JP6639211B2 - Phosphate fertilizer production method and phosphate fertilizer production apparatus - Google Patents

Description

The present invention relates to a phosphate fertilizer production method and a phosphate fertilizer production apparatus for producing a phosphate fertilizer from rice processing wastewater such as rice bran, and in particular, not only a batch type phosphorus recovery technique, but also a continuous method capable of coping with large-scale treatment. It relates to technologies including the method of phosphorus recovery.
Related.

  Rice processing wastewater containing rice bran and rice and soup discharged from rice processing factories and the like is wastewater containing starch, proteins, lipids, and the like. The characteristics of such rice processing wastewater are that it contains a large amount of starch and therefore has high COD (Chemical Oxygen Demand), which is an indicator of the organic carbon source concentration, and contains protein-derived nitrogen components. Have been. In addition, when producing rice oil from rice bran, there is a step of removing impurities in which phospholipids are combined with calcium, magnesium ions and the like in the refining stage. Therefore, the wastewater from the purification process is characterized by containing a high concentration of phosphoric acid, and the rice processing wastewater is a wastewater in which components which are regarded as problematic in water pollution are mixed at a high concentration.

As a general phosphorus removal method, there is a coagulation precipitation method in which precipitation is performed by forming a metal salt using an aluminum salt or an iron salt or a calcium salt using calcium chloride or slaked lime. In recent years, as a method of removing only phosphorus or a method of simultaneously removing nitrogen and phosphorus, a biological dephosphorization method such as an AO method or an A ₂ O method is used in a sewage treatment facility or the like. In the AO method, phosphorus is released in an anaerobic step and phosphorus is ingested in an aerobic step by phosphorus accumulating bacteria (PAO), and phosphorus is taken into sludge from wastewater to remove phosphorus in the wastewater. Further, as described in Patent Document 2, the A ₂ O method comprises an anaerobic step, an anoxic step, and an aerobic step, wherein the nitrifying bacteria perform the nitrifying action in the aerobic step, and the denitrifying bacteria cause the nitrifying action. A denitrification action is performed in the oxygen step, and nitrogen in the wastewater is removed.

However, in the coagulation sedimentation method, the running cost of the coagulant is high, and the phosphate contained in the sludge is passive, so that the value as a sludge fertilizer is low and sludge disposal is difficult. On the other hand, the AO method and the A ₂ O method described in Patent Literature 2 have lower running costs than the coagulation sedimentation method, and have high value as a sludge fertilizer because the sludge contains polyphosphoric acid. However, it is unstable against seasonal fluctuations such as wastewater composition and temperature, and the electricity cost for aeration in the aerobic process and the fuel cost for drying sludge (heavy oil cost) account for the majority of running costs, and factory wastewater In order to spread the method, it is required to stabilize the processing and further reduce the running cost.

JP-A-11-169895 JP 2011-194373 A

  Therefore, the inventors of the present application have reduced the amount of generated sludge, and stably manufactured the sludge with an increased phosphorus content in dried sludge, and reduced the running cost by selling it as fertilizer. Thought it could be lowered. However, rice processing wastewater has a high BOD because it contains bran with a high lipid content, and the wastewater contains many hardly decomposable organic substances and organic phosphoric acid. In addition, hardly decomposable organic matter is an organic matter that microorganisms do not easily decompose, and its presence causes phosphorus-accumulating bacteria responsible for phosphorus removal in wastewater to fail to take in organic matter under anaerobic conditions, resulting in unstable process operation. As a result, the phosphorus recovery efficiency is reduced. Further, fluctuations in pH and temperature also cause instability of the process operation state, and lower phosphorus recovery efficiency.

  Therefore, if the hardly decomposable organic substances and organic phosphoric acid are decomposed, the activity of microorganisms can be improved and the content of phosphorus contained in sludge can be increased. However, if not only the phosphorus-accumulating bacteria but also the non-phosphorus-accumulating bacteria grow, the ratio of the phosphorus content in the sludge decreases, and the value as fertilizer decreases.

In view of the above circumstances, at least one embodiment of the present invention provides a phosphate fertilizer production method and a phosphate fertilizer production apparatus capable of producing sludge obtained from rice processing wastewater as a fertilizer having a high phosphorus content. The purpose is to:
Another object of the present invention is to provide not only a batch-type phosphorus recovery technique but also a continuous-type phosphorus recovery technique capable of coping with large-scale processing.

