You are here: Glossary


Ammonia sanitation: In a closed and non-corrosive vessel, faecal material can be mixed with water to form a sludge with a water content of at least 75%. The sludge is then mixed with 2% urea (by wet weight). The degradation of this urea to ammonia and carbon dioxide is facilitated by urease, which is naturally present in the faeces. The ammonia is toxic to viruses, bacteria and helminths. Safe sanitation is then achieved by just storing this sludge in the closed vessel.

Anaerobic baffled reactor (ABR):
Could be described as an upgraded septic tank. It consists of an initial settling compartment followed by a series of baffled reactors (three baffles or more). The baffles are used to direct the flow of wastewater in an upflow mode through a series of simple sludge blanket reactors. This configuration provides for intimate mixing and contact between anaerobic microbes in the sludge and the wastewater, which improves nutrient removal.

Anaerobic digester: Is a unit in which organic material is broken down under anaerobic conditions (without oxygen). This process produces biogas (consisting about two thirds - by volume - of methane), which can be used for cooking and lighting. In some countries, the digester is common for households with animal husbandry activities where it can be used to meet or partially meet the daily energy needs. It is also possible to use this technology for domestic wastewater, especially when the user prefers a low flush toilet.

Arbor Loo Pit: Is a special case of a single pit. The pit is shallow, about 1.0 to 1.5m deep, and the site is temporary. Excreta, soil, ash and leaves are added to the pit to minimize the risk of odour and flies and to facilitate composting. The Arbor loo unit, which consists of a ring beam, slab and structure - moves from one site to the next (i.e. when full) at 6 to 12-month intervals. The full pit is covered with at least 20-30 cm of soil and left to compost. A tree is planted on the old site, preferably during the rains.

Aquaprivy: Is similar to a septic tank; it can be connected to flush toilets and take most household wastewater. It consists of a large tank with a water seal formed by a simple down pipe into the tank to prevent odour and fly problems. Its drawback is that water must be added each day to maintain the water seal, and this is often difficult to do unless water is piped into the home.

Beigewater: Is anal cleansing water. It is generated by those who use water, rather than dry material for washing.  

Blackwater: Is the mixture of urine, faeces and flushing water, along with anal cleansing water (if anal cleansing is practiced) or dry cleansing material (e.g. toilet paper).

Cesspit or Cesspool: In the UK, a cesspit or cesspool is a watertight pit, holding tank, or covered cistern, which can be used for the temporary storage of any kind of wastewater and must be emptied if full. In US, it often means a septic tank with a leach-field.

Co-composting: Is the same as composting in that it is the controlled aerobic degradation of organics; the difference is that co-composting incorporates more than one feedstock.  Faecal sludge has a high moisture and nitrogen content but a low carbon content.  The carbon to nitrogen ration (C:N) of sludge is between 5-10, while a bulking material such as wood chips has a C:N around 500. As well, solid waste has good bulking properties (i.e. it allows air to flow and circulate). Thus, by combining the two, the benefits of each can be harnessed to optimize the composting process.  

Composting chamber: The basic principle of a composting chamber is to facilitate the biological degradation of excreta (and toilet paper if included) in a specially designed container. A ventilation system is highly recommended in order to stimulate aeration and prevent odour. The system can either be designed with or without urine diversion.

Conventional activated sludge: The Activated Sludge Process is an engineered process in which microorganisms are ‘activated’ or encouraged to rapidly degrade organic material.  In the presence of oxygen, microorganisms break down complex organic molecules into their simple constituents such as carbon dioxide and water: the oxygen can be supplied from air or pure oxygen. By supplying the microorganisms with excess oxygen, the time for degradation is reduced to hours instead of days.

Dehydrating toilet/latrine: This is similar to the double chamber, however in a dehydration toilet, the processing chambers are constructed in a way to enhance the drying of excreta inside the chamber with the help of sun, natural evaporation and ventilation. They are sometimes called solar toilets and versions with just one chamber are also used. The toilet should not contain flushing water or anal cleansing water but in hot, dry climates urine can be included.

