WO2002035908A2

WO2002035908A2 - Air and water purification using continuous breakpoint halogenation and peroxygenation

Info

Publication number: WO2002035908A2
Application number: PCT/US2001/043720
Authority: WO
Inventors: Roy Martin
Original assignee: United States Filter Corporation
Priority date: 2000-11-06
Filing date: 2001-11-06
Publication date: 2002-05-10
Also published as: EP1332112A2; WO2002035908A3; CA2428058A1; AU2002216705A1

Abstract

A process for optimizing the rate of oxidation in aquatic facilities using a combination of halogen, e.g. chlorine donors and peroxygen, e.g. potassium monopersulfate. The peroxygen compound elevates the oxidation-reduction potential of the body of water being treated. Simultaneously, a halogen donor is added to the body of water to maintain a ppm level of free halogen sufficient to insure sanitization. The amount of free halogen is reduced and the ORP effective range expanded to 700 mV-850 mV by addition of an effective amount of a coagulating agent. The feed rates and concentrations of both oxidizers are optimized so as to achieve and maintain the targeted parameters. A high level of oxidation is maintained which removes by-products from the water and surrounding air.

Description

AIR AND WATER PURIFICATION USING CONTINUOUS BREAKPOINT HALOGENATION AND PEROXYGENATION

Background of the Invention

1. Field of the Invention

This invention relates to the maintenance of aquatic facilities, particularly to the optimization ofthe feed rates of a sanitizer/oxidizer and peroxygen compound, and most particularly to the incorporation of a coagulant effective to reduce oxidizer demand.

2. Description ofthe Related Art

The use of closed recirculating water reservoirs for use by the general public, for example, swimming pools, spas, hot tubs, decorative fountains, cooling towers and the like, can lead to a variety of water quality problems. For instance, improper chemical balances in the water can lead to various types of contamination including bacterial and viral contamination.

The use of chemical sanitizers is one standard water sanitation method. Addition of so-called halogen donor compounds or halogen donor sources, such as chlorine or bromine, can be effective sanitizers so long as they are maintained at well defined and constantly controlled concentration levels in the water. The concentration of these chemical sanitizers should not be allowed to become too high because it may cause irritation to the users and damage to the water system. However, insufficient sanitizers result in a contaminated condition.

The difficulties in maintaining a proper balance of sanitizers may arise from numerous load factors that are difficult, if not impossible, to predict. For instance, in a pool the load factor is typically caused by varying numbers of users. In hot tubs the use of air jets and high water temperatures tend to destroy or remove the sanitizer from the water. Cooling towers can be subject to environmental conditions, such as fluctuations in temperature. Indoor decorative fountains may be affected by the air quality in the building, while the fountain water can also affect the air in the building.

Various testing devices exist for determining the chemical balance ofthe water of pools, spas and the like, for example, colorimetric chemical test kits are available that utilize liquid droplets, test strips or tablets which dissolve in the water to indicate a particular level or concentration of sanitizing agents. By removing a test sample of water, for example via a scoop or cup, a seemingly representative sample is deemed to have been taken. A staining agent is then added by means such as an eye dropper or the like. The degree of staining relates to the amount of sanitizer in the water. The amount of sanitizer present is determined by visually comparing the degree of coloring ofthe test sample against a test scale previously formulated. Further complicating the task of maintaining sanitary conditions in such bodies of water is the fact that studies now indicate there may be little correlation between the free halogen, e.g. chlorine, residual readings which are normally used to monitor such bodies of water and the actual bacteriological quality ofthe reservoirs themselves. Pool and spa maintenance officials have long gone under the assumption that maintaining a free chlorine residual of two milligrams per liter or two parts per million (ppm) will insure a safe water condition. Thus, the ppm reading, which can be determined via the stain comparison, may reflect the sum ofthe free chlorine and combined chlorine compounds such as chloramine in the water. These combined chlorine derivatives do not protect from bacteria and/or viral contamination. Additionally, since organic and chemical loading drastically reduce the ability of free chlorine to overcome bacteria, the available free chlorine test kits may be of questionable value unless the exact levels of organic contaminants and the particular pH ofthe water being tested is known.

U.S. Patent No. 4,752,740 suggests the use of monitoring the oxidation-reduction potential (ORP) as a method of measuring the sanitization levels of water.

There exists a need for a method of reducing or eliminating impurities present in the air and water associated with aquatic facilities while maintaining the required levels of sanitization, and simultaneously reducing oxidizer demand by reducing or removing the amount of soluble (reactive) organic demand present within the system.

