October 21, 2010

Edward Nevers, Kenneth Sedmak, Donohue & Associates, Inc.

• Anaerobic Digestion Foam– What is it?– What problems does it create?– What causes it?

• Anaerobic Digestion Data• Case Histories

– Marquette, MI– Sun Prairie, WI

• Lectins

• Tip cover• Overflow tank• Plug gas collection system• Operational adjustments result in less

effective digestion– Reduced mixing time and/or intensity– Lowered water level

• Dead bacteria cells – phospholipids – cell membrane

• Bacteria cell parts and enzymes• Mass sticks together and forms a film that

collects gas and forms many bubbles• Filamentous bacteria• Paper at WEFTC by Shimp (B & V) identified

foam as high concentration of solids at 2 – 3 times digester solids content.

Gram stain image

Gram stain image

• Activated sludge feed to digesters• High “slug” loading to digester• Filamentous bacteria in aerobic system• Hydrophobic surfactants?• Fine gas bubbles from gas mix systems• High energy mechanical mixing systems• Temperature variability

Facility Type of Feed Sludge

Distension Time

Type of Mixing

Sludge Transfer from Primary

Digestion

Temperature Maintained

Temperature Consistency

Volatile Solids

Reduction

History of Digester Foaming

History of Aeration

Basin Foaming

Marquette, MI 50% Pri /50% WAS

26 days (mo. avg.) Pumped Nozzle Pumped from Bottom 95 degrees F Var. by more

2 degrees/day 40% to 50 %None Prior to RBC Conversion to AS, Periodically Severe

Periodic

Sun Prairie, WI 60% Pri /40% Was

34 days (annual avg.) Pumped Nozzle Pumped from Bottom 94 to 95 deg. Var. by less

1 degree/day 55%

None Prior to RBC Conversion to AS,

Periodic, but Reducing, High Tend In winter

None

Rantoul, IL 50% Pri /50% Fixed Film

30 days (mo. avg.) Pumped Nozzle Pumped from Bottom 91 degrees F Consistent 38% None NA

LaCrosse, WI 40% Pri /60% WAS 17 days Heat Exc. Pump

OnlyBoth Pumped and Gravity Overflow

85 to 90 degDown to 80 in

winterVariable 48%

Feb. thru June, esp. Spring when

Wasting down AS System

Microthrix during winter

Grafton, WI 54% Pri /46% WAS 27 days External Draft Tube Pumped from Bottom 95 degrees F Generally Consistent 62.5%

None until Aerobic Digester Phased

out and WAS taken to Dig. More foam with Additional of

GBT

None

Wheaton, SD 40% Pri /60% WAS 26 days Pumped Nozzle Gravity Overflow 94 to 96 deg. Consistent 70% None None

Evansville, IN 50% Pri /50% WAS 32 days Avg. Pumped Nozzle Pumped from Bottom 95 degrees Consistent ???? Periodic Periodic

Sheboygan WI 60% Pri / 40% WAS 30 days Recirculation

Pump Pumped from Bottom 95 degrees Consistent 40%Periodic, related to

high strength waste load

None

Jackson, WI 100% WAS 26 days Perth Gravity Overflow 95 degrees Var. by less1 degree/day 48%

Always mild foaming, occasionally on gas holder sidewall

Minimal

Facility Type of Feed Sludge

Distension Time

Type of Mixing

Sludge Transfer from Primary

Digestion

Temperature Maintained

Temperature Consistency

Volatile Solids

Reduction

History of Digester Foaming

History of Aeration

Basin Foaming

Marquette, MI 50% Pri /50% WAS

26 days (mo. avg.) Pumped Nozzle Pumped from Bottom 95 degrees F Var. by more

2 degrees/day 40% to 50 %None Prior to RBC Conversion to AS, Periodically Severe

Periodic

Sun Prairie, WI 60% Pri /40% Was

34 days (annual avg.) Pumped Nozzle Pumped from Bottom 94 to 95 deg. Var. by less

1 degree/day 55%

None Prior to RBC Conversion to AS,

Periodic, but Reducing, High Tend In winter

None

Rantoul, IL 50% Pri /50% Fixed Film

30 days (mo. avg.) Pumped Nozzle Pumped from Bottom 91 degrees F Consistent 38% None NA

