Alternative Treatment Strategy for Different Streams of Tannery Wastewater

This article discusses the results of laboratory tests aimed to determine the effectiveness of tannery wastewater treatment in the process of enhanced oxidation using Fenton reagent. The general sewage from the tannery located in Mazowieckie Province was used for the research. The process was carried out using two doses of iron of 0.45 g Fe²⁺/dm³. and 0.56 g Fe²⁺/dm³, and H₂O₂ from 2.21 g/dm³ to 4.08 g/dm³. All the tests were performed for a constant optimum pH of 3.0. Wastewater was characterized by basic physico-chemical indicators (pH, conductivity, COD, chromium, ammonium nitrogen). The efficiency of the process was determined mainly on the basis of changes in the organic pollutants identified as COD. The efficacy of the Fenton process for different doses of Fe²⁺ and Fe²⁺ / H₂O₂ ratio of 1: 5, 1: 6 and 1: 7 was from 69 to 80% COD reduction in relation to raw sewage. Another aspect of the study was determining the possibility of removing sulphides from the wastewater by catalytic oxygenation with oxygen from air in the presence of manganese. In this case, the wastewater produced during leather manufacture in tanneries located in the southern part of Poland was examined. The subject of the study described in the paper was to determine the optimum manganese dose and oxidation time to simultaneously remove the sulphides and organic pollutants expressed as COD. The change in pollutant content in the wastewater over time indicates that the reduction of parameters takes place within one hour after the addition of manganese. Using the process of catalytic oxidation with 0.1 g/dm³ to 0.6 g/dm³ manganese and a reaction time of 1, 3, 24 h, the sulphides were removed in the range of 50 to 99% and organic compounds in 12 to 65%.