Relating to the Treatment of Matrices and/or the Contents of Matrices

Abstract

A method and apparatus break down organic materials, typically contaminants, through oxidation. The method for the treatment of a volume of material, provides: a) introducing at least two electrodes into a location, the location containing the volume of material and the volume of material containing one or more species for treatment; b) providing connections between a voltage source and the at least two electrodes; c) applying a voltage of a first polarity to the connections for a first period of time, under the control of a voltage controller; d) applying a voltage of a second, reversed, polarity to the connections for a second period of time, under the control of the voltage controller; e) repeating steps c) and d) a plurality of times; preferably with steps c), d) and e) promoting oxidation of one or more of the one or more species for treatment.

Claims

1. A method for the treatment of a volume of material causing breakdown of one or more species, the species being organic contaminants in the volume of material the volume of material being a matrix formed of a mixture of liquid and of solids, the solids providing a surface, the volume of material being a slurry or sludge, the method comprising: a) introducing at least two electrodes into a location, the location containing the volume of material and the volume of material containing one or more species for treatment; b) providing connections between a voltage source and the at least two electrodes, the voltage source having an output of between 2 V and 50 V; c) applying a voltage of a first polarity to the connections for a first period of time, under the control of a voltage controller, to generate a current with a defined current pulse profile; d) applying a voltage of a second, reversed, polarity to the connections for a second period of time, under the control of the voltage controller, to generate a reverse current with a reverse defined current pulse profile; e) repeating steps c) and d) a plurality of times; wherein, as a result of the applied voltages: i) one or more components of the matrix become charged by the current and the reverse current according to the natural capacitance of the system; ii) free radicals are generated at the surface of one or more of the solids within the matrix due to current and the reverse current; iii) the defined current pulse profile is provided during step c) in the matrix; iv) the reverse defined current pulse profile is provided during step d) in the matrix, with a reverse polarity to that of step c); wherein the defined current pulse profile has a first section, second section and third section, the first section having a start current value and an end current value, the first section start current value being zero and the first section end current value being the maximum current for the defined current pulse profile, and the first section having a duration of less than 0.5 ms; the second section having a start current value and an end current value, the second section start current value being the maximum current for the defined current pulse profile and the second section end current value being a declined current value, and the second section having a duration of up to 500 ms; and the third section having a start current value and an end current value, the third section start current value being less than the maximum current for the defined current pulse profile, the third section end current value being zero, and the third section having a duration of less than 0.5 ms; wherein, as a result of the applied voltages, a reverse defined current pulse profile is provided during step d) within the matrix with a reverse polarity to that of step c); wherein the reverse defined current pulse profile has a first reverse section, second reverse section and third reverse section, the first reverse section having a start current value and an end current value, the first reverse section start current value being zero and the first reverse section end current value being the maximum current for the reverse defined current pulse profile, and the first reverse section having a duration of less than 0.5 ms; the second reverse section having a start current value and an end current value, the second reverse section start current value being the maximum current for the reverse defined current pulse profile and the second reverse section end current value being a reverse declined current value, and the second reverse section having a duration of up to 500 ms; and the third reverse section having a start current value and an end current value, the third reverse section start current value being less than the maximum current for the reverse defined current pulse profile, the third reverse section end current value being zero, and the third reverse section having a duration of less than 0.5 ms.

2. The method according to claim 1, in which steps c), d) and e) promote oxidation of one or more of the one or more species for treatment.

3. The method according to claim 1, wherein the treatment reduces the volume of one or more compounds present in the location and/or the treatment reduces the level of one or more compounds present in the location and/or the treatment alters the form of one or more compounds.

4. The method according to claim 1, in which the one or more species is/are one or more of the following: light hydrocarbons (C10 or less), heavy hydrocarbons (C11 or more), benzene, toluene, ethyl benzene, xylenes, polycyclic aromatic hydrocarbons, chlorinated phenyls, chlorophenols, polychlorinated biphenyls, biphenols, perchloroethylenes, tricholorethylenes, dioxins, perfluorooctanesulfonic acids, perfluorooctanoic acids or other hydrocarbons.

