Biocidal control in aqueous membrane separation systems

Abstract

The present invention provides a process for microbial control in an aqueous membrane separation system, in which microbial control is provided by a bromine-containing biocide.

Description

Technical Field

[0001] Related Applications This application claims the benefit of U.S. Provisional Patent Application No. 63 / 532,796, filed on August 15, 2023. The entire disclosure of the provisional application is incorporated herein by reference.

[0002] The present invention relates to biocidal control in aqueous membrane separation systems.

Background Art

[0003] Microorganisms, such as bacteria, fungi, and algae, that enter an aqueous membrane separation system can deposit on the membrane, grow into biofilms, and negatively affect the performance of the membrane. Biofilms can affect the water passing through the membrane, block the membrane, and / or reduce the efficiency of the membrane.

[0004] Various methods have been developed to control or minimize the growth of microorganisms and biofilm formation, particularly on the membrane(s) of the system. Some of these methods use biocides that contact the membrane, which can potentially damage the membrane. There is still a desire for a method to minimally suppress or prevent biofilm formation on the membrane(s) without damaging the membrane.

[0005] The subject matter of this disclosure can be better understood by referring to the following illustrative drawings. Components in the drawings are not necessarily proportional to actual size; instead, the emphasis is on illustrating (often graphically) the principles of the subject matter of this disclosure. Similar reference numbers in the drawings designate corresponding parts across several drawings. A further understanding of the subject matter of this disclosure can be obtained by referring to the embodiments shown in the drawings of the accompanying drawings. The illustrated embodiments are for the purpose of illustrating examples of systems for carrying out the subject matter of this disclosure, but both the configuration and operation methods of the subject matter of this disclosure, along with their further purposes and advantages, can generally be better understood by referring to the drawings and the following description. The drawings are not intended to limit the scope of the subject matter of this disclosure, which is described in detail in the accompanying or subsequently amended claims, and are merely intended to clarify and provide examples of the subject matter of this disclosure. [Brief explanation of the drawing]

[0006] [Figure 1] This graph shows data from experiments conducted to test the progression of membrane degradation. [Overview of the project]

[0007] The present invention provides a process for controlling and minimizing microbial growth, particularly biofilm growth in aqueous membrane separation systems. In the process of the present invention, biofouling is effectively minimized or controlled with little to no contact between the biocide and the membrane, thereby minimizing or preventing biocide damage to the membrane. By implementing the present invention, effective minimization of microbiological contamination of water and membranes(s) can be achieved.

[0008] One embodiment of the present invention is a process for controlling biofouling in an aqueous membrane separation system comprising water and one or more protective membranes. This process is I) Producing treated water by bringing the supply water into contact with a biocides containing bromine in biocidal amounts upstream of the protective membrane(s). II) At the monitoring position located downstream of the contact in I) and upstream of the protective film (or multiple films), in the treated water To measure the bromine residue, III) The method includes bringing treated water into contact with one or more reducing agents in an amount to be reduced, near or downstream of the monitoring position and upstream of the protective membrane(s). The reducing agents in these processes can reduce biocide bromine to bromide ions. In these processes, the bromine-containing biocides include the following: A) One or more 1,3-dibromo-5,5-dialkylhydantoins, B) One or more N,N'-bromochloro-5,5-dialkylhydantoins, C) Optionally, (i) one or more bromide sources and (ii) one or more alkali metal hypobromite and / or one or more alkaline earth metal hypobromite formed in water from one or more hypochlorite and / or hypochlorous acid, D) (i) one or more bromide sources, (ii) an oxidizing agent, optionally (iii) at least one inorganic base, and optionally (iv) a brominated biocide formed in water from sulfamic acid and / or a metal salt of sulfamic acid. E) (i) Bromine chloride or bromine chloride and bromine, with or without chlorine, and (ii) Overbasic alkali metal salts of sulfamic acid and / or sulfamic acid, alkali metal base, and water, which are formed in water, where (i) and (ii) have a relative ratio of nitrogen atoms to active bromine greater than 0.93, and the bromine biocide has a pH greater than 7. F) Brominated biocides formed in water by ozonation of ammonium bromide, hydrogen bromide, one or more alkali metal bromides, one or more alkaline earth metal bromides, and one or more bromide sources selected from any two or more of the above mixtures, or G) A brominated biocide formed in water by electrolysis from one or more bromide sources selected from ammonium bromide, hydrogen bromide, one or more alkali metal bromides, one or more alkaline earth metal bromides, and a mixture of any two or more of the above.

[0009] These and other embodiments and features of the present invention will be further revealed from the following description and the appended claims. [Modes for carrying out the invention]

[0010] As used throughout this specification, the term “biocidal mass” means that the amount used controls, kills, or otherwise reduces the bacterial or microbial content of the treated water by a statistically significant amount.

[0011] Unless otherwise specifically stated herein, the term ppm means parts per million (by weight).

[0012] Throughout this specification, the "aqueous membrane separation system" may be referred to as the "aqueous membrane system" or the "membrane system."

[0013] Throughout this specification, the term “protective membrane” refers to a membrane in an aqueous membrane separation system that does not come into contact with the biocide, or has minimal contact with the biocide. Similarly, as used throughout this specification, the term “non-protective membrane” refers to a membrane that comes into contact with, or can come into contact with, the biocide in an embodiment of the present invention.

[0014] As used throughout this specification, “downstream” means the direction of flow of the feedwater and treatedwater, and “upstream” means opposite (reverse) to the direction of flow of the feedwater and treatedwater. In aqueous membrane separation systems, the protective membrane is typically downstream of the feedwater, and the non-protective membrane is generally upstream of the protective membrane.

[0015] In the process of the present invention, a biocide containing bromine is brought into contact with the feedwater for treatment. Water is generated. The bromine-containing biocide in the treated water is measured as a bromine residue at monitoring positions located downstream of the contact between the feedwater and the bromine-containing biocide and upstream of the protective membrane(s). The treated water and one or more reducing agents are brought into contact near or downstream of the monitoring positions and upstream of the protective membrane(s). The bromine-containing biocide in the process of the present invention includes the bromine-containing biocides A), B), C), D), E), or F) described above. The reducing agent in the process of the present invention has the ability to reduce biocide bromine to bromide ions.

[0016] An aqueous membrane separation system is an aqueous system containing one or more membranes, where one or more membranes are used as part of the separation process. In some aqueous membrane separation systems, there is one membrane that acts as a protective membrane. In other aqueous membrane separation systems, there are two or more membranes, at least one of which is a protective membrane. When there are two or more membranes in an aqueous membrane separation system, at least one protective membrane and at least one non-protective membrane may coexist.

[0017] Various aqueous membrane separation systems can be processed according to the present invention. Non-limiting examples of aqueous membrane separation systems that can be processed include microfiltration systems, ultrafiltration systems, nanofiltration systems, reverse osmosis systems, and / or electrodialysis systems. Reverse osmosis systems are preferred aqueous membrane separation systems for the processes of the present invention.

[0018] In some embodiments, the aqueous membrane separation system is a reverse osmosis (RO) system having a membrane upstream of the RO membrane, where the upstream membrane may be an unprotected membrane, while the RO membrane is a protective membrane. In other embodiments, both the upstream membrane and the RO membrane are protective membranes.

[0019] As used throughout this specification, the term “supply water” refers to the water for the aqueous membrane separation system prior to contact with the bromine-containing biocide. The supply water includes the water that will be supplied to the aqueous membrane separation system. As used throughout this specification, the term “treated water” refers to the water (supply water) that has come into contact with the bromine-containing biocide according to the present invention.

[0020] The feed water can be derived from any convenient source, including demineralized water, industrial water, river water, wetland water, brackish surface water and groundwater, and seawater. 〔

[0021] Contact between the bromine-containing biocide and the feed water is typically achieved by introducing the bromine-containing biocide into the feed water. Bromine-containing biocides A) and B) are solids and can contact the feed water in solid form and / or can be dissolved in water and then contacted with the feed water. Preferably, bromine-containing biocides A) and B) are dissolved in water and then contacted with the feed water. Bromine-containing biocides C), D), E), F), and G) are aqueous solutions and can be diluted with water prior to contact with the feed water to form diluted bromine-based biocides of C), D), E), F), and G), or the bromine-based biocides of C), D), E), F), and G) can be used without dilution for contact with the feed water.

