Effect of alternating anaerobic and aerobic phases on the performance of a SBR treating effluents with high salinity and phenols concentration

• SBR suitable for treatment of brines from olive processing (> 60 mS/cm).
• Anaerobic/aerobic alternating phases (0/22, 8/14, 14/8 and 22/0 h) were performed.
• Anaerobic phases for more than 8 h reduce COD elimination.
• Phenol removal is less affected than COD removal by decreasing aeration time.
• Extension of anaerobic phases to 8 h reduce energy consumption.

The biological treatment of hypersaline wastewaters with high COD and phenols concentration requires long hydraulic retention times and much energy for aeration. In this work aeration time reduction in the reaction phase was studied in two sequential batch reactors (SBR) treating fermentation brine from table olive processing wastewater. To study the influence of an anaerobic phase on the SBR performance (for COD and phenolic compound removal efficiencies), different anaerobic/aerobic reaction times were evaluated. SBR-1 was operated with an anaerobic/aerobic hours ratio of 0/22, 8/14 and 14/8 and SBR-2 with a ratio of 22/0, 14/8 and 8/14. Results showed that the maximum organic matter reduction was obtained under aerobic reaction conditions (ratio 0/22) with a 82.3% and 77.9% of COD and total phenols removal, respectively. However, optimal conditions were considered to prevail for an anaerobic/aerobic ratio of 8/14, since the reactors performances were similar with lower energy consumption. Thus, 82.3% and 79.5% of COD and 77.9% and 78.3% of total phenols were removed in SBR-1 and SBR-2, respectively.