Effect of aeration on hydrodynamic characteristics in flat-sheet MBR

以实际平板膜生物反应器为研究对象,以自由曝气为对照,考察了在不同曝气强度（0.625,1.25,2.5,5L/min）和不同曝气频率（0.17,0.33,0.42,0.56,0.83Hz）下,活塞流曝气对膜表面压力及其变化系数的影响.结果表明,在试验所设范围内,当曝气频率一定时,活塞流曝气引起的平板膜表面压力变化与强度有关;在相同曝气强度下,存在一个最佳的曝气频率范围,使活塞流曝气引起的膜表面压力最大.在相同曝气强度下,可控制的活塞流曝气可以获得比自由曝气更佳的压力变化效果.当曝气量为2.5L/min时,曝气频率0.33Hz的活塞流曝气所带来的压力系数变化高于曝气量为5.0L/min的自由曝气

Leaching impacts Ni toxicity differently among soils but increases its predictability according to nitrification assay

<div class="normal">Deriving toxicity thresholds through bioassays has become the scientific basis for the risk assessment of metal contamination in soils, but few studies have been reported for Ni toxicity in Chinese soils. In addition, although leaching has been recommended to increase the ecological relevance of the output of soil toxicity bioassays, its impacts on Ni threshold and soil solutions in soils remained to be shown. Therefore, in this study, 17 soils were collected throughout China and were assessed for Ni toxicity using substrate-induced nitrification (SIN) assay for both un-leached and leached treatments. Meanwhile, soil solutions of all Ni treatments were extracted and analyzed. This study provides information for the development of a terrestrial biotic ligand model (TBLM) for Ni in Chinese soils. </div

溶氧状况对美人蕉根系特征和畜禽废水处理效果的影响

分别采用标准氧化染色法和正立荧光电子显微镜研究了美人蕉在自然、缺氧和好氧3种溶氧条件下的根部径向泌氧(radial oxygen loss,ROL)类型和特征以及不同ROL位置的空隙和泌氧屏障变化,分析溶氧条件对美人蕉浮床系统处理畜禽废水的影响。自然状况下ROL在任何位置都很强,且不随根的部位的变化而变化;缺氧情况下,根尖区域泌氧最强烈,沿根基方向迅速降低;好氧条件下,根部任何位置泌氧都非常微弱。ROL越强对应的根部孔隙越大,泌氧屏障也越厚。水体缺氧时泌氧作用能使水体达到好氧状态。好氧条件下,美人蕉浮床

Characterization of extracellular polymeric substances from biofilm in the process of starting-up a partial nitrification process under salt stress

In this study, the characteristics of extracellular polymeric substance (EPS) fractions of biofilm during the process of establishing a partial nitrification under salt stress were analyzed in terms of concentrations, molecular weight distribution, and three-dimensional excitation-emission matrix (EEM) ？uorescence spectroscopy. <br />A partial nitrification was formed successfully with a salinity of 1%. Results indicated that the amount of total EPS increased from 54.2 mg？g-1 VSS-1 on day 1 to 99.6 mg？g-1 VSS-1 on day 55 due to the NaCl concentration changed from 0 to 10.0 g？L-1 in a biofilm reactor. The changes of loosely bound EPS (LB-EPS) compounds under different salt concentrations appeared to be more significant than those of the tightly bound EPS (TB-EPS). A clear release of polysaccharides in the LB-EPS fraction was detected during the enhancement of salinity. This was considered as a protective response of bacteria to the salinity. Three ？uorescence peaks were identi？ed in the EEM ？uorescence spectra of the EPS fraction samples. Two peaks were assigned to the protein-like ？uorophores, and the third peak was located at the excitation/emission wavelengths of 275nm/425-435 nm of the spectra of EPS fractions till the salinity maintained constant at 1%. This information is valuable for understanding the characteristics of EPS isolated from biomass in a saline nitrogen removal system

Characterization of water-soluble inorganic ions in size-segregated aerosols in coastal city, Xiamen

