Effects of Antibacterial Agents on Nitrification in an Aquatic Recirculating System

Treatment of recirculating systems with a single dose of erythromycin (50 mg/liter) resulted in nitrate reduction and stopped nitrification for 14 days as evidenced by changes in pH and ammonia, nitrite and nitrate concentrations. Treatment of systems with 2-chloro-6-(trichloromethyl) pyridine, a known nitrification inhibitor, inhibited nitrification similarly. Treatment with chloramphenicol (50 mg/liter), oxytetracycline (50 mg/liter), sulfamerazine (50 mg/liter), or nifurpirinol (1 mg/liter) had no effect on nitrification.