Predicting disinfection by-product formation potential in water

Formation of regulated and non-regulated disinfection by-products (DBPs) is an issue at both potable water and wastewater treatment plants (W/WWTPs). Water samples from W/WWTPs across the USA were collected and DBP formation potentials (DBPFPs) in the presence of free chlorine and chloramine were obtained for trihalomethane (THM), haloacetic acid (HAA), haloacetonitrile (HAN), and N-nitrosodimethylamine (NDMA). With nearly 200 samples covering a range of dissolved organic carbon (0.6-23 mg/L), ultraviolet absorbance (0.01-0.48 cm⁻¹ at 254 nm wavelength), and bromide (0-1.0 mg/L) levels, power function models were developed to predict the carbonaceous DBP (C-DBP) and nitrogenous DBP (N-DBP) precursors spanning 3 orders of magnitudes. The predicted THM and HAA formation potentials fitted well with the measured data (analytical variance of less than 22%). Inclusion of dissolved organic nitrogen (DON) into the HANFP model improved the predictions. NDMAFP was the most difficult one to predict based upon the selected water quality parameters, perhaps suggesting that bulk measurements such as DOC or UVA₂₅₄ were not appropriate for tracking NDMAFP. These are the first such DBPFP models for wastewater systems, and among the few models that consider both C-DBPs and N-DBPs formation potentials from the same water sources.     

Modeling the effect of immobilization of microorganisms on the rate of biodegradation of phenol under inhibitory conditions

The main objective of this research is to model the effect of biodegradation process of phenol at high initial concentrations using a well known immobilization technique of the biomass. This work focused on testing the effect of activated carbon and clay while considering the diffusive internal mass transfer limitations. Biodegradation of phenol was performed by using enriched microorganisms from a compost of agricultural wastes. The average phenol biodegradation rate (uptake) of free biomass system was 235.3 mg g⁻¹ h⁻¹ at initial concentration range of 212-260 mg/L. However, the values for the systems of immobilized biomass in alginate and activated carbon (1 mm), alginate, activated carbon (4 mm), alginate, activated carbon and clay (1 mm) and alginate, activated carbon and clay (4 mm) were 64.9, 27.6, 27.5, and 8 mg g⁻¹ h⁻¹ respectively. The effective diffusion factors in different matrix were obtained using an intra-particle diffusion-based mathematical model. Diffusion limitation was observed when the matrix contained clay in addition to activated carbon. The diffusion coefficient was decreased from 1.6 × 10⁻⁸ to 1.2 × 10⁻⁹ cm²/s when clay was added to the matrix of 1 mm of alginate and activated carbon. Also, slight differences between the diffusion factors were observed for larger beads. The combination of clay and AC contributes to better mineralization of phenol at high concentrations. This could be attributed to the synergism of both additives.     

中外合作办学大学数学教学模式研究

目前我国大学的中外合作办学专业主要是经管类和计算机类,属于应用型人才培养模式。大学数学正逐步成为经管类和计算机类专业学生的核心课程。在作为核心课程的教学实践探索过程中,提出了一种新型的大学数学教学模式,即学习过程模式,它包括合作型学习模块、计算机贡献模块和考试模块。通过对学习过程模式的理论研究,探讨了这一新型教学模式的优点及可行性,并在数学建模中对该教学模式进行了实践应用和综合评价。     

建筑信息模型在我国工程设计行业中应用障碍研究

建筑信息模型（BIM）是数字技术在建筑业中的直接表达,涉及整个建筑工程全寿命期的各个环节,而工程设计行业是应用BIM技术的先行军。文章通过深入分析现阶段BIM在我国工程设计行业中的主要应用障碍,提出促进工程设计行业BIM本土化应用和发展的实施建议。研究结果表明,BIM可以由工程设计先行并实现其阶段性的价值,而多数设计相关人员不了解BIM的真正内涵,以及现有建筑行业体制、行业规程及法律责任界限不明的等障碍,是现阶段建筑行业亟需突破的。     

世博轴阳光谷矩形钢管单层网格实体造型研究

世博轴阳光谷单层网格的节点数量大,杆件空间角度不同,各杆件在节点处存在高差与错边,导致各节点相似却不相同的特点。人工进行深化设计极易出错且很难校核和发现错误。本文以世博轴阳光谷建设为依托,针对复杂空间结构玻璃幕墙的连接构造和矩形管单层网格实体造型问题进行了研究。以“节点相邻面法线合矢量”为原则提出了矩形截面钢管在自由空间曲面上的合理定位方法,并将该方法通过计算机程序实现三维实体模型的自动生成与测评功能,提高了设计效率、规避了出图错误。在此基础上,对简化模型和精细模型进行了对比分析,总结各自的适用范围。最后,对幕墙玻璃的裁剪进行了几何分析,并编制自动裁剪程序。     

Nitritation performance in membrane-aerated biofilm reactors differs from conventional biofilm systems

Nitrogen removal via nitrite has gained increasing attention in recent years due to its potential cost savings. Membrane-aerated biofilm reactors (MABRs) are one potential technology suitable to achieve nitritation. In this study we compared lab scale MABRs with conventional biofilm reactors to evaluate the influence of environmental conditions and operational parameters on nitritation performance. The oxygen mass transfer rate is postulated as a crucial parameter to control nitritation in the MABR: Clean water measurements showed significant underestimation of the total oxygen mass transfer, however, accurate determination of the oxygen mass transfer coefficient (k_m) of the system could be achieved by adjusting the liquid-phase mass transfer resistance in the constructed model. Batch experiments at different initial ammonium concentrations revealed that the conventional biofilm geometry was superior for nitritation compared to MABRs. These differences were reflected well in estimates of the oxygen affinity constants of the key microbial players, AOB and NOB (K_O,AOB < K_O,NOB (in both systems) and K_O,NOB values smaller in the MABR vs. the conventional biofilm system). It also appeared that – in addition to oxygen limitation – the absolute and relative substrate concentrations in the biofilm (esp. of oxygen) are very important for successful nitritation. Initial biomass composition, furthermore, impacted reactor performance in the MABR systems indicating the need for appropriate inoculum choice.     

BIM的行业扩散特征及企业应用策略分析

从全球范围来看,BIM已被广泛视为集成建设项目生产流程进而解决建筑业绩效问题的重要手段,但其应用价值的发挥仍面临技术、流程、组织、文化等多方面障碍。论文结合国内外BIM应用实践及我国2D CAD技术的应用历程,分析了BIM在建筑业内的扩散特征,并初步分析了我国建筑业企业的BIM应用策略。面对建设项目设计施工过程中的信息割裂问题以及行业信息技术的迅速发展,建筑业企业需要平衡好成本领先战略和差异化竞争战略的实施,摆脱BIM应用过程中的“无意识性”特征,注重制定科学的多阶段BIM应用目标、系统规划BIM应用方案、并有效集成企业商业流程及项目实施流程,以更好地发挥BIM的应用价值。     

基于BIM的机电设备应急管理系统总体设计

对于大型商业和公共建筑物,机电设备的正常运作是物业管理的基本要求,但机电设备故障是无法避免的事实,一旦发生机电设备出现问题,如何快速确定故障点,并能快速处理事故,是大型商业和公共建筑物机电设备应急管理必须解决的问题。本文介绍基于BIM技术的建筑机电设备应急管理系统技术实现方法选择和总体设计。