JP2005046736A - Wastewater treating system and wastewater treating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wastewater treating technique, which makes it possible to carry out treatments of organic matter removal, nitrification, and denitrification certainly on wastewater containing a large quantity of oil, paste, a surfactant, or the like, and to reduce waste sludge produced at a wastewater processing facility. <P>SOLUTION: The wastewater treating system 1A comprises a first aerobic treating tank 30 in which original wastewater 4 is treated aerobically, a water supply means 26 which supplies wastewater 35 treated aerobically in the primary aerobic treating tank 30 and containing at least a nitrogen compound and a hydrogen donor, wastewater treating units 2(a), 2(b), 2(c), 2(d), etc., each provided with a container into which the wastewater 35 is directly fed by the water supply means 26 and which is partially or entirely water permeable, and is made of an immobilizing bed material capable of immobilizing aerobic bacteria and anaerobic bacteria, and a secondary aerobic treating tank 1 holding wastewater 7 in which wastewater treating units 2(a), 2(b), 2(c), 2(d), etc., are dipped. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is used in biological wastewater treatment, and in particular, wastewater treatment equipment for removing organic matter and nitrogen from wastewater containing a large amount of oil, surfactant, glue, etc., and wastewater treatment using the wastewater treatment equipment Regarding the method.

  Since dyeing factories use a large amount of urea, the waste water often contains a large amount of organic nitrogen (such as urea). Conventionally, these organic nitrogens were converted into ammonia and then removed physicochemically by a chlorine injection method. However, while the use of chlorine, which is a harmful substance, is regarded as a problem, the biological treatment method has been reviewed in place of the chlorine injection method. In the above-described biological treatment method, urea-derived organic nitrogen is produced by injecting oxygen-containing gas (such as air) into the waste water to oxidatively decompose the oxide. Nitric acid or nitrous acid) is converted from oxidized nitrogen to nitrogen gas by so-called anaerobic treatment in which wastewater is exposed to an atmosphere in which oxygen is blocked. As described above, processing of two or more steps is usually required. For this reason, most factories that exclusively perform aerobic biological treatment require additional anaerobic equipment to remove nitrogen. In addition, dyeing wastewater contains a large amount of oily components such as turpens, paste components such as polyvinyl alcohol, sodium alginate, carboxymethylcellulose (CMC), and surfactants, and these are used for biological treatment. It is a big burden. Therefore, although the dyeing specific components are removed by the coagulation sedimentation method or the pressure flotation method, a large amount of excess sludge is generated at that time.

  As described above, in order to remove organic matter and nitrogen from wastewater containing a large amount of oil, glue, and surfactant, oil, glue, and surfactant by the coagulation sedimentation method and pressure flotation method are used. Etc. and biological treatment that combines aerobic treatment and anaerobic treatment must be carried out. For this purpose, an increase in the installation space of the wastewater treatment facility and an economic burden are imposed. Moreover, since a large amount of excess sludge is generated in the above-described treatment method, industrial waste treatment becomes a big problem.

By the way, the present inventors have developed a technique for removing nitrogen compounds contained in waste water by nitrification and denitrification treatment, and disclosed in Patent Document 1 below. Such a waste water treatment apparatus is shown in FIG. The illustrated waste water treatment apparatus includes a waste water treatment unit 2 (2 (a), 2 (b), 2 (c)) and an aerobic treatment tank 3A in which the waste water treatment unit 2 is immersed and disposed in the waste water 7. Yes. The waste water treatment unit 2 is composed of a container body that has a fixed bed material that is water-permeable and can fix aerobic bacteria and anaerobic bacteria. The raw waste water 4 sent from the water pump 6 through the water supply line 5 is supplied to the container internal space 23. At the bottom of the aerobic treatment tank 3A, an air diffuser 10 for aeration of the oxygen-containing gas 8 from the compressor 9 is provided. According to this waste water treatment apparatus, waste water 11 from which organic substances and nitrogen have been removed can be obtained by nitrifying and denitrifying the waste water with the waste water treatment unit 2. Almost no excess sludge is generated.
JP, 2002-331298, A However, if oil content, paste content, surfactant, etc. are contained much like the above-mentioned dyeing drainage, oil content etc. will adhere to the fixed floor material of the container of drainage processing unit 2. It becomes clogged and nitrifying bacteria cannot live. For this reason, the function of turning nitrification and denitrification may not be exhibited.

