污泥龄对膜生物反应器性能的影响

研究了膜生物反应器污泥龄对胞外聚合物(EPS)含量、污泥特性、污泥颗粒粒径分布及膜过滤阻力的影响.结果表明,污泥龄(SRT)为30 d时混合液中胞外聚合物(EPS)和膜面上的EPS含量分别约为90 mg/g、0.8 g/m2,随污泥龄的延长二者同步增加,EPS在膜面上几乎没有积累;混合液EPS含量的增加改变了细菌表面电荷且增大了细菌表面亲水基和疏水基的比例,使细菌存在状态由不稳定型(R型)向稳定型(S型)转变.造成污泥的沉降困难;在长污泥龄运行中.混合液中污泥颗粒呈现双峰分布,泥龄30 d时在O.5 μm和16 μm处有2个峰且平均粒径约14μm,污泥龄延长双峰分布向颗粒小的方向移动;混合液中微细颗粒含量及粒径分布对膜污染起决定性作用.综合考虑膜污染和污泥特性,膜生物反应器的污泥龄应控制在优势菌最小世代时间(运行温度下的最大比增长速度)的120倍以下.     

Antibiotic resistance analysis of fecal coliforms to determine fecal pollution sources in a mixed-use watershed

Antibiotic resistance analysis was performed on fecal coliform(FC) bacteria from a mixed-use watershed to determine thesource, human or nonhuman, of fecal coliform contamination. The study consisted of discriminant analysis of antibioticresistance patterns generated by exposure to fourconcentrations of six antibiotics (ampicillin, gentamicinsulfate, kanamycin, spectinomycin dihydrochloride,streptomycin sulfate, and tetracycline hydrochloride). Areference database was constructed from 1125 fecal coliformisolates from the following sources: humans, domestic animals(cats and dogs), agricultural animals (chickens, cattle, andhorses), and wild animals. Based on similar antibioticresistance patterns, cat and dog isolates were grouped asdomestic animals and horse and cattle isolates were grouped aslivestock. The resulting average rate of correctclassification (ARCC) for human and nonhuman isolates was94%. A total of 800 FC isolates taken from the watershedduring either a dry event or a wet event were classifiedaccording to source. Human sources contribute a majority(>50%) of the baseflow FC isolates found in the watershed inurbanized areas. Chicken and livestock sources areresponsible for the majority of the baseflow FC isolates foundin the rural reaches of the watershed. Stormwater introducesFC isolates from domestic (16%) and wild (21%) sourcesthroughout the watershed and varying amounts (up to 60%) fromchicken and livestock sources. These results suggest thatantibiotic resistance patterns of FC may be used to determinesources of fecal contamination and aid in the direction ofwater quality improvement.     

预涂动态膜在乳化油废水处理中的阻力分布及其抗污染特性

为讨论预涂动态膜的抗污染特性,测定了陶瓷膜、高岭土预涂动态膜和高岭土/MnO2复合预涂动态膜分别在乳化油废水处理中的阻力分布,并用SEM扫描电镜对污染预涂动态膜形貌进行了表征。结果表明,乳化油污染阻力明显高于基膜(或陶瓷膜)固有阻力及涂膜粒子形成的阻力,乳化油对预涂动态膜或陶瓷膜的污染是导致膜通量衰减的主要原因;高岭土和复合预涂动态膜所用基膜污染阻力低于陶瓷膜的内部污染阻力,其中复合预涂动态膜所用基膜的污染阻力最小;复合动态膜层比高岭土动态膜层的污染程度低;污染预涂动态膜表面呈现明显的凝胶态物质,其基膜外壁面未呈现凝胶态物质。处理乳化油废水中,动态膜层可有效保护基膜,表现出了较强的抗污染性能。     

Biomonitoring marine habitats in reference to antibiotic resistant bacteria and ampicillin resistance determinants from oviductal fluid of the nesting green sea turtle, Chelonia mydas

