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.