Transport in preferential flow domains of the soil porous system: Measurement, interpretation, modelling, and upscaling

Abstract

Aeration is one mainstream technique to accelerate municipal solid waste (MSW) degradation in landfills. The determination of an appropriate aeration rate is critical to the design and operation of a landfill aeration system. In this study, we analyze 132 waste degradation tests reported in forty one studies in the literature. We use L min−1 kg−1 dry organic matter (L min−1 kg−1 DOM) as the uniform unit to quantify the aeration rates in all tests. The first order rate coefficient for chemical oxygen demand (COD) removal in leachate (kCOD) is selected as the parameter to characterize MSW degradation process. We further divide aerobic tests into five aerobic groups base on the respective aeration rates, i.e., <0.02, 0.02–0.1, 0.1–0.3, 0.3–1, and >1 L min−1 kg−1 DOM. With an increase in the aeration rate, the kCOD increases first and then decreases. The aeration rate between 0.1 and 0.3 L min−1 kg−1 DOM has the best enhancement on the kCOD. The kCOD values are not much higher than the anaerobic and semi-aerobic tests when the aeration rates are <0.1 L min−1 kg−1 DOM, because such aeration rates may be lower than the actual oxygen consumption rates. An aeration rate >0.3 L min−1 kg−1 DOM reduces the kCOD likely due to excess water evaporation and ventilation cooling. Among the analyzed results, the aeration rate is the most related to the kCOD in principal component analysis than the other factors, including liquid recirculation and addition, waste total density, waste degradation level, and waste initial temperature.