Fluorescence-informed water quality prediction in water distribution systems

Abstract

Conventional drinking water monitoring relies on laboratory-based chemical and microbiological analyses that are often time intensive. This study evaluates a rapid optical alternative by integrating excitation–emission matrix (EEM) fluorescence spectroscopy, parallel factor analysis (PARAFAC), and machine learning to predict intact cell count (ICC) within a chlorinated drinking water distribution system. A full scale network in the Okanagan Valley, Canada was monitored, and fluorescence-derived dissolved organic matter (DOM) components were used as predictors in tree-based classification models. Fluorescence alone showed moderate skill in predicting ICC, but incorporating contextual factors (chlorine residual and turbidity) markedly improved performance. The ICC models could categorically distinguish microbial levels within the distribution system, though absolute accuracy declined at sites not seen during training, indicating a need for site-specific calibration. Notably, this work is the first to assess fluorescence-based metrics for determining ICC in drinking water distribution systems. The findings demonstrate that a unified fluorescence-PARAFAC approach can provide timely alternative measures for water quality, as it shows promise for microbial risk indication when augmented with operational data. Overall, the work highlights the potential of fluorescence-informed machine learning to bridge conventional chemical and microbiological monitoring, offering a pathway toward more responsive water quality management.

Keywords

Fluorescence EEMs / PARAFAC / Intact cell count / Drinking water distribution systems / Machine learning classification / Chlorine residual

References

[1] Cai W, Ye C, Ao F, Xu Z, Chu W. Emerging applications of fluorescence excitation-emission matrix with machine learning for water quality monitoring: a systematic review. Water Res, 2025, 277 123281

[2] Coble PG. Characterization of marine and terrestrial DOM in seawater using excitation-emission matrix spectroscopy. Mar Chem, 1996, 51(4): 325-346

[3] Sciscenko I, Arques A, Micó P, Mora M, García-Ballesteros S. Emerging applications of EEM-PARAFAC for water treatment: a concise review. Chem Eng J Adv, 2022, 10 100286

[4] Ramírez-Castillo FY, Loera-Muro A, Jacques M, Garneau P, Avelar-González FJ, Harel J, Guerrero-Barrera AL. Waterborne pathogens: detection methods and challenges. Pathogens, 2015

[5] Safford HR, Bischel HN. Flow cytometry applications in water treatment, distribution, and reuse: a review. Water Res, 2019, 151: 110-133

[6] Van Nevel S, Koetzsch S, Proctor CR, Besmer MD, Prest EI, Vrouwenvelder JS, Knezev A, Boon N, Hammes F. Flow cytometric bacterial cell counts challenge conventional heterotrophic plate counts…. Water Res, 2017, 113: 191-206

[7] Gillespie S, Lipphaus P, Green J, Parsons S, Weir P, Juskowiak K, Jefferson B, Jarvis P, Nocker A. Assessing microbiological water quality… using flow cytometry. Water Res, 2014, 65: 224-234

[8] Helmi K, Watt A, Jacob P, Ben-Hadj-Salah I, Henry A, Méheut G, Charni-Ben-Tabassi N. Monitoring of three drinking water treatment plants using flow cytometry. Water Supply, 2014, 14(5): 850-856

[9] Nowicki S, Lapworth DJ, Ward JST, Thomson P, Charles K. Tryptophan-like fluorescence as a measure of microbial contamination risk in groundwater. Sci Total Environ, 2019, 646: 782-791

[10] Sorensen JPR, Vivanco A, Ascott MJ, Gooddy DC, Lapworth DJ, Read DS, Rushworth CM, Bucknall J, Herbert K, Karapanos I, Gumm LP, Taylor RG. Online fluorescence spectroscopy for the real-time evaluation of the microbial quality of drinking water. Water Res, 2018, 137: 301-309

[11] Baker A. Fluorescence EEM characterization of some sewage-impacted rivers. Environ Sci Technol, 2001, 35(5): 948-953

[12] Bridgeman J, Bieroza M, Baker A. Application of fluorescence spectroscopy… in drinking water treatment. Rev Environ Sci Bio Technol, 2011, 10(3): 277-290