5. The method according to claim 1, wherein the voltage is the voltage necessary to achieve an electric field of greater than 0.2V/m across the separation between the electrode of one potential and the electrode of a different potential which is closest to that electrode.

6. The method according to claim 1, wherein the voltage applied is in the form of a voltage pulse profile, the voltage pulse profile having a first section during which the voltage is at a maximum value, the voltage pulse profile having a first reversed section during which the voltage is at a maximum value, but of opposing polarity.

7. (canceled)

8. The method according to claim 1, wherein the defined current pulse profile continues at that declined current value for a fourth section of the defined current pulse profile, with the fourth section positioned intermediate the second section and the third section of the defined current pulse profile and wherein the reverse defined current pulse profile continues at that declined current value for a fourth reverse section of the reverse defined current pulse profile, with the fourth reverse section positioned intermediate the second reverse section and the third reverse section of the reverse defined current pulse profile.

9. (canceled)

10. (canceled)

11. The method according to claim 1, wherein the second section of the defined current pulse profile has a duration of between 10 ms and 500 ms.

12. The method according to claim 8, wherein the fourth section of the defined current pulse profile has a duration that is greater than 500 ms.

13. (canceled)

14. The method according to claim 8, wherein the first section and/or second section have a maximum current value in excess of a maximum current value of the fourth section due to a discharge of a charge provided to the volume or material or a part of the volume of material during an immediately previous fourth reversed section.

15. The method according to claim 1, wherein the second section includes a maximum current value above the declined current value due to the voltage applied causing one or more components of the material to become charged according to the natural capacitance of the system.

16. The method according to claim 8, wherein the fourth section provides a part of the defined current pulse profile during which the volume of material or a part of the volume of material becomes charged with a charge which contributes to the second reversed section of the defined current pulse profile.

17. The method according to claim 1, wherein the method promotes oxidisation by generating free radicals within the location.

18. The method according to claim 1, wherein the method promotes oxidisation by generating free radicals within the material at the surface of solid species within a matrix in the material.

19. The method according to claim 1, wherein the method has one or more or all of the following effects upon a matrix in the material and/or one or more species in the material between a first time at the start of the method's application and a second time after the method has been applied: a reduction in the concentration of C40 or more carbon atoms hydrocarbons by 20% or more; an increase in the concentration of C8 to C30 hydrocarbons by more than 100%; an increase in the concentration of less than C8 hydrocarbons by more than 25%; a reduction in the concentration of the C8 or greater hydrocarbons by 10% or more; the conversion of a part of the hydrocarbons to water and carbon dioxide.

20. The method according to claim 1, wherein the method includes repeating steps c) and d) through at least 1000 repetitions.

21. The method according to claim 1, wherein the method has one or more or all of the following effects upon a matrix in the material and/or one or more species in the material between a first time at the start of the method's application and a second time after the method has been applied: a reduction in the concentration of C40 or more carbon atoms hydrocarbons by 35% or more; an increase in the concentration of C8 to C30 hydrocarbons by more than 200%; an increase in the concentration of less than C8 hydrocarbons by more than 50%; a reduction in the concentration of the C8 or greater hydrocarbons by 20% or more; the conversion of a part of the hydrocarbons to water and carbon dioxide.

22. The method according to claim 1, wherein the method has one or more or all of the following effects upon a matrix in the material and/or one or more species in the material between a first time at the start of the method's application and a second time after the method has been applied: a reduction in the concentration of C40 or more carbon atoms hydrocarbons by 50% or more; an increase in the concentration of C8 to C30 hydrocarbons by more than 500%; an increase in the concentration of less than C8 hydrocarbons by more than 100%; a reduction in the concentration of the C8 or greater hydrocarbons by 30% or more; the conversion of a part of the hydrocarbons to water and carbon dioxide.

