Treatment Process Intensification for Sustainable Biological Nutrient Removal

Pusker RegmiVail Operator Training Seminar

13 October, 2016

Sustainability Goals

Energy reduction

Effluent quality goals

Reduction in chemical input

Treatment intensification

Sustainable

Wastewater

Treatment

Process Intensification

Brown and Caldwell 3

Reduction of:• Physical footprint

• Chemical use

• Energy demand

• Carbon footprint

• Chemically-enhanced primary treatment

• Membrane bio-reactors

• Ballasted biological processes

• Granular sludge processes

• AB Process

Common Process Intensification Technologies in the Wastewater Industry

4

• Chemically-enhanced primary treatment

• Membrane bio-reactors

• AB process

• Ballasted biological processes

• Granular sludge processes

Common Process Intensification Technologies in the Wastewater Industry

5

AB process Advanced aeration control and shortcut nitrogen removal

6

Carbon Management

Brown and Caldwell 7

Carbon re-direction N removal

Inf. Carbon

Anaerobic Digestion

• Adsorption/Oxidation; A/B Process (Bohnke 1977)

• HRAS always followed by a nutrient treatment process

• Originally designed for overall volume reduction and stable nitrification

• Nowadays mainly used for improving energy balance or capacity increase

A-Stage Process Sub-category of the HRAS

0

20

40

60

80

100

0.1 0.3 0.5 1 2

CO

D F

ract

ion

(%

)

SRT (days)

Mineralization

WAS

Effluent

Miller et al.

A/B Configuration Captures More Organics

9

Conventional scheme PT+AS

A/B scheme + side stream treatment

Modified from Wett et al.

100% PT AS

0%

CO

D3

3%

CO

D

8%

N15

% N

67% COD; 107% N

40

% C

OD

69

% N

24

% C

OD

18

% N

3% COD; 20% N

COD:N = 12 COD:N = 7

100% A-stage B-stage

6%

CO

D5

4%

CO

D

22

% N2

% N

40% COD; 80% N

20

% C

OD

48

% N

17

% C

OD

12

% N

3% COD; 20% N

COD:N = 12 COD:N = 6

The Way

Brown and Caldwell 10

C-redirectionShortcut Nitrogen Removal

Anaerobic

Digestion

Maximum energy

recovery from

concentrated organics

Minimum energy and chemical

consumption of remaining C and N

polishing

Biogas

Sludge

A/B Process

11

RAS WAS

AERPCL ANX AER SCL

MLR

RAS

B-stage

WAS

A-stage

TN 15-18 mg/L

Advantages Disadvantages

Increased sludge production Chemical addition for P removal

Redirect carbon for energy recovery B-stage is C limited

Low aeration energy requirement A-stage lacks process control

Lower overall volume (or increased removal

capacity)

B-stage needs carbon-efficient nitrogen removal!

Advanced aeration control with short-cut nitrogen

removal?

Ammonium-based Aeration Control (ABAC)

12

Controller

NH4-N

Control Algorithm

Blower

DO

Nitrification Kinetics

0 0.5 1 1.5 2 2.5 3 3.5 4

Nit

rifi

ca

tion

ra

te

Dissolved Oxygen (mg/L)

Ammonia based aeration control

7:40 AM 11:16 AM 2:52 PM 6:28 PM 10:04 PM 1:40 AM 5:16 AM

Air

flo

w r

ate

Am

mo

nia

Lo

ad

Ammonia Load Airflow rate

Limiting aeration

Reducing effluent ammonia peaks

Objectives of ABAC

15

Ammonia vs Nox (AvN) Control

Regmi et al., 2014 16

Aer

ob

ic F

ract

ion

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Nit

rog

en (

mg

/L)

0

2

4

6

8

10

Aerobic Fraction

NH4-N

NOx-N

24-hour

Dis

solv

ed O

xyg

en (

mg

/L)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

DO

1-hour

Dis

soved

Ox

ygen

(m

g/L

)

0.0

0.5

1.0

1.5

2.0

D.O.NO2-NNO3-N

NH4-N

Aerobic Duration

Controller/PLC

DOController/

PLC

DO = set point

NH4-N - NOx-N = setpoint

MAirS

Inflection Point:

Lowest TN @ Lowest

Energy

Optimum Nitrogen Removal

AEROBIC ANOXIC/ANAEROBIC

Grady et al (2011) Biological Wastewater Treatment, 3rd Edition

AvN Aeration Advantage

18Model-based evaluation of mechanisms and benefits of mainstream shortcut nitrogen removal processes (2014), Ahmed Al-Omari,

Bernhard Wett, Ingmar Nopens, Haydee De Clippeleir, Mofei Han, Pusker Regmi, Charles Bott, Sudhir Murthy. WWTMOD

Ammonia vs. NOx (AVN) Control

Nitrify only the amount of nitrogen that can be denitrified

• Minimizes energy consumption

• Achieves lowest possible TN with the given influent C:N ratio

• Maximize carbon redirection to anaerobic digestion

• Conserves alkalinity

HRSD Boat Harbor (25 MGD)

