Demonstration of ion exchange technology for phosphorus removal and recovery from municipal wastewater

Orthophosphate (PO4-P) removal and recovery from municipal wastewater were investigated in a 10 m3/day hybrid anion exchanger (HAIX) demonstration plant. To date, HAIX resins have been investigated for PO4-P removal at laboratory scale with promising results but there is a need to investigate the application of the technology at larger scale, over extended operation whilst establishing an efficient regenerant management solution. The HAIX removed an average of 6 mg PO4-P /L to >0.3 mg PO4-P/L, within 430 bed volumes, with a capacity of 4.1 mg PO4-P/g resin. To manage the regenerant (NaOH 2%) efficiently, this was reused up to 8 times, reaching 785 mg PO4-P/L, but the adsorption capacity was compromised, and it decreased to 1.5 mg PO4-P/g resin. By adding calcium hydroxide to the saturated NaOH, 95% of the PO4-P was recovered as hydroxyapatite, and at the same time the regeneration effectiveness was re-established, as <0.3 mg PO4-P/L was reached again in the effluent. The treated NaOH was reused as regenerant solution, ensuring high effluent quality of <0.2 mg PO4-P/L. This study confirmed the capability of HAIX technology to remove and recover PO4-P from wastewater offering a solution which ensures both a high effluent quality and a circular economy approach.