环境工程专业英语unit6.ppt

Unit 6 Water Supply System,05.11.18,The nature of the water source commonly determines the planning, design, and operation of the collection, purification, transmission, and distribution works. 一般说，水资源的自然状态决定了收集、净化、输送和配水工程的规划、设计和运行。,Profession-related English,Profession-related English,The two major sources used to supply community and industrial needs are referred to as surface water and groundwater. 为社区和工业需要提供水源，两个重要的来源是地表水和地下水。,Streams, lakes, and rivers are the surface water sources. 溪流、湖泊和河流属于地表水源。 Groundwater sources are those pumped from wells. 地下水是指从井里泵上来的水。,Fig. 2-1 depicts an extension of the water resource system to serve a small community. 图2-1描述了向小区供水的水资源系统范围。,The source in each case determines the type of collection works and the type of treatment works. 水源的具体情况决定了集水工程和处理工程的类型。 The pipe network in the city is called the distribution system. 城市管网叫作配水系统。,The pipes themselves are often referred to as water mains. water mains 给水干管 管道本身常常称作给水干管。 Water in the mains generally is kept at s pressure between 200 and 860 kilopascals (kPa). 干管中的水通常保持着200860千帕的压力。,Excess water produced by the treatment plant during periods of low demand (usually the nighttime hours) is held in a storage reservoir. 低需水量时期（常常是夜间），水处理厂多生产的水被储存在水库中。,The storage reservoir may be elevated (the ubiquitous water tower), or it may be at ground level. storage reservoir 蓄水池 蓄水池可以是高位的(如普遍使用的水塔),也可以在地下. The stored water is used to meet high demand during the day. 为了满足当日的最大需水量，需要使用这部分储存水。,（As a ）Storage compensates for changes in demand and allows a smaller treatment plant to be built（主句）. 因为有储备水来适应水量供求上的变化，水厂可以建得小一些。 Storage is also used to provide emergency backup in case of a fire. 储备水也被用来提供有火情情况下的紧急水源。,Population and water consumption patterns are the factors that govern the quantity of water required and hence the source and the whole composition of the water resource system.,One of the first steps in the selection of 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.,The average daily water consumption must be estimated for two reasons: (1) to determine the ability of the water source to meet continuing over critical periods when surface flows are low or groundwater tables are at minimum elevations;,(2) for purposes of estimating quantities of stored water that would satisfy demands during these critical periods.,The peak demand rates must be 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.,Many factors influence water use for a given system. For example, the mere fact that water under pressure is available stimulates 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.,The following factors have been found to influence water consumption in a major way: 1.Industrial activity; 2.Meterage; 3.System management; 4.Standard of living; 5.Climate.,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 capita water demand. 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.,The second most important factor in water use is whether individual consumers have water meters. Meterage imposes a sense of responsibility not found in unmetered residences and businesses.,This sense of responsibility reduces per capita water consumption because customers repair leaks and made more conservative water-use decisions almost regardless of price. Because water is so cheap, price is not much of a factor.,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.,Well-managed systems are those in which the managers know when and where leaks in the water mains occur and have them repaired promptly.,Industrial activity, meterage, and system management are more significant factors controlling water consumption than are either the standard of living or the climate.,The rationale for the latter two factors is straightforward. Per capita water use increases with an increased standard of living.,Highly developed countries use much more water than the less developed nations. Likewise, higher socioeconomic status implies greater per capita water use than lower socioeconomic status.,Higher average annual temperature implies higher per capita water use, whereas areas of high rainfall experience lower water use.,The average national value for water for water consumption in the United Stated in 1970 was 628 liters per capita per day (Lpcd). A similar study conducted in 1954 yielded a value of 556 Lpcd.,The average single-family residence used a