To

Secondary

Clarifiers

From Cell A

AVN

ControllerDO Controller /

PLC

NH4/ NOx

DO Cell C

Boat Harbor Instruments and Automation

Cell B Cell CAER

EFF

Surface

Aerator

Boat Harbor – AvN Control – ContinusousAeration

Mainstream shortcut nitrogen removal approaches and control strategies

23

Nitritation-Denitritation = “Nitrite Shunt”

1 mole Ammonia

(NH3 / NH4 +)

½ mol Nitrogen Gas

(N2 )

1 mole Nitrite

(NO2-)

1 mole Nitrite

(NO2-)

1 mole Nitrate

(NO3-)

Autotrophic Bacteria

Aerobic Environment

Heterotrophic Bacteria

Anoxic Environment

75% O2 (energy)

~100% Alkalinity

25% O2 (energy)

40% Carbon (BOD)

60% Carbon (BOD)

Ammonia Oxidizing Bacteria (AOB)

Nitrite Oxidizing .Bacteria (NOB)

Advantages:

• 25% reduction in oxygen demand (energy)

• 40% reduction in carbon (e- donor) demand

• 40% reduction in biomass production 24

Nitritation

Denitritation

Partial Nitritation-Anammox = “Deammonification”

1 mole Ammonia

(NH3 / NH4 +)

½ mol Nitrogen Gas (N2 ) +

a little bit of nitrate (NO3-)

0.5 mole Nitrite

(NO2-)

Autotrophic Bacteria

Aerobic Environment

Autotrophic Anoxic

Environment37% O2 (energy)

~50% Alkalinity Ammonia Oxidizing Bacteria (AOB)

Advantages:

• 63% reduction in oxygen demand (energy)

• Nearly 100% reduction in carbon demand

• 80% reduction in biomass production

• No additional alkalinity required

ANAMMOX“Anaerobic” Ammonia Oxidation - (New Planctomycete - Strous et al, 1999)

NH4+ + 1.32 NO2

- + 0.066 HCO3- + 0.13 H+

0.26 NO3- + 1.02N2 + 0.066 CH2O0.5N0.15 + 2.03 H2O

25

AnAOB = Anammox

Nitrite Oxidizing Bacteria (NOB)

AOB and NOB 1)share a synergistic relationship2) Are adapted in similar conditions Nitrite

rarely accumulates in the environment (Nature is with NOB)

BNR plants thus far are operated to avoid nitrite accumulation No knowledge on deliberate out-selection of NOB in a mainstream process

Nitrobacter ssp. was thought to be the dominant NOB in BNR plants Very little is known about NOB especially the more prevalent Nitrospira spp.

Recent Advances in N Removal started with Sidestream Treatment

27

Drivers for Mainstream Shortcut N Removal

• Eliminate External Carbon

• Energy• decreases aeration demand for N removal

• decreases aerobic COD oxidation

• diverts wastewater carbon for energy production

• Intensification• carbon diversion = much smaller aeration tank volume

required

Mainstream Short-cut Nitrogen Removal: Case Study

29

HRSD’s Approach

RAS

WAS

AER PCL

A-stage

HRAS

SCL

RAS

AER AER AER

IMLR

ANX

B-stage(AvN+)

AER

WAS

AvN Anammox MBBR

AER AER

Regmi et al. (2014)

Carbon redirection Nitrite-shunt Nitrogen

Polishing

Pilot Plant is Located in Hampton Roads Sanitation District’s

Chesapeake Elizabeth Treatment Plant, Virginia Beach.

A/B Process Pilot

Performance

Anammox Stability

0

2

4

6

8

10

12

14

16

18

20

0 5 10 15 20

NO

2 r

em

ove

d

NO2 influent (mgN/L)

Influent NH4-N = 25

mg/L

Ballasted Biological Process

34

Managing Risk: the BioMag™ Process Development Process: Demonstrations

Brown and Caldwell 35

0

2

4

6

8

10

12

14

16

18

20

2007 2008 2009 2010 2011 2012 2013 2014

Cu

mu

lait

ve

Bio

Ma

g I

ns

talla

tio

ns

Time

• Magnetite is Fe3O4, Doesn’t rust or degrade

Completely inert

• Two critical properties: It’s dense; SG: 5.2

Magnetically controllable

Magnetite

36

BioMag ProcessProcess Equipment

37

Recovery Drum

Make-up Tank & Return Pump

Magnetite Silo

BioMag Floc

BioMag Process

• Magnetite recovery rates – 85 to 95 percent based on WAS

• Magnetite lost in effluent not easy to quantify

• Magnetite-to-MLSS ratio of 0.8 to 1.5 (1 optimum) –depending on application

• Average cost for magnetite -- $0.25/lb

• Process not suited for intermittent operation

Things to Monitor/Application Issues

• Conveyance of sludge

• Mixing requirements

• Mixed liquor stratification

• Alpha values

• Wear of equipment

• Alkalinity/pH response

• Role and dose of coagulants

• Foaming

• Biosolids

BioMag Performance – Sturbridge, MA

Settling Test Results

MLSS and Magnetite Concentration

0

20

40

60

80

100

120

12/24/07 1/13/08 2/2/08 2/22/08 3/13/08 4/2/08 4/22/08

Cla

rifi

er

SL

R,

lb/d

ay-s

f

Date

BioMag Clarifier Solids Loading Rate

Typical Design Range for Extended Aeration = 5 to 24 lb/day-sf

Nitrogen Removal Performance

0.01

0.10

1.00

10.00Ef

flu

en

t N

itro

gen

Sp

eci

es

(mg/

L)

