The effects of microorganism-derived cellular material on the Atterberg limits of bentonite and kaolinite clays

Slope stability problems in residential areas are often associated with water introduced to the ground through septic systems. These septic systems can also introduce microorganisms to the ground. Research has shown that compounds in bacteria can be adsorbed by clay particles in the soil. Research on how these adsorbed compounds affect the engineering properties of clay is limited. The purpose of this thesis was to determine if compounds in microorganisms could affect the liquid limit and plastic limit of a kaolinite and a bentonite clay. Cell sap was mixed with clay and the Atterberg limits of the samples were tested. The results indicated that cell sap had no effect on kaolinite but the liquid limit of bentonite was reduced by up to 22% after the addition of cell sap. These results were discussed and related to research by other authors. Suggestions for improving the procedures were made.