Science of Water : Concepts and Applications

408 The Science of Water: Concepts and Applications
the effects of pollutants, pollution control, and the identifi cation and measurement of pollutants.
Additionally, they allot grants and loans for the construction of treatment works.
The act established national discharge standards with enforcement provisions.
The Federal Water Pollution Control Act established several milestone achievement
dates. It required secondary treatment of domestic waste by publicly owned treatment
works (POTWs), and application of the “best practicable” water pollution control technology
by the industry by 1977. Virtually all industrial sources have achieved compliance
(because of economic diffi culties and cumbersome federal requirements, certain POTWs
obtained an extension to July 1, 1988 for compliance). The act also called for new levels
of technology to be imposed during the 1980s and 1990s, particularly for controlling
toxic pollutants.
The act mandates a strong pretreatment program to control toxic pollutants discharged
by industry into POTWs. The 1987 amendments require that storm water from industrial
activity must be regulated.
Fertilizer Any of a large number of natural or synthetic materials, including manure and nitrogen,
phosphorus, and potassium compound, spread on or worked into soil to increase its
fertility.
Filtrate Liquid that has been passed through a fi lter.
Filtration A physical treatment method for removing solid (particulate) matter from water by
passing the water through porous media such as sand or a man-made fi lter.
Flocculation The water treatment process following coagulation. It uses gentle stirring to bring suspended
particles together so that they will form larger, more settleable clumps called fl oc.
Flood Any relatively high streamfl ow that overfl ows the natural or artifi cial banks of a stream.
Flood attenuation A weakening or reduction in the force or intensity of a fl ood.
Flood irrigation The application of irrigation water whereby the entire surface of the soil is
covered by ponded water.
Flood plain A strip of relatively fl at land bordering a stream channel that is inundated at times
of high water.
Flow line The idealized path followed by particles of water.
Flowpath An underground route for groundwater movement, extending from a recharge (intake)
zone to a discharge (output) zone such as a shallow stream.
Fluvial Pertaining to a river or stream.
Fresh water Water that contains less than 1000 mg/L of dissolved solids.
Freshwater chronic criteria The highest concentration of a contaminant that freshwater
aquatic organisms can be exposed to for an extended period of time (4 days) without
adverse effects.
G
Grab sample A single water sample collected at one time from a single point.
Groundwater The fresh water found under the Earth’s surface, usually in aquifers. Groundwater
is a major source of drinking water, and a source of a growing concern in areas where
leaching agricultural or industrial pollutants or substances from leaking underground
storage tanks are contaminating groundwater.
H
Habitat The part of the physical environment in which a plant or animal lives.
Hardness A characteristic of water caused primarily by the salts of calcium and magnesium.
It causes deposition of scale in boilers, damage in some industrial processes, and sometimes
objectionable taste. It may also decrease soap’s effectiveness.