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Sidestream Treatment for Nutrient Removal and Recovery

PNCWA Webinar April 23, 2015

1200 – 1300 PST

H. David Stensel, PhD, PE University of Washington Water Environment Resarch Foundation Nutrient Challenge Program

Wastewater Engineering: Treatment and Resource Recovery 5th Edition (2013) G. Tchobanoglous, H.D. Stensel, R. Tsuchihashi, F. Burton Metcalf & Eddy, McGraw-Hill

Motivation for Sidestream Treatment

•  Helps meet more stringent effluent nutrient concentration goals

•  Save energy •  Reduce carbon addition •  Sustainable environmental Engineering

– Reduce carbon footprint – Phosphorus recovery – Ammonia recovery

Anaerobic Digestion Filtrate/Centrate Return Flows Can Impact Nutrient Removal

Performance

Impacts •  High N and P

concentration •  Return

loadings may not be uniform

Characteristics

Parameter Units Value NH3-N mg/L 800-1800 Ortho-P mg/L 150-350 Alkalinity/N g as

CaCO3/g NH3-N

4.0-4.5

4

Primary Settling Tank

Sec. Clarifier

Centrate / Filtrate Dewatering

Gravity Thickener Anaerobi

c Digestion

Example N in centrate return can be 15-25% of influent load

BNR Activated Sludge

Waste primary sludge TN=240 kg/d

WAS TN=390 kg/d

Biosolids ~20% of Influent N Load NH3-N =800 – 1800 mg/L Alkalinity ~50% needed for full nitrification Relatively low carbon - rbCOD/TKN~0.40

TN=2,250 kg/d TN=2,010 kg/d

NdN =1,225 kg/d TSS = 10 mg/L TN = 8 mg/L = 400 kg/d

TN =630 kg/d

Soluble TN=440 kg/d Particulate TN=190 kg/d

TN=390 kg/d 19.4% of BNR influent

TN=240 kg/d

TKN = 45 mg/L BOD = 250 mg/L

SRT=12 days

How may high NH3-N in digestion centrate return impact N removal?

•  Nitrogen removal – High variable load hinders ability to meet low

effluent NH3-N and NOx-N concentrations –  Increases supplemental carbon demand for

NOx removal –  Increases energy and equipment for NH3-N

oxidation –  Increases alkalinity requirement

Issues with P release in anaerobic digestion

•  Phosphorus removal in EBPR systems – High variable load hinders ability to meet low

effluent P concentration –  Increases chemical dose for meeting low

effluent P concentration – Struvite formation in digester and digester

effluent

Sidestream Process Options to affect mainstream nitrification and

nitrogen removal •  Equalization •  Nitrification/bioaugmentation •  Reduce carbon and energy

– Nitritation/denitritation (SHARON) •  Use no carbon and even less energy

– Anammox/deammonification •  Ammonia removal/recovery – not subject of webinar

Without equalization nitrogen hourly loadings to mainstream can be higher

than 20% average load

Days Hours Percent of per week per day secondary load

7 24 20 7 8 60 5 8 84

Effect of 8-hour return flow period versus Uniform return flow to mainstream process

Review of Sidestream Biological Processes for N Management

•  Nitrification/bioaugmentation •  Nitration/denitritation (SHARON) •  Anammox/deammonification •  Biological process fundamentals

•  Examples of treatment schemes used

Sidestream Nitrification

•  Centrate + return activated sludge in separate aeration basin before mainstream –  Higher MLSS and higher nitrification rate/unit volume –  Decreases oxygen transfer needs in mainstream –  Plants with conventional plug flow configurations more easily

accommodate this design –  Nitrifiers produced in sidestream seed the mainstream reactor

•  bioaugmentation

•  hi [Centrate and return activated sludge reaeration basin (CaRRB)

Nitro-bacteria oxidize NO2 to NO3

Nitroso-bacteria oxidize NH4 to NO2

Quick review on nitrification/denitrification Nitrification is by two steps Uses oxygen and alkalinity

Overall two-step process

→

+ -4 2 3

- +2 5 7 2 2

1.0 NH + 1.404 O + 0.0743 HCO

0.985 NO + 0.0149 C H O N + 1.911H + 1.03 H 0

→

- + -2 2 4 2 3 2

-3 5 7 2

1.0 NO + 0.473 O + 0.005 NH + 0.020 CO + 0.005 HCO + 0.005 H O

1.0 NO + 0.005 C H O N

+ -4 2 2 3

- +3 5 7 2 2

1.0 NH + 1.86 O + 0.02 CO +0.079 HCO +

0.981 NO + 0.0197 C H O N + 1.902 H + 1.02 H O→

Biological denitrification uses carbon and produces alkalinity

3 4 3

2 5 7 2 2 3 2

NO H 0.33NH 1.45 CH COO

0.5N 0.33 C H O N 1.60H O 1.12HCO 0.12CO

− + + −

−

+ + +

→ + + + +

Acetate Nitrate

Alkalinity Nitrogen gas

• Heterotophic bacteria oxidize a carbon substrate with NO3-N or NO2-N •  produce alkalinity, 1 mole/mole

