Activated Sludge: See T.12: Activated Sludge

Aerated Pond: See T.06: Aerated Pond 

Aerobic: Describes biological processes that occur in the presence of oxygen.

Aerobic Pond: A lagoon that forms the third treatment stage in Waste Stabilization Ponds. See T.05: Waste Stabilization Ponds (WSP) (Syn.: Maturation Pond, Polishing Pond)

Anaerobic: Describes biological processes that occur in the absence of oxygen.

Anaerobic Baffled Reactor (ABR): See S.10: Anaerobic Baffled Reactor (ABR) and T.03: Anaerobic Baffled Reactor (ABR) 

Anaerobic Digester: See S.12: Biogas Reactor and T.17: Biogas Reactor  (Syn.: Biogas Reactor)

Anaerobic Digestion: The degradation and stabilization of organic compounds by microorganisms in the absence of oxygen, leading to production of biogas.

Anaerobic Filter: See S.11: Anaerobic Filter and T.04: Anaerobic Filter 

Anaerobic Pond: A lagoon that forms the first treatment stage in Waste Stabilization Ponds. See T.05: Waste Stabilization Ponds (WSP) 

Anal Cleansing Water: See Products

Anoxic: 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 of Dehydrated Faeces: See D.03: Application of Dehydrated Faeces

Application of Pit Humus and Compost: See D.04: Application of Pit Humus and Compost

Application of Sludge: See D.05: Application of Sludge

Application of Stored Urine: See D.02: Application of Stored Urine

Aquaculture: The controlled cultivation of aquatic plants and animals. See Fish Pond (D.9) and Floating Plant Pond (D.10)

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

Arborloo: See D.01: Fill and Cover/Arborloo

Bacteria: 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.

Bar Rack: See PRE: Pre-Treatment Technologies (Syn.: Screen, Trash Trap)

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).

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

Biogas: See Products

Biogas Combustion: See D.13: Biogas Combustion

Biogas Reactor: See S.12: Biogas Reactor and T.17: Biogas Reactor  (Syn.: Anaerobic Digester)

Biomass: See Products

Blackwater: See Products

Brownwater: See Products

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

Centralized Treatment: See Functional Group T

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

Cesspool: See Cesspit (Syn.)

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).

Cistern Flush Toilet: See U.05: Cistern Flush Toilet 

Clarifier: See T.01: Settler  (Syn.: Settler, Sedimentation/Settling Tank/ Basin)

C:N Ratio: The ratio of the mass of carbon to the mass of nitrogen in a substrate.

Coagulation: 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.

Co-Composting: See T.16: Co-Composting 

Collection and Storage/Treatment: See Functional Group S

Compost: See Products

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

Composting Chamber: See S.08: Composting Chamber 

Condominial Sewer: See C.04: Simplified Sewer | (Syn.: Simplified Sewer)

Constructed Wetland: A treatment technology for wastewater that aims to replicate the naturally occurring processes in wetlands. See T.07: Free-Water Surface Constructed Wetland | T.08: Horizontal Subsurface Flow Constructed Wetland | T.09: Vertical Flow Constructed Wetland 

Conventional Gravity Sewer: See C.06: Conventional Gravity Sewer 

Conveyance: See Functional Group C

Cyst: 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 Wastewater Treatment System (DEWATS): A small-scale system used to collect, treat, discharge, and/or reclaim wastewater from a small community or service area.

Dehydrated Faeces: See Products (Syn.: Dried Faeces) Dehydration Vaults: See S.07: Dehydration Vaults 

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

Detention Time: See Hydraulic Retention Time (Syn.)

Dewatering: 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).

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

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

Disposal: See Functional Group D

Double Ventilated Improved Pit (VIP): See S.04: Double Ventilated Improved Pit (VIP) 

Dried Faeces: See Products (Syn.: Dehydrated Faeces)

Dry Cleansing Materials: See Products

Dry Toilet: See U.01: Dry Toilet 

EcoHumus: See Pit Humus (Syn.)