  The present invention has been made in view of the above problems, and even for wastewater containing a large amount of oil, paste, surfactant, etc. that cannot be treated only with an existing aerobic treatment tank, organic matter removal, The purpose is to provide wastewater treatment technology that can reliably perform nitrification and denitrification treatment, and reduce excess sludge generated from wastewater treatment facilities.

  In order to achieve the above object, a wastewater treatment apparatus according to the present invention includes a primary aerobic treatment tank for aerobic treatment of raw wastewater, and aerobic treatment in the primary aerobic treatment tank to provide at least a nitrogen compound and hydrogen. A water supply means for supplying wastewater containing the body, and a container body to which the wastewater supplied by the water supply means is directly supplied, and a part or the whole of the container body is water-permeable, and aerobic bacteria and anaerobic A waste water treatment unit composed of a fixed bed material capable of immobilizing bacteria and a secondary aerobic treatment tank in which the waste water treatment unit is immersed in the waste water in the tank are provided.

  Moreover, the wastewater treatment method according to the present invention includes a step of aerobic treatment of raw wastewater in a primary aerobic treatment tank, a part or the whole of which is freely permeable, and can fix aerobic bacteria and anaerobic bacteria. Of a wastewater treatment unit that has a container body made of a fixed bed material and is immersed in the wastewater in the secondary aerobic treatment tank, and is aerobically treated in the primary aerobic treatment tank in the container body. An aerobic bacterium is immobilized on the outer surface side of the fixed bed material of the waste water treatment unit, and a secondary aerobic treatment is performed by the aerobic bacterium. When the wastewater in the tank is nitrified and the nitrified wastewater passes through the fixed bed material and flows into the container body, it is immobilized on the inner surface side of the fixed bed material along with the fixation of the aerobic bacteria. Flows into the container due to anaerobic bacteria Drainage is a method to be denitrified.

  According to the present invention, the raw waste water containing a large amount of oil, glue, surfactant and the like is subjected to an aerobic treatment step by aeration of oxygen-containing gas in the primary aerobic treatment tank, whereby oil, glue, Minerals, surfactants, etc. are reduced in molecular weight by decomposition and solubilized or dissolved in wastewater, or floated and removed. Therefore, even if the wastewater aerobically treated in the primary aerobic treatment tank is fed to the wastewater treatment unit by the water feeding means, the fixed floor material of the wastewater treatment unit is not adversely affected. In addition, nitrogen compounds and hydrogen donors remain in the wastewater that has been aerobically treated in the primary aerobic treatment tank, and since this wastewater is supplied directly into the container of the wastewater treatment unit, the wastewater is nitrified. And denitrification treatment can be performed efficiently. Moreover, organic substances are also efficiently removed in the entire primary aerobic treatment tank and the secondary aerobic treatment tank. And since only a simple primary aerobic treatment tank and water supply means are provided for the combined configuration of the existing aerobic treatment tank (secondary aerobic treatment tank) and the wastewater treatment unit, installation cost and installation space are small. That's it. Furthermore, since the activated sludge in the aerobic treatment tank is fixed to the fixed bed material, the generation of excess sludge is extremely reduced, and the amount of industrial waste can be reduced.

