eCompendium Glossary



Describes biological processes that occur in the presence of oxygen.

aerobic pond

A lagoon that forms the third treatment stage in Waste Stabilisation Ponds. See T.5 (Syn.: Maturation Pond, Polishing Pond)


Describes biological processes that occur in the absence of oxygen.

anaerobic digestion

The degradation and stabilisation of organic compounds by microorganisms in the absence of oxygen, leading to production of biogas.

anaerobic pond

A lagoon that forms the first treatment stage in Waste Stabilisation Ponds. See T.5

anal cleansing water

Water used to cleanse the body after defecating and/or urinating; it is generated by those who use water, rather than dry material, for anal cleansing. The volume of water used per cleaning typically ranges from 0.5–3 litres (but can be more in developed urban areas).


An oxygen depleted environment with partially aerobic and anaerobic conditions fluctuating in time and space


The controlled cultivation of aquatic plants and animals.


An underground layer of permeable rock or sediment (usually gravel or sand) that holds or transmits groundwater.



Simple, single cell organisms that are found everywhere on earth. They are essential for maintaining life and performing essential “services”, such as composting, aerobic degradation of waste, and digesting food in our intestines. Some types, however, can be pathogenic and cause mild to severe illnesses. Bacteria obtain nutrients from their environment by excreting enzymes that dissolve complex molecules into more simple ones which can then pass through the cell membrane.

biochemical oxygen demand (BOD)

A measure of the amount of oxygen used by microorganisms to degrade organic matter in water over time (expressed in mg/L and normally measured over five days as BOD5). It is an indirect measure of the amount of biodegradable organic material present in water or wastewater: the more the organic content, the more oxygen is required to degrade it (high BOD).


Biological transformation of organic material into more basic compounds and elements (e.g., carbon dioxide, water) by bacteria, fungi, and other microorganisms.


Common name for the mixture of gases released from the anaerobic digestion of organic material. Biogas comprises methane (50 to 75 %), carbon dioxide (25 to 50 %) and varying quantities of nitrogen, hydrogen sulphide, water vapour and other components, depending on the material being digested. Biogas can be collected and burned for fuel (like propane).


Refers to plants or animals grown using the water and/or nutrients flowing through a sanitation system. The term biomass may include fish, insects, vegetables, fruit, forage or other beneficial crops that can be utilised for food, feed, fibre and fuel production.


Mixture of urine, faeces and flushwater along with anal cleansing water (if water is used for cleansing) and/or dry cleansing materials. Blackwater contains the pathogens, nutrients and organic matter of faeces and the nutrients of urine that are diluted in the flushwater.


C:N ratio

The ratio of the mass of carbon to the mass of nitrogen in a substrate.

capital costs

Funds spent for the acquisition of a fixed asset, such as sanitation infrastructure.

cash transfer programming (CTP)

A modality of Market-Based Programming. See X.13


An ambiguous term either used to describe a Soak Pit (Leach Pit), or a Holding Tank. (Syn.: Cesspool)

chemical oxygen demand (COD)

A measure of the amount of oxygen required for chemical oxidation of organic material in water by a strong chemical oxidant (expressed in mg/L). COD is always equal to or higher than BOD since it is the total oxygen required for complete oxidation. It is an indirect measure of the amount of organic material present in water or wastewater: the more the organic content, the more oxygen is required to chemically oxidise it (high COD).

cholera treatment center (CTC)

Special medical units to treat cholera.

cistern flush toilet

A type of flush toilet.


The destabilisation of particles in water by adding chemicals (e.g., aluminium sulphate or ferric chloride) so that they can aggregate and form larger flocs.

collection and storage/treatment

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.


Decomposed organic matter that results from a controlled aerobic degradation process. In this biological process, microorganisms (mainly bacteria and fungi) decompose the biodegradable waste components and produce an earth-like, odourless, brown/black material. Compost has excellent soil-conditioning properties and a variable nutrient content. Because of leaching and volatilisation, some of the nutrients may be lost, but the material remains rich in nutrients and organic matter. Generally, excreta or sludge should be composted long enough (2 to 4 months) under thermophilic conditions (55 to 60 °C) in order to be sanitised sufficiently for safe agricultural use.


