课后作业参考答案

1、unit 2 water sources1.（1）（2）because the flow of a river fluctuates and, after long periods of little or no rain over its catchment area, it may diminish to a trickle or even cease. it is essential to build reservoirs to keep enough water during dry spells where a water supply scheme depends on a riv

2、er as its source. 3. (1)water is stored and transmitted through the hydrological cycle. the water is held temporarily in, and can therefore be drawn from the groundwater system, ponds, lakes, and stream channels. during dry weather the drainage of these subsystems of the hydrological cycle provides

3、the supply upon which all human endeavor depends. it needs to be stressed that surface water and groundwater supplies are related. water can flow from one subsystem to the other, and the use of disruption of one component can impair the value of the other.水通过水文循环储存和传输，由于水具有流动性，只能在某一瞬间储存在地球上的不同空间位置，因

4、此我们可以从地下水系统、池塘、湖泊、水渠中抽取水。在干旱期，水文循环中这些子系统的出水量取决于人类的努力程度。需要注意的是地表水和地下水是相关的，水可以从一个子系统流动到另一个子系统，因此当其中一部分水被利用或补给中断后，另一部分的水量就会减少。4.(1) surface water and ground water(2) the ratio of the volume of water that can be drained by gravity to the gross volume of soil(3) free surface of unconfined aquifer and hyd

5、rostatic pressure of confined aquifer(4) both wells and infiltration galleries are collection works.(5) when a well is pumped, the cone of depression is encountered in aquifer.unit 3 the property of water3. (1)the biological characteristics of water, related primarily to the resident aquatic populat

6、ion of microorganisms, impact directly on water quality. water may serve as a medium in which literally thousands of biological species spend part, if not all, of their life cycles. aquatic organisms range in size and complexity from the smallest single-cell microorganisms to the largest fish.与水生微生物

7、的含量密切相关的生物特征能够直接影响水质。水可以作为生物的生活媒介，成千上万中生物在水里度过它们生命的某些阶段，有的甚至一生都在水里度过。水生生物的体积变化范围很大，组成也很复杂，既有世界上最小的单细胞微生物，也有世界上最大的鱼类。4（1）such as the concentrations of the compound of calcium hydroxide, magnesium carbonate, and sodium bicarbonate（2）nonbiodegradable organic matter（3）trace nutrients in water（4）paramete

8、rs associated with physical characteristics of water include odor, turbidity and suspended solids.（5）the total coliform group is usually used as indicator organism.unit 5 water-supply system1(1) it is the area which drains towards the supply.(2)because even if the community water supply includes all

9、 springs as well as all the surface water in the area, it still does not obtain all the rainfall because of evaporation and the needs of plant life.3(2)water utilities use long-range water demand forecast modeling to design their facilities and plan for future water needs. as water-supply systems be

10、come stressed because of population growth, industrialization, and other socioeconomic factors, water utilities must optimize the operation and management of their existing water-supply systems. in addition, water utilities need to avoid costly overdesign of facilities. one critical aspect for optim

11、izing water-supply system operation and management is the accurate prediction of short-term water demands. 自来水公司通过远期需水量预测模型设计水处理设施并预测未来需水量。由于人口增长，工业化以及其他社会经济因素的影响，供水系统压力变大，因此自来水公司必须优化现有供水系统的运行与管理。另外，在设计自来水厂的时候要避免代价高昂的超标准的设施。优化供水系统运行和管理的一个重要方面是要准确预测短期需水量。4（1） purification works（2） infiltration water（

12、3） suspended impurities（4） in the united states, some of whose cities have the largest water use in the world per person, the average use per person varies from 200 to 5,000 litters per day.（5） the supply and storage equipment must be designed to be large enough for this period.unit 6 pumps3.(1)a pu

13、mping station will generally consist of two parts, the substructure and the superstructure. while the substructure is basically a matter for engineering design, the superstructure should preferably be designed by an architect. if the substructure is divided into wet and dry wells, it is usual for th

14、e dry well to be directly under the superstructure and to have access from inside the building. access to the wet well should be from the open air.泵站通常由两部分组成，底层结构和上层结构。虽然底层结构通常由工程师设计，上层结构应该最好由建筑师设计。如果将底层结构分成干式井和湿式井两种，那么干式井一般直接安装在上层结构下面，入口在建筑物内部，湿式井的入口通常在室外。4（1） turbine casing（2） pump lift/head of pu

15、mp（3） propeller pumps and centrifugal pumps（4） as such, it varies with required flows and with changes in storage and suction levels.（5） open-impeller pumps are usually used to pump wastewaters and sludges.unit 7 plumbing1.(1)good health practices require that plumbing in a community be free of cros

16、s-connections, backflow connections, submerged inlets, and poor venting.(2)no, we cant make sure of the current plumbing status since data is lacking in this area.3.(2)the piping with the plumbing system must be made of durable material and be free of defects to give a long expected life of service.

17、 the trap seal must be protected in the design of the drainage system by providing adequate circulation of air in all pipes and by eliminating the possibility of siphonage, aspiration or breaking of the trap seals under ordinary use conditions. if a plumbing drainage system is subject to backflow of

18、 sewage from the public sewers, adequate protective measures should be used to keep the sewage from entering the building.管道工程的管材必须耐用，并且为了满足预期的服务时间要求、不能有任何缺陷。在排水系统设计中必须要注意保护水封，在正常使用的情况下，要提供足够的流通空气，并且要消除虹吸、吸入或者水封破坏现象。如果公共污水管的污水倒流到管道的排水系统中，应当采用适当的保护措施以免污水进入建筑物。4（1） public health personnel（2） repairs o

19、f plumbing（3） have a better understanding of plumbing and its effects on health（4） it is essential in our modern society to recognize that plumbing is to society what the circulatory system is to man.（5） these cross connections make possible the contamination of portable water with nonportable water

20、 or contaminated water.unit 8 wastewater collection and sewer design3.(1)chicago and its surrounding 51 communities cover an area of 375 square miles and have a population of over 3million people. this metropolis is served by a combined sewer network carrying both raw sewage and stormwater in a sing

21、le pipe. since a majority of the natural porous ground surfaces has been covered over with buildings, streets and pavements, stormwater runoff into the combined sewers frequently exceeds their capacities. when it occurs, excess flows bypass the treatment plants and this rainwater, mixed with the raw sewage, spills directly into area rivers and streams at hundreds of locations throughout the city. these combined sewage overflows (csos) result in severe pollution of the waterways as well as flooding. during particularly heavy rains, overloaded river