Emily Frett (Minnesota) coauthored “Carbon Supplementation and Bioaugmentation to Improve Denitrifying Woodchip Bioreactor Performance Under Cold Conditions” published in Ecological Engineering, Volume 191 on June 1, 2023.

Emily’s coauthors were Gary Feyereisen, Hao Wang, Ping Wang, Jeonghwan Jang, Ehsan Ghane, Jeffrey Coulter, Carl Rosen, Michael Sadowsky, and Satoshi Ishii.

Emily is a Professional Scientist based in Minnesota who focuses on forensics and litigation support.

Ecological Engineering is a journal for those involved in designing, monitoring, or restoring ecosystems, and serves as a bridge between the fields of ecology and engineering. “Ecological engineering” has been defined as the design of ecosystems for the mutual benefit of humans and nature, and, as such, topics covered in this journal typically involve ecosystem restoration, ecotechnology, and bioengineering. The journal is published by Elsevier.

Cold temperatures limit nitrate-N load reductions of woodchip bioreactors in higher-latitude climates. This two-year, on-farm (Willmar, Minnesota) study was conducted to determine whether field-scale nitrate-N removal of woodchip bioreactors can be improved by the addition of cold-adapted, locally isolated bacterial denitrifying strains (bioaugmentation) or dosing with a carbon (C) source (biostimulation). In Spring 2017, biostimulation removed 66% of the nitrate-N load, compared to 21% and 18% for bioaugmentation and control, respectively. The biostimulation nitrate-N removal rate (NRR) was also significantly greater, 15.0 g N m−3 d−1, versus 5.8 and 4.4 g N m−3 d−1, for bioaugmentation and control, respectively. After 5 weeks of operation, bioclogging of the biostimulation beds limited dosing for the remainder of the experiment; NRR was greater for biostimulation in Fall 2017, but in Spring 2018 there were no differences among treatments. Carbon dosing did not increase outflow of dissolved organic C concentration. The abundance of one of the inoculated strains, Cellulomonas cellacea strain WB94, increased over time, while another, Microvirgula aerodenitrificans strain BE2.4, increased briefly, returning to background levels after 42 d. Eleven days after inoculation in Spring 2017, outflow nitrate-N concentrations of bioaugmentation were sporadically reduced compared to the control for two weeks, but the effects were insignificant over the study period. The study suggests that biostimulation and bioaugmentation are promising technologies to enhance nitrate removal during cold conditions. A means of controlling bioclogging is needed for biostimulation, and improved means of inoculation and maintaining abundance of introduced strains is needed for bioaugmentation. In conclusion, biostimulation showed greater potential than bioaugmentation for increasing nitrate removal in a woodchip bioreactor, whereas both methods need improvement before implementation at the field scale.

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