OA17027A - Localized desinfection system for large water bodies. - Google Patents

Abstract

The present disclosure relates to a method for controlling the microbiological properties of a portion of water within a large body of water by treating such zone with chemical agents, according to the temperature of the water, its salinity power and the diffusion of chemicals within the large water body.

Description

LOCALIZED DISINFECTION SYSTEM FOR LARGE WATER BODIES

FIELD OF THE INVENTION

The présent disciosure relates to a method for controlling the microbiologlcal properties of a portion of water within large water bodies, by focusing on treating such portion of water, where said portion of the large water body compiles with spécifie microbiologlcal sanitary conditions. The présent disciosure allows people to use large water bodies for recreational purposes in a safe manner, avoiding the treatment ofthe total water body. The method also comprises dispensing chemicals govemed by a parameter détermination method based on the ORP, the température, the salinity, and optionally the diffusion of chemicals, and the dilution power of the water as weil. This results in using in orders of magnitude less chemicals to treat water and iow energy consumption. Thus, the présent disciosure can allow people to use certain zones within large artifidai or natural water bodies, such as large iakes, iagoons, réservoirs, dams, spas, ponds, or the sea; for recreational purposes in a safe manner, overcoming the limitation or impossibilityof treating the whole water body.

BACKGROUND

Several studies throughout the world show that the water quality found in several large water bodies, such as Iakes, réservoirs, dams, and the sea, hâve bacteriological and physical characteristics that do not comply with safety standards and or water quality required for recreational purposes. Therefore, the use of such large water bodies for recreational purposes can pose health threats to the people, and adversely effect the surrounding communities and geographies.

Water pollution can relate to the change in the chemical, physical and biological characteristics of a water body due to human activity. As the worid's population has grown exponentiaily over the years, it demande more living and recreational space, therefore using natural or artificial water bodies for different purposes. The increasing population is occupying the periphery of large dties, Increasing land demand and related utilities. Furthermore, the number of industries has multiplied, which has caused several environmental conséquences that also affect the quality of such large water bodies.

One contributor to poor water quality is water pollution. Water can be contaminated by sewage disposai, industrial contamination, overdevelopment on the edge of water bodies, runoff from agriculture and urbanization, air pollution, etc. Aiso, higher températures can adversely affect the microbiological and physical properties of water and allow for a rapid prolifération of microorganisms that may negatively affect the human health. These examples can cause the water quality to drop below the standards required for recreational water.

The effects of water pollution indude the impact over the health of living organisais within the water bodîes, and eventually the health of humans that can use such water for direct or indirect purposes.

Also, the amount of nutrients entering large water bodîes has intensified greatly over the years, mainly due to Increased urbanlzation and agriculture, leading to an Increased microbiological growth or eutrophication of the water body. Under eutrophic conditions, the amount of nutrients causes the metabolic rate of aquatic plants to Increase, thus Increasing the biochemical oxygen demand and redudng the wateris dissolved oxygen levels. Moreover, the température also affects the water*s dissolved oxygen level, as warm water has a reduced capability of holding dissolved oxygen. Therefore, combining both oxygen réduction effects, such as larger amount of nutrients and higher températures, results In a weakening of the organisais as they become more susceptible to diseases, parasites, and other pollutants. Ail of such problems produce a négative Influence on the water quality, causlng the prolifération of algae and other microorganisms, which later die and croate an unsafe recreational environment for the people. Also, global warming will tend to increase this klnd of problem throughout the worid.

Many studies and analysis hâve been performed on large water bodîes used for recreational purposes. Large water bodîes are used for a wide variety of recreational purposes that Indude bathlng, waterskiing, wîndsurfing, boating, and many other activities. However, several water bodîes used for such recreational purposes do not comply with spécifie microbiological sanitary conditions applied to the water body. For example, an EPA study was performed on more than 1,000 lakes across the U.S. to analyze the potential risks of using such lakes for direct-contact recreational purposes, and It was found that more than 30% of ail the lakes potentially hâve wide ranging impacts on human health, and over 41% of lakes pose a high or moderato exposure potential to algal toxins. Also, It has been found that microbial counts and toxin concentrations are greater In near shore résiduels than in open water areas.

Many countries throughout the worid hâve régulations for using bodîes of water for direct contact recreational purposes, such as bathing, In safe and hygienic conditions, and there are generally two types of régulations regarding recreational use of such water bodîes. The first type of régulation Is directed to swimmlng pools, and essentially requires maintaining a high permanent chlorine buffer In order to maintain low microorganisms levels and also to avoid the contamination of the water when new bathers enter the swimming pool. The chlorine buffer neutralizes contaminants and kilts microorganisms brought to the swimming pool water by bathers, amongst many other pollutants, thus maintaining a high water quaüty suitable for recreational purposes. The second type of régulation applies to naturel or artificlal large water bodies, such as lakes, the sea, lagoons, réservoirs, or dams, among other large water bodies, and It is referred to as the criteria for bathing with fui! body contact for recreational waters. This régulation is based on the diluting power of water. When the water has acceptable microorganisms' levels, and new bathers enter into a body of water, the contaminants are diluted in such way that the contaminants do not attain a concentration in the body of water that causes sîgnificant effects. Therefore, in large water bodies, a disinfectant buffer is not needed due to the high diluting power of the large water volume, and because of its naturel capacity to malntain sanltary conditions.

Direct-contact recreational water régulations, like the one applied to lakes, the sea, lagoons or dams; require the water quality to comply with severel standards that allow the safe use of such bodies. In order to evaluate the suitabllity of the large water bodies for direct-contact recreational purposes, the most Important standards are the microbiological parameters of the water. For example, the EPA (Environmental Protection Agency) criteria for bathing with fut! body contact In recreational waters points out that as for freshwater, E. Coli must not exceed 126 CFU per 100 ml of water, and that Enterococci must not exceed 33 CFU per 100 ml of water. For seawater, the EPA rules that the Enterococci must not exceed 35 CFU per 100 ml of water. As another example, in Chile, the Norm NCh1333 for direct-contact recreational waters states that the water must not contain over 1000 CFU of fecal coliforms per 100 ml of water (induding E. Coli, among others). Therefore, strict norms apply when such large water bodies are used for direct-contact recreational purposes.

It is therefore a significant challenge to obtain such required spécifie microbiological conditions in large water bodies which are currentiy unsuitable for recreational purposes, as the application of large quantifies of chemical agents and disinfectants throughout the complété large water body to comply with spécifie microbiological sanltary conditions is unfeaslble technically, economically and environmentally. Thus, the treatment of the complété water body to comply with spécifie microbiological sanitary conditions applied to the water body is impossible most of the fîmes.

