JPH06285493A - Fixed bed denitrification method - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] Like the wet catalytic oxidation treated water of human waste, TOC
In the fixed-bed denitrification method for raw water whose concentration changes greatly, it is possible to stably and efficiently obtain treated water of high water quality by reliably controlling the amount of organic substances added. [Structure] Oxidation and reduction of the treated water treated in the denitrification tank when the raw water containing NOx and BOD components is passed through the denitrification tank 3 in which the fixed bed 3A of denitrifying bacteria is formed to perform the denitrification treatment. The potential or sulfur ion concentration is measured, and the organic matter is added to the raw water based on the measured value, while the NO flowing into the denitrification tank is measured.
The x concentration and the organic matter concentration are measured, and the theoretical concentration of the organic matter necessary for denitrifying all NOx flowing into the denitrification tank is calculated based on the measured values, and the theoretical concentration and the measured value of the organic matter are calculated. In comparison, when the measured organic matter value is lower than the theoretical concentration, at least a part of the organic matter amount corresponding to the difference between the two is added to the raw water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixed bed denitrification method, and more particularly to a nitrate denitrification tank in which a fixed bed of denitrifying bacteria is formed, and / or nitrate nitrogen (nitrate ion) and / or nitrite nitrogen (nitrite). (Nitrate ion) and BOD components are added to the raw water after adding an organic substance as a hydrogen donor to the raw water for denitrification by passing water through the organic carbon / nitrogen The present invention relates to a method of stably and efficiently obtaining treated water of high water quality by adjusting the (C / N) ratio to an optimum range.

[0002]

2. Description of the Related Art A wet catalytic oxidation treatment method is known as a treatment method for waste liquid containing ammonia and organic substances such as human waste. When the liquid waste containing such ammonia and organic matter is subjected to wet catalytic oxidation treatment, treated water containing low concentrations of nitrate nitrogen, nitrite nitrogen and organic carbon is obtained depending on the treatment conditions. Therefore, nitrate nitrogen (hereinafter referred to as "NO ₃ -N") such as treated water of this catalytic wet oxidation treatment is used.
Is abbreviated. ) And / or nitrite nitrogen (hereinafter “NO ₂
And abbreviated as -N ", NO ₃ -N, the NO ₂ -N" NOx "
Collectively. ) And water containing organic carbon are further treated by biological denitrification. In this case, NOx in raw water,
When the BOD concentration changes, the C / N ratio changes, and stable treatment cannot be performed. Therefore, in order to adjust the C / N ratio, an organic substance such as methanol is added to the raw water as a hydrogen donor, but the addition amount should be the minimum amount necessary to maintain the treated water quality high. is important.

It has been known that the floating denitrification method is related to the oxidation-reduction potential (hereinafter referred to as "ORP") and NOx. A method of controlling the addition amount of organic substances has been proposed (Japanese Patent Publication Nos. 63-22877 and 64-684).
No. 0).

In the fixed bed denitrification method, the O
A method has been proposed in which the amount of organic substance added is controlled based on the measured value of RP (Japanese Patent Application No. 2-306622).

Further, as an alternative method to the ORP measurement control method, a method of measuring the sulfur ion (S ²⁻ ion) concentration of denitrification-treated water and controlling the amount of organic substances added based on the measured value is also proposed. (Japanese Patent Application No. 4-241864).

By the way, the wet catalytic oxidation treated water of human waste is
Usually, the TOC concentration varies with time in a very wide range from 10 mg / l, the following to several hundred mg / l. In the denitrification treatment using such wet catalytic oxidation treated water as raw water, the ORP and S ²⁻ ion concentration of the denitrification treated water are measured,
Addition of organic matter to denitrification raw water based on this measurement value ON-O
In the method of controlling the FF operation, the addition control of the organic substances cannot sufficiently follow the change in the TOC concentration of the raw water, and the C / N ratio cannot be adjusted to the optimum value. That is, TO of denitrification raw water
The variation range of the C concentration is reflected in the variation range of the TOC of the denitrification treated water, and the TOC concentration of the denitrification treated water also greatly varies. For such a large variation range, the addition ON-O
Sufficient adjustment cannot be made with FF operation. In particular, when the TOC is extremely high, it is difficult to measure the ORP accurately. For this reason, there is a drawback in that the optimum C / N ratio cannot be reliably maintained and high-quality treated water cannot be stably obtained.

The present invention solves the above-mentioned conventional problems, and in a method of fixed bed denitrification treatment of raw water whose TOC concentration varies greatly, such as wet catalytic oxidation treated water of night sewage, the amount of organic matter added is ensured. It is an object of the present invention to provide a fixed bed denitrification method capable of stably and efficiently obtaining treated water of high water quality by controlling the above.

[0008]

The fixed bed type denitrifying method of the present invention comprises a denitrification tank in which a fixed bed of denitrifying bacteria is formed.
A method for denitrification by passing raw water containing BOD and BOD components, wherein the oxidation-reduction potential or sulfur ion concentration of the treated water treated in the denitrification tank is measured, and the raw water is added based on the measured value. In the fixed bed denitrification method of adding organic matter, the NOx concentration and the organic matter concentration of the inflow water of the denitrification tank are measured, and it is necessary to denitrify all the NOx flowing into the denitrification tank based on the measured values. The theoretical concentration of the organic substance is calculated, the theoretical concentration is compared with the measured value of the organic substance, and when the measured value of the organic substance is lower than the theoretical concentration, at least part of the amount of the organic substance corresponding to the difference between the two is added to the raw water. It is characterized by doing.

[0009]

In the fixed bed denitrification method of the present invention, the ORP or S ²⁻ ion concentration of the treated water treated in the denitrification tank is measured, and the organic matter is added to the raw water based on the measured value (hereinafter, This addition control is referred to as "addition control I".) On the other hand, the NOx concentration and the organic matter concentration of the denitrification tank inflow water are measured, and all the NOs flowing into the denitrification tank are measured based on the measured values.
The theoretical concentration of the organic substance required to denitrify x is calculated, and the theoretical concentration is compared with the measured value of the organic substance, and when the measured value of the organic substance is lower than the theoretical concentration, the amount of the organic substance corresponding to the difference between At least a portion is added to raw water (hereinafter, this addition control is referred to as "addition control II"). In this way, the addition of the organic matter is controlled by the addition control I by the measured value of the ORP or S ²⁻ ion concentration of the denitrification treated water and the difference between the measured value of the organic matter with respect to the theoretical concentration of the organic matter necessary for the denitrification of NOx in the raw water. The C / N ratio in the denitrification process can be adjusted to an optimum value by performing two types of control in combination with the basic addition control II.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to the drawings.

FIG. 1 is a system diagram showing a method of an embodiment of the fixed bed denitrification method of the present invention.

In FIG. 1, 1 is a raw water tank, 2 is an organic matter (methanol) storage tank, 3 is a fixed bed type biological denitrification tower, 4 is a nitric acid waste liquid storage tank, 6 is an ORP meter, 7 is a pH meter, and 8 is a TOC.
A total of 10 is a controller, and P _{1 to} P ₄ are pumps.

In the method of this embodiment, the raw water is pipe 11,
It is introduced into the biological denitrification tower 3 through a raw water tank 1 and a pipe 12 provided with a pump P _3, and the denitrification treated water is discharged from the pipe 13 to the outside of the system.

The raw water tank 1 is constructed such that the methanol in the methanol storage tank 2 is injected from a pipe 14 having a pump P ₁ and intermittently from a pipe 15 having a pump P ₂ .

An extraction pipe 16 is connected to the upper part of the fixed bed 3A of the biological denitrification tower 3, the ORP meter 6 measures the ORP of the denitrification treated water, and the measured water is stored in the raw water tank 1. It is configured to be returned. The pump P ₂ for intermittent injection of methanol is provided so as to be turned on and off via the controller 10 based on the measured value of the ORP meter 6. The pH meter 7 is for controlling the pH of the inflow water of the tower 3 so that the pH during the ORP measurement is constant, and is provided in the branch pipe 17 connected to the pipe 12, and the biological denitrification tower. The water used for measuring the pH of the inflow water of No. 3 is returned to the raw water tank 1.

The TOC of the raw water is measured by the TOC meter 8 provided in the pipe 11. And the above pH
The NOx measurement value measured by the total 7 and the TOC measurement value measured by the TOC meter 8 are input to the controller 10, and the theoretical concentration of organic matter required for denitrification is determined from the NOx measurement value. Theoretical concentration of organic matter> Organic matter measurement In case of value, theoretical concentration of organic matter −
At least part of the measured organic matter, preferably 70-95
The operation of the pump P ₁ is controlled by the controller 10 so that methanol corresponding to 100%, more preferably 75 to 90%, is added to the raw water tank 1 through the pipe 14.

