Step-feed biofiltration: a low cost alternative configuration for off-gas treatment

Clogging due to biomass accumulation and the loss of structural stability of the packing media are common operational drawbacks of standard gas biofiltration inherent to the traditional biofilter design, which result in prohibitive pressure drop buildups and media channeling. In this work, an innovative step-feed biofilter configuration, with the air emission supplied in either two or three locations along the biofilter height, was tested and compared with a standard biofilter using toluene as a model pollutant and two packing materials: compost and perlite. When using compost, the step-feed biofilter supported similar elimination capacities (EC ≈ 80 g m(-3) h(-1)) and CO2 production rates (200 g m(-3) h(-1)) to those achieved in the standard biofilter. However, while the pressure drop in the step-feed system remained below 300 Pa m bed(-1) for 61 days, the standard biofilter reached this value in only 14 days and 4000 Pa m bed(-1) by day 30, consuming 75% more compression energy throughout the entire operational period. Operation with perlite supported lower ECs compared to compost in both the step-feed and standard biofilters (≈ 30 g m(-3) h(-1)), probably due to the high indigenous microbial diversity present in this organic packing material. The step-feed biofilter exhibited 65% lower compression energy requirements than the standard biofilter during operation with perlite, while supporting similar ECs. In brief, step-feed biofiltration constitutes a promising operational strategy capable of drastically reducing the operating costs of biofiltration due to a reduced energy consumption and an increased packing material lifespan.