FI13238Y1 - System for eliminating waterborne pathogenic microbes from a hydroponic water system during the growing season - Google Patents

Abstract

1. A system for removing water-borne pathogenic microbes, such as Pythium and bacterial disease microbes, from the water system of a recirculating water culture during the growing season, in which the water passing through the pipelines is recycled in the system, which system includes a nutrient-rich recirculating water stream continuously circulating in the system, plants (140) cultivated in grower tubes (201), where the grower tubes ( 201) the circulating water stream is adapted to circulate around the roots of the plants (140), a collection pipe (131) which is adapted to collect the return water used for fertilizing the plants (140) into a single circulating water stream, which contains a significant amount of oxygen-consuming organic matter, especially biodegradable material, a storage tank (23) for the circulating water for temporary storage, a fertilizer and water mixing device (14) for mixing the fertilizer in the circulating water stream, and an ozone generator (12) for supplying ozone to the circulating water stream, characterized in that the system includes va the ozone generator (12) is adapted to raise the ozone concentration of the circulating water locally to a level that kills pathogenic microbes, and that the storage tank (23) and/or the fertilizer and water mixing device (14) are located in the direction of flow of the circulating water after the ozone generator (12) and before the growth tubes (201) adapted to create a delay to eliminate residual ozone . In addition, protection requirements 2-5.

Description

SYSTEM FOR REMOVING PATHOGENIC MICROBES CARRIED WITH WATER FROM THE WATER SYSTEM OF A CIRCULATING WATER CULTURE CULTURE-

DURING THE FLOWERING SEASON The subject of the invention is a system for removing water-borne pathogenic microbes, such as Pythium and bacterial disease microbes, from the water system of a circulating water culture during the growing season, in which the water in the pipelines is recycled in the system, which includes e a nutrient-rich circulating water stream that circulates continuously in the system, e plants cultivated in growing tubes, in which the circulation water flow is adapted to circulate around the roots of the plants in the grow pipes, e a collection pipe, which is adapted to collect the return water used for fertilizing the plants into one circulation water flow, which contains a considerable amount of oxygen-consuming organic matter, especially biodegradable material, e a storage tank for the temporary storage of the circulation water, e fertilizer and water mixing device for mixing the fertilizer in the circulation water stream, and N e ozone generator for supplying ozone to the circulation water stream.

Q - Modern circulating water cultivation, or hydroponics, developed from the research methods of soil and crop chemists, in which the D nutrients in water were tested in studies of plant nutrients.

S 30 The first hydroponics experiments used in Finland at the practical N level were done with greenhouse cucumbers in the 1980s. This circulating water cultivation technique was applied almost identically to potted lettuce cultivation and to the irrigation of potted plants on the tables, as north-west irrigation.

Common to these cultivations is a large fravinne water tank, into which, as needed, more nutrient water is pumped as plant-specific fertilization according to the water consumption of the plants.

In pot lettuce cultivation, the seedlings grow in narrow gutters about 15 cm apart.

At the bottom of the gutters, either continuously or intermittently pumped into the circulation, the nutrient solution flows, which partially returns back to the nutrient tank.

In Vuoksiluode cultivation, the potted plants growing on the cultivation table are watered by pumping the nutrient solution in the tank onto the tables, the unused part of which is returned to the tank after about 10-15 minutes.

This cultivation technique works flawlessly as long as root-destroying pathogens have not gotten lost in the water.

Pathogens enter the water as contamination caused by basic work or with dirty raw water.

Raw water that is especially susceptible to disease is surface water taken from nature near fields in the summer.

In practice, the appearance of diseases occurs 3-12 months after the establishment of a new plantation.

By far the most important microbes that cause root diseases are Pythium fungi, which cause yield and quality losses of 20-50%, especially in warm N summers. Even losses of over 70% are very common in O 25.

Close relatives of Pythium fungi, Phytopthora fungi, are also very common in the southernmost countries. > In Scandinavia, the occurrence of these fungi in greenhouses is = random.

In Finland, since the 1980s, research into diseases caused by the Pythium fungus has been led by prof.

Risto Tahvonen S 30 with sugar beet in seedling burning studies, in the development of biological N plant protection, in peat and moss growing medium 5 studies and in the last 6 years in ozone studies at the University of Helsinki and since 1983 at the Earth and Food Economy Research Center (MTT) and the current

In the Natural Resources Center (LUKE). In this long chain of research, a lot of published information has been created, but also a lot of so-called gray information, on the basis of which it was possible to successfully develop a new system for keeping the waters of recirculation farms clean of Pythium disease.

Swarm spores of the Pythium fungus swimming in the water attack the roots of salads and herbs grown in circulating aquaculture.

Mycelium of the fungus develops in the root hairs to constantly produce new swarmers, and the roots are badly damaged, which means that crop losses are very high, especially in warm summer times.

The sand and stone wool slow filters used in cultivation reduce solids from the water, but in addition to bacteria, swarmers of Pythium fungi of the same size pass through them.

Continuous control of swarm spores requires continuous disinfection of the circulating water.

Chemical substances cannot be used in circulating water systems.

The use of ozone dissolved in water in the disinfection of circulating water is known as a state of the art.

Ozone is a highly effective naturally occurring oxidizer.

However, the unicellular root hairs at the tip of the root are as sensitive to ozone water as the bacteria, so a momentary loss of root hairs reduces the AN yield.

As a continuous dose, ozone would practically destroy at least the plants at the beginning of the O 25 growing channel. 3 2 Patent publication JP 2002191244 A is known as the state of the art. = The publication presents the use of concentrated ozone fed into water, made of pure oxygen, 3 to disinfect circulating water and pipelines.

In the publication, the plant growth tubes are emptied of N circulating water before treatment with ozonated water.

Ozone-rich raw water is fed into the growing tubes for the plant roots.

Circulating water is collected in a storage tank, to which ozone-rich raw water is fed as a separate step.

The problem is the destruction of the plants' sensitive roots in the ozone treatment. In state-of-the-art solutions, the yield is lost because the roots of the plants cannot withstand treatment with ozonated water.

