基于PLC的水厂石灰投加系统的设计与应用

在自来水厂的整体净水工艺流程中石灰投加是调节pH,确保水质的重要环节,随着社会发展,人们对供水质量和生产可靠性要求不断提高,将自动控制技术融入石灰投加流程,自动化石灰投加系统的应用越来越受行业所重视.以金华仙源湖水厂为研究对象,结合其水厂升级改造实际应用,阐述可编程逻辑控制器(PLC)在石灰投加系统中的应用模式.根据石灰投加系统的功能需求和操作要求,介绍编程实现逻辑及程序源代码.在自动投加系统中,投加的控制方式对系统整体运行效果起决定性作用,仙源湖水厂结合精细投药算法,采用流量比例复合环计算控制方式,引入在线pH仪实时测量值,进行反馈对比运算,对扰动进行有效补偿,提高系统运行稳定性,投加效果更佳.经水厂实际运行验证,运用基于PLC的自动控制技术对石灰投加系统整体性能有较好提升,非常适合水厂日常生产.     

深圳梅沙片区供水管网黄水成因分析及控制对策

通过深圳梅沙片区供水管网突发黄水现象的成因分析,明确水源切换时水质发生了变化,特别是pH值降低引起的水质化学稳定性下降是该区黄水产生的主要原因。水厂采用投加石灰的方法提高水质化学稳定性,当控制出厂水的pH值为8.0～8.5时,该方法可有效提高出厂水的水质化学稳定性,实现水厂内控制管网腐蚀的目的。     

南方某水厂生产性再矿化系统设计与运行

南方地区低p H值、低硬度和低碱度的水质特点加剧了供水管道的腐蚀,导致管道渗漏、爆管以及"黄水"现象频繁发生。某水厂设计了清水池投加石灰上清液的再矿化系统对出厂水进行再矿化处理,以改善出厂水水质,提高水质化学稳定性。介绍了该水厂再矿化系统的设计方法,并在调试运行期间对再矿化实施前后出厂水p H值、浊度和余铝的变化进行比较。结果表明,再矿化系统根据进水量动态投加石灰水的运行方法可以有效提高出厂水p H值,且对出厂水浊度及其他常规指标影响较小。再矿化系统投入使用后石灰消耗量同比有小幅度的下降,主要原因在于清水池投加石灰减少了前段工艺的石灰投加量。     

水厂制水工艺中亚硝酸盐成因及处理办法的调研

对制水厂的出厂水亚硝酸盐指标较高的原因进行了调查分析，找出了在水厂制水工艺流程中产生大量亚硝酸盐的根源，通过对水厂的试验及积累的水质数据的分析，找出了解决制水厂亚硝酸盐超标的方法。     

制水生产中毛翅目幼虫的发生与防治研究

毛翅目幼虫广泛分布于清洁水体中,是对水质污染最敏感的水生昆虫之一.文中介绍了国内外毛翅目幼虫的研究进展,分析了制水生产流程中的毛翅目昆虫对水厂制水生产的影响,进一步对H市水厂进行了毛翅目昆虫污染来源和特征进行调查表明,毛翅目昆虫污染主要来源于制水厂进厂原水,大多分布在沉淀池.通过灯光诱杀、调整工艺参数、滤池的浸泡消毒和投加化学药剂消杀等措施,沉淀池滤后水对比沉淀池出口水的毛翅目昆虫污染情况得到较好的改善.     

解决水库水pH值低的对策研究

水厂原水pH值随季节变化，夏季有时低于6．5。为了保证出厂水水质，水厂在水处理过程中加碱。本文比较了几种酸碱调节剂的投加效果及其生产成本，讨论了不同碱剂对水质稳定参数的影响，并通过大理石实验，给出了本厂水质稳定性参数的范围。介绍了水厂石灰自动化投加系统情况。     

全封闭新型石灰投加系统的设计与应用

自来水厂传统石灰投加方式具有扬尘污染严重、工人劳动强度大、工作环境恶劣的不足,为此介绍了新型散装石灰投加工艺及其工艺参数设计方法.实际应用效果表明,该工艺有效地解决了石灰扬尘问题,且自控水平高,是现代化水厂的发展方向.     

