Greywater reuse: an analysis of microbial performance surrogates applied to ultraviolet irradiation

• Author / Creator

  Shoults, David, C.

• The potential constraints and testing needs surrounding safe greywater reuse are poorly understood. Given the wide variety of contaminants present in different greywater from home to home and even between sources within the same home, there are unique treatment needs and considerations for each. The aim of the work performed in this thesis was to assess these needs and provide an improved way to test greywater treatment performance over current use of coliforms. A literature review was performed, indicating significant variances in faecal indicator bacteria (FIB) across sources, and even within the same sources. While FIB (e.g. faecal coliforms/E. coli & enterococci) are useful to verify municipal water treatment, the same cannot be said for greywater. Thus, an alternative target is needed to not only indicate the presence of non-enteric pathogenic organisms present in greywater, but also to be indigenous to greywater at a high enough level to assess at least a four-log10 bacterial treatment reduction. Given the high prevalence of total staphylococci on human skin, total staphylococci were selected as a potential surrogate to represent bacterial reduction when exposed to the most commonly used greywater disinfection process, ultraviolet (UV) irradiation. Staphylococcus spp. and select FIB were subjected to UV irradiation; while the potentially pathogenic Staphylococcus aureus was found to be less resistant to UV than FIB, other Staphylococcus spp., such as S. haemolyticus and S. hominis were significantly more resistant than S. aureus and a range of FIB. UV was used to treat raw hand-rinse water from five participants to assess the efficacy of total staphylococci as an endogenous surrogate to assess bacterial reduction; total staphylococci made up the majority of the culturable bacteria before and after irradiation which suggests it would act as an adequate surrogate. While UV is an attractive and relatively low maintenance disinfection method, there are efficacy and safety considerations. Of particular concern, through cyclic growth and exposure, S. aureus can theoretically become enriched in a circulating greywater reuse system, with strains becoming more resistant to UV irradiation. Additionally, given the prevalence of personal care products (PCP) in wastewater, especially in greywater, the efficacy of UV towards S. aureus in the presence the sunscreen oxybenzone, was assessed. When present in water at a concentration of 10 mg.mL-1, oxybenzone was shown to decrease the efficacy of UV-C by nearly one order of magnitude.

• Subjects / Keywords

  • Greywater
  • staphylococci
  • Staphylococcus
  • performance testing
  • greywater testing
  • greywater standards
  • S. aureus

• Graduation date

  Spring 2018

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3X63BM4K

• License

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