1、TextEnvironmental engineering is essential for development of facilities for protection of the environment and for the proper management of natural resources.The environmental engineer places special attention on the biological,chemical,and physical reactions in the air,land,and water environments a
2、nd on improved technology for integrated management systems,including reuse,recycling,and recovery measures.Environmental engineering began with societys need for safe drinking water and management of liquid and solid wastes.Urbanization and industrialization significantly contributed to the formati
3、on of unsanitary conditions in many areas.The terms“public health”and“sanitary”were first applied to those engineers seeking solutions to the elimination of waterborne disease in the 1800s.More recently,abatement of air and land contamination became new challenges for the environmental engineer.Toda
4、y,management of toxic and hazardous wastes are additional focus areas.The principal environmental engineering specialties are well established:air quality control,water supply management,wastewater disposal,storm water management,solid waste management,and hazardous waste management.Other specialtie
5、s include industrial hygiene,noise control,oceanography,and radiology.TextAir quality controlAir quality control needs vary from correction of air pollution problems originating from relatively small areas,such as an industrial park impacted by one or more emission sources,to those from large areas,
6、such as an urban area impacted by a number of sources and a variety of contaminants.Air pollution is used to describe the presence in the atmosphere of one or more contaminants in quantities and/or characteristics that will,over a period of time be injurious to or unreasonably interfere with public
7、health and welfare or natural environmental processes.Contaminants are categorized as particulate matter and gases and their associated forms,including dust,smoke,fumes,mist,and vapor.The primary gaseous air contaminants are carbon monoxide,hydrocarbons,nitrogen oxides,and sulfur oxides.Meteorologic
8、al and topographical factors contribute to the creation and continuation of air pollution under specific site conditions1.Temperature inversions prevent upward diffusion,and very low wind speeds allow emissions to remain near their source.Some terrains cause emissions to follow specific patterns fro
9、m one area to another.TextGenerally,sources of air contaminants may be classified as stationary,mobile,or fugitive.Respectively,they are attributed to point sources,such as industrial stack emissions;transportation activities,such as automobile emissions;and uncontrolled(fugitive)sources,such as win
10、d-blown dusts from stockpiles.The environmental engineer is instrumental in controlling particulate and gas sources of air contaminants.Source control is the first abatement method considered.For particulates,settling chambers,inertial separators,wet scrubbers,and fabric filters are used.Gas control
11、s include absorption,adsorption,condensation,flaring,and incineration.Other areas of practice address acid rain issues,fugitive emissions,odor control,indoor air quality,and noise abatement.Water supply managementHistorically,the environmental engineer has found ways and means to provide ample quant
12、ities of quality drinking water for domestic use as well as quality water for commercial and industrial uses.Water supply issues include demand projections,quality requirements,surface water and groundwater source evaluations,groundwater production,surface water collection,surface water treatment,sa
13、line water treatment,nonconventional water production,and treated water distribution2.TextThe typical surface water treatment plant uses chemicals to enhance removal of suspended solids and for disinfection.Physical treatment processes include simple settling and filtration.In sequence,the tradition
14、al unit processes are rapid mix,coagulation,flocculation,sedimentation,filtration,and disinfection.Auxiliary systems are needed for chemical feed facilities and for sludge handling.More specialized processes include carbon adsorption,ion exchange,and softening.Treatment of other sources generally re
15、quires site-specific determination of raw water quality.Often,the quantity of demand will influence the cost-effective selection of treatment processes.Groundwater supplies require well development and treatment,such as aeration,softening,and/or disinfection.Brackish and saline waters also require s
16、ite-specific determination of treatment processes3.Typical processes include membrane technology,such as reverse osmosis and electrodialysis.The water distribution system includes(small)service and distribution lines,(large)transmission mains,and storage facilities.Elevated storage tanks with gravit
17、y distribution and/or ground storage tanks with distribution pumping are designed to provide the quantity and pressure required to satisfy system demands.Generally,fire demands control design.Since the early 1900s,the American Water Works Association(AWWA)has been developing standards for the drinki
