# BOD exertion



## Calixico (Sep 7, 2009)

Cerm (10th edition, equation 28.29) lists this formula as BOD(t)= BODu*(1-10^(-k*dt) and the Fundamental Engineering Reference Manual (created by NCEES)listed this as Y(t) = L (1 - e^(-kt)).Where both formula is written to fine the BOD at a given time t.

I know this is the same formula except that CERM replaces the "e^-kt" with 10^(-kt). This produces a tootal different answer for the two equation. Is this an error on CERM's part? One of this formual is incorrect or am I missing something.


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## Summ97 (Sep 8, 2009)

Both formulas are correct (if my memory hasn't failed me). Sometimes the 'k' value is given in base e, sometimes it is given in base 10.

Which base is used determines what formula you should use.


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## RIP - VTEnviro (Sep 8, 2009)

'K' is your reaction coefficient, determined empirically. It will vary depending on whether it is base 10 or base e.

I've almost exclusively seen base e used.


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## Capt Worley PE (Sep 8, 2009)

I was sooo expecting something dirty....


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## RIP - VTEnviro (Sep 8, 2009)

Better?


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