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    • 专利摘要:
    Method for the treatment of brackish or sea water by reverse osmosis. The object of the invention is a process for the treatment of brackish or sea water comprising subjecting the stream to a filtration stage, obtaining a permeate stream and a brine stream that is sent to an additional filtration stage, obtaining a second permeate stream and a second brine stream where, continuously, a pressure control is carried out so that once fouling samples are observed in the first membrane, its operation is stopped, and it is then subjected to a step of cleaning during which the current supply is subjected to a first filtering step through a reverse osmosis membrane operating in parallel with respect to the first reverse osmosis membrane and where the process is continuously repeated alternately. The system to carry it out is also the object of the invention. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2708126A1
    申请号:ES201731181
    申请日:2017-10-06
    公开日:2019-04-08
    发明作者:Moro Maria Teresa Bergaz
    申请人:Moro Maria Teresa Bergaz；
    IPC主号:
    专利说明:

    [0001]
    [0002]
    [0003]
    [0004] Technical field
    [0005] The present invention belongs to the technical field of the chemical industry and, more particularly, refers to an improved method for the treatment of brackish or sea water by reverse osmosis, as well as the installation to carry it out.
    [0006]
    [0007] Background
    [0008] The main problem of operation faced by sea and brackish water treatment plants through reverse osmosis technology is the biofouling of reverse osmosis membranes, which causes a loss of efficiency in the facilities when requiring a greater energetic consumption in operation due to said fouling. This biological fouling is one of the biggest operational problems in certain geographical areas such as the Middle East, the Mediterranean Sea, the oceanic ocean and the China Sea, where there are frequent episodes of "red tide" (red tide) and "algae bloom" ( algae flowering) that are caused by high concentrations of organic matter (NOM ) in solution in the feed water to desalination plants of seawater. It is also a type of fouling that usually occurs in the industrial sector, such as paper mills and tertiary wastewater treatment plants.
    [0009]
    [0010] One of the main characteristics of the biological fouling is that it is produced mainly in the reverse osmosis membranes located in the first positions of the pressure tubes in which they are installed, which makes it difficult for the water to pass to the following membranes connected in series to continuation This causes a reduction in the production capacity of said membranes, which forces to increase the operating pressure to achieve the passage of water to the last membranes placed inside the pressure tubes.
    [0011]
    [0012] The basic scheme of a reverse osmosis membrane installation is shown in Figure 1. This figure shows 7 membranes of reverse osmosis connected in series inside a pressure tube. The usual number of membranes in the pressure tubes is 6 or 7. The numerical references 1 to 7 refer to each of the membranes of the installation, being (1) the first membrane, (2) the second membrane and so on consecutively. AR1 is the current corresponding to the reject water.
    [0013]
    [0014] The problems associated with biological fouling in seawater and brackish water plants are reflected in the graph shown in Figure 2, where it can be observed that the organic matter is deposited preferentially in the first membranes (positions 1 and 2), preventing the passage of water to the following membranes (positions 3, 4, 5, 6 and 7). This causes a reduction in the production capacity and affects the energy consumption of the installation. All this without citing the problems originated in the plants of reverse osmosis motivated by the forced stops of production in order to carry out the cleaning of the membranes to recover their production. It should be noted that the increase of the salinity of the feed water to the membranes allows to reduce the problem of the biological fouling along the membranes connected in series, due to the osmotic shock that is generated as a result of said increase in salinity, which makes impossible to biofouling or biological fouling to develop in such conditions. In this way, as the water passes through the membranes, the brine content increases, reducing the impact of biofouling. That is why the last membranes are barely contaminated.
    [0015]
    [0016] The main problems derived from this type of biological fouling are summarized in Table 1. The currents (Q) and pressures (P) are those corresponding to the currents shown in Figure 2, where:
    [0017] . P1: The pressure of the seawater or brackish water stream fed to the system;
    [0018] . Q1: The flow of the seawater or brackish water stream fed to the system;
    [0019] . P2: The pressure of the reject water stream (corresponding to the brine stream);
    [0020] . Q2: The flow rate of the reject water stream (corresponding to the brine stream);
    [0021] . Q3: The flow of the water flow corresponding to the final product.
    [0022]
    [0023] In particular, the scheme located in the upper part of Figure 2 is the one corresponding to the installation without problem of biofouling, with 7 membranes numbered consecutively from 1 to 7, while the scheme located in the lower part of Figure 2 is the of a plant affected by said problem (the pressures and flow rates have been identified in the same way as described above for the case of the installation without fouling problems, with the addition of sub-index "b" for its differentiation):
    [0024] T l 1. Prin ilrlm riv lni mi nili
    [0025]
    [0026]
    [0027]
    [0028]
    [0029] The problems summarized in Table 1, associated with biological fouling in sea and brackish water plants are explained in more detail below:
    [0030]
    [0031] a) Higher operating pressure and, consequently, greater energy consumption. The present invention is based on the real design of a seawater plant by reverse osmosis in the Middle East. For the design of the same one a series of projections was carried out for a production by frame of 1 MLD (1000 m3Ma). The differences observed between its design and the actual results of operation were the supporting basis of the present invention, because said plant was subject to a problem of biofouling by red tides, algae bloom and organic matter present in seawater (NOM, Natural Organic Material), something extremely common in the sea water that bathes the countries of the Middle East and other geographical areas of the world.
    [0032]
    [0033] In the simulation phase of the seawater plant designed for the desalination operation it was impossible to determine the effect of biofouling during the actual operation of the plant. In this way, as can be seen in Table 2, the operating pressure expected after three years of operation was 61.4 bar, considering a severe biofouling of the membranes because it is an open sea intake. In turn, the design recovery was 42% and the production of desalinated water of 41.67 m3 / h. However, the presence of organic matter in the feeding water, as well as having suffered different episodes of red tide and algae bloom, had consequence that the real results after one year of operation did not reach the design values, as shown in Table 2. In this Table 2 a comparison between the design values and the real ones of operation can be observed. As shown in said Table 2, the operating pressure was notably higher (69 bar) and the production and recoveries were affected, causing a higher energy consumption (7.21% higher) per cubic meter produced.
    [0034]
    [0035] Table 2. Comparison of operation data between design and real data finally obtained
    [0036]
    [0037]
    [0038]
    [0039]
    [0040] b) Loss of production by membrane installed in the pressure tubes
    [0041] In a reverse osmosis plant of conventional seawater, the membranes that desalinate the water are introduced in a pressure tube that can contain between six (6) and seven (7) membranes, each membrane capable of desalting / producing at most 10% of the flow that feeds it. The loss of production efficiency by membrane along the tube is due to the salinity of the water that feeds each membrane varies depending on the water produced by the previous, resulting in a feed water to each membrane of the tube of higher content saline than its predecessor, which reduces its production capacity.
    [0042]
    [0043] In this way, when designing a desalination frame by reverse osmosis, each membrane of the tube produces a different flow rate, as can be seen in the following table (Table 3). In this way, the final production corresponds to the sum of the individual productions of each of the membranes connected in series in each tube.
    [0044] Table 3. Comparison of membrane production within a pressure tube between the design values and the actual data obtained_________________________________ 3____________________
    [0045]
    [0046]
    [0047] In view of the results shown in Table 3, a loss of production can be observed, fundamentally produced in the first membranes installed in the pressure tube. This loss of production forces to raise the pressure of operation in the pressure tube that contains the membranes of reverse osmosis in order to achieve that a greater amount of water permeates through them, producing an increase in the energetic consumption and a worsening of the problem due to biofouling as soon as more organic matter is deposited on the surface of the membranes. With all this, in addition to the increase in energy consumption of 7.21% that was described in the previous section, there was also a loss of production of desalinated water of 12% (see Table 3).
