给排水环工 专业英语(华南理工大学)课文翻译 下

《给水排水专业英语》Lesson 1specific yield [spə'sifik] [ji:ld] 单位产水量mass curve 累积曲线capital investment 投资recurring natural event ['nætʃərəl] 重现历史事件subterranean [sʌbtə'reiniən] 地下的groundwater 地下水surface water 地表水tap [tæp]开关、龙头；在…上开空（导出液体）swampland ['swɔmplænd] n. 沼泽地；沼泽地带capillary [kə'piləri] n. 毛细管adj. 毛状的,毛细管的hygro- [词头] 湿（气），液体hygroscopic [,haigrəu'skɔpik] adj. 易湿的，吸湿的hygroscopic moisture 吸湿水stratum ['streitəm] n. [地质学]地层，[生物学]（组织的）层aquifer ['ækwəfə] ['ækwifə] n.含水层，地下蓄水层saturation [,sætʃə'reiʃən] n.饱和(状态)，浸润，浸透，饱和度hydrostatic [,haidrəu'stætik] adj. 静水力学的, 流体静力学的hydrostatic pressure 静水压力water table 1. 地下水位，地下水面，潜水面2. 【建筑学】泻水台；承雨线脚；飞檐；马路边沟[亦作water-table]Phreatic surface [fri(:)'ætik]地下水（静止）水位，浅层地下水面Superficial [sju:pə'fiʃəl] adj. 表面的,表观的，浅薄的Porosity [pɔ:'rɔsiti] n. 多孔性,有孔性,孔隙率Unconfined ['ʌnkən'faind] adj. 无约束的，无限制的Permeability [,pə:miə'biliti] n. 弥漫, 渗透, 渗透性Permeameter [pə:mi'æmitə] n.渗透仪,渗透性试验仪)Clay [klei] n. 粘土，泥土gravel ['ɡrævəl]n.[总称]砾，沙砾，小石；砾石cone of depression [kəun] 下降漏斗, [水文学]下降锥体drawdown ['drɔ:daun] n. 水位下降(降落,消耗,减少)integrate ['intigreit] 【数学】作积分运算；求积分observation well [,əbzə:'veiʃən] 观测井，观测孔extraction [ik'strækʃən] n. 抽出，取出，提取（法），萃取（法）derivation [deri'veiʃən] n. 1. 导出，引(伸)出，来历，出处，得出，得到；诱导，推论，推理；溯源【数学】1) (定理的)求导，推导2) 微商，微分，导数【语言】词源，衍生deplete [di'pli:t] v. 耗尽, 使...衰竭refuse [ri'fju:z] n. 废物,垃圾vt. 拒绝，谢绝dump [dʌmp] n. 垃圾场，垃圾堆，堆存处vt. 倾卸，倾倒(垃圾)unconfined aquifer 潜水含水层，非承压含水层，无压含水层confined aquifer 自流含水层，承压含水层homogeneous [,hɔməu'dʒi:njəs] adj. 同类的,相似的，均匀的，均相的；同种类的，同性质的；相同特征的Aquaclude 不透水层，难渗透水的地层Offset ['ɔ:fset] n.偏移量抵销，弥补，分支，胶印，平版印刷，支管，乙字管Vt. 弥补,抵销,用平版印刷vi. 偏移，形成分支sophisticated [sə'fistikeitid] adj. 复杂的，需要专门技术的；诡辩的,久经世故的equilibrium [,i:kwi'libriəm] n. 平衡,均衡Water Supply（给水工程）A supply of water is critical to the survival of life, as we know it.（众所周知，水对生命的生存至关重要。

《给水排水专业英语》译文：（第一课）给水工程我们知道，水的供应对生命的生存至关重要。

人类需要喝水，动物需要喝水，植物也需要喝水。

社会的基本功能需要水：公共卫生设施的冲洗，工业生产过程耗水，电能生产过程的冷却用水。

在这里，我们从两方面讨论水的供给：）1、地下水供给2、地表水供给地下水是通过打井而得到的重要直接供水水源，也是一种重要的间接供水水源，因为地表溪流（或小河）会经常得到地下水的补给。

