Combination of forward osmosis (FO) process with coagulation/flocculation (CF) for potential treatment of textile wastewater

• Published in: Water research (Oxford) Vol. 91; pp. 361 - 370
• Main Authors: Han, Gang, Liang, Can-Zeng, Chung, Tai-Shung, Weber, Martin, Staudt, Claudia, Maletzko, Christian
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 15-03-2016
• Subjects: Coagulation and flocculation; Coloring Agents - chemistry; Dyes; Filtration - instrumentation; Filtration - methods; Flocculation; Forward osmosis; Fouling; Membranes; Membranes, Artificial; Osmosis; Reuse; Textile Industry; Textile wastewater treatment; Textiles; TFC membrane; Waste Disposal, Fluid - instrumentation; Waste Disposal, Fluid - methods; Waste water; Waste Water - analysis; Wastewater treatment; Water Pollutants, Chemical - chemistry; Water reuse; Textile wastewater treatment; TFC membrane; Forward osmosis; Water reuse; Coagulation and flocculation
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2016.01.031

A novel combination of forward osmosis (FO) process with coagulation/flocculation (CF) (FO–CF) has been experimentally conceived for the treatment and reuse of textile wastewater. FO is employed to spontaneously recover water from the wastewater via osmosis and thus effectively reduces its volume with a dramatically enhanced dye concentration. CF is then applied to precipitate and remove dyes from the FO concentrated stream with much improved efficiency and reduced chemical dosage. The FO–CF hybrid system exhibits unique advantages of high water flux and recovery rate, well controlled membrane fouling, high efficiency, and minimal environmental impact. Using a lab-made thin-film composite (TFC) FO membrane, an initial water flux (Jw) of 36.0 L m−2 h−1 with a dye rejection of 99.9% has been demonstrated by using 2 M NaCl as the draw solution and synthetic textile wastewater containing multiple textile dyes, inorganic salts and organic additives as the feed under the FO mode. The Jw could be maintained at a high value of 12.0 L m−2 h−1 even when the recovery rate of the wastewater reaches 90%. Remarkable reverse fouling behavior has also been observed where the Jw of the fouled membrane can be almost fully restored to the initial value by physical flushing without using any chemicals. Due to the great dye concentration in the FO concentrated wastewater stream, the CF process could achieve more than 95% dye removal with a small dosage of coagulants and flocculants at 500–1000 ppm. The newly developed FO–CF hybrid process may open up new exploration of alternative technologies for the effective treatment and reuse of textile effluents.
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•Novel FO−CF hybrid process for the treatment and reuse of synthetic textile wastewater.•High-performance TFC-FO membranes with mesh-reinforced hydrophilic substrates.•High water flux, great water recovery and salt/dye rejection but low fouling propensity.•The efficiency of CF could be significantly improved and the chemical dosage is reduced.•CF can remove more than 95% dye with a small dosage of coagulants/flocculants.