用氧化还原电位(ORP)控制加氯量

水处理工程中通常用剩余氯值来控制加氯量的方法不太准确,有时也不很有效。但用氧化还原电位(ORP)控制加氯量却非常有效。实际需氯量是氯和物质起氧化还原反应所需的氯量。当手动控制加氯量时,需氯量变化即系统中氯的消耗速度变化,剩余氯值也变化,在剩余氯和需氯量之间存在着相反的关系。由于需氯量受到pH、温度等许多因素的影响,因此固定的加氯量不能满足需氯量的要求,不是加氯量过多,就是加氯量不足。在大多数情况下过量加氯浪费了氯仍不能保证有效地杀死微生物。 氯加入水中后形成次氯酸,这是一种活性氧化剂。次氯酸离解成次氯酸盐,在有H~+离子存在时,OCl~-的氧化能力只有HOCl的1％。     

采用蒸发器增大氯瓶出氯量

加氯消毒都要求氯瓶能稳定均衡的向加氯机供给充足的氯气。但氯瓶液氯受到自身蒸发能力的限制,出氯量不可能太大。根据国内一些水厂的实际运行经验,随着季节和气温的变化,氯瓶最大出氯量约为5～10公斤/时。而我国生产的加氯机最大加氯量可达45公斤/时。加氯机的投加量虽大,可是因为氯瓶出氯量有限,所以要满足大投氯量时,就要增加氯瓶和加氯机的个数。与此同时还要有相当大的加氯间才能容纳,无疑必将增加加氯间的建     

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。     

建筑生活热水二次消毒的微生物灭活效能及化学安全性研究

针对建筑生活热水系统水力停留时间长、余氯含量低、微生物超标等问题,采用二次加氯方式进行二次消毒,研究二次加氯的消毒效能、余氯衰减及消毒副产物生成特性等。结果表明,二次加氯消毒可有效保障生活热水的生物安全性,投加0.2～0.5 mg/L次氯酸钠均可完全灭活细菌总数和总大肠菌群,投加0.3～0.5 mg/L次氯酸钠在24～48 h内持续消毒效果良好。生活热水的余氯衰减速率和三氯甲烷生成量明显高于二次供水,存在消毒副产物超标的风险;随着水温和有机物含量的升高,余氯衰减速率、三氯甲烷生成速率和生成量均明显提高。综合考虑生活热水的生物和化学安全性、水力停留时间和持续消毒作用等方面的要求,0.3 mg/L次氯酸钠为二次加氯消毒的最适宜投加量。研究结果为生活热水系统二次加氯消毒技术的应用和水质安全保障提供了技术支持。     

常规处理工艺中加氯方式与三氯甲烷变化规律研究

以南方某市S给水厂为研究对象,试验研究了在常规处理工艺条件下对水中三氯甲烷的生成量进行控制。研究结果表明,饮用水中三氯甲烷随前、后加氯量以及余氯量的增加而增加,而随氨氯比的增加而减少。分次投加前氯0．5mg／L和后氯1mg／L要比一次性投加1．5mg／L氯明显降低出厂水中的三氯甲烷。合理采用加氯方式,严格控制消毒剂用量,可以把出厂水中的三氯甲烷生成量控制在最低水平。     

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。     

城乡统筹供水管网加氯优化及水质均匀度评价

针对城乡统筹供水模式下乡镇供水管网的特点,构建了以合格水百分比和加氯总量为优化目标的供水管网二次加氯优化模型,采用NSGA-Ⅱ算法实现该优化问题的求解,在此基础上,提出了均匀系数实现对管网中余氯均匀度的量化评价,并以苏州北部某城乡统筹供水管网为实例进行了应用。结果表明,与传统加氯相比,二次加氯能显著提高管网中合格水的百分比和水质均匀度,从整体上改善管网水质。     

郑州地区黄河水作为饮用原水的加氯消毒研究

首次对郑州地区不作为饮用原水进行加氯消毒处理后产生的副产物作了全面探讨。采用气相色谱仪对郑州自来水公司柿园水厂原水加氯消毒后的副产物进行了测定。实验结果表明：黄河水作为饮用原水加氯消毒的同时会产生对人体健康有害的物质－－三氯甲烷，且三氯甲烷的生成量会随着加氯量的大小、氯与不接触时间的长短、水温的高低而不同，加氯量越大、氯化时间越长、水温越高，三氯甲烷含量越高。     

滤后加氯不同因素对生成三卤假甲烷的影响

以滤后未加氯的水为研究对象,考察了投氯量、氯化时间、pH以及分次加氯等反应条件对三卤甲烷(THMS)生成量的影响,借此提出通过优化消毒来降低三卤甲烷等消毒副产物生成的控制方法.     

加氯模糊控制方法介绍

结合净水厂工程实例介绍加氯模糊专家控制方法。该方法能够解决水厂后加氯、补加氯中存在的非线性、时滞性和模糊性问题,从而实现现场后加氯、补加氯自动控制。提出采用自学习的模糊专家控制系统进行加氯自动控制实现氯气的最佳投加,以一个水厂模糊专家控制器工作原理为例说明加氯模糊专家控制系统的核心技术的设计原理。提出的方法经工程实践取得了预期成效。     

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.     

An experimental study for chlorine residual and trihalomethane formation with rechlorination.

