Abstract
An anaerobic fluidized pellet bed bioreactor (AFPB bioreactor) system combined with a contact aerator can effectively remove SS, COD, nitrogen and phosphorus. The formation mechanism of sludge pellets and the features of nitrification-denitrification in this system were investigated. By adding polymerized aluminum chloride and weak anionic polymer, the sludge pellets with high density were formed in the AFPB bioreactor above 15°C of water temperature and possessed a high microbial activity such as denitrification and sulfate reduction. A filamentous bacteria was greatly responsible for the formation of this kind of sludge pellets. The filamentous bacteria was identified as a microaerobe, Beggiatoa sp. based on the morphological and physiological features. As most of the SS and COD components were removed as sludge pellets in the AFPB bioreactor, the loading of these substances to the contact aerator was remarkably decreased. Consequently, the solid retention time of the contact aerator, apporoximately 20 day, was long enough to sustain the sufficient growth of nitrifies. Therefore, the system proposed in this study, had a high nitrifying and denitrifying ability in the wide range of temperature.
