Microwave enhanced advanced oxidation process for sewage sludge treatment: The effects of ozone addition

Microwave enhanced advanced oxidation processes (MWAOP), with combinations of oxidants, were studied for sewage sludge treatment. Various operating conditions, using a computer statistical software design, were selected to determine the importance of factors affecting solids destruction and nutrients release from sewage sludge. For phosphate solubilization, the most significant factors, in the order from most to least, are heating temperature, ozone dosage, and a combined effect of temperature and hydrogen peroxide. For ammonia release, these are hydrogen peroxide dosage, a combined effect of hydrogen peroxide and temperature, and then temperature and ozone. For the destruction of sludge particles, the most significant factors are hydrogen peroxide and temperature. The best solubilization result was obtained with additions of 2% hydrogen peroxide by weight, 5.09 mg/mL of ozone, and microwave heating at 120 °C. About 95%, 32%, and 78% of TP, TKN, and COD were released into the solution, respectively. Results showed that addition of ozone improved the MWAOP process. A higher amount of oxidants used in the MWAOP facilitated the release of nutrients and sludge solids disintegration.