GB2522234A

GB2522234A - Apparatus and method for waste treatment

Info

Publication number: GB2522234A
Application number: GB1400833.8A
Authority: GB
Inventors: Nigel Brown; Edward Roberts; Donald Eaton; Akinlabi Adeyemi
Original assignee: Arvia Technology Ltd
Current assignee: Arvia Technology Ltd
Priority date: 2014-01-17
Filing date: 2014-01-17
Publication date: 2015-07-22
Anticipated expiration: 2034-01-17
Also published as: GB201400833D0; GB202019287D0; GB2591181A; GB2591181B; GB2522234B

Abstract

A method and apparatus for the treatment of a waste liquid, the method comprises mixing a contaminated waste liquid with an acid to form a treatment mixture and contacting the treatment mixture with a carbon-based adsorbent material to adsorb contaminant. The adsorbent is regenerated by passing an electric current therethrough to release from the adsorbent gaseous products derived from the contaminant. The apparatus comprises a reservoir 4006 for waste liquid to be treated; the reservoir comprising acid for mixing with the waste liquid. A carbon-based adsorbent material 4002 capable of electrochemical regeneration is provided in the reservoir and a means for regenerating 4008 the adsorbent by passing an electric current therethrough. An agitator distributes the carbon-based adsorbent material in waste liquid contained in the treatment reservoir. Further methods and apparatus are disclosed. Advantageously the waste liquid requiring treatment is maintained at a low pH without the need for an external dosing tank thus reducing the cost and complexity of treatment.

Description

APPARATUS AND METHOD FOR

WASTE TREATMENT

The present invention relates to methods and apparatus for the treatment of wastes contaminated with organic matter, in either dissolved or dispersed forms. These include wastes that have been created through emulsification, dispersion and dissolving. The present invention has particular, but not exclusive, application in the treatment of organic wastes containing radioactive species including actinides and lanthanides.

Many methods have been developed to treat aqueous organic wastes. Prior art methods typically exploit the treatment of aqueous organic wastes through the contacting of the waste with a porous material (industrially the most widely used adsorbent is activated carbon), Porous materials contain internal pores, into which organic components are either adsorbed or absorbed, depending upon the nature of dissolution of the organic component in the water. Irrespective of the take-up mechanism, the presence of internal pores has negative implications for the electrochemical regeneration of porous materials. As established in "Electrochemical regeneration of granular activated carbon"; R M Narbaitz, J Cen; Wat. Res. 28 (1994) 1771-1778, the electrochemical regeneration of such materials is limited because electrochemical oxidation of the adsorbed contaminants can only occur on the external surface of the adsorbent material. Organic components adsorbed or absorbed into the internal pores of the material are not oxidised when exposed to an electric current. As a result, loaded porous materials must be disposed of to landfill, incinerated with the ash going to landfill, or are regenerated using a thermal regeneration process.

However, thermal regeneration requires transportation to specialist off-site regenerators and is a high temperature, high cost process that results in a material loss of 5-10%. For the treatment of organic wastes contaminated with one or more types of radionuclide, the loaded porous material becomes a secondary radioactive waste with additional treatment complexities and cannot be sent to landfill.

The system and method described in UK patent no. GB2470042B and International patent applications W02013054101 and PCT/GB2013/051823 obviates or mitigates many of the problems previously associated with the removal of organic components from aqueous waste. The inventions described in these cases relate to the treatment of aqueous organic wastes by the adsorption of the organic components followed by subsequent oxidation of the organic components and sequential or simultaneous regeneration of the adsorbent, within a single unit, using relatively low power and circumventing the need to dispose of, or thermally regenerate, the material used during treatment.

UK Patent no GB2470042 and European patent no EP2029489 provide methods and apparatus for the batch treatment of the above wastes, International application W02013054101 provides a method and apparatus for the continuous treatment of waste water, while unpublished International application PCT/GB2013/051823 provides an improvement to both the batch and continuous processes by teaching a method in which the direction in which the regenerating current is passed through the spent adsorbent is periodically reversed.

Waste produced during the operation of nuclear power plants is often contaminated with a wide range of radionuclide. The exact concentration and form of these active species is not often known, providing a difficulty in ensuring safe treatment. These types of waste are classified according to the concentration of radionuclides contained in the waste and the type of radioactivity that the contained radionuclides emit. Traditionally these wastes are either stored on-site or are sent for incineration. For storage purposes, the storer must have a licence to store radioactive material. The Nuclear Decommissioning Authority has recently issued a £70 billion legacy for the treatment of radioactive wastes and storage is no longer a preferable option. For incineration, there are a limited number of incinerators throughout the UK and each incinerator has a limited capacity for the incineration of radioactive material Consequently, organic wastes particularly, but not only, those containing intermediate levels of radioactivity are unjustifiably expensive to incinerate and only small volumes at a time can be incinerated. Other conventional treatment options for the treatment of radioactive waste are not suitable for organic waste, for example the long term storage in the form of grouting or cementation, because the organics have a tendency to leach out into the environment, distributing radioactivity. There is therefore a need to develop improved processes and apparatus for the treatment of radioactive organic waste. International patent application W02010/149982 describes methods for the treatment of such waste however further refinement and improvement of these methods is desirable.

In prior art methods employing electrochemical regeneration of the adsorbent, when the electric current is applied, charged inorganic species in the aqueous organic waste migrate to the oppositely charged electric current feeder and some species undergo electrodeposition at the electric current feeder, converting from solution phase species to solid phase species, for example, copper. This can lead to a build-up of electrodeposited inorganic species on the electric current feeders, which, when working with radioactively contaminated organic wastes is particularly undesirable because of the risk of criticality from the electrodeposition of certain radionuclides. The solubility of radioactive species is complex and process conditions need to be managed appropriately to prevent formation of precipitated species.

During the further development of the systems described in UK patent no. GB2470042B and International patent application W02010/149982 it has become apparent that their performance in certain circumstances may be enhanced by the use of an external chemical dosing tank to maintain a low p1-i within the treatment zone for optimal performance. While performance advantages can be obtained by using an external means to maintain a low pH, it would be desirable to obviate the need to provide the dosing tank since this adds to the cost and complexity of the overall decontamination process.

In prior art systems, such as those described in UK patent no. GB2470042B and International patent application W02010/149982, the cathode is typically provided in an isolated cathode compartment fed with an electrolyte to ensure a high conductivity and therefore a low voltage between the electric current feeders. The electrode assembly consists of a micro-porous membrane, a cathode and chemical dosing system built into one inseparable, sealed "unit" to prevent catholyte leakage or the migration of adsorbent material from the anode compartment through to the cathode compartment. By way of example, one electrode assembly of size 500 mm x 500 mm may weigh approximately six kilograms and there can be a number of assemblies in any one unit. If there is a fault with an individual part of the assembly, the entire assembly must be removed from the treatment tank and replaced. To maintain high conductivity in the cathode compartment, a membrane defining micro-pores maintains a high concentration of ionic components in the cathode compartment, The small diameter of the micro-pores prevents the rapid diffusion of ionic components from the solution in the cathode compartment into the solution in the anode compartment, however, suitable micro-porous materials can be unstable in alkaline conditions, which can add additional complexity to the overall treatment process, Furthermore the micro-porous material typically cannot prevent the osmosis of water from the anode compartment into the cathode compartment, which dilutes the electrolyte solution in the cathode compartment and necessitates the addition of further electrolyte throughout operation of the system. There is also the possibility of hydrogen accumulating in the electrode assembly due to the catholyte compartment being isolated. Conveniently, the chemical dosing system may be used to transport away any hydrogen that is produced, however, as mentioned above it would be desirable to obviate the need for the dosing system to reduce the cost and complexity of the system.

An object of the present invention is to obviate or mitigate one or more of the problems currently associated with existing methods for treating contaminated fluids.

According to a first aspect of the present invention there is provided a method for the treatment of a waste liquid, the method comprising: mixing a contaminated waste liquid with an acid to form a treatment mixture; contacting the treatment mixture with a carbon-based adsorbent material to adsorb contaminant therefrom; and regenerating the adsorbent by passing an electric current therethrough to release from the adsorbent gaseous products derived from the contaminant.

According to a second aspect of the present invention there is provided an apparatus for the treatment of a waste liquid, the apparatus comprising: i) a reservoir for waste liquid to be treated, the reservoir comprising acid for mixing with the waste liquid; U) carbon-based adsorbent material capable of electrochemical regeneration provided in the reservoir; iii) a means for regenerating the carbon-based adsorbent by passing an electric current therethrough to release from the adsorbent gaseous products derived from the contaminant; and iv) an agitator operable to distribute the carbon-based adsorbent material in waste liquid contained in the treatment reservoir.

The system of the first and second aspects of the present invention provides strongly acidic conditions in the treatment reservoir and maintains a low pH when mixed with waste liquid to be treated. This is to be contrasted with prior art systems in which neutral or weakly acidic solutions were used since they were thought to be the optimum environment for electrochemical waste treatment. The system of the first and second aspects of the present invention offers a number of

advantages over the prior art.

Firstly, it has been surprisingly found that the potential for formation of certain metal precipitates is significantly reduced. As a result, significantly less precipitation occurs during operation of the treatment system. This has the consequence that the system of the present invention requires less cleaning to remove such precipitates and parts are less likely to be rendered inoperable due to precipitate formation precipitates.

Secondly, the use of acid increases the electrical conductivity of the liquid to be treated as compared to when only a weakly acid solution is used, thus lowering the electrical resistance of the liquid to be treated. For example, and without exemplifying the invention, it has been observed that when operating a system with a solvent incorporating 75% sulphuric acid at a current of 5 A, the voltage across two electrodes is approximately 2V as compared with a voltage of approximately YV when operating an electrochemical system in a pure water solvent. Consequently, the systems according to the first and second aspects of the invention can utilise lower cell voltages, lower cell energy requirements and so lower treatment costs.

Thirdly, some materials can passivate upon attempted electrochemical regeneration) often due to the formation of undesirable surface layers. The increased solubility of metals at lower pH means that formation of a surface layer on the adsorbent material occurs to a significantly reduced extent and hence the risk of passivation is similarly reduced.

Fourthly, the presence of acid ensures that any hydroxide ions produced during treatment are neutralised. Thus, the mixture to be treated maintains a low pH without use of an external chemical dosing tank, reducing the cost and complexity of the overall decontamination process.

Without wishing to be bound by theory, it is thought that the acidic nature of the mixture used, and potential of the system, affects the speciation of ions in solution, which in turn affects solubility.

The waste may be an aqueous organic waste. In a preferred embodiment of the first and/or second aspects of the present invention the method and apparatus can be adapted for the treatment of waste containing radionuclides without having to employ incineration or other undesirable prior art treatment options. In this way, radionuclides contained in the organic component of the waste are transferred into an acid phase upon oxidation of the organic components. As the formation of metal precipitates is reduced, the risk of criticality from the electrodeposition of certain radionuclides is similarly reduced. Additionally, the acidic mixture used in the treatment process can also be re-used for decontamination of further radioactive contaminated waste. As a result, minimal radioactively contaminated secondary waste is produced. The present invention therefore offers a solution to the decontamination of radioactive organic waste that previously had no viable treatment options other than the process described in International patent application W020101149982.

Preferably, the acid for mixing with the waste liquid comprises nitric acid or sulphuric acid. The acid may comprise a mixture of acidic compounds, such as a mixture of nitric acid and sulphuric acid, or may consist only of a single acidic compound. The concentration of the or each acid in the treatment mixture may be greater than about 10%, such as greater than about 25%. In embodiments the concentration of the or each acid in the treatment mixture may be greater than about 50%, such as greater than about 75%.

Metal cations, including actinides and Lanthanides, can form soluble complexes with other anionic groups, which can reduce the possibilities of producing precipitates. Increasing the concentration of anionic species suitable for complexation with such metal cations by using strong acids can increase this complexation and hence further reduce precipitate formation. Uranium, for example, can create a soluble complex with nitrates to form U02(N03)2(I-1202)2. 1-lence the choice of acid can aid in keeping these active species in solution.

The treated liquid, containing a lower concentration of organic components, can either be subjected to one or more further treatment cycles or it can be removed from the treatment reservoir.

The various aspects of the present invention can each be carried out continuously, semi-continuously or on a batch basis. Thus, fluid in need of treatment can be continuously passed through the adsorbent, or individual volumes of fluid to be treated can be contacted by the adsorbent as a batch, with the adsorbent material being regenerated during treatment of the respective batch or between batch treatments as appropriate.

An eminently suitable system for a continuous operation of the method and apparatus of the first and second aspects of the present invention is described in European patent no. EP2029489. In accordance with this system, a first preferred embodiment of the method of the first aspect present invention further comprises passing the treatment mixture through a reservoir containing the adsorbent material while recycling the adsorbent material along a path including passage through a regeneration chamber within the reservoir. A voltage is applied to cause passage of the electric current. The recycling path for the adsorbent material comprises the regeneration chamber and at least one adjacent treatment chamber within the reservoir, which chambers define substantially parallel sections of the recycling path. In such a method, air under pressure is delivered to the base of the reservoir to move the adsorbent material along the recycling path and the adsorbent material in the chamber is regenerated as it is recycled through the regeneration chamber.

In a related preferred embodiment, it is preferred that the apparatus of the second aspect of the present invention further comprises a regeneration chamber provided in the reservoir, the agitating means being adapted for recycling adsorbent material along a path including passage through the regeneration chamber and in a body of treatment mixture in the reservoir. The regeneration chamber is defined between two electrodes for coupling to a source of electrical power. The recycling path for the adsorbent material comprises the regeneration chamber and at least one adjacent treatment chamber within the reservoir, which chambers define substantially parallel sections of the recycling path. The agitating means comprises means for delivering air under pressure to the base of the reservoir to move the adsorbent material along the recycling path.

The treatment and regeneration process according to the first embodiment can be continuous or semi-continuous. An individual volume of liquid can be treated as a batch, with the adsorbent material being regenerated as the respective batch is treated, or between batch treatments. Some compounds may also be treated within an undivided cell, provided there is no continuous electrical connection between the cathode and anode through the solid conducting adsorbent material. In a continuous or semi-continuous process the flow rate of the liquid through the apparatus is determined and controlled to ensure a sufficient dwell time in contact with the recycling adsorbent.

An eminently suitable system for batch-wise operation of the method and apparatus of the first and second aspects of the present invention is described in International application W02010128298. In accordance with this system, a second preferred embodiment of the method of the first aspect of the present invention further comprises delivering the treatment mixture to a treatment reservoir containing the adsorbent material in the form of a bed of particles at a base of the treatment reservoir. The bed is agitated within the treatment reservoir to assist distribution of the adsorbent material in the fluid and adsorption of contaminants from the fluid. The agitation is ceased and the adsorbent material is allowed to settle. Treated liquid is removed from the reservoir.

Agitation may be provided in any convenient manner, such as by use of a mechanical mixer, but is most conveniently provided by delivery to the treatment unit of pressurised fluid, e.g. air and/or a quantity treatment mixture.

In a related preferred embodiment, it is preferred that the apparatus of the second aspect of the present invention is further characterised in that the reservoir for the treatment mixture has an upper and a lower section, and contains the adsorbent material in the form of a bed of particles supported in the lower section at the base of the reservoir. In such an apparatus, the agitator is adapted for agitating the bed to distribute the particles in liquid contained in the reservoir including the upper section. Regeneration is achieved by providing electrodes on opposite sides of the lower section for delivering electric current to pass through the bed of particles, According to the second embodiment, the bed is agitated for a period to distribute the adsorbent material in the liquid and adsorb contaminant therefrom, at the end of which period the agitation ceases, allowing the bed of material to settle, During this settlement period the adsorbent will separate from the liquid. The degree of separation depends upon the length of time allowed. It is possible to adjust the time scale according to the nature of the liquid being treated. The adsorbent is then regenerated, during or after settlement, by passing an electric current through the bed to release from the adsorbent gaseous products derived from the contaminant in bubbles rising through the decontaminated liquid in the reservoir, which is then removed. The liquid can of course be removed before the adsorbent is finally regenerated. At different stages of the regeneration period, the current can be adjusted. For example, at the beginning of the regeneration period, only a very thin layer of the adsorbent will have settled so a smaller current is required than later in the regeneration period when substantial settlement has occurred.

