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 to quantify 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 complex interactions 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，but which 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。
Some important definitions 一些重要的定义
Where they are first used in this book，definitions are introduced in block form，as shown here，or printed in bold type.
如果他们是第一次使用这本书，定义介绍采用块形式，像这里显示的一样，或印成黑体字。
Environment is the physical and biotic habitat which surrounds us；that which we can see，hear，touch，smell，and taste.
环境是围绕在我们周围物质生命的栖息地，在那里我们可以看到，听到，触到，闻到和品尝到。
System，according to webster’s dictionary，is defined as “a set or arrangement of things so related or connected as to form a unit or organic whole；as，a solar system，irrigation system，supply system，the world or universe”.
系统，依据韦伯斯特的字典，被定义为“一组或一系列能形成一个整体或者有机整体的相互关联的事物;比如，太阳系统，灌溉系统，供水系统，世界或宇宙” 。
Pollution can be defined as an undesirable change in the physical，chemical，or biological characteristics of the air，water，or land that can harmfully affect the health，survival，or activities of humans or other living organisms.
污染可以被定义为有害影响健康，生存，活动的人或其它生物体的空气，水，或土地的物理，化学或生物特性的不应该有的变化，。
When the goal of improving environmental quanlity is taken to be improving human wellbeing，the word “environment” broadens to include all kinds of social，economic，and cultural aspects. Such broadness is unworkable in many real situations and impractical in a text book designed for a one semester course. Our examination of environmental problems is therefore limited by our definition of “environment”.
当改善环境质量的目标是用来改善人类的福祉， “环境” 这个词扩大到包括社会，经济，文化等所有方面的内容。这种扩大化在许多实际情况下是不可行的，在本被设计为一学期课程的教科书中也是不切实际的。因此，我们对环境问题的考察限于我们定义的“环境”。
Interaction of Systems互动系统
A number of different environmental problems are associated with water, air, or land systems. 许多不同的环境问题都涉及到水，空气，或土壤。
Many of these problems will apply only within one of these systems, justifying the breakdown into these categories.许多这些问题只适用于在其中一个系统，这为这些种类中的细目分类提供了充分的理由。
Such a classification is also useful for easier comprehension of related problems within one system.这种分类也有助于更容易理解一个系统里的相关问题。
Moreover, it is sensible because, for manager and administrative reasons, such subfields as air pollution, water supply, wastewater disposal, and solid waste disposal are often dealt with separately by governmental agencies.
此外，这样做是明智的，因为是行政管理的原因，空气污染，水供应，固体废物处置和废水处理，往往是由政府机构分别处理的。
Unfortunately, many important environmental problems are not confined to an air, water, or land system, but involve interactions between systems.很遗憾的是，许多重要的环境问题不只局限于一个空气，水，或土壤系统，更涉及系统之间的相互作用。
A current example is the acid rain problem stemming from the emission of sulfur dioxide and nitrogen oxide gases into the atmosphere from the stacks of generating stations, smelters, and automobile exhausts。目前的一个例子是酸雨问题，根源是许多发电站，冶炼，汽车排出的废气中进入大气的二氧化硫和氮氧化物气体。
These gases are then transported by air currents over wide regions.这些气体被气流运送到广阔的区域。
Rainfall “washes them out”, creating acid rain which is harmful to aquatic life, forests, and agricultural crops.雨水“将它们洗去”，产生了对水生生物，森林和农作物有害的酸雨。Two examples of interaction between systems that cause major environmental disturbances are presented-the buildup of atmospheric carbon dioxide, a global problem, and the acid rain problem, normally of regional nature.
两个有关于系统间相互作用引起的环境问题有：空气中的二氧化碳的增加的全球性问题以及具有地域性质的酸雨问题。
Environmental Disturbances环境扰乱
Many major improvements to our standard of living can be attributed to the application of science and technology.
我们的生活水平的许多重大改进，可以归因于科学和技术的应用。
A few examples are noted here. Can you think of others?
