Enhancement of Activated Sludge Dewaterability by Using Filamentous Fungi as Bioadditives

In this study, the dewaterability of activated sludge inoculated with spores of two filamentous fungi (Trichoderma reesei and Aspergillus oryzae) was evaluated. The reduction of capillary suction time (CST) and the increase of sludge solids content were used as parameters to assess the dewaterability of the sludge. Furthermore, the transformation of the extracellular polymeric substances (EPS) of the sludge during the fungal conditioning and the interaction of microbial and fungal populations were addressed. Fungal conditioning reduced the CST by 25% and increased the sludge solids content by 16%, denoting the enhancement of the sludge dewaterability. The optimum fungal conditioning time was three to four days. Fungi hydrolyzed the sludge EPS, allowing the release of water from the flocs matrix. Fungal conditioning increased the fungal and microbial communities. Furthermore, the increase of the fungal population augmented the hydrolytic activity of enzymes over the sludge EPS, enhancing the water release and consequently the dewaterability of the activated sludge.