Operational variables of technological interest in the application of the Fenton process to leachate treatment

H.D. TRAID; M.L. VERA; C.G. SILVA; A.N. DWOJAK; I.E. LÓPEZ; M.I. LITTER

Congreso; WCCE11- 11th world Congress of Chemical Engineering, Buenos Aires; 2023

By a combination of physical, chemical, and microbial processes, a municipal solid waste (MSW) generates a leachate where the pollutants contained in the solid are transferred to the liquid phase. In a sanitary landfill, the MSW final disposal site, the characteristics of the leachate depends on the MSW composition, landfilling technology, weather, and leachate age. The variability and heterogeneity of the leachates render a conventional treatment sequence insufficient to achieve the decontamination degree required by the regulations; thus, additional stages are necessary to complete the purification process.In the Fenton process, a widely applied Advanced Oxidation Process in leachate treatment, the H2O2 is activated by Fe2+ to generate very reactive hydroxyl radicals (HO•). The influence of the main variables of the Fenton process, such as temperature, reagent concentration, reagent ratios, pH, etc., on the efficiency of the leachate treatment has been widely reported [1]. The present work explores the influence of other variables of high technological interest: magnetic stirring (1 vs. 24 h), settling (supernatant vs. homogenized treated leachate), antifoam addition (no addition vs. 1%/v), acidifying agent (H2SO4 vs. H3PO4), reagent quality (reagent vs. industrial grade) and H2O2 addition methodology (all volume at once vs. pulses of 10% of the total volume per min).The assays were realized at bench scale on real leachate samples taken from the Fachinal sanitary landfill (Misiones, Argentina), in the best operational conditions founded in previous assays [2]: atmospheric pressure, room temperature, initial pH 3, [H2O2] = 0.2 M, [H2O2]/[Fe] = 50 (molar ratio) and magnetic stirring. The chemical oxygen demand (COD) was used to follow the behavior of the process, as a global decontamination parameter. Na2CO3 was used as an inhibitor to avoid the influence of the remaining H2O2 on the COD determination.Settling operation of 1 h, after the Fenton process, influenced the COD reduction: the supernatant (liquid phase) showed an 81% of COD removal against a 63% of a sample with resuspending and homogenizing solids. On the other hand, agitation time, quality of the reagents, addition of an antifoam agent, nature of the acidifier, and methodologies for H2O2 addition had a minor influence, which may represent important economical savings.The results clarify some operational aspects scarcely reported, relevant for the application of the Fenton technology at a real scale for leachate treatment. Several operational variables studied can be managed allowing achieving a process with the lowest costs without loss in the treatment efficiency.