UV-C LED Photolysis for Microbial Inactivation in Textile Industry Wastewater

Limited information is available regarding the effectiveness of UV-C LEDs operating at 280 nm, either alone or combined with hydrogen peroxide, for reducing microbial loads in industrial wastewater streams prior to membrane filtration. Real water samples were collected at an industrial site, before and after ultrafiltration and reverse osmosis treatment processes, and subjected to direct photolysis. The samples were exposed to light-emitting diodes (LEDs) that emit UV-C light at 280 nm, followed by the evaluation of microbial growth to determine disinfection efficacy relative to the UV fluence applied. Additionally, ultrafiltration permeate samples were also subject to indirect photolysis, being exposed to UV-C LEDs with hydrogen peroxide added at different concentrations (10, 20, 40, and 60 mg/L) to assess the most effective combination for microbial inactivation. The lowest tested UV fluence at which all microorganisms in the ultrafiltration permeate were inactivated through direct photolysis to levels below detection was 27 mJ/cm2. It was also demonstrated that indirect photolysis does not achieve better disinfection results, likely due to the low absorbance of hydrogen peroxide at 280 nm. The application of direct photolysis prior to membrane filtration is expected to reduce the microbial load entering downstream treatment units, even in challenging matrices such as textile industry effluents, and may therefore contribute to lowering biofouling risk and improving industrial water treatment performance.