An eminently suitable system for continuous operation of the method and apparatus of the first and second aspects of the present invention is described in International application W02013054101. In accordance with this system, a third preferred embodiment of the method of the first aspect of the present invention is characterised in that the carbon based adsorbent is in the form of a bed of material and that the step of contacting the treatment mixture with the adsorbent is conducted by admitting the treatment mixture into the bed of adsorbent at a flow rate which is sufficiently high to pass the mixture through the bed but below the flow rate required to fluidise the adsorbent material within the bed, In a related preferred embodiment, it is preferred that the apparatus of the second aspect of the present invention is characterised in that the adsorbent material is provided as a bed and that the means for regenerating being provided by at least one pair of electrodes operable to pass the electric current through said bed to regenerate the adsorbent material. In such an apparatus, the agitator is adapted to admit the treatment mixture into said bed to contact said adsorbent material at a flow rate which is sufficiently high to pass the mixture through the bed but below the flow rate required to fluidise the bed of adsorbent material.

In this way, controlling the flow rate of the treatment mixture entering the adsorbent material bed so as to pass the treatment mixture through the bed but ensure the adsorbent material remains within the bed for regeneration enables the adsorption and regeneration processes to be carried out simultaneously within the same bed of adsorbent material. It is therefore preferred to pass an electric current through the bed simultaneously with the admission of contaminated treatment mixture through the bed. The adsorbent material can adsorb contaminants from the treatment mixture whilst, within the same adsorbent bed, an applied electric current causes gaseous products derived from the adsorbed contaminant to be released from the adsorbent material thereby regenerating the adsorbent material and restoring its ability to adsorb further quantities of contaminant.

Contacting of the treatment mixture with the adsorbent material may be achieved through controlled agitation of the adsorbent. Controlled agitation may be achieved by feeding one, or more preferably multiple, parallel jet streams of the liquid under pressure to the adsorption bed. Each individual stream of treatment mixture will generate a cylindrical or funnel shaped passage of treatment mixture through the adsorbent bed, drawing particulate adsorbent material from the lower region of the adsorbent bed and carrying it upward through the adsorbent bed. A downward flow of adsorbent material is produced around the upward flow of treatment mixture and entrained adsorbent material thereby defining a discrete, endless stream of adsorbent material within the adsorbent bed flowing along an endless path.

During the upward passage of treatment mixture and adsorbent material, the adsorbent material separates contaminants from the treatment mixture by a process of adsorption whereby contaminants attach to the surfaces of the particles of the adsorbent material.

When the upward passage of contaminated liquid and particulate adsorbent is at the top of the adsorbent bed, the treatment mixture will cumulate or build-up in the liquid reservoir and the adsorbent material will remain within the adsorbent bed. The decontaminated liquid is free or substantially free of used adsorbent material and can then be released as desired via the outlet feed.

The degree of decontamination of the treatment mixture can be monitored by taking one or more samples of the accumulated liquid from the reservoir, and the liquid subjected to further treatment accordingly.

As the endless streams of adsorbent material are established in the adsorbent bed the electrodes are operated to pass an electric current through the adsorbent bed. The regions of adsorbent material flowing downwards possess a high enough packing (number of adsorbent particles per unit area) to be sufficiently electrically conductive to facilitate electrochemical regeneration of the adsorbent material. This oxidises the adsorbed contaminants releasing them in the form of carbonaceous gases and water thereby regenerating the adsorbent material and restoring its ability to adsorb further quantities of contaminant.

The treatment mixture in need of treatment must be contacted by the adsorbent material for a sufficient period of time to achieve satisfactory separation of the various components, i.e. transfer of target component(s) from the treatment mixture to the adsorbent material. Satisfactory contact time is ensured by controlling the velocity of the fluid through the adsorbent bed. This depends upon the initial velocity of the treatment mixture injected into the tank and the density and height of the adsorbent bed.

The maximum velocity of the treatment mixture within the adsorbent bed is just below the velocity that would cause fluidisation of the adsorbent particles. Fluidisation is produced when the velocity of the treatment mixture is above the sedimentation rate of the adsorbent particles. The sedimentation rate of the adsorbent particles can be calculated according to Stokes's law and depends upon particle size, particle density and particle shape. The minimum velocity of the treatment mixture is the velocity required to define an endless path along which the adsorbent material can flow within the adsorbent bed. Paths of adsorbent material are produced when the adsorbent bed is of a low enough density to allow free movement of the adsorbent material.

However, the efficiency of the adsorbent bed to undergo electrochemical regeneration depends upon a high density of adsorbent material within the adsorbent bed. Thus, the velocity of the treatment mixture through the adsorbent bed and the density of the adsorbent bed are interdependent and each parameter should be optimised while taking into account the other parameter.

An eminently suitable system for batch-wise operation of the method and apparatus of the first and second aspects of the present invention is described in unpublished International application no. PCT/GB2013/051823. In accordance with this system, a fourth preferred embodiment of the method of the first aspect of the present invention is characterised in that the waste liquid is admitted into first and second treatment zones of a treatment reservoir, the first and second treatment zones being separated by a porous membrane and the carbon based adsorbent being provided in said first and second treatment zones. In this method, the adsorbent material is distributed in the treatment mixture within each treatment zone and allowed to settle. First and second electric current feeders are operably connected to the first and second treatment zones respectively and are operated to pass an electric current in one direction through the carbon-based adsorbent material within each treatment zone to regenerate the carbon-based adsorbent material in one of the first and second treatment zones. The first and second electric current feeders are operated to reverse the direction of the current applied to the carbon-based adsorbent material in the first and second treatment zones to regenerate the carbon-based adsorbent material in the other of the first and second treatment zones.

In a related preferred embodiment, it is preferred that the apparatus of the second aspect of the present invention is further characterised in that the treatment reservoir defines first and second treatment zones separated by a porous membrane, the carbon-based adsorbent material being provided in said first and second treatment zones. The agitator is operable to distribute the carbon-based adsorbent material in treatment mixture contained in each of the first and second treatment zones. A first electric current feeder is operably connected to the carbon-based adsorbent material in the first treatment zone and a second electric current feeder operably connected to the carbon-based adsorbent material in the second treatment zone. A controller is provided to operate the first and second electric current feeders to pass an electric current through the carbon-based adsorbent material in the first and second treatment zones in one direction to regenerate the carbon-based adsorbent material in one of the first and second treatment zones and to then reverse the direction of the current applied to the carbon-based adsorbent material in the first and second treatment zones to regenerate the carbon-based adsorbent material in the other of the first and second treatment zones. When the electric current is fed through the beds of adsorbent material the bed adjacent to the positive electric current feeder may be considered to behave as an anode and the bed adjacent to the negative electric current feeder may be considered to behave as a cathode.

The treatment reservoir may be in the form of a tank or a chamber. A lower section of the treatment reservoir may define a smaller horizontal cross-sectional area than an upper section of the treatment reservoir, which may facilitate settling of the carbon-based adsorbent following agitation.

The first and second treatment zones may be defined within the treatment reservoir so as to be provided at any desirable location with respect to the treatment reservoir and with respect to one another provided the porous membrane defines an interface between the two treatment zones. It will be appreciated that the treatment reservoir may define two or more treatment zones with a porous membrane defining an interface between neighbouring treatment zones. The porous membrane may be configured to prevent carbon-based adsorbent material from passing between the first and second treatment zones but to permit water and/or ionic species to pass between the first and second treatment zones. In a preferred embodiment, the treatment reservoir contains two parallel or side-by-side beds of the carbon-based adsorbent material capable of electrochemical regeneration, Each treatment zone may be provided with a dedicated agitator to agitate the carbon-based adsorbent material contained within its respective treatment zone. The agitator may be adapted to fluidise the carbon-based adsorbent material. The or each agitator preferably comprises one or more nozzles, inlets or apertures defined by a wall, preferably the base, of the respective treatment zone through which a fluid under pressure can be admitted into the carbon-based adsorbent material retained in the respective treatment zone. The agitator preferably further comprises a chamber under the treatment reservoir defining said one or more inlets and a pump to deliver fluid under pressure through said inlet(s). The fluid may be air, treatment mixture and/or waste liquid requiring treatment.

It is preferable to maintain the applied electric current in this first direction for a sufficient period of time to oxidise organic components adsorbed on to the adsorbent material from the treatment mixture and to thereby regenerate the adsorbent material. During this process, protons are produced in the bed behaving as an anode and hydroxide ions are produced in the bed behaving as the cathode. Reversal of the direction of the applied current switches the formerly positive current feeder so that it is a negative current feeder and the formerly negative current feeder so that it is positive. As a result the bed of adsorbent material that formerly behaved as an anode now behaves effectively as a cathode and the bed that formerly behaved as a cathode now behaves as an anode.

This then enables organic components from the treatment mixture that have been adsorbed on to the adsorbent material in the bed now acting as an anode to be oxidised and the adsorbent material in that bed regenerated.

The steps of distributing the carbon-based adsorbent material in the treatment mixture and allowing the carbon-based adsorbent material to settle may be repeated one or more times to remove organic matter from the treatment mixture prior to operating the first and second electric current feeders to reverse the direction of the current applied to the carbon-based adsorbent material.

S

Alternatively or additionally, the steps of distributing the carbon-based adsorbent material in the treatment mixture and allowing the carbon-based adsorbent material to settle may be repeated one or more times to remove organic matter from the treatment mixture prior to removing the treated liquid from the treatment reservoir.

Preferably the or each cycle of distribution and settling steps is effected over a time period of ito 60 minutes. Where more than one cycle is employed, each cycle may be effected over the same time period or different time periods may be employed, In a preferred embodiment the or each cycle of distribution and settling steps is effected over a time period of around 20 minutes. is

Distribution of the carbon-based adsorbent material is preferably effected by admitting a fluid under pressure into the carbon-based adsorbent material. Any suitable fluid may be used, for example the fluid may comprise air, treatment mixture and/or waste liquid in need of treatment.

Charged inorganic species are generated during the passage of the electric current through the carbon-based adsorbent material in the first and second treatment zones. The current feeders may be operated to minimise the electrodeposition of said charged inorganic species on the current feeders during operation, It is preferred that the first and second current feeders are operated to pass the electric current through the carbon-based adsorbent material in the treatment zones in said one direction for a time period of 1 to 240 minutes, and/or in said other direction for 1 to 240 minutes. The electric current may be passed through the carbon-based adsorbent in each direction for a similar time period, such as around 120 minutes, 5 minutes or different time periods may be employed. Where different time periods are employed for each direction, the time period over which the electric current is applied in either direction may vary throughout the period over which treatment is being effected or it may remain the same.

The first and second current feeders may be operated to apply any suitable electric current density to the carbon-based adsorbent material in the first and second treatment zones to effect the desired level of oxidation of adsorbed organic matter. An electric current density of 1 to 30 mAcm2 may be employed, more preferably an electric current density of around 6 to 20 mAcm2, and most preferably an electric current density of around B mAcm 2 may be applied by the current feeders to the carbon-based adsorbent material in each treatment zone.

The first and second current feeders may be operated to apply any suitable electric current to the carbon-based adsorbent material in the first and second treatment zones to effect the desired level of oxidation of adsorbed organic matter. An electric current of 1 to 10 amps may be employed, in one embodiment an electric current of around 5 amps may be applied by the current feeders to the carbon-based adsorbent material in each treatment zone, The current feeders may be operated to provide any desirable pH in the treated liquid. For example they may be operated to provide a low pH.

It will be appreciated that the ability to treat the treatment mixture whilst periodically reversing the direction of the electric current provides a method with significant advantages as compared to prior art methods, even those described in UK patent no. GB2470042 and International patent application W020101149982, which themselves represented significant advances over earlier methods.

As mentioned above, proton species are produced in the bed acting as an anode and hydroxide species are produced in the bed acting as the cathode. During operation, the proton and hydroxide species are distributed in the liquid undergoing treatment resulting in the liquid pH of the liquid being maintained consistently. The fourth embodiment thus enables the apparatus to operate without an external chemical dosing tank because the periodic reversing of the electric current maintains a consistent pH within the treatment system. The elimination of a chemical dosing tank reduces the complexity of the system, eliminates the need for chemicals to be delivered to the site on which the equipment is installed, and minimises the secondary waste associated with the treatment process.

Another advantage of the system of the fourth embodiment over the systems described in the prior art is that a variety of different materials can be used for the porous membrane or divider which separates the first and second treatment zones. In the systems described in UK patent no. GB 2470042 and International patent application W02010/149982 the solution in the cathode compartment has a high conductivity, whereas the solution in the anode compartment does not need to be conductive, To maintain high conductivity in the cathode compartment, a porous membrane material containing micro-pores maintains a high concentration of ionic components in the cathode compartment. The necessarily small diameter of the micro-pores prevents the rapid diffusion of ionic components from the solution in the cathode compartment into the solution in the anode compartment. Preferred materials containing micro-pores can be unstable in alkaline conditions, adding to the complexity of the treatment process. Furthermore the micro-porous material typically used cannot prevent the osmosis of water from the anode compartment into the cathode compartment, which results in dilution and an increase in the volume of the solution in the cathode compartment. The solution in the cathode compartment becomes a secondary waste upon completion of the treatment, so an increase in volume of said solution is not desirable. In the fourth embodiments of the present invention, since both treatment zones contain adsorbent material, and a quantity of treatment mixture for treatment is distributed homogenously throughout the two treatment zones, there are no issues associated with the mixing of the treatment mixture in the treatment zone that behaves effectively as a "cathode compartment" and the treatment mixture in the other treatment zone which behaves effectively as an "anode compartment". Consequently, a range of different membrane materials can be used in the apparatus and method of the fourth embodiment of the present invention, enabling more stable materials with a larger pore diameter to be used if desired. The benefit of using a material with a larger pore diameter is that it offers a lower electrical resistance and therefore a lower voltage across the beds of adsorbent material.

A further advantage of the method of the fourth embodiment of the present invention over the methods described in UK patent no. GB 2470042 and International patent application W02010/149982 is that it can operate at low power and therefore low operating cost, without the presence of an isolated catholyte compartment. Low power operation is a consequence of a low voltage between the electric current feeders. Voltage is inversely proportional to solution conductivity and in the systems described in the prior art the isolated catholyte system provides a high conductivity and therefore a low voltage between the electric current feeders. An implication of the elimination of the catholyte system in the fourth embodiments of the present invention is a decrease in conductivity of the solution between the electric current feeders. However, as established in "Electrochemical regeneration of a carbon-based adsorbent loaded with crystal violet dye"; N W Brown, E P L Roberts, A A Garforth and RAW Dryfe; Electrachemica Acta 49 (2004) 3269- 3281, cell voltage is proportional to the electric current density, which is a measure of electric current per unit area of the electrode and is therefore inversely proportional to the surface area of the electrode.

In the "cathode compartment" of the fourth embodiments of the present invention, the bed of adsorbent material effectively behaves as a cathode which significantly increases the effective surface area of the "cathode" as compared to the cathode used in prior art methods, thereby lowering the current density and therefore affording a lower voltage. Consequently these embodiments facilitate low power operation without the need for a separate catholyte compartment. That being said, since a low voltage across the beds of adsorbent material is preferable, it may still be desirable to add an electrolyte to the bed of adsorbent material behaving as the high surface area cathode. The fourth embodiments of the present invention allow for operation without an electrolyte but do not negate the use of an electrolyte if desired to lower the applied voltage beyond that achievable using the apparatus and methods of present reverse current inventions. The addition of an electrolyte is optional for the treatment of radioactive wastes because the treatment mixture can be re-used in the treatment cycle and so the volume of electrolyte required is extremely low compared to a continuous system for example whereby an electrolyte may need to be continuously added to the liquid undergoing treatment.

A further advantage of the apparatus and method of the fourth embodiments of the present invention over prior art systems, in particular those described in UK patent no. GB 2470042 and International patent application W02010/149982 is that they allow a simplification of the complex electrode assemblies previously employed. As explained above, many prior art systems utilise an electrode assembly consisting of a micro-porous membrane, cathode and chemicol dosing system built into one inseparable, sealed "unit". As a result, if there is a fault with an individual part of the assembly the entire assembly must be removed from the treatment reservoir and replaced.

Moreover, in view of the sealing of the catholyte compartment there is also a risk of hydrogen building up in the electrode assembly, which is typically handled by the chemical dosing system.

