JPS6044996B2 - How to remove phosphates from liquid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing phosphates present in tap water, sewage, human waste water, industrial water, factory wastewater, boiler water, and all other liquids.

The various liquids mentioned above that are generally discharged into natural water systems include:
Orthophosphates, various condensed phosphates, and organic phosphates exist in various states as inorganic phosphates, and the presence of these phosphates causes the closure of lakes, inland seas, and inner bays. "Blue water" and "red tide" in water or stagnant water
Biological slime is generated in equipment and piping when water is used for various purposes.
In addition, chemical scale is formed, which is a serious cause of accidents.

Therefore, various phosphorus removal methods are being considered in order to remove the phosphates present in these liquids, and the representative ones include biological treatment, ion exchange resin method, and chemical treatment. Among these methods, the chemical coagulation-sedimentation method is regarded as a somewhat completed treatment technology, and treatment equipment on an actual treatment scale is already in operation in many places.

The removal of phosphates by this chemical flocculation treatment is a method of removing phosphates present in the liquid as insoluble phosphates by adding a specific flocculant. Usually, slaked lime [Ca(0H)2], aluminum sulfate [Al. (SO4)3], ferric chloride [Fe
Cl3] etc. are used.

However, the biggest drawback of the chemical coagulation-sedimentation method is that it generally requires a large amount of flocculant and the processing cost is high, regardless of the type of flocculant used. A large amount of sludge is generated in proportion to the amount of two major chemical injections, and the settling and thickening properties of this sludge are extremely poor (with the exception of lime sludge).

3 Furthermore, this sludge has poor dewatering properties (lime sludge is an exception).

However, because it requires a large sludge treatment facility and processing costs, it has many practical problems despite being a current technology.

In addition, the inventors of the present invention have developed a novel treatment method in which a cylindrical or conical dephosphorization tower is filled with phosphate minerals containing calcium phosphate having a certain particle size, and the PH of the liquid to be treated is is adjusted to a range of 6 to 11, and the solubility contained in the liquid to be treated is adjusted to a range of 6 to 11. By adding a calcium agent such as calcium chloride according to the concentration of phosphates and bringing them into contact with each other at a constant flow rate, calcium hydroxyapatite crystals are crystallized on the surface of the filled phosphate minerals. , fixed with soluble phosphoric acid. Methods for removing salts have also been proposed.

The typical chemical reactions in this Yanghe phosphate mineral table are as follows. By applying this new dephosphorization method, it is extremely easy to separate and dehydrate phosphate minerals with fixed calcium hydroxyapatite. This is an excellent dephosphorization technology that not only does not require conventional sludge treatment facilities such as equipment, dehydrators, and dryers, but also can recover phosphorus as a resource.

However, in this new catalytic dephosphorization method, in order to fix the soluble phosphates contained in the liquid as crystals of calcium hydroxyapatite [Ca5(0H)(PO4)3], appropriate pH conditions are required. CaCI2, Ca(0H)2-, etc. are added as calcium agents, but if the liquid to be treated contains an alkalinity component, calcium carbonate is produced according to the following reaction formula.

Is the pH of this calcium carbonate liquid in a pH range suitable for producing calcium hydroxyapatite?
Alternatively, if the pH was adjusted, the apatite production rate would be higher than the calcium carbonate production rate, so it would not be produced, but it is difficult to completely control the pH in actual processing equipment, and if the alkalinity component is concentrated. It is inevitable that the reaction of formula (2) proceeds to some extent the moment the calcium agent is added.

Although the amount of calcium carbonate crystals produced under these conditions is extremely small, the calcium carbonate crystals gradually grow fixedly on the surface of the phosphate mineral over a long period of time.

As a result, the surface activity of the phosphate mineral deteriorates, the dephosphorization function decreases, and the dephosphorization effect can no longer be expected to be as high as it was initially. In this way, the catalytic dephosphorization method has limited applicability to liquids that contain large amounts of alkalinity components and also soluble phosphates, but it is possible to remove alkalinity components by some method. If removed, the scope of application of the catalytic dephosphorization method will be expanded.

