consolider ws 4 [compatibility mode]

8/22/2019 Consolider Ws 4 [Compatibility Mode]

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DANIEL FERNANDEZ GARCIA

Calidad del Agua: Atenuacin

Natural y Mezcla

Daniel Fernndez-Garcia

Doctor Ingeniero de Caminos

PhD Environmental Science & Engineering

Universitat Politcnica de Catalunya

< [email protected] >


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How contaminants move

LeBlanc et al. [1991]

Observations:

As contaminants move with water

they gradually occupy more space(Dispersion)

Maximum concentrations decrease

with time


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Mechanisms

Advection

Hydrodynamic Dispersion

Reactions

Molecular Diffusion

Mechanical Dispersion


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Advection

C= 0

C= C0

L

C0

C

tiempo

Darcy

Continuous injection


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Hydrodynamic Dispersion

C= 0

C= C0

L

C0

C

time

Sum of:Molecular Diffusion



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Molecular diffusion

t = 0 t t = infinity

Random movement of water molecules (temperatura)

It is apparent when concentration gradients exist

Mass seems to be transferred from areas of high concentrations to

areas of low concentrations


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Molecular diffusion

Ficks Law

ri Molecular radius of specie i

R Gas constant

T Temperature

di

RT

D 6 r

J


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FICKs Law in porous media

Soil material is an obstacle for particles to move

Tortuosity is less than 1 (0.7)

: Tortuosity


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Mechanical DispersionVelocity in pores is not constant

It only occurs when water moves

Field heterogeneity enhances mechanical dispersion


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SOLUTE

Averagedconcentration


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Depende de

la velocidad


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0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 50 100 150 200 250 300 350

x

Concentracindesoluto

C/Co

tDL LD 23

tvtqL xeff

x

A

LD 2/1

0max

4 tDCC

L


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Degradation of organic matter

2 2 2Microorganismos M.O. O Microorganismos CO H O

3 2 2 2Microorg. M.O. NO H Microorg. CO N H O

Oxgeno (oxidacin) Nitratos y nitritos (desnitrificacin) xidos de

manganeso Hidrxidos de hierro Sulfatos Metanognesis

2 4 2Microorg. M.O. CO Microorg. CH CO


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Chemical Reactions

Chemical Reactions

HeterogneasHomogneas

Equilibrium Cinetic

Homogeneous Heterogeneous

- Sorption

- Ion exchange

- Precipitation - disolution

Equilibriumconditions depend on water velocityand time for the reaction to occur

- Redox

- Acid / Base

- Complexation

- biochemical reactions

- radioactive decay

- disolution minerals


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BioDegradation

growth

B Bt

Growth in terms of BIOMASS

Time

Log

Biomass

max

C

C1 B

B t K C

At some stages of growth, or in a continuous culture at

a steady state, all the components in cells remain in the

same proportion:

Monod model of growth kinetics

is also a function of pH, temperature, nutritional status (i.e.

serum), waste products,


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BioDegradation

growth

B Bt

Growth in terms of BIOMASS

max

C

C1 B

B t K C

Monod model of growth kinetics

bio bio

C 1 BB

t Y t Y

-1max

3

3

C

:maximum growth rate [T ]

B: viable microbial biomass concentration [M/L ]

Y: Yield coefficient, microbial cell conc yield / organic conc utilized [M/M]

K : Michaelis half-saturation constant [M/L ]


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BioDegradation

max

bio C

BCC 1

t K C Y

-1

max

3

3

C

:maximum growth rate [T ]

B: viable microbial biomass concentration [M/L ]

Y: Yield coefficient, microbial cell conc yield / organic conc utilized [M/M]K : Michaelis half-saturation constant [M/L ]

Monod model for microbial biotransformation rate


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BioDegradation

max

bio M

BCC 1

t K C Y

Under typical environmental conditions, the concentration of

dissolved organics (C


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Modifications of the Monod modelSubstrate inhibition

Product inhibition

max

n

C I

C1 B

B t K C K C

max

n

C I

C1 BB t (K C)(K P )

C

P

P=0


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Bio-DegradationBiodegradation is affected by numerous factors that influenced

biological growth:

Temperature: Arrhenius type relationship

Nutrients: Often limit growth

Acclimation: A shock load of toxicant may kill !!!

Population density or biomass comcentration: Organisms must

be present in large enough numbers


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Bio-Degradation

Some organics can be degraded only under aerobic and some

only under anerobic conditions (BTEX cease to be degraded

with oxygen)


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Bio-Degradation

2

2max

bio C B/ C O 2

OBCC 1t K C Y K O

Multiplicative Monod Model Dissolved oxygen

Dissolved oxygen is

completely consumed

in the interior, but

aerobic oxidation

occurs at the edges

Funciones

switch


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BioDegradation

2

2 3

2 3 2

i,O2 3

O NO

O 2 NO 3 i,O 2bio

KC O NOC C

t K O K NO K O

Multiplicative Monod Model for serialreactions

2 2

2

2 2

O / C O

O 2bio

O OY Ct K O

2

3 3

3 2

i,O3 3NO / C NO

NO 3 i,O 2bio

KNO NOY C

t K NO K O

INHIBITIONCONSTANT

2 2

2 3 4 4O NO Fe SO CH


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BioDegradation

2

2max

bio B/ C C O 2

OBCC 1t Y K C K O

Multiplicative Monod Model

2

2 2maxO/ C

C B/ C O 2

O OBC 1Y

t K C Y K O

2

2maxB/ oc oc oc B

C O 2

OBCBY C B

t K C K O

NATURAL ORGANIC CARBON DECAY

ELECTRON ACCEPTOR


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Bio-Degradation Sequence of reactions

Biologically mediatedreductions.

It is influenced by pH,T,

redox state,microorganisms

present, other chemicals

PCE MCL = 5 ug/L

TCE MCL = 5 ug/L

DCE MCL = 70 ug/L

VC MCL = 2 ug/L


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Biodegradation: Sequence of reactions

PCE

bio

[PCE][PCE]

t

ii

bio

i CSt

M

TCE / PCE PCE TCE

bio

[TCE]Y [PCE] [TCE]

t

DCE / TCE TCE DCE

bio

[DCE]Y [TCE] [DCE]

t

VC/ DCE DCE VC

bio

[VC]

Y [DCE] [VC]t


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Mixing Mixing changes the composition and induces chemical reactions


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Example

0

1

2

3

4

5

0 1 2 3 4 5

water2

water1

mixture

c1

c2

1 2cc K

(a)

C1+C2=M

Keq=C1C2

consolider ws 4 [compatibility mode]

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