Biocidal control in aqueous membrane separation systems

Abstract

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

Description

Related applications

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 532,796, filed August 15, 2023, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0002] This invention relates to biocidal control in aqueous membrane separation systems. Background Technology

[0003] Microorganisms, such as bacteria, fungi, and algae that enter aqueous membrane separation systems, can deposit on the membrane and form biofilms, negatively impacting membrane performance. Biofilms can affect the water passing through the membrane, clog the membrane, and / or reduce membrane efficiency.

[0004] Various methods have been developed for controlling or minimizing microbial growth and biofilm formation (particularly on one or more membranes in a system). Some of these methods employ biocides that contact the membrane, which can damage it. There remains a need for methods to minimize or prevent biofilm formation on one or more membranes without damaging the membrane. Attached Figure Description

[0005] The subject matter disclosed herein can be better understood by referring to the following exemplary figures. The components in the figures are not necessarily drawn to scale, but rather the emphasis is on illustrating the principles of the subject matter disclosed herein (generally schematic). In the figures, the same reference numerals denote corresponding parts in different views. A further understanding of the subject matter disclosed herein can be obtained by referring to the embodiments illustrated in the figures. Although the illustrated embodiments are merely examples for the purpose of demonstrating systems for implementing the subject matter disclosed herein, the organization and operation of the subject matter disclosed herein, as well as its further purposes and advantages, can generally be more readily understood by referring to the figures and the following description. The figures are not intended to limit the scope of the subject matter disclosed herein, which is specifically set forth in the appended or subsequently amended claims, but are merely for illustrating and providing examples of the subject matter disclosed herein.

[0006] Figure 1 This is a graphical description of data from experiments used to test the progress of membrane degradation. Summary of the Invention

[0007] This invention provides a method for controlling and minimizing microbial growth, particularly biofilm growth, in aqueous membrane separation systems. In the method of this invention, biofouling is effectively minimized or controlled with minimal or no contact between the biocide and the membrane, which in turn minimizes or prevents damage to the membrane by the biocide. By implementing this invention, effective minimization of microbial contamination of water and one or more membranes can be achieved.

[0008] One embodiment of the present invention is a method for controlling biofouling in an aqueous membrane separation system comprising water and one or more protected membranes. The method includes: I) Contact feed water with a biocidal amount of brominated biocide upstream of one or more protected membranes to form treated water; II) Measure the bromine residue in the treated water at monitoring locations downstream of the contact in I) and upstream of the one or more protected membranes; and III) Contact the treated water with a reduced amount of one or more reducing agents near or downstream of the monitoring location and upstream of the one or more protected membranes.

[0009] The reducing agents in these methods can reduce biocidal bromine to bromide ions. In these methods, bromine-containing biocides include: A) One or more 1,3-dibromo-5,5-dialkylhydantoin; B) One or more N,N'-bromochloro-5,5-dialkylhydantoin; C) One or more alkali metal hypobromide and / or one or more alkaline earth metal hypobromide, which are optionally formed in water from (i) one or more bromide sources and (ii) one or more hypochlorite and / or hypochlorous acid; D) A bromine-based biocide formed in water from (i) one or more bromide sources, (ii) an oxidizing agent, optionally (iii) at least one inorganic base and optionally (iv) a sulfamic acid and / or a metal salt of a sulfamic acid. E) A bromine-based biocide formed in water from (i) bromine chloride or bromine chloride and bromine, with or without the combined use of chlorine and (ii) a highly basic alkali metal salt of aminosulfonic acid and / or aminosulfonic acid, alkali metal base and water, wherein the relative proportions of (i) and (ii) result in an atomic ratio of nitrogen to active bromine greater than 0.93, and wherein the bromine-based biocide has a pH greater than 7. F) A brominated biocide formed in water by ozonation of one or more bromide sources, wherein the bromide sources are selected from ammonium bromide, hydrogen bromide, one or more alkali metal bromides, one or more alkaline earth metal bromides, and mixtures of any two or more of the foregoing; or G) A brominated biocide formed by electrolysis in water from one or more bromide sources, wherein the bromide sources are selected from ammonium bromide, hydrogen bromide, one or more alkali metal bromides, one or more alkaline earth metal bromides, and any two or more mixtures thereof.

[0010] These and other embodiments and features of the invention will become more apparent from the following description and the appended claims. Detailed Implementation

[0011] As used throughout this document, the phrase “biomass” refers to the amount of bacteria or microorganisms used to control, kill, or otherwise reduce the amount of water being treated to a statistically significant level.

[0012] Unless otherwise expressly stated herein, the term ppm refers to parts per million (wt / wt).

[0013] Throughout this document, "aqueous membrane separation system" is sometimes referred to as "aqueous membrane system" or "membrane system".

[0014] Throughout this document, the phrase "protected membrane" refers to a membrane in an aqueous membrane separation system that is not in contact with biocides or has minimal contact with biocides. Similarly, as used throughout this document, the phrase "unprotected membrane" refers to a membrane that is in contact with or permitted to be in contact with biocides in the practice of this invention.

[0015] As used throughout this article, "downstream" refers to the direction of travel of the influent and treated water, and "upstream" refers to the opposite direction of travel of the influent and treated water. In aqueous membrane separation systems, the protected membrane is typically located downstream of the influent, and the unprotected membrane is typically located upstream of the protected membrane.

[0016] In the method of this invention, a biocidal amount of brominated biocide is contacted with influent to form treated water; the brominated biocide in the treated water is measured as bromine residue at monitoring locations downstream of the influent and upstream of one or more protected membranes; and the treated water is contacted with one or more reducing agents near or downstream of the monitoring locations and upstream of the one or more protected membranes. The brominated biocide in the method of this invention includes brominated biocides A), B), C), D), E), or F as described above. The reducing agent in the method of this invention is capable of reducing biocidal bromine to bromide ions.

[0017] An aqueous membrane separation system is an aqueous system containing one or more membranes, wherein the one or more membranes are used as part of a separation process. In some aqueous membrane separation systems, there is one membrane that is protected. In other aqueous membrane separation systems, there are two or more membranes, and at least one of these membranes is protected. When there are two or more membranes in an aqueous membrane separation system, there may be both at least one protected membrane and at least one unprotected membrane.

[0018] The present invention can process various aqueous membrane separation systems. Non-limiting examples of processable aqueous membrane separation systems include microfiltration systems, ultrafiltration systems, nanofiltration systems, reverse osmosis systems, and / or electrodialysis systems. Reverse osmosis systems are preferred aqueous membrane separation systems for use in the methods of the present invention.

[0019] In some implementations, when the aqueous membrane separation system is a reverse osmosis (RO) system and there is a membrane upstream of the RO membrane, the upstream membrane may be an unprotected membrane, while the RO membrane is a protected membrane. In other implementations, both the upstream membrane and the RO membrane are protected membranes.

[0020] As used throughout this document, the phrase "inlet water" means water used in an aqueous membrane separation system before it comes into contact with the brominated biocide; inlet water includes water fed into the aqueous membrane separation system. As used throughout this document, the phrase "treated water" means (feed) water that has already been contacted with the brominated biocide according to the invention.