The phosphate fertilizer production method according to at least one embodiment of the present invention,
A phosphate fertilizer production method for producing phosphate fertilizer from rice processing wastewater,
In the presence of yeast and koji mold, the rice processing wastewater is subjected to microbial treatment including anaerobic treatment to decompose organic phosphoric acid in the rice processing wastewater into orthophosphoric acid, and the pH of the rice processing wastewater is adjusted. A pretreatment step to obtain conditioned wastewater;
The adjusted wastewater treated with microorganisms in the pretreatment step is supplied, and in the presence of at least phosphorus-accumulating bacteria, microorganism treatment is performed in the order of anaerobic treatment and aerobic treatment, and orthophosphoric acid into the phosphorus-accumulating bacteria is A phosphorus recovery step to promote uptake,
A solid-liquid separation step of separating the phosphoric acid-containing sludge and treated water by sedimenting the microorganism-treated solution subjected to the microorganism treatment in the microorganism treatment step in a sedimentation vessel,
In the phosphorus recovery step, while activating the phosphorus-accumulating bacteria, adjusting the temperature of the adjusted wastewater to a temperature at which the growth of non-phosphorus-accumulating bacteria other than the phosphorus-accumulating bacteria present in the adjusted wastewater can be suppressed. Is performed.

  And the said phosphorus collection process may employ | adopt the batch system which repeats process water mixing, anaerobic process, and aerobic process batchwise under temperature control, and also the continuous system which can respond to a large-scale process, Specifically, Adopts a continuous method that circulates anaerobic treatment and aerobic treatment of the circulating sludge under temperature control and returns the return sludge solid-liquid separated after the phosphoric acid recovery step to the phosphorus recovery step, while dominating the phosphorus-accumulating bacteria. May be.

  According to the method for producing a phosphate fertilizer, an anaerobic treatment is performed in the pretreatment step to decompose organic substances into low-molecular-weight organic substances and orthophosphoric acid which are easily assimilated by phosphorus-accumulating bacteria. By adjusting the pH of the rice processing wastewater in the pretreatment step, phosphorus intake can be stabilized by the phosphorus-accumulating bacteria in the next step (phosphorus recovery step) and subsequent steps. By supplying the adjusted wastewater obtained in the pretreatment step to the batch type or continuous type phosphorus recovery step, it is possible to supply the adjusted wastewater having a high concentration of phosphorus to the phosphorus recovery step. In addition, microbial treatment with phosphorus-accumulating bacteria in the phosphorus recovery process in the order of anaerobic treatment and aerobic treatment activates phosphorus uptake by phosphorus-accumulating bacteria and promotes uptake of orthophosphate into phosphorus-accumulating bacteria. can do. In the phosphorus recovery step, the temperature of the adjusted wastewater is adjusted so that the phosphorus-accumulating bacteria are activated and the growth of non-phosphorus-accumulating bacteria other than the phosphorus-accumulating bacteria present in the adjusted wastewater is suppressed. Therefore, the growth of non-phosphorus accumulating bacteria can be suppressed, and the phosphorus accumulating bacteria can be stably dominated. Therefore, the phosphoric acid content in the sludge obtained by the solid-liquid separation step can be increased, and the sludge can be used as a phosphate fertilizer having a high fertilizer effect. Therefore, a phosphate fertilizer with high added value can be produced, and by selling this, the running cost can be reduced. Therefore, a phosphate fertilizer production method capable of producing a high value-added phosphate fertilizer from rice processing wastewater can be realized.

Also, in some embodiments,
The pretreatment means may adjust the pH so that the pH of the rice processing wastewater is 4 or more.

  In this case, when the pH of the rice processing wastewater is set to about 4 or less, the cells of the phosphorus-accumulating bacteria responsible for phosphorus intake by the phosphorus-accumulating bacteria in the phosphorus recovery step are damaged, and the phosphorus intake by the phosphorus-accumulating bacteria is stabilized. Can not be done. Therefore, by performing the pH treatment in the pretreatment means so that the pH of the rice processing wastewater becomes 4 or more, it is possible to stabilize the phosphorus uptake by the phosphorus accumulating bacteria in the phosphorus recovery step.

  Further, in a batchwise method in which treated water mixing, anaerobic treatment and aerobic treatment are repeatedly performed in batches under temperature control, in the anaerobic treatment of the phosphorus recovery step, the temperature of the adjusted wastewater is 30 ° C. to 35 ° C. In the aerobic treatment of the phosphorus recovery step, the temperature is preferably adjusted so that the temperature of the adjusted wastewater is 25 ° C to 30 ° C.

  In this case, the temperature of the adjusted wastewater is adjusted to 30 ° C. to 35 ° C. in the anaerobic treatment in the phosphorus recovery step, so that the growth of non-phosphorus accumulating bacteria can be suppressed, and the phosphorus accumulating bacteria involved in phosphorus uptake become dominant. Can be done.

  In the aerobic treatment in the phosphorus recovery step, it is preferable that the temperature is adjusted so that the temperature of the adjusted wastewater is 25 ° C to 30 ° C.

  In this case, the temperature of the adjusted wastewater is adjusted to 25 ° C. to 30 ° C. by the aerobic treatment in the phosphorus recovery step, so that an environment for activating the phosphorus uptake of the phosphorus accumulating bacteria can be created, and the amount per unit cell mass can be increased. The phosphorus content can be increased.

