JP3288097B2 - Purification method of nitrogen-containing polluted water - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a purification method for purifying nitrogen-containing contaminated water, for example, coating wastewater, by biological treatment using microorganisms.

[0002]

2. Description of the Related Art Nitrogen is present in coating wastewater such as electrodeposition coating, and a biological treatment method utilizing microorganisms such as bacteria is effective in purifying the nitrogen, and has been widely used in recent years. . Nitrogen in wastewater can be classified into ammonia nitrogen (NH ₄ -N), which is easily oxidized and absorbed by microorganisms, and organic nitrogen (so-called Kjeldahl nitrogen (K-N)), which is hardly decomposed and therefore hardly treated by microorganisms.

[0003]

In the biological treatment of nitrogen-containing polluted water, urea is supplemented as a nutrient for the microorganism before introducing the microorganism into the polluted water. It is widely known and implemented that the amount of urea to be replenished satisfies the following equation. BOD: N: P = 100: 5: 1 (weight ratio) where BOD; biochemical oxygen demand, N; nitrogen amount,
P; Phosphorus The biochemical oxygen demand (BOD) is the amount of dissolved oxygen consumed by the growth or respiration of aerobic microorganisms in water, and is used as an index of pollution in rivers and the like. It is. For example, Kjeldahl nitrogen is 30 to 40
When treating polluted water containing mg / l, 30 to 40 mg / l of Kjeldahl nitrogen is converted to a BOD of 600 to 700.
Since it corresponds to mg / l, the nitrogen amount of about 20 times
Replenish the urea in an amount of 0 mg / l, and then purify with bacteria in the aeration tank. However, according to this method, about 20 mg / l of Kjeldahl nitrogen remains even after the treatment, and a more efficient purification treatment method has been desired. In particular, the nitrogen amount of the treated water after the final treatment is 1
It is required to be below 0 mg / l.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a radical review of a widely known biological treatment method has been made. Purification of nitrogen-containing polluted water by biological treatment that decomposes organic nitrogen with high efficiency. It provides a processing method.

[0005]

DISCLOSURE OF THE INVENTION The present invention fundamentally revises a conventional purification treatment method by biological treatment, and as a result of diligent research, it has been found that the conventional amount of urea suppresses the decomposition of Kjeldahl nitrogen. It was made by finding
In a purification treatment method in which urea is added to nitrogen-containing polluted water to perform biological treatment, the BOD of the polluted water is 100% by weight.
In addition, the biological treatment is performed by adding urea in an amount that gives a nitrogen amount of 0.5 to 2.

[0006]

According to the purification method of the present invention, a specific amount of urea is added as a nutrient in biological treatment, which prevents the incorporation of extra urea, promotes the decomposition of Kjeldahl nitrogen that is hardly oxidized and absorbed by microorganisms, and reduces pollution. Reduce the amount of nitrogen in water significantly.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As one embodiment of the present invention, a method for purifying nitrogen-containing wastewater generated by electrodeposition coating will be described with reference to FIG. In electrodeposition coating, mainly electrocoating drainage and coating booth circulating water are generated, and both of these drainage contain ammoniacal nitrogen that is easily decomposed and nitrogen that is hardly decomposed. This nitrogen-containing polluted water is collected and temporarily stored in a raw water tank. Since this solution is weakly alkaline, it is pumped into the reaction neutralization flocculation tank and neutralized. Then, the primary treatment water obtained via the pressure floating tank is stored in the primary treatment tank. In the primary treatment tank, the BOD, COD (chemical oxygen demand) and the total phosphorus amount of the primary treatment water are measured. Next, this primary treated water is biologically treated.
The primary treated water is supplied to an aeration tank composed of a high-load aeration tank for biological treatment and a normal aeration tank. The concentration of the bacteria for biological treatment in the aeration tank is 5000 to 5500 mg / l. At this time, urea is added to the aeration tank from the urea tank as a nutrient for bacteria. Urea is the primary treated water B measured earlier
The amount of nitrogen is added to an amount of 0.5 to 2 with respect to 100 of OD. After sufficient decomposition by bacteria, the obtained secondary treated water is fed from the aeration tank to the sedimentation basin. The secondary treatment water is fed from the sedimentation tank to the coagulation sedimentation tank via the second coagulation tank. After that, BOD, CO
Inspect D, Kjeldahl nitrogen, ammonia nitrogen,
Check that the standard value is met before releasing. Sludge is returned from the sedimentation pond after the aeration tank to the high-load aeration tank and the aeration tank.

