25. How do I incorporate twin-pit latrines, composting toilets, urine-diverting dry toilets (UDDT), dehydration vaults, container-based toilets and aqua-privy toilets on the SFD GG?

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:

  • Twin-pit latrines in areas where there is a low risk of groundwater pollution: in Step One, select “Lined pit with semi-permeable walls and open-bottom with no outlet or overflow”, this is system T1A5C10. In Step Two, on the SFD Matrix, input the proportion of the population using the system in the first box and then in the next available box to the right, under F3 “proportion of this type of system from which faecal sludge is emptied”, input 0%. Since the FS remains in the container until it is safe to handle, the SFD Generator models the excreta as “FS contained – not emptied”, i.e. safely managed and therefore a green arrow (F8) on the SFD Graphic. (F4 and F5 should also be set to 0% on the SFD Matrix).
  • Twin-pit latrines in areas where there is a significant risk of groundwater pollution: in Step One, select “Lined pit with semi-permeable walls and open-bottom with no outlet or overflow”, this is system T2A5C10. In Step Two, on the SFD Matrix, input the proportion of the population using the system in the first box and then in the next available box to the right, under F3 “proportion of this type of system from which faecal sludge is emptied”, input 0%. Since there is a significant risk that the FS will cause pollution of groundwater used as a drinking water source, the SFD Generator models the excreta as “FS not contained – not emptied”, i.e. unsafely managed and therefore a red arrow (F15) on the SFD Graphic. (F4 and F5 should also be set to 0% on the SFD Matrix).
  • Composting toilets and Dehydration vaults (used with urine diverting toilets): in Step One, select “Fully lined tanks (sealed) with no outlet or overflow”. This is system T1A3C10 and will model the excreta as “FS contained” on the graphic. In Step Two, on the SFD Matrix, input the proportion of the population using the system in the first box and then in the next available box to the right, under F3 “proportion of this type of system from which faecal sludge is emptied”, input 0%. Since the FS remains in the container until it is safe to handle, the SFD Generator models the excreta as “FS contained – not emptied”, i.e. safely managed and therefore a green arrow (F8) on the SFD Graphic. (F4 and F5 should also be set to 0% on the SFD Matrix). In the case of urine diverting dry toilets, the urine fraction is also considered to be safely managed and included in the green arrow F8.
  • Container-based toilets: in Step One, select “Fully lined tanks (sealed) with no outlet or overflow”. This is system T1A3C10 and will model the excreta as “FS contained” on the graphic. In Step Two, input the proportion of the population using container-based toilets in the first box and then in the next available box, under F3 “proportion of this type of system from which faecal sludge is emptied”, input 100%. This indicates that all users have their container emptied regularly. Next, under F4 “proportion of faecal sludge emptied, which is delivered to treatment plants”, enter the proportion you estimate is delivered to treatment. If the service is functioning well, this is likely to tend to 100%. Finally, under F5 “proportion delivered to treatment, which is treated”, enter the proportion you estimate is treated. This proportion is considered safely managed and will be represented by a green arrow labelled “FS treated” (F5) on the SFD Graphic.
  • Aqua-privy toilets: in Step One, select “Septic tanks” and the relevant technology that it is connected to from List B. For instance, if it is connected to a “soak pit” and there is a low risk of groundwater pollution, select T1A2C5. This will model the excreta as “FS contained” on the graphic. In Step Two, input the proportion of the population using aqua-privy toilets in the first box and then in the next available box to the right, under F3 “proportion of this type of system from which faecal sludge is emptied”, input the proportion of the aqua-privy toilets from which faecal sludge is emptied. Next, under F4 “proportion of faecal sludge emptied, which is delivered to treatment plants”, enter the proportion you estimate is delivered to treatment. Finally, under F5 “proportion delivered to treatment, which is treated”, enter the proportion you estimate is treated. This proportion is considered safely managed and will be represented by a green arrow labelled “FS treated” (F5) on the SFD Graphic.
  • Hanging latrines: in Step One, select “No onsite container connected to a water body”. This is system T1A1C7 and will model the excreta as “FS NOT contained” on the graphic. In Step Two, input the proportion of the population using hanging latrines in the first box.

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.