CROSS REFERENCE TO RELATED APPLICATIONS

[0001 ] This application claims the benefit of United States Provisional Patent

Application No. 62/522,662 filed on June 20, 2017, incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

[0002] The present invention pertains to a dark water disinfection and quality control system. The present system and method are directed to the measurement and control of disinfectant concentration in dark water and dark water systems.

BACKGROUND

[0003] Tools for accurate and precise measurement of water quality and added disinfectants are very important for proving the end to end integrity of water safety and quality in a water distribution network. With emerging contaminants and pathogens, the need for more sustainable and effective water treatment and water quality control systems has become paramount.

[0004] Dark water is water that contains dissolved and/or suspended solids, causing turbidity and discolouration. Matrix effects in the dark water, in particular the properties of the water caused by the presence, identity and amount of components contained or dissolved in the water other than water, can cause a change in the look or chemical behaviour of the water. Matrix effects can include but are not limited to: colour, amounts and types of dissolved metals and minerals, total suspended solids, and total dissolved solids. Dark water can be process or raw water with a distinct discolouration, for example greater than 30 TCU (True Colour Units), or have detectable turbidity, which is the cloudiness or haziness of a fluid caused by high concentration of dispersed or suspended particles. Turbidity and discolouration in water confers completely different water matrix effects compared to clean water used for drinking water, and challenges can arise in measuring the concentration of disinfectant in dark water systems. Dark water can further contain high levels of total organic carbon (TOC) resulting from decaying vegetation, bacterial growth, and metabolic activities of living organisms or chemicals. Algal blooms and bacterial growth can also increase the TOC of dark water and make disinfection of water more difficult.

[0005] Chlorination is the most common disinfection method for water. In one example,

United States patent 9,593,026 to Boal et al. describes the use of a combination of chlorine- based oxidant solution and UV light for destroying organic contaminants in a fluid. However chlorine reduction or replacement has become a priority due to the carcinogenic by-products of chemical chlorination of organic compounds. Chlorination also becomes a less and less acceptable solution with increased organic content in the water and deterioration of raw water quality because when raw water has organic content, disinfection through

chlorination may generate high levels of disinfection by-products resulting in an unpleasant taste and odour. In addition, disinfection by-products of chlorination include trihalomethanes and haloacetic acids, which are known or potential carcinogens and there is no known threshold concentration under which these disinfection by-products are completely safe.

[0006] Bacterial disinfection of water can also be performed using ultraviolet (UV) lamps alone. In an example, United States patent 9,260,323 to Boodaghians et al. describes a UV light emitting diode (LED) water treatment device that can treat water at its point of use.

However, in dark water system containing water with low transparency and high turbidity, large amounts of energy is required for UV light to penetrate the water to achieve adequate disinfection. [0007] Certain new generations of hydrogen peroxide that are better stabilized, such as stabilized hydrogen peroxides (SH Ps) have been shown to be more effective than native hydrogen peroxides (NH P) with respect to disinfectant capacity and biofilm control. SH Ps have even been shown to rival chlorine in efficacy, at like for like concentrations, in the lab and more importantly in the field. SH Ps can remain residual in non-ideal water matrices such as dark water, however accurately measuring the hydrogen peroxide residual in dark water can be challenging within a process environment. Tools for accurate and precise measurement of water quality and disinfectants are very important for proving the end to end integrity of the water distribution network for water safety and quality.

[0008] While it may be possible to use other methods for in-line peroxide concentration measurement such as ion-selective probes, these methods generally require frequent or constant re-calibration through colorimetric or laboratory means. Measurement of disinfectant concentrations in water is traditionally done via a manual, semi quantitative means such a test strip, whereby the user would only achieve a semi-quantitative estimate. Handheld

measurement devices are also available, however these require periodic checking by a person. To maintain reliable water quality, disinfectant concentration measurements must be done consistently and on a near real time basis, preferably in-line and with ongoing control.

Continuous monitoring systems also enable operators to quickly determine if and when water network integrity has become compromised and timely react. Accordingly, there remains a need for an effective and reliable in-line method and system for accurate and continuous measurement and control of water integrity in dark 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 system and method for disinfecting dark water having a dilution pump to dilute a dark water supply, and an colorimetric analytical apparatus for measuring the amount of disinfectant in the diluted sample. A disinfectant reservoir pumps adds disinfectant to the dark water supply in response to the colorimetric measurement obtained from the measurement cell to maintain the disinfectant in the dark water at appropriate levels.

[001 1 ] In an aspect there is provided a system for disinfecting dark water, the system comprising: a dilution pump connected to a clear water supply and a dark water supply; an analytical apparatus comprising: a colorimetric measurement cell; a reagent reservoir; a reagent valve fluidly connected to the reagent reservoir; a controller comprising a processor and a memory; a disinfectant reservoir; and a disinfectant pump in fluid connection with the dark water supply to add disinfectant from the disinfectant reservoir to the dark water supply in response to the colorimetric measurement obtained from the measurement cell.

