Electrode assembly, electrocoagulation systems and method of purifying water

Abstract

An electrode assembly comprising a hollow electrode comprising a cavity, a casing that encompasses the hollow electrode, a rod electrode in the cavity of the hollow electrode, a hollow electrode electrical connection in the casing, a rod electrode electrical connection in the casing, wherein the casing comprises a fluid inlet and a fluid outlet in fluidic communication via the cavity of the hollow electrode.

Description

[0001] Electrochemical cell

[0002] The present disclosure relates to an electrode assembly, electrocoagulation systems, and a method of purifying water.

[0003] Background

[0004] Coagulation is a ubiquitous process in water treatment systems across the globe. The process objective is to capture (dissolved or suspended) contaminants in a waste stream and render their physical removal from the liquid phase (water) possible and / or efficient.

[0005] An alternative to chemical coagulation is electrocoagulation (EC). The fundamental principles of contaminant removal in EC are the same as in chemical coagulation; the difference lies in the mechanism of sourcing the coagulation agent. While in chemical coagulation this is achieved via dosing a reagent (a soluble metal salt, e.g. ferric chloride) into the effluent stream, in EC this is carried out by controlled corrosion of metallic plates (electrodes), typically of aluminium or steel. The rate of corrosion (which equates to the amount of metal / coagulant dosed into solution), may be controlled by adjusting the current provided to the EC reactors.

[0006] The process is carried out by circulating effluent through EC reactors whilst these are energised. By controlling the effluent flow rate and current intensity, the treatment intensity (the dosing rate) is controlled. Electrode material is spent as part of the process, and consequently the reactors have a finite lifetime. Furthermore, most EC reactors are designed to operate on large industrial scales. Thus, there is a need to provide low-cost easy-to-maintain EC cells and reactors suited to smaller scale commercial and domestic applications such as swimming pool water treatment and the removal of phosphorous from domestic effluent.

[0007] Summary

[0008] This summary introduces concepts that are described in more detail in the detailed description. It should not be used to identify essential features of the claimed subject matter, nor to limit the scope of the claimed subject matter. The inclusion of multiple statements in the same paragraph of the summary does not imply that there is a structural or functional relationship between such statements. In one aspect, a tubular cell (also known as an electrode assembly or electro-coagulation reactor) comprises a hollow electrode and a casing that encompasses the hollow electrode. This is a novel cell design which is very compact and simple to use in small scale electrocoagulation systems. The hollow electrode comprises a cavity, and a rod electrode is positioned in the cavity of the hollow electrode. The electrode assembly comprises a hollow electrode electrical connection (also known as a hollow electrode electrical connector or socket) in the casing and a rod electrode electrical connection (also known as a rod electrode electrical connector or socket) in the casing. The casing comprises a fluid inlet and a fluid outlet in fluidic communication via the cavity of the hollow electrode. An important advantage of the design is that the hollow electrode can be made from off-the-shelf components and fit snuggly inside a standard pipe (the casing), for example of nominal 1 inch (2.54 cm) diameter. Thus, a way to use standard size pipes and fittings to produce a low-cost and easy-to-maintain electrode assembly for use in an electrocoagulation system has been developed.

[0009] The hollow electrode electrical connection may expose an outer surface of the hollow electrode, so as to facilitate access to the hollow electrode for establishing an electrical connection. In particular, the hollow electrode electrical connection may be in a side of the casing, such as a lateral side of the casing. In some examples, the hollow electrode electrical connection comprises an opening in (or protruding from) the casing and a female connector in the casing, wherein the opening is configured to receive a male connector and establish an electrical connection. In such examples, the connectors may be perpendicular to the hollow electrode and the female connector may enable the male connector to be pressed directly against the outer surface of the hollow electrode to establish the electrical connection. The connector of the hollow electrode electrical connection may be received and held in place using any of various means known to the skilled person, such as a snap or screw fit connection.

