JPH1080697A - Complete treatment of organic sewage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the need for a nitration stage needing a long time, to regenerate zeolite and to rationally dispose of a regenerated waste liq. by recycling the regenerated waste water from a zeolite regenerating stage to a biological dentrification part. SOLUTION: A slurry 3 discharged from a denitrification tank 2 is aerobically treated in an aeration tank 4, the treated slurry 6 is introduced into a settling tank 7 to settle and separate sludge, and the supernatant water 8 is sent to a first zeolite-packed tank 10 to remove ammonia. The water leaving the first zeolite-packed tank 10 is mostly drawn off as a treated water 13. A part of the treated water 13 is introduced into a second zeolite-packed tank 11 having adsorbed ammonia, air 12 is blown into the tank, hence the water is biologically treated to regenerate zeolite, and the discharged water is joined to raw water 1 as a biologically regnerated waste water 14. The two zeolite-packed tanks are prepared in this way, the raw water is introduced into the one zeolite-packed tank 10 while the other zeolite-packed tank 11 is biologically regenerated to adsorb and remove ammonia, and the process is alternately repeated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a treatment method for highly purifying organic sewage containing ammonia nitrogen, such as sewage, and more particularly to a method of removing ammonia nitrogen from the organic sewage which is significantly higher than the prior art. The present invention relates to a method for treating organic sewage that can be removed by a method.

[0002]

2. Description of the Related Art The most typical technique for treating organic sewage containing ammoniacal nitrogen, such as sewage, to remove the nitrogen is a nitrification liquid circulation type biological nitrification denitrification method. In this technology, organic sewage is first supplied to a biological denitrification section, where it is mixed with a nitrification solution circulated from a subsequent nitrification section to cause a denitrification reaction, and the denitrification liquid obtained there is converted to a nitrification section. To nitrify (oxidize) ammonia, circulate a part of the nitrification liquid to the above-mentioned denitrification part, supply the other part to the sedimentation tank, separate the settling activated sludge, and treat the supernatant liquid It is a method of obtaining a liquid. As an improved method of the nitrification denitrification method, a technique of increasing the nitrification rate by introducing a gel carrier having nitrifying bacteria immobilized in a nitrification section having a low reaction rate has recently been put to practical use. In the conventional method, when the sewage is treated, a nitrogen removal rate of about 80% is obtained, and the treatment is performed until almost no ammonia remains in the treated water, but about 10 mg / liter of nitrate nitrogen remains. There is a problem. Therefore, in this method, the nitrogen removal rate is 90%.
It was impossible in principle to do the above, and it was extremely insufficient to prevent eutrophication of the discharge water area.

Further, there is a disadvantage that the amount of water circulating the nitrification solution to the denitrification section is enormous (three times or more the amount of raw water), and the power required to drive the circulation pump is large. Also,
As a method for chemically removing ammonia from organic sewage, a selective ion exchange adsorption method using zeolite is known, and after treating sewage with a normal activated sludge method in which biological nitrification denitrification is not performed, zeolite is used. In the past, methods for adsorbing and removing ammonia have been studied in the past, but because of the use of aqueous sodium chloride as a regenerating chemical for ammonia-adsorbed zeolites, a large amount of regenerated effluent containing sodium chloride and ammonia at high levels Occurred and this disposal was also extremely difficult. Therefore, there was no example in which this method was put to practical use.

[0004] From such a technical background, the present inventor:
A new technology combining a biological nitrification denitrification method and a zeolite adsorption method has been presented (JP-A-8-52494).
With this method, the nitrogen removal rate is as high as about 95%,
This is an excellent method in which the total nitrogen content of the treated water is as low as about 2 mg. However, even with this method, there is a problem in disposal of the zeolite regenerated effluent, and a regenerated effluent containing high-concentration sodium chloride and ammonia is generated, and thus cannot be rationally disposed. In addition, the nitrification step that requires a long time and the nitrification liquid circulation step that requires a large amount of power required by the pump could not be omitted.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems associated with a treatment method combining a biological nitrification denitrification method and a zeolite adsorption method. It is an object of the present invention to provide a novel treatment method which can eliminate the need for a step and can regenerate zeolite and rationally dispose of a regenerated effluent.

