JP4192079B2 - Sludge treatment apparatus and sludge treatment method - Google Patents

Description

  The present invention relates to a sludge treatment apparatus and a sludge treatment method for reducing the amount of organic sludge generated from an activated sludge treatment facility for wastewater.

  The activated sludge treatment process is the most popular wastewater treatment process as industrial wastewater treatment including domestic wastewater and BOD. While the establishment of a recycling-oriented society is being sought, the activated sludge treatment process that generates a large amount of excess sludge is entering a major turning point.

  Conventionally, surplus sludge has been mechanically dehydrated after concentration and has been treated by drying / incineration, landfill disposal, ocean dumping, etc., but the treatment cost is high. In addition, it causes environmental destruction such as soil pollution due to landfill disposal, air pollution due to drying and incineration, and ocean pollution due to ocean dumping. And disposal of these surplus sludges has become difficult in recent years to secure landfill sites and to dispose of oceans, and there is an increasing demand for reducing surplus sludge.

  Against this background, various methods have been proposed as methods for reducing the amount of organic excess sludge.

  Among them, there is a method in which the generated excess sludge is solubilized by crushing by a wet medium stirring mill treatment, converted to a BOD component, and biologically treated again to reduce the amount (see, for example, Patent Document 1). Further, a method using beads having a true specific gravity of 5.0 or more as a medium for crushing when sludge containing an organic substance is crushed by a wet medium agitation mill treatment has been proposed (see, for example, Patent Document 2). In these methods, crushing efficiency is increased by using crushing beads having a large specific gravity, and the efficiency of sludge refinement is slightly improved, but the quality of treated water such as COD is not improved. In addition, problems such as clogging or blockage due to foreign matters such as sand and hair remain.

The activated sludge treatment process generates a large amount of excess sludge. The surplus sludge has been treated by incineration, landfill disposal, ocean dumping, etc., but it also causes environmental destruction such as soil pollution, air pollution, and ocean pollution. And in recent years, disposal of these surplus sludge has made it difficult to secure landfill sites and dispose of the ocean, and demand for reduction of surplus sludge has increased.
JP 11-300393 A (Claims, paragraph number [0005]) JP 11-156394 A (claims, paragraph number [0009])

  As a method of reducing the amount of organic surplus sludge generated in an external activated sludge treatment facility, the present inventors have made various studies in order to solve the above problems. Knowing that sludge that has been crushed and solubilized and separated from sludge and media that have been crushed and solubilized by centrifugation, and that the sludge that has been separated can be efficiently reduced by aeration treatment. The invention has been completed.

  Accordingly, an object of the present invention is to provide a sludge treatment apparatus and a sludge treatment method that solve the above problems.

  The present invention for achieving the above object is described below.

  [1] A reaction tank that performs aerobic aeration treatment of solubilized sludge, and a mixing tank that mixes reaction tank sludge generated by aerobic aeration treatment in the reaction tank and surplus sludge generated at an external activated sludge treatment facility. And a sludge treatment comprising a solid-liquid separation tank for solid-liquid separation of a mixed liquid of reaction tank sludge and excess sludge sent from the mixing tank, and a solubilizer for solubilizing sludge separated in the solid-liquid separation tank The solubilizer has a structure capable of continuously crushing and solubilizing the sludge separated in the solid-liquid separation tank, and is used for separating the sludge that has been crushed and solubilized from the media. Sludge treatment equipment consisting of a wet ball mill with no separator and centrifugal separation mechanism.

  [2] A reaction tank that performs aerobic aeration treatment of solubilized sludge, and a mixing tank that mixes reaction tank sludge generated by aerobic aeration treatment in the reaction tank and surplus sludge generated in an external activated sludge treatment facility And a sludge treatment comprising a solid-liquid separation tank for solid-liquid separation of a mixed liquid of reaction tank sludge and excess sludge sent from the mixing tank, and a solubilizer for solubilizing sludge separated in the solid-liquid separation tank In the equipment, the sludge separated in the solid-liquid separation tank by the wet ball mill of the solubilizer is crushed and solubilized, and the crushed and solubilized sludge and media are separated by centrifugation, and the solubilized sludge separated is separated. A sludge treatment method that reduces the sludge by introducing aeration into the reaction tank and aeration treatment.

