MIXED LIQUOR FERMENTATION FOR CARBON AUGMENTATION – BREAKING FREE FROM AN UNFAVORABLE INFLUENT CARBON BALANCE

Matt Bond, Associate Vice President

Patrick Dunlap, Wastewater Process Specialist

UNDERSTANDING BIO-P TRADITIONAL FLOW DIAGRAMS FOR BIOLOGICAL NUTRIENT REMOVAL (BNR)

2 Aerobic Anoxic Anaerobic

O P O

O

O

O P O

O

O

O P O

O

O

VFA

UNDERSTANDING BIO-P ANAEROBIC CONDITIONS PHOSPHORUS RELEASE AND POLY-P DEPLETION

Bio-battery for energy storage N

N

H2N

N

N

O

OH OH

O P O

O

O

O P O

O

O

O P O

O

O

Volatile Fatty Acids

Phosphate

Using Energy

VFA VFA VFA

PHB PHB PHB PHB

Poly-P

Magnesium ATP

Poly-P Poly-P Poly-P

Adenosine Tri-Phosphate

3

Poly-P

Poly-P

PHB

Electron microscope – Poly-P stains black, PHB stains white

November 16-18, 2010

UNDERSTANDING BIO-P AEROBIC CONDITIONS PHOSPHATE UPTAKE AND POLY-P PRODUCTION

Aeration Basin

Phosphate

Making Energy

Poly-P

Magnesium

Poly-P Poly-P

Poly-P

Bio-battery is recharging

OH OH

N

N

H2N

N

N

O O P O

O

O

O P O

O

O

O P O

O

O

ATP

PHB PHB PHB PHB PHB

5

May 11-14, 2010

B&V - 6

Poly-P

Poly-phosphate

stored in the

aerobic zone.

Phosphorus is

removed with

the WAS.

January 21, 2011, 2010

7

• Why is Bio-P Removal Perceived to be Inconsistent?

• We have over 20 years of Bio-P history and many plants perform exceptionally well

• However some plants with COD:P > 40 ratio don’t remove P to below permit or will in the summer but not in the winter

• WHY???

NOT ALL INFLUENT COD IS EQUAL: INFLUENT QUALITY IS THE KEY TO SUCCESSFUL BIO-P PERFORMANCE

Biological phosphorus removal is notoriously unreliable Recent IWA Conference Paper Biological phosphorus removal is something you design for, hope for, then add chemicals if is doesn’t work Poul Harremoes 1998

Particulate &

Degradable

Particulate &

Non-biodegradable

Soluble &

Non-biodegradable

Soluble &

Degradable

THE IMPORTANCE OF INFLUENT SAMPLING

Particulate &

Degradable

Particulate &

Non-biodegradable

Soluble &

Non-biodegradable

Soluble &

Degradable

Wastewater Chemical Oxygen Demand Methods for Wastewater Characterization in Activated

Sludge Modeling (Melcer et al., 2003)

BNR will work. BNR will not work. Chemicals or a fermenter required.

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THE IMPORTANCE OF INFLUENT SAMPLING

0.0

5.0

10.0

15.0

20.0

25.0

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Fraction of rbCOD that is VFA

rbC

OD

/P r

atio

Eagle’s Point

Durham

VIP

Reedy Creek

McDowell Creek

At or above curve plants achieve good BPR

Below the curve plants struggle with BPR

9

WHY WOULD ODOR COMPLAINTS FROM THE COLLECTION SYSTEM EVER BE A GOOD THING?

• Fermentation produces H2S (odor) and also influent rbCOD and VFA

• Collection System factors promoting VFA formation • High Water Temperature • Long Travel Time • Flat (Solids Accumulation) • Forcemains (No Headspace)

WHAT FACTORS AFFECT INFLUENT SOLUBLE COD AND VFA? OR….

10

CASE IN POINT: HENDERSON NV

• Plant was consistently achieving permit limit … and then it wasn’t

• Plant had entirely lost biological phosphorus removal

• Sampling revealed VFA was not longer present in influent

• What happened?

• A casino had began to discharge nitrates for odor control downstream of their discharge.

