【作者】 王震文；

【导师】 修光利；

【作者基本信息】 华东理工大学 ， 环境科学与工程， 2014， 博士

【摘要】 与传统的物理、化学方法相比,生物过滤技术对于大流量低浓度的挥发性有机化合物(VOCs)处理有着较大的优势。但是传统的生物过滤技术尚有许多不足,例如：占地面积大、容易堵塞以及对于低溶解度和产酸物质处理效果不佳等,这些都限制了其更为广泛的应用。膜生物膜反应器(MBfR)作为一种新型的生物反应器类型,结合了生物过滤技术以及膜技术的优势,对于VOCs的控制起到了强化作用。论文比较了6种膜材料,包括三种平板PVDF/PET复合膜以及PVDF、PS、PP毛细管式微孔膜,筛选出了实验用膜材料。采用孔径为0.03μm的平板PVDF/PET复合膜对于混合二甲苯进行了非生物性传质实验,发现在气/气实验中,当气体停留时间(GR7)为20s时,去除效率达到95%以上；而在气/液实验中,去除效率不佳。在液相驯化阶段末期,出水水质良好。轮虫等原、后生动物的出现表明了污泥较为成熟。平板式MBfR启动挂膜中,不断改变操作条件促使生物膜生长,并直至反应器的降解效率(DE)/去除能力(EC)达到稳定。论文比较了不同营养物质对于MBfR性能的影响,发现以NO3-作为氮源比以NH4+作为氮源更能确保MBfR长期运行的稳定性。此外,与传统的生物反应器类似,进气浓度和气体停留时间直接影响了MBfR的性能。混合二甲苯的降解效率随着进气浓度的增加而下降；随着气体停留时间的增加而提升。实验中以平板式MBfR降解混合二甲苯,当GRT在20s时,降解效率极佳；当进气浓度低于938mg·m-3时,出气浓度低于《大气污染物综合排放标准》对于混合二甲苯的最高允许排放浓度论文比较了6种污染物在MBfR中的降解效果,其中丙酮的降解效率最佳,其他依次为乙酸乙酯、正丁醇、甲苯、正己烷以及二氯甲烷,这与物质的可生化性和溶解度有着直接的关系。对于以MBfR降解二元体系的结果表明,混合二甲苯对乙酸乙酯的抑制作用较小,甚至可以忽略,而混合二甲苯受到乙酸乙酯极大的抑制；正己烷和混合二甲苯相互抑制,降解效果均变差；由于二氯甲烷的毒性,所以混合二甲苯在不同负荷区间均受到很大的抑制作用,而二氯甲烷在低负荷区间由于共代谢,去除能力有所提升,但在高负荷区间则受到混合二甲苯的抑制作用。MBfR降解混合二甲苯3种同分异构体之间仍然存在一定的抑制作用。邻二甲苯受到的抑制作用大于间、对二甲苯。就降解效果而言,间二甲苯优于对二甲苯和邻二甲苯。在气相驯化过程中,在循环营养液中加入低浓度甲醇后,MBfR对于DMS去除效率有了明显的提高。DMS的进气浓度和气体停留时间同样直接影响了MBfR对于DMS的降解效果。DMS降解效率随着进气浓度的增加而下降,随着气体停留时间的增加而提升。未在循环营养液中添加甲醇的MBfR对于DMS的降解效果一般,ECv,max仅为65g·m-3·h-1。但在循环营养液中添加甲醇的MBfR对DMS的降解同时存在促进和抑制作用。当GRT为20s时,最佳配比为1500mg·Nm-3(DMS):1000mg·L-1(甲醇)。论文比较了三套平板式MBfR对于混合二甲苯的降解效率过,其膜材质分别为不同孔径的PVDF/PET膜。结果发现使用孔径为0.03μm膜材料的平板式MBfR降解效果最佳。相比平板式MBfR,毛细管式MBfR结构复杂,但提供了更大的气液传质面积,更有利于微生物的挂膜。因此,实验中其启动阶段较平板式MBfR更短,且获得更大的降解效果。同理,中空纤维式MBfR比毛细管式MBfR更有优势。MBfR对于实际工况下的间歇运行和瞬态负荷冲击有着更好的适应能力。对于长期运行条件下,耦合低浓度臭氧不仅可以有效地提高去除能力还可以抑制微生物过度生长所导致膜材料的污染。论文通过碳平衡的方法计算了生物质的产量,并与生物能学方法的估算值进行了比较。比较包括推流式一级动力学模型、完全混合式一级动力学模型、推流式Michaelis-Menten动力学模型、完全混合流Michaelis-Menten动力学模型以及Stover-Kincannon模型在内的5种动力学模型,结果表明推流式Michaelis-Menten动力学模型能较好地表达甲苯在平板式MBfR的降解行为。此外,通过CFD的方法初步比较了6种MBfR中气相污染物的流动情况,为今后MBfR的结构优化提供了一定的理论依据。更多还原

