JPS5855838B2 - Method for removing ammonia nitrogen from wastewater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention deals with the treatment of ammonia nitrogen (hereinafter referred to as NH3-
NH) removal method using zeolite.
NH3-N from wastewater equipped with an adsorption unit suitable for adsorption and removal of 3-N and a zeolite separation and recovery device.
Regarding the removal method.

The activated sludge method and activated carbon adsorption method, which are the mainstream treatment methods for industrial wastewater and domestic sewage, can remove organic matter from sewage and make it clear, but NH3-N in sewage cannot be removed and is released as is. Ru.

However, this NH3-N serves as a nitrogen supply source for algae, which promotes eutrophication of wastewater and disrupts the balance of biological growth, causing what is called red tide, resulting in mass die-off of fish, and rivers, rivers, etc. In lakes and marshes, it is a source of foul odors.

For this reason, NH3-N in wastewater has attracted the attention of society as a pollution problem, and the release of NH3-H is being regulated by law, and there is a strong desire to establish a technology for removing NH3-N as soon as possible.

Various methods such as asmonia stripping, biological treatment, chemical treatment, and adsorption methods have been attempted to remove NH3-H from wastewater, but each method has its own advantages and disadvantages, and there is still no definitive method. Not developed.

Natural zeolites such as clinoptilolite, mordenite, and chabasite, as well as synthetic zeolites produced by crystallizing raw materials that serve as silica and alumina sources, are used to produce NH.
NH3-N by treating sewage and wastewater containing NH3-N
It is a simple and excellent method to adsorb and remove wastewater from wastewater.

Zeolite is a crystalline hydrated aluminosilicate with a three-dimensional structure consisting of tetrahedrons of Sin and AlO4.
The lack of charge caused by O4 is compensated by alkali metal or alkaline earth metal ions.

Since these cations are exchangeable, zeolite has cation exchange ability and is used to selectively remove cations from water.

Among these zeolites, those called clinoptilolite and mordenite selectively adsorb and remove ammonium ions (hereinafter referred to as NH4+).

For this reason, inexpensive natural zeolites (clinoptilolite, mordenite, etc.) are often used to remove NH3-H from wastewater using zeolites.

When using zeolite to remove NH3-N from wastewater, it is desirable from an economic standpoint to adopt a cycle system in which adsorption operations and regeneration operations of the zeolite that has adsorbed NH3-N are repeated.

Therefore, granular zeolite (particle size of several mm) is packed into a packed tower similar to that used in water purification equipment and water softening equipment that use ion exchange resins, which have been carried out industrially in the past, and the liquid to be treated is passed through it. After -N is adsorbed and removed, aqueous solutions of alkali metal and alkaline earth metal hydroxides, carbonates, chlorides, etc. NH3-N
A regeneration method is being used to recover the NH3-N adsorption ability of zeolite by desorbing it.

However, in the packed column type NH3-N removal method described above, N
Because the adsorption speed of H4+ to zeolite is slow, NH4+ may leak from the tip of the packed column, and Na+, K+,
When cations such as Ca+2 coexist, the adsorption capacity for NH and L+ decreases.In addition, in the zeolite regeneration method that passes a solution such as alkali metal hydroxide, it takes a long time for regeneration, and NH3 The discharge of highly contaminated recycled wastewater containing -N is unavoidable.

On the other hand, 50% of zeolite adsorbed NH3-N
The thermal regeneration method, in which ammonia gas (NH3) is desorbed by heating to 0 to 600°C, does not require the discharge of recycled waste liquid (it is an excellent regeneration method).

However, in a method in which granular zeolite is packed into a packed column, the zeolite must be taken out from the packed column and regenerated in a heating furnace during regeneration, and it is a difficult task to extract a large amount of zeolite from the packed column in actual equipment. At the same time, powdering of the granular zeolite occurs.

Furthermore, it is very difficult to transport granular zeolite containing a large amount of water to a heating regeneration furnace.

The purpose of the present invention is to increase the rate of adsorption of NH3-H onto zeolite.

