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

Abstract

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.