[0010] The rod electrode electrical connection may be configured to receive the rod electrode. For example, the electrical connection may comprise a female connector configured to receive or grip the rod electrode. In some examples, the rod electrode electrical connection is at an end of the casing, where the electrical connection may comprise a proximal cap configured to mate with a proximal or first end of the casing. The rod electrode may be configured to extend from the proximal cap. Advantageously, the proximal cap allows a secure fit between the rod electrode electrical connection and the casing, to provide a stable electrical connection with the rod electrode. The proximal cap may be configured to mate with the proximal end of the casing with a screw fit, a friction fit, or any other suitable fitting known to the skilled person. In some examples it is advantageous to seal the rod electrode to or against the proximal cap. To achieve this, the assembly can additionally comprise an O-ring configured to seal the rod electrode to the proximal cap. Alternatively, a seal can be made with a sealant, such as a silicone sealant or epoxy resin. In some examples, the proximal cap is configured to position the rod electrode inside the cavity of the hollow electrode. In particular, the proximal end of the casing may comprise a proximal centring piece configured to position the rod, e.g. centre the rod within the cavity of the hollow electrode.

[0011] The hollow electrode electrical connection and / or the rod electrode electrical connection may comprise a threaded connection. Additionally or alternatively, the connection may comprise snap / lock connections, friction fit connections or any other suitable connection known to the skilled person.

[0012] Optionally, the electrode assembly comprises a centring piece at an end of the casing opposite the rod electrode electrical connection and configured to secure the rod electrode. The centring piece may be located in a distal cap at the corresponding end of the casing. In any case, by providing one or more centring pieces, e.g., at the proximal, distal, and / or intermediate portions of the electrode assembly, the rod electrode can be better fitted and secured within the cavity of the hollow electrode, reducing the risk of incorrect placement or unintentional contact between the electrodes.

[0013] The hollow electrode may be configured to operate as a cathode and the rod electrode configured to operate as an anode, or, alternatively, the hollow electrode may be configured to operate as an anode and the rod electrode configured to operate as a cathode. In either case the function of the assembly for electro-coagulation is equivalent, however, it may be advantageous to tailor the polarity of the electrodes in different setups, e.g., for ease of replacement of the anodic electrode which is gradually consumed during operation.

[0014] The hollow electrode may a tube, or substantially tubular in shape, and may be made of iron, steel, aluminium, or any other metal suitable for the purposes of electrocoagulation. The rod electrode may be made of any of the aforementioned materials, and may be made of the same or different material as the hollow electrode.

[0015] The hollow electrode may be sealed against or attached to the casing. For example, the outer surface of the hollow electrode may be sealed against or attached to the casing. The seal is preferably a water-tight seal. The hollow electrode may be sealed or attached using a sealant such as an epoxy sealant or silicone sealant or using an O-ring to provide a seal between the hollow electrode (e.g. a stainless pipe that can operate as a cathode) and the casing (e.g. a plastic pipe).

[0016] In some examples, the rod electrode is a cylinder. The rod electrode may also be concentric with the hollow electrode. Advantageously, this provides the surface of the rod electrode with an equal radial distance to the inner surface of the hollow electrode at all points, which may facilitate a more homogenous degradation of the anode during operation and lengthen the functional duration of the tubular cell, while reducing operating voltage.

[0017] The fluid inlet and / or the fluid outlet may be configured to be connected to inlet and outlet pipes, via hydraulic connectors, to provide a fluid flow through the cavity of the hollow electrode. In some examples, the fluid inlet and / or fluid outlet comprise reversible connectors. Each reversible connector may be configured to connect to a complimentary reversible connector, optionally wherein each reversible connector comprises a union nut, a threaded region, a screw connection or fitting, bayonet mount or fitting, clip fitting, lockable fitting or connector, clamp connector, or latch connecter, or any other kind of suitable connector known to the skilled person.

[0018] The casing is made of an electrically insulating material, such as plastic. Suitable plastics include acrylonitrile butadiene styrene and polyvinylchloride.

[0019] In another aspect, an electrocoagulation system comprises an electrode assembly as described above.