Further, the phosphate fertilizer production apparatus according to at least one embodiment of the present invention,
A phosphate fertilizer production device for producing phosphate fertilizer from rice processing wastewater,
A pretreatment tank for storing the rice processing wastewater,
PH adjusting means for adjusting the pH of rice processing wastewater in the pretreatment tank,
Pretreatment for obtaining conditioned wastewater by anaerobically treating the rice processing wastewater to decompose organic phosphoric acid into low-molecular organic matter and orthophosphoric acid by yeast and koji mold present in the rice processing wastewater in the pretreatment tank. Means,
Main treatment tank for storing the adjusted wastewater obtained by the pretreatment means,
A regulated wastewater supply means for supplying the regulated wastewater batchwise or continuously to the main treatment tank,
Phosphorus recovery means for treating the conditioned wastewater in the treatment container at least in the presence of phosphorus-accumulating bacteria in the order of anaerobic treatment and aerobic treatment to promote the uptake of orthophosphoric acid into the phosphorus-accumulating bacteria When,
Temperature adjusting means for adjusting the temperature of the adjusted wastewater in the treatment container to a temperature at which the phosphorus-accumulating bacteria are activated and the growth of non-phosphorus-accumulating bacteria can be suppressed,
A solid-liquid separation tank is provided for separating and separating the sludge containing phosphoric acid and the treated water by storing and sedimenting the microorganism-treated solution treated with the microorganisms by the phosphorus recovery means.

  Further, according to the phosphorus recovery technology of the continuous treatment method, a circulating sludge line from the temperature-controlled aerobic treatment region toward the anaerobic treatment region, and a return sludge line from the solid-liquid separation tank toward the anaerobic treatment region are used. The anaerobic treatment vessel is connected to the anaerobic treatment vessel and the aerobic treatment vessel by a circulating sludge line, and is provided on the downstream side. The treatment is performed in the order of anaerobic treatment and aerobic treatment in order to predominate the phosphorus-accumulating bacteria to promote the uptake of orthophosphate into the phosphorus-accumulating bacteria.

  According to the phosphate fertilizer production apparatus, rice processing wastewater stored in a pretreatment tank is subjected to anaerobic treatment by pretreatment means, and organic matter is decomposed into low-molecular-weight organic matter and orthophosphoric acid that are easily assimilated by phosphorus-accumulating bacteria. To adjust the COD concentration. Therefore, phosphorus intake can be stabilized by phosphorus-accumulating bacteria in the subsequent phosphorus recovery means. In addition, by adjusting the pH of the rice processing wastewater in the pretreatment step, phosphorus intake can be further stabilized by phosphorus-accumulating bacteria in the next step (phosphorus recovery step) and subsequent steps. Further, by supplying the regulated wastewater obtained in the pretreatment step to the main treatment tank in a batchwise manner by the regulated wastewater supply means, the regulated wastewater with a high concentration of phosphorus can be supplied to the main treatment tank. In addition, by performing microbial treatment with phosphorus-accumulating bacteria in the order of anaerobic treatment and aerobic treatment in the phosphorus recovery means, the phosphorus uptake by phosphorous-accumulating bacteria is activated, and the uptake of orthophosphate into phosphorus-accumulating bacteria is promoted. can do. Further, in the phosphorus recovery step, the temperature of the adjusted wastewater is adjusted by the temperature adjusting means to a temperature at which the growth of non-phosphorus accumulating bacteria can be suppressed, so that the phosphorus accumulating bacteria can be stably dominated. Then, the microorganism treatment liquid is stored and settled in the solid-liquid separation tank, thereby separating the sludge containing phosphoric acid and the treated water. Therefore, the phosphoric acid content in the sludge can be increased, and the sludge can be used as a phosphate fertilizer having a high fertilizer effect. Therefore, it is possible to realize a phosphate fertilizer production apparatus capable of producing a phosphate fertilizer with high added value.

  According to at least some embodiments of the present invention, sludge obtained from rice processing wastewater can be used as a fertilizer by producing sludge having a high phosphorus content.

It is a schematic structure figure of a phosphate fertilizer manufacturing device concerning one embodiment of a batch system of the present invention. It is a flowchart of the phosphate fertilizer manufacturing method concerning one embodiment of the batch system of the present invention. It is a graph which shows the relationship between the elapsed time after the start of pretreatment, and orthophosphoric acid concentration. It is a graph which shows the relationship between elapsed time after the start of preprocessing and COD. It is a table | surface which shows the temperature condition in a tank in an aerobic process. It is a graph which shows the relationship between MLSS concentration and aerobic process tank temperature. It is a graph which shows the relationship between sludge phosphorus content and phosphorus recovery / MLSS concentration. It is a schematic structure figure of a phosphate fertilizer manufacturing device concerning one embodiment of a continuous system of the present invention. It is a flowchart of the phosphate fertilizer manufacturing method concerning one embodiment of the continuous system of the present invention.

