Chapter 9
HAA Formation and Speciation during Chloramination 1
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Downloaded by GEORGETOWN UNIV on August 24, 2015 | http://pubs.acs.org Publication Date: August 5, 2008 | doi: 10.1021/bk-2008-0995.ch009
Tanju Karanfil , Ying Hong , Hocheol Song 1
Department of Environmental Engineering and Science, Clemson University, Clemson, SC 29634 Black & Veatch, 201 South Orange Avenue, Suite 500, Orlando, FL, 32801
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The main objective of this study was to systematically examine the roles of dissolved organic matter characteristics, pH and bromide in the formation and speciation of dihalogenated acetic acids, the major class of haloacetic acids (HAA) formed during chloramination. This chapter also summarizes briefly the potential reaction routes of HAA formation, HAA formation kinetics, and the effect of quenching agent use during chloramination.
Introduction The use of chloramine, in the form of monochloramine (NH C1), has gained increasing popularity in the United States drinking water industry during the last two decades, primarily due to the increasingly stringent regulations imposed by the United States Environmental Protection Agency (USEPA) under the Disinfectants/Disinfection Byproducts Rule (D/DBPR). Stage 2 of the D/DBPR, published in January 2006, requires water utilities to comply with the maximum contaminant levels (MCLs) of 80 μg/L total trihalomethanes (THMs: chloroform, bromodichloromethane, dibromochloro-methane, and bromoform) and 60 μg/L five haloacetic acids (HAA5: the sum of mono-, di-, and trichloro2
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© 2008 American Chemical Society In Disinfection By-Products in Drinking Water; Karanfil, T., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2008.
125 acetic acids, and mono- and dibromoacetic acids) at each individual monitoring location in a distribution system (i.e., locational running annual averages) (1). The most recent survey of 363 drinking water utilities across all 50 states showed that 68 and 29% used chlorine and chloramines as a secondary disinfectant, respectively, and 3% did not use any secondary disinfectant (2). Of those 257 utilities using chlorine or no secondary disinfectant, seven planned to convert to chloramines, and another seventy seven were considering switching to chloramines with the implementation of the Stage 2 D/DBPR. Chloramination (using preformed NH C1) almost completely suppresses THM formation and reduces HAA concentrations to 3-30% of the amounts formed during chlorination (3-6). Dihalogenated haloacetic acids (DXAAs) are the primary regulated DBP species formed during chloramination, whereas the formation of monohalogenated (MXAAs) and trihalogenated haloacetic acids (TXAAs) is significantly suppressed (5,7,8). Although chloramination does not completely eliminate HAA formation, it may provide a viable alternative to some water utilities complying with the Stage 2 D/DBPR. This and control of THMs are the main reasons for the increased use of chloramination by the drinking water treatment industry in the US in recent years. The main objective of this chapter is to examine the formation and speciation of HAA during chloramination of two natural waters with different dissolved organic matter (DOM) characteristics (i.e., one with a high specific ultraviolet absorbance (SUVA) and the other with a low SUVA value) under similar experimental conditions. In addition, the potential reaction routes of HAA formation, HAA formation kinetics, and the effect of quenching agent use during chloramination are also briefly summarized.
Downloaded by GEORGETOWN UNIV on August 24, 2015 | http://pubs.acs.org Publication Date: August 5, 2008 | doi: 10.1021/bk-2008-0995.ch009
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Materials and Methods Reverse Osmosis (RO) Isolation of DOM Two DOM solutions were concentrated from the influents of drinking water treatment plants in South Carolina, Greenville (GV) and Myrtle Beach (MB), using a RO system, described elsewhere (9). The selected water quality characteristics of the source waters are provided in Table 1. The RO isolation enabled performing the chloramination experiments of the two different source waters at the same organic carbon concentration. Good DOM recoveries (88% for GV and 99% for MB) were obtained based on dissolved organic carbon (DOC) during the isolation. The reactivity tests confirmed that there was no impact of RO isolation on the DOM reactivity during chlorination and chloramination (10,11).
In Disinfection By-Products in Drinking Water; Karanfil, T., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2008.
126 Table 1. Selected physicochemical characteristics of the source waters Parameter DOC UV SUVA Bromide PH Alkalinity (as CaC0 ) Ionic Strength 254
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Unit
Greenville
Myrtle Beach
(mg/L) (cm" ) (L/mg-m)
0.8 0.015 1.9
