JPH0117437B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a wastewater treatment system, and in particular is used to remove nitrogen from organic wastewater, such as domestic wastewater and industrial wastewater, which contains organic matter (hereinafter referred to as BOD) that can be used by microorganisms and nitrogen compounds. and a wastewater treatment device using denitrifying bacteria. Wastewater containing BOD and nitrogen compounds is normally converted into ammonia nitrogen (hereinafter referred to as NH ₄ ⁺ -N) by nitrifying bacteria under aerobic conditions, that is, in the presence of oxygen, and nitrite nitrogen (hereinafter referred to as NO _{2 )} . ^- -N) and nitrate nitrogen (hereinafter referred to as NO ₃ ^- -N). Then, under anaerobic conditions, that is, in the absence of oxygen, NO ₂ ^{- -N} is reduced to nitrogen gas (hereinafter _referred to as N ₂ ) by denitrifying bacteria, and at the same time
BOD is decomposed. This is because denitrifying bacteria produce NO ₂ ^- -N and
NO ₃ ^{- -} Occurs because the oxygen in the N is used to decompose BOD. Nitrifying bacteria are active under aerobic conditions;
Inert under anaerobic conditions. Denitrifying bacteria are active under both aerobic and anaerobic conditions. Denitrifying bacteria are
It is a type of BOD oxidizing bacteria, and BOD oxidizing bacteria, except for denitrifying bacteria, are generally active under aerobic conditions and inactive under anaerobic conditions. In general, BOD oxidizing bacteria use dissolved oxygen in wastewater to oxidize BOD, and denitrifying bacteria exceptionally use oxygen in nitrogen compounds to oxidize BOD. Therefore, when treating wastewater using microorganisms, it is necessary to artificially create an aerobic atmosphere and an anaerobic atmosphere during the treatment process. For these reasons, conventional reaction tanks of this type of wastewater treatment equipment have been provided with a nitrification tank under aerobic conditions and a denitrification tank under anaerobic conditions. According to this device,
The wastewater first flows through the nitric acid tank and then through the denitrification tank. However, as mentioned later, in the nitrification reaction, the pH
decreases and PH increases in the denitrification reaction, so with such an apparatus, it is necessary to input a large amount of neutralizing agent. In particular, the rate of decrease in PH in the nitrification tank is greater than the rate of increase in PH in the denitrification tank, so
Large amounts of alkali were required. Furthermore, in the denitrification tank, in addition to adding acid, an organic carbon source such as methanol was required to activate the action of denitrifying bacteria. The first measure to reduce neutralizing agents and organic carbon sources is
A wastewater treatment device having a reaction tank as shown in the figure has been proposed. This reaction tank is composed of a circulation path through which waste water circulates. That is, the wastewater is introduced into an area with an anaerobic atmosphere (hereinafter referred to as the anaerobic zone) in the reaction tank, then into an area with an aerobic atmosphere (hereinafter referred to as the aerobic zone), and then again into the anaerobic zone. has been introduced. This will be explained with reference to FIG. The reaction tank 1 consists of a first reaction tank 1A and a second reaction tank 1B. The first reaction tank 1A is sealed except for three types of flow paths described later, and a stirrer 4 is installed in the center. The three types of flow paths are a wastewater supply section 3 that opens at the top of the first reaction tank 1A, and an untreated water connection that circulates incompletely treated wastewater (hereinafter referred to as untreated water) from the aerobic zone to the anaerobic zone. This is an untreated water communication port 11a that is connected to the channel 11b and the second reaction tank 1B at the bottom. In addition to the untreated water communication port 11a, an oxygen or oxygen-containing gas supply unit 6 is opened at the bottom of the second reaction tank 1B, an untreated water communication path 11b is opened at the top, and the open upper surface is treated with Water discharge part 12 is open. Untreated water connection route 11
A circulation pump 9 is provided in the middle of b. A dispersion plate 7 is provided above the oxygen or oxygen-containing gas supply section 6, and a tube 8 is disposed above the oxygen or oxygen-containing gas supply section 6 so as to face the top surface. Therefore, the flows of the waste water 2 and untreated water 10 are as follows. The waste water 2 containing BOD and nitrogen compounds is fed into the first reaction tank 1A via the waste water supply section 3. In addition to the waste water 2, untreated water 10 is supplied to the first reaction tank 1A via an untreated water communication path 11b.
