Photodegradation of Antibiotics Used in Aquaculture

EPA Grant Number: F6B20734
Title: Photodegradation of Antibiotics Used in Aquaculture
Investigators: Guerard, Jennifer
Institution: The Ohio State University
EPA Project Officer: Lee, Sonja
Project Period: September 1, 2006 through September 1, 2009
Project Amount: $111,172
RFA: STAR Graduate Fellowships (2006) RFA Text |  Recipients Lists
Research Category: Fellowship - Environmental Chemistry and Environmental Material Science , Academic Fellowships , Aquatic Ecosystems


Antibiotics are a class of pharmaceuticals engineered to kill pathogenic bacteria, and are heavily used in aquaculture. The catfish industry is one of the largest of these industries in the U.S., and utilizes antibiotics extensively. Little is known about their fate, and presence in the environment may affect on bacteria and ecosystems in surface waters. Terramycin (oxytetracycline) and Romet-30 (sulfadimethoxine, ormetoprim) will be studied. It may be possible for degradation to non-active forms through photochemical pathways catalyzed by dissolved organic matter (DOM). DOM is ubiquitous to all natural waters, comprised of plant and algal degradation products. Studies will investigate the effect of DOM on phototransformation of these three antibiotics and examine microbial efficacy of the antibiotics.

The goal of this study is to determine the photochemical fate of three antibiotics used in catfish aquaculture, by characterizing the phototransformation of oxytetracycline, sulfadimethoxine and ormetoprim in natural waters in clean systems and with DOM. This will involve investigating effects of pH, reactive oxygen species (ROS), and photo-Fenton reactions (a pathway that forms additional ROS) on the phototransformation and microbial efficacy of these antibiotics, as well as the analysis of any photochemical byproducts produced.


Water samples will be collected from catfish farm ponds and their receiving water. The photodegradation kinetics of each of these samples will be investigated using a solar simulator (Suntest CPS+) as well as experiments in natural sunlight. The kinetics of photodegradation of oxytetracycline, sulfadimethoxine, ormetoprim separately, a Romet-30 mixture, and all three drugs together will be studied, as both Terramycin and Romet-30 could be used at the same time. Experiments in MilliQ water and natural waters will be run, and detection done by reverse phase HPLC with a UV detector (Du et. al, 1995). Differing pH levels will be used to test the effect of pH on photodegradation, and molecular probes that can scavenge ROS will be used to assess importance of indirect photodegradation, either from production of ROS directly by DOM or by iron in photo-Fenton pathways (Southworth, 2003). Photoproducts will be characterized with an electrospray ionization mass spectrometer (ESI-MS) system. Escherichia coli will be used as a bacterial probe to test microbial efficacy of these compounds by measuring zone of inhibition of these compounds before and after photolysis.

Expected Results:

1. DOM will promote the photodegradation of these antibiotics by providing alternate pathways of phototransformation to biologically inactive substances.
2. Degradation of these antibiotics could be enhanced via side reactions such as the photo-Fenton interactions in the presence of iron.

Supplemental Keywords:

fellowship, antibiotics, dissolved organic matter, aquaculture, catfish, oxytetracycline, ormetoprim, sulfadimethoxine, photodegradation, reactive oxygen species, photo-Fenton, fate modeling,, Scientific Discipline, Water, Environmental Chemistry, Analytical Chemistry, Environmental Monitoring, Engineering, Chemistry, & Physics, aquaculture, antibiotics, chemical kinetics, photodegradation, chemical oxidation

Progress and Final Reports:

  • 2007
  • 2008
  • Final