Teaching Ecological Sanitation in Schools Demonstrations in recycling pit compost taken from BVIP toilet pits in vegetable gardens and orchards

Transcription

1 Teaching Ecological Sanitation in Schools Demonstrations in recycling pit compost taken from BVIP toilet pits in vegetable gardens and orchards Peter Morgan and Annie Kanyemba

2 Introduction So far in this series of manuals we have described the concept of ecological sanitation, the construction of toilets from which processed excreta can be recycled and also various methods of using urine to hasten the growth of trees and vegetables. Now we turn to the recycling of nutrients found in the more solid material extracted from shallow to medium depth pit (BVIP) toilets. This material is a mix of excreta (urine and feaces), plastic, rags and other garbage. Toilet paper is rarely available in most schools and rural homesteads, and rags, plastic and cloth are used for anal cleansing. These end up in the pit contents. There are various ways of accelerating the conversion of pit material into a more manageable product and also various ways of extracting and processing it. Whilst we have used the name pit compost for the material, once it is mixed with soil and left to change into a more manageable product, it is not really true compost, but rather partly dehydrated and decomposed material, becoming a mix of excreta, soil, ash (if added) and the various other additions (rags, plastic etc). True compost contains a high content of vegetable matter. This material has valuable nutrients, but has a low content of vegetable matter. In this work in the school environment, we have not used urine diversion technology, as our own belief is that this technology is too sensitive in the local school environment, and likely to be abused. Our observations consistently confirm that school toilets are frequently poorly maintained and even the washing down of slabs, may be far less frequent than the ideal which is frequently. We are also aware that many objects enter toilets pits other than excreta. We have therefore chosen to maintain the use of BVIP toilets of various types, as this has been standardised by the Government of Zimbabwe for schools for several decades. Most schools in the rural and even 2

3 many peri-urban settlements are multi-compartment BVIPs. These can have a long life of 25 years or more. Urine can be collected in tanks (see the manual on collecting urine from the boys urinal) or in bottles and other containers. Diluted urine can be used to accelerate the growth of green vegetables, maize and certain trees such as Eucalyptus (gum tree). We now turn to the important aspect of recycling more solid excreta deposited in pit toilets. The fluidity of this material varies considerably from almost solid to liquid. In the case of conventional school toilets, these consist of a series of 3m deep separate pit chambers, some rectangular, some round. The standard is a multicompartment unit consisting of 10 cubicles. There is some variation in design, such as one of the boy s cubicles being turned into a urinal. Some multi-compartment toilets have 5 cubicles. In this new experimental approach to building toilets at the school, single units have been chosen. We have seen that where this approach is used, the pupils can participate in the construction of the toilets if they are given enough support. This would be quite impossible if multi-compartment toilets were chosen. Also shallower but wider brick lined pits have been chosen. These can be built, one at a time, which requires less expense than the construction of the more elaborate multi-compartment structure. In most of these units a labourer/artisan digs the pit and lines it with bricks. He may also make the slab extension. The pupils are able to make the slab and build the brick superstructure. The roof comes in components (wooden frame and tin sheets) and these can also be put together and fitted by the pupils. However it must be stressed that this study reveals that pupils are able to construct toilets as part of their extracurricular activity, but the normal procedure would be for artisans to construct the entire unit for the school. 3

4 Removal of pit material. The question therefore remains how can we remove and recycle the material contained in pits, once they are full or nearly full. This has been the subject of international research and debate for many years because it involves the removal of unpleasant and dangerous material from the pit which is a mix of excreta and garbage. Much of this non organic material consists of rags or plastic. Huge numbers of pit toilets are full in Africa, the question is what to do. The problem may be solved by not removing the material at all, but removing the slab and structure, topping up the pit with soil, and then planting a tree directly on top of the pit. This is the concept of the Arborloo. This concept also involves the construction of a new pit structure and superstructure to fit on top. Space is required for this technique. The concept was designed for households with very poor sanitation or no sanitation at all. Most Arborloo pits are shallow and unlined, and do not really suit the school environment. The problem can also be solved by using the concept of the Fossa alterna, where two pits are used alternately. The additions to the pit, which is in use, also include soil and ash and even some vegetable matter like leaves, as these hasten the conversion of raw excreta into a product which can more easily be dug out with a shovel by hand. Adding soil and ash regularly also reduces the smell and fly problem. In the short cycle Fossa alterna (12month cycle) the superstructure, which is best made as a portable unit, is moved from one pit to the other at yearly intervals. In the long cycle Fossa alterna, the period of changing pits (which are larger) can be increased to around 5 years. There are many variations in the design of Fossa alterna toilets. Fossa alterna pits are normally lined with bricks. However we have not followed the Fossa alterna route at the school in this research, as, like the Arborloo, it was really designed for family use. 4