[0021] The influent can come from any convenient source, including desalinated water, industrial water, river water, swamp water, brackish surface water and groundwater, and seawater.

[0022] Contact between brominated biocides and influent water is typically achieved by introducing the brominated biocides into the influent water. Brominated biocides A) and B) are solids and can contact the influent water in solid form, and / or the solids can be dissolved in water before contacting the influent water. Preferably, brominated biocides A) and B) are dissolved in water before contacting the influent water. Brominated biocides C), D), E), F), and G) are aqueous solutions and can be diluted with water before contacting the influent water to form diluted brominated biocides of C), D), E), F), and G), or the brominated biocides of C), D), E), F), and G) can be used undiluted for contacting the influent water.

[0023] Contact between the brominated biocide and the feed water can occur anywhere upstream of one or more protected membranes. Preferably, the brominated biocide is brought into contact with the feed water as far upstream as possible from one or more protected membranes. Early contact between the brominated biocide and the feed water allows for a longer contact time to maximize the benefit from the brominated biocide. Due to the presence of the brominated biocide, the treated water has a more positive potential than the feed water.

[0024] In some implementations, the influent is introduced from a container, such as a storage tank, into the aqueous membrane separation system. In implementations where the influent is contained in or passes through a container, the contact between the brominated biocide and the influent preferably occurs in the pipeline that delivers the influent into the container.

[0025] The amount of brominated biocide used depends on the requirements of the influent and the amount of microbial load (e.g., biofilm) present in or in contact with the influent. Preferably, the amount of brominated biocide used is sufficient to control or satisfy the microbial load, or more preferably, the amount of brominated biocide satisfies the microbial load and provides bromine residue in the treated water. When the amount of brominated biocide provides bromine residue in the treated water, the bromine residue in the treated water, calculated as free bromine, is from about 0.2 ppm to about 20 ppm, preferably from about 0.5 ppm to about 10 ppm, more preferably from about 0.5 ppm to about 2 ppm (wt / wt). When the influent comes into contact with the brominated biocide, the influent becomes treated water.

[0026] When the amount of brominated biocide that comes into contact with the influent is ineffective for biocide control, additional brominated biocide can be introduced into the treated water at any point upstream of the monitoring location. Preferably, the additional brominated biocide is introduced into the treated water as far upstream as possible from the monitoring location. The additional brominated biocide may be the same as or different from the brominated biocide initially introduced into the influent.

[0027] The term "active bromine" refers to all bromine-containing substances capable of exhibiting biocidal activity. Generally, all bromine in the +1 oxidation state is considered biologically active and is therefore included in the term "active bromine." As is well known in the art, bromine, bromine chloride, hypobromic acid, and hypobromate ions (OBr) are examples. - Tribromide, tribromide ions, and organic N-brominated compounds contain bromine in the +1 oxidation state. Therefore, these and other substances containing bromine in the +1 oxidation state, in their quantity, constitute the active bromine content of the brominated biocide used in the practice of this invention.

[0028] To measure residual bromine in treated water, monitoring points are located downstream of the influent where the bromine-containing biocide comes into contact with the water and upstream of one or more protected membranes. Preferably, the monitoring points are located at a distance upstream of the protected membrane, allowing time for the reducing agent to come into contact with the bromine-containing biocide.

[0029] In some implementations, measuring residual bromine in treated water at monitoring locations includes chemical methods such as N,N'-diethyldiphenyldiamine (DPD) testing and spectroscopic methods such as UV / visible spectroscopy.

[0030] The presence of brominated biocide provides an oxidation potential in treated water. In some embodiments, this potential is measured and correlated with the amount of brominated biocide in the treated water. In practice, two methods for monitoring the potential of treated water are preferred: oxidation-reduction potential (ORP) and current analysis. Both methods involve placing a probe in the treated water and measuring the water's potential, which provides an indication of the concentration of the brominated biocide at the monitoring location. Both current analysis and ORP monitoring can be configured for intermittent or continuous measurement of the potential of the treated water. ORP sensors and controllers are commercially available, as are galvanometer electrodes and controllers.

[0031] Oxidation-reduction potential (ORP) measures the potential of treated water, typically in millivolts; a positive value indicates an oxidizing environment, and an increase in the ORP value relative to the influent indicates the presence of brominated biocide; a negative value indicates a reducing environment, meaning that sufficient reducing agent has come into contact with the treated water to react with all brominated biocides in the treated water (“neutralization”).

[0032] In some implementations, the required ORP value after the treated water comes into contact with the reducing agent is approximately +250 mV to approximately -5 mV.

[0033] In practice, the ORP value of the treated water is measured at a monitoring location, and the required amount of reducing agent is brought into contact with the treated water. Preferably, sufficient reducing agent is brought into contact with the treated water to prevent oxidation.

[0034] In some implementations, the ORP can be connected to a controller for the reductant feed, and once the ORP value in the treated water reaches a preset value, the ORP can communicate with the reductant controller to stop the introduction of the reductant.

[0035] The galvanometry method measures the change in current when a fixed potential is applied to treated water; a positive value indicates an oxidizing environment, meaning that a brominated biocide is present; a negative value indicates a reducing environment, meaning that sufficient reducing agent has come into contact with the treated water to react with all the brominated biocides in the treated water (“neutralization”).

[0036] In practice, the current potential of the treated water is measured at a monitoring location, and a required amount of reducing agent is brought into contact with the treated water. Preferably, sufficient reducing agent is brought into contact with the treated water to prevent oxidation.

[0037] In some implementations, the ammeter can be connected to a controller for the reductant feed, and once the potential in the treated water reaches a preset value, the ammeter can communicate with the reductant controller to stop the introduction of the reductant.

[0038] The contact between the reducing agent and the treated water is at or downstream of the monitoring location, and also upstream of the protected membrane, or upstream of the first protected membrane when the aqueous membrane separation system has more than one protected membrane.

[0039] In some implementations, there is more than one monitoring location, with the second monitoring location downstream of the first monitoring location; the monitoring methods at each monitoring location may be the same or different. As needed or desired, additional reducing agents may be introduced into the water of the aqueous membrane separation system near or downstream of the second monitoring location and upstream of one or more protected membranes.

[0040] In practice, the reducing agent can be directly incorporated into the treated water. If desired, one or more reducing agents can be premixed with water before being introduced into the treated water.

[0041] The amount of reducing agent used typically depends on the amount of brominated biocide in the treated water. The reducing agent reduces the amount of brominated biocide in contact with the protected membrane by consuming at least a portion of the brominated biocide. As a result of measuring bromine residue in the treated water, the amount of reducing agent that will contact the treated water can be adjusted manually or automatically to consume a specific amount, or preferably all, of the brominated 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 the brominated biocide in the treated water.

