Emission characteristics of odorous compounds during short-term pre-aeration of municipal solid waste prior to landfilling

An important advantage of using a short-term pre-aeration of municipal solid waste (MSW) with high organic fractions prior to landfilling is that it intensively decomposes a part of organic matter, especially easily biodegradable fractions in waste, and thus regulates the subsequent anaerobic degradation of MSW under landfill conditions, meanwhile conserving the bio-methane potential as much as possible. However, this organic matter degraded during the pre-aeration process is converted by aerobic microorganisms into high concentrations of organic leachate and exhausted gases (e.g. NH3 and volatile organic compounds), which are also potential pollution sources to the surrounding environment. In this study, the emission characteristics of leachate and odorous gases generated during a short-term pre-aeration process of MSW are investigated in a laboratory reactor. It is found that MSW, pre-treated aerobically for 7 days, results in ~28.1% of weight loss and ~30.3% of capacity loss, respectively. Due to the initial hydrolysis, acidification and leaching of organic solids, TOC concentrations in leachate generated during the pre-aeration process increase rapidly at the beginning, and then are maintained at relatively stable levels, averaging from 16,700 to 26,000 mg/L. A certain amount of VFAs, mainly butyric acid (50-75%) and acetic acid (20-50%), is detected in leachate, with the concentration range of 1,000-18,000 mg/L, which can increase the odorous risk from leachate storage and treatment operation. NH3 emission in the exhaust gases is highly consistent with the degradation of proteins and temperature evolution, with the maximum release capacity of ~37.6 mg/(kg DM.h) occurring at day 4. Compared to the initial untreated waste, the release strength of halocarbons and aromatic hydrocarbons from the pre-aerated waste is obviously decreased, whereas higher concentrations of organosulfurs, such as ethanethiol and dimethyl disulfide, and alkanes are observed (~10 times higher). This finding suggests that more attention should be paid to control the odorous charge during the subsequent storage, transportation and landfilling operation of the pre-aerated waste.