• Fixed odor problems but also removed the VFA

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POTENTIAL SCENARIOS FOR VFA

• Plenty of VFA in influent wastewater means VFA augmentation not needed – fermentation has already occurred in the sewer

• Plenty of rbCOD (not much VFA) in influent means that fermentation occurs in the anaerobic zone

• Not enough VFA or rbCOD means rbCOD and VFA must be made elsewhere on site or added as supplemental carbon – augmentation needed • Direct rbCOD Supplementation • Primary Fermentation • RAS Fermentation • Mixed Liquor Fermentation

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FERMENTATION OPTIONS 1. Primary Sludge

2. Return Activated Sludge

3. Mixed Liquor

13 WAS

Anaerobic

Influent

Anoxic Aerobic

Primary Sludge

2

3

1

Fermentation Substrate

rbCOD

Methane

Hydrolysis

VFAs

Fermentation

Methane Formation

PRIMARY FERMENTATION

0.0

5.0

10.0

15.0

20.0

25.0

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Fraction of rbCOD that is VFA

rbC

OD

/P r

atio

Eagle’s Point

Durham

VIP

Reedy Creek

McDowell Creek

At or above curve plants achieve good BPR

Below the curve plants struggle with BPR

To Digesters

Anaerobic

Optional Recycle

PST

Raw Influent

• Highest Yield of VFA for amount of VSS destroyed

• Relatively complex operation

• Additional facilities needed

• Removes a potential for energy generation

• Odors control will likely be needed

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RAS FERMENTATION

• RAS Fermenter receives 4-7 % or RAS Flow for 30-40 Hours HRT (Vollertsen, 2006)

• Much more common in Northern Europe. For example, this is used at more than 30 plants in Denmark.

• Lower VFA yield per VSS destruction than with primary sludge (Yuan, 2010)

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WAS RAS Fermenter

Anaerobic

Secondary Influent

VFA

Anoxic Aerobic

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WAS

Mixed Liquor Fermenter

Anaerobic

Secondary Influent

Anoxic Aerobic

WAS

Unmixed Anaerobic

Secondary Influent

Anoxic Aerobic

Mixed Liquor Recycle from Anaerobic Zone • ~10% of Influent Flow • Particulate BOD

incorporated into MLSS • OHOs Present

Fermenter • Unmixed for solids accumulation • SRT > 2 days • Mixed for several minutes per day for wasting

rbCOD and VFA returned to Anaerobic or Anoxic Zone

Fermenter • Production of rbCOD

• Particulate BOD hydrolyzes • OHOs lyses/hydrolyze

• BioP bacteria accumulate some VFA

MIXED LIQUOR FERMENTATION

Sidestream Mixed Liquor Fermenter In-Line Mixed Liquor Fermentation

ADVANTAGES OF MIXED LIQUOR FERMENTATION • Primary Sludge Fermentation

• Need Primaries

• More Complex Operation

• Higher Capital Investment

• Higher Odor

• RAS

• Low Yield

• Mixed Liquor Fermentation

• Inline – Simple operation

• Combination of sources

• Increased Yield

• Doesn’t rely on a single source

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HENDERSON NV

18

Turning off mixer is the same as bypassing flow around the anaerobic cell Ferments about 10-15% of the MLSS

SURFACE APPEARANCE OF HENDERSON PLANT

Some hours after mixer off

During mixing

19

OLATHE KANSAS HAS A FRESH INFLUENT WITH LOW VFA AND LOW rbCOD

20

• Influent has enough BOD to support BNR but a low soluble BOD fraction

• Special sampling and modeling demonstrated that system is deficient in soluble carbon

• Pump into Fermenter (from end of AN zone)

• Intermittent mixing

• Overflow out of Fermenter • To AN Zone • Or AX Zone

UNIQUE FERMENTER FLOW PATH

21

Fermenter

Modified feed to distribute evenly along the bottom

Fermenter (opposite end)

FERMENTER STARTUP

• Weekly solids inventory

• Mixers control wasting and solids retention time

• Mix 3 min/day

• 2–5 days SRT

24

OLATHE WITH MIXED LIQUOR FERMENTATION

0.0

5.0

10.0

15.0

20.0

25.0

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Fraction of rbCOD that is VFA

rbC

OD

/P r

atio

Olathe

Durham

VIP

Reedy Creek

McDowell Creek

At or above curve plants achieve good BPR

Below the curve plants struggle with BPR

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OLATHE EFFLUENT SINCE STARTUP

Permit limits go into effect July 1, 2013

No Chemical Addition

26

TEN MILE CREEK MIXED LIQUOR FERMENTATION DEMONSTRATION

Ae

An

Unused

Unused

Ae Primary Clarifier Secondary

Clarifier

Basin 5

Basin 4

Basin 3 Demo

To Gravity Thickener (Not Pictured)

Phase 1 : Baseline Phoredox Phase 2 : Fermentation in Sludge Blanket Phase 3 : Dedicated Mixed Liquor Fermenter

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MODELING MIXED LIQUOR FERMENTATION

• Working on comparing VFA and rbCOD yield from VSS destruction from projects to Model predictions

• Main SRT, MLF SRT, Influent, Primary Removal All impact VFA yeild

• Consulting with Envirosim (BioWin) on this

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ACKNOWLEDGEMENTS

• City of Henderson NV

• City of Olathe Kansas

• Trinity River Authority

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KELLER | FERMENTATION: UNLEASHING THE POWER AND MAKING IT WORK

QUESTIONS ?