RU2818213C2 - Method and device for removal of iron from water with high content of humus - Google Patents

Abstract

FIELD: filtration.

SUBSTANCE: present invention relates to a method and a device for removing iron from water with high content of humus. Treated water is passed through filter (4), wherein said filter (4) contains filter material (4a). Before passing water through filter (4), the water pH value is reduced to such a level that the water pH value, which has been filtered by filter (4), ranges from 3.6 to 6.0 to prevent chemical deposition and create favorable conditions for ferruginous bacteria. Further, water is aerated. Iron is removed from water as it precipitates when ferruginous bacteria oxidise it by biological means. Precipitated iron captures humus with it, and both iron and humus adhere to filtering material (4a).

EFFECT: creation of environmentally safe method of biological removal of iron together with humus.

11 cl, 3 dwg

Description

TECHNICAL FIELD OF THE INVENTION

The present invention relates to the method given in the restrictive part of claim 1 of the claims.

Advantageously, the present invention relates to a method and apparatus for removing iron from water with a high humus content. The method and apparatus of the present invention, which are hereinafter collectively referred to as the “solution of the present invention,” can be used to purify, for example, groundwater in water purification plants in areas where the groundwater contains iron and humus. The solution of the present invention can also be used to treat other types of water, not just groundwater.

Iron content is one of the indicators that indicate the possibility of using groundwater. If the iron content is high, then the possibility of using the water as domestic water is low. The iron content of water is expressed in micrograms per liter of water (µg/l) or milligrams per liter (mg/l). High iron content gives household water an unpleasant taste and odor. In swamp-type aquatic systems, the iron content correlates with the presence of humus. In water, iron ions react with oxygen to form iron oxide and rust-colored compounds that discolor and make household water cloudy and form deposits on the interior surfaces of household electrical appliances that use water.

The iron content of groundwater and well water is affected by, among other things, the composition of the bedrock, the pH value of the water, the conditions for redox reactions and the amount of organic matter in the water. Iron from bedrock minerals dissolves in groundwater. Sand, gravel, and moraine contain iron, which dissolves in groundwater. If centralized water intake is used, the risk of capturing too much iron is low because the iron content is controlled in the water treatment plants. The iron content of water can be determined by the brown color of drinking water or by the deposition of iron in the form of rust stains on the surface of household electrical appliances.

Groundwater with a high humus content usually contains more iron than normal levels. The iron content represents a value that is typical for each water system. 400-600 µg/l can be considered a normal level. In water with a high humus content that is characterized by a rich brown color, such as swamp water, the iron content can be up to 20.0 mg/l. High iron levels can occur even with low humus levels. In addition, groundwater from arable soils usually has a high iron content.

Iron can be a harmful component of drinking water if its levels are too high. Good quality domestic water contains less than 0.1 mg/l of iron, and the recommended maximum iron content for domestic water supply to residential areas is 0.2 mg/l. Iron, along with manganese, is the most common element that degrades the quality of drinking water from wells.

The requirements for the quality of drinking and domestic water do not specify any limit value for the maximum iron content. Instead, there is a quality guideline that must be followed. The quality recommendation is based on the organoleptic characteristics of the water, i.e. smell, taste and color of water, but it also protects against health risks. The recommended maximum iron content is 200 µg/l for water distributed, for example, through water supply systems, and 400 µg/l for private wells.

BACKGROUND OF THE ART

Various types of water treatment methods are known in the prior art, as well as different types of water treatment equipment with specific objectives for treating different types of water.

Groundwater with a high humus content is quite widespread throughout the world, which is characterized by high values of chemical oxygen demand (COD - Chemical Oxygen Demand), high values of total organic carbon (TOC - English: Total Organic Carbon) and high iron and manganese content. Humus inhibits iron removal and thus conventional iron removal methods are ineffective in treating groundwater with high humus content. For water with high humus content, various types of water purification processes are used, the most common examples of which are given below.

1) Chemical precipitation using aluminum or iron salt. This process includes, among other things:

- aeration, mixing, sedimentation, filtration;

- adding an alkaline agent at the beginning and before or after filtration;

- usually also adding potassium permanganate to oxidize iron and manganese.

With this treatment, high quality water can be obtained. However, this method has problems such as high investment and operating costs. Additionally, the precipitating agent and potassium permanganate are expensive chemicals. In addition, the process requires a large staff to operate.

2) DynaSand filtration. This process includes, among other things:

- aeration;

- adding an oxidizing agent, for example potassium permanganate, to oxidize iron and manganese;

- adding an alkalizing agent to adjust the pH value of the treated water;

- adding aluminum or iron salt; - DynaSand filtration;

- optional addition of an additional oxidizing agent. This water treatment process only works if the iron content in the water is not too high. In addition, investment and operating costs are quite high.

