JP2008259990A - Waste water treatment system and waste water treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waste water treatment system and a waste water treatment method where the quantity of the excess sludge to be generated is reduced, and management is facilitated. <P>SOLUTION: Disclosed is a waste water treatment system 1 comprising: a first tank 7 holding waste water comprising organic matter in an anaerobic atmosphere; a second tank 11 holding the waste water and activated sludge passed through the first tank and performing aeration treatment; an activated sludge transferring means 22 transferring a part of the activated sludge in the second tank 11 to the first tank 7; a detecting means 35 detecting the amount of dissolved oxygen in the waste water in the second tank 11; and a blowing air amount controlling means 37 controlling the amount of blowing air in the aeration treatment in accordance with the detected result by the detecting means 35. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a wastewater treatment apparatus and a wastewater treatment method for treating, for example, wastewater discharged from a milking facility on a ranch.

  In the dairy farm where dairy cows are farmed, milking is performed from dairy cows using a milking device 2 to 3 times a day, once stored in a tank, and then shipped as raw milk. The pipelines and tanks of the milking device are regularly cleaned, and the waste water discharged from the ranch includes the cleaning water. The wastewater from the ranch is also mixed with swarf and manure brought by dairy cows. Furthermore, when antibiotics are administered to sick cows, or when dairy cows are just born, milk is discarded without being shipped, and this is also included in the wastewater.

The BOD concentration of such wastewater is as high as 1000-2500 mg / L. However, in most ranches, the amount of wastewater is less than 50 m ³ / day, which is the lower limit of the amount of wastewater specified by the Water Pollution Law. It is not subject to wastewater regulations such as factory wastewater or septic tanks, and installation of wastewater treatment facilities is not obligatory.

  Therefore, in many cases, the wastewater discharged from the ranch is discharged without being treated and contributes to the pollution of the surrounding river. In recent years, the magnitude of the influence on the surrounding environment of wastewater has been pointed out, and it has been required to reduce the BOD concentration of wastewater.

  The most economical method for treating wastewater containing organic matter, such as wastewater discharged from ranches, is to use bacteria and protozoa that naturally occur during the treatment process. As such methods, an activated sludge method, a contact aeration method, a carrier flow aeration method and the like are known. Among them, the activated sludge method is suitable for wastewater having a high BOD concentration of 1000 to 2500 mg / L, such as wastewater from a ranch (see Patent Document 1).

There are two types of activated sludge methods, a continuous treatment activated sludge method and a batch activated sludge method. The continuous treatment type activated sludge method is a method in which an aeration tank for aerobically treating wastewater and a sedimentation tank for separating microbial sludge generated by the aeration treatment are provided in series. On the other hand, the batch activated sludge method is a method in which an aeration process in which the entire amount of waste water is received in a single treatment tank and air is supplied and a precipitation process in which the generated microbial sludge is settled and separated are sequentially controlled by a timer. The principle of purification of wastewater by the activated sludge method is the same in any of the above methods. Air is supplied into the aeration tank to grow aerobic microorganisms that use organic components in the wastewater as nutrient sources. By doing so, the waste water is purified.
JP 2003-53364 A

  When performing the activated sludge method, it is desirable to maintain the sludge concentration in the aeration tank at 4000 to 5000 mg / L. However, when the wastewater is treated by the activated sludge method, surplus sludge derived from organic substances contained in the wastewater is generated. Therefore, as the wastewater treatment is continued, the sludge concentration in the aeration tank gradually increases.

  Therefore, in order to maintain the sludge concentration in the aeration tank within an appropriate range, it is necessary to periodically discharge excess sludge to the outside of the tank. However, there is a problem that it takes cost and labor to periodically discharge excess sludge. In addition, in a small-scale facility that does not have an administrator for appointment, excess sludge cannot be discharged sufficiently, and the sludge concentration exceeds the preferred range, and as a result, the wastewater cannot be treated sufficiently. Sometimes.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a wastewater treatment apparatus and a wastewater treatment method that have a small amount of excess sludge and are easy to manage.

The present invention
A first tank that holds waste water containing organic substances in an anaerobic atmosphere, a second tank that holds the waste water and activated sludge that has passed through the first tank and performs an aeration process, and the activity in the second tank The gist of the present invention is a wastewater treatment apparatus comprising activated sludge transfer means for transferring a part of sludge to the first tank.

