Membrane photoreactor treatment of 1,4-dioxane-containing textile wastewater effluent: Performance, modeling, and fouling control

A membrane photoreactor (MPR) system was investigated for the purification of textile wastewater effluent containing 1,4-dioxane for potential reuse. The effects of TiO₂ dosage, alkalinity, particulate matter, and sunlight radiation on the removal of 1,4-dioxane from the effluent were evaluated. The photocatalytic 1,4-dioxane degradation followed pseudo-first order reaction kinetics. A considerably large dose of TiO₂ catalyst (5 g/L) was required for maximal 1,4-dioxane degradation by MPR. The high alkalinity (~550 mg/L) of the textile wastewater effluent negatively affected the 1,4-dioxane degradation rate, whereas 1,4-dioxane degradation was not impacted by the presence of particulate matter. Solar photocatalysis of 1,4-dioxane was as effective as that achieved with UV lamps in the MPR, which could lead to energy savings. Continuous flow MPR was effective for continuous degradation of 1,4-dioxane; the unsteady- and steady-state performances were well-predicted at various hydraulic residence times (HRTs). The quality of the MPR product obtained at an HRT of 8.57 h satisfied the drinking water guidelines. The transmembrane pressure (TMP) buildup, which is indicative of fouling, was dependent on the TiO₂ dose and permeate flux. The TMP buildup was marginal at low flux, but increased dramatically beyond a flux level of >60 L/m²-h. However, the fouling layer could be sufficiently removed by periodic backwashing, even at an extremely high flux of 100 L/m²-h. The membrane permeability was sustained without any sign of irreversible fouling during MPR treatment of textile wastewater effluents.