在靠近地表的通气层中，土壤孔隙内同时包含着空气和水。

这一地层，其厚度在沼泽地可能为零，在山区则可能厚达数百英尺，蕴涵三种类型的水分。

重力水，是在暴雨过后进入较大的土壤孔隙中的水。

毛细水是在毛细作用下进入较小的土壤孔隙中的水，它能够被植物吸收。

吸湿水是在不是最干燥的气候条件下由于分子间引力而被土壤稳定下来的水。

地表通气层的湿气是不能通过凿井方式作为供水水源的。

位于通气层以下的饱和层，土壤孔隙中充满着水，这就是我们通常所说的地下水。

包含大量地下水的地层称为含水层。

通气层和含水层之间的水面称为地下水位或浅层地下水面，地下水静压力与大气压力相等。

含水层可延伸相当深度）, but because the weight of overburden material generally closes pore spaces（但因为地层负荷过重会压缩（封闭、关闭）土壤孔隙，深度超过600m，即2000英寸，就基本找不到地下水了。

能够含水层中自由流出的水量称为单位产水量。

The flow of water out of a soil can be illustrated using Figure 1（土壤中水流如图1所示）. The flow rate must be proportional to the area through which flow occurs times the velocity（流量与流水面积成比例，流经该土壤面积的流量等于面积与速率成的乘积）, orQ=AvWhere（此式中）Q=flow rate , in m3/sec（流量，单位为m3/s）【cubic meter per second】A=area of porous material through which flow occurs, in m2（渗透性土壤的流水断面，单位为m2）v=superficial velocity, in m/sec（表观流速（表面流速），单位为m/s）表观流速当然不是水在土壤中流动的真实速度，因为土壤固体颗粒所占据的体积大大地降低了水流通过的空间。

Unit one Environmental Engineering环境工程What is this book about？这本书是关于什么的？The objective of this book is to introduce engineering and science students to the interdisciplinary study of environment problems；their cause，why they are of concern，and how we can control them. The book includes:这本书的目的是使理工科的学生了解跨学科间的研究环境问题;它们的起因，为什么它们受到关注，以及我们怎样控制它们。

这本书包括：●Description of what is meant by environment and environmental systems描述环境和环境系统意味着什么●Information on the basic causes of environmental disturbances关于引起环境干扰基础原因的基本信息●Basic scientific knowledge necessary to understand the nature of environmental problems and to be able toquantify them理解环境问题本质，并能够定量计算它们所必要的基本科学知识●Current state of the technology of environmental control in its application to water，air and pollution problems目前适用于水，空气和环境污染问题的环境控制技术的现状●Considerable gaps in our current scientific knowledge of understanding and controlling many of the complexinteractions between human activities and nature我们目前的科学知识在理解和控制人类活动和自然之间复杂的相互作用的科学知识上存在相当大的缺陷●Many environmental problems which could be eliminated or reduced by the application of current technology，butwhich are not dealt with because of society’s lack of will to do so，or in many instance because of a lack of resources to do so.许多环境问题可以应用现有技术消除或减少，但没有得到处理是因为社会缺乏这样做的意愿，或者像许多例子那样因为缺乏资源。

Unit one Environmental Engineering环境工程What is this book about？这本书是关于什么的？The objective of this book is to introduce engineering and science students to the interdisciplinary study of environment problems；their cause，why they are of concern，and how we can control them. The book includes:这本书的目的是使理工科的学生了解跨学科间的研究环境问题;它们的起因，为什么它们受到关注，以及我们怎样控制它们。

这本书包括：●Description of what is meant by environment and environmental systems描述环境和环境系统意味着什么●Information on the basic causes of environmental disturbances关于引起环境干扰基础原因的基本信息●Basic scientific knowledge necessary to understand the nature of environmental problems and to be able toquantify them理解环境问题本质，并能够定量计算它们所必要的基本科学知识●Current state of the technology of environmental control in its application to water，air and pollution problems目前适用于水，空气和环境污染问题的环境控制技术的现状●Considerable gaps in our current scientific knowledge of understanding and controlling many of the complexinteractions between human activities and nature我们目前的科学知识在理解和控制人类活动和自然之间复杂的相互作用的科学知识上存在相当大的缺陷●Many environmental problems which could be eliminated or reduced by the application of current technology，butwhich are not dealt with because of society’s lack of will to do so，or in many instance because of a lack of resources to do so.许多环境问题可以应用现有技术消除或减少，但没有得到处理是因为社会缺乏这样做的意愿，或者像许多例子那样因为缺乏资源。

