Molecular analysis of long-term biofilm formation on PVC and cast iron surfaces in drinking water distribution system

To understand the impacts of different plumbing materials on long-term biofilm formation in water supply system, we analyzed microbial community compositions in the bulk water and biofilms on faucets with two different materials-polyvinyl chloride （PVC） and cast iron, which have been frequently used for more thanlO years. Pyrosequencing was employed to describe both bacterial and eukaryotic microbial compositions. Bacterial communities in the bulk water and biofilm samples were significantly different from each other. Specific bacterial populations colonized on the surface of different materials. Hyphomicrobia and corrosion associated bacteria, such as Acidithiobacillus spp., Aquabacterium spp., Limnobacter thiooxidans, and Thiocapsa spp., were the most dominant bacteria identified in the PVC and cast iron biofilms, respectively, suggesting that bacterial colonization on the material surfaces was selective. Mycobacteria and Legionella spp. were common potential pathogenic bacteria occurred in the biofilm samples, but their abundance was different in the two biofilm bacterial communities. In contrast, the biofilm samples showed more similar eukaryotic communities than the bulk water. Notably, potential pathogenic fungi, i.e., Aspergillus spp. and Candida parapsilosis, occurred in similar abundance in both biofilms. These results indicated that microbial community, especially bacterial composition was remarkably affected by the different pipe materials （PVC and cast iron）.     

Effects of disinfection efficiency on microbial communities and corrosion processes in drinking water distribution systems simulated with actual running conditions

The effects of disinfection efficiency on microbial communities and the corrosion of cast iron pipes in drinking water distribution systems (DWDSs) were studied. Two annular reactors (ARs) that simulated actual running conditions with UV/Cl₂ disinfection and chlorination alone were used. High chlorine consumption and corrosion rate were found in the AR with UV/Cl₂. According to functional genes and pyrosequencing tests, a high percentage of iron recycling bacteria was detected within the biofilm of the AR with Cl₂ at early running stage, whereas siderophore-producing bacteria were dominant in the biofilm of the AR with UV/Cl_2. At the early running stage, the sequential use of UV light and an initial high chlorine dosage suppressed the biomass and iron-recycling bacteria in both bulk water and biofilms, thereby forming less protective scales against further corrosion, which enhanced chlorine consumption. Non-metric multidimensional scaling analysis showed that the bacterial communities in the ARs shaped from within rather than being imported by influents. These results indicate that the initial high disinfection efficiency within the distribution system had not contributed to the accumulation of iron-recycling bacteria at the early running stages. This study offer certain implications for controlling corrosion and water quality in DWDSs.     

Genotoxicity of drinking water treated with different disinfectants and effects of disinfection conditions detected by umu-test

The genotoxicity of drinking water treated with 6 disinfection methods and the effects of disinfection conditions were investigated using the umu-test. The pretreatment procedure of samples for the umu-test was optimized for drinking water analysis. The results of the umu-test were in good correlation with those of the Ames-test. The genotoxicity and production of haloacetic acids (HAAs) were the highest for chlorinated samples. UV + chloramination is the safest disinfection method from the aspects of genotoxicity, HAA production and inactivation effects. For chloramination, the effects of the mass ratio of Cl₂ to N of chloramine on genotoxicity were also studied. The changes of genotoxicity were different from those of HAA production, which implied that HAA production cannot represent the genotoxic potential of water. The genotoxicity per chlorine decay of chlorination and chloramination had similar trends, indicating that the reaction of organic matters and chlorine made a great contribution to the genotoxicity. The results of this study are of engineering significance for optimizing the operation of waterworks.     

Revealing the changes of bacterial community from water source to consumers tap: A full-scale investigation in eastern city of China

This study profiled the bacterial community variations of water from four water treatment systems,including coagulation,sedimentation,sand filtration,ozonation-biological activated carbon filtration(O₃-BAC),disinfection,and the tap water after the distribution process in eastern China.The results showed that different water treatment processes affected the bacterial community structure in different ways.The traditional treatment processes,including coagulation,sedimentation and sand f...     

