DE3312241A1 - Process for the electrochemical treatment of wastewaters and arrangement for carrying out the process - Google Patents

Abstract

The process for the electrochemical treatment of sea water-containing wastewaters (effluents) includes the recovery of a coagulant in the interelectrode space between insoluble and soluble electrodes of a diaphragm electrolysis cell and the subsequent discharge of the purified water. According to the invention, the coagulant is recovered in the interelectrode space by passing a current through only the insoluble electrodes, the current strength of which is sufficient to displace the potentials of the soluble electrodes to the range of their active dissolution, while the total concentration of coagulants in the interelectrode space between the insoluble and soluble electrodes is constant, which the self-regulation ensures. The arrangement for carrying out the process contains a diaphragm electrolysis cell having two or more electrode pairs, each of which is composed of a bottom insoluble electrode (2) and a top soluble electrode (3), which are arranged axially to each other. According to the invention, in each electrode pair, the insoluble electrode (2) is separated from the soluble electrode (3) by a dielectric intermediate layer (4), the outline of which coincides with an end surface of the insoluble electrode (2) which faces the soluble electrode (3), the length ratio between the soluble electrode (3) and the insoluble electrode (2) being at least 1 : 2. <IMAGE>

Description

Process for the electrochemical treatment of waste water and arrangement for carrying out the process

The present invention relates to environmental protection and more specifically relates to a method and arrangement for the electrochemical treatment of marine water Wastewater with a variable salt content in the wastewater drains to be cleaned.

The problem of contamination of the biosphere is e.g. B. of global character. Take a special place in the total pollution of the biosphere pollutants from A water basin, which are caused by sewage · The rapid development of shipping led to a sudden increase in the proportion of ship sewage in the total volume of wastewater that enters the world ocean got. In this context, most countries have taken measures to allow Ships into the territorial waters of these countries that are not equipped with any systems for cleaning and disinfecting ship sewage, as well as their use in inland water traffic forbidden is.

In the development of ship systems for cleaning of wastewater is given to increase the cleaning reliability special attention. This can be explained by the fact that electrochemical processes are currently used Most commonly used wastewater treatment in which the Waste waters are treated with coagulants that are formed during the electrochemical dissolution of metals · The practical application of such coagulants however, it is difficult for a number of reasons. One of them is the formation of salt deposits on the electrodes. The salt deposits increase the resistance of the electrodes, so that a reduction in the current flowing through the electrodes (so-called passivation) is effected, from which a reduction in the concentration of a coagulant formed in the interelectrode space results is introduced into the wastewater drains to be treated. This reduces the effectiveness of the cleaning process. Also, the salt deposits clog up in some Cut the space between the electrodes in such a way that the flow of the liquid to be treated between the electrodes

CGPT

stops at all, which interrupts the cleaning process will. This circumstance is particularly characteristic of the ship conditions under which one flows overboard Water used to flush sanitary facilities, which contains sea salt, its concentration changes within wide limits and depends on the location of the ship. Hence, it is considered one of the problems removing salt deposits on the electrodes when cleaning ship's sewage.

For example, a method for purifying waste water and an arrangement for realizing the same are known, which are described in the SU copyright certificate no. 739004 Int. Cl ² 002 P 1/46 are described. This method consists in that the seawater-containing wastewater is treated in the cathode chamber of a diaphragm electrolysis cell, whereupon a magnesium-containing sludge is separated and this is treated in the anode chamber of the diaphragm electrolysis cell, while the magnesium-containing liquid is passed from the anode chamber into the cathode chamber, when this process is carried out it is possible to avoid considerable salt deposits on the electrodes, but the following difficulties are encountered, which do not allow the cleaning of seawater-containing wastewater to be carried out effectively enough with the desired degree of reliability:

- with repeated processing of the sludge in the anode chamber with subsequent supply of the magnesium-containing one Liquid in the cathode chamber results in an increase in the concentration of magnesium ions in the treated Drain what happens when the solution is saturated. a precipitation of magnesium salts and an impurity the purified wastewater due to these salts and thus a reduced effectiveness of the cleaning process Consequence has;

- if the wastewater is only treated in the cathode chamber of the electrolysis cell, the energy consumption is high, because half the amount of electrical energy ι not immediately mg is used for wastewater purification, but to dissolve the sludge containing magnesium;

- "when treating the sludge in the anode chamber the electrolytic cell must, in order to avoid the anode space clogging by the sludge, a space in this space have large volume, 'including the distance between the

got to

The anode and the cathode be large, with ohmic losses as a result In the electrolyte, the voltage across the diaphragm electrolysis cell reaches high values, which in turn creates a causes increased energy expenditure for the treatment of the wastewater;

- the separation of the magnesium-containing sludge requires! additional containers, which significantly increases the dimensions of the arrangement for wastewater treatment, while under the ship's conditions, d. H. in the event of heeling, rolling and vibrations, the effectiveness of the cleaning process is reduced considerably.

Further, a better method and arrangement for carrying it out are disclosed in U.S. Pat. 4188278, Int.Cl ² C02B 1/82 known. This method of treating liquids consists in flowing a liquid through an electrolytic cell over an area of variable potential and changing the direction of this variable potential, the liquid being acted on by accelerating and decelerating forces in the course of its flow, creating an intense vortex between the individual liquid layers formed · this method is realized by means of an arrangement which includes a pair of main electrodes and a series of mounted between these auxiliary electrodes, wherein the main electrode composed of a series of electrically ve ^l rbundener rods, which lie in a same plane while each auxiliary electrode consists of electrically insulated rods. The main electrodes create an area of variable potential between them through which the liquid flows; the removal of the developed gas bubbles from the electrodes is carried out by ultrasound.

The energy consumption for carrying out this method is also high because of the arrangement An ultrasonic vibrator is available, which serves to avoid salt deposits on the cathode surface.

In addition, if the electrodes are arranged transversely to the liquid flow, sticking of fibrous ones can occur "The electrodes are contaminated and cannot be removed by ultrasound because the specific gravity of the impurities and the liquid to be treated are equal to each other. The intense, Turbulence zones behind the electrodes destroy flakes of coagulated impurities, thereby the coagulation of the colloidal impurities is disturbed

10 · and ultimately a reduction in the quality of wastewater treatment is caused. In addition, the turbulence of the wastewater flow to be treated causes an intensive one Mixing of the liquid layers near the electrodes, which reduces the pH value of the layers near the electrodes and as a result salt deposits on the surface of the electrodes are formed. A network intended to split the wastewater flow to be treated into jets complicates the arrangement for carrying out the method and affects its reliability as a result of a possible clogging of the network. To put the electrodes on to fasten the walls of the housing of the electrolytic cell so that it is electrically isolated from the housing walls insulation shims must be attached between the electrodes and the housing walls or the housing walls be made of an insulating material, which complicates the construction of the electrolytic cell significantly.

