Nutrient Removal ProcessesMARK GEHRINGTECHNICAL SALES MGR., BIOLOGICAL TREATMENT

Presentation Outline

1. Nutrient removal, treatment fundamentals2. Treatment strategies

• Treatment methods: CAS, SBR, Ox Ditch• Case stories

• Mixing integration

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Wastewater Treatment Basics

• Nutrients» Nitrogen and Phosphorus» More difficult to remove» Promote aquatic plant growth, resulting in

Hypoxia = Low dissolved oxygen caused by decaying aquatic plant life

• Point and non-point sources» Point (WWTP)» Non-point (run-off)

• Biological Oxygen Demand (BOD)» Depletes oxygen» Relatively Easy to Remove

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Technologies Available

Biological• Activated Sludge• Removal of BOD, TSS,

Nitrogen & Phosphorus

Physical & Chemical• Tertiary Filtration• Removal of TSS, which also

captures N and P that are contained in the mixed liquor solids

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Activated Sludge –what is this stuff?Culture of microorganisms mixed with wastewater in an aerobic/anoxic/anaerobic environment for the removal of organic matter and nutrients.

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Basic Terminology

MLSS: Mixed Liquor Suspended Solids, biomass or microorganism mass including other particulates.

F/M Ratio: “F” is the food or biodegradable organic matter (BOD5). “M” are the microorganisms or MLSS.

SRT (or MCRT): solids retention time or mean cell residence time is the average duration of time an organism spends in the system. Often the first step in plant design, dictated by need to nitrify and wastewater temperature.

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Solids Retention Time (SRT)

VolumeVolumeWAS (lbs/d)WAS (lbs/d)

SRT =SRT =

Defines Tank VolumeDefines Tank Volume

SRTSRT

MLSS (lbs)MLSS (lbs)

Effluent TSS (lbs)Effluent TSS (lbs)

WAS (lbs/d)WAS (lbs/d)

MLSS (lbs) = V (MG) * [MLSS] (mg/L) * 8.345

MLSS (lbs)MLSS (lbs)

SRT =SRT =V (MG) * [MLSS] (mg/L)V (MG) * [MLSS] (mg/L)

Q (MGD) * [MLSS] (mg/L)Q (MGD) * [MLSS] (mg/L)

WAS (lbs/d) = Qwas (MGD) * [MLSS] (mg/L) * 8.345

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Sludge Age Impacts…

- Oxygen Demand (endogenous respiration) - Sludge Quantity & Composition- Nitrification- Phosphorus Removal- Alkalinity

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Bacteria – Impact of SRT

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Anaerobic:

Anoxic:

Aerobic:

Absent of dissolved oxygen and chemically bound oxygen.

Dissolved oxygen andchemically bound oxygen present.

Absent of dissolved oxygen, chemically bound oxygen present (NO3-N).

Basic Terminology

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Bacteria – who and what are they?

Microorganisms that use CO2 as their (only) C source. Most absorb the C as soluble inorganic material from aqueous or gaseous environment.

Microorganisms that use organic carbon compounds as their C source. Most absorb the C as soluble material from environment.

HETEROTROPHS (BOD OXIDIZING ORGANISMS)

AUTOTROPHS (AMMONIA OXIDIZING ORGANISMS)

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Influent Parameters and Design Impacts1. Flow

» Basin size2. BOD5 Mass Load

» Basin size» Aeration system size

3. TSS» Basin Size

4. Nitrogen» Aeration system size» Aerobic/anoxic environment

5. Phosphorus» Anaerobic environment

6. Temperature» Basin size

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Nitrification• Temperature 4 - 45° C

For every 10°C drop, nitrifier growth rate will drop by 50%

• Alkalinity 50 mg/l as CaCO3 min.• pH 6.5 - 8.8

• D.O. 0.5 - 2.5 mg/l (>2.0)• ORP +250 mV

• SRT 10 - 25 days (temp dependent)

• Nitrifiers (autotrophic) are more susceptible to toxicity than BOD removers (heterotrophic) and slowest growing.