In some state-of-the-art solutions, the problem is also that a very high ozone concentration must be fed into the return water for a long time in order to effectively destroy pathogens. The use of a high ozone concentration involves a considerable risk of occupational safety. At the same time, valuable fertilizers are also destroyed from the circulating water, which also leads to calcification of the pipes.

The purpose of the invention is to create a new system for destroying disease-causing microbes from the circulating water flow of aquaculture during the growing season in a safe manner for the plants, the system, the farmer and the environment. The characteristic features of this invention can be seen in the attached protective claim 1.

The system according to the invention for removing pathogenic microbes that travel with water, such as Pythium and bacterial disease N microbes, from the water system of circulating water culture O 25 during the cultivation season, where the water passing through the pipelines x in the system is recycled, includes in the system > a continuously circulating, nutrient-rich circulating water flow, in the growing pipes = cultivated plants in which in the growing pipes, the circulating water stream is 3 adapted to circulate around the roots of the plants, a collection pipe, which is S 30 adapted to collect the N return water used for fertilizing the plants into one circulating water stream, which contains a considerable amount of 5 oxygen-consuming organic matter, especially biodegradable material, a storage tank for the temporary storage of circulating water, a mixing device for fertilizer and water for mixing the fertilizer in the circulating water stream, and an ozone generator for supplying ozone to the circulating water stream. The ozone generator included in the system is adapted to raise the ozone concentration of the circulating water locally to a level that kills 5 pathogenic microbes. The storage tank and/or the fertilizer and water mixing device are located in the flow direction of the circulation water after the ozone generator and before the growth tubes, adapted to create a delay to eliminate residual ozone.

In this way, the ozone-sensitive roots of plants cultivated in hydroponics are not damaged by the continuous disinfection of circulating water during cultivation, but pathogens in the circulating water can be effectively destroyed.

Preferably, the ozone generator is adapted to maintain an ozone concentration of 100-500 ppb, most preferably 150-350 ppb in the circulation water flow at the point of the water system where the circulation water flow at an average flow rate lasts 15-600 s from the ozone supply point. In this way, sufficient time can be arranged for the ozone to act in the circulating water stream. Ozone treatment can N be carried out in its entirety in the water system's pipeline or O 25 partly in tanks that are part of the pipeline, or completely x in a separate tank. Preferably, a sufficient > processing time is arranged, during which ozone is allowed to act in the circulating water. = The killing effect of ozone on pathogenic microbes is 3 immediate, but a sufficient duration of action ensures that the entire circulating water flow can be treated with ozone S 30.

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S > Advantageously, the system includes a filter that lowers the concentration of organic matter in the circulating water, which is adapted to create a filtered circulating water stream that contains a fraction, 0-40%,

preferably 0-20% of oxygen-consuming organic matter compared to the unfiltered circulating water flow and pathogenic microbes carried along with the water, and the ozone generator is located in the direction of the circulating water flow after the filter and before the breeding tubes.

The percentages described here refer to mass percentages.

It has surprisingly been found that the most sensitive organisms are damaged even by a very low ozone concentration of 100 ppb.

Thanks to the filtration, a surprisingly low ozone concentration can be used, thus avoiding the adverse effects caused by a high ozone concentration, such as jeopardizing work safety and clogging of pipes, as well as the loss of valuable fertilizer from the circulating water.

By using a small, but lethal to pathogenic microbes, ozone concentration, it is also possible to reduce the ozone concentration of the circulating water to a safe level for the plants before directing the circulating water to the roots of the plants.

If the ozone content of the circulating water were to be raised to a high level, valuable fertilizers such as calcium and magnesium would be lost from the circulating water.

Thanks to the invention, the fertilizers in the circulating water are not needlessly destroyed, but the harmful pathogenic microbes can be destroyed with a carefully selected N ozone concentration.

At the same time, calcification of pipelines caused by excessive ozone O 25 supply is avoided. 3 2 Ozone also does not end up in the possible = filter of the water system, which may have its own beneficial bacteria strain. 3 The system according to the invention therefore does not destroy this beneficial bacterial strain of the filter S 30. > The filter is preferably a slow filter.

In this case, circulating water can be more effectively cleaned of pathogenic microbes by filtration and ozone treatment as a whole.

Advantageously, the system comprises a three-way valve, with which circulating water can be led in the system alternatively to circulate from the ozone generator to the roots of the plants or back to the ozone generator via a pipe. In this way, a lower ozone concentration can be used by increasing the treatment time with more ozone treatments. On the other hand, if the circulating water is poorly filtered, for example using a sand filter, or is completely unfiltered, the circulating water can be circulated through the ozone generator more than once before being led back to the roots of the plants, in which case the circulating water can be effectively cleaned by ozone treatment. Preferably, the system includes at least one ozone concentration sensor that measures the ozone concentration of the circulation water at the point in the water system where the flow of circulation water at an average flow rate lasts 15-600 s from the ozone supply point. In this way, maintenance of the selected ozone level in the circulating water flow can be ensured. Alternatively, sufficient ozone concentration can be determined by calculation and verified by calibration measurements. Advantageously, the system includes a delay tank to increase the effect time of ozone in the circulating water. In this way, disease-causing O 25 microbes can be more effectively destroyed from the water system.

Q = Preferably, the supply pipe used for ozone supply is connected to 3 circulating water pipes. By feeding ozone into the circulating water pipe S 30 instead of the storage tank, the ozone treatment can be made more efficient, N because ozone mixes better with the circulating water. 5 The system according to the invention can be used to implement a method of water-borne pathogenic microbes,

such as Pythium and bacterial disease microbes, from the water system of the recirculation culture during the growing season, in which the method for fertilizing plant roots uses a continuously circulating, nutrient-rich recirculating water stream containing nutrients in a soluble form, the return water used for fertilizing the plants is collected in a single recirculating water stream, which contains a significant amount of oxygen-consuming organic matter, especially biodegradable material, and pathogenic microbes are destroyed from the circulating water stream by ozone treatment, where the ozone concentration of the circulating water is raised to a selected level. The continuously circulating circulating water stream is filtered with a filter that lowers the concentration of organic matter in the circulating water, creating a filtered circulating water stream that contains a fraction, 0-40%, preferably 0-20%, of organic matter that consumes oxygen compared to the unfiltered circulating water stream, and waterborne pathogens- and microbes. The circulating water stream is treated locally after filtration and before it is led to the roots of the plants with ozone water by increasing the ozone concentration of the circulating water to an ozone concentration that kills pathogenic microbes, and the ozone is allowed to act in the circulating water for a selected time so that the ozone concentration of the circulating water stream is 100-500 ppb, preferably 150-350 ppb in the water system point where the circulation water flow N at an average flow rate takes 15-600 s from the ozone O 25 supply point. The circulating water is fertilized to raise the fravinne concentration x to the selected level before the circulating water > is directed to the roots of the plants. The ozone concentration of the circulating water stream is calculated = in the range 0-80 ppb, preferably 0-30 ppb before it is fed to the 3 plant roots. S 30

