Degremont水处理手册(第7版)-2

Degremont水处理手册(第7版)-23BASICPHYSICAL-CHEMICALPROCESSESINWATERTREATMENT1.COAGULATION-FLOCCULATION1.1.GENERAL1.1.1.Suspendedsolidsandcolloids1.1.1.1.DefinitionsWatercontainsmanycompounds,whichcanbeclassifiedinthreecategories(seepage5)..SuspendedsolidsTheseproductsmaybemineralinorigin(sand,silt,clays,etc.)ororganic(productsresultingfromthedecompositionofplantoranimalmatter,humicorfulvicacids,forexample).Addedtothesecompoundsaremicroorganismssuchasbacteria,plankton,algaeandviruses.Thesesubstances,inparticular,areresponsibleforturbidityandcolour..Colloidalparticles(lessthan1micron)TheseareSSofthesameoriginastheabovebutofsmallersizeandwithasettlingratethatisextremelyslow.Theyarealsoresponsibleforturbidityandcolour..Dissolvedsubstances(lessthanseveralnanometres)Theseareusuallycationsoranions.Partoftheorganicmatterisalsodissolved.Gasesarealsopresent(O2,CO2,H2S,etc.).1.1.1.2.Theroleofcoagulation-flocculationThecoagulation-flocculationprocessesfacilitatetheremovalofSSandcolloids.Thisoccursinafina