余氯静态衰减过程及影响因素分析

通过西安市供水管网的出厂水和管网末梢水的余氯静态衰减试验,利用相关系数分析,将水体中余氯的衰减分为两大类,一阶段型和两阶段型,并建立了水体中余氯衰减的数学模型;通过相对关联度的分析,分别确定了余氯衰减系数k1、k2及分割时间tb三个指标的主要影响因素;通过比较铁、锰对k1、k2及tb的S2A/S2T,分析了铁、锰对余氯衰减过程的影响;试验证明,余氯静态衰减过程中溶解态铁、锰的浓度变化主要受氯氧化作用的影响,总铁、锰的含量,pH和浊度的变化不受余氯浓度的影响。     

配水管网中水质变化规律及主要影响因素分析

安全输配是饮用水水质保障的关键。在对中国南方 S 市配水管网水质大量调查的基础上,分析了余氯、浊度、铁、三卤甲烷、卤乙酸、AOC 等主要水质指标在管网中的变化规律,发现余氯沿管线逐渐降低,浊度和铁基本沿管线逐渐增加,其主要影响因素有管道属性、温度及水力条件等;三卤甲烷在管网中表现出增加的趋势,而卤乙酸则在管网中表现出降低的趋势,其主要影响因素有余氯浓度、水质条件、温度条件及水力条件等;供水系统中 AOC 以 AOC-P17为主要组分,沿供水系统有逐渐增加的趋势,其浓度、组成以及在管网中的变化规律呈现明显的季节性。     

基于支持向量回归的水体余氯衰减规律研究

根据耗氯试验历史数据,基于支持向量回归方法建立了水体余氯衰减模型,并分析其主要影响因素.利用核函数的非线性特征,得到较为满意的模型拟合精度与预测性能.发现余氯衰减规律可分为两段,初期衰减非常快,其后衰减明显变慢,且不能用一级反应动力学描述。     

紫外线消毒对水中余氯衰减规律的影响研究

对经紫外线消毒后水中余氯的衰减规律进行了研究,考察了pH、有机物含量、紫外线强度及剂量等因素对氯衰减速率的影响。结果表明:紫外线剂量低于40mJ/cm2时紫外线消毒对氯衰减基本没有影响,而当紫外线剂量大于40mJ/cm2时会加速氯的衰减速度,紫外线剂量从40mJ/cm2提高到1 000mJ/cm2时,水中余氯由3.2mg/L下降到2.8mg/L;低紫外线强度下氯的衰减速度低于高紫外线强度情况,如紫外线剂量为100mJ/cm2,紫外线强度为0.113 00mW/cm2和0.028 25mW/cm2时,水中余氯分别为2.31mg/L和2.63mg/L;在同一紫外线剂量下,pH偏酸性时氯衰减速度高于高pH情况;增加水中有机物浓度会加快氯的衰减速度。在实际应用低紫外线强度进行消毒时,如降低投氯量将不能有效保证管网水中的余氯量。     

供水管网中余氯衰减情况的试验研究及分析

针对供水管网中的余氯衰减展开深入研究,在构建的管网模拟试验平台和计算机模型上进行了相关的水质分析。在大量实测数据的基础上采用一级动力学模型建立了系统余氯衰减模型,确定系统总的余氯衰减系数k、主体水中余氯衰减系数kb及管壁处余氯衰减系数kw,并总结出各余氯衰减系数与各影响因素的具体关系式。     

高层建筑转输供水系统余氯衰减规律与补氯特点研究

针对高层建筑转输供水系统的二次供水水质安全问题,研究了水力停留时间、补氯量、水温、有机物等因素对余氯衰减特性的影响。结果表明,水箱中0.1mg/L余氯量的进水停留4h后余氯不达标并出现微生物滋生的问题,同时随着停留时间的延长,浊度升高,有机物含量下降;二次供水系统中余氯的衰减符合一级动力学模型,余氯衰减受补氯量、TOC含量和水温的影响,显著程度依次为水温补氯量TOC含量,其中补氯量、水温与TOC含量对余氯衰减的交互作用比较显著;补氯后余氯的衰减速率增大,且补氯量越低,TOC含量、水温越高,余氯的衰减速率越快;因此,在高层和超高层建筑的转输供水系统中进行补氯时,补氯点的设置和优化需要考虑二次供水水质、补氯量、余氯衰减速率、水温、有机物含量等因素。     