The main conventional methods for removing alkalinity components in liquids, that is, the main softening methods, are the stripping method under acidic conditions and the softening method by adding Ca(0H)2 (a type of coagulation-sedimentation treatment). Each method has significant drawbacks. In other words, the former method of stripping under acidic conditions requires an acid to make the liquid acidic and an alkaline agent to return the pH to the original level after treatment, which not only increases processing costs but also increases process costs. It is complex and lacks processing stability.

In addition, the latter chemical softening method by adding Ca(0H)2 not only requires a large amount of softener (slaked lime), but also generates a large amount of sludge that is difficult to treat, and post-treatment is also complicated and uneconomical. be. The present invention is an effective method for solving these conventional problems, and is an effective method for removing phosphates accurately and efficiently.
The purpose of this invention is to provide a method that enables stable processing operations over a long period of time and greatly improves the operating rate.

Another object of the method of the present invention is to provide a useful method that can economically obtain treated water of extremely high quality through extremely simple treatment operations, and that can easily reduce treatment equipment costs and treatment costs. It's about doing.

The present invention is characterized in that a liquid containing phosphates is brought into contact with a cement-alkaline agent composite consisting of a calcium monocarbonate-containing mineral, and then brought into contact with a phosphate mineral whose main component is calcium phosphate for treatment. This is a method for removing phosphates present in the liquid.

The composite consisting of cement-alkaline agent monocalcium carbonate-containing mineral used in the method of the present invention is cement-alkali agent+calcium carbonate-containing mineral=3:1~
It is effective to use a composite having a blending composition of 1:15, and further alkali agent:calcium carbonate-containing mineral=1:1 to 1:10.

In this case, the cements include boltland cement, slag cement, silica cement, alumina cement, mixed cement, etc., and the alkaline agents include slaked lime, quicklime, hydrocarbon soda, hydropotassium, etc., and minerals containing calcium carbonate. There are marble, marl, dolomite, calcite, coralline limestone, coral sand, etc., and these are used alone or in combination of two or more types, but this cement, alkali agent, calcium carbonate-containing minerals are used in granular, powdered, granular, Mix it into a lump or powder, and knead it as it is or add an appropriate amount of water to it to obtain a particle size of 0.37T$t~10077W! It is molded into a composite. The shape of the composite can be powdered or
Any powder, granule, or block may be used. In any case, by bringing the liquid to be treated into contact with a composite consisting of a cement-alkaline agent calcium monocarbonate-containing mineral, 0H- ions,
Ca2+ from cement or calcium carbonate-containing minerals
Since the ions are dissolved, the alkalinity component contained in the liquid to be treated becomes calcium carbonate according to equation (2) above, and the generated calcium carbonate is crystallized into the undissolved parts of the complex, especially the surface of calcium carbonate-containing minerals. After solidification, a softening process is performed through a decarboxylation process. Therefore, unlike the conventional softening method of adding Ca(0H)2, no sludge is generated, and sludge treatment and disposal are unnecessary.

In the softening method according to the method of the present invention, depending on the properties of the liquid to be treated, the content of cement-alkaline agent-calcium carbonate-containing mineral in the composite may be changed, or the contact time of the composite and the liquid to be treated may be changed. By changing the amount of 0H- ions and Ca2+ ions dissolved in the complex, it is possible to control the amount of 0H- ions and Ca2+ ions that are sufficient to soften the liquid to be treated. It becomes necessary. Next, in the liquid to be treated that has come into contact with the composite and has been chemically softened, 0H- ions and Ca2+ ions that do not participate in the production of calcium carbonate remain, so the molar ratio of C
a/PO4≧0.7 preferably 1-5, PH=8-1C
Phosphates can be removed from the liquid to be treated by crystallizing and fixing calcium hydroxyapatite crystals, preferably under conditions of pH=8.5 to 9.5. The chemical reaction formula on the surface of this phosphate mineral is as shown in formula (1) above. Furthermore, if the molar ratio of calcium ions to the phosphates in the liquid to be treated is Ca/PO4=0.7, calcium ions are added to the liquid to be treated after chemical softening. By doing this, it becomes possible to crystallize and fix calcium hydroxyapatite crystals on the surface of the phosphate mineral and remove them from the liquid to be treated, but slaked lime is used as an alkali agent for the complex. And from slaked lime, 0H- ion,
Since Ca2+ ions are dissolved, they contribute to both the softening of the alkalinity components of the liquid to be treated and the removal of phosphates, and are therefore highly effective.