N N Advantageously, before the circulating water is directed to the roots of the plants, the circulating water stream containing 5 ozone is collected in the main storage tank, where the ozone concentration decreases. In this way, the ozone concentration of the circulating water can be lowered to a safe level for plants. In a storage tank typical of modern farms, the water is stored for at least two hours, during which the ozone is largely broken down into oxygen during this delay.

Advantageously, in the storage tank, the ozone concentration of the circulating water drops to the range of 50-100 ppb, when the circulating water is led from the storage tank to the fertilizer and water mixing device before the circulating water is led to the roots of the plants. The ozone concentration of circulating water can also drop below 50 ppb in the storage tank.

Preferably, before the circulating water is fed to the roots of the plants, the circulating water stream containing ozone is fed to the fertilizer and water mixing device, where the pH of the circulating water stream rises, causing the ozone to break down and the ozone reacts with the fertilizer, whereby the ozone content of the circulating water fed to the plant roots decreases. In this way, the ozone content of the circulating water can be lowered to a safe level for the plants before the circulating water is directed to the roots of the plants.

Preferably, in the fertilizer and water mixing device, the ozone concentration of the circulating water drops to the range of 0-80 ppb, most preferably 0-30 ppb.

N Preferably, the ozonated circulation water is led to the storage tank O 25 before the circulation water is led to the fertilizer and water mixing device. In this case, the ozone concentration first decreases in the storage > tank, after which the remaining ozone breaks down in the fertilizer and water mixing device.

5 S 30 Preferably, the ozone consumption of circulating water without filtration would be N 3-20 times compared to the ozone 5 consumption of filtered circulating water. By filtering most of the organic matter from the circulating water, the amount of ozone needed is considerably reduced.

Preferably, a delay tank is used to increase the effect time of ozone in the circulating water, providing an ozone treatment time of 120-600 seconds at the specified minimum ozone concentration.

In this way, disease-causing microbes can be effectively destroyed, when the exposure time of ozone in the circulating water is increased.

Preferably, ozone is fed into the circulating water in gaseous form as a mixture of dry air, forming a bubble mixture in which ozone dissolves into the circulating water during a selected delay, killing pathogenic microbes.

In this case, the ozone concentration of the circulating water will never rise to a harmfully high level.

Supplying ozone in gaseous form creates bubbles in the circulating water, from which the ozone slowly dissolves into the circulating water, so that the ozone content of the circulating water can be kept in the closed part of the water system for a longer time at a level that kills pathogenic microbes.

Ozone can be fed into the circulating water at 1 to 15 g/1000 1, preferably 2 to 7 g/1000 1 of circulating water.

In this way, the ozone concentration of the circulating water is locally high enough to destroy disease-causing microbes, but the ozone concentration does not become harmfully high.

AN Of the supplied ozone, 1-25%, preferably 2-15% can remain O 25 in the circulating water in gaseous form as bubbles.

The storage tank has x free liquid surface, so the remaining bubbles in the circulating water > evaporate into the surrounding air in the storage tank. x a < Preferably, the mixture of gaseous ozone and air is fed into S 30 circulating water, the pressure of which is 0.5-5 bar, preferably 0.8-2 bar.

N In this way, the dissolution of ozone into the circulation water can be improved, 5 whereby the ozone concentration of the circulation water can be raised to a higher level without the need to increase the ozone concentration of the supply air.

Preferably, the circulating water flow is lowered into the storage tank with a small back pressure from the pipe coming into the storage tank so that the pressure difference between the water in the storage tank and the water in the pipe is 0.05-0.5 bar, preferably 0.1-0.2 bar. Due to the placement of the pipe entering the storage tank, the liquid column in the storage tank produces counter pressure, thanks to which the ozone is not wasted, but the ozone fed into the circulating water is effectively used to destroy disease-causing microbes. Preferably, the ozone concentration of the circulating water is monitored with an ozone concentration sensor and the supply of ozone to the circulating water is adjusted based on the reading of the ozone concentration sensor in order to achieve the selected ozone concentration. In this way, the ozone concentration of the circulating water can be kept at a continuously selected level. The ozone content of the circulating water can also be monitored at regular intervals. In this case, continuous measurement is not needed, but the ozone generator is calibrated upon commissioning, so that check measurements can be made at regular intervals in the future. Alternatively, the amount of ozone fed into the circulation water can also be determined by calculation.

N S 25 Advantageously, frac water is added to the circulating water flow according to plants x water use. In this way, it can be ensured that > the cultivated plants get enough water. x a < Preferably, the filtered circulating water is treated with ozone water S 30 at least twice before directing the circulating water to the N roots of the plants. In this way, a lower ozone concentration can be used by increasing the treatment time with more ozone treatments. On the other hand, if the circulating water is poorly filtered, for example by using a sand filter, the circulating water can be circulated through the ozone generator more than once before being led back to the roots of the plants, in which case the circulating water can be effectively cleaned by ozone treatment.

Preferably, the filter that can be used for circulating water filtration is a slow filter. In this case, the circulating water can be efficiently cleaned by filtration, in which case the need for ozonation is lower, which means that a lower ozone concentration can be used. In this case, circulating water can be more effectively cleaned of disease-causing microbes by filtration and ozone treatment as a whole.

