Purification Mechanism And Enhancement Of Cephalosporins And Sulfonamides By Chlorella And Scenedesmus

As a kind of drug to resist bacterial infection,antibiotics are widely used in medicine,aquaculture,animal husbandry and other fields.In the past decades,due to the unrestricted production and use of antibiotics,a large number of antibiotics without complete metabolism have entered aquatic environment,which has an adverse impact on aquatic organisms and human health.Microalgae-based wastewater remediation technology has attracted extensive attention because of its low cost,solardriven and environment-friendly advantages.In this paper,cefradine(RAD)and sulfadimethoxine(SDM)were used as target pollutants to investigate the removal efficiency of two antibiotics by two freshwater microalgae,Chlorella sp.L166 and Scenedesmus quadricauda.At the same time,UV pretreatment were used to strengthen the removal of antibiotics by microalgae.The main results of this paper are as follows:(1)During the culture period,RAD inhibited the growth of two microalgae,and the inhibition increased with the increase of concentration.The growth inhibition rate of the two microalgae decreased with the extension of culture time,two microalgae showed a certain recovery ability.Chlorella sp.L166 and Scenedesmus quadricauda could effectively purify RAD.When the concentration of RAD was 5 mg/L,the removal rates could reach 97.27% and 98.50%,respectively.Seven by-products were identified by UPLC-MS.Three degradation pathways including decarboxylation,demethylation,hydrolysis,side chain cleavage and hydrogenation were proposed.(2)UV pretreated RAD alleviated the toxicity to Chlorella sp.L166,but exacerbated the toxicity to Scenedesmus quadricauda.When the concentration of cefradine was 100 mg/L,UV pretreatment increased the biomass of Chlorella sp.L166 by 12.01% and decreased the biomass of Scenedesmus quadricauda by 6.16%.It is worth noting that RAD after UV treatment is easier to photolysis and can be removed faster when combined with microalgae technology.(3)High concentration of SDM damaged the cytochrome and biofilm system of the two microalgae species,resulting in strong inhibition of the growth of the two microalgae species.With the extension of culture time,Chlorella sp.L166 had a certain recovery ability,while the inhibition on the growth of Scenedesmus quadricauda increased.On the 12 th day,the inhibition rate of 150 mg/L SDM on the biomass of Chlorella sp.L166 decreased to 34.57%,while the inhibition rate on Scenedesmus quadricauda increased to 61.65%.Compared with the high removal rate of RAD,the removal rates of 25 mg/L SDM by Chlorella sp.L166 and Scenedesmus quadricauda were only 13.96% and 11.43%.(4)SDM after UV treatment significantly increased the biomass and photosynthetic pigment content of the two microalgae,which was conducive to the elimination of reactive oxygen species under oxidative stress,and the toxicity was alleviated.The biomass of the two microalgae increased and the toxicity was alleviated.The combination of UV pretreatment and microalgae culture increased the removal rates of 25 mg/L SDM by Chlorella sp.L166 and Scenedesmus quadricauda to 34.73% and 23.72%,respectively,but the removal rates were still poor.