Oxidation, coagulation and filtration processes for the removal of sulfides and organic matter from the effluents of a tannery

Abstract

Currently, the tanneries in the Río Seco Industrial Park discharge their liquid effluents into the sewer system, which then flows into the Añashuayco Stream, passing through nearby settlements, the Sillar tourist route, and agricultural areas. Finally, it enters the Chili River via the San Jacinto Stream, impacting agriculture in the lower Chili River Basin. In response to this problem, an alternative study is underway to achieve effluent treatment through oxidation, coagulation, and filtration processes. Two wastewater treatments were carried out. The first involved varying pH values ​​and doses of H₂O₂ and FeCl₃, with a 24-hour sedimentation period followed by filtration. The treatment resulted in filtration, achieving 97% and 99% removal of COD and sulfides, respectively. The pH was not significant, but the H₂O₂ dose did influence the removal of sulfides and COD. In a second treatment, a combination of peroxone and H₂O₂/O₃ was applied, varying the sample concentration and H₂O₂ dosage while maintaining a constant pH of 8.5, flow rate, and O₃ concentration of 1000 mg/L. Oxidation was carried out for one hour, achieving COD removals of 81.7% and sulfide removals of 93.8%. Both treatments proved efficient for sulfide removal, but the peroxone treatment did not efficiently remove COD. It was concluded that both treatments remove sulfides below permissible levels, but the peroxone treatment uses less H₂O₂. The results obtained warrant further studies using oxygen for the simultaneous removal of sulfides and COD.

Keywords: chemical treatment, environmental, tanneries.