Phosphorus compounds extraction from the ash after the sewage sludge combustion

This paper presents the research results on phosphorus recovery from the ash after the sewage sludge combustion. The sewage sludge produced in Municipal Sewage Treatment Plant ,,Kujawy" in Cracow was incinerated at the temperature of 1223K and leached with phosphoric acid. The goal of the conducted research was the greatest phosphorus concentration in the solution considering its future reuse as a raw material for phosphorus recovery. The experiment was carried out in five trials using the increasing mass ratio of the ash to the constant acid mass. The analytical control allowed to determine PO4(3-) Ca, Fe, Mg, Cr, Pb, Co, Cd, Ni, Zn,Cu concentrations in the obtained extracts and the solid residue. The application of phosphoric acid causes the increase of phosphorus concentration in the extracts and enlarges its attractiveness as the phosphorus source for the fertilising purposes.