A laboratory study on the anaerobic digestion of yeast waste

Abstract

This thesis reports the establishment of a new type of internally clarified digester as a means of treating a strong industrial waste. Factors pertaining to both the system and the waste itself were investigated. A batch system was used to determine the susceptibility of the waste chosen, viz. that from the first separator of a local yeast factory, to anaerobic digestion. The reactor-clarifiers were constructed and operated at a wide range of loadings. A constant hydraulic retention time was maintained for each of the digesters and sufficient sludge withdrawn daily to maintain a constant sludge concentration over the range of loadings used. The ability of each of the parameters used to monitor digestion, to predict periods of digester imbalance was investigated. A mathematical model was derived to describe the process and the kinetic parameters related to the anaerobic digestion of yeast waste evaluated. Possible inhibitory substances present in the waste and/or generated during digestion and their influence on the system were investigated.