Greenleaf Filter ControlSimple, effective technology for efficient rapid gravity filter control...

P.O. Box 71390Richmond, VA 23255-1390 USAPhone: (800) 446-1150

(804) 756-7600Fax: (804) 756-7643www.infilcodegremont.com

Contact us for information on cost-effective water treatment solutions.

Copyright © 2005 Infilco Degremont, Inc. 8/2005 DB310

GreenleafFilter ControlThe Greenleaf filter system is simple, flexible, and accessible• Low-maintenance siphon technology

• Operates in two-thirds the space of conventional systems

• Compact design greatly reduces initial capital

• Common wall construction

• Centralized controls for easy access

Conventional filtration High particulate-level water Potable water treatmentAdvanced wastewater treatment Industrial filtration

Greenleaf Filter Controlfeaturing Monoflor

® HD and TETRA™ Block Underdrains

Simple, effective technology for efficient rapid gravity filter controlInfilco Degremont’s Greenleaf Filter

Control uses low-maintenance siphon

technology to control the operation

of multiple granular media gravity

filters. Our unique design eliminates

bulky piping and valves and complex

instrumentation, delivering low-cost,

trouble-free performance in hundreds

of installations.

Greenleaf triumphs over conventional systems Improved plant performance

Greenleaf filters offer excellent stability

because they are always under a

positive head. All flow rate changes are

gradual to eliminate the shocks and

surges that can upset the filter bed.

Flow is equally divided among operating

filters using simple hydraulics — no

mechanical flow controllers are required.

Centralized controls

Centralized control economizes

operation. Operators can easily select

and control any filter cell from a central

control center. Choose from local or

remote operation and any degree of

automation. Housed in free-standing

modular cabinets, all controls are visible

and readily accessible for maintenance

and service.

Operational efficiency

Our filters are designed to your

specifications, so in many cases, a filter

cell may be backwashed with effluent

from remaining filter cells without

depleting the clearwell capacity.

Siphon valves that initiate and stop

the flow during both the filtering and

backwash cycles are easy to operate

from the control center.

Reduced capital costs

The Greenleaf Filter Control offers

significant savings over conventional

control systems in equipment cost, site

preparation, excavation, and installation.

Prefabricated assemblies that require

fewer components reduce field

construction costs, and common wall

construction with a neighboring clarifier

affords additional savings.

Design flexibility and small footprint

The Greenleaf Filter Control can be

designed for plant flows of less than

1 mgd to much larger systems — and

requires only two-thirds of the space

needed for a conventional system

operating at the same filter rate.

Greenleaf’s clearwell need not be

located under the filters, avoiding

substantial costs in excavation and

support structures, especially where

poor subsurface conditions such as

rock or groundwater exist.

Underdrain optionsMonoflor® HD UnderdrainThe Monoflor HD Underdrain

incorporates the proven efficiency of

air scour backwash in a single, poured-

in-place concrete unit. By eliminating

precast concrete components, it

provides superior structural strength

without the need for sealants or the

shipping, storage, and handling costs

associated with pre-cast systems.

Monoflor offers concrete advantages

• Easy installation with a single pour ofconcrete

• High-impact polystyrene form reducesthe chance of leaks

• Twice the nozzle concentration for better cleaning — and install easily

• Six standard structural designs to handle nearly any applied load

TETRA U Block™ UnderdrainTetra U Block is a high-density,

compensating, dual-parallel, lateral

underdrain system that provides

superior distribution of both water and

air, for either concurrent or sequential

backwash. Air is distributed across the

entire filter bottom to scour the media

and to provide an airlift that, with water,

removes released solids from the filter.

This dual backwash action provides

intense washing energy throughout

the filter bed.

Benefits of the TETRA U Block

• Snap fit, single gasket, bell-and-spigot

joint assembly ensures a tight fit with

no leaking.

• Long, maintenance-free life with no

moving parts or corrosive materials.

• Easily adapted to new or old filter

designs for hydraulic only, or air/water

backwash applications.