[0020] In another aspect, an electrocoagulation system comprises a pump configured to receive and pressurise feed water; an electrocoagulation reactor configured to receive the feed water from the pump and dose the feed water with a coagulation agent to make dosed water; a mix tank configured to receive the dosed water from the electrocoagulation reactor and allow a precipitate to form in the dosed water; and a filter configured to receive the dosed water and precipitate from the mix tank and remove the precipitate, wherein the pump is configured to pressurise the mix tank. The mix tank may be closed or otherwise sealed to the atmosphere, to enable the pump to pressurise the mix tank. Advantageously, this means that the system only requires a single pump, where conventional systems require multiple pumps e.g. a first pump to pass feed water through an electrocoagulation reactor and a second pump after an open mix tank, because the water needs to be repressurised due to the open nature of the mix tank. The electrocoagulation reactor may be the tubular cell described above.

[0021] The mix tank may be directly connected to the filter meaning, for example, that there is no pump between the mix tank and the filter. For example, the mix tank may be directly connected to the filter via a pipe or connected only via a pipe. The filter may be or comprise a sand filter, a membrane rig, mesh filter, settling tank and / or skimmer. The mix tank may comprise a gas release or degas valve. This may be configured to enable purging of hydrogen generated during operation, improving the safety of the system.

[0022] The feed water may be waste water, such as sewage, agricultural runoff, farming waste, mining waste, swimming pool water or rain water.

[0023] In another aspect, a method of purifying water using an electrocoagulation system comprises receiving feed water at a pump; pressurising the feed water using the pump; receiving the feed water from the pump at an electrocoagulation reactor; dosing the feed water with a coagulation agent using the electrocoagulation reactor to make dosed water; receiving the dosed water from the electrocoagulation reactor in a mix tank; allowing a precipitate to form in the dosed water in the mix tank; receiving the dosed water and precipitate from the mix tank in a filter; and removing the precipitate from the dosed water using the filter, wherein pressurising the feed water using the pump also comprises pressurising the dosed water in the mix tank using the pump. The electrocoagulation system may be the same as any of the systems described above.

[0024] In another aspect, a closed loop electrocoagulation system comprises a settling tank comprising a main inlet for receiving waste water; an electrocoagulation reactor configured to dose the waste water with a coagulation agent; a first conduit fl uidically connecting the settling tank and an inlet of the electrocoagulation reactor; a second conduit fluidically connecting the settling tank and an outlet of the electrocoagulation reactor; and a pump configured to circulate the waste water between the settling tank and the electrocoagulation reactor via the first and second conduits. The electrocoagulation reactor may be the tubular cell described above. Advantageously, this system is particularly suited to purifying relatively small volumes of water delivered at a relatively slow rate (for example, as is the case for domestic or commercial waste water generation in comparison to industrial scale waste water generation) using a low-capacity electrocoagulation reactor. This is possible because the electrocoagulation reactor is in a parallel closed loop with the settling tank, where conventionally it would be in line with the settling tank. Due to the low throughput, waste water in the settling tank can be slowly pumped through the reactor, dosed with coagulant, and returned to the settling tank where precipitates are removed under gravity. The purified supernatant can then be removed from the tank with a lower environmental impact / reduced need for downstream processing.

[0025] The settling tank may further comprise a main outlet for removing water from the settling tank. The first conduit may be configured to extract a supernatant component of the waste water from the settling tank. The settling tank may be a septic tank.

[0026] In another aspect, a method of purifying water comprises pumping water into the settling tank of any of the electrocoagulation systems described above; allowing particulates in the water to settle in the settling tank, to form a settled component and a supernatant component; pumping the supernatant component into the electrocoagulation reactor; dosing the supernatant component with a coagulation agent in the electrocoagulation reactor; and returning the supernatant component in the electrocoagulation reactor to the settling tank. The water may be waste water such as sewage, agricultural runoff, farming waste, mining waste, swimming pool water or rain water.

