Urine-Diverting Flush Toilet (UDFT)

The urine-diverting flush toilet (UDFT) is similar in appearance to a cistern flush toilet except for the diversion in the bowl. The toilet bowl has two sections so that the urine can be separated from the faeces. Both sitting and squatting models exist.

Introduction

Urine is collected in a drain in the front of the toilet and faeces are collected in the back. The urine is collected without water, but a small amount of water is used to rinse the urine-collection bowl when the toilet is flushed. The urine flows into a storage tank for further use (use of urine at small or large-scale)or processing (storage, desiccation, struvite production), while the faeces are flushed with water to be treated (onsite pre-treatment and treatment in septic tanks, biogas settlers, anaerobic baffled reactors; semi-decentralised treatment units, e.g. DEWATS systems; centralised sewage treatment plants).

Design Considerations

The system requires dual plumbing, i.e., separate piping for urine and brownwater (faeces, dry cleansing material and flushing water).

The toilet should be installed carefully with an understanding of how and where clogs may occur so that they can be prevented and easily removed. For the discharge of urine, plastic pipes should be used to prevent corrosion. To limit scaling, all connections (pipes) to storage tanks (see urine storage tank) should be kept as short as possible; whenever they exist, pipes should be installed with at least a 1% slope, and sharp angles (90°) should be avoided. A pipe diameter of 50 mm is sufficient for steep slopes and where maintenance is easy. Larger diameter pipes (> 75 mm) should be used elsewhere, especially for minimum slopes, and where access is difficult.

Appropriateness

A UDFT is adequate when there is enough water for flushing, a treatment technology for the brownwater and a use for the collected urine. To improve diversion efficiency, urinals for men are recommended (U.3) (see also urinals).

UDFTs are suitable for public and private applications, although significant training and awareness is required in public settings to ensure proper use and minimize clogging.

Since this technology requires separate pipes for urine and brownwater collection, the plumbing is more complicated than for cistern flush toilets. Particularly, the proper design and installation of the urine pipes is crucial, and requires expertise.

Health Aspects/Acceptance

Information cards and/or diagrams are essential for ensuring proper use and for promoting acceptance. If users understand why the urine is being separated they will be more willing to use the toilet properly. Proper plumbing will ensure that there are no odours.

Operation & Maintenance

As with any toilet, proper cleaning is important to keep the bowl(s) clean and prevent stains from forming. Because urine is collected separately, calcium- and magnesium-based minerals and salts can precipitate and build up in the fittings and pipes. Washing the bowl with a mild acid (e.g., vinegar) and/or hot water can prevent the build-up of mineral deposits and scaling. Stronger (> 24% acetic) acid or a caustic soda solution (2 parts water to 1 part soda) can be used for removing blockages. However, in some cases manual removal may be required. 

References

Further Readings

  • Cover image of a reference book or miscellany.

    TILLEY, E.; ULRICH, L.; LUETHI, C.; REYMOND, P.; SCHERTENLEIB, R.; ZURBRUEGG, C. (2014): Compendium of Sanitation Systems and Technologies (Arabic). 2nd Revised Edition. Duebendorf, Switzerland: Swiss Federal Institute of Aquatic Science and Technology (Eawag). PDF

    This is the Arabic version of the Compendium of Sanitation Systems and Technologies. The Compendium gives a systematic overview on different sanitation systems and technologies and describes a wide range of available low-cost sanitation technologies.

  • Cover image of a reference book or miscellany.

    MUENCH, E., v.; WINKER, M.; GIZ (Editor) (2011): Appendix 1 for technology review of urine diversion components. Worldwide listing of suppliers for waterless urinals. Eschborn: Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) GmbH. URL [Accessed: 29.04.2011]. PDF

    This document contains a worldwide list of suppliers for waterless urinals. The tables of suppliers provided here are not complete listings but give only an indication of available products. If you spot errors or omissions, please contact the authors at ecosan@giz.de. In the brackets below each listing the date for provision of the information/last update of information is given. Please be aware that not all information is from 2011. An entry in this list does not imply a recommendation by GIZ. Costs are indicative only.

  • Cover image of a reference book or miscellany.

    MUENCH, E., v.; WINKER, M.; GIZ (Editor) (2011): Appendix 2 of technology review of urine diversion components. Worldwide listing of suppliers for urine diversion squatting pans (for UDDTs or for urine diversion flush toilets). Eschborn: Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) GmbH. URL [Accessed: 29.04.2011]. PDF

    This document contains a worldwide list of suppliers for urine diversion squatting pans. The tables of suppliers provided here are not complete listings but give only an indication of available products. If you spot errors or omissions, please contact the authors at ecosan@giz.de. In the brackets below each listing the date for provision of the information/last update of information is given. Please be aware that not all information is from 2011. An entry in this list does not imply a recommendation by GIZ. Costs are indicative only.

  • Cover image of a reference book or miscellany.

    TOUBKISS, J. (2010): How to Manage Public Toilets and Showers. Cotonou and Paris: Partenariat pour le Développement Municipal (PDM) and Programme Solidarité Eau (pS-Eau). URL [Accessed: 19.10.2011]. PDF

    The purpose of this decision-making aid is to provide practical advice and recommendations for managing toilet blocks situated in public places. It is primarily aimed at local decision-makers in developing countries and at their partners (project planners and managers).

Case Studies

Awareness Material

  • Cover image of a reference journal article.

    GEORGE, R. (2009): Yellow is the new Green. In: The New Your Times, 27.URL [Accessed: 27.07.2010]. PDF

    This opinion contribution from Rose George published in the New York Times emphasises the enormous potential urine as a sustainable fertiliser source.

Important Weblinks

  • http://www.dubbletten.nu [Accessed: 10.08.2010]

    Homepage of a Swedish urine diversion flush toilet supplier (only in Swedish).

  • http://www.eawag.ch/forschung/sww/gruppen/rttc/ [Accessed: 17.10.2013]

    Introducing the Reinvent the Toilet Challenge project at Eawag in cooperation with EOOS and Makerere University in Uganda, funded by the Bill & Melinda Gates Foundation.

  • http://www.flickr.com/photos/gtzecosan/sets/72157626481209996/ [Accessed: 17.10.2013]

    SuSanA Flickr picture collection on UDFT.

  • http://www.novaquatis.eawag.ch/ [Accessed: 10.08.2010]

    Novaquatis – a cross-cutting Eawag research project was concerned with urine source separation as a new element in wastewater management.

  • http://www.saniresch.de/ [Accessed: 10.08.2010]

    This is the main homepage of the SANIRESCH project (SANItaryRecycling ESCHborn) which focuses on the treatment and recycling of the urine, brown- and greywater collected at the headquarters of the German Technical Cooperation (GTZ) GmbH in Eschborn, Germany.