FAQ by Other Users
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Need assistance on your SFD? Post your questions and discuss with other SuSanA members on the SuSanA Forum.
A Shit Flow Diagram (SFD) is an easy-to-understand advocacy and decision-support tool comprising a report (SFD Report) which contains a graphic (SFD Graphic). An SFD summarises service outcomes in terms of the flow and fate of excreta in urban areas. It includes a qualitative assessment of the context in which service delivery takes place and a complete record of data sources. The process of developing the report is as important as the report itself; use of the SFD method enables a standardised assessment of excreta flows in urban areas. Due to the sensitivity around the term “shit” the following terms are often used interchangeably: Excreta Flow Diagram or Faecal Waste Flow Diagram.
The SFD Graphic indicates where the problems lie in an urban area, but without understanding the local context you cannot understand why these situations occur. The SFD Report will help to answer questions such as “Why is only half of the excreta produced onsite collected?” or “why is only half of the wastewater that reaches the treatment facilities treated?” The SFD Report provides information on the institutional frameworks, roles and responsibilities, regulatory aspects, and other issues that directly or indirectly impact the provision of sustainable sanitation services. It also includes the assumptions used to prepare the SFD Graphic.
The SFD Graphic is a visual representation that enables stakeholders to identify service outcomes in terms of the flow and fate of excreta produced by the population. Excreta which is safely managed and move along the sanitation service chain are represented by green arrows moving from left to right in the graphic, while excreta which are unsafely managed are represented by red arrows. Unsafely managed flows discharging to the environment are represented by red arrows turning towards the bottom of the graphic. The width of each arrow is proportional to the percentage of the population whose excreta contribute to that flow.
The point at which the arrows drop down to the bottom of the graphic, gives a general indication of how far the excreta has travelled from the initial population centre. For example open defecation normally occurs in the ‘local area’ close to where people live, whereas untreated wastewater in open drains or sewers may flow out of the ‘local area’ through the ‘neighbourhood’ to the edge of a ‘city’. The endpoint of the different arrows provides an indication of the likely location and scale of discharge of unsafely managed excreta to the environment.
The SFD Process methodology includes the most widely accepted sanitation-related technical terms and their definitions according to several high quality resources and papers. All the technical terms used in the SFD Process are explained in the SFD Glossary which also includes some of the commonly used local variants. However, it is recognised that there are regional variations in both technical term usage and their definitions. To keep the SFD Graphic clear and uncluttered, very few technical terms are displayed on the Graphic; instead generic terms are used to describe both the sanitation chain and service outcomes in terms of the flow and fate of excreta.
Where changes to these and other terms help local understanding, users are encouraged to highlight these changes and all other assumptions in the SFD Report.
The SFD Graphic represents the excreta produced by the total population of an urban area from the point where it originates. It therefore includes excreta from households, schools, institutional toilets, hospitals, workplaces etc. The places where excreta originate are known as categories of origin in the SFD Manual (see Volume 1, section 5.2.1, Version 2.0). Excreta flows may need to be split between different categories (for example home and school) and these must be clearly stated in the report.
The SFD describes all of the excreta flows across the city or town, and through all stages of the sanitation service chain. This includes:
The width of each arrow on the SFD Graphic is proportional to the percentage of the population whose excreta contribute to that flow, not volumes of excreta or waste. This is because data on the types of sanitation systems used are normally available via national census data or health surveys, and are based on the number of people. To convert this data to volumes would require a large number of assumptions to be made such as:
Typically very little data are available to enable accurate or credible estimates to be made on the basis of volumes. Population percentages are also relatively easy to comprehend for non-technical stakeholders.
The SFD Graphic shows the percentage of the population whose excreta are considered to be either safely managed or unsafely managed. Safely managed and unsafely managed in this context indicates the likelihood of a population being exposed to a hazard as a result of the flow of excreta through the sanitation service chain, rather than absolute risk. Estimating the absolute risk would require accurate information on the level of hazard (concentrations and volumes of known pathogens at any point in the service chain), etiology and dose-response curves for those known pathogens, and information on the timing, duration and age profile of population exposed to the hazard; assessing these would require significant additional data collection and analysis.
