(Semi-) centralized treatment refers to a group of treatment technologies that are generally appropriate for large user groups (i.e., neighbourhood to city level applications). The operation, maintenance, and energy requirements of technologies within this functional group are generally higher than for smaller-scale technologies. See also decentralised sanitation.

The term acidic is used to describe a material having a pH value of less than 7.

The term aerobic describes biological processes that occur in the presence of oxygen.

An aerobic pond is a lagoon that forms the third treatment stage in waste stabilization ponds. (Syn.: maturation pond, polishing pond)

The term alkaline is used to describe a material having a pH value greater than 7.

Describes biological processes that occur in the absence of oxygen.

See (syn.) Biogas Reactor.

Anaerobic digestion refers to the degradation and stabilization of organic compounds by microorganisms in the absence of oxygen, leading to the production of biogas.

Describes the process by which nitrate is biologically converted to nitrogen gas in the absence of oxygen. This process is also known as denitrification.

Application cases are the cases or context to which a given sanitation technology or system is to be applied. This could be a village or a district inside a bigger city. They can be defined by physical, socio-demographic or political boundaries and are characterised by geo-physical, technical, socio-cultural, legal, financial as well as criteria concerning capacity and management.

An appropriate sanitation technology is one that provides a socially and environmentally acceptable level of service at affordable cost. This can be translated into geo-physical, technical, socio-cultural, legal, financial as well as criteria concerning capacity and management. An appropriate or contextualized sanitation system is one that is composed of appropriate technologies.

Appropriateness attributes are the variables that are identified for a given appropriateness criterion to measure and to report, either qualitatively or quantitatively, how well an option performs with respect to the criteria.

The appropriateness profile contains the appropriateness attributes that describe a given sanitation technology or application case.

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

The arborloo is a shallow pit that is filled with excreta and soil/ash and then covered with soil; a tree planted on top of the nutrient-rich pit will thrive.

Attributes are the variables that are identified for an decision criteria or objective to measure and to report, either qualitatively or quantitatively, how well an option performs with respect to this criteria or objective.

Bacteria are 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.

Screening aims to prevent coarse solids, such as plastics, rags and other trash, from entering a sewage system or treatment plant. Solids get trapped by inclined screens or bar racks. (Syn.: bar rack, trash trap)

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).

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

Biofuel sanitation refers to sanitation systems in which biofuel such as biogas or briquettes is produced. This biofuel can then be used either for heating, cooking, or producing electricity

Biomass refers to any of the sanitation products compost, stored faeces, dried faeces, biochar, pellets, pit humus

Blackwater sanitation refers to wet sanitation systems in which blackwater is produced and treated.

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).

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

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

The case or context to which the presented procedure is applied. This could be a village or a district inside a bigger city. 

A modality of market-based programming.

Centralised sanitation refers to sanitation system in which the treatment of sanitation products happens at a large-scale centralised location. Centralised systems contain at least one technology from each of the functional groups U, C, T, and D. They must not contain technologies from S.

Centralised sanitation systems are designed to handle large volumes, typically the sanitation products from a city district or an entire city.

An ambiguous term either used to describe a soak pit (leach pit), or a holding tank.

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 oxidize it (high COD).

Special medical units to treat cholera.

City Sanitation Planning (CSP) is a comprehensive citywide planning and decision-making framework that consequently includes stakeholders to plan citywide sanitation by prioritising investments and selecting the most viable projects.

Citywide Inclusive Sanitation abbreviated (CWIS) is an approach to urban sanitation, where all members of the city have equitable access to adequate and affordable improved sanitation services through a mix of locally appropriate technologies of all scales and along the entire sanitation value chain, without any health risk and contamination to the environment.

See (syn.) Settler. 

The destabilization 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 the ways of collecting, storing, and sometimes treating the products generated at the user interface. The treatment provided by these technologies is often a function of storage and is usually passive (e.g., requiring no energy input). Thus, products that are ‘treated’ by these technologies often require subsequent treatment before use and/or disposal.

Community-Led Urban Environmental Sanitation (CLUES) is comprehensive guidelines for the planning and implementation of environmental sanitation infrastructure and services in disenfranchised urban and peri-urban communities, emphasising stakeholder participation.

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

See (syn.) simplified sewer.

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

Conveyance 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 the most important gap is between user interface or collection and storage/treatment and (semi-) centralized treatment.

