This page will host the FAQs for the SWOT soon. For the time being, we present below full responses to audience questions to the panel that we didn't get time to respond to during our Virtual Launch Event on November 25th, 2020. In the responses to each question below, members of the SWOT Team panel, including Matt Arnold (MA), Jeff Fesselet (JF), and Syed Imran Ali (SIA), offer their thoughts

1. A specific one on HEV as it’s been mentioned. We know HEV shows a certain resistance to chlorine (which level is still unknown as far as I know). Would the SWOT newly recommended FRC levels (i.e. 0.8-1.0 mg/L) be sufficient to tackle HEV? Would that be a field for further research?

MA, SIA: The potential for HEV (Hepatitis E) and other pathogenic organisms to be resistant to chlorination at concentrations recommended for public water supply has been the subject of much discussion in the humanitarian sector. However, a recent paper indicates that chlorination of water, when applied at typical concentrations, is adequate for the inactivation of HEV (and similar to other reference viruses); https://pubmed.ncbi.nlm.nih.gov/25252347/

Moreover, the SWOT is not necessarily about increasing the levels of free residual chlorine (FRC) at tapstands. It is primarily about matching tapstand FRC levels to the local site conditions. Think of it as a tool to help improve the management of water chlorination practice to achieve safe water at the household level. Generally speaking, the SWOT aims to deliver 0.2 mg/L FRC at the household, but this target can be adjusted depending on the context, such as during an outbreak, or if a different indicator of safe water (>=0.2mg/L as FRC) is required. The SWOT is part of an overall safe water supply toolkit and cannot be separated from wider considerations of water supply. It needs to be part of a comprehensive water safety plan which deals with the full chain of water supply from the source to the household, and all the choices for each of those stages. Good water source selection, appropriate treatment, safe distribution, and safe water collection and storage methods are all likely to reduce post abstraction contamination and, in turn, reduce the overall FRC requirement. The SWOT helps field workers adapt water chlorination to the overall WASH context.

More information on the inactivation of various pathogens by chlorine can be found here:


See also Q6.

2. I would like to ask if the implementation of SWOT has led to increased consumer rejection rates due to Cl2 taste and odour thresholds being exceeded?

MA, SIA: We know from research and field experience that chlorine taste/odour acceptability is highly population specific. Different populations have different thresholds at which they first sense, find objectionable, and then reject chlorinated water.  For instance, in a study on chlorine dosing for household water treatment in LMIC settings, Lantagne (2008) found 2.0 mg/L to be the upper limit above which user acceptability became a concern based on focus group testing in Ethiopia and Zambia (paper available at: https://doi.org/10.1002/j.1551-8833.2008.tb09704.x). More recently, Crider et al. (2018) found a median acceptability threshold of 1.25 mg/L FRC among adults in urban Bangladesh (paper available at: https://doi.org/10.1016/j.scitotenv.2017.09.135). Other reports in the grey literature indicate higher and lower acceptability thresholds. Chlorine acceptability thresholds are not fixed and can be modified through organoleptic habituation and/or health promotion messaging on the public health importance of water chlorination (Piriou et al., 2015: https://doi.org/10.2166/aqua.2014.097; Sikder et al., 2020: https://doi.org/10.1016/j.watres.2020.115854).

In two of the three SWOT trial sites (Bangladesh and Tanzania), chlorine taste and odour concerns have not been reported as a problem. In fact, the KAP survey conducted during the SWOT proof-of-concept study in Bangladesh indicated a very good acceptance of the chlorinated supply. In Nigeria a plan is being implemented to gradually increase the chlorination level to suit acceptability, necessary given that there are other non-chlorinated water sources available to the population.

In addition, the SWOT will not necessarily recommend increasing chlorination levels and the decision to implement other measures, such as safe water collection and household storage, are likely to have a positive impact on FRC decay and lower the level of chlorination required at the distribution points to achieve safe water at the point of consumption in the household.

To address some of the issues around the quantification of water chlorination acceptability, the SWOT team has included the development of rapid tools for evaluating chlorine taste/odour acceptability in upcoming research. This is an acknowledgement of two key perception issues, that of the population (which is critical) and that of humanitarian workers, who tend to assume that chlorination will be poorly received and/or use methods that confirm this bias. Irrespective of any findings, it goes without saying that providing communities with information around chlorination (or any other forms of treatment) is a critical part of any water supply intervention and acceptance is likely to fail without this.

3. Is there any guideline to collect 100 to 150 paired data in the software or any other platform?

MA, SIA: Yes, there is guidance available from the SWOT team on collecting data using the KoBoCollect application, a mobile phone based data collection solution designed for humanitarians. In addition, technical support is available from the SWOT team to develop data collection solutions that suite the specific context and needs of the water supply team. Data collected on KoBo or other digital platforms can then be easily imported into the SWOT. SWOT Version 2 (expected Summer 2021) will also feature streamlined API integration with the KoBo platform so that there can be a seamless transfer of water quality data.

For any support using the SWOT please send a mail to: support@safeh2o.app.

4.  Mobile data collection was listed as a future state. Can you discuss how the SWOT could be expanded into citizen-led data collection, for areas outside of Refugee camps maybe, but that still struggle with a reliable source of clean drinking water?

MA, SIA: See Q3. The idea of citizen led data collection is a great one as it might be a way to encourage sustainability as well as offer a solution outside of the typical humanitarian ‘camp’ setting. There is no reason why, given the appropriate tools and training, this cannot be implemented. However, for most humanitarian settings the SWOT team believe that monitoring of water chlorination must be an integral part of system operation and resources dedicated accordingly. Household water quality monitoring provides an important opportunity for humanitarian responders to be in the community with the affected population, understand their situations, and act and advocate accordingly. There are also likely to be limitations in the sustainability of participatory monitoring if there is an over dependence on unremunerated labour.

