Proof-of-concept evaluation at Cox’s Bazar of the Safe Water Optimization Tool: water quality modelling for safe water supply in humanitarian emergencies
Introduction Waterborne diseases are leading concerns in emergencies. Humanitarian guidelines stipulate universal water chlorination targets, but these fail to reliably protect water as postdistribution chlorine decay can leave water vulnerable to pathogenic recontamination. The Safe Water Optimizat...
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| Format: | Article |
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BMJ Publishing Group
2025-08-01
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| Series: | BMJ Global Health |
| Online Access: | https://gh.bmj.com/content/10/8/e018631.full |
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| author | Tarra L Penney James Orbinski Syed Imran Ali Michael De Santi Matt Arnold Usman T Khan Syed Saad Ali Jean-François Fesselet |
| author_facet | Tarra L Penney James Orbinski Syed Imran Ali Michael De Santi Matt Arnold Usman T Khan Syed Saad Ali Jean-François Fesselet |
| author_sort | Tarra L Penney |
| collection | DOAJ |
| description | Introduction Waterborne diseases are leading concerns in emergencies. Humanitarian guidelines stipulate universal water chlorination targets, but these fail to reliably protect water as postdistribution chlorine decay can leave water vulnerable to pathogenic recontamination. The Safe Water Optimization Tool (SWOT) models chlorine decay to generate context-specific chlorination targets that ensure water remains protected up to point-of-consumption. The SWOT has not been tested in an active humanitarian response, so we conducted a proof-of-concept evaluation at a Cox’s Bazar refugee settlement to validate its modelling and assess its efficacy and effectiveness.Methods We trained the SWOT using data collected from July to September 2019 and evaluated using data from October to December 2019 (n=2221). We validated the SWOT’s modelling by comparing performance using training and testing data sets. We assessed efficacy using binary logistic regression comparing household free residual chlorine (FRC) when the SWOT target was delivered at tapstands versus the status quo target, and effectiveness using interrupted time series analysis of the proportion of households with protective FRC before and after SWOT implementation.Results The SWOT generated a context-specific FRC target of 0.85–1.05 mg/L for 15-hours protection. Validation of the SWOT’s process-based model showed R2 decreased from 0.50 to 0.23 between training and testing data sets, indicating periodic retraining is required. The SWOT’s machine-learning model predicted a 1%–9% probability of household FRC<0.2 mg/L at 15 hours, close to the observed 12% and in line with the observed 7% risk during baseline and endline, respectively. Households that collected water meeting the SWOT target were more likely to have sufficient protection after 15 hours compared with the status quo target (90% vs 35%, p<0.01), demonstrating the SWOT’s efficacy. The SWOT target was not fully implemented at tapstands, so we did not observe change in household FRC during endline.Conclusion The SWOT can generate context-specific chlorination targets that protect water against pathogenic recontamination. Improving feedback between monitoring and treatment would help system operators unlock the SWOT’s full water safety potential. |
| format | Article |
| id | doaj-art-95c062f69f104420ac1cf73f9b3cb1c3 |
| institution | Kabale University |
| issn | 2059-7908 |
| language | English |
| publishDate | 2025-08-01 |
| publisher | BMJ Publishing Group |
| record_format | Article |
| series | BMJ Global Health |