In addition, in the dephosphorization step, phosphate minerals containing calcium phosphate having a certain particle size, such as L Jordan,
From Florida, from Mexico, from Canada, from Kurokura, Kanagawa Prefecture,
It is carried out by passing liquid through a packed tower filled with phosphate rock from Ashio Copper Mine in Tochigi Prefecture, Yoron Island, Nagatari in Fukuoka Prefecture, Daiku Mine in Hokkaido, etc. The liquid passing method may be either a fluidized bed method or a fixed bed method, and in the fixed bed method, either an upward flow or a downward flow may be used.

In the fluidized bed method, this liquid passing condition is generally 10~10 as S■.
100d/7T1-Hr, 1 as SV in fixed layer method
A range of ~10 d/d-Hr is suitable. Furthermore, during the liquid passage treatment, the pH value of the liquid should normally be in the range of 8.0 to 11.0, and the injection rate of calcium ions varies depending on the concentration of various phosphates dissolved in the liquid, but usually Ca
/0.5~2CE or 1.0~5.0 as PO4
It is added within the range of . Further, one embodiment of the present invention will be explained with reference to the drawings. The liquid to be treated containing phosphates and alkalinity components is filtered through a sedimentation tank or a simple sand filter to remove suspended substances remaining in the liquid. Later inflow pipe 1
and introduced into the first tank 2.

This first tank 2 is filled to a certain height with composites 3 made of cement-alkaline agent calcium monocarbonate-containing minerals whose particle size has been adjusted to a certain level. When passing through the tank 2, it comes into contact with the complex 3, dissolves the complex 3, 0H- ions and Ca2+ ions are eluted, and the alkalinity component in the liquid to be treated becomes calcium carbonate and the complex 3 is dissolved. Crystallizes and adheres to undissolved parts of the body. The second tank 6 is filled with phosphate mineral 7 whose main component is calcium phosphate, which has been adjusted to a certain particle size. When the liquid is introduced and passes through the second tank 6, the phosphates in the liquid become hydroxyapatite, which crystallizes and adheres to the surface of the phosphate mineral 7, and is removed. discharge treated water. Furthermore, if there is insufficient Ca2+ ion to generate hydroxyapatite, for example, if the molar ratio is Ca/PO4<0.7, Ca
By adding 2+ ions, the molar ratio Ca/PO43-
D 1-5 is good.

As described above, the present invention removes alkalinity components contained in the liquid as much as possible by bringing the alkalinity components contained in the liquid into contact with a composite consisting of cement and an alkaline agent and minerals containing calcium monocarbonate. , Ca2 which brings about the effect of removing phosphates in the subsequent contact step with phosphate minerals.
Phosphate salts in the liquid can be removed for a long period of time with extremely simple operations such as omitting the addition of alkaline agents to increase the amount of SOON and adjust the pH, and furthermore, the need for disposal equipment can be reduced. .

Next, examples of the present invention will be described.

Example 1 Cement-alkali agent A composite consisting of calcium monocarbonate-containing minerals was prepared by adding 2 parts by weight of cement, 1 part by weight of slaked lime as an alkali agent, 7 parts by weight of coral sand as a charcoal-containing mineral, and 5 parts by weight of water. The mixture was added and kneaded well to form a paste.

From this paste-like material, the particle size is 0.5Tm to 1.0T! Rl
n granules were molded and adjusted. The above granular composite was packed into a container having a diameter of 20 cm and a height of 200C71 as a softening column (32e (filling height: 100 cm)).

Diameter 10cm 1 height 100cm as a column for dephosphorization
A container was filled with 8e (filling height: 100 cm) of Jordanian phosphate rock having a particle size of 0.6 Tf$l to 0.8 TfUTL. The activated sludge-treated sewage water shown in Table 1 was used as raw water and was passed through the above-mentioned softening column in an upward flow, and then passed through the dephosphorization column in an upward flow.

