closed tank receiving wastewater for sedimentation and sludge digestion, closed sedimentation tank in which settled sludge is in immediate contact with the wastewater flowing through the tank, and the organic solids are partially decomposed by anaerobic bacterial action, pealt kinnine setiti reovee kogumiseks, heljumi sadestamiseks ning sette stabiliseerimiseks (kääritamiseks), pealt kinnine setiti, millesse sadestunud, läbivoolava reoveega kokku puutuva sette orgaaniline aine laguneb anaeroobselt
