Improving leachate quality and landfill gas production in pilot scale landfill bioreactors containing sewage sludge and geotextile biofilters

Abstract

In this study, three pilot scale reactors simulating anaerobic landfill bioreactors (R1, R2 and R3) were operated to improve leachate quality and landfill gas (LFG) production. For this purpose, the effect of sewage sludge co-disposal (at 1/20 weight ratio) and influence of geotextile biofilters on both LFG production and leachate quality was investigated. To improve the leachate quality, R2 consisted of a permeable geotextile biofilter in its drainage layer. Additionally, sewage sludge was added to R1 and R2 to improve the LFG production. Lastly, a control reactor, R3, was run without leachate recirculation similar to that of conventional landfills. All reactors were inoculated with 30 liters of anaerobic seed sludge. Temperature was maintained at 37 ºC to sustain mesophilic conditions inside the reactors. Quantity and composition of both leachate and LFG have been monitored for 540 days. LFG quantity, chemical oxygen demand (COD), 5-day biochemical oxygen demand (BOD5), pH, oxidation reduction potential (ORP), and other operating parameters were regularly monitored. Since there was not leachate recirculation in R3, leachate quality parameters were not evaluated in the control reactor. The final steady state pH values for all reactors were between 7.8 - 8.05. The final BOD5 and COD concentrations were 390 and 180 mg/L for R1 and R2 respectively. The BOD5 removal rates were 98% and 99% and the COD removal rates were 92% and 94% for R1 and R2, respectively. Though there was a negligible amount of LFG still being produced, at the end of the study, a total of 7504 L, 22408 L and 10901 L of LFG was produced for R1, R2 and R3 respectively. The highest cumulative LFG production was observed in R2, which consisted of sewage sludge mixed with municipal solid waste (MSW) and a geotextile biofilter in the drainage layer. © 2019 Elsevier B.V., All rights reserved.