Technical field The disclosure herein generally relates to an apparatus and. a method for electrolytic treatment of water.

Background

Polluted water may require treatment to remove the pollution from the water. One method of removing pollution from water is electrolytic treatment wherein an electrically generated floe captures pol 1 utants i n the water.

The electrolytic treatment of polluted water may be able to effectively clean polluted water using a continuous process, which is amenable to the treatment of large volumes of heavily polluted water. Electrolytic water treatments include electrocoagulation, electroflotatton and

electroflocculation, each of which includes the step of operating electrodes in the water being treated.

Electrocoagulation includes the step of passing an electric current between electrodes disposed in water. The electric current in the water alters the charge of pollution particles, which

subsequently gather together to form larger particles that may be removed by, for example, a water filtering step. Electroflotation requires the use of inert electrodes disposed in water. Operating the electrodes causes the release of hydrogen at the cathode and oxygen at the anode. The resulting bubbles may capture pollutants from, the water and float the resulting floe to the surface for subsequent separati n.

Electroflocculation includes the step of operating a sacrificial anode electrode in the water being treated. The metal at the anode electrode is dissolved into the water during operation. The resulting metal ions formed bond to pollutants in the water, which subsequently aggregate via the flocculation process. Gasses released at one or more of the electrodes float some of the pollutants to the surface.

The aggregated pollutants may: ^♦ in the ease of electrof] otation and electrofloceulation, be settled and/or floated to the surface, under the influence of released oxygen and hydrogen gas bubbles, for removal; and

^♦ in the case of el ectrocoaguSation, be filtered and/or settled for removal. in the case of electrofloceulation, the aggregated pollutants ("floe") floated to the surface may be forced over a spillway. Efficient floe removal requires that the water level should be at or near the top of the spillway, so that the floe is removed with minimum loss of water over the spillway.

Contemporary electrolytic treatment systems may, however, have disadvantages that prevent more common acceptance in regions that require water treatment. At some locations, example of which include but are not limited to a mine at a remote location and a developi ng country, it may not be practical to prepare an ideal site at which the electroly tic treatment apparatus is to be located. The electrolytic water treatment apparatus may be placed on an uneven or sloping surface. Consequential tilting of the apparatus may interfere with operation of the electrolytic treatment apparatus, Summarv

Disclosed herein is an apparatus for electrolytic treatment of water received thereby . The apparatus comprises a pluralit of co municating chambers for the water when so received, and an eleetrode assembl operable to form a floe in the water when so received, wherein each of the plurality of communicating chambers has a spillway arranged for discharge of the floe when so formed. The height of the spillway of at least one of the plurality of communicating chambers is adjustable to the height of the spillway of another one of the plurality of communicating chambers.

When the apparatus is initially located on a sloping surface, for example, the height of the spillways may be different and the water level in each of the plurality of communicating chambers may not be the same. Consequentially, the floe may be unable to be discharged from a higher one of the spillways. This may result in the water retaining pollution that may otherwise have been removed. Too much water may flow from a lower one of the spillways, which may waste water or render the apparatus inoperable, The apparatus may, however, be adjusted after it is located to ameliorate this problem b adjusting the spillway of the one of the plurality of communicating chambers to be the same height as the spillway of the other one of the plurality of communicati g chambers. in an embodiment, the spillway of the at least one of the plurality of communicating chambers comprises a lip attached to a pivot operable to change the height of the spillway. The pivot may be operable to change the height of the lip. The pivot may be operable to swing the lip outwardly to change the height of the spillway. When the lip is so outwardly swung, the lip may slope upwardly. The lip may comprise an impermeable sheet material. The impermeable sheet material may extend below the lip and be pressed against a wall of the at least one of the plurality of communicating chambers to form a seal The lip may extend substantially between two walls of the one of the plurality of communicating chambers. The Hp may extend between the two walls of the one of the plurality of com muni eating chambers. The two walls may press the

impermeable sheet material to form a plurality of seals between the lip and the two walls.

An embodiment may comprise a floe mover arranged to move the floe over the spillway. The floe mover may be arranged to move the floe over the lip. For example, an embodiment comprises a wave generator at the one of the plurality of communicating chambers. The wave generator may be arranged to generate waves in the water directed at the lip. The slope may promot the breaking of a wave at the lip, which may resul t in more efficient removal of floe from the surface of the water. Alternatively, Hie floe mover may comprise a floe wiper.

