Patent ID: 6962662

Claim:
A method for removing small concentrations of metal sulfate contaminants from a stream of water including the steps, in operable order: (a) injecting a conductivity control solution into the stream wherein said solution is selected to increase the conductivity of the stream to a value wherein in a following step(b), the ion state of each metal is modified by passing the stream between electrodes of each pair of an array of pairs of electrodes, each electrode having a selected voltage with respect to the other member of the pair of electrodes; (b) passing the stream between electrodes of each pair of an array of pairs of electrodes, each electrode having a selected voltage with respect to the other member of the pair of electrodes; (c) increasing a value of pH of the stream to a value where precipitate of the metal sulfates are formed in said stream; (d) removing the precipitate from said stream whereby a reduced amount of sulfate ions remains in said stream; (e) adding a precipitating chemical to the stream in sufficient concentration to precipitate most of the remaining sulfate ions from said stream; (f) removing precipitated sulfate salt from said stream.