MEANS FOR ELECTROCHEMICAL TREATMENT OF WATER The present invention relates to a device for treating water, e. g. for use in connection with fish farfning, such as for hatching hard roe, for fish in cages, for slaughter of fish and for transport of fish. The device may also be employed in connection with other things than fish. The device comprises electrodes between which the water passes. The electrodes are made of a material with high specific resistance. The electrodes are supplied with pulsed direct or alternating voltage.

THE STATE OF THE ART A number of different systems are known for water treatment as well as for providing special favourable conditions, e. g. in connection with cultivation of plants or fish farming. These forms of water treatment, however, have either been too complicated and expensive or have not been sufficiently efficacious.

It is therefore an object of the invention to provide a simpler and better method and device for water treatment, which provide an alteration in the quality or composition of the water, thus having a positive effect in connection with the use of the water. This object is achieved by the features set forth in the patent claims.

The main feature of the device according to the invention is that a voltage is supplied by means of an electrode set, which may be designed it many different ways to suit the specific area of application. Broadly speaking, the electrodes are a conductive material, which may, for example, form a part of a cage. A semiconductor material may also be used as a conductor. The most expedient method is to arrange the voltage with the positive connection on the net of the actual cage and the negative connection is aitanged on a device in or on the outside of the cage.

The voltage may also be altered permanently or alternately in the opposite direction. A reversal of the current direction may also be employed in order to remove coating which has been deposited on the cage or the positive conductor as a result of the current flow.

When designing the system, a choice may be made between the following alternatives : 1. Fixed voltage or regular or irregular voltage pulses/sequence waves of current.

2. A combination of fixed low voltage (for example 2V) and stronger pulses (50V).

3. Voltages in the range 0.1 to 100 volts.

When applying a fixed voltage, it should be understood that this may either be permanently on, interrupted at regular or irregular intervals or combined with a pulsed current, The choice is made on the basis of the local conditions with regard to fouling, sea currents, etc.

The device according to the invention is especially intended for the following applications : 1. Preventing the growth of algae by being deposited on the nets in fish cages.

2. Use in safety nets round one or more cages, where one net is supplied with negative voltage and the other net with positive voltage. Safety nets are normally used to prevent fish escaping, or to prevent attack from outside by, for example, seals, sharks, etc.

3. Preventing the growth of algae on cables, rope and moorings. Fouling problems on moorings are a well-known problem, as is fouling on cables used in seismic surveys.

A PRESENTATION OF THE INVENTION AND A DESCRIPTION OF THE DRAWING FIGURES The invention will now be described in more detail with reference to drawings which illustrate embodiments of the invention and which are not limiting for the concept of the invention.

Fig. 1 is a connection diagram for the device.

Fig. 2 illustrates voltage measured between electrodes in sea water as a function of time.

Fig. 3 illustrates a vessel for hatching hard roe.

Fig. 4 illustrates the net in a fish fanning cage.

Fig. 5 illustrates a vessel for purification of water.

Fig. 6 illustrates a vessel for production of ice.

Fig. 1 depicts a connection diagram for a device for treating water where 1 is a transformer which is connected on the primary side to mains voltage, usually 230 volts. The secondary voltage can be regulated either step by step or

continuously to the desired voltage and supplied to a rectifier 2. A pulse former 3 may be supplied with direct voltage from rectifier 2 through a reverser 4, which is then connected to connection points 5. The pulse former 3 may also be supplied with alternating voltage and the reverser 4 is then connected to connection points 6. The pulse former 3 converts the direct voltage or alternating voltage to pulses, and the number of pulses per second can be regulated. Electrodes 8 are supplied with voltage from the pulse former 3 through connection points 7, The electrodes 8 are placed in water, usually sea water, and the number and dimensions of the electrodes are determined by the area of application The electrodes 8 are supplied with pulsed voltage. The voltage's amplitude can be regulated from 0. 1 volts up to the level which is permitted in the country where the device is to be used. According to"The Regulations for Electrical Installations", 48 volts direct voltage and alternating voltage are the highest voltage which are allowed to be used outdoors in Norway, Indoors, and e. g. closed, insulated containers, higher voltage can be employed. The device may be built in such a manner that, e. g. , it covers the voltage range from 0. 1 to 1000 volts.

The number of pulses per second supplied to the electrodes 8 may be regulated within wide limits, e. g. from 1 pulse per 24 hours to 1000 pulses per second.

