Numerical simulation of baffle effect on the performance of sedimentation basin

Sedimentation basin is an important component of every water treatment process. In order to improve the sedimentation efficiency (SE) of rectangular sedimentation basins, many researchers have proposed various methods. Among the suggested methods, the change of the geometry with installation of baffle in the basin floor is simple and completely economic. In this research, the hydraulic characteristics of the flow with various baffle configurations in the basin floor have been evaluated and the best geometry of the baffle has been presented. The agreement between numerical and experimental results was good. The results showed that the flow in the sedimentation basin is strongly influenced by the baffle. Also, the baffles installed with lower height and closer to the basin inlet and baffles with high height and far from the basin inlet have the greatest effect on the SE.     

Simulation of depth and wind effects on the hydraulic efficiency of sedimentation tanks

In this research, we aim to investigate the effects of the depth and wind effect on the surface of water on the hydraulic efficiency of the sedimentation tanks in water and wastewater treatments plants. A verified two‐dimensional numerical study was performed to evaluate hydraulic performance of series settling tanks by four different depths of 2.5, 3, 3.5 and 4 (m). Wind velocities of 5 and 7 (m/s) in co‐current and counter‐current direction of water flow in sedimentation tank were applied on the surface of the water. In this study, k–ε turbulent model and passive scalar tracer were used to perform the simulations. The research confirms that wind influence on the surface of water causes recirculation zones and increases the length of recirculation zones. In both windy and normal situation, the Real Hydraulic Retention Time and the effective volume of sedimentation tanks increases widely as the depth of the tank.     

平流式沉淀池中部进水流场测量与数值模拟

为了深入了解与分析沉淀池内流场的特性,采用激光多普勒测速仪(Laser Doppler Velocimeter,LDV)对平流式模型沉淀池内中部进水情形时的流场进行了测量,限于三维测量的难度,初步进行了三维速度的精确测量,实验结果表明沉淀池内不同区域存在不同程度的三维流动。采用k-ε模型对流场进行了模拟,计算结果与实验结果总体吻合良好。就风速对流场产生的影响进行了初步的测量及探讨,发现风对沉淀池流场具有明显的影响,然而建立相应的理论模型还需要进一步研究。     

本辽高速跨越沉淀池路段路基处治方案设计

主要阐述了本溪—辽中高速公路K48＋080-K48＋200沉淀池尾矿渣的工程地质特征，分析了该路基处治的主要技术问题，并对跨越该路段路基进行合理设计，对同类工程设计有一定的指导意义。     

The effect of primary sedimentation on full-scale WWTP nutrient removal performance

Traditionally, the performance of full-scale wastewater treatment plants (WWTPs) is measured based on influent and/or effluent and waste sludge flows and concentrations. Full-scale WWTP data typically have a high variance which often contains (large) measurement errors. A good process engineering evaluation of the WWTP performance is therefore difficult. This also makes it usually difficult to evaluate effect of process changes in a plant or compare plants to each other. In this paper we used a case study of a full-scale nutrient removing WWTP. The plant normally uses presettled wastewater, as a means to increase the nutrient removal the plant was operated for a period by-passing raw wastewater (27% of the influent flow). The effect of raw wastewater addition has been evaluated by different approaches: (i) influent characteristics, (ii) design retrofit, (iii) effluent quality, (iv) removal efficiencies, (v) activated sludge characteristics, (vi) microbial activity tests and FISH analysis and, (vii) performance assessment based on mass balance evaluation. This paper demonstrates that mass balance evaluation approach helps the WWTP engineers to distinguish and quantify between different strategies, where others could not. In the studied case, by-passing raw wastewater (27% of the influent flow) directly to the biological reactor did not improve the effluent quality and the nutrient removal efficiency of the WWTP. The increase of the influent C/N and C/P ratios was associated to particulate compounds with low COD/VSS ratio and a high non-biodegradable COD fraction.     

