Potential of non-thermal plasmas for helping the biodegradation of volatile organic compounds (VOCs) released by waste management plants

This paper investigates the feasibility of exploiting a non-thermal plasma (NTP) to treat the gaseous effluents released by the mechanical-biological treatments (MBTs) of waste and overcome the typical disadvantages of biofilters, whose removal efficiency is limited during acclimatization of bacteria, peaks of pollutant concentration or unstable airflow rates. A dielectric barrier discharge was applied to two mixtures of volatile organic compounds (VOCs) and air. Ethanol and ethyl acetate (Mixture 1) and benzene, toluene and octane (Mixture 2), in addition to being typical constituents of the waste air released by MBTs of waste, also represent real emissions from two specific sectors that use biofiltration for air pollution control (APC): the printing (Mixture 1) and the petrochemical industries (Mixture 2). At the highest specific energy densities applied to the discharge (900-2520 J L-1), all the initial VOCs were removed by 95-100%. With respect to ethyl acetate, the maximal CO2 selectivity and the maximal energy yield resulted in 62-70% and 6-11 g kW-1 h-1, respectively; with regards to benzene, the same parameters resulted in 52-90% and 0.17-0.72 g kW-1 h-1, respectively. At medium-low energy, acetaldehyde and acetic acid were detected as the main byproducts of Mixture 1, while several trace compounds were found as the byproducts of Mixture 2. Interestingly, the byproducts generated are more polar than the initial compounds and, thus, their solubility in water is higher. Therefore, NTPs can be considered as a promising technology to help the biodegradation of VOCs in facilities where biofilters are used as APC systems.