Optimization of mild solar TiO2 photocatalysis as a tertiary treatment for municipal wastewater treatment plant effluents

The appropriate catalyst concentration for industrial wastewater treatment is several hundred milligrams per liter in solar photoreactors. Nonetheless, when the purpose of eliminating emerging contaminants in municipal wastewater treatment plant effluents is for reuse of the water, and they are present at extremely low concentrations, a tertiary treatment with a much lower photocatalyst concentration might be possible. TiO2 concentrations of only tens of mg L−1 were selected to evaluate the influence of catalyst load, initial hydrogen peroxide dose and radiation intensity on the degradation rate of five emerging contaminants (100 μg L−1 of ofloxacin, sulfamethoxazole, flumequine, carbamazepine, and 2-hydroxy-biphenyl) spiked in a real municipal wastewater treatment plant effluent. Response surface methodology based on a spherical central composite design was used to optimize the parameters to find the maximal degradation rate. The experiments were carried out using an Evonik P-25 titanium dioxide suspension in a Suntest solar simulator. It has been demonstrated that the use of hydrogen peroxide is highly recommendable for working with TiO2 at low concentrations and high photon flux must be avoided. It has also been demonstrated that too low (less than 40 mg L−1) TiO2 concentration is not recommendable.

Effect of H2O2 dosing in photocatalytic reaction rate at low solar radiation intensity and working with low TiO2 photocatalyst concentration.Figure optionsDownload as PowerPoint slideHighlights
► Solar photocatalytic treatment for eliminating emerging contaminants.
► We studied it in municipal wastewater treatment plant effluents.
► Hydrogen peroxide is highly recommendable with TiO2 at low concentrations.
► High photon flux must be avoided.
► Too low (less than 40 mg L−1) TiO2 concentration is not recommendable.