US 5,330,658 AGranted

Solution decontamination method using precipitation and flocculation techniques

AssigneeWestinghouse Electric Corp.

InventorsDavid C. Grant, Edward J. Lahoda, Ching-Yu Lin, Francis Talko

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Abstract

Solutions such as for example groundwater, drinking water, extracting solutions and effluents contaminated with metals, radioactive species and organics, singly or in combination, are treated by first removing undesirable oxidizing agents from the contaminated solution. Then the contaminated solution is separately treated with aqueous solutions of ferrous sulfate and hydroxide, which precipitate substantially all of the contaminants. Next, the precipitate is treated with a flocculant and/or a coagulant to form an easily dewaterable and separable solid. The solid contaminants are readily removed from the cleansed solution. The process utilizes a novel combination of steps which maximizes contaminant removal, minimizes waste volume, and produces a recyclable solution and a manageable waste stream. The preferred hydroxide solutions are sodium hydroxide, calcium hydroxide, and ammonium hydroxide.

Claims17

Dependent claims

A method for removing heavy metal and/or radioactive contaminants and oxidizing agents selected from the group consisting of hydrogen peroxide, ozone, chlorine, chlorine dioxide, potassium permanganate, manganese dioxide, nitric acid, sodium hypochlorite, potassium hypochlorite, magnesium hypochlorite and calcium hypochlorite, from a contaminated stream, said method including the steps of:

a. removing substantially all of said oxidizing agents from said contaminated stream by adjusting the pH of the stream, and/or aerating said stream for from between about 1 to 24 hours;
b. treating said stream with aqueous ferrous sulfate solution to reduce and/or precipitate said contaminants;
c. treating said stream with an effective amount of a hydroxide solution sufficient to increase the pH of the stream to between about 9 to 12 such that the precipitates, the contaminants, and/or the ferrous ions form coprecipitates with the hydroxide ion which are substantially insoluble in said stream;
d. treating said stream with a flocculant;
and
e. separating said coprecipitates from the stream;
wherein step (a) is performed prior to steps (b) and (c).

4 more elements

Dependencies are inferred from the claim text.