Also, although some water bodies can comply with microbiological régulations for direct contact recreational waters, or more stringent régulations applied to the water body, there are pathogenic organisms such as protozoa, and specifically amoebas, among others, that can be présent In such water bodies espedaliy in low salinity waters or high température waters. Therefore, there are no guarentees that maintaining bacteriological régulations for direct contact recreational waters, can allow safe bathing conditions permanently.

Currentîy, water treatment technologies applied to swimming pools require the addition of chemical agents to maintain a permanent chlorine buffet of at least 1.5 ppm or to malntaln a permanent ORP of at least 750 mV. Currentîy, there are no known practical methods to treat large water bodies contaminated by mlcroorganlsms, such as lakes, the sea, lagoons, réservoirs, or dams because current methods are technically, economicaily, and envlronm entai ly un viable for large water bodies. The ORP has increasingly becorne a primary approach to standardizing water disinfection parameters. The metabolism of mlcroorganlsms and consequently their abllity to survive and propagate are influenced by the ORP (Oxidation Réduction Potential) of the medium in which they live. From a bacteriological point of view, an oxidizing compound removes and accepts the électrons from the cell membrane (reduction-oxldation reaction), causing the cell to become unstable and leading to a rapld death.

The Oxidation Réduction Potential (ORP), l.e., the tendency of a chemical compound to acqulre électrons from another spedes, may be controlled by the addition of different disinfectants that allow treating the water and the killing of dangerous microorganisms that can create an unsafe environment for recreational purposes. Also, the température of the water canies an important rôle on its bacteriological characteristics and microorganism prolifération, where microorganism prolifération tends to increase at higher températures. Furthermore, the salinlty of the water also cardes an important rôle on Its bacteriological properties, as some microorganisms require spedfic salinity levels In order to be able to proliferate, and do not withstand médiums with different salinities. For example, some pathogenic protozoa only grow in water with salinities lower than 2% in weight, therefore for higher salinities such microorganisms will not grow nor proliferate.

Swimming pool water treatment technologies require the addition of large quantifies of chemical agents, in order to maintain suitabie disinfection parameters. For large water bodies, the application of current swimming pool disinfecting technologies is unviable technically and economicaily, because of the large amount of chemicals that would be needed, and that would cause Important envlronmental damage.

Currentîy, there are no known practical methods to disinfect large water bodies, and treating such large water bodies, such as lakes, the sea, lagoons, réservoirs, or dams. If traditional disinfection technologies are utilized, a proper treatment and disinfection would be technically, economicaily, and environmentally unviable. Therefore, it is desired to provide a method for treating large water bodies, and preferably defined portions thereof in order to provide a zone that compiles with spécifie microbiological sanitary conditions, and using them for recreational purposes In a safe way.

Therefore, there Is an unresolved problem regarding recreational uses on natural or artlfictal large water bodies such as lakes, iagoons, the sea, or dams, with poor water quality. The mlcrobiological characteristics of such large water bodies must comply with direct-contact water régulations or more stringent régulations that apply to the particular water body, ln order to allow the safe practice 5 of recreational purposes within the water bodies, and also to avoid any health threats to the community or nearby terrains, which currently does not occur in many of the large water bodies throughout the world.

State of the Art

US Patent N® 6231268 discloses a method and apparatus for treatment of large water bodies by 10 directed circulation, where the device and method from US6231268 Is directed to malntain water »

circulation within large water bodies to avoid lack of oxygen, stagnant areas, freezing, and other non-uniform conditions. US6231268 does not mention nor disclose a method fortreating a portion of water within a large water body ln order to comply with spécifie mlcro-bacteriological sanitary conditions, but only discloses a method for maintainlng circulation within the large water body. The 15 method from US6231268 does not apply chemlcals through diffusor means in order to croate a sanitary-compliant zone, but maintains a circulation within the water body, which would disperse the chemlcals throughout the water body, not allowîng the création of a sanitary-compliant zone.

Patent US N’ 6317901 discloses a fresh or saltwater pool, where the pool Is created over a natural or artificiel water body that allows using the water from such body to avoid the contamination due to 20 soil or other sédiments contained in the large water body by means of physical barrière that allow the passing through of water and not contaminants, which requïres the Installation of physical containing means within the large water body.

Patent CN 102092824 discloses a water circulation System for ponds, lakes, municipal tanks, and other water bodies, where the water circulation System allows creating a flow from the bottom water 25 to the surface water, avoiding the eutrophication of the water body. Patent CN102092824 does not mention nor disclose a method for controllïng the microbiological properties of a portion of water within the large water bodies, in order to croate sanitary-compliant zones that allow recreational purposes.

SUMMARY

Surprisingly, the présent disclosure controls the microbiological properties in large water bodies by treating a portion of the large water body, where the portion of the large water body compiles with spécifie microbiological sanitary conditions without having to treat the whole water body, providing thus a sanitary-compliant zone, which is located in order to cover the area being used for recreational purposes, allowing the water quality to comply with spécifie mlcrobiological sanitary conditions.

The method allows treating a small part of the total water volume. Therefore, the method requlres only a small amount of chemicals as well as low consumption of energy due to the use of dispenser means that allow créa tin g safe sa ni tary-com pliant zones without needing to treat the entire water body. Thus, the présent disclosure can allow people to use certain zones within large water bodies for recreational purposes in a safe manner, overcoming the limitation or impossibility of treating the whole water body, but only treating the zone that will be used for such purposes, and also allows using countless lakes, seashores, lagoons, and many water bodies that are unusable today due to safety or sanitary problème, generating unprecedented recreational and touristic opportunlties that can change the lifestyle of people around the world.

The method can be performed on naturel or artificiel large water bodies, such as lakes, the sea, estuaries, réservoirs, dams, and lagoons. Also, the water contained In such large water bodies can be fresh water, brackish water, salty water, or sea water.

Accordîngly, in some embodiments, the présent disclosure relates to a method for controlling the mlcrobiological properties of water by Identîfyîng a portion of the water. The method further Includes malntaining at least a minimum ORP In the water for at least a minimum period of time dependlng on the salinity and the température of the water, and dispenslng chemical agents In order to maintain at least the minimum ORP at least during the minimum period of time. The dispensation of chemical agents may preferably be performed through dispenser means that allow creating safe sanitary-compliant zones. The dispensation of chemical agents may additionally be based on the diffusion of chemicals in the water and the dilution power In the water.

In one embodiment, the method of the présent disclosure includes:

a. identifying a portion of water Intended for recreational purposes within the large water body and defining dispenser means;

b. maintaining at least a minimum ORP level in such portion of water for at least a minimum period of time, wherein the minimum ORP level and the minimum period of time cannot be lower than the values calculated by.

