EN
The influence of different doses of CaO (10, 20, 30, 40%) added to waste activated sluges on the Pb, Cd, Ni and Cr fraction was investigated for extraction H₂O, 0,1 mol KCl, 0,1 mol NaOH were used. In water extractet under the addition of CaO the content of Pb, Cd and Cr was decreased but the content of Ni and Cu was increased. In 0,1 mol NaOH extract the contennt of determinated heavy metals were similar like in water extract except Ni. which the content under the influence of CaO decreased. In 1 mol KCl extract the addition of CaO increased the content of determinated heavy metals. The highest concentration of was determinated in extracts got after addition of 10% CaO but for Cd, Cu when 30% CaO were added.