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    • 专利摘要:
    The disclosure relates to a method for regenerating a filter (100) comprising a plurality of diatomite aggregates (105), wherein said diatomite aggregates (105) are coated with an iron based metal oxide, the method comprising: adding (S01) a first solution comprising one or more of a first compound selected from a group consisting of: hydroxide, hydrogen carbonate and ammonia, to the filter, whereby phosphate bound to said diatomite aggregates (105) is released from said diatomite aggregates (105), transferring (S02) the first solution comprising the released phosphate from the filter to a tank (102) separate from the filter (100), adding (S03) one or more of a second compound selected from a group consisting of: CaCl2, other calcium salt, magnesium salt, and hydrocalumite, to the tank, thereby forming a mixture of the first and second solutions, wherein phosphorus is precipitated from the mixture by phosphorus binding to a positive ion of the second compound.
    公开号:DK202170522A1
    申请号:DKP202170522
    申请日:2021-10-27
    公开日:2021-11-02
    发明作者:Heiberg Lisa
    申请人:Diapure Ab；
    IPC主号:
    专利说明:

    DK 2021 70522 A1 1METHOD FOR REGENERATING A FILTER COMPRISING A PLURALITY
    OF DIATOMITE AGGREGATES AND A SYSTEM THEREFOR Field of invention The present invention relates to a method for regenerating a filter comprising a plurality of diatomite aggregates. The present invention also relates to a method for removing phosphorus from water, which method includes the method of regenerating the filter. The invention also relates to a system for removing phosphorus from water. The water may e.g. be wastewater. Technical Background Wastewater from households contain different pollutants such as phosphorus that can harm the environment. Thus, wastewater is treated to remove phosphorus before the wastewater reaches nature.
    It is common to treat wastewater with the aim of removing pollutants such as phosphorus using porous media in different contexts. One example of wastewater treatment is in the form of a filter bed placed at the end-of-pipe in connection with a small-scale constructed wetland. Another example of use of a porous media is in a flow-through filter structure in ditches.
    Common filters often comprise porous materials that contain a removing agent, i.e. a filter material or a sorbent, in order to efficiently remove pollutants from the wastewater in the aqueous phase.
    A common filter material that is commercially available is iron oxides formulated as small particles and which is efficient for phosphate removal from a solution. However, the iron oxide particles are often in the micrometer size range, and the use results in a filter having low hydraulic conductivities. Another example of a filter material is diatomite aggregates. However, the typical size of stable diatomite aggregates is less than 0.5 mm in diameter, which is unsuitable as a filter material. These filter materials have low hydraulic conductivities in addition to low water treatment efficiency.
    DK 2021 70522 A1 2 In this context we would like to mention EP3194340, which discloses a method of forming iron oxide coatings on diatomite aggregates.
    Another problem for most common filters are that they are typically heavy.
    A filter for removing phosphorus being designed to filter water from a typical household typically weighs about 1000kg, and these filters need typically to be exchanged once per year to ensure efficient water treatment as well as securing satisfactory hydraulic conductivity.
    Such heavy filters require special equipment for installations and replacements, and they are typically also quite expensive.
    Hence, there is room for improvements to filters for treating water with the purpose of removing phosphorus from a flow of water.
    Summary of invention It is an object of the invention to address the issues stated above related to treatment of water to remove phosphorus.
    This object has been achieved by a method for regenerating a filter comprising a plurality of diatomite aggregates, the method comprising: filtering water through a filter comprising a plurality of diatomite aggregates, wherein said diatomite aggregates are coated with an iron based metal oxide such that phosphorus containing compounds present in the water bind to oxygen of the iron based metal oxide forming phosphate bound to said diatomite aggregates, temporarily stopping the filtering of water through the filter, adding a first solution comprising one or more of a first compound selected from a group consisting of: hydroxide, hydrogen carbonate, and ammonia, to the filter, wherein said first compound is provided in such an amount in the first solution that the filter and the phosphate bound to said diatomite aggregates is subjected to a pH level above 9, whereby the phosphate bound to said diatomite aggregates is released from said diatomite aggregates into said first solution, transferring the first solution comprising the released phosphate from the filter to a tank separate from the filter,
    DK 2021 70522 A1 3 adding one or more of a second compound selected from a group consisting of: CaClx(calcium chloride), other calcium salt, magnesium salt, and hydrocalumite, to the tank, thereby forming a mixture including the first solution and the second compound, wherein phosphorus is precipitated from the mixture by phosphorus binding to a positive ion of the second compound, and removing the precipitated phosphorus.