I. determinlng the most unfavorable zone within the portion of water;

ii. determinlng the salinity of the water at the most unfavorable zone;

üi. determining the minimum ORP value based on the salinity of the water where:

- for salinities In the water between 0% and up to 1.5% the minimum ORP level is 550 mV;

- for salinities in the water higher than 1.5%, and up to 2.5%, the minimum ORP level Is calculated by the following équation:

[Minimum ORP, mV] = 625 - 50*[Saîinity of the Water, % (Weight Percent)]; and

- for salinities in the water higher than 2.5%, the minimum ORP level Is 500 mV; and

Iv. determining the température of the water in the most unfavorable zone; and

v. determining the minimum period of time based on the water température, where:

- for water températures from 5’C to 35^eC, the minimum period of time is calculated by the following équation:

[Minimum period of time, min] = 80 - 2*[Temperature of the water, *C]; and

- for water températures between 35‘C and up to 45’C, the minimum period of time is calculated by the following équation:

- [Minimum period of time, min] = 5*[Temperature of the water, ’C] -165;

c. dispensing an effective amount of chemical agent In order to maintain at least the minimum ORP level during at least the minimum period of time at the most unfavorable zone, and

d. Repeating step c In order to avoid the ORP in the most unfavorable zone to decrease by more than 20% of the minimum ORP value.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying drawings, which are incorporated herein and constitute a part of this disclosure, illustrate various embodiments of the présent invention. In the drawings:

Figure 1 shows a top view of a small section of the large water body (2), and the sanîtary-compliant zone (1).

Figure 2 shows a top view of an even smaller section of the large water body, and in particular, the sanitary compilant zone (1), the dispenser means (3) and the delimiting zone (4).

Figure 3 shows a chart representing the variation of the minimum ORP value of the water according to the wateris salinity, as a resuit from an embodiment of the method of the présent invention.

Figure 4 shows a chart representing the variation of the minimum period of time that the minimum ORP value is maintained according to the wateris température, as a resuit from an embodiment of the method of the présent invention.

In accordance with common practice, the various described features are not drawn to scale but are drawn to emphasize spécifie features. Référencé characters dénoté like features throughout the Figures.

DETAILED DESCRIPTION

The following detailed description refers to the accompanying drawings. While some embodiments may be described, modifications, adaptions, and other implémentations are possible. For example, substitutions, additions, or modifications may be made to the éléments illustrated in the drawings, and the methods described herein may be modified by substitutlng, reordering, or adding steps to the disclosed methods. Accordingly, the following detailed description does not limît the scope of the disclosure. While Systems and methods are described in ternis of “comprising various apparatus or steps, the Systems and methods can also consist essentïally of or consist of the various apparatus or steps, unless stated otherwise.

Définitions

In the light of the présent disclosure, the following ternis or phrases should be understood with the meanings described below:

As used herein, the general types of water and their respective Total Dissolved Sollds (TDS) concentration (in mg/L) are: Fresh, with TDSS1.500; Brackish, with 1,5OO<TDSS10,000; Salty, with * 10,000<TDSi30,000; and Seawater, with TDS > 30,000. The TDS can be measured for example using a conductivity meter or by applying gravimétrie methods evaporating the solvent and weighlng the mass of resldues left.

As used herein, sanitary-compliant zone refers to the portion of water, within the large water body, which is established for recreational purposes, and required to comply with spécifie microbiological sanitary conditions, when used for recreational purposes or when it ls needed. It must be noted that the sanitary-compliant zone may not be permanently the same physical zone, but it may change according to the requirements of the people for recreational purposes.

As used herein, spécifie microbiological sanitary conditions refers to the microbiological propertïes/conditions that need to be achieved within the sanitary-compliant zone In order to allow recreational purposes. Such conditions can be determined by spécifie local, state, fédéral régulations for reducing certain spécifie organisme, or different predetermined spécifie conditions.

As used herein, minimum ORP level refers to the minimum ORP that can be allowed in the most unfavorable zone, in order to properiy control microbiological properties in such zone.

As used herein, “minimum period of time’ refers to the minimum amount of time that the minimum ORP ievel of the water at the most unfavorable zone must be maintained, in order to aliow the required sanitary conditions.

As used herein, the “delimlting zone* corresponds to a virtuai zone that delimits the sanitarycompilant zone, and does not require a physical barrier.

As used herein, the “most unfavorable zone corresponds to the zone that shows the lowest ORP values within the identified portion of water, espedally after appiying a determined amount of chemical agents. The most unfavorable zone is often, but not necessarily always, found on the delimiting zone ofthe identified portion of water and the farthest from the chemical dispenser.

As used herein, the dispenser means refer to any means for appiying one or more chemical agents to the water, and may be selected from the group consisting of an injector, diffusor, sprinkler, weight dispenser, piping, manuai application, and combinations thereof; pipes; valves; and connecting éléments that aliow the proper application of chemicals into the established portion of water to be treated.

As used herein, the chemlcal agents that are applied to the water body refer to any chemical agent that allows achieving the desired ORP level In the water. The effective amount of chemical agents corresponds to the minimum amount of chemicals that can be applied to the water in order to maintain at least the minimum ORP level during at least the minimum period of time at the most unfavorable zone.

Methods of the Présent Disclosure

The présent disclosure allows controllîng the microbiological properties in large water bodies by treating a portion of the large water body, so that said portion of the large water body compiles with spécifie microbiological sanitary conditions when required, thus overcoming the limitation or Impossibility of treating the whole water body. Sanitary-compliant zones are created, which are strategically located in order to widely cover the area being used for recreational purposes.

The disclosed method requires a smaller amount of chemicals and reduced energy consumption because it does not require treating the complété water body with this spécifie method (the water body may be subject to other treatments different to the disclosed method). Thus, the présent disclosure allows people to use certain zones within large water bodies for recreational purposes in a safe manner, and overcomes the économie, technical and environmental limitation or Impossibility of treating the whole water body, and also allows using countless lakes, seashores, lagoons, and many water bodies that are unusable today due to safety or sanîtary problems, generating unprecedented recreational and touristic opportunities that can change the lifestyle of people around the world.

