Air emissions from the automobile manufacturing industry a bio-oxidation pilot study of paint emissions control
Bio•Reaction Industries (BRI) was contacted by Toyota to assess the abatement potential of an engineered bio-oxidation system (biofilter). The proposed intent of the pilot was to evaluate the effectiveness of biofiltration as available alternative to traditional VOC removal technology on an existing 3 stage wheel paint booth. A pilot unit consisting of a biotrickling filter and a separate biomatrix chamber with a common, biologically active, sump was prepped and transported to the site where it was connected to the exhaust system serving the paint booths. Over a five day period, adjustments were made to airflow (adjusting residence time) and sump water recirculation spray (biotrickling filter flow rate and biomatrix chamber timing) while monitoring the VOC inlet and outlet concentrations using a gas chromatograph equipped with a flame ionization detector (FID - Method 25A). Rapid acclimation of the system was noted, with destruction efficiency (Dre) exceeding 70% at the end of the start-up period. After 6 weeks of operation DRE remained in the 65 to 75% range with fluctuations corresponding to changes in operating temperature. The removal efficiency fluctuations were directly related to the ambient air temperatures of the paint booths 60 - 68°F (15.6 - 20°C) and the effect of ambient temperatures on the airflow in the temporary ducting system to the pilot, having a direct influence on the operating temperatures of the bio-oxidation unit. Subsequent installation of a heating system produced consistent DRE’s exceeding 75% that varied little during the duration of the pilot test. With an empty bed residence time (EBRT) varying from 15-35 seconds and operating at a consistent temperature the pilot unit achieved consistent VOC DRE greater than 85%. Limited speciation of inlet and outlet VOCs was performed in an attempt to assess overall system function for specific compounds as well as to evaluate individual performance of the biotrickling filter and the biomatrix chamber.