Some wastewater has a BOD5 of 150 mg/L at 20° C. The reaction rate k at that temperature has been determined to be 0.20/day. Find BOD5 (in mg/L) at 15° C.

The value of

Explanation:

From the given information:

To find the BOD5 (in mg/L) at 15° C; we need to know the ultimate carbonaceous BOD and the reaction rate coefficient at  15° C.

So, to start with the calculation of the ultimate carbonaceous BOD by using the formula:

where;

= Biochemical oxygen demand at t days

= the ultimate carbonaceous

∴

Thus, the ultimate carbonaceous BOD = 237.30 mg/L

For the reaction rate coefficient; we use the formula:

where;

= rate of the reaction constant at various temperature (T) = 15

= rate of the reaction constant at standard laboratory = 0.20

= constant = 1.047

∴

Thus, at 15° C, the reaction constant (k) = 0.1590 / day

Finally, the BOD5 (in mg/L) at 15° C can be calculated by using the formula:

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explanation: