JP2001162277A - Method for removing ammoniacal nitrogen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reuse a regenerated waste liquid by facilitating the treatment of the concentration of halogen ions present in the regenerated waste liquid after treatment in using a bromide solution as a regeneration agent of an ion exchanger to treat the regenerated waste liquid with ozone in the presence of bromide ions. SOLUTION: A first process for adsorbing ammoniacal nitrogen in waste water by an ion exchanger, a second process for desorbing anmoniacal nitrogen adsorbed on the ion exchanger by a bromide solution and third process for removing ammoniacal nitrogen from the regenerated waste liquid obtained in the second process by ozone are provided. The concentration of anmoniacal nitrogen contained in the regenerated waste liquid is measured before the third process and the supply amount of ozone bringing the final concentration of anmoniacal nitrogen to a range of 1-20 mg/L calculated from the supply amount of already supplied ozone and the concentration of anmoniacal nitrogen during the supply of ozone in the third process to supply ozone.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for removing ammoniacal nitrogen contained in wastewater of a factory or the like by an ion exchanger, and more particularly to a method for removing ammonia from the ion exchanger after removing the wastewater by a regenerant. The present invention relates to a method for efficiently and safely treating a regenerated effluent obtained by desorbing reactive nitrogen.

[0002]

2. Description of the Related Art As a method for removing ammonia nitrogen contained in wastewater from factories and the like, nitrification and denitrification treatment by living organisms is generally used, but it is not suitable for treatment of high-concentration wastewater.
Since the processing time is long, there is a problem that the equipment scale becomes large.

[0003] On the other hand, an ion exchange method using an ion exchanger of an ion exchange resin or zeolite is a method applicable to the treatment of high-concentration wastewater. In the ion exchange method,
Ammonia nitrogen is adsorbed on the ion exchanger as described above. Then, the ion exchanger is brought into contact with a sodium chloride solution or a mixed solution obtained by adding sodium hydroxide to a sodium chloride solution, that is, a regenerant,
The ion exchanger is regenerated by desorbing the ammoniacal nitrogen adsorbed on the ion exchanger. At this time, processing of the high-concentration regenerated effluent generated becomes a problem. Examples of a method for treating a high-concentration regenerated effluent include an ammonia stripping method, a discontinuous point chlorination method, a catalytic oxidation method, and a bromine-ozone oxidation method.

The ammonia stripping method is a method in which ammonia is released into the atmosphere by aeration under alkaline conditions. However, the cost of chemicals for adjusting the pH is high, and as a post-treatment, treatment of the released ammonia is carried out. Need.

[0005] The discontinuous point chlorination method is a method in which ammonium ions are treated as chlorine gas by reaction with chlorine, but requires about 10 times as much chlorine as ammoniacal nitrogen, and further requires post-treatment of residual chlorine. It is.

[0006] The catalytic oxidation method is a method for decomposing and removing ammonia at high temperature and pressure and in the presence of an oxidizing agent. However, special equipment is required, and a high concentration of halogen is present in the regenerated effluent. Therefore, it is necessary to take measures against corrosive gas generated by the reaction.

The bromine-ozone oxidation method is a method of treating ammonia by reacting it with ozone in the presence of bromine ions. However, since it is necessary to add bromine ions to the regenerated effluent, the regenerated effluent after treatment is treated. The concentration of halogen ions therein increases, and its treatment becomes a problem.

[0008]

SUMMARY OF THE INVENTION The present invention provides a method for removing ammoniacal nitrogen from wastewater, wherein a bromide salt solution is used as a regenerant for the ion exchanger, and the regenerated effluent is treated with ozone in the presence of bromine ions. It is an object of the present invention to facilitate the treatment of the concentration of halogen ions present in the regenerated effluent after the treatment and to make it reusable.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have reached the present invention.

That is, the method of the present invention for removing ammonia nitrogen from waste water comprises a first step of adsorbing ammonia nitrogen in waste water to an ion exchanger, and a step of removing ammonia nitrogen adsorbed to the ion exchanger by a bromide salt. It comprises a second step of desorbing with a solution and a third step of removing ammoniacal nitrogen with ozone from the regenerated effluent obtained in the second step.

Before the third step, the concentration of ammonia nitrogen contained in the regenerated effluent is measured, and during the supply of ozone in the third step, the ozone supply amount already supplied and the ammonia nitrogen concentration are used. The ozone supply is performed by calculating the ozone supply amount so that the final ammonia nitrogen concentration is in the range of 1 to 20 mg / liter.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the method of the present invention will be described below.

The method of the present invention for removing ammoniacal nitrogen from wastewater comprises the following three steps.

