清水池设计改进原理和应用

为了优化消毒效果,达到既提高消毒效率又减少消毒副产物的目的,对清水池进行优化设计,阐述了改进的原理和应用。介绍了描述消毒剂在清水池实际停留时间的函数t_(10)的含义,提高t_(10)/T的意义,影响t_(10)/T的主要因素和对几个清水池的研究结果,提出了以提高t_(10)/T为目的的清水池设计原则。     

网格絮凝—平流沉淀池与清水池叠合工艺设计总结

清远江南水厂采用网格絮凝+平流沉淀池与清水池叠合工艺,单组平流沉淀池与清水池设计规模均为10万m~3/d,单组网格絮凝池设计规模为2.5万m~3/d。总结介绍了叠合构筑物的设计参数以及在均匀配水、水流速度梯度、排泥优化和清水池消毒时间等方面的设计特点。     

应用停留时间分布评价絮凝池整体运行状况的探讨

分别对栅条絮凝池和折板絮凝池进行示踪试验,从反应器角度出发,借助轴向扩散模型,利用反应器工作原理中的停留时间分布,诊断出两者流动状况的差异.从而论证了应用停留时间分布评价絮凝池运行状况的方法是可行的,也为今后水处理絮凝池运行管理提供了新的思路.     

改良型化粪池水力状态评价的探讨

依据反应器的相关原理,对改良型化粪池进行示踪试验,通过分析反应器本身的水力停留时间分布函数以及返混系数等对改良型化粪池内部水流状态进行评估。试验结果表明,D/(vL)=0.087 2,改良型化粪池内部存在一部分非理想状态流动的情况,且该化粪池的平均停留时间τ与理论水力停留时间T存在一定的差距,化粪池中存在一定的死区。本试验有助于进一步了解化粪池内部结构变化对水流态的影响,对化粪池结构的改进具借鉴意义。     

不同臭氧接触池性能的CFD模拟

利用计算流体力学(CFD)技术,通过对不同结构臭氧接触池流场的模拟和累积停留时间的计算,分析研究了不同结构臭氧接触池的性能。结果表明:接触池内存在明显的回流现象和短流现象,当在接触池内增加挡板后回流区域和短流现象都有减弱。尽管有竖直挡板时和没有竖直挡板时臭氧接触池的流场不同,但是它们的停留时间分布差别较小,这说明停留时间分布不只是受到流场的单一影响。但是在水平方向增加挡板后,对停留时间分布产生很大影响:停留时间的分布范围变小,T10值得到明显提高。     

溢流池体型优化及泄流能力模型试验

按照重力相似准则,采用正态模型,建立溢流池水工模型,模拟原型溢流池的水力条件,观察不同溢流流量下溢流水深以及溢流池外连接池水深,观察溢流通道水流有无掺气和气阻,通过不同方案的对比试验,优化溢流池体型设计.试验发现,采用连接池与出水管道平滑过度的方案,能够有效地减少气阻和掺气,同时避免了水跃.为工程设计提供技术支撑,也为类似工程提供参考.     

曝气生物滤池升级改造中深度脱氮的试验研究

某城市污水处理厂以曝气生物滤池(BAF)为主要处理工艺,现面临升级改造。设计处理水量2m3/d的中试装置,分别进行前置反硝化和以甲醇为碳源的后置反硝化试验研究,并优化各处理单元的运行参数。其中前置反硝化工艺回流比为125%,单池水力停留时间为20min,CN池和N池的气水比分别为4∶1和3∶1,后置反硝化工艺的水力停留时间为45min,CN池和N池的气水比分别为6∶1和5∶1,甲醇投加量为30mg/L。通过核算建设成本与运行费用,推荐了以前置反硝化为核心的升级改造方案。     

定床泥沙示踪试验述评及示踪沙设计示例

本文对于利用河工定床模型,摸拟原型为动床的泥沙颗粒运动的示踪试验,在模型相似方面所存在的问题,以及应用这种定床泥沙示踪试验成果于实际工程时应该注意的问题,提出了意见。定床泥沙示踪试验的模型设计,在模型几何比尺和模型沙材料已经确定的条件下,便归结为示踪模型沙粒径比尺的确定问题;但在这方面存在一些值得讨论的问题,以往的研究很少涉及。本文按照示踪试验的要求和需要摸拟的泥沙临界运动状态——起动、悬移和扬动等,提出了各自应该满足的相似条件和粒径比尺关系式,并列举设计示例以供参考。     

小红门污水处理厂A~2/O工艺优化运行研究

针对广泛采用的A2/O工艺,以北京市小红门污水处理厂为例,研究了通过改善生化处理单元的运行方式,同步提高生物脱氮和除磷的效果,并通过现场运行进行了验证.在工艺系统分析的基础上,考察了溶解氧、水力停留时间和二沉池运行对A2/O工艺反硝化过程的影响,考察了硝酸盐浓度对厌氧释磷过程的影响,提出了通过优化曝气控制和二沉池运行同步改善生物脱氮和除磷的效果.生产性试验表明,该方法简单可行,在不改造现有工艺设施的基础上即可实现达标排放.     

