Study On Characteristics Of Simultaneous Nitrogen Removal And Degradation Of Ciprofloxacin By Sulfur Autotrophic Denitrification Coupled With Anaerobic Ammonia Oxidation Process

Anammox is a kind of low energy consumption and sustainable biological nitrogen removal process for the treatment of high ammonia nitrogen wastewater,which has broad prospects in the field of ammonia nitrogen wastewater treatment.However,the application of Anammox process is limited by the environmental sensitivity of Anammox and the inhibition of An AOB by antibiotics widely existing in the actual ammonia nitrogen wastewater,resulting in high nitrate concentration in effluent and difficult degradation of antibiotics.Sulfur autotrophic denitrification coupled anaerobic ammoxidation process can solve the above problems.Sulfur autotrophic denitrifying bacteria uses sulfur source as electron donor,and the11%nitrate remaining in the anaerobic ammoxidation reaction acts as electron acceptor for sulfur autotrophic denitrification process,which reduces the concentration of nitrate in effluent.Sulfur autotrophic denitrifying bacteria contain cytochrome P450 enzyme（CYP450）,which has drug and metabolic functions for antibiotics,and achieve effective biodegradation of antibiotics.Based on this,this paper first selected ciprofloxacin（CIP）as a typical antibiotic target pollutant,and studied the effect of environmental dose CIP on the efficiency of anaerobic ammonia oxidation denitrification system.On this basis,in view of the technical problems of high nitrate concentration in the effluent from anaerobic anammox process and the inability to effectively remove CIP,the sulfur autotrophic denitrification process coupled with anaerobic ammox process was constructed to achieve synchronous removal of nitrate and CIP,and the key role of CYP450 in CIP degradation process and its degradation pathway were analyzed by key enzyme inhibition method.The evolution of functional microorganisms in the system was analyzed by high throughput sequencing and metagenomic sequencing.The main contents and conclusions are as follows:（1）The upflow continuous flow sludge reactor was used to investigate the effects of low concentration to high concentration（0,0.5,5,10 mg/L）of ciprofloxacin on nitrogen removal performance and microbial community in the short-cut nitrification and anammox process.The denitrification efficiency of the four stages was analyzed.In the stable period,the NO₃^--N concentration of the effluent was 28.7 mg/L,the NO₃^--N concentration increased to 44.3 mg/L after the addition of CIP,and finally decreased to 19.6 mg/L after a period of adaptation.Microorganisms showed resistance to CIP.Finally,the PN/A system recovery of nitrogen removal efficiency.When CIP concentration increased from 0 mg/L to 10 mg/L,the reactive oxygen species level and lactate dehydrogenase release increased by 172%and 24%,respectively.Three-dimensional fluorescence data showed that the fluorescence intensities of tryptophan and aromatic proteins in dissolved microbial products increased to 431.6 and 979.8,respectively.The abundance of Candidatus＿Kuenenia was increased from 4.1%to 9.4%in PN/A system.（2）The coupled integrated anaerobic anammox process of sulfur autotrophic denitrification with the addition of circulating sulfur components was established to study the characteristics of efficient nitrogen removal and CIP degradation.Compared with the control group,the removal rate of total inorganic nitrogen was increased by 37.4%,the average removal rate of CIP was increased by 5.1 times,the activity of AOB and NOB was increased by 18%and 30%,the activity of anammox was increased by 4.7%,and the PN（LB-EPS and TB-EPS）was increased by 38%and 39%,respectively.The concentrations of PS（LB-EPS and TB-EPS）increased by 2.2 and 1 times,respectively.Three kinds of CIP degradation pathway were detected by CYP450 enzyme,and three possible degradation pathways were deduced from the transformation products.It was found that sulfur autotrophic denitrifying bacteria with the core of Thiobacillus and Sulfurimonas were enriched and loaded with CYP450 enzyme,which was the key to CIP degradation.Sulfur autotrophic denitrification anaerobic ammonia oxidation process（3）By adding Na2S into the simulated wastewater of Anammox reactor as a sulfur source,an anaerobic environment is established to realize the coupling of sulfur autotrophic denitrification coupled anaerobic anammox process,so as to achieve the purpose of simultaneously alleviating CIP toxicity,inhibiting and reducing residual nitrate.The degradation effect of CYP450 on CIP in the process is studied.And the resistance genes and microbial communities were deeply explored.In SAD-Anammox system,the effluent NH₄⁺-N concentration is 0,NO₂^--N and NO₃^--N concentrations are 4.9 mg/L and 26.3 mg/L respectively,and the total inorganic nitrogen removal rate reaches 86.5%,which increases by 7.3%.The removal rate of CIP was stable at 55%,and CYP450 enzyme degrade CIP by the hydroxylation of-F,manly.