An environmentally resistant stage of a microorganism that helps it to survive periods of environmentally harsh conditions. Some protozoan parasites form infective, highly resistant cysts (e.g., Giardia) and oocysts (thick-walled spores, e.g., Cryptosporidium) during their life cycle.

Decentralised sanitation refers to a sanitation system in which the treatment of sanitation products happens at a decentralised location (usually where sewer networks are not available). Decentralised systems contain at least one technology from each of the functional groups U, T, and D. They must not contain any technology from C. They can but must not contain technologies from S.

Decentralised sanitation systems are designed to handle small volumes, typically the sanitation products of one to several households up to that of an entire neighbourhood.

A small-scale system used to collect, treat, discharge, and/or reclaim wastewater from a small community or service area.

Decision criteria are used to assess and compare different decision options. Their corresponding attributes are the variables that are identified for each criterion to measure and to report, either qualitatively or quantitatively, how well an option performs with respect to the criteria. Together, objectives, criteria and attributes do two critical things: they drive the search for creative decision options and they form a consistent and transparent framework for comparing them.

Decision objectives or planning objectives describe a desired result that a person, a system or an organization envisions, plans and commits to achieve with a given decision: a personally or organizationally desired end-point of development. The joint definition of decision objectives (is crucial to align different actors’ perspectives, define a joint vision and thus a joint story line.

Decision options, also called planning options or decision alternatives, are possible courses of actions in the planning process. In this guide, the decision options represent either different sanitation technologies or sanitation systems. The number of options in sanitation system selection is however too large to be considered in its entirety. Local conditions can be used to pre-select locally appropriate technology and system options from which the final option can be derived while carefully balancing for trade-offs and stakeholder preferences.

See (syn.) dried faeces.

Dehydration vaults are used to collect, store and dry (dehydrate) faeces. Faeces will only dehydrate when the vaults are well ventilated, watertight to prevent external moisture from entering, and when urine and anal cleansing water are diverted away from the vaults. (Syn.: double vault UDDT)

The process by which nitrate is biologically converted to nitrogen gas in the absence of oxygen.

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

See (syn.) hydraulic retention time.

The process of reducing the water content of 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).

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

The elimination of (pathogenic) microorganisms for tertiary treatment of effluent by inactivation (using chemical agents, radiation or heat) or by physical separation processes (e.g., membranes).

See use and/or disposal (U).

Dry cleansing materials are 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. Although extremely important, a separate product name for menstrual hygiene products like sanitary napkins and tampons is not included in this definition. In general (though not always), they should be treated along with the solid waste generated in the household.

Dry sanitation refers to sanitation systems in which faeces and excreta are not mixed with water. This allows to keep volumes low which in return makes the handling easier.

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

See (syn.) pit humus.

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 minimized. (Syn.: resources-oriented sanitation)

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. (Syn.: Use)

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.

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

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

Evapotranspiration is the combined loss of water from a surface by evaporation and plant transpiration.

A facultative pond is a lagoon that forms the second treatment stage in waste stabilization ponds.

A chemical or natural substance rich in plant nutrients (such as nitrogen, phosphorus, potassium and sulphur) that can be applied in agriculture to improve the soil nutrient composition and increase yields of grown crops.

The liquid that has passed through a filter.

Filtration is 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 chemically destabilized particles and can then be removed by settling or filtration.

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

Groupings of technologies that have similar functions. There are five different functional groups from which technologies can be chosen to build a system

- the user interface (e.g. pour flush toilet)

- the collection and storage/treatment (e.g. septic tank)

- the conveyance (e.g. solid free sewer)

- the (semi-) centralized treatment (e.g. activated sludge)

- the use and/or disposal (e.g. biogas combustion).

The goal of the grease trap is to trap oil and grease so that they can be easily collected and removed. Grease traps are chambers made out of brickwork, concrete or plastic, with an odour-tight cover. Baffles or tees at the inlet and outlet prevent turbulence at the water surface and separate floating components from the effluent. A grease trap can either be located directly under the sink or, for larger amounts of oil and grease, a bigger grease interceptor can be installed outdoors. 

Where subsequent treatment steps could be hindered or damaged by sand in the wastewater, grit chambers or sand traps allow for the removal of such heavy inorganic materials by settling them out. There are three general types of grit chambers: horizontal-flow, aerated, and vortex chambers. All of these designs allow heavy grit particles to settle out, while lighter, principally organic particles remain in suspension. (Syn.: sand trap)

Water that is located beneath the earth’s surface.

