JPS5938838B2 - Wastewater denitrification equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a denitrification device for removing nitrogen from wastewater by a biological method. There is a particular thing.

Among the treatment technologies applied for the purpose of removing organic matter from wastewater, the activated sludge method is expected to be the most effective in practical terms. There is a problem that nutrient salts such as nitrogen and phosphorus cannot be removed.

For example, under the activated sludge method, the nitrogen components contained in wastewater are reduced to NH3-
Up to N03 are synthesized.

However, since nitrogen components cannot be removed at this stage, if the secondary treated water is released into natural water systems while still containing these nutrients, it may cause abnormal phenomena such as red tide.

In this way, even if BOD is completely removed, as long as nitrogen and phosphorous components remain, organic matter will be synthesized again, which will undermine the significance of wastewater treatment.

From this point of view, in recent years wastewater denitrification technology has been developed using the ammonia stripping method and the addition of organic acids, methanol, etc. as nutrients, to denitrify the activated sludge through the physiological action of denitrifying bacteria living in the activated sludge. Nitrogen treatment methods have been developed, but they have not reached the level of practical use because they are expensive and require complicated processing steps.

For example, the latter method combines the physiological effects of nitrifying bacteria and denitrifying bacteria that are found wild in activated sludge, and basically consists of Process-1 as shown in Figure 7.

In the figure, A is a nitrification tank treated in an aerobic state, B is a denitrifying rosewood treated in an anaerobic state, D is a methanol supply tank, E is a re-aeration tank, F is a settling tank, and G is a return sludge.

In the nitrification process, nitrogen components in wastewater are synthesized to NO3 through the biological oxidation reaction of nitrifying bacteria (nitrate bacteria and nitrite bacteria).

This biological oxidation reaction is expressed by the following equation.

Nitrobacterium: Nitrobacter: NO2+-172
02-NO "...■In the denitrification process,
Anaerobic biological treatment, that is, the respiration reaction of denitrifying bacteria, reduces NO
, -・NO" converts the nitrogen components in nitrogen sludge (N2), but since most of these denitrifying bacteria are heterotrophic bacteria, they convert the nitrogen components from NO2 and NO3 generated in the nitrification process above into nitrogen sludge (N2). A nutrient source (as a hydrogen donor) is required for the decomposition to take place.

As shown in the figure, methanol (CH30H) is used as this nutrient source due to its price.

The respiratory reaction is as follows: 1st stage: 6NOi+2CH30H → 6NO, +2C02+4H, 20...■2nd stage:
6 NO? +3CH30H → N2+7H20+60 "......It is expressed by the formula of ■, but in reality, 25 to 30 of methanol
Since the methanol is consumed by cell growth of the denitrifying bacteria, the amount of methanol required is an amount larger than that calculated from the above reaction formula.

Incidentally, the required amount of methanol is: Cw=2.47NO+ 1.53N 1 +0.87
It is DO.

In this way, conventional denitrification methods use a large amount of methanol, which increases costs.Moreover, the denitrification effect of the single-stage treatment shown in the figure is extremely small, making it economically unviable within the practical range. Therefore, it is not possible to ensure the denitrification effect and denitrification effect.

Research has also begun on a method of using part of the raw water instead of methanol to turn the organic matter contained in the raw water into a nutrient source for denitrification; Not only the nitrogen components that were not present, but also the nitrogen components contained in the raw water diverted to the denitrification process are discharged unnitrified and undenitrified, so there was a fateful limit to the nitrogen removal rate.

Of course, in order to improve the nitrogen removal rate, it is possible to alternately repeat the nitrification process (aerobic reaction) and the denitrification process (anaerobic reaction) in multiple stages as shown in Figure 8. In order for sludge to form, it is necessary that there be an appropriate nutrient source and return sludge G generated from the nutrient source.On the other hand, the 8.0. Since D decreases as both processes are repeated, this method eventually no longer holds true.

