Filter Material for Water Treatment

Abstract

A first filter material for water treatment comprising a first granulate containing calcium carbonate and a second granulate containing magnesium oxide, wherein the first and the second granulate each independently having a bulk density of 1.00 to 1.40 t/m.sup.3; a second filter material for water treatment comprising 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 the second granulate; a method for manufacturing the filter material; a filter containing the filter material; a use of the filter material for treating water; and a water treatment method are described.

Claims

1. A filter material for water treatment comprising: a first granulate containing calcium carbonate; and 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/m.sup.3.

2. The filter material according to claim 1, wherein the first and/or the second granulate each independently has a bulk density of 1.10 to 1.38 t/m.sup.3.

3. The filter material according to claim 1, wherein the filter material contains the first granulate in an amount of 55 to 85% by weight based on the sum of the amounts of the first and the second granulate.

4. The filter material according to claim 1, wherein the first granulate contains calcium carbonate in an amount of at least 90% by weight based on the total dry weight of the first granulate.

5. The filter material according to claim 1, wherein the second granulate contains magnesium oxide in an amount of at least 80% by weight based on the total dry weight of the second granulate.

6. The filter material according to claim 1, wherein the first granulate contains magnesium oxide in an amount of at most 1% by weight based on the total dry weight of the first granulate, and/or the second granulate contains calcium carbonate in an amount of at most 3% by weight based on the total dry weight of the second granulate.

7. The filter material according to claim 1, wherein the first and the second granulate are each independently a substantially spherical granulate.

8. The filter material according to claim 1, wherein the first granulate has a particle size range of 0.01 to 8 mm, with an undersize percentage of less than 10% by weight, and with an oversize percentage of less than 10% by weight.

9. The filter material according to claim 1, wherein the second granulate has a particle size range of 0.01 to 12 mm, with an undersize percentage of less than 10% by weight, and with an oversize percentage of less than 10% by weight.

10. A filter material for water treatment comprising: 55 to 85% by weight of a first granulate containing calcium carbonate; and 15 to 45% by weight of a second granulate containing magnesium oxide, in each cased based on the sum of the amounts of the first and the second granulate.

11. The filter material according to claim 10, wherein the first and the second granulate each independently has a bulk density of 1.00 to 1.40 t/m.sup.3.

12. A Filter comprising the filter material according to claim 1.

13. The filter according to claim 12, wherein 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.

14. The filter according to claim 13, wherein the filler material is selected from supporting gravel, sand, kieselgur, 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 range of 0.1 to 12 mm, with an undersize percentage of less than 15% by weight, and an oversize percentage of less than 15% by weight.

15. The filter according to claim 12, wherein the filter has a diameter of 100 to 3500 mm and/or a height of 500 to 10000 mm.

16. (canceled)

17. A method for treating water, comprising: (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 have a bulk density of 1.00 to 1.40 t/m.sup.3; (b) introducing water into the filter; (c) bringing the introduced water into contact with the filter material; and (d) removing the water previously brought into contact with the filter material from the filter.

Description

EXAMPLE

[0080] FIG. 1 shows the pH value of water which has been treated with the inventive filter material

[0081] A filter having a diameter of 300 mm and a height of 3000 mm was initially filled with 34 kg support gravel (height 300 mm) as filler material with a particle size range of 2.0 to 3.15 mm (oversize and undersize percentage less than 10% by weight). Then 40 kg filter material (height 500 mm) was poured into the filter. The filter material was made of 26.7 kg of a first granulate (Akdolit® Hydro-Calcit C G) containing approximately 97% by weight 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% by weight magnesium oxide, based on the dry weight of the second granulate.

[0082] The filled filter was then flushed with raw water for 10 minutes in order to prevent the filter from silting up.

[0083] Then raw water having a temperature of about 9° C., a pH value of about 7.25, a base capacity up to pH 8.2 (K.sub.B 8.2) of 0.2 mmol/l and an acid capacity up to pH 4.3 (K.sub.S 4.3) of 1.6 mmol/l was pumped through the filter at a water flow rate of 0.3 to 0.6 m.sup.3/h. The daily running time was 5 to 10 hours. After a treatment volume of about 100 m.sup.3 of water, 10 kg of the filter material described above was added to the filter material already introduced into the filter. The filled filter was then flushed again for about 10 minutes as described above.

[0084] After a 600 m.sup.3 total treatment volume of water, the filter was emptied and refilled with fresh support gravel (10 kg, particle size range 3.15 to 5.6 mm, oversize and undersize percentage content less than 10% by weight; height in the filter 300 mm) and fresh filter material (19.5 kg total; 13 kg Akdolit® Hydro-Calcit C G and 6.5 kg Akdolit® Hydrolit-Mg) and flushed 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 m.sup.3/h for 5 to 10 hours daily. Refilling took place when the filtrate fell below the treatment target of pH 7.7.

[0085] The treated water was checked regularly for pH, hardening, and turbidity. As can be seen from FIG. 1, the pH of the treated water was between 7.5 and 9 over the entire duration and thus clearly distanced from the lower and upper limit values for drinking water according to the Drinking Water Ordinance. The filter material in the filter remained sufficiently active for deacidifying 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 over the entire test period. In addition, no significant fluctuations in the pH value could be observed.

[0086] The water was checked for hardening at regular intervals (approximately every two weeks). The values for calcium and magnesium ions were determined by means of ion chromatography in accordance with DIN EN 14911:1999, the values for the hydrogen carbonate concentration by means of titrimetry in accordance with DIN 38409-H7:2005. The theoretical values are Ca.sup.2+:Mg.sup.2+:HCO.sub.3.sup.−=1:1:4, the measured values for Ca.sup.2+:Mg.sup.2+:HCO.sub.3.sup.−=1.0:1.4:4.6. The magnesium oxide component consequently reacted somewhat faster than the calcium carbonate component. Overall, however, the measured values were in good agreement with the expected theoretical hardening values.

[0087] The turbidity of the treated water was checked by means of nephelometry at regular intervals of about 2 weeks. The turbidity of the treated water was tested in accordance with DIN EN ISO 7027:2000. In most of the measurements, the treated water had a very low turbidity of less than 0.1 NTU. The turbidity limit of the drinking water ordinance of 1 NTU was not exceeded in any of the measurements.

[0088] The raw water treated with the inventive filter material consequently met the quality requirements according to the Drinking Water Ordinance. The inventive filter material is therefore extremely well suited for the treatment of drinking water, in particular for the deacidification and/or remineralization of drinking water.