Preferably, ozone is fed into the circulating water with a supply pipe connected to the circulating water pipe. By feeding ozone into the circulating water pipe instead of the storage tank, the ozone treatment can be made more efficient, because the ozone mixes better with the circulating water.

The invention is described in detail in the following by referring to the accompanying drawings illustrating some applications of the invention, where Figure 1 shows a principle drawing of a system according to the invention for cleaning circulating water, S 25 Figure 2 shows a principle drawing of another x system according to the invention for cleaning circulating water, = Figure 3 shows a principle drawing of a third 3 for cleaning the circulation waters S 30 of the system according to the invention, N Figure 4 schematically shows the steps of a method implemented with a system according to the invention.

Figure 1 shows a technical solution according to the invention for disinfecting recycled water for aquaculture, where the Pythium mushroom swarm spores that travel with the water, i.e. zoospores, and other harmful microbes are killed from the ozone-treated water during the growing season, so that there is no longer a harmful amount of ozone in the water that travels back to the roots of the plants 140 140 for the hair roots at the tips of the roots.

At the same time, the water in the water cycle is supplemented with raw water, fertilizers and acidity control according to the needs of the cultivated plants 140.

In the application form shown in Figure 1, the plants 140 are cultivated using a hydroponics method, in which the fertilizing irrigation water of the plants 140 is recycled.

Plants 140 are grown in cultivation troughs, i.e. growing tubes 201 or other similar growing containers.

The growing tubes 201 have holes 202 for the plants 140.

Figure 1 shows as a simple principle drawing only one growth pipe 201 illustrating the invention, which is slightly tilted relative to the horizontal plane, so that the water flows in the growth pipe 201 by gravity.

In reality, there can be a large number of growing tubes 201 distributed in one or more greenhouses or in the open air.

The flow pipe 114 and the return pipe 115, shown with a dashed line in Figure 1, illustrate that the pipeline can at this point branch off, for example, into different greenhouses.

O 25 The roots of the plants 140 can be in the growing tubes 201 in soil or x other medium or in free flowing water.

It is clear > that in such a growing system the pathogens present in the roots of the plants 140 can spread with the recycled water 3 from one plant 140 to another and from the plants 140 the disease-causing microbes spread into the system's pipelines.

I The water returning from the breeding pipes 201 is collected in the collection pipe 131 and in the common collection tank 24, which can have a volume of, for example, 1000-2000 1. The collection tank 24 can be larger,

to be sized according to the amount of irrigation water. When there is enough of this return water, the water is transferred through the filter 133, which can be, for example, a slow filter or a sand filter, into the used water tank 25 of a similar size. The water in the used water tank 25 no longer contains a lot of ozone-consuming organic solids, because the solids have remained at least mostly in the filter 133.

A sand filter is a simple mechanical device for removing solid matter from circulating water. The sand filter comprises a sand mattress, the grain size of which can be selected according to the application. Circulating water is led through a sand mattress, whereupon solid matter that consumes oxygen and ozone is filtered out of it.

A slow filter, or biofilter, comprises a growth medium, for example rock wool, on which a bacterial membrane is grown. Circulating water is led through a large-surface hbacterial membrane, whereby the bacteria remove organic oxygen-consuming substances from the water. The slow filter also removes disease-causing microbes from the circulating water, but it is not enough on its own to completely clean the circulating water, in which case ozone treatment is also needed.

N The filter 133 can also be omitted completely, in which case significantly more ozone O 25 must be fed into the circulation water compared to the filtered x circulation water, or the > feedback according to figures 2 and 3 must be used in order to clean the circulation water E efficiently.

5 S 30 In the next intermediate tank 22 in the flow direction, N used recycled water and new raw water to be added to the system, which is fed into the intermediate tank 22 through pipe 51, are mixed. This mixture also ensures the disinfection of new raw water, especially when the frac water source is a disease-susceptible surface water source such as lake and river water. If it is not necessary to clean the raw water, the raw water can also be fed directly to the storage tank 23 through the pipe 52. The mixture of recycled and raw water is pumped into the ozone generator 12.

In the ozone generator, i.e. ozonator 12, ozone is supplied to the circulation water in the simplest way by a supply pipe 121 connected to the circulation water pipe, from which gaseous, ozone-rich air is supplied to the circulation water. The ozone generator 12 can be used, for example, by Prominent Gmbh (DE) model Ozonfilt OZVb 2A together with a separate compressor. In the ozone generator 12, ozone is produced from dry compressed air by corona discharge. Compressed air drying is important and therefore the device contains an air dryer, preferably an absorption dryer. Humid air leads to the creation of nitric acid, which is something we try to avoid. Ozone gas made from air is mixed with water, so that part of the ozone dissolves in the water and some gets into the water as insoluble small bubbles. In this system, the amount of ozone fed into the circulation water per unit of time and volume of circulation water can be precisely determined, so the ozonation of the circulation water is controlled. However, continuous measurement of ozonation is not necessary, as the continuous effectiveness of ozonation remains the same without daily/weekly/monthly maintenance.

N S 25 The ozonator 12 is supplied with dry compressed air at a pressure of about 5-6 bar x. The circulating water pressure in the ozonator 12 is 0.5—5 bar, > preferably 0.8—2 bar, in which case the ozone is absorbed into the circulating water = well. The pressure 3 of the ozone-rich air supplied to the circulating water is set slightly higher than the pressure of the circulating water. The pressure of the circulating water S 30 can vary as long as it remains within the permitted N limits, the pressure of the ozonated air can be adjusted according to the pressure of the circulating water S. If the pressure of the circulating water drops too much, the ozonator 12 is adapted to switch off automatically, because otherwise there would be a danger of blowing really concentrated ozonated air into the unpressurized pipeline. If the pressure of the circulating water becomes too high, or the pressure of the supplied compressed air drops below the pressure of the circulating water, the ozonator 12 is also adapted to shut down and close all its internal valves. This ensures that the circulation water does not under any circumstances flow into the ozone-rich air supply pipe 121. In another application form, ozone is first fed into the raw water and highly ozone-rich raw water is fed into the circulation water, which raises the ozone concentration of the circulation water to a locally selected level. In this way, however, there is a risk that the ozone concentration of the circulating water will temporarily rise to a very high level, in which case valuable nutrients will be lost and there is a risk of calcification of the pipes.

