Electrically charged forward osmosis for enhancing urea recovery from synthetic urine

Abstract

Human urine, known as liquid gold, provides 80 % of the nitrogen sources in wastewater treatment plants through urea, making urea recovery an effective method for recycling nitrogen resources. In this work, a novel urea electrically charged forward osmosis (UEFO) system was used to treat human urine to enhance the accumulation of water penetration and urea recovery by overcoming concentration polarization and reverse solute flux. The system contained four chambers with an effective volume of 28 mL and was equipped with external glass vials. The feed solution was 40 mL of urine and the draw solution was 50 mL of potassium chloride solution. With the addition of an electric field, Cl−, SO42− and PO43− were transported from the feed solution (FS) to the anode chamber through the AEM, while OH– and SO42− were transported from the cathode chamber to the draw solution (DS) through the AEM, resulting in high osmotic pressure difference between the DS and FS, which enhanced the urea recovery. With the enhancement of current intensity from 0 to 0.04 A, water flux and urea increased from 8.02 LMH and 39.78 mg to 12.74 LMH and 56.16 mg (accounting for 76.82 % of total urea), respectively. These results demonstrated that the UEFO system could overcome the limitations of traditional FO systems (50 % recovery barrier) and showcased a promising performance for urea recovery from human urine by integrating electrochemical and osmotic-driven processes.