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The biological treatment of a tri-component mixed waste gas system in BRC1 and BRC2 biofilters packed with rock wool-compost media was studied. The model gases were NH(3), H(2)S and toluene. The gases were fed initially at about 50-55 ppm each. H(2)S was found to have the shortest start-up while toluene had the longest. Under two different NH(3):H(2)S:toluene concentration ratios of 250:120:55 and 120:220:55 (in ppm) for BRC1 and BRC2, the removal efficiencies of NH(3), H(2)S and toluene were found to be affected by their respective loading rate. On the other hand, toluene removal was observed to be inhibited at H(2)S concentration of 220 ppm as well. Almost complete removal of NH(3) and H(2)S was achieved when loading rate was applied up to 16.14 g-NH(3)/(m(3) bed h) and 36.09 g-H(2)S/(m(3) bed h), respectively. The maximum elimination capacity for NH(3) was determined to be 23.67 g-NH(3)/(m(3) bed h) at 78.6% removal efficiency and for H(2)S, 38.50 g-H(2)S/(m(3) bed h) at 68.1% removal efficiency. The maximum toluene elimination capacity was 30.75 g-toluene/(m(3) bed h) at 87.9% removal efficiency when the concentration of NH(3):H(2)S:toluene was 250:120:55 in BRC1, and was 16.60 g-toluene/(m(3) bed h) at 45.5% removal efficiency when the concentration of NH(3):H(2)S:toluene was 120:220:55 in BRC2. The pressure drops along both columns were low and the ratio of bed compactions over biofilter height was observed to be less than 0.02.

A pilot-scale two-step biofilter system was evaluated in treating food waste composting emission for 220 days. Wood chips were packed at the bottom section while mixture of rock wool and earthworm compost (6% w/v) was packed at the top section. Inlet ammonia concentration was found to be dominant and intermittent. The overall ammonia removal of over 98% was achieved, 70% of which was removed in the wood chip section. The highest ammonia elimination capacity was determined to be 39.43 g-NH(3)/m(3)/h at 99.5% removal efficiency. From biodegradation kinetic analysis, the maximum removal rate, V(m), of the wood chip section was determined to be 200 g-NH(3)/m(3)/h and the saturation constant, K(s), 180 mg/m(3). For the rock wool-earthworm cast mixture section, the V(m) was 87 g-NH(3)/m(3)/h and K(s) was 87 mg/m(3). Complete removal of hydrogen sulfide and most trace compounds were achieved by the biofilter. Highest hydrogen sulfide elimination rate was 0.22 g-H(2)S/m(3)/h. The biofilter was optimized from 24 to 16 s EBRT with resulting low average pressure drops of 16 and 29 mm H(2)O/m, respectively.

The biological treatment of a tri-component mixed waste gas system in BRC1 and BRC2 biofilters packed with rock wool-compost media was studied. The model gases were NH3, H2S and toluene. The gases were fed initially at about 50–55ppm each. H2S was found to have the shortest start-up while toluene had the longest. Under two different NH3:H2S:toluene concentration ratios of 250:120:55 and 120:220:55 (in ppm) for BRC1 and BRC2, the removal efficiencies of NH3, H2S and toluene were found to be affected by their respective loading rate. On the other hand, toluene removal was observed to be inhibited at H2S concentration of 220ppm as well. Almost complete removal of NH3 and H2S was achieved when loading rate was applied up to 16.14g-NH3/(m3 bedh) and 36.09g-H2S/(m3 bedh), respectively. The maximum elimination capacity for NH3 was determined to be 23.67g-NH3/(m3 bedh) at 78.6% removal efficiency and for H2S, 38.50g-H2S/(m3 bedh) at 68.1% removal efficiency. The maximum toluene elimination capacity was 30.75g-toluene/(m3 bedh) at 87.9% removal efficiency when the concentration of NH3:H2S:toluene was 250:120:55 in BRC1, and was 16.60g-toluene/(m3 bedh) at 45.5% removal efficiency when the concentration of NH3:H2S:toluene was 120:220:55 in BRC2. The pressure drops along both columns were low and the ratio of bed compactions over biofilter height was observed to be less than 0.02. [Copyright &y& Elsevier]