Hereinafter, an embodiment of a batch-type phosphate fertilizer production technique of the present invention will be described with reference to FIGS. In addition, the rice processing wastewater to be treated in the following embodiment is rice bran processing wastewater containing rice bran discharged from a rice processing factory or the like, and rice processing wastewater containing BOD, COD, nitrogen, and phosphorus. is there. Further, the materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely illustrative examples.
Hereinafter, embodiments of a batch-type phosphate fertilizer production method and a phosphate fertilizer production apparatus of the present invention will be described with reference to FIGS. 1 and 2 according to the accompanying drawings. In addition, the rice processing wastewater to be treated in the following embodiment is rice bran processing wastewater containing rice bran discharged from a rice processing factory or the like, and rice processing wastewater containing BOD, COD, nitrogen, and phosphorus. is there. Further, the materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely illustrative examples.

  FIG. 1 is a schematic configuration diagram of a phosphate fertilizer production apparatus which is an embodiment of the batch system of the present invention. First, before describing the phosphate fertilizer production method, a phosphate fertilizer production apparatus will be described. As shown in FIG. 1, the phosphate fertilizer production apparatus 1 mainly includes a pretreatment tank 3, a pH adjusting means 17, a pretreatment means 23, a main treatment tank 8, a microorganism treatment means 24, Means 21 and 26 and solid-liquid separation tank 14 are provided.

  The treatment tank 8 may be provided with a plurality of tanks for separately performing an anaerobic treatment step and an aerobic treatment step, which will be described later, and these may be connected in series, or conditions in the tank may be changed as shown in FIG. The anaerobic treatment step and the aerobic treatment step may be performed in a plurality of tanks, each of which is performed in each tank. However, since the installation area of the apparatus and the size of the apparatus can be reduced, the entire processing tank 8 is particularly simple. It is preferably one tank.

  Hereinafter, a detailed configuration of the phosphate fertilizer production device 1 will be described.

  The pretreatment tank 3 is provided with a stirrer 5 for stirring the inside of the tank and a sensor 4 for measuring the pH and temperature of the rice processing wastewater.

  The rice processing wastewater discharged from the pretreatment tank 3 is sent to a main treatment tank 8 by a pump 6 via a wastewater supply line 7. An aeration device 15 and a pump 16 are connected to the main processing tank 8. The aeration device 15 and the pump 16 are devices for supplying air into the wastewater to make the inside of the processing tank 8 aerobic.

  Further, a chiller 25 which is a part of a temperature adjusting means 21 for adjusting the temperature in the tank is connected to the pretreatment tank 3 via circulation lines 19a and 19b. Similarly, a chiller 27 which is a part of a temperature adjusting means 26 for adjusting the temperature inside the tank is connected to the main processing tank 8 via circulation lines 22a and 22b. A stirrer 9 for stirring the inside of the tank and a sensor 10 for measuring the pH, temperature, and dissolved oxygen of the wastewater in the main processing tank 8 are provided.

  When a series of processing steps including an anaerobic processing step and an aerobic processing step is completed in the main processing tank 8, the processing water is discharged from the discharge line 12 and sent to the solid-liquid separation tank 14 at the subsequent stage.

  The data of the measured values of pH and temperature measured by the sensors 4 and 10 installed in the pretreatment tank 3 and the main treatment tank 8 are transmitted to controllers 18 and 20 described later.

  The pretreatment tank 3 is connected with pH adjusting means 17 for adjusting the pH of the wastewater to be treated. The pH adjusting means 17 includes a pH adjusting agent tank 17a for storing a pH adjusting agent for adjusting the pH of wastewater to be treated and a pH adjusting agent in the pH adjusting agent tank 17a in the pretreatment tank 3. And a pH adjusting pump 17b for sending out. The controller 18 described later controls the pH adjustment pump 17b, so that the amount of the pH adjuster delivered from the pH adjustment pump 17b into the pretreatment tank 3 is controlled.

  In addition, as the pH adjusting pump 17b, for example, an electromagnetic metering pump can be used. Further, as the pH adjusting agent, an acidic aqueous solution can be used for alkaline wastewater, and a basic aqueous solution (for example, sodium hydroxide) can be used for acidic wastewater. In one embodiment, a 40% by mass aqueous sodium hydroxide solution is used as a pH adjuster to increase the pH of rice bran processing wastewater (rice processing wastewater) having a low pH.

  The controller 18 receives the data of the measured values of pH and temperature transmitted from the sensor 4 installed in the pretreatment tank 3 and controls the pH adjusting means 17 based on these values. For example, when the pH transmitted from the sensor 4 installed in the pretreatment tank 3 to the controller 18 is out of a certain range (for example, 4.0 or more and 7.0 or less), the pH falls within the above range. The pH adjusting pump 17b is controlled so that a necessary amount of the pH adjusting agent stored in the pH adjusting agent tank 17a is sent into the pretreatment tank 3.