<p>The samples of water-soluble inorganic ions (WSIs), including anions (F^&minus;, Cl^&minus;, SO₄^2&minus;, NO₃^&minus;) and cations (NH₄⁺, K⁺, Na⁺, Ca²⁺, Mg²⁺) in 8 size-segregated particle matter (PM), were collected using a sampler (with 8 nominal cut-sizes ranged from 0.43 to 9.0&nbsp;&mu;m) from October 2008 to September 2009 at five sites in both polluted and background regions of a coastal city, Xiamen. The results showed that particulate matters in the fine mode (PM_2.1, Dp&nbsp;&lt;&nbsp;2.1&nbsp;&mu;m) comprised large part of mass concentrations of aerosols, which accounted for 45.56&ndash;51.27%, 40.04&ndash;60.81%, 42.02&ndash;60.81%, and 40.46&ndash;57.07% of the total particulate mass in spring, summer, autumn, and winter, respectively. The water-soluble ionic species in the fine mode at five sampling sites varied from 15.33 to 33.82 (spring), 14.03 to 28.06 (summer), 33.47 to 72.52 (autumn), and 48.39 to 69.75&nbsp;&mu;g&nbsp;m^{&minus;&nbsp;3} (winter), respectively, which accounted for 57.30&nbsp;&plusmn;&nbsp;6.51% of the PM_2.1 mass concentrations. Secondary pollutants of NH₄⁺, SO₄^2&minus; and NO₃^&minus; were the dominant contributors of WSIs, which suggested that pollutants from anthropogenic activities, such as SO₂, NOx were formed in aerosols by photochemical reactions. The size distributions of Na⁺, Cl^&minus;, SO₄^2&minus; and NO₃^&minus; were bimodal, peaking at 0.43&ndash;0.65&nbsp;&mu;m and 3.3&ndash;5.8&nbsp;&mu;m. Although some ions, such as NH₄⁺ presented bimodal distributions, the coarse mode was insignificant compared to the fine mode. Ca²⁺ and Mg²⁺ exhibited unimodal distributions at all sampling sites, peaking at 2.1&ndash;3.3&nbsp;&mu;m, while K⁺ having a bimodal distributions with a major peak at 0.43&ndash;0.65&nbsp;&mu;m and a minor one at 3.3&ndash;4.7&nbsp;&mu;m, were used in most of samples. Seasonal and spatial variations in the size-distribution profiles suggested that meteorological conditions (seasonal patterns) and sampling locations (geographical patterns) were the main factors determining the formation of secondary aerosols and characteristics of size distributions for WSIs.</p><!-- articleText --

Effect of Interspecies Quorum Sensing on the Formation of Aerobic Granular Sludge

<p>Quorum sensing (QS) is a form of microbial communication that relies on small signal molecules to regulate group behaviors such as biofilm formation in response to population density. In this study, we attempted to apply the paradigm of bacterial QS to aerobic granular sludge (AGS) formation for wastewater treatment. An essential element of interspecies QS signals, boron, was added to a sequencing batch reactor (SBR) to stimulate AGS growth. Bioassays elaborated the activity of autoinducer-2 (AI-2). We found that boron accelerated AGS growth, resulting in improved settlement performance and increased biomass in the SBR. During continuous SBR operation, the AGS showed an obvious increase in AI-2 activity, which implies that interspecies QS was closely associated with AGS formation. Analysis of EPS showed that boron stimulated tryptophan production, and increased the hydrophobia of AGS. From these results, it was speculated that the addition of boron may have promoted the formation of boron complexed to (R)-4, 5-dihydroxy-2,3-pentanedione (DPD) as the precursor of AI-2, which resulted in accelerated interspecies QS. The results also suggested QS as a novel regulation target for the biogranulation process, such as AGS formation.</p

Concentrations of some heavy metals in water, suspended solids, and biota species from Maluan Bay, China and their environmental significance

<p>Concentrations of heavy metals (Cu, Zn, Cd, and Pb) in surface water (including total recoverable, dissolved, suspended solids) and in aufwuchs encrusted on Moerella iridescens Benson from seven selected sites and two reference sites in Maluan Bay were investigated in order to understand current metal contamination due to industrialization and urbanization in Xiamen, China. The muscle tissues of the study species (Penceus penicillatus, Scylla serrata Forskal, Harengula zunasi Bleeker, Tillapia nilotica) from a trawling area within Maluan Bay were also analyzed in order to evaluate its safety as seafood. Based on the obtained data, metal concentrations in surface water were compared with Marine Seawater Quality Standards of China and the US EPA acute and chronic criteria, which showed that Maluan Bay may be subjected to different levels of contamination by the metals. Metal concentrations under study in the edible parts (muscle) of the investigated biota species were within the safety permissible levels for human consumption. Through Pearson's correlation analysis, the relationships between metal concentrations in surface water and in M. iridescens were evaluated. Copper concentrations in M. iridescens were more strongly positively correlated with particulate copper in suspended solids and total recoverable copper in water rather than with dissolved copper at the sampling sites. The data suggested that copper-rich suspended solids contributed substantially to copper accumulation by M. iridescens and played a critical role in the pathway of copper into the food chain. The conclusions of this investigation are likely to be applicable to other relevant scenarios.</p

Pd/γ-Al2O3催化对烟气中多环芳烃的氧化性能研究

实验采用等体积浸渍法制备了系列Pd/&gamma;-Al2O3催化剂。采用模拟实验装置并结合XRD、N2吸/脱附、TEM、H2-TPR和SEM-MAPS等手段对催化剂的组成及结构进行了表征,系统地考察了各催化剂对燃煤烟气中PAHs的催化氧化性能。结果表明,催化剂对烟气中PAHs排放总量的氧化效率为67.3%~93.5%,且烟气中PAHs的转化率随着Pd负载量的增加而提高;而催化剂的氧化性能随着PAHs环数(3~6)的增加而提高,对烟气中各PAHs排放毒性当量去除率超过90%。其中,Pd负载量为0.2%、催化剂焙烧温度为600℃条件下制备的催化剂具有最佳的PAHs消除性能,PAHs的氧化效率可达93.5%