Methane Production and Nutrient Recovery after Applying MW Technology in Sewage Sludge Pretreatment

Abstract

Abstract This study investigates the effect of microwave (MW) treatment on the disintegration of municipal activated sludge. Sludge samples underwent heating at a targeted temperature of 90°C for 35 minutes, with a 5-minute retention time. Soluble chemical oxygen demand (sCOD), sugars, proteins, nitrogen (N), and phosphorus (P) exhibited notable increases compared to untreated samples. Results indicate a substantial (42-45%) rise in methane production during the anaerobic digestion process of the disintegrated sludge compared to the untreated counterpart Methane production was estimated using a transference model, which showed the best fit compared to other models. Further experimentation involved testing digested sludge with excess soluble ammonium for the recovery of struvite at a 1.50/1/1 (Mg/N/P) ratio. The findings reveal that up to 90.09% and 90.43% of orthophosphate and ammonium, respectively, can be efficiently removed from the solution. Despite the increased methane output, the energy recovered was insufficient to offset the electrical energy used by the MW. Notably, the sludge filter resistance performance deteriorated significantly, increasing from 1.64×1014 m/kg for the control sludge to 3.76×1014 m/kg for the treated sludge.