System and method for measurement of chloramines

Abstract

A method and system for measurement of chloramine species concentrations in a chlorinated water system or reservoir and the air above the water reservoir in an indoor environment. Colorimetric methods in combination with a controlled and delayed reaction cascade of chlorine species reactions can be used to differentiate between chloramine speciation in chlorinated test water such that the trichloramine content in the water and air can be accurately determined, providing an indication of trichloramine concentration in the air in the indoor environment. Remediating measures can be taken based on the chlorine species concentration.

Description

SYSTEM AND METHOD FOR MEASUREMENT OF CHLORAMINESCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to United States provisional patent application US63 / 580,262 filed on 01 September 2023 , which is hereby incorporated by reference herein in its entirety.FIELD OF THE INVENTION

[0002] The present invention pertains to the measurement of chloramine species concentrations in water and air. The present invention also pertains to colorimetric methods of measuring concentration of chloramines in water in pools and other chlorinated water bodies.BACKGROUND

[0003] Recreational water systems such as swimming pools and spas most often use chlorinebased disinfection systems with chlorine chemical disinfectants usually in the form of sodium hypochlorite, or sodium chloride in the case of saltwater pools. Generally, both indoor and outdoor pools are treated with hypochlorous acid (HOC1) and / or hypochlorite, also referred to as active chlorine or free chlorine, which can convert into mono-, di-, and tri-chloramines upon reaction with amines (-NH, -NH2, or ammonia) in the pool water. Amines in indoor pool water generally originate from human body slough and body fluids, as well as from water-borne bacteria, algae, and other microorganisms. The addition of active chlorine to water causes sources of nitrogen in the water, such as urine, sweat, lotions, or ammonia-based cleaning agents, to form chloramines. These chlorinated compounds are often associated with unpleasant or irritating smell, itchy skin, and breathing complaints from the public, in particular in indoor pool areas with high levels of trichloramine in the air. Visitors and pool staff are exposed to chloramines through, for example, swimming, showering, breathing indoor air in treated areas, splash pads, and other spray features. Swimmer and staff safety is a major concern in recreational water systems, and increased levels of trichloramine in indoor environments can affect human health as well as cause corrosion to building and plumbing infrastructure, increasing energy costs for running heating, ventilation, and air conditioning (HVAC) systems, building and pool maintenance costs, and costs for increased liquid and air waste streams.

[0004] In chlorine-based water disinfection, hydrochlorous acid chlorine, and monochloramine are the most often used oxidant species for both primary and secondary water treatment. The chloramine disinfection by-product compounds (DBPs) of water treatment with chlorine species are the inorganic chloramines mono-, di-, and tri-chloramine, as well as organic chloramines, commonly referred to as combined chlorine, that can contain other DBPs. All of the inorganic chloramines are stable in water, however trichloramines are also highly volatile compounds and escape into the atmosphere via aerosolization, for example through splashing and surface disturbances in large, chlorinated water supplies such as pools. Trichloramines can thereby affect both air and water quality of indoor pools. The recommended maximum trichloramine guideline in various jurisdictions is 0.35 mg / m3of air.

[0005] Traditionally, to measure the amount of trichloramine in indoor pool air, air samples are collected at different heights around the pool deck. In this method, filters are connected to a calibrated air sampling pump, and the air is sampled at an appropriate flow rate for at least one hour and up to six hours. The filter is then sent to an accredited lab for analysis of trichloramines. Normal timing would include setting up filters around the pool deck and allowing absorption to take place during one to six hours of air flow going through the filter. A lab technician would then return to the site to collect the filters, which can be stored if analysis is delayed. To analyze the filters, the chlorides are brought into solution and then the solution samples are sent to for analysis, after which a calculation will happen incorporating the absorbed cubic meters of air to arrive at a trichloramine concentration in the air. The total regular process time from pool to lab analysis and reporting is typically about two weeks, by which time the air conditions in the pool will have changed. Local pool conditions are changing all the time, and inexpensive and frequent monitoring is required to maintain pools safe for people, both from a microbiological and a chemical perspective.

[0006] In one example of measuring the amount of free chlorine in a water supply, United States patent U9,746,451B2 to West et al. describes a method of determining a concentration of free chlorine (hypochlorous acid plus hypochlorite) in an aqueous sample using reaction kinetics by a reagent being reactive with free chlorine at a first kinetic rate and reactive with at least one chloramine at a second kinetic rate, measuring an absorbance response over time resulting from reaction of the free chlorine and the at least one chloramine with the reagent over time, anddetermining the concentration of the free chlorine in the sample based on a determined rate of change of the absorbance response over time.

[0007] Test strips and test kits are available for measuring free chlorine, total chlorine, bromine, total hardness, total alkalinity, cyanuric acid, and pH in pools, and regular monitoring of pools is recommended at least 3-4 times / day to maintain safe water conditions for swimmers. Test strips are an estimate of levels and cannot be relied on for accurate and precise measurement. However, these parameters can shift to unsafe levels quickly, and modem water sensors and measurement systems are recommended for regulatory monitoring and process control, especially in high use indoor pools, to enable safer and more sustainable standards for safe water supply for recreational water systems. The current regulatory standard is 0.5mg of trichloramine per cubic metre of air (L1Association frangaise de normalisation (AFNOR) rules integrated in France, Belgium, and the Netherlands) with more stringent standards coming into effect with the new Dutch swimming pool water regulations on 01 January 2024 that also requires the combined chlorine level to be below 0.6mg / l. The rest of the European Union will follow suit soon thereafter and will require a much tighter process profile for maintaining pool safety which conventional monitoring and control technology with tests strips and typical chemical test kits cannot achieve. In particular, new standards require chlorine and pH levels to be managed in such a way to reduce the amount of disinfection by-products, such as trihalomethanes and trichloramines, in water and indoor air, as well as comply with microbiological disinfection safety standards. Two standard DPD colorimetric methods generally recognized in the international community are the Standard Methods 4500-C1 G used in North America and International Organization for Standardization (ISO) Method 7393 / 2 adopted by most of the members of the European Union. New standards also introduce safety parameters around concentrations of chloride, nitrate, urea, chlorate, bromate, trichloramine, trihalomethane (as CHCh), total organic carbon (TOC), and ozone in pools and in the indoor air in a pool enclosure. The new standards also apply to reactivity and water properties, such as colour, oxidizability, transparency, and turbidity, and to acceptable levels of particular microbes such as, for example, enterococci, pseudomonas aeruginosa, sulfite reducing clostridia, staphylococcus aureus, and legionella. All of these species and extensive water properties will now have to be measured and reported at regular intervals in order to comply with updated health and safetystandards. In a public pool environment and other regulatory water quality environments, artifacts can creep into data through inaccurate grab samples, inaccurate or imprecise sensors, and outdated regulatory frameworks have ranges that are too wide to create the optimal safe and healthy pool. An optimized pool will enable more stringent standards with less total chlorine and disinfection by-products, optimal pH, optimal filtration, and optimal disinfection levels, optimizing and prioritizing human health and safety.

