Evaluation of trickle-bed air biofilter performance for styrene removal

A pilot-scale trickle-bed air biofilter (TBAB) was evaluated for the removal of styrene from a waste gas stream. Six-millimeter (6-mm) Celite pellets (R-635) were used as the biological attachment medium. The operating parameters considered in the study included the styrene volumetric loading, the empty-bed residence time (EBRT), the frequency and duration of backwashing, and nutrient–phosphorous (nutrient–P) management as a biomass control strategy. The aim of the study was to demonstrate that high removal efficiencies could be sustained over a long period. Periodic backwashing of the biofilter with full-medium fluidization was necessary for removing excess biomass and attaining stable, long-term high removal efficiencies. Styrene removal efficiencies in the 99%+ level were achieved for volumetric loading rates up to 2.93 kg COD/m3•day and a 1-min EBRT. With a COD volumetric loading rate of 4.26 kg COD/m3•day and a 0.67-min EBRT, removal efficiencies in the 97–99% level were achieved. Evaluations of pseudo steady-state performance data, 1 day following backwashing, yielded first order removal rate constants that were dependent on EBRT. Nutrient–phosphorus (nutrient–P) limitations failed to provide a strategy for biomass control while at the same time maintaining acceptable performance.