5 This leaves the challenge of emptying medium depth (2m) to deeper pits (3m). The question arises, what is the best method of pit content removal. Many methods have been devised internationally over the years, from suction tankers, to many gadgets designed for the purpose. Various methods are also being tried in the outreach area of the schools project. One challenging method is to take steps which make the pit easier to empty by hand. One method involves removing the structure and slab, and ramming in soil into the pit, waiting and then removing the semi composted material by hand, mixing with more soil, bagging and then applying to tree pits or under the topsoil of vegetable gardens. This is the method used at the school. The mix of soil and excreta improves the handling properties of the material. Semi dried pit contents can also be drilled with an earth auger and the holes filled with dry soil. This also increased the ratio of soil to excreta in the pit especially deeper down. These methods are applicable only when the superstructure and slab are removed. The more challenging method involves removing the pit contents with the slab and structure still in place. This normally involves digging down a trench by the side of the pit, and using various tools to withdraw the contents into the side pit. The tools used will vary according to the state of the pit contents and can include an Archimedes screw, shovels, rakes and hoes. The removed material is then relocated to a nearby site where it is mixed with more soil in layers, completely covered with soil and left to compost. After some months the material is dug out, bagged, and conveyed to the site (tree site or vegetable garden site) where the material is used to enhance the organic and nutrient content of the soil. The simpler method used at the school is described here. More detailed descriptions of an extended series of methods of pit extraction are described in other documents. They are not included in this series of manuals. 5

6 The method used at the school on shallow pits Removing the slab and structure and accelerate the conversion of excreta into a product which can be dug out by adding soil Where the superstructures are portable, it is very easy to remove the structure and then the concrete slab to gain access to the pit direct. Where the superstructure is made from bricks, it is still possible to take the structure apart, clean and store the bricks and roof, and then use these components again on a new structure. The method of using weaker mixes of mortar (20:1) lends itself to this technique, as prolonged evidence shows that the structures remain firm, but are also easily taken apart. Roofs made of wooden frame and tin are easily removed and replaced on new structures. Over a period of years, several methods have been used in the school and schools outreach program to empty pits and recycle the contents. One used at the school is described here. Remove structure and slab and accelerate composting In this case the structure, both brick and lighter weight portable, were removed or taken apart and the slab removed. This revealed a pit with raw or decomposing excreta together with other garbage. In each case soil was added on top of the excreta. Structures on 10 th May On the left photo the toilet on the left was lined using the corbelling technique by school pupils and the brick superstructure was also built by the pupils. The green portable structure was removed during the week of 14 th May and the pit covered with soil and rammed. On the right photo both the doored brick structure and spiral brick structure were taken apart during the same week, the slabs removed and soil added above the pit contents. Soil was also rammed into the pit contents with a pole. 6

7 The three pits on 18 th May, The pits were shallow about 1.5m deep. In each case the pit contents were covered with soil and rammed. Pit 1 (on left) was filled with soil to ground level. Pits 2 and 3 on 18 th may The pit contents were covered with soil. In each case dry soil was added on top of the excreta, and then more soil added to the body of the pit further down. The method of adding soil deeper into the pit was carried out using two methods, ramming with a pole and using an Archimedes screw. 1. The ramming method Pit number one was exposed (with superstructure and slab removed) on 14 th May and more soil driven into the pit by a process of ramming using a gum pole. Since the pit was shallow, this helped to distribute dry soil more widely through the pit contents. 7

8 The pit contents are covered with dry soil and this is rammed into the body of the pit. Excavating the pit Pit no.1. The first pit was excavated 2 weeks after the soil had been added to the pit (14 th May) contents, on 29 th May. This was possible because the pit was shallow and ramming throughout the pit was relatively easy. Also the pit was only partly lined, with pit contents exposed to the soil which accelerates conversion. In fully lined pits the conversion rate is slower as the exposure to the soil is less. Emptying the pit with a shovel. The pit contents were not completely converted into compost, but were easy to handle in a controlled environment. 8

