IL289359B2

IL289359B2 - Apparatus for treating water to be purified, namely fresh water, salt water or brackish water, in particular for desalinating water to be purified; reverse osmosis unit for treating water to be purified, namely fresh water, salt water or brackish water, in particular for desalinating water to be purified; method for treating water to be purified, namely fresh water, salt water or brackish water, in particular for desalinating water to be purified

Info

Publication number: IL289359B2
Application number: IL289359A
Authority: IL
Inventors: Wilhelm Michael Stirn
Original assignee: Wilhelm Michael Stirn
Priority date: 2019-06-26
Filing date: 2020-02-11
Publication date: 2025-12-01
Also published as: IL289359B1; IL289359A; WO2020259733A1; EP3990156A1; HRP20241226T1; ES2987772T3; MA56380B1; MA56380A; EP3990156C0; EP3990156B1; DE112020003080A5

Description

Dr STIRN, Wilhelm; 74074 Heilbronn DEVICE FOR THE TREATMENT OF WATER TO BE CLEANED, NAMELY FRESH WATER, SALT WATER OR BRACKISH WATER, IN PARTICULAR, FOR THE DESALINATION OF WATER TO BE CLEANED; METHOD FOR THE TREATMENT OF WATER TO BE CLEANED, NAMELY FRESH WATER, SALT WATER OR BRACKISH WATER; IN PARTICULAR, FOR THE DESALINATION OF WATER TO BE CLEANED Prior art The invention is based on a device for the treatment of water to be cleaned, namely fresh water, salt water or brackish water, in particular, for the desalination of water to be cleaned, according to the preamble of Claim 1, and a method for the treatment of water to be cleaned, namely fresh water, salt water or brackish water, in particular for desalination of water to be cleaned, according to the preamble of Claim 9. Filters are used for the treatment of water to be cleaned, as it is necessary that the water to be cleaned, in particular, is freed of coarse particles, suspended solids and flavourings, lime, minerals, pesticides, and nitrate. Provided that drinking water is to be produced by the treatment of the water to be cleaned, which can be fresh water, salt water or brackish water, the requirements for drinking water quality are very high. Increasing water consumption worldwide leads to a water shortage, which makes clean drinking water scarce and thus an extremely valuable commodity. Since water covers more than two-thirds of the earth's surface, there have been efforts for some time to obtain drinking water from seawater (salt water). For this purpose, it is imperative to desalinate the seawater. Prior art already includes seawater desalination methods for the production of drinking water. The disadvantage here is that these are very energy-consuming. because this requires either very high temperatures or electric current if the method relies on electrolysis. Another possibility of drinking water production is reverse-osmosis seawater desalination.

