Speciation of heavy metals in municipal sewage sludge from the three sewage treatment plants

The mobility of heavy metal on sludge from three municipal sewage treatment plants are presented in this article. Heavy metals were present mainly in the immobile sludge fractions. The capacities of the plants did not show any explicit influence on the forms of the heavy metals present. The copper forms in sewage sludge are characteristic feature of this chemical element. The per cent contributions of zinc, lead, cadmium, nickel and chromium in the BCR fractions did not depend significantly on the method of sludge stabilisation.