In the apparatus of the fourth embodiment of the present invention, the aforementioned sealed "unit" is not necessary because there is no chemical dosing system or need to isolate the cathode compartment. Furthermore, since there are no negative implications associated with the mixing of the treatment mixture in the first and second treatment zones or with the migration of the adsorbent material there is no need to seal the porous membrane in between the two treatment zones. Instead of the complicated, sealed "unit" currently employed, it is possible to insert a more simple porous membrane between the two beds of adsorbent material. By way of example, a porous membrane that is 500 mm x 500 mm typically weighs only around 0.2 kg and the overall cost of the system is approximately 20 times lower than a system containing an electrode assembly in the form of the sealed "unit" described above. If there is a fault with any individual part of the treatment apparatus, the faulty item can be replaced individually, rather than having to replace the entire assembly. Additionally, the risk of hydrogen building up within the assembly is eliminated because the treatment zone containing the bed of adsorbent functioning as the "catholyte compartment" no-longer needs to be isolated.

Another advantage of the apparatus and method of the fourth embodiment of the present invention over the methods described in UK patent no. GB 2470042 and International patent application W02010/149982 is that the build-up of electrodeposited inorganic components from the treatment mixture is reduced or eliminated by periodically reversing the applied current. As a result, any inorganic components that become electrodeposited during the application of the electric current in a first direction are re-dissolved when the electric current is applied in the reverse direction. It may be desirable to optimise the process to ensure that the direction of the electric current is reversed at the correct time interval(s) to reduce or avoid the partial build-up of electrodeposited inorganic components during each individual phase of the regeneration cycle, ie. during the application of the current in any single direction.

During the adsorption stage of a treatment cycle, the beds of adsorbent material are agitated for a sufficient period of time to distribute the adsorbent material within the treatment mixture and adsorb organic components therefrom. At the end of the agitation period the agitation ceases, allowing the beds of material to settle. During this settlement period the adsorbent will separate from the treatment mixture. It will be appreciated that the degree of separation depends upon the length of time allowed. During and/or after settlement of the loaded adsorbent material, i.e. adsorbent material carrying adsorbed organic components, the electric current is applied which causes oxidation of the adsorbed organic components in the treatment zone behaving effectively as an "anode compartment", producing gaseous products and water, and thereby regenerating the adsorbent material and restoring its ability to adsorb further quantities of organic component. It is possible to adjust the time scale according to the degree of contamination of the treatment mixture being treated.

At different stages of the regeneration period, the electric current can be adjusted. For example, at the beginning of the regeneration period, only a very thin layer of the loaded adsorbent material will have settled so a smaller electric current is required than later in the regeneration period when a substantial quantity of the loaded adsorbent material will have settled. By way of a further example, at the beginning of a regeneration period, the particles of the adsorbent material are fully loaded with organic components and so a larger electric current is required than later in the regeneration period when a substantial amount of the adsorbed organic components will have already been oxidised.

Removal of the treated liquid from the treatment reservoir may be effected in any convenient way.

For example, one or more pumps may be used to cause the treated liquid to flow out of the treatment reservoir for storage or any desirable further use. Alternatively or additionally, removal may be effected by control of valves or partitions in between the treatment reservoir and an adjacent vessel, such as a storage tank.

Further embodiments of the present invention are directed specifically at continuous methods for treating wastes. These embodiments represent a synergistic combination of the third and fourth embodiments mentioned above. A fifth embodiment of the method of the first aspect of the present invention is characterised in that the treatment mixture is admitted into a first treatment zone of a treatment reservoir which reservoir also includes a second treatment zone, the first and second treatment zones being separated by a porous membrane and the carbon based adsorbent being provided in said first and second treatment zones in the form of beds provided in each zone.

The treatment mixture is admitted into said first treatment zone to contact the bed of adsorbent in the first treatment zone at a flow rate which is sufficiently high to pass the treatment mixture through the bed in the first zone but below the flow rate required to fluidise the bed in the first zone. First and second electric current feeders, which are operably connected to the first and second treatment zones, are respectively operated to pass an electric current in one direction through the carbon-based adsorbent material within each treatment zone to regenerate the carbon-based adsorbent material in said first treatment zone. The treatment mixture is admitted into said second treatment zone to contact the bed of adsorbent in the second treatment zone at a flow rate which is sufficiently high to pass the treatment mixture through the bed in the second zone but below the flow rate required to fluidise the bed in the second zone. The first and second electric current feeders are operated to reverse the direction of the current applied to the carbon-based adsorbent material in the first and second treatment zones to regenerate the carbon-based adsorbent material in the second treatment zone.

In the method according to the fifth embodiment of the present invention there is provided a method for treating waste in a continuous manner whereby it is possible to obtain a treated liquid.

The above steps may be repeated any desirable number of times to effect the desired level of decontamination of the required volume of treatment mixture. Organic components in the treatment mixture are adsorbed on to the carbon-based adsorbent material and are electrochemically oxidised by the application of the electric current. Application of the electric current is preferably effected while the treatment mixture is passing through its respective bed of adsorbent material. As a result of the manner in which the treatment mixture to be treated is admitted into each treatment zone, the treated liquid accumulates in a region above the beds of adsorbent material in the treatment zones.

Contacting of the treatment mixture with the carbon-based adsorbent material may be achieved through the controlled agitation of the adsorbent. Controlled agitation may be achieved by feeding one, or more preferably multiple, parallel jet streams of the treatment mixture under pressure to the bed of adsorbent material via inlets. Each individual stream of treatment mixture will generate a cylindrical or funnel shaped passage of treatment mixture through the adsorbent bed, drawing particulate adsorbent material from the lower region of the adsorbent bed and carrying it upward through the adsorbent bed. A downward flow of adsorbent material is produced around the upward flow of treatment mixture and entrained adsorbent material thereby defining a discrete, endless stream of adsorbent material within the adsorbent bed flowing along an endless path.

In a related preferred embodiment, it is preferred that the apparatus of the second aspect of the present invention is further characterised in that the treatment reservoir defines first and second treatment zones separated by a porous membrane, the carbon-based adsorbent material being provided in said first and second treatment zones. The agitator is a pump operable to admit the treatment mixture selectively into each of said first and second treatment zones to contact carbon-based adsorbent material in the respective treatment zone at a flow rate which is sufficiently high to pass the treatment mixture through the carbon-based adsorbent material but below the flow rate required to fluidise the carbon-based adsorbent material. A first electric current feeder is operably connected to the carbon-based adsorbent material in the first treatment zone and a second electric current feeder is operably connected to the carbon-based adsorbent material in the second treatment zone. A controller is provided to operate the first and second electric current feeders to pass an electric current through the carbon-based adsorbent material in the first and second treatment zones in one direction to regenerate the carbon-based adsorbent material in one of the first and second treatment zones and to then reverse the direction of the current applied to the carbon-based adsorbent material in the first and second treatment zones to regenerate the carbon-based adsorbent material in the other of the first and second treatment zones.

The apparatus preferably comprises one or more spaced inlets through which the treatment mixture is admitted under pressure into the bed of adsorbent material. The apparatus may comprise a plurality of said inlets spaced apart by a sufficient distance to establish a corresponding plurality of discrete liquid flow paths through the adsorbent bed. The spacing of the plurality of inlets is preferably sufficient to define a region around each liquid flow path through which adsorbent material that has adsorbed contaminant can flow so as to define a discrete, endless stream of adsorbent material within the bed of adsorbent material.

It is preferred that the apparatus comprises a reservoir in fluid communication with the adsorbent bed, the reservoir being adapted to receive liquid from the bed which has been contacted by the adsorbent material.

The control of the flow rate and path of the treatment mixture entering the adsorbent bed so as to pass the liquid through the bed but ensure the adsorbent material remains within the bed for regeneration enables the adsorption and regeneration processes to be carried out simultaneously within the same bed of adsorbent material. A flow rate of ito 500 L per hour may be employed. In one embodiment a flow rate of around 150 L per hour may be employed. The adsorbent material can adsorb organic components from the treatment mixture whilst, within the same adsorbent bed, an applied electric current causes gaseous products derived from the adsorbed organic component to be released from the adsorbent material thereby regenerating the adsorbent material and restoring its ability to adsorb further quantities of organic component.

During operation of the apparatus it is preferred that the electric current is applied such that the positive electric current feeder is operably connected to the bed of adsorbent material through which the treatment mixture is passed. In common with the fourth embodiments of the first and second aspects of the present invention this results in this bed effectively behaving as an anode while the bed of adsorbent material in the other treatment zone behaves as a cathode. In this way, organic components adsorbed on to the adsorbent material in the "anode bed" are oxidised to carbon dioxide and water, while any residual water present in the "cathode bed" is reduced. As before, proton species are produced in the "anode bed" and hydroxide species are produced in the "cathode bed". It will be appreciated that the treated liquid which accumulates in the region above the beds of adsorbent material contains the proton species that are generated during the electrochemical oxidation process and any liquid in the "cathode bed" contains the hydroxide ions generated during the corresponding reduction process. Preferably liquid that has contacted the carbon-based adsorbent material is passed to a reservoir in fluid communication with the corresponding bed of carbon-based adsorbent material in which it can be stored, recycled back to the treatment apparatus or passed elsewhere.

After a first cycle of adsorption and electrochemical regeneration has taken place the pump is controlled to cease admitting treatment mixture to the first treatment zone and instead to admit treatment mixture to the second treatment zone containing carbon-based adsorbent material capable of adsorbing organic components from the treatment mixture. The direction in which the electric current is applied via the electric current feeders is reversed so that the bed of adsorbent material that was previously behaving as the cathode now behaves as the anode and the bed of adsorbent material that was previously behaving as the anode behaves as the cathode. Any liquid containing hydroxide species is mobilised by the incoming stream of treatment mixture and mixes with the treated liquid in the region above the beds of adsorbent material. Proton and hydroxide species are then produced in the beds of adsorbent material in the second and first treatment zones respectively such that a pH maintaining effect continues with the or each subsequent reversal in direction of the applied current and change in the treatment zone into which the liquid to be treated is admitted. In this way, the pH is maintained in the treated liquid without the need for any after-treatment steps to adjust the pH of the treated liquid, such as a chemical dosing system. The process allows a treated liquid with a desired pH to be obtained, depending upon the cycle time employed, i.e. the length of time between each change in current direction and treatment zone to which the liquid to be treated is admitted, the concentration of organic components in the treatment mixture, and the volume of liquid in the liquid reservoir.

As with the fourth embodiment of the present invention, charged inorganic species are generated in the system of the fifth embodiment during the passage of the electric current through the carbon-based adsorbent material in the first and second treatment zones. It is preferred that the current feeders and pump are operated to minimise the electrodeposition of said charged inorganic species on the current feeders during operation of the apparatus to effect the treatment method.

Performance of the system according to the fifth embodiment of the invention can be improved by S operation in different modes. This can be achieved by admitting treatment mixture into different treatment zones at different times. As mentioned above, each zone is provided with an electrode.

The electrode which acts as the anode (as dictated by current direction) causes the corresponding zone to act as an anode compartment, oxidation of the organics (and regeneration of adsorbent) occurs in this zone. Similarly, the electrode which acts as the cathode causes the corresponding zone to act as a cathode compartment.

In a first mode, treatment mixture is fed into the first zone (behaving as an anode compartment) during regeneration of the adsorbent material in that zone. In a second mode, treatment mixture is fed into the second zone (behaving as the cathode compartment) during regeneration of the adsorbent material in the other zone (i.e. the zone behaving as the anode compartment). In a third mode, the treatment mixture is fed into the two zones concurrently. This is illustrated in the table below.

Mode 1 Mode 2 Mode 3 Anode feed Cathode feed Simultaneous feed Zone 1 Treatment mixture No feed Treatment mixture feed feed Zone? No feed Treatment mixture Treatment mixture feed feed Zone 1 electrode Anode Anode Anode Zone 2 electrode Cathode Cathode Cathode

Table 1: Flow modes.

After a suitable period, the bed of adsorbent material into which the liquid to be treated is admitted is changed and the direction of the electric current is reversed by operation of a controller so that the bed of adsorbent material that was previously behaving as a cathode behaves as an anode and the bed of adsorbent material that was previously behaving as an anode behaves as a cathode.

The adsorbent material provided in the zone into which fluid is delivered is able to adsorb contaminants from the waste as the treatment mixture passes therethrough. Thus, in Mode 1, where treatment mixture is delivered into zone 1 (behaving as the anode compartment), adsorption and regeneration occur simultaneously in the same zone.

In Mode 2, where treatment mixture is delivered into zone 2 (behaving as the cathode compartment), adsorption occurs in zone 2, while regeneration occurs in zone 1 (behaving as the anode compartment).

In Mode 3, where treatment mixture liquid is delivered into both zones concurrently, adsorption occurs in both zones, while regeneration occurs in the zone 1 (behaving as the anode compartment).

Hence adsorption occurs in the cathode zone and both adsorption and regeneration occurs simultaneously in the anode zone.

Modes 2 and 3 have distinct advantages compared with Mode 1. It has been surprisingly found that, in Mode 2, the voltage of the system is lower than when operating in Mode 1. For example, when operating a system with tap water at a current of 4 A, the voltage across the 2 electrodes is approximately 17.SV when operating in Mode 2, compared with a voltage of 21V when operating in Mode 1. This gives a significant cost saving as the energy usage is 20% less. Similar energy savings have been observed when using aqueous solutions containing electrolyte at a concentration of 0.3% and 3% sodium chloride, Mode 3 has a benefit when the system is adsorption limited. In Mode 3, treatment mixture is treated by twice the mass of adsorbent. Hence approximately twice as much adsorption can be achieved. Whilst operating in Mode 3, the voltage is comparable to Mode 1, despite achieving twice as much adsorption.

Accordingly, it is preferred that the method of the fifth embodiment of the present invention is operated such that liquid is admitted into the treatment zone behaving as a cathode compartment during regeneration in the treatment zone behaving as an anode compartment, the anode and cathode compartments being defined by the direction of electric current. In a particularly preferred embodiment, liquid is admitted into both treatment zones concurrently during regeneration in the anode compartment. Preferably, the liquid being admitted into the cathode compartment, and/or into the cathode and anode compartments concurrently, is the treatment mixture.

Similarly, it is preferred that the apparatus according to the fifth embodiment of the present invention is characterised in that the pump is adapted to admit liquid into the treatment zone behaving as a cathode compartment during regeneration in the treatment zone behaving as an anode compartment, the anode and cathode compartments being defined by the direction of S electric current. In a particularly preferred embodiment, the pump is adapted to admit liquid into the both treatment zones concurrently during regeneration in the anode compartment. Preferably, the liquid being admitted into the cathode compartment, and/or into the cathode and anode compartments concurrently, is the treatment mixture.

The method and apparatus according to the fifth embodiment of the present invention preferably utilise electrodes having a surface area of greater than or equal to about 1,000 cm2, more preferably greater than or equal to about 2,500 cm2. The electrodes may, for example, have dimensions of 50 cm by 50 cm, giving a surface area of 2,500 cm2, or have dimensions of 40 cm by 40 cm, giving a surface area of about 1,600 cm2. The electrodes may have be of any appropriate shape in order to achieve such a surface area. The electrodes may, for example, have dimensions of 30cm by 50 cm, giving a surface area of about 1,500 cm2.

The liquid may be admitted into the or each treatment zone at a flow rate of between about to 500 Lh', more preferably about 20 to 250 Lh', and yet more preferably 20 to 25 Lh1. A flow rate of 25 Lh1, for example, would be suitable for use in a system having a single cell utilising electrodes having dimensions of, for example, 25cm by 25cm or 50cm by 50cm.

Preferred features described above in relation to the fourth embodiment of the present invention also represent preferred features of the fifth embodiment of the present invention, and vice versa, subject to a technical incompatibility that would prevent such a combination of preferred features.

Furthermore, it will be evident to the skilled person that certain advantages set out above in respect of the fourth embodiment of the present invention are also offered by the fourth and fifth embodiments of the present invention.

The abovementioned advantages associated with operation in different treatment mixture delivery modes are also achieved in systems for the treatment of wastes which are not mixed with acid.