  In the wastewater treatment apparatus of the present invention, a part of the activated sludge in the second tank is transferred to the first tank by the activated sludge transfer means. And the activated sludge transferred is melt | dissolved in wastewater in the 1st tank which is an anaerobic atmosphere. Therefore, even if the wastewater treatment apparatus of the present invention is used for a long period of time, the activated sludge hardly increases in the apparatus, and therefore management is very easy.

  The amount of activated sludge transferred by the activated sludge transfer means can be set to an amount that maintains the amount of activated sludge in the second tank within a suitable range. As a suitable range of the activated sludge amount in the second tank, for example, there is a range in which the sludge concentration in the wastewater is 4000 to 5000 mg / L when aeration processing is performed in the second tank. Moreover, as a suitable range of the activated sludge quantity in a 2nd tank, there exists a range from which the value of SV30 in a 2nd tank will be 45 to 50%. In addition, SV30 is the ratio (%) of the activated sludge volume (ml) which settled after putting the waste water (a thing containing activated sludge) in a 2nd tank into a 1L graduated cylinder and leaving it to stand for 30 minutes.

  The wastewater treatment apparatus of the present invention further includes a detection unit that detects the amount of dissolved oxygen in the wastewater in the second tank, and a sending unit that controls the amount of air blown in the aeration process according to a detection result by the detection unit. And an air volume control means.

  If the amount of dissolved oxygen in the waste water in the second tank is too small, it becomes unsuitable for aerobic microorganisms, and aeration treatment cannot be performed sufficiently. Conversely, if the amount of dissolved oxygen is too large, the decomposition of microorganisms occurs. However, if the amount of dissolved oxygen in the wastewater is maintained within an appropriate range by the detection means and the air flow control means, the aeration process in the second tank can be performed more efficiently. The amount of dissolved oxygen in the wastewater in the second tank is preferably in the range of 1.5 to 2.0 mg / L.

The present invention also provides:
A first step of holding waste water containing organic matter in an anaerobic atmosphere in the first tank, and a process of transferring the waste water from the first tank to a second tank holding activated sludge for aeration. A gist of the wastewater treatment method is characterized in that a part of the activated sludge retained in the second tank is transferred to the first tank.

  In the wastewater treatment method of the present invention, a part of the activated sludge in the second tank is transferred to the first tank. And the activated sludge transferred is melt | dissolved in wastewater in the 1st tank which is an anaerobic atmosphere. Therefore, even if the wastewater treatment method of the present invention is used for a long time, the activated sludge hardly increases in the first tank and the second tank, so that the management of the first tank and the second tank is very easy.

In the wastewater treatment method of the present invention, it is preferable that the amount of dissolved oxygen in the wastewater in the second tank is detected, and the amount of air blown in the aeration process is controlled according to the detection result.
If the amount of dissolved oxygen in the waste water in the second tank is too small, it becomes unsuitable for aerobic microorganisms, and aeration treatment cannot be performed sufficiently. Conversely, if the amount of dissolved oxygen is too large, the decomposition of microorganisms occurs. However, if the amount of dissolved oxygen in the wastewater is maintained within an appropriate range by controlling the air flow rate in the aeration process, the aeration process in the second tank can be performed more efficiently.

  The pH of the wastewater in the first step is preferably in the range of 4-6. When the pH is within this range, the activated sludge transferred from the second tank can be more efficiently dissolved.

Examples of the organic matter contained in the wastewater include livestock milk, scum, and manure.
The anaerobic atmosphere refers to a state in which air is not supplied to the inside of wastewater by a blower or the like. The surface of the waste water may be in contact with air.

  In the second tank, it is preferable to add fine particles made of an inorganic substance that serve as a carrier for activated sludge. By the presence of the fine particles, the aeration process can be performed more efficiently. Examples of the fine particles include alumina fine particles. The amount of the fine particles is preferably in the range of 1 to 2 mg with respect to 1 L of the waste liquid in the second tank.

