JP2609195B2 - Organic wastewater purification method and apparatus - 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 and a purification apparatus for biologically nitrifying and denitrifying organic sewage containing ammoniacal nitrogen to a high degree.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 3, two treatment tanks each having a fixed immersion filter bed filled with a filter medium of granular minerals such as anthracite are used, and a first treatment tank is provided with a denitrification filter medium. Bacteria are retained to form a denitrification filter bed 21. In the second treatment tank, nitrifying bacteria are retained in a filter medium to form a nitrification filter bed 22, and these denitrification filter beds 21 and nitrification filter beds 22 are arranged in series. Then, the denitrified water obtained by flowing raw water from the raw water supply pipe 20 into the first denitrification filter bed 21 and passing it downflow is passed through the circulation pipe 32 to the nitrification filter of the second processing tank. While flowing into the bed 22 from above and passing water downward, air is blown from the air diffuser 23 below the filter bed 22 to perform aerobic nitrification, and the effluent (referred to as nitrification liquid) is once treated. After being stored in the water tank 24, it is circulated to the denitrification filter bed 21 by the pump 31.
Biological nitrification denitrification processes using a base immersion fixed filter are known.

However, this conventional technique has the following drawbacks, and there is an urgent need to develop a more excellent technique. Organic wastewater containing SS flows into the denitrification filter bed 21, but clogging of the filter bed progresses quickly, and a settling basin is provided first to reduce the SS load, but the filter bed is washed more frequently. It must be made. As a result, the consumption of washing water and the generation of washing wastewater are large. There is an inconvenience that the denitrification filter bed 21 and the nitrification filter bed 22 must be washed separately. In addition, the amount of generated washing wastewater increases. Since the nitrification reaction rate and the denitrification reaction rate are low, the reaction tank is large, and the construction cost and installation space are increased. The removal rate of COD and chromaticity is extremely low. For this reason, there is a demand for a compact apparatus capable of more efficient and stable nitrification denitrification and removing COD and chromaticity.

[0004]

An object of the present invention is to provide a new technique capable of solving the above-mentioned disadvantages. 1) SS, BOD, nitrification denitrification, CO
D, enabling chromaticity removal. 2) Reduce the filter bed blockage and significantly reduce the frequency of washing the filter bed. 3) The nitrification and denitrification rates are significantly improved. 4) Eliminate the need for an initial settling basin. It is an object to provide a compact device having the above functions.

[0005]

The above object is achieved by the invention of an upflow type biological treatment apparatus described below. That is, 1) sewage containing ammoniacal nitrogen is passed through fixed bed A filled with granular material having a three-dimensional network structure in an upward flow, thereby biologically denitrifying and removing SS contained in sewage. After that, fixed bed B filled with granular activated carbon provided in one tank
And passed through up-flow or down-flow under conditions of aerobic performs biological nitrification and COD removal, that allowed to circulate a portion of the effluent from the fixed bed B in the fixed bed A A method for purifying organic wastewater, comprising:

[0006] 2) A fixed bed A filled with granular material having a three-dimensional network structure, in which sewage containing ammoniacal nitrogen is passed in an upward flow to perform biological denitrification and remove SS. And a fixed bed B filled with granular activated carbon for carrying out biological nitrification and COD removal by flowing the effluent from the fixed bed A provided in the same apparatus in an upward flow under aerobic conditions. Organic sewage having a circulation path for circulating a part of the effluent from the fixed bed B to the fixed bed A, and an empty washing member provided below the fixed bed A. Purification device.

[0007] Preferably, 3) a single tank is filled with particulate matter having a three-dimensional network structure on the upstream side through a partition wall, and is subjected to biological denitrification and contamination.
A fixed bed A for removing SS contained in water, a fixed bed B filled with granular activated carbon on the downstream side and provided with an oxygen-containing gas diffusing member for biological nitrification and COD removal are arranged, and ammonia nitrogen is removed. After passing the sewage containing water through the fixed bed A in the upward flow , it is configured to pass through the fixed bed B in the downward flow through the partition wall, and a part of the effluent from the fixed bed B is sent to the fixed bed A. This is an organic sewage purification apparatus provided with means for circulating.

