Application of numerical simulation on optimum design of two-dimensional sedimentation tanks in the wastewater treatment plant

The paper establishes the relationship between the settling efficiency and the sizes of the sedimentation tank through the process of numerical simulation, which is taken as one of the constraints to set up a simple optimum designing model of sedimentation tank. The feasibility and advantages of this model based on numerical calculation are verified through the application of practical case.

Numerical modeling method on the movement of water flow and suspended solids in two-dimensional sedimentation tanks in the wastewater treatment plant

Taking the distributing calculation of velocity and concentration as an example, the paper established a series of governing equations by the vorticity stream function method, and dispersed the equations by the finite differencing method. After figuring out the distribution field of velocity, the paper also calculated the concentration distribution in sedimentation tank by using the two dimensional concentration transport equation. The validity and feasibility of the numerical method was verified through comparing with experimental data. Furthermore, the paper carried out a tentative exploration into the application of numerical simulation of sedimentation tanks.

Impact of Untreated Sedimentation Tank Sludge Water Recycle on Water Quality During Treatment of Low Turbidity Water

The overall purpose of this research is to examine the impact of untreated sedimentation tank sludge water( USTSW) recycle on water quality during treatment of low turbidity water in coagulation—sedimentation processes. 950 m L of raw water and different concentrations of 50 m L USTSW are injected into six 1 000 m L beakers without coagulant.The results indicate that USTSW characterized as accumulated suspended solids and organic matter has active ingredients,which possess the equivalent function of coagulant. The optimal blended water turbidity is in the range of 10-20 NTU,within which USTSW recycle achieves the highest save coagulant rate. The mechanism of strengthening coagulation effect when USTSW recycle mainly depends on the chemical effect and physical effect. What is more,through scanning electron microscopy( SEM),it is found that the floc structures with USTSW recycle are more compact than those without USTSW recycle. Besides,the water quality parameters of color,NH3-N,CODMn,UV254,total aluminum,total manganese when USTSW recycle is better than the raw water without recycle,indicating that USTSW recycle can improve water quality with strengthening coagulation effect.

Experimental study and numerical simulation of the sludge concentration in a sedimentation tank

Sedimentation tanks and clarifiers play a significant role in an active sludge system, and the efficiency of the whole system is closely related with the design and operation of the sedimentation tanks. This paper focuses on the sludge concentration in each cross-section of the sedimentation tank. We measured the sludge concentration to explore its distribution inside the tank, carried in-situ tests to research the fluid pattern and real operational rules of the sedimentation tank. We also used the computational fluid dynamics (CFD) software, PHOENICS 3.5, to simulate the solid-liquid two-phase fluid inside the tank and describe the sludge concentration distribution. The numerical results indicate obviously a sludge-water interface and a compression interface inside the sedimentation tank, a stratified sedimentary region with uniform concentration and a compression region with high concentration at the bottom of the tank. Although the simulated concentrations deviated slightly from those of in-situ tests, they were still acceptable for identifying the sludge interfaces and fluid pattern inside a sedimentation tank, which are important parameters for optimizing the tank size and improving the settling efficiency.

Assessment of Seasonal Sedimentation in Rain-fed Irrigation Reservoirs by a Hillslope Erosion Modeling Approach

A distributed hillslope model is presented for the computation of seasonal sediment loads flowing into the rain-fed irrigation reservoirs (tanks) from the mountainous catchments in Sri Lanka. The model is based on the subdivision of the catchment into hillslopes and application of a sediment transport capacity equation at hillslope scale and computation of sediment loads transported to the tanks. Coarse and fine sediment loads due to hourly excess rainfall during a season are separately estimated. The model depends on fewer parameters and can be easily calibrated for a tank. The model calibration only requires measurements of coarse and fine sediment loads transported into the tank due to several rainfalls of different intensities from a representative subcatchment of the tank. Coarse sediment loads are measured by using a sediment trap installed across an ephemeral stream draining the subcatchment. Fine sediment loads are obtained by measuring the discharge and accompanied sediment concentrations over the sediment trap. The model is calibrated, verified and applied for an irrigation tank in Sri Lanka to estimate the seasonal sedimentation loads.

