Patent Description:
Purification of water is important as regards human activity and environmental protection, firstly, to produce drinking water and secondly, to control environmental load. For example, purification of water, such as wastewater, is needed in the industry, such as the paper, mining and chemical industries, and for purification of service waters, such as greywater (various cleaning waters) or blackwater (toilet wastewater) used in communities (e.g., residential areas) or vessels (e.g., ships).

A solution for purification of such waters is based on electroflotation. In electroflotation, the purification of water takes place by means of electric current. Electric current is conveyed to two electrodes: an anode, to which a voltage is applied, and a cathode, to which a voltage negative with respect to said anode is applied, such as ground potential. Water for purification is arranged between said electrodes, thus water to be purified functioning as an electrolyte. A suitable soluble metal electrode is typically used as the anode. Such apparatuses and methods are described in patent publications <CIT> and <CIT>, for example.

Wastewater treatment in large quantities requires several purifiers, or it is possible to arrange several separate cylindrical purification channels inside one purifier, as illustrated in the aforementioned publications. However, it has been discovered that such a solution is not fully optimal regarding its use of space and, therefore, its material costs. In addition, supplying electricity into the apparatus typically requires suitable lead-throughs for electric wires, which is difficult in terms of the manufacturing technology, at least if there are several purification channels. Furthermore, regarding the use of space of purification plants, it would be necessary to be able to manufacture a purifier that is small in size but has a high purification capacity.

The object of the present invention is to provide a solution for supplying electricity to the inner electrode(s) of the apparatus in such a way that the electrodes are aligned relative to each other. This is achieved with a solution in which the flange of the inner electrode (anode) simultaneously supports the inner electrode and enables supply of electricity from the outside of the outer electrode (cathode). The object of an embodiment is to propose an apparatus with a compact size and reliable operation. This is achieved with a solution in which at least three electrodes are arranged within each other in such a way that at least two flow channels, or gaps, are formed between said three electrodes for water to be purified. Specifically, in such a solution, the precise alignment of the electrodes and supply of electricity would be problematic without the solution proposed now. The invention is set forth more precisely in the independent claim <NUM>. Advantageous embodiments are described in the dependent claims.

In this application, the term "cylindrical shell" means the plane that a line segment forms when passing along a closed curve, the direction of which forms an angle with the longitudinal direction of said line segment in each of its points. The longitudinal direction of a cylindrical shell z means the direction of this line segment. Advantageously, cylindrical shell means the shell of a cylinder with a circular bottom, i.e., the shell of a cylinder. An example of a cylindrical shell, which is simultaneously a shell of a cylinder, is the longitudinal section of a pipe with a circular cross-section. Transverse direction means any direction perpendicular to the longitudinal direction.

In this application, symbols x, y and z mean three different directions perpendicular to each other, of which direction z is the aforementioned longitudinal direction. Advantageously, the aforementioned longitudinal direction z is oriented essentially in the vertical direction during the use of the apparatus. Direction z is oriented essentially in the vertical direction, when said direction z forms an angle of a maximum of <NUM> degrees with the vertical direction (or such an angle is not formed; i.e., it is zero). Advantageously, said angle is less than <NUM> degrees or less than <NUM> degrees.

The figures illustrate apparatuses <NUM> for purifying water. Referring to <FIG>, the apparatus <NUM> includes a cathode arrangement 20a and an anode arrangement 20b. Either one or both of the arrangements can have several electrodes. As will be described below, in an embodiment, the apparatus <NUM> includes a secondary cathode arrangement 20c, in which case the cathode arrangement 20a can be called a primary cathode arrangement. In addition, in an embodiment, the apparatus includes a secondary anode arrangement 20d, in which case the anode arrangement 20b can be called a primary anode arrangement.

The cathode arrangement 20a includes a first cathode <NUM>. The first cathode has the shape of a cylindrical shell (i.e., hollow); in other words, its cross-section forms a closed curve. The first cathode <NUM> has the shape of a longitudinal z profile. In an embodiment, the first cathode <NUM> forms at least a part of the outer casing of the apparatus. In an embodiment, the apparatus <NUM> additionally includes an outer casing (not shown). The first cathode <NUM> is made of an electrically conductive material. Electrically conductive material means material whose resistivity is at most <NUM>-<NUM> Ωm at <NUM>.

