Flocculator Types, Choosing The Best For Each Process

Velocity Gradient

Flocculation Design

Flocculation SelectionHydraulic Baffled Wall FlocculatorHyperbolic Flocculator

Impeller Flocculator

Vertical Paddle Wheel Flocculator

Horizontal Paddle Wheel Flocculator

Walking Beam Flocculator

Flocculator Types Recap

Velocity Gradient

• The general equation for Velocity gradient (G-Value) is a function of power input per unit volume at a given temperature or G = (P/µV)^0.5

Where:• G = Velocity Gradient• P = Power Input• µ = Absolute Viscosity of

Water at a given temperature• V = Volume of the tank

• The formula for mechanical mixers expands to:

G = CD A r3 ^0.5 2 ν V

Where:• G = Velocity Gradient• CD = Paddle/Blade Coefficient of Drag• A = Area of paddles/blade• r = Relative Velocity of the Paddle• ν = Kinematic Viscosity of the fluid• V = Volume of the tank

General Flocculator Design• Ten States’ Standards:• Detention time of 20-30 min• Maximum tip speed 3 ft/s• Flow-through velocity range of

0.5 ft/min – 1.5 ft/min

• Flocculator Design Guidelines:• Design Water Temperature: 35° F

- 45° F

• Tapered Velocity Gradient over 3 Stages

• Stage 1: 15-30 sec-1

• Stage 2: 30-50 sec-1

• Stage 3: 50-70 sec-1

Flocculator Selection

Considerations When Selecting Flocculator:• Basin Flow• Basin Dimensions• New or Existing Basins• Budget• Redundancy

Requirements

Hydraulic Baffled Wall Flocculator

Hydraulic Baffled Wall Advantages/Disadvantages

Advantages

• Very little maintenance required

• No moving mechanical parts requiring maintenance

• Minimal wear items

• No electricity cost

Disadvantages

• Difficult to finely adjust flocculation mixing intensity

• Significant headloss is created across the basin

• Floc particle created is not as good as other technologies

Choose Hydraulic Baffled Wall Flocculatorswhen:

• Initial cost must be as low as possible

• Energy usage must be as low as possible

Hyperbolic Flocculator

Hyperbolic Flocculator Advantages/Disadvantages

Advantages

• All mechanical parts above the water line

• Minimal wear items

• Easy access for maintenance

• Optimum process control

• Claims to use less energy by taking credit for turbulence induced in water

Disadvantages

• High tip speed and high turbulence shears some floc particles and violates Ten States’ Standards

• Limited installations in water plants

• Patents prevent competition

• High initial cost compared to other vertical type flocculators

• One motor operates one hyperbolic impeller

Choose Hyperbolic Flocculators when:• Initial cost is not a concern

• Reduced energy usage is worth a lower quality floc particle

• Mechanical components are above water line

Impeller Flocculator

• Drive Assembly• Typically no vertical thrust bearing or

radial bearing other than drive itself.

• Shaft

• Impeller Blade

Impeller Flocculator Advantages/Disadvantages

Maintenance Advantages

• All mechanical parts above the water line

• Minimal wear items

• Easy access for maintenance

• Optimum process control

Disadvantages

• High tip speed shears some floc particles and violates Ten States’ Standards

• Floc particle created is not as good as paddlewheel flocculators

• Relies on pumping action of water instead of impeller blades themselves to flocculate

• One motor operates one hyperbolic impeller

• Choose Impeller Flocculators when:

• Small production water plants

• Maximum process control is desired

• Mechanical components are above water line

Mega-FLOC (VPWF)• Drive Assembly

• Chain Coupling

• Thrust collar with double shear bolt arrangement

• Radial Thrust Bearing Assembly

• Drive Shaft Assembly

Mega-FLOC (VPWF) Advantages/DisadvantagesAdvantages

• All mechanical parts above the water line

• Minimal wear items

• Easy access for maintenance

• Optimum process control

• Fully complies with Ten States Standards• Low tip speed

• Maintenance benefits of a vertical style mixer with process performance of a paddle style flocculator

• Homogeneous mixing• High quality floc formation

Disadvantages

• One motor operates one flocculator reel

• More wiring and drive supports than Horizontal Paddlewheel or Walking Beam Flocculators

Mega-FLOC (VPWF) OverviewChoose Vertical Flocculatorswhen:• Smaller Production Water Plants

• Maximum process control is required

• Desire for primary components to stay above the water line

• Better quality floc is desired

Mega-FLOC (HPWF)• Stainless steel sprockets with

UHMW-PE teeth

• Stuffing box

• Drive assembly with integral chain tensioning

• Stainless steel bearing housing with HPVT bearing liner

• 17-4ph stainless steel solid shafting at bearing

Mega-FLOC (HPWF) AdvantagesAdvantages• Most economical flocculation system per

MGD

• One drive can power up to 10-15 floc reels

• Fully complies with Ten States Standards

• Low tip speed

• Process performance of a paddle style flocculator

• Homogeneous mixing• High quality floc formation

Disadvantages• Journal bearings require replacement every

• 7-10 years for UHMW-PE• 15-20 years for HPVT composite

• Less redundancy if a drive fails than vertical flocculators

Mega-FLOC (HPWF) Overview

Choose Horizontal Flocculators when:

• Ideal for large production water plants

• Most economical flocculation per volume of water ratio

Mega-FLOC (WBF)

• Torque Arm

• Connecting Rod

• Connecting Rod Bearing Assembly

• Riser Beam and Haunch Assembly

• Walking Beam and Haunch Assembly

• Walking Beam and Drop Rod Bearing Assembly

Mega-FLOC (WBF) AdvantagesAdvantages

• All mechanical parts above the water line

• Minimal wear items• (No chains, stuffing boxes, journal bearing, etc.)

• All bearings are heavy duty roller bearings

• Eliminates the potential for mass rotation of fluid which is present in all other mechanical flocculation equipment

• Oscillating motion ideal for flocculation. Varying tip speeds throughout a given cycle promote high level floc formation

• Fully complies with Ten States Standards• Low tip speed

Disadvantages

• Drive location is unique and can be challenging on existing basins

Mega-FLOC (WBF) Overview

Choose Walking Beam Flocculators when:

• All rotating components are above water

• Optimum up-down motion vs. rotating motion, eliminating mass-rotation.

• Ideal for basins with high depth to width ratios.

Flocculator Types Recap

CharacteristicTechnology

Floc Particle Quality

Capital Cost Redundancy Maintenance

Ability to Finely Adjust Velocity

Gradient (Flexibility)

Power Usage

History of Usage in Water

Treatment Plants

Walking Beam Paddlewheel Flocculator Excellent Good OK OK Good Good Excellent

Horizontal Paddlewheel Flocculator Good Good OK OK Good Good Excellent

Vertical Paddlewheel Flocculator Good OK Good Good Excellent Good Excellent

Vertical Impeller Flocculator OK OK Good Good Excellent Good Good

Vertical Hyperbolic Flocculator

OK OK Good Good Excellent Good Bad

Hydraulic Baffle Flocculator OK Excellent Excellent Excellent Bad Excellent Good