Ammonium recovery from wastewater by Donnan Dialysis: A feasibility study

Abstract Alternative ammonium management other than removal is desired with the development of the circular economy. A proof-of-concept study using a cost-effective Donnan dialysis to recover ammonium from wastewater was herein performed. The results showed that the cross-flow velocity of the feeding and receiving solution only affected the mass transfer rate of ammonium rather the final equilibrium, which was determined by the concentration of both the driving and target ionic species. The monovalent and divalent co-existing cation reduced the ammonium migration given an equally high quantity, with the order of the sequence for the interference as Mg2+>K+. Interestingly, a selective membrane can effectively suppress the negative impact of Mg2+ but hardly for K+, the latter being of the same diffusion coefficient to ammonium resulting into unsatisfactory separation. A final case study using synthetic typical domestic wastewater shows when the total co-existing cation concentration accounts for 30% of that for NH4+ in equivalence, the recovery of ammonium remained ca.90%. The herein high ammonium recovery was easily achieved at small quantity of salt, suggesting Donnan dialysis could be a promising option towards nutrient recovery from wastewater, especially in remote area.