The present invention will be specifically described.
1. Configuration of Waste Water Treatment Device The configuration of the waste water treatment device 1 will be described with reference to FIG. The wastewater treatment apparatus 1 is a treatment apparatus for wastewater containing waste milk that is discharged from a milking facility on a ranch. The wastewater treatment apparatus 1 includes a raw water tank 3, a screen 5, an anaerobic filter bed tank 7, a mixing tank 9, a batch aeration tank 11, a pipe 13 extending from the raw water tank 3 to the screen 5, and a screen 5 extending to the anaerobic filter bed tank 7. Pipe 15, pipe 17 from the anaerobic filter bed tank 7 to the mixing tank 9, pipe 19 from the mixing tank 9 to the batch aeration tank 11, pipe 21 for discharging waste water from the batch aeration tank 11, and batch aeration An activated sludge pipe 22 for transferring activated sludge from the tank 11 to the anaerobic filter bed tank 7 and the mixing tank 9 is provided.

  The raw water tank 3 is a tank that first receives waste water discharged from the milking field. The raw water tank 3 is provided with a float switch 23, and when the level of waste water in the raw water tank 3 exceeds a predetermined first reference water level, a float pump (not shown) is turned on. The float pump transfers the waste water in the raw water tank 3 to the screen 5 through the pipe 13. When the waste water level in the raw water tank 3 is lower than the second reference water level that is lower than the first reference water level, the float switch 23 turns off the above-described float pump and stops the transfer of waste water.

  The screen 5 is a 0.3 mm edge wire screen set in a room on the ground. The screen 5 has a function of removing impurities (such as cow hair, straw, feces) contained in the wastewater. The waste water that has passed through the screen 5 is sent to the anaerobic filter bed tank 7 through the pipe 15 due to a natural drop.

The anaerobic filter bed tank 7 is a concrete underground tank having a capacity of 30 m ³ and is a tank for fermenting and decomposing organic substances (particularly milk components) contained in wastewater in an anaerobic atmosphere. The anaerobic filter bed tank 7 is divided into three tanks 7A to 7C by partitions 25 and 27 that open only upward. The capacity of the three tanks 7A to 7C is 10 m ³ , respectively. 7A-7C is equipped with the stirring pump 29 which always stirs wastewater in the vicinity of each bottom face. Moreover, 7B and 7C are each provided with the filter medium 30 shown in FIG. The packed filter medium 30 is formed in a cylindrical shape by intertwining commercially available polypropylene (diameter 3 mm). The packed filter medium 30 occupies 44% of the volume of 7B and 28% of the volume of 7C.

  The pipe 15 for sending waste water from the screen 5 is connected to 7A, and the waste water that flows in first fills 7A. When the wastewater further flows, the wastewater overflows over the partition 25 and flows into 7B. When 7B is also filled, the wastewater overflows over the partition 27 and flows into 7C. A pipe 17 leading to the mixing tank 9 is connected to 7C, and waste water in 7C is sent to the mixing tank 9 via the pipe 17.

The mixing tank 9 is a tank for storing waste water sent from the anaerobic filter bed tank 7 through the pipe 17. The mixing tank 9 is provided with a float switch 31, and the flow of the waste water from the anaerobic filter bed tank 7 is controlled by using the float switch 31, and the amount of the stored waste water is adjusted to 10 m ³ . A mixing tank pump 20 for transferring waste water in the mixing tank 9 to the batch aeration tank 11 is provided in the middle of the pipe 19 from the mixing tank 9 to the batch aeration tank 11.

The batch aeration tank 11 is a horizontal cylindrical tank made of FRP having a capacity of 50 m ³ and is installed underground. The batch aeration tank 11 contains activated sludge and alumina fine particles (trade name: Posnia, manufactured by Nidec) as a carrier. In addition, the batch aeration tank 11 includes a blower 33 that blows out air sent from the air pipe 32 in the vicinity of the bottom surface thereof. Therefore, waste water can be aerated by putting waste water into the batch aeration tank 11 and blowing out air from the blower 33 in a state where it is mixed with activated sludge.

  Further, a sensor 35 for measuring the dissolved oxygen concentration (DO value) in the wastewater is provided in the batch aeration tank 11. In accordance with the measurement result by the sensor 35, the control device 37 changes the frequency, the number, and the number of rotations of the blower motor that is the drive source of the blower 33 as shown in Table 1, and adjusts the blower amount of the blower 33. That is, if the amount of dissolved oxygen is large, the amount of blown air is reduced. Conversely, if the amount of dissolved oxygen is small, the amount of blown air is increased.

