Application of iron waste catalyzed ozonation for inactivation and destruction of antibiotic resistance bacteria (ARBs) and genes (ARGs) present in municipal wastewater

Abstract

Abstract Introduction: Conventional disinfection methods are not able to completely destroy ARB and ARGs. Ozone-based advanced oxidation processes are widely used as an important option for removing microorganisms in water and wastewater due to its high oxidation Potential. The aim of this study is to investigate the effecincy of iron shaving catalyzed ozonation in removal these factors from municipal wastewater. Materials and method: In this study, at first, the resistance of bacteria isolated from wastewater samples at the inlet, outlet of the biological treatment system and after the disinfection unit was investigated against different antibiotics and concentrations. Sampling of wastewater was done in spring and summer. After microbial cultures to accurately identify the bacteria and also the presence of beta-lactamase, Sul1 and qnrS genes in these bacteria, PCR method was used. Then the effect of ozone and catalyzed ozonation with iron shaving on the removal of resistant bacteria Escherichia coli, Pseudomonas aeruginosa and Acinetobacter baumannii and the corresponding resistant genes in initial concentrations of 104, 106 and 108 and different doses of ozone from 0.12 to 0.48 gO3/gCOD and contact times from 1 to 15 minutes were investigated. Three methods including culture, PMA-qPCR and qPCR were used to determine the efficiency of removing bacteria and antibiotic resistant genes. In this study, analysis of variance and modified Bonferroni test were used for data analysis. Results: The results of the investigation of antibiotic resistance showed that the resistance of bacteria to at least 4 antibiotics was 100% and the highest resistance was related to the sulfamethoxazole. blaTEM and sul1 genes were the most abundant in the isolated bacteria with 92 and 83%, respectively. The results showed that the removal efficiency of bacteria and genes increased with the increase of input ozone dose and CT. The results showed the rate of removal increased with the decrease of the initial concentration of bacteria. In general, the amount of removal of Acinetobacter baumannii, Escherichia coli and Pseudomonas aeruginosa in the cultivation method at the ozone dose 0.48 gO3/gCOD and CT 7.2 (gO3/gCOD.min) were 7, 6.4 and 4.4, log respectively. The results of study showed that the rate of reduction of Pseudomonas aeruginosa was lower than that of Escherichia coli and Acinetobacter baumannii. Statistical analysis showed that the rate of inactivation of Escherichia coli, Pseudomonas-aeruginosa by culture method was higher than the rate measured by PMA-qPCR. In iron shaving catalyst the average removal of ARB and ARGs were 3.5 ± 1.9 and 2.2 ± 0.86 log, respectively. The amount of removal of ARB and ARGs in ozonation catalyzed was higher than ozonation, however, this difference was not statistically significant for ARB (p>0.05), but this difference was significant in ARGs (p<0.05). Also, the removal efficiency of ARB compared to ARGs in both processes was about 59% higher on average. Conclusion: In addition to the fact that wastewater treatment plants do not have sufficient efficiency in removing resistant bacteria and genes, the abundance of ARGs in treated wastewater also increases. Also, genes showed more resistance to ozonation and catalytic ozonation than bacteria. However, catalytic ozonation had a better performance in reducing genes. Therefore, the use of strong disinfection processes such as ozonation or catalyzed ozonation can play a significant role in reducing the spread of resistant genes and bacteria to the environment. Keywords: Urban wastewater, Antibiotic-resistant bacteria, Antibiotic-resistant genes, ozonation, iron shaving catalyzed ozonation