Grasas y Aceites, Vol 45, No 3 (1994)

Anaerobic digestion of waste waters after washing olives used for oil production: Influence of harvest time on the kinetics of the process


https://doi.org/10.3989/gya.1994.v45.i3.984

R. Borja-Padilla
Instituto de la Grasa (C.S.I.C.), Spain

J. Alba-Mendoza
Instituto de la Grasa (C.S.I.C.), Spain

F. Hidalgo-Casado
Instituto de la Grasa (C.S.I.C.), Sevilla, Spain

Abstract


A kinetic study was carried out of anaerobic digestion of waste waters after washing olives used for oil production, collected at three different harvest times (December 1992, January and February 1993). A 1-litre mixed batch bioreactor operated at 35°C and containing a sepioliteimmobilized biomass was used.
Assuming that the overall anaerobic digestion process conforms to a first-order kinetics, experimental data pairs, namely methane volume yield (G) and time (t), fit Roediger's equation, from which the rate coefficient values, K0, were determined in each of the situations studied. The rate coefficient considerably decreased with the han/est time, over the substrate concentration range studied (0.5-2.5 g COD/l). The average values obtained were: 1.67,1.13 and 0.75 days-1 for the waste waters corresponding to the three harvest times considered. Also, the methanogenic activity decreased with the ripening of the olives; the observed differences increased when the substrate concentration in the digester increased.
The coefficients of methane yield, Yp, ranged between 0.263 (first harvest time) and 0.298 l CH4/g COD removed (third harvest time). The elimination of COD exceeded 64% in all cases.

Keywords


Anaerobic digestion; Harvest time; Kinetics; Olive; Waters from washing

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