In the method of this embodiment, the nitric acid waste liquid storage tank 4 is provided, and the amount of organic substances in the raw water is remarkably large and the amount of NOx is insufficient, so that a large amount of organic substances can remain in the denitrification-treated water. Controller 10
An operation signal of the pump P ₄ is output from the pump P ₄ , and a nitric acid waste liquid (a nitrogen supply source such as) is added to the raw water tank 1 through the pipe 18 to adjust the C / N ratio of the denitrifying raw water to an appropriate value, It is configured to reduce the organic matter concentration of the nitrification-treated water.

According to the method shown in FIG. 1, since the injection of methanol is carried out by the addition control I by the pump P ₂ and the addition control II by the pump P ₁ , the measured value of the organic matter is remarkably higher than the theoretical concentration of the organic matter. When it is low, the addition amount II compensates most of the deficiency amount to bring the amount of organic matter in the denitrification raw water close to the optimum value, and the addition amount is finely adjusted by intermittent injection according to the addition control I. , C / N ratio can be adjusted to an optimum value. When the measured value of the organic substance is higher than the theoretical concentration of the organic substance, the injection of the methanol by the addition control II is not performed, only the methanol injection control by the addition control I alone is performed, and the nitric acid waste liquid is injected as necessary.

In addition control, for example, when the theoretical concentration of the organic substance is higher than the measured value of the organic substance, the difference is calculated,
It is mentioned that the operation of the pump is controlled so that a preset ratio of methanol is injected with respect to the obtained difference. In this case, the preset ratio is preferably 70 to 95%, particularly preferably 75 to 90%, as described above. Even if this ratio is too small or too large, the addition control I and the addition control II according to the present invention are The effect of improving the C / N ratio adjustment cannot be obtained by the combined use of.

On the other hand, the addition control I operates the pump P ₂ when the measured value of the ORP meter 6 exceeds the first set value (O
N), and when it falls below the second set value, the pump P ₂ can be stopped (OFF). In this example, the amount of organic matter in the raw water was measured by the TOC meter 8
The amount of organic matter in the raw water is determined by UV in addition to the TOC meter.
It can also be determined by detection or the like. When measuring the TOC of raw water with a TOC meter, the organic matter (BOD) of the raw water is
It can be easily obtained from the TOC measurement value by a calculation formula determined for each raw water. Similarly, the theoretical concentration of organic substances can be calculated from the measured NOx values by a calculation formula defined for each raw water.

Further, in this embodiment, the addition control I is set to ORP.
The addition control I is performed based on the measured values of 6 in total, and H ₂ S
Based on measurements of S ^2- ion concentration by the sensor or the like, the pump P ₂ is turned OFF when the S ^2- ion denitrified water exceeds the first set value, lower than the second set value In that case, the pump P ₂ can be turned on.

In the present invention, addition control I of an organic substance such as methanol can be performed by ON / OFF operation of the injection pump or by increasing / decreasing the injection amount. Further, the addition control II is preferably performed by using ON / OFF operation of the injection pump and increase / decrease control of the injection amount in combination.

The present invention will be described in more detail with reference to specific examples.

Example 1 According to the method shown in FIG. 1, denitrification treatment was carried out by using wet catalytic oxidation treated water of human waste as raw water. Table 1 shows changes in the water quality of raw water and the amount of denitrification treatment.

In such a treatment, as organic matter, 5
A 0% aqueous methanol solution was injected at the rate shown in Table 1. The nitric acid waste liquid was not injected.

Regarding the raw water of this example, the relationship of BOD = 1.9 × TOC-15 is established, and the amount of organic matter required for denitrification is BOD.
It can be calculated by BOD = NO ₃ −N × 2.7 (mg / l) (for NO ₂ −N, BOD = NO ₂ −
It becomes N × 1.8. ).

Therefore, for example, in "the number of days 5", NO ₃ -N in the raw water is 106 mg / l, so that the amount of organic matter required for denitrification is BOD = 106 × 2.7 = 286 mg / l. Become.

On the other hand, the BOD conversion amount of the organic substance obtained from TOC 10 mg / l of the raw water is BOD = 1.9 × 10 −15 = 4 mg / l, so that the organic substance of 286−4 = 282 mg−BOD / l is insufficient. It will be.

On the other hand, the BOD of a 50% aqueous methanol solution is 50% aqueous methanol solution = 390 g-methanol / l =
It becomes 390 g-BOD / l.