In reverse osmosis, the water to be cleaned (fresh water, salt water or brackish water) is pressed through a semi-permeable membrane with a pore diameter of 0.5 to 5 nm to overcome the osmotic pressure under high pressure. This acts like a filter and only allows certain ions and molecules to pass through. Thus, a separation of the original solution is obtained. The membrane filter can be used, in particular, to retain salts, bacteria, viruses, an oversupply of lime and poisons, such as heavy metals. The osmotic pressure increases with increasing salt concentration, which would eventually cause the process to come to a standstill. Therefore, in reverse-osmosis seawater desalination, the water to be cleaned, namely the seawater for example, is pressed using high pressure through an osmosis membrane, the semi-permeable membrane, which only allows the ultrapure water, which then allows fresh water or drinking water to pass through. The pressure required for this is very high and is in the range of over 50 bar with currently available devices or osmosis membranes. It can even be 80 to 100 bar. In order to generate this pressure, for reverse-osmosis seawater desalination for example, electrically powered pumps have to push the seawater through the reverse-osmosis membrane throughout the entire day. The disadvantage here is the high energy consumption. Therefore, in utility model DE 20 2018 0627 U1, it is proposed that a high concrete silo is used to generate the required pressure, in particular, a silo up to 1m high, which is filled with the water to be cleaned. The idea behind this is that in addition to the normal atmospheric pressure (air pressure), which is about 1 bar, a change in depth in the water of 10 m causes a pressure change of 1 bar. Therefore, at the bottom of the 100 m high and water-filled silo, there is an ambient pressure of 11 bar, which results from the sum of air pressure and water pressure. Drinking water has an osmotic pressure of less than about 2 bar, the pressure applied for the reverse osmosis of drinking water is about to 30 bar, depending on the membrane and system configuration used. For seawater desalination, a pressure of about 50 to bar is required since seawater with about 30 bar has a much higher osmotic pressure than drinking water. The disadvantage is therefore that the additional pressure required for seawater desalination must continue to be generated by energy-consuming pumps. In addition, energy is needed to pump the seawater into the 100 m high concrete silo. Therefore, in the patent application open to public inspection DE 10 2012 213 214 A1, a device and a method for water desalination are proposed, wherein osmosis membranes are used, whereby water can be desalinated easily, efficiently and reliably, or drinking water can be obtained, since an osmosis membrane is sunk a few hundred metres deep in water, preferably at least 500 m or 800 m deep, and, on the inlet side of the osmosis membrane, the water pressure is applied and, on the other side of the osmosis membrane, an enclosed volume is arranged, wherein, behind the osmosis membrane, essentially atmospheric pressure prevails, and the desalinated water (ultrapure water) is pumped through a water pipe by means of pumps driven by working animals (e.g., donkeys, horses, camels)to the water surface or on land. To prevent the osmosis membrane from clogging within a very short time, it is necessary that each osmosis unit is preceded by a filter unit that filters the water to be cleaned (e.g., seawater), creating filtered water that can be pushed through the osmosis membrane. The disadvantage is that a filter unit clogs over time. On land, this would not be a significant problem, as the filter or the filter unit can be changed and cleaned at any time and with little effort. Under water, the situation is completely different. Here, it means an immense effort to lift the system to the surface, to replace the filters or the filter unit, and to set the system back in motion. The object of the invention is therefore to provide a device for the treatment of water to be cleaned, namely fresh water, salt water or brackish water, in particular, for the desalination of water to be cleaned, and a method for the treatment of water to be cleaned, namely fresh water, salt water or brackish water, in particular, for desalination of water to be cleaned, by which the disadvantages of the prior art are overcome.

