FILTER MATERIAL FOR WATER TREATMENT

Description

[0001] The invention relates to a first filter material for water treatment, a second filter material for water treatment, a method for producing the filter material, a filter comprising a filter material, the use of a filter material and a water treatment method.

[0002] In the treatment of drinking water, filter materials are used to deacidify the water. These typically contain mineral components. Filter materials containing calcium carbonate and / or magnesium oxide are particularly important in this regard. Semi-calcined dolomite, which is formed during the calcination of dolomite, also belongs to this group of filter materials.

[0003] Semi-calculated dolomite consists primarily of calcium carbonate and magnesium oxide. Granules made from semi-calculated dolomite exhibit particularly good deacidification properties in the treatment of drinking water. While calcium carbonate-based granules are not reactive enough for certain water treatment applications, magnesium oxide-based granules can be too reactive for some applications, resulting in the pH of the water exceeding an acceptable level for drinking water. Granules made from semi-calculated dolomite, on the other hand, exhibit an excellent reactivity profile, resulting from the beneficial interaction of the various components.

[0004] In addition, filter materials made of semi-calcined dolomite also meet the high safety and quality requirements that must be met in drinking water treatment. These requirements are regulated in the "Ordinance on the Quality of Water for Human Consumption (Drinking Water Ordinance - TrinkwV)." According to the Drinking Water Ordinance, only a few substances are permitted for deacidification and pH adjustment of drinking water.

[0005] One disadvantage of semi-calcined dolomite granules, however, is that they must be produced from dolomite stone in a complex, time-consuming, and energy-intensive manufacturing process. For processing, ground semi-calcined dolomite is mixed with dolomite hydrate, granulated, and recarbonated. The production of semi-calcined dolomite granules is therefore a complex, time-, labor-, and energy-intensive process.

[0006] Another disadvantage of semi-calcined dolomite granules is that further fine-tuning of the water's pH is not easily possible. The ratio of magnesium oxide to calcium carbonate is already predetermined in the raw dolomite. Further addition of magnesium oxide and / or calcium carbonate during the semi-calcined dolomite production process must be precisely calibrated, as this can negatively impact the material's granulation behavior.

[0007] Other filter materials containing calcium carbonate and magnesium oxide are already known. However, these do not exhibit the excellent deacidification properties of semi-calcined dolomite.

[0008] DE 1 592 133 A1, for example, describes a granular filter material for deacidifying water, which consists predominantly of calcium compounds. The core of the filter grain consists essentially of calcium hydroxide and the shell consists essentially of porous calcium carbonate. The core of the filter grain may also contain magnesium oxide. Due to the relatively high proportion of calcium hydroxide, the granular filter material according to DE 1 592 133 A1 exhibits a deacidification behavior that differs from the reactivity profile of semi-calcined dolomite. US Pat. No. 6,322,705 B1 also describes a multi-layer filter material for water deacidification.

[0009] Consequently, there is still a need for new filter materials that offer similarly excellent deacidification properties in drinking water treatment as semi-calcined dolomite granules. Furthermore, such filter materials would have to ensure that the treated water meets the high requirements of the Drinking Water Ordinance.

[0010] The present invention therefore aims to provide a filter material suitable for the treatment of drinking water. The filter material should have similar deacidification properties to granules made of semi-calcined dolomite.

[0011] Furthermore, the invention aims to provide a filter material that can be used to treat water so that it meets the high quality requirements of the Drinking Water Ordinance. In particular, the invention aims to provide a filter material that ensures that the water does not exceed the pH limit of 9.5 stipulated in the Drinking Water Ordinance during water treatment. Furthermore, the filter material should also meet the requirements for treatment substances stipulated in the Drinking Water Ordinance.

[0012] Furthermore, the present invention aims to provide a filter material that can be produced in a simple and cost-effective manner.

[0013] Finally, the present invention aims to provide a filter that enables high-quality and stable water deacidification over several months.

[0014] One or more of these objects are achieved by the products described in claims 1, 10 and 12 and by the use described in claim 16.

[0015] Advantageous embodiments of the invention are specified in the dependent claims and are explained in detail below.

[0016] The present invention relates to a first filter material for water treatment, which comprises a first granulate containing calcium carbonate and a second granulate containing magnesium oxide, wherein the first and the second granulate, each independently of one another, have a bulk density of 1.00 to 1.40 t / m 3 , and the filter material contains the first granulate in an amount of 55 to 85 wt.% based on the sum of the amounts of the first and second granules. Surprisingly, it has been found that such a filter material is outstandingly suitable for treating water, in particular drinking water. Furthermore, the pH value of drinking water can be precisely adjusted using the filter material according to the invention.