Needs carbon (BOD)

Produces alkalinity

Alkalinity is an important issue with regard to nitrification efficiency in sidestream treatment •  Digester produces alkalinity from

deamination and ammonia production – NH3 + CO2 + H2O NH4(HCO3)

•  1.0 mole alkalinity produced per mole NH3

•  Nitrification uses 2.0 moles alkalinity per mole of NH3 oxidized

•  Can get the other 1.0 mole from biological reduction of NO3 or NO2 produced

Needs carbon

Many Treatment Schemes used for sidestream nitrification

AT3, BAR, MAUREEN, CaRRB, InNitri

(carbon addition, anoxic tank, percent RAS added)

•  May be entirely aerobic or anoxic/aerobic •  Add and/or produce alkalinity •  SRT of 3 to 5 days •  HRT ~ 0.4 to 0.5 hrs

Proposed for bioaugmentation of nitrification

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New York City AT-3 Process (26th Ward plant) MAUREEN IS A MODIFIED VERSION

(Mainstream Autotrophic Recycle Enabling Enhanced N-removal)

Goal was nitrogen removal

PC

Influent Sec. Effluent

Activated Sludge Tank

RAS

WAS

Centrate (NH3-N) Nitrification

Reactor ~250C

Nitrifiers &

Methylotrophs

Seed

Methanol For NO3 reduction

Alkalinity

MAUREEN has recycle

NYC has switched to glycerol

BioAugmentation Reaeration (BAR) or Regeneration Denitrification-Nitrification (R-D-N) •  RAS added to plug flow nitrification tank •  HRT of 1-2 hrs •  May have ~1 hr anoxic zone in front end •  Nitrifiers grown at similar conditions as mainstream •  RAS alkalinity may be sufficient as flows may be 20-100 times centrate flow

•  Postanoxic with external carbon and primary effluent •  Minimal NO3/NO2 to feed to Enhanced Biological P Removal Process •  No internal recycle in RAS reaeration process •  HRT ~ 1 to 2 hrs

proposed for EBPR systems

•  Has been used for separate sidestream treatment •  SRT of ~ 10 days •  Alkalinity and external carbon can be added •  Mix during fill •  Intermittent aeration may be used during react period

In these schemes sidestream nitrifiers have same SRT as the activated

sludge in the mainstream •  What if the sidestream nitrifiers can be kept in the

mainstream reactor longer? –  Much greater impact of bioaugmentation

•  There may be a way! •  Grown them in aerobic granular sludge

What is Granular Sludge?

-23-

•  Large, dense, bio-aggregates (>0.2 mm; typ. 1-2 mm)

•  Rapid settling velocity (4 min versus 30 min for activated sludge flocs)

•  Gelatinous “hydro-gel” matrix

Existing main-stream activated sludge

(w/ appropriate modifications for N removal)

e.g., Floc SRT = 3 d Granule SRT = 20 d

PE

WAS (flocs)

Granule Generation

Side-Stream Reactor

Granule separator

Granule recharge option

Centrate (NH3-N) Carbon (optional) Primary Effluent (temperature control)

Granules fed to main-stream

Granules returned

Effl.

RAS

UW Research with King County Aerobic Granular Sludge

GranuNit Bioaugmentation Scheme

With: Bryce Figdore, Phd Student Dr. Mari Winkler, Assistant Professor

Review of Sidestream Biological Processes for N

•  Nitrification/bioaugmentation •  Nitration/denitritation (SHARON) •  Anammox/deammonification •  Biological process fundamentals

•  Examples of treatment schemes used

Nitritation-denitritation is done in the SHARON Process

•  Not named after someone named Sharon

•  Single Reactor High Activity Ammonium Removal Over Nitrite

Nitritation – Not Nitrification

•  Ammonia oxidation to only NO2

•  25% less oxygen is required

Nitroso-bacteria oxidize NH4 to NO2

→

+ -4 2 3

- +2 5 7 2 2

1.0 NH + 1.404 O + 0.0743 HCO

0.985 NO + 0.0149 C H O N + 1.911H + 1.03 H 0

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Nitrification - Denitrification