is supplied. Since the untreated water 10 has passed through the aerobic zone, nitrogen compounds are mainly
NO ₂ ^- -N and NO ₃ ^- -N. First reaction tank 1A
No air 5 is blown into the zone, and an anaerobic zone is formed by the action of the waste water 2 and microorganisms. Therefore, in the first reaction tank 1A, NO ₂ ^- -N and NO ₃ ^- -N in the untreated water 10 and the waste water 2 are
However, due to the action of denitrifying bacteria, the BOD in the wastewater 2 is reduced to _N2 as an organic carbon source. Among the nitrogen compounds in the waste water 2, NH ₄ ⁺ -N hardly changes in the first reaction tank 1A, and the untreated water connection port 11
It is sent to the second reaction tank 1B via a. The second reaction tank 1B is supplied with air 5 via an oxygen or oxygen-containing gas supply section 6 and a dispersion section 7, forming an aerobic zone. Therefore, the second reaction tank 1B
At the same time, the remaining BOD is oxidized and removed, and NH ₄ ^- -N is oxidized by the action of nitrifying bacteria to become NO ₂ ^- -N and NO ₃ ^- -N. This NO ₂ ^- -
The untreated water 10 containing N and NO ₃ ^- -N is sent to the first reaction tank 1A as described above. On the other hand, the treated water 13 (which may partially contain untreated water 10) that has reached the upper surface of the second reaction tank 1B is discharged via the treated water drainage section 12. By adopting such reaction tank 1, the reaction liquid in the aerobic zone and the reaction liquid in the anaerobic zone are circulated and mixed, so the amount of organic carbon sources and neutralizing agents other than wastewater 2 added can be reduced to a small amount. It is possible to stop it. However, at the same time as the reaction solution is circulated, sludge in which microorganisms such as BOD oxidizing bacteria and nitrifying bacteria coexist also circulates between the anaerobic zone and the aerobic zone. Therefore, in this method, the nitrification activity and denitrification activity per sludge are lower than when the nitrification tank and denitrification tank are completely separated. Therefore, in order to reduce the amount of neutralizing agent and organic carbon source added and to prevent a decrease in nitrification activity and denitrification activity, it is necessary to separate nitrifying bacteria and denitrifying bacteria. As a countermeasure for this, the first reaction tank 1A
and the second reaction tank 1B are separated by a semipermeable membrane,
It is conceivable to move only low molecules and not microorganisms, but this is not suitable for practical use due to problems such as the strength of the semipermeable membrane and clogging. An object of the present invention is to provide a wastewater treatment device that can separate nitrifying bacteria from denitrifying bacteria and improve the efficiency of nitrification and denitrification by effectively promoting the adhesion and growth of microorganisms on solid surfaces. It is in. In order to achieve the above object, the present invention configures a reaction tank with a circulation path, provides two fixed beds in the path with solid surfaces on which microorganisms can attach and grow, and one path connecting both fixed beds has a BOD. and nitrogen compounds, and oxygen or oxygen-containing gas is supplied to the other routes, respectively. That is, the present invention provides a wastewater treatment device equipped with a reaction tank that uses microorganisms to remove nitrogen from wastewater containing organic matter and nitrogen compounds, in which the reaction tank is separated from a first chamber by a substantially vertical partition plate. The reaction tank is divided into a second chamber, and the first chamber and the second chamber communicate with each other at the bottom of the reaction tank. A first fixed bed and a second fixed bed capable of adhering and growing microorganisms are provided above and below the waste water supply section of the chamber, and at the bottom of the second chamber, oxygen is provided above the lower end of the partition plate. Alternatively, an oxygen-containing gas supply section is provided, and a cleaning gas supply section is provided facing the lower part of the first fixed bed and the second fixed bed, and the upper end of the partition plate is arranged such that when the reaction tank is filled with a predetermined amount of wastewater, The reactor is characterized in that a treated drainage section is provided at the upper end of the reaction tank at a level lower than the water level and approximately at the same height as the water level. Embodiments of the present invention will be described below based on the drawings. In the examples shown below, air was used as the raw material gas (oxygen or oxygen-containing gas) for dissolving oxygen in the circulating flow. FIG. 2 is a sectional view of an embodiment of the wastewater treatment device according to the present invention. The reaction tank 1 has a substantially cylindrical shape that is open upward, and the inside of the reaction tank 1 is partitioned into two chambers in the longitudinal direction by a partition plate 14. However, the two partitioned rooms are connected at the bottom. Further, the partition plate 14 is provided so that its height is lower than the water surface of the reaction tank 1. Of the two partitioned rooms, the first room on the right side of Figure 2 has a
Parallel plate groups 15a and 15b each consisting of a plurality of parallel plates 15 parallel to the partition plate 14 on the upper and lower sides.