[0012] In another aspect there is provided a system for disinfecting dark water, the system comprising: a dilution pump connected to a clear water supply and a dark water supply for diluting the dark water at a dilution ratio; an analytical apparatus comprising: a colorimetric measurement cell comprising a measuring chamber, light transmitter, and light receiver, the colorimetric measurement cell for obtaining a colorimetric measurement of disinfectant concentration in the diluted dark water; a reagent valve fluidly connecting a reagent reservoir and the colorimetric measurement cell; a controller comprising a processor and a memory, the controller for controlling the reagent valve and colorimetric measurement cell; and a disinfectant reservoir in fluid connection with the dark water supply to supply disinfectant to the dark water supply in response to the colorimetric measurement of disinfectant

concentration in the diluted dark water. [0013] In an embodiment, of the system, the disinfectant reservoir comprises hydrogen peroxide. In another embodiment, the hydrogen peroxide is stabilized hydrogen peroxide.

[0014] In another embodiment, the system is a closed system, and the dark water supply is in continuous circulation. In another embodiment, the clear water supply comprises a clear water reservoir. In another embodiment, the dark water supply comprises a dark water reservoir. In another embodiment, the dosing pump is a dual-headed peristaltic dosing pump.

[0015] In another aspect there is provided a method for disinfecting dark water, the method comprising: calculating a dilution ratio of the dark water; diluting dark water from a dark water supply with clear water by the calculated dilution ratio to obtain a diluted sample; measuring a residual amount of disinfectant in the diluted sample; calculating an amount of disinfectant to add to the dark water supply to disinfect the dark water based on the dilution ratio and measured amount of residual disinfectant in the diluted sample; adding the calculated amount of disinfectant to the dark water to disinfect the dark water.

[0016] In an embodiment, the dark water is in a circulating water system. In another embodiment, the method is carried out periodically and continuously, every few seconds or every few minutes. In another embodiment, the dilution ratio of dark water to clean water is between 1 :1 and 1 :20. In another embodiment, the method further comprises measuring colorimetric transmittance of dark water in a dark water supply. In another embodiment, the method further comprises automatically calculating the dilution ratio based on the

transmittance measurement in the colorimetric measurement cell.

[001 7] In another embodiment of the method, the dark water is from a food processing facility, agricultural runoff, greenhouse irrigation water, water used for fluming fruits and vegetables, sewage treatment facility, storm water reservoir, water treatment system, lake, pond, dam, river, artificial reservoir, municipal waste water, or industrial waste water from food processing. [0018] In another embodiment of the method, the disinfectant is stabilized hydrogen peroxide.

BRIEF DESCRI PTION OF THE FIGURES

[0019] For a better understanding of the present invention, as well as other aspects an further features thereof, reference is made to the following description which is to be used in conjunction with the accompanying drawings, where:

[0020] Figure 1 is a schematic of a dark water disinfection system;

[0021 ] Figure 2 is a schematic of a dark water disinfection system with reservoirs;

[0022] Figure 3 is an image of an analytical apparatus for determining the

concentration of residual disinfectant in a diluted dark water sample;

[0023] Figure 4 is a close up image of the colorimetric measurement cell and buffer jar

[0024] Figure 5A is a close up of the measurement cell;

[0025] Figure 5B is a close up of fluid flow into the measurement cell;

[0026] Figure 6 is a block schematic of the analytical apparatus;

[0027] Figure 7 is a user interface reporting system status; and

[0028] Figure 8 is a graph of the peroxide concentration in a dark water system.

DETAILED DESCRI PTION OF THE INVENTION

[0029] 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. [0030] As used in the specification and claims, the singular forms "a", "an" and "the" include plural references unless the context clearly dictates otherwise.

[0031 ] The term "comprising" as used herein will 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.

[0032] 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.

[0033] The use of examples or exemplary language, e.g. "such as", "exemplary embodiment", and "for example" is intended to illustrate or denote aspects, embodiments, variations, elements or features of the invention and not intended to limit the scope of the invention.

[0034] The term "dark water" as used herein refers to water containing dissolved and/or suspended solids. The dissolved and/or suspended solids cause matrix effects in the dark water such as turbidity and discolouration. Dark water can be found, for example, in food processing facilities, agricultural runoff, greenhouse irrigation water, water used for fluming fruits and vegetables, sewage treatment facilities, storm water reservoirs and treatment systems, lakes, ponds, dams, rivers, artificial reservoirs, municipal waste water, and industrial waste water from food processing, mining, tailings ponds, and other industries.