The anode arrangement 20b includes a first anode <NUM> having the shape of a bar (solid) or a cylindrical shell (hollow). The longitudinal direction of the first anode <NUM> is the same as that of the first cathode <NUM>. The first anode <NUM> is made of an electrically conductive material. The first cathode <NUM> encircles the first anode <NUM> in the transverse directions perpendicular to the longitudinal direction z in such a way that a first gap <NUM> remains in the transverse direction between them <NUM>, <NUM>) for transporting water to be purified. In the arrangement, the first anode <NUM> is the electrode that wears during use. In addition, the first anode <NUM> is supplied with voltage that is higher than voltage supplied to the first cathode <NUM>. For example, the first cathode <NUM> can be supplied with ground potential. Voltages are described in more detail in the aforementioned publications describing prior art. If the apparatus <NUM> has secondary electrode arrangements (20c, 20d) referred to below, the apparatus also has a secondary gap <NUM>. In such a case, the first gap <NUM> can be called a first primary gap.

If the innermost electrode of the anode or cathode arrangement (20a, 20b), such as 1a in Figure <NUM>, is hollow, the flow of water through it can be prevented with a plug <NUM> (<FIG>). When using the apparatus, all water to be purified is conveyed to the gap <NUM> or gaps <NUM>, <NUM>, <NUM>, <NUM> between the electrodes.

The first cathode <NUM> is the outermost electrode of the apparatus and supplying it with voltage is easy. The cathode <NUM> can include a screw, for example, or similar for connecting the first electric wire <NUM>. Instead, voltage supply to the first anode <NUM> is more difficult, particularly if nested anodes or cathodes are more than one. In addition, to avoid uneven wear of anodes, it is important that the width of the gap <NUM> is constant in the longitudinal direction z.

Due to these reasons, the anode arrangement 20b includes a flange <NUM>. The flange <NUM> is connected to an anode support <NUM>, which is further connected to the first anode <NUM>. The anode arrangement 20b is illustrated in more detail in <FIG> and depicted as a part of the apparatus <NUM> in <FIG>. The first anode <NUM> is only able to move relative to the flange <NUM> within the limits of the material flexibility; that is, almost not at all. The first anode <NUM> can be welded, for example, to the anode support <NUM>. The anode support <NUM> and the flange <NUM> can be parts of one casting of a suitable shape. The first anode <NUM> is supported to the first cathode <NUM> in such a way that the flange <NUM> is mechanically supported to the first cathode <NUM> in said longitudinal direction z. With such an anode arrangement, particularly because the flange <NUM> is supported to the first cathode <NUM>, the longitudinal direction of the first cathode <NUM> is parallel to that of the first anode <NUM> in the apparatus <NUM>.

The anode arrangement 20b additionally includes a connection point <NUM> for connecting a second electric wire <NUM> to the flange <NUM>. In addition, the anode support <NUM> and the flange <NUM> include electrically conductive material for supplying electricity from the connection point <NUM> to the first anode <NUM>. Furthermore, the connection point <NUM> is at least as far from the longitudinal centre axis Ax of the cathode arrangement 20a as such of point of the first cathode <NUM> that is closest to said connection point <NUM>. In such a solution, the connection point <NUM> is on the outer surface, or where the outer surface is composed of a part other than the cathode <NUM>, the connection point is at least as far from the centre axis Ax as the cathode <NUM>. This has the advantage that the second electric wire <NUM> is easily connectable to the connection point <NUM>. Advantageously, the connection point <NUM> is at least <NUM> farther away from the longitudinal centre axis Ax of the cathode arrangement 20a than such a point of the first cathode <NUM> that is closest to said connection point <NUM>. The connection point <NUM> can include a screw connection, for example, for connecting the second electric wire <NUM>.

In an embodiment, the flange <NUM> encircles the centre axis Ax. In other words, the flange <NUM> goes round the entire first anode <NUM> tangentially, perpendicularly against its longitudinal direction z. Thus, there is a good mechanical support to the first cathode <NUM>. To enable the flow of water in such a case, the anode support <NUM> delimits the opening <NUM>, as shown in <FIG>. Water can flow from the opening <NUM> to the gap <NUM>, as in <FIG>, or from the gap <NUM> to the opening <NUM>, as in <FIG>. Depending on the arrangement, the first anode <NUM> can extend from the flange <NUM> in the downstream direction and/or in the upstream direction relative to the flow direction of water to be purified. In terms of the manufacturing technique, it is advantageous that the first anode <NUM> remains completely on one side of the flange <NUM> only (downstream or upstream side, as in <FIG>, respectively). "IN" appearing in the figures indicates the part of the apparatus <NUM> to which water for purification is supplied and "OUT" indicates the part from which purified water is taken out.