[13] Stedmon CA, Bro R. Characterizing DOM fluorescence with PARAFAC: a tutorial. Limnol Oceanogr Methods, 2008, 6(11): 572-579

[14] Schuster J, Huber J, Stumme J, Grieb A, Ernst M (2022) Combining real-time fluorescence spectroscopy and flow cytometry. Front Environ Chem 3. https://doi.org/10.3389/fenvc.2022.931067

[15] Lacalamita D, Mongioví C, Crini G (2024) COD and BOD analysis of laundry discharge waters. Front Environ Sci 12. https://doi.org/10.3389/fenvs.2024.1387041

[16] Kumar Panigrahi S, Kumar Mishra A. Inner filter effect in fluorescence spectroscopy…. Journal of Photochemistry and Photobiology C, 2019, 41 100318

[17] Goletz C, Wagner M, Grübel A, Schmidt W, Korf N, Werner P. Standardization of fluorescence EEMs…. Talanta, 2011, 85(1): 650-656

[18] Kothawala DN, Murphy KR, Stedmon CA, Weyhenmeyer GA, Tranvik LJ (2013) Inner filter correction of DOM fluorescence. Limnol Oceanography: Methods 11:616–630. https://doi.org/10.4319/Iom.2013.11.616

[19] Murphy KR. Note on determining extent of the water Raman peak…. Appl Spectrosc, 2011, 65(2): 233-236

[20] Hambly AC, Wünsch UJ (2024). Fluorescence EEM spectroscopy. In Experimental Methods for Membrane Applications. IWA Publishing. https://doi.org/10.2166/9781789062977_0265

[21] Bahram M, Bro R, Stedmon C, Afkhami A. Handling of rayleigh and raman scatter… using interpolation. J Chemometr, 2006, 20(3–4): 99-105

[22] Murphy KR, Stedmon CA, Graeber D, Bro R. Fluorescence spectroscopy and multi-way techniques. PARAFAC. Anal Methods, 2013, 5(23): 6557-6566

[23] Coble PG, Spencer RGM, Baker A, Reynolds DM (2014) Aquatic organic matter fluorescence. In Aquatic Organic Matter Fluorescence, pp 75–122. Cambridge University Press. https://doi.org/10.1017/CBO9781139045452.006

[24] Bro R. PARAFAC. Tutorial and applications. Chemometr Intell Lab Syst, 1997, 38(2): 149-171

[25] Stedmon CA, Markager S, Bro R. Tracing DOM… using a new approach to fluorescence spectroscopy. Mar Chem, 2003, 82(3): 239-254

[26] Cuss CW, Guéguen C, Andersson P, Porcelli D, Maximov T, Kutscher L. Residuals analysis for determining number of PARAFAC components…. Appl Spectrosc, 2016, 70(2): 334-346

[27] Yu H, Liang H, Qu F, Han Z, Shao S, Chang H, Li G. Impact of dataset diversity on PARAFAC accuracy…. Sci Rep, 2015, 5(1 10207

[28] Murphy KR, Stedmon CA, Wenig P, Bro R. OpenFluor… online spectral library…. Anal Methods, 2014, 6(3): 658-661

[29] Heibati M, Stedmon CA, Stenroth K, Rauch S, Toljander J, Säve-Söderbergh M, Murphy KR. Assessment of drinking water quality at the tap using fluorescence spectroscopy. Water Res, 2017, 125: 1-10

[30] Sorensen JP, Carr AF, Nayebare J, Diongue DM, Pouye A, Roffo R, Taylor RG. Tryptophan-like and humic-like fluorophores are extracellular in groundwater: implications as real-time faecal indicators. Sci Rep, 2020, 10(1 15379

[31] Pucher M, Wünsch U, Weigelhofer G, Murphy K, Hein T Graeber D (2019) staRdom: versatile software for analyzing spectroscopic data of dissolved organic matter in R. Water 11(11):2366. https://doi.org/10.3390/w11112366

[32] Peleato Nicolás M., Andrews Robert C.. Comparison of three-dimensional fluorescence analysis methods for predicting formation of trihalomethanes and haloacetic acids. Journal of Environmental Sciences, 2015, 27: 159-167

