Treatment of domestic wastewater phosphate by electrocoagulation using Fe and Al electrodes: A comparative study

In this work, phosphorus removal from domestic wastewater was studied through electrocoagulation (EC) using iron (Fe) and aluminium (Al) anodes in a batch EC reactor. Key parameters investigated include; initial pH, initial phosphorus concentration (Ci), reaction time, current density (j), metal-to-phosphorous ratio, charge loading (q) and electrode type. The Al/P mole ratio at current densities of 10, 20, 30 and 40 A/m2 was obtained as 0.84, 1.68, 0.95 and 0.77, respectively, while the Fe/P mole ratio for these current densities was calculated as 1.81, 3.29, 4.09 and 4.48, respectively. The optimums to obtain <0.01 mg/L effluent P concentration at Ci = 52 mg/L PO4-P were; pHi = 4, j = 20 A/m2 and EC time = 100 min (q = 954C) for Fe electrode, whereas for Al electrode, the optimums were; EC time = 50 min (q = 372C), pHi = 4, j = 20 A/m2. Also, the final pHf increased with increase in EC time; when pHi = 4, Ci = 52 mg/L and j = 20 A/m2, the final pHf was 8.52 at 50 min for Al electrode and 10.62 at 100 min for Fe electrode. The operating costs, energy and electrode consumptions were calculated as 1.032 $/m3, 1.143 kWh/m3 and 0.218 kg/m3 respectively for Al electrode and 1.343 $/m3, 4.179 kWh/m3 and 0.884 kg/m3, respectively for Fe electrodes. Overall, Al anodes provided a higher phosphorus removal efficiency in a shorter EC time and lesser metal-to-phosphorous ratio compared to Fe anodes.