Effects of carbon load on nitrate reduction during riverbank filtration: Field monitoring and batch experiment

Xiaosi Su; Zhuyan Zheng; Yaoxuan Chen; Yuyu Wan; Hang Lyu; Weihong Dong

doi:10.1016/j.scitotenv.2022.157198

Effects of carbon load on nitrate reduction during riverbank filtration: Field monitoring and batch experiment

Sci Total Environ. 2022 Nov 1:845:157198. doi: 10.1016/j.scitotenv.2022.157198. Epub 2022 Jul 8.

Authors

Xiaosi Su¹, Zhuyan Zheng², Yaoxuan Chen³, Yuyu Wan⁴, Hang Lyu⁴, Weihong Dong¹

Affiliations

¹ Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun 130026, China; Institute of Water Resources and Environment, Jilin University, Changchun 130026, China; College of New Energy and Environment, Jilin University, Changchun 130026, China.
² College of Construction Engineering, Jilin University, Changchun 130021, China; Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun 130026, China; Institute of Water Resources and Environment, Jilin University, Changchun 130026, China.
³ Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun 130026, China; Institute of Water Resources and Environment, Jilin University, Changchun 130026, China; College of New Energy and Environment, Jilin University, Changchun 130026, China. Electronic address: chenyaoxuan92@163.com.
⁴ Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun 130026, China; College of New Energy and Environment, Jilin University, Changchun 130026, China.

PMID: 35810902
DOI: 10.1016/j.scitotenv.2022.157198

Abstract

Riverbank filtration (RBF) is a well-established technique worldwide, and is critical for the maintenance of groundwater quality and production of clean drinking water. Evaluation of the decay of exogenous nitrate (NO₃^-) in river water and the enrichment of ammonium (NH₄⁺) in groundwater during RBF is important; these two processes are mainly influenced by denitrification (DNF) and dissimilatory nitrate reduction to ammonium (DNRA) controlled by the groundwater carbon load. In this study, the effects of carbon load (organic carbon [OC]: NO₃^-) on the competing nitrate reduction (DNRA and DNF) were assessed during RBF using field monitoring and a laboratory batch experiment. Results show the groundwater OC: NO₃^- ratio did not directly affect the reaction rate of DNRA and DNF, however, it could control the competitive partitioning between the two. In the near-shore zone, the groundwater OC: NO₃^- ratio shows significant seasonal variations along the filtration path owing to the changing conditions of redox, OC-rich, and NO₃^--limited. A greater proportion of NO₃^- would be available for DNRA in the wet season with higher OC: NO₃^- ratio (> 10), resulting in a significantly NH₄⁺-N enrichment rate (from 1.43 × 10^-3 to 9.54 × 10^-4 mmol L^-1 d^-1) in the near-shore zone where the zone of Mn (IV) oxide reduction. However, the activity of DNRA was suppressed with lower OC: NO₃^- ratio (< 10) in the dry season, resulting in a stable NH₄⁺-N enrichment rate (from 3.12 × 10^-4 to 1.30 × 10^-4 mmol L^-1 d^-1). Benefiting from seasonal variation of OC-rich and NO₃^--limited conditions, DNRA bacteria outcompeted denitrifiers, which eventually led to seasonal differences in NO₃^- reduction in the near-shore zone. Overall, under the effect of DNRA induced by continuous high carbon load in RBF systems, nitrogen input is not permanently removed but rather retained in groundwater during RBF.

Keywords: Carbon load; DNRA; Denitrification; NH(4)(+) enrichment; NO(3)(−) reduction; Riverbank filtration.

MeSH terms

Ammonium Compounds*
Carbon
Denitrification
Nitrates*
Nitrogen
Nitrogen Oxides
Organic Chemicals
Oxidation-Reduction

Substances

Ammonium Compounds
Nitrates
Nitrogen Oxides
Organic Chemicals
Carbon
Nitrogen