Ultraviolet-Induced Effects on Chloramine and Cyanogen Chloride Formation from Chlorination of Amino Acids

Ultraviolet (UV)-based treatment is commonly used to augment chlorination in swimming pools. However, the effects of combined application of UV₂₅₄/chlorine on disinfection byproduct (DBP) formation are incompletely defined. To examine this issue, experiments were conducted with amino acids (l-arginine, l-histidine, and glycine) that are representative of those introduced to swimming pools via human body fluids. For each precursor, stepwise experiments were conducted with chlorination and UV₂₅₄ exposure, with/without post-chlorination. Net formation and decomposition of chloramines and cyanogen chloride (CNCl) were measured for a range of chlorine/precursor (Cl/P) molar ratios and UV₂₅₄ doses. Substantial production of NH₂Cl from l-arginine and l-histidine was observed at Cl/P = 1.0 and 2.0 when post-chlorination was applied to UV₂₅₄-irradiated samples. These results suggested a mechanism of rapid N-chlorination, followed by cleavage of NH₃ by UV₂₅₄ irradiation. CNCl formation was observed from UV₂₅₄-irradiated samples of l-arginine and l-histidine when Cl/P = 2.0 and 3.0, as well as from glycine for Cl/P ≤ 1. Structurally related precursor compounds were examined for CNCl formation potential in chlorination/UV experiments. CNCl formation was promoted by UV₂₅₄ exposure of chlorinated imidazole and guanidine compounds, which suggested that these groups contributed to CNCl formation. The results have implications with respect to the application of chlorine and UV for water treatment in swimming pools and other settings, such as water reuse and advanced oxidation processes

Reduction of Human Norovirus GI, GII, and Surrogates by Peracetic Acid and Monochloramine in Municipal Secondary Wastewater Effluent

The objective of this study was to characterize human norovirus (hNoV) GI and GII reductions during disinfection by peracetic acid (PAA) and monochloramine in secondary wastewater (WW) and phosphate buffer (PB) as assessed by reverse transcription-qPCR (RT-qPCR). Infectivity and RT-qPCR reductions are also presented for surrogate viruses murine norovirus (MNV) and bacteriophage MS2 under identical experimental conditions to aid in interpretation of hNoV molecular data. In WW, RT-qPCR reductions were less than 0.5 log₁₀ for all viruses at concentration–time (CT) values up to 450 mg-min/L except for hNoV GI, where 1 log₁₀ reduction was observed at CT values of less than 50 mg-min/L for monochloramine and 200 mg-min/L for PAA. In PB, hNoV GI and MNV exhibited comparable resistance to PAA and monochloramine with CT values for 2 log₁₀ RT-qPCR reduction between 300 and 360 mg-min/L. Less than 1 log₁₀ reduction was observed for MS2 and hNoV GII in PB at CT values for both disinfectants up to 450 mg-min/L. Our results indicate that hNoVs exhibit genogroup dependent resistance and that disinfection practices targeting hNoV GII will result in equivalent or greater reductions for hNoV GI. These data provide valuable comparisons between hNoV and surrogate molecular signals that can begin the process of informing regulators and engineers on WW treatment plant design and operational practices necessary to inactivate hNoVs

Comparative Inactivation of Murine Norovirus and MS2 Bacteriophage by Peracetic Acid and Monochloramine in Municipal Secondary Wastewater Effluent

Chlorination has long been used for disinfection of municipal wastewater (MWW) effluent while the use peracetic acid (PAA) has been proposed more recently in the United States. Previous work has demonstrated the bactericidal effectiveness of PAA and monochloramine in wastewater, but limited information is available for viruses, especially ones of mammalian origin (e.g., norovirus). Therefore, a comparative assessment was performed of the virucidal efficacy of PAA and monochloramine against murine norovirus (MNV) and MS2 bacteriophage in secondary effluent MWW and phosphate buffer (PB). A suite of inactivation kinetic models was fit to the viral inactivation data. Predicted concentration–time (CT) values for 1-log₁₀ MS2 reduction by PAA and monochloramine in MWW were 1254 and 1228 mg-min/L, respectively. The 1-, 2-, and 3-log₁₀ model predicted CT values for MNV viral reduction in MWW were 32, 47, and 69 mg-min/L for PAA and 6, 13, and 28 mg-min/L for monochloramine, respectively. Wastewater treatment plant disinfection practices informed by MS2 inactivation data will likely be protective for public health but may overestimate CT values for reduction of MNV. Additionally, equivalent CT values in PB resulted in greater viral reduction which indicate that viral inactivation data in laboratory grade water may not be generalizable to MWW applications

The Presence of Pharmaceuticals and Personal Care Products in Swimming Pools

The introduction of pharmaceuticals and personal care products (PPCPs) into the environment can be partially attributed to discharges of human wastes, which is also relevant in swimming pool settings. Little or no information exists to address this issue in the literature. Therefore, experiments were conducted to examine the presence and behavior of PPCPs in swimming pools. Among 32 PPCPs amenable to analysis by an available method, <i>N</i>,<i>N</i>-diethyl-<i>m</i>-toluamide (DEET), caffeine, and tri­(2-chloroethyl)­phosphate (TCEP) were found to be present in measurable concentrations in pool water samples. Examination of the degradation of selected PPCPs by chlorination illustrated differences in their stability in chlorinated pools. These results, as well as literature information regarding other attributes of PPCPs, indicate characteristics of these compounds that could allow for their accumulation in pools, including slow reaction with chlorine, little potential for liquid → gas transfer, and slow metabolism by humans (among orally ingested PPCPs). The findings of this study also suggest the potential for accumulation of topically applied PPCP compounds in pools. More generally, the results of this study point to the importance of proper hygiene habits of swimmers. The potential for the accumulation of PPCPs in pools raises questions about their fate and the risks to swimming pool patrons