Urine-diverting dry toilet

Double-vault UDDT, waterless urinal and shower integrated into a household's bathroom in non-sewered area of Lima, Peru

A urine-diverting dry toilet (UDDT) is a type of dry toilet with urine diversion that can be used to provide safe, affordable sanitation in a variety of contexts worldwide. Through the separate collection of faeces (feces) and urine without any flush water, many advantages can be realised, such as odour-free operation and pathogen reduction by drying. While dried faeces and urine harvested from UDDTs can be and are routinely used in agriculture (respectively as a soil amender and nutrient rich fertilizer - this practice being known as resource recovery), many UDDTs installations do not make use of any sort of recovery scheme. UDDTs are often considered a good example of a sustainable sanitation option because with UDDTs it is relatively easy to satisfy the five sustainability criteria of sustainable sanitation to a quite high degree, in particular with regards to environmental, technology and operation as well as financial and economic sustainability factors.

A UDDT can be configured as a sitting toilet (with a urine diversion pedestal or bench) or as a squatting toilet (with a urine diversion squatting pan). The most important design elements of the UDDT are: source separation of urine and faeces; waterless operation; and ventilated vaults (also called "chambers") or movable containers for faeces storage and treatment. UDDTs may be constructed with two dehydration vaults that are used alternately or one single vault into which interchangeable containers are placed. The UDDT is a dry excreta management system (or "dry sanitation" system) and can be an alternative to pit latrines and flush toilets in certain contexts where they are particularly suitable.

Various types of cover material, such as ash, sawdust, soil, sand, dried leaves, lime, compost can be added to the faeces chamber of a UDDT. Addition of one or more of these materials acts to reduce odour and to speed up the drying process. If anal washing takes place with water (applies to people called "washers") rather than by using toilet paper (people called "wipers"), then this anal washwater must be drained separately and not be allowed to enter the faeces vault.

UDDTs are often equated as being synonymous with the approach to sanitation known as ecosan (ecological sanitation) or with composting toilets. However, neither of these associations are accurate or acceptable due to the fact that not all UDDTs  are used in conjunction with  the practice of reusing excreta and many times any composting that takes place in conjunction with the use of UDDTs occurs outside of or separate from the structure of the toilet itself.

Terminology

Schematic of the dehydration vaults of a UDDT with two vaults

UDDT at Gebers collective housing estate near Stockholm, Sweden

Double vault UDDT used in squatting position in Ouagadougou, Burkina Faso

3-hole urine diversion squatting pan to accommodate anal washing in Krishnagiri District, Tamil Nadu

Exchanging the faeces container of a low-cost single vault UDDT at a household in Addis Ababa, Ethiopia

An alternative name for a UDDT is "urine diversion dehydration toilet", or "urine diversion desiccation toilet", although with this term more emphasis is placed on the process of dehydration in the vault of the toilet and it should only be used to describe UDDTs that feature two vaults or for UDDTs that feature a built-in electrical fan.

This type of toilet is also called by many people an "ecosan toilet" as this name is quite easy to communicate at the local level with potential users. However, the term ecosan is in fact much broader and not limited to this type of toilet.

Urine-diverting composting toilets are similar to UDDTs as they collect urine and faeces separately. However, treatment is achieved through the composting process, which is a process quite different from pathogen removal by dehydration.

Appropriateness

UDDTs are particularly suitable in situations where:

1. Water is scarce or costly, such as in arid or semi-arid climates; 
2. Sewerage infrastructure costs are prohibitive, such as instances of unfavourable terrain, sprawling settlement patterns or poverty;
3. Frequent flooding would impact pit latrines and septic tank systems, resulting in inoperable toilet systems and the contamination of water resources;
4. Unfavourable soil conditions, such as unstable or rocky soil and high water table, make pit-based sanitation difficult and expensive;
5. Groundwater is the primary source of drinking water and is likely to be contaminated by pit-based sanitation;
6. Limited land space restricts the excavation of new pits if full pit latrines are usually not emptied;
7. Indoor installations are preferred as they provide greater comfort and security at night thus making them more accessible for all;
8. Local agriculture and diminishing soil fertility create demand for affordable fertiliser and soil conditioner.

