Synergistic effects of aluminum/iron oxides and clay minerals on nutrient removal and recovery in water filtration media

Abstract

The eutrophication of water bodies due to excessive amounts of nutrients is an ongoing issue that coincides with the depletion of the commercial and affordable phosphorus reserves that are required for food production. This paper presents the investigation of Advanced Green Environmental Media (AGEM) for nutrient removal and recovery, in stormwater runoff or agricultural discharge, via a laboratory-scale fixed-bed column study. The water filtration media mix of AGEM was compared to existing Iron-filings Based Green Environmental Media (IFGEM) for performance assessment. Synergistic effects among iron, aluminum, and clay resulted in different capacities for removal and recovery of ammonia, nitrate, and phosphate simultaneously in IFGEM and AGEM due to their different sorption functionalities. Research findings indicate that AGEM and IFGEM removed 52% and 42% of the nitrate load, respectively. While both filtration media exhibited elevated phosphate removal than before, 98% and 96% of the total phosphate load can be removed by IFGEM and AGEM, respectively. The discovery that the AGEM mix exhibited synergy among clay, iron, and aluminum particles with higher application potential on a long-term basis is the first of its kind in water filtration media. In this process, optimal phosphate removal was achieved by utilizing ammonia, a byproduct of nitrate reduction, which precipitated to form ammonium-phosphate salt. Finally, the synergistic effects of iron, aluminum, and clay for promoting urban farming, stormwater treatment, and hydrogen gas production simultaneously was confirmed in an urban food-energy-water nexus.