Removal of NH3, H2S and toluene by biofilters packed with rock wool-compost media

Biofiltration is carried out in packing materials where attached microorganisms degrade the passing contaminant. In this work, a new packing material was introduced and evaluated for the treatment of malodorous gases-ammonia and hydrogen sulfide and a volatile organic compound-toluene in three biofilters, BF1, 13172, and BF3, respectively. The new composite rock wool-compost media consisted of rock wool and compost in 70:30 weight ratios. Above 95 % removal efficiencies were obtained as the inlet concentrations of ammonia, hydrogen sulfide and toluene were increased up to 155, 150 and 260 ppm(v), respectively in the biofilters at an empty bed residence time of similar to 65 s. The removal efficiencies in the hydrogen sulfide (13172) and toluene (13173) biofilters immediately decreased when the frequency of water irrigation was reduced. However, hydrogen sulfide removal in the BF2 could be improved in some. extent by maintaining pH of above 5. Parameters such as pH, microbial count, and pressure drop along the biofilters were also evaluated. The highest elimination capacities obtained from the study were 6.4 g-NH3/m(3)/h, 12.1 g-H2S/m(3)/h, and 57.6 g-toluene/m(3)/h, indicating that the rock wool-compost media can be suitably and effectively applied for biofiltration.