Low-Resistance GO–POM Composite Cathode and Asymmetric Geometry Reduce Energy Consumption by 37% in Electrocoagulation of Hypereutrophic Lake Wastewater

Electrocoagulation (EC) is a promising technology for hypereutrophic wastewater treatment, yet reactor geometry, electrode passivation, and energy inefficiency remain key limitations. This study developed a graphene oxide–phosphomolybdate (GO–POM) composite cathode integrated into an asymmetric electrode configuration (anode:cathode area ratio = 1:10) to simultaneously address charge-transfer resistance, passivation, and energy consumption in the EC treatment of Lake Mariut wastewater (Cairo, Egypt). The GO–POM composite exhibited a charge-transfer resistance of 2.34 ± 0.09 Ω·cm2, significantly lower than that of a graphite rod (4.12 ± 0.31 Ω·cm2), carbon felt (3.28 ± 0.24 Ω·cm2), and SS316 (6.84 ± 0.45 Ω·cm2). Under optimized conditions (j = 10 mA/cm2, pH 6.0, 60 min), the asymmetric GO–POM system achieved 92.2 ± 1.8% TOC removal with a specific energy consumption of 4.4 ± 0.3 kWh/m3—a 37% reduction compared to the symmetric conventional baseline (6.1 ± 0.4 kWh/m3). The treated effluent met the discharge limits set by Egyptian Law 48/1982 for COD, BOD, and TSS. Preliminary techno-economic and life-cycle analyses identified Al electrode consumption as the dominant cost and carbon driver, with a solar-powered continuous-flow operation as the priority pathway for further energy reduction.