The SFD Graphic and process is related to the sanitation service chain; the service chain for solid waste would be different. The SFD Graphic Generator cannot be used directly to model solid waste flows across a city or town, but the existing SFD Manual (Version 2.0, July 2017 and process could be adapted to develop solid waste flow diagram tools.
Other tools have been developed that also explore the flows of faecal waste through the sanitation service chain. These include:
The SFDs Worldwide tab on the web portal includes a large number of completed SFD Reports. These clearly set out the assumptions used and the basis of the data and estimates used to prepare the SFD Graphics in each case.
This process originated from the work of Andy Peal, Barbara Evans, and the World Bank on faecal sludge management which is documented in the following papers:
A good way to start the SFD process is by reading the SFD Manual (Version 2.0, July 2017).
The terms desk-based and field-based were in use as reports were prepared in Phase 1 of this project, following the methodology recommended in the initial SFD Manual (Version 1.0, October 2015). The terms do not indicate where the study was carried out, but rather related to the level of data collection and analysis required.
When you look at SFD Graphics and SFD Reports from the SFD library, for these earlier reports the SFD Level will show as “Level not set”. The basis on which they were developed has been updated and the terms desk-based and field-based have been replaced by three Levels of SFD Report.
If you want to make adjustments to an existing SFD Graphic and Report – or make your own SFD Report and SFD Graphic, then the Level at which you create the new SFD Graphic and SFD Report will be determined by the new definitions. These are given in the FAQ #16 “What are the different Levels of SFD Report?”
There are three main Levels of SFD Report that can be prepared:
Initial – ideal for advocacy purposes and initiating dialogue around sanitation services with key stakeholders
Intermediate – when a more ‘robust’ and credible report is needed
Comprehensive – good for supporting discussions into investments and planning for improved sanitation services
The level of SFD Report that you develop will depend on 5 key criteria:
A further option available to you is to prepare an “SFD Lite” report. This type of report is based around preparing an SFD Graphic with a minimum amount of supporting data and referenced sources for that data. The result can be presented in a very brief reporting format.
Detailed information on the different levels are available in the the SFD Manual (Version 2.0, July 2017). The templates for the SFD Reports are here.
Stakeholder engagement is a strongly recommended part of the SFD process. It is necessary as a means of gaining acceptance and support for the study. Experience has proven that the higher the level of stakeholder engagement the more likely the SFD Report and SFD Graphic will be used by decision makers. Guidance on stakeholder engagement can be found in Part B the SFD Manual (Version 2.0, July 2017).
The amount of time required to complete an SFD Report will depend on the Level of study you develop, the amount of data available and your access to key informants. During the piloting of our methods we found that a desk-based study (roughly equivalent to an Initial or Intermediate Level SFD Report) took between three to five weeks and a field-based study (roughly equivalent to a Comprehensive Level SFD Report) took up to two months. Where you are familiar with the town or city being studied the time involved is likely to be significantly shorter. It was also found that significant additional time may need to be factored in for stakeholder approval of the final SFD report.
A good starting point can be official documents from governments, such as census data or strategic plans. In addition, documents, studies and reports from institutions working in the town or city, e.g. NGOs or UN Agencies, can be very helpful sources of information. Municipalities, utilities or private local service providers may keep useful records relating to their activities such as design documents, legislation and bylaws, yearly reports, licenses, treatment plant registers, etc.
We also recommend that you read through previous SFD reports produced for a city or town in your country, as this may highlight data sources which you can also use. SFD reports are available via http://sfd.susana.org/sfd-worldwide.