    [0048]
    [0049] c) Greater differential pressure in the reverse osmosis frame
    [0050] Differential pressure is understood as the difference in pressure between the feed to the reverse osmosis membranes installed in the pressure tube and the outlet pressure of the concentrate or brine, that is, the difference between P1 and P2 in Figure 2. A pressure differential greater than the design in a tube, frame or reverse osmosis membrane train results in a loss of efficiency of the energy recovery system and, also, in a greater energy consumption. In this way, because the effect of biological fouling or biofouling is impossible to evaluate in the design phase of the reverse osmosis plant, in case of using a booster pump in a system of energy recovery of isobaric chambers there will be a greater difficulty in determining if the curve and characteristics of the booster pump will allow to face the unpredictable effect of biofouling efficiently. One of the advantages of the design object of the present invention is that it allows to solve this problem, guaranteeing the value of differential pressure of design in the frames of reverse osmosis and, with it, the election of more efficient pumps to overcome the drop of pressure. In this way, it is possible to avoid a greater energetic consumption derived from the loss of efficiency of the pumping equipment and energy recovery.
    [0051]
    [0052] d) Severe deterioration of the reverse osmosis membranes placed in the first and second position of the pressure tube
    [0053] As described above, as a consequence of the biological fouling, a serious deterioration of the reverse osmosis membranes placed in the first and second position of the pressure tube occurs. In these membranes a greater biological growth or biofouling is produced, which is deposited on the surface of said membranes and their spacers, blocking the passage of feed water to the following membranes. In this way, the operating pressure must be increased to guarantee the passage of water through the membranes, as well as the design recovery.
    [0054]
    [0055] e) High cost of investment in pre-treatment
    [0056] To avoid the problem of biofouling or fouling of the membranes, in the design of seawater or brackish water treatment plants, large investments are often made in complex pre-treatments (conventional physical-chemical, flotation by dissolved air or DAF, microfiltration, ultrafiltration, etc.). These processes require a large energy and chemical consumption, which results in a higher cost of investment and operation in the desalination plants that suffer from this problem.
    [0057]
    [0058] f) Production losses associated with the cleaning of the membranes
    [0059] Biological fouling or biofouling causes the stops of the reverse osmosis production trains beyond what is considered in the design phase for the cleaning of the membranes, with the consequent loss of production. Likewise, given the organic nature of the soiling, the chemical products used in their elimination have a high operative cost.
    [0060]
    [0061] In view of the above problems, different solutions have been described in the state of the art to solve the drawbacks derived from biological fouling or biofouling.
    [0062]
    [0063] Thus, for example, the invention described in WO2013163146 relates to a reverse osmosis system which comprises removing the organic matter present in a feed stream by means of a pre-treatment process which in turn comprises an initial stage of ultrafiltration.
    [0064]
    [0065] Likewise, in the application WO2008038575 a system for preventing pressure loss in a reverse osmosis system is described. For this, a pre-treatment unit is used through which the problem of biological fouling or biofouling is eliminated , increasing the efficiency of the treatment plant.
    [0066]
    [0067] As non-patent literature it is worth mentioning the publication of the authors Abdullah Said AL-Sadi and Alaa Elsayed Ali at the World Congress of the International Desalination Association on Desalination and Water Reuse held in San Diego (USA) in 2015. In this document the problem of biofouling is exposed and how, with expensive pre-treatments, the problem is not solved due to the organic matter of low molecular weight that crosses the membranes. The authors of this publication propose solutions for the future that entail a greater investment. Faced with these solutions, the present invention offers the advantage of avoiding incurring such extra costs.
    [0068]
    [0069] In general, all preventive techniques for elimination of biofouling due to organic matter or NOM ( Natural Organic Material) prior to the feeding of water to reverse osmosis membranes have proven to be, in most cases, inefficient The fundamental reason is due to the enormous cost of investment and operation required, not being able in most cases to retain the organic matter generated by biofouling due to the low molecular weight of the same and as a result of which most of the said organic matter is in solution, instead of in suspension. It is for this reason that the present invention aims to solve in an economically viable and efficient way the problem of the high costs and technological difficulties associated with the production of water by means of reverse osmosis technology in waters with a high content of soluble organic matter. and of low molecular weight and / or operational problems due to biofouling or biological fouling. The main objective is to "coexist" with the problem instead of eliminating it by means of expensive pre-treatments, reducing to the maximum the impact of biofouling due to the organic matter of low molecular weight which, in most cases, is capable of traversing any conventional pre-treatment system.
    [0070]
    [0071] General description of the invention
    [0072] For the purposes of the present description, for simplicity, each membrane element located inside a pressure tube has been called a "membrane".
    [0073]
    [0074] Thus, a first method of the invention is a method for the treatment of brackish or sea water by means of reverse osmosis technology, characterized in that it comprises:
    [0075] (a) feeding a stream of brackish or seawater to a first stage of filtration that takes place through at least a first reverse osmosis membrane located inside at least one first pressure tube located in a first frame or support structure. The feeding of the brackish or sea water current will be carried out at a pressure higher than the osmotic pressure corresponding to the salt concentration of said raw water stream fed to the system. Of As usual, the pressure of the feed stream will depend on the salinity of the raw water, the recovery of the unit or the quality of the permeate water (the higher the pressure, the higher the quality of the permeate). In general, this pressure can vary between 57 and 70 bar for sea water and between 6 and 42 bar for brackish water. Also, the number of reverse osmosis membranes located in the pressure tube (s) of the first filtration stage will preferably be one or two, in which case the membranes will be located in series. In turn, the total number of pressure tubes will be a function of the flow rate of the water to be treated and that which one wishes to produce. In this sense, it must be borne in mind that reverse osmosis membranes have limited individual capacity for production. Therefore, if you need to treat a larger volume of feedwater to obtain more product water, it will be necessary to increase the number of membranes in the installation. However, as the system is efficient with a limited number of membranes connected in series, the solution to treat a higher flow rate will increase the number of tubes operating in parallel. In general, the number of tubes operating in parallel can vary between 2 and 500;
    [0076] (b) after the passage of seawater or brackish water through the first stage of desalination, a first permeate stream and a first stream of brine (or first rejection) is obtained, which is sent to a second stage of filtration, which preferably comprises five ( 5) or six (6) reverse osmosis membranes connected in series and installed in the interior of at least one pressure tube. In this second filtration step a second permeate stream (which can be unified with the first permeate stream, corresponding to the first filtration stage) and a second brine stream (second rejection) is obtained;
    [0077] (c) continuously, during the whole process, a pressure control is carried out, so that once samples of contamination in the membrane (s) are observed, as for example by an increase in the differential pressure in the membrane (s) of the first stage of filtration and / or of the pressure of the feeding current necessary to reach a certain production, the operation of said membrane (s) is stopped, being subjected to a cleaning step, during which the feeding of the brackish or seawater stream to be treated is subjected to a first filtration step through at least a first reverse osmosis membrane located in the inside of at least one second pressure tube located in a second frame or support structure parallel to the first frame. The step of cleaning the first (s) reverse osmosis membrane (s) located in the first frame will preferably be carried out using the second brine stream (second rejection), preferably after passing through at least one re-entraining device which may consist of a centrifugal type pressure exchanger (such as an ERI exchanger, manufactured by Energy Recovery, Inc. ), a piston exchanger (such as a DWEER, of English, Double Work Energy Exchanger Recovery) or a turbocharger (Turbocharger). This stream (also known as the cleaning stream) may flow in the opposite direction to the flow of the brackish water or seawater to be treated or in the same direction as the flow of said stream, depending on the severity of the fouling and the type of membrane used.