In the first step, ammoniacal nitrogen-containing waste water is brought into contact with the ion exchanger, whereby ammonia-nitrogen is selectively adsorbed on the ion exchanger by the ion exchange action of the ion exchanger and removed from the wastewater. Is done.

When an ion exchange resin is used as the ion exchanger, a strongly acidic cation exchange resin in the form of Na or a weakly acidic resin can be used. When zeolite is used, mordenite or mordenite exhibiting remarkable selectivity to ammonium ions can be used. Clinoptilolite is recommended. Examples of the shape of the ion exchanger include powder, pellet, bead, and honeycomb.

In the second step, after removing the waste water, the ammonia nitrogen adsorbed on the ion exchanger is regenerated by a regenerating agent,
That is, the ion exchanger is regenerated by desorption with a bromide salt solution. By using a bromide salt solution as a regenerating agent, it is not necessary to newly add bromine ions in ozone treatment of the regenerated effluent in the subsequent stage. As the bromide salt solution, a sodium bromide solution or a potassium bromide solution can be used. As a regeneration method, a cocurrent type, a countercurrent type, and a continuous type can be applied.

In the third step, the regenerated effluent obtained in the second step is brought into contact with ozone in the presence of bromine ions,
The ammonia nitrogen in the regenerated effluent is removed as nitrogen gas. Ozone produces the secondary oxidant hypobromous acid in the presence of bromine ions. When the hypobromite reacts with ammonia, an inorganic nitrogen generation reaction occurs, and the ammonia nitrogen is converted into nitrogen gas and removed.

When the ammonia nitrogen in the regenerated effluent is completely decomposed, bromate ions and bromine gas are generated, and the bromine ion in the regenerated effluent is reduced. Then, the supply of ozone is stopped, and the third step is terminated.

Most of the substances that react with ozone in the regenerated effluent are bromide ions and ammonia nitrogen, so the rate of reduction of ammonia nitrogen can be assumed to be a pseudo zero-order reaction. Therefore, by measuring the ammonia nitrogen concentration in the regenerated effluent before the treatment with ozone and the ammonia nitrogen concentration in the regenerated effluent during the treatment, the ammonia nitrogen in the regenerated effluent can be reduced to a desired level. It is possible to accurately estimate the processing time at which the density is reached. As described above, the concentration of ammonia nitrogen at the time of stopping the supply of ozone is preferably 1 to 20 mg / liter in consideration of the error between the estimated value and the actually measured value.

As for the method of measuring the concentration of ammonia nitrogen, it can be easily measured by using a diaphragm type ammonium ion electrode.

Before the third step, the concentration of ammonia nitrogen contained in the regenerated effluent is measured, and during the supply of ozone, the final ammonia ammonia concentration is determined from the ozone supply amount and the ammonia nitrogen concentration already supplied. Nitrogen concentration 1-20m
Calculate the ozone supply amount within the range of g / liter,
Supply ozone.

The contact method between the ozone and the regenerated effluent is as follows.
A turbo mixing system, an air diffuser system, and the like can be given.
In the turbo mixing method, pressurized mixing is performed using a vortex pump.

The pH during the reaction is preferably from 5 to 7. When the pH is less than 5 or more than 7, a large amount of by-product nitrate ion is generated.

As the weight ratio of bromide ion / ammonium nitrogen is higher, the rate of reduction of ammonia nitrogen is higher and the generation of nitrate ion as a by-product can be suppressed, but the weight ratio may be 1 or more. Normally, since the weight ratio of bromine ion / ammonium nitrogen is 1 or more in the regenerated effluent, it is not necessary to newly add bromine ion.

Most of the components in the regenerated effluent are alkali metal ions such as ammonium nitrogen and sodium and bromine ions, and do not contain organic substances. Therefore, even if the regenerated effluent is treated with the ozonized gas, almost no organic bromine compound is generated. Further, components in the regenerated effluent after ozone treatment are alkali metal ions such as sodium, bromide ions, hypobromous acid, and the like. Hypobromous acid is
Since it returns to bromine ions, it can be reused as a regenerating agent.

[0026]

EXAMPLES The method of the present invention will be described below in detail, but the present invention is not limited thereto.

Example 1 First Step About 50 mm of synthetic mordenite zeolite (hereinafter referred to as zeolite) of about 1 mm was placed in a cylindrical column having an inner diameter of 30 mm.
Drainage filled with ml and containing ammonia nitrogen at 500 mg / l was passed through the column from the top at a SV (space movement speed) of 3 h ^-1 . Up to 8 hours later, the concentration of ammoniacal nitrogen in the treated wastewater was below 10 mg / l.

Water was passed until the concentration of ammoniacal nitrogen in the treated water increased to 13 mg / liter, that is, until a saturated state was recognized. Thereafter, the wastewater was completely removed.