Summary ofthe Invention In one embodiment, the present invention provides a process for treating water systems. The method comprises the steps of monitoring the ORP ofthe water system, comparing the monitored ORP to a set-point value calculated to be within a range effective to permit oxidation of said halogenated compounds, adding a halogen donor source in an amount and at a rate sufficient to realize an optimum free halogen level sufficient to sanitize water in the water system and adding a coagulating agent in an amount effective to reduce the amount of halogen donor required to maintain the ORP within said effective range. Other advantages and novel features ofthe invention will become apparent from the following detailed description ofthe invention when considered in conjunction with the accompanying drawings, which are schematic and are not intended to be drawn to scale. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment ofthe invention shown where illustration is not necessary to allow those of ordinary skill in the art to understand the invention.

Brief Description of the Drawings

Preferred, non-limiting embodiments ofthe present invention will be described by way of examples and with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic representation ofthe process ofthe instant invention;

Figure 2 is a Circuit Diagram ofthe Air and Water Flow in the test device according to Example 1 ;

Figure 3 is a graphical representation of actual field conditions at the facility described in Example 5 prior to incorporating the teachings ofthe instant invention; and Figure 4 is a graphical representation of actual field conditions at the facility described in Example 5 subsequent to incorporating the teachings ofthe instant invention.

Detailed Description ORP defines the potential of a sanitizer such as chlorine, bromine or ozone to react with various contaminants. These compounds are known as oxidizers and have the property of "burning off' impurities in the water, for example, body wastes, algae and bacteria. The use of an ORP sensor allows the pool maintenance engineer to measure the potential generated by the active form ofthe sanitizer and not the inactive forms such as the combined chlorine derivatives. Additionally, ORP monitoring has an advantage in that it can be an ongoing electronic process requiring no test chemicals or agents and monitoring of sanitation levels can be constantly performed as opposed to being performed on some predetermined schedule basis. Since the potential for disease transmission due to organic loading can be far more significant in public spas and pools, the use of ORP measurement can reduce the risk of contamination and disease transmission. In accordance with standards set forth by the World Health Organization in 1972, maintenance of an ORP level of 650 millivolts (mN) can be deemed to result in a water supply that should be disinfected and in which viral inactivation should be virtually instantaneous.

Chlorine is believed to be the most widely used oxidizer in the aquatic industry, the primary use being for sanitation ofthe water in pools and spas. Chlorine, being an oxidizer, can also be involved in oxidation reactions with various organics, as well as inorganic and organic nitrogen based substances such as, but not limited to, urea, uric acid, amino acids, etc. The use of chlorine can result in the production of chlorinated byproducts as one consequence of incomplete oxidation. These byproducts are typically volatile and can produce undesirable side effects such as irritation ofthe eyes, sinuses, skin, foul smelling air, and corrosion of air handling equipment.

