河谷型城市风场及污染物扩散的CFD数值仿真

为研究河谷型城市地形及其引起的风场和污染物扩散的复杂问题,利用CFD（计算流体力学）方法和复杂地形网格生成技术,建立河谷型城市风场及大气污染分布的数值仿真模型,实现CFD方法在复杂地形空气运动和污染物扩散方面的应用.分别使用LES（large eddy simulation）模型和mixture模型研究兰州市地面风场特征和污染物扩散形态,计算得到的污染物分布结果与实测结果分布一致.结果表明:复杂地形对空气运动的影响很大,如风速因山体屏障作用会呈现带状分布特征,山体后侧易出现弱风区域;同时,风场会密切影响污染物扩散,决定了污染物扩散形态,如幅散能够影响污染物扩散范围及污染水平.而给定西北风条件下,如地面以上10 m、风速为5 m/s、不受地形阻挡情况下,工业区污染物浓度被稀释10倍,约扩散2.2 km;山体阻挡会抑制污染物纵向扩散,表现在山体阻挡情况下污染物稀释100倍时的扩散长度约为相对平坦区域的1/3.此外,不同的入口风向会引起空气运动与山体相互作用发生变化,进而会使得地面风速、局部风场存在差异,造成污染物扩散及分布形态差异.研究显示,CFD方法可行,模型可靠,可以用来研究地形对风场和污染物扩散的影响.      

A green method to synthesize flowerlike Fe(OH)3 microspheres for enhanced adsorption performance toward organic and heavy metal pollutants

Dyestuffs and heavy metal ions in water are seriously harmful to the ecological environment and human health.Three-dimensional(3 D) flowerlike Fe(OH)_3 microspheres were synthesized through a green yet low-cost injection method,for the removal of organic dyes and heavy metal ions.The Fe(OH)_3 microspheres were characterized by thermal gravimetric analysis(TGA),Fourier transform infrared(FT-IR),and transmission electron microscopy(TEM) techniques.The adsorption kinetics of Congo Red(CR) on Fe(OH)_3 microspheres obeyed the pseudo-second-order model.Cr~(6+) and Pb~(2+) adsorption behaviors on Fe(OH)_3 microspheres followed the Langmuir isotherm model.The maximum adsorption capacities of the synthesized Fe(OH)_3 were 308,52.94,and 75.64 mg/g for CR,Cr~(6+),and Pb~(2+) respectively.The enhanced adsorption performance originated from its surface properties and large specific surface area of 250 m~2/g.The microspheres also have excellent adsorption stability and recyclability.Another merit of the Fe(OH)_3 material is that it also acts as a Fenton-like catalyst.These twin functionalities(both as adsorbent and Fenton-like catalyst) give the synthesized Fe(OH)_3 microspheres great potential in the field of water treatment.     

有机化合物的生物降解性能和生物毒性

有机化合物在环境中的出现是当今世界的重大挑战之一,80年代以来,对于有机化合物在生化处理系统中的归宿和对生物的影响已引起普遍的关注。迄今为止,有关这个课题的研究和资料仍然很少。文章对有机化合物的生物降解性能和生物毒性作一综述,以供同行参考。     

A comparison of chemical MSW compositional data between China and Denmark

Chemical waste compositions are important for municipal solid waste management, as they determine the pollution potentials from different waste strategies. A representative dataset for chemical characteristics of individual waste fractions is frequently required to assess chemical waste composition, but it is usually reported in developed countries and not in developing countries. In this study, a dataset for Chinese waste was established through careful data screening and assessment, named as CN dataset. Meanwhile, a dataset for Danish waste (DK dataset) was also summarized based on previous studies. In order to quantitatively evaluate the reliabilities of CN and DK datasets, the chemical waste compositions in four Chinese cities were estimated by utilizing both of them, respectively. It is indicated that the usage of CN datasets led to significantly lower discrepancies from the actual values based on laboratory analysis in most cases. Within the datasets, the moisture contents of food waste, paper, textiles, and plastics, the carbon content of food waste, as well as the oxygen content of plastics would induce significant divergences, which should be paid special attention when gathering the information. In addition, the fractional waste compositions in China showed similar features with other developing countries but differ significantly with developed countries. Thus the above-mentioned conclusions could also be true in other developing countries.     