23.-29. (canceled)

30. A method for the treatment of a volume of material causing breakdown of one or more organic contaminants in the volume of material, the method comprising: a) introducing at least two electrodes into a location, the location containing the volume of material and the volume of material containing one or more species for treatment; b) providing connections between a voltage source and the at least two electrodes, the voltage source having an output of between 2 V and 50 V; c) applying a voltage of a first polarity to the connections for a first period of time, under the control of a voltage controller; d) applying a voltage of a second, reversed, polarity to the connections for a second period of time, under the control of the voltage controller; e) repeating steps c) and d) a plurality of times; wherein, as a result of the applied voltages, a defined current pulse profile is provided during step c) and step d); wherein the method includes repeating steps c) and d) through at least 1000 repetitions; wherein the defined current pulse profile has a first section, second section and third section, the first section having a start current value and an end current value, the first section start current value being zero and the first section end current value being the maximum current for the defined current pulse profile, and the first section having a duration of less than 0.5 ms; wherein the defined current pulse profile has the second section having a second section start current value and a second section end current value, the second section start current value being the maximum current value for the defined current pulse profile, with the current declining between the second section start current value and the second section end current value, the second section end current value being a declined current value, the declined current value being the value that the current declines to from the maximum current value, with the passage of time and representing a steady state current reached after that period of time, and the second section having a duration of up to 500 ms; and wherein the third section has a start current value and an end current value, the third section start current value being less than the maximum current for the defined current pulse profile, the third section end current value being zero, and the third section having a duration of less than 0.5 ms.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0124] The invention will now be described, by way of example only, and with reference to the accompanying drawings in which:

[0125] FIG. 1a is a schematic perspective view of a volume of matrix and compounds being treated according to an embodiment of the invention;

[0126] FIG. 1b is a detailed view of part of the schematic of FIG. 1a and showing pH treatment;

[0127] FIG. 2 is an illustration of the voltage pulse shape applied to the electrodes in the matrix over a series of pulses;

[0128] FIG. 3a is an illustration of a detailed view of a part of the current pulse shape, showing the preferred form of that part of the pulse in one embodiment of the invention;

[0129] FIG. 3b is an illustration of the same detailed view of a part of the current pulse shape as FIG. 3a, but with too long a duration before the polarity is reversed for that embodiment of the invention;

[0130] FIG. 3c is an illustration of the same detailed view of a part of the current pulse shape as FIG. 3a, but with too short a duration before the polarity is reversed for that embodiment of the invention;

[0131] FIG. 4 is a schematic illustration of the use of the invention in another situation;

[0132] FIG. 5 is a schematic illustration of a still further embodiment of the invention;

[0133] FIG. 6 illustrates results for the operation of the method on one mixture;

[0134] FIG. 7 is a schematic illustration of the use of the invention in another situation where an emulsion layer requires treatment

[0135] FIG. 8a illustrates an alternative current pulse shape provided in an embodiment of the invention;

[0136] FIG. 8b illustrates a detail of a part of the current pulse shape of FIG. 8a

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0137] In FIG. 1, a large tank 1 is provided which is designed to have significant capacity for the storage of a mixture 3 which is fed to the tank via inlet 5 from a previous process, not shown. The mixture 3 includes solids, liquids and compounds arising from the previous process.

[0138] For example, the previous process may be a drilling operation and the mixture 3 may be a drilling sludge containing a mixture of heavy and light hydrocarbons, clay and salt water or brine.

[0139] Previous treatment attempts at the treatment of the mixture 3 may have included settling and decanting the liquid, in-situ chemical treatment or the removal of part of the mixture for treatment in another stage. These all have limitations in terms of costs and/or effectiveness and they are also time consuming to achieve.

[0140] The present invention provides a series of electrodes 10 arranged across the length 12 and width 14 of the matrix 16 in the form of the mixture 3. The electrodes 10 also have a depth 18 within the matrix 16. The electrodes 10 are provided in a regular array in this example, but other configurations can be used. Titanium (with a mixed oxide coating or surface, to avoid any insulating layer) and steel represent preferred materials for the electrodes. The electrodes are typically 5 m to 10 m apart from each other along the width and the length of the regular array. The electrodes will typically extend down at least 50% of the depth of the matrix 16 being treated. The electrodes typically have a diameter in excess of 1 cm. The wiring 20 for the electrodes 10 connects them as a first set 22 of electrodes 10, a second set 24 of electrodes 10, a third set 26 of electrodes 10, a fourth set 28 of electrodes 10 and so on. The potential is applied so as to generate a voltage drop between the first set 22 of electrodes 10 and the second set 24. A voltage drop is also generated between the third set 26 and the fourth set 28. This also generates a voltage drop between the second set 24 and third set 26 and between other sets of electrodes 10. The flexibility of the connections provided by the wiring 20 allows for different combinations of electrodes 10 to be connected to form pairs. Suitable power sources 30 and power control units 32 are provided to generate the desired voltage drops and potentials within the system, and hence voltage pulses. The system is driven with a constant voltage supply, typically from 6V to 25V. Thus the current output level depends upon the circuit resistance. The circuit resistance is affected by the electrical conductivity of the matrix 16, and particularly the fluid contained therein, as well as the number of electrodes provided and the separation between them.