To be able to reliably support the anode arrangement 20b to the first cathode <NUM>, the apparatus <NUM> includes, in an advantageous embodiment, fastening means <NUM> for fastening said flange <NUM> to the first cathode <NUM>. For example, such fastening means <NUM> may consist of a bolt and a nut and/or a clip, possibly together with a clamping ring 214b (<FIG>). Advantageously, the first cathode <NUM> includes a projection <NUM>, such as a cathode flange, which extends away from said centre axis AX in said transverse direction, and said fastening means are arranged to fasten said flange <NUM> to said projection <NUM>. For example, the projection <NUM> can have a hole for a bolt, a clip can be fastened to the projection, or the projection can be pressed to the flange <NUM> with the clamping ring 214b. Such a projection <NUM> (cathode flange) is shown in <FIG>, <FIG> and <FIG>, inter alia. This type of fastening can also be used in relation to the other embodiments.

Regarding the operation of the apparatus, it is essential that the cathode arrangement 20a is electrically isolated from the anode arrangement 20b. For this reason, in an embodiment, insulating material <NUM> is arranged between the flange <NUM> and the first cathode <NUM> in said longitudinal direction z. Such insulating material <NUM> may consist of a ring manufactured from a polymer, such as polyethylene (PE) and/or polypropylene (PP). Advantageously, insulating material <NUM> is sufficiently hard to ensure stable supporting of the anode arrangement 20b to the cathode <NUM>. Advantageously, hardness of insulating material <NUM> is at least <NUM> Sh(A) (i.e., Shore hardness measured on scale A), more preferably at least <NUM> Sh(A). For example, several polyethylenes (PE) have such hardness. The apparatus can additionally include sealing material, such as silicone, between the flange <NUM> and the first cathode <NUM> in the longitudinal direction z.

It has been discovered that the anode arrangement 20b wears during the use of the apparatus - as a consequence of electrochemical reactions - particularly in the connection point between the first anode <NUM> (and also the second anode <NUM>, if provided) and the anode support <NUM>, unless electrochemical reactions are prevented in these points. Wearing would have the effect that the anode(s) (<NUM>, <NUM>) would detach from the anode support <NUM>, and the apparatus would fail. For this reason, in an advantageous embodiment, this kind of electrochemical reactions are prevented in these points. However, they are not prevented relating to the actual anode <NUM> in order that purification of water is possible. This prevention can be implemented using a suitable watertight and electrically insulating coating, such as paint, lacquer or glue. An example of these are epoxy based coatings. In an advantageous embodiment, in the anode arrangement 20b, at least [A] the anode support <NUM> and [B] the connection point of the anode support <NUM> and the first anode <NUM> are coated with a water-insoluble and electrically insulating coating, such as lacquer, paint or glue. However, the first anode <NUM> (and any other anodes, such as <NUM>) is/are uncoated for their other parts. The aforementioned connection point <NUM> is also uncoated for connecting the second electric wire <NUM>. The flange <NUM> can be coated for its other parts.

In an advantageous embodiment, the anode support <NUM> and the first anode <NUM> are made of the same metal. Although the anode support <NUM> can in some cases be made of a different metal than the first anode <NUM>, it would be very difficult to connect the anode <NUM> to the anode support 22a, particularly when using aluminium, if the anode support <NUM> were made of a material other than that of the anode <NUM>. More generally, it is easier to connect similar materials to each other by welding as compared to different materials. Advantageously, the anode support <NUM> and the first anode <NUM> are connected to each other by welding.

The first anode <NUM> is made of an anode material. If the apparatus has two different anode arrangements 20b and 20d, this anode material can be called `primary anode material'. For example, the anode material can be one of the following: aluminium (Al), iron (Fe), magnesium (Mg), carbon (C), chromium (Cr), copper (Cu), manganese (Mn), tin (Sn), lead (Pb) and bismuth (Bi). The first cathode <NUM> is made of a cathode material. If the apparatus has two different cathode arrangements 20a and 20c, this cathode material can be called `primary cathode material'. For example, the cathode material can be one of the following: steel, acid-proof steel, stainless steel and graphite. Advantageously, the cathode material is more electronegative than the anode material.

