1. Filter Parts – Why General Filter
MULTIBLOCK, MULTICRETE II, ESSD Washtroughs,
Media & In-Bed Air Wash Grids

2. What is The General Filter Advantage? UNDERSTANDING FILTRATION
Can improve operation an existing plant. (expansion & upgrades)
Thoroughly backwash filter media with air/water
Provide even distribution of backwash water and air throughout the filter basin.
Reduce backwash waste
Reduce off line time with shorter backwash durations
Complete the scope for a new plant.

3. We have the complete Filter System!
WASHTROUGHS
CONTROLS
MEDIA
AIR GRIDS
UNDERDRAINS

4. MULTIBLOCK® Underdrain Details Similar to Other Block Underdrains
12” tall x 11” wide 36” length
HDPE structural foam
Compensating dual lateral design
Media retaining or gravel support designs
Snap fit connection.
NSF/ANSI STANDARD 61
With or without Laser Shield®
Competitor
W x H L
Block Connection
Leopold-S®
11” x 12”
48”
Snap fit
Severn Trent –U Block™
12” x 12”
36”
Snap fit, single gasket
Inflico Tetra™ –U
Roberts Trilateral®
10 5/8” x 12 1/2”
Bell & spigot and O-ring
These are the overall details of the underdrain. Spacing of the laterals are on 12” centers. The blocks are joined to form longer laterals. The make up blocks (those that are not full length) are factory cut to length.
HDPE (high density polyethylene) is the same material used by the other block manufacturers. The blocks are injection molded.
The compensating lateral design is explained further later on but this is simply having more than one chamber inside the block to allow balancing of flow down a length of lateral.

5. Modular Design Easy to Install
Blocks snap together to form laterals
25 lbs/block - HDPE material
MULTIBLOCK Shield factory installed (if used)
Rebar pullout tested prior to block installation
Laterals installed in rows
+/- 1/8” level
Set on 3/4” grout bed
Joints filled with grout
Max length 30’ on each side of flume

6. Laser Shield® Provides Unique Direct Media Retention
0.06” stainless steel plate
0.008” (0.2 mm) slot openings
Minimizes opening surface area per volume
Stainless steel screws
Based on nozzle design

7. Comparison of the Two Shields We Offer
Porous bead design
3,000 sq.in. / sq.ft. of filter
Laser Shield
16 sq.in. / sq.ft. of filter
Porous bead difficult to clean
No clear passage for water
Lower profile
Clearly defined, sharp edge openings
Retains smaller media
MS-500 Shield
500 micron
3/4" thickness
Laser Shield
0.20 mm slots
0.06" thickness

8. MULTIBLOCK Cover A Wide Range of Flow Conditions
Backwash
Water only 5-30 gpm/sq.ft.
Air only 1-5 scfm/sq.ft.
Combined backwash
5 gpm/sq.ft. and 3 scfm/sq.ft. is typical
consult us for specific applications
Filtration
2-10 gpm/sq.ft.
Maldistribution in large basins
Less than +/- 10%
Typical flow rates for backwash and filtration. Combined air-water rates other than those listed may be possible depending on the length of the lateral and the volume of air and water we are trying to pass.

9. General Filter Scope of Supply
Underdrain blocks
Media retaining Laser Shield™
Rebar over flume
Flume bridges
End caps
Ancillary equipment
Air headers, washtroughs, media, controls, etc.
Pre-treatment equipment
Don’t forget backwash waste treatment products, such as:
ContraFAST
Packaged Plate Settlers
Here is what we provide. Basically everything needed for the filter system can be provided by us.
One of our differentiating qualities against other block underdrain suppliers is that we offer a wide range of other equipment items for a plant. This provides single source responsibility for the entire plant, and not just the filter.

10. Application Areas Single, Dual and Mixed media Concrete filters
Conventional layout
CenTROL® filter
Steel filters
Packaged plants
Trident® and Trident HS Systems
Aquarius® Systems
MULTIBLOCK can be used in almost any gravity filter system. Installations (some may not be in operation yet) to date include conventional concrete filters, CenTROL, steel gravity filters and ACTIFLOC & Aquarius units.
We prefer not to use the Shield on wastewater applications due to potential biological fouling. This may change after we gain more operating experience.