[0042] When the amount of reducing agent that comes into contact with the treated water is insufficient to effectively reduce the residual bromine in the treated water to the desired level, an additional reducing agent may be introduced into the treated water at any point downstream of the monitoring location and upstream of one or more protected membranes. This additional reducing agent may be the same as or different from the one initially introduced into the treated water.

[0043] The treated water, upon contact with a reducing agent, forms reduced or neutralized water that can contact and pass through one or more protected membranes with minimal or no damage. Here, the term "neutralized" indicates that the reducing agent has been added in an amount sufficient to quench or neutralize the oxidizing power of the brominated biocide. When using a reducing agent sufficient to consume all the brominated biocide, contact between the brominated biocide and the protected membrane is prevented.

[0044] The brominated biocide used in this invention is an oxidizing biocide.

[0045] The 1,3-dibromo-5,5-dialkylhydantoin and N,N'-bromochloro-5,5-dialkylhydantoin used according to the present invention are solids and can be directly incorporated into the influent. Preferably, the 1,3-dibromo-5,5-dialkylhydantoin and N,N'-bromochloro-5,5-dialkylhydantoin are premixed with water before contact with the influent. In the premixed water (typically a solution), the microbial activity of one or more 1,3-dibromo-5,5-dialkylhydantoin or one or more N,N'-bromochloro-5,5-dialkylhydantoin 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 (wt / wt), based on free bromine.

[0046] In practice, one or more 1,3-dibromo-5,5-dialkylhydantoin have an alkyl group containing 1 to about 4 carbon atoms. Preferably, the 1,3-dibromo-5,5-dialkylhydantoin has one alkyl group being methyl and the other alkyl group containing 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 mixtures of any two or more thereof. Among these biocides, from a cost-effectiveness point of view, 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. For the aforementioned mixtures of 1,3-dibromo-5,5-dialkylhydantoins, it is preferable to use 1,3-dibromo-5,5-dimethylhydantoin as one component, and more preferably a mixture of 1,3-dibromo-5,5-dimethylhydantoin and 1,3-dibromo-5-ethyl-5-methylhydantoin. A particularly preferred 1,3-dibromo-5,5-dialkylhydantoin is 1,3-dibromo-5,5-dimethylhydantoin.

[0047] Methods for producing 1,3-dibromo-5,5-dialkylhydantoin are known and reported in the literature, and some of them are commercially available.

[0048] One or more N,N'-bromochloro-5,5-dialkylhydantoin used in the practice of this invention are N,N'-bromochloro-5,5-dialkylhydantoin wherein each alkyl group independently contains carbon atoms in the range of 1 to 4. 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 mixtures of any two or more of the foregoing. N,N'-bromochloro-5,5-dimethylhydantoin is most preferred.

[0049] When using a mixture of two or more N,N'-bromochloro-5,5-dialkylhydantoin biocides according to the present invention, the individual biocides in the mixture can be in any proportion relative to each other. Small amounts (less than 50 wt%) of one or more mono-N-bromo-5,5-dialkylhydantoin may also be present, either as a mixture of two or more N,N'-bromochloro-5,5-dialkylhydantoin biocides or as a single N,N'-bromochloro-5,5-dialkylhydantoin biocide. A suitable mixture has a major amount of N,N'-bromochloro-5,5-dimethylhydantoin by weight and small proportions of 1,3-dichloro-5,5-dimethylhydantoin and 1,3-dichloro-5-ethyl-5-methylhydantoin by weight.

[0050] Methods for producing such N,N'-bromochloro-5,5-dialkylhydantoin are known and reported in the literature, and some of them are commercially available. For example, N,N'-bromochloro-5,5-dimethylhydantoin can be marketed under the name BromiCide. ® The biocides were purchased commercially from BWA Water Additives UK Limited.

[0051] Biocid C) is one or more alkali metal hypobromide and / or one or more alkaline earth metal hypobromide, preferably formed in water from (i) one or more bromide sources and (ii) hypochlorite and / or hypochlorous acid.

[0052] In practice, the bromide source and hypochlorite and / or hypochlorous acid can be contacted separately with the inlet water (e.g., through a separate inlet); or the bromide source and hypochlorite and / or hypochlorous acid can be fed to a mixing point (e.g., a mixing tee) or mixing device (preferably an online mixing device) and then contacted with the inlet water; or the bromide source and hypochlorite and / or hypochlorous acid can be combined in water to form an aqueous solution that contacts the inlet water.

[0053] To form a bromide-containing biocide C), suitable bromide sources for component (i) include ammonium bromide, hydrogen bromide, inorganic bromide salts, and mixtures of any two or more of the foregoing. 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. If desired, mixtures of two or more bromide sources can be used. Preferred bromide sources are sodium bromide, particularly sodium bromide in which trace amounts of alcohols such as methanol have been removed.

[0054] 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. Alkali metal hypochlorites and alkaline earth metal hypochlorites include lithium hypochlorite, sodium hypochlorite, potassium hypochlorite, calcium hypochlorite, magnesium hypochlorite, etc.; sodium hypochlorite and calcium hypochlorite are preferred hypochlorites. Due to toxicological concerns, the use of bromides or hypochlorites of Be, Sr, or Ba is not recommended. Therefore, the term "alkaline earth metal" as used herein does not include Be, Sr, and Ba. When ammonium bromide is the bromide source, it is desirable to mix ammonium bromide with hypochlorite in the manner described in U.S. Patent No. 6,478,973.

[0055] The interaction between the bromide source and hypochlorite and / or hypochlorous acid results in an aqueous solution with a suitably high bromine residue. If an excess of hypochlorite is used relative to the amount of bromide salt used, the resulting solution will contain chlorine-based substances as well as bromine residue. These chlorine-based substances are harmless, provided the desired bromine residue is present in the solution used.

[0056] In some embodiments, one or more bromide sources and one or more hypochlorites and / or hypochlorous acids for forming biocide C) are respectively contacted with the influent, and an alkali metal hypobromite and / or one or more alkaline earth metal hypobromites are formed in the influent. In these embodiments, the bromide source is typically solid and may be contacted with the influent in solid form and / or preferably dissolved in water to form an aqueous solution, and then contacted with the influent. In these embodiments, the hypochlorite and / or hypochlorous acid are typically and preferably contacted with the influent in aqueous form, although, if desired, the hypochlorite may be contacted with the influent in solid form.

[0057] In other embodiments, one or more bromide sources and one or more hypochlorite and / or hypochlorous acid sources are combined to form biocide C) prior to contact with the influent. In these embodiments, the bromide source is preferably dissolved in water to form an aqueous solution prior to combination with the hypochlorite and / or hypochlorous acid. In these embodiments, when combined with the bromide source, the hypochlorite and / or hypochlorous acid are typically and preferably in the form of an aqueous solution.

[0058] When a bromide source and hypochlorite and / or hypochlorous acid are combined in water to form an aqueous solution, the aqueous solution may be diluted with water before contact with the influent to form a diluted brominated biocide C) solution, or the brominated biocide C) solution may be used undiluted for contact with the influent.

[0059] Brominated biocides D) and E) are aqueous solutions and contain active bromine, also known as bromine residues. Brominated biocides D) and E) containing sulfamic acid and / or metal salts of sulfamic acid are stable brominated biocides.

