JP4167964B2 - Control method of organic wastewater treatment equipment - Google Patents

Description

  The present invention provides a sludge solubilization degree control means for reducing the amount of excess sludge generated when biologically treating organic wastewater in an activated sludge method or the like for aerobically treating organic wastewater with activated sludge. The present invention relates to a method for controlling an organic wastewater treatment apparatus.

  In the biological oxidation treatment such as the activated sludge method, the biggest problem is that the amount of excess sludge generated is generally very high, 0.6 to 0.8 kg · ss (sludge) per 1 kg of BOD to be removed. . Conventionally, these sludges have been treated by dehydration, drying, incineration, etc., but the treatment is very expensive. Moreover, since the excess sludge is difficult to dehydrate, its processing method is a problem.

  As a method for reducing the generation of surplus sludge, a method of adding an alkali agent to surplus sludge (for example, see Patent Documents 1 and 2) is known. The solubilization treatment with the agent required a long time, which was not preferable. As a method for solving the problems caused by the use of an alkaline agent, a method of treating surplus sludge by ultrasonic waves, a homogenizer, a mixer, destruction by rapid pressure fluctuation, oxidative decomposition with ozone gas, or the like (see Patent Document 3) has been proposed. However, sludge carcasses caused by the destruction of sludge cell walls and cell membranes have high molecular weight, are hardly soluble in water, and are hardly degradable with respect to activated sludge. is there.

  Then, the method (refer patent document 4) which improves the deterioration of water quality is performed by performing the solubilization process of an excess sludge in combination with the process by an alkaline agent, and the process by a homogenizer, a mixer, etc.

  However, surplus sludge volume reduction technology solubilizes part of the sludge (ie, microorganisms) extracted in the solubilization treatment tank, returns it to the biological treatment tank as a microorganism source, and then performs biological treatment in the biological treatment system. When the amount of sludge solubilized is too small, the effect of suppressing the generation of excess sludge is small. On the other hand, in the case of excess, if the biological treatment tank does not have the load treatment capacity corresponding to the increase due to the solubilization treatment, the treatment efficiency of the waste water is lowered and the quality of the treated water is deteriorated. Furthermore, the solubilization treatment of excess sludge reduces the amount of microorganisms in the biological treatment tank, resulting in an increase in COD and SS of treated water. Therefore, in order to suppress the generation of excess sludge and maintain stable biological treatment of wastewater, it is necessary to keep the amount of solubilized microorganisms appropriate.

  However, the amount of microorganisms solubilized is determined by the amount of sludge (product of sludge concentration and flow rate) sent to the solubilization treatment tank and the treatment strength of the solubilization treatment apparatus. In actual biological treatment equipment, even if the same biological treatment tank and solid-liquid separation tank are used, depending on various conditions such as wastewater load at that time, biological treatment tank sludge concentration, temperature, pH, sludge sedimentation The concentration of sludge sent to the solubilization tank changes greatly. Therefore, even if the flow rate of the sludge entering the solubilization tank is made constant, the amount cannot be kept constant. In addition, by controlling the flow rate according to the sludge concentration, the amount of sludge entering the solubilization treatment tank can be kept constant, but if the flow rate changes, the residence time in the solubilization treatment tank changes, solubilizing It is difficult to maintain a constant amount of microorganisms. For these reasons, in the method described in Patent Document 4, in order to perform a stable solubilization treatment, it is necessary to investigate in advance the type of drainage and the concentration change of the sludge to be treated and determine the treatment conditions.

  On the other hand, the concentration of sludge sent to the solubilization tank is measured with an MLSS meter, and the amount of sludge to be treated is adjusted by changing the capacity of the solubilization tank according to the measured value, and the predetermined residence time is set. A method of securing and maintaining a constant treatment condition for sludge per unit (see Patent Document 5) has been proposed.

  However, since the measurement of the sludge concentration with the MLSS meter is just before being sent to the solubilization treatment tank, the variation of the MLSS value is large, and the change in the sludge concentration that changes with time is fed back to the operating conditions of the solubilization treatment device. It is difficult. Moreover, it is necessary to change the conditions of solubilization processing greatly with the change of the mixing conditions in a processing tank.

