JP2003033788A - Method for treating raw water containing phosphorus and ammoniacal nitrogen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently remove phosphorus and ammoniacal nitrogen at reduced costs incurred in equipment and operation when raw water containing phosphorus and ammoniacal nitrogen is treated by a dephosphorization process, a nitrite- conversion process and a denitrogenation process. SOLUTION: Raw water is fed to a nitrite-conversion process 1 and at least a part of ammoniacal nitrogen in the raw water is converted to nitrite nitrogen which is fed to a dephosphorization process 2 afterwards to remove the phosphorus. Then, it is fed to a denitrogenation process 3 to perform a denitrogenation treatment by reacting the ammoniacal nitrogen and nitrite nitrogen by means of the action of denitrifying microorganisms in which the ammoniacal nitrogen acts as an electron donor and nitrite nitrogen as an electron acceptor. Alternatively, raw water is fed to a nitrite-conversion process 1 and ammoniacal nitrogen is converted to nitrite nitrogen. Subsequently, it is fed to a denitrogenation process 3 to perform a denitrogenation process and then, fed to a dephosphorization process 2 to remove the phosphorus.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dephosphorization step, a nitrite conversion step, and a dewatering step of treating raw water containing phosphorus and ammonia nitrogen, such as digestion desorption liquid discharged from an anaerobic digestion process of organic sludge. And a method of treating by a nitrification process.

[0002]

2. Description of the Related Art Wastewater containing phosphorus and ammoniacal nitrogen is discharged from a wastewater treatment process. In particular, the digestive desorption liquid discharged from the anaerobic digestion process of organic sludge contains a large amount of ammoniacal nitrogen and phosphorus. This effluent is usually returned to another biotreatment process. For example, in sewage treatment, it is returned to the activated sludge process.
Ammonia nitrogen and phosphorus contained in the desorbed liquid returned as return water become a load of the activated sludge process. Further, when the ammoniacal nitrogen and phosphorus are not removed in the activated sludge process, they are discharged into the treated water and discharged, which causes eutrophication. Therefore, it is necessary to remove phosphorus and ammonia nitrogen contained in the return water such as digestion / desorption solution before returning.

Conventionally, as a method of removing phosphorus in waste water,
There is a crystallization method. The crystallization method is to add calcium salt such as lime or magnesium salt such as magnesium hydroxide to the waste water, adjust the pH of the solution to be alkaline by adding alkali, and to dissolve phosphorus into sparingly soluble calcium phosphate or magnesium ammonium phosphate. (MAP) is deposited and separated,
It is to be collected.

On the other hand, as a method for removing ammoniacal nitrogen in waste water, there is an alkali stripping method. In this method, alkali is added to the waste water so as to have a pH of 9 or more, preferably 10 or more, and then the gas is aerated to volatilize ammoniacal nitrogen as ammonia gas. The stripped ammonia-containing gas is acid-cleaned with a scrubber or the like, and ammonia is recovered as an acidic concentrated liquid containing ammonium salts.

As a method for biologically treating ammoniacal nitrogen in wastewater, the ammoniacal nitrogen is oxidized to nitrite nitrogen by ammonia-oxidizing bacteria, and the nitrite nitrogen is converted to nitrate nitrogen by nitrite-oxidizing bacteria. A nitrification process that oxidizes and a denitrification process that decomposes these nitrite nitrogen and nitrate nitrogen into nitrogen gas by utilizing organic substances as electron donors by denitrifying bacteria that are heterotrophic bacteria There is a method of decomposing into nitrogen gas through a biological reaction.

However, this nitrification and denitrification method has a drawback that the running cost is high because a large amount of an organic substance such as methanol is required as an electron donor in the denitrification step and a large amount of oxygen is required in the nitrification step. .