这里举几个例子，你可以想到其他例子吗？
●The production of more and better quality food
生产更多更好的优质食品
●The creation of housing as protection from extremes from climates and as living space
创造能避免极端的气候的保护所和生活空间
●The building of fast and reliable means of transportation
建设快速和可靠的运输方式
●The invention of various systems of communication
发明各种通信系统
●The invention of machines to replace human or animal power
发明机器来取代人类或动物体力
●The supply of safe water and the disposal of wastes
安全水的供应和废物处理
●The elimination of many infectious diseases
消灭多种传染疾病
●The elimination of most waterborne diseases in the developed world through improved water technology
在多数发达国家中通过改善水技术来消除大部分水源性疾病
●The availability of leisure time through greater productivity, providing the opportunity for cultural and recreational activities
通过提高生产力，腾出闲暇时间，为进行文化和娱乐活动提供机会
●The protection from the worst effects of natural disasters such as floods, droughts, earthquakes, and volcanic eruptions.
防止最严重的自然灾害的影响，如洪水，干旱，地震和火山爆发
With these improvements, however, have come disturbing side effects, such as lost arable land, disappearing forests, environmental pollution, and new organisms resistant to controls.然而,随着(科学技术的)发展,产生了不良的副作用,比如,可耕地丢失,森林消失,环境污染,微生物滋长.
Many effects originally considered to be just nuisances are now recognized as potential threats to nature and to humans.起初只是让我们觉得讨厌的许多事物现在被认为对自然和人类存在的潜在威胁。
In an agrarian society, people lived essentially in harmony with mature, raising food, gathering firewood, and making clothing and tools from the land.在农业社会，人们基本上能与自然和谐地相处,他们在陆地上种植食物,收集木材,做衣服和工具。
The wastes from animals and humans were returned to the soil as fertilizer. Few, if any, problems of water, land, or air pollution occurred.动物和人类排放的废物作为肥料又返到土地中。很少有水污染、土地污染、和空气污染问题产生。
The cities of ancient times, particularly those of the Roman Empire, had systems to supply water and to dispose of wastes.在古代的城市，特别是像罗马帝国那类，就已经存在供水系统和处置废物系统。
The aqueducts supplying the ancient city of Rome (population about 1 million) with safe water from the Cloaca Maxima, the best known and one of the earliest sewers to be built, are examples of such systems.从一个最早建成之一且最有名的污水管-----古罗马大排泄沟，向古代的罗马城市提供安全的水的渠道，就是这样的系统的例子。
The municipal technology of ancient cities seems to have been forgotten for many centuries by those who built cities throughout Europe.古代的城市的市政技术似乎已经被那些在整个欧洲建设城市的人遗忘了许多个世纪。
Water supply and waste disposal were neglected, resulting in many outbreaks of the nineteenth century, it was not realized that improper wastes disposal polluted water supplies with disease-carrying organisms.供水和废物处置的忽略，导致爆发了许多疾病，如痢疾、霍乱、伤寒和其它水传染的疾病。
The industrial revolution in nineteenth-century Britain, Europe, and North America aggravated the environmental problems since it brought increased urbanization.直到19世纪中期，人们才意识到废物的不正确处置导致引起疾病的微生物污染了供水。
Both phenomena, urbanization and industrialization, were and are fundamental cause of water and air pollution which the cities of that time were unable to handle. 19世纪在英国、欧洲和北美的工业革命带来了工业化和城市化的增加，也加重了环境问题。城市化和工业化在过去和现在都是引起水和空气污染的根本原因，这在当时的城市还不能够处理。
Rapid advances in technology for the treatment of water and the partial treatment of wastewater took place in the developed countries over the next few decades. This led to a dramatic decrease in the incidence of waterborne diseases.在接下来的几十年，水处理和废水的部分处理技术在发达国家快速发展，这导致水传染疾病的发生率大量地减少。Note that all wastes discharge into environment, and thus pollute out water, air, and land system.注意，所有的废物排放到环境中都会污染我们的水、空气和土地系统。
Unit Two Historical Overview of Hazardous Substance Disposal in the USA
回顾美国处置危险物品的历史
Hazardous substance disposal practices in the United States have traveled full circle.在美国，处理危险物品的做法走过了迂回的道路。
Prior to 1978 there were few if any regulations regarding the disposal of these materials. 1978年之前，很少有任何关于如何处置这些物品的法规。
Improper disposal of many of these chemicals resulted in health problems for many citizens, contaminated water supplies, and destruction of wildlife. 这些化学物品的不当处置使市民陷入健康问题，水供应受污染和野生生物死亡。
