Water filters, their use and methods for treating drinking water

Abstract

Water filter (1) comprising a membrane filter with a filtration membrane, which is designed as an ultrafilter or microfilter and which has a flow direction (D) and comprises an alkalizing and / or oxidizing material (3) which provides a zone in which a biocidal contact material is present due to the alkalizing and / or oxidizing material (3), wherein the membrane filter comprises a folded membrane pack (5) in which the open ends of the hollow fiber membranes (4) are held in a potting compound (6) on the outlet side, and wherein the alkalizing and / or oxidizing material (3) is arranged upstream of the membrane pack (5) on the inlet side.

Description

Field of invention

[0001] The invention relates to a water filter, its use, and a method for treating drinking water. Background of the invention

[0002] Drinking water can be supplied from different sources depending on the application situation, including a tank or a water pipe.

[0003] In particular, there is a risk that microorganisms such as bacteria, fungi, or algae can multiply in pipes during periods of stagnation. A stagnation period is a time when no water is drawn. The term "microorganisms" used below refers to both algae and organisms such as bacteria and fungi that can cause harmful processes.

[0004] To counteract the proliferation of microorganisms, it is common practice to heat the water in the storage container to kill them. This can be done, for example, periodically by heating the entire water container. This method is complex and energy-intensive.

[0005] Furthermore, microorganisms can form, particularly near the outlet of a water dispenser, which are naturally not reached by the heated water, but are rinsed out when the water dispenser is activated.

[0006] To remove microorganisms from drinking water, devices and methods for ultrafiltration and microfiltration are known. For example, bacteria generally cannot pass through an ultrafilter. Microfiltration is a process for filtration through membranes with a pore size between 0.1 µm and 1 µm, which also prevents most bacteria from passing through a microfiltration membrane. In contrast, the pore size in ultrafiltration is less than 0.1 µm. In particular, capillary membranes are known as filter media for ultrafiltration or microfiltration, where the wall of the capillary forms the membrane.

[0007] During ultrafiltration or microfiltration, increased bacterial growth and biofilm formation can occur on the concentrate side. In this process, microorganisms adhere to the membrane during filtration and become embedded in a matrix of extracellular polymeric substances (EPS). EPS are produced by microorganisms and released into their environment. The composition of the EPS depends on the species involved in the biofilm. The EPS ensure the adhesion of the microorganisms to the membrane surface and provide mechanical and chemical stability to the biofilm. As the biofilm thickness increases, the membrane's filtration efficiency decreases. Furthermore, the increased bacterial growth on the concentrate side can lead to uncontrolled backflow contamination into the pipe network.

[0008] Document US 2008 / 0105618 A1 shows an ultrafilter with an additional filter stage made of magnesium oxide. Document DE 103 16 921 A1 shows the addition of hydrogen peroxide upstream of a catalytic filter. Document DE 603 ​​06 401 T2 shows an oil filter. Document DE 10 2015 011 752 A1 shows a microfilter with activated carbon. Document DE 10 2012 105 720 Al shows an ultrafilter designed as a membrane pack. Object of the invention

[0009] Against this background, the invention is based on the objective of providing drinking water that is as germ-free as possible. In particular, it is an objective of the invention to increase the service life and reliability of a membrane filter, especially a microfilter or an ultrafilter, while simultaneously protecting the piping system from bacterial recontamination.

[0010] The invention is intended to provide a device and a method which enables the extraction of drinking water without contamination by microorganisms, even after a prior period of stagnation in the extraction. Summary of the invention

[0011] The object of the invention is already achieved by a water filter with the features of claim 1 and by a method for filtering drinking water with the features of claim 11.

[0012] The invention provides a water filter with a filtration membrane, in particular comprising an ultrafilter, especially with a membrane pack for ultrafiltration, which has a flow direction and includes an alkalizing and / or oxidizing material which, viewed in the flow direction, is positioned directly in front of or within the membrane space. The direct contact of the alkalizing and / or oxidizing material with the membranes directly counteracts the formation of a biofilm.

