A VOLTAMMETRY PROCEDURE WITH MEDIUM EXCHANGE FOR THE SPECIATION OF HEAVY-METALS IN WASTE-WATER OF A SEWAGE-TREATMENT PLANT

A scheme is proposed for the speciation of heavy metals based on the N urnberg scheme with two modifications: the application of medium excha nge to the anodic stripping voltammetric (ASV) measurement, and the de struction of organic matter and particulate. The protocol is suitable for making operational divisions of four categories for the elements z inc, cadmium, lead and copper in wastewater. Three of these elements c an be simultaneously determined by ASV (cadmium is not detected). The parameters of the determination include: electrodeposition potential - 1.2 V, time of deaerating 300 s, time of the electrolysis 90 s (with s tirring) and the rest time 40 s. Medium exchange is done after the ele ctrodeposition step. We have applied this procedure to the study of me tal speciation in effluent from a conventional wastewater treatment pl ant of the city of Seville (Spain).