Cr(VI)对活性污泥硝化活性的抑制及在污泥中的分布特点

重金属铬(Cr(VI))是废水中常见的、困扰很多污水生物处理系统运行效果的污染物.本文通过静态试验和静态冲击试验,研究了Cr(VI)在活性污泥系统中的分布特点和对硝化效率、活性等的影响,并进行了模型分析.结果表明,活性污泥对Cr的吸附很快,但吸附量有限,Cr(VI)投加浓度为1、5、10和30 mg · L^-1的溶液中,Cr的12 h-吸附量分别为0.79、1.98、3.19和5.78 mg · g^-1.Cr(VI)投加到活性污泥混合液中后形态分为溶解态、可洗脱和不可洗脱态,可洗脱的Cr能够向不可洗脱态转变.Cr(VI)对活性污泥硝化活性的抑制程度随着Cr(VI)浓度的增大而提高.静态试验中,1、3、5、10和30 mg · L^-1 Cr(VI)对氨氮平均降解速率的抑制率分别为5.25%、9.80%、10.41%、17.54%和21.38%.Cr(VI)对微生物的抑制作用大小是:氨氧化菌 >亚硝酸盐氧化菌 >异养菌.模型分析发现,Cr(VI)对氨氧化菌和异养菌比耗氧速率的抑制符合Haldane动力学模型,属于非竞争性抑制.冲击试验表明Cr对硝化等的抑制主要是不可洗脱的Cr造成的,抑制效果的出现具有滞后性.     

硫代氨基甲酸酯类杀菌剂代森锰锌及其降解产物乙撑硫脲的技术进展研究

综述了国内外硫代氨基甲酸酯类杀菌剂代森锰锌及其降解产物乙撑硫脲的研究进展,详细介绍了代森锰锌和乙撑硫脲的性质,并对乙撑硫脲的降解研究进展、分析研究进展和残留动态研究进展进行了阐述.从中重点论述了食品中乙撑硫脲的多种分析检测技术,根据乙撑硫脲的性质分别选择气相色谱法和高效液相色谱法进行检测.总结了目前中国对该类农药的使用方式、方法,指出了硫代氨基甲酸酯类杀菌剂在农副产品以及在食品加工方面的研究方向.     

Evaluating the Impacts of Environmental Flow Alternatives on Reservoir and Recreational Operations Using System Dynamics Modeling

Providing environmental flows is increasingly a management obligation in many water resource systems. Evaluating the impacts of environmental flow alternatives on other water uses in a basin can be a challenge, especially when collaborating with stakeholders. We demonstrate the use of system dynamics (SD) modeling to assess the impacts of four environmental flow alternatives in the Rio Chama, New Mexico. The model was developed to examine impacts of each alternative on reservoir storage and releases, hydropower production and revenue, and whitewater boating access. We simulated each alternative within a stochastic framework in order to explicitly incorporate hydrologic uncertainty into the analyses. The environmental flow alternatives were developed at a collaborative workshop of geomorphology, hydrology, and ecology experts. Results from the model indicate that the proposed flow recommendations on the Rio Chama will generally decrease annual reservoir storage, increase median flows, and have minimal impacts on hydropower production and whitewater rafting on the system. The Rio Chama case study is a promising example of how SD modeling can be used in the early stages of environmental flow studies and why it is compatible with collaborative modeling.     

