteria (SRB). The inoculated column achieved greater As immobilization than the sterilized column due to additional sulfide formation. In contrast, manganese removal was mainly through adsorption onto ZVI and to a lesser extent through carbonate precipitation, with higher effectiveness observed in the sterilized setting, likely due to the biodegradability of compost reducing its capacity for Mn2+ immobilization. This study concludes that combining sheep manure with ZVI in PRBs enhances the immobilization of arsenic compared to using ZVI alone.