WO1987001690A1

WO1987001690A1 - Method and device for the oxygen enrichment of waters

Info

Publication number: WO1987001690A1
Application number: PCT/AT1986/000056
Authority: WO
Inventors: Hans Oppitz
Original assignee: Eltac Nogler & Daum Kg
Priority date: 1985-09-20
Filing date: 1986-09-16
Publication date: 1987-03-26
Also published as: DE3690472D2; AU6372486A; EP0238511A1

Abstract

A method and device for the enrichment of the water (1) in standing water basins or water streams with oxygen, in which the oxygen is introduced into the waters (1) from their bottom. A current flow is generated through the waters, which act as an electrolyte, between the anode and cathode zones of an electrode (15) arranged over a large surface of the bottom of the waters.

Description

Method and device for enriching water with oxygen

The invention relates to a method for enriching water in standing or flowing water with oxygen, in which the oxygen is supplied to the water in the bottom area, and a device for carrying out the method.

Various methods for the remediation of eutrophied lakes are already known. Eutrophication of a body of water means the natural or artificial, e.g. nutrient enrichment caused by human influences such as fertilization, concentrated fattening cattle, detergents. A key factor for the trophy of a body of water (lake) is the nutrient phosphorus. Under natural conditions, inorganic phosphorus compounds occur only in small amounts, often only in trace amounts, in a body of water. Phosphorus as an essential plant nutrient for primary producers is therefore usually a minimum factor, i.e. the amount of phosphorus in a body of water determines the intensity of primary production. This means that the increase in phosphates leads to water reutrophication. Since there are usually enough nitrogen compounds in this situation, primary production often increases to a considerable extent. To put it simply, primary production means the build-up of organic matter, e.g. Carbohydrates from inorganic substances under the influence of light and in the presence of the green color chlorophyll. This can be shown in a schematic photosynthesis equation as follows:

6C0 ₂ + 12H ₂ 0 + light energy ^C 6 ^H 12 ° 6 ^{+ 6H} 2 ° ^{+ 60} 2

From this it can be seen that the plant builds organic substances from the inorganic substances carbon dioxide and water. For the metabolic processes following the assimilation now require the plant nutrients such as nitrogen compounds, potassium, calcium, phosphorus and other trace elements.

Plants floating in the water, especially phytoplankton, usually also referred to as algae, provide the necessary energy for heterotrophic living beings as primary producers. The heterotrophic organisms are those that feed on existing organic matter.

Primary producers as autotrophic beings and heterotrophs form food chains in the ecosystem which are networked with one another via multiple cross-connections. The bottom of these food chains includes people with fishing, water birds, water use and the like.

Another process is crucial for an ecosystem, namely the degradation of organic matter. This is called breathing or better dissimilation and is used to generate energy for metabolic processes, whereby it should not be overlooked that not only animals but also plants breathe.

The dissimilation process can be interpreted as a reversal of the assimilation and can be represented schematically as follows:

^C 6 ^H 12 ° 6 ⁺ 60, - * 6C0 ₂ + 6H ₂ 0 + energy

This equation also shows the close connection between building-up - assimilatory - and dismantling - dissimilatory - processes. The role of bacteria was not taken into account in this schematic representation of the lake ecosystem. They play a major role in the reprocessing of dead organic matter. Bacteria are thus significantly involved in the renewed availability of nutrients and trace elements. If one considers the minimum factor phosphorus in this connection, it can be seen that the phosphate is adsorbed on Sede particles under the presence of oxygen, ie aerobic conditions, or is precipitated as iron phosphate (FePO.). EisendII) phosphat is insoluble as long as the redox potential is greater than 0.2 volts. As long as in the water layers above the sediment

If oxygen is contained, the uppermost sediment layers act as a barrier. Already at less than 3 mg 0 ₂ l

Release of phosphate from the sediment. This release can result in

3 "^' oligotrophic lakes up to 0.5 mg P0 ^ / l. When the lake is fully circulated under aerobic conditions, some of the phosphate is returned to the ground as FePO.

