Performance Of Nitrogen And Carbon Removal In Simultaneous Heterotrophic Nitrification Aerobic Denitrification Process Under Antibiotics Stress

In this work,marine simultaneous heterotrophic nitrification aerobic denitrification bacteria were inoculated in sequencing batch reactors?SBRs?to treat high-salinity wastewater containing ampicillin or mixed antibiotics?ampicillin,sulfamethoxazole and tetracycline?.The pollutants removal mechanisms and genetic responses of simultaneous heterotrophic nitrification aerobic denitrification under different antibiotics were studied:The nitrogen and carbon removal performance and genetic responses in simultaneous heterotrophic nitrification aerobic denitrification under ampicillin stress were investigated.The changes of physiological status and intracellular substances of marine simultaneous heterotrophic nitrification aerobic denitrification bacteria were also analyzed.The results showed that when ampicillin concentration was no more than 10mg/L,heterotrophic nitrification aerobic denitrification could efficiently remove nitrogen and carbon.The nitrogen removal rate?NRR?and organics removal rate?ORR?were higher than 0.76 and 6.83 kg/?m³·d?,respectively.The half inhibitory concentration of ampicillin on marine simultaneous heterotrophic nitrification aerobic denitrification bacteria was 50 mg/L.With increased ampicillin concentration,the relative abundances of ampicillin resistance genes were first decreased and then increased.When ampicillin concentration was 10 mg/L,the relative abundance of resistance genes was 8.53×10^-5copies/16s rRNA.Compared with the control,the diversities and abundances respectively increased by 2.5 and 13.6 fold under 50 mg/L ampicillin stress.The role of antibiotics resistance genes in marine simultaneous heterotrophic nitrification aerobic denitrification bacteria was as follows:extended-spectrum types>metal types>AmpC types.Ampicillin could stimulate the production of reactive oxygen species and induced apoptosis of marine simultaneous heterotrophic nitrification aerobic denitrification bacteria.Ampicillin promoted the production of extracellular polymeric substance and enhanced sludge settleability in simultaneous heterotrophic nitrification aerobic denitrification.The nitrogen and carbon removal performance and genetic responses in simultaneous heterotrophic nitrification aerobic denitrification under mixed antibiotics stress were investigated.The results showed that when antibiotics concentrations were no more than 12 mg/L,marine heterotrophic nitrification aerobic denitrification bacteria could efficiently remove nitrogen and carbon.The nitrogen removal rate?NRR?and organics removal rate?ORR?were higher than 0.71 and 7.06 kg/?m³·d?,respectively.When antibiotics concentrations were 48 mg/L,the activity of marine heterotrophic nitrification aerobic denitrification bacteria was significantly inhibited.With increased antibiotics concentrations,the abundances of resistance genes were first increased and then decreased.When antibiotics concentrations were 48 mg/L,the absolute abundance of resistance genes was 1.30×10¹¹ copies/mg.Sulfonamides and tetracyclines resistance genes showed common genetic responses to antibiotics.The role of antibiotics resistance genes in marine simultaneous heterotrophic nitrification aerobic denitrification bacteria was as follows:Sulfonamides types>tetracyclines types>?-lactam types.Besides,marine simultaneous heterotrophic nitrification aerobic denitrification bacteria produced more extracellular polymeric substance under antibiotics stress.