[0008] The configuration of a processing tank that enables SS, BOD, nitrification denitrification, COD, and chromaticity removal in a single processing tank includes a fixed bed A and a fixed bed B having different functions in a single processing tank. For example, fixed bed A is an area for biological denitrification and filtration of raw water SS, and fixed bed B is biological nitrification, advanced filtration of SS, and COD. This can be achieved by setting a region where chromaticity removal is performed. Here, the two types of fixed beds having different functions are set in the processing tank as follows: (1) A single processing tank is provided with vertically divided areas, and fixed beds A and B are respectively provided. And (2) a method in which a partition is provided in a single processing tank, areas divided into left and right are provided, for example, a fixed bed A is provided on the left side, and a fixed bed B is provided on the right side. obtain. In addition, in the case where the upper and lower partitioned areas of (1) are provided, the fixed bed A may be installed either above or below. However, the raw water is first passed through the fixed bed A to perform biological denitrification and filtration of the raw water SS. I do.

FIGS. 1 and 2 show a specific example of the present invention, and a specific configuration of the present invention will be described with reference to the drawings.
However, the present invention is not limited by the following description.

In the single treatment tank shown in FIG. 1, a porous member 6 is stretched in the middle of the treatment tank 1, the lower part is a fixed bed A, and the upper part is a fixed bed B. There may be a space between the fixed bed A and the fixed bed B that is not filled with the filter medium. The fixed bed A is filled with a granular material having a three-dimensional network structure, and biological denitrification and filtration of the raw water SS are performed. The fixed bed B is filled with granular activated carbon to perform biological nitrification, advanced filtration of SS, COD, and chromaticity removal.

A fine grid on which the granular activated carbon to be filled in the fixed bed B does not fall, above the porous member 6 defining the upper limit of the fixed bed A, and at the same plane position as the diffuser pipe 9 for supplying oxygen-containing gas to the fixed bed B. The supporting member 5 of the eye is stretched to be a supporting bed of the fixed bed B, and gas is supplied from the oxygen-containing gas supply source 12 through the diffuser 9 to sufficiently mix the granular activated carbon with the water to be treated in the fixed bed B. I do. A porous member 4 is stretched over the fixed bed B, or a layer of granular solid is provided to suppress the outflow of granular activated carbon and to allow clear treated water to flow out. .

Organic wastewater containing ammonium nitrogen such as sewage (hereinafter referred to as raw water) is passed through a raw water supply pipe 2 to a treatment tank 1.
And flows through the fixed bed A in the upward direction together with the nitrifying circulating water from the circulation path 3. At the lower part of the fixed floor A, an air washing member 10 for supplying air for air washing at the time of washing from a blower 13 is provided. At the top of the treatment tank 1, a drain pipe 7 for draining treated water and a circulation path 3 having a circulation pump 11 and a valve are provided. Fixed floor A and fixed floor B
Cleaning drain pipe 8 with a valve for discharging the cleaning drain
Is provided, and a porous member 17 is stretched to prevent the filter medium from flowing out therefrom. Further, the porous member 6, the upper porous member 4, which separates the fixed bed A and the fixed bed B, the support members 5 and 14 of the fixed bed A and the fixed bed B, and the porous member 17 of the drain discharge portion are nets, It is composed of a porous water-permeable member such as a perforated plate, grating, or grid. The above is the configuration of the processing tank of the present invention in the form divided into upper and lower sections.

In the single treatment tank shown in FIG. 2, granular activated carbon is provided on the downstream side with a fixed bed A consisting of a packed bed filled with granular material having a three-dimensional network structure on the upstream side (left side in the figure) and a partition wall C. A fixed bed B comprising a packed packed bed is provided. The fixed bed A is an area for performing biological denitrification of raw water and filtering SS, and the fixed bed B is an area for performing biological nitrification, advanced filtration of SS, COD, and chromaticity removal.