An embodiment comprises a vessel and the plurality of communicating chambers are within an interior volume of the vessel. The plurality of chambers may be defined by a plurality of walls di viding the interior volume of the vessel. In an embodiment, the height of the spillway of the other of the plurality of communicating chambers is vertically adjustable. If there is yet another communicating chamber, for example, the height of the two- aforementioned spillways may be adjusted to the height of the yet other communication chamber. The height of the spillway of the yet other communicating chamber may be, but not necessarily, vertically adjustable, In an embodiment, a plurality of spillways of the pluralit of communicating chambers are adjusted to the height of the other one of the plurality of communicating chambers.

An embodiment comprises a spillway immobi liser arranged to immobilise the spillway of the at least one of the plurality of communication chambers.

An embodiment comprises a water outlet having a floe barrier, the water outlet being of adjustable height. Disclosed herein is a method for electrolytic treatment of water. The method comprises the ste of a plurality of communicating chambers receiving the water, each of the communicating chambers having a spillway. The method comprises the step of adjusting the height of a spillway of at least one of the plurality of communicating chambers to the height of another one of the plurality of communicating chambers. The method comprises the step of forming a floe in the water. The method comprises the step of causing the floe to spill over the spillway of each of the plurality of communi cating chambers.

In an embodiment, the step of adjusting the height of the spillway of the at least one of the plurality of communicating chambers comprises operating a pivot attached to a lip of the spillway of the at least one of the plurality of communicating chambers.

An embodiment comprises the step of operating the pivot to swing the li outwardly. Operating the pivot to swing the lip outwardly may orientate the lip to slope upwardly.

An embodiment comprises the step of generating waves directed at the spillway.

An embodiment comprises the step of dividing an interior volume of a vessel with a pluralit of walls to form the plurality of communicating chambers.

An embodiment comprises the step of adjusting the height of the spillway of the other one of the plurality of communicating chambers.

An embodiment comprises the step of adjusting the height of a plurality of spillways of the plurality of communicating chambers to the height of the other one of the plurality of

communicating chambers.

An embodiment comprises the step of immobilising the lip.

An embodiment comprises the step of adjusting the height of a water outlet having a floe barrier.

Any of the various features of each of the above disclosures, and of the various features of the embodiments described below, can be combined as suitable and desired. Brief description of the figures

Embodiments will now be described b wa of example only with reference to the

accompanying figures in which; Figure 1 shows an outline front elevation view of one embodiment of an apparatus for electrolytic treatment of water received t ereby.

Figure 2 shows an outline side elevation view of the apparatus of figure 1, Figure 3 shows a side elevation view of one example of a spillway, Figure 4 shows a front elevation view of the spillway of figure 3.

Figure 5 shows plan view of the spillway of figure 3,

Figure 6 shows an outline front elevation view of the apparatus of figure 1 without hinged membrane mechanisms.

Figure 7 shows an outline side elevation view of the apparatus of fi gure 6, Figure 8 shows a plan view of the apparatus of figure I chamber including a wave generator.

Figure shows another elevation side view of the embodiment of figure 1 including a water inlet and a water outlet.

Figure 10 is a plan view of an example of the electrode assembly of the apparatus of figure 1.

Figure 1 1 is a schematic of an electrode plate of the electrode assembly of figure 10,

Figure 12 is a side view of the electrode assembly of figure 10.

Figures 13 and 14 show front and side views of an. example of the wave generator of the apparatus of figure 1. Figures 15 and 16 are plan and side view respectively of an example of an oscillating floe wiper mechanism that may be used with the apparatus of figure 1 ,

Description of embodiments

Figures 1 and 2 respectively show a simplified schematic front elevation view and a simplified schematic side elevation vie of one embodiment of an apparatus for electroly tic treatment, of water received thereby, the apparatus being generall indicated by the numeral 10. In those illustrations the front surface is shown transparent, in order to di splay the features in the context of the apparatus. The apparatus 10 comprises vessel 21 having a plurality of chambers 31 , 32, 33 and 34 for the water when so received. The chambers are separated from each other by a substantially water tight wall 23 , The walls 23 stop at a height lower than the spillways 41-44 at the top of the vessel's front wall 1 1, over which polluted floe can be directed into a floe capture means in the form of a gutter 27 with front retaining wall 18, at the bottom of which is a drain 29 to allow the floe to drain away.