In an embodiment, the apparatus <NUM> additionally includes a power source (not shown) and electric wires <NUM>, <NUM>, <NUM>. The power source is arranged to provide a first voltage, and a first electric wire <NUM> is arranged to supply the first voltage to the first cathode <NUM>. The first electric wire <NUM> can be connected to the first cathode <NUM>. The power source is arranged to provide a second voltage, and a second electric wire <NUM> is arranged to supply the second voltage to the first anode <NUM>. During use, the second electric wire <NUM> is connected to said flange connection point <NUM> (<FIG>). The second voltage is higher than the first voltage. Voltage magnitudes are described in above mentioned prior art. The apparatus <NUM> does not necessarily include a power source and electric wires, but these can be sold separately. If the apparatus includes a secondary anode arrangement 20d, the power source is arranged to provide a third voltage and a third electric wire <NUM> is arranged to supply the third voltage to a first secondary anode <NUM>. The secondary cathode arrangement 20c may have the same potential as the primary cathode arrangement 20a.

In <FIG>, the width of the first gap <NUM> is indicated with the symbol d1. The width of the first gap <NUM> may initially be in the range of <NUM> to <NUM>, for example. During use, the width of the gap increases as the anode <NUM> wears. A corresponding width applies to the other gaps <NUM>, <NUM>, <NUM> of the apparatus, if provided. During use, the apparatus is advantageously oriented in such a way that water to be purified flows essentially upwards in said first gap <NUM> and also in the other gaps <NUM>, <NUM>, <NUM>, if provided.

As described above, water is purified at least in the first gap <NUM>. When processing large amounts of water, several gaps (<NUM>, <NUM>, <NUM>, <NUM>) of this kind are needed. It has been discovered now that, regarding the use of space in water purification plants, it is efficient to use such electrode arrangements 20a, 20b that such gaps (<NUM>, <NUM>, <NUM>, <NUM>) are also nested within each other. For example, in such a way that the first gap <NUM> encircles a second gap <NUM> in the transverse directions perpendicular to said longitudinal direction z. Thus, the first anode <NUM> remains between said gaps <NUM>, <NUM>. Thus, the first anode <NUM> wears during use on both of its sides as a consequence of cell reactions.

Referring to <FIG> and <FIG>, in this embodiment, the first anode <NUM> has the shape of a cylindrical shell (i.e., hollow) so that said second gap <NUM> remains within it. In addition, in this embodiment, the cathode arrangement 20a includes a second cathode <NUM>. The second cathode <NUM> can have the shape of a cylindrical shell (hollow) or a bar (solid). The second cathode <NUM> has the shape of a profile, the longitudinal direction of which is the same as that of the first cathode <NUM>. The first anode <NUM> encircles the second cathode electrode <NUM> in the transverse directions in such a way that a second gap <NUM> remains between the first anode <NUM> and the second cathode <NUM> in the transverse direction for transporting water to be purified (see <FIG> and <FIG>). Such an arrangement doubles the purification capacity compared to a solution in which only one gap <NUM> is used. Advantageously, the first cathode <NUM> and the second cathode <NUM> are made of the same material. Cathode materials are listed earlier.

Referring to <FIG>, in this kind of embodiment, the cathode arrangement includes a cathode support <NUM>, which is arranged to support the second cathode <NUM> to the first cathode <NUM> and to conduct electricity between these. If the second cathode <NUM> is hollow, the support <NUM> can serve as a plug <NUM> for preventing the flow of water into the second cathode (at least if a second anode <NUM> is not used). Alternatively, another plug <NUM> or a solid (or bar-shaped) cathode can be used. For example, the cathode support <NUM> may have the shape of a set of bars, the longitudinal direction of which is perpendicular to said longitudinal direction z. For example, the cathode support <NUM> can have the shape of a plate with holes perforated therein to enable the flow of water. A net can function as the cathode support <NUM>. The cathode support <NUM> includes electrically conductive material in the way as is described in this application regarding electrical conductivity.

Advantageously, the electrodes (i.e., anodes and cathodes) <NUM>, <NUM> (optionally also <NUM>, <NUM>, <NUM>) have the shape of a cylindrical shell with a circular bottom. This is advantageous as regards, inter alia, the manufacturing technique of the electrode arrangements 20a and 20b. Electrochemical cell reactions do not require such a shape; nested electrodes with other shapes, for example with polygonal cross-sections, are also possible.