    [0078]
    [0079] The above process will be repeated continuously, so that when the membrane (s) of the first stage of reverse osmosis filtration in the operating phase present (n) fouling symptoms (for example, by an increase in differential pressure) in said membrane (s)), it will proceed to stop its operation, going to cleaning mode, while the membrane (s) of the first stage of filtration by reverse osmosis that was (n) until that moment in cleaning mode they will be or will be fed with the sea or brackish water to be treated. This type of operation is called the "revolver" type, due to the alternation in the phases of operation and cleaning of the first stages of reverse osmosis filtration, which operate in parallel and alternately.
    [0080]
    [0081] For the purposes of this patent, brackish water means water with a salt content generally higher than 0.05% and less than 3% by volume. In turn, seawater or salt water is understood as water with a salt content generally higher than 3% and lower than 5.5% by volume.
    [0082]
    [0083] In particular, the process will be suitable for treating brackish or sea water with a content of dissolved organic matter of low molecular weight (generally, below 100,000 g / mol), such as for example fulvic acids with a molecular weight between 500 and 2,000 g. / mol, humic acids of molecular weight between 50,000 and 100,000 g / mol or carboxylic acids of molecular weight equal to 5,000 g / mol. This ability to reduce the impact of biofouling due to the content of organic matter of low molecular weight present in the water to be treated is a special advantage over other methods of pre-treatment of the state of the art, which fail to eliminate this type of compounds
    [0084] Additionally, biofouling or biological soiling is understood as the effect caused by the accumulation of organic matter that adheres to the membranes of the reverse osmosis system.
    [0085]
    [0086] In turn, the permeate flow of the process corresponds to the water current that passes through the membranes and contains a lower salt content than the water stream fed to the system. On the other hand, the reject current corresponds to water with a high salt concentration, which can either be poured or it can be reused in the system as cleaning water.
    [0087]
    [0088] In this way, the flow rate of the water to be treated flows from the end of the feed to the opposite end of reject or brine, so that the reject current of each of the membranes is transformed into the feed of the successive membrane. In turn, the permeate of each membrane is collected in a single stream, corresponding to the desalinated water stream (or final product of the process).
    [0089]
    [0090] Thanks to the described method (based on an operation type "revolver" in which a series of membranes are in operation while others, in parallel, are in the cleaning phase and vice versa) it is possible to reduce or even eliminate the problem of soiling biological (or biofouling) that takes place in water treatment plants by reverse osmosis, in this way, the membrane (s) located in the first stage of filtration (preferably one or two) are kept clean, reducing The energy consumption of the operation, which can be carried out automatically and continuously This reduction in energy consumption compared to the consumption required in the usual brackish or sea water treatment plants can be at least 7% and, in particular embodiments of the invention, of up to 15%.
    [0091]
    [0092] On the other hand, by reusing part or all of the reject stream (s) (preferably from 80 to 100% by volume) in the cleaning of the membranes, the use of the chemicals is usually reduced used in said cleaning operation (which may consist, for example, of tetrasodium EDTA, NaOH, HCl, hydroxycitric acid, etc.).
    [0093]
    [0094] Likewise, an additional advantage of the cleaning operation in those cases in which it is carried out in the opposite direction of the reject current (s) (in relation to the power supply current), is that it increases the efficiency in the elimination of deposits (biological or not) that could be plugging the spacers of the first membrane (s). On the other hand, the cleaning of one or two membranes (preferential number of membranes in the first stage of filtration) allows to maximize the flow rate of surface sweeping of the membranes and, with it, the dragging capacity of the material deposited on its surface and in the spacers of the membranes, improving the efficiency of the cleaning process. This is a great advantage over conventional systems, which are limited by the pressure of operation of the washings, usually not exceeding 4 bar, as well as by the pressure drop that occurs in each of the membranes contained in the pressure tubes, being the usual number of membranes of 6 or 7. However, the invention is not limited to the washing process is carried out in countercurrent, it can also be carried out in the direction of the flow of water supply of sea or brackish in production mode. In this case, the technical concepts explained above will also apply.
    [0095]
    [0096] Likewise, an additional advantage of the process derived from the elimination of the problem associated with the biological fouling of the membranes is the possibility of guaranteeing in the real operation the values obtained in the design phase (both in terms of production levels and energy consumption, required volume of chemicals, etc.).
    [0097]
    [0098] Additionally, it is also the object of the invention the system to carry out the method described above. Said system is characterized in that it comprises:
    [0099] (a) a first membrane module comprising at least a first reverse osmosis membrane located in the interior of at least one first pressure tube located in a first frame or support structure and at least one first reverse osmosis membrane located in the inside of at least one second pressure tube located in a second frame or support structure, where the first reverse osmosis membrane located in the first pressure tube and the first reverse osmosis membrane located in the second pressure tube are configured to operate in parallel. Preferably, the number of reverse osmosis membranes located in each of the pressure tubes of the first membrane module will be one or two. Likewise, at least one valve or device suitable for discriminating the supply to the first reverse osmosis membrane located in the first pressure tube or to the first reverse osmosis membrane located in the first or second reverse osmosis membrane will be located in the brackish or sea water supply conduit. second pressure tube, so that during the operation phase it is possible to direct the flow of the feed stream towards the membrane in the production phase while the alternative membrane is in the cleaning phase; Y
    [0100] (b) at least one second membrane module preferably comprising between five and six additional reverse osmosis membranes connected in series and located in the interior of at least one third pressure tube located in a third frame or support structure, where said The second membrane module is connected in series with respect to the first membrane module through at least one first outlet conduit of the first membrane module. This first outlet conduit of the first membrane module is located at the opposite end of the input current supply and, in particular, is the one corresponding to the reject current, a second outlet conduit being the first module of the first input module. membranes corresponding to the output of the final product (brackish or seawater with a salt content lower than the input stream). Preferably, successive membrane modules will be located in series with respect to the second membrane module, the total number of membrane modules preferably being equal to 2 for seawater and 3 for brackish water; and wherein the second membrane module or the last module in case of successive serial modules is characterized in that it comprises at least two outlet ducts, a first outlet duct corresponding to the output of the final product (water with a lower content of salts with respect to the initial content of brackish or seawater) and a second outlet conduit corresponding to the reject stream. Said second conduit (corresponding to the reject current) is preferably connected to the first membrane module (both to the first frame and to the second frame) at the opposite end to that of the brackish or sea water supply, in case it is chosen by washing in the opposite direction to the flow of the feed water, or at the same end as that of the feed to the system, in the case that it is preferred to wash the membranes in the same direction as the raw water flow in mode production. Additionally, both the first and the second frame or support structure of the first membrane module will comprise at least one duct for the discharge of the rejection corresponding to the cleaning current, said duct being located at the opposite end to the one of the power supply of the current cleaning, namely, at the end corresponding to the supply of brackish water or sea to be treated if the membranes were washed countercurrently or at the end corresponding to the first rejection in the event that the membranes were cleaned in the direction of the gross water flow in the production phase.
    [0101] Preferably, the membranes used in the process will be aromatic polyamide and will be placed inside the pressure tubes, wound in a spiral shape.
    [0102]
    [0103] Brief description of the figures
    [0104] For a better understanding of the present descriptive memory, the following figures are accompanied, by way of illustration and not limitation of the invention:
    [0105] . Figure 1 represents a general outline of the state of the art corresponding to a particular distribution of the reverse osmosis membranes in 7 membranes connected in series and installed inside a single pressure tube.
    [0106] . Figure 2 represents the effect of biofouling. In particular, in the upper part a general scheme of the state of the technique corresponding to a particular distribution of 7 reverse osmosis membranes connected in series and installed inside a single pressure tube is shown. In the lower part, the same scheme affected by the biofouling problem is represented .
