Hydroxyl and sulfate radical advanced oxidation processes: Application to an agro-industrial wastewater

In this study, the effectiveness of a UV-A LEDs system, transition metal activators (Fe and Co) and different oxidants (hydrogen peroxide, H2O2; peroxymonosulfate, PMS and persulfate, PS) were evaluated in the degradation of an elderberry wastewater. Several oxidation processes can be applied using the pointed out oxidants, UV radiation and transition metals, which can be classified as hydroxyl radical advanced oxidation processes (HR-AOPs) and sulfate radical advanced oxidation processes (SR-AOPS). The initial trials achieved 99% of TOC removal in UV-A LED/H2O2 (with multi-step additions)/Fe2+ and with PMS (single addition)/Co2+ processes, which were afterwards optimized for metal activator dosage. The UV-A LED/H2O2 (multi-step addition)/Fe2+ process demonstrated a lower TOC removal when the Fe2+ concentration was reduced (50 mg/L - 99% removal and 25 mg/L only 75%). On the other hand, PMS (single step addition)/Co2+ process still presented 99% of TOC removal, even when the Co2+ concentration decreased from 50 to 25 mg/L. Bearing in mind this performance, the Co2+ concentration was optimized achieving the following optimal operational conditions: [PMS] = 45 mM; [Co2+] = 7.5 mg/L; pH = 3 and reaction time = 120 min. In addition, PMS/Co2+ process allows to increase the biodegradability (BOD5/COD) ratio from 0.30 to 0.53 mg O-2/L of treat water. Hence, the PMS/Co2+ oxidation process can be considered a promising technology for application in real scale agro-food wastewater treatment plants, since it shows a very good compromise in terms of TOC removal and reduced carbon footprint. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

This study evaluated and optimized the degradation process of elderberry wastewater using a UV-A LED system, transition metal activators, and different oxidants, achieving high TOC removal rates and increased biodegradability ratio in the PMS/Co2+ process.