In situ sludge reduction assisted by alternating electrode-based electrochemical treatment

The massive production of sludge from municipal wastewater treatment plants poses a significant challenge to its disposal and management. This study proposes a sustainable in situ sludge reduction technology. A sequencing batch reactor (SBR) was used to investigate the process feasibility. The activated sludge from the SBR was first subjected to pH adjustment to dissociate the extracellular polymeric substances (EPS) of the microorganisms, which serve as a protective layer. The vulnerable microorganisms are then treated by electrochemical oxidation, which disrupts the cells and releases the organic matter. Equal volumes of sludge were treated at pH 2 and 12, respectively, and combined for 20 min electrochemical treatment at 15 V with a 2 cm electrode spacing, a 3 mL dosage of 1 M CaCl₂, and a stirring speed of 500 rpm. Around 22 % sludge disruption has been obtained. Alternating polarity has been shown to effectively prevent electrode passivation, achieving a 25 % improvement in sludge disruption. The treated sludge solution was then reintroduced into the SBR for metabolic assimilation. The results indicate that the SBR process can maintain a self-sustaining condition with up to 10 % sludge recirculation volume. The study provides new insights into in situ sludge reduction, with promise for widespread application and further optimization in future wastewater treatment systems.