Dry Toilet Or Urine-Diverting Dry Toilet (UDDT) with Onsite Treatment in Alternating Pits Or Compost Chamber

WHO SANITATION SYSTEM FACT SHEET

Fact sheet 2 Dry toilet or urine-diverting dry toilet (UDDT) with onsite treatment in alternating pits or compost chamber

Toilet Containment Conveyance End use / disposal

Dry toilet or urine Fossa alterna, double VIP Manual emptying Pit humus or compost diverting dry toilet or compost chamber and transport used as a soil conditioner

Summary This system is designed to produce a solid, earthlike ma- useable compost. For these reasons it is included in this terial by using alternating pits or a composting chamber. fact sheet. Inputs to the system can include urine, faeces, organics, cleansing water, and dry cleansing materials. There is no This system is different from the system shown in Fact use of flushwater. sheet 5 regarding the treatment product generated at the containment step. In the other system, the sludge re- A dry toilet is the recommended toilet for this system, quires further treatment before it can be used, whereas although a urine-diverting dry toilet (UDDT) or a urinal the pit humus or compost produced in this containment could also be used if the urine is highly valued for ap- technology is ready for end use and/or disposal. plication. A dry toilet does not require water to function and in fact, water should not be put into this system; cleansing water should be kept at a minimum or even excluded if possible. Applicability

The dry toilet is directly connected to a double ventilated Suitability: Because the system is permanent and can improved pit (double VIP), fossa alterna or a composting be indefinitely used (as opposed to the single pits in chamber for containment. Two alternating containers, Fact sheet 1, which are backfilled and covered), it can as in the double VIP or fossa alterna, give the material be used where space is limited. an opportunity to drain, degrade, and transform into pit humus (sometimes also called ecohumus), a nutri- Additionally, because the treatment product must be ent-rich, hygienically improved, humic material which manually removed, this system is suitable for dense is safe to excavate. areas that cannot be served by trucks for motorized emptying. This system is especially appropriate for When the first pit is full, it is covered and temporarily water-scarce areas and where there is an opportunity taken out of service. While the other pit is filling with to use the compost or humic product as soil conditioner. excreta (and potentially organics), the content of the first pit is allowed to rest and degrade for at least two Cost: For the user, this system is one of the least ex- years before use. Only when both pits are full is the first pensive in terms of capital cost. The only maintenance pit emptied and put back into service. This cycle can be costs will be for cleaning of the toilet, upkeep of the indefinitely repeated. superstructure and arranging for periodic emptying of A composting container can also have alternating containers 2, 3 ; and it produces an end product that the chambers and, if properly operated, produces safe, user may be able to use or sell.

FACT SHEET 2. DRY TOILET OR URINE-DIVERTING DRY TOILET (UDDT) 1 WHO SANITATION SYSTEM FACT SHEET

Fly screen

Vent pipe

Cubicle kept dark to encourage ies to seek light in the Squat hole vent pipe covered

Vent pipe hole covered

Pit access cover

Pit 1 Pit 2 (not in use) (in use)

Source: WEDC

Figure 1. A twin-pit latrine (fossa alterna)

Design considerations drinking water. If groundwater is not used for drinking or alternative cost effective sources can be used, then Toilet: The toilet should be made from concrete, fibre- these options should be explored before assuming that glass, porcelain or stainless steel for ease of cleaning groundwater contamination by pit latrines is a problem. and designed to prevent stormwater from infiltrating Where groundwater is used for drinking and to prevent or entering the container 2, 3. its contamination, the bottom of the pit should be at least 1.5m above the water table 3. In addition, the pit Containment: For the pit-based technologies, the should be installed in areas located down gradient of water table level and groundwater use should be tak- drinking water sources, and at a minimum horizontal en into consideration in order to avoid contaminating distance of 15m 4.

