argon (0.93% volume mixing ratio), helium, radiatively active greenhouse gases
such as carbon dioxide (0.035% volume mixing ratio), and ozone. In addition the
atmosphere contains water vapor, whose amount is highly variable but typically
1% volume mixing ratio. The atmosphere also contains clouds and aerosols.
Atmospheric lifetime Atmospheric lifetime is the average time that a molecule
resides in the atmosphere before it is removed by chemical reaction or deposition.
This can also be thought of as the time that it takes after the human-caused
emission of a gas for the concentrations of that gas in the atmosphere to return to
natural levels. Greenhouse gas lifetimes can range from a few years to a few
thousand years.
Attached-growth biological processes In an attached-growth biological process
system, the biomass responsible for biochemical reactions is attached on the
surface of rocks, sands, woods, disks, screens, etc., where the wastewater passes
through, and the organic pollutants and nutrients are removed. They include:
trickling filters, denitrification filter using coarse media; denitrification filter using
fine media, slow sand filters, rotating biological contactors, etc. The effluent from
an attached-growth bioreactor discharges to a water-solid separator (sedimentation clarifier, or flotation clarifier, or membrane filter) for further processing.
Attribute It is a characteristic of a geographic feature, typically stored in tabular
format and linked to the feature in a relational database. The attributes of a wellrepresented point might include an identification number, address, and type.
Autotrophic organisms Organisms that use carbon dioxide, sunlight, or other
inorganic substances for their cell growth (Nitrifying bacteria are autotrophic).
Auxiliary engine It is used to suitably power the hydraulic system and other
auxiliary functions on certain type of dredges.
Bacteria They are living organisms, microscopic in size, which usually consist of a
single cell. Most bacteria use organic matter for their food and produce waste
products as the result of their life processes.
Baffle It is a flat board or plate, deflector, guide, or similar device constructed or
placed in flowing water, wastewater, or slurry systems to cause more uniform
flow velocities, to absorb energy, and to divert, guide, or agitate liquids (water,
chemical solutions, slurry).
Bar screens There are two types of bar screens (or racks). The most commonly
used, and oldest technology, consists of hand-cleaned bar racks. These are
generally used in smaller wastewater treatment plants (WWTPs). The second
type of bar screen is the type that is mechanically cleaned, which is commonly
used in larger facilities.
Base layer It is a primary layer for spatial reference, upon which other layers are
built. Examples of a base layer typically used are either the parcels, or street
centerlines.
Base, alkalinity (a) A substance, which takes up or accepts protons; (b) A substance, which dissociates (separates) in aqueous solution to yield hydroxyl ions
(OH
À ); (c) A substance containing hydroxyl ions, which reacts with an acid to
form a salt or which may react with metals to form precipitates; (d) A substance
that may raise pH.
12 Glossary of Natural Resources and Environmental Pollution Control
429
such as carbon dioxide (0.035% volume mixing ratio), and ozone. In addition the
atmosphere contains water vapor, whose amount is highly variable but typically
1% volume mixing ratio. The atmosphere also contains clouds and aerosols.
Atmospheric lifetime Atmospheric lifetime is the average time that a molecule
resides in the atmosphere before it is removed by chemical reaction or deposition.
This can also be thought of as the time that it takes after the human-caused
emission of a gas for the concentrations of that gas in the atmosphere to return to
natural levels. Greenhouse gas lifetimes can range from a few years to a few
thousand years.
Attached-growth biological processes In an attached-growth biological process
system, the biomass responsible for biochemical reactions is attached on the
surface of rocks, sands, woods, disks, screens, etc., where the wastewater passes
through, and the organic pollutants and nutrients are removed. They include:
trickling filters, denitrification filter using coarse media; denitrification filter using
fine media, slow sand filters, rotating biological contactors, etc. The effluent from
an attached-growth bioreactor discharges to a water-solid separator (sedimentation clarifier, or flotation clarifier, or membrane filter) for further processing.
Attribute It is a characteristic of a geographic feature, typically stored in tabular
format and linked to the feature in a relational database. The attributes of a wellrepresented point might include an identification number, address, and type.
Autotrophic organisms Organisms that use carbon dioxide, sunlight, or other
inorganic substances for their cell growth (Nitrifying bacteria are autotrophic).
Auxiliary engine It is used to suitably power the hydraulic system and other
auxiliary functions on certain type of dredges.
Bacteria They are living organisms, microscopic in size, which usually consist of a
single cell. Most bacteria use organic matter for their food and produce waste
products as the result of their life processes.
Baffle It is a flat board or plate, deflector, guide, or similar device constructed or
placed in flowing water, wastewater, or slurry systems to cause more uniform
flow velocities, to absorb energy, and to divert, guide, or agitate liquids (water,
chemical solutions, slurry).
Bar screens There are two types of bar screens (or racks). The most commonly
used, and oldest technology, consists of hand-cleaned bar racks. These are
generally used in smaller wastewater treatment plants (WWTPs). The second
type of bar screen is the type that is mechanically cleaned, which is commonly
used in larger facilities.
Base layer It is a primary layer for spatial reference, upon which other layers are
built. Examples of a base layer typically used are either the parcels, or street
centerlines.
Base, alkalinity (a) A substance, which takes up or accepts protons; (b) A substance, which dissociates (separates) in aqueous solution to yield hydroxyl ions
(OH
À ); (c) A substance containing hydroxyl ions, which reacts with an acid to
form a salt or which may react with metals to form precipitates; (d) A substance
that may raise pH.
12 Glossary of Natural Resources and Environmental Pollution Control
429