A method for the treatment of liquids, which by means of an arrangement according to the SU copyright Mr. 912664, Int.Cl. C02 F 1 / 4-6 is considerable more effective than the above. This known method consists in that one waste water from the anode and the cathode chamber of a diaphragm electrolytic cell with insoluble electrodes. Waste water is alkalized in the cathode chamber and in the anode chamber acidified, whereupon the acidic anolyte is passed into an electrical coagulator, in which chromium is replaced by divalent Iron ions are reduced, which are formed when the soluble iron anodes of the electrical coagulator dissolve. The anolyte is brought out of the electric co-gulator

Flotator, into which the alkaline catholyte also gets, the discharged from the cathode chamber of the diaphragm electrolysis cell whereupon the solid and liquid phases are separated in the flotator and in the filter. Although this known method is sufficiently effective, it ensures low puncture reliability, because with a change in the salinity of the sewage, which is inevitable under the ship's conditions occurs, the current flowing through the electrodes of the diaphragm electrolysis cell also changes undergoes a change in the pH of the wastewater leaving this cell and the rate of dissolution of the electrodes of the electrical coagulator. As a result, the concentration of the coagulant changes in the wastewater drains to be treated, while in the cathode compartment of the diaphragm electrolysis cell as a result of the in. Magnesium ions present in the waste water precipitate magnesium hydroxide, which blocks the electrodes, making it impossible will be able to sufficiently effectively purify ship's wastewater.

In addition, with such a scheme of treating ship sewage is practically impossible from the surface remove magnesium hydroxide by reversing the polarity of the insoluble electrodes, because the polarity is reversed in the electrical coagulator Abwasserabflus.se are performed, which have an alkaline reaction, whereby the soluble electrodes are passivated «For mechanical cleaning however, these electrodes either require complicated equipment or the arrangement must be periodic can be turned off to clean these facilities or replace the iron electrodes.

Also known are a method for treating a liquid and an associated arrangement for carrying it out, which can be seen in ITr in the SU UrJaeb. 874-653, Int. Cl.- ³ C02 F 1/46 are dealt with. This process, which is carried out in a coagulation device, consists in supplying a liquid to be treated to an anode compartment of insoluble electrodes, from where it flows into an anode compartment of soluble electrodes. The comes from the anode compartment of the soluble electrodes

COPY

treating liquid flow into the cathode compartment of the soluble Electrodes and then into the cathode compartment of the insoluble electrodes. From the cathode compartment of the insoluble Purified water is discharged from electrodes.

The wastewater treatment by means of this known arrangement is carried out by taking electrical current flows through both the insoluble electrodes and the soluble electrodes, the concentration of the coagulant occurring in the interelectrode space depends on the water salt content and changes when the Salinity as a result of the variable electrical conductivity of the solution and, as a result, that caused by the electrodes flowing current changes

Because the current is made to flow through the soluble electrodes directly from the electrical power source and the concentration of the coagulant in the inter-electrode spaces undergoes changes, the consumption is very high in soluble electrode material if wastewater is treated with a high concentration of sea salt The fact that the flow of liquid is passed from the anode compartment into the cathode compartment also arises a deposit on the surface of the soluble cathode, because hydrogen ions that form on the anode dissolve Metal hydroxide on the soluble anode to dissolve a. at the cathode through chemical conversion of a metal (e.g. from aluminum) with water, metal hydroxide is formed on which no protective oxide film is formed during cathode polarization (the concentration of hydrogen ions, which come from the anaenous space of the soluble electrodes is not sufficient to dissolve that which is deposited on the soluble cathode Hydroxide from) '

In addition, hydroxyl ions migrate, which are attached to the insoluble Cathodes form, in the form of developing hydrogen bubbles, to the surface of the soluble cathode.

Because of this, the pH is not near the cathode sufficient for the formation of soluble compounds of a metal, especially aluminum compounds.

Because the waste water to be treated is passed from the anode into the cathode chamber, no

Magnesium hydroxide, which is also a good coagulant, can be formed in the cathode compartment. The sewage drains, which exhibit a neutral reaction when entering the arrangement, namely who are acidified to the anode and then alkalized in the cathode compartment to the pH value of the starting liquid, while the formation of ν cn magnesium hydroxide is only possible at pH values above 8.9. When using such a scheme of wastewater flows with a larger number of electrode pairs, the structure of the arrangement is complicated because it is a zigzag Provide for the passage of the liquid streams to be treated got to.

Because the distance between the non-erasable and soluble electrodes at a low content of seawater in the sewer to be treated is large, the field of the insoluble electrodes affects slightly on the soluble ones and on the content of that accumulating in the interelectrode space of the soluble electrodes Coagulant not off.

The present invention is based on the object, seawater-containing wastewater with different salt contents Purify in an electrochemical process in which the potential of the soluble electrodes in the active Area is moved.

The object is achieved in that the known method for the electrochemical treatment of a Liquid, which the production of a coagulant in the interelectrode space of the insoluble electrodes and the subsequent removal of the cleaned water includes, according to the invention, the waste water as separate Currents are fed to an anode and a cathode compartment of an electrolytic cell, the insoluble electrodes are traversed by an electric current by placing a coagulant in the spaces both between

- t χ u ^ -. »■.

BATH ORIGINAL

COPY

It was found experimentally by the inventors that, thanks to such a solution, the Task, "in which you can only pass the electric current through the insoluble electrodes by the soluble'electrodes are electrically isolated, can flow, a current spread and discharge in the direction of flow of the liquid flow takes place from the insoluble electrodes to the soluble ones, whereby the potentials of the soluble electrodes in be moved to an area for their active resolution and thus dissolution of the soluble electrodes, especially those made of aluminum, takes place

Such implementation of the method according to the invention makes it possible to purify wastewater, the seawater with different. Contains salt content · When passing through the wastewater to be treated with a low content of sea salt through the electrolysis cell has the wastewater a low conductivity. In this case, when you see the electric current will flow through the soluble electrodes lets, the dispersibility of the wastewater is increased, whereby there is a greater influence of the field of the insoluble electrodes on the soluble ones. The potential of the soluble Electrode is shifted to a large extent in their active dissolution range, which increases the speed of dissolution of the soluble electrodes is increased, while the concentration of ions in the liquid to be treated soluble metal, due to the colloidal impurities are coagulated in the wastewater increases · The content of magnesium ions is due to the low salt content the sewage runoff is low. That is why it forms in the room between the insoluble electrodes a relatively small amount of magnesium hydroxide · If you have wastewater with conducts a high content of sea salt through the electrolysis cell, the dispersibility of the liquid to be treated is reduced and the action of the field that of a current traversed insoluble electrodes on the soluble - Electrodes weaker. The shift in the potentials of the soluble electrodes is reduced, so that the soluble Electrodes almost never come off. In this case it serves as a coagulant magnesium hydroxide, which is during

the electrolysis in the alkalization of the wastewater in Cathode space of the insoluble electrodes forms.

It was also found experimentally that the ratio of the current strength to the flow rate of the wastewater to be treated Cd. H. the amount of electricity per unit volume) is at least 0.01 ' A. h , this value for

Shifting the potential of the soluble electrodes into the active resolution range of the same is sufficient and the possibility offers a constant total concentration of To maintain coagulants in the interelectrode space ".

B _e of salinity i change of the effluent to be treated depends on the amount of dissolvable aluminum from SaIzgehalt the waste water from, and indeed it is at low SaIzgehalt increased the sewage to be treated and decreases with increasing salt content, the total concentration remains constant of coagulant and thus the self-regulation of the wastewater treatment process comes about and the consumption of aluminum electrodes is 2 to 4 times lower.

If the wastewater to be treated is allowed to flow first between the insoluble electrodes and then between the soluble electrodes, it is first acidified and alkalized in the vicinity of the insoluble electrodes, whereby the electrochemical solution of the aluminum electrodes results in the formation of soluble products _r aluminum ions and aluminates - is guaranteed, so that the formation of salt deposits on the soluble electrodes is prevented.

It is appropriate to use one of the insoluble electrodes to supply non-stabilized direct current.

The use of the non-stabilized direct current allows a greater shift in the potentials of the soluble electrodes in the area of their active resolution in comparison with the stabilized direct current of the same amperage to reach.

It is advisable to carry out the treatment process in such a way that the pH value in the anode compartment is in a range of 2 to 3f6 and in the cathode compartment in a range from 10.5 to

COPY

12.5 is held.

Carrying out the method under such conditions ensures complete inactivation of pathogenic microorganisms in the wastewater, because the pathogenic microorganisms in the cathode and anode compartment of the electrolytic cell die under the action of an alkali and an acid, which are formed after the reactions: 2H ₂ O + 2e = H ₂ + 2OH "(on the cathode) H ₂ O - 2e = 2H ⁺ + 1/2 O ₂ (on the anode) ^r .

It is recommended to use the cathode and anode compartments to mix treated wastewater;

When the waste water flows out of the cathode and anode compartment are mixed, the waste water is neutralized according to the following reactions: 2H ₂ O + 2e = H ₂ + 20H ~ (at the cathode)

H ₂ O - 2e = 2H ⁺ + 1/2 O ₂ (at the anode). The object is also achieved in that, in the arrangement for carrying out the method according to the invention, which contains a diaphragm electrolysis cell which has at least two pairs of electrodes, each of which consists of an insoluble and a soluble electrode which are axially to one another and the electrode pairs in the The anode compartment and the cathode compartment are arranged alternately, according to the invention in each pair of electrodes the insoluble electrode is separated from the soluble electrode by a dielectric intermediate layer, the contour of the intermediate layer coinciding with an end face of the insoluble electrode that of the soluble electrode

and
The length ratio between the soluble electrode and the insoluble electrode is at most 1: 2. The fact that the electrodes are arranged axially to one another creates the best operating conditions for the electrodes because the waste water stream flowing along the surface of the electrodes provides optimal conditions for the action of an electric field generated by the insoluble electrodes through which a current flows on the soluble electrodes that are not traversed by any current is guaranteed.

By the presence of the dielectric intermediate layer between the insoluble and soluble electrodes, the electrodes are prevented from making electrical contact stand together and the soluble electrodes receive the potential occurring at the insoluble electrodes. this in turn makes it possible to avoid passivation of the soluble electrodes and their excessive consumption To reduce electrodes in the case of a high salt content in the wastewater to be treated. The use of the dielectric Intermediate layer, the contour of which coincides with an end face of the insoluble electrode, which is the Soluble electrode facing, provides maximum exposure to that built up by the insoluble electrodes electric field on the soluble electrode safely · In addition, takes place in such a shape of the dielectric Intermediate layer no mixing of the layers near the electrodes of the wastewater to be treated with the rest Flow of the liquid to be treated takes place, causing a formation of salt deposits on the surface of the soluble Electrodes are avoided

When a current flows through the insoluble electrodes, the pH value experiences a maximum change in the vicinity of the electrodes, whereby it is very important that the flow of the liquid in the space near the electrodes does not Has time to mix with the rest of the flow of the liquid to be treated, which has a high alkalinity and Acidity in the space near the electrodes of the soluble electrodes ensures the formation of insoluble salt deposits when dissolving soluble electrodes, e.g. B.

made of aluminum is prevented.

The fact that the one pair of electrodes, consisting of an insoluble and a soluble electrode, which through the dielectric intermediate layer are separated from each other in the anode compartment and the other pair of the same electrodes in the Are arranged cathode compartment, soluble products of the electrolysis both in the cathode compartment and in the anode compartment of the electrolytic cell with parallel passage of the currents of the liquid to be treated .. formed.

3OPY i

In addition, when the polarity is reversed, the insoluble Electrodes prevent magnesium hydroxide from depositing on their surface and additional activation the soluble electrodes guaranteed. When the aspect ratio between the soluble and insoluble electrodes is not greater than 1: 2, the potentials of the soluble electrodes will be in their active dissolution area all over the Moved height of soluble electrodes. If this ratio is greater than 1/2, the lines of force of the through the generated by an electric current flowing through electrodes Field does not hit the far part of the soluble electrodes.

It is advisable that the soluble electrodes have a thickness greater than the thickness of the insoluble electrodes is.

Such a design of the soluble electrodes allows a stronger action of the by the electrical Electricity flowing through it generated insoluble electrodes electric field on the soluble electrodes, which are not traversed by any current. This will make the shift the potentials of the soluble electrodes in their active dissolution area are increased, the greater the The thickness of the soluble electrodes, the more the electric field of the insoluble electrodes acts on them.

It is expedient to design the insoluble electrodes in such a way that those facing the soluble electrodes Ends of the insoluble electrodes have a decreasing cross section.

This allows the action of the electrical field to amplify the soluble electrodes through which the electric current flows, because in this case the lines of force of the electric field from any point, even from those on the inclined sections of the upper End of the insoluble electrode, directed perpendicular to the surface of the ^ soluble electrode and in a are effective at high altitudes.

It is advantageous that the diaphragm of the electrolytic cell over the face of the soluble electrodes in protrudes at a distance of at least 5 mm.

This embodiment of the diaphragm is characterized in that "when using the arrangement for purification of waste waters with low sea salt content, the aluminum, which is called the resolution v <m soluble. ELc'-t.rüar-Ti, r wishes ond ere. ' ^δ

'Aluminum electrodes, forms, in a pH range of 8 and above or of 4 and below in the dissolved state in the wastewater to be treated remains, which is why Hydroridgel only

is formed when the anolyte and catholyte are mixed. Such a design of the diaphragm prevents the formation of hydroxide on the upper edge of the soluble electrodes and helps it to form in a volume of liquid away from the soluble electrodes is. This prevents deposits from occurring on the soluble electrodes and enables wastewater to be cleaned, which contain sea water with different salinity.

It is advisable that the dielectric spacer consists of individual plates.

Thereby, one can achieve a desired effect, i. H. the insoluble electrode from the soluble electrically. insulate, as well as reinforce the effect of electrical damage on the soluble electrode and the insulating material save on. ,

The invention will be described below on the basis of specific exemplary embodiments with reference to the enclosed Drawings explained in more detail. It shows:

1 shows an anode polarization curve for an aluminum electrode in a sea salt solution;

Fig. 2 graphical representation of the change in the pH value in a volume of liquid at various distances between the surface of the electrode and the diaphragm;

Fig. 3 graphical representation of the dependence of the volume Amount of electricity (per unit volume) "passed through the insoluble electrodes" from various Concentrations of seawater contained in the wastewater to be treated remain the same Concentration of coagulant in them;

2 ¹ Ig

BATH ORIGINAL

ST '

COPY

see medium at different wastewater flow rates;

Pig. 5 schematically shows a longitudinal section of the arrangement according to the invention for carrying out the method according to the invention for the electrochemical treatment of ship sewage;

Fig. 6 shows another embodiment of the Arrangement;·

Pig. 7 another embodiment of the ' Arrangement;

Pig. 8 another embodiment of the arrangement;

Pig. 9 also a variant of the arrangement!

Pig. 10 graphical representation of the dependence of the shift in the potentials of the soluble electrodes on a distance that they are away from the insoluble electrodes.

The procedure is carried out as follows. Man directs the wastewater to be treated in the interelectrode space of insoluble electrodes, in particular graphite electrodes, along the same as well as along soluble electrodes, in particular made of aluminum. At the same time you leave through the graphite electrodes, a stabilized or a unstabilized direct current flow (the latter by "rectification is obtained without smoothing current pulsations").

When the electric current flows through the \ _ Electrolysis of water in the cathode and anode compartment according to the following reactions:. -.

2H ₂ O + 2e = H ₂ + 20H ~ (KatOde) (1)

H ₂ O - 2e = 2H ⁺ + 1/2 O ₂ (anode) (2). Under the action of an alkali and an acid, which are formed in the cathode and anode compartment of the electrolysis cell after reactions (1) and (2), pathogenic microorganisms die and the waste water is decontaminated.

The neutralization of the wastewater occurs when it is mixed the currents, ie the cathode and anode compartment leave, after the following reactions:

2H ₂ O + 2e = H ₂ + 2OH ~ (cathode) H ₂ O - 2e = 2H ⁺ + 1 O ₂ (anode) 3H ₂ O = H ₂ + 1/2 O ₂ + 2H ₂ O

The volumetric quantity of electricity regulates UAN in 5 ^N depending on the salt content of the effluent to be treated discharges so that a change of the salt content, the total concentration of coagulants, that is, magnesium hydroxide and aluminum, remains constant in the inter-electrode spaces. When using water flowing overboard in ship sanitary facilities, the concentration of sea water in the wastewater to be treated can be changed from 0.1 g / l (in rivers) to 35 g / l (in the ocean), depending on the location of the ship.

If you treat wastewater with a low salt content, the field generated by the insoluble electrodes shifted the potential of the soluble electrodes in their active resolution range. The potential of the In the anode compartment located soluble electrode in the negative direction and the potential of that accommodated in the cathode compartment soluble electrode shifted in the positive direction.

In Table 1 below, there is a dependence of the potential of the soluble electrodes on the volume Amount of electricity that is conducted through the insoluble electrodes, represented for the pail that the The concentration of sea salt in the wastewater to be treated is 0.2 g / l.

Table 1

- J

In terms of volume
Electricity I

amount, Ajh _: Q 0.02 0.030 0.033 0.04

Anode potential, V, γ _Α -1.2 -1.4 -1.6 -1.7 cathode potential, Vtf _K 0.8 2.3 2.4 2.5.

From the comparison of the potential values, which at the soluble electrodes with the flow of different volumetric Amounts of electricity obtained by the insoluble electrodes and those shown in Table 1

copy

Values as well as the anode polarization curve shown in FIG it can be determined that a potential range of -1.2 to -0.5 V corresponds to the passive state of aluminum, while areas of potentials which are more negative than -1.2 V or more positive than -0.5 V, the area of the active Correspond to dissolution of aluminum.

In order to generate potentials that correspond to the range of active dissolution of aluminum, either the current applied to the insoluble electrodes in a range of 20 to 60 A or changes the flow rate of the to treating liquid within a range of 120 to 1200 l / h with the same amperage.

After the waste water has been treated with the help of the insoluble graphite electrodes, it reaches the interelectrode space along the insoluble and soluble electrodes with minimal mixing, where the aluminum electrodes are loosened under the effect of an electric field generated by the graphite electrodes. During their dissolution, ions of the soluble metal get into the waste water drains, which coagulate the colloidal impurities is, in which a dependence of the concentration of Mg (OH) ₂ and Al ^ ⁺ on the volume of electricity that is conducted through the insoluble electrodes, is given at a sea salt concentration of 0.2 g / l. \

JOU / .4 I -HO-

Table 2

In terms of volume

Electricity _I_ 0.02 0.03 0.033 0, J47 0.06 quantity, Ah Q

"T"
concentration

of magnesium C _{Mg (0H)}

hydroxide, mg / 1 ^ 0.53 0.70 0.67 1.43 2.0 concentration

on aluminum C

ions, mg / 1 2.5 3.10 3.9 5.0 5.7

Total magnesium hydroxide concentration
and aluminum ions, mg / 1 C _{Mg (OH) +}

Al ³⁺ 3.04 3.80 4.2 6.4 7.7

The wastewater supplied to the anode and cathode compartments of the soluble electrodes is given by them Using the insoluble electrodes, electrolysis is carried out to achieve a pH value, which is an area of existence of soluble compounds a metal, e.g. B, from aluminum, corresponds to which the soluble electrodes are made Table 3 below shows a dependency of the pH value in the anode and cathode compartment by means of the Soluble electrodes treated wastewater from the amount of electricity by volume at a concentration of sea salt expressed by 0.2 g / l wastewater.

copy

Tubelle 3

Volumetric

Electricity- _I_ ⁰ » ⁰² °» ° 3 ° »° 4 0.053 0.06

amount, Ah Q

Hydrogen exponent for pH.

the anode 3.4 2.9 2.6 2.8 2.6

Hydrogen-

exponent for ρΗ _χ 11.0 11.1 11.3 11.3 11.4 1 <D the cathode

As the wastewater streams to be treated flow along the insoluble and soluble electrodes, will the layers of sewage near the electrodes weakly mixed together, like this from Pig. 2 shows the curves "a" and "b" for the graphite electrodes along with curves "a" and "d" for the aluminum electrodes a relationship between the pH value of the waste water layers near the electrodes and the distance to the diaphra * represent gma in the cathode and anode compartments of the electrodes.

If you treat wastewater with a high sea salt content, then the electric field generated by the insoluble electrodes has a very weak effect on the soluble electrodes a. Therefore, the potential of the soluble electrodes, which are located in the anode and cathode compartments, becomes low Dimensions changed and is located within the potential ■ area that is the passive state of the soluble electrodes is equivalent to,

In Table 4 below is a dependency the potential of the soluble electrodes on the amount of electricity by volume which the insoluble electrodes flowing through, shown at a sea salt content of 35 g / l.

YY 1

- 22 table

Volume-related electricity - —i—

amount, ^ 0.01 0.02 0.033 0.04 0.053

Anode potential, V, «f ^ -0.52 -0.60 -0.62 -0.64 -0.66 cathode potential, V, -P ^ -1.01 -1.06 -1.08 -1.10 -1.14

By comparing the potential values given in Table 4 with that in Pig. The anode polarization curve shown in FIG. I shows that the potentials of the soluble electrodes in this case lie in a potential area that corresponds to their passive state. Here, aluminum is slightly dissolved, while the coagulation of impurities is caused by the magnesium hydroxide given off by the seawater, which can be seen in Table 5 below, in which a relationship between the concentration of Mg (OH) ₂ and Al ^ ⁺ and the volume of electricity, which is passed through the insoluble electrodes is shown at a sea salt concentration of 35 g / l.

Tabel

Volume of electricity, ^ y ± ί 0.01 0.02 0.03 0.04 0.047 0.053 0.06.

Concentration of magnesium hydroxide, mg / l C ^ (OH) 5.35 6.62 10.2 10.7 15.9 19.36 21.8

Concentration ^ of aluminum ions, mg / 1 C _A1 3+ 0.89 0.93 0.75 0.83 0.65 0.77 0.7 Total concentration of magnesium hydroxide and aluminum ions, mg / 1 ⁰ Mg (OH) + ⁶ ' ^{24 7 '55 10> 94 1: L} »53 16.55 20.13 22.5

Magnesium hydroxide is made by the alkalization of the

copy

Waste water in the layer near the electrode of the insoluble Electrodes are formed through which an electric current is allowed to flow as soon as the pH value reaches 3.9. Sin context between the pH values of the wastewater of the cathode compartment of the insoluble electrodes and the volumetric The amount of electricity is shown in Table 6 at a sea salt concentration of 35 g / l.

Table 6

Volume-wise
Amount of electricity, I
Ah Q 0.01 0.02 0.03 0.033 0.04 0.047 0.053 0.06

Hydrogen exponent
of the cathode pH _K 9.9 10.3 10.3 10.4 10.4 10.4 10.4 10.5

The total concentration of the coagulant is by regulating the volumetric quantity of electricity depending on the Atwassersalzgehalt at a constant flow rate of the waste water is kept constant · The current intensity must be changed Finances Act in dependence on salt content for a ^G, which is shown graphically in Fig. 3, where curves "a "and" b "and" c "correspond to a constant coagulant concentration of 6-7, 7-8 or 10-11 mg / liter of wastewater to be treated. Such a change in the current intensity depending on the salt content can be ensured by an automatic parametric converter for converting the electrical voltage into an electrical current or by a microprocessor

It follows from Fig. 3 that if the total concentration is kept constant of the coagulant in the waste water, the volume of electricity produced by the insoluble Electrodes is conducted, with decreasing salinity increases.

JJ I LLL ₁ , ι

- 24 -

If a non-stabilized direct current is allowed to flow through the insoluble electrodes, the shift in the potentials of the soluble electrodes becomes considerable
larger, which offers the possibility of obtaining a high concentration of dissolved aluminum in the solution with one and "the same volume of electricity.

An optimal distance between the insoluble and soluble electrodes was found experimentally, the dependence of the shift in the potentials of the soluble electrodes on the distance of the same from
the insoluble electrodes at a sea salt concentration of 0.2 g / l are shown in Table 7.

Tabel

Volume-wise

Electricity Rod. γγ, -γη «- A 'Jl, J- f ^ electricity quantity, Λ Q Anode potential not- (stabilized f stab. Current), V, current Anode potential Rod. (unstable ^ v- current ized current), V, Cathode potential not rod. (stabilized ■ f _K current Current), V, ^v Cathode potential ' (non-stabilizing ^ ter current), V ^{v C} Al3 + concentration of the coagula agent (Al ³⁺ ), mg / 1

0.047 0.053 0.09

-1.0 -1.1 -1.3

-1.4 -1.6 -1.9

+1.55 +1.6 '+1.65 +1.8.9 +2.1 +2.2

7.6 8.4 10.8

COPY

1 22A 1 - 25 ^-:: .Λ ^..:. T ^: .. ^: - .. ^:

Regardless of the speed at which the sewage get into the anode and cathode compartments of the electrolysis cell are shown by the waste water flows at the electrolysis cells run a neutral reaction, because the decomposition of water in the electrolysis according to reactions (1) and (2) with formation of hydroxyl ions and hydrogen ions in equivalent amounts happens.

In Pig. 4 is a dependence of the pH value of the wastewater graphically shown in the anode and cathode compartment of the amperage at different wastewater flow rates. Experimentally it has been found that the sewage is the most complete be disinfected when the pH value in the anode compartment is between 2 and 3.6 and in the cathode compartment between 10.5 and 12.5 lies.

Concrete exemplary embodiments of the present invention are given below.
example 1

Wastewater with a sea salt content of 0.2 to 0.5 g / l is passed into the inter-electrode space of the insoluble graphite electrodes along these electrodes and the soluble aluminum electrodes electrically insulated from them. Simultaneously with this, a stabilized direct current is allowed to flow through the graphite electrodes, the strength of which supplies a volume of electricity of 0.06 to 0.1 A *, h. It is determined in the initial wastewater

and in the treated wastewater the concentration of suspended substances, the biochemical oxygen consumption over a period of 5 days (BSV ₁ -), the content of coli bacteria and the salt content *

The tests are carried out in a system with a

flow rate of 18 m wastewater / day carried out. The exam results are summarized in Table 8.

- 26 table

Serial suspen Output wastewater KoIi-In- salt Kr dated
Fabrics dex salary mg / l 5 MiHer-ie-nHö 3mg g / l 2 mg / l 4th 5 1 890 3 2-10 ⁹ 0.2 1 730 400 2.10 ⁹ 0.28 2 900 380 1.5-1O ⁹ 0.3 3 500 420 8.1O ⁸ 0.5 4th 620 180 5-10 ⁸ 0.51 5 690 215 4-1O ⁹ 0.40 6th 240

Table 8 (Ports.)

Serial
No. suspen
dated
Fabrics Purified water mg / l 33Y ₁ , KoIi-In-
dex 1 6th mg / l Number of KoIi-B. 10ümg 1 30th 7th 8th 2 14th 28 100 12th 16 100 28 18th 25th 5 ■ 36 20th 30th 6th 41 30th 25th 43 20th

As can be seen from Table 8, the degree of purification of the treated wastewater corresponds to the international one Norms.

Example 2

Waste water with a sea salt content of 8 to 15 g / l becomes insoluble in the interelectrode space

BATH ORIGINAL

Graphite electrodes along this and the soluble aluminum electrode: !! those of the insoluble electrodes are electrically isolated, conducted. At the same time, the graphite electrodes are stabilized by a Direct current flowed through it, the strength of which amounts to a volume of electricity from 0.03 to 0.06 ^ y- supplies. It is determined in the outlet basin

and the concentration of suspended substances in the treated wastewater, the biochemical oxygen consumption during 5 days (BSV ^), the content of coli bacteria and the salt content.

The tests were carried out in a plant with a flow rate of 15 nr wastewater / day at a Heel angle of 15 ° was carried out in two mutually perpendicular planes. The exam results are summarized in Table 9.

BAD ORiGlNAL ßk

Table 9

Serial 3Jr. suspen Initial waste ser Salinity dated BSV KoIi index Fabrics mg / l s / i 3 mg / 1 Number of EoIi-
Bacteria 100mg 6th 1 2 636.0 4th 5 12.6 1 17th 305.0 312.0 2-10 ⁸ 12.6 2 18th 1070.0 192.0 4-10 ⁸ 12.6 3 19th 1050.0 100.0 3-10 ⁸ 12.6 4th 20th 759.0 56.0 3-10 ⁸ 11.0 5 5 2294.0 489.0 1.0-ΙΟ ⁹ 12.0 6th 6th 2162.0 981.0 ι, ο-ιο ⁹ 9.2 7th 7th 3282.0 800.0 1.0-10 ⁹ 8.0 8th 8th 1266.0 929.0 1.0.10 ⁹ 14.6 9 9 2464.0 724.0 2-10 ⁷ 14.0 10 10 2485.0 1100.0 2 10 ⁷ 10.8 11th 11th 1100.4 6-10 ⁷

Copy

Table 9 (cont.)

suspen Purified V / ater Koli index T -PA dated hl U.
No. Fabrics BSV mg / l Number of KoIi-B
100mg 7th 9 17.0 mg / 1 10 1 14.0 8th 10 1 14.0 6.0 10 2 21.0 6.0 10 3 15.0 6.0 10 4th 17.0 13.0 10 5 23.0 27.0 10 6th 21.0 27.0 10 7th 54.0 12.0 10 8th 33.0 28.0 10 9 47.5 43.0 10 10 28.0 11th 22.0

- JU -

As can be seen from Table 9, corresponds to Degree of purification of the treated wastewater is international Norms,

Example 3

Wastewater with a salt content of 26 to 35 g / l is placed in the central electrode compartment of the insoluble graphite electrodes along this and the soluble aluminum electrodes, electrically isolated from the insoluble electrodes. Simultaneously with this one lets through the graphite electrode flow a stabilized current, the strength of which has a volumetric amount of electricity from 0.01 to

Delivers 0.03 AJh.
1

The tests were carried out in a plant with a flow rate of 18 m waste water / day. The exam results are listed in Table 10.

The concentration of suspended substances, the biochemical ones, is determined in the initial wastewater and in the purified wastewater Oxygen consumption within 5 days ), the content of KoIi bacteria and the salt content.

COPY \

- 3i -

Table 10

No. suspended Output wastewater Koli index 3 Salinity Fabrics BSV 3-1O ⁶ mg / l / ^ ani der ü.011-
¹¹¹ S / ¹ bacteria 100mg 4-10 ⁶ g / i 1 2 3-1O ⁶ 4th 1030.0 153> O 3-10 ⁶ 27.0 1 1490.0 108.8 2.5 · 1Ο ⁹ 28.0 2 1165.0 163.2 2, O.1O ⁹ 30.0 3 745.0 148.0 2.0.10 ⁹ 33.0 4th 909.0 128.0 3, O.1O ⁹ 26.0 5 1574.0 220.0 26.0 6th 1200.0 170.0 26.0 7th 1719.0 125.0 26.0 8th

Table 10 (Ports.)

No. suspended Purified water Koli index Fabrics BSV mg / l iüani der & 0I1-
Bacteria 100mg 5 mg / l 7th 19.0 6th 10 1 20.0 I.
34.0 10 CV 21.0 30.0 10 3 16.0 26.0 . 10 4th 31.0 '26 .0 110 5 22.0 27.0 65 6th 21.0 24.0 63 7th 13.0 26.0 10 8th 25.0

oo iz ^ 4 ι - 32 -: "....

From Table 10 it follows that the degree of purification of the treated wastewater corresponds to international standards. Example 4

Wastewater with a sea salt content of 0.5 to 3.0 g / l becomes in the interelectrode space of the insoluble graphite electrodes along the same and the soluble aluminum electrodes, which are electrically isolated from the insoluble ones. Simultaneously with this, the graphite electrodes are flowed through by a non-stabilized direct current. In the initial wastewater and in the treated wastewater, the concentration of suspended substances is determined, the biochemical oxygen consumption within 5 days (BSV [O, the content of coli bacteria and the salt content. The Tests were carried out in a facility with a flow rate 18 m wastewater / day carried out.

The test results are summarized in Table 11.

copy

Table 11

No. suspen Outlet water KoIi index Salt dated BSV stop Fabrics mg / 1 Number of KoIi-
Bacteria 100mg g / i 1 2 mg / l 4th 5 1 395.0 3 4-1O ⁹ 0.5 2 311.0 206.0 6-10 ⁹ 0.5 3 525.0 251.0 4-1O ⁹ 0.5 4th 500.0 396.0 3-1O ⁹ 0.6 5 1795.0 351.0 - 3-10 ⁸ 0.8 6th 1740.0 400.0 4-10 ⁸ 2.1 7th 1821.0 772.0 2Ί0 ⁸ 0.93 8th 490.0 768.0 3-10 ⁷ . 2.7 9 215.0 279.0 4-10 ⁷ 2.0 10 126.0 139.6 3-1O ⁷ 2.7 11th 560.0 93.0 4 · 10 ⁷ 2.3 12th 1167.0 339.6 5 ', O.io ⁷ 2.9 13th 655.0 740.0 2, ° .1O ⁶ 2.0 14th 1500.0 428.4 5 1Ο ⁹ 2.7 15th 1265.0 1112.2 8-10 ⁹ 1.8 816.0
I.

Table 11 (cont.)

No. suspen Purified V / ater dated BSV ₅ Koli index Fabrics mg / l 6th mg / 1 Number of KoIi-B.
£ 100m 1 11.0 7th 8th 1 14.0 8.0 15th 2 24.0 21.0 30 * 3 13.0 22.0 30th 4th 7.0 17.0 60 5 24.0 29.0 10 6th 21.0 33.0 40 7th 20.0 34.0 40 8th 18.0 38.9 10 9 11.0 29.0 10 10 16.0 24.9 10 11th 18.5 32.0 10 12th . 7th 19.0 10 13th 11th 26.0 30th 14th 12.5 36.0 45 15th 21.0 45

Sludge paper was fed into the plant.

COPY

As follows from Table 11, the degree of purification is shown of the treated wastewater with the international standards in accordance.

The order to carry out the notified proceedings contains a housing 1 (Pig x 5), inside which insoluble and soluble electrodes 2 and 3, respectively, are arranged which are fastened in a suitable manner, in particular by means of plastic screws (not shown). Between the electrodes there is an intermediate layer 4 made of a plastic film and attached to a forehead surface of the insoluble electrode 2 is glued, which faces the soluble electrode 3. The insoluble electrode 2 and the soluble electrode 3 separated from the former by the interlayer dielectric layer 4, the bounded by the contour of the end face of the insoluble electrode, form a pair of electrodes that are axial and to each other in the same line in the direction of flow of the to be treated, by arrows in the drawing indicated sewage are arranged, each pair of electrodes of the Another pair of electrodes is separated by a diaphragm 5 made of glass fabric or another acid and alkali-resistant Fabric is executed. The same pairs of electrodes are arranged in the anode compartment 6 and in the cathode compartment 7, wherein the aspect ratio between the soluble and insoluble electrodes is at most 1: 2. Through such a Aspect ratio of the electrodes is made possible at the surface of the soluble electrodes to increase a potential generate the area of active dissolution of the soluble Electrodes. A current is applied to the insoluble electrodes 2 by means of. Connection lines 8 and 9 from a power source (not shown). The insoluble electrodes are connected in parallel to each other (Pig. 5) ·

According to another embodiment of the invention, the ends facing the soluble electrodes 3 have the insoluble ones Electrodes 2 have a decreasing cross-section which is symmetrical to the axis of the electrode (Pig. 6), what it allows the action of the field generated by the insoluble electrodes on the soluble electrodes to the maximum to take advantage of.

In a further embodiment of the invention have the soluble electrodes 3 have a thickness which is greater than the thickness of the insoluble electrodes 2 (Pig. 6) .ist. at Increasing the thickness of the soluble electrodes 3 becomes the action of the electric field of the insoluble electrodes 2 amplifies, to which an electric current is fed .

According to another embodiment of the invention the diaphragm 5 is designed so that it over the end face of the soluble electrodes at a distance of at least 5 mm (Pig. 7) protrudes.

Such a diaphragm contributes to the formation of aluminum hydroxide in a volume of liquid which is in the Space above the electrodes, which prevents deposits from forming on the soluble aluminum electrodes will.

Another embodiment of the invention is conceivable in which the electrical intermediate layer is made up of individual plates (Pig. 8), which offers the possibility of achieving a desired effect, i. H. the insoluble electrode to isolate from the soluble and thus to save the insulating material

The arrangement works as follows.

Waste water is passed into the anode space β and cathode space 7 of the diaphragm electrolysis cell separated by the diaphragm 5 with the same flow rate. The insoluble electrodes 2 are fed by the power source via the connecting lines 8 and 9. The soluble electrodes 3 are not connected to the power source. Because the wastewater in the liquid stream to be treated is subjected to electrolysis, the concentration of OH ~ ions in the cathode compartment 7 and the concentration of H ⁺ ions in the anodan compartment 6 increases . Because the arrangement is provided with the diaphragm 5 and the electrodes are arranged in the same line in the direction of flow of the waste water to be treated, an acidic solution generated near the anode is not mixed with an alkaline solution generated near the cathode . The unsolvable

Union electrodes 2 of the electrolytic cell are fed with an electric current that varies depending on the salt content the waste water coming to the cleaning changes and such Has characteristic values which ensure the implementation of the method according to the invention.

A wastewater stream sliding along the surface of the insoluble electrodes 2 washes around the soluble electrodes 3 _5, which are electrically isolated from the insoluble electrodes 2, whereby the potentials of the soluble electrodes are shifted into their active dissolution range thanks to the liquid flow and the dispersibility of the wastewater to be treated Electrodes 3 dissolved with the formation of aluminum ions (with a low salt content of the wastewater to be cleaned), through which impurities were coagulated. Because the wastewater stream flows first along the surface of the insoluble and then the soluble electrodes, it is supplied to the soluble electrodes through the acidification in the anode compartment and the alkalization in the cathode compartment with minimal mixing.

This allows you to close the surface of the soluble Set the electrodes to a pH value that prevents the formation of insoluble compounds on the surface of the soluble electrodes 3 is sufficient.

The soluble electrodes 3 have a greater thickness compared to the insoluble electrodes 2 (Pig. 6), the arrangement works similarly, only with the difference that the electrical pressure of the insoluble electrodes acts more strongly on the soluble electrodes.

An arrangement in which the the soluble electrodes 3 facing ends of the insoluble electrodes 2 are trapezoidal Have cross-section acts similar to the embodiment of the arrangement in which the soluble The end face facing the electrodes has a different shape. The trapezoidal cross-section enables an even stronger one Effect of the electric field of the insoluble electrodes 2 on the soluble electrodes 3. ^

If the arrangement is provided with a diaphragm 5, that over the soluble electrode 3 at a distance of more when 5 ram_ (Pig. 7) protrudes, it works just like the

management form of the arrangement, whose diaphragm in the same Height and the soluble electrode 3 consists of individual plates (Pig. 8), functions in a similar way to that Embodiment of the arrangement in which a continuous intermediate layer is provided between the electrodes.

In Pig. 8 shown embodiment is still the polarization of the soluble electrodes is improved.

If the electrodes are operated within 1000 hours with a variable salt content (e.g. within of 200 hours with a salt content of 0.2 g / l, 200 hours with a salt content of 5 g / l »200 hours with a Salt content of 35 g / l and 200 hours with 20 g / l) the total consumption of electrodes is 2 g / m 2 of the electrodes to be treated Sewage. If you only use soluble electrodes through which an electric current flows, amounts to the consumption of electrodes at least 15 g / m.

Thus, when carrying out the method considered above by means of the arrangement according to the invention, there is no formation of deposits on the soluble electrodes, whereby the service life is extended and the electrode consumption is reduced, e.g. B. in the operation of the arrangement for the purification of ship sewage with a high sea salt content by coagulating the impurities with magnesium hydroxide and in the purification of sewage with a low sea salt content by dissolving the electrodes. The method according to the invention for the electrochemical treatment of wastewater offers the possibility of purifying practically any wastewater that contains seawater of different salinity. This makes the method according to the invention and the associated arrangement universal and allows them to be used on ships with an unlimited sailing range ",. · ^:

The inventive method makes it possible to automate the cleaning of ship sewage because a desired concentration of coagulant in the waste water through the self-regulation of the cleaning process is automatically maintained.

The design of the electrodes according to the proposed invention allows a degree of purification within

COPY

half a lunger time regardless of the salt content of the-zu to keep treated ship wastewater constant.

Claims (1)

FlNCK _v ρ ONER _t t, ti ι ·> ■ - ·· , τ ,, ^ ηΡΕΑΝ PATENT ATTORNEYS PATENT LAWYERS fc υ κ υ> - ^ MAPIAHILFPLATZ 2 & 3, MÖNCHEN 9O POSTAOfT MiF = PDSTFACH PS O1 F.f .. D-WClCl MUNCHF N «'· Leningradslcij technologiceskij
institute holodilnoj promyslennosti DEAA-30877.0 April 5th 1983 VERPAHREI TO ELEKT; LOCHSUlSCHEU BEHAiJDLUHG VOH SEWAGE AND ARRANGEMENT FOR PUMPING THE PAIRED Patent claims: 1. Process for the electrochemical treatment of wastewater containing seawater, which includes: - the recovery of a coagulant in the space between insoluble and soluble electrodes and - the subsequent discharge of the purified water ,. characterized in that - The wastewater is fed as separate streams to an anode and a cathode compartment of an electrolytic cell will, - taking the insoluble electrodes from an electric Current flowed through it by placing a coagulant in the spaces both between the insoluble as well as between the soluble electrodes, which are electrically isolated from the insoluble electrodes will, and - That the ratio of the current strength to the flow rate of the wastewater to be treated is at least G, 01 ^h . ? .. The method according to claim 1, characterized in that a non-stabilized direct current is supplied to the insoluble electrodes. 3. The method according to claim 1, characterized in that it is carried out so that the pil-V / ert im Anode compartment in a range from 2 to 3.6 and in the cathode compartment is kept in a range of 10.5 to 12.5. 4. The method according to claims 1, 3 »characterized in that the in the cathode and in the anode compartment treated wastewater runoffs are mixed together. 5. Arrangement for performing the method according to claim 1, the - contains a diaphragm electrolysis cell which has at least two pairs of electrodes, - Each of these pairs consists of an insoluble and a soluble electrode which are axially to one another are arranged, characterized in that - the insoluble electrode in each pair of electrodes (2) is separated from the soluble electrode (3) by a dielectric intermediate layer (4), - The contour of the intermediate layer (4) with a The end face of the insoluble electrode (2) which faces the soluble electrode (3) coincides, - the electrode pairs alternately in the anode compartment (6) are arranged in the cathode compartment (7), - the length ratio between the soluble electrode (3) and the insoluble electrode (2) at most 1-2 is. • 6. Arrangement according to claim 4, characterized in that the soluble electrodes (3) facing Ends of the insoluble electrodes (2) have a decreasing cross section. 7. Arrangement according to claim 6, characterized in that the soluble electrodes (3) have a thickness which is greater than the thickness of the insoluble electrodes (2) BATH ORIGINAL COPY is. B. arrangement according to Claim 5 _5, that a diaphragm (5) projects the electrolysis Selle to prevent deposition on the end surface of the soluble electrode (3) on the end face of the soluble electrode (3) at a distance of at least 5 mm. • 9. Arrangement according to claim 5 »characterized in that that the dielectric intermediate layer (4) between the insoluble electrode (2) and the soluble electrode (3) consists of individual plates.