JP2001269682A - Method for back-washing drain cleaning device using floating filter material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of back-washing a drain cleaning device using a floating filter material with the washing water quantity less than heretofore while suppressing the deterioration of biological activity. SOLUTION: In the backwashing method of the drain cleaning device in which the granular floating filter material carrying a biological membrane is packed in a tank and the drain is passed through in upward stream from the lower part of the tank while diffusing air from a middle step of a packed layer. Simple backwashing is performed when a filtering resistance of the packed layer reaches a set value S and normal backwashing is performed when the difference (F-A) between a filtering resistance F just after the simple backwashing and a filtering resistance A just after the normal backwashing reaches a prescribed resistance difference Δ. Water washing and air washing are repeated for several times at the normal backwashing, and the water washing and the air washing are performed one time each.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for backwashing a wastewater purifying apparatus using a floating filter.

[0002]

2. Description of the Related Art As a waste water purifying apparatus capable of performing nitrification and denitrification in one tank, a waste water purifying apparatus using a floating filter material as shown in FIG. 1 is known.
This device has a structure in which a floating filter medium 2 made of granular expanded polystyrene or the like is filled in a tank 1 to support a biofilm on the surface thereof, and air is diffused from a diffuser pipe 3 in a middle stage of the packed layer. is there. Drainage from the raw water supply pipe 4 at the bottom of the tank to the tank 1
The water is passed upward in the inside of the tank 1, and is taken out from the upper end of the tank 1 as treated water, and a part of the treated water is returned to the tank bottom by the return pipe 5.

[0003] Since oxygen is not supplied to the lower part of the diffuser 3, the lower part of the packed bed becomes an anaerobic denitrification part 6, and conversely, sufficient oxygen is supplied to the upper part of the diffuser 3. The upper part of the packed bed becomes the aerobic nitrification part 7. For this reason, nitrate nitrogen in the wastewater flowing into the denitrification section 6 from the lower part of the tank is converted into nitrogen gas by the denitrifying bacteria and removed from the water, and the BOD component is also removed. Also, ss in the drainage is captured and removed by the floating filter medium 2 at the lower part of the packed bed.
Next, the wastewater flows into the nitrification section 7 at the upper part of the packed bed, and the ammonia nitrogen in the wastewater is converted into nitrate nitrogen by the nitrifying bacteria, and the BOD component remaining by the denitrification reaction is removed.
Part of the treated water containing nitrate nitrogen is sent again to the denitrification section 6 by the return pipe 5, and the nitrification denitrification by the nitrification liquid circulation method is performed. A perforated plate 9 is provided in the upper part of the tank so that the floating filter medium 2 does not flow out.

[0004] The above-mentioned wastewater purifying apparatus using the floating filter medium can easily cope with load fluctuation of the inflowing wastewater, and can be easily started and stopped. In addition, since the concentration of cells can be increased by the biofilm, there is an advantage that the wastewater treatment capacity per installation area is excellent. The details are described in, for example, JP-A-5-96.
292.

[0005] In such a wastewater purification apparatus,
It is necessary to discharge the captured ss and excess sludge generated by the biological reaction to the outside of the tank by back washing. So conventionally,
Normally, the backwash was performed once every 24 hours or once every 48 hours by a timer. This normal backwash
The washing is performed by repeating the water washing in which the treated water flows downward from the upper part of the tank 1 in a downward flow and the air washing by aeration from the washing air supply pipe 8 in the lower part of the tank several times. If the filtration resistance of the packed bed reaches the set value before the normal cleaning time, the filtration resistance may be reduced by supplementing the simple cleaning in which water cleaning and air cleaning are performed once each. Is being done.

[0006] However, as described above, when the normal backwash is performed at regular intervals by the timer, there is a problem that a large amount of treated water is required as the wash water. In addition, since the washing with water and the washing with air are repeatedly performed, the floating filter medium is violently agitated, and there is a problem that a biological film supported on the surface is damaged and biological activity is reduced. If the setting time of the timer is set longer than this, these problems are alleviated to some extent, but the filtration resistance of the packed bed due to the captured ss becomes too high, so that smooth drainage treatment cannot be performed.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned conventional problems, and enables the backwashing of a wastewater purification apparatus using a floating filter medium with a smaller amount of washing water than before and a reduction in biological activity. The purpose of this method is to provide a method that can be performed reliably.