Umbrella Labyrinth Sedimentation Device Study

Umbrella-type mud-water diversion labyrinth sedimentation device,which is characterized by the combination of two swash plate and wing plate into an umbrella type with a set angle,the angle range of the two swash plate is 15º--100º,the vertical height of the swash plate is 60-70 mm,the parallel axis of the wing plate is the vertical direction,the height is 10-20 mm.the whole adopts the modular combination mode,and can be freely combined and disassembled according to different pond design,swash plate The interval(sedimentation distance)can be freely adjusted,mud take the mud road and water take the water road,to avoid the mutual interference of the water and mud road,to achieve the stability of the water quality.The turbidity of the sedimentation pond is low,stable in 0.3-2.0 NTU.

无线通信技术在二水厂沉淀池自动控制系统中的应用

本文主要阐述无线通信技术在净水厂排泥系统中的应用。在水厂生产过程中,应用无线AP技术,通过PLC自动控制,能够有效解决人工排泥效率差的问题。无线AP技术能够在雷雨、高温等恶劣的露天环境中为沉淀池自动控制系统提供稳定可靠的数据通信,保障水厂生产的正常连续运行。实际应用表明,该系统运行效果良好,既降低排泥用水消耗,减少人工工作量,又降低人身安全风险,为净水厂排泥系统提供了一种较好的选择方案。

沉积层海底界面Scholte波水池实验

海底界面Scholte波具有衰减小、传播距离远等特点,可应用于水下目标探测与海底参数反演。在实际海洋环境中,海水与弹性海底之间的沉积层会对Scholte波的激发和传播产生显著影响。该文利用缩比原理设计并开展水池实验研究,将实际海洋环境按1:5000的比例缩比至实验室水池尺度,利用声压场Scholte波识别方法在包含沉积层的实验环境下对Scholte波的激发与传播规律进行探究。实验结果表明,该实验条件下,1 mm厚度的沉积层时海底界面依然有Scholte波激发,但沉积层的存在会增大其衰减;而厚度超过1 mm的沉积层会导致Scholte波无法激发。根据缩比原理,实验环境对应为声源频率10 Hz、水深3000 m、沉积层厚度5 m的实际海洋环境,即在上述实际海洋环境中,海底界面Scholte波仍可以正常激发,而厚度大于5 m的粉沙质沉积层会导致Scholte波无法激发。

广东某污水处理厂氧化沟工艺提质增效改造工程设计

广东省某污水处理厂一期工程原采用氧化沟为主体的工艺,提标改造后要求出水指标达到《城镇污水处理厂污染物排放标准》(GB 18918-2002)一级A标准及《广东省地方标准水污染物排放限值》(DB44/26-2001)的第二时段一级标准的两者较严值,实际出水部分指标(如COD、SS、TP、TN)已临近排放限值,BOD_(5)、NH_(3)-N常有超标现象。提质增效工程旨在对原有生化池、消毒池等进行改造优化,并在二沉池后端新增“高效沉淀+滤布滤池”深度处理单元。提质增效后的运行数据表明,出水COD≤14 mg/L、BOD_(5)≤3.1 mg/L、ρ(TN)≤9.5 mg/L、ρ(TP)≤0.24 mg/L、ρ(SS)≤5.1 mg/L,去除率均>90%,出水水质稳定达到设计标准,同时氧化沟曝气单位能耗降低25%,单位成本低于同类型项目水平。

南水北调中线沉藻池布置方案优化

南水北调中线总干渠联通工程处拟新建沉藻池,实现总干渠藻类等混合物集中沉降和处理。通过现场试验研究总干渠水体藻类等混合物沉降特性,并采用二维水动力数值仿真分析沉藻池在设计工况条件下的水流特性,提出导流墩的优化布置思路。结果表明:在水深基本一致条件下,随着断面平均流速的增加,有效沉降距离增加,有效沉降率有所降低;在沉藻池初始设计方案下,藻类等混合物可在沉藻池内进行沉降,但沉藻池利用效率不足;布置纵向导流墩后,可有效改善沉藻池内水流平顺性和水体交换能力;在设计工况下,沉藻池内回流区水域面积占比从57%降低至7%,池内水流平均流速从约0.10 m/s降低至约0.07 m/s,平均水龄从约18 h降低至约6 h。研究成果可为中线沉藻池工程布置提供基本技术支撑。

