| Summary: | 碩士 === 國立高雄海洋科技大學 === 海洋環境工程研究所 === 95 === The process of food waste composting includes low-temperature fermentation, high-temperature fermentation, and temperature recovery stages. Microbial communities are abundant in these stages. In the high-temperature fermentation stage, the degradation ability of microbial communities is especially stronger. Besides, the rich composition of lipid in food waste (animal oil or vegetable oil) can be gradually degraded in the composting process. Thus, it was believed that in the food waste-degrading microbial community, there would be oil degrading bacteria or affinitive strains capable of degrading oil pollution.
In the traditional studies of biodegradation, the research focus was usually placed on isolation, purification, and culture of the so-called “super oil-phile bacteria”. Despite the fact that many successful reports have been provided, when applied to the practical pollution treatment, the proposed methods were not effective due to inapplicable “environmental conditions”. Thus, without following the traditional research direction, this study did not stress purification and culture of “oil-phile bacteria” but the “environmental conditions” for microbial reproduction. This innovative idea was to use “raw food waste” as the “primary food” of the microbia and control the environmental development (moisture, pH, and temperature) within the normal conditions for composting to ensure the activity and reproduction of food waste degrading bacteria. Meanwhile, the relatively less polluting oils, diesel and fuel oil, were provided as the “complementary food” of the food waste degrading bacteria, although they might be spicy and distasteful. However, the “prosperously reproduced food waste degrading bacteria” indeed “degraded” the provided polluting oils.
This study encompassed three aspects, including diesel degradation, fuel oil degradation, and the detection of VOC (volatile organic compound) generated in the degradation process. The research results were concluded as follows:
(1) In the aspect of diesel degradation, 10000 mg/Kg diesel was added in the experimental compost. Through microbial degradation, the diesel concentration decreased to 1800 mg/Kg on Day 15, and the removal rate reached 84 %. On Day 43, the concentration declined to below 300 mg/Kg, and the diesel removal rate was above 97 %. (2) As to fuel oil degradation, 7000 mg/Kg fuel oil was added in the experimental compost, and a four-month long observation was conducted. On Day 8, the characteristic peaks of fuel oil had disappeared, TPH-d concentration decreased to 4600 mg/Kg, and the removal rate reached 33 %. On Day 180, TPH-d concentration declined to 380 mg/Kg, and the removal rate reached 95 %. (3) The variations of temperature, pH, and biological activity of the oil-added compost were not significantly different from those of normal food waste composts. It could be inferred that no matter 10000 mg/Kg diesel or 7000 mg/Kg fuel oil was added into the compost, the microbial growth was not significantly influenced. (4) In the detection of VOCs, during the first 14 days of composting normal food waste, 38 VOCs were detected, and sulfide was the main source of the VOCs. VOCs detected from the compost added with diesel and fuel oil were mainly derived from alkanes and aromatic compounds. (5) The test of VOCs indicated that aromatic VOCs would be generated in oil degradation. Thus, if food waste compost is applied to treat oil-contaminated soil in the future, it is necessary to install air pollution prevention facilities to avoid secondary pollution.
According to the above conclusions, the food waste composting technique has significant effects on the degradation of diesel and fuel oil. In the future, oil-contaminated soil can be used in the lab experiment. If good experimental effects can be obtained, this technique can be extensively applied to the treatment of petroleum hydrocarbon contaminated sites.
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