[0022] Contact between the bromine-containing biocide and the feed water can occur at any location upstream of the protective membrane(s). Preferably, the bromine-containing biocide is contacted with the feed water as far upstream of the protective membrane(s) as possible. Early contact between the bromine-containing biocide and the feed water allows for a longer contact time between the bromine-containing biocide and the feed water, resulting in the greatest benefit from the bromine-containing biocide. Due to the presence of the bromine-containing biocide, the treated water has a positive potential compared to the potential of the feed water. [[ID=\\(11\\)]] <00\\(00095\\)]]

[0023] In some embodiments, the feed water is introduced into the aqueous membrane separation system from a container such as a storage tank. In embodiments where the feed water is contained in or passes through a container, contact between the bromine-containing biocide and the feed water preferably occurs in the line transporting the feed water to the container.

[0024] The amount of bromine-containing biocide used is the requirement in the feed water and present in the feed water, or <000\\(0100\\)]] The amount of microbial load (e.g., biofilm) in contact with the feedwater depends on the amount of microbial load in contact with the feedwater. Preferably, the amount of bromine-containing biocide used is sufficient to control or satisfy the microbial load, or more preferably, the amount of bromine-containing biocide satisfies the microbial load and provides a bromine residue in the treated water. If the amount of bromine-containing biocide results in a bromine residue in the treated water, the bromine residue in the treated water is about 0.2 ppm to about 20 ppm, preferably about 0.5 ppm to about 10 ppm, more preferably about 0.5 ppm to about 2 ppm (by weight) as free bromine. When the feedwater comes into contact with the bromine-containing biocide, the feedwater becomes treated water.

[0025] If the amount of bromine-containing biocide in contact with the feedwater is not effective in controlling biocidal activity, additional bromine-containing biocide can be brought into contact with the treated water at any point upstream of the monitoring location. Preferably, the additional bromine-containing biocide is brought into contact with the treated water as far upstream as possible from the monitoring location. The additional bromine-containing biocide may be the same as or different from the bromine-containing biocide that was initially brought into contact with the feedwater.

[0026] The term "active bromine" refers to all bromine-containing species that can possess biocidal activity. Generally, all bromine in the +1 oxidation state is considered to be biocidal and therefore included in the term "active bromine." As is well known in the art, this includes bromine, bromine chloride, hypobromous acid, and hypobromous acid ions (OBr). - ), hydrogen tribromide, tribromide ions, and organic-N-bromide compounds have bromine in the +1 oxidation state. Therefore, as with other species having bromine in the +1 oxidation state, they constitute the active bromine content of the bromine-containing biocides used in the practice of the present invention, insofar as they are present.

[0027] To measure bromine residue in the treated water, the monitoring position is set up downstream of the contact between the brominated biocide and the feedwater, and upstream of the protective membrane(s). Preferably, the monitoring position is located upstream of the protective membrane so that the reducing agent has time to come into contact with the bromine-containing biocide.

[0028] In some embodiments, the measurement of bromine residue in treated water at the monitoring location includes chemical methods such as the N,N'-diethyldiphenylenediamine (DPD) test and spectroscopic methods such as UV / visible light spectroscopy.

[0029] The presence of bromine-containing biocides results in an oxidation potential in treated water. In some embodiments, this potential is measured and is related to the amount of bromine-containing biocide in the treated water. In the implementation of the present invention, two methods (oxidation-reduction potential and amperometry) are preferred for monitoring the potential of the treated water. Both methods involve placing a probe in the treated water and measuring the potential of the water, which provides an indicator of the concentration of bromine-based biocides at the monitoring location. Both amperometry and oxidation-reduction potential monitoring can be set up to measure the potential of the treated water intermittently or continuously. ORP sensors and controllers are commercially available, as are ammeter electrodes and controllers.

[0030] The oxidation-reduction potential (ORP) is measured in millivolts, typically to indicate the potential of treated water. A positive value indicates an oxidizing environment, and an increase in the ORP value from that of the feedwater indicates the presence of bromine-containing biocides. A negative value indicates a reducing environment, meaning that enough reducing agent has come into contact with the treated water to react with (neutralize) all of the bromine-containing biocides in the treated water.

[0031] In some embodiments, the desired ORP value after contact between the treated water and the reducing agent is approximately +250mV to approximately -5mV.

[0032] In the implementation of the present invention, the ORP value of the treated water is measured at a monitoring location, and a desired amount of reducing agent is brought into contact with the treated water. Preferably, a sufficient amount of reducing agent is brought into contact with the treated water to make it non-oxidizing.

[0033] In some embodiments, ORP can be connected to a controller for reducing agent supply, and when the ORP value in the treated water reaches a preset value, ORP can communicate with the reducing agent controller to stop supplying the reducing agent.

[0034] Amperometry measures the change in current when a fixed potential is applied to treated water. Positive values ​​indicate an oxidizing environment, meaning that bromine-containing biocides are present. Negative values ​​indicate a reducing environment, meaning that enough reducing agent has come into contact with the treated water to react with (neutralize) all of the bromine-containing biocides in the treated water.

[0035] In carrying out the present invention, the amperometric potential value of the treated water is measured at a monitoring position, and a desired amount of reducing agent is brought into contact with the treated water. Preferably, a sufficient amount of reducing agent is brought into contact with the treated water to make the treated water non-oxidizing.

[0036] In some embodiments, the ammeter can be connected to a controller for supplying the reducing agent, and when the potential measured in the treated water reaches a preset value, the ammeter can communicate with the reducing agent controller to stop supplying the reducing agent.

[0037] Contact between the reducing agent and the treated water occurs at the monitoring location or downstream thereof, and simultaneously upstream of the protective membrane, or upstream of the first protective membrane if the aqueous membrane separation system has two or more protective membranes.

[0038] In some embodiments, there are multiple monitoring locations, with the second monitoring location being downstream of the first monitoring location, and the monitoring methods at each monitoring location may be the same or different. If necessary or desired, additional reducing agents may be added to the water in the aqueous membrane separation system near or downstream of the second monitoring location and upstream of the protective membrane(s).

[0039] In carrying out the present invention, the reducing agent can be directly mixed with the treated water. If desired, the reducing agent(s) can be pre-mixed with water before being added to the treated water.

[0040] Typically, the amount of reducing agent used depends on the amount of bromine-containing biocide in the treated water. The reducing agent reduces the amount of bromine-containing biocide that comes into contact with the protective film by consuming at least a portion of it. Based on the measurement of bromine residue in the treated water, the amount of reducing agent that comes into contact with the treated water can be adjusted manually or automatically to consume a specific amount, or preferably all, of the bromine-containing biocide in the treated water. Preferably, the amount of reducing agent used is sufficient to minimize the amount of bromine residue in the treated water, or more preferably, the amount of reducing agent is sufficient to consume all of the bromine-containing biocide in the treated water.

[0041] If the amount of reducing agent brought into contact with the treated water is not effective in reducing the bromine residue in the treated water to the desired level, additional reducing agent may be brought into contact with the treated water at any point downstream of the monitoring location and upstream of the protective membrane(s). The additional reducing agent may be the same as or different from the reducing agent initially brought into contact with the treated water.

[0042] Contact between treated water and a reducing agent produces reduced or neutralized water that can pass through the protective membrane(s) with minimal or no damage to the protective membrane(s). Here, the term “neutralized” indicates that the reducing agent is added in an amount sufficient to quench or neutralize the oxidizing power of the bromine-containing biocide. When enough reducing agent is used to consume all of the bromine-containing biocide, contact between the bromine-containing biocide and the protective membrane is prevented.