[0060] D) The brominated biocide 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) a sulfamic acid and / or a metal salt of a sulfamic acid. This brominated biocide is preferably prepared as a concentrated aqueous solution; preferably, the concentrated solution is contacted with the influent water.

[0061] When using inorganic bases, the pH is typically about 7 or higher, and preferably higher than 7, for example, in the pH range of about 10 to about 14.

[0062] To form the brominated biocide D), suitable bromide sources for component (i) include ammonium bromide, hydrogen bromide, inorganic bromide salts, and mixtures of any two or more of the foregoing. 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. If desired, mixtures of two or more bromide sources can be used. Preferred bromide sources are sodium bromide, particularly sodium bromide in which trace amounts of alcohols such as methanol have been removed.

[0063] Oxidizing agents include chlorine oxidizing agents and oxygen-based oxidizing agents. Chlorine oxidizing agents include elemental chlorine (Cl2), hypochlorite, trichloroisocyanurate, and sodium dichloroisocyanurate. When the chlorine oxidizing agent is hypochlorous acid or hypochlorite, an inorganic base is usually present; preferably, aminosulfonic acid and / or metal aminosulfonate 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 aminosulfonic acid (and / or metal salt of aminosulfonic acid) are usually present; preferably, both an inorganic base and aminosulfonic acid (and / or metal salt of aminosulfonic acid) are present.

[0064] In some embodiments of brominated biocides (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.

[0065] Sulfoamic acid and / or its metal salts are optional, but preferred in some brominated biocides (D). The metal salts of sulfamic acid are typically alkali metal salts, including lithium sulfamate, sodium sulfamate, and potassium sulfamate. Sulfoamic acid can be used alone or in combination with one or more metal salts of sulfamic acid. Sulfoamic acid and / or sodium sulfamate are preferred. Sulfoamic 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 its metal salts are preferred.

[0066] In some preferred embodiments of the brominated biocide (D), the oxidant is trichloroisocyanurate or sodium dichloroisocyanurate, and an inorganic base is present.

[0067] If an excess of chlorine oxidant is used relative to the amount of bromide salt used, the resulting solution will contain chlorine-based substances and residual bromine. These chlorine-based substances are harmless, provided that the desired residual bromine is present in the solution used.

[0068] Commercially available aqueous brominated biocides (D) that can be used to implement this invention can be traded under the name Sta•Br•Ex. ® This biocide is obtained from Ecolab USA Inc. This product contains active bromine, which is stabilized by the addition of aminosulfonate to prevent chemical decomposition and physical evaporation. Further details regarding the preparation of aqueous biocide solutions stabilized with aminosulfonate can be found in U.S. Patent Nos. 6,007,726; 6,156,229; and 6,270,722.

[0069] Another brominated biocide (D) is commercially available under the trade name BromMax® Biocide (Enviro Tech Chemical Services, Inc.). This product contains active bromine, which is stabilized by the addition of an aminosulfonate to prevent chemical decomposition and physical evaporation. Further details regarding the preparation of this type of brominated biocide (D) stabilized with aminosulfonate can be found in U.S. Patent Nos. 7,045,153; 7,309,503; and 7,455,859.

[0070] Another commercially available brominated biocide (D) that can be used to implement this invention is available under the trade name Justeq07 biocide (Justeq, LLC). This product contains an active halogen substance stabilized by the addition of an aminosulfonate. In some embodiments, the biocide can be prepared by generating a chloroaminosulfonate from a chlorination oxidant (preferably hypochlorite) and an aminosulfonic acid and / or a metal salt of an aminosulfonic acid, followed by the introduction of a bromide source. Methods for producing aqueous solutions of this type of biocide are described in U.S. Patent Nos. 6,478,972; 6,533,958; and 7,341,671.

[0071] E) The brominated biocide is formed in water from (i) bromine chloride or bromine chloride and bromine, with or without the combined use of chlorine, and (ii) a highly basic alkali metal salt of aminosulfonic acid and / or aminosulfonic acid, alkali metal base and water, wherein the relative proportions of (i) and (ii) result in an atomic ratio of nitrogen to active bromine greater than 0.93, and wherein the brominated biocide has a pH greater than 7. Brominated biocide D) is preferably prepared as a concentrated aqueous solution; preferably, the concentrated solution is contacted with the influent water.

[0072] Methods for producing an aqueous brominated biocide (E) are described in U.S. Patent Nos. 6,068,861 and 6,299,909B1. The brominated biocide (E) containing more than 50,000 ppm of active halogen can be branded as STABROM. ® 909 biocides (Albemarle Corporation) are commercially available from Albemarle Corporation; the pH of the received aqueous product is typically in the range of 13 to 14.

[0073] When forming a brominated biocide (E), an inorganic base is used, and the pH is typically at least 7, and preferably always above 7, for example, in the range of 10-14. Preferred bases are alkali metal bases, preferably oxides or hydroxides of lithium, sodium, and / or potassium, more preferably sodium hydroxide and / or potassium hydroxide. If sulfamic acid is used to form a concentrated aqueous solution of the biocide, the solution should also be provided with a base, preferably sufficient to maintain the alkalinity of the solution, i.e., a pH above 7, preferably about 10 or higher, and most preferably about 13 or higher.

[0074] For component (i) of brominated biocide E), bromine chloride, a mixture of bromine chloride and bromine, or a combination of bromine and chlorine are used, wherein the molar amount of chlorine is equal to or less than the molar amount of bromine, and the biocide aqueous solution is based on bromine, because most chlorine typically forms chloride salts, such as sodium chloride, as alkali metal bases such as sodium hydroxide are typically used in treatment to raise the pH of the product solution to about 13 or greater.

[0075] When preparing concentrated aqueous solutions of brominated biocides (E), the active bromine content of such biocidal solutions is typically about 50,000 ppm (wt / wt) or higher; preferably about 100,000 ppm (wt / wt) or higher, for example, up to about 105,000 to about 215,000 ppm of active bromine. Such concentrated biocidal solutions have a pH greater than 7, preferably about 10 or higher, more ideally about 12 or higher, and even more ideally about 13 or higher, and the atomic ratio of nitrogen to active bromine in these individual biocidal solutions is greater than 0.93.

[0076] A brominated biocide (F) is formed in water by ozonation of one or more bromide sources. This brominated biocide is prepared by ozonating an aqueous solution containing bromide ions through an ozonation device. The ozonated solution contains biologically active bromine and is typically contacted with the influent shortly after ozonation, preferably by directly transferring the solution from the ozonation process to contact with the influent.

[0077] To form a brominated biocide (F), suitable bromide sources include ammonium bromide, hydrogen bromide, inorganic bromide salts, and mixtures of any two or more of the foregoing. 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. If desired, mixtures of two or more bromide sources can be used. A preferred bromide source is sodium bromide, particularly sodium bromide in which trace amounts of alcohols such as methanol have been removed.

