WO2012026827A1

WO2012026827A1 - Water treatment installation, method and use for removal, under water, of at least one undesirable component from water

Info

Publication number: WO2012026827A1
Application number: PCT/NO2011/000233
Authority: WO
Inventors: David Pinchin; Helge Lunde
Original assignee: Seabox As
Priority date: 2010-08-25
Filing date: 2011-08-24
Publication date: 2012-03-01
Also published as: NO20101192A1

Abstract

Water treatment installation (2) and method for removal of at least one undesirable component from water. The water treatment installation (2) comprises: a receptacle (30) with a filtration membrane dividing the receptacle (30) into an upstream receiving chamber (34) and a downstream permeate chamber (38); wherein the filtration membrane is structured for retention of a retentate (42) comprising at least one first component from a supply water (6); and wherein the filtration membrane is structured for through-put of a permeate (16) comprising at least one second component from the supply water (6); and a means of conveyance connected, in a flow-communicating manner, to the receiving chamber (34) for transport of supply water (6) to the receiving chamber (34) and permeate (16) out of the permeate chamber (38). The water treatment installation (2) is also structured for remote operation under water; wherein the water treatment installation (2) is submerged in a body of water (6); wherein an inlet (28) in the receiving chamber (34) is connected, in a flow- communicating manner, to the body of water (6) within which the water treatment installation (2) is placed; and wherein an outlet (36; 40) for desirable product water (42; 16) in the at least one receptacle (30) is connected, in a flow-communicating manner, to a transfer pump for transport of product water (42; 16) to a receiving location.

Description

WATER TREATMENT INSTALLATION, METHOD AND USE FOR REMOVAL, UNDER WATER, OF AT LEAST ONE UNDESIRABLE COMPONENT FROM WATER

Field of the invention

The invention concerns a water treatment installation, a method and a use for removal, under water, of at least one undesirable component, for example solid particles, bacteria, viruses, salts and sulphates, from supply water being conducted into the water treatment installation. Further, the invention assumes remote operation of the water treatment installation under water.

Background of the invention

The background of the invention relates to problems with the prior art within two related technical fields.

The one technical field concerns injection of water into subterranean hydrocarbon reservoirs in order to increase the degree of recovery from such reservoirs, so-called secondary recovery. Water injection constitutes the most common method of increasing the degree of recovery of crude oil from a reservoir. The water used in this context is frequently taken from the most proximate 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 context of such water injection, it is common to remove, reduce and/or render harmless various undesirable components in the supply water (raw water) before being pumped down into an injection well. This is carried out in order to avoid or reduce undesirable adverse effects of such components when they come into contact with well-related equipment, process-related equipment, personnel and/or fluids in a subterranean reservoir. Such adverse effects may, for example, relate to wear, corrosion and/or scaling on well-related and/or process-related equipment. It may also relate to undesirable components inhibiting the sweep of an injection water front through a subterranean reservoir, whereby the rate of recovery and/or the degree of recovery from the reservoir is reduced. In this context, the undesirable components may predominantly be comprised of solid particles of different particle sizes; various organic material, for example bacteria; various salts and sulphates, for example sodium chloride (NaCI) and calcium sulphate (CaS0₄); and gases, for example oxygen (0₂) and carbon dioxide (C0₂). The most undesirable and problematic bacteria in this context are bacteria that cause fouling of various equipment and pipe connections, and also anaerobic and sulphate-reducing bacteria that generate hydrogen sulphide gas (H₂S). Hydrogen sulphide is very corrosive and may cause vast corrosion damages on well equipment, process equipment and pipe connections. Moreover, the gas is very toxic to human beings. Hydrogen sulphide also causes souring of hydrocarbon fluids in subterranean reservoirs, so-called reservoir souring. All of these problems are well-known within the petroleum industry.

The other technical field concerns purification and production of freshwater, preferably for drinking water purposes. Problems associated with production and/or provision of clean freshwater are also a well-known problems in a number of geographic regions in the world, particularly in so-called developing countries. In such regions, drinking water is usually taken from the most proximate water source, for example directly from a sea, lake, river, spring, or groundwater occurrence. It is also known that many such water sources are unsuitable for drinking water purposes, for example due to a large salt content, large bacterial content and/or strong contamination. Nevertheless, such unsuitable water is used for drinking water purposes, which frequently is due to poor economy, insufficient or absent infrastructure, and/or due to lack of a better alternative. Corresponding drinking water problems may arise in regions subjected to large natural disasters, for example flooding, large waves, landslides, volcanic eruptions or similar, or in context of certain military operations. Under such

conditions, an immediate need for freshwater and, thus, an immediate need for mobilizing and providing suitable equipment for making freshwater, generally arises at, or in vicinity of, the particular region.

Prior art and disadvantages thereof

According to prior art, and regardless of whether the supply water (the raw water) is to be treated for injection into a well or is to be purified for production of freshwater, it is customary to pump up the supply water from a water source and onwards to a surface installation for further treatment of the supply water. On such a surface installation, the supply water is subjected to different types of treatment adapted to the particular purpose and to the particular quality of the supply water. Typically, undesirable components are removed through various filtration of the supply water. Furthermore, the supply water is oftentimes subjected to various chemical treatments. Chemicals used in this context may be organism-killing and/or organism-inhibiting chemicals, such as chlorine and biocide. In this context, also other types of chemicals are generally supplied, including deoxygenation agents, corrosion inhibitors and scale inhibitors. It is also relatively customary to conduct the supply water through equipment for deaeration, thereby removing undesirable gases.

With respect to filtration of the supply water, mainly two types of filtration methods are used, including (1) conventional dead-end filtration, and (2) so-called cross-flow filtration, also termed tangential flow filtration.

Conventional dead-end filtration

In context of conventional dead-end filtration, the supply water is forced or sucked against an upstream side of a semi-permeable filter/membrane. Thereby, a liquid permeate of the supply water will flow through the filter/membrane to a downstream side of the filter/membrane, whereas a retentate in the form of a filter cake is retained at the upstream side of the filter/membrane. Normally, such a filter cake will plug pores and openings in the filter/membrane relatively quickly, whereby the

filter/membrane must be replaced relatively frequently. On the other hand, dead-end filters/

-membranes are relatively cheap as compared to cross-flow membranes.

Dead-end filters/-membranes constitute prior art and generally comprise a wire mesh or a membrane having a suitable mesh size, and with a certain depth extent. Such wire meshes and membranes for treatment of liquids are usually formed from metal or synthetic material, for example polymer material. Dead-end 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 filtration

In context of cross-flow filtration, pressurized supply water is generally conducted against an upstream side of a semi-permeable cross-flow membrane and alongside the membrane (i.e. transverse with respect to the membrane). During this course of cross flow, a permeate of the supply water is forced through the cross-flow membrane to a downstream side of the membrane and discharges as a branch flow therefrom. A retentate of the supply water, i.e. a relatively large proportion of the supply water containing a larger concentration of the undesirable component(s), however, is conducted away from the upstream side of the membrane and discharges as a separate branch flow. In context of cross-flow filtration, two separate branch flows will therefore discharge from the cross-flow membrane, including one branch flow containing the permeate and one branch flow containing the retentate.

