Dechlorination method and solution

Abstract

An improved sulfurous acid dechlorination method of chlorinated waters to increase sulfites, prevent SO.sub.2 gassing off, and off-setting monovalent chlorides in the treated water for land application.

Claims

1. A sulfurous acid dechlorination method of chlorinated waters to increase sulfites, prevent sulfur dioxide gassing off, and off-set monovalent chlorides in treated water for land application, comprising: (a) forming a concentrated sulfurous acid bisulfite/sulfite dechlorination solution by: (1) injecting sulfur dioxide (SO.sub.2) into water or wastewater to provide H.sup.+, SO.sub.2, SO.sub.3.sup., HSO.sub.3.sup., dithionous acid (H.sub.2S.sub.2O.sub.4), and other sulfur intermediate reduction products, via a sulfurous acid generator producing sulfur dioxide on an as needed basis to admix with water or wastewater forming a sulfur dioxide treated water or wastewater at a pH between approximately 1.5 and 3.5, and (2) adjusting the pH of the sulfur dioxide treated water or wastewater with alkaline reagents to above approximately 4 to convert the sulfur dioxide to bisulfite and sulfite species optimizing the presence of bisulfite and sulfite species for chlorine reduction, and (b) admixing the dechlorination solution with chlorinated waters and wastewaters for dechlorinating by the bisulfites and sulfites without sodium addition.

2. A sulfurous acid dechlorination method according to claim 1, wherein the alkaline reagents comprise spent lime and/or lime to provide bivalent calcium ions to off-set monovalent salts for land application.

3. A sulfurous acid dechlorination method according to claim 1, wherein the alkaline reagents comprise ammonia for land application, where chlorides are not an issue.

Description

DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a graph of a titration curve of sulfurous acid and carbonic acid.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

(2) FIG. 1 is a graph of a titration curve of sulfurous acid and carbonic acid showing the distribution of sulfurous acid species SO.sub.2.sup.2, HSO.sub.3.sup., and SO.sub.3.sup.2 at different pH levels. At a pH of 4, bisulfites and sulfites are predominantly present in solution so sulfur dioxide will not gas off. Use of lime provides Ca.sup.+2 ions to off-set the chlorides as discussed above for land application.

(3) The present invention may be embodied in other specific forms without departing from its structures, methods, or other essential characteristics as broadly described herein and claimed hereinafter. The described embodiments are to be considered in all respects only as illustrative, and not restrictive. The scope of the invention is, therefore, indicated by the appended claims, rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.