Energetically efficient microwave disintegration of waste activated sludge for biofuel production by zeolite: Quantification of energy and biodegradability modelling

Abstract

Hydrolysis of waste activated sludge (WAS) is a challenging process towards enhanced biofuel production. In this study, an attempt has been made to improve hydrolysis of WAS by zeolite that acts as a cation binding agent and deaggregates sludge flocs and deflocculates it by removing extracellular polymeric substances. The overall result confirmed that 0.04 g/g SS of zeolite was perceived to be the optimum dosage for deaggregation of flocs. The degree of dissociation was in the range of 93%, which reveals that 0.04 g/g SS (suspended solids) of zeolite was best for the deaggregation of flocs. To evaluate the impact of deaggregated WAS on biomass disintegration, the WAS was exposed to microwave (MW) liquefaction. The result of the MW disintegration shows that the solids reduction and lysis rate of floc deaggregated (zeolite mediated microwave liquefaction) (Ze-MWL) sample with the optimum (0.04 g/g SS) dosage of zeolite was 33.1% and 42.8% comparatively more than microwave liquefaction (MWL) (21% and 26.8%) sample alone. Chiefly zeolite usage reduced microwave specific energy applied for liquefaction of sludge. The outcome of hydrogen and methane potential assay (0.18 and 0.59 L/gCOD achieved for Ze-MWL) revealed the role of zeolite in improving microwave mediated WAS liquefaction. Quantification of energy and estimation of cost revealed that the Ze-MW liquefaction was cost-effective by achieving net yield of 26 €/Ton of sludge.