Experimental Study of Biodegradation of Ethanol and Toluene Vapors

Biomass and benzyl
alcohol concentrations,
g/L
2
1.5
1
0.5
0
DO
X
Cb
0 0.1 0.2 0.3
Dilution rate, h -1
8
7
6
5
4
3
2
1
0
Dissolved Oxygen, mg/L
Figure 5-19. Continuous removal of toluene and benzyl alcohol
(C b0 = 0.6 g/L; y t,in = 12.0 mg/L)
Figure 5-20 reveals that at a benzyl alcohol concentration of 1.2 g/L, the system
could be operated at steady state for dilution rates up to 0.11 h -1 with a toluene gas inlet
concentration of 5 mg/L. When dilution rates are higher than 0.11 h -1 , the DO level
drops to a value that is below the critical value for bacteria growth. Thus oxygen mass
transfer becomes a rate–limiting factor at these conditions while cells are washed out,
and no consumption occurs. The sharp corner observed in the predicted DO curve
shown in Figure 5-20 occurs due to the program setting the biomass concentration to
zero. The prediction results also indicate that at a benzyl alcohol feed concentration of
148