AU595294B2

AU595294B2 - Process formetabolism and/or growth increasing treatment of micro-organisms

Info

Publication number: AU595294B2
Application number: AU69629/87A
Authority: AU
Inventors: Heinz Doevenspeck
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-10-26
Filing date: 1987-03-03
Publication date: 1990-03-29
Anticipated expiration: 2007-03-03
Also published as: DE3538194A1; DE3683259D1; AU6962987A; EP0223110B1; EP0223110A1; ATE71143T1

Abstract

The method entails the microorganisms being exposed to electric fields whose field strength is pulsatile and whose peak does not exceed 3.5 kV/cm.

Description

Form COMMONWEALTH OF AUSTRALIA PATENTS ACT 1962469 COMPLETE SPEC IFICATION

(ORIGINAL)

Class Application Number: 69629/87 Lodged: 03.03.1987 Int. Clasn 595294 Complete Specification Lodged: Accepted: Published: Priority: Related Art: This documen t ti aains the arendm,'m 110d uO~ SC!'2iom 49 kmid :s ccrcct fcf priritinrg.

Name of Applicant: HEINZ DOEVENSPECK Address of Applicant: Sigurdstr. 1, D-4950 Minden, West Germany.

Actual Inventor: HEINZ DOEVENSPECK Address for Service EDWD. WATERS SONS, 50 QUEEN STREET, MELBOURNE, AUSTRALIA, 3000.

Complete Specif ication for the invention entitled: PROCESS FORMETABOLISM AND/OR GROWTH INCREASING TREATMENT OF

MICRO-ORGANISMS

The following statement is a full description of this invention, including the best method of performing it known to us us 3 i 2 The invention concerns a process for metabolism and/or growth increasing treatment of micro-organisms.

It is well known that electric fields have an effect on micro-organisms (bacteria, fungi). Specifically, when bacteria are subjected to electric fields whose patterns over time can be described as pulse shaped, it has been shown that field intensities of 6-20 kV/cm have an especially marked lethal effect on the bacteria (see for example Hulsheger et al: Radiation and Environmental ".T:I0O Biophysics (1981) 20: 53-65 and loc. cit. (1980) 9't 18:281-288).

In many cases, however, it is not desired to kill the micro-organisms, but on the contrary actually to cultivate them. For example, if one wishes to clarify sewage by ^means of microbial processes -it is specifically a matter of cultivating the micro-organisms which metabolize the substances to be broken down. To achieve this it is a well known procedure to add certain substances to sewage t in order, for example, to make available nitrifying bacteria which are required for the metabolism of the sewage. Furthermore, the procedures are carried out as far as possible at temperatures at which the micro-organisms have the highest possible metabolism and multiplication rates. However, in many cases this is not sufficient to keep the desired process in operation in an economically efficient manner.

Proceeding on the basis of the above state of the art, the objective of the present invention is to demonstrate a f 3 process for the metabolism and/or growth increasing treatment of micro-organisms which is inexpensive, simple and effective to carry out.

This objective is achieved according to the invention by subjecting the micro-organisms to electric fields whose field intensity follows a pulse-shaped pattern and does not exceed 3.5 kV/cm. Surprisingly, it has been found CZrt jj that in contrast to the use of high field intensities, the U t use of low field intensities is associated with an i~t 10 10 increase in the growth of the micro-organisms. This increase in growth can be shown particularly in terms of their metabolic rates.

It is particularly advantageous to carry out the process when one increases the field intensity to the lj 15 15 maximum within 1 ms at the most, and allows it to diminish exponentially. This pulse shape, if a charged capacitor is connected via a switch to a load resistance via which the capacitor then discharges, has proved to be particularly effective.

It is advantageous to have the field intensity increase to the maximum value within 100 ms, preferably within 50 ms. It is also relevant that the increase (within certain limits) should proceed as steeply as possible. The decrease (following an e function) is advantageously allowed to take place within 10-100 ms.

The process is particularly effective where the field intensity is restricted in its maximum value to up to 0.1 1 kV/cm, but particularly to 0.2 0.5 kV/cm.

4 i Furthermore, it is especially advantageous if the field intensity direction alternates in relation to the direction of flow of the liquid to be treated. This is indicated particularly in the context of large systems witi several electrode groups connected in series, where to change the direction of field intensity several sets of electrodes are connected in series. Alternatively the change of the field intensity direction can also take place by means of the pole reversal of the (pulse) generator, so that the successive pulses have different field intensity directions. This is indicated particularly for small systems.

