UV Disinfection of Hand-Rinse Greywater and Performance Testing Using Indigenous Staphylococcus spp.

Abstract

Greywater reuse is a feasible solution for decreasing raw water extraction in urban and rural settings. However, pathogen-specific performance guidelines and regulations have only recently been recommended; practical means to assess performance are missing. Here we examine the efficacy of Staphylococcus spp. as an endogenous surrogate for greywater pathogen reduction performance testing, by evaluating UV-C irradiation of hand-rinse greywater, and the variability in UV resistance between different wild Staphylococcus species. Hand-rinse greywater samples were collected from five participants, and a collimated UV-C beam (256 nm) was used to assess log 10 reductions. Assays of colony-forming units on tryptic soy agar (TSA) were compared to mannitol salt agar (MSA) using Lysostaphin TM to confirm Staphylococcus spp. After irradiating raw hand-rinse samples to a dose of 220 mJ·cm −2 , log 10 reductions of Staphylococcus spp. were similar (2.1 and 2.2, respectively, p = 0.112). The similarity of the reduction based on TSA and Staphylococcus-specific culture assays following UV irradiation and the dominating presence of Staphylococcus spp. suggests that Staphylococcus spp. could be used as an endogenous performance surrogate group for greywater treatment testing. Suspended wild Staphylococcus isolates were irradiated with 256 nm UV-C to compare the variability of different Staphylococcus species. Staphylococcus isolates exhibited significant variance in log 10 reduction values when exposed to 11 mJ·cm −2 of UV-C. Staphylococcus hominis subsp. hominis exhibited surprising resistance to UV-C, with only a 1.6-log 10 reduction when exposed to 11 mJ·cm −2 of UV-C (most other isolates exhibited > 5-log 10 reduction). The efficacy of UV-C was also significantly reduced when the sunscreen oxybenzone was present at a possible endogenous greywater concentration.

Sustainable wastewater management

“…Studies conducted by (Eriksson et al, 2002;Ottoson & Stenstrom, 2003) revealed a large collection of excreta-related pathogens associated with greywater. Other studies have further identified a number of pathogens in greywater and these are Pseudomonas (Benami, Gillor, & Gross, 2015a;Khalaphallah & Andres, 2012), Legionella (Birks, Colbourne, Hills, & Hobson, 2004), Giardia (Birks et al, 2004;Birks & Hills, 2007), Cryptosporidium (Birks et al, 2004), and Staphylococcus Aureus (Benami et al, 2015a;Kim et al, 2009;Maimon et al, 2014;Shoults & Ashbolt, 2017) in greywater. Table 2.3 presents some selected biological parameters with their concentrations as reported in other studies.…”

“…Table 2.3 presents some selected biological parameters with their concentrations as reported in other studies. (Atanasova et al, 2017;Friedler, Kovalio, & Ben-Zvi, 2006;Khalaphallah & Andres, 2012;Kim et al, 2009;Paulo, Begosso, Pansonato, Shrestha, & Boncz, 2009) Fecal coliforms Up to 1x10 6 (Halalsheh et al, 2008;Mandal et al, 2011;Masi et al, 2010) Pseudomonas aeruginosa 1.4x10 4 (Benami et al, 2015a;Khalaphallah & Andres, 2012) Staphylococcus aureus 1.2x10 2 -1.8x10 3 (Benami, Gillor, & Gross, 2015b;Kim et al, 2009;Maimon et al, 2014;Shoults & Ashbolt, 2017) Salmonella typhi 5.4x10 3 (Kim et al, 2009) Salmonella spp 3.1x10 3 (M. T Tr re ea at tm me en nt t s sy ys st te em ms s…”