Simultaneous nutrient removal and selective recovery of nitrogen and phosphorus from municipal wastewater: A novel combined ion exchange–surface precipitation process from proof of concept to pilot scale

The simultaneous removal and separate recovery of ammonium and phosphate from mechanical sludge dewatering effluents was successfully performed via ion exchange and surface precipitation using natural zeolites. Ammonium ion exchange on Ca-regenerated clinoptilolite was combined with simultaneous air stripping of the regeneration fluid to retrieve nitrogen and periodic acid flushing of the zeolite to recover precipitated phosphates within a single process (modified ion exchanger loop stripping process). System performance was evaluated by comparing removal rates, zeolite loadings and recovery fluid concentrations across different scales ranging from laboratory experiments to pilot-scale implementation at a wastewater treatment plant. Ammonium removal rates from effluents ranged from 50% to 80%, while phosphorus removal rates were between 73% and 82%. Ammonium concentrations in the N-recovery solutions exceeded twice the initial concentrations in the wastewater, while phosphate concentrations in the P-recovery solutions were over four times higher. These results, along with pilot-scale insights, suggest that the process is viable for larger-scale application at wastewater treatment plants to recover renewable ammonium and phosphate. • N&P were simultaneously removed from wastewater by ion exchange and precipitation • Both elements were selectively recovered by using air stripping & acid flushing • A stable process with low demand on chemicals, energy & infrastructure was developed • Upscaling from the lab to the pilot scale on site was successfully demonstrated