Effect of heavy metals (Cu, Pb, and Ni) on the compositions of EPS in biofilms

A series of batch adsorption tests to estimate the biofilm capacity for rem oval of the heavy metals (Cu, Pb, and Ni) in wastewater were carried out. T he metal sorption results were fitted to the Freundlich isotherm model to c ompare their sorption capacity. The change of the composition of EPSs (extr acellular polymeric substances) was simultaneously represented by the ratio of carbohydrate to protein (C/P) when the biofilm was exposed to the heavy metals. EPS composed of slime loosely bound to the cell and capsular mater ials was extracted by the four general extraction methods including regular centrifugation, regular centrifugation with formaldehyde, EDTA extraction and steam extraction. Although the various extraction methods showed differ ent results, CIP ratio of biofilm exposed to copper and lead metal ions was generally lower than that of control.