Assessing the use of aluminium electrodes on the electrokinetic dewatering and stabilization of dredged mud slurries

Every year a large amount of dredged sediments are disposed or used for land reclamations. To reduce the time lag for construction purposes, electrokinetic stabilization is suggested as an environmentally friendly and cost effective method to dewater and stabilize the dredged mud deposited in the paddocks. However, the physiochemical changes due to the electrochemical reactions in the dredged sediments are drawbacks of this technique that need to be investigated. The type of electrode to be used in the stabilization affects the physiochemical changes, and therefore using the correct type of electrodes is important. Different electrodes are used to stabilize different types of soils. Literature suggests that aluminum is a good option as it improves the soil and causes electrochemical strengthening by inducing Al3+ ions into the soil. In this study, the effect of aluminum mesh electrodes on the electrokinetic stabilization of the dredged mud is investigated. After the completion of the electrokinetic stabilization, samples are taken from different depths and water content, pH, electrical conductivity and atterberg limits are determined. From cathode to anode, the liquid limit decreases and plastic limit increases significantly. Near the anode, pH is reduced by 90% and the electrical conductivity increased. Higher salt content is also observed near the anode at the bottom of the column. The lowest water content and highest strength are obtained near the anode. Almost 54 % of the water is removed from the system due to electroosmosis. Despite the electrochemical changes in the soil, its settlement was about 17% which was not very significant; however, variation of electric current shows that the aluminum mesh is corroded before the settlement of the soil is completed. Therefore aluminum mesh electrodes are not suggested to be used for electrokinetic stabilization of dredged mud sediments