Alternatively, the ozone fed into the circulating water can also be produced electrolytically from water in such a way that the water molecule is broken down by an electrolytic cell into elements that form oxygen and ozone molecules.

Ultraviolet radiation is poorly suited for ozone production in this system. In this case, the ozone concentration fed into the circulating water cannot be determined, in which case ozonation is not controlled. N On the other hand, ozone production is also not sufficient for effective O 25 disinfection of circulating water. The problem with the source of ultra-x violet radiation immersed in the circulating water is the turbidity of the circulating water, which > prevents the propagation of ultraviolet radiation. In this case, the source of ultraviolet radiation E must also be constantly maintained by cleaning. 5 S 30 In the direction of flow, the circulating water moves from the ozonator 12 to the storage tank 23 of des-N-infused water, which is dimensioned in such a way that the amount of water in the storage tank 23 is sufficient for the culture's water needs even at maximum consumption for about 4 hours. Between the ozonator 12 and the storage tank 23, the ozone concentration of the circulating water is kept at a level that kills pathogenic microbes. When the circulating water stagnates in the storage tank 23, the rest of the ozone reacts with the fertilizers and humus substances in the water. In this tank, the ozone concentration drops to <100 ppb. This water is further transferred in the direction of flow via the fertilizer and water mixing device 14 back to the growing tubes 201 for the roots of the plants 140. Finally, in the fertilizer and water mixing device 14, the remaining ozone has broken down into oxygen. When fertilized ozone water had stood in the pure water nutrient test for more than 2 hours, the ozone concentration was <10 ppb.

The purified, nutrient-rich circulation water is lowered back to the roots of the plants 140 in such a way that the water is lowered into the growing pipes 201 from the nozzle 141, which is free in the air. In this case, the ozone concentration of the circulating water will surely drop to a safe level of 140 for plants at the latest at this stage as the circulating water passes through the air.

In this application form, there is a small delay tank 26 between the ozonator 12 and the storage tank 23 to increase the processing time of the circulation water disinfection. The delay tank 26 is a small tank with a volume of about 200 1, where the delay time of the circulation water is N 1-10 minutes. The circulating water is in the delay tank 26 at the same O 25 pressure as in the pipeline between the ozonator 12 and the storage tank 23 x. In the storage tank 23, the air and ozone bubbles remaining in gaseous form in the water are removed from the circulation water through the free = liquid surface. The circulation water outlet pipe 3 112 of the storage tank 23 is at the bottom of the tank or near the bottom, so the weight of the liquid in the tank S 30 creates a small pressure in the outlet pipe.

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S > The ozone concentration of the circulating water is measured with the ozone concentration sensor 36 at a selected distance from the supply point, i.e. the ozonator 12. The ozone concentration sensor 36 is placed in the pipeline in such a way that at the average flow rate, the flow of circulating water from the ozonator 12 to the measurement point of the ozone concentration sensor 36 takes 15-600 seconds. However, the ozone concentration sensor 36 is always placed upstream of the storage tank 23.

The ozone concentration sensor 36 is connected to the control unit 30, which controls the production and addition of ozone to the circulating water. The ozone concentration of the water measured with the ozone concentration sensor 36 is fixed at the measurement point to, for example, a value of 300 ppb.

The electrochemical ProMinent DULCOTEST ozone sensor (0ZE 3-mA-2 ppm), whose measurement range is 0.02-2.0 mg/l, can be used for real-time measurement of the ozone concentration in circulating water. To analyze the ozone content of the ozone water sample and calibrate the electrochemical sensor, you can use, for example, ProMinent's photometer (DT1B), which has a measurement range of 0.03-4.0 mg/l.

This ozonation system can be used as a common system for several greenhouses, whereby the water from different greenhouses is returned to ozonation through tank 24, but the disinfected water storage tank 23 is correspondingly larger. In this N example case, the size of the storage tank 23 is 10 m3.

S 25 x The described system (picture 1) is also suitable for complete disinfection of the pipelines of the entire water recycling > system, when there is a stoppage in the cultivation of plants 140 =. In full disinfection, the old water used in the entire system is removed and filled with S 30 unfertilized raw water and the filter 133 is bypassed.

N In full disinfection, raw water is recycled and at the same time it is ozonated at maximum power until the ozone concentration of the water circulating in the system rises to 300-500 ppb. Full disinfection of the water recycling system's pipelines is carried out inexpensively

before the introduction of the system according to the invention in the continuous cleaning of the circulating water stream during the cultivation season.

In the second application shown in Figure 2, the ozonated water is led to be diluted in the storage tank 23 before the fertilization performed with the fertilizer and water mixing device 14. In the third application form shown in Figure 3, the ozonated circulating water is first led to the fertilizer and water mixing device 14 for fertilization and only then to the storage tank

23. With both arrangements (pictures 2 and 3), the result is the same, i.e. the ozone concentration of the circulating water drops sufficiently before it reaches the culture, i.e. the growing tubes 201.

In Figures 2 and 3, the ozone content of the circulating water can be increased by recirculating the ozonated circulating water through the three-way valve 124 and along the pipe 125 back to the intermediate tank 22. This is especially necessary when the temperature of the circulating water rises, when the solubility potential of ozone deteriorates. The circulating water can also be cooled before the circulating water is led to the ozone generator 12, in which case the solubility of ozone in the circulating water can be improved.