The process by which biodegradable components are biologically decomposed by microorganisms (mainly bacteria and fungi) under controlled aerobic conditions.

constructed wetlands

A treatment technology for wastewater that aims to replicate the naturally occurring processes in wetlands. See T.6

container-based toilets

Sanitation system where toilets collect human excreta in sealable, removable containers that are transported to treatment facilities. See S.10


Describes the transport of products from one functional group to another. Although products may need to be transferred in various ways between functional groups, the longest, and most important gap is usually between the user interface or collection and storage/treatment and (semi-) centralised treatment. Therefore, for simplicity, conveyance only describes the technologies used to transport products between these two functional groups. In the technology overview graphic, the conveyance functional group is subdivided into the two subgroups: “Emptying and Transport” and “Intermediate Storage”. This allows for a more detailed classification of each of the listed conveyance technologies.



The process of removing the accumulated sludge from a storage or treatment facility.


The process of reducing the water content of a sludge or slurry. Dewatered sludge may still have a significant moisture content, but it typically is dry enough to be conveyed as a solid (e.g., shovelled).


Abbreviation for Decentralised Wastewater Treatment System, a small-scale system used to collect, treat, discharge, and/or reclaim wastewater from a small community or service area.


The solid and/or liquid material remaining after undergoing anaerobic digestion.


The elimination of (pathogenic) microorganisms by inactivation (using chemical agents, radiation or heat) or by physical separation processes (e.g., membranes). See POST

dried faeces

Faeces dehydrated to an extend until they become a dry, crumbly material. Dehydration takes place by storing faeces in a dry environment with good ventilation, high temperatures and/or the presence of an absorbent material. Very little degradation occurs during dehydration and this means that the dried faeces are still rich in organic matter. Faeces reduce by around 75 % in volume during dehydration and most pathogens die off. There is a small risk that some pathogenic organisms (e.g. helminth ova) can be reactivated under the right conditions, particularly, in humid environments.

dry cleaning materials

Solid materials used to cleanse oneself after defecating and/or urinating (e.g. paper, leaves, corncobs, rags or stones). Depending on the system, dry cleansing materials may be collected and separately disposed of or dealt with alongside the other solid materials in the sanitation system.


E. coli

Escherichia coli, a bacterium inhabiting the intestines of humans and warm-blooded animals. It is used as an indicator of faecal contamination of water.

ecological sanitation (ecosan)

An approach that aims to safely recycle nutrients, water and/or energy contained in excreta and wastewater in such a way that the use of non-renewable resources is minimised.


General term for a liquid that leaves a technology, typically after blackwater or sludge has undergone solids separation or some other type of treatment. Effluent originates at either a collection and storage or a (semi-) centralised treatment technology. Depending on the type of treatment, the effluent may be completely sanitised or may require further treatment before it can be used or disposed of.

emerging technology

A technology that has moved beyond the laboratory and small-pilot phase and is being implemented at a scale that indicates that expansion is possible.


The utilisation of products derived from a sanitation system.

environmental sanitation

Interventions that reduce peoples’ exposure to disease by providing a clean environment in which to live, with measures to break the cycle of disease. This usually includes hygienic management of human and animal excreta, solid waste, wastewater, and stormwater; the control of disease vectors; and the provision of washing facilities for personal and domestic hygiene. Environmental Sanitation involves both behaviours and facilities that work together to form a hygienic environment.


The enrichment of water, both fresh and saline, by nutrients (especially the compounds of nitrogen and phosphorus) that accelerate the growth of algae and higher forms of plant life and lead to the depletion of oxygen.


The phase change from liquid to gas that takes place below the boiling temperature and normally occurs on the surface of a liquid.


The combined loss of water from a surface by evaporation and plant transpiration.


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.


facultative pond

A lagoon that forms the second treatment stage in Waste Stabilisation Ponds. See T.5


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.