[0006]

In order to solve the above-mentioned problems, the present inventor has set forth the causes and problems of the problems associated with the above-described treatment method combining the biological nitrification denitrification method and the zeolite adsorption method. As a result of examining the combination of steps, it was found that the above problem can be solved by changing the process configuration of the activated sludge process and integrating the selective ion exchange method and the regeneration method using zeolite in a novel manner. That is, the present invention has solved the above-mentioned problems by the following means. (1) Organic wastewater containing ammoniacal nitrogen is supplied to a biological denitrification unit to denitrify, and then subjected to aerobic biological treatment, and the biologically treated water is supplied to a zeolite packed bed to adsorb and remove ammonia. Wastewater treatment process (A) to obtain treated water
While supplying water to the ammonia-adsorbed zeolite layer, aerating with oxygen-containing gas from the lower part of the layer, nitrifying bacteria adsorbed on zeolite by nitrifying bacteria fixed to the zeolite, and desorbing from zeolite to regenerate zeolite An adsorbent regeneration step (B) for causing the regeneration wastewater to flow out, and a circulation step (C) for supplying the regeneration wastewater from the regeneration step (B) to the biological denitrification unit. Advanced treatment of sewage.

The term "zeolite" used in the present invention is a general term for zeolite minerals such as zeolite, model knight, clinoptilite and synthetic zeolite. Since the conventional biological nitrification denitrification method has a basic design concept of not leaving ammonia in the treated water, the denitrification section is introduced first, then the denitrification section is introduced into the nitrification section, and the It is essential that the effluent slurry be guided to a sedimentation tank to obtain treated water containing residual nitrogen in the form of nitrate nitrogen. The same applies to the case where nitrification and denitrification are performed in two stages.

On the other hand, according to the present invention, an anaerobic denitrification section is provided in the former stage of the activated sludge aeration tank except for a step of nitrification section, and nitrate nitrogen in biologically regenerated water of zeolite described later is converted to organic. It denitrifies using the organic carbon source of sewage. Next, a small amount of residual BOD in the effluent of the biological denitrification tank flows into an aerobic biological treatment, for example, an activated sludge treatment tank, and the BOD is removed. In this activated sludge treatment step, it is not necessary to cause nitrification, and it is only necessary to remove the BOD. This is because when nitrate nitrogen is generated, it is not adsorbed by the zeolite adsorption tower in the subsequent stage and enters the treated water.

Next, the slurry discharged from the activated sludge treatment tank is guided to a solid-liquid separation tank (such as a sedimentation tank), and treated water in which ammonia is intentionally left is supplied to a granular zeolite packed tank, and ammonia is selectively ionized. It is removed by exchange adsorption to obtain treated water from which ammonia has been highly removed. When the raw water flow rate to zeolite is applied to sewage treatment, SV3 to 30
(1 / H), preferably SV 4 to 8 (1 / H). If the operation is continued in this manner, the amount of adsorbed ammonia on the zeolite is saturated. At this point, the flow of water is stopped, and the granular zeolite is regenerated. As a result of studying various methods as a regeneration method, it was found that the granular zeolite can be effectively biologically regenerated by performing the following method.

That is, the flow of the raw water (flow over the sedimentation basin) is stopped, and a part of the treated water of the zeolite filling tank is passed through the zeolite filling tank 11 having a zeolite layer as shown in FIG. Is preferable), and an oxygen-containing gas (any of air, oxygen, and oxygen-enriched air) is aerated from the lower part of the zeolite packed tower 11. As a result, nitrifying bacteria naturally grow on the surface of the zeolite and are immobilized. Ammonia adsorbed on zeolite by the nitrifying bacteria is oxidized to nitrate nitrogen by the following reaction. NH ₄ ⁺ + 2O ₂ → NO ₃ ⁻ + 2H ⁺ + H ₂ 0 (1) Further, it was estimated that the following reaction occurred simultaneously. NH ₄ ⁺ + NO ₃ ⁻ → N ₂ + 2H ₂ 0 (2) Since the generated nitrate nitrogen and nitrogen gas do not have adsorbability to zeolite, they are separated from zeolite and migrate to the liquid side to regenerate zeolite. You. The regenerated wastewater containing nitrate nitrogen is supplied to the biological denitrification section, and the organic carbon source (BOD) in the raw water is biologically reduced to nitrogen as an organic carbon source for denitrifying bacteria and denitrified. Nitrogen.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, an embodiment of the present invention will be described. Raw water 1 is introduced into a denitrification tank 2 to carry out a denitrification reaction.
The slurry is put into a sedimentation tank 7 for sludge sedimentation separation, and the supernatant water 8 is sent to a first zeolite filling tank 10 to remove ammonia. Most of the water flowing out of the first zeolite filling tank 10 is taken out as treated water 13. Most of the sludge 9 from the settling tank 7 is returned to the denitrification tank 2 as returned sludge 15.
And the remaining sludge is discharged out of the system as surplus sludge 16. The second that has already used the process to adsorb ammonia
A part of the treated water 13 is introduced into the zeolite filling tank 11,
The zeolite is regenerated by blowing air 12 and performing biological treatment. The water discharged from the tank 11 is biological regeneration wastewater 14
And merge with the raw water 1.