There are likely to be gaps in the data for your town or city. You should try to fill these gaps by looking at grey literature (internal, unpublished reports) and conducting key informant interviews. Wherever possible, any data should be cross-checked (triangulated) with data from other sources. You will probably have to make assumptions about your city and town. When assumptions are made you should state clearly in the report the logic behind them. These assumptions should also be clearly explained in Section 7 of the Executive Summary (see SFD Report Template). By reviewing the reports from other cities you can see how other authors have overcome a lack of data.
The efficiency of the treatment plant is affected mainly by:
Data about this can be found from:
Based on this, the efficiency can be determined regarding the standard parameters and effluent quality; if the effluent does not meet the national standards the efficiency cannot be considered 100%. If the facility is well maintained and it is not working under capacity, the treatment could be considered to be at least partially treated (50%). If the effluent is not monitored then assumptions regarding operation and based on expert opinion can be made as long as the report shows all the assumptions made by the author. For instance, in Kumasi, where effluent is not being monitored, it was assumed that the plant was partially treating the waste due to the following observation: although there was a lack of maintenance and the amount of waste arriving was close to the treatment capacity limit (working some days over capacity), the treatment plant was still working and the effluent was of a nationally accepted quality.
Where possible, authors must agree on the percentage of waste being treated with the relevant stakeholders. In the absence of specific data the following three percentages can be used as a guiding principle: 0% where there is no treatment, 50% where there is “some” level of treatment, and 95% where almost all the waste is being treated.
The SFD is a good first step for a city or town that wants to address sanitation challenges. It represents a preliminary assessment which can help to identify important data gaps, priority areas for further analysis or to gain consensus on the need for critical interventions. The process of assembling the data for an SFD can facilitate better information sharing and a more accurate appraisal of the current situation from a wide range of stakeholders. The potential of the SFD process is being documented by the SFD Promotion Initiative. Case studies can be found here.
Transient and non-resident populations are groups of people who do not stay in the city or town all day, every day. This may include commuters, traders, students, tourists, pilgrims, etc. Information on this group is difficult to establish and you need to balance the effort used to make credible estimates with the significance of this group to the SFD as a whole. As a first step, estimate the percentage of the total population which is transient and non-resident. Data on these populations may be available in census data, and from the tourist ministry or hotel associations.
As a rough guide it is suggested that a transient and non-resident population which makes up less than 5% of the total population can be assumed to make a negligible contribution and can be excluded. Modelling of larger transient/ non-resident populations will require estimates of their patterns of latrine usage and overall sanitation service delivery outcomes. Remember that they may use institutional toilets in hostels or public places. Be aware of temporal effects. For example, if you are including the impact of an annual pilgrimage event, which takes place over two weeks, then the effective contribution of one person from this population would be 2/52 of the contribution made by someone from the permanent population.
Where transient and non-resident populations make a significant impact at certain times, it may be useful to generate a specific SFD Graphic to examine this effect.
The risk of groundwater pollution can be estimated using the groundwater pollution risk estimation tool in the SFD Graphic Generator on the SFD web portal. Risk in this case is a function of both the probability of pathogens from sanitation systems reaching groundwater and the probability of exposure to this hazard by people drinking that groundwater. The user is prompted to answer six questions in order to obtain an estimate of the risk of groundwater pollution. Risk can be estimated for the city as a whole, or separately for different areas of the city. The tool provides a general estimate expressed as either ‘low’ or ‘significant’ risk, which can then be used to select appropriately from the SFD Selection Grid.
To assess risk of groundwater pollution you will need information on the:
Remember to state clearly in the SFD Report the data used and any assumptions made.
The SFD Selection Grid in Step One of the SFD Graphic Generator allows the user to choose from a number of frequently used technologies for example; toilets connected to sewers, septic tanks and fully lined tanks, as well as those using different types of pit latrines.
The SFD Selection Grid can also be used to model other systems and some suggestions for how to do this are included follows below:
When modelling these systems, remember to state clearly in the SFD Report the method used, any assumptions made and any concerns identified relating to the actual management of the systems.