11. Competition: Block Underdrains-Standard Height
We are seeing more and more installations where porous caps style underdrains are starting to fail. They have accumulated enough solids over the years that result in higher and higher backwash pressure resulting in ultimate failure
Leopold Type S
IMS Cap (porous bead) used for direct retention.
Patented water recovery channel and inside baffles
Severn Trent – Also Offered By IDI
Porous bead plate used for direct retention
Roberts Filter Group
Will use this to get in the door to promote Infinity. Lately have been very aggressive. In promoting the Air Grids.
Main selling feature is the single 30 ft block. This eliminates the joints, clips and seals. Backwash with water only, use air grid above. Can be retrofitted into existing
low profile filter cells.

12. Competition-Low Profile Underdrains
Limited to basins less than 20’ from feed flume.
Concern for dead spots on top of pyramids or between units.
Maldistribution is a key point to compete against.
Maximum air and backwash water rates may be limited.
AWI Phoenix Underdrain System
Used with our MULTIWASH Troughs
Ovivo EWT™ Flexscour®
WesTech hasn’t seen a lot of these.
EIMCO
Folded Plate
Not seen many of these
Johnson TRITON®
Used by WesTech in various applications.
Not suitable for high A/W rates
Leopold LP
Max length 16’ from flume
Highly competitive.

13. MULTICRETE II Underdrain Provides Installation Options
Standard ACI 318 loadings
1,600 psf , 1,400 psf 
Doweled Rebar Design
Exploded view shows the parts of the underdrain system. Pier forms are 6” dia. sch 40 PVC. We used to notch these at the top to lock in the forms but have moving the locking mechanism to the form itself (details in a couple of slides from here). The underdrain pans have also been changed (details in a few slides) to make them stronger and easier to install. We provide the piers, pans, inserts and nozzles. Contractor supplies the concrete and rebar. Two side attachment options are shown: The keyway design eliminates the doweling of the rebar into the wall. A stainless steel angle is used to support the pans at the perimeter during concrete pouring. The doweled design requires horizontal rebar to be drilled into the wall and is shown here with a poured concrete ledge (2” wide required). A perimeter angle can also be used.
Keyway Design

14. MULTICRETE II® Offers Long-Term Experience
Floor and nozzle design based on pre-cast design from 1960’s
Monolithic construction with over 19 years experience
Eliminated most joints
Light weight forms easier to handle
Nozzle design and spacing remained
MULTICRETE II 653,225sq.ft sites Millions of nozzles
We originally had pre-cast concrete panels for our MULTICRETE underdrain. These were heavy and could crack during shipment. The biggest downside was the underdrain had multiple joints where the panels joined together. To eliminate the multiple joints the MULTICRETE II underdrain was first installed in The same nozzles used for MULTICRETE are used for MULTICRETE II and also in steel plate underdrain filters we sell. Our experience with nozzle underdrains is extensive and very positive with very few failures with MULTICRETE II. For MULTICRETE II, over 50 installations are lime softening, over 40 are wastewater and the balance being surface water clarification or iron/manganese removal plants.
Mid 1960’s
1986
Today

15. Quarter-Turn Insert Reduces Installation Time, Ensures Proper Fit
MULTICRETE II Form (from below)
Insert (inverted) and form opening
Our new concrete insert design uses an elliptica shape on the bottom of the insert and a matching opening in the form. The inserted is installed in the opening and turned about ¼ of a turn until it hits the stop lobe. At this point the insert is in tight without a chance of working free or being kicked over during concrete installation. Our old design required attachment with ABS solvent which took longer for the contractor to install and if they didn’t the inserts attached right, they may kick them over during the concrete pour.
Stop Lobe
Pier locking ring
Insert installed in form
Less than 1/8” deflection during installation

16. MULTICRETE II Provides Simple Formwork Installation
Inspected by our Service Personnel
Install nozzles after curing
Here is the basic installation process. Vertical rebar are pulled tested to 3,600 lbs uplift to ensure they are properly installed prior to placing the forms. 10% of the anchors are randomly tested and if any fail in a cell, all anchors are tested. Once the forms and rebar are installed, our field service engineers inspect the installation. Elevation tolerance is +/- ¼” measured at the top of the inserts. Concrete pour for the floor and support piers happens at the same time. Concrete along the walls and into the pier supports is vibrated to eliminate voids. Concrete is finished to the top of the red protector caps, no more or no less. Once the concrete has cured for at least 48 hours the red caps can be removed and the nozzles installed.
Anchorage pull tested
Concrete installed

17. Dual Air Distribution Ensures Uniform Backwash
Identical headloss nozzles
Air blanket (secondary distribution)
A visual description of what the air wash header and nozzles air metering orifices are doing during backwash. Remember the blanket moves in all directions to ensure uniform distribution.
Air header & risers (primary distribution)
Low headloss open plenum

