環(huán)境工程概論-sanitary sewer system

Chapter8.SanitarySewerChapter8.SanitarySewer-UnderstandthebasicconceptofsanitaryChapter8.SanitarySewerAsewagecollectionsystemconsistsofanetworkofpipes,pum station,channel,andappurtenanncesthatconveyswastewatertoapointoftreatment,storage,ordisposal.ChapterChapter8.SanitarySewerCombinedChapter8.SanitarySewerProblemsofthecombinedsewer:lowflowduringdryweather;highflowduringwetweather;Sothecombinedsewerstypicallyconsistoflarge-diameterpipesortunnels.VeryheavyrainoutoftreatmentcapacityCSO(combinedseweroverflow)ChapterChapter8.SanitarySewer1.CSO:WWTPdonothavethecapacitytohandlethehugevolumeofstormwaterdevelopedwhenitrains.Consequently,stormwatermixedwithsanitarysewagemustbebypassedaroundWWTPdirectlyintoreceivingwaterscausinwaterollution.Chapter8.SanitarySewerSeparatesewer Sanitarysewer:pipelinesthattransmitwastewater roduceSSOsanitarseweroverflow Stormsewer:pipelinesthattransmitstormwaterSSOaredischargesofraw(untreated)sewagefrommunicipalsanitarysewerWhichofthefollowingWhichofthefollowingstatementisCombinedsewercarrieswastewaterfromindustryandCombinedsewercarriesCombinedsewerincludessanitarysewerandstorm7Chapter8.SanitarySewer2.Sewer *(1inch=2.54Outsidethebuildingfoundation,conveywastewaterfromthebuildingstolateralorbranchsewers;canbe15cm;collectwastewaterfromoneormorebuildingsandconveyittoamainsewer.Minimum20collectwastewaterfromoneormorelateralsewerstotrunksewersortointerceptingsewers.conveywastewaterfrommainsewerstotreatmentplantsortolargeinterceptingsewers.LargesewersthatareusedtointerceptanumberofmainortrunksewersandconveythewastewatertotreatmentorotherdisposalChapterChapter8.SanitarySewer3.MaterialsandTheThejointsbetweensewerpipeManhole,invertedsiphons,liftstation,flowChapterChapter8.SanitarySewer3.MaterialsandCheap,resisttoaciderosion,butbrittle;relativelysmall(D<=1m,L<=2m)Chapter8.SanitarySewerStrong,andcanbeconstructedinlargediameter(D<=6m,L<=8m),butnotresistanttoaciderosionneedlinerinsideChapter8.SanitaryChapter8.SanitarySewerLight,resistanttoaciderosion,goodhydroliccharacteristicsmorecommonlyusednowPolyvinylchloride(PVC):D<=75cm,L<=6mHigh-densitypolyethelyne(HDPE)Chapter8.SanitarySewerductileiron（球墨鑄鐵）steelareusedforforcedor ductileComparedComparedtoreinforcedconcretepipe,vitrifiedclaypipehastheadvantageCanbemadeinlargeResistanttoacidChapter8.SanitarySewerProvideaccesstothesewerpipelineforpipecleaning,flowmeasurement.CircularincrossconcretebottomChapterChapter8.SanitarySewerManholesareusedinthefollowingwhenthereisachangeinpipewhenthereisachangeinpipewhenthereisachangeinpipedirection;datallieintersectionsattheuppermostendofeachatintervalsnotexceeding150Chapter8.SanitarySewerChapter8.SanitaryChapter8.SanitarySewerChapter8.SanitarySewerwhenthecollectionpipeismuchdeeperthanthelateralpipe.ToreducetheamountofexcavationneededbyallowingthelateraltomaintainashallowThesewagedropsintothelowersewerthroughaverticalpipetoprotecttheworkerfromthe WhichWhichofthefollowingstatementisnotManholesareusedwhensewerchangesitssize,directionorslopeManholesareusedthereisaconnectionManholesareusedwhenthestraightpipeis15meterorChapter8.SanitarySewerCrossastream,highway,railway,Invertedsiphonordepressedsewer倒虹管）alwaysfullandunderpressure;multiplepipes(tomaintaincertainvelocitytopreventsettling);velocityChapterChapter8.SanitarySewerSewerlocationand Amapmustbepreparedsothatapreliminarylayoutcanbemade; sewerlinelocation(generallylocatedinthepublicright-of-way,nearthecenterofthestreet)anddirection(gravityflow,downhill);manholes; Forcemainsandtherequiredpum stationsareavoidedbecauseoftheaddedexpenseandpotentialoperatingproblems; Detailedmapsofeachstreet;profiledrawingsbelowthelayout;location,depth,diameter,andslopeChapter8.SanitarySewerChapter8.SanitarySewerChapter8.SanitarySewer tyofSewersmustbeabletocarrythepeakflow:4timesoftheaverageflowforsmallpipes(lateralandsubmainsewers)and2.5timesforlargepipes(mainortrunksewers)Underdesign（Qisunderestimated)surcharge過載）sewagemayoverflowoutofthemanholeOverdesign（Qisoverestimated)cost;attractmorelanddevelopmentChapterChapter8.SanitarySewer5.tyofFlowrateisrelatedto:populationdensity,waterconsumptionrate(100gpd/,370Lpd/),commercialorindustrialactivity,infiltrationandinflow(I/I)Infiltration:theamountofgroundwatersee thepipelineInflow:SurfacewaterthatentersasewersystemthroughpoorlysealedmanholecoversorthatcomesfromintentionalconnectionstoroofdrainsandbasementsumppumpsonaprivatepropertyWhendesigningasanitarysewer,whatshouldbeincludedwhenestimatingtheflowrate?WastewatergenerationrateandpopulationIndustryandcommercialInfiltrationandAllChapterChapter8.SanitarySewer6.Depthandvelocity???Minimumcoverabovethecrownofthesewerpipe2mGreaterdepthincreasethecost.Generally,<=6mVerydeepbasementorbuildingmayrequirepumthesewageupintothepublicsewerunitstoMinimumvelocity0.6m/s(self-cleansingvelocity,KeepsolidssusendedintheflowMax.velocity3m/s(topreventexcessiveandwearofthepipewallfromsandandChapter8.SanitarySewer7.CrownThesulfuricacid(H2SO4)reactswithandweakenstheconcrete,causingtheproblemProperhydraulicdesigntomaintainself-cleaningflowvelocitiescanhelpavoidthisChapter8.SanitarySewerChapter8.SanitarySewer8Size,slope,and evations(管底標(biāo)高Slopeandsizeadjustmenttomeetthevelocityrequirementprefertofollowthegroundslope(reduceexcavation)Min.diameteroflateralsewers200mm(8Theinverevation(thebottominsidewallsurfaceofthepipe)=Groundelevation-soilcover-pipediameterP231,ExampleChapter8.SanitarySewerSanitaryseweroverflowsSSOisdischargeofraw(untreated)sewagefrommunicipalsanitarysewersystem.SSOcanreleaserawsewageintobasementso