Heavy metal removal in anaerobic semi-continuous stirred tank reactors by a consortium of sulfate-reducing bacteria

Removal of heavy metals by an enriched consortium of sulfate-reducing bacteria (SRB) was evaluated through the abundance of SRB, sulfate reduction, sulfide production and heavy metal precipitation. Five parallel anaerobic semi-continuous stirred tank reactors (CSTR, V = 2 L) (referred as R1-R5) were fed with synthetic wastewater containing mixtures of Cu²⁺, Zn²⁺, Ni²⁺, and Cr⁶⁺ in the concentrations of 30, 60, 90, 120, and 150 mg L⁻¹ of each metal and operated with a hydraulic retention time of 20 days for 12 weeks. The loading rates of each metal in R1-R5 were 1.5, 3, 4.5, 6, and 7.5 mg L⁻¹ d⁻¹, respectively. The results showed that there was no inhibition of SRB growth and that heavy metal removal efficiencies of 94-100% for Cu²⁺, Zn²⁺, Ni²⁺, and Cr⁶⁺ were achieved in R1-R3 throughout the experiment and in R4 during the first 8 weeks. The toxic effect of heavy metals on the SRB consortium was revealed in R5, in which no SRB could survive and almost no heavy metal precipitation was detected after four weeks of operation.     

Exploring landscape changes using an envisioning system in rural community workshops

In order to understand land use changes it is useful to provide communities with visions of how their landscape may change. For this purpose, we have developed an envisioning system, which can help communities contemplate alternative land use configurations. This system links a geographic information system, virtual reality, mobile computing devices, and environmental process models into a platform that allows visual exploration and evaluation of future landscape scenarios. Alternative land use configurations can be suggested using the GIS interface, which can be viewed via an immersive 3D environment permitting immediate evaluation. Using personal digital assistants, opinions on visible changes can be expressed by a choice of responses. These are fed back to the system, where they are collected. People can then determine if the probable changes accord with their judgements and values and adjust the extent or nature of the changes accordingly. The aim of the envisioning system is to help communities learn about their local landscape, to examine the consequences of applying different values, and to support informed decisions on land use planning issues. We tested the portable envisioning system platform in two public workshops in the Cudgewa Valley of northeastern Victoria, Australia. It is expected that the current land use will diversify, under economic pressures, from predominantly cattle farming as neighbouring valleys have done already.     

Relationship between phenol degradation efficiency and microbial community structure in an anaerobic SBR

Phenol is a common wastewater contaminant from various industrial processes, including petrochemical refineries and chemical compounds production. Due to its toxicity to microbial activity, it can affect the efficiency of biological wastewater treatment processes. In this study, the efficiency of an Anaerobic Sequencing Batch Reactor (ASBR) fed with increasing phenol concentrations (from 120 to 1200 mg L⁻¹) was assessed and the relationship between phenol degradation capacity and the microbial community structure was evaluated. Up to a feeding concentration of 800 mg L⁻¹, the initial degradation rate steadily increased with phenol concentration (up to 180 mg L⁻¹ d⁻¹) and the elimination capacity remained relatively constant around 27 mg phenol removed?gVSS⁻¹ d⁻¹. Operation at higher concentrations (1200 mg L⁻¹) resulted in a still efficient but slower process: the elimination capacity and the initial degradation rate decreased to, respectively, 11 mg phenol removed?gVSS⁻¹ d⁻¹ and 154 mg L⁻¹ d⁻¹. As revealed by Denaturing Gradient Gel Electrophoresis (DGGE) analysis, the increase of phenol concentration induced level-dependent structural modifications of the community composition which suggest an adaptation process. The increase of phenol concentration from 120 to 800 mg L⁻¹ had little effect on the community structure, while it involved drastic structural changes when increasing from 800 to 1200 mg L⁻¹, including a strong community structure shift, suggesting the specialization of the community through the emergence and selection of most adapted phylotypes. The thresholds of structural and functional disturbances were similar, suggesting the correlation of degradation performance and community structure. The Canonical Correspondence Analysis (CCA) confirmed that the ASBR functional performance was essentially driven by specific community traits. Under the highest feeding concentration, the most abundant ribotype probably involved in successful phenol degradation at 1200 mg L⁻¹ was affiliated to the Anaerolineaceae family.     

