WO2004071969A1

WO2004071969A1 - Method for removing phosphate from water

Info

Publication number: WO2004071969A1
Application number: PCT/DE2004/000260
Authority: WO
Inventors: Korinna Kedves
Original assignee: Söll Gmbh
Priority date: 2003-02-14
Filing date: 2004-02-13
Publication date: 2004-08-26
Also published as: DE10327199A1; EP1597203A1

Abstract

The invention relates to a method for removing phosphorus compounds from water. Said method is characterised in that the water is brought into contact with an anionic polymer, which contains a cation or cations selected from the earth alkaline metal ions Fe 2+, Fe 3+, AI3+, V5+, NH4+, Cr3+, Co2+, Cd 2+, Cu2+, Pb2+, Mn2+, Ag+, Sn2+, Zn2+.

Description

_PROCEDURE N FOR REMOVING PHOSPHATE FROM WATER

The present invention relates to a method for removing phosphorus compounds, anions such as, in particular, arsenates, nitrite and nitrate from water, such as still and flowing water and waste water.

Water, soil, sediments and / or sludge always contain a certain amount of organic materials. Especially with water, i.e. for both water and waste water, determined u. a. the proportion of organic compounds the water quality. The organic materials on the one hand increase the COD and BOD values and on the other hand they lead to the formation of detritus over time, i.e. for silting and in extreme cases for silting up.

High COD and BOD values mean that they contain materials that have a high oxygen requirement and lead to a lack of oxygen for the microorganisms and other living things and ultimately to their death. The mined material is in the water as an additional organic material, e.g. B. as suspended particles, before, which entails a further reduction in water quality.

In order to avoid silting up of water, in particular ponds, the sludge formed must be mechanically removed at regular intervals. This mechanical removal of the sludge requires a sufficient particle size. Floating particles cannot usually be removed.

The pollution of water, soil, sediments and / or sludge also adversely affects the activity of the microorganisms living therein, which in turn leads to a disturbance in the natural balance.

Another problem, particularly in inland waters, is the phosphate content, which is responsible for the eutrophication of water. Reducing the phosphate concentration in eutrophicated waters is usually the key to successful nation, that means to improve the water quality and the possible uses. For this reason, more or less successful efforts have been made for more than two decades to lower the phosphate concentration, especially in lakes and in the course of sewage treatment plants. Established processes work using iron and aluminum salts as precipitants. Recent developments deal with the optimization of the biological phosphate elimination as well as with the technical control of the autochthonous calcite precipitation and the rinsing of inland sea chalk deposits as possibilities of the ecotechnological water remediation.

However, the known methods for removing phosphate have the disadvantage that the precipitation of phosphate takes place only incompletely and is also technically complex in some cases. By adding Al or Fe compounds, aluminum and iron ions as well as neutral salts such as sulfate or chloride are also introduced into the water, which does not always have a positive effect on the water quality.

In a further process known from the prior art, contaminated water is treated with a mixture of Ca (OH) ₂ and H ₂ O ₂ . These processes are also known as precipitation processes, in which the phosphate present is precipitated as calcium hydrogen phosphate.

A disadvantage of the precipitation processes known from the prior art is that the solubility product of the compounds to be precipitated is strongly dependent on the pH. A state of equilibrium is formed with the components present in the aqueous environment. In some cases, the hydrogen phosphate even dissolves again.

In aqueous systems with a small water volume there is also the disadvantage that the precipitated substances, if they do not go back into solution, accumulate as an insoluble sediment which, as a rule, can only be removed when the water is completely exchanged.

For relatively small volumes, such as ponds or aquariums, filter cartridges etc. have proven to be advantageous. Water flows through them, the substances to be removed are held in the filter material and when the filter is saturated, it can be easily replaced. Filters of this type are used, in particular, for removing suspended matter, etc. For other substances which are to be removed from the water, the filter activity is inadequate. The present invention was therefore based on the object of providing a method for removing phosphorus compounds from water, such as still and flowing water and waste water, with which it is possible to remove phosphorus compounds, in particular phosphate, without the phosphate being added corresponding chemical agents must be precipitated. Another task was to reduce the growth of algae in water.