5. It was mentioned access to data as being one issue, how are you planning on tackling this issue and to ensure reliable data? And what do you see as the best coordination mechanisms to ensure both quality and sustainability?

MA, SIA: We are currently engaged with a few agencies implementing in the field and would like all humanitarian water supply projects to use the SWOT as part of their monitoring activities. We can provide all the support necessary to achieve this and ensure that the right choices are made to get reliable data.

The safety of water up to the point of consumption is recognised as a key outcome of water supply projects but might sometimes be deprioritised. The sector is moving in this direction; for instance, in the 2018 revision of the Sphere Handbook, household water quality monitoring is now recommended (although it is not yet a requirement, which we advocate for). We believe that offering a solution to this problem and providing the necessary support is the key to success - keeping things simple to use, whilst making them meaningful. The SWOT is about ultimately about making monitoring and data collection useful for operations. It has two key benefit streams – overall accountability to populations and donors as well as the core public health benefits. By demonstrating that the solution is effective and efficient we believe that the various humanitarian coordination mechanisms will be more likely to adopt it. We also seek to work with donors to include household water quality monitoring and usage of the SWOT in funding agreements as a means of programmatic quality assurance. Through these pathways we aim achieve sustainable usage in the humanitarian sector.

6. How does SWOT deal with chlorine-resistant pathogens? For example, has there been any giardiasis outbreaks where chlorine disinfection was ineffective?

MA: Yes, there have been reported outbreaks of giardiasis in piped and chlorinated water supplies, see here for one example: https://pubmed.ncbi.nlm.nih.gov/2253152/. Other pathogenic protozoa have similar resistance issues and require quite high concentrations of chlorine to inactivate them; https://www.cdc.gov/safewater/effectiveness-on-pathogens.html

However, it is important to recognise that the SWOT is just one aspect of managing safe water supply, it is not a silver bullet for all problems related to water quality! The SWOT’s recommendation can be tailored to specific circumstances, but this might not deal with major contamination of source water, the likely origin of these types of pathogens. The SWOT encourages data collection and record keeping that will, in turn, better inform the overall management of water supply. If additional treatment measures are put in place to deal with source water contamination of this nature, residual chlorine will still need to be supplied to ensure protection beyond that point and up to the household level.

It is best to view the SWOT as the intermediary between management and treatment of source water and post-distribution issues, informing activities that might go beyond purely managing FRC levels. We recommend integrating the SWOT into a detailed water safety plan which includes a thorough risk assessment and can help to eliminate problems with resistant organisms at their source.

JF: The SWOT is not designed to deal with specific pathogen but to make sure the level of chlorine in the water is adequate from the time the water is collected till it is consumed (up to 24h00, at least from our experience. Minimum of 0.2 mg/l to match WHO recommended minimum). However, if there would be a need to increase the level of chlorine (above 0.2 mg/l) because of for example resistant bacteria or the presence of an outbreak (WHO, in case of cholera or HepE would recommend 0.8 mg/l or even 1 mg/l) this could be factored in for a specific site.   

7. How sensitive is the SWOT recommended chlorine dose to time? For example, would a dose that guarantees safe FRC levels 24h after collection be over the taste and odour thresholds if it were to be consumed immediately?

MA: Whichever factors might influence the decay in chlorine, they are usually represented over time. As such, any recommendation the SWOT gives needs to be tailored to the context and the water collection and storage habits of the population, including the typical length of storage at the household level. In some contexts, this might be excessively long and lead to problems of rejection of water at earlier times. Under these conditions we believe that the SWOT and the data collected is likely to better inform decisions around water supply. If populations are storing water for long periods of time, what is the cause of this? Perhaps there are access issues or intermediate supply problems that need to be dealt with. If FRC decay is being driven by factors related to household storage, then what can be done to improve this?

In the short term, and particularly during disease outbreaks, the SWOT is simply about adjusting the FRC target at distribution points but beyond this it becomes an argument for other interventions to improve overall safe water supply.

JF: The dose recommended is based on an average length time of household storage selected by the “user” and is determined by how long refugees or IDPs are storing their water at home before they get a new supply, which is often dependent when the water is available from the network (when supply is intermittent, which is often the case). So basically, the longer the water is  stored (depending on conditions, especially temperature), the higher the level at the tap and higher the potential risk for odour or taste to be a limiting factor. Taste and odor have been on our radar for a long time as this is a hot debate in the sector. However, we have had very positive experience overcoming the initial “reaction” from users with proper communication and active discussions with community leaders.  We will be doing research next year on this specific topic next year in order to produce a rapid field tool for determining population-specific chlorine taste/odour acceptance thresholds.

8. Can SWOT be used in conjunction with household-level safe water practices? For example, if the FRC level at the tapstand is sufficient and then the household employs a SODIS technique of storing water in clear containers in direct sunlight until consumption to ensure a multi-barrier disinfection approach?

MA: The SWOT can certainly be used in conjunction with improvements to household-level safe water practices, we would even say that this is mandatory!

However, the example of SODIS would not work well with the SWOT as sunlight and heat will cause more rapid FRC decay, eliminating any residual protection and rendering the household measurements meaningless. The provision of decent water storage containers with taps is likely to lessen the risk of contamination in the household, reduce the overall chlorine demand, and have the added benefit of keeping water cooler. This is exactly the sort of solution we would hope would be put in place.