DE2607114A1 - PROCEDURE FOR REMOVING NITROGEN COMPOUNDS IN WATER - Google Patents

Description

PATENT LAWYERS

813 STASH »SG be: Munches

Administration ^ B, Storngat ^ n j.4, 211 20 MALMÖ, Sweden.

Process tin removing nitrogen compounds in water

The invention relates to a method for removing harmful substances Nitrogen compounds in water, especially groundwater that is still in the soil and not already in has accumulated in a groundwater well or other type of water supply.

It is already known that nitrates and especially nitrites in drinking water can be harmful to health. It is also known that nitrogen compounds occur generally in soil and not only in organic compounds and organic residues but also among other things as ammonium, nitrate and nitrite ions are found that are involved in the nitrogen cycle of the Participate in nature and are formed and broken down in accordance with the law, often in a microbiological way. Some bacteria can thus Convert ammonia into nitrogen dioxide while other bacteria are able to. To convert nitrogen dioxide into nitrogen trioxide. However, there are also bacteria that convert nitrogen trioxide into nitrogen gas and nitrous gases, in particular nitrogen oxide, through so-called Able to convert denitrification.

Several alternative methods for removing harmful nitrogen compounds in protruding soil and well water are conceivable.

The water can, for example, be treated physically and chemically by ion exchange, reverse osmosis, electrodialysis, etc. will. However, it is likely that the investment and energy costs required for such treatment methods make these methods less appealing.

The object of the invention is to eliminate harmful nitrogen compounds in, among other things, groundwater and well water in a simple and economical way.

It has now been shown in accordance with the invention that harmful nitrogen compounds, in particular nitrates and nitrites, can be removed from water in a surprisingly simple and economical manner, especially if the water is still present as groundwater in the groundwater-bearing soil and before it drains into a water source, such as a Groundwater well, is included. According to the invention, denitrification takes place with the aid of RB / pm

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of microorganisms instead, which are preferably suspended in a nutrient solution. To do this, the nutrient solution is pumped into the soil, which surrounds the water supply or the groundwater well, from which one of harmful nitrogen compounds wants to promote freed water up to human consumption.

The groundwater-bearing soil layers at a certain depth, e.g. more than 5 meters, are mainly sterile. According to the invention, the nutrient solution with its content of denitrification microorganisms is used through a plurality of pipes attached to one another at appropriate intervals into these soil layers pumped down. For example, the pipes can be placed at a distance of 30-100 m from each other and 30-100 m from the water source.

If the groundwater flows in a certain direction in the ground, the pipes must of course be upstream of the water deposit into the ground, so that preferably only the water that collects in the water deposit and is to be conveyed up therefrom, is subjected to a denitrification treatment.

The advantage achieved directly with the method according to the invention is that only a small amount Water is treated (with additives) and used to treat soil layers through which large amounts of water flow, while b - ii conventional methods of water purification by e.g. Ion exchange, reverse osmosis and electrodialysis remove the water masses in their entirety through special treatment vessels have to happen.

The nutrient solution with the microorganisms is expediently prepared in that a relatively small amount of the water lifted up from the water source, e.g. a Part of the water lifted up from a groundwater well is diverted continuously or intermittently, and that well-measured quantities of nutrient solution and cultures of denitrification microorganisms are added to this diverted water, after which the solution thus obtained is pumped down through said pipes into the groundwater-bearing soil layers.

The nutrient solution is preferably a sugar solution, e.g. a glucose solution, or a starch suspension or also waste water from a process for the production of sugar, cellulose, whey

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rice products or the like. Used.

The groundwater-bearing soil layers should be proportionate be strongly acidic, i.e. have a pH of about 5.5-6.0, and the deritrification organisms used have such If they are inhibited in an acidic environment, it is advisable to make the nutrient solution basic, e.g. with an alkali hydroxide do.

Appropriate anaerobic microorganisms with powerful denitrification capabilities are types of bacteria such as Pseudomonas, Achromobacter and Bacillus that are involved in the breakdown of domestic sludge Wastewater can be used.

In a preferred embodiment of the invention, the nutrient solution with the denitrification microorganisms is deaerated by vacuum treatment before the solution is pumped down into the groundwater-bearing soil layers. This creates a more anaerobic environment for the denitrification microorganisms, which are usually most productive in a decidedly anaerobic environment. However, there are so-called heterotrophic microorganisms _; isms that can carry out the denitrification work in a vigorously aerobic environment, whereby a deaeration treatment of the water with the denitrification additives is unnecessary.