天津地区典型家用生物质颗粒采暖炉污染物排放分析

为调查研究天津市家用生物质颗粒采暖炉的污染物排放性状,同时为政府的政策制定提供技术依据,研究了天津地区生物质燃料成分和采暖炉不同运行负荷对污染物排放的影响.结果表明：稻杆和棉杆两种成型燃料在同一采暖炉的相同工况下燃烧时,稻杆灰分含量较棉杆高,造成较高的烟尘和CO排放,同时稻杆较棉杆S元素含量低,导致SO₂排放较低.棉杆成型燃料在同一容量的采暖炉上燃烧时,随着燃烧器负荷的增加,CO和SO₂的排放增加,NO_x的排放减少.两种生物质成型燃料在该采暖炉上燃烧排放的挥发性有机物的主要种类均依次为酮类、苯系物、醛类.本工作试验用家用生物质颗粒采暖炉运行过程中NO_x、CO、SO₂、烟尘的平均排放值分别为672.70,2297.94,124.00,109.35mg/m³,存在污染物排放超标的现象,可通过增添水浴除尘设施,合理调节不同燃烧负荷下的风机送风量,维持适宜过量空气系数,以降低污染物排放.同时还需制定合理的标准和政策加强对家用采暖炉和成型燃料质量的监管.     

不同排海方式城市尾水微生物扩散规律

尾水中含有大量病原菌,回用或排入自然水体后会对人群健康和生态安全构成威胁.为了探究不同排海方式对微生物扩散规律的影响,本研究利用高通量测序技术对春季污水处理厂尾水细菌群落结构、优势菌群、典型致病菌及其随扩散距离的变化进行研究.结果发现,先排河后排海的尾水物种更加丰富,分布在58个菌纲,相对丰度大于1%的细菌有32种,而直接排海的尾水中仅有41个菌纲,相对丰度大于1%的细菌有28种.相对于直排过程,间排方式微生物群落结构相对丰度更高,说明尾水的直接排海使得微生物更易扩散.同一污水处理厂优势菌门所占比例随着扩散距离的增大整体呈下降趋势,蓝藻菌门(Cyanobacteria)等由于在自然水体中的高浓度出现随扩散距离增大整体上升的趋势.两个系统的优势菌门都属于变形菌门(Proteobacteria)、拟杆菌门(Bacteroidetes)及厚壁菌门(Firmicutes),纲、种水平重合度较低,但整体来讲排污口附近微生物多样性及丰度远高于海水(空白样品),且污水处理相关菌种丰度较高.另外,尾水中存在一定量的致病菌和条件致病菌,其中Pseudoalteromonas haloplanktis、Pseudomonas anguilliseptica致病性极强,扩散后相对丰度仍然很高,且弓形杆菌属(Arcobacter spp.)与人类和动物的腹泻、菌血症等疾病密切相关.因此,尾水排放过程中应对这几种细菌重点监测.     

污水生物处理中抗生素的去除机制及影响因素

环境中的抗生素污染日益严重,其诱导产生的抗生素抗性成为人类健康的重大威胁.通过对世界多地污水处理厂进、出水中抗生素浓度水平的文献调研汇总,发现当前的污水处理工艺不能实现抗生素的有效去除.吸附和生物降解是污水中抗生素的主要去除途径,因此本文深入地分析了吸附的作用机制和不同种类抗生素吸附程度的差异;从生物降解性能、降解菌和降解产物等方面分析抗生素在污水生物处理过程中的生物降解作用;分析讨论了水力停留时间、污泥停留时间、温度和工艺选型(传统活性污泥法、膜生物反应器和生物脱氮工艺)等污水生物处理工艺的运行条件对吸附和生物降解途径的影响,进而解析对抗生素去除效果的影响.菌群组成、生长基质供应情况和微污染物共存情况等因素对污水生物处理中抗生素迁移转化的影响需要更深入地研究.     