[0017] The deacidification behavior of the filter material according to the invention is very similar to that of granules made of semi-calcined dolomite and remains stable even over several weeks with a daily operating time of almost 10 hours. The filter material according to the invention ensures consistent deacidification of drinking water. Water treated with the filter material according to the invention meets the quality requirements of the Drinking Water Ordinance and does not exceed the pH limit of 9.5. During water treatment, the filter material also leads to iron and manganese removal and remineralization of the drinking water, thereby further improving its quality.

[0018] Without wishing to be bound to any particular scientific theory, the excellent deacidification behavior of the filter material appears to be attributable to the interaction between the first and second granules. The filter material according to the invention behaves like granules made of semi-calcined dolomite, although it comprises granules of different types. This homogeneous deacidification behavior appears to be attributable in particular to the corresponding bulk density of the first and second granules. If both the first and second granules independently have a bulk density of 1.00 to 1.40 t / m3, the filter material results in a homogeneous mixture of both granules, the distribution of which does not change significantly even over a longer period of time under the influence of water.In this way, there is no demixing in the filter and the filter material has a stable ratio of first and second granules throughout the entire filter.

[0019] Granules within the meaning of the invention include grains, each grain being an agglomerate of smaller particles. Consequently, pure powders are not granules within the meaning of the invention.

[0020] If the bulk density of the first and / or second granules is less than 1.00 t / m³, the granules are not sufficiently stable to react even when large quantities of water are used in industrial water treatment. Such granules may become detached and irregular. If, on the other hand, the first and / or second granules have a bulk density of more than 1.40 t / m³, the particles from which the granules are formed do not form a loose bond with one another, but are packed too tightly, resulting in unstable granules. Granules obtained in this way are not sufficiently stable for applications in industrial water treatment of drinking water and do not exhibit the required reactivity for the deacidification process.

[0021] According to an advantageous embodiment of the filter material according to the invention, the first and / or the second granulate, each independently of one another, has a bulk density of 1.10 to 1.38 t / m 3 , preferably 1.15 to 1.35 t / m 3 , or particularly preferably 1.20 to 1.32 t / m 3 . If the first and / or the second granulate has such a bulk density, a particularly constant pH adjustment of drinking water can be achieved with the filter material.

[0022] According to a particularly preferred embodiment of the invention, both the first and the second granulate have a bulk density of 1.10 to 1.38 t / m 3 , more preferably 1.15 to 1.35 t / m 3 or particularly preferably 1.20 to 1.32 t / m 3 . The more similar the bulk densities of the first and second granulates of the filter material are, the more uniform and stable the effect of the filter material in water treatment. Particularly preferably, the bulk density of the first granulate is at most 20%, in particular at most 10% or at most 5% above or below the bulk density of the second granulate, based on the value of the bulk density of the first and second granules in t / m 3 . This means that, for example, if the bulk densities of the first and second granules differ by no more than 10% and the second granule has a bulk density of 1.15 t / m 3<, the first granule has a bulk density of 1.04 to 1.26 t / m 3<.

[0023] Methods for determining bulk density are known to those skilled in the art. In particular, the determination of the bulk density of the granules according to the invention is carried out according to DIN EN 12902, Section 5.2, particularly preferably according to DIN EN 12902:2004, Section 5.2. The granules according to the invention are granular material as defined in Table 1 in Section 5.2.4 of DIN EN 12902:2004.

[0024] The deacidification behavior of the filter material according to the invention has proven particularly effective and consistent because the filter material contains the first granulate in an amount of 55 to 85 wt.%, preferably in an amount of 60 to 80 wt.%, more preferably in an amount of 62 to 75 wt.%, more preferably in an amount of 65 to 70 wt.%, or particularly preferably in an amount of 66 to 68 wt.%, based on the sum of the amounts of the first and second granulate. If the filter material contains the first and second granulate in such a ratio, the deacidification behavior of the filter material according to the invention corresponds particularly to that of granules made of semi-calcined dolomite. Furthermore, in this case, the filter material exhibits a particularly long-lasting, stable deacidification behavior.

