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Tannery wastewater treatment by alternative procedures


According to Banco Nacional de Desenvolvimento Econômico e Social (BNDES), in 2001 the brazilian leather industry had 450 tanneries. They were located in thirty seven cities of São Paulo state, five among them were in the Ribeirão Preto region. Typical wastewater of tanneries are characterized by a high Chemical Oxygen Demand (COD), high salt content (chromium, sulphides, chlorides, etc.), ammonia and high content of phenolic substances. Even after conventional treatment some wastewater parameters as COD, salinity, ammonia and surfactants content, many present values above the allowed limits. The main reason for that is the high resistance of some organic compounds to the chemical and biological treatments. By this reason it is necessary to develop alternative methods to destroy these residues. In this work the electrochemical, photocatalytic and photoelectrochemical processes are proposed in order to eliminate these persistent organic compounds of tanneries wastewater. The degradation of tannery wastewater will be monitored by their Total Organic Carbon (TOC) quantity, Biochemical Oxygen Demand (BOD), COD, phenolic compounds quantity, absorbance, pH, conductivity and the content of Organically Bound Chlorines compound (AOX). This class of substance presents a high toxicity and can be formed in tanneries wastewater since the presence of chlorides is very frequent in these media. The degradation methods will be evaluated regarding their efficiency, decrease in toxic potential and energy consumption. (AU)

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