In Step Two of the SFD Graphic Generator, users enter the proportion of the contents of each type of on-site container which are faecal sludge and which may be periodically emptied from tanks and pit latrines. The remaining fraction is dealt with in different ways depending on the types of systems. For guidance on what value to enter, users can refer to the detailed schematics of each system in the SFD Glossary. A general summary of recommended values is given below. These values should be used in cases where there is no specific additional data on which more accurate estimates can be made:
Where tanks are connected to soak pits, use the default "100%" value. This will model the proportion of the contents which are emptied periodically (you will enter this value in the SFD matrix under F3) as 100% faecal sludge. The remaining not emptied fraction is made up of faecal sludge, which remains in the container, and infiltrate which soaks into the ground. For systems in locations where risk of groundwater pollution is low, this fraction comprises variable F8. For systems in locations where risk of groundwater pollution is significant, this fraction comprises variable F15. (Refer to schematics L7 & S2)
Where tanks are connected to water bodies or to open ground use the default "100%" value. This will model the proportion of the contents that are emptied periodically (you will enter this value in the SFD matrix under F3) as 100% faecal sludge. The remaining not emptied fraction is made up of faecal sludge, which remains in the container and supernatant discharging to water bodies or open ground. This fraction comprises variable F15. (Refer to schematic L9)
Where fully lined tanks have no outlet or overflow, use the default "100%" value. This will model the contents as 100% faecal sludge and a proportion of this may be emptied periodically (you enter this value in the SFD matrix under F3). The remaining not emptied fraction is made up of faecal sludge and supernatant, which remain in the container. This fraction comprises variable F8. (Refer to schematic L10)
Where lined tanks with impermeable walls and open-bottoms and/or pits (all types) have no outlet or overflow (for example many “cubluks” in Indonesia), use the default "100%" value. This will model the contents as 100% faecal sludge and a proportion of this may be emptied periodically (you enter this value in the SFD matrix under F3). The remaining not emptied fraction is made up of faecal sludge, which remains in the container, and infiltrate which soaks into the ground. For systems in locations where risk of groundwater pollution is low this fraction comprises variable F8. For systems in locations where risk of groundwater pollution is significant this fraction comprises variable F15. (Refer to schematics L11 & S4)
Where septic tanks and fully lined tanks are connected to a sewer network, use a value of "50%". This will model half the contents as faecal sludge and a proportion of this may be emptied periodically (you enter this value in the SFD matrix under F3). The remaining not emptied fraction will comprise faecal sludge, which remains in the container, and is represented by variable F8. The other half of the contents is modelled as supernatant discharging into the sewer network, represented by variable S6. (Refer to schematic L6)
Where lined tanks with impermeable walls and open-bottoms are connected to a sewer network, use a value of "50%". This will model half the contents as faecal sludge and a proportion of this may be emptied periodically (you enter this value in the SFD matrix under F3). The remaining not emptied fraction will comprise faecal sludge, which remains in the container, and infiltrate which soaks into the ground. For systems in locations where risk of groundwater pollution is low this fraction comprises variable F8. For systems in locations where risk of groundwater pollution is significant this fraction comprises variable F15. The other half of the contents is modelled as supernatant discharging into the sewer network; where there is a low risk of groundwater pollution this is represented by variable S6, and where there is a significant risk of groundwater pollution this is represented by variable S7. (Refer to schematics L6 and S3)
Where tanks are connected to open drains, use a value of "50%". This will model half the contents as faecal sludge and a proportion of this may be emptied periodically (you enter this value in the SFD matrix under F3). The remaining not emptied fraction will comprise faecal sludge, which remains in the container and is represented by variable F15. The other half of the contents is modelled as supernatant discharging into the open drains, represented by variable S7. (Refer to schematic L8)
In situations where there is a mixture of sanitation system (for example, some septic tanks are connected to soak pits and some are connected to open drains) , the user can calculate the ratio of the systems to estimate the proportion of the content of the tanks which is faecal sludge.