[0078] Brominated biocides (G) are formed in water by electrolysis of one or more bromide sources. These brominated biocides are prepared by electrolyzing an aqueous solution containing bromide ions to produce bromine, typically by passing the bromide-containing solution through an electrogenerating system. The electrolyzed solution contains biologically active bromine and is typically contacted with the influent shortly after electrolysis, preferably by directly conveying the solution from the electrolysis process to contact with the influent.

[0079] To form brominated biocides (G), suitable bromide sources include ammonium bromide, hydrogen bromide, inorganic bromide salts, and mixtures of any two or more of the foregoing. 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. If desired, mixtures of two or more bromide sources can be used. Preferred bromide sources are sodium bromide, particularly sodium bromide in which trace amounts of alcohols such as methanol have been removed.

[0080] Among the several types of bromine-containing biocides that can be used in the practice of this invention, preferred bromine-containing biocides include N,N'-bromochloro-5,5-dialkylhydantoin, 1,3-dibromo-5,5-dialkylhydantoin, and bromine-based biocides formed in water by bromine chloride or by 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 by bromine chloride; particularly preferred are bromine-based biocides formed in water by bromine chloride.

[0081] The desired bromine residue in the brominated biocide solution prior to contact with the influent can depend on a variety of factors, such as the known microbial requirements of the influent and downstream of the contact site with the brominated biocide. In some embodiments, after contact with the brominated biocide, the bromine residue in the influent, calculated as free bromine, is from about 0.2 ppm to about 20 ppm, preferably from about 0.5 ppm to about 10 ppm, and more preferably from about 0.5 ppm to about 2 ppm (wt / wt).

[0082] This invention allows the use of brominated biocides and one or more other compatible microbial agents. Preferably, according to this invention, the brominated biocides are the sole source of microbial activity in the water.

[0083] The reducing agent used in this invention can reduce biocidal bromine to bromide ions (Br). - The reducing agent that can be used in the practice of this invention is any reducing agent that can effectively reduce a bromine-based oxidant, or a reducing agent that can effectively reduce one or more specific bromine-based oxidants present in the membrane separation system. Typical reducing agents used in the practice of this invention include sulfur dioxide, sodium metabisulfite, sodium bisulfite, sodium sulfite, sodium bisulfite, sodium bisulfite, sodium thiosulfate, ammonium bisulfite, and ammonium thiosulfate. Mixtures of any two or more reducing agents can be used. In some embodiments, it is convenient to use a single reducing agent instead of a mixture of reducing agents.

[0084] The term "free bromine" is used to describe bromine oxidants present in aqueous solutions in a free or relatively fast-reacting form. In the case of bromine-containing biocides used in the practice of this 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" expressed in ppm Cl2 by 2.25, which is the molecular weight ratio of Br2 to Cl2. Similarly, when a given halogen concentration is reported as Br2, it can be converted to a Cl2 value by dividing by 2.25 (the molecular weight ratio of Cl2 to Br2).

[0085] The term "bromine residue" refers to the amount (concentration) of bromine present in water and used for disinfection. Depending on the analytical testing method employed, the residue can be determined as "free" or "total." In the context of this invention, the bromine residue values ​​are given herein on a free bromine basis. Such values ​​can be monitored using the analytical procedure for "free chlorine" given below. However, if desired, bromine residue can be monitored on a "total bromine" basis using the analytical procedure for "total chlorine" given below. In either case, the obtained values ​​are in chlorine terms, and thus such values ​​are multiplied by 2.25 to obtain the corresponding bromine value. Generally, the "total bromine" value for a given sample will be higher than the "free bromine" value for the same given sample. It is important to understand that this invention relates to bromine residue actually present in treated aqueous media, regardless of whether the value is determined using a free chlorine test procedure or a total chlorine test procedure, but the free chlorine test procedure is recommended.

[0086] Suitable methods for determining "bromine residues" are known and reported in the literature. See, for example, StandardMethods 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), pp. 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 Catalogue Card No. 76-27257), 1976, pp. 24-29. Although these references usually refer to "chlorine residue," the same technique is used to determine "bromine residue" given the higher atomic weight of bromine compared to chlorine.

[0087] The content of active halogens, whether active chlorine, active bromine, or both, can be determined by conventional starch-iodine titration.

[0088] The standard test for determining low levels of reactive halogens is called the DPD test, and it is based on the classic test procedure developed by Palin in 1974. See AT Palin, "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, 28 , 139. Although there are various modernized versions of the Palin program, the recommended version for this test is... Hach Water Analysis HandbookThe 3rd edition, copyrighted in 1997, provides a complete description. "Total chlorine" (i.e., active chlorine) is identified in this publication as Method 8167, appearing on page 379. In short, the "total chlorine" test involves introducing a powder containing a DPD indicator powder (i.e., N,N'-diethyldiphenyldiamine, KI, and buffer) into a diluted water sample containing an active halogen. The active halogen present reacts with KI to generate iodine, which turns the DPD indicator red / pink. The intensity of the staining depends on the concentration of the "total chlorine" (i.e., active chlorine) present in the sample. This intensity is measured by a colorimeter calibrated to convert the intensity reading into a "total chlorine" value expressed in mg / L Cl2. If the active halogen present is active bromine, the result expressed in mg / L Cl2 is multiplied by 2.25 to express the result for active bromine expressed in mg / L Br2.

[0089] In more detail, the DPD test procedure is as follows: 1. To determine the amount of substances in water that react with the "total chlorine" test, the water sample should be analyzed within minutes of sampling, preferably immediately after sampling.

[0090] 2. Hach Method 8167, used to test the amount of a substance in a water sample that reacts to the “Total Chlorine” test, involves the use of a Hach DR 2010 colorimeter. The stored program number for chlorine determination is invoked by typing “80” on the keypad and then setting the absorbance wavelength to 530 nm by rotating the dial on the side of the instrument. Fill two identical sample cells to the 25 mL mark with the water being investigated. Randomly select one cell as a blank. Add the contents of the DPD total chlorine powder pillow to the second cell. Shake it for 10–20 seconds to mix, as the appearance of a pink color indicates the presence of a substance in the water that reacts positively to the DPD “Total Chlorine” test reagent. On the keypad, press the SHIFT TIMER key to begin the three-minute reaction time. After three minutes, the instrument will beep, indicating the reaction is complete. Place the blank sample cell into the sample chamber of the Hach DR 2010 and close the shield to prevent stray light effects. Then press the ZERO key. After a few seconds, the display shows 0.00 mg / LCl2. Next, remove the blank sample cell used for instrument zeroing from the cell compartment of the Hach DR 2010 and replace it with the test sample containing the DPD "Total Chlorine" test reagent. Then, close the light shield as you would with a blank sample and press the READ button. The result (mg / L Cl2) will appear on the display within seconds. This is the "Total Chlorine" level of the water sample under investigation. It should be noted that the test sample may need to be diluted with halogen-free water so that the chlorine measurement is within the instrument's measurement range. This dilution needs to be taken into account when determining the actual chlorine content of the sample.

