Pilot Ecosan Project. Mombasa 2003

Transcription

1 Pilot Ecosan Project. Mombasa 2003 A brief technical review of a series of eco-toilets built in the Mombasa area during a course held by the Coast Development Authority and sponsored by RELMA. This was a practical training programme held in Mombasa and environs with participants from Kenya, Uganda, Ethiopia, Zambia, Rwanda and Tanzania. The aim was to introduce or expand on existing knowledge on the construction of eco-toilets and their use in ecosanitation based projects. In the second part a wider group came together to discuss the whole subject and make a tour of the eco-toilet constructions made earlier by the group. Several constructions of eco-toilets were undertaken in the following sites: 1. School 1 (Mtomondoni Primary School) 2. School 2 (Marimani PS) 3. Village site (Bengala Village - a peri-urban settlement) 4. Beach site (Pirates - public beach site) Constructions built 1. School 1 (Mtomondoni Primary School) This was the primary site where all concrete slabs were built at an early stage to facilitate curing. It was a site also where school children participated in the construction of slabs and low cost pedestals. A series of concrete slabs and concrete ring beams were made. School children making slab at Mtomomondi Primary School.

2 The final constructions included. 1a. One Uganda model urine diverting toilet with twin vault, the process of excreta processing advocated being dessication. Built with commercially available urine diverting squat plate. Depth of vault one metre. For technical details see Construction Plan from Uganda. 1b. One Arborloo built on concrete ring beam to be used by children. Pit depth 0.9m. Slab 0.9m X 1.2m. Structure wooden frame and corrugated iron sheet. 1c. One Fossa alterna to be used by children. One pit protected with concrete ring beam only (pit depth 1.39m) and the second pit protected with an upper pit lining of coral limestone blocks down to 0.5m (pit depth 1.10m). Single slab alternating between the two pits. Slab size 0.9m X 1.2m. Structure wooden frame and corrugated iron sheet. Second pit covered with wooden frame and corrugated iron lid and left empty or partly filled with compost). 1d. Three low cost pedestals were also made. Making the ring beams for Fossa alterna 2. School 2 (Marimani PS). 2a. A urine diverting single vault eco-toilet intended for secondary composting at ambient temperature (Skyloo) with commercial squat type diverter. The process of excreta processing advocated being ambient temperature composting. Vault depth approx 0.5m. Built together with external shallow twin pit composter. For use by teachers. Fitted with plastic basin placed in vault which fills up with a mix of faeces and soil/ash, which are regularly deposited into one side of the shallow pit composter together with additional soil. Once the first side has almost filled up with compostable ingredients, the additions from the basin are added to the second pit of the composter. Once humus is fully formed it is removed from the composter. Urine led to 20 litre container on side of vault. Structure wooden frame and corrugated iron sheet.

3 3. Village site (Bengala Village - a peri-urban settlement) 3a. Two Fossa alterna units built in two homesteads. Both in unstable soil areas - hence full brick lining to above ground level. Single slab in each case of 0.9m X 1.2m. Structures wooden frame and corrugated iron sheet. Second pits covered with wooden frame and corrugated iron lid and left empty or partly filled with compost). Fossa 1. Pit depths of used pit 1.5m and second pit 1.5m. Fossa 2. Pit depth of used pit 1.5m and second pit 1.5m. Fossa alterna at Bengala village 3b. A urine diverting single vault ecotoilet intended for secondary composting (Skyloo) with commercial squat type diverter. Vault depth approx 0.5m. Built together with external shallow twin pit composter. For use by family homestead.. Fitted with plastic basin placed in vault which fills up with a mix of faeces and soil/ash, which are regularly deposited into one side of the shallow pit composter together with additional soil. Process the same as above. Urine led to 20 litre container on side of vault. Structure wooden frame and corrugated iron sheet. Constructing the single vault of Skyloo in Bengala village