Disposal: Describes the technologies and/or methods which allow the flowstreams to be returned to the environment in a benign/non-detrimental way.

Dry toilet: Is simply a toilet without flushing water. The toilet may be raised as a seat (pedestal) or else it is a squat pan over which the user squats. Pedestals and squatting platforms can be made locally using concrete or other materials. Dry toilets do not have odour seals. Therefore, the odour may have to be controlled by other means such as ventilation and/or use of cover material (in the case of dry faecal collection without any urine or water).

Excreta: Is the mixture of urine and feaces that is not mixed with any flushing water (although small amounts of anal cleansing water may be included.

Faecal Sludge: Is the general term for the undigested or partially digested slurry or solid that results from the storage or treatment of blackwater or excreta.

Faeces: Refers to (semi) solid excrement without any urine or water.

Floating macrophyte ponds: These are ponds that are covered in floating plants. The plants float on the water with their leaves close to the surface and their roots hang down into the pond water column to absorb nutrients. Some plant types commonly used are Eichhornia sp. (water hyacinth), Lemna sp. (duckweed), Pistia sp. (water lettuce or water cabbage) and Cyperus sp. (papyrus).

Flowstream: This describes the path that the product takes as it moves from the point of generation to the point of disposal: from ‘cradle to grave’.  It could be described as the lifecycle of the product as it passes through the various process steps, which transform and transfer the product to its ultimate release into the environment.

Green walls: Developed by a Swedish horticulturist, green walls/vertical gardens are a container gardens for intensive horticulture for dry tropical areas.  They are based on walls with built-in growth boxes made of hollow concrete blocks.

Greywater: Is used water which results from bathing, hand-washing, cooking or clothes washing. It is sometimes mixed with, or treated along with, other types of products.

Greywater gardens (mulch trenchs):
Are simple greywater management systems that allow for the direct utilisation of the water, facilitate the breakdown of organic compounds and recover nutrients. If site conditions (e.g. available space, soil conditions, etc.) are favourable, the easiest way to apply greywater for subsurface irrigation purposes is to drain it to swales or trenches, which are filled with mulch material

High-volume cistern-flush toilets: Flush toilets use water to flush excreta into a subsequent storage, transport or treatment process. After the toilet is used and flushed, water from the cistern automatically fills the bowl, which is then drained away along with the excreta, leaving the bowl clean. Flush toilets normally have a U-shaped conduit partly filled with water (U trap) under the pan. The U trap overcomes the problems of flies, mosquitoes, and odour by serving as a water seal. Conventional cistern-flush toilets use between 10 and 20 litres per flush. The toilet can be constructed as pedestal or squatting pan depending on the socio-cultural preferences.

Horizontal subsurface-flow constructed wetland (HSSF CW- planted horizontal flow filter): Consist of a bed lined with impermeable material (clay packing, plastic or gum liner) and filled with sand and gravel. The greywater entering the filter bed through an inlet zone devoid of vegetation flows horizontally through the bed. The water line lies below the filter surface and is controlled by an outlet level control arrangement.

Horizontal surface-flow constructed wetland (HSF CW): In this type of wetland, wastewater is fed in at the inlet and flows slowly over the surface of the plant bed in a horizontal path until it reaches the outlet of zone before leaving via the level control arrangement at the outlet. In a HSF CW, the plants can contribute to treatment through uptake of nutrients and other wastewater constitutes, but the most important parts are the submerged portion of leaves, stalks, and litter, which serve as a substrate for attached microbial growth.

Low flush urinals: Urinals, like toilets, use large amounts of water. Low flush urinals are intended to help reduce water consumption by providing a financial incentive to replace high-volume flush toilets and urinals.

