Electrochemical oxidation for aquaculture wastewater treatment: comprehensive assessment of pollutant removal, microbial inactivation, and operational economics in Nile Tilapia systems

Intensive tilapia aquaculture generates substantial wastewater containing elevated levels of nitrogenous compounds, organic matter, and pathogenic microorganisms that pose significant environmental risks. This study evaluated graphite electrode-based electrochemical treatment for the remediation of brackish tilapia ( Oreochromis niloticus ) aquaculture effluent. A laboratory-scale electrolytic system was designed with parallel graphite electrodes (570 cm² surface area) operating at 6 mA·m -2 current density with 2 cm electrode spacing. Five treatment durations (0, 15, 30, 45, and 75 minutes) were evaluated using a completely randomized design (n=3). Water quality parameters, pollutant removal efficiency, energy consumption, and economic feasibility were assessed. Electrochemical treatment significantly improved dissolved oxygen (from 29% to >97% saturation), pH (from 6.74 to 7.53), and oxidation-reduction potential (112 to 232 mV). Total ammonia nitrogen decreased by 91.6% (0.046 mg.L -1 ), nitrite by 94.9% (0.012 mg.L -1 ), BOD₅ by 63.2% (11.67 mg.L -1 ), and COD by 53.6% (30.0 mg.L -1 ) after 75 minutes. Microbial inactivation achieved 5.3 log reduction (99.999% removal) with exceptional disinfection kinetics. Energy consumption ranged from 1.35 to 9.40 kWh.m -3 , with optimal cost-effectiveness at 15-30 minute treatments. Chlorinated byproducts (chlorate: 0.102 mg.L -1 , chlorite: 0.046 mg.L -1 ) remained below regulatory limits. Economic analysis revealed treatment costs of $0.68-1.72/m³, with 15-minute treatment providing maximum efficiency per unit cost. The technology demonstrates significant potential for sustainable aquaculture wastewater management, while balancing environmental benefits with operational feasibility.