The ozone-activated peroxymonosulfate process (O3/PMS) for removal of trace organic contaminants in natural and wastewater: Effect of the (in)organic matrix composition

Abstract

• PMS addition improves TrOC removal during ozonation of natural waters. • Higher loads of (in)organic matter in effluent reduces the added value of O 3 /PMS. • Increase in IOD after PMS addition is a good indicator of radical production. • ● OH is the dominant species for TrOC removal by O 3 /PMS in real (waste)water. • Chloride ions are most likely responsible for conversion of SO 4 ●- into ● OH. The ozone-activated peroxymonosulfate process (O 3 /PMS) is an emerging advanced oxidation process for the removal of trace organic contaminants (TrOCs) in water, because it produces both hydroxyl and sulfate radicals. Its potential has been shown in distilled water, but limited research has been performed in real (waste)waters. Therefore, this work focuses on the added value of PMS in ozonation and on fundamental aspects of the process in three different types of water, i.e. secondary effluent, surface water and groundwater. The instantaneous ozone demand (IOD) of the different waters, representing the ozone decomposition by highly ozone reactive species, increased by adding PMS. This effect is more pronounced in surface water and groundwater than in secondary effluent, which indicates more reaction between O 3 and PMS and thus a higher potential for radical production in less loaded matrices. This is also reflected in the (increased) removal of atrazine (ATZ) and chloramphenicol (CHLOR) when applying the O 3 /PMS process. Compared to ozonation, the removal efficiency obtained with O 3 /PMS was 12% higher in secondary effluent, while this was up to 35% and 43% higher in respectively surface water and groundwater. Scavenging experiments and removal of p-nitrobenzoic acid (pNBA), an ● OH probe, showed that hydroxyl radicals rather than sulfate radicals are the main species contributing for > 60% to O 3 /PMS induced TrOC removal in natural and wastewaters. Next to the bulk organic matter, chloride proved to be a crucial matrix constituent that might be responsible for the conversion of sulfate into hydroxyl radicals.