CIRCULAR

CLARIFICATION

EQUIPMENT

& PROCESSES

Taking care of the worlds water.

100% water

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.

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

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.

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

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

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

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

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

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

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

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

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.

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

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

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