The SFD Graphic shows the percentage of the population whose excreta is either safely managed or unsafely managed. Generally, data on sanitation services at the household level are expressed in terms of the percentage of population, but further along the sanitation chain data are more commonly expressed as volumes per day; for instance wastewater flows and faecal sludge deliveries to a treatment plant. Local expert opinion and the views of local stakeholders can help in agreeing a method for converting these volumetric flows to population-based estimates. The factors that may need to be considered include:
Remember to state clearly in the SFD Report the method used and any assumptions made.
For each type of onsite system the user needs to enter a value for the variable F3 “proportion of this type of system from which faecal sludge is emptied”. The true value is a function of the percentage ever emptied and the proportion of the contents removed during emptying. However, estimating both these may be challenging.
The SFD Process defines emptying as “the manual or motorised emptying of faecal sludge from onsite sanitation systems”. The emptying event or service should remove a substantial amount of the faecal sludge from the container which would then be transported away and should certainly comprise more than just unblocking septic tanks or flushing out pit latrines. However, the SFD Process does not define an acceptable emptying frequency; this is very context specific and dependent on many factors.
A pragmatic approach is to estimate the proportion of households with a specific type of system who ever have them emptied. In some cases there will be data from household surveys and situational analyses. There may also be data on the capacity of the emptying service providers (i.e. numbers and volume of trucks) and their service history; these could provide a useful cross-check. In many locations however these data will not be available. Calculating F3 will then depend on expert opinion and should be discussed by stakeholders as part of the SFD process. It is important to state clearly in the SFD Report the method used and any assumptions made.
These terms are clearly defined in the SFD Glossary. There is no difference in the way that the SFD process models the performance of decentralised and centralised sewers. This distinction is included to facilitate discussion in cites/towns where there is both a centralised sewer network and one or more small scale or pilot decentralised systems which may have distinct performance characteristics. In that case, different percentages can be assigned to variables, for example the percentage delivered to treatment and percentage treated in each case.
If there are multiple systems and the SFD Graphic is complex, this is likely to be a 1% rounding error, which is unavoidable with so many calculations. If it is larger than this, then it is more likely to be an error in the input data and users are advised to check their working. Where a small rounding error is encountered which makes understanding difficult and/or delays agreement amongst stakeholders, then users are encouraged to make minor adjustments in the estimated percentages to eliminate this. If this proves difficult you can contact the SFD Helpdesk who will endeavour to identify the problem and provide assistance with making the most appropriate adjustments.
The SFD Graphic is produced as a png (picture file), pdf (portable document format) or svg file (scalable vector graphic). With experience, by simply adjusting the input data users can draw any scenario, and are expected to document this process in the accompanying report. Alternatively, minor layout edits can be done in the svg file using graphic editor programmes, like Adobe Illustrator or Inkscape. Please contact the SFD Helpdesk in order to find out how to make appropriate adjustments.
If Open Defecation in your city equals 0%, then ticking this box and clicking “Draw SFD Graphic” will cause a gold star to appear next to the open defecation box on the SFD Graphic.
Each cell of the SFD Selection Grid represents a system. You can select each one by clicking on it, and deselect it by clicking on it again.
If you only want to deselect one system, click on it and it will disappear; then click the “Create SFD Matrix” button. This will redraw the matrix without that system, but ALL other data is kept.
If you want to keep working on the same city but start afresh, then deselect all the systems, select the new set of systems and then click “Create SFD Matrix”. This will draw a new SFD Matrix, which is empty and ready for you to populate with data but the general information data you entered about the city will be retained.
To clear all data and start a new SFD, click the reset button located both at the top and bottom of the SFD Graphic Generator page. This will clear all input data - the city general information input boxes, the SFD Selection Grid and the SFD Matrix data - enabling you to start again. But before you do these, remember to save any data you want to keep.
The SFD process can be used to produce an SFD for any urban area, which is of particular interest. For example, it may be useful to produce an SFD on a district within a city where it is understood that sanitation service delivery is relatively low, or for areas of a city where it is reported that a significant proportion of the population, often the most vulnerable, rely on unimproved services.
