Method and apparatus for desalinating seawater using reverse osmosis

Abstract

The invention relates to a method for desalinating seawater and an apparatus for carrying out said method, having the steps of: providing a reverse osmosis module (1) fluidically connected to the upper end of a marine body of water at a depth ht with i as element of the natural numbers and i>0, within the body of water, wherein the reverse osmosis module (1) comprises a cavity having a process water space (4) with a feed (2) and a discharge (3) and having a permeate water space (5), said process water space and permeate water space being separated from one another by at least one osmosis membrane filter (6); providing an outlet distributor (7) fluidically connected to the outlet of the process water space (4) at an outlet depth h a in the body of water, wherein the outlet distributor (7) has an outlet directed towards the surrounding water; and pumping the permeate water out of a permeate water space (5); wherein a process water flow is formed from the feed of the process water space (4) to the discharge of the process water space (4), said process water flow having a hydrostatic process water pressure p 1 in the reverse osmosis module (1) which is built up as a result of the depth h 1 of the at least one reverse osmosis module (1) in the body of water. The invention further relates to an apparatus for carrying out the method according to the invention.

Description

[0001] Method and device for desalination of seawater by reverse osmosis

[0002] The invention relates to an energy-efficient, wear-reducing and environmentally friendly process for desalinating water from a marine body of water by means of reverse osmosis, as well as to a device developed therefor, which also helps to reduce the space requirements of such systems, which are typically installed near the coast.

[0003] Marine waters are generally defined as bodies of water that belong to the sea, i.e. are part of a sea or are connected to it to the extent that the water has seawater quality, in particular a high salt content that is unsuitable for industrial water and / or drinking water.

[0004] Seawater desalination plants (MWS plants) supply an increasing proportion of the world's population with water and are now an indispensable component of urban infrastructure in arid areas, which is being increasingly expanded.

[0005] At the same time, MWS systems are criticized for various reasons: The systems, which in most practical cases are based on reverse osmosis, are energy-intensive. This even forces operators to build MWS systems near power plants whenever possible in order to minimize further costs related to grid expansion and load. The concentrated wastewater from MWS systems is usually returned to the sea near the coast. This poses ecological risks, partly due to the high salt concentration and the chemicals added to the saltwater stream during water extraction, but also because saltwater chemically attacks pumps and other metallic technical equipment, meaning that the reaction products also occur in the wastewater. The technical equipment exposed to saltwater, especially the high-pressure pumping technology and valves, is subject to significant corrosion-related wear.The construction of MWS plants, which leads to high land consumption near the coastline, creates conflicts of interest with other uses. This also applies to energy-saving concepts that draw energy for water production from, for example, water movement near the coast.

[0006] Within a MWS system, salt water is extracted from a nearby body of water (sea, ocean). This water is pressurized, pre-filtered, and concentrated using reverse osmosis. The majority of the energy required for seawater desalination via reverse osmosis is used to generate this highly pressurized salt water, which is necessary to force a portion of the salt water through the osmosis membrane filters against its osmotic potential. This initially required pressure of approximately 20 bar must reach up to 80 bar as the salt water flowing past the osmosis membrane filters becomes increasingly concentrated. This pressure is required to overcome its growing osmotic potential, achieve sufficient water flow (permeation) through the osmosis membrane filters, and thus generate the desired mass flow of desalinated water.

[0007] To explain the invention, the pre-filtered salt water is referred to below as permeate water and the water permeating into a separate collecting container, the permeate water chamber, is referred to as permeate water.

[0008] Currently operating reverse osmosis systems achieve a separation efficiency of approximately 0.5. This means that approximately 1 liter of demineralized water can be obtained from 2 liters of salt water, which can then be further treated, for example, to achieve drinking water quality.

[0009] The invention is based on the object of providing a process for the desalination of seawater by means of reverse osmosis and a corresponding device for carrying out the process, which make it possible to make the desalination of seawater more energy-efficient and environmentally friendly than is possible in conventional MWS systems.

[0010] The problem is solved in terms of the method by the features of independent patent claim 1 and in terms of the device by the features of independent patent claim 6. Further expedient embodiments of the invention are the subject of the dependent patent claims. To solve the problem, a method for desalinating seawater is proposed, comprising the steps of: o providing at least one reverse osmosis module fluidically connected to the upper end of a marine water body at a depth h with i as an element of the natural numbers and i > 0, within the water body, wherein the reverse osmosis module comprises an outwardly encapsulated cavity with a process water chamber having an inlet and an outlet, and a permeate water chamber, which are separated from one another by at least one osmosis membrane filter; o providing an outlet distributor fluidically connected to the outlet of the process water chamber of the reverse osmosis module at an outlet depth h awithin the water body, wherein the outlet distributor has an outlet directed towards the ambient water; o Providing an outlet distributor fluidly connected to the outlet of the process water chamber of the reverse osmosis module at an outlet depth h a within the water body, wherein the outlet distributor has an outlet directed towards the ambient water; o Pre-filtration of a part of the water body flowing into the process water space before its contact with the osmosis membrane filter, to form process water; o Positioning of the reverse osmosis module in the water body at a depth h t such that a part of the water body flows through the inlet of the process water chamber to its outlet, to form a process water flow in the process water chamber; o Formation of a hydrostatic process water pressure p tin the process water chamber of the reverse osmosis module by adjusting a depth hi of the at least one reverse osmosis module in the water body such that a pressure gradient is formed from the process water chamber to the permeate water chamber and, as a result, at least a portion of the process water is pressed through the osmosis membrane filter along the pressure gradient; and

[0011] - Pumping out permeate water from the permeate water chamber.

[0012] According to the invention, a water flow of sea water of the water body, hereinafter referred to as process water flow, is formed from the inlet of the process water space to the outlet of the process water space, which has a depth h tof the hydrostatic process water pressure pt established in the reverse osmosis module by at least one reverse osmosis module in the water body. Apparently, the usable process water pressure pt is limited to a system-specific, determinable maximum value, up to which the system components are protected from overload.

[0013] The process is based on a system concept in which functional modules are positioned on / near the water surface or at different depths within the water body and are fluidically linked to one another by means of pipes or hoses and the necessary connecting elements.

[0014] To implement the invention, a single reverse osmosis module is sufficient. To better illustrate the operating principle, the invention is described using several reverse osmosis modules, which—unless expressly stated otherwise—are arranged in series.

[0015] Various functional modules are listed below as examples, although not all of the functional modules listed below are absolutely necessary to achieve the object of the invention: Reverse osmosis modules including any buoyancy bodies that may be present Outlet distributor Pump and, in some embodiments, processing platform Processing and control modules on the processing platform Pre-filtration modules and / or pre-filtration devices formed in other components or in fluidic connections.