[0091] 3. One method for measuring free chlorine is Hach method 8021. This tests the amount of a substance present in a water sample that reacts to the "free chlorine" test. The test involves using a Hach DR 2010 colorimeter. The stored procedure number for chlorine determination is invoked by typing "80" on the keypad and then setting the absorbance wavelength to 530 nm by rotating the dial on the side of the instrument. Two identical sample cells are filled to the 25 mL mark with the water being investigated. One cell is randomly selected as a blank. The blank sample cell is placed in the sample chamber of the Hach DR 2010, and the shielding is closed to prevent stray light effects. The ZERO key is then pressed. After a few seconds, the display shows 0.00 mg / L Cl2. The blank sample cell used for instrument zeroing is then removed from the cell compartment of the Hach DR 2010. The contents of the DPD free chlorine powder pillow are added to the second cell. Shake the sample for 10-20 seconds to mix, as the appearance of a pink color indicates the presence of a substance in the water that reacts positively to the DPD "Free Chlorine" test reagent. Immediately (within one minute of reagent addition), place the prepared sample into the pool holder. Then close the light shield as you would with a blank sample and press the READ button. The result (mg / L Cl2) will appear on the display within seconds. This is the "Free Chlorine" level of the water sample under investigation. Note that the test sample may need to be diluted with halogen-free water so that the chlorine measurement is within the instrument's measurement range. Dilution will need to be considered when determining the chlorine level of the sample.

[0092] 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 dissolved in the water before contact with the feed water. In these embodiments, a redox potentiometer is preferably used to measure the potential of the treated water. When bromine residue is present in the treated water, the bromine residue, expressed as free bromine, is from about 0.2 ppm to about 20 ppm, preferably from about 0.5 ppm to about 10 ppm, more preferably from about 0.5 ppm to about 2 ppm (wt / wt).

[0093] In other embodiments, the aqueous membrane separation system is a reverse osmosis system, and the biocide is a bromine-based biocide formed in water from bromine chloride or bromine chloride and bromine, more preferably a bromine-based biocide formed in water from bromine chloride, and the biocide is preferably in contact with the feed water without dilution. In these embodiments, a redox potentiometer is preferably used to measure the potential of the treated water. When bromine residue is present in the treated water, the bromine residue, expressed as free bromine, is from about 0.2 ppm to about 20 ppm, preferably from about 0.5 ppm to about 10 ppm, more preferably from about 0.5 ppm to about 2 ppm (wt / wt).

[0094] In other 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 preferably contacts the feed water in solid form. In these embodiments, it is preferred to use a galvanometer to measure the potential of the treated water. When bromine residue is present in the treated water, the bromine residue, expressed as free bromine, is from about 0.2 ppm to about 20 ppm, preferably from about 0.5 ppm to about 10 ppm, more preferably from about 0.5 ppm to about 2 ppm (wt / wt).

[0095] In other embodiments, the aqueous membrane separation system is a reverse osmosis system, and the biocide is a bromine-based biocide formed in water from bromine chloride or bromine chloride and bromine, more preferably a bromine-based biocide formed in water from bromine chloride, and the biocide preferably comes into contact with the feed water without dilution. In these embodiments, it is preferable to use a galvanometer to measure the potential of the treated water. When bromine residue is present in the treated water, the bromine residue, expressed as free bromine, is from about 0.2 ppm to about 20 ppm, preferably from about 0.5 ppm to about 10 ppm, more preferably from about 0.5 ppm to about 2 ppm (wt / wt).

[0096] The following examples are presented for illustrative purposes and are not intended to limit the scope of the invention.

[0097] Example 1 Swamp water is fed into a storage tank via a 1200-foot (365-meter) hose. A biocidal agent is added to the hose 20 feet (6.1 m) before it connects to the tank. Water is then fed from the tank into a reverse osmosis (RO) system equipped with an ultrafiltration (UF) membrane upstream of the RO membrane. In this system, the UF membrane is unprotected, while the RO membrane is protected. Oxidation-reduction potential (ORP) electrodes are placed in the water upstream and near the RO membrane, and are connected to the ORP controller unit (ORP electrode: RD2, Hach Company). Measurements from the ORP are monitored, and a reducing agent is pumped downstream of the ORP electrode into the RO system as needed, as indicated by the ORP readings from the ORP electrode.

[0098] The biocides tested were bleach, 1,3-dibromo-5,5-dimethylhydantoin (Br2DMH; Albemarle Corporation), and an aqueous solution (BrCl / sulfamic acid; STABROM) containing more than 50,000 ppm of active halogen in a pH range of 13 to 14, formed by bromine chloride and sulfamic acid. ® 909 bactericide (Albemarle Corporation). The reducing agent used with each biocide is sodium bisulfate.

[0099] Water samples were taken at different times upstream and near the UF membrane, and also at different times upstream and near the RO membrane. Tests for each biocide lasted approximately 30 days. The function of the RO membrane, the type of microorganisms at the treated RO membrane, the efficacy of the biocide against microorganisms in the water, and the efficacy of the biocide against biofilm growth were determined. The data are summarized in Tables 1-4.

[0100] Table 1

[0101] 1 Compare.

[0102] For each biocide, tests were conducted 30 days after the RO membrane was exposed to the biocide / reducing agent system. The data in Table 1 are derived from membrane dissections and indicate whether the residual amount of biocide, or at least the amount in contact with the RO membrane, had a negative impact on the membrane. The data in Table 1 show that bleach had the greatest negative impact on the RO membrane.

[0103] Table 2

[0104] 1 Compare.

[0105] The data in Table 2 were generated from RO membranes as part of a membrane dissection following 30 days of exposure to biocides. Table 2 shows that BrCl / sulfamic acid is the most effective biocide against both aerobic bacteria and yeast / mold.

[0106] Table 3

[0107] 1 Compare.

[0108] For the data in Table 3, water samples were taken upstream and near the UF membrane and upstream and near the RO membrane. The data in Table 3 are the average values ​​of the samples with reduced phytoplankton biocide levels over several days.

[0109] Table 4

[0110] 1 Compare.

[0111] For the data in Table 4, water samples were taken upstream and near the RO membrane, and biofilm test strips were tested using a modified Robbins apparatus. The numbers in the table are RLU units, which measure the amount of ATP present on the test strip. Higher RLU values ​​indicate the presence of a larger number of bacteria. Each value in the table is the average of 3 or 4 test strips. The data in Table 4 indicate that BrCl / sulfamic acid is the best-performing biocide against biofilms.

[0112] Example 2 Experiments were conducted and data were collected, illustrating the progress of membrane degradation as tested using standard membrane testing procedures and static membrane immersion tests, in which the membrane was directly contacted for several days in wide-mouth bottles with bleach solutions of varying concentrations of RO-1 biocides.

[0113] The tests were conducted on a test bench, with six cells arranged in two parallel groups of three cells each, using components purchased separately. The test temperature was maintained between 18 and 22 degrees Celsius, which has minimal impact on the estimation of membrane salt rejection. A conductivity meter (Hach) was used to measure permeate and feed conductivity to estimate the rejection rate. See Table 5.

