Effects Of Process Parameters Of Anaerobic Sludge Digestion System On Degradation And Migration Of Antibiotics

As emerging contaminants,antibiotics could enter the environment through the sludge treatment and disposal processes in the wastewater treatment plants,which brings up the potential threat to human health.Currently,there are limited reports about the effects of process parameters of anaerobic digestion system on the removal of antibiotics.In this study,batch experiments were conducted to investigate the degradation and migration of 12 typical antibiotics in 4 categories?sulfonamides,macrolides,tetracyclines and quinolones?during the anaerobic sludge digestion at different initial pH values?5.5-10.5?,alkalinities?700-6000 mg/L CaCO₃?and ammonia nitrogen concentrations?170-3000 mg/L?.Results show that sulfonamide antibiotics were not detected in the waste activated sludge.The other three antibiotics could be degraded through anaerobic sludge digestion with the removal efficiencies in the descending order of macrolides,tetracyclines and quinolones.In the anaerobic sludge digestion process,antibiotics adsorbing in the solid phase dissolved into the liquid phase obviously.Statistical analysis shows that the dissolution efficiency of antibiotics was significantly related to the removal efficiency of antibiotics.This means that the more antibiotics migrated into the liquid phase,the higher removal efficiencies of antibiotics,and vice versa.Results show that initial pH of 7.5 was more beneficial to the removal of antibiotics in the sludge digestion system.Additionally,increasing the alkalinity of anaerobic digestion systems also had the promoting effects on the removal of antibiotics.On the contrary,there was a significant negative correlation between the ammonia nitrogen concentration and the removal efficiency of antibiotics.The increase of ammonia nitrogen concentration could inhibit the degradation of antibiotics.In the anaerobic sludge digestion system,antibiotics removal was mainly due to the microbial degradation,and thus microbial community structure in the sludge has an important influence on the removal of antibiotics.In this study,degradation of antibiotics was likely related to the acid-producing bacteria Clostridiales and Lactobacillales.