[0035] The term "disinfectant" as used herein refers to an antimicrobial or

antibiological agent that is added to water. Preferable disinfectants for use with the present system and method are hydrogen peroxide (H2O2) and stabilized hydrogen peroxide. Other disinfectants may be used, however, such as but not limited to chlorine, ozone, and other oxidizing agents. Peroxide will be referred to herein as the disinfectant, however it is understood that other disinfectants may be used with corresponding colorimetric reagents. [0036] The term "stabilized hydrogen peroxide" (SH P) as used herein refers to a solution of hydrogen peroxide in water comprising a stabilizer. A variety of stabilizers can be used, such as, for example, low concentrations of metal ions such as copper or silver. One preferable stabilizer is silver ions or silver colloid in minute concentrations used for water disinfection, an example of which is HUWA-SAN™ manufactured by Roam Technology NV of Houthalen, Belgium which contains 0.013-0.01 7% ionic silver. Depending on the solution, the silver prevents the hydrogen peroxide from oxidizing too quickly when it contacts water, thereby allowing the solution to mix with the water before binding to and disinfecting undesirable microorganisms and chemicals. Other stabilizers may also be added, such as low concentrations of organic compounds. Preferable stabilized hydrogen peroxide solutions are stabilized by silver ions or silver colloid, also known as oligodynamic silver, in minute concentrations. Drinking water disinfection using hydrogen peroxide and silver has been approved by jurisdictions worldwide including the United States Environmental Protection Agency (USEPA), the Drinking Water I nspectorate (DWI) in the United Kingdom, the Ontario Ministry of the Environment, and by health authorities in Australia, among others.

[0037] The present system and method are directed to the measurement and control of disinfectant concentration in dark water and dark water systems. The present system and method make it possible to measure disinfectant and peroxide residual in water not only for raw or treated water of drinking water quality, but also process water. An in-line automated colorimetric measurement apparatus, or analytical apparatus, allows for continuous

measurement of disinfectant within the process water matrix. Water in the present systems can carry a disinfectant residual, such as, for example, H ₂ O ₂ or SH P. Together, this system with the apparatus provide in situ control, automatically and continuously sampling disinfectant concentration residual in the water. Accurate measurement and control of disinfectant residual is therefore provided by the present in-line colorimetric apparatus and system in a greatly extended scope of water matrixes and within the matrix effects of real world process water. [0038] The present system can be used in circulating as well as non-circulating water systems. Some non-limiting examples of circulating water systems can include swimming pools, spas, greenhouses, ballast water, heating ventilation and air conditioning (HVAC) systems, and municipal reservoirs. Non-circulating systems wherein some or all of the water in the system is shunted for disposal can include, for example, municipal water systems, home water systems, building water systems, industrial water systems, and water systems in transportation vehicles such as aircraft, trains, ships and boats.

[0039] Figure 1 is a schematic of a dark water disinfection system 10. Process water is obtained from a process water inlet 12, which can be a reservoir or supply line or tap in a circulating water system. Sample process water is extracted or tapped from the water matrix of interest, preferably at a point within a process reservoir or at the end of a supply line where the peroxide or disinfectant residual would be lowest due to water use conditions. Process water obtained from the water inlet 12 is preferably pressurized, or alternatively the process water is pressurized using an additional pump (not shown) such that process water flows under pressure through the system. A flow diverter 14 diverts a small fraction of the process water from the process water inlet 12 to the dilution pump 20 and the bulk of the process water is directed downstream to a flow meter 16. For example, preferably 1 -20%, or more preferably 1 -10% of the process water is shunted through the dilution pump 20, and the remainder is directed to the process water outlet 30. The flow meter 16 measures the pressure and volume of the bulk of the process water flow through the system to provide an additional flow control feedback that the system is pressurized and working adequately.

[0040] An additional optional flow sensor can be situated between dilution pump 20 and dilute water flow diverter 22 to ensure that water is flowing in the system. Another optional flow sensor can be situated between flow diverter 14 and dilution pump 20 to ensure flow of process water into the dilution pump. This network of flow meters provides additional confirmation that accurate measurements of diluted sample water are flowing through and being measured in analytical apparatus 24. Should any of the flow sensors detect lack of water flow this can signal to the analytical apparatus not to take a measurement and stop the controller which controls the disinfectant pump.

[0041 ] Clear water from a clear water inlet 18 can be supplied from a clear water reservoir or inlet pipe. Residual additives to the clear water such as chlorine are preferably removed from the clear water, for example via filtration, deionization or distillation, prior to entering the system so that such additives do not influence the peroxide or disinfectant residual measurement in the process water.

[0042] Clear water and process water are received into dilution pump 20 for mixing.