[0027] Brief Description of the Drawings

[0028] Specific embodiments of the present disclosure will now be described, by way of example only, for the purpose of illustration and with reference to the accompanying drawings, in which:

[0029] Figure 1 illustrates a tubular cell;

[0030] Figures 2 to 4 illustrate closeups of electrical and hydraulic connections of the tubular cell of Figure 1;

[0031] Figure 5 illustrates a cross-sectional view of a hollow electrode electrical connection;

[0032] Figure 6 illustrates a cross-sectional view of a rod electrode electrical connection;

[0033] Figure 7 illustrates a cross-sectional view of the top portion of the tubular cell of Figure 1; Figure 8 is a schematic drawing of an electrocoagulation system with a single pump;

[0034] Figure 9 is a schematic drawing of an electrocoagulation system with two pumps;

[0035] Figures 10a-d illustrate a portion of an electrocoagulation system;

[0036] Figure 11 is a flow diagram for a method of purifying water using an electrocoagulation system; Figure 12 is a schematic drawing of a closed-loop electrocoagulation system; and Figure 13 is a flow diagram for a method of purifying waste water.

[0037] Detailed Description

[0038] Figures 1 to 7 illustrate a tubular cell or electrode assembly 100 for electrochemical water purification. The tubular cell 100 comprises a casing 102 that encompasses a tubular hollow electrode 104 (i.e. a hollow cylinder). An outer surface of the hollow electrode 104 is sealed against the casing 102 with an epoxy sealant, forming a water-tight seal. The casing 102 is electrically insulating and made of acrylonitrile butadiene styrene, although other plastics known to the skilled person are also suitable, such as polyvinylchloride. A cylindrical rod electrode 108 is positioned inside a cavity 106 of the hollow electrode 104. As best illustrated in Figures 5 to 7, which show a cross-section of the tubular cell 100, the rod electrode 108 is concentric with the hollow electrode 104.

[0039] The casing 102 comprises a hollow electrode electrical connection 110 and a rod electrode electrical connection 112. As best illustrated in Figure 5, the hollow electrode electrical connection 110 is in a lateral side of the casing 102 and exposes an outer surface of the hollow electrode 104. The hollow electrode electrical connection 110 is a female connection that extends perpendicularly out of the casing 104 and has internal threading 111. In use, a first external wire 118 for supplying an electrical potential is connected to the hollow electrode 104 via the hollow electrode electrical connection 110. Specifically, the first external wire 118 is mounted in a first external connector 122. The first external connector 122 is a male connector with external threading 123 that mates with the internal threading 111 of the hollow electrode electrical connection 110, although the opposite configuration is of course possible. The first external wire 118 is held in a first conducting block 126 (a machined brass connector or saddle), centred by a locating component 125 inside the first external connector 122 where it is secured to the conducting block 126 using grub screws. The locating component 125 is a 3D printed plastic component that fits inside first external connector 122 (which can be standard piping) to enable insertion of the first conducting block 126 (which can be a brass connector / saddle) that is not unnecessarily large but also enables the first external wire 188 to be safely embedded into the cap. When the first external connector 122 is screwed into the hollow electrode electrical connection 110, the first conducting block 126 is forced into direct contact with an external surface of the hollow electrode 104, thus forming an electrical connection between the hollow electrode 104 and the first external wire 118. The hollow electrode electrical connection 110 is positioned adjacent to the fluid inlet 114, described below; however, it can be located anywhere in the lateral side of the casing 102.