    The inventive concept will provide a cost-efficient filter.
    The regeneration of the filter further provides a cost-efficient method for removing phosphorus from water.
    The regeneration of the filter allows for the filter to be efficient in absorbing phosphorus from water for an extended time period without needing to exchange the filter every time it has reached a point of low absorption capacity.
    Further to being cost-effective, the method is environmentally friendly since there is a reduction in the need to produce filters, due to the regenerative ability.
    Moreover, by providing a regenerative ability, the filter may be made having a low total weight, in comparison to common filters, thus making the filter easier to exchange when it is needed.
    It should in this context be noted that the filter comprising a plurality of diatomite aggregates coated with an iron based metal oxide is capable of binding phosphorus containing compounds present in the water to oxygen of the iron based metal oxide forming phosphate bound to said diatomite aggregates, without any need to change the chemical composition of the water to be filtered.
    Thus, there is no need to add any chemical compound or solution to the water before it is introduced into the filter and there is no need to continuously add any chemical compound or solution to the filter and water during the filtering.
    The first solution disclosed above is intended to be introduced after the filtering has temporarily been stopped.
    By raising the pH level to above 9, the phosphate is released from said diatomite aggregates in an efficient and quick manner.
    This is beneficial since it reduces the time it takes for the filter to effectively regenerate and it reduces the time the filtering has to be temporarily stopped.
    The filter comprising diatomite aggregates coated with an iron based oxide are stable within the
    DK 2021 70522 A1 4 filter and thus allow the filter to be able to receive high loads of water flowing through the filter.
    The hydroxide may e.g. be provided as a soluble metal hydroxide, such as sodium hydroxide or potassium hydroxide. Preferably, the first solution comprises one or more of a first compound selected from a group consisting of: hydroxide and hydrogen carbonate.
    The feature such that phosphorus containing compounds present in the water bind to sorption sites of the iron based metal oxide forming phosphate bound to said diatomite aggregates may alternatively be expressed as such that phosphorus containing compounds present in the water bind to oxo- or hydroxy functional groups of the iron based metal oxide forming phosphate bound to said diatomite aggregates.
    The second compound may be added in various forms. In one example, the second compound may be added as a powder comprising the second compound. Alternatively, or in addition, the second compound may be added in the form of a second solution one or more of the second compound. In the following the description will refer to an embodiment wherein the second compound is added as a solution; a second solution.
    The second compounds may be divalent metal ions, such as CaClz, MgCla.
    It may be noted that the diatomite aggregates may be based on moclay. Such aggregates typically comprise both diatomite and clay. When such a material is fired (calcined) it forms large porous aggregates.
    It may be noted that the iron based metal oxide coating may contain other materials. It may e.g. include aluminium. It may be doped with metals like lanthanum and cerium to increase the sorption affinity.
    As an example it may be mentioned that when e.g. calcium salt is provided as the second compound, Ca-phosphate is precipitated.
    It may be noted that after the first solution comprising the released phosphate from the filter, the filter is ready to be used again for filtering water.
    Removing the precipitated phosphorus may e.g. be accomplished by removing the phosphorus from the tank at the filtering site, such as by suction
    DK 2021 70522 A1 or scraping. Alternatively, the tank may be removed from the site and the precipitated phosphorus be removed from the tank at a different location. In such a case the removed tank may be replaced by a clean tank or by the same tank after the phosphorus has been removed. 5 This kind of removing the precipitated phosphorus after the filter has been regenerated is beneficial since the phosphorus can be recycled.
    It may be noted that the precipitation stage may be performed after the other steps have been performed more than once. Thus, the tank may be large enough to receive the first solution from more than one regeneration cycle before the second solution is added to the tank. It may also be noted that the step of removing the precipitated phosphorus from the tank may be performed after the first and second solutions has been transferred/ added to the tank from more than one cycle. It may also be noted that second solution may be present in the tank already when the first solution is transferred to the tank., and be present in such an amount that it is sufficient to accomplish the desired precipitation for one transfer of the first solution or alternatively for more transfers of the first solution from more than one filter regeneration cycle. Thus, the step of removing phosphorus may be done after the tank is full, or at any other time.