The dilution pump 20 dilutes the dark process water shunted from the flow diverter 14 with clear water from the clear water inlet 18 to an acceptable dilution ratio such that the analytical apparatus can obtain an accurate measurement of disinfectant in the diluted process water sample. The turbidity and colour of the dark water entering dilution pump 20 is analysed by turbidity and/or colour measurement sensors and the dilution factor is calculated based on the matrix of the dark water being sampled. Dark water with more turbidity and/or colouration generally needs greater dilution than water with lower turbidity and colouration. Adjustment of the dilution pump can be done using a dilution pump controller and adjustable solenoid valves, for example. The dilution pump 20 can be a dual headed pump, or can be two separate pumps, independently controlled, to provide the desired dilution factor and therefore acceptable transmittance in the measurement cell in the analytical apparatus 24. Alternatively, the dilution pump can comprise at least one servo-driven pump that is capable of adjusting the ratio of the dilution of dark water at different levels depending on the cofactors of turbidity, colour, or turbidity and colour, as represented by the null value. A servo-driven dilution pump can be controlled by input from turbidity and/or colour measurement sensors, i.e. the cell null value, to provide an appropriate dilution for the dark water. Any other known ratio systems, or variants thereof, could also be employed for process water dilution via dilution pump 20. In one method, pressure regulation by opening up pressure regulators of different flow speeds can be adjusted to provide the desired ratio. Other automated flow devices can also provide different mixing flow rates. In one example, the dilution pump is a fixed, dual-headed, peristaltic pump and the dilution pump 20 sets the ratio based on the sizes of tubes utilized in the peristaltic pump. Alternatively, other pump types and combinations can be used to quantitatively mix the dark process water with the clear water in the desired ratio. The dilution factor is then used to calculate the actual disinfectant concentration in the undiluted dark water, which then dictates the required dose of disinfectant for maintaining water integrity.

[0043] Acceptable dilution ranges can also be dependent on the amount of disinfectant in the process water. While cleaner process water would perhaps only need 1 :1 dilution to attain accurate readings using the colorimetric principle of the analytical apparatus, for dark water systems which the present system is capable of servicing and maintaining adequate peroxide disinfectant levels, greater dilution is generally required to dilute the coloured and turbid components from the water for accurate analysis. For example, where high residuals exist (50-200ppm) in the process water, dilution rates can be at a higher range of, for example,

10:1 to 20:1 . Measurements within systems requiring higher disinfectant residuals, such as peroxide, greatly increases in particular in the upper measurement range of the analytical apparatus with appropriate dilution. This is because with a high residual, the dilution factor can be greater and the concentration of peroxide or other disinfectant can still measured accurately. When lower residual concentrations of peroxide are desirable in the system, the dilution ratio may be limited due to the minimum concentration of peroxide or disinfectant that can be measured accurately by the analytical apparatus. If the dark water has higher colour and/or turbidity, the dilution factor must be higher to enable accurate measurement at the measurement cell. In one lower limit example, if the process water has very high

colour/turbidity and very low desired H2O2 residuals, for example less than 5 ppm, a high dilution value of, for example 10:1 , would be required to make the water readable in the system. This would also contribute to a very low H2O2 residual, such as from 5ppm undiluted to 0.5ppm at the measurement cell. The dilution ratio of clear water to dark water can therefore range from, for example, 1 :1 to 20:1 or higher. Preferably the ratio of clear water to dark water is between 5:1 and 10:1 , most preferably about 8:1 . An automatic adjustment of the dilution ratio can also be done by measuring the turbidity and/or colouration and calculating a dilution radio based on the quality of the process water. Turbidity is the cloudiness or haziness of a fluid caused by suspended solids often invisible to the naked eye. Turbidity is an important determinant of water quality and is often measured in nephelometric turbidity units (NTU) using a nephelometer or turbidimeter. Turbidity is a measure of the intensity of light scattered as a beam of light passes through a water sample. Colour in water is an indication of dissolved solids or contaminants in water. Colour in water is measured by total colour units (TCUs) or absolute colour units (ACUs) using a colorimeter. An in-line turbidimeter and/or colorimeter in the present system can allow for automatic and regular in-line measurements of the system water turbidity and automatic dilution adjustment for water entering the analytical apparatus 24. The null measurement taken in the measurement cell of the apparatus with dark water only can also be used as an output value to serve as an input value to an automated type of ratio system, whereby if the water were becoming too dark, the ratio of clear water to process water (dark water) could be increased to a certain specified limit such that accurate analysis can be obtained. One or more controllers can be used to control the dilution pump(s), the analytical apparatus, and the dosing pump(s). Data to the controller can come from multiple sources in the system, including from one or more flow meters, the dilution pump(s), dosing pump(s), and from the analytical apparatus. Measurements of concentration of adenosine triphosphate (ATP) can also provide an indication of microbiological load in the system, and can be done by extracting sample water from the system or in-line using an in-line ATP measurement system. ATP measurement systems may also be sensitive to colour and turbidity during measurement and may also benefit from controlled dilution to provide an extrapolated concentration of ATP in the undiluted dark water. In a system with an in-line ATP measurement apparatus, diluted dark water with known dilution downstream the dilution pump can be directed to the in-line ATP measurement apparatus to provide a reading of ATP concentration in the diluted dark water.

