Environmental characterization of metal finishing sludges

Metal finishing industries generate effluents with high contents of heavy metal, inorganic anions and minor amounts of organic compounds, which must be treated by specific physicochemical processes leading to complex sludges. The characterization of these wastes is necessary to assess their environmental impact and to establish management. In this work two different methods of characterization, based on the Spanish Regulations and European Economic Community suggestions, have been applied to 32 wastes from 16 metal finishing facilities. The ecotoxicity values, EC50, of the TCLP leachates show a high variability among different metal finishing activities and batches of the same activity, ranging from 1 000 mg l(-1) to 1 000 000 mg l(-1). Results of chemical characterization of leachates, according to the DIN 38414-S4 leaching procedure show a high concentration of SO42-, Cr and Ni. The paper establishes the characterization parameters of sludge wastes from the physicochemical treatment of metal finishing effluents.