环境工程专业外语.docx

环境工程专业外语.docx

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环境工程专业外语

UNITONE

TextCollectionofWastewater

●Backgroundknowledge（在排水管网中将要学到相关知识！

）

废水的来源：

废水产生了，怎么办？

利用管道收集系统（分为分流制管道系统、合流制管道系统、混合制管道系统）进行收集，收集以后怎么办呢？

修建污水处理设施（污水处理厂）将污水进行处理后达标排放。

污水收集系统本身可根据收集污水的范围分为室内污水管道系统、室外污水管道系统。

在污水管道收集系统中，除了想要收集的这部分污水外，还不可避免地会收集到渗入的地下水以及雨天进入系统的雨水（流入水）。

●NewWordsandExpressions

（1）closetn.盥洗室，厕所（wc）

（2）sanitarywaste生活污水，生活废物，卫生设备排出的废物（3）seweragen.污水（排水）工程，排水系统；污水（4）sewagen.污水;下水道（系统）（5）inflown.流入物,流入（量）,进水（气）（6）manholen.人孔,检查井（孔）,检修孔,探井（7）flumen.水（渡）槽（8）mandatorya.必须遵循的,强制性的（9）detrimentala.有害的,不利的（10）easementn.附属建筑物（11）keepclearof避开,不接触（12）perforatev.穿[钻,打,冲]孔（13）elevationn.高程[度,地];上升,提高（14）evenvt.使平均[平衡]（15）conduitn.水[输送]管,水道,水（沟）渠（aquiduct）（16）terrainn.地带,地形,场所（17）collectingsewer污水支管（18）sizen./vt.尺寸,大小;依一定尺寸制造,（管材,轧管）定径（19）surchargevt.超（过）载,（使负担）过重（20）asbestosn.石棉（21）interceptvt.截取（断,击）,拦截（22）colloquiallyad.口语地,通俗地（23）interceptorn.截流管,截水沟

●

TextCollectionofWastewater

Inoldcities,drainageditcheswereconstructedforthesolepurposeofmovingstormwateroutofthecities.Eventually,theseditcheswerecoveredoverandbecamewhatwenowknowasstormsewers.

[2]Aswatersuppliesdevelopedandtheuseoftheindoorwaterclosetincreased,theneedfortransportingdomesticwastewaters,calledsanitarywastes,becameobvious.Thiswasaccomplishedinoneoftwoways:

（1）dischargeofthesanitarywastesintothestormsewers,whichthencarriedbothsanitarywastesandstorm-water,andwereknownascombinedsewers,and

（2）constructionofanewsystemofundergroundpipesforremovingthewastewater,whichbecameknownassanitarysewers.

Newercities,andmorerecentlybuilt（post-1900）partsofoldercitiesalmostallhaveseparatesewersforsanitarywastesandstormwater.Inthistext,stormsewerdesignisnotcoveredindetail.Emphasishereisonestimatingthequantitiesofdomesticandindustrialwastewatersandinthedesignoftheseweragesystemstohandletheseflows.

Thetermsewageisusedheretomeanonlydomesticwastewaters.Inadditiontosewage,however,sewersalsomustcarryindustrialwastes,infiltrationandinflow.

Thequantityofindustrialwastescanusuallybeestablishedbywateruserecords.Alternatively,theflowcanbemeasuredinmanholeswhichserveonlyaspecificindustry,usingasmallflowmeterinamanhole.Typically,aParshallflumeisused,andtheflowrateiscalculatedasadirectproportionoftheflowdepth.Industrialflowsoftenvaryconsiderablythroughoutthedayandcontinuousrecordingismandatory.

Infiltrationistheflowofgroundwaterintosanitarysewers.Sewersareoftenplacedunderthegroundwatertableanycracksinthepipeswillallowwatertoseepin.Infiltrationistheleastfornewwell-constructedsewers,andcangoashigh500m3/km-day（200,000gal/mi-day）.Commonly,foroldersystems,700m3/km-day（300,000gal/mi-day）isusedinestimatinginfiltration.Thisflowisofcoursedetrimentalsincetheextravolumeofwatermustgothroughthesewersandthewastewatertreatmentplant.Itthusmakessensetoreducethisasmuchaspossiblebymaintainingandrepairingsewers,andkeepingsewerageeasementsclearoflargetreeswhichcouldsendrootsintothesewersandcauseseveredamage.

Thethirdsourceofflowinsanitarysewersiscalledinflow,andrepresentsstormwaterwhichiscollectedunintentionallybythesanitarysewers.Acommonsourceofinflowisaperforatedmanholecoverplacedinadepression,sothatstormwaterflowsintothemanhole.Sewerslaidnexttocreeksanddrainagewayswhichriseuphigherthanthemanholeelevation,orwherethemanholeisbroken,arealsoamajorsource.Lastly,illegalconnectionstosanitarysewers,suchasroofdrains,cansubstantiallyincreasethewetweatherflowoverthedryweatherflow.Commonly,theratioofdryweathertowetweatherflowisbetween1:

1.2and1:

4.

[8]Domesticwastewaterflowsvarywithseason,dayoftheweekandthehouroftheday.Thethreeflowsofconcernwhendesigningsewersaretheaverageflow,thepeakormaximumflow,andtheextrememinimum.Theratioofaveragetoboththemaximumandminimumflowsisafunctionofthetotalflow,sinceahigheraveragedailydischargeimpliesalargercommunityinwhichtheextremesareevenedout.

Sewersthatcollectwastewaterfromresidencesandindustrialestablishmentsalmostalwaysoperateasopenchannels,orgravityflowconduits.Pressuresewersareusedinafewplaces,buttheseareexpensivetomaintainandareusefulonlywhenthereeitheraresevererestrictionsonwateruse,ortheterrainissuchthatgravityflowconduitscannotbeefficientlyconstructed.