[0044] In practice, the light transmittance at a particular wavelength of the diluted dark water is measured using LED transmittance, where the wavelength corresponds to the transmittance wavelength of the reagent. At this wavelength the null value or null

measurement provides a baseline transmittance at the particular wavelength, which is then subtracted from the transmittance of the same diluted sample in the presence of reagent. This provides a measurement of the concentration of disinfectant in the diluted dark water. When the disinfectant is hydrogen peroxide, the transmittance wavelength is approximately 400 nm when the reagent is potassium bis (oxalato) oxotitanate (IV) Dl. Different pairs of wavelength and reagent can be used for reagents with different colour transmittances.

[0045] Diluted dark water, also referred to as diluted sample water, is then directed to dilute water flow diverter 22. Dilute water flow diverter 22 preferably has a continuous flow of diluted sample water through it such that a sample can be diverted to the analytical apparatus 24 at any time for measurement of disinfectant concentration. The dilute water flow diverter 22 can be, for example a buffer jar which serves as a reservoir continuously replenished with diluted sample water and an overflow tube returning diluted sample water to process water outlet 30. Diluted sample water for analysis is directed from flow diverter 22 to analytical apparatus 24 for colorimetric measurement of disinfectant concentration in a measurement cell. After analysis, sample containing reagent is directed for disposal 32. Calculation of the amount of disinfectant in the diluted sample water with the known dilution factor applied at the dilution pump 20 provides a measurement of the total concentration of disinfectant in the dark process water. Control of the peroxide residual in the dark process water can be done via electronic or electrical signal to a dosing pump 26 capable of adding peroxide to the process water from disinfectant supply 28 based on the measurement taken at the analytical apparatus 24. Dosing pump 26 can add disinfectant at a rate of, for example, 0 to multiple litres per hour. [0046] Measurements can be regularly taken, perhaps as often as once every few seconds or every few minutes, or at a longer desired interval. In a continuously operating water system, the disinfectant residual concentration should also be tracked 24hr/day x 365days/year to ensure adequate levels of disinfectant in the system. Also, the levels of disinfectant can be logged over time to detect patterns and provide an alarm system for early warning if residuals start trending in a non-desired way. A hand held or field device can also be used as a site specific backup measurement or calibration device such that an operator can make accurate measurements at different branches of the network on a once/day or week basis. Data obtained by hand from specific sites in the system can also be used to complement data automatically collected from the present system.

[0047] Figure 2 is a schematic of a dark water disinfection system 200 with a clear water storage 202 and a process water storage 204. Process water flows from a process water supply and a fraction of the process water is diverted to process water storage 204. The bulk of the process water is directed through flow meter 206 and to a process water return. The dark water storage 204 as shown has a drain valve 208 for draining the reservoir, which may be manually operated and be used for maintenance draining of the reservoir or to allow a constant minimal flow, and a float valve 210 for measuring the water level in the storage tank which can shut off the process water flow into the process water storage 204 if the overflow from the tank should become blocked. The process water that flows through the overflow and the drain valve is returned to the process water return either by gravity, or is collected in a separate reservoir and then pumped back to the process water reservoir or return.

[0048] Clear water is directed from, for example, a city water supply or well, into clear water storage 202, in this case, through a filter 216 to remove particulate and disinfectant in the clear water supply and to remove dissolved chemicals in the clear water which could influence the reading of peroxide or disinfectant residual. In particular, any chlorine residual in the clear water storage 202 could cause drift in the peroxide or disinfectant residual reading once the clear water is mixed with process water. The filter 216 is preferably a granular activated carbon filter capable of removing chlorine and other chemical contaminants from the clear water supply. Clear water storage 202 also has a float valve 214 to shut off clear water flow to the clear water storage 202 should the flow process need to be stopped for any reason, and optionally also an overflow shunt line (not shown). Clear water storage drain valve 212 can also be provided for maintenance draining of the reservoir or to allow a constant minimal flow out of clear water storage 202. Process water shutoff valve 218 shuts off water flow to process water storage 204 and clear water shutoff valve 220 shuts off water flow to clear water storage 202. Shutoff valves 218 and 220 can also be used to shut off flow for maintenance purposes. The process water that flows through the overflow and the drain valves can be set to drain either by gravity or may be collected in a reservoir and then pumped back to the drain.

