To decommission a pit or trench, it can be topped up with soil and covered. Similarly, untreated (faecal) sludge and excreta can be disposed of in a Deep Row Entrenchment. The covered full pit or trench poses no immediate health risk and the contents will degrade naturally over time. Trees can be planted on top of the nutrient-rich pits and trenches and will grow vigorously.Consists of urine and faeces that are not mixed with any flushwater. Excreta is relatively small in volume, but concentrated in both nutrients and pathogens. Depending on the characteristics of the faeces and the urine content, it can have a soft or runny consistency.Refers to (semi-solid) excrement that is not mixed with urine or water. Depending on diet, each person produces approximately 50–150 L per year of faecal matter of which about 80 % is water and the remaining solid fraction is mostly composed of organic material. Of the total essential plant nutrients excreted by the human body, faeces contain around 39 % of the phosphorus (P), 26 % of the potassium (K) and 12 % of the nitrogen (N). Faeces also contain the vast majority of the pathogens excreted by the body, as well as energy and carbon rich, fibrous material.Mixture of solids and liquids, containing mostly excreta and water, in combination with sand, grit, metals, trash and/or various chemical compounds. A distinction can be made between faecal sludge and wastewater sludge. Faecal sludge comes from on-site sanitation technologies, i.e. it has not been transported through a sewer. It can be raw or partially digested, a slurry or semisolid, and results from the collection and storage/treatment of excreta or blackwater, with or without greywater. Wastewater sludge (also referred to as sewage sludge) originates from sewer-based wastewater collection and (semi-)centralised treatment processes. The sludge composition will determine the type of treatment that is required and the end-use possibilities.The liquid produced by the body to rid itself of nitrogen in the form of urea and other waste products. In this context, the urine product refers to pure urine that is not mixed with faeces or water. Depending on diet, human urine collected from one person during one year (approx. 300 to 550 L) contains 2 to 4 kg of nitrogen. The urine of healthy individuals is sterile when it leaves the body but is often immediately contaminated by coming into contact with faeces.Describes technologies for on-site collection, storage, and sometimes (pre-) treatment of the products generated at the user interface. The treatment provided by these technologies is often a function of storage and is usually passive (i.e. requires no energy input), except a few emerging technologies where additives are needed. Thus, products that are ‘treated’ by these technologies often require subsequent treatment before use and/or disposal. In the technology overview graphic, this functional group is subdivided into the two subgroups: “Collection/Storage” and “(Pre-)Treatment”. This allows a further classification for each of the listed technologies with regard to their function: collection and storage, (pre-) treatment only or both.Refers to the methods through which products are returned to the environment, either as useful resources or reduced-risk materials. Some products can also be cycled back into a system (e.g. by using treated greywater for flushing).A functional group is a grouping of technologies that have similar functions. The compendium proposes five different functional groups from which technologies can be chosen to build a sanitation system:
User interface (U), Collection and Storage/Treatment (S), Conveyance (C), (Semi-) Centralised Treatment (T), Use and/or Disposal (U).
A sanitation system is a multi-step process in which sanitation products such as human excreta and wastewater are managed from the point of generation to the point of use or ultimate disposal. It is a context-specific series of technologies and services for the management of these sanitation products, i.e. for their collection, containment, transport, treatment, transformation, use or disposal. A sanitation system comprises functional groups of technologies that can be selected according to context. By selecting technologies from each applicable functional group, considering the incoming and outgoing products, and the suitability of the technologies in a particular context, a logical, modular sanitation system can be designed. A sanitation system also includes the management and operation and maintenance (O & M) required to ensure that the system functions safely and sustainably. The utilisation of products derived from a sanitation system.
Any substance that is used for growth. Nitrogen (N), phosphorus (P) and potassium (K) are the main nutrients contained in agricultural fertilisers. N and P are also primarily responsible for the eutrophication of water bodies.
A sanitation system in which excreta and wastewater are collected and stored or treated on the plot where they are generated.
An organism or other agent that causes disease.The means of safely collecting and hygienically disposing of excreta and liquid
wastes for the protection of public health and the preservation of the quality of public water bodies and, more generally, of the environment.

Waste matter that is transported through the sewer.
An open channel or closed pipe used to convey sewage. See C.3 and C.4
The organic molecule (NH2)2CO that is excreted in urine and that contains the nutrient nitrogen. Over time, urea breaks down into carbon dioxide and ammonium, which is readily used by organisms in soil. It can also be used for on-site faecal sludge treatment. See. S.18Used water from any combination of domestic, industrial, commercial or agricultural activities, surface runoff/stormwater, and any sewer inflow/infiltration.

