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Microscale Oxygen Dynamics in Onsite Wastewater Treatment

Miniature Nitrogen Removing Biofilters (NRBs) were setup in a CCWT laboratory using material excavated from a full-scale NRB to study oxygen dynamics at the nitrification-denitrification interface during dosed artificial wastewater application. Oxygen images were captured by planar  optode  imaging. Oxygen images were then used to calculate geochemical parameters such as how many times each pixel changed from anoxic to  oxic  back to anoxic per hour.  

Miniature NRBs with oxygen  optodes  (A) were developed using excavated material to mimic the interface of a field scale NRB (B). Images were taken every 30 seconds over 11 days to understand oxygen distribution during artificial wastewater application. The O2 image (C) shows oxygen is present in the nitrification layer and absent in the denitrification layer. Average O2 concentrations over time (D), calculated for a depth profile of 0.5 cm x 0.5 cm squares, reveals depth specific oxygen dynamics.  Oxic -anoxic oscillation images (E) over 11 days show reproducible oxygen dynamics at the interface of a functional system while dynamics in a partially clogged system are more complex. This new, unprecedented understanding of the microscale oxygen dynamics in NRBs is being used to relate microbial community composition to system function. Further, this insight will enable improvements to the engineering design and effectiveness of this new treatment approach.

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