Sewerage System with Urine Diversion

This is a water-based sewer system that requires a Urine Diverting Flush Toilet (UDFT). The UDFT is a special User Interface that allows for the separation and collection of Urine without water, but that also uses water to flush Faeces.

The inputs to the system can include, Faeces, Urine, Flushwater, Anal Cleansing Water, Dry Cleansing Material, Stormwater, and Greywater. There are two User Interface Technologies that can be used for this system, a UDFT and a Urinal. The Urinal however, should be used in conjunction with the UDFT, as an alternative for men who do not wish to sit on the pedestal.

Both Brownwater and Urine are separated at the User Interface. Brownwater bypasses a Collection and Sto - rage/Treatment facility and is conveyed directly to a (Semi-) Centralized Treatment facility using a Simplified Sewer network or a Gravity Sewer network. Greywater is also transported in the sewer and is not treated separately. In some circumstances, Stormwater can be connected to a Gravity Sewer network, although Stormwater overflows are required.

Urine separated at the User Interface is directly linked to a Storage Tank. The Stored Urine is transferred for Use and/or Disposal using a Jerrycan - tank or Motorized E&T for Urine Application to agricultural lands. Brownwater is treated at a (Semi-) Centralized Treatment facility using one of the Technologies T1 to T10. The Faecal Sludge generated from the treatment of the Technologies T1 to T10 must be further treated in a dedicated Faecal Sludge treatment facility (Technologies T11 to T15) prior to using the Land Application or Surface Disposal Use and/or Disposal technologies. Technologies for the Use and/or Disposal of the treated Effluent collected from one of the Technologies T1 to T10 include Irrigation, Aqua culture, Macrophyte Pond or Discharge to a water body or Recharge to Groundwater.

Considerations

UDFTs are not common and the capital cost for this system can be high. This is partly due to the fact that there is limited competition in the market and also because high quality plumbing is required for the dual plumbing system. The Gravity Sewers require extensive excavation and installation can be expensive, whereas Simplified Sewers are generally less expensive if the site conditions permit a condominial design. This system is only appropriate when there is a need for the separated Urine and/or when there is a desire to limit water consumption by collecting Urine without flushing water. The system still re quires a constant source of water and uses significantly more than a waterless system.

Depending on the type of sewers used, this system can be adapted for both dense urban and peri-urban areas. It is not well-suited to rural areas. There must be a constant supply of water to ensure that the sewers do not become blocked. This system is appropriate where there is a need and a desire to collect, transport and use the Urine. There may also be benefits to the treatment plant if it is normally overloaded; the reduced nutrient load (by removing the Urine) could optimize treatment. However, if the plant is currently, underloaded (i.e. the plant has been overdesigned) then this system could further aggravate the problem.

Depending on the sewer type and management structure (simplified vs gravity, city-run vs community operated) there will be varying degrees of operation or maintenance responsibilities for the homeowner.

References

• Elizabeth Tilley et.al (2008). Compendium of Sanitation Systems and Technologies (low res version). Department of Water and Sanitation in Development Countries (Sandec) at the Swiss Federal Institute of Aquatic Science and Technology (Eawag). (Provides a full overview of sanitation systems.)