Online Sensors for Sidestream Treatment of Centrate – A Sensor Evaluation and Lessons

Learned

Acknowledgements

• Sanitation Districts of Los Angeles County • Robert Morton, Supervising Engineer • Wastewater Research Section • JWPCP Laboratory

• YSI, a Xylem brand

• Herb Fancher • Uli Franke

2

Presenters

• Rob Smith • YSI, a Xylem brand • Applications Engineer • Online monitoring • P.E., BCEE, Ph.D.

• Nick Smal • Sanitation District of

LA County • Project Engineer • P.E.

3

Topics

• The problem with centrate nitrogen • Evolution of sidestream treatment • Introducing the LA County Sanitation District

JWPCP • Centrate treatment pilot plant • Online nitrogen monitoring results • Summary

4

The Problem with Centrate Nitrogen

5

Fate of Nitrogen Removed from Wastewater

For every 1 mil. gal. of water treated:

6

Primary Settler

Primary Sludge (30 lbs. N)

Waste Activated Sludge (140 lbs. N)

330 lbs. N

Anaerobic Digestion Releases Captured Nitrogen Ammonia is recycled to main-stream in centrate

7

Primary Settler

Sludge Thickener

Anaerobic Digester

Sludge Dewatering Cake

N = 300 to 1,000 mg/L ~10% of influent load

N x 1

Imported Sludge

Increases the mass of nitrogen in centrate

8

Primary Settler

Sludge Thickener

Anaerobic Digester

Sludge Dewatering Cake

Imported Sludge

Increases the mass of nitrogen in centrate

9

Primary Settler

Sludge Thickener

Anaerobic Digester

Sludge Dewatering Cake

N x 2

Imported Sludge

Increases the mass of nitrogen in centrate

10

Primary Settler

Sludge Thickener

Anaerobic Digester

Sludge Dewatering Cake

N x 3

Solids Pre-Treatment

Increases the mass & concentration of nitrogen in centrate

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Primary Settler

Sludge Thickener

Anaerobic Digester

Sludge Dewatering Cake

N = 1,500 to 3,000 mg/L

Centrate Handling Alternatives

• Do Nothing

• Export

• Attenuate

• Treat • Integrated treatment

• Separate treatment

12

Why Sidestream Treatment?

• Anaerobic digestion/centrate dewatering • Medium to Very Large • Nutrient limits • Regional solids handling facilities • Sustainability

Characteristics of utilities with most to gain:

13

Evolution of Side-Stream Treatment

14

Integrated Treatment – In-Line

RAS f 1 - f

15

Integrated Treatment – Off-Line

Nitrate to Headworks

16

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

Nitrification / Denitrification

Aerobic Anoxic

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Separate Treatment – SHARON

Complete Mix

Plug Flow

Concentric

MeOH

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Centrate

Centrate

1 mole Ammonia (NH3 / NH4

+)

1 mole Nitrite (NO2

-) 1 mole Nitrite

(NO2-)

1/2 mole Nitrogen gas (N2)

75% O2 60% Carbon

Nitritation / Denitritation

Aerobic Anoxic

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Separate Treatment - Deammonification

• Anaerobic (no oxygen) • Autotrophic (no organic C) • Requires ammonium + nitrite • Very slow growing • Nitrite toxicity?

Anammox reaction

37.5% O2

1/2 mole Ammonia (NH3 / NH4

+)

1/2 mole Nitrite (NO2

-)

1/2 mole Nitrogen gas (N2)

Aerobic Anoxic

Deammonification

Anaerobic 21

Major Deammonification Technologies

3 commercial technologies • SBR (DEMON, Clear Green)

• Granular sludge (ANAMMOX)

• MBBR (ANITA Mox)

Sanitation District of Los Angeles County

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Joint Water Pollution Control Plant

N

Primary Anaerobic Digesters

Secondary Solids Processing

JWPCP Overview

NaOCl

Centrate Treatment Pilot Plant - MBBR

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Sidestream Treatment Nitrogen Removal

