NO20101192A1 - Water treatment installation, method and application for removal, underwater, of at least ± one undesirable component from water - Google Patents

Abstract

Water treatment installation (2) and method for removing at least one unwanted component from water. The water treatment installation (2) comprises: - a container (30) having a filtration membrane dividing the container (30) into an upstream receiver chamber (34) and a downstream permeate chamber (38); wherein the filtration membrane is arranged for retention of a retentate (42) comprising at least one first component of a supply water (6); and - wherein the filtration membrane is arranged to flow through a permeate (16) comprising at least one second component and a means of transport flow-wise connected to the receiving chamber (34) for transporting supply water (6) to the receiving chamber (34) and permeate (16) out of the permeate chamber ( 38). The water treatment installation (2) is also arranged for remote controlled operation underwater; - wherein the water treatment installation (2) is immersed in a water body (6); - where the inlet chamber (34) of its inlet (28) is flow-related to the water heater (6) in which the water treatment installation (2) is located; and - wherein an outlet (36; 40) for the desired product water (42; 16) in the at least one container (30) is flow-related with a transfer pump for transporting product water (42; 16) to a receiving site.

Description

WATER TREATMENT INSTALLATION, METHOD AND APPLICATION FOR REMOVING, UNDERWATER, OF AT LEAST ONE UNDESIRABLE COMPONENT FROM WATER

Field of the invention

The invention relates to a water treatment installation, a method and an application for the removal, under water, of at least one unwanted component, for example solid particles, bacteria, viruses, salts and sulfates, from supply water fed into the water treatment installation. Furthermore, the invention requires remote controlled operation of the water treatment installation under water.

The background of the invention

The invention has its background in problems with prior art within two related, technical areas.

One technical area concerns the injection of water into underground hydrocarbon reservoirs to increase the recovery rate from such reservoirs, so-called secondary recovery. Water injection is the most common method of increasing the recovery rate of crude oil from a reservoir. The water used in this context is often taken from the nearest water source, for example directly from a sea, lake, river or delta, and/or the water source may be produced water from a separation plant for crude oil or hydrocarbon condensate.

In connection with such water injection, it is common to remove, reduce and/or neutralize various unwanted components in the supply water (raw water) before it is pumped down into an injection well. This is done to avoid or reduce unwanted damage effects of such components when they come into contact with well-related equipment, process-related equipment, personnel and/or fluids in an underground reservoir. Such damage can, for example, concern wear, corrosion and/or deposits ("scaling") on well-related and/or process-related equipment. It may also be the case that unwanted components inhibit the spread ("sweep") of an injection water front through an underground petroleum reservoir, so that the recovery rate and/or degree of recovery from the reservoir is reduced. In this context, the unwanted components are essentially made up of solid particles of different particle sizes; various organic matter, such as bacteria; various salts and sulfates, such as sodium chloride (NaCl) and calcium sulfate (CaSO4); and gases, such as oxygen (02) and carbon dioxide (C02). The most unwanted and problematic bacteria in this context are bacteria that cause fouling on various equipment and pipe connections, as well as anaerobic and sulfate-reducing bacteria that generate hydrogen sulfide gas

(H2S). Hydrogen sulphide is very aggressive and can cause extensive corrosion damage to well equipment, process equipment and pipe connections. In addition, the gas is highly toxic to humans. Hydrogen sulphide also causes acidification of hydrocarbon fluids in underground reservoirs, so-called reservoir acidification. All of these problems are well known within the petroleum industry.

The other technical area concerns the purification and production of fresh water, preferably for drinking water purposes. Problems with the production and/or procurement of clean fresh water are a well-known problem in a number of geographical areas in the world, particularly in so-called developing countries. In such areas, drinking water is usually taken from the nearest water source, for example directly from a sea, lake, river, catchment or groundwater body. It is also known that many such water sources are unsuitable for drinking water purposes, for example due to high salt content, high bacteria content and/or strong pollution. Nevertheless, such unsuitable water is used for drinking water purposes, which often has its cause in poor economics, insufficient or absent infrastructure, and/or in the absence of a better alternative. Similar drinking water problems can arise in areas exposed to major natural disasters, such as floods, tidal waves, landslides, volcanic eruptions and the like, or in connection with certain military operations. Under such conditions, there is usually an urgent need for fresh water and thereby an urgent need to mobilize and procure suitable equipment to make fresh water in or near the area in question.

Known technique and disadvantages with this

According to known technology, and regardless of whether the supply water (raw water) is to be treated for injection into a well or purified for the production of fresh water, it is common to pump up the supply water from a water source and on to a surface installation for further treatment of the supply water.

At such a surface installation, the supply water is subjected to different types of treatment adapted to the relevant purpose and the relevant quality of the supply water. Unwanted components are typically removed through various filtrations of the supply water. In addition, the supply water is often subjected to various chemical treatments. Chemicals used in this context can be organism-killing and/or organism-growth inhibiting chemicals, such as chlorine and biocides. In this context, other types of chemicals are also often added, including oxygen scavengers, corrosion inhibitors and deposit inhibitors. It is also relatively common to pass the supply water through equipment for degassing ("deaeration") in order to thereby remove unwanted gases.

When it comes to filtering the supply water, mainly two types of filtering methods are used, of which (1) conventional straight-flow filtration ("dead-end filtration"), and (2) so-called cross-flow filtration ("cross-flow filtration"), also called tangential-flow filtration ("tangential flow filtration").

Conventional direct current filtering

In conventional straight-flow filtration ("dead-end filtration"), the supply water is pushed or sucked towards the upstream side of a semi-permeable filter/membrane. Thereby, a liquid permeate of the supply water will flow through the filter/membrane to the downstream side of the filter/membrane, while a retentate in the form of a filter cake is retained on the upstream side of the filter/membrane. Usually, such a filter cake will relatively quickly clog pores or openings in the filter/membrane, so that the filter/membrane must be replaced relatively often. In contrast, direct flow filters/membranes are relatively cheap compared to cross flow membranes.

Direct current filters/membranes constitute known technology and usually comprise a wire cloth or a membrane with a suitable mesh size and with a certain depth extent. Such wire cloths or membranes for treating liquids are often designed in metal or synthetic material, for example polymer material. Direct flow filtration is typically used for conventional coarse filtration to fine filtration of inorganic and organic solid particles suspended in the supply water, for example sand, silt, clay, soil, zooplankton, phytoplankton, and even certain types of bacteria and viruses.

Cross-flow filtering

In cross-flow filtration ("cross-flow filtration"), pressurized supply water is usually led towards the upstream side of a semi-permeable cross-flow membrane and passes this along (i.e. across the membrane). During this cross-flow process, a permeate of the supply water is pushed through the cross-flow membrane to the downstream side of the membrane and exits as a branch flow from it. A retentate of the supply water, i.e. a relatively large proportion of the supply water containing a greater concentration of the unwanted component(s), is, on the other hand, led away from the upstream side of the membrane and exits as a separate branch flow. With cross-flow filtration, two separate branch streams will therefore exit from the cross-flow membrane, of which one branch stream with the permeate and one branch stream with the retentate.

