JP2002263688A - Method and device for treating organic polluted water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for treating organic polluted water including a new biological regeneration method using zeolite. SOLUTION: The treatment includes the following steps A, B and C. In the step A, organic discharged water containing ammonia nitrogen and the regenerated discharged water from a zeolite packed layer are supplied to a biological denitrification part to be denitrified and then subjected to solid liquid separation. The separated water is supplied to a granular zeolite packed layer to adsorb and remove ammonia. In the step B, the zeolite adsorbing ammonia is biologically regenerated by nitrifying bacteria deposited on the granular zeolite and the regenerated discharged water is supplied to the biological denitrification part. In the step C, a part of the sludge in the above biological treatment process is drained, treated with an alkali and subjected to solid liquid separation. The separated liquid is supplied to the zeolite layer during the biological regeneration of the zeolite.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a technology for highly purifying ammonia-containing wastewater such as sewage, and more particularly to a novel technology capable of removing nitrogen at a significantly higher removal rate than conventional technologies.

[0002]

2. Description of the Related Art The most typical technique for removing ammonia nitrogen contained in sewage such as sewage is a nitrification liquid circulation type biological nitrification denitrification method. This technology supplies organic wastewater to a biological denitrification unit, supplies the denitrification solution to a nitrification unit to nitrify ammonia, circulates a part of the nitrification solution to the denitrification unit, and Is supplied to a sedimentation tank to separate activated sludge, thereby obtaining treated water. In addition, a technique of introducing a gel carrier on which nitrifying bacteria are immobilized into a nitrification unit has recently been put to practical use. This method has a problem that when the sewage is treated, a nitrogen removal rate of about 80% is obtained, and almost no ammonia remains in the treated water, but about 10 mg / liter of nitrifying nitrogen remains. Therefore, in this method, it was theoretically impossible to make the nitrogen removal rate 90% or more, and it was extremely insufficient to prevent eutrophication of the discharge water area. Further, since the nitrification rate is low, a large-volume nitrification tank is required, and furthermore, the power of a circulation pump for circulating a large-capacity nitrification liquid to the denitrification tank needs to be large.

[0003] As a method for chemically removing ammonia, a selective ion exchange adsorption method using zeolite is known, and sewage is treated by an ordinary activated sludge method without biological nitrification and denitrification, and then treated with zeolite. A method of adsorbing and removing ammonia has been studied in the past, but the ammonia adsorption capacity of zeolite is very small, requiring frequent regeneration, and a large amount of wastewater containing sodium chloride and ammonia in high concentration is generated. However, disposal of this waste liquid is also extremely difficult, and there have been no practical applications due to these circumstances. From such a technical background, the present inventor has previously disclosed a novel technique combining a biological nitrification denitrification method and a zeolite adsorption method in JP-A-8-52494. But,
The technology disclosed in the publication also has some difficulties in the disposal of the zeolite regenerated waste liquid, and a regenerated waste liquid containing high-concentration sodium chloride and ammonia is generated. .

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the technical drawbacks described in Japanese Patent Application Laid-Open No. Hei 8-52494, filed earlier by the present inventor. The present invention provides a method and an apparatus for treating organic sewage, including a novel method for regenerating a biological zeolite.

[0005]

Means for Solving the Problems The present inventor has changed the process configuration of the biological denitrification method for organic wastewater containing ammoniacal nitrogen and has developed a selective ion exchange method and a regeneration method using zeolite. It has been found that the above-mentioned problems can be achieved by integrating in an appropriate manner. That is, the present invention has the following configurations.

(1) Organic wastewater containing ammoniacal nitrogen and zeolite-packed bed reclaimed wastewater are supplied to a biological denitrification unit to denitrify and then solid-liquid separated, and the separated water is added to a granular zeolite packed bed. A step A of supplying and adsorbing and removing ammonia, a step B of biologically regenerating the ammonia-adsorbed zeolite by nitrifying bacteria attached to the granular zeolite, and supplying the regenerated wastewater to the biological denitrification unit; And a step C of drawing out a part of the sludge in the biological treatment step, subjecting the sludge to alkali treatment, and then performing solid-liquid separation, and supplying the separated liquid to a zeolite layer during the biological regeneration of the zeolite. Processing method.

(2) A biological denitrification tank for denitrifying the organic wastewater containing ammonia nitrogen and the regenerated wastewater of the zeolite packed bed, and a solid-liquid slurry discharged from the biological denitrification tank Means for separating, a granular zeolite packed bed for adsorbing and removing ammonia in the separated water after the solid-liquid separation, a means for alkali-treating a part of the separated sludge after the solid-liquid separation, A means for solid-liquid separation of the alkali-treated sludge, and a solid-liquid separation of the alkali-treated sludge in a granular zeolite packed layer obtained by adhering nitrifying bacteria to the granular zeolite for biologically regenerating the ammonia-adsorbed zeolite. And a means for supplying an alkali separation liquid, which is a liquid component after the separation.

