Chlorine speciation in seawater; a metastable equilibrium model for ClI and BrI species

A thermodynamic model for the inorganic, fast-reacting fraction of the total residual oxidant produced by chlorination in marine waters reveals that Br^I species are more stable than Cl^I species. At typical amino-N levels, HOBr, NBr₃, and NHBr₂ predominate. Data on organic byproducts of chlorination generally support the model calculations.     

Making chlorine greener: performance of alternative dechlorination agents in wastewater

The residual chlorine in chlorine-disinfected and dechlorinated wastewater was characterized using a liquid chromatograph that was switched between reversed-phase separation and flow injection analysis modes, permitting measurement of fractionated and total residual chlorine, respectively. Residuals were detected in the effluent of an operating wastewater treatment plant employing chlorine disinfection and sulfite dechlorination. Despite dechlorination, an estimated total residual chlorine of 3 microM (0.2 ppm as Cl2) was detected in the effluent. To improve dechlorination effectiveness, four alternative agents (ascorbic acid, iron, sulfite plus iodide mediator, thiosulfate) were compared to sulfite on laboratory-chlorinated wastewater. Listed in order of decreasing relative effectiveness, we found: iron metal > sulfite plus iodide approximately = thiosulfate > sulfite > ascorbic acid. Only the iron metal column was completely effective at rapidly removing all traces of residual chlorine.