JP2002143889A - Waste water treatment equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide waste water treatment equipment which is capable of performing dentrification treatment by crushing carriers in the dentrification treatment using the carriers which is weak to shearing force. SOLUTION: This waste water treatment equipment has a reaction chamber 1 for a treating liquid 20, an agitator 4 which has agitator blades 3 which agitate the treating liquid 20 and discharges the liquid in a horizontal direction, a baffle 2 which is installed in the central part at the bottom of the reaction vessel chamber 1, reflects the treating liquid 20 flowing from above and allows the liquid to flow upward and the carries 5 which hold the anaerobic bacteria dispersed in the treating liquid 20 of the reaction chamber 1. The equipment is provided with the baffle 2 fixed to the bottom of the chamber and the agitator having the agitator blades for discharging the treating liquid 20 in the horizontal direction, by which the flowage state of the small shearing force of the treating liquid 20 is obtained and the dentrification treatment in the waste water is efficiently performed without crushing the carriers weak to the shearing force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wastewater treatment apparatus, and more particularly to a method for removing nitrate nitrogen compounds, ammonium nitrogen compounds, and organic nitrogen compounds in wastewater discharged from a semiconductor manufacturing plant, a metal surface treatment plant, and the like using microorganisms. The present invention relates to a fluidized bed type drainage device for converting nitric acid and nitrite nitrogen generated by nitrification into harmless nitrogen compounds for treatment.

[0002]

2. Description of the Related Art Nitrogen compounds are considered to be eutrophic substances in closed water bodies such as lakes and marshes, and their effluent concentrations are regulated. In particular, nitrate nitrogen compounds have been attracting attention as groundwater contaminants due to the recent increase in the consumption of nitrogen fertilizer. It has been reported to cause the disease. Therefore, in Japan, Heisei 1
In one year, nitrate nitrogen and nitrite nitrogen were newly added as items of “Environmental standards for protection of human health related to water pollution”.

Hitherto, a biological treatment method has been most widely used as a method for treating a nitrate / nitrite nitrogen compound. In this method, activated sludge method is generally used,
By stirring the inside of the reaction tank to which various denitrifying bacteria are added under anaerobic conditions, nitric acid / nitrite nitrogen is finally converted into nitrogen and treated. However, this activated sludge method has a drawback that it is difficult to maintain a high concentration of bacterial cells in the reaction tank, and the treatment capacity is low.

[0004] As a method which has been used in recent years to solve this drawback, there is a fluidized bed type denitrification treatment method. In this method, a carrier in which a denitrifying bacterium is maintained at a high concentration is caused to flow in a reaction tank, and is brought into contact with wastewater under anaerobic conditions to advance a denitrification reaction. Polyethylene glycol as a carrier,
When the carrier diameter of cellulose, polyester, polypropylene, urethane sponge or the like is several mm or more, and activated carbon, alumina, silica, glass, or the like, the carrier diameter is a fine particle of several mm or less and a relatively large specific gravity is used. There are cases.

[0005]

The above-mentioned carriers having a diameter of several mm or more, such as polypropylene, are often weak in mechanical shearing force. For example, pitching paddle type or propeller type stirring, which is most commonly used, is used. There is a problem that the carrier is easily crushed when stirred by a stirrer having blades. To solve this problem, Japanese Patent Application Laid-Open No. H10-15572 proposes a processing method in which the shape of the inside of a reaction tank is made special and a liquid jet mechanism is combined. This method has a problem that the apparatus is complicated because a special shape of the reaction tank is required.

Further, the diameter of the above-mentioned carrier such as activated carbon is several mm.
When the following fine particle carriers are used, a method in which the carriers are filled in a tower-shaped treatment apparatus and the wastewater is passed upward from the lower part of the tower and treated with water is disclosed in JP-A-60-232295,
-34794 and JP-A-10-15582.

[0007] However, in these methods, if the microbial particles grow excessively on the surface of the carrier, the specific gravity of the carrier changes, and it becomes difficult to uniformly flow all the carriers, and as a result, the stability of the treatment is lacking. There was a problem. Further, in order to detach the excessively grown cells from the carrier surface, it is necessary to temporarily or constantly increase the upward streamline velocity to fluidize the carrier, and the carrier is likely to flow out from the upper part of the tower. Therefore, consideration must always be given to the upward streamline velocity in the tower, and there has been a problem in terms of operation controllability.

