JP2977002B2 - Wastewater treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating sewage, and more particularly, to a method for treating sewage in a combined septic tank.

[0002]

2. Description of the Related Art Conventionally, in a combined septic tank, for example, as shown in FIG. 2, sewage 1 is supplied to a pretreatment facility 2, where a rough screen having a width of about 50 mm, an aerated sand settling tank, and a crushing facility are provided. Pre-treatment such as removal of sand and large foreign matter by such as, and if the inflow of sewage is large,
A flow control tank is installed to control the flow.

[0003] The pretreated sewage is supplied to an aeration tank 4 by a pump 3. At this time, in order to further remove impurities in the sewage not removed by the pretreatment facility 2, the sewage is supplied from the pretreatment facility 2. A fine-grained screen 5 having a width of about 1 mm is provided in the flow path to the aeration tank 4, and the screen 5 from which impurities are removed is supplied to the tank 4 as raw water 6.

[0004] In the tank 4, the mixed solution in the tank is biologically treated with activated sludge under a condition that air can be supplied by a blower 7 or the like, and a pump is supplied to a membrane separation device 8 immersed in the tank 4. By applying a negative pressure at 9 and filtering by suction, the activated sludge and the permeated water 10 are separated.

[0005] Further, the membrane permeated water 10 taken out by the membrane separation device 8 is sent to a disinfection facility 11 and disinfected.
The water is taken out via the like and discharged as treated water 13.

[0006]

However, the above-mentioned sewage contains foreign matter mainly composed of fibers having a property of agglomerating by stirring. In the above-mentioned conventional flow, the stirring time in the pretreatment equipment 2 is too short, and is supplied to the fine-grain screen 5 before being agglomerated. For this reason, there is a problem that foreign matter that has passed through the fine-grain screen 5 agglomerates due to the concentration action in the aeration tank 4 and the membrane separation device is easily blocked.

An object of the present invention is to solve the above-mentioned problem and to remove foreign substances condensed in an aeration tank and to prevent the membrane separation device from being clogged.

[0008]

In order to solve the above problems, the present invention supplies raw water sent from a pretreatment facility to a filtration means, and supplies water to be treated which has passed through the filtration means to an aeration tank. In the method of treating wastewater, which is biologically treated with activated sludge in an aeration tank and is separated into activated sludge and membrane permeated water by a membrane separator immersed in the aeration tank, an intermediate tank is provided upstream of the aeration tank. After supplying the raw water to the intermediate tank, the raw water is sent to the filtration unit, and the water to be treated that has passed through the filtration unit is supplied to the aeration tank, and a part of the mixed liquid in the aeration tank is returned to the intermediate tank. It is characterized by.

[0009]

According to the above construction, an intermediate tank is provided in a stage preceding the aeration tank, and raw water is supplied to the intermediate tank and then sent to the filtration means.
By supplying the water to be treated which has passed through the filtration means to the aeration tank and returning a part of the mixed solution in the aeration tank to the intermediate tank, impurities in the raw water are removed to some extent by the filtration means, and The contaminants condensed in the aeration tank without being removed by the means are returned to the intermediate tank and removed again by being sent to the filtering means, thereby increasing the removal rate of the foreign substances.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a wastewater treatment method according to one embodiment of the present invention will be described.
This will be described with reference to the overall configuration diagram of FIG.

As shown in FIG. 1, the configuration of the sewage treatment method of the present invention is different from the configuration of the conventional sewage treatment method in that an intermediate tank 14 is provided between the pretreatment equipment 2 and the aeration tank 4. Is a point. The details will be described below.

The sewage 1 is supplied to a pretreatment facility 2 in which sand and large foreign matters are removed, and when the inflow of the sewage 1 fluctuates greatly, the flow rate is adjusted. Is supplied to the intermediate tank 14 as raw water 6.

In the intermediate tank 14, when the raw water 6 is supplied and the mixed liquid 18 in the tank 4 is returned from the aeration tank 4 in the subsequent stage, the liquid 14a is stored in the tank and the liquid 14a in the tank is stored.
Is sent to a fine screen 16 by a pump 15.