On the other hand, in recent years, an autotrophic microorganism having ammonia nitrogen as an electron donor and nitrite nitrogen as an electron acceptor is used to react ammonia nitrogen with nitrite nitrogen. A method of denitrification was proposed. This method does not require addition of organic matter, and thus can reduce the cost as compared with the method using heterotrophic denitrifying bacteria. Also, the yield of autotrophic microorganisms is low,
Since the amount of sludge generated is significantly smaller than that of the heterotrophic microorganisms, the amount of excess sludge generated can be suppressed. In addition, there is no generation of N ₂ O observed in the conventional nitrification and denitrification method, and there is a feature that the load on the environment can be reduced.

This autotrophic denitrifying microorganism (hereinafter referred to as “ANA
MMOX microorganism ". ) Is used for the biological denitrification process (ANAMMOX process) by Strous, M, et al.,
Appl. Microbiol. Biotechnol., 50, p.589-596 (199
8), and it is considered that ammonia nitrogen and nitrite nitrogen react with each other in the following reaction and decompose into nitrogen gas.

[0009]

[Chemical 1]

Therefore, when the denitrification treatment is carried out by utilizing this ANAMMOX microorganism, the water to be treated (raw water) flowing into the ANAMMOX reaction tank holding the ANAMMOX microorganism.
Must contain ammoniacal nitrogen and nitrite nitrogen. The nitrite nitrogen necessary for this ANAMMOX reaction is
Ammonia nitrogen in waste water is also produced by being oxidized by ammonia-oxidizing bacteria. In this case, in the above-mentioned nitrification step, it is necessary to perform nitrite type nitrification in which the production of nitrate nitrogen from nitrite nitrogen is suppressed and the oxidation of ammonia nitrogen is stopped by nitrite nitrogen.

[0011] Conventionally, as a technique for performing nitrite type nitrification, a nitrite process for suppressing nitration and producing nitrite nitrogen by utilizing the toxicity of free nitrite (HNO ₂ ). Reported (Anthoniesen).

Since nitrous acid dissociates like HNO ₂ ⇔ H ⁺ + NO ₂ ⁻ , the free nitrite concentration increases as the pH decreases. Therefore, this nitrite process cannot be operated on the alkaline side. In particular, when the pH exceeds 8, the toxicity of free nitrite can hardly be expected, nitrification further progresses, and nitrite nitrogen is oxidized to nitrate nitrogen. Then, in this case, the denitrification process by the above-described ANAMMOX microorganism cannot be applied. on the other hand,
When the pH becomes 5 or less, the whole nitrification reaction is hindered and stopped. From these things, the nitrite type nitrification which oxidizes ammoniacal nitrogen to nitrite nitrogen is normally performed on conditions of pH 6-8.

Further, when ammoniacal nitrogen coexists in the reaction system, the nitrification is likely to stop in the nitrite type due to the toxicity of the ammoniacal nitrogen.

Further, in order to carry out nitrite type nitrification, it is preferable to maintain the dissolved oxygen (DO) concentration in the reaction solution as low as about 1 mg / L, and to maintain more stable nitrite type nitrification. It is preferable to keep the water temperature within 30 ° C.
Furthermore, by further holding the microorganisms in the form of a biofilm in the reaction tank to carry out the reaction, further stabilization can be achieved.

[0015]

Alkali is necessary for chemically removing phosphorus by the crystallization method. And
Since the treatment liquid from which phosphorus has been removed by the crystallization method is strongly alkaline and cannot be discharged as it is, it needs to be neutralized with an inorganic acid. Further, in order to carry out the crystallization reaction rapidly, calcium salt and magnesium salt are usually added in excess of the reaction equivalent to phosphorus in the waste water. For this reason, the processing cost by the crystallization method is considerably high, which has been an obstacle to the practical use of the crystallization method.

Further, in the crystallization method, fine crystals may be formed by the addition of excess calcium salt or magnesium salt. Since these do not settle easily, they flow out into the treatment liquid (supernatant liquid), which causes the phosphorus removal efficiency to decrease.

