JP2009066589A - Wastewater treatment method and wastewater treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wastewater treatment method which enables the proper evaluation of a clogging risk before a membrane is clogged and the stable and efficientle solid-liquid separation of activated sludge and a treated liquid by taking a necessarily sufficient measure. <P>SOLUTION: In the wastewater treatment method using a membrane separation activated sludge method, the activated sludge or organic wastewater is brought into contact with a multivalent cation capturing means when the concentration of a uronic acid unit in the activated sludge becomes a predetermined value or above or when a value, which is obtained by multiplying the concentration of the uronic acid unit in the activated sludge by the concentration of the multivalent cation in the organic wastewater becomes a predetermined value or above before subjected to solid-liquid separation by a separation membrane device. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for treating wastewater by a membrane separation activated sludge process for treating organic wastewater.

  As one of the wastewater treatment methods, there is a membrane separation activated sludge method in which a membrane cartridge is immersed in an activated sludge tank and solid-liquid separation between the activated sludge and the treatment liquid is performed by filtration. In this method, the activated sludge concentration (MLSS: Mixed Liquor Suspended Solid) can be made extremely high from 5000 to 20000 mg / L for solid-liquid separation, so the volume of the activated sludge tank can be reduced, or the reaction time in the activated sludge tank. Can be shortened. In addition, suspended solids (SS: Suspended Solid) are not mixed in the treated water because of filtration through a membrane, so the final sedimentation tank is not required and the site area of the treatment facility can be reduced, regardless of whether activated sludge sedimentation is good or bad. Since solid-liquid separation can be performed, there are many advantages such as reduced activated sludge management, and it has been rapidly spreading in recent years.

  As the membrane cartridge, a flat membrane or a hollow fiber membrane is used. The membrane-separated activated sludge method reduces the effective membrane area and reduces the filtration efficiency by attaching to the membrane surface biological polymers that metabolize microorganisms in activated sludge, activated sludge itself, and contaminants brought in from raw water. Since it decreases, long-term stable filtration may not be possible.

  As a method for removing deposits on the membrane surface, there is backwashing in which a medium such as filtered water is ejected in the direction opposite to the filtration direction.

  Conventionally, air is aerated from the lower part of the membrane cartridge in order to avoid accumulation of activated sludge and contaminants between the membrane surface and between the membranes, and the vibration effect of the membrane and the stirring by the upward movement of bubbles Due to the effect, activated sludge aggregates between the membrane surface and between the membranes, and contaminants brought in from the raw water are peeled off. For example, in Japanese Patent Laid-Open No. 2000-157846 (Patent Document 1), in a hollow fiber membrane cartridge of a filtration device, a cartridge head and a skirt are separated, and a hollow portion at the end of the hollow fiber membrane on the cartridge head side is opened. A configuration is disclosed in which the hollow portion at the end portion of the hollow fiber membrane on the skirt side is sealed, and a plurality of through holes are provided in the skirt side adhesive fixing layer. According to such a configuration, during the air bubbling operation in the filtration apparatus, the separation action of the suspension deposited on the outer surface of the hollow fiber membrane is increased, and the separated suspension is excluded from the hollow fiber membrane cartridge. It's easy to do.

  However, depending on the composition of the organic wastewater that flows into the activated sludge tank, microorganisms secrete a large amount of components that can trap the membrane unless the activated sludge treatment conditions are set appropriately. It may become impossible to perform solid-liquid separation.

  On the other hand, clogging can be made difficult to occur by setting the membrane filtration flux low, but if such a method is excessively performed, there is a problem that the efficiency of wastewater treatment is reduced.

  Japanese Patent Application Laid-Open No. 2004-290765 (Patent Document 2) discloses that at least one selected from the group consisting of antibiotics, uncouplers, and chelating agents in a treatment tank or a soluble organic substance-containing liquid in a membrane separation activated sludge method. Methods for adding types have been proposed. In the Examples, it is shown that the viscosity of the sludge liquid is improved when an antibiotic and / or an uncoupler is added, but there is no description about the detailed conditions when a chelating agent is added.

