Forward osmosis (FO)-based spent dialysate regeneration

Abstract

Hemodialysis is the most commonly used treatment for renal replacement therapy (RRT) and dominates the global dialysis market. As one of the most water-consuming treatments in medical procedures, hemodialysis has room for improvement in reducing wastewater effluent. In recent years, research on recovering water from spent dialysate is being actively conducted as a new attempt to reduce water consumption and cost in the medical industry. However, there are few proposals to utilize the forward osmosis (FO) process. This study was performed to evaluate the feasibility of the FO for reuse of spent dialysate using a commercial thin-film composite (TFC) membrane with high water permeability and salt rejection. The performance of FO and pressure-assisted forward osmosis (PAFO) by the operating conditions was compared, and the transition ion concentration, the removal of urea and creatinine, and membrane fouling of FO were investigated. In the results, the average water flux in active layer facing feed solution (AL-FS) mode was more than twice that of active layer facing draw solution (AL-DS) mode, and FO showed a relatively stable flux reduction for 12 hours. High reverse salt flux was observed in PAFO due to membrane deformation. In addition, polyvalent ions, urea and creatinine in solutions removed during the membrane filtration process affected scaling and membrane fouling. To operate the spent dialysate reuse system with FO, a flux of 50 LMH or more and a membrane area of 5-7.5 m2 were required. Although an additional water supply is expected, this study has shown the potential for FO to reuse spent dialysate to save water consumed in hemodialysis.