9 The emptied pit. On the right taking apart the upper brick work (ring beam). Note the pile of semi composted excreta/soil mix on the upper right hand side of right photo On the left the semi composted pit contents. On the right these are completely covered with a layer of soil to protect them from interference. This heap was then left to compost further for some months. In this case the upper rim brickwork of the pit was removed and a new much larger pit dug and lined for a new toilet. Pit no 2. This second pit was also rammed with a pole, pushing soil down into the body of the pit. The pit contents were covered on 14 th May and excavated on 12 th July, about 2 months after the pit contents were covered with soil. This pit was slightly deeper than pit 1 (above) and fully lined with bricks. The conversion process (before ramming) was therefore slower, than with a nearly fully unlined pit (with brick ring beam). Nevertheless, the pit was easily emptied as shown below. 9

10 The pit being rammed. The brick side walls were dismantled as digging down into the pit proceeded. The intension in this case was to empty the pit and redig and line a new and larger pit on the same site. Digging out the pit contents Heaping the removed pit contents on to a pile to one side which was covered with soil and left to compost over a period of 3+ months. After this period (during the dry season) it was bagged and taken to the recycling location (vegetable garden, orchard or woodlot). 10

11 Processing the dug-out pit contents Soil is added to the dug-out pit contents, both within the pit (by ramming or in tubes drilled with the Archimedes screw) as described earlier, and also when the pile is built up outside the pit. Piles of pit contents mixed with soil are covered with a generous layer of soil to protect them against tampering and left to process for 3 months (preferably in the dry season). The extracted pit contents, mixed with soil, can also be bagged (in old cement bags for instance) at this stage, but preferably after the 3 + month period following extraction from the pit, mixing with soil and covering. It is important to mix soil with the extracted pit contents, as this helps the composting process and also adds beneficial soil bacteria to the mix. Photos of bagging the processed pit compost Digging out a pile of removed pit soil and adding to a bag for transport to site of recycling The same process of digging out the processed soil from the pile and adding this to bags. In this case the extracted pit contents were placed into a mound and a layer of soil added as the mound was built up. This mound was covered by an extra layer of dry soil. This was left for 3 months or more (in the dry season). After this period the top of layer of soil was removed and the darker layer of pit contents removed with a shovel and bagged in old cement bags. 11

12 Recycling of processed and bagged pit material Normally the processed pit material will be placed in bags and then moved to the site where it will be recycled. In this case sites were chosen in the vegetable garden and the orchard of the Chisungu Primary school, where the extracted and processed pit material was used to fertilise the vegetable beds or tree pits. Some processed and bagged pit material was brought into the school from other pit excavation sites in the area around the school. This work is described elsewhere. Care is required when handling extracted toilet pit contents, even if it is processed. The handling of the contents should be undertaken by trained gardeners or other adults. If the material is still not fully composted it is best to add the bagged material to tree pits, cover with soil and then plant a tree. If there is garbage in the pit material, the tree roots will simply grow around the garbage. Trees are best planted at the start of the rainy period if regular watering cannot be guaranteed. When the pit soil is added to vegetable beds it is formed in a layer below the surface, with topsoil added on top. This covering layer provides a degree of protection from any harmful bacteria (which will quickly die off) or helminth worm eggs. In Zimbabwe, helminth eggs are rarely found in pit contents, especially at the higher altitudes, but it is wise to be careful at all times when handling and using the material. It is best to plant green vegetables, like rape, covo, spinach on vegetable beds and not root vegetables like carrots. The process of composting and degradation of the material will continue in the beds or pits. Cover the pit compost. Where the pit compost is used in beds, the bed is dug down to about 20cm depth, then a layer of about 10cm of pit compost is added and spread throughout the bed and this is covered again with the removed topsoil. This extra topsoil layer provides a barrier between the pit material and the open environment. In the case of planting trees in tree pits, the bagged material is added to the base of the pit which measures 60cm in diameter (or 60cmX60cm) and 60cm deep. Two bags of pit compost are required per pit. This is then covered with soil, the young tree added and then a mix of normal garden compost and soil is built up around the tree. Both beds and tree pits are watered thoroughly after the seedlings or young trees are planted. This upper layer of soil acts as a health barrier in each case. 12

