Tubular biofilter for toluene removal under various organic loading rates and gas empty bed residence times

A tubular biofilter (TBF) which consisted of a closed chamber, a polyurethane sponge tube and a nutrient solution distributor was developed and evaluated under organic loading rates (OL) ranging from 18.7 to 149.3 g m−3 h−1 and gas empty bed residence times (EBRTs) of 30–5.0 s. Using toluene as model VOC, the startup of the TBF lasted approximately 7 weeks. The removal efficiency decreased from 99% to 52.2% when OL was increased from 18.7 to 149.3 g toluene m−3 h−1 at 15 s, but did not decline significantly when the EBRT was reduced from 30 to 5.0 s at 18.7 g m−3 h−1. Biomass concentration did not increase significantly within the sponge tube during the 391 days’ operation as observed through the Plexiglas pipe of the TBF. The TBF is suitable for treating waste gases with low toluene concentrations even at high gas flow and over long periods.