Cr(Ⅵ)对活性污泥硝化活性的抑制及在污泥中的分布特点

重金属铬(Cr(Ⅵ))是废水中常见的、困扰很多污水生物处理系统运行效果的污染物.本文通过静态试验和静态冲击试验,研究了Cr(Ⅵ)在活性污泥系统中的分布特点和对硝化效率、活性等的影响,并进行了模型分析.结果表明,活性污泥对Cr的吸附很快,但吸附量有限,Cr(Ⅵ)投加浓度为1、5、10和30 mg·L-1的溶液中,Cr的12 h-吸附量分别为0.79、1.98、3.19和5.78 mg·g-1.Cr(Ⅵ)投加到活性污泥混合液中后形态分为溶解态、可洗脱和不可洗脱态,可洗脱的Cr能够向不可洗脱态转变.Cr(Ⅵ)对活性污泥硝化活性的抑制程度随着Cr(Ⅵ)浓度的增大而提高.静态试验中,1、3、5、10和30 mg·L-1Cr(Ⅵ)对氨氮平均降解速率的抑制率分别为5.25%、9.80%、10.41%、17.54%和21.38%.Cr(Ⅵ)对微生物的抑制作用大小是:氨氧化菌亚硝酸盐氧化菌异养菌.模型分析发现,Cr(Ⅵ)对氨氧化菌和异养菌比耗氧速率的抑制符合Haldane动力学模型,属于非竞争性抑制.冲击试验表明Cr对硝化等的抑制主要是不可洗脱的Cr造成的,抑制效果的出现具有滞后性.     

Numerical study of the effects of Planetary Boundary Layer structure on the pollutant dispersion within built-up areas

The effects of different Planetary Boundary Layer (PBL) structures on pollutant dispersion processes within two idealized street canyon configurations and a realistic urban area were numerically examined by a Computational Fluid Dynamics (CFD) model. The boundary conditions of different PBL structures/conditions were provided by simulations of the Weather Researching and Forecasting model. The simulated results of the idealized 2D and 3D street canyon experiments showed that the increment of PBL instability favored the downward transport of momentum from the upper flow above the roof to the pedestrian level within the street canyon. As a result, the flow and turbulent fields within the street canyon under the more unstable PBL condition are stronger. Therefore, more pollutants within the street canyon would be removed by the stronger advection and turbulent diffusion processes under the unstable PBL condition. On the contrary, more pollutants would be concentrated in the street canyon under the stable PBL condition. In addition, the simulations of the realistic building cluster experiments showed that the density of buildings was a crucial factor determining the dynamic effects of the PBL structure on the flow patterns. The momentum field within a denser building configuration was mostly transported from the upper flow, and was more sensitive to the PBL structures than that of the sparser building configuration. Finally, it was recommended to use the Mellor–Yamada–Nakanishi–Niino (MYNN) PBL scheme, which can explicitly output the needed turbulent variables, to provide the boundary conditions to the CFD simulation.     

机动车加油过程中气液两相流动特性的CFD数值模拟

随着环保法规的不断完善,机动车加油过程中所产生的油气排放污染问题越来越受到重视.国外自20世纪90年代中后期开始采用数值模拟手段对机动车的加油过程进行研究,而国内迄今尚处于空白阶段.对机动车加油过程所涉及的＂加油枪喷嘴＋加油管＋油箱＋回气管＂物理体系进行适当简化,采用商业计算流体动力学（CFD）软件Fluent中提供的VOF气液两相流模型和RNG k-ε湍流模型,在基于Gambit软件确定网格划分方案和进行适当的边界条件设置后,建立了合理可行的加油过程气液两相流动CFD数值模拟模型,讨论了加油速度对油箱内气相空间静压力的影响,揭示了汽油在加油管内的回流现象.结果表明,加油枪的流量越大,油箱内气相空间的静压总体上也逐渐增大;同时油箱内气相空间的静压总体上可以划分为3个较为明显的阶段.而当加油流量较大时,往往会引起汽油在加油管油帽段内回流,从而使得加油枪过早跳枪.本研究为国内自主开展机动车加油以及油气排放污染控制技术和设备方面的研究开发奠定了一定基础.     