Referring to <FIG>, this kind of apparatus <NUM> can additionally include a distribution chamber <NUM>, which is arranged to distribute water for purification to said first gap <NUM> and said second gap <NUM>. Referring to <FIG>, in an embodiment, the distribution chamber <NUM> is arranged to distribute water to the gaps <NUM>, <NUM> for making the water flow essentially upwards in said gaps <NUM>, <NUM>. Referring to <FIG>, the apparatus <NUM> can include a collector chamber <NUM>, which is arranged to receive said water from the first gap <NUM> and the second gap <NUM>. In an embodiment, the collector chamber <NUM> is arranged above said electrodes <NUM>, <NUM>, <NUM>. If the apparatus <NUM> includes secondary anode and cathode arrangements 20c, 20d, the collector chamber <NUM> can be arranged to receive said water at least from the first secondary gap <NUM> (see <FIG>). In an embodiment, the collector chamber <NUM> is arranged above the secondary anode arrangement 20d. Referring to <FIG>, although the apparatus would have only one gap <NUM>, the apparatus can have a corresponding distribution chamber <NUM> and/or collector chamber <NUM>.

Referring to <FIG>, the purification capacity relative to the use of space can be improved by using even more gaps <NUM> and <NUM>. In one such embodiment, the anode arrangement 20b includes a second anode <NUM> so that a third gap <NUM> remains outside the second anode <NUM>. Correspondingly, the second cathode <NUM> is hollow. To provide even a fourth gap <NUM> inside the second anode <NUM>, the second anode <NUM> has the shape of a cylindrical shell (i.e., hollow). In addition, in this embodiment, the cathode arrangement 20a includes a third cathode <NUM>. The third cathode <NUM> can have the shape of a cylindrical shell (hollow) or a bar (solid). The longitudinal directions of the electrodes (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) are the same. The anode support <NUM> can be used to provide voltage to the second anode <NUM>. The cathode support <NUM> can be used to provide voltage to the third cathode <NUM>. The second anode <NUM> is made of the same anode material as the first anode <NUM>.

In an evident way, it is also possible to use more anodes and/or cathodes, thus forming more nested gaps for purifying water. It is also possible that the apparatus includes a second anode <NUM> but does not include a third cathode <NUM>, in which case there are only three gaps (<NUM>, <NUM>, <NUM>). In practice, the manufacture of cathodes is inexpensive, which is why there is advantageously one more cathode than there are anodes thus obtaining an even number of gaps. In addition, this has the advantage that the anode (e.g., <NUM> or <NUM>) wears on both of its sides during use, whereupon the gaps (<NUM>, <NUM>, <NUM>, <NUM>) will widen less per the amount of water to be purified compared to a case where the anode would only wear on one of its sides. This is advantageous as regards the control of operating voltage. Furthermore, in such a solution, the replacement need of the anode is reduced because it is possible to use thicker anodes initially. More precisely, in an embodiment, the cathode arrangement 20a includes a first number N1 of cathodes (<NUM>, <NUM>, <NUM>) penetrating a plane P and the anode arrangement 20b includes a second number N2 of anodes (<NUM>, <NUM>) penetrating said plane P. As described above, N1=N2+<NUM>, in other words, the first number N1 is one greater than the second number N2. Thus, the number of gaps (<NUM>, <NUM>, <NUM>, <NUM>) penetrating the plane P is also even. 'Even' means a multiple of number two.

Cathodes <NUM>, <NUM>, <NUM> can be made from a pipe with its wall thickness ranging between <NUM> and <NUM>, such as <NUM> - <NUM>, such as approximately <NUM>. The thickness can be small, because cathodes do not wear. The length of cathodes can be selected as needed. Most suitably, the length is greater than the diameter. For example, the length can be at least <NUM>, such as <NUM> - <NUM> or <NUM> - <NUM> or <NUM> - <NUM>. The innermost electrode can be bar-shaped (solid). However, it may be more advantageous to use a hollow electrode as the innermost electrode as well, plugged with a plug <NUM>.

Anodes <NUM>, <NUM> can be made from a pipe with its wall thickness ranging, for example, between <NUM> and <NUM>, such as <NUM> - <NUM>. Compared to the cathode, a large thickness ensures that it is not necessary to replace anode(s) too often. The length of the anode can be similar to the length of the cathode. Referring to <FIG>, anodes <NUM>, <NUM> do not extend to the cathode support <NUM> to avoid short circuiting electrodes. Advantageously, cathodes <NUM>, <NUM>, <NUM> do not extend to the anode support <NUM>. However, if the aforementioned coating is sufficiently thick, such a coating prevents short circuits of electrodes with the anode support <NUM>.

As is known from prior art, water can be purified with successive electrodes made of different materials. For example, water can be purified first with an iron electrode, which functions as the primary anode, and then with aluminium, which functions as the secondary anode. In this case, it is possible to use the two above-described electrode pair arrangements in succession, i.e., in a cascade. The cathode(s) of the latter electrode pair arrangement can be included in the secondary cathode arrangement 20c and the anode(s) can be included in the secondary anode arrangement 20d. Such arrangements are illustrated in <FIG>, <FIG> and <FIG>.

