JP6405411B2 - High concentration organic wastewater treatment method and high concentration organic wastewater treatment system - Google Patents

Description

  The present invention relates to a treatment method and a treatment system for high-concentration organic wastewater discharged from a food factory.

  For example, since waste water discharged from a food factory contains high concentrations of organic matter and oil, it is generally discharged after waste water treatment is performed until a predetermined water quality standard is satisfied.

  FIG. 1 shows an example of a multistage wastewater treatment system for the purpose of such wastewater treatment.

  The illustrated wastewater treatment system is an advanced wastewater treatment system that can purify organic wastewater to a high level of water quality. A wastewater treatment system is mainly configured by a first processing unit 101 that performs a suspended solid removal process, a second processing unit 102 that performs biological treatment, and a third processing unit 103 that performs ozone treatment.

  In this wastewater treatment system, wastewater first flows into the first treatment unit 101 after large debris is removed by a screen or the like. Since the waste water contains a large amount of contaminants such as fine food waste, soluble organic matter, and oil, fine suspended matter and oil are removed by the first processing unit 101.

  In the first processing unit 101, a pressure levitation process or a coagulation precipitation process is usually performed by adding a coagulant.

  In order to remove the organic matter remaining in the wastewater treated by the first treatment unit 101, the second treatment unit 102 performs biological treatment by a catalytic oxidation method, an activated sludge method, or the like. That is, organic substances are removed by utilizing the decomposition action by microorganisms. In biological treatment, solid-liquid separation treatment such as a sedimentation basin may be performed.

  If it falls below a predetermined water quality standard in biological treatment, it can be discharged as it is, but this wastewater treatment system is provided with a third treatment unit 103 that performs ozone treatment so that the water quality can be improved to a higher level. .

  Ozone has a very strong oxidizing power and has effects such as sterilization, decolorization, deodorization, and decomposition of hardly decomposable substances. However, it reacts with suspended substances and organic substances and is consumed. Used for advanced treatment after removal of organic substances such as substance removal treatment and biological treatment.

  When the discharge destination is a sewer, etc., the discharge standard may be satisfied by only one-stage wastewater treatment for removing suspended solids and discharge may be possible.

  For example, Patent Document 1 discloses a wastewater purification system that purifies wastewater from homes and factories with a purification tank and discharges it.

  Specifically, it is a method of floating suspended substances with ultrafine bubbles, and ozone is used together to remove chromaticity and odor.

  Patent Document 2 discloses a water treatment facility for treating sewage into reclaimed water. This water treatment facility is provided with a mechanism for discharging scum (turbid accumulation) accumulated on the water surface. That is, the target water is water after removal of suspended matter and organic matter after removal of suspended matter and biological treatment.

JP 2003-154357 A JP 2011-218266 A

  In a multi-stage wastewater treatment system for high-concentration organic wastewater treatment, if a flotation agent is added to remove suspended solids and pressurized flotation treatment or coagulation sedimentation treatment is performed, the amount of waste recovered will be The amount of flocculant is added to the amount of substances, and the increase in the size of equipment such as waste storage equipment and dewatering equipment and the processing costs are a major burden on companies.

  In addition, since the flocculant contains metal salts, chemical substances, etc., if it is a food factory, the suspended substances that are originally discharged are only food residues and can be recovered as valuable resources. Wastes derived from suspended solids cannot be recycled into livestock feed etc., and must be treated as industrial waste. Also, if the wastewater load becomes higher than the design value of the existing wastewater treatment system due to changes in the product, etc., and treatment becomes difficult, load reduction measures are required. It is necessary to newly install a flotation treatment device and a coagulation sedimentation treatment device, or to add a new aeration tank for biological treatment in order to enhance the organic matter removal capability, but the cost is enormous and waste Since processing costs also increase, it becomes a heavy burden on the operator.

