Biological Augmentation Eliminates Grease and Oil in Bakery Wastewater

The feasibility of a biological augmentation approach to eliminate oil and grease in the wastewater of a large bakery was evaluated and experimentally tested. The approach, based on approximation of a treatment tank with a model of a continuous culture of bacteria (chemostat), was evaluated first. Bacteria appropriate for use in biological augmentation were selected according to theoretical requirements. Results of subsequent field tests corresponded fairly well to predicted values, although oil and grease content in the outflow was still greater than the allowable level. To further increase cell concentration in the treatment tank, a solid support for bacterial growth, a biological filter, was added next and was successful. As a result, a bioremediation scheme was devised that included pH adjustment and mixing–aeration systems, an external biological reactor system for production and periodic injection of the appropriate bacteria to the treatment tank, and a biological filter. A dramatic reduction of oil and grease in the bakery waste from approximately 1.5 g/L to less than 0.03 g/L, which is three times less than accepted regulatory limits, resulted. Reliable functioning of the bioremediation system has been observed during an extended period of time (20 months).