Effect Of Two Antibiotics On Partial Denitrification System And Its Removal Efficiency

Anaerobic Ammonium Oxidation（Anammox）has attracted much attention due to its high efficiency and energy saving,but its application and development are greatly hindered due to its inability to steadily obtain nitrite as substrate and excessive effluent nitrate.While the Partial denitrification（PD）process can achieve nitrite accumulation at the same time as nitrate reduction,which can effectively solve the problems of an Anammox process,and has the advantages of less organic carbon source demand,high reaction rate and low sludge yield.Therefore,It is of great scientific and engineering significance to study Partial denitrification.On the other hand,Pharmaceuticals and personal care products（PPCPs）,as a new pollutant,have attracted more and more attention due to their potential harm to aquatic organisms and human health.Antibiotics are an important component of PPCPs,which are widely used in medical and animal husbandry industries.Due to their continuous input into the environment and refractory degradation characteristics,they are widely detected in water environment and soil.The influence of antibiotics in water on the denitrification performance of PD process and whether antibiotics can be removed in the denitrification reaction are the focus of this study.Therefore,the experiment realized the start of PD by inoculating sludge in the second sedimentation tank of Guangzhou Lekau Sewage Treatment Plant as the inoculating sludge,and used Ciprofloxacin(The effects of antibiotics on nitrogen removal and microbial community structure of PD system were studied by CIP and SMX.The removal of PD to these two antibiotics during nitrogen removal was discussed.the results of the study are as following:Under the condition of 30mg/L nitrate and C/N ratio of 2.5,the PD-SBR reactor was successfully started for 60 days,and the Nitrite accumulation rate（NAR）was maintained at about 75%.During the test,CIP and SMX antibiotics of different types were added to the two PD reactors respectively,and the concentration of antibiotics was continuously increased（from 50μg/L to 1000μg/L）.By monitoring the changes of nitrogen,organic matter and polyglycoprotein contents in PD system under the influence of antibiotics,combined with FTIR and 3D-EEM fluorescence spectrum analysis,the results of the influence of antibiotics on the operation efficiency of PD-SBR reactor showed that:NAR in PD system decreased first and then increased,while the content of PN and PS in EPS increased,indicating that the microbial activity related to nitrite accumulation in PD system was inhibited in the early stage,and the microbial activity gradually recovered after the screening and adaptation process in antibiotic environment in the later stage.In addition,under the stimulation of antibiotics,microorganisms secrete EPS to protect cells from acute injury and maintain system stability.In the process of adding antibiotics for a long time,the content of antibiotics in the inlet and outlet water of PD system was detected,and the removal of antibiotics by the system was studied.The average removal rate of CIP alone increased from 9.83%to30.15%,while the average removal rate of SMX alone remained at about 40%.In order to further study the way and mechanism of PD antibiotic removal,the contents of PD adsorbed and degraded antibiotics were detected and the percentages of PD adsorbed and degraded antibiotics were calculated respectively.The results showed that CIP removal was mainly dominated by sludge adsorption and biodegradation;The removal of SMX is mainly by biodegradation and adsorption.According to the results of high-throughput sequencing technology,CIP and SMX have significant effects on the microbial community structure in PD system.At the phylum level,the changes of microbial community composition were similar,but the proportion of species abundance was different.At the genus level,the abundance of Thaure related to NO_2^--N accumulation gradually decreased under the influence of antibiotics.