Biofilm2009_HaraldHorn

Technische Universitt MnchenInstitut fr Wasser und UmweltLehrstuhl fr Siedlungswasserwirtschaft

Why using biofilm systems?

Harald Horn TU Mnchen


Basics of biofilm processes

Mass transport and reaction

Advantage of biofilm reactors

Example

Conclusion


Why should I attach to an interface ?


Joining a community Living in ecological niches Sharing substrates

Protection against a rough environment Biocides, antibiotics, pH shocks, shear stress

Creating a playground for researchers

Some reasons to form a biofilm:


90 % of my colleagues could

not be wrong !


So lets start forming a biofilm !


1. Conditioning of substratum

2. Suspended cells attach

3. Reversible adhesion of cells

4. De-adhesion

5. Irreversible adhesion of cells

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6. Growth and cell accumulation

7. Detachment by erosion

8. Detachment by sloughing

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31. Conditioning of substratum

2. Suspended cells attach

3. Reversible adhesion of cells

4. De-adhesion

5. Irreversible adhesion of cells


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Wet biomass in g/m2

Thickness by CLSM in m

Mass EPS + bacteria in g/m2

150 m

The same development measured with CLSM biofilm out of a rotating annular reactor


What are the driving forces in biofilms?

Growth and detachment are the main processes, which shape the biofilm structure

Structure on the other hand influences growth

Biochemical reaction kinetics are strongly coupled to transport processes

Furthermore, the population dynamics of microorganisms is responsible for the function of a biofilm





Example

Conclusion


Ring sparger

Riser

Downcomer

Effluent

Settling space

Arrangement for maintaining temperature

Influent

Reactor

Particle loading [gparticle L-1reactor volume]Particle size [mm]

5.0 /2. 5

0.8 - 1.5

No. 1 / No. 2

Particle supported biofilms


Particle supported biofilms Results: CLSM 3D-rendering

Box length 501 m Box length 501 m

Reactor No. 1 Reactor No. 2

Bacteria red, EPS-glycoconjugates green

2 mm2 mm


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Rep =288

BiofilmBulk

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Active layer

Particle supported biofilms No. 1: oxygen concentration profiles


No. 2: oxygen concentration profiles

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Rep = 410



Particle supported biofilms No. 1: oxygen concentration profiles

iici r

z

jt

c+

=

dzdc

Dfj iiDi =

)(z

c iFiBi

i

ccD

=

Transport and reaction of dissolved components can be described by:

Boundary condition at z = LF is:

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Diffusion coefficient D

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Biofilm density [kg/m3]

f

D

Zhang and Bishop (1994)Fan et al. (1990)

OxygenNaNO3NaCl

fD = DF / DW

Mass transfer coefficients for tubes


Results: CLSM: distribution of bacteria and EPS

Reactor No. 1 (n = 13)


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Results: CLSM: distribution of bacteria and EPS

Reactor No. 2 (n = 11)Reactor No. 1 (n = 13)


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How to describe the growth of a biofilm?

XiXii rz

jt

X+

=

iFXi Xuj =

Biofilm at time t +dt

0

Biofilm at time t

L Fz'0

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Bulk

z

dzrzuuFL n

i i

iXFF

=

+==0 1

)0(

Wanner and Gujer, 1986L

F+ d L

Fz' + dz'


Biofilm density -

a key factor forturnover and stability





Example

Conclusion


Comparison of biofilm reactor and CSTR with suspended biomass


Comparison of biofilm reactor and CSTR with suspended biomass

Biofilm reactor

V = 2 x 3 m3AF = 400 m2/m3LF = 500 mcO2 = 8 g/m3

Qin = 60 m3/d

cCOD_in = 300 g/m3

cNH4-N_in = 40 g/m3

Qin = 60 m3/d

cCOD_in = 300 g/m3

cNH4-N_in = 40 g/m3

Activated sludgereactor

V = 2 x 3 m3X = 3 kg/m3 biomasscO2 = 1.5 g/m3 Recirculation 100 %


4 x Q_in

Simulation of a hydraulic peak flow in both reactor systems !

AQUASIM has been used for the simulation (Reichert, 1993)


Biochemical processes considered for the simulation

Growth of heterotrophic microorganisms (het, KS, KO2,YX/S) Inactivation of heterotrophic microorganisms (kI) Respiration of heterotrophic microorganisms (kresp, KO2)

Growth of autotrophic microorganisms (aut, KNH4, KO2,YX/NH4) Inactivation of autotrophic microorganisms (kI) Respiration of autotrophic microorganisms (kresp, KO2)


Ammonium effluent concentration in both reactors !