[0043] The bromine-containing biocide used in accordance with the present invention is an oxidizing biocide.

[0044] The 1,3-dibromo-5,5-dialkylhydantoin and N,N'-bromochloro-5,5-dialkylhydantoin used in accordance with the present invention are solids and can be directly mixed with feedwater. Preferably, the 1,3-dibromo-5,5-dialkylhydantoin(s) and N,N'-bromochloro-5,5-dialkylhydantoin(s) are pre-mixed with water before contact with feedwater. In the pre-mixed water (usually a solution), the microbial killing amount of one or more 1,3-dibromo-5,5-dialkylhydantoins or one or more N,N'-bromochloro-5,5-dialkylhydantoins is preferably sufficient to provide a bromine residue in the range of about 300 ppm to about 3500 ppm, more preferably about 500 ppm to about 1200 ppm, and even more preferably about 800 ppm to about 1000 ppm (by weight) as free bromine.

[0045] In the embodiment of the present invention, one or more 1,3-dibromo-5,5-dialkylhydantoins have alkyl groups containing 1 to about 4 carbon atoms. Preferably, one of the alkyl groups is a methyl group, and the other alkyl groups contain 1 to about 4 carbon atoms. Therefore, preferred 1,3-dibromo-5,5-dialkylhydantoin includes 1,3-dibromo-5,5-dimethylhydantoin, 1,3-dibromo-5-ethyl-5-methylhydantoin, 1,3-dibromo-5-n-propyl-5-methylhydantoin, 1,3-dibromo-5-isopropyl-5-methylhydantoin, 1,3-dibromo-5-n-butyl-5-methylhydantoin, 1,3-dibromo-5-isobutyl-5-methylhydantoin, 1,3-dibromo-5-sec-butyl-5-methylhydantoin, 1,3-dibromo-5-tert-butyl-5-methylhydantoin, and any two or more mixtures thereof. Of these biocides, 1,3-dibromo-5-isobutyl-5-methylhydantoin, 1,3-dibromo-5-n-propyl-5-methylhydantoin, and 1,3-dibromo-5-ethyl-5-methylhydantoin are preferred from a cost-effectiveness viewpoint. Regarding the above mixtures of 1,3-dibromo-5,5-dialkylhydantoins, it is preferable to use 1,3-dibromo-5,5-dimethylhydantoin as one of the components, and a mixture of 1,3-dibromo-5,5-dimethylhydantoin and 1,3-dibromo-5-ethyl-5-methylhydantoin is more preferred. A particularly preferred 1,3-dibromo-5,5-dialkylhydantoin is 1,3-dibromo-5,5-dimethylhydantoin.

[0046] Methods for producing 1,3-dibromo-5,5-dialkylhydantoin are known and reported in the literature, and some of them are commercially available.

[0047] One or more N,N'-bromochloro-5,5-dialkylhydantoins used in the embodiment of the present invention are N,N'-bromochloro-5,5-dialkylhydantoins, where each alkyl group independently contains 1 to about 4 carbon atoms. Suitable compounds of this type include, for example, N,N'-bromochloro-5,5-dimethylhydantoin, N,N'-bromochloro-5-ethyl-5-methylhydantoin, N,N'-bromochloro-5-propyl-5-methylhydantoin, N,N'-bromochloro-5-isopropyl-5-methylhydantoin, N,N'-bromochloro-5-butyl-5-methylhydantoin, N,N'-bromochloro-5-isobutyl-5-methylhydantoin, N,N'-bromochloro-5-sec-butyl-5-methylhydantoin, N,N'-bromochloro-5-tert-butyl-5-methylhydantoin, N,N'-bromochloro-5,5-diethylhydantoin, and any mixture of two or more of the above. Most preferred is N,N'-bromochloro-5,5-dimethylhydantoin.

[0048] A mixture of two or more N,N'-bromochloro-5,5-dialkylhydantoin biocides When the material is used in accordance with the present invention, the individual biocides in the mixture may be in any proportion to each other. Small amounts (less than 50% by weight) of mono-N-bromo-5,5-dialkylhydantoin(s) may be present together with any mixture of two or more N,N'-bromochloro-5,5-dialkylhydantoin biocides, or just one N,N'-bromochloro-5,5-dialkylhydantoin biocides. One suitable mixture has a principal amount (by weight) of N,N'-bromochloro-5,5-dimethylhydantoin together with small amounts (by weight) of 1,3-dichloro-5,5-dimethylhydantoin and 1,3-dichloro-5-ethyl-5-methylhydantoin.

[0049] Methods for producing N,N'-bromochloro-5,5-dialkylhydantoin are known, reported in the literature, and some are commercially available. For example, N,N'-bromochloro-5,5-dimethylhydantoin is commercially available under the trademark name BromiCide® (registered trademark) biocides (BWA Water Additives UK Limited).

[0050] The biocide C) is one or more alkali metal hypobromite and / or one or more alkaline earth metal hypobromite, and is preferably formed in water from (i) one or more bromide sources and (ii) hypochlorite and / or hypochlorous acid.

[0051] In carrying out the present invention, the bromide source and the hypochlorite and / or hypochlorous acid can be brought into contact with the feedwater separately (for example, by separate inlets to the feedwater). Alternatively, the bromide source and the hypochlorite and / or hypochlorous acid can be supplied to a mixing point (e.g., a mixing T-tube) or a mixing device (preferably an in-line mixing device) and then brought into contact with the feedwater. Alternatively, the bromide source and the hypochlorite and / or hypochlorous acid can be combined in water to produce an aqueous solution, which can then be brought into contact with the feedwater.

[0052] For forming bromine-containing biocide C), suitable bromide sources for component (i) include ammonium bromide, hydrogen bromide, inorganic bromide salts, and any mixture of two or more of the above. The inorganic bromide salt is preferably one or more alkali metal bromides and / or one or more alkaline earth metal bromides. Preferred bromide sources are ammonium bromide, hydrogen bromide, alkali metal bromides (including lithium bromide, sodium bromide, and potassium bromide), and alkaline earth metal bromides, particularly MgBr2 and CaBr2. A mixture of two or more bromide sources may be used if desired. A preferred bromide source is sodium bromide, particularly sodium bromide from which trace amounts of alcohol such as methanol have been removed.

[0053] In the formation of biocide C), hypochlorite is preferred, and the hypochlorite is an inorganic hypochlorite, preferably one or more alkali metal hypochlorites and / or one or more alkaline earth metal hypochlorites. Examples of alkali metal hypochlorites and alkaline earth metal hypochlorites include lithium hypochlorite, sodium hypochlorite, potassium hypochlorite, calcium hypochlorite, and magnesium hypochlorite, with sodium hypochlorite and calcium hypochlorite being preferred hypochlorites. Bromids or hypochlorites of Be, Sr, or Ba are not recommended due to toxicological concerns. Therefore, the term “alkaline earth” as used herein excludes Be, Sr, and Ba. When ammonium bromide is the bromide source, it is desirable to mix the ammonium bromide with the hypochlorite by the method described in U.S. Patent No. 6,478,973.

[0054] The interaction between the bromide source and hypochlorite and / or hypochlorous acid yields an aqueous solution with a suitably high bromine residue. When an excess amount of hypochlorite is used relative to the amount of bromide salt used, the resulting solution contains chlorine species and bromine residue. These chlorine species are not harmful as long as the desired bromine residue is present in the solution used.

[0055] In some embodiments, one or more bromide sources and one or more hypochlorites and / or hypochlorous acid used to form biocide C) are brought into contact with feedwater separately, and alkali metal hypobromite and / or one or more alkaline earth metal hypobromite are formed in the feedwater. In these embodiments, the bromide sources are usually solid and can be brought into contact with feedwater in solid form, and / or preferably dissolved in water to produce an aqueous solution which can then be brought into contact with feedwater. In these embodiments, the hypochlorites and / or hypochlorous acid are usually, and preferably, brought into contact with feedwater as an aqueous solution, although the hypochlorites can be brought into contact with feedwater in solid form if desired.

