Use of municipal sewage sludge ash for fertilizing purposes. An analysis of possibilities in Poland

Ashes from thermal transformation of municipal sewage sludge were thermochem. modified at 1000 degrees C in the presence of NaHCO3 and sewage sludge to obtain CaNaPO4 and reduce the content of heavy metals in the produced fertilizer. Its bioavailability was more than 99% higher than that of raw ashes (50%). The nutrient content was 13.56% Ca, 6.33% p, 4.36% K and 5.0% Fe. The content of heavy metals in fertilizer products met the std. requirements and was exceeded only in the case of Pb (278.3 mg/kg d.m.).