In the present invention, "zeolite" refers to a zeolite-based mineral such as zeolite, mordenite, clinoptilite and synthetic zeolite. In addition, those having a selective ion exchange ability with respect to ammonia may be used for convenience. It is generically called zeolite.

[0009]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a system diagram of the treatment method of the present invention, in which an organic wastewater 1 containing ammonia such as sewage (hereinafter abbreviated as organic wastewater 1) is removed from a biological denitrification tank 2 (hereinafter, a denitrification tank). 2). This denitrification tank 2
Then, nitrate nitrogen in the zeolite biological regeneration waste liquid 17 described below is reduced to nitrogen gas using BOD in the organic wastewater 1. The slurry 2a discharged from the denitrification tank 2 is introduced into the settling tank 4, and most of the settled sludge 7 is removed from the denitrification tank 2.
Will be returned to In addition, after the denitrification tank 2, an aeration tank 3 of a short residence time for removing residual BOD may be provided. The effluent 4a of the settling tank 4 is supplied to the zeolite filling tank 5,
Ammonia is adsorbed and removed. At this time, SS is also removed by filtration, and clear treated water 6 is obtained.

The sludge 8, which becomes a part of the sludge flowing out of the settling tank 4, is hydrolyzed by adding an alkali agent 9, for example, sodium hydroxide, and performing an alkali treatment 10, thereby improving the bioassimilation. . Thereafter, solid-liquid separation treatment 11
Then, an alkali separation liquid 13 is obtained. Separation liquid 13
Is supplied to the zeolite layer 14 during zeolite biological regeneration, and is used as an alkali component for maintaining nitrification activity.
Since the alkali-treated sludge 12 is biodegraded when returned to the denitrification tank 2, an effect of reducing the amount of surplus sludge is produced. In addition, B eluted from sludge by alkali treatment
Since OD serves as a hydrogen donor for denitrifying bacteria, BOD for denitrification does not become insufficient.

When the operation of the zeolite packed bed 5 is continued, the amount of adsorbed ammonia on the zeolite is saturated. At this point, the flow of water is stopped, and biological regeneration of the granular zeolite is performed.
Two zeolite-packed layers 5 are prepared, and during the biological regeneration of zeolite, the effluent 4a of the sedimentation tank 4 is passed through the other zeolite-packed layer to adsorb and remove ammonia. That is, the flow of the overflow of the sedimentation basin is stopped, and the regeneration water 15 which is a part of the treatment water 6 of the zeolite packed bed 5 and the alkali separation liquid 1 in the phosphorus recovery step (solid-liquid separation treatment 11)
3 through the zeolite layer (during biological regeneration) 14
2 is preferable), while oxygen-containing gas, for example, air 16 is aerated from the lower part of the zeolite packed layer 14. As a result, the ammonia adsorbed on the zeolite by the nitrifying bacteria attached to the surface of the zeolite is oxidized to nitrate nitrogen by the following reaction (1).

[0012]

Embedded image

This reaction produces a large amount of hydrogen ions. If the hydrogen ions are not neutralized, the pH of the zeolite layer is reduced, the activity of nitrifying bacteria is reduced, and the regeneration effect is greatly reduced. Therefore, conventionally, it was necessary to add an alkali agent. On the other hand, in the present invention, since the alkali separation liquid 13 generated for reducing excess sludge is used, an alkali agent for biological regeneration of the zeolite layer 14 can be eliminated. Since the generated nitrate nitrogen has no adsorptivity to zeolite, it is desorbed from zeolite and migrates to the liquid side to regenerate zeolite. The nitrate nitrogen in the zeolite biological regeneration waste liquid 17 is supplied to the denitrification tank 2 and reduced to nitrogen gas by the denitrification bacteria to be removed.

The following method is recommended in order to promote the attachment of nitrifying bacteria to zeolite and to allow the biological regeneration to proceed immediately and smoothly from the start of the treatment. That is,
When the air 16 is aerated as oxygen-containing gas from the lower part of the zeolite packed bed (during biological regeneration) 14 while passing the ammonia-containing sewage 1 at the beginning of the operation, the nitric acid bacterium has a high concentration on the zeolite surface after a required time. Fixed to
If aeration is stopped after this state is reached, the ammonia is adsorbed on the zeolite, and the nitrification reaction proceeds promptly during the biological regeneration of the zeolite. The time required for biological regeneration of the zeolite layer (during biological regeneration) 14 varies depending on the amount of ammonia adsorbed on the zeolite, and the greater the amount of ammonia adsorbed on the zeolite at the time of starting regeneration, naturally the longer the regeneration time becomes. Adsorption amount is 5
In the case of 10 mgN / g-zeolite, the alkaline separation solution of the present invention is supplied to prevent a decrease in pH, and when aerated, it becomes 8%.
It was recognized that sufficient reproduction was possible in about 12 hours. As another embodiment of the present invention, a method of improving the denitrification rate by coexisting a microorganism-adhering carrier such as a granular gel in the denitrification part of the biological treatment step may be applied.