[0025] Particularly good results in water treatment can be achieved if the first granulate of the filter material contains calcium carbonate in an amount of at least 90 wt.%, preferably at least 93 wt.%, more preferably at least 95 wt.%, or particularly preferably at least 96 wt.%, based on the total dry weight of the first granulate. According to a particularly preferred embodiment of the invention, the first granulate contains calcium carbonate in an amount of approximately 97 wt.%, based on the total dry weight of the first granulate. According to a further embodiment, the first granulate contains calcium carbonate in an amount of at least 97 wt.%, at least 98 wt.%, or at least 99 wt.%, based on the total dry weight of the first granulate. According to a further particularly preferred embodiment of the invention, the first granulate meets the purity criteria for calcium carbonate according to DIN EN 1018:2013, Section 5.Such a high calcium carbonate content in the first granulate ensures that the quality of the water treatment remains stable over a large number of water cycles. Furthermore, a filter material in which the first granulate contains such a quantity of calcium carbonate has a particularly high deacidification potential. With a first granulate containing the stated calcium carbonate content or the stated calcium carbonate purity, the treated water also has a particularly low turbidity of less than 2 NTU, preferably less than 1.5 NTU, or particularly preferably less than 1 NTU.

[0026] According to a further preferred embodiment of the invention, the second granulate of the filter material contains magnesium oxide in an amount of at least 80 wt.%, preferably at least 85 wt.%, or particularly preferably at least 90 wt.%, based on the total dry weight of the second granulate. According to a further embodiment of the invention, the second granulate contains magnesium oxide in an amount of at least 93 wt.%, at least 95 wt.%, at least 97 wt.%, at least 98 wt.%, or at least 99 wt.%, based on the total dry weight of the second granulate. According to a particularly preferred embodiment of the invention, the second granulate preferably has a magnesium oxide purity corresponding to the requirements of the standard DIN EN 16004:2012-02, Section 4. If the second granulate has such a proportion of magnesium oxide, the pH of water can be adjusted particularly efficiently.In addition, the pH value of the water can be adjusted very precisely with such a filter material. With a second granulate with the stated magnesium oxide content or the stated magnesium oxide purity, the treated water also has a particularly low turbidity of less than 2 NTU, preferably less than 1.5 NTU, or particularly preferably less than 1 NTU.

[0027] Methods for determining the turbidity of a water sample are known to those skilled in the art. The turbidity of a water sample can be determined, in particular, using nephelometry. The method according to DIN EN ISO 7027:2000 can be used for this purpose.

[0028] The first granulate may contain other components besides calcium carbonate. It has proven particularly advantageous if the first granulate contains magnesium oxide in an amount of no more than 1 wt.%, in particular no more than 0.5 wt.%, based on the total dry weight of the first granulate. If the first granulate contains only these small amounts of magnesium oxide, the pH of the treated water can be precisely adjusted and predicted. With significantly higher amounts of magnesium oxide (e.g., over 10 wt.%) in the first granulate, temporary and / or short-term increases in the pH (peaks) may occur under certain circumstances, which are undesirable for water treatment.

[0029] According to one embodiment, the first granulate contains, as further components, magnesium carbonate, preferably from 0.01 to 2.0 wt.%, free calcium oxide, preferably from 0.1 to 2.0 wt.%, iron and aluminum oxide, preferably together from 0.01 to 0.5 wt.%, and / or silica, preferably from 0.05 to 0.5 wt.%, each based on the total dry weight of the first granulate. Granules containing some or all of these further components are comparatively inexpensive and simultaneously exhibit excellent water treatment quality.

[0030] The second granulate may contain other components in addition to magnesium oxide. According to one embodiment of the invention, the second granulate contains calcium carbonate in an amount of at most 3 wt.%, in particular at most 2 wt.%, at most 1 wt.%, or at most 0.5 wt.%, based on the total dry weight of the second granulate. This ensures that the second granulate has a high deacidification potential.

[0031] According to one embodiment, the second granulate contains, as further components, free calcium oxide, preferably from 0.1 to 2.0 wt.%, iron and aluminum oxide, preferably together from 0.1 to 2.0 wt.%, and / or silica, preferably from 0.05 to 2.0 wt.%, each based on the total dry weight of the second granulate. Granules containing some or all of these additional components are comparatively inexpensive and simultaneously exhibit excellent water treatment quality.

[0032] Unless otherwise stated, the content or purity of calcium carbonate is determined according to DIN 12485, in particular according to DIN EN 12485:2017-10.