TETRA LP Block™ UnderdrainTETRA LP Block’s lower profile allows

for the retrofit of existing shallow filters

with air/water backwash, greater media

depth, and freeboard.

The LP Block offers all the

advantages of the U Block, plus:

• 6” wider profile means fewer blocks,

fewer joints, and less grout.

• Block can be cut in half lengthwise

to avoid grouting space that will not

accommodate a full- width block.

• Patented LP “Grout-Grip” integral

grip resists pullout failures.

Monoflor HD Underdrain

TETRA LP Block™

Underdrain

TETRA U Block™

Underdrain

1. Startup

Water from the pre-treatment unit enters

the control center through a pipe or

flume and is distributed through an

annular launder (A). An inlet siphon (B)

for each cell draws water into an inlet

weir chamber (C), where individual inlet

weirs (D) equalize the flow through a

forebay and into each cell.

These inlet weirs replace conventional

rate controllers by remaining at a

constant level after initial adjustment.

Water enters the filter cell through a

wash trough as the forebay of each cell

fills, passing through the filter bed and

underdrain to a common filtered water

chamber. Water rises behind the effluent

control weir (E) to maintain a positive

head on the filter bed.

2. Initial Filtration Operation

The Greenleaf filtration rate is set and

maintained by the inlet flow rate for the

system. Initial headloss through the filter

media and underdrain system causes

filter cell levels to rise slightly higher

than the effluent control weir (E). Once

the effluent weir chamber (F) is filled,

filtered water is delivered to storage or

pumped directly into service.

The effluent weir chamber, which may

be designed in any shape or volumetric

capacity, is incorporated as part of the

clearwell. This provides “ground-level”

storage, which minimizes construction

costs and allows positive head on the

transfer pumps.

PretreatedWater Flume


Underdrain

Filter Cell Filter CellFilter CellFilter Cell

High

Low

High

Low

WashTrough

WashTrough

Effluent

DrainBackwashWaste Section

Forebay

Effluent Control Weir


Annular Distribution Channel

Inlet Siphon

Inlet Weir Chamber

Effluent Weir Chamber

Inlet Weir

To Vacuum Pump

Vacuum Tank Vacuum Tank

AA

E

F

E

CB

D

UnderdrainEffluent


FilteredWater

Forebay

The Greenleaf Filtration Sequence

Figure 1: Startup Figure 2: Initial Filtration Operation

3. Mid-Cycle Filtration Operation

Headloss across individual filter cells

increases as the filtration cycle continues.

This is measured by the difference

between the water level of an individual

filter cell and the filtered water overflow

above the effluent control weir (E).

Because headloss, which varies for

each cell, is overcome by increasing

the positive head above the filter media,

the water level in the various filter cells

is seldom equal. The Greenleaf system

allows individual cells to be backwashed

as required without taking the entire

filter out of service to backwash all the

cells at the same time.

4. Maximum Headloss in Individual Cells

The control center provides automatic

filter overflow protection at each cell’s

point of maximum headloss, when

the filter cell level reaches that of the

backwash siphon (G). If backwash is not

initiated, excess water from the cell will

overflow into the backwash siphon weir

(H) and the backwash waste section.

Manually controlled filters signal that

backwashing is required through a float

switch or electrode in the filter cell.

Unlike the large gates or butterfly valves

used in conventional filters, a simple

three-way actuating valve (I) allows the

operator to vent the inlet siphon (B) to

the cell. In automatic filters, electrodes in

the various filter cells actuate timers to

initiate and control the backwash cycle.

Filtered water is either utilized for

backwash or flows into the clearwell.

While one cell is backwashed, the

other filter cells remain in service,

compensating for the reduced number

of operating cells by operating at

proportionately higher filter rates.


