Investigating high-power ultrasonic vibration and vacuum as methods to enhance the extraction of water from municipal wastewater sludge

摘要

The main objective of this thesis is to uncover and investigate physical mechanisms that can be used to develop efficient ways to remove water from municipal wastewater sludge. The essential criterion will be to minimize energy expenditure. For this purpose, the main theories regarding mechanical dewatering and drying, related methods, and normally available dewatering and drying machinery are discussed.Using vacuum to enhance drying and applying high-power ultrasound to enhance dewatering or drying are two areas of particular interest. The potential advantage of vacuum is discussed in brief, and a series of experiments performed to investigate its effect on drying kinetics are described. To introduce high-power ultrasound, some basic theoretical data about vibration translation, standing waves, and air columns in musical instruments are presented. Then, the basic mechanisms and equipment of ultrasonic processing related to water extraction technologies are discussed. Finally, testing was carried out at the Pusonics Co. in Spain to explore the use of ultrasonic waves for dehydration.The investigation and testing show that both vacuum-enhanced drying and high-power ultrasound-enhanced dewatering or drying could be used to develop more effective and more energy efficient ways of removing water from municipal wastewater sludge.