| Along with the development of petrifaction industry, the by-product, which thevolatile organic compounds (VOCs) are the representative contaminant, had mademore serious environmental pollution. It was including many compounds which wouldbe hazardous to human health and environmental in VOCs. Therefore, more attentionhas been focused on the treatment of VOCs recently. In various technologies of VOCstreatment, bio-trickling filtration which has many advantages such as low investmentand operating costs, high efficiency, stable operation,convenient management and nosecondary pollution got more application and would be had a favorable future.The bio-trickling filter was used to the treatment of VOCs which produced by thewastewater pretreatment unit of one plant of Daqing Petrochemical Company. Theecosystem in single-stage bio-trickling filter was also researched. Microorganisms onfiller have been counting, separation and identification. When the single-stage bio-trickling filter was operated at pH 6.3~6.9, 12~25°C, the removal efficiency of VOCswas enhanced along with the decrease of concentration. The increase of liquid sprayingrate would also result in the enhancement of removal efficiency. The maximumefficiency was achieved when the spraying rate was 25 L/h. However, the efficiencywould be declined when air flow increased from 0m~3/h to 10 m~3/h. When ZAT-2 fillerwas used for filling dielectric of the single-stage bio-trickling filter, the removalefficiencies of benzene, toluene and xylene were slightly higher than the plasticcomplex spheres.When the single-stage bio-trickling filter was used, the removal efficiency ofbenzene, toluene, xylene and nonmethane hydrocarbon were 98.2, 98.8, 98.8 and96.7%. For the three-stages-series-connection bio-trickling filters, the removalefficiency of benzene and nonmethane hydrocarbon have increased to 99.4% and97.4%, respectively. When the three-stages-series-connection bio-trickling filters wasused for the treatment of real exhaust gas, the removal efficiency of benzene, toluene,xylene and nonmethane hydrocarbon were 98.2, 98.7, 94.6 and 98.7%, and the outletconcentrations were 8.3, 4.0, 4.3and 14.9 mg/m~3, respectively. All of pollutants met therequirements of integrated emission standard of air pollutants. The treatmental loads of benzene, toluene and xylene were 98.2 g/(m~3·h),60.3 g/(m~3·h) and 12.0 g/(m~3·h). Theresults of microorganisms counting in the single-stage bio-trickling filter which havebeen operating for twenty days showed that the colony number in the top filler layerwere 2.7×10~6 cfu/g (upper), 2.9×10~6 cfu/g (middle) and 3.0×10~6 cfu/g (lower),respectively. While for the bottom filler layer, it were 3.0×10~6 cfu/g (upper), 3.1×10~6cfu/g (middle) and 3.2×10~6 cfu/g (lower). The number of microorganisms wasincreased with the decrease of the filler's height. The screened microorganisms whichhave the highest removal efficiency for VOCs were identified as Pseudomonas andBrevibacterium by colony morphology observation and physiological tests. The resultsof PCR-DGGE about microorganisms indicated that both of the sequences which weresimilar to Arthrobacter and Xanthomonas respectively were 12% of totalmicroorganism amounts. They were the dominant microorganisms on the filler in thesingle-stage bio-trickling filter.According to the calculating results of Shannon index, the diversity ofmicroorganisms in the single-stage bio-trickling filter was increased from upper tolower of filler.Based on the results of real exhaustion gas detection, the three-stages-series-connection bio-trickling filters with bio-pretreatment for VOCs in one plant of DaqingPetrochemical Company were designed. The treated gas was exhausted to air bychimney. The inlet gas of bio-trickling filters was higher than 95% humidity, 30°C andpH=6~7. The inlet air rate was 10m~3/h, and the spraying rate was 40 L/h. The optimalspraying time was operated 3min after 180min intermission. The technical andeconomical analyses indicate that total investment of system construction was 9.6133million yuan. After the system operated, new increased cost was 1.1639 million yuanannually.
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