Abstract
Occurrence of emerging organic micropollutants in water bodies and their effects are a concern related to quality of reused water. Advanced oxidation processes have demonstrated promising results to address this challenge. Nonetheless, these processes may lead to the generation of more toxic oxidation by-products. The aim of this study was to investigate the coupling of ozonation and nanofiltration (NF) applied to carbamazepine (CBZ). It consisted in monitoring the degradation and fate of CBZ and its subsequent by-products, their fate and toxicity. CBZ was completely degraded after 5 min of ozonation and six identified transformation by-products were formed: I (hydroxycarbamazepine), BQM [1-(2-benzaldehyde)-4-hydro-(1H, 3H)-quinazoline-2-one], II (2-(1H)-quinazolinone), BaQM [1-(2-benzoic acid)-4-hydro-(1H, 3H)-quinazoline-2-one], BQD [1-(2-benzaldehyde)-(1H, 3H)-quinazoline-2,4-dione] and BaQD [1-(2-benzoic acid)-(1H, 3H)-quinazoline-2,4-dione]. Mineralization rate of ozonation never exceeded 12% even with high ozone dose. Bioassays with Vibrio fischeri revealed that BQM and BQD are responsible for toxicity. NF is able to remove total organic carbon with removal rate up to 93% at 85% of permeate recovery rate. CBZ and its different ozonation by-products were almost completely retained by NF, except the II, which had an MW slightly lower than the membrane molecular weight cut-off, for which the removal rate was still between 80 and 96% depending on the recovery rate.
Highlights
Domestic wastewater (DWW) reuse is increasingly considered a promising solution to the growing water scarcity in many areas around the world (Cirelli et al, 2012; Kellis et al, 2013; Lyu et al, 2016; Gude 2017)
This study aimed to investigate the fate and toxicity of CBZ and its oxidation by-products in a pre-ozonation and NF coupling process
It consisted in monitoring the degradation kinetics of CBZ, establishing the ozone-based degradation chemical pathway and assessing the removal rate of the identified by-products in the combined NF process
Summary
Domestic wastewater (DWW) reuse is increasingly considered a promising solution to the growing water scarcity in many areas around the world (Cirelli et al, 2012; Kellis et al, 2013; Lyu et al, 2016; Gude 2017). Various organic micropollutants (OMPs) are found widespread in MBR secondary effluent at concentration range of ng.L-1-μg.L-1 (Dong et al, 2016; Gogoi et al, 2018). To make DWW reuse possible, Wastewater Reuse: Ozonation and Nanofiltration wastewater treatment plant (WWTP) effluent must undergo efficient and sustainable tertiary treatment processes (Po et al, 2005; Baawain et al, 2020). Advanced oxidation processes (AOPs) are attractive solutions for post-treatment of DWW as those processes allow the elimination of a wide range of OMPs from wastewater. Bourgin et al (2018) demonstrated removals higher than 80% for the 12 micropollutants used as indicator substances in the Swiss legislation throughout the processes of an entire WWTP upgraded with an ozonation step (0.5 gO3/gC) (Bourgin et al, 2018). Different mechanisms and agents are involved during ozonation: combination of molecular ozone and byproducts, radicals from ozone self-decomposition or from the reaction of ozone with colloidal and dissolved organic mater (Huber et al, 2003; Ternes et al, 2003; Dodd et al, 2006; Ikehata et al, 2006; Snyder et al, 2006; Javier Benitez et al, 2009; Wert et al, 2009)
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