4 The completed Skyloo in Bengala village. The photo on left also shows the separate secondary composter site. On the right the rear vault door and the urine collection chamber can be seen. The commercially made urine diverting squat plate inside Skyloo (left). On the right the secondary compost site is inspected.. 4. Beach site (Pirates - public beach site) 4a. Uganda model twin double vault urine diverting eco-toilet intended for dessication. Vault depth one metre. Using one commercial diverting pedestal and one commercial squat type urine diverting plate. Two 20 litre containers used for urine collection. Structure wooden frame and corrugated iron sheet. 4b. One Fossa alterna with full brick (coral lime stone brick) lined twin pits in very unstable soil site with loose sand. Hence full lining. Used pit depth 1.3m. Second pit depth 1.2m. Fitted with single slab (0.9m X 1.2m) and low cost pedestal (non urine diverting). Two wheel barrow makuti added to used pit - this is the composting remains of used palm thatching leaf). Structure wooden frame and corrugated iron sheet. Second pit covered with wooden frame and corrugated iron lid and left empty or partly filled with compost).

5 The beach site. On the left making the two coral limestone lined pits of a Fossa alterna. On the right adding makuti into the pit which will be used first. This will help to promote composting. Notes The Arborloo, Fossa alterna and urine diverting method with ambient composting (Skyloo) are all new to the area. Thus in each case close monitoring is required. Also in each case the users, whether they be family based or school children or teachers should be given some background information on the type of system in use and how to manage it. Information sheets might be attached to the inside of the structure. In all cases (Arborloo, Fossa alterna, Skyloo, a mix of soil and ash is added to the system after solids are deposited) The Arborloo In the case of the single arborloo built at the Mtomondoni Primary School, this will need to be moved down a line to the left of the original site. The ring beam, slab and structure must be moved when the pit is almost fill with the excreta/soil/ash mix. The next site can be about 1-3m away depending on the tree planted. Paw paw and palm trees do not take much lateral space. Gum trees in an intermediate position. Larger trees like mango will take more space. Once full the used pit is topped up with fertile soil to about 150mm depth and a tree can be planted and protected. It is also possible to allow the contents of the pit to compost until the rainy season, when a tree is planted. Trees planted on arborloo sites must be planted in soil placed above the excreta layer, otherwise they will die. A wide range of fruit, ornamental and indigenous trees will grow in Arborloo pits if properly planted, watered and protected from animals.

6 The Fossa alterna In the case of the Fossa altera, the conversion of excreta to humus is encouraged by the frequent addition of soil and wood ash and also preferably some leaves, so the pit is filled with a mixture of these ingredients. It helps a great deal to charge the new pit with leaves or composting material. In the case of the Fossa alterna at the beach site, two wheel barrow fulls of Makuti (semi composted palm leaves discarded from old roofing material) were added to the base of the used pit. This seems to be a very good material to add to the pits. Ideally this materials should taken also to be added to the other Fossa alterna sites in the project. The overall aim of the Fossa alterna is to encourage composting in the pit (by the addition of these additional ingredients) so that the humus is fully formed within the time it takes to fill the alternative pit. With the Fossa alterna the pit filling time is dictated by the number of users and by the volume of the pit. Pit depth for the Fossa alterna normally lies between 1.2m and 1.5m depth for both pits. In the current example pit depth varied from 1.1m to 1.5m. The cross sectional area of these pits was 0.7 sq.m. (0.7m X 1.0m). So total volumes of pits lie between 0.77 cu.m. and 1.05 cu.m. The additional material added to these pits (soil and wood ash) is about equal in volume to the solid excreta added. The volume of solid excreta is reduced over time. Any leaves added are also considerably reduced in volume. The addition of leaves improves texture and final nutrient level of humus. It will be important to closely monitor the Fossa alterna toilets to ensure that soil and wood ash are being added. Also a requirement of the Fossa alterna is that no garbage or non compostable material is added like plastic, rags, bottles etc. The ingredients contained by the pit must be human excreta, soil and wood ash (and leaves if possible). During the filling of the Fossa alterna there is a tendency for the waste material to rise in the form of a cone under the drop hole. The owner/user should take a stick and attempt to flatten out the pit ingredients from time to time. It will also be important to monitor the rate of filling of the Fossa alterna pits and relate this to family size (or number of users). With the Fossa alterna a full 12 months of composting should be allowed before the humus is dug out. If a Fossa alterna is overused and the pit filling time is less than a year, then an additional pit must be dug so that the slab and structure rotates between 3 pits (or more). The Fossa alterna is not ideally suited to areas with a very high water table. In each case the Fossa alterna sites are seen as experimental units, with information being required on acceptance of the unit, numbers of users and rate of filling etc. Subsequently the safety of the humus can be tested by bacteriological testing. The Skyloo In the case of the Skyloo (one built in family site and one at school site), this is also new to the area and once again the two should be closely monitored and the users educated in the proper use and management and how the system works. In the Skyloo, the solid faeces (together wish soil and ash) are held in a bucket or basin within the vault. When the bucket or basin is nearly full (or even before) the contents are

