Bacteriophages as indicators of faecal pollution and enteric virus removal

Abstract

Bacteriophages are an attractive alternative to faecal indicator bacteria (FIB), particularly as surrogates of enteric virus fate and transport, due to their closer morphological and biological properties. Based on a review of published data, we summarize densities of coliphages (F+ and somatic), Bacteroides spp. and enterococci bacteriophages (phages) in individual human waste, raw wastewater, ambient fresh and marine waters and removal through wastewater treatment processes utilizing traditional treatments. We also provide comparisons with FIB and enteric viruses whenever possible. Lastly, we examine fate and transport characteristics in the aquatic environment and provide an overview of the environmental factors affecting their survival. In summary, concentrations of bacteriophages in various sources were consistently lower than FIB, but more reflective of infectious enteric virus levels. Overall, our investigation indicates that bacteriophages may be adequate viral surrogates, especially in built systems, such as wastewater treatment plants.

Significance and impact of the study: Bacteriophage are alternative fecal indicators that may be better surrogates for viral pathogens than fecal indicator bacteria (FIB). This report offers a summary of the existing literature concerning the utility of bacteriophage as indicators of viral presence (fecal sources and surface waters) and persistence (in built infrastructure and aquatic environments). Our findings indicate that bacteriophage levels in all matrices examined are consistently lower than FIB, but similar to viral pathogens. Furthermore, in built infrastructure (e.g. wastewater treatment systems) bacteriophage closely mimic viral pathogen persistence suggesting they may be adequate sentinels of enteric virus removal.

Keywords: ambient water; bacteriophage; faecal indicators; viruses; waste; wastewater treatment.

Figure 1

Mean concentrations and 95% confidence intervals of FIB and bacteriophages (expressed as CFU, PFU or MPN), as well as viral pathogens (expressed as MPN for infectious viruses or genomic copies for all others) in untreated wastewater. The size of the symbol is proportionate to the number of studies* (given in parentheses) used to derive the data. *References: (Tartera et al. 1989; Calci et al. 1998; Chauret et al. 1999; Puig et al. 1999; Baggi et al. 2001; Quinonez-Diaz et al. 2001; Rose et al. 2001; Uemura et al. 2002; Alcaide et al. 2003; Lucena et al. 2003; Queralt et al. 2003; Veschetti et al. 2003; Lucena et al. 2004; Payan et al. 2005; Blanch et al. 2006; Haramoto et al. 2006; Ebdon et al. 2007; Zhang and Farahbakhsh 2007; Reinoso et al. 2008; Petrinca et al. 2009; Boczek et al. 2010; Bonilla et al. 2010; Fu et al. 2010; Santiago-Rodriguez et al. 2010; Vijayavel et al. 2010; Wu et al. 2010; Ebdon et al. 2012; Flannery et al. 2012; Francy et al. 2012; Muniesa et al. 2012a; Harwood et al. 2013; Pradhan et al. 2013; Santiago-Rodriguez et al. 2013; McMinn et al. 2014; Haramoto et al. 2015; Montazeri et al. 2015).

Figure 2

Reported and/or calculated log₁₀ reduction of FIB, bacteriophages and viral pathogens through wastewater treatment processes. Reduction data per organism type are pooled irrespective of the particular unit of operation (e.g. primary treatment, secondary treatment, disinfection). Box is delimited by 25^th and 75^th percentiles, solid line within the box represents median and dashed line represents average. Whiskers are 10^th and 90^th percentile values. Values outside of the range are depicted as filled dots. Number in parenthesis indicate number of studies* used to derive the data. *References: (Bonadonna et al. 1993; Chauret et al. 1999; Baggi et al. 2001; Bourrouet et al. 2001; Rose et al. 2001; Tanji et al. 2002; Lucena et al. 2004; Harwood et al. 2005; Haramoto et al. 2006; Mandilara et al. 2006; Ottoson et al. 2006; Zhang and Farahbakhsh 2007; Carducci et al. 2008; Costan-Longares et al. 2008; Gomila et al. 2008; Petrinca et al. 2009; Aw and Gin 2010; Boczek et al. 2010; Fu et al. 2010; Ebdon et al. 2012; Flannery et al. 2012; Francy et al. 2012; Muniesa et al. 2012a; Hata et al. 2013; Pradhan et al. 2013; Kitajima et al. 2014; Ulbricht et al. 2014; Dias et al. 2015; Haramoto et al. 2015; Montazeri et al. 2015; Yahya et al. 2015; Mayer et al. 2016).

Figure 3

Mean concentrations and 95% confidence intervals of FIB and bacteriophages (expressed as CFU, FU or MPN), as well as viral pathogens (expressed as MPN for infectious viruses or genomic copies for all others) in freshwater (empty symbols) and marine waters (filled symbols). The size of the symbol is proportionate to the number of studies* (given in parentheses) used to derive the data. *References: (Tartera et al. 1989; Cornax 1991; Lucena 1996; Araujo et al. 1997; Muniesa et al. 1999; Contreras-Coll et al. 2002; Duran et al. 2002; Skraber et al. 2002; Hot et al. 2003; Lucena et al. 2003; Moce-Llivina et al. 2003; Choi and Jiang 2005; Lodder and de Roda Husman 2005; Montemayor et al. 2005; Ebdon et al. 2007; Ibarluzea et al. 2007; Boehm et al. 2009b; Lodder et al. 2010; Vijayavel et al. 2010; Gomez-Donate et al. 2011; Lee et al. 2011; Nnane et al. 2011; Viau et al. 2011; Santiago- Rodriguez et al. 2012; Wyer et al. 2012; Love et al. 2014; Rezaeinejad et al. 2014; Vijayavel 2014; Vergara et al. 2015; Santiago-Rodriguez 2016).