As shown in FIG. 1, two zeolite-filled tanks each having a zeolite-filled layer are prepared, and raw water is passed through another zeolite-filled tank 10 during biological regeneration of one zeolite-filled tank 11. It is better to adsorb and remove ammonia. The following method can be recommended in order to promote the attachment of nitrifying bacteria to zeolite and make the biological regeneration proceed smoothly from the start-up. That is,
When oxygen-containing gas is supplied from the lower part of the zeolite packed bed while supplying raw water to the zeolite packed bed at the beginning of operation and aeration is performed, nitrifying bacteria are immobilized on the zeolite surface at a high concentration after a lapse of a required time. When the aeration was stopped and the raw water passed through in this state, it was recognized that the ammonia was adsorbed on the zeolite, and that the nitrification reaction proceeded promptly during the biological regeneration of the zeolite.

According to an experiment conducted by the present inventor, the time required for zeolite biological regeneration varies depending on the amount of ammonia adsorbed on the zeolite, and the longer the amount of ammonia adsorbed on the zeolite at the start of regeneration, the longer the regeneration time is naturally. However, it was recognized that sufficient regeneration was possible in about 12 to 24 hours when the amount of adsorbed ammonia was 5 to 10 mg N / g zeolite. As another embodiment of the present invention other than the above, the following method can be adopted. A method for improving the BOD removal rate and the denitrification rate by coexisting a microorganism-adhering carrier such as a granular gel in the activated sludge treatment step or the denitrification section. An anaerobic tank is added before the denitrification tank in the biological treatment step, and raw water and returned sludge are supplied to the anaerobic tank, and then flow into the denitrification section in FIG. 1 to generate biological dephosphorization. A method of adding an inorganic coagulant to a biological treatment tank to coagulate and remove phosphorus.

[0014]

The present invention will be described below in detail with reference to examples. However, the present invention is not limited to only these examples. Example 1 A verification test of the method of the present invention was performed on sewage having an average water quality shown in Table 1 in accordance with the processing steps shown in FIG.
The granular zeolite is a natural granular zeolite produced in Yamagata Prefecture (average particle size of 2
3 mm). Table 2 shows the test conditions.

[0015]

[Table 1]

[0016]

[Table 2]

As a result of the experiment, the water quality of the effluent of the zeolite tank after the treatment was in a steady state was as shown in Table 3 in which nitrogen was highly removed and the TN was 2 mg / liter or less. Water was obtained stably.

[0018]

[Table 3]

[0019]

The present invention has the following effects. (1) Combine biological denitrification technology with selective ion exchange reaction with zeolite in a novel manner, and regenerate particulate zeolite by a novel biological regeneration method, and dispose of regenerated wastewater in a biological denitrification section. As a result, very small amounts of ammonia nitrogen and nitrate nitrogen remain in the treated water, and a high nitrogen removal rate can be stably obtained. (2) The nitrification process, which has a slow reaction rate, is not required, and the nitrification solution is not required to be circulated to the denitrification section. Therefore, the required volume of the biological treatment tank is small, the construction cost is low, and the circulating pump power is unnecessary. Therefore, energy can be saved. (3) Since the filtration of SS can be performed simultaneously in the zeolite filling tank, there is an effect of two birds per stone. (4) Since zeolite is biologically regenerated, a zeolite regenerating chemical is unnecessary. Also, disposal of the regenerated effluent can be biologically easily performed.

[Brief description of the drawings]

FIG. 1 is a process chart showing one embodiment of an advanced treatment method for organic wastewater of the present invention.

[Explanation of symbols]

 Reference Signs List 1 raw water 2 denitrification tank 3 outflow slurry 4 aeration tank 5 air 6 slurry 7 settling tank 8 supernatant water 9 sludge 10 first zeolite filling tank 11 second zeolite filling tank 12 air 13 treated water 14 biological regeneration wastewater 15 return sludge 16 surplus Sludge

Claims (1)

[Claims] Claims 1. An organic wastewater containing ammonia nitrogen is supplied to a biological denitrification unit to denitrify, and then subjected to aerobic biological treatment, and the biologically treated water is supplied to a zeolite packed bed to remove ammonia. A sewage treatment step (A) in which treated water is obtained by adsorption and removal, while supplying water to the ammonia-adsorbed zeolite layer, aerating with oxygen-containing gas from the lower part of the layer, and converting the zeolite into zeolite by nitrifying bacteria fixed to the zeolite. An adsorbent regeneration step (B) in which the adsorbed ammonia is nitrified and desorbed from the zeolite to regenerate the zeolite and drain the regeneration wastewater, and the regeneration wastewater from the regeneration step (B) is supplied to the biological denitrification unit Advanced treatment method for organic sewage, comprising a circulating step (C).