13 Using the processed pit contents to enhance the nutrient content of vegetable beds In this case two beds were prepared in the school garden, each measuring 1m wide and 3m long. The soil was dug out to form a wide trench in each case about 20cm deep. In practice the trench was initially dug 1m wide and 6m long and then divided into two later. The beds being prepared in the school garden The bagged pit contents were then taken to the site of the beds. Taking the bagged pit contents to the school garden 13

14 Distributing the pit compost over the surface of the dug-out beds Four bags were used on each of the two beds. Once spread out the layer of pit compost The four bags of pit soil have been placed in one side of the long bed and levelled out. The instructor then shows the pupils how the topsoil removed from the trench is then placed back over the pit soil. Once the top soil has been placed back on top of the pit soil and levelled off, the bed is generously watered. Holes are then made in the moistened soil ready for planting the vegetable seedlings. 14

15 Planting the seedlings in the prepared beds In this first demonstration case, two type of vegetables were used, sweet cabbage and spinach. Many types of green leafy vegetables can be used but not root vegetables like carrot. The seedling were purchased from a local seedling producer at $1 per bundle good value for money! Individual seedlings were placed next to the prepared holes by the demonstrater. Then the pupils planted the seedlings (sweet baggage) Once all the seedlings had been planted, the bed was re-watered. 15

16 The second bed was then processed and planted Once again the pit soil was spread out over the bed in a layer and covered with the topsoil originally removed from the trench. This was watered, and then holes made with a stick for planting the seedlings. The seedlings (in this case spinach) were then laid by each hole. The seedlings were then planted in each hole, the soil being pressed down firmly in each case around the seedling roots. Once again the whole bed of planted seedlings was watered. A large number of pupils, some teachers and gardeners watched the demonstration. 16

17 A garden tour Following the preparation of the special beds and planting of seedlings, the pupils were taken to the garden of Mr Takawira who had used the same method of enhancing the fertility of his own vegetable garden, using the same technique. He also performed controlled experiments, where some beds were fertilised with toilet pit compost, and other were not fertilised in this way. The value of adding this material, extracted and processed from pit toilets was well demonstrated. During the training and exercise and tour the importance of taking care when using material extracted and processed from pits was constantly emphasised. These operations should be performed by gardeners and adults. Where vegetable seedlings or young trees are planted by pupils, it should be under the supervision of adults. Pupils inspect the beds which have been fertilised in the same way with toilet pit compost Mr Takawira performed controlled experiments in his garden. On the left, two beds of tsunga, closer bed fertilised with toilet compost, further bed without toilet compost. On the right the right bed of sweet cabbage has been fertilised with toilet compost, the left bed unfertilised in this way. The beneficial effect of using toilet compost is well demonstrated. 17

18 Beds fertilised and cared for in this way produce healthy vegetables. Two beds of carrots (root vegetables) were inspected, but in this case toilet pit compost was not used. Healthy vegetables are always welcome in the kitchen 18

19 Using pit compost in tree pits The same bagged pit compost can be used to enhance the fertility of soil in the base of pits into which trees can be planted. These trees can form parts of both orchards planted with fruit trees and woodlots planted with gum trees in the school environment. So far in this book, we have described how the growth of trees can be enhanced by the regular addition of diluted urine. This method may not work well for all trees, but works well for gum trees planted in woodlots, as we have seen. However there is no doubt that trees planted into pits with rich composted soil at their base can accelerate the growth of the tree. In fact the addition of well composted soil to tree pits is a far better practice than adding diluted urine, especially for fruit trees, many of which will be citrus, which may not respond well to urine application. It is the quality of the soil, in which trees (and vegetables) are planted that is most important factor in determining the health of the plants.. In this case tree pits are dug 60m in diameter, or in a square shape 60cm X 60cm and 60cm deep. The processed pit material is added to the base of the tree pit and then soil is added on top to a depth of about10cm to 15cm deep. Then the young tree (which is usually purchase from a nursery and planted in a plastic bag) is planted on the soil layer above the pit soil and the space around is filled with a mix of garden compost and soil. The soil is bedded down, a rim of soil made around the tree site, which is thoroughly watered. The young tree roots first invade the soil beneath them and not the richer pit soil, which is still maturing, will soil all around it, and top and bottom. Under the ground soil bacteria and other beneficial microbes are at work enhancing the quality of the soil. The growing tree itself is also testing the quality of the soil material beneath it. Tree roots will not grow into soil which is too rich. A balance is struck between the living tree and the environment in which it has been planted. There is a variation amongst trees in the way they react to the environment in which they are planted. 19

