Electrocoagulation removes pollutant material from water by a combination of coagulant delivered from a sacrificial aluminium anode and hydrogen bubbles evolved at an inert cathode. Rates of clay particle flotation and settling were experimentally determined in a 7 L batch reactor over a range of currents (0.25-2.0 A) and pollutant loadings (0.1-1.7 g/L). Sedimentation and flotation are the dominant removal mechanism at low and high currents, respectively. This shift in separation mode can be explained by analysing the reactor in terms of a published dissolved air flotation model.