The Development of the Membrane-Filter Press System(MFPS) by Utilizing Ultrasonic Waves for Treating Sewage Sludge

Abstract

Sewage treatment plants produce large amounts of sewage sludge yearly in Korea. In this study, a Membrane-Filter Press System (MFPS) using ultrasonic waves was developed to treat sewage sludge at the Seonam sewage treatment plant in Seoul. The MFPS consists of an ultrasonic extractor, a polymer injection tank, a membrane-filter press, and a centrate tank for improving sludge dewatering and phosphorus recovery. Two types of sewage sludge were used: digested raw sludge and digested excess sludge. In lab-scale experiments with an ultrasonic extractor, the concentration of phosphorus was 214.9 mg/L at 50 rpm after sonication at 500 W for 20 min, which was around 4.9 times higher than non-treated sludge. In the pilot-scale experiment, dewaterability of the digested raw and excess sewage sludge was investigated in the MFPS under three sets of operating conditions involving modifier injection, ultrasonication, and polymer injection. it was found that the moisture content of the dewatered digested raw and excess sewage sludge cakes was reduced to 50.5% and 54.3%, respectively. Lowering the moisture content reduced the total volume of the sludge by approximately 40% compared to a conventional centrifugal dehydrator. It is expected that the MFPS will reduce the disposal cost of sludge and offers a sustainable solution for recycling resources.