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 '''Dehydration vaults are used to collect, store and dry (dehydrate) faeces. Faeces will only dehydrate when the vaults are well ventilated, watertight to prevent external moisture from entering , and when urine and anal cleansing water are diverted away from the vaults.'''

When faeces are not mixed with urine is separated from faecesand other liquids, the faeces they dry quickly. In the absence of moisture, organisms cannot grow and as such, smells are minimized and pathogens are destroyed. Vaults used for drying faeces in the absence of urine have various local names. One of the most common names for this technology is the Vietnamese Double Vaults. Excreta may dry inside the vault as a result of sun radiation, natural evaporation and ventilation. Absorbents such as lime, ash or dry soil should be added to the chamber after each defecation in order to absorb moisture, making the pile less compactsmells minimized. The product from a dehydration process is a kind use of mulch, rich in humus, carbon, fibrous material, phosphorous and potassium. It should be stored, sun-dried or composted in order to kill off all pathogens. A family of 6 will produce 500L of faeces in approximately six months. For design purposes it is recommended to assume that one person will require almost 100L of faeces storage space every six months. The vaults should be slightly oversized to account for airflow, visitors and the non-even distribution of faeces in the chamber. Each vault is sized to accommodate sixmonths of faeces accumulation which in turn, results in a six month drying time in the out-of-service vault. Two two alternating vaults allow allows the faeces to dehydrate in one vault while the other vault fills. When one vault is full it is sealed with a lid and , the [Urine Diverting Dry Toilet | Urine-Diverting Dry Toilet] (UDDT (U2, U.2) is moved to the second vault. While the second vault fills up, the faeces in the first vault slowly dry and decrease in volume. When the second vault is full, it is sealed, the dry material from the first vault one is removed emptied and the first vault is then put back into service. To prevent flies, minimize odours and encourage drying, a small amount of ash, lime, dry soil or sawdust should be used to cover faeces after each use.

The ===Design Considerations=== Dehydration vaults must can be watertight constructed indoors or with a separate superstructure. A vent pipe is required to keep remove humidity from the faeces as dry as possiblevaults and control flies and odours. The chambers should be airtight for proper functioning of the ventilation. Chambers They should be constructed made of sealed block brickwork or formed concrete to ensure that rainwater, surface run-offrunoff cannot enter. The WHO recommends a minimum storage time of 6 months if ash or lime are used as cover material (alkaline treatment), greywater and urine are prevented from entering otherwise the vaults. Urine can storage should be collected in a bucket for at least 1 year for warm climates (>20 °C average) and discharge for 1.5 to the ground (garden) or stored in a tank 2 years for future transport and usecolder climates.

A vent In case of alkaline treatment, each vault is required sized to help keep accommodate at least 6 months of faeces accumulation. This results in a 6 month storage and dehydration time in the out-of-service vault. The vault dimensions should account for cover material, airflow, the vaults uneven distribution of faeces, and possibly visitors and dry cleansing materials. It can be assumed that one person will require around 50 L of storage volume every 6 months. A minimum chamber height of 60 to 80 cm is recommended for easy emptying and control flies and odoursaccess to the urine pipes.

- Significant reduction in pathogens<br>- Can be built and repaired with locally available materials. <br> - Because double pits are used alternately, their life is virtually unlimited. <br> - Potential for use of dried faeces as soil conditioner<br>- Good in rocky and/or flooded areas. <br> - Excavation of dried faeces is easier than faecal sludge. <br> - No real problems with flies or odours if used correctly(i.e. <br> - Does not require a constant source of water, kept dry). <br> - Suitable for all types of user (sitters, squatters, washers and wipers). <br> - Low (but variable) capital costs depending on materials; no or low operating costs. <br> - Small land area required. | con=- Requires education training and acceptance to be used correctly. <br> - Requires constant source of cover material, e.g. ash, sand or lime. <br> - Requires a place where urine and treated Manual removal of dried faeces can be used or discharged. <br> - Urine and faeces require manual removal. is required

===AdequacyAppropriateness===Dehydration Vaults vaults can be installed in almost every setting , from rural to dense urban areas, because of the small land area required, the minimal odours and the ease of use. They If used in an urban context, this technology relies on a transport service for the dried faeces (and urine) since urban users normally do not have an interest and/or opportunity to use it locally. Dehydration vaults are especially appropriate for water -scarce and rocky areasor where the groundwater table is high. In They are also suitable in areas that are frequently flooded, Dehydration Vaults are appropriate because they are constructed built to be watertight. Furthermore, where there is no plot of land available, the vaults can be installed indoors, which also makes this technology applicable for colder climates (where leaving the house is less desirable). ===Health Aspects/Acceptance ===[[Image:Dehydration.PNG‎|thumb|right|200px|[[Dehydration |Dehydration]], in Ecuador (for credits, click the picture)]]Dehydration Vaults can be a clean, comfortable, and easy-to-use technology. When users are well educated and understand how the technology works they may be more willing to accept it as a viable sanitation solution. When the vaults are kept dry, there should be no problems with flies or odours. Faeces from the double vaults should be very dry and relatively safe to handle provided they were continuously covered with material and not allowed to get wet. There is a low health risk for those whom have to empty or change the urine container. Faeces that have been dried for over one year also pose a low health risk.