  [3] The sludge treatment method according to [2], wherein the solubilized sludge is aerobically aerated and nitrified in a reaction tank.

  [4] The sludge treatment method according to [2], wherein the solubilized sludge is aerated in the reaction tank and then denitrified in the mixing tank by an operation under anoxic conditions.

  [5] The sludge treatment method according to [2], wherein the reaction tank sludge aerated in the reaction tank and the sludge separated in the solid-liquid separation tank are mixed in the mixing tank.

  [6] The sludge treatment method according to [2], wherein solid-liquid separation is performed by membrane separation.

  According to the sludge treatment method of the present invention, the amount of sludge is reduced, and COD reduction and denitrification treatment are also performed. Since the sludge treatment apparatus of the present invention is independent of the existing treatment equipment, it does not depend on the status of the existing treatment equipment (load, presence / absence of nitrogen removal, etc.). Moreover, there are few concerns which influence the existing processing equipment by the process by the sludge processing apparatus of this invention.

  In addition, since the sludge treatment method of the present invention is a process of only physical sludge crushing, sludge that could not be reduced in weight can be used effectively not only as waste but also as compost.

  The sludge treatment apparatus of the present invention employs a wet ball mill having a structure having a separation mechanism by centrifugation without using a separator for separation of a medium and a treated product. Clogging or blockage can be prevented.

  Hereinafter, the present invention will be described in detail.

  The sludge treatment apparatus of the present invention employs a system in which facilities for sludge reduction are newly installed independently from other wastewater treatment facilities.

  The treated water discharged from the sludge treatment apparatus of the present invention and the unreduced sludge are basically not returned to the existing water treatment facility. The sludge that did not exist is basically dehydrated, composted, etc., and carried out of the facility so that it does not affect the operation of the existing water treatment facility.

  FIG. 1 is a schematic diagram showing an example of an operation flow in the sludge treatment apparatus of the present invention.

  In FIG. 1, 10 is a reaction tank for treating the solubilized sludge described later in an aerobic organism. Reference numeral 11 denotes a mixing tank, which mixes reaction tank sludge generated by aerobic aeration treatment in the reaction tank 10 and surplus sludge generated from an activated sludge treatment facility for other waste water outside the apparatus. A solid-liquid separation tank 12 is used for solid-liquid separation of a mixed liquid of reaction tank sludge and excess sludge sent from the mixing tank 11.

  The solid-liquid separation tank 12 for separating sludge and treated water is not particularly limited in the separation method such as gravity precipitation method, flotation separation method, membrane separation method, etc., but enables operation with high MLSS (active sludge suspended solids) concentration. It is desirable to use a membrane separation method because of the ease of maintenance.

  13 is a sludge solubilizer (wet ball mill). In the conventional wet ball mill structure, a separator (separation structure) such as a comb or a slit is used to separate the stirring medium and the processed material. In this conventional wet ball mill, the separator may be clogged in the crushing of sludge containing impurities such as fibers. Therefore, the wet ball mill used in the present invention does not use a separator to separate the media and the processed material. A wet ball mill having a structure having a separation mechanism by centrifugation and having a structure capable of preventing clogging is used.

  Specifically, as the wet ball mill, a “centrifugation type media agitation type wet pulverizer” described in a patent (Japanese Patent Application No. 2003-30897) previously filed by a research group to which the present inventors belong can be used. .

  The said reaction tank 10, the mixing tank 11, the solid-liquid separation tank 12, and the solubilization apparatus 13 are connected by the transport means which consists of L1-L9. In addition, as a transportation means in the example of FIG. 1, piping, dredging, a pump, and the like can be used.

  In the sludge treatment method using the sludge treatment apparatus of this example, the inflow sludge is circulated between the reaction tank 10, the mixing tank 11 and the solid-liquid separation tank 12, and the solubilizer 13. This is a sludge treatment method intended to gasify BOD corresponding to the minute to reduce or eliminate sludge.

