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Nitrogen-Sparging Assisted Anoxic Biological Drinking Water Treatment System
Citation:
Keithley, A., P. Woodruff, D. Williams, N. Dugan, AND D. Lytle. Nitrogen-Sparging Assisted Anoxic Biological Drinking Water Treatment System. AWWA Water Science. John Wiley & Sons, Inc., Hoboken, NJ, 5(5):e1359, (2023). https://doi.org/10.1002/aws2.1359
Impact/Purpose:
This study evaluated biological treatment systems to remove nitrate, a regulated contaminant, from drinking water. A nitrogen-sparged contactor and downflow filter were compared. Both reactors achieved nitrate and nitrite treatment targets, and the nitrogen-sparged contactor required a lower acetic acid dose and was easier to operate. Different packing media for the nitrogen-sparged contactor were evaluated, and gravel achieved the treatment targets at the highest loading rate. The innovative reactor developed in this work could be beneficial over existing technologies, particularly for small systems. This study may be of interest to drinking water engineers and operators.
Description:
Existing heterotrophic denitrification reactors rely on microorganisms to consume dissolved oxygen and create conditions suitable for denitrification, but this practice leads to excessive microbial growth and increased organic carbon doses. An innovative reactor that uses nitrogen gas sparging through a contactor to strip dissolved oxygen was developed and tested in the lab. It reduced influent nitrate from 15 mg N/L to < 1 mg N/L with nitrite accumulation < 1 mg N/L. It maintained a consistent flow rate and developed minimal headloss, making it easier to operate than the denitrifying dual-media filter that was operated in parallel. Gravel, PVC pieces, and no packing media were assessed as options for the nitrogen-sparged contactor, and gravel was found to support denitrification at the highest loading rate and was resilient to nitrogen sparging shutoffs and intermittent operation. This innovative reactor appears promising for small drinking water systems.