When the permeate is a liquid, which it normally is, the pressure in the supply water must, among other things, exceed a so-called transmembraneous pressure ("TMP") for allowing the permeate to flow through the cross-flow membrane. The size of the transmembraneous pressure will depend on the type of cross-flow membrane used in the specific case. Further, the transmembraneous pressure may vary from an insignificant overpressure to a significant overpressure, for example several tens of bars. If the permeate is a gas, however, the permeate may possibly be sucked through the cross-flow membrane.

Even though cross-flow filtration may be used for filtration of various inorganic and organic solid particles suspended in the supply water, for example of the above- mentioned types, cross-flow filtration is typically used for removal of smaller and generally very small components in the supply water, including dissolved components, such as salts and sulphates in the supply water. Typically, cross-flow filtration is 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 transmembraneous pressure increases as the size of those components to be removed by means of the particular cross-flow membrane, becomes smaller. Further, cross-flow filtration is used in a number of processing plants at the surface, i.e. in water purification plants and within the food industry, among others, for purification of water or other liquids.

Cross-flow membranes constitute prior art and exist in a number of designs and material types, including spiral wound membranes, plate- or frame membranes, tubular or straw membranes, and hollow fiber membranes. The membranes may also have a symmetric or asymmetric construction. The membranes may also comprise porous and/or non-porous materials as well as constructions of thin-film composite ("TFC"). Such cross-flow membranes are generally made of polymer materials, cellulose materials, and/or ceramic materials. For microfiltration, the following materials are typically used : acrylonitrile, various ceramic materials, polypropylene, polysulphone, polytetrafluor ethylene (PTFE), polyvinylidene fluoride (PVDF), and thin-film composite (TFC). Ultrafiltration typically makes use of: aromatic polyamide, various ceramic materials, cellulose acetate, polypropylene, polysulphone, polyvinylidene fluoride (PVDF), and Teflon®.

Nanofiltration typically makes use of: cellulose materials, aromatic polyamide, polysulphone, polyvinylidene fluoride (PVDF), and thin-film composite (TFC). Reverse osmosis filtration typically makes use of: cellulose materials, aromatic polyamide, and thin-film composite (TFC).

In context of cross-flow filtration, it is not unusual for 40-80 % of the supply water to be conducted away from the membrane as a retentate and to be dumped as a waste product, or for the retentate to be conducted onwards for further water treatment before being dumped at the end. The proportion of supply water being dumped depends on the specific type of cross-flow membrane being used. This situation implies that typically 40-80 % of the supply water being pumped up to a surface installation is dumped at the end. This also implies that typically 40-80 % of the pump energy being expended to pump up the supply water, and/or to increase the pressure sufficiently to allow the filtration process to be executed, is lost during said dumping and, therefore, is wasted energy.

Moreover, filtration of supply water (raw water) on surface installations offshore is encumbered with a number of disadvantages, which are applicable independent of whether the treatment of the supply water is carried out by means of dead-end filtration and/or cross-flow filtration.

Most surface installations offshore are technically complicated, very compact and also encumbered with substantial space- and weight limitations. These are the conditions that constitute the most important design criteria for such surface installations. This also causes surface installations offshore to become very expensive to install and operate and, therefore, they are generally used only in context of water injection into large petroleum reservoirs offshore.

Large installation- and operational costs associated with such surface installations offshore are also the most important reasons for water injection being 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 production and conveyance of freshwater, for example for drinking water purposes. The technical extent and the technical complexity normally associated with such surface installations offshore will also reduce the technical reliability for such installations. Generally, a reduced technical reliability will cause relatively frequent and/or long operational interruptions, an increased maintenance extent and/or repair extent and also increased costs associated with this.

Furthermore, such an offshore surface installation will usually take its supply water from a surface layer of a water source within which the installation is placed, for example from a surface layer of a sea, lake, river or delta. However, the water quality in such a surface layer may vary a lot due to weather-dependent and seasonal influences. As such, the water quality in the surface layer may fluctuate due to seasonal variations in the temperature, salt content, sediment content, current conditions and/or biological activity of the water. Such fluctuations in the water quality generate relatively unstable operating conditions for surface installations offshore.

Objects of the invention

The primary object of the invention is to avoid or reduce the above-mentioned disadvantages of the prior art, or at least to provide a useful alternative to the prior art.

Another object is to provide a technical solution for reducing, at least, the technical and cost-related disadvantages associated with water treatment on a surface installation offshore or onshore.

A more specific object is to provide a technical solution for avoiding utilization of a surface installation in context of water treatment offshore, thereby also avoiding the technical, space-related, weight-related and cost-related disadvantages that such a surface installation offshore typically is encumbered with.

A further object is to provide a technical solution which is substantially simpler, more flexible and more cost-effective with respect to production of freshwater.

General description of how the objects are achieved

The objects are achieved by virtue of features disclosed in the following description and in the subsequent claims.

According to a first aspect of the invention, a water treatment installation for removal of at least one undesirable component from water is provided, wherein the water treatment installation comprises: - at least one receptacle provided with at least one semi-permeable filtration membrane dividing the receptacle into at least one upstream receiving chamber and at least one downstream permeate chamber; wherein the filtration membrane is structured for retention, at an upstream side of the membrane, of a retentate comprising at least one first component from a supply water; and wherein the filtration membrane is structured for through-put, to a downstream side of the membrane, of a permeate comprising at least one second component from the supply water; and

- at least one means of conveyance connected, in a flow-communicating manner, to an inlet in the receiving chamber for transport of supply water to the receiving chamber, and for transport of said permeate of the supply water out of the permeate chamber via an outlet in the permeate chamber. The distinctive

characteristic of the water treatment installation is that it is structured for remote operation under water;

- wherein the water treatment installation is submerged in a body of water;

- wherein the inlet in the receiving chamber is connected, in a flow-communicating manner, to the body of water within which the water treatment installation is placed; and

- wherein an outlet for desirable product water in the at least one receptacle is connected, in a flow-communicating manner, to at least one transfer pump for onwards transport of product water to a receiving location via at least one transfer line.

Upon using such a submerged water treatment installation, use of a surface installation, for example a platform, for such water treatment offshore is avoided, for example. By so doing, said technical, space-related, weight-related and cost-related disadvantages that such a surface installation typically is encumbered with, are avoided. By so doing, it is also economically feasible to carry out water injection into smaller petroleum reservoirs offshore so as to increase, in this manner, the rate of recovery and/or the degree of recovery from such reservoirs.

If, for example, such a water treatment installation is placed on a seabed, one is not encumbered with the same space- and weight limitations typically applicable to a surface installation offshore. This allows for a substantially larger technical flexibility concerning selection of equipment and placement of the equipment in the present water treatment installation. By so doing, the water treatment installation will also be capable of achieving a substantially better technical reliability than that of a surface installation. Moreover, the submerged water treatment installation may take its supply water from a bottom layer of the water source within which the installation is placed. At such a bottom layer, the water quality is generally substantially less influenced by weather conditions and seasonal fluctuations in said water parameters than at a surface layer of the same body of water. Thereby, the water quality in the bottom layer becomes substantially more stable than in the surface layer. Thereby, relatively stable operating conditions for such a submerged water treatment installation may also be achieved.

