EFFECT OF SOIL CONTENT ON COMPOSTING OF DIESEL FUEL CONTAMINATED SOILS

摘要

The purpose of this study was to investigate the effect of soil content on the thermophilic stage of composting. A total of thirty-six bench-scale biocell reactors were prepared. Each biocell started with 6.5 kg (wet basis) of biosolids and woodchips. The ratio of woodchips to biosolids used was 0.4:1 (wet basis) to achieve a target moisture content of 55%. Sand or silt was added to the biocells in increasing amounts. The amount of sand added in the compost mixture ranged between 0% to 64% on a wet weight basis, while the amount of silt ranged from 0% to 48% on a wet weight basis. Soils were contaminated with 5000 mg of diesel fuel per kg of dry soil before addition to biocells. Diesel-~(14)C octadecane mixture was also added to the reactors to trace the mineralization of hydrocarbon as ~(14)CO_2. The biocell aeration and temperature were monitored and controlled to simulate the thermophilic stage of composting. Each run lasted for 14-days. As a measure of composting microbial activity, the relative heat generation and volatile solids removal were measured. The results of this study indicated that thermophilic microbial activity was not affected by the sand or silt content tested. No significant release of ~(14)C as CO_2 from reactors was observed during the fourteen days of composting. It is expected that the production of ~(14)C would increase with increased composting time. While the thermophilic microbial activity observed was not affected with sand or silt content tested, further investigations are suggested to confirm our work with clay soil and to compare those results with other researchers.