Assessment of the anaerobic acidogenesis of wet olive cake from a two-phase olive oil mill.

A study of the anaerobic acidogenesis of wet olive cake or olive mill solid waste (OMSW) from the two-phase olive oil mill industry was carried out. Eight different hydraulic retention times (HRTs) ranging from 50.0-10.7 days were studied. An increase of 935.7 % in total volatile fatty acids (VFA) over the initial acidic concentration in the OMSW (1.4 g L(-1) expressed as acetic acid) was achieved. The results showed a maximum total VFA generation rate of 5.05 g COD L(-1)d(-1), this rate being achieved at the same hydraulic retention time as the maximum acetic acid production (8.2 g L(-1)) and as the maximum acidification degree (34.4 %).