In context of cross-flow filtration in such a submerged water treatment installation, using pump capacity for pumping up and processing water from an underlying water source is not required. This stands in stark contrast to cross-flow filtration on a surface installation, where typically 40-80 % of the pump capacity is expended on pumping up and processing water to be dumped at the end as an undesirable retentate (cf. the above discussion on this). Thereby, the pump capacity in the submerged water treatment installation may be limited to the very filtration process in the water treatment installation only, whereby the pump capacity is reduced significantly relative to the corresponding pump capacity on a surface installation.

The present water treatment installation may also be structured as a relatively compact and mobile unit capable of being installed or transferred at a relatively short notification. Such an installation may also be very useful for immediate production of freshwater, for example for drinking purposes, in regions where freshwater is not available for some reason or other. It may relate to, for example, an immediate need for freshwater in regions subjected to large natural disasters, or in context of certain military operations.

Further, the water treatment installation may comprise an assembly of several receptacles, wherein each receptacle may be provided with at least one semipermeable filtration membrane. Each receptacle may also comprise several filters/membranes of known types, and of different types, constructions, designs and/or material types, as described under prior art above.

The water treatment installation may comprise a suitable number of receptacles and/or filtration membranes adapted to the particular application and need. The receptacles and/or the filtration membranes may also be assembled in series and/or in parallel, where also the assembly/assemblies is/are adapted to the particular application and need. Thus, the water treatment installation may be structured for filtration of a number of undesirable components from the supply water. Besides this, the water treatment installation must be provided with various couplings, seals/gaskets, valves, pipes, regulating equipment, etc., and to the extent required in the particular situation. Furthermore, the equipment included in the water treatment installation must be structured and adapted so as to be able to be operated at the particular water depth in the body of water into which the installation is to be submerged. This, however, is considered to be obvious to the skilled professional and hence will not be discussed in further detail herein.

According to a first embodiment variant of the water treatment installation, said receptacle may be provided with at least one semi-permeable dead-end membrane, or dead-end filter, structured for retention, at the upstream side of the membrane, of a retentate comprising a first component comprised of at least one of solid particles, bacteria and viruses suspended in the supply water;

- wherein the dead-end membrane is structured for through-put, to the downstream side of the membrane, of a permeate comprising a second component comprised 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 embodiment variant, reference is made to conventional 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.

Normally, the pores or openings in such a dead-end membrane (or dead-end filter) will be plugged relatively quickly by a filter cake (retentate) on the upstream side of the membrane. For this reason, the dead-end membrane may be formed as an elongated strip, wherein at least one end of the strip is wound onto a rotatable spool core, and wherein a portion of the strip is extended from the spool core so as to provide a utility section of the membrane. The spool core may be connected to a rotary motor for rotation of the spool core and feeding of an unused and clean utility section of the membrane, whereas the opposite end of the strip may be connected to a feed device for simultaneous feeding of a used and soiled utility section of the membrane. As an example, such a feed device may be comprised of one or more conveyor belts or similar devices. As another example, the feed device may be comprised of a further rotatable spool core onto which the opposite end of the membrane strip is wound, the spool core of which may also be connected to a further rotary motor for rotation of the further spool core. In this manner, a strip-shaped dead-end membrane will operate almost like an endless band. Such a strip solution will also require that the receptacle is structured in a manner allowing it to provide a pressure-tight connection around the utility section of the membrane during filtration of supply water.

As an alternative or addition, a dead-end membrane may be structured as a releasable cassette. Thereby, a soiled membrane in the cassette may be replaced via an intervention operation carried out from e.g. a surface vessel. Alternatively, the cassette may be pushed away from its position of use in the water treatment installation and be replaced by another cassette containing a clean and unused deadend membrane. The latter embodiment assumes that the installation is structured in a manner allowing it to replace the cassette when required. This may be carried out by means of a magazine or a carousel provided with at least one unused cassette capable of being inserted into a position of use in the water treatment installation by means of an associated propulsion arrangement, for example via a displacement device or a rail arrangement or similar.

Further, said at least one means of conveyance may comprise a feed pump disposed upstream of the receiving chamber and connected, in a flow-communicating manner, to the inlet of the receiving chamber. By so doing, the supply water may be pressurized before being conducted into the at least one receptacle of the water treatment installation. As an alternative or addition, the at least one means of conveyance may comprise an ejector pump disposed downstream of the permeate chamber and connected, in a flow-communicating manner, to the outlet of the permeate chamber. Such an ejector pump will suck the permeate out of the permeate chamber.

According to a second embodiment variant of the water treatment installation, said receptacle may be provided with at least one semi-permeable cross-flow membrane structured for retention, at the upstream side of the membrane, of a retentate comprising at least one first component;

- wherein the cross-flow membrane is structured for through-put, to the downstream side of the membrane, of a permeate comprising a second component comprised of water filtered from the supply water and containing a smaller concentration of said first component, the filtered water constituting said product water; and

- wherein the water treatment installation also comprises a means of conveyance structured for onwards transport of the retentate out of the receiving chamber via an outlet therein.

For this second embodiment variant, reference is made to cross-flow filtration under water. The manner of operation for cross-flow filtration is described more thoroughly under prior art above. Cross-flow filtration is well suited for removal of smaller and generally very small components in the supply water.

Also in context of such cross-flow filtration, said first component may comprise at least one of solid particles, bacteria and viruses suspended in the supply water. Membranes structured for so-called microfiltration are suitable for removal of solid particles and various bacteria suspended in the supply water, whereas membranes structured for so-called ultrafiltration may, in addition, 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 sulphate ions, for example calcium sulphate ions, magnesium sulphate ions, strontium sulphate ions and/or barium sulphate ions. Such sulphate ions may, among other things, form very problematic scaling in pipes and equipment that they come into contact with, for example on well-related and/or process-related equipment.

Membranes structured for so-called nanofiltration are suitable for removal of multivalent ions in addition to 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 comprise chloride ions, for example sodium chloride ions and potassium chloride ions. Such chloride ions may, among other things, form salt deposits and also cause vast corrosion damages on well equipment, process equipment and pipe connections. The presence of a relatively small amount of dissolved chloride ions in water will also render the water unsuitable for drinking water purposes. Membranes structured for so-called reverse osmosis filtration are suitable for removal of monovalent ions in addition to removal of the above-mentioned, coarser components.

Accordingly, said first component may comprise 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. 0233

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In context of cross-flow filtration, the outlet of the receiving chamber may also be connected to an energy recovery device for recovery of pressure energy in the retentate discharging from the receiving chamber. As such, a so-called energy recovery turbine and/or a so-called pressure exchanger may be used.

All of the membranes discussed until now are suitable for removal of solids-containing and/or liquid-containing components from the supply water.