Further, when wastewater containing ammoniacal nitrogen and phosphorus is treated by a crystallization method, phosphorus and ammoniacal nitrogen react with each other under a pH alkaline condition to be crystallized in a crystallizer to improve the phosphorus removal efficiency. At the same time, the pipes and the like may be clogged due to crystal precipitation.

The crystallized phosphorus can be effectively used as a slow-acting fertilizer. In this case, it is desired that the crystals have high purity, and for example, calcium phosphate may be added to MA.
When P is mixed, it is difficult to use and the commercial value is inferior.

On the other hand, the method of removing ammoniacal nitrogen in the waste water by stripping it requires the addition of a large amount of both alkali and acid, which requires a great deal of operation.
Particularly when attempting to strip ammonia with high efficiency, the amount of alkali added needs to be 10 times or more that in the case where phosphorus is removed by the crystallization method.

When the waste water containing ammoniacal nitrogen and phosphorus is stripped, phosphorus and ammonia may react under high pH conditions to cause crystallization in the stripping device. In this case, Ammonia removal performance deteriorates, and the pipe may be blocked by crystals.

Further, in the denitrification treatment using the above-mentioned ANAMMOX microorganism, the activity of the ANAMMOX microorganism is unstable, and it is easily deactivated particularly in the dispersed state. ANAM
Since MOX microorganisms prefer to grow in the form of biofilms,
It is desired to add a carrier to the reaction tank to form a biofilm of the ANAMMOX microorganism on the carrier. Many types of artificial carriers used as carriers for microorganisms have been commercialized, but these are generally expensive, which increases the capital investment cost.

Further, the activity of the ANAMMOX microorganism is lowered when the phosphorus concentration in the reaction system is high, so that the denitrification performance is lowered.

From the above, conventionally, a large-capacity reaction tank is required to remove ammoniacal nitrogen and phosphorus, and a large amount of chemicals, carriers and the like are required, resulting in equipment cost and operation. Expenses were expensive.

Further, when treating wastewater containing phosphorus and ammonia nitrogen in high concentrations such as digestive desorption liquid discharged from the anaerobic digestion process of organic sludge, the individual treatment processes as described above are performed. Although it is possible to combine them, as described above, each process has drawbacks, and there is a problem when phosphorus and ammoniacal nitrogen coexist.
No industrially advantageous method has been found.

The present invention has been made in view of the above conventional circumstances, and is a method of treating raw water containing phosphorus and ammoniacal nitrogen by a dephosphorization step, a nitrite nitration step and a denitrification step. Therefore, it is an object of the present invention to provide a method for efficiently removing phosphorus and ammonia nitrogen while reducing equipment costs and operating costs.

[0026]

A method for treating raw water containing phosphorus and ammoniacal nitrogen comprises the steps of: dephosphorizing the raw water containing phosphorus and ammoniacal nitrogen; In the method of treatment with the process, first, raw water is supplied to the nitrite conversion step to convert at least a part of ammoniacal nitrogen in the raw water into nitrite nitrogen, and then supplied to the dephosphorization step to remove phosphorus. Then, it is supplied to the denitrification step to react ammonia nitrogen and nitrite nitrogen by the action of a denitrifying microorganism that uses ammonia nitrogen as an electron donor and nitrite nitrogen as an electron acceptor. Characterized by denitrification.

The method for treating raw water containing phosphorus and ammonia nitrogen according to claim 2 is a method of treating raw water containing phosphorus and ammonia nitrogen by a dephosphorization step, a nitrite nitration step and a denitrification step. In, in the raw water is first supplied to the nitrite process, at least a portion of the ammoniacal nitrogen in the raw water is converted to nitrite nitrogen, and then supplied to the denitrification process,
Ammoniacal nitrogen and nitrite nitrogen are reacted by the action of a denitrifying microorganism that uses ammoniacal nitrogen as an electron donor and nitrite nitrogen as an electron acceptor to denitrify, and then,
It is characterized in that it is supplied to a dephosphorization step to remove phosphorus.