Furthermore, in the case of developed countries, UDDTs can also be suitable in situations where:

• An individual, family or community wants to increase the resilience of their existing sanitation system in the face of possible natural disasters (i.e. climate change, earth quakes) or possible rising energy prices; and
• Following approval by local building inspectors and health department authorities, an individual or family seeks to reduce or perhaps eliminate the need for a septic tank system to reduce their environmental footprint (particularly when the UDDT is used in conjunction with an on-site greywater treatment system).

UDDTs can also be built for schools (many examples exist for example in Kenya, Rwanda and Uganda). However, these school UDDTs suffer from the same issues as any other type of school toilets related to the maintenance of the school toilets: If clear responsibilities and a dedicated budget for school toilets' maintenance is lacking, then the toilets may easily fall into disrepair, e.g. with blocked urine pipes or faeces vaults that are not being emptied.

Design considerations

2-hole (pink) and 3-hole (blue) urine diversion ceramic squatting pan from Indian NGO EEDS

Fundamentals

Urine diversion takes advantage of the anatomy of the human body, which excretes urine and faeces separately. In a UDDT, the urine is drained via a basin with a small hole near the front of the user interface, while faeces fall through a larger drop-hole at the rear. This separate collection – or "source separation" – does not require the user to change positions between urinating and defecating, although some care is needed to ensure the right position over the user interface. Female users may find that some urine may enter the vault during normal operation. This is typically a small amount and does not significantly affect the function of the toilet.

Designers and users of UDDTs should strive to keep the faeces pile as dry as possible as this is the key factor in prevention of odour and flies. During storage, the faeces’ natural moisture slowly evaporates and is exhausted through the vault’s ventilation system, or is absorbed by the dry cover material. This process is called dehydration.

A UDDT consists of eight basic functional elements:

1. Urine diversion toilet seat or squatting pan;
2. One or two faeces vaults (also called "chambers"; with or without removable containers), usually above ground, or one shallow pit for faeces collection and storage;
3. Urine piping system leading from the user interface to an infiltration or collection system;
4. Ventilation pipe to exhaust moisture and odours from the vault or pit; 
5. If required: An anal cleansing area with mechanisms for the separate collection and drainage of anal wash water; 
6. Toilet super-structure, unless the toilet is installed inside an existing house or is of the standalone or portable variety;
7. Bucket with dry cover material (see below);
8. Hand washing facility with soap and water - like any other toilet should have. 

Bench design

UDDTs can also be built with a bench style toilet seat. This design has been standardised by the company Rotaria del Peru who have built by now 800 double vault bench UDDTs in and around Lima, Peru. This type of toilet has a wide, spacious bench or box, covering both faeces chambers, into which two urine diversion toilet seats are integrated.

Users with disabilities can benefit from this kind of design as it is very sturdy (compared to the option of a chair or commode over a pit latrine). The wide bench provides space for an assistant if needed, and handrails can easily be fixed to the walls next to the toilet. Most importantly, this type of UDDT is accessible directly from the ground level and does not require access steps or ramps unlike conventional raised UDDTs.

Waterless urinals

UDDTs are often installed alongside waterless urinals particularly in lavatories or bathrooms frequented by male users. This is done for the convenience of male users and to address the problem of male users standing over the UDDT to urinate and inadvertently directing urine into the faeces vault or faeces container.

Accessibility

UDDTs are sometimes built with very steep stairs without handrails which is not recommended as it could leave people with disabilities struggling to access even the door of the toilet. The needs of people with disabilities should always be considered and less steep stairs or ramps should be used. The bench design UDDT can even completely overcome the need for stairs.

If a squatting toilet is built, it can be useful to add handle bars for holding onto for people who need support while squatting. For people with disabilities who need physical support while squatting, particularly when cleaning afterwards, a portable seat can be placed on the squat toilet to allow people to sit. When not needed, it can be placed out of the way.

Designs for flood prone areas

In flood prone locations faeces containers or vaults should be located above the flood water levels. If this is not feasible, it is possible to use ferrocement walls to keep the flood waters out. Urine can be collected in tanks or it can seep away into the ground where it gets at least some basic treatment before reaching the groundwater and eventually other surface water in the environment.