In context of dead-end filtration and/or cross-flow filtration, said at least one receptacle in the water treatment installation may also be provided with at least one semi-permeable cross-flow membrane structured for through-put, to the downstream side of the membrane, of a permeate comprising a second component comprised of at least one type of gas dissolved in the supply water;

- wherein the cross-flow membrane is structured for retention, at the upstream side of the membrane, of a retentate comprising a first component comprised of water containing a smaller concentration of dissolved gas, the gas-deprived retentate water constituting said product water; and

In context of removal of gas dissolved in water, the at least one semi-permeable cross-flow membrane advantageously may comprise a hollow fiber membrane, which typically is used for this purpose. For example, the dissolved gas may comprise oxygen and/or carbon dioxide. The presence of oxygen may, among other things, contribute to corrosion damages in well equipment, process equipment and associated pipe connections. It is perhaps more damaging that the oxygen in the water preserves life in various aerobic bacteria, which cause fouling of various equipment and pipe connections that the bacteria come into contact with. Such bacteria may also be very harmful to organisms drinking the water. Upon removing the oxygen from the water, the basis of existence for aerobic bacteria is also removed.

In context of such gas removal, said at least one means of conveyance may comprise a pumping means connected, in a flow-communicating manner, to the outlet of the permeate chamber for transport of said gas permeate out of the permeate chamber. This pumping means may, for example, comprise a vacuum pump. T/NO2011/000233

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

As another alternative, the permeate chamber may also be provided with an inlet;

- wherein said at least one means of conveyance comprises a gas extraction device, which includes a pumping means and an associated flow circuit connected, in a flow- communicating manner, to the inlet and outlet of the permeate chamber;

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

- wherein the pumping means is structured for transport of the carrier gas and the gas permeate out of the permeate chamber. This carrier gas may, for example, comprise nitrogen.

In context of cross-flow filtration, said at least one means of conveyance may comprise a feed pump disposed upstream of the receiving chamber and connected, in a flow-communicating manner, to the inlet of the receiving chamber. If the water treatment installation comprises several receptacles and several cross-flow

membranes structured for removal of different types of undesirable components, the water treatment installation may therefore comprise several feed pumps. By so doing, each feed pump may, in combination with a hydrostatic pressure, deliver supply water at an overpressure suitable for operation of the particular cross-flow membrane connected to the feed pump. Thereby, the individual cross-flow membrane may be provided with sufficient transmembraneous pressure for allowing the associated permeate to flow through the membrane.

Further, a cross-flow membrane, or an assembly of cross-flow membranes, may be structured as a releasable cassette. This assumes that the cross-flow membrane, or the assembly of cross-flow membranes, has/have a design suitable to be structured as a cassette. Further, this releasable cassette may be associated with the water treatment installation and be handled in the same manner described for the cassette mentioned above in context of the discussion on a dead-end membrane.

In the following, further features applicable to the water treatment installation, when structured for dead-end filtration and/or cross-flow filtration, are disclosed.

Said filtration membrane in the water treatment installation may, in the first place, be connected, in a flow-communicating manner, to a backflow device structured in a manner allowing it to backflow permeate from the permeate chamber and through the membrane for removal of an undesirable coating on the upstream side of the membrane. Such a backflow device may ensure that a partial flow of the permeate is flowed back periodically through the membrane for cleaning thereof.

As an alternative or addition, the downstream side of said filtration membrane may be connected, in a flow-communicating manner, to a backflow device structured in a manner allowing it to backflow a cleaning fluid through the membrane for removal of an undesirable coating on the upstream side of the membrane. Such a backflow device may ensure that the cleaning fluid is flowed back periodically through the membrane for cleaning thereof.

As a further alternative or addition, the upstream side of said filtration membrane may be connected, in a flow-communicating manner, to a supply device structured in a manner allowing it to supply a cleaning fluid to the membrane for removal of an undesirable coating on the upstream side of the membrane. Such a supply device may ensure that the cleaning fluid is flowed back periodically against the upstream side of the membrane for cleaning thereof.

As a further alternative or addition, the upstream side of said filtration membrane may be connected, in a flow-communicating manner, to a cleaning-in-place installation for removal of an undesirable coating on the upstream side of the membrane. Such cleaning-in-place installations constitute prior art and will not be discussed in further detail herein.

As a further alternative or addition, the water treatment installation may 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.

Further, said receiving location for product water may be located onshore.

Thus, the receiving location may, for example, be a well onshore, wherein said at least one transfer pump may comprise an injection pump connected, in a flow- communicating manner, to the well for injection of the desirable product water into the well. The injection pump may be structured for remote operation.

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

Thus, the receiving location may, for example, be an underwater well offshore, wherein said at least one transfer pump may comprise an injection pump connected, in a flow-communicating manner, to the underwater well for injection of the desirable product water into the underwater well. The injection pump may be structured for remote operation.

In context of application offshore, the receiving location may be a surface installation, for example a platform or some other type of surface structure. Alternatively, the receiving location may be a floating vessel, for example a floating rig, a ship or a military vessel .

Further, the water treatment installation may be structured for remote operation via at least one cabled connection for transmission of motive power and control signals to the installation. Thus, the water treatment installation may be cable-connected to a remote plant or unit for supply of motive power and control signals to the installation, for example a plant onshore or a platform offshore.

As an alternative, the water treatment installation may be structured for remote operation via at least one cabled connection structured for transmission of motive power to the installation, and via at least one wireless connection for transmission of control signals to the installation. Thus, the water treatment installation may be cable- connected to a remote plant or unit for supply of motive power to the installation, whereas control signals are transmitted wirelessly to the installation from, for example, a floating vessel in vicinity of the installation.

As a further alternative, the water treatment installation may be structured for remote operation via at least one wireless connection for transmission of control signals to the installation. Moreover, the water treatment installation is provided with at least one energy source for independent provision of motive power to the installation. Such an energy source may comprise at least one battery. Also in this situation, control signals may be transmitted wirelessly to the installation from, for example, a floating vessel in vicinity of the installation.

Further, the upstream side of the water treatment installation may be connected, in a flow-communicating manner, to an underwater device for removal, without filtration, of undesirable 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 structured so as to allow the supply water to be led directly into a lower portion of the closed space, the space of which is aiso structured so as to allow treated water to be led out of an upper portion of the closed space. This closed space also has a cross-sectional area structured so as to allow the water to flow from the lower portion to the upper portion at a flow velocity being sufficiently low for N 2011/000233

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undesirable solid particles to precipitate from the water by means of gravitation.

Further, this closed space may be formed as a receptacle or module being placed on, for example, a seabed or similar.

Yet further, the present water treatment installation, and preferably the upstream side of the installation, may be connected, in a flow-communicating manner, to at least one device for chemical treatment of the supply water. Similar to the present water treatment installation, also this device for chemical treatment of the supply water may be submerged in said body of water. An example of such a chemical treatment device is described in WO 2004/090284 Al. This patent publication concerns a method and an apparatus for underwater chemical treatment of injection water, wherein a module- based underwater apparatus being connected to an injection well for injection of the water is used. The apparatus contains at least one receptacle provided with at least one type of water-soluble solid-state chemical. The receptacle may, for example, be replaced by means of a remote-controlled underwater vehicle ("ROV"). Then, the water is brought into contact with the solid-state chemical, whereby it is gradually dissolved and mixed with the water. The finally treated water is then injected into a reservoir associated with the well. By so doing, chemical treatment and water injection may be carried out without having to use an immediately overlying surface installation or -vessel. The water-soluble solid-state chemical may comprise chlorine and/or biocide, but also various other chemicals, such as said deoxygenation agents, corrosion inhibitors and scale inhibitors. This chemical treatment device may be comprised of a separate unit or be incorporated in the above-mentioned underwater device for removal, without filtration, of undesirable solid particles from the supply water.

