Biofiltration of methane in presence of ethylbenzene or xylene

Abstract

Landfill gases (LFGs) are gaseous emissions containing several harmful compounds such as volatile organic compounds (VOCs), volatile inorganic compounds (VICs) along with methane (CH4) which is a powerful greenhouse gas. In the case of small or older landfills, disposal of LFG can be economically challenging, and a possible solution is biofiltration. Biofiltration of CH4 in the presence of two VOCs was studied, ethylbenzene (EB) for biofilter 1 (BF1) and xylene (X) for biofilter 2 (BF2). Both biofilters were packed with inorganic packing materials and operated with an empty bed residence time (EBRT) of 4.5 min. Methane concentrations varied from 2000 to 10,000 ppmv along with 2 concentrations for both VOCs i.e., 200 and 500 ppmv. In the case of individual VOC's removal, the acclimation period of the microorganisms to EB and X were close to 30 days, indicating a similar adaptation period for X and EB. The addition of CH4 under low inlet concentration of 2000 ppmv had minor effect on VOCs biodegradation such that the average VOC removal efficiencies (REs) remained above 85% for VOC inlet concentrations of 200 ppmv while the average CH4-RE were around 56% in both biofilters. When CH4 inlet concentration increased up to 10,000 ppmv, inhibition became an issue for all VOC concentrations and dropped VOC and CH4-REs down to 80% of their original values. The type and concentration of the VOC played a key role in the intensity of the inhibition. In general, mass transfer was controlling the elimination of the three substrates.