When the permeate is a liquid, which it usually is, the pressure in the supply water must, among other things, exceed a so-called transmembrane pressure ("transmembraneous pressure" - TMP") in order for the permeate to be able to flow through the cross-flow membrane. The size of the transmembrane pressure will depend on the type of cross-flow membrane used in the individual case. Furthermore, the transmembrane pressure can vary from an insignificant overpressure to a significant overpressure, for example several tens of bar If, on the other hand, the permeate is a gas, the permeate can possibly be sucked through the cross-flow membrane.

Although cross-flow filtration can be used for filtering various inorganic and organic solid particles suspended in the supply water, for example of the types mentioned above, cross-flow filtration is typically used for the removal of smaller and often very small components in the supply water, including dissolved components such as salts and sulphates in the supply water. Cross-flow filtration is typically associated with so-called microfiltration, ultrafiltration, nanofiltration and reverse osmosis filtration. Each of these respective filtration types successively removes smaller components from the supply water, where said transmembrane pressure increases with decreasing size of the components to be removed by means of the cross-flow membrane in question. Furthermore, cross-flow filtration is used in a number of process plants on the surface, e.g. in water treatment plants and within the food industry, for the purification of water or other liquids.

Cross-flow membranes constitute known technology and are found in a number of designs and material types, including spiral wound membranes ("spiral wound membranes"), plate or frame membranes ("plate/frame membranes"), tubular or straw-shaped membranes ("tubular membranes" or "straw membranes ") and hollow fiber membranes ("hollow fiber membranes"). The membranes can also have a symmetrical or asymmetrical structure. The membranes can also include porous and/or non-porous materials as well as structures of thin-film composite ("thin-film composite" - TFC). Such cross-flow membranes are often made of polymer materials, cellulose materials and/or ceramic materials.

The following materials are typically used for microfiltration: acrylonitrile, various ceramic materials, polypropylene, polysulfone, polytetrafluoroethylene (PTFE), polyvinylidene fluoride

(PVDF) and thin film composite (TFC). For ultrafiltration, the following are typically used: aromatic polyamide, various ceramic materials, cellulose acetate, polypropylene, polysulfone, polyvinylidene fluoride (PVDF) and Teflon<®>. The following are typically used for nanofiltration: cellulose materials, aromatic polyamide, polysulfone, polyvinylidene fluoride (PVDF) and thin film composite (TFC). For reverse osmosis filtration, cellulose materials, aromatic polyamide and thin film composite (TFC) are typically used.

In connection with cross-flow filtration, it is not uncommon for 40-80% of the feed water to be carried away from the membrane as a retentate and dumped as a waste product, or for the retentate to be carried on for further water treatment before finally being dumped. The proportion of supply water that is dumped depends on the current type of cross-flow membrane used. This ratio means that typically 40-80% of the supply water that is pumped up to a surface installation is eventually dumped. This also means that typically 40-80% of the pumping energy that is used to pump up the supply water and/or to increase the pressure sufficiently to be able to carry out the filtering process itself, is lost during said dumping and energy is thereby wasted.

Filtration of supply water (raw water) on surface installations offshore is also burdened with a number of disadvantages that apply regardless of whether the treatment of the supply water is carried out using straight-flow filtration and/or cross-flow filtration.

Most surface installations offshore are technically complicated, very compact and burdened with significant space and weight restrictions. It is these conditions that constitute the most important design criteria for such surface installations. This also means that surface installations offshore become very expensive to install and operate, and they are therefore mostly only used in connection with water injection in large petroleum reservoirs offshore.

Large installation and operating costs associated with such surface installations offshore are also the most important reasons why water injection is used to a small extent in smaller petroleum reservoirs offshore. For the same economic reasons, surface installations offshore are used to a very small extent for the production and delivery of fresh water, for example for drinking water purposes.

The technical scale and technical complexity usually associated with such surface installations offshore will also reduce the technical reliability of such installations. Reduced technical reliability will usually result in relatively frequent and/or long operational interruptions, an increased scope of maintenance and/or scope of repairs as well as increased costs associated with this.

In addition, such an offshore surface installation will usually take its supply water from a surface layer of a water source in which the installation is located, for example from a surface layer of a sea, lake, river or delta. However, the water quality in such a surface layer can vary widely due to weather-dependent and seasonal influences. Thus, the water quality in the surface layer can fluctuate due to seasonal fluctuations in water temperature, salinity, sediment content, flow conditions and/or biological activity. Such fluctuations in water quality create relatively unstable operating conditions for surface installations offshore.

Purpose of the invention

The primary purpose of the invention is to avoid or reduce the above-mentioned disadvantages of the known technique, or at least to provide a useful alternative to the known technique.

Another purpose is to provide a technical solution to at least reduce the technical and cost disadvantages associated with water treatment at a surface installation offshore or on land.

A more specific purpose is to provide a technical solution to avoid the use of a surface installation in connection with water treatment offshore, thereby also avoiding the technical, space-related, weight-related and cost-related disadvantages that such a surface installation offshore is typically burdened with.

A further purpose is to provide a technical solution which is significantly simpler, more flexible and more cost-effective with regard to the production of fresh water.

General description of how the objectives are achieved

The purposes are achieved through features which are indicated in the following description and in the subsequent patent claims.

According to a first aspect of the invention, a water treatment installation is provided for the removal of at least one unwanted component from water, where the water treatment installation comprises: - at least one container provided with at least one semi-permeable filtration membrane that divides the container into at least one upstream receiving chamber and at least one downstream permeate chamber; wherein the filtration membrane is arranged for retention, on the upstream side of the membrane, of a retentate comprising at least one first component from a supply water; and wherein the filtration membrane is arranged for the flow through, to the downstream side of the membrane, of a permeate comprising at least one second component

from the supply water; and

- at least one conveying means flow-wise connected to an inlet in the receiving chamber for transporting supply water to the receiving chamber, and for transporting said permeate of the supply water out of the permeate chamber via an outlet in the permeate chamber. The special feature of the water treatment installation is that it is designed for remote-controlled operation under water; - that the water treatment installation is submerged in a body of water; - that the inlet of the receiving chamber is flow-wise connected to the body of water in which the water treatment installation is located; and - that an outlet for the desired product water in the at least one container is flow-wise connected to at least one transfer pump for onward transport of product water to a receiving location via at least one transfer line.

By using such a submerged water treatment installation, one avoids, for example, having to use a surface installation, for example a platform, for such water treatment offshore. This also avoids the aforementioned technical, space-related, weight-related and cost-related disadvantages that such a surface installation is typically burdened with. Thereby, it is also economically possible to inject water into smaller petroleum reservoirs offshore in order to increase the recovery rate and/or degree of recovery from such reservoirs.

If, for example, such a water treatment installation is placed on a seabed, you are also not burdened with the same weight and space restrictions that typically apply to a surface installation offshore. This allows for significantly greater technical flexibility when it comes to the choice of equipment and the placement of the equipment in the relevant water treatment installation. Thereby, the water treatment installation will also be able to achieve significantly better technical reliability than on a surface installation. In addition, the submerged water treatment installation can take its supply water from a bottom layer of the water source in which the installation is located. With such a bottom layer, the water quality is generally significantly less affected by weather conditions and seasonal fluctuations in said water parameters than with a surface layer of the same body of water. As a result, the water quality in the bottom layer is significantly more stable than in the surface layer. Thereby, relatively stable operating conditions can also be achieved for such a submerged water treatment installation.