The liquid 14a sent from the intermediate tank 14 is supplied to the aeration tank 4 as water to be treated 17 after being filtered through a fine mesh screen 16 to remove some impurities. The water to be treated 17 supplied to the aeration tank 4 is mixed with the activated sludge in the tank 4, and is biologically treated by the activated sludge under the condition that stirring or air can be supplied by the blower 7 or the like. The mixed liquid in the tank 4 is separated into activated sludge and membrane permeated water 10 by applying a negative pressure to the membrane separation device 8 immersed in the tank 4 with a pump 9 and performing suction filtration. The mixed liquid 18 overflowing from 4 is returned to the intermediate tank 14.

At this time, impurities mainly contained in the fiber which are contained in the water to be treated 17 and are not removed by the fine mesh screen 16 and supplied to the aeration tank 4 are stirred in the aeration tank 4. Agglomerates in between. When the mixed liquid 18 is returned to the intermediate tank 14 as described above, the condensed contaminants are included in the mixed liquid 18 and returned.
Is sent to the fine-grain screen 16 again, and is removed by the fine-grain screen 16.

The membrane permeated water 10 from the aeration tank 4 is supplied to a disinfection facility 11
Pumps after being sent to
It is taken out by 12 and discharged as treated water 13. In the case of a septic tank, the SS is usually operated with a concentration of about 200 times. In other words, SS and organic matter are
Although it is about 50-100 mg / L, it is converted into sludge in the aeration tank and becomes a high concentration of about 15000 mg / L, so the concentration rate at this time is 15000 / (50-100) = 150-300 times Becomes Due to such high concentration, the fiber content agglomerates in the aeration tank. By doing so, it is easily removed. At this time, the activated sludge itself is also agglomerated and removed together with the fiber and the like, so that a very high-concentration screen residue is separated. In the above case, the screen residue showed a solids concentration of about 3-8%.

In the above method, the intermediate tank can be provided with a denitrification function by gently stirring the liquid in the intermediate tank. If the purpose is to remove nitrogen, the transfer amount from the intermediate tank to the fine mesh screen should be at least three times the raw water amount,
It should be less than 10 times. As an example of the nitrogen removal rate,
In the case of raw water having a TN of about 30 to 40 mg / L, a treated water having a TN of about 5 to 10 mg / L was obtained by transferring 5-fold amount.

[0018]

As described above, according to the present invention, an intermediate tank is provided before the aeration tank, and the liquid mixture in the aeration tank is returned to the intermediate tank, and is further sent from the intermediate tank to the fine mesh screen. By doing so, the removal rate of foreign matter, which is mainly fiber components, agglomerated in the aeration tank is increased, and it is possible to prevent clogging of the membrane separation device by foreign matter.

Also, the liquid in the tank is gently stirred in the intermediate tank, so that the intermediate tank can also have a denitrification function.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram illustrating a wastewater treatment method according to an embodiment of the present invention.

FIG. 2 is an overall configuration diagram illustrating a conventional method for treating wastewater.

[Explanation of symbols]

 4 Aeration tank 6 Raw water 14 Intermediate tank 16 Fine screen 17 Water to be treated 18 Mixed liquid

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hirokazu Ikeji 1-47, Shikitsuhigashi, Namiwa-ku, Osaka-shi, Osaka Kubota Co., Ltd. (56) References JP-U 4-99297 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) C02F 3/12

Claims (1)

(57) [Claims] 1. Raw water sent from a pretreatment facility is supplied to a filtration means, and water to be treated permeated through the filtration means is supplied to an aeration tank, where it is biologically treated with activated sludge in the aeration tank. In a method for treating sewage in which activated sludge and membrane permeated water are separated by a membrane separation device immersed in an aeration tank, an intermediate tank is provided in a preceding stage of the aeration tank, and the raw water is supplied to the intermediate tank, and then filtration means And supplying the treated water that has passed through the filtration means to the aeration tank, and returning a part of the mixed liquid in the aeration tank to the intermediate tank.