BUBBLE COLUMN FERMENTATION OF OLIVE MILL WASTEWATERS BY ASPERGILLUS-NIGER

A bubble column (tower) fermenter was used to study the growth of Aspergillus niger on olive mill wastewaters (OMW). The gas hold-up. mixing time and oxygen transfer coefficient values were studied in terms of superficial air velocity. These characteristics were clearly affected by OMW. The growth of A. niger resulted in a filamentous suspension with no pellet formation and the specific growth rate was 0.2 h-1. The growth rate was limited by the oxygen transfer rate at 90 mmol dm-3 h-1 when pO2 was lower than 2 %.