Double vault Urine Diversion Dry Toilets (UDDT) can be used as an alternative to pit latrines in refugee camps. They utilise two chambers for faeces, one of which is in use whilst the other is full and drying so that it can be safely disposed of after an appropriate period of time.
Advantages of UDDTs compared to pit latrines:
- UDDTs can be used indefinitely, which can result in them being more economical than pit latrines which need periodic replacement every two - three years.
- UDDTs are built above ground, which makes the especially suitable for rocky areas, collapsing soils, or high water tables.
- UDDTs do not smell, which is a frequent problem with pit latrines.
- UDDTs are relatively easy and safe to empty using only a spade, and much easier to empty than pit latrines.
The design philosophy of the UDDT in these standard operating procedures has been to balance cost, ease of construction, and user acceptability. The aim is to have a design that can be easily rolled out to thousands of households in a camp setting. The design does not require specialists to build and uses local or readily available materials and construction methods. The construction costs are comparable to that of a household latrine. The design has been tested at scale in Refugee Camps in the Somali and Gambella Regions of Ethiopia.
This is the second edition of the standard operating procedures for camps, based on additional learning from Gambella as the programme progressed. The first edition of these Standard Operating Procedures were developed by Oxfam under UNHCR’s “Waste to Value” Project, which was funded by the Bill and Melinda Gates Foundation. They were largely based on UDDTs developed under the Waste to Value Project in Jewi refugee camp in the Gambella Region of Ethiopia, as well as those developed previously by Oxfam and the Norwegian Refugee Council in Melkadida Refugee Camp in the Somali Region of Ethiopia.
A variety of different designs can be used for collecting and separating the urine and faeces. The design used here is a simple squatting pan design that is likely to be suitable for many parts of the world and is relatively easy to form using cement. Other options include seated versions and pans with separate holes for urine and anal wash water.
There is a wide range in the quantity of faeces that one person produces, from 44 to 146 kg per year (Rieck et al, 2012). However, faeces are 80% water and after some months this moisture content will have reduced significantly. The density of UDDT contents has been measured as between 1,350 and 1,450 kg/m3 (Strande et al, 2014). The design in this document has a vault size 80 x 80 x 80 centimetres, which is approximately 500 litres (0.5 m3), which may be adequate for a five person household for twelve months. An example sizing is below, based on The Technology Review of Urine-Diverting Dry Toilets (Rieck et al, 2012):
Faeces Quantity 2 Adults 0.4 kg/p/day = 0.80 kg/day 3 Children 0.15 kg/p/day = 0.45 kg/day Whole Family = 1.25 kg/day = 456 kg/year Moisture loss -25% = -114 kg/year Cover material 0.1kg/p/day = 180 kg/year Factor of safety 20% = 131 kg/year Total design weight = 655 kg/year Required vault volume (@1,450 kg/m3) = 452 litres
The doors on the vaults must be secure and seal well to keep the contents safely contained, prevent the ingress of rainwater and keep the inside of the vault dark and less visible to the user. For this reason painted steel doors are used – they are robust, secure, and can be easily fabricated. Alternative, low-cost designs are unlikely to be adequate.
A risk of using steel doors is corrosion. As such, a removable barrier should be used inside the doors to prevent faeces inside the vault from resting against the door. This could be wooden planks, or concrete blocks loosely placed inside.
Inclined Vault Doors
A solar UDDT uses inclined vault doors to absorb more solar radiation, resulting in higher temperatures and faster drying of the vault contents. However, Winderberg & Otterphol (2016) found that solar UDDTs are not necessarily effective and recommended the construction of non-solar UDDTs. Rieck et al (2012) also rec-ommend non-solar UDDTs, additionally citing the more complicated construction and increased likelihood of rainfall intrusion with solar versions. This design is for a non-solar UDDT with vertical vault doors.
After each use of the toilet a cup – approximately 200 ml, or enough to completely cover the fresh faeces – of cover material is poured in the vault over the faeces both for aesthetic purposes and to eliminate smell and flies. This cover material can be ash, dry soil, or sawdust.
The urine is disposed of into a soakaway as the alternative, collection and reuse, requires intensive management. The size of the soakaway should be adjusted to local conditions, and an infiltration test may be required to optimise this. Using stones rather than aggregate means that there is more space for potential detritus before it backs up into the urine pipe. The soakaway pit does not need a cover, but the urine pipe should extend below the surface.
Preventing Blockages of the Urine Pipe
There is a high probability of the urine pipe blocking unless properly designed and built. The following recommendations are a direct result of problems experienced, and later resolved, in Gambella:
- The pipe to the soakaway should not be less than 2” (50mm).