[0033] Unless otherwise stated, the magnesium oxide content in the dry matter is determined in accordance with DIN EN 12485, in particular DIN EN 12485:2017-10, point 6.9.

[0034] When determining the content of a substance according to one of the analytical methods listed in the standard DIN EN 12485, in particular DIN EN 12485:2017-10, it must be noted that the analytical methods must be carried out on material obtained after determining the loss on ignition at 550 °C. At this temperature, for example, calcium hydroxide is converted to calcium oxide. Likewise, magnesium hydroxide is converted to magnesium oxide at this temperature. Thus, when determining the magnesium oxide content in the dry matter according to DIN EN 12485, in particular according to DIN EN 12485:2017-10, point 6.9, both the magnesium oxide contained in the material before the loss on ignition and the magnesium hydroxide are equally recorded as magnesium oxide in the dry matter. Magnesium oxide in the dry matter therefore includes in particular the magnesium oxide and magnesium hydroxide contained in the sample before the loss on ignition.Likewise, when determining free calcium oxide according to DIN EN 12485, in particular DIN EN 12485:2017-10, Section 6.8, both the calcium oxide and calcium hydroxide contained in the material before loss on ignition are equally recorded as free calcium oxide. Free calcium oxide therefore includes, in particular, the calcium oxide and calcium hydroxide contained in the sample before loss on ignition.

[0035] In principle, the first and / or second granules can be present in a wide variety of shapes. For example, the first and / or second granules can be cylindrical, spherical, lenticular, rectangular, cubic, or prismatic. If the first and second granules, each independently of one another, are essentially spherical, the filter material can be introduced into the filter particularly uniformly and in a space-saving manner. Furthermore, the degradation of the spherical granules during the deacidification process occurs particularly uniformly, so that the filter material still provides a uniform and stable water treatment result even after a prolonged period of operation. According to a particularly preferred embodiment, both the first and second granules are essentially spherical.

[0036] In principle, the size of the first granulate for the filter material according to the invention can range within a wide range. It has proven particularly advantageous if the first granulate has a grain size group of 0.01 to 8 mm, preferably from 0.1 to 6 mm, more preferably from 0.3 to 4 or particularly preferably from 0.5 to 3.2 mm, with an undersize fraction of less than 10 wt.%, preferably a maximum of 2 wt.%, and with an oversize fraction of less than 10 wt.%, preferably a maximum of 7 wt.%. If the first granulate has such a grain size group, an optimal surface-to-volume ratio is achieved for water treatment. In addition, with this size of the first granulate, the water can easily pass through the filter material in the filter and at the same time interact sufficiently with the granulate to ensure complete water treatment.

[0037] The size of the second granulate can be selected within a wide range. It has proven particularly suitable for the filter material if the second granulate has a grain size group of 0.01 to 12 mm, preferably 0.1 to 10 mm, more preferably 0.2 to 5 mm, or particularly preferably 0.5 to 2.5 mm, with an undersize fraction of less than 10 wt.%, preferably a maximum of 3 wt.%, and an oversize fraction of less than 10 wt.%, preferably a maximum of 9 wt.%. With this grain size group, the reactivity of the second granulate towards water is particularly advantageous. In addition, with this size of the second granulate, the water can easily pass through the filter material in the filter and at the same time interact sufficiently with the granulate to ensure complete water treatment.

[0038] According to DIN EN 12901:1999, a grain group includes all grain sizes between two test sieve widths, with the grain group being described by these test sieve widths with the largest grain and the smallest grain. The largest grain is the upper test sieve width when examining a grain size distribution, and the smallest grain is the lower test sieve width when examining the grain size distribution. The oversize grain fraction corresponds to the mass fraction in % (m / m) of a grain mixture that is retained by the test sieve with the largest sieve width for the respective grain group. The undersize grain fraction corresponds to the mass fraction in % (m / m) of a grain mixture that passes the test sieve with the smallest sieve width for the respective grain group.

[0039] Methods for measuring grain size are known to those skilled in the art. Grain size can be determined, in particular, by means of sieve experiments.

[0040] According to a further preferred embodiment of the invention, the filter material according to the invention has a reactivity such that a raw water is treated by treatment with the filter material according to the invention within an EBCT value (Empty Bed Contact Time; at 10 °C) of less than 20 minutes, preferably less than 15 minutes, more preferably less than 12 minutes, particularly preferably less than 10 minutes, to such an extent that the water subsequently has a calcite dissolving capacity of less than 5 mg / l.