The health department generally regulates the concentration of free (HOCL & OCL) chlorine in the water. In some locations, sufficient HOCL may not be available to maintain a sufficient rate of oxidation ofthe demand being contributed to the water. This allows for the accumulation of these undesirable substances. Substances, which oxidize following substoichiometric oxidation, react with the chlorine producing substoicliiometric and/or stoichiometric compounds. Further oxidation, with HOCL for example, can eventually lead to increased concentration of substances that follow stoichiometric oxidation, such as monochloramines. If enough HOCL cannot be maintained to meet the stoichiometric ratios needed to drive oxidation ofthe chloramines, no demand on the HOCL may be experienced. However, when the chlorine donors are controlled using ORP control, with, for example, an optimized ORP setting of between 780 mN - 800 mN, the buffering effect chloramines place on the ORP can become a significant factor. The buffering effect provided by the chloramines, it is believed, reduces the impact on ORP provided by the addition of more chlorine donors. Thus, the controller can feed more one or more chlorine donors to achieve the optimized ORP. This can lead to levels of Free Chlorine that exceed local maximum limits. In order to meet the maximum limits of free chlorine, the ORP can be reduced to not exceed the established limit. This allows for the volatile chlorinated compounds to accumulate, thereby increasing the partial pressure which promotes fouling ofthe air. Numerous attempts have been made at addressing this problem. "Shocking" of the pool water requires dosing the water with stoichiometric concentrations of chlorine to oxidize the substances. One problem with this method is that there should not be any bathers present due to the excessive concentrations of chlorine required to meet the stoichiometric levels needed when said undesirable substances have been allowed to accumulate. Another issue is this method is generally applied after the symptoms have appeared, i.e. high combined chlorine, foul odors, etc. In many cases this method fails to rid the water and air of these substances since the concentration of chlorine required is at best a rough estimate (incorporates measuring the combine chlorine in the water.) Measuring the concentration of combined chlorine in the water does not take into consideration the accumulated demand that is non-aqueous, e.g. that accumulated on the filter media, walls ofthe pools, etc. As the chlorine levels rise, some ofthe accumulated demand is liberated. This gives the appearance that the system had not been driving breakpoint when indeed it probably did for awhile. The fact that the free chlorine levels drop considerably, and the combined chlorine level still appears, can be an indication that the HOCL must have oxidized the combined chlorine and/or accumulated demand, thereby providing a source of readily available oxidizable substances not originally detected in the water. When the free chlorine levels rise, they oxidize substances in the filters and the remaining system. This releases more substances into the water which were not accounted for, the stoichiometric ratio of HOCL is overtaken, and breakpoint is not achieved. Ozone has been used as a side stream treatment to destroy these undesirable substances. While it may be effective, ozone typically cannot be applied to the bulk water ofthe pool where the contaminants are being added. Also, because ozone typically cannot be used as a stand-alone treatment, since it cannot maintain a residual in the water, chlorine or bromine is typically used as the primary sanitizer. Besides being expensive and often requiring extensive de-ozonation equipment, e.g. such as activated carbon, ozone can destroy chlorine by attacking the hypochlorite ions, thereby further increasing operational and maintenance cost. Bromine can be used in place of chlorine because ofthe belief that it does not produce the air fouling byproducts produced by chlorine. However, while bromamines are typically not as volatile as chloramines, they can possess an odor and can irritate the eyes. Bromine also typically requires an oxidizer such as, but not limited to, chlorine or ozone to activate the bromide ion. Operating costs tend to be high and it can be difficult to maintain water quality because, it is believed, ofthe difficulty in differentiating between free or combined bromine. Also, hydantoin, an additive that can be used to pelletize the bromine chlorine combination, can reduce the oxidizing power ofthe bromine, as the hydantoin accumulates in the water. This makes it more difficult to reduce the accumulation of undesirable brominated compounds.

Non-chlorine shock treatments incorporating peroxygen compounds, e.g. potassium monopersulfate (MPS), such as OXY-BRITE^® bleach, available from Great Lakes Biochemicals, can be used for addressing the chloramine issue. Despite the application of this product following manufacturer's guidelines, many systems continue to experience air and water quality problems. The method of shock feeding can be a means of addressing the symptoms resulting after the problem makes them apparent, e.g. high chlorine concentration and foul odors. MPS, in some cases, can be used as a shock treatment even while bathers are present. However, when applied to systems using chlorine donors, for example, which can be fed using ORP control, the system can experience undesirable side effects from MPS shock feeding. The addition of MPS can increase the ORP ofthe chlorine donor system. When MPS is added, the ORP ofthe system can rise above that provided by the chlorine donors. It is believed that as long as the ORP value remains above the set point established for the chlorine donor system, no chlorine donor is fed. Since many ofthe contaminants entering the water do not react directly with MPS without first being oxidized by, for example, the chlorine donors, these substances further accumulate, thereby compounding the problem.

This invention incorporates an innovative process that allows the aquatic facility to maintain the desired ORP and oxidize the chlorinated volatile substances in the bulk water, while not exceeding the free chlorine limits established by local health departments.

This process can incorporate optimization ofthe rate of oxidation by controlling the feedrate and ratio of, in some embodiments, two oxidizers, a primary oxidizer being a halogen donor source, e.g. trichloroisocyanuric acid, dichloroisocyanuric acid, sodium bromide, hydantoin based bromines, gaseous chlorine, calcium hypochlorite, sodium hypochlorite, lithium hypochlorite and mixtures thereof; and other oxidizer being, in some embodiments, a peroxygen compound selected from, for example, hydrogen peroxide, sodium peroxide, sodium perborate, potassium monopersulfate, sodium peroxydisulfate, potassium peroxide, potassium perborate, sodium monopersulfate, potassium peroxydisulfate, ammonium peroxydisulfate, ammonium monopersulfate and mixtures thereof. In a preferred embodiment the peroxygen compound is MPS.

