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1、Chapter3WastewaterTreatment1TermsSanitarysewage,municipalsewage,preliminary,primary,secondary/biologicaltreatment,biochemicaloxygendemand(BOD),chemicaloxygendemand(COD),totalsuspendedsolids(TSS),treatment/removalefficiency,primaryeffluent,sewageeffluent/emissionstandards.
2、Screen,gritchamber,primary/secondaryclarifiersorsettlingtanks/basins,detentiontime,outletweir.Microbe/microorganism,bacteria,fungi(fungus),activatedsludgeprocess,aerationtank/clarifier/basin,supernatant,ruturn/excesssludge,food-to-microorganism(F/M)ratio,mixedliquorsuspen
3、dedsolids(MLSS),sludgevolumeindex(SVI),sludgebulking,processflowdiagram.2FlowchartofawastewatertreatmentsystemAflowchartshowingthetypicalsequenceofwastewatertreatmentprocessesisgiveninFigure1,wherescreening,gritremoval,andprimarysedimentationareprimarytreatmentprocesses.S
4、econdarytreatmentusuallyinvolvesbiologicalprocessesandadditionalsettling.Notallsewagetreatmentplantsrequiretertiary(advanced)treatmentofnitrogenandphosphorus.废水处理的典型工艺流程图如图1所示。筛滤、砂砾的去除、自然沉淀属一级处理过程。二级处理通常包括生物处理和二次沉淀。Figure1Schematicoverviewofawastewatertreatmentsystem不是所有废
5、水处理厂都需要去除氮和磷的三级或者深度处理。3PrimarytreatmentInatypicalsequenceofwastewatertreatmentprocesses,screening,gritremoval,andprimarysedimentationareprimarytreatmentprocesses.Primarytreatmentprocessesincludepreliminarytreatmentandprimarysedimentation.3.1PreliminarytreatmentsystemsPrel
6、iminarytreatmentsystemstypicallyincludescreensandgritchambers.Thefirsttreatmentprocessforrawwastewateriscoarsescreening.Itretainsfloatingdebrissuchaswood,rags,orotherbulkyobjects,thatcouldclogpipesordamagemechanicalequipmentintherestoftheplant.废水的第一个处理过程是初格栅。它能去除悬浮碎片，比如木头
7、，碎屑或者其它大体积的物质，这些物质能堵塞处理厂后续处理设备的管道，或者损坏其机械设备。3.2PrimarysedimentationAlthoughthegritwillsettleoutatthisreducedvelocity,thelightersuspendedorganicsolidswillstillbecarriedthroughtothenexttreatmentunit.Afterpreliminarytreatmentbyscreeningandgritremoval,thewastewaterstillcontai
8、nssuspendedorganicsolidsthatcanberemovedbyplainsedimentation.尽管沙砾在这个速度能沉降下来，密度较小的悬浮有机固体仍将进入下一个处理
