Meeting Nutrient Limits with Activated Sludge and Control Strategies | Wastewater

Meeting Nutrient Limits with Activated Sludge & Strategies

MRWS ANNUAL CONFERENCE GREAT FALLS, MT

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Nutrients Promote Growth of Algae

• Human health • Environmental • Economic

Excessive Algal Growth Has Many Undesirable Effects

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Numeric Water Quality Standards for N & P

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Status of Numeric Nutrient Water Quality Standards Montana Standards for Wadeable Streams Adopted

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Montana Base Numeric Nutrient Standards

• TP – 25 to 150 µg/L • TN – 250 to 1,300 µg/L • Varies by USEPA Ecoregion • Seasonal • These are in-stream concentrations, not end-of-pipe

limits • Lakes/Reservoirs, Non-Wadeable Streams Standards

Development Ongoing

Wadeable Streams

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Base Numeric Nutrient Standards Guidance Version 1.0 (July 2014)

• Facilities < 1 mgd • By 2016: 15 mg TN/L; 2.0 mg TP/L • After 3 x 5-yr. permit cycles: 8 mg TN/L; 0.8 mg TP/L

• Facilities > 1 mgd • By 2016: 10 mg TN/L, 1.0 mg TP/L • After 2 x 5-yr. permit cycles: 8 mg TN/L; 0.5 mg TP/L • TBD

• Monthly averages • Individual variances also possible

General Nutrient Standards Variance N&P Reduction Steps

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Treatment Technology

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1.0 mg/L (Clarifiers) 0.5 mg/L (Filters) 0.01 mg/L (Membranes)

Total Nitrogen

The LOT with Conventional Treatment Processes is 3 mg/L TN

0.1 – 0.6 mg/L Ammonia-N

Nitrate - N

Dissolved

Org-N (DON)

Part. Org. N (pON)

0.6 – 1.6 mg/L

1.0 - 1.5 mg/L

3 m

g/L

TN

Biological Nitrogen Removal

N Removed by Synthesis

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Source: Sedlak, R. Phosphorus and Nitrogen Removal from Municipal Wastewater Principles and Practice, 2nd ed., Lewis Publishers, 1991.

50

0

10

20

30

40 “more bugs”

1 mole Ammonia (NH3 / NH4

+)

1 mole Nitrite (NO2

-)

1 mole Nitrate (NO3

-)

1 mole Nitrite (NO2

-)

1/2 mole Nitrogen gas (N2)

75% O2

25% O2 40% Carbon

60% Carbon

N Removal by Denitrification

Aerobic Anoxic

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Total Phosphorus The LOT with Conventional Treatment Processes is 0.1 mg/L TP

Influent 6.0 mg/L 3.0 1.0 0.5 0.1 0.01

Second. Treatment

EBPR & Chem-P Removal

Conventional Filter

Tertiary Treatment

Effluent TP

Phosphorus Removal

Some ‘P’ Removal Occurs Normally

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Soluble - P (Ortho-P)

Particulate P

Influent

Soluble - P

Particulate P

Secondary Effluent

TP

P removal by assimilation

WAS

Bio or Chem P Removal

Phosphorus Removal

Some ‘P’ Removal Occurs Normally

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Soluble - P (Ortho-P)

Particulate P

Influent

Soluble - P

Particulate P

Particulate P

Treated Effluent

Effluent TP

WAS

Secondary Effluent

TP

Soluble - P P removal by assimilation

Nitrogen Removal

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Clarifier

Modified Ludzack-Ettinger (MLE)

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Anoxic Oxic

RAS

Q

NO3-N

NO3-N NO3-N

NH3 NO3 NO3 N2

NO3

NH3

3-4 Q NO3-N

BOD

IMLR or NRCY

Nitrate Monitoring Applications - Denitrification

Source: Jon van Dommelen, Ohio EPA

Anoxic Oxic

A N A N O

ISE ammonium and nitrate

Reagentless Probes

• Measuring electrodes: NH4+, NO3

-,

• Compensation electrodes: K+, Cl-

• Stable calibration • Replaceable electrodes • Large measuring range

Optical DO measurement

No Calibration, Less Maintenance

• Very stable factory calibration • Less maintenance

• Missoula – 4 hrs./wk. w/ old probes / 1 hr./wk with new optical probes

• Removable sensor caps last 2 years • Calibration constants stored in

sensor cap

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Scioto Reserve WWTP

• 0.423 mgd Design Flow • Land applies treated wastewater to an impoundment for

irrigation of golf course • In 2012, rules for land application change and

implementation begins • Effluent limits required 10 mg/L TIN

Scioto Reserve WWTP original design does not provide for denitrification

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1

2

3

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5

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919

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2/12/2014 2/13/2014 2/14/2014 2/15/2014 2/16/2014 2/17/2014 2/18/2014 2/19/2014