  Accordingly, an object of the present invention is to provide a high-concentration organic wastewater treatment method capable of removing suspended solids by performing ozone treatment instead of adding a flocculant in high-concentration organic wastewater discharged from a food factory, and It is to provide an organic wastewater treatment system.

  The present invention is a multistage wastewater treatment system including a first treatment unit that receives organic wastewater from which large debris has been removed by a screen or the like and removes suspended solids. The first processing unit includes a processing tank for storing the organic waste water, an ozone injection device for injecting ozone into the processing tank, and a scum recovery mechanism for recovering scum generated in the processing tank. Have.

  This organic wastewater treatment system is a multi-stage wastewater treatment system and is composed of a plurality of treatment steps. Conventionally, ozone, which is generally used after advanced treatment after removing suspended matter / organic matter, is applied before removing suspended matter / organic matter. In other words, the first processing unit collects suspended solids as scum by using the aggregating action of ozone.

  Normally, a flow rate adjusting tank or the like installed in a general multi-stage organic wastewater treatment system is installed, but these flow rate adjusting tanks and the like can also be used as an ozone treatment tank. Therefore, if you want to add suspended solids removal treatment when there is no suspended solids removal treatment in existing equipment, this flow rate adjustment can be done without installing a new pressurized floating treatment device or coagulation sedimentation treatment device. If the tank is used as an ozone treatment tank, it can be realized with a simple modification. In addition, there is a floating substance removal treatment facility in the existing facilities, but it is not necessary to newly provide an ozone treatment tank when ozone treatment is desired.

  The amount of ozone injected into the treatment tank is preferably set to be less than the consumption inside the treatment tank.

  If the objective is decolorization or decomposition of specific persistent organic substances for water from which suspended solids and organic substances have been removed, as in the case of conventional advanced treatment, no matter how much the reaction efficiency is improved, the exhaust ozone will be zero. However, since it is not a concentration that can be directly released into the atmosphere, it is necessary to install an exhaust ozone decomposition facility. However, it was found that if the purpose is to aggregate suspended solids in high-concentration organic wastewater, a sufficient amount of ozone can be injected into the high-concentration organic wastewater. As a result, it was also found that there is an effect that exhaust ozone is not emitted and an exhaust ozone decomposition facility is unnecessary.

  In other words, using the fact that the amount of organic matter in the organic wastewater is high, if the amount of ozone injected into the treatment tank is set to be less than the consumption, ozone will not leak from the treatment tank, Installation of waste ozone decomposing equipment can be eliminated.

  The ozone injection device includes an ejector that mixes the organic wastewater and ozone to form an ozone mixed wastewater, and an injection mechanism that injects the ozone mixed wastewater into the treatment tank, and the ozone mixed wastewater. The mixing ratio of the ozone to the organic waste water can be set to 0.5 or less.

  By doing so, it is possible to prevent difficulty in separation and recovery due to foaming of scum by preventing ozone gas from becoming fine bubbles while sufficiently dissolving ozone.

  It is preferable to further include a second processing unit that performs biological processing continuously to the first processing unit.

  The ozone gas injected in the first processing unit is often manufactured from oxygen gas industrially from the viewpoint of cost. Therefore, oxygen is simultaneously injected into the wastewater flowing out from the first processing unit by ozone injection, and as a result, the concentration of dissolved oxygen in the waste water is very high when it flows out from the first processing unit. If biological treatment is performed in the second treatment section, the amount of dissolved oxygen in the organic wastewater can be used effectively, and the amount of aeration air necessary for supplying oxygen may be reduced.

  In addition, in the case where two ozone treatments of a third treatment unit that performs ozone treatment for advanced treatment are provided after the second treatment unit, the first treatment unit and the third treatment unit may provide ozone. It is good to share the supply source.

  This will reduce the initial cost. In addition, if the existing wastewater treatment system has ozone treatment equipment for advanced treatment and there is a surplus in the amount of ozone generated, it is only necessary to make a relatively simple modification to the ozone treatment tank as described above. The waste water treatment system of the present invention can be realized.

