Techno-economic assessment of a submerged photocatalytic membrane reactor for efficient treatment of dye-containing saline wastewater

The treatment of dye-containing saline wastewater remains challenging due to the energy-intensive nature of conventional treatment processes. In this study, a submerged photocatalytic membrane reactor (PMR) combining TiO₂ as a photocatalyst with a hollow fiber polyvinylidene fluoride (PVDF) ultrafiltration (UF) membrane was systematically investigated. Response surface methodology (RSM) coupled with a central composite design (CCD) was applied to develop predictive models and assess the effects of key operational parameters on the removal of RB5 and RR120, as well as operational expenditure (OPEX). Five independent variables—salinity, UV power, irradiation time, dye concentration, and photocatalyst dosage—were evaluated against dye removal efficiencies and OPEX as response variables. Statistical analysis revealed that UV power and irradiation time were most influential factors governing dye removal, while salinity showed a relatively minor effect, indicating the suitability of the system for RO concentrate treatment. Under optimized conditions, removal efficiencies of 92.2% for RR120 and 98.0% for RB5 were achieved. Moreover, the optimized PMR system exhibited a low operational cost of 0.74 $/m3 of influent wastewater, demonstrating its economic and technical viability for textile wastewater treatment.