are provided as first and second fixed beds. The parallel plates 15 are spaced apart from each other by 10 to 35 mm, and each parallel plate 15 is a plastic plate whose surface is processed to have an uneven surface. As mentioned later, drainage 2
And when the untreated water 10 circulates, the parallel plate group 15
The area where a is provided becomes an aerobic zone, and the area where the parallel plate group 15b is provided becomes an anaerobic zone. A cleaning gas supply section 22a is provided near the lower end of the gap between the parallel plates 15 constituting the parallel plate group 15a. Similarly, a cleaning gas supply section 22b is provided for the parallel plate group 15b. A PH sensor 18 is attached near the upper end of the parallel plate group 15a, and the treated drainage section 12 is open. The lower end of the parallel plate group 15a and the parallel plate group 15b
A drainage water supply section 3 is opened between the upper end of the drain and the upper end. Of the two partitioned chambers, the second chamber on the left side in FIG. 2 has an oxygen or oxygen-containing gas supply section 6 opening downward, and above the opening, this chamber is connected to a reaction tank. Five dispersion plates 7 are provided to partition the chamber into six chambers in the longitudinal direction of the chamber 1, and a neutralizing agent supply section 21 is opened above. The aperture ratio of the dispersion plate 7 is 30 to 60.
%belongs to. Next, the outside of the reaction tank 1 will be explained. The PH sensor 18 is electrically connected to the PH controller 17. Neutralizer tank 1 storing acid
A neutralizing agent transfer pipe 23a equipped with an injection pump 20a is connected to a neutralizing agent tank 19b storing alkali.
A neutralizing agent transfer pipe 23b provided with an injection pump 20b is connected to each of the neutralizing agent transfer pipes 23b. Furthermore, the neutralizing agent transfer tube 23a and the neutralizing agent transferring tube 23b join together to reach the neutralizing agent supply section 21. On the other hand, treated water drainage section 1
2 is provided with a sedimentation separation tank 16 in the middle. In such a wastewater treatment device, wastewater 2 containing BOD and nitrogen compounds is supplied into the reaction tank 1 via the wastewater supply section 3, and flows through the parallel plate group 15b in a circulating flow to be described later. . The wastewater 2 and the untreated water 10 described later pass through the parallel plate group 15b, undergo BOD oxidation reaction and denitrification reaction by microorganisms attached and grown on the surface of the parallel plate 15 in the manner described later, and then undergo a reaction. It flows into the adjacent second chamber via the bottom of the tank 1 and reaches the oxygen or oxygen-containing gas supply 6 . Air 5 is supplied from an oxygen or oxygen-containing gas supply section 6 . The untreated water 10 that has reached the oxygen or oxygen-containing gas supply section 6 rises together with the bubbles 5a, and the bubbles 5a are divided into small pieces by the plurality of dispersion plates 7. In this process, the untreated water 10 takes in oxygen, and the partition plate 14
reaches the upper end of the chamber and overflows into the adjacent first chamber. This overflowing untreated water 10 flows through the parallel plate group 15a, undergoes a nitrification reaction by microorganisms grown on the surface of the parallel plate 15 as described later, and then reaches the wastewater supply section 3 again. Contains wastewater 2. Thereafter, the above steps are repeated according to the circulation flow. The circulation flow is generated by slippage between water and bubbles 5a generated by the supply of air 5. Next, the manner in which microorganisms adhere to and grow on the parallel plate 15 will be described. At the start of operation, the reaction tank 1 is first filled with water, and air is blown from the oxygen or oxygen-containing gas supply section 6. In this state, water circulation begins and the supply of waste water 2 begins. Therefore, shortly after the start of operation, the supplied waste water 2 flows through the parallel plate group 15b.