- The pipe must slope downwards along its whole length, and experience has shown that it is better if this is at a 45 degree angle.
- Do not economise on the strength of the pipe, and to use the toughest pipe locally available.
- At the entrance to the pipe either mesh or a floor drain should be used to prevent detritus entering (Figure 2).
- The design of the squatting pan must minimise dust or dirt entering the urine pipe.
After six to twelve months inside the faeces vault, the contents should be inoffensive (virtually odourless and with no visible live insects etc) and have significantly reduced pathogen load. This happens through a combination of dehydration, increased temperature and increased pH. At this point the vaults are safe to empty, so long as precautions are maintained.
CDC Study on Pathogen Reduction in UDDT Vaults
The Centre for Disease Control (CDC) in Atlanta, USA, conducted a study on UDDT toilets in Hiloweyn Refugee Camp, Ethiopia. They tested the contents of the vaults of several UDDTs for meeting the 2006 WHO Guidelines for Safe Agricultural Reuse for Agriculture. These guidelines are conservative if the waste is disposed of rather than reused, but there are no other guidelines available for this. The study found that UDDTs in dry, arid, hot environments like Hiloweyn have the capability to meet the WHO guidelines after 12 months of storage, although this is not guaranteed. CDC concluded that “findings indicate that the UDDTs in Hiloweyn camp could be managed on a 12 month emptying cycle, as the program planned, with care to ensure appropriate precautions are taken to prevent exposure during waste handling and in a secondary storage site location.”
View the Full Report
Stairs and accessibility
UDDTs are raised above the ground and require stairs to access them. To ensure ease of access the height gap between steps should be kept small, and a handrail may need to be added.
For wheelchair users other types of latrine may be considered, as the complexity and cost of adapting a UDDT for wheelchair users is likely to be prohibitive.
Adapting for Local Conditions
The design should be adapted according to the local context. The superstructure in particular should use typical construction materials and methods for the context, ensuring that the solution provides privacy and security for users. A roof is normally required to prevent precipitation, but in particularly dry climates could be omitted. Other parts of the UDDT could also be changed depending on the context, and The Technology Review of Urine-Diverting Dry Toilets (Rieck et al, 2012) provides a good overview of potential alternatives.
Ensuring the correct use of a UDDT is a much more involving endeavour than for a ‘standard’ pit latrine, thus a person experienced in engaging with communities must be involved throughout implementation. A good knowledge and understanding of community engagement techniques is a pre-requisite, and a comprehensive community consultation process should promote a sense of ownership and trust in the UDDTs.
From a user’s perspective one of the key selling points is that UDDTs have no flies and do not smell when used properly.
1. Awareness creation on Urine Diversion Dry Toilets
Prior to construction, community meetings should be organized to share information about urine-diversion principles, benefits and the proposed implementation of the UDDTs. These community meetings should provide a forum to identify and dispel rumours and myths associated with the latrine (based on culture), and offer feedback to any questions and concerns that the proposed users may have. Depending on the context, it’s advisable to have flyers with pictures of the UDDTs or a demonstration toilet where the community can see the actual structure.
Ideally, meetings with opinion leaders such as community leaders, teachers or health incentive workers should be conducted first; but all members of the community must be involved afterwards: men, women, youth, and people with disabilities. During the discussions, enough time should be allowed for questions and answers to make sure the community digest the idea and express any fears or concerns they may have. Involving these stakeholders from the onset of all discussions regarding UDDTs will not only ensure sustainability, but can also teach new skills and broaden awareness about health and hygiene issues.
If the UDDT is accepted by the community, the next step is to discuss how they’ll be actively involved in problem solving, planning and decision making and as far as possible, taking responsibility for the toilets. Participation enables the community to shape the project so that it works for them.
2. Training of community including community mobilisers to help with follow-up
Community engagement must be led by people from within that community for it to be effective. While creating awareness, the team from the implementing agency should identify (with the help of leaders), people that will be good community mobilisers. Ideally these people should be literate, with good communication skills and females. It’s advisable to use existing community mobilisers (if any), because they’re well known to the community. The number of community mobilisers will depend on the context – for instance; 2 mobilisers were found to be ideal for a block with 128 households in Jewi Refugee Camp in Ethiopia. Through the community mobilisers, the team should mobilize the community for training while construction goes on. Training should be provided directly to users on appropriate use and maintenance of the UDDTs, including proper explanation of any anticipated re-use of the by-products.
3. Community forums to train and support proper use
As soon as the construction of the latrines is completed, a handover ceremony to the community should be conducted. This event should include distribution of NFIs essential for proper use and maintenance of the UDDTs and practical demonstrations on how to use them, on squatting to use the urine & faeces holes, respectively, anal cleansing (if applicable), addition of ash, cleaning excess ash with broom before leaving the latrine and washing hands with soap as the final step. These community forums should be segregated by sex to encourage users to participate without inhibition.
