Influence of in situ biofilm coverage on the radionuclide adsorption capacity of subsurface granite

Any migration of radionuclides from nuclear waste repositories is expected to be mitigated by adsorption to the host rocks surrounding hydraulically conductive fractures. Fluid rock interfaces are considered to be important barriers for nuclear waste disposal schemes but their adsorptive capacity can be affected by the growth of microbial biofilms. This study indicates that biofilms growing on fracture surfaces decrease the rocks adsorption capacity for migrating radionuclides except for trivalent species. Potential suppression of adsorption by biofilms should, therefore, be accounted for in performance safety assessment models. In this study, the adsorptive capacity of in situ anaerobic biofilms grown 450 m underground on either glass or granite slides was compared to the capacity of the same surfaces without biofilms. Surfaces were exposed to the radiotracers 60Co(II), 147Pm(III), 241Am(III), 234Th(IV), and 237Np(V) for a period of 660 h in a pH neutral anaerobic synthetic groundwater. Adsorption was investigated at multiple time points over the 660 h using liquid scintillation and ICP-MS. Results indicate that these surfaces adsorb between 0 and 85% of the added tracers under the conditions of the specific experiments. After 660 h, the distribution coefficients, R (ratio between what is sorbed and what is left in the aqueous phase), approached 3 x 10(4) m for 60Co, 3 x 10(5) m for 147Pm and 241Am, 1 x 10(6)m for 234Th, and 1 x 10(3) m for 237Np. The highest rate of adsorption was during the first 200 h of the adsorption experiments and started to approach equilibrium after 500 h. Adsorption to colloids and precipitates contributed to decreases of up to 20% in the available 60Co, 147Pm, 241Am, and 237Np in the adsorption systems. In the 234Th system 95% of the aqueous 234Th was removed by adsorbing to colloids. Although the range of Rvalues for each surface tested generally overlapped, the biofilms consistently demonstrated lower R values except for the trivalant 147Pm and 241Am adsorption systems.     

Effect of different operational conditions on biofilm development, nitrification, and nitrifying microbial population in moving-bed biofilm reactors

In this study, the effect of different operational conditions on biofilm development and nitrification in three moving-bed biofilm reactors (MBBRs) was investigated: two reactors were operated in a continuously fed regime and one in sequencing-batch mode. The presence of organic carbon reduced the time required to form stable nitrifying biofilms. Subsequent stepwise reduction of influent COD caused a decrease in total polysaccharide and protein content, which was accompanied by a fragmentation of the biofilm, as shown by scanning electron microscopy, and by an enrichment of the biofilm for nitrifiers, as observed by fluorescent in situ hybridization (FISH) analysis. Polysaccharide and protein concentrations proved to be good indicators of biomass development and detachment in MBBR systems. Ammonium- and nitrite-oxidizing bacteria activities were affected when a pulse feeding of 4 g of NH(4)-N/(m(2)·day) was applied. Free nitrous acid and free ammonia were likely the inhibitors for ammonium- and nitrite-oxidizing bacteria.     

Affinity of microbial fuel cell biofilm for the anodic potential

In analogy to the well established dependency of microbial reactions on the redox potential of the terminal electron acceptor, the dependency of the microbial activity in a highly active microbial fuel cell on the potential of the electron-accepting electrode (anode) in a microbial fuel cell (MFC) is investigated. An acetate-fed, pH-controlled MFC was operated for over 200 days to establish a highly active MFC anodic biofilm using ferricyanide as the catholyte and granular graphite as electrode material. From the Coulombic efficiency of 83% of the MFC the microbial activity could be recorded by online monitoring of the current. Our results suggest that (1) in analogy to the Michaelis-Menten kinetics a half-saturation anodic potential (here termed k(AP) value) could be established at which the microbial metabolic rate reached half its maximum rate. This k(AP) value was about -455 mV (vs Ag/AgCl) for our acetate-driven MFC and independent of the oxidation capacity of the cathodic half-cell; (2) a critical AP (here termed AP(crit)) of about -420 mV (vs Ag/AgCl) was established that characterizes the bacterial saturation by the electron-accepting system. This critical potential appeared to characterize the maximum power output of the MFC. This information would be useful for modeling and optimization of microbial fuel cells and the relative comparison of different microbial consortia at the anode.     