With the enactment of the Resource Conservation and Recovery Act (RCRA) of 1978, manufacturing facilities now have an obligation to account for all waste materials that are generated by the facility. 随着《资源回收法》（1978年）的颁布，工厂有责任处置生产设施所产生的所有废弃材料 。
Implementation of RCRA has been slow. 但是《资源回收法》的实施一直进展缓慢。
From the very early industrial period in the United States, which started about 1920, until several years after the Second World War, there was little concern for the proper methods of disposal of waste materials that were generated as by-products during manufacturing processes. 在美国，从大约1920年开始的早期工业时代，到第二次世界大战结束后几年里，几乎没人关注处理在生产过程中作为副产品产生的废弃材料的合理方法。Up until the 1960’s it was quite common to find fresh water rivers and streams fouled with waste chemicals from manufacturing, salt water from oil production wells and waste acids from steel mill activities. 直到1920年，随处可见被生产过程产生的废化学品、油井排出的盐水和炼钢厂排出的废酸所污染的淡水河流和溪涧。
Virtually every conceivable waste oil, solvent, or resin waste could be found in the rivers.事实上，所有能够想象到的废物如废油、溶剂、废树脂都可以在河流里面找到。
The laws of the time were either non-existent or not enforced. 然而当时的相关法律要么不存在，要么是没有被实施。
The literature has many examples of health problems of individuals as well as destruction of fish and wildlife habitat. 文献记载了许多关于个体的健康问题以及鱼类、野生动物栖息地被破坏的例子。
Many other cases occurred that were not reported in the literature.许多其他发生的事件并未记载在文献上。
Other waste materials were dumped haphazardly in makeshift excavations either at the factory side or throughout the country side. 其他废弃物质被草率地埋在临时挖掘在工厂还有乡村旁边的坑洞里面。
Because of ignorance and lack of economic incentives to do so, the factories made no attempt to prevent contamination of underground water supplies by the chemicals that were disposed of. 因为对环境的忽视以及缺少经济刺激，各企业完全没有意识来保护被化学物质污染的地下水供应。
In fact, knowledgeable scientists of the time accepted land irrigation and percolation into the porous underground formations as methods of waste treatment. 事实上，当代有见识的科学家，已经接受了土地清洗以及过滤可渗透地底层这两种可作为处理废弃物治理的方法。
Although these treatment methods may have been intended for non-hazardous materials, they were employed for hazardous materials as well. 尽管这些治理方法或许用于无毒害的物质，同时也可用于有毒害的物质。
Again, there were no governmental regulations protecting the underground aquifers from these practices. 再者，并没有政府法规因保护地下蓄水层而禁止这些处理方法。
The problem of disposal of hazardous chemicals did not improve with the creation of the Environmental Protection Agency (EPA) in the 1996. 处理有毒化学物品的问题并没有因为在1996年环境保护局的成立而有所改善。
The first task of the new agency was to clean up rivers and streams. 此新兴机构的首要任务是清理干净河流水道。
Unfortunately, no one in power in the government at the time had insight into the problems that were to be created by the new agency. 不幸的是，当时政府的执政人员没有一个洞察到那个新兴机构带来的问题。
The EPA was quite successful in those early days in the enforcement of the many water pollution laws that evolved. 环境保护局在早些年的时候，对于强制执行污染法的发展还是做的相当成功的。
As the practice of the dumping of hazardous materials into the rivers and streams was eliminated, those same materials created other disposal problems. 随着往河道排放有毒物质的习惯的消除，但这些相同的物质造成了其他处理问题。
Many of the chemicals saved from the sewer were either worthless or of such a low value as to render recovery uneconomical. 在下水道中回收到的物质不是没价值的就是低廉到不足以恢复利用.
In some cases, recovery was technically impossible. As a result, the waste chemicals were disposed of by any convenient method. 一些情况下,回收在技术层面上是不可能的.所以,很多废弃的化学药物都被很简单地扔掉了.
The makeshift dumps sites were expanded. Because there were no regulations regarding disposal, 临时的垃圾场已经不得不扩大,因为没有任何关于废物丢弃的法规.
persons with no technical expertise entered into the business of waste disposal. The profits were high because these individuals did not treat the chemicals. 很多不具备专业技术知识的人就进入了废物处理的行业,由于这些人并没有真正处理掉化学药物，所以这个行业的利润相当高。
In most cases, the waste materials were transported to impounding areas located on privately owned land. 很多情况下,废弃的化学物品会被运到私有土地上的贮物地.
The factories that generated the waste felt secure in the belief that the waste transporter was disposing of the materials in an acceptable manner. 那些产生废弃物的厂家之所以感到安心是因为他们相信废物处理者会用一种合理的方法来处置掉废物.