[0008] There remains a need for the rapid, accurate, and reliable measurement of the amount and species of chloramines in chlorinated water systems.

[0009] This background information is provided for the purpose of making known information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.SUMMARY OF THE INVENTION

[0010] An object of the present invention is to provide a rapid method and system to monitor and control chlorine and disinfection by-product disassociation species, which results in mitigation of disinfection by-products, reducing remediation costs, energy, water and chemical waste related to poor water and air quality control and ensures a safer aquatic environment.

[0011] In an aspect there is provided a colorimetric method of determining concentration of chloramine species in a chlorinated water reservoir, the method comprising: measuring the concentration of free available chlorine in the water reservoir; determining the concentration of free active chlorine in the water reservoir; measuring the concentration of monochloramine in the water reservoir; measuring the concentration of dichloramine in the water reservoir; and determining the concentration of trichloramine in the water reservoir.

[0012] In another aspect there is provided a method of determining concentration of chloramine species in a chlorinated water system, the method comprising: obtaining a water sample from a chlorinated water system; in a colorimeter, measuring a concentration of free available chlorine in the water sample; determining a concentration of free active chlorine in the water sample; in the colorimeter, after a delay time, measuring a concentration of monochloramine in the water sample; in the colorimeter, measuring a concentration of dichloramine in the water sample; and determining a concentration of trichloramine in the chlorinated water system.

[0013] In an embodiment, the colorimeter is an in-line colorimeter or a mobile colorimeter.

[0014] In another embodiment, the chlorinated water system comprises one or more pool, spa, hot tub, waterslide, lazy river, lap pool, and splash pad.

[0015] In another embodiment, determining the concentration of free active chlorine in the water sample comprises measuring pH of the water sample and comparing the measured free available chlorine concentration against a calibration curve to determine the concentration of free active chlorine.

[0016] In another embodiment, measuring pH of the water sample is done using a colorimeter with a pH sensitive indicator or a potentiometer.

[0017] In another embodiment, measuring the concentration of free available chlorine in the water sample comprises measuring the absorbance measurement of an instantaneous reaction of one or more of chlorine (Ch), hypochlorous acid (HOC1), and hypochlorite anion ( OC1) with N,N-di ethyl -p-pheny 1 enedi amine (DPD) .

[0018] In another embodiment, the delay time for measuring the concentration of monochloramine in the water sample is between about 15 seconds and 5 minutes.

[0019] In another embodiment, the method is performed in an automated system.

[0020] In another embodiment, the method further comprises calculating a concentration of total chlorine in the water sample.

[0021] In another embodiment, measuring a concentration of dichloramine in the water sample comprises measuring a reaction of dichloramine with a low concentration iodide and DPD.

[0022] In another embodiment, the steps of measuring the concentration of free available chlorine, measuring the concentration of monochloramine, and measuring the concentration of dichloramine in the water sample are done successively in different cuvettes in the colorimeter.

[0023] In another embodiment, the method further comprises dosing chlorine into the chlorinated water system when the concentration of free active chlorine is below a desired free active chlorine concentration threshold.

[0024] In another embodiment, at least one of the concentration of free active chlorine in the water, concentration of combined chlorine, and concentration of trichloramine coming out of the water in the air above the water reservoir is maintained in compliance with a safety or regulatory standard.

[0025] In another embodiment, the determined concentration of trichloramine in solution is indicative of an air concentration of trichloramine above the chlorinated water system.

[0026] In another embodiment, measuring the concentration of free active chlorine in the water reservoir comprises measuring pH and comparing the measured free available chlorine concentration against a calibration curve to determine the level of free active chlorine.

[0027] In another embodiment, measuring the concentration of free available chlorine in the water reservoir comprises measuring the concentration of total chlorine, determining the concentration of combined chlorine, which is the difference between the concentration of total chlorine and the concentration of free available chlorine in the water reservoir.

[0028] In another embodiment, the method further comprises calculating a concentration of total chlorine in the water reservoir.

[0029] In another aspect there is provided a system for determining a concentration of trichloramine in a chlorinated water system, comprising: a colorimeter for receiving a water sample from the chlorinated water system and measuring a concentration of free available chlorine in the water sample, a concentration of monochloramine in the water sample, and a concentration of dichloramine in the water sample; and a processor configured to determine a concentration of trichloramine in the water sample based the measured concentration of free available chlorine, measured concentration of monochloramine, and measured concentration of dichloramine in the water sample.

[0030] In an embodiment, the colorimeter is a dual cell colorimeter.

[0031] In another embodiment, the system is automated on site of the chlorinated water system.

[0032] In another embodiment, the colorimeter comprises a control system to control supply of reagents to a cuvette in the colorimeter.

[0033] In another embodiment, the processor predicts a concentration of tri chloramine in air above the chlorinated water system.

[0034] In another embodiment, the system further comprises a graphical user interface for reporting the concentration of trichloramine in the chlorinated water system.

