Photodegradation of pharmaceutical compounds in partially nitritated wastewater during UV irradiation

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Abstract

The first step of an anaerobic ammonia oxidation (anammox) system is typically the formation of nitrite (NO2-) via partial nitritation, which can generate hydroxyl radical (OH) when irradiated with ultraviolet (UV) light. This study demonstrated that the presence of nitrite in buffer and wastewater matrices during medium-pressure UV irradiation (at λ ≥ 220 or ≥ 280 nm) enhanced the degradation of select pharmaceutical compounds of different therapeutic classes (atenolol, carbamazepine, fluoxetine, and trimethoprim). Total pharmaceutical removals in a wastewater matrix irradiated at λ ≥ 280 for 120 minutes were 47% for trimethoprim, 50% for carbamazepine, 60% for atenolol, and 57% for fluoxetine at fluences of 58.6 mEi m-2 (2033.1 mJ cm-2). When irradiated at λ ≥ 220 for 60 minutes, removals were 52% for trimethoprim, 56% for carbamazepine, 69% for atenolol, and 90% for fluoxetine at fluences of 634.7 mEi m-2 (23:969.2 mJ cm-2). Reaction with OH accounted for ∼78-90% of pharmaceutical removal at λ ≥ 280 nm. Although direct photolysis did contribute to target compound removal for irradiation with λ ≥ 220 nm, much of the light was absorbed in the buffer and wastewater matrices, and reaction with OH accounted for ∼70-93% of pharmaceutical removal. Quencher experiments with isopropanol confirmed the importance of reaction with OH as the main contributor to pharmaceutical removal. para-Chlorobenzoic acid was used as a probe to estimate steady-state OH concentrations, which averaged 8.58 × 10-15 M for both matrices at λ ≥ 280 nm and 3.50 × 10-14 M for both matrices at λ ≥ 220 nm. Nitrosamines were formed and accumulated during the UV treatment step, however, concomitant with their direct photochemical destruction. Presence of the pharmaceutical micro-pollutants studied, such as the secondary-amine containing atenolol and fluoxetine, did not elevate nitrosamine formation.

Original languageEnglish (US)
Pages (from-to)897-909
Number of pages13
JournalEnvironmental Science: Water Research and Technology
Volume5
Issue number5
DOIs
StatePublished - May 2019

Bibliographical note

Funding Information:
The authors acknowledge funding provided by the University of Minnesota, NSF Sustainability Research Networks grant (1444745), and the Environment and Natural Resources Trust Fund as recommended by the Legislative Citizen Commission on Minnesota Resources. We would like to thank Kira Peter-son and J. Cesar Bezares-Cruz for help with reactor set-up, operation, and maintenance, Teng Zeng and Chancheng Pu at Syracuse University for performing the TONO analyses, and Griffin Dempsey for assistance with laboratory work.

Publisher Copyright:
© 2019 The Royal Society of Chemistry.

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