Evaluation of Trickle-Bed Air Biofilter Performance for Removal of Paint Booth VOCs under Stressed Operating Conditions

摘要

Biofiltration has recently emerged as an attractive option for controlling volatile organic compounds (VOCs). Our study has focused on expanding the application of biofiltration to treat VOCs under variable flow rate and unsteady loading for obtaining consistently high removal efficiencies. Four trickle-bed air biofilters were employed to control paint booth VOCs as single contaminants - toluene, styrene, methyl ethyl ketone (MEK), and methyl isobutyl ketone (MIBK). The biofilter performance was evaluated for different stressed operating conditions (i.e., biomass control strategy, non-use periods) at different inlet VOC concentration (50, 100, and 250 ppmv). A biomass control strategy is required to maintain consistent long term efficient performance of biofiltration. A periodic in-situ upfiow washing (backwashing) was approached in this study. For 50 and 100 ppmv of inlet VOC concentration, the removal efficiencies of four biofilers were maintained above 99 % by backwashing at a rate of 1 hour/ week. After backwashing, reacclimation of the biofilter performance was dependent on the VOC loading rate. Two different non-use periods of two days/ week were investigated to mimic a shutdown for equipment repair or during weekend and holidays. The first was a period without chemical loading (pure air with nutrients passes through the biofilter), and the second was a stagnant period which refiects no fiow (chemical, nutrient and air) passing through the biofilter. Both non-use periods showed that the biofilter performance was similar as that under the backwashing. This suggested that the non-use periods can be considered as another mean of the biomass control. However, at 250 ppmv of inlet VOC concentration, the reacclimation performance after the non-use periods was apparently different as compared to the reacclimation after the backwashing.