Enhancement of textile wastewater treatment process using Nanofiltration

Abstract

In the present work, the performances of the use of Nanofiltration (NF) as a post treatment after Coagulation–flocculation (CF) which was used to treat a mixture of effluents coming from different textile industry operations (dying, bleaching…), are studied. At first, the fluctuation of the characteristics of the different effluents coming from the different treatment steps of cotton clothes is determined. Then, the effects of operating conditions, like pressure and temperature on the permeate flux and retention of chemical oxygen demand (COD), color and salinity are investigated. Critical flux concept is used to study the effect of salt on the performance of Nanofiltration. It is concluded that it is more difficult to eliminate the salts when the concentration is higher than 9 g/L. The Nanofiltration experiments showed that the permeate flux was about 24 L/h.m 2 obtained at a Volume Reduction Factor (VRF) of 3 under optimal pressure and temperature of 10 bar and 40 °C. The best pollutant retention was: 57% for COD, 100% for color and 30% for salinity. Finally, it is demonstrated that the use of Microfiltration (MF) instead of Coagulation–flocculation as pretreatment prior to Nanofiltration leads to the enhancement of the effluent treatment performances mostly regarding to salinity and COD retention.