LaCrosse, WI 40% Pri /60% WAS 17 days Heat Exc. Pump

OnlyBoth Pumped and Gravity Overflow

85 to 90 degDown to 80 in

winterVariable 48%

Feb. thru June, esp. Spring when

Wasting down AS System

Microthrix during winter

Grafton, WI 54% Pri /46% WAS 27 days External Draft Tube Pumped from Bottom 95 degrees F Generally Consistent 62.5%

None until Aerobic Digester Phased

out and WAS taken to Dig. More foam with Additional of

GBT

None

Wheaton, SD 40% Pri /60% WAS 26 days Pumped Nozzle Gravity Overflow 94 to 96 deg. Consistent 70% None None

Evansville, IN 50% Pri /50% WAS 32 days Avg. Pumped Nozzle Pumped from Bottom 95 degrees Consistent ???? Periodic Periodic

Sheboygan WI 60% Pri / 40% WAS 30 days Recirculation

Pump Pumped from Bottom 95 degrees Consistent 40%Periodic, related to

high strength waste load

None

Jackson, WI 100% WAS 26 days Perth Gravity Overflow 95 degrees Var. by less1 degree/day 48%

Always mild foaming, occasionally on gas holder sidewall

Minimal

Facility Type of Feed Sludge

Distension Time

Type of Mixing

Sludge Transfer from Primary

Digestion

Temperature Maintained

Temperature Consistency

Volatile Solids

Reduction

History of Digester Foaming

History of Aeration

Basin Foaming

Marquette, MI 50% Pri /50% WAS

26 days (mo. avg.) Pumped Nozzle Pumped from Bottom 95 degrees F Var. by more

2 degrees/day 40% to 50 %None Prior to RBC Conversion to AS, Periodically Severe

Periodic

Sun Prairie, WI 60% Pri /40% Was

34 days (annual avg.) Pumped Nozzle Pumped from Bottom 94 to 95 deg. Var. by less

1 degree/day 55%

None Prior to RBC Conversion to AS,

Periodic, but Reducing, High Tend In winter

None

Rantoul, IL 50% Pri /50% Fixed Film

30 days (mo. avg.) Pumped Nozzle Pumped from Bottom 91 degrees F Consistent 38% None NA

LaCrosse, WI 40% Pri /60% WAS 17 days Heat Exc. Pump

OnlyBoth Pumped and Gravity Overflow

85 to 90 degDown to 80 in

winterVariable 48%

Feb. thru June, esp. Spring when

Wasting down AS System

Microthrix during winter

Grafton, WI 54% Pri /46% WAS 27 days External Draft Tube Pumped from Bottom 95 degrees F Generally Consistent 62.5%

None until Aerobic Digester Phased

out and WAS taken to Dig. More foam with Additional of

GBT

None

Wheaton, SD 40% Pri /60% WAS 26 days Pumped Nozzle Gravity Overflow 94 to 96 deg. Consistent 70% None None

Evansville, IN 50% Pri /50% WAS 32 days Avg. Pumped Nozzle Pumped from Bottom 95 degrees Consistent ???? Periodic Periodic

Sheboygan WI 60% Pri / 40% WAS 30 days Recirculation

Pump Pumped from Bottom 95 degrees Consistent 40%Periodic, related to

high strength waste load

None

Jackson, WI 100% WAS 26 days Perth Gravity Overflow 95 degrees Var. by less1 degree/day 48%

Always mild foaming, occasionally on gas holder sidewall

Minimal

Facility Type of Feed Sludge

Distension Time

Type of Mixing

Sludge Transfer from Primary

Digestion

Temperature Maintained

Temperature Consistency

Volatile Solids

Reduction

History of Digester Foaming

History of Aeration

Basin Foaming

Marquette, MI 50% Pri /50% WAS

26 days (mo. avg.) Pumped Nozzle Pumped from Bottom 95 degrees F Var. by more

2 degrees/day 40% to 50 %None Prior to RBC Conversion to AS, Periodically Severe

Periodic

Sun Prairie, WI 60% Pri /40% Was

34 days (annual avg.) Pumped Nozzle Pumped from Bottom 94 to 95 deg. Var. by less

1 degree/day 55%

None Prior to RBC Conversion to AS,

Periodic, but Reducing, High Tend In winter

None

Rantoul, IL 50% Pri /50% Fixed Film

30 days (mo. avg.) Pumped Nozzle Pumped from Bottom 91 degrees F Consistent 38% None NA