According to a third aspect of the present invention there is provided a method for the continuous treatment of an aqueous organic waste liquid, the method comprising admitting the aqueous organic waste liquid into first and second treatment zones of a treatment reservoir, the first and second treatment zones being separated by a porous membrane, each treatment zone containing carbon-based adsorbent material capable of electrochemical regeneration; distributing the carbon-based adsorbent material in the aqueous organic waste liquid within each treatment zone; allowing the carbon-based adsorbent material to settle within each treatment zone; operating first and second electric current feeders operably connected to the first and second treatment zones respectively to pass an electric current in one direction through the carbon-based adsorbent material within each treatment zone to regenerate the carbon-based adsorbent material in one of the first and second treatment zones; and operating the first and second electric current feeders to reverse the direction of the current applied to the carbon-based adsorbent material in the first and second treatment zones to regenerate the carbon-based adsorbent material in the other of the first and second treatment zones; wherein liquid is admitted into the treatment zone behaving as a cathode compartment during regeneration in the treatment zone behaving as an anode compartment, the anode and cathode compartments being defined by the direction of electric current.

The method may comprise a preliminary step of mixing the aqueous organic waste liquid with an acid. The waste liquid may be contaminated with radioactive species. The radioactive species may be present in the treated liquid.

In a preferred embodiment, liquid is admitted into both treatment zones concurrently during regeneration in the anode compartment. Preferably, the liquid being admitted into the cathode compartment, and/or into the cathode and anode compartments concurrently, is the aqueous organic waste liquid.

According to a fourth aspect of the present invention there is provided a method for the continuous treatment of an aqueous organic waste liquid, the apparatus comprising a treatment reservoir defining first and second treatment zones separated by a porous membrane, carbon-based adsorbent material capable of electrochemical regeneration provided in said first and second treatment zones, an agitator operable to distribute the carbon-based adsorbent material in aqueous organic waste liquid contained in each of the first and second treatment zones, a first electric current feeder operably connected to the carbon-based adsorbent material in the first treatment zone and a second electric current feeder operably connected to the carbon-based adsorbent material in the second treatment zone, and a controller to operate the first and second electric current feeders to pass an electric current through the carbon-based adsorbent material in the first and second treatment zones in one direction to regenerate the carbon-based adsorbent material in one of the first and second treatment zones and to then reverse the direction of the current applied to the carbon-based adsorbent material in the first and second treatment zones to regenerate the carbon-based adsorbent material in the other of the first and second treatment zones, wherein the agitator is adapted to admit liquid into the treatment zone behaving as a cathode compartment during regeneration in the treatment zone behaving as an anode compartment, the anode and cathode compartments being defined by the direction of electric current.

The treatment reservoir may be provided with an acid for mixing with the aqueous organic waste liquid.

In a particularly preferred embodiment, the agitator is adapted to admit liquid into both treatment zones concurrently during regeneration in the anode compartment. Preferably, the liquid being admitted into the cathode compartment, and/or into the cathode and anode compartments concurrently, is the aqueous organic waste liquid.

Preferred features described above in relation to the fourth and fifth embodiments of the first and second aspects of the present invention also represent preferred features of the third and fourth aspects of the present invention subject to a technical incompatibility that would prevent such a combination of preferred features. Furthermore, it will be evident to the skilled person that advantages set out above in respect of the first and second aspects of the present invention are also offered by the third and fourth aspects of the present invention.

According to a fifth aspect of the present invention there is provided a method for the continuous treatment of an aqueous organic waste liquid, the method comprising operating a pump to admit aqueous organic waste liquid into a first treatment zone of a treatment reservoir which also includes a second treatment zone, the first and second treatment zones being separated by a porous membrane, the aqueous organic waste liquid being admitted into said first treatment zone to contact carbon-based adsorbent material in a bed in the first treatment zone at a flow rate which is sufficiently high to pass the aqueous organic waste liquid through the bed carbon-based adsorbent material but below the flow rate required to fluidise the bed of carbon-based adsorbent material; operating first and second electric current feeders operably connected to the first and second treatment zones respectively to pass an electric current in one direction through the carbon-based adsorbent material within each treatment zone to regenerate the carbon-based adsorbent material in said first treatment zone; admitting aqueous organic waste liquid into said second treatment zone to contact carbon-based adsorbent material in a bed in the second treatment zone at a flow rate which is sufficiently high to pass the aqueous organic waste liquid through the bed of carbon-based adsorbent material but below the flow rate required to fluidise the bed of carbon-based adsorbent material; and operating the first and second electric current feeders to reverse the direction of the current applied to the carbon-based adsorbent material in the first and second treatment zones to regenerate the carbon-based adsorbent material in the second treatment zone; wherein liquid is admitted into the treatment zone behaving as a cathode compartment during regeneration in the treatment zone behaving as an anode compartment, the anode and cathode compartments being defined by the direction of electric current.

Preferably, liquid is admitted into both treatment zones concurrently during regeneration in the anode compartment. Preferably, the liquid being admitted into the cathode compartment, and/or into the cathode and anode compartments concurrently, is the aqueous organic waste liquid.

According to a sixth aspect of the present invention there is provided apparatus for the continuous treatment of an aqueous organic waste liquid, the apparatus comprising a treatment reservoir defining first and second treatment zones separated by a porous membrane, carbon-based adsorbent material capable of electrochemical regeneration provided in said first and second treatment zones, a pump operable to admit aqueous organic waste liquid selectively into each of said first and second treatment zones to contact carbon-based adsorbent material in the respective treatment zone at a flow rate which is sufficiently high to pass the aqueous organic waste liquid through the carbon-based adsorbent material but below the flow rate required to fluidise the carbon-based adsorbent material, a first electric current feeder operably connected to the carbon-based adsorbent material in the first treatment zone and a second electric current feeder operably connected to the carbon-based adsorbent material in the second treatment zone, and a controller to operate the first and second electric current feeders to pass an electric current through the carbon-based adsorbent material in the first and second treatment zones in one direction to regenerate the carbon-based adsorbent material in one of the first and second treatment zones and to then reverse the direction of the current applied to the carbon-based adsorbent material in the first and second treatment zones to regenerate the carbon-based adsorbent material in the other of the first and second treatment zones, wherein the pump is adapted to admit liquid into the treatment zone behaving as a cathode compartment during regeneration in the anode compartment, the anode and cathode compartments being defined by the direction of electric current.

Preferably, the pump is adapted to admit liquid into both treatment zones concurrently during regeneration in the anode compartment. Preferably, the liquid admitted into the cathode compartment, and/or into the cathode and anode compartments concurrently, is the aqueous organic waste liquid.

The current feeders may be operated to provide any desirable pH in the treated liquid. For example they may be operated to provide an alkaline pH, i.e. a pH greater than 7. Alternatively, in a preferred embodiment the current feeders are operated to provide an acidic pH, i.e. a pH of less than 7, in the treated liquid, more preferably a pH of around ito 4 in the treated liquid.

Preferred features described above in relation to the fourth and fifth embodiments of the first and second aspects of the present invention, and of the third and fourth aspects of the present invention, also represent preferred features of the fifth and sixth aspects of the present invention subject to a technical incompatibility that would prevent such a combination of preferred features.

Furthermore, it will be evident to the skilled person that advantages set out above in respect of the first, second, third and fourth aspects of the present invention are also offered by the fifth and sixth aspects of the present invention.

Carbon-based adsorbent materials suitable for use in the method and apparatus of the present invention are solid materials capable of convenient separation from the liquid phase and electrochemical regeneration. Preferred adsorbent materials comprise adsorbent materials capable of electrochemical regeneration, such as graphite, unexpanded graphite intercalation compounds (UGICs) and/or activated carbon, preferably in powder or flake form. Typical individual UGIC particles suitable for use in the present invention have electrical conductivities in excess of 10,000ff cml It will be appreciated however that in a bed of particles of the adsorbent material this will be significantly lower as there will be resistance at the particle/particle boundary, Hence it is desirable to use as large a particle as possible to keep the resistance as low as possible. In addition the larger particles will settle faster allowing a higher flow rate to be achieved. However, increasing the particle size will result in a reduction in the available surface area, so a balance is required over high settlement rates and low cell voltages against the reduction in adsorptive capacity from a reduction in surface area. It will be appreciated however that a large number of different UGIC materials have been manufactured and that different materials, having different adsorptive properties, can be selected to suit a particular application of the method of the present invention. The adsorbent material may consist only of UGICs, or a mixture of such graphite with one or more other adsorbent materials. Individual particles of the adsorbent material can themselves comprise a mixture of more than one adsorbent material. The kinetics of adsorption should be fast because the adsorbent material has no internal surface area and therefore the kinetics are not limited by diffusion of the organic component to the internal surface.

The capability of materials to undergo electrochemical regeneration will depend upon their electrical conductivity, surface chemistry, electrochemical activity, morphology, electrochemical corrosion characteristics and the complex interaction of these factors. A degree of electrical conductivity is necessary for electrochemical regeneration and a high electrical conductivity can be advantageous.

Additionally, the kinetics of the electrochemical oxidation of the adsorbate must be fast. The kinetics depend upon the electrochemical activity of the adsorbent surface for the oxidation reactions that occur and also on the pH of the liquid phase. Electrochemical regeneration will generate corrosive conditions at the adsorbent surface. The electrochemical corrosion rate of the adsorbent material under regeneration conditions should be low so that the adsorption performance does not deteriorate during repeated cycles of adsorption and regeneration. Moreover, some materials can passivate upon attempted electrochemical regeneration, often due to the formation of a surface layer of non-conducting material. This may occur, for example, as a result of the polymerisation of the contaminant, for example phenol, on the surface of the adsorbent, Additionally, electrochemical destruction of the organic components on the adsorbent material will generate reaction products which must be transported away from the surface of the adsorbent material. The structure of the adsorbent material being regenerated can influence the rate of transport of the products away from the surface of the adsorbent material, and it will be appreciated that it is desirable to use adsorbent materials that facilitate this transport process. This will depend upon both the surface structure and chemistry of the adsorbent material.

It will be appreciated that preferred adsorbent materials for the present invention will desirably have an ability to adsorb organic compounds. The ability of the material to absorb is not essential, and in fact may be detrimental. The process of adsorption works by a molecular interaction between the organic component and the surface of the adsorbent, By contrast, the process of absorption involves the collection and at least temporary retention of an organic component within the pores of a material. By way of example, expanded graphite is known to be a good absorber of a range of contaminants (e.g. up to 86 grams of oil can be taken-up' per gram of compound). UGICs have effectively no absorption capacity. They can adsorb, but the adsorption capacity is very low as the surface area is low (eg. up to 7 milligrams of oil can be taken-up' per gram of compound per adsorption cycle). These figures demonstrate a difference of four orders of magnitude between the take-up capacity of expanded graphite and that of UGICs. The selection of UGICs for use in the present invention arises from carefully balancing its high regeneratability against its relatively low take-up capacity.

The electric current feeders preferably extend across the full height and width of the adsorbent beds to maximise their proximity to adsorbent particles loaded with organic component in need of regeneration. The electric current feeders will typically be provided on opposite sides of the beds of adsorbent material provided in the first and second treatment zones. A plurality of electric current feeders may be disposed along each side. Alternatively, multiple electric current feeders may be installed horizontally to allow different electric currents to be applied at different heights across the adsorbent beds during operation. In use, a voltage can be applied between the electric current feeders, either continuously or intermittently, to pass electric current through the adsorbent material and regenerate it in the manner described in "Electrochemical regeneration of a carbon-S based adsorbent loaded with crystal violet dye"; N W Brown, E P L Roberts, A A Garforth and R A W Dryfe; Electrachemica Acta 49 (2004) 3269-3281 and "Atrazine removal using adsorption and electrochemical regeneration"; NW Brown, £ P L Roberts, A Chasiotis, T Cherdron and N Sanghrajka; Water Research 39 (2004) 3067-3074.

The invention will now be described by way of example and with reference to the accompanying drawings wherein: Figure 1 is a vertical cross-section through apparatus suitable for use with the first embodiment of the invention; Figure 2 is a horizontal cross-sectional view of the apparatus shown in Figure 1; Figure 3 is a perspective view of apparatus suitable for use with the second embodiment of the invention; Figure 4 is a top plan view of the base of the reservoir in Figure 3, upon which a bed of adsorbent is supported; Figure 5 is a schematic perspective view of apparatus suitable for use with the third embodiment of the present invention; Figure Eisa horizontal cross-sectional view of a lower section of the apparatus shown in FigureS; Figure 7a is a schematic perspective view of apparatus configured according to highly preferred features of the fourth embodiment of the first and second aspects, or the third and fourth aspects of the present invention; Figure 7b is a schematic perspective view of apparatus configured according to preferred features of the fifth embodiment of the first and second aspects, or the fifth and sixth aspects of the present invention; Figure 8 is a schematic perspective view of an alternative form of apparatus according to the fourth embodiment of the first and second aspects, or the third and fourth aspects of the present invention; Figure 9 illustrates the use of multiple cells in the base of apparatus according to the fourth embodiment of the first and second aspects, or the third and fourth aspects of the present invention; Figure 10 is a schematic representation of an alternative form of apparatus configured according to preferred features of fifth embodiment of the first and second aspects, or the fifth and sixth aspects of the present invention; and Figure 11 is a schematic representation of apparatus configured according to a similar apparatus as illustrated in Figure 10, but which is not capable of being operated such that the direction of current applied can be reversed.

Figures land 2 show an apparatus suitable for use with the first embodiment of the invention. The drawings show a reservoir 1002 of generally rectangular cross-section defined by front and rear walls 1004 and 1006, and side walls 1008. Within the reservoir, inner walls 1010 define a regeneration chamber that extends the whole width of the reservoir between the front and rear walls. The base of the regeneration chamber is defined by convergent walls 1012, which form an opening 1014 for the discharge of particulate adsorbent material 1016 from the regeneration chamber. Upper walls 1018 define a central zone over the regeneration chamber.

When the apparatus is ready for use, an adsorbent material is loaded into the regeneration chamber 1010 in the required amount. The contaminated waste liquid is mixed with acid to provide a treatment mixture which is then delivered to the reservoir through inlets 1020, and filled to a level just below that of the discharge outlet 1022 between the upper walls 1018. Air under pressure is then delivered through openings in the base of the reservoir as indicated at 1024. This generates bubbles in the treatment mixture, and draws particulate adsorbent material from below the opening 1014 at the bottom of the regeneration chamber, and carries it upward through treatment chambers 1026 defined in the reservoir between the respective walls 1008 and 1010. As the adsorbent material is carried upwards through the treatment mixture, it absorbs pollutants in the treatment mixture. The rising air carries the adsorbent material around and over the top of the walls 1010, where it is directed by the walls 1018 back into the regeneration chamber. Obstacles 1028 and 1030 are installed at the top of the regeneration chamber to control the flow of the solid, liquid and gaseous phases in the reservoir. They can break up any coagulated particles and guide them into the chamber. They also serve to discourage adsorbent particles from entering the zone between the walls 1018, from which treated liquid is discharged, and prevent bubbles generated in the bed of adsorbent materials in the regeneration chamber from entering this zone. Treatment mixture to be treated is delivered to the reservoir through the inlets 1020 at a flow rate selected to match its required residence time in the reservoir and contact with the adsorbent material sufficient to enable absorption of pollutants therefrom. Its general flow is upwards through the reservoir, and it is discharged by overflow through the port 1022. It will be noted that the treatment mixture can only reach the discharge port 1022 by upward flow from the top of the regeneration chamber, between the walls 1018. The walls 1018 thus define a quiescent zone protected from movement generated by the air bubbling through the liquid in the treatment chambers.

While a generally upward flow of treatment mixture is preferred, the opposite arrangement can also be used. Thus, treatment mixture to be treated could be admitted at ports indicated at 1032, and withdrawn from discharge points 1034. Some form of filter would be required at the discharge points because of the proximity of the adsorbent material, but the air flowing upwards from the reservoir base should prevent blockages. The direction of flow of treatment mixture through the reservoir will of course be selected on the basis of the system requirements, but there may be some benefit in having the flow of treatment mixture generally opposite to the flow of adsorbent material in the treatment chambers. That would be case if the general direction of flow of treatment mixture in the reservoir was downwards rather than upwards.

As noted above, the apparatus may be used for the separate treatment of individual volumes of treatment mixture. In this variant, the reservoir is filled with liquid to the required level, and the adsorbent material recycled through the regeneration chamber for a period of time appropriate to complete the treatment. The liquid is then removed, for example by drainage from discharge port 1034, and a fresh charge of treatment mixture delivered to the reservoir. The adsorbent material will normally be regenerated while it is recycled during the treatment process.

In apparatus of the first embodiment of the invention, the adsorbent material is continuously or intermittently regenerated while it passes through the regeneration chamber in its recycling path.

