Study On The Effect Of Antibiotics On Biological Nitrogen Removal System And Its Removal Efficiency

Antibiotics are commonly used in industries such as medical and animal husbandry.Because of their continuous input into the environment and their non-degradable properties,they exhibit "false persistence" and are widely detected in water environments.In this study,the sludge from the secondary sedimentation tank of Guangzhou Lijiao Sewage Treatment Plant was used as the inoculation sludge to start Sequencing Biofilm Batch Reactor(SBBR)and Biological Aerated Filter(BAF).The effect of antibiotics on the biological nitrogen removal system and its removal are discussed.Through the addition of trimethoprim(TMP)and ciprofloxacin(Ciprofloxacin,CIP)two kinds of antibiotics,the changes of COD,nitrogen and microbial community structure were investigated.And the effect of the two antibiotics in the biological nitrogen removal process was studied.Furthermore,BAF with volcanic rock as filler was used to study the removal efficiency of two antibiotics.The main research results are as follows:In the short term,the administration of TMP alone will not have a significant effect on nitrification,while high concentration(10 mg/L)CIP will affect nitrification,and the two antibiotics did not significantly inhibit denitrification.In the long-term impact test,the biological denitrification capacity in the early stage was inhibited by TMP and CIP,and the TMP dosing group could recover in the later period.In the experimental group with CIP dosing,AOB was restored but NOB was still inhibited,and the mixed dosing group was inhibited.Stronger.While the biological denitrification ability was suppressed,the EPS content in the reactor also decreased significantly.TMP alone increased the species abundance and diversity,and the CIP-dosed group decreased the species abundance and diversity.At phylum level,although the proportion of dominant bacteria in different reactors has changed to some extent,they are still Bacteroides,Proteobacteria,and Chloroflexi.At class level,the degeneration of the α-denatured bacteria is inhibited by two antibiotics,and the γ-modified bacteria has a strong tolerance to CIP.At genus level,the denitrification-related Zooloea and Rhodobacter spp The adaptability of antibiotics is stronger.The q PCR results show that antibiotics can inhibit the activity of biological denitrification functional bacteria,but the absolute number of functional bacteria will not decrease,but will increase to a certain extent.After antibiotics have been domesticated for a long time,,the TMP removal rate increased significantly from the initial 10% to 65% in the case of single dosing.However,due to the influence of CIP,the TMP removal rate did not increase significantly in the mixed dosing.In contrast,the removal rate of CIP was relatively high in the early stage and decreased to about 5% in the later stage.It is speculated that the removal route was mainly adsorption.The cycle test shows that the removal of TMP and CIP is significantly related to the removal of total nitrogen.The nitrification test showed that compared with the TMP alone group,the NOB in the CIP alone group and the two antibiotics mixed group was still inhibited to a certain extent,and the cumulative amount of nitrous nitrogen reached 11.2 mg/L and 20.2 mg/L at 6 hours.The removal of TMP and CIP is significantly related to the removal of ammonia nitrogen during the nitrification process.TMP is mainly removed by biodegradation during the nitrification process,and CIP is mainly removed by adsorption.The denitrification test showed that the denitrification process of CIP alone and mixed with two antibiotics was promoted to some extent compared to the TMP alone group.When only TMP was added alone,its removal was significantly related to the removal of nitrate during denitrification,but its correlation was smaller than that of nitrification.In the CIP single-dosed and mixed-dosed experimental groups,the removal of TMP and CIP was not significantly related to denitrification.In addition,the removal rate of TMP before and after domestication did not change significantly,and CIP was mainly removed by adsorption.In BAF,the addition of two antibiotics has no obvious effect on the denitrification performance,especially the nitrification performance,and the ammonia nitrogen removal capacity is more than 92%.TMP and CIP had a significant impact on the species abundance and diversity in BAF.The addition of TMP alone increased the species abundance in the reactor,while in the experimental group with CIP addition,both species abundance and diversity were significant decline.At class level,the relative proportion of Nitrospira,Alphaproteobacteria and Gammaproteobacteria has obvious advantages in each reactor(more than 30%).The removal rate of TMP added alone increased gradually to about 90%,and the removal rate of TMP was not significantly increased under the influence of CIP in the mixed addition.The CIP removal rate fluctuated between 30% and 60% in both dosing methods.Batch tests show that BAF with volcanic rock as filler has both physical adsorption and biodegradation for antibiotics.Among them,TMP is mainly biodegradable,and CIP is mainly adsorption removal.