The utilization of yeast in heavy wastewater treatment

Wastewater discharged from vermicelli factories has high concentration of COD and BOD, it is considered to be heavy wastewater. Strach degrading yeast was isolated and applied to treat the vermicelli wastewater. A semicontinuous yeast dominant activated sludge method and an immobilized yeast cells system were used in treating the clarified vermicelli wastewater. When the solid retention time and hydraulic retention time were kept at 7.14 days, using a semicontinuous culture, the solid loading was 0.48 g COD/g MLSS.day, volumetric loading was 1.03 kg COD/m3.day, and the COD removal was about 92%. When the yeast cells were immobilized with 1% Na-alginate solution, in the batch culture system, the COD removal of the immobilized cells was about 73% in 12 hours; with the air bubble system, the immobilized cells had the ability to remove COD of 90%. It indicated that the immobilized cells can treat heavy wastewater directly, and the hydraulic retention time could be reduced from 7.14 days to 24 hours.