Donnan Dialysis for scaling mitigation during electrochemical ammonium recovery from complex wastewater

Inorganic scaling is often an obstacle for implementing electrodialysis systems in general and for nutrient recovery from wastewater specifically. In this work, Donnan dialysis was explored, to prevent scaling and to prolong operation of an electrochemical system for TAN (total ammonia nitrogen) recovery. An electrochemical system was operated with and without an additional Donnan dialysis cell, while being supplied with synthetic influent and real digested black water. For the same Load Ratio (nitrogen load vs applied current) while treating digested black water, the system operated for a period three times longer when combined with a Donnan cell. Furthermore, the amount of nitrogen recovered was higher. System performance was evaluated in terms of both TAN recovery and energy efficiency, at different Load Ratios. At a Load Ratio 1.3 and current density of 10 A m⁻², a TAN recovery of 83% was achieved while consuming 9.7 kWh kg_N⁻¹.