In view of such a situation, the present inventors have developed a fluidized bed type denitrification treatment apparatus and a tower-like treatment apparatus which can uniformly mix carriers with a simple device without crushing the carriers. An object of the present invention is to provide a fluidized bed type denitrification treatment apparatus (a wastewater treatment apparatus) which uses a fine particle carrier having a large specific gravity without using it and has excellent operation controllability.

[0009]

A first aspect of the present invention provides a wastewater treatment apparatus for storing wastewater containing nitric acid / nitrite nitrogen compound, a wastewater treatment apparatus, a wastewater treatment apparatus, and a wastewater treatment apparatus. A stirrer having a stirring blade that discharges outwardly, a baffle plate installed at the bottom of the reaction tank and reflecting the drainage flowing from above and flowing upward, and dispersed in the drainage, A carrier holding an anaerobic bacterium for denitrifying the contained nitric acid / nitrite nitrogen compound.

In the wastewater treatment apparatus of the first configuration of the present invention, the shape of the baffle plate may be a truncated cone, a truncated spherical surface, or a truncated pyramid (triangular or more) having a small upper cross-sectional area. Also, the discharge angle of the drainage from the stirring blade is preferably 0 to 30 ° downward with respect to the horizontal direction.

[0011] A wastewater treatment apparatus having a second configuration according to the present invention comprises a reaction tank for storing wastewater containing nitric acid and nitrite nitrogen compounds;
A stirrer that is installed in the reaction tank and has a stirring blade that stirs and discharges the wastewater to the outside, and a baffle plate that is installed at the bottom of the reaction tank and reflects the wastewater flowing from above and flows upward. A carrier holding an anaerobic bacterium dispersed in the wastewater and denitrifying the nitrate / nitrite nitrogen compound contained in the wastewater, and a lower part of the reaction tank separated by the reaction tank and a partition plate And a sedimentation tank communicating with the reaction tank.

In the wastewater treatment apparatus of the second configuration according to the present invention, as in the wastewater treatment apparatus of the first configuration,
The shape of the baffle plate may be a truncated cone, a truncated spherical surface, or a truncated pyramid (a triangular shape or more) having a small upper cross-sectional area. Also, the discharge angle of the drainage from the stirring blade is preferably 0 to 30 ° downward with respect to the horizontal direction.

According to the present invention, the baffle plate fixed to the bottom of the reaction vessel is combined with a stirrer having a stirring blade for discharging the wastewater downward at an angle of 0 to 30 ° with respect to the horizontal direction, so that the vessel wall is formed. On the side, a rotating flow that swirls and descends gently is obtained, and a strong tornado-like upward flow is obtained at the center of the tank, so that an effective one-loop flow pattern can be formed. The shear force obtained by the combination of the baffle plate and the stirrer is smaller than that of a general stirrer using pitched paddle type or propeller type stirring blades, and crushing of the carrier can be minimized.

The ascending flow velocity at the center of the reaction vessel obtained in the present invention is very large, so that even when a carrier having a relatively large specific gravity is used, it is possible to uniformly mix in the reaction vessel, and tornado-like flow As a result, the detachment of the cells from the carrier is promoted.

Further, in the case where a sedimentation tank communicated with each other is installed in the lower part of the reaction tank (the above-mentioned second configuration), the treated water and the carrier flow into the lower part of the sedimentation tank through the communicating part, but the carrier in the settling tank Alone settles by its own weight and can be returned to the reaction tank by itself and retained in the reaction tank, while the treated water flows out of the settling tank as supernatant water. Therefore, even when fine particles are used as the carrier, the carrier does not flow out unless the upward linear flow velocity in the settling tank is equal to or higher than a certain value, so that the operation controllability is good.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the wastewater treatment apparatus according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is an explanatory view of a wastewater treatment apparatus according to a first embodiment of the present invention. The wastewater treatment apparatus according to the present embodiment is applied when a carrier having a diameter of several mm or more is used.

