The Evaluation of Potential Forward Osmosis Draw Solutes for Seawater Desalination in Hawai’i

Abstract

In response to the increasing scarcity of freshwater globally due to overconsumption and shifting precipitation patterns in response to climate change, this thesis focuses on testing a potentially energy efficient method of seawater desalination called forward osmosis. The focus of the thesis is to assist in determining some of the best draw solutions for seawater desalination in the Forward Osmosis process. The research began by literature review of water purification methods mostly focused on forward osmosis. A forward osmosis water purification system was assembled, and three different inorganic draw solutes selected. Three different concentrations (0.6M, 1M, 2M) of the draw solutions were tested for their effectiveness against deionized water as feed solution. The performance of the best draw solution concentrations; NaCl (2M), NH4Cl (2M), KCl (2M) were tested against Seawater feed solution obtained from Ala Moana Beach Park. The 2M KCl draw solution had the best performance against both 2M NaCl and 2M NH4Cl draw solutions as determined by water flux analyses and change in draw solution mass during FO process. The diluted draw solution products (NH4Cl and KCl) of FO process have potential for minimizing the amount of freshwater used in fertigation (N and K sources).