NH4 NO2 NO3

0

0.2

0.4

0.6

0.8

1

1.2

1.4

12/24/07 1/13/08 2/2/08 2/22/08 3/13/08 4/2/08 4/22/08

Eff

luen

t T

P, m

g/L

Date

BioMag Effluent Total P w/o Filtration

Future Effluent TP Limit = 0.2 mg/l

• St. Mary’s County Metropolitan Commission

• Currently meets BNR requirements for TN of less than 10 mg/L

• It has a rated capacity of 6 MGD AADF

• In August 2015, plant needs to meet ENR requirements

• ENR limit TN and TP goals of 73,093 lb/year and 5,483 lb/year

Marlay Taylor WRF

•Four-stage Bardenpho process for N removal

• Conventional with tertiary filtration

• IFAS with tertiary filtration

• BioMag

•Chemical P precipitation with FeCl3

Alternative Analysis

Process model was used to assess the Biological Process Requirements

Marlay Taylor – Differential NPV Comparison

Aerobic Granular Sludge

Aerobic Granulation

• A biological process in which slow-growing populations (nitrifiers, polyphosphate-accumulating organisms, and anaerobic ammonia oxidizers) can be maintained within a fast-settling particles

• Established by applying high substrate gradients, a certain degree of shear stress, and selection of fast-settling particles.

• Most importantly: natural (bio-)physical phenomenonNot triggered by gene expressions / quorum sensing / etc… of

bacteria to grow in granules.

Barriers for wide-scale adoption?

• Internal settling selection requires continuous washout of slow-settling biomass to maintain granular sludge elevated effluent suspended solids levels purposefully built, post-treatment unit.

• Minimum critical settling velocity (vmin) > 10 m hr-1 (to select and retain only fast-settling particles)

• Unique reactor design (tall SBRs)

•restricts existing plant retrofits

Can we achieve aerobic granulation in plug-flow configuration?

Myth or Truth: A lot of COD (bulk concentration) needed to be able to form granules

High COD loading is required

But, if influent COD is very low, the reactor design will be hydraulically constrained

WERF Project

Balancing Flocs and Granules For Activated Sludge Process Intensification in Plug Flow Configurations

55

• Discrete and dense particles (defined as granules) can be selected in a plug flow bioreactor configuration

• External settling selectors can allow for poor-settling microorganisms to be selectively wasted

• If a wastewater treatment plant has an anaerobic selector, an external settling selector can stabilize bio-P

• Even if no AN selector is present, selection of granules can create microenvironments that allow PAOs to perform

WERF specific hypotheses

56

Lawrence, KS – Pilot Plant

Impact of rbCOD on Granulation for Low-strength WW

57

Strass WWTP

Cyclones for Settling Control

58

Strass WWTP – 10 Year SVI Profile

0

50

100

150

200

250Jan-96

Jul-96

Jan-97

Jul-97

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Jan-99

Jul-99

Jan-00

Jul-00

Jan-01

Jul-01

Jan-02

Jul-02

Jan-03

Jul-03

Jan-04

Jul-04

Jan-05

Jul-05

SVI B-stage

SVI (

ml/

g)

Wett, et al.

Strass WWTP – SVI Comparison (3-years)

020406080

100120140160180200

1-Dec 31-Dec 30-Jan 1-Mar 31-Mar 30-Apr 30-May

year 1 _ SVI year 2 _ SVI year 3 _ SVI

SV

I (m

l/g

)

Daily SVI measurement

over the last three winter

seasons (2010-2013)

Wett, et al.

James River Treatment Plant - HRSD

Strass WWTP – Settleability Comparison (3 min)

FEED

OVERFLOW

UNDERFLOW

OVERFLOWFEED UNDERFLOW

Wett, et al.

Strass WWTP – Settleability Comparison (3 min)

0

100

200

300

400

500

600

700

800

900

1000

0 5 10 15 20 25 30

H(feed) H(OF) H(UF)

time (min)

slu

dge

volu

me

(ml)

FEED

OVERFLOW

UNDERFLOW

Wett, et al.

• AB process is an intensification technology• It requires advanced aeration control and/or shortcut nitrogen

removal to meet low TN limits

• Ballasted floc technology increases the capacity of treatment within the existing footprint.• Intensive O&M is required in the long-term

• Granular sludge presents a possibility of combined N and P removal in small footprint• Granulation within the existing infrastructure and low influent

carbon still remains a challenge

Take Home

Brown and Caldwell 64

Pusker RegmiPh.D.

Email: pregmi@brwncald.com

Presenter contact information