Japanese Unexamined Patent Publication No. 2000-265193 (Patent Document 3) discloses a method of treating activated sludge by adding a predetermined chelate compound to washing wastewater for fermented food components. Since the chelate compound used in the method is easily biodegradable, the burden can be reduced during the decomposition treatment with activated sludge. However, in the comparative example to which EDTA, which is widely used as a chelating agent, was added (Example 4), it was hardly biodegraded after 14 days and the environmental load was large.
Japanese Patent Laid-Open No. 2000-157846 JP 2004-290765 A JP 2000-265193 A

  As described above, some chelating agents are inferior in biodegradability, and there is a problem that the environmental burden increases when added in excess, so it is important to add the necessary and sufficient amount.

  Therefore, the present invention can stably and efficiently perform solid-liquid separation between activated sludge and treatment liquid by appropriately evaluating the risk of clogging before the membrane is clogged and taking necessary and sufficient measures. The object is to provide a way to make it possible.

As a result of intensive studies, the present inventors have found that a substance that adheres to the outer surface of the membrane and inhibits filtration is mainly composed of uronic acid and has a molecular weight of several hundreds of thousands to several millions of uronic acid-containing polymer. I found out. Furthermore, the carboxylic acids in the uronic acid are intermolecularly cross-linked by polyvalent cations such as Ca ²⁺ and Mg ²⁺ , and many molecular chains cross-link and become bulky, causing clogging of the separation membrane. I found. If the polyvalent cations that cause crosslinking are removed, the cross-linked molecular chains can be loosened, passing through the pores of the separation membrane and being discharged out of the system without being clogged on the separation membrane surface. It was confirmed. At this time, measure the clogging risk by measuring the uronic acid unit concentration in the activated sludge tank and / or the polyvalent cation concentration in the organic wastewater, and remove the polyvalent cation when the risk becomes high. As a result, the present inventors have found that necessary and sufficient processing can be performed and have completed the present invention.

That is, the present invention
[1] Organic wastewater is allowed to flow into an activated sludge tank containing activated sludge, the organic wastewater is biologically treated with the activated sludge, and the activated sludge is separated by the activated sludge tank or a separation membrane device installed in the subsequent stage. A method for treating wastewater by a membrane-separated activated sludge apparatus for solid-liquid separation, wherein the activated sludge or the organic property is obtained when the uronic acid unit concentration in the aqueous phase of the activated sludge becomes a predetermined value or more. A wastewater treatment method in which wastewater is brought into contact with a polyvalent cation capturing means and then solid-liquid separation is performed by the separation membrane device;
[2] The above-mentioned [1], wherein when the uronic acid unit concentration (mg / L) becomes 20 or more, the activated sludge or the organic waste water is brought into contact with the polyvalent cation capturing means. Wastewater treatment method;
[3] Organic wastewater is allowed to flow into an activated sludge tank containing activated sludge, the organic wastewater is biologically treated with the activated sludge, and the activated sludge is separated by the activated sludge tank or a separation membrane device installed in the subsequent stage. A method for treating wastewater by a membrane-separated activated sludge apparatus for solid-liquid separation, wherein the concentration of polyvalent cations in the organic wastewater (mg / L) is increased to the uronic acid unit concentration (mg / L) in the aqueous phase of the activated sludge. When the value multiplied by mg / L) becomes a predetermined value or more, the activated sludge or the organic waste water is brought into contact with the polyvalent cation capturing means, and then the solid-liquid separation is performed by the separation membrane device. Wastewater treatment method;
[4] When the value obtained by multiplying the uronic acid unit concentration (mg / L) by the polyvalent cation concentration (mg / L) becomes 600 or more, the activated sludge or the organic waste water is captured by the polyvalent cation. The wastewater treatment method according to [3] above, which is brought into contact with means;
[5] The wastewater treatment method according to any one of [1] to [4], wherein the polyvalent cation capturing means is a chelating agent or an ion exchange resin;
[6] The wastewater treatment according to any one of [1] to [5], including a step of washing the separation membrane device with a washing liquid containing a polyvalent cation trapping means in the middle of the solid-liquid separation. Method;
[7] An activated sludge tank that contains activated sludge and biologically treats organic wastewater, and a separation membrane that is installed in or at the subsequent stage of the activated sludge tank and that separates the activated sludge from the treatment liquid by the activated sludge A wastewater treatment apparatus comprising: a means for measuring a uronic acid unit concentration in the aqueous phase of the activated sludge and / or a polyvalent ion concentration in the organic wastewater; and the activated sludge or the organic wastewater. A wastewater treatment apparatus comprising a polyvalent cation trapping means for removing polyvalent cations from water.
[8] The wastewater treatment apparatus according to [7], wherein the polyvalent cation capturing unit is a chelating agent addition unit;
[9] The wastewater treatment apparatus according to [7], wherein the polyvalent cation capturing means is an ion exchange resin tower; and [10] Further, the uronic acid unit concentration (mg / L) is a predetermined value. Or when the value obtained by multiplying the uronic acid unit concentration (mg / L) by the polyvalent cation concentration (mg / L) exceeds a predetermined value The present invention relates to the waste water treatment apparatus according to any one of [7] to [9], comprising control means for automatically functioning the means.