[0041] The raw water treated with shaped bodies according to the invention preferably has a water temperature of approximately 5 to 15°C, a pH value of less than or equal to 7.25, a base capacity up to pH 8.2 (KB 8.2 ) of greater than or equal to 0.2 mmol / l, and an acid capacity up to pH 4.3 (Ks 4.3 ) of greater than or equal to 0.5 mmol / l. The specified EBCT value is preferably achieved with an open filter with a filter material layer thickness of 1000 to 2000 mm. The filter speed is advantageously 10 m / h.

[0042] The calcite dissolving capacity is calculated in particular according to the standard DIN 38404 C 10, preferably according to the standard DIN 38404-10:2012-12 (Title: German standard methods for the analysis of water, wastewater and sludge - Physical and physico-chemical substance characteristics (Group C) - Part 10: Calculation of the calcite saturation of a water (C 10)).

[0043] The EBCT value specifically describes a measure of the time that the raw water to be treated is in contact with the treatment medium in a tank, assuming that all the raw water flows through the tank at the same velocity. The EBCT value can be calculated as the quotient of the volume of particles in the treatment medium divided by the volumetric flow rate.

[0044] According to a preferred embodiment of the invention, the filter material according to the invention consists essentially of the first granulate containing calcium carbonate and the second granulate containing magnesium oxide. When it is mentioned here that the filter material consists essentially of the first and second granulates, this means that the amount of first and second granulates together is at least 95 wt.%, preferably at least 98 wt.%, based on the total dry weight of the filter material.

[0045] According to a further preferred embodiment of the invention, the filter material according to the invention consists of the first granulate containing calcium carbonate and the second granulate containing magnesium oxide.

[0046] According to a further embodiment of the invention, the filter material according to the invention consists of a first granulate consisting essentially of calcium carbonate and a second granulate consisting essentially of magnesium oxide. When it is mentioned here that the first granulate consists essentially of calcium carbonate, this means that the amount of calcium carbonate in the first granulate is at least 95% by weight, in particular at least 97% by weight, more preferably at least 98% by weight or particularly preferably at least 99% by weight, based on the total dry weight of the first granulate. When it is mentioned here that the second granulate consists essentially of magnesium oxide, this means that the amount of magnesium oxide in the second granulate is at least 95% by weight, in particular at least 97% by weight, more preferably at least 98% by weight or particularly preferably at least 99% by weight, based on the total dry weight of the second granulate.More preferably, the first and / or second granules consist of calcium carbonate or magnesium oxide, respectively.

[0047] The invention further relates to a second filter material for water treatment, which contains 55 to 85 wt.% of a first granulate containing calcium carbonate and 15 to 45 wt.% of a second granulate containing magnesium oxide, in each case based on the sum of the amounts of the first and second granulates. This second filter material is outstandingly suitable for water treatment and behaves very similarly to granules made of semi-burned dolomite during water treatment. According to a preferred embodiment, the first and second granulates, each independently of one another, have a bulk density of 1.00 to 1.40 t / m 3 . With such a bulk density, the second filter material, in particular, does not cause any demixing effects in the filter.

[0048] What has been said in connection with the first filter material according to the invention regarding the first granulate also applies equally to the first granulate of the second filter material according to the invention.

[0049] What has been said in connection with the first filter material according to the invention regarding the second granulate also applies equally to the second granulate of the second filter material according to the invention.

[0050] A process for producing a filter material according to the invention comprises at least the steps: a. Providing a first granulate containing calcium carbonate and a second granulate containing magnesium oxide, wherein the first and second granulates, each independently of one another, have a bulk density of 1.00 to 1.40 t / m 3 ; b. Mixing the first and second granulates to produce the filter material.

[0051] The process produces a homogeneous and well-mixed filter material.

[0052] According to one process option, the mixing in process step b. takes place in a mixer selected from the group consisting of a rotating drum mixer, a trough mixer, a pan mixer, and a mechanical agitator mixer. These mixers can produce a particularly homogeneous filter material. The rotating drum mixer has proven particularly suitable for mixing the first and second granules.

[0053] What has been said in connection with the first filter material according to the invention regarding the first granulate also applies equally to the first granulate of the process according to the invention for producing the filter material.

[0054] What has been said in connection with the first filter material according to the invention regarding the second granulate also applies equally to the second granulate of the process according to the invention for producing the filter material.

[0055] The invention further relates to a filter containing the filter material according to the invention.

