Simultaneous recovery of nitrogen and phosphorus from actual digester centrate in an electrochemical membrane system.

• Successful recovery of both nitrogen and phosphorus from real digester centrate is realized. • Addition of cation exchange membrane helps maintain pH in different chambers. • By-product of electrolysis - acid can be used for ammonia recovery. • Energy consumption and cost for nitrogen recovery can be potentially competitive. Recovering nutrients from wastewater will not only address pollution issues, but also reduce the need for nutrient from energy/resource - intensive production. Herein, a four-chamber electrochemical membrane system (4C-EMS) was developed to recover both nitrogen and phosphorus from real digester centrate through synergistically coupling electrodialysis with membrane contactor. The 4C-EMS successfully recovered more than 95 % of nitrogen and 85 % of phosphorus. The lowest specific energy consumption of 8.2 ± 0.2 kWh kg⁻¹ N was achieved under 1.25 mA cm⁻². A byproduct of the electrolysis – acid could compensate for 10∼32 % of total acid needed for ammonia absorption. The 4C-EMS effectively reduced heavy metals in struvite by 98 % compared to the struvite formed directly from the digester centrate. A preliminary cost analysis examined the relationship between acid price and dosage and estimated the operating cost of $0.58∼0.83 kg⁻¹ N; simultaneously recovered phosphorus would further increase the benefit of this system. [Display omitted] [ABSTRACT FROM AUTHOR]