75% O2

25% O2

40% Carbon

60% Carbon

Nitrification-Aerobic Denitrification-Anoxic

1 mol Nitrite (NO2-)

1 mol Nitrite (NO2-)

1 mol Nitrate (NO3-)

½ mol Nitrogen Gas (N2)

1 mol Ammonia (NH3/ NH4 +)

Autotrophs Heterotrophs

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Nitritation - Denitritation

75% O2

60% Carbon Nitritation -Aerobic

Denitritation -Anoxic

1 mol Nitrite (NO2-)

1 mol Nitrite (NO2-)

½ mol Nitrogen Gas (N2)

1 mol Ammonia (NH3/ NH4 +)

Heterotrophs

Autotrophs

Advantages; 25% Reduction in Oxygen Demand 40% Reduction in Carbon (e- donor) Demand 40% Reduced Biomass Production

How do you stop NH3 oxidation to only NO2 (nitritation)?

•  Short SRT for high temperature centrate treatment (<1.5 d) •  Low pH •  Low DO concentration •  Elevated NH3 toxic to NO2 oxidizers (higher pH encourages free

ammonia toxicity) •  Cyclic aeration helps

SHARON PROCESS in operation at New York City Wards Island WWTP (400 Mgd) Since December 2010. Two Trains with capacity of 1.0 Mgal/d of centrate treatment In each train

30-40ºC500-1500 mg/L NH3-N

Carbon

Heat Exchangers OXIC ANOXIC

6-9 Q RecycleNitrified & Denitrified Effluent

No ClarifierHRT ~ SRT

Dewatering Sidestream

Alkalinity

Wards Island SHARON Process

New York City SHARON PROCESS 1.0 Mgal/day (Recirculation anoxic to

aerobic ~4Q)

Changed carbon From methanol To glycerol

Review of Sidestream Biological Processes for N

•  Nitrification/bioaugmentation •  Nitration/denitritation (SHARON) •  Anammox/deammonification •  Biological process fundamentals

•  Examples of treatment schemes used

What is deammonification?

•  Partial nitritation is followed by anaerobic ammonia oxidation

•  Partial nitritation – Only about 50% of feed NH3 is oxidized to

NO2

•  Anaerobic ammonia oxidation – ANAMMOX Process – Biological oxidation of ammonia with NO2 – Product is nitrogen gas and about 11% NO3

How was anammox discovered? •  Mulder (1995) observes ammonia removal in

fluidized denitrification bed- called it “anammox” •  Van de Graaf (1995) Tests with 15N confirm NH4

and NO2 removal to produce N2 gas

•  Strous (1999) Identify previously undiscovered bacteria in order Planctomycetales by 16sRNA

•  About 7 species found but none yet isolated

How Common? All over the place – marine sediments, fresh water sediments, Wastewater plants, wetlands, even in the arctic

Deammonification Reactions

−

+ −→

+4 2 3

5 7 2 4 2 2 2

2.33NH + 1.87O + 2.66HCO

0.02C H NO + NH + 1.32NO + 2.55CO + 3.94H O

Partial Nitritation:

Anaerobic reaction: +

4 2 3

2 3 2 0.5 0.15 2

NH + 1.32NO + 0.066HCO + 0.13H

1.02N + 0.26NO + 0.066CH O N + 2.03H O

+ − −

−→

30.26(100)Percent NO -N = = 11.2%1.0+1.32

Anammox bacteria are much slower than ammonia-oxidizing bacteria

"Parameter"

"Units"

AOB*"(200C)"

Anammox"(30-350C)"

umax" gVSS/gVSS-d" 0.90" 0.06 -0.07"KNH4" g/m3" 0.50" <0.10"

0.07"KNO2" g/m3" <0.10"Yield" gVSS/gNH4-N" 0.12" 0.07 - 0.13"

AOB* - ammonia oxidizing bacteria"

•  Sensitive to elevated NO2-N (<40 mg/L) •  Sensitive to free NH3-N •  Reversible inhibition by DO

Produces a large very dense granular floc- long SRT possible

9/25/2013 -40-

1 mol Nitrate (NO3

-)

0.57 mol Nitrite (NO2

-) 1 mol Nitrite

(NO2-)

