Selection of leaching agent for phosphorus compounds extraction from the sewage sludge ash

This paper presents research results of phosphorus recovery from ash after sewage sludge combustion. The sewage sludge from Municipal Sewage Treatment Plant ,,Kujawy" in Cracow after incineration at temperature of 1223K was leached with mineral (phosphoric and nitric) acids. The goal of the study was a comparison between those two agents considering future reuse of extracts as raw material for phosphorus recovery by its precipitation. An application of phosphoric acid causes an increase of phosphorus concentration in extracts and enlarges its attractiveness as phosphorus source for fertiliser purposes. Nitric acid gives both higher extraction degree of phosphorus compounds and higher efficiency but lower phosphorus concentrations in the extracts.