With cross-flow filtration in such a submerged water treatment installation, you also do not need to use pumping capacity to pump up and process water from an underlying water source. This is in stark contrast to cross-flow filtration on a surface installation, where typically 40-80% of the pump capacity is used to pump up and process water that is eventually dumped as an unwanted retentate (cf. the above discussion of this). Thereby, the pumping capacity in the submerged water treatment installation can be limited to only the filtering process itself in the water treatment installation and thereby be significantly reduced in relation to the corresponding pumping capacity on a surface installation.

The water treatment installation in question can also be designed as a relatively compact and mobile unit that can be installed or moved at relatively short notice. Such an installation can be very useful for emergency production of fresh water, for example for drinking water purposes, in areas where fresh water is not available for one reason or another. It could, for example, be about an urgent need for fresh water in areas that have been exposed to major natural disasters, or in connection with certain military operations.

Furthermore, the water treatment installation can comprise an assembly of several containers, where each container can be provided with at least one semi-permeable filtration membrane. Each container can also comprise several filters/membranes of known types, and of different types, designs, designs and/or material types, as described under known technology above.

The water treatment installation can include a suitable number of containers and/or filtration membranes that are adapted to the relevant application and needs. The containers and/or filtration membranes can also be assembled in series and/or in parallel, where the assembly(s) are also adapted to the relevant application and needs. Thus, the water treatment installation can be designed for filtering a number of unwanted components from the supply water.

Furthermore, the water treatment installation must be provided with various connections, seals, valves, pipes, regulating equipment, etc. to the extent that this is necessary in the current situation. In addition, equipment included in the water treatment installation must be designed and adapted to be able to be operated at the relevant water depth in the body of water in which the installation is to be submerged. However, this is considered professional and will therefore not be discussed in more detail here.

According to a first embodiment variant of the water treatment installation, said container can be provided with at least one semi-permeable straight-flow membrane ("dead-end membrane"), or straight-flow filter, arranged for retention, on the upstream side of the membrane, of a retentate comprising a first component consisting of at least one of solid particles, bacteria and viruses suspended in the supply water; - where the direct flow membrane is arranged for the flow through, to the downstream side of the membrane, of a permeate comprising a second component which consists of water filtered from the supply water and containing a smaller concentration of at least one of suspended solid particles, bacteria and viruses, the filtered water constituting said product water.

For this first variant, it concerns conventional straight-flow filtration ("dead-end filtration") of the supply water under water. This type of filtration of the supply water is best suited for conventional coarse filtration to fine filtration of inorganic and organic solid particles suspended in the supply water, for example sand, silt, clay, soil, zooplankton, phytoplankton, and even various types of bacteria and viruses.

The pores or opening in such a direct flow membrane (or direct flow filter) will usually be blocked relatively quickly by a filter cake (retentate) on the upstream side of the membrane. For this reason, the direct current membrane can be designed as an elongated strip, where at least one end of the strip is wound on a rotatable coil core, and where part of the strip is stretched out from the coil core to thereby provide a usable part of the membrane. The coil core can be connected to a turning motor for turning the coil core and feeding out an unused and clean usable part of the membrane, while the opposite end of the strip can be connected to a feed device for simultaneously feeding a used and soiled usable part of the membrane. As one example, such a conveyance device can consist of one or more conveyor belts or similar devices. As another example, the advance device can be constituted by a further rotatable coil core on which the opposite end of the membrane strip is wound, and which can also be connected to a further turning motor for turning the further coil core. Thus, a strip-shaped direct current membrane will act almost like an endless band. Such a strip solution will also require that the container is arranged to be able to provide a pressure-tight connection around the usable part of the membrane when filtering supply water.

As an alternative or addition, a direct flow membrane can be arranged as a removable cartridge. Thereby, a soiled membrane in the cassette can be replaced via an intervention operation carried out from, for example, a surface vessel. Alternatively, the cassette can be pushed away from its position of use in the water treatment installation and replaced with another cassette containing a clean and unused direct flow membrane. The latter design assumes that the installation is designed to be able to replace the cassette if necessary. This can be done by means of a magazine or a carousel provided with at least one unused cassette which can be brought into use position in the water treatment installation by means of an associated advance arrangement, for example via a displacement device and a rail arrangement or the like.

Furthermore, said at least one conveying means may comprise a feed pump arranged upstream of the receiving chamber and connected flow-wise with the inlet of the receiving chamber. Thereby, the supply water can be pressurized before it is fed into at least one container of the water treatment installation. As an alternative or addition, the at least one transport means may comprise an ejector pump arranged downstream of the permeate chamber and connected flow-wise with the permeate chamber's outlet. Such an ejector pump will suck the permeate out of the permeate chamber.

According to a second embodiment of the water treatment installation, said container can be provided with at least one semi-permeable cross-flow membrane ("cross-flow membrane") arranged for retention, on the upstream side of the membrane, of a retentate comprising at least one first component; - where the cross-flow membrane is arranged for flow, to the downstream side of the membrane, of a permeate comprising a second component which is made up of water filtered from the supply water and containing a smaller concentration of said first component, the filtered water constituting said product water; and - where the water treatment installation also comprises a means of transport arranged for further transport of the retentate out of the receiving chamber via an outlet therein.

For this second embodiment, it concerns cross-flow filtration under water. The operation of cross-flow filtering is described in more detail under known technology above. Cross-flow filtration is well suited for the removal of smaller and often very small components in the supply water.

Also with such cross-flow filtration, said first component can comprise at least one of solid particles, bacteria and viruses suspended in the supply water. Membranes designed for so-called microfiltration are suitable for removing solid particles and various bacteria suspended in the supply water, while membranes designed for so-called ultrafiltration can also remove various viruses suspended in the supply water.

As an addition or alternative, said first component may comprise at least one type of multivalent ions dissolved in the supply water. These dissolved, multivalent ions may comprise sulfate ions, for example calcium sulfate ions, magnesium sulfate ions, strontium sulfate ions and/or barium sulfate ions. Such sulfate ions can i.a. form very problematic deposits in pipes and equipment that they come into contact with, for example on well-related and/or process-related equipment. Membranes designed for so-called nanofiltration are suitable for the removal of multivalent ions in addition to the removal of the above-mentioned, coarser components.

As a further addition or alternative, said first component may comprise at least one type of monovalent ions dissolved in the supply water. These dissolved, monovalent ions may include chloride ions, for example sodium chloride ions and potassium chloride ions. Such chloride ions can i.a. form salt deposits and cause extensive corrosion damage to well equipment, process equipment and pipe connections. The presence of a relatively small amount of dissolved chloride ions in water will also make the water unsuitable for drinking water purposes. Membranes designed for so-called reverse osmosis filtration are suitable for the removal of multivalent ions in addition to the removal of the above-mentioned coarser components.

Thus, said first component can include components selected from a group consisting of: - at least one of solid particles, bacteria and viruses suspended in the supply water;

- at least one type of multivalent ions dissolved in the supply water; and

- at least one type of monovalent ions dissolved in the supply water.