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Denitrification

• Nitrate and organic carbon in presence of facultative heterotrophs + anoxic conditions results in O2 + N2 » 2.86 g O2 recovered / g NO3-N denitrified

• External carbon source (requirements based on influent) -ratio of 5 to 1 BOD to TKN is ideal

• Alkalinity recovered » 3.54 g as CaCO3 / g of NO3-N denitrified

• Oxidation reduction potential (ORP) -50 to +50 mV

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Phosphorus

Macronutrient for biomass (100C:2P)Domestic sewage total-P

• 6 - 20 mg/l• Typical U.S. municipal = 8 mg/l or 0.0067 lb/d/cap

Organic-P (organically bound-tissue) 2 - 5 mg/lInorganic-P (ortho- and poly-P) 4 - 15 mg/lP content in sludge 2% - 7%Biological, chemical, and physical removal processes

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Enhanced Biological Phosphorus Removal

Step 1: Anaerobic Phase

Step 2: Aerobic Phase• Phosphorus uptake and creation of new PAOs• Phosphorus removal by sludge wasting

• Phosphorus release

Create environment favorable to Phosphorus Accumulating Organisms (PAO’s)

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Enhanced Biological Phosphorus Removal

Successful bio-P removal depends on:- Anaerobic conditions (zero dissolved oxygen and zero nitrate)- Volatile fatty acids (VFA, rbCOD)- Solids management (SRT, WAS, and side streams)

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Factors Affecting Biological Phosphorus Removal

D.O. (aerobic phase) 2 mg/lD.O. (anaerobic phase) 0 mg/lORP >- 50 mVSRT (Days) 10 - 15BOD / P 20 (minimum)Minimal Nitrate

TPout = TPin - {(BODin - BODout) x Y x TPps}

2. Treatment Strategies

Nutrient Removal Heat Map

EPA Identified Nutrient Removal Priority States*:WI, MN, FL, NY, NJ, MA, DE, RI, HI, NE, SC, WV

Watersheds:Chesapeake BayMississippi River

* ID as either 1, 2 or more waterways with N and/or P criteriahttp://cfpub.epa.gov/wqsits/nnc-development/npmap.html

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Nitrification

1. Organic N in influent converted to Ammonia2. Autotrophs oxidize ammonia to Nitrate in Aerobic zone

Aerobic Clarifier

RAS

Influent Effluent

WAS

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Denitrification

1. Organic N in influent converted to Ammonia2. Autotrophs oxidize ammonia to Nitrate in Aerobic zone

Aerobic Clarifier

RAS (50-100% Q)

Influent (Q)

Effluent

WAS

Anoxic

Internal Recycle (100-400% Q)

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Denitrification

1. Nitrates from Aerobic zone recirculated to Anoxic zone2. Facultative Heterotrophs use Nitrates to oxidize influent

BOD in Anoxic stage, producing Nitrogen Gas

Aerobic Clarifier

RAS (50-100% Q)

Influent (Q)

Effluent

WAS

Anoxic

Internal Recycle (100-400% Q)

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Advanced Denitrification

1. Anoxic 2 zone reactions similar to zone 1, except BOD produced by endogenous respiration or carbon addition

2. Post aeration to promote aerobic conditions prior to clarifier

PostAerobic

Clarifier

RAS (100% Q)

Influent (Q)

Effluent

WAS

Anoxic 2

Internal Recycle (400 % Q)

AerobicAnoxic 1

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Basic Biological Phosphorus Removal

1. Phosphorus release in Anaerobic Zone2. Phosphorus uptake in Aerobic zone

Clarifier

RAS (50-100% Q)

Influent (Q)

Effluent

WAS

AerobicAnaerobic

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Enhanced Biological Phosphorus Removal

1. Phosphorus release in Anaerobic Zone2. Denitrification in Anoxic Zone3. Mixed liquor recycle from Anoxic to Anaerobic zone to

minimize nitrate concentration in Anaerobic zone

Clarifier

RAS (50-100% Q)

Influent (Q)

Effluent

WAS

Internal Recycle (100-200% Q)

AerobicAnoxicAnaerobic

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Advanced Nitrogen and Phosphorus Removal

1. Mixed liquor recycle from Anoxic zone to Anaerobic Zone is not necessary, as nitrate concentration in the RAS stream is low.