In the process of flowing through, in an aerobic atmosphere where BOD is present, BOD oxidizing bacteria grow attached to the surface of the parallel plate 15, overcoming the competition for survival with nitrifying bacteria. The path from the parallel plate group 15b to the oxygen or oxygen-containing gas supply section 6 is such that dissolved oxygen in the waste water 2
It is consumed by BOD oxidizing bacteria and becomes an anaerobic atmosphere. After passing through the oxygen or oxygen-containing gas supply section 6, the amount of dissolved oxygen in the water gradually increases, and the untreated water 10 incorporating oxygen flows through the parallel plate group 15a.
Both BOD oxidizing bacteria and nitrifying bacteria can grow in an aerobic atmosphere, but since most of the BOD in the untreated water 10 flowing through the parallel plate group 15a has been oxidized and removed, the parallel plate 15 of the parallel plate group 15a On the surface of
Nitrifying bacteria grow more favorably than BOD oxidizing bacteria, which uses BOD as an organic carbon source. Nitrifying bacteria in untreated water 10
NO ₄ ⁺ −N is nitrified using dissolved oxygen in
Change to NO ₂ ^- -N or NO ₃ ^- -N. Therefore, after a while after the start of operation, the dissolved oxygen concentration of the untreated water 10 that has passed through the parallel plate group 15a becomes low. In other words, the parallel plate group 15b gradually becomes an anaerobic zone from the upper end to the lower end, and there is already attached growth.
Among the BOD oxidizing bacteria, denitrifying bacteria that can adhere and grow even in an anaerobic atmosphere remain. Denitrifying bacteria use BOD as an organic carbon source and reduce NO ₂ ^- -N and NO ₃ ^- -N to N ₂ . In this way, the parallel plate group 15a turns into an aerobic zone, where nitrifying bacteria mainly adhere and grow on the surface of the parallel plate 15, and becomes an area mainly responsible for the nitrification reaction, and the parallel plate group 15b turns into an anaerobic zone.
Denitrifying bacteria mainly adhere to and grow on the surface of the parallel plate 15, which becomes a region responsible for the denitrifying reaction. Next, the PH sensor 18 provided at the upper end of the parallel plate group 15a and the neutralizing agent supply section 21 provided on the upward flow side of the reaction tank 1 will be explained. As described later, the untreated water 10 has HCO ^- ₃ as a whole circulating flow.
is decreasing, and the PH detected by the PH sensor 18
Based on the value, the PH controller 17 is used to supply neutralizing agent from the neutralizing agent supply section 21 during the upward flow, and the PH is
Control so that it is between 7.5 and 8.5. Normally, alkali is supplied during the upward flow, and the PH controller 17 supplies the alkali to the injection pump 2.
0b, and from the neutralizing agent tank 19b to the neutralizing agent transfer pipe 2
3b and the neutralizing agent supply section 21. Furthermore, when the pH increases due to disturbances such as load fluctuations, the PH controller 17 operates the injection pump 20a to supply the neutralizing agent from the neutralizing agent tank 19a to the neutralizing agent transfer pipe 23a and the neutralizing agent supply section 21. This is done through the Next, the treated water 13 is drained and the cleaning gas supply section 22
While the sequential supply of the waste water 2 and the circulation of the untreated water 10 described with respect to the cleaning gas supply section 22b and the cleaning gas supply section 22b continue, a large amount of microorganisms adhere to and grow on the surface of the parallel plates 15 of the parallel plate group 15a. When the microbial film reaches a certain thickness, the supply of air 5 from the oxygen or oxygen-containing gas supply section 6 is stopped, and the circulation of water is stopped. Thereafter, air or nitrogen gas is blown between the parallel plates 15 from the cleaning gas supply section 22a and the cleaning gas supply section 22b to remove the microbial film consisting of nitrifying bacteria, denitrifying bacteria, etc. adhering to the surface of the parallel plate 15. Then, the operation is started again and air 5 is supplied from the oxygen or oxygen-containing gas supply section 6, while the peeled microbial film is removed together with the treated water 13.
