but not always, preceded by primary clarification (either primary sedimentation
clarification or primary flotation clarification). The mixture of microorganisms
and wastewater formed in the aeration basins, called mixed liquor (ML), is
transferred to secondary clarification (either secondary sedimentation clarification
or secondary flotation clarification) for liquid-solid separation. The major portion
of the microorganisms separated from the secondary clarifiers (secondary sedimentation clarifiers or secondary flotation clarifiers) is recycled to the aeration
basins to be mixed with incoming wastewater, while the excess, which constitutes
the waste activated sludge (WAS), is sent to the sludge-handling facilities. The
rate and concentration of the returned activated sludge (RAS) returned to the
aeration basins determines the mixed liquor suspended solids (MLSSs) level
developed and maintained in the aeration basins. During the oxidation process,
a certain amount of the organic material is synthesized into new cells, some of
which then undergoes auto-oxidation (self-oxidation, or endogenous respiration)
in the aeration basins, the remainder forming net growth or excess sludge.
Oxygen is required in the process to support the oxidation and synthesis reactions. In the conventional activated sludge plant, the wastewater is commonly
aerated for a period of 4 to 8 hours (based on average daily flow) in a plug flow
hydraulic mode. Either surface or submerged aeration systems can be employed
to transfer oxygen from air to wastewater. (b) It is a suspended-growth biological
wastewater treatment process, which speeds up the decomposition of wastes in
the wastewater being treated. Activated sludge is added to wastewater, and the
mixture (mixed liquor) is aerated and agitated. After some time in the aeration
tank, the activated sludge is allowed to settle out by sedimentation and is disposed
of (wasted) or refused (returned to the aeration tank) as needed. The remaining
wastewater then undergoes more treatment.
Adaptation Adjustment or preparation of natural or human systems to a new or
changing environment, which moderates harm or exploits beneficial
opportunities.
Adaptive capacity The ability of a system to adjust to climate change (including
climate variability and extremes) to moderate potential damages, to take advantage of opportunities, or to cope with the consequences.
Adsorption flotation When powdered activated carbon (PAC) is used in conjunction with a flotation clarifier for water or wastewater treatment, the unit process is
also called “adsorption flotation.”
Advanced waste treatment It is any process of water renovation that upgrades
treated wastewater beyond secondary treatment to meet specific reuse requirements. Typical processes include chemical treatment, granular activated carbon,
and pressure filtration. Also called tertiary treatment.
Advisory A notice that highlights special weather conditions that are less serious
than a warning. They are for events that may cause significant inconvenience, and
if caution is not exercised, the conditions could lead to situations that may
threaten life and/or property.
12 Glossary of Natural Resources and Environmental Pollution Control
425
clarification or primary flotation clarification). The mixture of microorganisms
and wastewater formed in the aeration basins, called mixed liquor (ML), is
transferred to secondary clarification (either secondary sedimentation clarification
or secondary flotation clarification) for liquid-solid separation. The major portion
of the microorganisms separated from the secondary clarifiers (secondary sedimentation clarifiers or secondary flotation clarifiers) is recycled to the aeration
basins to be mixed with incoming wastewater, while the excess, which constitutes
the waste activated sludge (WAS), is sent to the sludge-handling facilities. The
rate and concentration of the returned activated sludge (RAS) returned to the
aeration basins determines the mixed liquor suspended solids (MLSSs) level
developed and maintained in the aeration basins. During the oxidation process,
a certain amount of the organic material is synthesized into new cells, some of
which then undergoes auto-oxidation (self-oxidation, or endogenous respiration)
in the aeration basins, the remainder forming net growth or excess sludge.
Oxygen is required in the process to support the oxidation and synthesis reactions. In the conventional activated sludge plant, the wastewater is commonly
aerated for a period of 4 to 8 hours (based on average daily flow) in a plug flow
hydraulic mode. Either surface or submerged aeration systems can be employed
to transfer oxygen from air to wastewater. (b) It is a suspended-growth biological
wastewater treatment process, which speeds up the decomposition of wastes in
the wastewater being treated. Activated sludge is added to wastewater, and the
mixture (mixed liquor) is aerated and agitated. After some time in the aeration
tank, the activated sludge is allowed to settle out by sedimentation and is disposed
of (wasted) or refused (returned to the aeration tank) as needed. The remaining
wastewater then undergoes more treatment.
Adaptation Adjustment or preparation of natural or human systems to a new or
changing environment, which moderates harm or exploits beneficial
opportunities.
Adaptive capacity The ability of a system to adjust to climate change (including
climate variability and extremes) to moderate potential damages, to take advantage of opportunities, or to cope with the consequences.
Adsorption flotation When powdered activated carbon (PAC) is used in conjunction with a flotation clarifier for water or wastewater treatment, the unit process is
also called “adsorption flotation.”
Advanced waste treatment It is any process of water renovation that upgrades
treated wastewater beyond secondary treatment to meet specific reuse requirements. Typical processes include chemical treatment, granular activated carbon,
and pressure filtration. Also called tertiary treatment.
Advisory A notice that highlights special weather conditions that are less serious
than a warning. They are for events that may cause significant inconvenience, and
if caution is not exercised, the conditions could lead to situations that may
threaten life and/or property.
12 Glossary of Natural Resources and Environmental Pollution Control
425