回分ばっ気槽１１内の廃水は、配管２１の途中に設けられた放流ポンプ３９の駆動力により、配管２１を経て、外部に放出される。回分ばっ気槽１１は、フロートスイッチ４０を備えおり、回分ばっ気槽１１内の水位が高すぎるときは、混合槽９からの廃水の流入を止め、逆に、水位が低すぎるときは、廃水の外部への放出を止める。

Waste water in the batch aeration tank 11 is discharged to the outside through the pipe 21 by the driving force of the discharge pump 39 provided in the middle of the pipe 21. The batch aeration tank 11 is provided with a float switch 40. When the water level in the batch aeration tank 11 is too high, the inflow of waste water from the mixing tank 9 is stopped, and conversely, when the water level is too low, the waste water Stops the release to the outside.

Further, an excess sludge transfer pump 41 is provided in the middle of the pipe 22 connecting the batch aeration tank 11 and the anaerobic filter bed tank 7, and the activated sludge in the batch aeration tank 11 is driven by this driving force. A part of (including alumina fine particles) is sent to the anaerobic filter bed tank 7 through the pipe 22.
2. Method for Using Waste Water Treatment Device A method for treating waste water using the waste water treatment device 1 will be described. The outline of the method of treating wastewater using the wastewater treatment apparatus 1 is as follows. Wastewater discharged from the milking farm is first stored in the raw water tank 3 and then sent to the anaerobic filter bed tank 7 through the screen 5. Therefore, the organic matter (especially waste milk) in the wastewater is fermented and decomposed in an anaerobic atmosphere, and further, the wastewater is sent to the batch aeration tank 11 through the mixing tank 9, where the aeration treatment is performed, and finally the wastewater is externalized To be released. Moreover, apart from the flow of waste water, a part of the activated sludge in the batch aeration tank 11 is periodically sent to the anaerobic filter bed tank 7 where the activated sludge is dissolved in the waste water.

  Next, based on the time chart of FIG.1 and FIG.3, the method to process wastewater using the wastewater treatment apparatus 1 is demonstrated in detail. The wastewater treatment apparatus 1 is continuously operated for 24 hours, and the daily operation can be divided into three cycles. Here, one cycle starting at 5:30 am will be described as an example, but the other two cycles are the same.

  From 5:30 am to 8:30 am, milking is performed at the milking place, and 10 tons of waste water including waste milk flows into the raw water tank 3. Waste water contains about 2% of waste milk, and its BOD is about 2100-3800 mg / L. When the wastewater level in the raw water tank 3 exceeds a predetermined first reference water level due to the inflow of wastewater, the float switch 23 is turned on, and the wastewater is transferred to the anaerobic filter bed tank 7 via the screen 5. When the wastewater level in the raw water tank 3 becomes lower than the second reference water level due to the transfer of the wastewater, the float switch 23 is turned OFF and the transfer of the wastewater is stopped.

  At 9:00 am, blowing of the blower 33 in the batch aeration tank 11 is stopped. Until 9:00 am, air was blown into the mixed solution of waste water and activated sludge that flowed in the previous cycle by the blower 33 to perform aeration. The blower stop of the blower 33 continues until 10:15 minutes.

At 9:20 am, since sufficient time has passed since the blower 33 stopped blowing, the activated sludge settles downward in the batch aeration tank 11, and the supernatant becomes waste water that does not contain activated sludge. Yes. Therefore, the surplus sludge transfer pump 41 is driven for 10 minutes based on the timer from this time, and a part of the precipitated activated sludge is sent to the anaerobic filter bed tank 7 through the pipe 22. The amount of activated sludge sent is about 1.2 m ³ . This amount is a value set so that the amount of activated sludge in the batch aeration tank 11 is constant over the long term.

  At 9:40 am, the discharge pump 39 is driven, and the waste water is discharged from the batch aeration tank 11 through the pipe 21 to the outside. At this time, since the batch aeration tank 11 is separated into the precipitated activated sludge layer and the supernatant waste water as described above, the discharged waste water is taken out from the supernatant. The discharge of waste water is performed for 10 minutes based on a timer, and the discharge amount is 10 tons.