碱度对水厂生物砂滤池去除氨氮的影响

本文从南方地区某两间给水处理厂（A水厂和B水厂）的实际生产中,生物砂滤池对氨氮的去除情况,探讨碱度对水厂生物砂滤池去除氨氮的影响。据此可以得出结论：在常规水处理工艺中,对于低pH、低碱度的水源水,在混凝反应前投加石灰,增加待滤水的碱度（pH）,可以有效提高生物砂滤池对水中氨氮的去除率。     

典型南水北调水厂对水源水质变化的适应性研究

南水经长距离输送至郑州后,水质发生改变,藻类爆发成为其主要问题.为指导受水厂调整制水工艺,降低生产风险,本文通过研究郑州市LD水厂藻类爆发期间原水水质变化、水厂所采取工艺调整措施和出水效果,总结运行经验发现潜在风险.通过开展水厂生产环节间水质指标相关系数研究,得出工艺调整方向.结果表明采用常规工艺的水厂,通过调整工艺运行参数,可以应对原水藻类爆发.LD水厂如适当提高沉淀池之前液氯投加量,降低聚合氯化铝投加量,可进一步降低滤池出藻风险.     

常规净水厂几个问题的探讨

针对水厂施工图审核过程中多次发现的问题,探讨了水厂常规制水系统设计中应该注意的一些细节。主要包括投加混合、平流沉淀池、V型过滤、清水池和水厂自用水等方面。     

石灰法出水对冷却系统腐蚀、结垢的影响

石灰法是城市污水再生回用于工业循环冷却系统的重要技术.为考察石灰法处理出水对冷却系统的影响,将北京某城市污水厂二沉池出水经石灰法处理后回用于电厂循环冷却系统,试验结果表明,与二沉池出水相比,石灰法出水具有更强的腐蚀性,并且易生成碳酸钙和磷酸钙,但不易生成硫酸钙和硅酸镁;通过采取缓蚀阻垢措施可以很好地防止循环冷却水腐蚀和结垢状况对机组运行的影响.     

石灰法投药量对循环冷却水水质的影响

介绍了将高碑店污水厂的二沉池出水经过石灰法处理后用作华能北京热电厂循环冷却水的试验情况，分析了不同石灰投量对冷却水主要水质参数的影响。试验结果表明，经过石灰法处理的二沉池出水可以满足热电厂循环冷却水的水质要求。     

The bactericidal effect of lime flocculation/flotation as a primary unit process in a multiple system for the advanced purification of sewage works effluent

An important advantage of using lime as flocculant in water purification processes is that bacteria are not only removed by coagulation but also destroyed by the hydroxide alkalinity. This communication deals with the bactericidal effect of lime in a flocculation/ flotation unit which is the primary and key process in a multiple system experimental plant for the reclamation of potable water from secondary treated sewage effluent. Laboratory and field tests revealed a marked difference in the survival of Gram-negative, Gram-positive and acidfast bacteria. Previous studies on the bactericidal effect of lime in water treatment processes included only Gram-negative organisms. These bacteria were considerably more sensitive than the other two groups and possible reasons for the differentiation in resistance are discussed. Raising the pH value of humus tank effluent to 11·5 for a period of 1 hr destroyed all Gram-negative bacteria and reduced the plate count by more than 99 per cent. Surviving organisms consisted mainly of spore-formers. This treatment had almost no effect on mycobacteria.     

Heavy metal removal from waste water from wet lime(stone)—gypsum flue gas desulfurization plants

Waste water from wet lime(stone) gypsum flue gas desulfurization processes for coal-fired boilers contains suspended solids (gypsum, silica, hydroxides of iron and aluminum) and soluble salts (chlorides and sulfates of calcium, sodium and magnesium). Furthermore, small amounts of heavy metals such as As, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Se and Zn are present in these waste water streams. A treatment method has been developed to remove these heavy metals very efficiently. This method has been based on coprecipitation of metal hydroxides and sulfides. The hydroxide and sulfide precipitates are removed by a coagulation/flocculation technique followed by gravity settling. The coprecipitation can be carried out with sodium hydroxide or with lime. Both cases were investigated in two different pilot plants with synthetically composed waste water and with actual waste water from three different types of wet lime(stone)—gypsum flue gas desulfurization plants (lime—gypsum FGD plants without a prescrubber, one using seawater and another using river water as process water; a limestone—gypsum FGD plant with a prescrubber using river water as process water).     

