Rapid recovery of bacterial cells from a stable dispersion by heterocoagulation to a fibrous collector

Rapid recovery of five heterotrophs, Escherichia coli, Pseudomonas putida, Pseudomonas aeruginosa, Alcaligenes sp., and Alcaligenes faecalis, was investigated at various pH and ionic concentrations and the results were compared with data of the electrophoretic mobility of cells and substrata. Cell recovery was performed by a column bed packed with fibrous ferro-nickel slag, which was utilized as the collector media of bacterial cells. In the case of P. putida, which showed negative electrophoretic mobility, a low cell recovery was obtained at pH 7.0, whereas the cell collection ratio gradually increased as the pH decreased. The collection of A. faecalis improved as the ionic concentration increased. Considering the adhesion of bacterial cells to fibrous slag as the heterocoagulation between cell and substrata, these findings were explained by the reduction of electrostatic repulsive interaction between cell and substrata, leading to an increase of cell recovery. On the other hand, separation of P. aeruginosa, whose electrophoretic mobility was almost zero under all experimental conditions, hardly depended on the chemical properties of the suspension. Cell collection behavior was qualitatively in good agreement with electrokinetic properties of cells and slag, suggesting that cell recovery based on surface characteristics is a promising method, especially for stable bacterial dispersion.