[0056] In other embodiments, one or more bromide sources used to form biocide C) are mixed with one or more hypochlorite and / or hypochlorous acid before contact with the feedwater. In these embodiments, it is preferable that the bromide sources be dissolved in water to produce an aqueous solution before being mixed with the hypochlorite and / or hypochlorous acid. In these embodiments, the hypochlorite and / or hypochlorous acid are usually preferred in aqueous solution form when mixed with the bromide sources.

[0057] When a bromide source and hypochlorite and / or hypochlorous acid are mixed in water to produce an aqueous solution, the aqueous solution can be diluted with water before contact with the feedwater to produce a diluted bromine-containing biocide C) solution, or the bromine-containing biocide C) solution can be used without dilution for contact with the feedwater.

[0058] The brominated biocides of D) and E) are aqueous solutions and contain active bromine, also known as bromine residue. The brominated biocides of D) and E) that contain sulfamic acid and / or metal salts of sulfamic acid are stabilized brominated biocides.

[0059] The brominated biocide of D) is formed in water from (i) one or more bromide sources, (ii) an oxidizing agent, optionally (iii) at least one inorganic base, and optionally (iv) sulfamic acid and / or a metal salt of sulfamic acid. This brominated biocide is preferably prepared as a concentrated aqueous solution, and preferably the concentrated solution is brought into contact with feedwater.

[0060] When inorganic bases are used, the pH is usually about 7 or higher, preferably higher than 7, for example, in the range of about 10 to about 14.

[0061] Suitable bromide sources for forming brominated biocide D) include ammonium bromide, hydrogen bromide, inorganic bromide salts, and any mixture of two or more of the above. The inorganic bromide salt is preferably one or more alkali metal bromides and / or one or more alkaline earth metal bromides. Preferred bromide sources are ammonium bromide, hydrogen bromide, alkali metal bromides (including lithium bromide, sodium bromide, and potassium bromide), and alkaline earth metal bromides, particularly MgBr2 and CaBr2. A mixture of two or more bromide sources may be used if desired. A preferred bromide source is sodium bromide, particularly sodium bromide from which trace amounts of alcohol such as methanol have been removed.

[0062] Oxidizing agents include chlorine-based oxidizing agents and oxygen-based oxidizing agents. Chlorine-based oxidizing agents include chlorine (Cl2), hypochlorite, trichloroisocyanurate, and sodium dichloroisocyanurate. When the chlorine-based oxidizing agent is hypochlorous acid or hypochlorite, an inorganic base is usually present, and preferably sulfamic acid and / or metal sulfamic acid salts are also present. Oxygen-based oxidizing agents include ozone, peracetic acid, and hydrogen peroxide. When the oxygen-based oxidizing agent is ozone, an inorganic base and / or sulfamic acid (and / or metal sulfamic acid salts) are usually present, and preferably both an inorganic base and sulfamic acid (and / or metal sulfamic acid salts) are present.

[0063] In some embodiments of the brominated biocide D), an inorganic base is present. Preferred inorganic bases are alkali metal bases, more preferably oxides or hydroxides of lithium, sodium, and / or potassium, and even more preferably sodium hydroxide and / or potassium hydroxide.

[0064] Sulfamic acid and / or metal salts of sulfamic acid are optional but preferred in some brominated biocides D). Metal salts of sulfamic acid are typically alkali metal salts, including lithium sulfamate, sodium sulfamate, and potassium sulfamate. Sulfamic acid can be used alone or in mixtures with one or more metal salts of sulfamic acid. Sulfamic acid and / or sodium sulfamate are preferred. Sulfamic acid is more preferred. Inorganic bases are optional but preferred when sulfamic acid is used to form brominated biocides D). In some embodiments of brominated biocides D), sulfamic acid and / or metal salts of sulfamic acid are preferred.

[0065] In some preferred embodiments of the brominated biocide D), the oxidizing agent is trichloroisocyanurate or sodium dichloroisocyanurate, and an inorganic base is present.

[0066] When an excessive amount of chlorine-based oxidizing agent is used relative to the amount of bromide salt used, the resulting solution will contain chlorine compounds in addition to bromine residue. These chlorine compounds are not harmful as long as the specified amount of bromine residue is present in the solution during use.

[0067] A commercially available aqueous brominated biocide D) that can be used in carrying out the present invention is sold under the trademark name Sta·Br·Ex® Biocides (Ecolab USA Inc.). This product contains active bromine stabilized against chemical decomposition and physical evaporation of the active bromine species by including a sulfamate. Further details regarding the preparation of aqueous biocidal solutions stabilized with sulfamic acid are described in U.S. Patents 6,007,726, 6,156,229, and 6,270,722.

[0068] Another brominated biocide D) is marketed under the trademark name BromMax® Biocides (Enviro Tech Chemical Services, Inc.). This product contains active bromine stabilized against chemical decomposition and physical evaporation of the active bromine species by including a sulfamate. For further details regarding the preparation of this type of brominated biocide D) stabilized with sulfamic acid, see U.S. Patents 7,045,153, 7,309,503, and 7,455,859.

[0069] Another commercially available brominated biocide D) available for use in carrying out the present invention is marketed under the trade name Justeq07 Biocides (Justeq, LLC). This product contains an active halogen species stabilized by including a sulfamate. In some embodiments, this biocide may be produced by producing a chlorosulfamate from a chlorine-based oxidizing agent, preferably a hypochlorite, and a metal salt of sulfamic acid and / or sulfamic acid, and then introducing a bromide source. Processes for producing aqueous solutions of this type of biocide are described in U.S. Patents 6,478,972, 6,533,958, and 7,341,671.

[0070] The brominated biocides of E) are formed in water from (i) bromine chloride or bromine chloride and bromine, with or without chlorine, and (ii) an overbasic alkali metal salt of sulfamic acid and / or sulfamic acid, an alkali metal base, and water. Here, (i) and (ii) are present in relative proportions such that the atomic ratio of nitrogen to active bromine is greater than 0.93, and the pH of the brominated biocide is greater than 7. Brominated biocides D) are manufactured as concentrated aqueous solutions. Preferably, the concentrated solution is brought into contact with the feed water.

[0071] The process for producing brominated aqueous biocides E) is described in U.S. Patent Nos. 6,068,861 and 6,299,909 B1. Brominated aqueous biocides E) containing more than 50,000 ppm of active halogen are marketed by Albemarle Corporation under the trademark STABROM® 909 biocides (Albemarle Corporation). The pH of the aqueous product in this state is typically in the range of 13 to 14.

[0072] When forming a brominated biocide E), the pH is usually at least 7, and preferably always higher than 7, for example, in the range of 10 to 14, by the use of an inorganic base. Preferred bases are alkali metal bases, preferably oxides or hydroxides of lithium, sodium, and / or potassium, and more preferably sodium hydroxide and / or potassium hydroxide. When sulfamic acid is used to produce a concentrated biocide aqueous solution, the solution should also be provided with a base, preferably a base sufficient to maintain the solution alkaline, i.e., at a pH greater than 7, preferably about 10 or higher, and most preferably about 13 or higher.

[0073] Regarding component (i) of brominated biocides E), which is bromine chloride, a mixture of bromine chloride and bromine, or a mixture of bromine and chlorine in which the molar amount of chlorine is equal to or less than the molar amount of bromine used, the biocide aqueous solution is brominated because most of the chlorine usually forms chloride salts such as sodium chloride (this is because alkali metal bases such as sodium hydroxide are typically used in the treatment to raise the pH of the product solution to about 13 or higher).

[0074] When preparing a concentrated aqueous solution of a brominated biocide E), the active bromine content of such an aqueous biocide solution is usually about 50,000 ppm (by weight) or more, preferably about 100,000 ppm (by weight) or more, for example, containing about 105,000 to 215,000 ppm of active bromine. The pH of such a concentrated aqueous biocide solution is greater than 7, preferably about 10 or more, more preferably about 12 or more, and even more preferably about 13 or more, and the atomic ratio of nitrogen to active bromine in these separate aqueous biocide solutions is greater than 0.93.