The disclosed methods can be performed on naturel or artificial large water bodies, such as lakes, the sea, estuaries, réservoirs, dams, and lagoons. The disclosed methods can be used with different water types including fresh, brackish, salty, and sea water. In one embodiment, the method for controlling the microbiological properties of a portion of water within large water bodies Includes:

a. identifying a portion of water Intended for recreational purposes within the large water body and defining dispenser means;

b. maintaining at least a minimum ORP level In such portion of water for at least a minimum period of time, wherein the minimum ORP level and the minimum period of time cannot be lower than the values calculated by:

l. determining the most unfavorable zone within the portion of water;

it. determining the salinity of the water at the most unfavorable zone;

lii. determining the minimum ORP value based on the salinity of the water where:

- for salinities in the water between 0% and up to 1.5% the minimum ORP level Is 550 mV;

- for salinities in the water higher than 1.5%, and up to 2.5%, the minimum ORP level Is calculated by the following équation:

[Minimum ORP, mV] = 625 - 50*[Salinity of the Water, % (Weight Percent)]; and

- for salinities In the water higher than 2.5%, the minimum ORP level is 500 mV; and

Iv. determining the température of the water In the most unfavorable zone; and

v. determining the minimum period of time based on the water température, where

- for water températures from 5*C to 35*C, the minimum period of time Is calculated by the following équation:

[Minimum period of time, min] = 80 - 2*[Temperature of the water, ’C]; and

- for water températures between 35’C and up to 45*C, the minimum period of time Is calculated by the following équation:

- [Minimum period of time, min] = 5‘[Temperature of the water, *C] -165;

c. dispensing an effective amount of chemical agent In order to maintain at least the minimum ORP level during at least the minimum period of time at the most unfavorable zone, and

d. Repeating step c in order to avoid the ORP in the most unfavorable zone to decrease by more than 20% of the minimum ORP value.

The location of the most unfavorable zone, the water salinity and température of the water may vary Independently from each other as a resuit of extemal conditions. Thus, the method of the disclosure may optionally comprise a further step e., where steps b., c. and d. are canied out once agaln or repeatediy.

To détermine the zone that must comply with spécifie microbiologicai sanitary conditions applied to the water body, a strategie analysis could be done in order to provide an accessible zone that can ailow safe recreatlonal purposes.

The dispensation of the chemical agent, preferably through dispenser means, Is controlled by a parameter détermination method that combines the effects of the ORP of the water, its salinity and its température. Optionally, the diffusion of chemicals, and the dilution power of the water may be further considered in the parameter détermination method. Due to the combined effect of the disinfection properties of the water (ORP), the résistance of certain microorganisms depending on the salinity of the water, the température, and optionaliy the dilution power of the water, the présent disclosure allows to use much less chemical agents than required by swimming pools In order to comply with spécifie microbiologicai sanitary conditions applied to the water body, which was a resuit of extensive research. In the state of the art, there are currentiy two ways for maintalning a water quality compilant with spécifie microbiologicai sanitary conditions applied to the water body, which reiate to the addition of large quantifies of disinfection agents, or instead relying on the dilution power of the water. The présent disclosure combines both effects in order to make the most of their synergies and thus provide an effective and sustainable method for zones that comply with spécifie microbiologicai sanitary conditions.

Identifving the portion of water to be treated

The location of the portion of water to be treated, which after the process of the invention will be designated as the sanitary-compliant zone, can be determined by strategically identîfying the portion of the water most likely to be used for recreational purposes. This location can be 11 determined by examining where usera are likely to enter the water, the depth of the water, the purpose of the water (e.g., bathing, swimming, skiing, boating, fishing, etc.), the température of the water, and the like. For example, If a body of water 1s located next to a hôtel, the sanitarycomplalnt zone will likely be the portion of the water next to the hôtel where usera are most likely to 5 enter the water. This Is shown In Figures 1 and 2, which show the sanitary-compliant zone 1 located on an edge of the large water body 2. In other cases, the sanitary-complaint zone can be In the center of a body of water and surrounded by the large water body. In some cases, the sanitarycompliant zone may correspond to a recreational area that is visuaily roped off or otherwise physically separated from the rest of the water (e.g., fenced off, partitioned off with a wall).

Referendng Figures 1 and 2, the zone 1 compiles with predetermlned sanitary conditions. As discussed, the sanitary conditions may be determined by local, state, or fédéral régulations or different predetermlned spécifie conditions. Exemplary régulations for recreational water state that E. Coli must not exceed 126 CFU per 100 ml of water, and that Enterococcl must not exceed 33 CFU per 100 ml of water. For seawater, the EPA régulations state that Enterococd must not 15 exceed 35 CFU per 100 ml of water. In Chile, the Norm NCh1333 for direct-contact recreational waters state that the water must not contain over 1000 CFU of fecal coliforms per 100 ml of water (induding E. Coli, among others). Aitematively, the sanitary conditions or microbial properties may be determined by referendng the concentration of certain microorganisms. In any case, the sanitary-compliant zone 1 meets the sanitary conditions, while the rest of the water volume 2 may 20' not comply with spedfic sanitary conditions applied to the sanitary-compliant zone.

Additionally, the sanitary-complaint zone may Include one or more dispensera 3 for dispensing chemical agents where the rest of the water body 2 may not indude the dispensera 3.

The sanitary-compliant zone is vîrtually bounded by the delimiting zone 4. The deiimlting zone 4 is a virtual barder that may comprise but does not require a physical barder.

The présent disdosure does not require dreuiating water throughout the various zones - sanitarycompliant zone, delimiting zone, and most unfavorabie zone. In fact, in some embodiments, the water is spedfically not drculated. For the large water bodies described herein, it may be economically, technically and environmentally unviable to dreuiate the water withln the large water body. The présent disdosure treats the water in the Identified portion of water with chemical agents to allow such zone to comply with spécifie microbioiogical sanitary conditions for such area. While dispersion of the chemical agents from the sanitary-compliant zone to other zones may naturaliy occur within the water body, it is not requlred by the présent disdosure. Therefore, in some embodiments, maintaining water circulation throughout the complété water body would be counterproductlve with the disclosed methods.

After the portion within the large water body to be used for recreational purposes has been identified or established, the dispenser means, which are controlled by a parameter détermination method based on the ORP of the water, its salinity, its température, and optionally the diffusion of chemicals as well as the dilution power of the water, may be defined.

The dispenser means 3 may be selected from one or more than one diffùsors, injectore, sprinkiers, dispensera by weight, piping, manual application, or combinations thereof. The dispenser means are adapted to discharge an effective amount of chemicals into the water body; and also may comprise the required equipment to allow its proper operation, such as pipes, valves, and connecting éléments.

In order to create the zones that comply with spécifie microbiological sanitary conditions applied to the water body, chemical concentrations must be appiied according to a parameter détermination method based on the ORP, the salinity, the température, and optionally the diffusion of chemicals and the dilution power of the water as well. The chemicals may preferably be applied by dispenser means 3 that are defined in order to cover the water volume used for recreational purposes.