[0016] The initialization of the multi-stage water desalination can comprise the following process steps: Positioning of the following components in the water body i) the processing platform near the water surface and, if necessary, pre-filtration modules for pre-filtration of water to be desalinated, ii) the reverse osmosis modules in deeper water layers (depths hi, with i =

[0017] 1, 2, 3 ...) of the water body and iii) the outlet distributor in again greater water depths h a , with a = I, II, III ... for the discharge of process water via (optionally) adjustable nozzles into the water body and fluidic connection of the modules carrying the water flow, whereby pre-filtration modules are fluidic connected to the process water side inlets of the reverse osmosis modules, the process water side outlets of these with the process water side inlets of any further reverse osmosis modules positioned deeper in the water body or the outlet distributors, as well as fluidic connection of the permeate water side inlets and outlets of the respective reverse osmosis modules with the processing and control modules on the processing platform with pipes or hoses in order to carry the permeate water flow and if necessary a gas or air flow.

[0018] The seawater desalination itself now takes place in several process steps, whereby not all of the following steps are absolutely necessary to achieve the object of the invention and freshwater extraction can in principle also be realized with only one of the reverse osmosis modules: Pre-filtration of seawater, for example near-surface seawater, by means of a pre-filtration module or a pre-filtration device to provide the process water and feeding the process water on the process water chamber side to the osmosis membrane filter of the at least one reverse osmosis module positioned at the depths h, and regulation of differential pressures between their process and permeate water chambers separated from each other by osmosis membrane filters by conveying permeate water from the permeate water chambers with pressurized water pumps integrated into the reverse osmosis modules, which leads to a filtration of further, under the hydrostatic pressures p,in the process chambers of the respective reverse osmosis modules, process water present in the process chambers of the respective reverse osmosis modules is drawn through the osmosis membrane filters into their permeate water chambers, as long as the permeate water pressures in these are smaller than the differences between the hydrostatic process water pressures less the salinity-dependent osmotic pressures and demand-dependent modulation of the feed rates of permeate water from the respective reverse osmosis modules as well as continuous replacement of the concentrated process water with less concentrated water by feeding the process water through the process water chambers of the reverse osmosis modules to the outlet distributors located deeper in the water body via pipe or hose connections and from there being discharged into the surrounding water body via oriented / orientable outlet nozzles,and lifting the permeate water from the respective permeate water chambers to the processing and control modules, for example, on the processing platform, by means of pressurised water pumps integrated in / on the reverse osmosis modules, which must at least partially overcome the respective pressure levels up to the processing modules; and recording and, if necessary, controlling the hydrostatic pressures in the process water chambers of the reverse osmosis modules by lowering or raising the reverse osmosis modules in the water body; and recording and, if necessary, controlling the differential pressures in the reverse osmosis modules by recording and, if necessary, regulating the hydrostatic pressures in the permeate water chambers; and, if necessary, pressurising the permeate water chambers with gases, gas mixtures or air and optionally hygienising substances via ventilation lines.

[0019] In the following, the term vascular system refers to the entirety of fluidically connected modules as well as the connecting elements, i.e. suitable hoses or pipes including, if necessary, couplings that can be sealed on both sides, by means of which the fluidic connections described below are formed.

[0020] A body of water is generally defined as a quantity of water, with the boundary surfaces of the body of water being imaginary for the purposes of the invention, since the process according to the invention is preferably carried out directly in a marine body of water, and mixing of the process water to be discharged with the surrounding water is advantageous. However, it is also possible for the process according to the invention to be carried out in a physically enclosed body of water, for example, in a tank.

[0021] During prefiltration, the seawater is passed through filters and / or membranes to separate small and larger organisms, particles, suspended solids, or colloids – materials that do not dissolve – from the water to be desalinated. The degree of prefiltration required to filter out such materials depends on the properties of the osmosis membrane filter and is specified by the manufacturer. Such prefiltration methods for osmosis and reverse osmosis, as well as suitable filter devices, are known to those skilled in the art, so that, based on their knowledge of the properties of the osmosis membrane filter, they can select suitable processes and devices. Depending on the selected process, the prefiltration of the water to be desalinated can take place at various points before the water is fed into the osmosis membrane filter.For example, pretreatment takes place close to / at the water surface in a prefiltration module, thus enabling easy cleaning and maintenance of the filters. Prefiltration can also take place in the fluid connection to the reverse osmosis module, or, if there are multiple modules, at least to the first one in a series, or even in the process water chamber, provided this is done in such a way that the osmosis membrane filter is only exposed to prefiltered water, i.e., process water.

[0022] The notations h, with (j = 1, 2, 3 ... ) and h awhere (a = I, II, III ...) indicate the depth of the "i"-th reverse osmosis module or the "a"-th outlet distributor in the water body. All depth values ​​are assumed to be equal to the vertical positive distance of the respective module from the water surface. The water surface itself is assigned the reference height ho = 0. The hydrostatic process water pressure in the respective reverse osmosis module is accordingly referred to as pressure p. The effective pressure for reverse osmosis on the process water side is derived from this, minus the salinity-dependent osmotic pressure.

[0023] The process water in the reverse osmosis module leaves it either through the drain located in the process water chamber or, after passing through the osmosis membrane filters, via a permeate water drain located in the permeate water chamber.

[0024] Advantageously, a process water flow is formed from the inlet of the process water chamber to the outlet of the process water chamber, wherein the process water flow in the reverse osmosis module has a hydrostatic process water pressure pt, which flows through the process water-filled vessel area to the depth h t of the reverse osmosis module. The depth h t defines the vertical positive distance of the outlet of the i-th reverse osmosis module from the water surface, in other words the vertical distance measured from the water surface to the upper edge of the reverse osmosis module plus the vertical of the construction height of the reverse osmosis module arranged in the water body, for example floating.

[0025] The difference between the process water pressure pt and the pressure in the permeate water chamber is set so that it is greater than the osmotic pressure, which results from the difference in the different osmotic potentials of the process water and the permeate water. As a result, at least a portion of the process water is forced through the osmosis membrane filters along the pressure gradient. For this purpose, a pressure gradient is set for the pressure drop determined by the immersion depth h. tof the reverse osmosis module, a lower pressure in the permeate water chamber is set such that the pressure difference to the process water pressure enables efficient flow through the osmosis membrane filters, but does not destroy them or wear them out prematurely. For this purpose, the permeate water chamber can be ventilated via an aeration line, while the accumulating permeate water is pumped out of the permeate water chamber using a pressurized water pump arranged in the permeate water chamber. If less or more permeate water is pumped out than is simultaneously replenished via the osmosis membrane filters, the permeate water chamber and the aeration pipe will fill until an equilibrium is established between the replenished and the pumped out permeate water. The pressure in the permeate water chamber increases proportionally to the fill level in the aeration pipe and thus reduces the differential pressure to the process water chamber that determines the water flow.If the differential pressure drops to the salinity-dependent osmotic potential of the process water, no further permeate water is formed.

