with settling in clarifiers, or may interfere with drainage through a filter.
(b) Organisms that grow in a thread or filamentous form. Common types are
Thiothrix and Actinomycetes. A common cause of sludge bulking in the activated
sludge process.
Filtration It is usually a granular medial filtration process, which involves the
passage of wastewater or water through a bed of filter media with resulting
deposition of suspended solids. Eventually the pressure drop across the bed
becomes excessive or the ability of the bed to remove suspended solids is
impaired. Cleaning is then necessary to restore operating head and effluent
quality. The time in service between cleanings is termed the filter run time or
run length. The head loss at which filtration is interrupted for cleaning is called
the terminal head loss, and this head loss is maximized by the judicious choice of
media sizes. Dual media filtration involves the use of both sand and anthracite as
filter media, with anthracite being placed on top of the sand. Gravity filters
operate by either using the available head from the previous treatment unit, or
by pumping to a flow split box after which the wastewater flows by gravity to the
filter cells. Pressure filters utilize pumping to increase the available head. A filter
unit generally consists of a containing vessel, the filter media, structures to
support the media, distribution and collection devices for filter influent, effluent,
and backwash water flows, supplemental cleaning devices, ad necessary controls
for flows, water levels, and backwash sequencing. Backwash sequences can
include air scour or surface wash steps. Backwash water can be stored separately
or in chambers that are integral parts of the filter unit. Backwash water can be
pumped through the unit or can be supplied through gravity head tanks.
Fire-resistant material A material designed to withstand heat and resist burning to
aid in saving lives and protecting property.
First responder Includes organizations and individuals who assume an emergency
management role. Also known as emergency management or response personnel.
Floc (a) Collections of smaller particles that have agglomerated together into larger,
more separable, floatable or settleable particles as result of the coagulation
process; (b) clumps of bacteria and particles or coagulants and impurities that
have come together and formed a cluster. Found in aeration tanks, secondary
clarifiers, and chemical precipitation processes.
Flocculation (a) A water treatment unit process following coagulation that uses
gentle stirring to bring suspended particles together so that they will form larger,
more separable (floatable or settleable) floc. (b) The gathering together of fine
particles after coagulation to form larger particles by a process of gentle mixing.
Flocculator A process device to enhance the formation of floc in a water. Mixing
energy can be provided by slow turning mechanical means or head loss.
Flood A general and temporary condition of partial or complete inundation of
normally dry land areas from overflow of inland or tidal waters, unusual or
rapid accumulation or runoff of surface waters, or mudslides/mudflows caused
by accumulation of water.
Flotation cell A dissolved air flotation cell or unit process.
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M.-H. S. Wang and L. K. Wang
(b) Organisms that grow in a thread or filamentous form. Common types are
Thiothrix and Actinomycetes. A common cause of sludge bulking in the activated
sludge process.
Filtration It is usually a granular medial filtration process, which involves the
passage of wastewater or water through a bed of filter media with resulting
deposition of suspended solids. Eventually the pressure drop across the bed
becomes excessive or the ability of the bed to remove suspended solids is
impaired. Cleaning is then necessary to restore operating head and effluent
quality. The time in service between cleanings is termed the filter run time or
run length. The head loss at which filtration is interrupted for cleaning is called
the terminal head loss, and this head loss is maximized by the judicious choice of
media sizes. Dual media filtration involves the use of both sand and anthracite as
filter media, with anthracite being placed on top of the sand. Gravity filters
operate by either using the available head from the previous treatment unit, or
by pumping to a flow split box after which the wastewater flows by gravity to the
filter cells. Pressure filters utilize pumping to increase the available head. A filter
unit generally consists of a containing vessel, the filter media, structures to
support the media, distribution and collection devices for filter influent, effluent,
and backwash water flows, supplemental cleaning devices, ad necessary controls
for flows, water levels, and backwash sequencing. Backwash sequences can
include air scour or surface wash steps. Backwash water can be stored separately
or in chambers that are integral parts of the filter unit. Backwash water can be
pumped through the unit or can be supplied through gravity head tanks.
Fire-resistant material A material designed to withstand heat and resist burning to
aid in saving lives and protecting property.
First responder Includes organizations and individuals who assume an emergency
management role. Also known as emergency management or response personnel.
Floc (a) Collections of smaller particles that have agglomerated together into larger,
more separable, floatable or settleable particles as result of the coagulation
process; (b) clumps of bacteria and particles or coagulants and impurities that
have come together and formed a cluster. Found in aeration tanks, secondary
clarifiers, and chemical precipitation processes.
Flocculation (a) A water treatment unit process following coagulation that uses
gentle stirring to bring suspended particles together so that they will form larger,
more separable (floatable or settleable) floc. (b) The gathering together of fine
particles after coagulation to form larger particles by a process of gentle mixing.
Flocculator A process device to enhance the formation of floc in a water. Mixing
energy can be provided by slow turning mechanical means or head loss.
Flood A general and temporary condition of partial or complete inundation of
normally dry land areas from overflow of inland or tidal waters, unusual or
rapid accumulation or runoff of surface waters, or mudslides/mudflows caused
by accumulation of water.
Flotation cell A dissolved air flotation cell or unit process.
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M.-H. S. Wang and L. K. Wang