Emission Characteristics of Ammonia and Methyl Mercaptan in the High-temperature Microbial Decomposition Treatment Process of Organic Wastes

Abstract
Emission characteristics of ammonia(AM)and methyl mercaptan(MM)as odorants from the biological decomposition treatment of organic wastes were investigated experimentally using a high-temperature decomposition apparatus with a semi-sealed air circulation system. In result, it was found that the time dependent characteristics of both components in the batch processing were based on changes of their apparent Henry's law constants(H')and pH. Long-term decomposition experiments under the repeated input of dog food(DF)or prepared kitchen refuse(KR)showed that Am concentration in circulated air of the apparatus rapidly rose at around pH8 or more with the accumulation of ammonium types of nitrogen and an increase of H' with pH. However pHs of two kinds of microbial beds differed at the same magnitude of accumulated NH4-N concentration because of their alkali buffer capacities. On the other hand, there was a correlation between MM and carbon dioxide concentration in the circulated air in the processing of the DF, and it was supposed that differences of MM concentration between DF and KR were dependent upon their protein contents. The analysis of the mass-balance of nitrogen in the processing of DF made it clear that contained nitrogen was decomposed and converted into NH4-N which accumulated in the microbial bed at lower pH but released as the pH rose up to a stable range.

Key words: organic wastes, biological decomposition treatment under high-temperature condition, ammonia, methyl mercaptan, pH, henry's law constant