孔径对微孔曝气充氧性能的影响

孔径是微孔曝气产品最重要的参数之一,研究孔径对微孔曝气氧传质的影响对于提高微孔曝气器充氧性能有重要意义。本研究在1.5 m水深条件下对不同大小孔径的钟罩型塑料微孔曝气器充氧性能进行评价。结果发现,在实验条件下,微孔曝气器的阻力损失RL、标准氧总转移系数KLas、标准氧转移速率SOTR,标准氧转移效率SOTE及理论动力效率E随孔径增大而显著减小。     

钛合金表面微弧氧化涂层在模拟海洋环境下摩擦腐蚀规律研究

目的 研究TC17钛合金及其表面微弧氧化(Microarc Oxidation,MAO)涂层在模拟海洋大气环境下发生摩擦腐蚀行为的规律及特征.方法 利用微弧氧化技术,在TC17钛合金表面原位生长MAO涂层,通过SEM、EDS以及XRD对MAO涂层微观结构、元素分布以及相组成进行检测分析.采用电化学工作站和摩擦腐蚀设备研...     

洪涝灾害后城镇景观长距离输水系统水文风险评估

对输水系统运作过程存在风险采取准确评估,可有效维护洪涝灾害后城镇景观设施完整性.该文提出一种基于MS-AR模型的长距离输水系统水文风险评估方法,首先分析输水节点结构重要性与网络结构抗毁性的耦联关系,推算平均节点结构重要度,明确节点对系统损坏贡献水平,利用节点结构重要度离散性质表示输水系统网络结构抗毁性,获取长距离输水系...     

长期饥饿下厌氧氨氧化反应器的启动与恢复性能

厌氧氨氧化菌生长缓慢,其富集过程困难,是限制厌氧氨氧化技术应用的瓶颈. 因基质供应不足导致的功能菌长期饥饿使厌氧氨氧化（ANAMMOX）反应器稳定运行面临更大挑战. 从长期饥饿的视角出发,重新审视厌氧氨氧化反应器的启动和恢复性能、揭示其抗性机制具有现实意义. 分别采用硝化和反硝化污泥在不同运行条件下成功启动了厌氧氨氧化反应器,分析了长期饥饿后不同启动策略下反应器的恢复性能,及污泥对长期饥饿的耐受机制. 结果表明,接种反硝化污泥的反应器采用高基质浓度低流速运行更稳定,运行85 d后NH₄⁺-N、NO₂^--N和总氮去除率分别高达98.7%、99.3%和89.3%;但长期饥饿（144 d）后采用低基质浓度高流速运行的氮去除性能更优,NH₄⁺-N、NO₂^--N和总氮去除率可在30 d后分别恢复至99.8%、99.8%和93.6%. 研究发现,饥饿期胞外多聚物将厌氧氨氧化菌包裹,有助于保持细胞完整以抵抗长期饥饿胁迫;nirS、hzsA和hdh基因的表达,保证了亚硝酸盐/一氧化氮氧化还原酶、联氨合成酶和联氨脱氢酶的合成,有助于维持厌氧氨氧化活性. 饥饿恢复前后厌氧氨氧化菌属的相对丰度无显著差异,其中Candidatus Kuenenia经30 d恢复后相对丰度提升86%以上,表明其对长期饥饿更具耐受性.     

石斛气生的兰科菌根组织结构及其对御旱研究

基于过去对铁皮石斛(Dendrobium candidum Wall.Ex Lindl.)气生的兰科菌根适应干旱环境胁迫机理的研究鲜为涉及,现开展了培养基质的不同水分质量分数(w(水分)=43.6%、16.8%、5.5%)对兰科菌根的外部形态以及内部组织结构影响的研究。研究结果表明:基质水分质量分数降低使石斛菌根外部形态发生多样变化;随着基质水分质量分数的不断降低,石斛的生长受到显著的抑制。当基质水分质量分数为5.5%时,石斛的多数生长指标均小于其它处理,但是根冠比(R/S)增加显著,高达2.22;通过不同切片多重镜检测定和图像分析,发现菌根的形态结构产生了天然的适应突变,独特的根被组织细胞层数多达5层以上,细胞壁相对加厚,细胞腔内网、羽状结构比其它两处理明显增多,石斛菌根通过形态结构的改变来适应水分胁迫并维持其生长发育,石斛菌根组织结构的这些改变大大提高了石斛御旱的能力;水分质量分数高低与菌根感染率呈负相关,越是干旱条件菌根真菌繁衍越活跃,菌丝团结构相持时间越长,菌根的这些适应性响应都提高了石斛的抗旱能力。     