The ratio of MPS to halogen donor, e.g. chlorine donors, can be optimized to sustain the desired ppm range of chlorine, while achieving an ORP of 780 mN - 820 mN. By optimizing and controlling the feedrate and ratios of a halogen donor to maintain the desired ORP, the rate of oxidation can be maintained at a level that is sufficient to prevent the accumulation of undesirable halogenated byproducts. When applied to an aquatic facility, the effects of poor air and water quality can be reduced and even eliminated.

The process can optimize the ORP by incorporating the necessary process control and feed equipment to sustain a set-point, thereby controlling the concentration of undesirable by-products in the water.

In another embodiment, the process teaches the step of feeding coagulating agents to neutralize the charge density of water-soluble organic complexes thereby making them water-insoluble. The water-insoluble precipitates can be separated from the oxidizers utilizing, for example, settling, filtration, flocculation (agglomeration) followed by settling, or flocculation followed by filtration.

In one embodiment, the invention can eliminate volatile halogenated compounds from water and air by maintaining a level of oxidation potential. The feedrate and ratio of halogen donor and peroxygen compound can be optimized to sustain the desired ppm range of halogen and sustain an ORP of, for example, 780 mN - 820 mN. Sustaining these parameters should prevent or even reverse the accumulation of combined halogen and other halogenated volatile compounds, which contaminate the air and water of aquatic facilities, in particular indoor aquatic facilities. Furthermore, the demand for oxidizers can be substantially reduced by incorporation of a coagulating agent effective to reduce the demand for oxidizers by reducing the soluble (reactive) organic demand from the system. Accordingly, in one embodiment, the present invention can provide for the controlled addition of coagulating agents and, in some embodiments, control the coagulant addition at an amount that optimizes or reduces the amount of halogen donors and the peroxygen compound, or both. In another embodiment, the invention provides a process of operating an aquatic facility under conditions of "Continuous Breakpoint Halogenation and Peroxygenation." In another embodiment, the invention can improve the air quality around closed water systems by, for example, the removal of halogenated compounds through re-absorption followed by oxidation thereof with, e.g. HOCL. Referring to Figure 1, a typical indoor aquatic facility according to one embodiment ofthe present invention is characterized. Water from the pool or spa typically flows past an ORP sensor. Optionally, the water may further flow past a sensor, which can measure any of total dissolved solids (TDS), temperature and pH. Output from the ORP sensor can be transmitted to a controller, which can call for the addition of any of a halogen donor source and a peroxygen source to the pool water in accordance with selected process parameters. In some cases, controller can further regulate the addition of a coagulating agent.

An innovative process has been developed that allows the aquatic facility to maintain the desired ORP, oxidize the halogenated volatile substances in the bulk water, while not exceeding the free halogen limits established by local health departments.

Oxidation Reduction Potential can be a qualitative measurement ofthe oxidation or reduction power of a solution. While ORP can be used as the primary indicator of determining the inactivation rates of various bacteria and viruses, dosing aquatic water with ppm measurement of halogen has been the method used for meeting the oxidation needs ofthe aquatic facility. For example, while 650 mN is commonly used as the minimum required oxidation potential to ensure sanitized conditions in a pool or spa, health departments typically still require ppm levels of halogen, e.g. chlorine.

Despite maintaining health departments levels of halogen and/or operating with ORP levels in excess of 650 mN, following prescribed methods of superchlorination (breakpoint chlorination) as described, for example, in the product literature and in the "Certified Pool Operators" (CPO) training course, problems resulting from incomplete oxidation can still persist. In one embodiment, the present invention incorporates optimizing the rate of oxidation by controlling the feedrate and ratio of, for example, two oxidizers, wherein the primary oxidizer is typically a halogen donor and the other can be a peroxygen compound, e.g. MPS. The ratio of MPS to halogen donor can be optimized to sustain the desired ppm range of halogen, while achieving an ORP of, in one embodiment, 780 mN - 820 mN. By optimizing and controlling the feedrate and ratios of a halogen donor to maintain the desired ORP, the rate of oxidation should be maintained at a level that is sufficient to prevent the accumulation of undesirable chlorinated byproducts. Accordingly, when the system and method ofthe present invention is applied to an aquatic facility, the effects of poor air and water quality can be reduced and even eliminated. Optimizing the ratio of halogen donor to peroxygen compound, while controlling their combined feedrate using ORP, can effectively reduce or even eliminate the problems resulting from the accumulation of volatile halogenated substances. This can be achieved while maintaining lower ppm levels of free halogen than is otherwise required in a strictly halogen donor system.