    [0107] . Figure 3A represents a first particular embodiment of the invention where the first membrane module comprises at least a first reverse osmosis membrane (1A) in the operation phase located inside at least one first pressure tube located in a first frame or support structure and at least one first reverse osmosis membrane (1B) in a cleaning phase located inside at least one second pressure tube located in a second frame or support structure.
    [0108] . Figure 3B represents a second particular embodiment of the invention. This second embodiment corresponds to the first embodiment, with the difference that the first membrane module comprises at least two first membranes of reverse osmosis (1A) and (2A) connected in series and in phase of operation located inside the less a first pressure tube located in a first frame or support structure and at least two first membranes of reverse osmosis (1B) and (2B) connected in series and in phase of cleaning located in the interior of at least a second tube of pressure located in a second frame or support structure.
    [0109] . Figure 4A represents a third particular embodiment of the invention where the first membrane module comprises at least a first reverse osmosis membrane (1A) in the cleaning phase located inside at least one first pressure tube located in a first frame or support structure and at least a first reverse osmosis membrane (1B) in operation phase located inside at least one second pressure tube located in a second frame or support structure.
    [0110] Figure 4B represents a fourth particular embodiment of the invention. This fourth embodiment corresponds to the third embodiment, with the difference that the first membrane module comprises at least two first membranes of reverse osmosis (1A) and (2A) connected in series and in the cleaning phase located inside the less a first pressure tube located in a first frame or support structure and at least two first membranes of reverse osmosis (1B) and (2B) connected in series and in phase of operation located in the interior of at least one second tube of pressure located in a second frame or support structure. Figure 5 represents a flow diagram of a particular embodiment of the system comprising:
    [0111] a first frame or support structure (5 ') constituted by 14 pressure tubes connected in parallel, each of them containing in its interior two membranes of reverse osmosis;
    [0112] a second frame or support structure (6 '), parallel to the first frame or support structure (5'), which in turn consists of 14 pressure tubes, each containing two reverse osmosis membranes inside it ; Y
    [0113] a third frame or support structure (7 '), in series with respect to the first frame or support structure (5') and to the second frame or support structure (6 '), wherein said third frame or support structure (7') ) includes 12 pressure tubes that contain each of them, inside, five membranes of reverse osmosis connected in series.
    [0114]
    [0115] Currents:
    [0116] . In figures 3A, 3B, 4A and 4B the lines represented correspond to the following streams:
    [0117]
    [0118]
    [0119] . In turn, in figure 5, the lines represented correspond to the following currents:
    [0120]
    [0121]
    [0122]
    [0123]
    [0124] List of numerical references:
    [0125] 1. First membrane module
    [0126] IA. First reverse osmosis membrane of the first membrane module (corresponding to the first filtration stage), installed in a first pressure tube located in a first frame;
    [0127] IB. First reverse osmosis membrane of the first membrane module (corresponding to the first filtration stage) installed in a second pressure tube located in a second frame, parallel to the first frame;
    [0128] 2A. Additional reverse osmosis membrane of the first membrane module (corresponding to the first filtering stage), located inside the first pressure tube, in series with respect to the first reverse osmosis membrane (1A) located in the first frame;
    [0129] 2B. Additional reverse osmosis membrane of the first membrane module (corresponding to the first filtering stage), located inside the second pressure tube, in series with respect to the first reverse osmosis membrane (1B) located in the second frame;
    [0130] 2. Second reverse osmosis membrane
    [0131] 3. Third reverse osmosis membrane
    [0132] 4. Fourth reverse osmosis membrane
    [0133] 5. Fifth reverse osmosis membrane
    [0134] 6. Sixth reverse osmosis membrane
    [0135] 7. Seventh reverse osmosis membrane
    [0136] one'. First pressure pump
    [0137] two'. Storage tank qwmica cleaning solution
    [0138] 3'. Second pressure pump ( booster pump )
    [0139] 4'. Energy recovery device (ERD, for its acronym in English)
    [0140] 5'. First frame or support structure
    [0141] 6 '. Second frame or support structure
    [0142] 7 '. Third frame or support structure
    [0143] 8 '. Third pressure pump (corresponding to the chemical product stream of cleaning and recirculation of the cleaning solution)
    [0144]
    [0145] Detailed description of the invention
    [0146] The following is a detailed description of particular embodiments of the invention, as shown in Figures 3A, 3B, 4A, 4B and 5.
    [0147]
    [0148] Thus, in Figure 3A a particular embodiment of the invention is observed in which the method for the treatment of brackish or sea water is characterized in that it comprises:
    [0149] (a) feeding a stream of brackish or seawater to a first stage of filtration that takes place through at least a first reverse osmosis membrane (1A) located within at least one first pressure tube located in a first frame or support structure. Preferably, the total number of membranes in each pressure tube in this first frame will be one or two. The feeding of the brackish or sea water current will be carried out at a pressure higher than the osmotic pressure corresponding to the salt concentration of said raw water stream fed to the system. For this, prior to feeding to the first reverse osmosis membrane (1A), said brackish or sea water stream will be conducted through at least one first pressure pump (1 ');
    [0150] (b) after the first filtration step occurring in the first reverse osmosis membrane (1A) a first permeate stream (product water) and a first brine stream (or first reject) is obtained which is then sent to a second filtration stage consisting of six (6) reverse osmosis membranes connected in series. After this second stage of filtration, a second permeate stream or product water is generated, which is unified with the first permeate stream or product water (corresponding to the first filtration stage) and a second brine stream (second rejection). );
    [0151] (c) the previous steps will be carried out until the first fouling samples are observed in the first reverse osmosis membrane (1A) located in the first frame, for example when observing an increase in differential pressure in said first reverse osmosis membrane (1A). At that moment, its operation will stop, being subjected to a cleaning stage. Until then, as seen in Figure 3A, will be at least a first reverse osmosis membrane (1B) located inside at least one second pressure tube located in a second frame or support structure, parallel to the first rack, which is being subjected to a cleaning process. Preferably, the total number of membranes in each pressure tube in this second frame will also be one or two.
    [0152]
    [0153] As also seen in Figure 3A, the cleaning step of the first reverse osmosis membrane (s) (1B) located in the second frame is carried out using part or all of the brine stream or rejection of the last stage of filtration, after passing through at least one energy recovery device (4 '). Said brine stream or rejection of the last filtration stage is therefore the cleaning stream, which in this particular embodiment is circulated in the opposite direction to the flow of the brackish or sea water stream to be treated. , in order to guarantee the maximum flow and elimination of the biological contaminant by osmotic shock and, in turn, to be able to carry out a sweep of the solids in suspension that could have been deposited in the head of the first reverse osmosis membrane (1B) located in the second frame. This is achieved because, as a consequence of the characteristics of the method object of the invention, it is possible to achieve a higher flow rate of the cleaning current to the reverse osmosis membranes than is achieved in a conventional cleaning process. On the other hand, as described above, in other embodiments (not shown in Figure 3A) the process may be carried out in the same manner as described in this section, except that the flow of the brine stream that is used in the cleaning will have the same sense as the flow of the raw water stream of alimentation.
