1、Unit26Environmental EngineeringTextEnvironmental 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 ai
2、r,land,and water environments and 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 significa
3、ntly contributed to the formation 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
4、the environmental engineer.Today,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 wa
5、ste management.Other specialties 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 sou
6、rces,to those from large areas,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 unre
7、asonably interfere with public 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
8、,and sulfur oxides.Meteorological 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
9、to follow specific patterns from 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 uncontroll
10、ed(fugitive)sources,such as wind-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 fabr
11、ic filters are used.Gas controls 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 a
12、nd means to provide ample quantities 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 collec
13、tion,surface water treatment,saline 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 filtr
14、ation.In sequence,the traditional 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.Treatmen
15、t of other sources generally requires 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 a
16、nd saline waters also require site-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.Ele
17、vated storage tanks with gravity 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 deve
18、loping standards for the drinking 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,indust
19、rial facilities,and institutions,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 pollut
20、ants,such as phosphorus from a 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 d
21、omestic wastewaters.Additional 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 m
22、atter,either of which may damage 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 orga
23、nics generally are treated with 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
24、 or brewery wastes,are considered 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 mos
25、t practiced means of final disposal.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,
26、which historically included pond 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
27、the production,movement,and control 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 w
28、ashes deposited materials directly 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 sy
29、stems to minimize environmental 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 colle
30、cted in the same(combined)sewer.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
31、for combined sewer overflow treatment 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 increa
32、se,the environmental engineer also 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,a
33、nd the amount varies by source,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,w
34、hich also may be used for codisposal 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.Sour
35、ce or central facility separation 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 managementHazar
36、dous wastes are present throughout 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 p
37、roducts pose unreasonable risks 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,reactiv
38、ity,and/or EP toxicity.Household 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 a
39、nd/or adaptation of proven practices 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
40、,solid waste treatment,solidification 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 o
41、f the waste into the environment.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,en
42、vironmental engineers drew their 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,chemistr
43、y,and hydrology.Since the environmental 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 environ
44、mental engineers work in the academic 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
45、；焚化amplea.丰富的；足够的；宽敞的salinea.盐的；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 matt
46、ern.颗粒物point sourcen.点源（污染源）reverse 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
47、素对空气污染的形成和持续起到重要作用。（2）Water supply 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
48、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、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
49、 which may damage or interfere 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,a
50、nd major stream channel improvements.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 so