18. Nozzle Design Ensures Uniform Distribution
Assembly screws
 slot openings > tailpipe area
To prevent plugging we use a wedge wire opening in the nozzle head as shown in the nozzle cross section. If debris in the filter cell gets into the slot opening and get pushed in they get into a larger space and will push through rather than becoming stuck. In addition, the tailpipe opening area is actually smaller than the nozzle slot open area. This allows a small degree of nozzle fouling without effecting distribution. The tailpipe is actually the hydraulic control point of the nozzle assembly.
Tailpipe section (control orifice)
Nozzle cross-section

19. Application Areas All concrete filter applications Conventional layout
CenTROL®
MULTIWASH Filtration Process
Our preferred underdrain for Wastewater Filtration
Single, Dual and Mixed media
Mixed media needs support gravel
MULTIBLOCK can be used in almost any gravity filter system. Installations (some may not be in operation yet) to date include conventional concrete filters, CenTROL, steel gravity filters and ACTIFLOC & Aquarius units.
We prefer not to use the Shield on wastewater applications due to potential biological fouling. This may change after we gain more operating experience.

20. Competition: Monolithic Floor Underdrains
IDI Form
Using tighter nozzle spacing (4”-6”) to keep others out
IDI has good experience base.
Orthos Underdrain
Orthos much lower experience on complete supply
Eimco Castkleen
Large underdrain form = 48” square. Will use concrete pre-poured support walls or piers
Adjustable insert height for leveling

21. MULTIBLOCK or MULTICRETE II?
Lower profile
No access
Packaged steel plants
Concrete tanks
Gravel or gravelless
Limited water/air rates
Mixed media
MULTICRETE II
Larger plenum
Less headloss
Plenum access
Concrete tanks
Gravel or gravelless
WTP and WWTP
Unlimited water/air rates

22. ESSD™ Washtroughs Deliver Durability and Cost Effectiveness
417+ installations
Light gage (12-16 ga.) material
Webbing adds strength

23. ESSDs Apply To Range Of Systems
Hydraulic capacity same as other troughs
Also used in pre-treatment basins
CONTRAFLO® Units
Settling basins
Clarifiers
Longer unsupported span compared to FRP
Up to 36 ft. length vs. 24 ft.
MULTIWASH ® baffles factory attached to trough

24. General Filter offers a number of filter Medias to complete a “system” package
Sand media
Depth 24”
Size – 0.45 – 0.55 mm
Fe < 0.3 ppm
Anthracite
Size mm
Fe < 4 ppm
Dual media
12” sand 0.45 – 0.55 mm
18” of anthracite
0.8 – 1.0 mm or
1.0 – 1.2 mm
Fe < 7 ppm
Mixed Media
Garnet, Sand, Anthracite
Manganese Anthra/Sand
Natural media
Media conditioned in the field
Developed in 1980’s
Overcomes shortcomings of greensand
Various media sizes available
Media selection is based on
Raw water quality
Desired effluent quality
252+ installations since 1980
Largest installation – 39.7 MGD – Eagan, MN
All granular media configurations can be coated as Manganese ANTHRA/SAND.
Our advantage is that since our media is coated in-situ, everything is coated even the support gravel, making effective use of all the material in the vessel.

25. Manganese Anthra/sand Still Outstanding compared to competition.
Recent studies (2012) by John E. Tobiason, PhD, PE, BCEE, Professor, Environmental and Water Resources Graduate Program, Department of Civil and Environmental Engineering, University of Massachusetts conducted some recent lab testing comparing Manganese Anthra/sand to macrolite and pyrolucite and reported
“In general, Jonathan found that the coating method worked well and seemed to provide a coating that worked well very soon after being put into service. “
This favorable results is expected to help increase sales in the Northeast.

26. In-Bed Air Wash Grids Located at media- gravel interface Headers
PVC
Stainless Steel
Laterals
Polyethylene
Distributors
ABS plastic
Slotted lateral

27. Filter Parts Summary Many options for all situations
more options than any other manufacturer
Cost effective designs
MULTIBLOCK or MULTICRETE with MULTIWASH is an AWESOME SYSTEM!!!!!!!!!
Sell the features and benefits to beat the competition:
Plant tours
Increasing your offering to enhance your position
Case Studies…. We’ve done quite a few of them this year!

28. Filter Parts – Why General Filter?
MULTIBLOCK, MULTICRETE II, ESSD Washtroughs,
Media & In-Bed Air Wash Grids