Inhibitory Effect Of Antibiotics On The Performance And Microbial Population Structure Of EBPR

Nitrogen and phosphorus are the main factors leading to eutrophication of water bodies.In recent years,as the problem of water pollution has become more serious,the water quality standards have become more and more strict on the concentration of nitrogen and phosphorus in the effluent of sewage treatment plants.As a highly effective fungicide,antibiotics are widely used in human medicine and aquaculture.Due to its dependence,the abuse of antibiotics is becoming more and more serious.Most antibiotics cannot be absorbed by organisms.To the sewage treatment plant,the ng.L^-1 or even mg.L^-1 level is reached in the influent concentration of the domestic sewage treatment plant and the aquaculture sewage treatment plant,which has adverse effects on the nitrogen and phosphorus removal functional microorganisms.The effect of nitrogen phosphorus removal is of great significance to ensure the normal operation of the wastewater treatment plant.This experiment is based on the enhanced biological phosphorus removal?EBPR?system to simulate the quality of domestic sewage.The influent PO₄^3--P concentration is8mg.L^-1,the NH₄⁺-N is 40mg.L^-1,and the COD is 400mg.L^-1.The effects of sulfamethoxazole?SMZ?and ciprofloxacin?CIP?and their combination on the nitrogen and phosphorus removal performance of EBPR system and their removal effects in EBPR system were studied.By fitting the ratio of phosphorus uptake sPUR,ratio of phosphatase sPRR,nitration rate sAUR and nitrification rate sNUR to the polyphosphate bacteria PAOs,ammonia oxidizing bacteria AOB and nitrifying bacteria by SMZ and CIP The inhibitory effect of NOB was calculated,and the IC₅₀ of the respective semi-inhibitory concentration values was calculated.At the same time,the changes of the performance index of activated sludge and the composition of EPS of extracellular polymer in different concentrations of SMZ and CIP in long-term exposure experiments were studied.The activated sludge was domesticated from the activated sludge from the Qilihe Wastewater Treatment Plant in Lanzhou.After the system was stabilized,the phosphorus removal rate was maintained above90%,the ammonia nitrogen removal rate was maintained above 95%,and the COD effluent concentration was around 50 mg.L^-1.,good performance.In addition,the experiment also set the control reactor R₂ to observe the impact of different concentrations of SMZ and CIP on the system during short-term impact.The experiment was divided into three stages.The first stage was 110 days.The effects of different concentrations of SMZ on the performance of nitrogen and phosphorus removal in EBPR system were studied.SMZ used 1,2,5,10,20,50 mg.L^-1.Concentration gradients.Studies have shown that low concentration SMZ(1,2mg.L^-1)has almost no effect on nitrogen and phosphorus removal and COD removal performance of the system.Then,with the increase of SMZ concentration,the phosphorus removal rate of each system is reduced to89%.81.9%,76.4%,66.18%,ammonia nitrogen removal rate decreased to 94.3%,90.6%,87%,83%;PAOs phosphorus uptake stage can be obtained by calculating the maximum sPUR,sPRR,sAUR and sNUR in the typical period of each working condition.The IC₅₀value was 45.84 mg.L^-1,and the IC₅₀ value of the phosphorus release stage could not be accurately determined because it was greater than 50 mg.L^-1,and was calculated to be about81.2 mg.L^-1 according to the fitting curve equation.The IC₅₀ value of AOB is 28.86mg.L^-1,and the EC₅₀ value of NOB is also less than 50mg.L^-1.It can not be accurately determined.According to the curve of the fitting curve,it is about 104.6mg.L^-1,so that NOB is resistant to SMZ.The most severely affected,followed by PAOs,the weakest AOB.The degradation of SMZ in EBPR system is closely related to microbial activity.The maximum degradation during the long-term exposure experiment is 1.26mg.L^-1,and the maximum removal during the short-term impact is 2.36mg.L^-1.The main removal phase in the cycle is Anaerobic phase and nitrification phase.In the second stage,a total of 107 days,the effects of different concentrations of CIP on the performance of nitrogen and phosphorus removal in EBPR system were studied.CIP used4 concentration gradients of 0.5,1,1.5 and 2 mg.L^-1.The results show that with the