Effect of EDTA on activated sludge properties

Bacterial extracellular polymers have been found to be important in bioflocculation of activated sludge. In this study ethylene diamine tetra acetic acid (EDTA) method of extracting bacterial extracellular polymers is examined. Following extractions, it is observed that EDTA extracted significant amounts of biopolymers. However, the chemical treatment causes serious changes in sludge properties. Sludge particle size is reduced from 21 mum to 14.6 mum, filtration properties of sludge deteriorates, indicated by an increase of capillary suction time (CST) from 48.1 sec to 232 sec and the viscosity of sludge increases from 5.5 cP to 7.1 cP. The effects are so dramatic, that it is concluded that beyond extracting biopolymers, this technique damages the microbial cell walls and solubilizes some cells.