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<!{|style="float: left;"|{{Language-- table at top of page with logo, picture, Application level, Management level, and input-output tables -->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}}|}

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]]

[[Image:Icon_fossa_alterna.png |right|95px80px]]'''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 Cover material should be added to each other the pit after defecation (0.5 ­ 1.5 metre deepnot urination). One of the Fossa Alterna pits should fill over The soil and leaves introduce a period variety of 12–24 months depending on the size of the pit organisms like worms, fungi and bacteria which help in the number of usersdegradation process. When a pit is fullAlso, the concrete slab and portable superstructure are placed on the second pit. The full pit degrades during the period of time that the second pit pore space is fillingincreased, whichallows for aerobic conditions. Additionally, ideallyash helps to control flies, should take one year. The material in reduces odours and makes the full pit will degrade into a dry, earth-like mixture that can be easily removed manuallymix slightly more alkaline.

[[Image:Fossa_alternaThe full pit degrades while the second pit is filling, which, ideally, should take one year.PNG|thumb|right|150px|[[Fossa alterna |Fossa alterna]]The material in the full pit will degrade into a dry, in Epworth (for creditsearth-like mixture that can be easily removed manually. Because of the added carbon-rich bulking material, the degradation process is accelerated, click and the picture)]]content is ready for excavation and use much faster than in a Double VIP.

Soil, ash, and/or leaves should be added to the pit after defecation (not urination)[[Image:Fossa_alterna. The soil and leaves introduce a variety of organisms like wormsPNG|thumb|right|200px|[[Fossa alterna |Fossa alterna]], fungi and bacteria which help in the degradation process. Also, the pore space is increased, which allows Epworth (for anaerobic conditions. Additionallycredits, click the ash helps to control flies, reduce odours and make the mix slightly more alkaline.picture)]]

The ===Design Considerations=== A Fossa Alterna should be used for urinepit would fill over a period of 12 to 24 months depending on its size and the number of users. Even though the pits are shallow (1 to 1.5 m), but water should not be added (small amounts each of anal cleansing water them can be tolerated). Water encourages the development used by a family of vectors and pathogens but it also fills the porespaces and deprives the aerobic bacteria of the oxygen that is required six for degradationone year. The choice of User Interface Fossa Alterna technology will determine only work properly if the material that enters the pittwo pits are used sequentially and not concurrently. Since bulking material is used to continuously Therefore, an adequate cover for the excreta, smells are reduced but the addition out of a ventilation pipe can reduce the smells even furtherservice pit is required.

The Fossa Alterna pits are relatively shallow with a depth of 1.5m. Even though the pits are shallowshould be used for urine, this but water should not be more than enough space to accommodate a family added (small amounts of 6 for one yearanal cleansing water can be tolerated). To optimize Water encourages the spacedevelopment of vectors and pathogens, but it also fills the material that mounds in pore spaces and deprives the centre aerobic bacteria of the pit oxygen that is required for degradation. A UDDT (underneath the toiletU.2) should can be pushed to the sides periodically. Unlike a simple or ventilated pit which will be covered or emptied, the material in used with the Fossa Alterna is meant to be reused. Therefore, it is extremely important that no garbage is put into but only in circumstances when the pit as it will reduce soil cannot sufficiently absorb the quality of urine or when the material recovered, and may even make it unusableurine is highly valued for application.

After compostingSince cover material is used to continuously cover the excreta, smells are reduced. To reduce the content of the first pit smells even further, a ventilation pipe can be used as fertiliseradded. The best compost time In flood-prone areas and where the groundwater table is more than 12 months. The material can be excavated earlier at 6 monthstoo high, but is best transferred at this stage to a pit in which a tree will be planted.  Emptying 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

==Adequacy=Appropriateness= == 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 a Double VIP, although if given the wateropportunity to use one, pits people should be shallow. The conversion have a good appreciation of excreta into humus will not take place if the pit is flooded with wateradvantages. Therefore, the pit should not Demonstration units can be sealed and water used for anal cleaning should not enter the to show how easily one can empty a Fossa Alterna in comparison to emptying a double pit.

