Biofiltration combined with non-thermal plasma for air pollution control: A preliminary investigation

Biological technologies have been often employed to remove volatile organic compounds (VOCs) at low concentrations from air streams. However, biodegradation is very sensitive to variations of inlet concentrations and flow rate that usually occurs in real industrial processes; furthermore, an acclimation period is required by microorganisms to adapt to new conditions of flow rate and concentration. A possible solution to overcome these issues is represented by a pre-treatment with non-thermal plasma (NTP). The synergy between an NTP reactor and a biofilter in removing a mixture of VOCs from air is the object of this paper. A mixture of five VOCs (benzene, ethylbenzene, p-xylene, n-heptane and toluene) and humid air was chosen to represent the gaseous effluent stripped from an industrial wastewater treatment plant. A sudden increase in the VOC concentrations was intentionally induced to understand if NTP can manage peaks of the inlet concentration of pollutants and help the biodegradation carried out in the biofilter. NTP revealed to be capable of both pre-treating concentrations peaks and converting the initial VOCs in more soluble compounds; in conclusion, NTP is able to help biodegradation, allows controlling unsteady conditions and prevents stress to bacteria