DE202018006098U1 - Means for lowering the phosphate content in waste water - Google Patents

Abstract

Composition for reducing the phosphate content in wastewaters comprising, in each case based on its total weight,> 50.0 wt .-% calcium carbonate and at least 1.0 wt .-% of an iron salt, characterized in that the calcium carbonate has a water solubility of less than 20 mg / 1000 ml of water at 25 ° C.

Description

The present invention relates to a means for lowering the phosphate content in wastewaters.

To reduce the phosphate content in wastewater, chemical phosphate precipitation (P precipitation) by addition of precipitants and biological phosphorus elimination (P elimination) by metabolism of the phosphates in the biomass of the activated sludge are generally known.

The chemical P precipitation is usually divided into simultaneous precipitation, pre- and post-precipitation.

In aqueous systems dissolved phosphates - especially ortho-phosphates - can be converted by means of suitable precipitants in undissolved phosphates and removed as a solid from the aqueous system, together with other solids. The deposited phosphates are then part of the sludge.

• ◯ Eisenchloride (FeCl₂ oder FeCl₃)
• ◯ Eisenchloridsulfat (FeClSO₄)
• ◯ Eisen(II)-sulfat / Grünsalz (FeSO₄)
• ◯ Aluminiumsulfat (Al₂(SO₄)₃)
• ◯ Aluminiumchloride (AlCl₃)
• ◯ Polyaluminiumchloride (Al_x(OH)_yCl_z)
• ◯ Natriumaluminate (NaAl(OH)₄)
• ◯ Kalkmilch (Ca(OH)2),

wobei Eisen- und Aluminiumsalze oder Lösungen dieser Salze als Fällungsmittel bevorzugt eingesetzt werden.Common precipitants are:

• ◯ iron chlorides (FeCl ₂ or FeCl ₃ )
• ◯ iron chloride sulfate (FeClSO ₄ )
• ◯ iron (II) sulfate / green salt (FeSO ₄ )
• ◯ aluminum sulphate (Al ₂ (SO ₄ ) ₃ )
• ◯ aluminum chlorides (AlCl ₃ )
• ◯ polyaluminium chlorides (Al _x (OH) _y Cl _z )
• ◯ sodium aluminates (NaAl (OH) ₄ )
• ◯ lime milk (Ca (OH) 2),

wherein iron and aluminum salts or solutions of these salts are preferably used as precipitant.

If the precipitants are added directly to the biological treatment stage, this is referred to as simultaneous precipitation. Simultaneous precipitation is a precipitation reaction in which ions dissolved in the water are converted into a water-insoluble compound by addition of a precipitant. Furthermore, the addition of precipitants leads to an improved sludge structure and better Absetzzeigenschaften. Simultaneous precipitation is thus often carried out not only for reasons of nutrient removal, but also because of the improvement of plant operation, since it improves the separation of activated sludge and purified wastewater in the secondary clarifier.

Pre-precipitation is the removal of phosphorus from wastewater by transfer to undissolved metal salts. This precipitation is made before the biological stage. For example, the primary clarifier can be used for settling the precipitated products.

The focus in the pre-precipitation is not the phosphate precipitation itself, but the relief of the biological stage. Especially obsolete sewage treatment plants are often overloaded. If the renewal is delayed for a variety of reasons, pre-precipitation can also be used to comply with the current discharge values. Disadvantages of this process are a very high amount of primary sludge and a very high consumption of precipitants, in particular in the form of trivalent metal salts.

In the post-precipitation, the phosphorus precipitation takes place after the secondary clarification. Trivalent metal salts are used in particular. The replenishment ensures very low phosphorus drainage, but the consumption of precipitants is very high. In addition, a downstream separation of the resulting flakes via a separate filtration stage is necessary.

