JPS5843281A - Treatment of water containing phosphate - Google Patents

Abstract

PURPOSE:To maintain a high rate of removal of phosphate by bringing water contg. Mg ions and phosphate into contact with activated crystal seeds contg. calcium phosphate in the presence of Ca ions under conditions of >=7pH. CONSTITUTION:Activated liquid having pH higher than the pH in the stage of crystallization and contg. calcium ions of a concn. higher than the concn. of the calcium ions in the stage of crystallization is brought into contact with crystal seeds such as hydroxyapatite or the like, whereby the crystal seeds are activated. Water contg. magnesium ions and phosphate is brought into contact with the above-described activated crystal seeds contg. calcium phosphate in the presence of calcium ions under conditions of >=7pH, whereby crystallization is effected. The absolute quantity of the calcium ions in said activated liquid is more preferably >=30wt% the phosphorus crystallized under the presence of magnesium ions prior to the activation treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating water containing phosphate to remove phosphate.

In recent years, the progress of eutrophication in closed water bodies such as lakes, marshes, and inner bays has become a serious problem.

As a cause of eutrophication, phosphates present in water are ``J-Supp'', and their removal is an urgent issue.
It has been taken up as Phosphorus N' causes eutrophication
Z J')ul kJWater, sewage, industrial water, engineering''Easy 1
Contained in water, point water, etc., orthophosphate,
It exists in the form of inorganic phosphates such as condensed phosphoric acid and organic phosphorus particles.

As a method for removing such phosphates, a method has been proposed in which water containing phosphates is brought into contact with crystal species containing calcium phosphate, such as phosphate rock, in the presence of calcium ions (Dissertatiori Abstr.
acts International, Vol.
33. &, 12. Part I.

587B-8, etc.). This method includes: 1- Phosphate ions contained in water are removed by converting them into calcium phosphate such as hydroxyapatite and crystallizing them as crystal seeds, and the operating method is simpler than the conventional flocculation method. Not only that, but the processing efficiency is also significantly improved, so it has been attracting particular attention in recent years.

However, this method has the disadvantage that the presence of magnesium ions in the tt, oxidation water deteriorates the phosphate removal efficiency.

The purpose of this invention is to eliminate the above-mentioned drawbacks of the conventional method, and it maintains a high phosphate removal rate by contacting and activating the crystal 131i combination/7-1 oxidizing solution. The aim is to provide a method for treating water containing phosphates that can be used to treat water containing phosphates.

In this invention, magnesium ions: l'+'', I and phosphate are added to water containing calcium ions:
'lJ?-:) Under conditions of 11117 or higher, calcium phosphate is? [J\'Crystallization method for crystallization by contacting crystals after crystallization], 4, 1. and) activating the crystal seeds by contacting the crystal seeds with an activating solution having a pH higher than the pH value and containing calcium ions at a concentration higher than the concentration of cyrano-ion at the time of crystallization. This is a method for treating water containing phosphate.

The reaction that occurs when water containing phosphate is brought into contact with crystalline clay containing calcium phosphate in the presence of calcium ions varies depending on the reaction conditions, but is usually expressed by the following equation.

5Ca"+ 7011--l-3H□PO4-→Ca5
(OH) (PO4)3-1-61120...(1
) However, when magnesium ions are present in water,
The reaction of formula (1) becomes difficult to proceed, and the removal rate of phosphate becomes poor.

Although the detailed mechanism of the inhibition reaction by magnesium ions is not necessarily clear, it is believed that a product such as Ca4H(PO4)3, which has a higher solubility than hydroxyapatite, precipitates and inhibits the crystal formation of hydroxyapatite. □ Inhibition +, 4': The phosphate scavenging activity of Ii crystals decreases/(and': 4).