肯斯瓦特水电站消力池试验研究及优化设计

以肯斯瓦特水电站模型为基础,对原有设计方案进行试验分析,同时,通过设置T形墩对消力池的尺寸进行了优化,得到该工程适宜的消力池尺寸长52.5 m、深6.0 m,并对T形墩进行了优化试验。     

环沟型改良A~2/O工艺中试研究

环沟型改良A2/O工艺是集高效初沉发酵池、回流污泥反硝化池、厌氧池及双沟道氧化沟工艺于一体的新型污水处理工艺。对该工艺去除污染物的效果进行试验研究,结果表明,在生物系统水力停留时间不足8h的条件下,达到了较好的除磷脱氮效果,出水水质稳定达到《城镇污水处理厂污染物排放标准》(GB 18918—2002)一级A标准。研究结果同时表明,该工艺具有很好的节能降耗潜力。     

斜管沉淀池布水均匀性模拟计算与工艺参数分析

水量负荷的增大和水质标准的提高,迫使许多水厂不得不将平流沉淀池改造为斜管沉淀池,然而改造过程中所遇到的斜管布水均匀性问题一直没从理论上得以解决。通过建立包括长宽比、斜管管径、布水区高度等多个影响布水均匀性因素的水力学方程,定量分析了各种因素的影响规律。模拟计算结果表明:沉淀池长宽比(L/B)对均匀布水性影响最大,当L/B接近6时,布水渠末端的斜管流量极小,布水极不均匀;增大布水渠高度和沿池长方向上减小斜管管径有利于提高布水均匀性。据此在L/B较大的平流沉淀池改造工程中可采取由沿宽度方向布水改为沿长度方向,将沉淀池分格改造为多个斜管沉淀池以及斜管管径沿布水方向由小变大等技术措施提高布水均匀性。     

Modelling spatio‐temporal flow characteristics in groyne fields

The spatio‐temporal distribution of residence times and water ages in groyne fields plays an important role for a number of biotic processes, particularly conditioning nutrient dynamics and phytoplankton growth. Experimental determination of these parameters involves time‐consuming field work and is often limited to the water surface depending on the methodology applied. Computational fluid dynamics (CFD) can be used as efficient tool for direct modelling of residence times, limiting additional field work to collect data necessary for model calibration and validation. The objective of this study is to derive, test and apply a numerical particle‐tracing method to model these flow characteristics based on the output of a three‐dimensional hydrodynamic model for turbulent river flow. This allows for an evaluation of residence times and water ages at an arbitrary elevation within the water column. Virtual particles are released in a control volume, and their paths and travel times to and from the main stream are traced using a random‐walk approach based on the spatial distribution of turbulent kinetic energy to account for turbulent fluctuations. The modelling approach was successfully validated for the water surface using field data measured in a groyne field of the Danube River in Austria. Particle‐tracing experiments were carried out for several discharges to study the evolution of residence times and water ages with varying runoff. It was found that discharges at which overtopping of the groynes begins lead to significantly higher residence times and water ages than runoff higher or lower than this characteristic value. These findings are expected to be transferable for groyne fields of similar geometry and crest height. Copyright © 2008 John Wiley & Sons, Ltd.     

径流过程水分滞留时间研究进展

径流过程水分滞留时间可以揭示有关水的储存、水流路径和水分来源的信息,用于表征和比较不同的水文系统,并且广泛地用来描述流域功能。在前人对径流过程水分滞留时间研究的基础上,系统地总结了地形、土壤覆盖和气候等因素对流域水分滞留时间的影响,分析了同位素和水化学示踪剂在滞留时间评估中的应用,综述了估算水分滞留时间的集总参数模型的研究进展。水文示踪和集总参数模型是研究水分滞留时间的有效手段,强化流域水文循环全要素监测,系统研究关键带径流组分滞留时间是未来深入揭示流域水文过程响应机制的重要内容和研究方向。     

高负荷螺旋桨水动力性能试验研究

以某大型集装箱船高负荷螺旋桨为研究对象,分别采用大侧斜、反弯扭叶片和毂帽鳍等技术进行螺旋桨优化设计,以改善螺旋桨的空泡和水动力性能.设计了5型螺旋桨,分别在空泡水筒进行了模拟伴流场中的空泡和激振力试验,并在拖曳水池进行了敞水试验.试验结果表明,采用大侧斜可有效减小螺旋桨诱导船艉激振力;反弯扭叶片螺旋桨空泡性能较好,有较低的螺旋桨诱导船艉激振力水平;桨毂帽鳍可改善毂涡空泡,模型试验状态下可提高推进效率2%左右.     

