Long‐term performance of peat biofilters treating ethyl acetate, toluene, and its mixture in air

Three laboratory‐scale peat biofilters were operated at 90 s empty bed residence time (EBRT) for over a year. Biodegradation of ethyl acetate, toluene, or a 1:1 mixture were investigated. In first stage, inlet concentration was progressively increased from 0.4 to 4.5 g/m 3 . The maximum elimination capacity (EC) found for ethyl acetate was 190 gC/m 3 ·h, and it was not affected by toluene. The maximum EC found for toluene as a sole contaminant was 150 gC/m 3 ·h, but the presence of ethyl acetate decreased the toluene maximum EC to 80 gC/m 3 ·h. From respirometry monitoring, values of 3.19 g CO 2 /gC and 3.06 g CO 2 /gC for pure ethyl acetate and pure toluene, respectively, were found, with overall yield coefficients of 0.13 g dry biomass produced per gram ethyl acetate consumed and 0.28 g dry biomass produced per gram toluene consumed. CO 2 production in the 1:1 mixture was successfully simulated. Dynamics of living and dead cells were monitored in four sections of the biofilters. Concentrations ranged between 2.6 × 10 9 and 3.0 × 10 10 cells per gram‐dry peat for total bacteria, and 2.4 × 10 9 –1.9 × 10 10 cells per gram‐dry peat for living bacteria. At high loads loss of bacterial density in the inlet zones, and increase in the dead cells percentages up to 60% was observed. In second stage, long‐term performance at an inlet concentration of 1.5 g/m 3 was evaluated to show the process feasibility. Good agreement with previous data was obtained in terms of EC and CO 2 production. Restoration of living cells proportion was also observed. Biotechnol. Bioeng. 2007;96:651–660. © 2006 Wiley Periodicals, Inc.