Biological treatment of hypersaline wastewater from table olive processing: Process performance and protist population under different operating conditions

Biological treatment of fermentation brines from table olive processing (FTOP) entails many difficulties due to their very high salinity and high COD concentration, which include some phenolic compounds. These extreme conditions limit the biodiversity of the microbial population. Experiments treating FTOP were performed in laboratory sequencing batch reactors (SBR) changing operating conditions during their operation, in order to study the effects on the SBR performance and on the protist population. The statistical study showed that the SBRs with high influent COD, pH and volatile solids and low influent phenol concentration, hydraulic retention time and temperature achieved the highest COD removal efficiencies. These operational conditions also provided the highest ciliate population and the lowest flagellate presence.