3) Slow filtration. This process includes, among other things:

- removal of most of the iron using contact filtration, which includes the following steps:

- aeration;

- adding potassium permanganate;

- sand filtration;

- slow filtration.

The slow filtration process is quite expensive. Among other things, it requires a very large pool. One of the problems is that due to the large size of the pool, there is no flushing system. Consequently, iron that accumulates on the surface of the pool must be removed manually, which is a slow and expensive process.

4) Membrane filtration. This process includes, among other things:

- reverse osmosis or nanofiltration;

- aeration;

- additional processing, such as lime filtration.

The problems inherent in membrane filtration are related to the high cost of membranes. In addition, to date there is only little experience with this method. An additional problem is that filter clogging is not always controllable.

The publication of RF patent RU2158231 C2 discloses a method for removing humic substances and iron from water with a high humus content. Humus is removed from the water in the first stage of filtration and iron is removed in the second stage of filtration as a chemical process.

US Patent Publication US4459149, relating to the process of treating humic materials, discloses a method for removing humus from water by lowering the pH of the water and passing the water through a filter. However, nothing is said about iron removal.

Japanese Patent Publication JP2011200829 A relates to a method and apparatus for removing iron from untreated water through a biological process. This document discloses the use of ferruginous bacteria to remove iron by filtration, but does not say anything about humus removal or the need to maintain certain pH values during the iron removal process.

High investment costs, high operating costs, the use of chemicals and destructive and environmentally harmful impacts on the environment can be considered common problems for all known solutions for iron removal and groundwater treatment.

In the prior art, many studies have been carried out on the removal of iron from water with high humus content, but a solution for biological water treatment in accordance with the present invention has not been found.

PURPOSE OF THE INVENTION

The aim of the present invention is to overcome the above disadvantages and to provide a fully automated, biological, affordable, simple and reliable solution for the removal of iron and humus from groundwater. Another object of the present invention is to provide treatment of iron-containing groundwater with high humus content to produce potable water in an environmentally friendly, low cost manner.

The method in accordance with the present invention is characterized by the features presented in the distinctive part of claim 1 of the claims. Other embodiments of the present invention are characterized by the features presented in the remaining claims.

BRIEF DESCRIPTION OF THE INVENTION

In the method according to the present invention, favorable conditions are created for iron bacteria, while these conditions do not contribute to the chemical precipitation of iron. By maintaining the pH value of the water at a favorably low level, chemical precipitation of iron can be prevented and favorable conditions are created for iron bacteria to biologically filter iron from the water.

Typically, the method of the present invention involves removing iron from water with a high humus content biologically by passing the water through a filter, said filter comprising a filter material. The filter material can be, for example, natural sand, materials made from clay, or anthracite. In accordance with the present invention, the pH value of the water being treated is reduced before passing the water through the filter. Advantageously, the pH value of the treated water is reduced by adding acid to the water.

The device according to the present invention provides for the removal of iron from water with a high humus content by biological means. Thus, the device contains at least a filter containing filter material through which the water to be treated is provided to pass.

Advantageously, the device contains a section for increasing acidity to reduce the pH value of the treated water.

Biological removal of iron and manganese from water as such is known in the prior art and is a standard procedure. The new method in accordance with the present invention is also based on biological water treatment, while there are no methods comparable to the method in accordance with the present invention, and the proposed method differs from existing biological water supply systems.

Iron in water can be oxidized by air either chemically or biologically. Chemical oxidation typically requires a pH value above 7. The sediment produced during chemical precipitation is fine-grained and quickly causes filter clogging. Therefore, the filter or filter material should usually be washed when the iron content reaches 0.2 kg per 1 m ² of filter material.

In the case of biological filtration, iron penetrates deeper into the filter and the iron content can be more than 1.0 kg per 1 m ² of filter material before the filter needs to be washed. In addition, in the case of biological filtration, the iron removal process is simpler. Typically, in biological iron removal, the oxygen content is low to prevent chemical oxidation of the iron. However, usually some of the iron is still chemically deposited, which impairs the filter's performance.

Manganese is removed biologically in a separate step after iron removal. Manganese removal begins slowly, but humus does not have any negative effect on removal.

In the case of standard biological removal of iron from water with a high humus content, an acceptable result cannot be achieved. The iron and humus contents remain quite high. Iron content can range from 1 to 2 mg/L after treatment, with the recommended level being 0.2 mg/L. Iron content below 0.1 mg/l should be considered as a target value.

