The F-diagram shows faecal-oral disease transmission routes. Faeces which are not disposed or stored safely represent a health risk for humans, since pathogens in faeces can be transmitted through many different routes to humans – i.e. flies, contaminated foods, fingers (unwashed hands), through fields (crops) and fluids (water). The F-diagram depicts those relationships in a simple manner so that everyone can understand them.

Facultative Pond
A lagoon that forms the second treatment stage in waste stabilisation ponds (WSPs). It is a shallow pond (1 to 2m) consisting of an aerobic zone close to the surface and a deeper, anaerobic zone. AS algae grow on the surface they produce oxygen, which is consumed by aerobic bacteria in the middle of the pond degrading the BOD. In the lower zones of the pond, anaerobic digestion takes place. Synonyms: FP
Faecal Coliform
Faecal coliforms are a group of bacteria (e.g. Escherichia coli) present in excreta. They are not necessarily harmful, but they are present in high numbers and relatively easy to detect. Therefore they are used to indicate the presence of other faecal bacteria, which may be present in small numbers only, but associated to a high health risk. Synonyms: FC
Abbreviation: FC

Faecal Indicator Bacteria
Faecal indicator bacteria are bacteria used as indicator organism of faecal contamination. Typical faceal indicator bacteria are faecal coliforms or E. coli.

Faecal Sludge
Faecal sludge comes from onsite sanitation technologies, and has not been transported through a sewer. It is raw or partially digested, a slurry or semisolid, and results from the collection, storage or treatment of combinations of excreta and blackwater, with or without greywater. Examples of onsite technologies include pit latrines, unsewered public ablution blocks, septic tanks, aqua privies, and dry toilets. Faecal sludge management includes the storage, collection, transport, treatment and safe enduse or disposal of faecal sludge. Faecal sludge is highly variable in consistency, quantity, and concentration. Synonyms: Fecal Sludge
Faecal Sludge Management
Faecal sludge management includes the storage, collection, transport, treatment and safe enduse or disposal of faecal sludge. Synonyms: Fecal Sludge Management, FSM
Abbreviation: FSM
Faecal Sludge Management
Faeces refer to (semi-solid) excrement that is not mixed with urine or water. Depending on diet, each person produces approximately 50 L per year of faecal matter. Fresh faeces contain about 80% water. Of the total nutrients excreted, faeces contain about 12% N, 39% P, 26% K and have 107 to 109 faecal coliforms in100 mL. Synonyms: Feces
Describes people or cultural groups who feel or express a relatively low inhibition when being exposed to or handling excreta

Describes people or cultural groups who react inhibited or dismissive in when being exposed to or handling excreta

Feedstock is the raw material entering anaerobic digesters and which is transformed for the production of biogas. Such feedstock can be agricultural wastes and manures, municipal or industrial wastewater, organic solid wastes or any other biodegradable vegetables (e.g. maïze, water hyacinths) or non-vegetal material.

This is the iron-salt-dependent decomposition of hydrogen peroxide, generating the highly reactive hydroxyl radical. This reaction is enhanced by solar irradiation (referred to as photo-Fenton).
Fermentation is the second step of anaerobic digestion. Fermentative bacteria transform sugars and other monomeric organic products from hydrolysis into organic acids, alcohols, carbon dioxide (CO2), hydrogen (H) and ammonia (NH3). Synonyms: Acidogenesis

Ferric Chloride
Ferric Chloride Synonyms: FeCl3
Abbreviation: FeCl3

Ferric Sulphate
Ferric Sulphate Synonyms: FeSO4
Abbreviation: FeSO4

The combined irrigation and fertilisation is called fertigation. There are different way how fertigation can be done: mixing chemical fertiliser with irrigation water; using partly treated wastewater which contains still nutrients; mixing (separately collected) urine as a nutrient source and mixing it to the irrigation water. Fertigation helps saving freshwater resources and decreases the dependency on depleting mineral fertilisers. Generally, drip irrigation and subsurface drip irrigation are the most appropriate application method for fertigation.

Fertigation Water
Fertigation water is the water used for fertigation (the combined irrigation and fertilisation). In the SSWM toolbox, it refers to wastewater that has been partly treated but still contains sufficient nutrients to be used in fertigation. Fertigation water, depending on its initial composition, should have undergone both physical treatment, to prevent clogging of the irrigation system, and biological treatment to reduce pathogens and to limit the risk of crop contamination and the health risk to workers and end consumers.

