Sewage sludge treatment using microwave‐enhanced advanced oxidation processes with and without ferrous sulfate addition

BACKGROUND: Microwave‐enhanced advanced oxidation processes with and without the addition of ferrous sulfate (MW/H₂O₂/Fe²⁺‐AOP and MW/H₂O₂‐AOP respectively) were studied for reduction of solids and solubilisation of nutrients from secondary sewage sludge. RESULTS: For the MW/H₂O₂/Fe²⁺‐AOP the yields of solubilisation of orthophosphate and ammonia decreased with increasing temperature. The best results (88.1 mg L^?1 for orthophosphate and 22.7 mg L^?1 for ammonia) were obtained at a treatment temperature of 40 °C. In contrast, the MW/H₂O₂‐AOP had an advantage when it was operated at higher temperatures of 60 and 80 °C. The highest yields of solubilisation were obtained at 60 °C for orthophosphate (81.1 mg L^?1) and at 80 °C for both ammonia (35.0 mg L^?1) and soluble chemical oxygen demand (1954 mg L^?1). Over the temperature range used in this study, the MW/H₂O₂‐AOP gave a better performance than the MW/H₂O₂/Fe²⁺‐AOP. CONCLUSION: For sewage sludge treatment the MW/H₂O₂‐AOP is more effective than the MW/H₂O₂/Fe²⁺‐AOP in terms of solid reduction and nutrient solubilisation. It will also be more cost‐effective, as it does not require iron addition in the process. Copyright © 2008 Society of Chemical Industry