  According to the present invention, the uronic acid unit concentration in activated sludge and / or the polyvalent cation concentration in organic wastewater is measured to evaluate the risk of clogging before the membrane is clogged. Capturing cations can prevent clogging. According to the present invention, solid-liquid separation can be performed stably for a long period of time without causing the problem of adding a chelating agent more than necessary to increase the environmental load.

  Below, preferable embodiment of the waste water treatment method which concerns on this invention is described.

  First, a wastewater treatment method using the general membrane separation activated sludge apparatus shown in FIG. 1 will be described. In FIG. 1, the organic waste water 1 flowing into the membrane separation activated sludge tank is temporarily stored in the flow rate adjusting tank 3 after removing impurities by a pretreatment facility 2 such as a fine screen or a drum screen. Thereafter, the organic waste water 1 is supplied from the flow rate control tank 3 to the membrane separation activated sludge tank (aeration tank) 4 at a constant flow rate in order to keep the membrane filtration flux in the separation membrane device constant.

  In the membrane separation activated sludge tank 4, the organic matter (BOD component) in the organic wastewater 1 is decomposed and removed by the microorganisms in the activated sludge. Solid-liquid separation of the activated sludge mixed liquid in the membrane separation activated sludge tank 4 is performed by an immersion type separation membrane apparatus 5 immersed in the tank, and the filtrate 9 is sterilized in a sterilization tank 10 as necessary, and then treated water 11 As obtained. In the membrane separation activated sludge tank 4, the microorganisms proliferate while decomposing the BOD component in the organic wastewater 1.

  As described above, the present inventors have found that the separation membrane can be prevented from being clogged by removing the polyvalent cation in the activated sludge. In particular, since it is the carboxylic acid portion of the uronic acid-containing polymer that is cross-linked by the polyvalent cation, the uronic acid concentration in the activated sludge is measured, and when the concentration exceeds a predetermined concentration, the polyvalent cation By catching, the risk of clogging can be avoided sufficiently. The polyvalent cation is preferably captured when the uronic acid concentration exceeds 20 mg / L, preferably 30 mg / L.

  Moreover, the polyvalent cation concentration in organic wastewater is measured together with the uronic acid unit concentration in the activated sludge, and the value obtained by multiplying the uronic acid unit concentration (mg / L) by the polyvalent cation concentration (mg / L) is The risk of clogging can be avoided sufficiently and sufficiently also by capturing the polyvalent cation when the value exceeds a predetermined value. The polyvalent cation is preferably captured when the value obtained by multiplying the uronic acid unit concentration (mg / L) by the polyvalent cation concentration (mg / L) is 600 or more.