In <FIG>, the apparatus <NUM> additionally includes a secondary cathode arrangement 20c and a secondary anode arrangement 20d. What is stated above relating to the cathode arrangement 20a also applies to the secondary cathode arrangement 20c mutatis mutandis. What is stated above relating to the anode arrangement 20b also applies to the secondary anode arrangement 20d mutatis mutandis. Consequently, the secondary anode arrangement 20d is electrically isolated from the secondary cathode arrangement 20c using secondary insulating material <NUM>, for example.

In such an embodiment, the secondary cathode arrangement 20c includes a first secondary cathode <NUM>, which has the shape of a cylindrical shell, the longitudinal direction of which is the same as the longitudinal direction z of the first cathode <NUM>. The longitudinal directions are the same, since during use, the longitudinal direction of the primary cathode arrangement 20a is advantageously vertical, as well as that of the secondary cathode arrangement 20c. Referring to <FIG>, in an embodiment, this also has other technical benefits. Referring to <FIG>, the centre axis Ax of the primary cathode arrangement 20a is not necessarily in the same position as the centre axis Ax2 of the secondary cathode arrangement 20c.

Referring further to <FIG>, the secondary anode arrangement 20d includes (i) a first secondary anode <NUM>, which has the shape of a bar or a cylindrical shell, the first secondary anode <NUM> thus having the shape of a longitudinal z profile; (ii) a secondary electrically conductive flange <NUM>; (iii) an electrically conductive secondary anode support <NUM>, which is connected to the first secondary anode <NUM> and the secondary flange <NUM> and arranged to supply electricity to the first secondary anode <NUM>; and (iv) a secondary connection point <NUM> for connecting a third electric wire <NUM> to the secondary flange <NUM>. In the secondary anode arrangement 20d, the secondary flange <NUM> extends in the transverse direction (x, y) from the first secondary anode <NUM>.

Secondary electrode arrangements 20c, 20d are arranged in such a way that the first secondary cathode <NUM> encircles said first secondary anode <NUM> in transverse directions so that a first secondary gap <NUM> remains between the first secondary anode <NUM> and the first secondary cathode <NUM> in said transverse direction for transporting said water. In addition, the secondary flange <NUM> is mechanically supported to the first secondary cathode <NUM> in the longitudinal direction z. In addition, the secondary connection point <NUM> is at least as far from the longitudinal centre axis Ax2 of the secondary cathode arrangement 20c as such a point of the first secondary cathode <NUM> that is closest to the secondary connection point <NUM>.

In such an arrangement, electrically insulating secondary insulating material <NUM> is advantageously arranged between the secondary flange <NUM> and the first secondary cathode <NUM> in the longitudinal direction z. Hardness of the secondary insulating material <NUM> is preferably at least <NUM> Sh(A), more preferably at least <NUM> Sh(A). The apparatus can additionally include sealing material, such as silicone, which remains between the secondary flange <NUM> and the first secondary cathode <NUM> in said longitudinal direction z.

In an embodiment, the first anode <NUM>, or the first anode of the primary anode arrangement 20b, includes primary anode material, which is selected from the group of aluminium (Al), iron (Fe), magnesium (Mg), carbon (C), chromium (Cr), copper (Cu), manganese (Mn), tin (Sn), lead (Pb) and bismuth (Bi). In addition, the first secondary anode <NUM>, or the anode of the secondary anode arrangement 20d, includes secondary anode material, which is selected from the group of aluminium (Al), iron (Fe), magnesium (Mg), carbon (C), chromium (Cr), copper (Cu), manganese (Mn), tin (Sn), lead (Pb) and bismuth (Bi). Furthermore, the primary anode material is a different material than the secondary anode material. Particularly advantageously, the primary anode material includes iron and the second anode material includes aluminium. In addition, the anode arrangements are arranged relative to each other in such a way that the secondary anode arrangement 20d is downstream of the primary anode arrangement 20b, as shown in <FIG> and <FIG>.

When a different material is used in the anode arrangement 20b than in the secondary anode arrangement 20d, different voltage is also preferably used in these. On the other hand, the same potential, such as ground potential, is advantageously present in both the cathode arrangement 20a and the secondary cathode arrangement 20c. This is advantageous in terms of user safety. Due to these reasons, the primary anode arrangement 20b is advantageously electrically isolated from the secondary anode arrangement 20d. In <FIG>, this is realised in a natural way. In <FIG>, second insulating material <NUM> is arranged between the flange <NUM> and the secondary flange <NUM> in the longitudinal direction z for electrically isolating the primary anode arrangement 20b from the secondary anode arrangement 20d.