During the egg-laying process, oviductal fluid was collected using a non-invasive procedure from the cloacal vent of the green turtles. Forty-two independent isolates of antibiotic-resistant bacteria from 11 genera were obtained from 20 turtles during nesting. The dominant isolate was Citrobacter (52.4%), followed by Pseudomonas, Proteus, Enterobacter, Salmonella, Escherichia coli, Shigella, Edwardsiella, Morganella, Providencia and Arcomobacter. Most of the isolates were resistant to ampicillin. Ampicillin-resistant isolates showed variations in their resistance for the following classes of β-lactamases: extended-spectrum β-lactamases (EBSLs), AmpC type β-lactamases C (AmpC), and screen-positive β-lactamase. None of the isolates produced metallo β-lactamase. Some ampicillin-resistant genes were detected by multiplex polymerase chain reaction (PCR) only. Inhibitor based test (IBT) categorized some isolates as AmpC β-lactamase producers. β-Lactamase genes were detected from a few strains. The sequencing of those genes revealed the presence of cephamycinase (CMY) and AmpC β-lactamases. The oviductal fluid was used in this study as a source of bacterial antibiotic-resistant determinants for biomonitoring marine turtles exposed to contaminated effluents. This data can be of value in understanding the decline of this endangered species as a result of exposure to marine pollution which is threatening their survival.     

Environmental pollution by antibiotics and by antibiotic resistance determinants

Antibiotics are among the most successful drugs used for human therapy. However, since they can challenge microbial populations, they must be considered as important pollutants as well. Besides being used for human therapy, antibiotics are extensively used for animal farming and for agricultural purposes. Residues from human environments and from farms may contain antibiotics and antibiotic resistance genes that can contaminate natural environments. The clearest consequence of antibiotic release in natural environments is the selection of resistant bacteria. The same resistance genes found at clinical settings are currently disseminated among pristine ecosystems without any record of antibiotic contamination. Nevertheless, the effect of antibiotics on the biosphere is wider than this and can impact the structure and activity of environmental microbiota. Along the article, we review the impact that pollution by antibiotics or by antibiotic resistance genes may have for both human health and for the evolution of environmental microbial populations.     

定向钻穿越管道阴极保护数值模拟评价方法

目的通过数值模拟的方法探索定向钻穿越管道的阴极保护评价。方法根据一条5130 m长度的定向钻穿越管道的实际参数,基于CDEGS软件计算方法,应用涂层耐受电压与电流密度的关系,计算定向钻管道浅埋层和岩石层中的管道的电位分布。结果通过调整土壤分层电阻率参数及土壤分层厚度进行计算,得到了定向钻穿越管道在分层土壤电阻率条件下的阴极保护电位分布规律。结论明确了土壤电阻率是影响定向钻管道电位分布的主要因素,形成了基于定向钻管道两端阴极保护电位和土壤分层电阻率,推导了整条定向钻穿越管道的阴极保护电位分布情况的评价方法。     

Isolation and characterisation of cadmium-resistant bacteria from an industrially polluted coastal ecosystem on the southeast coast of India

A total of 35 bacterial strains were isolated from the industrially polluted Cuddalore coast, on the southeast coast of India. Of these, 17 strains were cadmium resistant and the remainder were sensitive. Six strains (C-1, C-8, C-10, C-12, C-14 and N-1) were selected based on high levels of cadmium tolerance (>150 mg L^?1) and were termed highly cadmium-resistant bacteria (HCRB). These HCRB were identified on the basis of morphological, biochemical and partial sequencing of their 16S rRNA genes. The antibiotic-susceptibility patterns and minimum inhibitory concentrations (MIC) of different metals (Cu²⁺, Pb²⁺ and Zn²⁺) against each HCRB were determined. Among the isolates, C-14 showed high degrees of metal and antibiotic resistance compared with other HCRB. Growth rates of HCRB at two different Cd²⁺ concentrations (50 and 100 mg L^?1) and under different metal conditions (Cd²⁺, Cu²⁺ and Pb²⁺) were also investigated. HCRB growth rates were lower in the metal-treated condition than in the untreated condition. Isolates C-14 and N-1 removed>80% of Cd²⁺ from cadmium-treated broth. However, isolate C-14 removed 92.3% of Cd²⁺ compared with 86.5% for isolate N-1. Bacteria showing residual growth rates under metal stress conditions might be useful in metal removal applications under growing conditions.     

