circular clarifiers
DESCRIPTION
CLARIFIER INFORMATIONTRANSCRIPT
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CIRCULAR
CLARIFICATION
EQUIPMENT
& PROCESSES
Taking care of the worlds water.
100% water
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Two basic design concepts are available.
Each has a wide range of sizes and
options to select from, allowing every cir-
cular clarifier to be tailored to meet spe-
cific application requirements.
The bridge supported design (full
bridge) consists of a bridge spanning the
tanks diameter, with the sludge collector
mechanism supported from the bridge.
The center pier supported design (half
bridge) consists of a mechanism support-
T H E R I G H T C H O I C E F O R R E L I A B I L I T Y A N D VA L U E
2.
DESIGN CONCEPTS
DESIGN PARAMETERS
For more than half a century, U.S. Filter/Envirex has provided customdesigned, circular sludge collector mechanisms for municipal and industrialwater and wastewater treatment applications.
The quality of the engineered designs, the superior fabrication of the finishedproducts and the consistency of experienced, after-installation services havecontributed to U.S. Filter/Envirexs reputation as a leading supplier of provenclarifier equipment.
The basic operating parameter of a
clarifier is to remove settled solids from
the bottom of the clarifier tank as quick-
ly as possible. This improves the efficien-
cy of other treatment processes.
Inlet design, flocculation, scum
removal and operator needs should be
considered to match the needs of the
installation.
The objective is to provide a hydrauli-
cally quiescent tank with the greatest
detention time practical to improve the
ability of solids to settle to the bottom of
the tank.
Considerations involving inlet energy
dissipation, solids settling characteristics,
liquid flow patterns and effluent collec-
tion are part of this design parameter.
ed on a center pier, with an access bridge
leading to it from the tanks wall.
Both designs incorporate a minimum of
two sludge scraper arms per mechanism.
Sludge removal mechanisms are designed
for continuous operation over the life of
the clarifier, and are based on the concept
that solids within the water or wastewater
will settle out in a quiescent tank.
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T H E R I G H T C H O I C E F O R R E L I A B I L I T Y A N D VA L U E
3.
Half Bridge Clarifier
Beginning with tanks ten feet in diam-
eter and larger, U.S. Filter circular sludge
collectors are available in either full or
half bridge designs.
Every clarifier is equipped with a U.S.
Filter built drive designed to AGMA
standards, assuring proper torque ratings
and longevity under continuous opera-
tion.
COMMON FEATURES OF
U.S. FILTER CLARIFIERS
U.S. Filter drives perform...providing
years of reliable service.
Surface skimmers, sludge scraper arms
and other components are welded in the
shop to reduce field installation time.
Only bridge splices are field welded assur-
ing quality fabrication. All components
are preassembled at the factory, an opera-
tion that reduces field fitup time and erec-
tion costs.
Each custom designed U.S. Filter cir-
cular sludge collector can be provided
with features such as center drive plat-
form, choice of walkway and handrail
OPTIONS material and styles special service protec-
tive coatings, special material assembly
bolts, etc. For details, contact your local
U.S. Filter representative.
Circular Collector Components-General Benefits
Cast iron drive housings Shop fabricated for bolted
field assembly Full surface adjustable
skimmers Reinforced influent well Ample walkway and drive
platform widths Deep scraper blades and
adjustable squeeges No underwater bearings Designed to exacting
specifications
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Scraper arms are bolted to the torque
tube and rotate with it. The scraper arms
are engineered to complement the drive
and anticipated sludge loads. Scraper
arms extend from the torque tube to the
periphery of the basin. A minimum of
two scraper arms are provided, allowing
the basin floor to be scraped at least twice
in each removal.
Each scraper arm is furnished with a
number of scraper blades that are
arranged to collect and direct the sludge
to the center of the tank for hydraulic
removal.
INFLUENT FEEDWELL
F U L L B R I D G E C I R C U L A R C L A R I F I E R S
4.