Evaluating Infiltration Mechanisms Using Breakthrough Curve and Mean Residence Time

Determination of infiltration mechanism is crucial for the calculation of infiltration flux in the soil which would influence the water balance computation. Two infiltration experiments with different isotopic compositions of rainfall were conducted to analyze the infiltration type by measuring isotopic concentrations (deuterium and oxygen 18) of collected outflow water samples. Models with three transfer functions were used to simulate the isotopic variation of outflows in a soil column. The model performance was evaluated with the comparison of computed and observed isotopic values of outflow. Breakthrough curve based on the isotopic composition of rainfall, initial soil water and outflow, and mean residence time estimated on the best fitting transfer function model were applied to identify the infiltration type in the soil. The results show that infiltration type determination using the comparison between estimated and observed mean residence time and breakthrough curve are similar. Furthermore, we found that soil structure and isotope measurement error affected the determination of mean residence time. Results from this study may provide a framework for describing the infiltration processes in the soil column.     

Short circuiting in a denitrifying activated sludge tank.

The presence of a short circuit flow in a denitrifying activated sludge tank was identified and modelled. Tracer tests with pulse addition of lithium salt were used to investigate the hydraulics of the tank. The lithium concentration in the effluent was detected and residence time distribution (RTD) curves were generated. Hydraulic models based on completely stirred tank reactors (CSTRs) in series were generated from the RTD curves and the models were compared. The short circuit problem was successfully described using the Martin model, where the inflow is divided into two strands. Each strand was modelled as a number of CSTRs in series. At a normal flow the results of the model show that the tank has 12.8% dead volume, 85.8% main volume and 1.3% short circuiting volume. The inflow was divided into 91.9% entering the main volume and 8.1% entering the short circuiting volume. The mean velocity of the short circuiting stream was estimated to 0.4 m/s. At maximum flow the short circuiting stream was even larger and handled 24.3% of the flow. The short circuiting stream was identified in the upper part of the tank due to the position of the inlet and the outlet. The configuration of a tank including the use of baffles, the geometry of the inlet and mixer configuration should be considered carefully if short circuiting is to be avoided.     

Regional scale analysis for the design of storage tanks for domestic rainwater harvesting systems

A regional scale analysis for the design of storage tanks for domestic rain water harvesting systems is presented. The analysis is based on the daily water balance simulation of the storage tank by the yield-after-spillage algorithm as tank release rule. Water balances are applied to 17 rainfall gauging stations in Sicily (Italy). Compared with literature existing methods, a novel dimensionless parameter is proposed to better describe the intra-annual character of the rainfall patterns. As a result, easy-to-use regional regressive models to evaluate the water saving performance and the overflow discharges from the tank are provided along with a stepwise procedure for practical application. The regional models demonstrate good fits between model predictions and simulated values of both water savings and overflows from the tank.     

氯离子浓度和碱度对给水管网管垢重金属锰释放的影响

通过静态释放实验,研究了水源切换造成原水中不同浓度的氯离子和碱度对管网管垢中重金属锰释放的影响。选取郑州市给水管网管段,设计模拟释放反应装置,配制不同浓度氯离子(5 mg/L、23.1 mg/L、60 mg/L、90mg/L)和碱度(52.5mg/L、125mg/L、200mg/L)的实验用水,比较分析氯离子浓度和碱度变化对管垢重金属锰释放的影响。根据实验结果初步推断:氯离子浓度和碱度与管垢中金属锰的释放浓度有较高相关性,且实验中氯离子浓度是影响管网管垢锰释放的首要因素。当氯离子浓度为30 mg/L,停留时间60h,锰的释放量达到最大为108mg/L,之后释放浓度趋于平稳。在氯离子浓度促进锰释放的条件下,碱度与管垢中锰的释放量表现出明显相关性。实验结果可为水源切换引起的水质差异对给水管网管垢锰释放问题提供一定参考。     

某厂清水池壁细菌生长特性研究

附着在清水池壁生长的生物膜可能使出厂水的细菌数增加,对饮用水的安全性造成威胁。以北京市某水厂清水池壁上自然生成的生物膜为样本,研究了构成该生物膜的微生物种类,形成了比较系统的菌种鉴定方法。研究发现清水池壁的生物膜中存在细菌、放线菌、真菌和酵母菌等多种微生物,这些微生物以革兰氏染色阳性菌为主。这是因为革兰氏阳性菌细胞壁和细胞膜的通透性比较低,不易被消毒剂杀灭,而革兰氏阴性菌的细胞壁和细胞膜的通透性比较高,消毒剂容易透过细胞壁和细胞膜把细菌杀灭。