Pilot-scale magnesium electrocoagulation for saline fish processing wastewater: Technology assessment, sludge valorization and cost implications

Saline fish processing wastewater remains difficult to treat because high organic loading, nutrients, suspended solids and salinity can destabilize conventional biological processes. This study combined bibliometric analysis, literature-based technology assessment and pilot-scale validation to identify suitable physicochemical treatment strategies and evaluate magnesium electrocoagulation as a treatment–resource recovery option for Pangasius processing wastewater. Bibliometric and thematic analyses showed that advanced physicochemical treatment is a central research direction in this field, linking pollutant removal, process optimization and resource recovery. Technology comparison further indicated that membrane systems provide high effluent quality but are constrained by fouling and limited loading tolerance, whereas electrochemical processes offer a broader operating window for saline and high-strength wastewater. Guided by these findings, a continuous-flow Mg-electrode electrocoagulation system was tested under pilot-scale conditions. At pH 9, 60 min and 18.78 A/m², the system removed 63.90% COD, 75.86% turbidity, 68.40% NH₄⁺–N and 84.95% PO₄³⁻–P. The generated sludge contained 24.0% organic carbon, 5.67% total nitrogen, 8.32% P₂O₅ and 1.14% total magnesium, indicating its potential as a nutrient-bearing precursor after safety verification and nutrient adjustment. Cost analysis showed that redirecting sludge from disposal to reuse reduced the estimated operating cost from 7.34 to 5.09 USD/m³, equivalent to a 30.65% reduction. These results suggest that Mg-electrode electrocoagulation can serve as a practical treatment pathway for saline fish processing wastewater when pollutant removal, sludge valorization and operating cost are considered together.