Simulated cotton dye effluents treatment and reuse by nanofiltration

The textile industry uses enormous quantities of water which in many cases are disposed to the environment with inadequate treatment. The effluent contains high salts and organics concentrations and they are therefore difficult to be treated. In this work the effluents from the cotton textile industry was treated by nanofiltration membrane in order to reduce the quantity of the disposed water and at the same time to reuse the treated water. A detailed investigation of the quality of the treated wastewater was performed at various operating and feed solution conditions even at extremely high recoveries and feed concentrations. An excellent performance for the TRISEP (4040-XN45-TSF) nanofiltration membrane was found. This type of membranes can achieve complete decolorization of the cotton dye effluents and they reduce the total salt concentration more than 72%. They practically zero the organic matter content in the permeate water. These membranes can be used even at high recoveries and reasonably low pressures, producing high quality water, which can be re-used. On the other hand the quantity of the disposed wastewater, with high salt and dye concentration is less than 10% of the initial treated quantity, leading to a better management of the wastewater.

Nanofiltration has been proved an efficient process to remove and separate dyes and salts from wastewaters of dye industry. It was shown in this work that TRISEP (4040-XN45-TSF) nanofiltration membranes have excellent decolorization efficiency combined with adequate salt rejection properties at reasonable energy consumption. These membranes can be used not only to treat the dye industry effluents but also to recycle and reuse the wastewater. It must be pointed out that the treatment of dye effluents by nanofiltration is a separation process and even at high recoveries splits the feed wastewater to permeate and brine. The permeate water can be reused with no other treatment. The much smaller quantities of wastewater at higher pollutants concentration than the initial feed solution should be treated before disposed to the environment. Consequently the nanofiltration technology for the treatment of dye industry effluents should always be combined with another industrial wastewater method for the integrated management of the industrial wastes.