氢基质生物膜反应器在饮用水处理中的研究进展

该文对氢基质生物膜反应器(MBf R)的作用机理、特性以及对饮用水中氧化性污染物的去除可行性进行了论述,并对国内外利用该技术去除饮用水中常见氧化性污染物(如:重金属离子:重铬酸盐、砷酸盐、硒酸盐等;无机阴离子:硝酸盐、溴酸盐、高氯酸盐;卤代有机化合物:对氯硝基苯、三氯乙烷、三氯乙烯、氯仿)的研究现状进行了总结。最后指出了MBf R研究中存在的问题以及在工程应用上的现状和发展前景。     

Introducing a Semi-Coated Model to Investigate Antibacterial Effects of Biocompatible Polymers on Titanium Surfaces

Peri-implant infections from bacterial biofilms on artificial surfaces are a common threat to all medical implants. They are a handicap for the patient and can lead to implant failure or even life-threatening complications. New implant surfaces have to be developed to reduce biofilm formation and to improve the long-term prognosis of medical implants. The aim of this study was (1) to develop a new method to test the antibacterial efficacy of implant surfaces by direct surface contact and (2) to elucidate whether an innovative antimicrobial copolymer coating of 4-vinyl-N-hexylpyridinium bromide and dimethyl(2-methacryloyloxyethyl) phosphonate (VP:DMMEP 30:70) on titanium is able to reduce the attachment of bacteria prevalent in peri-implant infections. With a new in vitro model with semi-coated titanium discs, we were able to show a dramatic reduction in the adhesion of various pathogenic bacteria (Streptococcus sanguinis, Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis), completely independently of effects caused by soluble materials. In contrast, soft tissue cells (human gingival or dermis fibroblasts) were less affected by the same coating, despite a moderate reduction in initial adhesion of gingival fibroblasts. These data confirm the hypothesis that VP:DMMEP 30:70 is a promising antibacterial copolymer that may be of use in several clinical applications.     

Identification of Pathogenicity-Related Genes in Biofilm-Defective Acidovorax citrulli by Transposon Tn5 Mutagenesis

Biofilm formation is important for virulence of a large number of plant pathogenic bacteria. Indeed, some virulence genes have been found to be involved in the formation of biofilm in bacterial fruit blotch pathogen Acidovorax citrulli. However, some virulent strains of A. citrulli were unable to format biofilm, indicating the complexity between biofilm formation and virulence. In this study, virulence-related genes were identified in the biofilm-defective strain A1 of A. citrulli by using Tn5 insertion, pathogenicity test, and high-efficiency thermal asymmetric interlaced PCR (hiTAIL-PCR). Results from this study indicated that 22 out of the obtained 301 mutants significantly decreased the virulence of strain A1 compared to the wild-type. Furthermore, sequence analysis indicated that the obtained 22 mutants were due to the insertion of Tn5 into eight genes, including Aave 4244 (cation diffusion facilitator family transporter), Aave 4286 (hypothetical protein), Aave 4189 (alpha/beta hydrolase fold), Aave 1911 (IMP dehydrogenase/GMP reductase domain), Aave 4383 (bacterial export proteins, family 1), Aave 4256 (Hsp70 protein), Aave 0003 (histidine kinase, DNA gyrase B, and HSP90-like ATPase), and Aave 2428 (pyridoxal-phosphate dependent enzyme). Furthermore, the growth of mutant Aave 2428 was unaffected and even increased by the change in incubation temperature, NaCl concentration and the pH of the LB broth, indicating that this gene may be directly involved in the bacterial virulence. Overall, the determination of the eight pathogenicity-related genes in strain A1 will be helpful to elucidate the pathogenesis of biofilm-defective A. citrulli.     

Nitritation performance in membrane-aerated biofilm reactors differs from conventional biofilm systems

Nitrogen removal via nitrite has gained increasing attention in recent years due to its potential cost savings. Membrane-aerated biofilm reactors (MABRs) are one potential technology suitable to achieve nitritation. In this study we compared lab scale MABRs with conventional biofilm reactors to evaluate the influence of environmental conditions and operational parameters on nitritation performance. The oxygen mass transfer rate is postulated as a crucial parameter to control nitritation in the MABR: Clean water measurements showed significant underestimation of the total oxygen mass transfer, however, accurate determination of the oxygen mass transfer coefficient (k_m) of the system could be achieved by adjusting the liquid-phase mass transfer resistance in the constructed model. Batch experiments at different initial ammonium concentrations revealed that the conventional biofilm geometry was superior for nitritation compared to MABRs. These differences were reflected well in estimates of the oxygen affinity constants of the key microbial players, AOB and NOB (K_O,AOB < K_O,NOB (in both systems) and K_O,NOB values smaller in the MABR vs. the conventional biofilm system). It also appeared that – in addition to oxygen limitation – the absolute and relative substrate concentrations in the biofilm (esp. of oxygen) are very important for successful nitritation. Initial biomass composition, furthermore, impacted reactor performance in the MABR systems indicating the need for appropriate inoculum choice.     