The water enters chamber 31 and flows progressively through to chamber 34. Electrode assemblies 28 are located in chambers 31 and 32, and in use are submerged i the water. The electrode assemblies 28 are operable to form a floe in the water when so received. A portion of the floe that ma have captured pollutant from the water floats to the water's surface, A series of barriers 12 are associated with separation walls 23. These barriers 12 prevent the surface floating floe from passing from one chamber to another, while still allowing the water to pass through passages 25 into the next chamber. In some of the chambers, the barrier 12 directs the water to the bottom of the next chamber, as shown in chambers 32 and 33. Others direct the water to the top of the chamber, as shown in. the water entry to chamber 34.

In order to adequately remove the surface floe from the top of the water, the water level is generally within a few millimetres (say less than 10 mm) of the spillways 41-44. If the spillways are not substantially at the water level of each of the chambers, surface floe removal may not be efficient from some of the chambers, and/or the water may flow continuously out of .one or more of the chambers. Either of these events greatly reduces the efficiency of the process and may even prevent it from working. To overcome this possibility ⁷ , the height of the spil l way of any one of the plurality of communicating chambers 31 to 34 is adjustable to the height of the spillway of any other one of the plurality of communicating chambers 31 to 34.

Adjusting the spillways 41 to 44 may compensate for a tilt of the apparatus when located, for example, on uneven ground or small dimensional errors introduced during manufacture. An alternative embodiment may comprise, for example, a vessel for each of the plurality of communicating chambers, the vessels being connected by hoses, for example. The apparatus may generally have any suitable configuration.

Details of the spillways having, adjustable height are now given. Figure 3 shows a side elevation view of one example a spillway in the form of a hinged membrane mechanism 42. Figure 4 shows a front elevation view of the spillwa 42 of figure 3. Figure 5 shows a plan view of the spillway 42 of figure 3. When in use, floe is forced over a lip 13 of the spillway 42. The hinged membrane mechanism 42 consists of an impermeable flexible membrane 36 connected to a hinge consisting of lower leaf, 15, connected to an upper leaf 14, that move about a pin centred on pivot line 16. Depending upon the size of the hinge, it may be necessary to have reinforcing plates, 37 and 38, to hold the flexible membrane in place against the hmge(s) and the wall. 11. When the lip 13 is so outwardly swung the membrane 36 may slope upwardly towards lip 13. The membrane 36 provides a watertight seal . The spillways 41 -44 may be altered to the desired height. The membrane ma extend all the way between the partitions 12. The membrane may be pressed and/or attached to the spillway wall 1 1 by the lower leaf 15. The reinforcing plate 38, or leaf 15 may extend almost all the way between the partitions 12. The membrane may be firmly attached so that water does not leak through or past it The pivot point 1 may be near to or above the upper level of wall 1 . The membrane may be firmly attached to leaf 1.4, with the reinforcing plate 37, or hinge part 14, extending al most all the way (or al l the way to form seals) between the partitions 12. The various components may be held in position by any suitable means, examples of which include but are not limited to fasteners, e g. screws, fixed into the walls of the chamber, rivets penetrating the wail or bolts and nuts, gluing or welding the components together, or any combination or variation thereof, An appropriate water sealing means may be used around any mechanical fasteners, for example a silicone or a polyurethane such as SIKAFLEX

The material for the water impermeable flexible membrane 36 may be, for example, any suitable natural or synthetic rubber or a plastic. Generally, any material that is sufficiently flexible to bend about the pivot 16 and make a seal may be suitable. Optionally, a sealing compound (examples of which include but are not limited to a silicone and SI AFLEX) may be used to make the seal at the partition walls 1 1, or seal any leaks that may occur.