建筑工程及给排水专业中英文对照翻译Laminar and Turbulent FlowObservation shows that two entirely different types of fluid flow exist. This was demon- strated by Osborne Reynolds in 1883 through an experiment in which water was discharged from a tank through a glass tube. The rate of flow could be controlled by a valve at the outlet, and a fine filament of dye injected at the entrance to the tube. At low velocities, it was found that the dye filament remained intact throughout the length of the tube, showing that the particles of water moved in parallel lines. This type of flow is known as laminar, viscous or streamline, the particles of fluid moving in an orderly manner and retaining the same relative positions in successive cross- sections.As the velocity in the tube was increased by opening the outlet valve, a point was eventually reached at which the dye filament at first began to oscillate and then broke up so that the colour was diffused over the whole cross-section, showing that the particles of fluid no longer moved in an orderly manner but occupied different relative position in successive cross-sections. This type of flow is known as turbulent and is characterized by continuous small fluctuations in the magnitude and direction of the velocity of the fluid particles, which are accompanied by corresponding small fluctuations of pressure.When the motion of a fluid particle in a stream is disturbed, its inertiawill tend to carry it on in the new direction, but the viscous forces due to the surrounding fluid will tend to make it conform to the motion of the rest of the stream. In viscous flow, the viscous shear stresses are sufficient to eliminate the effects of anydeviation, but in turbulent flow they are inadequate. The criterion which determines whether flow will be viscous of turbulent is therefore the ratio of the inertial force to the viscous force acting on the particle. The ratioμρvl const force Viscous force Inertial ?= Thus, the criter ion which determines whether flow is viscous or turbulent is the quantity ρvl /μ, known as the Reynolds number. It is a ratio of forces and, therefore, a pure number and may also be written as ul /v where is the kinematic viscosity (v=μ/ρ).Experiments carried out with a number of different fluids in straight pipes of different diameters have established that if the Reynolds number is calculated by making 1 equal to the pipe diameter and using the mean velocity v , then, below a critical value of ρvd /μ = 2000, flow will normally be laminar (viscous), any tendency to turbulence being damped out by viscous friction. This value of the Reynolds number applies only to flow in pipes, but critical values of the Reynolds number can be established for other types of flow, choosing a suitable characteristic length such as the chord of an aerofoil in place of the pipe diameter. For a given fluid flowing in a pipe of a given diameter, there will be a critical velocity of flow corresponding to the critical value of the Reynolds number, below which flow will be viscous.In pipes, at values of the Reynolds number > 2000, flow will not necessarily be turbulent. Laminar flow has been maintained up to Re = 50,000, but conditions are unstable and any disturbance will cause reversion to normal turbulent flow. In straight pipes of constant diameter, flow can be assumed to be turbulent if the Reynolds number exceeds 4000.Pipe NetworksAn extension of compound pipes in parallel is a case frequently encountered in municipal distribution system, in which the pipes are interconnected so that the flow to a given outlet may come by several different paths. Indeed, it is frequently impossible to tell by inspection which way the flow travels. Nevertheless, the flow in any networks, however complicated, must satisfy the basic relations of continuity and energy as follows:1. The flow into any junction must equal the flow out of it.2. The flow in each pipe must satisfy the pipe-friction laws for flow in a single pipe.3. The algebraic sum of the head losses around any closed circuit must be zero.Pipe networks are generally too complicated to solve analytically, as was possible in the simpler cases of parallel pipes.A practical procedure is the method of successive approximations, introduced by Cross. It consists of the following elements, in order:1. By careful inspection assume the most reasonable distribution of flows that satisfies condition 1.2. Write condition 2 for each pipe in the formh L = KQ n(7.5) where K is a constant for each pipe. For example, the standard pipe-friction equation would yield K= 1/C2and n= 2 for constant f. Minor losses within any circuit may be included, but minor losses at the junction points are neglected.3. To investigate condition 3, compute the algebraic sum of the head losses around each elementary circuit. ∑h L= ∑KQ n. Consider losses from clockwise flows as positive, counterclockwise negative. Only by good luck will these add tozero on the first trial.4. Adjust the flow in each circuit by a correction, ΔQ , to balance the head in that circuit and give ∑KQ n = 0. The heart of this method lies in the determination of ΔQ . For any pipe we may writeQ = Q 0 ＋ΔQwhere Q is the correct discharge and Q 0 is the assumed discharge. Then, for a circuit100/Q h n h Q Kn Q K Q L L n n ∑∑∑∑?-=-=- (7.6) It must be emphasized again that the numerator of Eq. (7.6) is to be summed algebraically, with due account of sign, while the denominator is summed arithmetically. The negative sign in Eq.