Japanese Patent Publication No.49-11813 Japanese Examined Patent Publication No. 6-61550 Japanese Patent Publication No.57-19719 JP 2002-113487 A Japanese Patent Laid-Open No. 11-188394

  Therefore, the present invention provides a monitoring means for the amount of microbial solubilized that can perform simple operation control and stable sludge reduction without deteriorating the quality of treated water even when the volume of excess sludge is reduced. It aims at providing the control method of the organic waste water treatment equipment containing.

  In view of such circumstances, the present inventors have intensively studied a method for appropriately maintaining the amount of microorganisms solubilized in the sludge solubilization treatment of excess sludge, and as a result, the sludge solubilization treatment tank was solubilized in the subsequent stage. By providing means for monitoring the amount of microorganisms, and by feeding back the value of the amount of microorganisms to the sludge solubilization process, it was found that the amount of microorganisms solubilized can be properly maintained by controlling the solubilization conditions. Completed the invention.

That is, the present invention, after biologically treating organic wastewater in a biological treatment tank, solid-liquid separates the biological treatment mixture, the organic matter in the sludge can be sludged to a part or all of the solid-liquid separated sludge. In the organic wastewater treatment apparatus that performs the solubilization treatment in the solubilization treatment tank and then returns to the biological treatment tank, by providing a monitoring means for the amount of microorganisms solubilized in the subsequent stage of the sludge solubilization treatment tank, a control method of organic waste water treatment apparatus, characterized by controlling the process conditions for the solubilization process.
The present invention also provides a biological treatment tank for biological treatment of organic wastewater, followed by solid-liquid separation of the biological treatment mixture, and organic substances in the sludge can be sludged into a part or all of the solid-liquid separated sludge. In the organic wastewater treatment apparatus that performs the solubilization treatment in the solubilization treatment tank and then returns to the biological treatment tank, by providing a monitoring means for the amount of microorganisms solubilized in the subsequent stage of the sludge solubilization treatment tank, Provided is an organic wastewater treatment apparatus characterized by controlling treatment conditions for solubilization treatment.

  According to the present invention, the amount of microorganisms solubilized by a simple apparatus configuration / control method can be maintained more appropriately. As a result, even if high-efficiency sludge volume reduction treatment is continued, excess sludge generated by biological treatment of organic wastewater can be more efficiently solubilized, and the quality of treated water can be prevented from deteriorating. be able to.

  The organic wastewater treatment apparatus control method of the present invention can be applied to various organic wastewater biological treatment apparatuses provided with a solubilization treatment apparatus that generates excess sludge. The biological treatment may be an aerobic biological treatment or an anaerobic biological treatment. As the aerobic biological treatment, there is an activated sludge method. The activated sludge method is an aerobic biological treatment method for treating organic wastewater in the presence of activated sludge. Organic wastewater is aerated while being mixed in an aeration tank, and the mixture is concentrated with a concentrator and concentrated sludge. A standard activated sludge method in which a part of the water is returned to the aeration tank is generally used, but a modified version thereof may be used. Examples of the anaerobic biological treatment include an anaerobic digestion method and a high-load anaerobic treatment method. Among these biological treatments, the activated sludge method that is frequently used for the treatment of organic waste water is preferable. Hereinafter, the present invention by the activated sludge method will be described in detail with reference to FIG.

  The processing flow of the conventional standard activated sludge method is shown in FIG. Organic waste water is supplied from the line 1 to the aeration tank 14. The organic waste water is aerated in the aeration tank 14 and undergoes aerobic biological treatment, and the treated water flows into the sludge separation tank 15 via the line 2. The treated water and sludge are separated from the inflow water, and the treated water is discharged through the line 3, and the sludge is further concentrated by a dehydrator through the line 4, and then discharged from the line 5 as excess sludge.

