A Drinking Water Relevant Water Chemistry Model for the Free Chlorine and Cyanuric Acid System from 5°C to 35°C

Wahman, David G.; Alexander, Matthew T.

doi:10.1089/ees.2018.0387

Cited by 4 publications

(18 citation statements)

References 20 publications

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“…For the AES experiment, Figure summarizes a comparison of simple model‐simulated, absorbance, AES, and colorimetric DPD FreeCl concentrations, along with colorimetric DPD TOTCl concentrations. Including the uncertainty in the simple model equilibrium constants (Morris, ; Wahman, ; Wahman & Alexander, ), the absorbance‐determined actual FreeCl concentrations were not significantly different ( t ‐test, α = 0.05) than the simple‐model‐simulated actual FreeCl concentrations at cyanuric acid additions of 0, 2, 3, and 4 mg/L. Subsequently, simple‐model‐simulated FreeCl concentrations were used to interpret experiment results without further verification.…”

Section: Resultsmentioning

confidence: 99%

“…As previously discussed, the absorbance FreeCl method is applicable for high purity waters absent of known interferences (e.g., NOM and nitrate). In addition and as discussed by Wahman and Alexander (), experimental conditions (e.g., pH and expected actual FreeCl concentrations) and equipment (e.g., 10‐cm absorbance cell path length) must be appropriately selected to determine actual FreeCl concentrations by the absorbance FreeCl method.…”

Section: Resultsmentioning

confidence: 99%

“…Amperometric electrodes measure a positive bias from chlorinated cyanurates and overestimate the FreeCl concentration, with a measured value between the actual FreeCl and TOTCl concentrations (Canelli, ; Jensen & Johnson, ; Jensen, Le Cloirec, & Johnson, ). O'Brien et al () used spectroscopy at wavelengths between 196 and 292 nm to directly determine actual FreeCl concentrations, and more recently, Wahman and Alexander () used absorbance at 292 nm to determine actual FreeCl concentrations when developing the simple model. Extension of the spectroscopy method to drinking waters is improbable because of limitations resulting from interferences at relevant wavelengths (i.e., 200–300 nm) from constituents such as natural organic matter (NOM) (e.g., Korshin, Li, & Benjamin, ; Sohn, Amy, & Yoon, ; Strickler & Kasha, ) or nitrate (e.g., Bastian, Weberling, & Palilla, ) and required detection limits for drinking water samples.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, Wahman and Alexander () reduced the full model by only including equilibrium expressions important under relevant drinking water conditions (i.e., 6.5 ≤ pH ≤ 9.5, TOTCl ≤ 10 mg Cl 2 /L, and TOTCy ≤ 10 mg Cy/L). This model was termed the simple model (Figure b and Table , “Simple model”) and included only four ( K , K 6 , K 7a , and K 9a ) temperature‐dependent equilibrium expressions, temperature dependence from 5 to 35°C, and six chemical species: FreeCl (HOCl and OCl − ), cyanuric acid and its first dissociation product (H 3 Cy and H 2 Cy − , respectively), and two chlorinated cyanurates (HClCy − and Cl 2 Cy − ).…”

Section: Introductionmentioning

confidence: 99%

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Chlorinated cyanurates in drinking water: Measurement bias, stability, and disinfectant byproduct formation

2019

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Two chlorinated cyanurates, commonly referred to as dichlor (anhydrous sodium dichloroisocyanurate or sodium dichloroisocyanurate dihydrate) and trichlor (trichloroisocyanuric acid), may be approved for use in U.S. drinking water systems as chlorine sources. One complication with dichlor or trichlor's application in drinking water is that the actual free chlorine concentration in these systems cannot be quantified accurately by currently approved methods. Based on known water chemistry, two hypothesized advantages of dichlor or trichlor use are potential increased residual chlorine stability and decreased regulated disinfectant byproduct (DBP) formation. To inform these practical considerations, the current research investigated measurement bias in N,N‐diethyl‐p‐phenylenediamine (colorimetric and portable parallel analyzer), indophenol, amperometric titration, and amperometric electrode free chlorine methods. In addition, hold studies using a surface water and dosed with either free chlorine only, dichlor, or trichlor provided the first side‐by‐side comparisons of disinfectant residual stability and regulated DBP formation.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Chlorinated cyanurates in drinking water: Measurement bias, stability, and disinfectant byproduct formation

