Simultaneous biofiltration of H2S, NH3 and toluene using cork as a packing material

Simultaneous removal of ternary gases of NH3, H2S and toluene in a contaminated air stream was investigated over 185 days in a biofilter packed with cork as microbial support. Multi-microorganisms including Nitrosomonas and Nitrobactor for nitrogen removal, Thiobacillus thioparus (ATCC 23645) for H2S removal and Pseudomonas aeruginosa (ATCC 15692), Pseudomonas putida (ATCC 17484) and Pseudomonas putida (ATCC 23973) for toluene removal were used simultaneously. The empty bed residence time (EBRT) was 40–120 seconds and the inlet feed concentration was 50-180 ppmv for NH3, 30–160 ppmv for H2S and 40–130 ppmv for toluene, respectively. The observed removal efficiency was 45–100% for NH3, 96–100% for H2S, and 10–99% for toluene, respectively. Maximum elimination capacity was 5.5 g/m3/hr for NH3, >20.4 g/m3/hr for H2S and 4.5 g/m3/hr for toluene, respectively. During long-term operation, the removal efficiency of toluene gradually decreased, mainly due to depositions of elemental sulfur and ammonium sulfate on the cork surface. The results of microbial analysis showed that nearly the same population density was observed on the surfaces of cork chips collected at each sampling point. Kinetic model analyses showed that there were no particular evidences of interactions or inhibitions among the microorganisms.