An SFD Report should always include a full description of the concerned urban area and full details of the qualitative and quantitative data collection methods used – as described in the SFD Manual. However, if any disaggregation of quantitative data into sub-groups is made, for example to produce two SFD Graphics representing a) the city as a whole, and b) those living in low-income areas, the SFD Report must also include both the method used and an estimation of the level of confidence in the data. A method for disaggregating quantitative data is not included within the SFD Manual, but is available at: http://documents.worldbank.org/curated/en/461321468338637425/Fecal-sludge-management-diagnostics-for-service-delivery-in-urban-areas-tools-and-guidelines.
The SFD process can be used to produce an SFD Report for any town or city, regardless of population size or level of sanitation service. For example, to date the process has been used in small towns with populations of less than 50,000 people and in large cities with populations of over five million people.
Section 4.1.3 of the SFD manual gives examples of the type of information to collect that will help identify the extent to which sanitation technologies and services are meeting the needs of the urban poor. The type of information includes, for example, the sanitation technologies the urban poor rely on, levels of access and affordability of different service options. This information will provide you with evidence to write about inequalities in access to sanitation services in the SFD Report.
If you want to develop this further and prepare an SFD Graphic to highlight inequalities (for example to show how the SFD Graphic for an area with high levels of unimproved services compares to the city as a whole), this is explained further in FAQ #35: Can I use the SFD process to make an SFD for a sub-area within a city, or for a particular sub-group within the city population?
In many cities the definitions of septic tanks, lined tanks and various types of pit are used interchangeably. It is therefore important that those providing the data for the city understand the types of sanitation system in use and how they function. When producing an SFD it is recommended that where possible discussions are held with stakeholders to ensure that the functionality of each system is understood. You can use the Sanitation System Classification Tool to help select from the SFD selection grid the correct sanitation systems in use in your city. If you require any assistance in classifying the system you are considering the SFD Helpdesk would be happy to help you.
There are many terms used to describe the locations that a containment technology can be connected to, so it is not possible to include them all on the SFD selection grid; therefore generic terms have been used for the options in List B along the top of the grid. In making the right selection, it is important to consider how the system functions, rather than just what it is called locally. For example, in some cities toilets discharge to covered drains, which are not shown on the SFD selection grid as an option. When producing an SFD it is recommended that where possible discussions are held with stakeholders to ensure that the functionality of each system is understood. You can use the Sanitation System Classification Tool to help select from the SFD selection grid the correct sanitation systems in use in your city. If you require any assistance in classifying the system you are considering the SFD Helpdesk would be happy to help you.
In some locations pit contents are "flooded out" or "flushed out" when full: that is, the side of the pit is broken open to allow the contents to flow out, or the contents of the system are flushed out using water. This often occurs during the rainy season. These systems should be categorised as "Toilet failed, damaged, collapsed or flooded" connected to "Open ground".
In other situations people use "pit diversion": that is, another hole is dug next to the pit in use and the contents are then drained, flushed, or otherwise transferred into the new hole. For the purposes of the SFD, if the contents of the hole are backfilled and covered over so that humans are separated from excreta, the contents are considered "contained". These systems should be classified as "Toilet never emptied but abandoned when full, adequately covered with soil". However, if the contents are NOT properly covered over with a significant risk of humans being exposed to the excreta, then the contents are considered "NOT contained" and these systems should be classified as "Toilet never emptied but abandoned when full, NOT adequately covered with soil".
In some locations it is common for toilets, pits or tanks to be connected to storm drains which are covered and referred to locally as sewers. However, since the covering is often done informally with the covering being incomplete and/or not extending over the full length of the drain, they do not separate humans from excreta. Where used, this practice can therefore present a significant public health risk and for the purposes of the SFD, the excreta is considered NOT contained. Therefore when using the SFD Selection Grid, any toilet, pit or tank technology connected to an open drain, storm drain, storm sewer, or open sewer (covered or otherwise) should be classified as being connected "to open drain or storm sewer".