Biosolids produced in wastewater treatment plants can be applied to agriculture fields as fertilizers or soil amendment. However, the presence of pharmaceuticals in biosolids has raised concern on the long-term ecological impacts of biosolids land application. Sunlight photodegradation is an important dissipation pathway for pharmaceuticals in water and on soil. However, this process has not been considered in biosolids, a reaction environment enriches in organic matter with high moisture. In this study, two anti-inflammatory drugs present at high concentrations in biosolids, ibuprofen and naproxen, were selected as model compounds to evaluate the sunlight photodegradation of pharmaceuticals in biosolids. Reactions were conducted in water and on kaolinite surfaces, and the effects of dissolve organic matter extracted from biosolids (BDOM) were evaluated. In water, ibuprofen did not undergo direct photolysis whereas naproxen exhibited rapid decay (0.72 h-1), consistent with their respective sunlight absorption spectra. In the presence of 5 mg C/L BDOM, ibuprofen degradation was observed (0.003 h-1), but naproxen degradation was not affected. On kaolinite, the presence of BDOM accelerated ibuprofen and naproxen degradation by 1.5 and 1.1 times, respectively. These kinetics results suggest that BDOM can induce pharmaceutical decay both in water and on solid surface. A comparison of the excitation emission matrix (EEM) spectra of BDOM and soil-DOM showed that BDOM contains a more diverse range of fluorophores and has stronger signals in the fluorescence regions corresponding to humic acid-like and aromatic protein. On kaolinite with BDOM, ibuprofen degraded 1.3 times faster in the deoxygenated reaction environment suggesting the triplet DOM plays an important role during the photolysis reaction. Work is underway to evaluate the decay of ibuprofen and naproxen in authentic biosolids sample, and probe compounds will be applied to illustrate the important reactive species generated by the biosolids in the photolysis reaction.

Sunlight photodegradation of pharmaceuticals in land-applied biosolids: Case study of ibuprofen and naproxen

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.