In view of this current situation, the present invention improves economic efficiency by diverting a portion of raw water and using the organic matter contained in the raw water as a nutrient source for denitrification, and by omitting equipment such as a settling tank. At the same time, since there is no return sludge process, the nitrification process and denitrification process can be repeated in any number of stages, resulting in a high treatment effect. By using a string-like contact material, B,
An apparatus for removing O, D and nitrogen components,
an aeration type nitrification tank A in which the string-like contact material is installed;
A plurality of denitrifying rosewood B are arranged alternately, and each of the denitrifying rosewood B is configured to be supplied with a part of the raw water as a nutrient source for the denitrifying bacteria. It is characterized by a structure in which reactions and anaerobic reactions are performed alternately and consecutively.

Embodiments of the present invention will be described below based on the drawings.

1 to 4 show a denitrification device according to the present invention,
Reference numeral 1 denotes a tank body with an open top, and the tank body 1 is divided by a plurality of first partition plates 2a and second partition plates 2b, and the upper ends of each of the first partition plates 2a and second partition plates 2b are By airtightly covering the space between the sections with the lid body 3, nitrification tank A, which controls an aerobic reaction, and denitrification rosewood B, which controls an anaerobic reaction, are formed alternately.

These nitrification tanks A and denitrification rosewood B are each formed in an arbitrary plural number, but the denitrification rosewood is installed for each nitrification tank An so that the nitrification tank B is located at the most upstream and the most downstream. It is assumed that n-1 pieces of B are formed.

The most upstream nitrification tank AK is connected to a raw water inlet passage 4, and the most downstream nitrification tank A is connected to a treated water output passage 5. Each denitrification rosewood B has a first partition. An inflow path 6 is formed at the bottom of the plate 2a, and an outflow path 7 is formed at the top of the second partition plate 2b.

A raw water supply channel 8 branched from the raw water supply channel 4 is connected to the lower part of each denitrifying rosewood B, and a part of the raw water is separated and supplied to each of these various Bs. .

9 is an aeration pipe inserted in the lower side of each nitrification tank A, which drives the blower B1 to process the inside of the nitrification tank A by the air lift action of the air diffused from the limb pipe 9 or pure oxygen. The water is configured to swirl as shown in FIGS. 2 and 3.

In addition, a similar air diffuser 10 is placed on the lower side of each denitrifying rosewood B.
・ is installed, and by sucking the gas on the water surface in each tank B with blower B2 and diffusing it into tank B, the treated water in denitrification tank B becomes as shown in Figure 4. rotate.

Inside the nitrification tank A and the denitrification tank B, a plurality of rectangular frames 11 and 12 are arranged parallel to each other at small intervals, and each of these frames 11 and 12 contains nitrifying bacteria,
A string-like contact made from a fibrous string-like base fabric with countless fiber gaps and countless league-like piles planted on its outer surface so that activated sludge bacteria such as denitrifying bacteria can easily colonize and multiply. Material C is stretched over the sludge, and the structure is such that an aerobic reaction and an anaerobic reaction can be carried out without requiring return sludge.

For example, in the most upstream nitrification tank A, a plurality of these string-like contact materials C are stretched parallel to each other as shown in FIG. 2, and in other nitrification tanks A, as shown in FIG. At the same time, the mesh of the grid is made finer as it reaches the downstream tank A, so that the upstream tank A is sparsely connected to the downstream tank A.
Arrange them so that they are reasonably dense.

This is because the concentration of BOD components in the treated water is higher as it goes upstream.
The growth of purification microorganisms is remarkable, and the amount of activated sludge increases.
On the downstream side, on the other hand, the concentration of BOD components is low and the amount of activated sludge is small, so consideration was given to avoid any inconvenience caused by this.

The string-like contact materials C in the denitrification tank B are also arranged in a grid pattern, as illustrated in FIG.

This contact material C may also be arranged densely as it reaches the tank B on the downstream side, as in the case of the nitrification tank.