With complete loss of oxygen in the eutrophic lake (during stagnation), Fe is reduced to Fe. The result is that Fe goes into solution with the phosphate. In shallow water, for example ponds, considerable amounts of iron and phosphate reach the trophogenic zone, namely the epilimnion. In eutrophic lakes, this amount can be up to 12mg PO. / l. This phenomenon is one of the reasons for the high trophy level in shallow lakes. Under these conditions, phosphorus is no longer a limiting factor. As a result, the algae population multiplies many times up to "water bloom". A critical condition has been reached. Due to the strong turbidity of the ^" water through the algae, the penetration depth of the light decreases. They only colonize the uppermost water layers. The darkness (night) causes the oxygen content to drop sharply. If the nutrient supply continues, algae growth is limited to a" thin "water layer Layers underneath show drastically decreasing oxygen contents or oxygen-free areas down to the bottom of the water, aerobic bacteria, eg nitrificants, die, replaced by anaerobic forms, ie heterotrophic bacteria and forms that gain chemosynthetic energy become active “Putrefaction processes” enrich methane and hydrogen sulfide, both of which are toxic substances, and as the situation worsens, it often shifts also the PH range. If the pH value increasingly increases in the alkaline environment, then there is not ammorium, but the toxic ammonia in the solution, so that fish die. Due to the enormous algae biomass, full circulation is made difficult or even impossible. The state of the water continues to deteriorate, primarily due to the biological, chemical and physical gradients. The anaerobic area is increasing.

Apart from the necessary reduction of pollution, in particular through phosphates, various methods have been proposed for the restoration of a eutrophic lake.

By mechanically removing the anaerobic microorganisms and the organic substances bound in the sediment, an attempt is made to create aerobic conditions under natural conditions (when full circulation occurs).

One of the most radical measures is dredging the sediment _* Another possibility is to cover the sediment with plastic foils, sand or other materials. Since these processes are very complex and cost-intensive, attempts have now been made to improve the oxygen conditions in the hypolimnion by means of deep water drainage. The hydrostatic pressure was made use of by a so-called

Olzewski pipe is used, which begins at the deepest point of the lake and leads to the drain. In this way, deep water is no longer drained from the lake, but deep water.

It has also been proposed to aerate the hypolimnion so that the sediment oxidizes. The procedure was such that the deep water was pumped to the surfaces by means of a riser pipe, where it was oxidized with air in large containers and then led back into the hypolimnion using downpipes. This method has proven itself in preventing contamination with hydrogen sulfide in lakes from which drinking water can be obtained wanted to.

Another method is to force the lake into circulation so that the water is circulated. The procedure here is such that compressed air is blown in through a pipe leading to the lake bottom in order to supply oxygen to these layers. As a result of the overpressure, the rising air causes heavy deep water to be torn up and then to sink again. In the course of this circulation process, it is possible to add oxygen to the epilimnion and metalimnion. This procedure is simple and cheap in itself, but the effects are unpredictable. The forced circulation also distributes the nutrient quantity of the hypolimnion evenly over the entire water column, which is a heavy fertilization.

In addition to increased algae production and the associated side effects, this causes the various water layers to swirl and the temperature in the deep water areas to rise. However, this should be prevented, since the efforts are aimed at preventing large algal populations and maintaining the natural stratification of the water.

Such methods are described, for example, in an article by Dr. Hamm and Dr. Kucklentz "Opportunities and Chances of Success for Lake Restoration, Munich, December 1980, Ed .: Bavarian State Ministry for Regional Development and Environmental Issues" as well as in an article by Jorgensen S.E. "Lake Management, Pergamon, Press. Oxford, New York".

Another known method for water purification or improvement - according to US Pat. No. 4,039,439 - is to improve the oxygen content of the water by adding hydrogen bubbles of a defined size in a separate size above the bottom of the

Water installed electrolysis pump are generated. Through the Hydrogen gas bubbles with a diameter of 100 to 600 micrometers should pull the water, which is lacking in oxygen, up to the surface in order to take over oxygen from the air or from the air-facing water layers enriched with oxygen. This method requires precise monitoring of the electrolysis process in order to be able to produce gas bubbles of the appropriate size, this method being able to be carried out only selectively by the devices required for this purpose and therefore it is usually not possible to achieve a greater degree of water improvement.

Another method for water improvement - according to US Pat. No. 4,005,014 - is an electrolysis system arranged in a container. Dome-like caps arranged above the electrolysis device are intended to delay the passage of water and oxygen in the direction of the water surface. so that an intensive mixing and oxygen uptake takes place in the water. With this method it is possible to bring about an improvement in the water quality in closed water supply systems, but it is hardly possible for use in bodies of water which have a substrate that is strongly enriched with minerals.