Filter CellFilter Cell

Filter Media Filter Media

High

Low

WashTrough


Effluent WeirChamber

Vacuum Tank

Top of Basin

Top of Basin

F Backwash Siphon G

Inlet Siphon BackwashSiphon Weir B

Inlet SiphonActuating ValveI

H

EUnderdrain

Effluent


FilteredWater

Forebay




High

Low

WashTrough

Vacuum Tank

UnderdrainEffluent


FilteredWater

Forebay

Figure 3: Mid-Cycle Filtration Operation Figure 4: Maximum Headloss

1. Filter Cell Drain

When the inlet siphon (B) is vented, the

water level in that filter cell gradually

returns to the same level as the filtered

water overflow in the effluent weir

chamber (F). The other filter cells remain

in service and the total filtration capacity

of the filter is not reduced. Flow to the

system is equally and automatically

redistributed among the cells in service

without the use of filter effluent control

valves or complicated automatic con-

trols required by conventional systems.

2. Initiation of Cell Backwash

Backwash is initiated by closing the

backwash siphon actuating valve (J),

which connects the backwash siphon

(G) of the filter cell to the high section

of the vacuum tank. The vacuum draws

water from the forebay and the backwash

waste section up the two legs of the

backwash siphon. Siphon action is

established once both legs are full

of water. The process is initiated slowly

while head gradually becomes available

for backwash as water flows through

the siphon. Unlike conventional systems,

flow reversal through the underdrain is

also gradual, making it impossible to

“shock” or upset the underdrain and

filter media.

Inlet SiphonB




High

Low

WashTrough

Vacuum Tank

UnderdrainEffluent

DrainBackwashWaste Section Filtered

Water

Forebay

Backwash SiphonG

Inlet Siphon ValveB




High

Low

WashTrough

Vacuum Tank

UnderdrainEffluent

DrainBackwashWaste Section Filtered

Water

Forebay

Backwash SiphonActuating ValveJ

The Greenleaf Backwash Sequence

Figure 1: Filtered Cell Drain Figure 2: Initiation of Cell Backwash

Effluent WeirChamberF

3. Cell Backwash

Adequate head for backwash is

determined by the difference between

the elevation of filtered water overflow

in the efficient weir chamber (F) and

the level at lip of the wash trough.

The backwash rate can be adjusted

for seasonal temperature changes

by adjusting the height of the effluent

control weir (E).

Head required for backwash siphon

flow is determined by the difference

between the water level in the forebay

and in the backwash waste section

above the drain funnel. Filtered water

produced by other filter cells that remain

in service is used to backwash the

individual cell. Under typical conditions,

filtered water production will exceed

backwash requirements and the excess

flow will be available for service or

storage. No backwash pump or flow

controller is required.

Because water pressure is equally

distributed beneath the underdrain,

equal distribution of backwash water

is obtained without high headloss,

resulting in significant savings in basin

height. The only significant design

consideration in the backwash system

is the head required to fluidize the filter

media.

4. End of Backwash Cycle (Bed Settle)

Once the filter media have been

cleaned, the backwash cycle ends by

venting the backwash siphon actuating

valve (J) to reduce the water level in the

backwash siphon (G).

Upward flow through the underdrain

gradually decreases as the water level

in the filter cell rises to the elevation of

the filtered water overflow in the effluent

weir chamber (F). The filter media

settles gradually during this period.

The backwashed filter is returned to

service by opening the inlet siphon

actuating valve (I).

The entire backwash sequence can be

easily automated or semi-automated

using level-sensing electrodes, sequence

timers with adjustable cams, relays,

and small three-way valves. Automatic

control equipment can be mounted at

any convenient location.

BackwashSiphonG

Inlet SiphonB

J




High

Low

WashTrough

Vacuum Tank

UnderdrainEffluent


Inlet Siphon Actuating ValveI

EffluentControl WeirE




High

Low

WashTrough

Vacuum Tank

UnderdrainEffluent


FilteredWater

Forebay

FilteredWaterEffluent

Control WeirE

Backwash SiphonActuating Valve

Figure 3: Cell Backwash Figure 4: End of Backwash Cycle



Greenleaf Filter ControlSimple, effective technology for efficient rapid gravity filter control...

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