In biological phosphorus removal (Bio-P for short) polyphosphate accumulating organisms (PAO) are put into a stressful situation in an anoxic environment. If these microorganisms have no oxygen and nitrate available, the primary food sources are deprived and the microorganisms would have to die off. To prevent this, the microorganisms in this situation release the phosphates stored in their cells, releasing energy that they use for survival. When the microorganisms subsequently enter an aerobic, oxygen-rich environment, they re-absorb the previously released phosphate and store more phosphates in their cells, reducing the total phosphate content in the water.

In practice, a combination of the different methods is usually used.

The registration JP 11319411 A discloses a high solubility water purifier capable of binding and precipitating rich nutrient sources, water contaminants and bacterial groups. The water purifier comprises a powder of clam shells, preferably Hokkaido clam shells, wherein the water purifier further preferably comprises a precipitant, especially aluminum sulphate. The ratio of mussel shells to precipitant should preferably be in the range of 8/2 to 6/4. For water purification, the water purifier should preferably be added to the water to be purified at a concentration of 0.5% by weight or less, based on the clam shells. Alternatively, the water purifier could also be used in an amount of 12 to 13 kg per tsubo (3.3 m ² ) are added to the water to be purified. For the purification of heavy metal-containing water, the use of a precipitant such as ferric chloride after or together with the water purifier of JP 11319411 A proposed to precipitate the heavy metals.

The document indicates that the mussel shells consist mainly of calcium carbonate, but which has a significantly higher water solubility than commercially available calcium carbonate, which is obtained from limestone by purification. More specifically, the solubility of this calcium carbonate should be 40.59 mg / 100 mg.

In the only example of the document, a water purifier consisting of 70 wt .-% Hokkaido mussel shells and 30 wt .-% aluminum sulfate powder for purifying seawater at a concentration of 0.1 wt .-%, based on the water to be purified, and found a decrease in the total phosphorus level from the original 1.4 mg / L to 0.1 mg / L or less.

The registration JP 09-038414 A relates to a precipitant with a high rate of descent which, when added to waste water, forms large flocs and facilitates the treatment of sewage sludge. The coagulating bedding agent contains two kinds of calcium carbonate, coarse particles having an average particle diameter of 50-500 μm, and fine particles having an average particle diameter of 1-30 μm. The weight ratio of the coarse particles and the fine particles is preferably in the range of 2: 1 to 40: 1. The amount of the calcium carbonate is preferably at least 60% by weight. In addition, the coagulant-bedding agent preferably contains a soluble aluminum salt, a soluble iron salt or a polymeric precipitant of an organic system. In this connection, aluminum sulfate, polyaluminum chloride, ferrous sulfate and ferric sulfate are exemplified.

In the examples of this document, a precipitant consisting of coarse-grained calcium carbonate particles having an average particle diameter of 100 .mu.m, fine calcium carbonate particles having an average particle diameter of 3.1 .mu.m, aluminum sulfate, calcium hydroxide and polyacrylamide, tested for the purification of dirty water. An improvement in filterability, floc size, sedimentation rate, transparency and pH of the purified water were observed compared to the untreated sewage. Statements on the phosphorus content of the dirty water and / or the purified water, however, can not be found in the document.

The item "Nutrient removal and sludge production in the coagulation-flocculation process" by Aguilar, MI, Sacz, J., Llorens, M., Soler, A. and Ortuno, JF in Water Resarch (2002), 36 (11), page 2910 -2,919 deals with the treatment of sewage of a slaughterhouse. Fe ₂ (SO ₄ ) ₃ , Al ₂ (SO ₄ ) ₃ and polyaluminum chloride were used as coagulants. Activated silica, activated charcoal, precipitated calcium carbonate (PCC), cationic polyacrylamide, polyacrylic acid, anionic polyacrylamide and polyvinyl alcohol were used as coagulants with calcium carbonate used only in combination with Al ₂ (SO ₄ ) ₃ or polyaluminum chloride. For Fe ₂ (SO ₄ ) ₃ , regardless of the coagulant, a removal of ortho-phosphate of 100% and a total removal of phosphorus of at least 99.53% are reported. Irrespective of the coagulant, Al ₂ (SO ₄ ) ₃ is reported to have a removal of orthophosphate of 100% and a total removal of phosphorus of at least 98.88%, with the use of PCC as the coagulant agent giving the worst results. For polyaluminum chloride, irrespective of the coagulant, the removal of orthophosphate is reported to be 100% and the overall removal of phosphorus to be at least 99.70%, with the use of PCC as coagulant to give worse results than the use of polyaluminum chloride without further coagulant.

