真菌降解废气中邻-二甲苯试验研究

Degradation of o-xylene in off-gas by fungi

采用真菌降解废气中的邻-二甲苯,试验装置为真菌生物滤池.将滤池内填料分成3段,考察每一段的负荷能力、去除效率以及pH值、温度、湿度的变化特点等.邻-二甲苯的进气浓度为400～700mg·m-3,气量为0 25m3·h-1,停留时间为100s.试验结果表明,真菌能够有效地去除废气中的邻 二甲苯,总去除率达到90%以上.其中,从上到下各段的去除率分别为36 8%,28 6%和25 5%.生物滤池内产生CO2的浓度与邻 二甲苯的降解有密切关联,通过在线监测进出气中的CO2浓度变化,可以间接反映出生物滤池的运行状况和生物生长量.在本研究中,降解的邻二甲苯中的碳约74%转化成CO2.微生物鉴定结果表明,降解邻 二甲苯的微生物主要是青霉菌和诺卡氏菌.

The aerial mycelia of fungi form a very large surface area, which can directly contact with the off-gases flowing through the bioreactor. Therefore, fungi can degrade certain hydrophobic compounds faster than bacteria, and have higher elimination capacity. A bench scale biofilter with fungi had been used to treat off-gas with o-xylene. Inlet was on the top of the bilfiter and outlet was on the bottom. The sampling ports were located at the inlet and outlet of the biofiltration column for the measure of experimental compound concentrations in untreated and treated gas respectively. In order to investigate fungal ability to degrade o-xylene, the packing material in the biofilter was divided into three zones. During the experimental program, changes of pH, temperature, humidity, loading rates and removal efficiencies of o-xylene in each zone were investigated. The inlet concentrations of o-xylene varied from 400～700mg·m^(-3),the air flow rate was 0.25m^3·h^(-1), equivalent to empty bed residence time of 100s. The experimental results showed that over 90% of total removal efficiency was obtained. The removal efficiencies of each zone were 36.8%, 28.6%, 25.5%, respectively. The elimination of o-xylene could be estimated by the CO_2 concentration in the outlet gas of the bioreactor. It was a strong correlation between the CO_2 production and inlet o-xylene concentration. The average value of CO_2 as a percentage of the amount expected upon total oxidation of o-xylene to CO_2 and water was 74%. The results in microbial analyses had proven that o-xylene was biodegraded by different kinds of microorganisms in each zone of the biofilter and the main microorganisms were Penicillium and Nocardia.