A better understanding of large spiral wound forward osmosis (SW FO) module operation is needed to provide practical insight for a full-scale FO desalination plant. Therefore, this study investigated two different 8" SW FO modules (i.e. cellulose tri acetate, CTA and thin film composite, TFC) in terms of hydrodynamics, operating pressure, water and solute fluxes, fouling behaviour and cleaning strategy. For both modules, a significantly lower flow rate was required in the draw channel than in the feed channel due to important pressure-drop in the draw channel and was a particularly critical operating challenge in the CTA module when permeate spacers are used. Under FO and pressure assisted osmosis (PAO, up to 2.5 bar) operations, the TFC module featured higher water flux and lower reverse salt flux than the CTA module. For both modules, fouling tests demonstrated that feed inlet pressure was more sensitive to foulant deposition than the flux, thus confirming that FO fouling deposition occurs in the feed channel rather than on the membrane surface. Osmotic backwash combined with physical cleaning used in this study confirmed to be effective and adapted to large-scale FO module operation.
The pilot-scale fertiliser driven forward osmosis (FDFO) and nanofiltration (NF) system was operated in the field for about six months for the desalination of saline groundwater from the coal mining activities. Long-term operation of the FDFO-NF system indicates that simple hydraulic cleaning could effectively restore the water flux with minimal chemical cleaning frequency. No fouling/scaling issues were encountered with the NF post-treatment process. The study indicates that, FDFO-NF desalination system can produce water quality that meets fertigation standard. This study also however shows that, the diffusion of solutes (both feed and draw) through the cellulose triacetate (CTA) FO membrane could be one of the major issues. The FO feed brine failed to meet the effluent discharge standard for NH 4 + and SO 4 2+ (reverse diffusion) and their concentrations are expected to further increase at higher feed recovery rates. Low rejection of feed salts (Na + , Cl-) by FO membrane may result in their gradual build-up in the fertiliser draw solution (DS) in a closed FDFO-NF system eventually affecting the final water quality unless it is balanced by adequate bleeding from the system through NF and re-reverse diffusion towards the FO feed brine. Therefore, FO membrane 2 with higher reverse flux selectivity than the CTA-FO membrane used in this study is necessary for the application of the FDFO desalination process.
8Two spiral wound forward osmosis (SWFO) membrane modules with different spacer design (CS; 9 corrugated spacer and MS; medium spacer) were investigated for the fertilizer drawn forward osmosis 10 desalination of brackish groundwater (BGW) at a pilot-scale level. This study mainly focused on 11 examining the influence of various operating conditions such as feed flow rate, total dissolved solids 12 (TDS) concentration of the BGW feed, and draw solution (DS) concentrations using ammonium 13 sulphate ((NH 4 ) 2 SO 4 , SOA) on the performance of two membrane modules. The feed flow rate played 14 a positive role in the average water flux of the pilot-scale FO membrane module due to enhanced 15 mass transfer coefficient across the membrane surface. Feed TDS and DS concentrations also played a 16 significant role in both FO membrane modules because they are directly related to the osmotic driving 17 force and membrane fouling tendency. CS module performed slightly better than MS module during 18 all experiments due to probably enhanced mass transfer and lower fouling propensity associated with 19 the corrugated spacer. Besides, CS spacer provides larger channel space that can accommodate larger 20 volume of DS and hence could maintain higher DS concentration. However, the extent of dilution for 21 the CS module is slightly lower. 22 23
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.