[0141] The profile of the voltages applied and the impact of the applied voltages on the matrix and compounds are described further below.

[0142] During the method, the process conditions are most effective when the pH is within certain bounds. Natural redox reactions and/or reactions caused by the operation of the method can cause a decrease in pH around the anode and/or an increase in pH around the cathode. If the pH becomes too low then electro-osmosis at the anode stops which impairs the operation of the process. If the pH becomes too high then that can have deleterious effects on the process, for instance heavy metal ions may no longer be present in soluble form for removal (the specific pH varies with the specific heavy metal(s) being treated). However, it is believed that the process is still effective at lower pH's than can be tolerated in electro-osmotic based processes where transportation is being sought, as the process is seeking to provide oxidation of organic species.

[0143] To ensure the appropriate pH, the system, as shown in detail in FIG. 1b, may include additional water treatment apparatus 40. The water treatment apparatus 40 receives water from around the electrodes 10. A perforated tube 42 is provided around each electrode 10 so as to provide a reservoir 44 of water in contact with the matrix 16. Pumps 46 draw water from the reservoirs 44 along pipes 48 to the water treatment apparatus 40. The water treatment apparatus 40 includes a pH adjustment stage 50 and a heavy metal ion removal stage 52, for instance ion exchange or the like. Clean pH adjusted water arises from these stages and can be returned via pipes 54 to the reservoirs 44. In this way optimum water conditions are provided within the reservoirs 44 and for the process as a whole.

[0144] Significantly, the power consumption with the approach of the invention is very low. The voltage pulse profile is illustrated in FIG. 2. As can be seen, the voltage pulse profile consists of alternate pulses of opposite polarities with time. The voltage pulses are generally square shaped pulses for both polarities and are of equal duration. Hence, the pulses are used to apply the voltages to the matrix 16 but have no net transport effect on the matrix 16 or more particularly the liquid and compounds within it.

[0145] The square voltage pulse profile features a rapid change from one polarity to the other and then back again. Thus regular square shaped pulses are provided rather than a sinusoidal or other gradual form of changing pulse.

[0146] Whilst the voltage pulse profile is generally square shaped, there are important details in the shape of the current pulse which are sought for the optimum operation of the invention. As shown in FIG. 3a, when the rapid change in polarity is applied, the current profile rises quickly and reaches a maximum level 100. From the maximum level 100 the level gradually declines, for instance along an elliptical curve 102, to a reduced consistent level 104. A short time 106 after the reduced consistent level 104 is reached, the polarity is reversed and the current profile quickly switches to a maximum level, not shown, of the opposing polarity.

[0147] Typical voltage pulse lengths are between 20 and 200 ms. Short rests may be provided to the system between pulses of one polarity and the other. The rests may be 0.5 ms to 50 ms in duration.

[0148] The maximum level 100 is reached as a consequence of the voltage applied causing the matrix, and potentially the liquid, to become charged according to the natural capacitance of the system. This charge is gradually discharged overtime as reflected in the current pulse shape. The maximum level 100 and gradual reduction is indicative of the formation of free radicals within the matrix. These are very beneficial to the overall process, in particular these free radicals are believed to be involved in the oxidation reactions which treat the compounds, such as contaminants.

[0149] Beneficially the free radicals are generated exactly where they are needed for the method to provide the desired treatment, namely at the pore surfaces within the matrix. As a consequence, redox reactions are promoted at those locations too.