    Such a method comprising said filter has the ability to handle high hydraulic loads and hence efficiently treat large volumes of water. This further enables the possibility to connect house-hold wastewater systems to the filter. For example, wastewater and drinking water may be connected to the filter. By the temporarily stopping of filtering through the water while the first solution is transferred to the separate tank, the water flowing through the filter may be turned on again after the temporary stop. Thus, the efficiency of water filtration may improve as the filtering is only temporarily stopped for the regeneration of the filter to be achieved.
    The method may further comprise a step of exchanging the filter comprising the diatomite aggregates after the steps of filtering, temporarily stopping filtering, and regenerating have been repeated at least two times, preferably at least three times, more preferably at least four times.
    DK 2021 70522 A1 6 Thus, the regeneration process may be performed at least two times, extending the life-span of the filter. It is to be understood that the steps of filtering, temporarily stopping filtering, and regenerating may be repeated only once before the filter is exchanged, however it is preferred that the filter is arranged such that it can be regenerated several times before the filter is exchanged.
    At least 75%, by weight, of the plurality of diatomite aggregates may have a diameter in the interval from 1 mm to 4 mm. The benefit of having diatomite aggregates with a larger diameter is that it increases the ability to filter high loads of water flow without hindering the flow of water through the filer. Moreover, the filter is less likely to be clogged by particles in the water. The iron based metal oxide may ensure that the diatomite aggregates of a greater diameter are stable when present in the filter.
    At least 90%, by weight, of the diatomite aggregates may have a specific surface area of at least 30 m2/g, determined by BET (N,). By a larger specific surface area, the diatomite aggregates may bind a greater amount of phosphorus present in the water. By this, the efficiency of the filter may be increased. The BET-method or theory is e.g. disclosed in the article Brunauer, S., Emmett, P.H., Teller, E., 1938. Adsorption of gases in multimolecular layers. J. Am. Chem. Soc. 60, 309-319 (https://doi.org/10.1021/ja01269a023).
    The iron based metal coating may be added by an amount such that there is about 100-3000 mmol iron per kilogram of the diatomite aggregates coated with the iron based metal coating, i.e. per kilogram of the aggregates including the coating. 100-3000 mmol Fe/kg corresponds to about 5 to 150 g Fe per kg of the product. Thereby there is provided an efficient removal of phosphorus from water as the water passes through the filter.
    The diatomite aggregates may be coated with one or more layers of the iron based metal oxide. Providing the coating in a single layer may be beneficial since it typically reduces production time. Providing the coating in more than one layer may be beneficial since it may facilitate adding the desired amount of coating and still allowing the aggregates to present the large surface area.
    DK 2021 70522 A1 7 A strong coating having high amounts of iron is beneficial since it may increase the number of times the step of filtering may be repeated before there is a need to start the regeneration process.
    Moreover, it may increase the number of times the regeneration may be performed before the filter aggregates need to be replaced.
    This since some of the iron based metal coating may decay during the filtering and/or during the regeneration when the first solution is added and then transferred to the tank.
    The above mentioned object has also been accomplished by a system for removing phosphorus from water, the system comprising: a filter, a tank and a connection arranged between or being configured to be connected between the filter and the tank, the filter comprising:
    one or more inlets configured to receive water to be filtered in the filter and to receive a first solution comprising one or more of a first compound selected from a group consisting of: hydroxide, hydrogen carbonate, and ammonia, to the filter,
    a plurality of diatomite aggregates coated with an iron based metal oxide configured to bind the phosphorus present in the water to oxygen of the iron based metal oxide forming phosphate bound to said diatomite aggregates, and one or more outlets configured to permit water that has passed through the filter to exit the filter,
    wherein said first compound is provided in such an amount in the first solution that the filter and the phosphate bound to said diatomite aggregates is subjected to a pH level above 9, whereby the phosphate bound to said diatomite aggregates is released from said diatomite aggregates into said first solution,
    the connection between the filter and the tank being configured to transfer the first solution comprising the released phosphate a from the filter to the tank,
    the tank comprising:
    DK 2021 70522 A1 8 one or more inlets configured to receive the first solution comprising the released phosphate and to receive one or more of a second compound selected from a group consisting of: CaCl, other calcium salt, magnesium salt, and hydrocalumite, to the tank, thereby forming a mixture including the first solution and the second compound, wherein phosphorus is precipitated from the mixture by phosphorus binding to a positive ion of the second compound.