• „Die in der Bundesrepublik Deutschland in die Fließwässer eingetragenen Phosphorfrachten können etwas halbiert werden, wenn bei allen Kläranlagen mit Anschlussgrößen über 20 000 EW Phosphor eliminiert wird. Dadurch wird die Gefahr extremer Eutrophierungserscheinungen vermindert. Unter Gesichtspunkten der Zweckmäßigkeit und Wirtschaftlichkeit sollten die Eliminationsleistungen in Abhängigkeit von der jeweiligen Anschlussgröße zwischen etwa 70% und 95% gestaffelt und insbesondere auch die Leistungsfähigkeiten chlorid- und sulfatfreier Fällungsverfahren sowie biologischer Verfahren zur Phosphorelimination voll ausgeschöpft werden. Die mit einer Phosphorelimination verbundenen positiven Nebeneffekte würden ebenfalls erheblich zum Gewässerschutz beitragen.“

The publication "Nitrogen and Phosphorus in Running Waters", Working Report of the ATV Committee 2.1, Correspondence Wastewater 11/87 deals with the need for extensive nitrogen oxidation in sewage treatment plants, extensive nitrogen elimination in sewage treatment plants and the need for phosphorus removal in rivers. With regard to the origin of phosphorus loads in the rivers, it is assumed that most of them originate from punctiform sewers. It is stated:

• "The phosphorus loads in the Federal Republic of Germany can be reduced by half if phosphorus is eliminated in all sewage treatment plants with connection sizes over 20,000 PE. This reduces the risk of extreme eutrophication phenomena. From the point of view of expediency and efficiency, the elimination rates should be scaled up to between about 70% and 95%, depending on the size of the connection, and in particular the performance of chloride-free and sulphate-free precipitation and biological processes be fully exploited for phosphorus elimination. The positive side effects associated with phosphorus removal would also contribute significantly to water protection. "

Calcium carbonate is not mentioned in the publication.

The utility model CN 205328829 U discloses a restaurant wastewater treatment apparatus comprising a phosphorus removal zone comprising a mixture of limestone and aluminum filler. Iron salts, however, are not mentioned in the utility model.

1. a) ein erstes Kation zum Abwasser zugibt, um Fluorsilikat aus dem Abwasser auszufällen;
2. b) ein zweites Kation zum Abwasser zugibt, um Fluorid aus dem Abwasser auszufällen;
3. c) den pH des Abwassers erhöht, um das zweite Kation aus dem Abwasser auszufällen;
4. d) verbleibende Silica aus dem Abwasser entfernt und
5. e) Phosphat aus dem Abwasser ausfällt.

WO 2013/040716 A1 describes a process for the treatment of phosphate-containing wastewater, in which

1. a) adding a first cation to the wastewater to precipitate fluorosilicate from the wastewater;
2. b) adding a second cation to the effluent to precipitate fluoride from the effluent;
3. c) increasing the pH of the effluent to precipitate the second cation from the effluent;
4. d) remaining silica removed from the wastewater and
5. e) phosphate precipitates out of the wastewater.

Step a) should preferably comprise increasing the pH of the effluent to about 2.0 to precipitate the fluorosilicate.

The addition of the second cation should preferably comprise the addition of limestone.

Step e) should preferably comprise the addition of a third cation and / or a fourth cation to precipitate the phosphate as a struvite analog, which is preferably to comprise iron ammonium phosphate.

Other references to iron salts are not found in the patent application.

