Membrane scaling and flux decline during fertiliser-drawn forward osmosis desalination of brackish groundwater.
Fertiliser-drawn forward osmosis (FDFO) desalination has been recently studied as one feasible application of forward osmosis (FO) for irrigation. In this study, the potential of membrane scaling in the FDFO process has been investigated during the desalination of brackish groundwater (BGW). While most fertilisers containing monovalent ions did not result in any scaling when used as an FO draw solution (DS), diammonium phosphate (DAP or (NH4)2HPO4) resulted in significant scaling, which contributed to severe flux decline. Membrane autopsy using scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), and x-ray diffraction (XRD) analysis indicated that the reverse diffusion of DAP from the DS to the feed solution was primarily responsible for scale formation during the FDFO process. Physical cleaning of the membrane with deionised water at varying crossflow velocities was employed to evaluate the reversibility of membrane scaling and the extent of flux recovery. For the membrane scaled using DAP as DS, 80-90% of the original flux was recovered when the crossflow velocity for physical cleaning was the same as the crossflow velocity during FDFO desalination. However, when a higher crossflow velocity or Reynolds number was used, the flux was recovered almost completely, irrespective of the DS concentration used. This study underscores the importance of selecting a suitable fertiliser for FDFO desalination of brackish groundwater to avoid membrane scaling and severe flux decline.
Centre for Technology in Water and Wastewater, School of Civil and Environmental Engineering, University of Technology, Sydney (UTS), Broadway, NSW 2007, Australia.
Sherub
S
Phuntsho
Centre for Technology in Water and Wastewater, School of Civil and Environmental Engineering, University of Technology, Sydney (UTS), Broadway, NSW 2007, Australia.
Fezeh
F
Lotfi
School of Civil, Environmental & Architectural Engineering, Korea University, 1, 5-ka, Anam-Dong, Sungbuk-Gu, Seoul 136-713, Republic of Korea.
Seungkwan
S
Hong
Department of Chemical and Environmental Engineering, Yale University, P.O. Box 208286, New Haven, CT 06520-8286, USA.
Devin L
DL
Shaffer
Department of Chemical and Environmental Engineering, Yale University, P.O. Box 208286, New Haven, CT 06520-8286, USA.
Menachem
M
Elimelech
School of Civil, Environmental & Architectural Engineering, Korea University, 1, 5-ka, Anam-Dong, Sungbuk-Gu, Seoul 136-713, Republic of Korea. Electronic address: shonhokyong@yahoo.co.kr.
Ho Kyong
HK
Shon
D005308:Fertilizers / Q000032:analysis*; D060587:Groundwater / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D009995:Osmosis; D054712:Salinity; D013052:Spectrometry, X-Ray Emission; D018508:Water Purification / Q000379:methods*; D014961:X-Ray Diffraction
D005308:Fertilizers
Brackish groundwater; Desalination; Forward osmosis; Inorganic fouling; Membrane scaling