Fertilisers are soil amendments applied to promote plant growth; the main nutrients present in fertiliser are nitrogen (N), phosphorus (P), and potassium (K) (the macronutrients). Other nutrients (micronutrient) are sometimes added in smaller amounts. There are inorganic fertilisers (mined or synthetically produced) or organic fertilisers. Due to a growing world population, today, the mineral resources of the main components of fertiliser (e.g. P) are depleting leading to exaggerate prices and the difficulty of small-farmer to provide them with sufficient fertiliser for food production. In sustainable sanitation systems, nutrients, initially contained in food, is recycled from wastewater products (e.g. urine, faeces etc.) providing an affordable and environmentally sound source of fertiliser at a local level. Synonyms: Fertilizer
Field Capacity
Field capacity is the amount of soil moisture or water content held in soil after excess water has drained away and the rate of downward movement has materially decreased, which usually takes place within 2–3 days after a rain or irrigation in previous soils of uniform structure and texture.
Field Trenches
Field trenches increase precipitation harvesting by breaking the slope of the ground and therefore reducing the velocity of water runoff. By decreasing runoff, they enhance water infiltration and prevent soil erosion. Trenches can be seen as an extended practice of ploughing fields. They may be applied to all soil types and are not dependent on slope or rainfall conditions Synonyms: Contour Furrows
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.
Financial Sustainability of WASH Services
Financing WASH Services sustainably – in the sense of securing service delivery after implementation – has proven to be a challenge. This is mainly due to a lack of planning and knowledge of post-installation costs and assigned responsibilities. Hence, a planning tool, such as an indicator framework for financial sustainability of WASH services is needed. Different organisations have recently produced such frameworks (e.g. the life-cycle cost approach from WASHCOST) that provide an overview of important aspects for reaching financial sustainability. Synonyms: Financial Sustainability Framework

Financing means the organisation and acquisition of funds to pay for the full costs of a project (planning, building/ carrying out, operation & maintenance, monitoring & evaluation, etc.).

First Flush Device
First flush devices are used in rooftop rainwater harvesting (RTRWH) systems, in order to prevent debris, dirt, dust and droppings that collect on the catchment area from entering the collection and storage tank. Different types exist, such as float valve types, overflow flow types, flow rate types or electronic conductivity types. First flush diverter devices improve water quality, reduce tank maintenance and protect pumps. Synonyms: First Flush Diverter, First Water Diverter
Rainwater Harvesting
Fish Pond
Fish can be grown in ponds that receive effluent or sludge where they can feed on algae and other organisms that grow in the nutrient-rich water. The fish, thereby, remove the nutrients from the wastewater and are eventually harvested for consumption. See also aquaculture.
Fixed Bed Reactor
Fixed bed, fixed film or attached growth reactors are biological wastewater treatment processes that employ an inert medium such as rock, plastic, wood, or other natural or synthetic solid material, that will support attached growth of active biomass responsible for degradation on its surface and within its porous structure reactors. Typical aerobic fixed bed reactors are trickling filters and biological disks or moving bed reactor (of type Kalness or Biostyr). Typical anaerobic fixed film reactors are anaerobic upflow filters. Synonyms: Attached Growth Reactor, FBR, Fixed Film Reactor
Abbreviation: FBR

Fixed-film System
Fixed-film systems (also attached-growth systems) are biological wastewater treatment processes that employ a inert medium such as rock, plastic, wood, or other natural or synthetic solid material, that will support attached growth of biomass on its surface and within its porous structure. Wastewater comes into contact with the film contaiining the active fixed biomass either by pumping the water past the media in packed towers (i.e. trickling filter) or by moving the media past the wasewater to be treated (e.g. rotating biological contactor). Synonyms: Attached-growth Systems, FFS
Floating Plant Ponds
A floating plant pond is a modified maturation pond with floating (macrophyte) plants. Plants such as water hyacinths or duckweed float on the surface while the roots hang down into the water to uptake nutrients and filter the water that flows by. Synonyms: Macrophyte Pond
A very fine, fluffy mass formed by the aggregation of fine suspended particles, as in a precipitate. See also 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. Flocculation is often used in combination with coagulation.
The process whereby lighter fractions of a wastewater, including oil, grease, soaps, etc., rise to the surface, and thereby can be separated. Synonyms: Floatation
Flow Rate
The volumetric flow rate is the volume of fluid which passes through a given surface per unit time (e.g. m3/s, cubic meters or litres per second). Mass flow rate is the mass of substance which passes through a given surface per unit time. Synonyms: Q
Abbreviation: Q