It is already known that iron, which is harmful for human consumption, is obtained from water that is carried up from a groundwater well is to be removed by adding water containing oxygen or oxygen-releasing substances to the groundwater Soil in the vicinity of the well. It will iron oxides are formed from the iron, which in turn precipitate and filter off during the flow of the groundwater through the soil will.

One embodiment of the invention relates to a combination a method of removing iron from groundwater in the soil, e.g., the method just described, with the method for removing harmful nitrogen compounds from the groundwater in the soil. The iron can first be extracted from the groundwater are removed and then the nitrogen compounds, optionally with deaeration of the denitrification microorganisms and Water containing nutrient solution before it settles into the soil

will lead. Alternatively, the nitrogen compounds can be removed first and then the iron, but the Remove nitrogen compounds and iron at the same time using one and the same treatment water. For the latter Alternatively, however, it is a prerequisite that decidedly aerobic and heterotrophic microorganisms are used.

A particularly meaningful embodiment of the invention is then applicable if an inventive denitrification in the groundwater-bearing soil layers due to the soil conditions is hardly possible or practically feasible. In such a case, one drains groundwater from a well, preferably has been freed of iron, e.g. as described above, by a treatment tower with a bed of groundwater Filling material reminiscent of soil layers, e.g. of an organic nature, such as peat litter, or plastic bodies flow. The particles or bodies forming this filler material should be one

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large total area and a biological coating, coating or Have skin with organisms that can cause denitrification of water bring about, which is made to flow through the filler material under the action of gravity, for example.

In another embodiment of the invention, an iron is used and raw water containing harmful nitrogen compounds from a groundwater well in a first tower for removing the Iron and then treated in a second tower with the contents described above to remove the nitrogen compounds, venting of the water by means of a vacuum expediently takes place before the denitrification step. The raw water will alternatively first in the denitrification tower and then in the Iron removal tower treated, with venting likely unnecessary.

When groundwater does not have large amounts of iron and nitrogen compounds as contains nitrate and nitrite, which it generally does not, it should be sufficient e.g. for a farm household that The filling material in the tower and in the towers should only be replaced once a year if the material volume is about 1 m or more.

The following embodiments illustrate the invention, however, must not be interpreted in a limiting sense.

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example 1

In a larger water resource, there was an unsatisfactorily high nitrate content of 215 mg NO per liter of groundwater measured. The direction of flow of the groundwater in the soil layers was determined. 50 and 70 m upstream from the well two holes were drilled. A stream of water was carried up from the hole 70 m from the well, and that into a closed one Container was passed, where the water was a mixture of the organisms Pseudomonas SPS, Achromobacter SPS and Bacillus SPS was added in equal parts along with a 20% glucose solution as a nutrient liquid. The container was evacuated, to remove dissolved oxygen from the water. The degassed water with the said organisms and the nutrient fluid was pumped down as treatment liquid into the groundwater flow through the hole 50 m from the well.

During a month, a stream of treatment liquid of this type was continuously drawn down in an amount corresponding to 5% of the maximum possible withdrawal from the well. The temperature of the groundwater stream was 7.5-8 ° C. It was found that the nitrate content in the withdrawn water _{had decreased from 215 mg NO 3} per liter to 8 mg NO ₃ per liter.

Example 2

In a smaller water source one had unsatisfactory high nitrate content of 270 mg NO ~ per liter of groundwater measured. From the water deposit, water was passed over a tower with a filling mass of particles or bodies, which with a biological Layer were covered, which among other things the organisms Pseudomonas SPS, Achromobacter SPS and Bacillus SPS in equal amounts contained. The load was 65 liters per m² hour and the residence time was 15 minutes at 15 ° C. In the tower was a 15% Glucose solution introduced as a nutrient source. It was shown in the tests that the nitrate content in the water with the current had decreased through the material bed in the tower from 270 mg NO, per liter to 9 mg NO, per liter.

Example 3

In a groundwater reservoir, the nitrate content measured was unsatisfactory, at around 170 mg NQ per liter. The groundwater was therefore passed through a treatment tower, the

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had a height of 2 m and contained fine sand. The grains of sand were covered by a biological skin, the cultures from among others the microorganisms Pseudomonas SPS, Achromobacter SPS and Bacillus SPS contained mainly the same amount and was formed by one of these three microorganism cultures containing 1% glucose solution was passed through the sand after it was washed by a pressurized water treatment had been.

That by the sand bed in the tower in an amount of about 50

2
A 15% glucose solution in an amount of about 0.001 liters per liter of groundwater was added to liters per m of inner tower area and h of groundwater fed (the residence time was 8 hours at 15 ° C.). The nitrate content in the water downstream of the tower was about 170 mg NO-. per liter has been reduced to about 9 mg NO ₃ .