Scioto Reserve WWTPVARiON Data

Aeration Tank NH3-N and DO

AT - DO AT - NH3-N

Tank Parameter

Date Time

Average of Concentration

Dissolved Oxygen and Performance

Balancing Nitrification - Denitrification

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% o

f max

pro

cess

rate

Dissolved oxygen

Source: Gustaf Olsson, Lund University, Sweden

100%

0%

Anoxic Zone Monitoring

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Nitrate Monitoring Applications - Denitrification

Source: Jon van Dommelen, Ohio EPA

Anoxic Oxic

A N A N O

Oxic Nitrate High / Anoxic Nitrate Low

Nitrate Limited - Increase IMLR • Missoula example • Increase IMLR if

Anoxic NO3-N > 1 mg N/L

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Nitrate Monitoring Applications - Denitrification

Source: Jon van Dommelen, Ohio EPA

Anoxic Oxic

A N A N O

Oxic nitrate high / anoxic nitrate high

Carbon Limited - Increase External Carbon

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TIN limit = 10 mg/L

Applications – Denitrification Carbon Source Evaluation

Boulder, CO 75th St. WWTP • Maximum Daily Limit • Carbon limited • MLE configuration

Image Source: Henderson, M., Sigmon, C., Wastewater, Carbon, and Beer., Rumbles, July 2015.

Optical nitrate

Principle: UV Light Absorption

• Factory calibrated • Multiple measurements, NO3/TSS/COD • Higher acquisition cost than ISEs • No electrodes/less calibration

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Applications – Denitrification Carbon Source Evaluation

Carbon Dosing Solution for Small Plants

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Phosphorus Removal

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Chemical vs. Biological P Removal to Achieve 1.0 mg TP/L

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Chemical Removal Biological Removal Capital Cost Low Moderate to High O&M Cost Low Moderate Cost of Chemicals Moderate to High Low Sludge Disposal Cost Increase Same or Lower Sustainability Low High Retrofit Simple Modest complexity Reliability High High (w/ chemical back-up)

Fox River WPCC, Brookfield, WI

‘P’

Fe P700

Orthophosphate Monitoring

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Nitrogen & Phosphorus Removal

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Why EBPR works? Energy Released by PHB oxidation is 24-36 times energy required for PHB storage

Enhanced Biological P Removal

Aerobic Anaerobic

Waste Sludge Loaded with P

BOD (VFA) uptake & C (PHB) Storage P release

Feed condition Battery charging

Ortho- P

• PHB Oxidized

• Excess P Uptake

Starved condition Battery discharging

Modified Johannesburg Process for Biological N and P Removal Kalispell AWWTP; also Missoula

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Natvik, O, Dawson, B., Emrick, J., Murphy, S., “BNR “Then” vs “Now” A Case Study - Kalispell Advanced Wastewater Treatment Plant”, WEFTEC 2003

DO control strategy

• Provide maximum DO concentration at head of first aerobic zone

• Missoula – 2.5 mg/L • Provide minimum DO at end of aeration tank

• Missoula – 1.0 mg/L • Monitor at control points

• Missoula – 1 sensor in each oxic cell

Guidelines

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Summary

• Nutrient limits are coming • Activated sludge can be modified to achieve biological

nutrient removal • Process control is critical • Modern sensor technology is readily available for reliable

continuous monitoring of DO, nitrate, ammonium, ortho-phosphate and other important parameters

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Acknowledgements

• Ben Lewis, Ambiente H2O • Jon van Dommelen Ohio EPA • Gene Connell, Missoula Wastewater Division

Questions?

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Ben Lewis

217 11th Street West Billings, MT 59102 [email protected] 406-969-2022 406-850-0030 Cell, 303/380-0664 fax