ANAMMX

ANITA Mox System

Centrate Water Quality – Grab samples

Parameters Unit

Pre-DAF

8/21/2013-

11/15/2013

Post-DAF

5/20/2013-

08/20/2013

Nitrogen

TKN mg N/L 585 469

NH4-N+ mg N/L 573 463

Organic matter

COD mg/L 345 181

sCOD mg/L 136 128

BOD mg/L 49 21

TSS mg/L 201 64

Alkalinity mg CaCO3/L 2290 1930

Pilot System

ANITA Mox / Veolia

• Drum screen - 60 µm mesh panels • Feed tank (equalization) • Reactor

• Volume ~ 950 gal • Media type: AnoxKaldnes K5

(800m2/m3) • Media Fill: 47% • Seed Ratio: 100%

Pilot System Operation

• Instrumentation and Control • DO/Aeration • Feed Flow • pH • Temperature

Feed Pump

Reactor

Air Mass Flow Controller

DO pH

Flow Meter

Plant Air

Feed Tank

Why Online Monitoring Over a 25% Reduce in weekly laboratory demand

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Category Parameter Influent EffluenttCOD W WsCOD W WtBOD W WsBOD W WTSS D DVSS D DTKN W WNH4-N D DNO2-N W DNO3-N W DPO4-P W --Alkalinity D DBiomass -- WpH D OnlineDO -- OnlineTemperature -- Online

Others

Organics

Solids

Nitrogen

Category Parameter Influent EffluenttCOD W OnlinesCOD W OnlinetBOD W OnlinesBOD W OnlineTSS D DVSS D DTKN W OnlineNH4-N D OnlineNO2-N W OnlineNO3-N W OnlinePO4-P W --Alkalinity D DBiomass -- WpH D OnlineDO -- OnlineTemperature -- Online

Organics

Solids

Nitrogen

Others

91 Samples 65 Samples

Ammonium (NH4+) & nitrate (NO3

-)

Ion selective electrodes (ISE) • Potentiometric (like pH)

• Requires calibration at commissioning (matrix adjustment)

• More potential for drift

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Detector

Lamp

mea

s. c

hann

el

ref.-

chan

nel

Nitrite (NO2-) & Nitrate (NO3

-)

UV spectral sensor for nitrate & nitrite • Optical • 256 wavelengths

scanned • Factory calibrated

(Application specific) • Built-in ultrasonic

cleaning • Much lower potential

for drift • Quadruple sensor

with COD/BOD

Monitoring Results

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How Nitrogen Measurements Can Be Used to Better Control the Process • Ammonia (NH3-N)

• Check of feed rate loop • Above 200 mg / L– Reduce feed

• Nitrate (NO3-N) • Check of DO loop • Above 35 mg / L – Reduce DO

• Nitrite (NO2-N) • Toxicity / Check of DO loop • Above 8 mg / L – Depends on NH4 and

NO3 concentrations

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1/2 mole Ammonia (NH3 / NH4

+)

1/2 mole Nitrite (NO2

-)

1/2 mole Nitrogen gas (N2)

37.5% O2

Aerobic Anoxic

Deammonification

Anaerobic 37

(AOB) Anammox

NO3-

11% to nitrate

1/2 mole Ammonia (NH3 / NH4

+)

1/2 mole Nitrite (NO2

-)

1/2 mole Nitrogen gas (N2)

37.5% O2

Aerobic Anoxic

Deammonification

Anaerobic 38

(AOB) Anammox

NO3-

> 11% - NOB

Great

Nitrate ISE

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Nitrate Monitoring

“Very impressed with nitrate ISE” • Easiest to use • Calibrate • Clean (air

cleaning) • 32/33 within 20% of

lab photometer

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Nitrate Monitoring

UV

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User calibration

Nitrate Monitoring

Not as good as nitrate ISE • Cleaning more tedious

• No air cleaning • 28/41 within 20% of

lab photometer • Online measurement

tended to underestimate

• Better calibration needed (more points)

42

Good

Ammonium ISE trending

43

Stress testing

Ammonium Monitoring

• Good trending during stress testing

• 19/34 within 20% of lab photometer

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Bad to Good (with user calibration)

Nitrite UV

45

User calibration Overestimate

Nitrite Monitoring

After user calibration • Most interested in monitoring nitrite

• Toxicity concerns

• 12/24 within 20% of lab photometer

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Why Is It So Difficult to Measure Nitrite?

Overlapping spectra • Lots of wavelengths required (256)

• High resolution (0.74 nm)

• Compensation for COD and turbidity important

• Application specific

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wavelength [nm]

Inte

nsity

Pilot Study/Sensor Evaluation Summary

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LA County Take-Aways

• Sensor accuracy satisfactory for the short duration of the trial. • Very pleased with the nitrate ISE

• Sensors provided real time observation of the process – better understanding of dynamics. • Nitrite toxicity not as critical to process • Nitrate/ammonium maybe more critical

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YSI Take-Aways

• The human is the most important factor • Objective • Puts in time when needed

• Stay close to the customer • Training • Configuration • Intervention

• Data evaluation reveals successes and how things that could be done better

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Rob Smith rsmith@ysi.com Questions and comments very welcome

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