  At 10:10 am, the mixing tank pump 20 is driven, and the waste water in the mixing tank 9 is transferred to the batch aeration tank 11 through the pipe 19. In addition, the waste water which was in the mixing tank 9 at this time flows into the waste water treatment apparatus 1 in the cycle before that. This wastewater is transferred for 30 minutes based on a timer, and the transfer amount is 10 tons, which is the same as the amount discharged from the batch aeration tank 11 previously. Therefore, the amount of waste water in the batch aeration tank 11 returns to the amount before 9:40 am.

  As described above, 10 tons of waste water is transferred from the mixing tank 9 to the batch aeration tank 11, but the same amount of new waste water is sent from the anaerobic filter bed tank 7 to the mixing tank 9. That is, when the waste water in the mixing tank 9 decreases, the float switch 31 in the mixing tank 9 is turned ON, and the inflow of waste water from the anaerobic filter bed tank 7 is permitted. The float switch 31 prohibits the inflow of waste water from the anaerobic filter bed tank 7 when the amount of waste water in the mixing tank 9 reaches a predetermined amount.

  At 10:15 am, the blower 33 resumes air blowing. Therefore, the aeration process of the wastewater is performed in the batch aeration tank 11 from this time until the blowout is stopped in the next cycle (17:00 pm).

In addition, the stirring pump 29 in the anaerobic filter bed tank 7 is always operated, and the anaerobic filter bed tank 7 always decomposes organic substances in an anaerobic atmosphere.
3. Effects of wastewater treatment apparatus 1 and wastewater treatment method
(i) The wastewater treatment apparatus 1 has been operated continuously for more than one year since November 2005. Then, in February, June, July, September, and December of the following year, the waste water in the raw water tank 3, the waste water in the anaerobic filter bed tank 7, and the discharged water from the batch aeration tank 11, respectively. Water quality was analyzed. The analysis method was in accordance with JIS K0102. The results are shown in Table 2.

表２から明らかに、放流水における各測定値は、処理前の廃水（原水槽３内の廃水）に比べて、大幅に減少していた。特に、６月以降の測定値は、著しく減少していた。この測定結果は、廃水処理装置１の有機物分解効果が高いことを立証している。

Obviously from Table 2, each measured value in the discharged water was greatly reduced compared to the waste water before treatment (waste water in the raw water tank 3). In particular, the measured values after June have decreased significantly. This measurement result proves that the organic matter decomposition effect of the wastewater treatment apparatus 1 is high.

  One of the reasons why the wastewater treatment apparatus 1 has a high effect of decomposing organic substances is to decompose milk proteins in the anaerobic filter bed tank 7 in addition to the batch aeration tank 11. That is, in the anaerobic filter bed 7, the fermentation decomposition of milk protein to butyric acid or lactic acid progresses in Chemical Formula 1 and the organic substance becomes low-molecular and soluble, contributing to the reduction of BOD. It is done.

嫌気濾床槽７内で、乳蛋白が発酵し、乳酸や酪酸などの有機酸に分解されることは、表３に示すように、嫌気濾床槽７、原水槽３、及び回分ばっ気槽１１内における廃水のｐＨをそれぞれ測定したところ、原水槽３、及び回分ばっ気槽１１では７以上であったのに対し、嫌気濾床槽７のみでは、４〜６という低い値であったことにより裏付けられる。

The fact that milk protein is fermented and decomposed into organic acids such as lactic acid and butyric acid in the anaerobic filter bed tank 7, as shown in Table 3, the anaerobic filter bed tank 7, the raw water tank 3, and the batch aeration tank. When the pH of the waste water in each was measured, it was 7 or more in the raw water tank 3 and the batch aeration tank 11, whereas it was a low value of 4 to 6 only in the anaerobic filter bed tank 7. Is supported by

また、嫌気濾床槽７内で、乳蛋白が発酵し、乳酸や酪酸などの有機酸に分解されることは、表４に示すように、嫌気濾床槽７、原水槽３、及び混合槽９内における廃水の温度をそれぞれ測定したところ、嫌気濾床槽７の温度は、他の槽に比べて顕著に高い（発酵熱によるものと考えられる）ことによっても裏付けられる。

In addition, as shown in Table 4, anaerobic filter bed tank 7, raw water tank 3, and mixing tank indicate that milk protein is fermented and decomposed into organic acids such as lactic acid and butyric acid in anaerobic filter bed tank 7. When the temperature of the waste water in 9 is measured, it is supported also by the temperature of the anaerobic filter bed tank 7 being remarkably high compared with other tanks (it is considered to be due to fermentation heat).

