Overview of Fenton pre-treatment of sludge aiming to enhance anaerobic digestion

Availability of the biodegradable matter in wastewater sludge limits the anaerobic digestion (AD) process efficiency. Therefore, sludge pre-treatment is required to increase sludge solid degradability and, in turn, AD efficiency. Advanced oxidation processes, particularly Fenton pre-treatment, are emerging as popular methods aiming to enhance sludge biodegradability. This review summarizes the major findings of Fenton pre-treatment application in sludge disintegration and dewaterability, and elucidates the impacts on both mesophilic and thermophilic digestion. Efforts are made to understand the effect of the Fenton pre-treatment of wastewater sludge on enhancing AD efficiency (increased biogas production and solids reduction) and outline the future research direction. A case study of mass–energy balance and greenhouse gas (GHG) emission computations for mesophilic and thermophilic digestion of control (without pre-treatment) and Fenton pre-treatment sludge at different sludge retention times is also illustrated.