Removal of phosphate from wastewaters for further utilization using electrocoagulation with hybrid electrodes – Techno-economic studies

Abstract

The electrocoagulation (EC) process employed in the removal of phosphate from synthetic wastewater (SWW, 30mg/l) was optimized, followed by successful scale-up experiments. The optimum process conditions (96% phosphate removal) for laboratory-scale SSW were found to be: anode/cathode=Al/Fe (although Fe/Al performed similarly), initial pH=5, current density=100A/m2, treatment time=15min, supporting electrolyte=1.0g/l NaCl and electrode gap=7mm.Real industrial phosphate-containing mining wastewater (MWW) and dairy wastewater (DWW) were also treated with EC, with high pollutant removal efficiencies (optimal phosphate removal of 79% and 93% in 30min and 60min, respectively) achieved over the wide initial pH range studied. Electricity consumption and operating costs values in optimum conditions were low for all wastewaters: 0.75kWh/m3 and 0.17€/m3 for SSW (laboratory scale), 2.11kWh/m3 and 0.28€/m3 for MWW, and 1.46kWh/m3 and 0.31€/m3 for DWW. To summarize, the feasibility of using EC in removing phosphate from the wastewater types studied was proven. Utilization of the resulting EC sludge – a potentially valuable phosphorus source in the future (especially in granulated bio ash-based fertilizer products) – was also studied and is discussed.