Influent enters the tank from the side
of the basin and is fed into the center
influent feedwell. The feedwell reduces
the influents energy while eliminating or
reducing density currents. The feedwell
permits only a low velocity flow to enter
the tank, assuring maintenance of quies-
cent conditions and the most efficient
removal of solids.
SCRAPER ARMS
For wastewater applications, the feed-
well is equipped with baffled scum ports
that permit floating material to escape
from the feedwell while preventing short
circuiting.
The feedwell is supported from either
the bridge or beams spanning the tank as
dictated by the design.
SUPPORT BRIDGE The support bridge provides access to
the drive mechanism. For operator con-
venience and safety, the bridge is
provided with a minimum three foot
wide walkway. All walkways have
handrails and a four inch high kickplate
along both sides and around the drive.
U.S. Filter full bridge (F Type) sludge collector mechanisms are available in
sizes beginning at ten feet in diameter. Generally, the economics of the design
limit the F Type to 50 feet in diameter, although larger sizes can be built for
special requirements.
In the F Type design, a structural steel bridge spanning the tanks diameter sup-
ports the drive mechanism. A center torque tube bolted to the drive, supports
and rotates the sludge collector mechanism.
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F U L L B R I D G E C I R C U L A R C L A R I F I E R S
5.
Various skimming and effluent
arrangements are available for water and
wastewater treatment circular clarifiers.
Generally, a full radius, surface scum
blade directs floating material to the
peripheral scum skimmer. The skimmer
SKIMMING/EFFLUENT WEIRS concentrates the floating material and
deposits it in the scum trough.
Adjustable weirs are generally located
on the periphery of the basin, although
radial and other arrangements are
employed.
35' diameter industrial
Full Bridge Clarifier
Installation
Full Bridge Clarifer
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F U L L B R I D G E D R I V E T Y P E F B U I LT T O U G H
6.
Specifically designed for the particular
demands and operating conditions of
water and wastewater treatment plants,
the U.S. Filter Type F drive is built for
years of continuous service with a mini-
mum of maintenance.
Each custom designed Type F drive is
completely manufactured by U.S. Filter,
providing owners with one source of
responsibility for service assistance and
replacement parts. In addition to new
installations, U.S. Filter Type F drives are
available for retrofit and upgrade applica-
tions.
A large diameter ball bearing supports
the worm gear. This bearing provides the
worn gear with a stable, vibration free,
low friction platform that translates into
extended, durable drive performance.
An outboard bronze steady bearing
supports and stabilizes the torque tube.
In doing so, it reduces and/or eliminates
tipping loads on the main gear and bear-
ing. Without this unique feature, unequal
and unbalanced loads could cause prema-
ture failure of the main gear or bearing.
The U.S. Filter Type F drive is designed
for the loads applied by a circular clarifi-
er mechanism. This is an important con-
sideration, since it is in direct contrast to
off-the-shelf drive units that are not
designed for the loads or conditions
encountered by circular clarifiers.
The primary reduction unit is a heavy
duty helical gear designed for efficient
speed reduction. It is coupled to the sec-
ondary reduction unit by a chain and
sprocket that can be equipped with
shear pin overload protection.
The secondary reduction unit consists
of a cut tooth steel worm and cast worm
gear. The worm gear is supported by a
precision bearing. This bearing operates
within an oil bath.
Overload protection, including alarm
and shutdown micro-switches, operates
from the thrust of the worm shaft.
All U.S. Filter Type F drive compo-
nents are designed to AGMA standards
for worm gears. The use of the external
steady bearing eliminates the need for an
underwater bearing.
CUSTOM DESIGNED
STABLE, VIBRATION FREE
LOW FRICTION PLATFORM
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F U L L B R I D G E D R I V E T Y P E F F O R Y E A R S O F E F F I C I E N T S E R V I C E
7.
