JP2013208594A - Method and apparatus for anaerobic wastewater treatment of organic wastewater - Google Patents

Abstract

In an anaerobic treatment of an organic wastewater containing a scale component generated in an acidic organic substance and an alkaline region, a method and an apparatus capable of stably controlling the generation of scale are provided.
SOLUTION: In a method for treating anaerobic wastewater by introducing waste water containing an acidic organic component and a scale component precipitated in an alkaline region into a methane fermentation tank via a pH adjusting means, a target pH in the pH adjusting means is set. Set at least two points, pH _a1 and pH _a2 , as pH _t1 and pH _t2 as the set pH of the effluent from the methane fermenter, and when the pH of the effluent from the methane fermenter is below pH _t1 , The pH adjusting means so that the target pH at the pH adjusting means becomes pH _a1 when the pH of the effluent from the methane fermentation tank exceeds pH _t2 so that the target pH at the pH adjusting means becomes pH _a2. An anaerobic wastewater treatment method and apparatus characterized by adding acid and / or alkali to the methane fermentation tank to adjust the pH of the inflow water.
[Selection figure] None

Description

  The present invention is anaerobically by passing organic wastewater containing acid components and scale components precipitated in an alkaline region to a methane fermentation tank in which anaerobic sludge is retained via a pH adjustment tank. The present invention relates to an anaerobic wastewater treatment method and apparatus for treating the wastewater, and an anaerobic wastewater treatment method and apparatus for suppressing the precipitation of scale components and performing the treatment stably and efficiently.

The anaerobic wastewater treatment method is an energy-saving and cost-saving wastewater treatment method that generates less sludge and consumes less power.
The anaerobic wastewater treatment method is a method for decomposing organic substances by anaerobic treatment comprising an acid-producing phase by acid-producing bacteria and a methane-producing phase by methanogenic bacteria. In particular, the UASB (Upflow Anaerobic Sludge Blanket) method, the EGSB method (Expanded Granular Sludge Bed) method, the fluidized bed method, etc. can maintain a high concentration of microbial groups centering on methanogens in the methane fermentation tank. Therefore, it is a method with high wastewater treatment efficiency.

  In these anaerobic wastewater treatment methods, organic substances such as carbohydrates, proteins, and lipids are first decomposed into acidic organic substances by the action of acid-producing bacteria. And methane production | generation is performed from an acidic organic substance by methanogen. In the methane fermenter, the methane production is performed to increase the pH, and the pH of the effluent water from the methane fermenter is usually 6.5 to 8.5.

Therefore, when anaerobic treatment is performed using the scale component precipitated in the acidic organic substance and the alkaline region as the water to be treated, the scale may be precipitated.
For example, the wastewater containing the distillation residue discharged from the whiskey distillation process has a high organic substance concentration of 30,000 to 100,000 mg / L, total phosphorus of 500 to 1,000 mg / L, and organic nitrogen of 1,000 to 3,000 mg / L. , And may contain 100-300 mg / L of magnesium.

When magnesium, ammonia nitrogen and orthophosphoric acid coexist, MgNH ₄ PO ₄ .6H ₂ O (magnesium ammonium phosphate (hereinafter abbreviated as MAP)) crystals are formed when the pH is higher than the neutral condition ( This is well known. Usually, this precipitation is said to proceed under conditions of NH ₄ —N> 100 mg / L on the alkali side.

In anaerobic treatment of whiskey distillate, organic nitrogen compounds contained in wastewater are reduced in molecular weight and decomposed into ammonia nitrogen at the stage of acid fermentation. In the methane fermenter, methane is converted from acidic organic matter in the treated water. As the pH increases, the pH rises, the pH in the tank becomes 6.5 to 8.5, and the solubility decreases, so that MAP is likely to be generated.
The MAP crystals are deposited not only in the sludge and in the reaction tank, but also in pipes and pumps with a high flow velocity, and cause problems such as pipe clogging and pump malfunction.

  Therefore, the following Patent Document 1 proposes a method of controlling the amount of MAP scale precipitation by adjusting the pH of the inflow water to the methane fermentation tank to 5.8 to 6.5.

