Dental Chatter: Bacterial Cross-Talk in the Biofilm of the Oral Cavity

Dental biofilms are composed of hundreds of bacterial species. These biofilms are diverse biological structures due to the heterogeneity of the many different types of supports in the oral cavity. The bacteria immobilized in these biofilms are exposed to rapid environmental changes such as pH, temperature, nutrition and anti-plaque agents. One mode in which these bacteria adapt in the dental biofilm is by quorum sensing. This cell-cell communication regulates diverse sets of adhesion modes, physiological changes, virulence properties, allowing the bacteria to persist in the dental biofilm under rapid environmental changes. In this review, we will concentrate mostly on the cariogenic bacterium Streptococcus mutans as one of the pivotal microorganisms in the supra-gingival biofilm that plays a major role in dental caries.     

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     

生物栅-复合人工湿地系统对黑臭河水的中试处理

针对黑臭河水溶解氧极低、有机物污染重的特点,充分利用生物栅技术和人工湿地技术组合而成生物栅-复合人工湿地系统(BFG-IVCWs),来净化黑臭河水降低COD等污染物质。试验结果表明:软性填料槽对COD的去除率为30%~40%,人工湿地对COD的去除率保持在45%,梭鱼草及蜂巢石对COD去除效果明显。该系统运行期间TP去除率为58.13%~83.25%,对TN去除效果初期较好,达到58.14%。     

Characteristics of hydrogen evolution and oxidation catalyzed by Desulfovibrio caledoniensis biofilm on pyrolytic graphite electrode

Hydrogenase, an important electroactive enzyme of sulphate-reducing bacteria (SRB), has been discovered having the capacity to connect its activity to solid electrodes by catalyzing hydrogen evolution and oxidation. However, little attention has been paid to similar electroactive characteristics of SRB. In this study, the electroactivities of pyrolytic graphite electrode (PGE) coated with SRB biofilm were investigated. Two corresponding redox peaks were observed by cyclic voltammetry detection, which were related to the hydrogen evolution and oxidation. Moreover, the overpotential for the reactions decreased by about 0.2 V in the presence of the SRB biofilm. When the PGE coated with the SRB biofilm was polarized at 0.24 V (vs. SHE), an oxidation current related to the hydrogen oxidation was found. The SRB biofilm was able to obtain electrons from the −0.61 V (vs. SHE) polarized PGE to form hydrogen, and the electron transfer resistance also decreased with the formation of SRB biofilm, as measured by the non-destructive electrochemical impendence spectroscopy detection. It was concluded that the hydrogen evolution and oxidation was an important way for the electron transfer between SRB biofilm and solid electrode in anaerobic environment.     

膜-序批式生物膜法(MSBBR)处理生活污水试验研究

采用膜-序批式生物膜法(MSBBR)处理高校校园生活污水,研究了系统稳定运行后的处理效果.结果表明,系统出水COD平均为44mg·L-1,NH3-N、TN、TP的平均质量浓度分别2、34、8.20、0.326 mg·L-1,对COD、NH3-N、TN、TP的平均去除率分别达到83.4%、87.01%、67.46%、84.34%,且系统具有较强的抗冲击负荷能力.     

SBBR废水生物处理新工艺的研究发展及应用

介绍了序批式生物膜反应器（SBBR）这种新型废水处理工艺技术的基本原理及特点,概括了SBBR在国内外污水处理中的研究现状以及有待发展与完善的问题,同时指出该工艺是一种很有竞争力的污水处理工艺,拥有良好的发展前景。     

铁炭微电解—混凝沉淀—MBBR工艺处理腈纶废水

腈纶废水对微生物活性具有不良影响,采用铁炭微电解—混凝沉淀-MBBR工艺对其进行处理.通过正交试验,探索了铁炭微电解预处理腈纶废水的最佳工艺条件;再以MBBR为生物反应器,进一步处理经过铁炭微电解预处理的腈纶废水.结果表明,最终出水COD可稳定至100 mg/L以下,氨氮接近15 mg/L.该工艺是处理腈纶废水的有效方...     

移动床生物膜反应器污水处理技术简介

简述了移动床生物膜反应器的工艺原理和特点,详细介绍了国内外移动床生物膜反应器的研究现状,最后提出移动床生物膜反应器在实际工程应用和理论研究中的发展趋势。