In this embodiment, 282 mg-
About 214 mg-BOD corresponding to about 76% of BOD / l
In order to inject 1 / l, an aqueous methanol solution of 7.64 cc / min calculated by the following formula was injected by operating the pump P ₁ .

(282 × 830 × 0.76) ÷ 390 =
4.56 liters / hr = 7.64 cc / min At the same time, based on the measured value of the ORP meter, 9.7 to 10 cc
/ Min of 50% aqueous methanol solution at ORP of -10
If 0 mV or more, turn on the methanol injection pump P ₂ ,
If it was −150 mV or less, the methanol injection pump P ₂ was turned off and intermittent injection was performed.

Similarly, in the case of "9 days", the equivalent amount of BOD converted to the amount of organic matter is 131 x 2.7- (1.9 x 70-15) = 235 mg.
-BOD / l, which is almost the same as in the case of "5 days", so the injection control of the 50% aqueous methanol solution was continued in the same manner as above.

In "14 days", there is a shortage of organic matter BOD
The converted amount is 97 x 2.7- (1.9 x 166-15) = -38 mg.
The injection from the pump P ₁ was stopped because the amount of organic matter was -BOD / l.

Table 1 shows the water quality of the obtained treated water.

[0035]

[Table 1]

Comparative Example 1 Without injecting the aqueous methanol solution from the pump P ₁ ,
The denitrification treatment was performed in the same manner as in Example 1 except that only intermittent injection from the pump P ₂ was performed, and the results are shown in Table 2.

[0037]

[Table 2]

From the results of Tables 1 and 2, the following is clear. That is, in Comparative Example 1 in which only intermittent injection of methanol based on the ORP value of the conventional denitrification treated water is performed, the TOC of the raw water fluctuates, and if the raw water TOC is lower than the raw water NO ₃ -N, the treated water NO ₃ 0. -N is high, conversely, raw water TOC is raw water N
If it is higher than O ₃ -N, the TOC of the treated water will be high, and in any case, treated water of high quality cannot be obtained.

On the other hand, according to the method of the present invention, the deficiency of the organic matter is obtained in advance from the measurement result of the raw water, most of the deficiency is injected, and then the methanol based on the ORP value of the denitrification treated water is added. According to example 1 was subjected to intermittent injection, NO ₃ -N, TOC together is significantly reduced, a high quality treated water can be obtained stably and reliably.

[0040]

As described above in detail, according to the fixed bed denitrification method of the present invention, when denitrifying a raw water in which the amount of organic matter fluctuates greatly, the amount of organic matter added in the raw water is controlled to an optimum value. As a result, it is possible to obtain the treated water of high quality in a stable and reliable manner.

The fixed bed denitrification method of the present invention as described above is
It is extremely effective when water with a large fluctuation range of the amount of organic matter is used as raw water, such as wet catalytic oxidation treated water of human waste, and according to the method of the present invention, the amount of residual organic matter in the denitrification treated water is minimized. By suppressing, it is possible to significantly reduce the inflowing organic matter load into the re-aeration tower (aerobic biological filtration tower) in the subsequent process, improve the water quality and treatment efficiency of the final treated water, and reduce the treatment cost. .

[Brief description of drawings]

FIG. 1 is a system diagram illustrating a method of an embodiment of a fixed bed denitrification method of the present invention.

[Explanation of symbols]

 1 Raw water tank 2 Methanol storage tank 3 Biological denitrification tower 4 Nitric acid waste liquid storage tank 6 ORP meter 7 pH meter 8 TOC meter 10 Controller

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yoshihiro Eto 3-4-7 Nishishinjuku, Shinjuku-ku, Tokyo Kurita Industry Co., Ltd.

Claims (1)

[Claims] 1. A nitrate denitrification tank and / or a nitrite nitrogen (hereinafter referred to as "NO" in a denitrification tank in which a fixed bed of denitrification bacteria is formed.
x ”. ) And a BOD component are passed through to denitrify the raw water, and the redox potential or sulfur ion concentration of the treated water treated in the denitrification tank is measured, and the raw water is based on the measured value. In the fixed-bed denitrification method of adding organic matter to, the NOx concentration and the organic matter concentration of the inflow water of the denitrification tank are measured,
Based on this measurement value, all NOx flowing into the denitrification tank
Calculate the theoretical concentration of organic matter required to denitrify, compare this theoretical concentration with the measured value of organic matter, and when the measured value of organic matter is lower than the theoretical concentration, the amount of organic matter corresponding to the difference between them. A fixed bed denitrification method, characterized in that at least a part of the above is added to raw water.