In most cases, this was not a correct assumption. 但很多情况下,事实并非如此.
The unregulated dumps grew both in size and complexity. 乱堆放的大小规模和复杂度上都在增长.
When the dumps were in close proximity to populated areas or public water supplies, a series of problems begin to develop. 当垃圾场很接近居住区或公共水源的话,一系列的问题将会开始产生.
Citizens in the vicinity of some of the dumps began to experience adverse health problems such as skin rashes, paralysis, cancer, and birth defects. 在一些垃圾场附近的居民会开始遇到一些像皮肤疹.麻痹.癌症.先天缺陷等不利的健康问题.
In some cases, these problems have been attributed to contamination from the chemicals. 有时候,这些问题会归属于受到化学药物的污染而产生的.
Because of these concerns, the United States Congress enacted a new legislation that dealt with the issues of disposal of hazardous wastes. 由于这些担心，美国国会通过了一个新的处理有害废物过程中出现问题的法规。
This was the Resource Conversation and Recovery Act of 1987.这就是1987年的资源回收保护法。
The purpose of the Act was to allow regulation of hazardous substance disposal. 这项法案的目的是同意有害物质处理的方法。
As a result, industries that generated large quantities of these waste materials now had to ensure that the materials were disposed of in the a manner that was safe for the environment.结果导致产生大量废物的企业现在不得不确保这些物质被以对环境安全的方法处理。
Many of the improper dumps that were created prior to the RCRA legislation were created by persons with little or no financial resources.在资源回收保护法由很少或者没有经济资源的人确立之前 ，很多不合理的堆放已经造成。
As a result, the cleanup of the old sites has been taken over by the government under legislation. 使得清理旧的堆放点的工作由政府接管。
As of this time, the results of these clean up efforts have been ineffective. 在这一时期，这些清理的努力效率不高。
Because of the abuses and problems of the past, regulations have been enacted that force American industry to be responsible for hazardous waste disposal.由于过去的这些问题，强制美国工业承担有害物质处理的责任的相关法规已经颁布。
The problems were brought about by a lack of economic indentives to the industrial community.这些问题是由对工业界缺少经济动力带来的。
The problems were compounded by the inexperience and lack of insight by elected governmental officials and the governmental agencies charged with the task of regulation.政府官员缺乏经验和洞察力以及政府机构对法规的控制任务使得问题复杂化。Although sufficient legislation is now in place to solve the problem of hazardous waste disposal, it is unlikely that a true solution will be achieved for 20 years or longer.尽管现在有足够的法规来解决有害物质的处理问题，但是在二十年或更长的时间内是不可能真正的解决的。
Only through interaction between industry scientists, and government regulators will true solutions be finally realized.只有通过工业界，科学家和政府部门的共同努力，才能最终得到解决。
Unit 5 Type and Sources of Air Pollutants
空气污染物的类型和来源
What is air pollution? Air pollution is normally defined as air that contains one or more chemicals in high enough concentration to harm humans, other animals, vegetation or materials. 什么是空气污染 ？空气污染通常是指那种包含一种或多种化学物质富集到高浓度并足以伤害人类、其他动物、植物或材料的空气。There are two major types of air pollution.主要有两种类型的空气污染 。A primary air pollution is a chemical added directly to the air that occurs in a harmful concentration.初级空气污染是指有害的浓度直接进入到空气中的化学物质。It can be a natural air component, such as carbon dioxide, that rise above its normal concentration, or something not usually found in the air, such as a lead compound emitted by cars burning leaded gasoline. 这种化学物质可以是一个自然的空气成分，如超过了正常浓度的二氧化碳，，或通常不会在空气中发现的，如汽车燃烧含铅汽油所排放出来的主要尾气。A secondary air pollution is a harmful chemical formed in the atmosphere through a chemical reaction among air components.次生空气污染是指在大气中由气体成分之间发生化学反应的有害化学物质。Serious air pollution usually results over a city or other area that is emitting high levels of pollutants during a period of air stagnation.严重的空气污染通常是因为一个城市或其他地区在空气流动停滞期间排放了高浓度污染物。The geographic location of some heavily populated cities, such as Los Angeles and Mexico City, makes them particularly susceptible to frequent air stagnation and pollution buildup.一些人口稠密的城市的地理位置，例如洛杉矶和墨西哥城，使他们特别容易受到频繁的空气停滞和空气污染累积的影响。
We must be careful about depending solely on concentration values in determining the severity air pollutants.在仅从浓度来决定严重空气污染物方面，我们必须十分小心。 By themselves , measured concentrations tell us nothing about the danger caused by pollutants , because threshold levels , synergy, and biological magnification are also determining factors.通过测出的浓度自身并不能告知我们有关污染物所带来的危险的信息，因为临界浓度、协同作用还有生物放大效应都是决定因素。In addition, we run into the issue of conflicting views of what constitutes harm. 除此之外，我们碰到关于什么才构成危害的问题的争论。
Major air pollutants following are the 11major types of air pollutants.