The biofilm forming potential of bacterial species in the genus Campylobacter

The biofilm forming abilities of 16 strains representative of 14 of the 16 species comprising the genus Campylobacter were determined on glass, stainless steel, and polystyrene plastic. The formation of biofilms has been suggested as a means by which Campylobacter is able to persist within an inhospitable environment. Of the eight microaerophilic Campylobacter species, including two strains each of Campylobacter jejuni and Campylobacter fetus, only C. jejuni strain 81–176 reliably produced a visible biofilm on multiple surfaces. Alternately, all six strains of the anaerobic Campylobacter species reliably produced visible biofilms on multiple surfaces. Electron micrographs of the individual biofilms showed relatively homogeneous biofilms produced by the anaerobic strains, while the microaerophilic C. jejuni strain 81–176 produced a biofilm containing similar quantities of both the spiral and coccoid forms. This survey suggests a difference in the biofilm forming potentials and the morphologies of the bacteria comprising the biofilms between anaerobic and microaerophilic species of Campylobacter. Additionally, differences observed in the biofilm forming ability of two strains of C. jejuni suggest the need for a further investigation of the biofilm forming potential of this species using a larger number of strains.     

Growth potential and biofilm development of nonstarter bacteria on surfaces exposed to a continuous whey stream

Commercial Cheddar cheese production uses an automated, continuous production system that provides favorable conditions for specific undesirable bacterial subpopulations in certain sections of the processing system. The draining and matting conveyor (DMC) is a large, fully enclosed series of conveyor belts that separates curd and whey on the first drain belt and supports the cheddaring process in subsequent sections. In a previous study, we demonstrated that coliforms increase in the draining section of the DMC (pH 6.0–6.3, 36°C) over a typical 18-h production shift and can lead to detectable coliforms in finished cheese. Sampling at the commercial plant indicated 2 sources of very low levels of coliforms: (1) subpasteurized whey and curd entering the DMC and (2) surfaces in the DMC after sanitation. Mitigation of these sources would require different approaches. The aim of this study was to investigate whether naturally low levels of coliforms in whey could increase in the bulk liquid and attach to different surface materials within 18 h. A laboratory-scale system was created to mimic the conditions of the initial draining section of the DMC and consisted of single-pass, naturally contaminated whey (pH 6.3, 35°C) flowing through a bioreactor (1.11 L/h) containing coupons of surface types found in the DMC (stainless steel and polypropylene). Whey inside the bioreactor chamber and surface coupons were enumerated for bacterial subpopulations on selective media for planktonic and attached bacteria, respectively, at 0, 12, 15, and 18 h. Bacterial isolates were identified by 16S rDNA sequencing. Nonstarter bacteria present in the whey at 0 h included coliforms (Enterobacter), Pseudomonas, and Acinetobacter (0.80, 2.55, and 2.32 log cfu/mL, respectively), with each increasing significantly in whey (6.18, 7.00, and 5.89 log cfu/mL) and on coupons (5.20, 6.85, and 5.29 log cfu/cm², respectively) after 18 h in the continuous flowing system. Scanning electron microscopy confirmed bacterial attachment on both surfaces, with early biofilm development evident on polypropylene coupons by 18 h. Results from this laboratory-scale study demonstrated that naturally low levels of coliforms entering the DMC in the whey could replicate within the conditions of the draining section of the DMC to the levels found in the commercial production environment.     

圆压圆烫金优势明显

首台高科技的圆压圆烫金机自1995年在Drupa印刷博览会上推出以来,其明显的技术优势正在逐步为业内人士所认知,并将成为近期内包装印刷行业的一个新的投资热点.其明显的技术优势表现在如下几个方面:     

Interactions between perchlorate and nitrate reductions in the biofilm of a hydrogen-based membrane biofilm reactor

We studied the microbial functional and structural interactions between nitrate (NO(3)(-)) and perchlorate (ClO(4)(-)) reductions in the hydrogen (H(2))-based membrane biofilm reactor (MBfR). When H(2) was not limiting, ClO(4)(-) and NO(3)(-) reductions were complete, and the MBfR's biofilm was composed mainly of bacteria from the ε- and β-proteobacteria classes, with autotrophic genera Sulfuricurvum, Hydrogenophaga, and Dechloromonas dominating the biofilm. Based on functional-gene and pyrosequencing assays, Dechloromonas played the most important role in ClO(4)(-) reduction, while Sulfuricurvum and Hydrogenophaga were responsible for NO(3)(-) reduction. When H(2) delivery was insufficient to completely reduce both electron acceptors, NO(3)(-) reduction out-competed ClO(4)(-) reduction for electrons from H(2), and mixotrophs become important in the MBfR biofilm. β-Proteobacteria became the dominant class, and Azonexus replaced Sulfuricurvum as a main genus. The changes suggest that facultative, NO(3)(-)-reducing bacteria had advantages over strict autotrophs when H(2) was limiting, because organic microbial products became important electron donors when H(2) was severely limiting.     