    The tank is separate from the filter in the sense that the first solution added to the filter may be removed from the filter and transferred to the tank such that the filter no longer is submerged in or holds the first solution and such that the filter may once again be used to filter water while the steps of adding the second solution and/or removing the phosphorus may be performed to the solution in the tank independently from the filtering of water in the filter.
    The filter may comprise less than 200 kg of coated diatomite aggregates per household delivering water to the filter.
    Advantages associated with the different features and preferred embodiments have been discussed in detail in the above in relation to the method for regenerating a filter. That discussion is equally valid in relation to the system for removing phosphorus from water and reference is therefore made to the above discussion. It may be noted that the various preferred embodiments or optional features are equally applicable to the system.
    The invention may also in short be said to relate to a method for regenerating a filter comprising a plurality of diatomite aggregates, wherein said diatomite aggregates are coated with an iron based metal oxide, the method comprising: adding a first solution comprising one or more of a first compound selected from a group consisting of: hydroxide, hydrogen carbonate and ammonia, to the filter, whereby phosphate bound to said diatomite aggregates is released from said diatomite aggregates, transferring the first solution comprising the released phosphate from the filter to a tank separate from the filter, adding a second solution comprising one or more of a second compound selected from a group consisting of: CaCly, other calcium
    DK 2021 70522 A1 9 salt, magnesium salt, and hydrocalumite, to the tank, thereby forming a mixture of the first and second solutions, wherein phosphorus is precipitated from the mixture by phosphorus binding to a positive ion of the second compound.
    Brief description of the drawings The invention will by way of example be described in more detail with reference to the appended schematic drawings, which shows a presently preferred embodiment of the invention. Figure 1 discloses a system for removing phosphorus from water. Figure 2 discloses in a flowchart a method for regenerating a filter comprising a plurality of diatomite aggregates. Figure 3 discloses in a flowchart a method for removing phosphorus from water.
    Detailed description of preferred embodiments Figure 1 shows a system comprising a filter 100, a tank 102 and a connection 103 between the filter 100 and the tank 102. The tank 102 is separate from the filter 100. In figure 1, the tank 102 is arranged relative to the filter 100 such that liquids will by gravity flow from the filter 100 to the tank
    102. It is to be understood that the filter 100 and the tank 102 may be arranged adjacent to each other or basically any other relative placement. However, some placements may require the use of a pump or the like to transfer any liquid from the filter 100 to the tank 102. It may also be noted that itis conceivable that the tank 102 is movable, such as being of a size allowing it to be carried or moved on a trolley or the like, or being of a size configured to be positioned on a motor driven vehicle and that the tank 102 is brought to the filter 100 when it is time to regenerate the filter 100. In figure 1, the filter 100 is a column filter. Alternatively, the filter 100 may be a filter bed. It may be noted that the physical configuration of the filter 100 may be basically any kind of filter type.
    DK 2021 70522 A1 10 The filter 100 comprises an inlet 104a configured to receive a flow of water to be filtered. The filter 100 further comprises a plurality of diatomite aggregates 105. The filter further comprises an outlet 106a allowing water that has passed through the filter 100 to exit the filter 100.
    The water may contain compounds comprising phosphorus. It is to be understood that the filter 100 may receive different types of water. By way of example, the water may be wastewater, or drainage water, or polluted water.
    The filter further comprises an inlet 104b configured to receive a first solution. The first solution comprises one or more of a first compound selected from a group consisting of: hydroxide, hydrogen carbonate, and ammonia. The first solution is e.g. provided via a tank or container 111.
    It may be noted that the inlets 104a and 104b may be a single inlet and that the flow of water and the addition of the first solution may be selectively introduced through the single inlet via a valve system selectively connecting the filter 100 to a water piping or to the container 111.