The present invention has for its object to provide a method with which it is possible to change the oxygen content of the water in flowing or standing water. In addition, it should be possible to degrade the anaerobic sediment layers formed in waters by natural, but above all also due to civilization-related eutrophication, or to prevent their build-up and, if appropriate, prevent one

To enable or leave circulation of the water layers.

This object of the invention is achieved in that a current flow through the water serving as the electrolyte between an anodic and a cathodic area arranged in the area of the bottom of the body of water extends over a large area extending electrode is built. The fact that the water or the sediment is used as the electrolyte produces oxygen in the course of the electrolysis that occurs in the process. In addition to the oxygen supply of the sediment at the bottom of the water and in the bank area, better mixing of the water layers with oxygen may also be achieved. This is also the case if all of the oxygen produced by the electrolysis is required in the area of the sediments - in particular in the initial stage of the remediation - in order to make the soil areas aerobic. The presence of oxygen in the soil area leads to an oxidation of the sediment layers so that they function again as phosphate traps and the polluted water can thus be cleaned up. This means that the living conditions for anearobatic organisms no longer exist and thus the production of hydrogen sulfide and methane is avoided. The further surprising effect of this solution, however, is that the hydrogen released by the electrolysis bubbles up through the water and causes a uniform flow in the direction of the water surface, so that water particles are carried up and slowly sink back from there. This transport brings water particles into the area of the trophogenic zone so that they can be enriched with oxygen there. The essential finding of the invention is, however, that the constant electrolysis of the water column maintains constant, constant circulation without the disadvantages that occur, for example, in the known methods of forced circulation. Rather, an oxidation of the sediment layers and a thorough mixing of the water layers is made possible. The biological advantage of the method is that the "living conditions" are improved. Due to the oxygen enrichment in the sediment, the strictly aerobic microorganisms find the best conditions that die anaerobically. The activity of the aerobic bacteria creates particularly usable nitrogen compounds for algae. These ensure further oxygenation. Now consumers of various orders are also becoming active. The conspicuous organic dead substance is in turn degraded aerobically. This makes it possible to improve the water in the direction of decreasing nutrient content. A prerequisite for this is a reduction in the anthropogenic introduction of nutrients. The possibility of regulating the amount of oxygen and hydrogen liberated in the electrolysis by the current flow in the region of the electrolyte also makes it possible to influence various eutrophication states in the waters to be rehabilitated. Another advantage of the arrangement of the electrodes in the bottom area of the water is that the different minerals present in the bottom area lead to the build-up of local elements between the minerals and an electrode deposited in the bottom area. Due to the various soil materials, the electrolyte has different pH values. These different PH values occur local elements which lead to an electrolysis of the water or the electrolysis, if d ^'hese formed by an active or passive electrode system support. The electrode, which extends over a large area and the resulting large number of local elements or the large-area electrolysis, produces the oxygen in molecular droplets in the finest droplets. The molecularly dissolved oxygen connects directly to the surrounding water. If a water layer is saturated with molecularly dissolved oxygen, the oxygen is passed on to the next layer, from which it is rapidly absorbed. The

Disadvantages, which arise in conventional electrolysis processes for generating oxygen due to the small electrode spacings and the high conductance values of the electrolyte, such as the outgassing of oxygen, are thereby prevented.

According to a further advantageous feature of the invention, it is provided that the level of the current supplied to the electrodes is regulated so that, depending on an amount of oxygen given off during the electrolysis, the water has an oxygen content which is between approximately 5 mg and the oxygen saturation of the water, which means that the water Use of the method described has so much oxygen that it enables sufficient living conditions for carp, but it is prevented that the oxygen begins to bubble out due to excessive electrolysis.

Furthermore, it is also possible for a chemically inert electrode, the length or area of which is a multiple of the cross-section, to be placed on the bottom of the water, which has a positive potential compared to the normal hydrogen electrode, which, in conjunction with the in the sediments

Minerals a variety of local elements is built up, which have a positive potential compared to the normal hydrogen electrode.

