Denitrifying bioreactors resist disturbance from fluctuating water levels

Sarah K. Hathaway, Nicholas A. Bartolerio, Luis F. Rodrìguez, Angela D. Kent, Julie L. Zilles

Research output: Contribution to journalArticle

Abstract

Nitrate can be removed from wastewater streams, including subsurface agricultural drainage systems, using woodchip bioreactors to promote microbial denitrification. However, the variations in water flow in these systems could make reliable performance from this microbially-mediated process a challenge. In the current work, the effects of fluctuating water levels on nitrate removal, denitrifying activity, and microbial community composition in laboratory-scale bioreactors were investigated. The performance was sensitive to changing water level. An average of 31% nitrate was removed at high water level and 59% at low water level, despite flow adjustments to maintain a constant theoretical hydraulic retention time. The potential activity, as assessed through denitrifying enzyme assays, averaged 0.0008 mg N2O-N/h/dry g woodchip and did not show statistically significant differences between reactors, sampling depths, or operational conditions. In the denitrifying enzyme assays, nitrate removal consistently exceeded nitrous oxide production. The denitrifying bacterial communities were not significantly different from each other, regardless of water level, meaning that the denitrifying bacterial community did not change in response to disturbance. The overall bacterial communities, however, became more distinct between the two reactors when one reactor was operated with periodic disturbances of changing water height, and showed a stronger effect at the most severely disturbed location. The communities were not distinguishable, though, when comparing the same location under high and low water levels, indicating that the communities in the disturbed reactor were adapted to fluctuating conditions rather than to high or low water level. Overall, these results describe a biological treatment process and microbial community that is resistant to disturbance via water level fluctuations.

Original languageEnglish (US)
Article number35
JournalFrontiers in Environmental Science
Volume5
Issue numberJUN
DOIs
StatePublished - Jun 28 2017

Fingerprint

bioreactor
water level
disturbance
nitrate
microbial community
assay
enzyme
nitrous oxide
community composition
denitrification
water flow
hydraulics
wastewater
reactor
sampling

Keywords

  • Denitrifying bioreactors
  • Denitrifying enzyme assays
  • Disturbance
  • Fluctuating water level
  • Nitrate removal
  • NosZ, subsurface drainage

ASJC Scopus subject areas

  • Environmental Science(all)

Cite this

Denitrifying bioreactors resist disturbance from fluctuating water levels. / Hathaway, Sarah K.; Bartolerio, Nicholas A.; Rodrìguez, Luis F.; Kent, Angela D.; Zilles, Julie L.

In: Frontiers in Environmental Science, Vol. 5, No. JUN, 35, 28.06.2017.

Research output: Contribution to journalArticle

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