In this way, fr, the crystal seeds with reduced viscosity are
ll J-'J, , -l, 1) When brought into contact with an activating solution containing 11 ions of calcium ions and a calcium ion concentration higher than the calcium ion concentration at the time of crystallization, the crystal seeds are (1) activated 1 to 1. , and then for a while, the raw water containing magnesium 4
: Activity is maintained even when processed. Therefore, if the treatment is continued while being activated intermittently, phosphates can be removed at a commercial removal rate. This tendency is activated to further fluoride! This becomes noticeable when the proboscis/r-on is included.

The reason why the crystal seeds are activated in this way is not clear, but the rifling Ca4t crystallized on the surface of the crystal seeds
This is because l(PO4)a changes to stable Ca, (OH)(PO4)s, that is, hydroxyanotopite, and the presence of fluoride ions accelerates the reaction and further makes some of it more Stable ff with low solubility
, Ca, li'(POl)3, ie, fluoroapatite. Hydroxia like this
Mitite, fluoroapatite, etc. are extremely active.
If crystallization is performed using the thus activated crystal seeds, efficient crystallization can be performed even in threads in which magnesium ions coexist.

The activation liquid has a pH of 1 or higher than the pH at the time of crystallization, that is, pH 7.
This pH is suitable for commercial use. pH during crystallization
If it is less than that, it cannot be activated well. The upper limit is determined by economics.

The calcium ion concentration of the activation liquid is set to be higher than the calcium ion concentration in the water to be treated during crystallization.

Further, the absolute amount thereof is desirably 60% by weight or more of the phosphorus crystallized in the coexistence of magnesium ions before the activation treatment. This amount is practically about 1 when fluoride ions are present.
The amount of calcium ion can be reduced to 1/3 or more, and the amount of fluoride ion is 1 to 20 Il/l.

It is desirable that the activation liquid does not contain magnesium ions. When using water containing magnesium ions, for example treated water, adding slaked lime at a high concentration will cause the magnesium ions to be coagulated and removed, so it is better to use it in that state.

The contacting method is to pass the activating liquid through the crystal seed packed bed and circulate the activating liquid flowing out, and in practical terms, the time may be limited to about 5 to 48 hours. The method of passing the liquid may be either a fluidized bed type or a fixed bed type, and may be either an upward flow or a downward flow.

By contacting with the activating liquid in this manner, the crystal seeds are reactivated. The sustainability of the treatment effect after activation depends on the phosphate concentration in the raw water and treatment conditions, but
Usually, water containing magnesium ions can be stably treated for about one month, and high-quality treated water can be obtained.

Crystallization is carried out by adding calcilano, a reagent and/or an alkaline agent to the water to be treated, bringing the mixture into contact with crystal 1111 at a pH of 7 or higher, and carrying out a reaction according to formula (1) above.

In this case, the generated calcium phosphate crystals are crystallized in a stable form because the crystal seed table ff1i is activated, and the phosphate concentration in the treated water is reduced.

In this invention, the water to be treated is 7 types of water, 7 types of water, and 7 types of water. 1,7 Yakoto i1. . Yes, we may contain it in the form of magnesium phosphate. Examples of such water include sewage water diluted with seawater and human waste treatment plant discharge water systems.

The amount of calcium agent or alkaline agent to be added to the raw water should be in excess of the reaction equivalent expressed by the formula (]), but if too large a amount is added, fine precipitates may precipitate in places other than the crystal seeds. Furthermore, since impurities such as calcium carbonate may be generated, the temperature should be within a range where these are not generated. In other words, the amounts of calcium ions and hydroxyl ions are determined by the conditions under which hydroxyapatite is produced at a concentration that is lower than the solubility of hydroxyapatite produced in equation (1) but lower than its supersolubility, that is, the concentration is in the metastable range. do. Here, supersolubility is the concentration at which crystals begin to precipitate when crystal seeds are present in the reaction system.

The calcium and ip+1 values that bring the amount of hydroxyapatite within the semi-animal range are 1:: for each reaction system.

It can be determined experimentally by changing the value, but the approximate range is when the phosphate ion is less than 501rQ/l.
', the calcium ion is 10-1001197
1° pH is about 7-12.