以下11个主要类型的空气污染物是主要空气污染物：
1 .Carbon oxides: carbon monoxide, carbon dioxide.
1. 碳氧化物： 一氧化碳 ， 二氧化碳。
2. Sulfur oxides: sulfur dioxide, sulfur trioxide.
2. 硫氧化物： 二氧化硫 ， 三氧化硫。
3. Nitrogen oxides: nitrous oxide, nitric oxide, nitrogen dioxide.
3. 氮氧化物： 一氧化二氮 ， 一氧化氮 ， 二氧化氮.
4. Hydrocarbons (organic compounds containing carbon and hydrogen): methane, butane, benzene.
4. 碳氢化合物（有机含有碳氢化合物）： 甲烷 丁烷 苯。
5. Photochemical oxidants: ozone, PAN, and various aldehydes.
5. 光化学氧化剂： 臭氧，一组过氧酰基硝酸酯 和 各种醛。
6. Particulates (solid particles or liquid droplets suspended in air): smoke, dust, soot, asbestos, metallic particles (such as lead, beryllium cadmium), oil, salt spray, sulfate salts.
6. 颗粒（在空气中的固体颗粒或液滴悬浮）：烟雾，尘埃，烟尘，石棉，金属粒子（例如铅，镉铍），石油，盐雾，盐硫酸。
7. Other inorganic compounds: asbestos, hydrogen fluoride, hydrogen sulfide, ammonia, sulfur acid, nitric acid.
7. 其他无机化合物：石棉，氟化氢，硫化氢，氨气，硫酸，硝酸。
8. Other organic compounds: pesticides, herbicides, various alcohols, acids, and other chemicals.
8. 其他有机化合物： 杀虫剂， 除草剂， 各种醇， 酸 和 其他化学品。
9. Radioactive substances: tritium, radon, emissions from fossil fuel and nuclear power plants.
9. 放射性物质： 氚， 氡， 矿物燃料排放物 和 核能发电厂。
10. Heat. 10. 热。 11. Noise. 11. 噪声。
The following table summarizes the major sources of these pollutants.
Carbon oxides Carbon Monoxide (CO) :
Forest fires and decaying organic matter; incomplete combustion of fossil fuels (about two-thirds of total emissions) and other organic matter in cars and furnaces; cigarette smoke森林火灾和腐烂的有机物质;不完全燃烧矿物燃料（约占三分之二的总量）和其他来自汽车和炉的有机质;香烟烟雾
Carbon dioxide (CO2) : Natural aerobic respiration of living organisms; burning of fossil fuels
自然有氧呼吸的生物体; 燃烧化石燃料
Sulfur oxides (SO2 and SO3) ：Combustion of sulfur-containing coal and oil in homes, industries and Power plants; smelting of sulfur-containing ores; volcanic eruptions 家庭、工厂和发电厂燃烧含硫的煤和石油；冶炼含硫矿石；火山爆发
Particulates dust soot and oil : 煤烟粉尘颗粒物和石油
forests fires , wind erosion, and volcanic eruptions; coal burning; farming, mining construction, road building ,and other land-clearing activities; chemical reactions in the atmosphere; dust stirred up by automobiles; automobile exhaust; coal-burning electric power and industrial plants 森林火灾，风蚀，和火山爆发; 燃煤; 农业，采矿工程，道路建设，以及其他土地清理活动; 大气中的化学反应；汽车引发的粉尘 ；汽车尾气；燃煤电力厂房和工业厂房
Nitrogen oxides (NO and NO2):
High-temperature fuel combustion in motor vehicles and industrial and fossil fuel power plants; lighting 高温燃料燃烧机动车辆，工业和矿物燃料发电厂;照明
Photochemical oxidants 光化学氧化剂
Sunlight acting on hydrocarbons and nitrogen oxides
碳氢化合物和氮氧化物在阳光下反应
Hydrocarbons 碳氢化合物
Incomplete combustion fossil fuels in automobiles and furnaces; evaporation of industrial solvents and oil spills; tobacco smoke; forest fires; plant decay (about 85 percent of emissions ) 不完全燃烧化石燃料的汽车和火炉；蒸发的工业溶剂和石油泄漏；烟草烟雾；森林火灾；植物的腐烂（大约百分之85的排放）
Pesticides and herbicides :
Agriculture; forestry; mosquito control农业;林业;蚊虫控制
Asbestos:石棉Asbestos mining; spraying of fireproofing insulation in buildings; deterioration of brake linings 石棉开采;防火隔热建筑的喷漆;制动片的变质
Metals and Metal Compounds: 金 属 和 金 属 化合 物
Mining； industrial processes; coal burning; automobile exhaust挖掘；工业生产过程;燃煤;汽车尾气