Nitrification in the biofilm reactor recovers within 4 to 5 days whereas the activated sludge system needs more than 10 days to recover!


Population dynamics in activated sludge tanks !

The autotrophic biomass was simply washed out of the system during the peak flow!


Population dynamics in the biofilm of the 3rdcompartment (out of 4) !

Day 60

Day 65 Day 75





Example

Conclusion


DWA-task group IG-5.6 Biofilm technologies

biofilm reactors


DWA-task group IG-5.6 Biofilm technologies

biofilm reactors

Nicolella, C.; van Loosdrecht, M. C. M.; Heijnen, J. J. 2000.


Reactor type H/D ratio Tank geometry

Loading Biomass concentration

Removal rate Retentiontime [h]

ICInternal circulation*

3 - 6 COD: 31 kg/m3 d 31 kg/m3 COD: 22 25 kg/m3 d 24

BASBiofilm Airlift Suspension

4 5 COD: 4 - 14 kg/m3 dNH4-N: 1 - 2 kg/m3d .COD: 9.4 kg/m3 dNH4-N: 0.9 kg/m3d

15 30 kg/m310 40

30

NH4-N: 1.2 kg/m3d (20C)COD: 6.4 kg/m3 dNH4-N: up to 0.8 kg/m3d

0.4 4

Moving bed (MBBR)(KaldnesTM)

Reactors are typically constructed as rectangular tanks

COD: 7.1 kg/m3 d.

COD: 1.3 kg/m3 dNH4-N: 0.21 kg/m3d****

3 kg/m3(plus biomass on carriers)

COD: 6.0 kg/m3 d

NH4-N: 0.2 kg/m3d****

-

2

Aerobic granular biofilm reactors

app. 8 **optimal >5

BOD5: 2 kg/ m3 dNH4-N: app. 0.3 kg/m3dCOD: 4.5 5.9 kg/ m3 dTotal N: 0.2 kg/m3 dCOD: 4.2 5.5 kg/ m3 dNH4-N: 0.23 kg/m3d

8 12 kg/m3

3.8-6.2 kg/m3

8 - 11 kg/m3

Nearly full elimination

COD: 4 5.3 kg/m3dTotal N: 0.16 kg/m3 d

Nearly full elimination

-

Biocompounds 4 - 6 Total N: 0.08 0.2 kg/m3d

app. 7 kg/m3 Total N: up to 0.2 kg/m3d 12

*anaerobic, ** Lab or pilot plant, *** municipal waste water, **** with respect to moving bed tank,***** artificial waste water,******only nitrogen removal, removal rate for total N means nitrification/denitrification

Examples for biofilm reactors with high removal rates


AerationInfluent

Effluent

Down-comer

Riser

Airlift reactor for biocompounds

Aeration Influent

Effluent

Bubble column for aerobic granules


Biofilm reactor with biocompounds for simultaneous nitrification/denitrification



Vreactor = 2 x 30 L

Abiocomp = 50 m2/m3



N-load up to 0.2 kg/m3d(95 % removal efficiency)

b)



anoxic

aerobic

c

z

O2

NH4-N

NO3-N


day of cultivation [d]200 250 300 350

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cbiomass ~ 3.5 kg/m3


day of cultivation [d]160 180 200 220 240 260 280 300 320 340

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DO = 1 3 mg L-1DO = 1 3 mg L-1



* surface specific denitrification rate related to Biocompound surface



Parameter Load Turnover

Volumetric flow rate [L/d]COD [g/m3d]

11.05 4.79101 52.8

-

56.6 8.44

Ammonium [g/m3 d]Denitrification* [g/m2d]

210 120-

200 1182.76 1.49

* surface specific denitrification rate related to Biocompound surface






Example

Conclusion


The main characteristics of biofilms, which are easy to measure, are thickness and biomass density

Turnover of substrate and/or oxygen in biofilms is diffusion limited

by this different ecological environments can be created inside the same reactor (i.e. biofilm)

Biofilm systems/reactors provide a better and more stable environment for slow growing micro organisms compared to activated sludge reactors

Biofilm reactors need more control especially oxygen supply, hydrodynamic conditions and biomass removal

The foot print of biofilm reactors is much smaller compared to activated sludge systems

Conclusions


Cooperations:

Thomas Neu, UFZ Leipzig-HalleClemens Ochmann, VertUm GmbH,

Sponsors:BMBF, FNR, DBU, DFG, Ministery of Environment Bavaria,Siemens AG, Veolia,

Documents

Biofilm2009_HaraldHorn