    The first compound is provided in such an amount in the first solution that the filter 100 and the phosphate bound to said diatomite aggregates 105 is subjected to a pH level above 9. Consequently, phosphate bound to said diatomite aggregates 105 is released from said diatomite aggregates 105 into said first solution.
    The plurality of diatomite aggregates 105 are coated with an iron based metal oxide. The iron based metal oxide may be iron oxide. The iron based metal oxide preferably comprises mainly ferrinydrite (amorphous iron oxide). Alternatively, it may mainly comprise the iron oxides goethite, lepidocrocite, feroxyhite and/or hematite. Combinations of the above discussed iron based metal oxides are also conceivable as well as combinations also with other iron based metal oxides.
    The diatomite aggregates may be coated with one or more layers of the iron based metal oxide.
    The iron based coating of the diatomite aggregates 105 may be added by an amount such that there is about 100-3000 mmol iron per kilogram of the diatomite aggregates 105 coated with the iron based metal oxide.
    DK 2021 70522 A1 11 The diatomite aggregate 105 is made of a diatomite containing material. The diatomite aggregate 105 may comprise approximately 1/3 clay and 2/3 diatomite. This ratio between clay and diatomite makes it possible to obtain aggregates larger than 2 mm which may be further stabilized through treatment, for example through calcination (so-called calcined diatomaceous earth, CDE). The diatomite aggregate 105 may be naturally formed and come from naturally occurring formations. The diatomite aggregates may consist of millions of micrometer-sized particles (amorphous silicate shells from diatomite algae). The diatomite aggregate 105 may comprise internal pores.
    Such pores may allow for diffusion of a liquid into the diatomite aggregate
    105. Said internal pores may be inter-connected. The diameter of said pores may be ranging from less than 10 micrometer to less than 1 micrometer. The diatomite aggregate 105 may further comprise intra pores to allow for diffusion of a liquid. The diatomite aggregate 105 may be thermally treated. The diatomite aggregate 105 may be calcined.
    It is preferred that the diatomite aggregates 105 are stable in wet condition. Stability in wet condition may be achieved by treating the diatomite aggregates 105. The diatomite aggregates 105 may be thermally treated, such as by calcination or flux calcination. Calcination is the process of burning at high temperatures, typically 700-800°C, resulting in CDE. During the calcination, small aggregates may sinter together to form big and stable aggregates. The calcination may contribute to obtaining a diatomite aggregate 105 with a diameter larger than 2 mm. After the calcination has been performed, the aggregates may be fractioned such that they have the desired size distribution.
    Calcination of the diatomite aggregates 105 may further contribute to stabilizing the diatomite aggregates 105 in wet condition, by making them resistant to disintegration in water. Furthermore, calcination may ensure that the material can be transported and packed into columns without physical disintegration. Un-calcined diatomaceous earth may slake in water.
    The diatomite aggregates 105 may have a diameter in the interval from 1 to 4 mm. Preferably, at least 75% by weight, of the plurality of diatomite
    DK 2021 70522 A1 12 aggregates have a diameter in the interval from 1 mm to 4 mm. Thus, it should be noted that the filter may comprise diatomite aggregates having a diameter smaller than 1 mm. Accordingly, the filter may comprise diatomite aggregates having a diameter larger than 4 mm. Preferably, at least 75% by weight, of the plurality of diatomite aggregates have a diameter in the interval from 2 mm to 4 mm.
    The diatomite aggregates 105 may have a specific surface area of at least 30 m /g, determined by BET (N2). The diatomite aggregates 105 may have a specific surface area of at least 40 m /g, determined by BET (Nz). The diatomite aggregates 105 may have a specific surface area of at least 50 m /g, determined by BET (N2). The diatomite aggregates 105 may have a specific surface area of at least 60 m /g, determined by BET (Nz). The diatomite aggregates 105 may have a specific surface area of at least 70 m /g, determined by BET (N,). The diatomite aggregates 105 may have a specific surface area of at least 80 m /g, determined by BET (Nz). The diatomite aggregates 105 may have a specific surface area of at least 90 m /g, determined by BET (N,). The diatomite aggregates 105 may have a specific surface area of at least 100 m /g, determined by BET (N).
    The iron based metal oxide is configured to bind phosphorus present in the water to sorption sites of the iron based metal oxide. Thus forming phosphate bound to said diatomite aggregates 105.
