A comparative study of hydrogen peroxide oxidation and electrocoagulation using aluminum, iron, and zinc electrodes for urban sludge disintegration

Municipal and industrial wastewater treatment plants produce large amounts of sludge containing high levels of organic, chemical, and microbial pollutants. Unless stabilized completely and discharged safely, they may become potential pollution sources threatening soil and water bodies. This study investigated H₂O₂ oxidation and electrocoagulation as pretreatments to improve stabilization of an urban sludge. The H₂O₂ oxidation was optimized with respect to H₂O₂ dosage and initial sludge pH-H₂O₂. Batch electrocoagulation experiments were conducted using aluminum, iron, and zinc electrodes to investigate the effect of treatment period, current density, and pH. The effectiveness was compared in terms of solubilization of sludge, disintegration degree, and reduction of total solids. Sludge settling velocity after disintegration by both H₂O₂ oxidation and electrocoagulation were measured with respect to the operating conditions. The obtained results indicated that the high rate of sludge disintegration (63.3%) was obtained with aluminum electrodes, which has lower operating costs than iron and zinc electrodes. The H₂O₂ oxidation reached a maximum disintegration degree of 50%. Additionally, with aluminum and iron electrodes, sludge settleability was enhanced with both H₂O₂ oxidation and electrocoagulation.