Buildingconnectionsareusuallymadewithclayorplasticpipe,6in.indiameter,tothecollectingsewerswhichcommonlyrununderthestreet.Collectingsewersaresizedtocarrythemaximumanticipatedpeakflowswithoutsurcharging（fillingup）andarecommonlymadeofclay,asbestos,cement,concreteorcastironpipe.Theydischargeinturnintointerceptingsewers,knowncolloquiallyasinterceptors,whichcollectlargeareasanddischargefinallyintothewastewatertreatmentplant.

Collectingandinterceptingsewersmustbeplacedatasufficientgradetoallowforadequatevelocityduringlowflows,butnotsogreatastopromoteexcessivelyhighvelocitieswhentheflowsareattheirmaximum.Inaddition,sewersmusthavemanholescommonlyevery120-180（400-600ft）tofacilitatecleaningandrepair.Manholesarealsonecessarywheneverthesewerchangesgrade（slope）,sizeordirection.

Insomecasesitbecomeseitherimpossibleoruneconomicaltousegravityflow,andthewastewatermustbepumped.

EXERCISES

Readingcomprehension:

saywhetherthefollowingstatementsareTrue（T）orFalse（F）accordingtothetext.

1.Sewersforbothsanitarywasteandstormwatercanbefoundinalmostallnewcitiesandmanypartsofoldcities.（）

2.Therearealtogetherthreesourcesofflowinsanitarysewers.（）

3.WhenaParshallflumeisused,wecangettheflowratefromtheflowdepthwithoutanycalculation.（）

4.Inflowmainlyreferstothestormwaterwhichcomesintothesewersfromthemanholes.（）

ReadingMaterialAStormSewerSystem

Surfacewatersenterastormdrainagesystemthroughinletslocatedinstreetguttersordepressedareasthatcollectnaturaldrainage.Coolingwaterfromindustriesandgroundwaterseepagethatentersfootingdrainsarepumpedtothestormsewer,sincethepipesaretobackflowwhenthepipesurcharges.Thecurbinlethasaverticalopeningtocatchgutterflow.Althoughtheguttermaybedepressedslightlyinfrontoftheinlet,thistypeoffersnoobstructionstotraffic.Thegutterinletisanopeningcoveredbyagratethroughwhichthedrainagefalls.Thedisadvantageisthatdebriscollectingonthegratemayresultinpluggingofthegutterinlet.Combinationinletscomposedofbothcurbandgutteropeningsarealsocommon.Streetgrade,curbdesign,andgutterdepressiondefinethebesttypeofinlettoselect;nevertheless,minimizingtrafficinterferenceandeliminatingpluggingoftentakeprecedenceoverhydraulicefficiency.

Catchbasinsunderstreetinletsareconnectedtothemainstormsewerlocatedinthestreetright-of-way,oftenalongthecentreline,byshortpipelines.Manholesareplacedatcurbinlets,intersectionsofsewerlines,andatregularintervalstofacilitateinspectionandcleaning.Pipelinegradientsfollowthegeneralslopeofthegroundsurfacesuchthatwaterenteringcanflowdownhilltoaconvenientpointfordischarge.Sewerpipesaresetasshallowaspossibletominimizeexcavationwhileproviding0.6to1.2mofcoverabovethepipetoreducetheeffectofwheelloadings.Seweroutletsthatterminateinnaturalchannelssubjecttotidesorhighwaterlevelsareequippedwithflapgatestopreventback-floodingintothesewersystem.Backwatergatesarealsousedoncombinedseweroutfallsandeffluentlinesfromtreatmentplantswhereneeded.

Therationalmethodisusedtocalculatethequantityofrunoffforsizingstormsewers.Climateconditionsareincorporatedbyusinglocalrainfallintensity-durationformulasorcurves.Indryregions,sewersmaybeplacedonlyinhigh-valuedistricts,whilestreetsandroadsideditchesserveassurfacedrainsinsparselypopulatedareas.Ontheotherhand,inregionsofthecountryhavingintensethunderstormweather,linedopenchannelsareoftenfoundtobemoreeconomicalcomparedwithlargeburiedconduits;sewersleadingfromsmalldrainageareasterminateingrassedorconcrete-linedditchesthatdischargetosurfacewatercourses.

Flowingfullvelocitiesusedindesignofstormsewersareinaminimumof0.90m/sandamaximumofabout3.0m/s.Thelowerlimitissetsothatthelinesareself-cleaningtoavoiddepositionofsolids,andtheupperlimitisfixedtopreventerosionofthepipebygrittransportedinthewater.

Amajordifferenceindesignphilosophybetweensanitaryandstormsewersisthatthelatterareassumedtosurchargeandoverflowperiodically.Forexample,astormdrainsizedonthebasisofa10yearrainfallfrequencypresumesthatonestormevery10yearswillexceedthecapacityofthesewer.Sanitarysewersaredesignedandconstructedtopreventsurcharging.Wherebackupofsanitarysewersdoesoccur,itismorefrequentlyattributabletoexcessinfiltrationofgroundwaterthroughopenpipejointsandunauthorizeddrainconnections.Asecondeasilyrecognizabledifferencebetweensanitaryandstormsewersisthepipesizesthatareneededtoserveagivenarea.Stormdrainsaremanytimeslargerthanthepipescollectingdomesticwastewater.Consequently,onlyasmallamountofinfiltratingrainwaterresultsinoverloadingdomesticsewers.

ReadingMaterialBSanitarySew