In one embodiment, the present invention typically involves: achieving and sustaining an optimum concentration of free halogen, e.g. free chlorine, of between 0.2 ppm -10 ppm; addition of peroxygen to raise the solution's ORP to 750 mN - 850 mN, preferably 760 mN - 800 mN; controlling the feed of both oxidizers using an ORP controller; and optimizing the ratio of halogen donor to peroxygen compound to sustain the optimized halogen donor while achieving the desired ORP. By sustaining these conditions, the problems created by poor air and/or water quality resulting from the presence of these undesirable byproducts can be reversed.

This invention can ensure a sustained high rate of oxidation in the bulk water of the pool, spas, and other aquatic water systems despite the presence of accumulated demand. It has been found that the undesirable byproducts should not be sustained in an environment possessing this level of oxidation potential. Therefore, by implementing this invention, the aquatic facility can be operated under "Continuous Breakpoint Chlorination." By operating in the conditions described, the byproducts, which can result from intermediate steps in the continuing process of oxidation and can be produced during the initial step of oxidation, should not accumulate. While these byproducts can be initially produced, they should not accumulate, and shortly thereafter, are typically destroyed by the continued oxidation. By preventing the accumulation of these volatile byproducts, their respective partial pressures can be minimized, and, accordingly, the problems of poor air quality can be minimized or prevented. Also, in aquatic facilities that currently experience these problems, by implementing this application, the problems of poor air quality resulting from these chlorinated compounds can be reversed through re- absorption ofthe volatile chlorinated compounds, followed by oxidation, even while maintaining substoichiometric levels of free halogen. The re-absorption process follows Henry's Law of Diffusion. This development can be important to the aquatics industry because its implementation means halogen feedrates can be controlled below maximum regulated levels while preventing or even reversing the accumulation of combined halogen and other chlorinated volatile compounds which contaminate the air and water of aquatic facilities, in particular, indoor aquatic facilities. The present invention, in another embodiment, provides for the feed of coagulating agents that can be used to neutralize the charge density of water-soluble organic complexes, thereby making them water-insoluble. The water-insoluble precipitates can be separated from the oxidizers utilizing, for example, settling, filtration, flocculation, agglomeration and, in some cases, followed by settling, or flocculation followed by filtration.

In some cases, the present invention can feed coagulating agent, sometimes referred to as a polymer, to the system, which can convert water-soluble organics into water-insoluble organics thereby allowing separation from the oxidizer. Reduced organic demand on oxidizer enhances the oxidation potential ofthe oxidizer and further enhances efficient continuation of breakpoint halogenation. In some embodiments, the controlled addition ofthe coagulating agent can reduce, or optimize, the amount of halogen donor or peroxygen compound, or both. The present invention can, in some embodiments, further reduce any volatile byproducts associated with incomplete oxidation. The controlled addition of coagulation agents can reduce the amount of halogen donor or peroxygen compound addition and, thus, the likelihood of incomplete oxidation, which should reduce volatile byproducts. The coagulating agent can be fed at a sufficient frequency and level of concentration to allow halogen to remain in optimum range while sustaining desired ORP, e.g. within an effective range of 700 mN - 850 mN with chlorine levels in the range of 0J ppm - 10 ppm.

In some cases, the use of coagulating agents can significantly reduce the demand for oxidizers by removing the soluble (reactive) organic demand from the presence ofthe oxidizers. This practice can significantly reduce the use of oxidizers needed to oxidize the contaminants added to the pool to maintain air and water quality. Also, this practice can significantly reduced the concentration of free chlorine to maintain the ORP, while reducing the combined chlorine measured in the water. Useful coagulants include, for example, Alum, poly-aluminum chloride, sodium aluminate, polyamines, polyquaternary compounds, polydiallyl-dimethyl ammonium chloride, chitosan (poly-D-glucosamine) and chitin (poly-n-acetyl-D-glucosamine) alone or in any combination.

In other cases, the use of coagulating agents can enhance the existing described art, while further expanding the operating range of ORP to achieve continuous breakpoint halogenation. By reducing the organic nitrogen load (lower combined chlorine), lower concentrations of chlorine can be utilized to achieve the same result. Because free chlorine concentration can be controlled by ORP, lower ORP set-points can be employed where desired while achieving continued Break-Point Halogenation, stoichiometric- based chemistry, without compromising performance. For example, an ORP range of 700 mN - 850mN is attainable when utilizing this method. In some embodiments, the coagulant dosage rates can be 0.01 ppm - 10 ppm.