  According to the wastewater treatment system of the present invention, suspended solids can be removed from high-concentration organic wastewater without adding a flocculant in the previous stage. In addition, it is possible to take measures at a low cost in a wastewater treatment facility that requires a load reduction.

It is a block diagram which shows an example of the conventional multistage wastewater treatment system. It is a block diagram which shows an example of the multistage wastewater treatment system of embodiment. It is the schematic which shows the specific structure of a 1st process part and a 2nd process part. It is the schematic which shows a modification.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the following description is merely illustrative in nature and does not limit the present invention, its application, or its use.

  FIG. 2 is a block diagram of an organic wastewater multi-stage treatment system (also simply referred to as wastewater treatment system 1) to which the present invention is applied.

  The wastewater treatment system 1 has substantially the same configuration as a conventional advanced wastewater treatment system, and performs a first treatment unit 10 that performs a suspended solid removal process, a second treatment unit 20 that performs a biological treatment, and an ozone treatment. The third processing unit 30 is configured. The organic wastewater to be treated is first received by the first processing unit 10 and then sequentially processed with the second processing unit 20 and the third processing unit 30 and discharged into a river or the like.

  Wastewater to be treated is food-derived wastewater discharged from food factories, and is high-concentration organic wastewater containing a high concentration of contaminants such as food waste and oil generated during production (also simply referred to as wastewater) ).

  The relatively large pollutants contained in the wastewater are removed using a mesh screen or the like before flowing into the wastewater treatment system 1, but the wastewater still contains fine food waste, soluble organic matter, oil, etc. Contained in a suspended state.

  The concentration of pollutants in the waste water is, for example, 500 mg / L (BOD) or more as the concentration of organic matter. Further, the concentration of oil is 10 mg / L (normal hexane extract substance content) or more, and the suspended matter amount (SS) is 50 mg / L or more.

  FIG. 3 shows specific configurations of the first processing unit 10 and the second processing unit 20.

  The first processing unit 10 includes a processing tank 11, an ozone injection device 12, a scum recovery tank 13, and the like.

  The treatment tank 11 continuously receives and stores the waste water discharged from the drain pipe 2. The processing tank 11 of the present embodiment includes a storage tank 11a in which waste water is stored and a scum discharge groove 11b provided adjacent to the storage tank 11a. The capacity of the storage tank 11a is appropriately selected according to the amount of wastewater treated.

  The storage tank 11 a and the scum discharge groove 11 b are partitioned by a partition wall 11 c that is lower than the side wall of the processing tank 11. A scum discharge pipe 11d extending toward the scum recovery tank 13 is connected to the scum discharge groove 11b. The partition wall 11c, the scum discharge groove 11b, the scum discharge pipe 11d, and the scum recovery tank 13 constitute a scum recovery mechanism. A scum discharge pump may be installed in the middle of the discharge pipe.

  Although not shown, the waste water in the storage tank 11a is controlled to move up and down within a certain range, and at the highest water level, the water level of the waste water is slightly below the upper end of the partition wall 11c. It is set to be located.

  The ozone injection device 12 includes an ejector 12a, a pump 12b, a waste water introduction pipe 12c, an injection pipe 12d, and the like. One end of the waste water introduction pipe 12c is connected to the drain pipe 2, and the other end of the waste water introduction pipe 12c is connected to the ejector 12a. The pump 12b is installed in the middle of the waste water introduction pipe 12c, and is appropriately controlled so as to feed a certain amount of waste water to the ejector 12a.

  A certain amount of ozone is also supplied to the ejector 12 a through the gas pipe 3. In the ejector 12a, waste water and ozone are mixed to form ozone mixed waste water. One end of the injection pipe 12d is connected to the discharge port of the ejector 12a, and the other end of the injection pipe 12d is connected to the bottom wall of the storage tank 11a and communicates with the inside of the storage tank 11a.