Effect of cow slurry amendment on atrazine dissipation and bacterial community structure in an agricultural Andisol

Atrazine is a commonly used herbicide for maize production in Chile, but it has recently been shown to be ineffective in soils that receive applications of cow slurries generated from the dairy industry. This effect may be caused either by the sorption of the pesticide to organic matter or more rapid degradation in slurry-amended soils. The objectives of this study were to evaluate the effects of cow slurry on atrazine dissipation, the formation of atrazine metabolites and the modification of bacterial community in Andisol. The cow slurry was applied at doses of 100,000-300,000 L ha^− 1. After 4 weeks, atrazine was applied to the slurry-amended soils at concentrations of 1-3 mg kg^− 1. The amounts of atrazine and its metabolites were determined by high performance liquid chromatography (HPLC). The soil microbial community was monitored by measurement of CO₂ evolution and changes in bacterial community using PCR-DGGE of 16S rRNA genes. The results show that cow slurry applications had no effect on atrazine dissipation, which had a half-life of 15-19 days. The atrazine metabolites were detected after 20 days and were significantly higher in soils amended with the slurry at both 20 and 40 days after application of the herbicide. Respiration rates were elevated after 10 days in all soils with atrazine addition. Both the atrazine and slurry amendments altered the bacterial community structures, indicated by the appearance of specific bands in the DGGE gels after 10 days. Cloning and sequencing of the 16S rRNA genes from the DGGE gels showed that the bands represented various genera of β-proteobacteria that appeared in response to atrazine. According to our results, further field studies are required to explain the lower effectiveness of atrazine in weed control. These studies may include the effect of dissolved organic carbon on the atrazine mobility.     

Changes in phosphorus removing performance and bacterial community structure in an enhanced biological phosphorus removal reactor

A lab-scale-enhanced biological phosphorus removal (EBPR) reactor was operated for 204 days to investigate the correlation between phosphorus removing performance and bacterial community structure. The phosphorus removing performance was good from day 1 to 92 and from day 172 to 204. However, the removal activity was in a deteriorated state from day 93 to 171. From day 69 (2 weeks before the beginning of the deterioration) to 118 (2 weeks after the beginning of the deterioration), sludge P content decreased. The amounts of ubiquinone-8 and menaquinone-8 (H(4)) decreased during this period while the amount of ubiquinone-10 increased. The comparison of these changes and the general attribution of each quinone to the bacterial phylogenetic groups suggested that beta proteobacteria and Actinobacteria contributed to EBPR positively, and that alpha proteobacteria were related to this EBPR deterioration. Glycogen accumulating organisms (GAOs) are considered to detrimentally affect EBPR ability by outcompeting the phosphorus accumulating organisms by using aerobically synthesized glycogen as the energy source to assimilate organic substrates anaerobically to form polyhydroxyalkanoates. However, in this research, there was nearly no substrate uptake during the anaerobic period at the middle of the deteriorated performance period. This suggests that the deterioration observed in this research does not agree with the GAOs inhibition model. In this research, the excess P release at the anaerobic period was concluded to cause the deterioration.     

等截面圆环连体筒仓整体滑模施工技术

湖南岳阳城陵矶粮库立筒仓库工程,由１８个连体筒仓组成,施工采用整体液压滑模方案,工程质量优良。本文介绍其施工方法、纠扭纠偏方法和技术措施。     

Microbial community structures and in situ sulfate-reducing and sulfur-oxidizing activities in biofilms developed on mortar specimens in a corroded sewer system