The Fossa Alterna is not appropriate Keeping the contents sealed in the pit for greywater as the pit is shallow duration of at least one year makes the material safer and the conditions must remain aerobic for degradationeasier to handle. Another greywater treatment system must be used in parallel. A [[Urine Diverting Dry Toilet]] can The same precautions that are taken when handling compost should be used taken with the humus derived from the 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 ===Operation & Maintenance=== When the Fossa Alterna (it first pit is dug output into use, not pumped out)a layer of leaves should be put onto the bottom of the pit. Periodically, so vacuum truck access more leaves should be added to increase the pits is not necessaryporosity and oxygen availability. The Fossa Alterna technology will only work properly if Following the two pits are used sequentially addition of faeces to the pit, a small amount of soil, ash, and not concurrently/or leaves should be added. ThereforeOccasionally, an adequate cover for the out mounded material beneath the toilet hole should be pushed to the sides of service the 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 in order to dig) or for areas that flood frequentlyoptimise the use of space.

As with many sanitation systemsUnlike a [[Single Pit | Single]] or [[Single Ventilated Improved Pit | Ventilated]] Pit (S.2, household members need S.3) which will be covered or emptied, the material in the Fossa Alterna is meant to understand be used as a soil conditioner. Therefore, it is extremely important that no garbage is put into the key principles for efficient operation pit. Emptying the Fossa Alterna is easier than emptying other pits; the pits are shallower and maintenance the addition of soil, ash, and discipline /or leaves means that the contents are less compact. The material that is removed is required for adding soil after each defecationnot offensive and presents a reduced threat of contamination.

==Health Aspects/Acceptance== By covering faeces with soil/ash, flies and odours are kept to a minimum. Users may not understand Depending on the difference between dimensions of the Fossa Alterna and a [[Double Ventilated Improved Pit|Double VIP]]pits, although if given the opportunity to use one, people contents should have a good appreciation of the advantages. Demonstration units can not be used to show how easily one can empty a Fossa Alterna in comparison to emptying emptied more often than once a Double Pit. Keeping the contents sealed in the pit for the duration of at least one year makes the material safer and easy to handle. The same precautions that are taken when handling compost should be taken with the humus derived from the Fossa Alterna.

==Maintenance=Field experiences= ==The following project(s) utilize fossa alterna.<br>When the first pit is put into use, a layer of leaves should be put into the {|style="border: 2px solid #e0e0e0; width: 20%; text-align: justify; background-color: #e9f5fd;" cellpadding="2"|- style="vertical-align: top"|[[Image:akvorsr logo_lite.png|center|60px|link=http://akvo.org/products/rsr/]]|- style="vertical-align: bottom of the pit"|[[Image:project 644. Periodically, more leaves should be added to increase the porosity and oxygen availabilityjpg |thumb|center|140px|<font size="2"><center>[http://rsr. Following the addition of faeces to the pit, a small amount of soil or ash should be addedakvo. To lengthen the filling time of the pit soil is not added to the pit following urinationorg/project/644/ RSR Project 644]<br>Rwenzori Integrated School WASH Project</center></font>|link=http://rsr.akvo. org/project/644/ ]] |}

Occasionally<br>===Manuals, the mounded material beneath the toilet hole should be pushed to the sides of the pit for an even distribution of materialsvideos, and links===This [https://sswm. Depending on the dimensions info/taxonomy/term/3916/fossa-alterna document] contains a lot of the pitsinformation about building, materials should be emptied every yearmaintaining a fossa alterna.

==Manuals, videos, =References and external links==This [http://www.bvsde.paho.org/bvsacd/cd66/ToiletsCompost/cap4.pdf document] contains a lot of information about building, maintaining a fossa alterna. =

* Morgan, P. R. (20072009) Toilets That Make Compost: Low-cost, sanitary toilets that produce valuable compost for crops in an African context. Stockholm Environment Institute, Sweden. Available: [http://www.ecosanres.org (Step/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.)

===Acknowledgements===