Evaluation of a combined activated carbon prefilter and biotrickling filter system treating variable ethanol and ethyl acetate gaseous emissions

Abstract

AbstractThe removal of a 1:1 by weight mixture of ethanol and ethyl acetate was studied in a gas phase biotrickling filter running under conditions that simulated industrial emissions from the flexographic sector, i.e. discontinuous loading (twelve hours per day and five days per week) and oscillating concentration of the inlet stream. Three sets of experimental conditions were tested in which empty‐bed residence time varied from 60 to 25 s (inlet loads from 50 to 90 g C m−3 h−1). The biotrickling filter reached a maximum elimination capacity of 48.5 g C m−3 h−1 (removal efficiency=68.9%) for an empty‐bed residence time of 40 s. A decrease in the residence time from 40 to 25 s adversely affected the elimination capacity (40.3 g C m−3 h−1, removal efficiency=46.6%). For the three tested residence times, outlet concentrations during pollutant feeding were above 100 mg C m−3 (EU legal limit for flexographic facilities). Then an activated carbon prefilter was installed to buffer the fluctuating concentration, enabling a more stable operation. The desorbed pollutant from the activated carbon during non‐feeding hours also served as an extra source of substrate, avoiding severe starvation. The use of the activated carbon prefilter with a volume 25 times lower than that of the bioreactor was shown to reach an average outlet emission concentration lower than 50 mg C m−3 operating the biotrickling filter at an empty‐bed residence time of 40 s, with a maximum elimination capacity of 59.6 g C m−3 h−1 (removal efficiency=92.0%).