Refers to when treated effluent and/or stormwater is directly discharged into the ground to recharge aquifers.

It is 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. The groundwater table is not static and can vary by season, year or usage. (Syn.: water table)

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.

Hybrid sanitation refers to sanitation systems in which some sanitation products are treated on the plot or in the neighbourhood (onsite or decentralized), and others are collected, conveyed and treated centralized (offsite). Hybrid systems contain at least one technology from each of the functional groups U, S, C, T and D.

A type of activated sludge system.

Facilities that ensure hygienic separation of human excreta from human contact.

A product that can be used as a raw material in an industrial production process, e.g., as an additive to fertiliser production or other product.

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

Jerrycans are light, plastic containers that are readily available and can be easily carried by one person. When sealed, they can be used to safely store or transport urine.

Leachate is the liquid fraction that is separated from the solid component by gravity filtration through 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).

Concentrated liquid solutions that act as a fertiliser. See also fertiliser.

Refers to organism removal efficiencies. 1 log unit = 90%, 2 log units = 99%, 3 log units = 99.9%, removal 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), submerged (watermilfoil, bladderwort) or floating (duckweed, lily pads).

See (syn.) floating plant pond.

Refers to the ways of supporting local sanitation market systems.

Material flow analysis (MFA) is an analytical method to quantify flows and stocks of materials or substances in a well-defined system. MFA is an important tool to study the bio-physical aspects of human activity on different spatial and temporal scales. MFA is used to study flows across different industrial sectors in a given territory (e.g. agriculture at national level), at a single industrial installation level (e.g. a wastewater treatment plant) or within ecosystems. In addition, MFA is an important tool to study the circular economy potential of a given activity or sector.

See (syn.) aerobic pond.

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.

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

A pollutant that is present in extremely low concentrations (e.g., trace organic compounds).

It is a membrane filter with a pore size ranging from 1 to 10 nanometers.

A historical term for faecal sludge.

Nitrogen is both, an essential nutrient and a potential environmental pollutant. Excess nitrogen in water body cuases plant growth and may also algae bloom, leading to excessive oxygen consumption and oxygen free zones. Adverse impacts on humans are caused by nitrite in drinking water. In the form of free ammonia gas, it becomes toxic to fish. During nitrogen conversions in wastewater treatment processes, nitrous oxide is released to the air, and therefor contributes to climate change. During composting and drying of faeces and sludge, a high percentage of nitrogen volatises. The rest remains retained in the biosolid that could be reused. High nitrogen recoveries can be achieved by converting urine. For the sanitation substance flow model in SaniChoice, we use Total Nitrogen (TN) to measure nitrogen flows and recovery and loss potentials.

Any substance that is used for growth. Nitrogen (N), phosphorus (P) and potassium (K) are the main nutrients contained in agricultural fertilizers. N and P are also primarily responsible for the eutrophication of water bodies.

Objective hierarchies are hierarchical structures that organize decision objectives into higher-level and lower-level decision objectives. Decision objective hierarchies help organize and thus to communicate better with different stakeholders and to validate the completeness and lack of redundancies in the system of decision objectives. However, how different objectives are hierarchies also influences how much important they take in the evaluation of decision options.

Offsite sanitation referes to sanitation systems in which sanitation products are collected and conveyed away from the plot where they are generated and treated decentralised or centralised. See also centralised sanitation and decentralised sanitation.

Onsite sanitation referes to sanitation systems in which excreta and wastewater are collected, stored and/or treated on the plot where they are generated. Onsite systems contain at least one technology from each of the functional groups U, S, and D. They do not contain any technologies from S and T.

There are two main categories of on-site sanitation technologies: wet sanitation systems which require water for flushing; and dry sanitation systems which do not require any water for flushing.

See (syn.) cyst.

Practice of defecating outside in the open environment.

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

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.

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).

The remains of pharmaceuticals that have not been fully metabolised by the human body. Pharmaceutical residues are primarily excreted through urine.

Phosphorus is both, an essential nutrient and a potential environmental pollutant. Excess phosphor in water body causes plant growth and may also trigger algae bloom, leading to excessive oxygen consumption and oxygen free zones. As phosphates are not reduced like organic matter, but remain in the cycle, the discharge of effluents from sanitation systems containing phosphorus thus can be problematic. Because phosphorus is also an important plant nutrient, the recovery of phosphorus from sanitation systems is financially and environmentally attractive and can be achieved through different methods (e.g. irrigation with effluent, composting of sludge). For the sanitation substance flow model in SaniChoice, we use Total Phosphorus (TP) to measure phosphorus flows and recovery and loss potentials.

See (syn.) aerobic pond.

See (syn.) tertiary treatment.

Pre-treatment is the preliminary removal of wastewater or sludge constituents, such as oil, grease, and various solids (e.g., sand, fibres and trash). Built before a conveyance or treatment technology, pre-treatment units can retard the accumulation of solids and minimize subsequent blockages. They can also help to reduce the abrasion of mechanical parts and extend the life of the sanitation infrastructure.

Pre-treatment products are materials separated from blackwater, brownwater, greywater or sludge in preliminary treatment units, such as screens, grease traps or grit chambers. Substances like fats, oil, grease, and various solids (e.g. sand, fibres and trash), can impair transport and/or treatment efficiency through clogging and wear. Therefore, early removal of these substances is crucial for the durability of a sanitation system.

The process by which materials (e.g., solids, particles and organic matter) that are suspended in a liquid (e.g., wastewater) are allowed to settle out at the bottom of a reactor or a storage tank, usually by the addition of precipitation chemicals that clump the material into larger aggregates that allow for increased settling rates. Gravitational forces acting on the suspended material naturally drive precipitation.

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.

When microbiological activity is hampered not by the degradation of organic material but by adverse conditions such as low water content, high ammonia concentrations, etc. Pseudo-stable material may continue to be degraded if the adverse conditions are changed, e.g., if dry material is rewetted.

Resource recovery from sanitation refers to sanitation systems where sanitation products are safely converted in order to recover some either nutrients, organics, energy, or water. To be safe, the final products should not pose any significant health threat or environmental impact. When correctly used resources recovered from sanitation systems can make a critical contribution to a circular economy and a more sustainable society. They potentially also contribute to cost recovery.

See (syn.) ecological sanitation.

Safe use of treated sanitation products such as compost, or water.

A membrane filtration process that uses high pressure and a semi-permeable membrane to remove ions, unwanted molecules, pathogens and larger particles from water. Reverse osmosis membranes have pore sizes that are less than 1 nm.

See (syn.) surface runoff.

See (syn.) grit chamber.

SaniChoice criteria are criteria used in SaniChoice for selecting and comparing locally appropriate sanitation options. Criteria for pre-filtering include existing infrastructure, the development phase, or the application level which are called preconditions. Criteria to assess the local appropriateness of technologies are named appropriateness or screening criteria. Appropriateness criteria have to be non-negotiable, meaning they are independent from stakeholder preferences, and have to be quantifiable at an early planning phase. They can be grouped into geo-physical, technical, socio-cultural, legal, financial as well as criteria concerning capacity and management. Criteria that are negotiable (not unanimously agreed and involving conflict of interests) are used in a later stage for the detailed evaluation of options and negotiation of trade-offs and preferences. These negotiable criteria are called System Evaluation Criteria.

Sanitation refers to the safe management of excreta and liquid wastes for the protection of public health and the environment. This involves the technical and non-technical aspects of four required sub-systems: excreta management, wastewater management, solid waste management, and stormwater management.

Sanitation 21 is a planning framework based upon international best practices and which has a citywide perspective, and provides a holistic planning framework rather than detailed technical guidance.

Sanitation products are the material that enter or are generated by sanitation technologies. Some sanitation products are generated directly by humans (urine or faeces), others are required in the functioning of technologies (flush water to move excreta through sewers, etc.) and some are generated as a function of storage or treatment (sludge, effluent, etc.).

A sanitation system is defined as a set of sanitation technologies which, in the given configuration, manage sanitation products from its point of generation to the final point of reuse or disposal. A sanitation system is valid if it consists of compatible technologies only and every sanitation product either finds its way into a subsequent technology or a sink. Two sanitation technologies are compatible if the output product of one can be the input product of the other or vice versa.