In case of cross-flow filtration, the receiving chamber's outlet can also be connected to an energy recovery device for recovering pressure energy in the retentate that exits from the receiving chamber. Thus, a so-called energy recovery turbine ("energy recovery turbine") and/or a so-called pressure exchanger ("pressure exchanger") can be used.

All of the membranes that have been discussed so far are suitable for removing solid-containing and/or liquid-containing components from the wastewater.

In the case of straight-flow filtration and/or cross-flow filtration, said at least one container in the water treatment installation can also be provided with at least one semi-permeable cross-flow membrane ("cross-flow membrane") arranged for the flow through, to the downstream side of the membrane, of a permeate comprising a second component which consists of at least one type of gas dissolved in the supply water; - where the cross-flow membrane is arranged for the retention, on the upstream side of the membrane, of a retentate comprising a first component which is made up of water containing a smaller concentration of dissolved gas, the gas-poor retentate water constituting said product water; and - where the water treatment installation also comprises a means of transport arranged for further transport of the retentate out of the receiving chamber via an outlet therein.

When removing gas-dissolved water, the at least one semi-permeable cross-flow membrane can advantageously comprise a hollow fiber membrane, which is typically used for this purpose. The dissolved gas may for example include oxygen and/or carbon dioxide. The presence of oxygen in the supply water can, among other things, contribute to corrosion damage in well equipment, process equipment and associated pipe connections. Worse, perhaps, is that the oxygen in the water keeps various aerobic bacteria alive, which cause fouling on various equipment and pipe connections that the bacteria come into contact with. Such bacteria can also be very harmful to organisms that drink the water. By removing the oxygen from the water, the basis of life for aerobic bacteria is also removed.

In such gas pumping, said at least one conveying means can comprise a pumping means which is flow-wise connected to the permeate chamber's outlet for transporting said gas permeate out of the permeate chamber. This pumping means can, for example, comprise a vacuum pump.

As an alternative or addition, the permeate chamber can also be provided with an inlet for the introduction of a carrier gas for the gas permeate. This carrier gas can, for example, comprise nitrogen.

As another alternative, the permeate chamber can also be provided with an inlet; - where said at least one conveying means comprises a gas extraction device including a pumping means and an associated flow circuit which is flow-wise connected to the inlet and outlet of the permeate chamber;

- where the flow circuit contains a carrier gas for the gas permeate; and

- where the pumping means is designed to transport the carrier gas and the gas permeate out of the permeate chamber. This carrier gas can, for example, comprise nitrogen.

In the case of cross-flow filtration, said at least one conveying means can comprise a feed pump arranged upstream of the receiving chamber and connected flow-wise

with the receiver chamber inlet. If the water treatment installation includes several containers and several cross-flow membranes arranged for the removal of different types of unwanted components, the water treatment installation may therefore include several feed pumps. Thereby, each feed pump, in combination with hydrostatic pressure, can deliver

supply water at an excess pressure that is suitable for operating the relevant cross-flow membrane connected to the feed pump. Thereby, the individual cross-flow membrane can be supplied with sufficient transmembrane pressure ("transmembraneous pressure") so that the associated permeate can flow through the membrane.

Furthermore, a cross-flow membrane, or an assembly of cross-flow membranes, can be arranged as a detachable cassette. This assumes that the cross-flow membrane, or the assembly of cross-flow membranes, has a design suitable for being arranged as a cassette. Furthermore, this removable cassette can be assigned to the water treatment installation and handled in the same way as described for the cassette mentioned above in connection with the mention of a direct flow membrane.

In the following, further features are specified that apply when the water treatment installation is designed for straight-flow filtration and/or cross-flow filtration.

Firstly, said filtration membrane in the water treatment installation can be flow-wise connected with a backflow device designed to be able to flow back permeate from the permeate chamber through the membrane to remove unwanted coating on the upstream side of the membrane. Such a backflow device can ensure that a partial flow of the permeate periodically flows back through the membrane to clean it.

As an alternative or addition, the downstream side of said filtration membrane can be flow-wise connected with a backflow device designed to be able to flow back a cleaning fluid through the membrane to remove unwanted coating on the upstream side of the membrane. Such a backflow device can ensure that the cleaning fluid periodically flows back through the membrane to clean it.

As a further alternative or addition, the upstream side of said filtration membrane can be flow-wise connected with a supply device designed to be able to supply the membrane with a cleaning fluid for removing unwanted coating on the upstream side of the membrane. Such a supply device can ensure that the cleaning fluid periodically flows towards the upstream side of the membrane for cleaning it.

As a further alternative or addition, the upstream side of said filtration membrane can be flow-wise connected with a cleaning-in-place ("cleaning-in-place") facility for removing unwanted coating on the upstream side of the membrane. Such cleaning-on-site facilities constitute known technology and will not be discussed in more detail here.

As a further alternative or addition, the water treatment installation can be located on a bottom underlying said body of water, for example on a seabed or on the bottom of a lake, river or delta.

Furthermore, said receiving location for product water can be located on land.

Thus, the receiving location can for example be a well on land, where said at least one transfer pump can comprise an injection pump flow-wise connected to the well for injection of the desired product water into the well. The injection pump can be designed for remote-controlled operation.

Alternatively, said receiving location for product water can be located offshore.

Thus, the receiving site can for example be an underwater well offshore, where said at least one transfer pump can comprise an injection pump flow-measuringly connected to the underwater well for injection of the desired product water into the underwater well. The injection pump can be designed for remote-controlled operation.

When used offshore, the receiving location can be a surface installation, for example a platform or another type of surface structure. Alternatively, the receiving location may be a floating vessel, for example a floating rig, a ship or a military vessel.

Furthermore, the water treatment installation can be arranged for remote-controlled operation via at least one wired connection for the transmission of drive power and control signals to the installation. Thus, the water treatment installation can be cable-connected to a remote facility or device for supplying drive power and control signals to the installation, for example a facility on land or a platform offshore.

As an alternative, the water treatment installation can be arranged for remotely controlled operation via at least one wired connection arranged for the transmission of driving power to the installation, and via at least one wireless connection for the transmission of control signals to the installation. Thus, the water treatment installation can be connected by cable to a remote plant or unit for supplying motive power to the installation, while control signals are transmitted wirelessly to the installation from, for example, a floating vessel in the vicinity of the installation.

As a further alternative, the water treatment installation can be arranged for remotely controlled operation via at least one wireless connection for transmitting control signals to the installation. In addition, the water treatment installation is provided with at least one energy source for the independent provision of driving power for the installation. Such an energy source may comprise at least one battery. Here, too, control signals can be transmitted wirelessly to the installation from, for example, a floating vessel in the vicinity of the installation.

Furthermore, the upstream side of the water treatment installation can be flow-wise connected to an underwater device for removing, without filtration, unwanted solid particles from the supply water. An example of such an underwater device is described in WO 2007/035106 Al. This underwater device comprises a closed space which is designed to allow the supply water to be led directly into a lower part of the closed space, and which is also designed to be able to allow treated water to be led out of an upper part of the closed space. This closed space also has a cross-sectional area which is adapted to allow the water to flow from the lower part to the upper part at a flow rate sufficiently low for unwanted solid particles to fall out of the water by gravity. Furthermore, this closed space can be designed as a container or module which is placed on, for example, an ocean floor or the like.