[0056] According to a preferred embodiment of the filter according to the invention, the filter comprises at least a first and a second layer, wherein the first layer comprises a filler material and the second layer comprises the filter material according to the invention. This enables particularly economical water treatment. Furthermore, the filler material layer ensures that the filter material layer is particularly stable and does not become disturbed.

[0057] In principle, any common filler known to those skilled in the art can be used. Filling materials selected from supporting gravel, sand, diatomaceous earth, silica gel, molecular sieve, zeolite, cellulose, cellulose derivatives, carbon fibers, ceramics, synthetic resin, rock flour, fiberglass, silicates, glass beads, and mixtures thereof have proven particularly suitable. These fillers exhibit excellent properties for use in filters for the treatment of drinking water.

[0058] According to a preferred embodiment of the filter according to the invention, the filler material has a grain size of 0.1 to 12 mm, preferably 0.5 to 10 mm, more preferably 1 to 8 mm, or particularly preferably 2 to 6 mm, with an undersize fraction of less than 15 wt.%, preferably a maximum of 10 wt.%, and an oversize fraction of less than 15 wt.%, preferably a maximum of 10 wt.%. Filler materials with such a grain size have proven to be particularly suitable for use in filters for drinking water treatment. With such a grain size, the water can flow evenly and constantly through the filler material.

[0059] According to a further preferred embodiment of the invention, the filter has a diameter of 100 to 3500 mm and / or a height of 500 to 10000 mm. A filter with a diameter of 200 to 2000 mm has proven particularly suitable for water treatment. A particularly preferred filter height is 2000 to 4000 mm. With these dimensions, the filter is particularly well suited for drinking water treatment and can ensure time- and cost-effective water treatment.

[0060] What has been said in connection with the first filter material according to the invention regarding the first granulate also applies equally to the first granulate of the filter material contained in the filter according to the invention.

[0061] What has been said in connection with the first filter material according to the invention regarding the second granulate also applies equally to the second granulate of the filter material contained in the filter according to the invention.

[0062] The invention further relates to the use of the filter material according to the invention for treating water, preferably for deacidifying and / or remineralizing water. The use of the filter material according to the invention for deacidifying and / or remineralizing drinking water is particularly preferred.

[0063] The invention also relates to the use of the filter according to the invention for treating water, preferably for deacidifying and / or remineralizing water. The use of the filter according to the invention for deacidifying and / or remineralizing drinking water is particularly preferred.

[0064] What has been said in connection with the first filter material according to the invention regarding the first granulate also applies equally to the first granulate of the filter material of the uses according to the invention.

[0065] What has been said in connection with the first filter material according to the invention regarding the second granulate also applies equally to the second granulate of the filter material of the uses according to the invention.

[0066] Furthermore, the invention relates to a water treatment process, in particular for drinking water treatment, comprising at least the steps a. Providing a filter containing a filter material which comprises a first granulate containing calcium carbonate and a second granulate containing magnesium oxide, wherein the first and the second granulate, each independently of one another, have a bulk density of 1.00 to 1.40 t / m 3< and the filter material contains the first granulate in an amount of 55 to 85 wt.% based on the sum of the amounts of the first and second granules, b. Introducing water into the filter, c. Bringing the introduced water into contact with the filter material, d. Carrying out the water previously brought into contact with the filter material from the filter.

[0067] According to a preferred embodiment of the water treatment process according to the invention, the water is passed through the filter at a rate of 5 to 30 m / h, preferably 8 to 20 m / h, or particularly preferably 10 to 15 m / h. In this way, a particularly efficient water treatment process can be carried out, providing treated water of excellent quality.

[0068] According to a further preferred embodiment, the contact time of the water with the filter material in process step c. is from 1 to 30 minutes, preferably from 5 to 15 minutes, or particularly preferably from 6 to 10 minutes. This contact time has been found to be sufficient for water treatment and simultaneously enables a high water throughput.

[0069] According to a further preferred embodiment of the water treatment method according to the invention, filter material is refilled into the filter after 5 to 15%, in particular 8 to 10%, of the filter material volume required for the treatment objective, i.e., the filter material originally introduced into the filter, has been consumed. The refill volume of filter material is preferably calculated from the difference between the filter material volume required for the treatment objective and the volume of filter material in the filter at the time of refilling. This ensures long-term, stable water treatment.