Microbially induced concrete corrosion (MICC) caused by sulfuric acid attack in sewer systems has been a serious problem for a long time. A better understanding of microbial community structures of sulfate-reducing bacteria (SRB) and sulfur-oxidizing bacteria (SOB) and their in situ activities is essential for the efficient control of MICC. In this study, the microbial community structures and the in situ hydrogen sulfide production and consumption rates within biofilms and corroded materials developed on mortar specimens placed in a corroded manhole was investigated by culture-independent 16S rRNA gene-based molecular techniques and microsensors for hydrogen sulfide, oxygen, pH and the oxidation-reduction potential. The dark-gray gel-like biofilm was developed in the bottom (from the bottom to 4 cm) and the middle (4–20 cm from the bottom of the manhole) parts of the mortar specimens. White filamentous biofilms covered the gel-like biofilm in the middle part. The mortar specimens placed in the upper part (30 cm above the bottom of the manhole) were corroded. The 16S rRNA gene-cloning analysis revealed that one clone retrieved from the bottom biofilm sample was related to an SRB, 12 clones and 6 clones retrieved from the middle biofilm and the corroded material samples, respectively, were related to SOB. In situ hybridization results showed that the SRB were detected throughout the bottom biofilm and filamentous SOB cells were mainly detected in the upper oxic layer of the middle biofilm. Microsensor measurements demonstrated that hydrogen sulfide was produced in and diffused out of the bottom biofilms. In contrast, in the middle biofilm the hydrogen sulfide produced in the deeper parts of the biofilm was oxidized in the upper filamentous biofilm. pH was around 3 in the corroded materials developed in the upper part of the mortar specimens. Therefore, it can be concluded that hydrogen sulfide provided from the bottom biofilms and the sludge settling tank was emitted to the sewer atmosphere, then oxidized to corrosive compounds in the upper and middle parts of the manhole, and only the upper part of the mortar specimens were corroded, because in the middle part of the manhole the generated corrosive compounds (e.g., sulfuric acid) was reduced in the deeper parts of the biofilm.     

Biological nitrogen and phosphorus removal and changes in microbial community structure in a membrane bioreactor: effect of different carbon sources

Bacterial community structures in four sequencing anoxic/anaerobic-aerobic membrane bioreactors (SAMs) that were fed with synthetic medium composed of different organic compounds in substrate as carbon source; acetate-dominant (acetate/propionate = 4/1), propionate-dominant (acetate/propionate = 1/4), glucose-dominant (glucose/acetate = 4/1) and methanol-dominant (methanol/acetate/propionate = 6/3/1) were analyzed by respiratory quinone profile and fluorescent in situ hybridization (FISH) techniques. The SAMs were operated at controlled pH range 7-8.5 and at constant temperature 25 degrees C. Total nitrogen (TN), total phosphorus (TP) and COD removal performances were also evaluated and compared. In addition, trans-membrane pressure was monitored to observe the impact of substrate composition on membrane fouling. The dominance of the mole fraction of ubiquinone (UQ-8) in the SAMs indicated dominance of the beta-subclass of Proteobacteria; however, its population comparatively decreased when the substrate was glucose dominant or methanol dominant. A relatively higher and stable enhanced biological phosphorus removal performance was observed when methanol-dominant substrate was used concurrently with an increase in the gamma-subclass of Proteobacteria. The population of the alpha-subclass of Proteobacteria slightly increased along with a decrease in phosphate removal activity when the substrate was glucose-dominant. Results from FISH analysis also supported the findings of the quinone profile. The trans-membrane pressure variation in the SAMs indicated that fouling was relatively rapid when propionate-dominant or methanol-dominant substrate was used and most stable when glucose-dominant substrate was used. A combination of methanol and acetate would be a better choice as an external carbon source when nutrients removals, as well as fouling, are considered in the membrane bioreactor- (MBR-) coupled biological nutrients removing (BNR) process.     

Microbial reduction of uranium under iron- and sulfate-reducing conditions: Effect of amended goethite on microbial community composition and dynamics

There is a growing need for a better understanding of the biogeochemical dynamics involved in microbial U(VI) reduction due to an increasing interest in using biostimulation via electron donor addition as a means to remediate uranium contaminated sites. U(VI) reduction has been observed to be maximized during iron-reducing conditions and to decrease upon commencement of sulfate-reducing conditions. There are many unknowns regarding the impact of iron/sulfate biogeochemistry on U(VI) reduction. This includes Fe(III) availability as well as the microbial community changes, including the activity of iron-reducers during the uranium biostimulation period even after sulfate reduction becomes dominant. Column experiments were conducted with Old Rifle site sediments containing Fe-oxides, Fe-clays, and sulfate rich groundwater. Half of the columns had sediment that was augmented with small amounts of Fe(III) in the form of ⁵⁷Fe-goethite, allowing for a detailed tracking of minute changes of this added phase to study the effects of increased Fe(III) levels on the overall biostimulation dynamics. Mössbauer spectroscopy showed that the added ⁵⁷Fe-goethite was bioreduced only during the first thirty days of biostimultuion, after which it remained constant. Augmentation with Fe(III) had a significant effect on the total flux of electrons towards different electron acceptors; it suppressed the degree of sulfate reduction, had no significant impact on Geobacter-type bacterial numbers but decreased the bacterial numbers of sulfate reducers and affected the overall microbial community composition. The addition of Fe(III) had no noticeable effect on the total uranium reduction.     

