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<small{|style="float: left;"|{{Language-title />box|english_link=Fossa_Alterna|french_link=Latrine_à_fosses_alternées_(Fossa_Alterna)|spanish_link=Fossa Alterna (Español)|hindi_link=coming soon|malayalam_link=coming soon|tamil_link=coming soon | korean_link=coming soon | chinese_link=Coming soon | indonesian_link=Coming soon | japanese_link=Coming soon}}<!-- table at top of page with logo, picture, Application level, Management level, and input-output tables -->|}

Input1=Excreta|Input2=Faeces |Input3=Organics | Input4=Anal cleansing water| Input4= |Input5=Dry Cleansing Materials|Output1=Compost - EcoHumusPit Humus| Output2= | Output3= | Output4= | Output5=|english_link=Fossa_Alterna|french_link=Latrine_à_fosses_alternées_(Fossa_Alterna)|spanish_link=Fossa_Alterna_sp

|[[Image:Fossa_alterna.png |right|300px500px]]

'''The Fossa Alterna is an a short cycle alternating, waterless (dry) double pit technology. Compared to the [[Double Ventilated Improved Pit|Double VIP]] (S.4) which is just designed to collect, store and partially treat excreta, the Fossa Alterna is designed to make [[Sanitation Products#Compost an earth-like product that can be used as a nutrient- EcoHumus|EcoHumus]]rich soil conditioner. The Fossa Alterna is dug to a maximum depth of 1.5 m and requires a constant input of cover material (soil, ash, and/or leaves).''' 

Two shallow pits are dug next to each other (0.5 ­ 1.5 metre deep). One of the Fossa Alterna pits should fill over a period of 12–24 months depending on the size of the pit and the number of users. When a pit is full, the concrete slab and portable superstructure are placed on the second pit. The full pit degrades during the period of time that while the second pit is filling, which, ideally, should take one year. The material in the full pit will degrade into a dry, earth-like mixture that can be easily removed manually. Because of the added carbon-rich bulking material, the degradation process is accelerated, and the content is ready for excavation and use much faster than in a Double VIP.

Soil, ash, and/or leaves should be added to the ===Design Considerations=== A Fossa Alterna pit after defecation (not urination). The soil and leaves introduce would fill over a variety period of organisms like worms, fungi and bacteria which help in the degradation process. Also, the pore space is increased, which allows for anaerobic conditions. Additionally, the ash helps 12 to control flies, reduce odours and make the mix slightly more alkaline. The Fossa Alterna should be used for urine, but water should not be added (small amounts of anal cleansing water can be tolerated). Water encourages the development of vectors 24 months depending on its size and pathogens but it also fills the porespaces and deprives the aerobic bacteria of the oxygen that is required for degradation. The choice number of User Interface will determine the material that enters the pitusers. Since bulking material is used to continuously cover the excreta, smells are reduced but Even though the addition of a ventilation pipe can reduce the smells even further. The Fossa Alterna pits are relatively shallow with a depth of (1 to 1.5m. Even though the pits are shallow5 m), this should each of them can be more than enough space to accommodate used by a family of 6 six for one year. To optimize the space, the material that mounds in the centre of the pit (underneath the toilet) should be pushed to the sides periodically. Unlike a simple or ventilated pit which The Fossa Alterna technology will be covered or emptied, only work properly if the material in the Fossa Alterna is meant to be reusedtwo pits are used sequentially and not concurrently. Therefore, it is extremely important that no garbage is put into an adequate cover for the out of service pit as it will reduce the quality of the material recovered, and may even make it unusableis required.

After compostingThe Fossa Alterna should be used for urine, the content but water should not be added (small amounts of the first pit anal cleansing water can be used as fertilisertolerated). The best compost time Water encourages the development of vectors and pathogens, but it also fills the pore spaces and deprives the aerobic bacteria of the oxygen that is more than 12 monthsrequired for degradation. The material A UDDT (U.2) can be excavated earlier at 6 monthsused with the Fossa Alterna, but only in circumstances when the soil cannot sufficiently absorb the urine or when the urine is best transferred at this stage to a pit in which a tree will be plantedhighly valued for application.

Emptying Since cover material is used to continuously cover the excreta, smells are reduced. To reduce the smells even further, a ventilation pipe can be added. In flood-prone areas and where the groundwater table is too high, the Fossa Alterna is easier than emptying other pits: could be raised or built entirely above ground to avoid water intrusion and groundwater pollution. Raising the pits are shallower could also be an option for rocky ground and the addition of soil means compacted soils that the material is less compactare difficult to dig. The material that is removed If space is abundant and emptying not offensive desired, the [[Fill and presents a reduced threat of contaminationCover - Arborloo | Arborloo]] (D.1) can be an alternative Disposal option. Pits should not be lined if used as an Arborloo.