    The iron based metal oxide may comprise an amorphous oxide. The iron based metal oxide may alternatively, or in addition comprise crystalline forms of oxides. The iron based metal oxide coating may be prepared by soaking CDE in a solution of Fe, such as a solution of iron(III) salt, such as for example iron(III) chloride or iron(lll) sulphate. The material is then typically, but not necessarily, dried. This is followed by neutralizing of the acidity by adding a base solution such as for example sodium hydroxide, or sodium bicarbonate, or ammonia. The neutralization may be partly performed with NaHCO; before the soaking process. The neutralization is performed to reduce the required amount of base to be added to the CDE after soaking, and in order to minimize acid dissolution of Fe oxides already coated onto the
    DK 2021 70522 A1 13 CDE.
    After base neutralization and washing to remove excess salts, the product is dried.
    A purpose of coating the aggregates 105 with an iron based metal oxide, is that phosphate can sorb strongly to iron oxides.
    Thus, the iron oxide may achieve several effects.
    The filter material may sorb phosphate strongly and fast.
    The filter material may have a slow desorption of phosphate due to phosphate captured within the pores of the aggregate 105. It is preferred that the filter 100 comprises less than 200 kg of coated diatomite aggregates 105 per household delivering water to the filter.
    In figure 1 is schematically disclosed how a filter 100 is connected to two houses, with one household in each house.
    It should be noted that the filter may be arranged receive water from a variety of water delivery systems.
    The filter may for example receive drainage water from fields or drainage water from green houses.
    In such cases the filter may comprise more than 200 kg of coated diatomite aggregates to ensure efficiency of the filter.
    Thus, it should be understood that the filter may be arranged with different amounts of coated diatomite aggregates to ensure long life span, with regard to how much water is to be filtered through the filter.
    The outlet 106a is configured to permit water that has passed through the filter 100 to exit the filter 100. The outlet 106a may be connected to a water pipe for directing the water to a further cleaning process or for releasing the water to a desired location.
    The filter 100 is further provided with an outlet 106b configured to be connected to the connection 103. It may be noted that the outlets 106a and 106b may be a single outlet and that the flow of water and/or first solution from the filter 100 may be selectively guided from the outlet 106 via a valve system selectively connecting the filter 100 to a water removal piping of basically any kind or to the connection 103. The connection 103 is configured to transfer the first solution from the filter 100 to the tank 102. When the first solution is transferred from the filter 100 to the tank 102, the first solution comprises the released phosphate.
    It is to be understood that the connection 103 may take various forms.
    By way of example, the connection may be a fall through.
    Alternatively, the connection
    DK 2021 70522 A1 14 103 may be a pipe. The connection may have a pump system for pumping the first solution from the filter 100 to the tank 102.
    The tank 102 comprises a tank inlet 108a. The tank inlet 108a is configured to receive the first solution comprising the released phosphate.
    The tank further comprises a tank inlet 108b configured to receive a second solution. It may be noted that the inlets 108a and 108b may be a single inlet and that the flow of water and first solution from the connection 103 and the addition of the second solution may be selectively introduced through the single inlet via a valve system selectively connecting the tank 102 to the connection 103 or to the container 112 holding the second solution.
    The second solution comprises one or more of a second compound selected from a group consisting of: CaCl», other calcium salt, magnesium salt, and hydrocalumite. When the tank 102 has received the second solution, a mixture of the first and second solutions is formed. By this, phosphorus is precipitated from the mixture by phosphorus binding to a positive ion of the second compound.
    With reference to Figures 2 and 3, there is also disclosed a method for removing phosphorus from water and a method for regenerating the filter 100. Before the filter 100 is regenerated, a fluid such as water may have been filtered FO1 through the filter 100. During such filtering FO1, phosphorus containing compounds present in the water bind to oxygen of the iron based metal oxide forming phosphate bound to the diatomite aggregates of the filter
    100. The filtering FO1 is temporarily stopped FO2, to allow the regeneration FO3 process of the filter 100 to run. To regenerate FO3 the filter, the flow of water to be cleaned through the filter 100 is temporarily stopped FO2. The filtering is temporarily stopped FO2, the first solution is added and the filtering is temporarily stopped FO2 until the first solution has exited the filter 100.
