Acknowledgements
• Sanitation Districts of Los Angeles County • Robert Morton, Supervising Engineer • Wastewater Research Section • JWPCP Laboratory
• YSI, a Xylem brand
• Herb Fancher • Uli Franke
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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.
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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
Fate of Nitrogen Removed from Wastewater
For every 1 mil. gal. of water treated:
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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
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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
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Primary Settler
Sludge Thickener
Anaerobic Digester
Sludge Dewatering Cake
Imported Sludge
Increases the mass of nitrogen in centrate
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Primary Settler
Sludge Thickener
Anaerobic Digester
Sludge Dewatering Cake
N x 2
Imported Sludge
Increases the mass of nitrogen in centrate
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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
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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:
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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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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)
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
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
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
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)
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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
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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