GPS-X Technical Reference

279 Digestion Models
Based on the above rates, the net rate of generation of methanogens (rxmh) is:
Equation 10.5
Toxic Substances
A rate of toxic substance degradation (r5) is incorporated in the basic model. The rate of
degradation is assumed to be first order with respect to the concentration of toxic
substances:
Equation 10.6
where:
kb
= toxic substance degradation rate
Total Volatile Fatty Acids
The kinetic expression for total volatile fatty acids (slf) can be established using the
previously presented kinetic expressions and appropriate yield coefficients:
Equation 10.7
where:
(ya r1)
-r2/yc
= rate of generation of slf by hydrolysis
= rate of utilization of slf by the growth of methanogens
GPS-X Technical Reference