[0026] The functional mechanism described above is not dependent on the aeration capability of the permeate water chamber, and thus on a ventilation system. The ventilation system allows the specification of a minimum pressure that would occur in the permeate water chamber if the resulting permeate water were completely removed. If no ventilation system is present or if it is closed, this minimum pressure is theoretically limited by the vapor pressure of the water under operating conditions.

[0027] While the minimum pressure in the permeate water chamber, possibly filled with air, gas, or water vapor, defines the state that allows for maximum permeate water flow under given operating conditions, the setting of the hydrostatic pressure pt minus the effective pressure in the permeate water chamber, now filled with permeate water, for example, determines the state at which the permeate water flow disappears. Between these two states lies an "inner control range" for regulating the permeate water flow.

[0028] Analogously, a hydrostatic pressure in the reverse osmosis module, which is equal to the osmotic pressure, defines the minimum required hydrostatic pressure above which a filtration flow through the respective osmosis membrane filter can begin. The maximum possible hydrostatic pressure is defined by the load-bearing capacity of the system components, the thickness of the water body, and practical considerations for the system's operation. Between these two states lies the "outer control range" for the permeate water flow, within which the depth of the reverse osmosis module in the water body is (dynamically) adjusted.

[0029] In order to achieve the desired filtration flow of the process water through the osmosis membrane filters, the at least one reverse osmosis module is installed according to one embodiment at a depth h t located more than 200 m below the water level.

[0030] The system is adjusted, for example, for a sealed permeate water chamber initially filled with water. When the reverse osmosis module is lowered or raised within the water column, the hydrostatic pressure in the process water chamber changes, which drives the flow of water through the osmosis membrane filters and results in the hydrostatic pressure being adjusted in the permeate water chamber minus the osmotic pressure determined by the difference in salt content between the process water and the permeate water. The pressurized water pump can now be switched on. Its flow rate is increased until the pressure in the permeate water chamber (e.g., visible via the water level in the aeration pipe or a pressure sensor) indicates a sufficient differential pressure to the pressure in the process water chamber, or until the currently desired flow rate is reached.

[0031] The reverse osmosis module is positioned in the water body in such a way that the inlets and outlets of the module are suitably oriented within the water body, depending on its technical design. For example, all fluidic connections, i.e. inlets and outlets, could be located at the bottom or top edge of the module, which would position the module above or below the connections in the water body, or the inlet of the process water chamber, for example, could be positioned higher in the water body than the outlet of the reverse osmosis module. In the case of buoyancy-based positioning, the position of a gas storage tank acting as a buoyancy body, which is located in the reverse osmosis module or is mechanically connected to it, can be determined in such a way that the common center of gravity of the arrangement of the buoyancy body and reverse osmosis module defines the orientation of the reverse osmosis module in the water body.

[0032] In the reverse osmosis module, concentrated process water, i.e. process water with a higher salt concentration than that of the surrounding seawater, is accelerated towards the lower outlet distributor due to its increased density compared to seawater and is thus moved from the inlet of the process water chamber of the reverse osmosis module towards its outlet.

[0033] If several reverse osmosis modules are operated, they can be operated serially, ie one after the other in the flow direction of the process water (also referred to as "in series"), with each additional reverse osmosis module being installed at a depth h different from h t , (j = 2, 3, 4 ... ). Alternatively or additionally, several reverse osmosis modules can be operated in parallel and with separate / split process water flows, whereby the reverse osmosis modules can be installed at the same depth h or at different depths h #= h t, (j = 2, 3, 4 ... ). Possibilities for fluidic connection within the vascular systems are explained in more detail below using the figures as examples.

[0034] The design and adjustment of the depths is plant- and operation-specific, and in the case of a serial arrangement, it depends on the separation efficiency of any reverse osmosis modules already flowing through by the process water. The osmotic pressures of the process water to be compensated in the respective reverse osmosis modules are incorporated into the criterion for adjusting the hydrostatic pressures on the process water side as a minimum value.

[0035] The removal of water in the reverse osmosis modules leads to a gradual concentration of salts in the process water as it passes through the vessel system. This increases the density p^z) of the process water within the vessel system. The hydrostatic pressure at the outlet manifold thus reaches p t = ptgha , where g is the acceleration due to gravity and p t = h a ~ Pt(z)dz is the mean density that forms in the vessel system along z. The hydrostatic pressure in the water body, which is at the depth of the outlet distributor h a prevails, be p a = pgh a . Here let p = h^ 1 / p(z)dz which over the depth h a average density and p(z) the depth-dependent density distribution in the water body. Each hydrostatic pressure difference Ap = pt - p a However, for p t > p to a volume flow of process water emerging from the outlet distributor, whereby the reverse osmosis modules located above are also supplied with additional process water.

[0036] In the stationary state, a flow through the vascular system with a volume flow Q wwhose size along the vessel system is determined by the separation efficiency of the reverse osmosis modules, their depth in the water body, the depth of the outlet distributors and the hydraulic resistances in the vessel system and can be determined within wide limits by the design of the MWS system.

[0037] Since the outlet distributor in an advantageous embodiment has the largest vertical distance h a The area between the upstream reverse osmosis module and the outlet manifold, which has the greatest depth of all the components in the MWS system, contains the most highly concentrated process water. This area can therefore significantly influence a density-based acceleration of the process water flow through the vessel system, which is particularly taken into account in the design of the MWS system.

[0038] The density-based volume flow reduces the energy expenditure required for the process water throughput in the entire device or enables, e.g. if the outlet distributors are sufficiently deep, a completely passively operated supply of process water.

[0039] Any initial energy expenditure required to quickly initiate the process water flow can thus be at least partially offset by the development of a density- or gravity-driven flow through the vessel system. In particular, a system-specific design of the distance between the outlet manifold and the upstream reverse osmosis module thus enables the energy expenditure required to generate the necessary process water throughput to be reduced to a minimum with comparatively little effort (there are only a minimum of connecting elements).

[0040] The process water discharged from the outlet manifolds is directed into the water body via a conveniently adjustable outlet nozzle, so that the recoil from the process water entering the water body moves the outlet manifold within the water body. This creates a large dilution volume. At the same time, the mixture with the existing water causes oxygen enrichment, which can promote aerobic life and fish growth, as well as inhibit anaerobes (and the potentially linked FLS formation).

[0041] The extraction of permeate water is possible with a dynamic regulation of the depths of the individual modules depending, for example, on their separation performance, the permeate water requirement or the optimal process water throughput (external control).