The present invention accordingly relates to a process for the treatment of water, such as still and flowing water and waste water, characterized in that the water is brought into contact with a polymer which, as the cation (s), is selected from alkaline earth metal ions, Fe ²⁺ , Fe ³⁺ , Al ³⁺ , V ⁵⁺ , NH ₄ ⁺ , Cr ³⁺ , Co ²⁺ , Cd ²⁺ , Cu ²⁺ , Pb ²⁺ , Mn ²⁺ , Ag ⁺ , Sn ²⁺ , Zn ^{2 +} has.

In the anionic polymer used in the process according to the invention, preference is given to fixing those cations which, alone or in combination with other cations, form poorly soluble compounds with the phosphorus compounds present in the waters, such as phosphate. When the water containing phosphorus compounds enters the polymer structure, the Ca ⁺ concentration in the gel is so high that the solubility product of calcium phosphate is exceeded at every point and this precipitates directly as a solid. On

Most of the precipitation product obtained remains directly in the polymer structure and can be removed from the water with the polymer after all Ca ions have been used up, i.e. when the filter has reached its saturation limit.

The waters from which the phosphorus compounds can be removed with the aid of the process according to the invention include all water- and moisture-containing systems. Waters in the sense of the present invention are natural and artificial, standing and flowing waters, such as ponds and lakes, sewage systems, drinking water systems, aquariums, water from water circuits in industrial plants and household plants, etc.

Polymers which form gels in water have proven to be particularly suitable for use in water-carrying systems. These polymers have the advantage that they can absorb and store water and that the water can pass through the gel structure. Examples of suitable polymers are polymeric polysaccharides, such as alginates, agarose or bellulose, proteins, such as gelatin, gum arabic, albumin or fibrinogen, ethyl cellulose, methyl cellulose, carboxymethylethyl cellulose, cellulose acetates, alkali cellulose sulfate, polyanillin, polyethylene imine, polypyrrole, polyvinyl pyrolidide , Polyvinyl chloride, polyvinyl alcohol, polyethylene, polypropylene, copolymers made of polystyrene and maleic anhydride, epoxy resins, polyethyleneimines, copolymers made of styrene and methyl methacrylate, polystyrene sulfonate, polyacrylates and poly methacrylates, polycarbonates, polyesters, silicones, methyl cellulose, mixtures of gelatin and water glass Gelatin and polyphosphate, cellulose acetate and phthalate, gelatin and copolymers of maleic anhydride and methyl vinyl ether, cellulose acetate butyrate, chitosan, polydialkyldimethylammonium chloride, mixtures of polyacrylic acids and polydiallyldimethylammonium chloride and any mixtures of the preceding before ends.

The polymers are preferably selected from alginates and / or alginate derivatives, alkali cellulose sulfate, polyethyleneimines and / or polydialkyldimethylammonium chlorides

In a particularly preferred embodiment, purified alginates are used as gel-forming materials, in particular the alginates described under CAS numbers 9005-38-3 and 9005-32-7. The purified alginates have the advantage that they contain only small amounts of free organic substances, which may impair the stability and activity of microorganisms. The alginates used preferably have a high proportion of L-guluronic acid units.

Another advantage of the gel-forming polymers that are preferably used is that they can be in any form and can accordingly be adapted to their place of use. Examples of suitable shapes are spheres, blocks, grids, sheets, foils, etc. Spheres (hereinafter also referred to as capsules) have the advantage that they are pourable and have a high bulk density, so that they can be easily filled into filter systems or filter cartridges and can also be removed from them.

In a further preferred embodiment, layer and framework silicates, particularly preferably zeolites, are added to the polymers. With their lattice structures, the silicates stabilize the gel material and slow down the decomposition process of the alginate with simultaneous adsorption of ammonium and calcium on the mineral component of the matrix. The zeolites used consist of over 70% clinoptilotite with inert minerals such as quartz. The grain size of the mineral admixtures is less than 600 μm. The admixture is 0.5 to 50 percent by mass of the alginate dry matter used. 5-30% w minerals are preferably used, particularly preferably w (zeolite) = 15-30% to 70-85% alginate.

