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A novel system for removing toluene, p-xylene, and ethylene was developed that combines a biotrickling filtration system with a nonthermal plasma reactor. The limitations of an individual biotrickling filter for treating slowly biodegradable volatile organic compound (VOC) gases with high concentrations were thereby avoided. Performance for removing toluene, p-xylene, and ethylene of a biotrickling filter and a plasma reactor was investigated at a variety of flow rates and inlet concentrations of the test gases. The biotrickling filter was exposed to toluene gas only for over 1 month, to cultivate specific micro-organisms. Biofiltration treatment removed toluene more efficiently than p-xylene and ethylene. However, the nonthermal plasma removed ethylene more effectively than p-xylene and toluene, due to the fact that ethylene has a weak π bond. For the case of the plasma-pretreated biotrickling system, the efficiency with which toluene, p-xylene, and ethylene were removed was 95.2 ± 0.1%, 95.8 ± 0.2%, and 81.3 ± 0.8%, respectively, at an inlet concentration of 116.5, 132.4, and 127.5 ppm and gas flow rate of 20 L/min. Results obtained showed that the performance of the combination system of nonthermal plasma and biotrickling filter was much better than the stand-alone biotrickling filter for removing p-xylene and ethylene (improvements of 28.0 ± 2.0%, and 29.7 ± 1.95%, respectively), while it was a little better for removing toluene (improvement of 5.3 ± 4.0%). Results suggest that a combined nonthermal plasma/biofiltration system can be used effectively to remove slowly biodegradable pollutants with high concentrations that are different from the gases that were used to cultivate the micro-organisms. [ABSTRACT FROM AUTHOR]