In the method of the first aspect, first, ammoniacal nitrogen in the raw water is converted to nitrite nitrogen in the nitrite-forming step, and then phosphorus is removed in the dephosphorization step. Therefore, in the dephosphorization step, it is possible to avoid troubles such as the blockage of the pipe due to the generation of crystals in the crystallizer due to the coexistence of ammoniacal nitrogen. Then, in the dephosphorization step, M
It is possible to recover highly pure crystals of calcium phosphate containing almost no AP and thus having high commercial value as fertilizers. Furthermore, by denitrifying the treatment liquid of the dephosphorization step by an ANAMMOX reaction, the fine crystals contained in the treatment liquid of the dephosphorization step function as a carrier for the ANAMMOX microorganisms, and the surface of the fine crystals contains the organisms of the ANAMMOX microorganisms. The membrane can be stably grown and efficient denitrification treatment can be performed. Therefore, it is not necessary to separately add an artificial carrier, and the outflow of fine crystals flown from the dephosphorization step can be prevented.

In the method of claim 2, since the ammonia nitrogen is removed in the nitrite-nitrating step and the denitrification step and then the phosphorus is removed in the dephosphorization step, the presence of ammoniacal nitrogen in the dephosphorization step results in It is possible to avoid troubles such as pipe clogging due to the generation of crystals in the crystallizer.
Then, in the dephosphorization step, for example, by adding a calcium salt, it is possible to recover a crystal of calcium phosphate having a high purity and having a high commercial value as a fertilizer that hardly contains MAP.

Further, since the method of the present invention removes ammoniacal nitrogen in the nitrite-nitriding step and the denitrifying step, there is no problem of crystal precipitation due to the coexistence of phosphorus as in the conventional ammonia stripping.

The method for treating raw water containing phosphorus and ammoniacal nitrogen according to the present invention is obtained by solid-liquid separation of the digestion desorption liquid discharged from the process of anaerobic digesting organic sludge. It is suitable for treating separated water.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the method for treating raw water containing phosphorus and ammonia nitrogen according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a system diagram showing an embodiment of the present invention.

In the method for treating raw water containing phosphorus and ammoniacal nitrogen according to claim 1, as shown in FIG. 1 (a), raw water is sequentially treated in a nitrite nitration step 1, a dephosphorization step 2 and a denitrification step 3. To do.

That is, first, raw water is introduced into an aeration tank in which sludge of ammonia-oxidizing bacteria is held, and ammonia nitrogen in raw water is oxidized to nitrite nitrogen under aerobic conditions. In this aeration tank, in order to prevent the production of nitrate nitrogen and perform nitrite type nitrification, the DO concentration is 0.5 to 1.5 mg / L,
It is preferable to perform the treatment at a water temperature of about 25 to 35 ° C. Further, in order to adjust the pH to 6 to 8, an alkali such as NaOH is added as necessary to adjust the pH.

The treated water in the nitrous acid process 1 is then supplied to the dephosphorization process 2 to be dephosphorized. The dephosphorization treatment in the dephosphorization step 2 is preferably performed by a crystallization method. Therefore,
Calcium salt such as calcium chloride and calcium carbonate, or magnesium salt such as magnesium hydroxide is added to the treated water in the nitrite conversion step 1 in an amount of about 1.5 to 10 times the amount of phosphorus to be removed, and if necessary. An alkali such as NaOH is added to adjust the pH, and water is passed through a crystallization dephosphorizer containing calcium phosphate, magnesium ammonium phosphate, calcium silicate, etc. as seed crystals. The pH is adjusted to pH 8.5 or more in the case of calcium phosphate and pH 8.6 to 8.8 in the case of magnesium ammonium phosphate.
Is preferred.