  When measuring the uronic acid unit concentration, it is preferable to measure the activated sludge after filtration through a filter medium having a larger pore size than the separation membrane of the separation membrane device such as filter paper to obtain a sludge filtrate. By this operation, only the suspended matter in the activated sludge is captured by the filter medium, and the uronic acid component passes through the filter paper. Therefore, if the uronic acid unit concentration in the filtrate is measured, the concentration of the uronic acid-containing polymer that becomes the clogging substance of the membrane can be measured more accurately.

  The pore diameter of the filter medium at this time is preferably 5 times or more, more preferably 10 times or more the separation membrane pore diameter provided in the separation membrane device. Further, the upper limit is about 100 times or less the pore size of the separation membrane provided in the separation membrane device, and it is more preferably 10 μm or less. The material of the filter medium is preferably a hydrophilic material with little adsorption of the uronic acid component. As such a filter medium, for example, a filter paper made of cellulose can be used.

Concentration of uronic acid unit is according to NELLY BLUMENKRANTZ, GUSTAV ASBOE-HANSEN, “New Method for Quantitative Acid of Aid” published by ANALITICAL BIOCHEMISTRY Vol. It can be measured by a calibration curve prepared using polygalacturonic acid. Specifically, the following procedure may be performed.
1) Take 0.5 mL of sludge filtrate and a known concentration of polygalacturonic acid aqueous solution into a test tube, and add 3.0 mL of 0.0125 M Na ₂ B ₄ O ₇ concentrated sulfuric acid solution to each.
2) Shake each solution of 1) well, warm in a boiling water bath for 5 minutes, and then cool in ice water for 20 minutes.
3) Add 50 μL of 0.15% m-hydroxydiphenyl in 0.5% NaOH to each solution of 2).
4) Each solution of 3) is stirred well and allowed to stand for 5 minutes. The absorbance at 520 nm is measured, and the concentration of the polygalacturonic acid aqueous solution having a known concentration is compared with the value of the sludge filtrate to determine the concentration.

  On the other hand, the method for measuring the polyvalent cation in the organic wastewater is not particularly limited, and those skilled in the art can easily measure using a known method or a method equivalent thereto. In particular, it is preferable to analyze the organic wastewater before flowing into the activated sludge tank 4 by inductively coupled plasma (ICP) emission spectrometry or ICP-mass spectrometry (MS). Advantageously, cations can be analyzed at once.

  As means for capturing the polyvalent cation, elemental analysis of the cation in the organic wastewater 1 flowing into the activated sludge tank 4 is performed in advance, and a chelating agent suitable for the element can be selected. Examples of the chelating agent include ethylenediaminetetraacetic acid (EDTA) and glycol etherdiaminetetraacetic acid (EGTA). Further, it is more preferable that the chelating agent is biodegradable. The chelating agent may be charged into the activated sludge tank or may be charged into the organic waste water before the activated sludge tank is charged.

By determining the addition amount of the chelating agent based on the polyvalent cation concentration in the organic wastewater, the polyvalent cation can be captured more efficiently and necessary. For example, when the polyvalent cation contained in the organic waste water 1 is Mg ²⁺ or Ca ²⁺ , the chelating agent is 1 to 3 times, preferably about 2 times the molar concentration of Mg ²⁺ and Ca ^2+. It is preferable to add an equivalent amount to the activated sludge tank 4 because Mg ²⁺ and Ca ²⁺ efficiently bind to the chelating agent. Thus, by determining the addition amount of a chelating agent, it can prevent adding an excessive chelating agent and increasing an environmental load.

An ion exchange resin can also be used as a means for capturing the polyvalent cation. In the case of an ion exchange resin, the organic waste water 1 is brought into contact with the ion exchange resin to remove polyvalent cations such as Mg ²⁺ and Ca ²⁺ in advance and then flow into the activated sludge tank 4 or ion exchange. There is a method of dispersing the resin in the activated sludge tank 4. Also in this case, it is possible to efficiently and sufficiently capture the polyvalent cation efficiently and sufficiently by determining the amount of the ion exchange resin introduced based on the polyvalent cation concentration in the organic waste water. As the ion exchange resin, for example, Diaion SK1B (Na) manufactured by Mitsubishi Chemical and Amberlite IR120B (Na) manufactured by Organo can be used.

