JP2013248566A - Membrane separation activated sludge process and reforming method of activated sludge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new membrane separation activated sludge process capable of efficient treatment while reducing a treatment cost, and to provide a reforming method of activated sludge.SOLUTION: A membrane separation activated sludge method includes: an activated sludge treatment of organic wastewater while maintaining DO to 10 mg/L or more in an aeration tank; and a membrane filtration treatment of the organic wastewater that has been subjected to the activated sludge treatment. A method for reforming activated sludge to separate the organic wastewater that has been subjected to the activated sludge treatment into solid and liquid by the membrane filtration treatment includes an activated sludge treatment of the organic wastewater while maintaining DO to 10 mg/L or more in the aeration tank.

Description

  The present invention relates to a membrane separation activated sludge method and a method for reforming activated sludge.

  As a method for purifying sewage such as organic wastewater, for example, activated sludge treatment is performed, and then a membrane separation activated sludge method (for example, Patent Document 1) in which solid-liquid separation is performed using a membrane, or activated sludge treatment is performed, followed by natural sedimentation There is an activated sludge method such as a standard activated sludge method for solid-liquid separation. Among these, the membrane separation activated sludge method can increase the volume load because it can maintain the MLSS concentration at the time of activated sludge treatment higher than the standard activated sludge method. As a result, there is an advantage that the size of the tank for performing the activated sludge treatment can be reduced, and initial costs such as construction costs can be reduced. In addition, the membrane separation activated sludge method also has an advantage that it is simple in terms of operation management because less activated sludge flows out during solid-liquid separation after the activated sludge treatment compared to the standard activated sludge method.

  On the other hand, since the membrane separation activated sludge method uses a filtration membrane for solid-liquid separation, initial cost for installing the filtration membrane and maintenance of the filtration membrane are required, which is required for sewage treatment compared with the standard activated sludge method. Running costs are high. For this reason, for example, it has been proposed to reduce the above-mentioned cost by improving the amount of permeated water per membrane area and reducing the membrane area to be installed. As a method of improving the amount of permeated water, for example, a method of performing membrane filtration treatment after reducing the MLSS concentration after activated sludge treatment (for example, Patent Document 2), or an activated sludge treatment tank in which a filtration membrane is disposed. Is divided into two tanks, and the MLSS concentration of one tank is set lower than that of the other, thereby improving the membrane filtration performance (for example, Patent Document 3). Other methods include, for example, a method of preventing clogging of membrane filtration by improving the cleaning efficiency of the separation membrane, thereby improving the amount of permeated water (for example, Patent Document 4), or by using a flocculant. There are methods for improving the amount of permeated water (for example, Patent Documents 5 and 6).

JP 2008-188548 A JP 2005-246310 A JP 2006-235099 A JP 2004-230222 A JP 2010-125366 A JP 2009-297688 A

  However, when the membrane filtration treatment is performed with the MLSS concentration lowered as in the method of Patent Document 2, the permeated water amount is improved, but there is a problem that sufficient treatment capacity cannot be obtained. In the case of the method of Patent Document 3, since a special treatment tank is required, there is a problem that the initial cost is increased. Although the method of Patent Document 4 enables efficient membrane cleaning, it cannot be said that the amount of permeated water can be sufficiently improved. In the methods of Patent Documents 5 and 6, surplus sludge increases due to the addition of the flocculant, and there is a problem that the sludge treatment cost increases. For this reason, the new method which can be processed efficiently is calculated | required, reducing the cost required for processing of sewage, such as organic waste water.

  The present invention provides a new membrane separation activated sludge method that can be efficiently treated while reducing the treatment cost, and a method for reforming activated sludge.

  The present invention, as one aspect, treats organic wastewater with activated sludge while maintaining dissolved oxygen (DO) at 10 mg / L or more in the aeration tank, and membrane-filters the organic wastewater treated with the activated sludge. The present invention relates to a membrane separation activated sludge method.

  In another aspect, the present invention is a method for modifying activated sludge in order to solid-liquid-separate the organic sludge treated with activated sludge by membrane filtration, and the DO is increased to 10 mg / L or more in the aeration tank. The present invention relates to a method for reforming activated sludge, including treating activated wastewater with activated sludge while maintaining.

  ADVANTAGE OF THE INVENTION According to this invention, the new method which can be processed efficiently can be provided, reducing processing cost.

FIG. 1 is a schematic configuration diagram illustrating an example of a configuration of an apparatus used in the first embodiment. FIG. 2 is a schematic configuration diagram illustrating another example of the configuration of the apparatus used in the first embodiment. FIG. 3 is a schematic configuration diagram illustrating still another example of the configuration of the apparatus used in the first embodiment.

