New Generation Dresden NPP Demineralizer Vault Cleanup Project - 8377

摘要

Electro-coagulation (EC) is a technique that facilitates rapid destabilization and flocculation of colloidal suspensions to cause the suspended solids to separate from slurry phase. It is generally accepted that coagulation is brought about primarily by the reduction of the net surface charge to a point where the colloidal particles, previously stabilized by electrostatic repulsion, can approach closely enough for van der Waal's forces to hold them together and allow aggregation. In the EC process, the coagulant is generated in situ by electrolytic oxidation of an appropriate anode material (aluminum in this case). In this process, charged ionic species, metals or otherwise, and suspended solids are removed from wastewater by allowing them to interact with an ion having opposite charge, or with floc of metallic hydroxides generated electrochemically within the effluent. Typically, no supplementary organic polymer coagulant addition is required.Thus, electro-coagulation (EC) was found to be an attractive treatment option to rapidly destabilize the colloidal particulate phase, allowing more facile particulate removal by decantation and/or coarse filtration. However, the liquid medium must have some conductivity (≥ 100 μmho is preferred), in order to allow effective electrical coupling with the EC electrodes. A very small amount of aluminum or sodium sulfate salts can be added to the feed slurry, adjusting the water quality parameters to a conductivity of ≥100 μmho and a pH value near 6.0-7.0. The EC-treated vault slurry had a pH value near 6.5 (within the pH range for minimal solubility of amphoteric aluminum hydroxide).