Continued optimization of a microelectrolysis treatment process for removal of arsenic from landfill gas condensate, characterization of materials, and evaluation of Fe as a predictor of treatment monitoring

Abstract

Landfill gas condensate is formed during landfill gas (LFG) purification that must be carried out to produce pipeline-quality renewable natural gas. LFG condensates (LGC) are known to contain high levels of arsenic whose presence may result in exceeding applicable discharge limits. Arsenic speciation in LGC is dominated by organo-As compounds that are difficult or impossible to remove by conventional methods. This difficulty may be circumvented via microelectrolysis (ME) treatment that uses a combination of zero-valent iron (ZVI) and granular activated carbon (GAC). This study compared the performance of alternative types of ZVI/GAC media and examined effects of other treatment variables including pH, agitation methods, and media cycling. This study also addressed the significance of iron release as a treatment indicator. Experimental results showed the ME treatment reliably removes up to >90% of arsenic from LGC in several consecutive treatment cycles. Release of dissolved iron from the treatment media tends to be correlated with arsenic removal and the quantification of iron release in ME treatment may be a suitable option to monitor the efficiency of arsenic removal in field conditions.