A quantitative method for assessing the toxic effects of some water soluble substances, based on changes in periphyton community structure

A method to assess the potential damage of a particular water soluble compound when released in lakes and streams is described. The results of a test using germanium dioxide which has a known effect, provided evidence that quantitative changes in the species composition of the colonizing periphyton community reflect the nature of the toxicant to which they were exposed. Natural diatom growth in the presence of germanium was inhibited and the ensueing changes in the species composition of the treated community were reflected in changes in the index of diversity calculated for that community. The advantages and disadvantages of this approach are discussed.     

Characterization of sulfate-reducing granular sludge in the SANI process

Hong Kong practices seawater toilet flushing covering 80% of the population. A sulfur cycle-based biological nitrogen removal process, the Sulfate reduction, Autotrophic denitrification and Nitrification Integrated (SANI^®) process, had been developed to close the loop between the hybrid water supply and saline sewage treatment. To enhance this novel process, granulation of a Sulfate-Reducing Up-flow Sludge Bed (SRUSB) reactor has recently been conducted for organic removal and provision of electron donors (sulfide) for subsequent autotrophic denitrification, with a view to minimizing footprint and maximizing operation resilience. This further study was focused on the biological and physicochemical characteristics of the granular sulfate-reducing sludge. A lab-scale SRUSB reactor seeded with anaerobic digester sludge was operated with synthetic saline sewage for 368 days. At 1 h nominal hydraulic retention time (HRT) and 6.4 kg COD/m³-d organic loading rate, the SRUSB reactor achieved 90% COD and 75% sulfate removal efficiencies. Granular sludge was observed within 30 days, and became stable after 4 months of operation with diameters of 400–500 μm, SVI₅ of 30 ml/g, and extracellular polymeric substances of 23 mg carbohydrate/g VSS. Fluorescence in situ hybridization (FISH) analysis revealed that the granules were enriched with abundant sulfate-reducing bacteria (SRB) as compared with the seeding sludge. Pyrosequencing analysis of the 16S rRNA gene in the sulfate-reducing granules on day 90 indicated that the microbial community consisted of a diverse SRB genera, namely Desulfobulbus (18.1%), Desulfobacter (13.6%), Desulfomicrobium (5.6%), Desulfosarcina (0.73%) and Desulfovibrio (0.6%), accounting for 38.6% of total operational taxonomic units at genera level, with no methanogens detected. The microbial population and physicochemical properties of the granules well explained the excellent performance of the granular SRUSB reactor.     

社区空间结构的防灾特性解析

从社区空间结构的内涵出发,对当前社区空间结构及其在防灾方面存在的问题进行调研分析,归纳出主要的社区空间结构类型,并分析了不同社区空间结构的防灾特性,为今后的社区规划提供了借鉴。     

Microbial community changes with decaying chloramine residuals in a lab-scale system

When chloramine is used as a disinfectant, managing an acceptable “residual” throughout the water distribution systems particularly once nitrification has set in is challenging. Managing chloramine decay prior to the onset of nitrification through effective control strategies is important and to-date the strategies developed around nitrification has been ineffective. This study aimed at developing a more holistic knowledge on how decaying chloramine and nitrification metabolites impact microbial communities in chloraminated systems. Five lab-scale reactors (connected in series) were operated to simulate a full-scale chloraminated distribution system. Culture independent techniques (cloning and qPCR) were used to characterise and quantify the mixed microbial communities in reactors maintaining a residual of high to low (2.18–0.03 mg/L). The study for the first time associates chloramine residuals and nitrification metabolites to different microbial communities. Bacterial classes Solibacteres, Nitrospira, Sphingobacteria and Betaproteobacteria dominated at low chloramine residuals whereas Actinobacteria and Gammaproteobacteria dominated at higher chloramine residuals. Prior to the onset of nitrification bacterial genera Pseudomonas, Methylobacterium and Sphingomonas were found to be dominant and Sphingomonas in particular increased with the onset of nitrification. Nitrosomonas urea, oligotropha, and two other novel ammonia-oxidizing bacteria were detected once the chloramine residuals had dropped below 0.65 mg/L. Additionally nitrification alone failed to explain chloramine decay rates observed in these reactors. The finding of this study is expected to re-direct the focus from nitrifiers to heterotrophic bacteria, which the authors believe could hold the key towards developing a control strategy that would enable better management of chloramine residuals.     