[0114] Table 5 - Membrane Testing Conditions

[0115] This data shows that at a concentration of 50 ppm, the membrane rapidly deteriorated from near-perfect retention of salt concentration in the solution summarized in the influent feed parameters to approximately 20% after 20 days of exposure, while the degradation rate of RO-1 appeared to be much more gradual until exposure to significantly higher concentrations of 200 ppm and 1,000 ppm for 8 days. See Table 6 and...Figure 1 .

[0116] Table 6

[0117] Even at such high concentrations, membrane samples tested after being immersed in a 1,000 ppm RO-1 solution for over 20 days are expected to maintain higher performance than those exposed to 50 ppm bleach for the same duration. The concentration chosen for RO-1 does not represent the level of biocide to be applied for biocide control of the membrane in a biofouling environment, but rather a selection for accelerated degradation studies to rapidly compare the extent to which the membrane is affected by its direct contact.

[0118] Other embodiments of the present invention include, but are not limited to: A) A method for controlling biofouling in an aqueous membrane separation system comprising water and one or more protected membranes, the method comprising: I) Contact the influent with a biocidal amount of brominated biocide upstream of one or more protected membranes to form treated water; II) Measure the bromine residue in the treated water at monitoring locations downstream of the contact described in I) and upstream of the one or more protected membranes; and III) Contact the treated water with a reduced amount of one or more reducing agents near or downstream of the monitoring location and upstream of the one or more protected membranes; The reducing agent described herein can reduce the biocidal bromine to bromide ions; and The brominated biocides mentioned above include: a) One or more 1,3-dibromo-5,5-dialkylhydantoin; b) One or more N,N'-bromochloro-5,5-dialkylhydantoin; c) One or more alkali metal hypobromides and / or one or more alkaline earth metal hypobromides, which are optionally formed in water from one or more bromide sources and one or more hypochlorites and / or hypochlorous acids; d) A brominated biocide formed in water from (i) one or more bromide sources, (ii) an oxidizing agent, optionally (iii) at least one inorganic base and optionally (iv) a sulfamic acid and / or a metal salt of a sulfamic acid. e) A bromine-based biocide formed in water from (i) bromine chloride or bromine chloride and bromine, with or without the combined use of chlorine and (ii) a highly basic alkali metal salt of aminosulfonic acid and / or aminosulfonic acid, alkali metal base and water, wherein the relative proportions of (i) and (ii) result in an atomic ratio of nitrogen to active bromine greater than 0.93, and wherein the bromine-based biocide has a pH greater than 7; f) Brominated biocides formed in water by ozonation of one or more bromide sources; or g) Brominated biocides formed by electrolysis of one or more bromide sources in water.

[0119] B) The method as described in A), wherein the brominated biocide comprises one or more N,N'-bromochloro-5,5-dialkylhydantoin, one or more 1,3-dibromo-5,5-dialkylhydantoin, or the brominated biocide of e).

[0120] C) The method as described in A), wherein the brominated biocide comprises N,N'-bromochloro-5,5-dimethylhydantoin, 1,3-dibromo-5,5-dimethylhydantoin, or e) a brominated biocide formed in water by bromine chloride.

[0121] D) The method as described in B) or C), wherein the brominated biocide comprises a brominated biocide formed in water from the components of brominated biocide e), and wherein: (ii) The alkali metal base mentioned is sodium hydroxide; The biocide has an active bromine content of about 100,000 ppm or higher; and / or The pH is approximately 10 or higher.

[0122] E) The method as described in any one of A)-C), wherein the one or more 1,3-dibromo-5,5-dialkylhydantoin and / or one or more N,N'-bromochloro-5,5-dialkylhydantoin are premixed with water before contact with the influent, and optionally wherein, in the premixed water, the amount of the one or more 1,3-dibromo-5,5-dialkylhydantoin and / or one or more N,N'-bromochloro-5,5-dialkylhydantoin is sufficient to provide bromine residue in the range of about 300 ppm to about 3500 ppm (wt / wt) based on free bromine.

[0123] F) The method as described in D), wherein the brominated biocide in e) is diluted prior to contact with the influent to form the diluted brominated biocide in e).

[0124] G) The method as described in A), wherein the brominated biocide comprises f) Brominated biocides; or brominated biocides (g).

[0125] H) The method as described in A), wherein the biocide is N,N'-bromochloro-5,5-dialkylhydantoin or 1,3-dibromo-5,5-dialkylhydantoin, and wherein the contact with the influent is carried out using the biocide dissolved in the water.

[0126] I) The method as described in H), wherein the biocide is N,N'-bromochloro-5,5-dimethylhydantoin or 1,3-dibromo-5,5-dimethylhydantoin.

[0127] J) The method as described in A), wherein the biocide is a bromine-based biocide formed in water from bromine chloride or bromine chloride and bromine, and wherein the contact between the bromine-based biocide and the influent is carried out without diluting the biocide.

[0128] K) The method as described in J), wherein the brominated biocide is formed in water from bromine chloride.

[0129] L) The method as described in A), wherein the one or more bromide sources of biocide c) are alkali metal bromides, and / or wherein the one or more hypochlorites and / or hypochlorous acid of biocide c) are alkali metal hypochlorites.

[0130] M) The method as described in L), wherein the bromide source is an alkali metal bromide, and / or wherein the chlorine source is a hypochlorite.

[0131] N) The method as described in L), wherein the bromide source is sodium bromide, and / or wherein the chlorine source is sodium hypochlorite.

[0132] O) As described in A), wherein in biocidal d) The oxidant is a chlorine oxidant or an oxygen oxidant, and an inorganic base is present; The oxidant is a chlorine oxidant or an oxygen oxidant, and contains aminosulfonic acid and / or a metal salt of aminosulfonic acid; or The oxidant is a chlorine oxidant or an oxygen oxidant, and contains an inorganic base and a metal salt of aminosulfonic acid and / or aminosulfonic acid.

[0133] P) The method of any one of A)-O) wherein the brominated biocide provides bromine residue in the treated water in the range of about 0.2 ppm to about 20 ppm (wt / wt) based on free bromine.

[0134] Q) The method of any one of A)-O), wherein the brominated biocide provides bromine residue in the treated water in the range of about 0.5 ppm to about 10 ppm (wt / wt) based on free bromine.

[0135] R) The method as described in any one of A)-Q), wherein the measurement is performed by a chemical method or by a spectroscopic method.

[0136] S) The method as described in R), wherein the measurement is a measurement of the potential of the treated water.

[0137] T) The method described in S), wherein the measurement is performed by a redox meter.

[0138] U) The method described in S), wherein the measurement is performed by a galvanometer.

[0139] V) The method as described in any one of A)-U), wherein the aqueous membrane separation system is a reverse osmosis system.