The raw water flows into the fixed bed A of the treatment tank 1 via the raw water supply pipe 2, passes through the fixed bed A as an upward flow, enters the fixed bed B from the overflow weir liquid 15 above it, and forms a downward flow. The water flows, enters the treated water outflow passage 16 at the lower part of the fixed bed B, rises and flows out of the treated water outflow pipe 7. A part of the treated water is converted into nitrification circulating water by the circulation pump
Into the raw water supply pipe 2 and flow into the fixed bed A together with the raw water

A porous member 6 for covering the upper portion of the fixed bed A to prevent the flowing out of the filter medium of the fixed bed A is provided on the upper portion of the treatment tank 1, and a lower portion of the fixed bed A and a lower portion of the fixed bed B are provided. Support floors 14 for preventing falling of the filled filter media.
And 5 are stretched. Of these, the support bed 5 stretched on the bottom of the fixed bed B is preferably a fine gravel layer because it supports granular activated carbon having a small particle size, and an air diffusion member for supplying an oxygen-containing gas installed below the fixed bed B. 9 is preferably installed in this gravel layer.

An oxygen-containing gas is supplied from the oxygen-containing gas supply source 12 into the fixed bed B from the air diffusion member 9 to disturb the granular activated carbon so as to be sufficiently mixed with the water to be treated. A porous member 4 is stretched over the fixed bed B to suppress the outflow of granular activated carbon and to allow clear treated water to flow out. An air washing member 10 for washing the air is provided below the fixed floor A, and supplies air from the blower 13 through the air diffusing member 10 when the fixed floor A is washed. The above is the configuration of the processing tank of the present invention in the form of being divided into right and left by the partition wall C.

The granular material having a three-dimensional network structure constituting the filter medium to be filled in the fixed bed A shown in FIG. 1 and FIG.
A three-dimensionally integrated mesh structure forms a granular material.
It is formed to have a continuous hole from the surface to the inside . This is only from a skeleton having a network structure from a foam produced by a known foaming method or the like.
To form a three-dimensional network structure . As the material of the granular material, a urethane resin or the like having moderate elasticity and strength of the material itself is preferable. Filter media, for example, three-dimensional porous body such as polyurethane foam
The target network structure is cut into a desired shape and size to form granules and used.

For example, the size is 10 to 30 mm, preferably 15 to 20 mm, and the shape can be square, spherical, or various other shapes, but square is preferred. The specific gravity of the material is usually preferably about 1.0 to 1.2. Also,
The porosity is preferably 90% or more. The pore diameter, that is, the pore diameter is desirably selected from the range of 0.1 to 6 mm, preferably 2 to 4 mm. Further, the number of holes per 1 cm length is preferably 5 to 20. Further, the granular activated carbon of the fixed bed B preferably has a particle size of 2 to 3 mm.

(Operation) The operation of the present invention will be described below with reference to FIGS. Raw water flows into the fixed bed A from the lower part of the treatment tank 1, and flows through the fixed bed A together with nitrification circulating water as upward flow. The filter medium made of granular material having a three-dimensional network structure filled in the fixed bed A has 15 meshes in the network structure.
Since a high concentration of denitrifying bacteria as high as 000 to 18000 mg / liter (actual value) is immobilized, the BOD in raw water
Nitrification circulating water NO _X -N (the nitrate nitrogen) N with
Reduce to _two gases. The reaction performed by this denitrifying bacterium is represented by the following equation. Note that aerobic denitrification may be performed by constantly discharging a small amount of air from the diffuser member 10, and the aerobic denitrification method is more preferable because the generated N ₂ gas is easily expelled.