Hydrogen Sulfide (H2S): Chemical industry; petroleum refining化学工业;石油炼制
Ammonia (NH3) : Chemical industry; petroleum refining化学工业;石油炼制
Sulfuric Acid (H2SO4) :
Reaction of sulfur trioxide and water vapor in atmosphere; Chemical industry三氧化硫和水汽在大气中反应; 化学工业
Nitric Acid (HNO3) :
Reaction of sulfur trioxide and water vapor in atmosphere;
Chemical industry三氧化硫和水汽在大气中反应; 化学工业
Noise : Automobiles, airplanes, and trains; industry; construction
汽车，飞机，列车;产业建设
Other Inorganic Hydrogen Fluoride (HF) :
Petroleum refining; glass etching; aluminum and fertilizer production
石油炼制;玻璃刻蚀;铝和化肥生产
Exercises
4 .To eacape the smog you might go home, close the doors and windows, and breathe in clean air. But a number of scientists have found that the air inside homes and offices is often more polluted and dangerous than outdoor air on a smoggy day. The indoor pollutants include: (1) nitrogen dioxide and carbon monoxide from gas and wood-burning stoves（炉） without adequate（适当的） ventilation（通风）; (2) carbon monoxide, soot（煤烟）,and cancer-causing benzopyrene（苯并芘） (from cigarette smoke); (3) various（各种） organic compounds（化合物） from aerosol（气溶胶、气雾剂、烟雾剂） spray（喷射） cans and cleaning products; (4) formaldehyde（甲醛） (which causes cancer in rats) from urea－formaldehyde（尿素甲醛） foam（泡沫材料） insulation（绝缘材料）,plywood（夹板）,carpet（地毯） adhesives（黏合剂）,and particle（微粒） board; (5)radioactive（放射性的） radon and some of its decay（衰退） products from stone, soil, cement（水泥）,and bricks（砖）;and (6) ozone（臭氧） from the use of electrostatic air cleaners. 为了逃避烟雾，你需要回到家中，关闭门窗，并且在干净的空气中呼吸。但一些科学家发现，在烟雾弥漫的日子，家中以及办公室中的空气经常比室外的空气含有更多的污染物和危险物。室内污染物包括：（1）来源于煤气以及在没有适当的通风下火炉中木的燃烧所产生的二氧化氮和一氧化碳；（2）一氧化碳，煤烟，致癌物质苯并芘（来源于香烟）；（3）从气雾剂喷射罐和清洁用品挥发的各种有机物化合物；（4）从尿素甲醛泡沫绝缘材料、夹板、地毯黏合剂和微粒木板中散发出的甲醛（可以在老鼠身上致癌）；（5）放射性射线和其几种从石头、沙、水泥、砖中放射出的衰退物；（６）使用电空气清新器所产生的臭氧。
Unit 7 Conventional Technology of Air Pollution Control
大气污染控制的常规技术
The principal means for control of particulate emissions from industrial sources are cyclones，electrostatic precipitators, fabric filters and scrubbers. 控制工业来源的颗粒物的排放的主要方法是利用旋风分离器、静电除尘器、布袋过滤器和洗涤器。In addition to these conventional devices, granular bed and panel bed filters have been applied to a limited extent and research is being conducted on devices or combinations of conventional devices, such as charged drop let scrubbers.除了以上的常规设备以外，颗粒层过滤器和平板过滤器在一定程度上得到应用，并且正在开展对设备或组合常规设备的研究，例如荷电液滴洗涤器。
Cyclones
旋风分离器
Cyclonic collectors are round conically shaped vessels in which the gas stream enters tangentially and follows a spiral path to the outlet. 旋风分离吸收器是圆锥形的容器，气体流切向进入并且顺着螺旋状的管道到出口。The spiral motion produces the centrifugal forces that cause the particulate matter to move toward the periphery of the vessel and collect pm the walls and fall to the bottom of the vessel. 这种螺旋运动产生离心力，使颗粒物沿着容器的外围移动被聚集在壁面然后掉落在容器底部。 The centrifugal force is the major force causing separation of the particulate in a cyclone separator.离心力是引起颗粒物在旋风分离器里分离主要作用力。