[0008]

Means for Solving the Problems In order to solve the above problems, the present invention provides a method for backwashing a wastewater purifying apparatus using a floating filter medium, comprising the steps of placing a granular floating filter medium carrying a biofilm in a tank. A backwash method of a wastewater purification device that fills and diffuses wastewater in an upward flow from the lower part of the tank while diffusing from the middle stage of the packed bed,
When the filtration resistance of the packed bed reaches the set value, simple backwashing is performed.When the difference between the filtration resistance immediately after simple backwashing and the filtration resistance immediately after normal backwashing reaches a predetermined resistance difference, the next reverse washing is performed. It is characterized in that washing is usually backwashing.

[0009] Backwashing is performed by a combination of water washing in which the treated water flows downflow in the tank and air washing by aeration from the lower part of the tank. Is repeated a plurality of times, and the simple backwashing is performed by reducing the number of repetitions of water washing and air washing as compared with the normal backwashing. Also, when the difference between the filtration resistance immediately after simple backwashing and the filtration resistance immediately after normal backwashing reaches a predetermined resistance difference,
Normal backwashing may be performed immediately, or a method in which normal backwashing is not performed immediately and then normal backwashing is performed when the filtration resistance of the packed bed reaches a set value.

[0010] According to the present invention, the frequency of normal backwashing can be greatly reduced as compared with the related art, so that the amount of washing water can be reduced as compared with the related art, and a decrease in biological activity can be suppressed. Moreover, in a wastewater purification system using a floating filter material, most of the ss in the wastewater is captured at the lower part of the packed bed, so when the filtration resistance of the packed bed reaches the set value, simple cleaning can be performed simply. It is possible to restore the filtration resistance.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below. A wastewater purifying apparatus using a floating filter medium to be backwashed in the present invention is also as shown in FIG.
That is, during normal operation, drainage is supplied from the lower raw water supply pipe 4 into the tank 1, and while water is passed through the inside of the packed bed of the floating filter medium 2 in an upward flow, the lower part of the air diffuser 5 is removed. The capture and denitrification of ss are performed in the nitrogen unit 6, and nitrification is performed in the upper nitrification unit 7. Part of the treated water that has passed through the perforated plate 9 is returned to the return pipe 5
To the denitrification section 6 again, where nitrification denitrification by the nitrification liquid circulation method is performed.

When such wastewater treatment is continued, ss in the wastewater is trapped in the packed bed, so that the filtration resistance of the packed bed gradually increases as shown in FIG. In the present invention, backwashing and simple backwashing are usually performed in order to recover the increased filtration resistance. First, normal backwashing includes water washing in which treated water is passed downflow in the tank as shown in FIG. 3 and air washing by aeration from the washing air supply pipe 8 in the lower part of the tank as shown in FIG. Is repeated a plurality of times (for example, three times). On the other hand, the number of repetitions in the simple backwash is smaller than that in the normal backwash, and each of the simple backwash in this embodiment is performed only once. In this case, the amount of washing water required for simple backwashing is usually about half the amount of washing water required for backwashing.

The backwashing method of the present invention will be described below with reference to FIG. 2. For convenience of explanation, the filtration resistance of the packed bed immediately after the normal backwashing is denoted by A, and the drainage treatment is started from the state of A. It has been resumed. As described above, when the wastewater treatment is continued, the filtration resistance of the packed bed gradually increases from A. In the present invention, the simple backwashing is performed when the filtration resistance reaches the set value S. As a result, the floating filter medium 2 is lightly agitated and ss trapped in the lower part of the packed bed is discharged from the lower part of the tank, and the filtration resistance is reduced. However, the filtration resistance does not recover to the filtration resistance A immediately after the backwashing, and becomes B.

Thereafter, when the drainage treatment is continued again, the filtration resistance of the packed bed increases again, and when the set value S is reached, simple backwashing is performed again. As a result, the filtration resistance decreases to C, and the same cycle is repeated thereafter. However, as the simple backwashing is repeated, the recovery width of the filtration resistance gradually decreases, and when reaching F in FIG.
Then, the difference FA of the filtration resistance A immediately after the latest normal backwash reaches the predetermined resistance difference Δ. When this condition is reached, simple backwashing alone is no longer sufficient to recover the filtration resistance of the packed bed,
Normal backwashing in which water washing and air washing are repeated a plurality of times is performed.
As a result, the filtration resistance is restored to G. G is substantially equal to A, and thereafter, each time the filtration resistance reaches the set value S, the simple backwashing is repeated.

In FIG. 2, the filtration resistance F immediately after the simple backwashing is shown.
When the difference FA of the filtration resistance A immediately after the latest normal backwashing reaches the predetermined resistance difference Δ, the normal backwashing is not immediately performed,
Next, when the filtration resistance of the packed bed reached the set value S, normal backwashing was performed. However, the normal backwash may be performed immediately when the FA reaches the predetermined resistance difference Δ.