Since the filter medium made of three-dimensional mesh-like granular material constituting the fixed bed A is also excellent in the filtration performance of the SS, the SS in the raw water is filtered and removed by passing through the fixed bed A, and the fixed bed is removed. The SS of the effluent from A usually drops below 5 mg / l. Incidentally, the polyurethane foam granules sterically reticulated granules, particularly and preferably used a polyurethane foam granules having a specific gravity of about 1.1 to 1.2, and N ₂ gas generated by denitrification As a result of the CO ₂ gas bubbles being captured by the network structure of the polyurethane foam, the apparent specific gravity becomes 1.0 or less, and the fixed bed A is formed at the lower part of the porous member 6 as a floating packed layer.

Thus, the fixed bed A from which most of the BOD and SS in the raw water and the NO _X -N in the circulating nitrification water were removed.
Effluent from the fixed bed B where the biological nitrification reaction proceeds
To enter. The granular activated carbon constituting the fixed bed B includes:
Since nitrifying bacteria are immobilized on the surface at a high concentration, NH ₃ -N in raw water is Nitrogen is nitrified at a high rate by the reaction, COD and chromaticity are also removed by the action of activated carbon and activated carbon-adhering organisms, SS is further removed by filtration, and becomes extremely clear treated water flowing out of the treated water outlet pipe 7 out of the system. I do. In the present invention, once the activated carbon is filled, no artificial regeneration is required and the activated carbon can be used permanently.

According to the present invention, as a filter medium to be filled in the fixed bed A, a filter medium consisting of a three-dimensional mesh-like granular material is specified and used. It is important that the fixed bed B of granular activated carbon is provided after such (specific) denitrification section A to promote nitrification and COD removal. In particular, the configuration is important. With this configuration, even if the dissolved oxygen concentration in the raw water or the circulating nitrification solution is high, the denitrification reaction proceeds in the fixed bed A without any problem. Because dissolved oxygen hardly diffuses into the filter medium made of a three-dimensional mesh-like granular solid, NO _x
With -N, the denitrification reaction proceeds effectively. Further, since the fixed bed A filled with the three-dimensional mesh-like granular material has a large SS capturing capacity, the fixed bed A is hardly clogged, and the fixed bed A needs to be washed less frequently.

Further, since almost all of the SS in the raw water is removed by filtration in the fixed bed A, the fixed bed B filled with the granular activated carbon is used.
Has the advantage that the clogging is negligibly small.
Since the fixed bed A is clogged with the operation, a method of cleaning the processing apparatus at that time will be described with reference to FIGS. First, a description will be given of a method of cleaning the apparatus in a case where the inside of the single processing tank shown in FIG. 1 is divided into upper and lower sections and a fixed bed A and a fixed bed B are provided respectively. When the purification process of the sewage proceeds and the accumulation of SS in the fixed bed A increases and the filtration pressure of the fixed bed A rises, the valve of the raw water supply pipe 2 is closed, the circulation pump is stopped, and the valve of the circulation path 3 is stopped. And drain tube 8
Is opened to drain the water to be treated on the fixed bed B. This operation sufficiently cleans the fixed bed B. However, if necessary, the valve of the raw water supply pipe 2 is opened, the valve of the drain pipe 8 is closed, the raw water is injected into the fixed bed B, and the drain operation is performed once again. repeat.

Next, the valve of the drain pipe 8 is closed and the blower 1
The valve from 3 to the empty washing member 10 is opened, and air is blown into the fixed bed A to perform empty washing. After flushing, close the valve to the flushing member 10,
The valve of the washing drainage pipe 18 is opened to discharge the water to be treated in the treatment tank 1, and after the discharge of the water to be treated is completed, the valve of the washing drainage pipe 18 is closed, and the valve of the raw water supply pipe 2 is opened to fix the fixed floor A. , The valve to the empty washing member 10 is opened again, and air is blown into the fixed bed A to perform the empty washing. By repeating this empty washing, the fixed bed A is sufficiently washed.