[0150] The duration of the pulse is beneficial in generating electro-osmotic forces in a first direction, and then when the polarity is reversed, in the opposite direction for any one species present (depending upon its charge). Thus the charged contents of the pore water move quickly back and forward with the polarity changes. This causes freshly formed oxygen and hydroxyl free radical formed in these electrochemical reactions to move back and forth. This also promotes their involvement in the oxidisation of the compounds present. For instance the free radicals can cause hydrocarbon chains to breakdown into lighter fractions and form carbon dioxide and water as by products. The capacitive nature of the matrix and reactions occur at the grain surface where the pollution is.

[0151] The physical nature of the matrix in many cases, small particulate matter with a moderate or low degree of compaction, means that the electrophoretic forces generated (which generally oppose the direction of electro-osmotic forces) cause small amounts of movement by the particulate material. This is particularly the case for grainy materials and/or particles in slurry or sludge like matrices. The movement is believed to be beneficial in causing reaction product displacement away from the surfaces and/or pH balance.

[0152] The process conditions are optimised to give the desired current pulse profile illustrated in FIG. 3a in one embodiment. The overshoot in the level and the current pulse length which gives the full gradual discharge are desirable.

[0153] FIG. 3b illustrates a situation where the duration before the polarity is reversed is potentially too long. As a consequence, the same maximum level 100 is provided and the same gradual decay to the reduced consistent level 104, but that level is present for a much longer time frame. This reduced consistent level 104 is believed to reduce the efficiency of the process reactions as the free radical generation has stopped or is present at a lower rate during this phase. However, it may assist with the charging for the reversed polarity part and hence with the effects desired from that reverse polarity when it too discharges.

[0154] FIG. 3c illustrates another version of the same current pulse, but with a shorter time period before the polarity is reversed. As a result, the maximum level 100 is present but the reduced consistent level 104 has not been reached by the time the polarity is reversed. As a result it is believe that some of the free radical generating capacity within the system is not exploited and instead energy must be used to reverse the remaining natural part of the capacitance of the system. A detrimental effect on the charging for the reverse polarity part may also occur as a result.

[0155] The power supply conditions needed to provide the current pulse profile of FIG. 3a may vary from matrix to matrix and compound to compound situations. However, investigative measurements can be conducted on the particular system to provide the power supply conditions necessary for the desired profile shape and hence process conditions within the matrix.

[0156] The role of the free radicals generated is to promote oxidisation reactions. Similar oxidising reactions are used in bioremediation and/or chemical treatment, but the method in which they are generated and promoted is different in this process. The conditions in the matrix are optimised in the present invention, thus adding strength of oxidising to any naturally occurring bioremediation and/or chemical treatment.

[0157] Test operations have demonstrated that the process is effective to oxidise a wide variety of organic compounds. Examples include aliphatic organics with C10 to C40, benzene, toluene, ethyl benzene, xylenes, polycyclic aromatic hydrocarbons, chlorinated phenyls, polychlorinated biphenyls and dioxins, as well as PFOS, PFOA.

[0158] Further experimental results from the treatment of a first polluted mixture containing polycyclic aromatic hydrocarbons and taken from an in-situ, real world occurrence of the pollutants are detailed in the table below. Samples were taken from Sampling Point 1 at a location in the mixture which was representative of the mixture's pollutant content, at different times after the commencement of the treatment process. The pollutants are measured in terms of mg/kg of sample.

TABLE-US-00001 Two Three Fourth Sampling point 1 Time 0 Months Months Months Naphatalene 0.073 0 0 0 Acenaphtalene 0.071 0 0 0 Acenaphthylene 0.024 0 0 0 Fluorene 0.066 0 0 0 Phenantrene 0.302 0.035 0 0 Anthracene 0.076 0 0 0 Fluoranthene 0.742 0.094 0 0 Pyrene 0.662 0.102 0 0 Benzo(a)anthracene 0.131 0 0 0 Chrysene 0.471 0.026 0 0 Benzo(b)fluoranthene 0.518 0.049 0 0 Benzo(k)fluoranthene 0.26 0 0 0 Benzo(a)pyrene 0.198 0.036 0 0 Indeno(1,2,3-cd)pyrene 0.192 0 0 0 Dibenz(a,h)anthracene 0.035 0 0 0 Benzo(g,h,i)perylene 0.215 0.02 0 0

[0159] As can be seen from the above results, the treatment process results in material reduction in the extent of a wide range of different organic species present in the mixture at the outset. With three months treatment, each of the organic species is practically eliminated by conversion to carbon dioxide or other low molecular weight organic species.

[0160] Further evidence of the effectiveness of the treatment process is seen in the results obtained from the treatment of a second polluted mixture, this time containing perchloroethylenes and tricholorethylenes. In this large scale sample treatment two sampling points at a material distance from one another were used to evaluate the process over time. The contaminants are expressed as μg/kg of sample.

TABLE-US-00002 Sampling point 1 Mar-15 May-15 Jun-15 Jul-15 Reduction Pentachloroethylene (PCE) 341365 51450 94982  2718 99% Trichloroethylene (TCE)   4079  1803  1152   290 93% Sum of 1,2 dicloroethylenes  35044  4975  8570  2930 92% Sampling point 2 Mar-15 May-15 Jun-15 Jul-15 Pentachloroethylene (PCE)  46320 43879 51643 35128 24% Trichloroethylene (TCE)   2593  2277  2817  1345 48% Sum of 1,2 dicloroethylenes   8777  7048  7790  5562 37%

[0161] Again, a very material improvement through the reduction of the level of organic pollutants present is achieved.

[0162] The following table provides evidence of the increased oxygen content present in a sample treated according to the present invention. This is a third example and again features a variety of pollutant species within it. A series of eight separate sampling points were used for the measurement of the oxygen content; expressed as mg/l.

TABLE-US-00003 Oxygen Content in Ground Water Sampling Day 0 Day 44 Day 73 Day 108 Point Start value From start From start From start SP 1 1.63 3.41 1.74 2.72 SP 2 1.05 0.80 1.63 1.40 SP 3 0.59 1.57 0.62 1.10 SP 4 1.66 — 1.81 — SP 5 0.83 1.53 1.60 1.77 SP 6 2.68 2.70 2.08 2.36 SP 7 2.16 2.57 1.05 1.02 SP 8 1.81 3.04 2.06 2.94

[0163] Whilst readings were not possible from all sampling points at all times, the table clearly shows the immediate increase in the oxygen content and the maintenance of this at enhanced levels over time.

[0164] The oxygen generated is beneficial to the treatment process in a number of ways, including the promotion of conditions suitable for microbes already present, with those microbes having an enhanced bioremediation effect as a result.

[0165] By changing the pulse shape it is possible to cause a net movement of the water through the matrix and/or of soluble heavy metal ions. In this respect, the square pulse approach is retained, but the duration of the pulse of one polarity is made longer than the other such that there is net transportation which is not fully counteracted when the polarity is reversed. Generally the pulse operative in the direction of travel will be between twice and five times the duration of the opposing polarity pulse in such cases. A rest with no or little applied voltage may be used between polarity reversals. Other movement mechanisms can be used to replace or supplement the movement caused by the potential's polarity, for instance the application of pressure to the fluid within the system.

[0166] The process has many beneficial effects upon the matrix and/or upon the compounds within it. These include: [0167] Breaking down one or more compounds present to smaller compounds—these may have reduced toxicity or other undesirable characteristics and/or may be more mobile within the matrix or even soluble; [0168] Reducing the level of contaminants present in the water drawn off the system, other through breakdown those compounds or changing their form; [0169] Changing the surface chemistry of the matrix or species which form the matrix—either in terms of the physical chemistry of the matrix itself or in terms of the ions or other species present at the surface or the charge level of the surface—these can promote better settling of the matrix and/or flocculation of the matrix or other desirable actions—these can result in a large reduction in the volume of the matrix compared with its untreated form—in some test results a volume reduction to 50% or less of the volume observed before treatment started were observed.

[0170] The process can be used to treat a wide variety of matrices including soil, groundwater, aquifers and sludges from industrial processes, sewage, contaminated land or soil or material, including when excavated and removed to a treatment site or dumping site.

[0171] FIG. 4 illustrates an embodiment of the invention similar to the embodiment in FIG. 1, but deployed on a larger scale matrix 200 and only in respect of a part 202 of that matrix. In this case, the matrix and the compounds are less susceptible to the negative effects of pH variation and so those aspects of the process relating to the control of pH have been omitted. Otherwise, similar elements are given matching reference numerals to those in FIG. 1 and the accompanying description.