The coagulant may be fed to the system by any known method effective to introduce the coagulant to the water treatment system, such as, but not limited to, low level continuous feed, feed on demand, e.g. ORP activated, and periodic feed under timer based control. The present invention will be further illustrated through the following examples, which are illustrative in nature and are not intended to limit the scope ofthe invention.

Example 1 A testing device was designed and built to simulate the water and air environment of an indoor aquatic facility. The system was designed to control the following: H₂O temperature;

Air circulation rates; Air exchange rates; Water turnover rates (filtered water);

Water exchange rates

Instrumentation for automatic monitoring and recording of ORP and pH were incorporated. A condenser was installed in the air circulation system. The condenser allowed for scheduled sampling ofthe condensate. A micro-titration system was incorporated for precise feed of various reagents for adjusting ORP, pH, etc. The test device was initially prepared for use by the addition of water to 50 % ofthe skimmer line. The tank representing the surge pit was filled to 50 %. The tank lid was sealed.

Condensate samples were collected by chilling the air prior to the air circulation pump. Condensate was collected for 20 minutes; the measured sample was tested using standard DPD methods for chlorine that incorporated a Model DR/2000 spectrophotometer from HACH Company (Loveland, Colorado).

Laboratory grade ammonium chloride was used as the nitrogen source for the generation of chloramines. A measured amount was added to the water ofthe test device. The water and air circulation pumps were activated and adjusted to achieve desired circulation and exchange rates.

A measured dosage of chlorine, in the form of 5.25 % liquid bleach, was added to the water to induce the formation of combined chlorine. After providing sufficient contact time, incremental dosages of bleach were added to achieve and sustain the desired ORP of 800 mN.

Condensate and water samples were periodically tested for free and total chlorine using standard methods. ORP and pH readings were also recorded.

Table 1

Results demonstrate that a comparable rate of chloramine destruction can be achieved while sustaining lower concentrations of free available chlorine, at an oxidation potential of approximately 780 mV.

Example 2

An indoor aquatic facility with a 166,500 gallon lap-pool, and a 14,400 gallon splash pool incorporating a water slide had experienced chronic air and water quality problems. Combined chlorine in the water of both pools (water was mixed in the surge tank) was consistently above 1.0 ppm. Odors in the air were strong from chloramines. The facility had utilized an ORP control system with calcium hypochlorite as the primary sanitizer/oxidizer. Potassium monopersulfate had been fed at 4 times the suggested concentrations as described on the manufacturer's directions. Superchlorination had been incorporated every 3 weeks at a concentration three times that taught by the CPO and the Aquatic Facilities Operator (AFO) courses. Initially, condensate from the air handling systems dehumidifier was collected and tested using standard methods FAS-DPD test for chlorine.

Day One ~ 3:00 p.m 0.6 ppm total chlorine

Day One — 7:00 p.m 0.8 ppm total chlorine

Day Two — 9:00 a.m. 0.8 ppm total chlorine Initially, the system was started using calcium hypochlorite to achieve the targeted ORP of 780 mN. The Free Chlorine levels needed to sustain the ORP at 780 mN generally ranged from 4 to 6 ppm, with one day requiring 18 ppm during a high chlorine demand period.

The two oxidizer approach in accordance with the teachings ofthe instant invention was then instituted using calcium hypochlorite and potassium monopersulfate. The oxidizers' feed rate was optimized to achieve the desired free chlorine concentration in the water (1.5 ppm - 2.0 ppm), while sustaining the targeted ORP of 780 mN using MPS.

Within 3 days of implementing the new program, the combined chlorine in the water dropped to undetectable levels using FAS-DPD test for chlorine & Total Oxidant. Free chlorine was consistently between the 1.0 ppm - 2.0 ppm, and ORP was held at 780 mV ± 1.0 %. The odors and skin and eye irritation problems were eliminated. To help quantify the reduction in chloramines from the air, condensate samples were later tested following standard DPD methods.

Day One — 6:30 a.m 0.0 ppm (no color change after 2 minutes)

Day One -- 7:30 p.m 0.0 ppm (no color change after 2 minutes) Day Two — 9:00 a.m 0.0 ppm (no color change after 2 minutes)

Along with the dramatic improvements in air and water quality, chemical use dropped:

Chemical used Before (lbs/week) After (lbs/week)

Monopersulfate 74 55 Calcium hypochlorite 80 25

Chlorine shock 69 0

Example 3 A 72,000 gallon pool with zero depth entry, located near Denver, Colorado, experienced excessive bather use that produced undesirable air and water quality. The purpose of this treatment was to evaluate any reduction in the reactive water-soluble organic contaminants in the water, which should reduce the demand for halogen oxidizer.