The treated water is removed from the reaction tank 1 through the drainage section 12, enters the sedimentation separation tank 16, and is separated and recovered. The treated water 13 is discharged through a sedimentation separation tank 16. According to this embodiment, the following effects are achieved. (1) Nitrification and denitrification efficiency is improved because the nitrifying bacteria-attached growth area (aerobic zone) and the denitrifying bacteria-attached growth area (anaerobic zone) are fixed in the circulating flow. Furthermore, the amount of neutralizing agent added can be much smaller than in the prior art. (2) By partitioning the interior of the reaction tank 1 into two chambers with the partition plate 14, it becomes possible to form a circulation path with a single tank, and the apparatus can be made more compact. (3) Transport of untreated water 10 and wastewater 2 using air bubbles 5a
Since the circulation flow is generated by the upward flow caused by the slip between the water and the water, there is no need to provide a separate circulation pump, which is economical. Note that the circulation flow rate can be adjusted by adjusting the linear velocity of the air 5 blown in and the cross-sectional areas of the rising and falling surfaces. (4) Since the oxygen or oxygen-containing gas supply section 6 is located below the reaction tank 1, the bubbles 5a and the untreated water 1
The contact time with oxygen becomes longer, which is advantageous for dissolving oxygen. (5) Since multiple dispersion plates 7 are provided, air bubbles 5
The combination and separation of a is carried out several times,
As above, it is advantageous for dissolving oxygen. (6) By employing the cleaning gas supply section 22a and the cleaning gas supply section 22b, there is no fear that the microbial film adhering to the parallel plate 15 will inhibit water circulation. (7) The optimum pH for the nitrification reaction is 7.5 to 8.5, and the reaction hardly occurs below 6.0. On the other hand, the optimum pH for denitrification reaction is 7 to 8.5. The nitrification/denitrification reaction, if bacterial synthesis is ignored, is NH ₄ ⁺ −N+2O ₂ +2HCO ₃ ⁻ →NO ₃ ⁻ −N+2H ₂ CO ₃ +H ₂ O ………(1) NO ₃ ⁻ −N+0.833CH ₃ OH＋0.167H ₂ CO ₃ →0.5N ₂ +1.33H ₂ O＋HCO ₃ ^- ………(2) The pH of water is PH＝pK ₁ −log(H ₂ CO ₃ )/(HCO ₃ ⁻ ) ......(3). As is clear from equations (1) to (3) above, the PH decreases in the nitrification reaction, and the PH increases in the denitrification reaction. According to this example, HCO ₃ ^- is consumed in the aerobic zone, but partially recovered in the anaerobic zone. However, overall, HCO ₃ ^- decreases due to the reactions shown in equations (1) and (2). Therefore, PH
Adoption of controls will further improve reaction efficiency. (8) The neutralizing agent supply section 21 is a second one without the parallel plate 15.
Since it is installed in the chamber and is located before the PH sensor 18, it is possible to ensure that the pH of the water entering the aerobic zone is between 7.5 and 8.5, and it is also possible to ensure that the pH of the water entering the aerobic zone is between 7.5 and 8.5. Good mixing is achieved. (9) As mentioned above, denitrification in the anaerobic zone is carried out using BOD in the wastewater 2.
Therefore, if the amount of nitrogen removed is
If the amount is low, an organic carbon source such as methanol may be added to the waste water 2 or to the anaerobic zone. In any case, according to this embodiment, the input amount of organic carbon sources such as methanol can be much smaller than in the prior art. Example 1 Nitrogen was removed from synthetic wastewater using the apparatus shown in FIG. The main specifications of the device are shown in Table 1.

[Table] Further, on the downflow side, dissolved oxygen meter sensors were fixed to the upper, middle, and lower parts of the partition plate 14, respectively. The removal of nitrogen from synthetic wastewater with BOD 65ppm and NH ₄ ⁺ -N 30ppm was investigated. Temperature is 25℃, PH is PH
It was controlled by controller 17 at 8.2±0.2. In addition, the amount of blown air is 100/min.
Treatment was started with the input amount of wastewater 2 being 90/hr. The results are shown in FIG. FIG. 3 is a diagram plotting the concentrations of BOD, NH ₄ ⁺ -N, and NO ₃ ^- -N in the treated water, as well as the dissolved oxygen concentrations in the upper, middle, and lower parts of the downstream side, against the number of treatment days. Curve A shows the dissolved oxygen concentration at the top, curve B shows the middle, and curve C shows the dissolved oxygen concentration at the bottom.
