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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.
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
General term for undigested or partially digested sludges of variable consistency (slurry or solid) collected from on-site sanitation systems storing or treating blackwater and excreta (e.g. latrines, non-sewered public toilets, septic tanks, aqua privies, cesspits, etc.).
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 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
Filtrate is the liquid that has passed through a filter.
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
Flocculation is the agglomeration of destabilized particles into microfloc and after into bulky floccules which can be settled called floc. The addition of another reagent called flocculant or a flocculant aid may promote the formation of the floc. Floculation is used to separate solids from a solution; most commonly, after coagulation.
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
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”
Cistern flush toilets consist of a toilet bowl and a cistern. The siphon provides a water seal against odours from the effluent pipe. Excreta are flushed away with water stored in the cistern (depending on the type between 6 to 20 litres per flush). Dual flush toilets (with two different flush-volumes) are available to reduce water used to flush urine. There are also flush toilets on the market that collect the urine separately and use a very low-flush volume to flush the urine away. Cistern-flush toilets provide a high level of convenience for the user but they use large amounts of water. Installing them results in a significantly increase of the water consumption by the users and the generation of huge amounts of wastewater that needs to be treated. Synonyms: Cistern Flush Toilet
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 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.
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.
The fossa alterna toilet system consists of two partially lined pits, pit covers with a hole or a toilet bowl and a superstructure. One of the pits is used at a time. When the first pit is filled up it is closed and the other pit is put in use. Soil, ash, and/or leaves should be added to the pit after each defecation or urination. The soil and leaves introduce a variety of organisms, which help in the degradation process. The dry material also absorbs humidity (reducing flies and odours), adjusts the C/N ratio and leads to an increased pH (pathogen die-off). After one year the decomposed faecal material can be used as compost (ecohumus) to improve soil quality.
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
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 Constructed Wetland
In surface flow constructed wetlands (CW), the water moves above the soil in a planted marsh or swamp exposed to the air and direct sunlight. Although the soil layer below the water is anaerobic, the plant roots release oxygen into the areas immediately surrounding the root hairs, thus creating an environment for complex biological and chemical degradation. Synonyms: Free Water Surface Flow CW (FWS CWs), Free-Surface Constructed Wetland, Free-Surface CW, FWS, Surface Flow Constructed Wetland
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.