Cell Immobilized FOG-Trap System for Fat, Oil, and Grease Removal from Restaurant Wastewater

Cell immobilized lipase-producing bacteria on three different matrices were incorporated in a fat-, oil-, and grease (FOG) trap system for restaurant wastewater treatment. During a 16-day laboratory-scale experiment for the treatment of synthetic FOG wastewater containing soybean oil, no significant difference (two-tailed t test at 95% confidence interval) in the FOG removal between two systems was observed at FOG influent ≤ 1,000?mg/L. However, the typical trap showed lower FOG removal efficiency than the matrix-based system when the influent FOG concentration was increased to ≥ 5,000?mg/L. In addition, the matrix-based trap system was able to sustain a stable high FOG removal, with <100?mg/L effluent, even at 10,000 mg/L influent FOG. Based on FOG heights measured and mass balance calculations, 97.4 and 99.5% of the total FOG load for 16 days were removed in a typical trap and matrix-based system, respectively. About 93.6% of the removal in the matrix-based was accounted to biodegradation. The 30-day full-scale operations demonstrated a distinguishably better performance in the matrix-based system (92.7±9.06% of 1,044.8±537.27?mg FOG/L) than in the typical trap system (74.6±27.13% of 463.4±296.87?mg FOG/L) for the treatment of barbeque restaurant wastewater. Similarly, matrix-based system revealed higher chemical oxygen demand removal (85.9±11.99%) than the typical trap system (60.4±31.26%). Characterizations of the influent, emulsified, adsorbed and effluent FOG indicated that straight saturated fatty acids constituted the cause of clogging problems in the FOG-trap and piping system.     

Exploratory Study of Submerged Hydraulic Jumps with Blocks

A preliminary study on submerged jumps with baffle walls and blocks downstream of a sluice gate was conducted. Two series of experiments were carried out on baffle walls and baffle blocks. The momentum equation was utilized to derive a relation for the drag coefficient that was validated by the experimental data of the baffle wall series. The baffle block series consisted of five Froude numbers and a range of submergence factors with one configuration of baffle blocks. The inlet depth factor was found to be a function of the submergence and Froude number. It was observed that the energy dissipation efficiency was a function of submergence with the maximum efficiency being in excess of that of the corresponding free jump.     

Design of Secondary Settling Tanks Using a CFD Model

A computational fluid dynamics (CFD) model is presented and applied in the design of the secondary settling tanks of Psyttalia Wastewater Treatment Plant in Athens, Europe’s largest sewage treatment facility. The tanks are of the Gould Type II consisting of the following regions: an inlet-flocculation chamber with an inlet baffle, two zones of settling separated by an intermediate baffle, an outlet region, and a sludge collection region. The number of tanks and their dimensions were determined with an empirical design procedure. Then, theoretical considerations, information from similar existing tanks, and preliminary CFD calculations were combined to determine the dimensions of the main regions and the positions of the baffles. Finally, detailed CFD calculations were performed to examine the performance of the tanks for various design conditions. Computations showed that the flow in the inlet-flocculation region was completely mixed; while in the settling regions a “three-layer” structure with relatively constant layer heights was observed. CFD results were processed to determine parameters of practical interest, including the heights of the sludge blankets and the effluent suspended solids concentrations; these parameters were correlated satisfactorily with the Hazen number, which is used as a scaling parameter in primary settling tanks.     

Tribological Behavior of Lanthanum Phosphate and Zinc Dialkyldithiophosphate and Their Mixture as Additives in Lithium Grease

Tribological Behavior of Lanthanum Phosphate and Zinc Dialkyldithiophosphate and Their Mixture as Additives in Lithium Grease     

Comparison of Computation Fluid Dynamics Simulation against Tracer Data from a Scale Model and Full-Sized Waste Stabilization Pond

The use of computation fluid dynamics (CFD) for waste stabilization pond design is becoming increasingly common but there is a large gap in the literature with regard to validating CFD pond models against experimental flow data. This paper assesses a CFD model against tracer studies undertaken on a full-sized field pond and then on a 1:5 scale model of the same pond operated under controlled conditions in the laboratory. While the CFD tracer simulation had some discrepancies with the field data, comparison to the laboratory model data was excellent. The issue is, therefore, not in the way the model solves the problem, for example, the choice of turbulence model or differencing scheme, but rather with how accurately the physical conditions in the field are defined. Extensive survey of the sludge layer and transient input of changing flow rates, wind velocities, and temperature could allow closer alignment of CFD simulations to field data. However, in the practical application of CFD where a modification such as baffle installation results in a large change, then a simple pragmatic model, while not exact, can still provide valuable design insight.     