Referring to FIG. 1, a wastewater treatment apparatus according to the present embodiment includes a treatment liquid 20 (a wastewater containing nitric acid and nitrite nitrogen).
And a stirrer 4 provided in the reaction tank 1 and provided with a stirring blade 3 for stirring the processing liquid 20 and discharging the processing liquid 20 to the outside, and a stirrer 4 installed in the center of the bottom of the reaction tank 1 and flowing from above. A baffle plate 2 for reflecting the treated solution 20 and flowing upward, and a carrier 5 holding anaerobic bacteria dispersed in the treated solution 20 in the reaction tank 1 are provided. Raw water 6 is supplied to the reaction tank from above the reaction tank 1. The stirrer 4 is desirably installed at a position higher than half the depth of the processing liquid 20 in the reaction tank 1.

The shape of the baffle plate 2 is suitably a truncated cone, truncated spherical surface or truncated pyramid (trigonal or larger) having a small upper cross-sectional area. The baffle plate 2 may be formed integrally with the reaction tank 1 at the bottom of the reaction tank 1.

The treatment liquid 2 from the stirring blade 3 of the stirrer 4
The discharge angle of 0 is suitably 0 to 30 ° below the horizontal direction.

As shown in FIG. 1, the wastewater treatment apparatus according to the present embodiment agitates a treatment liquid 20 in a reaction tank 1 by a stirring blade 3 and a baffle plate 2 into a fluidized state as schematically shown in FIG. The carrier can be uniformly dispersed in the processing liquid 20. As a result, the nitric acid / nitrite nitrogen compound in the treatment liquid 20 can be treated efficiently.

Raw water 6 containing a nitric acid / nitrite nitrogen compound is added to the reaction tank 1, comes into contact with the carrier 5 in the reaction tank 1, and is biochemically treated by anaerobic bacteria on the surface of the carrier 5. Water 8 flows over the reaction tank 1. A wire net 9 (blocking means for the carrier 5) is provided at the tank outlet so that the carrier does not flow out at the same time as the treated water 8.

In the wastewater treatment apparatus of the present embodiment, the carrier 5
For example, polyethylene glycol, cellulose, polyester, polypropylene, urethane sponge or the like having a diameter of several mm or more is used.

Incidentally, the biological denitrification reaction proceeds according to the following equation. (1) When raw water is nitrous acid NO ₂ ⁻ + 3H ⁺ → 1 / 2N ₂ ↑ + H ₂ O +
OH ^- (2) If the raw water is nitrate ^{_{NO 3 - + 5H + → 1}} / 2N 2 ↑ + 2H 2 O
+ OH-Accordingly, hydrogen is required for the reaction to proceed. If the raw water 6 contains a BOD component, it can be used as a hydrogen donor. However, if there is not enough hydrogen or if there is no hydrogen in the raw water 6, the hydrogen donor 7 is removed from the top of the reaction tank 1 as necessary. It is added into the reaction tank 1. In addition, as the hydrogen donor 7, for example, methanol, acetic acid, or the like can be used.

Since OH ^- is generated, a pH adjusting mechanism for adjusting the pH of the processing solution 20 by adding an acid can be added as needed.

Next, a second embodiment of the wastewater treatment apparatus of the present invention will be described in detail with reference to the drawings.

FIG. 2 is an explanatory view of a wastewater treatment apparatus according to a second embodiment of the present invention. The wastewater treatment apparatus of the present embodiment is applied to both carriers having a diameter of several mm or more and fine particle carriers having a diameter of several mm or less.

Referring to FIG. 2, the wastewater treatment apparatus according to the present embodiment has a reaction tank 1 for treating liquid 20 and a stirring blade installed above reaction tank 1 for stirring treatment liquid 20 and discharging it to the outside. 3, a baffle plate 2 installed at the center of the bottom of the reaction tank 1 for reflecting the processing liquid 20 flowing from above and flowing upward, and dispersed in the processing liquid 20 of the reaction tank 1. Carrier 5 holding anaerobic bacteria, reaction tank 1 and partition plate 1
And a sedimentation tank 9 which is separated from the reaction tank 1 and communicates with the reaction tank 1 at the lower part of the reaction tank 1. Raw water 6 is in reaction tank 1
From the upper part of the reactor. In addition, the discharge angle of the processing liquid 20 from the stirring blade 3 of the stirrer 4 is suitably 0 to 30 degrees downward with respect to the horizontal direction.