[0042] In another embodiment, the depths ht of the individual modules or module groups are controlled via cables from the processing platform (external control). In this embodiment, neither aeration lines nor buoyancy bodies are required. The pressurized water pumps are controlled by pressure measurements in the permeate water chambers of the reverse osmosis modules (internal control).

[0043] In a further embodiment, such depth regulation can be achieved at least partially based on buoyancy by partially filling the buoyancy bodies with gas or gas mixtures or water. Air is particularly suitable as a gas mixture, and permeate water or something else is particularly suitable as a water mixture. In this embodiment, the buoyancy body can be fluidically connected to the aeration line of the permeate water chamber. If the buoyancy body is located outside the reverse osmosis module, it would, for example, be coupled into the aeration line close to its upper boundary. The deeper the reverse osmosis module is to be positioned within the water body, the more gas in the buoyancy body must be replaced by water. In this embodiment, the pressurized water pumps pump so much accumulating permeate water that the gas level and, if applicable, its pressure in the buoyancy body can be controlled via them (external control on the permeate water side).

[0044] In another embodiment, while maintaining a constant depth of the reverse osmosis modules, the differential pressures and thus the permeate water flows are regulated by modulating the pump flow rate (internal control). As described above, the differential pressures for the respective permeate water pressure in the reverse osmosis module will adjust, for example, according to the respective height difference between the water levels in the aeration pipes and the water surface and could be varied within wide limits by modulating the pump flow rate (internal control). In this embodiment, the buoyancy body can be equipped with valves to close it after it has been filled to a defined level (external control). Alternatively, the depth of the reverse osmosis modules in the water body is controlled and fixed mechanically via cables from the processing platform. A buoyancy body is then unnecessary.

[0045] The options listed for controlling the system and thus the different

[0046] Options for external and internal regulation to adjust the

[0047] Permeate water stream can be combined according to the invention and thus enable robust and efficient plant operation.

[0048] The setting of the pressure conditions desired for efficient filtration in the reverse osmosis modules is carried out, as described above, by the external and internal controls specifically for each reverse osmosis module.

[0049] Due to its concept, the MWS system according to the invention operates more efficiently in terms of energy than the systems currently used in practice, which is demonstrated by the following explanation:

[0050] Suppose that on the permeate water side of a reverse osmosis module the overpressure or underpressure p p , related to the air pressure (here p p= 0). Then the pressure water pump connected in or to the permeate water chamber must have a maximum pressure of p r = p H 2oghi ~ P p The work required to lift the volume of water V is p r V = (p t - p p )V, which results in a pump power P = (p t - p p )Q. The efficiency is neglected here. If one compares this pump performance for approximately the same pressure conditions with a state-of-the-art system in which the pump conveys the process water flow, then the latter must have the performance P t = PiQ w , achieving a maximum separation efficiency of 0.5 as described above. This means that the pump must have a flow rate of approximately 2 Q wPump process water to generate the volume flow Q of permeate water. Based on the power of the pressure water pump of the MWS system according to the invention, pumping this process water flow requires twice the energy output Q w / Q ■ P = 2 P = Pt . This applies correspondingly to the work required. In this estimate, it was assumed that the effort required for pre-filtration is the same in both system types. For the system according to the invention, a conservative assumption was made on the permeate water side, assuming existing air pressure in the permeate water chamber, and the additional power required in conventional systems for the throttle valves and possibly additional pumps that move the permeate water flow was neglected.

[0051] The described method according to the invention therefore has the effect, on the one hand, that the hydrostatic pressure pt itself controls the reverse osmosis as a function of the permeate water side counterpressure via the pressure difference pt - pp Therefore, no further energy is required and a control of pt (external control) and / or p p (internal control) allows for the permanent adjustment of optimal operating conditions. Furthermore, the process ensures that the energy consumption depends only on raising the actual filtered water volume to the water surface, which can significantly reduce the required pump capacity compared to current technology.

[0052] The density-driven flow through the vessel system that develops during the flow through the system according to the invention reduces the energy and plant engineering expenditure for generating the necessary process water throughput to a minimum.

[0053] The pumps, valves, and other technical components required for reverse osmosis operation in the MWS system according to the invention are now largely exposed only to demineralized permeate water and thus operate under largely non-corrosive conditions, compared to process water, which increases the service life of these components. Furthermore, the permeate water chamber is free of particles and biological substances that could potentially reduce the service life of pumps, valves, sensors, and other components.

[0054] Substances that would be dissolved on the process water side as a result of corrosion are only produced in significantly reduced quantities within the plant according to the invention, relative to the state of the art, thus reducing the entry of potential pollutants into the water body.

[0055] The inventive design further allows for the metered addition of various auxiliary substances, gases, and / or chemical substances to the permeate chamber side and, if necessary, their distribution over the membrane surface. Since osmosis membranes are permeable or diffusively permeable to different substances, and the driving force required for permeation results from the difference in substance-specific chemical potentials (e.g., concentration differences), this provides opportunities to supply the osmosis membranes with these substances during operation, both on the permeate water side and on the process water side, without significantly affecting the process water. This can be used to protect the osmosis membrane filters against precipitation, biofilms, or other changes to the membranes or membrane surfaces that could reduce the permeability or service life of the osmosis membrane filters.

[0056] If the permeate water chamber is exposed to nitrogen instead of oxygen-containing air, for example, or if a vacuum / partial vacuum or water vapor pressure is used to adjust the pressure on the permeate water side, the deposition of metal hydroxides, for example, on the osmosis membranes can be reduced, thus extending their service life. The controlled dosing of gases and / or substances for sanitizing the obtained permeate water is also possible in a simple and efficient manner. Since not all of the process water needs to be enriched with these chemicals, this procedure would allow the use of such auxiliary substances to be kept to a minimum.

[0057] Furthermore, it is possible to backwash the osmosis membrane filters during operation by reversing the pressure conditions. This detaches flocculants and deposits from the process water-side surfaces of the osmosis membrane filters and flushes them out. For example, the pressurized water pump in the permeate water chamber would be closed with a valve, and the permeate water collected there would be forced through the osmosis membrane filters on the process water side by applying compressed air or a pressurized gas or gas mixture.

[0058] For regeneration, maintenance or repair of the reverse osmosis modules, they are lifted to the surface using ropes, via the pipe system or buoyancy-based, which is possible, especially with modules operated in parallel, without interrupting the production of permeate water by the remaining modules.