The best embodiment of the present invention will be described with reference to the drawings. The embodiment described below is merely an example embodying the present invention, and does not limit the technical scope of the present invention. FIG. 1 is a schematic configuration diagram showing a waste water treatment apparatus according to an embodiment of the present invention.
In the figure, the wastewater treatment apparatus 1A of the present embodiment is a primary aerobic that aerobically treats a water pump 33 that feeds the raw waste water 4 and the raw waste water 4 that is supplied by the water pump 33 via the water feed pipe 34. A treatment tank 30, a water feeding means 26 for feeding the waste water 35 aerobically treated in the primary aerobic treatment tank 30, and a plurality of waste water treatment units 2 (directly supplied with the waste water 35 fed by the water feeding means 26 ( 2 (a), 2 (b), 2 (c), 2 (d),...), And a secondary aerobic treatment tank 1 in which these waste water treatment units 2 are immersed in the waste water 7 in the tank. And. The primary aerobic treatment tank 30 and the secondary aerobic treatment tank 1 are formed by dividing the interior of the integrated tank 3 whose upper surface is opened by a partition wall 38, respectively.

  The tank wall 31 on the side of the primary aerobic treatment tank 30 of the integrated tank 3 is connected with a take-out conduit 40 for taking out the suspended matter 39 separated from the water and floating on the water surface. An extraction conduit 41 for discharging the treated water 11 is connected to the tank wall 37 on the secondary aerobic treatment tank 1 side of the integrated tank 3. In addition, an air diffuser 32 is provided at the bottom of the primary aerobic treatment tank 30, and an air diffuser 10 is provided at the bottom of the secondary aerobic treatment tank 1. A compressor 9 is connected to the air diffuser 32 and the air diffuser 10, and the oxygen-containing gas 8 is released from the air diffuser 32 and the air diffuser 10 by driving the compressor 9. The oxygen-containing gas 8 is not particularly limited as long as it contains oxygen. For example, safe and freely available air itself, or a nitrogen mixed gas with an increased oxygen concentration, or the like can be used. The water supply means 26 includes a water supply pump 6 for sending the drainage 35, a suction pipe 36 having one end opened at a lower position in the primary aerobic treatment tank 30 and the other end connected to a suction port of the water supply pump 6. , One end is connected to the discharge port of the water supply pump 6, and the other end is branched into a plurality of water supply pipes 5 that open directly into each waste water treatment unit 2.

  As shown in FIGS. 2 and 3, the waste water treatment unit 2 is configured based on a container frame 15 having a concave shape in front view and having an appropriate front-rear width. On both the front and rear surfaces of the container frame 15, in order from the side close to the container frame 15, a sheet packing 17 having a water passage opening 16, a holding frame 19 having a water passage opening 18, a water-permeable fixed floor material 20, and a passage. The holding frames 22 having the water openings 21 are overlapped and fixed with bolts 27 or the like. As a result, the container body 14 having the upper surface opened and having the container inner space 23 is completed. That is, in the waste water treatment unit 2, the fixed floor material 20 is used for a part of the container body 14.

In addition, the waste water treatment unit 2 used in the present invention can physically create a space portion surrounded by the fixed floor material 20, and the waste water 7 in the secondary aerobic treatment tank 1 converts the fixed floor material 20. It may be of a type that cannot move inside and outside the unit unless it passes through. The container body 14 of the waste water treatment unit 2 may be an open type as in this embodiment or a sealed type.
Examples of the fixed floor material 20 constituting the waste water treatment unit 2 include non-woven fabrics, knitted fabrics, or those processed into a sheet shape, but water can freely pass through, and aerobic bacteria and anaerobic bacteria. If it is the material which can fix | immobilize, it will not specifically limit. Although the fixed bed material 20 is also permeable to air, oxygen in the air is consumed by aerobic bacteria on the outer surface side of the fixed bed material, and therefore hardly enters the container body 14.