[33] Bianchi TS, Osburn C, Shields MR, Yvon-Lewis S, Young J, Guo L, Zhou Z (2014) Deepwater horizon oil in gulf of Mexico waters after 2 years: transformation into the dissolved organic matter pool. Environmental Science & Technology 48(16):9288–9297. https://doi.org/10.1021/es501547b

[34] Dainard PG, Guéguen C, Yamamoto‐Kawai M, Williams WJ, Hutchings JK (2019) Interannual variability in the absorption and fluorescence characteristics of dissolved organic matter in the Canada basin polar mixed waters. Journal of Geophysical Research: Oceans 124(7) 5258–5269. https://doi.org/10.1029/2018JC014896

[35] Murphy KR, Butler KD, Spencer RGM, Stedmon CA, Boehme JR, Aiken G R (2010) Measurement of dissolved organic matter fluorescence in aquatic environments: an interlaboratory comparison. Environmental Science & Technology 44(24):9405–9412. https://doi.org/10.1021/es102362t

[36] Morten Søndergaard, Colin A. Stedmon, Niels Henrik Borch (2003) Fate of terrigenous dissolved organic matter (DOM) in estuaries: aggregation and bioavailability. Ophelia 57(3) 161–176. https://doi.org/10.1080/00785236.2003.10409512

[37] Yamashita Youhei, Boyer Joseph N., Jaffé Rudolf. Evaluating the distribution of terrestrial dissolved organic matter in a complex coastal ecosystem using fluorescence spectroscopy. Continental Shelf Research, 2013, 66: 136-144

[38] Du Yingxun, Zhang Yuanyuan, Chen Feizhou, Chang Yuguang, Liu Zhengwen. Photochemical reactivities of dissolved organic matter (DOM) in a sub-alpine lake revealed by EEM-PARAFAC: An insight into the fate of allochthonous DOM in alpine lakes affected by climate change. Science of The Total Environment, 2016, 568: 216-225

[39] Murphy KR, Timko SA, Gonsior M, Powers LC, Wünsch UJ, Stedmon CA (2018) Photochemistry illuminates ubiquitous organic matter fluorescence spectra. Environmental Science & Technology 52(19):11243–11250. https://doi.org/10.1021/acs.est.8b02648

[40] Daniel Graeber, Youngdoung Tenzin, Marc Stutter, Gabriele Weigelhofer, Tom Shatwell, Wolf von Tümpling, Jörg Tittel, Alexander Wachholz, Dietrich Borchardt (2021) Bioavailable DOC: reactive nutrient ratios control heterotrophic nutrient assimilation—an experimental proof of the macronutrient-access hypothesis. Biogeochemistry 155(1):1–20. https://doi.org/10.1007/s10533-021-00809-4

[41] Vladimir A. Kholodov, Natalia N. Danchenko, Aliya R. Ziganshina, Nadezhda V. Yaroslavtseva, Igor P. Semiletov (2024) Direct salinity effect on absorbance and fluorescence of chernozem water-extractable organic matter. Aquatic Geochemistry 30(1):31–48. https://doi.org/10.1007/s10498-024-09423-w

[42] Kowalczuk Piotr, Tilstone Gavin H., Zabłocka Monika, Röttgers Rüdiger, Thomas Rob. Composition of dissolved organic matter along an Atlantic Meridional Transect from fluorescence spectroscopy and Parallel Factor Analysis. Marine Chemistry, 2013, 157: 170-184

[43] Rafael Gonçalves-Araujo, Mats A. Granskog, Astrid Bracher, Kumiko Azetsu-Scott, Paul A. Dodd, Colin A. Stedmon (2016) Using fluorescent dissolved organic matter to trace and distinguish the origin of Arctic surface waters. Scientific Reports 6(1):33978. https://doi.org/10.1038/srep33978

[44] Maxime Wauthy, Milla Rautio, Kirsten S. Christoffersen, Laura Forsström, Isabelle Laurion, Heather L. Mariash, Sari Peura, Warwick F. Vincent (2018) Increasing dominance of terrigenous organic matter in circumpolar freshwaters due to permafrost thaw. Limnology and Oceanography Letters 3(3):186–198. https://doi.org/10.1002/lol2.10063

Funding

NSERC Canada(ALLRP 570897-21)

Telus Inc.

RIGHTS & PERMISSIONS

The Author(s)