[0172] Other scenario where the invention can be deployed include high liquid content and low matrix content systems such as lakes, ponds or the sediments within them.

[0173] FIG. 5 illustrates a further embodiment of the invention in which the vertically arranged electrodes 100 are provided in a similar regular array 118 to the FIG. 1 embodiment. In this cases, however, a series of horizontally extending electrodes 150 are provided. These are connected to the same wiring system. They can be used to form pairs of electrodes amongst themselves and/or be combined with vertically provided electrodes. These electrodes are provided at a depth d below the surface s of the volume of material. These electrodes can be driven into the matrix, placed in drilled holes or inserted in other ways. For instance, the generally horizontal electrodes may be allowed to settle into the material to reach the desired location. The generally horizontal electrodes may be rods or wires or cables, ideally devoid of insulating material. They are used in a similar manner to the vertical electrode operation described above. The combination of electrode arrangements is used to increase the volume of material being treated or in closer proximity to an electrode. The combined use of generally vertical and generally horizontal electrodes is preferred.

[0174] FIG. 6 illustrates the variation observed in a number of characteristics of a mixture when treated according to the method of the present invention over an extended time (in hours) on the x axis.

[0175] At the start of the method, the heavier hydrocarbons (black line) are present at a concentration of over 200,000 mg/kg of the mixture. As the method is performed, the method serves to breakdown the heavier hydrocarbons to lighter forms and so the concentration declines. The method reduces the concentration to around ¼ of its original value.

[0176] At the start of the method, the lighter hydrocarbons (red line) formed a relatively small part of the mixture and hence the concentration is low at less than 20,000 mg/kg of mixture. As the process converts the heavier hydrocarbons to lighter hydrocarbons, then this concentration increases. The method increases the concentration to around 10 times its original value.

[0177] FIG. 7 illustrates an embodiment of the invention similar to the embodiment in FIG. 1, in many respects, but deployed in a completely different situation. In this instance, the hydrocarbons 3 are contained within an emulsion layer 200 present with an appreciable depth 202 on the top of a volume of water 204 in a lake 206 or man-made liquid retaining structure (not shown). These situations are common in Venezuela with nature and man-made occurrences.

[0178] As shown, the electrodes 200 are provided in an array 202 supported by floats 204 which are buoyant on the lake 206 and preferably on top of the emulsion layer 200. The electrodes 200 are connected together in sets in the manner described above and the voltage pulse profiles and current pulse profiles described are employed.

[0179] The emulsion is formed to a significant degree of asphaltenes and various resins. The oxidation provided by the process of the present invention breaks those species down and so results in the breakdown of the emulsion too, as the resulting species do not or are less capable of forming emulsions. The process results in the release of the oil held up previously in the emulsion and the settling of that oil into layers. The lighter API fraction will form an oil layer on top of the water and any heavier oil layer present will form a layer below the water layer. The layers which form due to gravity settling can then be removed by pumping. The distinct layer of water which forms can also be pumped off, for further treatment or subjected to that further treatment in-situ. The result is the generation of useful oil products with commercial value and the treatment of an otherwise undesirable location from an environmental point of view.

[0180] FIG. 8a illustrates a preferred current pulse profile for some methods. Each cycle includes a positive polarity triggered current part 500 and a negative polarity triggered reverse current part 502. The current part 500 is formed of a first section 504, second section 506, fourth section 508 and third section 510 which occur in that sequence. Matching but reversed sections are provided for reverse current part 502, such that it has a first reversed part 512, second reversed part 514, fourth reversed part 516 and third reversed part 518. The next positive current part would then be present as the cycle is repeated over and over by the application of an appropriate voltage pulse profile (not shown).

[0181] FIG. 8b shows the peak part of the pulse in more detail. The first section 504 shows the current increasing quickly as it is encouraged by the change in the voltage pulse profile. As a result the voltage induced current and the current caused by the discharge of the capacitance built up during the previous reversed current part (not shown) occurs. These two current elements rapidly cause the peak current 520 to be reached.