Analysis of electrokinetic sedimentation of dredged Welland River sediment

The Welland River is a tributary of the Niagara River. In the late 1980s it was discovered that a section of the Welland River was contaminated with heavy metals as a results of two sewer outfalls that has been used by a steel plant and local industrial and municipal operations for the last 50-60 years. One of the major problems encountered in the treatment of the dredged Welland River sediment is a slow rate of sedimentation due to the large proportion of fine solids in the sediment. In this study, the results of electrokinetic sedimentation of the Welland River sediment are analyzed based on the principles of gravitational and electrokinetic sedimentation. It was found that the effects of electric field intensity and the initial solid concentration of the suspension are the dominating factors governing the average particle settling velocity, the coefficient of free settling in the free settling stage and the coefficient of sedimentation in the hindered settling stage. The electrokinetic treatment is proven to be effective in terms of increasing the free and hindered settling velocities, reducing the overall sedimentation time and increasing the final solid concentration of the sediment. Thus, electrokinetics can be used to accelerate sedimentation of dilute solid suspensions, such as dredged sediment, wastewater and mine tailings. (C) 2001 Elsevier Science B.V All rights reserved.