The present invention therefore an object of the invention to show better ways to reduce the phosphate content in wastewater, especially in municipal and industrial wastewater. In particular, more effective ways to remove phosphates from wastewater should be found. The properties of the wastewater should not be adversely affected as much as possible, but should be improved as much as possible. In addition, the properties of the activated sludge, in particular its settling behavior, should as far as possible not be adversely affected, but should be improved as much as possible. Furthermore, the phosphate pollution of flowing waters into which the wastewater to be treated should be introduced should be reduced and as much as possible an over-fertilization of the flowing water should be avoided. Furthermore, a cost-effective solution of these tasks was sought, which can be implemented in the simplest possible way.

These objects are achieved by providing a means for reducing the phosphate content in waste water with all features of independent claim 1. The dependent claims referred to claim 1 describe preferred embodiments of the inventive composition.

By providing an agent which, based on its total weight, comprises> 50.0% by weight of calcium carbonate and at least 1.0% by weight of an iron salt, the calcium carbonate having a water solubility of less than 20 mg / 1000 ml Having water at 25 ° C, it is possible in a surprising manner, a means for reducing the phosphate content in wastewater, especially in municipal and industrial wastewater, accessible, which allows more effective removal of phosphates from wastewater. The properties of the wastewater are not adversely affected, but significantly improved in particular by the pH-buffering effect of the agent. In addition, the properties of the activated sludge, in particular its settling behavior, are not adversely affected but significantly improved. Furthermore, according to the invention, the phosphate load on flowing waters, into which the purified effluents are introduced, is markedly reduced and an over-fertilization of the flowing waters is optimally avoided. Furthermore, an extremely powerful solution of the problems underlying the invention has been found, which can be realized in a very simple manner.

By using the agent according to the invention, more phosphate dissolved in the wastewater is removed than when iron or aluminum salts are used alone. In addition, the agent according to the invention prevents a decrease in the pH at the point of addition, as a result of which more phosphate can be precipitated.

In addition, the use of corrosive substances is optimally reduced or even avoided by the agent according to the invention.

A further advantage of a particularly preferred embodiment of the agent according to the invention is that it does not constitute a dangerous good under the European Convention on the International Carriage of Dangerous Goods by Road (ADR) and can therefore be handled and used in a simple manner.

Furthermore, the agent according to the invention is particularly environmentally friendly. The salination of the purified water according to the invention is significantly lower than by conventional methods for the purification of wastewater.

The present invention accordingly provides a means for lowering the phosphate content in wastewaters, in particular the orthophosphate content.

In this context, waste water is a generic term for waters originating from different sources and passing through structures, and includes, in particular, rainwater, in particular precipitation water draining from paved areas; Dirty water, especially by use contaminated ("changed in its properties or its composition") water, especially gray water (according to EN 12056-1 fäkalienfreies, low polluted wastewater, such as when showering, bathing or washing hands, but also from the washing machine and can be used for treatment to industrial or process water, rainwater draining from the roof or balcony is also included.); Black water (according to ISO 6107-7: 1997 domestic wastewater containing urine and / or fecal solids, in particular comprising yellow water (urine with rinsing water) and brown water (faeces, rinsing water and toilet paper, without urine)); Foreign water, which enters the sewage system due to structural damage.

Wastewater is collected and transported in the sewage system in the course of sewage disposal, usually treated in sewage treatment plants in Central Europe and then discharged into receiving waters or by infiltration, trickling or agitation into the groundwater.

In the context of the present invention, the wastewater to be purified usually has a pH, measured at 25 ° C., in the range from 5.0 to 10.0, in particular in the range from 6.0 to 9.0. After the wastewater treatment according to the invention, the pH of the purified water, measured at 25 ° C, preferably in the range of 5.0 to 10.0, in particular in the range of 6.0 to 9.0.

Phosphates are the salts and esters of orthophosphoric acid (H ₃ PO ₄ ) In a broader sense, the condensates (polymers) of orthophosphoric acid and their esters are called phosphates. Phosphorus is present in all of these compounds in the oxidation state (V).