increase of CIP concentration,the phosphorus removal rate of the system is reduced to 80%,68.1%,55%and 49.19%,respectively,and the ammonia nitrogen removal rate is reduced to 86.31%,76.9%,67%,57.4%.By calculating the maximum sPUR,sPRR,sAUR and sNUR in the typical period of each working condition,the IC₅₀ value of the phosphorus release stage of PAOs is 1.93mg.L^-1,and the IC₅₀ value of the phosphorus uptake stage is 1.50mg.L^-1,and the IC₅₀ value of AOB For 1.17mg.L^-1,the EC₅₀ value of NOB is 1.22mg.L^-1,but due to the strong inhibition of AOB activity,the supply of NO₂^--N is insufficient,and the nitrification rate is affected,so the IC₅₀ value of NOB is not accurate..It can be seen that PAOs are most resistant to CIP,AOB is the least tolerant,and NOB cannot be estimated due to changes in objective conditions.The degradation of CIP in EBPR system is closely related to microbial activity.The maximum cycle degradation in the long-term exposure experiment is 0.15mg.L^-1,and the maximum removal in the short-term impact is 0.41mg.L^-1.PAOs,AOB and NOB all have certain degradation ability.In the third stage,a total of 111 days,taking the IC₅₀ value of the specific phase phosphorus release rate of the first and second stages of PAOs and the whole IC₅₀ value,respectively,studied the effect of the combined action of SMZ and CIP on the performance of nitrogen and phosphorus removal of EBPR system.The results show that the phosphorus removal rate is 54.2%and 42.5%under the two conditions,and the ammonia nitrogen removal rate is 56.1%and 44.8%.The maximum sPUR in the typical period is calculated by the fitting curve and the corresponding CIP concentration value is 1.68mg.L^-1.2.17 mg.L^-1,sAUR was 1.61 mg.L^-1 and 2.04 mg.L^-1.The effect of SMZ and CIP on the EBPR system is much greater than that of the SMZ alone,and to a certain extent stronger than the CIP alone.The combination of the two shows significant synergy.Through the study of the performance of the system's activated sludge and EPS composition and composition,it is found that the ratio of TB-EPS concentration to its constituent components in EPS composition is highly correlated with the performance of activated sludge.With the increase of SMZ and CIP concentration,the microbial activity and total bacterial flora of activated sludge decreased gradually,the sludge activating property deteriorated,the SV and SVI values both decreased,the SV mean decreased from 26%to12%,and the SVI was 80mL.g^-1 reduced to 38 mL.g^-1,and the TB-EPS concentration was reduced from 85.77 mg.?gVSS?^-1 to 45.33 mg.?gVSS?^-1.In the composition of TB-EPS,the DNA concentration was proportional to the activity of activated sludge.In the long-term exposure experiment of SMZ,the mean f value decreased from 0.82 to 0.73,and the DNA concentration decreased from 2.54 mg.?gVSS?^-1 to 1.92 mg.?gVSS?^-1,in the CIP long-term exposure experiment,the f value decreased from 0.82 to 0.70,the DNA concentration decreased from 2.62 mg.?gVSS?^-1 to 1.51 mg.?gVSS?^-1;PN and PS concentration and proportion It showed a great correlation with the appearance of sludge.In the long-term exposure experiment of SMZ,the activated sludge gradually became granulated,and the PN ratio increased from 44.1%to 56.55%,and PS decreased from 52.4%to 39%.In the CIP long-term exposure experiment,the granulation of activated sludge is more obvious,the proportion of PN is higher,from 46%to 67%,and PS is reduced from 50.5%to 29%.High-throughput sequencing of activated sludge before and after long-term exposure experiments in the R₁ experimental group reactor showed that after the long-term exposure experiment of SMZ,the total number of OUT and microbial diversity of the EBPR system decreased,and the dominant species were dominant.The proportion is even larger.It is particularly obvious at the genus level,the diversity is reduced,the structure of the flora is changed,and the original dominant genus Chloroflexus disappears.The original genus Zoogloea has become a new dominant genus and accounts for more Big.Among the functional microorganisms related to nitrogen and phosphorus removal,the abundance of Nitrospira and Dechloromonas decreased significantly,the abundance of Candidatus Accumulibacter increased,and the abundance of Candidatus competibacter decreased significantly.PAOs are also more tolerant to SMZ than GAOs.