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.     

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。     

Inhibition of Gallic Acid on the Growth and Biofilm Formation of Escherichia coli and Streptococcus mutans

New strategies for biofilm inhibition are becoming highly necessary because of the concerns to synthetic additives. As gallic acid (GA) is a hydrolysated natural product of tannin in Chinese gall, this research studied the effects of GA on the growth and biofilm formation of bacteria (Escherichia coli [Gram‐negative] and Streptococcus mutans [Gram‐positive]) under different conditions, such as nutrient levels, temperatures (25 and 37 °C) and incubation times (24 and 48 h). The minimum antimicrobial concentration of GA against the two pathogenic organisms was determined as 8 mg/mL. GA significantly affected the growth curves of both test strains at 25 and 37 °C. The nutrient level, temperature, and treatment time influenced the inhibition activity of GA on both growth and biofim formation of tested pathogens. The inhibition effect of GA on biofilm could be due to other factors in addition to the antibacterial effect. Overall, GA was most effective against cultures incubated at 37 °C for 24 h and at 25 °C for 48 h in various concentrations of nutrients and in vegetable wash waters, which indicated the potential of GA as emergent sources of biofilm control products.     

序批式生物膜法的脱氮特性研究

对序批式生物膜工艺的脱氮特性进行了探讨，并提出了过量储存-SND脱氮作用机理，即厌氧段脱氮主要靠生物膜对含碳、氮有机物的过量储存作用，而好氧段脱氮则靠生物膜的同步硝化反硝化(SND)作用，反硝化的有机碳源主要为生物膜在厌氧段过量储存的有机物。镜检发现反应器中的优势菌属为假单胞菌属，其次为气单胞菌属、芽孢杆菌属、微球菌属、硝化杆菌属。     

亚甲基蓝对单增李斯特菌菌膜的光动力杀伤作用

探讨单增李斯特菌（Listeria monocytogenes,LM）生物菌膜的生长特性及亚甲基蓝对LM生物菌膜光动力杀伤作用。通过结晶紫染色法判断与观察LM生物菌膜的形成并用酶标仪在595 nm波长处对其不同生长阶段的生物量进行测定,同时通过细菌平板菌落计数法研究亚甲基蓝对LM生物菌膜的光动力杀伤作用。结果表明：结晶紫染色法可用于定性判断与观察LM生物菌膜,且随着培养时间的延长,LM生物菌膜生物量不断增加,形成的网状结构越来越致密。当光敏剂质量浓度为10 μg/mL的亚甲基蓝在光功密度为200 mW/cm2 的可见光照射30 min时,即可使LM生物菌膜的失活率达到99.99%以上,其菌落数降低了4.08（lg（CFU/mL））。亚甲基蓝对LM生物菌膜的光动力灭活作用非常显著,其杀伤效果主要取决于光敏剂质量浓度和光照时间。     

氨溴索联合左氧氟沙星对肺炎克雷伯菌生物膜抑制和清除能力的研究

目的：研究氨溴索联合左氧氟沙星对肺炎克雷伯菌生物被膜的抑制和清除作用,旨在为临床提供拮抗肺炎克雷伯菌生物膜形成和治疗的新策略。方法：收集不同耐药性肺炎克雷伯菌各15株,将其分为敏感组（野生菌组）、超广谱β-内酰胺酶（extended spectrum β-Lactamases, ESBLs）组、耐碳青霉烯类肺炎克雷伯菌（carbapenem resistant Klebsiella pneumoniae, CRKP）组,采用结晶紫染色法进行生物被膜半定量检测,再从各组中选取3株生物被膜产量相近的菌株,采用微量肉汤稀释法测定氨溴索和左氧氟沙星对肺炎克雷伯菌的最低抑菌浓度（MIC）;棋盘稀释法测定不同浓度氨溴索对左氧氟沙星MIC的影响以及通过计算部分抑菌浓度指数（FIC）判断联合效果和选择最佳协同浓度;采用结晶紫法联合激光扫描共聚焦荧光显微镜研究不同浓度药物对肺炎克雷伯菌生物被膜的形成抑制试验和清除试验。结果：3组细菌生物被膜均在第5天达到成熟,两两比较发现敏感组较ESBLs组和CRKP组更易形成且产量更多（F=3.725,P=0.032）;棋盘稀释法显示,随着氨溴索浓度的增加,3组细菌左氧氟沙星MIC值的几何均数均明显下降,呈显著的负相关,且联合药敏结果显示,两药组合均呈现协同作用;在生物被膜形成抑制试验中,随着氨溴索浓度的增加,其抑制率均达到了75%以上,但其生物被膜清除率却未达到70%。 结论：氨溴索联合左氧氟沙星对临床早期抑制肺炎克雷伯菌生物被膜形成具有指导意义,且其最佳协同浓度为0.49 mg/mL氨溴索+4 μg/mL左氧氟沙星。     

食源性混合菌生物被膜的形成和相互作用机制

在食品加工中,食源性病原菌生物被膜的存在会引发大量食品污染等安全问题。目前,国内外学者深入研究了单一菌生物被膜,然而对混合菌生物被膜的研究较少。本文在现有的研究基础上,归纳总结了食源性混合菌生物被膜的形成规律及混合菌生物膜中菌种间的相互作用,初步探讨了群体感应在混合菌生物膜中的作用,以期为食品领域应对和破解食源性混合菌生物被膜污染问题提供思路。     

基于膜电极的质子交换膜微生物燃料电池

通过采用传统电化学燃料电池的技术和材料,以寻求提高微生物燃料电池的电流密度,制作基于膜电极的微生物燃料电池。通过构建温控压力机,制作了一系列膜电极(MEA),并对作为正极的多种碳材料进行了筛选。使用定制的玻璃微生物燃料电池来放置膜电极和培养Geobacter sulfurreducens,对产生的电流进行评价。细胞的生长以乙醇为唯一碳源,因而代表了一种新型的乙醇/氧气燃料电池。相比以前的设计,基于膜电极的微生物燃料电池的电极表面每个单位会多产生出100倍的电流,并且可以被长久使用。     

碳材料在抗海洋生物污损领域中应用的研究进展

海洋生物污损一直是困扰全球海洋经济发展的重要问题之一。任何材料进入海洋环境,其表面不可避免地会遭受蛋白、多糖、细菌、海藻、软体动物等海洋生物贴附形成生物污损,不仅影响海上装备的正常运转和增加能源消耗,同时极易引起微生物腐蚀。因此,海洋抗污损新材料的开发显得极为迫切。目前碳纳米材料因具有优异的理化特性,而在海洋防腐、耐磨等工程上大量使用,其抑制海洋污损物贴附和生长的性能决定了碳材料在抗海洋生物污损领域具有广阔的应用前景。综述了石墨烯、类金刚石、金刚石、碳纳米管、富勒烯及其衍生物等典型碳纳米材料,在抗蛋白质、细菌、海藻等生物污损领域的应用现状以及抗污损机理。碳材料在海洋环境中优异的综合性能,预示其将给抗海洋生物污损新材料的开发和应用带来更多的机遇和可能。