(7.6) indicates that when there is an excess of head loss around a loop in the clockwise direction, the ΔQ must be subtracted from clockwise Q 0’s and added to counterclockwise ones. The reverse is true if there is a deficiency of head loss around a loop in the clockwise direction.5. After each circuit is given a first correction, the losses will still not balance because of the interaction of one circuit upon another (pipes which are common to two circuits receive two independent corrections, one for each circuit). The procedure is repeated, arriving at a second correction, and so on, until the corrections become negligible.Either form of Eq. (7.6) may be used to find ΔQ . As values of K appear in both numerator and denominator of the first form, values proportional to the actual K may be used to find the distribution. Thesecond form will be found most convenient for use with pipe-friction diagrams for water pipes.An attractive feature of the approximation method is thaterrors in computation have the same effect as errors in judgment and will eventually be corrected by the process.The pipe-networks problem lends itself well to solution by use of a digital computer. Programming takes time and care, but once set up, there is great flexibility and many man-hours of labor can be saved.The Future of Plastic Pipe at Higher PressuresParticipants in an AGA meeting panel on plastic pipe discussed the possibility of using polyethylene gas pipe at higher pressures. Topics included the design equation, including work being done by ISO on an updated version, and the evaluation of rapid crack propagation in a PE pipe resin. This is of critical importance because as pipe is used at higher pressure and in larger diameters, the possibility of RCP increases.Se veral years ago, AGA’s Plastic Pipe Design Equation Task Group reviewed the design equation to determine if higher operating pressurescould be used in plastic piping systems. Members felt the performance of our pipe resins was not truly reflected by the design equation. It was generally accepted that the long-term properties of modern resins far surpassed those of older resins. Major considerations were new equations being developed and selection of an appropriate design factor.Improved pipe performanceMany utilities monitored the performance of plastic pipe resins. Here are some of the long-term tests used and the kinds of performance change they have shown for typical gas pipe resins.Elevated temperature burst testThey used tests like the Elevated Temperature Burst T est, inwhich the long-term performance of the pipe is checked by measuring the time required for formation of brittle cracks in the pipe wall under high temperatures and pressures (often 80 degrees C and around 4 to 5-MPa hoop stress). At Consumers Gas we expected early resins to last at least 170 hrs. at 80 degrees C and a hoop stress of 3 MPa. Extrapolation showed that resins passing these limits should have a life expectancy of more than 50 yrs. Quality control testing on shipments of pipe made fromthese resins sometimes resulted in product rejection for failure to meet this criterion.At the same temperature, today’s resins last thousands of hours at hoop stresses of 4.6 MPa. Tests performed on pipe made from new resins have been terminated with no failure at times exceeding 5,700 hrs. These results were performed on samples that were squeezed off before testing. Such stresses were never applied in early testing. When extrapolated to operating conditions, this difference in test performance is equivalent to an increase in lifetime of hundreds (and in some cases even thousands) of years.Environmental stress crack resistance testSome companies also used the Environmental Stress Crack Resistance test which measured brittle crack formation in pipes but which used stress cracking agents to shorten test times.This test has also shown dramatic improvement in resistance brittle failure. For example, at my company a test time of more than 20 hrs. at 50 degrees C was required on our early resins. Today’s resins last well above 1,000 hrs. with no failure.Notch testsNotch tests, which are quickly run, measure brittle crack formation in notched pipe or molded coupon samples. This isimportant for the newer resins since some other tests to failure can take very long times. Notch test results show that while early resins lasted for test times ranging between 1,000 to 10,000 min., current resins usually last for longer than 200,000 min.All of our tests demonstrated the same thing. Newer resins are much more resistant to the growth of brittle crack than their predecessors. Since brittle failure is considered to be the ultimate failure mechanism in polyethylene pipes, we know that new materials will last much longer than the old. This is especially reassuring to the gas industry since many of these older resins have performed very well in the field for the past 25 yrs. with minimal detectable change in properties.While the tests showed greatly improved performance, the equation used to establish the pressure rating of the pipe is still identical to the original except for a change in 1978 to a single design factor for all class locations.To many it seemed that the methods used to pressure rate our pipe were now unduly conservative and that a new design equation was needed. At this time we became aware of a new equation being balloted atISO. The methodology being used seemed to be a more technically correct