  In the treatment of sewage using the standard activated sludge method and the membrane separation activated sludge method, the present invention can improve the amount of permeated water during membrane filtration by treating the organic wastewater with activated sludge while maintaining it at 10 mg / L or more. Based on this knowledge.

  The details of the mechanism that can improve the amount of permeated water during the membrane filtration treatment according to the present invention are unknown, but are estimated as follows. Estimated that the amount of permeated water during membrane filtration treatment is improved because the viscosity of activated sludge contained in the activated sludge treated water is reduced by treating the organic wastewater with activated sludge while maintaining DO at 10 mg / L or more. Is done. However, this assumption does not limit the present invention.

(Membrane separation activated sludge method)
In one aspect, the present invention is a membrane separation process comprising subjecting organic wastewater to activated sludge treatment and membrane filtration treatment of the organic wastewater treated with activated sludge while maintaining DO at 10 mg / L or more in an aeration tank. Activated sludge method (hereinafter also referred to as “membrane separation activated sludge method of the present invention”). According to the membrane separation activated sludge method of the present invention, the organic waste water is subjected to activated sludge treatment while maintaining DO at 10 mg / L or more, so that the amount of permeated water during membrane filtration can be improved. For this reason, according to the membrane separation activated sludge method of the present invention, for example, the installation area of the filtration membrane can be reduced, and since no special equipment is required, initial costs such as equipment costs, membrane management, etc. The running cost required for the operation can be reduced. Moreover, according to the membrane separation activated sludge method of the present invention, for example, a sufficient amount of permeate can be obtained without reducing the MLSS concentration, so that the sewage treatment efficiency can be improved.

  In the membrane separation activated sludge method of the present invention, the activated sludge treatment of organic waste water is performed while maintaining the DO in the aeration tank at 10 mg / L or more. The activated sludge treatment is preferably performed while maintaining in the range of 10 to 30 mg / L, more preferably in the range of 10 to 20 mg / L, and even more preferably 10 mg / L from the viewpoint of reducing the cost of gas introduction equipment and running cost. The range is more than L and less than 18 mg / L, more preferably about 15 mg / L.

  In the present specification, “activated sludge treatment” refers to treatment using a group of aerobic microorganisms having a function of decomposing organic matter, for example, by breeding microorganisms that degrade organic matter contained in sewage and wastewater. It can be carried out by aeration of organic waste water in the presence of the resulting mud precipitate. In this specification, “organic wastewater” refers to wastewater containing organic matter (BOD component), for example, domestic wastewater from homes, domestic wastewater such as human waste, organic industrial wastewater from factories such as food or devices. including. The dissolved oxygen concentration can be measured using a conventionally known dissolved oxygen concentration meter (DO meter).

  In the membrane separation activated sludge process of the present invention, the activated sludge treatment of organic wastewater is from the viewpoint of further stabilizing the dissolved oxygen concentration during the activated sludge treatment, reducing the running cost required for the sewage treatment, and improving the treatment efficiency. It is preferable to detect the dissolved oxygen concentration in the aeration tank and automatically control the DO in the aeration tank to be 10 mg / L or more using the detected dissolved oxygen concentration. The DO in the aeration tank can be controlled by controlling the amount of oxygen supplied to the aeration tank, and more preferably by supplying high-concentration oxygen. Therefore, it is preferable that the membrane separation activated sludge method of the present invention includes supplying high-concentration oxygen to the aeration tank. The supply of high-concentration oxygen can be performed, for example, by supplying high-concentration oxygen-containing gas, high-concentration oxygen-containing water, and / or activated sludge containing high-concentration oxygen to the aeration tank. You may carry out by supplying the activated sludge containing it, circulating. The high-concentration oxygen-containing gas refers to a gas having a higher oxygen-containing concentration than air (oxygen concentration: 21% by volume or more), for example, a gas containing 22% to 99.9% by volume of oxygen, preferably 30% oxygen. It is a gas containing volume% to 93 volume%. Examples of the high-concentration oxygen-containing gas include oxygen from an oxygen generator, oxygen from an oxygen cylinder, and waste oxygen from a nitrogen generator. High-concentration oxygen-containing water refers to water having a higher oxygen concentration than general water, for example, water containing 10 to 100 mg / L in DO, preferably water containing 50 to 100 mg / L in DO. . Examples of the high-concentration oxygen-containing water include water aerated with a high-concentration oxygen-containing gas, water obtained by pressurizing and dissolving a gas containing oxygen, and water generated by stirring and mixing a gas containing water and oxygen. Can be mentioned. Moreover, in order to make DO in the aeration tank uniform, supply of oxygen may be performed with stirring, for example.