    The regeneration steps are disclosed in more detail with reference to figure 3. A first solution is added S01 to the filter 100. The first solution comprises one or more of a first compound selected from a group consisting of: hydroxide, hydrogen carbonate and ammonia. The hydroxide may e.g. be provided by the first solution comprising NaOH. The hydrogen carbonate may
    DK 2021 70522 A1 15 e.g. be in the form of bicarbonate, such as sodium bicarbonate. The first compound is provided to raise the pH level in the first solution. The first compound is provided in such an amount in the first solution that the filter and the phosphate bound to said diatomite aggregates 105 is subjected to a pH level above 9. When the pH level is above 9, the phosphate bound to said diatomite aggregates 105 is released from said diatomite aggregates 105. The released phosphate is released into the first solution. Accordingly, at this stage, the first solution comprises the released phosphate. The first solution is circulated through the filter 100 until a sufficient amount of the phosphate bound to said diatomite aggregates 105 is released from said diatomite aggregates 105 into the first solution.
    The first solution exits the filter 100 through the outlet 106b. The first solution comprising the released phosphate is transferred S02 through the connection 103 to the tank 102. The first solution comprising the released phosphate enters the tank 102 through the tank inlet 108a. The tank 102 is separate from the filter 100. After the first solution has been removed from the filter 100, the filtering FO1 may once again commence irrespective of how the first solution is handled in the tank 102.
    A second solution is added S03 to the tank 102. The second solution comprises one or more of a second compound selected from a group consisting of: CaCl, other calcium salt, magnesium salt, and hydrocalumite. When both the first solution and the second solution are present in the tank 102, a mixture is formed.
    Phosphorus is precipitated from the mixture by phosphorus binding to a positive ion of the second compound thereby e.g. forming calcium phosphate precipitate.
    The precipitated phosphorus can then be removed S04 from the tank
    102.
    The filter 100 comprising the diatomite aggregates 105 may be exchanged at any point in time. However, it is preferred that the filter is exchanged after the regeneration process has been performed at least two times. It is also preferred that the exchange of the filter 100 is performed after
    DK 2021 70522 A1 16 a regeneration FO3 process has been performed, such that any phosphate bound in the filter has been released and collected for recycling.
    The regeneration process may be triggered in a variety of different ways.
    The regeneration process may be triggered by a manual control.
    The regeneration process may be triggered by an automatic control.
    The regeneration process may for be triggered after a set time interval.
    The regeneration process may be triggered when a certain amount of water has passed through the filter.
    To determine how much water has passed through the filter, sensors may be used.
    It is to be understood that there are many ways for how to measure the amount of water passing through the filter.
    The regeneration process may be triggered by a lowering in flow pressure of water exiting the filter.
    It is contemplated that there are numerous modifications of the embodiments described herein, which are still within the scope of the invention as defined by the appended claims.
    The tank 102 may for instance comprise a tank outlet.
    A tank outlet may provide a low-complexity way of removing the precipitated phosphorus.
    权利要求:
    Claims (8)
    [1] 1. Method for regenerating a filter (100) comprising a plurality of diatomite aggregates (105), the method comprising: filtering (FO1) water through a filter (100) comprising a plurality of diatomite aggregates (105), wherein said diatomite aggregates (105) are coated with an iron-based metal oxide such that phosphorus containing compounds present in the water bind to oxygen and/or sorption sites of the iron based metal oxide forming phosphate bound to said diatomite aggregates (105), temporarily stopping (FO2) the filtering of water through the filter (100), adding (S01) a first solution comprising one or more of a first compound selected from a group consisting of: hydroxide, hydrogen carbonate and ammonia, to the filter, wherein said first compound is provided in such an amount in the first solution that the filter (100) and the phosphate bound to said diatomite aggregates (105) is subjected to a pH level above 9, whereby the phosphate bound to said diatomite aggregates (105) is released from said diatomite aggregates (105) into said first solution, transferring (S02) the first solution comprising the released phosphate from the filter to a tank (102) separate from the filter (100), adding (S03) one or more of a second compound selected from a group consisting of: CaCl, other calcium salt, magnesium salt, and hydrocalumite, to the tank, thereby forming a mixture including the first solution and the second compound, wherein phosphorus is precipitated from the mixture by phosphorus binding to a positive ion of the second compound, and removing (S04) the precipitated phosphorus.