It is also advantageous if a reticulated electrode in the

Root area of bulrushes, which are located in a clarification pond, is arranged and that this reticulated electrode has a potential that is positive compared to the normal hydrogen electrode and is optionally connected to a magnesium electrode arranged in the bottom area, which acts as an anode. This simple process step makes it possible to increase the efficiency in the so-called rinsing plant. The rushes arranged in the sewage ponds release oxygen in the root area, which leads to an improvement in the oxygen saturation of the dirty water. The amount of oxygen released is multiplied by the network. Above all, it is achieved that the oxygen release is continued at night, which can reduce the oxygen consumption in the dirty water. In addition, a defined electric field for electrolysis can be achieved between the anode and the reticular electrode forming the cathode by connecting the reticular electrode to a magnesium electrode acting as an anode. The advantage of this system is that the use of reticulated electrodes does not impede or disturb the vegetation of the rushes or reeds. According to another embodiment variant, electrodes from lines or networks are placed on the bottom of the water at certain intervals from one another, one electrode of which has a potential which is positive compared to the normal hydrogen electrode and which forms the cathode and directly Adjacent electrode has a potential which is negative compared to the normal hydrogen electrode and forms an anode, so that according to the materials and surfaces used, a precisely defined current flow between the electrodes and thus electrolysis can be achieved to the desired extent.

Finally, the invention also includes a device for enriching a body of water with oxygen in the region of the soil for carrying out the method.

This device is characterized in that an electrode is placed in the bottom region of the body of water, the length or area of which is a multiple of the cross-section and the potential of which is positive against the normal hydrogen electrode. The use of such an electrode ensures that in the formation of local elements, for example in the case of strong hydrogen sulfide or phosphate pollution and when used in aggressive electrolytes, an ineffectiveness of the electrode and thus an interruption of the electrolysis can be counteracted. One advantage of the large-area electrode lies above all in the fact that a large number of different local elements can be formed over the surface by differences in pH in the electrolyte or by the different values in the voltage series of the materials. Due to this large-scale field structure and the associated large-scale electrolysis, the oxygen accumulates in the finest droplets in a molecular solution and can therefore be taken up directly by the oxygen-poor water. Due to the fact that the water body does not circulate, the colder water remains in the area of the floor and can absorb more oxygen than water due to the low temperature n

the surface. The living conditions for living beings in the immediate area of the device are thus improved.

It is advantageous if the electrode has a plurality of thread-like support bodies which are in one with carbon, e.g. Graphite-displaced, conductive plastic are embedded, since this ensures sufficient strength of the electrode against mechanical damage caused by attachments even in flowing water. In addition, electrodes of this type are suitable in conjunction with so-called externally operated systems, in which the electrodes are connected to the outputs of a low-voltage source in order to produce a controllable current flow between them.

Furthermore, it is also possible for the lines to be laid in the form of a network or to form threads of a network and preferably to be designed as a cathode; since a large surface area of the electrode is reached as a result of the network-shaped laying and a correspondingly effective electrolysis is triggered.

According to a further feature of the invention, it is provided that the electrode is formed by a conductor made of magnesium, which is provided with a coating in the longitudinally spaced areas, the potential of which is positive with respect to the normal hydrogen electrode, since it is in a simple manner between The magnesium serving as the anode and the coatings serving as the cathode are constructed with a large number of local elements which lead to electrolysis of the electrolyte located therebetween, namely the water. The number of elements formed can also be used to preselect the amount of electricity available in order to be able to produce a corresponding amount of oxygen. Furthermore, the magnesium ions remaining in the water during operation of the local element and the resulting dissolution and degradation of the anode are advantageous for the nutrient balance in the water, since aquatic plants also require magnesium for chlorophyll production. According to another embodiment variant, it is provided that the electrode having a positive potential with respect to the normal hydrogen electrode as the cathode is contacted with an electrode having a negative potential with respect to the normal hydrogen electrode as the anode, and that preferably that through the Water-formed electrolyte-accessible surface of the electrode having a negative potential is designed to have a presettable current flow through the electrolyte formed by the water. As a result, the amount of electricity available for processing the electrolysis can be regulated and the aeration of the sediment layers in the bottom area can be controlled. In addition, the hydroxides formed during electrolysis lead to a change in the pH value in the basic direction. The sufficient oxygen supply in the sediment, the breakdown of nutrients and the absorption of the same by primary producers enables the creation of aerobic conditions in the sediment. The prerequisite for this is the reduction of the nutrient entry into the water. Furthermore, this arrangement also enables plankton to be supplied in troughs, since an aerobic environment can be maintained and, with the appropriate supply of food and increasing temperature and sufficient oxygen supply, sufficient plankton can be produced.