  For example, oxygen can be supplied from a diffuser tube disposed in the tank to supply oxygen-containing gas such as high-concentration oxygen gas, to water containing oxygen higher than usual, or to an aeration tank, It can be controlled by supplying activated sludge water containing oxygen to the aeration tank. The supply of oxygen may be performed, for example, by supplying fine bubbles. For example, the fine bubbles may be dissolved by pressurizing a gas containing oxygen in water, or stirring a gas containing water and oxygen. It can be supplied by mixing and generating. When supplying fine bubbles, the gas may be air or the above-described high-concentration oxygen-containing gas. Alternatively, water and / or activated sludge water may be introduced into the fine bubbles in advance and supplied as high-concentration oxygen-containing water and / or activated sludge water.

  Since the membrane separation activated sludge method of the present invention performs activated sludge treatment while maintaining DO at 10 mg / L or more as described above, it is possible to efficiently membrane-treat the organic wastewater treated with activated sludge. The filtration membrane used for the membrane filtration treatment is not particularly limited, and examples thereof include an MF (precision filtration) membrane, a UF (ultrafiltration) membrane, and an NF (nanofiltration) membrane. The form of the filtration membrane is not particularly limited, and examples thereof include a flat membrane, a tubular membrane, and a hollow fiber. The filtration membrane may be, for example, an organic membrane or an inorganic membrane. The material of the organic film is not particularly limited, and examples thereof include PVDF, PE, PP, PTFE, CA, PAN, PI, PS, and PES. The material of the inorganic film is not particularly limited, and examples thereof include aluminum oxide, zirconium oxide, titanium oxide, SUS, and glass. The filtration membrane may be disposed so as to be immersed in the aeration tank, or may be disposed outside the aeration tank. In the case of being arranged outside the aeration tank, the filtration membrane may be a suction type membrane separation membrane arranged by being immersed in a processing tank different from the aeration tank, or a pressure type (external pressure type) separation membrane. Also good.

  The membrane filtration treatment is not particularly limited, and examples thereof include a suction type membrane filtration treatment and a pressure type membrane filtration treatment. The membrane filtration treatment may be performed, for example, by transferring the organic sludge treated with activated sludge to a solid-liquid separation tank and performing it in a solid-liquid separation tank, or in an aeration tank in which activated sludge treatment is performed, or an aeration tank. You may carry out by the filtration membrane arrange | positioned outside.

(Organic wastewater treatment method)
In another aspect, the present invention provides an activated sludge treatment step for treating organic wastewater with activated sludge while maintaining DO at 10 mg / L or more in the aeration tank, and membrane filtration of the organic wastewater treated in the activated sludge treatment step. The present invention relates to an organic wastewater treatment method (hereinafter, also referred to as “treatment method of the present invention”) including a separation step of treating and collecting sludge. According to the treatment method of the present invention, a sufficient amount of permeate can be obtained at the time of membrane filtration treatment by treating the organic wastewater with activated sludge while maintaining DO at 10 mg / L or more in the aeration tank. Organic wastewater can be treated efficiently while reducing costs. The activated sludge treatment step and the separation step in the treatment method of the present invention can be performed in the same manner as the activated sludge treatment and membrane filtration treatment of the membrane separation activated sludge method of the present invention, respectively.

(Modification method of activated sludge)
The present invention, as yet another aspect, is a method for reforming activated sludge in order to solid-liquid-separate the organic wastewater treated with activated sludge by membrane filtration, wherein DO is 10 mg / L or more in the aeration tank. The present invention relates to a method for reforming activated sludge (hereinafter, also referred to as “the reforming method of the present invention”), which comprises treating organic wastewater with activated sludge while maintaining the same. According to the reforming method of the present invention, it is possible to obtain activated sludge modified so as to exhibit a permeated water amount sufficient to enable efficient membrane filtration treatment. The activated sludge treatment in the reforming method of the present invention is the same as the activated sludge treatment in the membrane separation activated sludge method of the present invention.