5 and 6 show an example of a string-like contact material C, which is attached to one side of a string-like base fabric 13 knitted with vinylene chloride (Saran) or other highly corrosion-resistant hydrophilic fibers. The loop-shaped pile 1 is made by weaving vinylene chloride (Saran) into a loop-shaped pile 14, and twisting the string-shaped base fabric 13 so that its cross-sectional shape is circular.
4 are planted radially from the outer peripheral surface of the string-like base fabric 13 twisted into a cylindrical shape.

This contact material C has many fiber gaps, so nitrifying bacteria,
Denitrifying bacteria, other fungi, protozoa, and other microorganisms easily adhere to the contact material C, forming a thick porous sludge layer, and the loop-shaped pile 14 and the entire contact material C oscillate according to the water flow. Therefore, it does not block the treated water,
It is possible to create an environment suitable for the survival of these microorganisms, and there is no need for return sludge.

Next, the effects of the above configuration will be described.

The raw water sent to the most upstream nitrification tank A comes into contact with the string-like contact material C under aerobic conditions, and various active substances living in the porous sludge layer settle and multiply on the contact material C. The water is purified by microorganisms such as sludge bacteria, ROD in the water is removed, and N02-N, N02-N, etc. are accumulated in the water.

That is, BOD in raw water is oxidized and decomposed by aerobic microorganisms such as oxidizing bacteria, and NH3-N is converted from organic nitrogen by catabolic metabolism of NH3-N in raw water and activated sludge bacteria.
is produced by nitrifying bacteria (nitrite bacteria and nitrate bacteria).
Oxidized to N, No3-N.

In this nitrification process, nitrite bacteria (Ni trosomo
The details of the biological oxidation reaction of nitrate bacteria (Nas) and nitrate bacteria (N1trobacter') were previously described as equation 2.0.

The treated water that has been nitrified in the above process flows into the next denitrifying rosewood B, where it is placed under anaerobic conditions with almost no dissolved oxygen, and the string-like contact between the tank B and N02-N and N03-N in the treated water are converted to N2 by utilizing nitrate respiration or nitrite respiration of denitrifying bacteria in the sludge layer that has settled around material C8.
Reduce to dregs.

Denitrifying bacteria are facultative anaerobic bacteria that can grow in both aerobic and anaerobic conditions, and in anaerobic conditions they breathe NO2 or NO3 as hydrogen acceptors instead of molecular oxygen.

This respiration reaction is expressed by the equation A part of the water is diverted and supplied to the denitrifying rosewood B, and the organic matter in the raw water is used as a hydrogen donor. N2)→N2+2H〇-+4H
This will be expressed by Equation 20.

Among these formulas, N2 is given from a hydrogen donor (organic matter in the diversion raw water) via the respiratory enzyme system within the denitrifying bacteria.

In addition, since the string-like contact material C is installed in the nitrification tank A and the denitrification tank B in these nitrification and denitrification processes, nitrifying bacteria and denitrifying bacteria can easily colonize and multiply, and the activated sludge can It is fixed to the string-like contact material C, and the contact area with the treated water is extremely large, so the reaction due to contact is active and sufficient, and there is no need for return sludge.

Through the above denitrification process, a part of the nitrogen components in the treated water are removed as nitrogen residue N2.

However, the process up to this point (first stage process) is not much different from the treatment effect of the previous denitrification method that adds methanol, and can remove at most about 50% of the nitrogen components contained in the raw water. It's nothing more than that.

Therefore, in the present invention, similar nitrification steps and denitrification steps are alternately repeated in multiple stages as described below.

That is, the remaining nitrogen components that were not removed in the denitrifying rosewood B in the first step described above flow out to the nitrification tank A in the second step.

Also. BOD in the raw water diverted to the denitrifying rosewood B is hardly oxidized or decomposed under anaerobic conditions, so it flows out to the next nitrification tank A together with the remaining nitrogen components mentioned above without being nitrified.

In the nitrification tank A of this second stage process, aerobic bacteria (BOD oxidizing bacteria, nitrifying bacteria) grow using the above BOD as a nutrient source, under aerobic conditions as in the case of the first stage process 1-1. Below, BOD is oxidized, decomposed, and nitrified, as well as a small amount of unnitrified nitrogen components contained in the diverted raw water are nitrified.