[0035] Embodiments of the present invention as recited herein may be combined in any combination or permutation.BRIEF DESCRIPTION OF THE FIGURES

[0036] For a better understanding of the present invention, as well as other aspects and further features thereof, reference is made to the following description which is to be used in conjunction with the accompanying figures which illustrate embodiments or aspects of the invention, where:

[0037] Figure 1 illustrates a flowchart of chlorine species in a chlorinated water supply;

[0038] Figure 2A is a chemical equation showing the reaction of sodium hypochlorite with hydrogen chloride;

[0039] Figure 2B is a chemical equation showing the reaction of ammonia with chlorine;

[0040] Figure 2C is a set of equilibrium chemical reactions showing the formation of chloramines with ammonia;

[0041] Figure 3 is a graph of the ratio of HOC1 and OC1 based on pH;

[0042] Figure 4 illustrates the chemistry of the Wurster dye reaction with free active chlorine species;

[0043] Figure 5 is a schematic of one example system implementation of the present water measurement system;

[0044] Figure 6 is a schematic of another example system implementation of the present water measurement and control system with two colorimeters;

[0045] Figure 7 is a graph of concentrations of total chlorine, free chlorine, and combined chlorine over time as determined using the present method and system;

[0046] Figure 8 is a flowchart depicting a method as presently described;

[0047] Figure 9A is a graph of trichloramine results from a lap pool in a community centre;

[0048] Figure 9B is a graph of trichloramine results from a leisure pool in the community centre;

[0049] Figure 10A is a graph of tri chloramine results from a wave pool in a multi leisure pool complex;

[0050] Figure 10B is a graph of tri chloramine results from a lazy river in the multi leisure pool complex;

[0051] Figure 10C is a graph of tri chloramine results from an activity pool in the multi leisure pool complex; and

[0052] Figure 11 is a graphical user interface from the present system for measuring chloramines.DETAILED DESCRIPTION OF THE INVENTION

[0053] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Working examples provided herein are considered to be non-limiting and merely for purposes of illustration.

[0054] As used in the specification and claims, the singular forms “a”, “an” and “the” include plural references unless the context clearly dictates otherwise.

[0055] The term “comprise” and any of its derivatives (e.g. comprises, comprising) as used in this specification is to be taken to be inclusive of features to which it refers, and is not meant to exclude the presence of any additional features unless otherwise stated or implied. The term “comprising” as used herein will also be understood to mean that the list following is non- exhaustive and may or may not include any other additional suitable items, for example one or more further feature(s), component(s) and / or element(s) as appropriate.

[0056] As used herein, the terms “having,” “including” and “containing,” and grammatical variations thereof, are inclusive or open-ended and do not exclude additional, unrecited elements and / or method steps, and that that the list following is non-exhaustive and may or may not include any other additional suitable items, for example one or more further feature(s), component(s) and / or element(s) as appropriate. A composition, device, article, system, use, process, or method described herein as comprising certain elements and / or steps may also, in certain embodiments consist essentially of those elements and / or steps, and in other embodiments consist of those elements and / or steps and additional elements and / or steps, whether or not these embodiments are specifically referred to.

[0057] As used herein, the term “about” refers to an approximately + / - 10% variation from a given value. It is to be understood that such a variation is always included in any given value provided herein, whether or not it is specifically referred to. The recitation of ranges herein is intended to convey both the ranges and individual values falling within the ranges, to the same place value as the numerals used to denote the range, unless otherwise indicated herein.

[0058] The use of any examples or exemplary language, e.g. “such as”, “exemplary embodiment”, “illustrative embodiment" and “for example” is intended to illustrate or denote aspects, embodiments, variations, elements or features relating to the invention and not intended to limit the scope of the invention.

[0059] As used herein, the terms “connect” and “connected” refer to any direct or indirect physical association between elements or features of the present disclosure. Accordingly, these terms may be understood to denote elements or features that are partly or completely contained within one another, attached, coupled, disposed on, joined together, in communication with, operatively associated with, etc., even if there are other elements or features intervening between the elements or features described as being connected.

[0060] The term “chemical disinfectant” refers to any chemical additive to the water system that can reduce the microbial load in the water system. Chemical disinfectants include, for example, chlorine-based disinfectants, peroxide-based disinfectants, and peracetic acid

[0061] As used herein, the term “disinfection demand” refers to the amount of disinfectant required in the water system to maintain a healthy water supply with low microbial load. Disinfection demand can be measured in amount of disinfectant required over time, or can be understood by the disinfection setpoint, which is the concentration of disinfectant required by the system to maintain water integrity as calculated by the presently described system.

[0062] As used herein, the term “free available chlorine” is the combination of the total or concentration of hypochi orous acid and hypochlorite in the water. The free available chlorine can be measured and used together with the pH measurement and a calibration curve of the ratio of hypochlorous acid to hypochlorite based on pH to calculate the amount of free active chlorine in the water.

[0063] As used herein, the terms “free chlorine” and “free active chlorine” are understood to have a similar meaning, specifically the total concentration and ratio of hypochlorous acid (HOCI) and hypochlorite (CIO') in the water available for reaction, also referred to as the disinfectant capacity. Free chlorine is active as a disinfectant or sanitizer in the chlorinated water and reacts with amines to form inorganic chloramines and organic chloramines. The disinfectant capacity of chlorine species in the chlorinated water, which is dependent on the concentration of free active chlorine, can be determined from the measured concentration of free availablechlorine and the measured pH of the water. The concentration of free active chlorine should remain higher than the combined chlorine level to provide effective disinfection.

[0064] As used herein, the term “combined chlorine” is created when free chlorine oxidizes nitrogen-containing contaminants such as nitrogen and ammonia to form chloramines. In the process, the available chlorine is used up and becomes combined chlorine.

[0065] As used herein, the term “total chlorine” is the sum of the free chlorine and combined chlorine in the pool or water system.