(Membrane separation activated sludge treatment system)
The present invention, as yet another aspect, an aeration tank that performs activated sludge treatment of organic wastewater, a filtration membrane that performs membrane filtration treatment of organic wastewater that has been treated with activated sludge, and dissolved oxygen that measures the dissolved oxygen concentration in the aeration tank Based on the dissolved oxygen concentration measured by the dissolved oxygen meter and a membrane separation activated sludge treatment system (hereinafter referred to as a control unit for controlling the DO of the aeration tank so that the DO of the aeration tank is maintained at 10 mg / L or more) , Also referred to as “processing system of the present invention”). Since the treatment system of the present invention includes a control unit that controls the DO of the aeration tank so that the DO of the aeration tank is maintained at 10 mg / L or more, the membrane separation activated sludge method, the organic wastewater treatment method of the present invention, And the reforming method of activated sludge can be performed efficiently.

  The controller is preferably controlled so that the DO of the aeration tank is maintained at 10 mg / L or more based on the dissolved oxygen concentration measured by the dissolved oxygen meter. For example, the control unit preferably controls the amount of oxygen supplied to the aeration tank. For example, when the DO in the aeration tank falls below a preset reference value, oxygen is supplied, and when the DO exceeds a preset reference value, the supply of oxygen is stopped. As described above, this can be achieved by controlling the air diffuser arranged in the aeration tank and / or the oxygen supply means connected to the air diffuser.

  In the treatment system of the present invention, the filtration membrane may be arranged soaked in the aeration tank, or may be arranged as an external pressure type filtration membrane outside the aeration tank. Moreover, the processing system of this invention is provided with the processing tank for performing membrane separation different from an aeration tank, and the filtration membrane may be immersed by the processing tank.

  In order to make the dissolved oxygen concentration uniform, the aeration tank may be provided with an agitator such as a propeller type, a turbine type, a paddle type, and a screw type, or an inner cylinder for an air lift. Moreover, when the filtration membrane is arrange | positioned in the processing tank different from an aeration tank, said stirrer etc. may be arrange | positioned at the processing tank from the point of the improvement of filtration efficiency.

  Hereinafter, the present invention will be described in detail with reference to the drawings. However, the following description is merely an example, and it goes without saying that the present invention is not limited to this.

(Embodiment 1)
FIG. 1 is a schematic configuration diagram of an apparatus used in the membrane separation activated sludge method of the first embodiment. The apparatus of Embodiment 1 includes a raw water tank 1, an aeration tank 2, and a treated water tank 3. The raw water tank 1 and the aeration tank 2, and the aeration tank 2 and the treated water tank 3 are connected by pipes. The aeration tank 2 includes a filtration membrane 5, an oxygen supply air diffuser 4, an air diffuser (not shown) for supplying stirring air, and a dissolved oxygen meter (not shown). And a water level gauge (not shown). The filtration membrane 5 and the treatment tank 3 are connected so that the liquid component separated by the filtration membrane 5 can be sent to the treatment tank 3 through a pipe. For example, an oxygen supply means (not shown) such as a gas cylinder containing 99% oxygen is connected to one end of the oxygen supply diffuser tube 4.

  Below, an example of the membrane separation activated sludge method using the apparatus of Embodiment 1 is demonstrated.

  First, organic industrial wastewater (treated water) is quantitatively fed from the raw water tank 1 to the aeration tank 2. The treated water sent is aerated by supplying oxygen from the oxygen supply air diffuser 4 in the aeration tank 2 and being agitated by the air diffuser for supplying air for stirring, while the DO is 10 mg. Activated sludge treatment is performed in a state maintained at / L or more. Control of the dissolved oxygen concentration in the aeration tank 2 is controlled by the amount of oxygen supplied from the aeration tube 4, for example, the DO of the aeration tank 2 is measured with a dissolved oxygen meter installed in the aeration tank 2, and DO Is supplied to the aeration tank 2 so that the supply of oxygen is stopped when the DO falls below the preset reference value, and when the DO exceeds the preset reference value This can be done by controlling the oxygen. For example, the control method is not particularly limited. When the DO of the aeration tank 2 falls below 13 mg / L, the oxygen supply solenoid valve opens, and when it exceeds 17 mg / L, the oxygen supply solenoid valve is closed. There is a way. The stirring air may be intermittently operated from the viewpoint of suppressing the amount of oxygen used for aeration and reducing the running cost.

  When a predetermined amount of water to be treated is fed into the aeration tank 2, the liquid feeding means for filtering membrane suction is operated, and when the amount in the aeration tank 2 falls below the preset amount, the liquid feeding is performed. Control to stop the means. The liquid component sucked and separated into solid and liquid by the filtration membrane 4 is sent to the treated water tank 3.

