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Ultrason Sonochem. 2015 Jan;22:437-45. doi: 10.1016/j.ultsonch.2014.06.012. Epub 2014 Jun 24.

Application and optimization of electric field-assisted ultrasonication for disintegration of waste activated sludge using response surface methodology with a Box-Behnken design.

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  • 1Center for Water Resources Cycle Research, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul 130-650, South Korea. Electronic address: kw512@kist.re.kr.
  • 2Center for Water Resources Cycle Research, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul 130-650, South Korea.

Abstract

In the present study, an electric field is applied in order to disintegrate waste activated sludge (WAS). As a preliminary step, feasibility tests are investigated using different applied voltages of 10-100V for 60min. As the applied voltage increases, the disintegration degrees (DD) are gradually enhanced, and thereby the soluble N, P, and carbohydrate concentrations increase simultaneously due to the WAS decomposition. Subsequently, an optimization process is conducted using a response surface methodology with a Box-Behnken design (BBD). The total solid concentration, applied voltage, and reaction time are selected as independent variables, while the DD is selected as the response variable. The overall results demonstrate that the BBD with an experimental design can be used effectively in the optimization of the electric field treatment of WAS. In the confirmation test, a DD of 10.26±0.14% is recorded, which corresponds to 99.1% of the predicted response value under the statistically optimized conditions. Finally, the statistic optimization of the combined treatment (electric field+ultrasonication) demonstrated that even though this method is limited to highly disintegrated WAS when it is applied individually, a high DD of 47.28±0.20% was recorded where the TS concentration was 6780mg/l, the strength of ultrasonication was 8.0W, the applied voltage was 68.4V, and the reaction time was 44min. E-SEM images clearly revealed that the application of the electric field is a significant alternative method for the combined treatment of WAS. This study was the first attempt to increase disintegration using the electric field for a combined treatment with ultrasonication.

Copyright © 2014 Elsevier B.V. All rights reserved.

KEYWORDS:

Disintegration; Electric field; Electric field-assisted ultrasonication; Response surface methodology; Ultrasonication; Waste activated sludge

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