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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Presenter

Presentation Notes

Who? – Operators of WWTP What? - Manual control has been the dominant method for process control of Activated Sludge. However, the growing emphasis on sustainability and continued pressure on operating budgets are driving the industry towards automation for optimization. Why? – There are many important reasons. Incomplete understanding of the process, insufficient and unreliable instrumentation, and the cost and complexity of control systems to name a few. Also, the philosophy to meet effluent requirements under all conditions at all costs led to overdesign for typical loading scenarios and meant that effective automation was left out. Where? – WWTP When? – How? - This presentation will describe the types of control available with a focus on their application for aeration control because aeration is the largest consumer of energy in a typical WWTP.

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

Presenter

Presentation Notes

The NiCaVis measures and displays both nitrite and nitrate. The nitrite data revealed nitrite accumulation concurrent with MicroC dosing, a phenomenon I will discuss in more detail in the next example. At the same time, nitrate was driven to very low levels.

ISE ammonium and nitrate

Reagentless Probes

• Measuring electrodes: NH4+, NO3

-,

• Compensation electrodes: K+, Cl-

• Stable calibration • Replaceable electrodes • Large measuring range

Presenter

Presentation Notes

ORP

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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192:

394:

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305:

508:

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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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Anoxic Oxic

A N A N O

Presenter

Presentation Notes


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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Anoxic Oxic

A N A N O

Presenter

Presentation Notes


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

Presenter

Presentation Notes


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

Presenter

Presentation Notes

Rob Smith, P.E., BCEE, Ph.D. is Applications Engineer - Wastewater at YSI, Incorporated in Yellow Springs, Ohio. His main responsibility is to provide technical and applications support to wastewater treatment customers using online process instrumentation. The scope of his new position includes developing information about the use of YSI products in wastewater treatment, assisting customers in choosing the right product, troubleshooting, deployment and installation, and improving data quality. Rob previously worked as a consulting engineer for Malcolm Pirnie/ARCADIS, URS Corporation, and Jones & Henry Engineers specializing in process and detailed design of wastewater treatment systems. He earned a Ph.D. from the University of Cincinnati and a BSCE and MSCE from the University of Toledo. Rob is registered as a Professional Engineer (Ohio) and is certified by the American Academy of Environmental Engineers (AAEE) as a Board Certified Environmental Engineer (BCEE).