[0075] Brominated biocides F) are formed in water by ozonation of one or more bromide sources. These brominated biocides are produced by ozonating an aqueous solution containing bromide ions by passing the bromide ion-containing solution through an ozonation device. The ozone solution contains biocide-active bromine and is usually brought into contact with feedwater a short time after ozonation, preferably by transporting the solution directly from the ozonation process to the feedwater.

[0076] Suitable bromide sources for forming brominated biocides F) include ammonium bromide, hydrogen bromide, inorganic bromide salts, and any mixture of two or more of the above. The inorganic bromide salt is preferably one or more alkali metal bromides and / or one or more alkaline earth metal bromides. Preferred bromide sources are ammonium bromide, hydrogen bromide, alkali metal bromides (including lithium bromide, sodium bromide, and potassium bromide), and alkaline earth metal bromides, particularly MgBr2 and CaBr2. A mixture of two or more bromide sources can be used if desired. A preferred bromide source is sodium bromide, particularly sodium bromide from which trace amounts of alcohol such as methanol have been removed.

[0077] Brominated biocides (G) are formed by electrolysis in water from one or more bromide sources. These brominated biocides are manufactured by generating bromine by electrolysis in an aqueous solution containing bromide ions, and are generally produced by passing a solution containing bromide ions through an electrolysis system. The electrolyte contains biocide-active bromine and is usually brought into contact with feedwater a short time after electrolysis. Preferably, the solution is transported directly from the electrolysis process and brought into contact with feedwater.

[0078] Suitable bromide sources for forming brominated biocides G) include ammonium bromide, hydrogen bromide, inorganic bromide salts, and any mixture of two or more of the above. The inorganic bromide salts are preferably one or more alkali metal bromides and / or one or more alkaline earth metal bromides. Preferred bromide sources are ammonium bromide, hydrogen bromide, alkali metal bromides (including lithium bromide, sodium bromide, and potassium bromide), and alkaline earth metal bromides, particularly MgBr2 and CaBr2. A mixture of two or more bromide sources may be used if desired. A preferred bromide source is sodium bromide, particularly sodium bromide from which trace amounts of alcohol such as methanol have been removed.

[0079] Among several types of bromine-containing biocides that can be used in carrying out the present invention, preferred bromine-containing biocides include N,N'-bromochloro-5,5-dialkylhydantoin, 1,3-dibromo-5,5-dialkylhydantoin, and bromine chloride or bromine-based biocides formed in water from bromine chloride and bromine. More preferred bromine-containing biocides include N,N'-bromochloro-5,5-dimethylhydantoin, 1,3-dibromo-5,5-dimethylhydantoin, and bromine-based biocides formed in water from bromine chloride, with bromine-based biocides formed in water from bromine chloride being particularly preferred.

[0080] The desired bromine residue in the bromine-containing biocide solution before contact with the feedwater may depend on various factors, such as the demand of known microorganisms downstream of the contact point between the feedwater and the bromine-containing biocide. In some embodiments, the bromine residue after contact with the bromine-containing biocide in the feedwater is about 0.2 ppm to about 20 ppm, preferably about 0.5 ppm to about 10 ppm, and more preferably about 0.5 ppm to about 2 ppm (by weight) as free bromine.

[0081] The present invention enables the use of a bromine-containing biocide and one or more other compatible microbial agents. Preferably, the bromine-containing biocide is the sole source of microbial activity in the water according to the present invention.

[0082] The reducing agent used in accordance with the present invention is a biocide bromine that converts bromide ions (Br - ) has the ability to reduce to ). The reducing agents that can be used in carrying out the present invention are any reducing agent effective in reducing brominated oxidizing agents, or reducing agents effective in reducing specific brominated oxidizing agents (maybe more than one) present in a membrane separation system. Typical reducing agents in carrying out the present invention include sulfur dioxide, sodium metabisulfite, sodium bisulfite, sodium bisulfite, sodium sulfite, sodium bisulfite, sodium thiosulfate, ammonium bisulfite, and ammonium thiosulfate. A mixture of any two or more reducing agents may be used. In some embodiments, it is preferable to use a single reducing agent rather than a mixture of reducing agents.

[0083] The term "free bromine" is used to describe the free or relatively fast-reactive form of a bromine oxidizing agent present in an aqueous solution. In the case of bromine-containing biocides used in the implementation of the present invention, total bromine is the same as active bromine. To convert "free chlorine" and "total chlorine" values ​​(e.g., ppm Cl2) to "free bromine" and "total bromine" values ​​(e.g., ppm Br2), multiply the given concentration of "free chlorine" or "total chlorine" in ppm Cl2 by 2.25, which is the molecular weight ratio of Br2 to Cl2. Similarly, if a given concentration of halogen is reported as Br2, it can be converted to a value of Cl2 by dividing it by the molecular weight ratio of Cl2 to Br2, which is 2.25.

[0084] The term "bromine residue" refers to the amount (concentration) of bromine species present in water that are available for disinfection. The residue can be determined as either "free" or "total," depending on the analytical test method used. In this invention, the values ​​for bromine residue are given herein on a free bromine basis. Such values ​​can be monitored by using the "free chlorine" analytical procedure given below. However, if desired, the bromine residue can be monitored on a "total bromine" basis by using the "total chlorine" analytical procedure shown below. In either case, the obtained values ​​are in relation to chlorine, and therefore, such values ​​are multiplied by 2.25 to obtain the corresponding bromine value. Typically, the "total bromine" basis value for a given sample will be higher than the "free bromine" basis value for the same given sample. An important point to understand is that while this invention concerns the bromine residue actually present in the treated aqueous medium, regardless of whether the value is determined by using a free chlorine test procedure or a total chlorine test procedure, the free chlorine test procedure is preferred.

[0085] Suitable methods for determining "bromine residue" are publicly known and reported in the literature. For example, see Standard Methods For the Examination of Water and Wastewater, 18th Edition, 1992, from the American Public Health Association, 1015 Fifteenth Street, NW, Washington, DC 20005 (ISBN 0-87553-207-1), pages 4-36 and 4-37; Hach Water Analysis Handbook, Third Edition, 1997, by Hach Company, Loveland, Colorado, especially pages 1206 and 1207; and Handbook of Industrial Water Conditioning, 7th edition, Betz Laboratories, Inc., Trevose, PA 19047 (Library of Congress Catalog Card Number: 76-27257), 1976, pages 24-29. These references typically refer to "chlorine residue," but the same technique is used to determine "bromine residue" by taking into account the higher atomic weight of bromine compared to chlorine.

[0086] The active halogen content, whether active chlorine, active bromine, or both, can be determined using conventional starch-iodine titration.

[0087] A standard test for determining low levels of active halogens is known as the DPD test and is based on a classic test procedure devised by Palin in 1974. (ATPalin, “Analytical Control of Water Disinfection With Special Reference to Differential DPD Methods For Chlorine, Chlorine Dioxide, Bromine, Iodine and Ozone”, J.Inst.Water Eng., 1974) 28See page 139. While various modernized versions of the Parin procedure exist, the recommended version of this test is fully described in the Hach Water Analysis Handbook, 3rd edition, copyright 1997. The procedure for "total chlorine" (i.e., active chlorine) is identified in that publication as Method 8167, appearing on page 379. In summary, the "total chlorine" test involves introducing a powder containing DPD indicator powder (i.e., N,N'-diethyldiphenylenediamine, KI, and buffer) into a diluted water sample containing an active halogen. The active halogen species of the present invention reacts with KI to produce an iodine species, which changes the DPD indicator to red / pink. The intensity of the coloration depends on the concentration of the "total chlorine" species (i.e., active chlorine) present in the sample. This intensity is measured by a colorimeter calibrated to convert the intensity reading to a "total chlorine" value in mg / L Cl2. If the active halogen present is active bromine, multiply the result in mg / L Cl2 by 2.25 to obtain the active bromine value. This shows the results for the raw mg / L Br2.