A system (Environmental Control System, ECS) that utilizes the process of "Air and Water Purification using Continuous Break-Point Halogen and Peroxygenation" was installed. While air and water quality dramatically improved, the concentrations of halogen (Free Chlorine) required to oxidize the demand was above the Department of Health limitation of 5 ppm. Furthermore, the corresponding high use of halogen resulted in higher than desired cost of operation.

To enhance the performance ofthe ECS technology, a Poly- Aluminum Chloride feed system was installed. The system was set to feed a low level, e.g. about 0.5 ppm based on circulation rate, of coagulant prior to the filter system.

Prior to starting the system, the water chemistry parameters were as follows:

^• Free Chlorine (DPD method) 8 ppm - 10 ppm

^• Combined Chlorine, 1 ppm - 1.2 ppm After 28 days of operation, while experiencing excessive bather loads, the water chemistry parameters were reduced to:

^• Free Chlorine (DPD method) 3 ppm - 5 ppm ^• Combined Chlorine 0.6 ppm - 0.8 ppm

The dramatic reduction in required free chlorine also corresponded with a reduction in chlorine use.

The reduced demand for oxidizer by coagulation and separation of water-soluble organic demand significantly enhanced the overall performance and cost effectiveness of the system.

Example 4 A testing device was designed and built to simulate the water and air environment of an indoor aquatic facility. Figure 2 represents a circuit diagram of air and water flow through the test device. The system was designed to control the following: H₂O temperature; Air circulation rates; Air exchange rates; Water turnover rates (filtered water);

Water exchange rates

Instrumentation for automatic monitoring and recording of ORP and pH were incorporated.

A condenser was installed in the air circulation system. The condenser allowed for scheduled sampling ofthe condensate. A micro-titration system was incorporated for precise feed of various reagents for adjusting ORP, pH, etc. The test device was initially prepared for use by the addition of water to 50 % ofthe skimmer line. The tank representing the surge pit was filled to 50 %. The tank lid was sealed.

Condensate samples were collected by chilling the air prior to the air circulation pump. Condensate was collected for 20 minutes, the measured sample was tested using standard DPD methods for chlorine that incorporated a Model DR/2000 spectrophotometer from HACH Company (Loveland, Colorado).

Laboratory grade ammonium chloride was used as the nitrogen source for the generation of chloramines. A measured amount was added to the water ofthe test device. The water and air circulation pumps were activated and adjusted to achieve desired circulation and exchange rates. A measured dosage of chlorine in the form of 5.25 % liquid bleach was added to the water to induce the formation of combined chlorine. After providing sufficient contact time, incremental dosages of bleach were added to achieve and sustain the desired ORP of 800 mN.

Table 2 illustrates the rate of chloramine removal from the air (and subsequent water.) Sustaining the ORP at 800 mN with addition of a halogen donor (chlorine), the concentration of chloramines in the air was continually reduced over the test period. During the test period, the concentration of chloramines in the water was sustained, but did not accumulate. Mass balances calculations support the destruction of chloramines in the water equal to the rate of chloramine reduction in the condensate.

Table 2

Example 5

A 95,000 gallon indoor pool facility had experienced chronic problems with air and water quality resulting from high concentrations of chloramines in both the air and water. The water treatment system incorporated an ORP controller and used 12 % liquid bleach as the oxidant and sanitizer.

Superchlorination methods following industry standards were frequently incorporated in an attempt to reach breakpoint conditions, thereby ridding the facility of poor air and water quality. Complaints of skin irritation, rashes and burning eyes were common. Based on operator log sheets, combined chlorine levels were constantly > 0.5 ppm even after superchlorination.

Control ofthe water chemistry at the facility was initiated in accordance with the teachings ofthe instant invention. ORP and pH were automatically controlled and recorded and a grapliical representation ofthe results before and after implementation of the instant process are shown in Figures 3 and 4, respectively. The ORP set-point was 780 mN with a pH setting of 7.5. Chlorine concentrations and feedrates were controlled based on ORP. The free chlorine levels were measured using standard DPD methods, and generally ranged between 7 ppm - 10 ppm while sustaining the targeted ORP. After 7 days of operation, the combined, chlorine concentration in the pool water was recorded as zero ppm using a DPD colorimetric test. After 10 days, odors resulting from the presence of chloramines had been eliminated. After more than four months of continued operation the air remained free of any chloramine associated odors; furthermore, the process of superchlorination was eliminated.