[0070] To prevent silting of the filter due to contaminants from the raw water, according to a preferred embodiment, rinsing the filter containing the filter material according to the invention has proven advantageous. According to one embodiment, the filter is rinsed with an air-water mixture for 1 to 30 minutes, preferably for approximately 10 minutes, before being brought into contact with water in process step b., and then with water.

[0071] What has been said about the filter material in connection with the first filter material according to the invention also applies equally to the filter material used in the water treatment process according to the invention.

[0072] What has been said in connection with the first filter material according to the invention regarding the first granulate also applies equally to the first granulate of the water treatment process according to the invention.

[0073] What has been said in connection with the first filter material according to the invention regarding the second granulate also applies equally to the second granulate of the water treatment process according to the invention.

[0074] The invention is explained in more detail below by means of an example which, however, serves only for illustrative purposes and is not limiting. Example

[0075] Fig. 1 Figure 1 shows the pH value of water treated with the filter material according to the invention

[0076] A filter with a diameter of 300 mm and a height of 3000 mm was initially filled with 34 kg of supporting gravel (height 300 mm) as fill material with a grain size of 2.0 to 3.15 mm (oversize and undersize fraction less than 10 wt.%). Subsequently, 40 kg of filter material (height 500 mm) were filled into the filter. The filter material consisted of 26.7 kg of a first granulate (Akdolit ®< Hydro-Calcit CG) containing approximately 97 wt.% calcium carbonate, based on the dry weight of the first granulate, and 13.3 kg of a second granulate (Akdolit ®< Hydrolit-MG) containing approximately 95 wt.% magnesium oxide, based on the dry weight of the second granulate.

[0077] The filled filter was then rinsed with raw water for 10 minutes to prevent clogging of the filter.

[0078] Subsequently, raw water with a temperature of approximately 9°C, a pH value of approximately 7.25 and a base capacity up to pH 8.2 (KB 8.2 ) of 0.2 mmol / l and an acid capacity up to pH 4.3 (KS 4.3 ) of 1.6 mmol / l was pumped through the filter at a water flow rate of 0.3 to 0.6 m 3 / h. The daily running time was between 5 and 10 hours. After a water volume of approximately 100 m 3 had been treated, 10 kg of the filter material described above was added to the filter material already placed in the filter. The filled filter was then rinsed again for approximately 10 minutes as described above.

[0079] After a total water treatment volume of 600 m³, the filter was emptied and refilled with fresh supporting gravel (10 kg, particle size range 3.15 to 5.6 mm, oversize and undersize fractions less than 10 wt.%; filter height 300 mm) and fresh filter material (19.5 kg total; 13 kg Akdolit® Hydro-Calcit CG and 6.5 kg Akdolit® Hydrolit-Mg) and rinsed with raw water for 6 minutes. The raw water was then pumped through the filter again at a water flow rate of 0.3 to 0.6 m³ / h for 5 to 10 hours daily. Refilling occurred when the filtrate pH fell below the target treatment level of 7.7.

[0080] The treated water was regularly tested for pH, hardness, and turbidity. Figure 1As can be seen, the pH value of the treated water remained between 7.5 and 9 throughout the entire test period, significantly below the lower and upper limits for drinking water according to the Drinking Water Ordinance. The filter material in the filter remained sufficiently active to deacidify the water, even over a period of several months. At the same time, the activity of the filter material was never too high, but remained stable throughout the entire test period. Furthermore, no significant fluctuations in the pH value were observed.

[0081] The water hardness was checked at regular intervals (approximately every two weeks). The calcium and magnesium ion values ​​were determined using ion chromatography in accordance with DIN EN 14911:1999, and the bicarbonate concentration values ​​were determined using titrimetry in accordance with DIN 38409-H7:2005. The theoretical values ​​are Ca 2+< :Mg 2+< :HCO 3 -< = 1 : 1 : 4, while the measured values ​​are Ca 2+< :Mg 2+< :HCO 3 -< = 1.0 : 1.4 : 4.6. Consequently, the magnesium oxide component reacted somewhat faster than the calcium carbonate component. Overall, however, the measured values ​​were in good agreement with the expected theoretical hardness values.

[0082] The turbidity of the treated water was tested using nephelometry at regular intervals of approximately every two weeks. The turbidity of the treated water was tested according to DIN EN ISO 7027:2000. The majority of measurements showed very low turbidity of less than 0.1 NTU. None of the measurements exceeded the 1 NTU turbidity limit specified in the Drinking Water Ordinance.