Then, the water treatment effect | action by the waste water treatment apparatus 1A of the above-mentioned structure is demonstrated.
The raw wastewater 4 to be treated by the wastewater treatment apparatus 1A is discharged from, for example, a dyeing factory and contains a large amount of dyeing-specific components such as oil, glue, and surfactant. Therefore, the raw wastewater 4 supplied to the first aerobic treatment tank 30 by driving the water pump 33 is aerobically treated with the oxygen-containing gas 8 from the diffuser pipe 32 to become the wastewater 35. At this time, oil, paste, surfactant, etc. in the raw waste water 4 are decomposed by aeration. If the oil content is too high to be decomposed, the oil component is separated from the drainage 35 and floats on the water surface. These floating substances 39 such as oil can be taken out of the first aerobic treatment tank 30 by providing a take-out conduit 40. Dyeing-specific components in the waste water 35 treated in this way are considerably reduced, but some of these remain as organic substances (hydrogen donors) and nitrogen compounds.

Then, the internal space of the container from the upper surface opening of each container body 14 of the wastewater treatment units 2 (a), 2 (b), 2 (c), 2 (d),. The drainage 35 is supplied into 23. Thus, when the drainage 35 is supplied directly into the container space 23 of the container body 14 in each wastewater treatment unit 2, the drainage 35 once permeates the fixed floor material 20 and flows out into the second aerobic treatment tank 1. . At this time, since the oil content in the waste water 35 is small, the fixed floor material 20 is not clogged. On the other hand, the contained oil or the like (hydrogen donor) is supplied directly into the container space 23 and contributes to the denitrification process described later. The fixed bed material 20 is surrounded by the waste water 7 in the secondary aerobic treatment tank 1 in which the amount of dissolved oxygen is increased by aeration from the air diffuser 10. Therefore, the outer surface side of the fixed bed material 20 becomes an aerobic bacteria immobilization area 24, and the organic nitrogen in the surrounding waste water 7 is ammonia nitrogen (see FIG. 5) by the aerobic bacteria immobilized on the aerobic bacteria immobilization area 24. 4 (NH _{3 in} FIG. 4), and further changes to oxidized nitrogen (NO _{x in} FIG. 4) (nitrification). At this time, most of the dissolved oxygen in the waste water 7 located around the aerobic bacteria immobilization area 24 or the outside thereof is consumed by the nitrification treatment by the aerobic bacteria. Therefore, the water that permeates through the fixed bed material 20 and flows into the container space 23 contains almost no dissolved oxygen. That is, as the aerobic bacteria are immobilized, the inner surface side of the fixed bed material 20 inevitably becomes the anaerobic bacteria immobilization area 25, and the anaerobic bacteria are immobilized in this area.

Then, when the waste water 7 after nitrification flows into the container space 23, the oxidized nitrogen in the waste water is decomposed by anaerobic bacteria in the anaerobic bacteria immobilization area 25 and nitrogen gas (N _{2 in} FIG. 4). ) And discharged outside the tank (denitrification). The denitrified water passes through the fixed bed material 20 from the inner space 23 of the container and flows out again to the second aerobic treatment tank 1. Thus, the water from which the organic matter and the nitrogen compound have been removed after finishing the nitrification treatment and the denitrification treatment is discharged out of the second aerobic treatment tank 1 from the extraction pipe 41 as the treated water 11.

Next, examples of the present invention will be described. Prior to this, a general aeration system is shown by a solid line in FIG. 5 as a comparative example for the embodiment. In the aeration system, the raw waste water 4 supplied from the water supply pipe 62 is subjected to aerobic treatment by air aeration in the aerobic treatment tank 61, and then discharged as treated water 11a through the settling tank 63. Yes. Since the treated water from the aerobic treatment tank 61 also flows out with sludge inhabited by aerobic bacteria, the sludge is separated by the settling tank 63 and returned to the aerobic treatment tank 61 via the return pipe 64. It has become. The size of the aerobic treatment tank 61 was 1.24 m in length, 0.66 m in width, and 1.26 m in height.
Next, a fixed bed system as another comparative example is shown by a solid line in FIG. This fixed bed system is actually configured by omitting the settling tank 63 and the return pipe 64 in FIG. 5 and mounting the waste water treatment unit 2 in the aerobic treatment tank 61, and discharges the treated water 11b. That is, this fixed bed system corresponds to a configuration in which the raw waste water 4 is supplied to the aerobic treatment tank 3A side through the water supply pipe 12 instead of the water supply pipe 5 in the waste water treatment apparatus of FIG.