The treated water in the dephosphorization step 2 is then supplied to the denitrification step 3 to be denitrified by the ANAMMOX microorganism. The denitrification treatment by this ANAMMOX microorganism is
It is preferable to carry out the treatment at 6.5 to 8.0 and the temperature of 25 to 35 ° C. Therefore, pH is adjusted by adding an inorganic acid such as H ₂ SO ₄ to the treated water in the dephosphorization step 2.

In this denitrification step 3, since the water from which the soluble phosphorus has been removed in the dephosphorization step 2 is introduced, efficient denitrification treatment can be carried out without being affected by the reaction by phosphorus.
Also, in the dephosphorization step 2, fine crystals of calcium phosphate or the like that are produced by the addition of an excessive amount of calcium salt or magnesium salt and flow out into the treated water function as a carrier for the ANAMMOX microorganism, and the biofilm of the ANAMMOX microorganism is the surface of this fine crystal. By growing into, efficient denitrification treatment can be performed. Since the fine crystals that have flowed out from the dephosphorization step 2 are held as a carrier in the denitrification tank in this way, the problem of water quality deterioration due to the outflow of fine crystals can be solved.

In this denitrification process, the above-mentioned ANAMMOX is used.
As shown in the reaction formula, nitrite nitrogen (NO ₂ −) is present in the water to be treated with respect to ammonia nitrogen (NH ₄ —N).
N) is preferably contained in a proportion of 0.5 to 2 times, particularly 1 to 1.5 times.

Therefore, in order to introduce the ammonia nitrogen and the nitrite nitrogen into the ANAMMOX denitrification tank in such a ratio, the following treatment can be carried out. In the nitration step 1, only part of the ammoniacal nitrogen in the raw water is nitriteized to obtain nitrite-treated water containing ammoniacal nitrogen and nitrite nitrogen in the above ratio.
In this case, there is a concern that ammonia nitrogen will flow into the dephosphorization step 2, but its concentration is reduced to about half that of ammonia nitrogen in the raw water, which is a big problem. There is no such thing. Raw water is divided into two systems, only one system is introduced into nitrite process 1 to oxidize ammoniacal nitrogen to nitrite nitrogen, and the other system bypasses nitrite process 1 to dephosphorization process 2. Introduce. In this case, similar to the above, there is a concern that ammonia nitrogen flows into the dephosphorization step 2, but this is not a major problem. In the nitrite-treating step 1, the whole amount of ammoniacal nitrogen in the raw water is nitrite-nitrated, and in the denitrifying step 3, a chemical such as ammonia is added as an ammonia source. Alternatively, a separate system of ammonia-containing wastewater is added. In this case, the problem caused by the inflow of ammoniacal nitrogen in the dephosphorization step 2 is solved.

In the method for treating raw water containing phosphorus and ammoniacal nitrogen according to claim 2, as shown in FIG. 1 (b), the raw water is sequentially treated in a nitrite nitration step 1, a denitrification step 3 and a dephosphorization step 2. To do.

That is, first, raw water is introduced into the aeration tank in which sludge of ammonia-oxidizing bacteria is retained in the same manner as in the method of claim 1, and the ammoniacal nitrogen in the raw water is converted to nitrite under aerobic conditions. Oxidizes to nitrogen.

In the nitrite-forming step 1, it is preferable to adjust the pH to pH 6.5 to 7.5 which is a preferable pH in the denitrifying step 3 which is the next step.

The treated water in the nitrite-nitrating step 1 is then supplied to the denitrifying step 3 to be denitrified by the ANAMMOX microorganism.

The treated water in the denitrification step 3 is then supplied to the dephosphorization step 2 to be dephosphorized. That is, as in the method of claim 1 described above, calcium chloride is added to the treated water in the denitrification step 3,
Add calcium salts such as calcium carbonate and calcium phosphate, and add alkali such as NaOH to adjust pH.
Adjust to 8.5 or more and pass water through the crystallization dephosphorizer.

In this dephosphorization step 2, since ammoniacal nitrogen in the raw water is highly removed by the preceding nitrite nitration step 1 and denitrification step 2, there arises a problem due to the inflow of ammoniacal nitrogen. And a highly pure crystal can be obtained.