[0066] Herein is described an effective method to measure concentration of chloramine species in a chlorinated water system and to determine the concentration of trichloramine from the water chemistry. The present system and method has been developed to perform rapid measurement of trichloramine levels in water and to extrapolate these measurements to the air quality of an indoor chlorinated recreational water systems with one or more pool, spa, hot tub, waterslide, lazy river, lap pool, and splash pad. The presently described method follows stoichiometric principles to provide both accurate and precise measurements of chloramine concentrations in air and water. In particular, by measuring concentrations of various chloramine species at specific and exact times subsequent to controlled reaction conditions, chloramine species in and around a chlorinated body of water or chlorinated water system can be measured quickly and accurately. Liquid reagents allow for immediate mixing into the test solution with accurate and precise reactions. In addition, a dual measurement chamber and specific cuvettes in the colorimeter allow for a calibrated measurement at the same time as the test measurement remove any background colour or interference, both contributing to an on-site and rapid field test that can help swimming pool safety and sustainability. Automation of the concentrations of free, total, and combined chlorine readings are also vital in the understanding and reduction of disinfection by-products associated with wasted energy, water and chemical costs, as well as health hazards for all pool stakeholders.

[0067] Figure 1 illustrates a flowchart of chlorine species in a chlorinated water supply. In general, free chlorine provides hypochlorous acid (HOC1) and its counter ion hypochlorite ( OC1) and upon reaction with chloride ion (CT) under acidic conditions produce chlorine (Ch), as shown in Equation (I) below and in Figure 2A.NaOCl + 2HC1 -> Cl2+ NaCl + H2O(I) sodium hydrogen chlorine sodium water hypochlorite chloride chloride

[0068] The concentration of free chlorine, or free active chlorine is dependent on the concentration of free available chlorine calibration against pH relative to a speciation curve or calibration curve. The amount or concentration of free active chlorine, or free chlorine, in the chlorinated water supply provides the disinfectant capacity of the chlorine in the system. Free (available) chlorine can also be understood as the discoloration comparison against a titrimetric obtained three-point calibrated curve. The concentration or amount of combined chlorine is equivalent to the total chlorine minus the free available chlorine. Chlorine, hypochlorite, and hypochlorous acid are reactive oxidative compounds that quickly react with ammonia as well as nitrogen containing organic molecules in water. Figure 2B is a chemical equation showing the reaction of ammonia with chlorine. Figure 2C is a set of equilibrium chemical reactions showing the formation of chloramines with ammonia. Chloramines, which are nitrogen-containing organic molecules, can originate from, for example, body fluids like perspiration and urine, exfoliates such as skin and hair, and from other non-human sources such as algae and microbiota. Reaction of free available chlorine with ammonia (NH3) forms chloramines (mono-, di-, and trichloramine).

[0069] Hypochlorous acid is a weak acid and will disassociate according to:HOC1 H++ OC1 (II)

[0070] Figure 3 is a graph of the ratio of HOC1 and OC1 based on pH. This graph is used to determine the concentration or ratio of free active chlorine based on the pH concentration in the amount of free available chlorine in the water system. Specifically, the amount of available chlorine is measured, the pH is measured independently, and based on these the concentration of free active chlorine can be determined. In waters with pH between 6.5 and 8.5, the reaction of both species (HOC1 and OC1) will be present, however at different concentrations based on pH. Without being bound by theory, it has been found that hypochlorous acid provides the more potent disinfectant activity and contributes more to the disinfectant capacity of the chlorine in the system compared with hypochlorite. The presence of monochloramine and dichloramine in achlorinated water supply generally do not cause human health issues or significantly impact water quality. However, by measuring the concentrations of monochloramine and dichloramine in the water supply, these results can be used as a means for the graduated measurement that gives insight into the quantity of the trichloramine concentration coming out of the water and into the air which causes human health and infrastructure degradation in indoor pools.

[0071] Organic chloramines are molecules that have at least one chlorine atom bonded to the amine nitrogen in an organic molecule also containing carbon. Nitrogen containing organic molecules in pool water originate from human and other biological sources such as microbiota and algae, and are generally found as proteins, amino acids, nucleic acids, and larger biological molecules. Some examples of organic chloramines which result from chlorine species oxidation of nitrogen containing organic molecules are N-Chloramines, N-Chloraldimines, N-Chloramino acids, and N-Chloramides. It is noted that many of the chlorinated organic by-products of chlorine-mediated disinfection have been found to be carcinogenic, and due to the near unlimited number of potential by-products, the vast majority of chlorinated by-products have unknown toxicity. Additionally, halogenated organic by-products can be persistent in nature and can further degrade into more toxic compounds once released into the environment. Limiting the amount of chlorine used for water disinfection reduces the formation of these chlorinated inorganic by-products during chlorine disinfection and also reduces the amount of chlorine additive required for disinfection, providing a cost benefit as well as an environmental benefit.

[0072] The present system and method is able to automatically monitor free chlorine, total chlorine, and pH in one automated system that has an ongoing monitoring unit and a control unit, digitally connected into the one automation system, and is able to adjust free available chlorine (FAC) levels based on the measured active and combined chlorine levels to achieve an optimal chemical state in a chlorinated body of water that produces less disinfection by-products and has lower associated health risks, lower environmental costs, and lower maintenance costs. The present system is able to monitor and sample multiple pools, providing reliable safety and compliance insight in line with strict and stringent safety regulatory standards, combining monitoring and regulatory compliance with process control to enable chlorine and pH to meet a tight prescriptive standard for water quality.

[0073] Determination of Concentrations of Various Chlorine Species in Water

[0074] In order to understand how much of the chlorine in the water and air is in the form of each of mono-, di-, and trichloramines, the present method can be used by measuring some species and approximating a quantification of trichloramine concentration based on measurement. Mono-chloramine is formed soon after free chlorine reaction with ammonia in a chlorinated water reservoir such as pool water. This reaction continues to form di-chloramine and then tri-chloramines in water. Based on comparison with direct measurement methods, the present method has been found to provide an accurate approximation of trichloramine levels using indirect measurement techniques, with the advantage of rapid, on-site results.

