Challenges in Forward Osmosis of Seawater Using Ammonium Bicarbonate as Osmotic Agent

摘要

This study aimed at exploring whether product quality, membrane fouling and salt reverse flow would be challenges in forward osmosis (FO) of seawater using NH43 as an osmotic agent. Experiments were conducted with a lab scale FO system containing effective membrane area of 95 cm2. Synthetic seawater (SSW) with 3.5-7.0 mg/L boron and a real seawater (RSW) were used as feeds and 1.5-2.5 M NH43 as draw solutions. The experimental operation could be stablized within 0.5 h. For the SSW, boron rejection ranged of 47-85% and increased with increasing water flux while boron in the permeate was greater than 0.8mg/L. Water flux with RSW was 3 times lower than that with SSW, indicating that there might be serious membrane fouling with RSW. It was surprisingly observed that non volatile organic in the FO permeate was 8-10 mg/L, which was from the draw solution although NH43 used was analytical grade. Additional water cost would be $0.4/m3 because of NH43 loss. It was concluded that product quality in terms of high TOC contaminant in NH43 and low boron removal, serious fouling with RSW and salt reverse flow could be challenges for the FO process using NH43 as osmotic agent for seawater desalination.