Wastewater from prodn. of printed circuit boards was treated with CaO2, FeSO4 and H2SO4 at 18 degrees C and pH 2-4 for 60 min (Fe2+ concn. 400-600 mg/L, CaO2 concn. 7500-9500 mg/L). The COD value in the system decreased from 1690 mg/L down to even 339 mg/L. The results were presented as polynomial regression equations. The concn. of Cu2+, Ni2+ and Sn2+ ions in the system also decreased from 25.9 mg/L down to 0.2 mg/L, from 6.9 mg/L down to 0.1 mg/L and from 10.2 mg/L down to <0.05 mg/L, resp., with the increasing pH (up to 12).