N S 25 Feedback via pipe 125 back to intermediate tank 22 and x again to ozone generator 12 is necessary especially > for example when filter 133 is a sand filter or when = the system does not include filter 133 at all. Sand filter does not 3 clean organic substances from circulating water as effectively as S 30 slow filter, thus increasing the need for ozonation. Without the filter N 133, there is a lot of organic matter in the circulating water, so the need for ozonation increases significantly. With the feedback according to the invention, the circulation water can be circulated several times through the ozone generator 12, in which case a longer processing time is effectively achieved by multiple ozonation of the circulation water, so that a lower ozone concentration can be used. In this case, the pathogens in the circulating water can be destroyed very effectively with a low, controlled and safe amount of ozone. In some cases, it may be impossible to completely clean the circulating water of pathogens in one treatment without feedback, if the filter 133 is, for example, a sand filter or if the filter 133 is completely absent, because the ozone content of the circulating water cannot be raised to a sufficiently high level without feedback through the pipe 125. Circulating water is also directed from the valve 124 to circulate back to the intermediate tank 22 in a situation where the storage tank 23 is full. In this case, circulating water can be continuously circulated through the ozone generator 12, and when water from the storage tank 23 starts to be used again, purified water can be immediately lowered from the pipeline through the pipe 111 into the storage tank 23. Without feedback via pipe 125 (in the application form of Figure 1), when the storage tank 23 is full, the pumping and the ozone generator 12 is turned off. In this case, when the storage tank 23 starts to be filled again, there is a risk that there are pathogens in the stagnant water in the pipe 111. Thanks to the feedback, the circulating water can be N circulated continuously through the ozone generator 12, whose energy O 25 consumption is very small, less than 1 kW, so that the circulating water x does not have to stand in the pipeline, which is a risk in terms of the increase of disease carriers. x a < Also in the application forms of figures 2 and 3, the water tank 26 can be used, although it is not marked N in the respective figures for the sake of simplification.

N >”

Figure 4 schematically shows one step-by-step application form of the method implemented with the system according to the invention.

The return water used for fertilizing the plants 140 is collected in the same circulating water flow, step 61. The collected circulating water is directed through a possible filter 133, where fungal bands and solid matter that consumes a lot of ozone are removed from the circulating water. Nutrients, dissolved organic compounds, bacteria and fungal swarm spores remain in the circulating water, step 62. The circulating water is then collected in a possible intermediate tank 22, step 63. Raw water is added to the circulating water in the intermediate tank, step

81.

The circulating water is then directed through the ozonator 12, where the ozone concentration of the circulating water is raised to the selected level, step

64. Ozone-rich air is produced from dry air, step 82. This ozone-rich air is fed to the circulating water. Some of the ozone dissolves in the water, some remains in the water as bubbles, step 83.

Ozone is allowed to act in the circulating water for the selected delay time. Advantageously, a delay tank 26 is used to increase the exposure time of the ozone, step 65.

N S 25 Optionally, after the ozonator 12 x, the circulating water can be recirculated back to the possible intermediate tank 22 and directed > again through the ozonator 12, in which case the circulating water can = be treated several times with ozone before being directed back to the roots 3 of the plants 140, step 91.

: 30 N The circulating water is directed to the storage tank 23, where the ozone concentration 5 decreases. At the same time, gaseous air and ozone are released from the circulating water and exit through the free liquid surface into the surrounding air, step 66. The circulating water is directed to the fertilizer and water mixing device 14, where the ozone concentration drops to a safe level for the plants at the latest, step 67. Steps 66 and 67 can also be in the opposite order.

Ozone-free or very low ozone-containing, fertilizer-rich and pathogenic microbe-free water is directed to the 140 roots of the plants, step 68. After this, the return water is collected back into the same circulating water stream, returning to step 61. Epidemiology of the Pythium fungus in circulating water culture Pythium spp. in the vegetative growth phase, it forms multi-nucleated, partitionless mycelia with very weakly structured colonies, which are released immediately when the colony breaks - ciliated swarming spores that resemble the sperm of the animal kingdom.

These units, called zoospores, can move and survive for a few days only with water.

Swarmers infect plant root hairs, which are always present at the tip of the root.

Already in this place, the new production of swarmers begins, while the fungal mycelium penetrates the thicker parts of the root.

The destruction of the plant cell takes place immediately in the spreading zone enzymatically, which is visible to the naked eye as vitrification of the plant cell.

The growth of the fungus is very fast and aggressive.

N For example, with cucumber, the death of cricket seedlings from seedling blight O 25 occurs within 3 days of infection.

In the laboratory, the fungus x grows to fill the PDA substrate of a 9 cm petri dish in 1 day. > Contamination from one gutter in pot lettuce cultivation = spreads to all gutters during 4 weeks of cultivation, if there is no slow filter in connection with water 3 recycling.

Slow filters - S 30 time have a 60 cm layer of stone wool, where aerobic water N circulates all the time.

In 3-4 months, S aerobic bacteria form in stone wool, which destroys more than 95% of swarmers moving in water.

However, this does not always provide sufficient protection from the disease, as the pathogen remains infectious among the humus and organic waste stuck to the inner surfaces of pipes and cultivation troughs, from which small numbers of swarmers are constantly released. Inside the vitrified cell of plants, thick-shelled oospores can also be born asexually, which allow the fungus to survive in rotten and dried plant parts for up to 3-4 years, and for Phyopthoara fungi up to more than 10 years. When the egg hatches, swarmers are released from it again.

Pythium spp. and Phytopthora spp. seedling blight and root rot diseases Pathogens like Pythium fungi are all terrestrial diseases that cause seedling blight and root rot. Fungal mycelium can live and survive in the soil also as a saprophyte in organic matter. The species found in greenhouses, Pythium ultimum, hardly ever forms a congeneric oospore like P. de'baruanum, commonly found in field cultivation. Pythium disease is currently the most significant root disease in greenhouses, especially for cucumbers and lettuce and herbs.

The most common Phytopthora disease is P. cactorum root rot on strawberries, which is transmitted to the field in infected seedlings. Infection can only occur in dirty breeding facilities.

N S 25 Pythium fungus is very sensitive to ozone water both as mycelia x and as swarmers. Ozone cannot > be effective on already diseased plants, because the fungus is protected inside the plant. Even the roots = the surrounding growing medium prevents the fully effective use of ozone. 3 Due to the above, control and limitation of the Pythium disease S 30 is based on clean growing media, clean bio-filtered N irrigation water, disinfection of irrigation pipes, irrigation gutters and drainage pipes. Traditionally, these disinfection measures have always been carried out between growing seasons, when the greenhouse has been disinfected from the inside and the irrigation system flushed with nitrogen

polla and disinfectants almost without exception with poor success.