    [0154]
    [0155] Additionally, in particular embodiments in which it is desired to reinforce the cleaning operation of the first reverse osmosis membrane (1B) located in the second frame, it will be possible to additionally employ a conventional membrane washing system of those customarily employed in the state of the technique, consisting for example in a tank or storage tank (2 '), where a cleaning solution is diluted and stored, and a recirculation pump that allows the passage of the cleaning solution through the first membrane repeatedly of reverse osmosis (1B) located in the second frame. From the tank or storage tank (2 ') the cleaning stream is pumped to the second frame for cleaning the first reverse osmosis membrane (1B) located in said second frame and, after the passage of the cleaning solution for said second stage. first reverse osmosis membrane (1B), the same is collected in part or in its entirety in the tank or storage tank (2 ') from where it is again sent to the second frame, being a cleaning in closed circuit. The cleaning solution used in the system will be selected according to the degree of contamination of the membranes, being able, among other examples, to include tetrasodium EDTA, NaOH, HCl or metric acid. In a particular embodiment of the invention, said cleaning solution may comprise 5 ppm of EDTA and 7 ppm of NaOH, in case the membranes are subjected to an alkaline cleaning, or 6 ppm of HCl and 3 ppm of nitric acid, in case that the cleaning is acidic.
    [0156]
    [0157] In Figure 3B a method equivalent to that described above in relation to Figure 3A is observed. In this case, however, after the first filtration stage in at least one first reverse osmosis membrane (1A) a first permeate stream (product water) and a first stream of brine (or first reject) is obtained which is then sent to at least one additional reverse osmosis membrane (2A) also located in the first pressure tube, in series with respect to the first reverse osmosis membrane (1A). The brine stream obtained in the second filtration step that takes place in said additional reverse osmosis membrane (2A) is conducted to a third filtration stage and so on up to a seventh filtration stage, so that the rejection of each stage Filtration is the feeding of the next stage of filtration.
    [0158]
    [0159] As seen in Figure 3B, during the operation of the first reverse osmosis membrane (1A) and the additional reverse osmosis membrane (2A) located in the first frame, at least a first reverse osmosis membrane (1B) located in a second frame and at least one additional membrane of reverse osmosis (2B) also located in the second frame, in series with respect to the first membrane of reverse osmosis (1B), may be subjected to a cleaning step in case of presenting samples of soiling For this purpose, in the particular embodiment shown in Figure 3B, a part or all of the reject current corresponding to the last one will be circulated through them, in the opposite direction to the flow of the raw water supply stream. filtering step, preferably after passing through at least one energy recovery device (4 '). As described above, in embodiments alternatives of the invention, the process can be carried out as described, except that the rejection current corresponding to the last stage of filtration, used in the cleaning, will be circulated in the same direction as that of the flow of raw water stream from alimentation. On the other hand, in particular embodiments in which there is no energy recovery device, the reject current of the last filtering stage will be sent directly to the membrane (s) showing (n) fouling symptoms, for cleaning, after pressure reduction preferably up to a pressure equal to or less than 4 bar, which is the maximum pressure recommended for membrane cleaning. In this case, needle valves may preferably be used.
    [0160]
    [0161] Additionally, to reinforce the cleaning operation of the reverse osmosis membranes (1B) and (2B), it will be possible to additionally employ a conventional membrane washing system of those customarily employed in the state of the art. This washing system can comprise a tank or storage tank (2 ') where a cleaning solution and a recirculation pump are diluted and stored allowing the cleaning solution to pass through the membranes (1B) and (2B) ) many times. In this way, the cleaning solution is pumped from the tank or storage tank (2 ') to the reverse osmosis membranes (1B) and (2B) and, after the passage of the cleaning solution by said membranes, is collected all or part of it in the tank or storage tank (2 '), from where it will again be sent to the membrane (s) that require to be subjected to a cleaning process, being a cleaning in closed circuit.
    [0162]
    [0163] Although in FIGS. 3A, 3B, 4A and 4B a closed circuit has been shown in the cleaning operation, in other embodiments of the invention part or all of the reject current used in the cleaning of the membranes could be poured as drainage current.
    [0164]
    [0165] Figure 4A shows a particular embodiment of the method object of the invention, equivalent to that described in relation to Figure 3A, with the difference that in this case the first reverse osmosis membrane (1A) corresponding to the first stage of filtration, located in the first frame, it is in cleaning mode by circulating the reject current from the last filtration stage while, at the same time, the first reverse osmosis membrane (1B) corresponding to the first filtration stage, located in the second frame operating in parallel to the first reverse osmosis membrane (1A) of the first frame, it is in operation phase. Of this mode, the gross water stream fed to the system, after having been subjected to a pressure increase process through at least one first pressure pump (1 ') until reaching a pressure higher than the osmotic pressure corresponding to the concentration of salts of said stream of raw water (brackish or sea water) is fed to the first reverse osmosis membrane (1B) corresponding to the first filtration stage, located in the second frame. As described above, the rejection of this first filtering stage is the feeding of the next filtering step (corresponding to the second filtering stage) and so on until the last filtering stage (corresponding to the seventh filtering stage) . The cleaning process of the first reverse osmosis membrane (1A) located in the first frame will be equivalent to that described in relation to the realization shown in Figure 3A, using part or all of the reject current of the last one. filtering stage as a cleaning stream, which is driven through the first (s) reverse osmosis membrane (s) (1A) after passing through an energy recovery device (4 '), in a flow contrary to the direction of the gross water stream fed to the system. As has been described above, in alternative embodiments of the invention the process would be the same as that described, except that the flow of the last stage of filtration used in the cleaning would have the same meaning than that of the gross water stream fed into the system. As described above, the use of the energy recovery device (4 ') is optional, so in other particular embodiments of the invention, the reject current of the last filtering stage will be sent directly to the membrane (s). (s) that it is necessary to clean, after pressure reduction preferably up to a pressure equal to or less than 4 bar, which is the maximum pressure recommended for membrane cleaning.
    [0166]
    [0167] In Figure 4B, in turn, a system equivalent to that described in relation to Figure 4A is described, with the difference that after filtering the raw water stream (brackish or sea water) in at least one first membrane of reverse osmosis (1B) located in the second rack, corresponding to the first filtration stage, a permeate stream (product water) and a brine stream (or first reject) is obtained which is then sent to at least one additional reverse osmosis membrane (2B) also located in the second frame, in series with respect to the first reverse osmosis membrane (1B), where a second filtration stage takes place. The brine stream obtained in the second filtration stage is conducted to a third filtration stage and thus consecutively to a seventh filtration stage, so that the rejection of each filtration stage is the feeding of the next filtration stage.
    [0168] Likewise, in Figure 4B a realization is shown in which, at the same time as the first reverse osmosis membrane (1B) located in the second frame, corresponding to the first stage of filtration and an additional membrane of reverse osmosis (2B) are operating, the first reverse osmosis membrane (1A) located in the first frame and an additional membrane of reverse osmosis (2A) also located in the first frame, in series with respect to the first membrane of reverse osmosis (1A), is they are in the cleaning phase, making the reject current of the last stage of filtration (corresponding to the seventh stage of filtration) after having been subjected to a recovery process in countercurrent to the flow of the raw water stream fed to the system. of energy in at least one energy recovery device (4 '). Again, in alternative embodiments of the invention, the process may be carried out in the same manner as described, with the proviso that the flow of the last filtration stage stream, which is used in the cleaning, will be made circulate in the same direction as that of the feed stream of the raw stream to be treated. Again, in particular embodiments in which there is no energy recovery device (4 '), the reject current of the last filtration stage will pass directly through the membranes that are in cleaning mode, prior to pressure reduction preferably up to a pressure equal to or less than 4 bar, which is the maximum pressure recommended for cleaning membranes.
    [0169]
    [0170] Additionally, to reinforce the cleaning operation of the reverse osmosis membranes (1A) and (2A), a conventional membrane washing system of those customarily employed in the state of the art may be used additionally. Said washing system can consist of a tank or storage tank (2 '), where the cleaning solution is diluted and stored, and a recirculation pump that allows the passage of the cleaning solution through the membranes repeatedly ( 1A) and (2A) from the storage tank (2 '), where the cleaning solution is prepared and stored. After the passage of the cleaning solution by said membranes (1A) and (2A), it is collected in the storage tank (2 '), from where it is again sent to the membranes that require a cleaning process, being a closed circuit cleaning.