PostAerobic

Clarifier

RAS (100% Q)

Influent (Q)

Effluent

WAS

Anoxic 2

Internal Recycle (400% Q)

AerobicAnoxic 1

Anaerobic

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Limits of Enhanced Biological Phosphorus Removal

• With Anaerobic Zone, but without Anoxic Zone < 1 to 2 mg/l TP

• With Anaerobic and Anoxic zones < 0.5 to 0.8 mg/l

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Chemical Phosphorus Removal

Precipitation or adsorption with chemical addition- Ferric chloride (ferric)- Aluminum sulfate (alum)- Poly aluminum chlorides (PAC)

Effluent soluble P concentrations• Can be reduced to < 0.05 mg/l

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Benefits of Tertiary Treatment

Gravity separation (0.8 to 1.0 mg/L)

Physical removal—filter or membrane (0.05 mg/L to 0.5 mg/L)

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Tertiary Treatment vs. MBR

MBR- Higher chemical cost, as chemicals added to

precipitate phosphorus inhibit biological phosphorus removal

- Smaller Footprint

Tertiary Treatment • Lower chemical cost, as biological

process can be isolated from chemical precipitation process

• Larger footprint for filtration equipment

Sanitaire Bioloop Oxidation Ditch

Operating Flexibility

Tailored Process Design

Activated sludge process solving challenges of energy efficiency, nutrient removal, and flexibility with a complete system solution.

Energy Efficient

Energy EfficientBioloop

RECYCLE PUMPSAERATION MIXING OSCAR

Energy efficient equipment.

Independent aeration & mixing—dependency on aeration equipment for mixing is eliminated.

Deeper tanks lead to increase aeration efficiency compared to mechanical surface aerators.

Bioloop

AERATION MIXING OSCAR

Independent Aeration & Mixing

Operating Flexibility

Advanced Process Controls+ =

Optimize Treatment & Energy

Performance

Bioloop®

• Activated sludge, often characterized as “extended aeration”• Combination of anaerobic, anoxic, aerobic tanks• Multiple processes available:

• NIT: aerobic only

• MLE (Modified Ludzack-Ettinger): anoxic + aerobic

• A2O: anaerobic + anoxic + aerobic

• Bardenpho 4-stage• Bardenpho 5-stage• Multiple Ditches Series

Tailored Process Design

Combining Mixing and Aeration

•Liquid velocity to overcomelosses caused by aeration

•Minimizing local energy losses withoptimized placement of mixers and aeration

•Optimize bubble retention time in the water

• Optimized combination of aeration and mixer design is vital for the total efficiency

Bioloop® Applications

• Municipal & industrial wastewater

• Retrofit existing surface mechanical facilities

• Biological phosphorus removal

• BOD5 & TSS reduction

• Nitrification & denitrification

• Diffused aeration• Blowers• Mixers• Recycle Pumps• Controls &

Instrumentation• Process Design• Performance

Guarantee

Bioloop® System Scope of Supply

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Advanced Process Control Solution(OSCAR)

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Retrievable Aeration Systems

Benefits:• Fits where you can’t build a second basin• Lowers CAPEX• Reduces Footprint

Removal of the aeration system out of the basin without basin dewatering

Conversion of Ditches with Mechanical Aerators to Fine Bubble with Submersible Mixers

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South Water ReclamationFacility, Orlando, FL – 78 MLD

52% energy savings

Eunice, LA – 4 MLD

50% energy savings

Ditch in Series Retrofit

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Tifton, Georgia6 MGD

Previous mechanical surface aerator/mixer

Process design System responsibility Integrated control package DO/ORP control

Optional Performance Guarantees

Capable of BNR Effluent Quality:- TN < 5 mg/l (<3 with filter)- TP < 1 mg/l (<0.05 mg/l with

chemical polishing & filter) Effluent quality guarantee based on 30-day performance test

Two options for energy guarantee:

• Clean water shop test followed by field blower power test at design airflow rate

• 30-day field performance test

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Why Bioloop?

• Energy efficiency

• Independent aeration and mixing.