[0059] To achieve the object of the invention, a device is further provided, comprising: a fluid-connected to the upper end of a body of water, arranged in a first

[0060] Depth h arranged in the water body, first reverse osmosis module, wherein the reverse osmosis module comprises an outwardly encapsulated cavity with a process water chamber having an inlet and an outlet and a permeate water chamber, which are separated from each other by osmosis membrane filters;

[0061] - at least one pump which is designed and configured to pump the permeate water accumulating in the permeate water chamber;

[0062] - at least one outlet distributor, which is fluidly connected to the process water chamber of the reverse osmosis module by means of a drain and is arranged at an outlet depth h below the first depth h ais arranged within the water body and which has an outlet directed towards the ambient water; wherein the depth h is designed such that a process water flow flows through the reverse osmosis module from the inlet to the outlet with a hydrostatic process water pressure p present in the reverse osmosis module.

[0063] The device can have the following features, although not all features are mandatory: A floating processing platform that can be positioned on the water surface, with processing and control modules that are fluidically, electrically, control-technically and mechanically connected to the modules listed below, in the inflow of the water to be desalinated to the osmosis membrane filter, for example in the water body, positionable components or modules for pre-filtration of the water to be desalinated, reverse osmosis modules and one or more outlet distributors that are fluidically connected by means of suitable pipes or hoses via two separate water pipe systems and, if necessary,are connected to an aeration line and thus enable a process water flow that moves from the surface of the water body through the process water chambers of the reverse osmosis modules floating deeper in the water body to outlet distributors arranged deeper in the water body, as well as pressurised water pumps that convey the permeate water collected in the permeate water chambers of the reverse osmosis modules as permeate water flows to the processing modules on the processing platform, as well as an (optional) aeration flow that, starting from the processing and control modules on the processing platform, supplies the permeate water chambers of the respective reverse osmosis modules and, if applicable, buoyancy bodies arranged above or within them with gases, for example air, whereby the permeate water chambers within the reverse osmosis modules are equipped with: pressure sensors, a pressurised water pump located in a sump and, if applicable,Valves for closing the permeate water lines connected to the permeate water chambers and / or the aeration lines connected to these and are separated from the process water chambers by osmosis membrane filters, which have an inlet and an outlet for the process water and are flowed through by this, whereby this vessel system formed from the various modules and lines can be positioned by ropes lowered from the processing platform and / or buoyancy-based in the water body below, for example close to the processing platform, and the outlet distributors have outlet nozzles which are adjustable in their orientation and, if necessary, regulated in order to distribute the process water widely in the surrounding water body and in this respect benefit from the recoil which is created by the introduction of the process water into the water body.

[0064] According to a further embodiment, the device has a processing platform floating on the water surface with processing and control modules located thereon. A processing and control module serves to accommodate elements that are necessary for the mechanical, electrical, control and fluidic coupling with the pre-filtration modules, if applicable, the reverse osmosis modules, buoyancy bodies and outlet distributors as well as for the operation of the system. This is where the permeate water is taken in, its intended refinement and the discharge, further distribution and / or transfer of the treated permeate water to the consumer, the system is controlled, e.g. with regard to the depth regulation of the reverse osmosis modules, the pressure and flow rate control, if applicable the regulation of the process water discharged from the pre-filtration modules or pre-filtration devices, the orientation of the outlet nozzles, the dosing (if applicable).necessary gases and substances via the aeration line, etc. The permeate water reaching the processing module is refined there depending on its use (hygienized, enriched with missing minerals, etc.) and then brought ashore, for example, via a floating pipeline or one laid in the water body, optionally suspended, or by ship.

[0065] If part of the processing platform is designed as a water reservoir, the density difference compared to the surrounding seawater creates buoyancy, which can potentially be used to advantage in the design. To provide the necessary electrical energy, the processing platform can, if necessary, be equipped with an integrated power supply, depending on the various technical possibilities.

[0066] According to a further embodiment, the device comprises at least one pre-filtration module arranged near the water surface and / or at least one pre-filtration device which has at least one filter surface and / or membrane surface and is designed to receive seawater, pre-filter it, and feed it as process water into one or more process water lines. The pre-filtration module can be designed to float on the water surface or be integrated into a floating or buoyant processing module, for example the processing platform, or it can be located at or below the water surface and connected to the processing platform via a piping system. The pre-filtration module is encapsulated with respect to the seawater, thus preventing any uncontrolled water exchange between an interior of the pre-filtration module and the surrounding water body.

[0067] In the pre-filtration module and / or pre-filtration device, seawater is conditioned or pretreated into process water according to the plant-specific technical requirements of MWS systems by passing the seawater through suitable filters and / or membranes located in the pre-filtration module and / or pre-filtration device. It is assumed that the pressure drop of the water to be filtered during the water movement through the pre-filtration module and / or pre-filtration device can be neglected or remains small by using sufficiently large filter surfaces. Alternatively, pressure filtration can be performed (if necessary, in support) according to the state of the art.If filters or membranes within a pre-filtration module are mechanically connected, for example, to buoyancy bodies floating on the water surface, these can be moved in the filtration module depending on the surface waves of the water due to the comparatively greater inertia of the pre-filtration module, which can be used, for example, to clean filter surfaces and / or to press seawater through the filter device in a similar way to a membrane pump.

[0068] The process water pretreated in the pre-filtration module and / or in the pre-filtration device is fed to the reverse osmosis modules via the inlets.

[0069] According to the invention, there is at least one reverse osmosis module, which is fluidly connected via its inlet to an upstream pre-filtration module and / or to a pre-filtration device and is arranged at a depth h within the body of water. A location near the outlet of the reverse osmosis module, e.g., near its lower edge, is specified as the reference point for the respective depth specification. The determination of this reference point is motivated by the fact that it determines both the maximum effective hydrostatic process water pressure within the reverse osmosis module and the maximum hydrostatic pressure head to be overcome in order to convey the permeate water from an aerated permeate water chamber to the water surface.

[0070] The reverse osmosis module comprises an externally encapsulated cavity with a process water chamber and a permeate water chamber. Both chambers are separated from each other by at least one osmosis membrane filter. The process water chamber has an inlet and an outlet, while the permeate water chamber has at least one outlet, optionally also an inlet. A pressurized water pump including a pressure measuring device and a lockable check valve is installed in this permeate water chamber, preferably within a sump. This pump is designed and configured to convey the permeate water accumulating in the permeate water chamber via the permeate water line to the processing platform, while regulating the pressure within the permeate water chamber at a definable level.

[0071] For the purposes of the invention, an "outwardly encapsulated" cavity means that the outer wall of the cavity in the reverse osmosis module is made of an impermeable material and manufactured in such a way that any exchange of seawater, process water, permeate water, or gases through the wall is prevented. The outer wall of the reverse osmosis module can be made, in particular, of plastics, metals, or alloys, or a combination thereof. The supply of media (process water, permeate water, gases, chemical substances) is thus possible without exception via the corresponding connections to the process or permeate water chamber of the reverse osmosis module.