加长沉淀池集水槽降低出水浊度的实践

总结了南京市北河口水厂平流式沉淀池的运行特点，并探索了提高水厂出水水质的方法，分析了影响出水浊度偏高的原因，提出了采用加长平流式沉淀池集水槽长度对平流式沉淀池进行改造的方案，通过改造有效减少后续处理设备的负荷，提高了水厂的运行效率。     

集水孔面积的改变对平流沉淀池出水的研究

通过对南方某市一大型自来水厂集水槽的实验研究，得出了在集水总长不变的前提下，适当改变后段集水孔的面积，从而相对增大前段集水量和集水速度，可使槽前、槽后浊度差减小0．4NTU左右，集水总渠浊度降低0．2NTU左右的结论，具有较好的经济效益。     

新河水厂斜管沉淀池排泥系统改造

针对斜管沉淀池排泥效果不佳、沉泥上浮等问题,对天津塘沽新河水厂斜管沉淀池排泥系统进行了改造,结合测试结果分析了改造后排泥系统存在的问题以及排泥不畅的原因,并提出了具体的建议和解决方法,为同类改造提供了参考.     

周边进出水沉淀池进水槽水力分析及计算

分析了周边进出水沉淀池的池型和水流特征,根据水力学原理,推导出周边进出水沉淀池进水槽水深沿程变化的基本关系式,总结了三种配水途径,并结合工程实例详细介绍了进水槽配水设计计算过程.     

高位消防水箱设置探讨

结合GB 50045-95高层民用建筑设计防火规范,GB 50016-2006建筑设计防火规范,GB 50084-2001自动喷水灭火系统设计规范,对高位消防水箱设置的数量、方案进行了探讨,指出了高位水箱存在的问题,以指导相关设计工作。     

城市消防水池设计探讨

根据设计实践，探讨了城市消防水池的设计中应该注意的问题，并提出了建议。通过周密设计消防水池的选址、池型和池容，合理利用已有条件以减少池容、降低造价，以及发挥整体优势并合理设置消防水池等，能够实现消防水池的确保使用和经济设置。     

关于在广州新建小区取消化粪池的探讨

分析了现有化粪池污染的情况，通过资料收集和调查，从取消化粪池的条件、范围、投资比较、对污水厂的影响、应采取的措施等方面探讨了广州新建小区取消化粪池的必要性，以减少环境污染。     

浸入式中空纤维膜处理净水厂沉淀池排泥试验研究

首次采用浸入式中空纤维膜处理净水厂沉淀池排泥,对膜通量、过滤后水质及膜污染的清洗等问题进行了现场试验、分析和探讨。     

Effect of the model updating on the earthquake behavior of steel storage tanks

In this paper, effect of the finite element model updating on the earthquake behavior of steel storage tanks considering fluid-structure interaction is investigated. For this purpose, a cylindrical steel storage tank filled some liquid fuel oil located in Trabzon, Turkey is selected as an example. Initial finite element model of the storage tank is developed by ANSYS software and dynamic characteristics (natural frequencies, and mode shapes) are determined analytically. Ambient vibration tests are conducted on the storage tank under natural excitations to obtain dynamic characteristics (natural frequencies, mode shapes and damping ratios), experimentally. Peak Picking technique in the frequency domain is used to extract experimental dynamic characteristics. When the analytically and experimentally identified dynamic characteristics are compared to each other, some differences are found between both results. To minimize these differences, initial finite element model of the storage tank is updated according to experimental results using some uncertainties modeling parameters such as elasticity modulus. To investigate the effect of finite element model updating on the earthquake behavior of the storage tank, earthquake analyses are performed before and after model updating. In the earthquake analyses, YPT330 component of 1999 Kocaeli earthquake is selected and applied to the models in the horizontal directions. It is seen from the analyses that the displacements and the stresses after model updating are more effective than the displacements and the stresses before model updating.     

