The Orange County Water District (OCWD, CA) uses an advanced oxidation process (AOP) as the ultimate step for their wastewater treatment. The process consists of standard initial, primary, and secondary treatments performed at the nearby Sanitation District, followed by microfiltration (MF), reverse osmosis (RO), and ultimately an UV-H2O2 AOP at OCWD. In this last step hydroxyl radicals (●OH) are generated through UV photolysis of the hydrogen peroxide. The high reactivity and non-selective reaction of this radical ensures degradation of any remaining chemical contaminants in the wastewater. However, within this train chloramines (NH2Cl, NHCl2, NCl3) are deliberately generated through addition of a 12.5% basic hypochlorite solution to prevent biofouling of the RO membranes. Although all these chloramines benefit the OCWD water treatment process, their presence is extremely detrimental to the chemistry occurring within the AOP. Moreover, they may also thermally react with organic constituents in the train to produce organochlorinated byproduct species that may not be fully removed by the AOP. Speciation measurements on the RO permeate have shown that both mono- and dichloramine dominate, with only trace levels of trichloramine remaining. While considerable work has been reported for monochloramine reactions, little is known about dichloramine. Therefore, in this study the thermal reactivity of dichloramine with prototypical organic matter, amino acids, was investigated using absorption spectroscopy and stopped-flow kinetics. Absolute second-order rate constants were determined, with the different amino-acid functionality providing insight as to how general organic matter in wastewater would react with dichloramine under wastewater treatment conditions.

Reactions of dichloramine with amino acids in wastewaters: Kinetic study

2019 Fall National Meeting

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