Also in the method of claim 2, in the denitrification step, as shown in the above-mentioned ANAMMOX reaction formula, ammonia nitrogen (NH ₄ —N) is contained in the water to be treated.
On the other hand, nitrite nitrogen (NO ₂ —N) is 0.5 to 2 times,
In particular, it is preferable that the content is 1 to 1.5 times.

Therefore, in order to introduce the ammoniacal nitrogen and the nitrite nitrogen into the ANAMMOX denitrification tank in such a ratio, the following treatment can be carried out. In the nitration step 1, only part of the ammoniacal nitrogen in the raw water is nitriteized to obtain nitrite-treated water containing ammoniacal nitrogen and nitrite nitrogen in the above ratio. The raw water is divided into two systems, only one system is introduced into the nitrite conversion step 1 to oxidize ammoniacal nitrogen to nitrite nitrogen, and the other system bypasses the nitrite conversion step 1 and the denitrification step 3
To introduce. In the nitrite-treating step 1, all of the ammoniacal nitrogen in the raw water is nitrite-nitrated, and in the denitrifying step 3, a chemical such as sodium nitrite is added as a nitrite-nitrogen source. Alternatively, another system containing nitrite nitrogen-containing wastewater is added.

In any case, ammoniacal nitrogen hardly flows into the dephosphorization step, and the dephosphorization treatment can be stably performed to recover high-purity crystals.

[0050]

EXAMPLES The present invention will be described more specifically with reference to Comparative Examples and Examples below.

In the following, the anaerobic digestion desorption liquid discharged from the anaerobic digestion process of sewage sludge was centrifugally concentrated to give an ammoniacal nitrogen concentration of 2,800 mg-N / L,
The treatment was carried out using the supernatant liquid having a phosphorus concentration of 300 mg-P / L and pH 7.5 as raw water.

Comparative Example 1 (Ammonia Stripping → Crystalline Dephosphorization) 20 L / raw water was added to a 10 L ammonia stripping tank.
Water was passed at a rate of hr. NaOH was added so that the pH in the tank was 10.5, and air was aerated at a rate of 10 L / min. Since the pH in the tank gradually decreased due to CO ₂ contained in the air, a pump capable of additionally adding NaOH by a pH sensor was installed.

This treated solution was treated with a 10 L crystallization dephosphorization apparatus (2
(including 8 L of calcium phosphate having a diameter of mm), calcium chloride as a calcium source is 1000 mg-Ca /
L was added to give a concentration. In addition, Na as alkali
OH was added. However, when the same pH as that of the ammonia stripping tank was set to 10.5, the treated water became cloudy due to the formation of fine crystals. Therefore, inexpensive sulfuric acid was added to adjust the pH to 9
And phosphorus was crystallized.

On the 20th day after the start of operation, pH malfunction occurred in the ammonia stripping tank. The cause was that phosphorus and ammonia were crystallized on the surface of the pH electrode, and the compound, MAP, was deposited. Furthermore, blockage due to crystal precipitation occurred in the aeration device. The removal rate of ammonia by ammonia stripping was 95%, 2.5% was deposited as MAP in the tank, and the remaining 2.5% flowed into the crystallization dephosphorization device in the subsequent stage.

In the crystallization dephosphorization apparatus, sulfuric acid was added to p
When H was set to 9 and phosphorus was crystallized, a part of calcium was crystallized as calcium sulfate. When the breakdown of the crystallized calcium was analyzed, 70% by weight was calcium phosphate, 5% by weight was MAP, and 25% by weight was calcium sulfate, and it was not possible to obtain high-purity calcium phosphate.