[0075] Provided herein is a method and system that can be used to determine the concentration of the various chlorine species in water over time. Specifically, the concentrations of total chlorine, free chlorine, monochloramine, dichloramine, and trichloramine were tested and reported. The total chloramine reaction and conversion of chlorine species in the reaction cascade with ammonia can be discovered and verified using the prescribed method to differentiate between chloramine speciation in the test water such that the trichloramine content in the water can be accurately deduced, providing an accurate prediction of the risk of trichloramine levels in the air in a closed environment. The reactions of chlorine with nitrogenous organic compounds has already happened and / or is happening in the pool or chlorinated water system. The presently described test does not delay the reactions, instead it is able to differentiate accurately what levels of each species is currently present in a sample of the total water chlorinated water supply so as to accurately predict the air quality and can also mitigate the chemical process to support a more favourable outcome. By separating the exact testing parameters of the chloramine reactions the present method and system can provide insight into the monochloramine, dichloramine, and trichloramine levels in the water reservoir.

[0076] Free Available Chlorine

[0077] Free available chlorine reacts instantly with DPD (N,N-diethyl-p-phenylenediamine) to form the colored Wurster dye radical, as shown in Figure 4. The concentration of free available chlorine (FAC), also referred to as free chlorine, is measured based on the colorimetric of reaction of chlorine (Ch), hypochlorous acid (HOC1), or hypochlorite anion ( OC1) with DPD. When DPD reacts with small amounts of chlorine at a near neutral pH, the Wurster dye is theprincipal oxidation product. At higher oxidant levels, the formation of the unstable colorless imine is favoured, resulting in apparent “fading” of the colored solution. The DPD Wurster dye color can be measured photometrically at wavelengths ranging from 490 to 555 nanometers (nm), and it is preferable that absorption measurements are made between 510 and 515 nm. To measure the concentration of FAC in a water sample the colorimeter is first flushed and a zero measurement is taken of the water without additives. This baseline measurement can also be done in two channels in a dual measurement chamber to calibrate the instrument, and to make allowance for any background colour of the water sample. This can also be done relative to the baseline in a digital photometric hand meter. After calibration the same or a new water sample is added to a FAC measurement cuvette in the chlorine measurement cuvette chamber. The same calibration cuvette can be used together with the chlorine species measurement cuvette. To measure the FAC concentration, 250 pL of Start reagent, l-2mL of sample test water, and 250 pL of DPD reagent are added to the cuvette while the cuvette is in the colorimeter and an immediate colorimetry reading is taken. Chlorine, hypochlorous acid, and hypochlorite anion are all strong oxidants and react with DPD instantaneously to create the Wurster dye radical. The DPD solution comprises between about 5-20mg / L EDTA, between 5-20mg / L hydrogen sulphate, or other similar acid, and between about 3 and 15g / L DPD powder. The Start reagent comprises phosphate buffer, and preferably a combination of disodium hydrogen phosphate and potassium dihydrogen-EDTA phosphate at a concentration of between about 0.5 and 150 g / L, between about 10 and 50 g / L, between 50 and 150g / L, or between 0.5 and lOg / L in aqueous solution. The Start reagent functions as a buffer in the test water to adjust the sample pH to a more acidic pH, for example between 6.2 and 6.5. The slightly acidic pH is preferred to quantitatively resolve the chloramine species. The colorimetric measurement taken immediately, Value A, illustrated in Table 1, is a result of the immediate reaction of free active chlorine species with DPD in the test water and is attributed to free chlorine in the test water. Based on the absorbance measurement the concentration of FAC in the water can then be determined, for example in mg / L or ppm, using a photometric system or colorimeter according to a standard lab calibrated curve that has been established by accurate and precise titrimetric measurements in the lab, using at least three calibration points. In one example the three-point calibration can be set using 0.52ppm, 1.02ppm, and 1.52 ppm FAC.

[0078] The concentration of hypochlorite to hypochi orous acid is highly dependent on pH, as shown in Figure 3. By measuring the pH in the water supply the ratio of OCFHOC1 can be determined, which can then be used to calculate the amount of each species in the system. The amount of “free active chlorine” measures the disinfectant capacity of the chlorine species based on the ratio of HOCF’OCl. The pH can be determined accurately, for example, in a colorimetric measurement with a pH sensitive indicator, or using a probe that creates a millivolt signal consisting of a potentiometer that measures the voltage difference between a glass electrode and a reference electrode and calculates the pH value, together with a pH electrode for completing the circuit. Calibration solutions can also be used to calibrate the pH probe or colorimeter. In one example calibration, before measuring the pH of a sample, a measurement is taken at two or more reference solutions of known pH values, for example at pH 4 and 7.

[0079] If the concentration of free available chlorine in the test water sample is high, the test water sample can be optionally diluted with chlorine and oxidant-free water in a known dilution factor to reduce the concentration of FAC and the colorimetric measurement can be taken. The total concentration of FAC in the test water can then be determined using the dilution factor. The test water from the FAC cuvette is used in the chlorine speciation cuvette in the photometric measurement chamber. The original calibration cuvette remains in the calibration channel of the digital colorimeter. This is to avoid cross contamination and artifacts. No further reagents are added, and the test solution value is observed.

[0080] Monochloramine

[0081] Monochloramine is also an oxidant, however, is not as strong as the FAC components chlorine, hypochlorous acid, and hypochlorite. As such, monochloramine reacts at a much slower rate with DPD than the FAC oxidants. In the test water, monochloramines are spontaneously released and detected in the DPD containing solution by the liberation of chlorine species over time, leaving nitrogen gasses as a reaction. At an appropriate pH as provided by the Start buffer reagent, monochloramine (NH2CI) reacts further with DPD after a delay time, with negligible reaction of dichloramine or trichloramine. Adding any other reagents at this time would interfere with subsequent speciation. Stabilizing the pH with buffer is essential is for measuring FAC, without which the following speciation steps cannot be completed accurately (see Fig. 2C). Thechange in colorimetric measurement value observed during the delay time can thereby be attributed to the reaction of monochloramine with DPD.

