F-H

Facultative ponds

In a waste stabilisation pond system for wastewater treatment, ponds that have oxygen at the top near the surface and are without oxygen at the bottom of the pond (11)

Faecal coliforms

Coliform bacteria that originate from faeces (2)

Filtration

Separation of solids from a liquid using a filter (5)

Fine screens

(in water treatment) steel bars with a spacing of 5–20 mm (5)

Flash flood

Short-duration flooding that occurs due to sudden heavy rainfall that is unable to drain away into the ground (14)

Flocculant

Chemical that assists the process of flocculation (5)

Flocculation

Process whereby the size of particles increases as a result of particles combining together (5)

Flooding

Abnormal rise in water level that can cause damage (14)

Fluoridation

Addition of fluoride to water (5)

Fluorosis

Abnormal human condition that results from an excess of fluoride in the body (2)

Full cost recovery

Where both initial capital costs and operation and maintenance (O&M) costs are all recouped (13)

Geothermal energy

Energy derived from the heat of the earth (1)

Ground penetrating radar

Device used to detect water leaks from pipes by identifying where the ground has cavities, or has been disturbed (7)

Groundwater

Water that is held in underground rocks (1)

Hazard

Anything that can cause harm or damage (8)

Hazardous event

An event that can introduce a hazard to a water supply (8)

Helminths

Worms that live as parasites in humans and other animals (2)

Household sand filter

Device for purifying water using gravel, coarse sand and fine sand (10)

Hydroelectric power

Power produced by harnessing the energy of moving water (1)