Next, a description will be given of a method of cleaning the apparatus in the case where the inside of the single processing tank shown in FIG. 2 is divided into right and left, and fixed beds A and B are provided respectively. In this case, for cleaning the fixed bed B, the valve of the raw water supply pipe 2 is closed, the circulation pump 11 is stopped, the valve of the circulation path 3 is closed, the supply of the raw water and the nitrification circulating water is stopped, Cleaning of the fixed bed B is sufficient by discharging water, but if necessary, the valve of the raw water supply pipe 2 is opened and raw water is injected into the fixed bed B,
The water to be treated in the fixed bed B is discharged by once again discharging the water to be treated from the washing drainage pipe 19.

Next, the valve from the blower 13 to the cleaning member 10 is opened, and air is blown into the fixed bed A to perform the cleaning. After the washing, the valve to the washing member 10 is closed, the valve of the washing drainage pipe 18 is opened to discharge the water to be treated in the treatment tank 1, and the valve of the raw water supply pipe 2 is opened to inject the raw water into the fixed bed A. Then, the valve to the empty washing member 10 is opened again, and air is blown into the fixed bed A to perform the empty washing. By repeating this empty washing, the fixed bed A is sufficiently washed. At this time, it is important to lower the water level on the fixed bed A side from the overflow weir 15 so that the washing water with high turbidity does not reach the fixed bed B of the granular activated carbon. The cleaning method of A is not limited to the above.

In any of the treatment tanks shown in FIGS. 1 and 2 which are divided into upper and lower parts and those divided into right and left parts by partition walls C, the lower part of the fixed bed A, more specifically, the empty washing member It is also possible to provide a baffle or an SS sedimentation section below the raw water supply section 2 below the raw water supply section 10 and remove the deposited SS by drain.

[0028]

EXAMPLE The raw water having the quality shown in Table 1 was passed through a coarse screen having an opening of 10 mm through a coarse screen, and the sewage was directly treated using a treatment apparatus of the present invention without previously providing a sedimentation tank. Demonstrated effect. Table 1 (Water quality of raw water) Water temperature: 15 to 18 ° C pH: 7.2 to 7.3 SS: 92 to 170 mg / liter BOD: 120 to 180 mg / liter COD: 38 to 46 mg / liter Total nitrogen: 29 to 36 mg / liter

Table 2 shows the processing conditions. Table 2 (Treatment conditions) Dimensions of treatment equipment: Dimensions 0.4 mx 0.8 m square tank with two tanks of 0.4 mx 0.4 m juxtaposed with a height 4.5 m of fixed floor A Height 2.0 m Height of fixed bed B 2.0 m Sewage flow rate: 5.76 m ³ / day Filtration speed: 36 m / day Air supply from diffuser: 15 Nm ³ / day Nitrification liquid circulation: 6 m ³ / day The filter medium to be filled in the packed layers A and B is a rectangular piece of polyurethane foam having a cell size of 13 × 25 × 25 mm and 13 cells.

Under the treatment conditions of Table 2, the sewage of water quality of Table 1 was reduced to 10
Continuous treatment for months. In the 30 days after the start of water passage, denitrifying bacteria and BOD-utilizing bacteria were sufficiently immobilized on the filter medium of the granular pieces of polyurethane foam. Therefore, a composite sample was collected once every day except Saturday and Sunday for 24 hours from the 31st day. (soil,
No sampling on the day) and water quality analysis was performed. Table 3 shows the results. Table 3 (Water quality) pH: 6.8 to 7.0 SS: 2.0 to 4.3 mg / liter BOD: 2 to 4 mg / liter COD: 3.8 to 4.7 mg / liter Total nitrogen : 6.1 to 8.6 mg / L Chromaticity: 5 or less As apparent from Table 3, SS, BOD, COD, T-
N, clear water with extremely low chromaticity was obtained.