  The rice bran processing wastewater discharged from the pretreatment tank 3 is sent to the main treatment tank 8 at the subsequent stage as pretreated pretreatment wastewater. The temperature in the main processing tank 8 is adjusted to 25 to 35 ° C. by a chiller 27 or the like, which can be cooled or adjusted according to need.

  Next, a method for producing a phosphate fertilizer according to one embodiment will be described with reference to FIG. FIG. 2 is a flowchart of the method for producing a phosphate fertilizer according to one embodiment. The phosphate fertilizer production method according to the present embodiment mainly includes a pretreatment step 60, a phosphorus recovery step 61 including an anaerobic treatment step 61a and an aerobic treatment step 61b, and a solid-liquid separation step 62.

  Next, each step of the rice processing wastewater treatment method according to an embodiment of the batch-type phosphate fertilizer production method of the present invention will be described.

  In the pretreatment step 60, in the presence of yeasts and koji molds, rice processing wastewater is subjected to microbial treatment including anaerobic treatment to decompose organic phosphoric acid in rice processing wastewater into orthophosphoric acid, To obtain conditioned wastewater. The pH of the rice processing wastewater is adjusted by adding an aqueous solution of sodium hydroxide so that the pH becomes 4.0 or more and 7.0 or less. When the pH is adjusted in this manner, the water to be treated whose pH has been adjusted to a neutral value of 5.0 or more and around 8.0 in the subsequent phosphorus recovery step 61 is passed through. Damage to the bacteria (phosphorus accumulating bacteria) in the activated sludge that is carried is reduced. As a result, phosphorus intake can be activated, and the dominance of phosphorus-accumulating bacteria in the phosphorus recovery step 61 can be stably maintained.

  In addition, the temperature of the rice processing wastewater in the pretreatment step 60 is set within the range of 25 to 35 ° C., and the time of the pretreatment step 60 is preferably at least 20 hours.

  In the phosphorus recovery step 61 of the present embodiment, a microorganism treatment including anaerobic treatment and aerobic treatment in this order is performed on the adjusted wastewater obtained in the pretreatment step 60 in the presence of phosphorus-accumulating bacteria, and adjusted by the phosphorus-accumulating bacteria. Intake phosphorus from wastewater.

  The anaerobic treatment step 61a anaerobically treats the adjusted wastewater obtained in the pretreatment step 60 in the presence of phosphorus-accumulating bacteria. Here, the phosphorus-accumulating bacteria take in a carbon source (organic matter) contained in the conditioned wastewater and release phosphorus. At this time, since the organic matter in the rice bran processing wastewater (adjusted wastewater) has been reduced in molecular weight in the pretreatment step 60, the carbon source is smoothly taken up in the anaerobic treatment.

  Here, when anaerobic treatment is performed using sludge containing phosphorus-accumulating bacteria, sludge containing phosphorus-accumulating bacteria is acclimated under anaerobic / aerobic conditions. By maintaining the temperature within the range, the growth of non-phosphorus accumulating bacteria is suppressed, and the phosphorus accumulating bacteria are made dominant. The pH of the adjusted wastewater during the anaerobic treatment is in the range of 6.5 to 7.5, and the time of the anaerobic treatment step 61a is preferably 6 to 10 hours.

  In the aerobic treatment step 61b, air is supplied to the conditioned wastewater to be treated to make it aerobic, and orthophosphoric acid is taken into the phosphorus accumulating bacteria and accumulated as polyphosphoric acid. When performing aerobic treatment using sludge containing phosphorus-accumulating bacteria, sludge containing phosphorus-accumulating bacteria is acclimated under anaerobic / aerobic conditions. By maintaining the temperature within the range, the growth of non-phosphorus accumulating bacteria is suppressed, and the phosphorus accumulating bacteria proliferate and predominate.

  The pH of the adjusted wastewater during the aerobic treatment is in the range of 7.5 to 8.0, and the time of the aerobic treatment step 61b is preferably 14 to 18 hours.

  The above-described phosphorus recovery step 61 is of a batch type. In this case, the microorganism treatment liquid remaining in the phosphorus recovery step 61 may be returned and returned to the anaerobic treatment step 61a via a treated water mixing step 61c for mixing with the adjusted wastewater supplied from the pretreatment step 60.

  After the end of the aerobic treatment step 61b, a solid-liquid separation step 62 for separating excess sludge and treated water is performed. In the solid-liquid separation step 62, for example, a known method such as sedimentation or membrane separation is used, and a coagulant may be added to coagulate and precipitate sludge. The precipitated sludge contains high phosphorus and becomes a phosphate fertilizer.