7 transferred to a secondary composting site where the main excreta processing takes place. In both cases built in this project, the secondary composting site is a twin shallow pit composter. This consists of two shallow pits, the upper part of each being lined with bricks which rise above ground level and are covered with lids (in this case wooden frames fitted with corrugated tin covers). The bucket/basin contents are regularly added to one side of the twin pit composter and covered with fertile soil. This process continues until one side is almost full (with a mix of faeces, soil and ash and more soil). The contents are kept slightly moist by addition of water from time to time. Once almost full the contents of the bucket (or basins) are added to the second pit of the twin pit composter. The contents of the first pit are then allowed to compost until the humus is fully formed and safe. Normally this will be between 6-12 months. Current studies show that with this system the pathogenic bacteria die out within 3 months. The fate of worm eggs needs further investigation. The tin roof will help to elevate temperatures within the composters. Once the humus is formed it can be dug out of the composter and used on gardens etc. It will be rich in nutrients and a valuable material. The urine will be led to a 20 litre container which should be emptied once full and preferably mixed with three times the volume of water and added to vegetable gardens or trees/flowers/shrubs to encourage growth. In each case the owner should ensure that a mix of soil and ash, held within a bucket is available inside the toilet and that after each addition of faeces, some soil and ash are added. This can be premixed at about 4 parts dry soil to one part ash, or the soil and ash can be added separately. The amount of soil and ash added is a small mug full. A small soil/ash dispenser can be made or the hand used. Once again (as with the Fossa alterna and the Arborloo) ) the Skyloo units should be inspected from time to time to see how the users are coping with the management. Note with the Skyloo, since the human material is not held directly in the vault, the whole structure can periodically be washed down and cleaned. Conclusion General This is a most valuable introduction to the concept of eco-san in the Coast Province of Kenya. A wide range of concepts has been introduced (Arborloo, Fossa alterna, Urine diversion with dessication, Urine diversion with composting). Close monitoring is required of all units put into place. This information will be most valuable for the future uptake of ecosan in the Province. Technical Note also the vent pipes on these toilets should be fitted with a fly screen. This should be mosquito netting made of aluminium or stainless steel laid across the top of the pipe and wired on. All wood work should ideally be treated with preservative to counteract insect activity and rot.

8 The writer would appreciate the construction of a very traditional structure suitable for the Coast (Coralloo) sometime, using palm poles for the frame and makuti leaves for the side walls and roof. School projects It would be very encouraging to ask staff at the Mtomondoni Primary School to organise the children to build more slabs, ring beams and even learn how to lay bricks and even make structures, so that there is more involvement in the construction of these simple toilets by the pupils themselves. This exercise has shown clearly that both staff and pupils are interested and capable of undertaking this sort of development. In fact well motivated school children and staff are quite capable of doing the whole job. It would be a very good exercise for the schools. Where there is space, the Arborloo is a good concept to use at a school. Each class can build its own Unit (ring beam, slab and some sort of structure for privacy). Each class can dig its own shallow pit (normally about one metre). Each class can use and maintain its own structure, and subsequently plant its own tree. This would be an excellent school sanitation project and the Arborloo is low cost and particularly suitable if there is space available for an orchard or wood lot. Feedback I greatly look forward to getting more feedback from the various sites and hope it will be possible to build more units and add these to the list of experimental toilets to be monitored closely during the next year. Using information gained from these various units it will be possible to build up much knowledge on how to undertake future programmes of ecological sanitation in the area. Peter Morgan Harare July 2003