System 9: Sewerage System with Urine Diversion

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 using a low-flush Urine-Diversion Flush Toilet (although the system still requires a constant source of water). 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., it has been overdesigned), then this system could further aggravate the problem. 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 with low housing densities. Since the sewer network is (ideally) watertight, it is also applicable for areas with high groundwater tables.

Dry Cleansing Materials can be handled by the system or they can be collected and separately disposed of (e.g. Surface Disposal (Solids)).

Urine-Diversion Flush Toilets are not common and the capital cost for this system can be very high. This is partly due to the fact that there is limited competition in the User Interface market and also because high quality workmanship is required for the dual plumbing system. Conventional Sewers (Combined Sewers) require extensive excavation and installation which is expensive, whereas Simplified and Condominal Sewers are generally less expensive if the site conditions permit a condominial design. Users may be required to pay user fees for the system and its maintenance. Depending on the sewer type and management structure (Simplified vs. Conventional, city-run vs. community-operated, Urine transport and Application) there will be varying degrees of operation or maintenance responsibilities for the homeowner.

This system is most appropriate when there is a high willingness and ability to pay for the capital investment and maintenance costs and where there is a pre-existing treatment facility that has the capacity to accept additional flow.

Guidelines for the safe use of wasterwater excreta and greywater. Volume IV. Excreta and Greywater Use in Agriculture of Urine, Effluent and Sludge have been published by the World Health Organization (WHO) and are referenced on the relevant technology information sheets.