Full Bridge Drive-General Benefits
Cast iron construction Designed per AGMA
20-year continuous duty requirements
Factory assembled Extended torque tube
steady bearing Large diameter
worn gearing Helical gear primary
reduction Electro-Mechanical
overload protection Oil bath lubricated Condensate taps
Full Bridge Drive
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MAIN COMPONENTS
H A L F B R I D G E C I R C U L A R C L A R I F I E R S
8.
The U.S. Filter/Envirex half bridge, pier supported circular sludge collector isavailable as small as 30 feet in diameter, although the economics of construction generally favor half bridge designs no less than 40 feet diameter.
There is no upper limit on the diameter of the collector other than process con-siderations. For clarifiers between 40 and 50 feet in diameter, operator prefer-ence will usually decide between the full bridge and half bridge designs.
The pier supported design consists of a
support pier, influent feedwell, rotating
cage and scraper arms, and access bridge
spanning from the tank wall to the center
column and H Type drive unit. A wide
range of scraping, skimming and process
options are available with this design.
INFLUENT FEEDWELL
AND PIER
Flow enters the influent dispersion well
through the center support pier or a side
feed pipe. If a side feed is used, the pipe
is supported from the bridge structure.
When used as an influent pipe, the
support pier is provided with a large inlet
area designed to reduce inlet turbulence.
Depending on the process, the well can
be a simple influent well with baffle
arrangement or a flocculation well. In all
instances, the well is designed to diffuse
and disperse inlet water energy, based on
process requirements.
The well can be supported from the
sludge scraper arms, from the cage or
from the access bridge, depending on
design conditions.
For wastewater applications, the influ-
ent well is equipped with baffled scum
ports that permit floating material to
escape from the feedwell while prevent-
ing short circuiting.
Storm water clarifier installation with walk through truss bridge
Half Bridge Drive
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H A L F B R I D G E C I R C U L A R C L A R I F I E R S
9.
SCRAPER ARMS A minimum of two scraper arms, each
with individual scraper blades, move set-
tled sludge toward the center sludge hop-
per for removal. Scraper blades are
arranged to scrape the floor twice in each
revolution.
Some applications require four scraper
arms to achieve the required sludge
removals. In all designs, sludge scrapers
arms are supported and rotated by a
center cage supported from the Type H
drive unit.
Scraper arms and the rotating cage are
constructed of structural steel. All weld-
ing is done in the factory to assure quality
fabrication and to minimize field erection
requirements. All submerged structural
material is a 1/4 inch minimum thickness.
Depending on the size of tank, the access
bridge to the drive mechanism will be of
beam or truss design. Handrail and four
inch kickplate are provided for operator
safety with the beam design. In the truss
ACCESS BRIDGE design, the truss acts as the handrail and
kickplate. A platform is normally pro-
vided at the drive mechanism for safety
and efficient maintenance.
SKIMMING/EFFLUENT WEIRS Various skimming effluent arrangements
are available for water and wastewater
treatment circular clarifiers. Generally, a
full radius, surface scum blade directs
floating material to the peripheral scum
skimmer. The skimmer concentrates the
floating material and deposits it in the
scum trough.
Adjustable weirs are generally located on
the periphery of the basin, although
radial and other arrangements may be
employed.
Half Bridge Clarifier
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H A L F B R I D G E D R I V E T Y P E H T H O U S A N D S A R E I N S TA L L E D
10.
Designed to AGMA standards and
manufactured by U.S. Filter for circular
sludge collector operations, the Type H
drive will provide the full rated torque
over its 20 year service life. That is one
assurance of dependable sludge collector
performance.
Another is in the field, where thou-
sands of H Type drives are installed in
municipal and industrial water and
wastewater treatment facilities world-
wide.
In addition, each Type H drive is
backed by U.S. Filter, so owners have sin-
gle source responsibility for service and
replacement parts, if required.
The Type H drive consists of primary,
intermediate and final reduction units,
designed as a workhorse system with a
low power draw.
A helical gear unit serves as the prima-
ry reducer. Power is transmitted from it
to the intermediate worm gear reduction
unit via a chain and sprocket coupling
arrangement. This can be provided with
a shear pin overload device, if desired.