    [0171]
    [0172] The process described in the four previous embodiments, as shown in Figures 3A, 3B, 4A and 4B, is carried out continuously and can be reversed as soon as an increase in differential pressure is observed in the first (s) membranes in phase operation (corresponding to the first or second stage of filtration), due to the biological fouling of the reverse osmosis membranes corresponding to said first stages of filtration. At that time, the membrane (s) in operation phase will pass as a cleaning, washing it (s) with the reject current (brine) from the last stage of filtration, making it circulate in the opposite direction to the flow of the raw water feed stream to the system, or in the same direction. At the same time, the localized reverse osmosis membrane (s) will start to operate in parallel to the membrane (s) in the cleaning phase and so on.
    [0173]
    [0174] In this way, the process will alternate as the membrane (s) located in the first or second filtration stage show signs of fouling, at which time they will enter the cleaning mode and the membrane (s) ( s) that were in cleaning mode with brine will enter production mode. Hence, the concept of operation in "revolver" mode.
    [0175]
    [0176] While in the figures accompanying this description two racks are shown operating in parallel in the first filtering stage, in other particular embodiments of the invention the system may comprise additional racks (one or more) operating in parallel in the first stage of the invention. filtration. Each of them will be in the cleaning phase or in operation (treating a certain percentage of the feed water), depending on the conditions of the process, the operation may be reversed at the time between the operation or cleaning phase, as has been described above.
    [0177]
    [0178] Example
    [0179] To check the efficiency of the process object of the invention, a simulation of a particular embodiment of the invention was carried out, as can be seen in Figure 5.
    [0180]
    [0181] In particular, the feed current object of the simulation fulfilled the following technical characteristics:
    [0182]
    [0183] Table 4. Characteristics of the feed stream
    [0184]
    [0185]
    [0186]
    [0187]
    [0188]
    [0189]
    [0190]
    [0191]
    [0192] The simulated process, as shown in Figure 5, is characterized in that it comprises subjecting a stream of brackish or seawater with the characteristics collected in Table 4 to a first step of increasing the pressure in the first pressure pump (1 ') until reaching a pressure of 61.1 bar. Next, said stream of brackish or sea water is fed to a first reverse osmosis membrane located inside each of the 14 pressure tubes located in a first frame or support structure (5 '). The reject current obtained in said first reverse osmosis membrane is then sent to a second reverse osmosis membrane located in series with respect to the first reverse osmosis membrane, inside each of the 14 pressure tubes located in the first frame or support structure (5 '). After filtering in the second filtration stage, a first permeate stream (corresponding to desalinated water or final product) and a stream of brine (or second rejection) is obtained, which is then sent to a third filtration stage, placed in series with respect to the previous one and so on, so that the reject current of each filtering stage is the supply of the next filtering stage. The total number of stages of filtration is 7, counting the first two stages mentioned above. In particular, the third to the seventh stages of filtering take place in the third frame or support structure (7 '), which comprises 12 pressure tubes containing each of them, inside, 5 membranes of reverse osmosis. After these filtration steps, a second permeate stream (which is unified with the first permeate stream, corresponding to the first filtration stage) and a brine stream corresponding to the rejection of the last filtration stage is generated.
    [0193] Continuously, during the whole process, a pressure control is carried out, so that once an increase in the differential pressure is observed in the first membrane (s) and / or it is required to increase the Feeding pressure to the membranes of the first and / or second stage of filtration to maintain the production, it will proceed to stop its operation, being subjected to continuation to a cleaning stage. In this cleaning stage, the feeding of the brackish or seawater stream to be treated is subjected to a first filtration stage through a first reverse osmosis membrane located inside each of the 14 located pressure tubes. in a second frame or support structure (6 '), parallel to the first frame (5'). As in the previous case, the rejection current obtained in said first reverse osmosis membrane located in the second frame (6 ') is then sent to an additional reverse osmosis membrane located in series with respect to the first reverse osmosis membrane, inside each of the 14 pressure tubes of the second frame or support structure (6 '). After filtering in the second filtration stage, a permeate stream (corresponding to the desalted water or final product) and a brine stream (or second rejection) are obtained, which are then sent to a third filtration stage, located in series with respect to to the previous one and so on, so that the reject current of each filtering stage is the feeding of the next filtering stage. As described above, the total number of filtration stages is 7, counting the first two stages mentioned above. During the operation of these reverse osmosis membranes, the first membranes of reverse osmosis will be cleaned, preferably using part or all of the brine stream corresponding to the rejection of the last filtration stage, after passing through a device of energy recovery (ERD; Energy Recovery Device, in English) (4 ') where it is depressurized decreasing its pressure preferably up to 1.5 bar. Another part of the final brine stream can be returned to the sea, preferably in a percentage lower than 20%, although this percentage may vary depending on the number of racks installed in the first filtration stage and operating in parallel in mode to stir. In the particular embodiment shown in Figure 5, this brine stream is circulated in the opposite direction to the flow of the brackish or seawater stream to be treated, although in other embodiments it could be circulated in the same direction of the flow of the sea or brackish water stream to be treated. As also described above, in order to reinforce the cleaning operation, a conventional membrane washing system can be used additionally to those customarily employed in the state of the art, consisting of a storage tank (2 '), where the cleaning solution is diluted and a recirculation pump (8 ') that allows the passage of the cleaning solution repeatedly through the membrane (s) that are in cleaning mode. After the cleaning solution passes through said membranes, all or part of it is again collected in the storage tank (2 '), from where it will again be sent to the frame that is in cleaning mode (5'). ) or (6 '), being a cleaning in closed circuit.
    [0194]
    [0195] It has been shown that the design of the operation as described above allows solving the problems of the state of the art that have been enumerated in the background section of the invention. Below we will explain in detail the way in which each of these problems have been solved:
    [0196]
    [0197] (a) Resolution of the problem of higher operating pressure and, with it, greater energy consumption associated with desalination plants that suffer from biological fouling
    [0198]
    [0199] Since the proposed design makes it possible to permanently clean the membranes located in the first position (and, in particular embodiments of the invention, also in the second) when washing them with brine, the effects of biological fouling or biofouling are avoided , which allows the operating conditions over time are coincident with the design conditions.
    [0200]
    [0201] Thus, in the following table (Table 5) a comparison is made of the results obtained in the design phase in an operation carried out in a conventional system, as shown in Figure 1, with the values obtained during the actual operation of the system (operating according to the conventional system) and the design values in a realization as described and shown in Figure 5.
    [0202]
    [0203] Table 5. Com arative design results real results of o eracion
    [0204]
    [0205]
    [0206]
    [0207]
    [0208] As can be seen in the table above (table 5), the fact that the design and mode of operation of the system object of the invention allows to keep under control the effects of biofouling makes it possible to operate under the original design conditions and even improve them It is thus demonstrated that the method and system object of the invention manages to avoid the overpressures produced in the actual operation by the harmful effects of the biological fouling.
    [0209]
    [0210] In the following table (Table 6) the improvement in the energetic consumption of the design object of the invention (as shown in Figure 5) is observed, by keeping the bilogic fouling (biofouling) under control . The comparison has been made with the values obtained in the plant operating according to the conventional system:
    [0211]
    [0212] Table 6. Comparison of energy consumptions
    [0213]
    [0214]
    [0215]
    [0216] As can be seen in table 6, there is an improvement in energy consumption of up to 13.20%, mainly motivated by maintaining permanently clean membranes located in the first and second stages of filtration.