Furthermore, the relevant water treatment installation, and preferably the upstream side of the installation, can be flow-wise connected with at least one device for chemical treatment of the supply water. Similar to the water treatment installation in question, this device for chemical treatment of the supply water can also be submerged in the aforementioned body of water. An example of such a chemical treatment device is described in WO 2004/090284 Al. This patent publication deals with a method and an apparatus for underwater chemical treatment of injection water, where a module-based underwater apparatus is used which is connected to an injection well for injecting the water. The apparatus contains at least one container which is provided with at least one type of water-soluble solid chemical. The container can, for example, be replaced using a remotely operated underwater vehicle ("ROV"). The water is then brought into contact with the solid chemical, so that it gradually dissolves and mixes with the water. The pre-treated water is then injected into a reservoir connected to the well. Chemical treatment and water injection can thereby be carried out without having to use an immediately overlying surface installation or vessel. The water-soluble solid chemical may include chlorine and/or biocide, but also various other chemicals, such as the aforementioned oxygen scavengers, corrosion inhibitors and deposit inhibitors. This chemical treatment device can be a separate unit or be incorporated into the above-mentioned underwater device for the removal, without filtration, of unwanted solid particles from the supply water.

As an alternative or addition, the water treatment installation, and preferably the upstream side of the installation, can be flow-wise connected with at least one device for destroying organic matter in the supply water. Similar to the water treatment installation in question, this device for destroying organic material in the supply water can also be submerged in the aforementioned body of water. An example of such a destruction device is described in WO 2007/073198 Al. This patent publication deals with a method and a device for destroying organic material in injection water for an injection well. The device uses at least one electrochemical cell with associated operating means for in situ electrolytic production from water of at least short-lived, free hydroxyl radicals. With the aid of the operating means, the electrochemical cell is arranged to be able to pass the injection water through it as starting material for the in situ production of at least the aforementioned free hydroxyl radicals from the injection water. Such free hydroxyl radicals will immediately destroy organic material with which they come into contact in the injection water. This destruction device can be made up of a separate unit or be incorporated into the above-mentioned underwater device for removing, without filtering, unwanted solid particles from the supply water. As a further alternative, the destruction device can be combined with the above-mentioned chemical treatment device.

According to a second aspect of the invention, a method for removing at least one unwanted component from water is provided, where the method makes use of the following equipment: - at least one container provided with at least one semi-permeable filtration membrane that divides the container into at least one upstream receiving chamber and at least one downstream permeate chamber; wherein the filtration membrane is arranged for retention, on the upstream side of the membrane, of a retentate comprising at least one first component from a supply water; and where the filtration membrane is arranged for the flow through, to the downstream side of the membrane, of a permeate comprising at least one second component from the supply water; and - at least one conveying means flow-wise connected to an inlet in the receiving chamber and an outlet in the permeate chamber. The peculiarity of the method is that it comprises the following steps: - assembling the container and the at least one means of transport as a water treatment installation; - to prepare the water treatment installation for remotely controlled underwater operation; - submerging the water treatment installation into a body of water; - placing the inlet of the receiving chamber in flow-wise connection with the body of water in which the water treatment installation is located; - in a remote-controlled manner, and with the help of said at least one means of transport, to introduce the supply water into the receiving chamber via its inlet and to transport said permeate of the supply water out of the permeate chamber via its outlet; - in a flow-wise manner, to connect an outlet for the desired product water in at least one

container with at least one transfer pump; and

- using said transfer pump, to transport said product water further to a receiving location via at least one transfer line.

The same comments that are mentioned in connection with the description of the water treatment installation according to the first aspect of the invention also apply to the method according to this second aspect of the invention.

According to a first embodiment variant, the method can also comprise a step of supplying said container with at least one semipermeable straight-flow membrane (dead-end membrane) which is arranged for: (a) retention, on the upstream side of the membrane, of a retentate comprising a first component which consists of at least one of solid particles, bacteria and viruses suspended in the supply water; and (b) flow through, to the downstream side of the membrane, a permeate comprising a second component which is constituted by water filtered from the feed water and containing a smaller concentration of at least one of suspended solid particles, bacteria and viruses, the filtered water constituting said product water.

In the case of direct flow filtering, the method may also include the following steps:

- shaping the direct flow membrane as an elongated strip; - winding one end of the strip on a rotatable coil core; - stretching the strip out from the coil core to thereby provide a usable part of the membrane; - connecting said coil core with a turning motor for turning the coil core and feeding out an unused and clean usable part of the membrane; and - to connect the opposite end of the strip with a conveying device for simultaneously conveying a used and soiled part of the membrane.

As an alternative or addition, a direct flow membrane can be arranged as a detachable cassette, for example as described in connection with the above mentioned water treatment installation.

Furthermore, said at least one means of conveyance may comprise a feed pump which is arranged upstream of the receiving chamber and connected flow-wise to the inlet of the receiving chamber. Thereby, the supply water can be pressurized before it is fed into at least one container of the water treatment installation. As an alternative or addition, the at least one means of conveyance may comprise an ejector pump which is arranged downstream of the permeate chamber and is flow-wise connected to the permeate chamber's outlet, so that the ejector pump can suck the permeate out of the permeate chamber.

According to a second embodiment, the method can also include the following steps:

- to provide said container with at least one semi-permeable cross-flow membrane (cross-flow membrane) which is arranged for: (a) retention, on the upstream side of the membrane, of a retentate comprising at least one first component; and (b) flow through, to the downstream side of the membrane, a permeate comprising a second component which is constituted by water filtered from the feed water and containing a smaller concentration of said first component, the filtered water constituting said product water; and - by means of a transport means associated with the water treatment installation, to transport the retentate further out of the receiving chamber via an outlet therein.

For this second embodiment, it concerns cross-flow filtration under water. The operation of cross-flow filtering is described in more detail under known technology above.

In connection with this method, said first component may comprise at least one of solid particles, bacteria and viruses suspended in the supply water. So-called microfiltration and ultrafiltration are suitable for this purpose.

As an addition or alternative, said first component may comprise at least one type of multivalent ions dissolved in the supply water. These dissolved, multivalent ions may comprise sulfate ions, for example calcium sulfate ions, magnesium sulfate ions, strontium sulfate ions and/or barium sulfate ions. So-called nanofiltration is suitable for this purpose.

As a further addition or alternative, said first component may comprise at least one type of monovalent ions dissolved in the supply water. These dissolved, monovalent ions may include chloride ions, for example sodium chloride ions and potassium chloride ions. So-called reverse osmosis filtration is suitable for this purpose.

Thus, said first component can include components selected from a group consisting of: - at least one of solid particles, bacteria and viruses suspended in the supply water;

- at least one type of multivalent ions dissolved in the supply water; and

- at least one type of monovalent ions dissolved in the supply water.

In the case of cross-flow filtration, the method can also include a step of connecting the outlet of the receiving chamber with an energy recovery device for recovering pressure energy in the retentate that exits from the receiving chamber. For this purpose, and as mentioned above, an energy recovery turbine and/or a pressure exchanger can be used.