また、嫌気濾床槽７は、その内部に充填濾材３０を備えることにより、乳蛋白が発酵する作用を一層促進することができる。
(ii)平成１８年の１月から１２月まで、１月おきに、回分ばっ気槽１１内の活性汚泥沈殿率（ＳＶ３０）、回分ばっ気槽１１内の活性汚泥濃度（ＭＬＳＳ）、嫌気濾床槽７内の汚泥濃度（ＳＳ）を測定した。ＳＶ３０は、１Ｌのメスシリンダーに回分ばっ気槽１１内の廃水（活性汚泥を含むもの）を入れ、３０分間放置した後に沈殿した活性汚泥容積（ｍｌ）の割合（％）である。測定結果を表５に示す。なお、表５には、それぞれの月での、処理前の廃水における平均ＢＯＤ濃度も併せて示す。

Moreover, the anaerobic filter bed tank 7 can further promote the action of fermenting milk proteins by providing the filled filter medium 30 therein.
(ii) From January to December 2006, every other month, the activated sludge sedimentation rate (SV30) in the batch aeration tank 11, the activated sludge concentration (MLSS) in the batch aeration tank 11, and anaerobic filtration The sludge concentration (SS) in the floor tank 7 was measured. SV30 is the percentage (%) of the activated sludge volume (ml) that settles after putting wastewater (including activated sludge) in the batch aeration tank 11 into a 1 L graduated cylinder and leaving it for 30 minutes. Table 5 shows the measurement results. Table 5 also shows the average BOD concentration in the wastewater before treatment in each month.

表５から明らかに、ＳＶ３０、ＭＬＳＳ、ＳＳの値に増加傾向は見られない。廃水に含まれる有機物を回分ばっ気槽１１内で分解すると、必ず汚泥が発生する。１日当りの廃水の量を３０トン、処理前後における廃水のＢＯＤを、それぞれ、２０００ｍｇ／Ｌ、１２０ｍｇ／Ｌとし、除去されたＢＯＤの３０％が汚泥になるとすると、１日に発生する汚泥の量は１６．９Ｋｇとなる。汚泥が含水率９８％の濃縮汚泥であるとして、体積に換算すると、一日に発生する汚泥の体積は０．８４５ｍ³であり、１年では３０８ｍ³である。この量は、回分ばっ気槽１１の容量（５０ｍ³）、嫌気濾床槽７の容積（３０ｍ³）に比べて非常に多い量である。

As apparent from Table 5, there is no increasing tendency in the values of SV30, MLSS, and SS. When organic substances contained in the wastewater are decomposed in the batch aeration tank 11, sludge is always generated. If the amount of wastewater per day is 30 tons, the BOD of wastewater before and after treatment is 2000 mg / L and 120 mg / L, respectively, and if 30% of the removed BOD becomes sludge, the amount of sludge generated per day Is 16.9 kg. As sludge is a water content of 98% concentrated sludge, in terms of volume, the volume of sludge generated in a day is 0.845M ^3, in one year is 308m ^3. This amount is much larger than the capacity of the batch aeration tank 11 (50 m ³ ) and the volume of the anaerobic filter bed tank 7 (30 m ³ ).

  However, as described above, the amount of activated sludge in the batch aeration tank 11 and the anaerobic filter bed tank 7 has not increased throughout the year. This is because the activated sludge sent out from the batch aeration tank 11 to the anaerobic filter bed tank 7 is dissolved in the wastewater in the anaerobic filter bed tank 7.

Therefore, even if the wastewater treatment apparatus 1 is used for a long time, the activated sludge does not increase in the wastewater treatment apparatus 1, so that it is not necessary to extract excess activated sludge, and the management of the wastewater treatment apparatus 1 is very easy.
(iii) Since the wastewater treatment apparatus 1 adjusts the amount of air blown into the blower 33 according to the amount of dissolved oxygen in the wastewater in the batch aeration tank 11, the amount of dissolved oxygen in the wastewater must be maintained within an appropriate range. Can do. This is supported by the following experiment. First, as shown in Table 1, the wastewater treatment apparatus 1 was operated under the condition that the air blowing amount of the blower 33 was adjusted according to the dissolved oxygen amount in the wastewater. And, when 10 tons of new wastewater flows into the batch aeration tank 11, the dissolved oxygen amount (DO value) in the wastewater in the batch aeration tank 11 and the air volume of the blower 33 are measured every hour. did. Similarly, even under the condition that the air volume of the blower 33 is constant, the amount of dissolved oxygen in the waste water and the air volume of the blower 33 are changed every hour from when 10 tons of new waste water flows into the batch aeration tank 11. And measured. The results are shown in Table 6.