In this but not necessarily in every embodiment, each hinged membrane mechanism 42, has an immobiliser 17 that holds the hinged membrane mechanism in a desired position. Figure 3 shows a exam pi e of an i mm obili s er com pri sing a brack et attach ed to the reinforcing pi ate 37, for example, at each end near the partitions. The bracket has a threaded hole. In operation, an immobiliser screw or bolt 19, is screwed through 17 such that it presses up against partition 1 2 and holds the hinged membrane mechanism in place, In other embodiments, the immobiliser may take any suitable form, examples of whi ch include but are not limited to a cam or a clamp. In operation the vessel 21 ma be disposed on a surface, with or without the hinged membrane mechanisms 41 , 42, 43 , 44 attached. If the vessel is horizontally level, then the top of the front wall 1 1 will be at the same level for all of the chambers. In this case there is no need for the hinged membrane mechanism to be installed on the vessel and it could be operated as indicted in figures 6 and 7. If the vessel i s not horizontally level, for example because it is disposed on an uneven or sloping surface, then the top of the front wall 1 1 will be at different levels for at least some of -the plurality of chambers. In this undesirable case, (a) floe may, for example, not be effectively moved over the higher of the spillways, and/or (b) the water in the vessel may freely flow over the lower of the spillways and subsequently lost, in this case, the hinged membrane mechanisms may be installed as required and individually adjusted such that the top edges of the lip 13 of each of the chambers is at the same height . The flexibility of the hi nges, reinforci ng plates and membrane of hinged membrane mechanism 42, as described, may enable the mechanism to be set at a higher level at one end than at the other. The impermeable sheet material 36 may press against one of the plurality of communicating chambers to form water tight seal.

The spillways of the other of the plurality of communicating chambers 32, 33, 34 may, but not necessarily, be similarly configured so that their height can be adjusted.

Each of the chambers 31 to 34 inclusive has a wave generator 5 1 mounted on the rear wall 21 of the plurality of communicating chambers, as shown in figure 8. The wave generators 51 are arranged to generate waves i the water when so received directed at the lip 13. The slope may promote the breaking of a wave at the lip 24, which: generally results in more efficient removal of floe from the surface of the water. Another embodiment has a floe scrapper that moves across the surface of the water, either alternative to or additional to the wave generator. Generally any suitable means may be employed to move the floe over the spillways.

Figure 9 shows another el evation side view of the embodiment of figure .1. Water flows into the first chamber 31 via water inlet 80. The inlet 80 is in this but not necessarily in all embodiments positioned so that the water enters at a point substantially close to the regio where th water first passes through the electrodes 28. The water progresses through the system 30, into the final chamber 34. The final chamber contains a water outlet of adjustable height 82. The water outlet has a opening at the water surface. The water outlet may have a floe barrier, not shown, that blocks the floe from entering the water outlet rim 82. In this embodiment, the floe barrier may take any suitable farm. The outlet rim 82 is connected to a down pipe 84 through which the treated water flows, a height adjuster 86 in the form of a screw mechanism (or any other suitable mechanism, examples of which include but are not limited to a concertinaed or telescopic pipe section). The outlet 82 has a water outflow conduit in the form of a water outflow pipe 88. The water outflow pipe 83 may have a larger area overflow weir to allow better adjustment of the height of the water with changes of flow rate through the system, The water outflow component 83 may also be used to adjust the height of the water outflow level to maintain the ^' water just below the spillway levels 13.

Changing the heights of the adjustable spillways ma change the level of the water in the outlet chamber 34. In order to maintain the appropriate water height required for pollutant removal, the height of the outlet 82 may also be changed. Incorrect adjustment may result in non removal of the pollutant in one or more of the chambers.

The correct height of the outlet 82 may be matched to the level, of the water in each of the chambers, ensuring correct operation of the system even when not installed on a smooth horizontal surface, Sealant may be used to improve the water tightness, examples of which include a silicone, epoxy. Alternatively gaskets may be used to provide seals.

The impermeable sheet 36 is attached to the rigid supports 34, 15. The rigid supports are, in this but not necessarily in all embodiments, sheets of stainless steel , but may be of a polymer or generally any suitable material in other embodiments. Rigid support 14 is part of the lip 13 and is attached to the impermeable sheet 36. Attachment may be by fasteners, or bonding by, for example, an adhesive or a heat fusion treatment. Rigid support 15 is attached to the front wall by fasteners in the form of a bolt and nut, although any suitable attachment may be used, for example rivets and self-taping screws, 52, may b used, or the rigid support may be attached by a weld. In alternative embodiments, the hinges may be replaced with a single hinge that is long enough to extend the entire distance between the vessel end wails and have sufficiently wide and rigid leaves. The pins of the hinges are positioned such that the bottom of the lip is located at the top of the front wall. Having the pin above the top may raise the level of the water. Havin the pin below the top may provide a cavity where some of the floe is caught. The water may generally be polluted by any pollutants that may or may not include at least one of oil, living biological material, dissolved molecules, suspended solids, chemicals and minerals. The apparatus may be operable to remove at least portion of the pollution.

