Treatment of a mixture of pharmaceuticals, herbicides and perfluorinated compounds by powdered activated carbon and ozone: Synergy, catalysis and insights into non-free OH contingent mechanisms.

Powdered activated carbon (PAC) is a strong adsorbent also capable of catalyzing ozonation processes. Ozone (O3) and PAC were simultaneously applied to treat a mixture of 17 micropollutants (MPs) at low concentrations, including 13 compounds that were studied for the first time by simultaneous addition of O3 and PAC system. Synergy and catalysis improved the removals and specific degradation rates of MPs in the first minute of the treatment. Radical probing experiments showed that scavenging hydroxyl radicals (OH) did not have a significant impact on the removals, while scavenging other reactive oxygen species was more influential. A detailed study by electron paramagnetic resonance spectroscopy ascertained that the decomposition of ozone in presence of PAC at neutral pH did not boost the generation of free OH. Instead, adsorbed OH was likely produced as PAC-HO along with other oxidizing species resulting from adsorbed singlet oxygen and superoxide radicals.

Advancing the treatment of primary influent and effluent wastewater during wet weather flow by single versus powdered activated carbon-catalyzed ozonation for the removal of trace organic compounds.

For the first time, single and PAC-catalyzed ozonation were explored for the wastewater treatment during wet weather flow in a prompt and efficient process. The effect of varying the ozone (O3) specific dose on the removal of micropollutants (MPs) was first investigated with a mixture of pharmaceuticals, herbicides and perfluorinated compounds in clean water. Most MPs showed higher affinity towards catalytic ozonation. Carbamazepine and Atrazine were found to be good surrogates for fast and slow reacting compounds, respectively. Applying single or PAC-catalyzed ozonation for 1 min only after coagulation was more efficient than applying them simultaneously. PAC-catalyzed ozonation was more efficient for the removal of organics and O3-resistant MPs. Both single and PAC-catalyzed ozonation achieved 4 log removal of E. coli, reduced the acute and genetic toxicity, and estrogenic activity of the wastewater. A detailed cost analysis revealed that applying single ozonation after coagulation costs between 0.06 and 0.32 $/m3 while applying PAC-catalyzed ozonation costs between 0.32 and 0.63 $/m3 for a flow rate between 100 and 600 MLD. Through a comprehensive performance assessment, PAC-catalyzed ozonation was deemed superior with one drawback related to the disposal of PAC.