Biological mitigation of methane in presence of xylene and ethylbenzene in biofilters: Effect of pollutants concentrations and empty bed residence time

Abstract

Landfill gas emissions cause serious environmental concerns due to the presence of methane (CH4), an important greenhouse gas (GHG) and several harmful volatile organic compounds (VOCs) such as xylene (X) and ethylbenzene (EB). A series of 9 up-flow biofilters (3 sections of 0.3 m each) packed with inorganic materials were used to eliminate CH4 as a single pollutant, a binary mixture of X and EB and a ternary mixture of CH4, X and EB. The CH4 concentration range was 2000–10000 ppmv while the VOCs (X and EB) individual concentrations were 200, 400 and 600 ppmv for empty bed residence times (EBRTs) ranging from 2.25 to 9 min over a period of 242 days. The highest CH4 removal efficiency (RE) in the ternary mixture was 41 ± 3% at a CH4 concentration of 2000 ppmv and X and EB individual concentrations of 200 ppmv for an EBRT of 9 min. Meanwhile, the highest X and EB-REs of 58 ± 3 and 57 ± 3% were obtained respectively, at the same concentrations of the components but at a shorter EBRT of 4.5 min. Almost 40% of CH4 biodegradation took place on the top section of the bioreactor while 50–60% of the VOCs biodegradation occurred in the middle section.