The aerobic treatment tank 61 of the aeration system and the fixed bed system described above is filled with water, and the returned sludge (bacterial cell concentration (MLSS) = about 8000 to 10,000 ppm) of the dyeing factory is MLSS = 5000 ppm in these aerobic treatment tank 61 I put it in. Then, air aeration was performed for one day, and the dissolved oxygen concentration (DO) was maintained at 2 to 3 mg / L. Thereafter, the raw waste water 4 was supplied in an amount of residence time of 2 days, and continuous operation was performed. As the raw waste water 4, waste water discharged from the dyeing factory was used.
During operation, raw wastewater 4 and treated waters 11a and 11b are sampled, and the total nitrogen of each is measured with a nitrogen analyzer according to total nitrogen organic carbon form (catalytic oxidation-reduction method, manufactured by Shimadzu Corporation). It was measured by a copper / cadmium reduced N- (1-naphthyl) ethylenediamine spectrophotometric method specified in -K-0102.

The test results obtained in this manner are shown in FIG. In FIG. 7, the short broken line A is the total nitrogen (TN) concentration of the raw waste water 4, the long broken line B is the total nitrogen (TN) concentration of the treated water 11a obtained by the aeration system, and the solid line C is the treated water obtained by the fixed bed system. 11b Total nitrogen (TN) concentration, solid line D connected with black circles is oxidized nitrogen (NO _x ) concentration of treated water 11a obtained by the aeration system, solid line E connected with black squares is treated water obtained with the fixed bed system 11b is an oxide nitrogen (NO _X) concentration.
As is apparent from the graph of FIG. 7, it can be seen that almost no oxidized nitrogen (nitrate nitrogen: NO _x ) is generated by either the aeration system or the fixed bed system as the comparative example. This is because the nitrifying bacteria in the tank and the wastewater treatment unit 2 are inhibited by the oil contained in the raw wastewater 4 in a large amount, and in the worst case, the raw wastewater 4 is killed. By the way, throughout this experiment period, about 50 to 200 mg / L of ammonia nitrogen in the treated water has been detected.

Thereafter, in the aeration system of FIG. 5, the primary aerobic treatment tank 30 (shown by a one-dot chain line in the figure. The tank dimensions are 1.24 m long, 0.66 m wide, and height 1 in front of the aerobic treatment tank 61. The raw wastewater 4 is treated by the system equipped with .26m). First, the raw waste water 4 is supplied to the primary aerobic treatment tank 30 through the water supply pipe 34, and the waste water 35 obtained by the primary aeration (the air aeration amount is 50 L / min) for 8 hours is aerobic through the pipe 36. It supplied to the processing tank 61 and the secondary aeration was carried out. The residence time of the waste water in the aerobic treatment tank 61 is set to 2 days.
The result is shown in FIG. In FIG. 8, the white circle is the total nitrogen concentration of the raw waste water 4, the black circle (connected by the broken line L) is the total nitrogen concentration of the obtained treated water, and the black triangle is the ammonia concentration of the obtained treated water. , Black squares (connected by solid line M) indicate the oxidized nitrogen concentration of the treated water obtained.

In FIG. 8, the experiment period is divided into a period F (first day to 46th day) in which the wastewater treatment unit 2 is not used and a period I (from the 47th day) in which the wastewater treatment unit 2 is used. In addition, the total nitrogen (open circle) in the raw waste water 4 varies depending on the day.
First, in the period F in which the waste water treatment unit 2 is not used, since nitrifying bacteria are rarely settled from the start of operation until around the 10th day (period G), the nitrification reaction hardly occurs (oxidized nitrogen (black square)). A large amount of ammonia (black triangle). In about 10 days, the nitrifying bacteria grow to a certain level or more, and from the 10th day (period H), the nitrification reaction in the aerobic treatment tank 61 is accelerated so that the nitrogen compounds in the wastewater pass through the ammonia. (Black triangle is near 0 mg / L) It is oxidized nitrogen (black square). Such oxidized nitrogen is stably produced at about 150 mg / L. In addition, as a result of aeration in the primary aerobic treatment tank 30 in advance, the concentration of hexane extract in the treated water also decreased from 150 mg / L of the raw waste water 4 to 30 mg / L, and it was confirmed that the oil was removed. ing.