[0049] Dilution pump 222 draws liquid from both the clear water storage 202, and the process water storage 204. The dilution pump 222 can be a fixed speed, peristaltic pump, or any other dual-headed pump capable of drawing fluid of quantified volume. At the dilution pump the ratio of the clear water to process water drawn from each respective reservoir is adjusted, and clear water and process water are diluted to an appropriate ratio. Diluted sample is then directed to analytical apparatus 224. Once the concentration of disinfectant in the diluted sample water is measured and knowing the dilution ratio used in dilution pump 222, the relative original amount of disinfectant in the undiluted process water can be calculated from the dilution ratio. The acceptable levels of disinfectant in the raw process water is known and the amount of disinfectant required to raise the disinfectant level in the process water is calculated. The disinfectant dosing pump 226 then adjusts the concentration of disinfectant in the process water by adding disinfectant from the disinfectant supply 228 in an amount to adjust the residual disinfectant concentration level in the process water to acceptable levels and the process water is then returned via the process water outlet. [0050] Figure 3 is a close-up image of an analytical apparatus 300 for determining the concentration of residual disinfectant in a diluted dark water sample. The analytical apparatus 300 has an the inlet tube connector 302 for receiving diluted dark water sample from the dilution pump. Isolation valve 304 is open when the system is running and can remain open for continuously flowing systems which continuously measure disinfectant concentrations in dark water. The isolation valve 304 can be closed to clean prefilter 306. Optional prefilter 306 is a filter capable of removing suspended particular from the diluted dark water such that filtered water flows into the buffer jar 310. Prefilter 306 as shown is a 200μΜ filter, though may have a variety of different pore sizes. Flow regulator 308 can be used to adjust the flow rate of diluted dark water into the buffer jar 310. A speed of 25 L/h has been found to be preferable, though can be adjusted up or down as required. Buffer jar 310 acts as a flow diverter and is constantly being filled with sample water from the dilution pump such that measurements of the disinfectant concentration in the sample water are taken at the same time as the process water is flowing through the system. This continuous flow allows for rapid and timely measurement of the amount of disinfectant concentration in the raw process water at any given time, and timely adjustment of the disinfectant level based on near real-time concentration readings. Diluted flowing sample water from the buffer jar is directed through the return tube connector 320 for joining with the bulk flow of raw process water. Controller 312 has a memory and processor and controls flow of water through the measurement cell, records data, performs calculations, controls ratios of sample water, controls addition of reagent and controls addition of disinfectant. Shown is a single controller, however the system may comprise a plurality of controllers to control all aspects of the system. Water that has been tested and gone through the measurement cell and contains reagent is diverted to a waste stream through drain tube connector 318. Other sensors can also be added to the present system to detect pressures and flows to put in feedback loops and flow controllers.

[0051 ] Figure 4 is a close up image of the colorimetric measurement cell and buffer jar.

The colorimetric measurement cell comprises a measurement cell 340, which consists of a measuring chamber, light transmitter and light receiver. Sample tap 360 allows for manual extraction of sample fluid flowing through the buffer jar. Fluid manually taken through sample tap 360 can also be used to calibrate the system by confirming the disinfectant concentration with a calibrated external reference system. This can be a handheld meter, laboratory titration system, or sample can be sent to a laboratory for further analysis. Reagent supply tube 364 supplies reagent from reagent reservoir 352, which is refilled from a reagent bottle 348, all housed within removable housing 350.

[0052] Diluted dark water is directed into the buffer jar 310 through check valve 262 to prevent backflow of sample water. The water in the buffer jar 310 overflows through the overflow tube 330 and maintains a constant level. The static level (head) is determined by the height of overflow tube 330. In a system for continuous sampling of dark water in the system, the buffer jar 310 is continuously filled diluted dark water from the dilution pump and excess diluted sample water returns to the process water return system. The buffer jar has also a check valve 362, which is a one way valve connecting the dilute water from the dilution pump to the overflow tube in the buffer jar and prevents backflow of water. Check valve 362 can also be used to take a sampling of water or drain the buffer jar 310 during maintenance.

[0053] Only a small amount of sample water flows through the conical filter 332 and the sample water outlet 334 to the sample water outlet valve. Due to the constant head pressure in the buffer jar 310 the water is driven into the measurement cell 340. Because pressure is constant, there is a stable amount of water in the system and a consistent amount of water is injected into the measurement cell 340. A sample water inlet valve 344 is a timed valve controlled by the controller such that opening of the valve for a specific time provides desired water volume into the measurement cell. The amount of reagent added through the reagent valve 346 is determined by the amount required to fully interact with the residual disinfectant in the sample water and give an accurate reading of disinfectant concentration in the sample water. [0054] In measuring the concentration of disinfectant in the diluted sample water, the measurement cell 340 is filled with sample water via the sample water inlet valve 344. Reagent is added by the reagent valve 346. The reagent holder 348 fills the reagent reservoir 352 at a fixed level. The static height of the reagent fluid in the reagent reservoir ensures that the amount of injected reagent is fixed and only controlled by the opening time of the reagent valve 346. The measurement cell 340 is emptied after analysis by drain valve 352. Riser tube 342 prevents the measurement cell for overflow. Drain valve 352 drains the measurement cell 340 gravitationally to the drain valve 352. The three valves 344 (sample water inlet valve, 346 (reagent valve) and 352 (drain valve) can be analytical solenoid valves that controlled in a preprogramed cycle by the controller 212.

[0055] The measurement cell 340 has a light source transmitter and associate receiver for measuring transmittance through the cell. The light source can have an adjustable wavelength transmitter or single or multiple wavelength transmitter, and corresponds to an acceptable wavelength at which to measure the reagent-disinfectant reaction or interaction product. In the example in Figure 4, measurement cell 340 has a blue LED as a light transmitter 470nm and a photodiode as a light receiver. The measurement cell works according to the Lambert-Beer law.