method of analyzing the data and offered a number of advantages.Thermal Expansion of Piping and Its CompensationA very relevant consideration requiring careful attention is the fact that with temperature of a length of pipe raised or lowered, there is a corresponding increase or decrease in its length and cross-sectional area because of the inherent coefficient of thermal expansion for the particular pipe material. The coefficient of expansion for carbon steel is 0.012 mm/m?Cand for copper 0.0168mm/m?C. Respective module of elasticity a re for steel E = 207×1.06kN/m2 and for copper E = 103×106 kN/m2. As an example, assuming a base temperature for water conducting piping at 0?C, a steel pipe of any diameter if heated to 120?C would experience a linear extension of 1.4 mm and a similarly if heated to copper pipe would extend by 2.016 mm for each meter of their respective lengths. The unit axial force in the steel pipe however would be 39% greater than for copper. The change in pipe diameter is of no practical consequence to linear extension but the axial forces created by expansion or contractionare con- siderable and capable of fracturing any fitments which may tend to impose a restraint;the magnitude of such forces is related to pipe size. As an example,in straight pipes of same length but different diameters, rigidly held at both ends and with temperature raised by say 100?C, total magnitude of linear forces against fixed points would be near enough proportionate to the respective diameters.It is therefore essential that design of any piping layout makes adequate com- pensatory provision for such thermal influence by relieving the system of linear stresses which would be directly related to length of pipework between fixed points and the range of operational temperatures.Compensation for forces due to thermal expansion. The ideal pipework as far as expansion is concerned, is one where maximum free movement with the minimum of restraint is possible. Hence the simplest and most economical way to ensure com- pensation and relief of forces is to take advantage of changes in direction, or where this is not part of the layout and long straight runs are involved it may be feasible to introducedeliberate dog-leg offset changes in direction at suitable intervals.As an alternative,at calculated intervals in a straight pipe run specially designed expansion loops or “U” bends should be inserted. Depending upon design and space availability, expansion bends within a straight pipe run can feature the so called double offset “U” band or thehorseshoe typ e or “lyre” loop.The last named are seldom used for large heating networks; they can be supplied in manufacturers’ standard units but require elaborate constructional works for underground installation.Anchored thermal movement in underground piping would normally be absorbed by three basic types of expansion bends and these include the “U”bend, the “L”bend and the “Z”bend.In cases of 90 changes indirection the “L” and “Z”bends are used.Principles involved in the design of provision for expansion between anchor points are virtually the same for all three types of compensator. The offset “U” bend is usually made up from four 90° elbows and straight pipes; it permits good thermal displacement and imposes smaller anchor loads than the other type of loop. This shape of expansion bend is the standardised pattern for prefabricated pipe-in-pipe systems.All thermal compensators are installed to accommodate an equal amount of expansion or contraction; therefore to obtain full advantage of the length of thermal movement it is necessary to extend the unit during installation thus opening up the loop by an extent roughly equal the half the overall calculated thermal movement.This is done by “cold-pull” or other mechanical means. The total amount of extension between two fixed pointshas to be calculated on basis of ambient temperature prevailing and operational design temperatures so that distribution of stresses and reactions at lower and higher temperatures are controlledwithin permissible limits. Pre-stressing does not affect the fatigue life of piping therefore it does not feature in calculation of pipework stresses .There are numerous specialist publication dealing with design and stressing calculations for piping and especially for proprietary piping and expansion units; comprehensive experience back design data as well as charts and graphs may be obtained in manufacturers’publications, offering solutions for every kind of pipe stressing problem.As an alternative to above mentioned methods of compensation for thermal expansion and useable in places where space is restricted, is the more expensive bellows or telescopic type mechanical compensator. There are many proprietary types and models on the market and the following types of compensators are generally used.The bellows type expansion unit in form of an axial compensator provides for expansion movement in a pipe along its axis; motion in this bellows is due to tension or compression only.There are also articulated bellows units restrained which combine angular and lateral movement; they consist of double compensator units restrained by straps pinned over the center of each bellowsor double tied thus being restrained over its length.Such compensators are suitable for accommodating very pipeline expansion and also for combinations of angular and lateral movements.层流与紊流有两种完全不同的流体流动形式存在，这一点在1883年就由Osborne Reynolds 用试验演示证明。

