Peracetic Acid (PAA) Disinfection: Inactivation of Microbial Indicators and Pathogenic Bacteria in a Municipal Wastewater Plant

Silvia Bonetta,Elisabetta Carraro,Giorgio Gilli,Lorenza Meucci,Eugenio Lorenzi,Margherita De Ceglia,Cristina Pignata,Sara Bonetta

doi:10.3390/w9060427

Silvia Bonetta, Elisabetta Carraro + Show 6 more

Open Access

https://doi.org/10.3390/w9060427

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Journal: Water	Publication Date: Jun 13, 2017
Citations: 15	License type: CC BY 4.0

Affiliation: University of Turin, Metropolitana Milanese (Italy)

Abstract

Several studies have noted that treated and untreated wastewaters are primary contributors of a variety of pathogenic microorganisms to the aquatic ecosystem. Conventional wastewater treatment may not be sufficient to achieve microbiologically safe effluent to be discharged into natural waters or reused, thus requiring wastewater effluents to be disinfected. In recent years, peracetic acid (PAA) has been adopted as a disinfectant for wastewater effluents. The aim of this study was to evaluate the disinfection efficiency of PAA at low doses (range 0.99–2.10 mg/L) against microbial indicators and pathogenic bacteria in a municipal wastewater plant. Samples of untreated sewage and effluents before and after PAA treatment were collected seasonally for 1 year and were analysed for pathogenic Campylobacter, Salmonella spp., E. coli O157:H7 and E. coli virulence genes using molecular methods; moreover, the detection of specific microbial indicators (E. coli, faecal coliforms, enterococci, C. perfringens) and Salmonella spp. were carried out using culturing methods. Salmonella spp. DNA was found in all untreated sewage and effluent before PAA treatment, whereas it was recovered in 50% of the samples collected after PAA treatment. Although E. coli O157:H7 was never identified, the occurrence of Shiga-like toxin I amplicons was identified in 75% of the untreated sewage samples, in 50% of the effluents assayed before PAA treatment, and in 25% of the effluents assayed after PAA treatment, whereas the stx2 gene was never found. Campylobacter coli was only detected in one effluent sample before PAA treatment. In the effluents after PAA treatment, a lower load of indicator bacteria was observed compared to the effluents before treatment. The results of this study highlight that the use of low doses of PAA seems to lead to an improvement of the microbiological quality of the effluent, although it is not sufficient to guarantee its suitability for irrigation. These results underscore the need for additional studies to further assess the efficiency of PAA disinfection in municipal wastewater plants.

Highlights

Several studies have noted that treated and untreated wastewaters are primary contributors of a variety of pathogenic microorganisms, pollutants, and chemicals to the aquatic ecosystem [1,2].Numerous studies have indicated that primary and secondary wastewater treatment typically achieves90–99% reductions of enteric microbial numbers
The C. jejuni strain was cultivated on blood-free Campylobacter medium base (Karmali; Biolife, Milan, Italy) or Bolton broth (Oxoid, Cambridge, UK) at 42 ◦ C under a microaerobic atmosphere (Campygen; Oxoid, Cambridge, UK), and E. coli O157:H7 and S. typhimurium were grown on tryptic soy agar (TSA; Applichem, Darmstadt, Germany) or in tryptic soy broth (TSB; Applichem, Darmstadt, Germany) at 37 ◦ C
Untreated sewage and effluents before and after peracetic acid (PAA) treatment were collected from an Italian wastewater treatment plant located in the Piedmont region

Summary

Introduction

Several studies have noted that treated and untreated wastewaters are primary contributors of a variety of pathogenic microorganisms, pollutants, and chemicals to the aquatic ecosystem [1,2].Numerous studies have indicated that primary and secondary wastewater treatment typically achieves90–99% reductions of enteric microbial numbers. Several studies have noted that treated and untreated wastewaters are primary contributors of a variety of pathogenic microorganisms, pollutants, and chemicals to the aquatic ecosystem [1,2]. Numerous studies have indicated that primary and secondary wastewater treatment typically achieves. This treatment may not be sufficient to. Water 2017, 9, 427 produce microbiologically safe effluent that can be discharged into natural waters [3,4]. The microbiological quality of wastewater can pose a number of potential risks in terms of public health and environmental contamination when considering the possible reuse of wastewater effluents [7]. To achieve more efficient microbial elimination, a further treatment such as disinfection is necessary

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