Dissemination prevention of antibiotic resistant and facultative pathogenic bacteria by ultrafiltration and ozone treatment at an urban wastewater treatment plant

Johannes Alexander,Arne Wieland,Thomas Schwartz,Christian Hiller,Norman Hembach

doi:10.1038/s41598-019-49263-1

Johannes Alexander, Arne Wieland + Show 3 more

Open Access

https://doi.org/10.1038/s41598-019-49263-1

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Abstract

Conventional wastewater treatment is not sufficient for the removal of hygienically relevant bacteria and achieves only limited reductions. This study focuses on the reduction efficiencies of two semi-industrial ultrafiltration units operating at a large scale municipal wastewater treatment plant. In total, 7 clinically relevant antibiotic resistance genes, together with 3 taxonomic gene markers targeting specific facultative pathogenic bacteria were analysed via qPCR analyses before and after advanced treatment. In parallel with membrane technologies, an ozone treatment (1 g ozone/g DOC) was performed for comparison of the different reduction efficiencies. Both ultrafiltration units showed increased reduction efficiencies for facultative pathogenic bacteria and antibiotic resistance genes of up to 6 log units, resulting mostly in a strong reduction of the bacterial targets. In comparison, the ozone treatment showed some reduction efficiency, but was less effective compared with ultrafiltration due to low ozone dosages frequently used for micro-pollutant removal at municipal wastewater treatment plants. Additionally, metagenome analyses demonstrated the accumulation of facultative pathogenic bacteria, antibiotic resistance genes, virulence factor genes, and metabolic gene targets in the back flush retentate of the membranes, which opens further questions about retentate fluid material handling at urban wastewater treatment plants.

Highlights

Antibiotic resistance genes (ARGs) and facultative pathogenic bacteria from different origins that pass through treatment plants or agricultural runoffs can lead to a contamination of environmental water resources
This study aimed to develop a deeper understanding of the ultrafiltration reduction efficiencies of facultative pathogenic bacteria and ARGs in comparison to ozonation at an urban wastewater treatment plant (WWTP)
The total abundances of the three facultative pathogenic bacteria (E. coli, A. baumannii, enterococci) reached together a calculated number of 2.66 × 1013 cell equivalents per day that are released to the riverside, when 90,000 m3 of conditioned wastewater per day was released from the WWTP into the receiving river

Summary

Introduction

Antibiotic resistance genes (ARGs) and facultative pathogenic bacteria from different origins (hospitals, nursing homes, housing areas, slaughter houses etc.) that pass through treatment plants or agricultural runoffs can lead to a contamination of environmental water resources. In certain circumstances this could cause an impairment of human health in case of direct contact and colonisation[1,2,3,4]. Their distribution via horizontal gene transfer can occur regardless of their initial origin species, and once released to the environment they are able to transfer to autochthonous bacteria as well as other facultative pathogenic bacteria[6] This critical ability might lead to an www.nature.com/scientificreports/. Another drawback of ozonation is the unpredictable formation of unwanted by-products[5,17,18]

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