3个树种凋落叶水浸提液对三叶鬼针草生长及抗性生理的影响

入侵植物三叶鬼针草(Bidens pilosa)对农业生产、生物多样性和生态系统安全有极大的威胁,利用植物间的化感作用抑制有害植物生长或开发植物源除草剂,是减少化学除草剂对环境负面影响的良好措施。常见树种巨桉(Eucalyptus grandis)、香樟(Cinnamomum camphora)和核桃(Juglans regia)叶片所含次生代谢物质对植物和微生物具有较强的化感潜力,可能会在入侵草本植物的防治上起到重要作用。选用巨桉、香樟和核桃凋落叶,分别制成不同浓度水浸提液,结合培养皿萌发试验和盆栽试验,通过测定三叶鬼针草发芽率、发芽速度、幼苗植株鲜质量、抗氧化酶活性以及渗透调节物质含量,综合评价3个树种凋落叶浸提液的作用效果。巨桉和香樟凋落叶浸提液可显著抑制三叶鬼针草的发芽。三叶鬼针草地上部分鲜质量明显受到高浓度巨桉凋落叶浸提液的抑制,而香樟和核桃凋落叶浸提液的抑制作用微弱;3个树种凋落叶浸提液对三叶鬼针草过氧化物酶(POD)和超氧化物歧化酶(SOD)活性具有促进作用,而对其过氧化氢酶(CAT)活性具有抑制作用;巨桉凋落叶浸提液处理三叶鬼针草抗氧化酶系统表现出"钝化"响应,而其体内丙二醛(MDA)含量则显著增加;对巨桉和香樟凋落叶浸提液而言,三叶鬼针草可溶性蛋白和可溶性糖含量均随浸提液剂量的增加而升高,而在核桃凋落叶浸提液处理下则表现出低促高抑的效应。总体来看,3个树种凋落叶含有干扰三叶鬼针草生长的物质,但效应因树种和浸提液浓度而异。相比较而言,巨桉凋落叶浸提液的综合抑制作用最强,香樟次之,核桃最弱。     

抗生素单一及联合暴露对RP4质粒介导的抗性基因水平转移的hormesis效应研究

抗生素滥用导致的抗性基因(ARGs)泛滥问题引起人们的日益关注。目前关于抗性基因的研究主要集中在环境监测方面,但是关于抗生素对ARGs传播的影响研究还相对缺乏。质粒是ARGs传播的重要载体,因此以基于RP4质粒的大肠杆菌(E.coli)接合转移体系为研究对象,探讨了盐酸四环素、甲氧苄啶、磺胺氯哒嗪、磺胺异唑在单一暴露条件下对RP4质粒接合转移的影响。根据单一暴露的结果设计混合抗生素的浓度比,探究抗生素联合暴露实验对质粒接合转移的影响。结果表明:在单一暴露条件下,只有盐酸四环素对含有四环素抗性的RP4质粒的接合转移频率有低促高抑的hormesis效应;在联合暴露条件下,对RP4质粒接合转移无促进作用的抗生素会抑制四环素的hormesis效应,这一定程度上降低了抗生素的环境风险。并且用受体理论解释了抗生素对质粒接合转移的hormesis效应产生机制,为目前尚无定论的hormesis受体理论机制提供了证据支持。     

磁混凝对市政污水中抗生素抗性基因和重金属抗性基因的削减效能

污水中抗性基因给环境和人类健康带来潜在的危害.本研究通过调查市政排口污水磁混凝处理过程中抗性基因绝对含量和相对丰度变化,考察磁分离技术对市政污水中抗性基因的削减效果.结果表明,加入磁种和絮凝剂的一级搅拌和二级搅拌对抗生素抗性基因(ARGs)、重金属抗性基因(MRGs)和可移动遗传元件均有较好地去除效果,但出水中部分抗性基因的绝对含量增加,这可能是由于出水中依然具有较高含量的水平转移元件(int1,2. 00×10¹⁰ copies·mL^-1; int2,1. 91×10⁸ copies·mL^-1; Tn916/1545e,5. 38×10⁸ copies·mL^-1).网络分析和主成分分析结果表明,磁混凝处理过程中ARGs与MRGs呈显著正相关(P <0. 05),城市污水中常规污染物如悬浮物、磷和COD等是影响抗性基因去除效率的重要因子.这些结果表明,磁混凝可通过有效削减污水中常规污染物进而制约抗性基因的传播和转移;但需要关注磁混凝的出水及脱水污泥的...