Unit 6Water Supply System水源的性质一般决定了规划、设计和运行的收集、净化、传输和分配工作。

两个主要来源用于供应社区和工业需求被称为地表水和地下水。

溪流、湖泊和河流水源的表面。

地下水资源是那些从井泵。

无花果。

2 -1描述了一个扩展的水资源系统为一个小的社区。

源在每种情况下确定集合的类型作品和治疗类型的作品。

在城市的管道网络称为分销系统。

管道本身通常被称为水电源。

水在电源一般保持在200和860帕之间的压力(kPa)。

多余的水处理厂产生的时期,低需求(通常在夜间小时)举行。

可能较高的蓄水库(无处不在的水塔),或者可能是在地面上。

存储的水是用来满足白天的高需求。

存储可以弥补需求变化和允许一个较小的处理厂建成。

存储也是用来提供应急备份以防火灾。

人口和水的消费模式是主要因素,执政所需的水的数量,因此源和整个组成的水资源系统。

第一个步骤选择一个合适的供水来源是确定需求,将放在它。

水需求的基本要素包括日均耗水量和峰值速率的需求。

每日平均的水消费必须估计有两个原因:(1)确定水源的能力以满足持续要求在关键时期当表面流低或地下水的表都处于最低海拔;(2)为目的的估计量的储存水,将满足要求在这些关键的时期。

