| dc.description.abstract | Due to climate change and population explosion, shortage of clean and safe water resources is becoming an increasingly serious problem worldwide. Development of reuse of domestic wastewater could be one of the solutions. Ultimately, it is aimed to use recycled wastewater in agricultural irrigation and even in drinking water. To meet this goal, the water quality of recycled wastewater has to be demanded absolutely safe at every level, both chemically and biologically. Given that wastewater treatment plants (WWTPs) have been considered hot spots for the proliferation of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs), investigating the dynamics of ARB and ARG levels during the wastewater treatment process and their association with other generic water quality parameters will be one step closer to the goal of wastewater reuse. In this study, influents and effluents of each operating unit of three WWTPs were collected in the Fall and Spring. In addition to generic water quality parameters, the collected samples were analyzed for the abundance of ARB ARGs via cell incubation and qPCR methods. Results show that: (1) After MBR treatment, the absolute abundances of ARB (from 5.2log – 6.2log CFU/mL to 1.1log – 3.4log CFU/mL), ARGs (from 5.4log – 13.1log copy/L to 0.6log – 8.2log copy/L) and class 1 integron (from 11.5log – 12.9log copy/L to 3.8log – 3.9log copy/L) are substantively reduced; (2) The absolute abundance of ARB is significantly decreased after chlorination or UV disinfection (p < 0.05) (plant Acl: from 4.3log – 6.1log CFU/mL to as low as 1.2log – 3.7log CFU/ml; plant Cuv: from 3.0log – 4.6log CFU/mL and reduced to 1.3log – 3.2log CFU/mL), and the removal rates between the two plants are significantly different (p < 0.05); (3) Neither chlorination nor UV disinfection results in a significant decrease in the absolute abundance of ARG and intI (p > 0.05) (plant Acl: 5.5log – 11.2log copy/L reduced to 5.5log – 11.1log copy/L, plant Bmbr: 0.6log – 8.2log copy/L reduced to 1.6log – 5.6log copy/L, plant Cuv: 3.5log – 7.6log copy/L reduced to 3.4log – 8.5log copy/L); (4) higher removal efficiency of ARGs and class 1 integron relative abundance is observed in MBR treatment; (5) chlorination and UV disinfection do not significantly affect relative abundances of ARGs; (6) RDA show that relative abundances of ARGs and class 1 integron correlate well with COD, total phosphorus, total nitrogen, total Kjeldahl nitrogen concentration and pH, and little with nitrate nitrogen, nitrite nitrogen, dissolved oxygen concentration and temperature. Together, these results indicate that WWTPs implementing MRB can have better ARB and ARGs removal efficiency, and current disinfection units that use chlorination and UV may need to adjust operating parameters or to adopt more effective technologies (e.g., ozonation, Fenton oxidation) to reduce the risk of higher levels of ARGs appearing in the recovered water. In addition, the strong association between ARGs and certain anaerobic parameters suggests that future investigation on this regard is warranted. | en_US |