Effects of antibiotic resistance genes on the performance and stability of different microbial aggregates in a granular sequencing batch reactor

Wenci Zou, Bin Xue, Weijia Zhi, Tianyu Zhao, Dong Yang, Zhigang Qiu, Zhiqiang Shen, Junwen Li, Bin Zhang, Jingfeng Wang

Tianjin Institute of Health and Environmental Medicine, Tianjin Key Laboratory of Risk Assessment and Control for Environment and Food Safety, Tianjin 300050, PR China.

Abstract

Antibiotic resistance genes (ARGs) have emerged as key factors in wastewater environmental contaminants and continue to pose a challenge for wastewater treatment processes. With the aim of investigating the performance of granular sludge system when treating wastewater containing a considerable amount of ARGs, a lab-scale granular sequencing batch reactor (GSBR) where flocculent and granular sludge coexisted was designed. The results showed that after inoculation of donor strain NH₄+-N purification efficiency diminished from 94.7% to 32.8% and recovered to 95.2% after 10 days. Meanwhile, RP4 plasmid had varying effects on different forms of microbial aggregates. As the size of aggregates increased, the abundance of RP4 in sludge decreased. The residence time of RP4 in granules with particle size exceeding 0.9 mm (14 days) was far shorter than that in flocculent sludge (26 days). Therefore, our studies conclude that with increasing number of ARGs being detected in wastewater, the use of granular sludge system in wastewater treatment processes will allow the reduction of ARGs transmissions and lessen potential ecological threats.

Keywords: Antibiotic resistance genes; Treatment performance; Granular sequencing batch reactor; Microbial aggregates; Granule size.