  The processing flow of the typical activated sludge method of this invention is shown in FIG. The process in which the sludge separated in the sludge separation tank 15 is discharged as excess sludge from the line 5 is the same as in the conventional method. Thereafter, a part of the excess sludge flows through the line 6 and flows into the sludge solubilization treatment tank 18 and undergoes solubilization treatment. The aqueous solution (solubilized solution) after the solubilization treatment is returned to the aeration tank 14 after undergoing neutralization treatment or decolorization treatment with an oxidizing agent as necessary via the line 8. In the present invention, means for monitoring the solubilized microorganism amount and controlling the conditions of the solubilization process based on the value of the microorganism amount is incorporated in the subsequent stage of the sludge solubilization treatment tank. Here, the latter part of the sludge solubilization treatment tank includes both the vicinity of the outlet in the treatment tank and the rear of the treatment tank. After the treatment tank is preferable. Specifically, after the sludge solubilization treatment tank 18, the solubilization degree measuring device 16 for measuring the solubilized microorganism amount, the value of the measured microorganism amount is fed back to the solubilization treatment device and solubilized. A controller 20 for adjusting processing conditions is incorporated.

  The amount of microbial solubilized is monitored by measuring the amount of microorganism actually solubilized. The amount of microorganisms solubilized indicates the amount of microorganisms that have been solubilized by sludge being crushed in a sludge solubilization treatment tank. Specifically, the on-line COD meter, BOD meter, MLSS meter, respiration rate measuring device, ATP measuring device, etc. are installed on the line 8 to determine the amount of the microorganisms. , BOD, SS, etc.), the dry weight of the dissolved substance in the aqueous phase, the respiratory activity of microorganisms, the amount of ATP in cells, etc., can be measured and automatically calculated from the measured values. Moreover, you may calculate manually from measured values, such as load amount. Among these, it is preferable to measure the load amount in the aqueous phase of the solubilized liquid, and it is particularly preferable to measure BOD, COD, and MLSS.

  In the control method of the present invention, the treatment conditions of the solubilization treatment are controlled based on the value of the solubilized microorganism amount. That is, if the flow rate or concentration of sludge sent to the solubilization tank changes, the amount of sludge entering the solubilization tank also changes, but the solubilized microorganisms are always used regardless of the amount of sludge sent to the solubilization tank. Based on quantity value. When the amount of solubilized microorganisms is higher than the expected value, the strength of the solubilization treatment is reduced, while when it is low, the strength of the solubilization treatment is increased.

  The solubilization treatment is one or more kinds selected from treatment with an alkali agent, treatment with a homogenizer, treatment with a mixer, treatment with a mill, and treatment with high pressure and instantaneous decompression while keeping the water level of the solubilization tank constant. It is preferable to carry out by treatment. That is, the cells of the microorganisms constituting the sludge are chemically destroyed by the treatment with the alkaline agent, and the cells of the microorganisms constituting the sludge are also physically destroyed by the treatment with the homogenizer. The amount of the alkali agent used can be reduced by combining the treatment with the alkali agent with a treatment having a strong grinding force such as a mill or a mixer. In order to promote solubilization, it may be heated to 50 to 100 ° C.

  A processing device that performs processing by a homogenizer or the like or processing by high pressure and instantaneous decompression expansion is incorporated so that the circulation line of the processing device is connected to the solubilization processing tank. The water level of the solubilization tank is adjusted by a water level meter provided in the solubilization tank and a controller for controlling the flow rate provided on the line 8 and electrically connected to the water level meter. By keeping the water level of the solubilization tank constant, the stirring and mixing conditions in the tank are kept uniform.

  The strength of the solubilization treatment can be controlled by the flow rate of the alkaline agent charged into the solubilization tank for the treatment with the alkaline agent. Further, the processing by a homogenizer, mixer, mill, and processing by high pressure and instantaneous decompression expansion can be controlled by adjusting the number of rotations, the number of vibrations, the number of driving voltages, the frequency by inverter control, and the like. Any factor that affects the shearing force, grinding force, and crushing force of each treatment may be used for adjustment. For example, when using a homogenizer, the rotation speed of the homogenizer is adjusted based on the value of the solubilized microorganism amount fed back from the solubilization degree measuring apparatus. On the other hand, if the solubilization process is performed without adjusting the rotation speed, the quality of the sedimentation tank effluent water may deteriorate.