<FIG> illustrates a compact water purifier, in which two different anode materials can be used. In the apparatus according to <FIG>, the primary anode arrangement 20b extends from the primary flange <NUM> in the longitudinal direction z towards a first direction -z. During use, the primary flange <NUM> is thus in the upper part of the primary anode arrangement 20b. In addition, the secondary anode arrangement 20d extends from the secondary flange <NUM> in the longitudinal direction z towards a second direction +z, which is opposed to the first direction -z. In other words, the first secondary anode <NUM> extends from the secondary flange <NUM> in the longitudinal direction z towards the second direction +z. During use, the secondary flange <NUM> is thus in the lower part of the secondary anode arrangement 20d. In addition, electrode arrangements are centered relative to each other in such a way that the longitudinal centre axis Ax of the primary cathode arrangement 20a is also the longitudinal centre axis Ax2 of the secondary cathode arrangement 20c.

Advantageously, an additive for enhancing floc formation is utilised in water purification. Such an additive can be supplied with equipment <NUM> suitable for the purpose (<FIG>, <FIG> and <FIG>). The additive is advantageously supplied to water at a point, which is located after the anode or cathode arrangement(s) 20a, 20b (or 20a, 20b, 20c and 20d, if provided) of the apparatus <NUM>, in the flow direction of water.

For this reason, in an embodiment, the apparatus additionally includes equipment <NUM> for supplying an additive for enhancing floc formation to water at a point, which is located after the cathode electrode arrangement 20a in the flow direction of water. In an embodiment, the apparatus includes a secondary cathode arrangement 20c and additionally equipment <NUM> for supplying an additive for enhancing floc formation to water at a point, which is located after the secondary cathode electrode arrangement 20c in the flow direction of water. In an embodiment, equipment <NUM> for supplying an additive for enhancing floc formation is arranged to supply said additive as an aqueous solution or powder. In an embodiment, the additive includes a polymer, such as a water-soluble polymer, such as polyacrylamide, for example, cationic, anionic or neutral polyacrylamide. Dry polyacrylamide can be used as an additive. For example, such an agent is known under the trademark Superfloc®. The charge of polyacrylamide may be cationic, anionic or neutral. The additive is advantageously supplied as an aqueous solution.

<FIG> is an exploded view of the electrode arrangements of an apparatus. In the bottom left corner of the figure, there is a bottom plate (not numbered), which delimits the distribution chamber for distributing water to the gaps, as described above.

After this, in the longitudinal direction z, there is a primary clamping ring 214b, which can be used to clamp the projection <NUM> (cathode flange) of the first primary cathode <NUM> to the flange <NUM> of the primary anode arrangement 20b.

After this, in the longitudinal direction z, there is the primary cathode arrangement 20a, which includes a first, a second and a third cathode <NUM>, <NUM>, <NUM>. A projection <NUM>, which in this case is a cathode flange, is arranged in the first cathode <NUM>. After this, in the z direction, there is insulation <NUM> for isolating the primary anode arrangement 20b from the primary cathode arrangement 20a. After this, in the z direction, there is the primary anode arrangement 20b. The primary anode arrangement 20b includes a first and a second anode <NUM>, <NUM>, as well as an anode support <NUM>, a flange <NUM> and a connection point <NUM>. In addition, a second electric wire <NUM> is depicted (not necessarily a part of the apparatus <NUM>, if the power source is sold separately). In the figure, the second electric wire <NUM> is connected to a connection point <NUM>. As shown in the figure, the connection point <NUM> is substantially farther away from the centre axis <NUM> than, for example, the projection <NUM> of the cathode.

When using the apparatus, the anodes <NUM>, <NUM> of the primary anode arrangement 20b are pushed between the cathodes <NUM>, <NUM>, <NUM> of the primary cathode arrangement 20a for forming the above-described gaps <NUM>, <NUM>, <NUM>, <NUM>, as illustrated in <FIG>, for example.

After this, in the longitudinal direction z, there is an insulating ring made of second insulating material <NUM> for isolating the primary anode arrangement 20b from the secondary anode arrangement 20d. Advantageously, the second insulating material <NUM> is also suitably hard. Hardness of the second insulating material <NUM> can be at least <NUM> Sh(A), more preferably at least <NUM> Sh(A). The apparatus <NUM> can additionally include sealing material, such as silicone, which remains between the primary flange <NUM> and the secondary flange <NUM> in the longitudinal direction z.

