Evaluation of pre-magnetization on the dewaterability of waste activated sludge treated by ozonation

Abstract

The dewaterability of waste activated sludge (WAS) plays the key role in sludge dewatering in wastewater treatment plants. The magnetic field as a source of clean energy has been reported to be able to cause changes in sludge properties and to enhance sludge dewatering by chemical treatment. This paper focuses on the effect of pre-magnetization on the sludge dewatering performance by ozonation. The results showed that ozonation reduced the capillary suction time (CST) and water content of sludge cake (W_sc) of WAS. The CST reduced from 21.5 ​s to 12.7 ​s; and the W_sc reduced from 85.6% to 85%. However, the addition of pre-magnetization with a magnetic field did not make much improvement of the dewaterability. Further investigation on sludge properties such as EPS, TOC, particle size, and the SEM images of the treated WAS showed that the pre-magnetization prior to ozonation led to stronger oxidation and WAS particle broken, which was proofed not necessarily correlated to sludge dewaterability enhancement.