2009注冊(cè)環(huán)保專業(yè)水污染i附件02a沉淀理論

1.沉淀的類型依據(jù)可沉物質(zhì)的性質(zhì)、濃度、凝聚性能，分為：自由沉淀

(Discretesettling)：

絮凝沉淀（也稱干涉沉淀）(Flocculantsettling)成層沉淀（區(qū)域沉淀，擁擠沉淀）

(Zonesettling/Hinderedsettling)壓縮沉淀（Compressionsettling)1)自由沉淀(Discretesettling)

LowSSconcentration,nonagglomerating；

Theparticleremainsitsindividualityanddoesnotchangeinsize,shape,ordensityduringdiscretesettling.

Theparticlesdonotinteractandthesettlingvelocityisconstant.

可用牛頓第二定律及斯托克斯公式描述

ingritchamber&primarysettingtank(lowSS).2）絮凝沉淀(Flocculantsettling)SS=50-500mg/L；

Theparticlesinteractandagglomerateduringtheflocculantsettling,thusresultsinanincreaseintheparticlesize.Theagglomerationresultsinanincreaseinsettlingrate.Theflocdensitygenerallydecreaseswithagglomeration.Theoverallsettlingvelocityincreases.Inprimarysettingtankandsecondarysettlingtank(upperlayer)（也稱干涉沉淀）3）成層沉淀(區(qū)域沉淀，擁擠沉淀)

(Zonesettling/Hinderedsettling)SS>500mg/L;顆粒在沉淀過(guò)程中互相擁擠，互相干擾；上清液與顆粒群之間有清晰的界面(Theparticlesareinintimatecontactwithotherparticlesandmaintainaspecialrelationship,settlingasamass,andexhibitingadistinctinterface).Themassofparticlestendtosettleslowerthanindividual,flocculatedparticles.

Insecondarysettlingtank&condenser(upperlayer)Highconcentrationofparticles;Theparticlesrestuponeachotherandthebottommasssupportstheabovelayersofparticles.(互相接觸，互相支撐)Themassisconcentratedorcompressedbecausetheweightofupperparticlesslowlysqueezeswaterfromthebottomlayers.4）壓縮沉淀（Compressionse