As an alternative or addition, the water treatment installation, and preferably the upstream side of the installation, may be connected, in a flow-communicating manner, to at least one device for destruction of organic material in the supply water. Similar to the present water treatment installation, also this device for destruction of organic material in the supply water may be submerged in said body of water. An example of such a destruction device is described in WO 2007/073198 Al. This patent publication concerns a method and a device for destructing organic material in injection water for an injection well. The device makes use of at least one electrochemical cell with associated operating means for in situ electrolytic generation, from water, of at least short-lived, free hydroxyl radicals. By means of the operating means, the

electrochemical cell is structured in a manner allowing it to conduct the injection water therethrough as a source material for in situ generation of at least said free hydroxyl radicals from the injection water. Such free hydroxyl radicals will immediately destruct organic material engaged in the injection water. This destruction device may be comprised of a separate unit or be incorporated in the above-mentioned underwater device for removal, without filtration, of undesirable solid particles from the supply water. As a further alternative, the destruction device may be assembled together with the above-mentioned chemical treatment device.

According to a second aspect of the invention, a method for removal of at least one undesirable component from water is provided, wherein the method makes use of the following equipment:

- at least one receptacle provided with at least one semi-permeable filtration membrane dividing the receptacle into at least one upstream receiving chamber and at least one downstream permeate chamber; wherein the filtration membrane is structured for retention, at an upstream side of the membrane, of a retentate comprising at least one first component from a supply water; and wherein the filtration membrane is structured for through-put, to a downstream side of the membrane, of a permeate comprising at least one second component from the supply water; and

- at least one means of conveyance connected, in a flow-communicating manner, to an inlet in the receiving chamber and to an outlet in the permeate chamber. The distinctive characteristic of the method is that it comprises the following steps:

- assembling the receptacle and the at least one means of conveyance into a water treatment installation;

- structuring the water treatment installation for remote operation under water;

- lowering the water treatment installation into a body of water;

- placing the inlet of the receiving chamber in flow-communication with the body of water within which the water treatment installation is placed;

- conducting, in a remote-controlled manner, and by means of said at least one means of conveyance, the supply water into the receiving chamber via the inlet thereof, and transporting said permeate of the supply water out of the permeate chamber via the outlet thereof;

- connecting, in a flow-communicating manner, an outlet for desirable product water in the at least one receptacle to at least one transfer pump; and

- transporting, by means of said transfer pump, said product water onwards to a receiving location via at least one transfer line. The same comments made in context of the description of the water treatment installation according to the first aspect of the invention, also apply for the method according to this second aspect of the invention.

According to a first embodiment variant, the method may also comprise a step of providing said receptacle with at least one semi-permeable dead-end membrane structured for:

(a) retention, at the upstream side of the membrane, of a retentate comprising a first component comprised of at least one of solid particles, bacteria and viruses suspended in the supply water; and

(b) through-put, to the downstream side of the membrane, of a permeate comprising a second component comprised 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.

In context of dead-end filtration, the method may also comprise the following steps:

- forming the dead-end membrane as an elongated strip;

- winding one end of the strip onto a rotatable spool core;

- extending the strip from the spool core so as to provide a utility section of the membrane;

- connecting the spool core to a rotary motor for rotation of the spool core and feeding of an unused and clean utility section of the membrane; and

- connecting the opposite end of the strip to a feed device for simultaneous feeding of a used and soiled utility section of the membrane.

As an alternative or addition, a dead-end membrane may be structured as a releasable cassette, for example as described in context of the above-mentioned water treatment installation.

Further, said at least one means of conveyance may comprise a feed pump being disposed upstream of the receiving chamber and being connected, in a flow- communicating manner, to the inlet of the receiving chamber. By so doing, the supply water may be pressurized before being conducted into the at least one receptacle of the water treatment installation. As an alternative or addition, the at least one means of conveyance may comprise an ejector pump being disposed downstream of the permeate chamber and being connected, in a flow-communicating manner, to the outlet of the permeate chamber, whereby the ejector pump may suck the permeate out of the permeate chamber. According to a second embodiment variant, the method may also comprise the following steps:

- providing said receptacle with at least one semi-permeable cross-flow membrane structured for:

(a) retention, at the upstream side of the membrane, of a retentate comprising at least one first component; and

(b) through-put, to the downstream side of the membrane, of a permeate comprising a second component comprised of water filtered from the supply water and containing a smaller concentration of said first component, the filtered water constituting said product water; and

- transporting, by means of a means of conveyance associated with the water treatment installation, the retentate onwards and out of the receiving chamber via an outlet therein.

For this second embodiment variant, reference is made to cross-flow filtration under water. The manner of operation for cross-flow filtration is described more thoroughly under prior art above.

In context of 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 sulphate ions, for example calcium sulphate ions, magnesium sulphate ions, strontium sulphate ions and/or barium sulphate 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 comprise chloride ions, for example sodium chloride ions and potassium chloride ions. So-called reverse osmosis filtration is suitable for this purpose.

- 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 context of cross-flow filtration, the method may also comprise a step of connecting the outlet of the receiving chamber to an energy recovery device for recovery of pressure energy in the retentate discharging from the receiving chamber. For this purpose, and as mentioned above, an energy recovery turbine and/or a pressure exchanger may be used.

In context of dead-end filtration and/or cross-flow filtration, the method may also comprise the following steps:

- providing said receptacle with at least one semi-permeable cross-flow membrane, for example a hollow fiber membrane, structured for:

(a) through-put, to the downstream side of the membrane, of a permeate comprising a second component comprised of at least one type of gas dissolved in the supply water, for example oxygen and/or carbon dioxide; and

(b) retention, at the upstream side of the membrane, of a retentate comprising a first component comprised of water containing a smaller concentration of dissolved gas, the gas-deprived retentate water constituting said product water; and

In context of such gas removal, the method may also comprise a step of transporting said gas permeate out of the permeate chamber by means of a means of conveyance comprising a pumping means, for example a vacuum pump, connected, in a flow- communicating manner, to the outlet of the permeate chamber.

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.

As another alternative, the method may also comprise the following steps:

- providing the permeate chamber with an inlet;

- using a means of conveyance 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;

- connecting, in a flow-communicating manner, the flow circuit to the inlet and outlet of the permeate chamber; and

- transporting, by means of said pumping means, the carrier gas and the gas permeate out of the permeate chamber. In context of cross-flow filtration, a feed pump for the supply water may also be disposed upstream of the receiving chamber and be connected, in a flow- communicating manner, to the inlet of the receiving chamber. If the water treatment installation comprises several receptacles and several cross-flow membranes structured for removal of different types of undesirable components, several feed pumps may be disposed in the water treatment installation. By so doing, each feed pump may deliver supply water at an overpressure suitable for operation of the particular cross-flow membrane, whereby the individual cross-flow membrane is provided with sufficient transmembraneous pressure for allowing the associated permeate to flow through the membrane.