  In addition, an electrodialyzer using an ion exchange membrane can also be used. In this case, it is particularly preferable to use an ion exchange membrane electrodialyzer capable of selectively concentrating divalent or higher cation.

  Furthermore, when clogging occurs in the separation membrane, the membrane surface can be washed by reducing the bulk of the uronic acid-containing polymer with a liquid containing a polyvalent cation trapping means. In this case, it is preferable to add a polyvalent cation capturing means to filtered water or tap water to obtain a cleaning liquid, and to flow the cleaning liquid into the separation membrane device in the opposite direction to the filtration. It is more preferable to prepare a solution obtained by adding a polyvalent cation capturing means to filtered water or tap water, and immerse the separation membrane device in this solution. Here, this invention is applicable also when the membrane separation activated sludge tank 4 is an aerobic tank-an oxygen-free tank for denitrification. Further, the present invention can be applied even when the separation membrane device is provided in the subsequent stage of the activated sludge tank.

  The present invention also provides a wastewater treatment apparatus that can suitably carry out the above-described wastewater treatment method according to the present invention. The wastewater treatment apparatus according to the present invention contains activated sludge and is installed in or in the activated sludge tank for biological treatment of organic wastewater, and the activated sludge is solid-liquid separated from the treatment liquid by activated sludge. Means for measuring uronic acid unit concentration and polyvalent cation concentration in the aqueous phase of activated sludge, and multivalent cation trapping means for removing polyvalent cations from activated sludge or organic wastewater It is characterized by providing.

  An example of the wastewater treatment apparatus according to the present invention will be described with reference to FIGS. 4 and 5.

  The uronic acid unit concentration measuring means can be, for example, the uronic acid unit measuring device 13 shown in the figure, attached to the activated sludge tank 4, and the time when the uronic acid unit concentration in the aqueous phase of the activated sludge tank 4 is set. Measure automatically every time. The uronic acid unit measuring means 13 can be, for example, liquid chromatography. Moreover, since it is preferable to filter activated sludge with a filter medium in order to measure a uronic acid unit density | concentration as above-mentioned, it is also preferable that the uronic acid unit measuring apparatus 13 is equipped with this filter medium.

  The means for measuring the polyvalent cation concentration can be, for example, the cation measuring device 14 in the figure, and measures the concentration of organic waste water that passes through the flow path between the flow control tank 3 and the activated sludge tank 4. It can be arranged as possible. The measuring means 14 of the polyvalent cation concentration can be, for example, an inductively coupled plasma (ICP) emission spectrometer or an ICP mass spectrometer (ICP-MS). As shown in the figure, the cation measuring device 14 may be disposed between the flow rate control tank 3 and the activated sludge tank 4 or may be disposed upstream of the flow rate control tank 3.

  The polyvalent cation capturing means can be a chelating agent adding means or an ion exchange resin tower. The chelating agent addition means can be, for example, the EDTA addition device 15 shown in FIG. 4, but is not limited to this, and other types of chelating agents may be introduced, or a plurality of types of chelating agents may be added. It is also preferable to prepare a chelating agent so that an appropriate amount of a chelating agent different depending on the type of polyvalent cation can be added. Further, as shown in FIG. 4, the chelating agent may be installed in the activated sludge tank, or installed in a place where the chelating agent can be introduced into the waste water before flowing into the activated sludge tank (for example, the flow control tank 3). Also good.

  When an ion exchange resin tower is used as the polyvalent cation trapping means, for example, the cation exchange resin tower 16 shown in FIG. 5 can be used. The ion exchange resin tower can be arranged in parallel with a normal line between the flow control tank and the activated sludge tank. With such a configuration, it is possible to switch the line as necessary, and to flow the organic waste water in the flow rate control tank into the activated sludge tank via the ion exchange resin tower.

