Described herein are systems, methods, and apparatuses for aggregating microorganism in an aqueous suspension. In particular, are systems, methods, and apparatuses that apply an electrical field and/or acoustic energy to an aqueous suspension comprising microorganisms as the aqueous suspension follows a flow path to cause aggregation of the microorganisms. The electrical field may be continuous or pulsed. In some embodiments, the flow path for the aqueous suspension may vary. In some embodiments, the cross-sectional area of the electrical field may be tuned.