Korshin, Gregory VRifkin, Gabriel2021-07-072021-07-072021Rifkin_washington_0250O_22568.pdfhttp://hdl.handle.net/1773/47027Thesis (Master's)--University of Washington, 2021Landfills are commonly used to store municipal solid waste. Leachate is produced within these landfills through infiltration of water and landfill gas (LFG) is produced through anaerobic decomposition of organic material. The composition of both leachate and LFG is influenced by factors such as precipitation, temperature, refuse type and others. At Cedar Hills Regional Landfill (CHRLF) in Washington State, the leachate and LFG condensates have been shown to have elevated levels of arsenic, a highly toxic and carcinogenic compound that needs to be removed. Arsenic chemistry within the landfill, which provides a reductive environment, is complex but the presence of arsenic in LFG condensates indicate the prominent role of methylation pathways and ensuing formation of volatile arsines. This thesis focused on two different but related aspects of arsenic contamination at CHRLF. First, it evaluated the efficacy of microelectrolysis (ME) technology to remove arsenic from landfill leachate and especially from LFG condensate, as sufficient arsenic removal through conventional treatment was deemed not possible. ME uses zero-valent iron (ZVI) combined with activated carbon in an electrolytic solution to form galvanic cells that reduce and/or immobilize arsenic. Second, this thesis focused on the quantification and mobilization of arsenic in spent LFG treatment solids used by BioEnergy Washington (BEW), an on-site gas refinery company that has historically disposed of the solids in CHRLF. In this study, fixed bed columns were utilized to treat leachate and LFG condensate samples from CHRLF. The columns were packed with ZVI and carbon media to perform ME treatment, and numerous other media were tested to determine possible pre-treatment steps. Permanganate oxidation, zeolite and perlite adsorption pre-treatment methods did not result in improved arsenic removal. Fixed bed columns using microelectrolysis technology were often able to remove >90% of arsenic for a relatively limited number of bed volumes. However, results were inconsistent and further experimentation is required to determine if this treatment scheme can remove As from these matrices in a cost-effective manner. Spent LFG treatment solids were exposed under conditions understood to regulate arsenic mobilization in the landfill. Analytical data indicated that arsenic and co-occurring contaminants are mobilizable, especially under reducing conditions. Environmental conditions such as redox potential, temperature, mass dose and particle size have observable implications on the re-release of toxic compounds into landfill sites. Further experiments are required to better understand this phenomenon and ultimately to improve LFG processing and landfilling operations so as to decrease the risks of increased As mobility potentially associated with landfill gas treatment for renewable energy.application/pdfen-USCC BY-NCarsenicgas treatment solidsLandfillLandfill gas condensateLeachatemicroelectrolysisEnvironmental engineeringEnvironmental managementCivil engineeringCivil engineeringThesis