Electrokinetic sedimentation of contaminated Welland River sediment

Abstract

An experimental study on electrokinetic sedimentation of contaminated sediment is conducted. The sediment dredged from the Welland River in Ontario is heavily contaminated by metals, oil, and grease as a result of industrial activities over past decades. Characterization of the sediment is presented, followed by descriptions of the sedimentation columns used in the experiments and testing procedure. The application of electrokinetics on the Welland River sediment suspensions significantly increases the free settling velocity (up to 110%) and final solid concentration (up to 33%) and reduces the coefficient of sedimentation (up to 111%) and overall sedimentation time (up to 50%). These changes are functions of the initial solid concentration and applied electric field intensity. Based on the evaluation of all influencing factors, it is concluded that a continuous dc current generates better performance than intermittent current and electrokinetic sedimentation is more effective than chemical coagulation. All other conditions being equal, the combined application of electrokinetics and FeCl3 generated the best dewatering effect. The electrokinetic treatment generates pH changes ranging from pH 6.0 at the anode to pH 9.4 at the cathode which will generate a negligible environmental impact, as most metal contaminants will not be released to water in this pH range.Key words: electrophoresis, electrokinetics, sedimentation, contaminated sediment, waste management.