[0013] A biocidal effect can be achieved, for example, by increasing the pH value above 9, in particular to a pH value above 10, but preferably below 13, via the alkalizing and / or oxidizing material.

[0014] Furthermore, the material can have an oxidizing effect, in particular by forming an oxidizing substance, such as hydrogen peroxide.

[0015] According to a further embodiment, the water filter comprises a microfilter with a membrane assembly for microfiltration, which has a flow direction and contains alkalizing and / or oxidizing material positioned directly in front of or within a membrane chamber in the flow direction. The direct contact of the alkalizing and / or oxidizing material with the membranes counteracts the formation of a biofilm.

[0016] As the incoming water flows through the filter according to the invention, it passes through a zone in which a biocidal contact material is present due to the alkalizing and / or oxidizing agent. A "biocidal contact material" is understood to be a material that has a bactericidal and / or fungicidal and / or algicidal effect upon contact with water. By positioning the alkalizing and / or oxidizing agent on the membrane pack for ultrafiltration or microfiltration, the growth of biofilms on the inlet side of the membrane pack is prevented.

[0017] The alkalizing and / or oxidizing material prevents the growth of a biofilm into the membrane package or the growth of a biofilm through the membrane package.

[0018] By using a membrane package for ultrafiltration or microfiltration, the invention makes it possible to forgo germicidal measures such as dosing silver ions or chlorine to inhibit germ growth or other techniques, since these microorganisms cannot pass through the membranes and thus clean water exits the filter according to the invention.

[0019] The water filter can therefore be designed to be silver-free and / or chlorine-free.

[0020] According to the invention, a water filter with an effect against microorganisms is thus provided in a surprisingly simple manner. Its biocidal effect is based on an increase in the pH value and / or on the oxidative effect of the material located in front of or directly in contact with the membrane pack.

[0021] In a preferred embodiment of the invention, the alkalizing and / or oxidizing material is in direct contact with the membrane package.

[0022] The invention enables the provision of virtually germ-free drinking water by means of the material positioned in front of or directly on the membrane assembly. According to the invention, the filtration of the drinking water simultaneously counteracts the growth of biofilms on the membrane. Furthermore, it allows for the reliable extraction of drinking water without contamination by microorganisms, even after a period of stagnation.

[0023] In a further advantageous embodiment of the invention, the alkalizing and / or oxidizing material contains at least one material selected from the group of carbonates, oxides or peroxides.

[0024] Calcium carbonate, magnesium carbonate, calcium oxide, magnesium oxide, magnesium peroxide, calcium peroxide, sodium peroxide, potassium peroxide and zinc peroxide, as well as mixtures of at least two of the aforementioned materials, are particularly suitable for use in the context of the invention.

[0025] Agglomerated materials, which largely prevent dust formation, are particularly easy to handle. An alkalizing and / or oxidizing material is preferred, which has particles with a particle size of less than 5 mm, preferably less than 3 mm, most preferably in the range between 0.2 mm and 10 mm, and most preferably in the range between 0.5 mm and 2.5 mm.

[0026] The particle sizes specified above refer to the initial state of the respective alkalizing and / or oxidizing material. The upper limit for the particle size of the material is determined in particular by the desired dissolution kinetics. In principle, the use of powder is also possible within the scope of the invention. Materials with particles larger than 20 micrometers are preferred, particularly larger than 100 micrometers, and most preferably larger than 200 micrometers, so that the flow resistance of the material is reduced compared to a bed of smaller particles.

