In-situ fluorescence spectroscopy is a more rapid and resilient indicator of faecal contamination risk in drinking water than faecal indicator organisms

James P R Sorensen; Jacintha Nayebare; Andrew F Carr; Robert Lyness; Luiza C Campos; Lena Ciric; Timothy Goodall; Robinah Kulabako; Catherine M Rushworth Curran; Alan M MacDonald; Michael Owor; Daniel S Read; Richard G Taylor

doi:10.1016/j.watres.2021.117734

In-situ fluorescence spectroscopy is a more rapid and resilient indicator of faecal contamination risk in drinking water than faecal indicator organisms

Water Res. 2021 Nov 1:206:117734. doi: 10.1016/j.watres.2021.117734. Epub 2021 Oct 3.

Authors

Affiliations

¹ British Geological Survey, Maclean Building, Wallingford, OX10 8BB, United Kingdom of Great Britain and Northern Ireland UK; Department of Geography, University College London, London WC1E 6BT, United Kingdom of Great Britain and Northern Ireland UK. Electronic address: jare1@bgs.ac.uk.
² Department of Geology and Petroleum Studies, Makerere University, Uganda.
³ Department of Geography, University College London, London WC1E 6BT, United Kingdom of Great Britain and Northern Ireland UK.
⁴ Department of Civil, Environmental & Geomatic Engineering, University College London, London WC1E 6BT, United Kingdom of Great Britain and Northern Ireland UK.
⁵ UK Centre for Ecology & Hydrology (UKCEH), Maclean Building, Wallingford, OX10 8BB, United Kingdom of Great Britain and Northern Ireland UK.
⁶ Department of Civil and Environmental Engineering, Makerere University, Uganda.
⁷ Catherine M Rushworth Curran Ltd., 27 Silverhall Street, Isleworth, TW7 6RF, United Kingdom of Great Britain and Northern Ireland UK.
⁸ British Geological Survey, Lyell Centre, Research Avenue South, Edinburgh EH14 4AP, United Kingdom of Great Britain and Northern Ireland UK.

PMID: 34655933
DOI: 10.1016/j.watres.2021.117734

Abstract

Faecal indicator organisms (FIOs) are limited in their ability to protect public health from the microbial contamination of drinking water because of their transience and time required to deliver a result. We evaluated alternative rapid, and potentially more resilient, approaches against a benchmark FIO of thermotolerant coliforms (TTCs) to characterise faecal contamination over 14 months at 40 groundwater sources in a Ugandan town. Rapid approaches included: in-situ tryptophan-like fluorescence (TLF), humic-like fluorescence (HLF), turbidity; sanitary inspections; and total bacterial cells by flow cytometry. TTCs varied widely in six sampling visits: a third of sources tested both positive and negative, 50% of sources had a range of at least 720 cfu/100 mL, and a two-day heavy rainfall event increased median TTCs five-fold. Using source medians, TLF was the best predictor in logistic regression models of TTCs ≥10 cfu/100 mL (AUC 0.88) and best correlated to TTC enumeration (ρ_s 0.81), with HLF performing similarly. Relationships between TLF or HLF and TTCs were stronger in the wet season than the dry season, when TLF and HLF were instead more associated with total bacterial cells. Source rank-order between sampling rounds was considerably more consistent, according to cross-correlations, using TLF or HLF (min ρ_s 0.81) than TTCs (min ρ_s 0.34). Furthermore, dry season TLF and HLF cross-correlated more strongly (ρ_s 0.68) than dry season TTCs (ρ_s 0.50) with wet season TTCs, when TTCs were elevated. In-situ TLF or HLF are more rapid and resilient indicators of faecal contamination risk than TTCs.

Keywords: Coliforms; Groundwater; Humic-like fluorescence; Indicator; Microbial contamination; Tryptophan-like fluorescence.

MeSH terms

Drinking Water*
Environmental Monitoring
Feces
Groundwater*
Spectrometry, Fluorescence
Water Microbiology

Substances

Drinking Water