The determination of the phosphate content in the wastewater, in particular the ortho-phosphate content, can be carried out in a manner known per se. A determination of the phosphate content in the wastewater, in particular of the orthophosphate content, has proved particularly useful by means of commercially available photometric tests. Alternatively, the determination of the phosphorus content can also be carried out by means of ICP-OES.

The composition according to the invention for reducing the phosphate content in wastewaters comprises, in each case based on its total weight,
> 50.0 wt .-%, preferably> 60.0 wt: -% to 99.0 wt .-%, particularly preferably> 60.0 wt .-% to 80.0 wt .-%, in particular 65.0 Wt .-% to 75.0 wt .-%, calcium carbonate and
at least 1.0% by weight, preferably at least 10.0% by weight, more preferably from 20.0% by weight to <40.0% by weight, in particular from 25.0% by weight to 35.0 Wt .-%, of an iron salt.

Particularly preferably, the proportion by weight of calcium carbonate and iron salt together in the composition according to the invention is> 51.0% by weight, preferably> 60.0% by weight, expediently> 70.0% by weight, even more preferably at least 80.0% by weight .-%, most preferably at least 90.0 wt .-%, in particular at least 99.0 wt .-%. In a very particularly preferred embodiment of the present invention, the agent according to the invention consists exclusively of calcium carbonate and at least one iron salt.

The water solubility of the calcium carbonate at 25 ° C is less than 20 mg / 1000 ml of water, preferably less than 16 mg / 1000 ml of water, more preferably less than 15 mg / 1000 ml of water, most preferably less than 14 mg / 1000 ml of water, desirably less than 12 mg / 1000 ml of water, preferably less than 10 mg / 1000 ml of water, more preferably less than 8 mg / 1000 ml of water, in particular less than 7 mg / 1000 ml of water.

The water solubility of the calcium carbonate can be determined in a manner known per se by stirring the calcium carbonate in CO ₂ -free distilled water at 25 ° C. for at least 1 h and subsequent determination of the amount of calcium carbonate dissolved, preferably by means of photometric methods.

The composition according to the invention comprises at least one iron salt, preferably an iron (II) salt or a ferric salt. Preferred iron salts are FeSO ₄ , FeSO ₄ .H ₂ O, FeSO ₄ .4H ₂ O, FeSO ₄ .5H ₂ O, FeSO ₄ .6H ₂ O, FeSO ₄ .7H ₂ O, FeCl ₃ , FeCl ₃ .6H ₂ O , FeCl _2, FeCl ₂ .4H ₂ O, Fe ₂ (SO _{4) 3,} Fe ₂ (SO _{4) 3} · 1H ₂ O and FeCl (SO _4). For the purposes of the present invention, iron (II) salts, in particular iron (II) sulfates, are particularly suitable.

Basically, the calcium carbonate is not subject to any further restrictions and can basically be chosen freely. For the purposes of the present invention, however, the use of calcium carbonates having an average particle size in the range of 5 microns to 30 microns has proven particularly useful. Furthermore, the calcium carbonate preferably has a BET specific surface area in the range from 0.4 m ² / g to 10.0 m ² / g, preferably in the range from 0.6 m ² / g to 6.0 m ² / g, in particular Range from 0.8 m ² / g to 2.0 m ² / g, on.

Furthermore, a ground calcium carbonate is preferably used in the context of the present invention. For the purposes of the present invention, ground calcium carbonate (GCC) is a calcium carbonate obtained from natural sources such as marble, chalk, limestone or dolomite. GCC is commonly obtained by milling, classifying, sifting and / or wet or dry fractionating. Due to its natural origin, GCC may contain certain amounts of magnesium, such as GCC made from dolomitic limestone.

GCC differs from PCC ("precipitated calcium carbonate"), a synthetic material usually obtained by precipitation after reaction of carbon dioxide with calcium hydroxide in an aqueous environment, by precipitation of a calcium and a carbonate source in water or by precipitation of calcium and carbonate ions, for example, CaCl ₂ and Na ₂ CO ₃ , is obtained from solution.