Further, a cross-flow membrane, or an assembly of cross-flow membranes, may also be structured as a releasable cassette, for example as described in context of the above-mentioned water treatment installation. This assumes that the cross-flow membrane, or the assembly of cross-flow membranes, has/have a design suitable for being structured as a cassette. Further, this releasable cassette may be associated with the water treatment installation and be handled in the same manner described for the cassette mentioned above in context of the discussion on a dead-end membrane.

In the following, further features applicable to the method, when used in context of dead-end filtration and/or cross-flow filtration, are disclosed.

The method may, in the first place, comprise the following steps:

- connecting, in a flow-communicating manner, the downstream side of said filtration membrane to a backflow device being in hydraulic communication with permeate in the permeate chamber; and

- backflowing, by means of the backflow device, permeate from the permeate chamber and through the membrane for removing an undesirable coating on the upstream side of the membrane. By so doing, a partial flow of the permeate may be flowed back periodically through the membrane for cleaning thereof.

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

- connecting, in a flow-communicating manner, the downstream side of said filtration membrane to a backflow device being in hydraulic communication with a cleaning fluid; and

- backflowing, by means of the backflow device, the cleaning fluid through the membrane for removing an undesirable coating on the upstream side of the membrane. By so doing, the cleaning fluid may be flowed back periodically through the membrane for cleaning thereof.

As a further alternative or addition, the method may also comprise the following steps:

- connecting, in a flow-communicating manner, the upstream side of said membrane to a supply device being in hydraulic communication with a cleaning fluid; and

- supplying, by means of the supply device, the cleaning fluid to the membrane for removing an undesirable coating on the upstream side of the membrane. By so doing, the cleaning fluid may be flowed back periodically against the upstream side of the membrane for cleaning thereof.

As a further alternative or addition, the method may also comprise a step of connecting, in a flow-communicating manner, the upstream side of said membrane to a cleaning-in-place installation for removing an undesirable coating on the upstream side of the membrane.

Further, said receiving location for product water may be located onshore.

Thus, the receiving location may, for example, be a well onshore, and said at least one transfer pump may comprise an injection pump, said injection pump being connected, in a flow-communicating manner, to the well so as to allow the desirable product water to be injected down into the well. The injection pump may be structured for remote operation.

Thus, the receiving location may, for example, be an underwater well, and said at least one transfer pump may comprise an injection pump, said injection pump being connected, in a flow-communicating manner, to the underwater well so as to allow the desirable product water to be injected down into the underwater well. The injection pump may be structured for remote operation.

In context of application offshore, the receiving location may be a surface installation, for example a platform or some other type of surface structure. Alternatively, the receiving location may be a floating vessel, for example a floating rig, a ship or a military vessel.

Further, the water treatment installation may be operated remotely via at least one cabled connection for transmission of motive power and control signals to the installation. Thus, the water treatment installation may be cable-connected to a remote plant or unit for supply of motive power and control signals to the installation, for example a plant onshore or a platform offshore.

As an alternative, the water treatment installation may be operated remotely via at least one cabled connection for transmission of motive power to the installation, and via at least one wireless connection for transmission of control signals to the installation. Thus, the water treatment installation may be cable-connected to a remote plant or unit for supply of motive power to the installation, whereas control signals are transmitted wirelessly to the installation from, for example, a floating vessel in vicinity of the installation.

As a further alternative, the water treatment installation may be operated remotely via at least one wireless connection for transmission of control signals to the installation, whereas the water treatment installation receives independent motive power from at least one energy source associated with the installation. Said energy source may comprise at least one battery. Also in this situation, control signals may be transmitted wirelessly to the installation from, for example, a floating vessel in vicinity of the installation.

Further, the method may comprise a step of connecting, in a flow-communicating manner, the upstream side of the water treatment installation to an underwater device for removal, without filtration, of undesirable solid particles from the supply water; see for example patent publication WO 2007/035106 Al.

Yet further, the method may comprise a step of connecting, in a flow-communicating manner, the water treatment installation (and preferably the upstream side thereof) to at least one device for chemical treatment of the supply water. Similar to the water treatment installation, also this device for chemical treatment of the supply water may be submerged in said body of water; see for example patent publication

WO 2004/090284 Al . This chemical treatment device may be comprised of a separate unit or be incorporated in the above-mentioned underwater device for removal, without filtration, of undesirable solid particles from the supply water. As an alternative or addition, the method may comprise a step of connecting, in a flow-communicating manner, the water treatment installation (and preferably the upstream side thereof) to at least one device for destruction of organic material in the supply water. Similar to the water treatment installation, also this device for destruction of organic material in the supply water may be submerged in said body of water; see for example patent publication WO 2007/073198 Al. This destruction device may be comprised of a separate unit or be incorporated in the above- mentioned underwater device for removal, without filtration, of undesirable solid particles from the supply water. As a further alternative, the destruction device may be assembled together with the above-mentioned chemical treatment device.

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

Hereinafter, a non-limiting exemplary embodiment of a water treatment installation according to the invent/on will be shown.

Short description of the figure

Figure 1 shows, very schematically, an example of a water treatment installation according to the invention, wherein the installation is connected, among other things, to an injection pump and a proximate underwater injection well.

The figure only shows main equipment, the equipment of which is very distorted with respect to relative dimensions, and it is depicted in a very simplified design and richness of detail.

Description of the exemplary 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 sea water 6 and a sea level 8.

At its downstream side, the installation 2 is connected to an injection pump 10 connected, in a flow-communicating manner, to a wellhead 12 for a water injection well 14. Finally treated product water 16 is pumped, by means of the injection pump 10, from the installation 2 and down into the well 14, after which the product water 16 is conducted through well perforations 18 and onwards into a subterranean petroleum reservoir 20 in order to increase the degree of recovery from the reservoir 20. The direction of flow for the product water 16 is depicted with downstream-directed arrows N 2011/000233

25

in figure 1.

At its upstream side, as viewed 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.

Supply water, here in the form of salty sea water 6, is conducted, by means of the feed pump 24, directly into the primary water treatment module 22, then via the secondary water treatment module 26 and onwards into and through an inlet 28 in the present water treatment installation 2. The direction of flow for the sea water 6 is also depicted with downstream-directed arrows in figure 1.

In this embodiment, an introductory coarse filtration of the sea water 6 is carried out in the primary water treatment module 22, within which larger organic and inorganic solid particles are removed from the sea water 6 by means of conventional filters made of wire mesh or similar. As an alternative or addition (not shown in figure 1), the primary water treatment module 22 may be comprised of an underwater device for removal, without filtration, of undesirable solid particles from the sea water 6, such as the device described in WO 2007/035106 Al (mentioned above).

Then the coarsely filtered and/or the gravitationally precipitated water from the primary water treatment module 22 is conducted onwards and into the secondary water treatment module 26, here comprising a device for chemical treatment of the sea water 6. In this embodiment, the chemical treatment device is of a type described in WO 2004/090284 Al (mentioned above). This chemical treatment device comprises several replaceable receptacles (not shown in figure 1), each of which is provided with one type of water-soluble solid-state chemical. In this case, the chemical treatment device is provided with chlorine and biocide for killing of bacteria and similar in the sea water, and also deoxygenation agents, corrosion inhibitors and scale inhibitors. In context of flowing through the secondary water treatment module 26, the sea water 6 is brought into contact with the respective water-soluble solid-state chemicals, whereby they are gradually dissolved and mixed with the sea water 6.

