Effect Of Antibiotics On Microbial Diversity In Piggery Wastewater During Anaerobic Biological Treatment

Tetracyclines had a significant impact on anaerobic biological treatment of wastewater in piggery wastewater. This paper offered references for handling the tetracyclines in piggery wastewater by anaerobic treatment system on microbial diversity.The results showed that:(l)Under anaerobic condition of35±2℃,the concentration of COD in the experimental groups influenced by the chlortetracycline were higher than the control group and the volume of methane gas on the contrary.With the increase of the concentration of the chlortetracycline, the range of the difference value of methane gas was from6.9%to29.2%,the removal rate of COD was from80.89%down to76.96%while the control group was84.46%;as the chlortetracycline concentration increased, analysis of the statistics of the microbial diversity in the anaerobic sludge by PCR-DGGE method revealed that the bacterial species richness of the sludge was from0.913to0.652.The comparison of these factors, the gap between the treatment group and the control group was enlarging as the coefficient similarity was from97.6down to78.9;the results of Real-time PCR showed that:without adding chlortetracycline,the16S rRNA maximum average number of copies was7.88×106copies/μL; when the concentration of the chlortetracycline was0.4mg/L, the16S r RNA average minimum copies number was5.01×106copies/μL.With increasing concentrations of chlortetracycline, bacteria species showed a decreasing trend but the bacteria absolute content showed increasing trend.(2) Under anaerobic condition of35±2℃, the COD concentration of the treatment groups influenced by oxytetracycline was higher than the control group, methane production volume was smaller. As oxytetracycline concentration improved, the difference value range of methane produce was from12.5%to53.79%, and the COD removal rate dropped from82.18%to74.1%,COD removal rate of the control group was83.73%.As the increases of oxytetracycline concentration,the COD removal rate inhibition rate was increased from1.86%to11.50%.As oxytetracycline concentration increased, analysis of statistics of microbial diversity in the anaerobic sludge by PCR-DGGE method revealed that the bacterial species richness of the sludge was from0.864to0.455.By comparison of factors, the gap between the treatment group and the control group was enlarging neither the similarity coefficient was92.7down to62.5;the results of Real-time PCR showed that:without adding oxytetracycline, the16S rRNA maximum average number of copies was7.88×106copies/μL;when concentration of chlortetracycline was60mg/L, the16S rRNA average minimum copy number was5.06x106copies/μL. With increasing concentrations of oxytetracycline, the bacteria species showed a decreasing trend ant the bacteria absolute content was also decreasing.(3) Under anaerobic condition of35±2℃, the COD concentration of treatment groups influenced by chlortetracycline and oxytetracycline was higher than the control group, methane production was smaller. As the concentration of the chlortetracycline and oxytetracycline improved, the difference value range of methane produce was from18.34%to55.46%, the antagonistic relationship between chlortetracycline and oxytetracycline had an impact on the volume of methane production. The COD removal rate dropped from79.74%to60.38%.As the increases of the chlortetracycline and oxytetracycline concentration, the COD removal rate inhibition rate was increased from4.16%to24.84%. The enhanced relationship between chlortetracycline and oxytetracycline had an impact on the COD removal rate. As the chlortetracycline and oxytetracycline concentration increased,analysis of statistics of microbial diversity in the anaerobic sludge by PCR-DGGE revealed that the bacterial species richness of the sludge was from0.968to0.645.By the comparison of these factors, the gap between the treatment group and the control group was enlarging neither the similarity coefficient from91.5down to55.6; the results of Real-time PCR showed that:with chlortetracycline and oxytetracycline concentration increased, the16S rRNA average number of copies appears increasing trend, ranged from5.61×106copies/μL to1.75×107copies/μL, and then appeared declining trend compared while the previously still appeared increasing trend. This situation was an opposite relationship to changes of bacteria population.(4) As chlortetracycline concentration increased, ammonium oxidizing bacteria (amoA) gene average copies number appeared the trend of reducing firstly then instead of increasing.There was a larger concentration of inhibition of the anaerobic ammonium oxidizing bacteria at around0.8mg/L. In the context of0.8mg/L to4mg/L, chlortetracycline played a promoted role for the existence of the anaerobic ammonium oxidizing bacteria. As oxytetracycline concentration increased, especially in the range from0to40mg/L, anaerobic ammonium oxidizing bacteria gene average copies number appeared reducing trend. But in the range of40to80mg/L, there was a growing trend. In the dual function of chlortetracycline and oxytetracycline, there was a complex relationship between the antibiotics concentration and the anaerobic ammonium oxidizing gene average copy number. With the increase of the antibiotics concentration, the ammonia oxidizing bacteria had an increasing trend generally.(5) In antibiotic-free conditions, the types of the anaerobic ammonium oxidizing bacteria in the activated sludge, were exactly similar with Nitrosomonas eutropha and Nitrosomonas SP. In the condition of chlortetracycline concentration for4mg/L, the anaerobic ammonium oxidizing bacteria in the sludge were exactly similar with Nitrosomonas eutropha,Nitrosomonas SP, Uncultured ammonia-oxidizing Bacterium and Nitrosomonas eutropha ammonia (amoA).In the condition of oxytetracycline concentration for80mg/L, the anaerobic ammonium oxidizing bacteria in the sludge were exactly similar with Nitrosomonas eutropha. In the condition of lower concentration of chlortetracycline and oxytetracycline, the anaerobic ammonium oxidizing bacteria were exactly similar with Nitrosomonas eutropha. In the condition of higher concentration both, the anaerobic ammonium oxidizing bacteria in the sludge were exactly similar with Nitrosomonas eutropha.