Fate of sulfur(IV) dechlorinating agents in natural waters: effect of suspended sediments

• Published in: Environmental science & technology 1988-10, Vol.22 (10), p.1171-1177
• Main Authors: Kijak, Philip J, Helz, George R
• Format: Article
• Language: English
• Subjects: Applied sciences; Biological and physicochemical phenomena; Exact sciences and technology; Natural water pollution; Pollution; Water treatment and pollution
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es00175a007

Suspensions of standard sediment MESS-1 (1 g per litre) were equilibrated with synthetic river water containing 120 mM sodium chloride and 1 mM buffer at pH 7.1 or 8.4 for 2 days at 25C. Metal and sulphate concentrations were determined before addition of sulphite. Reductive dissolution of iron and manganese oxyhydroxides accounted for little oxidation of sulphur(IV) in unilluminated samples. Significant oxidation occurred only in aerobic conditions. Natural effluent/river water mixtures were also used and soluble components released catalysed the oxidation of sulphur(IV). Particles exerted a slight inhibitory effect. Intermediate sulphur species did not accumulate and bioactive products such as peroxymonosulphate were formed at very low concentrations. At sediment concentrations of 20 g per litre, nonoxidative loss of sulphur(IV) was observed. Sulphur(IV) reductively dissolved from the sediment at pH 8.4 but not at pH 7.1. Loss of sulphur(IV) in air saturated solutions could be described by a half order rate law. Rate of loss of sulphur(IV) was twice as fast in natural water mixtures and was attributed to higher concentrations of trace metals.