  Examples of the alkali agent used for the treatment with the alkali agent include sodium hydroxide, sodium carbonate, sodium hydrogen carbonate, calcium hydroxide, calcium carbonate, calcium oxide and the like, and sodium hydroxide or calcium oxide is preferable. The addition amount of the alkaline agent is preferably 0.005 to 0.1N, particularly preferably 0.01 to 0.05N, with respect to the excess sludge to be solubilized.

  The treatment with a homogenizer, a mixer and a mill is carried out under alkaline conditions. If it is under alkaline conditions, it may be carried out while adding an alkali agent or after completion of the addition, but it is preferable to carry out while adding an alkali agent from the viewpoint of processing efficiency. As a homogenizer or the like, any known one can be used as long as it can apply mechanical shear stress or grinding force to the cells of the microorganisms constituting the sludge and can destroy the cell membrane and cell wall of the cells. . Specifically, let the excess sludge added with alkaline agent pass through a pipe with a baffle plate at high speed, or sharp edge like a food mixer at high speed in excess sludge added with alkaline agent. One that rotates or passes through a narrow space between two disks that rotate at high speed, such as a mill that turns food into powder.

  The treatment time of the solubilization treatment combining treatment with an alkaline agent and treatment with a homogenizer or the like is generally 1 minute to 5 hours, preferably 1 minute to 3 hours, particularly preferably 2 minutes to 2 hours. The solubilization time can be significantly shortened as compared with the solubilization treatment only with the treatment with the alkali agent.

In the treatment by high pressure and instantaneous decompression expansion, the excess sludge to which the alkali agent is added is pressurized to a high pressure of, for example, 70 to 180 kg / cm ² , and the pressure is reduced instantaneously from the high pressure. This is done by instantaneously expanding the sludge and destroying the cells of the microorganisms that make up the sludge. This treatment may be performed, for example, by inserting excess sludge to which an alkali agent is added into a pipe containing a baffle plate at a high pressure, and then discharging the sludge from the pressurized pipe to a normal pressure tank. it can. The treatment time of the solubilization treatment combining treatment with an alkaline agent, treatment with high pressure and instantaneous decompression expansion is generally 1 to 60 minutes, preferably 5 to 30 minutes. The solubilization time can be significantly shortened as compared with the solubilization treatment only with the treatment with the alkali agent.

  A processing device that performs processing by a homogenizer or the like or processing by high pressure and instantaneous decompression expansion is incorporated so that a circulation line of these processing devices is connected to the solubilization processing tank.

  The strength of the solubilization treatment per unit time controlled in this way is fed back to the control of the amount of sludge to be solubilized. Therefore, in the control method of the present invention, without installing a measuring device or the like for measuring the constantly changing sludge flow rate and concentration in the previous stage of the sludge solubilization treatment tank, The amount of solubilized microorganisms can be kept appropriate only by installing a controller for solubilizing strength and a solubilization degree measuring device for measuring the amount of solubilized microorganisms.

  The solubilized solution after the solubilization treatment may be neutralized or decolorized with an oxidizing agent as necessary. For the neutralization treatment, a mineral acid such as sulfuric acid, a spent waste acid or the like can be used. As the oxidizing agent, hydrogen peroxide, sodium peroxide, sodium percarbonate, etc., which have strong oxidizing power and change itself to be harmless to activated sludge after decomposition, are preferable, and hydrogen peroxide is particularly preferable.