The microbiological self-cleaning process of the water can be additionally activated and / or supported or taken over entirely by using microorganisms. Such microorganisms are generally used when harmful nitrogen compounds are also to be broken down, which are converted by the microorganisms into harmless compounds, such as elemental nitrogen.

In a particularly preferred embodiment, the microorganisms are present in encapsulated form in the polymer material.

Any microorganisms suitable for treating water can be used as microorganisms, including marine microorganisms, algae and fungi. The microorganisms are preferably selected chemolithoautotrophic nitrificants, such as the ammonia oxidants and the nitrite oxidants, which can be selected from the nitrifying microorganisms, in particular bacteria of the genera Nitrosomonas, Nitrosoccus, Nitrosospira, Nitrosovibrio and Nitrosospira, in particular the species Nitrosomonas halophila, Nitrosomonas and Nitrosomonas europaea, Nitrosomonas oligotropha, Nitrosomonas ureae, Nitrosomonas aestuarii, Nitrosomonas marina, Nitrosomonas sp. 3 Nm 51, Nitrosomonas communis, Nitrosomonas nitrosa, Nitrosomonas sp. 1 Nm 33, Nitrosomonas sp. 2 Nm 41, Nitrosomonas cryotolerans, and the nitrite-oxidizing bacteria of the genera Nitrobacter and Nitrospira, especially Nitrobacter winogradskyi.

Also suitable are heterotrophic nitrificants, such as fungi of the genus Aspergillus, Penicillium and Cephalosporium, algae, Arthrobacter sp., Alcaligenes faecalis, Nocordia sp. As well as heterotrophic denitrifiers, such as Paracocus sp., In particular Paraccocus pantothrophas, and Pseudomonas sp. Any combinations, ie mixed cultures, of microorganisms can also be used. By using mixed cultures, synergistic effects can be obtained with regard to activity and degradation. Examples of mixed cultures are e.g. B. Combinations of the species Nitrosomonas and Nitrobacter and possibly heterotrophic microorganisms. In a particularly preferred embodiment, communities of different bacteria are used to break down organic and inorganic nitrogen compounds. The species used can first be grown in pure culture according to their specific growing conditions and then immobilized. Growing the bacteria in pure culture makes it possible to put together almost any species communities in almost any species ratio. An example of a particularly preferred species community in the immobilizate consists of a) ammonia-oxidizing (eg Nitrosomonas) and b) nitrite-oxidizing (eg Nitrobacter) and possibly c) nitrate and nitrite-reducing bacteria (eg Paracoccus). It has proven to be preferred if the type ratio of the cell numbers in the immobilizate preferably in the range from a: b 1: 10,000 to 1: 1 and particularly preferably from 1: 1000 to 1:10 and the type ratio of b: c preferably between 1000: 1 to 1: 1 and particularly preferably between 100: 1 to 5: 1.

Depending on the application, the specialist can, based on his specialist knowledge and, if necessary,

Conducting tests or using computer simulations the corresponding *

Determine species and their relationship to each other.

In order to be able to start a system microbiologically in a short time, it has proven useful if the starter cultures are added in a sufficiently high concentration.

To prepare immobilized bacteria, cell suspensions are usually first grown in pure culture in a concentration of 1 × 10 ⁶ to 5 × 10 ⁹ cells / ml. In order to obtain the highest possible concentration of microorganisms in the polymer, for example in a microcap, the cell suspensions obtained are then preferably concentrated to 5 × 10 ⁸ to 6 × 10 ⁹ cells / ml. Concentration can be carried out using conventional filtration processes known from the prior art.

In particular when nitrifying microorganisms are immobilized, it has proven to be particularly suitable to use the microorganisms in the form of aqueous cell suspensions. In a particularly preferred embodiment, stabilized microorganisms are used, in particular those of cultivation and stabilization are carried out by adding NO and / or NO _{2 in} accordance with the process described in German patent application 199 08 109.3-41. Particularly good stabilization of the microorganisms can be achieved if they are used as a cell suspension which contains a buffer system. Examples of suitable buffers are acetic acid / acetate, HCO ₃ 7CO ₃ ^{2 "} , phosphoric acid / H ₂ PO ₃ 7HPO ₃ ^2" , citric acid / citrate, lactic acid / lactate, solid CaCO ₃ , etc.