[0040] As best illustrated in Figure 6, the rod electrode electrical connection 112 is at a proximal end of the casing 102. The rod electrode electrical connection 112 is configured to both receive the rod electrode 108 and enable an external electrical connection to be made to the rod electrode 108. The rod electrode electrical connection 112 comprises a male connection portion 130 with external threading 131 and a proximal cap or rod electrode cap 132 with internal threading 134. A proximal centring piece 138 is located in the male connection portion 130 of the rod electrode electrical connection 112 and is configured to centre the rod electrode 108 within the cavity 106 of the hollow electrode 104. In other examples, the proximal centring piece 138 may be integral with the male connection portion 130. The rod electrode 108 passes through the proximal centring piece 138 and the rod electrode cap 132. An O-ring 136 is positioned around the rod electrode 108 and is also positioned between the centring piece 138 and the rod electrode cap 132. The proximal centring piece 138 comprises a lip (or is otherwise similarly configured) to fix it between the male connection portion 130 and rod electrode cap 132 when the rod electrode cap 132 is screwed on. Accordingly, the components are configured such that when the rod electrode cap 132 is screwed onto the male connection portion 130, the O- ring 136 forms a water-tight seal between the rod electrode 108 and the rod electrode electrical connection 112 while allowing a portion of the rod electrode 108 to protrude from the rod electrode electrical connection 112. In other examples, instead of using an O-ring, a seal can be made with a sealant such as a silicone sealant or epoxy resin.

[0041] When in use, a second external wire 120 for supplying an electrical potential is connected to the protruding portion of the rod electrode 108. Specifically, the second external wire 120 is mounted in a second external connector 124 (also known as an anode plug or rod electrode plug). The second external wire 120 is held in a second conducting block 128 (a machined brass connector or saddle) in the second external connector 124. The second external connector 124 comprises a cavity configured to receive the protruding portion of the rod electrode 108, wherein the second conducting block 128 is secured in place against the protruding portion of the rod electrode 108 using a grub screw, thus creating an electrical connection between the rod electrode 108 and the second external wire 120. When the rod electrode 108 is spent, the second external connector 124 is simply disconnected, the rod electrode cap 132 is loosed and the rod electrode 108 slid out of the cell 100 to allow a new electrode to be fitted. The casing 102 comprises a fluid inlet 114 and a fluid outlet 116 (also known as hydraulic connections) in fluidic communication via the cavity 106 of the hollow electrode 104. In operation, water can be pumped through the cavity 106 of the hollow electrode 104 inside the casing 102 via the fluid inlets 114, 116, in order to be electrochemically dosed with coagulant. The fluid inlet and outlet 114, 116 are openings in the casing 102 that extend perpendicularly from the lateral side of the casing 102. The openings of the inlet / outlet comprise / are configured to connect to a water supply via conventional union fittings. Of course, any connection known to the skilled person - permanent or reversible - could be used instead. The fluid inlet 114 and fluid outlet 116 are at opposite ends of the casing 102 e.g. the fluid inlet 114 is at the proximal end of the casing 102 and fluid outlet 116 is at the distal end of the casing 102, or vice-versa. This is ideal as it encourages fluid flow over the entire length of the electrodes, however, this positioning is not essential.

[0042] As best illustrated in Figure 7, the distal end of the casing 102 also comprises a distal cap 142 opposite the rod electrode electrical connection 112. The distal cap 142 mates with, and is configured to provide a water-tight seal to, the end of the casing 102. A distal centring piece 140, also positioned in the distal end of the casing 102, is configured to receive the rod electrode 108 and beneficially centres the distal end of rod electrode 108 within the cavity 106. The distal centring piece 140 may be tapered to facilitate the placement of the rod electrode 108.

[0043] As would be understood by the skilled person, the casing 102 together with the electrical connections 110, 112, fluid inlet and outlet 114, 116, and distal cap 142 can be a single integrated component or can comprise various sub-components joined together e.g. with screw or push fittings, optionally held together with or without a sealant or adhesive. These may be conventional off-the-shelf components. For example the main body of the casing 102 may be a length of pipe and the fluid inlet and outlet and hollow electrode electrical connection may be made from T-pieces inline with the pipe. Similarly, the rod electrode electrical connection 112 may be made, at least in part, from off-the-shelf components. Components such as the centring pieces and parts of the external connectors may be 3D printed or otherwise manufactured from materials such as acrylonitrile butadiene styrene.

