Ozonation mechanism of carbamazepine and ketoprofen in RO concentrate from municipal wastewater treatment: Kinetic regimes, removal efficiency and matrix effect

• Published in: The Science of the total environment Vol. 717; p. 137150
• Main Author: Deng, Hui
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.05.2020; Elsevier
• Subjects: Carbamazepine; Environmental Sciences; Ketoprofen; Kinetic regimes; Micropollutants; Ozonation; Ozone; Reverse osmosis concentrate; Waste Disposal, Fluid; Waste Water; Water matrix; Water Pollutants, Chemical; Water Purification; Ozonation; Micropollutants; Water matrix; Kinetic regimes; Reverse osmosis concentrate
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2020.137150

A relatively important disadvantage of reverse osmosis (RO) application to municipal wastewater reclamation is related to management of a concentrated waste stream containing high levels of organic contaminants. The present study investigated ozonation performance of RO concentrate from municipal wastewater treatment in a stirred semi-batch reactor. In this work, carbamazepine (CBZ, as a representative of ozone-reactive micropollutants) and ketoprofen (KET, one of ozone-resistant organic chemicals) were selected as target micropollutants. The absence of dissolved ozone within the first 60 min corresponding to initial ozone demand (IOD) complement suggested that chemical reactions took place quite fast, and ozone mass transfer was considered as a limiting step. A complete elimination of CBZ and an excellent removal of KET were observed in this period, indicating that molecular ozone was a dominated oxidant responsible for the decomposition of the target micropollutants in RO concentrate containing initial dissolved organic carbon (DOC0, ~50.8 mg L−1). >90% of ozone-reactive CBZ was eliminated at a low ozone dose of 0.33 g consumed ozone per g DOC0. More ozone dose requirement for an equivalent removal of KET was ascribed to its low ozone kinetic rate constant below 10 L mol−1 s−1. In addition, the presence of high contents of organic matters and alkalinity in RO concentrate exhibited pronounced effects on the degradation of KET because of a competition with oxidants. Overall, ozonation appeared to be a promising alternative for disposal of RO concentrate in terms of micropollutant removal. However, additional technologies should be followed to further enhance the degradation rate of organic matters for a zero liquid discharge treatment scheme. [Display omitted] •Chemical reactions occurred at a fast rate during the first 60 min ozonation, and then transitioned to a moderate regime.•A satisfactory removal of micropollutants by ozonation was achieved before initial ozone demand was fulfilled.•Ozonation was less effective to eliminate ozone-refractory KET than ozone-reactive CBZ.•The presence of organic matters and alkalinity in RO concentrate exhibited strong impacts on KET decomposition by ozonation.•Transformation of organic compounds was a dominated step instead of mineralization.