Municipal sewage sludge dewatering performance enhancement by ultrasonic cavitation and advanced oxidation: A case study

Abstract

The number of published literature on the effect of ultrasonic cavitation and advanced oxidation pretreatment on the dewatering performance of anaerobically digested sludge is very limited. This study aims at determining the optimum operating conditions of large-scale filtering centrifuges in wastewater treatment plants. The optimum dose of hydrogen peroxide, ultrasonic power, ultrasonic duration, ultrasonic pulse and particle size distribution for improved dewatering performance were determined in this study. In addition, shear stress–shear rate and viscosity–shear rate rheograms were developed to show the rheological flow properties for varying ultrasonic power and treatment duration. Optimum sonication power, time, pulse and amplitude were determined to be 14 W, 1 min, 55/5 and 20%, respectively. At a pH of 6.8, the optimum concentration of hydrogen peroxide was found to be 43.5 g/L. The optimum hydrogen peroxide dose in the combined conditioning experiments was determined to be 500 mg/L at a pH of 3. Under these optimum conditions, capillary suction time was reduced significantly by 71.1%. This study helps to reduce polymer consumption and provides the optimum pretreatment and dewatering operating conditions, and better monitoring and control in the dewatering unit has significant impact in the overall economy of wastewater treatment plants. HIGHLIGHTS Digested sludge dewatering is a cost-intensive operation in wastewater treatment plants.; The proposed ultrasonic and advanced oxidation pretreatment significantly improves the dewatering performance.; Rheological flow characteristics of digested sludge also improved after ultrasonic pretreatment.; Sonication and advanced oxidation can be used along with conventional dewatering polymers for better performance.;

Keywords

• advanced oxidation
• dewaterability
• sludge rheology
• ultrasonication