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Experiments were performed in the presence and absence of background ammonia tostudy the significance of the direct reaction(s) of monochloramine (NHsub2/subCl) with dissolvedorganic matter (DOM) in the haloacetic acid (HAA) formation during chloramination. Directreactions were found to play a major role in the HAA formation compared to the reactions ofNHsub2/subCl decomposition products (i.e., hypochlorous acid and dichloramine) with DOM.Dihalogenated HAAs (DXAA) constituted the major HAAsub9/sub species formed duringchloramination. The extent of DXAA formation decreased with increasing pH. Experimentsconducted with sodium sulfite (Na2SO3) and ammonium chloride (NH4Cl) showed that selectionof quenching agent is important to obtain reliable results from chloramination kineticexperiments. When preformed chloramines are employed, the use of NHsub4/subCl, the quenchingagent recommended by USEPA Method 552.3 for HAA samples, may result in false high HAAconcentrations at early reaction periods. The type of quenching agent used in different studiesappears to be the cause of different kinetic patterns reported for chloramination kinetics in theliterature. Includes 16 references, tables, figures.

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Edition: Vol. - No. Published: 06/17/2005 Number of Pages: 16File Size: 1 file , 1.2 MB