- Can be built and repaired with locally available materials. <br> - Because double pits are used alternately, their life is virtually unlimited. <br> - Excavation of humus is easier than faecal sludge <br> - Significant reduction in pathogens <br> - Generates nutrient- Potential rich humus with good potential for use of stored faecal material as soil conditioner. <br> - Flies and odours are significantly reduced (compared to non-ventilated pits). <br> - Does not require a constant source of water. <br> -Shallow depth of pit required Can be built and repaired with locally available materials <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 if self-emptied. <br> - Small land area required. <br> - Significant reduction in pathogens. | con=- Requires constant source of cover material (soil, ash, leaves, etc.) <br> - Manual removal of humus is required<br>- Garbage thrown in the pit may ruin reuse end-use opportunities of Compost/EcoHumus. the product

===AdequacyAppropriateness=== The Fossa Alterna is appropriate for rural and peri-urban areas. It is especially suitable to water-scarce environments. It is a useful solution for areas that have poor soil and could benefit from the use of the stabilized humic material as a soil amendment. The Fossa Alterna is not appropriate for greywater as the pit is shallow and the conditions must remain aerobic for degradation. The material is manually emptied from the Fossa Alterna (it is dug out, not pumped out); thus, vacuum truck access to the pits is not necessary.

The Fossa Alterna is appropriate not suited for rural and peri-urban areas. It is especially adapted rocky or compacted soils (that are difficult to waterscarce environments. It is a useful solution dig) or for areas that have poor soil and could benefit from flood frequently, except if the composted humic material as a soil amendment. A constant source of soil, ash and/or leaves is requiredpits are raised.

Not applicable in areas ===Health Aspects/Acceptance=== By covering faeces with a high water tablesoil, with very loose soil (which could collapse)ash, and/or very solid soil which would prevent drainageleaves, flies and odours are kept to a minimum. In order to prevent water tables penetrating Users may not understand the difference between the pits Fossa Alterna and contaminating the watera Double VIP, pits should be shallow. The conversion of excreta into humus will not take place although if given the pit is flooded with water. Thereforeopportunity to use one, the pit people should not be sealed and water used for anal cleaning should not enter have a good appreciation of the pitadvantages. The Fossa Alterna is not appropriate for greywater as the pit is shallow and the conditions must remain aerobic for degradation. Another greywater treatment system must Demonstration units can be used in parallel. A [[Urine Diverting Dry Toilet]] to show how easily one can be used with the empty a Fossa Alterna, but only in circumstances when the soil cannot sufficiently absorb the urine or when urine is highly valued for application. The material is manually emptied from the Fossa Alterna (it is dug out, not pumped out), so vacuum truck access comparison to the pits is not necessary. The Fossa Alterna technology will only work properly if the two pits are used sequentially and not concurrently. Therefore, an adequate cover for the out of service emptying a double pit is required. The Fossa Alterna is especially appropriate when water is scarce. It is not suited for rocky or compacted soils (that are difficult to dig) or for areas that flood frequently.

As with many sanitation systems, household members need to understand Keeping the contents sealed in the key principles pit for efficient operation the duration of at least one year makes the material safer and maintenance and discipline is required for adding soil after each defecationeasier to handle. The same precautions that are taken when handling compost should be taken with the humus derived from the Fossa Alterna.

===Health Aspects/AcceptanceOperation & Maintenance=== By covering faeces with soil/ash, flies and odours are kept to a minimum. Users may not understand When the difference between the Fossa Alterna and a [[Double Ventilated Improved Pit|Double VIP]], although if given the opportunity to first pit is put into use one, people a layer of leaves should have a good appreciation be put onto the bottom of the advantagespit. Demonstration units can Periodically, more leaves should be used added to show how easily one can empty a Fossa Alterna in comparison to emptying a Double Pitincrease the porosity and oxygen availability. Keeping Following the contents sealed in addition of faeces to the pit for the duration , a small amount of at least one year makes soil, ash, and/or leaves should be added. Occasionally, the mounded material safer and easy to handle. The same precautions that are taken when handling compost beneath the toilet hole should be taken with pushed to the humus derived from sides of the Fossa Alternapit in order to optimise the use of space.

===Maintenance=== When Unlike a [[Single Pit | Single]] or [[Single Ventilated Improved Pit | Ventilated]] Pit (S.2, S.3) which will be covered or emptied, the first pit material in the Fossa Alterna is put into usemeant to be used as a soil conditioner. Therefore, a layer of leaves should be it is extremely important that no garbage is put into the bottom of the pit. Periodically, more leaves should be added to increase Emptying the Fossa Alterna is easier than emptying other pits; the porosity pits are shallower and oxygen availability. Following the addition of faeces to the pitsoil, ash, a small amount of soil and/or ash should be addedleaves means that the contents are less compact. To lengthen the filling time of the pit soil The material that is removed is not added to the pit following urinationoffensive and presents a reduced threat of contamination.

Occasionally, the mounded material beneath the toilet hole should be pushed to the sides of the pit for an even distribution of materials. Depending on the dimensions of the pits, materials the contents should not be emptied every more often than once a year.

This [httphttps://wwwsswm.bvsde.paho.orginfo/bvsacdtaxonomy/cd66term/ToiletsCompost3916/cap4.pdf fossa-alterna document] contains a lot of information about building, maintaining a fossa alterna.

* Morgan, P. R. (2007) . [http://www.ecosanres.org /pdf_files/ToiletsThatMakeCompost.pdf Toilets That Make Compost: . Low-costCost, sanitary toilets that produce valuable compost Sanitary Toilets That Produce Valuable Compost for crops Crops in an African contextContext]. Stockholm Environment Institute, SwedenStockholm, SE. * Morgan, P. R. (2009). [http://www. Stepecosanres.org/pdf_files/EcologicalToilets-byPeterMorgan-step guide for building a Fossa AlternaMar2009.pdf Ecological Toilets. Start Simple and Upgrade from Arborloo to VIP]. Stockholm Environment Institute, Stockholm, SE.