The cyclonic collectors are generally of two types: the large diameter, lower efficiency cyclones, and the small diameter, lower efficiency cyclones, and the small diameter, multitube high-efficiency units. 旋风分离除尘器大致分为两种：大径低效分离器和小径多管高效分离器。The larger cyclones have lower efficiencies especially on particles less than 50 um. 大直径的旋风分离除尘器的效率会比较低特别是对直径小于50微米的颗粒。However, they have low initial cost and usually operate at pressure drips of 1 to 3 inches of water. 但是，它们的运行成本较低，一般在1到3英寸水柱的压力降下运行。The multitube cyclones are capable of efficiencies exceeding 90% but the cost is higher and their pressure drop is usually 3 to 5 inches of water. 多管式的旋风分离除尘器效率通常能够达到90%以上，不过它的运行成本就比较高，一般在3到5英寸水柱的水压降下运行。They are also more susceptible to plugging and erosion. 它们经常被堵塞和更加容易受到腐蚀。The large cyclones are often used as a part of the process when the gas stream is heavily laden with part of the product such as in coal dryers, alfalfa dehydrators and milling operations. 大直径的旋风分离除尘器经常用作于当气流里充满产物的一部分时的过程，比如煤干燥器、紫苜宿脱水器、碾磨的运转。They are widely used in grain elevators, sawmills, asphalt plants and detergent manufacture. 它们被广泛运用于谷物运输、锯木、沥青制造装置和清洁剂的生产中。
Fabric Filters
布袋过滤器
Fabric filter systems, i.e., baghouses, usually consist of tubular bags made of woven synthetic fabric or fiberglass, in which the dirty gases pass through the fabric while the particles are collected on the upstream side by the filtering action of the fabric. 布袋过滤器系统，例如，布袋除尘器，通常由合成纤维或玻璃纤维制成的管状布袋组成，含尘气体通过布袋时颗粒物在纤维的过滤作用下累计在布袋上游。 The dust retained on the bags is periodically shaken off and falls into a collecting hopper for removal.定期将留在布袋里的尘土敲下并让它掉入收集漏斗以便清除。
Fabric filters usually provide very high collection efficiencies, exceeding 99.5%, at pressure drops usually ranging from 4 to 6 inches of water. 布袋过滤器通常有较高的除尘效率，超过99.5%，压力降一般在4~6英寸水柱之间。The amount of filter area required is often based on an air-to-cloth ratio of 11.5 to 3.0 cfm of gas/ft2 of cloth. 必需的过滤面积经常基于11.5~3.0cfm/ft2 布的气布比。The maximum operating temperature for a baghouse is 550°F using fiberglass bags. 利用玻璃纤维制成布袋除尘器最高的运行温度是550°F。However , there may also be a minimum temperature limitation so as to maintain the g as temperature 50°F to 75°F to above the dew point. 然而，也存在最低的温度限制使得气体温度维持在高于露点温度50°F到75°F之间。Inlet dust loadings range from 0.1 to 10.0 grains/ft3 of gas. 进口粉尘浓度在0.1~10.0grains/ft3 气体之间。Higher concentrations in some industries are removed by a precleaning device, such as a low efficiency cyclone. 在某些工厂里高浓度的含尘气体要先用预洗涤装置分离，比如低效旋风分离器。
The baghouse has found wide application in many industries, including mining operations, food processing, grain elevators, soap and detergents, plastics manufacture and numerous other. 布袋分离器已经在很多工业领域中得到广泛的应用，包括采矿业，食品加工，谷物提升，肥皂和清洁剂，塑料制造以及众多其他工业。Some of the industries that employ large baghouse operations are carbon black, cement, electric arc furnaces, foundry cupolas and nonferrous smelting operations.一些工业生产使用大型布袋除尘器运作，例如碳黑，水泥，电弧炉，炼铁炉和有色技术冶炼作业。
Gas cleaning by fabric filtration is suited for applications where dry particulates are handled or where water in the process gases is in the vapor stage. 布袋过滤净化气体适用于干燥颗粒物少的情况或者水在工业废气中是蒸汽状态的情况。The basic filter collector or baghouse is capable of operating in excess of 99% efficiency, although satisfactory operation of the system is contingent upon the characteristics of the gas stream and the particulate matter being removed. 尽管系统是否良好地运转视气流的特性和颗粒物的分离量而定，但标准过滤器或者布袋除尘器能运行达到99%的效率。Basically, the unit consists of compartments containing rows of filter bags or tubes. 运作单元主要由包含一排排的过滤袋或者滤管的过滤单元组成的。