Effects of Inlet Position and Baffle Configuration on Hydraulic Performance of Primary Settling Tanks

Circulation regions always exist in the settling tanks. These regions reduce the tank’s performance and decrease effective volume of the tank. Recirculation zones would also result in short-circuiting and high flow mixing problems. Inlet position would have an effect on these, too. Use of good baffle configuration may increase performance of settling tanks. One method for comparison performance of different tanks with each other is to use flow through curves (FTCs). In this note using FTCs, effects of inlet position and baffle configuration on the hydraulic performance of primary settling tanks are studied. The best position of baffle is also determined.     

半圆管挡板搅拌槽内的固液悬浮

为了提高固液悬浮性能,设计了一种半圆管挡板搅拌槽。采用数值模拟和试验测试相结合的方法,研究了半圆管挡板Rushton桨搅拌槽内石英砂—水的混合特性,分析了固液悬浮特征、固相浓度分布和功率消耗情况,并与标准平直挡板搅拌槽内的悬浮性能进行了对比。结果表明,同一搅拌转速时,半圆管挡板能改善悬浮性能,低固含率(5%)时效果更好。整体而言,半圆管挡板搅拌时石英砂的浓度分布比标准平直挡板搅拌时均匀,而且功率准数低13%左右,节能效应明显。研究结果为半圆管挡板的工业应用奠定了基础。     

Numerical Simulations of Efficiency of Curb-Opening Inlets

The geometry of highway pavement and drainage inlets, especially cross slope, longitudinal slope, and local depression and transition length, usually determine the highway surface drainage capacity. In this study, a three-dimensional computational fluid dynamics (CFD) software, FLOW-3D, is used to develop models simulating unsteady, free-surface, shallow flow through curb-opening inlets, thereby demonstrating that an advanced CFD model can be used as a virtual laboratory to evaluate performance (i.e., inlet efficiency) of curb-opening inlets with different geometry conditions. Predicted intercepted flow and inlet efficiency agree well with laboratory measurements. Flow simulations were extended to smaller cross slopes for which laboratory tests were not conducted but which can occur in a highway transition.     

铜闪速炉沉淀池流场及温度场仿真优化

选择了适当的流体计算模型,利用商业流体计算软件CFX4.3模拟了“四高”生产条件铜闪速炉沉淀池的三维流场及温度场。结果表明:沉淀池入口区流动紊乱,主流区流动平稳且以平推流为主;主流区流体流速及温度场分布不均匀,不利于硫颗粒沉降。对不同放渣口与放硫口的组合模拟表明:不同放渣口及放硫口的组合对熔池内流场及温度场分布有较大影响。选择不同放硫口放硫可起到调节熔池温度的作用,而采用靠近渣口的铜硫口放硫,则有利于熔池内流场与温度场均匀。     

Hydrodynamics of Secondary Settling Tanks and Increasing Their Performance Using Baffles

Generally, the flow in settling tanks is stratified, but the effect of buoyancy force on the flow field depends on the inlet concentration of particles and flow bulk velocity. A common approach for increasing settling tanks performance is to use baffles which can reduce effects of the unfavorable phenomena such as short circuiting between inlet and outlet and density currents in primary and secondary settling tanks, respectively. The suitable position of the baffles is related to the importance of buoyancy force. As a result, effects of inlet Reynolds and Froude numbers on the strength of buoyancy force are studied for a secondary settling tank and the results show that neither Reynolds nor Froude numbers are sufficient to be considered alone. Effect of buoyancy force on the suitable baffle position is also investigated. Results show that in high Reynolds numbers, the flow field and baffle position are not affected by the inlet Froude number.     