Comparative Example 2 (Crystalline Dephosphorization → Ammonia Stripping) For the purpose of recovering phosphorus as MAP, magnesium chloride was added instead of calcium chloride in an amount of 1,000 mg-Mg / L, and the same crystallization removal as in Comparative Example 1 was performed. Phosphorus was removed by filling the phosphorus device with MAP particles and passing raw water through. Here, the pH was set to 8.6 in order to prevent the generation of the odor of ammonia. Then, NaOH was further added to the treated water of the crystallization dephosphorization apparatus to adjust the pH to 10.5, and ammonia was removed in the same ammonia stripping tank as in Comparative Example 1.

As a result, the concentration of phosphorus in the treated water in the crystallization dephosphorizer was 30 mg / L, and about 90% of phosphorus was removed by the crystallization dephosphorizer, but about 10% remained in the treated water. 15 mg / L of the phosphorus in the treated water was soluble, and the rest was present as fine MAP particles. When the pH was raised to 9, the phosphorus concentration in the treated water could be reduced to 20 mg / L. In this case, however, a strong ammonia odor was generated in the crystallization dephosphorization device due to its alkaline nature.

Example 1 (nitrite type nitrification → crystallization dephosphorization → A
Denitrification by NAMMOX Microbialization) Raw water was passed through a 10 L aeration tank containing activated sludge at a concentration of 3,000 mg / L at a rate of 10 L / hr to carry out nitrification operation. The aeration tank maintained the DO concentration at 0.2 to 2 mg / L and the water temperature at 25 to 35 ° C. The pH in the aeration tank was adjusted to 6.5 to 7.5 by adding NaOH. Nitrous nitrogen was detected in the treated water for one week after the start of operation, but thereafter, the activated sludge changed into particles (granule) with a diameter of about 1 mm, and nitrate nitrogen was no longer detected, All the ammoniacal nitrogen in the raw water was nitrified to nitrite nitrogen. The VSS / SS ratio of the granule was 0.6, and the inorganic substances were calcium, aluminum, iron and the like.

After adding calcium chloride as a calcium source to the treated water so as to have a concentration of 1,000 mg-Ca / L, NaOH was added as an alkali to adjust pH.
The crystallization dephosphorization apparatus was adjusted to 8.8 and the same crystallization dephosphorization apparatus as in Comparative Example 1 was used.
Water was passed through at 0 L / hr for dephosphorization treatment.

The phosphorus concentration of the treated water obtained by this dephosphorization treatment was 30 mg / L, and 90% of phosphorus could be removed. Of the phosphorus in the treated water, 20 mg / L was fine calcium phosphate crystals. Further, it was possible to recover high-purity calcium phosphate having a calcium phosphate content of 90% by weight.

Next, the treated water in the crystallization dephosphorization apparatus was treated with 10
Water was passed through a 20 L ANAMMOX denitrification tank at L / hr.
The denitrification tank holds granulated ANAMMOX sludge at a concentration of 10,000 mg / L as VSS. Since all the nitrogen in the treated water in the aeration tank for nitrite type nitrification in the previous stage was nitrite nitrogen, 2300 mg / L of ammonia as a chemical was added as ammoniacal nitrogen, and sulfuric acid was added to pH 6.5 to 7. Adjust to 5 and 35
Denitrification treatment was performed at ℃.

The denitrification treatment can be carried out extremely stably,
The ANAMMOX sludge gradually grew into granules using fine crystals in dephosphorized water as a carrier. The VSS / SS of this granule was 0.4, and the inorganic substance was mainly calcium.

The final treated water obtained from the denitrification tank is stable at ammoniacal nitrogen of 10 mg-N / L or less, phosphorus of 10 mg / L or less, and nitrite nitrogen of 50 mg-N / L or less, and is of extremely high water quality. I was able to get water.