Application of game theory in risk management of urban natural gas pipelines

This paper presents a game theory methodology for risk management of urban natural gas pipelines, which is a collaborative participation mechanism of the stakeholders, including government, pipeline companies, and the public. Firstly, the involvement proportion of stakeholders in risk management under rational conditions is estimated by the static game theory. Subsequently, the system dynamics (SD) simulation is used to establish an evolution game model of stakeholders in risk management under the irrational conditions, in which the stability of the evolution game process is analyzed. The stakeholders’ involvement proportions from the static game model are utilized as the inputs for the evolution game model to simulate the dynamic evolution behavior of risk management strategies with different involvement proportions of stakeholders. Eventually, the dynamic evaluation game can extract an optimal strategy for risk management of urban natural gas pipelines. A case study is used to illustrate the methodology. In essence, this methodology can be extended for implementing risk management of urban infrastructure.     

Numerical simulation of the thermal inertia of an adiabatic reaction calorimeter in reaction thermal safety process

Obtaining accurate thermal risk assessment parameters of chemical processes and substance properties is essential for improving the safety of chemical production and substance use and storage, and the adiabatic reaction calorimeter (ARC) has been employed by many researchers for this purpose. However, with the improvement and upgrading of the instrument, an examination of the factors that affect its detection accuracy is warranted. A simplified reaction model of the adiabatic thermal decomposition of tert-butyl peroxyacetate was constructed using computational fluid dynamics in which the adiabatic thermal decomposition kinetic model and fluid-solid coupling model were combined to simulate heat transfer. To verify the reliability of the parameters of the numerical calculation model, the effects of the sample cell's material, wall thickness, and mass were investigated in relation to the thermal inertia of the ARC. The results indicated that the thermal inertia of the system was lowest when the sample cell was composed of titanium. When the sample pool's composition is determined, the thermal inertia of the system can be reduced to a certain extent through an approximate increase in the sample mass. Finally, an analysis of the heat flow cloud diagram of the wall of sample pools made from different materials revealed that the thermal conductivity of titanium was high; this information can assist in controlling the adiabatic process.     

基于结构参数响应的内循环流化床流体特性优化数值模拟

流化床是一种结构复杂而能量转化高效的反应器型式,为了实现系统化的内循环流化床优化设计,利用欧拉-欧拉双流体模型构建了不同结构的CFD流化床模型,在分别改变高径比、导流筒与反应器的直径比和底隙高度3个结构因素的情况下,考察流化床内全流场、局部流场、液相运动速度及气含率等气液两相流的响应特性,分析结构因素及操作因素对流体运动的内在影响,阐明工程优化设计的方向.数值模拟结果表明:高径比主要影响气液流动型态,低高径比时容易出现漩涡和返混,工程中应采用导流内构件并重视气体分布装置的合理设计;导流筒与反应器的直径比主要影响液体循环速度,存在一个合理的区间,考虑流动速度与气含率,流化床直径比可取0.6～0.8,最佳取值为0.7;底隙高度影响流化床底泥区的流体运动,应约等于流化床下降区的缝隙长度.CFD模拟可作为污染控制技术工业放大和优化设计的辅助工具.     

池塘养殖(青虾)生态系统服务价值的系统动力学模型

生态服务价值的评估在近10 a来受到广泛关注,但大多基于静态评估框架,缺少动态分析。研究运用系统动力学的原理和方法,分析了青虾池塘养殖生态系统服务价值评估系统的内部结构,描绘了因果关系图及流图,建立了相应的系统动力学模型,初步预测不同决策方案下食物供给、固碳、释放氧气价值和富营养化环境成本在30 a内的变化趋势,结果表明:①无论采取何种决策,若系统外部环境不变,生态系统净服务价值的供给趋于稳定;②在池塘养殖生态系统中,释放氧气和固定二氧化碳等非市场价值是生态系统服务价值重要稳定的来源;③青虾养殖中投资变动在短期内往往会造成水产品市场价值的大幅波动,长期里则因投入的增加而增加,但增加率逐渐减少,最终达到稳定值;④在当前条件假设和环境参数的约束下,模型模拟结果与实测结果基本一致。