核心优势是品牌之本

在全球铅笔行业,没有人不知道马可铅笔。作为世界铅笔的主要生产厂家,马可引领着书写(绘画)工具的潮流,也铸就了马可辉煌的今天。1)公司和产品概况上海马可文化用品有限公司成立于1992年。专业生产和销售木制铅笔、油画棒、蜡笔、橡皮等文     

Membrane-aerated biofilm reactor for the treatment of acetonitrile wastewater

A membrane-aerated biofilm reactor (MABR) was studied for the treatment of wastewater containing acetonitrile, a typical organonitrile compound. The MABR used hydrophobic hollow fiber membranes as the diffusers for bubbleless aeration as well as the carriers for biofilm growth. The objectives were to prevent the stripping-loss of acetonitrile during aeration and to achieve acetonitrile biodegradation plus nitrogen removal simultaneously in a single biolfilm on the membranes. In the MABR, oxygen and substrates were supplied to the biofilm from opposite sides, in contrast to those from the same side in conventional biofilm bioreactors. Operational factors, including surface loading rate and upflow fluid velocity in the bioreactor, on the effect of acetonitrile biodegradation performance were examined. The profiles of dissolved oxygen concentration and microbial activities and populations in the biofilm were investigated. Experimental results showed that, with the adapted microorganisms, removal of acetonitrile at approximately 98.6 and 83.3%, in terms of total organic carbon and total nitrogen, were achieved at a surface loading rate (in terms of membrane surface) of up to 11.29 g acetonitrile/ m2 x d with an upflow fluid velocity of 12 cm/s and a hydraulic retention time of 30 h. The biofilm on the membranes developed an average thickness of about 1.6 mm in the steady state and consisted of oxic/anoxic/anaerobic zones that provided different functions for acetonitrile degradation, nitrification, and denitrification. The acetonitrile-degrading bacteria in the MABR appeared to secrete more extracellular polymeric substances that enhanced the attachment and development of the biofilm on the membranes. The study demonstrated the potential of using the MABR for the treatment of organonitrile wastewater.     

Methanogenic communities on the electrodes of bioelectrochemical reactors without membranes

Methane fermentation was successfully carried out in bioelectrochemical reactors without membranes under a working potential of − 0.6 or − 0.8 V (vs. Ag/AgCl) and neutral pH conditions. The hydrogenotrophic methanogens that dominated on the anodic and cathodic electrodes differed from those found on the electrodes in the control reactors without electrochemical reactions.     

Effectiveness of oxidation-reduction potential and pH as monitoring and control parameters for nitrogen removal in swine wastewater treatment by sequencing batch reactors

Two bench-scale sequencing batch reactors (SBRs) were operated in a fixed hydraulic retention time study to investigate the effectiveness of oxidation-reduction potential (ORP), pH and dissolved oxygen as parameters for indicating denitrification followed by nitrification in SBRs for swine wastewater treatment. The ORP and pH profiles were monitored and evaluated under different denitrification and nitrification conditions with and without a supplemental carbon source. With a low C/N ratio, and using a suitable C/N ratio adjustment control, ORP and pH could be used as monitoring and control parameters in both the anoxic and oxic phases for practical swine wastewater treatment. High-level accumulation of nitrate was observed without any C/N ratio adjustment. In this case, ORP and pH were not useful for monitoring denitrification followed by nitrification in SBRs. According to our research, with regard to N removal, it would be better to use pH as a parameter during the oxic phase and ORP as a parameter during the anoxic phase. Using a suitable adjustment of a ON ratio in the influent by adding swine slurry, a high total nitrogen removal efficiency of up to 95.5% was reached. It was found that, in this case, the use of ORP and pH as parameters for real-time control processes was possible in swine wastewater treatment.     

食品加工过程中细菌生物被膜的危害及控制

生物被膜中的微生物生活在一个由胞外聚合物（EPS）形成的环境中,它的形成是微生物生长过程中的一个保护模式,允许细胞在恶劣的环境中生存并分散到新的环境中。食品加工过程中有害菌形成的生物被膜对食品工业的危害极大,可使微生物残存增加,加工设备无法严格清洗、消毒,导致产品受到污染。该文在收集、研究现有文献的基础上归纳介绍了生物被膜的特点及其形成过程和形成机制,概述了生物被膜的危害、控制及检测方法,旨在提高人们对生物被膜的认识,推动该领域的研究发展。     