Japanese Patent No. 3358348

As described above, Patent Document 1 proposes a method of controlling the amount of MAP scale precipitation by adjusting the pH of the inflow water to the methane fermenter to 5.8 to 6.5.
However, this method adds Mg salt, suppresses MAP precipitation in the inflow pipe to the methane fermentation tank, and precipitates MAP on the sludge retained in the methane fermentation tank to improve the sedimentation property of the sludge. The purpose is to improve. Therefore, in the anaerobic wastewater treatment of wastewater containing a large amount of scale components precipitated in the acidic organic matter and alkaline region, there is a risk that a MAP scale may be generated in the reaction tank or in the piping of the effluent due to the pH increase of the effluent.

  Therefore, a method of setting the pH of the influent water to be lower so that the pH of the outflow water does not become an alkaline region is also conceivable. However, if the pH falls below the range suitable for methane bacteria, it causes a decrease in activity. In addition, if the pH of the water to be introduced is set low in anticipation of an increase in pH in the tank, the acidic organic matter contained in the water to be treated when the flow of water to be treated into the methane fermentation tank is stopped and the circulation operation is continued When the concentration of is extremely reduced, the pH increase due to anaerobic treatment does not occur at all or the pH hardly increases, so that the pH in the reaction tank decreases to substantially the same value as the influent water pH. As a result, the activity of methane bacteria decreases, and even if the inflow of treated water is restarted, the quality of treated water will deteriorate.

  Therefore, the problem to be solved by the present invention is to solve the above-mentioned problems, suppress the generation of scale in the anaerobic treatment of organic wastewater containing acidic organic substances and scale components generated in the alkaline region, and stabilize It is an object of the present invention to provide a method and an apparatus that can be processed.

As a result of intensive studies and experiments conducted to solve such problems, the present inventors have unexpectedly found that the above problems can be solved by using the following pH adjusting means, and have completed the present invention. It is a thing.
That is, the present invention is as follows.

[1] In a method for treating anaerobic wastewater by introducing wastewater containing an acidic organic component and a scale component that precipitates in an alkaline region into a methane fermentation tank as a treated water via a pH adjusting means,
At least two points of pH _a1 and pH _a2 (where pH _a1 <pH _a2 ) are set as target pHs in the pH adjusting means, and pH _{t1 is} set as the set pH of the effluent from the methane fermenter. And pH _t2 (however, pH _t1 ≤ pH _t2 ), and when the pH of the effluent from the methane fermentation tank is below pH _t1 , the target pH in the pH adjusting means is set to pH _a2. On the other hand, when the pH of the effluent from the methane fermenter exceeds pH _t2 , acid and / or alkali is added to the pH adjusting means so that the target pH in the pH adjusting means becomes pH _a1. And adjusting the pH of the inflow water to the methane fermentation tank.

[2] The pH _a1 , pH _a2 , pH _t1 , and pH _t2 are pH 5.8 or higher, and the bacterial cell ratio (VSS / SS ratio) in the sludge retained in the methane fermentation tank is 60% or higher. The anaerobic wastewater treatment method according to [1], which is defined within the range of the upper limit value of the pH of the effluent from the methane fermentation tank.

  [3] The anaerobic wastewater treatment method according to [1] or [2], wherein the water to be treated includes an organic component that generates ammonia by biodegradation.

  [4] The anaerobic wastewater treatment method according to [3], wherein the water to be treated is an organic wastewater containing a distillation residual liquid discharged from a whiskey distillation process.

[5] The organic wastewater includes a whiskey distillation residue having a magnesium concentration of 150 mg / L or more and a total phosphorus (TP) of 500 mg / L or more, and a total chemical oxygen demand (T- COD _Cr ) (mg / L) Anaerobic as described in [4] above, wherein waste alcohol having a mass of 200,000 or more and general wastewater are mixed and diluted 2- to 4-fold with the general wastewater. Wastewater treatment method.

  [6] The anaerobic wastewater treatment method according to any one of [1] to [5], wherein the scale component is magnesium ammonium phosphate (MAP).

[7] The pH _a1 and pH _a2 are set in the range of pH 5.8 to 6.8, and the pH of the effluent water from the methane fermenter is 6.0 to 7.0. The anaerobic wastewater treatment method according to any one of [2] to [6], wherein the pH of the influent water of the methane fermentation tank is adjusted.

  [8] The anaerobic wastewater treatment method according to [7], wherein the water to be treated is diluted with dilution water so that a precipitation limit pH value of a scale component produced in the methane fermentation tank is 7.0 or less. .

