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The impacts of changes in hydraulic retention time (HRT) on nitrogen elimination, the activity of sludge and the structure of microbial communities in a sequencing batch reactor under the joint stress of ibuprofen (IBP) and ciprofloxacin (CIP) were investigated. Under the combined stress of IBP (belonged to nonsteroidal anti-inflammatory drugs) and CIP (belonged to antibiotics), the elimination level of ammonia nitrogen, chemical oxygen demand, and the rate of specific ammonia oxidation, specific nitrite oxidation, specific nitrate reduction in activated sludge declined with the shortening of HRT. Under the joint stress of IBP and CIP, the content of polysaccharide (PS) and protein (PN) together with the ratio of PN to PS in the extracellular polymeric substances grew with the shortening of HRT, and the content of aromatic proteins increased significantly, which indicated that aromatic proteins were the major protective response substances to the shortening of HRT. Under the joint stress of IBP and CIP, with the reduction of HRT, and the reduction rate of relative abundance of nitrifying bacteria was more evident than that of denitrifying bacteria. This exploration gives novel thoughts for understanding the impacts of HRT on biological nitrogen removal of wastewater under combined stress of IBP and CIP. [ABSTRACT FROM AUTHOR]

[Display omitted] • ARG is more cleared by mixed Fe6+/SO 3 2- at acid pH than at neutral and alkaline pH. • Acid pH activates more bacterial DNA metabolism in a ARG removal by mixed Fe6+/SO 3 2-. • Germs have more pyrimidine biosynthesis and salvage in a mixed Fe6+/SO 3 2- at acid pH. The variations of the antibiotic resistance genes removal and the bacterial nucleotide metabolism function in the wastewater by the combined ferrate and sulfite treatment at different pH levels were investigated. The total DNA as well as the genes sul2, sul3 and intI1 removal by the combined 10 mg/L ferrate and 28.5 mg/L sulfite treatment and the contributions of the sulfate radicals and the hydroxyl radicals produced by the reaction of ferrate with sulfite to the DNA removal decreased as the pH increase from 6.0 to 9.0. Bacterial nucleotide metabolism level changes affected the DNA removal, and the highest nucleotide degradation metabolism level and the lowest level of the nucleotide biosynthesis and salvage metabolism were found at pH 6.0. The reduction of the genes sul2 , sul3 and intI1 host level contributed to the genes sul2 , sul3 and intI1 removal. This study provides novel insights into the antibiotic resistance genes removal by the combined ferrate and sulfite treatment at different pH levels. [ABSTRACT FROM AUTHOR]

The impact of polytetrafluoroethylene-nanoplastics (PTFE-NPs) on biological sewage disposal was delved, containing nitrogen remotion, microbiological activity and composition of extracellular polymer (EPS). The addition of PTFE-NPs reduced the removal efficiencies of chemical oxygen demand (COD) and ammonia nitrogen (NH 4 +-N) by 3.43 % and 2.35 %, respectively. In comparison with no PTFE-NPs, the specific oxygen uptake rate (SOUR), specific ammonia oxidation rate (SAOR), specific nitrite oxidation rate (SNOR) and specific nitrate reduction rate (SNRR) decreased by 65.26 %, 65.24 %, 41.77 % and 54.56 %, respectively. The PTFE-NPs inhibited the activities of nitrobacteria and denitrobacteria. It was worth noting that, nitrite oxidized bacterium was more resistant to adverse environments than ammonia oxidizing bacterium. Compared with no PTFE-NPs, the reactive oxygen species (ROS) content and lactate dehydrogenase (LDH) grew by 130 % and 50 % under PTFE-NPs pressure. The appearance of PTFE-NPs affected the normal function of microorganisms by inducing endocellular oxidative stress and destroying the completeness of the cytomembrane. The protein (PN) and polysaccharide (PS) levels in loosely bound EPS (LB-EPS) and tightly bound EPS (TB -EPS) increased by 4.96, 0.70, 3.07 and 0.71 mg g−1 VSS, under PTFE-NPs. Meanwhile, the PN/PS ratios of LB-EPS and TB -EPS increased from 6.18 and 6.41–11.04 and 9.29, respectively. The LB-EPS might provide sufficient binding sites for PTFE-NPs adsorption due to its loose and porous structure. The defense mechanism of bacteria against PTFE-NPs was mainly the PN in loosely bound EPS. Moreover, the functional groups referred to the complexation of EPS with PTFE-NPs were mainly related to N-H, C O, and C-N in proteins and O-H in polysaccharides. • The PTFE-NPs inhibited the activities of nitrobacteria and denitrobacteria. • The PTFE-NPs caused the ROS content and LDH release to increase. • The PN levels in LB-EPS and TB-EPS were higher than those of PS at PTFE-NPs pressure. • The main functional groups of EPS bound with PTFE-NPs were N-H, C O, C-N and O-H. [ABSTRACT FROM AUTHOR]

[Display omitted] • PTFE-NPs weaken the Cu(II) and CIP antagonism on sludge activities. • Nitrifier was more alive to Cu(II) and CIP than denitrifier with or without PTFE-NPs. • Adsorption of CIP and Cu(II) by PTFE-NPs was synergistic. • PN level in EPS was decreased by PTFE-NPs at mixed Cu(II)/CIP. • PTFE-NPs abated the binding of functional groups in PN and PS to mixed Cu(II)/CIP. The work aimed to explore effects of polytetrafluoroethylene nanoplastics on joint inhibitions of ciprofloxacin and bivalent copper on the nitrogen removal in a sequencing batch reactor and its potential mechanisms. The addition of bivalent copper and/or ciprofloxacin reduced the ammonia nitrogen elimination rate with or without polytetrafluoroethylene nanoplastics. Adsorption kinetics and thermodynamics showed the binary bivalent copper and ciprofloxacin promoted their adsorptions by polytetrafluoroethylene nanoplastics. Polytetrafluoroethylene nanoplastics enhanced combined toxicities of ciprofloxacin and bivalent copper to sludge activities and microbial community involved into nitrification and denitrification due to the adsorption of ciprofloxacin and bivalent copper by polytetrafluoroethylene nanoplastics. With or without polytetrafluoroethylene nanoplastics, bivalent copper and/or ciprofloxacin caused more obvious level changes of protein than polysaccharide. This study provides novel insights for understanding the effect of combined heavy metals and antibiotics on the performance in a sequencing batch reactor with the nanoplastics stress. [ABSTRACT FROM AUTHOR]