Process optimization on clean water recovery from real reactive dyeing effluents by nanofiltration

Koçer Oruç, Burcu
Clean water recovery from the reactive dyeing effluent of a cotton textile mill with membrane filtration was investigated. Lab-scale experiments were performed with wastewater samples taken from the last three steps of the dyeing line, comprising four sequential baths of dyeing, warm rinsing, washing with soap, and lukewarm rinsing. Waste dyeing bath was deliberately excluded considering its extremely high salt and color contents. Two sets of experiments were performed; direct nanofiltration (NF) and NF with pretreatment. In the direct application, NF90 membrane was tested at total recycle mode (TRM), under different trans-membrane pressures (TMPs) and cross-flow velocities (CFs). The best permeate quality was achieved at 14 bar TMP and 58.9 mL/s CF, with 99% TOC and 96% conductivity retentions where the permeate flux was 21.12 L/m2h. Increase in CF did not cause any significant improvements in permeate quality and flux; while TMP increase reduced osmotic pressure influence. When the designated optimal conditions were tested at concentrated mode, till 2.06 volume reduction factor, permeate quality remained satisfactory. In the second part, firstly, 0.45 µm MF and 150 kDa UF membranes were tested. UF was found more promising, so, NF after pretreatment studies were completed with UF. Minor improvements in NF permeate color were achieved. Besides, NF flux increased to 35.08 L/m2h at 14 bar, due to serious reductions in concentration polarization and fouling. Also, the possible effects of the inclusion of dyeing bath to the feed were examined. UF performance was not influenced; however, NF permeate quality and flux deteriorated dramatically.
Citation Formats
B. Koçer Oruç, “Process optimization on clean water recovery from real reactive dyeing effluents by nanofiltration,” M.S. - Master of Science, Middle East Technical University, 2017.