LaCrosse, WI 40% Pri /60% WAS 17 days Heat Exc. Pump

OnlyBoth Pumped and Gravity Overflow

85 to 90 degDown to 80 in

winterVariable 48%

Feb. thru June, esp. Spring when

Wasting down AS System

Microthrix during winter

Grafton, WI 54% Pri /46% WAS 27 days External Draft Tube Pumped from Bottom 95 degrees F Generally Consistent 62.5%

None until Aerobic Digester Phased

out and WAS taken to Dig. More foam with Additional of

GBT

None

Wheaton, SD 40% Pri /60% WAS 26 days Pumped Nozzle Gravity Overflow 94 to 96 deg. Consistent 70% None None

Evansville, IN 50% Pri /50% WAS 32 days Avg. Pumped Nozzle Pumped from Bottom 95 degrees Consistent ???? Periodic Periodic

Sheboygan WI 60% Pri / 40% WAS 30 days Recirculation

Pump Pumped from Bottom 95 degrees Consistent 40%Periodic, related to

high strength waste load

None

Jackson, WI 100% WAS 26 days Perth Gravity Overflow 95 degrees Var. by less1 degree/day 48%

Always mild foaming, occasionally on gas holder sidewall

Minimal

Facility Type of Feed Sludge

Distension Time

Type of Mixing

Sludge Transfer from Primary

Digestion

Temperature Maintained

Temperature Consistency

Volatile Solids

Reduction

History of Digester Foaming

History of Aeration

Basin Foaming

Marquette, MI 50% Pri /50% WAS

26 days (mo. avg.) Pumped Nozzle Pumped from Bottom 95 degrees F Var. by more

2 degrees/day 40% to 50 %None Prior to RBC Conversion to AS, Periodically Severe

Periodic

Sun Prairie, WI 60% Pri /40% Was

34 days (annual avg.) Pumped Nozzle Pumped from Bottom 94 to 95 deg. Var. by less

1 degree/day 55%

None Prior to RBC Conversion to AS,

Periodic, but Reducing, High Tend In winter

None

Rantoul, IL 50% Pri /50% Fixed Film

30 days (mo. avg.) Pumped Nozzle Pumped from Bottom 91 degrees F Consistent 38% None NA

LaCrosse, WI 40% Pri /60% WAS 17 days Heat Exc. Pump

OnlyBoth Pumped and Gravity Overflow

85 to 90 degDown to 80 in

winterVariable 48%

Feb. thru June, esp. Spring when

Wasting down AS System

Microthrix during winter

Grafton, WI 54% Pri /46% WAS 27 days External Draft Tube Pumped from Bottom 95 degrees F Generally Consistent 62.5%

None until Aerobic Digester Phased

out and WAS taken to Dig. More foam with Additional of

GBT

None

Wheaton, SD 40% Pri /60% WAS 26 days Pumped Nozzle Gravity Overflow 94 to 96 deg. Consistent 70% None None

Evansville, IN 50% Pri /50% WAS 32 days Avg. Pumped Nozzle Pumped from Bottom 95 degrees Consistent ???? Periodic Periodic

Sheboygan WI 60% Pri / 40% WAS 30 days Recirculation

Pump Pumped from Bottom 95 degrees Consistent 40%Periodic, related to

high strength waste load

None

Jackson, WI 100% WAS 26 days Perth Gravity Overflow 95 degrees Var. by less1 degree/day 48%

Always mild foaming, occasionally on gas holder sidewall

Minimal

Facility Type of Feed Sludge

Distension Time

Type of Mixing

Sludge Transfer from Primary

Digestion

Temperature Maintained

Temperature Consistency

Volatile Solids

Reduction

History of Digester Foaming

History of Aeration

Basin Foaming

Marquette, MI 50% Pri /50% WAS

26 days (mo. avg.) Pumped Nozzle Pumped from Bottom 95 degrees F Var. by more

2 degrees/day 40% to 50 %None Prior to RBC Conversion to AS, Periodically Severe

Periodic

Sun Prairie, WI 60% Pri /40% Was

34 days (annual avg.) Pumped Nozzle Pumped from Bottom 94 to 95 deg. Var. by less