[0027] These granulated materials dissolve in water so slowly that the pH value of the water in the water filter is only increased during the stagnation phase, thus enabling the desired biocidal effect. Therefore, with the aid of the invention, biofilm formation and algae growth in the ultrafilter or microfilter, as well as the release of microorganisms into the water drawn immediately after the stagnation phase, can be reduced or even almost completely prevented compared to devices without a material positioned according to the invention. Influence of pH value on bacterial growth:

[0028] All microorganisms have a pH range within which growth is possible, or rather, an optimal pH range. Most natural environments have a pH between 4 and 9, and there are many microorganisms whose optimum pH lies precisely within this range. The most common bacteria found in drinking water, such as Legionella, Pseudomonas, E. coli, and Enterococci, have their optimum pH in exactly this range. bacterium pH optimum pH range in which growth is possible E. coli 7-7, 5 5, 5-9 Enterococci 7, 5 4, 6-9, 9 Legionella 7 5-8, 1 Pseudomonas ae. 7, 0-7, 5 4, 5-9, 5

[0029] While the extracellular pH influences bacterial growth, the intracellular pH must remain close to neutral (except for extremely acidophilic or alkaliphilic bacteria), as DNA is acid-labile and RNA is alkali-labile. If the extracellular pH falls outside the optimum range or the range in which growth is still possible (see table), the bacteria are no longer able to stabilize the intracellular pH. This slows down or stops bacterial growth, or leads to bacterial death.

[0030] As soon as water is drawn through the water filter according to the invention, the water standing in the filter is mixed with fresh water and the pH value of the drawn water is lowered.

[0031] In particular, the alkalizing and / or oxidizing material is configured such that after a stagnation phase of 5 hours the OH- -Concentration increases to such an extent that the pH value rises to 10 to 13.

[0032] Furthermore, an amorphous silicate material can be added to the alkalizing and / or oxidizing material. The silica dissolved in water stabilizes the pH value on the filtrate side.

[0033] In ultrafiltration, the pore size ranges between 0.01 µm and 0.1 µm. This method separates, for example, macromolecules, proteins, and sometimes viruses. In microfiltration, the pore size is greater than 0.1 µm. This method separates, for example, bacteria, yeasts, particles, etc.

[0034] A membrane is typically used to convert the entire quantity of raw or incoming water into filtrate or output water. An advantage of this method is the sterility of the resulting filtrate, as well as the removal of microplastics.

[0035] The filter material is designed as a hollow membrane material. The special arrangement of the membranes and the size and shape of the pores in these membranes achieve filtration of the finest particles on the surface without noticeably clogging the membrane, thus ensuring a continuous flow rate within the device and preventing any potential pressure differential downstream of it.

[0036] In one embodiment of the invention, the membranes of the membrane assembly are designed as capillary membranes. With such capillary membranes, the walls of the membranes provide a large surface area through which the medium to be filtered can pass through the ultrafilter or microfilter. The open end of the membranes forms the permeate side. This means that the capillary membranes are bent so that the open ends of the membranes form the outlet.

[0037] The water to be filtered thus flows into the membranes from the outside and exits through the open end of the capillary membranes.

[0038] The capillary membranes preferably have a mean diameter (outer diameter) of 0.5 to 5 mm.

[0039] Furthermore, the invention relates to a method for treating drinking water, in particular using a water filter as described above, wherein the drinking water is provided in a water source, in particular a water pipe or a water tank. The method for treating drinking water has a stagnation phase in which the drinking water does not flow from the water source, and a withdrawal phase in which the drinking water is withdrawn and replenished from the water source.

[0040] During the extraction phase, the drinking water according to the invention passes through an alkalizing and / or oxidizing material and a membrane filter, in particular a membrane pack for ultrafiltration or microfiltration. The process according to the invention can, for example, be used not only to provide essentially germ-free drinking water but also to produce a hot or cold beverage. Description of the drawings:

[0041] The invention is described using a schematically illustrated embodiment according to Fig. 1 shown in more detail. Fig. Figure 1 shows an embodiment of a water filter 1, which is designed as an ultrafilter.

[0042] This includes a housing with an inlet 8 and an outlet 7, thereby defining a flow direction D.

[0043] Inside the housing, a membrane package 5 with a multitude of hollow fiber membranes 4 is arranged.

[0044] The membrane assembly 5 is folded, and the open ends of the hollow fiber membranes 4 are held in a potting compound 6 on the outlet side. Water thus flows in from the outside through the inlet 8 and exits from the open ends of the hollow fiber membranes 4.