4. Routine follow-up
The community outreach agents should carry out routine follow-up on the use of the UDDTs using both focus group discussions and house-to-house visits. The frequency of the meetings/visits will largely depend upon the distance between households. For instance, in a refugee camp setting where 16 households make 1 community (Ethiopia), the best practice is to conduct house-to-house visits in the morning (say from 9 – 12 noon) to observe on-going practices and then conduct a discussion with same household owners in the afternoon (say 3-4pm) on challenges they could be facing or areas that need improvement. This is because one community has 8 HHs on a single stretch opposite another 8 households, sharing a common sanitation corridor. With appropriate skills and practice, it’s possible to conduct a house-to-house visit in an average of 10 minutes (all 16 HHs will take less than 3 hours) and the afternoon focus group discussions in less than 2 hours.
The routine follow-up should focus on sharing the key information as well as the linkage to the proper use of the NFIs provided. For example, UDDT requires one vault to be used at a time - the observation during house-to-house visit should check that there is one vault, with a concrete cover slab, that is not in use and another vault, with a easily moveable cover, that is in use. Observation of the pit in use should confirm that ash is visible, and the latrine should be visibly clean and without noticeable odors or flies.
Key aspects for community engagement
- Provide correct and accurate information on UDDTs including expectations regarding contribution towards construction, operation and maintenance.
- Consult targeted households on the items to be included in the latrine cleaning kits – especially the appropriateness in relation to cultural beliefs.
- The requirements of men, women, young people, children, those with special needs and disabilities in relation to UDDT will be different. Therefore, consult these groups of people and address their needs as much as possible within budget limitations.
- Prioritise the right messages, reinforcing doable, practical and evidence actions, tailored to community member’s information gap (based on monitoring over several months of use of the UDDTs by the community)
User Operation and Training
Items to be distributed with the UDDTs
To facilitate proper use of the UDDTs, several items should be distributed during the handover process. These may be contextualized but could include:
- metal bucket for ash,
- a scoop (e.g. plastic cup) for ash,
- child’s potty,
- broom or mop,
- container (e.g. jug) for anal cleansing water if appropriate
- hand washing container/station.
- soap (cheapest available locally to maximise the chance the user will purchase replenishments)
Every household should be trained in the use of UDDTS. Messages to cover include the following:
- Only defecate in the faeces hole (avoid water/urine here) and urinate/dispose anal wash water in the urine hole.
- Use one chamber at a time – cover the chamber currently in used with a cover that’s easy to lift; cover the other chamber not in use with a concrete slab.
- Maintain an adequate of ash in the metal bucket provided – the ash should be added to fresh faeces using the plastic scoop after defecation to reduce smells and flies.
- Dispose children’s faeces into the latrine – use potties for children who are unable to use the UDDTs;
- The UDDT should be kept clean - the urine area can be cleaned with soap and water once a week (especially if the people are not washers) to remove/prevent bad smells. Care should be taken during cleaning that water does not splash into the faeces vaults.
- If people practice anal cleansing with water, then they should ensure the wash water goes into the urine hole and not in the vault.
- If people practice anal wiping, then bio-degradable materials such as paper or grass should be used.
- Ensure that the handwashing container always contains water and that all users wash their hands with soap or ash after using the latrine.
- The UDDTs should not be used for bathing or showering.
- Avoid disposing non-degradable materials such as disposable pads, bottles, dry cell batteries, broken glass, metal etc in the toilet.
A pictorial guide should be placed on the door of the UDDT. This can be useful to reinforce key messages, and for visitors or members of the household who have not undergone training. This poster should be laminated and cover the key messages for using the latrine:
- Only faeces and cover material should enter the vaults
- Use the urine hole for urination, anal wash water and toilet cleaning water.
- Pour enough cover material in the latrine after each use to stop smell and flies.
- Wash your hands with soap or ash after using the latrine.
Emptying and maintenance
Vault Closing Procedure
To simplify monitoring and emptying operations, UDDT vaults should be closed in groups – this could be ‘communities’, ‘blocks’ or ‘zones’ in the camp. The procedure for closing a vault is as follow:
- The drop hole covers are switched, and the vault cover of the closed vault is sealed with a cement mortar to physically prevent it from being used.
- The date of closing is painted on the vault door and a paper record kept (Figure 3).