The curve shows the concentration of NH ₄ ⁺ -N, and the curve shows the concentration of NO ₃ ^- -N. As is clear from the figure, BOD is removed first, and accordingly the dissolved oxygen concentration in the middle and lower parts begins to decrease. At this time, bacterial cells were adhering and growing on the parallel plate to the extent that they could be observed. Furthermore, as the BOD removal rate increased, the dissolved oxygen concentration in the middle and lower portions decreased proportionally, eventually reaching almost zero. It took 20 days to reach this point. This decrease in the amount of dissolved oxygen is due to the action of bacterial cells grown on the parallel plates. on the other hand,
NH ₄ ⁺ -N was also gradually nitrified, and NH ₂ ^- -N increased. From this, it is clear that nitrifying bacteria are increasing on the parallel plates of the parallel plate group 15a. After the 20th day, the increasing rate of NO ₃ ^- -N, which had been on the rise, gradually slowed down and finally began to decrease. At this time, NH ₄ ⁺ -N also decreased, and the dissolved oxygen concentration in the middle and lower portions was almost zero. This indicates that a disadaptation reaction is occurring. According to this treatment, the composition of treated water 13 became stable after 40 days. After stabilization, the removal rates of BOD and NH ₄ ⁺ -N were 92% and 91%, respectively. Note that the volumetric load at this time was 0.7Kg-NH ₄ ⁺ -N/m ³ ·day. Also, the amount of alkali added is 11.5g-NaOH/hr
This was 62% of the amount obtained using the nitrification tank alone. Experimental Example 2 The apparatus used in Experimental Example 1 was used to remove nitrogen from actual wastewater. The processing conditions were also the same as in Experimental Example 1. After 90 days of treatment, the results shown in FIG. 4 were obtained. The curved image shows the concentration of BOD in the wastewater, the curve shows the concentration of BOD in the treated water, the curve shows the concentration of NH 4 + -N in the wastewater, and the curve shows the concentration of NH ₄ ⁺ -N in the treated water, and the curve shows the concentration of BOD in the wastewater. Each figure shows the concentration of NO ₃ ^- -N in the treated water. BOD and NH ₄ ⁺ -N in the actual wastewater fluctuated, but BOD and NH ₄ ⁺ -N in the treated water showed stable values. At this time, the average removal rate was 80% for BOD and 80% for BOD, respectively.
NH ₄ ⁺ -N was 88%. Furthermore, the average removal rate of total inorganic nitrogen was 85%. In this process, no organic carbon source such as methanol was added from outside the system.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a conventional wastewater treatment device, FIG. 2 is an explanatory diagram of an embodiment of the wastewater treatment device of the present invention, and FIG.
This figure is an explanatory diagram of the result of treating synthetic wastewater using the apparatus shown in FIG. 2, and FIG. 4 is an explanatory diagram of the result of treating actual wastewater using the apparatus of FIG. 2. 1; Reaction tank, 2; Drainage, 3; Drainage supply section, 5;
Air, 5a; Bubbles, 6; Oxygen or oxygen-containing gas supply unit, 10; Untreated water, 13; Treated water, 14; Partition plate, 15; Parallel plates, 15a, 15b; Parallel plate group, 22a, 22b; Cleaning Gas supply section.

Claims (1)

[Claims] 1. In wastewater containing organic matter and nitrogen compounds,
In wastewater treatment equipment equipped with a reaction tank that removes nitrogen by using microorganisms, the reaction tank is divided into a first chamber and a second chamber by a nearly vertical partition plate, and the first chamber and the second chamber are is connected to the bottom of the reaction tank, and a wastewater supply section is provided at a position approximately midway in the vertical direction of the first chamber, and microorganisms are attached and cultivated in the upper and lower portions sandwiching the wastewater supply section of the first chamber. A possible first fixed bed and a second fixed bed are provided, an oxygen or oxygen-containing gas supply section is provided above the lower end of the partition plate in the lower part of the second chamber, and the first fixed bed and the second fixed bed are provided. A cleaning gas supply unit is provided facing the lower part of the fixed bed, and the upper end of the partition plate is set lower than the water level when the reaction tank is filled with a predetermined amount of wastewater, and the treated water is placed at approximately the same height as the water level. A wastewater treatment device characterized in that a discharge part is provided at the upper end of a reaction tank.