Since the Pythium fungus is very sensitive to ozonated water, the use of ozone is a very quick and effective measure for shaking empty farms.

In addition, the advantage over other disinfection measures is the ease, safety and speed of processing.

For the treatment of dry, basic cleaned premises, it is sufficient to irrigate the cultivated areas with ozonated water.

Likewise, flushing irrigation systems with ozone so that the water coming from the upper end of the pipes has more ozone than the lowest ozone concentration required for disinfection of fungal diseases, about 300-500 ppb.

The use of ozone to clean irrigation pipes is also possible during the growing season, because when ozone comes into contact with the organic mass of the growing medium or rockwool, it immediately breaks down into oxygen molecules or reacts directly with the growing medium into a harmless oxide.

The use of ozone water in the cleaning of empty spaces is an ideal solution because, compared to other disinfectants, no toxic residues can be created and the cultivation spaces can be used even on the same day, because the ozone has broken down after 2 hours at the latest below the threshold of sensitive root hairs.

N Cleaning of the fertilization and irrigation system from disease-carriers O 25 is always done at the time of plant change 3 by running concentrated ozone water 2 into the pipelines and drip pipes 2 for 15-30 minutes.

If, during the growing season, it is suspected that Pythium fungus has entered the fertilization water, the irrigation fertilization is interrupted for 3 minutes and ozone water is introduced into the pipeline for approx. 15 minutes.

S 30 Ozone water may go from the nozzles to the growing medium.

After this, N can immediately resume normal watering programs.

The cleaning of the pipes used for over-irrigation 5 water circulation is done by feeding ozone water into the pipes until clean water with sufficient ozone content comes out of the top end of the pipe.

In recirculating lettuce cultivation, the basic problem in terms of the spread of disease is the ozonation of the constantly circulating water. Plant roots secrete energy-rich root secretions into their environment, which maintain beneficial saprophyte bacteria and fungi growing in the root zones, which significantly protect plant roots from real diseases. At the same time, these materials also protect plant roots from moderate ozone concentrations. In terms of the plant's nutrient intake, the most important part of the roots are the root hairs that constantly appear at the tip, which use a lot of energy to "pump" ionized nutrients from the fertilizer water into the more concentrated growth cell. When concentrated ozone water was poured into the upper end of the lettuce trough once a week, the lettuce yield was reduced by 6-7% in the first 4 seedlings.

At one and a half meters from the upper end of the gutter, the ozone concentration had dropped to one-tenth, and at 3 meters the concentration was already zero. This simple test showed that lettuce roots decomposed the concentrated ozone in 10-20 seconds, but the destruction of bare root hairs as little as once a week reduced the yield. In practice, this means that continuous ozonation of the roots at concentrations that are certainly known to be sufficient to disinfect fungi destroys the plants' ability to take nutrients from the aqueous solution for good growth. Based on the tests, unicellular N unprotected root hairs of plants are as O 25 sensitive to ozone as fungal mycelia and fungal spores. x So far, there is no first mention of the sensitivity of swarmers of Pythium fungi > in the world literature. It is well = assumed that the sensitivity of Pythium swarmers is 3 similar to that of living bacteria, which have a lower sensitivity S 30 than fungal spores. Investigating the matter has been practically impossible in epidemiological research until recently. In 5 exposure experiments with cucumbers, a concentration of 100 ppb in air reduced the infection of powdery mildew, which already suggests that completely unprotected parts of the most sensitive fungi can be destroyed even at a concentration of less than 100 ppb.

There is no significant difference in the effect on microbes in the ozone concentrations of air and water.

Effect of continuous ozonation of recycled water on water quality and Pythium mushroom swarmers In 2021, the effect of ozonation of new fertilizer water and continuously recycled water for lettuce on changes in ozone concentrations and possible precipitation of nutrients and the ability of waterborne swarmers to cause disease was tested with the Pythium test.

From two farms, J and O, fresh recycled water was obtained for Pythium testing.

Farmer J had been producing salads in the system for more than 20 years.

The system did not use sand or slow filters, which would have removed the solids from the peat used in the seedling pots from the water.

Viljelm had a lot of Pythium disease, especially during the summer.

Viljelmä O basically produced salads using the same techniques, but the recycled water was constantly passing through a slow filter, so the water that reached the filter had to be cleaner in terms of solids than the other water source.

The O sample was taken before the slow filter.

N 2 g/l of the complete nutrient used in solution fertilization was added to clean tap water and ozonated (1500 ppb) tap water O 25. x The hypothesis was the deficiency symptoms of some nutrients in cucumber > seedling cultivation on a peat substrate.

There were no growth differences in plant development.

The nutrient composition of the water and other 3 important water properties were analyzed at S 30 Hortilab Oy in Närpiö (Table 1). Ozonation significantly decreased the pH number, i.e. 3 units, but the conductivity, which describes the total amount of soluble 5 nutrients, did not change.

The number of calcium and magnesium decreased.

These changes had already been noted earlier when ozonating the used circulation water.

The concentration of soluble iron and zinc increased. All changes, except for acidity, were insignificant in quantity.

Table 1. Effect of nutrient solution and ozonated nutrient solution on water compositions. From the 20 different objects studied, only the most important main nutrients and changed micronutrients have been included in the table.

Ozonated Measurement Nutrient solution nutrient solution "Conductivity mS/cm 2.9 2.9 — Acidity (pH) 6.5 3.6 Nitrate nitrogen (NO3-N) mg/l 300 290 Phosphorus (P) mg/l 58 59 Potassium (K) mg/l 350 340 Calcium (Ca) mg/l 250 230 Magnesium (Mg) mg/l 35 31 Iron (Fe) mg/l 2.4 2.9 Zinc (Zn) mg/l 0.41 0.73 Table 2. Mixing recycled water from two different lettuce farms with ozonated tap water and the effect of ozonation on the N properties of the water 10 minutes after the start of ozonation, and the health level of the water determined by the O Pythium test on a scale of 0 to 100. 3 The test was done in the middle of winter 2021, when the disease rate on farms is 2 15 always at its lowest. O was in use in the water cycle E a stone wool slow filter, which removes solids from the water, + but not all bacteria and the size class of bacteria: swarmers of the Pythium fungus.

