Civil and Environmental Engineering


First Advisor

Dr. Chittaranjan Ray

Date of this Version

Summer 7-29-2022

Document Type



Walkenhorst, L. (2022, July 29). Efficiency of Bank Filtration in the Removal of Cyanotoxins Under Different Levels of Nutrients.


A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Civil Engineering, Under the Supervision of Professor Chittaranjan Ray. Lincoln, Nebraska: August, 2022

Copyright © 2022 Luke D. Walkenhorst


Harmful Algal Blooms (HABs) are an increasing concern not only in Nebraska, but across the world. Increasing global temperatures in conjunction with overuse of synthetic fertilizers are leading causes to the increasing frequency and concern of HABs. In the present work, the effectiveness of simulated bank filtration (BF), as an economical water treatment option, to remove cyanotoxins under different levels of nutrients (nitrates and phosphates) was investigated. Vertical flow-through columns pre-acclimated with two levels of nutrients (e.g., nitrate and phosphate—10 vs. 50 mg/L) were exposed to two different levels of cyanotoxins (10 vs. 75 μg/L). Results from the study confirmed the ability of simulated BF to remove cyanotoxins. High cyanotoxins removals (>70%) were achieved regardless of the levels of nutrients and cyanotoxins. It can be recommended to guarantee enough travel time (>7 d) to enhance the removal of cyanotoxins. The majority (42 – 60%) of the overall removal occurred within the top 10 cm of the column, thus representing the effect of biodegradation. An additional 6% - 35% cyanotoxin removal occurred within the remaining 150 cm, thus representing the physicochemical processes within the packing material. Among the removal mechanisms, biodegradation was the predominant removal mechanism.

Advisor: Chittaranjan Ray