Sustainable Management of Textile Wastewater: A Hybrid Tight Ultrafiltration/Bipolar-Membrane Electrodialysis Process for Resource Recovery and Zero Liquid Discharge

Sustainable textile wastewater treatment strongly demands an indispensable paradigm shift from removal of contaminants to effective recovery of resources. In this work, a hybrid tight ultrafiltration (TUF) and bipolar-membrane electrodialysis (BMED) process was explored to recover resources (i.e., dye extraction, acid/base conversion, and pure water regeneration) from highly saline textile wastewater. Using a TUF membrane with 5000 Da molecular weight cutoff (MWCO) can obtain a sufficient rejection (>99.6%) of both reactive and direct dyes, due to the dye aggregation. Additionally, the considerably large pore size of the TUF membrane endowed the process with free transport of NaCl and Na2SO4(i.e., >99.42%), exhibiting promise as an alternative means of separation of dyes and Na2SO4. Additionally, an integrated TUF-based diafiltration was designed to separate the model dye (i.e., reactive blue 194) and Na2SO4. Particularly, reactive blue 194 was remarkably concentrated from 997.9 to 7952.8 mg·L–1by the TUF membrane with 99.5% dye recovery and 99.95% desalination efficiency after 8.0 diavolumes. Furthermore, a trace amount (i.e., 2.7 mg·L–1) of reactive blue 194 was observed in Na2SO4-containing TUF permeate, enabling a subsequent BMED operation. With the implementation of BMED, the Na2SO4-containing TUF permeate was sufficiently desalinated for acid/base conversion and pure water regeneration with no obvious fouling on the ion exchange membranes. These results demonstrate a potential applicability of the hybrid TUF/BMED process for sustainable management of textile wastewater, providing a strategy for practical applications in treatment of other high-salinity wastewaters.