[0082] To measure the concentration of monochloramine in the water the reaction mixture created to measure the concentration of FAC, specifically the test water, DPD reagent, and Start reagent, are allowed to sit for a delay time in the chlorine speciation cuvette, after which the original FAC sample water is evaluated again. This is shown as Value B in Table 1. The delay time can be anywhere between, for example, 15 seconds and 5 minutes, or can be, for example, 30 seconds, 45 seconds, 1 minute, 90 seconds, or 2 minutes. The colorimetric measurement in the concentration of DPD reagent or absorbance of the test water is measured as Value B. The colour difference between the immediate FAC measurement (Value A) and the measurement after the delay time (Value B) is attributed to the concentration of monochloramine in the test water, and the difference in colour can be used to calculate the concentration of monochloramine can then be determined in mg / L or ppm using the same standard curve.

[0083] Dichloramine

[0084] To measure the concentration of dichloramine in solution a source of iodide is used. Iodide reactions can be carried out in a separate cuvette either in the same or different colorimeter to avoid interference. To encourage reaction of di chloramine with the DPD a source of iodide is added to a separate measurement cuvette. The water from the monochloramine cuvette can be added to this dedicated cuvette to detect dichloramine. It is not possible to use the same cuvette as iodide addition will contaminate and render an inaccurate monochloramine level. The iodide reacts with di chloramine to expel the chlorine and bring in place the iodine, by the chemical rule that a higher halogen expels the lower halogen out of the chemical bond in a substitution reaction. The concentration of iodide is small enough to only develop or react with the dichloramines in the solution.

[0085] In one example, a low concentration of iodide, or approximately 50 pL of 0.02- 0.08mL / 8mL of iodide is added to the specific dichloramine test water chlorine measurement cuvette, which, after a delay time, gives a dichloramine concentration value in the test water. The iodide can be added as a soluble salt in water, for example as potassium iodide, or sodium iodide, at concentrations between 0.02 and the 0.08 mg / 8ml. The delay time for reaction of dichloramine with iodide and subsequently with already present DPD can be anywhere between, for example,15 seconds and 5 minutes, or can be, for example, 30 seconds, 45 seconds, 1 minute, 90 seconds, or 2 minutes.

[0086] Once a designated amount of delay time has elapsed, the reaction of f with HNCh will be complete and all dichloramine will have reacted with the DPD in the test water. After the spontaneous value determination of monochloramine (Value B) the change in absorbance measurement at the DPD wavelength provides the measurement of dichloramine concentration in the test water, in the presence of the small amount of iodide. The colorimetric measurement (see Value C in Table 1) reflects the sum of the dichloramine + monochloramine + free chlorine present in the test water sample. The total amount of dichloramine in the test water sample can then be determined by subtracting Value B from Value C and comparing the difference in absorption to a standard curve. Mono- and di- chloramines are not an issue that impact water quality but can used as a means for the graduated measurement that gives insight into the quantity of the trichloramine concentration in the water, and coming out of the water into the air, as deduced and caused by and from the water quality based on concentrations of other chloramines.

[0087] Trichloramine

[0088] To determine the concentration of trichloramine in the test water a higher concentration of iodide of between about 0.15 mg / 8mL and 0.30 mg / 8mL added to the cuvette reacts with the remaining chlorine species to detect the amount of trichloramine in solution. The colorimetric measurement at Value D in Table 1 reflects the trichloramine + dichloramine + monochloramine + free chlorine present in the test water. The total amount of trichloramine in the test water can then be determined by subtracting Value C from Value D and comparing the difference in absorption to a standard curve. If trichloramine prediction is high, besides water chemistry and filtration adjustments, fresh air and / or HVAC adjustments can deal with the immediate issue to reduce trichloramine in air above the chlorinated water reservoir. The root causes of excess trichloramine can also be solved by improved water chemistry, filtration, and other process optimizations.

[0089] Total Chlorine

[0090] Total chlorine is measured by adding 0.2 and 0.4 ml of iodide solution in one measurement cuvette of 8ml immediately with or after the FAC reagents have been added. Theamount of combined chlorine is the sum of the free available chlorine and the total chlorine. The amount of combined chlorine is another important indicator for possible total disinfection byproducts in pools but does not provide specific quantifiable insight into chlorine speciation or air quality.

[0091] Table 1 : Chlorine Species Measurement

[0092] The present method for measuring all of the chloramine species can be done using a single digital colorimeter with one or multiple cuvettes, correct dosing, calibration and timing of the reagents alongside pH measurement, such as with a mobile colorimeter, or preferably with anonline or inline colorimeter. A dual cell colorimetry system with multiple cuvettes can also be used, where one of the measurement cells measures the free chlorine and chloramine concentration while also measuring the pH in the sample reservoir continuously, to provide the ratio of OCFHOCl in the water reservoir according to Figure 3, which is calculated on an ongoing basis. The other cell can measure the di and trichloramines or the total chlorine concentration, depending on the settings in the system, and can also calculate the combined chlorine level on an ongoing basis

[0093] Figure 5 is a schematic of one example system implementation of the present colorimetry system for measuring chloramines. The system in Figure 5 can be a fully automated system, or can comprise one or more mobile components whose measurement data is directed to the data analysis system 24 for analysis. Water measurement system 10 comprises a test water supply 28 for supplying sample water to a colorimetric apparatus 16. Colorimetric apparatus 16 has colorimetric test cells 26a, 26b, with a first colorimetric cell being dedicated to DPD- mediated colorimetric measurement and a second colorimetric cell dedicated to iodide-mediated colorimetric measurement. A control system on colorimetric apparatus 16 can control supply of reagents to a cuvette in colorimeter 20. A pH meter 22, can be a second colorimeter, potentiometer, or other device for accurately measuring pH. Data analysis system 24 receives colorimetric and pH data to interpret results.

