Solar disinfection – An appropriate water treatment method to inactivate faecal bacteria in cold climates
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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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Date
2022-06-25
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Language
en
Pages
11
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Science of the Total Environment, Volume 827
Abstract
Solar disinfection (SODIS) is an inexpensive drinking water treatment method applied in tropical and sub-tropical low-income countries. However, it has been unclear whether it functions adequately also in colder climates. To investigate this issue, SODIS experiments were performed in the humid continental climate of Finland by exposing faecally contaminated drinking water to natural solar radiation at different water temperatures (8–23 °C) and UV intensities (12–19 W/m2) in polyethylene (PE) bags. To establish an adequate benchmark, SODIS experiments with the same experimental design were additionally conducted in the Mediterranean climate of Spain in typical conditions of SODIS application (~39 °C and 42 W/m2). Out of all experiments, the highest coliform and enterococci inactivation efficiencies in terms of lowest required doses for 4-log disinfection (25 Wh/m2 and 60 Wh/m2, respectively) were obtained in humid continental climate at the lowest studied mean water temperature (8–11 °C). Despite the low mean UV irradiance (~19 Wh/m2), 4-log disinfection of coliforms and enterococci were also reached fast in these conditions (1 h 27 min and 3 h 18 min, respectively). Overall, the doses required for disinfection increased as the water temperatures and UV intensities of the experiments rose. Disinfection of 4-logs (> 99.99%) of both bacteria was reached in all SODIS experiments within 6 h, suggesting SODIS could be a sufficient household water treatment method also in colder climates, unlike previously thought. The effects of different water temperatures on bacterial inactivation were also tested in the absence of sunlight. Together the obtained results indicate that while water temperatures below or close to the optima of coliforms and enterococci (~10 °C) alone do not cause inactivation, these temperatures may enhance SODIS performance. This phenomenon is attributed to slower bacterial metabolism and hence slower photorepair induced by the low water temperature.Description
Funding Information: This study was financially supported by Maa- ja vesitekniikan tuki ry. (MVTT), Aalto University, Foundation for Aalto University Science and Technology, Tekniska f?reningen i Finland (TFiF) and the Liisa and Aarre Koskenalusta Foundation. We thank the laboratory staff of Aalto Water Building for all their help in enabling the research. We also want to thank the DNA Sequencing and Genomics Laboratory of the Institute of Biotechnology (BI) at the University of Helsinki for providing sequencing services. Furthermore, we thank Shivani Singhal and Emilia Awaitey for finding local prices of PE bags in India and Ghana, and Sara Saukkonen for designing the graphical abstract. Publisher Copyright: © 2022 The Authors
Keywords
Emergency water purification, Frugal technologies, Household water treatment and safe storage (HWTS), Low temperature disinfection, SODIS, Waterborne disease
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Citation
Juvakoski, A, Singhal, G, Manzano, M A, Moriñigo, M Á, Vahala, R & Levchuk, I 2022, ' Solar disinfection – An appropriate water treatment method to inactivate faecal bacteria in cold climates ', Science of the Total Environment, vol. 827, 154086 . https://doi.org/10.1016/j.scitotenv.2022.154086