The invention and its advantages The device according to the invention for the treatment of water to be cleaned, namely fresh water, salt water or brackish water, in particular, for the desalination of waterto be cleaned, with the features of Claim 1 and the method according to the invention for the treatment of water to be cleaned, namely fresh water, salt water or brackish water, in particular, for the desalination of water to be cleaned, with the features of Claim 9, on the other hand, have the advantage thatat leasttwo filterunits and a reverse-osmosis unit are used for the production of filtered water or ultrapure water (e.g., drinking water), wherein the reverse-osmosis unit is placed centrally between the two filter units, and the filter units are inversely arranged on both sides of the reverse-osmosis unit, wherein thewater to be cleaned or water filtered by another filter is flowed in the flow direction through a first filter unit, which serves to generate filtered water, wherein the filtered water is separated by means of the reverse-osmosis unit into concentrated water and ultrapure water, wherein the concentrated water is flowed backwards through the inversely arranged second filter unit, which is arranged in flow direction downstream from the reverse-osmosis unit, and the flow direction in the reverse-osmosis unit and in the filter units can be reversed in such a way that a filter unit is loaded via filtering the water to be cleaned and a filter unit is purged, whereby the service life of the filter units can be prolonged. The device according to the invention can be used on land, on the water surface and/or under water. When using a filter unit in which the flow direction is reversible, a clogging of the filter unit is reliably prevented by at least partial cleaning of the filter unit since, for the at least partial cleaning of the filter unit, via which the filter unit is purged by means of liquid, in particular, by means of water to be cleaned, pre-filtered water, ultrapure water and/or concentrated water, the flow direction within the filter unit is reversed. Thus, cleaning of the filter unit is also possible under water. The structure of aplant according to the invention for seawater desalination, in particular a plant according to the invention for seawater desalination, should preferably be modularly structured. As a result, the capacity of the system can essentially be dimensioned by the number of similar modules (units) and only the necessary filter modules (e.g., UV light).In the following, the essential assemblies of a module will be described. In accordance with a favourable embodiment of the device according to the invention, the at least one reverse-osmosis unit comprises at least one osmosis membrane, wherein the water filtered by the filter unit is pressed through and/or sucked through the osmosis membrane or the osmosis membranes by means of at least one pump at high pressure in such a way that the filtered water is separable into ultrapure water and concentrated water. The core piece can be the reverse-osmosis unit. It consists of roller-shaped or stacked membrane sheets, onto which water to be cleaned (fresh water) or with already enriched brine is flowingly applied on the outer side. On the inner side, the separated ultrapure water (fresh water) escapesand is supplied for further use, for example, to the consumer on the water surface. The necessary pressure on the outside of the osmosis membrane is provided by the hydrostatic ambient pressure at a water depth of 550 to 800 metres. If sufficient water depth is not available, the prevailing hydrostatic pressure can be increased to the required 55 to 80 bar with the help of an additional pump. In each of these modules, there is a low-pressure pump that ensures the turbulent overflow of the sheet surfaces. Two valves, which allow targeted control of theflow rate, control the inflow of cleaned fresh water (ultrapure water) and the outflow of enriched brine (concentrated water). The separated fresh water is not connected to the osmosis circuit in terms of flow technology and therefore does not require quantity control. In accordance with an additional favourable embodiment of the device according to the invention, the liquid used for at least partial cleaning of the filter unit is water to still be cleaned, filtered water and/or ultrapure water in addition to the concentrated water. In accordance with an additional favourable embodiment of the device according to the invention, in addition to the concentrated water, water to be cleaned, filtered water and/or ultrapure water flows backwards through the inversely arranged second filter unit, which is arranged in the flow direction downstream from the reverse-osmosis unit. In accordance with an additional favourable embodiment of the device according to the invention, the at least one osmosis membrane is surrounded by a pressure tank. In accordance with an additional favourable embodiment of the device according to the invention, the at least one reverse-osmosis unit comprises at least one osmosis membrane and comprises at least one reverse-osmosis unit (e.g., a low-pressure pump) for generating a turbulent flow at the osmosis membrane. At a constant channel width, low viscosity requires higher flow rate, and, at a constant flow rate, lower viscosity requires a smaller gap width to ensure a turbulent flow. The Raynolds number itself is empirically determined for different flow geometries and allows an assessment of the presence of a turbulent flow. The core of the patent idea is therefore: The osmosis membrane is constructed either with a roller-shaped by means of long webs or stacked over round membrane plates. The pressure on the outside of the membranes is provided by the hydrostatic ambient pressure at sea depth. A pump (low-pressure pump) ensures a circular flow with such a high flow rate that there is a certain turbulent flow between adjacent membrane surfaces After the brine can be enriched to about 10 % salinity, about half of the fresh water can be separated as fresh water. With the above estimated separation rate at a flow rate of approx. 