The frequency of cleaning the fixed bed A is 1 to 3 to 4 days.
The filtration can be repeated for a very long time. (The conventional apparatus of FIG. 3 requires cleaning once a day.) The cleaning of the activated carbon fixed bed B was sufficient about once a month.

[0032]

According to the present invention, the following effects can be obtained by treating organic wastewater. 1. There is no need to install a sedimentation basin, and sewage with a high SS can be directly treated, so that the size can be reduced. 2. Clogging of the filter bed is remarkably reduced, and the frequency of filter bed cleaning is drastically reduced. Therefore, maintenance is easy and the amount of generated washing wastewater is small. 3. The denitrifying bacteria were fixed at a high concentration inside the filter medium consisting of three-dimensional mesh-like granular materials, and the nitrifying bacteria were fixed at a high concentration on the surface of the granular activated carbon. 3 to 4 times larger. In addition, since COD decomposing bacteria grow on the surface of activated carbon, COD can be removed for a long time without regenerating activated carbon. Furthermore, chromaticity can be removed. 4. Since nitrification and denitrification, as well as removal of COD and chromaticity can be performed at high speed, the installation space for the apparatus is small, and the filter bed can be washed rationally.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of a biological nitrification and denitrification treatment tank of the present invention in a vertically partitioned manner.

FIG. 2 is a schematic view showing an example of a biological nitrification and denitrification treatment tank of the present invention in a mode of being divided into right and left by a partition C.

FIG. 3 is a schematic view showing a typical example of a conventional biological nitrification denitrification treatment apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Treatment tank 2 Raw water supply pipe 3 Circulation path 4 Porous member 5 Support member 6 Porous member 7 Drain pipe 9 Air diffuser member 10 Empty washing member 11 Circulation pump 12 Oxygen-containing gas supply source 13 Blower 14 Support member 15 Overflow weir Reference Signs List 16 treated water outflow passage 17 porous member 18 washing drainage pipe 19 washing drainage pipe 20 raw water 21 denitrification filter bed 22 nitrification filter bed 23 diffuser pipe 24 treatment water tank 25 washing water supply pipe 26 washing water supply pipe 27 gas supply pipe 28 washing drainage Pipe 29 Cleaning drainage pipe 30 Pump 31 Pump 32 Circulation pipe 33 Circulation pipe 34 Circulation pipe A Fixed floor B Fixed floor C Partition wall

Claims (3)

(57) [Claims] 1. A sewage containing ammoniacal nitrogen is passed through a fixed bed A filled with granular material having a three-dimensional network structure in an upward flow to biologically denitrify and remove SS contained in the sewage.
After removal of water , water is passed through fixed bed B filled with granular activated carbon provided in one tank under an aerobic condition in an upward flow or a downward flow to perform biological nitrification and COD removal, The fixed floor B
A method for purifying organic sewage, comprising circulating a part of effluent from a fixed bed A. 2. A fixed bed A filled with granular material having a three-dimensional network structure, which performs a biological denitrification and an action of removing SS by passing wastewater containing ammonia nitrogen in an upward flow. , The effluent from the fixed bed A provided in the same apparatus is passed in an upward flow under aerobic conditions, and the biological nitrification and C
It has a fixed bed B filled with granular activated carbon for OD removal,
An organic sewage purification apparatus having a circulation path for circulating a part of the effluent from the fixed bed B to the fixed bed A, and having an empty washing member provided below the fixed bed A. 3. In a single tank, upstream through a partition,
A fixed bed A that is filled with granular material having a three-dimensional network structure and biologically denitrifies and removes SS contained in sewage, and is equipped with a granular activated carbon filled downstream and an oxygen-containing gas diffusing member. Fixed bed B which performs selective nitrification and COD removal,
After passing the sewage containing ammoniacal nitrogen through the fixed bed A in the upward flow , it is configured to pass through the fixed bed B in the downward flow past the partition wall, and a part of the effluent from the fixed bed B is An organic sewage purification apparatus comprising a means for circulating the fixed bed A.