Biofiltration for odour control in livestock facilities

Biofilters can be used to treat odours produced from animal facilities. However, their performance decreases with the presence of ammonia (NH 3) and hydrogen sulfide (H2S) gases. The objective of this research was to determine the effect of NH3 and H2S on biofilter performance and design a biofilter system to treat the NH 3 and H2S compounds in the odourous exhaust air from animal facilities.; In the first experiment, a combined bioscrubber and biofilter (with sulfuric acid and no acid) was designed with background NH3 and H2S concentrations of 21.4+/-5.2 and 3.0+/-1.6 ppmv, respectively. Elimination capacity (EC) and the removal efficiency (RE) of the bioscrubbers and EC, RE, and pH of the biofilters were significantly different (p<0.05). The concentrations of NH3 and H2S contributed to the variation in pH of biofilter leachate. With a 10s empty bed retention time (EBRT), odour concentrations were reduced by 66% and the concentrations of NH3 and H2S were reduced by 100 and 75%, respectively.; In the second experiment, a combination of one bioscrubber and four biofilters was designed. This system operated with 2, 20, 45, and 90 ppmv NH3 injected into the biofilters. The ammonia concentrations significantly affected the EC, RE, and pH of the biofilters (p<0.05). No nitrate was produced in the biofilter with 90 ppmv NH3 and the nitrate production in the biofilter with 45 ppmv NH3 was negligible. There were no significant differences (p>0.05) in the total amount of nitrite and nitrate produced in the biofilters that were operated with 20, 45, and 90 ppmv ammonia concentrations. The ECs of the biofilters for ammonia nitrogen with the above concentrations of ammonia were 11.6+/-2.6, 111+/-5.6, 183+/-10.9 and 242+/-21.8 g/m3/d. Meanwhile, the overall total nitrite and nitrate nitrogen were 8.6+/-1.5, 42.1+/-3.9, 40.8+/-4 and 31.9+/-5 g/m3/d, respectively. The daily accumulation of NH3-N + NH4+-N in the biofilters were 3.4+/-2.9, 70.6+/-5.9, 143.4+/-10.5, and 211.6+/-21.5 g/m3/d, respectively. Olfactometry tests indicated that the odour concentration was reduced 50% by bioscrubber and 72% by combination of bioscrubber and biofilter with no NH3 injection.; Nitrogen mass balance data were used to develop a prediction model. The outcome of this model predicted the amount of water, media volume, and EBRT based on NH3, H2S, airflow, and temperature input.