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.
Polymer Used with other chemical coagulants to aid in binding small suspended
particles to larger chemical flocs for their removal from water.
Polyphosphate (Poly-P) (a) Inorganic phosphorus derived from synthetic detergents. May be hydrolyzed into orthophosphates. (b) It is a large molecule
containing many individual molecules of orthophosphate. Total phosphorus
includes orthophosphate, polyphosphate, and organic phosphate.
Ponding A condition occurring on trickling filters when the hollow spaces (voids)
become plugged to the extent that water passage through the filter is inadequate.
Ponding may be the result of excessive slime growths, trash, or media
breakdown.
Postaeration 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 postaeration 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 postaerate the plant effluent before discharge.
Pour-flush latrine It is a latrine where a small quantity of water is poured in to flush
excreta through a water seal into a pit.
Powdered activated carbon adsorption Powdered activated carbon (PAC) is used
in both water and wastewater treatment. For water treatment, PAC systems
generally involve dosing powdered activated carbons in slurry form to rapid
mixers and flocculators (for mixing and flocculation, and adsorption) before
reaching clarifiers for PAC-floc separation and clarifier effluent discharge. For
wastewater treatment, powdered activated carbon in slurry form is dosed to either
mixing/flocculation chambers (if they exist), or to an aeration basin directly to be
mixed with mixed liquor for adsorption reactions. The spent PAC again is
recovered or removed by a subsequent clarifier (either sedimentation clarifier or
flotation clarifier). When PAC is used in conjunction with a flotation clarifier, it is
also called “adsorption flotation.”
Preaeration Preaeration 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
preaeration as one unit process. Since dissolved air flotation (DAF) will provide
aeration for grease separation, odor control, and oxidation, preaeration is not
needed if DAF is used for primary flotation clarification (instead of sedimentation
clarification).
12 Glossary of Natural Resources and Environmental Pollution Control
473
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.
Polymer Used with other chemical coagulants to aid in binding small suspended
particles to larger chemical flocs for their removal from water.
Polyphosphate (Poly-P) (a) Inorganic phosphorus derived from synthetic detergents. May be hydrolyzed into orthophosphates. (b) It is a large molecule
containing many individual molecules of orthophosphate. Total phosphorus
includes orthophosphate, polyphosphate, and organic phosphate.
Ponding A condition occurring on trickling filters when the hollow spaces (voids)
become plugged to the extent that water passage through the filter is inadequate.
Ponding may be the result of excessive slime growths, trash, or media
breakdown.
Postaeration 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 postaeration 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 postaerate the plant effluent before discharge.
Pour-flush latrine It is a latrine where a small quantity of water is poured in to flush
excreta through a water seal into a pit.
Powdered activated carbon adsorption Powdered activated carbon (PAC) is used
in both water and wastewater treatment. For water treatment, PAC systems
generally involve dosing powdered activated carbons in slurry form to rapid
mixers and flocculators (for mixing and flocculation, and adsorption) before
reaching clarifiers for PAC-floc separation and clarifier effluent discharge. For
wastewater treatment, powdered activated carbon in slurry form is dosed to either
mixing/flocculation chambers (if they exist), or to an aeration basin directly to be
mixed with mixed liquor for adsorption reactions. The spent PAC again is
recovered or removed by a subsequent clarifier (either sedimentation clarifier or
flotation clarifier). When PAC is used in conjunction with a flotation clarifier, it is
also called “adsorption flotation.”
Preaeration Preaeration 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
preaeration as one unit process. Since dissolved air flotation (DAF) will provide
aeration for grease separation, odor control, and oxidation, preaeration is not
needed if DAF is used for primary flotation clarification (instead of sedimentation
clarification).
12 Glossary of Natural Resources and Environmental Pollution Control
473