Then, the treated water that has had BOD removed in this tank A and that contains N02-N and N03-N due to nitrification flows into the next denitrifying rosewood B, and is sent to the denitrifying rosewood B, which is the first stage of the denitrifying process. Similarly, denitrification is performed using organic matter in the raw water as a hydrogen donor (nutrient source).

This second stage process also uses the string-like contact material C, so there is no need for return sludge.

In this way, since no sludge is returned, it is possible to alternately repeat the nitrification process and the denitrification process as many times as necessary, and by repeating these steps in the third and fourth stages, the treated water The concentration of nitrogen components gradually decreases, and denitrification is finally carried out to below the permissible concentration.

In the above-mentioned embodiment, the gas containing carbon residue generated at the top of each denitrified rosewood B is passed through the diffuser pipe 10 using the blower B2.
The water to be treated in each tank B is configured to rotate by dispersing air from the aeration pipe 1o and the blower B2.
It goes without saying that instead of using a water wheel or a pump, the water to be treated in each tank B may be rotated.

As described above in detail based on the examples, according to the present invention, a string-like contact material having numerous loop-shaped piles planted on the outer surface is installed in the nitrification tank and the denitrification tank that are arranged alternately. This ensures that nitrifying bacteria and denitrifying bacteria colonize and proliferate on these string-like contact materials, and that activated sludge is fixed.In other words, the loop-shaped piles hold the attached sludge like reinforcing bars in reinforced concrete. Because it is firmly held, the adhered sludge does not fall off easily due to water flow, and the aerobic and anaerobic reactions by these bacteria occur alternately and efficiently.
These reactions can be carried out in multiple stages while eliminating the need for sedimentation separation or return of sludge.

Therefore, equipment such as settling tanks in the activated sludge treatment method is omitted, and organic matter in the raw water of the diversion l- is used as a nutrient source (hydrogen donor) for denitrification to be supplied to each denitrifying rosewood. By eliminating the need for chemicals such as methanol, it is possible to achieve a high treatment effect (denitrogenization) by repeating nitrification and denitrification in multiple stages while ensuring sufficient economic efficiency.

In particular, when the string-like contact material is formed from a string-like base fabric twisted into a cylindrical shape and loop-shaped piles radially planted on the outer peripheral surface of the string-like base fabric, the fiber gaps of the string-like base fabric itself are In addition to the fiber gaps between the loop piles, the cylindrical hollow part of the string-like base fabric is also used for the colonization of denitrifying bacteria, etc., and these bacteria can colonize and multiply better, improving the treatment effect. It is.

[Brief explanation of the drawing]

The drawings show an embodiment of the denitrification apparatus according to the present invention, in which FIG. 1 is a schematic longitudinal sectional side view of the whole, FIG. 2 is a sectional view taken along the line ■-■ in FIG. 1, and FIG. 1ll-1 line sectional view, FIG. 4 is a sectional view taken along IV-IV line in FIG. 1, FIG. 5 is a side view of the string-like contact material, FIG. 6 is a plan view of the string-like contact material, FIG. FIG. 8 is a flow sheet for explaining a conventional example. A: Nitrification tank, B: Denitrifying rosewood, C: String-like contact material.

Claims (1)

[Claims] 1. Removal of B, O, D and nitrogen components in wastewater by using a string-like contact material having countless loop-shaped piles on the outer surface and activated sludge settled around the string-like contact material. An aeration type nitrification tank A in which the above-mentioned string-like contact material is installed.
and a plurality of denitrifying rosewood B are arranged alternately, and
Each denitrifying rosewood B is configured so that a portion of the raw water is divided and supplied as a nutrient source for denitrifying bacteria, so that aerobic reactions and anaerobic reactions are performed alternately and continuously. A wastewater denitrification device characterized by: 2. The string-like contact material is made of a string-like base fabric that is knitted into stockinette and twisted into a cylindrical shape, and a loop-like pile that is radially knitted around the outer periphery of the string-like base fabric. The wastewater denitrification device according to item 1.