  According to the present embodiment, in the batch-type phosphorus recovery step 61, while activating the phosphorus-accumulating bacteria, the temperature is controlled so that the growth of non-phosphorus-accumulating bacteria other than the phosphorus-accumulating bacteria present in the adjusted wastewater can be suppressed. Since the temperature of the adjusted wastewater is adjusted, the growth of non-phosphorus-accumulating bacteria can be suppressed, and the phosphorus-accumulating bacteria can be stably dominated. Therefore, the content of phosphoric acid in the sludge obtained in the solid-liquid separation step 62 can be increased, and the sludge can be a phosphate fertilizer having a high fertilizer effect. Therefore, a phosphate fertilizer with high added value can be produced, and by selling this, the running cost in phosphate fertilizer production can be reduced. Therefore, it is possible to realize a phosphate fertilizer production method and a phosphate fertilizer production capable of producing a high value-added phosphate fertilizer from rice processing wastewater.

[Example 1]
Example 1 As Example 1, a test was conducted to examine the changes over time in the concentration of orthophosphoric acid, COD and pH in the pretreatment of rice bran processing wastewater.

Using the phosphate fertilizer production apparatus 1 shown in FIG. 1, the pretreatment step 60 of the pretreatment step 60 and the phosphorus recovery step 61 was performed under the following conditions.
<Conditions in the pretreatment step>
Pre-processing time: 24h
Pretreatment temperature: 30 ° C
Initial COD concentration: 6950 mg / L
Initial orthophosphoric acid concentration: 189 mg / L
Initial pH: 5.04
FIGS. 3 and 4 show the results of measuring the changes over time in the concentration of orthophosphoric acid, COD and pH in the pretreatment of rice bran processing wastewater.

  3 and 4, the abscissa represents the elapsed time (unit: time) from the start of the pretreatment, the ordinate of FIG. 3 represents the orthophosphoric acid concentration (unit: mg / L), and the ordinate of FIG. (Unit: mg / L).

  Orthophosphoric acid increased with time and reached about 4 times in 20 hours from the start of pretreatment. The COD concentration decreased with time, and could be reduced by about 30% in 20 hours from the start of the treatment.

[Example 2]
As Example 2, a test for examining the relationship between the MLSS concentration in the treatment of rice bran processing wastewater and the temperature in the aerobic process tank was performed.

Using the phosphate fertilizer production apparatus 1 shown in FIG. 1, the aerobic treatment step 61b of the pretreatment step 60 and the phosphorus recovery step 61 was performed under the following conditions. The aerobic process was performed on the rice bran processing wastewater having a COD of 900 to 5720 mg / L, an orthophosphoric acid concentration of 134 to 415 mg / L, and a pH of 6.18 to 8.18 at the start of the phosphorus recovery process under the temperature conditions shown in FIG.
FIG. 6 shows the relationship between the MLSS concentration and the temperature in the aerobic process tank. As a result, the lower the temperature, the lower the MLSS concentration was kept. Thereby, it turned out that MLSS density | concentration can be adjusted by the temperature in a tank.

[Example 3]
As Example 3, a test for examining the relationship between sludge phosphorus content and phosphorus recovery / MLSS concentration in the treatment of rice bran processing wastewater was performed.

The pretreatment step 60 and the phosphorus recovery step 61 were performed using the phosphate fertilizer production apparatus 1 shown in FIG. 1 under the following conditions. Phosphorus recovery of rice bran processing wastewater with a COD of 900 to 5720 mg / L, an orthophosphoric acid concentration of 134 to 415 mg / L, and a pH of 6.18 to 8.18 at the start of the phosphorus recovery step under anaerobic time, aerobic time and temperature conditions shown in FIG. The process was performed.
FIG. 7 shows the relationship between sludge phosphorus content and phosphorus recovery / MLSS concentration. As a result, a high sludge phosphorus content was obtained when the phosphorus recovery amount / MLSS concentration was 0.1 or more. Thereby, it turned out that a phosphate fertilizer containing high phosphoric acid can be obtained by using the production method and the production apparatus according to one embodiment of the present invention.

Next, a description will be given of a continuous phosphorus recovery technique capable of handling large-scale processing.
FIG. 8 is a schematic configuration diagram of the continuous phosphorus recovery process, and FIG. 9 is a continuous process drawing corresponding to FIGS. 1 and 2 of the batch method, respectively.
As shown in FIG. 8, a circulating sludge line 70 is connected from the aerobic treatment tank to the anaerobic treatment tank, and a return sludge line is connected from the solid-liquid separation step to the anaerobic treatment step (tank). As a result, in this embodiment, the processing method can be changed from the batch method to the continuous tank method. In other words, in order to obtain a processing capacity that can withstand a practical level, the reason why the batch system was changed to the continuous system was that the anaerobic process and the aerobic process were performed in the same tank in the batch system, but each process was made independent in the continuous system. A processing apparatus comprising an anaerobic tank and an aerobic tank can be configured. In the continuous tank system, a circulation line from the aerobic tank to the anaerobic tank is created to keep the microorganisms in an anaerobic / aerobic environment, and each processing time is adjusted according to the amount of circulation.
In the present invention, the processing target is a vegetable oil production wastewater containing rice bran processing wastewater (dissolved phosphoric acid: 150 to 800 mg / L (orthophosphoric acid: 70 to 450 mg / L) COD: 4000 to 18000 mg / L Temperature (15 to 800 mg / L) (40 ° C.) ・ The pH (4.0 to 7.0) is used, and the following first to third steps are carried out.