Use is preferably made of from 0. 1 to 10 pulses per second.

The electrodes 8 are made of a material with high specific resistance and normally designed as filaments or bands with specific dimensions which are adapted to suit the area of application. The specific resistance in the electrodes may be in the range from 0. 01 to 100 Q cm, preferably in the range from 5 to 10 Sa cm. As electrode materials use may be made of so-called semiconductor materials which have a specific resistance in the range between good electrical conductors and the insulator. These include silicon carbide and carbon. Such semiconductor materials can also be produced from various organic materials to which conductive particles are added.

For use in fish farming there have been developed flexible electrodes of silicon caoutchouc to which are added electrically conductive particles such as carbon particles. As core filament in such electrodes use can be made of carbon fibre.

It has been found that by using electrodes with high specific resistance to which pulsed voltage is supplied, this combination provides a voltage between

the electrodes which has variable amplitude, in addition to which the voltage does not drop to 0 between each voltage pulse. This is one of the advantages of the invention.

Fig. 2 illustrates the voltage measured between electrodes in sea water as a function of time. Here the voltage is set at 48 volts direct voltage and the pulse frequency is set at 2 pulses per second. As the figure shows, a variable voltage is obtained between the electrodes, in addition to which the voltage does not drop to 0 between each pulse.

By means of the device, free ions are introduced into water passing between the electrodes. The variable voltage between the electrodes causes several different ions and combinations of ions to be easily formed in sea water, and a number of chemical substances are precipitated. On analysis of gas bubbles from sea water the following ions and substances have been found : hydroxyl ions, hypochlorite ions, oxygen, hydrogen, chlorine, ozone and hydrogen hyperoxide.

The combination of the electrode design to which pulsed voltage is supplied results in the formation of small, atomise gas bubbles in the water, thus ensuring rapid and efficient absorption of ions and substances in the water.

This is an advantage of the invention. The voltage supplied to the electrodes and the number of pulses per second determine the intensity of the gas development and which substances are preferably formed. This is a further advantage of the invention. When higher voltage is supplied to the electrodes, the development of chlorine gas, e. g., increases. The above-mentioned ions and substances have a disinfectant effect on the sea water and also have positive effects on the health of the fish over the entire cycle of aquaculture from roe, larva/yolk sac, fry, smolt, small fish, large fish.

Fig. 3 illustrates a container such as a vessel 1 for hatching roe from fish, shellfish, mussels and similar marine organisms. The vessel 1 has an inlet 2 for sea water 8 near the bottom of the vessel 1, and an outlet 3 near the top of the vessel 1. The bottom of the vessel 1 is covered by a thick layer of sand 4, and the roe 5 which have to be hatched are placed on the sand layer 4. Electrodes 6 are placed in the sand 4 and covered by a sand layer 4. Two or more electrodes 6 are placed side by side and the electrodes 6 are connected alternately to positive and negative voltage. Such electrodes 6 may preferably be attached to a frame 7, which is made of an electrically insulating material such as plastic.

The frame 7 is illustrated in a separate drawing and can be placed horizontally or vertically in the vessel 1. The spacing between the electrodes 6 may be from 5 to 100 mxn, preferably from 10 to 50 mm.

For hatching roe, the electrodes 6 are preferably supplied with pulsed direct voltage. Sea water 8 is pumped into the vessel I through the sand layer 4, and ions and substances which are formed in the sea water 8 when the electrodes 6 are supplied with pulsed direct voltage have a disinfectant effect on the sea water 8 and have a positive effect on the health of the fish. Fungal and bacterial growth in the water are prevented, thus improving the fertilisation and hatching of the eggs and reducing"failure"and malformation of the fry. In addition the oxygen content in the water will develop larger gills and larger lower taws even at the yolk sac stage. Larger gills are important for oxygen absorption of fry and fish and larger lower jaws are important for absorption of feed. These advantages cause the fish fry to grow more rapidly in sea water treated according to the invention and are one of the advantages of the invention.

Fig. 4 illustrates parts of the net 1 in a fish farm cage. To the net 1 are attached electrodes 2. The electrodes 2, which are flexible, can either be braided into the mesh of the net 1 or attached to the mesh in the net 1 in the known manner, and can be alternately connected to positive and negative voltage. In a preferred embodiment the electrodes 2, which are braided into the mesh of the net 1 or attached to the mesh in the net 1, are connected to positive voltage. An electrode 3, which is connected to negative voltage, is placed under the net 1.

This electrode 3 may, e. g., be in spiral form or folded so as to provide a sufficiently large surface, or it may be in the form of a wide band.

Ions and substances which are formed in the sea water when the electrodes 2,3 are supplied with pulsed voltage have a disinfectant effect on the sea water and in addition have a positive effect on the health of the fish in the cage, increasing their ability to thrive and prosper. The disinfectant water will prevent fouling of the net. In addition it will prevent the intrusion into the cage of poisonous algae, jellyfish chains, fungi and other organisms which are harmful to the fish. This is one of the advantages of the invention.

In a fish farm cage the electrodes will preferably be supplied with high voltage amplitudes. Experiments have shown that it is a combination of the electric field between the electrodes and the disinfectant effect of ions and substances

formed in the sea water which have the greatest bactericidal effect. Such bacteria will become attached to a net and fonn a slimy layer.

In growing vessels for smolt the water must be cleaned of feed remnants and faeces. In the same way, after slaughter of fish the water must be cleaned of blood and waste particles.

Fig. 5 illustrates a container such as a vessel 1 for purifying water 8. The vessel 1 has an inlet 2 for water near the bottom of the vessel 1 and an outlet 3 near the top of the vessel 1. In the bottom of the vessel 1 there is provided a channel 4, in which there is placed a sludge pump 5, which may be in the form of a screw. Two or more electrodes 6 are placed in the vessel 1, and the electrodes 6 are alternately connected to positive and negative voltage. The electrodes 6 may be laid along the bottom of the vessel or attached to a frame 7, which is made of an electrically insulating material such as plastic. A frame 7 with electrodes 6 is illustrated in fig. 3. One or more frames 7 may be placed either horizontally or vertically in the vessel 1.

When the electrodes 6 are supplied with pulsed voltage, ions and substances are formed in the water 8, thus providing a disinfectant effect and preventing the growth of bacteria and fungi. For deposition of particles in the water a silicide is added, e. g. a silicate such as sodium silicate. The device may be used for purifying and depositing particles in process water from the fishing industry where sea water is used for purification of process water from industry, agriculture and housekeeping where fresh water is employed. To fresh water are added salts such as sodium chloride or sea water in order to increase the conductivity and to form chlorine gas.

During transport of fish, the fish is cooled to a temperature near freezing point in order to increase the lasting quality of the fish flesh. As a coolant during transport ice is normally used. Experiments have shown that ice produced irom sea water in vessels where electrodes according to the invention are placed and where the electrodes are supplied with pulsed voltage, will absorb gases and substances which are formed in the sea water. Ice produced in this manner contains trapped gas bubbles and has a milky consistency. When such ice melts, it will emit the trapped gases.

Fig. 6 illustrates a container such as a vessel for production of ice according to the invention. The vessel 1 is equipped with one or more refrigerating/freezing elements 2, and is supplied with sea water 8 through inlet 3 placed near the

bottom of the vessel 1, and an outlet 4 may be located near the top of the vessel. Electrodes 5 are placed in the vessel I and supplied with pulsed voltage, Two or more electrodes 5 are placed side by side and the electrodes 5 are connected alternately to positive and negative voltage. In a preferred embodiment the electrodes 5 are attached to a frame 7, which is made of an electrically insulating material such as plastic, and which is illustrated in fig.

3. The cooling/ireezing elements 2 are designed in such a manner that the water is frozen into ice in blocks and the dimensions of the blocks can be adapted to suit the purpose. Sea water 8 is pumped into the vessel through inlet 3. When the sea water 8 passes between the electrodes 5, ions and substances will be formed as gas bubbles in the water. The gas bubbles will be trapped in the ice which is produced. This is an advantage of the invention.

In the same way as ions and substances formed in sea water treated according to the invention have a disinfectant effect on the sea water, experiments show that ice produced according to the invention also has a disinfectant effect.

When fish is refrigerated, such ice, in addition to cooling the fish, will also emit gases which provide a disinfectant effect, thus extending the lasting quality of the fish flesh. This is one of the advantages of the invention. By using ice produced according to the invention, experiments show that the amount of ice can be reduced substantially compared to the use of untreated ice. A reduction of 85% in weight of coolant can be achieved. This means a considerable reduction in the transport weight and provides major savings in freight costs.

Many modifications both with regard to type of voltage and design of electrodes are possible within the scope of the invention. With regard to the use of pulsed direct voltage, both voltage variations and intermittent voltage supply may be involved.