  In the control method of the present invention, after the solubilization treatment, in order to monitor the treated water that has been solubilized while being stored in the solubilization treatment tank for a certain period of time, the quality of the treated water is solubilized. The value of the amount of microorganisms is less varied than the value of the amount of microorganisms before entering the solubilization apparatus. For example, even if there is a variation in the value before the solubilization treatment, it is averaged during the treatment, so that it is not necessary to control the solubilization treatment apparatus. In addition, since the value of the solubilized microorganism amount monitored by the monitoring means is fed back to the operating conditions of the solubilization treatment apparatus, the solubilized microorganism amount can always be kept appropriate. Can be stabilized.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention in more detail, this invention is not limited to these Examples.

Example 1
Factory wastewater (BOD 100-110 mg / L, SS 30-40 mg / L), aeration time 8 hr, activated sludge MLSS 3000-3500 mg / L 40 L aeration tank (BOD-MLSS load 0.09-0.11 (kgBOD / kgMLSS · day)), and then activated sludge was separated in a 20 L settling tank. In the above factory wastewater treatment, the factory wastewater amount was set to 0.12 m ³ / day, and 200 ml / day of the precipitated sludge was led to the sludge solubilization treatment tank. The precipitated sludge was in the range of 0.5 to 1% by weight of the solid matter concentration. It continued to change. This precipitated sludge was introduced into a batch type sludge solubilization treatment tank having a residence time of 30 minutes. The sludge solubilization treatment tank has a connection line to the homogenizer (Polytron PT45-80) at the bottom and a circulation line from the homogenizer to the top of the tank. As an alkaline agent, sodium hydroxide was added from the upper part of the tank so as to have a concentration of 0.05 N (pH about 12.5). After solubilization of the sludge, it was neutralized with 2N sulfuric acid so as to have a pH of 8, and added to the aeration tank for aerobic biological treatment. About 50 ml of the sludge solubilized solution after neutralization is sampled once, and the solid matter is separated into membranes, and then the dissolved material in the sludge solubilized solution is analyzed by an automatic BOD measuring device (BF-1000 manufactured by Oji Scientific Instruments). The BOD value is measured, and from the obtained BOD value, when it is 1000 mg / L or more, the rotation speed of the homogenizer at the next solubilization treatment is 8000 rpm, and when 600 to 1000 mg / L, it is 10000 rpm, less than 600 mg / L. In this case, control was carried out to 12000 rpm. As a result of continuing the operation according to the above conditions for about one month, the quality of the sedimentation tank effluent water was BOD 5-10, SS 5-8 mg / L, and pH was 7.0. Moreover, the surplus sludge amount in the meantime was about 42 g / L.

Comparative Example 1
The water quality of the settling tank effluent was measured under the same conditions as in Example 1 except that the operation was carried out with the homogenizer rotating at a constant 12000 rpm. As a result, the water quality of the sedimentation tank effluent fluctuated in the range of BOD 5-13, SS 6-15 mg / L, and the pH was 7.0. Moreover, the surplus sludge amount in the meantime was about 50 g / L.

Comparative Example 2
The water quality of the settling tank effluent was measured under the same conditions as in Example 1 except that sodium hydroxide was not charged into the sludge solubilization tank and the treatment with the homogenizer was omitted. As a result, the water quality of the sedimentation tank effluent fluctuated in the range of BOD 5-8, SS 4-7 mg / L, and the pH was 7.0. Moreover, the surplus sludge amount during that time was about 120 g / L.