Characterization of bacterial community dynamics in a full-scale drinking water treatment plant

Understanding the spatial and temporal dynamics of microbial communities in drinking water systems is vital to securing the microbial safety of drinking water. The objective of this study was to comprehensively characterize the dynamics of microbial biomass and bacterial communities at each step of a full-scale drinking water treatment plant in Beijing, China. Both bulk water and biofilm samples on granular activated carbon (GAC) were collected over 9 months. The proportion of cultivable cells decreased during the treatment processes, and this proportion was higher in warm season than cool season, suggesting that treatment processes and water temperature probably had considerable impact on the R2A cultivability of total bacteria. 16s rRNA gene based 454 pyrosequencing analysis of the bacterial community revealed that Proteobacteria predominated in all samples. The GAC biofilm harbored a distinct population with a much higher relative abundance of Acidobacteria than water samples. Principle coordinate analysis and one-way analysis of similarity indicated that the dynamics of the microbial communities in bulk water and biofilm samples were better explained by the treatment processes rather than by sampling time, and distinctive changes of the microbial communities in water occurred after GAC filtration. Furthermore, 20 distinct OTUs contributing most to the dissimilarity among samples of different sampling locations and 6 persistent OTUs present in the entire treatment process flow were identified. Overall, our findings demonstrate the significant effects that treatment processes have on the microbial biomass and community fluctuation and provide implications for further targeted investigation on particular bacteria populations.     

基于活性微生物特征的供水管壁生物膜生长特性

管网生物膜由各种活性微生物、微生物残体及有机无机杂质组成,管网生物膜的生长会导致机会致病菌寄居、管道腐蚀以及水质恶化等系列饮用水卫生问题.为研究供水管壁生物膜形成过程和附着生长活性微生物的分布特征,采用异养菌平板计数(HPC)、流式细胞术(FCM)和16S rRNA高通量测序对3种典型室内供水管材:聚氯乙烯(PVC)、无规共聚聚丙烯(PPR)、不锈钢(STS)内壁活性微生物的生长特性和群落多样性进行了分析.结果表明,PVC管壁生物量在第73 d最先达到峰值,3种管材内壁单位面积最大生物量、生物膜成熟时期生物量均呈现PVC PPR STS的规律. 3种管材表面活性细菌群落结构组成上,PVC管表面主要以硝化螺旋菌门为主,PPR和STS管以疣微菌门为主,其中STS管壁上生物膜物种丰富度最低、多样性最小,群落结构最简单. PVC和PPR管内壁表面相较STS管存在更多的蓝藻细菌和放线菌,在饮用水输配过程中更易引发饮用水嗅味问题.管材介质对管壁生物膜上微生物群落结构存在一定影响.     

给水管网中耐氯性细菌的灭活特性研究

使用4种常见消毒剂对从实际管网中分离出来的7株耐氯性细菌进行消毒实验.结果表明,这7株细菌均具有较高的耐氯性,其中1株耐氯性最高的类龟分支杆菌自由氯99.9%灭活的CT值为120 mg.(L.min)-1,另外2株血红鞘氨醇单胞菌和甲基杆菌99.9%灭活的CT值分别为7 mg.(L.min)-1和4 mg.(L.min)-1.比较4种消毒剂的消毒效果发现,二氧化氯和单过硫酸氢钾的消毒效果较好,能够在30 min内使分支杆菌的灭活率达到5个数量级.自由氯由于衰减较快,消毒效果不佳.一氯胺能够维持一定的消毒剂浓度,但由于其氧化性较弱,因此需要提高浓度,才能满足消毒要求.能在1 h内灭活3个数量级以上分支杆菌的消毒剂投加量为:3.0 mg/L一氯胺、1.0 mg/L二氧化氯(以Cl2计)和1.0 mg/L单过硫酸氢钾(以Cl2计).考虑到我国水厂消毒的实际情况,建议采用间歇性提高一氯胺浓度或改换二氧化氯消毒的方法,提高对耐氯性细菌的灭活效果.     

