The distribution dynamics and desorption behaviour of mobile pharmaceuticals and caffeine to combined sewer sediments.
Pharmaceuticals are discharged to the environment from wastewater resource recovery facilities, sewer overflows, and illicit sewer connections. To understand the fate of pharmaceuticals, there is a need to better understand their sorption dynamics to suspended sediments (SS) and settled sediments (StS) in sewer systems. In this study, such sorption dynamics to both SS and StS were assessed using a batch equilibrium method under both static and dynamic conditions. Experiments were performed with natively occurring and artificially modified concentrations of sewer pharmaceuticals (acetaminophen, theophylline, carbamazepine, and a metabolite of carbamazepine) and caffeine. Differences in apparent distribution coefficients, Kd,app, between SS and StS were related to differences in their organic carbon (OC) content, and the practice of artificially modifying the concentration. Kd,appvalues of modified contaminant concentrations and high OC sediments were substantially higher. Pseudo-second order desorption rates for these mobile compounds were also quantified. Successive flushing events to simulate the addition of stormwater to sewer networks revealed that aqueous concentrations would not necessarily decrease, because the added water will rapidly return to equilibrium concentrations with the sediments. Sorption and desorption kinetics must be considered in addition to dilution, to avoid underestimating the influence of dilution on concentrations of pharmaceuticals discharged to the environment.
Canada Research Chair in Source Water Protection, Department of Civil, Geological and Mining Engineering, Polytechnique Montréal, C.P. 6079, Succursale Centre-ville, Montréal, QC, H3C 3A7, Canada; NSERC Industrial Chair in Drinking Water Treatment, Department of Civil, Geological and Mining Engineering, Polytechnique Montréal, C.P. 6079, Succursale Centre-ville, Montréal, QC, H3C 3A7, Canada. Electronic address: mariamhajjm@gmail.com.
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Hajj-Mohamad
Department of Chemistry, Université de Montréal, C.P. 6128, Succursale Centre-ville, Montreal, Qc, H3C 3J7, Canada.
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Darwano
Department of Chemistry, Université de Montréal, C.P. 6128, Succursale Centre-ville, Montreal, Qc, H3C 3J7, Canada.
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Duy
Department of Chemistry, Université de Montréal, C.P. 6128, Succursale Centre-ville, Montreal, Qc, H3C 3J7, Canada.
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Sauvé
NSERC Industrial Chair in Drinking Water Treatment, Department of Civil, Geological and Mining Engineering, Polytechnique Montréal, C.P. 6079, Succursale Centre-ville, Montréal, QC, H3C 3A7, Canada.
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Prévost
Norwegian Geotechnical Institute (NGI), P.O. Box 3930 Ullevål Stadion, N-0806, Oslo, Norway.
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Arp
Canada Research Chair in Source Water Protection, Department of Civil, Geological and Mining Engineering, Polytechnique Montréal, C.P. 6079, Succursale Centre-ville, Montréal, QC, H3C 3A7, Canada.
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Dorner
D002110:Caffeine; D019015:Geologic Sediments; D062065:Wastewater
D002110:Caffeine; D062065:Wastewater
Anthropogenic tracers; Batch equilibrium; Emerging contaminants; Settled sediment; Stormwater; Suspended solids