Improved waste-activated sludge dewatering using sludge/oil emulsion, ultrasonic and microwave technologies

Abstract

Conventional dewatering technologies, such as centrifuges, belt filter presses, and rotary vacuum filters, are not effective methods for treating sewage sludge with high water content. This study evaluated the field-scale feasibility of new technologies that use emulsion, ultrasonication, and microwaves to dewater sludge. Emulsion technology lowered the water content in sludge to 60%, but the overall process was too complex to incorporate into the design of commercial plants due to the requirement for oil- and methanol-recovery facilities. Ultrasonication had low dewatering and energy efficiency with long irradiation times, indicating that it would be difficult to implement in a field plant. The water content of sludge was reduced to 60% within 120 s using microwaves, but dewatering efficiency depended on the thickness and volume of the sludge. In a pilot-scale test, the average energy consumption was 0.54 kWh/kg of water removed, and the final water content of the sludge cake reached 60% within 30 min.