After this, in the longitudinal direction z, there is the secondary anode arrangement 20d. The secondary anode arrangement 20d includes a first secondary anode <NUM>, a second secondary anode <NUM>, a secondary anode support <NUM>, a secondary flange <NUM> and a secondary connection point <NUM>. In addition, the figure depicts a third electric wire <NUM>, which can be connected to the secondary connection point <NUM>. As shown in the figure, the secondary connection point <NUM> is substantially farther away from the centre axis Ax than, for example, the projection <NUM> of the secondary cathode.

After this, in the longitudinal direction z, there is electrically insulating secondary insulating material <NUM>, which remains between the secondary flange <NUM> and the first secondary cathode <NUM>. Sealing, such as silicone, can also be present between these, as necessary. Preferable hardness of the secondary insulating material is indicated above.

After this, in the longitudinal direction z, there is the secondary cathode arrangement 20c. The secondary cathode arrangement 20c includes a first, a second and a third secondary cathode (<NUM>, <NUM>, <NUM>) and a secondary cathode support <NUM> (corresponding to the primary cathode support <NUM>, cf. <FIG>) and a projection <NUM> for the secondary cathode, such as a secondary cathode flange.

When using the apparatus, the anodes <NUM>, <NUM> of the secondary anode arrangement 20d are pushed between the cathodes <NUM>, <NUM>, <NUM> of the secondary cathode arrangement 20c for forming the above-described secondary gaps (inter alia, the first secondary gap <NUM>).

After this, in the longitudinal direction z, there is a secondary clamping ring 414b, which can be used to clamp the projection <NUM> (cathode flange) of the first secondary cathode <NUM> to the flange <NUM> of the secondary anode arrangement 20d.

Furthermore, the figure depicts the cover plate of the apparatus, which forms the collector chamber for receiving purified water from the secondary gaps (<NUM> inter alia) formed by the secondary anode and cathode arrangements (20c, 20d).

The parts of the embodiment according to <FIG> can be connected to each other with a bolt and a nut, for example, in such a way that the primary clamping ring 214b is clamped to the secondary clamping ring 414b with bolts and nuts, for example, so that the seals and flanges remaining between the clamping rings 214n, 414b are pressed to each other.

Claim 1:
An apparatus (<NUM>) for purifying water, the apparatus (<NUM>) including
- a cathode arrangement (20a), which includes
• a first cathode (<NUM>) having the shape of a cylindrical shell, thus the first cathode (<NUM>) having the shape of a longitudinal (z) profile and
- an anode arrangement (20b), which is electrically isolated from the cathode arrangement (20a), the anode arrangement (20b) including
• a first anode (<NUM>) having the shape of a bar or a cylindrical shell, the longitudinal direction of which is the same as the longitudinal direction of the first cathode (<NUM>),
• an electrically conductive flange (<NUM>),
• an electrically conducting anode support (<NUM>), which is connected to the first anode (<NUM>) and the flange (<NUM>) and arranged to supply electricity to the first anode (<NUM>), and
• a connection point (<NUM>) for connecting an electric wire (<NUM>) to the flange (<NUM>), in which apparatus (<NUM>)
- the first cathode (<NUM>) encircles said first anode (<NUM>) in the transverse directions perpendicular to said longitudinal direction (z) in such a way that a first gap (<NUM>) remains in the transverse direction between the first anode (<NUM>) and the first cathode (<NUM>) for transporting water, and
- said flange (<NUM>) is mechanically supported to the first cathode (<NUM>) in the longitudinal direction (z),
- the first cathode (<NUM>) includes cathode material,
- the first anode (<NUM>) includes anode material, which is selected from the group of aluminium (Al), iron (Fe), magnesium (Mg), carbon (C), chromium (Cr), copper (Cu), manganese (Mn), tin (Sn), lead (Pb) and bismuth (Bi), characterised in that
- said connection point (<NUM>) is at least as far from the longitudinal centre axis (AX) of the cathode arrangement (20a) as such a point of the first cathode (<NUM>) that is closest to said connection point (<NUM>), and
- in the anode arrangement (20b), at least said anode support (<NUM>) and the connection point of said anode support (<NUM>) and the first anode (<NUM>) are coated with a water-insoluble and electrically insulating coating and the first anode (<NUM>) is uncoated for their other part.