Alternatively the field intensity direction can be kept constant, i.e. one can operate with direct current pulses. Because the discharges are solely pulse-shaped, the electrolysis effect in this context can essentially be disregarded. Thermal effects, because of the small amount of energy conveyed into the liquid, can also essentially be disregarded In a preferred embodiment of the process the electric pulses are applied at repetition rates which are low in comparison with the pulse durations. That is to say, one has pauses between individual electric pulses. It is particularly advantageous in this context to have repetition rates of between 5 and 15 Hz.

It is advantageous that the electric pulses be applied only in pulse groups, hence not in a continuous pulse train, and that pauses be made between such pulse groups.

i i 111~1~~1~ 5 Surprisingly, it has actually proved to be the case that such pauses do not in fact lead to any decrease in the effect of the electric pulses, but rather to an increase in the effect. It is advantageous to select pulse groups and pause intervals between the pulse groups as shorter than 30 min in each case, and preferably shorter than S min.

An especially preferred application for the procedure t.

2 is the microbial generation of methane gas or biogas (manure gas), or the treatment of sewage in anaerobically operated reactions. Along with the abovementioned growth increasing or metabolism enhancing effects of the electric pulses, it has surprisingly proved to be the case that when one operates according to the process pursuant to the invention the production of volatile sulphur compounds is ct i 2' drastically reduced. Indeed, generally normal biogas contains a considerable proportion of hydrogen sulphide or other volatile sulphur compounds, which first have to be removed from the gas before the further use of the gas, e.g. in gas engines, is possible. When the process according to the invention is applied to the production of biogas such sulphur compounds are only detectable when they can be detected at all in drastically reduced concentration levels in the gas produced, so that the gas can be produced not only in increased quantities (due to the use of the process according to the invention), but also in a significantly more easily used quality, i.e. in a better quality than was previously the case. Even in -~eQ~DL-~ 6 4 instances where the process according to the invention runs other than with its optimal parameters (pulse amplitude, pulse duration, pulse frequency, etc), there is istill a significant improvement in the production of biogas as regards efficiency as a result of the use of the Sprocedure, since the said harmful substances only occur in the gas in reduced quantities.

A further significant possibility for the use of the process according to the invention is the microbiological production of enzymes or other non-gaseous products.

Appropriate for the implementation of the procedure is a device with at least one reactor with inlet and outlet I line, this device having at least one pair of capacitor electrodes which are arranged in such a manner that at least some of the contents of the reactor are located at 4 least temporarily between the electrodes. These electrode plates are connected with a pulse generator circuit for supply with an electrical voltage. In this context is is possible to arrange the electrodes in the reactor enclosure in such a way that the entire contents of the reactor are always between the plates. Preferably, however, the electrodes are arranged in an enclosure which is separate in terms of flow in such a way that flow connection exists between the space between the electrodes and the inside of the reactor via ducting means. The contents of the reactor are hence passed through the space between the electrodes, so that only a fraction of the reactor contents are constantly between the plates.

-7- The main portion of the reactor volume is therefore essentially field-free, although naturally spreadage of the fields generated between the electrode plates into the inside of the reactor is possible (or probable), both via the fluid connection between the electrodes and the inside of the reactor and via the electromagnetic connection.

{ICirculation in such systems may be created by appropriate arrangement of the ducts (inlet and outlet) between the reactor and the electrode enclosure, but it is preferable that a circulating pump be placed in one of the ducts.

In one advantageous example of the embodiment of the device according to the invention several electrodes are arranged in series (in terms of flow), so that the liquid (with micro-organisms) drawn through the area travels across a longer space between the electrodes, and hence spends a longer time between the electrodes. With such an arrangement the electrodes may be connected in parallel, so as to generate the same voltage patterns between all electrcn pairs, but may also be connected in series if different voltage patterns are to be generated between the electrode pairs.

It is advantageous to have the electrodes arranged in the enclosure so as to form a labyrinth, through which the Sliquid flows. In this way one obtains a particularly compact enclosure which nonetheless ensures a longer duration of the treatment of the liquid passed through the area.

8 Sin a further preferred embodiment of the invention the electrodes are arranged coaxially to one another. This embodiment leads to a compact enclosure with particularly good flow conditions which only has a small number of static zones (in flow terms) at which solids could build up.