  At this time, an electrodialyzer using an ion exchange membrane can be used instead of the ion exchange resin tower.

  In addition, the wastewater treatment apparatus according to the present invention provides a polyvalent cation in the organic wastewater when the uronic acid unit concentration is equal to or higher than a predetermined value, or when the uronic acid unit concentration and the uronic acid unit concentration (mg / L). It is also preferable to provide a control means for automatically functioning the polyvalent cation capturing means when the value obtained by multiplying the ion concentration (mg / L) becomes a predetermined value or more. Here, automatically functioning means, for example, when the polyvalent cation capturing means is a chelating agent adding means, selecting a suitable chelating agent and adding an appropriate amount to an activated sludge tank or the like. When the polyvalent cation capturing means is an ion exchange resin tower, it means that the line is switched from a normal line to an ion exchange resin tower.

  Examples of the present invention will be described below, but the present invention is not limited thereby.

  According to the following method, it was confirmed that the membrane filtration pressure was stably changed according to the wastewater treatment method of the present invention.

First, the activated sludge containing organic wastewater is filtered through a filter paper (Advantech, made of cellulose, 5C (trade name)) having a pore size of 1 μm, and the obtained filtrate (hereinafter referred to as “sludge filtrate”), A hollow fiber membrane having a pore size of 0.1 μm (Asahi Kasei Chemicals, PVDF, membrane area (outer surface) 0.02 m ² , effective membrane length 15 cm, inner diameter / outer diameter: 0.6 / 1.2 mm) 9 cycles of filtration and 1 minute of backwashing were performed for 7 cycles.

  There is a relationship such as the following formula (I) between the filtration resistance Rc and the transmembrane pressure difference Pn. The values (transmembrane pressure difference, viscosity, Flux) obtained as a result of the above membrane filtration experiment were plotted, an approximate line of the relationship between Pn / (μJ) and n was drawn, and Rc was obtained from the slope.

Pn / (μJ) = n × Rc (I)
In the formula (I), n is the number of filtration cycles, Pn is the average value of the transmembrane pressure difference at the nth cycle [Pa], μ is the viscosity of the membrane filtrate [Pa · s], and J is the flux [m / D]. Represents.

  Two sludge filtrates were prepared. Both uronic acid unit concentrations in this sludge filtrate were 35 mg / L. EDTA was added to one sludge filtrate so that the final concentration was 0.5 mM. The other measured the filtration resistance without adding anything.

After 70 minutes, the sludge filtrate to which EDTA has not been added has a filtration resistance value of 6.1 × 10 ¹¹ (FIG. 2), whereas the addition of EDTA has a filtration resistance value of 2.8. It was maintained at × 10 ¹¹ (FIG. 3). Thus, it was confirmed that the filtration resistance value can be reduced by capturing the polyvalent cation.

  Three membrane separation activated sludge apparatuses of the system of FIG. 1 were prepared, and one (hereinafter referred to as “membrane separation activation apparatus A”) was kept in the flow of FIG. In another unit (hereinafter referred to as “membrane separation activation device B”), as shown in FIG. 4, an ICP emission spectrometer as a multivalent cation measuring means is provided between the flow rate control tank 3 and the activated sludge tank 4. 14 (ICPS-7000, manufactured by Shimadzu Corporation) was attached, the EDTA automatic addition device 15 was attached to the activated sludge tank 4, and the liquid chromatography 13 was attached to the activated sludge tank 4 as a uronic acid unit concentration measuring means. When the value obtained by multiplying the uronic acid unit concentration (mg / L) by the polyvalent cation concentration (mg / L) exceeds 600, the EDTA automatic addition device is activated and the double cation concentration is doubled. EDTA was set to be automatically added to the organic wastewater in the flow control tank 3.