Source of UDDT components

The toilet bowls or squatting pans for UDDTs can be commercially manufactured from plastic or ceramic and transported to the user. Alternatively, they can be built locally out of concrete at the users' premises by local companies, NGOs or artisans. Complete UDDT toilet solutions (with or without in-built electrical fans) made of plastic are also commercially available.

Urban multi-storey buildings

Faeces collection chutes in the basement below the UDDTs that are on the different floors of a multi-storey building in Erdos Eco-Town, China

UDDTs can also be installed in urban multi-storey buildings although this has only been implemented successfully in very few examples. It currently still requires rather committed, "eco-minded" users such as those living in the Gebers collective housing estate in Orhem, Sweden. In another large-scale urban housing project for 3000 residents in multi-storey buildings in China where this has been attempted, the UDDTs were removed after a few years due to several technical and non-technical challenges. This project was called the "Erdos Eco-Town Project" and was in a town called Erdos in the Inner Mongolia Autonomous Region of China. Urine-diverting dry toilets (with bins in the basement), greywater treatment facilities, solid waste composting and the reuse as a fertiliser in the agriculture were implemented during 2003-2009 with the aim to reduce the impacts of the water scarcity in Erdos City, Inner Mongolia. This project is well documented and has raised more awareness of the challenges and disadvantages of UDDTs in multi-storey buildings.

The plumbing pipework for the urine pipes and the ventilation system needs a high level of engineering and skilled workers who follow the designs accurately. In the example of the Erdos Eco-Town Project there were problems related to air pressure differences caused by high winds, open bathroom windows and kitchen air fans that caused ventilation abnormalities. Furthermore, the frozen ventilation pipes which caused havoc during the extremely cold winters of 2007 and 2008 were mainly caused by lack of pipe insulation in the attics and above the roof, an item lacking in the building codes in China. The main reasons for why this UDDT project ran into problems were:

• Lack of a dedicated owner who would feel responsible for solving maintenance issues.
• Water shortage was – at least temporarily – no longer a problem since the pipeline was built to the Yellow River and deeper fossil water resources were extracted.
• The standard of living in the Erdos area rose dramatically during the project. Dry toilets were considered by some residents as something backward in a modern urban setting.
• The odour problems during the extreme cold winter of 2007 acted as a negative tipping point for the project.
• A stakeholder approach among tenants to encourage early participation and learning in use and maintenance of the UDDTs was not possible, since the tenants arrived on the scene as buyers after the apartments were built.
• The household committee stated to the local government that they were not capable of taking on the costs of continuing the scheme, and the District Governor responded by investing in the flush toilets.

Major types

Single vault construction

UDDTs with a single vault have interchangeable containers to collect the faecal material. Depending on the size of the vault, two or more containers can be stored inside. Containers should be limited to a maximum volume of 50 litres, so that they still can be manually moved when they fill up. Once a container is full, it can be left for further dehydration or removed for further treatment. Removing of the container has to take place carefully due to fresh, potentially pathogen-loaded faeces being on top of the pile in the container. Because of the limited ventilation within the container, single vaults cannot reduce the pathogen load as effectively as double vaults. Therefore, a post-treatment of the faecal material is usually required. This can be achieved through further dehydration, composting processes or heat treatments.

Double vault construction

In double vault UDDTs the faecal material dehydrates in situ. The two aboveground vaults are used alternately. While one vault is filling up, the other (full) one stores the faecal material under dry conditions for at least six months. No fresh faeces is allowed to be added to the vault that is resting during that dehydration process. In order to switch from one vault to the other, the user interface can either be switched or both vaults can be equipped with fixed seats. When the second vault is full, the first one is emptied with a shovel. The vaults are commonly sized so that one vault fills up in six to 12 months.

Health aspects

During normal use, this type of toilet is just as hygienic and safe to use as any other type of toilet. Health aspects need to be considered during emptying of the urine and faeces containers of a UDDT. Here the health risks for the person doing the emptying are significantly lower compared to the person having to empty the pit of a pit latrine. but they are higher compared to the situation of a flush toilet where the user does not have to carry out any emptying tasks at the household level.

