Keywords: air pollution, volatile organic compounds, VOC, hydrophobic compounds, biofiltration, ultraviolet, photooxidation, UV photolysis, UV photocatalysis
Biofiltration of hydrophobic VOCs pretreated with UV photolysis and photocatalysis
The effects of pretreatments on the biofiltration of gas phase α-pinene, a poorly water soluble Volatile Organic Compound (VOC), was evaluated in a controlled and long-term experimental investigation. Ultraviolet (UV) photolysis and photocatalysis were used and compared as pretreatment techniques. A control experiment involving biofiltration alone allowed for the direct evaluation of the coupled UV-biofiltration. α-Pinene contaminated streams with flow rates of 5?6.5 l/min and concentrations of up to 130 ppmv were passed through the systems. UV pretreatment on average converted between 20 and 50% of α-pinene into water soluble intermediates. When comparing the effectiveness of each pretreatment process, UV photocatalysis provided greater α-pinene conversion, especially at low retention times and high contaminant loading. The untreated α-pinene along with the by-products of UV photooxidation was then removed effectively in the biofiltration stage. The UV-biofiltration process offered 50?80% more α-pinene removal compared to the control biofilter. Regardless of their effectiveness at removing the contaminant, photolysis and photocatalysis pretreatments had similar synergistic impact on the performance of the downstream biofilter.