The water flow rate for the softening column is SV=1 (1/Hr),
The dephosphorization column was set to S■=4 (1/Hr). This experiment continued for about 4 months, and in order to check the deterioration of the activity of phosphate rock when water was passed for a long period of time, during the first week after the start of operation,
A precise analysis was conducted on the final treated water in the third month.

The results are shown in Table 1, and according to the present invention, no reduction in the dephosphorization effect was observed at all even after one week and three months after the start of water flow.

On the other hand, as a comparative example, the pH was adjusted to 8.8 to 9.2 without passing the raw water through the softening column, and the raw water was directly passed through the dephosphorization column (
Table 2 shows the results of water flow under the same water flow conditions.

Although the dephosphorization effect is noticeable at the beginning of water flow, after 3 months,
The dephosphorization performance deteriorated significantly. Example 2 The shapes of the softening column and dephosphorization column were the same as in Example-1.

Cement - alkaline agent A complex consisting of calcium monocarbonate-containing minerals is prepared by adding 3 parts by weight of cement, 1 part by weight of granular soda as an alkali agent, 6 parts by weight of coral sand as a calcium carbonate-containing mineral, and 5 parts by weight of water. Add it and knead it well to make a paste.

From this paste-like material, the particle size is 0.5Tm! n~1.07T
A granular material of $L was molded and adjusted. The column for softening was packed with 32e of the above granular composite, and the column for dephosphorization was packed with 8' of Jordanian phosphate rock having a particle size of 0.4 Tnm to 0.6 Tnm.

The treated water of the nitrification and denitrification method of human waste shown in Table 3 (1@diluted water of human waste) was used as raw water and passed through the softening column in an upward flow.

The water flow rate for the softening column is S = 0.5 (1/h)
The dephosphorization column was set at SV=2 (1/Hr). The phosphoric acid concentration of the raw water is 40 to 60 mg/l as PO43-, and the Ca2+ ion concentration is 10 to 20 mg/'.
Add 100mg/Ca2+ ion to the treated water of the softening column.
The dephosphorization treatment was continued for one month by adding f. Table 3 shows the results 3 weeks after the start of water flow.

On the other hand, as a comparative example, Ca was added to the treated water of the softening column.
Table 4 shows the results obtained without adding 2+ ions.
From the results in Table 4, the dephosphorization performance was significantly degraded when Ca2+ ions were not added.

[Brief explanation of drawings]

The drawings are schematic diagrams illustrating one embodiment of the method of the invention.

Claims (1)

[Claims] 1. A solution to be treated containing phosphates is brought into contact with a composite consisting of cement, an alkaline agent, and a calcium carbonate-containing mineral to remove alkalinity components in the solution as calcium carbonate, and then the calcium phosphate is removed. A method for removing phosphates from a liquid, the method comprising treating the phosphates by bringing them into contact with phosphate minerals as the main component. 2 The decarboxylation step is performed using cement: alkaline agent + calcium carbonate-containing mineral = 3:1 to 1:15, and alkaline agent:
The method for removing phosphates according to claim 1, wherein the method is carried out in contact with a complex of calcium carbonate-containing minerals in a ratio of 1:1 to 1:10. 3. Claim 1 or 3, wherein the dephosphorization process is performed by injecting calcium ions in the range of 1.0 to 20 as Ca/PO_4 into the decarboxylation process effluent supplied to the dephosphorization tower. The method for removing phosphates according to item 2. 4. The phosphor according to claim 1, 2, or 3, wherein the composite consisting of cement, alkaline agent, and calcium carbonate-containing mineral is treated with slaked lime as an alkaline agent. Method for removing acid salts. 5. Claim 1, wherein the dephosphorization step involves passing the liquid through a dephosphorization tower filled with phosphate minerals having a particle size of 0.1 to 1.0 mm in a fixed bed system or a fluidized bed system, Section 2,
The method for removing phosphates according to item 3 or 4. 6. Claims 1, 2, and 3, wherein the dephosphorization step is performed by adding calcium ions as Ca/PO_4 in a range of 1.0 to 5.0 to the softening treatment solution. , the method for removing phosphates according to item 4 or 5.