Low-volume cistern flush toilets: Those which are designed to use four to six litres of water per full flush. This reduces water requirements in single-family residences significantly, by at least 20%. Although a low flush toilet looks like a conventional cistern flush toilet, it has several unique features. Most low flush toilets use gravity to speed the course of water through the bowl and trap. The rim wash comes through an open slot rather than small holes. The bowl may have steep sides and a narrow trap opening to decrease volume of the U-bend. Low flush toilets generally have a smaller pool or "water spot" than in conventional toilets. Some toilets also offer the option of a half flush of two to three litres or a full flush, which is twice the size.

Membrane biological reactor (MBR): Is a special process that can be used in water reclamation facilities to remove nearly all bacteria. MBRs include a semi-permeable membrane barrier system either submerged in, or following, an activated sludge process. The performance of MBR systems is directly proportional to nutrients reduction efficiency of the activated sludge process. The microscopic holes in the membrane are smaller than bacteria so that they are filtered.  

On-site Collection, Storage & Treatment: Describes the technologies that can be used at the household/compound level to collect, store and (partially) treat different flowstreams.

Pour-flush toilets: It includes both a spot for squatting or sitting and a water seal that helps control odour and flies. Below, or connected to the pan by small diameter pipes, can be single or double leach pits, a cesspit or septic tank. Water, which is poured by hand into the pan, transports the excreta through the water seal and connecting pipes into the collection technology. The flush volume required varies, but can be as low as 2-3 litres.

Reuse: Describes the technologies and /or methods which allow some benefit to be derived from a flowstream.

Sanitation system: This describes a comprehensive combination of product-specific technology components designed to process each product from the point of generation until the point reuse or disposal (from cradle to grave).

Septic tank: Generally consists of a watertight tank that is connected to an inlet pipe at one end, and to a leach field, a constructed wetland, or another disposal or treatment technology at the other. Pipe connections are generally made of a T pipe which allows liquid to enter and exit without disturbing any of the crust on the surface.

Single pit latrine: Is the most commonly used sanitation technology in developing countries. Pit latrines consist of a superstructure and a hole for defecation. A pit cover slab can be used to reduce odour and hinder flies. The average depth is 3 m. but is usually limited by the groundwater table or bedrock.  The walls of the latrine should be water pervious and it is strongly recommended that the guidelines on vertical safety distance between the bottom of the pit and the groundwater be followed. Dry anal cleansing is advantageous to minimise water content and extend the life of the pit.

Sludge Planted drying bed / reedbed: Is similar to an unplanted drying bed but with the benefit of increased transpiration. This technology has the benefit of dewatering as well as stabilizing the sludge.  Also, the roots of the plants create pathways through the thickening sludge to allow water to escape more easily.
Sludge Unplanted drying bed: Is a simple, permeable bed that collects percolated leachate and allows the sludge to dry by evaporation. About 50-80% of the sludge volume drains off as liquid. The sludge however, is not stabilized or treated.

Stormwater: Is the general term for the rainfall that runs off of roofs, roads and other surfces before flowing towards low-lying land. It is the portion of rainfall that does not infiltrate into the soil.

Struvite precipitation from urine: Precipitation of MgNH4PO4*6H20 as the white mineral struvite (also called magnesium ammonium phosphate, MAP) is a nutrient recovery option, which has been used in full-scale wastewater treatment for over 20 years.  More recent research has focused on its recovery from animal manure and human urine. The production of struvite would be possible anywhere that there are sufficient, and continuous quantities of urine.

Surface Disposal: Is simply the stockpiling of biosolids for non-beneficial use. Surface disposal is the final disposal site; the biosolids are not used later.

Technology: Is a product-specific method or tool designed to collect, store, transform (change), move, or dissipate a product.   Each technology component is responsible for performing a process (task).

Tower gardens: Are a user-friendly, low-cost and low-tech greywater reuse system, where gardening does not have to rely on rainfall and where nutrients are derived from the greywater.

Transport: Describes the way in which flowstreams are transferred from the household to a centralized treatment/use facility.

Treatment off site: Describes the technologies used to reduce the pathogenicity and/or nutrient loads of the various flowstreams.