Wet Scrubbers
湿式洗涤器
Wet collectors use water“sprays”to collect and remove particulate matter.湿式洗涤器利用水喷雾收集和分离颗粒物。Here are many variations of wet collectors but they may generally be classified as low of high energy scrubbers. 湿式洗涤器有很多种类，但是它一般分为低能和高能洗涤器。Low energy scrubbers of 1 to 6 inches of pressure drop may consist of simple spray tower, packed tower or impingement plate tower. 压降在1至6英寸的低能洗涤器可能是简单的喷雾塔，填料塔或撞击板塔组成。The water requirement may be 3 to 6 gal/1,000ft³ of gas and collection efficiencies can exceed 90 to 95%.水的要求是3至6 gal/1000ft ³的气体，收集效率可以超过90至95 ％。The lower energy scrubber finds frequent application in incinerators, fertilizer manufacturing, lime kilns. And iron foundries.低能洗涤器在焚化装置，肥料生产，石灰炉和铸铁车间得到广泛的应用.
The high energy scrubber, or Venturi, imparts high velocity to the gas stream by means of converging-diverging duct section, and contact the stream with injected water.高能洗洗涤器或者文丘里管，用收缩—扩大管截面的方法给气流提供高速，与上面注入的水流接触。The high velocities provide increased collection efficiency, up to 99.5%, but the pressure drop may range from 10 to 60 inches of water. This requires a draft fan with high power input. 高速供给提高了吸收效率，高达99.5%，但是压力将会达到10~60英寸水柱，这就要求有一个高能输入的引风机。The Venturi scrubber is often used in conjunction with steel furnaces, pulp mills and foundry cupolas.文丘里洗涤器经常应用于炼钢炉、造纸厂和炼铁炉中。
The wet scrubbers can provide high collection efficiency but may involve treatment of liquid wastes with settling ponds.湿洗涤器可提供高效率，但可能涉及治疗液体废物的沉淀池。They also saturate the gas stream and produce a resultant steam plume. 他们还浸透的天然气流和由此产生蒸汽柱。The principal mechanisms involved in wet scrubbing are： increasing the size of the particles by combination with liquid droplets thereby increasing their size so they may be collected more easily ，and \or trapping them in liquid film and washing them away.湿洗的主要原理是：越来越多的小粒子的结合成液滴从而增加其大小，以便可以更容易地收集他们，或者用液膜捕获他们和洗去他们。
Electrostatic Precipitators
静电除尘器
Gas cleaning by electrostatic precipitation is particularly suited for gas streams which can be easily ionized and which contain either liquid or solid particulate matter. 静电除尘器的气体清除尤其适合容易带电的气流和包含液体或固体的带电物质。 The method of removal consists of passing the particle-laden gas through an electrostatic field produced by a high voltage electrode and grounded collection surface.去除方法为使载满微粒的气体通过一个高压电极和接地捕集板产生的静电区域。The gas is ionized by the high voltage discharge and the particulate matter is charge by the interaction of the gas ions.气体被高压电极电离，同时气体离子的相互作用使颗粒物带上电荷。The particle migrate to the collecting surface which has an opposite polarity and neutralized.接着颗粒物移动到与它相反的极性收集板上，然后中和。
The operating principle of electrostatic precipitation thus requires three basic steps :(1)electrical charging of the suspended particulate matter; (2)collection of the charged particulate matter on a grounded surface ;（3）removal of the particulate matter from the collecting surfaces by mechanical or flushing with liquids. 因此静电的操作原理需要三个基本步骤：(1) 悬浮颗粒物的电能交换；(2)带电粒子物质在接地板的收集；(3)通过机械刮除或者用水冲洗收集表面的颗粒物质。
