may be accomplished using low-speed paddles analogous to standard flocculation
equipment. Flotation clarification follows the denitrification step with the floated
sludge being either returned to the head end of the denitrification system or
wasted. An intermediate aeration step for stabilization (much less than
40 minutes) may be needed to guard against carryover of carbonaceous materials.
The denitrification reactor may be covered but not air-tight to assure anaerobic
conditions.
Denitrification followed by membrane clarification: Same as “denitrification
followed by flotation clarification” except that the flotation clarification is
replaced by a membrane filtration reactor.
Denitrification followed by sedimentation clarification: The process involves the
reduction of nitrates and nitrites to nitrogen gas through the action of facultative
heterotrophic bacteria. In suspended-growth separate-stage denitrification processes, nitrified wastewater containing primarily nitrates is passed through a
mixed anaerobic vessel containing denitrifying bacteria. Since the nitrified feedwater contains very little carbonaceous materials, a supplemental source of
carbon (such as methanol, sugar, acetic acid, ethanol, or other compounds) is
required to maintain the denitrifying biomass. This supplemental energy is
provided by feeding methanol, for instance, to the biological reactor along with
the nitrified wastewater. Mixing in the anaerobic denitrification reaction vessel
may be accomplished using low-speed paddles analogous to standard flocculation
equipment. Following the reactor, the denitrified effluent is aerated for a short
period (5–10 minutes) to strip out gaseous nitrogen formed in the previous step
which might otherwise inhibit sludge settling. Sedimentation clarification follows
the gas stripping step with the collected sludge being either returned to the head
end of the denitrification system or wasted. An intermediate aeration step for
stabilization (about 50 minutes) between the denitrification reactor and the
stripping step may be used to guard against carryover of carbonaceous materials.
The denitrification reactor may be covered but not air-tight to assure anaerobic
conditions.
Denitrification: The biochemical reduction reaction of reducing nitrate nitrogen to
nitrogen gas in an anoxic environment.
Disinfection: Potable water disinfection is used in an attempt to destroy all pathogenic agents in drinking water for public health protection. Wastewater disinfection is used in an attempt to destroy pathogenic agents in a wastewater stream and
protect the best uses of the receiving stream or groundwater. Environmental
disinfection is used in an attempt to destroy pathogenic agents in rooms, houses,
swimming pools, buildings, restaurants, streets, parks, etc., to prevent the spread
of pathogenic agents, such as pathogenic bacteria and coronavirus in the environment. Typical disinfection techniques used include chlorine (gas), sodium
hypochlorite (liquid), bromine (gas), bromine dioxide (gas), UV (light), ozone
(gas), and cationic surfactant (water-soluble solid).
Dispersion: A uniform and maximum separation of extremely fine particles, often
of colloidal size.
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L. K. Wang et al.
equipment. Flotation clarification follows the denitrification step with the floated
sludge being either returned to the head end of the denitrification system or
wasted. An intermediate aeration step for stabilization (much less than
40 minutes) may be needed to guard against carryover of carbonaceous materials.
The denitrification reactor may be covered but not air-tight to assure anaerobic
conditions.
Denitrification followed by membrane clarification: Same as “denitrification
followed by flotation clarification” except that the flotation clarification is
replaced by a membrane filtration reactor.
Denitrification followed by sedimentation clarification: The process involves the
reduction of nitrates and nitrites to nitrogen gas through the action of facultative
heterotrophic bacteria. In suspended-growth separate-stage denitrification processes, nitrified wastewater containing primarily nitrates is passed through a
mixed anaerobic vessel containing denitrifying bacteria. Since the nitrified feedwater contains very little carbonaceous materials, a supplemental source of
carbon (such as methanol, sugar, acetic acid, ethanol, or other compounds) is
required to maintain the denitrifying biomass. This supplemental energy is
provided by feeding methanol, for instance, to the biological reactor along with
the nitrified wastewater. Mixing in the anaerobic denitrification reaction vessel
may be accomplished using low-speed paddles analogous to standard flocculation
equipment. Following the reactor, the denitrified effluent is aerated for a short
period (5–10 minutes) to strip out gaseous nitrogen formed in the previous step
which might otherwise inhibit sludge settling. Sedimentation clarification follows
the gas stripping step with the collected sludge being either returned to the head
end of the denitrification system or wasted. An intermediate aeration step for
stabilization (about 50 minutes) between the denitrification reactor and the
stripping step may be used to guard against carryover of carbonaceous materials.
The denitrification reactor may be covered but not air-tight to assure anaerobic
conditions.
Denitrification: The biochemical reduction reaction of reducing nitrate nitrogen to
nitrogen gas in an anoxic environment.
Disinfection: Potable water disinfection is used in an attempt to destroy all pathogenic agents in drinking water for public health protection. Wastewater disinfection is used in an attempt to destroy pathogenic agents in a wastewater stream and
protect the best uses of the receiving stream or groundwater. Environmental
disinfection is used in an attempt to destroy pathogenic agents in rooms, houses,
swimming pools, buildings, restaurants, streets, parks, etc., to prevent the spread
of pathogenic agents, such as pathogenic bacteria and coronavirus in the environment. Typical disinfection techniques used include chlorine (gas), sodium
hypochlorite (liquid), bromine (gas), bromine dioxide (gas), UV (light), ozone
(gas), and cationic surfactant (water-soluble solid).
Dispersion: A uniform and maximum separation of extremely fine particles, often
of colloidal size.
144
L. K. Wang et al.