The influence of macrophytes on sedimentation and nutrient retention in the lower River Spree (Germany)

Nutrient retention due to sedimentation in running waters has been little studied. The knowledge about the processes of self-purification is important for the management of rivers. The principal aim of our investigations was to quantify nutrient retention by sedimentation within and adjacent to stands of submerged macrophytes. In addition, we examined the relationship between deposition and sedimentation patterns and the flow regime. In the summer of 2001, investigations were performed in the lower River Spree with sediment traps and sediment cores and measurement of flow velocities. The spatial distribution of macrophytes was described and related to sedimentation and flow patterns. Water and sediment samples were analysed for total phosphorus and total organic nitrogen concentrations. Macrophytes significantly enhanced water residence time by factors between 2 and 18. Trapping rates were high within and downstream of macrophyte stands due to the prevailing quiescent conditions. Trapping rates were low in regions not covered by macrophytes, where flow velocities were high. Calculated deposition of organic matter due to trapping rates accounted for 15-49% of observed deposition between May and September, the vegetation period. The difference between calculated and observed deposition can partly be attributed to an incomplete erosion of the organic sediments between October and April. Between May and September, nitrogen and phosphorus were retained by deposition by as much as 2.5% and 12.2%, respectively (% of total load). Therefore, macrophytes considerably contributed to total monthly phosphorus retention (up to 25%) by increasing deposition of particulate organic matter.     

Effects of baffles on the performance of model waste stabilization ponds

The performance of three baffled laboratory-scale facultative stabilization ponds were compared with that of an unbaffled control pond. The hydraulic characteristics of the ponds were estimated from the results of tracer tests.The biochemical oxygen demand (BOD₅) removals achieved with the control pond and with the ponds having 3, 6 and 9 baffles were 79, 81, 86 and 89% respectively and the chemical oxygen demand (COD) removals were 81, 84, 84.2 and 84.2%. The reductions in total solids (TS) were respectively 43, 46, 51 and 64%. Dispersion indices of 0.161, 0.126, 0.112 and 0.096 were obtained for the control, 3, 6 and 9 baffle ponds respectively, which indicated a trend of decreasing dispersion index with increasing number of baffles.     

新型悬浮填料滤池取代二沉池研究

悬浮填料滤池是基于轻质悬浮填料技术而提出的新型高效固液分离技术,不但可以代替传统二沉池完成固液分离、污泥浓缩,而且具有占地省、出水表面无飘泥、出水水质好、冲洗简易方便以及一定的后续生物氧化作用等特点。在填料层高度为2.0m、填料比表面积为285m2/m3、表面负荷为1.98m3/(m2.h)、污泥回流比为200%、滤池冲洗时间为2~3h的工况下,滤池稳定期长达4~9d,出水SS可达到《城镇污水处理厂污染物排放标准》(GB18918—2002)的一级标准。     

石家庄采暖室外计算温度的变化分析

采暖室外计算温度的合理确定直接影响采暖设计热负荷的计算准确度,进而影响暖系统的热舒适性、能耗及投资情况.采用更接近实际情况的室外计算温度,会提高建筑节能分析研究、设计和运行的精确度,有利于促进建筑节能技术的发展.在分析石家庄冬季气温变化特点及发展趋势的基础上,比较现行国家规范GB50172-93<民用建筑热工设计规范>和河北省DB13(J)63-2007<居住建筑节能设计标准>分别给出的石家庄采暖室外计算温度参数.并与2007、2008年度采暖期室外温度实际情况进行一致性对比分析.结果表明,河北省DB13(J)63-2007<居住建筑节能设计标准>提供的石家庄采暖室外计算温度更为接近当前的实际情况,更有利于提高建筑节能设计质量.     

The effect of earthquake frequency content on the seismic behavior of concrete rectangular liquid tanks using the finite element method incorporating soil-structure interaction

A three-dimensional soil-structure-liquid interaction is numerically simulated using the finite element method in order to analyze the seismic behavior of partially filled concrete rectangular tanks subjected to different ground motions. In this paper, the effect of earthquake frequency content on the seismic behavior of fluid rectangular tank system is investigated using four different seismic motions. A simple model with viscous boundary is used to include deformable foundation effects as a linear elastic medium. This method is capable of considering both impulsive and convective responses of liquid-tank system. Six different soil types defined in the well-recognized seismic codes are considered. The sloshing behavior is simulated using linear free surface boundary condition. Two different finite element models corresponding with flexible shallow and tall tank configurations are studied under the effects of longitudinal, transversal and vertical ground motions. By means of changing the soil properties, comparisons are made on base shear, base moment and sloshing responses under different ground motions. It is concluded that the dynamic behavior of the fluid-tank-soil system is highly sensitive to frequency characteristics of the earthquake record.