饮用水常规处理工艺中细菌群落的时空分布

为弄清饮用水常规处理工艺过程中细菌群落的时空分布和动态变化规律,以我国南方某市一常规处理工艺水厂为研究对象,采用Illumina HiSeq高通量测序技术对夏季和冬季原水、沉后水、滤后水、出厂水和滤砂生物膜等细菌群落进行解析.结果表明,出厂水pH值、浊度、COD_Mn、菌落总数等指标均满足《生活饮用水卫生标准》（GB5749-2006）的要求.夏季细菌多样性明显高于冬季,混凝沉淀和消毒是影响细菌群落多样性和组成的主要工艺单元.细菌群落组成呈现一定的季节性变化,水样中优势菌门主要包括变形菌门（Proteobacteria）、放线菌门（Actinobacteria）、蓝细菌门（Cyanobacteria）等,在滤砂生物膜样品中,变形菌门（Proteobacteria）亦占绝对优势.在属水平上,检测到的条件致病菌属包括弧形菌属（Vibrio）、不动杆菌属（Acinetobacter）和分支杆菌属（Mycobacterium）.水温和溶解氧是影响细菌群落的主要水质参数.     

利用DGGE-菌落原位杂交法分离土壤中精喹禾灵降解菌

从自然环境中分离到的可降解农药的土著微生物,因其对环境的友好性及原位修复的可行性,受到了高度关注.为从土壤中筛选精喹禾灵降解菌株,首先利用PCR-DGGE技术分析了除草剂精喹禾灵胁迫下土壤细菌群落结构及多样性的变化.结果表明,添加精喹禾灵后,土壤细菌群落结构发生了明显的改变.精喹禾灵使细菌多样性呈现出增加-减少-增加的变化趋势,其中第9 d变化最大,后期趋于稳定.根据DGGE图谱条带的测序结果推断,Pseudomonas、Massilia、Burkholderia等属中的细菌对精喹禾灵具有耐受性或降解潜力,这些微生物类群可作为减少农药残留的土著微生物资源进行分离筛选.根据条带的测序结果,合成了地高辛(Digoxigenin)标记的探针,并进行了菌落原位杂交,筛选到了3株具有降解潜力的菌株,其中L1可以利用精喹禾灵作为唯一碳源生长,经16S rRNA基因鉴定该菌株属于假单胞菌属(Pseudomonas sp.).利用高效液相色谱法测定了菌株L1在无机盐培养基中降解精喹禾灵的效果.结果表明,培养7 d后,精喹禾灵的含量减少了近50%,且随着精喹禾灵含量的降低,L1菌体数量增加,证实了菌株L1具有降解精喹禾灵的能力.这一结果为今后研究菌株L1降解精喹禾灵的机制、功能基因等奠定了基础.     

氨氮在饮用水生物滤池内的去除机制

为探讨饮用水生物滤池对NH4+-N的去除机制,测定生物滤池进出水中NH4+-N、NO2--N、NO3--N、高锰酸盐指数、总磷、单质氮(N2)、温度和溶解氧(dissolved oxygen,DO)等指标,并采集生物滤池不同层高(0、10、20、40、60 cm)活性炭生物填料,应用分子生物学技术,对样品中的细菌种群进行研究.结果表明,根据进水NH4+-N浓度分为3个阶段,第一、二和三阶段都发生了"氮亏损"现象(出水无机氮之和小于进水无机氮之和),氮亏损的量(出水无机氮之和与进水无机氮之和的差值)分别为0.94、0.32和0.15 mg.L-1.氮亏损的量与进水中NH4+-N浓度有很好的正相关性,但与进水中高锰酸盐指数浓度没有线性关系.第一阶段水中N2的平均浓度随着生物滤池填料层高呈上升趋势,进水中N2平均浓度是14.04 mg.L-1,出水N2平均浓度为14.67 mg.L-1.测序结果显示活性炭上生物膜中氨氧化细菌(ammonia-oxidizing bacteria,AOB)全部归为3个常见属:Nitrosococcus、Nitrosomonas和Nitrosospira.当生物滤池进水NH4+-N浓度较高时,生物滤池中发生的"氮亏损"现象是由AOB的作用.     

