Abstract
Wastewater treatment plants (WWTPs) have been identified as potential sources of antibiotic resistance genes (ARGs) but the effects of tertiary wastewater treatment processes on ARGs have not been well characterized. Therefore, the objective of this study was to determine the fate of ARGs throughout a tertiary-stage WWTP. Two ARGs, sul1 and bla, were quantified via quantitative polymerase chain reaction (qPCR) in solids and dissolved fractions of raw sewage, activated sludge, secondary effluent and tertiary effluent from a full-scale WWTP. Tertiary media filtration and chlorine disinfection were studied further with the use of a pilot-scale media filter. Results showed that both genes were reduced at each successive stage of treatment in the dissolved fraction. The solids-associated ARGs increased during activated sludge stage and were reduced in each subsequent stage. Overall reductions were approximately four log10 with the tertiary media filtration and disinfection providing the largest decrease. The majority of ARGs were solids-associated except for in the tertiary effluent. There was no evidence for positive selection of ARGs during treatment. The removal of ARGs by chlorine was improved by filtration compared to unfiltered, chlorinated secondary effluent. This study demonstrates that tertiary-stage WWTPs with disinfection can provide superior removal of ARGs compared to secondary treatment alone.
Highlights
Antibiotic resistant bacteria (ARB) are having profound effects on the treatment of human diseases.In the United States, the number of ARB-related hospitalizations continues to increase [1] with an estimated cost of up to $30 billion annually [2]
All three gene targets were readily detected in the raw sewage ; concentrations of blaSHV/TEM in the secondary effluent, and sul1 and blaSHV/TEM in the final effluent were found to be below the detection limit of the method in all unconcentrated samples analyzed (n = 6)
The results showed an average recovery after concentration of 57% which demonstrated that the method could be used as an effective means to concentrate antibiotic resistance genes (ARGs) in these waters
Summary
In the United States, the number of ARB-related hospitalizations continues to increase [1] with an estimated cost of up to $30 billion annually [2]. Antibiotic resistant genes in the environment have the potential to spread into the human population presenting a possible public health problem. The full impact of environmental transfer of antibiotic resistance genes (ARGs) on public health is not currently known, several reports have highlighted the presence of ARB and ARGs in wastewater treatment plants [3,4,5,6,7,8], agricultural feedlots [9,10,11]. As the number and cost of ARB-related illnesses continues to grow, multifaceted efforts are needed to control ARB in the clinic along with further investigation into potential impacts arising from environmental sources
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