Ozone (O 3 ) Ozone is a toxic and corrosive oxidant, or disinfectant. Ozone gas
cannot be stored and must be produced on site. Ozone is produced by passing air
or oxygen between oppositely charged plates or through tubes in which a core and
the tube walls serve as the oppositely charged surfaces. Ozone is an excellent
disinfectant or oxidant, but is harmful lung irritant. Therefore, un-reacted ozone
must be vented through a destruction unit (usually thermal destruction).
Ozone-depleting substance (ODSs) A family of man-made compounds that
includes, but are not limited to, chlorofluorocarbons (CFCs), bromofluorocarbons
(halons), methyl chloroform, carbon tetrachloride, methyl bromide, and
hydrochlorofluorocarbons (HCFCs). These compounds have been shown to
deplete stratospheric ozone, and therefore are typically referred to as ODSs.
Ozone layer The layer of ozone that begins approximately 15 km above Earth and
thins to an almost negligible amount at about 50 km, shields the Earth from
harmful ultraviolet radiation from the sun. The highest natural concentration of
ozone (approximately 10 parts per million by volume) occurs in the stratosphere
at approximately 25 km above Earth. The stratospheric ozone concentration
changes throughout the year as stratospheric circulation changes with the seasons.
Natural events such as volcanoes and solar flares can produce changes in ozone
concentration, but man-made changes are of the greatest concern.
Ozone precursors Chemical compounds, such as carbon monoxide, methane,
nonmethane hydrocarbons, and nitrogen oxides, which in the presence of solar
radiation react with other chemical compounds to form ozone, mainly in the
troposphere.
Ozone Ozone, the triatomic form of oxygen (O 3 ), is a gaseous atmospheric constituent. In the troposphere, it is created by photochemical reactions involving
gases resulting both from natural sources and from human activities (photochemical smog). In high concentrations, tropospheric ozone can be harmful to a wide
range of living organisms. Tropospheric ozone acts as a greenhouse gas. In the
stratosphere, ozone is created by the interaction between solar ultraviolet radiation and molecular oxygen (O 2 ). Stratospheric ozone plays a decisive role in the
stratospheric radiative balance. Depletion of stratospheric ozone, due to chemical
reactions that may be enhanced by climate change, results in an increased groundlevel flux of ultraviolet (UV) B radiation.
Package treatment plant A prefabricated water or wastewater treatment plant
consisting of two or more unit processes.
Packing Also called fill, this is a product placed within the tower to promote
uniform water flow distribution and to enhance water-air contacts. (Note:
Again, note the similarity to wet scrubbing applications.)
Parasite It is an organism that lives in or on another organism (its host) and benefits
by deriving nutrients at the host’s expense.
Particulate matter (PM) Very small pieces of solid or liquid matter such as
particles of soot, dust, fumes, mists, or aerosols. The physical characteristics of
particles, and how they combine with other particles, are part of the feedback
mechanisms of the atmosphere.
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M.-H. S. Wang and L. K. Wang
cannot be stored and must be produced on site. Ozone is produced by passing air
or oxygen between oppositely charged plates or through tubes in which a core and
the tube walls serve as the oppositely charged surfaces. Ozone is an excellent
disinfectant or oxidant, but is harmful lung irritant. Therefore, un-reacted ozone
must be vented through a destruction unit (usually thermal destruction).
Ozone-depleting substance (ODSs) A family of man-made compounds that
includes, but are not limited to, chlorofluorocarbons (CFCs), bromofluorocarbons
(halons), methyl chloroform, carbon tetrachloride, methyl bromide, and
hydrochlorofluorocarbons (HCFCs). These compounds have been shown to
deplete stratospheric ozone, and therefore are typically referred to as ODSs.
Ozone layer The layer of ozone that begins approximately 15 km above Earth and
thins to an almost negligible amount at about 50 km, shields the Earth from
harmful ultraviolet radiation from the sun. The highest natural concentration of
ozone (approximately 10 parts per million by volume) occurs in the stratosphere
at approximately 25 km above Earth. The stratospheric ozone concentration
changes throughout the year as stratospheric circulation changes with the seasons.
Natural events such as volcanoes and solar flares can produce changes in ozone
concentration, but man-made changes are of the greatest concern.
Ozone precursors Chemical compounds, such as carbon monoxide, methane,
nonmethane hydrocarbons, and nitrogen oxides, which in the presence of solar
radiation react with other chemical compounds to form ozone, mainly in the
troposphere.
Ozone Ozone, the triatomic form of oxygen (O 3 ), is a gaseous atmospheric constituent. In the troposphere, it is created by photochemical reactions involving
gases resulting both from natural sources and from human activities (photochemical smog). In high concentrations, tropospheric ozone can be harmful to a wide
range of living organisms. Tropospheric ozone acts as a greenhouse gas. In the
stratosphere, ozone is created by the interaction between solar ultraviolet radiation and molecular oxygen (O 2 ). Stratospheric ozone plays a decisive role in the
stratospheric radiative balance. Depletion of stratospheric ozone, due to chemical
reactions that may be enhanced by climate change, results in an increased groundlevel flux of ultraviolet (UV) B radiation.
Package treatment plant A prefabricated water or wastewater treatment plant
consisting of two or more unit processes.
Packing Also called fill, this is a product placed within the tower to promote
uniform water flow distribution and to enhance water-air contacts. (Note:
Again, note the similarity to wet scrubbing applications.)
Parasite It is an organism that lives in or on another organism (its host) and benefits
by deriving nutrients at the host’s expense.
Particulate matter (PM) Very small pieces of solid or liquid matter such as
particles of soot, dust, fumes, mists, or aerosols. The physical characteristics of
particles, and how they combine with other particles, are part of the feedback
mechanisms of the atmosphere.
470
M.-H. S. Wang and L. K. Wang