It must be noted that the présent disclosure does not require a physical barrier in order to contain the portion of water to be treated, but instead chemical concentrations are applied to the portion of water in order to comply with spécifie microbiological sanitary conditions applied to such area the water body.

The dispenser means are controlled by a parameter détermination method based on the ORP of the water, its salinity, its température, as weli as optionally the diffusion of chemicals and the dilution power of the water. The dispenser means applies chemicals into the water in order to ailow proper diffusion conditions within the water body and comply with spécifie microbiological sanitary conditions applied to the water body. The dispenser means may be strategicaliy configured, and positioned relative to and/or with the portion of water intended for recreational purposes in order to provide the required chemical concentrations at the sanitary-compliant zone.

Number end Location of Dispensera

In one embodiment, the dispensera are located or used in order to cover the water volume In the sanitary-compliant zone. The number and location of the dispensera for dispensing the chemical agents may be determined by the spécifie conditions of each portion of water that will be treated. The total amount of dispensera can be calculated according to the chemical flow that is to be 13 applîed to the water body, and such chemical flow may be divlded Into a sériés of dispensera in order to allow Its homogeneous application throughout the portion of water to be treated.

For example, for treating the same portion of the water body, there is an effective amount of chemicals to be added. The effective amount may preferably be added through several small-flow dispensera, or just a few large-flow dispensera, depending on several variables such as for exampfe wind, water currents, and many other variables that may influence the homogeneity of the chemical application within the water body.

The dispensera can generally be located on the perimeter of the portion of water that will be treated, ln order to fully cover such portion, but they can also hâve other configurations regarding the spécifie requirements of the portion of water ln order to malntaln the homogeneity of the chemical application and allow the chemical diffusion throughout the portion of water.

Types of Dispensais

The types of dispensera that can be used In the disclosed method can be variable according to the requirements for chemical application, and may comprise diluters, injectors, dispensera by weight, manual application, manifolds, piping, sprinklers, nozzles, or combinations thereof. The dispensera used ln the dîsclaimed method are preferably nozzles, and more preferably Injectors.

Dlscharglng an Effective Amount of Chemical Agents

Chemical agents are used to croate the sanitary-compliant zone by rodudng the number of microorganisms in the sanitary-compliant zone to below a predetermlned amount The concentration of the chemical agents in the sanitary-compliant zone can be controlled by the amount of chemical agent dispensed from a single dispenser as well as the total number of dispensera. For example, It may be désirable to dispense less chemical agent from a single dispenser, but to increase the number of dispensera in the sanitary-compliant zone. An example of the use of multiple dispensera is shown in Figure 2 where a plurality of dispensera 3 are located around the periphery of the sanitary-compliant zone. The number and location of the dispensera for dispensing the chemical agents are determined in order to cover the water volume ln the sanitary-compliant zone, ln one embodiment.

The dispenser 3 may be a diffusor, injector, sprinkler, dispenser by weight, piping, manual application, or combinations thereof. The dispenser discharges an effective amount chemical agent into the water body. The dispenser also Includes any requlred equlpment to allow the dispenser to operate, such as pipes, valves, and connecting éléments.

Exemplary chemical agents Include antimlcrobial agents such as ozone, chlorine, and chlorine compounds, blguanide products, halogen-based compounds, bromlne-based compounds, and combinations thereof.

The total amount of chemlcals added to achieve a certain ORP ievei in the water dépends on severai variables, such as for example the pH, meteoroioglcai conditions, rain, levels of use, organlc load, salinity, température, alkalinity, disinfectant concentration, and/or concentration of metals and contaminants, among many other factors. The ORP Is a measure of the tendency for oxldlzlng or reducing certain species found within the water body, and therefore does not represent the amount of chemical agents contained in the water. ORP measurements présent the advantage of measuring not only the concentration of the sanitizer, but also Its actîvity in the water and Its effectiveness on killing germs and bacteria.

There are no known équations that can relate the température of the water, Its salinity, and the dilution power for maintaining a minimum ORP in a certain portion of the water for a minimum period of time according to the diffusion of chemicals In the water, due to the complexity of the variables and its mutuai influences, and therefore extensive research was performed. An intricate model must be built In order to estimate the amounts of chemicals to be applied in the water body. Since the portion of water is contained within a large water body, when the chemicals are applied, they will diffuse throughout the portion of water creating a chemical gradient that wiii be higher near the dispensera and lower near the most unfavorable zone.

It must be noted that when the application of chemicals begins, at first there wiii be no significant change in the ORP of the water since the chemicals wiii be oxidizing severai other compounds in the water. However, at some point the application wiii allow generating a residual concentration of chemicals that will help raise the ORP up to the desired levels and thus provide the desired disinfection capadty. Therefore, it must be noted that the chemical consumption Is divided into two groups:

- The amount of chemicals appiied that help oxidizing diverse compounds that do not affect ORP significantly. Such chemical consumption must be determined on-site, as it completely dépends on the water quality of the raw water. Also, such concentration could be determined by an intricate model based on the water quality physicochemical parametera.

- The amount of chemicals applied that generate a residual concentration in the water and thus increase the ORP in the water. Such chemical concentration can be estimated on site or according to diverse methods depending on water quality and physicochemical conditions or parametera.

Notwithstanding the foregoing and without limiting the invention, the oxidant application ranges for different oxidants vary according to the properties of the water. Usually utilized ranges of some oxidizlng agents are the following:

Oxidant	Range of Application (Residual Concentration)
Chlorine	0.01 - 5 ppm
Sodium Hipochlorite	0.01 -2 ppm
Bromlnes	0.01 -2.3 ppm
Ozone	0.01 - 0.75 ppm

The applicant will provide some embodiments to estimate the amount of resldual chemicals in the water:

a. One could estimate the minimum amount of oxidants that must be applied in the water in order to obtain a certain ORP in the entire portion of water to be treated, assuming the portion of water behaves as a dosed body. For example, the minimum amount of chemicals could be estimated In order to achieve a certain ORP in the total volume of the portion of water. For example, if the portion of water has a volume of 1,000 m³, and the portion of water Is considered a ciosed water body, it can be estimated that for achieving an ORP of 550 mV in the water, a residual concentration of 0.07 ppm of sodium hypochlorite must be maintained. In order to obtain the residual concentration of 0,07 ppm, a first dosage of 1.2 ppm of sodium hypochlorite was added In order to meet the chlorine demand of the water and did not generate any residual concentration. Afterwards, a dose of 0.07 ppm was added to obtain the required residual concentration and obtain the desired ORP level of 550 mV. Therefore, the amount of sodium hypochlorite added to the water can be caiculated according to its concentration in the water body as follows:

First dose:

1.2 ppm =

1.2 ppm sodium hypochlorite

Hier of water

1,000 m*xl.000 Hters m³

Total Sodium Hypochlorite = 1,200 kg

Residual concentration:

07 ppm = 0.07 J ooo m-.uoom.,, ^rr iiter of water lm’

Total Sodium Hypochlorite = 70 kg

Therefore, a total amount of 1270 kg of sodium hypochlorite should be added to obtaln a homogeneous resîdual concentration of sodium hypochlorite ln the water of 0.07 ppm, and thus obtaln an ORP of 550 mV ln such zone. Since ln reality the portion of water Is found within a large water body, the concentration will not be homogeneous, and then the prevlously calculated dose can be consldered as a minimum for obtaining such ORP due to the diffusion of chemlcals produced by currents.

b. One could also use the free chlorine method, which allows calculatlng the ORP of the water based on the pH and the free chlorine concentration ln the water. When the pH Is maintained at a constant value, there Is a linear relationship between ORP and free chlorine. Thus the amount of chemicals required to achieve a certain amount of free chlorine can be calculated subject to the ORP level as follows:

ORP	PH	Residual Chlorine Concentration
600 mV	7.0	0.06 ppm
8.0	0.20 ppm
9.0	1.60 ppm
700 mV	7.0	0.30 ppm
8.0	1.00 ppm
9.0	2.70 ppm

c. Addition of chemicals with periodic monitoring in order to stop the addition when a certain ORP is reached is a further option. This method is a trial and error method, which allows adding chemicals by periodlcally monitoring the ORP, and when the desired ORP is reached, the chemical addition must be stopped.

d. Another method used for determining the amount of chemicals consiste of taklng a small water sample and perform a small-scale test to détermine the amount of chemicals that must be applied to achieve a certain ORP level. This method is commonly used and ailows estimating the amount of chemicals, although it does not consider diffusion or other variables. Therefore, the results from this method are to be considered as a minimum amount of chemicals required.

In some embodiments, it 1s désirable to apply additional chemical agents before the ORP level In the most unfavorable zone decreases by about 0.1%, 1%, 5%, 10%, 15%, 20%, 25%, 50%, 75%, or 100%.

In certain embodiments of the Invention, where there is an intensive use of the sanitary- compilant zone due to large amounts of people, or if there are many currents that affect the disinfection characteristics of the sanitary-compllant zone, or due to safety or other reasons, the ORP may be malntained permanently within the sanitary compilant zone for certain periods of time.

Also, in certain embodiments of the Invention, the water treatment Is only utilized when bathers are présent in the sanitary-compliant zone, and therefore the treatment may not operate ail day nor permanently. For example, the water treatment may operate only during the day, and It can be stopped during the night, when there are no bathers in the sanitary-compliant zone. Therefore, the water treatment method Is applied when the sanitary-compliant Is effectiveiy used for recreatîonal purposes.

In some embodiments, it may be désirable to improve the water quality in the sanitary-compliant zone by supplying fresh water or water from different portion within the large water body. This may be bénéficiai, for example, to dilute the effect of contaminants from usera but may produce an unwanted diffusion effect on the chemicals.

The minimum effective amount of disinfectant composition may be calculated by the following équations: (Boyce & Hamblin, 1975) (Boyce & Hamblin, 1975)

C-™ z^-Z-d'*¹’(A)^Κ<,(“’^r)

r = (x²+y²)5

Where the above équation is the solution for a point source discharging continuously at a constant volumétrie rate Qi and at a concentration C[ [μΜ] at the source In a fluid of depth Z [m], with x [m] and y [m] being the horizontal and vertical distances respectively. D is the diffusion coefficient of the spécifie chemical in the water, and Ko is the modified Bessel fonction of the second kind. U [cm/s] is the uniform current of the water body through the x axis, and y[-] Is the decay process of the chemical In a time scale.

Most unfavorable zone

In order to comply with spécifie microbiological sanitary conditions applied to the water body, the most unfavorable zone of the established portion of water Is to be determined. The most unfavorable zone corresponds to the one having the lowest ORP values, espedally after applying a predetermined amount of chemicals through dispenser means in the established portion of water, and it may be found on the delimiting zone or the furthest from the dispenser means. The predetermined amount of chemicals can be determined on-site and its only purpose is to détermine the zone with lowest ORP values within the portion of water to be treated.

If the water body has a surface area smaller than 5 hectares, the most unfavorable zone is usually the centrai zone of the water body.

A parameter détermination method is defined to take In account the different operation conditions of the system. It should be noted that it is unviable to perform constant measures on the water body, thus the présent disciosure allows provlding a water quality that compiles with spedfic microbiological sanitary conditions without requiring constant measures.

The parameter détermination method Is based on the wateris ORP, Its salinity, Its température, and optionally the diffusion of chemicals and its dilution power within the identified portion of water. The ORP, salinity, and température of the water can be determined by empirical methods, such as Visual inspection, methods based on expérience, and analytical methods. The présent disciosure has related these variables and has solved a very complex interaction regarding water quality, after very extensive research.

The salinity can be determined by empirical or analytical methods such as Visual tests; salinometers that are based on the conductivity of electridty In the water; hydrometers that are based on the spedfic gravity of the water; or refractometers that are based on the index of refraction of the water; or may be publically known or can be Information from other sources, among others.

The température of the water can be determined by empirical or analytical methods such as Visual tests; thermometers; thermocouples; résistance température detectors; pyrometers; or infrared devices; or may be publically known or can be information from other sources, among others.

The ORP of the water can be determined by empirical or analytical methods, such as using ORP met ers that hâve électrodes in order to measure the voltage across a circuit within the water.

It must be noted that the ORP of the water, its température, its saiinity, and the dilution power may be previously known or empirically determined, therefore the method from the présent disclosure can be applied into the predefined portion of water In knowledge of these variables.

The parameter détermination method comprises maintaining at least a minimum ORP level in the most unfavorable zone for at ieast a minimum period of time in order to ensure the required sanitary conditions throughout the entire established portion of water within the large water body.

The minimum ORP level may dépend on the saiinity of the water, as certain types of microorganisms, such as some pathogenic protozoa, can only grow and live inslde water bodies with maximum salinities of 2% in weight. Therefore, the minimum ORP level may dépend on the saiinity properties of the water, as for certain saiinity concentrations the water will not serve as a media for some microorganisms to grow and thus pose health threats and un-hygienlc conditions.

