JP2001334285A - Apparatus for biologically treating organic wastewater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently treat organic wastewate having a high concentration of organic substances. SOLUTION: The concentration of BOD of raw water in a raw water tank 10 is measured by a BOD analyzer 22. A control unit 24 controls a nitrogen pump 32 and a phosphorus pump 34 so that the addition amounts of nitrogen and phosphorus become smaller than theoretical values in the case of high concentration as compared with the case of low concentration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic wastewater biological treatment apparatus for performing aerobic biological treatment by adding a nutrient so that the amount of a nutrient containing nitrogen or phosphorus becomes an appropriate amount in the organic wastewater. About.

[0002]

2. Description of the Related Art Conventionally, biological treatment such as an activated sludge method has been widely used as a treatment of organic waste water. In this activated sludge method, activated sludge composed of microorganisms is accommodated, and wastewater is introduced into an aeration tank into which air is introduced and aerated, where organic substances are decomposed by the action of microorganisms. Then, the aerated mixed solution in the aeration tank is introduced into the sedimentation tank, sludge is settled and separated, returned to the aeration tank, and the supernatant is discharged as treated water.

In this activated sludge method, it is necessary that the microorganisms in the aeration tank grow sufficiently. For this purpose, not only are the microorganisms supplied with predetermined organic substances and oxygen, but also the microorganisms grow. The necessary nutrients need to be supplied. In particular, special organic wastewater may be deficient in nitrogen or phosphorus.
It is necessary to add a nutrient containing phosphorus.

[0004] Proper growth of microorganisms requires that nitrogen and phosphorus be supplied together with organic matter in a ratio similar to that of C (carbon): N (nitrogen): P (phosphorus) in the microorganism. Therefore, BOD (biochemical oxygen demand) in the aeration tank inflow and drainage: N: P = 100:
It is common practice to add nutrients in a 5: 1 ratio.

[0005] Thus, an appropriate nutrient substance is supplied to the microorganisms, and it is possible to prevent deterioration of the settleability of the activated sludge and deterioration of the treated water.

[0006] The same applies to the aerobic biological treatment other than the activated sludge method such as the biofilm treatment method.

[0007]

However, in actual treatment, despite the addition of such nutrients,
In some cases, good processing could not be performed. That is, in the case where the organic matter concentration of the wastewater to be treated becomes high, there are many cases where sufficient treatment cannot be performed even if the addition of the nutrient according to the theoretical value as described above.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a biological treatment apparatus for organic wastewater capable of performing sufficiently satisfactory treatment on wastewater having a high concentration of organic substances.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a biological wastewater treatment system in which a nutrient is added to an organic wastewater so that the amount of nutrients containing nitrogen or phosphorus becomes an appropriate amount to perform aerobic biological treatment. In the treatment device, an organic matter concentration measuring means for measuring the organic matter concentration of the wastewater to be treated, and a nutrient so that the amount of the nutrient substance with respect to the organic matter is substantially theoretically appropriate when the measured organic matter concentration is less than a predetermined value. A nutrient addition control means for adding a nutrient so that the amount of the nutrient with respect to the organic substance concentration is less than the theoretically appropriate amount if the measured organic matter concentration is a high concentration equal to or higher than a predetermined value. , Is characterized by having. Thus, when the BOD concentration of the wastewater to be treated is high, the amounts of nitrogen and phosphorus added are reduced. Thereby, the amounts of nitrogen and phosphorus to be added can be maintained at appropriate levels, and the quality of treated water can be improved and the sedimentation of sludge can be improved. Further, the operation cost can be reduced by reducing the amount of the nutrient added.

[0010] The predetermined value of the organic substance concentration is BOD.
It is preferable that the amount of nitrogen is 3 or less and the amount of phosphorus is 0.7 or less when the BOD is 100, which is less than the theoretically appropriate amount. B
When the OD concentration is low, a nutrient source according to the theoretical value required for the growth of the microorganism is required, and when the OD concentration is high, the autoxidation of the sludge proceeds, and the amount of addition of nitrogen and phosphorus is small. It is considered something.

It is preferable that the aerobic biological treatment is an activated sludge treatment using an immersion membrane using an immersion membrane to hold microorganisms in an aerobic treatment tank and obtain treated water as permeate. . By the activated sludge treatment using the submerged membrane, the activated sludge concentration can be made high to efficiently treat the high-concentration organic wastewater.

[0012]

Embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an organic wastewater treatment apparatus according to an embodiment. Raw water to be treated is a raw water tank 1.
0 is introduced. Here, the raw water is a wastewater containing a large amount of organic substances such as a pulp and paper mill wastewater and a wastewater generated in the steam regeneration of activated carbon to which an organic solvent has been adsorbed, but containing almost no nutrient sources such as nitrogen and phosphorus.

