High increase in biodegradability of coking wastewater enhanced by Mn ore tailings in Fenton/O₃ combined processes

Abstract: Coking wastewater contains high concentration of organic pollutants and seriously endangers the natural ecological balance and human health. This study proposes a novel pre-treatment method that can significantly improve removal efficiency of organic pollutants in coking wastewater by the concept of “treating waste with waste.” Three two-step advanced oxidation processes were proposed by combining Fenton, ozonation with manganese tailings: (i) O₃/Mn tailings + H₂O₂, (ii) O₃/Mn tailings + Fenton and (iii) Fenton + O₃/Mn tailings. Results show that (1) Fenton + O₃/Mn tailings presented the best removal efficiency in the three combined processes. The reaction process was carried out by first performing Fenton reaction on the wastewater for 65 min, and then, the reaction wastewater was subjected to ozone and manganese tailings mixed reaction for 30 min, and the chemical oxygen demand (COD) and chromaticity were reduced by 61.0% and 96.1%, respectively. (2) After pre-treated with Fenton, the biodegradability of the wastewater can be significantly increased. When Fenton + O₃/Mn ore tailings were used to pre-treat the raw water, the biodegradability (BOD₅/COD) of the wastewater was increased to 0.54. It is proved that the combined process Fenton + O₃/Mn ore tailings has better performance than the ordinary single advanced oxidation process. Compared with the existing methods, the addition of manganese tailings containing manganese oxides as catalytic free radicals can significantly improve the treatment activity of advanced oxidation process (AOPS). Graphic abstract: [Figure not available: see fulltext.]