MSBR+高效沉淀池组合工艺在高排放标准下污水厂的应用

广西某污水处理厂设计能力为5×10^(4)m^(3)/d,采用10格MSBR+高效沉淀池处理工艺,出水作为环境综合整治后河道的生态补水。通过对处理水量达设计规模后的运行工况变化较大情况下的运行效果总结分析,并对超负荷运行、污泥浓度控制、出水带泥等问题提出了调控建议;实际运行数据表明,该组合工艺出水NH_(3)-N、TN、TP、SS平均消减效率分别达到99.6%、76%、97%、98.9%,主要指标甚至满足《地表水环境质量标准(GB3838-2002)》Ⅳ类水标准,具有污水处理效果稳定,耐冲击负荷强等特点,在南方丰水、雨污合流城市高排放标准污水处理方面有着较高的推广应用价值。

化粪池夏季温室气体排放特征分析与CH_(4)排放因子测算

化粪池是城市粪便污水系统温室气体的主要排放源,但目前人们对化粪池温室气体的排放特征仍不太了解,碳排放核算也缺乏基础参数。夏季是化粪池温室气体排放的主要季节,通过试验模拟了华北某小区夏季化粪池对实际生活污水的厌氧降解过程,考察了温室气体的排放特征和影响因素,并测算了该小区化粪池的CH_(4)排放因子。结果表明,25~28℃时,模拟化粪池系统对COD和VFA的去除率分别为53.4%~76.9%和13.6%~24.9%,其CH_(4)和CO_(2)排放强度分别为3.1~8.1 mg/L和10.3~16.7 mg/L;化粪池对COD的去除率随化粪池底部沉积物的增多、进水水量降低及水温的升高而增大,CH_(4)排放强度呈现相同的规律,沉积物高度、进水流量对化粪池CO_(2)的排放强度影响较小,但是水温升高后CO_(2)的排放强度将明显增加;化粪池排放的CH_(4)主要以气态形式存在于反应器的顶部空间,CO_(2)主要溶解于液相,随水流排出;在28℃和25℃条件下,化粪池去除单位质量(1 kg)COD产生的CH_(4)量分别为0.103 kg和0.077 kg,排放的CH_(4)量分别为0.029 kg和0.021 kg,居民人均CH_(4)产量分别为12.36 g CH_(4)/(cap·d)和9.24 g CH_(4)/(cap·d)。

基于CFD的斜板沉淀池沉淀特性分析

采用欧拉-拉格朗日方法研究了普通斜板沉淀池内水流的流态,利用单向耦合的离散项模型(DPM),计算了普通斜板沉淀池在不同工况条件下颗粒沉积特性及池内流动特性。针对普通斜板沉淀池沉淀效果差,颗粒容易再次上浮,设计了一种改良V型斜板沉淀池,并且结合标准k-ε模型,利用PISO算法,通过北京云超算中心计算了不同颗粒粒径下改良V型斜板沉淀池内颗粒运动的轨迹。结果表明:使用改良V型斜板后,颗粒物的沉降性路径减小,但是涡流强度增加,此时能量耗散更快,有利于固液分离;粒径大的颗粒也更容易沉淀。

入池流量与倾角对鱼鳃式沉沙池内水沙二相流的影响分析

为提高沉沙池的除沙效果,提出了一种新型除沙措施即鱼鳃式沉沙池。鱼鳃式沉沙池在池室内部布设多组倾斜的过滤网片,利用滤网拦截泥沙,提高泥沙沉降效率。采用物理模型试验和数值计算方法,分析不同流量和滤网角度下的流场分布和除沙效果,以此得到较优的结构型式,为该类沉沙池的工程设计和技术推广提供理论参考。结果表明,植入鱼鳃装置后沉沙池的泥沙截除率提高了12.5%~22.0%。数模计算进一步揭示,鱼鳃式沉沙池内流速变化分为五个区域,含沙量变化沿程呈现四个不同阶段。在泥沙沉积量计算中,最大泥沙沉积区出现在第一、二片滤网底部,建议增大鱼鳃装置前部的滤网孔径,使鱼鳃装置设置更加合理。

