Removal of volatile organic compounds in a pilot-scale biocover installed in a municipal waste landfill

Abstract

A pilot-scale biocover was installed at a sanitary landfill for municipal waste, and the removal of volatile organic compounds (VOCs) by the biocover was evaluated for a long period of 550 days. The biocover (2.5 m W × 5 m L × 1 m H) was constructed with the mixture of soil, perlite, earthworm cast and compost (6:2:1:1, v/v). The total VOCs concentration of the inlet gas into the biocover was 820.3 ppb~7,217.9 ppb, and the total VOCs concentration of the outlet gas from the surface of the biocover was 12.6 ppb~1,270.1 ppb. The average removal efficiency of total VOCs was 87.6 ± 11.0% (60.5% for minimum and 98.5% for maximum). Toluene concentration was the highest among the inlet VOCs, followed by ethylbenzene, m, p-xylene and o-xylene. These aromatic VOCs accounted for more than 50% of the total VOCs concentration. Other than these aromatic VOCs, hexane, cyclohexane, heptane, benzene, and acetone were major VOCs among the inlet VOCs. Compared with the VOC profiles in the inlet gas, the relative contribution of dichloromethane to the outlet VOCs emitted from the biocover layer increased from 0.1% to 15.3%. The average removal efficiencies of BTEX in the biocover were over 84% during the operation period of 550 days. The average removal efficiencies of hexane, cyclohexane and heptane in the biocover were 86.0 ± 18.9%, 85.4 ± 20.4% and 97.1 ± 4.0%, respectively. The removal efficiency of VOCs in the biocover decreased not only when the ambient temperature had fallen below 5oC, but also when the ambient temperature had risen above 23oC. Information on the VOCs removal characteristics of the biocover installed in the landfill field can be useful for commercializing the biocover technology for the treatment of VOCs.