The shape of the baffle plate 2 is suitably a truncated cone, a truncated spherical surface or a truncated pyramid (trigonal or larger) having a small upper cross-sectional area. The carrier 5 is made of polyethylene glycol, cellulose, polyester, polypropylene, urethane sponge or the like having a diameter of several mm or more, or activated carbon, alumina, silica, glass or the like, and is a fine particle having a carrier diameter of several mm or less and having a relatively specific gravity. Can be used.

Referring to FIG. 2, the processing solution 20 and the carrier 5 treated in the reaction tank 1 flow into the lower part of the sedimentation tank 9 through the communicating part of the lower part of the tank. It settles, is returned to the reaction tank 1 by itself, and is held in the reaction tank 1. On the other hand, the water treated in the reaction tank 1 is
The water proceeds in the upward flow, and the treated water 8 is obtained by the overflow.

At this time, it is more convenient if the bottom surface of the settling tank 9 is inclined toward the reaction tank 1 so that the carrier 5 can be easily returned to the reaction tank 1.

In FIG. 2, the carrier 5 flows out if the upward linear flow velocity in the sedimentation tank 9 is too high, so that the sedimentation tank is determined using the amount of raw water 6 flowing in and the sedimentation velocity of the carrier 5. It is necessary to determine the water area of 9 and prevent the carrier 5 from flowing out.

Hereinafter, the present invention will be described in more detail with reference to Examples.

(Example 1) An example of treatment of waste water containing nitric acid and nitrite nitrogen by the continuous treatment apparatus shown in FIG. 1 will be described in the order of steps.

First, 3 L of a 4 mm square carrier 5 made of cellulose was charged into a 10 L reactor 1, and the stirrer 5 was operated. The carrier 5 maintains an appropriate fluid state in the reaction tank 1. Next, using artificial drainage shown in Table 1 as raw water 6,
The mixture was continuously introduced into the reaction tank 1 so that the residence time in the reaction tank 1 was 5 hours. At the same time, methanol was used as the hydrogen donor 7 and continuously flowed into the reaction tank 1 at an addition concentration of 2000 mg / L.

The NO ₃ -N concentration and NO ₂ -N concentration of the treated water 8 on the 20th, 25th and 30th days after the start of the operation are respectively 20
After day: 15 mg / L ・ 7 mg / L, After 25 days: 5 mg / L
L · 6 mg / L, 30 days later: 7 mg / L · 8 mg / L. Comparative Example 1 In Example 1, the baffle plate 2 of the reaction tank 1 was removed, and the stirring blade 3 was changed to a propeller type. Other conditions were the same as those in Example 1, and after starting operation, 2
NO ₃ -N concentration · N of treated water 8 on days 0, 25 and 30
The O ₂ -N concentrations were respectively after 20 days: 118 mg / L ·
92 mg / L, 25 days later: 194 mg / L, 103 mg
/ L, 30 days later: 188 mg / L • 119 mg / L. In addition, the carrier was crushed, and a part of the finely crushed carrier 5 flowed out of the gap of the wire mesh 9.

(Example 2) An example of treating waste water containing nitric acid and nitrite nitrogen by the continuous treatment apparatus shown in Fig. 2 will be described in the order of steps.

First, the sedimentation tank 9 is placed in the reaction tank 1 having a volume of 10 L.
The partition plate 10 was set so that the water area was 10 cm ² . The communicating part at the bottom of the tank was 5 cm. Next, 3 L of a 4 mm square carrier 5 made of cellulose was charged into the reaction tank 1,
The stirrer 5 was operated. Others were treated under the same conditions as in Example 1. The NO ₃ -N concentration and NO ₂ -N concentration of the treated water 8 on the 20th, 25th and 30th days after the start of operation were 2 respectively.
After 0 days: 21 mg / L ・ 12 mg / L, After 25 days: 14
mg / L · 9 mg / L, after 30 days: 10 mg / L · 9 m
g / L. (Example 3) In Example 2, 3 L of porous silica having an average particle diameter of 0.8 mm and a specific gravity of 1.25 was used as the carrier 5. Others were treated under the same conditions as in Example 1, and the NO ₃ − of the treated water 8 on the 20th, 25th and 30th days after the start of operation
The N concentration and the NO ₂ -N concentration were respectively 35 days after 20 days.
g / L · 19 mg / L, after 25 days: 29 mg / L · 28
mg / L, after 30 days: 38 mg / L and 20 mg / L. (Example 4) In Example 2, 3 L of activated carbon having an average particle diameter of 1.3 mm and a specific gravity of 1.13 was used as the carrier 5. Others were treated under the same conditions as in Example 1, the operation starts after 20 days, 25 days, NO ₃ -N concentration, of 30 days the treated water 8
The NO ₂ -N concentrations were respectively 20 days later: 42 mg / L ·
11 mg / L, 25 days later: 30 mg / L · 21 mg /
L, 30 days later: 20 mg / L · 9 mg / L.

