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Benzotriazoles & benzothiazoles in a WWTP in Greece: Occurrence and removal efficiencies. Alexandros G. Asimakopoulos 1 ,2 , Kurunthachalam Kannan 2 , Nikolaos S. Thomaidis 1. 1 Laboratory of Analytical Chemistry, Department of Chemistry,
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Benzotriazoles & benzothiazoles in a WWTP in Greece:Occurrenceand removal efficiencies Alexandros G. Asimakopoulos1,2, KurunthachalamKannan2, Nikolaos S. Thomaidis1 1Laboratory of Analytical Chemistry, Department of Chemistry, University of Athens, Panepistimioupolis Zografou, Athens, Greece. 2Wadsworth Center, New York State, Department of Health, and Department of Environmental Health Sciences, School of Public Health, State University of New York at Albany, Albany, NY, USA.
Benzotriazoles (BTRs) – Benzothiazoles (BTHs): Uses & Applications • BTRs contain the 1,2,3-benzotriazole skeleton in their structure. : R: chemical group or atom • BTHs contain the 1,3-benzothiazole skeleton in their structure. R: chemical group or atom
Target chemicals assessed in the WWTP BTRs : • 1H-benzotriazole (1H-BTR) 2.1-hydroxy-benzotriazole (1-OH-BTR) 3. Tolyltriazole (TTR, a mixture of isomers of 4-methyl-1H-benzotriazole [4-Me-1H-BTR] and 5-methyl-1H-benzotriazole [5-Me-1H-BTR]) • Xylyltriazole (XTR, or 5,6-dimethyl-1H-benzotriazole [5,6-diMe-1H-BTR]) BTHs: • benzothiazole (BTH) 2.2-hydroxy-benzothiazole (2-OH-BTH) • 2-methylthio-benzothiazole (2-Me-S-BTH) • 2-amino-benzothiazole (2-amino-BTH) • Polar compounds. • BTRs are weak bases. • BTHs present both acidic and basic properties.
Sample collection • Wastewater and sludge sampleswere collected from a WWTP that serves a population of 3.700.000, in Athens. • Samples were collected in April 2012; the average flow rate of sewage was approx. 743.000 m3/day, and the average production of dewatered sludge was approx. 112.000 kg/day. • Influent and effluent samples (50 mL), primary sludge (5 mL), secondary sludge (20 mL), and mixed liquor samples from the bioreactors (20 mL) were immediately filtered after collection. • The filtered wastewater samples were acidified to pH 2.50±0.10, and stored in the dark at 4 °C until analysis. • All solid samples were stored at −20 °C until analysis.
Schematic diagram of the analytical method Filter Filtrate
Occurrence in 24-h composite flow proportional Influent and Effluent samples .
Occurrence in primary and secondary sludge & influent bioreactor samples . • A major portion is biotransformed during the activated sludge treatment process.
Occurrence in Sewage sludge . • Removal by sorption onto sludge seems insignificant.
Distribution of BTRs and BTHs between aqueous phase and suspended solids in influent and effluent wastewater • The presence of exocellular biopolymers on the surfaces of biosolidsfollowing secondary treatment creates favorable conditions for higher sorption onto particulates present in bioreactors and secondary sludge.
Solid-Liquid Distribution Coefficients, Log Kd of BTRs & BTHs *Concentrations were not detectable • Both BTRs & BTHs have low affinity for primary sludge and this changed gradually in biosolids from the bioreactor and the secondary sludge. However, log Kd values were lower than 2.5.
Summary (1/2) • Biotransformation of some BTHs had been reported, and this contributes significantly to their removal during wastewater treatment. A similar mechanism is expected for BTRs. • The removal efficiencies for BTHs calculated agree with the results from previous studies. • The concentrations of 1H-BTR and TTR in sludge from Athens were similar to those reported previously. Only one study had reported BTH concentrations in sludge, where BTH, 2-Me-S-BTH and 2-OH-BTH were found approximately three times higher than the values reported here.
Summary (2/2) • Based on the results of the influent and effluent wastewater samples, most of the target analytes were determined in all samples at concentrations similar to or lower than those reported for other WWTP samples. • This is the first environmental studythat analyzed the particulate matter of wastewaterfor these compounds. • Distribution between aqueous phase and suspended solids in influent and effluent wastewater, and calculation of solid-liquid distribution coefficients were reported for the first time for these compounds.
Acknowledgements This project was implemented under the Operational Program“Education and Lifelong Learning” and funded by the EuropeanUnion (European Social Fund) and National Resources — THALIS.
