American Journal of Water Resources, 2013, Vol. 1, No. 3, 51-55 Available online at http://pubs.sciepub.com/ajwr/1/3/6 © Science and Education Publishing DOI:10.12691/ajwr-1-3-6 Challenges in Forward Osmosis of Seawater Using Ammonium Bicarbonate as Osmotic Agent Jian-Jun Qin 1,* , Gayathri Danasamy 2 , Winson C.L. Lay 1 , Kiran A Kekre 1 1 PUB, Singapore’s National Water Agency, Singapore 2 Imperial College London, UK *Corresponding author: qin_jianjun@pub.gov.sg Received December 23, 2012; Revised October 17, 2013; Accepted November 13, 2013 Abstract This study aimed at exploring whether product quality, membrane fouling and salt reverse flow would be challenges in forward osmosis (FO) of seawater using NH 4 HCO 3 as an osmotic agent. Experiments were conducted with a lab scale FO system containing effective membrane area of 95 cm 2 . 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 NH 4 HCO 3 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 NH 4 HCO 3 used was analytical grade. Additional water cost would be $0.4/m 3 because of NH 4 HCO 3 loss. It was concluded that product quality in terms of high TOC contaminant in NH 4 HCO 3 and low boron removal, serious fouling with RSW and salt reverse flow could be challenges for the FO process using NH 4 HCO 3 as osmotic agent for seawater desalination. Keywords: seawater desalination, forward osmosis, ammonium bicarbonate, boron removal, membrane fouling, salt loss Cite This Article: Jian-Jun Qin, Gayathri Danasamy, Winson C.L. Lay, and Kiran A Kekre, “Challenges in Forward Osmosis of Seawater Using Ammonium Bicarbonate as Osmotic Agent.” American Journal of Water Resources 1, no. 3 (2013): 51-55. doi: 10.12691/ajwr-1-3-6. 1. Introduction Forward osmosis (FO) is known as the net movement of water across a semi-permeable membrane driven by a difference in chemical potential across the membrane, i.e., passage of water is from lower concentration side to higher one because the lower the concentration, the higher the water chemical potential. Although the FO phenomenon was observed in 1748, the interests in research on FO and in engineered applications of FO have been increasingly attractive since 2000 [1,2]. However, there are still three major challenges of FO in municipal scale seawater desalination: a) fabrication of FO membranes with high water flux and high draw solute rejection; b) being lack of appropriate draw solutions; and c) cost-effective post-treatment on a total system approach [3]. In desalination application, the energy consumption for seawater desalination using reverse osmosis (RO) is currently 3-3.5 kWh/m 3 . Newly developed FO technology could potentially lower desalination energy consumption since osmotic pressure, not hydraulic pressure as in the case of RO, provides a natural driving force for water transport through the FO membrane. It is reported that the Manipulated Osmosis Technology developed by University of Surrey could reduce energy consumption to <1.6 kWh/m 3 using proprietary osmotic agents as a draw solution. The proprietary process had also been demonstrated using a 1 m 3 /h pilot unit and is now ready for commercialization [4]. Khaydarov [5] developed a solar powered direct osmosis desalination process with a pilot testing of 1 m 3 /h capacity. He reported the specific power consumption of the desalination process could be less than 1 kWh/m 3 excluding the requirement on solar energy. In recent years, there has been increasing interest in an integrated FO process for seawater desalination developed and intensively studied by Elimelech and his research group at Yale University [6,7,8,9]. In the process, ammonium bicarbonate (NH 4 HCO 3 ) is utilized as the osmotic agent and a thermal process such as the distillation is proposed as the post-treatment to strip and recover the osmotic agent. Potential advantages of NH 4 HCO 3 osmotic agent include high osmotic pressure which can result in high water flux and utilisation of waste heat (if available) to recover the osmotic agent at <60 ºC. Other researchers [10-16] have also studied the FO process with NH 4 HCO 3 as the osmotic agent. However, existing studies on the NH 4 HCO 3 concept focus mainly on effects such as osmotic agent concentration, temperature, and role of internal concentration polarization on water flux. Study of this process using real seawater as a feed