表６から明らかに、ブロワー３３の風量を廃水中の溶存酸素量に応じて調整すると、廃水中の溶存酸素量が高くなり過ぎず、適正な範囲に維持できることが分かる。一方、ブロワー３３の風量を一定にすると、時間の経過につれて、廃水中の溶存酸素量が高くなり続けてしまう。

From Table 6, it is clear that adjusting the air volume of the blower 33 according to the amount of dissolved oxygen in the wastewater does not increase the amount of dissolved oxygen in the wastewater, and can be maintained in an appropriate range. On the other hand, if the air volume of the blower 33 is kept constant, the amount of dissolved oxygen in the wastewater continues to increase as time passes.

If the amount of dissolved oxygen is too small, it will be unsuitable for aerobic microorganisms and aerobic treatment will not be possible. On the other hand, if the amount of dissolved oxygen is too large, the disassembly of microorganisms will occur, but the wastewater treatment equipment Since 1 can maintain the amount of dissolved oxygen in wastewater in an appropriate range as described above, the aeration treatment can be more stably performed.
(iv) Since the wastewater treatment apparatus 1 includes alumina fine particles that act as a carrier for activated sludge in the batch aeration tank 11, the aeration treatment can be performed more efficiently. A part of the alumina fine particles is sent to the anaerobic filter bed tank 7 together with the activated sludge, but later returns to the batch aeration tank 11 together with the waste water, so that the batch aeration tank 11 is not replenished with the alumina fine particles 11. May be.

In addition, this invention is not limited to the said embodiment at all, and it cannot be overemphasized that it can implement with a various aspect in the range which does not deviate from this invention.
For example, the wastewater treatment apparatus 1 may not include the mixing tank 9 and may transfer the wastewater from the anaerobic filter bed tank 7 to the batch aeration tank 11.

It is explanatory drawing showing the structure of the waste water treatment apparatus. It is explanatory drawing showing the structure of the filling filter medium 30, (a) is a front view, (b) is a side view. 3 is a time table showing an operation cycle of the wastewater treatment apparatus 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Waste water treatment apparatus 3 ... Raw water tank 5 ... Screen 7 ... Anaerobic filter bed tank 9 ... Mixing tank 11 ... Batch aeration tank 13, 15, 17, 19, 21, ..Piping 22 ... Activated sludge piping 25, 27 ... Partition 29 ... Agitation pump 30 ... Filled filter media 31, 40 ... Float switch 32 ... Air piping 33 ... Blower 35 .... Sensor 37 ... Control device 39 ... Discharge pump

Claims (7)

A first tank for holding wastewater containing organic matter in an anaerobic atmosphere;
A second tank for holding the wastewater and activated sludge that has passed through the first tank and performing an aeration process;
Activated sludge transfer means for transferring a part of the activated sludge in the second tank to the first tank;
A wastewater treatment apparatus comprising: Detection means for detecting the amount of dissolved oxygen in the wastewater in the second tank;
In accordance with the detection result by the detection means, the air volume control means for controlling the air volume in the aeration process,
The wastewater treatment apparatus according to claim 1, comprising:   The wastewater treatment apparatus according to claim 1 or 2, wherein the organic matter is livestock milk. A first step of holding wastewater containing organic matter in an anaerobic atmosphere in the first tank;
A second step of transferring the waste water from the first tank to a second tank holding activated sludge and performing an aeration process;
A part of the activated sludge retained by the second tank is transferred to the first tank.   The wastewater treatment method according to claim 4, wherein the amount of dissolved oxygen in the wastewater in the second tank is detected, and the amount of air blown in the aeration process is controlled according to the detection result.   The wastewater treatment method according to claim 4 or 5, wherein the pH of the wastewater in the first step is in the range of 4-6.   The wastewater treatment method according to any one of claims 4 to 6, wherein the organic matter is livestock milk.

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