Abstract
The aerobic granular sludge wastewater treatment technology has numerous advantages as compared to the conventional flocculent sludge technologies. However, the filamentous fungi overgrowth (FFO) is a major operational problem that is hindering its widespread application. This study evaluated the behaviour and mechanisms of the FFO, and its impact on granulation, treatment performance and microbial community structure. The overgrown filamentous organisms were developed in an aerobic granular sludge reactor operated for 274 days. The filamentous organisms were identified to be yeast-like fungi belonging to the moulds Geotrichum of the phylum Ascomycota. The removal of carbon and nitrogen were slightly affected, while phosphorus removal was largely impacted. The FFO development was found to disrupt the structural integrity of granules, cause their disintegration and washout, and lead to a microbial community shift towards a structure lacking bacteria genus that are essential for efficient granulation. Limitations of the currently used routine measurements were discussed.