Performance and applicability limits of membrane distillation for real textile industry wastewaters

Membrane distillation (MD) has emerged as a promising approach for the reuse of textile wastewaters, due to its tolerance to high salinity, temperature, and pH. However, its application to real effluents remains uncertain. This study critically assesses MD performance using two real textile wastewaters from cotton fabric dyeing (DYE) and polyester fiber alkaline deweighting (DEW) processes, both characterized by low surface tension (39 and 24 mN m−1, respectively) compared to that of pure water (72.7 mN m−1). Direct contact MD experiments on untreated wastewaters showed early loss of permeate quality occurring at ∼30% recovery for DYE and ∼ 7% for DEW, indicating rapid membrane wetting. Among several tested pre-treatment options, only adsorption on activated carbon restored surface tension to values comparable to pure water. The adsorption pre-treatment delayed the onset of membrane wetting to 50–60% recovery for DYE and 40–50% for DEW, and improved distillate quality, but did not fully prevent MD performance deterioration. Operation under vacuum conditions increased fluxes by more than twofold, although fouling and wetting remained the limiting factors. Preliminary cost analysis indicated operational costs between ∼4.3 € m−3 and ∼ 63.4 € m−3 for a reuse scheme comprising adsorption and MD, strongly dependent on recovery, adsorption demand, and energy management. Overall, the results suggest that the applicability of MD to textile wastewaters is highly dependent on wastewater characteristics and must therefore be evaluated on a case-by-case basis.