2 WHO GUIDELINES ON SANITATION AND HEALTH WHO SANITATION SYSTEM FACT SHEET

Excreta, cleansing water and dry cleansing materials can vourable for pathogens survival, which die off over time. usually be collected in the pit or chamber, especially In the pit, any leachate permeates into the surrounding if they are carbon-rich (e.g., toilet paper, newsprint, soil and pathogens contained in the liquid are filtered corncobs, etc.) as this may help degradation and airflow. out, adsorbed onto particles, or die off during their slow Other inputs such as menstrual hygiene products and travel through soil 2, 3. other solid wastes are common and may contribute significantly to the contents. Where they cause the con- During rains, the slab and the pit or composting cham- tainer to fill up more rapidly and make it more difficult ber contain the fresh excreta and prevent it from being to empty, an appropriate container for disposal of these washed away into surface water bodies, while squat- wastes should be provided in the toilet cubicle. hole covers or lids can reduce disease transmission by preventing disease carrying vectors from entering and Greywater must be collected and treated separately. leaving the pit 2, 3. Too much moisture in the container will fill the air voids and deprive the microorganisms of oxygen, which may Conveyance: Any non-degradable solid waste removed impair the degradation process. from the container needs to be disposed of properly, for example through a regulated solid waste management End use/disposal: As the excreta in the resting contain- service or, where this is not available, through burial. er is draining and degrading for at least two years, the resulting pit humus or compost needs to be manually End use/disposal: Since it has undergone significant removed using shovels (the material is too dry for mo- degradation, the pit humus or compost is quite safe torized emptying) and can be used in agriculture as a to handle and use as a soil conditioner in agriculture. If soil conditioner 5. there are concerns about the pathogen level or quality of the pit humus or compost, it can be further compost- Operation and ed in a dedicated composting facility before it is used. If there is no end use for the treatment product, it can maintenance considerations be permanently disposed of. Toilet and containment: The user is commonly respon- sible for the construction of the toilet and container, although they may pay a mason to carry out the work. The user will be responsible for cleaning of the toilet and References are most likely to be responsible for removing the pit The text for this fact sheet is based on Tilley, et al. 1 unless humus or compost, although they may pay a labourer otherwise stated. or service provider to do this. 1. Tilley E, Ulrich L, Lüthi C, Reymond P, Schertenleib At shared facilities, a person (or persons) to clean and R, and Zurbrügg C (2014). Compendium of Sanitation carry out other maintenance tasks (e.g. repairs to super- Systems and Technologies. 2nd Revised Edition. Swiss structure) on behalf of all users needs to be identified. Federal Institute of Aquatic Science and Technology The success of this system depends on proper oper- (Eawag). ation and an extended storage period. If a suitable and continuous source of soil, ash or organics (leaves, 2. Brikké F, and Bredero M (2003). Linking Technology grass clippings, coconut or rice husks, woodchips, etc.) Choice with Operation and Maintenance in the Context is available, the decomposition process is enhanced of Community Water Supply and Sanitation. A refer- and the storage period can be reduced. The required ence document for planners and project staff.Geneva, storage time can be minimized if the material remains Switzerland. well aerated and not too moist. 3. Reed R A, Scott R E, and Shaw R J (2014). WEDC Guide End use/disposal: The material removed from the con- No. 25: Simple Pit Latrines. WEDC, Loughborough tainer or compost chamber should be in a safe, useable University, UK. form, although workers must wear appropriate personal 4. Graham J, and Polizzotto M (2013). Pit latrines and protection during removal, transport and end use. their impacts on groundwater quality: A systematic review. Environmental Health Perspectives. Mechanisms for protecting public health 5. Strande L (2017). Introduction to Faecal Sludge Management. Online Course available at: www. Toilet and containment: The toilet separates users sandec.ch/fsm_tools (accessed March 2017). Sandec: from excreta and the container isolates the excreta and Department of Sanitation, Water and Solid Waste pathogens within from physical human contact. for Development Eawag: Swiss Federal Institute of Aquatic Science and Technology. The main mechanism for pathogen reduction is through long storage time. The conditions in the pit are not fa-

This fact sheet is one of a set of fact sheets in WHO Guidelines on Sanitation and Health 3 For further information: www.who.int/water_sanitation_health