The driven worm shaft in turn drives
the main worm gear. Overload protec-
tion, including alarm and shutdown
micro-switches, operates from the
thrust of the worm shaft. Stability of
the large diameter worm gear is assured
by a hardened, precision ball bearing.
The final reduction pinion gear, driv-
en by the worm gear, engages the spur
gear to complete the transmission of
power. The spur gear is supported by a
large diameter ball bearing, contained in
a raceway with removable liners.
All gears and bearings run in an oil
bath for extended and trouble free oper-
ation. Oil levels are easy to monitor and
maintain. An easy to reach drain makes
changing oil simple.
The spur gear is split for easy access to
the ball bearing and raceway liners. The
gear, bearings and liners can be replaced
without moving the access bridge.
With this feature, not commonly avail-
able in the water and wastewater market-
place, maintenance costs can be signifi-
cantly reduced. In most instances, a
worn spur gear, bearings and raceway
can be replaced for far less than the cost
of a new drive.
MAIN COMPONENTS
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H A L F B R I D G E D R I V E T Y P E H 20 Y E A R S E R V I C E L I F E
11.
Half-Bridge Drive-General Benefits
Cast iron construction All gear sets designed
to meet AGMA20-year life requirements
Replaceable hardened alloy steel bearing racesindependent of gear
Factory assembled Oil bath lubricated Intermediate worm
gear reduction Large diameter split
internal main gear Electro-Mechanical
overload protection Condensate taps
H-90 Half Bridge Drive Platform
H-90 Floc-clarifier
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FOR SIMULTANEOUS FLOCCULATION
AND CLARIFICATION
U.S . F I LT E R F L O C-C L A R I F I E R S
12.
A U.S. Filter floc-clarifier reduces over-
all operating costs and initial capital outlay,
when compared to separate flocculation
and clarification units. It combines the
basic components of the circular clarifier
with flocculation.
The U.S. Filter floc-clarifier can be
applied to process requirements such as
water treatment (removal of color, partic-
ulates, chemicals) or wastewater treatment
(phosphorous removal, trickling filter
solids contact systems).
Changes to the design include a larger
influent well, sized to provide the
required flocculation time. In some
instances, modifications to the bridge and
supporting structure may be required.
Mixing is also added to achieve eco-
nomical flocculation. Proven designs
include mechanical mixing, air supply, or
hydraulic baffles.
Mechanical flocculation is provided by
either concentric stacked drives or
independent mixes.
A special adaptation to the U.S. Filter
floc-clarifier is the reactor clarifier. It
employs sludge recirculation with in the
clarifier to increase floc formation and
particle interaction and uses the sludge
recirculation within the clarifier to
increase floc formation and particle
interaction and uses the sludge bed to
filter the effluent flow. While it is an
excellent performer, it is more restrictive
regarding application than a floc-clarifier.
REACTOR CLARIFIER
C O N C E N T R I C F L O C-C L A R I F I E R
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U.S . F I LT E R F L O C-C L A R I F I E R S
13.
This special drive concept provides the
most positive method of achieving com-
plete flocculation and generally reduces
capital and operating costs. It employs a
Type H or Type F drive for flocculation,
stacked on top of the respective Type H or
Type F drive used for the circular clarifier
mechanism.
The Type CF drive allows the use of a
full concentric flocculation device within
the flocculation well. As contrasted to
CONCENTRIC-FLOC DRIVES
TYPE CF
GRAVITY
THICKENERS
independent mixers, all incoming flow
must pass through the flocculating device
ensuring complete flocculation of all flow
entering the clarifier. Variable speed units
match mixing speed to the required floc-
culation intensity.
All concentric drives are designed to the
same high standards as used for U.S.
Filters clarifier drives. The result is a low
maintenance unit with extended longevity.
U.S. Filters gravity thickeners are heavy
duty circular collectors, custom designed
for handling concentrated industrial and
municipal sludges. To meet the increased
sludge loads, gravity thickeners are
designed with higher service factors.