In direct-flow filtration and/or cross-flow filtration, the method can also include the following steps: - supplying said container with at least one semi-permeable cross-flow membrane ("cross-flow membrane"), for example a hollow fiber membrane, which is designed for: (a) flow through, to the downstream side of the membrane, of a permeate comprising a second component which consists of at least one type of gas dissolved in the supply water, for example oxygen and/or carbon dioxide; and (b) retaining, on the upstream side of the membrane, a retentate comprising a first component consisting of water containing a smaller concentration of dissolved gas, the gas-poor retentate water constituting said product water; and - by means of a transport means associated with the water treatment installation, to transport the retentate further out of the receiving chamber via an outlet therein.

In such gas removal, the method can also include a step of transporting said gas permeate out of the permeate chamber by means of a conveying means comprising a pumping means, for example a vacuum pump, which is flow-wise connected to the permeate chamber's outlet.

As an alternative or addition, the method may also comprise a step of introducing a carrier gas, for example nitrogen, for the gas permeate into the permeate chamber via an inlet in the permeate chamber.

Alternatively, the method may also include the following steps:

- providing the permeate chamber with an inlet; - using a transport means for the permeate comprising a gas extraction device which includes a pumping means and an associated flow circuit containing a carrier gas, for example nitrogen, for the gas permeate; - in a flow-wise manner, to connect the flow circuit with the permeate chamber inlet and outlet; and - using said pumping means, to transport the carrier gas and the gas permeate out of the permeate chamber.

In the case of cross-flow filtration, a feed pump for the supply water can also be arranged upstream of the receiver chamber and connected flow-wise to the inlet of the receiver chamber. If the water treatment installation comprises several containers and several cross-flow membranes arranged for the removal of different types of unwanted components, several feed pumps can be arranged in the water treatment installation. Thereby, each feed pump can deliver supply water at an excess pressure that is suitable for operation of the cross-flow membrane in question, so that the individual cross-flow membrane is supplied with sufficient transmembrane pressure ("transmembraneous pressure") for the associated permeate to be able to flow through the membrane.

Furthermore, a cross-flow membrane, or an assembly of cross-flow membranes, can also be arranged as a detachable cassette, for example as described in connection with the above-mentioned water treatment installation. This assumes that the cross-flow membrane, or the assembly of cross-flow membranes, has a design suitable for being arranged as a cassette. Furthermore, this removable cassette can be assigned to the water treatment installation and handled in the same way as described for the cassette mentioned above in connection with the mention of a direct flow membrane.

In the following, further features are specified that apply when the method is used in connection with direct flow filtering and/or cross flow filtering.

First, the method may also include the following steps:

- in a flow-wise manner, to connect the downstream side of said filtration membrane with a return flow device which is in hydraulic connection with permeate in the permeate chamber; and - by means of the backflow device, to backflow permeate from the permeate chamber through the membrane to remove unwanted coating on the upstream side of the membrane. Thereby, a partial flow of the permeate can periodically flow back through the membrane for cleaning it.

As an alternative or addition, the method may also include the following steps:

- in a flow-wise manner, to connect the downstream side of said filtration membrane with a return flow device which is in hydraulic connection with a cleaning fluid; and - by means of the backflow device, to flow back the cleaning fluid through the membrane to remove unwanted coating on the upstream side of the membrane. Thereby, the cleaning fluid can periodically flow back through the membrane to clean it.

As a further alternative or addition, the method may also comprise the following steps: - in a flow-wise manner, to connect the upstream side of said membrane with a supply device which is in hydraulic connection with a cleaning fluid; and - by means of the supply device, to supply the cleaning fluid to the membrane in order to remove unwanted coating on the upstream side of the membrane. Thereby, the cleaning fluid can periodically flow towards the upstream side of the membrane to clean it.

As a further alternative or addition, the method may also comprise a step of connecting, in a flow-wise manner, the upstream side of said membrane with a cleaning-in-place ("cleaning-in-place") facility to remove unwanted coating on the -current side of the membrane.

As a further alternative or addition, the water treatment installation can be placed on a bottom underlying said body of water, for example on a seabed or on the bottom of a lake, river or delta.

Furthermore, said receiving location for product water can be located on land.

Thus, the receiving location can for example be a well on land, and said at least one transfer pump can comprise an injection pump, where said injection pump is connected, in a flow-wise manner, to the well in order to be able to inject the desired product water into the well. The injection pump can be set up for remote operation.

Alternatively, said receiving location for product water can be located offshore.

Thus, the receiving location can for example be an underwater well, and said at least one transfer pump can comprise an injection pump, where the injection pump is connected, in a flow-wise manner, to the underwater well in order to be able to inject the desired product water into the underwater well. The injection pump can be set up for remote operation.

When used offshore, the receiving location can be a surface installation, for example a platform or another type of surface structure. Alternatively, the receiving location may be a floating vessel, for example a floating rig, a ship or a military vessel.

Furthermore, the water treatment installation can be operated remotely via at least one wired connection for the transmission of drive power and control signals to the installation. Thus, the water treatment installation can be connected by cable to a remote facility or unit for supplying drive power and control signals to the installation, for example a facility on land or a platform offshore.

As an alternative, the water treatment installation can be operated remotely via at least one wired connection for transmitting drive power to the installation, and via at least one wireless connection for transmitting control signals to the installation. Thus, the water treatment installation can be connected by cable to a remote plant or unit for supplying motive power to the installation, while control signals are transmitted wirelessly to the installation from, for example, a floating vessel in the vicinity of the installation.

As a further alternative, the water treatment installation can be operated remotely via at least one wireless connection for transmitting control signals to the installation, while the water treatment installation receives independent driving power from at least one energy source associated with the installation. Said energy source may comprise at least one battery. Here, too, control signals can be transmitted wirelessly to the installation from, for example, a floating vessel in the vicinity of the installation.

Furthermore, the method may comprise a step of connecting, in a flow-wise manner, the upstream side of the water treatment installation with an underwater device for removing, without filtration, unwanted solid particles from the supply water; see, for example, patent publication WO 2007/035106 Al.

Furthermore, the method can also include a step of connecting, in a flow-wise manner, the water treatment installation (and preferably the upstream side thereof) with at least one device for chemical treatment of the supply water. Like the water treatment installation, the device for chemical treatment of the supply water can also be immersed in the said body of water; see, for example, patent publication WO 2004/090284 Al. This chemical treatment device can be made up of a separate unit or incorporated into the above-mentioned underwater device for the removal, without filtration, of unwanted solid particles from the supply water.

As an alternative or addition, the method may comprise a step of connecting, in a flow-wise manner, the water treatment installation (and preferably the upstream side thereof) with at least one device for the destruction of organic matter in the supply water. Like the water treatment installation, the device for the destruction of organic matter in the supply water can also be immersed in the said body of water; see, for example, patent publication WO 2007/073198 Al. This destruction device can be made up of a separate unit or incorporated into the above-mentioned underwater device for removing, without filtering, unwanted solid particles from the supply water. As a further alternative, the destruction device can be combined with the above-mentioned chemical treatment device.

Finally, and according to a third aspect of the invention, an application of a water treatment installation according to the above-mentioned first aspect of the invention is provided for the removal, under water, of at least one undesirable component from supply water fed into the water treatment installation.

In what follows, a non-limiting embodiment example of a water treatment installation according to the invention will now be shown.

