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

Abstract

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 x 10(9) and 3.0 x 10(10) cells per gram-dry peat for total bacteria, and 2.4 x 10(9)-1.9 x 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.