Examples of calcium agents used in this invention include calcium hydroxide and calcium chloride, and examples of alkaline agents include sodium hydroxide, potassium hydroxide, and calcium hydroxide.

Crystal seeds containing calcium phosphate include hydroxyapatite (Ca, (0]1) (P(11)31), fluoroapatite (Ca5(F)(PO4,)3) and kl tricalcium phosphate (Ca3(PO4)l). ) can be used, and natural phosphate rock has these calcium phosphates as its main component and is suitable as a crystal seed.Also, crystal seeds containing calcium phosphate precipitated on the surface of filter media such as sand can also be used. Can be used.

It is desirable that the crystal seeds be those whose main component is calcium phosphate, which is the same type of calcium phosphate produced by the reaction. For example, in a system that produces hydroxyapatite,
When hydroxyapatite is collected in a mass of 1, new crystals are precipitated into a circle 11at, and phosphorus fl'l IA+i is efficiently removed, resulting in a removal rate of -1, phosphate-containing water and crystal seeds. The contact method may be a fixed bed type or a fluidized bed type. The smaller the size of the crystal seeds, il', 1lll, the larger the specific surface area and the easier it is for new crystals to precipitate, but if the size is too small, it will be difficult to contact or separate the crystal seeds from water. Furthermore, if the particle size is too large, the specific surface area per unit filling amount will be small, so particles of about 9 to 3,00 mesh are usually used. The larger ones are suitable for fixed beds, and the smaller ones are suitable for fluidized beds.

In the case of a fixed bed, crystal seeds having a particle size of 9 to 35 meshes are packed, and water is passed upwardly or downwardly at a flow rate of SV1 to 10 hr-' to precipitate calcium phosphate crystals. When water is passed in an upward flow, suspended f@ materials can be captured in the large particle size portion of the lower layer, and crystallization can be performed in the small particle size portion of the upper layer that is less active. Similarly, when water is passed in a downward flow, in order to avoid adhesion of suspended matter to the surface of the crystal seeds, a filter A with a smaller specific gravity and larger particle size than the crystal seeds is layered on the crystal seed fixed layer. , it is desirable to remove suspended solids by this filter medium. Crystals during water flow It is desirable to remove it completely.

The water flow conditions during backwashing are 1 to 1, and the flow rate is 20 to 80 m /
The backwashing time is about 5 to 60 minutes and 4"i degree.

By the crystallization operation as described above, the phosphates in the raw water are completely removed, and the phosphate concentration in the treated water is reduced. If such operations are continued and the activity of the crystal A width decreases and the quality of the treated water deteriorates, by performing the above-mentioned i'i' :Can perform iJi.

As described above, according to the present invention, the product 1 no 11f, °i
(1') Phosphate removal effect is achieved by applying active 1'l-1cy-c treatment which has a pH of 1 or less and contains calcium ions at the time of crystallization. The low 1'171r-l1iI'; cultivar can be reactivated; this (r(J'), for raw water containing limadanesium ions, also removes phosphates with a sieve removal rate; Treated water with low phosphate-m:.

Obtainable.　　　　　　　　　　　　　 Next, examples of the present invention will be described.

Example 1 Phosphoric acid from water containing 40 to 60 #I9/l of magnesium ions and 1 to 2 rv/l of phosphate (the same applies hereinafter) was placed in an acrylic column with an inner diameter of 60 sieve and a length of 50 on. 16-3 used for about 6 months to remove salt
2 men's sandstone ore from Jordan 'jp' 1507n
e filling, phosphate concentration 11I+zo/14. Total alkalinity approximately 100 mg/l, magnesium (, t 7 concentration 5
Column people [1
An aqueous solution of calcium and hydroxide was cooled to a concentration of 80 to 851n.
On September 14th, after adjusting the pH to 188 to 90, water was continuously passed through the phosphate rock packed bed at a flow rate of 600 me/br using a fixed bed water flow system, and all crystallization was carried out. The phosphate concentration in the treated water was 0.19 m9/l immediately after water flow started, but it gradually increased to 0.3 m9/l after 8 days.
It reached A. At this time, the amount of total 1-zophosphoric acid base crystallized and removed in the sieve was approximately 900 m9/e. :1 ::,.