In order to achieve an optimum activity of the microorganisms, the pH in the gel capsules is preferably between 4 and 9, particularly preferably between 5 and 8 and in particular between 6.5 and 8.5. If adjustable under the application conditions, the starter cultures according to the invention are preferably carried out in a temperature range from 8 ° C. to 35 ° C., particularly preferably in a range from 15 ° C. to 30 ° C. and in particular between 20 ° C. and 30 ° C.

The microcapsules can be produced in a manner known per se by encapsulating cell suspensions or solutions. For example, known microencapsulation processes are suitable for the production. Examples of possible production processes are phase separation processes, also called coacervation, mechanical-physical processes, interfacial polymerization and adsorptive processes.

Coacervation means that a dissolved polymer is converted into a polymer-rich, solvent-containing phase by means of desolvation. The coacervate attaches to the interface of the material to be encapsulated to form a coherent capsule wall and is solidified by drying or polymerization.

Mechanical-physical processes are also suitable for coating solid core materials, in which the coating takes place in the fluidized bed or by spray drying.

In the interfacial polymerization processes mentioned, the wall is formed by polycondensation or polyaddition from monomeric or oligomeric starting materials at the interface of a water / oil emulsion.

In the adsorptive process, layers of polyanionic and polycationic polymers are applied and thus form the capsule wall, which can usually consist of 2 to 20 layers.

The polymers used are preferably used in the form of their solutions, suspensions or emulsions. For microencapsulation, there are aqueous solutions Suspensions or emulsions with a concentration of 0.5 to 10% by weight have been found to be suitable.

For the production of microcapsules from alginate, a 1 to 5%, in particular 1, 5 to 2.5%, alginate is preferably used and encapsulated in a manner known per se.

Are the polymers used according to the invention in particulate or solid, z. B. used as balls, blocks, grids, sheets and / or foils, they can be supplied to the water to be cleaned and / or processed in a manner known per se. However, the particles or solids are preferably introduced into a container which can be permanently installed in the water to be cleaned. It is also possible that the particles or solids are fixed solely on the basis of their specific weight, i.e. are no longer carried by the current.

In a particularly preferred embodiment, the particles or solids obtained are introduced into a filter and fixed by the surrounding filter material.

When used in a body of water to be cleaned, the water flows through the filter unit and comes into contact with the particles or solids. Due to the preferably network-like structure of the polymer material, the water to be cleaned penetrates into the structure and thus comes into contact with the polymer. The harmful substances are removed.

The present invention further relates to the use of anionic polymers which, as cations, are selected from alkaline earth metal ions, Fe ²⁺ , Fe ³⁺ , Al ³⁺ , V ⁵⁺ , NH ₄ ⁺ , Cr ³⁺ , Co ²⁺ , Cd ²⁺ , Cu ²⁺ , Pb ²⁺ , Mn ²⁺ , Ag ⁺ , Sn ²⁺ , Zn ²⁺ contain, for the removal of phosphorus compounds from water.

Yet another object of the present invention relates to the use of anionic polymers which, as cations, are selected from alkaline earth metal ions, Fe ²⁺ , Fe ³⁺ , Al ³⁺ , V ⁵⁺ , NH ₄ ⁺ , Cr ³⁺ , Co ^{2 +} , Cd ²⁺ , Cu ²⁺ , Pb ²⁺ , Mn ²⁺ , Ag ⁺ , Sn ²⁺ , Zn ²⁺ , to reduce the growth of algae in water. Examples

Water contaminated with phosphate was brought into contact with spherical alginates. The phosphate content was reduced below the maximum permitted for drinking water.

Claims

claims

1. A process for the removal of phosphorus compounds from water, characterized in that the water is brought into contact with an anionic polymer which, as the cation (s), is selected from alkaline earth metal ions, Fe ²⁺ , Fe ³⁺ , Al ³⁺ , V ^{5 +} ,

Contains NH ₄ ⁺ , Cr ³⁺ , Co ²⁺ , Cd ²⁺ , Cu ²⁺ , Pb ²⁺ , Mn ²⁺ , Ag ⁺ , Sn ²⁺ , Zn ²⁺ .

