An Adaptable, Interactive Computer Program to Predict the Fate and Transport of Antibiotics in Streams Impacted by Wastewater Effluent

Antibiotics are considered contaminants of emerging concern due to their potential to contribute to the growing threat of antimicrobial resistance. Some studies have focused on assessing antibiotic concentration in rivers and lakes within a wide geographic distribution; however, knowledge gaps involving data and models to predict the fate and transport of antibiotics and other organic pollutants in low-order streams impacted by wastewater effluent discharge remain. This work details the development of a program to model the concentrations of antibiotics downstream from a single discharge point. This focus is on the fate and transport of five classes of antibiotics (i.e., sulfonamides, macrolides, tetracyclines, fluoroquinolones, and beta-lactams) in streams, but the model is readily usable for other contaminants, such as pesticides, other pharmaceuticals, or industrial chemicals. A multiple-segment linear transport and reaction model was used to simulate the processes in the stream. Trained using occurrence data from June to October of 2023 and 2024 from three Minnesota sites impacted by wastewater effluent, this software program uses known rate constants, physico-chemical information about the compounds (e.g., absorption spectra, partitioning coefficients), measurements of stream flow and water quality, and information from databases about environmental and solution conditions to estimate rates of direct and indirect photolysis, sorption to particles and settling, air-water exchange, flushing, hydrolysis, and biodegradation. The novel aspect of this program is that it allows the user to interact with the graphical interface, selecting which compound to view and using sliders of variables to actively see how the transport of the compound changes in real-time. Further, the program outputs a sensitivity analysis interface where the user can select the compound/variable combination for which they would like to view a graphical representation. If the user has input known downstream values of the compound, the program iterates through combinations of parameters to find a fit to the data. This program was designed to be as adaptable and user-friendly as possible, requiring the user to only input the necessary information in a spreadsheet template and can be modified to encompass a broad range of organic pollutants.