Waterless Pit System without Sludge Production

This system is designed to produce a dense, compost-like material by using alternating pits without the addition of Flushwater.

The inputs to the system can include Urine, Faeces, Organics, Anal Cleansing Water, and Dry Cleansing Materials.

A Dry Toilet is the only recommended User Interface for this system. A Dry Toilet does not require water to function and in fact, water should not be input into this system; Anal Cleansing Water should be kept to a minimum or even excluded from this system if possible. Depending on the Collection and Storage/Treatment technology, the Dry Cleansing Materials can be added to the pit, otherwise they should be collected separately and directly transferred for disposal (Surface Disposal).

Excreta is produced at the User Interface. The User Interface is connected directly to a Collection and Storage/Treatment technology: a Double VIP, Fossa Alterna or a Composting Chamber. Alternating the pits gives the material an opportunity to drain, degrade, and transform into a nutrient-rich, hygienically-improved, humic material that can be used or disposed of safely.

While one pit is filling with Excreta (and potentially organic material), the other pit remains out of service. When the first pit is full, it is covered and temporarily taken out of service. The drained and degraded Excreta within the second pit is emptied and the pit is put back into service. The second pit collects Excreta until it is filled, covered and taken out of service and the cycle is repeated indefinitely. Although a Composting Chamber is not strictly an alternating pit technology, it can have multiple chambers and produces a safe, useable compost-Product. For these reasons it is included in this System Template.

The Compost/EcoHumus that is generated from the Collection and Storage/Treatment Technology can be removed and transported for Use and/or Disposal manually using a Human-Powered Emptying and Transport Conveyance Technology. Since it has undergone significant degradation, the humic material is quite safe to handle and use in agriculture. If there are concerns about the quality, it can be composted further in a dedicated composting facility but there is no need to transport the Compost/EcoHumus to a (Semi-) Centralized Treatment facility as decomposition of the Excreta takes place onsite.

For the Use and/or Disposal of Compost/EcoHumus, the Application of Compost - Eco-Humus technology is utilized.

This system is different than System 1 because of the Conveyance and Use and/or Disposal options: in the previous system, the sludge requires further treatment before it can be used, whereas the Compost/EcoHumus produced in this system is ready for Use and/or Disposal following Collection and Storage/Treatment.

Considerations

Because the system is permanent and can be used indefinitely (as opposed to some single pits, which may be filled and covered), it can be used where space is limited. Additionally, because the Product must be removed manually, this system is appropriate for dense areas that do not have access to mechanical emptying/trucks.

The success of this system depends on an extended storage period. If a suitable and continuous source of soil, ash or organic matter (leaves, grass clippings, coconut or rice husks, woodchips, etc.) is available, the decomposition process is enhanced and the storage period can be reduced. The storage period can be minimized if the material in the pit remains well aerated and not too moist. Therefore, the Greywater must be collected and treated separately. Too much moisture in the pit will fill the air-voids and deprive the microbes of oxygen, which may impair the degradation process.

This system is especially appropriate for water-scarce areas and where there is an opportunity to use the humic material. Dry cleansing materials can be discarded into the pit/chamber, especially if they are carbonaceous (e.g. toilet paper, newsprint, corncobs, etc.) as this may help with degradation and airflow.

References

• Elizabeth Tilley et.al (2008). Compendium of Sanitation Systems and Technologies (low res version). Department of Water and Sanitation in Development Countries (Sandec) at the Swiss Federal Institute of Aquatic Science and Technology (Eawag). (Provides a full overview of sanitation systems.)