Fine sand was used as a filler in the turn, however is also peat litter and even synthetic materials, e.g. plastic powder with grains in a size of e.g. 0.01-1 mm, with good results as a carrier for the denitrification microorganisms containing skin has been used.

The biological skin can expediently be formed thereby and maintained that an aqueous nutrient solution into which the microorganisms with denitrifying ability are confined continuously or intermittently through the treatment tower. In an experimental way it can be determined how the quantities of nutrient solution and cultures of denitrification microorganisms are to be measured, both immediately as well as good results can be achieved in the long run.

Example 4

A cylindrical container with a volume of 10 liters was filled with fine-grain sand. The sand was treated as in Example 3, so that biological skins formed on the grains of sand.

Groundwater according to example 3, i.e. with a nitrate content of about 170 mg NO_, was passed through the container so that the dwell time was only one hour at 15 ° C. About 90% of the water withdrawn from the container continued to become the container returned. A 15% glucose solution in

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the amounts given in Example 1 are added. In the amount of water that was not returned (10%), the nitrate content was low, i.e. 10 mg per liter.

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Claims (18)

CLAIMS 26071U 1. Process for removing from water such harmful nitrogen compounds that are present in water sources such as groundwater, and are contained in water that is in a water source Od. Like. Has accumulated, characterized in that the water is treated with microorganisms that remove the harmful nitrogen compounds convert into harmless compounds. 2. The method according to claim 1, characterized in that microorganisms with denitrification capacity containing water in an area of a groundwater-bearing soil layer in which Groundwater flows to a water source, is continuously or intermittently discharged to, among other things, nitrates and Nitrites in the groundwater flowing to the groundwater reservoir in situ by means of the microorganisms thus introduced into the soil to convert into ammonia, nitrogen gas and nitrous gases. 3. The method according to claim 1, characterized in that the water through a denitrification bed of material particles with a permeability similar to that of a groundwater-bearing soil layer, in which bed the particles with a Substance are documented that contains those microorganisms that convert the harmful nitrogen compounds into non-harmful compounds convert. 4. The method according to claim 2 or 3, characterized in that the microorganisms bacteria, in particular of the classes Pseudomonas, Achromobacter and Bacillus, are. 5. The method according to claim 2 or 3, characterized in that the microorganisms are heterotrophic bacteria. 6. The method according to claim 4 or 5, characterized in that a water-soluble nutrient, such as sugar, starch and Wastewater from a process for the production of sugar, cellulose, sugar-containing products, starchy products such as dairy products, each on their own or mixed with each other, the water to be conducted into the soil is added to provide a nutrient for the called microorganisms to form. A method according to claim 2, characterized in that the water to be conducted into the ground is made basic, for example with The help of an alkali hydroxide in case the soil has an acidic reaction. 609837/0707 9 26071U 8. The method according to any one of claims 2-7, characterized in, that the water used to drain the microorganisms into the soil is part of that from the water supply elevated water is. 9. The method according to any one of claims 2 and 4-8, characterized in that that the water with the microorganisms in the groundwater Soil layers are drawn down by pipes, which occur at distances of about 30 to about 100 m from the water deposit and spaced from about 30 to about 100 meters. 10. The method according to claim 9, characterized in that the pipes, if the groundwater generally in a certain Direction flows, can be attached upstream of the water reservoir. 11. The method according to any one of claims 2 and 4-10, characterized in that oxygen or oxygen-releasing substances containing water is carried down into the water-bearing soil layers in the same way as the water containing microorganisms where zones are created on the one hand for de-ironing of the groundwater and on the other hand for denitrification of the water will. 12. The method according to claim 11, characterized in that distinct zones for de-ironing at greater distances from the Groundwater resources can be arranged as distinct zones for denitrification. 13. The method according to claim 12, characterized in that distinct zones for denitrification at greater distances from the Groundwater resources can be arranged as distinct zones for iron removal. 14. The method according to claim 12, characterized in that aerobic, heterotrophic microorganisms are used. 15. The method of claim 3, characterized in that said bed of material particles is in a water treatment tower attached through which the water to be treated is directed from top to bottom. 16. The method according to claim 3, characterized in that iron-containing water is de-ironed before flowing through the denitrification bed. 6 0 9 8 3 7/0707 17. The method according to claim 3, characterized in that iron-containing water is de-ironed after treatment in the denitrification bed. 18. The method according to claim 3, characterized in that the denitrification bed consists of fine particles such as sand, which are covered with the said substance. 609837/0707