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

• TiO2 photocatalysis of 1,4-dioxane with simultaneous coagulation was investigated.
• Proper flocculation under artificial and solar UV achieved drastic 1,4-dioxane removal.
• Sunlight radiation under cloudy condition was effective for decomposing 1,4-dioxane.
• Unlike clay particles, algae had a negative effect on 1,4-dioxane photocatalysis.

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 <1.0 kJ 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 ∼115 NTU) 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.

Figure optionsDownload as PowerPoint slide