When pits S.3 S.4 or trenches S.1 are full “Fill and Cover”, i.e. filling the remainder of the pit and covering it, is an option. The Arborloo is a shallow pit designed specifically on this principal, with a tree being planted in the pit once it is full, and the superstructure, ring beam and slab moved to a new shallow pit. Before an Arborloo pit is first used, a layer of leaves is put on the bottom of the empty pit. A cup of soil, ash or a mixture of the two should be added to the pit to cover excreta after each defecation. If available, leaves can be occasionally added to improve the porosity and air content of the pile. When the pit is full (usually every 6 to 12 months), the top 15 cm is filled with soil and a tree is planted. Banana, papaya and guava trees (among many others) have proven to be successful. Deep Row Entrenchment is a method that can be considered as both a treatment and disposal option. It consists of digging deep trenches, filling them with sludge and covering them with soil. As with the Arborloo, trees can be planted on top, which benefit from the organic matter and nutrients that are slowly released from the sludge.

Design Considerations

An Arborloo is an option if the site is suitable for a tree to grow with enough available space. A shallow pit, about 1 m deep, is needed for an Arborloo. A tree should not be planted, however, directly in the raw excreta. It should be planted in the soil on top of the pit, allowing its roots to penetrate the pit contents as it grows. It may be best to wait for the rainy season before planting if water is scarce. Deep Row Entrenchment is usually constructed with a backhoe. Dimensions are typically 1.2–1.5 m deep, about 0.6–1 m wide and with a length of several meters, depending of the space available. Space between rows can be 2 m or more edge-to-edge. The depth of the trench is determined by the volume of sludge to be applied. The trench is filled with sludge to within 0.3 m of the surface and then backfilled with the overburden heaped. Trees or other vegetation are planted on or between trenches. Aspects to consider are trench dimensions, spacing, method of filling (layered with soil or co-composted with vegetable matter), species, composition and density of vegetation and end purpose.

Materials

Tools are needed to dig the pit hole, and a backhoe is useful in the case of Deep Row Entrenchment. Small trees should be available for transplanting.

Applicability

Fill and Cover is an adequate solution when emptying is not possible or where there is space to continuously dig new pits. The Arborloo can be applied in rural, peri-urban, and even denser areas if enough space is available. Planting a tree in the abandoned pit is a good way to reforest an area, provide a sustainable source of fresh fruit and prevent people from falling into old pit sites. The same principle can be applied to trench latrines. Depending on the local conditions, however, the content of a covered pit or trench could contaminate groundwater resources until it is entirely decomposed. Deep Row Entrenchment can be considered where there is land available with adequate size and no groundwater contamination risk. These options can be applied in all phases of emergency, as soon as a pit or trench is full.

Operation and Maintenance

For the Arborloo a cup of soil and/or ash should be added to the pit after each defecation and leaves should be periodically added. Ideally, the contents of the pit should be periodically levelled with a stick to prevent a cone shape from forming in the middle. Once the pit is full, the latrine superstructure needs to be moved to a new pit. There is little maintenance associated with a closed pit or trench other than taking care of the tree or plant. Trees planted in filled pits and trenches should be regularly watered. Small fences should be constructed around saplings to protect them from animals.

Health and Safety

There is minimal risk of infection if the filled pit or trench is properly covered and clearly marked. It may be preferable to cover a pit and to plant a tree rather than emptying it, especially if there is no appropriate technology available to remove and treat the faecal sludge and space is no constraint. Operators do not come into direct contact with the faecal material and, thus, there is a very low risk of pathogen transmission. As for Deep Row Entrenchment, personal protective equipment is required during sludge collection and disposal into the trench.

Costs

Fill and Cover is a low-cost solution. The main cost items are tools, machinery and staff needed to dig the pits or trenches. Trees and edible crops can generate income or reduce food expenses.

Social Considerations

Arborloo and Deep Row Entrenchment are simple and do not produce visible or olfactory nuisance, except during sludge transport for the latter. They also reduce the risk of exposure to pathogens after covering. Arborloo demonstration projects that allow for the participation of community members are useful to display the ease of the system, its inoffensive nature, and the nutrient value of human excreta.