• Wide range of operation

• Deeper tanks (smaller footprint)

• Proven effluent quality

• Avoids misting / icing in cold climates

ICEAS

• Intermittent Cycle Extended Aeration System• Continuous Flow Sequencing Batch Reactor

ICEAS Single Basin Reactor

Conventional ASP

SBR Plant

HEAD WORKS

HEADWORKS

ASP

FC

SBR 1

SBR 2

SBR 3

SBR 4

BENEFITS

30-50% Less land area

Lower Construction costs

Less mechanical equipment

Reduced pipework complexity

Comparative requirements - SBR vs ASP

RAS

PC

PC FC

SBR Fill and Draw Theory

3. Settle

4. Draw Effluent

2. React1. Fill(Aerobic / Anoxic)

Influent

5. IdleWaste SludgeInfluent valves required

1. React 2. Settle

3. Decant Treated Effluent

Continuous Flow

Waste Sludge

ICEAS Operating Cycle

Continuous Flow

Complete System: Process Equipment & Controls

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ScreenedDegritted Influent

Final Effluent

SBR 1

SBR 2

Conventional SBR vs. ICEAS

Shortcomings of Batch SBR vs. ICEAS:Need 2 reactors or balancing tankComplicated valve arrangements & controlCannot easily remove basin from service for maintenanceCarbon source interrupted in react phase reducing ability to remove nitrogen and phosphorusUnequal loading of basins during diurnal cycle causes control problems. Each tank is a treatment plant.

ICEAS/SBR vs. Conventional BNR

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ICEAS vs. Conventional SBR

• Smaller Footprint• Aerobic, Anoxic, Anaerobic & Settling Occurs in Same Basin

• Time Based Control

• Built in Decanter

• High Peak to Average Flow Ratio (5:1)

• Less Mechanical Components

• Ease of Process Upgrades

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Summary

Planning for future BNR requirements during initial design will ease the upgrade process.

Preparing:• Basin Size• Blower and Grid Size• Control Panel• Mixers

Can lead to meeting and exceeding design parameters.

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ICEAS Experience

Operating in the U.S since 1985 Over 600 ICEAS Facilities in USA

(>900 worldwide) 10,000 GPD - 120 MGD ADF Municipal and Industrial

Applications Proven BNR Effluent Quality- TN < 5 mg/l (<3 with filter)- TP < 1 mg/l (<0.05 mg/l with

chemical polishing & filter)

Optional Performance Guarantees

• Effluent quality guarantee based on 30-day performance test

• Two options for energy guarantee

• Clean water shop test followed by field blower power test at design airflow rate

• 30-day field performance test

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Mixers in wastewater treatment

biological treatment

retentionbasin

pumpstation

gritchamber

digesterssludge holding

Flygt Mixer portfolio

4610-20 4630-40 4650-60 4670-80

4410 4430 4460

JT4715 JT4720 JT4730 JT4735JT4710 JP4710 JP4715 JP4720

4850 4860 4870Submersible compact mixers

Submersible low-speed mixers

Jet mixers Hydro ejectors

Top entry agitators

4650 LSPM

Compact HE

Submersible midsize

4530

Installation Equip.

Ultra-low-head pumps

PP4630-PP4680

4460 7.5kW

• Oxidation ditch – blending, circulation, suspension

• BNR – blending, solids distribution, suspension

Selection guidelines - summary

4400 series 4600 series 4800 series JT4700 series JP4700 series

Liquid

Wastewater √√√ √√√ √√√ √√√ √√√

Thick sludge (> 4%) - √√√ √√√ √√ √√

Abrasive or corrosive fluid √√√ √√√ √√√ √ √

Tank

Horizontal flow, flat tank √√√ √√√ - √√√ √√√

Vertical flow, tall tank - √ √√√ √ -

Sealed tank √ √ √√ √√√ -

Low liquid level (< 1 m) - √ - √√√ √√√

Economy

Energy efficient √√√ √√ √√√ √ √

Lean installation √√ √√√ √ √√ √√√

Easy service √√ √√ √√√ √√√ √

Durability √√√ √√ √√√ √√ √√

Other Motor type integrated integrated standard integrated integrated

√√√ = excellent √√ = good √ = average - = typically not recommended

Exceptions apply. Each case must be considered individually.

Questions?