Electrodialytic remediation of sediments

Sediments of harbors and freshwaters are regularly dredged for various reasons: maintenance of navigational depths, recovery of recreational locations, and even environmental recovery. In the past, sediments dredged from harbors have been dumped at sea, however, environmental regulations now, in many cases, prohibit this due to contamination by primarily heavy metals and TBT. Similarly, sediments of fresh waters could potentially be used as soil amendment material for poor agricultural soils utilizing their often high content of phosphate and nitrogen. However, again, heavy metal contamination often hinders this usage. Hence, for both types of sediments, expensive deposition at hazardous waste landfills is required. Electrodialysis is presently being developed as an alternative method for treatment of such contaminated sediments. Heavy metals are removed by treating the sediments in suspension with an electric DC field, while ion-exchange membranes constitute a barrier between the sediment being treated and the concentrate liquid in which the contaminants are collected.