Biodegradability improvement and toxicity reduction of soil washing effluents polluted with atrazine by means of electrochemical pre-treatment: Influence of the anode material

• Published in: Journal of environmental management 2020-02, Vol.255, p.109895-109895, Article 109895
• Main Authors: Carboneras Contreras, María Belén, Villaseñor Camacho, José, Fernández-Morales, Francisco Jesús, Cañizares, Pablo Cañizares, Rodrigo Rodrigo, Manuel Andrés
• Format: Article
• Language: English
• Subjects: Anodic oxidation; Atrazine; Biodegradability; Diamond; Electrodes; Oxidation-Reduction; Soil; Soil washing effluent; Toxicity; Water Pollutants, Chemical
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2019.109895

This work focuses on the partial anodic electro-oxidation of atrazine-polluted soil washing effluents (SWE) in order to reduce its toxicity and to improve its biodegradability. Concretely it has been evaluated the influence of the anodic material used. It is hypothesized that such partial oxidation step could be considered as a pre-treatment for a subsequent biological treatment. At first, atrazine was extracted from a polluted soil by means of a surfactant-aided soil-washing process. Then, four different anodic materials were studied in partial electro-oxidation pre-treatment batch experiments at different electric charges applied: Boron Doped Diamond (BDD), Carbon Felt (CF), and Mixed Metal Oxides Anodes with Iridium and Ruthenium. Atrazine, TOC, surfactant and sulphate species concentrations, as well as changes in toxicity and biodegradability, were monitored during electrochemical experiments, showing important differences in their evolution during the treatment. It was observed that BDD was the most powerful anodic material to completely degrade atrazine. The other materials achieve an atrazine degradation rate about 75%. Regarding mineralization of the organics in SWE, BDD overtakes clearly the rest of anodes tested. CF obtains good atrazine removal but low mineralization results. All the anodes tested slightly reduced the ecotoxicity of the water effluents. About the biodegradability, only the effluent obtained after the pre-treatment with BDD presented a high biodegradability. In this sense, it must be highlighted the mineralization obtained during the BDD pre-treatment was very strong. These results globally indicate that it is necessary to find a compromise between reaching efficient atrazine removal and biodegradability improvement, while also simultaneously avoiding strong mineralization. Additional efforts should be made to find the most adequate working conditions. [Display omitted] •Anode material influences electrooxidation of atrazine in soil washing effluents.•BDD completely removes atrazine but also produces strong mineralization of surfactant.•Rest of anodes reached approximately 75% atrazine removal and partial mineralization.•Toxicity slightly decreased in all cases.•Biodegradability improved only when using BDD, but mineralization should be reduced.