Pretreatment of Yeast Industry Wastewater in an Aerated Balancing Tank and Its Effect on the Municipal Treatment Plant Performance

Organic shook loads from a yeast plant caused severe operational problems and unacceptable effluent qualities at the chemical/biological wastewater treatment plant serving the City of Oslo. to alleviate these problems a pretreatment concept for the yeast wastewater, based on an aerated balancing tank without following solids separation, was proposed. Laboratory tests with aeration of yeast wastewater at hydraulic residence times of 0.5 to 2.3 days showed 25 to 67% removal of soluble COD. Jar-tests indicated that with proper balancing, yeast wastewater aerated for at least 0.8 days would have a very limited influence on the pre-precipitation process at the municipal treatment plant. Based on this information, a full-scale aerated balancing tank was constructed. After pretreatment of the yeast wastewater was introduced, data from the municipal treatment plant show very low and stable effluent concentrations.