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 minimized. (Syn.: Resources-Oriented Sanitation)

Effluent: See Products

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.

End-Use: The utilisation of products derived from a sanitation system. (Syn.: Use)

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.

Eutrophication: 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.

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

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

Excreta: See Products

Facultative Pond: A lagoon that forms the second treatment stage in Waste Stabilization Ponds. See T.05: Waste Stabilization Ponds (WSP) 

Faecal Sludge: See Related ProductsProducts

Faeces: See Products

Fill and Cover: See D.01: Fill and Cover/Arborloo 

Filtrate: The liquid that has passed through a filter.

Filtration: 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.

Fish Pond: See D.09: Fish Pond 

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

Floating Plant Pond: See D.10: Floating Plant Pond  (Syn.: Macrophyte Pond)

Flocculation: 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 destabilized particles and can then be removed by settling or filtration.

Flushwater: See Products

Fossa Alterna: See S.05: Fossa Alterna 

Free-Water Surface Constructed Wetland: See T.07: Free-Water Surface Constructed Wetland 

Grease Trap: See PRE: Pre-Treatment Technologies

Greywater: See Products

Grit Chamber: See PRE: Pre-Treatment Technologies (Syn.: Sand Trap)

Groundwater: Water that is located beneath the earth’s surface.

Groundwater Recharge: See D.11: Water Disposal/Groundwater Recharge 

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 (Syn.: Water Table).

Helminth: 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, wastewa- ter and sludge. They are very resistant to inactivation and may remain viable in faeces and sludge for several years.

Horizontal Subsurface Flow Constructed Wetland: See T.08: Horizontal Subsurface Flow Constructed Wetland 

Human-Powered Emptying and Transport: See C.02: Human-Powered Emptying & Transport 

Humus: 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. (Syn.: Detention Time)

Imhoff Tank: See T.02: Imhoff Tank 

Improved Sanitation: Facilities that ensure hygienic separation of human excreta from human contact.

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

Irrigation: See D.06: Irrigation 

Jerrycan: See C.01: Jerrycan/Tank 

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

Leach Field: See D.08: Leach Field 

Leach Pit: See Soak Pit (Syn.)

Lime: 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).

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

Macrophyte Pond: See D.10: Floating Plant Pond (Syn.: Floating Plant Pond)

Macrophyte: 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). Maturation Pond: See Aerobic Pond (Syn.)

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

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

Motorized Emptying and Transport: See C.03: Motorized Emptying & Transport 

Night Soil: A historical term for faecal sludge.

Nutrient: 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.

Offsite Sanitation: A sanitation system in which excreta and wastewater are collected and conveyed away from the plot where they are generated. An off-site sanitation system relies on a sewer technology (see C.04: Simplified Sewer | C.05: Solids-Free Sewer | C.06: Conventional Gravity Sewer) for conveyance.

Onsite Sanitation: A sanitation system in which excreta andwastewater are collected and stored or treated on the plot where they are generated.

Oocyst: See Cyst

Operation and Maintenance (O&M): Routine or periodic tasks required to keep a process or system functioning according to performance requirements and to prevent delays, repairs or downtime.

Organics: See Products

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

Pathogen: An organism or other agent that causes disease.

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

pH: 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: See Products (Syn.: EcoHumus)

Planted Drying Beds: See T.15: Planted Drying Beds

Polishing Pond: See Aerobic Pond (Syn.)

Post-Treatment: See POST: Tertiary Filtration and Disinfection (Syn.: Tertiary Treatment)

Pour Flush Toilet: See U.04: Pour Flush Toilet 

Pre-Treatment: See PRE: Pre-Treatment Technologies

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

Product: See Products

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

Resources-Oriented Sanitation: See Ecological Sanitation (Syn.)

Reuse: Use of recycled water. Runoff: see Surface Runoff

Sand Trap: See PRE: Pre-Treatment Technologies (Syn.: Grit Chamber)

Sanitation: 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.