In another preferred embodiment of the invention the I electrodes have gaps in them and are so arranged in the enclosure with respect to one another that the liquid flows through them essentially perpendicularly to their surface. With an appropriate arrangement of the apertures j in the enclosure it is possible in this case also to create a flow pattern which is essentially free of static zones or surfaces on which material might accumulate.

ii 15 It is advantageous to have the feed into and discharge from the reactor pass via a common electrode passage.

This is particularly the case where the temperature of the reactor contents is different from the temperature of the liquid conveyed to it. Indeed where this is the case it promotes the metabolism of the m~crobes if the newly conveyed substrate is pre-heated essentially to the reactor temperature so that the micro-organisms do not suffer any temperature shock. Where one wishes for example, to keep thermophilic microbes in the reactor, i.e. microbes which operate in temperature ranges up to or 80 0 C (with high metabolic rates), it is particularly advantageous if an electrode passage is introduced between the inlet and the outlet line.

9 It is further of great advantage if degerminating devices are incorporated in the inlet and the outlet line. A degerminating devices in the feed has the effect that the contents of the reactor can be "injected" only with those micro-organisms which one actually wishes to have in the reactor, while alien micro-organisms conveyed by the sewage are killed. As regards the micro-organisms J which pass from the outlet line into other plant A t downstream, it is also advantageous to keep these away from the downstream plant.

In a particularly preferred embodiment of the device according to the invention the degerminating device is incorporated in the electrode passage: the electrode passage here consists similar to the device for increasing growth of capacitor plates which are S connected to a pulse generating device. In this case, however, the pulses were such a strong selection (as regards their maximum field intensity) that the lethal effect mentioned at the beginning of this document occurs.

In a preferred embodiment of the invention the generator circuit has a power unit and at least one storage capacitor, along with at least one reversing switch which is connected in circuit with the power unit and storage capacitor and with the electrodes, in such a manner that in a first switch position the storage capacitor is charged by the power unit and in a second switch position it is discharged via the electrodes. This relatively simple circuit is however very effective, since the pulses

I

i 10 are conveyed to the micro-organisms in the optimal form.

Admittedly, one can operate the reversing switch mechanically, but it is particularly advantageous if one has this reversing switch operated electrically. Examples of such a reversing switch would be ignitrons, thyristors, transistors etc. These electrically operated switches are advantageously connected with a control oscillator. The oevice is particularly simple where the reversing switch SIconsists of two on/off switch elements, with the first switch element arranged between the storage capacitor and the power unit, and the second switch element arranged between the capacitor and electrodes; the device is operated in such a manner that initially the second switch (connection between storage capacitor and electrodes) is disconnected, whereas the first switch element is t t.t connected, so that the capacitor is charged by the power unit. As soon as the capacitor is charged the first switch is opened so that the capacitor is now left "hanging in the air". The second switch is then closed, 20 20 thus connecting the capacitor to the electrodes. In this way one obtains precisely defined on and off switching patterns.

It is advantageous if the control oscillator has a pulse generator whose output pulses can be periodically blocked by control means of a generator. The output pulses of the pulse generator give rise to the switching process between charging and discharging of the storage capacitor; during the time for which the output pulses from the pulse generator are blocked from the (further) U I i 11 generator the capacitor plates are no longer connected to the capacitor.

Other preferred embodiments of the invention can be seen from the embodiment examples described below, which will be explained in more detail with reference to the Figures. These show the following: Fig. I a theoretical arrangement for the implementation of the process according to S the invei.tion; o 10 Fig. 2 a first preferred embodiment of the electrode device in longitudinal section; ot t SFig. 3 the electrode device according to Fig. 2 with two sets of electrodes; Fig. 4 a second preferred embodiment of the electrode device in longitudinal section; j Fig. 5 a third preferred form of embodiment of the electrode device in longitudinal section; Fig. 6 the electrode device according to Fig. with bipolar electrodes; Fig. 7 a preferred embodiment of an electrode j passage in longitudinal section; Fig. 8 the electrode passage according to Fig. 7 with two sets of electrodes in series; Fig. 9 a first (theoretical) circuit for the 25 implementation of the process according to the invention; and Fig. 10 a second diagrammatical representation which essentially shows the functions seen in Fig.

6.