As an alternative (not shown in figure 1), the secondary water treatment module 26 may be comprised of an assembly of said underwater device for removal, without filtration, of undesirable solid particles in the sea water 6 (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 may be connected to a device for 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 may be incorporated in the primary water treatment module 22 or the secondary water treatment module 26, and possibly together with an underwater device for removal, without filtration, of undesirable solid particles from the sea water 6 (cf. WO 2007/035106 Al).

The water treatment installation 2 comprises at least one receptacle 30 provided with at least one semi-permeable cross-flow membrane 32. For the sake of simplicity, figure 1 shows only one receptacle 30 and one cross-flow membrane 32. In practical embodiments, however, the water treatment installation 2 may comprise several receptacles 30 and several cross-flow membranes 32, the membranes of which are generally structured for removal of different undesirable components in the sea water 6 (cf. the above discussion on this).

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

Further, the cross-flow membrane 32 is structured for retention, at an upstream side of the membrane 32, of a retentate 42 comprising, herein, bacteria and also multivalent and monovalent ions dissolved in the sea water 6, i.e. mainly dissolved sulphates and salts. It is particularly desirable to remove such components from the sea water 6 before being pumped down into the injection well 14 for water flooding of the reservoir 20. The cross-flow membrane 32 is also structured for through-put, to a downstream side of the membrane 32, of a permeate comprising water filtered from the sea water 6 and containing a substantially smaller concentration of said bacteria, multivalent ions and monovalent ions. This permeate is what constitutes said product water 16, the water of which may be classified, in this exemplary embodiment, as freshwater.

Pressurized sea water 6, which already has been pre-treated in the primary water treatment module 22 and in the secondary water treatment module 26, is pumped, by means of said feed pump 24, into the receiving chamber 34 via the inlet 28 thereof. Here, cross-flow filtration is carried out by virtue of the pressurized sea water 6 being conducted against and alongside the cross-flow membrane 32. By so doing, said permeate 16 (product water) is forced through the membrane 32, into the permeate chamber 38 and onwards via the outlet 40 thereof. On the other hand, said retentate 42, which in this case consists of a relatively large proportion of sea water 6

containing a very large concentration of said bakteria, multivalent ions and monovalent ions, is conducted out of the receiving chamber 34 via the outlet 36 thereof. Thereby, two branch flows discharge from the receptacle 30, including one branch flow containing the retentate 42 and one branch flow containing the permeate/product water 16. The direction of flow for the retentate 42 and the permeate 16 is also depicted with downstream-directed arrows in figure 1.

This exemplary embodiment may just as well be adapted for transport of product water 16 to a receiving location onshore, for example an injection well or a freshwater receiving station onshore. In this case, at least one transfer line must be extended between the water treatment installation 2 and the receiving location onshore, and the injection pump 10 must possibly be replaced by at least one transfer pump of a suitable type.

Claims

C l a i m s

1. A water treatment installation (2) for removal of at least one undesirable

component from water;

- wherein the water treatment installation (2) is structured for remote operation under water and is submerged in a body of water;

- wherein the water treatment installation (2) comprises at least one receptacle (30) provided with at least one semi-permeable filtration membrane dividing the receptacle (30) into at least one upstream receiving chamber (34) and at least one downstream permeate chamber (38);

- wherein the filtration membrane is structured for retention, at an upstream side of the membrane, of a retentate (42) comprising at least one first component from a supply water (6) from the body of water;

- wherein the filtration membrane is structured for through-put, to a

downstream side of the membrane, of a permeate (16) comprising at least one second component from the supply water (6) ; and

- wherein said receptacle (30) comprises an outlet (36; 40) for desirable product water (42; 16) connected, in a flow-communicating manner, to at least one transfer pump for onwards transport of the product water (42; 16) to a receiving location via at least one transfer line, c h a r a c t e r i z e d i n that an upstream side of the water treatment installation (2) is connected, in a flow- communicating manner, to an underwater device for removal, without filtration, of solid particles from the supply water (6);

- wherein also the underwater device is structured for remote operation under water;

- wherein an upstream side of the underwater device is connected, in a flow- communicating manner, to said body of water;

- wherein the underwater device comprises a closed space having a lower portion and an upper portion, wherein the closed space is structured so as to allow untreated supply water (6) from the body of water to be led directly into the lower portion of the space, wherein the closed space has a cross-sectional area structured so as to allow the supply water (6) to flow from the lower portion to the upper portion at a flow velocity being sufficiently low for solid particles to precipitate from the supply water (6) by means of gravitation, wherein the closed space is structured so as to allow treated supply water (6) to be led out of the upper portion of the space, and wherein the upper portion is connected, in a flow-communicating manner, to an inlet (28) in the receiving chamber (34) of the water treatment installation (2), thereby being connected, in a flow- communicating manner, to the water treatment installation (2);

- wherein at least one pumping means (24) is connected, in a flow- communicating manner, to said underwater device and to said inlet (28) in the receiving chamber (34) of the water treatment installation (2) for transport of supply water (6) from the underwater device to the receiving chamber (34), and for transport of said permeate (16) of the supply water (6) out of an outlet (40) in the permeate chamber (38) of the water treatment installation (2); and

- wherein both the underwater device and the water treatment installation (2) are placed at a bottom (4) underlying said body of water.

2. The water treatment installation (2) according to claim 1,

c h a r a c t e r i z e d i n that said receptacle (30) in the water treatment installation (2) is provided with at least one semi-permeable dead-end membrane structured for retention, at the upstream side of the membrane, of a retentate (42) comprising a first component comprised of at least one of solid particles, bacteria and viruses suspended in the supply water (6); and

- wherein the dead-end membrane is structured for through-put, to the downstream side of the membrane, of a permeate (16) comprising a second component comprised 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) constituting said product water.

3. The water treatment installation (2) according to claim 1 or 2,

c h a r a c t e r i z e d i n that said receptacle (30) in the water treatment installation (2) is provided with at least one semi-permeable cross- flow membrane (32) structured for retention, at the upstream side of the membrane (32), of a retentate (42) comprising at least one first component;

- wherein the cross-flow membrane (32) is structured for through-put, to the downstream side of the membrane (32), of a permeate (16) comprising a second component comprised 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

- wherein the water treatment installation (2) also comprises a pumping means (24) structured for onwards transport of the retentate (42) out of the receiving chamber (34) via an outlet (36) therein.

4. The water treatment installation (2) according to claim 1, 2 or 3,

c h a r a c t e r i z e d i n that said receptacle (30) in the water treatment installation (2) is provided with at least one semi-permeable cross- flow membrane (32) structured for through-put, to the downstream side of the membrane (32), of a permeate (16) comprising a second component comprised of at least one type of gas dissolved in the supply water (6); and

- wherein the cross-flow membrane (32) is structured for retention, at the upstream side of the membrane (32), of a retentate (42) comprising a first component comprised of water (42) containing a smaller concentration of dissolved gas, the gas-deprived retentate water (42) constituting said product water; and

5. The water treatment installation (2) according to any one of claims 1-4,

c h a r a c t e r i z e d i n that said receiving location for product water (42; 16) is located onshore.

