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 degrees C. In contrast, the MW/H2O2-AOP had an advantage when it was operated at higher temperatures of 60 and 80 degrees C. The highest yields of solubilisation were obtained at 60 degrees C for orthophosphate (81.1 mg L-1) and at 80 degrees 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. (c) 2008 Society of Chemical Industry.