Population Growth Modeling

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dc V dt dc V dt Population Growth Modeling

description

Population Growth Modeling. Begin with a mass balance on microbial growth. X = population biomass, mg/L V = volume, L Q = flow, L/d k = 1 st order rate coefficient, 1/d t = time, d. Exponential growth model. - PowerPoint PPT Presentation

Transcript of Population Growth Modeling

Page 1: Population Growth Modeling

dcVdt

dc

Vdt

Population Growth Modeling

Page 2: Population Growth Modeling

Begin with a mass balance on microbial growth

in

dXV Q X Q X Reactiondt

dXV V k Xdt

dXk X

dt

X = population biomass, mg/LV = volume, LQ = flow, L/dk = 1st order rate coefficient, 1/dt = time, d

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(Mihelcic 1999, Figure 5.4)

Exponential growth model

max

dXX

dt

( )0

ttX X e

when applied to growth rate calculations, the notation for the 1st order rate coefficient (k) is replaced by , termed the specific growth rate coefficient.

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Environmental Resistance

(Mihelcic 1999, Figure 5.5)

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Logistic growth model

max 1dX X

Xdt K

(Mihelcic 1999, Figure 5.7)

K = carrying capacity, mg/L

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Example: carry capacity effects

(Mihelcic 1999, Figure 5.6)

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Monod Model

maxs

dX SX

dt K S

(Mihelcic 1999, Figure 5.8)

Consider S,X = f (t)

S = food, mg/LKs = half-saturation constant, mg/L

Low values of Ks indicate an ability to acquire food resources at low concentrations.

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Example: resource competition

(Mihelcic 1999, Figure 5.9)

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The Yield Coefficient

XY

S

1dS dX

dt Y dt

Y = yield coefficient, mgX/mgS

Consider Y to be the amount of biomass produced per unit food consumed.

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The Death (Respiration) Coefficient

d

dXk X

dt

kd = death coefficient , 1/d

It isn’t really death, a singular event, but rather losses of biomass to respiration.

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Putting It All Together

max

max

1

11

ds

s

dX X Sk X

dt K K S

dS X SX

dt Y K K S

(Mihelcic 1999, Figure 5.10)

These differential equations are solved using numerical methods.