  The ozone mixed waste water is injected into the storage tank 11a through the injection pipe 12d. In the present embodiment, an injection mechanism is configured by the pump 12b, the injection pipe 12d, and the like. By injecting the ozone-mixed wastewater, an aggregating action of ozone works inside the storage tank 11a, and suspended substances contained in the wastewater are separated as scum.

  At this time, if unreacted ozone leaks from the storage tank 11a, the human body and the surrounding environment are adversely affected. Therefore, normally, an exhaust ozone facility for collecting and decomposing the leaking ozone is installed, but the waste water treatment system 1 does not require an exhaust ozone facility.

  The reason is that all of the injected ozone is decomposed into oxygen inside the storage tank 11a by causing a small amount of ozone to directly act on high-concentration organic wastewater. That is, the amount of ozone injected into the storage tank 11a is set to be smaller than the amount of ozone consumed inside the storage tank 11a.

  In the present embodiment, in the ozone mixed waste water formed by the ejector 12a, the mixing ratio (liquid gas ratio) of ozone to the waste water is set to 0.5 or less.

  When the liquid gas ratio is larger than 0.5, the ozone is not sufficiently dissolved, and the ozone from the storage tank 11a leaks unreacted and a sufficient effect cannot be obtained. In addition, exhaust ozone treatment is required. On the other hand, if the liquid gas ratio is 0.5 or less, the ozone sufficiently reacts with the high-concentration organic wastewater, and all of the injected ozone can be consumed inside the storage tank 11a. Therefore, exhaust ozone treatment is not necessary, and it is not necessary to install exhaust ozone equipment.

  The liquid gas ratio is preferably set to 0.1 or more. If it is less than 0.1, the bubbles become fine and the scum S is foamed, making it difficult to collect the scum S.

  By injecting moderate ozone into the wastewater, the pollutants contained in the wastewater agglomerate and rise. As a result, scum S (a collection of aggregates) is formed, and a large amount of scum S accumulates on the surface of the wastewater stored in the storage tank 11a. The scum S accumulated on the water surface flows over the partition wall 11c and flows into the scum discharge groove 11b due to the rise of the water level.

  The scum S may be forced to flow into the scum discharge groove 11b. For example, a scum discharge device having a slide arm can be separately provided in the first processing unit 10. Then, when the water level reaches the upper level, the slide arm is slid on the water surface portion of the waste water to bring the scum S close to the scum discharge groove 11b, and the scum S is forced to flow into the scum discharge groove 11b.

  The scum S that has flowed into the scum discharge groove 11b is stored in the scum recovery tank 13 through the scum discharge pipe 11d. The scum S stored in the scum recovery tank 13 does not contain a metal salt or chemical substance such as an aggregated precipitate by an aggregating agent, and is composed only of a food-derived substance, so that it can be recycled to livestock feed and the like. The amount of scum S is also small compared to the conventional case.

  The waste water from which the scum S has been removed in the first processing unit 10 is sent to the second processing unit 20 through the first water pipe 5 by the water pump 4. The second processing unit 20 includes a biological treatment tank 21 and an aeration device 22.

  Activated sludge is accommodated inside the biological treatment tank 21. Therefore, the organic matter remaining in the wastewater is decomposed by microorganisms while staying in the biological treatment tank 21.

  The aeration apparatus 22 is installed at the bottom of the biological treatment tank 21. When the aeration apparatus 22 sends air to the wastewater, oxygen is supplied to the aerobic microorganisms, and the decomposition of the organic matter is promoted.

