Biofiltration is becoming an established economical air pollution control technology for removing volatile organic compounds (VOCs) from waste air streams. This study utilizes diethyl ether as a VOC substrate and nitrate as a nitrogen nutrient source to investigate the effect of nitrate on VOC removal. Two trickle bed biofilters with pelletized media were operated co-currently at ether loading rates of 1.78 and 3.56 kg COD/m3·day respectively, with a low empty bed retention time of 25 seconds, inlet gas flow rate of 8.64 m3/day and nutrient liquid flow rate of 1 1/day. The ether removal efficiencies improved from 72% to over 99% with increasing influent nitrate concentration from 66.7 to 266 mg NO3-N/l in the higher loaded column. Throughout the experiment, nitrate persisted in the liquid effluent. The lower ether removal at low influent nitrate concentrations was not due to nitrogen shortage, which suggests that the nitrate diffusion in the biofilms is rate determining. The higher COD:N consumption ratio in the biofilter with higher ether loading also indicates that ether removal may benefit from the utilization of nitrate as an alternative electron accepter in the deeper layers of the biofilm where the oxygen may be limited.

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