Stoichiometric and Kinetic Coefficients

Since Monod's first experiments and kinetic studies in 1942 and 1950 and those by Herbert (1958), a large number of papers concerning the kinetics of bacterial growth and carbon removal have been published. The yield and kinetic coefficients are again typically defined by Eqs. (6.83) to (6.85):

with:

and:

In contrast to Herbert, Pirt (1965) introduced a kinetic expression considering the endogeneous mass consumption into the balance for substrates. Here, we follow the concept of Herbert, which is usually used in kinetic descriptions of biological wastewater treatment.

Some measurements led to results which are listed in Table 6.1. Although different substrates and mixed cultures were used, the pmax values do not differ considerably. However, KS and K' scatter remarkably. Because of the low values of K', an exact measurement of low dissolved oxygen concentration is necessary. In last time, O2 electrodes with higher precision have become available, so that more exact measurements are possible. We do not want to present here all these results.

Nearly all yield coefficients are influenced by bacterial decay (see Eq. 4.27) or endogenous respiration. More exact studies are needed for us to be able to distinguish the true yield coefficient Yo from the real yield coefficient Y.

Some published ranges of data from several textbooks are compiled in Table 6.2. On the basis of these values, new mean data will be recommended.

Table 6.1 Published coefficients and recommended ranges of values from some papers for laboratory-scale CSTR measurements.

Reference

Basis

T

H™

Ksb)

K 'b)

YX/S

YO2/S

kd

ke

(°C)

(h-1)

(h-1)

(h-1)

Reynolds and

CODc)

20

0.80

345

-

0.39

-

0.0071

-

Yang (1966)

Benedek and

CODd)

18

0.16

22

-

0.67

-

0.0029

-

Horvath (1967)

Peil and

CODd)

23

0.45

55

-

-

-

-

-

Gaudy (1971)

Strnivasaraghanan

CODe)

25

0.49

115

-

0.59

-

0.0058

-

and Gaudy (1974)a)

Button and

_f)

35

0.506

-

0.45

-

1.2-1.8

-

-

Gurver (1966)

Sinclair and

_f)

35

0.54

4.6

0.084

0.55

1.41

-

0.01

Ryder (1972)

Putnaerglis (1987)

DOCg)

17

0.32

-

0.22

-

-

-

0.03

a) Batch, b) Values given in mg L-1, c) Synthetic, d) Municipal, e) Synthetic, f Glycerine, g) Filtrate of excess sludge after thermal conditioning.

a) Batch, b) Values given in mg L-1, c) Synthetic, d) Municipal, e) Synthetic, f Glycerine, g) Filtrate of excess sludge after thermal conditioning.

Table 6.2 Ranges of measured kinetic and stoichiometric coefficients for aerobic degradation of organic compounds in municipal and domestic wastewater.

Reference

Basis

T

H™

KS

YX/S

kd

K '

(°C)

(d-1)

(mg L-1)

(d-1)

(mg L-1 O2)

Sundstrom and Klei

(1979)

bod5

-

9.6-13.2

50-120

0.5-0.67a)

0.048-0.072

-

Henze et al. (2002)

COD

20

4.0-8.0

3-30

0.5-0.7b)

0.1-0.2

0.5-1.0

Chow et al. (1979)

bod5

-

0.8-8.0

25-100

0.4-0.8c)

0.025-0.075

-

a) Value given in g MLSS (gBODs)-1

c) Value given in g MLVSS (gBODs)-1

a) Value given in g MLSS (gBODs)-1

c) Value given in g MLVSS (gBODs)-1

0 0

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