As described above, in the present invention, when the filtration resistance of the packed bed reaches the set value S, simple backwashing is performed, and the difference between the filtration resistance immediately after simple backwashing and the filtration resistance immediately after normal backwashing is determined. Since the normal backwash is performed only when the predetermined resistance difference Δ is reached, the frequency of the normal backwash can be significantly reduced as compared with the conventional method of performing the normal backwash periodically. it can. For this reason, the amount of washing water can be reduced to about 40% of the conventional amount, and a decrease in biological activity due to normal backwashing can be suppressed.

[0017]

As described above, according to the present invention, backwashing of a wastewater purifying apparatus using a floating filter material can be reliably performed with a smaller amount of washing water than before, and while suppressing a decrease in biological activity. There are advantages that can be. In addition, the filtration resistance of the packed bed is always kept below the set value, so that an appropriate wastewater treatment effect can be maintained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a drainage purification device using a floating filter medium.

FIG. 2 is a graph showing a change in filtration resistance due to backwashing.

FIG. 3 is a cross-sectional view illustrating water washing.

FIG. 4 is a sectional view illustrating air cleaning.

[Explanation of symbols]

1 tank, 2 floating filter media, 3 diffuser pipe, 4 raw water supply pipe,
5 return pipe, 6 denitrification section, 7 nitrification section, 8 cleaning air supply pipe, 9 perforated plate

 ──────────────────────────────────────────────────の Continued on the front page (71) Applicant 000005083 Hitachi Metals, Ltd. 1-2-1, Shibaura, Minato-ku, Tokyo (72) Inventor Yuzo Okamoto 2-56, Suda-cho, Mizuho-ku, Nagoya-shi, Aichi Japan Insulator Inside (72) Inventor Shigeki Takeda 2-56 Suda-cho, Mizuho-ku, Nagoya-shi, Aichi Japan Inside Insulator Co., Ltd. (72) Inventor Shoji Harada 3-1-1 Takasago, Urawa-shi, Saitama Saitama Prefecture Office (72) Inventor Yozo Uchino 3-15-1, Takasago, Urawa-shi, Saitama Prefecture, Saitama Prefecture Office (72) Inventor Kenichi Matsumoto 3-1-1, Takasago, Urawa City, Saitama Prefecture Saitama Prefecture Office (72) Inventor Kobayashi Yu 3-15-1, Takasago, Urawa-shi, Saitama Saitama Prefecture Office (72) Inventor Yoichi Takano 3-1-1, Takasago, Urawa-shi, Saitama Saitama Prefecture Office (72) Inventor Kiyohito Chikazawa Nishishin, Shinjuku-ku, Tokyo 3-7-4 Kurita Industrial Co., Ltd. (72) Inventor Yuji Yamada 5200 Sankejiri, Kumagaya-shi, Saitama F-term within Hitachi Metals Co., Ltd. 4D003 AA05 AB02 AB03 CA02 CA08 DA22 EA19 EA28 FA01 FA05 4D040 BB05 BB07 BB23 BB42 BB52 BB82 BB91

Claims (4)

[Claims] 1. A method for backwashing a wastewater purifying apparatus in which a granular floating filter material carrying a biofilm is filled in a tank, and the wastewater is passed upward from the lower part of the tank while diffusing from a middle stage of the packed bed. When the filtration resistance of the packed bed reaches a set value, simple backwashing is performed, and when the difference between the filtration resistance immediately after simple backwashing and the filtration resistance immediately after normal backwashing reaches a predetermined resistance difference. A method for backwashing a drainage water purification device using a floating filter material, wherein the next backwash is usually a backwash. 2. Backwashing is performed by a combination of water washing in which treated water flows downflow in a tank and air washing by aeration from the lower part of the tank. 2. The method according to claim 1, wherein the simple backwashing is performed by reducing the number of repetitions of water washing and air washing as compared with the normal backwashing. Washing method. 3. When the difference between the filtration resistance immediately after simple backwashing and the filtration resistance immediately after normal backwashing reaches a predetermined resistance difference,
2. The method according to claim 1, wherein the normal backwashing is not performed immediately, but the normal backwashing is performed when the filtration resistance of the packed bed reaches a set value.
A method for backwashing a wastewater purification device using the floating filter medium according to the above. 4. When the difference between the filtration resistance immediately after simple backwashing and the filtration resistance immediately after normal backwashing reaches a predetermined resistance difference,
2. The method for backwashing a drainage water purification device using a floating filter medium according to claim 1, wherein the backwash is immediately performed immediately.