Disaggregation of Granular Sludge during Methane Fermentation Treatment for Methanol-containing Wastewater

It is a challenge to maintain the granular sludge during the treatment of wastewater containing methanol by UASB, since few methanogens can utilize methanol as a substrate. In this study, for the treatment of actual wastewater containing methanol, the change in the microbial community and particle distribution of granular sludge were observed during the acclimatization process of seed granular sludge for the continuous operation of an UASB (Up-flow Anaerobic Sludge Blanket) system with sludge returning after solid-liquid separation. Methanosarcina-like methanogens in the granular sludge became dominant during the acclimatization, and the dominant species was found to be Methanomethylovorans. After their DNA exceeded 80%, the collapse of the granular sludge progressed and the particle diameter became less than 0.5 mm. However, stable performance still could be obtained because of sludge returning after solid-liquid separation, even after the collapse of granular sludge.