给水排水专业英语(李田)7课件

1、Unit 7Selection of Water Treatment Processes1New words and expressionswatershed n. 流域 分水岭screen n. 筛子 vt. 筛分presedimentation n. 预沉降desilt v. 挖除淤泥 沉砂pretreat vt. 预先处理,预处理coagulation n. 混凝 coagulant 混凝剂bacterial adj. 细菌的bacterium n. 细菌 pl. bacteria.polyelectrolyte pliilektrulait n. 聚合(高分子)电解质alum n. 明

2、矾, 矾 aluminium 铝sulfide n. 硫化物 hydrogen sulfide taste and odor 嗅味chlorine n. 氯气 氯chlorine dioxide 二氧化氯2New words and expressionspotassium ptsim n. 钾permanganate n. 高锰酸 高锰酸盐trihalomethane n. 三卤甲烷oxidize v. (使)氧化flexibility n. 弹性, 适应性, 机动性, 挠性feedline n. 进料管线feeder n. 进料器 投加装置land-runoff n. 地表径流eutrop

3、hic ju:trfik adj. 富营养的suppress vt. 镇压 抑制 suppress a smile.aerator n. 通风装置 曝气器 tray aeratorfloc n. 絮凝体 絮状物 filter n. 滤池 过滤器 vt. 过滤3Watershed management should be considered part of the operation of a water-supply system, which is very important to protect raw water quality. Behind an intake structure

4、, there comes water treatment process.1-15Current pretreatment processes in municipal water treatment are screening, presedimentation or desilting, chemical addition, and aeration. Screening is practiced in pretreating surface waters. Presedimentation is regularly used to remove suspended matter fro

5、m river water. 2-16Chemical treatment, in advance of in-plant coagulation, is most frequently applied to improve presedimentation, to pretreat hard-to-remove substances, such as taste and odor compounds and color, and to reduce high bacterial concentrations. 2-27Conventional chemicals used with pres

6、edimentation are the polyelectrolytes and alum. Aeration is customarily the first step in treatment for the removal of iron and manganese from well waters and a standard way to separate dissolved gases such as hydrogen sulfide and carbon dioxide. 2-38For example, activated carbon, chlorine, chlorine

7、 dioxide, and potassium permanganate are all used for taste and odor control. Excess chlorination, although least expensive, can create undesired trihalomethanes; activated carbon is the most effective chemical.3-210There is no fixed rule for color removal applicable to all waters. Alum coagulation

8、with adequate pretreatment, and applying oxidizing chemicals or activated carbon, may provide satisfactory removal. On the other hand, a more expensive coagulant might prove to be more effective and reduce overall chemical costs.3-412Multiple chemical feeders and storage tanks should be supplied so

9、that various chemicals can be employed in the treatment process.Degradation of the raw-water quality, or changes in costs of chemicals, may dictate a change in the type of coagulant or auxiliary chemicals used in coagulation. 4-214In the case of surface-water treatment plants it is desirable to prov

10、ide space for the construction of additional pretreatment facilities. The flow in river may change due to construction of dams, channel improvements, or upstream water use. 4-315The quality of water changes due to human alteration and occupation of the watershed. Concentrations of pollutants from di

11、sposal of municipal and industrial wastes and agricultural land-runoff may increase. Lakes can become more eutrophic.4-416 17The treatment plant described in Fig. 2-2 is a groundwater plant with provisions for iron and manganese removal and lime softening. 5-118After installation, the plant capacity

12、 has been expanded and the treatment process converted to only iron and manganese removal by increasing the aerator capacity, adding chlorine feed after the aeration, and using the settling basin as a detention tank.5-220At present this plant is only capable of performing oxidation by aeration and c

13、hlorination for iron and manganese removal and disinfection.Finished water quality is excellent all year round because of the stable character of the well supply.5-321Activated carbon, chlorine dioxide, and various auxiliary chemicals for improved chemical treatment are now available to the operator

14、 during critical periods of poorer raw-water quality. 6-223During most of the year the finished water is very palatable, but tastes and odors cannot be completely removed during spring and fall lake overturns.6-324A general treatment scheme consists of plain sedimentation for desilting; mixing follo

15、wed by sedimentation, using coagulants as necessary; split treatment for partial softening and coagulation in flocculator-clarifiers; dual-media filtration; and chemical additions for chlorine residual, pH adjustment, and control of scaling.7-226Operation of this plant is varied from day to day and from season to season depending on the raw-water quality.Even though, some refr