Exploring high charge of phosphate as new draw solute in a forward osmosis-membrane distillation hybrid system for concentrating high-nutrient sludge

Nguyen Cong Nguyen; Hau Thi Nguyen; Su-Thing Ho; Shiao-Shing Chen; Huu Hao Ngo; Wenshan Guo; Saikat Sinha Ray; Hung-Te Hsu

doi:10.1016/j.scitotenv.2016.03.025

Exploring high charge of phosphate as new draw solute in a forward osmosis-membrane distillation hybrid system for concentrating high-nutrient sludge

Sci Total Environ. 2016 Jul 1:557-558:44-50. doi: 10.1016/j.scitotenv.2016.03.025. Epub 2016 Mar 17.

Authors

Nguyen Cong Nguyen¹, Hau Thi Nguyen¹, Su-Thing Ho², Shiao-Shing Chen³, Huu Hao Ngo⁴, Wenshan Guo⁵, Saikat Sinha Ray², Hung-Te Hsu⁶

Affiliations

¹ Institute of Environmental Engineering and Management, National Taipei University of Technology, No. 1, Sec. 3, Chung-Hsiao E. Rd, Taipei 106, Taiwan, ROC; Faculty of Environment and Natural Resources, DaLat University, Viet Nam.
² Institute of Environmental Engineering and Management, National Taipei University of Technology, No. 1, Sec. 3, Chung-Hsiao E. Rd, Taipei 106, Taiwan, ROC.
³ Institute of Environmental Engineering and Management, National Taipei University of Technology, No. 1, Sec. 3, Chung-Hsiao E. Rd, Taipei 106, Taiwan, ROC. Electronic address: f10919@ntut.edu.tw.
⁴ School of Civil and Environmental Engineering, Faculty of Engineering and Information Technology, University of Technology Sydney, Broadway, NSW 2007, Australia. Electronic address: h.ngo@uts.edu.au.
⁵ School of Civil and Environmental Engineering, Faculty of Engineering and Information Technology, University of Technology Sydney, Broadway, NSW 2007, Australia.
⁶ Department of Environmental Engineering, Chung Yuan Christian University, Chung Li 32023, Taiwan, ROC.

PMID: 26994792
DOI: 10.1016/j.scitotenv.2016.03.025

Abstract

For the first time, a high charge of phosphate was used as the draw solute in a forward osmosis-membrane distillation (FO-MD) hybrid system for concentrating high-nutrient sludge. A high water flux (12.5L/m(2)h) and a low reverse salt flux (0.84g/m(2)) were simultaneously achieved at pH9 by using 0.1M Na3PO4 as the draw solute and deionized water as the feed solution in the FO process. The specific reverse salt flux of 0.1M Na3PO4 (Js/Jw=0.07g/L) was considerably less than that of 0.1M NaCl (Js/Jw=0.37g/L) because the complexion between Na(+) and HPO4(2-) at pH9 led to the reduction of free Na(+) ions, which subsequently reduced the reverse salt diffusion substantially. Moreover, for a feed solution with an initial sludge concentration of 3500mg/L, the sludge concentration could be concentrated to 19,800 and 22,000mg/L in the pressure-retarded osmosis (PRO) and FO membrane orientations, respectively, after 15h of operation. Four types of MD membranes were selected for draw solution recovery; of these, a polytetrafluoroethylene membrane with a pore size of 0.45μm was the most effective in achieving a high water flux (10.28L/m(2)h) and high salt rejection (approximately 100%) in a diluted Na3PO4 draw solution.

Keywords: Complexion; Draw solution; Forward osmosis; High charge; Membrane distillation.