Nitrate removal in aerobic sediments of freshwater systems

Poster 242 – Click on poster below to view presentation from author.

Click on poster to view presentation from author.

Kim Risaduzzaman

Georgia Southern University

Co-Authors: Francisco Cubas Suazo

Denitrification is controlled by seasonally varying factors such as temperature and oxygen concentrations. In the Occoquan Reservoir, a water reclamation plant purposely discharges nitrate to the reservoir to protect its water quality. This management strategy is effective during the summer months (May-September) when denitrification rates are highest, but it is inefficient during the winter when the water temperature is low, and oxygen is high. This study examined the feasibility of adding nitrate to the reservoir during the shoulder months (March-April and October) when denitrification is expected to be minimal. Field data revealed that in March and April, when the water temperature was >12ºC, oxygen concentrations rapidly decreased from 10 – 2 mg/L, revealing a high oxygen and nitrate demand before the onset of thermal stratification. In microcosms, sediments from the reservoir depleted nitrate when oxygen values were ~2 mg/L, suggesting that denitrification occurred deeper in the anaerobic sediments. Lower denitrification rates in sediments were the result of nitrate transport limitations, as nitrate had to transfer deeper into the sediments to reach the anoxic layer and not the result of lower denitrifying bacteria activity. These results will help reexamine the concept that denitrification occurs strictly under anaerobic conditions, expanding the nitrogen cycle knowledge.

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All posts are publicly visible after review by site administrator. Students’ responses to posted questions is factored into scoring for the poster competition. Finalists announced May 25 and awards presented May 26, 2021.

One thought on “Nitrate removal in aerobic sediments of freshwater systems

  1. Thank you for your presentation. I’m curious as to how you chose those specific DO and temperature ranges in which you expect denitrification to occur?

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