Management of high-rate trickle bed biofilters

The 1990 Amendments to the Clean Air Act have stimulated strong interest in the use of biofiltration for the economical engineered control of VOCs in effluent air streams. Trickle bed biofilters are especially applicable for treating VOCs at high loadings. For long term, stable operation of such biofilters, removal of excess accumulated biomass is essential. Previous research demonstrated that suitable biomass control for such biofilters was achievable by backwashing. Backwashing was performed by fluidizing the pelletized biological attachment media. This paper presents an evaluation made of the impact of backwashing on the performance of two such highly loaded biofilters. The inlet VOC concentration studied was 500 ppmv toluene, and the empty bed residence times (EBRTs) and loadings were 4.1 and 6.2 kg COD/m{sup 3} day, and 2.0 and 1.33 minutes, respectively.