This is accomplished by the application of an electrical voltage between an anode 1036 and a cathode 1038 disposed on opposite faces of the chamber 1016. Pollutants are released by the regenerating adsorbent material in gaseous form, from the top of the reservoir. These released gases can be discharged to the atmosphere, but can of course be subject to separate treatment if required. The cathode is housed in a separate compartment 1042 defined by a conductive membrane 1040. This enables a catholyte to be pumped through the compartment, and the membrane protects the cathode from direct contact with the adsorbent material.

The purpose of the membrane 1040 is to prevent the solid adsorbent particles coming into contact with the cathode 1038 as this could result in the electrons going direct from cathode 1038 to anode 1036 without passing through the treatment mixture being treated. In this case there would be no organic oxidation and no regeneration of the adsorbent. The membrane 1040 must allow the transfer of ions or electrons through it to complete the electric circuit. However, this introduces an additional resistance into the system. Such membranes also only operate well at certain pH levels. In this case the oxidation of the water on the anode side (giving acid conditions) and reduction of water on the cathode side (giving alkali conditions) necessitates pH adjustment to keep the membrane functioning with an acceptable voltage. In practice this requires the catholyte to be monitored and adjusted to keep it acidic, for example by the constant addition of acid, which is undesirable, the pumping of catholyte through the cathode compartments, and suitable pH monitoring and adjustment equipment involving tanks, pumps and probes, which incurs further capital, operational and maintenance costs.

An alternative to the use of a conductive membrane is to use a porous filter. This would prevent the contact of the solid with the cathode, but allow the passage of water and ions. The constant reduction of water at the cathode would result in the catholyte becoming more alkaline, giving a higher conductivity and lower cell voltages.

Figure 3 illustrates an apparatus suitable for use with the second embodiment of the invention. The figure shows a simple tank 2002 of rectangular horizontal cross-section. In the lower section 2004 of the tank a bed of particulate adsorbent material is supported on a plate 2006. Beneath the plate 2006 is a chamber 2008 for receiving a fluidising medium, such as air, from inlet pipe 2010.

Figure 4 is a horizontal cross-sectional view of the lower section 2004 of the tank 2002, specifically showing the plate 2006 and the inlet pipe 2010. Figure 4 also shows the openings 2012 in the plate for the passage of fluidising medium from the chamber 2008 below, On the opposite longer sides of the plate 2006, and extending upwardly therefrom, are two banks 2014 of electrodes 2016. The bed of adsorbent material is supported on the plate 2006 within the walls of the container 2002, between the banks 2014 of electrodes 2016.

The adsorbent material used in the practice of the second embodiment of the present invention is carbon based, and provided in particulate form that can be readily fluidised within a body of liquid.

Preferred adsorbents are those disclosed in the Patent Publications and Applications referred to above. In use of the apparatus of Figures 3 and 4, the contaminated waste liquid is mixed with acid to form a treatment mixture and delivered to the tank 2002 which is normally open at the top. The adsorbent material is then fluidised by delivery of a suitable medium through input 2010 to distribute the adsorbent material within the body of treatment mixture then contained in the tank.

The adsorbent takes contaminants from the treatment mixture which attach to the surfaces of the adsorbent particles, After a predetermined period of time, the flow of fluidizing medium is stopped with the consequence that the adsorbent material settles on the plate 2006 between the banks 2014 of electrodes 2016. At this point the decontaminated liquid can be removed through discharge 2018 but its removal may be deferred. Its degree of decontamination can be measured, and if this is now acceptable then it may be removed. If further decontamination is required, it is retained in the tank 2002.

If required, additional agitation of the treatment mixture in the upper section of the tank 2002 can be provided by a mechanical mixer. This can be a simple paddle, which will normally be sufficient if it is to function in conjunction with the fluidising medium delivered through the plate 2006. If it is to be the only agitating mechanism, then it can be installed within or under the bed to urge the adsorbent material into the upper section, but it can be installed in the upper section itself.

Particularly if disposed at the surface of liquid of the reservoir it can be used to coagulated particles.

Whether or not the decontaminated liquid has been removed, the adsorbent material in the bed supported on the plate 2006 can now be regenerated. This is accomplished by passing an electric current through the material of the bed between the electrodes 2016. This releases the adsorbed contaminants in the form of carbonaceous gases and water. The gases are released either through the open top of the tank 2002, or if the top is closed, through a separate exhaust duct 2020, possibly for subsequent treatment. If the decontaminated liquid remains in the tank, the released gases merely bubble through it. Treatment mixture retained in the tank after regeneration of the adsorbent material can of course now be further decontaminated by re-fluidization of the bed to distribute the particulate adsorbent once more within the treatment mixture. This sequence can be repeated, with the degree of decontamination of the treatment mixture being monitored after each treatment.

In the apparatus of Figure 3 the bed of adsorbent material; the means for fluidizing the bed to distribute the material within treatment mixture in the tank; and the electrodes for regenerating the adsorbent after a decontamination treatment, are all integrated in the tank construction. However, it will be appreciated then, that the tank is a mobile decontamination unit that can be moved between sites where one or more batches of treatment mixture must be decontaminated, but where a permanent installation is not required. If a suitable tank is already on site, then it is the decontamination system; the bed of adsorbent and fluidizing mechanism that can be delivered separately.

Figure 5 illustrates an apparatus suitable for use with the third embodiment of the present invention. The figure shows a simple tank 3001 of rectangular horizontal cross section. In the lower section of the tank 3001 a bed of particulate adsorbent material 3002 is supported on a plate 3003.

Beneath the plate 3003 is a chamber 3004 for receiving a fluidising medium (not shown), such as a contaminated liquid or treatment mixture, from an inlet feed 3005. Above the bed of adsorbent material 3002 is a liquid reservoir 3006 for the mixture of the acid and contaminated waste liquid to be treated. An additional liquid reservoir can be housed in a separate compartment (not shown).

Outlet feeds 3007 are provided towards the top of the liquid reservoir 3006. The plate 3003 defines three equally spaced openings 3008 through which the liquid can be admitted into the bed of adsorbent material 3002 from the chamber 3004. Any desirable number of openings 3008 may be used, of any desirable size and/or shape. They may be generally circular as illustrated, or they may have a different cross-sectional profile, for example, elliptical, rectangular or square. Moreover, the openings 3008 may all be of the same size and shape, or they may vary from one to another.

Furthermore, one or more of the circular openings 3008 may be replaced with a plurality of smaller openings grouped or clustered together to define an array of small openings. Electrodes required for regeneration of the adsorbent material after it has contacted the treatment mixture are omitted from FigureS for clarity but are described below with reference to Figure 6.

Figure 6 is a horizontal cross-sectional view of a lower section of the tank 3001 showing the plate 3003 and the openings 3008 in greater detail. Also shown in Figure 6 are two banks 3009 of electrodes 3010 which extend along opposite longer sides of the plate 3003 and extend upwardly therefrom to the top of the bed of adsorbent material 3002 beneath the liquid reservoir 3006. The bed of adsorbent material 3002 is supported on the plate 3003 within the walls of the tank 3001, between the banks 3009 of electrodes 3010. The apparatus 3002 to 3010 as described constitute a treatment zone.

The banks of electrodes 3010 are operable to pass an electric current through material present in between the electrodes. The cathode will normally be housed in a separate compartment (not shown) defined by a porous membrane or filter cloth to protect it from direct contact with the adsorbent material. A porous membrane enables a catholyte, which can be sodium chloride/sulphate or any other salt which will provide conductivity, to be pumped through the compartment, serving both to provide a means for controlling the pH level and as a coolant for removing heat generated during the passage of an electric current through the adsorbent material.

The catholyte also provides conductivity between the cathode and the membrane ensuring low cell voltages.

The adsorbent material used in the practice of the present invention is carbon based and provided in particulate form.

In use, acid is mixed with contaminated waste to form a treatment mixture and delivered to the chamber 3004 via the inlet pipe 3005. The treatment mixture is under sufficient pressure that it will enter the adsorbent bed 3002 through openings 3008. The openings 3008 are far enough apart to ensure that there is no general flow of treatment mixture up through the adsorbent bed 3002, but rather that a generally columnar or, more specifically funnel-like, uplift of treatment mixtureis established within the adsorbent bed 3002 from each opening 3008 which entrains particulate adsorbent material. This funnel-like behaviour of the treatment mixtureand entrained adsorbent is illustrated schematically in Figure 5 as a triangle emanating from each opening 3008. The spacing of the openings 3008 should be chosen to ensure that each funnel of rising treatment mixtureand entrained adsorbent does not interfere with neighbouring funnels to any significant extent. There must also be sufficient space between the openings 3008 to ensure that the funnels of rising treatment mixtureand entrained adsorbent are far enough apart to allow the adsorbent particles to drop down through the adsorbent bed 3002 under gravity after reaching the top of the adsorbent bed 3002.

The uplift of treatment mixturepushes the adsorbent particles within the adsorbent bed 3002 further apart producing a localised expanded bed of adsorbent particles associated with each opening 3008. During this upward movement of the treatment mixtureand the adsorbent material, the adsorbent material separates contaminants from the treatment mixtureby a process of adsorption whereby contaminants attach to the surfaces of the particles of the adsorbent material, When the passages of treatment mixtureand particulate adsorbent reach the top of the adsorbent bed 3002, the decontaminated liquid will accumulate in the reservoir 3006. The flow rate of the treatment mixturepassing through the openings 3008 into the adsorbent bed 3002 is controlled so that it is below the rate required to cause fluidisation of the adsorbent particles, As a result, the adsorbent material at the top of the adsorbent bed 3002 remains in the adsorbent bed 3002 and flows downwards around the funnel-like upward flow of treatment mixtureand adsorbent material.

The downward flow of adsorbent particles is further aided by the positioning of the openings 3008 at the bottom of the adsorbent bed 3002 because the ingress of the treatment mixtureentrains adsorbent particles in the vicinity of the openings 3008, i.e. towards the bottom of the adsorbent bed 3002, In this way multiple, discrete endless paths for adsorbent material are established within the adsorbent bed 3002. This is a fundamental and important difference between this invention and prior art systems. Rather than establishing only single endless path for the adsorbent material between a pair of electrodes within a tank, the present invention provides a relatively simple and convenient means for establishing any desirable number of endless paths along which adsorption, separation and regeneration can take place within a single tank.

Once the adsorbent material reaches the top of the adsorbent bed 3002 it is loaded with adsorbed contaminant which needs regenerating as it drops down towards the bottom of the adsorbent bed 3002. while the adsorbent material is passing along the endless paths established within the adsorbent bed 3002, the electrodes 3010 are operated to pass an electric current through the adsorbent bed 3002. The more conductive sections of the adsorbent bed 3002 are those regions having a higher density of the adsorbent material. Since the higher density regions are those in which the loaded adsorbent material is flowing downwards through the adsorbent bed 3002 the regenerative electric current flows through the regions of the adsorbent bed 3002 where it is most needed. Electrochemical regeneration of the adsorbent particles releases the adsorbed contaminants in the form of carbonaceous gases and water. The gases are released either through the open top of the tank 3001, or if the tank is closed, through a suitable valve or port (not shown), optionally for subsequent treatment.

Figure 7a illustrates apparatus that is particularly suitable for use in a batchwise process of the fourth embodiment of the first and second aspects, or the third and fourth aspects of the present invention. Referring to Figure 7a there is shown an open-toped tank 4001 of rectangular horizontal cross section, in the lower section of the tank 4001 two parallel beds of particulate adsorbent material 4002 are supported on a plate 4003. Beneath the plate 4003 is a chamber 4004 for receiving a fluidising medium or liquid to be treated (such as a treatment mixture comprising organic waste and acid when operating in accordance with the fourth embodiment of the first and second aspects of the present invention, or aqueous organic waste liquid when operating in accordance with the third and fourth aspects of the invention) from an inlet feed 4005, Above the beds of adsorbent material 4002 is a liquid reservoir 4006. At least one outlet feed or weir 4007 is provided towards the top of the liquid reservoir 4006. Electric current feeders 4008 required for regeneration of the beds of adsorbent material 4002 are positioned at either side of the tank 4001, only one of the current feeders 4008 being visible in Figure 7a. A controller 4009 is provided to control the direction in which the electric current is applied to the beds of adsorbent material 4002 via the electric current feeders 4008. Equidistant between the electric current feeders 4008, and separating the two beds of adsorbent material 4002, is a porous divider 4010. The plate 4003 defines parallel lines of equally spaced openings 4011, at least one line on each side of the porous divider 4007, through which a fluidising medium or liquid can be admitted into the beds of adsorbent material 4002 from the chamber 4004. Any desirable number of openings 4011 may be used, of any desirable size and/or shape. A pump 4012 is provided to selectively admit fluidising medium or liquid to the beds of adsorbent material 4002. In the present embodiment, the pump 4012 is configured to admit fluidising medium or liquid to one or both of the two beds of adsorbent material 4002 depending upon the direction of the applied electric current. The pump may be configured to admit fluidising medium during regeneration of the adsorbent material. The pump may be configured to admit fluidising medium or liquid into the bed of material behaving as the cathode, and may also be configured to admit fluidising medium or liquid into the bed of material behaving as the anode concurrently, during regeneration, such as when operating in accordance certain embodiments and aspects of the present invention.

In use, liquid to be treated is admitted to the tank 4001. When used in accordance with the fourth embodiment first and second aspects of the invention, the liquid to be treated comprises a mixture of acid and contaminated waste liquid. When used in accordance with the third and fourth aspects of the invention, the liquid to be treated comprises aqueous organic waste liquid. The beds of adsorbent material 4002 are then fluidised by the delivery of a suitable medium through openings 4011 to distribute the adsorbent material 4002 within the body of liquid to be treated contained in the tank 4001. when operating in accordance with the third and fourth aspects of the present invention, aqueous organic waste liquid is delivered into the bed of material behaving as the cathode, and may also be delivered into the bed of material behaving as the anode concurrently, during regeneration. The organic components of the liquid to be treated are adsorbed on to the adsorbent material 4002. If required, additional agitation of the liquid to be treated in an upper section of the tank 4001 can be provided by a mechanical mixer (not shown). After a predetermined period of time, the flow of fluidizing medium and/or mechanical mixing is stopped with the consequence that the beds of adsorbent material 4002 settle on the plate 4003 between the electric current feeders 4008 and either side of the porous divider 4010. Electrochemical regeneration is accomplished by passing an electric current through the beds of adsorbent material 4002 between the electric current feeders 4008. The bed of adsorbent material 4002 next to the positive current feeder behaves as an anode and adsorbed organics in this bed are oxidised and then released in the form of carbonaceous gases and water. The bed of adsorbent material 4002 next to the negative current feeder behaves as a cathode and water present in that bed is reduced. The produced gases are released either through the open top of the tank 4001, or if the tank 4001 is closed, through a separate exhaust duct (not shown), possibly for subsequent treatment. After a period of regeneration, the direction of the applied electric current is reversed so that the bed of adsorbent material 4002 that was previously behaving as the cathode behaves as the anode and the bed of adsorbent material 4002 that was previously behaving as the anode behaves as the cathode, initiating electrochemical regeneration of the bed of adsorbent material 4002 next to the current feeder 4008 that is now the anode, which helps to maintain an acidic pH in the tank 4001. If necessary, liquid retained in the tank 4001 after regeneration of the beds of adsorbent material 4002 can now undergo further removal of organic matter by re-fluidization of the beds of adsorbent material 4002 to re-distribute the particulate adsorbent material 4002 once more within the liquid requiring treatment, followed by further electrochemical regeneration of the adsorbent material 4002. This sequence can be repeated any desirable number of times on the same batch of liquid to be treated if, for example, it is particularly heavily contaminated; on different batches of liquid to be treated if, for example, a single treatment cycle including a single electric current reversal is sufficient; on mixed batches of liquid to be treated; or a batch of liquid to be treated to which further organic components are added during treatment. If required, the level of decontamination can be monitored constantly or periodically using conventional means throughout operation of the apparatus of Figure 7a.

Figure 7b illustrates apparatus that is particularly suitable for use in a continuous process, which represents a preferred manner of operating the apparatus and methods representing the fifth embodiment of the first and second aspects, or the fifth and sixth aspects of the present invention.

