Long term performance of biotrickling filters removing a mixture of volatile organic compounds from an artificial waste gas: dichloromethane and methylmethacrylate

Two problems still hamper the widespread industrial application of biotrick ling filters (BTFs) for waste gas treatment in practice: clogging of the fi lters at higher carbon loads and a decrease in the elimination of a target compound when more than one compound is present in the waste gas. To invest igate these phenomena three identical BTFs removing dichloromethane (DCM) f rom an artificial waste gas were operated counter-current wise for 12 month s at a DCM load of 0.94 Cmole-DCM/(m(r)(3) . h). After five months of opera tion methylmethacrylate (MMA) was added to the waste gas. Three different M MA loads were applied: 0.5, 1.0 and 1.5 Cmole-MMA/(m(r)(3) . h). Although t he elimination of DCM in all three BTFs decreased after the introduction of MMA to the air stream, it stabilised at a lower steady-state value than be fore the MMA addition. MMA was completely degraded during the applied stand ard conditions. In all three filters biomass accumulation eventually caused clogging of the packing. In the filter with the lowest MMA load the first signs of clogging were observed only after 7 months of stable operation, il lustrating the need for long term studies to evaluate process stability. Sh ort term experiments have provided information about the system's dynamics and showed that an accumulation of intermediates and a subsequent adaptatio n of the biomass in the BTF will occur upon a step increase in MMA load. To evaluate whether a stable BTF operation without clogging is possible, a no vel process parameter (the rate of Carbon Conversion per unit void packing Volume) is introduced which possibilities and limitations are discussed.