The Repository @ St. Cloud State

Open Access Knowledge and Scholarship

Date of Award


Culminating Project Type




Degree Name

Biological Sciences - Cell and Molecular: M.S.




College of Science and Engineering

First Advisor

Heiko Schoenfuss

Second Advisor

Satomi Kohno

Third Advisor

Jennifer Lamb

Fourth Advisor

Nathan Buender, Richard Kiesling

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Keywords and Subject Headings

Wastewater, Contaminants, Membrane Bioreactor, Adverse Outcome


Wastewater originates from industrial, commercial, and residential sources. Each source has the potential to add contaminants of emerging concern (CECs) that may interact with an organism’s cellular pathways and metabolic processes. Wastewater treatment plants (WWTP) are built to remove macro pollutants, nutrients, and microorganisms through three-stage processes but are not optimized for CEC removal. In the three-stage process primary treatment removes macro-pollutants, tertiary treatment disinfects, and the secondary treatment removes micro-pollutants such as CECs. Secondary treatment technologies range from well-established oxidation treatments to membrane bioreactors (MBR). Oxidation treatments use agitators to promote bacterial growth and nutrient removal, while MBRs uses a similar biological treatment but add membrane filtration. Studies have shown that the effluent released after oxidation treatments still contains CECs. While studies on MBR have shown better removal of CECs than oxidation treatments it is not known how the effluent affect exposed fish. The Hutchinson, MN WWTP splits its primary treatment effluent into both a MBR treatment and oxidation treatment allowing for direct comparison of the efficacy of CEC removal. The objective of the current study was to compare CEC removal efficacy between these wastewater treatment technologies through analytical chemistry and replicate exposure of fathead minnows (Pimephales promelas). Fathead minnows were exposed for 21-days via a flow through system to four treatments including a reference control, primary treatment effluent, oxidation treatment effluent, and MBR effluent. The results show that both secondary treatments reduce exposure activity ratios for all measured chemicals when compared to the primary treatment effluent. While fish did not survive in primary treated effluent the survival rate increased to >94% for fish exposed to MBR and oxidation treatment effluent. The reduction in exposure activity ratios for bisphenols and alkylphenols were similar between MBR and oxidation treatments, but there were notable differences in pesticide removal. MBR treatment resulted in significant decreases in gene expression for aerobic metabolism regulators in the liver when compared to control in the first exposure. Meanwhile results in the second exposure show significant differences in gene expression for reproductive pathways when the oxidation treatment was compared to control. The molecular endpoints are not reflected at the tissue or organ levels indicating that the impacts are subtle. Oxidation treatment, though it is not removing CECs as well as MBR, is providing better outcomes for fathead minnows. These results demonstrate that both treatments greatly improve the quality of effluent when compared to the influent. Meanwhile when comparing the secondary treatments CEC removal differs creating complex mixtures that are leading to better outcomes in fish treated with oxidation treatment effluent.

Supplemental.pdf (134 kB)
List of Chemicals measured



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