Sludge bulking is defined as a phenomenon that sludge granules in a wastewater treatment reactor float on and overflow from the reactor. Sludge bulking cause a decrease of COD removal in a wastewater treatment. Quite interesting sludge bulking was observed in a mesophilic, full-scale Upflow Anaerobic Sludge Blanket (UASB) reactor treating wastewater from a canned corn factory. Because the sludge bulking was occurred on the UASB reactor, the granule sludge of the reactor was washed out then the COD removal of the reactor was drastically decreased. In order to confirm the reason of the phenomenon, we observed the washed-out granules. As a result, we found out the white-filament-formed materials on the surface of the granules. The sludge configuration is different from any other previously reported bulking sludge; therefore, the causing microorganisms of this sludge bulking are still unclear.
Hence we explore the microorganisms, which cause this sludge bulking.