  The solubilized sludge treated by the solubilizer 13 is supplied to the reaction tank 10 that performs the aerobic aeration treatment via the line L9. The reaction tank 10 is required to be diffused by a diffuser having a high oxygen dissolution efficiency with the operation of a high BOD volume load. For this reason, although not shown in FIG. 1, it is desirable to use an aeration apparatus having a stirring function.

  As an aeration apparatus having this agitating function, an axial flow agitating and aeration apparatus manufactured by Mitsui Mining Co., Ltd., a trade name “Mitsui Dynafoil Aerator”, and the like can be used. In the reaction vessel 10, most COD resulting from BOD is decomposed and mineralized, and further a nitrification reaction is performed.

  The surplus sludge is administered from the line L1 to the mixing tank 11 that receives the organic surplus sludge generated from the activated sludge treatment facility for other waste water outside the apparatus. The reaction tank sludge that has been aerated in the reaction tank 10 is administered to the mixing tank 11 via a line L2. The administered reaction tank sludge is mixed with organic surplus sludge generated from the activated sludge treatment facility for waste water.

  The sludge treatment in the mixing tank 11 and the solid-liquid separation tank 12 described later is intended to improve the COD of the treated water. In this sludge treatment, adsorption of filtrate COD by sludge (thus, there is no change in COD of the entire sludge, but filtrate COD in the sludge is expected to decrease before and after the mixing tank and the solid-liquid separation tank).

  Moreover, nitrogen removal is also attained by making the mixing tank 11 oxygen-free. The mixing and stirring in the mixing tank 11 may be mechanical stirring or stirring by aeration. However, in the case of stirring by aeration, in order to perform NOx-N denitrification in stirring under anoxic conditions, the dissolved oxygen concentration (DO) in aeration is preferably 0.5 mg / L or less.

  The mixed liquid of reaction tank sludge and excess sludge is supplied to the solid-liquid separation tank 12 from the mixing tank 11 via the line L3. In the separation of the sludge and the treated water in the solid-liquid separation tank 12, it is preferable to employ a membrane separation method and employ an immersion membrane as the membrane. In this separation method, when a high MLSS operation (MLSS concentration of 10,000 mg / L or more) is performed, a high BOD volume load operation is possible.

For example, an operation in which the average pore diameter of the immersion membrane to be used is 0.25 μm is usually performed at a membrane permeation flow rate of 0.15 m ³ / m ² · day and sucked at a constant flow rate. When the water level of the mixing tank 11 becomes high, the valve (not shown in FIG. 1) is opened and treated water is discharged from the system L4 to the outside of the system by the necessary amount.

  Next, the circulating sludge is supplied to the mixing tank 11 through a line L6 by a pump (not shown in FIG. 1) installed in the solid-liquid separation tank 12. The circulation sludge is supplied with a sufficient circulation amount so that a difference in MLSS concentration does not occur between the mixing tank 11 and the solid-liquid separation tank 12. Further, the sludge (unreduced sludge) is extracted from the line L7 so that the MLSS concentration of the sludge circulating through the mixing tank 11 and the solid-liquid separation tank 12 is 12000 mg / L, and the sludge concentration is adjusted. In the example of FIG. 1, the mixing tank 11 and the solid-liquid separation tank 12 are separated, but they may be combined into one tank.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.

Example 1 and Comparative Example 1
A test was conducted to examine the effect of sludge reduction in the operation flow shown in FIG. As the supplied sludge, organic sludge generated from a food wastewater treatment facility was used. The concentration of this sludge was 5000 mg / L, and the treatment amount was 400 to 900 L / day.

The apparatus is composed of ^three tanks comprising a reaction tank 10 (tank capacity 0.5 m ³ ), a mixing tank 11 (tank capacity 0.5 m ³ ) and a solid-liquid separation tank 12 (tank capacity 0.8 m ³ ), a solubilizer 13, That is, it consists of a wet ball mill [Mitsui Mining Co., Ltd. SC-220X]. An immersion membrane (average pore diameter of 0.25 μm) was installed in the solid-liquid separation tank 12.