The present invention is a method for adsorbing and removing ammonia nitrogen from waste water by bringing the waste water containing ammonia nitrogen into contact with zeolite, and the method includes the following means (a) to (d): (a) installed vertically; Using a fluidized bed adsorption tower, in the absence of activated sludge and under non-aerated conditions, sewage was first introduced from the bottom of the tower, and the sewage was separated by 100 m from the bottom of the tower.
Ammonia nitrogen is adsorbed by contacting powdered zeolite with a particle size that passes through the esh under stirring to adsorb ammonia nitrogen, and then raising the column and maintaining contact between wastewater and powdered zeolite at the top of the column without stirring. a fluidized bed adsorption means configured to continue adsorbing nitrogen, (b) sending the wastewater and zeolite that have been subjected to the fluidized bed adsorption to a fixed bed adsorption chamber equipped with a swamp material, where the zeolite is absorbed by the swamp material; (c) means for separating, recovering and regenerating the flocculated zeolite from the treated water; and (d) means for regenerating the regenerated zeolite from the fluidized water. It is characterized by comprising means for circulating supply again to the bed adsorption means.

The present inventors focused on and studied the adsorption rate of NH3-N to zeolite, and as a result, they confirmed through experiments that the adsorption rate is greatly influenced by the particle size of the zeolite and the contact state between the wastewater and the zeolite.

That is, it was confirmed that the adsorption rate increases as the particle size of the zeolite becomes smaller and as the wastewater is stirred.

Furthermore, the present inventors obtained the following new knowledge, and thereby completed the present invention.

That is, the adsorption phenomenon of NH3-N to 1-olide in fluidized bed adsorption is a process from the liquid to the zeolite surface,
The process is roughly divided into the exchange adsorption process between NH3-h and Na'', Ka, etc. on the zeolite surface. Of these, the former process is effective in shortening the adsorption time by stirring the wastewater, but the latter process is almost impossible. Therefore, it was confirmed that stirring was only necessary at the initial stage of adsorption.

For example, if wastewater is introduced from the tangential direction of the circumference into the lower part of a fluidized bed adsorption tower with a relatively small diameter, a turbulent flow is created and stirred, and then it is raised and taken out from the upper part of the tower. In this case, stirring and ensuring residence time in the upper part of the column can be performed in one column.

In this way, it is only necessary to stir at the initial stage of adsorption, that is, at the bottom of the fluidized bed adsorption tower. There is no need to provide it in the device.

Moreover, an increase in energy consumption due to the addition or enlargement of the stirring device is not caused.

The particle size of the powdered zeolite is preferably 100 mesh or less.

Reference examples, conventional examples, and examples of the present invention are shown below.

FIG. 1 is a graph showing the relationship between elapsed time (processing time) and NH4+H4 ratio in Reference Examples 1 to 3 and Experimental Example 1.2 below.

Conventional example 1 Natural zeolite (clinoptilolite, cation exchange capacity 160 meq/100?) in a packed column with an inner diameter of 20φ
8~20mesh (0.84~2.38mm)90
? Filled bed height 30 cIrL), NH,, ll-
Sewage containing 30pp (NH4Cl dissolved in distilled water) was heated at a superficial velocity (LV) of 10 m/h and a space velocity (Sv1
When I flushed it at 32h', it was 0,8-1 from the beginning of water flow.
ppm of NH4+' leaked, and breakthrough of NH4+ was observed when the treated water amount/zeolite amount (CV) was around 150.

Conventional Example 2 Natural zeolite of Conventional Example 1 in a packed column with an inner diameter of 20φ) 32
~60mesh (0.25~0.5mm) 90?
Packed bed height 30 crfL) NH4+30
When wastewater (NH4Cl dissolved in distilled water) containing N ppm was flowed at a superficial velocity of Ion/h and a space velocity of 3211-1, 0.7 to 0.9 ppm of N was detected from the initial stage of water flow.
H4-+- leaked and the amount of treated water/zeolite amount was 150
Breakthrough of NH4+ was observed.

Conventional Example 3 Natural zeolite 60~ of Conventional Example 1 is packed in a packed column with an inner diameter of 20φ.
100mesh (0.149~0.25mm) 90?
Filled bed height 30cm) NH4+30ppm
(NH4Cl dissolved in distilled water)
When flowing at a superficial velocity of 10 m/h and a space velocity of 32 h, 0.4 to 0.5 ppm of NH,I
+ leaked and N from the 150th position of treated water amount/zeolite amount
Breakthrough of H4+ was observed.