高峰需求的利率必须估计为了确定管道和管大小、压力损失和存储需求需要充足的水供应的高峰时期水需求。

有很多因素会影响水的利用对于一个给定的系统。

例如,事实是,水压力下的是其使用,通常可用刺激过度,灌溉草坪和花园,洗汽车,对于操作空调设备,和用于执行许多其他活动在家里和在行业。

以下因素影响了水消费的重要途径: 1。

工业活动;2。

测量;3。

系统管理;4。

的生活标准;5。

气候。

下列因素也影响着水消费程度较轻:污水处理程度,系统压力、水价格和可用性的私人水井。

行业的影响是提高人均水需求。

小乡村和郊区社区将使用更少的水人均工业化社区。

行业可能是最大的单一因素影响人均用水量。

第二个最重要的因素是消费者个人用水是否有水米。

第四单元给水系统一般来说，供水系统可划分为四个主要组成部分:（1）水源和取水工程（2）水处理和存储（3）输水干管和配水管网。

常见的未处理的水或者说是原水的来源是像河流、湖泊、泉水、人造水库之类的地表水源以及像岩洞和水井之类的地下水源。

修建取水构筑物和泵站是为了从这些水源中取水。

原水通过输水干管输送到自来水厂进行处理并且处理后的出水储存到清水池。

处理的程度取决于原水的水质和出水水质要求。

有时候，地下水的水质是如此的好以至于在供给给用户之前只需消毒即可。

由于自来水厂一般是根据平均日需求流量设计的，所以，清水池为水需求日变化量提供了一个缓冲区。

水通过输水干管长距离输送。

如果输水干管中的水流是通过泵所产生的压力水头维持的，那么我们称这个干管为增压管。

另外，如果输水干管中的水流是靠由于高差产生的可获得的重力势能维持的，那么我们称这个干管为重力管。

在输水干管中没有中间取水。

与输水干管类似，在配水管网中水流的维持要么靠泵增压，要么靠重力势能。

一般来说，在平坦地区，大的配水管网中的水压是靠泵提供的，然而，在不平坦的地区，配水管网中的压力水头是靠重力势能维持的。

一个配水管网通过引入管连接配水给用户。

这样的配水管网可能有不同的形状，并且这些形状取决于这个地区的布局。

一般地，配水管网有环状或枝状的管道结构，但是，根据当地城市道路和街区总体布局计划，有时候环状和枝状结构合用。

城市配水管网大多上是环状形式，然而，乡村地区的管网是枝状形式。

由于供水服务可靠性要求高，环状管网优于枝状管网。

配水管网的成本取决于对管网的几何形状合适的选择。

城市计划采用的街道布局的选择对提供一个最小成本的供水系统来说是重要的。

环状管网最常见的两个供水结构是方格状、环状和辐射状；然而，我们不可能找到一个最佳的几何形状而使得成本最低。

一般地，城镇供水系统是单入口环状管系统。

如上所说，环状系统有一些通过系统相互连接的管道使得通过这些连接接的管道，可以供水到同一个需水点。

There are several species of bacteria that are widely found in the aquatic environment but so not normally cause illness in the immuno-competent. They are not therefore particularly associated with health problems from drinking-water. It is important to be aware of them nevertheless, as they have occasionally been associated with disease where people may already be ill with other conditions or their immune system is reduced and unable to cope (Dufour 1990).They are usually known as environmental bacteria, but I have also come across the terms adventitious or heterotrophic in this context (although heterotrophic strictly means they get their source of energy and cellular carbon from the oxidation of organic material, that is, by feeding on plants or animals-rather than photosvnchesis). Where laboratories carry out plare counts, it is often these bacteria that are cultured. There will be many different types of environmental bacturia but the imporiant ones for drinking-water safety are listed here.AeromonasAeromonas are commonly found in both fresh and salt waters. There are several species, each one favouring a particular environmental niche. Aeromonas bydropbila is found mainly in clean river water, Aeromonas sobria in stagnant water and Aeromonas caviae in marine water. They are so common that people have tried to use them in rivers as indicators of pollution. They are known to cause diarrhoea and infection in soft tissue where damaged skin comes into contact with contaminated river or lake water.Aeromonas caviae is the one most commonly associated with diarrhoea. Diarrhoeal infection is usually mild, although more severe symptoms have occasionally been known, including bloody diarrhoea and chronic colitis (inflammation of the colon).Aeromonas have been found in treated chlorinated water and sometimes, there is re-growth in the distribution pipes. Chlorine only appears to have a temporary effect on them and this may mean that it stops them from reproducing but does not kill them. If left (presumably so they can get their breath back and have a bit of a rest after the chlorine attack) they can continue as normal.有一些种类的细菌在水生环境中被发现,但通常不引起疾病immuno-competent。

Unit 12水的净化水分子是没有记忆的,所以去讨论你所喝的水是被污染了并净化了多少次是可笑的(市没有意义的 , 好像水分子逐渐厌烦了(逐渐被耗尽了。

最重要的是你喝的水纯度如何。

对水的净化方法已发展到了很详细并且尖端的技术。

然而通常采用的净化水的方法对水污染的性质的通常的理解应该是容易理解的,并在某些情况下是显而易见的。

水中的杂质可分为悬浮的,胶体态的或溶解态的。

由于悬浮的颗粒大足以被沉淀或被过滤掉。

胶体态的或溶解态的杂质较难以去除掉。

去除他们的一个可能的方法是以某种方法把这些微小的颗粒物结合成比较大的颗粒然后采用去除悬浮物的方法来处理。

另一种可能的方法是把他们转变为气态然后是他们从水中散发到大气中,无论采用哪一种方法,有一点必须记住的是提升水或用泵将水输送通过滤床都需要能量。

根据这些原则,来考虑用于净化城市污水的步骤。

第一步是废水的收集系统。

从家庭、医院、学校排放的水中的污染物包含食物残渣、人类排泄物、纸张、肥皂、洗涤剂、污垢、织物和其他混杂的残骸,当然还有微生物。

这些混合物被称为厕所污水或生活污水。

这里 Sanitary 这个形容词比较不恰当,因为它几乎没有描述污水的情况,他只笼统地指人产生的污染物被污水管所排走。

这些污水,有时与污水管网中从商业建筑来的污染物、工业污染物及雨水污染物合流。

有些体系把污水与雨水分流而有些是合流。

合流制的管道便宜,并在旱季时是合理的,但在暴雨期时的总流量容易超过处理厂的容量,结果应允许有些水溢流而直接进入受体河流中。

初级处理当污水进入处理厂时,首先通过一系列的格栅以去除其中大的物体如老鼠或葡萄柚,然后通过一个磨碎装置以便把剩余的物体的大小减小至足够小以至在后续的工艺中可以有效的处理。

下一步是一系列的沉淀室来去除重的粗沙例如雨水冲刷路面带入的沙粒,然后其他悬浮的固体(包括有机营养物缓慢的沉淀而得到去除,这个过程需耗时大约一小时。

从开始到这个过程的整个工艺称为处级处理,这一级处理的费用相对低,但是没有完成多少任务。