| spelling | doaj-art-95c062f69f104420ac1cf73f9b3cb1c32025-08-21T03:55:15ZengBMJ Publishing GroupBMJ Global Health2059-79082025-08-0110810.1136/bmjgh-2024-018631Proof-of-concept evaluation at Cox’s Bazar of the Safe Water Optimization Tool: water quality modelling for safe water supply in humanitarian emergenciesTarra L Penney0James Orbinski1Syed Imran Ali2Michael De Santi3Matt Arnold4Usman T Khan5Syed Saad Ali6Jean-François Fesselet7Dahdaleh Institute for Global Health Research, York University, Toronto, Ontario, CanadaDahdaleh Institute for Global Health Research, York University, Toronto, Ontario, CanadaDahdaleh Institute for Global Health Research, York University, Toronto, Ontario, CanadaDahdaleh Institute for Global Health Research, York University, Toronto, Ontario, CanadaDahdaleh Institute for Global Health Research, York University, Toronto, Ontario, CanadaDahdaleh Institute for Global Health Research, York University, Toronto, Ontario, CanadaDahdaleh Institute for Global Health Research, York University, Toronto, Ontario, CanadaPublic Health Department, Médecins Sans Frontières, Amsterdam, The NetherlandsIntroduction Waterborne diseases are leading concerns in emergencies. Humanitarian guidelines stipulate universal water chlorination targets, but these fail to reliably protect water as postdistribution chlorine decay can leave water vulnerable to pathogenic recontamination. The Safe Water Optimization Tool (SWOT) models chlorine decay to generate context-specific chlorination targets that ensure water remains protected up to point-of-consumption. The SWOT has not been tested in an active humanitarian response, so we conducted a proof-of-concept evaluation at a Cox’s Bazar refugee settlement to validate its modelling and assess its efficacy and effectiveness.Methods We trained the SWOT using data collected from July to September 2019 and evaluated using data from October to December 2019 (n=2221). We validated the SWOT’s modelling by comparing performance using training and testing data sets. We assessed efficacy using binary logistic regression comparing household free residual chlorine (FRC) when the SWOT target was delivered at tapstands versus the status quo target, and effectiveness using interrupted time series analysis of the proportion of households with protective FRC before and after SWOT implementation.Results The SWOT generated a context-specific FRC target of 0.85–1.05 mg/L for 15-hours protection. Validation of the SWOT’s process-based model showed R2 decreased from 0.50 to 0.23 between training and testing data sets, indicating periodic retraining is required. The SWOT’s machine-learning model predicted a 1%–9% probability of household FRC<0.2 mg/L at 15 hours, close to the observed 12% and in line with the observed 7% risk during baseline and endline, respectively. Households that collected water meeting the SWOT target were more likely to have sufficient protection after 15 hours compared with the status quo target (90% vs 35%, p<0.01), demonstrating the SWOT’s efficacy. The SWOT target was not fully implemented at tapstands, so we did not observe change in household FRC during endline.Conclusion The SWOT can generate context-specific chlorination targets that protect water against pathogenic recontamination. Improving feedback between monitoring and treatment would help system operators unlock the SWOT’s full water safety potential.https://gh.bmj.com/content/10/8/e018631.full |
| spellingShingle | Tarra L Penney James Orbinski Syed Imran Ali Michael De Santi Matt Arnold Usman T Khan Syed Saad Ali Jean-François Fesselet Proof-of-concept evaluation at Cox’s Bazar of the Safe Water Optimization Tool: water quality modelling for safe water supply in humanitarian emergencies BMJ Global Health |
| title | Proof-of-concept evaluation at Cox’s Bazar of the Safe Water Optimization Tool: water quality modelling for safe water supply in humanitarian emergencies |
| title_full | Proof-of-concept evaluation at Cox’s Bazar of the Safe Water Optimization Tool: water quality modelling for safe water supply in humanitarian emergencies |
| title_fullStr | Proof-of-concept evaluation at Cox’s Bazar of the Safe Water Optimization Tool: water quality modelling for safe water supply in humanitarian emergencies |
| title_full_unstemmed | Proof-of-concept evaluation at Cox’s Bazar of the Safe Water Optimization Tool: water quality modelling for safe water supply in humanitarian emergencies |
| title_short | Proof-of-concept evaluation at Cox’s Bazar of the Safe Water Optimization Tool: water quality modelling for safe water supply in humanitarian emergencies |
| title_sort | proof of concept evaluation at cox s bazar of the safe water optimization tool water quality modelling for safe water supply in humanitarian emergencies |
| url | https://gh.bmj.com/content/10/8/e018631.full |
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