[Digestion] Digestion Digest, Vol 6, Issue 4

[finstein at envsci.rutgers.edu]

Thanks Marcus for your response to my query:


> All,
>
> Do you know of (have) a way to "translate" BOD and/or COD to methane
> potential? It would of course have to be in terms of BOD/COD removed
> giving rise to so much methane.
>
> Mel


Hi Mel,
>
> if you consider the removed COD is completely transferred to CH4 in the
> Biogas (CO2=0 COD) you can calculate:
>
> 1g COD removed ->  0,25g CH4
> Or 1g COD removed -> 0,35 L CH4 (273K, 1013 mbar).
>
> If you want to estimate more exactly you may consider that some fo the
> removed COD flows into H2 and microbial biomass.
>
> Markus

Your calculation, however, is at odds with the statement in Grady et al.
1999, page 600 in "Biological Wastewater Treatment 2nd edition" Marcel
Dekker. The statement is that 4 kg COD removed generates 0.35 m3 of
methane (0.35 L CH4/4 g COD removed). Also that figure or nearabouts is
found in other documents. Apparently it was derived from theoretical
calculation (not understood by me) and also from serious observation of
real systems. If repetition = validity, thhan th figure is usable.

Perhaps others can weigh in on the theoretical end, or report other
"sightings of the translation.

Mel