A sanitation technology is defined as any process, infrastructure, method or service that is designed to contain, transform or transport sanitation products. It is characterized by its name, the input and output products and how they relate to each other (e.g. blackwater or greywater -> septic tank -> sludge and effluent). Additionally, technologies can be further described by using appropriateness attributes such as water, energy, or space requirements.

A sanitation system can also be defined as the sanitation value chain comprising of five functional groups that include technologies with similar functions: The user interface (U), the onsite collection and/or storage (S), the conveyance (C), the decentralized or centralized treatment (T), and the reuse or disposal (D). See also sanitation system.

Reduction of disease-causing microorganisms/pathogens (not necessarily all) to a degree that is considered safe for humans, animals and the environment.

Screening aims to prevent coarse solids, such as plastics, rags and other trash, from entering a sewage system or treatment plant. Solids get trapped by inclined screens or bar racks. (Syn.: bar rack, trash trap)

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

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. (Syn.: settling)

See (syn.) Settler.

A historical term to define sludge removed from septic tanks.

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

See (syn.) solids-free sewer.

See (syn.) sedimentation.

See (syn.) settler.

Sewage is the waste matter that is transported through the sewer.

A sewer is an open channel or closed pipe used to convey sewage.

An SDS is like a transfer station but is directly connected to a conventional gravity sewer main. Sludge emptied into the SDS is released into the sewer main either directly or at timed intervals (e.g., by pumping) to optimize the performance of the sewer and the wastewater treatment plant, and/or reduce peak loads.

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

Someone who prefers to sit on the toilet, rather than squat over it.

Sludge is a 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 onsite 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. For a more detailed characterization of faecal sludge refer to Strande et al., 2014. Wastewater sludge (also referred to as sewage sludge) is sludge that originates from sewer-based wastewater collection and (semi-) centralized treatment processes. The sludge composition will determine the type of treatment that is required and the end-use possibilities.

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

Solid chemical or organic material that acts as a fertiliser. See also fertiliser.

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

Someone who prefers to squat over the toilet, rather than sit directly on it.

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

Structured decision-making is an organized, inclusive and transparent approach that has been developed to tackle environmental decision problems. SDM is based on an in-depth understanding of both values of people (what is important) and factual information concerning the potential consequences of actions (what’s likely to happen if an alternative is implemented). It combines analytics methods drawn from decision analysis and environmental science with insights into human judgment and behaviour. It helps to understand the complex problem and to generate and evaluate creative options in ways that in ways that help individuals and groups build common understanding and balancing for opposing preferences. SDM usually requires that each of the following steps is addressed: (1) Clarification of the decision context (scope and bounds of the decision problem); (2) Identification of objectives and performance measures; (3) Identification of decision options (actions or strategies under consideration); (4) Evaluation of consequences of these actions or strategies (including uncertainties); (5) Evaluation of trade-offs and stakeholder preferences; selection of preferred option; (6) Implementation, monitoring, and reviewing. Environmental science provides the tools for step 3 and 4. Decision analysis and behavioral theory provide the methodologies to combine this expert knowledge with the values of stakeholders, to evaluate trade offs and to make a final decision (step 2 and 5).

Substance flow modelling (SFM) uses material flow analysis (MFA) to quantify flows and stocks of substances in a well-defined system. SFM is an important tool to study the bio-physical aspects of human activity on different spatial and temporal scales. Applied to sanitation, SFM can be used to quantify substances such as nutrients, organic matter, or water within sanitation systems.

A substance is any (chemical) element or compound composed of uniform units. Substance flows describe the pathways that a substance takes within a defined system such as an industrial sector or a geographical area considering all stocks and processes as defined by substance flow modelling.

A historical term for greywater.

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

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

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

A sustainable sanitation system is one that not only provides appropriate technologies that protect human health and the environment but are also economically viable, socially acceptable, and institutionally applicable (SuSanA, 2008). This definition can be translated into five main objectives for sustainable sanitation: protection of health, protection of the environment and natural resources, economic viability, technological and institutional appropriateness, socio-cultural acceptance. The definition of sustainable sanitation largely overlaps with appropriate sanitation but includes a few more aspects such as the resource efficiency. The sustainability of entire sanitation systems depends on each of the technology, how they fit to the local conditions and how they are combined (hardware aspects). In addition other aspects such as the service delivery model and the enabling environment (favourable legal, political, and socio-economic conditions) are as much important than the technologies.