    [0217]
    [0218] (b) Resolution of the problem of loss of production by membrane installed in the pressure tubes
    [0219]
    [0220] As described above, in conventional systems there is a loss of production which, in general, forces the operating pressure to rise in the pressure tube or tubes containing or containing the reverse osmosis membranes in order to achieve a more water permeate through the membranes. This implies, as has been described, an increase in the energetic consumption and a worsening of the problem due to biofouling, as more organic matter is deposited on the surface of the membranes. With all this, in addition to the increase in energy consumption, there is also a loss of production of desalinated water of up to 12%, which affects the production objectives.
    [0221]
    [0222] As can be seen in Table 7, the design and operation object of the present invention allows to maintain the production of the reverse osmosis membranes in their design values, since at all times the state and cleanliness of the membranes placed in the first positions. This guarantees optimal production of the same and the passage of water to the membranes installed in the following positions.
    [0223]
    [0224] Table 7. Comparison between original design data, actual operation data (according to conventional design) and design data according to the invention as shown in Figure 5 Pr inrmmrnmh
    [0225]
    [0226]
    [0227]
    [0228]
    [0229] (c) Resolution of the problem of higher differential pressure in the reverse osmosis frame
    [0230]
    [0231] As described above, because the effect of biological fouling or biofouling is impossible to determine in the design phase of the reverse osmosis plant, there is great difficulty in evaluating whether the curve and characteristics of the booster pump or other pumps or energy recovery systems installed in the system will allow to face the unpredictable effect of biofouling efficiently. The design object of the present invention, however, makes it possible to guarantee the value of the differential pressure of design in the frames of reverse osmosis and, with this, the choice of more efficient pumps, avoiding in this way the greater energetic consumption derived from the loss of efficiency of pumping equipment and energy recovery.
    [0232]
    [0233] As can be seen in table 8, which establishes a comparison between the pressure drop in the membranes installed according to the original design, the actual operation data and the design and operation mode object of the invention, It can be concluded that the operation "revolver" type system allows to maintain the differential pressure in each membrane at its design values at all times. This is so since whenever there is an increase in the pressure drop in the first membranes, where the effect of the biological fouling occurs, said membranes will be put in the washing mode, the membranes that were up to that moment entering into operation. washing mode, guaranteeing the latter a pressure drop according to design because they are clean.
    [0234] Table 8. Comparison between original design data, actual operation data (according to the conventional design design data according to the invention is shown in Figure 5).
    [0235]
    [0236]
    [0237]
    [0238]
    [0239] In the previous table (Table 8) a real operating pressure of the design and operation according to the present invention is shown to be greater than that of design, since an aging factor of the membranes has been considered. However, as described above, being able to replace the first membranes that start to suffer biological fouling (biofouling) problems by washed membranes guarantees that the pressure drop in the first membranes remains constant, not as in the current systems where The drop in pressure due to biological fouling is concentrated in the first membranes, affecting the rest of those installed in the system.
    [0240]
    [0241] (d) Resolution to the problem of serious deterioration of the reverse osmosis membranes placed in first or second and second position of the pressure tube
    [0242]
    [0243] As described above, in the reverse osmosis membranes of the first and second stages of filtration it is in the (s) that there is a greater biological growth or biofouling that is deposited on its surface and in its spacers, blocking the passage of water from alimentation to the following membranes. The passage of water to the following membranes is thus reduced and the operating pressure is increased in order to guarantee the design recovery of the reverse osmosis membranes. Likewise, the production capacity of the system is reduced, due to the reduction of the water passage to the following membranes connected in series with respect to the first (s) membrane (s) of reverse osmosis of the installation.
    [0244]
    [0245] It is a fact also contrasted in practice that plants suffering from severe biological fouling are forced to replace the membranes installed in the first positions of the tubes more frequently than normally considered by design. With the design and mode of operation object of the invention this problem is solved, since at the slightest indication of fouling of the membranes placed in the first positions are washed with brine, allowing to maintain its production according to design.
    [0246]
    [0247] It should be noted that the membrane flow is defined as the amount of water that passes through the membrane per square meter of surface area per hour. This flow is determined in units l / m2h (liters per square meter of membrane surface and per hour). The higher its value, the greater the production effort to which the membrane is subjected, increasing the risk of dirtying it. Thanks to the design and mode of operation object of the invention, the membranes occupying the positions 1 or 1 and 2 have a lower membrane flow, which implies that they suffer less fouling. On the other hand, the design and the mode of operation object of the invention make it possible to maintain the constant membrane flow values, according to design, since it is ensured that the membranes placed in the first positions remain clean at all times. In this way, in case of a decrease in the flow in the membranes located in the first positions, there will not be an increase in the operating pressure of the system, but simply the module that until then was in the cleaning phase will come into operation with brine, thus reestablishing the membrane flow associated with clean and / or new membranes.
    [0248]
    [0249] In the following table (Table 9) it is observed how the fluxes vary by membrane in the original design and in the design object of the present invention. The results reflected in this table allow us to conclude that the membrane flow in the proposed design is less aggressive than in the conventional design, ensuring a longer life to the membranes and a better performance of them during their time of use.
    [0250]
    [0251] T l. mr iv fl r vi lmmrnmi inv r
    [0252]
    [0253]
    [0254]
    [0255]
    [0256]
    [0257] (e) Resolution of the problem of the high cost of investment in the pre-treatment
    [0258]
    [0259] As described above, the solution object of the present invention allows the installation of much less demanding systems in operation and investment than in the case of a conventional system, since it is based on coexisting with the problem of biofouling keeping it controlled at all times , instead of eliminating it absolutely. In this way, the saving in the investment cost can be up to 30%.
    [0260]
    [0261] (f) Resolution of the problem associated with the loss of production due to the cleaning of the membranes
    [0262]
    [0263] As described above, the biological fouling to which it is subjected to the reverse osmosis membranes causes, beyond higher energy consumption and production losses, stops in the production of the reverse osmosis trains to carry out the cleaning of the membranes. The frequency of these stops will depend on the severity of the biological fouling and its frequency will increase the operation cost of the desalination plants. Likewise, the greater the severity of the biological contamination and, with it, the number of cleaning of the membranes, the greater the cost of the chemical products used, as well as the expenses associated with the cleaning (personnel expenses, chemical products). , production stops, logistics, etc.).
    [0264]
    [0265] On the other hand, when a cleaning is carried out in a pressure tube, frame or reverse osmosis train, chemical products are usually used, which are aggressive against all the installed membranes, including those that are in perfect condition (the corresponding ones). to filtration stages 3 to 7). This entails a lower efficiency of the chemical reagents used, which have to pass through all the membranes with the consequent pressure drop, as well as a longer time required for cleaning.
    [0266]
    [0267] With the solution object of the present invention only the membranes placed in first position are subjected to cleaning with brine coming from the rejection of the last stage of filtration, all without stopping the production. In this way, it is possible to avoid the occurrence of a severe soiling, as well as to identify it when it begins to occur, at which point it is stopped by continuous cleaning with brine. It has been shown that the high salinity of the brine manages to cause an osmotic shock in the biofouling deposited on the surface of the membranes, causing it to detach and disappear. Additionally, it is possible to avoid an increase in the energetic consumption associated with the cleaning, since the exit brine of the reverse osmosis is pressurized when using preferably systems of recovery of ene ^ a with isobaric chambers that generally require a minimum counter pressure prior to its discharge of 1.5 bar, energy that is currently being wasted and that is used by the present invention to perform the washing of the membranes located in the first position (s) with the exit brine from the reverse omosis. At the same time, it is possible to avoid or reduce the use of chemical products, which can severely damage the membranes. In case of not using energy recovery systems, the pressure available for cleaning the membranes with brine would be much higher than 1.5 bar and should be regulated so that it does not exceed, preferably, 4 bar of pressure.