    [2] 2. Method according to claim 1, further comprising exchanging the filter (100) comprising the diatomite aggregates (105) after the steps of filtering (FO1), temporarily stopping (FO2) filtering, and
    DK 2021 70522 A1 18 regenerating (FO3) have been repeated at least two times, preferably at least three times, more preferably at least four times.
    [3] 3. The method according to any of the preceding claims, wherein at least 75%, by weight, of the plurality of diatomite aggregates (105) have a diameter in the interval from 1 mm to 4 mm.
    [4] 4. The method according to any of the preceding claims, wherein at least 90%, by weight, of the diatomite aggregates (105) have a specific surface area of at least 30 m2/g, determined by BET (Ny).
    [5] 5. The method according to any of the preceding claims, wherein the iron based metal coating is added by an amount such that there is about 100- 3000 mmol iron per kilogram of the diatomite aggregates (105) coated with the iron based metal coating.
    [6] 6. The method according to any of the preceding claims, wherein the diatomite aggregates (105) are coated with one or more layers of the iron based metal oxide.
    [7] 7. System for removing phosphorus from water, the system comprising: a filter (100), a tank (102) and a connection (103) arranged between or being configured to be connected between the filter (100) and the tank (102), the filter (100) comprising: one or more inlets (104a, 104b) configured to receive water to be filtered in the filter (100) and to receive a first solution comprising one or more of a first compound selected from a group consisting of: hydroxide, hydrogen carbonate, and ammonia, to the filter (100), a plurality of diatomite aggregates (105) coated with an iron based metal oxide configured to bind the phosphorus present in the water to
    DK 2021 70522 A1 19 oxygen of the iron based metal oxide forming phosphate bound to said diatomite aggregates, and one or more outlets (106a, 106b) configured to permit water that has passed through the filter (100) to exit the filter (100) and to be connected to the connection (103), wherein said first compound is provided in such an amount in the first solution that the filter (100) and the phosphate bound to said diatomite aggregates (105) is subjected to a pH level above 9, whereby the phosphate bound to said diatomite aggregates (105) is released from said diatomite aggregates (105) into said first solution, the connection (103) between the filter (100) and the tank (102) being configured to transfer the first solution comprising the released phosphate from the filter (100) to the tank (102), the tank (102) comprising: one or more tank inlets (108a, 108b) being configured to receive the first solution comprising the released phosphate and to receive one or more of a second compound selected from a group consisting of: CaCl, other calcium salt, magnesium salt, and hydrocalumite, to the tank (102), thereby forming a mixture including the first solution and the second compound, wherein phosphorus is precipitated from the mixture by phosphorus binding to a positive ion of the second compound.
    [8] 8. The system according to claim 7, wherein the filter (100) comprises less than 200 kg of coated diatomite aggregates (105) per household delivering water to the filter (100).
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    同族专利:
    公开号 | 公开日
    SE1950390A1|2020-09-30|
    WO2020204787A1|2020-10-08|
    SE543367C2|2020-12-22|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US3984313A|1973-09-18|1976-10-05|Chemical Separations Corporation|Preferential removal of ammonia and phosphates|
    JP2006341226A|2005-06-10|2006-12-21|Nippon Steel Corp|Method for removing phosphorus from water|
    BRPI0809250A2|2007-03-19|2014-09-09|Easymining Sweden A|Phosphorus Recovery|
    WO2009063456A1|2007-11-12|2009-05-22|Technion Research And Development Foundation Ltd|Method for adsorption of phosphate contaminants from water solutions and its recovery|
    WO2013062989A2|2011-10-24|2013-05-02|Metamateria Technologies, Llc|Porous composite media for removing phosphorus from water|
    法律状态:
    2021-11-02| PAT| Application published|Effective date: 20211027 |
    优先权:
    申请号 | 申请日 | 专利标题
    SE1950390A|SE543367C2|2019-03-29|2019-03-29|Method for regenerating a filter comprising a plurality of diatomite aggregates and a system therefor|
    PCT/SE2020/050318|WO2020204787A1|2019-03-29|2020-03-27|Method for regenerating a filter comprising a plurality of diatomite aggregates and a system therefor|
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