Effect of organic fouling on nutrient recovery from municipal wastewater in magnesium anode-based electrodialysis processes

This study investigated the effects of organic concentration in wastewater on nutrient recovery in a 5-cell electrodialysis (ED) system with sacrificial magnesium (Mg) anode under different current densities and linear flow velocities. Municipal wastewaters without/with dosed alginate were used as feed solutions to simulate diverse organic concentrations. The results revealed that increasing organic concentration in the feed (1) had a more significant effect on the overall ED stack resistance at a lower applied current density than at a higher current density; (2) promoted more organic foulant accumulation on the cation exchange membrane (CEM) than that on the anion exchange membrane (AEM) due to organics-cation interaction causing charge neutralization. Furthermore, the fouled membrane (24-h operation) caused a decrease of ammonia transport by ∼ 11 % and an increase of phosphate transport by ∼ 33 %, which was possibly associated with dissimilar compositions and electrical resistances of the foulants on CEM and AEM. Increasing linear flow velocity in the ED cells more significantly improved the ammonia transport rate (averagely 29-fold) than phosphate transport rate (averagely 8-fold) due to more reduction of foulant electrical resistance on the CEM than that on the AEM. This study highlights the organic fouling behaviours and their relationship with the nutrient recovery in the ED process, offering important information for further development of membrane fouling control strategies.