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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.
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 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
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
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
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.
FinancingWASH 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
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.
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
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 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”
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
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.
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 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
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.