[0088] More specifically, the DPD test procedure is as follows: 1. To determine the amount of species present in the water that respond to the "total chlorine" test, the water sample should be analyzed within a few minutes of being taken, preferably immediately after taking the sample. 2. Hach method 8167 for testing the amount of species present in a water sample that respond to the "total chlorine" test involves the use of a Hach Model DR 2010 colorimeter. The saved program number for chlorine measurement is recalled by typing "80" on the keyboard and then rotating the dial on the side of the instrument to set the absorbance wavelength to 530 nm. Fill two identical sample cells with the water under investigation up to the 25 mL mark. One of the cells is arbitrarily selected to be left blank. Add the contents of the DPD total chlorine powder pillow to the second cell. Mix by shaking for 10-20 seconds. This is because the appearance of pink to red indicates the presence of species in the water that respond positively to the DPD "total chlorine" test reagent. On the keypad, press the SHIFT timer key to start a 3-minute reaction time. After 3 minutes, the instrument will beep to indicate that the reaction is complete. Place the blank sample cell in the sample compartment of the Hach Model DR 2010 and close the shield to prevent stray light effects. Then press the zero key. After a few seconds, the display will record 0.00 mg / L Cl2. Next, remove the blank sample cell used to zero the instrument from the cell compartment of the Hach Model DR 2010 and replace it with a test sample to which DPD "total chlorine" test reagent has been added. Then, close the light-shielding shield as in the case of the blank and press the read key. The result will be displayed on the screen in mg / L Cl2 within a few seconds. This is the "total chlorine" level of the water sample being investigated. Note that the test sample may need to be diluted with halogen-free water in order for the chlorine measurement to be within the instrument's measurement range. This dilution should be considered to determine the actual chlorine level of the sample. 3. One method for measuring free chlorine is the Hach method 8021. This tests the amount of species present in a water sample that responds to the "free chlorine" test. This test involves the Hach method. The procedure includes using a Model DR 2010 colorimeter. The saved program number for chlorine measurement is recalled by typing "80" on the keyboard and then rotating the dial on the side of the instrument to set the absorbance wavelength to 530 nm. Two identical sample cells are filled to the 25 mL mark with the water under investigation. One of the cells is arbitrarily selected to be a blank. The blank sample cell is then used with the Hach Model DR Place the sample in the 2010 sample compartment and close the shield to prevent stray light effects. Then press the zero key. After a few seconds, the display will record 0.00 mg / L Cl2. Next, remove the blank sample cell used to zero the instrument from the cell compartment of the Hach Model DR 2010. Add the contents of the DPD free chlorine powder pillow to the second cell. Mix by shaking for 10-20 seconds. This is because the appearance of pink to red indicates the presence of species in the water that respond positively to the DPD "free chlorine" test reagent. Immediately (within 1 minute of reagent addition) place the prepared sample in the cell holder. Then, close the light-shielding shield as in the case of the blank and press the read key. The result will be displayed on the screen within a few seconds, in mg / L Cl2. This is the "free chlorine" concentration of the water sample being investigated. Note that the test sample may need to be diluted with halogen-free water in order for the chlorine measurement to be within the instrument's measurement range. When measuring the chlorine concentration in a sample, this dilution must be taken into consideration.

[0089] In some embodiments, the aqueous membrane separation system is a reverse osmosis system, and the biocide is N,N'-bromochloro-5,5-dialkylhydantoin or 1,3-dibromo-5,5-dialkylhydantoin, preferably N,N'-bromochloro-5,5-dimethylhydantoin or 1,3-dibromo-5,5-dimethylhydantoin, more preferably 1,3-dibromo-5,5-dimethylhydantoin, and the biocide is preferably, It is dissolved in water before contact with the feedwater. In these embodiments, the potential of the treated water is preferably measured using an oxidation-reduction potential meter. If bromine residue is present in the treated water, the amount of free bromine is about 0.2 ppm to about 20 ppm, preferably about 0.5 ppm to about 10 ppm, and more preferably about 0.5 ppm to about 2 ppm (by weight).

[0090] In other embodiments, the aqueous membrane separation system is a reverse osmosis system, the biocide is bromine chloride or a brominated biocide formed in water from bromine chloride and bromine, more preferably a brominated biocide formed in water from bromine chloride, and the biocide is preferably brought into contact with the feedwater without dilution. In these embodiments, the potential of the treated water is preferably measured using an oxidation-reduction potential meter. If bromine residue is present in the treated water, the bromine residue is about 0.2 ppm to about 20 ppm, preferably about 0.5 ppm to about 10 ppm, more preferably about 0.5 ppm to about 2 ppm (by weight) as free bromine.

[0091] In other embodiments, the aqueous membrane separation system is a reverse osmosis system, the biocide is N,N'-bromochloro-5,5-dialkylhydantoin or 1,3-dibromo-5,5-dialkylhydantoin, preferably N,N'-bromochloro-5,5-dimethylhydantoin or 1,3-dibromo-5,5-dimethylhydantoin, more preferably 1,3-dibromo-5,5-dimethylhydantoin, and the biocide is preferably brought into contact with the feedwater in solid form. In these embodiments, the potential measurement of the treated water is preferably performed using an ammeter. If bromine residue is present in the treated water, the bromine residue is about 0.2 ppm to about 20 ppm, preferably about 0.5 ppm to about 10 ppm, more preferably about 0.5 ppm to about 2 ppm (by weight) as free bromine.

[0092] In yet another embodiment, the aqueous membrane separation system is a reverse osmosis system, the biocide is bromine chloride or a brominated biocide formed in water from bromine chloride and bromine, more preferably a brominated biocide formed in water from bromine chloride, and the biocide is preferably brought into contact with the feedwater without dilution. In these embodiments, the potential measurement of the treated water is preferably performed using an ammeter. If bromine residue is present in the treated water, the bromine residue is about 0.2 ppm to about 20 ppm, preferably about 0.5 ppm to about 10 ppm, more preferably about 0.5 ppm to about 2 ppm (by weight) as free bromine.

[0093] The following embodiments are provided for illustrative purposes only and are not intended to limit the scope of the invention. [Examples]

[0094] Example 1 Wetland water was supplied to a storage tank via a 1200-foot (365 m) hose. A biocide was added to the hose 20 feet (6.1 m) before connecting it to the storage tank. The water was supplied from the storage tank to a reverse osmosis (RO) system with an ultrafiltration (UF) membrane upstream of the RO membrane. In this system, the UF membrane was unprotected, and the RO membrane was protective. An oxidation-reduction potential (ORP) electrode was submerged in water upstream of and near the RO membrane, and the ORP electrode was connected to an ORP controller unit (ORP electrode: RD2, Hach Company). Measurements from the ORP were monitored, and reducing agents were pumped into the RO system downstream of the ORP electrode as needed, as indicated by the ORP reading from the ORP electrode.

[0095] The biocides tested were bleach, 1,3-dibromo-5,5-dimethylhydantoin (Br2DMH, Albemarle Corporation), and bromine chloride and sulfur containing active halogens exceeding 50,000 ppm with a pH in the range of 13-14. It was an aqueous solution produced from famic acid (BrCl / sulfamic acid, STABROM® 909 biocide, Albemarle Corporation). The reducing agent used in each biocide was sodium bisulfate.

