Sustainable water recovery from oily wastewater via forward osmosis-membrane distillation (FO-MD).
This study proposed and investigated a hybrid forward osmosis - membrane distillation (FO-MD) system for sustainable water recovery from oily wastewater by employing lab-fabricated FO and MD hollow fiber membranes. Stable oil-in-water emulsions of different concentrations with small droplet sizes (<1 μm) were firstly prepared and applied as the feed solution in the FO process. Fouling was immediately observed in the FO mode and was low on the cellulose triacetate (CTA) - based thin film composite (TFC) membranes. Moreover, slight increment of fouling was observed in the first few hours and the water flux was then stabilized over 24 h. The characterizations of water flux and solute rejection in separate FO and MD processes revealed that a high water flux, good NaCl rejection, impressively high retention of oil droplets and partial permeation of acetic acid could be achieved. Finally, an integrated FO-MD system was developed to treat the oily wastewater containing petroleum, surfactant, NaCl and acetic acid at 60 °C in the batch mode. The water flux in FO undergoes three-stage decline due to fouling and reduction in osmotic driving force, but is quite stable in MD regardless of salt concentration. Oily wastewater with relatively high salinity could be effectively recovered by the FO-MD hybrid system while maintaining large water flux, at least 90% feed water recovery could be readily attained with only trace amounts of oil and salts, and the draw solution was re-generated for the next rounds of FO-MD run. Interestingly, significant amount of acetic acid was also retained in the permeate for further reuse as a chemical additive during the production of crude oil. The work has demonstrated that not only water but also organic additives in the wastewater could be effectively recovered by FO-MD systems for reuse or other utilizations.
Department of Chemical and Biomolecular Engineering, National University of Singapore, 117576 Singapore, Singapore.
Sui
S
Zhang
Department of Chemical and Biomolecular Engineering, National University of Singapore, 117576 Singapore, Singapore.
Peng
P
Wang
Department of Chemical and Biomolecular Engineering, National University of Singapore, 117576 Singapore, Singapore.
Xiuzhu
X
Fu
Department of Chemical and Biomolecular Engineering, National University of Singapore, 117576 Singapore, Singapore. Electronic address: chencts@nus.edu.sg.
Tai-Shung
TS
Chung
D019342:Acetic Acid / Q000737:chemistry; D002482:Cellulose / Q000031:analogs & derivatives; D057168:Distillation; D008567:Membranes, Artificial; D009995:Osmosis; D010578:Petroleum; D014865:Waste Disposal, Fluid / Q000379:methods*; D062065:Wastewater / Q000737:chemistry*; D018508:Water Purification / Q000295:instrumentation / Q000379:methods*
D019342:Acetic Acid; D002482:Cellulose; D008567:Membranes, Artificial; D010578:Petroleum; D062065:Wastewater; C024671:cellulose triacetate
Forward osmosis; Integrated system; Membrane distillation; Oily wastewater; Water reuse