Abstract: In the treatment of a contaminated liquid, an additive, such as finely divided adsorbent particles, is introduced into the liquid so that it combines physically, chemically or electrically with the contaminant to form a dispersion suspended in the liquid. Then, net unipolar charge is introduced into the liquid and, in a separation vessel, migration of the dispersion takes place under the interaction between charge on the dispersion and an induced electric field in the liquid. The migrating dispersion conglomerates on one or more collector surfaces which can be the internal surfaces of the separation vessel and, preferably also, the exposed surfaces of densely packed beads in the separation vessel. The treatment process is especially intended for use where the contaminant is dissolved in the liquid phase.