[0094] Figure 6 is a schematic of another example system implementation of the present water measurement system with two colorimeters. In this setup the system can measure water from multiple chlorinated water reservoirs, or multiple locations in one or more chlorinated water reservoir. Water measurement system 10 comprises water reservoirs 12a, 12b, 12c and water reservoir pumps 14a, 14b, 14c for supplying sample water to one or more colorimetric apparatus 16a, 16b. In this system setup colorimetric apparatus 16a comprises an iodide cell for water monitoring, and colorimetric apparatus 16b comprises a DPD colorimetric cell for water monitoring and control. It is understood that the iodide cell and DPD cell may also be in the same colorimeter. A control system 18a on colorimetric apparatus 16a controls supply of reagents to a cuvette in colorimeter 20a, and a control system 18b on colorimetric apparatus 16b controls supply of reagents to a cuvette in colorimeter 20b. Data analysis system 24 receives colorimetric and pH data to interpret results, which can be output to a graphical user interface.

[0095] Figure 7 is a graph of concentrations of total chlorine, free chlorine, pH, and combined chlorine over time in a pool network as determined using the present method and system. There were fifteen-minute intervals between each reading in each pool. Calculations of the concentrations of all chlorine species were done and reported after each reading.

[0096] Figure 8 is a flowchart depicting a method of measuring chloramine in a chlorinated water reservoir or chlorinated water system as presently described. First a zero measurement is obtained of test water in colorimeter to determine baseline 102. The test water is then reacted with DPD and Start reagent to obtain colorimeter reading, and pH is used to calculate the free active chlorine concentration measurement 104 in the chlorinated water reservoir. Then the system waits for a delay time, and then obtains colorimeter reading to provide monochloramine measurement 106. Total reagent is then added to a separate and specific iodide cuvette, and filled with the previous test water from the free chlorine cuvette, the system waits a delay time, then obtains a colorimeter reading to provide dichloramine measurement 108. Total reagent is then added to the test water, wait a delay time, obtain colorimeter reading to provide trichloramine measurement 110. Finally, a trichloramine concentration measurement can be calculated 112.

[0097] Example 1 - Public Indoor Pool Testing for Chloramine Species

[0098] Two public pools were selected to conduct on site measurements of chloramine species. Water samples were collected from different locations of the pool, for example at the deck, shallow and deep ends. Water samples were taken 20-30 cm below the surface level to avoid any water-air interferences. The test procedure was carried out to measure mono-, di-, and trichloramines. Concentrations of chloramine species at a public pool were measured using the present method. The results are shown in Table 2 below.

[0099] Table 2: Chlorine speciation verification for Pool A

[0100] Based on the solution colorimetry results of the concentration of tri chloramine measured using the presently described method, a stoichiometric conversion using air flow was done to project the air concentration of tri chloramine at different locations above the pool. The projected results are shown in Table 3.

[0101] Table 3 : Projected Tri chloramine concentration in air for Pool A

[0102] An air filter was also positioned between the Main Pool and the Hot Tub above Pool A and air was pumped through the air filter for one hour during maintenance hours, at the same time as the water colorimetric analysis happened on deck (no guests) to measure trichloramine level in the air using the standard air flow method. The second reading was taken on the pool deck between the lifeguard station and the shallow end. The results are shown in Table 4.

[0103] Table 4: Trichloramine concentration measured using a standard air flow method for Pool A

[0104] The combined chlorine or chloramine concentrations were below 0.5 mg / L in the water tested. The Shallow Area had a tri chloramine concentration of 0.13 mg / L at the surface. This amount was slightly higher than the air quality reading of 0.11 mg / m3of air, which could be due to the slight difference in sampling location. The pool water quality measurements were taken from about 20 cm below the surface area. Both the air and water quality tests for trichloramine were conducted at the quietest time of the swimming pool (no swimmers). A significantly higher concentration of trichloramine is expected during the busy times (evenings and weekends) and season (summer).

[0105] Table 5: Chlorine speciation verification for Pool B

[0106] To measure tri chloramine levels in the air above pool B an air filter was positioned at multiple locations and air pumped through filter for 2-4 hours during normal guest occupancy.

[0107] Table 6: Trichloramine concentration measured using a standard air flow method forPool B

[0108] The water quality data of mono-, di-, tri chloramines also closely aligned with the trichloramine air filter data. Overall, the water quality tests for chloramine using a colorimeter provided an accurate and fast indication of trichloramine levels in the air. Pool operators could potentially use this test as a rapid way to understand trichloramine issues in pool water and how to reduce them. Air filter tests are costly, take time (approximately seven to ten workdays) and will not enable pools to make process changes in a timely fashion.

[0109] Example 2: Trichloramine Estimation / Prediction in a Community Centre Pool Complex

[0110] The community centre is an older aquatic facility with a 25 metre lap pool and leisure pool in Ontario, Canada. The community centre has a sub-optimal HVAC system that typically runs at 15% of capacity due to functional life degradation. The pools in the community centre have a high bather load, with between 500 and 700 guests daily, and operate between 5 AM and 10 PM. The pools historically had severe air quality issues with frequent guest complaints. The presently described method and system for trichloramine detection and prediction was used to measure the concentration of chloramines in water and to predict or estimate the concentration oftrichloramine in the water and surrounding air. The development of a predictor tool for predicting trichloramine concentration using the present method has allowed rapid insight and resolution of the sub-optimal treatment systems and water chemistry. Results of the predictor tool are shown in Examples 2 and 3. In response to data obtained using the predictor tool in the present system, the community centre started actively adjusting water chemistry and filtration backwash to ensure the water and air quality remained safe and comfortable for guests. Testing for trichloramine provides a tool for indicating that the pool conditions require attention by adjusting the water chemistry and cleaning and / or backwashing the filtration system to ensure the water and subsequent air quality improves.

[0111] Figure 9A is a graph of tri chloramine results from a lap pool in a community centre and Figure 9B is a graph of trichloramine results from a leisure pool in the community centre. The trichloramine predictor tool continuously tracks, predicts, and manages water and air quality, keeping the levels below 0.35mg. At time points T1 and T2 in Figure 9A, trichloramine spikes are detected and addressed immediately by ensuring the chemistry is controlled to stop the development of tri chloramines and the filter backwashing procedure is adjusted. It can be seen that as a result of changing pool treatment methods there is a rapid reduction in trichloramines, well below the 0.35mg / L levels in the water and subsequently supporting good air quality. The long-term use of predictive analytics allows for a general downward trend, even amid the busiest summer programming.

