| Raw material products from natural rubber processing plants provide huge benefits to human beings as they are exploited to manufacture many kinds of important rubber goods. However, a large number of odorous substances have been produce during the production process of natural rubber. The contradictions between the development of rubber production and environmental protection have become increasingly prominent with the expansion of rubber production. Therefore, it is need that using environmental friendly methods to solve the problem of odor pollution.In this paper, the main odor components resulting from the production process of natural rubber were analyzed and the odor-degrading microorganisms have been isolated based on those odor components. Furthermore, six biotrickling filters were designed and made, which were characterized by using coke and phosphate rock as the packing to immobilize the odor-degrading microorganisms and then to degrade the odor components producing the process of natural rubber production, respectively. In addition, the degradation mechanisms were explored. The results were showed as follow:(1) The odor components resulting from the production process of natural rubber were analyzed using UV spectrophotometer, gas chromatography and gas chromatography/mass spectrometry (GC/MS) associated with head space sampling technique. The results showed that the odorous components from the natural rubber plant include amines, ketones, ethers, acids, et al., Of which, volatile fatty acid, ammonia, hydrogen sulphide and methyl sulfide were identified as the typical components;(2) A volatile fatty acids-degrading microorganism, DA-1, was isolated from the sludge from wastewater treatment plant of natural rubber production by using formic acid, propionic acid and n-valeric acid (the quality ratio:1:1:1) as odor and carbon source. Further, DA-1was immobilized on coke (reactor1) and phosphate rock (reactor2), which used to degrade volatile fatty acids in the two biotrickling filters, respectively. The results showed that the elimination capacity of volatile fatty acids always increased during the experiment at the inlet concentration of205.80-677.40mg/m3and pH of6.0-7.0; A methyl sulfide-degrading microorganism, DJ-1, DJ-2and DJ-3were isolated from the sludge of wastewater treatment plant of natural rubber production by using dimethyl sulfide as carbon source. The optimum growth conditions for DJ-2were pH7,30℃, and C/N ratios of5. Further, DJ-2was immobilized on coke (reactor3) and phosphate rock (reactor4), which used to degrade the dimethyl sulfide in the two biotrickling filters, respectively. The results showed that the elimination capacity of dimethyl sulfide reached6.60g/(m3-h) in reactor3and6.08g/(m3·h) in reactor4at odor flow rate of0.50L/min and pH of6.0-7.0on the45th day; The biotrickling filter using coke as the packing was better than that using phosphate rock as the packing. The reason probably lied that coke with respect to the phosphate rock having a larger specific surface area and porosity, greater water holding capacity, and thus demonstrate better purifying capability because coke has a specific surface area of312.40m2/g, the water holdup of28%and the porosity of45.98%, while phosphate rock has a specific surface area of0.38m2/g, the water-holding rate of7.5%and a porosity of43.76%; Two sets of biotrickling filters were built, one (reactor5) packed with volatile fatty acids-degrading microorganism in the lower part and the other (reactor6) packed with methyl sulfide-degrading microorganism in the upper parter. Further, the two biofilters to be used to degrade the mixtures of volatile fatty acids and methyl sulfide from air streams. The results showed that reactor5and6both can withstand shock loading and will maintain stably under relative low concentration of odorous volatile fatty acids and methyl sulfide inlet gas. However, the bioreactor6was ineffective in removing methyl sulfide under the inlet load too high. The purification rate of dimethyl sulfide dropped to53.13%at VFAs mass loadings up to5.71g/m3-h and methyl sulfide loadings up to2.12g/m3-h;(3) In addition, the mechanism about the degradation of volatile fatty acids and dimethyl sulfide were explored. The results showed that oxygen played an important role in the biological degradation process. The VFAs and dimethyl sulfide would be degraded to CO2, H2O and H2SO3provided the oxygen was supplied sufficiently. In contrast, the VFAs and dimethyl sulfide would be degraded to CO2, CH4and H2S respectively. |
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