[0044] The rod electrode 108 is made of aluminium and is a sacrificial electrode. Other suitable materials include iron, including steel and other alloys of iron. The hollow electrode 104 is made of steel and is a counter electrode. Other suitable materials for the hollow electrode 104 include any material that is a conductor and inert or moderately inert at reductive potentials and suitable for use as a counter electrode, such as aluminium. In operation, the hollow electrode 104 is configured to operate as a cathode and the rod electrode 108 is configured to operate as an anode. This configuration is preferred since the sacrificial rod electrode 108 is easier to replace and will need to be replaced more frequently; however, the electrodes can be reversed such that the rod electrode 108 is the counter electrode / cathode and the hollow electrode 104 is the sacrificial electrode / anode.

[0045] In another aspect, an electrocoagulation system comprises the electrode assembly 100 described above. The electrocoagulation system further comprises a current source connected to the electrode assembly; a process unit comprising a pump configured to circulate fluid in the system; a mixing unit configured to receive fluid from a reactor unit comprising the electrode assembly and agitate the fluid; and a filtration unit configured to concentrate or remove coagulated particles from a fluid, for example as described in UK patent application GB2613533 published on 14 June 2023.

[0046] With reference to Figure 8, in another aspect, an electrocoagulation system 200 for use with a swimming pool comprises a pump 204 configured to receive and pressurise water from a swimming pool backwash water holding tank 202; an electrocoagulation reactor 206 configured to receive the feed water from the pump 204 and dose the feed water with a coagulation agent to make dosed water; a mix tank 208 configured to receive the dosed water from the electrocoagulation reactor 206 and allow a precipitate to form in the dosed water; and a sand filter 210 configured to receive the dosed water and precipitate from the mix tank 208 and remove the precipitate. A UV unit 212 then sterilises the water before it passes into a swimming pool 214. Importantly, the pump 204 is configured to pressurise the mix tank 208 as well as the electrocoagulation reactor 206. As such, the mix tank 308 is sealed to the atmosphere, to better enable the pump 204 to pressurise the mix tank 208. The mix tank 208 is directly connected to the filter 210 via a pipe since there is no need for a pump between the mix tank 208 and the filter 210. In other examples, the feed water may be waste water, such as sewage, agricultural runoff, farming waste, mining waste or rain water. In some examples, the sealed mix tank 308 comprises a gas release or degas valve configured to enable purging of hydrogen generated during operation, improving the safety of the system.

[0047] In contrast to Figure 8, a conventional electrocoagulation system 300 for a swimming pool is illustrated in Figure 9. It comprises a first pump 304 configured to receive and pressurise feed water from a feed water holding tank 302; an electrocoagulation reactor 306 configured to receive the feed water from the first pump 304 and dose the feed water with a coagulation agent to make dosed water; a mix tank 308 configured to receive the dosed water from the electrocoagulation reactor 306 and allow a precipitate to form in the dosed water. The mix tank 308 is a conventional mix tank that is open to the ambient atmosphere (an open vessel). As such, a second pump 310 configured to receive and pressurise precipitate and dosed water from the mix tank 308 is required. A sand filter 312 is configured to receive the repressurised dosed water and precipitate from the second pump 310 and remove the precipitate. A UV unit 314 then sterilises the water before it passes into a swimming pool 316.

[0048] Advantageously, the system 200 of Figure 8 only requires a single pump, where the conventional system 300 requires multiple pumps i.e. a first pump 304 to pass feed water through an electrocoagulation reactor and a second pump 310 after an open mix tank 308, because the water needs to be repressurised due to the open nature of the mix tank 308. That is to say that mix tank 208 of system 200 is a closed vessel capable of withstanding sufficient pressure, such that a single pump 204 can drive the feed water through the whole system 200. This simplifies the system 200 and reduces power consumption, but also improves the performance of the filter as fine particles that have been coagulated / agglomerated as part of the electrocoagulation process are not broken up by a downstream pump. This is particularly relevant where recovered / treated water needs to be below a threshold of particulate concentration to specific water quality standards, such as for swimming pools.

[0049] Figures 10a-d are photographs of an exemplary portion of the electrocoagulation system 200 showing the pump 204, electrocoagulation reactor 206, mix tank 208 and sand filter 210. We note that in this example the electrocoagulation reactor 206 is the electrode assembly 100 described above.