Finally, however, it is also possible for the two electrodes to be connected to an output of a low-voltage source and to have a voltage slightly above the decomposition voltage of the water, a control device preferably being assigned to the low-voltage source, the oxygen quantity measuring elements and / or temperature sensors are assigned and when the oxygen saturation is reached, the control device is acted on in the sense of a reduction in the current output of the low-voltage source, as a result of which, when measuring the various reference variables in the system, simple control and adaptation of the required amount of current for the Electrolysis to maintain a corresponding amount of oxygen in the sediment or water is achieved. For a better understanding of the invention, it is explained in more detail below with reference to the exemplary embodiments shown in the drawings.

Show it:

Fig. 1 shows a part of a body of water with a device according to the invention arranged in the bottom region of the body of water in a simplified diagrammatic representation with a schematically indicated process of the invention

Procedure;

2 shows an embodiment variant of a device according to the invention using a cathode and an anode as local elements;

Figure 3 shows the arrangement of an inventive device in a lake in a simplified schematic representation.

4 shows an embodiment variant of a device according to the invention with an active method using an anode and a cathode and an external voltage source contacted with these two;

5 shows a local element formed from an electrode having an anodic and a cathodic region with a coating influencing the active surface of the anode;

Fig. 6 is a diagram of the nitrogen cycle in the water.

In Fig. the water 1 of a part of a body of water 2 is shown schematically. In this pond, the eutrophication process has been accelerated due to environmental influences such as detergents, nitrate feed from over-fertilization or concentrated fattening cattle farming. The pond therefore has one stratification corresponding to a eutrophic state. This is characterized in that the water layer extending from the water surface 3 in the direction of a bottom 4, namely the epilimnion 5, is less deep and warmer than an oligotrophic layer 5. The same applies to that

Metalimnion 6, which also has only a small depth and in which a blatant drop in temperature in the direction of the bottom 4 of the water 2 can be determined. The adjoining one, which extends to the bottom 4 of the water

IQ ^" layer", namely a hypolimnion 7, on the other hand, has a very large depth. In comparison, the depths of the epilimnion 5 and metalimnion 6 of an oligotrophic body of water are drawn purely schematically by means of dashed lines. Furthermore, the water 2 in the area of the water surface 3, in particular due to

15 the mixing of the water 1 with the surrounding air, as symbolically indicated by arrows 8, oxygen - 02 - supplied. Furthermore, light radiates from the water surface 3 in the direction of the metal ion and hypolimnion - indicated schematically by arrows 9. In the area of the bottom 4 are in particular

In the region of a sediment layer 10 or a soil layer 11, various minerals 12 or 13 are present. Furthermore, there are aquatic plants 14 at the bottom 4 of the water, e.g. Algae and the like available. These aquatic plants and algae will mainly be blue-green algae if the water is eutrophic

25.Ξ act- ..

Furthermore, an electrode 15 is arranged in the area of the bottom 4. This electrode 15 consists, for example, of a network 16 provided with an electrically conductive surface coating,

30 with carbon in the surface coating, e.g.

Graphite are embedded, if possible, in a plastic that is inverted against soil minerals. Due to the carbon contained in the electrode surface, the electrode 15 is electropositive, but acts due to the direct contact with it

35 surrounding minerals 12, 13 contained in the bottom 4 and the short circuit caused thereby as cathode. The minerals 12,13 Therefore, together with the electrode 15, form a large number of local elements, and between the minerals 12, 13 and the electrode 15, which acts as the cathode, there is a structure, indicated schematically by field lines 17, of a large-area electrical field 19 which practically spans the entire floor surface 18 Due to the different voltage spacings of the minerals 12, 13 and the electrode 15, for example a normal hydrogen electrode, this electric field 19 results in a decomposition voltage of the water.

103 the voltage difference and a corresponding current flow, through which the water 1 is electrolytically broken down into hydrogen - H2 - and oxygen - 02 -. This is shown schematically in the drawing by arrows 20, 21. While the oxygen at the voltage achieved by the local elements in the electrical

15 trisehen field which is usually just above the decomposition voltage of the water - approx. 1.2 volts - the oxygen accumulates in the finest droplets in a molecular solution. This molecularly dissolved oxygen connects directly to the surrounding water and does not bubble out.

20th

The hydrogen produced during the electrolysis, on the other hand, bubbles out, as is also symbolically indicated in the drawing by gas bubbles in the region of the arrows 20, and bubbles through the water to the water surface 3, that is to say from gas. By for the

25. ^' variety of local elements required small amounts of

Minerals and the high mineral content in the area of the bottom 4 of the body of water 2, a constant electrolysis of the water is achieved over a long period of time, which also takes place regardless of the time of day - i.e. also in the dark phase - and thus

30 there is a continuous supply of oxygen into the hypolimnion and, if oxygen saturation is achieved in the hypolimnion, in the overlying water layers.

Due to the sufficient supply of oxygen, the 35 in Fig. shown eutrophic waters 2 for a rapid increase in the nitrifi anten, which are aerobic and thus cause that the anaerobic assimilation or dissimilation process swings into an aerobic assimilation or dissimilation process. Due to the constant supply of oxygen due to the electrolysis taking place in the electrical field 19 in the area 4 of the water 2, the increased oxygen requirement resulting from the conversion of the ammonium into nitrite and from nitrite into nitrate, that is to say the nitrifi anten I and II is required to be provided. This development triggers an even greater accumulation of nutrients formed by nitrogen compounds. The sufficient amount of phosphorus in eutrophic waters now leads to the development of photoautotrophic organisms such as algae under the influence of light. These can now incorporate and convert the nutrients. In the course of this nutrient installation and conversion, oxygen is added to the water. This keeps the material conversion going.

In addition, the effect of the electric field 19 and the electrode 15 and its polarity with the sediments contained in the sediment layer 10 build up a material gradient which promotes the development of the microlife world. This means that the nutrients, which are largely ionic in aqueous solution, migrate to the electrically charged poles. Furthermore, the development of microorganisms and protoplasts by the electric field 19 should also be favored. In addition, there are the bacterial substance conversions present in the water, which are promoted by the amount of oxygen released at the network 16 or the electrode 15.

The structure of the electric field 19 and the oxygen supply obtained by the electrolysis make it possible to inhibit the progress of eutrophication in a body of water. If it is also possible to reduce the supply of nutrients into the water, in particular by adding phosphates and nitrates, such as by over-fertilization and concentrated fattening cattle, the eutrophication can be slowed down or the water can be returned to an oligotrophic state. In addition, with the The method and the device according to the invention can more easily overcome critical disturbance phases in a biological ecosystem and it is possible to stabilize the ecosystem. By improving the breakdown and conversion of nutrients, aerobic conversion is favored in the smallest space.

2 shows an embodiment variant of a device 22 for enriching a water 1 of a body of water 23. For the same parts, the same reference numerals as in Fig.! used.

In the present exemplary embodiment, the device 22 comprises, in addition to the electrode 15 formed by a network 16, a further electrode 24 which is formed by a rod 25, for example made of magnesium or a magnesium alloy. The rod 25 is driven so far into the sediment layer 10 or the bottom 4 of Ge 23 wässers that its water ^* is 1 end facing approximately in the region of the electrode 15 and the network sixteenth A contact cap 26 is provided on the side of the rod 25 facing the electrode 15, the cross-sectional area of which is larger than the mesh size of the electrode 15 formed by the network 16. The rod 25 is now driven into the sediment layer 10 or the bottom 4 of the water 23 , the rod 25 is contacted directly with the electrode 15 or short-circuited. By comparison ^'use of a carbon-containing coating material for the electrode 15 is built up a großfl chiges electric field due to the voltage difference from magnesium and carbon versus a normal hydrogen electrode between the rod 25 and the electrode 15, in which the electrode 15 as cathode and with Magnesium 25 or consisting of purely magnesium rod 25 acts as an anode. In the field 28 schematically indicated by field lines 27 there is an electrolysis of the water and thus an oxygen supply - indicated schematically by arrow 21 - into the water 1 and a degassing of the hydrogen, as indicated by the arrows 20. The process of electrolysis and the oxygenation of the water 1 is in accordance with the explanations for Fig.1.

Due to the size of the electric field or the ratio of the area of the electrode 24 acting as an anode to the electrode 15 serving as the cathode and the voltage difference between the two electrodes 15 and 24 corresponding approximately to the decomposition voltage of the water, a large-area electrolysis is generated by the Outgassing of oxygen due to excessive production, caused by excessive electrolysis, is avoided.

In FIG. 3, in order to clarify the method according to the invention and the design of the device, it is shown that, in contrast to known electrolysis devices, water 30 formed by a lake 29 is made by inserting large-area electrodes 15 formed by networks 16. The mode of operation of such devices can then be both according to the embodiment in FIG. as well as according to the embodiment in Fig.2.

4 shows another embodiment variant of a device 31, which is a so-called active system. In this case, an electrode 32 acting as an anode is connected to a voltage source 34 via a line 33. A reticulated moved through a network 35 or conductor 36 formed ^"electrode 37, which acts as the cathode, is connected via a line 38 to the negative potential of the voltage source 34 in. In such powered by a voltage source devices 31 is in designing and producing of electrodes 32 and 37, only make sure that materials that are resistant to soil and minerals are used.

By using the voltage source 34, the voltage difference between the two electrodes and also the current passage through the electric field, which extends between the electrode 32 and the electrode 37 and is schematically indicated by field lines 39, can be regulated. The mode of operation of the device 31 corresponds essentially to that of FIG. and 2 described mode of operation with the difference that the voltage and current strength in the electrical field can be controlled with a control element 40. In connection with an oxygen quantity measuring element 41 and a temperature sensor 42, the control element 40 can be acted upon via a control device 43 in such a way that the voltage and current strength in the electrical field - indicated schematically by field lines 39 - accelerate or reduce the electrolysis, so that during electrolysis resulting oxygen the oxygen demand of the

Water 1 or the respective liquid and the oxygen requirement of the nitrifiers or the other bacteria and plants in the water is adapted.

Of course, it is possible to use individual conductors 36 instead of the network 35, which are deposited in a network at the bottom of the water. It should only be pointed out for the sake of order that the network can rest directly on the sediment layer 10 or the bottom 4 of the body of water or can be arranged at a certain distance above it. In addition, the network must be designed in such a way that it is flexible in all spatial directions and adapts to the surface conditions of the sediment layer 10 or of the soil 4.

The advantage of using electrodes formed by nets is furthermore that the aquatic plants or the algae have the possibility of growing upwards through the nets, so that the soil flora in water is not impeded by the device according to the invention.

This is particularly important when the device according to the invention is used in clarifying ponds which are provided with rushes for the oxygenation of the water.

In settling tanks of this type, in particular when such brushes are provided, but also in other settling tanks Partially if a further electrode 45 is held in a certain area below a water surface 44, for example above floating bodies 46. If such an electrode 45 is used, it is applied to the negative potential of the voltage source 34 as well as the electrode 37. As a result, due to the voltage conditions in the water, algae 47 deposit on the electrode formed by the network and it comes directly in the area the surface of the water - from which area in clarifiers the water is fed to a stream 10 "or the like after the final clarification - to a very high oxygen concentration again, which strengthens the final purification of the water.

FIG. 5 shows a rod 25, which can be used, for example, for an electrode 15 24 - as described in FIG. 2. This rod 25 is made of pure magnesium or a magnesium alloy or another base metal, which has the greatest possible voltage separation from the contact cap 26, which consists, for example, of carbon or a plastic enriched with carbon.

Base metals should preferably be used here which have a voltage distance from the carbon or possibly platinum-doped electrode which essentially corresponds to the decomposition voltage of the water in order to ensure sufficient electrolysis of the electrolyte formed by the water in the course of the er¬ enable method according to the invention when used with the device according to the invention.

30 After the field strength of the electric field built up between the anode and the cathode is dependent on the surface of the rod 25, it is desirable to adapt the action of the anode and thus the surface of the rod 25 to different conditions of use. One possibility is that ever

35 the surface according to the application - as with dashed lines

Lines indicated - provided with a carbon coating 48 is, so that the effective surface is reduced or - as shown in full lines - over the surface of the rod 25 diaphragm or a sponge 49 - which can of course also be formed by any more or less open-celled elastic or rigid plastic - vorge¬ see. The maximum area of access from the electrolyte to the rod 25 regulates the voltage strength or the amount of current between the two electrodes.

: In Fig. 6 is a scheme of the nitrogen cycle for better understanding of the invention, which is decisive for the condition of a body of water, whether oligotrophic or eutrophic. As can be seen from this, ammonium is converted into a nitrifier I, namely nitrite, by reducing oxygen in the water. Under aerobic conditions - and correspondingly sufficient oxygen in the water - a further reduction of the oxygen in the water from the nitrifying agent I forms a nitrifying agent II, ie the nitrite is converted into a nitrate by reducing oxygen from the water. Due to the presence of phosphorus in eutrophic waters to a sufficient extent and therefore not as a minimum factor, the development of photoautotrophic organisms such as algae can take place under the influence of light. These algae can now incorporate and convert the nutrients. This leads subsequently to a renewed increase in oxygen, as these ^'green plants oxygen dispose to the water. In addition, some algae and some phanerogams are able to absorb ammonium directly from the water. This process, also referred to as assimilation, is now followed by metabolic processes, since the plant requires nutrients, for example nitrogen compounds, potassium, calcium, phosphorus and the like, and trace elements. The plants floating in the water, the phytoplanktones or algae, as the primary producer, provide the necessary energy for heterotrophic organisms, which therefore feed on existing organic substances.

The breakdown of the resulting organic substances is also very important for the ecosystem. This is also known as respiration or better known as dissimilation and is used to generate energy for the metabolic processes. Bacteria play an important role in this degradation process, and they work up the dead organic substance again. This closes the natural cycle, i.e. the ecosystem, and preserves the oligotrophic state of the water.

Of course, it should also be taken into account that in the event of such a water being rehabilitated, an attempt should absolutely be made to prevent the supply of nutrients, especially nitrates.

Of course, the invention is not tied to the exemplary embodiments shown, but any other inert electrodes suitable for this application can be used instead of the electrodes shown in order to achieve a corresponding field build-up and thus electrolysis of the water and oxygen recovery.

Claims

1. A method for enriching water in standing or flowing water with oxygen, in which the oxygen is supplied to the water in the bottom area, characterized in that a current flow through the water serving as the electrolyte between an anodic and a cathodic area is arranged in the region of the bottom of the water and extends over a large area.

2. The method according to claim 1, characterized in that the level of the current supplied to the electrodes is regulated so that, depending on an amount of oxygen given off during electrolysis, the water has an oxygen content which is between approximately 5 mg and the oxygen saturation of the water lies.

3. The method according to any one of claims 1 or 2, characterized gekenn¬ characterized in that a chemically inert electrode, the length or area of which is a multiple of the cross section, is deposited on the bottom of the water, which is compared to the normal hydrogen electrode positive potential up ^"points.

4. The method according to any one of claims 1 to 3, characterized gekenn¬ characterized in that a net-shaped electrode is arranged in the root region of rushes, which are located in a clarification pond, and that this net-shaped electrode is opposite to the

Normal hydrogen electrode has a positive potential and is optionally connected to a magnesium electrode arranged in the bottom area, which acts as an anode.

5. The method according to any one of claims 1 to 4, characterized gekenn¬ characterized in that at the bottom of the water at certain intervals electrodes from lines or nets are placed on top of each other, of which one electrode has a potential that is positive with respect to the normal hydrogen electrode and forms the cathode and the immediately adjacent electrode has a potential that is negative with respect to the normal hydrogen electrode and forms an anode.

6 ... Device for enriching a body of water with oxygen in the region of the soil for carrying out the method according to one of claims 1 to 5, characterized in that an electrode is placed in the region of the body of water, the length or area of which is a multiple of the cross section and whose potential is positive against the normal hydrogen electrode.

7. The device according to claim 6, characterized in that the electrode has a plurality of thread-shaped support body which in one with carbon, e.g. Graphite offset, conductive plastic are embedded.

8. The device according to claim 6 or 7, characterized in that the lines are laid in a network or form threads of a network and are preferably designed as a cathode.

9-., Device according to one of claims 6 to 8, characterized gekenn¬ characterized in that the electrode is formed by a conductor made of magnesium, which is provided in the longitudinal direction spaced areas with a coating, the potential of the normal hydrogen electrode is positive.

10. Device according to one of claims 6 to 9, characterized gekenn¬ characterized in that the electrode having a positive potential with respect to the normal hydrogen electrode as a cathode with an electrode having a negative potential with respect to the normal hydrogen electrode as anode is contacted and that the surface of the electrode having a negative potential that is accessible to the electrolyte formed by the water is preferably designed to have a presettable current flow through the electrolyte formed by the water.

11. Device according to one of claims 6 to 10, characterized in that the two electrodes are connected to an output of a low-voltage source and to this a voltage slightly above the decomposition voltage of the

Water is present, preferably a control device is assigned to the low-voltage source, the oxygen quantity measuring devices and / or temperature sensors are assigned, and when the oxygen saturation is reached, the control device is acted on in order to reduce the current output of the low-voltage source.