denitrification are required, certain portion of the ditch must be operated under
anoxic condition (instead of normal aerobic oxidation condition); the process
should be renamed as “oxidation-denitrification ditch.”
Oxidation-reduction potential (ORP): The potential required to transfer electrons
from the oxidant to the reductant; the quantitative measure, in mV, of the state of
oxidation in wastewater treatment.
Oxidation: The addition of oxygen, removal of hydrogen, or removal of electrons
from a compound (for instance, organic matter may be oxidized to a more stable
compound).
Particulate: Solids suspended in water, wastewater, or air that can vary widely in
shape, size, density, and charge.
Phosphate: PO 4
3À ion
Phosphorus (P): P is an essential element and nutrient for all life forms. Occurs as
orthophosphate, polyphosphate, and organic phosphates, the sum of which is total
phosphorus.
Phosphorus-accumulating organisms (PAOs): Microorganisms (bacteria) that
are capable of uptaking and storing orthophosphate in excess of their biological
requirements.
Polyhydroxyalkanoates (PHAs): Energy-rich carbon polymers inside a bacterial
cell, which are converted from readily available organic molecules, such as
volatile fatty acids (VFAs) in the wastewater. PHAs are the intracellular energy
storage of the phosphorus-accumulating organisms (PAOs). The PAOs utilize
PHA as an energy source to uptake phosphorus from the wastewater in the
aerobic zone of the biological phosphorus removal process.
Polyphosphate (Poly-P): Inorganic phosphorus derived from synthetic detergents.
May be hydrolyzed into orthophosphates.
Polyphosphate: It is a large molecule containing many individual molecules of
orthophosphate. Total phosphorus includes orthophosphate, polyphosphate, and
organic phosphate.
Post-aeration: It is one of the tertiary treatment processes. Because of the more
stringent water quality standards being adopted by various regulatory agencies,
the practice of post-aeration has increased substantially in recent years. The
introduction of water quality-based effluent standards and permits that include
high dissolved oxygen levels has made it necessary for many wastewater treatment plants to post-aerate the plant effluent before discharge.
Pre-aeration: Pre-aeration is one of the preliminary treatment processes. It promotes a more uniform distribution of suspended and floating solids. Aerating
wastewater prior to primary clarification (sedimentation or flotation) can also
improve its treatability; provide grease separation, odor control, grit removal, and
flocculation; and increase BOD removals. It is now common to combine grit
removal with pre-aeration as one unit process. Since dissolved air flotation (DAF)
will provide aeration for grease separation, odor control, and oxidation,
pre-aeration is not needed if DAF is used for primary flotation clarification
(instead of sedimentation clarification).
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anoxic condition (instead of normal aerobic oxidation condition); the process
should be renamed as “oxidation-denitrification ditch.”
Oxidation-reduction potential (ORP): The potential required to transfer electrons
from the oxidant to the reductant; the quantitative measure, in mV, of the state of
oxidation in wastewater treatment.
Oxidation: The addition of oxygen, removal of hydrogen, or removal of electrons
from a compound (for instance, organic matter may be oxidized to a more stable
compound).
Particulate: Solids suspended in water, wastewater, or air that can vary widely in
shape, size, density, and charge.
Phosphate: PO 4
3À ion
Phosphorus (P): P is an essential element and nutrient for all life forms. Occurs as
orthophosphate, polyphosphate, and organic phosphates, the sum of which is total
phosphorus.
Phosphorus-accumulating organisms (PAOs): Microorganisms (bacteria) that
are capable of uptaking and storing orthophosphate in excess of their biological
requirements.
Polyhydroxyalkanoates (PHAs): Energy-rich carbon polymers inside a bacterial
cell, which are converted from readily available organic molecules, such as
volatile fatty acids (VFAs) in the wastewater. PHAs are the intracellular energy
storage of the phosphorus-accumulating organisms (PAOs). The PAOs utilize
PHA as an energy source to uptake phosphorus from the wastewater in the
aerobic zone of the biological phosphorus removal process.
Polyphosphate (Poly-P): Inorganic phosphorus derived from synthetic detergents.
May be hydrolyzed into orthophosphates.
Polyphosphate: It is a large molecule containing many individual molecules of
orthophosphate. Total phosphorus includes orthophosphate, polyphosphate, and
organic phosphate.
Post-aeration: It is one of the tertiary treatment processes. Because of the more
stringent water quality standards being adopted by various regulatory agencies,
the practice of post-aeration has increased substantially in recent years. The
introduction of water quality-based effluent standards and permits that include
high dissolved oxygen levels has made it necessary for many wastewater treatment plants to post-aerate the plant effluent before discharge.
Pre-aeration: Pre-aeration is one of the preliminary treatment processes. It promotes a more uniform distribution of suspended and floating solids. Aerating
wastewater prior to primary clarification (sedimentation or flotation) can also
improve its treatability; provide grease separation, odor control, grit removal, and
flocculation; and increase BOD removals. It is now common to combine grit
removal with pre-aeration as one unit process. Since dissolved air flotation (DAF)
will provide aeration for grease separation, odor control, and oxidation,
pre-aeration is not needed if DAF is used for primary flotation clarification
(instead of sedimentation clarification).
152
L. K. Wang et al.