Engineering and microstructure properties of contaminated marine sediments solidified by high content of incinerated sewage sludge ash

Management of incinerated sewage sludge ash(ISSA) and dredged contaminated marine sediments(CMSs) is a great challenge for Hong Kong and other coastal cities due to limited landfilling capacity.The present study investigates the use of high content(20% of sediment by mass) of ISSA in combination with cement/lime for solidification/stabilization(S/S) treatment of CMSs to provide a way to reuse the wastes as construction materials.The results showed that ISSA being a porous material was able to absorb a large amount of water rendering a more efficient solidification process of the marine sediment which normally had a very high water content(～80%).The S/S treatment improved the engineering properties of the sediment,but reduced the workability,especially for the lime-treated samples.Lime can be used to replace ordinary Portland cement(OPC) for better heavy metal immobilization and carbon emission reduction.The hardened sediment samples prepared with 10% of lime and 20% of ISSA could attain a strength of 1.6 MPa after 28 d of curing.In addition,leaching tests confirmed that there was no environmental risk induced by these stabilized materials.The formation of hydrated cementitious compounds including calcium silicate hydrate(C-S-H)/calcium aluminate silicate hydrate(C-A-S-H)/hydrocalumite/calcite was mainly responsible for the strength development in the ISSA/lime-treated sediments.     

Color removal in groundwater through the enhanced softening process

The source of water for Miami-Dade County, Florida is groundwater derived from the Biscayne aquifer. The raw water is rich in natural organic material producing correspondingly high color levels. Currently, breakpoint chlorination is used at the water treatment plant to control the color problem. However, this results in the formation of disinfection by-products. Proposed alternatives to reduce color and avoid by-product formation include the addition of coagulants such as ferric chloride and organic polymers, and the operation of the existing lime softening process at a higher pH. This study uses jar tests to evaluate the relative effectiveness of the proposed alternatives. Results indicate that significant color reduction is achieved using the existing lime softening process with activated silica coagulant by increasing the softening pH to 11 or more. Elevated pH also produced a > 30% reduction in total organic carbon. In the presence of higher raw water color (> or = 80 units), the addition of ferric chloride as coagulant at dosages of 80 mg/L is recommended.     

Stabilization of a Saudi calcareous marl soil

Due to the inferior characteristics of indigenous soils in eastern Saudi Arabia, marl is being utilized to improve their properties. Marl is calcareous in nature and it is well known for its heterogeneous nature in terms of composition and properties. Moreover, it is sensitive to changes in water content and it often requires prior treatment without which a significant strength loss will occur upon water flooding. This paper presents the results of a laboratory investigation focused on the improvement of indigenous marl for its use as a road base material. Various tests were conducted to both characterize and quantify the strength and durability of the studied marl under different field-simulated conditions with and without chemical treatment (lime and cement). The improvement in strength was assessed using California Bearing Ratio (CBR), Clegg Impact Hammer (CIH) and unconfined compressive strength tests and the durability was evaluated using standard and modified durability tests. The results indicated that cement is superior to lime both in terms of strength improvement and durability requirements.     

污泥石灰处理工程中的物料优化管理

介绍了污泥石灰处理的物料优化管理,涉及原始污泥、石灰粉料、处理后出泥以及废气的收集。在此基础上介绍了相关案例,得出以下几个结论值得在工程设计实施中参考:原始污泥含水量过高会增加石灰消耗;污泥石灰处理宜选用粒度小、活性高的粉料;污泥出泥及废气收集方案需根据原始污泥的特点和处理目标的具体情况进行优化设计。     

Dewatering municipal sludges by osmosis

Treatment, handling, and disposal of municipal sludges constitute a difficult and expensive aspect of wastewater treatment. One of the steps in the procedure is dewatering—the reduction of water content to something less than 85%. Conventionally, the dewatering is done by vacuum filtration or by centrifugation, though some other means, such as filter presses, are sometimes used. With most of these processes, some sort of sludge pretreatment, such as the addition of lime or ferric chloride, is normally used. Such additions are not only expensive but render the resulting dewatered sludge less amenable to incineration, because of potentially corrosive products of combustion, or to the spreading of the sludge on agricultural land, because of the unwanted lime, in some areas, and iron. Vacuum filtration of biological sludges rarely produces a sludge of less than 82% moisture, with some passthrough of fines to the filtrate. Centrifugation can produce a drier sludge but normally at the cost of an even higher passthrough of fines. The research for this paper shows that sludges can be dewatered to 70% or less less water content, by osmosis, without the addition of lime or ferric chloride or other pretreatment, though some sort of sludge thickening prior to the osmotic process would lessen the time in the process. Although the work was all done at bench scale, a proposed commercial design is presented.     

利用磷石制造建筑石膏的研究

通过水洗净化法、石灰水中和法、生石灰中和法等多种方法对磷石膏加以处理,试图探讨不经水洗制造性能良好的建筑石膏的途径,研究结果表明,生石灰中和法工艺简单,可制成一级建筑石膏。