The method in accordance with the present invention relates to the biological removal of iron and humus from groundwater with a high humus content. In this method, the pH of the water supplied to the filter is adjusted by adding acid to such a level that the pH of the filtered water after the filter is approximately 3.1 to 6.0, preferably 4.1 to 4.5. The adjustment depends on the water used, its alkalinity, content of carbon dioxide, iron, humus and other substances. The removal of iron that occurs in the filter lowers the pH value of the water. To prevent this, it is usually sufficient that the pH value of the groundwater being filtered is adjusted before filtration to a value that is calculated in advance and maintained substantially constant, the value depending on the flow rate of the water being treated, the iron content of the water and the alkalinity of the water. After the filter, the pH value of the water is measured using a separate measuring device. Mainly, the adjustment of the pH value is planned before the treatment process based on the specific case for each source of groundwater, since the method depends on the pH value, iron content and humus content in the groundwater. For example, the source of groundwater can be a well. The use of wells is designed in such a way as to prevent adverse changes in water quality. Technological and detailed designs are usually drawn up for each groundwater source before the iron removal process begins. The acid consumption is estimated based on the iron content of the water, and therefore the required level of acidification can also be estimated. This pre-design is often sufficient without requiring filter feedback to indicate the pH value of the water that has passed through the filter.

However, the use of a feedback system is a more advanced method of adjusting the pH and/or alkalinity of the treated water. In this case, the pH value of the water entering the filter is adjusted based on the pH value of the filtered water leaving. According to this method, it is necessary to measure the pH value of filtered water and adjust the amount of increase in acidity of the water that is supplied to the filter, i.e. increase or decrease the amount of acid during the acidification stage based on the feedback measurement result.

In the method of biological removal of iron and humus according to the present invention, favorable conditions are created for iron-precipitating bacteria, and therefore they can optimally precipitate iron in water when removing humus from water.

Removing iron reduces the alkalinity and, at the same time, the pH value of the treated water, i.e. The pH value of the water decreases due to the removal of iron inside the filter. Advantageously, the pH and/or alkalinity of the treated water is adjusted to such a level that the pH value of the filtered water after the filter is from about 3.1 to 6.0, preferably from 4.1 to 4.5. The adjustment can be made in advance based on the properties of the water being treated or using a feedback system such as described above. The iron content of each groundwater is a characteristic characteristic of each specific area and is not a variable for the operation of the present invention. Therefore, automatically adjusting the pH value so that it is substantially constant with respect to water flow, without a feedback system, is usually not a problem for adjusting the pH value to the proper value.

Iron is removed biologically from the water in the filter along with humus, adhering to the filter material. The filter is washed periodically, removing sediment in the form of iron and humus, after which the filter can be reused.

A typical iron removal process in accordance with the present invention includes:

- lowering the pH value with an acid, such as sulfuric acid;

- aeration;

- fast filtration.

If the pH value of the water is low, iron cannot be chemically precipitated. Consequently, there is virtually no filter clogging. Iron, which is deposited directly on the surface of the filter material, removes humus from the water. Thus, humus does not interfere with the removal of iron, resulting in water that is essentially iron-free and low in humus. The subsequent process depends on other qualities of the water. The next stage could be, for example, aeration and lime filtration.

ADVANTAGES OF THE PRESENT INVENTION

The solution according to the present invention has several advantages, which include, inter alia, the following:

- lowering the pH of water by adding acid, which prevents chemical oxidation of iron and ensures effective removal of humus;

- no precipitating agent is required (polyaluminum chloride, ferrous sulfate);

- no oxidizing agent is required (for example, potassium permanganate, sodium hypochlorite);

- the process is environmentally friendly;

- the amount of rinsing water is insignificant;

- the process can be easily automated, which therefore requires minimal labor costs;

- low investment costs;

- significantly lower operating costs.

The purpose and main advantage of the solution according to the present invention is to reduce operating costs and reduce destructive and environmentally harmful impacts on the environment through an automated process and elimination of the use of expensive and polluting chemicals. Another advantage is that the device is affordable to manufacture due to its simple design.

Thanks to the solution in accordance with the present invention, it is possible to ensure reliable, environmentally friendly and affordable exploitation of groundwater sources in new areas.

LIST OF GRAPHIC MATERIALS

The present invention will now be described in detail with the help of examples and with reference to the accompanying simplified and schematic drawings, where

in fig. 1 is a simplified and schematic illustration of a water purification device used in the method according to the present invention;

in fig. 2 is a simplified and schematic representation of the device shown in FIG. 1, and a biofiltration or lime filtration device connected thereto in accordance with the prior art; And

in fig. 3 is a simplified and schematic illustration of a method according to the present invention for removing iron from groundwater with a high humus content.