The vessel 21 ma comprise any one of a tank, container, receptacle, vat, cistern, repository, reservoir, vessel or basin, and any other suitable structure for containing water. Water may be communicated between the chambers by water conduits in the form of hoses, gutters or any suitable means. In this embodiment, the vessel 21 and chambers 31-34 are open at their top. however in other embodiments at least some of the containers may be closed. Generally any suitable configuration of containers and vessels may be used.

Electrode assemblies 28 are disposed in two of the chambers. Other embodiments, however, may have an electrode assembly in more or less chambers. The electrode assembli es comprise electrodes i the form of a plurality of electrode plates. The electrode assemblies are operable to form a fl oc in the water. The passage of a current (generally less than 200 amps per square meter and u to 500 amps per square meter of active electrode area) through the water between the electrode assembly plates causes reactions at both anode and cathode plates. Chamber 31 has a electrode assembly with iron anodes and iron or stainless steel cathodes, however in some embodiments the electrode assembly may have aluminium anodes and stainless steel cathodes. An embodi ent has inert anode and cathode electrodes, for example stainless steel o platinum electrodes, Generally any suitable electrode assembly may be used.

In the embodiment of figure 1, two- of the- lurality of communicating chambers 33, 34 are each without an electrode assembly. After electrolytic treatment in chambers 31, 32, there may still be a signifi cant quantity of floe within the water, for example there may be between 10% and 20% of the total generated floe. It may be desirable that some time be allowed for this floe to settle out of the water, either by rising up or settling down, A chamber or container without an electrode assembly provides a "resting" phase, one that does not involve the use of active electrodes. A single chamber or container with the passage of water talcing approximately 12 min may allow about half of the residual floe to separate out. Further settling may take longer.

Maximum floe removal ma occur after 12 hours settling. This may be too long to be viable in a single vessel, but may be performed by using a separate settling tank. Having a plurality of resting chambers or containers ma yield better results than a single container of the same volume as the plurali ty of resti ng containers, Figure 10 is a plan view of an example of the electrode assembly 28 of the apparatus 10 of figure 1. The electrode assembly 28 consists of a plurality of parallel electrode plates, for example plates 108. A single electrode plate 103 is shown in Figure 1.1, Each electrode plate 103 may have at least two holes 104 and 106, by which they can be connected. Some of the electrode plates may act as an anode and others may act as cathodes. If the electrode plates are of the same size, each may have a corner section of plate opposite hole 104 removed as illustrated b 105, Thi s may allo alternative plates to be connected. Holes 104 may allow insulating means 128, in this embodiment being cylindrical insulating spacers of appropriate di ensions, to be supported by an insulating rod 127, The plurality of plate electrodes 108, each of which ^' has a configuration similar to 103, are electrically connected to each other by conducting spacers 114 and held by a threaded or other means 1 16 passing between holes 104. These conducting spacers 1 14 may have an insulating layer on their surface to prevent them from being eroded during operation. Interspaced approximately equally spaced between the plurali ty of pl ate electrodes 108 is another plurali ty of plates electrodes I 10, each and all subsequent of which has a configuration similar to electrode plate 103, similarly electrically connected to each other by conducting spacers 1 14, also held rigidly together by threaded or other means.

Spacers 1 14 make an electrical connection from plates 1 10 to another set of plates 1 12. In turn plate 1 12 have another set of plates 1 18 interspaced approximately equally between them, which set of plates 118 may also be electrically connected to each other through conducti ng spacers.

Similarly, plates 118 are electrically connected t plates 120 also via conducting spacers. Plates 120 have plates 122 interspaced between them. In turn plates 122 are electrically connected to plates 124 which have plates 126 interspaced between them .