1. In the first step (anaerobic step: pretreatment tank), yeast and koji mold were used as main microorganisms.
1.1 The purpose of this step is to (i) decompose the dissolved phosphoric acid into orthophosphoric acid and facilitate the bioassimilation of the phosphorus component in the third step. (Ii) Decompose the device into low molecular weight organic acids to facilitate bioassimilation of organic carbon in the second step. (Iii) It is to stabilize the second and subsequent steps by adjusting the pH to 4.0 or more using sodium hydroxide.
1.2 Operating conditions-Operation: Stir under anaerobic conditions.
・ Time: 20 hours or more ・ Temperature: 25-35 ° C
PH: 4.0 to 7.0 (adjusted to pH 4.0 or lower by adding sodium hydroxide)
1.3 Results (i) The total amount of dissolved phosphoric acid was decomposed into orthophosphoric acid, and the concentration of orthophosphoric acid increased.
(Ii) COD was reduced by half and the organic acid concentration was increased.
(Iii) pH was adjusted to 4.0 to 7.0.

2 Second step (anaerobic step: anaerobic tank 66a) Phosphorus-accumulating bacteria (PAO) were used as the main microorganism.
2.1 The purpose of this step is to (i) take in low molecular organic acids into the body by utilizing the energy when phosphorus-accumulating bacteria (PAO) degrade polyphosphate in the body and release orthophosphate out of the body, It is to accumulate PHA (Poly Hydroxyl Alkanonate). (Ii) By maintaining a predetermined temperature and pH at a high organic acid concentration, the growth of a competing bacterium is suppressed, and PAO predominantly assimilate the low molecular organic acid.
2.2 Implementation conditions-Operation: Stir under continuous conditions under anaerobic conditions.
・ Time: 6-10 hours ・ Temperature: 30-35 ° C
-PH: 6.5 to 7.5
2.3 Results (i) Wastewater flows from the pretreatment tank into the continuous treatment tank, resulting in an environment with a high orthophosphoric acid concentration (150 mg / L or more).
(Ii) As the anaerobic time progresses, the concentration of orthophosphoric acid can be increased (orthophosphoric acid release) and COD can be reduced (organic acid uptake).

3 Third step (aerobic step: aerobic tank 66b)
Major microorganisms: Phosphorus-accumulating bacteria (PAO)
3.1 The purpose of this step is (i) Phosphorus-accumulating bacteria (PAO) multiply using PHA in the body and utilize the energy at that time to release orthophosphoric acid in wastewater more than anaerobic release. It is taken into the body and accumulated as polyphosphate. (Ii) By maintaining a high orthophosphoric acid concentration, a predetermined temperature, and a pH, the growth is suppressed with respect to competing bacteria, and the PAO grows predominantly and takes up orthophosphoric acid.
3.2 Operating conditions-Operation: Stir under aerobic conditions in a continuous manner.
・ Time: 14-18 hours ・ Temperature: 25-30 ° C
PH: 7.5 to 8.0
-Dissolved oxygen: 0.5-2mg / L
・ Sludge concentration (MLSS): 1500 to 2000 mg / L
3.3 Results (i) At the end of the aerobic period, the concentration of orthophosphoric acid was reduced to 50 mg / L.
(Ii) The sludge concentration (MLSS) increased to 2000 mg / L at the end of the aerobic.
(Iii) The sludge phosphorus content increased to 15% at the end of aerobic.
Therefore, the stirring can be terminated under the aerobic condition by judging that at least the orthophosphoric acid concentration has dropped to 50 mg / L.