The liquid that has passed through a filter.


A mechanical separation process using a porous medium (e.g., cloth, paper, sand bed, or mixed media bed) that captures particulate material and permits the liquid or gaseous fraction to pass through. The size of the pores of the medium determines what is captured and what passes through.


The process by which the size of particles increases as a result of particle collision. Particles form aggregates or flocs from finely divided particles and from chemically destabilised particles and can then be removed by settling or filtration.


The process whereby lighter fractions of a wastewater, including oil, grease, soaps, etc., rise to the surface, and thereby can be separated.

flush water

Water discharged into the user interface to clean it and transport the contents into the conveying system or to the on-site storage. Freshwater, rainwater, recycled greywater, or any combination of the three can be used as a flushwater source. Many sanitation systems do not require flushwater.

functional group

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).



Total volume of water generated from washing food, clothes and dishware, as well as from bathing, but not from toilets (see blackwater). It may also contain traces of excreta (e.g. from washing diapers) and, therefore, some pathogens. Greywater accounts for approximately 65 % of the wastewater produced in households with flush toilets.


Water that is located beneath the earth’s surface.

groundwater table

The level below the earth’s surface which is saturated with water. It corresponds to the level where water is found when a hole is dug or drilled. A groundwater table is not static and can vary by season, year or usage



A parasitic worm, i.e. one that lives in or on its host, causing damage. Some examples that infect humans are roundworms (e.g., Ascaris and hookworm) and tapeworms. The infective eggs of helminths can be found in excreta, wastewater and sludge. They are very resistant to inactivation and may remain viable in faeces and sludge for several years.


The stable remnant of decomposed organic material. It improves soil structure and increases water retention, but has no nutritive value.

hydraulic retention time (HRT)

The average amount of time that liquid and soluble compounds stay in a reactor or tank.


immersed membrane bioreactor (IMBR)

A type of Activated Sludge system. See T.13

improved sanitation

Sanitation facilities that ensure hygienic separation of human excreta from human contact.


The general name for the liquid that enters into a sanitation system or process (e.g., wastewater).



The liquid fraction that is separated from the solid component by gravity filtration through a media (e.g., liquid that drains from drying beds).


The common name for calcium oxide (quicklime, CaO) or calcium hydroxide (slaked or hydrated lime, Ca(OH)2). It is a white, caustic and alkaline powder produced by heating limestone. Slaked lime is less caustic than quicklime and is widely used in water/wastewater treatment and construction (for mortars and plasters). It can also be used for on-site treatment of faecal sludge. See S.17

log reduction

Organism removal efficiencies. 1 log unit = 90 %, 2 log units = 99 %, 3 log units = 99.9 %, and so on.



An aquatic plant large enough to be readily visible to the naked eye. Its roots and differentiated tissues may be emergent (reeds, cattails, bulrushes, wild rice), submergent (water milfoil, bladderwort) or floating (duckweed, lily pads).

market-based programming

Ways of supporting local sanitation market systems. See X.13

maturation pond

A lagoon that forms the third treatment stage in Waste Stabilisation Ponds. See T.5 (Syn.: Aerobic Pond, Polishing Pond)

menstrual hygiene products

Include sanitary napkins, tampons or other materials used by women and girls to manage menstruation. As they are often disposed alongside dry cleaning materials in a sanitation system, some specific precautionary measures are advisable (e.g. separate bins). Generally, they should be treated along with the generated solid waste (see X.8).


A colourless, odourless, flammable, gaseous hydrocarbon with the chemical formula CH4. Methane is present in natural gas and is the main component (50–75%) of biogas that is formed by the anaerobic decomposition of organic matter.


Pollutant that is present in extremely low concentrations (e.g. trace organic compounds).


Any cellular or non-cellular microbiological entity capable of replication or of transferring genetic material (e.g. bacteria, viruses, protozoa, algae or fungi).


night soil

A historical term for faecal sludge.