Tables 2 and 3 summarize the above.

[0040]

[Table 1]

[0041]

[Table 2]

[0042]

[Table 3]

[0043]

As described above, the fluidized-bed biological treatment apparatus (drainage treatment apparatus) of the present invention has a stirrer having a baffle plate fixed to the bottom of a tank and a stirring blade for discharging horizontally in an upper part of the tank. By providing the above, a flow state with a small shear force can be obtained, and the denitrification treatment in the wastewater can be performed without crushing the carrier weak in the shear force.

The fluidized-bed biological treatment apparatus (drainage treatment apparatus) of the present invention further comprises a sedimentation tank which communicates with the reaction tank at the lower part, thereby achieving excellent uniform dispersion of solid particles and exfoliation of cells. The flow pattern with high performance can be obtained, and the carrier can be returned to the reaction tank by the sedimentation tank and held by itself.
Even when a fine particle carrier having a relatively large specific gravity of less than m is used, there is an effect that denitrification treatment in wastewater can be performed efficiently.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a wastewater treatment device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a wastewater treatment device according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reaction tank 2 Baffle plate 3 Stirrer blade 4 Stirrer 5 Carrier 6 Raw water 7 Hydrogen donor 8 Treated water 9 Wire mesh 10 Partition plate 20 Treatment liquid

Claims (9)

[Claims] 1. A reactor for storing waste water containing nitric acid and nitrite nitrogen compounds, a stirrer provided in the reactor, and having a stirring blade for stirring the waste water and discharging the waste water to the outside, and a bottom of the reactor. A baffle plate that reflects the wastewater flowing from above and flows upward, and an anaerobic that is dispersed in the wastewater and denitrifies the nitric acid and nitrite nitrogen compounds contained in the wastewater. A wastewater treatment apparatus comprising a carrier holding bacteria. 2. The reactor according to claim 1, wherein the reactor has an overflow outlet for the denitrified wastewater.
The wastewater treatment device as described in the above. 3. The wastewater treatment apparatus according to claim 1, wherein the upstream overflow drainage port is connected to the reaction tank via a blocking means for the carrier. 4. A stirrer having a reaction tank for storing waste water containing nitric acid / nitrite nitrogen compound, a stirrer installed in the reaction tank, and a stirring blade for stirring the waste water and discharging the waste water to the outside, and a bottom part of the reaction tank. A baffle plate that reflects the wastewater flowing from above and flows upward, and an anaerobic that is dispersed in the wastewater and denitrifies the nitric acid and nitrite nitrogen compounds contained in the wastewater. A wastewater treatment apparatus comprising: a carrier holding bacteria; and a sedimentation tank separated by the reaction tank and a partition plate and communicated with the reaction tank at a lower part of the reaction tank. 5. The wastewater treatment apparatus according to claim 4, wherein a bottom surface of the settling tank is inclined toward the reaction tank. 6. The sedimentation tank has an overflow outlet for the denitrified wastewater.
Or the wastewater treatment apparatus according to 5. 7. The wastewater treatment according to claim 1, wherein the shape of the baffle plate is a truncated cone, a truncated spherical surface, or a truncated pyramid (trigonal or larger) having a small upper cross-sectional area. apparatus. 8. The wastewater treatment apparatus according to claim 1, wherein the discharge angle of the wastewater from the stirring blade is 0 to 30 ° below the horizontal direction. 9. The wastewater treatment apparatus according to claim 1, wherein a pH adjusting mechanism for adjusting the pH of the wastewater is added to the reaction tank.