DESCRIPTION OF SYMBOLS 1 Phosphate fertilizer manufacturing apparatus 3 Pretreatment tank 4, 10 Sensors 5, 9 Stirrer 6 Pump 7 Wastewater supply line 8 Main treatment tank 12 Wastewater line 14 Solid-liquid separation tank 15, 16 Aerator 17 pH adjusting means 17a pH adjuster tank 17b pH adjustment pump 18, 20 Controller 19a, 19b, 22a, 22b Circulation line 21, 26 Temperature adjustment means 23 Pretreatment means 24 Microbial treatment means 25, 27 Chiller 60 Pretreatment step 61 Phosphorus recovery step 61a Anaerobic treatment step 61b Aerobic Treatment process 61c Treated water mixing process 62 Solid-liquid separation process 70 Circulating sludge line 80 Return sludge line

Claims (8)

A phosphate fertilizer production method for producing phosphate fertilizer from rice processing wastewater,
In the presence of yeast and koji mold, the rice processing wastewater is subjected to microbial treatment including anaerobic treatment to decompose organic phosphoric acid in the rice processing wastewater into orthophosphoric acid, and the pH of the rice processing wastewater is adjusted. A pretreatment step to obtain conditioned wastewater;
The adjusted wastewater treated with microorganisms in the pretreatment step is supplied, and in the presence of at least phosphorus-accumulating bacteria, microorganism treatment is performed in the order of anaerobic treatment and aerobic treatment, and orthophosphoric acid into the phosphorus-accumulating bacteria is A phosphorus recovery step to promote uptake,
A solid-liquid separation step of separating the sludge containing phosphoric acid and the treated water by sedimenting the microorganism treatment liquid subjected to the microorganism treatment in the phosphorus recovery step in a sedimentation vessel,
In the phosphorus recovery step, while activating the phosphorus-accumulating bacteria, adjusting the temperature of the adjusted wastewater to a temperature at which the growth of non-phosphorus-accumulating bacteria other than the phosphorus-accumulating bacteria present in the adjusted wastewater can be suppressed. Is carried out.   In the phosphorus recovery step, the adjusted wastewater treated by the microorganism in the pretreatment step is supplied batchwise, and in the presence of at least phosphorus-accumulating bacteria, performs a microorganism treatment in the order of anaerobic treatment and aerobic treatment, The method for producing a phosphate fertilizer according to claim 1, which is a phosphorus recovery step for promoting the uptake of orthophosphoric acid into a phosphorus-accumulating bacterium. The phosphorus recovery step, the concentration of phosphorus-containing sludge while returning the further the re down recoverable step after solid-liquid separation was returned sludge while circulating sludge is circulated anaerobic treatment and aerobic treatment under temperature control to the phosphorus recovery step The method for producing a phosphate fertilizer according to claim 1, wherein the method is a continuous method. The phosphorus recovery step for promoting the uptake of orthophosphoric acid, wherein the first step of anaerobic using yeast and koji mold as main microorganisms, the second step of anaerobic using the phosphorus-accumulating bacteria as main microorganisms, The method for producing a phosphate fertilizer according to claim 3, wherein the method comprises a third step of aerobic using the phosphorus-accumulating bacterium , and these steps are performed under continuous stirring conditions.   The method for producing a phosphate fertilizer according to any one of claims 1 to 4, wherein in the pretreatment step, the pH is adjusted so that the pH of the rice processing wastewater is 4 or more.   In the anaerobic treatment of the phosphorus recovery step, the temperature of the adjusted wastewater is adjusted to 30 ° C. to 35 ° C., and in the aerobic treatment of the phosphorus recovery step, the temperature of the adjusted wastewater is adjusted to 25 ° C. to 30 ° C. The method for producing a phosphate fertilizer according to claim 2, wherein the temperature is adjusted. A phosphate fertilizer production device for producing phosphate fertilizer from rice processing wastewater,
A pretreatment tank for storing the rice processing wastewater,
PH adjusting means for adjusting the pH of rice processing wastewater in the pretreatment tank ,
Pretreatment for obtaining conditioned wastewater by anaerobically treating the rice processing wastewater to decompose organic phosphoric acid into low-molecular organic matter and orthophosphoric acid by yeast and koji mold present in the rice processing wastewater in the pretreatment tank . Means,
Main treatment tank for storing the adjusted wastewater obtained by the pretreatment means,
Adjustment wastewater supply means for supplying the adjustment wastewater to the treatment tank in a batchwise manner,
Phosphorus recovery means for treating the adjusted wastewater in the treatment tank at least in the presence of phosphorus-accumulating bacteria in the order of anaerobic treatment and aerobic treatment to promote the uptake of orthophosphoric acid into the phosphorus-accumulating bacteria When,
Temperature adjusting means for adjusting the temperature of the adjusted wastewater in the main treatment tank to a temperature at which the phosphorus-accumulating bacteria are activated and the growth of non-phosphorus-accumulating bacteria can be suppressed,
A phosphate fertilizer production apparatus, comprising: a solid-liquid separation tank that separates a phosphoric acid-containing sludge and treated water by storing and sedimenting a microorganism-treated solution treated with microorganisms by the phosphorus recovery unit. In the continuous treatment type phosphate fertilizer production device, a circulating sludge line from the aerobic treatment area for performing the aerobic treatment to the anaerobic treatment area for performing the anaerobic treatment, and from the solid-liquid separation tank to the anaerobic treatment area. 8. The apparatus for producing a phosphate fertilizer according to claim 7, wherein sludge lines returned toward the respective fertilizers are connected to each other.

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