The smaller the particle size of the zeolite is than the conventional examples 1 to 3 above, the
The NH4+ concentration in the zeolite is lower, and the rate of adsorption of NH4+ into the zeolite is clearly faster.

If the zeolite particle size is further reduced (io.mesh
(below) The effect is expected to be significant.

However, in the packed column adsorption system, the zeolite particle size and column pressure loss are inversely proportional, and the smaller the particle size, the greater the column pressure loss.

For this reason, the zeolite particle size in the packed column type adsorption system is practically about 20 mesh at most.

Under the treatment conditions of Conventional Examples 1 to 3 using zeolite having a particle size of 2° mesh, about 1 pl)m of NH4+ leaks, which is not preferable.

To avoid this, it is necessary to reduce the superficial velocity and space velocity, that is, to reduce the throughput of the adsorption tower.

Conventional Example 4 Natural zeolite 8 to 2 of Conventional Example 1 was placed in a packed column with an inner diameter of 2oφ.
0mesh (0.84~2.38mm)90? Filled bed height 30CrIl), NH4+30 ppm
, Na+6.0 1 Ca+7.3ppm 1
When sewage (NH4Cl dissolved in tap water) containing 100 pm 2.5 ppm of Mg and 0.09 ppm of Fe was flowed at a superficial velocity of 10 n/h and a space velocity of 32 h-', from the initial stage of water flow, 1. .5 to 1.8 ppm of NH4+ leaked, and breakthrough of NH4+ was observed from the treated water amount/zeolite level of 70.

Conventional Example 5 Natural zeolite 32~ of Conventional Example 1 was placed in a packed tower with an inner diameter of 20φ.
60mesh (0.25~0.5mm) 90? Filled bed height 30cIfL), NH4+30ppm
10 Na 6. Oppm, Ca + 7.3 ppm, Mg 1,111 2,5 ppm, Fe 0.09 ppm
When sewage containing NH4Cl (NH4Cl dissolved in tap water) was flowed at a superficial velocity of 10 m/h and a space velocity of 32 h-', 1.0 to 1.2 ppm of NH,l was detected from the beginning of water flow.
+ leaks and NH4 from the treated water amount/zeolite 80th position
+ breakthrough was observed.

Conventional Example 6 Natural zeolite of Conventional Example 1 6 o in a packed tower with an inner diameter of 20φ
~i 00mesh (0,149~0.25mm)
90S' packed bed height 30cIrL), NH,l
+30ppm, Na”6.0, Ca+7
．． 3 ppm, 99m Mg ” 2.5 ppm, Fe +0.09 p
Sewage containing pm (NH4Cl dissolved in tap water)
When the water was flowed at a superficial velocity of 10 m/h and a space velocity of 32 h-', 0.6 to 0.8 ppm of NH was detected from the beginning of water flow.
4+ leaked, treated water amount/zeolite) N from 110th position
Breakthrough of H,+ was observed.

From the above conventional examples 4 to 6, Na+ other than NH and I+ is present in the wastewater.
It can be seen that when such cations coexist, the NH4+ adsorption capacity of zeolite decreases significantly and the leakage NH4+ concentration also increases.

However, these adverse effects are alleviated by reducing the particle size of the zeolite used.

This is because the smaller the particle size of zeolite, the faster the adsorption rate of NH4+, which reduces the influence of coexisting cations, and N
It is considered that the leak NH4+ concentration is also reduced without causing a significant decrease in the H4+ adsorption capacity.

Reference example 1 Natural zeolite of conventional example 1 8 to 20 mesh (0.84
~2.38mm) 5? Wastewater containing NH4+50ppm (NH4Cl dissolved in distilled water) 5001r
When the zeolite was poured into Ll and stirred at 200 rpm, the zeolite was found to be sedimented without floating.

When the relationship between the elapsed time and the NH4+ removal rate was determined, the NH,l+ removal rate gradually improved as the elapsed time increased.

Reference example 2 Natural zeolite of conventional example 1 8 to 20 mesh (0.84
~2.38mm) 5? Wastewater containing NH4 + 50 ppm (NH4Cl dissolved in distilled water) 500
ml and stirred at 600 rpm, some of the zeolite floated.

