A scanning electron microscopy study of the interactions between sludge organic components and clay particles

Scanning electron microscopy was used to observe the effects of the addition of water-extracted components from sewage sludge on the fabric of kaolinite and montmorillonite saturated with Na or Ca. The SEM micrographs showed that organic components of the sludge bind the clay particles together and promote microaggregation. Possible binding mechanisms include bridge formation by organic fibers as well as coating and envelopment of the clay particles by organic substances. Application of a drying and wetting cycle to a Ca-montmorillonite/sludge mixture enhanced irreversible aggregation of the material. The organo-mineral interactions observed here for pure clays may shed light on the mechanisms involved in the stabilization of soil structure due to sludge disposal.