饮用水常规处理工艺中细菌群落的时空分布

为弄清饮用水常规处理工艺过程中细菌群落的时空分布和动态变化规律,以我国南方某市一常规处理工艺水厂为研究对象,采用Illumina HiSeq高通量测序技术对夏季和冬季原水、沉后水、滤后水、出厂水和滤砂生物膜等细菌群落进行解析.结果表明,出厂水pH值、浊度、COD_Mn、菌落总数等指标均满足《生活饮用水卫生标准》（GB5749-2006）的要求.夏季细菌多样性明显高于冬季,混凝沉淀和消毒是影响细菌群落多样性和组成的主要工艺单元.细菌群落组成呈现一定的季节性变化,水样中优势菌门主要包括变形菌门（Proteobacteria）、放线菌门（Actinobacteria）、蓝细菌门（Cyanobacteria）等,在滤砂生物膜样品中,变形菌门（Proteobacteria）亦占绝对优势.在属水平上,检测到的条件致病菌属包括弧形菌属（Vibrio）、不动杆菌属（Acinetobacter）和分支杆菌属（Mycobacterium）.水温和溶解氧是影响细菌群落的主要水质参数.     

Effects of O3/Cl2 disinfection on corrosion and opportunistic pathogens growth in drinking water distribution systems

The effects of O_3/Cl_2 disinfection on corrosion and the growth of opportunistic pathogens in drinking water distribution systems were studied using annular reactors(ARs).The corrosion process and most probable number(MPN) analysis indicated that the higher content of iron-oxidizing bacteria and iron-reducing bacteria in biofilms of the AR treated with O_3/Cl_2 induced higher Fe_3O_4 formation in corrosion scales.These corrosion scales became more stable than the ones that formed in the AR treated with Cl_2 alone.O_3/Cl_2 disinfection inhibited corrosion and iron release efficiently by changing the content of corrosion-related bacteria.Moreover,ozone disinfection inactivated or damaged the opportunistic pathogens due to its strong oxidizing properties.The damaged bacteria resulting from initial ozone treatment were inactivated by the subsequent chlorine disinfection.Compared with the AR treated with Cl_2 alone,the opportunistic pathogens M.avium and L.pneumophila were not detectable in effluents of the AR treated with O_3/Cl_2,and decreased to(4.60 ± 0.14) and(3.09 ± 0.12) log10(gene copies/g corrosion scales) in biofilms,respectively.The amoeba counts were also lower in the AR treated with O_3/Cl_2.Therefore,O_3/C_l2 disinfection can effectively control opportunistic pathogens in effluents and biofilms of an AR used as a model for a drinking water distribution system.     

单过硫酸氢钾复合粉在饮用水消毒过程中的副产物生成特性及遗传毒性变化

以北京田村山净水厂原水和炭后出水作为试验用水,对新型消毒剂单过硫酸氢钾复合粉消毒后生成的消毒副产物(disinfection by-products,DBPs)进行定性分析.向受试水样中分别投加单过硫酸氢钾复合粉和次氯酸钠,比较了复合粉消毒和氯消毒的DBPs生成量,并通过umu试验对水样消毒后的遗传毒性变化进行测试.结果表明,测试水样投加单过硫酸氢钾复合粉消毒前后的有机物种类变化不大,但仍有新的卤代烃和卤代物生成.与氯消毒相比,单过硫酸氢钾复合粉消毒后生成的三卤甲烷(THMs)和卤乙酸(HAAs)的含量更低.另外,根据umu测试的结果,经单过硫酸氢钾复合粉消毒后原水和炭后水的遗传毒性均明显低于氯消毒.然而在水中有机物较多和消毒剂投加量较大时,单过硫酸氢钾复合粉用于消毒仍有一定安全风险.     

NirS-type denitrifying bacteria in aerobic water layers of two drinking water reservoirs: Insights into the abundance, community diversity and co-existence model

The nirS-type denitrifying bacterial community is the main drivers of the nitrogen loss process in drinking water reservoir ecosystems.The temporal patterns in nirS gene abundance and nirS-type denitrifying bacterial community harbored in aerobic water layers of drinking water reservoirs have not been studied well.In this study,quantitative polymerase chain reaction (qPCR) and Illumina Miseq sequencing were employed to explore the nirS gene abundance and denitrifying bacterial community structur...     

