The use of Advanced Oxidation Processes (AOP) such as UV/H as a final wastewater remediation treatment step is becoming more enticing due to ever-increasing need for potable water. Before wastewater is subjected to an AOP it typically passes through several pre-treatment steps, including microfiltration (MF) and Reverse Osmosis (RO). These membranes will undergo biofouling, decreasing their efficiency.  For large-scale treatment chloramines are generated prior to the membranes via addition of 12.5% basic hypochlorite to the wastewater stream. The hypochlorite reacts with the ammonia in wastewater to produce primarily trichloramine at the point of injection.  While chloramines maintain MF and RO membrane quality, there presence is detrimental to the efficiency of the subsequent AOP, as they will absorb UV radiation reducing the yield of hydroxyl radicals. Moreover, chloramines can also react with dissolved organic matter to produce potentially harmful halogenated byproducts. Although these reactions have been studied previously, the kinetics of thermal chloramine reactions have not been reported.  The purpose of this project was to establish absolute rate constant values for trichloramine reaction with organics in wastewaters.  Because of the vast extent of organic content in wastewater, amino acids were used as an elementary model contaminant.  Experiments were conducted using stopped flow spectrophotometry and absorption spectroscopy to observe the rate of decay of trichloramine in the presence of these acids. Second-order reaction rate constants were calculated using solution pH’s of ca. 12, which mimics the initial conditions of the trichloramine point source addition.

Kinetics of trichloramine reactions with organic species under AOP conditions

2019 Spring National Meeting

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