Example 2
Factory wastewater (BOD 100-110 mg / L, SS 30-40 mg / L), aeration time 8 hr, activated sludge MLSS 3000-3500 mg / L 1 m ³ aeration tank (BOD-MLSS load 0.09-0.11 (kgBOD / KgMLSS · day)), the activated sludge was separated in a 0.5 m ³ sedimentation tank. In the above factory wastewater treatment, the amount of factory wastewater was 3 m ³ / day, and the precipitated sludge 0.9 L / hr was continuously led to a 1 L sludge solubilization treatment tank. % Continued to change. The sludge solubilization treatment tank has a connection line to the pipeline homomixer (special machine industry Co., Ltd. product PL-SL) at the bottom, and a circulation line from the mixer is connected to the top of the tank. Yes. Precipitated sludge is drawn into the tank from the top of the tank, and the solubilized sludge solubilized liquid is connected to the liquid level from the side of the reaction tank, drained by overflow, passed through the neutralization tank, and again pumped into the aeration tank. did. As an alkaline agent, sodium hydroxide was added from the upper part of the tank so as to have a concentration of 0.05 N (pH about 12.5). In the neutralization tank, neutralization was performed using 2N sulfuric acid so that the pH became 8. About 50 ml of the sludge solubilized solution after neutralization is separated once with an automatic sampling device, and the solid matter is separated into membranes, and then in the sludge solubilized solution with an automatic BOD measuring device (BF-1000 manufactured by Oji Scientific Instruments). The BOD value of the lysate was measured every 2 hours. The obtained BOD value was automatically controlled so that the rotation speed of the mixer was 7000 rpm when it was 1000 mg / L or more, 8000 rpm when it was 600 to 1000 mg / L, and 9000 rpm when it was less than 600 mg / L. As a result of continuing the operation according to the above conditions for about one month, the water quality of the sedimentation tank effluent was BOD 7-11, SS 5-7 mg / L, and pH was 7.0. Moreover, the amount of generated sludge per day during that period was about 90 g / day.

Comparative Example 3
The water quality of the settling tank effluent was measured under the same conditions as in Example 2 except that the mixer was operated at a constant rotation speed of 9000 rpm. As a result, the water quality of the sedimentation tank effluent fluctuated in the range of BOD 6-16, SS 8-17 mg / L, and the pH was 7.0. During that time, the amount of generated sludge per day was about 85 g / day.

Comparative Example 4
The water quality of the settling tank effluent was measured under the same conditions as in Example 2 except that the addition of sodium hydroxide in the sludge solubilization treatment tank and the treatment by the mixer were omitted. As a result, the water quality of the sedimentation tank effluent varied in the range of BOD 6 to 10 and SS 4 to 8 mg / L, and the pH was 7.0. During that time, the amount of excess sludge generated per day was about 194 g / day.

It is a figure which shows the control method of the conventional organic waste water treatment equipment. It is a figure which shows the control method of the organic waste water treatment equipment of this invention.

Explanation of symbols

1 Line 2 Line 3 Line 4 Line 5 Line 6 Line 8 Line 9 Line 14 Aeration tank 15 Sludge separation tank 16 Solubilization measuring device 18 Sludge solubilization treatment tank 19 Surplus sludge 20 Controller

Claims (4)

After biological treatment of organic wastewater in a biological treatment tank, the biological treatment mixture is subjected to solid-liquid separation, and organic substances in the sludge can be added to a part or all of the solid-liquid separated sludge in a sludge solubilization treatment tank. In the organic wastewater treatment equipment that performs the solubilization treatment and then returns it to the biological treatment tank, the treatment conditions for the solubilization treatment are provided by providing a monitoring means for the amount of microorganisms solubilized after the sludge solubilization treatment tank. the method of organic wastewater treatment apparatus and controls the.   The said solubilization process performs 1 or more types of processes chosen from the process by a homogenizer, the process by a mixer, the process by a mill, and the process by high pressure and instantaneous decompression expansion with the process by an alkaline agent. Control method for organic wastewater treatment equipment.   After biological treatment of organic wastewater in a biological treatment tank, the biological treatment mixture is subjected to solid-liquid separation, and organic substances in the sludge can be added to a part or all of the solid-liquid separated sludge in a sludge solubilization treatment tank. In the organic wastewater treatment equipment that performs the solubilization treatment and then returns it to the biological treatment tank, the treatment conditions for the solubilization treatment are provided by providing a monitoring means for the amount of microorganisms solubilized after the sludge solubilization treatment tank. Organic waste water treatment equipment characterized by controlling   The said solubilization process performs 1 or more types of processes chosen from the process by a homogenizer, the process by a mixer, the process by a mill, and the process by high pressure and instantaneous decompression expansion with the process by an alkaline agent. Organic wastewater treatment equipment.

Images