2019

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“…O'Brien et al [2] reported the best available estimates of the cyanurate equilibrium constants at 25 • C, and these estimates are used in this paper. Recently, Wahman [3] and Wahman and Alexander [4] have reported the temperature dependence of the three equilibrium constants (K 6 , K 7a , and K 9a ) which are most relevant at swimming pool pH. Swimming pool operators use test kits that measure what is referred to as FC [5].…”

Section: Cyanurate Chemistrymentioning

confidence: 99%

Assessing the Impact of Cyanuric Acid on Bather’s Risk of Gastrointestinal Illness at Swimming Pools

Falk

Blatchley

Kuechler³

et al. 2019

Water

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Current regulatory codes for swimming pool disinfection separately regulate free chlorine (FC) and cyanuric acid (CYA). It is well-known that CYA affects disinfection rates by reversibly binding to FC in aqueous solutions. However, limits for these regulated parameters have neither systematically accounted for this chemistry nor been based on the risk of gastrointestinal illness. This study was intended to determine the minimum concentration of FC relative to CYA based on the risk of gastrointestinal illness from normal fecal sloughing of selected pathogens and to find a simple regulatory rule for jointly managing FC and CYA for consistent disinfection. Literature data on CYA’s effect on microbial inactivation rates were reanalyzed based on the equilibria governing hypochlorous acid (HOCl) concentration. A model was developed that considers the rates of pathogen introduction into pool water, disinfection, turbulent diffusive transport, and pathogen uptake by swimmers to calculate the associated risk of illness. Model results were compared to U.S. Environmental Protection Agency (EPA) untreated recreational water acceptable gastrointestinal illness risk. For Cryptosporidium, correlation between log inactivation and Chick–Watson Ct was far better when C refers to HOCl concentration than to FC (r = −0.96 vs. −0.06). The HOCl concentration had a small variation (± 1.8%) at a constant CYA/FC ratio for typical FC and CYA ranges in swimming pools. In 27 U.S. states, the allowed FC and CYA results in HOCl concentrations spanning more than a factor of 500. Using conservative values for a high bather load pool with 2 mg/L FC and 90 mg/L CYA, the model predicted a 0.071 annual probability of infection for Giardia, exceeding the EPA regulatory 0.036 limit for untreated recreational waters. FC and CYA concentrations in swimming pools should be jointly regulated as a ratio. We recommend a maximum CYA/FC ratio of 20.

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A High-Radical-Yield Advanced Oxidation Process Coupling Far-UVC Radiation with Chlorinated Cyanurates for Micropollutant Degradation in Water

Zhao

Shang

Yin

2023

Environ. Sci. Technol.

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Increasing the radical yield and reducing energy consumption would enhance the sustainability and competitiveness of advanced oxidation processes (AOPs) for micropollutant degradation in water. We herein report a novel AOP coupling far-UVC radiation at 222 nm with chlorinated cyanurates (termed the UV222/Cl-cyanurates AOP) for radical generation and micropollutant abatement in water. We experimentally determined the concentrations of HO•, Cl•, and ClO• in the UV222/Cl-cyanurates AOP in deionized water and swimming pool water. The radical concentrations are 10–27 times and 4–13 times, respectively, higher than those in the UV254/Cl-cyanurates AOP and the well-documented UV254/chlorine AOP under comparable conditions (e.g., same UV fluence and oxidant dosing). We determined the molar absorption coefficients and innate quantum yields of two chlorine species and two Cl-cyanurates at 222 nm and incorporated these parameters into a kinetic model. The model enables accurate prediction of oxidant photodecay rates as well as the pH impact on radical generation in the UV222/Cl-cyanurates AOP. We predicted the pseudo-first-order degradation rate constants of 25 micropollutants in the UV222/Cl-cyanurates AOP and demonstrated that many micropollutants can be degraded by >80% with a low UV fluence of 25 mJ cm–2. This work advances the fundamental photochemistry of chlorine and Cl-cyanurates at 222 nm and offers a highly effective engineering tool in combating micropollutants in water where Cl-cyanurates are suitable to use.

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A Drinking Water Relevant Water Chemistry Model for the Free Chlorine and Cyanuric Acid System from 5°C to 35°C

Cited by 4 publications

References 20 publications

Chlorinated cyanurates in drinking water: Measurement bias, stability, and disinfectant byproduct formation

Chlorinated cyanurates in drinking water: Measurement bias, stability, and disinfectant byproduct formation

Assessing the Impact of Cyanuric Acid on Bather’s Risk of Gastrointestinal Illness at Swimming Pools

A High-Radical-Yield Advanced Oxidation Process Coupling Far-UVC Radiation with Chlorinated Cyanurates for Micropollutant Degradation in Water

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