[0050] With reference to Figure 11, in another aspect, a method M-100 of purifying water using an electrocoagulation system comprises receiving M-102 feed water at a pump; pressurising M-104 the feed water using the pump; receiving M-106 the feed water from the pump at an electrocoagulation reactor; dosing M-108 the feed water with a coagulation agent using the electrocoagulation reactor to make dosed water; receiving M- 110 the dosed water from the electrocoagulation reactor in a mix tank; allowing M-112 a precipitate to form in the dosed water in the mix tank; receiving M-114 the dosed water and precipitate from the mix tank in a filter; and removing M-116 the precipitate from the dosed water using the filter, wherein pressurising the feed water using the pump also comprises pressurising the dosed water in the mix tank using the pump. The electrocoagulation system may be the same as any of the systems described above.

[0051] With reference to Figure 12, in another aspect, a closed-loop electrocoagulation system 400 comprises a settling tank 402 comprising a main inlet 404 for receiving waste water; an electrocoagulation reactor 406 configured to dose the waste water with a coagulation agent; a first conduit 408 fluidically connecting the settling tank 402 and an inlet of the electrocoagulation reactor 406; a second conduit 410 fluidically connecting the settling tank 402 and an outlet of the electrocoagulation reactor 406; and a pump 412 configured to circulate the waste water between the settling tank 402 and the electrocoagulation reactor 406 via the first and second conduits 408, 410. The settling tank 402 further comprises a main outlet 414 for removing water from the settling tank 402. The first conduit 408 is configured to extract a supernatant component of the waste water from the settling tank 402. In the present example, the electrocoagulation reactor 406 is the electrochemical cell 100 described above and the settling tank is a septic tank.

[0052] With reference to Figure 13, in another aspect, a method M-200 of purifying waste water comprises pumping M-202 waste water into the settling tank 402 of the electrocoagulation system 400 described above; allowing M-204 particulates in the waste water to settle in the settling tank 402 to form a settled component and a supernatant component; pumping M-206 the supernatant component into the electrocoagulation reactor 406; dosing M-208 the supernatant component with a coagulation agent in the electrocoagulation reactor 406; returning M-210 the supernatant component in the electrocoagulation reactor 406 to the settling tank; and removing M-212 the supernatant component from the setting tank 402 via a main outlet 414.

[0053] The embodiments of the invention shown in the drawings and described above are exemplary embodiments only and are not intended to limit the scope of the appended claims, including any equivalents as included within the scope of the claims. Various modifications are possible and will be readily apparent to the skilled person in the art. It is intended that any combination of non-mutually exclusive features described herein are within the scope of the present invention. That is, features of the described embodiments can be combined with any appropriate aspect described above and optional features of any one aspect can be combined with any other appropriate aspect.

Claims

Claims1. An electrode assembly comprising: a hollow electrode comprising a cavity; a casing that encompasses the hollow electrode; a rod electrode in the cavity of the hollow electrode; a hollow electrode electrical connection in the casing; a rod electrode electrical connection in the casing; wherein the casing comprises a fluid inlet and a fluid outlet in fluidic communication via the cavity of the hollow electrode.

2. The electrode assembly of claim 1, wherein the hollow electrode electrical connection exposes an outer surface of the hollow electrode.

3. The electrode assembly of claim 2, wherein the hollow electrode electrical connection is in a side of the casing.

4. The electrode assembly of any preceding claim, wherein the rod electrode electrical connection is configured to receive the rod electrode.

5. The electrode assembly of any preceding claim, wherein the rod electrode electrical connection is at an end of the casing.

6. The electrode assembly of claim 5, wherein the rod electrode electrical connection comprises a proximal cap configured to mate with a proximal end of the casing.

7. The electrode assembly of claim 6, wherein the rod electrode is configured to extend from the proximal cap.

8. The electrode assembly of claim 7, further comprising an O-ring configured to seal the rod electrode to the proximal cap.

9. The electrode assembly of claims 6 to 8, wherein the proximal cap is configured to position the rod electrode inside the cavity of the hollow electrode.

