Effects of quenching methods on HAA determination in chloraminated waters

Abstract

This study examined the effects of using ammonium chloride (NH4Cl), a chlorine quenching agent recommended by US Environmental Protection Agency method 552.3, on haloacetic acid (HAA) determination under different chloramination scenarios simulated in laboratory experiments. During the early reaction times for the surface water tested in this study (dissolved organic carbon of 3 mg/L), results showed that HAA concentration was overestimated up to 9 μg/L because of the use of NH4Cl. In all chloramination scenarios, positive errors decreased with increasing reaction time. Among the various quenching agents or methods tested, sodium arsenite (NaAsO2) and stoichiometric amounts of sodium sulfite (Na2SO3) were found to be appropriate for HAA determination in chloraminated samples. However, they have some limitations for use in practical applications. Immediate extraction of samples without using any quenching agent resulted in positive errors in HAA determination because of the low pH conditions (pH < 1) coupled with high temperature after the addition of sulfuric acid during HAA extraction. Adjusting sample pH to high values and using ascorbic acid for quenching chloramine were found to be unsuitable for HAA samples.

HAA formation during chloramination—significance of monochloramine's direct reaction with DOM

“…In this study, it was possible to recover 88 and 99% of organic carbon from the GV and MB waters, respectively, during the RO isolation. The authors' experiences in this and previous work have shown that higher DOM recoveries are obtained in waters having high SUVA and high DOC values than in waters having low SUVA and DOC (Karanfil et al, 2007; Kitis et al, 2001). This can be attributed to the generally increasing molecular weight of DOM components with increasing SUVA values.…”

“…There are significant differences among the reported HAA formation kinetics during chloramination (Figure 2). After close examination of the experimental conditions used in those studies and with the understanding of HAA formation routes gained from the current study, the authors hypothesized that the use of ammonium chloride (NH 4 Cl) as a quenching agent required by USEPA method 552.3 for DBP samples was the primary reason for the different HAA formation patterns in chloramination kinetic studies (Hong et al, 2005; 2007).…”

“…The minimum reporting level (MRL) was 1 μg/L for each of nine HAA species, and the relative standard deviations were no more than 8%. Details of the analytical methods are reported elsewhere (Karanfil et al, 2007).…”

“…Although DXAA formation increases with the decrease in pH during chloramination, it is independent of pH for chlorination (Karanfil et al, 2007; Hong et al, 2005; Speitel et al, 2004; Duirk, 2003; Wu et al, 2003; Diehl et al, 2000). THM formation, although minimal, increases with the decrease in pH during chloramination, whereas it increases with the increase in pH seen during chlorination (Wu et al, 2003; Diehl et al, 2000).…”

“…The two main objectives of this study were to systematically investigate the routes of HAA formation and elucidate the cause(s) of the inconsistent patterns reported for HAA formation kinetics during chloramination. This article was derived from a recently completed Awwa Research Foundation project (Karanfil et al, 2007).…”