The relationship between elapsed time and NH4+ removal rate was found to be 20m.
The NH4+ removal rate became constant after about 1 yr.

Reference Example 3 Natural zeolite of Conventional Example 1) 60 to 100 mesh (0,
149~0.25mm) 5 L? NH4+ 50p
Wastewater containing pm (NH4Cl dissolved in distilled water)
When the mixture was poured into 500 ml and stirred at 600 rpm, about half of the zeolite was suspended.

The relationship between elapsed time and NH4+ removal rate was found to be 15m.
The NH, I+ removal rate became constant at about m.

Conventional Example 7 The same natural zeolite (100me
sh passing) 52, NH4+50ppm, COD 10
0 ppm (glucose), activated sludge 2000 ppm
After pouring into 500ml of wastewater containing
5 ppm, No. 73 ppm.

In Conventional Example 7, since contact is made with microorganisms under aerobic conditions, the nitrification reaction of NH and l+ proceeds in parallel with the oxidation of COD components, and NO3- is produced.

NO3- cannot be removed by zeolite, which is a cation exchanger, and remains in the treated water.

Therefore, the removal of nitrogen components in this example involves only a small amount of NH, l+ partially remaining adsorbed on the zeolite, and the removal rate is as low as about 36%.

Experimental example 1 Natural zeolite of conventional example 1) 100 mesh or less (0,
Under 149maLl, 5g of powdered zeolite) was added to NH4+5
When the zeolite was poured into 500 ml of waste water containing 0 ppm (NH4C1 dissolved in distilled water) and stirred at 20 rpm, about half of the zeolite was suspended.

The relationship between elapsed time and NH4+ removal rate was found to be 8m1.
The NH4+ removal rate became constant at about n.

Experimental Example 2 Natural zeolite of Conventional Example 1) 100 mesh or less (0,1
49mm or less, powdered zeolite) 51 with NH-50p
When the zeolite was poured into 5007711 wastewater (distilled water containing NH4C1) containing 5007711 pm and stirred at 600 rpm, most of the zeolite was suspended.

The relationship between elapsed time and NH4+ removal rate was found to be 4m1.
The NH4+ removal rate became constant at about yr.

From the above Reference Examples 1 to 3 and Experimental Example 1.2, N to zeolite
It can be seen that the adsorption rate of H4+ is greatly influenced by the particle size of the zeolite as well as the state of contact between the zeolite and NH4+.

This is considered to be due to the fact that the NH4+ adsorption capacity of the zeolite itself is about 1%, and the number of NH, I+ adsorption points per culm of the COD adsorption capacity of activated carbon is very small.

Reference example 4 Natural zeolite of conventional example 1 8 to 20 mesh (0.84
~2.38 mm) 59 was poured into 500 ml of water, filtered through a filter with a hole diameter of 10 μm, and when the zeolite was peeled off from the top of the filter and poured into the water again, the shape on the filter immediately collapsed.

Reference example 5 Natural zeolite of conventional example 1 60 to 100 mesh (0
, 149-0.25 mm) was poured into water at 500 mA, filtered through a filter with a hole diameter of 10 μm, the zeolite was peeled off from the top of the filter, and the shape immediately collapsed on the Kokoro filter when it was put back into the water.

Experimental example 3 Natural zeolite of conventional example 1) 100 mesh or less (0
, 149 mm or less, 5 g of powdered zeolite) in 500 m of water
After pouring it into water, the zeolite was filtered through a filter with a hole diameter of 10μ, and the zeolite was peeled off from the top of the filter in the form of flakes.When this material was poured into water again, it maintained its shape on the filter for several minutes, then gradually disintegrated. did.

From Reference Example 4.5 and Experimental Example 3 above, it can be seen that zeolite with a small particle size agglomerated using P material maintains its shape in water for a short time and is easily separated from water. .

This is because zeolite with a small particle size is agglomerated under pressure using a baffle material, which causes adhesion between the zeodyte particles and solidifies them.

The above Experimental Example 3 is an example showing that powdered zeolite having a thread diameter of 100 mesh is suitable in the present invention.

Example FIG. 2 is a flowchart showing a specific embodiment of the present invention.

Sewage 1 and 150-2 containing NH, l+30 ppm
Powdered zeolite 3 (the amount of zeolite relative to wastewater is 2% by volume) of 50 mesh was introduced into a fluidized bed adsorption tower 4 using a pump 2 and subjected to adsorption treatment for 1 minute.

