title: Ultrasonic reduction of excess sludge from the activated sludge system.
abstract: Sludge treatment has long become the most challenging problem in wastewater treatment plants. Previous studies showed that ozone or chlorine effectively liquefies sludge into substrates for bio-degradation in the aeration tank, and thus reduces the excess sludge. This paper employs ultrasound to reduce the excess sludge from the sequential batch reactor (SBR) system. Partial sludge was disintegrated into dissolved substrates by ultrasound in an external sono-tank and was then returned to the SBR for bio-degradation. The results showed that ultrasound (25kHz) effectively liquefied the sludge. The most effective conditions for sludge reduction were as following: sludge sonication ratio of 3/14, ultrasound intensity of 120kW/kgDS, and sonication duration of 15min. The amount of excess sludge was reduced by 91.1% to 17.8mg/(Ld); the organic content and settleability of sludge in the SBR were not impacted. The chemical oxygen demand (COD) removal efficiency was 81.1%, the total nitrogen (TN) removal efficiency was 17-66%, and high phosphorus concentration in the effluent was observed.
authors.affiliation: School of Municipal & Environmental Engineering, Harbin Institute of Technology, 150090, China. gmgwen@gmail.com
authors.forename: Guangming
authors.initials: G
authors.lastname: Zhang
authors.forename: Panyue
authors.initials: P
authors.lastname: Zhang
authors.forename: Jinmei
authors.initials: J
authors.lastname: Yang
authors.forename: Yanming
authors.initials: Y
authors.lastname: Chen
mesh_terms: D006863:Hydrogen-Ion Concentration; D012722:Sewage / Q000737:chemistry*; D014465:Ultrasonics; D014865:Waste Disposal, Fluid / Q000379:methods*; D018508:Water Purification / Q000379:methods*
chemical_list: D012722:Sewage