The Degradatuion Mechanism Of Low Cefuroxime Axetil Concentrations By Different Biological Processes And A Study Of Antibiotic Resistance Genes

Pharmaceuticals and personal care products (PPCPs) refer to the organic pollutants that persist in the environment of low concentrations, which have brought so many adverse effects to the environment. The predominant aims of this paper is to discuss the mechanism of these three kinds of commonly used biological process CAS, SBR and SBBR removing the low concentration of cefuroxime axetil in simulation municipal sewage and antibiotic resistance genes. The conclusions are as follows:1. The final operational conditions of conventional activated sludge process(CAS) are:the concentration of cefuroxime axetil is 0.5mg/L, Ns is 0.4kgCOD/(kgMLSS-d), HRT is 12h; under these conditions, the CAS degradation rate is 95.82% for the COD,92.41% for the NH3-N, and 91.54% for the cefuroxime axetil in simulation municipal sewage. The final operational conditions of sequencing batch reactor activated sludge process(SBR) are:the concentration of cefuroxime axetil is 0.5mg/L, Ns is 0.3kgCOD/(kgMLSS-d), HRT is 12h, pH is 7.5; under these conditions, the SBR degradation rate is 98.80% for the COD,85.19% for the NH3-N, and 98.17% for the cefuroxime axetil in simulation municipal sewage. Meanwhile, the degradation process of cefuroxime axetil by SBR is most consistent with first-order kinetics. The final operational conditions of Sequencing Biofilm Batch Reactor(SBBR) are:the concentration of cefuroxime axetil is 0.5mg/L, Ns is 0.4kgCOD/(kgMLSS-d), HRT is 12h, pH is 7.5; under these conditions, the SBBR degradation rate is 92.46% for the COD,58.31% for the NH3-N, and 64.74% for the cefuroxime axetil in simulation municipal sewage. Simultaneously, the degradation process of cefuroxime axetil by SBBR is most consistent with zero-order kinetics.2. The intermediate and final degradation products of cefuroxime axetil by AS are similar with SBBR, which are small molecules partly branched off by cefuroxime axetil molecules. Finally the β-lactam ring destroyed means that cefuroxime axetil have been degraded.3. The order of microbial community diversity is AS reactor>inoculated sludge>SBBR reactor. Two kinds of dominant degradation strains have been selected from the reactors of AS, that CS2 is Ochrobactrum sp. and CS4 is Alcallgenes sp. Another two kinds have been selected from the reactors of SBBR, that BB3 and BB4 are all Alcaligenes sp.4. This study has detected 3 kinds of β-lactam antibiotic resistance genes from inoculated sludge, AS and SBBR reactor, which are OXA-1, OXA-2 and OXA-10.