18、ng water industry.The standards also are designed to enhance water utility operations while addressing hundreds of products and procedures.TextWastewater DisposalWastewater is the combination of liquid and water-transported wastes from homes,commercial buildings,industrial facilities,and institution
19、s,along with any groundwater infiltration and surface water and stormwater inflow that may enter the sewer system.At a minimum,treatment is required for suspended solids and for dissolved organics.Special processes may be necessary to achieve removal of specific pollutants,such as phosphorus from a
20、municipal source or heavy metals from a plating facility.The minimum levels of treatment are established by regulation.For example,in the United States,85%removal of oxygen-demanding organics and suspended solids and disinfection is the minimum level of treatment for domestic wastewaters.Additional
21、treatment,including nutrient removal,is dictated by receiving-stream assimilative capacity and downstream water uses.Physical processes are used to remove suspended solids.Screens remove debris and other large solids,and gravity or aerated grit chambers capture sandy matter,either of which may damag
22、e or interfere with subsequent pumping and treatment units4.Gravity sedimentation normally is used to remove finer(organic)suspended solids.For special applications,centrifugation,dissolved air flotation,and filtration are used to remove suspended solids.Dissolved organics generally are treated with
23、 biological processes.The more common systems are aerobic(with oxygen)and include aerobic or facultative pond,trickling filter,and activated sludge processes.TextConcentrated wastes,such as primary sludges,or high-strength industrial wastewaters,such as meat processing or brewery wastes,are consider
24、ed for anaerobic(without oxygen)treatment processes.Sludges,principally from biological processes,require special handling.The sequence of processes includes stabilization,conditioning,dewatering,drying,and residual disposal.Land application and landfilling are the most practiced means of final disp
25、osal.Special concerns for land-applied and composted sludges arise due to the concentration of contaminants,such as heavy metals,and presence of pathogens in these sludges.Of the many other types of treatment process,increased attention is now given to natural systems,which historically included pon
26、d systems and,later,various modes of land application.Newer technology uses natural and constructed wetlands to provide high-quality effluents.Storm water ManagementStormwater management encompasses all elements of the hydrologic cycle but focuses on how humans affect the production,movement,and con
27、trol of surface runoff.In a natural system,the rate of surface runoff is controlled by the rainfall rate,soil conditions,vegetation,and subsurface geology.TextUrbanization creates large impervious areas that increase the quantity and peak rate of runoff.Rainfall then washes deposited materials direc
28、tly into surface waters,causing stream pollution.Organics create oxygen demands,nutrients accelerate lake eutrophication,and heavy metals accumulate in bottom sediments.Environmental engineers use modern storm water management practices to employ natural and manmade systems to minimize environmental
29、 damage.A complete storm water management program contains many elements,including on-site infiltration and detention,collection and transport systems,regional flood control,and major stream channel improvements5.In years past,sanitary wastes and storm water were collected in the same(combined)sewer
30、.During heavy rainfall,the sewers would overflow,creating water pollution problems.Many of these combined sewers have been separated,and the remaining overflows are treated as point sources.Storm water management practices are used to lessen the requirements and costs for combined sewer overflow tre
31、atment facilities.Solid waste managementSolid waste management continues to progress from conventional collection techniques and disposal methods to an integrated approach focused on source reduction and recycling.TextAs land becomes more limited and regulations increase,the environmental engineer a
32、lso directs attention to development and application of advanced disposal technologies.Solid wastes are those materials,other than liquids or gases,that are deemed by their owner to no longer possess value and are discarded.They are generated by almost every activity,and the amount varies by source,
33、season,geography,and time.Historically,solid waste disposal consisted of open dumping but now is carried out in double-lined landfills with collection of and controls for gases and/or leachate.Other disposal means include composting and various incineration processes,which also may be used for codis