DETAILED DESCRIPTION OF THE INVENTION

In fig. 1 shows an advantageous device 10 in accordance with the present invention for biologically removing iron and humus from groundwater. Advantageously, the device includes an inlet 1 for treated water, through which the treated water is supplied to the device 10. The inlet 1 can be connected, for example, to a supply pipe or pipeline. After the inlet 1, viewed in the direction of movement of the water, the device 10 contains an acidification section 2, which is in contact with the water to be treated and through which acid is added to the water to be treated in order to reduce the pH value and/or alkalinity of the water. After the acidification section 2, as viewed in the direction of water movement, the device 10 further comprises an aeration section 3, which contains measuring and control equipment for measuring the oxygen content of the water and adjusting it to the desired level. The main task of aeration section 3 is to add oxygen to the treated water.

If you look in the direction of movement of the treated water, the device 10 additionally contains a filter 4, into which the direction of water leaving the aeration section 3 is provided. The filter 4 contains a filter material 4a, which is, for example, predominantly sand. There is no need to automatically adjust the amount of air in the water that is directed to the filter 4. However, the device 10 includes at least one oxygen analyzer for measuring the air content of the filtered water leaving the filter 4, as well as for monitoring the efficiency of aeration. However, the oxygen content is not critical provided that the oxygen content is high enough. Advantageously, the oxygen content is determined on a case-by-case basis.

The device 10 in accordance with the present invention further includes a filtered water outlet 1a through which filtered water is provided to pass for further treatment. The outlet 1a is preferably located in the filter 4 after the filter material 4a, when viewed in the direction of movement of the treated water.

In fig. 2 is a simplified and schematic representation of the device 10 shown in FIG. 1, and the additional processing device 11 connected to it. The additional treatment device 11 may be a device known from the prior art, which device may include an aeration section 3a for adjusting the oxygen content of the water being treated. In addition, the additional treatment device 11 may comprise a filter 5 downstream of the aeration section 3a, viewed in the direction of water flow, the filter 5 comprising, for example, a lime filter 5a for adjusting the pH value of the water being treated. Advantageously, the filters 4 and 5 are connected to each other by, for example, connecting the filtered water outlet 1a in the filter 4 to the inlet of the aeration section 3a of the post-treatment device 11 using, for example, a suitable piping or channel system. In addition, the filter of the additional treatment device 11 includes 1b, through which filtered water is additionally directed for subsequent treatment. Advantageously, the outlet 1b is located in the filter 5 after the filter material 5a, when viewed in the direction of movement of the treated water.

Device 10 for biological removal of iron and humus, shown in FIG. 2 is a modified version of the basic version of the device and contains a feedback system 7, which is connected between the outlet 1a of the filter 4 and the acidity increasing section 2. The feedback system 7 contains a measuring element 6 for measuring the pH value of water, and the measuring element 6 also contains equipment for transmitting measurement data to the acidity increasing section 2. Accordingly, the acidification section 2 includes equipment for receiving measurement data and controlling the acidification section 2 based on the measurement data to dose the acid to be added to the water being treated. Advantageously, the amount of acid added should be maintained such that the pH value of the water that has been filtered by the filter 4 is approximately 3.1 to 6.0, preferably 4.1 to 4.5, at the outlet 1a of the filter 4. Optimal the value is determined based on the specific case.

In fig. 3 is a simplified and schematic illustration of a method according to the present invention for removing iron from groundwater with a high humus content.

In the first step s1 of the method according to the present invention, the treated groundwater is directed into the device through the inlet 1, and in the second step s2 to the acidification section 2, where acid is added to the water to reduce the alkalinity of the water. Preferably, the acid added is sulfuric acid, but other acids such as hydrochloric acid can also be used instead of sulfuric acid. After increasing the acidity, the third stage s3 follows, during which the acidified water is sent to the aeration section 3, where the oxygen content of the water is measured and adjusted to the desired level. At the fourth stage s4, the acidified and aerated water is sent further to filter 4, where iron and humus are filtered out from the treated water using filter material 4a, mainly sand, inside filter 4. In filter 4, iron is removed from the water as it settles, when ferrous bacteria oxidize biologically, and at the same time, the precipitated iron takes humus with it, with both iron and humus sticking to the filter material 4a. After filtration, step s5 follows, during which the treated water is removed from the device 10 through outlet 1a and sent for further processing.