基于CFD模拟和热态实验的高炉冷却壁传热分析

基于计算流体力学(CFD)方法,建立了一种考虑冷却水进出口温差的冷却壁数值模型,并利用热态试验研究确立了更为准确的数值模拟边界条件.对比数值模拟与实验研究结果,两者吻合程度较高,验证了模拟方法的可靠性.同时也对是否考虑冷却水进出口温差的 2 种数学模型进行了比较,结果表明考虑冷却水温差模型有利于全面模拟冷却壁运行时各项指标.模拟结果也为高炉冷却壁在线智能监测提供了理论依据.     

干油集中润滑系统的特点及选用原则

介绍了干油集中润滑系统的特点 ,指出应根据不同的使用环境、润滑点数量以及不同的供油监控方式合理选择干油集中润滑系统 ,以达到既可满足润滑要求 ,又能节约投资的目的     

Two-Dimensional LDV Measurement, Modeling, and Optimal Design of Rectangular Primary Settling Tanks

To optimize the design parameters of rectangular primary settling tanks, we used two-dimensional laser Doppler velocimetry (2D LDV) to conduct flow field measurements in five cases and used a previous model to simulate the flow field. The relative baffle submergence height and the ratio of tank length to height were optimized in a low suspended solid (LSS) concentration (LSS<150–200?mg/L). The experimental and simulation results show that a large recirculation zone exists behind the reaction baffle and the flow magnitude is small in the recirculation region; the length of recirculation increases with an increasing flow rate; the length of recirculation increases as the depth of the submerged reaction baffle increases; and the variation of the reaction baffle height can affect the flow field more significantly than does the variation of the flow rate. We also determined that to reach a higher removal rate and to optimize the area dimensions of a sedimentation tank, a length-to-height design ratio between 8 and 12 is optimal.     

Using CFD Modeling to Improve the Inlet Hydraulics and Performance of a Storm-Water Clarifier

The feasibility of high-rate treatment of storm water achieving total suspended solids (TSS) removals in the range from 60 to 80% was studied using an available clarifier. The clarifier (3?m long, 1.4?m wide, and 2?m deep) was fitted with a removable lamella pack and had a limited flow capacity (surface load rate of 35?m/h). To achieve the desired removals of TSS, the clarifier required polymer feed (4?mg/L), which caused maintenance problems during intermittent storm-water treatment—laborious and costly cleaning of lamella plates after individual storm events. This problem posed the following challenge: was it feasible to avoid costly maintenance by removing the lamella pack and at the same time to retain the high TSS removals by improving the clarifier hydraulics by internal structural changes? The purpose of the paper is to evaluate such changes by focusing on different inlet configurations designed using computational fluid dynamics (CFD) simulations. This analysis resulted in adopting a U-tube duct inlet (inserted into the outer box of the original clarifier) with two special features: (1) three horizontal slot openings (width = 0.1?m) releasing flow into the clarifier and (2) a narrow slot opening in the bottom U bend allowing removal of grit. The flow release slots in the rising leg of the U tube were fitted, along the upper edge, with horizontal trailing plates protruding 0.15?m into the clarifier and forcing the flow to move horizontally. This clarifier design performed well, but storm-water grit accumulated at the bottom of the U tube, which had to be cleaned out after individual storms to avoid plugging. This issue was resolved by allowing grit to move into the sludge storage compartment of the clarifier through a narrow tilted slot opening in the U-tube bottom. The final clarifier design with polymer feed, without lamellas, produced TSS removals comparable to those in the original lamella clarifier (almost 80%), but at a higher surface loading rate (43?m/h, which was limited by the feed pump capacity). CFD modeling, in comparison to conventional methods of hydraulic design, served as a flexible and powerful tool providing distinct advantages with respect to the speed, efficiency and reduced cost of analysis, and a better understanding of the clarifier operation.     

