Study On The Removal Characteristics Of Ozone-Activated Carbon On Antimicrobial Agent Climbazole

In recent years,high ecological and environmental health risks have caused by the use and discharge of plentiful antimicrobial agents.This paper examined the distribution characteristics and removal rate of typical antibacterial agents in a drinking water treatment plant in the Pearl River Delta,and evaluated the risks to human health.The degradation kinetics of climbazole,a typical antimicrobial agent,in water bodies under ozonation was studied,and its degradation products were identified.The effect of activated carbon on the removal of climbazole in water bodies and its influencing factors were explored to understand the adsorption characteristics of climbazole.The removal effect of climbazole through ozone-activated carbon combined process was examined,and the change characteristics of microbial community in the treatment system were analyzed.The main study results are as follows:(1)This study selected a drinking water treatment plant with ozone-activated carbon combined processfor sampling and investigation,and found that 7 target antibacterial agents were detected in the water samples(at least one process section),with a concentration range of 0～2396.79 ng/L.Ozone～activated carbon combined process can effectively remove the antibacterial agents in the water body(removal rate range-27.52%～100.00%),but in a part of sections,the negative removal rate appears,especially for DEET.Human health risk evaluation shows that the target antimicrobial agent may not pose a high risk to human health,but considering the long-term exposure and combined toxicity of different antimicrobial agents,a more conservative evaluation system should be established.RDA analysis shows that water quality indicators such as p H and oxygen consumption have a certain impact on the removal of antibacterial agents,but the specific mechanism needs to be further explored.(2)The degradation characteristics of climbazolein water by ozonation were discussed,and the results showed that the higher the initial concentration of climbazole,the lower the degradation rate.The p H value in the solution increases into alkaline can significantly inhibit the ozonation of climbazole.As the ozone flow rate continues to increase,the degradation rate of climbazole also gradually increases,but when the flow rate increased to a certain range,the increase of the degradation rate of climbazole was becoming small.Both bicarbonate ion and humic acid can inhibit the degradation of climbazole by ozone oxidation.There is a high degradation rate of climbazole,as high as 95.81%,in the pure water system.At the same time,the degradation rate of climbazole is less than 50% in the other three natural water bodies.After the ozonation,climbazole formed two new degradation products TP269 and TP297,which have not been reported in other degradation forms,and the toxicity of the two degradation products need to be further studied.(3)The adsorption performance of different activated carbons for climbazole in water was explored.The results showed that coconut shell activated carbon was more suitable for adsorbing climbazole than apricot shell,peach shell,and coal.Its adsorption process conformed to the Freundlich model and belongs to multi-molecular layer adsorption.Under the neural conditions,coconut shell activated carbon showed best adsorptioneffect to climbazole.The temperature change has little effect on the adsorption effect of climbazole by coconut shell activated carbon,because the adsorption process was exothermic.Humic acid inhibited the adsorption effect of climbazole by coconut shell activated carbon.The reduction of the particle size of coconut shell activated carbon and the increase of the concentration of climbazole can accelerate the adsorption rate.Natural water contains a lot of organic matter,which can inhibit the adsorption effect of coconut shell activated carbon on antibacterial substances to a certain extent.(4)The removal effect and mechanism of climbazole in water by the simulated ozoneactivated carbon(coconut shell)combined process were explored.The results show that the ozone-activated carbon combined process can effectively remove the climbazole in water.When this process continuously operated from 0h to 480 h,the removal rate of climbazole was 50.68%～100%,of which the average contribution rate of ozonationdegradation was57.75%,and those for activated carbon adsorptionwas 42.25%.But the removal rate of activated carbon gradually decreased with the extension of operation time,and basically reached the dynamic balance within 260～480h.The activated carbon should be replaced or activated in time to maintain the normal operation of the system.According to the analysis results of microbial community structure of activated carbon samples of the system,it was preliminarily determined that the specific bacterial genus that can promote the degradation and transformation of climbazole in this research system are Pelomonas,while those for specific fungigenera were Malassezia and Aspergillus,and Nitrosarchaeum wasfor specific Archaea.