Question

A strain of bacteria has been isolated that can cometabolize tetrachloro¬ethane (TCA). This strain of bacteria can be used for the bioremediation of hazardous-waste sites contaminated with TCA. Assume that the bio¬degradation rate is independent of TCA concentration (i.e., the reaction is zero order). In a bioreactor it is observed that the rate for TCA removal was 1 µg/Lmin. What water retention time would be required to reduce the concentration from 1 mg/L in the influent to 1 µg/L in the effluent of a reactor?

Answer 1

It would be required 16.6 hours in the bioreactor for reduce the TCA concentration from 1 mg/L to 1 µg/L in the effluent.

Step-by-step explanation:

A zero order reaction is a chemical reaction in which the rate of reaction is constant and independent of the concentration of the reacting substances, as is assumed in this problem with the biodegradation rate for TCA:

Zero order reaction formula:

`[A] =[A]_(0) - kt`

Where

`[A]` and
`[A]_(0)` are TCA concentrations, 1 µg/L and 1 mg/L respectively.

t = time of reaction

k is a constant, in this case is the rate for TCA removal = 1 µg/Lmin

1 mg/l = 1000µg/L

`[A] =[A]_(0) - kt`

Replacing

`1 microgr/L = 1.000 microgr/L - (1microgr/Lmin*t)`

`(-999 microgr/L)/(-1microgr/Lmin) =t`

`t= 999min X 1hr/ 60 min = 16,6 hrs`