In Figure 7b the components corresponding to those described above in relation to Figure 7a take the same reference number but increased by 100. For example, in the apparatus shown in Figure 7b the open-toped tank takes reference number 4101. Those components which differ in function to a similar component in Figure 7a take the same reference number but increased by 200. Thus, for example, the pump which operates differently in the Figure 7b embodiment as compared to the Figure 7a embodiment takes reference number 4212.

When it is desired to carry out a continuous treatment process using the apparatus of Figure 7b liquid to be treated is admitted to the chamber 4104 via an inlet pipe 4105. when operating in accordance with the fifth embodiment of the first and second aspects of the present invention, the liquid to be treated comprises waste liquid mixed with acid. When operating in accordance with the fifth and sixth aspects of the present invention, the liquid to be treated comprise an aqueous organic waste liquid and may also comprise acid. The liquid to be treated is under sufficient pressure that it enters one or both of the beds of adsorbent material 4102 through openings 4111. Pump 4212 is configured to control the flow of the aqueous organic waste so that it can be selectively admitted via the openings 4111 into one or both of the beds of adsorbent material 4102 at a time. The pump may be configured to admit liquid medium during regeneration of the adsorbent material. During operation in accordance with the third and fourth aspects of the present invention the pump is configured to admit liquid into the bed of material behaving as the cathode, and may also be configured to admit liquid into the bed of material behaving as the anode concurrently, during regeneration. The pump 4212 is operated so as to provide a tunnel-like, uplift of liquid to be treated through the bed of adsorbent material 4102, entraining particles of the adsorbent material 4102 and initiating a downward flow of adsorbent material 4102 on either side of the upward tunnels of liquid to be treated, creating discrete endless paths of adsorbent material 4102 in the bed of adsorbent material 4102. while the adsorbent material 4102 is passing along the endless paths within the bed of adsorbent material 4102, electric current feeders 4108 are operated to pass an electric current through the two beds of adsorbent material 4102 thereby effectively achieving simultaneous adsorption of organic contaminants and electrochemical regeneration within the same bed of adsorbent material 4102. The controller 4109 is operated so that the positive electric current feeder 4108 is next to the bed of adsorbent material 4102 through which the liquid to be treated is admitted. As described above in relation to Figure 7a, the bed of adsorbent material 4102 next to the positive electric current feeder acts as an anode and effects electrochemical regeneration of the adsorbent material 4102 in that bed and releasing the adsorbed organic contaminants in the form of carbonaceous gases and water, In view of the manner in which fluidisation of the adsorbent material 4102 is carried out in this version of the apparatus, electrochemical regeneration of the adsorbent material 4102 is particularly efficient in the regions of the bed of adsorbent material 4102 having a higher density of adsorbent material 4102. At this stage of the treatment process, the parallel bed of adsorbent material 4102 into which no liquid requiring treatment has been admitted acts as a cathode and any water present in this treatment zone is reduced. As explained above, proton species are produced in the bed of adsorbent material 4102 acting as the anode and hydroxide species are produced in the bed of adsorbent material 4102 acting as the cathode.

As a result of operating the pump 4212 to admit the liquid to be treated into the bed of adsorbent material 4102 at a flow rate which is sufficiently high to pass the liquid to be treated through the adsorbent material 4102 but below the flow rate required to fluidise the adsorbent material 4102, when the liquid to be treated and adsorbent material 4102 reach the top of the bed of adsorbent material 4102, the treated liquid, containing the produced proton species, accumulates in a liquid reservoir 4106 above the beds of adsorbent material 4102.

After a suitable period of simultaneous adsorption and electrochemical regeneration, the bed of adsorbent material 4102 into which the liquid to be treated is admitted is changed and the direction of the electric current is reversed by operation of controller 4109 so that the bed of adsorbent material 4102 that was previously behaving as a cathode behaves as an anode and the bed of adsorbent material 4102 that was previously behaving as an anode behaves as a cathode. Any liquid containing hydroxide species in the bed of adsorbent material 4102 that was initially behaving as a cathode is mobilised upwardly by the incoming stream of liquid to be treated and mixes with the treated liquid containing proton species already present in the liquid reservoir 4106 and become neutralised. During subsequent treatment cycles proton and hydroxide species are produced in the beds of adsorbent material 4102 and the pH-neutralising effect in the treated liquid in the reservoir 4106 continues. The pH of the treated liquid in the liquid reservoir 4106 is at least partially determined by the time period over which each half of a treatment cycle is effected, i.e. by the length of time between reversal of the applied electric current and alternation of the bed of adsorbent material 4102 into which the liquid to be treated is admitted. The pH of the treated liquid in the reservoir 4106 may therefore be monitored continually or periodically to establish whether it lies within a desired range. If it is determined that the pH of the treated liquid is too high or too low then an appropriate signal can be sent to the controller 4109 and the pump 4212 to adjust the timing between each half of the treatment cycle and therefore correct the phi of the treated liquid so that it falls into the desired range, The treated liquid in the liquid reservoir 4106, which is free or substantially free of used adsorbent material 4102, and can be released as desired via the outlet feed 4107. Alternatively, the liquid can be fed from the outlet feed 4107 back into the inlet feed 4105 for further decontamination if required. The movement of the treated liquid from the liquid reservoir 4106 to an optional additional liquid reservoir (not shown) may, for example, be effected by controlling the depth of liquid within the liquid reservoir 4106 so that its surface is periodically higher than an upper edge of a dividing wall between the liquid reservoir 4106 and the additional liquid reservoir. In this way, treated liquid periodically flows over the upper edge of the dividing wall into the additional liquid reservoir.

Figure 8 shows an alternative preferred embodiment of the apparatus according to the fourth embodiment of the first and second aspects, or the third and fourth aspects of the present invention shown in Figure 7a. Similar components take the same reference numbers as in Figure 7a. The apparatus is effectively the same as the apparatus of Figure 7a except that the cross-sectional area of a lower section 4013 of the tank 4001 is smaller than that of an upper section 4014 of the tank 4001. In use, the beds of adsorbent material 4002 are fluidised in the same way as described above in relation to Figure 7a by delivery of a suitable fluidising medium (e.g. liquid to be treated) through the openings 4011. When delivery of the fluidizing medium is halted the adsorbent material 4002 is directed back to the lower section of the tank 4001 by the converging tank walls in between the larger upper section and the smaller lower section of the tank 4001.

Figure 9 illustrates another preferred embodiment of apparatus according to the fourth embodiment of the first and second aspects, or the third and fourth aspects of the present invention in which a multiplicity of electric current feeders 4008 can be closely aligned in a tank 4001 in a parallel arrangement. Application of a voltage across the outer current feeders 4008 polarises the intermediate electric current feeders 4008, so effectively a series of alternate positive and negative current feeders are established between the outermost positive current feeder 4008 and negative current feeder 4008. The use of bipolar current feeders 4008 in this way facilitates one current to be generated a number of times with a proportional increase in voltage. This has the advantage of S increasing the voltage to obtain a larger current in the adsorbent material 4002 in sections of the bed of adsorbent material 4002 between the electric current feeders 4008 than would be achieved by the simple application of a larger voltage across the combined width of all of the beds of adsorbent material 4002, By way of example, the distance between the electric current feeders 4008 can be up to about 25 mm, which is sufficient to allow the cell voltage to be kept at an acceptable level without creating blockages of the adsorbent material 4002 and to allow the oxidised organic components removed from the liquid being treated to escape in the form of bubbles.

It will be appreciated that the alternative embodiments of the apparatus shown in Figures 8 and 9 may be employed in methods according to the second aspect of the present invention or methods according to the fourth aspect of the present invention with suitable modification taking into account the description of the Figure 7b apparatus above.

Figure 10 illustrates apparatus that is particularly suitable for use in a continuous process, which represents a preferred manner of operating the apparatus and methods representing the fifth embodiment of the first and second aspects, or the fifth and sixth aspects of the present invention.

Referring to Figure 10 there is shown a tank 4015 of rectangular horizontal cross section with inlets 4016 at the base of the tank 4015 for supplying liquid to be treated thereto. The tank 4015 has two cells 4017, each containing beds of adsorbent material 4018 for treatment of waste water and each having electrodes 4019 for regenerating the adsorbent material 4018. Towards the top of the tank 4015 there is a liquid outlet 4020 for eluting treated organic waste and a hydrogen purge outlet for eluting hydrogen, A drain 4021 is provided towards the bottom of the tank 4015 for purging liquid from the system.

Each cell 4017 has one dedicated electrode 4019a and a further electrode 4019b is shared between the two cells 4017, Each cell 4017 has two parallel beds of particulate adsorbent material 4018 located between the electrodes 4019, the parallel beds 4018 being separated from one another by a membrane 4022 located equidistant between the electrodes 4019 in each cell 4017. The liquid to be treated (i.e. a treatment mixture comprising acid and the waste liquid in the instance of the fifth embodiment of the first and second aspects, or aqueous organic waste liquid in the instance of the fifth and sixth aspects) is held in a balance tank 4023 and is pumped into the tank 4015 via flow meters 4024 for controlling the rate of flow by means of feeding pump 4025. During operation in accordance with the third and fourth aspects of the present invention the pump is configured to admit liquid into the bed of material behaving as the cathode, and may also be configured to admit S liquid into the bed of material behaving as the anode concurrently, during regeneration. The inlets 4016 and the outlet 4020 are connected in a circuit to enable continuous circulation of the liquid to be treated through the tank 4015. A power supply 4026 supplies electric current to the electrodes 4019 in each cell 4017 and is operable to control the direction in which the electric current is applied. The balance tank 4023 has an outlet sampling port 4027 for monitoring the progress of treatment of the liquid.

Figure 11 illustrates apparatus that is configured according to a similar apparatus and method as illustrated in Figure 10, but which is not capable of being operated such that the direction of current applied can be reversed. The features of the apparatus of Figure 11 which are shared with the apparatus of Figure 10 will not be described in any detail. The tank 4028 of Figure 11 has four adjacent cells 4029, each provided with a bed of adsorbent material 4030 for treatment of liquid and each having electrodes 4031 for regenerating the adsorbent material 4030.

Each cell 4029 has one electrode 4031, a porous membrane 4032 located adjacent the electrode 4031 and a bed of particulate adsorbent material 4030 located adjacent the porous membrane 4032 on the side of the membrane 4032 which is distal from the electrode 4031. Together, the porous membrane 4032 of one cell and the electrode 4031 of an adjacent cell define a cavity for the particulate adsorbent material 4030. The region between the membrane 4032 and the electrode 4031 of one cell 4029 defines a catholyte compartment 4033 for holding catholyte. A supply of catholyte is held in a catholyte tank 4034 and is pumped into each catholyte compartment 4033 through a dedicated catholyte inlet 4035 in the floor of the tank 4028 via flow meters 4036 for controlling the rate of flow by means of the catholyte pump 4037. A power supply 4038 supplies electric current to the electrodes 4031 in each cell 4029.

EXAMPLE 1

An experiment was conducted to demonstrate the performance of the apparatus and method of the of the present invention. The oil used for the experiment was Shell's Tellus 46 Hydraulic Oil Lubricant. An oil/water emulsion was created by mixing 40 grams of oil with 4 litres of water in the presence of a minimal volume of an organic polymer and 26 grams of sodium chloride. The purpose of the organic polymer was merely to stabilise the emulsion. Any suitable organic polymer may be used as could be determined by the skilled person using their common general knowledge, Although the apparatus can be operated without an electrolyte the sodium chloride was added to provide the emulsion with conductivity and thereby achieve a low cell voltage. A portion of this emulsion was admitted into a treatment tank containing 2.2 kilograms of unexpanded intercalated graphite particles as the adsorbent. A number of adsorption/regeneration treatment cycles were carried out.

At various stages throughout the treatment, additional aliquots of the emulsion were admitted to the treatment tank.

The period of each adsorption phase was 20 minutes. During the regeneration phase an electric current was passed between the electric current feeders in one direction to initiate electrochemical oxidation of the adsorbed organic components and simultaneous regeneration of the adsorbent particles. After 120 minutes the direction of the electric current was reversed and the electric current feeders operated for another 120 minutes. An electric current density of 8 mAcm2 was used in each direction, making a total of 72,000 coulombs passed in one complete regeneration cycle.

After one adsorption phase, a sample of the adsorbent was removed from the system and the mass of oil on the adsorbent was quantified. After 240 minutes of electrochemical regeneration, another sample of the adsorbent was removed for quantification of the mass of oil on the adsorbent. The quantity of oil on the adsorbent over a number of treatment cycles is set out below in Table 2.

The pH of the emulsion was measured at regular intervals throughout the treatment. The initial pH of the emulsion was 3.78. The successful maintenance of an acidic pH over a number of treatment cycles can be determined from the results presented in Table 3 below.

EXAMPLE 2

Two experiments were conducted to demonstrate the improved performance of the apparatus and method of the present invention compared to an apparatus and method not capable of being operated such that the direction of current applied can be reversed (hereinafter described as the "Catholyte System". The organic component used for the experiments was KENANTHROL VIOLET 2B manufactured by KEMTEX Colours. 20 grams of the organic component was dissolved in 200 litres of water to produce an aqueous solution containing 100 parts per million of the organic component.

In both experiments the aqueous solution was circulated through a treatment tank, collected, and then recirculated through the same treatment tank to achieve further removal of the dissolved organic component. The solution was circulated at a flow rate of 150 litres per hour. The treatment tank contained 20 kilograms of unexpanded intercalated graphite particles as the adsorbent. An electric current was passed between electric current feeders in the treatment tank during circulation of the solution so as to initiate electrochemical oxidation of the adsorbed organic component and simultaneous regeneration of the adsorbent particles.

For the experiment demonstrating the present invention, the direction of the electric current was reversed every 5 minutes. The treatment tank contained four separate beds of unexpanded intercalated graphite particles. During the application of an electric current, in absence of a separate catholyte compartment, two of the beds acted as anodes, and two of the beds acted as cathodes. When the direction of the electric current was reversed, the beds that initially acted as anodes acted as cathodes and vice versa. An electric current of 10 amps was used in each direction, making a total of 72,000 coulombs passed during one hour of treatment.

For the comparative experiment using the continuous Catholyte System, 0.3 percent sodium chloride and 1 percent hydrochloric acid ware added to the separate catholyte compartment. The purpose of the sodium chloride and hydrochloric acid was to provide the conductivity required for low voltage operation. The treatment tank contained four separate beds of unexpanded intercalated graphite particles. During the application of an electric current in one direction only, the separate catholyte compartment acted as the cathode and each of the four beds acted as individual anodes. Consequently, double the charge was passed through the treatment tank compared to the charge passed during operation of the present invention. So as to conduct a comparative experiment, an electric current of 5 amps was used, making a total of 72,000 coulombs passed during one hour of treatment.

Samples of the treated liquid were taken after each individual pass through the treatment tank. The total organic content (TOC) of each sample was measured and the amount of organic removed from the system after each pass was quantified. The quantity of organic removed from the solution over a number of passes through the treatment tank, for the system of the present invention ("System of the invention") and for the Catholyte System, is set out below in Table 4. It can be seen that the system of the invention provides comparable organic removal to the Catholyte System, whilst also providing the numerous advantages described above.

The average voltage for operation of the Catholyte System was 16.2 volts. The average voltage for operation of the system of the invention was 29.2 volts. The higher average voltage of the system of the invention is predominantly due to operation at double the current, as described above. The average voltage for operation of the system of the invention when run at 5 amps would be 14.0 volts.