Based on treated water, calcium ion concentration Iji is added to 1
00m9/e, 7 element ion concentration 1i 15 mg/
/I' VC adjusted aqueous solution (pH 9,5) 1t
! I, l, 11: 'In, ψ, 24 in the stone-filled column
Time 11'f '':1 place''l! I-7(, (1'
f11'+'``1'! v)!+ ``l! fk, the phosphate rock packed bed was subjected to crystallization under the following conditions: tap water -C, iv f31g I-, lkofle, 1lif.
2/KotoC: ', +, tsunomi, , l'll lk's phosphate concentration gradually decreases (2,1 to 11f& has n,
12111! / /l, and since then about 2011
I was able to process the song as a constant (-). (Z+: :L
” , 6 months spent crystal seeds' (z used) & is to improve the whiteness of the effect of magnesilano and ions.Furthermore, after 10 days, the phosphate concentration in the treated water remains again. As a trend emerged, the above reactivation process was performed again.The amount of phosphate crystallized and removed during the 46 days from the start of the above continuous rotation was approximately 4 Q Q m/l, and the reactivation process was performed again. Calcium ion amount in the activation liquid if 3 [] The same operation was carried out except that 74 W of fluoride was added], 'ff, and (.The result -!, l, -1 The phosphoric acid island removal effect was almost the same as described above.

Example 2 In the same case as in Example 1, the phosphate concentration in the treated water reached 0.3 tng/11. I
Inner activation treatment of phosphate rock was performed at one point.

Add 11.55g of slaked lime to 1e of tap water (297g as Ca)
11jv) Added water solution / & (pH 12,1) to 800
m1/hr and 41. The solution was continuously circulated for 7 hours. After the circulation treatment, it was allowed to stand for 6F1, and then the packed bed was backwashed with tap water, and then phosphate-containing water was passed through it.

The phosphate concentration in the treated water was 41 after the start of water flow.The song was 01m.
y/lj or less, and after that it remained at 0 and 1 for about a month.
The treated water quality was disappointing at around 5m9/1.

In addition, the amount of lime added was 1.1g (Ca Toshide 5941).
When the same treatment as above was carried out except for the addition of (in 12.2), the result was 0.1 rng/l or less for 10 days after the start of water flow, and the r& was also stable.
．． It showed a processing performance of around 1 m9/1.

However, when 0.1 jj (50 rng as Ca) of lime was added (ptl 8.8)
, 2 [l after the start of water flow In 11-4, phosphorus Y in the treated water
-W salt concentration is 0. I l1ly / 1 remained around 1, but it remained in the plug: fii: increased, 1011th teU O, 31l19 / e Mill V & Tonatsu k.

Agent: Patent attorney Sei Yanagi Hara

Claims (1)

[Claims] (1) Magnesium ions and phosphorus particles? In the water containing r, in the presence of calcium ions and with a pH of 7J! A method of performing crystallization by bringing 1 g of calcium phosphate into contact with 1 g of - Shinagami under the conditions of -, 1, and having a pH of 1. And calcium ions during crystallization (Yl-1 containing calcium ions from 14-1) : ”：
'J-Place of water containing phosphate 1111 force θmi (2)
The activating liquid is 4 ribs: :l:
l:'s phosphorus? 'lν+! nt? i. Treatment method for water containing water (3) Activation liquid is crystallized Jl, 30 li of tarin:
Contains more than % of calcium ions! (4) The activating liquid contains calcium ions having a weight ratio of 10 or more of the crystallized phosphorus and 1 to 2 [ The method for treating water containing phosphate according to claim 2, which contains fluoride ions of 1rq)/e.