Photocatalysis was investigated as a pretreatment for hydrocarbon groundwater contamination at an abandoned oil field in Guadalupe, CA. A laboratory photoreactor, with a UV fluorescent lamp submerged in a suspension of TiO2 catalyst particles, was used to determine oxidation rates and the increase in biodegradability of the hydrocarbon mixture. Chemical oxidation demand (COD) and 5-day biological oxygen demand (BOD5) were measured as a function of exposure time using standard methods. During eight-hour photoreactor runs in a nitrogen atmosphere, the COD of diluent solutions in de-ionized water and diluent solutions in simulated groundwater both decreased by approximately 50%, while the BOD5 increased by a factor of 2 to 3. The biodegradability quotient, BOD5/COD, increased from initial values of between 0.03 and 0.06 up to final values of between 0.27 and 0.29 during the eight-hour photoreactor runs. Little or no decrease in the chemical oxygen demand was observed in a control with no UV light and a control with no TiO2, confirming the role of photocatalysis in these experiments. Based on the experimental oxidation and biodegradation kinetics, design parameters for ex-situ and in-situ remediation applications are presented.
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