The electrode assembly 28 is mounted on a mounting means 130 in the form of an electrically insulating stand, made from a suitable water resistant material such a high densit polyethylene (HDPE), high density polypropylene (HDPP) or similar. One end. of an electrical connector in the form of a cable 132 is connected to one polarity of the DC or rectified AC power supply* for example the positive terminal. The other end of the electrical connector is connected to the plate assembly 108 making plates 108 the anode. Another electrical connector 134 is connected to the other polarity of the DC or rectified AC power supply for example the negative terminal and also to the plate assembly 126 making plate 126 the cathode.

In operation the electrode assembly 28 is placed in either one of chamber 31 and chamber 32 for example. The electrodes are immersed. A DC voltage is applied between electrical leads connected to the electrode assembly . An electrical current will flow between the plates. The current comprises charged ions.

In the example shown in figure 10, each of the four sets of plates is shown consisting of 10 anode surfaces and 10 cathode surfaces, each surface being either side of the plates in the body of the sets, plus the inner surface of the two outer plates. Figure 1.0 shows that the outer plates may be either anode or cathode. The number of surfaces is not restricted to the embodiment shown in figure 10 Allowing that the potential applied between the anode 108 and cathode 126 by lead 134, is + 4V (in this but not necessarily in all embodiments), where V is a voltage, it is apparent that plates 108 will have a voltage of + 4V, plates 1 10 and 1 12 will have a voltage + 3 V, plates 118 and 120 will have a voltage of + 2 V, plates 122 and 124 will have a voltage of IV and plates 126 will have 0V. With plates 108 having a voltage of + 4V and plates 118 having a voltage of + 2 V the anode and cathode may only be only a short distance apart, 115. This is repeated between plate sets 1 12 and 122, (distance 1 17), and plate sets 1.20 and 126, (distance 119). With half of the voltage drop being across a short distance there may be strong attraction for the current to pass directly, for example, from plates 108 to plates 1 18 without passing through the intermediate plates 1 10 and 1 12. The same trend exists between plates 3 12 and 122 and plates 120 and 126. When current bypasses an intermediate plate set, not all of the reaction occurs in all of the plates, resulting in less efficiency of operation and a significant amount of metal remaining unreacted when some of the electrodes have been fully sacrificed, adding to the cost of the process. If the number of plates used gives less than six surfaces of each exposed to the other, th ions could still travel around the barriers meaning that intermediate anodes are not sacrificed. This results in significant loss of efficiency and increase in cost,

To overcome this, sheets of flexible electrical insulators 109 may be positioned between the sets of plates 108 and 118; 1 12 and 122; 120 and 126. The insulating slieets extend beyond the physical extent of the plates 102 and may extend to the walls of the chamber 32 into which the are to be inserted. The plates are held together in this assembly by rods 127, which also hold in place the insulating spacers 128, in this example being made of plastic cylinders cut to the same length, which keep the plates together in a rigid structure. In this manner, electrical connections are made between like plates and insulating spacers keep apart plates that will be used as cathodes and anodes. By placing insulating barriers 109 between the sets of plates 108 and 118; 1 12 and 122; arid 1 0 and 126, this forces ions to take a significantly longer path to get around the insulating barrier. This minimises the loss of current and increases the efficiency of the process.

Tire electrode assembly 28 comprises a plurality of plates that are spaced apart between 2% and 7% of the height of at least one of the plurality of plates. A desirable density of metal in the plate assembly may be achieved if the distance is less than 5% of the plate height, Some advantages may be gained if the maximum plate separati on is less than 4% of plate height. The applicant has found that this range is generally but not necessarily a suitable compromise between preventing clogging of the plates and sufficiently low electrical resistance between the plates to produce the flocculating ions at a sufficient rate. The height of the electrode assembly ma be at least one half of the height of the one of the plurality of communicating containers that the electrode assembly is disposed within. This may provide a substantial amount of sacrificial electrode material (at least one of aluminium and iron for this embodiment), which may increase the operational life of the electrodes compared to electrodes of lesser height.