基于Peano曲线的几何条纹形建筑纹样设计

分形作为一种设计语言,是创新的艺术表现方法。分形图形的对称、自相似、动态平衡等特性与几何条纹形的对称、连续的特点极其相似。将分形理论生成的规则分形图形应用于几何形建筑纹样设计中,不仅可以创作出新的几何形建筑纹样图形,而且丰富了几何形建筑纹样的设计方法。通过应用LS算法生成了两大类型多种Peano曲线,通过改变迭代次数,生成不同迭代深度的规则Peano曲线几何图形。将这些图形结合几何条纹形构成方法和图形特点应用于几何条纹形建筑纹样的设计,生成了如建筑窗格、建筑栏杆与建筑地坪等不同类型的几何条纹形建筑纹样,进而提出新的几何条纹形建筑纹样设计方法。     

Growth of sulfate-reducing bacteria under acidic conditions in an upflow anaerobic bioreactor as a treatment system for acid mine drainage

The aim of this investigation was to develop a system for the remediation of acid mine drainage using sulphate-reducing bacteria. An upflow porous medium bioreactor was inoculated with sulphate-reducing bacteria (SRB) and operated under acidic conditions. The reactor was operated under continuous flow and was shown to be capable of sulfate reduction at pH 4.5, 4.0, 3.5 and 3.25 in a medium containing 16.1 mM sodium lactate. This contrasted previously published work which showed that, at pH 3.8, organic acid concentrations greater than 5 mM completely inhibited biological sulfate-reduction. At pH 3.25 the reactor removed 38.3% of influent sulfate and raised the pH of the medium to 5.82. The lactate carbon source was exhausted under these conditions. At pH 3.0, sulfide production was below detectable levels, and sulfate removal fell to 14.4%. However, viable SRB were recovered from the column after 21 days of operation at pH 3.0, indicating that SRB are capable of withstanding pH 3.0 for extended periods. From these results we can conclude that an SRB process would be a viable method of remediating AMD.     

聚羧酸减水剂在水泥基材料中的结构变化研究

模拟了聚羧酸高效减水剂(PC)存在下水泥水化的强碱性环境,测试了PC分子结构在无水泥强碱性体系中(空白)及水泥浆体中的变化情况.采用乙醇提取法及硫酸腐蚀法提取硬化水泥试块中的PC作用物,并对纯化后的提取物进行了红外光谱分析,结果表明:PC在水泥浆体水化过程中的酯基与酰胺基已逐步被水解成羧基,PC在水泥浆体3h时酯基几乎...     

建筑装饰装修变动对建筑结构的影响

针对装饰装修施工可能会增加结构的荷载和改变结构、墙体等情况,就装饰装修变动对建筑结构的影响进行了论述,并对装饰装修应遵循的原则及施工中注意的安全问题作了总结,从而保证装饰装修工程质量。     

Diversity of sulfate-reducing bacteria in a plant using deep geothermal energy

Abstract Enhanced process understanding of engineered geothermal systems is a prerequisite to optimize plant reliability and economy. We investigated microbial, geochemical and mineralogical aspects of a geothermal groundwater system located in the Molasse Basin by fluid analysis. Fluids are characterized by temperatures ranging from 61°C to 103°C, salinities from 600 to 900?mg/l and a dissolved organic carbon content (DOC) between 6.4 to 19.3?mg C/l. The microbial population of fluid samples was analyzed by genetic fingerprinting techniques based on PCR-amplified 16S rRNA- and dissimilatory sulfite reductase genes. Despite of the high temperatures, microbes were detected in all investigated fluids. Fingerprinting and DNA sequencing enabled a correlation to metabolic classes and biogeochemical processes. The analysis revealed a broad diversity of sulfate-reducing bacteria. Overall, the detection of microbes known to be involved in biocorrosion and mineral precipitation indicates that microorganisms could play an important role for the understanding of processes in engineered geothermal systems.