Sodium diethyldithiocarbamate (DDTC) is used as a trapping agent and poly-ferric sulphate and polyacrylamide are used as flocculants to treat copper-electroplating wastewater. The influences on the precipitation and flocculation of Cu2+ cation are studied in details, such as the amount of complex copper (EDTA and NH4Cl are used as coordination agents), the addition of DDTC, poly-ferric sulphate and polyacrylamide (PAM) and pH of the solution. In addition, the influences on the trapping copper by different agents such as DDTC, diethylammonium diethyldithiocarbamate (DDC) and ammonium pyrrolidinedithiocarbamate (APDC) are studied as well. The results show that the dosage of DDTC depends only on the content of complex copper, but not on the total amount of copper in the wastewater. When the molar ratio of DDTC to Cu is between 0.8 and 1.2, Cu removal efficiency could be higher than 99.6%. Poly-ferric sulphate and PAM have little effects on the Cu removal, but they have significant effects on the flocculating volume, precipitation rate and nephelometric of the upper clean water. (C) 2002 Elsevier Science B.V. All rights reserved.