2. The method according to claim 1, characterized in that the waters are natural and artificial standing and flowing waters or water-carrying systems, such as ponds and lakes, sewage systems, drinking water systems, aquariums, water from water circuits of industrial plants and household systems, etc.

3. The method according to claim 1 or 2, characterized in that the anionic polymer is a gel-forming polymer.

4. The method according to any one of claims 1 to 3, characterized in that the polymers are selected from polymeric polysaccharides such as alginates, agarose or cellulose, proteins such as gelatin, arabic gum, albumin or fibrinogen, ethyl cellulose, methyl cellulose, carboxymethylethyl cellulose, Cellulose acetates, alkali cellulose sulfate, polyanillin, polypyrrole, polyvinyl pyrolidone, polystyrene, polyvinyl chloride, polyvinyl alcohol, polyethylene, polypropylene, copolymers of polystyrene and maleic anhydride, epoxy resins, polyethylene imines, copolymers of styrene and methyl methacrylates, polyacrylate, polyacrylate, polyacrylate, polyacrylate, polystyrene, polystyrene, polystyrene, polystyrene, polystyrene, polystyrene, polystyrene, polystyrene, polystyrene, polystate, acrylate, Polyester, silicones, methyl cellulose, mixtures of gelatin and water glass, gelatin and polyphosphate, cellulose acetate and phthalate, gelatin and copolymers of maleic anhydride and

Methyl vinyl ether, cellulose acetate butyrate, chitosan, polydialkyldimethylammonium chloride, mixtures of polyacrylic acids and polydiallyldimethylammonium chloride and any mixtures of the foregoing.

5. The method according to claim 4, characterized in that the polymers are selected from alginates and / or alginate derivatives.

6. The method according to any one of claims 1 to 5, characterized in that the polymers are in the form of spheres, blocks, grids, sheets and / or films.

7. The method according to any one of claims 1 to 6, characterized in that microorganisms are additionally used.

8. The method according to claim 7, characterized in that the microorganisms are selected from chemolithoautotrophic nitrificants, such as ammonia oxidants and nitrite oxidants, such as bacteria of the genera Nitrosomonas, Nitrosococcus, Nitrosospira, Nitrosovibrio and Nitrosospira, in particular the species Nitrosomonas halophila, Nitrosomonas eutropha and Nitrosomonas europaea, Nitrosomonas oligotropha, Nitrosomonas ureae, Nitrosomonas aestuarii, Nitrosomonas marina, Nitrosomonas sp. 3 Nm 51, Nitrosomonas communis, Nitrosomonas nitrosa, Nitrosomonas sp. 1 Nm 33, Nitrosomonas sp. 2 Nm 41, Nitrosomonas cryotolerans, Nitrobacter and Nitrospira, in particular Nitrobacter winogradskyi, heterotrophic nitrificants, such as fungi of the genus Aspergillus, Penicillium and Cephalosporium, algae, Arthrobactersp., Alcaligenes faecalis, Nocordia sp. heterotrophic denitrifiers such as Paracocus sp. and Pseudomonas sp. and any mixtures of the foregoing.

9. Use of anionic polymers which, as the cation (s), are selected from alkaline earth metal ions, Fe ²⁺ , Fe ³⁺ , Al ³⁺ , V ⁵⁺ , NH ₄ ⁺ , Cr ³⁺ , Co ²⁺ , Cd ²⁺ , Contain Cu ²⁺ , Pb ²⁺ , Mn ²⁺ , Ag ⁺ , Sn ²⁺ , Zn ²⁺ for the removal of phosphorus compounds from water.

10. Use according to claim 9, characterized in that the phosphorus compounds are phosphates.

11. Use of anionic polymers which are selected as cations

Alkaline earth metal ions, Fe ²⁺ , Fe ³⁺ , Al ³⁺ , V ⁵⁺ , NH ₄ ⁺ , Cr ³⁺ _, Co ²⁺ , Cd ²⁺ , Cu ²⁺ , Pb ²⁺ , Mn ²⁺ , Ag ⁺ , Sn Contain ²⁺ , Zn ²⁺ , to reduce the growth of algae in water.