Dewatering of Tunneling Slurry Waste Using Electrokinetic Geosynthetics

Laboratory experiments are described that investigate the potential for using electrokinetic geosynthetics (EKGs) [materials that permit the combined exploitation of geosynthetics with electrokinetics (EKs)] to dewater slurry waste from a tunneling operation. The results demonstrate that the EK is reproducible for different slurries and that the process can significantly dewater tunneling slurry wastes. Higher electrode element surface area, increased potential gradient, and longer processing time increase water removal from a slurry waste. Higher potential gradients and current densities were found to consume more energy, with thicker samples (lower voltage gradients) and close element spacing using less power to achieve a particular dewatering efficiency than other configurations tested. The resultant pH of the treated slurry and the effluent water were found not to be sufficiently altered by the EK process to prevent their safe disposal or reuse. The potential of three different forms of EKG to treat tunneling slurry are discussed and a conceptual scheme for an EK enhanced belt press is proposed. While further investigation would be required to optimize their operating parameters, preliminary designs, and cost estimates can be based on the results presented herein.