6. The water treatment installation (2) according to any one of claims 1-4,

c h a r a c t e r i z e d i n that said receiving location is an underwater well (14); and

- wherein said at least one transfer pump comprises an injection pump (10) connected, in a flow-communicating manner, to the underwater well (14) for injection of the desirable product water (16) down into the underwater well.

7. The water treatment installation (2) according to any one of claims 1-6,

c h a r a c t e r i z e d i n that the water treatment installation (2) is connected, in a flow-communicating manner, to at least one device for destruction of organic material in the supply water (6), wherein the device for destruction of organic material comprises at least one electrochemical cell with associated operating means for in situ electrolytic generation of at least shortlived, free hydroxyl radicals from the supply water (6), and wherein said electrochemical cell and operating means are structured in a manner allowing them to conduct the supply water (6) therethrough as a source material for in situ generation of at least said free hydroxyl radicals from the supply water (6).

8. The water treatment installation (2) according to claim 7,

c h a r a c t e r i z e d i n that the device for destruction of organic material is connected, in a flow-communicating manner, to the downstream side of said underwater device for removal, without filtration, of undesirable solid particles from the supply water (6).

9. The water treatment installation (2) according to claim 7 or 8,

c h a r a c t e r i z e d i n that the device for destruction of organic material is comprised of a separate unit or module.

10. The water treatment installation (2) according to claim 7 or 8,

c h a r a c t e r i z e d i n that the device for destruction of organic material is incorporated in said underwater device for removal, without filtration, of undesirable solid particles from the supply water (6).

11. The water treatment installation (2) according to any one of claims 1-10,

c h a r a c t e r i z e d i n that the water treatment installation (2) is connected, in a flow-communicating manner, to at least one device for chemical treatment of the supply water (6), wherein the device for chemical treatment comprises at least one replaceable receptacle provided with at least one type of water-soluble solid-state chemical which, upon contact with the supply water (6), is gradually dissolved and mixed with the supply water (6).

12. The water treatment installation (2) according to claim 11,

c h a r a c t e r i z e d i n that the device for chemical treatment is connected, in a flow-communicating manner, to the downstream side of said underwater device for removal, without filtration, of undesirable solid particles from the supply water (6).

13. The water treatment installation (2) according to claim 11 or 12,

c h a r a c t e r i z e d i n that the device for chemical treatment is comprised of a separate unit or module.

14. The water treatment installation (2) according to claim 11 or 12,

c h a r a c t e r i z e d i n that the device for chemical treatment is incorporated in said underwater device for removal, without filtration, of undesirable solid particles from the supply water (6).

15. A method for removal of at least one undesirable component from water,

wherein the method makes use of a water treatment installation (2) structured for remote operation under water and submerged in a body of water; the water treatment installation (2) comprising at least one receptacle (30) provided with at least one semi-permeable filtration membrane dividing the receptacle (30) into at least one upstream receiving chamber (34) and at least one downstream permeate chamber (38); wherein the filtration membrane is structured for retention, at an upstream side of the membrane, of a retentate (42) comprising at least one first component from a supply water (6) from the body of water; wherein the filtration membrane is structured for through-put, to a downstream side of the membrane, of a permeate (16) comprising at least one second component from the supply water (6); and wherein said receptacle (30) comprises an outlet (36; 40) for desirable product water (42; 16),

c h a r a c t e r i z e d i n that the method also comprises the following steps:

- placing the water treatment installation (2) and an underwater device for removal, without filtration, of solid particles from the supply water (6) at a bottom (4) underlying said body of water, wherein also the underwater device is structured for remote operation under water; the underwater device comprising a closed space having a lower portion and an upper portion, wherein the closed space has a cross-sectional area structured so as to allow the supply water (6) to flow from the lower portion to the upper portion at a flow velocity being sufficiently low for solid particles to precipitate from the supply water (6) by means of gravitation;

- connecting, in a flow-communicating manner, an upstream side of the water treatment installation (2) to said underwater device;

- connecting, in a flow-communicating manner, an upstream side of the underwater device to said body of water;

- connecting, in a flow-communicating manner, said upper portion of the closed space of the underwater device to an inlet (28) in the receiving chamber (34) of the water treatment installation (2) so as to be connected, in a flow- communicating manner, to the water treatment installation (2);

- connecting, in a flow-communicating manner, at least one pumping means (24) to the underwater device and to the inlet (28) in said receiving chamber (34);

- connecting, in a flow-communicating manner, an outlet (36; 40) for desirable product water (42; 16) in the receptacle (30) of the water treatment installation (2) to at least one transfer pump;

- leading, by means of said pumping means (24), untreated supply water (6) directly into the lower portion of the closed space of the underwater device;

- allowing the supply water (6) to flow from the lower portion to the upper portion at said low flow velocity so as to precipitate solid particles from the supply water (6) by means of gravitation;

- leading treated supply water (6) out of the upper portion of the closed space and onwards to said inlet (28) in the receiving chamber (34) of the water treatment installation (2);

- transporting, by means of said pumping means (24), said permeate (16) of the supply water (6) out of an outlet (40) in the permeate chamber (38) of the water treatment installation (2); and

- pumping, by means of said transfer pump, said product water (42; 16) from the water treatment installation (2) and onwards to a receiving location via at least one transfer line.

16. The method according to claim 15, c h a r a c t e r i z e d i n that said receiving location for product water (42; 16) is located onshore.

17. The method according to claim 15 or 16, c h a r a c t e r i z e d i n that the receiving location is an underwater well (14), and said at least one transfer pump comprises an injection pump (10); and

- wherein the method further comprises a step of connecting, in a flow- communicating manner, the injection pump (10) to the underwater well (14) so as to allow the desirable product water (16) to be injected down into the underwater well (14).

18. The method according to claim 15, 16 or 17, c h a r a c t e r i z e d i n that the method also comprises a step of connecting, in a flow-communicating manner, the water treatment installation (2) to at least one device for destruction of organic material in the supply water (6); the device for destruction of organic material comprising at least one electrochemical cell with associated operating means for in situ electrolytic generation of at least short-lived, free hydroxyl radicals from the supply water (6), and wherein said electrochemical cell and operating means are structured in a manner allowing them to conduct the supply water (6) therethrough as a source material for in situ generation of at least said free hydroxyl radicals from the supply water (6).

19. The method according to claim 18, c h a r a c t e r i z e d i n

connecting, in a flow-communicating manner, the device for destruction of organic material to the downstream side of said underwater device for removal, without filtration, of undesirable solid particles from the supply water (6).

20. The method according to any one of claims 15-19, c h a r a c t e r i z e d i n that the method also comprises a step of connecting, in a flow- communicating manner, the water treatment installation (2) to at least one device (26) for chemical treatment of the supply water (6); the device for chemical treatment comprising at least one replaceable receptacle provided with at least one type of water-soluble solid-state chemical which, upon contact with the supply water (6), is gradually dissolved and mixed with the supply water (6).

21. The method according to claim 20, c h a r a c t e r i z e d i n

connecting, in a flow-communicating manner, the device for chemical treatment to the downstream side of said underwater device for removal, without filtration, of undesirable solid particles from the supply water (6).

22. Use of a water treatment installation (2), as defined in any one of claims 1-14, for removal, under water, of at least one undesirable component from water.