Larson指数、溶解氧和余氯浓度变化对管网铁释放的影响

不同水质水源的更换可能会引起饮用水中铁含量超标。通过静态试验,分析了Larson指数变化对无内衬灰口铸铁管铁释放的影响,同时探讨了铁释放速率随溶解氧和余氯衰减的变化规律。研究结果表明,Larson指数是影响无内衬灰口铸铁管铁释放速率的重要因素,铁释放速率与Larson指数呈显著正相关,与溶解氧和余氯呈负相关,且在24h停留时间内,溶解氧和余氯呈现简单一级衰减规律,衰减系数随着Larson指数的增大而增大。     

给水管网中硝化作用与金属离子释放交互作用研究进展

氯胺消毒给水管网中伴随着硝化作用的发生,会造成亚硝酸盐含量升高,消毒剂衰减加速,pH、溶解氧降低,异养菌过度繁殖以及管网中金属离子的释放。重点介绍了给水管网中硝化作用引起金属离子释放的成因,硝化作用对管网水质参数的变化和金属离子释放的影响,以及金属离子对硝化的反作用,并阐述了金属离子释放的控制方法。     

灰色关联度分析在华北某市给水管网漏损因素评价中的运用

选取华北某市近5年管网破损记录中管材、管龄、管径、破损外因4个因素结合管网破损事件通过灰色关联评价方法进行分析,结果表明各影响因素对管网漏损的影响大小依次为:管材、管径、破损外因、管龄。经分析本地区管龄在10年左右,管径≤DN50的镀锌钢管和钢管更容易因管道腐蚀、配件质量、不均匀沉降问题而发生渗漏。     

氯胺消毒管网硝化作用控制方法研究

通过对比试验,探讨了二次加氯、短时自由氯消毒和定期折点加氯等方法控制氯胺消毒供水管网硝化作用的效果。结果表明,这些方法均可有效抑制管网的硝化作用,减少亚硝酸盐氮的积累,减缓余氯的衰减,有效灭活水中的异养菌和亚硝化细菌,确保在氯胺消毒管网内饮用水的安全。     

模拟输配水系统中化合氯衰减模型研究

通过模拟输配水系统和主体水烧杯试验模拟化合氯的衰减过程,考察了水温、pH、初始氯浓度以及水力流速等因素对化合氯衰减的影响.结果表明:管壁对化合氯衰减影响的速率常数kt远大于主体水化合氯自身的衰减速率常数kb.流速、水温与衰减系数成正比,pH、初始氯浓度与衰减系数成反比,同时建立了化合氯衰减速率常数与上述各因素的数学模型.同时发现,管道细菌繁殖和生物膜增长对化合氯衰减有重要影响,为提高管网水质,管道应定期清洗、消毒.     

给水管壁腐蚀对余氯衰减的影响

在参与供水管网余氯消耗的三种因素中,除了主体水和管壁生物膜的消耗外,管壁腐蚀也是不容忽视的因素,尤其在铸铁管中.从微观电化学反应的角度,得到了管壁腐蚀导致的余氯衰减模型,结果与实际情况符合较好.     

Water Supply System Performance for Different Pipe Materials Part I: Water Quality Analysis

The quality of potable water has been a major issue in the water industry for the last few decades. The deterioration of treated water can be due to physical, chemical or microbiological changes that occur in the water during distribution. In addition, pipe material and decay of a disinfectant agent can affect the quality of the water being distributed. In this study the purpose was to simulate the decay of chlorine in two networks, one made of old cast iron (CI) pipes and another of polyethylene (PE) pipes. In addition the performance of the network considering chlorine concentration, velocity, water age, and an intrusion of a contaminant – in this case organic material – into the network was evaluated. The simulations were performed with EPANET software using as the simulation network an example network from the program. It was found that the CI network requires higher initial chlorine concentrations than the PE network to maintain the required minimum chlorine concentration throughout the whole network. To maintain the chlorine concentrations required by WHO (Cl must be greater than 0.2 mg/l and lesser than 0.5 mg/l) re-chlorination stations were necessary to add into both networks. The performance of both networks before re-chlorination was low due to high initial chlorine concentrations, but after the addition of the re-chlorination stations it was 100% throughout the networks. The performance of the velocities was good in both networks. The performance of the water age was dependent mainly on the tank usage, and the performance of contamination by organic material depended on the coefficient that defines the decay rate of the organic material in the bulk phase.     