For the purposes of the present invention, particularly suitable GCC is obtained from limestone, preferably from reef limestone, more preferably from Devonian slaked lime, in particular from Lahnmarmor.

Limestone refers to sedimentary rocks consisting predominantly of the chemical calcium carbonate (CaCO ₃ ) in the form of the minerals calcite and aragonite.

Reef limestones (calcareous limestone) are limestones that emerge from massive accumulations of corals, sponges and other sea organisms. They occur mainly in coastal or other shallow marine regions. Unlike Schillkalken calcareous skeletons have not been washed together by ocean waves, but in the original habitat of the organisms, often in Lebendstellung (in situ), handed down.

Particularly powerful and extensive reef limestone deposits are often referred to as lime. Examples are known in Germany, for example, from the Rhenish Slate Mountains. Devonian reef limestones in the Eifel, in the Bergisch Land and Sauerland as well as in the Lahn-Dill area form extensive deposits, which are obtained in many places for cement production and as natural stones. These reef limes are composed to a significant extent of stromatopores (extinct sponge-like organisms) and extinct coral forms. Typical Leitfossilien this Massenalkalkes are the Armfüßer (Brachiopoda) Stringocephalus burtini and Uncites gryphus.

As Lahnmarmor (formerly called Nassauer marble) polishable limestones of the Middle Devon are summarized in the southeast of the Rhenish Slate Mountains. Centers of extraction were Balduinstein, Hahnstätten, Diez (Rhein-Lahn-Kreis, Rhineland-Palatinate), Villmar and Schupbach (both district Limburg-Weilburg, Hesse).

The preparation of the composition according to the invention can be carried out in a manner known per se by mixing the components. A comminution of the agent, for example by grinding, is usually not required.

The lowering of the phosphate content in waste water can be carried out by means of a process in which the agent according to the invention is to be purified, preferably in an amount in the range from 1 ppm to <1000 ppm, preferably in the range from 5 ppm to 500 ppm, more preferably in Range of 10 ppm to 400 ppm, suitably in the range of 15 ppm to 250 ppm, in particular in the range of 20 ppm to 100 ppm, based on the total weight of the waste water to be purified, added.

The addition point of the agent according to the invention for lowering the phosphate content can basically be chosen freely.

In the context of a first preferred embodiment, the addition of the agent according to the invention is carried out directly in a biological purification stage of wastewater treatment in order to achieve simultaneous precipitation, wherein the phosphate ions dissolved in the water are converted by the addition of the agent according to the invention into water-insoluble phosphate salts.

In the context of a further preferred embodiment, the addition of the agent according to the invention takes place before a biological stage of wastewater treatment, in order to achieve a pre-precipitation of phosphates from the wastewater by the conversion into undissolved metal salts.

Within the scope of yet a further preferred embodiment, the addition of the agent according to the invention takes place after a biological stage of the wastewater treatment in order to achieve a post-precipitation of phosphates after the secondary clarification.

• - in den Ablauf der Vorklärung,
• - in den Zu- oder Ablauf von Bio-P-Becken, Denitrifikationsbecken, Nitrifikationsbecken, Kombinationsbecken aus Deni und Nitrifikation sowie
• - in den Zulauf zur Nachklärung.

For sewage treatment plants, the following addition points have proven particularly useful:

• - in the course of primary treatment,
• - in the inflow or outflow of Bio-P basins, denitrification basins, nitrification basins, Deni combination basins and nitrification as well as
• - in the inflow for secondary clarification.

The agent may preferably be metered at a turbulent point directly into the activated sludge.

Particularly preferred according to the invention is the addition of the agent according to the invention directly into a biological purification stage of wastewater treatment and the addition of the agent according to the invention before a biological stage of wastewater treatment, wherein the best results are obtained when adding the agent according to the invention directly into a biological treatment stage of wastewater treatment.