【Abstract】 Compared with traditional physical and chemical methods, biofiltration technique has significant advantages in the treatment of volatile organic compounds (VOCs) with high flow rate and low concentration. However, the traditional biofiltration technique has some drawbacks such as requiring a large area of land, being prone to clogging, and having low efficiency in the removal of less soluble and acid-produced substances, which limit the wider application of biofiltration technique. As a novel type of bioreactor, membrane biofilm reactor (MBfR) combines the advantages of both biofiltration and membrane techniques, which is helpful for enhancment of the removal of VOCs.Six kinds of membranes were tested and compared including three different types of flat PVDF/PET compound membranes and three capillary type microporous membranes made of PVDF, PS and PP in this study. The flat compound membrane of PVDF/PET with pore size of0.03μm was used in the non-biological mass transfer experiment of mixed xylene. It was found that in the gas-gas experiment, when gas residence time (GRT) was20s, the removal efficiency was higher than95%; however, the lower removal efficiency was observed when the same membrane was used in the gas-liquid experiment. At the final stage of liquid-phase domestication of microorganisms, the effluent water was in good quality. The protozoa and metazoan such as rotifers were monitored which indicated that the sludge was successful. In order to promote biofilm formation, the operating conditions of flat MBfR in the start-up were modified until the degradation efficiency (DE)/elimination capacity (EC) was stable.The influence of different nutrients on the performance of the reactor was studied, and the results showed that NO3ˉwas a more suitable nitrogen source than NH4+to maintain long-term operational stability in the reactor. In addition, similar to the performance of traditional bioreactor, the inlet gas concentration and GRT could directly affect the performance of the MBfR. The DE of mixed xylene decreased with an increase in inlet gas concentration, while it increased with the increasing of GRT. The flat MBfR was used to remove mixed xylene in the experiment. When GRT was20s, the DE attained the highest level. With an inlet gas concentration lower than938mg·m-3, the xylene concentration in the outlet was below the allowable value of the "Integrated emission standard of air pollutants".This study compared the degradation effect of six pollutants in MBfR, The DE of acetone was the highest, followed by ethyl acetate, n-butyl alcohol, toluene, n-hexane and dichloromethane. This was directly related to the biodegradability and solubility of the substances. For the degradation of binary system in MBfR, the inhibition effect of mixed xylene on ethyl acetate was negligible, on the contrary, the presence of ethyl acetate significantly inhibited the degradation of mixed xylene. The n-hexane and mixed xylenes could inhibit the degradation mutually, which lead to a lower DE. In addition, the degradation of mixed xylene under most loading conditions were severely inhibited because of the toxicity of dichloromethane; the removal efficiency of dichloromethane was promoted under low loading condition due to the co-metabolism of these substances, while it was still inhibited by mixed xylenes under high loading conditions. For the degradation of the isomers of mixed xylene, inhibition effect was observed. The inhibition effect on o-xylene was more significant than on/w-xylene and p-xylene. In terms of the degradation effect, m-xylene was superior to p-xylene and o-xylene.In the gas phase domestication process, the DE of DMS in MBfR was significantly improved when low concentration methanol was added to the circulating nutrient solution. The degradation effect of DMS in MBfR was alse directly impacted by inlet concentration and GRT. The increased inlet concentration resulted in a decrease in the DE of DMS in reactor, while an increased GRT caused an increase in DE. The DE of DMS in the MBfR was not ideal when methanol was not added to the circulating nutrient solution, with anECv,max value of65g·m-3·h-1. The promotion and inhibition were synchronously existed in the DMS degradation in MBfR when methanol was added to the circulating nutrient solution. The best ratio of DMS to methanol was1500mg·Nm-3to1000mg·L-1when GRT was20s.The mixed xylene degradation effect of the three flat MBfR with PVDF/PET membranes of different pore sizes were examined in this study. The flat MBfR with0.03μm PVDF/PET membrane exhibited the best degradation effect. Compared with the flat MBfR, the structure of capillary MBfR was more complex, while its larger surface area improved gas-liquid mass transfer and promote the biofilm formation in the reactor. Thus, the start-up time required for capillary MBfR was shorter than flat MBfR, and degradation effect in capillary MBfR was better. Similarly, the hollow fiber MBfR has more advantages over capillary MBfR. MBfR has an excellent adaptability to the intermittent operation and transient loads in actual conditions. For long-term operation, the coupling of ozone with low concentrations could not only effectively improve the EC, but also inhibit the membrane fouling due to the excessive growth of microorganisms.The production of biomass was calculated by the carbon balance method, and the result was compared with estimated values from bioenergetics approaches in this study. Five kinetic models, namely the first order kinetics models in plug flow and completely mixed flow, the Michaelis-Menten kinetics models in plug flow and completely mixed flow, and the Stover-Kincannon kinetics model were examined. The results showed that the Michaelis-Menten kinetics model in plug flow could predict the toluene degradation in the flat MBfR accurately. The flow patten of gas pollutants in the above mentioned six types of MBfR were simulated by CFD method, and the results provide fundamental basis for optimizing the structure of the MBfRs.更多还原