污水生物脱氮除磷新工艺研究进展

近年来,生物脱氮除磷工艺取得了长足发展,出现了很多不同的处理工艺。这些新工艺在形式和流程上都优于传统工艺。文章在总结传统脱氮除磷工艺的基础上,介绍了近几年开发出的污水生物脱氮除磷新技术。随着生物脱氮除磷技术研究的进一步深入,高效、节能的生物膜与活性污泥组合的复合生物膜新工艺的将会成为脱氮除磷工艺的重要发展方向。     

Antimicrobial and antibiofilm activities of procyanidins extracted from laurel wood against a selection of foodborne microorganisms

This study aimed to evaluate the antimicrobial and antibiofilm activities of two procyanidins isolated from an ethyl acetate extract of laurel wood against a selection of foodborne pathogens. The analysis of the extract by HPLC–DAD/ESI–MS allowed us to detect the presence of two procyanidins, which were selectively isolated and identified by chromatographic and spectroscopic means as cinnamtannin B‐1 ( 1 ) and procyanidin B‐2 ( 2 ). Procyanidins 1 and 2 exhibited two biological activities: inhibition of bacterial growth at high concentrations and prevention of biofilm formation at lower concentrations. Synergistic effect was also detected when both compounds were tested in combination against Listeria monocytogenes. Significant effects were also detected on disruption of preformed biofilm. The ability of procyanidins to inhibit microbial growth and biofilm formation and to synergistically work with each other may stimulate a market as natural food preservatives, and/or natural sanitisers for processing equipment where foodborne pathogens reside.     

Inhibitory Activity of Paenibacillus polymyxa on the Biofilm Formation of Cronobacter spp. on Stainless Steel Surfaces

The objective of this study was to control the survival or biofilm formation of Cronobacter spp. on stainless steel surfaces using Paenibacillus polymyxa. The antibacterial activity of a cell‐free culture supernatant (CFCS) of P. polymyxa against Cronobacter spp. was found to vary with P. polymyxa incubation time. Maximum activity occurred when P. polymyxa was incubated at 25 or 30 °C for 96 h. When the CFCS was introduced to Cronobacter spp. adhered to stainless steel strips at 25 °C for up to 72 h, the CFCS successfully inhibited Cronobacter biofilm formation. Additionally, stainless steel surfaces with a preformed P. polymyxa biofilm were exposed to Cronobacter spp. suspensions in PBS or 0.1% peptone water at 3, 5, or 7 log CFU/mL to facilitate its attachment. The Cronobacter population significantly decreased on this surface, regardless of inoculum level or carrier, when the P. polymyxa biofilm was present. However, the microbial population decreased within 6 h and remained unchanged thereafter when the surface was immersed in an inoculum suspended in 0.1% peptone water at 5 or 7 log CFU/mL. These results indicate that P. polymyxa is able to use a promising candidate competitive‐exclusion microorganism to control Cronobacter spp.     

Biogas potential and microbial population distributions in flushed dairy manure and implications on anaerobic digestion technology

BACKGROUND: There remain technological deficiencies in the economical anaerobic digestion of the entire flow of flushed dairy manure on farms within cold climates. In order to develop an anaerobic digester tailored for this purpose, this study investigated the distributions of biomass and biogas generated in three particle‐size‐characterized zones of flushed dairy manure. RESULTS: Results demonstrate that comparable biogas generations are equally distributed between the solids and liquid phases of flushed dairy manure, implying that at least 50% of methane generation might be lost when utilizing existing processes that only selectively handle the liquid or solids phases. Microscopic and kinetic studies show that the majority of microorganisms in the manure are attached to the surface of undigested dairy manure fibrous solids. In particular, greater than 70% of acetate‐utilizing methanogens were found closely associated with the indigestible solids. This high microbial affinity to the dairy manure solids phase can be traced back to the selection pressure driven bacterial immobilization mechanism in cattle rumen. CONCLUSION: This study shows that dairy manure fibrous solids have the potential to act as effective natural biomass carriers for high rate and simultaneous methanation of both solids and liquid phases of flushed dairy manure in one digester. Copyright © 2010 Society of Chemical Industry     

白腐菌生物膜的形成及其性能的研究

用生物流化床研究了白腐菌形成生物膜的条件、生物膜的活性及其稳定性，自腐菌生物流化床处理2，4-二氯酚的效果。结果表明，选择适合的水力停留时间，自腐菌可以形成生物膜，生物膜的活性高，稳定性好。在生物膜流化床中自腐菌不易流失，能维持较高的浓度，处理2，4-二氯酚的效率达到91．2％，为自腐菌的工程应用探索了一条新的途径。     

铁氧化菌作用下316L不锈钢点蚀电化学特性的研究

采用电化学测量、交流阻抗技术、扫描电镜观察和能谱分析等实验方法,研究了316L不锈钢在铁氧化菌(IOB)溶液中的腐蚀电化学行为,分析了炼油厂冷却水系统微生物腐蚀的特征及机制,结果表明,在含有IOB溶液中的自腐蚀电位(Ecorr)、点蚀电位(Epit)和极化电阻(Rp)均随浸泡时间的增加呈现出降-升-降的变化趋势;在含有IOB溶液中的腐蚀速率均大于在无菌溶液中;IOB的生长代谢活动及其生物膜的完整性和致密性影响了316L不锈钢表面的腐蚀过程,使不锈钢表面的钝化膜层腐蚀破坏程度增加,加速了316L不锈钢的点蚀.