Interaction between components of electroplating industry wastes. Influence of the receiving water on the toxicity of the effluent.

A copper-cadmium-nickel-zinc mixture was assessed in seven different river waters to study metal toxicity to the ciliate protozoan Colpidium campylum, the interactions occurring between metals, and the influence of the receiving water on toxicity. In the range of concentrations tested, which are representative of electroplating industry wastes, the main part of the toxicity can be attributed to copper and to cadmium-copper synergy. A classification of waters, based on a principal component analysis (PCA), was used to examine the main parameters of the water, which can affect the toxicity of metal mixtures. It appears that the mineralization of the water, more than the total organic carbon (TOC), is an important parameter for the expression of toxicity. A strategy for the estimation of ecotoxicological hazard assessment, based on a simplified factorial experiment is proposed. It enables one to study, in a two-step bioassay, the toxicity of an effluent, the influence of river water on its toxicity, and the effects of contact time and dilution. By applying PCA to data from very different waters, it may be possible to estimate the ecotoxicological risk associated with the discharge of an effluent, on the basis of the chemistry of the receiving water.