Example of Project Competition of Ammonia-Oxidizing and Nitrite-Oxidizing Bacteria

CE 60330

Environmental Biotechnology

University of Notre Dame

Problem: Eutrophication

www.dep.state.pa.us

Major Cases of Eutrophication

http://www.longislandsoundstudy.net/pubs/reports/sh03_p1.pdf

Long Island Sound

http://www.cbf.org/site/PageServer?pagename=resources_facts_deadzone

Chesapeake Bay

http://www.ncat.org/nutrients/hypoxia/hypoxia.html

Gulf of Mexico

Biological Nitrogen Removal

1) Nitrification

Ammonia oxidizing bacteria (AOB) (Nitrosomonas)

NH4+ + O2 NO2

-

Nitrite oxidizing bacteria (NOB) (Nitrobacter, Nitrospira)

NO2- + O2 NO3

-

Biological Nitrogen Removal

2) Denitrification

Heterotrophic denitrifying bacteria (DB)

NO3- + BOD NO2

-

NO2- + BOD N2

N2 3e- 2e-

DB DBNO2-

Nitrogen Removal

NO2- NO3

-

AOB NOB

Conventional N removal

Shortcut N removal

NH4+

6e- 2e-

SHORTCUT: 25% reduction

in oxygen 40% reduction

in BOD

Nitrification

Under ambient conditions and DO over 2 mg/L, growth kinetics are similar for AOB and NOB

High temperatures: AOB significantly faster than NOB

Low DO: AOB outcompete NOB for oxygen

Hollow-Fiber Membrane-Supported Biofilms

281 m

1 m

Water

O2

O2

BOD

Hydrophobic polymers

High specific surface area

Variable driving force

J=K(CL-C)

Low energy consumption

Hollow-Fiber Membranes for Gas Transfer

1 mm

1 mm 2 m

Membrane Aerated Biofilm Reactor (MABR)

Biofilm

liquid (aerobic)

Solid attachment surface

DO

BOD

NB

LDL

HB

Biofilm

Membrane attachment

Liquid (anoxic)

BOD

DO

O2

LDL

NB

Alternative approach

HB

Research Needs

Under conditions observed in the HMBP process: How does bulk liquid DO impact stratification

and activity of AOB and NOB? How does membrane gas pressure impact

stratification and activity of AOB and NOB?

Reactor Conditions

Anticipated effluent ammonia will vary between 2 and 3 mgN/L

Expose pressurized single membrane in a column to 3 mgN/L ammonia at a very high loading rate Small decrease in ammonia will be observed

due to high loading

Reactor Conditions

What does bulk liquid concentration matter? Monod kinetics

Concentration observed by the biofilm controls growth of bacteria

Therefore, the effluent concentration expected in the HMBP will control the ecology of the biofilm

XSK

SYq

max

Modeling

Aquasim 2.0 software Biofilm compartment and

membrane compartment Simulates impact of bulk

liquid DO and membrane pressure on biofilm

Same modeling concepts as used for HMBP (Downing and Nerenberg, 2007b)

Modeling

Conditions modeled

50 day simulation Steady-state conditions

ExperimentAmmonia

Concentration

Intra-Membrane Pressure

Bulk Liquid Oxygen

  (mgN/L) (psi) (mg/L)

1 3 10 2

2 3 10 0

3 3 5 0

Modeling Results - Activity

0

0.5

1

1.5

2

2.5

3

0 10 20 30 40 50 60

Distance from Membrane (m)

Nit

rog

en C

on

cen

trat

ion

(gN

/m3 )

0

0.5

1

1.5

2

2.5

3

0 10 20 30 40 50 60

Distance from Membrane (m)

Nitr

ogen

Con

cent

ratio

n

(gN

/m3 )

0

0.5

1

1.5

2

2.5

3

0 10 20 30 40 50 60

Distance from Membrane (m)

Nit

rog

en C

on

cen

trat

ion

(gN

/m3 )

10 psi, 2 mg/L DO

10 psi, 0 mg/L DO

5 psi, 0 mg/L DOAmmonia (♦), nitrite (■), and nitrate (□).

0.0

0.2

0.4

0.6

0.8

1.0

0 20 40 60 80 100

Distance from membrane (m)

Fra

ctio

n of

Bio

mas

s

Modeling Results - Ecology

0.0

0.2

0.4

0.6

0.8

1.0

0 20 40 60 80

Distance from membrane (m)

Fra

ctio

n of

Bio

mas

s

10 psi, 2 mg/L DO

10 psi, 0 mg/L DO

5 psi, 0 mg/L DO

0

0.2

0.4

0.6

0.8

1

0 10 20 30 40 50 60 70

Distance from membrane (m)

Fra

ctio

n of

Bio

mas

s

AOB (♦) and NOB (◊)

Modeling Results - Ecology

0

0.05

0.1

0.15

0.2

0.25

0 20 40 60 80 100

Distance from membrane (m)

Fra

ctio

n of

Bio

mas

s

NOB biomass with 10 psi and 2 mg/L DO (▲), 10 psi and 0 mg/L DO (■), and 5 psi and 0 mg/L DO (♦)

•NOB yield: 0.083 mgVSS/mgNO2-

•AOB yield: 0.34 mgVSS/mgNH4+

Discussion

Oxygen gradients select for AOB over NOB Higher DO provides an advantage to NOB Oxidation to nitrite rather than nitrate saves

energy and addition of exogenous donor