  Naturally, ozone reacts with the components in the high-concentration organic wastewater and does not remain, so there is no concern that microorganisms in the activated sludge will be killed even if the wastewater is sent to the biological treatment tank 21. Moreover, the ozone gas injected in the first processing unit is often manufactured from oxygen gas industrially. Therefore, oxygen is also simultaneously injected into the wastewater flowing out from the first treatment unit by ozone injection, resulting in wastewater with a high dissolved oxygen concentration. Therefore, the dissolved oxygen amount of the wastewater discharged | emitted from a 1st process part is higher than usual. If biological treatment is performed in the second treatment section, the amount of dissolved oxygen in the organic waste water can be used effectively, and the equipment of the aeration apparatus 22 necessary for supplying oxygen for biological treatment can be reduced in size or power consumption. There is.

  Although not shown, the wastewater treated in the biological treatment tank 21 is sent to the third treatment unit 30 through the second water pipe 6 after solid-liquid separation is performed. In the 3rd process part 30, the advanced waste water process by an ozone process is performed like the past. Since most of the pollutants in the wastewater are removed by the first treatment unit 10 and the second treatment unit 20, the third treatment unit 30 efficiently removes the contaminants remaining in the wastewater at a low concentration by ozone. I can do it.

  In the wastewater treatment system 1 of the present embodiment, the first treatment unit 10 and the third treatment unit 30 share an ozone supply source, and the first treatment unit 10 and the third treatment unit 30 perform the first operation from the ozone generator 31 installed in the third treatment unit 30. Ozone is supplied to the ejector 12a of the processing unit 10.

  In this case, the third treatment unit 30 has already been incorporated as an existing wastewater treatment system, and the ozone generator has sufficient capacity. When it is desired to reduce the load on the biological treatment unit of this system, the ozone gas from the third treatment unit 30 is branched into the flow rate adjustment tank and an ozone dissolving device is installed. Since the wastewater treatment system 1 of the invention can be realized, the equipment cost can also be suppressed.

  In addition, the waste water treatment system concerning this invention is not limited to embodiment mentioned above, The other various structure is included.

  For example, as shown in FIG. 4, one end of the waste water introduction pipe 12c is connected to the storage tank 11a instead of the drain pipe 2, and ozone may be added while circulating the waste water stored in the storage tank 11a. .

  The wastewater treatment system 1 is an example, and a treatment unit other than the second treatment unit 20 and the third treatment unit 30 may be provided after the first treatment unit 10. For example, instead of the biological treatment tank 21, a membrane treatment may be installed, and a treatment unit that removes organic substances using the membrane may be provided.

  The third processing unit 30 is not essential. When the third processing unit 30 is not provided, it is necessary to install an ozone generator in the first processing unit 10, but even in that case, the amount of ozone injected may be relatively small, so that the cost can be reduced.

  A floating scum recovery device may be installed inside the processing tank 11. By doing so, recovery of the scum S can be promoted. One end of the wastewater introduction pipe 12c may be connected to the storage tank 11a.

  A scum collection | recovery mechanism is an illustration and can be suitably selected according to a specification.

DESCRIPTION OF SYMBOLS 1 Waste water treatment system 10 1st process part 11 Process tank 12 Ozone injection apparatus 20 2nd process part 30 3rd process part S Scum

Claims (1)

A method for treating organic wastewater containing food waste and oil discharged from a food factory,
Injecting ozone gas into the organic wastewater stored in the storage tank;
A step of generating scum by the injected ozone gas without adding a flocculant;
Recovering the recyclable scum,
The organic wastewater has a BOD of 500 mg / L or more, a normal hexane extract substance content of 10 mg / L or more , and a suspended matter amount (SS) of 50 mg / L or more,
In the step of injecting the ozone gas, the injection amount of the ozone gas is set to be less than the consumption amount of ozone inside the storage tank,
In the step of injecting the ozone gas, an ozone mixed waste water in which the organic waste water in the storage tank and the ozone gas are mixed is injected into the organic waste water in the storage tank by an ejector,
The method for treating organic wastewater, wherein a mixing ratio of ozone to the organic wastewater in the ejector is set to 0.1 or more and 0.5 or less.

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