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Real-time detection of faecally contaminated drinking water with tryptophan-like fluorescence: defining threshold values

Sorensen, James and Pedley, Stephen (2017) Real-time detection of faecally contaminated drinking water with tryptophan-like fluorescence: defining threshold values Science of the Total Environment, 622.

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Abstract

We assess the use of fluorescent dissolved organic matter at excitation-emission wavelengths of 280 nm and 360 nm, termed tryptophan-like fluorescence (TLF), as an indicator of faecally contaminated drinking water. A significant logistic regression model was developed using TLF as a predictor of thermotolerant coliforms (TTCs) using data from groundwater- and surface water-derived drinking water sources in India, Malawi, South Africa and Zambia. A TLF threshold of 1.3 ppb dissolved tryptophan was selected to classify TTC contamination. Validation of the TLF threshold indicated a false-negative error rate of 15% and a false-positive error rate of 18%. The threshold was unsuccessful at classifying contaminated sources containing < 10 TTC cfu per 100 mL, which we consider the current limit of detection. If only sources above this limit were classified, the false-negative error rate was very low at 4%. TLF intensity was very strongly correlated with TTC concentration (ρs = 0.80). A higher threshold of 6.9 ppb dissolved tryptophan is proposed to indicate heavily contaminated sources (≥ 100 TTC cfu per 100 mL). Current commercially available fluorimeters are easy-to-use, suitable for use online and in remote environments, require neither reagents nor consumables, and crucially provide an instantaneous reading. TLF measurements are not appreciably impaired by common intereferents, such as pH, turbidity and temperature, within typical natural ranges. The technology is a viable option for the real-time screening of faecally contaminated drinking water globally.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Civil and Environmental Engineering
Authors :
NameEmailORCID
Sorensen, James
Pedley, StephenS.Pedley@surrey.ac.uk
Date : 13 December 2017
Funders : Engineering and Physical Sciences Research Council (EPSRC)
Identification Number : 10.1016/j.scitotenv.2017.11.162
Copyright Disclaimer : © 2017 Natural Environment Research Council (NERC), as represented by the British Geological Survey (BGS). Published by Elsevier B.V. All rights reserved.
Uncontrolled Keywords : Tryptophan-like fluorescence; Fluorescence spectroscopy; Faecal contamination; Drinking water; Thermotolerant (faecal) coliforms
Depositing User : Clive Harris
Date Deposited : 20 Nov 2017 13:14
Last Modified : 14 Mar 2018 13:10
URI: http://epubs.surrey.ac.uk/id/eprint/844952

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