Nanofiltration and Reverse Osmosis for Reuse of Indigo Dye Rinsing Waters

WOS: 000277727100004A membrane based treatment strategy was developed for the possible recycling of rinsing wastewater from indigo dyeing to the process itself. Performances of three different nanofiltration (NF) (NF 270 and NF 90, Dow Film Tech, USA and NF 99, Alfa Laval, Denmark) and two different reverse osmosis (RO) (HR 98 PP and CA 995 PE, Alfa Laval, Denmark) membranes were investigated with wastewater collected from the first post-rinsing tank of indigo dyeing process of a denim manufacturing plant. Dead-end microfiltration with a 5 mu m filter was employed to remove coarse particles and minimize fouling of further NF and RO membranes. For NF and RO, a lab scale plate-and-frame membrane module was operated at a pressure of 5.07bar and at a 0.62m/s cross-flow velocity. The permeate quality from all the tested NF and RO membranes was acceptable for reuse in terms of COD and color. However, only the permeate from HR 98 PP RO and NF 90 membranes were with an acceptable conductivity. On the other hand, NF 270 membrane was superior to all the other NF and RO membranes in terms of the permeation rate. Flux declines obtained for all membranes were higher than 50% but fouling was not considerable and completely reversible. The good performance of NF 270 in terms of permeate quality (permeate conductivity, color, and COD values were 4.3mS/cm, 8 Pt-Co, and 87mg/L, respectively) together with a higher flux makes this membrane preferable over the other membranes to recycle denim textile rinsing wastewaters.Scientific and Technological Research Council of Turkey [CAYDAG-105Y088]The authors wish to express their gratitude to the Scientific and Technological Research Council of Turkey for funding the project (CAYDAG-105Y088) of which this study forms a part and also to METU Research Fund. Dow FilmTec (Minneapolis) and Alfalaval (Denmark) are thanked for supplying the membrane samples. Special thanks are extended to the textile mill administration for their technical support and for providing wastewater samples

Microfiltration/ultrafiltration as pretreatment for reclamation of rinsing waters of indigo dyeing

This paper focuses Oil the applicability of microfiltration (MF)/ultrafiltration (UF) as a pretreatment to nanofiltration (NF) for the reclamation of rinsing waters of indigo dyeing process. Two different MF alternatives, single 5 mu m MF and sequential 5 mu m + 0.45 mu m MF, were evaluated as prefiltration to improve the performance of the proceeding UF stage. UF tests performed after 5 pin MF Using 100 kDa, 50 kDa, 20 kDa, 2 kDa and 1 kDa membranes have indicated that all the UF membranes provided the same cumulative color retention of 98-99%. However, in terms of COD retention, UF membranes presented different performances and the highest retentions were by both 50 kDa (56%) and 100 kDa (59%) membranes. As regards permeation rate, 100 kDa and 50 kDa UF membranes appeared to have the highest flux decline chic to fouling. When sequential MF (5 mu m + 0.45 mu m) was adopted to decrease this fouling, 0.45 mu m MF before UF was found not to provide any significant improvement. Thus. single stage 5 mu m MF followed by 100 kDa UF was selected as the best prefiltration train to NF that permits the textile producer to reclaim indigo dyeing wastewater

Biological treatment and nanofiltration of denim textile wastewater for reuse

This study aims at coupling of activated sludge treatment with nanofiltration to improve denim textile wastewater quality to reuse criteria. In the activated sludge reactor, the COD removal efficiency was quite high as it was 91 +/- 2% and 84 +/- 4% on the basis of total and soluble feed COD, respectively. The color removal efficiency was 75 +/- 10%, and around 50-70% of removed color was adsorbed on biomass or precipitated within the reactor. The high conductivity of the wastewater, as high as 8 mS/cm, did not adversely affect system performance. Although biological treatment is quite efficient, the wastewater does not meet the reuse criteria. Hence, further treatment to improve treated water quality was investigated using nanofiltration. Dead-end microfiltration (MF) with 5 mu m pore size was applied to remove coarse particles before nanofiltration. The color rejection of nanofiltration was almost complete and permeate color was always lower than 10 Pt-Co. Similarly, quite high rejections were observed for COD (80-100%). Permeate conductivity was between 1.98 and 2.67 mS/cm (65% conductivity rejection). Wastewater fluxes were between 31 and 37 L/m(2)/h at 5.07 bars corresponding to around 45% flux declines compared to clean water fluxes. In conclusion, for denim textile wastewaters nanofiltration after biological treatment can be applied to meet reuse criteria