[0072] According to one embodiment, the reverse osmosis module for conveying the permeate water in its permeate water chamber has a deep sump, i.e. an area of ​​the permeate water chamber which is located lower than the part of the permeate water chamber in which the osmosis membrane filters are arranged and which is intended to accommodate a pressurized water pump for conveying the permeate water to the processing platform.

[0073] If suitable radially filtering osmosis membrane filters are used, the permeate water chamber within the reverse osmosis module is formed by its preferably cylindrical interior, plus the internal volume of the piping to additional osmosis membrane filters and to the connections for the pressurized water pump and, if applicable, the aeration line, as well as, if applicable, the internal volume of a suitably arranged buoyancy body. In this preferred arrangement, the process water chamber thus encloses the permeate water chamber on all sides.

[0074] Osmosis membrane filters are made of semipermeable membranes that are permeable to water molecules, yet virtually impermeable to salts and larger molecules, colloids, or particles. This allows only demineralized water, which is virtually free of dissolved or particulate matter, to enter the permeate water chamber. Substances retained by the osmosis membrane filter must be continuously removed, which is best achieved with the continuous process water flow along the process-side surface of the osmosis membrane filter.

[0075] According to a further embodiment of the device, the reverse osmosis module is designed such that, due to its buoyancy, it can be positioned in a floating position within the body of water. Advantageously, the reverse osmosis module has a buoyancy body that can be filled with gas and water for floating positioning. This buoyancy body is located within the reverse osmosis module or is mechanically coupled to it, preferably floating above the reverse osmosis module in the body of water. By regulating the gas / water ratio in this buoyancy body, the buoyancy and thus the depth of the reverse osmosis module within the body of water can be varied, and thus the hydrostatic pressure of the process water in its process water chamber.

[0076] As an alternative to a separate buoyancy body, the outer shell of the reverse osmosis module can also be designed to provide the desired buoyancy, allowing it to float within the body of water. This can be achieved, in particular, by using a double wall and / or a suitable material selection, which is within the scope of professional practice.

[0077] According to the invention, there is at least one outlet distributor which is fluidly connected to the process water space of the upstream reverse osmosis module via its outlet and is arranged at an outlet depth h a is arranged within the water body and which has an outlet directed towards the surrounding water.

[0078] Preferably, the outlet distributor is attached to a hose or flexible pipe and can thus move within the water body, for example, similar to a pendulum. The discharge of process water into the water body via the outlet distributor results in a force directed against the outlet distributor. The outlet distributor is thus subjected to recoil. This provides the opportunity for its movement within the water body, optionally by varying the outflow direction via an adjustable outlet nozzle. The process water can thus be mixed into the water body over a wide area and thus diluted over a large area.

[0079] Therefore, the outlet of the outlet manifold has at least one outlet nozzle through which the process water is discharged from the outlet manifold into the surrounding water. Preferably, the orientation of the outlet nozzle is variable. The variation in the orientation of the outlet nozzle can occur either passively (randomly), for example, due to the forces acting on the outlet nozzle associated with the flow in the vicinity of the outlet nozzle, or actively, for example, through a controlled orientation of the outlet nozzle.

[0080] The pipe and / or hose system used to supply the reverse osmosis modules and outlet manifolds with process water is subject to minimal differential pressure across its walls, as water of similar density is present on both the inside and outside of the pipe and / or hose system. This enables its flexible, i.e., non-rigid, design, thus allowing, within certain limits, free movement of the reverse osmosis modules and thus also their independent buoyancy-based depth regulation. Flexibility can also be achieved, for example, through movable cardan shafts within an otherwise rigid pipe system.

[0081] Accordingly, only small differential pressures across the walls apply to the permeate water lines to the water surface. Only the aeration lines, which may be provided, are intended to withstand a high differential pressure across the walls, but can have a cross-section 100 to 1000 times smaller than that of the permeate water lines, whereby the comparatively high curvature of their walls acts as a stabilizing factor against the external pressure. Therefore, relatively flexible materials can also be used for these lines, which may be provided with supporting spiral inserts. All supply and delivery lines can be combined, for example, in bundles and connected to the respective module connections of the vessel system using couplings that can be sealed watertight if necessary.

[0082] According to a further embodiment, at least one of the fluid connections between optionally a pre-filtration module, first reverse osmosis module, optionally further reverse osmosis modules and outlet distributor is formed by means of flexible pipes and / or hoses.

[0083] To implement the process according to the invention, a single reverse osmosis module positioned at a depth h in the water body is sufficient. As explained above, several reverse osmosis modules can also be coupled together, for example, to achieve the desired degree of salt concentration in the process water, to provide the desired amount of demineralized water, or to optimize the efficiency of the process.

[0084] According to a further embodiment, at least one further reverse osmosis module is arranged in the fluidic connection between the outlet of the process water chamber of the first reverse osmosis module and the outlet distributor at a depth h2 that differs from the depth h. The outlet of the upper reverse osmosis module is fluidically connected to the inlet of the underlying reverse osmosis module via flexible pipes and / or hoses, so that process water from the first reverse osmosis module is transferred into the process water chamber of the following reverse osmosis module and there partially passes through the osmosis membrane filters located therein. Such an arrangement of several reverse osmosis modules is referred to below as a series connection. By connecting several reverse osmosis modules in series, a gradual concentration of the salts in the process water occurs.

[0085] In such an embodiment, the depth of the first reverse osmosis module h and the further reverse osmosis modules located within the row h 2i h2... ht are set in such a way that the process water flow flowing through these modules produces hydrostatic process water pressures < p2< Pt < p i+1 ...which, taking into account the concentration of the process water, sufficiently outweighs the resulting increase in osmotic pressure and thus achieves a sufficiently high permeate water flow. The specific depths depend on the development of the osmotic pressure in the vascular system and thus on the technical design of the osmosis membrane filters in the respective reverse osmosis modules.

[0086] The cross-sections of the outlets and / or inlets of several serially arranged reverse osmosis modules may differ from each other. For example, they may increase with increasing depth h tin the water body, and thus be designed for smaller cross-sectional process water pipes. The latter would, for example, allow a uniform flow velocity of the process water stream to be maintained in the vessel system despite the reduction in the mass flow of process water resulting from the extraction of permeate water.

[0087] In a further embodiment of the invention, one or more further reverse osmosis modules can be arranged in the fluidic connection between the pre-filtration module(s) and the outlet distributor(s) at depths h that differ from the depth h of the first reverse osmosis module. t or approximately at depth h in the water body. Such an arrangement of multiple desalination lines is referred to below as a parallel arrangement of reverse osmosis modules.