1.25 %, this requires approx. 30 to 50 overflow processes. This means that all the fresh water must flow past the membrane surface about 30 to 50 times to achieve the desired degree of enrichment of the brine to about 10 %. In accordance with an additional favourable embodiment of the device according to the invention, the at least one reverse-osmosis unit comprises at least one osmosis membrane and water to be cleaned and/or through at least one filter filtered water is applied onto the at least one osmosis membrane at a pressure of more than 50 bar, in particular more than bar.In accordance with a corresponding favourable embodiment of thedevice according to the invention, the water to be cleaned and/or the water filtered by at least one filter is applied at the required pressure by means of a pump (e.g., high-pressure pump). The pressure is composed of hydrostatic ambient pressure plus additional pump pressure. This makes it possible to realise the embodiment according to the invention even in any water depth. The limits are set by onshore operation with a pump pressure of up to 80 bar and a submarine operation of theoretically 0 bar at a water depth of 800 m. In accordance with an additional favourable embodiment of the device according to the invention, a filter and/or a filter unit consist of a coarse and/or a fine filter and/or an absolute filter and/or an activated carbon filter. Each osmosis unit must be supplied with pre-filtered water (very pure fresh water, cleaned saline seawater). Therefore, each osmosis unit is preferably preceded by a filter unit. This essentially consists of a coarse filter to prevent coarse impurities, a fine filter to prevent impurities up to a diameter of about micrometres, and an absolute filter with a pore size of 0.microns. In accordance with a favourable embodiment of the method according to the invention for the treatment of water to be cleaned, namely fresh water, salt water or brackish water, in particular, for the desalination of water to be cleaned, comprising at least two filter units and a reverse-osmosis unit, wherein the reverse-osmosis unit is placed centrally between the two filter units, and the filter units are inversely arranged on both sides of the reverse-osmosis unit, wherein thewater to be cleaned or water filtered by another filter is flowed in the flow direction through a first filter unit, which is used to produce filtered water, wherein the filtered water can be separated by means of the reverse-osmosis unit into concentrated water and ultrapure water, wherein the concentrated water is flowed backwards through the inversely arranged second filter unit, which is arranged in the flow direction downstream from the reverse-osmosis unit, and the flow direction is reversed in the reverse-osmosis unit and in the filter units in such a way that a filter unit is loaded by filtering the water to be cleaned and a filter unit is purged and at least one reverse-osmosis unit comprises at least one osmosis membrane, wherein the water filtered by the filter unit is pushed through the osmosis membrane or osmosis membranes and/or sucked through by means of at least one pump at high pressure so that the filtered water is separated into ultrapure water and concentrated water. In accordance with an additional favourable embodiment of the method according to the invention, in addition to the concentrated water with water to still be cleaned, filtered water and/or ultrapure water flows backwards through the inversely arranged second filter unit, which is arranged in theflow direction downstream from the reverse-osmosis unit. In accordance with an additional favourable embodiment of the method according to the invention, the at least one reverse-osmosis unit comprises at least one osmosis membrane and a turbulent flow is generated by means of a pump (e.g., low-pressure pump) at the osmosis membrane of at least one reverse-osmosis unit. In accordance with an additional favourable embodiment of the method according to the invention, the at least one reverse-osmosis unit comprises at least one osmosis membrane and the water to be cleaned and/or water filtered by another filter is applied to an osmosis membrane at a pressure of more than 50 bar, in particular, more than 80 bar. In accordance with a corresponding favourable embodiment of themethod according to the invention, the water to be cleaned and/or water filtered by another filter by means of a pump (e.g., high-pressure pump) is applied at the required pressure or the at least one reverse-osmosis unit comprises at least one osmosis membrane and the osmosis membrane is arranged at such at depth in the water or in the sea that the water pressure present there is sufficient to penetrate. In accordance with an additional favourable embodiment of the method according to the invention, a filter and/or a filter unit are used, which consist of at least one coarse filter, at least one fine filter, at least one absolute filter and /or at least one activated carbon filter. It is conceivable that at least one filter and/or at least one filter unit is arranged upstream to and/or downstream from a gas-bubble filtration tank. Further advantages and favourable embodiments of the invention can be seen in the following description, the claims and the drawing.

