TY - JOUR

T1 - Photodegradation of micropollutants using V-UV/UV-C processes

T2 - Triclosan as a model compound

AU - Alfiya, Yuval

AU - Friedler, Eran

AU - Westphal, Janin

AU - Olsson, Oliver

AU - Dubowski, Yael

PY - 2017/12/1

Y1 - 2017/12/1

N2 - Non-potable reuse of treated wastewater is becoming widespread as means to address growing water scarcity. Removal of micropollutants (MPs) from such water often requires advanced oxidation processes using [rad]OH radicals. [rad]OH can be generated in-situ via water photolysis under vacuum-UV (λ < 200 nm) irradiation. The aim of this study was to investigate the potential of unmasking V-UV radiation from low pressure Hg lamps (emitting at 185 and 254 nm), commonly used in decentralized treatment systems, for enhancing MPs removal efficiency. Triclosan, a biocide of limited biodegradability, served as a model compound for MPs that are not very biodegradable. Its degradation kinetics and identification of intermediate products were investigated under 254 nm and under combined 254/185 nm irradiation both in dry thin films and in aqueous solutions. In the latter, degradation was faster under combined 254/185 nm radiation, although the 185 nm radiation accounted for only 4% of the total UV light intensity. In contrast, triclosan photodegradation in dry film did not show significant differences between these irradiation wavelengths, suggesting that the enhanced degradation of dissolved triclosan under combined radiation is mainly due to oxidation by [rad]OH formed via water photolysis under V-UV. This conclusion was supported by slower TCS degradation in aqueous solution when methanol was added as [rad]OH scavenger. Under both irradiation types (254, 254/185 nm) three transformation products (TPs) were identified: 2,8-dichlorodibenzo-p-dioxin, 5-chloro-2-(4- or 2-chlorophenoxy)phenol, and 2-hydroxy-8-chlorodibenzodioxin. In-silico QSAR toxicity assessment predicted potential toxicity and moderate-to-low biodegradability of these TPs. Removal of these TPs was faster under 254/185 nm irradiation. Considering the low cost, simple operation (i.e. no chemicals addition) and small size of such low-pressure mercury lamps, this is a promising direction. Further investigation of the process in flow-through reactors and real wastewater/greywater effluent is needed for its future implementation in small on-site systems for post-treatment of persistent pollutants.

AB - Non-potable reuse of treated wastewater is becoming widespread as means to address growing water scarcity. Removal of micropollutants (MPs) from such water often requires advanced oxidation processes using [rad]OH radicals. [rad]OH can be generated in-situ via water photolysis under vacuum-UV (λ < 200 nm) irradiation. The aim of this study was to investigate the potential of unmasking V-UV radiation from low pressure Hg lamps (emitting at 185 and 254 nm), commonly used in decentralized treatment systems, for enhancing MPs removal efficiency. Triclosan, a biocide of limited biodegradability, served as a model compound for MPs that are not very biodegradable. Its degradation kinetics and identification of intermediate products were investigated under 254 nm and under combined 254/185 nm irradiation both in dry thin films and in aqueous solutions. In the latter, degradation was faster under combined 254/185 nm radiation, although the 185 nm radiation accounted for only 4% of the total UV light intensity. In contrast, triclosan photodegradation in dry film did not show significant differences between these irradiation wavelengths, suggesting that the enhanced degradation of dissolved triclosan under combined radiation is mainly due to oxidation by [rad]OH formed via water photolysis under V-UV. This conclusion was supported by slower TCS degradation in aqueous solution when methanol was added as [rad]OH scavenger. Under both irradiation types (254, 254/185 nm) three transformation products (TPs) were identified: 2,8-dichlorodibenzo-p-dioxin, 5-chloro-2-(4- or 2-chlorophenoxy)phenol, and 2-hydroxy-8-chlorodibenzodioxin. In-silico QSAR toxicity assessment predicted potential toxicity and moderate-to-low biodegradability of these TPs. Removal of these TPs was faster under 254/185 nm irradiation. Considering the low cost, simple operation (i.e. no chemicals addition) and small size of such low-pressure mercury lamps, this is a promising direction. Further investigation of the process in flow-through reactors and real wastewater/greywater effluent is needed for its future implementation in small on-site systems for post-treatment of persistent pollutants.

KW - Engineering

KW - Advanced oxidation process

KW - Decentralized wastewater treatment

KW - Micropollutants

KW - Transformation products

KW - Triclosan

KW - Vacuum ultra-violet

KW - Chemistry

UR - http://www.scopus.com/inward/record.url?scp=85019773452&partnerID=8YFLogxK

U2 - 10.1016/j.scitotenv.2017.05.172

DO - 10.1016/j.scitotenv.2017.05.172

M3 - Journal articles

C2 - 28570974

AN - SCOPUS:85019773452

VL - 601-602

SP - 397

EP - 404

JO - The Science of The Total Environment

JF - The Science of The Total Environment

SN - 0048-9697

ER -