Breakpoint Chemistry and Volatile Byproduct Formation Resulting from Chlorination of Model Organic-N Compounds

Abstract

Aqueous solutions containing six model organic-N compounds (glycine, cysteine, asparagine, uracil, cytosine, and guanine) were subjected to chlorination at various chlorine (Cl) to precursor (P) molar ratios for 30 min. Chlorine residuals were determined by both DPD/FAS titration and the MIMS (Membrane Introduction Mass Spectrometry) method to evaluate breakpoint chlorination behavior, residual chlorine distributions, and byproducts. DPD/FAS titration was found to yield false-positive measurements of inorganic combined chlorine residuals in all cases. The breakpoint chlorination curve shape was strongly influenced by the structure of the model compound. Cyanogen chloride was found to be present as a byproduct in all cases, and the yield was strongly dependent on the Cl:P molar ratio and the structure of the compounds, with glycine being the most efficient CNCl precursor. Six byproducts other than cyanogen chloride were also identified. Free chlorine measurements by DPD/FAS titration and MIMS were in good agreement. This finding, together with the results of previously conducted research, suggests that both methods are capable of yielding accurate measurements of free chlorine concentration, even in solutions that contain complex mixtures of +1-valent chlorine compounds.

Seasonal dynamics of water and air chemistry in an indoor chlorinated swimming pool

“…Acute and chronic human health problems that have been associated with exposure to these DBPs in swimming pools include: promotion of asthma (Bernard et al, 2003(Bernard et al, , 2007; increased incidence of rhinitis and hay fever Bernard et al, 2009); as well as skin (contact dermatitis) and eye irritation (Fantuzzi et al, 2010;Safranek et al, 2007). DBP exposure in swimming pools has also been associated with an increased risk of bladder cancer (Villanueva et al, 2007). Therefore, it is important to understand the chemistry and physics that govern the formation, transfer, and decay of DBPs in pools; however, their behavior is complicated by competing reactions and transport phenomena, as well as a general lack of research for some of these DBPs.…”

“…Several organic-N compounds have been identified as cyanogen halide (CNX) precursors, including glycine, serine, threonine, and uric acid (Shang et al, 2000;Li and Blatchley, 2007;Lian et al, 2014). Among the amino acids, glycine appears to have the greatest potential to form cyanogen chloride (Na and Olson, 2006).…”

What Bathers Put into a Pool: A Critical Review of Body Fluids and a Body Fluid Analog

“…Earlier experiments by Shang et al (2000) with glycine, cysteine, and asparagine found that initial reaction with FAC produced 1 or 2-N chlorinated amino acids that detected as NH 2 Cl and NHCl 2 (or NCl 3 ) in the DPD-FAS titration. Chlorinated glycine appeared stable for 30 min at dosed FAC/glycine molar ratios up to 1.2 but at higher dosed molar ratios decomposition within 30 min occurred.…”

Formation of Disinfection By-Products from Bacterial Disinfection

“…This observation could also attribute to N-rich organic matter from bacterial cells. N-rich BOM could affect the residual chlorine in water throughout forming organic chlorine and breakpoint reaction, depending on the Cl-to-N ratio (40). In fact, studies had demonstrated that organic N could reduce THM formation during water chlorination (41).…”