The waste water is introduced from the tangential direction of the outer circumference at the bottom of the adsorption tower 4, forms a vortex, and comes into contact with the powdered zeolite while producing a stirring effect, and gradually rises and maintains sufficient contact with the powdered zeolite in a non-stirring state. To quickly adsorb NH4+ in wastewater onto zeolite.

Here, the vortex of the rising wastewater stops at the upper part of the adsorption tower 4 and becomes a mere upward flow, and is substantially in a non-agitation state.

Only the contact residence time is ensured.

Powdered zeolite that has adsorbed NH4+ in wastewater is transferred to separation column 5.
It is separated from water.

That is, the powdered zeolite becomes a zeolite fixed layer 7 on the p-material 6 and is separated.

The zeolite was fed into the separation column in such an amount that the thickness of the fixed bed was 1 and the filtration surface was In''.

A small amount of powdered zeolite that could not be completely separated in the separation column 5 is filtered through the p-passing column 8 that exits the separation column 5, and is discharged as treated water 9 that does not contain NH and I+.

After separating the predetermined zeolite, the separation tower 5 stops introducing wastewater, and then applies a timely back pressure to the slough material 6 to peel off the zeolite fixed layer on the surface of the material 1 into flakes 10, which are then peeled off at the bottom of the separation tower 5. It is separated and recovered as zeolite 11.

The exfoliated zeolite taken out from the separation column 5 is regenerated by a regenerator 12 using a known regeneration method and used again.

According to this example, powdered zeolite with a small particle size is used, and the zeolite and wastewater can sufficiently contact each other, so that the influence of coexisting ions such as Na and the like in the wastewater is small. Since a fixed layer adsorption portion is formed, leakage of low concentration Nf (J) is also prevented.

In fact, NH in treated water when treated up to CV150,
1+ amount is 0. It was lppm.

Furthermore, due to the particle size distribution of the powdered zeolite, the powdered zeolite itself acts as a p-material on the surface of the t-material (so-called self-precor)? Since filtration is carried out, the pressure drop in the separation column is as small as 1 ky/c7A at most.

The zeolite can be easily taken out from the separation tower since it maintains its flake-like shape at the time of separation, and since the zeolite taken out from the separation tower is a powder, it can be easily transported to the regenerator in the form of a slurry.

In the present invention, continuous operation is possible by providing a plurality of separation columns.

Furthermore, since the NH3-N adsorbed zeolite can be easily separated from water, a thermal regeneration method that does not require waste liquid treatment can be easily applied as a regeneration method.

As described above, according to the present invention, the rate of adsorption of NH3-N to zeolite can be increased.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the adsorption rate of NH4+, and FIG. 2 is a schematic diagram illustrating details of the present invention. 1... Sewage, 3... Powdered zeolite,
4... Fluidized bed adsorption tower, 5... Separation tower,
6... Swash material, 7... Zeolite fixed bed, 8... Swarf tower, 9... Treated water, 12
・・・・・・Playback device.

Claims (1)

[Scope of Claims] 1. A method for removing ammonia nitrogen from waste water by contacting waste water containing ammonia nitrogen with zeolite, the method comprising the following means (a) to (d): (a) installed vertically; Using a fluidized bed adsorption tower, in the absence of activated sludge and under non-aerated conditions, sewage was first introduced from the bottom of the tower, and powdered zeolite with a particle size that would pass through the sewage and 100 mesh was mixed at the bottom of the tower. A fluid flow system that adsorbs ammonia nitrogen by contacting it under stirring, then raises the inside of the column, and maintains contact between wastewater and powdered zeolite at the top of the column without stirring to continue adsorbing ammonia nitrogen. bed adsorption means, (b) sending the sewage and zeolite that have undergone the fluidized bed adsorption to a fixed bed adsorption chamber equipped with a bed material, where the zeolite is aggregated by the P material to form a fixed adsorption bed; (C) means for separating, recovering and regenerating the flocculated zeolite from the treated water; and (d) means for circulating and supplying the regenerated zeolite to the fluidized bed adsorption means. A method for removing ammonia nitrogen from wastewater, characterized by comprising: