Biological Treatment

Biological treatment combined anaerobic/aerobic system with nitrification/denitrification is the most common process which is applied for the wastewater treatment of baker’s yeast industry. Current biological treatment of baker’s yeast effluent involves combinations of anaerobic digestion and aerobic activated sludge systems that successfully reduced BOD to acceptable limits. The colored melanoidins are barely affected by conventional biological treatment. Anaerobic digestion can convert a significant portion of the COD to biogas, which may be used as fuel. Yeast industry produces a great amount of nitrogen compounds as a result of the use of water in biotechnological processing. Removal of nitrogen from baker’s yeast wastewater is a complex process, even for large wastewater treatment plants. Conventional nitrification-denitrification systems can be applied to remove nitrogen, from the baker’s yeast industry effluents. When an anaerobic pretreatment is operated, the anaerobic effluent has a low COD/N ratio, which can lead to an incomplete denitrification. It is possible either to opperate conventional nitrification-denitrification process with addition of an external carbon source or to combine the anaerobic digestion process with an aerobic nitrifying reactor and to recycle the nitrified effluent in the digestor. If nitrification and denitrification must be performed in the aerobic stage, it is necessery to add fresh wastewater to provide sufficient biodegradable COD for denitirification.