[0088] A MWS system configured in this way comprises several desalination lines that can be operated in parallel. The reverse osmosis modules of the different lines can be designed in the same way or differently. The inlet of each line can be supplied with process water from a separate filtration module, or the lines can use a common inlet fed by a common filtration module. The desalination lines can be routed to a common outlet manifold or have individual outlets leading to separate outlet manifolds.

[0089] The above explanations regarding the serial arrangement apply analogously to the individual desalination lines of the parallel arrangement. In particular, further reverse osmosis modules can be linked in series within the parallel lines.

[0090] For both serial and parallel arrangements, different reverse osmosis modules can be combined. For example, the modules can contain different numbers of osmosis membrane filters.

[0091] The invention will be explained in more detail below with reference to exemplary embodiments and the accompanying drawings.

[0092] Fig. 1: a schematic representation of a reverse osmosis module of a device according to the invention;

[0093] Fig. 2: an embodiment of the device according to the invention with several reverse osmosis modules connected in series;

[0094] Fig. 3: another embodiment of the device according to the invention with several reverse osmosis modules connected in series;

[0095] Fig. 4: an embodiment of the device according to the invention with several reverse osmosis modules connected in parallel; and

[0096] Fig. 5: another embodiment of the device according to the invention with several reverse osmosis modules connected in parallel.

[0097] The drawings show the device only schematically to the extent necessary to explain the invention. They make no claim to completeness or scale. A person skilled in the art would combine the features of the invention disclosed here in further embodiments, to the extent that this seems reasonable and possible.

[0098] Figure 1 shows a schematic representation of a reverse osmosis module 1 of a device according to the invention.

[0099] The reverse osmosis module 1 has an encapsulated cavity with a process water chamber 4 and a permeate water chamber 5. Optionally, the permeate water chamber 5 can have a gas-tight, sealable access (not shown), which can be used to ventilate the permeate water chamber 5.

[0100] The process sequence can be summarized as follows: Process water flows through an inlet 2 into the process water chamber 4, whereby the process water flow, including permeation, is schematically indicated by arrows in Figure 1. The hydrostatic process water pressure p prevailing in the reverse osmosis module 1 enables a portion of the process water to pass through the osmosis membrane filters 6 arranged between the process water chamber 4 and the permeate water chamber 5 and flow into the permeate water chamber 5, which is under lower pressure. Components 11 of the process water that cannot penetrate the osmotic membrane 6, such as dissolved salts, are retained in the process water chamber 4 by the osmosis membrane filters 6. Desalinated water, which is referred to as permeate water, flows into the permeate water chamber 5.

[0101] Concentrated process water remains in the process water chamber 4 and flows out through an outlet 3 located in the lower area of ​​the reverse osmosis module.

[0102] In the lower area of ​​the permeate water chamber 5 is a sump 12, i.e., a lower area compared to the rest of the permeate water chamber 5, in which a permeate water outlet 8 and a connected pump 13 for removing the permeate water are arranged. Figures 2 to 5 show different embodiments of the device according to the invention, each arranged within the body of water of a marine body of water, i.e., a sea or ocean, from which desalinated water is to be obtained.

[0103] Common to all embodiments shown is a processing platform 14 floating on the water surface, on which the control and processing modules of the MWS system are installed.

[0104] In the embodiment shown in Figure 2, a pre-filtration module 9 is arranged directly on the processing platform 14, in which the seawater is pre-conditioned into process water by suitable filters and membranes.

[0105] A first reverse osmosis module 1, which is located at a first depth h in the water body, i.e., below the water surface (reference height h0), is fluidly connected to the pre-filtration module 9 via a suitable hose- or tubular fluid connection 10. The hydrostatic process water pressure p prevails in the interior of the first reverse osmosis module 1. lt which is established by the depth h of the reverse osmosis module 1 in the water body. The process water enters the first reverse osmosis module 1 via the inlet 2 from the fluid connection 10 and leaves it via its outlet 3.

[0106] The concentrated process water, which leaves the process water chamber of the first reverse osmosis module 1 via the drain, reaches a further reverse osmosis module 1.1 located at a lower depth h2 below the water surface and has a hydrostatic process water pressure p2 in its interior, which is higher than p ± . In the second reverse osmosis module 1.1, the process water is further concentrated. The water then leaves the second reverse osmosis module 1.1 via an outlet and flows via another fluid connection into a third, lower-lying reverse osmosis module 1.2. This module is located at a third depth h3 below the water surface and has a hydrostatic process water pressure p3 in its interior that is higher than p2.

[0107] The further concentrated process water leaves the third reverse osmosis module 1.2 via an outlet manifold 7, which is fluidly connected to the outlet of the third reverse osmosis module 1.2, and is finally discharged into the ambient water. The outlet manifold is located at an outlet depth h a .

[0108] For the structure of the reverse osmosis modules, reference is made to Fig. 1 and its description. Alternative, functionally comparable designs are possible. Accordingly, the three reverse osmosis modules 1, 1.1, 1.2 each have a pump 13 in their respective permeate water chamber (as shown in Figure 1) for transporting the permeate water to the water surface (reference height h0), preferably to the processing platform 14. The fluid connections of the respective permeate water chambers to the processing module are advantageously also designed to be flexible and are not shown in Figures 2 to 5.

[0109] The embodiment shown in Figure 3 differs from the embodiment shown in Figure 2 only in that the pre-filtration module 9 is not arranged directly on the processing platform 14, but is connected to it via a fluid connection 10. The pre-filtration module 9 is also designed to float on the water surface.

[0110] The depth difference between h3 and h a Both Fig. 2 and Fig. 3 are shown only schematically. As described above, it is preferred that this be significantly larger, for example, at least as large as the depth differences between the individual reverse osmosis modules 1, 1.1, 1.2 or larger.

[0111] Figures 4 and 5 each show an embodiment of the device according to the invention with several reverse osmosis modules 1.1 connected in parallel.

[0112] In both embodiments, the prefiltration modules 9 are arranged directly on the processing platform 14. Alternatively, a flexible fluid connection of the prefiltration modules 9 to the processing platform 14 is also possible here.

[0113] In the embodiment shown in Figure 4, three reverse osmosis modules 1.1 are arranged in parallel at a depth h below the water surface. The process water pressure p prevails in the interior of all three reverse osmosis modules 1.1. lt which is established by the depth h of the reverse osmosis modules 1.1 in the water body. The concentrated process water leaves the device via an outlet distributor 7, which is located at the outlet depth h aFigure 5 shows an embodiment in which three reverse osmosis modules 1, 1.1, 1.2 are connected in parallel and each fluidly connected to its own pre-filtration module 9. A first reverse osmosis module 1 and another reverse osmosis module 1.1 are arranged at a first depth h below the water surface. Another reverse osmosis module 1.2 is arranged at a second depth h2.

