Two-stage treatment of edible oil-containing wastewater: Yeast coupled with activated sludge unit

Two Sequencing Batch Reactors (SBRs) were coupled to treat edible-oil containing wastewater directly. Ten yeast strains were inoculated to the first SBR to treat high-strength oil-containing wastewater. The effluents of the system were further degraded by activated sludge in the second SBR. The results show that each yeast can efficiently decompose edible oil-containing wastewater with the COD removal rate above 80%; The mixture of ten yeast stain can cultivated in an open system without any molds and bacteria inhibitor addition to produce yeast biomass which processes a good settle ability. In 100 day continuous wastewater treatment by the first stage, COD and Oil removal rate achieve 88.9–97.5% and 93.4–99.9% respectively under the influent conditions of the COD of 9500–24000 mg/L and Oil of 3300–14000 mg/L. The effluent with COD varied from 300 to 700mg/L was treated by the second stage and the final effluent of COD was below 100 mg/L which meets the standards for wastewater discharge.