Behavior of trickle bed air biofilter for VOCs removal: Effect of non-use periods

A laboratory scale trickle bed air biofilter was evaluated for the treatment of air contaminated with toluene, focusing on the effect of non-use periods on biofilter behavior for different VOC inlet loading and concentration. When the non-use period strategies were conducted, the overall VOC removal efficiency remained at the 99% range without backwashing for loading rates of 0.70 and 1.41 kg COD/cu m-day. While for a loading rate of 3.52 kg CO/cu m-day, it dropped occasionally below 90% due to the accumulation of excess biomass. The non-use period strategy provided similar biofilter performances as that with the backwashing strategy at 0.70 and 1.41 kg COD/cu m-day. For the backwashing strategy, the overall removal efficiency was initially below the 30% range but in increased over the 90% range within 600 min at all inlet concentrations The biofilter performance immediately after backwashing was unexpectedly poor due to the loss of active biomass. For the two different non-use strategies, the biofilter initially had relatively high removal efficiency as compared with that for the backwashing strategy. The active biomass played an important role in this effect without the loss of active biomass. At 250 ppmv of inlet concentration, higher removal efficiency was observed in the initial time after the restart-up following the non-use period. As the VOC loading rate was increased, much longer reacclimation period was necessary for biofilter performance to reach the 99% removal range for both the backwashing and the non-use period. This is an abstract of a paper presented at the 2004 AIChE National Spring Meeting (New Orleans, LA, 4/25-29/2004).