12 As can be seen from Fig. 1, the reactor 10 has a reactor enclosure for the implementation of the process according to the invention; in this enclosure there is (in customary fashion) an agitator 11. There are also heating means 14 connected with the inside of the reactor, which can for example be fed from a gas burner running on biogas, the biogas being taken from the inside of the reactor out of a gas outlet line 16 from the reactor The reactor 10 has an inlet line 12 (with valve) and an outlet line 13. Inlet and outlet lines 12/13 are led in counter-current through a heat exchanger The reactor 10 also has on its floor a circulation draining line 17 which leads into the suction inlet of a circulation pump 15. The pressure outlet of the circulation pump 15 leads into the inlet of an electrode ,device 20, described in more detail below. The outlet of the electrode device 20 is connected via a circulation return line 18 with the top cover of the reactor 10. In this way it is ensured, when the agitator 11 and the 20 circulation pump 15 are operating, that the contents of the reactor are conveyed in a regular manner (over time) through the electrode device Fig. 2 shows a preferred embodiment of the electrode device 20. In the figure the enclosure 21 of the electrode device 20 is made of a conductive material. In the enclosure 21 there are, horizontally arranged, two insulating electrode supports 24 with gaps 25. In the electrode supports 24 are held a central electrode 232 and -13a medial electrode 221; the gaps 25 are arranged in such a way that they connect the spaces between the outside wall of the enclosure 21 and the medial electrode 221 and between the medial electrode 221 and the central electrode 232 with the circulation draining line 17 and the circulation return line 18 of the device 20. In terms of the flow the two coaxial spaces are in this arrangement in parallel connection, while from the electrical point of view there are two electrodes connected in parallel, since the central electrode 232 is electrically connected with the enclosure 21 which is formed by the distal electrode 231, while the electrode 221 forms the counter-electrode for both the electrodes formed in this way. This pair of electrodes is connected with a generator 40, which is described in more detail below.

Fig. 3 shows an electrode device 20 with two sets of electrodes in series. In this arrangement one (upper) set t t of electrodes is formed by the positive electrodes 231 and 232 and a negative electrode 221. The (lower) set of electrodes consists of a positive electrode 233 and two negative electrodes, namely electrodes 222 and 223. Both r sets of electrodes are connected with a common generator If required it is also possible to have a separate generator 40 provided for each of the sets of electrodes.

The end walls of the electrodes 221, 231 and 232 and of electrodes 222, 223 and 233 which face towards one another are in this case connected by a further insulating electrode support 49. From the electrical t i 14 point of view this support divides the electrode device into two completely separate halves. In the electrode device 20 in Fig. 3 the coaxial spaces are hence interconnected both in series and in parallel, while in electrical terms there are both two parallel connected and series connected electrodes. Due to the opposite polarity of the electrode groups in series, two field intensity directions are created in the electrode device 20 of Fig.

3, which act in succession on the liquid (with bacteria) to be treated.

In the embodiment of the invention shown in Fig. 4 the electrodes 221 223 and 231 233 have gaps 25 and are placed transverse to the direction of flow in the enclosure 21. In contrast, in electrical terms the electrodes are connected in parallel and are connected with a generator In the case of the device shown in Fig. 5, again in longitudinal section, the electrodes 221 223 and 231 233 are also connected in parallel, while in terms of flow they are arranged in series in the form of a labyrinth in the enclosure 21, through which, via insulating elements 24, they are supported or passed. This circuit arrangement leads, in the same way as shown in Fig. 4, to a longer duration of flow through an inter-electrode space.

Fig. 6 shows the electrode device 20 according to Fig.

but with grouped electrodes. Disregarding the upper and lower electrodes 221 and 235 respectively, the remaining electrodes are built up as double electrodes 231, 222; 232, 223; 233, 244; 234, 225. They are :K ,ii.uaiIg me Desi memoa of performing it known to us .i 1 h 1~ .:x ~1 i I 15 ft., 9 *4 9 f ft t 'ti.

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Ir I It

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I #1 L I I II: t C insulated from each other by non conductive materials not shown in Fig. 6.

However, here again all the electrodes are fed from a common generator 40. The circuit connection of the electrodes is in this case carried out in such a way that electrodes of opposite polarity restrict the flow path of the liquid through the electrode device 20. This means that in each labyrinth section the field intensity acts on the bacteria-enriched liquid from a different direction.