1 mol Ammonia (NH3/NH4

+) 0.44 mol N2 0.11 mol NO3-N

Autotrophic Aerobic Environment

25% O2

40% O2

40% Carbon

60% Carbon

Heterotrophic Anoxic Environment

ANAMMOX

11% Carbon ANaerobic AMMonia OXidation

Comparison of sidestream N removal processes

Process Deammonification Nitritation/Denitritation Nitrification/Denitrification

Oxygen demand 1.84 g O2/g NH4-N

3.21 g O2/g NH4-N 4.25 g O2/g NH4-N

Acetate COD demand

0.7 g acetate COD/g N

4.0 g acetate COD/g NO2-N

6.7 g acetate COD/g NO3-N

Biomass production 0.12 g biomass VSS/g NH4-N

1.45 g biomass VSS/g NH4-N

2.12 g biomass VSS/g NH4-N

Advantages of deammonification: No carbon for anammox Small amount of carbon for NO3 removal 57% less aeration energy than nitritation/denitritation 25% less alkalinity than nitritation/denitritation Less sludge production

*acetate used as an example

Variety of Deammonification Processes Used in many facilities world wide

•  Stable deammonification achieved in single reactor

•  Deammonification accomplished in attached growth or suspended growth reactors

•  Anammox biomass forms dense granular sludge

•  Process operation tied to DO and pH measurements

•  Cyclic aeration at low DO may be used –  Air On: pH decreases due to nitritation –  Air Off: pH increases due to NO2/NO3 removal

DEMON® (DE-amMONnification) Sequencing Batch Reactor

NH3-N load 0.70 – 1.2 kg N/m3-d SRT 40 to 50 d (granules) 10-15 d (floc)

3 L

L3

L 33

3

L

QNoNH -N load = N = V

V No= Q N

N = kg NH -N/m -d

No = kg NH -N/mAt No = 1,000 mg/L, N = 0.70, V/Q = 1.4 days

@ 1.0 kgN/m3-d The O2 demand = 140 mg/L-h

ANITATMMox-Single stage moving bed biofilm reactor (MBBR) process

NH3-N load 0.70 – 1.2 kg N/m3-d SRT > 20 d AnoxKaldness plastic media TypeM 1200 m2/m3

50 percent fill fraction

Nitritation – Anammox -CANON

Anammox AOB • NH4+O2àNO2  

• NH4+NO2àN2  

AOB: 1NH4+ + 1.5 O2 → 1 NO2

- +1 H2O + 2 H+

Anammox: 1NH4+ + 1.3 NO2

- 1 N2 + 0.3 NO3-

12

→

Increase aeration

Management options for phosphorus-rich sidestream flows

•  Minimize variable loads to secondary treatment process – Equalization

•  Remove phosphorus from recycle stream – Chemical treatment of sidestream flow

•  Add alum or ferric – Convert soluble P to particulate P – Remove particulate P to biosolids

– Phosphorus recovery and reuse – Sidestream EBPR

Phosphorus Recovery

•  Phosphorus is a finite resource on the earth

•  Necessary for all living species (humans, food plants etc)

•  Using it once and throwing it away is not within sustainable resources or environment principles

P and N are recovered as struvite in crystalizers

•  Struvite – MgNH4PO4●6H2O

•  Molar ratios – Mg:N:P = 1:1:1

•  Mass ratios – Mg:N:P = 1.77:0.45:1.0

•  Percent N and P – N = 4.2 % – P = 9.4 %

Struvite crystallization recovery processes

AirPrexr process Cone-shaped fluidized bed- Multiform Harvest

Crystalactor® NuReSys® process Ostara Pearl® process Phosnix® process PHOSPAQTM process

Generally typical process parameters HRT ~ 1.0 hr MgCl2 and NaOH added for pH control Hydrodynamics vary with reactor design

Pearl® process

Example of crystallizer system

Ostara Pearl®,Tigard, Oregon Durham WWTP

Multiform Harvest, Yakima, WA

~ 85% P removal ~ 15% N removal

~ 80-90% P removal

Other issues with P recovery •  About 20-23% of influent P recovered •  Struvite formation in digester and effluent piping •  WAS P release before digester

Stripping CO2 by aeration indigester promotes internal struvite precipitation

Summary •  Digester centrate return can increase

mainstream N and P load by 15-30% •  Sidestream loads adds hinders reliably

meeting low effluent N and/or P concentrations.

•  A variety of process options have been shown for sidestream management of nutrients – each with its own advantages and unique

process considerations.

Summary •  Nitrification bioaugmentation •  Reduce carbon and energy for N removal –

SHARON Process •  Almost eliminate carbon, reduce energy, reduce

alkalinity needs – Deammonification/Anammox process

•  For sustainable environmental engineering practice, deammonification for nitrogen and struvite recovery for phosphorus are most attractive