Laboratory experiments were conducted to evaluate the potential to utilize ultraviolet (UV) photooxidation as a pre-treatment to render recalcitrant volatile organic compounds into more biodegradable compounds. α-Pinene was selected due to its low water solubility and low biodegradability. α-Pinene-contaminated gaseous streams with inlet loadings between 250 and 2500 g m −3 h −1 were passed through an annular reactor equipped with a UV lamp that emitted light at 254 nm and 185 nm wavelengths. The outlet stream containing UV photooxidation intermediates was then sparged through nanopure water that was then analyzed for its total organic carbon (TOC) content and subjected to batch biodegradability tests. UV photooxidation effectively degraded α-pinene with a maximum removal rate of about 700 g m −3 h −1 . The removal rate followed first order kinetics at low inlet loadings (less than 1200 g m −3 h −1 ) and approached zero order behavior at higher inlet loadings. The principal oxidizing species in the reactor was ozone. Of the total α-pinene removed, measured as TOC, 50% was converted to water-soluble and more biodegradable intermediates. The biodegradability of the resultant intermediates was similar to that of methyl ethyl ketone (MEK), which is 3-30 times more biodegradable than α-pinene. These results show that the use of UV photooxidation is a promising and effective pre-treatment technique for enhancing the biodegradability of hydrophobic and recalcitrant organic compounds such as α-pinene.

Ultraviolet (UV) photolysis was evaluated as a technique to convert recalcitrant aromatic volatile organic compounds (VOCs) into more biodegradable compounds. o-Xylene was investigated as the model compound due to its low biodegradability and low water solubility. o-Xylene contaminated gaseous streams with inlet loadings of up to 2700 g·m–3·h–1 were passed through an annular photoreactor equipped with a UV source emitting light at 254 nm and 185 nm wavelengths. Ultraviolet photolysis effectively degraded o-xylene at a maximum removal rate of about 700 g·m–3·h–1, with the principle oxidizing species being hydroxyl radical. Of the total o-xylene removed, measured as total organic carbon (TOC) or chemical oxygen demand (COD), between 30% and 50% was converted to water-soluble and more biodegradable intermediates. The biodegradability of the photolysis intermediates was comparable to that of methyl ethyl ketone (MEK), which is 2–10 times more biodegradable than o-xylene. These results show that the use of UV photolysis is a promising and effective pretreatment technique for enhancing the biodegradability of recalcitrant organic compounds such as aromatics. Key words: VOC, o-xylene, photolysis, biodegradation, air treatment, biofiltration, ozone, hydrogen peroxide.