Hauv cov txheej txheem tsim khoom noj thiab dej haus, ntau cov khoom siv raw ua kua, nrog rau cov kua txiv hmab txiv ntoo, kua txiv hmab txiv ntoo, cov khoom noj siv mis, cawv, thiab lwm yam, yuav tsum tau ua tiav.Suspended solids, sediment, thiab micro-organisms feem ntau muaj nyob rau hauv cov ntaub ntawv raw cov kua.Yog tias tsis muaj kev pom zoo tsis ua tiav, nws yuav tsum cuam tshuam rau qhov zoo thiab saj ntawm cov khoom.Cov ntsiab lus pom tuaj yeem tshem tawm cov impurities zoo thiab ua kom lub purity thiab ruaj khov ntawm cov ntaub ntawv raw cov kua.