催化氧化预处理及气浮-水解酸化-接触氧化工艺处理原料药废水

结合工程实例,介绍催化氧化预处理及气浮-水解酸化-接触氧化工艺在处理原料药废水工程中的实际应用。运行结果表明:该工艺运行稳定,处理效果好,COD去除率在90%以上。在进水COD值高于设计值15%的情况下,各项指标均能达到GB8978-1996《污水综合排放标准》二级排放标准。     

Analysis of antibiotic resistance of Escherichia coli isolated from the Yitong River in North-east China

The concentrations of four types of antibiotics in the Yitong River were detected. The concentration of total coliforms in summer was higher than that in spring. There was a seasonal difference in antibiotic resistance of E. coli. The E. coli in the Yitong River was found to have multiple antibiotic resistance. The Yitong River is one of the largest secondary tributaries of the Songhua River. The area where the Yitong River flows is densely populated and contains the livestock and poultry breeding areas of north-east China. These areas introduce a high risk of antibiotic contamination. In this study, the concentrations of four types of typical antibiotics including quinolones, tetracyclines, sulfonamides, and trimethoprim were determined by solid phase extraction-high performance liquid chromatography. The antibiotic resistance of Escherichia coli caused by antibiotic pollution was investigated. The concentration of total coliforms in the Yitong River was detected by the plate counting method. The antibiotic resistance of E. coli to quinolones, tetracyclines, sulfonamides, and trimethoprim was analyzed by the Kirby-Bauer method. The results showed that the concentration of total coliforms in the summer was higher than that in the spring. There was a seasonal difference in the resistance rate of E. coli to antibiotics except trimethoprim. The antibiotic resistance to fluoroquinolones was relatively low. The resistance rate to tetracyclines was higher during the summer. Moreover, resistance to several antibiotics was observed in all sections. This study provides basic data for research on pollution characteristics and prevention of antibiotic exposure in rivers.     

Detection of presumed genes encoding beta-lactamases by sequence based screening of metagenomes derived from Antarctic microbial mats

• Beta-lactamase genes were found in all samples from distant places in Antarctica. • Class C beta-lactamase coding genes were the most frequently found. • Diversity of sequences exceeds that of the beta-lactamases from clinical environment. Analysis of environmental samples for bacterial antibiotic resistance genes may have different objectives and analysis strategies. In some cases, the purpose was to study diversity and evolution of genes that could be grouped within a mechanism of antibiotic resistance. Different protocols have been designed for detection and confirmation that a functional gene was found. In this study, we present a sequence-based screening of candidate genes encoding beta-lactamases in 14 metagenomes of Antarctic microbial mats. The samples were obtained from different sites, representing diverse biogeographic regions of maritime and continental Antarctica. A protocol was designed based on generation of Hidden Markov Models from the four beta-lactamase classes by Ambler classification, using sequences from the Comprehensive Antibiotic Resistance Database (CARD). The models were used as queries for metagenome analysis and recovered contigs were subsequently annotated using RAST. According to our analysis, 14 metagenomes analyzed contain A, B and C beta-lactamase genes. Class D genes, however, were identified in 11 metagenomes. The most abundant was class C (46.8%), followed by classes B (35.5%), A (14.2%) and D (3.5%). A considerable number of sequences formed clusters which included, in some cases, contigs from different metagenomes. These assemblies are clearly separated from reference clusters, previously identified using CARD beta-lactamase sequences. While bacterial antibiotic resistance is a major challenge of public health worldwide, our results suggest that environmental diversity of beta-lactamase genes is higher than that currently reported, although this should be complemented with gene function analysis.     

厌氧-好氧处理磺胺废水实验研究

采用上流式厌氧污泥床和好氧复合反应器处理磺胺废水,在厌氧TOC负荷约1.2kg/(m³·d),好氧TOC负荷约0.6kg/(m³·d)的运行条件下,TOC厌氧去除率可达50%以上,TOC总去除率可达85%以上厌氧过程有约30%SO₄^2-被去除,无CH4产生,这表明TOC的厌氧去除为硫酸盐还原条件下的缺氧降解.     

火灾下钢管混凝土柱的耐火极限有限元分析

为研究将轻骨料混凝土作为防火保护层对钢管混凝土柱耐火极限的影响以及保护层厚度实用计算方法,采用有限元方法确定高温下钢管混凝土柱的温度场,通过ABAQUS有限元软件建立钢管混凝土柱的耐火极限模型,分析各参数对构件耐火极限的影响程度,基于数值模拟计算结果,给出在火灾下钢管混凝土柱在工程常用范围内的抗火实用计算公式,将计算结...