===UpgradingHealth Aspects/Acceptance=== Dehydration vaults can be a clean, comfortable, and easy-to-use technology. It is crucial, however, that the users are well trained to understand how the technology works and appreciate its benefits. When the vaults are kept dry, there should not be any problems with flies or odours. After the recommended storage time, the faeces should be very dry and relatively safe to handle, provided that they did not get wet. However, a low health risk remains. Single dehydration vaults or bins do not allow faeces to sufficiently dehydrate.

There is a risk however when using single vaultsWhen the full container needs emptying, that the faeces on top portion are still fresh. Hence, the risk associated with the handling of the faeces will not be fully dried and/or hygienizedfaecal matter is inherently higher in single vaults compared to double vault designs. Single vaults are not The use of alternating chambers is, therefore, recommended (because . However, research and field tests of the need to handle fresh sealed faecescontainers (or cartridges) for safe transportation and shouldeasy cleaning, whenever possible be upgraded to a double vaultalong with the corresponding logistics, are on-going.

===Operation & Maintenance=== Just like the faeces which are dried, but not degraded in the vaults, dry cleansing materials will not decompose in the chambers. Whenever the material is intended to be applied onto fields without further treatment, it is recommended to separately collect and dispose of the dry cleansing materials. Occasionally, the faeces that have accumulated beneath the toilet should be pushed to the sides of the chamber.

To prevent flies, minimize odours and encourage drying, a small amount of ash, soil, or lime should be used to cover faeces after each use. Care should be taken to ensure that no water or urine gets into the Dehydration Vaultdehydration vault. If this happens, extra soil, ash, lime, soil or sawdust can be added to help absorb the liquid. Because the faeces are not actually degraded (just dried), dry cleansing materials must not be added to the Dehydration Vaults as they will not decompose. Occasionally, the mounded faeces beneath the toilet hole should be pushed to the sides of the pit for an even drying. Where water is used for cleansing, an appropriate User Interface should be installed to divert and collect it separately. To empty the vaults, a shovel, gloves and possibly a face mask facemask (cloth) should be used to limit avoid contact with the dried faeces.

* Deegener, S., Samwel, M. and Gabizon, S. (2006). Urine Diverting Toilets. Principles, Operation and Construction. Women in Europe for a Common Future, Utrecht, NL and Munich, DE.:Available at: [http://zoomzapwww.com/manuals/SES/download-espwecf.php Manual del Sanitario Ecologico Secode wecf.de] A very comprehensive manual on dry chamber construction including detailed instruction (Photos and explanation of how to build a double vault and material lists. In Spanish.superstructure)

* GTZ Rieck, C., von Münch, E. and Hoffmann, H. (2012). Technology Review of Urine-Diverting Dry Toilets (UDDTs). Overview of Design, Operation, Management and Costs. Deutsche Gesellschaft für Internationale Zusammenarbeit (2005GIZ)GmbH, Eschborn, DE. :Available at: [http://www.sanimapsusana.netorg/xoops2library susana.org/uploads/gnavi/12_2.pdf Urine diverting dry toilets programme disseminationlibrary] (data sheet). GTZ, Germany. General overview of Dehydration Chambers with some dimensioning and materials lists.

* Winblad, U., and Simpson-HerbertHébert, M. (edsEds.) (2004). Ecological Sanitation. Revised and Enlarged Edition. Stockholm Environment Institute, Stockholm, SE.:Available at: [httpshttp://wikiwww.umnecosanres.edu/pub/EWB/Uganda/SIDAGuidebookorg ecosanres.pdf Ecological Sanitation - revised and enlarged editionorg]. SEI, Stockholm, Sweden. (A general description of various designs and adaptations, especially Chapter 3.)

* [http://wwwWHO (2006).wecfGuidelines for the Safe Use of Wastewater, Excreta and Greywater.eu/indexVolume 4: Excreta and Greywater Use in Agriculture.php Women in Europe for a Common Future] (2006)World Health Organization, Geneva, CH. :Available at: [http://www.permacultuurnederlandwho.org/permacultuurtk/urinedivertint who.pdf Urine diverting Toilets: Principles, Operation and Constructionint]. Photos and explanation of how to build a double vault and superstructure.