10 Fig. 7 shows a preferred embodiment of the electrode passage 30. The electrode passage here has a two-fold function: i.e. it is at the same time a heat exchanger and a degermination device. At opposite ends of the electrode passage 30 there are two intakes 31/33 and, also 15 at opposite ends, two outlets 32/34. The electrode passage 30 has an outer casing 35, an intermediate casing 36 and a central electrode 37. The intermediate casing 36 is situated between an inner space, which is closed off in terms of flow, and the outer space, also closed off in terms of flow. The throughflow occurs in countercurrent via the intermediate casing 36., The inner electrode 37 and the outer casing 35 are electrically connected, and the intermediate casing 36 forms the second electrode for both electrodes. This electrode pair is connected with a sterilizer-pulse generator 38, which conveys pulses of high field intensity onto the plates.

Fig. 8 shows an extension of the electrode passage shown in Fig 7; here, however, there are two sets of 16 electrodes arranged in series. The individual sets of electrodes are delimited by the insulating means 50, shown diagrammatically only in Fig. 8, through which in electrode passage 30 there are in each instance two electrodes, 35,36 or 37 arranged in series. Here the electrodes arranged in series are in each case of different polarity. In the embodiment example of Fig. 8 in the left half of the electrode passage 30 the electrodes 35 and 37 are poled positive, while the electrode 36 is poled negative. In contrast, in the right half of the electrode passage 30 the electrodes 35 and 37 are poled negative, whereas the electrode 36 placed between them is in this case poled positive.

In the above embodiment example each set of electrodes has a separate sterilizer-pulse generator 38. As an alternative it is however also possible to have both sets of electrodes supplied by a common sterilizer-pulse generator 38.

The electrical circuit of the pulse generator required for the implementation of the process according to the invention will now be described in more detail. This pulse generator has a pow unit 42 which in customary fashion consists of a mains switch, a transformer, a rectifier and a downstream filter capacitor. The power unit 42 is connected with one pole of a reversing switch 43, which can be switched via a control generator 41. The other pole of the reversing switch 43 is connected with an electrode 23. The middle pole of the reversing switch 43 _i ji 17 t 5 1 tr we~r *4* *l 4 s1* e is connected with one pole of a charging capacitor 44, whose other pole is selectively connected via a second reversing switch with the power unit 42 and the second capacitor plate 22.

When the reversing switch 43 is operated, the capacitor 44 is connected in initial position with the power unit 42, during switching-over it is divided from the power unit 42, and on completion of switching-over it is connected with the electrodes 22/23. There is hence a pause between the two phases, so that the electrodes 22/23 are not connected with the power unit 42.

In the embodiment of the invention shown in Fig. the switch 43 consists of a (single pole) reversing switch made up of two thyristors. The first thyristor Tyl is 15 connected between the power unit 42 and the storage capacitor 44, and the second thyristor (poled in the same direction) between the storage capacitor 44 and one electrode, 23. The other electrode 22 is directly connected with the other end of the storage capacitor 44 and the power unit 42. The control circuit of the first thyristor Tyl is connected via a time-lag element 45 with the control circuit of the second thyristor Ty 2 This connection point is on the pole of a (switching) field effect transistor 46, whose other pole is on the output of a pulse generator 48. The gate of the field effect transistor 46 is on the output of a further generator 47.

This arrangement makes up the drive pulse generator 41.

If pulse generator 48 feeds a pulse to its output and the ii i I~ i :ii i i-i- ;I 18 output of the other generator 47 is at this time on high level, then the field effect transistor 46 is conductive and the second thyristor Ty 2 is turned on. When this happens the charge stored in the capacitor 44 is discharged via the plates 22/23 and the electrolytes located between these plates (contents of the reactor).

As soon as the capacitor 44 has discharged the current flow through the thyristor Ty 2 stops, and the thyristor 10 hence shuts down automatically. The time constant of the *time-lag element 45 is selected such that now- after 4 *4 discharge of capacitor 44 via the electrodes 22/23 the first thyristor TyI is turned on. After activation of this first thyristor Ty I the capacitor 44 is now charged via the power unit 42. As soon as the capacitor 44 is charged, the current flow through the first thyristor Ty l ceases, the thyristor shuts down automatically, and the cycle can begin afresh.

The electrical circuit shown in Figs. 9 and 10 for the implementation of the process according to the invention can where appropriate be modified in such a way that the circuit has a periodically operating reversing switch facility, not shown, which the electrodes 22 and 23 can be alternately commutated to obtain a periodic reversal of the direction of the electric field. With such a pulse generator, given the electrode device 20 of Figs. 2 and and the electrode passage 30 of Fig. 7, alternately differently directed electric fields can be produced, without it being necessary to arrange several sets of 19 electrodes in series, as shown in figs. 3, 6 and 8, for example. This also makes it possible to obtain, in very simple fashion, field reversal in smaller, more compact plants U~ Ut U U U

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Claims

1. Process for metabolism and/or growth increasing treatment of micro-organisms, characterized in that the micro-organisms are subjected to electric fields whose field intensity follows a pulse-shaped pattern (electrical pulses) and does not exceed 3.5 kV/cm.