CFD Analysis of Turbulent Natural Ventilation in Double-Skin Fa?ade: Thermal Mass and Energy Efficiency

Double-skin fa?ade provides many opportunities for energy conservation in buildings. This work summarizes the results of a computational fluid dynamic (CFD) analysis, which was carried out to investigate the effect of blind and thermal mass concrete on the thermal performance of a double-skin fa?ade. Navier-Stokes equations, turbulent k-ε model, and discrete ordinates radiation model have been used to simulate the airflow and to study the airflow pattern. It was shown that the airflow patterns for natural ventilation with a blind and thermal mass concrete were very complex with multiple vortex structures. On the other hand, the heat flux and the airflow velocity at the inlet have a significant impact on the natural ventilation airflow rate. The Rayleigh number for turbulent flow was in the range of 107 ≤ Ra ≤ 108 using a blind. However, the Rayleigh number was less than 107 using thermal mass concrete. On the other hand, thermal mass increases the energy performance of natural ventilation. A good agreement was performed by comparing the experimental data and the simulation results.     

Development of Efficient Stilling Basins for Pipe Outlets

The results of experimental work leading to the development of shorter and improved stilling basins for pipe outlets are reported. The original USBR impact type VI stilling basin incorporates a floor that is depressed below the invert elevation of the pipe outlet. In the present study, efforts are made to develop an efficient stilling basin keeping the floor at the invert elevation of the pipe outlet. Experiments were conducted for two pipe diameters with Froude numbers ranging from 1.70 to 5.50. The new models were developed by conducting systematic experiments on a large number of stilling basins with different configurations of the appurtenances such as the splitter block, impact wall, baffle blocks, and end sill in terms of their shapes, sizes, and locations. A performance number has been defined to compare the performances of various stilling basins using a constant experimental running time and same erodible material for each model. The shapes and sizes of various appurtenances and corresponding performance results are presented. The performance of the newly developed efficient and economical stilling basins are compared with the performance of the USBR impact type VI stilling basins for pipe outlets within the range of the Froude numbers tested.     

Effect of Fluorides and Cerium Dioxide Additives onEP and Antiwear Performance of Grease

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Combined MRI and CFD analysis of fully developed steady and pulsatile laminar flow through a bend

A combined MR and computational fluid dynamics (CFD) study is made of flow in a simple phantom laboratory flow rig consisting of a 180 degree bend with straight entry and exit sections. The aim was to investigate the potential of the use of MRI-linked CFD simulations for in vivo use. To this end, the experiment was set up for both steady and pulsatile laminar flow conditions, with Reynolds and Dean numbers and Womersley pulsatility parameter representative of resting flow in the human aorta. The geometrical images of the pipe and the velocity images at entry to the bend were used as boundary conditions for CFD simulations of the flow. The CFD results for both steady and pulsatile cases compared favorably with velocity images obtained at exit from the bend. Additional information such as pressure and wall shear stress, which either could not be measured adequately via MRI, or could not be measured at all, was also extracted from the simulation. Overall, the results were sufficiently promising to justify pursuing subsequent in vivo studies.     

热轧板卷厂集中补脂系统的开发与应用

针对常规自动干油润滑系统补脂时存在的问题,开发了一套新型集中自动补脂润滑系统并应用于韶钢宽中厚板厂,取得了较好的效果。     

Shear Stress Distribution in Partially Filled Pipes

Boundary shear stresses have been calculated for circular pipes with a flat sediment bed using computational fluid dynamics (CFD). First of all, CFD simulations were carried out for rectangular channels in order to check the software package for its ability to reproduce experimental (literature) results. The influence of the applied turbulence model (isotropic or anisotropic) was also studied for rectangular channels. The simulations for circular pipes, using an isotropic turbulence model, were done for different filling ratios, mean flow velocities, and roughness heights. For validation, the numerical results were compared with former experimental work. With the help of the detailed shear stress distribution, sediment transport can be calculated more accurately than using the global shear stress, as is traditionally done. This method was applied to a simple flume experiment, subjected to a triangular inflow hydrograph, and the comparison with the traditional approach was made.