The System Appropriateness Score (SAS) expresses the confidence in how appropriate a system is for a given application case. It is obtained by aggregating the Technology Appropriateness Scores (TAS) of the technologies used in the system. The SAS can take values from 0 % to 100 % with 0 % being totally inappropriate and 100 % being perfectly appropriate.

A sanitation system template defines a class of sanitation systems with similar conceptual characteristics. It can be defined by using different technical characteristics such as if the system is dry, wet, produces biofuel or uses urine diversion or based on the systems’ level of decentralisation (onsite, decentralized, centralized or hybrid). Each sanitation system can be assigned to one unique template.

The Technology Appropriateness Filter (TAF) compares each technology profile to the case defined by the user. Each attribute is compared individually resulting in an attribute score. The aggregation of all attribute appropriateness scores (using a geometric mean) results in the Technology Appropriateness Score (TAS) for a given technology and given case. The TAS can take values from 0 % to 100 % with 0 % being fully inappropriate and 100 % being fully appropriate.

The Technology Appropriateness Score (TAS) is the result of evaluating the appropriateness criteria for a specific technology within SaniChoice and expresses the confidence in how appropriate a technology is for a given application case. It is quantified by defining for each criteria a pair of technology and case attribute. The TAS is then obtained by comparing a technology profile with the application case profile previously defined by the user. Each attribute is compared individually resulting in an attribute score. The aggregation of all attribute appropriateness scores (using a geometric mean) results in the Technology Appropriateness Score (TAS) for a given technology and given case. The TAS can take values from 0 % to 100 % with 0 % being fully inappropriate and 100 % being fully appropriate.

Application of filtration processes for tertiary treatment of effluent.

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. (Syn.: post-treatment)

User interface for urination and defecation.

Total Solids contain both organic and non-organics. The organic part is both, an essential fertiliser and a potential environmental pollutant. Excess total solids in water body causes plant growth and may also trigger algae bloom, leading to excessive oxygen consumption and oxygen free zones. In the substance flow model of SaniChoice, total solids are used as an indicator for both, the organic carbon as well as the energy contained in the combustible fraction of total solids potential lost or recovered in sanitation systems.

The transfer coefficient gives the fraction of the total substance that enters a technology with all input products, which is transferred into an output product. For instance, a septic tank is fed with the product “blackwater”, which contains a certain amount of the substance phosphorus (P). The output products of the septic tank are defined as “sludge” and “effluent”. The transfer coefficient defines how much of the phosphorus is transferred to the sludge and how much is transferred to the effluent (e.g. 80% and 17%, respectively). Additionally, there are also losses of substances into the air, soil or water, which have to be accounted for (e.g. 1 % each respectively). For every substance, the sum of all transfer coefficents for a technologiy is equal to 100%.

See (syn.) screen.

Syn.: transfer station

Urine diversion sanitation refers to sanitation systems in which urine is collected separately at the source and is then either treated or disposed of onsite or brought to a decentralised or centralised treatment. The separate collection of the urine makes the resource recovery, mainly nutrients, as well as treatment of micropollutants easier. Moreover, faeces are kept dry what makes their handling also easier.

Use and/or disposal (D) refers to the methods by which products are ultimately returned to the environment, either as useful resources or reduced-risk materials. Furthermore, products can also be cycled back into a system (e.g., by using treated greywater for flushing).

User interface (U) describes the type of toilet, pedestal, pan, or urinal with which the user comes in contact; it is the way by which the user accesses the sanitation system. In many cases, the choice of the user interface will depend on the availability of water. Note that greywater and stormwater do not originate at the user interface, but may be treated along with the products that originate from it.

It is 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.

An infectious agent consisting of 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).

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

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

Wastewater reuse is an important part of urban water cycles especially in areas affected by water scarcity where water prices are high. The nutrients and organics contained in some effluents can be reused in agriculture if wastewater is used for irrigation. Moreover, the availability can be linked to water consumption making it more controllable. As treated wastewater still contains pathogens, monitoring of quality and risk mitigation is important.
For the sanitation substance flow model in SaniChoice, many assumptions had to be made to define transfer coefficients. There is almost no change in quantities except where drying through evaporation or evapotranspiration are both considered important treatment processes.

See (syn.) groundwater table.

Wet sanitation refers to sanitation systems in which faeces and excreta are mixed with water by flushing resulting in blackwater. See also Blackwater Sanitation.

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