The adjustments for acidification, aeration and water flow are advantageously carried out in advance by measuring so that, when passing through the filter 4, the iron and humus contents and alkalinity of the water, where the alkalinity can be measured indirectly by the pH value of the filtered water, are reduced to the desired values.

As described above, the pH and/or alkalinity of the treated ground water is advantageously adjusted to such a level that the pH value of the filtered water after filter 4 is between approximately 3.1 and 6.0, preferably between 4.1 and 4.5. Since the iron content of each groundwater is a characteristic characteristic of each particular area and is not a variable for the operation of the present invention, the adjustment of the pH value can be performed automatically to be substantially constant with respect to the flow rate of the water. Thus, the adjustment can be calculated in advance based on the properties of the water being treated, for example, by measuring the pH value, iron content, alkalinity, humus content and water flow rate and by adjusting the increase in acidity and aeration, as well as the composition and amount of filter material so that resulting in filtered water that is substantially free of iron and humus, while the pH value of the filtered water is within the desired range. Advantageously, this kind of adjustment, which is carried out in advance, is adjusted from time to time using new measurements and tests.

If necessary, a feedback system 7, which is preferably connected between the outlet 1a of the filter 4 and the acidification section 2, can be connected to the device 10 for biological removal of iron and humus in accordance with the present invention. In this case, the increase in acidity of the treated water can be precisely controlled to obtain filtered water of uniform quality even if the properties of the incoming water change for any reason or the filtering ability of the filter material 4a changes during operation. In this case, the pH value of the water leaving the outlet 1a of the device 10 is measured, and the measurement data is transmitted to the acidification section 2 either continuously or periodically for use as control data, and in the acidification section 2, the amount of acid added to the water is adjusted based on measurement results so that at the outlet 1a of the filter 4, the pH value of the water that has been filtered by the filter 4 is as stable as possible and ranges from approximately 3.1 to 6.0, preferably from 4.1 to 4.5.

The basic idea of the present invention is an essentially biological, chemical-free solution for removing iron and humus, which includes, in its simplest form, only an acidification step s2, an aeration step s3 and a filtration step s4 without any chemical treatment.

It will be apparent to one skilled in the art that the present invention is not limited to the examples described above, but may vary within the scope of the claims below.

In addition, one skilled in the art will appreciate that the filters of the iron removal device and the post-treatment device may be, for example, filter elements.

Claims (15)

1. A water treatment method by which iron is biologically removed from humus-containing groundwater, wherein in said method the treated water is passed through a filter (4), wherein said filter (4) contains filter material (4a), characterized in that the method contains at least the following steps: Before passing the water through the filter (4), the pH value of the water is reduced to such a level that the pH value of the water that has been filtered through the filter (4) is from 3.6 to 6.0 to prevent chemical precipitation and create favorable conditions for glandular bacteria ; the water is aerated; iron is removed from water as it settles, when iron bacteria oxidize it biologically; And the precipitated iron takes humus with it, and both iron and humus adhere to the filter material (4a). 2. The method according to claim 1, characterized in that humus is removed from water by binding it with oxidized iron. 3. The method according to claim 1 or 2, characterized in that the pH value of the treated water is reduced by adding acid to the water. 4. The method according to claim 3, characterized in that the pH value of the treated water is reduced by adding sulfuric acid or hydrochloric acid to the water. 5. The method according to any of the previous paragraphs, characterized in that the quality characteristics of the treated water are measured to determine the amount of acid added to the water, which is required to remove iron. 6. The method according to claim 5, characterized in that the required amount of acid added to water is calculated based on the results of measurements of the quality characteristics of water before the iron removal process begins. 7. The method according to any of the previous paragraphs, characterized in that a technological design for the iron removal process is drawn up before the start of the iron removal process, and in the specified technological design at least one or more of the following quality characteristics are measured: iron content, oxygen content, pH value, alkalinity, carbon dioxide content, total organic carbon content. 8. The method according to any of the previous paragraphs, characterized in that the pH value of the filtered water is measured, and the amount of acid added to the treated water is regulated by feedback based on the measurement data. 9. Method according to any of the previous paragraphs, characterized in that the water to be treated is filtered through a washable filter (4). 10. Method according to any of the previous claims, characterized in that iron is removed from the treated water biologically using bacteria, such as ferruginous bacteria. 11. A method according to any of the previous paragraphs, characterized in that the amount of acid added to the water being treated is maintained in such a way that the pH value of the water that has been filtered through the filter (4) ranges from 3.6 to 6.0, preferably from 4 ,1 to 4.5.

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