With regards to health risks during reuse activities, the World Health Organisation's guidelines' from 2006 called “Guidelines for the safe use of wastewater, excreta and greywater in agriculture” explain how to manage the health risks associated with the use of excreta in agriculture. The key concept of these guidelines is the multiple barrier approach which can also be applied to reuse activities in connection with UDDTs.

Dried faecal matter from UDDTs after external composting, now ready for reuse (Addis Ababa, Ethiopia)

Usage

Wiping

For wiping of the anal area the users can use whatever they use normally when using other types of toilets as well. Suitable biodegradable materials available in the surroundings can also be used, such as leaves, corn cobs or sticks. This material decomposes together with the faeces. For example in Ecuador the soft, perfumed leaves of Piper auritum, Piperaceae and Melastomataceae are being used. Users have also used stones, although this makes the vault fill up very fast and is therefore not practical for UDDTs.

Anal washing with water

UDDTs can accommodate users who prefer anal cleansing with water by utilising either a three-hole urine diversion squatting pan or an area and drain next to the urine diversion pedestal where washing can take place - away from the urine and faeces holes. This is important as not to contaminate the urine and to keep the faeces as dry as possible.

Due to the faecal content of anal cleansing water, it should be considered a waste stream and treated or disposed of safely. Anal cleansing water can be drained into a soak pit, planted mulch bed or an infiltration trench. The anal cleansing water should be discharged into coarse material below the ground, but well above the water table to avoid groundwater pollution.

In some designs, the users are advised to do their anal cleansing above the urine compartment for simplicty reasons in order to avoid the need for a third drain pipe. This is possible provided it is clear to everyone involved that the mixture of urine and anal cleansing water requires further treatment to remove pathogens before it can be safely applied in agriculture.

The water supply for anal washing with water could be with a hose if piped water supply is available, from a sink with an overhead tank filled with rainwater, or from a water bottle or jug that the user carries into the toilet cubicle.

Cover materials added

For most UDDT types, users are encouraged to add a cup or scoopful of cover material atop fresh faeces for the following purposes: to promote dry conditions in the faeces vault, control odour, prevent infestation of flies and to create a visual barrier for the next user. Cover material can help to ensure good airflow through the pile of drying faeces. For this reason bulky or fibrous material that is dry and that decomposes slowly is recommended. All sorts of cover materials can be used, depending on what is readily available:

• Leaves are good, but intact they are too coarse to cover the faeces properly to keep flies from getting in and odour from getting out.
• Sawdust works and can smell nice, depending on the tree species.
• Rice hulls are suitable in areas where rice is grown.
• Soil is excellent, abundant and nearly universally available.
• Wood ash as a cover material is appropriate but might be not available in sufficient amount.
• Lime can be used but the environmental impacts through mining, processing and transporting should be considered. Ash and lime both have the advantage of raising the pH value in the faeces pile, thus adding to pathogen kill.
• In cases where the faeces are treated further in a composting process, it can be beneficial to select the cover material carefully in order to not only cover the faeces but also to inoculate them with beneficial soil microbes. In that case, finished compost could be used as cover material, although it is important that the users either do not touch this cover material with their bare hands or that the composting process is so well controlled that there are no remaining pathogens in the material.

No cover materials added

In some cirumstances and for reasons of simplicity, it can be sufficient to not use cover materials at all or to use the toilet paper itself as cover material. One example is the case where the UDDT has a mechanised ventilation system and a view guard, like the UDDT manufactured by Separett which has a removable bucket, in-built fan and blue plastic view guard which closes as the weight from the toilet seat is lifted after use. Also in the case of public toilets, it can be easier to let the caretaker do the adding of cover material, rather than the user. An example of this are the public single vault UDDTs operated by the not-for-profit company Sanergy in low-income urban areas in Kenya.

Sitting or squatting

UDDTs can be built as sitting or as squatting versions to accommodate the users' preference of defecation posture. Some people prefer squatting UDDTs in public places (thought to be more hygienic) but sitting UDDTs for households (thought to be more comfortable). It may be preferable to squat instead of sitting for colon health, although this is not specific for UDDTs but may refer to any type of toilet.