2. Process according to claim 1, characterized in h that the field intensity is increased within a maximum of i ms, preferably within 10 Vs, to the maximum value and is allowed to diminish exponentially, particularly within to 100 Ps.

3. Process according to one of the preceding claims, characterized in that the field intensity is allowed to increase to 0.1 1 kV/cm, preferably to 0.2 0.5 kV/cm.

4. Process according to one of the preceding claims, characterized in that the field intensity direction in relation to the direction of the flow of the liquid (with bacteria) to be treated is alternated. Process according to one of the preceding claims, characterized in that the electrical pulses are applied with repetition rates which are low in comparison with the pulse duration, particularly between 5 and 15 Hz.

6. Process according to one of the preceding claims, characterized in that the electrical pulses are applied in groups with pauses between them, with the pulse groups and pause intervals each being shorter than 30 min, preferably shorter than 15 min. SA 1. I 1* 21

7. Application of the process according to one or several of claims 1 to 6 to the microbial production of gaseous products, as for example biogas (methane).

8. Application of the process according to one or several' of claims 1 to 6 to the microbiological production of solid and/or liquid products, as for example enzymes.

9. Device for the implementation of the process according to one of the preceding claims, with at least one reactor with inlet and outlet ducting, characterized by at least one pair of electrodes which are so arranged that at least part of the contents of the reactor are at least temporarily between the electrodes and by a pulse generator circuit for supplying the electrodes with electrical voltage. Device according to claim 9, characterized in that the electrodes are arranged in an enclosure which is separate in terms of flow and in that the space between the electrodes is in flow connection with the inside of the reactor via ducts with a circulation pump preferably being arranged in one of the ducts.

11. Device according to claim 9 or 10, characterized in that several electrodes are connected in series in terms of flow.

12. Device according to one of claims 9 11, characterized in that the electrodes are arranged in the enclosure in labyrinth fashion.

13. Device according to one of claims 9 12, characterized in that the electrodes are arranged -22- coaxially with respect to each other.

14. Device according to one of claims 9 13, characterized in that the electrodes have gaps and are so arranged in the enclosure that they are flowed through essentially perpendicularly to their surfaces. Device according to one of claims 9 14, characterized in that the inlet and outlet ducts lead via a common electrode passage and/or a degerminating device.

16. Device according to claim 15, characterized in that the electrode passage has at least one pair of electrodes which are arranged in such a way as to allow flow through the spaces between the electrodes and in that the electrodes are connected with a further pulse generating generator circuit whose pulse output voltage increases steeply, but di'ninishes exponentially, and has a peak amplitude of more than 3.5 kV/cm.

17. Device according to one of claims 9 16, characterized in that the generator circuit comprises a power unit and at least one preferably electrically operable storage capacitor and at least one reversing switch which is connected in circuit with the power unit and the storage capacitor, and with the electrodes, in such a way that in a first switch position the storage capacitor is charged by the power unit and in a second switch position it is discharged via the electrodes.

18. Device according to claim 17, characterized in that the reversing switch is in controlled connection with a control oscillator whose output pulses are controllable V -23- periodically, preferably via control means of a generator.

19. Device according to one of claims 17 or 18, characterized in that the reversing switch has at least two on/off switching elements with the first switching element arranged between the storage capacitor and the power unit and the second switching element between the storage capacitor and the electrodes. Apparatus for metabolism and/or growth increasing treatment of micro-organisms substantially as herein described with reference to any one of the embodiments of the invention and with reference to the accompanying drawings.

421. A process for the metabolism and/or growth t increasing treatment of micro-organisms substantially as 441' horein described with reference to any one of the embodiments of the invention and with reference to the accompanying drawings.. VI 22. Micro-organisms when treated by the process, device or apparatus of any one of the preceding claims. DATED THIS 3rd day of March, 1987 HEINZ DOEVENSPECK certify that tjis 4 nd psg~1A es are a trxa EDWD. WATERS SONS, and e aclcopyPATENT ATTORNEYS, and-a etheC~~o 50 QUEEN STREET, Specificaition Orqigiaiv Wqe MELBOURNE. VIC. 3000.