Regeneration and modelling of a phosphorous removal and recovery hybrid ion exchange resin after long term operation with municipal wastewater

Adsorption represents one of the most promising process for phosphorous (P) removal and recovery from municipal wastewater, but questions about its long-term stability remain. The goals of this work were (i) to assess changes in morphology and adsorption performances of hybrid anion exchanger (HAIX) LayneRT after 2.5 years of operation in a 10 m3 d−1 demonstration plant fed with secondary-treated municipal wastewater, (ii) to optimize the LayneRT regeneration procedure, and (iii) to evaluate the suitability of the ion exchange model to describe P adsorption on LayneRT. LayneRT is composed of hydrated ferric nanoparticles dispersed in a strong base anion exchange resin. Batch and continuous flow adsorption/desorption tests were conducted with the resin used for 2.5 years, regenerated with two alternative solutions: NaOH, reactivating mainly the iron nanoparticles active sites, and NaOH + NaCl, also regenerating the active sites of the ion exchange media. The physicochemical characterization by Scanning Electron Microscope indicated that regeneration by NaOH significantly reduced the deterioration of the resin surface, even after 59 adsorption/desorption cycles. Lab-scale continuous flow tests showed that the resin regenerated with either solution featured P adsorption performances very close to that of the virgin resin. The isotherm tests showed that P adsorption by LayneRT was effectively simulated with the ion exchange model. This study confirms that LayneRT is a durable, resistant and promising media for P recovery from wastewater.