Fluidised-bed incinerator
A type of incinerator in which the stoker grate is replaced by a bed of limestone or sand that can withstand high temperatures. The heating of the bed and the high air velocities used cause the bed to bubble, which gives rise to the term “fluidised”
Flush Urinal
A flush urinal is a urinal used with water to flush away the urine. There are manual and automated flush techniques. Installing a flush urinal results in increased water consumption and the generation of the corresponding amount of wastewater. Waterless urinals, which work without water, have become increasingly popular. Synonyms: flush urinals, waterborn urinals

Flushing Point
A flushing point is a capped pipe which is accessible on the surface for maintenance. Blockages can be cleaned or flushed out. They can be found at pipe junctions or where small-bore sewers are connected to a conventional sewerage. Synonyms: Cleanout

Flushwater is the water discharged into the User Interface to transport the content and/or clean it. Freshwater, rainwater, recycled Greywater, or any combination of the three can be used as a flushwater source.
In the study of transport phenomena (heat transfer, mass transfer and fluid dynamics); flux is defined as flow per unit area, where flow is the movement of some quantity per unit time.
Fog is the same as clouds except that it touches the ground, whereas clouds have their base above the ground. When wind blows clouds over a mountain, fog is present wherever the clouds touch the ground. To a meteorologist, fog is present when visibility is less than 300 meters. Fog is composed of tiny liquid water droplets from less than a milimeter in diameter.
Fog Drip
Fog drip is a method to harvest the water contained in the fog. Fog harvesting provides a cheap complementary water source for arid and semiarid, rural regions. As the wind blows the fog through specially designed nets (fog collectors), tiny droplets of condensed water form on the mesh and are collected in a gutter and transported to a storage site. The collected water does meet the WHO standards and can be used as drinking water. One large fog collector, with a 40 m2 collecting surface, can produce up to an average of 200 litres per day throughout the year, costs around 1000 to 1500 USD each and can last 10 years.

Food Products
Any nutritious substance that people (or animals) eat or drink in order to maintain life and growth. Basic food products are produced in agriculture requiring soil, sun, water and nutrients.

Forage are plants grown to feed animals.

Fossa Alterna
The Fossa Alterna is a short cycle alternating, waterless (dry) double pit technology. Compared to the double VIP which is just designed to collect, store and partially treat excreta, the Fossa Alterna is designed to make an earth-like product that can be used as a nutrient-rich soil conditioner. The Fossa Alterna is dug to a maximum depth of 1.5 m and requires a constant input of cover material (soil, ash, and/or leaves).
Fouling refers to the accumulation of unwanted material on solid surfaces, most often in an aquatic environment. The fouling material can consist of either living organisms (biofouling) or a non-living substance (inorganic or organic). Fouling is usually distinguished from other surface-growth phenomena in that it occurs on a surface of a component, system or plant performing a defined and useful function, and that the fouling process impedes or interferes with this function. Synonyms: Biofouling, Inorganic fouling, Organic Fouling
Framework Issues
Frameworks include institutional and legal frameworks, the former meaning the different institutions that are involved in planning and managing water and sanitation issues, and the latter meaning the laws that regulate the management of water and wastewater.

Free-Water Surface Constructed Wetland
A free-water surface constructed wetland aims to replicate the naturally occurring processes of a natural wetland, marsh or swamp. As water slowly flows through the wetland, particles settle, pathogens are destroyed, and organisms and plants utilize the nutrients. This type of constructed wetland is commonly used as an advanced treatment after secondary or tertiary treatment processes. Synonyms: Free Water Constructed Wetland, Free Water Surface Flow Constructed Wetland, Free Water Surface Flow CW, Free-Surface Constructed Wetland, Free-Surface CW, FWS CW, Surface Flow Constructed Wetland
Water naturally occurring on the Earth's surface (lakes, rivers, etc) and underground (groundwater in aquifers and underground streams). Freshwater is characterized by having low concentrations of dissolved salts and other total dissolved solids. The term specifically excludes seawater and brackish water.

Fuel Cell
A fuel cell is an electrochemical cell that converts a source fuel into an electrical current. It generates electricity inside a cell through reactions between a fuel (often hydrogen) and an oxidant generating heat and water steam as by-products which then are transformed into mechanical energy and electricity. Natural gas is often used as a source of hydrogen and air as a source of oxygen.
Fulvic Acids
Fulvic acids are humic acids of lower molecular weight and higher oxygen content than other humic acids.
Functional Group
A functional group is a grouping of technologies that have similar functions. There are five different functional groups from which technologies can be chosen to build a system.