title: Enhancement of dewaterability of thickened waste activated sludge by freezing and thawing treatment.
abstract: The effect of freezing speed on dewaterability of waste activated sludge thickened by flotation was investigated. The average dewatering rate of the sludge after freezing/thawing treatment was remarkably increased, and was found to be larger in the order: slow-frozen (-10 degrees C, -20 degrees C) > fast-frozen (-80 degrees C) > unfrozen sludge. This order was consistent with those of the sludge settling, elution of intracellular water and the numbers of the viable bacteria in the sludges after freezing/thawing. The expression characteristics and the final moisture contents of unfrozen and frozen sludge were evaluated from expession experiments at constant pressure. The wet-basis moisture content of final cake of frozen sludge was about 10% lower than those of unfrozen sludge, and even the cake obtained under additional 2 kgf/cm2 pressure may burn without auxiliary fuel. In addition, the mechanism responsible for the sludge dewatering was also examined.
authors.affiliation: Department of Environmental Science and Engineering, Harbin Institute of Technology, Nagang, China.
authors.forename: Q
authors.initials: Q
authors.lastname: Wang
authors.forename: K
authors.initials: K
authors.lastname: Fujisaki
authors.forename: Y
authors.initials: Y
authors.lastname: Ohsumi
authors.forename: H I
authors.initials: HI
authors.lastname: Ogawa
mesh_terms: D005615:Freezing; D011312:Pressure; D012722:Sewage / Q000737:chemistry*; D014867:Water; D014871:Water Microbiology; D018508:Water Purification / Q000379:methods*
chemical_list: D012722:Sewage; D014867:Water