Second step A 0.2N sodium bromide solution adjusted to pH 11 with a sodium hydroxide solution was passed through the zeolite from the top of the column at SV 8h ^-1.
A regenerated effluent with a concentration of mg / l was obtained. The weight ratio of bromine ion / ammoniacal nitrogen in the regenerated effluent was about 10.

Third step : While controlling the pH of the regenerated effluent to 6 to 7, an ozonized gas having an ozone concentration of 100 g / Nm ³ was supplied to the regenerated effluent using an vortex pump, and the ozone injection rate was 184 mg (ozone). Per liter and allowed to react.

FIG. 1 shows the change with time of the ammonia nitrogen concentration at that time. The ammonia nitrogen concentration shown in FIG. 1 was measured by an ion electrode method.

As shown in FIG. 1, the concentration of ammoniacal nitrogen is
Since it decreases linearly, it is possible to predict the concentration of ammoniacal nitrogen after treatment.

The concentration of ammonia nitrogen 276 minutes after the start of the supply of ozone gas was calculated according to FIG.
In contrast to 2.3 mg / liter, the measured value was 1
It is 2.8 mg / liter, which indicates that the change in the ammonia nitrogen concentration can be sufficiently estimated by this method.

Table 1 shows the concentration of nitrate nitrogen and the residual ratio of bromine ions. The nitrate nitrogen concentration and the bromine ion residual ratio shown in Table 1 were measured by an ion chromatography method.

(Comparative Example 1) When the regenerated effluent obtained in the second step of Example 1 is reacted with ozone as a third step, p
Processing was performed in the same manner as in Example 1 except that H was controlled to 4.

276 from the start of the ozone gas supply in the third step
Minutes, the residual concentration of ammonia nitrogen in the treated water is 1
It was 2.4 mg / liter. Table 1 shows the nitrate nitrogen concentration and the bromine ion residual ratio.

The residual concentration of ammoniacal nitrogen was determined in Example 1.
As in the above, it can be seen that the concentration of nitrate nitrogen is high.

(Comparative Example 2) When the regenerated effluent obtained in the second step of Example 1 is reacted with ozone as a third step, p
Processing was performed in the same manner as in Example 1 except that H was controlled to 8.

276 from the start of the supply of ozone gas in the third step
Minutes, the residual concentration of ammonia nitrogen in the treated water is 1
2.2 mg / liter. Table 1 shows the nitrate nitrogen concentration and the bromine ion residual ratio.

The residual concentration of ammoniacal nitrogen was determined in Example 1.
As in the above, it can be seen that the concentration of nitrate nitrogen is high.

Comparative Example 3 The same procedure as in Example 1 was carried out except that the residual concentration of ammoniacal nitrogen was reduced to substantially zero when the regenerated effluent obtained in the second step of Example 1 was reacted with ozone as the third step. The treatment was performed in the same manner as in Example 1.

278 from the start of the ozone gas supply in the third step
Minutes, the residual concentration of ammoniacal nitrogen in the treated water is 0.1%.
It was 1 mg / liter or less. Table 1 shows the nitrate nitrogen concentration and the bromine ion residual ratio. The bromine ion residual ratio was significantly reduced.

[0043]

[Table 1]

In Example 1, unlike Comparative Examples 1 to 3, it is possible to treat ammoniacal nitrogen as nitrogen gas with almost no generation of nitrate nitrogen, and bromine ions are hardly reduced. It can be seen that the liquid can be reused.

[0045]

According to the method of the present invention, the recycled effluent can be reused, so that it is economical. In addition, organic halogen compounds and bromine which are formed by the bromine ion-ozone method and are problematic are problematic. Secondary pollution due to acid ions and the like can be prevented, and ammonia nitrogen can be removed from wastewater from factories and the like.

[Brief description of the drawings]

FIG. 1 shows the change over time in the concentration of ammoniacal nitrogen.

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Claims (2)

[Claims] 1. A method comprising: a first step of adsorbing ammonia nitrogen in wastewater to an ion exchanger; a second step of desorbing ammonia ion adsorbed by the ion exchanger with a bromide salt solution; and a second step. A third step of removing ammoniacal nitrogen from the recycled wastewater by ozone. 2. Before the third step, the concentration of ammonia nitrogen contained in the regenerated effluent is measured, and during the supply of ozone in the third step, the ozone supply amount and the ammonia nitrogen concentration already supplied are measured. The ozone supply is performed by calculating the amount of ozone supplied so that the final ammonia nitrogen concentration is in the range of 1 to 20 mg / liter, and the ammonia nitrogen is removed from the wastewater according to claim 1, how to.