Treatment and reuse or disposal of faeces and urine

Dehydration process for faeces

During the dehydration process moisture is evaporating from the faeces and microbes are degrading the organic material. It is the dry conditions and the storage time that lead to the decline of pathogens in the faeces. Fresh faeces consist of about 80% water and in the drying process, the water content of the faeces reduces. The water content of dried faeces after six months of drying is usually less than 25%. Depending on the degree of drying and the intended reuse application an additional post-treatment step, such as composting, might be necessary for reuse in agriculture.

Post-treatment of faecal matter for reuse in agriculture

The dried faeces are in almost all cases not entirely sanitised when removed from the vaults of the UDDT, so careful handling is obligatory. In scenarios with reuse of excreta in agriculture, a post-treatment of faecal matter and storage of urine is advisable to ensure adequate sanitisation. Faecal material from single vault UDDTs must always be post-treated. Material from double vaults has passed a certain storage time and is therefore already more sanitized. However, a post-treatment is optional but recommended for household systems and required for large-scale systems.

Post-treatment is usually done at community level rather than at household level and can include thermophilic composting where faecal material is composted by over 50 °C, prolonged storage with the duration of 1.5 to two years, chemical treatment with ammonia from urine to inactivate the pathogens, solar sanitation for further drying or heat treatment to eliminate pathogens.

Reuse of treated faecal matter in agriculture can result in increased crop production through fertilizing effects of nitrogen, phosphorus, potassium and improved soil fertility through organic carbon.

Treatment and reuse of urine

Urine is almost sterile and therefore does not require a time-consuming treatment by storing it for a long time, unless cross-contamination with faeces has taken place. Urine from the UDDTs can safely be used as nitrogen-rich and phosphorus and potassium containing fertiliser after a recommended storage period for pathogen kill (or without storing if it is used in the garden or field of the same household where it was generated).

Infiltration of urine

In cases where no reuse is possible or desired, urine is usually infiltrated in the soil unless this would cause groundwater pollution, for example with the UDDTs in eThekwini municipality in South Africa or the UDDTs in Lima, Peru. This can be done by directing the urine to a soak pit or by running a perforated urine pipe from the toilet to an area outside, where the hose is sloping gently downhill (for rural areas). Clogging of the pipe's holes can be avoided by ensuring there are no T-junctions, no joints and a plastic mesh is installed in the urine funnel of the toilet to keep everything other than urine out.

Advantages

Very simple home- made design for a UDDT with a funnel for urine collection and a bucket for faeces collection at a household in Addis Ababa, Ethiopia

Comparison with pit latrines

Reasons for keeping urine and feces separate in a UDDT compared to a pit latrine can be to:

1. reduce odour (a mix of urine and faeces causes substantial odour);
2. avoid production of wet, odorous faecal sludge, which has to be removed by someone when the pit latrine is full;
3. enable fast drying of faeces which makes handling of faeces more simple and hygienic;
4. reduce environmental impacts;
5. allow for the recovery of urine, which can be reused as fertiliser.

The advantage of UDDTs compared to pit latrines is the conversion of faeces into a dry odourless material and therefore a complete avoidance of the issues surrounding faecal sludge management. A well-maintained UDDT is an odour and insect free toilet which is appreciated by users and allows simple removal and less offensive and safer handling of the faecal material once the faeces vault has filled up. Moreover, the risk of water pollution is minimised through the safe containment of faces in aboveground vaults and this allows the toilets to be constructed in locations where pit-based systems are not appropriate.

UDDTs are also more permanent structures than most pit latrines which are typically relocated in rural areas when the pit is full instead of emptying the pit. Therefore, pit latrines need more space and people are less willing to invest in a higher quality super-structure as it will have to be dismantled and moved at some point.

Comparison with sewer-based sanitation

The comparison of UDDTs with sewer-based sanitation systems (sewerage and wastewater treatment plants) is not as straight forward as the comparison with pit latrines as a sewer does not only deal with excreta management like a UDDT does, but it also transports and treats greywater, municipal wastewater, stormwater and industrial wastewater. Obviously the installation of UDDTs in all households of a catchment would lead to reduced quantities of water, nutrients and organic matter arriving at the wastewater treatment plant.

Sewer-based excreta management is in any case impractical in many regions due to limited water supplies and the high cost of sewer systems and wastewater treatment plants. Furthermore, water-based sanitation systems (flush toilets) dilute excreta and create larger wastewater streams which UDDTs do not.

Decentralised sanitation systems which employ UDDTs offer the potential advantages of quick deployment (especially where there is no capable centralized institutional infrastructure in place or no financial ability to implement larger centralized systems) as well as greater local control.

Policies could encourage their development through: financial support of research programmes, enactment of regulations that require the recovery of resources from wastewater and adequately account for the reduced contaminant loading and incentives for resource recovery.

The separate, waterless collection of urine and faeces in UDDTs would prevent hormones and pharmaceutical residues (micro-pollutants which are contained in human excreta) entering drinking water sources via household wastewater (sewage), as such substances are not fully removed in conventional wastewater treatment plants. With sewer-based sanitation systems, the micro-pollutants hormones and pharmaceutical residues are not removed in conventional sewage treatment plants and are thus discharged into surface water bodies and can even reach the groundwater (detected concentrations of pharmaceutical residues in groundwater are in the order of 50 ng/L in several locations in Germany). If the excreta from UDDTs is treated further and then used as fertiliser then the pharmaceutical residues in the excreta will be degraded better in the soil because "Terrestrial systems (soil) are more suitable for natural degradation of pharmaceuticals than aquatic systems." Therefore, UDDTs (or in fact all urine diversion systems) have a certain advantage over sewer-based sanitation systems in this respect.

Disadvantages

School UDDT in rural areas of Western Kenya; the steep stairs are not recommended as they are a barrier for people with disabilities

General hurdles

Significant barriers to more universal acceptance of this technology include in the case of developing countries: lack of awareness, a limited supply of prefabricated UDDT components and a low interest in financing sanitation services for non-sewered areas of settlements. It is important for any type of sanitation system selected that it fits into an existing legal framework and that it has support at the local policy level amongst the various government departments affected.

Many users do not have an interest in handling their excreta which is understandable. Therefore, provisions should be made for door-to-door/curbside collection of these materials, similar to how existing municipal or private schemes collect household organic waste (from kitchens and gardens, etc.) and transport it to a centralised facility for composting or biogas generation.

Comparison with pit latrines

Disadvantages of UDDTs compared to pit latrines include: higher capital costs (although whole-of -life costs might be lower), more awareness required by the user who has to use it properly (no urination into faeces compartment) and react appropriately when the urine vessel is full (or there are problems with the urine soak pit), the urine pipe is blocked or the faeces vaults or containers are full.

Comparison with sewer-based sanitation

One disadvantage of a sanitation system with UDDTs - and perhaps even with resource recovery in agriculture - compared to a conventional sewer-based system is that it requires greater coordination and cooperation amongst stakeholders from different sectors.

Costs

UDDTs have been criticised for being too expensive compared to pit latrines. However, rather than looking only at the construction cost, the whole of life cost (or life-cycle cost) should be considered, as the regular emptying or re-building of pit latrines may add a significant expense to the households in the longer term. When a period of for example 10 years is considered in the analysis, UDDTs may well be the more economical alternative as emptying the faeces vaults is very simple and therefore low cost, even if the households decide to user an external service provider for this activity (if such a service provider exists already).

Compared to flush toilets connected to sewer systems and wastewater treatment plants, UDDTs are often thought to be cheaper. However, this needs to be assessed on a case-by-case basis because the two systems provide a different level of service (the sewer system also treats greywater whereas the UDDT does not); an example calculation exists for the case of Lima, Peru.

History

The UDDTs with double dehydration vaults that we know today were originally designed around 1950 in Japan and further developed in Vietnam in the 1960s as a means of increasing the hygienic safety of excreta reused in agriculture. This means their development was originally closely linked to the ecosan (ecological sanitation) approach to optimise resource recovery of nutrients and organic matter in agriculture. Later, from about the early 2000s onwards, UDDTs have been seen more and more as a toilet type that can also be advantageous to use without any reuse activities attached to it.

Since the 1990s, modifications of this design such as addition of ventilation pipes to the faeces vault have been developed in many countries. Prefabricated ceramic or plastic urine diversion squatting pans and pedestals have become available on the market, generally increasing the durability and perceived prestige associated with the system.

UDDTs have also been commercially produced in Sweden since the mid-1990s for example by the company Separett who have sold approximately 200,000 UDDTs between 1994 and 2010. Such off-the shelf commercial products are now also available in Do-it-yourself shops and are used in locations where piped sewerage is not available, such as remote summer cottages in Sweden or for camping activities.

Society and culture

Floor and roof of a low-cost UDDT in Ecuador

Demonstration of how this low-cost UDDT in Pumpuentsa, Ecuador would be used

Number of users worldwide

The exact number of UDDT users worldwide is impossible to determine, but a rough estimate by GIZ (German Development Cooperation) in 2012 based on known projects in 84 countries put the number at approximately 2 million users worldwide.

Examples

South Africa (eThekwini Municipality, Durban)

The highest number of UDDTs in one area have been installed by the eThekwini Municipality in the non-sewered peri-urban areas of Durban, South Africa. To date, about 80,000 UDDTs are in operation in that area, serving about 500,000 residents (reuse of urine or excreta is not taking place).

Haiti

The NGO SOIL in Haiti has built UDDTs and composting treatment plants in Port-au-Prince as part of the 2010 Haiti earthquake emergency relief effort and in northern Haiti. Their current design for households in Haiti is a small portable single vault unit made out of wood with a bucket for faeces collection. In fact, SOIL has in 2014 transformed all their old UDDT vault toilets to an open vault design with a removable plastic drum to collect excreta on a regular basis and transport to their waste treatment facility, therefore making it into a “container-based system”. This allows SOIL to respond to heavy use (their toilets were filling up too quickly) and ensure a safe final product for reuse.

SOIL "Poopmobile" delivering buckets of human extra from mobile household UDDTs to the SOIL composting facility in Port-au-Prince

SOIL continues to provide humanitarian relief in some of Haiti’s most vulnerable communities – notably those that have been particularly impacted by the cholera epidemic – by providing free access to public container-based UDDTs for over 3,500 people. In addition, over 2,500 people are currently accessing a SOIL "EcoSan toilet" through the "EkoLakay" business pilot, with another 500 waiting to join, thus demonstrating the market demand for affordable sanitation in even the world’s most impoverished communities.

Since building the first waste treatment facility in Haiti in 2009, SOIL has become one of the largest waste treatment operations in the country: SOIL’s two composting waste treatment facilities currently transform over 20,000 gallons (75,708 liters) of human waste into safe, organic, agricultural-grade compost every month. The compost produced at these facilities is sold to farmers, organizations, businesses, and institutions around the country to subsidize the cost of SOIL’s waste treatment operations.

Ecuador

Hundreds of UDDTs have been built in Ecuador, with various models adapted to different conditions, preferences, and budgets. There is even a minimalist model that costs essentially nothing and could be implemented by the poorest people for example in rainforest regions of Ecuador and for people affected by emergencies.

Boating and camping

• For the boating community, it can also be an interesting alternative to convert from conventional nautical toilets that store waste in black water tanks, or immediate discharge overboard, to a UDDT. Such UDDTs for nautical use are for example marketed in the US under the names of Nature's Head and Air Head Toilet.

• Camping - Leave no trace is not only a philosophy but a necessity in areas where human waste left behind would not decay naturally. There are now portable UDDTs available for example by the Swedish company Separett that allow feces to be collected and packed out. Only urine is left behind which is of less concern as urine is nearly pathogen free.

Other examples

• The NGO Women in Europe for a Common Future (WECF) and local partners have built many urine-diverting dry toilets for schools in Eastern Europe, Caucasus and Central Asia (EECCA region).
• NatSol, a UK company that specialises in urine diverting dry toilets, has developed a solution that avoids the usual problems of blockage and fouling of urine separating bowls. It uses the Coandă effect to divert and send urine to a soakaway, rather than rely on evaporation.
• In Namibia, UDDTs are known under the name of Otji toilets.
• More examples of installations of UDDTs in developing countries is available in 45 case studies of the Sustainable Sanitation Alliance that describe projects with UDDTs.

External links

• Documents on UDDTs in library of the Sustainable Sanitation Alliance
• UDDT photos in flickr photo database of the Sustainable Sanitation Alliance