Trickling filter: A filter that is filled with a high-surface area medium such as rocks, gravel, shredded PVC bottles, etc. (the higher the surface area to volume ratio, the better). Organisms that grow in a thin biofilm over surface of the media oxidise the organic pollution in the wastewater to carbon dioxide and water (and new biomass). Oxygen is obtained by direct diffusion from air into the thin biological film. After preliminary settlement the wastewater is “trickled” over the surface of the filters, often by rotating distribution pipes.

Upflow Anaerobic Sludge Blanket (UASB) Reactor: is a tank filled with anaerobic granular or flocculant sludge with good settling properties (the bacteria may spontaneously agglomerate to form granules). Influent wastewater is distributed at the bottom of the UASB reactor and travels in an upflow mode through the sludge blanket. Anaerobic degradation of organic substrates occurs in this sludge blanket and biogas is produced. The gases produced under anaerobic conditions (methane and carbon dioxide) mix the contents of the reactor as they rise to the surface.

Urinal: Is a specialized toilet designed to be used only for urination. The most common designs are for used by males, but designs for females are also available. In public toilets, the urinal often includes a mesh above to outlet to prevent solid objects such as cigarette butts and paper from entering the pipe and possibly causing a plumbing problem. Presently, most urinals use water for flushing, but waterless urinals are becoming increasingly more popular.

Urine: Is urine that is not mixed with any faeces or water.

Urine diversion toilet (dry or wet): It differs from an ordinary toilet as it is designed to collect the urine separately from the faeces. This is done to minimize the faecal contamination and the water dilution of the urine flowstream. It can offer the same comfort and functional service as non-diverting toilets.

Urine soakaway pit: Is a small soakaway (soak pit), loaded only with the urine. Since the flow is so small, it can be much smaller than normal soakaways. The low flow also means that the retention time of the urine will be long, which promotes a good reduction of nitrogen and phosphorus. However, the electrical conductivity of the urine is high. Therefore, in dry areas, plants close to the pit might suffer if their main liquid supply is from the urine. This risk can be decreased by irrigation with other water sources, thus diluting the electrical conductivity of the liquid available to the plants.

User Interface: Describes the way in which users access and interact with the sanitation system.

Vegetated leachfield: Is an open system in which pre-treated greywater (or primary-treated wastewater) is evenly distributed through a horizontal, perforated pipe laid in a gravel bed. The gravel bed is covered with sand then densely planted with fast-growing plants, which ‘harvest’ nutrients, the main pollutants found in ground and surface waters

Ventilated improved single pit latrine (VIP): Are designed to reduce two problems frequently encountered by traditional pit latrine systems: smells and flies (or other insects). A VIP latrine differs from a traditional latrine by having a vent pipe covered with a fly screen. Wind blowing across the top of the vent pipe creates a flow of air, which sucks out the foul-smelling gases from the pit. As a result, fresh air is drawn into the pit through the drop hole and the superstructure is kept free from smells. The vent pipe also has an important role to play in fly control.

Vertical flow constructed wetlands (VF CW): Are shallow excavations or above ground constructions with an impermeable liner, either synthetic or clay. The layer structure of a VF CW comprises a flat bed of gravel (min. 20 cm) topped with a layer of sand (min. 60 cm), which is again topped by a layer of gravel (min. 15 cm).

Waste stabilization ponds (WSP): WSPs are one of the main natural wastewater treatment methods. They are man-made earthen basins, which can be designed to work independently or as a sequence of several anaerobic, facultative and maturation ponds, depending on the effluent quality required. Primary treatment is carried out in anaerobic ponds, secondary treatment in facultative ponds, and tertiary treatment in maturation ponds. The type, number and sequence of ponds depend on what is to be done with the effluent.  

Waterless urinals: Collect undiluted urine, which can then be collected, transported, treated and used. Waterless urinals come in many shapes and materials; squatting slabs and wall mounted bowls are common while materials range from reused plastic vessels, concrete, high-quality plastics, porcelain to stainless steel.

Worm composting (vermicomposting): Is the process by which organic materials are converted into humus with the use of specific types of earthworms that breakdown the organic materials.