Direct contact membrane distillation applied to wastewaters from different stages of the textile process

Abstract

This study investigated the performance of DCMD applied to wastewaters from different stages of the textile process in the same operating system for water reclamation in a single process. High final color rejection (>98.7%) was obtained and water was recovered at the permeate side for polyester dyeing wastewater and textile effluent from the equalization tank (final permeate flux up to 15.8 kg·m−2·h−1). The color rejection was maintained possibly due to membrane internal hydrophobicity, which prevented total wetting. The possibility of wastewater treatment by the DCMD process was essentially dependent on textile wastewater composition. During cotton and viscose dyeing wastewater treatment, severe wetting of the membrane was due to the presence of cationic and nonionic surfactants in high concentration, requiring further studies. Different types of membrane fouling with textile wastewaters were observed, which may result in different cleaning procedures. Higher color rejection with textile wastewater, when compared to dye solutions, was due to deposition/adsorption of some elements on the membrane surface, which established a composite layer with higher wetting resistance. DCMD showed to be a promising technology for treating real textile wastewater due to its good performance in color rejection and water recovery.