EBIS(改良AO)+磁混凝工艺在陕西某城市污水厂提标改造工程中的应用

陕西某城市污水处理厂总设计规模80000 m^(3)/d,其中40000 m^(3)/d生化池利用现状的CASS池进行改造,另外新建40000 m^(3)/d生化池及80000 m^(3)/d规模的深度处理设施。污水处理厂进水主要来源为城市生活污水,混合少量的工业污水,处理工艺采用“预处理+EBSI生化池+磁混凝沉淀池+次氯酸钠消毒”主体工艺,介绍了工程的工艺流程、主要设计参数及运行效果等。出水水质监测指标表明,本项目出水完全满足《陕西省黄河流域污水综合排放标准》(DB61/224-2018)中A标准。

焦化废水处理工艺流程设计探索

为应对焦化废水不再用于熄焦补充水,在考察焦化项目并结合文献研究的基础上,提出焦化废水处理后直接排放工艺流程和间接排放工艺流程。间接排放采用“预处理—水解酸化—A/O生化—二沉池—活性炭加载高效沉淀池”的流程,可应用于原位提标升级改造,具有投入资金少、改造工期短、出水指标提升效果显著的特点;直接排放采用“预处理—水解酸化—A/O生化—二沉池—高效沉淀池—臭氧催化氧化—A/O生化—高效沉淀池”的流程,可应用于改扩建、新建项目,具有出水水质稳定、难降解有机物去除彻底的特点。对两种工艺流程设计的关键点和间接排放工艺流程的工程应用案例进行简要介绍,并根据工程应用中出现的问题提出“精细化运行管控”的建议。

三级AO+深度处理组合工艺在中小型城镇污水厂中的应用

由于排放标准的提高和进水水质的变化,成都市某污水厂需提标改造。改造后,处理规模为2 500 m^(3)/d不变,出水水质需达到《四川省岷江、沱江流域水污染物排放标准》(DB 51/2311—2016)。本工程采用充分利用原有的生化池,改建为三级AO池并新建深度处理设施的改造方式,该改造方式节省投资、不新征用土地、抗冲击负荷强,仅需约30 min短时间碰管停水,改造后工艺运行稳定可靠,达到DB 51/2311—2016的要求(CODCr≤30 mg/L,氨氮≤1.5 mg/L,总氮≤10 mg/L,总磷≤0.3 mg/L)。项目可为中小型城镇污水厂提标改造提供借鉴经验。

水处理中高密度沉淀池工艺的应用研究

针对当前很多企业的传统废水处理工艺已无法满足现代化废水处理要求和排放标准的情况,高密度沉淀池工艺自动化程度较高,且能有效处理废水悬浮物以及钙镁离子,在工业废水处理、生活废水处理等方面得到广泛应用。本次研究以某化工企业为研究对象,对高密度沉淀池工艺的应用进行研究,并分析应用效果,以期能够促进废水处理行业的发展。

大型覆土式储罐多工况强度可靠性分析

采用计算机仿真分析方法,对两种沉降方式下4种工况的覆土式储罐进行数值仿真计算,得到8种不同条件下覆土式储罐的应力应变分布云图,基于云图结果对储罐许用极限进行预测,同时进行强度与模态计算分析。计算结果显示,最大应力集中于壳体与气室连接处;由仿真模拟结果可得,计算屈服评价指标均小于实际工程要求的许用应力值,表明在8种工况下罐体满足强度要求;模态计算结果表明,覆土工况下的储罐处于稳定状态。

改良A^(2)O-臭氧-BAF工艺在地下式工业污水处理厂的设计应用

针对工业污水含特征污染物、可生化性较差,处理过程存在噪声、臭气等特点,以广东某工业园区地下式工业污水处理厂设计为例,介绍了全地埋式工业污水处理厂的进水水质特征与废水处理工艺和主要设计参数。工业污水经预处理+水解酸化+A^(2)O+高效沉淀+臭氧+BAF工艺处理后,确保出水能稳定达到《城镇污水处理厂污染物排放标准》(GB18918-2002)一级A标准。同时污水处理厂采用多种通风除臭措施,保障了操作人员的舒适度。地下式工业污水处理厂的设计不仅可以满足工业废水处理需求,而且也可以缓解用地紧张的压力,减少水厂运行过程中产生的环境风险。