The operation of the electrode assembly 28 may be significantly impeded by the build up of material on and/or between electrode plates during normal operation. The material may form an insulating layer on the electrode plates reducing current and electrical efficiency. Material build up on and/or between the plates al so may require the electrodes to be replaced before they are substantially consumed, that is before the end of their maximum achievable accumulated period of operation. Electrode replacement costs, which are a major expense, may be significantly reduced by reducing or eliminating the build up of material on and/or between electrode plates, which may subsequently allow the electrode plates to be operated until they are substantially consumed. The built up material may be an oxide of the cathode material . The hydroxide ions generated at the cathode plates may attack the metal cathode to form oxides and/or hydroxides. Aluminium oxides and/or hydroxides bond strongly to aluminium. Iron cathodes do not suffer from this problem. Embodiments described herein, but not necessarily all embodiments, that have an aluminium anode plate, have a stainless steel cathode plate to avoid oxide build up on the cathode. The may also have an iron cathode.

The vessel 21 and the walls thereof may be fabricated from a plastic, for example HDPE or HDPP, a metal, for example stainless steel, or generally any suitable material. The vessel 21. may have an exoskeleton, not shown, to strengthen the vessel for containing water.

Figures 13 and 14 show front and side views of an example of a wave generator 51 that may be used with the apparatus of figure 1. An electric motor 140 is mounted on a mounting board 142 and connected to a flywheel 144. The fl wheel 144 has a connecting rod 146 that is connected to a push mechanism 148, both connections being capable of allowing rotation. The push mechanism 148 has push rods 150 attached to them. Two of these are guided through a guide mechanism 152, which keeps their motion vertical, A wave making paddle 153 is at the bottom of these push rods. The mounting board i s positioned near the rear of the vessel 21, opposite the spillways. It is preferably attached to or near the rear wall, 36, of the vessel 21. The paddle is located adjacent the top of the water surface 54 when the pus rod is in the upper position, as indicated in figure 14. Applying a voltage to the electric motor causes the flywheel 144 to rotate, moving the connecting rod 146. This moves the push bar and the pushrods 150 and hence the paddle 153 moves up and down. The period of motion may be approximately 0.5 sec - 1, 5 sec . For ease of operation, the assembly may be mounted via hinge mechanism 161, such that it can he swung out of the way when it is necessary to exchange the electrode plate sets. Figures 15 and 16 are plan and side views respectively of a example of an oscillating floe wiper mechanism 167 that ma be used with the apparatus of figure 1. A motor with a limited angular travel, such as a windscreen wiper motor, 164, is placed upon the vessel adjacent the spillway, and being held in position by any suitable mounting 166 for example at least one clamp..

Rigidly attached to the motor's rotor is an arm 168, which has a guide slot 170 that enables a rod 1.7.2 to move through it if required. The rod 172 is rigidly attached to wiper 174 in the form of a sheet of ri gi d or semi rigid m ateri al, for exampl e l ow density polyethylene (LDPE), HDPE, polypropylene (PP), nylon or even metal sheet, of sufficient depth to extend above and below the water surface, which is set by the height of the spill ways,, so that it may move the floe that will accumulate at the top of the water, 54. The wiper 174 may substantially extend between both partitions and/or side walls at either side of each container. The end container's floe may b retained b a vessel's wall. At the wiper 174 end closest to the motor 164, the wiper means 174 may be hinged 176 in the corner between the vessels floe spillway 13 and the partition or wall 12. In its rest position the motor leaves the arm 168 against the floe barrier 12.

In operation a voltage is supplied to the motor 164. The motor rotates, moving the arm 168 in the direction indicated by the arrow 180. As arm 168 moves it takes the wiper 1 4 through the water bringing the wiper substantially against the spillway 1 1, pushing the floe ahead of it over into the floe gutter 21. The motor 164 returns the arm and hence wiper back to the floe retaining barrier. The floe withi the arc described by the wiper will be pushed off the water surface and over the spillway lip 13, removing the surface floe from the chamber. An mechanical disturbance, such as the activation of the wave generator 139, will cause floe to flow rapidly into this region. By this means, floe which has built up on the water's surface wilt be pushed into the floe gutter 27 and removed.

Variations and/or modifications ma be made to the embodiments described without departing from the spirit or ambit of the invention. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive,

Prior art, if any, described herein is not to be taken as an admission that the prior art forms part of the common general knowl edge in any juri sdiction. in the claims which follow and in the preceding description of the invention, except where the context requires othenvise due to express language or necessary implication, the word

"comprise" or variations such as "comprises" or "comprising" is used i an inclusive sense, that is to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodi m ents of the inventi on.