Brief mention of the teqninqsfiquren

Figure 1 shows very schematically an example of a water treatment installation according to the invention, where the installation is connected i.a. with an injection pump and a nearby subsea injection well. The figure shows only the main equipment, which is very marked with regard to relative dimensions, and which is indicated with a very simplified design and wealth of detail.

Description of the embodiment of the invention

Figure 1 shows an embodiment of a water treatment installation 2 according to the invention placed on a seabed 4 underlying salty seawater 6 and a sea surface 8.

On its downstream side, the installation 2 is connected to an injection pump 10 which is flow-wise connected to a wellhead 12 for a water injection well 14. By means of the injection pump 10, finished product water 16 is pumped from the installation 2 down into the well 14 to then be led through well perforations 18 and further into an underground petroleum reservoir 20 to increase the recovery rate from the reservoir 20. The flow direction of the product water 16 is shown with downstream arrows in Figure 1.

On its upstream side, and seen in the downstream direction, the installation 2 is connected to a primary water treatment module 22, a feed pump 24 and a secondary water treatment module 26, respectively.

With the aid of the feed pump 24, supply water, which here is in the form of salt seawater 6, is fed directly into the primary water treatment module 22, then via the secondary water treatment module 26 and further into the relevant water treatment installation 2 through an inlet 28. The direction of flow for the seawater 6 is also shown by downstream arrows in Figure 1.

In this embodiment, an initial coarse filtration of the seawater 6 can be carried out in the primary water treatment module 22, where larger organic and inorganic solid particles are removed from the seawater 6 using conventional filters made of wire cloth or the like. As an alternative or addition (not shown in Figure 1), the primary water treatment module 22 can be constituted by an underwater device for removing, without filtering, unwanted solid particles from the seawater 6, such as the device described in WO 2007/035106 Al (mentioned above).

The coarsely filtered and/or gravitationally settled water from the primary water treatment module 22 is then fed on into the secondary water treatment module 26, which here comprises a device for chemical treatment of the seawater 6. In this embodiment, the chemical treatment device is of a type as described in WO 2004/090284 Al (mentioned above). This chemical treatment device comprises several replaceable containers (not shown in Figure 1) each of which is provided with one type of water-soluble solid chemical. In this case, the chemical treatment device is supplied with chlorine and biocide to kill bacteria and the like in the seawater, as well as oxygen scavengers, corrosion inhibitors and deposit inhibitors. When flowing through the secondary water treatment module 26, the seawater 6 is brought into contact with the respective soluble solid chemicals, so that these are gradually dissolved and mixed with the seawater 6.

As an alternative (not shown in Figure 1), the secondary water treatment module 26 can be constituted by an assembly of said underwater device for removing, without filtration, unwanted solid particles in the seawater (cf. WO 2007/035106 Al) and said chemical treatment device (cf. WO 2004/090284 Al).

As a further alternative or addition (not shown in Figure 1), the water treatment installation 2 can be connected to a device for the destruction of organic material in the sea water 6, such as the destruction device described in WO 2007/073198 Al (mentioned above). Such a destruction device can be incorporated into the primary water treatment module 22 or the secondary water treatment module 26, and possibly together with an underwater device for removing, without filtering, unwanted solid particles from the seawater 6 (cf. WO 2007/035106 Al).

The water treatment installation 2 comprises at least one container 30 provided with at least one semi-permeable cross-flow membrane 32 ("cross-flow membrane"). For the sake of simplicity, Figure 1 shows only one container 30 and one cross-flow membrane 32. In practical embodiments, however, the water treatment installation 2 can include several containers 30 and several cross-flow membranes 32 which are preferably arranged for the removal of different

unwanted components in the seawater 6 (cf. the above discussion of this).

Said cross-flow membrane 32 divides the container 30 into an upstream receiver chamber 34 which is provided with said inlet 28 and an outlet 36, and a downstream permeate chamber 38 which is provided with an outlet 40.

Furthermore, the cross-flow membrane 32 is arranged for the retention, on the upstream side of the membrane 32, of a retentate 42 which here comprises bacteria as well as multivalent and monovalent ions dissolved in the seawater 6, i.e. mainly dissolved sulfates and salts. It is particularly desirable to remove such components from the seawater 6 before it is pumped down into the injection well 14 for water flooding of the reservoir 20. The cross-flow membrane 32 is also arranged for the flow through, to the downstream side of the membrane 32, of a permeate comprising water filtered from the seawater 6 and containing a significantly lower concentration of said bacteria, multivalent ions and monovalent ions. It is this permeate that makes up said product water 16, and which in this design example can be classified as fresh water.

By means of the aforementioned feed pump 24, pressurized seawater 6, which has already been pretreated in the primary water treatment module 22 and in the secondary water treatment module 26, is pumped into the receiving chamber 34 via its inlet 28. Here, cross-flow filtration is carried out by the pressurized seawater 6 being led towards and extends the cross-flow membrane 32. Thereby, said permeate 16 (product water) is pressed through the membrane 32, into the permeate chamber 38 and further out via its outlet 40. Said retentate 42, which here consists of a relatively large proportion of seawater 6 containing a very high concentration of said bacteria, multivalent ions and monovalent ions, on the other hand, are led out of the receiving chamber 34 via its outlet 36. Thereby, two branch streams exit from the container 30, of which a branch stream with retentate 42 and a branch stream with permeate/product water 16. Flow direction for the retentate 42 and the permeate 16 are also shown with downstream arrows in Figure 1.

This design example can just as well be adapted for the transport of product water 16 to a receiving location on land, for example an injection well or a fresh water reception on land. In that case, at least one transfer line must be stretched between the water treatment installation 2 and the receiving location on land, and the injection pump 10 must possibly be replaced with at least one transfer pump of a suitable type.

Claims (19)