34、posal of wastewater treatment sludges.These disposal means typically require controls for created pollutants,such as leachate and odor from compost operations and chemical and particulate emission from incinerator combustion.Recovery and reuse are practiced widely.Source or central facility separati
35、on is used for a variety of products including paper,glass,plastics,ferrous metals,and nonferrous metals.Also,refuse-derived fuels may be used for energy production,and yard wastes may be composted to produce a humus soil conditioner.TextHazardous waste managementHazardous wastes are present through
36、out the world as by-products of growth and development and include pesticides from agricultural lands,gasoline leakage from service stations,heavy metals from plating solutions,medical wastes from hospitals,and radioactive wastes from nuclear power plants,These waste products pose unreasonable risks
37、 to human health and safety,property values and utilization,and all other components of the environment.The U.S.Environmental Protection Agency regulations define hazardous wastes by inclusion of specific lists and by characteristics of ignitability,corrosivity,reactivity,and/or EP toxicity.Househol
38、d wastes,domestic sewage,and certain other wastes are excluded from these regulations.The technology for treatment and disposal of hazardous wastes is the most rapidly developing area of environmental engineering.A significant portion of this technology is refinement and/or adaptation of proven prac
39、tices in air quality control,wastewater treatment,and solid waste management.Also,the environmental engineer must learn more about hydrogeology to assess the subsurface disposition of hazardous wastes.Hazardous waste treatment is characterized as liquid waste treatment,solid waste treatment,solidifi
40、cation and stabilization,thermal destruction,and land disposal.TextRemedial action is distinguished as surface water control,air pollution control,or in situ treatment.At a hazardous waste treatment or disposal site,the environmental engineer must obstruct the routes of the waste into the environmen
41、t.Principal routes include surface water contamination from runoff or overflows;groundwater contamination from leaks or leachate;air contamination from open burning,evaporation,or fugitive dusts;fire and/or explosion;and health risks from human contact.Traditionally,environmental engineers drew thei
42、r basic education and training from civil engineering programs.In order to broaden their perspective and capabilities,contemporary environmental engineers pursue course work and postgraduate training in professional areas including biology,chemical engineering,chemistry,and hydrology.Since the envir
43、onmental engineer is now dealing with sensitive public issues,training in public education,public policy,and other social sciences is desirable.Principal areas of employment for practicing environmental engineers include consulting,industry,and government.Other environmental engineers work in the ac
44、ademic community or direct the development and production of equipment.After satisfying experience and testing requirements,the environmental engineer obtains professional engineering registration.abatementv.减少，减退；缩减hygienen.卫生；卫生学adsorptionv.吸附；表面吸收incinerationv.把烧成灰烬；焚化amplea.丰富的；足够的；宽敞的salinea.盐的
45、；含盐的infiltrationv.渗入，渗透eutrophicationn.富营养化pathogenn.病原体；病菌effluentn.污水；流出物；废气impervious a.不受影响的，无动于衷的；不能渗透的geographyn.地形；地势；地貌ferrousa.亚铁的；铁的，含铁的ignitabilityn.可燃性；易燃性hydrogeologyn.水文地质学remediala.治疗的；补救的；矫正的leachaten.沥出液，浸出液，沥滤液wastewater disposaln.废水处理particulate mattern.颗粒物point sourcen.点源（污染源）rev
46、erse osmosis v.反渗透sewer systemn.污水管道系统；排水系统dissolved organicsn.溶解性有机物hydrologic cyclen.水循环New Words and PhrasesNotes（1）Meteorological and topographical factors contribute to the creation and continuation of air pollution under specific site conditions.在特定环境条件下，气象学和地形学因素对空气污染的形成和持续起到重要作用。（2）Water sup
47、ply issues include demand projections,quality requirements,surface water and groundwater source evaluations,groundwater production,surface water collection,surface water treatment,saline water treatment,nonconventional water production,and treated water distribution.供水问题包括用水量预测、水质要求、地表水和地下水源评估、地下水开采
48、、地表水采集、地表水处理、盐水处理、非常规水生产和处理水的输配等。（3）Brackish and saline waters also require site-specific determination of treatment processes.对于咸水和盐水，还需要根据现场确定处理工艺。Notes（4）Screens remove debris and other large solids,and gravity or aerated grit chambers capture sandy matter,either of which may damage or interfere
49、with subsequent pumping and treatment units.筛网能够去除碎片和其他较大的固体，重力或曝气沉淀池能够捕获砂质，这两类杂质都可能损坏或妨碍后续的泵和处理设备。（5）A complete storm water management program contains many elements,including on-site infiltration and detention,collection and transport systems,regional flood control,and major stream channel improve
50、ments.一个完善的雨水管理计划包括许多方面，例如现场渗滤和截留、收集和运输系统、区域洪水控制和主河道改造等。1.从废水排入江河处的下游取引用水时，不仅要特别注意从废水中清除有机物，而且要注意微生物的消毒处理。2.臭氧是一种上好的化学消毒剂，因为它对细菌病毒和原生动物都是最有效的消毒剂；而且与氯不同，当水中存在有机物时，它不会形成致癌物。3.Solid waste generation can be subdivided into residential and nonresidential,depending on its source.Residential wastes are gen
