Total staphylococci as performance surrogate for greywater treatment

Area of Science:

• Environmental Microbiology
• Water Quality Monitoring
• Disinfection Technologies

Background:

• Faecal indicator bacteria (FIB) like E. coli are standard water quality metrics.
• Greywater contains skin microbes, and FIB may not accurately reflect pathogen load or treatment efficacy.
• Traditional FIB are unreliable surrogates for on-site greywater treatment due to fluctuating concentrations and potential for endogenous growth.

Purpose of the Study:

• To evaluate Staphylococcus spp. as potential surrogates for monitoring greywater treatment performance.
• To compare the UV inactivation efficacy of Staphylococcus spp. against traditional FIB and coliphage surrogates.
• To establish Staphylococcus spp. as a novel indicator for demonstrating log-reduction in greywater reuse systems.

Main Methods:

• Investigated UV inactivation efficacy of E. coli, Enterococcus spp., and Staphylococcus spp. using a collimated UV beam at varying wavelengths.
• Determined dose-response curves for UV inactivation of target microorganisms.
• Calculated relative inactivation credits based on doses required for 4- and 5-log10 reductions of Staphylococcus spp.

Main Results:

• Staphylococcus spp. (S. aureus, S. epidermidis) were less resistant to UV irradiation than E. coli, Enterococcus spp., and MS2 coliphage.
• Doses for 4- and 5-log10 reduction of Staphylococcus spp. yielded significantly lower reductions for other tested surrogates.
• Staphylococcus spp. occur at 3-5 log10 higher concentrations in greywater than FIB, offering a more robust indicator.

Conclusions:

• Staphylococcus spp. show promise as reliable endogenous surrogates for on-site greywater treatment.
• Their higher concentration and consistent presence make them suitable for demonstrating >5-log10 reductions.
• This research suggests a shift from FIB to skin-associated bacteria for effective greywater treatment monitoring.