Effective nutrient recovery from digester centrate assisted by in situ production of acid/base in a novel electrochemical membrane system

Nutrient recovery from wastewater is important to the circular economy and requires technological advancements. Herein, a novel electrochemical membrane system (EMS) was developed to recover both phosphorus and nitrogen from real digester centrate. The EMS synergistically coupled electrodialysis with membrane contactor to facilitate the selective recovery of individual nutrient. Under a constant current density of 10 mA cm−2, the EMS recovered more than 95% of PO43--P and 80% of NH4+-N, at energy consumption of 670 ± 48 kWh kg−1 P and 52 ± 2 kWh kg−1 N. It should be noted that the same energy was used to recover two nutrients. When the acid produced from the anodic reaction was directly reused for N absorption, the final concentrations of PO43--P and NH4+-N reached 144 ± 3 and 1232 ± 130 mg L−1, respectively. Adding extra acid did not affect phosphorus recovery but significantly enhance nitrogen recovery to 1797 ± 83 mg L−1. The results of this study have demonstrated the feasibility of the proposed EMS and encouraged further investigation to reduce its energy consumption and improve nutrient recovery.