[0096] Water samples were taken at various points in time upstream of and near the UF membrane, and water samples were also taken at various points upstream of and near the RO membrane. The testing period for each biocide was approximately 30 days. The functionality of the RO membrane, the types of microorganisms in the RO membrane after treatment, the effectiveness of the biocides against microorganisms in the water, and the effectiveness of the biocides against biofilm growth were measured. The data are summarized in Tables 1-4. [Table 1]

[0097] RO membranes were tested after exposure to each biocide / reducing agent system for 30 days. The data in Table 1 are from membrane autopsies and show whether the biocide, or at least the residual amount in contact with the RO membrane, adversely affected the membrane. The data in Table 1 shows that bleach had the most adverse effect on RO membranes. [Table 2]

[0098] The data in Table 2 were generated from RO membranes as part of a membrane autopsy after 30 days of exposure to biocides. Table 2 shows that BrCl / sulfamic acid was the most effective biocide against both aerobic bacteria and yeast / mold. [Table 3]

[0099] For the data in Table 3, water samples were taken upstream of and near the UF membrane, and upstream of and near the RO membrane. The data in Table 3 are averages of samples taken over several days to reduce planktonic biocidal activity. [Table 4]

[0100] In Table 4, water samples were taken upstream of and near the RO membrane, and biofilm specimens were tested using a modified Robbins device. The numbers in the table are in RLU units, which measure the amount of ATP present on the specimen. A higher RLU value indicates a greater presence of bacteria. Each value in the table is the average of 3 or 4 specimens. The data in Table 4 shows that BrCl / sulfamic acid is the most effective biocide against biofilms.

[0101] Example 2 Experiments demonstrating the progression of membrane degradation were conducted and data collected using standard membrane testing procedures, including a static membrane immersion test in which the membrane was in direct contact with RO-1 biocide and bleach solutions in a jar at multiple concentrations for comparison over several days.

[0102] The tests were conducted using a test bench with six cells arranged in two parallel sets of three cells each, using purchased components. The test temperature remained at 18–22°C, which is considered to have minimal impact on the estimation of membrane salt rejection. Rejection was estimated using a conductivity meter (Hach) to measure the conductivity of permeation and supply. See Table 5. [Table 5]

[0103] The data show that at a concentration of 50 ppm, the membrane rapidly declines from almost complete retention of the salt concentration in the solution, summarized by the influent water supply parameters, to about 20% after 20 days of exposure, while the degradation rate in RO-1 is relatively slower up to substantially higher concentrations of 200 ppm and 1,000 ppm over 8 days of exposure. See Table 6 and Figure 1. [Table 6]

[0104] Tests using membrane specimens immersed in a 1,000 ppm RO-1 solution for more than 20 days are expected to maintain higher performance even at such very high concentrations than those exposed to 50 ppm bleach for the same period. The concentration of RO-1 chosen is by no means an indication of the level of biocide to be applied for controlling the biocidal properties of membranes in a biofouling environment, but rather an option for accelerated degradation studies to rapidly compare the degree to which membranes are affected by direct contact.

[0105] Further embodiments of the present invention include, but are not limited to, the following:

[0106] A) A process for controlling biofouling in an aqueous membrane separation system comprising water and one or more protective membranes, the following: I) Upstream of the protective film (multiple films are possible), the supply water and a biocide containing bromine are brought into contact. And then, to generate treated water, II) Measuring the bromine residue in the treated water at a monitoring position located downstream of the contact in I) and upstream of the protective film(s). III) Bringing the treated water and one or more reducing agents in the amount to be reduced into contact near or downstream of the monitoring position and upstream of the protective membrane(s), The reducing agent has the ability to reduce biocide bromine to bromide ions. The bromine-containing biocides are as follows: a) One or more 1,3-dibromo-5,5-dialkylhydantoins, b) One or more N,N'-bromochloro-5,5-dialkylhydantoins, c) Optionally, one or more alkali metal hypobromite and / or one or more alkaline earth metal hypobromite, formed in water from one or more bromide sources and one or more hypochlorite and / or hypochlorous acid, d) (i) one or more bromide sources, (ii) an oxidizing agent, optionally (iii) at least one inorganic base, and optionally (iv) a brominated biocide formed in water from sulfamic acid and / or a metal salt of sulfamic acid. e) (i) a brominated biocide formed in water from (i) bromine chloride or bromine chloride and bromine, with or without chlorine, and (ii) an overbasic alkali metal salt of sulfamic acid and / or sulfamic acid, an alkali metal base, and water, wherein (i) and (ii) have a relative ratio of nitrogen atoms to active bromine of more than 0.93, and the brominated biocide has a pH greater than 7, f) Brominated biocides formed in water by ozone treatment of one or more bromide sources, or g) The process comprising contacting a brominated biocide formed by electrolysis in water from one or more bromide sources.

[0107] B) The process according to A), wherein the bromine-containing biocide comprises one or more N,N'-bromochloro-5,5-dialkylhydantoins, one or more 1,3-dibromo-5,5-dialkylhydantoins, or the brominated biocide of e).

[0108] C) The process according to A), wherein the bromine-containing biocide comprises N,N'-bromochloro-5,5-dimethylhydantoin, 1,3-dibromo-5,5-dimethylhydantoin, or the brominated biocide e) formed in water from bromine chloride.

[0109] D) The bromine-containing biocide includes a bromine-based biocide formed in water from the components of the bromine-based biocide e), The alkali metal base in (ii) above is sodium hydroxide, The biocide has an active bromine content of approximately 100,000 ppm or more, and / or The process according to B) or C), wherein the pH is approximately 10 or higher.

[0110] E) The process according to any one of A) to C), wherein the 1,3-dibromo-5,5-dialkylhydantoin(pl) and / or N,N'-bromochloro-5,5-dialkylhydantoin(pl) are pre-mixed with water before contact with the feedwater, and optionally, in the pre-mixed water, the 1,3-dibromo-5,5-dialkylhydantoin(pl) and / or N,N'-bromochloro-5,5-dialkylhydantoin(pl) are present in an amount sufficient to provide a bromine residue ranging from about 300 ppm to about 3500 ppm (by weight) as free bromine.

[0111] F) The process according to D), wherein the brominated biocide of e) is diluted before contact with the feedwater to form the diluted brominated biocide of e).

[0112] G) The bromine-containing biocide is f) Brominated biocides, or The process described in A), comprising the brominated biocide g).

[0113] H) The process according to A), wherein the biocide is N,N'-bromochloro-5,5-dialkylhydantoin or 1,3-dibromo-5,5-dialkylhydantoin, and the contact with the feedwater is carried out by dissolving the biocide in water.

[0114] I) The process according to H), wherein the biocide is N,N'-bromochloro-5,5-dimethylhydantoin or 1,3-dibromo-5,5-dimethylhydantoin.

[0115] J) The process according to A), wherein the biocide is bromine chloride or a brominated biocide formed in water from bromine chloride and bromine, and the contact of the brominated biocide with the feedwater is carried out without diluting the biocide.

[0116] K) The brominated biocide is formed from bromine chloride in water by the process described in J).

[0117] The process according to A), wherein the one or more bromide sources for biocide c) are alkali metal bromides, and / or the one or more hypochlorites and / or hypochlorous acid for biocide c) are alkali metal hypochlorites.

[0118] M) The process according to L), wherein the bromide source is an alkali metal bromide and / or the chlorine source is a hypochlorite.

[0119] N) The process according to L), wherein the bromide source is sodium bromide and / or the chlorine source is sodium hypochlorite.

[0120] O) Biocides d) In, The oxidizing agent is a chlorine-based oxidizing agent or an oxygen-based oxidizing agent, and an inorganic base is present. The oxidizing agent is a chlorine-based oxidizing agent or an oxygen-based oxidizing agent, and sulfamic acid and / or a metal salt of sulfamic acid are present, or The process according to A), wherein the oxidizing agent is a chlorine-based oxidizing agent or an oxygen-based oxidizing agent, and an inorganic base and sulfamic acid and / or a metal salt of sulfamic acid are present.

[0121] P) The process according to any one of A) to O), wherein the bromine-containing biocide provides a bromine residue in the treated water in the range of about 0.2 ppm to about 20 ppm (by weight) as free bromine.

[0122] Q) The process according to any one of A) to O), wherein the bromine-containing biocide provides a bromine residue in the treated water in the range of about 0.5 ppm to about 10 ppm (by weight) as free bromine.

[0123] R) The measurement is performed by a chemical method or a spectroscopic method, as described in any of A) to Q).

[0124] S) The process described in R), wherein the measurement is the measurement of the potential of the treated water.

[0125] T) The measurement is performed using a redox meter, as described in S).