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.


off-site sanitation

A sanitation system in which excreta and wastewater are collected and conveyed away from the plot where they are generated. An offsite sanitation system relies on a sewer or transport technology (C) for conveyance.

on-site sanitation

A sanitation system in which excreta and wastewater are collected and stored or treated on the plot where they are generated.

open defecation

Practice of defecating outside in the open environment.

operation and maintenance (O&M)

Routine or periodic tasks required to keep a sanitation process or system functioning according to performance requirements and to prevent delays, repairs or downtime.


Refer to biodegradable plant material (organic waste) that must be added to some technologies in order for them to function properly. Organic degradable material can include, but is not limited to, leaves, grass and food market waste. Although other products in this compendium contain organic matter, the term organics is used to refer to undigested plant material.



An organism that lives on or in another organism and damages its host.


An organism or other agent that causes disease.


The movement of liquid through a filtering medium with the force of gravity.

personal protective equipment (PPE)

Protective clothing including boots, masks, gloves, apron, etc. or other garments or equipment designed to protect the wearer's body from injury or infection from sanitation products.


The measure of acidity or alkalinity of a substance. A pH value below 7 indicates that it is acidic, a pH value above 7 indicates that it is basic (alkaline).

pit humus

Term used to describe the nutrient-rich, hygienically improved, humic material that is generated in double pit technologies (S.5, S.6) through dewatering and degradation. The various natural decomposition processes taking place in alternating pits can be both aerobic and anaerobic in nature, depending on the technology and operating conditions. The main difference of pit humus compared to compost is that the degradation processes are passive and are not subjected to a controlled oxygen supply and that the carbon to nitrogen ratio, humidity and temperature may be less favourable. Therefore, the rate of pathogen reduction is generally lower and the quality of the product, including its nutrient and organic matter content, can vary considerably. Pit humus can look very similar to compost and has good soil conditioning properties, although pathogens can still be present.

polishing pond

A lagoon that forms the third treatment stage in Waste Stabilisation Ponds. See T.5 (Syn.: Aerobic Pond, Maturation Pond)

pour flush toilet

A type of flush toilet.

pre-treatment products

Materials separated from blackwater, greywater or sludge in preliminary treatment units, such as screens, grease traps or grit chambers (see PRE). Substances like fat, oil, grease, and various solids (e.g. sand, fibres and trash), can impair transport and/or treatment efficiency through clogging and wear of pipes. Therefore, early removal of these substances can be crucial for the maintenance of a sanitation system.

primary treatment

The first major stage in wastewater treatment that removes solids and organic matter mostly by the process of sedimentation or flotation.


A diverse group of unicellular eukaryotic organisms, including amoeba, ciliates, and flagellates. Some can be pathogenic and cause mild to severe illnesses.



Use of recycled water or other sanitation products.



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.

sanitation product

Sanitation products can be materials that are generated directly by humans (e.g. urine, faeces and greywater from bathing, cooking and cleaning), that are required for the technologies to function (e.g. flushwater to flush excreta through sewers) or are generated as a function of storage or treatment (e.g. sludge). For the design of a robust sanitation system, it is necessary to identify all of the products that are flowing into (inputs) and out of (outputs) each of the sanitation technologies of the system. The products referenced within this text are described below. Solid waste is not included as a sanitation product as it should not enter the sanitation chain. It will be dealt with separately in the cross-cutting issue section (X.8).

sanitation system

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.

sanitation technology

Sanitation technologies are defined as the specific infrastructure, methods, or services designed to collect, contain, transform and treat products, or to transport products to another functional group. Each of the technologies included in this compendium is described on a 2-page technology information sheet in the technology compilation section. Only those sanitation technologies that have been sufficiently proven and tested are included, with a few notable exceptions of emerging technologies, which are clearly marked as such. The compendium is primarily concerned with systems and technologies directly related to managing human excreta. It does not specifically address greywater and only partially addresses stormwater management, although it does signal when a specific technology can be used to co-treat stormwater or greywater with excreta. Greywater and stormwater technologies are thus not described in detail, but are still shown as products in the system templates.


