Hydrogenotrophic denitrification (H
2Den) is a promising strategy for NO
3− removal from a supply water with low or negligible organic carbon content. However, its performance may be affected by emerging contaminants (ECs), which pose increasing risks to the environment and
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Hydrogenotrophic denitrification (H
2Den) is a promising strategy for NO
3− removal from a supply water with low or negligible organic carbon content. However, its performance may be affected by emerging contaminants (ECs), which pose increasing risks to the environment and human health. This study investigates the acute effect of two widely detected ECs, acetaminophen (ACN) and chloramphenicol (CHP), at a 200 mg/L concentration, on H
2Den using anaerobic granular sludge (AnGS) as inoculum. Acute exposure to ACN enhanced NO
3− removal, likely due to the formation of oxidizable metabolites serving as electron donors through the heterotrophic pathway. On day 3, the residual NO
3− concentration had already dropped below the regulatory limit of 50 mg/L, reaching 4.3 mg NO
3−/L. In contrast, CHP initially inhibited the denitrification process, resulting in limited NO
3− removal, i.e., a residual concentration of 145.4 mg NO
3−/L on day 3. Nevertheless, short-term microbial adaptation likely enabled performance recovery under CHP exposure. On day 6, both EC exposure tests allowed a NO
3− removal above 97%, although CHP resulted in residual NO
2−, i.e., 37 mg NO
2−/L. In the presence of ACN, the accumulation of gaseous denitrification intermediates was observed, with NO concentration in the headspace peaking at 9.5% (i.e., 16.2 × 10
−2 µg NO/min/g VS) on day 6. Thus, in terms of either the production of gaseous intermediates or the presence of residual nitrogen in the liquid phase, ACN and CHP significantly influenced the denitrification performance, highlighting the importance of considering their presence in the operation of the denitrification process.
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