Dissolved Air Flotation for Wastewater Lagoon Clarification

James E. Farmerie

Wastewater Clari-DAF LT Systems March 13, 2011 2

Aeration Lagoon

AerationLagoon Settling

Discharge

Typical Wastewater Lagoon System

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Settling StepRemoves

Colloidal & Suspended Solids

Precipitated Dissolved Solids

Biochemical Oxygen Demand (BOD) associated with the Suspended Solids (TSS)

Algae

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Why Flotation ?

Ideal for low density solids removal

Produces Consistent water quality effluent

Produces Consistently high sludge solids

Increases Dissolved Oxygen in discharge

Small footprint @ High loading gpm/ft2

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Lagoon Treatment ApplicationsAlgae laden waters with seasonal blooms contributing to TSS & BODLow Density Solids

MBBR Biological Solids Soluble Phosphate Water with low D.O.

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Saturator

Recycle Pump

Floc 1 Floc 2 Skimming Devise

Lateral Draw-off pipesNozzles/Valves

RAW WATER

Outlet

AirCompressor

Flash Mix

Saturator

Recycle Pump

Floc 1 Floc 2 Skimming Devise

Lateral Draw-off pipesNozzles/Valves

RAW WATER

Outlet

AirCompressor

Flash Mix

Saturator

Recycle Pump

Floc 1 Floc 2 Skimming Devise

Lateral Draw-off pipesNozzles/Valves

RAW WATER

Outlet

AirCompressor

Flash Mix

Saturator

Recycle Pump

Floc 1 Floc 2 Skimming Device

Lateral Draw-off pipesNozzles/Valves

RAW WATER

Outlet

AirCompressor

Flash Mix

Saturator

Recycle Pump

Floc 1 Floc 2 Skimming Device

Lateral Draw-off pipesNozzles/Valves

RAW WATER

Outlet

AirCompressor

Flash Mix

+ Coagulant

5-20 mins floc time 8 20 gpm/ft2 Loading Rate

Compressed Air dissolved in water at 80 psi

10 % Flow

How does it Work ?

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Air Flotation

Air is dissolved in water under pressure and mixed with waste containing coagulated solids

In the Unit, the pressure drops and allows the air to come out of solution and forms micro-bubbles

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Air bubbles attach to the surface of the solids and become entrapped in the floc as it forms

The resulting mass is buoyant and quickly rises to the surface

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Air Flotation

A float layer of sludge is formed at the surface of the Flotation Cell

Water is removed from the bottom of the tank through laterals that stretch across the length of the tank

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V = Time to Settle/Float G = Gravity P1 = Particle Density

P2 = Liquid Density D = Diameter of the Particle Viscosity of the Liquid

V = _______________ G (P1 P2) D2

18 u

Stokes Law

Wastewater Clari-DAF LT Systems

SIZE: Hundreds of MicronsSIZE: Hundreds of Microns

SIZE: Tens of MicronsSIZE: Tens of Microns

Particle Size Difference

Buoyancy Flotation

Bubble AdditionGravity Settling

Coagulant/Polymer Addition

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Small SystemsSteel Tank

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Large SystemField Erected Concrete Tanks

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The Saturator

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Dispersion Header Pipe

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Nozzles

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Saturated Water

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Sludge Skimmer

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Mechanical DesludgingReciprocating Skimmer

Low Maintenance

0.25 hp Motor

Gentle on fragile sludge

2 5 % Sludge Solids

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Hydraulic Desludging

Procedure

Effluent gate closed Water level rises Spray water turned on Sludge flows to trough 0.5 1.0 % Sludge Solids

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Mechanically Assisted Hydraulic Desludging

Actuated slide gate & reciprocating skimmer

Reduces time of hydraulic only desludging

Increases flowability of sludge

Solids between Mechanical & Hydraulic desludging

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Sludge

Polymer

Valve to Drop to Atmospheric

Air Compressor 50 psig

Saturator

Recycle Pumps

30%-70%Recycle

Skimmer Device

Loading Rate @ 1 4 gpm/sf

Water Draw-Off

Settled Sludge RemovalDistribution Header

Sludge Thickening DAF

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DAF Comparisons

10 - 50 m50 - 100 mBubble Size

Reaction ZoneRecycle LinePressure Drop Location

80 90 psig50 psigPressure

5 % - 15 %30 % - 70 %Recycle Rate

8 20 gpm/ft21 4 gpm/ft2Loading Rate

Rapid Mix/FlocculatorRecycle LineChemical Addition

NoYesBottom Sludge Collector

YesNoFlocculator(s)