    权利要求:
    Claims (14)
    [1]
    1. A process for the treatment of brackish or sea water characterized in that it comprises:
    (a) subjecting a stream of brackish or seawater to a first filtration stage through at least a first reverse osmosis membrane (1A) located inside at least one pressure tube located in a first frame (5) '), obtaining a first permeate stream and a first brine stream; (b) then, said first brine stream is sent to at least one additional filtration step, which takes place through at least one additional reverse osmosis membrane, located in series with respect to the first reverse osmosis membrane ( 1A) and located inside at least one pressure tube located in a third frame (7 '), obtaining a second permeate stream and a second brine stream;
    where, continuously throughout the process, a pressure control is carried out, so that once samples of contamination are observed in the first reverse osmosis membrane (1A), its operation is stopped, and it is then subjected to a cleaning step during which the feeding of the brackish or sea water stream is subjected to the first filtration stage through at least a first reverse osmosis membrane (1B) located inside at least one pressure tube located in a second frame (6 '), operating in parallel with respect to the first frame (5'), where said step of cleaning the first reverse osmosis membrane (1A) is carried out using the second brine stream, circulating in Inverse sense or in the same sense of the flow of brackish water or seawater fed to the process;
    and where the above process is continuously repeated alternately, so that when samples of fouling are observed in the first reverse osmosis membrane (1B) located in the second frame (6 '), in the operation phase, it is stopped its operation, going into cleaning mode, while the first reverse osmosis membrane (1A) located in the first frame (5 ') returns to operate, being fed with the brackish water or sea to be treated.
    [2]
    2. The method according to claim 1, where the supply of brackish water or seawater to the first stage of filtration is carried out at a pressure higher than the osmotic pressure corresponding to the salt concentration of said stream of brackish or sea water.
    [3]
    3. The method according to any one of the preceding claims, wherein the number of reverse osmosis membranes located in each pressure tube of the first filtration stage is one or two.
    [4]
    4. The method according to any one of the preceding claims, wherein the total number of stages of filtration in the process is 7.
    [5]
    The method according to any one of the preceding claims, wherein the first brine stream obtained in the first filtration step passes through at least one additional reverse osmosis membrane (2A) located in the first frame (5 '), in series with respect to the first reverse osmosis membrane (1A), before being sent to the additional reverse osmosis membrane located in the third frame (7 '), while the first reverse osmosis membrane (1B) located in the second frame (6 ') and at least one additional membrane of reverse osmosis (2B), also located in the second frame (6'), in series with respect to the first reverse osmosis membrane (1B) located in the second frame (6 ') ), are in cleaning mode.
    [6]
    The method according to any one of claims 1 to 4, wherein the first brine stream obtained in the first filtration step passes through at least one additional reverse osmosis membrane (2B) located in the second frame (6 ') , in series with respect to the first reverse osmosis membrane (1B), before being sent to the additional reverse osmosis membrane located in the third frame (7 '), while the first reverse osmosis membrane (1A) and less an additional reverse osmosis membrane (2A) located in the first frame (5 '), in series with respect to the first reverse osmosis membrane (1A) located in the first frame (5'), are in cleaning mode.
    [7]
    The method according to any one of the preceding claims, wherein the second stream of brine, used as a cleaning stream, is passed through an energy recovery device (4 ') before passing through the membrane (s). ) of reverse osmosis subjected to cleaning.
    [8]
    8. A system for carrying out the method according to any one of claims 1 to 7, characterized in that it comprises:
    (a) a first membrane module comprising at least a first reverse osmosis membrane (1A) located inside at least one pressure tube located in a first frame (5 ') and at least a first reverse osmosis membrane (1 B) located inside the at least one pressure tube located in a second frame (6 '), where the first reverse osmosis membrane (1A) located in the first frame (5') and the first reverse osmosis membrane (1B) located in the second frame (6 ') are configured to operate in parallel;
    (b) at least one second membrane module comprising at least one additional reverse osmosis membrane located inside at least one pressure tube located in a third frame (7 '), where said second membrane module is connected in series with respect to the first membrane module through at least one first outlet conduit of the first membrane module, located at the opposite end to that of the input current supply and, in particular, corresponding to the current conduit of rejection of the first membrane module, a second outlet conduit of the first membrane module being the one corresponding to the output of the final product;
    and wherein the second membrane module or the last module in case of successive membrane modules located in series is characterized in that it comprises at least two outlet ducts, a first outlet duct corresponding to the outlet of the final product and a second duct outlet corresponding to the reject current, said second conduit being connected to the first membrane module at the opposite end to that of the brackish or sea water supply or at the same end of the brackish or sea water supply.
    [9]
    9. The system according to claim 8, wherein the number of reverse osmosis membranes located in each of the pressure tubes of the first membrane module is one or two.
    [10]
    10. The system according to claim 8 or 9, wherein the number of reverse osmosis membranes in each pressure tube of the second membrane module is from 5 to 6.
    [11]
    11. The system according to any one of claims 8 to 10, wherein at least one valve for discriminating the feed to the first reverse osmosis membrane (1A) located in the feed channel to the first membrane module is located. the first frame (5 ') or the first reverse osmosis membrane (1B) located in the second frame (6').
    [12]
    12. The system according to any one of claims 8 to 11, wherein the connecting conduit between the second membrane module or the last module in case if there are successive membrane modules and the first membrane module comprises at least one energy recovery device (4 ').
    [13]
    The system according to any one of claims 8 to 12, characterized in that it comprises at least one storage tank (2 ') of a cleaning solution, where said storage tank (2') is connected to the first frame (5 ') and second frame (6') through a connecting conduit.
    [14]
    The system according to any one of claims 8 to 13, wherein in addition to the first frame (5 ') and the second frame (6'), the first membrane module comprises at least one additional frame located in parallel with respect to said first frame (5 ') and second frame (6').
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    同族专利:
    公开号 | 公开日
    WO2019068943A1|2019-04-11|
    EP3693343A4|2020-12-16|
    ES2708126B2|2019-09-18|
    EP3693343A1|2020-08-12|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US20040134521A1|2003-01-09|2004-07-15|Boris Liberman|Direct osmosis cleaning|
    WO2005123232A2|2004-06-21|2005-12-29|Membrane Recovery Ltd|Ro membrane cleaning method|
    WO2013058127A1|2011-10-18|2013-04-25|株式会社神鋼環境ソリューション|Seawater desalination method, and seawater desalination device|
    US20150053596A1|2013-08-26|2015-02-26|Hitachi, Ltd.|Desalination system|
    JP5600864B2|2006-09-25|2014-10-08|東レ株式会社|Operation method of reverse osmosis membrane filtration plant and reverse osmosis membrane filtration plant|
    CN106564990A|2012-04-23|2017-04-19|水技术国际有限责任公司|Low energy reverse osmosis process|
    JP6049498B2|2013-02-25|2016-12-21|三菱重工業株式会社|Reverse osmosis membrane device and operating method thereof|
    法律状态:
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    优先权:
    申请号 | 申请日 | 专利标题
    ES201731181A|ES2708126B2|2017-10-06|2017-10-06|METHOD FOR THE TREATMENT OF SALOBRE OR SEA WATER THROUGH REVERSE OSMOSIS|ES201731181A| ES2708126B2|2017-10-06|2017-10-06|METHOD FOR THE TREATMENT OF SALOBRE OR SEA WATER THROUGH REVERSE OSMOSIS|
    PCT/ES2018/070557| WO2019068943A1|2017-10-06|2018-08-10|Method for treating brackish water or seawater by reverse osmosis|
    EP18865022.0A| EP3693343A4|2017-10-06|2018-08-10|Method for treating brackish water or seawater by reverse osmosis|
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