多级生物膜反应器分段进水方式对脱氮效能影响研究

提出多级生物膜反应器,考察了分段进水方式对反应器处理城镇污水生物脱氮效能的影响.结果表明,分段进水点的数量、流量分配及容积分配对反应器脱氮效能的影响显著,分段进水方式有效地提高了碳源利用率以及反应器脱氮效能.在水温为25℃左右,溶解氧为5mg·L~(-1),挂膜密度为30%,COD负荷为1.2 kg·m~(-3)·d~(-1),总氮负荷为0.22 kg·m~(-3)·d~(-1)的条件下,反应器分段进水方式采用第1级、第3级、第6级分段进水,容积分配比为2:3:4,流量分配比为2:2:1时,可使出水COD为38 mg·L~(-1),出水NH_4~+-N和TN的质量浓度分别为1.5 mg·L~(-1)和11.1 mg·L~(-1),去除率分别为80.8%,95.3%和69.2%,与单点进水方式相比TN去除率提高了8.4%.     

生物陶粒MBBR同步硝化反硝化脱氮试验研究

利用生物陶粒作为移动床生物膜反应器(MBBR)的填料,通过试验考察了MBBR发生同步硝化反硝化(SND)的可能性。分析了溶解氧和碳氮质量比对SND的影响。试验结果表明:MBBR具有良好的有机物去除及同步硝化反硝化能力。溶解氧的质量浓度在3 mg/L左右时,不仅能够满足硝化作用的需要而且又不严重抑制反硝化作用,NH3-N去除率达到81.45%的同时TN去除率为60.35%;进水碳氮质量比在10左右时,NH3-N、TN去除率分别为81.65%、63.60%。     

复合生物反应器处理化学合成类制药废水研究

采用复合式生物膜反应器对化学合成类制药废水进行处理研究,试验内容包括反应系统的启动、运行及不同影响因素下的运行试验。结果表明,反应系统从启动到正式运行,COD去除率达到50%以上。在正式运行过程中,曝气量为0.36～0.52m3/h,溶解氧的质量浓度为5mg/L时,当进水COD的质量浓度为200～500mg/L时,最佳水力停留时间为6h,出水COD质量浓度可降低到180mg/L以下;当进水COD质量浓度为500～1700mg/L时,最佳水力停留时间为8h,COD去除率达到46%～72%。复合式生物膜反应器处理低浓度化学合成类制药废水时,出水水质可达到《化学合成类制药工业水污染物排放标准》(GB21904—2008)的排放要求。     

Effect of backwashing on perchlorate removal in fixed bed biofilm reactors

The influence of backwashing on biological perchlorate reduction was evaluated in two laboratory scale fixed bed biofilm reactors using 1- or 3-mm glass beads as support media. Influent perchlorate concentrations were 50 microg/L and acetate was added as the electron donor at a concentration of 2 mg C/L. Perchlorate removal was evaluated at various influent dissolved oxygen (DO) concentrations. Complete perchlorate removal was achieved with an influent DO concentration of 1mg/L resulting in bulk phase DO concentrations below the detection limit of 0.01 mg/L. The influence of increasing influent DO concentrations for 12 h periods was evaluated before and after individual backwash events. Partial perchlorate removal was achieved with an influent DO concentration of 3.5 mg/L before a strong backwash (bulk phase DO concentrations of approximately 0.2mg/L), while no perchlorate removal was observed after the strong backwash at the same influent DO level (bulk phase DO concentrations of approximately 0.8 mg/L). The immediate effect of backwashing depended on influent DO concentrations. With influent DO concentrations of 1 mg/L, strong backwashing resulted in a brief (<12 h) increase of effluent perchlorate concentrations up to 20 microg/L; more pronounced effects were observed with influent DO concentrations of 3mg/L. Daily weak backwashing had a small and, over time, decreasing negative influence on perchlorate reduction, while daily strong backwashing ultimately resulted in the breakdown of perchlorate removal with influent DO concentrations of 3 mg/L.     

Inhibition and recovery in a fixed microbial film leachate treatment system subject to shock loading of copper and zinc

The impacts of shock loadings of copper and zinc (up to 50 mg l(-1)) on the treatment efficiency of a mesoscale-fixed microbial film landfill leachate treatment system were investigated. Treatment inhibition and recovery were monitored in sequence over two 36 h experimental runs. The fate of added metals was also investigated. Copper, and to a lesser extent zinc, added to the treatment systems accumulated on the biofilm media. Increasing copper inputs (>10 mg l(-1)) progressively inhibited biological treatment of ammoniacal-nitrogen and carbon; this inhibition persisted into the recovery phase for nitrogen but not for carbon. Only the highest input of zinc affected media metal contents and carbon treatment rates; the latter inhibitory effect did not persist into the recovery phase. A small proportion of the metals accumulated on the biofilm media during the inhibition phase was released into the bulk leachate during the recovery experiment. These findings suggest a need to manage metal inputs into leachate treatment systems in order to ensure their continued efficacy.     

基于MABR的压裂返排液处理及微生物群落研究

压裂返排液含有多种复杂有机物,毒性高、盐度高以及可生化性差。设计了1个三级MABR系统用于压裂返排液的处理,该系统在最适宜运行参数下表现出优异的除碳脱氮性能,出水经过芬顿试剂处理后满足污水综合排放二级标准。MABR系统对COD、NH⁺₄-N和TN的去除率分别达到79.30%、96.06%和75.61%。微生物分析表明MABR生物膜富集了丰富的功能菌群,Proteobacteria(变形菌门)、Bacteroidetes(拟杆菌门)是生物膜中的优势菌群。阐明了MABR处理压裂返排液的技术可行性,为MABR在处理相关废水中的应用奠定了基础。