YesNoRapid Mix

Clarification DAFThickening DAF

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ExampleJohnstown, CO

Average Flow @ 400,000 gallon/day Discharge to Little Thompson River Average Influent TSS @ 195 mg/L Average Influent BOD @ 227 mg/L NPDES Permit for Effluent:

- TSS @ < 75 mg/L

- BOD @ < 30 mg/L

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AerationLagoon

AerationLagoon

SettlingLagoon

BOD-Excursions >30 mg/LTSS-Excursions >75 mg/L

When algae present

Johnstown, CO Lagoon System Performance

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Johnstown, CO Pilot StudyJuly 2000

Alum @ 100 mg/L polyDADMAC @ 0.25 mg/L Loading Rate @ 4-8 gpm/ft2 Sludge off the DAF

- 2% to 4 % dry solids

- 0.4 % if influent flow

- Drying bed test @ 6.88 % after 24 hours

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Johnstown, CO Pilot TestJuly 2000

Parameter DAF Influent DAF EffluentRange Average Range Average

Turbidity, NTU 18 to 80 40 2 to 28 15BOD, mg/L 24 to 35 27 3 to 13 10TSS, mg/L 19 to 62 35 8 to 25 11

LIMITS: TSS @ 75 mg/L BOD @ 30 mg/L

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Johnstown, CO Plant Design

Additional aeration in 2 lagoons

Moving Bed Biofilm Reactor (MBBR) for ammonia nitrogen removal

DAF for algae, TSS, and related BOD removal

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Aeration Pond

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MBBR

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DAF Operating

9612.4272976.32102006

975.8230992.52442005

959.3197993.52122004

88231849692332003

812816396113972002

8725186968.83082001

Removalmg/Lmg/LRemovalmg/Lmg/LYear

%EffluentInfluent%EffluentInfluent

TSSBOD

Johnstown CO Wastewater DATA

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Johnstown CO Wastewater Effluent 2001 - 2006

05

1015202530

1 2 3 4 5 6

Year

m

g

/

L TSSBOD

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Johnstown CO Wastewater Highest Monthly Average

2001-2006

0

50

100

150

1 2 3 4 5 6

Year

m

g

/

L TSSBOD

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Johnstown, COPlant Performance

Alum @ 60 mg/L (down from 100 mg/L) polyDADMAC @ 0 (down from 0.25mg/L) Loading @ 4 gpm/ft2

- Plant can double capacity to 8 gpm/ft2

Bonus Benefit in effluent:- Pre-DAF coliforms @ 5,000 CFU/100 ml

- DAF coliforms @ 250 CFU/100 ml

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Johnstown, CO Clari-DAF System

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Johnstown, COInfluent & Effluent Samples

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Greensboro, AL Pilot StudyOctober 2004

Polyaluminum Chloride @ 11 mg/L

Polymer @ 7 mg/L

Loading Rate @ 4 gpm/ft2

AL requires 65% removal BOD & TSS

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Greensboro, AL Pilot TestOctober 2004

BOD TSS Coliformsmg/L mg/L CFU/100 ml

Lagoon Influent Range 183 to 1,060 62 to 308 Average 442 179 241,920DAF Influent Range 11 to 26 56 to 67 Average 18 61 52,605DAF Effluent Range 1 to 7 5 to 17 Average 4 9 3,785

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Western Butler County Authority (WBCA)Zelienople, PADecember, 2005 January, 2006

Tested plant effluent Goal: P Removal through flotation Mixing Time: 12 to 20 minutes Loading Rate: 6 gpm/ft2 to 12 gpm/ft2 10 % Recycle Rate

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WBCADecember 2005 January 2006

Parameter DAF ALUM FerricInfluent 80 mg/L 60 mg/L

TSS - mg/L 3.85 2.00

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Questions ???