[0056] Figure 5A is a close up of the measurement cell 340 containing measurement water, with LED transmitter 370 and receiver 372. Figure 5B is a close up of the measurement cell showing fluid flow into the measurement cell, with solid arrows showing the direction of fluid flow. As shown, diluted sample water is supplied to the measurement cell 340 through inlet valve 344, and reagent is supplies to the measurement cell through reagent valve 346. Waste leaves measurement cell 340 through drain valve 352.

[0057] In practice, the method of measuring peroxide concentration in the sample water in a measuring cycle preferably begins with a complete fill of measurement cell 340 and riser tube 342 followed by empty of the measurement cell 340 and riser tube 342 through drain valve 352. Measurement cell and riser tube are then rinsed with sample water filled by inlet valve 344 and emptied by drain valve 352. To measure the amount of disinfectant in the dilute process water, a null measurement is taken with diluted sample water with no reagent to obtain a clarity measurement, which is a combination of turbidity and colouration in the water. The light in the measurement cell is turned on, and the fraction of transmitted light is measured by the light sensor in the measurement cell. Non-transmitted light is absorbed or scattered by the water. If the null measurement is within a certain range, such as greater than 70% transmittance, then the reagent can be added in a following measurement to measure the concentration of disinfectant in the dilute sample solution. Optionally, the transmittance measurement is used to change the dilution factor at the dilution pump to keep the

transmittance in the measurement cell above 70%, or as required by the standards of the cell. The reading of the null measurement from the measurement cell can be sent to the dilution pump to adjust the dilution ratio at the dilution pump.

[0058] One specific method of measuring disinfectant concentration in dark water is as follows. To obtain a control or baseline measurement, measurement cell 340 and riser tube 342 are filled, and the transmitter LED in the measurement cell 340 goes on for 15 sec. The transmittance value is measured and saved in the controller as a null or baseline measurement.

The null measurement determines the baseline color of the water. The measurement cell 340 and riser tube 342 are emptied by drain valve 352. The reagent valve 346 then injects a fixed amount of reagent in to the measurement cell 340. The measurement cell 340 is then filled

(volume of measurement cell is 1 .5ml_) with diluted sample water. An active measurement is then done, wherein the transmitter LED in the measurement cell 340 goes on for 15 sec. The transmittance value measured by the receiver is saved in the controller as an active

measurement. The measurement cell 340 is then emptied and re-filled with an additional another 1 .5mL. The transmitter LED in the measurement cell 340 then goes on for 15 sec. The value on the receiver is measured and saved in the controller as a control measurement. The peroxide value is then calculated, which is the null measurement minus the active measurement, and displayed on the LCD screen. The measurement cell and riser tube are then rinsed and filled by sample water inlet valve 344 and emptied by drain valve 352. The measurement cell 340 and riser tube 342 will be rinsed for another 3 times to clean the measurement cell. The measurement cell and riser tube are then filled until the next cycle. The controller also begins the countdown waiting time till next measurement.

[0059] Measurement speed of a single cycle can range, for example from less than one minute, one minute, 1 .5 minutes or so, to multiple minutes. The wait time between

measurements is adjustable from 5 seconds to 2 hours. A shorter wait time between cycles may provide more data and faster control and can be useful for newly installed systems to obtain data on the new system. Longer wait times save on wear and tear on moving parts and reagent and can be used with stable and predictable water systems. The analytical apparatus can measure, for example, from 0-1 OOppm of peroxide in the sample solution. In chlorine systems, disinfectant amounts can be in the range of 0-5ppm or more. Adjusted for dilution factor gives a broad reading range for disinfectant up to X times the dilution ratio in the raw water, such as from 1 X to 5X to 10X to 20X.

[0060] Colorimetric reagents can be selected from any colorimetric compound detectable by the measurement cell and interacting with the disinfectant. Preferable reagents for testing peroxide concentration in solution are those in which the color is developed instantly or quickly and remains stable for the duration of the analysis. Two preferable reagents for testing hydrogen peroxide concentration are titanium sulfonate and potassium bis (oxalato) oxotitanate (IV) Dl. A preferable reagent for testing chlorine concentration in solution is DPD (N,N Diethyl-1 ,4 Phenylenediamine Sulfate).

[0061 ] Figure 6 is a block schematic of the analytical apparatus 400. Flow sensor 402 detects and provides data on water flow to the controller 404. Controller 404 also receives data on the pH of process water from pH probe 440 taken from sample water buffer 430 through sample water inlet valve 432. The analytical apparatus also has a power supply (not shown). A cycle timer 410 controls sample water valve output 412, reagent valve output 414, LED output 416 to the measurement cell 428 and drain valve output 418. The reagent valve output 414 controls addition of reagent from a reagent storage 434 through a reagent valve 436 to the measurement cell 428. Also connected to the controller are output user interface 406, which can be an LCD screen or other visual output, and an input device 408, which can be a keyboard, buttons, switches, or other known input devices. Outputs from the controller 404 can include an alarm output 420, flow ok output 422, disinfectant pump output 424 to control the disinfectant pump, and a pH correction output 426 to control pH correction of the process water. The controller can be controlled remotely by connection to a wifi or modbus or TCP-I P or other internet connection module.