Screen: See PRE: Pre-Treatment Technologies (Syn.: Bar Rack, Trash Trap)

Scum: 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.

Sedimentation: Gravity settling of particles in a liquid such that they accumulate. (Syn.: Settling)

Sedimentation Tank/Basin: See T.01: Settler | (Syn.: Settler, Clarifier, Settling Tank/Basin)

Sedimentation/Thickening Ponds: See T.13: Sedimentation/Thickening Ponds

(Semi-) Centralized Treatment: See Functional Group T

Septage: A historical term to define sludge removed from septic tanks.

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

Septic Tank: See S.09: Septic Tank 

Settled Sewer: See C.05: Solids-Free Sewer | (Syn.: Solids-Free Sewer, Small-Bore Sewer)

Settler: See T.01: Settler  (Syn.: Clarifier, Sedimentation/Settling Tank/ Basin)

Settling: See Sedimentation (Syn.)

Settling Tank/Basin: See T.01: Settler (Syn.: Settler, Clarifier, Sedimentation Tank/Basin)

Sewage: Waste matter that is transported through the sewer.

Sewer: An open channel or closed pipe used to convey sewage. See C.04: Simplified Sewer | C.05: Solids-Free Sewer | C.06: Conventional Gravity Sewer 

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

Sewer Discharge Station: See C.07: Transfer Station (Underground Holding Tank) 

Simplified Sewer: See C.04: Simplified Sewer | (Syn.: Condominial Sewer)

Single Pit: See S.02: Single Pit 

Single Ventilated Improved Pit (VIP): See S.03: Single Ventilated Improved Pit (VIP)

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

Sludge: See Products

Small-Bore Sewer: See C.05: Solids-Free Sewer (Syn.: Solids-Free Sewer, Settled Sewer)

Soak Pit: See D.07: Soak Pit (Syn.: Leach Pit)

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

Solids-Free Sewer: See C.05: Solids-Free Sewer  (Syn.: Small-Bore Sewer, Settled Sewer)

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

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

Stabilization: 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: See Products

Stormwater: See Products

Sullage: A historical term for greywater.

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

Surface Disposal and Storage: See D.12: Surface Disposal and Storage

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.

System Template: See System Templates

Tertiary Filtration: Application of filtration processes for tertiary treatment of effluent. See POST: Tertiary Filtration and Disinfection

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: Tertiary Filtration and Disinfection (Syn.: Post-Treatment)

Thickening Ponds: See T.13: Sedimentation/Thickening Ponds

Toilet: User interface 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).

Transfer Station: See C.07: Transfer Station (Underground Holding Tank)  (Syn.: Underground Holding Tank)

Trash Trap: See PRE: Pre-Treatment Technologies (Syn.: Screen, Bar Rack)

Trickling Filter: See T.10: Trickling Filter 

Twin Pits for Pour Flush: See S.06: Twin Pits for Pour Flush 

Underground Holding Tank: See C.07: Transfer Station (Underground Holding Tank)  (Syn.: Transfer Station)

Unplanted Drying Beds: See T.14: Unplanted Drying Beds 

Upflow Anaerobic Sludge Blanket Reactor (UASB): See T.11: Upflow Anaerobic Sludge Blanket Reactor (UASB) 

Urea: 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.

Urinal: See U.03: Urinal 

Urine: See Products

Urine-Diverting Dry Toilet (UDDT): See U.02: Urine-Diverting Dry Toilet (UDDT) 

Urine-Diverting Flush Toilet (UDFT): See U.06: Urine-Diverting Flush Toilet (UDFT) 

Urine Storage Tank: See S.01: Urine Storage Tank/Container 

Use and/or Disposal: See Functional Group D

User Interface: See Functional Group U

Vector: 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: See T.09: Vertical Flow Constructed Wetland 

Virus: 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).

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

Waste Stabilization Ponds (WSP): See T.05: Waste Stabilization Ponds (WSP) 

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

Water Disposal: See D.11: Water Disposal/Groundwater Recharge  

Water Table: See Groundwater Table (Syn.)

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