Additionally, U.S. Filter gravity thicken-
ers can be provided with pickets for
dewatering, lifting devices for heavy solids
applications, etc.
Since gravity thickeners are designed
for sludge handling rather than liquid han-
dling, they are furnished with steeper
floor slopes than conventional clarifiers.
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S K I M M I N G E Q U I P M E N T S Y S T E M S F O R E V E RY N E E D
14.
FULL RADIUS SKIMMERS A full radius scum blade, skimmer and
stationary scum trough comprise the
standard circular collector skimming
device. The system moves floating mate-
rials to the periphery of the tank where it
is collected for further treatment.
To increase scum removal efficiencies, an
anti-rotation scum baffle, submerged
shelf scum trough or dual skimmers can
be furnished.
REVOLVING TROUGH SKIMMER The revolving trough skimmer is an
economical alternative to the ducking
skimmer. It is an easy to operate, high
volume scum removal skimmer. It incor-
porates a number of full radius, revolving
scum troughs with fixed skimmers trans-
porting scum into the troughs. Scum
flows to a center collection well where it is
removed by pumping.
Removal of floating debris from the surface of a circular clarifier is often one
of the most difficult tasks to accomplish in a treatment facility. U.S. Filter/Envirex,
with more than 50 years experience in designing skimmers and cixcular
collectors, has the knowledge and type of skimmers to provide positive removal.
Full radius skimmer in Half Bridge tank
Revolving trough skimmer with Tow-Bro Header
Extended beach trough with
flushing device
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S K I M M I N G E Q U I P M E N T S Y S T E M S F O R E V E RY N E E D
15.
For heavier scum removal needs, the
ducking skimmer is an efficient, high
volume scum removal device. It incorpo-
rates a rotating scum trough and multiple,
full radius skimmers.
It allows flexible control of scum
removal via electrical control, but is
more complex and involves more opera-
tor attention than other systems.
Additionally, it increases the amount of
liquid to be handled by the scum system.
DUCKING SKIMMER
Ducking Skimmer Installation
Revolving Scum Trough
Above: Revolving Trough Scum Well
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Bulletin No. U.S.F. 315-111R27.5M-9/97 Printed In U.S.A.
1997 UNITED STATES FILTER CORPORATION
P.O. Box 1604Waukesha, WI 53187
414.547.0141 phone414.547.4120 fax
http://www.usfilter.com
Taking care of the worlds water.
Products manufactured and marketedby U.S. Filter/Envirex are protected bypatents issued or pending in the UnitedStates and other countries.
U.S. Filter engineers have furnished proven designs for virtually every type ofapplication requiring clarification, floc-clarification, gravity thickening andskimming. With more than half a century experience, U.S. Filter can point toits equipment operating in industries and municipalities worldwide.From drive design to factory fabrication, U.S. Filter sets the standards for howa circular collector should be built. With reliability. With longevity. And with integrity.
OTHER CLARIFICATION
PROCESSES
The Rex Rim-Flo clarifier provides
economical, highly efficient secondary
and tertiary clarification using a peripher-
al influent/peripheral effluent design.
It is designed for greater capacity and a
higher overflow rate than a conventional
center feed unit because of its inherent
hydraulic efficiency. Increased efficiency
means either a smaller tank or a tank
with a conservative loading rate can be
designed.
The Rex Tow-Bro sludge removal
device is recommended to remove acti-
vated sludges. It offers rapid sludge pick-
up, minimum sludge agitation and
maximum solids concentration.
The Tow-Bro can be easily retrofitted
to an existing circular scraper sludge col-
lector providing increased sludge removal
concentrations and reduced floating
sludge problems.
For more information, contact yourlocal U.S. Filter sales
representative, or U.S. Filter/Envirex.
Rim-Flo Clarifier
Half Bridge Tow-Bro with pony truss bridge
S E T T I N G T H E S TA N D A R D S I N C I R C U L A R C O L L E C T I O N