不同运行策略下厌氧氨氧化的脱氮性能

采用厌氧氨氧化反应器(ASBR)处理模拟生活污水,考察低基质比、降温方式及pH对系统脱氮性能的影响.结果表明,温度为30℃时,控制进水NO_2~--N浓度为(30±0.2)mg·L~(-1),基质比(NO_2~--N/NH_4~+-N)由0.9升至1.4,系统NH_4~+-N和NO_2~--N去除率均值分别从54.4%和65.3%升至95.8%和92.5%;当基质比继续升高至1.6时,NH_4~+-N去除率基本不变,而NO_2~--N去除率降至54.6%,即基质比接近理论值1.32时,其厌氧氨氧化脱氮性能较强.当反应温度一次性从30℃降低至15℃时,NH_4~+-N和NO_2~--N的去除率由97.5%和98.5%分别降至35.2%和40.1%,当采用阶梯式降温方式(30℃→25℃→20℃→15℃)时,NH_4~+-N和NO_2~--N的去除率分别由97.7%和98.6%逐渐降至52.7%和62.4%.控制NO_2~--N/NH_4~+-N为1.4,逐步升高pH由7.7至8.5时,NH_4~+-N和NO_2~--N的去除率先增大后减小,当pH为8.3时系统脱氮性能最佳.     

Treatability studies of naphthalene in soil,water and air with persulfate activated by iron(Ⅱ)

Chemical oxidation was applied to an artificially contaminated soil with naphthalene (NAP). Evaluation of NAP distribution and mass reduction in soil, water and air phases was carried out through mass balance. Evaluation of NAP distribution and mass reduction in soil, water and air phases was carried out through mass balance. The importance of the air phase analysis was emphasized by demonstrating how NAP behaves in a sealed system over a 4 hr reaction period. Design of Experiments method was applied to the following variables: sodium persulfate concentration [SP], ferrous sulfate concentration [FeSO₄], and pH. The system operated with a prefixed solid to liquid ratio of 1:2. The following conditions resulted in optimum NAP removal [SP] = 18.37 g/L, [FeSO₄] = 4.25 g/L and pH = 3.00. At the end of the 4 hr reaction, 62% of NAP was degraded. In the soil phase, the chemical oxidation reduced the NAP concentration thus achieving levels which comply with Brazilian and USA environmental legislations. Besides the NAP partitioning view, the monitoring of each phase allowed the variabilities assessment over the process, refining the knowledge of mass reduction. Based on NAP distribution in the system, this study demonstrates the importance of evaluating the presence of semi-volatile and volatile organic compounds in the air phase during remediation, so that there is greater control of the system as to the distribution and presence of the contaminant in the environment. The results highlight the importance of treating the contaminant in all its phases at the contaminated site.     

电场与MnxCey催化剂在苯氧化反应中的协同效应及机理探究

挥发性有机物（VOCs）大量排放已成为日益严重的环境问题,为了实现VOCs的高效去除,本文采用自蔓延燃烧合成法制备了一系列锰铈复合氧化物催化剂,将稳恒直流电场引入典型VOCs气体苯的催化氧化过程,并基于不同电场条件下催化剂的理化性质表征结果进行机理分析.实验结果表明,Mn_xCe_y催化剂对含苯废气的去除有良好的效果,稳恒直流电场显著促进了催化剂的活性,其中Mn₁Ce₃的催化性能最佳,电流为5 mA时,Mn₁Ce₃催化剂在155℃可达到50%的苯转化率,在202.4℃可达到90%的苯转化率,对应的转化温度T₅₀和T₉₀比传统方法分别降低了62.4℃和48.3℃,且电场中的反应活化能由52.32 kJ·mol^-1降低至32.31 kJ·mol^-1.根据实验现象及表征结果,发现协同效应与活性位点的快速持续再生及活性氧物种的转化有关,由此提出苯在Mn_xCe_y催化剂上的氧化机理及电场协同催化的反应模型.