氯/氯胺和紫外顺序消毒对管网抗性基因的去除

为探究供水系统中氯/氯胺与低压紫外顺序消毒对抗生素抗性基因(ARGs)分布特征的影响,采用生物膜反应器模拟供水管网,对管网出水和生物膜进行60mJ/cm²低压紫外线(254nm)消毒,并利用高通量定量PCR技术检测模拟管网进、出水及生物膜内的典型ARGs和遗传原件(MGEs).结果表明,管网反应器运行150d,氯和氯胺管网出水ARGs总相对丰度分别为0.13和0.137,生物膜ARGs分别为2.45和0.277,表明供水管网中低剂量的氯或氯胺可有效降低水相和生物膜相中ARGs的相对丰度达90%,且氯胺消毒对生物膜中的ARGs控制作用更显著.氯和氯胺消毒后管网出水再经低压紫外线照射后,ARGs相对丰度分别为0.0682和0.0537,管网生物膜中ARGs的相对丰度分别为2.01和0.194.ARGs与MGEs间的相关性发生显著变化,转座子与strB和mepA的相关性增强,与ermX和tetM相关性减弱,而整合子与acrF、cmlA1-01、oprJ及tolC-01的相关性增强.研究表明,将紫外线消毒工艺设置在用水终端可以显著降低氯和氯胺管网水中ARGs丰度,但对管网生物膜中的ARGs影响较小.     

污水回用中主要病原菌解析及其紫外消毒效应

本研究以污水处理厂二级出水中的微生物为研究对象,通过454焦磷酸测序技术分析其群落结构组成,揭示了主要病源菌的种类和比例;通过培养法、q PCR、Q-RT-PCR这3种方法分析紫外剂量为60 m J·cm-2时对指示菌大肠杆菌和典型病原菌沙门氏菌及分枝杆菌的去除特性.结果表明,二级出水中共有11种病原菌,主要为梭菌属(2.96%)、弓形杆菌属(0.82%)和分枝杆菌(0.36%).60 m J·cm-2剂量的紫外消毒可以有效去除99.9%可培养的大肠杆菌和沙门氏菌,对可培养分枝杆菌的去除率不足90%.但是,该剂量紫外消毒对活性大肠杆菌、沙门氏菌和分枝杆菌的去除率较低,Q-RT-PCR检测方法可以较准确评价微生物的存活状态.60 m J·cm-2紫外剂量会导致大量病原菌进入具有活性但不可培养(VBNC)状态,需结合其他深度处理工艺进一步去除活性病原菌以保障污水回用的安全利用.     

典型油田多环芳烃污染对土壤反硝化微生物群落结构的影响

油田区土壤具有潜在的PAHs(polycyclic aromatic hydrocarbons)污染风险,而以硝酸根为电子受体的反硝化作用可能在PAHs的厌氧代谢中起到重要作用.以具有50多年历史的江汉油田区域为对象,从该油田的油井口附近采集了9个土壤样品,编号为JH-1~JH-9,以反硝化相关的nir K(Cu-亚硝酸还原酶基因)和nirS(细胞色素cd1-亚硝酸还原酶基因)为分子标识,通过定量PCR及克隆文库结合T-RFLP(terminal-restriction fragment length polymorphism)的方法,研究典型油田区土壤反硝化微生物的群落结构,并探讨其与土壤环境因子之间的关系.结果表明,该油田区土壤中nirK基因的丰度高于nirS基因,PAHs含量最高的土壤样品(JH-4)中反硝化功能基因nir K和nir S的丰度均最低,相关性分析表明,土壤nir K及nirS基因的丰度均与土壤PAHs含量呈显著负相关(nirK:R2=0.54,P0.05;nirS:R~2=0.58,P0.05).克隆文库及T-RFLP的结果则表明,该油田土壤中nirK基因的群落组成在不同样品间的变异较大,且PAHs含量最高的JH-4中该基因的群落组成与其它各样品有明显的不同,RDA(redundancy analysis)的分析结果进一步表明除有效氮、有效磷外,土壤PAHs含量也是影响nirK型反硝化微生物群落组成的重要因子.相较于nirK,该油田区土壤中nirS基因的群落组成在不同样品间的差异较小,但发现nirS型假单胞菌的丰度与土壤PAHs含量呈正相关,表明具备较强有机污染物降解能力的假单胞菌属可能在该区域土壤PAHs的反硝化代谢中起到重要作用.     