一体化运行的粮食物流园区竞争优势分析

一体化运行的粮食物流园区是一种粮食产业内相互联系的企业和机构在地域、空间上的企业集群,以粮食物流为主,融粮食批发、粮食信息、粮食加工、粮食检测、粮食及其加工品展示及资金流为一体,具有地域密集性、地方根植性、产业关联性、自发组织性等特性。粮食物流企业、粮食加工企业、粮食及其加工品的销售企业等粮食产业相关企业有效进行资源整合,构建粮食产业链,发挥粮食产业集聚效应,共同创造综合物流成本优势、信息与技术的传递优势、资源集聚优势、集群化成长优势、品牌创造优势。     

Effect of NaCl on the biofilm formation by foodborne pathogens

This study was designed to evaluate the effect of NaCl on the biofilm formation of Listeria monocytogenes, Staphylococcus aureus, Shigella boydii, and Salmonella Typhimurium. The biofilm cells were cultured in media containing different NaCl concentrations (0% to 10%) for 10 d of incubation at 37 °C using a 24-well polystyrene microtiter plate, collected by swabbing methods, and enumerated using plate count method. The attachment and detachment kinetic patterns were estimated according to the modified Gompertz model. The cell surface hydrophobicity and auto-aggregation were observed at different NaCl concentrations. Most strains showed 2 distinctive phases at lower than 6% NaCl, while the numbers of adhered cells gradually increased throughout the incubation period at 4% to 10% NaCl. At 0% NaCl, the numbers of adhered L. monocytogenes, S. aureus, S. boydii, and S. Typhimurium cells rapidly increased up to 7.04, 6.47, 6.39, and 7.27 log CFU/cm(2), respectively, within 4 d of incubation. The maximum growth rate (k(A)) and specific growth rate (μ(A)) of adherent pathogenic cells were decreased with increasing NaCl concentration. Noticeable decline in the numbers of adherent cells was observed at low concentration levels of NaCl (<2%). The adherence abilities of foodborne pathogens were influenced by the physicochemical surface properties. The hydrophobicity and auto-aggregation enhanced the biofilm formation during the incubation periods. Therefore, this study could provide useful information to better understand the adhesion and detachment capability of foodborne pathogens on food contact surfaces.     

Long-term performance of high-rate anaerobic reactors for the treatment of oily wastewater

Complex oily wastewater from a food industry was treated in three different UASB reactors at different operating conditions. Although all three systems achieved fat, oil, and grease (FOG) and COD removal efficiencies above 80% at an organic loading of 3 kg COD/m3 x d, system performance deteriorated sharply at higher loading rates, and the presence of high FOG caused a severe sludge flotation resulting in failure. Initially, FOG accumulated onto the biomass which led to sludge flotation and washout of biomass. The loss of sludge in the bed increased the FOG loading to the biomass and failure ensued. Contrary to previous findings, accumulation of FOG rather than influent FOG concentrations or volumetric FOG loading rate was the most importantfactor governing the high-rate anaerobic reactor performance. The critical accumulated FOG loading was identified as 1.04 +/- 0.13 g FOG/g VSS for all three reactors. Furthermore, FOG accumulation onto the biomass was identified mainly as palmitic acid (>60%) whereas the feed LCFA contained only 30% of palmitic acid and 50% of oleic acid.     

Comparative advantage: the impact of ISO 14001 environmental certification on exports

Relative to the enormous acceptance of the ISO 9000 quality standard, the ISO 14001 environmental management certification has been met with only moderate enthusiasm among industrial facilities. The literature on corporate motivation for ISO 14001 participation is relatively modest considering the enormous number of publications reviewing other aspects of its adoption and implementation. It would seem that the present "marketing" package supporting ISO environmental commitments does not seem to offer sufficiently persuasive incentives for increased sales, either domestically or internationally. While researchers assume that a higher export rate of companies is positively associated with higher ISO participation rates, there have been very few empirical studies that support this inference, and conclusions have not been based on data taken from importing countries orfrom a systematic evaluation of expressed corporate preference for products sold by ISO 14001 certified companies. The present study reports the results of a survey to firms in six countries that are Israel's leading trade partners, importing chemicals, textiles, and produce. The survey results confirm that while the international market still considers price and quality as the paramount factors in selection of suppliers, environmental management systems (EMS) are an important feature that is frequently taken into consideration. EMS certification appears to signify a supplier who is managing the business well and exhibiting ethical responsibility. The European market proved to be more environmentally conscious than those in other industrialized parts of the world. EMS offer a particularly valuable advantage for producers wishing to reach European markets. As policy-makers seek to expand the voluntary adoption of EMS, a clear advantage for exporters should be highlighted among national industries.