Example 6 Laboratory grade glycine was added to a water sample to achieve about 62 ppm as glycine. Chlorine, in the form of calcium hypochlorite, was added to achieve 0.8 ppm free chlorine, measured using standard DPD methods. The corresponding chemistry was: pH - 7.95 ORP - 360 mN Free Chlorine - 0.8 ppm

100 ppm of a 50/50 blend (as Al₂O₃) of Alum and PAC (poly-aluminum chloride) was added to the system. Almost immediately, the water appeared hazy due to the formation of insoluble particulate matter. After 60 seconds, the ORP was measured to be 455 mN. Removal ofthe soluble organics by precipitation with coagulation reduced chlorine demand and increased the oxidation potential ofthe solution. Similar increases in oxidizer efficiency due to coagulation should occur at breakpoint halogenation conditions yielding an effective range of ORP of about 700 mN - 850 mN.

Those skilled in the art would readily appreciate that all parameters and configurations described herein are meant to be exemplary and that actual parameters and configurations will depend on the specification application for which the systems and methods ofthe present invention are used. Those skilled in the art should recognize or be able to ascertain using no more than routine experimentation many equivalents to the specific embodiments ofthe invention described herein. It is, therefore, to be understood that the further embodiments are presented by way of example only and that, within the scope ofthe appended claims and equivalents thereto, the invention may be practiced otherwise as specifically described. For example, where reference is made to the use of MPS or peroxygen as an oxidizer, other oxidizers may be used as described. The invention is directed to each individual feature, system, or method described herein. In addition, any combination of two or more such features, systems, or methods provided at such features, systems, or methods that are not mutually inconsistent, is included within the scope ofthe present invention. What is claimed is:

Claims

1. A process for treating water systems comprising: monitoring a ORP ofthe water system; comparing the monitored ORP to a set-point value calculated to be within a range effective to permit oxidation of said halogenated compounds; adding a halogen donor source in an amount and at a rate sufficient to realize an optimum free halogen level sufficient to sanitize water in the water system; and adding a coagulating agent in an amount effective to reduce the amount of halogen donor required to maintain the ORP within said effective range.

2. The process as in claim 1, wherein the step of monitoring the ORP is performed continuously.

3. The process as in any preceding claim, further comprising the step of adding a peroxygen compound at a rate and in an amount sufficient to maintain the ORP within said effective range.

4. The process as in any preceding claim, further comprising the step of optimizing the ratio of halogen donor source to peroxygen compound to sustain the optimum free halogen level while maintaining the effective ORP value.

5. The process as in any preceding claim, wherein the effective range of ORP is from 700 mN - 850 mN.

6. The process as in any preceding claim, wherein said halogen donor source is selected from the group consisting of gaseous clilorine, calcium hypochlorite, sodium hypochlorite, lithium hypochlorite and mixtures thereof.

7. The process as in any preceding claim, wherein the effective range of ORP is

8. The process as in any preceding claim, wherein the optimum free halogen level is within a range of 0.2 ppm to 10.0 ppm.

9. The process as in any preceding claim, wherein the peroxygen compound is selected from the group consisting of hydrogen peroxide, sodium peroxide, sodium perborate, potassium monopersulfate, sodium peroxydisulfate, potassium peroxide, potassium perborate, sodium monopersulfate, potassium peroxydisulfate, ammonium peroxydisulfate and ammonium monopersulfate.

10. The process as in any preceding claim, further comprising the step of monitoring and/or controlling pH.

11. The process as in any preceding claim, wherein the coagulating agent is selected from the group consisting of alum, poly-aluminum chloride, sodium aluminate, poly amines, poly quaternary compounds, polydiallyl-dimethyl ammonium chloride, chitosan (poly-D-glucosamine) and chitin (poly-n-acetyl-D-glucosamine) alone or in any combination.

12. The process as in any preceding claim, wherein the coagulating agent is fed at a rate and in an amount effective to provide a concentration level of 0.01 ppm - 10 ppm.

13. The process as in any preceding claim, wherein the coagulating agent is fed by any of a low level continuous feed process, an on demand process, an ORP activated process and a periodic feed under timer based control process.