Bacterial succession in epiphytic biofilms and deciduous layer sediments during Hydrilla verticillata decay: A field investigation

Submersed macrophytes decay is an important natural process and has important role in mass and energy flow in aquatic ecosystems. However, little is known about the dynamical changes in nutrients release and bacterial community during submersed macrophyte decay in natural environment. In this study, a field observation was conducted in a wetland dominated with Hydrilla verticillata for 36 days. Increase of H₂O₂ and malondialdehyde (MDA) content and decrease of soluble proteins concentration were detected in leaves during H. verticillata decay. Meanwhile, ammonium-N, soluble microbial products (SMP) and TOC concentration increased in overlying water. According to bacterial 16S rRNA Illumina sequencing analysis, the Shannon values were lower in epiphytic biofilms than deciduous layer sediments. The relative abundances of Proteobacteria, Cyanobacteria and Actinobacteria were higher in epiphytic biofilms than in deciduous layer sediments (P < 0.05). Co-occurrence network analyses showed that a total of 578 and 845 pairs of correlations (|r| > 0.6) were identified from 122 and 112 genera in epiphytic biofilms and deciduous layer sediments, respectively. According to co-occurrence patterns, eight hubs were mainly from phyla Proteobacteria, Acidobacteria and Parcubacteria in epiphytic biofilms; while 37 hubs from the 14 phyla (Proteobacteria, Bacteroidetes, Acidobacteria, Chloroflexi, et al.) were detected in deciduous layer sediments. Our results indicate that bacterial community in deciduous layer sediments was more susceptible than in epiphytic biofilms during decay process. These data highlight the role of microbial community in deciduous layer sediments on nutrients removal during H. verticillata decay and will provide useful information for wetland management.     

Development of a field enhanced photocatalytic device for biocide of coliform bacteria

A field enhanced flow reactor using bias assisted photocatalysis was developed for bacterial disinfection in lab-synthesized and natural waters. The reactor provided complete inactivation of contaminated waters with flow rates of 50 m L/min. The device consisted of titanium dioxide nanotube arrays, with an externally applied bias of up to 6 V. Light intensity, applied voltage, background electrolytes and bacteria concentration were all found to impact the device performance. Complete inactivation of Escherichia coli W3110(~ 8 × 10~3CFU/m L) occurred in 15 sec in the reactor irradiated at 25 m W/cm~2 with an applied voltage of 4 V in a 100 ppm NaCl solution. Real world testing was conducted using source water from Emigration Creek in Salt Lake City, Utah. Disinfection of natural creek water proved more challenging, providing complete bacterial inactivation after 25 sec at 6 V. A reduction in bactericidal efficacy was attributed to the presence of inorganic and organic species, as well as the increase in robustness of natural bacteria.     

土壤环境中肠道致病菌的多重PCR检测研究初探

建立同时检测大肠杆菌、沙门氏菌、金黄色葡萄球菌、福氏志贺氏菌、铜绿假单胞菌等5种土壤常见肠道致病菌的多重PCR检测技术,为这些肠道致病菌感染的快速诊断提供实验依据.根据这些肠道病原菌的毒素基因、高度保守基因及特异性基因分别合成5对特异性引物,应用PCR扩增技术对目的菌株进行特异性检测.实验结果表明,5对寡核苷酸引物都具有较高的特异性和专一性,多重PCR检测限达到104cfu·g-1.多重PCR应用于土壤样品分析,极大的缩短了检测时间(仅需3～4h)、降低了检测成本,对控制病原菌的传播具有重要意义,可推广应用于环境监测、水源检测、食品卫生监督、商品检验检疫等领域.