Environmental Engineering Reference
In-Depth Information
waste, and fossil fuels, as well as from natural or anthropogenic
introduction of uncombusted coal and oil. PAHs included benzo(
a
)
pyrene, fluoranthene, and pyrene.
Population:
A collection of individuals of one species or mixed species mak-
ing up the residents of a prescribed area.
Porosity:
The ratio of the volume of voids in a rock or soil to the total volume.
Potable water:
Water that is safe and palatable for human consumption.
Precipitation:
Any or all forms of water particles that fall from the atmo-
sphere, such as rain, snow, hail, and sleet. The act or process of pro-
ducing a solid phase within a liquid medium.
Pretreatment:
Any physical, chemical, or mechanical process used before the
main water treatment processes. It can include screening, presedi-
mentation, and chemical addition.
Primary Drinking Water Standards:
Regulations on drinking water quality
(under the Safe Drinking Water Act) considered essential for preser-
vation of public health.
Primary treatment:
The first step of treatment at a municipal wastewater
treatment plant; typically involves screening and sedimentation to
remove materials that float or settle.
Public supply withdrawals:
Water withdrawn by public and private water
suppliers for use within a general community. The water is used for
a variety of purposes, such as domestic, commercial, industrial, and
public water use.
Public water system:
As defined by the Safe Drinking Water Act, any sys-
tem, publicly or privately owned, that serves at least 15 service con-
nections 60 days out of the year or serves an average of 25 people at
least 60 days out of the year.
Publicly owned treatment works (PoTW):
A waste treatment works owned
by a state, local government unit, or Indian tribe, usually designed to
treat domestic wastewaters.
R
Rain shadow:
A dry region on the lee side of a topographic obstacle, usu-
ally a mountain range, where rainfall is noticeably less than on the
windward side.
Reach:
A continuous part of a stream between two specified points.
Reaeration:
The replenishment of oxygen in water from which oxygen has
been removed.
Receiving waters:
A river, lake, ocean, stream, or other water source into
which wastewater or treated effluent is discharged.
Recharge:
The process by which water is added to a zone of saturation, usu-
ally by percolation from the soil surface.
Recharge area (groundwater):
An area within which water infiltrates the
ground and reaches the zone of saturation.