[0083] The raw water treated with the filter material according to the invention therefore met the quality requirements of the Drinking Water Ordinance. The filter material according to the invention is therefore ideally suited for the treatment, particularly the deacidification and / or remineralization, of drinking water.

Claims

1. Filter material for water treatment comprising: - a first granulate containing calcium carbonate, - a second granulate containing magnesium oxide, wherein the first and the second granulate each independently have a bulk density of 1.00 to 1.40 t / m3 and the filter material contains the first granulate in a quantity of 55 to 85% by weight, in relation to the sum of the quantities of the first and second granulate.

2. Filter material according to claim 1, characterized in that the first and / or the second granulate each independently has a bulk density of 1.10 to 1.38 t / m3, in particular 1.15 to 1.35 t / m3, or 1.20 to 1.32 t / m3.

3. Filter material according to one of claims 1 or 2, characterized in that the filter material contains the first granulate in a quantity of 60 to 80% by weight, of 62 to 75% by weight, of 65 to 70% by weight, or of 66 to 68% by weight, in relation to the sum of the quantities of the first and second granulate.

4. Filter material according to one of the preceding claims, characterized in that the first granulate contains calcium carbonate in a quantity of at least 90% by weight, in particular at least 93% by weight, at least 95% by weight or at least 96% by weight, in relation to the total dry weight of the first granulate.

5. Filter material according to one of the preceding claims, characterized in that the second granulate contains magnesium oxide in a quantity of at least 80% by weight, in particular at least 85% by weight, or at least 90% by weight, in relation to the total dry weight of the second granulate.

6. Filter material according to one of the preceding claims, characterized in that the first granulate contains magnesium oxide in a quantity of at most 1% by weight, in particular at most 0.5% by weight, in relation to the total dry weight of the first granulate, and / or the second granulate contains calcium carbonate in a quantity of at most 3% by weight, in particular at most 2% by weight, at most 1% by weight or 0.5% by weight, in relation to the total dry weight of the second granulate.

7. Filter material according to one of the preceding claims, characterized in that the first and second granulate are each independently an essentially spherical granulate.

8. Filter material according to one of the preceding claims, characterized in that the first granulate has a particle size fraction of 0.01 to 8 mm, in particular 0.1 to 6 mm, 0.3 to 4, or 0.5 to 3.2 mm, with an undersize fraction of less than 10% by weight, in particular a maximum of 2% by weight, and with an oversize fraction of less than 10% by weight, in particular a maximum of 7% by weight.

9. Filter material according to one of the preceding claims, characterized in that the second granulate has a particle size fraction of 0.01 to 12 mm, in particular 0.1 to 10 mm, 0.2 to 5 mm, or 0.5 to 2.5 mm, with an undersize fraction of less than 10% by weight, in particular a maximum of 3% by weight, and with an oversize fraction of less than 10% by weight, in particular a maximum of 9% by weight.

10. Filter material for water treatment comprising: - 55 to 85% by weight of a first granulate containing calcium carbonate, - 15 to 45% by weight of a second granulate containing magnesium oxide, in each case in relation to the sum of the quantities of the first and second granulate, the first and second granulate each independently having a bulk density of 1.00 to 1.40 t / m3.

11. Filter material according to claim 10, characterized in that the first and second granulates are defined as in one of claims 2 and / or 4 to 9.

12. Filter containing a filter material according to one of claims 1 to 11.

13. Filter according to claim 12, characterized in that the filter comprises at least a first and a second layer, wherein the first layer comprises a filler material and the second layer comprises a filter material according to any one of claims 1 to 11.

14. Filter according to claim 13, characterized in that the filler material is selected from supporting gravel, sand, kieselguhr, silica gel, molecular sieve, zeolite, cellulose, cellulose derivatives, carbon fibers, ceramic, synthetic resin, rock flour, glass fiber, silicates, glass spheres and mixtures thereof and / or in that the filler material has a particle size fraction of 0.1 to 12 mm, in particular 0.5 to 10 mm, 1 to 8 mm, or 2 to 6 mm, with an undersize fraction of less than 15% by weight, in particular a maximum of 10% by weight, and an oversize fraction of less than 15% by weight, in particular a maximum of 10% by weight.

15. Filter according to one of claims 12 to 14, characterized in that the filter has a diameter of 100 to 3500 mm and / or a height of 500 to 10000 mm.

16. Use of a filter material according to one of claims 1 to 11 and / or a filter according to one of claims 12 to 15 for treatment of water, in particular for deacidification and / or remineralization of water.