Example 2 After nitrite type nitrification of raw water was carried out in the same manner as in Example 1,
In the same manner as in Example 1, denitrification treatment was performed in the ANAMMOX denitrification tank. In this example, by adjusting the dissolved oxygen concentration and pH when performing nitrite type nitrification, about 55% of the ammoniacal nitrogen in the raw water was converted to nitrite nitrogen, and ammoniacal nitrogen was used. And nitrite nitrogen 1: 1.2
The treated water contained in (weight ratio) is obtained, and the treated water is treated with ANAMM.
It was treated with OX denitrification. In addition, in this example, the activity of the ANAMMOX microorganism was reduced due to the inhibition of phosphorus, so that in order to obtain the same denitrification efficiency as in Example 1, it was necessary to increase the volume of the denitrification tank by 1.5 times to 30 L.

When calcium chloride was added to this denitrification-treated water and the pH was adjusted in the same manner as in Example 1, water was passed through the crystallization dephosphorization device for dephosphorization treatment. Highly pure calcium phosphate having a purity of 98% or more could be obtained by inflowing the denitrification-treated water completely removed.

The final treated water obtained from the crystallization dephosphorization device is 10 mg-N / L or less of ammonia nitrogen and 10% phosphorus.
mg / L or less and nitrite nitrogen of 50 mg-N / L or less were stable, and treated water of extremely high quality could be obtained.

[0067]

As described above in detail, according to the method for treating raw water containing phosphorus and ammoniacal nitrogen of the present invention, the raw water containing phosphorus and ammoniacal nitrogen is subjected to a dephosphorization step and a nitrite nitration step. It is possible to efficiently remove phosphorus and ammonia nitrogen by reducing the equipment cost and the operating cost when performing the treatment by the denitrification process.

The method for treating raw water containing phosphorus and ammoniacal nitrogen according to the present invention is a separation water obtained by solid-liquid separation of a digestion desorption liquid discharged from a process of anaerobic digesting organic sludge. It is suitable for treating such waste water containing phosphorus and ammoniacal nitrogen at high concentrations.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a method for treating raw water containing phosphorus and ammoniacal nitrogen according to the present invention.

[Explanation of symbols]

1 Nitrite process 2 Dephosphorization process 3 Denitrification process

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Rei Imajo             Kurita, 3-4-3 Nishi-Shinjuku, Shinjuku-ku, Tokyo             Industry Co., Ltd. F-term (reference) 4D038 AA08 AB45 AB48 BB19                 4D040 AA12 AA31 BB02 BB42 BB52                       BB82

Claims (3)

[Claims] 1. In a method for treating raw water containing phosphorus and ammoniacal nitrogen by a dephosphorization step, a nitrite nitration step, and a denitrification step, the raw water is first supplied to the nitrite nitration step to obtain raw water. After converting at least a portion of the ammoniacal nitrogen in the solution to nitrite nitrogen, it is supplied to the dephosphorization step to remove phosphorus, and then supplied to the denitrification step to remove ammoniacal nitrogen and nitrite nitrogen. A method for treating raw water containing phosphorus and ammonia nitrogen, which comprises reacting by denitrification by the action of a denitrifying microorganism using ammoniacal nitrogen as an electron donor and nitrite nitrogen as an electron acceptor. 2. A method of treating raw water containing phosphorus and ammoniacal nitrogen by a dephosphorization step, a nitrite nitration step, and a denitrification step, in which raw water is first supplied to the nitrite nitration step to obtain raw water. After converting at least a portion of the ammoniacal nitrogen in the nitrous acid to nitrite nitrogen, it is supplied to the denitrification process to remove the ammoniacal nitrogen and the nitrite nitrogen, and the ammoniacal nitrogen as the electron donor to convert the nitrite nitrogen into A method for treating raw water containing phosphorus and ammoniacal nitrogen, which comprises reacting by the action of a denitrifying microorganism serving as an electron acceptor to perform denitrification treatment, and then supplying it to a dephosphorization step to remove phosphorus. . 3. The raw water is separated water obtained by solid-liquid separation of a digestion desorption liquid discharged from a process of anaerobically digesting organic sludge, and the raw water is separated water. Method for processing raw water containing phosphorus and ammoniacal nitrogen.