Technologies d'assainissement

A Deep Trench Latrine is a widely-used communal latrine option for emergencies. It can be quickly implemented (within 1–2 days) and consists of several cubicles aligned up above a single trench. A trench lining can prevent the latrine from collapsing and provide support to the superstructure.

Borehole Latrines are mainly provided in the acute response phase, when a large number of latrines are required quickly and the site conditions do not allow for the excavation of bigger pits. A borehole driller is the main requirement for implementation.

The Single Pit Latrine is one of the most widely used sanitation technologies. Excreta, along with anal cleansing materials (water or solids) are deposited into the pit. Lining the pit prevents it from collapsing and provides support to the superstructure.

The Single VIP is seen as an improvement over the Single Pit Latrine (S.3) because continuous airflow through the ventilation pipe prevents odours and acts as a trap for flies as they escape towards the light.

Twin Pit Dry Systems use two pits in alternating order. Twin pit systems include double Ventilated Improved Pits (VIP), and the fossa alterna (FA). Pit alternation allows for effluent to infiltrate into the soil and sludge to decompose in the one pit, while the other pit is in use. The alternating system reduces the amount of pit humus that needs to be emptied and makes the end product more hygienic.

This technology consists of two alternating pits connected to a Flush Toilet (U.4). The blackwater (and in
some cases greywater) is collected in one pit and allowed to slowly infiltrate into the surrounding soil. When full, one pit is closed and with time the solids are sufficiently dewatered and enabling manual removal, while the other pit is used.

Raised Latrines are alternatives to pit-based latrines in areas with rocky ground, high water tables or flood affected areas. Depending on site conditions they can either be built as autonomous facilities entirely above ground with a holding tank below the user interface or by raised partially above ground, reducing the risk of groundwater contamination.

The Single Vault UDDT is a Container-Based Toilet (S.10) that operates without water. Urine and faeces are collected separately. Unlike the Double Vault UDDT (S.9) it does not offer the possibility of prolonged storage and treatment and needs an appropriate management system for regular emptying, transport, treatment, reuse and/or safe disposal of collected excreta products.

Double Vault UDDTs operate without water. Urine and faeces are diverted using a Urine Diverting Dry Toilet (U.2) and are collected separately. While urine goes into a container (or is drained away), faeces are collected in vaults underneath, where they are stored and dried. Alternating vaults allow for prolonged storage and thereby treatment of collected faeces in the unused vault.

A Container-Based Toilet is an on-site sanitation solution, available in a variety of forms that work on the principle of containing the excreta. Faeces and urine are collected in sealable, removable containers (also sometimes called cartridges), where they are sealed and stored until they are transported to a Transfer Station [C.6] or treatment facility. The portable Container-Based Toilet allows for private in-home use and easy and convenient collection and transport. Very large containers also can be installed below multiple latrines to simplify emptying [S.7].

The Chemical Toilet, commonly referred to as a ‘portaloo’, can be used as an immediate solution in the acute response phase of an emergency. Chemical toilets are generally contained in a single prefabricated plastic portable unit, or cubicle, that collects human excreta in a sealed holding tank which contains chemicals that disinfects excreta and/or decreases odours.

The Worm-Based Toilet is an emerging technology that has been used successfully in rural, peri-urban and camp settings. It consists of a pour flush pan connected to a vermifilter (filter containing worms). The effluent infiltrates into the soil and the vermicompost (worm waste) is emptied approximately every 5 years.

A Septic Tank is a watertight chamber made of concrete, fibreglass, PVC or plastic, through which blackwater and greywater flows for primary treatment, before further treatment or infiltration. Settling and anaerobic processes reduce solids and organics. The liquid effluent is commonly disposed of in a Leach Field [D.9] or Soak Pit [D.10] which provides further treatment.

The Anaerobic Baffled Reactor (ABR) treats many different types of wastewater and can be considered an ‘improved’ Septic Tank [S.13] that uses baffles to optimise treatment. Treatment of the wastewater takes place as it is forced to flow upward through a series of chambers, where pollutants are biologically degraded in an active sludge layer at the bottom of each chamber.

An Anaerobic Filter (AF) can efficiently treat many different types of wastewater. An AF is a fixed-bed biological reactor with one or more filtration chambers in series. As wastewater flows through the filter, particles are trapped and organic matter is degraded by the active biofilm that is attached to the surface of the filter material.

A Biogas Reactor can efficiently treat different types of wastewater. It is an anaerobic treatment technology that produces a digested sludge (digestate) that can be used as a fertiliser and biogas that can be used for energy. Biogas is a mix of methane, carbon dioxide and other trace gases which can be converted to heat, electricity or light [D.7].

Hydrated Lime Treatment is a cost-effective chemical treatment for faecal sludge from pits and trenches. It uses hydrated or slaked lime (calcium hydroxide: Ca(OH)2) as an additive to create a highly alkaline environment. It significantly reduces the public and environmental health risks of latrine sludge.

Urea Treatment can be used on faecal sludge, blackwater or source separated urine and faeces. Urea, with the chemical formula CO(NH2), is used as an additive to create an alkaline environment in the sludge storage device and thereby helps sanitise the sludge.

Lactic Acid Fermentation (LAF) is a biological treatment option using lactic acid bacteria (LAB) with the ability to form significant quantities of lactic acid and thereby aid in inactivating pathogens in faecal sludge. LAB are easily obtainable and can be made from molasses, milk and probiotic drinks.

Caustic Soda Treatment is a cost-effective chemical treatment for faecal sludge from pits and trenches. It
uses caustic soda also known as lye (sodium hydroxide: NaOH) as an additive to create a highly alkaline environment and thereby sanitises sludge from human waste. It significantly reduces the public and environmental health risks of latrine sludge.