The layer of solids formed by wastewater constituents that float to the surface of a tank or reactor (e.g., oil and grease).

secondary treatment

Follows primary treatment to achieve the removal of biodegradable organic matter and suspended solids from effluent. Nutrient removal (e.g., phosphorus) and disinfection can be included in the definition of secondary treatment or tertiary treatment, depending on the configuration.


Gravity settling of particles in a liquid such that they accumulate.

semi-centralised treatment

Refers to treatment technologies that are generally appropriate for larger user groups (i.e. neighbourhood to city scale sanitation systems). The operation, maintenance, and energy requirements of technologies within this functional group are generally higher than for small-scale on-site technologies.


A historical term to define sludge removed from septic tanks.


Describes the conditions under which putrefaction and anaerobic digestion take place.


Waste matter that is transported through the sewer.


An open channel or closed pipe used to convey sewage. See C.3 and C.4

sewer discharge station

A type of Transfer Station and Storage. See C.6


The physical sewer infrastructure (sometimes used interchangeably with sewage).


A person who prefers to sit on the toilet.


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.

soil conditioner

A product that enhances the water and nutrient retaining properties of soil.

specific surface area

The ratio of the surface area to the volume of a solid material (e.g., filter media).


A person who prefers to squat over the toilet.


The degradation of organic matter with the goal of reducing readily biodegradable compounds to lessen environmental impacts (e.g., oxygen depletion, nutrient leaching).

stored urine

Stored urine has been hydrolysed naturally over time, i.e. the urea has been converted by enzymes into ammonia and bicarbonate. Stored urine in closed containers usually has a pH of 9 or higher. Most pathogens cannot survive at this elevated pH. After 1–6 months of storage, the risk of pathogen transmission is therefore considerably reduced.


General term for rainfall runoff collected from roofs, roads and other surfaces. Very often the term is used to refer to rainwater that enters a sewerage system. It is the portion of rainfall that does not infiltrate into the soil.


A historical term for greywater.


The above ground walls and roof built around a toilet or bathing facility to provide privacy and protection to the user.

surface runoff

The portion of precipitation that does not infiltrate the ground and runs overland.

surface water

A natural or man-made water body that appears on the surface, such as a stream, river, lake, pond, or reservoir.


tertiary filtration

Application of filtration processes for tertiary treatment of effluent. See POST

tertiary treatment

Follows secondary treatment to achieve enhanced removal of pollutants from effluent. Nutrient removal (e.g., phosphorus) and disinfection can be included in the definition of secondary treatment or tertiary treatment, depending on the configuration. See POST


User interface used for urination and defecation.

total solids (TS)

The residue that remains after filtering a water or sludge sample and drying it at 105° C (expressed in mg/L). It is the sum of Total Dissolved Solids (TDS) and Total Suspended Solids (TSS).



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.18


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.

use and/or disposal

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).

user interface

Describes the type of toilet, pedestal, pan, or urinal that the user comes into contact with; it is the way users access the sanitation system. In many cases, the choice of user interface will depend on the availability of water and user preferences. Additionally, handwashing facilities have been included here with a dedicated technology information sheet as a constant reminder that each sanitation user interface needs to be equipped with handwashing facilities for optimal hygiene outcomes.



An organism (most commonly an insect) that transmits a disease to a host. For example, flies are vectors as they can carry and transmit pathogens from faeces to humans.

vertical flow constructed wetland

A type of Constructed Wetland.


An infectious agent consisting of a nucleic acid (DNA or RNA) and a protein coat. Viruses can only replicate in the cells of a living host. Some pathogenic viruses are known to be waterborne (e.g., the rotavirus that can cause diarrheal disease).



A person who prefers to use water to cleanse after defecating, rather than wipe with dry material.


Used water from any combination of domestic, industrial, commercial or agricultural activities, surface runoff/stormwater, and any sewer inflow/infiltration.


Someone who prefers to use dry material (e.g., toilet paper or newspapers) to cleanse after defecating, rather than wash with water.