  The mixing tank 11 was aerated with a commonly used aeration device.

The operation of the solid-liquid separation tank 12 is carried out at a membrane permeation flow rate of 0.15 m ³ / m ² · day. In this test, the effect of sludge of this process on the suction of the membrane can be considered, so that the flow rate is constant without stopping The operation is basically performed by sucking and returning the membrane permeate to the mixing tank 11, and when the water level in the mixing tank 11 becomes high and reaches a set value, the valve is opened and treated water is discharged out of the system as much as necessary. In addition, a pressure sensor was installed on the suction side of the membrane (not shown in FIG. 1) so that changes in suction pressure could be recorded constantly. Circulation by a pump was performed between the mixing tank 11 and the solid-liquid separation tank 12 with a sufficient circulation amount so as not to cause a difference in MLSS concentration between the mixing tank 11 and the solid-liquid separation tank 12.

  Comparative Example 1 was simply circulated without using a solubilizer, and Example 1 was circulated to the solubilizer. The operation period was 45 days for each of Example 1 and Comparative Example 1.

  The solubilizer in Example 1 includes a wet ball mill (model SC220 / 70-x, rotor type 202 × 43 with rotor pin, casing content) manufactured by Mitsui Mining Co., Ltd. The product 2.65 L) was used.

  As a preliminary test of Example 1, the basic performance of the pre-wet ball mill for sludge solubilization (effect of rotor peripheral speed, influence of residence time in the equipment, relation to ball diameter used, influence of ball material, etc.) and stability of the equipment As a result, we found the operating conditions of a wet ball mill that uses glass beads of φ0.3 mm and a rotor peripheral speed of 13.1 m / s. .

  From this preliminary test, φ0.3 mm glass beads were filled at 70% of the internal volume of the apparatus, and the test was carried out under conditions of a rotor peripheral speed of 13.1 m / s and a residence time of 1.2 minutes in the apparatus.

Table 1 shows the operation results of Comparative Example 1 and Table 2 of Example 1. The results shown here are average values of water quality analysis values (4 data points) after 30 days have passed since the start of each operation. Table 3 shows the reduction rate of MLSS concentration, COD _cr concentration, and TN concentration in each operation.

表４に実施例における反応槽１１と混合槽１２の窒素成分の分析結果を示した。水質データは、表１〜表３と同様、運転の３０日経過後のデータ(データ数四点)の平均化したものである。

Table 4 shows analysis results of nitrogen components in the reaction tank 11 and the mixing tank 12 in the examples. Similar to Tables 1 to 3, the water quality data is obtained by averaging the data (4 data points) after 30 days of operation.

表４の結果より。濾液ＮＯｘ−Ｎ濃度が増加し全液Ｔ−Ｎ濃度(全液Ｋｊ−Ｎ濃度＋濾液ＮＯｘ−Ｎ濃度)が減少していることから、反応槽においても硝化が進んでいることが示された。反応槽では可溶化処理後の反応であるため、硝化や脱窒が起こらない懸念があったが、全液Ｔ−Ｎ濃度が混合槽よりも減少し、濾液ＮＯｘ濃度が増加していることから硝化及び脱窒が起こっていることがわかる。本実施例においては反応槽、混合槽及び固液分離槽においては、攪拌又は膜分離付着汚泥の除去等に曝気運転を行ったが、全液Ｔ−Ｎ濃度が減少していることから、プロセス系内に無酸素状況下の部分が一時的に若しくは連続的に発生していたと推測される。

From the results in Table 4. Since the filtrate NOx-N concentration increased and the total solution TN concentration (total solution Kj-N concentration + filtrate NOx-N concentration) decreased, it was shown that nitrification was also progressing in the reaction tank. . There was concern that nitrification and denitrification would not occur in the reaction tank after the solubilization treatment, but the total liquid TN concentration decreased from the mixing tank and the filtrate NOx concentration increased. It can be seen that nitrification and denitrification are occurring. In this example, in the reaction tank, the mixing tank, and the solid-liquid separation tank, aeration operation was performed for stirring or removal of the membrane separation adhering sludge. However, since the total liquid TN concentration decreased, It is presumed that a portion under anoxic conditions occurred temporarily or continuously in the system.