On the other hand, the minimum period of time may also dépend on the température of the water. The wateris température is a very Important factor for the prolifération of several microorganisms. For low water températures, the microorganisms will not proliferate as rapldly as for higher water températures, therefore this effect Is considered in the présent parameter détermination method. Until now, there were no known équations that can relate the température of the water, Its saiinity, and the dilution power for maintaining at least a minimum ORP in a certain portion of the water for at least a minimum period of time according to the diffusion of chemicals in the water, due to the complexity of the variables and its mutual influences. Such relations are product of an extensive research, and the minimum ORP level and the minimum period of time that are used for the method of the présent invention, in a preferred embodiment, cannot be lower than the values defined as follows:

Minimum ORP Level:

Once the saiinity is known from the most unfavorable zone, the minimum ORP level may be calculated by the following équations:

1. for salinities between 0% and up to 1.5% the minimum ORP of the water Is at least 550 mV;

ii. for salinities higher than 1.5%, and up to 2.5%, the minimum ORP of the water is calculated by the following équation:

[Minimum ORP, mV] = 625 - 50*[Salinity ofthe Water, % (Welght Percent)]; and iii. for salinities higher than 2.5%, the minimum ORP of the water is at least 500 mV.

The aforementîoned parameter détermination method is represented in a graph as shown in Figure 3.

For example, if the water has a salinity of 1% in weight (or 10,000 ppm) the minimum ORP of the water that has to be maintained, according to this embodiment, wili be 550 mV.

On the other hand, if the water has a salinity of, for example, 2% in weight (or 20,000 ppm) the minimum ORP of the water that has to be maintained is 525 mV, according to this embodiment, is calculated using the following équation:

[Minimum ORP, mV] = 625 - 50*[2] = 525 mV

Finaily, if the wateris salinity is higher than 2.5%, for example 3% in weight, the minimum ORP that has to be maintained is 500 mV.

Minimum Period of Time:

The minimum period of time is determined by the température ofthe water, and it can be calculated by the foliowing équations:

i. for water températures between 5’C and up to 35'C, the minimum period of time is calculated by the following équation:

[Minimum period of time, min] = 80 - 2*[Temperature of the water, ’C]; and ii. for water températures higher than 35’C and up to 45^eC, the minimum period of time is calculated by the foliowing équation:

[Minimum period of time, min] = 5*[Temperature ofthe water, ^eC] -165.

The curve showing howthe minimum period of time behaves is shown of Figure 4.

For example, if the wateris température is 20^eC, the minimum period of time is 40 minutes according to the foliowing équation:

[Minimum period of time, min] = 80 -2*[20] = 40 minutes

On another hand, if the wateris température is between 35’C and 45^eC, for example 40^eC, the minimum period of time Is 35 minutes according to the following équation:

[Minimum period of time, min] = 5*[40] -165 = 35 minutes

The parameter détermination method of the above embodiment Is described only In use for water températures between 5^eC and 45*C, since any other température may not be suitable for recreational purposes.

The parameter détermination method may also comprise applying chemicals agents through the dispenser means to avoid the ORP of the most unfavorable zone to be less than the minimum ORP levai.

When there are bathers in the sanitary-compliant zone, the ORP of the water wili decrease more rapldly than when there are no bathers in the water. Thus, the présent parameter détermination method allows including the effect of the amount of bathers In the sanitary-compliant zone, which in tum Is controlled by the dilution power of the water. The time taken to reach the minimum ORP level wili dépend on the use of the sanitary-compliant zone and the dilution encountered by the bathers. Therefore, the ORP decreaslng rate wili dépend on the amount of bathers in the water, and thus, on the dilution power of the water.

The variables of water salinity and température, ORP, and chemical concentration can vary and be affected by extemai factors. The disdosed methods allow for some variation In these factors such that constant monitoring of the water salinity, water température and recalculation of the minimum ORP and chemical concentration may not be required. Nevertheless, in some embodiments, the water salinity and water température can be constantly monitored on either a deiay or in real time, and provide feedback to a controller that automatically recalculâtes the minimum ORP, minimum period of time, and concentration of chemical agent accordingly. In some embodiments, the dispensera may be part of an automatic feedback loop where the dispensera automatically dispense additional chemical agents in response to a decrease In the minimum ORP. in some embodiments, it may be désirable to periodically measure the water salinity and température and recalculais the minimum ORP, minimum period of time, and chemical concentration. Such periodic measurements and calculations could take place every 15 minutes, every 30 minutes, every hour, every two houre, six times a day, four times a day, twice a day, once a day, once a week, or as needed.

It must be noted that the présent disclosure does not require a physlcal barrier In order to contain the portion of water to be treated. Rather, chemical concentrations are applied to the portion of water In order to comply with spécifie microbiological sanitary conditions applied to the water body.

The application of chemicals in order to maintain at least a minimum ORP level during at least the minimum period of time may be repeated before the ORP level decreases by more than 20% of the minimum ORP value in the most unfavorable zone. In an alternative embodiment, the location of the most unfavorable zone, the water salinity and température of the water may vary independently from each other as a resuit of extemal conditions. Thus, the method of the invention optlonally may comprise a further step e., where steps b., c. and d. are canied out once again or repeatediy.

Chemical agents can be added to the established portion of water within the large water body through dispenser means, where the dispenser means is driven by a parameter détermination method that combines the effects of ORP of the water, its salinity, its température, the diffusion of chemicals, and its dilution power.

The chemical agents are selected from ozone; chiorine and chlorine compounds; blguanide products; halogen-based compounds; bromine based compounds, or a combination thereof.

It is also possible to Improve the sanitary-compliant zone's water quality by supplying fresh water or water from different portion within the large water body into such portion In order to allow a dilution effect of batheris load of contaminants.

The following example is not intended to limit the scope of the daims of the invention but is rather intended to be exemplary of certain embodiment Any variations in the exemplified method which raise to the skilled in the art are Intended to fail within the scope of the présent invention.

EXAMPLE

The disdosed method was applied In Lake Rapel located in Navidad, Chile. The lake has over 8,000 hectares of surface, and more than 695 million cubic meters of fresh water. The lake is normally used for recreational purposes.

A portion of water within the large water body was established according to the lake's normal recreational use, which covered approximately 650 m² (correspond!ng to about 0.0008% of the total lake area). The portion was located on the edge of the lake. The spedfic mlcrobiological conditions required for this spécifie experiment corresponded to the mlcrobiological régulations for direct contact recreational waters as determined by the EPA.

Approximately 20 injectors were Installed on the north perimeter of the lake. Each injector had a maximum flow of 1.8 liters per hour. The chemical agent used was sodium hypochlorite, which was diluted proportional to the injector flow. A solution of chlorine in water was prepared in a plastic bin with a capacity of 1 m³. The pumping of the sodium hypochlorite solution was performed by an IWAKI magnetic pump with a capadty of 18 liters per minute.

During the experiment, the established portion of water had an average of 60 bathers on an hourly basis.