The raw water in the raw water tank 10 is supplied to the raw water pump 1.
2 is introduced into the aeration tank 14 via the raw water supply pipe 36. An air diffuser 16 is arranged at the bottom of the aeration tank 14. Compressed air from a blower or the like is supplied to the air diffuser 16, and bubbles are ejected from the air diffuser 16 to aerate the inside of the aeration tank 14. Thereby, the inside of the aeration tank 14 is maintained under aerobic conditions, and the activated sludge composed of aerobic microorganisms that oxidize the organic matter in the raw water proliferates.

Further, in the aeration tank 14, an immersion membrane separation device 18 is disposed. This immersion membrane separation device 18
The internal space is separated from the inside of the aeration tank 14 by a membrane having a fine pore diameter capable of separating activated sludge such as a polymer membrane, and a suction pump 20 is connected to the internal space. Accordingly, filtered water subjected to membrane filtration is obtained in the internal space of the immersion membrane separation device 18, and this is discharged out of the system as treated water by the suction pump 20. A part of the air diffuser 16 is provided below the immersion membrane separation device 18 so that the membrane in the immersion membrane separation device 18 is cleaned. When the membrane is clogged, the immersion membrane separator 18 is pulled up and the membrane is washed with a chemical.

The raw water tank 10 has a BOD analyzer 22.
Is provided, and the BOD concentration in the raw water tank 10 is constantly detected. Here, as the BOD analyzer 22, a continuous BOD analyzer of an electrode method or the like can be adopted, but a TOC (total organic carbon) analyzer, a COD (chemical oxygen demand) analyzer, or the like can be used.
It may be used in place of the OD analyzer and the detected value may be converted to BOD, or a TOD (total oxygen demand) meter.

The detected value of the BOD analyzer 22 is
4 is supplied. Also, the aeration tank 1 is controlled by the raw water pump 12.
The amount of raw water supplied to 4 is measured by a flow meter 26,
The measured raw water amount is also supplied to the control device 24.

The controller 24 includes a nitrogen storage tank 28 for storing a nutrient containing nitrogen and a nutrient for storing phosphorus based on the detection value of the BOD analyzer 22 and the detection value of the flow meter 26. A nitrogen pump 32 for supplying nitrogen and phosphorus from the phosphorus storage tank 30 to the raw water flowing through the raw water supply pipe 36;
The phosphorus pump 34 is controlled. That is, the control device 24
Calculates the integrated value of the amount of BOD flowing into the aeration tank 14 in the predetermined period by multiplying the detection value of the BOD analyzer 22 by the flow rate of the flow meter 26 in the predetermined period. Then, the nitrogen pump 32 and the phosphorus pump 34 are controlled so that nitrogen and phosphorus corresponding to the BOD inflow amount are added to the raw water flowing in the raw water supply pipe 36.

The reason why the integrated value of the predetermined period is used for the control is that it is not necessary to control the amounts of nitrogen and phosphorus added to the aeration tank 14 every moment.
This is because if the flow rate of 4 is not changed much, stable control can be performed. For example, it is preferable to use an integrated value of several hours.

Since nitrogen and phosphorus in the raw water are basically assumed to be zero or not fluctuated, the nitrogen and phosphorus concentrations in the raw water are not measured. However, if the concentrations of nitrogen and phosphorus in the raw water fluctuate, it is preferable to measure these concentrations and calculate the amounts of nitrogen and phosphorus added.

As a nitrogen source, urea, ammonium sulfate and the like are preferable.
Sodium phosphate (NaH₂PO
₄Or Na₂HPO₄), Phosphoric acid (H₃PO₄)
Phosphoric acid phosphate which is suitable and can supply both nitrogen and phosphorus
Monium ((NH₄)₃PO ₄) Are also suitable.

In the present embodiment, the control unit 24 changes the target amount of the nutrient to be added according to the analysis value of the BOD analyzer 22. That is, the control device 24
Means that if the BOD concentration of the raw water is less than 2000 mg / L, the raw water flowing into the aeration tank 14 is BOD: N: P = 1
The nitrogen pump 32 and the phosphorus pump 34 are controlled so that the ratio becomes 00: 5: 1. On the other hand, if the BOD concentration of raw water is 2000
In the case of mg / L or more, the raw water flowing into the aeration tank 14 is BOD: N: P = 100: 3: 0.7 or nitrogen,
The nitrogen pump 32,
The phosphorus pump 34 is controlled.

As described above, by changing the BOD: N: P ratio of the raw water flowing into the aeration tank 14 according to the BOD concentration of the raw water, more suitable treatment can be performed.

Here, when the BOD concentration in the raw water is high, the reason why it is better to reduce the amount of the nutrient source is considered to be due to the auto-oxidation of the activated sludge.
That is, when the raw water BOD concentration is high, the treatment is performed while keeping the sludge (microorganism) concentration in the aeration tank high accordingly. For this reason, the SRT (sludge residence time) in the treatment system becomes longer, and the autoxidation of the sludge proceeds. And nitrogen and phosphorus in microbial cells are eluted by the auto-oxidation of sludge,
It is considered that the amount of nitrogen and phosphorus to be added is small. In particular, when nitrogen is excessive, growth of microorganisms is inhibited.