[0045] A granular, alkalizing and / or oxidizing material 3 is located directly in front of or in contact with the membrane package 5.

[0046] On the inlet side, a sieve or retention grid 2 holds back the granular material.

[0047] The water to be filtered flows over the alkalizing and / or oxidizing material 3, then enters the membranes 4 from the outside and exits through the open end of the capillary membranes 4.

[0048] During stagnation phases, the membranes 4 are protected from microbial contamination on the inlet side by the alkalizing and / or oxidizing material 3. In particular, the formation of a biofilm through the growth of microbes retained by the membranes 4 is counteracted. Reference symbol list 1 water filter 2 restraint barriers 3 alkalizing and / or oxidizing material 4 Capillary membrane 5 Membrane package 6. Potting compound 7 Outlet 8 Admission D Flow direction

Claims

[1] Water filter (1) comprising a membrane filter with a filtration membrane, which is designed as an ultrafilter or microfilter and which has a flow direction (D) and comprises an alkalizing and / or oxidizing material (3) which provides a zone in which a biocidal contact material is present due to the alkalizing and / or oxidizing material (3), wherein the membrane filter comprises a folded membrane pack (5) in which the open ends of the hollow fiber membranes (4) are held in a potting compound (6) on the outlet side, and wherein the alkalizing and / or oxidizing material (3) is arranged upstream of the membrane pack (5) on the inlet side. [2] Water filter (1) according to the preceding claim, characterized by, that the alkalizing and / or oxidizing material (3) contacts the ultrafilter or microfilter membrane, in particular that the alkalizing and / or oxidizing material (3) is positioned directly in front of or inside the membrane package (5) and contacts it. [3] Water filter (1) according to any one of the preceding claims, characterized by , that the alkalizing and / or oxidizing material (3) contains at least one material selected from the group comprising oxides and / or carbonates and / or peroxides. [4] Water filter (1) according to claim 3, characterized by that the peroxide is present at least partially as magnesium peroxide, calcium peroxide, sodium peroxide, potassium peroxide and / or zinc peroxide, as well as mixtures of at least two of the aforementioned materials. [5] Water filter (1) according to claim 3, characterized by that the carbonate is present at least partially as calcium carbonate and / or magnesium carbonate. [6] Water filter (1) according to one of claims 4-5, characterized by that the oxide material is present at least partially as calcium oxide and / or magnesium oxide. [7] Water filter (1) according to any one of the preceding claims, characterized by , that the water filter (1) comprises a loose bulk alkalizing and / or oxidizing material (3). [8] Water filter (1) according to claim 7, characterized by , that the alkalizing and / or oxidizing material (3) comprises particles whose particle size is below 5 millimeters, preferably below 3 millimeters, particularly preferably in the range between 0.5 millimeters and 2.5 millimeters. [9] Water filter (1) according to any one of the preceding claims, characterized by , that the inlet side (8) is designed for attachment to the connection of a water pipe or water tank. [10] Use of a water filter (1) according to one of the preceding claims, wherein the water filter (1) is designed for use as a filter cartridge (1) for a machine for preparing hot and / or cold beverages and / or for an under-counter water filter. [11] Method for treating drinking water, in particular using a water filter (1) according to any one of claims 1 to 9, wherein the drinking water is provided in a water source, in particular a water pipe or a water tank, with a stagnation phase in which the drinking water does not exit the water source, and with a withdrawal phase in which the drinking water is withdrawn and replenished from the water source, wherein during the withdrawal phase the drinking water passes through an alkalizing and / or oxidizing material (3) which provides a biocidal contact material, and then through a membrane filter designed as an ultra- or microfilter, in particular a membrane pack (5) for ultra- or microfiltration. [12] Method according to the preceding claim, wherein the alkalizing and / or oxidizing material (3) is a material selected from the group comprising oxides and / or carbonates and / or peroxides.

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