Phosphorus Migration and Transformation in Activated Sludge by Ultrasonic Treatment

Abstract

Ultrasonic treatment is an effective method to disintegrate sludge and extract organic matter and nutrients, including nitrogen and phosphorus, from the sludge. This study investigated the transformation of phosphorus species during the ultrasonic treatment of sludge, to reveal the mechanism of phosphorus migration in the activated sludge structure. The experimental results indicated that power density and ultrasonic time were critical parameters affecting the energy input for sludge integration. The optimal phosphorus release performance was achieved at 2.5 W/mL 10 min. The release of phosphorus showed as a layer-by-layer pattern from the inner sludge core to the outer sphere of the multiple-layer structure of the sludge. The complex sludge structure played an important role in buffering the ultrasonication process and transfer of phosphorus. Mg-P, Ca-P, and organic phosphorus are the main phosphorus species that can be extracted from the sludge core into the supernatant. The three-stage process of phosphorus migration through the sludge layers, including dissolution, reprecipitation, and equilibrium, has been revealed.

Comparison of Solubilization Treatment Technologies for Phosphorus Release from Anaerobic Digestate of Livestock Manure

“…Within the sonication, the parameters of power density and reaction time play a vital role. Exceeding a certain power density threshold accelerates the release of intracellular substances, and the thermal effects at high power density contribute to the conversion of P forms [34]. During sonication, there is a notable increase in the release of P, primarily in the form of orthophosphate, within a short timeframe.…”