  Further, as shown in FIG. 5, the other unit (hereinafter referred to as “membrane separation activation device C”) is provided with a polyvalent cation measuring means 14 between the flow rate control tank 3 and the activated sludge tank 4. In addition to the existing piping from the flow control tank 3 to the activated sludge tank 4, a line passing through the ion exchange resin tower 16 (Mitsubishi Chemical Diaion SK1B (Na)) was newly attached. The activated sludge tank 4 was provided with a liquid chromatography 13 as a uronic acid unit concentration measuring means. When the value obtained by multiplying the uronic acid unit concentration (mg / L) by the polyvalent cation concentration (mg / L) exceeds 600, the piping is automatically switched to a line passing through the ion exchange resin tower, and activated sludge. It was set so that polyvalent cations were captured before flowing into the tank 4.

  In the membrane separation activated sludge apparatuses A to C, sugar factory wastewater having a BOD of 750 mg / L was treated. Initially, the sugar concentration and uronic acid unit concentration in the wastewater were 30 mg / L and 0 mg / L, respectively.

In any membrane separation activated sludge device, a separation membrane device in which a microfiltration hollow fiber membrane having a pore size of 0.1 μm is modularized (Asahi Kasei Chemicals, PVDF, membrane area 0.015 m ² , effective membrane length 15 cm, inner diameter / Outer diameter: 0.6 / 1.2 mm) was immersed in an activated sludge tank having an effective volume of 10 L. For aeration to the membrane, air was fed from the lower part of the membrane module at a flow rate of 200 NL / h.

  The MLSS concentration was constant at 10 g / L, and the residence time of the wastewater in the activated sludge tank 4 was 18 hours. The amount of activated sludge was always constant, a series of separation membrane devices were installed, the filtration flux was set to 0.6 m / D, and the entire amount of filtrate was discharged out of the activated sludge tank. The initial membrane filtration pressure was 5 kPa. On the 15th day of operation, the uronic acid unit concentration in the aqueous phase of the activated sludge was measured by the above-mentioned method, and all were the same at 30 mg / L. At this time, the membrane filtration pressure was 9 kPa.

Further, when the polyvalent cations in the sugar mill wastewater (in the flow control tank 3) were examined, most of the membrane separation activated sludge apparatuses were Ca ²⁺ and Mg ²⁺ , and the total concentration was 22 mg / L. Met.

  In the membrane separation activated sludge apparatus A, the membrane filtration pressure reached 25 kPa on the 20th day of operation, and it was necessary to clean the separation membrane.

  In the membrane separation activated sludge apparatus B, EDTA is automatically added every day from the 15th day when the value obtained by multiplying the uronic acid unit concentration (mg / L) by the polyvalent cation concentration (mg / L) exceeds 600. It was. The membrane filtration pressure on the 20th day of operation was 12 kPa, and solid-liquid separation could be achieved stably.

  In the membrane-separated activated sludge apparatus C, the sugar factory wastewater is converted to a cation exchange resin on the 15th day when the value obtained by multiplying the uronic acid unit concentration (mg / L) by the polyvalent cation concentration (mg / L) exceeds 600. The pipe from the flow control tank to the activated sludge tank was switched so as to pass through the tower (Mitsubishi Chemical Diaion SK1B (Na)), and the polyvalent cation concentration was lowered to 5 mg / L, and then introduced into the activated sludge tank. . The membrane filtration pressure on the 20th day of operation was 12 kPa, and solid-liquid separation could be achieved stably.

  Thus, as a guideline, the uronic acid unit concentration (mg / L) exceeded 30 mg / L, and the value obtained by multiplying the uronic acid unit concentration (mg / L) by the polyvalent cation concentration (mg / L) exceeded 600. Occasionally, clogging of the separation membrane could be prevented by capturing polyvalent cations.