Maintenance of adequate chlorine residuals and control of disinfection byproducts (DBPs) throughout water distribution systems is currently an important issue. In particular, rechlorination can be a powerful tool in controlling adequate chlorine residual in a large distribution system. The patterns of chlorine decay and formation of DBPs due to rechlorination are different from those of chlorination; chlorine decay is slower and trihalomethane (THM) formation is lower with rechlorination. The present study evaluates whether existing predictive models for chlorine residual and THM formation are applicable in the case of rechlorination. A parallel first-order decay model represents the best simulation results for chlorine decay, and an empirical power function model (modified Amy model) with an introduced correction coefficient (phi1, phi2) is more suitable to THM formation.     

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。     

给水管网中管材对水质变化的影响研究

研究了给水管网中镀锌钢管、铝塑管等常用管材中水质变化的规律,得出了三种管材中游离氯和化合氯的衰减规律,分析了金属离子溶出的影响因素.发现三种管材中旧镀锌钢管的余氯衰减最快,新镀锌钢管比铝塑复合管余氯衰减要快,旧镀锌钢管中余氯衰减呈现一级动力学特征,新镀锌钢管和塑料管余氯衰减呈现零级动力学特征.随着管网水停留时间的增加,锌、铁等金属离子浓度增加,溶出铁的含量与浊度、色度呈现很好的线性相关关系.     

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.     

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.     

Mathematical model for describing reactions of residual chlorine with organic matter in reclaimed wastewater.

Among several applications of urban wastewater reuse, use of reclaimed wastewater to sustain stream flows has become attractive in the urban area. Since these rivers are used for recreational purposes and for restoring aquatic eco-system, the adequate control of residual chlorine is essential. Mathematical model for describing reactions between residual chlorine and organic matter in reclaimed wastewater has been developed. The model considers the effect of molecular weight distribution of organic matter on the reaction rate. Lab-scale experiments were performed to estimate reaction rates constants and to examine their temperature dependency. The experiments showed that 1) the smaller organic matter gave the larger reaction rate; 2) temperature effect on reaction rate was described by the Arrhenius formula; 3) decline of free chlorine had more temperature dependency than combined chlorine. The comparison of computed results with data from lab-scale experiments confirmed the validity of the model. We used the one-dimensional dispersion model with proposed reaction model and examined the seasonal variation of residual chlorine profile along the river sustained by reclaimed wastewater in Sapporo. Simulation showed that seasonal variation of nitrification performance in secondary treatment as well as change in temperature caused seasonal variation in residual chlorine profile along the river.     

UV消毒用于楼宇水箱水质控制研究

结合实验室和现场的试验研究,探讨了UV消毒用于控制入户端——楼宇水箱水质的前景和问题。实验室研究结果表明,剂量为10mJ/cm2的UV照射,对HPC和E.coli能达到3log(99.9%)左右的灭活率。实际应用中UV消毒适用于微生物学指标较差、余氯很低的水箱,同时也出现了UV光强明显下降、紫外线照射促进余氯衰减等问题。     

次氯酸钠与液氯消毒在农村供水中的应用效果对比研究

为明确次氯酸钠消毒在农村供水工程中的实际应用效果,考察了南方某省以同一地表水为水源、水处理工艺相同、分别采用液氯和次氯酸钠消毒的具有一定代表性的两处农村供水工程(T水厂和H水厂)的余氯衰减、消毒效果和副产物生成情况。结果显示:在有效氯投加量分别为1.0 mg/L和2.0 mg/L时,2.4 h后H水厂出厂水的余氯值衰减率比T水厂分别低6.53%和3.30%,两者的消毒效果均较好,H水厂的管网末梢水菌落总数值比T水厂低40.62%,微生物安全性更高;当有效氯投加量由1.0 mg/L增至2.0 mg/L时,T水厂和H水厂出厂水的三氯甲烷生成量分别增长97.36%和59.35%,三卤甲烷分别增长122.64%和91.43%,而二氯乙酸和三氯乙酸生成量增长率相差不大。研究结果表明,次氯酸钠的稳定性及消毒效果略好于液氯,且消毒副产物三氯甲烷和三卤甲烷的生成量较小。由于两水厂在水源类型、水源水质特征、工程规模及水处理工艺方面具有一定代表性,经与其他研究进行对比分析认为,次氯酸钠消毒在农村供水中具有较好的应用前景。     

Improving Consumer Satisfaction in Water Distribution Networks Through Optimal Use of Auxiliary Tanks (A Case Study of Kashan City,Iran)

Temporal and spatial variations in pressure may lead to consumer dissatisfaction and distrust of water distribution networks when it comes to reliable performance. Pressure management is a set of programs and operations conducted in water distribution networks to adjust the pressure. Constructing new auxiliary tanks in proper locations at the best height for the area they serve minimizes the pressure fluctuations. Additionally, chlorine is often injected in the reservoirs and tanks to improve the water quality. The goal of this research was to improve the condition of the network by adding auxiliary tanks with appropriate locations, heights and chlorine concentration. An optimization model is prepared to optimize consumer satisfaction, water quality and the relevant costs as objective functions. The performance of the models are evaluated by a selected case study; and the objectives are optimized in three scenarios. Using the proposed model in a water distribution network, a trade-off diagram of reliability and costs is obtained, that lets the decision makers select the proper options considering the available fund. A new indicator, the consumer satisfaction index, is also proposed as a way to evaluate the performance of water distribution networks.