title: Long-term effects of antibiotics on the elimination of chemical oxygen demand, nitrification, and viable bacteria in laboratory-scale wastewater treatment plants.
abstract: Antibiotics and other pharmaceuticals are contaminants of the environment because of their widespread use and incomplete removal by microorganisms during wastewater treatment. The influence of a mixture of ciprofloxacin (CIP), gentamicin (GM), sulfamethoxazole (SMZ)/trimethoprim (TMP), and vancomycin (VA), up to a final concentration of 40 mg/L, on the elimination of chemical oxygen demand (COD), nitrification, and survival of bacteria, as well as the elimination of the antibiotics, was assessed in a long-term study in laboratory treatment plants (LTPs). In the presence of 30 mg/L antibiotics, nitrification of artificial sewage by activated sludge ended at nitrite. Nitrate formation was almost completely inhibited. No nitrification at all was possible in the presence of 40 mg/L antibiotics. The nitrifiers were more sensitive to antibiotics than heterotrophic bacteria. COD elimination in antibiotic-stressed LTPs was not influenced by ≤20 mg/L antibiotics. Addition of 30 mg/L antibiotic mixture decreased COD removal efficiency for a period, but the LTPs recovered. Similar results were obtained with 40 mg/L antibiotic mixture. The total viable count of bacteria was not affected negatively by the antibiotics. It ranged from 2.2 × 10(6) to 8.2 × 10(6) colony-forming units per milliliter (CFU/mL) compared with the control at 1.4 × 10(6)-6.3 × 10(6) CFU/mL. Elimination of the four antibiotics during phases of 2.4-30 mg/L from the liquid was high for GM (70-90 %), much lower for VA, TMP, and CIP (0-50 %), and highly fluctuating for SMZ (0-95 %). The antibiotics were mainly adsorbed to the sludge and not biodegraded.
authors.affiliation: Department of Biology for Engineers and Biotechnology of Wastewater Treatment, Karlsruhe Institute of Technology, Am Fasanengarten, 76131 Karlsruhe, Germany.
authors.forename: Susan
authors.initials: S
authors.lastname: Schmidt
authors.forename: Josef
authors.initials: J
authors.lastname: Winter
authors.forename: Claudia
authors.initials: C
authors.lastname: Gallert
mesh_terms: D000900:Anti-Bacterial Agents / Q000032:analysis / Q000633:toxicity*; D001419:Bacteria / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D001673:Biodegradation, Environmental; D057919:Biological Oxygen Demand Analysis; D058465:Nitrification / Q000187:drug effects; D014865:Waste Disposal, Fluid / Q000379:methods* / Q000706:statistics & numerical data; D062065:Wastewater / Q000737:chemistry / Q000382:microbiology*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*
chemical_list: D000900:Anti-Bacterial Agents; D062065:Wastewater; D014874:Water Pollutants, Chemical