Next, the period I using the wastewater treatment unit 2 (from the 47th day after the start of operation) will be described. The fixed floor material 20 of the used wastewater treatment unit 2 is composed of, for example, a nonwoven fabric made of polyester fiber (manufactured by Japan Vilene Co., Ltd., trade name: MBT9, roughness basis weight = about 250 g / m ² ). The vertical and horizontal dimensions of the fixed floor material 20 are, for example, 75 cm × 51 cm.

The primary aerobic treatment tank 30 as shown in FIG. 6 is obtained by immersing the waste water treatment unit 2 in the aerobic treatment tank 61 used above and omitting the settling tank 63 and the return pipe 64. The fixed floor system to be used is configured. The raw waste water 4 was supplied to the primary aerobic treatment tank 30 of this fixed bed system (period J). Such a configuration corresponds to a configuration in which the wastewater 35 of the primary aerobic treatment tank 30 is switched from the water supply line 5 to the water supply line 12 and supplied into the secondary aerobic treatment tank 1 in the wastewater treatment apparatus 1A of FIG.
As shown in FIG. 8, at the beginning of period J, the nitrification reaction was reduced due to a decrease in air supply efficiency due to nitrifying bacteria adhering to the fixed bed material 20 of the wastewater treatment unit 2. Thereafter, nitrifying bacteria grew in the fixed bed material 20 to recover the nitrifying reaction, and about 140 mg / L of oxidized nitrogen (black squares) was generated. However, the difference between the total nitrogen concentration of the raw waste water 4 (open circles) and the total nitrogen concentration of the treated water 11b (black circles) was reduced. That is, it can be seen that an important denitrification reaction hardly occurs.

  Therefore, as an embodiment of the present invention, from the 68th day (period K) after the nitrification treatment is recovered as described above, the waste water from the primary aerobic treatment tank 30 is sent from the water supply line 36 in FIG. It switched to the water pipeline 5 and supplied in the waste water treatment unit 2. FIG. This corresponds to a configuration in which the wastewater 35 of the primary aerobic treatment tank 30 is switched from the water supply pipe 12 to the water supply pipe 5 and directly supplied into the container body 14 of the wastewater treatment unit 2 in the wastewater treatment apparatus 1A of FIG. To do. As a result, as shown in FIG. 8, the total nitrogen (black circle) of the treated water is reduced to about 130 mg / L, and a nitrogen removal rate of about 40% is obtained with respect to the total nitrogen (open circle) of the raw waste water 4. It was.

  With respect to the series of experiments shown in FIG. 8, organic carbon was also measured using the above-described nitrogen analyzer for all nitrogen organic carbon forms during the same experimental period. The measurement results are shown in FIG. In FIG. 9, the white circles indicate the organic carbon concentration of the raw waste water 4, and the black circles indicate the organic carbon concentration of the obtained treated water. As shown in Fig. 9, the organic carbon concentration of the treated water (black circle) has decreased to about 50 mg / L regardless of fluctuations in the organic carbon concentration of the raw wastewater (open circle), and it has been steady throughout the entire operation. Further, it can be seen that the organic substances are removed by aeration in the primary aerobic treatment tank 30 and the secondary aerobic treatment tank 1.