  In addition, there was no remarkable transmembrane pressure difference in the operation 90 days of this Example 1, and it was 5 kPa or less.

  In the present Example 1, it was confirmed that sludge reduction can be performed about 40 to 50%. It was also confirmed that COD reduction and denitrification were performed.

  Since the sludge treatment apparatus used in Example 1 is independent of the existing treatment equipment, it does not depend on the status of the existing treatment equipment (load, presence or absence of nitrogen removal, etc.), and the treatment by this sludge reduction process. Therefore, there were few concerns that would affect the existing processing equipment. In addition, since the sludge treatment method involves only physical sludge crushing, sludge that could not be reduced in weight can be used effectively as compost instead of waste.

  Since the wet ball mill used in Example 1 has a structure having a separation mechanism by centrifugal separation without using a separator for separating a medium and a processed material, a wet ball mill having a structure capable of preventing clogging is used. It was possible to prevent clogging or obstruction caused by foreign matter such as hair and hair.

Comparative Example 2
A wet ball mill made by Mitsui Mining Co., Ltd. (model SC-220, rotor φ202 × 43 with rotor pin, casing inner volume 2.95 L) “slit type media stirring wet grinder” was used as the solubilizer In the same manner as in Example 1, a test for examining the effect of sludge reduction was performed in the operation flow shown in FIG.

  However, about 1 minute after the start of operation, foreign matter was caught in the slit of the separation mechanism and closed, and the crusher fell into an overload state, resulting in inoperability.

It is the schematic which shows an example of the operation | movement flow in the sludge processing apparatus of this invention of this invention.

Explanation of symbols

L1 to L9 Transport means 10 Reaction tank 11 Mixing tank 12 Solid-liquid separation tank 13 Solubilizer

Claims (6)

A reaction tank that performs aerobic aeration treatment of solubilized sludge, a mixing tank that mixes reaction tank sludge generated by aerobic aeration treatment in the reaction tank and surplus sludge generated in an external activated sludge treatment facility, and mixing A sludge treatment apparatus comprising a solid-liquid separation tank for solid-liquid separation of a mixed liquid of reaction tank sludge and excess sludge sent from the tank, and a solubilizer for solubilizing sludge separated in the solid-liquid separation tank. The solubilizer has a structure capable of continuously crushing and solubilizing the sludge separated in the solid-liquid separation tank, and has a separator for separating sludge and media that have been crushed and solubilized. A sludge treatment device consisting of a wet ball mill with a separation mechanism by centrifugal separation. A reaction tank that performs aerobic aeration treatment of solubilized sludge, a mixing tank that mixes reaction tank sludge generated by aerobic aeration treatment in the reaction tank and surplus sludge generated in an external activated sludge treatment facility, and mixing In a sludge treatment apparatus comprising a solid-liquid separation tank for solid-liquid separation of a mixed liquid of reaction tank sludge and excess sludge sent from the tank, and a solubilizer for solubilizing sludge separated in the solid-liquid separation tank, The sludge separated in the solid-liquid separation tank is crushed and solubilized by the wet ball mill of the solubilizer, and the crushed and solubilized sludge and media are separated by centrifugation, and the separated solubilized sludge is removed from the reaction tank. A sludge treatment method that reduces the amount of sludge by aeration treatment. The sludge treatment method according to claim 2, wherein the solubilized sludge is aerobically aerated and nitrified in the reaction tank. The sludge treatment method according to claim 2, wherein after the solubilized sludge is aerated in the reaction tank, denitrification treatment is performed in the mixing tank by operation under anoxic conditions. The sludge treatment method according to claim 2, wherein the reaction tank sludge aerated in the reaction tank and the sludge separated in the solid-liquid separation tank are mixed in the mixing tank. The sludge treatment method according to claim 2, wherein the solid-liquid separation is performed by membrane separation.

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