Electrical flocculation of the unicellular green alga Chlorella vulgaris Beijerinck

Abstract

Low-voltage electric fields (3-9 V cm^-1) and certain chemical factors known to influence the stability of colloids in suspension were applied to culture suspensions of the unicellular green alga Chlorella vulgaris Beijerinck. Passage of an electric current through the algal suspension caused formation of buoyant algal flocs, with the degree of flocculation being a function of the duration of the electric treatment under a set of conditions. Both the rate and the degree of algal flocculation depended on pH of the medium, electric field, cell density, and various counterionic additives. At pH of ca. 7.0, up to 90% of algal cells could be separated within 30 min by application of a 3 V cm^-1 electric field. A natural population of Chlorella and Scenedesmus showed an almost similar extent of flocculation after passage of electric current.