Long-term effects of antibiotics on the elimination of chemical oxygen demand, nitrification, and viable bacteria in laboratory-scale wastewater treatment plants

Arch Environ Contam Toxicol. 2012 Oct;63(3):354-64. doi: 10.1007/s00244-012-9773-4. Epub 2012 May 24.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / analysis
  • Anti-Bacterial Agents / toxicity*
  • Bacteria / drug effects*
  • Bacteria / growth & development
  • Bacteria / metabolism
  • Biodegradation, Environmental
  • Biological Oxygen Demand Analysis
  • Nitrification / drug effects
  • Waste Disposal, Fluid / methods*
  • Waste Disposal, Fluid / statistics & numerical data
  • Wastewater / chemistry
  • Wastewater / microbiology*
  • Water Pollutants, Chemical / analysis
  • Water Pollutants, Chemical / toxicity*

Substances

  • Anti-Bacterial Agents
  • Waste Water
  • Water Pollutants, Chemical