[0062] Figure 7 is an example of an output user interface reporting system status and providing remote access to the system. Data can also be obtained from the controller and displayed live and/or transmitted to other control systems by, for example by analog 4-20 mA signal or 0-10V signal. Remote connection by an operator can be used to remotely monitor settings, for example water quality and disinfectant concentration. The user interface can also be used to modify settings remotely such as dilution ratio, selection of and/or concentration of reagent, selection of light transmitter wavelength and/or intensity, pressures and flows, and valve opening times. Disinfectant volumes and levels can also be adjusted, including amounts and compositions of one or more disinfectant added to the system using one or more dosing pumps. Other water quality parameters and systems can be connected and remotely controlled, such as, for example, pH detection and other chemical and flow adjustment systems.

[0063] Reporting of water quality can be provided via connection to the controller of a data stream optionally displaying on a local or remote system such as a graphical user interface. Figure 8 is an example of a graphical user interface reporting system status with a graph of peroxide levels in a dark water system. Data can be displayed by graph to analyse functioning of the controlled disinfection system. Other displays such as trend lines and long range reporting can be of assistance in tracking system disinfectant levels over time and making appropriate adjustments. For example, downward drift of measurement cell null values can be indicative of system performance and can suggest, for example, contamination of the cell, darkening of the process water, or correlation of pump output as related to general water quality. Correlation of energy requirements of the various pumps to pumped water volume can also be indicative of process water quality and data can be compared and displayed to adjust setting and optimize process systems.

[0064] Example - Dark Water Disinfection

[0065] An organic herb and vegetable grower with an extensive greenhouse water distribution network had the present system installed to disinfect their circulating water system. Stabilized hydrogen peroxide was used as a disinfectant with the presently described system to maintain acceptable disinfection.

[0066] Water samples were taken over time with mixed (diluted) sample water and all dark water. The measurement unit obtained by the measurement cell is a factor that is specific to the present system and other colorimetric systems that follow the Beer-Lambert law. The CelLNull Value is a measurement of light is shone through the liquid only (without reagent) in the measurement cell. The value of light received is a fraction out of 1000. The Cell_Active measurement is the value of light, relative to the CelLNull, received through liquid + reagent water in the measurement cell. The lower the amount of light received, the higher the H2O2 residual in the water. The 2eCntrl is the value of light, relative to the CelLNull and the

Cell_Active, received through liquid + reagent + another small amount of water, in the measurement cell, to determine if enough reagent is being used for the Cell_Active

measurement. This number is a secondary troubleshooting tool to verify the accuracy of the system. I n a properly functioning system, the 2eCntrl value should be very close to the CelLActive reading. This value is also logged with each measurement.

[0067] A procedure for measuring residual disinfectant at a given time course was undertaken as follows. The system was reviewed as it runs normally, and the Cell_Null, the CelLActive and the 2eCntrl values were recorded for 3 subsequent measurements. Then the dilution pump was shut down such that only the undiluted water was entering the

measurement buffer jar. The Cell_Null, the CelLActive and the 2eCntrl values for the undiluted water for 3 subsequent measurements were recorded, and the dilution pump was restarted such that the diluted water once again entered the buffer jar and analytical apparatus. The CelLN ull, CelLActive and 2eCntrl values were then recorded for the diluted water for 2 subsequent measurements. The cell values from the analytical apparatus for the circulating water, for both dark water only and mixed water (dark diluted with clear) for the greenhouse system are shown in Table 1 .

Table 1 :

[0068] As observed, the Cell_Null Value drops about 80 "visibility" or transmittance points when comparing the diluted to the undiluted solutions. It is also noteworthy that only during the undiluted measurements it is observable that the Cell_Active value is lower than the reference CellNull Value. This normally cannot be so and is indicative of inaccuracy in the system, a further signal that process water dilution is required to obtain acceptable

concentration measurements of disinfectant. In particular, the Cell_Active value must be lower than the Cell_Null value if there is H2O2 in the water and serves as a control marker to ensure that the system is working properly. A higher Cell_Active value compared to the Cell_Null Value is highly anomalous and is indicative of a malfunctioning system.

[0069] This testing shows that the system is operating in a good range for the measurement of this amount of colour and turbidity in the process water. It is evident that operating the analytical system with undiluted process water makes the system unstable for performing residual measurements. In contrast, ratioed dilution of dark process water provides accurate and repeatable results and therefore dependable disinfectant control in a dark water system.

[0070] 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 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.