  In the first embodiment, the embodiment in which the filtration membrane 4 is immersed in the aeration tank 2 has been described as an example. However, the present invention is not limited to this, and for example, as shown in FIG. 4 may be in the form of being immersed in a treatment tank (treatment water tank 3) different from the aeration tank 2, and the filtration membrane 4 is arranged outside the aeration tank 2 as shown in FIG. Form may be sufficient.

  Hereinafter, although the present invention is explained using an example, the present invention is limited to this and is not interpreted.

Example 1
In the aeration tank (volume: 10 L) in which the filtration membrane was arranged, the activated sludge treatment of organic wastewater was performed while maintaining DO at 10 to 20 mg / L. The treatment was performed by setting the temperature in the aeration tank to 20 to 25 ° C. while supplying a high-concentration oxygen-containing gas (oxygen concentration: 99% or more). The input amount of organic wastewater into the aeration tank was 3 L / day, and the amount of treated water drawn through the filtration membrane was 3 L / day. The DO in the aeration tank was measured by using a dissolved oxygen meter (trade name: DO-31P, manufactured by Toa DKK Corporation) arranged in the aeration tank.

(Comparative Example 1)
The activated sludge treatment was performed under the same conditions as in Example 1 except that the DO in the aeration tank was about 2 mg / L.

[Measurement of filtered water volume]
The activated sludge was collected from the aeration tank that had been subjected to the activated sludge treatment in Example 1 and Comparative Example 1, and the amount of filtered water was measured using the collected activated sludge. Membrane filtration is performed by pouring 50 ml of activated sludge of Example 1 or Comparative Example 1 with a MLSS concentration of 5000 mg / L into a funnel set with folded filter paper (type 5 C defined in JIS P3801). The amount of filtered water was measured in 5 minutes from the time when the water began to drop. As a result, the amount of water filtered in 5 minutes was 35.5 ml for the activated sludge of Example 1, while 21.5 ml for the activated sludge of Comparative Example 1. In other words, by performing the activated sludge treatment while maintaining DO at 10 mg / L or more, the activated sludge was reformed and the amount of filtered water was improved.

[Activated sludge viscosity test]
An activated sludge viscosity test was also conducted using the activated sludge used to measure the amount of filtered water. The measurement was performed using a viscometer (manufactured by Toki Sangyo Co., Ltd., trade name: TVB-10M) using a rotational speed of 20 rpm and a rotor of M1. As a result, the viscosity of the activated sludge of Example 1 was 14.2 mPas, whereas the activated sludge of Comparative Example 1 was 18.0 mPas. The activated sludge of Example 1, which was treated with activated sludge while maintaining DO at 10 mg / L or higher, had a lower viscosity than the activated sludge of Comparative Example 1, which was treated while maintaining DO at less than 2 mg / L. Was confirmed.

  From the above results, it was suggested that the activated sludge treatment was carried out while maintaining the DO at 10 mg / L or more, whereby the viscosity of the activated sludge was reduced, and as a result, the amount of filtered water was improved.

Claims (9)

A membrane-separated activated sludge process comprising treating activated organic sludge with activated sludge while maintaining dissolved oxygen (DO) at 10 mg / L or more in an aeration tank, and subjecting the organic sludge treated with activated sludge to membrane filtration. . 2. The activated sludge method according to claim 1, comprising detecting DO in the aeration tank and automatically controlling the DO in the aeration tank to be 10 mg / L or more using the detected dissolved oxygen concentration. The activated sludge method according to claim 1 or 2, wherein the membrane filtration treatment is a submerged membrane filtration treatment or an external pressure membrane filtration treatment. The activated sludge method according to any one of claims 1 to 3, wherein the organic wastewater treated with activated sludge is transferred to a solid-liquid separation tank, and the membrane filtration treatment is performed in the solid-liquid separation tank. The activated sludge method according to any one of claims 1 to 3, wherein the membrane filtration treatment is performed in the aeration tank that performs the activated sludge treatment. The activated sludge method according to claim 1, comprising supplying high-concentration oxygen to the aeration tank. The high-concentration oxygen is supplied by supplying a high-concentration oxygen-containing gas or high-concentration oxygen-containing water to the aeration tank or by circulating and supplying activated sludge containing high-concentration oxygen. Activated sludge process. The activated sludge method according to any one of claims 1 to 7, comprising supplying fine bubbles or pressurized gas containing oxygen to the culture tank. A method of modifying activated sludge in order to perform solid filtration by subjecting organic wastewater treated with activated sludge to membrane filtration,
A method for modifying activated sludge, comprising treating organic wastewater with activated sludge while maintaining DO at 10 mg / L or more in an aeration tank.

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