Hybridization of TiO₂ photocatalysis with coagulation and flocculation for 1,4-dioxane removal in drinking water treatment

Photocatalysis is a promising method for degrading toxic water contaminants and has the potential to be utilized for safe drinking water treatment. This study focused on the degradation of 1,4-dioxane via hybridization of TiO₂ photocatalysis with coagulation and flocculation processes for emergency water treatment. The system performance was investigated considering three key factors, such as light radiation doses, flocculation conditions, and feedwater qualities. A photocatalytically enhanced water treatment system enabled the removal of 1,4-dioxane under artificial and solar UV irradiation (i.e., ~100% removal was achieved at a UV dose of <1.0kJ per liter of water). 1,4-Dioxane degradation efficiencies showed a strong linear relationship with the total amount of UV radiation supplied. Clay particles (up to ~115NTU) did not have a significant impact on photocatalysis, but algae (e.g., Chlororella vulgaris) did. Stronger agitation during flocculation improved 1,4-dioxane degradation, but at the expense of decreased turbidity removal. Although the coagulant added interfered with photocatalysis, proper flocculation achieved suitable 1,4-dioxane removal. Sunlight irradiation appeared to be as effective as artificial UV light regarding 1,4-dioxane removal, which could make this method viable with appropriate light exposure. A steady state model helped predict 1,4-dioxane removal efficiencies as a function of retention times at different light doses, G values, and algal levels.