The Orange County Water District (OCWD) specializes in wastewater treatment by augmenting standard primary and secondary treatments with a series of filtration steps (microfiltration, and reverse osmosis) prior to using an Advanced Oxidation Process (AOP). During their final AOP polishing step, the water is exposed to UV light in the presence of added hydrogen peroxide, which creates highly oxidizing hydroxyl radicals that can destroy any remaining organic chemicals. However, the efficiency of the AOP treatment depends on the wastewater matrix chemicals remaining at that stage. One major problem is the disinfectant chloramines that are generated in the water treatment train to prevent membrane biofouling. This is usually performed before the microfiltration step by adding bleach, which reacts with the natural ammonia present in the wastewater to produce a mixture of chloramines, particularly monochloramine (NH<sub>2</sub>Cl). Although monochloramine is beneficial in this way, it can also react with other organic matter present in the wastewater to create other chlorinated disinfection byproducts (DBP’s): toxic and hazardous chemicals that are highly regulated. As such, understanding monochloramine thermal chemistry under wastewater treatment conditions is essential. The focus of this project is to determine the temperature-dependent rate constants of monochloramine reactivity with a series of amino acids under various conditions. Amino acids were selected to mimic organic matter. These reactions were monitored through the decay of the NH<sub>2</sub>Cl absorbance peak at 243 nm in a UV-Vis spectrophotometer. From the changes in the decay rate of monochloramine with different amino acid concentrations, pseudo first order rate constants for the reaction kinetics were obtained. Reactivity-structure relationships and Arrhenius parameters for these reactions were established in order to better understand this DBP formation chemistry.

Monochloramine reactivity with amino acids in wastewater: Kinetic and temperature dependence

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.