It is best to meter the agent directly into the activated sludge at a point which is as turbulent as possible, advantageously between two activated sludge tanks at an overflow edge, before or after a pump or a hoist.

Preferably, the agent according to the invention is added to the effluent by means of a metering device, preferably by means of a screw, which is connected to a storage device, preferably a silo, as wastewater, desirably dry powdery composition. Another preferred dosage form is the direct dosage of the agent in the wastewater treatment plant, in particular a sewage treatment plant, by adding the agent, preferably from bagged or BigBags, expediently targeted in the activated sludge.

The metering of the agent according to the invention can be carried out batchwise or continuously, with as uniform as possible addition amounts being generally preferred in continuous processes. Particularly preferred are several times weekly or daily dosing. Ideally, larger treatment plants dosed the agent with a silo system with discharge system in small portions throughout the day. Due to the buffering effect of the agent according to the invention, however, it does not necessarily have to be continuously distributed uniformly around the clock.

By using the composition according to the invention, a reduction of the phosphate content in waste water, in particular of the orthophosphate content in waste water, can be achieved, which alone clearly exceeds the lowering effect of aluminum salts or iron salts alone. Since no comparable lowering effect can be achieved even with calcium carbonate alone, the synergistic effect observed in the context of the present invention using the agent according to the invention is particularly surprising.

The invention will be further illustrated by examples and comparative examples, without thereby limiting the inventive concept.

Determination of the water solubility of the calcium carbonate

The determination of the water solubility of the calcium carbonate was carried out in purest, CO ₂ -free water at 25 ° C by stirring the calcium carbonate for a 1 h and photometric determination.

calcium carbonate

• - Mittlere Teilchengröße d₅₀: 15,5 µm;
• - BET: 1,2m²/g;
• - Wasserlöslichkeit: 6 mg/L.

Devonian ground limestone (Lahnmamor, GCC) with the following properties was used for the examples according to the invention:

• Average particle size d ₅₀ : 15.5 μm;
• - BET: 1.2m ² / g;
• - Water solubility: 6 mg / L.

example 1

1. a) 70 mg CaCO₃
2. b) 70 mg CaCO₃ und 30 mg FeSO₄·H₂O
3. c) 30 mg FeSO_4·H₂O

und 5 h gerührt.An aqueous K ₂ HPO ₄ solution (phosphate content: 5.8 ppm, pH 7.7) was mixed with

1. a) 70 mg CaCO ₃
2. b) 70 mg CaCO ₃ and 30 mg FeSO ₄ .H ₂ O
3. c) 30 mg of FeSO ₄ .H ₂ O

and stirred for 5 h.

Results:

1. a) Phosphate content after treatment: 5.8 ppm; pH value: 7.5
2. b) phosphate content after treatment: 2.8 ppm; pH value: 7.2
3. c) phosphate content after treatment: 3.6 ppm; pH value: 6.4

Example 2

1. a) 70 mg CaCO₃
2. b) 30 mg FeSO₄·H₂O
3. c) 70 mg CaC03 und 30 mg FeSO₄-H₂O
4. d) 120 mg CaCO₃ und 30 mg FeSO₄·H₂O
5. e) 270 mg CaCO₃ und 30 mg FeSO₄·H₂O

An aqueous K ₂ HPO ₄ solution (phosphate content: 5 ppm, pH 7.7) was mixed with

1. a) 70 mg CaCO ₃
2. b) 30 mg FeSO ₄ .H ₂ O
3. c) 70 mg CaCO 3 and 30 mg FeSO ₄ -H ₂ O
4. d) 120 mg CaCO ₃ and 30 mg FeSO ₄ .H ₂ O
5. e) 270 mg CaCO ₃ and 30 mg FeSO ₄ .H ₂ O

Results:

1. a) Phosphatgehalt nach Behandlung: 5 ppm; pH-Wert: 7,5
2. b) Phosphatgehalt nach Behandlung: 3,1 ppm; pH-Wert: 6,1
3. c) Phosphatgehalt nach Behandlung: 2,9 ppm; pH-Wert: 7,3
4. d) Phosphatgehalt nach Behandlung: 2,8 ppm; pH-Wert: 7,5
5. e) Phosphatgehalt nach Behandlung: 2,6 ppm; pH-Wert: 7,2