20 Preparing the tree pit A suitable area is chosen in the school yard (or garden) and pits prepared for planting trees. These may be prepared in a school orchard or a school woodlot. The pits are dug 60cm round or 60cmX60cm square and 60cm deep. In the case of an orchard they are spaced 4 5 metres apart. For a woodlot of Eucalyptus (gum trees), the trees are spaced 2 metres apart. Two bags of processed pit compost are then added to the base of the pit and this is covered with topsoil on which the young tree is planted. This is surrounded and built up with a mix of topsoil and garden compost. Finally the soil is shaped into a basin. Ideally the basin should be topped up with a mulch of leaves to prevent too much evaporation after watering. The tree pit hole is dug. The various ingredients (young tree, 2 bags of pit compost, garden compost) are prepared. Two bags of pit compost are added to the base of the pit and levelled off. 20

21 A layer of soil about 10cm deep is then laid above the pit soil layer. This acts as a barrier between the tree roots and the rich pit soil. As time passes the pit soil composts further and the young tree roots develop and become stronger and more able to invade the richer soil beneath. The plastic bag is removed from the young tree and it is lowered on to the soil in the pit. In this case an orange and a naartjie tree were planted. More soil is added and mixed with garden compost. 21

22 The soil is then built up around the tree and the tree site thoroughly watered. The stages again Add pit soil to tree pit and cover with topsoil. Place the tree on soil. Add garden compost and soil around the tree 22

23 Mix the garden compost and soil Compact the soil and compost around the tree and build up more soil to make a bowl shaped surround to the tree which can be watered. Thoroughly water the tree and care for it 23

24 Using pit compost in tree pits placed within the orchard at the Domboramwari Secondary school, Epworth The Domboramwari Secondary School, is close to the Chisungu Primary school, where most of the activities described in these manuals have taken place. As an extension of the work carried out at Chisungu, further tree pits were dug within the existing orchard at the Domboramwari Secondary School. Processed pit compost was dug out from mounds consisting of a mix of excavated pit materials and soil, which had been left to process for months (detail of this procedure is described elsewhere). This material was bagged and taken to the site of the orchard, where new tree pits had been dug. In this case 12 new tree pits had been dug and 24 bags of pit material were brought in. 24 bags of processed pit material was brought in to the school on a truck and off-loaded in the orchard Two bags of pit material were added to each tree pit 24

25 The gardener then covered the pit material with a layer of soil, and then prepared a saucer shaped ring of soil which was then watered. This was left overnight to allow the water to soak in. Adding the young trees In this particular exercise 2 trees of 6 types were added making a total of 12 trees. These were apple, mango, peach, orange, naartjie (mandarin) and guava. In each case a hole was dug centrally in the tree pit with a badza (hoe), and the tree planted (after removal of the plastic bag). Digging the central hole and removing the plastic bag. 25

26 Trees being planted Trees being planted and the covered with dry leaves ( mulch ) Each tree pit was smartened up and then watered. 26

27 Care and maintenance of the orchard and vegetable gardens Both orchards and vegetable gardens require constant attention if the harvests of fruit or vegetables are too be plentiful. Regular watering is essential, particularly during the dry season. Also vegetable gardens will require weeding. Fruit trees may require protection from animals when they are young, especially when the school is open to goats and other animals wandering in to the school grounds. This also applies to vegetable gardens which should be protected behind a fence of some sort. Applying mulch The loss of water from a tree pit or vegetable garden by evaporation can be reduced considerably by adding a mulch of dry leaves or grass over the soil. This can also reduce the number of weeds growing in the bed or around the tree. Weeds can extract useful nutrients from the soil. Adding extra nutrients over time The initial boost in tree growth made by applying pit compost to a tree pit will have a positive effect during the first year or two of the trees growth. This is a crucial period and trees which start their lives in a healthy state, usually provide good yields of fruit. However as the tree grows larger, it will require additional nutrients if it is to maintain a good annual production of fruit. This can be supplied by adding a mix of manure and compost or garden compost to the soil around the tree and digging in. Trees are one of Nature s wonders preserve them. 27