[0126] U) The measurement is performed using an ammeter, as described in S).

[0127] V) The aqueous membrane separation system is a reverse osmosis system, according to any of the processes described in A) to U).

[0128] Any component referred to by a chemical name or chemical formula in this specification or in the claims, whether referred to in the singular or plural, is identified as existing before contact with another substance (e.g., another component, solvent, etc.) referred to by a chemical name or chemical type. It is irrelevant what kind of chemical changes, transformations, and / or reactions may occur in the resulting mixture or solution, for such changes, transformations, and / or reactions are natural consequences of bringing together specific components under the conditions required in accordance with this disclosure. Thus, this component is identified as the component that is brought together in connection with the performance of a desired operation or the formation of a desired composition. Furthermore, the following claims may refer to substances, components, and / or components in the present tense (e.g., “including,” “is”) as if this substance, component, or component existed immediately before it was first contacted, blended, or mixed with one or more other substances, components, and / or components in accordance with this disclosure. Therefore, there is no substantial concern that any substance, component, or ingredient may have lost its original identity through a chemical reaction or transformation during the course of an operation of contact, blending, or mixing, provided that such operation is carried out in accordance with the present disclosure and the ordinary skill of a chemist.

[0129] The present invention may include, consist of, or essentially consist of the materials and / or procedures listed herein.

[0130] As used herein, the term “about” modifying the amount of an ingredient in the composition of the present invention or used in the method of the present invention refers to the variation in numerical amounts that may occur, for example, due to typical measurement and liquid handling procedures used in the real world to produce concentrates or working solutions, careless errors in these procedures, differences in the manufacture, source, or purity of the ingredients used in the production of the composition or the implementation of the method. The term “about” also encompasses different amounts resulting from different equilibrium conditions of compositions obtained from a particular initial mixture. Whether modified by the term “about” or not, the claims include equivalent amounts.

[0131] Unless expressly indicated otherwise, the articles “a” or “an,” as used herein, are not intended, nor should they be construed as limiting the description or claims to a single element to which the article refers. Rather, as used herein, the articles “a” or “an,” unless otherwise specified in the text, are intended to encompass one or more such elements.

[0132] The present invention is susceptible to considerable variability in its implementation. Therefore, the above description is not intended to limit the invention to the specific examples presented above, nor should it be construed as such.

Claims

1. A process for controlling biofouling in an aqueous membrane separation system comprising water and one or more protective membranes, the following: I) Upstream of the protective membrane (or multiple membranes), the supply water and a biocides containing bromine are brought into contact to produce treated water. II) Measuring the bromine residue in the treated water at a monitoring position located downstream of the contact in I) and upstream of the protective film(s). III) Bringing the treated water and one or more reducing agents in the amount to be reduced into contact near or downstream of the monitoring position and upstream of the protective membrane(s), The reducing agent has the ability to reduce biocide bromine to bromide ions. The bromine-containing biocides are as follows: A) One or more 1,3-dibromo-5,5-dialkylhydantoins, B) One or more N,N'-bromochloro-5,5-dialkylhydantoins, C) Optionally, (i) one or more bromide sources and (ii) one or more alkali metal hypobromite and / or one or more alkaline earth metal hypobromite formed in water from one or more hypochlorite and / or hypochlorous acid, D) (i) one or more bromide sources, (ii) an oxidizing agent, optionally (iii) at least one inorganic base, and optionally (iv) a brominated biocide formed in water from sulfamic acid and / or a metal salt of sulfamic acid. E) A brominated biocide formed in water from (i) bromine chloride or bromine chloride and bromine, with or without chlorine, and (ii) an overbasic alkali metal salt of sulfamic acid and / or sulfamic acid, an alkali metal base, and water, wherein (i) and (ii) have a relative ratio of nitrogen atoms to active bromine of more than 0.93, and the brominated biocide has a pH greater than 7. F) Brominated biocides formed in water by ozone treatment of one or more bromide sources, G) The process comprising contacting a brominated biocide formed by electrolysis in water from one or more bromide sources.

2. The process according to claim 1, wherein the bromine-containing biocide comprises one or more N,N'-bromochloro-5,5-dialkylhydantoins, one or more 1,3-dibromo-5,5-dialkylhydantoins, or E) a brominated biocide.

3. The process according to claim 1, wherein the bromine-containing biocide comprises E) a brominated biocide formed in water from N,N'-bromochloro-5,5-dimethylhydantoin, 1,3-dibromo-5,5-dimethylhydantoin, or bromine chloride.

4. The bromine-containing biocide includes a bromine-based biocide formed in water from the components of the bromine-based biocide E), The alkali metal base in (ii) above is sodium hydroxide, The biocide has an active bromine content of approximately 100,000 ppm or more, and / or The process according to claim 2 or 3, wherein the pH is approximately 10 or higher.

5. The process according to any one of claims 1 to 3, wherein the 1,3-dibromo-5,5-dialkylhydantoin(pl) and / or N,N'-bromochloro-5,5-dialkylhydantoin(pl) are pre-mixed with water before contact with the feedwater, and optionally, in the pre-mixed water, the 1,3-dibromo-5,5-dialkylhydantoin(pl) and / or N,N'-bromochloro-5,5-dialkylhydantoin(pl) are present in an amount sufficient to provide a bromine residue ranging from about 300 ppm to about 3500 ppm (by weight) as free bromine.

6. The process according to claim 4, wherein the brominated biocide E) is diluted before contact with the feedwater to form a diluted brominated biocide E).

7. The bromine-containing biocide is F) Brominated biocides, or The process according to claim 1, comprising the brominated biocide G).

8. The process according to claim 1, wherein the biocide is N,N'-bromochloro-5,5-dialkylhydantoin or 1,3-dibromo-5,5-dialkylhydantoin, and the contact with the supply water is carried out by dissolving the biocide in water.

9. The process according to claim 8, wherein the biocide is N,N'-bromochloro-5,5-dimethylhydantoin or 1,3-dibromo-5,5-dimethylhydantoin.

10. The process according to claim 1, wherein the biocide is bromine chloride or a brominated biocide formed in water from bromine chloride and bromine, and the contact of the brominated biocide with the supply water is carried out without diluting the biocide.

11. The process according to claim 10, wherein the bromine biocide is formed from bromine chloride in water.

12. The process according to claim 1, wherein the one or more bromide sources for biocide C) are alkali metal bromides, and / or the one or more hypochlorites and / or hypochlorous acid for biocide C) are alkali metal hypochlorites.

13. The process according to claim 12, wherein the alkali metal bromide is sodium bromide and / or the alkali metal hypochlorite is sodium hypochlorite.

14. In biocide D), The oxidizing agent is a chlorine-based oxidizing agent or an oxygen-based oxidizing agent, and an inorganic base is present, or the oxidizing agent is a chlorine-based oxidizing agent or an oxygen-based oxidizing agent, and sulfamic acid and / or a metal salt of sulfamic acid are present, The process according to claim 1, wherein the oxidizing agent is a chlorine-based oxidizing agent or an oxygen-based oxidizing agent, and an inorganic base and sulfamic acid and / or a metal salt of sulfamic acid are present.

15. The process according to any one of claims 1 to 14, wherein the bromine-containing biocide provides a bromine residue in the treated water in the range of about 0.2 ppm to about 20 ppm (by weight) as free bromine.

16. The process according to any one of claims 1 to 14, wherein the bromine-containing biocide provides a bromine residue in the treated water in the range of about 0.5 ppm to about 10 ppm (by weight) as free bromine.

17. The process according to any one of claims 1 to 16, wherein the measurement is performed by a chemical method or a spectroscopic method.

18. The process according to claim 17, wherein the measurement is the measurement of the potential of the treated water.

19. The process according to claim 18, wherein the measurement is performed using an oxidation-reduction meter.

20. The process according to claim 18, wherein the measurement is performed using an ammeter.

21. The process according to any one of claims 1 to 20, wherein the aqueous membrane separation system is a reverse osmosis system.

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