[0112] Example 3: Trichloramine Prediction in a Multi Leisure Pool Complex

[0113] Multi leisure pool complex in Ontario, Canada, has multiple pools (8) with a high daily attendance of between 1500 and 2000 people. Historically, the complex had been diluting the water in the pools with freshwater to manage such a high bather load. They also would bring in laboratories to measure air quality to ensure they met the 0.35mg / m3standard or less every three months. The complex moved to use the presently described pro-active test method and trichloramine predictor tool, which provides much more frequent insight into the operational parameters of all of the pools and rapidly identifies possible trichloramine risk coming from each pool.

[0114] Data is provided for three of the pools in the complex, where figure 10A is a graph of tri chloramine results from a wave pool in a multi leisure pool complex, figure 10B is a graph oftri chloramine results from a lazy river in the multi leisure pool complex, and figure IOC is a graph of trichloramine results from an activity pool in the multi leisure pool complex.

[0115] The complex implemented the present system and method into their Wave Pool, Lazy River, and Activity Pool to track, predict, and manage water and air quality and to reduce freshwater make-up. Since the complex started to use the present system they have also begun to evaluate freshwater makeup and are now making adjustments to both the water treatment process and the amount of freshwater added to the process. Use of the present system after introduction of rapid and on-site measurement of trichloramine has resulted in a significant reduction in use of intake water as pool maintenance systems are being engaged earlier to reduce chlorine levels when they get high. As a result of the use of the present system and method the complex is saving money using rapid testing to obtain better operational process control of their pools and is also reducing their excess water makeup.

[0116] Figure 11 is a graphical user interface from the present system for measuring chloramines. In a graphical user interface is reported the concentrations of free chlorine, free chlorine extended, initial total chlorine, total chlorine, monochloramine, dichloramine, and trichloramine. Alert warnings can be provided in the graphical user interface as shown to indicate borderline or unsafe levels of any species in the system. This graphical user interface allows for automated chloramine method application, speciation, and dilution calculations and reporting for water management.

[0117] All publications, patents and patent applications mentioned in this specification are indicative of the level of skill of those skilled in the art to which this invention pertains and are herein incorporated by reference. The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that such prior art forms part of the common general knowledge.

[0118] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

Claims

CLAIMS:

1. A method of determining concentration of chloramine species in a chlorinated water system, the method comprising: obtaining a water sample from a chlorinated water system; in a colorimeter, measuring a concentration of free available chlorine in the water sample; determining a concentration of free active chlorine in the water sample; in the colorimeter, after a delay time, measuring a concentration of monochloramine in the water sample; in the colorimeter, measuring a concentration of dichloramine in the water sample; and determining a concentration of trichloramine in the chlorinated water system.

2. The method of claim 1, wherein the colorimeter is an in-line colorimeter or a mobile colorimeter.

3. The method of claim 1 or 2, wherein the determined concentration of tri chloramine is indicative of an air concentration of trichloramine above the chlorinated water system.

4. The method of any one of claims 1-3, wherein the chlorinated water system comprises one or more pool, spa, hot tub, waterslide, lazy river, lap pool, and splash pad.

5. The method of any one of claims 1-4, wherein determining the concentration of free active chlorine in the water sample comprises measuring pH of the water sample and comparing the measured free available chlorine concentration against a calibration curve to determine the concentration of free active chlorine.

6. The method of claim 5, wherein measuring pH of the water sample is done using a colorimeter with a pH sensitive indicator or a potentiometer.

7. The method of any one of claims 1-6, wherein measuring the concentration of free available chlorine in the water sample comprises measuring the absorbance measurement of an instantaneous reaction of one or more of chlorine (Ch), hypochlorous acid (H0C1), and hypochlorite anion ( OC1) with N,N-diethyl-p-phenylenediamine (DPD).

8. The method of any one of claims 1-7, wherein the delay time for measuring the concentration of monochloramine in the water sample is between about 15 seconds and 5 minutes.

9. The method of any one of claims 1-8, wherein the method is performed in an automated system.

10. The method of any one of claims 1-9, further comprising calculating a concentration of total chlorine in the water sample.

11. The method of any one of claims 1-10, wherein measuring a concentration of dichloramine in the water sample comprises measuring a reaction of dichloramine with a low concentration iodide and DPD.

12. The method of any one of claims 1-11, wherein the steps of measuring the concentration of free available chlorine, measuring the concentration of monochloramine, and measuring the concentration of dichloramine in the water sample are done successively in different cuvettes in the colorimeter.

13. The method of any one of claims 1-12, further comprising dosing chlorine into the chlorinated water system when the concentration of free active chlorine is below a desired free active chlorine concentration threshold.

14. The method of any one of claims 1-13, wherein at least one of the concentration of free active chlorine in the water, concentration of combined chlorine, and concentration oftrichloramine coming out of the water in the air above the water reservoir is maintained in compliance with a safety or regulatory standard.

15. A system for determining a concentration of trichloramine in a chlorinated water system, comprising: a colorimeter for receiving a water sample from the chlorinated water system and measuring a concentration of free available chlorine in the water sample, a concentration of monochloramine in the water sample, and a concentration of dichloramine in the water sample; and a processor configured to determine a concentration of trichloramine in the water sample based the measured concentration of free available chlorine, measured concentration of monochloramine, and measured concentration of dichloramine in the water sample.

16. The system of claim 15, wherein the colorimeter is a dual cell colorimeter.

17. The system of claim 15 or 16, wherein the system is automated on site of the chlorinated water system.

18. The system of any one of claims 15-17, wherein the colorimeter comprises a control system to control supply of reagents to a cuvette in the colorimeter.

19. The system of any one of claims 15-18, wherein the processor predicts a concentration of trichloramine in air above the chlorinated water system.

20. The system of any one of claims 15-19, further comprising a graphical user interface for reporting the concentration of trichloramine in the chlorinated water system.

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