1 degree/day 55%

None Prior to RBC Conversion to AS,

Periodic, but Reducing, High Tend In winter

None

Rantoul, IL 50% Pri /50% Fixed Film

30 days (mo. avg.) Pumped Nozzle Pumped from Bottom 91 degrees F Consistent 38% None NA

LaCrosse, WI 40% Pri /60% WAS 17 days Heat Exc. Pump

OnlyBoth Pumped and Gravity Overflow

85 to 90 degDown to 80 in

winterVariable 48%

Feb. thru June, esp. Spring when

Wasting down AS System

Microthrix during winter

Grafton, WI 54% Pri /46% WAS 27 days External Draft Tube Pumped from Bottom 95 degrees F Generally Consistent 62.5%

None until Aerobic Digester Phased

out and WAS taken to Dig. More foam with Additional of

GBT

None

Wheaton, SD 40% Pri /60% WAS 26 days Pumped Nozzle Gravity Overflow 94 to 96 deg. Consistent 70% None None

Evansville, IN 50% Pri /50% WAS 32 days Avg. Pumped Nozzle Pumped from Bottom 95 degrees Consistent ???? Periodic Periodic

Sheboygan WI 60% Pri / 40% WAS 30 days Recirculation

Pump Pumped from Bottom 95 degrees Consistent 40%Periodic, related to

high strength waste load

None

Jackson, WI 100% WAS 26 days Perth Gravity Overflow 95 degrees Var. by less1 degree/day 48%

Always mild foaming, occasionally on gas holder sidewall

Minimal

• Converted from RBC to activated sludge with biological phosphorus removal in 2007

InfluentScreen

ScreeningsTo Landfill

Grit to Landfill

Grit Removal Primary

Clarifiers

SecondaryTreatment

(RBC’s)SecondaryClarifiers Disinfection

To Carp River

AnaerobicDigester

BiosolidsStorage

BiosolidsDisposal/

Reuse

InfluentScreen

ScreeningsTo Landfill

Grit to Landfill

Grit Removal Primary

Clarifiers

Secondary Treatment(Activated SludgeAeration Tanks) Secondary

Clarifiers Disinfection

To Carp River

AnaerobicDigester

BiosolidsStorage

BiosolidsDisposal/

Reuse

BeltPress

• No foaming as RBC plant• Foaming occurs periodically after startup in 2007• Foaming tends to correspond with foaming in

activated sludge system• Reduction in sludge age reduced filamentous foaming

in aeration basin and probably anaerobic digestion • Reduced mixing cycle and intensity has quickly

reduced the impact of a foaming effect • Inconsistent temperature control-improvements

recently completed

• Converted from RBC to activated sludge with biological phosphorus removal in 2006

• No foaming as RBC plant• Foaming started shortly after startup in 2007• Initially foaming was relatively constant,

managed by hosing down on cover• Incremental changes have reduced problem

to currently an infrequent minor event

• Changed thickened activated sludge feed to digester from slug feed 3 days per week to near continuous

• Reduced mixing from 4 hours on / 4 hours off to half hour on / 4 hours off

• Reduced mixing intensity by significantly throttling mixing pump discharge valve

• Lowered primary clarifier sludge blanket level to reduce fermentation

• Currently increasing summertime sludge age from 9 days to 13 days

• Fimbriae or Pili are proteinaceous appendages on bacteria– Adhesion– Lectins– Store food as slimey proteins and sugars

• Park and Novak– “Characterization of Lectins and Bacterial

Adhesins in Activated Sludge Flocs” WEF Water Environment Research Journal, August 2009

• Lectins– Function

• Adhesion• Gather sugars

• Nature– Located on the fimbriae– Hydrophobic– Divalent cations such as Ca²⁺ and Mg²⁺– Target carbohydrates

• Degrade in Aerobic Digestion• Do not degrade in Anaerobic Digestion• May degrade in acid phase of Anaerobic

Digestion• More research is needed

• Change thickened activated sludge feed to digester from slug fees 3 days per week to near continuous

• Reduce mixing from 4 hours on / 4 hours off to half hour on / 4 hours off

• Reduced mixing intensity by significantly throttling mixing pump discharge valve

• Lowered primary clarifier sludge blanket level to reduce fermentation

• Currently increasing summertime sludge age from 9 days to 13 days

• Anaerobic digestion foaming has been a problem for many years

• Digestion foaming not well understood• More research needed• CS committee has been formed to study

foaming in anaerobic digestion