Combined Treatment Methods for Removal of Antibiotics from Beef Wastewater

Use of antibiotics is common practice in agriculture; however, they can be released into the environment, potentially causing antimicrobial resistance. Naturally mined diatomaceous earth with bentonite was tested as a remediation material for tylosin, chlortetracycline, and ceftiofur in wastewater from a beef cattle feedlot. Langmuir binding affinity in 10 mM sodium phosphate buffer at pH 6.7 was established prior to testing wastewater to determine binding potential. Chlortetracycline was found to have a binding affinity of 15.2 mM^-1 and a binding capacity of 123 mg per g of diatomaceous earth while ceftiofur showed a much lower binding affinity and loading at 7.8 mM^-1 and 3 mg per g of diatomaceous earth, respectively. From spiked wastewater, tylosin (50 μg mL^-1, pH 8) and chlortetracycline (300 μg mL^-1, pH 6) were removed (100 and 80%, respectively) when treated with 20 mg of diatomaceous earth while ceftiofur (300 μg mL^-1, pH 8) remained in solution. When the spiked wastewater was flocculated with aluminum sulfate, a change in pH from 8 to 4 was observed, and chlortetracycline was removed from the wastewater; tylosin and ceftiofur remained in solution. When subsequently treated with diatomaceous earth, ceftiofur and tylosin were completely removed by diatomaceous earth from the flocculated wastewater.