For this reason, the apparatus of the present embodiment for reducing the amounts of nitrogen and phosphorus added when the BOD concentration of the raw water is high can not only reduce the amount of nutrients added to perform economical operation but also reduce the amount of nutrients. The effect of improving the quality of the treated water and the sedimentation of sludge can be obtained by the high nitrogen and phosphorus concentrations.

In the case of treating high-concentration wastewater,
It is also preferable to perform aeration using an oxygen-enriched gas containing a high concentration of oxygen instead of aeration with air. Further, the excess sludge is directly extracted from the aeration tank 14, but by increasing the SRT, the amount of the excess sludge can be reduced, and can be reduced to 0 in a suitable case.

[0027]

EXAMPLE When the BOD concentration of raw water is 2000 mg / L (Example 1), BOD: N: P = 100: 3: 0.7 by the submerged membrane type activated sludge treatment apparatus shown in FIG. Nutrients, and the raw water BOD concentration is 10,000 m
In the case of g / L (Example 2), BOD: N: P = 10
The treatment was performed by adding a nutrient so that the ratio became 0: 2: 0.5.

As a comparative example, in the activated sludge treatment apparatus shown in FIG. 1, the raw water BOD concentration was 2000 mg.
/ L (Comparative Example 1), and BOD: N: P = 100: 5: 10,000 mg / L (Comparative Example 2).
The treatment was performed by adding a nutrient so as to be 1.

Table 1 shows these conditions.

[0030]

[Table 1]

The nitrogen concentration of the treated water in each case,
Table 2 shows the phosphorus concentration, COD concentration, filtration speed, and the presence or absence of scum. Here, the filtration speed is an index corresponding to the sedimentation property of the sludge, and is determined by using a predetermined filter paper (5 types C, JIS P38).
01) indicates the amount of filtered water per unit time (5 minutes) when the aerated mixed solution was filtered.

[0032]

[Table 2]

As is clear from Tables 1 and 2, according to the present embodiment, when the BOD concentration of the raw water is high, the amount of added nutrient (nitrogen and phosphorus) is reduced from the theoretical value, so that the quality of treated water and sludge are reduced. It is understood that properties (filtration property) and the like can be improved.

[0034]

As described above, according to the present invention,
When the wastewater to be treated has a high BOD concentration, nitrogen,
The amount of phosphorus added is reduced below the theoretically appropriate amount. This makes it possible to maintain appropriate amounts of nitrogen and phosphorus to be added, thereby improving the quality of treated water and improving the sedimentation of sludge. Further, the operation cost can be reduced by reducing the amount of the nutrient added.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of an apparatus according to an embodiment.

[Explanation of symbols]

10 raw water tank, 12 raw water pump, 14 aeration tank, 16
Diffuser tube, 18 immersion membrane separator, 20 suction pump,
22 BOD analyzer, 24 controller, 26 flow meter, 2
8 nitrogen storage tank, 30 phosphorus storage tank, 32 nitrogen pump, 3
4 phosphorus pump.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Ken Murakami F-term in Organo Co., Ltd. 1-2-8 Shinsuna, Koto-ku, Tokyo 4D006 GA02 HA93 KA31 KA33 KA44 KB22 KC07 KC16 KD11 KD30 KE12P KE30Q PA02 PB08 PC64 4D028 AA02 AC03 AC06 BC17 CA00 CA05 CB02 CC01 CC02 CD02 CD08 CE01

Claims (3)

[Claims] 1. An organic wastewater biological treatment apparatus for performing an aerobic biological treatment by adding a nutrient so that the amount of a nutrient containing nitrogen or phosphorus becomes an appropriate amount in the organic wastewater. An organic matter concentration measuring means for measuring an organic matter concentration, and adding a nutrient so that the amount of the nutrient substance with respect to the organic matter becomes substantially theoretically appropriate when the measured organic matter concentration is less than a predetermined value, and the measured organic matter concentration Nutrient addition control means for adding a nutrient so that the amount of the nutrient with respect to the organic matter concentration is less than the theoretically appropriate amount when is a high concentration equal to or higher than a predetermined value. Organic wastewater biological treatment equipment. 2. The apparatus according to claim 1, wherein the predetermined value of the organic substance concentration is 2000 mg as BOD.
/ L, and the amount less than the theoretically appropriate amount is B
Assuming that OD is 100, nitrogen is 3 or less and phosphorus is 0.1 or less.
A biological treatment apparatus for organic wastewater, wherein the number is 7 or less. 3. The apparatus according to claim 1, wherein the aerobic biological treatment uses an immersion membrane to retain microorganisms in an aerobic treatment tank using an immersion membrane and obtain treated water as permeated water. A biological treatment apparatus for organic wastewater, which is a type of activated sludge treatment.