Experimental Study of Biodegradation of Ethanol and Toluene Vapors

2.5
7
Biomass, benzyl alcohol and
ammonia (g/L)
2
1.5
1
0.5
X
Cn
DO
C b
6
5
4
3
2
1
Dissolved oxygen (mg/L)
0
0
0 0.05 0.1 0.15 0.2 0.25 0.3
Dilution rate, h -1
Figure 5-15b. Prediction of continuous removal of benzyl alcohol (C b0 =1.2 g/L)
Figure 5-15c gives the results at feed concentration of 1.54 g/L. The high level
of biomass concentrations demands more oxygen for the growth, and with the increase
of the dilution rates ( μ = D)
, the term in Equation 5-68 increases dramatically.
Q O2
Thus, the DO level drops quickly to a value that is close to the critical value. When the
dilution rate reaches 0.12 h
-1 , the DO level drops to 0.37 mg/L. With further increase of
dilution rate, the DO decreases to a level that is below the critical value which results in
cells being washed out. At this feed condition, the system can be operated at steady
state only for dilution rates up to 0.12 h -1 due to oxygen limitation.
138