[0015]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples. Example 1 A proof test of the present invention was performed on sewage having an average water quality shown in Table 1 according to the process shown in FIG. As the granular zeolite, a natural granular zeolite (average particle size of 2 to 3 mm) produced by Yamagata Prefecture, which is a product of Zikulite Industry Co., Ltd. was used. Table 2 shows the test conditions.

[0016]

[Table 1]

[0017]

[Table 2]

As a result of the test, the average water quality of the treated water 6 of the zeolite layer after the treatment became in a steady state was as shown in Table 3 where nitrogen was highly removed and the TN concentration was 1 mg /
Liters were obtained stably.

[0019]

[Table 3]

[0020]

Since the present invention is configured as described above, it has the following effects. 1. The biological denitrification technology and the selective ion exchange reaction with zeolite were regenerated by a new biological regeneration method, and the reclaimed wastewater was disposed of in the biological denitrification section. Only a very small amount of nitrate nitrogen remains, and a high nitrogen removal rate can be stably obtained. 2. Since zeolite can be biologically regenerated, a zeolite regenerating agent (such as saline) is not required.
Therefore, disposal of the reclaimed waste liquid is also simplified.

3. The waste liquid from the sludge alkali treatment step can be used as a large amount of alkali required for maintaining the nitrification activity during zeolite biological regeneration. 4. Since SS filtration can be performed simultaneously with the zeolite packed bed,
No other filtration layer is required, such as a sand filtration layer. 5. In the conventional biological nitrification and denitrification process, a large-volume nitrification tank is not required, and a pump for circulating a large amount of nitrification liquid is not required. 6. Since sludge is subjected to biological treatment after alkali treatment, the amount of excess sludge generated is reduced.

[Brief description of the drawings]

FIG. 1 is a process chart showing a method for treating organic wastewater of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Organic wastewater containing ammonia nitrogen 2 Biological denitrification tank 2a Outflow slurry 3 Aeration tank 4 Sedimentation tank 4a Outflow water 5 Zeolite filling tank 6 Treated water 7 Returned sludge 8 Sludge 9 Alkali agent 10 Alkali treatment 11 Solid-liquid separation Treatment 12 Alkali treated sludge 13 Alkali separation liquid 14 Zeolite layer (during biological regeneration) 15 Part of zeolite packed bed treated water 16 Air 17 Zeolite biological regeneration waste liquid

Continued on the front page F-term (reference) 4D003 AA01 AB11 BA02 CA03 CA07 CA08 EA01 EA14 EA24 FA03 FA04 FA06 FA07 4D024 AA04 AB13 BA07 BB01 CA01 CA05 DA08 DB12 DB15 DB16 4D028 BD16 BE04 BE08 4D040 BB05 BB42 BB57 AB024D0

Claims (2)

[Claims] 1. An organic wastewater containing ammoniacal nitrogen and a regenerated wastewater of a zeolite packed bed are supplied to a biological denitrification section to be denitrified and then subjected to solid-liquid separation, and the separated water is supplied to a granular zeolite packed bed. A to adsorb and remove ammonia
The ammonia-adsorbed zeolite is biologically regenerated by nitrifying bacteria attached to the granular zeolite, and the reclaimed wastewater is supplied to the biological denitrification step B, and part of the sludge of the biological treatment step is performed. A method for treating organic sewage, comprising a step C of drawing out and subjecting to alkali treatment, followed by solid-liquid separation, and supplying the separated liquid to a zeolite layer at the time of biological regeneration of the zeolite. 2. A biological denitrification tank for denitrifying an organic wastewater containing ammoniacal nitrogen and a regenerated wastewater of a zeolite packed bed, and a solid-liquid separation of a slurry discharged from the biological denitrification tank. A granular zeolite packed bed for adsorbing and removing ammonia in the separated water after the solid-liquid separation; a means for alkali-treating a part of the separated sludge after the solid-liquid separation; A means for solid-liquid separation of the treated sludge, and a granular zeolite packed layer obtained by attaching nitrifying bacteria to the granular zeolite for biologically regenerating the ammonia-adsorbed zeolite, the alkali-treated sludge was solid-liquid separated. A means for supplying an alkali separation liquid, which is a later liquid component.