[0140] Any component mentioned anywhere in this specification or its claims by chemical name or formula, whether in the singular or plural form, is confirmed to be present prior to contact with another substance (e.g., another component, solvent, etc.) mentioned by chemical name or chemical type. What kind of chemical change, transformation, and / or reaction (if any) occurs in the resulting mixture or solution is not important, as such change, transformation, and / or reaction is a natural result of bringing the specified components together under the conditions required by this disclosure. Therefore, these components are confirmed as ingredients brought together to perform the desired operation or form the desired composition. Furthermore, even though the claims below may refer to substances, components, and / or ingredients in the present tense (“comprising,” “is,” etc.), the stated substances, components, or ingredients are referred to as existing prior to their first contact, blending, or mixing with one or more other substances, components, and / or ingredients according to this disclosure. Therefore, the fact that a substance, component, or ingredient may lose its original properties during the contact, blending, or mixing process by chemical reaction or transformation, if done according to this disclosure and with the ordinary skill of a chemist, is not of practical significance.

[0141] This invention may include, consist of, or substantially consist of the materials and / or procedures described herein.

[0142] As used herein, the term "about" to modify the quantity of an ingredient in a composition of the invention or an ingredient used in a method of the invention refers to, for example, variations in numerical quantities that may occur in: typical measurement and liquid handling procedures used in the real world for preparing concentrates or using solutions; errors due to negligence in these procedures; differences in the manufacture, source, or purity of the ingredients used to prepare the composition or carry out the method; and so on. The term "about" also covers quantities that differ due to different equilibrium conditions of the composition resulting from a particular initial mixture. Whether or not modified by the term "about," the claims include equivalent values ​​of the quantities.

[0143] Unless otherwise expressly stated, the article “a / an” (if used herein and as is used herein) is not intended to limit the description or claim to the single element referred to by the article and should not be construed as limiting the description or claim to the single element referred to by the article. Rather, unless otherwise expressly indicated in the text, the article “a / an” (if used herein and as is used herein) is intended to cover one or more such elements.

[0144] The invention is susceptible to considerable variation in its practice. Therefore, the foregoing description is not intended to limit the invention to the specific embodiments presented above and should not be construed as limiting the invention to the specific embodiments presented above.

Claims

1. A method for controlling biofouling in an aqueous membrane separation system comprising water and one or more protected membranes, the method comprising: I) Contact the influent with a biocidal amount of brominated biocide upstream of one or more protected membranes to form treated water; II) Measure the bromine residue in the treated water at monitoring locations downstream of the contact in I) and upstream of the one or more protected membranes; as well as III) Contact the treated water with a reduced amount of one or more reducing agents near or downstream of the monitoring location and upstream of the one or more protected membranes; The reducing agent described herein can reduce the biocidal bromine to bromide ions; and The brominated biocides mentioned above include: A) One or more 1,3-dibromo-5,5-dialkylhydantoin; B) One or more N,N'-bromochloro-5,5-dialkylhydantoin; C) One or more alkali metal hypobromide and / or one or more alkaline earth metal hypobromide, which are optionally formed in water from (i) one or more bromide sources and (ii) one or more hypochlorite and / or hypochlorous acid; D) A brominated biocide formed in water from (i) one or more bromide sources, (ii) an oxidizing agent, optionally (iii) at least one inorganic base and optionally (iv) a sulfamic acid and / or a metal salt of a sulfamic acid. E) A bromine-based biocide formed in water from (i) bromine chloride or bromine chloride and bromine, with or without the combined use of chlorine and (ii) a highly basic alkali metal salt of aminosulfonic acid and / or aminosulfonic acid, alkali metal base and water, wherein the relative proportions of (i) and (ii) result in an atomic ratio of nitrogen to active bromine greater than 0.93, and wherein the bromine-based biocide has a pH greater than 7. F) Brominated biocides formed in water by ozonation of one or more bromide sources; or G) Brominated biocides formed in water by electrolysis of one or more bromide sources.

2. The method of claim 1, wherein the brominated biocide comprises one or more N,N'-bromochloro-5,5-dialkylhydantoin, one or more 1,3-dibromo-5,5-dialkylhydantoin, or E) brominated biocides.

3. The method of claim 1, wherein the brominated biocide comprises N,N'-bromochloro-5,5-dimethylhydantoin, 1,3-dibromo-5,5-dimethylhydantoin, or E) a brominated biocide formed in water by bromine chloride.

4. The method of claim 2 or 3, wherein the brominated biocide comprises a brominated biocide formed in water from a component of the brominated biocide E), and wherein: (ii) The alkali metal base mentioned is sodium hydroxide; The biocide has an active bromine content of about 100,000 ppm or higher; and / or The pH is approximately 10 or higher.

5. The method of any one of claims 1-3, wherein the one or more 1,3-dibromo-5,5-dialkylhydantoin and / or one or more N,N'-bromochloro-5,5-dialkylhydantoin are premixed with water before contact with the influent, and optionally wherein, In the premixed water, the amount of one or more 1,3-dibromo-5,5-dialkylhydantoin and / or one or more N,N'-bromochloro-5,5-dialkylhydantoin is sufficient to provide bromine residue in the range of about 300 ppm to about 3500 ppm (wt / wt) based on free bromine.

6. The method of claim 4, wherein the brominated biocide of E) is diluted prior to contact with the influent to form the diluted brominated biocide of E).

7. The method of claim 1, wherein the brominated biocide comprises: F) Brominated biocides; or Brominated biocides (G).

8. The method of claim 1, wherein the biocide is N,N'-bromochloro-5,5-dialkylhydantoin or 1,3-dibromo-5,5-dialkylhydantoin, and wherein the contact with the influent is carried out using the biocide dissolved in the water.

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

10. The method of claim 1, wherein the biocide is a bromine-based biocide formed in water from bromine chloride or bromine chloride and bromine, and wherein the contact between the bromine-based biocide and the influent is carried out without diluting the biocide.

11. The method of claim 10, wherein the brominated biocide is formed in water from bromine chloride.

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

13. The method of claim 12, wherein the alkali metal bromide is sodium bromide, and / or wherein the alkali metal hypochlorite is sodium hypochlorite.

14. The method of claim 1, wherein in biocide D) The oxidant is a chlorine oxidant or an oxygen oxidant, and an inorganic base is present; the oxidant is a chlorine oxidant or an oxygen oxidant, and aminosulfonic acid and / or a metal salt of aminosulfonic acid are present; or The oxidant is a chlorine oxidant or an oxygen oxidant, and contains an inorganic base and a metal salt of aminosulfonic acid and / or aminosulfonic acid.

15. The method of any one of claims 1-14, wherein the brominated biocide provides bromine residue in the treated water in the range of about 0.2 ppm to about 20 ppm (wt / wt) based on free bromine.

16. The method of any one of claims 1-14, wherein the brominated biocide provides bromine residue in the treated water in the range of about 0.5 ppm to about 10 ppm (wt / wt) based on free bromine.

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

18. The method of claim 17, wherein the measurement is a measurement of the potential of the treated water.

19. The method of claim 18, wherein the measurement is performed using a redox meter.

20. The method of claim 18, wherein the measurement is performed using a galvanometer.

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

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