The addition of hydrated lime (2-5% by weight), also known as calcium hydroxide or slaked lime, at the time of vault closure will increase the pH. While laboratory studies indicate an increase in microbial inactivation with the addition of lime, this is currently untested in the field. Under certain circumstances, the addition of hydrated lime should be considered if it is available at an affordable price. Examples of circumstances where this is recommended are:
- Where vaults will be emptied after a period of much less than 12 months, for example where the number of users is large relative to the vault size, for whatever reason;
- Where the waste will be reused as a soil conditioner
- Where handling risks are increased for any reason
Vault Emptying Procedure
The vaults should be emptied after twelve months. At this point the vault contents will have a significantly reduced pathogen load, but pathogens will not be eliminated completely and safe handling practices should be followed. The content of the vault will be inoffensive in terms of smell and aesthetics (Figure 4).
To empty the vault long-handled shovels are required. It has been found to be easiest to empty the waste directly into sacks, which means that the emptying is not slowed down by waiting for transportation of the waste, and keeps the area clean.
After emptying, the vault should also be securely re-sealed for future use, and the date on which the vault was closed should be removed to avoid confusion.
Safety of Workers
Technicians emptying vaults should be trained and equipped to undertake the procedure safely. As a minimum, liquid-repellent overalls, splash-proof face shields, respirators, boots and gloves should be provided. Workers should also be provided with Tetanus – Diphtheria immunisations. It is important that protective equipment is cleaned and disinfected thoroughly between uses or it will not serve its purpose. Disinfection could either be through boiling or washing with a disinfectant product. Training should include the following:
- Personal protective equipment should be worn at all times during the vault emptying process.
- Keep wounds covered with clean, dry bandages.
- Change into clean work clothing on a daily basis and reserve footgear for use at worksite or during waste transport.
- Wash hands thoroughly with soap and water after contact with waste; before you eat, drink, or smoke; and before and after using the toilet. Hand-washing stations with clean water and mild soap should be readily available whenever contact with waste occurs.
- Avoid touching face, mouth, eyes, nose, genitalia, or open sores and cuts while working with waste
- Eat in designated areas away from waste-handling activities.
- Do not smoke or chew tobacco or gum while working with waste.
- Remove excess waste from footgear prior to entering a vehicle or a building.
- Do not wear work clothes home or outside the work environment.
- Thoroughly, but gently, flush eyes with water if waste comes into contact with eyes.
The choice of disposal site will depend on the context. In Gambella various places just outside the camp were selected as disposal sites. At these sites wide, shallow pits were dug. As the pits were filled with waste they were progressively backfilled with soil, so that no waste was left exposed. Once one pit filled up another was dug alongside.
The pit should be at least thirty metres from all water sources and sixty metres from all dwellings and other camp facilities. The bottom of the pit should be at least 1.5 metres above the water table.
Urine Pipe Cleaning
The urine pipe may block periodically. It can easily be cleared using a piece of wire either from the top of the urine pipe. This is a simple operation and it is possible to train members of the community to do this.
The monitoring of the toilets has several objectives:
- To check that they are being used properly, and ensure any problems with use are rectified.
- To determine the filling rate of the toilets, to assist in the plans for emptying of the vaults.
- To determine improvements that can be made to the UDDTs or to the community mobilisation. The monitoring system should consist of continuous surveillance of the toilets, a systematic survey and focus group discussions.
Community mobilisers should be on the ground continuously, and through their routine visits they will have a good understanding of how the latrines are being used. Systems should be in place to capture any issues so that they can be dealt with in good time.
Conducting a systematic household survey every three months is useful to establish filling rates, trends and provide clear evidence of the performance of the UDDTs. Systematically sampling can provide representative information. An example checklist that can be used is included in the Annex. If the survey is installed on phones or tablets it is easier to track the data.
UDDTs will be emptied in groups, and so the monitoring should reflect this. For example, if the camp has blocks of 100 households, then all of the toilets in a block can be on the same emptying cycle, and therefore the same monitoring cycle. Every three months ten toilets from within the block can be surveyed and this taken as representative of the block.
Conducting a survey of UDDTs will typically require at least two people: one to fill in the forms whilst another checks inside the toilets and measure the depth of faeces in the vault. The vault doors at the back should not be opened during the survey: measurements of filled depth should only be taken through the faeces hole of the vault that is in use.
Focus Group Discussions
A sample focus group discussion template is in the Appendix. Given the personal nature of toilet use, focus group discussions should be held in small homogenous groups (men, women, children). Initially focus groups should be held regularly as attitudes and understanding may change quickly and changes are likely to be made as a result – either to aspects of the design such as the squatting hole arrangement, or changes to the way community engagement is conducted. Once the toilets have been established for some time it is easier to include questions about UDDTs into other monitoring activities, for example into focus groups held as part of an annual knowledge, attitudes and practice study.
An excellent guide to urine diversion toilets from GIZ: