DIG-L: extreme propionic acid conc.

["Wouter Platteau" <Wouter.platteau@gmx.net>]

Dear list member,

For the moment we are following the start-up of an anaerobic reactor
(completely stirred, around 10% dry matter) which works on kitchen waste,
vegetable waste (quite acid), a concentrated sugarsolution and flotation
sludge of a pig slaughterhouse. The reactor is giving biogas of good quality
(70% methane). Nevertheless, the concentration of propionic acid in the
reactor went from 500 ppm to a value of 4500 ppm in a month time. Even with
these high values of propionic acid the reactor works and produces biogas of
a good quality. Concentration of the other volatile fatty acids:

The concentration of acetic acid is now around 400 ppm. Butyric acid is 50
ppm. PH is 7.4. ammonia is around 2800 ppm.
What can be done to lower the concentration of propionic acid? For the
moment we try to respect a low organic loading rate and sometimes we also
add some water while feeding.

As the sludge was used to high ammonia concentrations, to our opinion there
is an inhibition of hydrogen.

Does anyone have experience with this kind of situation and these extremely
high concentrations of propionic acid, and especially with bringing the
concentrations down?



Jan Bruneel, Wouter Platteau


****************************
Wouter Platteau
bvba Johan Vanacker
Studiebureel "FLOS CAMPI"
Kouterweg 45
B-8800 Roeselare
Tel: +32(0)51 209356
Fax: +32(0)51 227931
GSM: +32(0)477 709130
e-mail: wouter.platteau@gmx.net


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