N 8 > Farmer J Kurkkukyl- Ozone, ppb pH The ability of the cord to live-% 5 mS/cm day from seedling 'Recycled water- 50 210 - 5.4 0.58 — si:ozone water* = 1:3 Recycled water- 40 160 6.3 1.13 si:ozone water* = 1:1 Recycled water 20 230 7 1.7 ozonation 10 minutes Non-ozonated 70 0 6.9 2.1 recycled water “(*ozone water: 1640 ppb) =<—<—<< Farmer O 'Recycled water- 40 oo 300 6.1 0.62 — si:ozone water* = 1:3 Recycled water- 50 240 6.4 1.17 si:ozone water*= 1:1 Recycled water 100 100 6.7 1.81 N ozonation 10

N S minutes 3 Unozonated 30 0 6.9 2.1 2 recycled water E “(*ozoned water: 1580 ppb) = =—=<—<—< x Tap water 85 0 3 O Ozonation of farmer O's recycled water all the time 10 minutes- = passing through the ozonator removed the swarmers of the Pythium fungus that infect the throat from the water. All 10 test plants remained healthy throughout the test. The water sample taken immediately after the first ozonation round had a concentration of approx. 400 ppb, i.e. approx. 50% of the ozonation of tap water. When water was circulated through the device for 10 minutes, the ozone concentration had dropped to 100 ppb. At this stage, ozonation was stopped and the concentrations of mixtures of recycled water and tap water were measured. The slow filter continuously removes the solid material detached from the peat, but the sugars produced by the roots, bacteria detached from the surfaces of the roots and swarming spores react very sensitively to ozone. The volume calculated based on the size of the swarming spore is only approx. 100 parts of the volume of the Fusarium oxysporum fungus, in which case the swarmers as mobile units are the first to be oxidized to exhaustion. In 2020, the amount of ozone required for the death of one reproductive unit of the fungus F.oxysporum was determined in the laboratory. If it is assumed that this fungus needs the same amount of ozone per weight to oxidize as a Pythium swarmer, then the swarmer consumes a minimal 3.5x10"%1 g of ozone during oxidation.

Farmer J's water sample, which did not have a slow filter to remove organic mass, contained too much ozonizable mass, so that the swarm spores would have been completely destroyed N. This farming area had been used for the production of O 25 without cleaning the equipment for twenty years. The least x infectious diseases in the winter season were in the non-ozonated > water sample test. In ozonated water samples, a lot of aerobic bacteria were denatured, so swarmers of the 3 Pythium fungus had a greater chance S 30 of causing disease in the test plants. In Finland, there is another farm in the N Turku area, where the lettuces have no root disease at all, even in summer, despite the long history of cultivation. Over the years, the cultivation system must have developed an aerobic bacterial population that eliminates the swarmers, like the density of the bacterial population in a biofilter. In the corresponding test by Farmer O, 30% of the test plants remained alive in non-ozonated water, while the corresponding figure for Farmer J was 70%.

The result of the continuous ozonation of recycled water resembled the cleaning process of recycled water collection pipes, where, depending on the dirtiness and length of the pipe, the cleaning has lasted from about 20 minutes to up to 12 hours before concentrations of more than 200 ppb start coming out of the end of the pipe. Even at this concentration, the disease is no longer detected with the Pythium test. After these experiments, continuous ozonation has been carried out with Happico Oy's commercial device with the recycled water of the farm in Orimatti. In these tests too, the ozone concentration was around 400-500 ppb at the very beginning, quickly falling to a level slightly above 200 ppb. These water samples did not have a measurable disease level on the test plants.

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Claims (5)

PROTECTION REQUIREMENTS 1. System for removing disease-causing microbes, such as Pythium and Bacteridia microbes, which travel with water, from a circulating water culture water system during the growing season, in which system water is circulated that travels in piping, which system comprises e a nutrient-rich circulating water flow that continuously circulates in the system, e plants (140) which are grown in cultivation tubes (201), in which cultivation tubes (201) the circulating water flow is arranged to circulate at the roots of the plants (140), e a collection pipe (131), which is arranged to collect return water which used for the fertilization watering of the plants (140) in a circulation water flow, which contains a considerable amount of oxygen-consuming organic material, in particular biodegradable material, e a storage container (23) for temporary storage of circulation water, e a mixing device (14) for fertilizers and water to mix the fertilizer in the circulation water flow, and e an ozone generator (12) for r to feed ozone into the circulation water flow, > characterized in that the 2 e ozone generator (12) belonging to the system is arranged to raise the ozone content of the circulation water locally to S 30 a level that kills disease-causing microbes, and that the storage container ( 23) and/or the mixing apparatus N (14) for fertilizer and water are located in the flow direction of the circulation water after the ozone generator (12) and before the cultivation tubes (201) arranged to achieve a delay for eliminating residual ozone. 2. System according to protection requirement 1, characterized in that the ozone generator (12) is arranged to maintain in the circulation water flow an ozone content of 100-500 ppb, preferably 150-350 ppb, at a place in the water system, where the circulation water flows at an average flow rate takes 15-600 s from the ozone feed point. 3. System according to protection requirement 1 or 2, characterized in that the system exhibits a filter (133) which lowers the content of organic material in the circulation water, which filter is arranged to produce a filtered circulation water flow, which contains a fraction, 0-40%, preferably 0-20%, of said oxygen-consuming organic material in relation to the unfiltered circulation water flow and of said disease-causing microbes that travel with the water, and the ozone generator (12) is located in the direction of flow of the circulation water after the filter (13) and before the cultivation tubes ( 201). 4. System according to protection claim 3, characterized in that the filter (133) is a slow filter. 5. System according to one of the protection requirements 1-4, characterized in that the system comprises a three-way valve (124), with N S 25 which circulation water can be led in the system alternatively S to circulate from the ozone generator (12) to the roots of the plants (140) © or back to the ozone generator (12) via the pipe = (125). a + O O + N N O N D