[Treatment example] Purification treatment of raw water having the properties shown in Table 1 was performed by the method of this embodiment. In addition, each of the following Tables 1
In 4, all units are mg / l.

[Table 1]

The raw water was subjected to a pressurized floating treatment to obtain a primary treated water having the properties shown in Table 2.

[Table 2]

[0010] Each amount of urea (Examples 1, 2 and Comparative Examples 1, 2, and 3) shown in Table 3 was added to the primary treated water, and the properties of the secondary treated water obtained after the biological treatment were examined. Was. Table 3 shows the measurement results.

[Table 3]

Further, the purification treatment was continued, and the properties of the treated water in the treated water tank after coagulation and sedimentation were examined. Table 4 shows the results
And FIG.

[Table 4]

The measurement results show that the smaller the amount of urea to be added, the lower the amount of residual Kjeldahl nitrogen and the amount of residual ammoniacal nitrogen after the treatment. In particular, the treatment effect of Kjeldahl nitrogen could be remarkably increased by reducing the amount of urea to be added. When the BOD ratio of the amount of added urea was smaller than 2, a high processing ability was surely exhibited. However, the BOD ratio of the amount of added urea was set to 0.
If it is less than 5, it is considered that it is difficult to further improve the processing ability. Therefore, in the present invention, the addition amount of urea is set to 0.5 to 2 with respect to 100 of the BOD of the polluted water to be treated. According to the method of the present embodiment, the decomposition of KN is promoted by biological treatment, and as a result, the amount of nitrogen including KN is drastically reduced.

Although the present embodiment has shown the wastewater treatment by electrodeposition coating, the present invention is not limited to this, and the present invention is not limited to the purification of nitrogen-containing polluted water using biological treatment with the addition of nutrients. Needless to say, it can be applied to other purification equipment.

[0014]

According to the purification method of the present invention, a biological treatment is carried out by adding urea to nitrogen-containing polluted water, and the Kjeldahl nitrogen in the raw water is BOD: N = 100:
When the BOD is present at a ratio of 5, the BOD of the contaminated water is 1 by weight.
The method is characterized in that urea is added in an amount that gives a nitrogen amount of 0.5 to 2 with respect to 00, and biological treatment is performed. ADVANTAGE OF THE INVENTION According to this invention, the addition amount of the nutrient which is indispensable for biological treatment can be restricted, the decomposition | decomposition of Kjeldahl nitrogen can be promoted, and the purification capability of nitrogen-containing polluted water can be improved. According to the purification treatment method of the present invention, it is possible to enhance purification ability, achieve improved water quality of treated water, and take measures against eutrophication of rivers and seas without investing in new equipment. Further, since the amount of urea as a necessary nutrient can be reduced, the processing cost in wastewater treatment can be reduced.

[Brief description of the drawings]

FIG. 1 is a process chart showing a purification treatment method according to the present embodiment.

FIG. 2 is a graph showing the relationship between the BOD ratio of the amount of added nitrogen and the amount of residual KN.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-54-162846 (JP, A) JP-A-55-44332 (JP, A) JP-A-57-136993 (JP, A) JP-A-58-1983 64197 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C02F 3/12

Claims (1)

(57) [Claims] 1. A purification treatment method in which urea is added to nitrogen-containing polluted water to perform biological treatment, wherein the amount of nitrogen is 0.5 to 2 with respect to the BOD of the polluted water being 100 by weight. A purification treatment method, wherein biological treatment is performed by adding urea.