1. Water treatment installation (2) for the removal of at least one unwanted component from water, where the water treatment installation (2) comprises: - at least one container (30) provided with at least one semi-permeable filtration membrane that divides the container (30) into at least one upstream receiving chamber (34) and at least one downstream permeate chamber (38); where the filtering membrane is arranged for the retention, on the upstream side of the membrane, of a retentate (42) comprising at least one first component from a supply water (6); and where the filtration membrane is arranged for the flow through, to the downstream side of the membrane, of a permeate (16) comprising at least one second component from the supply water (6); and - at least one conveying means flow-wise connected to an inlet (28) in the receiving chamber (34) for transporting supply water (6) to the receiving chamber (34), and for transporting said permeate (16) of the supply water (6) out of the permeate chamber (38) ) via an outlet (40) in the permeate chamber (38), characterized in that the water treatment installation (2) is designed for remotely controlled operation under water; - that the water treatment installation (2) is immersed in a body of water (6); - that the inlet (28) of the receiving chamber (34) is flow-wise connected to the body of water (6) in which the water treatment installation (2) is located; and - that an outlet (36; 40) for the desired product water (42; 16) in the at least one container (30) is flow-wise connected to at least one transfer pump for further transport of product water (42; 16) to a receiving location via at least one transfer - wire. 2. Water treatment installation (2) according to claim 1, characterized in that said container (30) is provided with at least one semi-permeable direct-flow membrane arranged for the retention, on the upstream side of the membrane, of a retentate (42) comprising a first component which consists of at least one of solid particles, bacteria and viruses suspended in the supply water (6); and - that the direct flow membrane is arranged for the flow through, to the downstream side of the membrane, of a permeate (16) comprising a second component which consists of water (16) filtered from the supply water (6) and containing a smaller concentration of at least one of suspended solid particles, bacteria and viruses, the filtered water (16) making up said product water. 3. Water treatment installation (2) according to claim 1 or 2, characterized in that said container (30) is provided with at least one semi-permeable cross-flow membrane (32) arranged for retention, on the upstream side of the membrane (32), of a retentate (42) comprising at least one first component; - that the cross-flow membrane (32) is arranged for the flow through, to the downstream side of the membrane (32), of a permeate (16) comprising a second component which consists of water (16) filtered from the supply water (6) and containing a smaller concentration of said first component, the filtered water (16) constituting said product water; and - that the water treatment installation (2) also comprises a transport means (24) arranged for further transport of the retentate (42) out of the receiving chamber (34) via an outlet (36) therein. 4. Water treatment installation (2) according to claim 3, characterized in that said first component comprises components selected from a group consisting of: - at least one of solid particles, bacteria and viruses suspended in the supply water (6); - at least one type of multivalent ions dissolved in the supply water (6); and - at least one type of monovalent ions dissolved in the supply water (6). 5. Water treatment installation (2) according to any one of claims 1-4, characterized in that said container (30) is provided with at least one semi-permeable cross-flow membrane (32) arranged for flow through, to the downstream side of the membrane (32), of a permeate (16) comprising a second component consisting of at least one type of gas dissolved in the supply water (6); and - that the cross-flow membrane (32) is arranged for the retention, on the upstream side of the membrane (32), of a retentate (42) comprising a first component which consists of water (42) containing a smaller concentration of dissolved gas, the gas-poor retentate water (42) constitutes said product water; and - that the water treatment installation (2) also comprises a transport means (24) arranged for further transport of the retentate (42) out of the receiving chamber (34) via an outlet (36) therein. 6. Water treatment installation (2) according to any one of claims 1-5, characterized in that said receiving location for product water (42; 16) is located on land. 7. Water treatment installation (2) according to any one of claims 1-5, characterized in that the receiving location is an underwater well (14); and - that said at least one transfer pump comprises an injection pump (10) flow-wise connected to the underwater well (14) for injection of the desired product water (16) into the underwater well. 8. Water treatment installation (2) according to any one of claims 1-7, characterized in that the water treatment installation (2) is flow-wise connected with at least one device (26) for chemical treatment of the supply water (6). 9. Water treatment installation (2) according to any one of claims 1-8, characterized in that the water treatment installation (2) is flow-wise connected to at least one device for destroying organic material in the supply water (6). 10. Method for removing at least one unwanted component from water, where the method uses the following equipment: - at least one container (30) provided with at least one semi-permeable filtration membrane that divides the container (30) into at least one upstream receiving chamber (34) and at least one downstream permeate chamber (38); where the filtering membrane is arranged for the retention, on the upstream side of the membrane, of a retentate (42) comprising at least one first component from a supply water (6); and where the filtration membrane is arranged for the flow through, to the downstream side of the membrane, of a permeate (16) comprising at least one second component from the supply water (6); and - at least one means of transport connected in terms of flow to an inlet (28) in the receiving chamber (34) and an outlet (40) in the permeate chamber (38), characterized in that the method comprises the following steps: - to assemble the container (30) and the at least one means of transport which a water treatment installation (2); - to prepare the water treatment installation (2) for remotely controlled underwater operation; - submerging the water treatment installation (2) into a body of water (6); - placing the receiving chamber (34)'s inlet (28) in flow-related connection with the body of water (6) in which the water treatment installation (2) is located; - in a remote-controlled manner, and with the help of said at least one means of transport, to introduce the supply water (6) into the receiving chamber (34) via its inlet (28) and to transport said permeate (16) of the supply water (6) out of the permeate chamber (38) ) via its outlet (40); - in a flow-wise manner, to connect an outlet (36; 40) for the desired product water (42; 16) in the at least one container (30) with at least one transfer pump; and - using said transfer pump, to transport said product water (42; 16) further to a receiving location via at least one transfer line. 11. Method according to claim 10, characterized in that the method also comprises a step of supplying said container (30) with at least one semi-permeable direct flow membrane which is arranged for: (a) retention, on the upstream side of the membrane, of a retentate (42) comprising a first component consisting of at least one of solid particles, bacteria and viruses suspended in the supply water (6); and (b) flow through, to the downstream side of the membrane, a permeate (16) comprising a second component which is constituted by water (16) filtered from the feed water (6) and containing a minor concentration of at least one of suspended solid particles, bacteria and viruses , with the filtered water (16) making up said product water. 12. Method according to claim 10 or 11, characterized in that the method also comprises the following steps: - supplying said container (30) with at least one semi-permeable cross-flow membrane (32) which is arranged for: (a) retention, on the upstream side of the membrane (32), of a retentate (42) comprising at least one first component; and (b) flow through, to the downstream side of the membrane (32), of a permeate (16) comprising a second component which is constituted by water (16) filtered from the feed water (6) and containing a smaller concentration of said first component, the filtered water (16) constituting said product water; and - by means of a transport means (24) associated with the water treatment installation (2), to transport the retentate (42) further out of the receiving chamber (34) via an outlet (36) therein. 13. Method according to claim 12, characterized in that said first component comprises components selected from a group consisting of: - at least one of solid particles, bacteria and viruses suspended in the supply water (6); - at least one type of multivalent ions dissolved in the supply water (6); and - at least one type of monovalent ions dissolved in the supply water (6). 14. Method according to any one of claims 10-13, characterized in that the method also comprises the following steps: - supplying said container (30) with at least one semi-permeable cross-flow membrane (32) which is arranged for: (a) flow through, to the downstream side of the membrane (32), of a permeate (16) comprising a second component consisting of at least one type of gas dissolved in the supply water (6); and (b) retention, on the upstream side of the membrane (32), of a retentate (42) comprising a first component consisting of water (42) containing a smaller concentration of dissolved gas, the gas-poor retentate water (42) constituting said product water ; and - by means of a transport means (24) associated with the water treatment installation (2), to transport the retentate (42) further out of the receiving chamber (34) via an outlet (36) therein. 15. Method according to any one of claims 10-14, characterized in that said receiving location for product water (42; 16) is located on land. 16. Method according to any one of claims 10-14, characterized in that the receiving location is an underwater well (14), and said at least one transfer pump comprises an injection pump (10); and - that the injection pump (10) is connected, flow-wise, with the underwater well (14) in order to be able to inject the desired product water (42; 16) into the underwater well (14). 17. Method according to any one of claims 10-16, characterized in that the method also comprises a step of connecting, in a flow-wise manner, the water treatment installation (2) with at least one device (26) for chemical treatment of the supply water (6). 18. Method according to any one of claims 10-17, characterized in that the method also comprises a step of connecting, in a flow-wise manner, the water treatment installation (2) with at least one device for destroying organic material in the supply water (6). 19. Use of a water treatment installation (2) as set forth in any one of claims 1-9, for the removal, under water, of at least one undesirable component from feed water (6) fed into the water treatment installation (2).