[0114] All three reverse osmosis modules 1, 1.1, 1.2 are each fluidically connected to their own outlet distributor 7. The outlet distributors are located at different outlet depths h h h n , h in arranged.

[0115] Membran Tech GmbH

[0116] 03042 Cottbus

[0117] Method and device for desalination of seawater by reverse osmosis

[0118] List of reference symbols

[0119] 1 reverse osmosis module

[0120] 2 Inlet

[0121] 3 Procedure

[0122] 4 Process water room

[0123] 5 Permeate water chamber

[0124] 6 osmosis membrane filters

[0125] 7 outlet distributors

[0126] 8 Permeate water drain

[0127] 9 Pre-filtration module

[0128] 10 Fluid connection

[0129] 11 filtered components

[0130] 12 Swamp

[0131] 13 Pump

[0132] 14 Processing module h0Sea level (equal to reference height) hi Depth of the respective reverse osmosis module in the water body h a Depth of the outlet distributor in the water body

[0133] Pi process water pressure

Claims

Patent claims 1. A process for obtaining desalinated water, called permeate water, from a marine water body, comprising the steps - Providing at least one reverse osmosis module (1) fluidly connected to the upper end of the marine water body at a depth h with i as an element of the natural numbers and i>0, within the water body, wherein the reverse osmosis module (1) comprises an outwardly encapsulated cavity with a process water chamber (4) having an inlet (2) and an outlet (3) and a permeate water chamber (5), which are separated from one another by at least one osmosis membrane filter (6); and - Providing an outlet distributor (7) fluidly connected to the outlet (3) of the process water chamber (4) of the reverse osmosis module (1) at an outlet depth h a within the body of water, wherein the outlet distributor (7) has an outlet directed towards the surrounding water; - Pre-filtration of a part of the water body flowing into the process water chamber (4) before its contact with the osmosis membrane filter (6) to form process water; - Positioning of the reverse osmosis module (1) in the water body at a depth h t such that a part of the water body flows through the inlet (2) of the process water chamber (4) towards its outlet (3), to form a process water flow in the process water chamber (4); - Formation of a hydrostatic process water pressure pt in the process water chamber (4) of the reverse osmosis module (1) by setting a depth h t of the at least one reverse osmosis module (1) in the water body such that a pressure gradient is formed from the process water chamber (4) to the permeate water chamber (5) and, as a result, at least a portion of the process water is pressed along the pressure gradient through the osmosis membrane filter (6); and - Pumping out permeate water from the permeate water chamber (5).

2. Method according to claim 1, wherein the depth h L of the at least one reverse osmosis module (1) and thus its hydrostatic process water pressure Pt in the process water chamber (4), is set within a pressure range which is limited by the minimum possible hydrostatic process water pressure Pi required to produce permeate water and a maximum value of the hydrostatic process water pressure p it up to which the system components are protected from overload.

3. Method according to one of claims 1 or 2, wherein the process water is provided by a pretreatment, in particular a prefiltration, of seawater.

4. Method according to one of claims 1 to 3, wherein the flow velocity of the process water through the process water space (4) by means of the difference depth between the depth h and the outlet depth h aof the at least one reverse osmosis module (1) in the water body, where hi < h a .

5. Method according to one of claims 1 to 4, wherein the depth h t of the at least one reverse osmosis module (1) is regulated by changing the buoyancy force of the reverse osmosis module (1).

6. Method according to one of claims 1 to 5, wherein the pressure difference between the process water chamber (5) and the permeate water chamber (4) and the permeate water inflow dependent thereon is regulated by means of the pressure in the permeate water chamber (5) by varying the permeate water discharge.

7. The method according to claim 6, wherein the permeate water inflow is regulated by supplying the permeate water chamber (5) with air or a gas or a gas mixture via a fluidic connection and maintaining a pressure gradient from the process water chamber (4) to the permeate water chamber (5) at a predefined overpressure or underpressure p p , relative to the air pressure, is maintained or varied.

8. The method according to any one of claims 1 to 7, wherein at least one auxiliary substance is added in a metered manner on the permeate chamber side.

9. Apparatus for carrying out the method according to one of claims 1 to 8, comprising: - a reverse osmosis module (1) comprising an outwardly encapsulated cavity with a process water chamber (4) having an inlet (2) and an outlet (3) and a permeate water chamber (5), which are separated from one another by at least one osmosis membrane filter (6); - at least one outlet distributor (7) which is fluidically connected to the outlet of the process water chamber (4) in order to be located below the reverse osmosis module (1) at an outlet depth h a to be arranged and has an outlet directed towards the surrounding body of water; - at least one pre-filtration module (9) and / or a pre-filtration device, comprising filters and / or membranes and designed to separate organisms, particles, suspended matter or colloids from the water to be desalinated before its contact with the osmosis membrane filter (6), to form process water; - wherein the reverse osmosis module (1) is designed to be positioned within a marine water body and operated with process water; - positioning means formed on the reverse osmosis module (1) for positioning it at a variable depth within a marine water body; - wherein the cavity of the reverse osmosis module (1), its inlet and outlet as well as the outlet distributor (7) are designed such that a process water flow flows through the process water space (4) solely due to the gravity of the process water and a hydrostatic pressure can be built up in the cavity, formed by the height of the process water above the reverse osmosis module (1) taking into account its average density; - at least one pump (13) which is designed and configured such that in the Permeate water accumulating in the permeate water chamber (5) is to be conveyed in such a way that its pressure in the permeate water chamber (5) is kept at a definable or variable level.

10. Device according to claim 9, wherein the positioning means are designed to position the reverse osmosis module (1) at a depth h in the water body to form a hydrostatic process water pressure p in the process water space (4).

11. Device according to claim 9 or 10, wherein at least one further reverse osmosis module (1.1, 1.2) is arranged in the fluidic connection between the upper end of the water body and the outlet distributor (7) at a depth h deviating from the depth h 2 or is arranged at depth h.

12. Device according to claim 9 or 10, wherein at least one further reverse osmosis module (1.1, 1.2) is arranged in the fluidic connection between the outlet (3) of the process water chamber (4) of the first reverse osmosis module (1) and the outlet distributor (7) at a depth h deviating from the depth h 2 is arranged.

13. Device according to claim 11 or 12, wherein at least one further outlet distributor (7.1, 7.2) is fluidly connected to at least one further reverse osmosis module (1.1, 1.2) via its outlet (3).

14. Device according to one of claims 9 to 13, wherein a reverse osmosis module (1) is designed such that it can be positioned in a floating manner within the body of water due to its buoyancy.

15. Device according to one of claims 9 to 14, wherein the outlet of the outlet distributor (7) has at least one outlet nozzle which is decentrally aligned with respect to a central axis of the fluid access of the outlet distributor (7) and / or whose alignment is variable.

Images