  In the above embodiments and examples, a part of the container body is composed of a fixed floor material, but the present invention is not limited thereto, for example, the entire container including the peripheral surface and the bottom part is freely permeable, And the waste water treatment unit etc. which consist of the container body comprised with the fixed bed material which can fix | similate an aerobic microbe and an anaerobic microbe may be sufficient. The shape of the container body is not limited to the bottomed square tube shape, and may be a bottomed round tube shape or a hollow sphere shape.

In addition, the water supply means of the present invention is not limited to the combined configuration of the suction pipe 36, the water supply pump 6, and the water supply pipe 5. For example, a weir (not shown) is provided on the partition wall 38 of the integrated tank 3 to overflow the drainage 35 of the primary aerobic treatment tank 30, and a water channel is provided that communicates the weir with the inside of the container body 14 of the wastewater treatment unit 2. By providing, the drainage 35 may be configured to flow directly into the container body 14.
Furthermore, in the above description, the primary aerobic treatment tank 30 and the secondary aerobic treatment tank 1 coexist in the integrated tank 3, but it is also possible to configure each of them as separate tanks.

It is a schematic block diagram which shows the waste water treatment equipment which concerns on one Embodiment of this invention. It is an assembly exploded view of the waste water treatment unit used for the waste water treatment apparatus. The said waste water treatment unit is shown, (a) is a front view, (b) is the sectional view on the AA line in (a), (c) is a top view. It is explanatory drawing which shows the change state of the nitrogen compound in the waste_water | drain which flows into the said waste_water | drain processing unit. It is a block block diagram which shows the aeration system which concerns on a comparative example. It is a block block diagram which shows the fixed floor system which concerns on another comparative example. It is a graph which shows the behavior of the nitrogen concentration of the raw wastewater supplied to each said comparative example system, and treated water. It is a graph which shows the behavior of the nitrogen concentration of the raw wastewater supplied to each said comparative example system and a present Example apparatus, and treated water. It is a graph which shows the behavior of the organic carbon density | concentration of the raw waste water supplied to each said comparative example system and a present Example apparatus, and a treated water. It is a schematic block diagram which shows an example of the conventional waste water treatment equipment.

Explanation of symbols

1A Wastewater treatment device 1 Secondary aerobic treatment tank 2 Wastewater treatment unit 4 Raw wastewater 5 Water supply pipe 6 Water supply pump 7 Drainage 8 Oxygen-containing gas 9 Compressor 10 Aeration pipe 11 Treated water 14 Container body 23 Inner space 24 Aerobic Bacteria immobilization area 25 Anaerobic bacteria immobilization area 26 Water supply means 30 Primary aerobic treatment tank 32 Aeration pipe 35 Drainage 36 Suction pipe

Claims (2)

A primary aerobic treatment tank for aerobic treatment of the raw waste water, a water supply means for aerobic treatment in the primary aerobic treatment tank to supply waste water containing at least a nitrogen compound and a hydrogen donor, and water supplied by the water supply means A wastewater treatment unit having a container body to which wastewater is directly supplied, a part or the whole of the container body being water-permeable, and made of a fixed floor material capable of immobilizing aerobic bacteria and anaerobic bacteria And a secondary aerobic treatment tank in which the wastewater treatment unit is immersed in the wastewater in the tank. A process of aerobic treatment of raw wastewater in a primary aerobic treatment tank, and a container body composed of a fixed bed material that is partially or entirely water-permeable and can immobilize aerobic bacteria and anaerobic bacteria. A wastewater treatment unit that is immersed in the wastewater in the secondary aerobic treatment tank and is aerobically treated in the primary aerobic treatment tank and contains at least a nitrogen compound and a hydrogen donor. The aerobic bacteria are immobilized on the outer surface side of the fixed floor material of the wastewater treatment unit, and the wastewater in the secondary aerobic treatment tank is nitrified by the aerobic bacteria. When the drained wastewater permeates the fixed bed material and flows into the container body, it flows into the container body due to the anaerobic bacteria immobilized on the inner surface side of the fixed bed material as the aerobic bacteria are immobilized. Wastewater treatment method in which wastewater to be denitrified