After a service life of 30 h, the following results were obtained:

1. a) phosphate content after treatment: 5 ppm; pH value: 7.5
2. b) phosphate content after treatment: 3.1 ppm; pH value: 6.1
3. c) phosphate content after treatment: 2.9 ppm; pH value: 7.3
4. d) phosphate content after treatment: 2.8 ppm; pH value: 7.5
5. e) phosphate content after treatment: 2.6 ppm; pH value: 7.2

Example 3

• Phase 1: FeSO₄·H₂O (2,1 kg/100 m³)
• Phase 2: FeSO₄·H₂O (2,1 kg/100 m³)+ CaCO₃ (4,9 kg/100 m³)
• Phase 3: CaCO₃ (4,9 kg/100 m³)

In a municipal sewage treatment plant (pH of the water: 6-9), the following precipitants were added in three phases.

• Phase 1: FeSO ₄ .H ₂ O (2.1 kg / 100 m ³ )
• Phase 2: FeSO ₄ .H ₂ O (2.1 kg / 100 m ³ ) + CaCO ₃ (4.9 kg / 100 m ³ )
• Phase 3: CaCO ₃ (4.9 kg / 100 m ³ )

The initial phosphate value was 2.2 ppm in the wastewater treatment plant, the amounts of individual components were kept constant.

The phosphate content in the wastewater treatment plant in phase 1 dropped to 1.2 ppm. The phosphate content in the wastewater treatment plant in phase 2 dropped to 0.5 ppm. The phosphate content in the wastewater treatment plant in phase 3 again approaches the starting phosphate content.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• JP 11319411 A [0012]
• JP 09038414 A [0015]
• CN 205328829 U [0020]
• WO 2013/040716 A1 [0021]

Cited non-patent literature

• "Nutrient removal and sludge production in the coagulation-flocculation process" by Aguilar, M.I., Sacz, J., Llorens, M., Soler, A. and Ortuno, J.F. in Water Resarch (2002), 36 (11), pages 2910-2919 [0017]

Claims (8)

Composition for reducing the phosphate content in wastewaters comprising, in each case based on its total weight,> 50.0 wt .-% calcium carbonate and at least 1.0 wt .-% of an iron salt, characterized in that the calcium carbonate has a water solubility of less than 20 mg / 1000 ml of water at 25 ° C. Means after Claim 1 Characterized in that the iron salt is selected from the group consisting of FeSO _4, FeSO ₄ H ₂ O, FeSO ₄ · 4H ₂ O, FeSO ₄ · 5H ₂ O, FeSO ₄ -6H ₂ O, FeSO ₄ .7H ₂ O, FeCl _3, FeCl ₃ · 6H ₂ O, FeCl _2, FeCl ₂ .4H ₂ O, Fe ₂ (SO _{4) 3,} Fe ₂ (SO _{4) 3} · 1H ₂ O and FeCl (SO ₄₎ is selected. Means after Claim 1 or 2 , characterized in that the iron salt is an iron (II) salt, in particular iron (II) sulfate. Composition according to at least one of the preceding claims, characterized in that the agent, in each case based on its total weight, comprises> 60.0 wt .-% calcium carbonate and at least 10.0 wt .-% of an iron salt. Composition according to at least one of the preceding claims, characterized in that the calcium carbonate has an average particle size in the range of 5 microns to 30 microns. Composition according to at least one of the preceding claims, characterized in that the calcium carbonate has a BET specific surface area in the range from 0.4 m ² / g to 10.0 m ² / g. Composition according to at least one of the preceding claims, characterized in that the calcium carbonate comprises ground calcium carbonate. Agent according to at least one of the preceding claims, characterized in that the calcium carbonate is derived from Lahnmarmor.