The détermination of the most unfavorable zone was performed by measuring the ORP in several places within the established portion of water using a HANNA ORP Hl 98201 ORP test equipment after discharging a predetermined amount of approximately 1.5 liters of a 10% solution of sodium hypochlorite Into the established portion of water. The most unfavorable zone was located on the center of the delimiting zone of the established portion of water. The wateris salinity was measured with a HANNA Hl 9311OON conductivity test. The salinity of the water was found to be 0.07% In welght, and the average water température 21 C as measured by a thermometer.

The minimum ORP level was determined where for saiinities between 0% and up to 1.5% the minimum ORP level of the water is at least 550 mV. Therefore, the minimum ORP level of the water with a salinity of 0.07% should be 550 mV.

The minimum period of time was determined, where for water températures between 5’C and up to 35*C, the minimum period of time is calculated by the following équation:

[Minimum period of time, min] = 80 - 2*[Temperature of the water, ’C]

Minimum period of time in minutes = 80 - 2*[21]

Minimum period of time = 38 min

Sodium hypochlorite was added through the injectors to maintain a ORP level of at least 550 mV in the most unfavorable zone for a minimum period of 38 minutes. At first, 1 ppm of sodium hypochlorite was added to treat the water. Afterwards, sodium hypochlorite was added in order to maintain a 0.10 ppm residual concentration, which allowed maintaining at least a 550 mV ORP level In the most unfavorable zone.

Once the total amount of sodium hypochlorite was discharged, the ORP of the most unfavorable zone was measured and determined to be 555 mV. Subséquent measures were carried out every 60 minutes. The ORP decreased to 490 mV (by about 11% from the determined minimum ORP) after about 30 minutes, at which point new sodium hypochlorite was dispensed.

The dilution power of the water is reflected in the average amount of bathers per hour In the sanitary-compliant zone: for Iower bather's densities, the water's ORP will decrease slower than for higher bather’s densities. Also, the decrease In ORP is affected by the sun and other variables.

This example confirmed that the sanitary-compliant zone complied with EPA’s spécifie microbiologicai régulations for direct contact recreational waters and even more stringent sanitary régulations, and allowed applying a small amount of chemicals by avoiding the treatment of the complété large water body, by treating the identified portion of water In order to create a sanitarycompliant zone.

The chemicals applied in the présent example were at least 100 orders of magnitude Iower compared to the amount of chemicals required to treat the complété water body. In order to treat the complété water body of Lake Rapel, which holds over 695 million cublc meters of fresh water, and allow Its use for recreational purposes, a certain amount of chemicals must be added that can ensure the safety of bathers. In order to maintain the same ORP level as for the example (a concentration of 0.10 ppm of sodium hypochlorite with the additional 1 ppm added beforehand to treat the water), the total amount of sodium hypochlorite that must be applied Is approximately 764.5 tons, which Is more than 100,000 times the amount of sodium hypochlorite that Is required for treating the portion of water from the aforementioned example, which Is economically and environmentally unvlable.

Claims (17)

1. Method for controlling the microbiological properties of a portion of a water body within large water bodies, comprising:

a. identifying a portion of water Intended for recreational purposes within the large water body and defining dispenser means;

b. maintaining at least a minimum ORP level in such portion of water for at least a minimum period of time, wherein the minimum ORP level and the minimum period of time cannot be lower than the values calculated by:

I. determining the most unfavorable zone within the portion of water;

ii. determining the salinity of the water at the most unfavorable zone;

iii. determining the minimum ORP value based on the salinity of the water where:

- for salinities in the water between 0% and up to 1.5% the minimum ORP level Is 550 mV;

- for salinities In the water higher than 1.5%, and up to 2.5%, the minimum ORP level is calculated by the following équation:

[Minimum ORP, mV] = 625 - 50*[Salinity of the Water, % (Weight Percent)]; and

- for salinities in the water higher than 2.5%, the minimum ORP level is 500 mV;

and iv. determining the température of the water in the most unfavorable zone; and

v. determining the minimum period of time based on the water température, where:

- for water températures from 5‘C to 35’C, the minimum period of time is calculated by the following équation:

[Minimum period of time, min] = 80 - 2*[Temperature of the water, *C]; and

- for water températures between 35*C and up to 45^eC, the minimum period of time Is calculated by the following équation:

[Minimum period of time, min] = 5*[Temperature of the water, ’C] -165;

c. dispenslng an effective amount of chemical agent in order to maintain at least the minimum ORP level during at least the minimum period of time at the most unfavorable zone, and

d. Repeating step c in order to avoid the ORP in the most unfavorable zone to decrease by more than 20% of the minimum ORP value.

2. The method of claim 1, further comprising repeating step b.

3. The method of claim 1, wherein the water body is a naturel or artificial body of water.

4. The method of daim 1, wherein the water body is selected from the group consistîng of a lake, sea, estuary, dam, lagoon, spa, pool, pond and réservoir.

5. The method of claim 1, wherein the water Is fresh water, brackish water, salty water, or sea water.

6. The method of daim 1, wherein the portion of water intended for recreational purposes is defïned by a delimiting zone.

7. The method of daim 1, wherein the portion of water intended for recreational purposes Is located on an edge of a large water body.

8. The method of daim 1, wherein the portion of water Intended for recreational purposes is located on the Interior of a large water body.

9. The method of daim 1, wherein the most unfavorable zone présents the lowest ORP value within the portion of water intended for recreational purposes after dispensing chemical agent.

10. The method of daim 1, wherein If the water body has a surface area smaller than 5 hectares, the most unfavorable zone Is the central zone of the water body.

11. The method of claim 1, wherein the chemical agent is selected from the group consisting of ozone; chlorine and chlorine compounds; blguanide products; halogen-based compounds; bromïne based compounds, and mixtures thereof.

12. The method of daim 1, wherein the chemical agent is dispensed using a dispenser selected from the group consisting of an Injector, diffusor, sprinkler, weight dispenser, piping, manual application, and combinations thereof.

13. The method of claim 1, wherein the ORP, the salinity, and the température of the water are determined by empirical methods.

14, The method of claim 1, wherein water from a different portion within the water body can be supplied into the portion of water intended for recreational purposes in order to allow a dilution effect.

5

15. The method of daim 1, wherein water from different portion within the water body can be supplied Into the portion of water Intended for recreational purposes in order to allow a dilution effect of bather’s load of contaminants.

16. The method of daim 1, wherein the ORP Is maintained permanently in the portion of water 10 intended for recreational purposes during a certain period of time according to the requirements of such zone.

17. The method of daim 1, wherein the method is applied when the portion of water is actually used for recreational purposes.