Evaluation of sewage sludge and yard waste compost as a biofilter media for the removal of ammonia and volatile organic sulfur compounds (VOSCs)

A biofiltration treatment without addition of water and inoculation has been studied to eliminate exhaust odors formed during the aerobic composting of a mixture containing sewage sludge and yard waste. Odorous compounds present in the air stream have been identified as well as their temporal variation for 27 days of composting. The main emitted pollutants are volatile organic sulfur compounds (VOSCs) with a total concentration of 3.28 ppmv and ammonia at a concentration above 70 ppmv at the 5th day of composting. An EBRT of 60 s was retained to design the experimental biofilter (EB) for a volumetric air flow rate of 15 m3 h−1. The behaviour of a mature compost containing sewage sludge and yard waste as packing material was studied for the simultaneous removal of ammonia and VOSCs. A removal efficiency (RE) close to 100% was obtained for ethanethiol, dimethylsulfide and dimethyl disulfide whatever the inlet mass loads are. For inlet mass loads between 0.4 and 2.5 g m−3 h−1, the mean RE value is 94% for NH3. In the case of H2S and methanethiol, after composting during 12 days, the concentration at the outlet at the biofilter was higher than in initial conditions. Emissions remain lower than the levels of toxicity but are above the olfactory thresholds determined for these compounds. A relationship between this emission, the participation of sulfates on the filter medium and the concentration of NH3 has been determined.