Textile dye wastewater treatment by direct contact membrane distillation: Membrane performance and detailed fouling analysis

The treatment of textile dye solution is considered one of the most challenging wastewater treatments, representing a major concern for the ecosystem. This study investigates the efficiency of direct contact membrane distillation (DCMD) for the treatment of synthetic textile solution in lab test membrane cells. The effect of the feed temperature and feed flow rate on the MD fouling were investigated at feed water temperatures of 40 °C, 60 °C, 80 °C and feed flow rates of 15 L/h, 30 L/h and 45 L/h. Results show that (i) negligible fouling was observed at a feed temperature of 40 °C, (ii) the increase in temperature impacted the process performance, leading to severe flux decrease (~70%) and to the formation of a thick fouling layer (240 μm) at a feed temperature of 80 °C, (iii) fouling thickness was reduced with increasing feed flow velocity, (iv) the fouling increased toward the inlet side of the membrane cell due to the variation of the driving force along the module. In-situ non-invasive fouling monitoring allowed evaluating the fouling spatial distribution on the membrane, and linking the MD process performance to the fouling accumulation, indicating a linear correlation between the flux decrease and the fouling deposition.