Advanced cork washing wastewater treatment using combined physicochemical and electrocoagulation techniques

The increased demand for improved finish quality of cork stoppers has raised significant environmental concerns, particularly regarding the treatment of cork washing wastewater (CWW), which contains high levels of organic and inorganic pollutants. This study investigates the application of a batch electrocoagulation (EC) process, with an iron anode and a stainless-steel cathode, as an effective post-treatment following conventional physicochemical methods. The influence of current density on pollutant removal and treatment cost was systematically evaluated. Results demonstrated that EC can significantly enhance CWW quality, with pollutant removal efficiencies and costs highly dependent on operational conditions. For scenarios where total nitrogen (TN) removal is not a priority, a current density of 67.6 A/m 2 provides optimal cost-efficiency, achieving 93.0 % chemical oxygen demand (COD) in just 1 min, and up to 98.2 % COD, 68.6 % total organic carbon (TOC), 30.9 % TN, and 98.7 % total suspended solids (TSS) after 30 min reaction time, with treatment costs ranging from 0.018 €/m 3 to 0.51 €/m 3 . When higher TN removal is required, a current density of 135 A/m 2 achieves maximum removal (99.2 % COD, 70.1 % TOC, 54.4 % TN, and 98.8 % TSS) at a cost of 2.25 €/m 3 . These findings confirm that EC is a promising, flexible and scalable technology for CWW treatment, particularly in contexts where biological treatment is limited by low biodegradability or toxicity. The process offers an effective balance between treatment performance and operational cost, supporting more sustainable wastewater management in the cork industry. • Boosted wastewater treatment efficiency by combining PC with EC. • Achieved 93.0 % COD removal in just 1 min when treating cork washing wastewater. • Significant total nitrogen elimination reached within 30 min of treatment. • Operational costs remain competitive, ranging from 0.018 to 2.25 €/m 3 . • Optimal cost-efficiency achieved at a current density of 67.6 A/m 2 .