Drawings Preferred exemplary embodiments of the object according to the invention are presented in the drawings and are explained in more detail in the following. The figures show: Fig. 1 a drawing of a basic structure of a reverse-osmosis unit,Fig. 2 a drawing of a filter unit Fig. 3 a sketched illustration of the overflow in the reverse-osmosis unit and Fig. 4 a sketched illustration of an alternative to the extraction of ultrapure water.

Description of the exemplary embodiments Fig. 1 shows a sketch of a basic structure of a reverse-osmosis unit 1, which can preferably be used under water; wherein Fig. is reduced to functional blocks; which are described in more detail below. The reverse-osmosis unit 1, which may be dispensed with in the treatment of fresh water, is placed in the middle between two filter units 2 (filter modules), which are inversely flanged on both sides of the reverse-osmosis unit 1.The water to be cleaned 3 (salt water, fresh water, brackish water) or water already filtered by another filter (pre-cleaned) is flowed through a filter unit 2 in the flow direction, which is used to generate filtered water, which water is pressed and/or sucked through the osmosis membranes or the osmosis membranes at high pressure by means of at least one pump (e.g., high-pressure pump) in such a way that the filtered water can be separated into concentrated water 4 and ultrapure water 5. In this flow direction, the filter unit subjected to the flow therefore preferably cleans the water to be cleaned 3 or the water already filtered by another filter (pre-cleaned) in a plurality of steps up to a degree of purity that makes reverse osmosis possible. The water to be cleaned 3; filtered water, ultrapure water 5 and/or concentrated water is flowed backwards through the inversely arranged filter unit 2, preferably from the finest to the coarsest filter of a filter unit 2, which is arranged in the flow direction downstream from the reverse-osmosis unit 1, thereby being cleaned. The flow reversal thereby causes in this arrangement that a filter unit 2 is loaded by filtering the water to be cleaned 3 and a filter unit 2 is purged. This should significantly increase the filter service life between two maintenance intervals compared to operation with a single filter unit 2. The geometric arrangement or capacity of the three units in a functional device is not specified by the schematic diagram. The capacity of a plant was determined by the parallel operation of similar modules. The symmetrical design of the filter units 2 is therefore an alternative to the prior art, since the flow direction in the reverse-osmosis unit 1 can be reversed. Thus, it is possible to flange a filter unit 2 symmetrically at both ends of the reverse-osmosis unit 1. During operation, a filter unit 2 will then clean the seawater and supply it cleaned to the reverse-osmosis unit 1. For example, the enriched brine from the reverse-osmosis unit 1 is flowed backwords through the symmetrically arranged filter unit 2 and purges the filters. This should drastically increase the service life of the filter units 2. The inversion of the reference numbers 3 and 4 indicates the flow reversal. Fig. 2 shows a filter unit 2 drawing. The filter unit 2 is preferably composed of at least three filtermodules in the flow direction. The coarse filter 6 could be, for example, a sand filter (e.g., sediment filter) that removes macroscopic impurities or coarse particles from the water to be cleaned 3. The second module, the fine filter 7, removes particles with diameters up to about 50 microns. Finally, the absolute filter consists of inert glass balls made of ruby and/or quartz with a certain diameter (e.g., 127 μm), for example, and can filter out dirt particles up to a diameter of about 0.2 micrometres reliably. Optionally, a fourth filter module, a sheet filter 9, is provided. however, if this sheet filter 9 is really necessary, this makes the discharge of the filter unit much more difficult, since sheet filter 9 can not be backwashed. A sheet filter 9 can therefore not be cleaned by flow reversal. In this case, the alternative shown in Fig. 4 is appropriate. The water 10 filtered by the filter modules is pumped by means of a pump 11 at a variable pressure to adjust the hydrostatic ambient pressure to the necessary pressure to the reverse-osmosis unit in order to flow around the osmosis membrane there. By reversing the flow direction within the filter modules in flow direction 12, the filter modules loaded with filtered material can be cleaned by purging. Preferably, an osmosis membrane could be based on graphene, i.e., carbon layers which, although only one atom thick, are extremely hard and have excellent conductivity levels. For the cost-effective and simple production of the osmosis membrane, graphene oxide, a chemical derivative that can be produced by oxidation, could be used; graphene oxide, for example, is applied as a solution to a substrate of desolate porous material, resulting in a thin membrane. The hard layer of graphene comprises holes that are so small (pore diameter, for example, one nanometre) that only water but no salt can fit through. In order to avoid swelling of the membrane consisting of graphene oxide through contact with water, whereby smaller salts could pass through the pores, it is conceivable that wafer-thin walls of epoxy resin, for example, are placed on both sides of the membrane, which. prevent swelling. Fig. 3 shows a sketched illustration of the overflow in the reverse-osmosis unit 1. Reverse osmosis takes place on membranes whose outside is exposed to filtered water 10. The inside, on the other hand, is in principle almost hermetically shielded. But only almost, since the outside and inside are connected by the finest channels, which allow water molecules to pass through but retain, for example, salt ions. This diffusing of the water molecules from the outside to the inside requires a significant pressure difference in the range of to 80 bar. The reverse osmosis process can only take place if the outside of the membrane is subjected to a turbulent flow. Otherwise, the pores that enable reverse osmosis immediately become clogged. Since the separation rate of ultrapure water (fresh water) is low in comparison to the overflowing mass flow rate, a low-pressure circulation pump 13 (low-pressure pump) is also used, which is used to provide a turbulent overflowing of the outer surface of the reverse-osmosis membrane 6. The mass flow that flows across the reverse-osmosis membrane 14 is a multiple of the supplied, cleaned ultrapure water 5, estimated to be a factor of 30 to 50 times that. The separated ultrapure water 5 (fresh water) is extracted via a high-pressure pump 15 (pressure requirement up to 80 bar) and pumped to the surface. The concentrated water 4. leaves the reverse-osmosis unit 1 and is released into the environment, for example, the sea. The osmosis membrane 14 of the reverse-osmosis unit 1 is surrounded by a pressure tank, in the interior of which a pressure of 80 bar prevails due to the water pressure that surrounds the pressure tank, or the pump 11. If the water depth is sufficient, pump 11 is not necessary. Therefore, the pump is used when the water pressure is not 80 bar to make up for the missing difference. Pump 11 is mandatory if the pressure tank is to be operated on land or on the water. The concentrated water 4 leaves the reverse-osmosis unit 1 through a valve (overpressure valve), which opens, for example, from a pressure of 77 bar. The ultrapure water 5 has low pressure when exiting the reverse-osmosis unit 1, which is 0 bar where applicable. To control the fresh-water discharge from the reverse-osmosis unit 1, the electrical conductivity of the ultrapure water is preferably used, since the electrical conductivity is an indicator of the purity of the water in such a way that a low electrical conductivity signals a high degree of purity and a higher electrical conductivity a lower degree of purity. Depending on the degree of dirtiness and salinity of the water to be cleaned, where applicable, it can be possible to dispense with the reverse-osmosis unit 1, which can be operated on land, on the water or under water, so that due to the treatment by means of gas-bubble filtration and/or using the filter unit 2, which can be also comprise a UV light module and/or a microplastic module and/or a centrifuge for cleaning the water,already ultrapure water 5 can be provided. Fig. 4 shows a sketched illustration of an alternative to the extraction of ultrapure water 5. With this method, the treatment of the water to be cleaned 3 and the reverse osmosis can be spatially separated. The connection between the two process carriers, cleaning and reverse osmosis, is made via flexible hose or pipe connections 16. In combination with reverse osmosis under water, seawater treatment at sea level and reverse osmosis under water will usually take place. The system structure can be outlined as follows. A low-pressure pump 17 fills a gas-bubble filtration tank 18 (boiler) with water to be cleaned 3. A gas pump 19 blows fizzy gas into this water to be cleaned 3. The effect of this improved filtration removes the contained dirt particles from the water to be cleaned 3. An activated carbon filter 20 may have to be connected downstream, for example, to remove dissolved heavy metal ions. The pre-filtered water is supplied by means of a pump. 11 via the flexible hose or pipe connection 16, which bridges the height difference 21 between water treatment at sealevel and reverse osmosis at depth, to the reverse-osmosis unit 1. The concentrated water 4 (enriched brine) is released into the environment. The ultrapure water 5 (separated fresh water) is supplied to the consumer on the surface or on land via a flexible hose or pipe connection 22. A fresh-water reservoir (intermediate storage) compensates for demand fluctuations. The advantage of this fresh-water cleaning lies in the basically infinite service life of a filter through improved filtration. Fig. 4 is an alternative. Above the water surface, either on land or on a float, in this case the water 3 to be cleaned is cleaned by a combination of improved filtering and other filter stages, for example activated carbon filter 20, and then fed via flexible pipe or hose connections 16 to a possibly remotely installed osmosis unit. The principle of operation of such filtering is simple. A gas-bubble filtration tank 18 is filled with water 3 to be cleaned. The fizzy gas is blown in near the ground. Due to the sealing difference between gas and water, the gas bubbles rise. The polar shape of the water molecule causes an electric dipole field in the gas bubbles. This attracts dirt particles, in particular organic impurities, andremoves them when rising from the water to be cleaned 3. Depending on requirements, another filter stage can be used for the post-cleaning of the fresh water, for example an activated carbon filter 20. Preferably, the gas-bubble filtration tank 18 is a preferably food-grade stainless steel or plastic tank and comprises a compressor for generating oil-free press gas with blow-in device, a tap for extracting the cleaned water and a device for removing the foam pad. Preferably, an upright, cylindrical tankis utilised, as it is used as a fermentation tank in wineries for example. Stainless steel can be used as a material, but can also be replaced, for example, by food-safe, glass-fibre-reinforced plastic. The horizontally orientated blow-in plane is installed above the bottom of the tank. If possible, it must cover the entire tank cross-section with a homogeneous film of fine gas bubbles. The distance between the bottom of the tank and the blow-in plane is between 5 % and % of the total tank height, depending on the tank height and the soil level of the water to be cleaned. The blow-in device consists of a compressor, which preferably produces oil-free, filtered compressed gas and a ring of fine nozzles distributed in a horizontal plane over the circumference of the tank. The compressed gas is blown into the liquid via these nozzles, wherein very fine bubbles form. Due to electrostatically induced dipoles, organic impurities are preferably attached to these bubbles. These are removed from the liquid volume by the rising gas bubbles and accumulate as a compact foam crown on the liquid surface. After a certain dwell time of minutes to half an hour, depending on the tank size, the foam crown can be removed. Depending on the type of contamination, this can possibly be used directly as fertilizer. Slightly above the blow-in plane, a extraction device, such as a faucet for example, can be installed, through which the cleaned water can be extracted. For maintenance purposes, it is advisable to makethe lid of the tank removable so that mineral components such as gravel and sand can be removed from time to time and the tank interior can be subjected to food-grade cleaning. The operation of the plant is preferably carried out in the following steps: - pre-cleaning of the water, for example via a sand filter and/or activated carbon filter (optional), - filling the tank with water to be cleaned or already pre-cleaned, - blowing in fine gas bubbles, for example, - dwell time for froth to form, - extracting the froth and - extracting the cleaned water. As already indicated above, in this way, colloidal, in particular, biological tissues, are removed. Chemically dissolved substances, such as salts, must be removed in subsequent processing steps, for example by precipitation or by further filters (e.g., reverse osmosis). This makes it possible; clean water in such a way that it can be used as drinking water or for other purposes, such as irrigation of agricultural crops for example. All features presented in the description, the following claimsand the drawings can be essential for the invention both individually as well as in any combination with each other.

Reference list 1 reverse-osmosis unit 2 filter unit 3 water to be cleaned 4 concentrated water 5 ultrapure water 6 coarse filter 7 fine filter 8 absolute filters 9 sheet filter 10 filtered water 11 pump 12 flow direction 13 low-pressure pump 14 osmosis membrane, reverse-osmosis membrane 15 high-pressure pump 16 hose or pipe connection 17 low-pressure pump 18 gas-bubble filtration tank gas pump activated carbon filters 21 height difference 22 hose or pipe connection 23 fresh-water reservoir 24 pressure tank

Claims

18 28.08.20

CLAIMS 1. A device for treating water (3) to be purified, more specifically fresh water, salt water, or brackish water, in particular for the purpose of desalinating water (3) to be purified, said device having at least two filter units (2) and a reverse-osmosis unit (1), wherein the reverse-osmosis unit (1) is placed centrally between the two filter units (2) and the filter units are flange-mounted on either side of the reverse-osmosis unit (1) in a mirror-inverted manner, wherein the water (3) to be purified or the water (10) that has been filtered by another filter passes, in the flow direction, through a first filter unit (2) which serves for producing filtered water (10), wherein the filtered water may be separated into concentrated water (4) and ultrapure water (5) by means of the reverse-osmosis unit (1), characterised in that the concentrated water (4) passes, in a backward direction, through the mirror-symmetrically disposed second filter unit (2) which is arranged downstream of the reverse-osmosis unit (1) when considered in the flow direction, and in that the flow direction in the reverse-osmosis unit (1) and in the filter units may be inverted, such that the second filter unit (2') is charged by a filtering of the water (3) to be purified and the first filter unit (2) is flushed clear. 2. Device according to Claim 1, characterized in that the at least one reverse-osmosis unit (1) comprises at least one osmosis membrane (14), wherein the water (10) filtered by the filter unit (2) is pressed through and/or sucked through the osmosis membrane (14) or the osmosis membranes (14) by means of at least one pump (11) at high pressure in such a way that the filtered water (10) can 19 28.08.20 be separated into ultrapure water (5) and concentrated water (4).

3. Device according to Claim 1, characterized in that, in addition to the concentrated water (4), water still to be cleaned (3), filtered water (10) and/or ultrapure water (5) is/are flowed backwards through the inversely arranged second filter unit (2), which is arranged in the flow direction downstream from the reverse-osmosis unit (1).

4. Device according to Claim 1, characterized in that the at least one reverse-osmosis unit (1) comprises at least one osmosis membrane (14) and that at least one osmosis membrane (14) is surrounded by a pressure tank (24).

5. Device according to Claim 1, characterized in that the at least one reverse-osmosis unit (1) comprises at least one osmosis membrane (14) and, for the generation of a turbulent flow at the osmosis membrane (14), at least one reverse-osmosis unit (14) comprises a pump (13).

6. Device according to Claim 1, characterized in that the at least one reverse-osmosis unit (1) comprises at least one osmosis membrane (14) and water to be cleaned (3) and/or water filtered by at least one filter (10) is applied to at least one osmosis membrane (14) at a pressure of more than 50 bar, in particular, more than 80 bar.

7. Device according to Claim 6, characterized in that 20 28.08.20 the water to be cleaned (3) and/or the water filtered by at least one filter (10) is applied at the required pressure by means of a pump (11).

8. Device according to Claim 1, characterized in that a filter unit (2) consists of at least one coarse filter (6), at least one fine filter (7), at least one absolute filter (8) and/or at least one activated carbon filter (20).

9. A method of treating water (3) to be purified, more specifically fresh water, salt water, or brackish water, in particular for the purpose of desalinating water (3) to be purified, said method involving at least two filter units (2) and a reverse-osmosis unit (1), wherein the reverse-osmosis unit (1) is placed centrally between the two filter units (2) and the filter units are flange-mounted on either side of the reverse-osmosis unit (1) in a mirror-inverted manner, wherein the water (3) to be purified or the water (10) that has been filtered by another filter passing, in the flow direction, through a first filter unit (2) which serves for producing filtered water (10), wherein the filtered water may be separated into concentrated water and ultrapure water (5) by means of the reverse-osmosis unit (1), characterised in that the concentrated water (4) passes, in a backward direction, through the mirror-symmetrically disposed second filter unit (2), which is arranged downstream of the reverse-osmosis unit (1) when considered in the flow direction, and in that the flow direction in the reverse-osmosis unit (1) and in the filter units is inverted, such that 21 28.08.20 the second filter unit (2') is charged by a filtering of the water (3) to be purified and the first filter unit (2) is flushed clear.

10. Method according to Claim 9, characterized in that, in at least one reverse-osmosis unit (1), which comprises at least one osmosis membrane (14), and that the water (10) filtered by the filter unit (2) is pressed and /or sucked through the osmosis membrane (14) or the osmosis membranes (14) by means of at least one pump (11) at high pressure in such a way that the filtered water (10) can be separated into ultrapure water (5) and concentrated water (4).

11. Method according to Claim 9, characterized in that, in addition to the concentrated water (4), water still to be cleaned (3), filtered water (10) and/or ultrapure water (5) is/are flowed backwards through the inversely arranged second filter unit (2), which is arranged in the flow direction downstream from the reverse-osmosis unit (1).

12. Method according to Claim 9, characterized in that, the at least one reverse-osmosis unit (1) comprises at least one, osmosis membrane (14) and, by means of a pump (13), a turbulent flow at the osmosis membrane (14) of at least one reverse-osmosis unit (1) is generated.

13. Method according to Claim 9, characterized in that, the at least one reverse-osmosis unit (1) comprises at least one osmosis membrane (14) and, the water to be cleaned (3) and/or water filtered by another filter (10) is applied to an osmosis membrane (14) at a pressure of more than 50 bar, in particular, more than 80 bar. 22 28.08.20

14. Method according to Claim 13, characterized in that, the water to be cleaned (3) and/or water filtered by another filter (10) is applied by means of a pump (11) at the required pressure or the at least one reverse-osmosis unit (1) comprises at least one osmosis membrane (14), and the osmosis membrane (14) is arranged so deep in the water or in the sea that the water pressure prevailing there is sufficient to penetrate through it.

15. Method according to Claim 9, characterized in that, a filter unit (2) is used consisting of at least one coarse filter (6), at least one fine filter (7), at least one absolute filter (8) and/or at least one activated carbon filter (20).

16. Device according to Claim 2, characterized in that, in addition to the concentrated water (4), water still to be cleaned (3), filtered water (10) and/or ultrapure water (5) is/are flowed backwards through the inversely arranged second filter unit (2), which is arranged in the flow direction downstream from the reverse-osmosis unit (1).

17. Method according to Claim 10, characterized in that, in addition to the concentrated water (4), water still to be cleaned (3), filtered water (10) and/or ultrapure water (5) is/are flowed backwards through the inversely arranged second filter unit (2), which is arranged in the flow direction downstream from the reverse-osmosis unit (1).