Laboratory evaluation of electrokinetic dewatering of dredged marine sediment as an option for climate change adaption

Abstract

The climate change affects the coastal infrastructure including ports. This effect is through changes in the tides, waves, wind and coastal erosion. As a result, sedimentation in harbours and coastal area increases and therefore there is a need for more regular dredging as well as adaption to climate change to reduce the vulnerability. More frequent dredging means higher amount of dredging sediments need to be disposed or treated. One of the methods to be proposed to reduce the impact of high amount of dredging and reducing the environmental wastes as a by-product of dredging is to reuse or reproduce the dredged sediments. Electrokinetic stabilization is one of the environmentally friendly methods to dewater and strengthen the engineering properties of the soils and dredged sediments. This study investigates the effect of electrokinetic stabilization to improve the engineering properties of the dredged mud as an alternative option to reduce the environmental impact and use of a sustainable method for climate change adaption. Two laboratory designs are tested to determine the most efficient electrokinetic dewatering configuration and to examine the potential use of this method for dewatering and improving dredged mud. Electrokinetic stabilization is a promising method to dewater and expedite the settlement of the dredged marine sediments. However, the placement of electrodes can affect the power consumption and the efficiency of the technique and the resistivity of the soil. Some studies in the literature determine the best electrode configuration to optimize the electrokinetic stabilization. However, a few studies examined the electrode placement for electrokinetic dewatering and sedimentation. This study investigates the effect of electrode placement based on the efficiency of the method depending on power consumption versus dewatering, soil electrical resistivity, the settlement of the sediments, and treatment time. To reduce the energy expenditure first a constant voltage of 20 V is applied and the variation of electric current during the electrokinetic stabilization is monitored. Once the electric current approached zero, the voltage is increased to 30 V. Using constant voltage for both cases of electrode placement (anode on top, cathode at the bottom; anode at the bottom, cathode on top), it was observed that higher efficiency based on dewatering and power consumption is obtained when the cathode is placed on top.