Adsorption! regeneration Mass of oil on adsorbent Mass of oil on adsorbent cycle particle after adsorption / g particle after regeneration! g 0 40.0 n/a 1 34.7 20.4 2 n/a 34.7 3 17.9 n/a 4 13.3 11.5 14.4 12.4 6 9.1 8.1 7 7.6 6.5 8 7.0 6.2 9 (re-spike) 45.3 37.0 32.6 22.5 11 21.1 19.0 12 14.3 13.0 13 12.2 11.4 14 11.2 11.6 9.8 9.2 16 8.1 7.8 17 10.1 9.3 18 9.3 9.0 19 8.5 8.4 7.8 7.9 21 7.1 7.5 22 7.0 6.9 23 6.9 6.0 24 5.7 5.6 5.4 5.4 26 5.1 6.0 27 (re-spike) 42.6 36.7 28 29.2 28.7 29 25.3 24.3 19.0 n/a

Table 2

pH of solution during consecutive regeneration_cycles _____ _____ Electric current Regeneration feederacting time 1 2 3 4 5 6 7 8 9 10 as anode / minutes n/a 0 1.86 2.48 1.93 2.07 2.06 1.81 1.73 1.88 1.88 1.84 1 60 1.90 2.17 1.99 2.07 1.81 1.90 1.79 2.03 2.01 2.22 1 120 2.04 n/a 2.14 2.06 2.13 2.16 2.02 2.63 2.09 3.65 2 180 2.09 2.12 2.16 2.13 2.11 2.06 2.09 2.66 2.11 2.64 2 240 2.08 2.16 2.22 2.01 2.05 2.25 3.20 2.50 2.22 3.37

Table 3

Cumulative percentage of bulk TOC removed / % Charged passed / Coulombs ___________________________ System of the invention Catholyte System 0 0.0 0.0 36,000 9.8 22.1 72,000 18.7 30.9 108,000 25.4 34.2 144,000 51.1 41.8 180,000 54.6 40.1 216,000 56.1 43.0 252,000 56.3 46.6

Table 4

Claims

CLAIMS1. A method for the treatment of a waste liquid, the method comprising mixing a contaminated waste liquid with an acid to form a treatment mixture; contacting the treatment mixture with a carbon-based adsorbent material to adsorb contaminant therefrom; and regenerating the adsorbent by passing an electric current therethrough to release from the adsorbent gaseous products derived from the contaminant.
2. The method according to claim 1, wherein the waste liquid is contaminated with radioactive species.
3. A method according to claim 2, wherein said radioactive species are present in said treated liquid.
4. The method according to any one of claims 1 to 3, wherein the waste liquid is an aqueous organic waste.
5. The method according to any one of claims 1 to 4, wherein the acid comprises nitric acid and/or sulphuric acid.
6. The method according to any one of claims 1 to 5, wherein the method further comprises passing the treatment mixture through a reservoir containing the adsorbent material while recycling the adsorbent material along a path including passage through a regeneration chamber within the reservoir, and applying a voltage to pass the electric current through the adsorbent material in the chamber to regenerate it as it is recycled therethrough, wherein the recycling path for the adsorbent material comprises the regeneration chamber and at least one adjacent treatment chamber within the reservoir, which chambers define substantially parallel sections of the recycling path; and further wherein air under pressure is delivered to the base of the reservoir to move the adsorbent material along the recycling path.
7. The method according to any one of claims ito 5, wherein the method further comprises delivering the liquid to a treatment reservoir containing the adsorbent material in the form of a bed of particles at a base of the treatment reservoir; agitating the bed to assist in the fluid and adsorption of contaminants from the fluid; ceasing the agitation, and allowing the material to settle; and removing the decontaminated liquid from the tank.
8. The method according to claim 7 wherein the agitation is achieved by delivery of pressurised fluid such as air and/or treatment mixture.
9. The method according to any one of claims ito 5, wherein the carbon based adsorbent is in the form of a bed of material and that the step of contacting the treatment mixture with the adsorbent is conducted by admitting the treatment mixture into the bed of adsorbent at a flow rate which is sufficiently high to pass the mixture through the bed but below the flow rate required to fluidise the adsorbent material within the bed.iOThe method according to any one of claims 1 to 5, wherein the step of contacting the treatment mixture with the adsorbent is conducted by admitting the treatment mixture into first and second treatment zones of a treatment reservoir, the first and second treatment zones being separated by a porous membrane and the carbon based adsorbent being provided in said first and second treatment zones; the method further comprising distributing the carbon-based adsorbent material in the treatment mixture within each treatment zone; allowing the carbon-based adsorbent material to settle in each treatment zone; operating first and second electric current feeders are operably connected to the first and second treatment zones respectively to pass an electric current in one direction through the carbon-based adsorbent material within each treatment zone to regenerate the carbon-based adsorbent material in one of the first and second treatment zones; and operating the first and second electric current feeders to reverse the direction of the current applied to the carbon-based adsorbent material in the first and second treatment zones to regenerate the carbon-based adsorbent material in the other of the first and second treatment zones.ii. A method according to claim 10, wherein the steps of distributing the carbon-based adsorbent material in the treatment mixture and allowing the carbon-based adsorbent material to settle are repeated one or more times to remove organic matter from the aqueous organic waste liquid prior to operating the first and second electric current feeders to reverse the direction of the current applied to the carbon-based adsorbent material.12. A method according to claim 10 or 11, wherein the steps of distributing the carbon-based adsorbent material in the treatment mixture and allowing the carbon-based adsorbent material to settle are repeated one or more times to remove organic matter from the aqueous organic waste liquid prior to removing the treated liquid from the treatment reservoir.13. A method according to claim 10, 1]. or 12, wherein the or each cycle of distribution and settling steps is effected over a time period of ito 60 minutes.14. A method according to claim 10, ii or 12, wherein the or each cycle of distribution and settling steps is effected over a time period of around 20 minutes.iS. A method according to any one of claims 10 to 14, wherein distribution of the carbon-based adsorbent material is effected by admitting a fluid under pressure into the carbon-based adsorbent material.16. A method according to claim 15 wherein the fluid comprises air, treatment mixture and/or aqueous organic waste liquid in need of treatment.17. The method according to any one of claims 10 to 16, wherein liquid is admitted into the treatment zone behaving as a cathode compartment during regeneration in the treatment zone behaving as an anode compartment, the anode and cathode compartments being defined by the direction of electric current.18. The method according to claim 17, wherein liquid is admitted into both treatment zones concurrently during regeneration in the anode compartment.19. The method according to any one of claims 17 or 18, wherein the liquid being admitted into the cathode compartment and/or into the cathode and anode compartments concurrently, during regeneration in the treatment zone behaving as an anode compartment is the treatment mixture.20. The method according to any one of claims 17 to 19, wherein the liquid is admitted into the or each treatment zone at a flow rate of between about 20 to 500 Lh-1.21. The method according to claim 20, wherein the liquid is admitted into the or each treatment zone at a flow rate of between about 20 to 250 Lh-1.22. The method according to claim 21, wherein the liquid is admitted into the or each treatment zone at a flow rate of between about 20 to 25 Lh-1.23. The method according to any one of claims 17 to 22, wherein the electric current delivered by electrodes having a surface area of 1,000 cm2 or more.24. The method according to claim 23, wherein the electric current delivered by electrodes having a surface area of 2,500 cm2 or more.25. The method according to any one of claims 1 to 5, wherein the step of contacting the treatment mixture with the adsorbent is conducted by operating a pump to admit the treatment mixture into a first treatment zone of the treatment reservoir, which reservoir also includes a second treatment zone, the first and second treatment zones being separated by a porous membrane, the treatment mixture being admitted into said first treatment zone to contact carbon-based adsorbent material in a bed in the first treatment zone at a flow rate which is sufficiently high to pass treatment mixture through the bed of carbon-based adsorbent material but below the flow rate required to fluidise the bed of carbon-based adsorbent material; the method further comprising operating first and second electric current feeders operably connected to the first and second treatment zones respectively to pass an electric current in one direction through the carbon-based adsorbent material within each treatment zone to regenerate the carbon-based adsorbent material in said first treatment zone; operating the pump to admit treatment mixture into said second treatment zone to contact carbon-based adsorbent material in a bed in the second treatment zone at a flow rate which is sufficiently high to pass the treatment mixture through the bed of carbon- based adsorbent material but below the flow rate required to fluidise the bed of carbon-based adsorbent material; and operating the first and second electric current feeders to reverse the direction of the current applied to the carbon-based adsorbent material in the first and second treatment S zones to regenerate the carbon-based adsorbent material in the second treatment zone.26. A method according to claim 25, wherein the treatment mixture is admitted under pressure through one or more inlets into each bed of carbon-based adsorbent material.27. A method according to claim 26, wherein the treatment mixture is admitted through a plurality of said inlets spaced apart by a sufficient distance to establish a corresponding plurality of discrete liquid flow paths through the bed of carbon-based adsorbent material in each treatment zone.28. A method according to claim 27, wherein the spacing of the plurality of inlets is sufficient to define a region around each liquid flow path through which carbon-based adsorbent material that has adsorbed contaminant can flow so as to define a discrete, endless stream of carbon-based adsorbent material within each bed of carbon-based adsorbent material.29. A method according to any one of claims 25 to 28, wherein liquid that has contacted the carbon-based adsorbent material is passed to a reservoir in fluid communication with the corresponding bed of carbon-based adsorbent material.30. A method according to any one of claims 25 to 29 wherein the treatment mixture is admitted at a flow rate of ito SOUL per hour.31. A method according to claim to 30 wherein the treatment mixture is admitted at a flow rate of around iSO L per hour.32. The method according to any one of claims 25 to 3i, wherein liquid is admitted into the treatment zone behaving as a cathode compartment during regeneration in the treatment zone behaving as an anode compartment, the anode and cathode compartments being defined by the direction of electric current.33. The method according to claim 32, wherein liquid is admitted into both treatment zones concurrently during regeneration in the anode compartment.34. The method according to any one of claims 32 or 33, wherein the liquid being admitted into the cathode compartment and/or into the cathode and anode compartments concurrently, during regeneration in the treatment zone behaving as an anode compartment is the treatment mixture.35. The method according to any one of claims 32 to 34, wherein the liquid is admitted into the or each treatment zone at a flow rate of between about 20 to 500 Lh 1 36. The method according to claim 35, wherein the liquid is admitted into the or each treatment zone at a flow rate of between about 20 to 250 Lh1.37. The method according to claim 36 the liquid is admitted into the or each treatment zone at a flow rate of between about 20 to 25 Lh'.38. The method according to any one of claims 32 to 37, wherein the electric current delivered by electrodes having a surface area of 1,000 cm2 or more.39. The method according to claim 38, wherein the electric current delivered by electrodes having a surface area of 2,500 cm2 or more.40. A method for the continuous treatment of an aqueous organic waste liquid, the method comprising admitting the aqueous organic waste liquid into first and second treatment zones of a treatment reservoir, the first and second treatment zones being separated by a porous membrane, each treatment zone containing carbon-based adsorbent material capable of electrochemical regeneration; distributing the carbon-based adsorbent material in the aqueous organic waste liquid within each treatment zone; allowing the carbon-based adsorbent material to settle within each treatment zone; operating first and second electric current feeders operably connected to the first and second treatment zones respectively to pass an electric current in one direction through the carbon-based adsorbent material within each treatment zone to regenerate the carbon-based adsorbent material in one of the first and second treatment zones; and operating the first and second electric current feeders to reverse the direction of the current applied to the carbon-based adsorbent material in the first and second treatment S zones to regenerate the carbon-based adsorbent material in the other of the first and second treatment zones; wherein liquid is admitted into the treatment zone behaving as a cathode compartment during regeneration in the treatment zone behaving as an anode compartment, the anode and cathode compartments being defined by the direction of electric current.41. The method according to claim 40, wherein the waste liquid is contaminated with radioactive species.42. A method according to claim 41, wherein said radioactive species are present in said treated liquid.43. A method according to any one of claims 40 to 42, comprising a preliminary step of mixing the aqueous organic waste liquid with an acid.44. The method according to any one of claims 40 to 43, wherein liquid is admitted into the cathode and anode compartments concurrently during regeneration in the anode compartment.45. The method according to any one of claims 40 to 44, wherein the liquid being admitted into the cathode compartment and/or into the cathode and anode compartments concurrently, during regeneration in the treatment zone behaving as an anode compartment is the aqueous organic waste liquid.46. A method according to any one of claims 40 to 45, wherein the current feeders are operated to provide a pH of less than 7 in the treated liquid.47. A method according to any one of claims 40 to 46, wherein the current feeders are operated to provide a pH of around ito 4 in the treated liquid.48. A method according to any one of claims 40 to 47, wherein the steps of distributing the carbon-based adsorbent material in the aqueous organic waste liquid and allowing the carbon-based adsorbent material to settle are repeated one or more times to remove organic matter from the aqueous organic waste liquid prior to operating the first and second electric current feeders to reverse the direction of the current applied to the carbon-based adsorbent material.49. A method according to any one of claims 40 to 48, wherein the steps of distributing the carbon-based adsorbent material in the aqueous organic waste liquid and allowing the carbon-based adsorbent material to settle are repeated one or more times to remove organic matter from the aqueous organic waste liquid prior to removing the treated liquid from the treatment reservoir.50. A method according to any one of claims 40 to 49, wherein the or each cycle of distribution and settling steps is effected over a time period of ito 60 minutes.51. A method according to claim 50, wherein the or each cycle of distribution and settling steps is effected over a time period of around 20 minutes.52. A method according to any one of claims 40 to 51, wherein distribution of the carbon-based adsorbent material is effected by admitting a fluid under pressure into the carbon-based adsorbent material.53. A method according to claim 52, wherein the fluid comprises air and/or aqueous organic waste liquid in need of treatment.54. A method for the continuous treatment of an aqueous organic waste liquid, the method comprising operating a pump to admit aqueous organic waste liquid into a first treatment zone of a treatment reservoir which also includes a second treatment zone, the first and second treatment zones being separated by a porous membrane, the aqueous organic waste liquid being admitted into said first treatment zone to contact carbon-based adsorbent material in a bed in the first treatment zone at a flow rate which is sufficiently high to pass the aqueous organic waste liquid through the bed carbon-based adsorbent material but below the flow rate required to fluidise the bed of carbon-based adsorbent material; operating first and second electric current feeders operably connected to the first and second treatment zones respectively to pass an electric current in one direction through S the carbon-based adsorbent material within each treatment zone to regenerate the carbon-based adsorbent material in said first treatment zone; operating the pump to admit aqueous organic waste liquid into said second treatment zone to contact carbon-based adsorbent material in a bed in the second treatment zone at a flow rate which is sufficiently high to pass the aqueous organic waste liquid through the bed of carbon-based adsorbent material but below the flow rate required to fluidise the bed of carbon-based adsorbent material; and operating the first and second electric current feeders to reverse the direction of the current applied to the carbon-based adsorbent material in the first and second treatment zones to regenerate the carbon-based adsorbent material in the second treatment zone; wherein liquid is admitted into the treatment zone behaving as a cathode compartment during regeneration in the treatment zone behaving as an anode compartment, the anode and cathode compartments being defined by the direction of electric current.55. A method according to claim 54, comprising a preliminary step of mixing the aqueous organic waste liquid with an acid.56. The method according to claim 54 or 55, wherein the waste liquid is contaminated with radioactive species.57. A method according to claim 56, wherein said radioactive species are present in said treated liquid.58. The method according to any one of claims 54 to 57, wherein liquid is admitted into the cathode and anode compartments concurrently during regeneration in the anode compartment.59. The method according to any one of claims 54 to 58, wherein the liquid being admitted into the cathode compartment and/or into the cathode and anode compartments concurrently, during regeneration in the treatment zone behaving as an anode compartment is the aqueous organic waste liquid.60. The method according to any one of claims 54 to 59, wherein the liquid is admitted into the S or each treatment zone at a flow rate of between about 20 to 500 Lh.61. The method according to claim 60, wherein the liquid is admitted into the or each treatment zone at a flow rate of between about 20 to 250 Lh.62. The method according to claim 61, wherein the liquid is admitted into the or each treatment zone at a flow rate of between about 20 to 25 Lh1.63. The method according to any one of claims 54 to 62, wherein the electric current delivered by electrodes having a surface area of 1,000 cm2 or more.64. The method according to claim 63, wherein the electric current delivered by electrodes having a surface area of 2,500 cm2 or more.65. A method according to any one of claims 54 to 64, wherein the current feeders are operated to provide a pH of less than 7 in the treated liquid.66. A method according to any one of claims 54 to 65, wherein the current feeders are operated to provide a pH of around ito 4 in the treated liquid, 67. A method according to any one of claims 54 to 66, wherein the aqueous organic waste liquid is admitted under pressure through one or more inlets into each bed of carbon-based adsorbent material.68. A method according to claim 67, wherein the aqueous organic waste liquid is admitted through a plurality of said inlets spaced apart by a sufficient distance to establish a corresponding plurality of discrete liquid flow paths through the bed of carbon-based adsorbent material in each treatment zone.69. A method according to claim 68, wherein the spacing of the plurality of inlets is sufficient to define a region around each liquid flow path through which carbon-based adsorbent material that has adsorbed contaminant can flow so as to define a discrete, endless stream of carbon-based adsorbent material within each bed of carbon-based adsorbent material.S70. A method according to any one of claims 54 to 69 wherein the aqueous organic waste liquid is admitted at a flow rate of 1 to 500 L per hour.71. A method according to claim to 70 wherein the aqueous organic waste liquid is admitted at a flow rate of around 150 L per hour.72. A method according to any one of claims 10 to 71, wherein charged inorganic species are generated during the passage of the electric current through the carbon-based adsorbent material in the first and second treatment zones and the current feeders are operated to minimise the electrodeposition of said charged inorganic species on the current feeders during operation.73. A method according to any one of claims 10 to 72, wherein the first and second current feeders are operated to pass the electric current through the carbon-based adsorbent material in the treatment zones in said one direction for a time period of ito 240 minutes.74. A method according to claim 73 wherein the first and second current feeders are operated to pass the electric current through the carbon-based adsorbent material in the treatment zones in said one direction for a time period of around 5 minutes.75. A method according to any one of claims 10 to 74, wherein the first and second current feeders are operated to pass the electric current through the carbon-based adsorbent material in the treatment zones in said other direction for a time period of ito 240 minutes.76. A method according to claim 75 wherein the first and second current feeders are operated to pass the electric current through the carbon-based adsorbent material in the treatment zones in said other direction for a time period of around 5 minutes.77. A method according to any one of claims 10 to 76, wherein the first and second current feeders are operated to apply an electric current density of around 1 to 30 mAcm2 to the carbon-based adsorbent material in each treatment zone.78. A method according to any one of claims 1 to 77, wherein the carbon-based adsorbent material is an unexpanded graphite intercalation compound and/or activated carbon.79. A method according to any one of claims 1 to 78, wherein the carbon-based adsorbent material is in powder or flake form.80. A method according to any one of claims 1 to 79, wherein said electric current is 1 to 10 amps.81. A method according to claim 80, wherein said electric current is around 5 amps.82. A method according to any one of claims 1 to 81, wherein an electrolyte is provided in the treatment reservoir.83. An apparatus for the treatment of a waste liquid, the apparatus comprising: i) a reservoir for waste liquid to be treated, the reservoir comprising acid for mixing with the waste liquid; ii) carbon-based adsorbent material capable of electrochemical regeneration provided in the reservoir; iii) a means for regenerating the carbon-based adsorbent by passing an electric current therethrough to release from the adsorbent gaseous products derived from the contaminant; and iv) an agitator operable to distribute the carbon-based adsorbent material in waste liquid contained in the treatment reservoir.84. The apparatus according to claim 83, further comprising a regeneration chamber provided in the reservoir, the agitating means being adapted for recycling adsorbent material along a path including passage through the regeneration chamber and in the treatment mixture in the reservoir, the regeneration chamber being defined between two electrodes for coupling to a source of electrical power, wherein recycling path for the adsorbent material comprises the regeneration chamber and at least one adjacent treatment chamber within the reservoir, which chambers define substantially parallel sections of the recycling path, and further wherein the agitating means comprising means for delivering air under pressure to the base of the reservoir to move the adsorbent material along the recycling path.85. The apparatus according to claim 83, wherein the reservoir for the treatment mixture has an upper and a lower section, and contains the adsorbent material in the form of a bed of particles supported in the lower section at the base of the reservoir; and the agitator is adapted for agitating the bed to distribute the particles in liquid contained in the reservoir including the upper section; the apparatus further comprising electrodes on opposite sides of the lower section for delivering electric current to pass through and regenerating the bed of particles.86. The apparatus according to claim 83, wherein the adsorbent is provided as a bed and the agitator is adapted to admit the treatment mixture into said bed to contact said adsorbent material at a flow rate which is sufficiently high to pass the mixture through the bed but below the flow rate required to fluidise the bed of adsorbent material, the apparatus further comprising at least one pair of electrodes operable to pass the electric current through said bed to regenerate the adsorbent material.87. Apparatus according to claim 86, wherein the agitator comprises one or more spaced inlets through which the contaminated liquid is admitted under pressure into the bed of adsorbent material.88. Apparatus according to claim 87, wherein the apparatus comprises a plurality of said inlets spaced apart by a sufficient distance to establish a corresponding plurality of discrete liquid flow paths through the adsorbent bed.89. Apparatus according to claim 88, wherein the spacing of the plurality of inlets is sufficient to define a region around each liquid flow path through which adsorbent material that has adsorbed contaminant can flow so as to define a discrete, endless stream of adsorbent material within the bed of adsorbent material.90. Apparatus according to any one of claims 86 to 89, wherein the apparatus comprises a reservoir in fluid communication with the adsorbent bed, the reservoir being adapted to receive liquid from the bed which has been contacted by the adsorbent material.91. Apparatus according to any one of claims 86 to 90, wherein the apparatus is configured to admit the treatment mixture at a flow rate of ito 500 L per hour.92. Apparatus according to claim 91, wherein the apparatus is configured to admit the treatment mixture at a flow rate of around 150 L per hour.93. The apparatus according to claim 83, wherein the treatment reservoir defines first and second treatment zones separated by a porous membrane, the carbon-based adsorbent material being provided in said first and second treatment zones and wherein the agitator is operable to distribute the carbon-based adsorbent material in aqueous organic waste liquid contained in each of the first and second treatment zones, the apparatus further comprising a first electric current feeder operably connected to the carbon-based adsorbent material in the first treatment zone and a second electric current feeder operably connected to the carbon-based adsorbent material in the second treatment zone, and a controller to operate the first and second electric current feeders to pass an electric current through the carbon-based adsorbent material in the first and second treatment zones in one direction to regenerate the carbon-based adsorbent material in one of the first and second treatment zones and to then reverse the direction of the current applied to the carbon-based adsorbent material in the first and second treatment zones to regenerate the carbon-based adsorbent material in the other of the first and second treatment zones.94. Apparatus according to claim 93, wherein the agitator comprises a chamber under the treatment reservoir defining one or more inlets and a pump to deliver fluid under pressure through said inlet(s).95. The apparatus according to any one of claims 93 or 94, wherein the agitator is adapted to admit liquid into the treatment zone behaving as a cathode compartment during regeneration in the treatment zone behaving as an anode compartment, the anode and cathode compartments being defined by the direction of electric current 96. The apparatus according to claim 95, wherein the agitator is adapted to admit liquid into the both treatment zones concurrently during regeneration in the anode compartment.97. The apparatus according to claim 95 or 96, wherein the liquid being admitted into the cathode compartment, and/or into the cathode and anode compartments concurrently, during regeneration in the anode compartment is the treatment mixture 98. The apparatus according to any one of claims 95 to 97, wherein the liquid is admitted into the or each treatment zone at a flow rate of between about 20 to 500 Lh 99. The apparatus according to claim 98, wherein the liquid is admitted into the or each treatment zone at a flow rate of between about 20 to 250 Lh1.100. The apparatus according to claim 99, wherein the liquid is admitted into the or each treatment zone at a flow rate of between about 20 to 25 Lh1.101. The apparatus according to any one of claims 95 to 100, wherein the electric current delivered by electrodes having a surface area of 1,000 cm2 or more.102. The apparatus according to claim 101, wherein the electric current delivered by electrodes having a surface area of 2,500 cm2 or more.103. The apparatus according to claim 83, wherein treatment reservoir defines first and second treatment zones separated by a porous membrane, the carbon-based adsorbent material being provided in said first and second treatment zones and wherein the agitator is a pump operable to admit the treatment mixture selectively into each of said first and second treatment zones to contact carbon-based adsorbent material in the respective treatment zone at a flow rate which is sufficiently high to pass the treatment mixture through the carbon-based adsorbent material but below the flow rate required to fluidise the carbon-based adsorbent material, the apparatus further comprising a first electric current feeder operably connected to the carbon-based adsorbent material in the first treatment zone and a second electric current feeder operably connected to the carbon-based adsorbent material in the second treatment zone, and a controller to operate the first and second electric current feeders to pass an electric current through the carbon-based adsorbent material in the first and second treatment zones in one direction to regenerate the carbon-based adsorbent material in one of the first and second treatment zones and to then reverse the direction of the current applied to the carbon-based adsorbent material in the first and second treatment zones to regenerate the carbon-based adsorbent material in the other of the first and second treatment zones.104. Apparatus according to claim 103, wherein the agitator comprises one or more spaced inlets through which the treatment mixture is admitted under pressure into the bed of adsorbent material.105. Apparatus according to claim 104, wherein the apparatus comprises a plurality of said inlets spaced apart by a sufficient distance to establish a corresponding plurality of discrete liquid flow paths through the adsorbent bed.106. Apparatus according to claim 105, wherein the spacing of the plurality of inlets is sufficient to define a region around each liquid flow path through which adsorbent material that has adsorbed contaminant can flow so as to define a discrete, endless stream of adsorbent material within the bed of adsorbent material.107. Apparatus according to any one of claims 102 to 106, wherein the apparatus comprises a reservoir in fluid communication with the adsorbent bed, the reservoir being adapted to receive liquid from the bed which has been contacted by the adsorbent material.108. Apparatus according to any one of claims 102 to 107, wherein the apparatus is configured to admit the treatment mixture at a flow rate of ito 500 L per hour.109. Apparatus according to claim 108, wherein the apparatus is configured to admit the treatment mixture at a flow rate of around 150 L per hour.110. The apparatus according to any one of claims 102 to 109, wherein the agitator is adapted to admit liquid into the treatment zone behaving as a cathode compartment during regeneration in the treatment zone behaving as an anode compartment, the anode and cathode compartments being defined by the direction of electric current 111. The apparatus according to claim 110, wherein the agitator is adapted to admit liquid into the both treatment zones concurrently during regeneration in the anode compartment.112. The apparatus according to claim 110 or 111, wherein the liquid being admitted into the cathode compartment, and/or into the cathode and anode compartments concurrently, during regeneration in the anode compartment is the treatment mixture 113. The apparatus according to any one of claims 110 to 112, wherein the liquid is admitted into the or each treatment zone at a flow rate of between about 20 to 500 Lh1.114. The apparatus according to claim 113, wherein the liquid is admitted into the or each treatment zone at a flow rate of between about 20 to 250 Lh'.115. The apparatus according to claim 114, wherein the liquid is admitted into the or each treatment zone at a flow rate of between about 20 to 25 Lh1.116. The apparatus according to any one of claims 110 to 115, wherein the electric current delivered by electrodes having a surface area of 1,000 cm2 or more.117. The apparatus according to claim 116, wherein the electric current delivered by electrodes having a surface area of 2,500 cm2 or more.118. Apparatus for the continuous treatment of an aqueous organic waste liquid, the apparatus comprising a treatment reservoir defining first and second treatment zones separated by a porous membrane, carbon-based adsorbent material capable of electrochemical regeneration provided in said first and second treatment zones, an agitator operable to distribute the carbon-based adsorbent material in aqueous organic waste liquid contained in each of the first and second treatment zones, a first electric current feeder operably connected to the carbon-based adsorbent material in the first treatment zone and a second electric current feeder operably connected to the carbon-based adsorbent material in the second treatment zone, and a controller to operate the first and second electric current feeders to pass an electric current through the carbon-based adsorbent material in the first and second treatment zones in one direction to regenerate the carbon-based adsorbent material in one of the first and second treatment zones and to then reverse the direction of the current applied to the carbon-based adsorbent material in the first and second treatment zones to regenerate the carbon-based adsorbent material in the other of the first and second treatment zones, wherein the agitator is adapted to admit liquid into the treatment zone behaving as a cathode compartment during regeneration in the treatment zone behaving as an anode compartment, the anode and cathode compartments being defined by the direction of electric current.119. The apparatus according to claim 118, wherein the reservoir further comprises acid for mixing with the aqueous organic waste.120. The apparatus according to claim 119, wherein the agitator is adapted to admit liquid into the both treatment zones concurrently during regeneration in the anode compartment 121. The apparatus according to any one of claims 118 to 120, wherein the liquid being admitted into the cathode compartment, and/or into the cathode and anode compartments concurrently, during regeneration in the anode compartment is the aqueous organic waste.122. The apparatus according to any one of claims 118 to 121, wherein the liquid is admitted into the or each treatment zone at a flow rate of between about 20 to 500 Lh1.123. The apparatus according to claim 122, wherein the liquid is admitted into the or each treatment zone at a flow rate of between about 20 to 250 Lh1.124. The apparatus according to claim 123, wherein the liquid is admitted into the or each treatment zone at a flow rate of between about 20 to 25 LEt1.125. The apparatus according to any one of claims 118 to 124, wherein the electric current delivered by electrodes having a surface area of 1,000 cm2 or more.126. The apparatus according to claim 125, wherein the electric current delivered by electrodes having a surface area of 2,500 cm2 or more.127. Apparatus according to any one of claims 118 to 126, wherein the agitator comprises a chamber under the treatment reservoir defining one or more inlets and a pump to deliver fluid under pressure through said inlet(s).128. Apparatus for the continuous treatment of an aqueous organic waste liquid, the apparatus comprising a treatment reservoir defining first and second treatment zones separated by a porous membrane, carbon-based adsorbent material capable of electrochemical regeneration provided in said first and second treatment zones, a pump operable to admit aqueous organic waste liquid selectively into each of said first and second treatment zones to contact carbon-based adsorbent material in the respective treatment zone at a flow rate which is sufficiently high to pass the aqueous organic waste liquid through the carbon-based adsorbent material but below the flow rate required to fluidise the carbon-based adsorbent material, a first electric current feeder operably connected to the carbon-based adsorbent material in the first treatment zone and a second electric current feeder operably connected to the carbon-based adsorbent material in the second treatment zone, and a controller to operate the first and second electric current feeders to pass an electric current through the carbon-based adsorbent material in the first and second treatment zones in one direction to regenerate the carbon-based adsorbent material in one of the first and second treatment zones and to then reverse the direction of the current applied to the carbon-based adsorbent material in the first and second treatment zones to regenerate the carbon-based adsorbent material in the other of the first and second treatment zones wherein the pump is adapted to admit liquid into the treatment zone behaving as a cathode compartment during regeneration in the anode compartment, the anode and cathode compartments being defined by the direction of electric current, 129. The apparatus according to claim 128, wherein the pump is adapted to admit liquid into the both treatment zones concurrently during regeneration in the anode compartment.130. The apparatus according to claim 128 or 129, wherein the liquid being admitted into the cathode compartment, and/or into the cathode and anode compartments concurrently, during regeneration in the anode compartment is the aqueous organic waste liquid.131. Apparatus according to any one of claims 128 to 130, wherein the apparatus comprises one or more spaced inlets through which the aqueous organic waste liquid is admitted under pressure into the bed of adsorbent material.132. Apparatus according to claim 131, wherein the apparatus comprises a plurality of said inlets spaced apart by a sufficient distance to establish a corresponding plurality of discrete liquid flow paths through the adsorbent bed.133. Apparatus according to claim 132, wherein the spacing of the plurality of inlets is sufficient to define a region around each liquid flow path through which adsorbent material that has adsorbed contaminant can flow so as to define a discrete, endless stream of adsorbent material within the bed of adsorbent material, 134. Apparatus according to any one of claims 128 to 133, wherein the apparatus comprises a reservoir in fluid communication with the adsorbent bed, the reservoir being adapted to receive liquid from the bed which has been contacted by the adsorbent material.135. Apparatus according to any one of claims 128 to 134, wherein the apparatus is configured to admit aqueous organic waste liquid at a flow rate of 1 to 500 L per hour, 136. Apparatus according to claim 135, wherein the apparatus is configured to admit aqueous organic waste liquid at a flow rate of around 150 L per hour.137. Apparatus according to any one of claims 93 to 136, wherein a lower section of the treatment reservoir defines a smaller horizontal cross-sectional area than an upper section of the treatment reservoir, 138. Apparatus according to any one of claims 93 to 137, wherein the porous membrane is configured to prevent carbon-based adsorbent material from passing between the first and second treatment zones but to permit water and/or ionic species to pass between the first and second treatment zones.139. Apparatus according to any one of claims 83 to 138, wherein the carbon-based adsorbent material is an unexpanded graphite intercalation compound and/or activated carbon.140. Apparatus according to any one of claims 83 to 139, wherein the carbon-based adsorbent material is in powder or flake form.141. Apparatus according to any one of claims 83 to 140, wherein the apparatus is configured to deliver an electric current of ito 10 amps.142. Apparatus according to claim 141, wherein the apparatus is configured to deliver an electric current of around S amps.