10. The electrode assembly of any preceding claim, further comprising a distal centring piece at an end of the casing opposite the rod electrode electrical connection and configured to secure the rod electrode.

11. The electrode assembly of claim 10, wherein the distal centring piece is located in a distal cap at the corresponding end of the casing.

12. The electrode assembly of any preceding claim, wherein the hollow electrode is configured to operate as a cathode and the rod electrode is configured to operate as an anode, or wherein the hollow electrode is configured to operate as an anode and the rod electrode is configured to operate as a cathode.

13. The electrode assembly of any preceding claim, wherein the hollow electrode is a tube.

14. The electrode assembly of any preceding claim, wherein the hollow electrode and / or rod electrode are made of iron, steel or aluminium.

15. The electrode assembly of any preceding claim, wherein the hollow electrode is sealed against the casing.

16. The electrode assembly of any preceding claim, wherein the rod electrode is a cylinder.

17. The electrode assembly of any preceding claim, wherein the rod electrode is concentric with the hollow electrode.

18. The electrode assembly of any preceding claim, wherein the fluid inlet and / or fluid outlet comprise reversible connectors.

19. The electrode assembly of any preceding claim, wherein the casing is made of an electrically insulating material.

20. The electrode assembly of any preceding claim, wherein the hollow electrode electrical connection and / or rod electrode electrical connection are threaded.

21. An electrocoagulation system comprising the electrode assembly of any preceding claim.

22. An electrocoagulation system comprising: a pump configured to receive and pressurise feed water; an electrocoagulation reactor configured to receive the feed water from the pump and dose the feed water with a coagulation agent to make dosed water; a mix tank configured to receive the dosed water from the electrocoagulation reactor and allow a precipitate to form in the dosed water; and a filter configured to receive the dosed water and precipitate from the mix tank and remove the precipitate, wherein the pump is configured to pressurise the mix tank.

23. The electrocoagulation system of claim 22, wherein the mix tank is directly connected to the filter.

24. The electrocoagulation system of claim 22 or 23, wherein the mix tank comprises a gas release valve.

25. A method of purifying water using an electrocoagulation system, the method comprising: receiving feed water at a pump; pressurising the feed water using the pump; receiving the feed water from the pump at an electrocoagulation reactor; dosing the feed water with a coagulation agent using the electrocoagulation reactor to make dosed water; receiving the dosed water from the electrocoagulation reactor in a mix tank; allowing a precipitate to form in the dosed water in the mix tank; receiving the dosed water and precipitate from the mix tank in a filter; and removing the precipitate from the dosed water using the filter, wherein pressurising the feed water using the pump also comprises pressurising the dosed water in the mix tank using the pump.

26. The method of claim 25, wherein the electrocoagulation system is the electrocoagulation system of any of claims 22 to 24.

27. An electrocoagulation system comprising:15a settling tank comprising a main inlet for receiving waste water; an electrocoagulation reactor configured to dose the waste water with a coagulation agent; a first conduit fluidically connecting the settling tank and an inlet of the electrocoagulation reactor; a second conduit fluidically connecting the settling tank and an outlet of the electrocoagulation reactor; and a pump configured to circulate the waste water between the settling tank and the electrocoagulation reactor via the first and second conduits.

28. The electrocoagulation system of claim 27, wherein the settling tank further comprises a main outlet for removing water from the settling tank.

29. The electrocoagulation system of claim 27 or 28, wherein the first conduit is configured to extract a supernatant component of the waste water from the settling tank.

30. The electrocoagulation system of any of claims 27 to 29, wherein the settling tank is a septic tank.

31. A method of purifying water comprising: pumping water into the settling tank of the electrocoagulation system of any of claims 27 to 30; allowing particulates in the water to settle in the settling tank, to form a settled component and a supernatant component; pumping the supernatant component into the electrocoagulation reactor; dosing the supernatant component with a coagulation agent in the electrocoagulation reactor; and returning the supernatant component in the electrocoagulation reactor to the settling tank.16

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