It is a block diagram which shows an example of the processing method of the organic wastewater which concerns on this invention. Arrows indicate the direction of fluid flow. It is a figure showing the time-dependent change of filtration pressure when measuring filtration resistance using a sludge filtrate. It is a figure showing the time-dependent change of filtration pressure when filtration resistance is measured using the sludge filtrate which added EDTA. It is a block diagram which shows an example of the waste water treatment apparatus which concerns on this invention. Arrows indicate the direction of fluid flow. It is a block diagram which shows an example of the waste water treatment apparatus which concerns on this invention. Arrows indicate the direction of fluid flow.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Organic waste water, 2 ... Pretreatment equipment, 3 ... Flow control tank, 4 ... Membrane separation activated sludge tank (aeration tank), 5 ... Hollow fiber membrane type separation membrane apparatus, 6 ... Skirt, 7 ... Blower, 8 DESCRIPTION OF SYMBOLS ... Suction pump, 9 ... Filtrate, 10 ... Sterilization tank, 11 ... Treated water, 12 ... Sludge extraction pump, 13 ... Uronic acid unit measuring device, 14 ... Multivalent cation measuring device, 15 ... EDTA automatic addition device, 16 ... Cation exchange resin tower

Claims (10)

Organic wastewater is allowed to flow into an activated sludge tank containing activated sludge, the organic wastewater is biologically treated with the activated sludge, and the activated sludge is solid-liquid separated by a separation membrane device installed in the activated sludge tank or in the subsequent stage. A wastewater treatment method using a membrane separation activated sludge device,
When the uronic acid unit concentration in the aqueous phase of the activated sludge becomes a predetermined value or more, the activated sludge or the organic waste water is brought into contact with the polyvalent cation trapping means, and then the solidified by the separation membrane device. Wastewater treatment method for liquid separation.   The wastewater treatment method according to claim 1, wherein when the uronic acid unit concentration (mg / L) is 20 or more, the activated sludge or the organic wastewater is brought into contact with the polyvalent cation capturing means. Organic wastewater is allowed to flow into an activated sludge tank containing activated sludge, the organic wastewater is biologically treated with the activated sludge, and the activated sludge is solid-liquid separated by a separation membrane device installed in the activated sludge tank or in the subsequent stage. A wastewater treatment method using a membrane separation activated sludge device,
When the value obtained by multiplying the uronic acid unit concentration (mg / L) in the aqueous phase of the activated sludge by the polyvalent cation concentration (mg / L) in the organic waste water is a predetermined value or more, A wastewater treatment method in which activated sludge or the organic wastewater is brought into contact with a polyvalent cation capturing means, and then solid-liquid separation is performed by the separation membrane device.   When the value obtained by multiplying the uronic acid unit concentration (mg / L) by the polyvalent cation concentration (mg / L) reaches 600 or more, the activated sludge or the organic waste water is brought into contact with the polyvalent cation capturing means. The wastewater treatment method according to claim 3.   The wastewater treatment method according to any one of claims 1 to 4, wherein the polyvalent cation capturing means is a chelating agent or an ion exchange resin.   The wastewater treatment method according to any one of claims 1 to 5, comprising a step of cleaning the separation membrane device with a cleaning liquid including a polyvalent cation trapping means in the middle of the solid-liquid separation. An activated sludge tank containing activated sludge and biologically treating organic wastewater;
A wastewater treatment apparatus that includes a separation membrane device that is installed in or at a subsequent stage of the activated sludge tank and separates the activated sludge from the treatment liquid by the activated sludge.
Means for measuring the concentration of uronic acid units in the aqueous phase of the activated sludge and / or means for measuring the concentration of polyvalent ions in the organic wastewater, and for removing polyvalent cations from the activated sludge or the organic wastewater. A wastewater treatment apparatus comprising: a valence cation capturing means.   The wastewater treatment apparatus according to claim 7, wherein the polyvalent cation capturing means is a chelating agent addition means.   The wastewater treatment apparatus according to claim 7, wherein the polyvalent cation capturing means is an ion exchange resin tower.   Further, when the uronic acid unit concentration (mg / L) is a predetermined value or more, or a value obtained by multiplying the uronic acid unit concentration (mg / L) by the polyvalent cation concentration (mg / L). The wastewater treatment apparatus according to any one of claims 7 to 9, further comprising control means for automatically functioning the polyvalent cation trapping means when the value becomes equal to or greater than a predetermined value.