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1、Part Water Supply,Unit 6 Water Supply System,New words and expressions,purification n. 净化 提纯 vt. purify works n. 工厂 构筑物 pipe network n. 管网 管道系统 distribution system n. 配水系统 分配系统 main n. 干管 干线 kilopascal n. 千帕斯卡 ubiquitous adj. 到处存在的, (同时)普遍存在的 water consumption n. 用水量 耗水量 emergency n. 紧急情况, 突然事件,New
2、words and expressions,backup n. 储备 备份 回溯 vt. 做备份 emergency backup 紧急情况的储备 plumbing n. 管道工程 室内管道系统 A plumber is a person who fits and mends the plumbing. meterage n. 计量 sewerage n. 排水系统 污水 per capita 每人 按人数平均 water meter 水表 leak n. 漏出物，泄漏，漏洞 vi. 泄漏 the roof leaks socioeconomic adj 社会经济学的 dwelling n.
3、住宅 住处,The nature of the water source commonly determines the planning, design, and operation of the collection, purification, transmission, and distribution works.,1-1,The two major sources used to supply community and industrial needs are referred to as surface water and groundwater. Streams, lakes
4、, and rivers are the surface water sources. Groundwater sources are those pumped from wells.,1-2,Fig. 2-1 depicts an extension of the water resource system to serve a small community. The source in each case determines the type of collection works and the type of treatment works.,2-1,Source (watersh
5、ed),Collection works (Reservoir),Transmission works,Treatment works (Filtration Plant),Distribution System,Treatment works (Softening plant ) or Iron Removal Plant,Storage Reservoir,Collection works (Well field),Source (Groundwater),Mixing and flocculation,Sedimentation,Filtration,Disinfection,The p
6、ipe network in the city is called the distribution system. The pipes themselves are often referred to as water mains. Water in the mains generally is kept at a pressure between 200 and 860 kilopascals (kPa). Excess water produced by the treatment plant during periods of low demand (usually the night
7、time hours) is held in a storage reservoir.,2-2,The storage reservoir may be elevated (the ubiquitous water tower), or it may be at ground level. The stored water is used to meet high demand during the day. Storage compensates for changes in demand and allows a smaller treatment plant to be built. S
8、torage is also used to provide emergency backup in case of a fire.,2-3,Population and water consumption patterns are the prime factors that govern the quantity of water required and hence the source and the whole composition of the water resource system.,3-1,One of the first steps in the selection o
9、f a suitable water supply source is determining the demand that will be placed on it. The essential elements of water demand include the average daily water consumption and the peak rate of demand.,3-2,The average daily water consumption must be estimated for two reasons: (1) to determine the abilit
10、y of the water source to meet continuing demands over critical periods when surface flows are low or groundwater tables are at minimum elevations; and (2) for purposes of estimating quantities of stored water that would satisfy demands during these critical periods.,3-3,The peak demand rates must be
11、 estimated in order to determine plumbing and pipe sizing, pressure losses, and storage requirements necessary to supply sufficient water during periods of peak water demand.,3-4,Many factors influence water use for a given system. For example, the mere fact that water under pressure is available st
12、imulates its use, often excessively, for watering lawns and gardens , for washing automobiles, for operating air-conditioning equipment, and for performing many other activities at home and in industry.,4-1,The following factors have been found to influence water consumption in a major way: 1. Indus
13、trial activity; 2. Meterage; 3. System management; 4. Standard of living; 5. Climate.,4-2,The following factors also influence water consumption to a lesser degree: extent of sewerage, system pressure, water price, and availability of private wells. The influence of industry is to increase per capit
14、a water demand.,5-1,Small rural and suburban communities will use less water per person than industrialized communities. Industry is probably the largest single factor influencing per capita water use.,5-2,The second most important factor in water use is whether individual consumers have water meter
15、s. Meterage imposes a sense of responsibility not found in unmetered residences and businesses.,6-1,This sense of responsibility reduces per capita water consumption because customers repair leaks and make more conservative water-use decisions almost regardless of price. Because water is so cheap, p
16、rice is not much of a factor.,6-2,Following meterage closely is the aspect called system management. If the water distribution system is well managed, per capita water consumption is less than if it is not well managed managed.,7-1,Well-managed systems are those in which the managers know when and where leaks in the water mains occur and have them repaired promptly.,7-2,Industrial activity, meterage, and system management are more significant factors controlling water