农村供水系统不同贮水材质水质变化特性分析

针对西部地区农村供水系统管线长、用水量小,水在调节池中停留时间较长而易造成供水系统二次污染的问题,选取工程上常用的混凝土、瓷砖、塑料和不锈钢材质,分别研究了不同环境条件下各贮水材质水体中余氯、pH、电导率和溶解氧等水质参数随时间的变化特征。结果表明:一定温度下不同材质调节池中,贮存水余氯衰减系数由大到小依次为混凝土、塑料、瓷砖、不锈钢;水体pH值变化也较为明显,其中混凝土及瓷砖内壁调节池pH值随储存时间增加呈现明显的上升趋势,不锈钢材质pH上升趋势平缓,而塑料材质pH值未发生显著变化;混凝土、瓷砖及不锈钢材质蓄水池电导率在初始阶段随时间的变化上升较快,而在后期随时间的变化趋势较为平稳;混凝土及不锈钢材质调节池溶解氧随时间的变化较为平稳,而瓷砖及塑料材质调节池溶解氧随时间的变化有升高的趋势。通过本研究进一步明确了不同材质调节池对水质的影响及其随环境因素变化的时间效应,以期为农村供水系统规划设计及运行管理提供一定参考。     

Evaluation of Chlorine Decay in Drinking Water Systems for Different Flow Conditions: From Theory to Practice

An intensive study was developed to assess the influence of different flow conditions in the chlorine decay of drinking water systems based on a series of experiments tested on a loop pipe linked to the Lisbon water distribution system. Water samples and chlorine measurements were taken under three distinct flow conditions: (1) steady-state regimes; (2) combined flow situations—an initial steady-state period, followed by successive transient events and a new steady-state period; (3) isolated flow tests—steady-state flow regimes and transient flow regimes performed independently. All the tests were replicated for a typical range of Reynolds numbers in real water distribution systems. More specifically, pressure and velocity variations associated with hydraulic transients or water hammer conditions may degrade water quality. The series of results obtained in steady-state flow conditions confirmed the rate of chlorine decay increases with the Reynolds number and provided evidence that hydraulic transients have a slowing-down effect on chlorine decay rates.     

Evaluating the Economic Residual Life of Water Pipes Using the Proportional Hazards Model

This paper provides a method for evaluating the residual lives of water pipes using the proportional hazards model (PHM) based on the economically optimal replacement times of pipes. The survival times, which are used in the proportional hazards modeling process, were defined as the economically optimal replacement times of pipes. The break rate of an individual pipe is estimated using the General Pipe Break Model (GPBM). The optimal replacement time of a pipe is obtained using the equivalence relationship between the GPBM and threshold break rate. In order to use the GPBM effectively, the process of estimating the GPBM has been modified in this paper by utilizing additional break data for the time of installation and adjusting the value of the weighting factor (WF) in the GPBM. The residual lives and hazard ratios of the case study pipes, of which the cumulative number of breaks was at least one, were estimated using the estimated survivor function of the constructed PHM. The time-dependency of the pipe material covariate caused the hazard rate of the cast iron pipes to become lower than the hazard rate of the steel pipes after 19 years since installation. The methodology developed in this paper may help utilities identify important factors related to the economics of water pipe maintenance and; therefore more efficiently maintain their water pipes.     

稔平半岛供水工程管材选择的经济分析

介绍了常用供水管材的性能及稔平半岛供水工程的概况,推导管道单位成本计算公式,对水利工程供水中常用管材———球墨铸铁管(DIP)、钢管(SP)和预应力钢筒混凝土管(PCCP)进行比选。得出在小管径情况下,球墨铸铁管相比钢管和预应力钢筒砼管有经济优势。但作为长距离的供水工程,供水结构形式及管材应因地制宜,采用多种方式,做到可靠经济。