  [9] Anaerobic as described in [8] above, wherein a part of the treated water separated and removed is used as the dilution water by adjusting the effluent water from the methane fermentation tank to pH 7.0 or more to precipitate the scale. Wastewater treatment method.

[10] Wastewater containing an acidic organic component and a scale component that precipitates in an alkaline region is introduced into a methane fermentation tank via pH adjusting means as treated water and used in a method for anaerobic wastewater treatment. An anaerobic wastewater treatment apparatus including a pH adjusting means and a methane fermentation tank, wherein pH _a1 and pH _a2 (where pH _a1 <pH _a2) are set as target pH values in the pH adjusting means. At least two points, and pH _t1 and pH _t2 (where pH _t1 ≤ pH _t2 ) are set as the set pH of the effluent from the methane fermenter, and the methane fermentation When the pH of the effluent from the tank is below pH _t1 , the target pH in the pH adjusting means is pH _a2 , while when the pH of the effluent from the methane fermentation tank exceeds pH _t2 , The pH is adjusted so that the target pH in the pH adjusting means is pH _a1. The anaerobic wastewater treatment apparatus comprising a pH setting control device for controlling the pH of the inflow water to the methane fermentation tank by adding acid and / or alkali to the adjusting means.

  If the anaerobic treatment method and apparatus of the present invention are used, in the anaerobic treatment of organic wastewater containing acidic organic substances and scale components that precipitate in the alkaline region, the generation of the scale is suppressed, and it is stable and efficient. Processing is possible.

3 is a processing flow in the first embodiment. It is a graph which shows transition of pH (measured value) of the pH adjustment tank in Example 1, pH (measured value) of the outflow water from a methane fermentation tank, and the flow volume of to-be-processed water. 4 is a graph showing the transition of the removal rate of COD _Cr in anaerobic treatment in Example 1. It is a graph which shows transition of Mg density | concentration in anaerobic treated water in Example 1. FIG. It is a flow which shows the anaerobic processing apparatus of the comparative example 1. It is a graph which shows transition of pH (measured value) of the pH adjustment tank in the comparative example 1, pH (measured value) of the outflow water from a methane fermentation tank, and the flow volume of to-be-processed water. 6 is a graph showing the transition of the removal rate of COD _Cr in anaerobic treatment in Comparative Example 1. It is a graph which shows transition of Mg concentration in anaerobic treated water in comparative example 1. It is a processing flow in Example 2. FIG. The graph which shows transition of pH (measured value) of the pH adjustment tank in Example 2, pH (measured value) of the outflow water from a methane fermentation tank, and VSS / SS ratio of the sludge currently hold | maintained in a methane fermentation tank It is.

  In the anaerobic treatment in which wastewater containing scale components precipitated in an acidic organic substance and an alkaline region is treated water, the present invention sets the target pH in the pH adjusting means within the range of pH 5.8 to a scale deposition limit pH described later. And anaerobic wastewater treatment method and apparatus, wherein two or more points are set, and the pH is adjusted so that the pH of the effluent from the methane fermentation tank is within the range of 5.8 to the scale precipitation limit pH It is.

In the present invention, the wastewater to be subjected to anaerobic treatment includes an acidic organic substance and a scale component that precipitates in an alkaline region, and is not limited as long as it can be anaerobically treated. Examples of such wastewater include whiskey distillation residue, shochu distillation residue, sugar making wastewater, starch wastewater and the like.
The treated water treated by the anaerobic wastewater treatment method according to the present invention contains an organic component that generates ammonia by biodegradation. The treated water can be an organic waste water containing a distillation residue discharged from the whiskey distillation process. In addition, the organic waste water has a whiskey distillation residue having a magnesium concentration of 150 mg / L or more and a total phosphorus (TP) of 500 mg / L or more, and a total chemical oxygen demand (T-COD). _The waste alcohol having a _Cr ) (mg / L) of 200,000 or more and the general waste water are mixed and diluted with the general waste water 2 to 4 times.

  The anaerobic treatment method may be either a two-phase method in which the acid generation phase and the methane generation phase are separated or a one-phase method in which these two phases are performed in one tank. As an anaerobic treatment method, a UASB method, an EGSB method, a fluidized bed method, or any other method can be employed.

  The acidic organic matter contained in the wastewater subject to anaerobic treatment only needs to be contained at the time of flowing into the methane fermentation tank, and even if it is originally contained as a component in the treated water, the carbohydrates contained in the treated water In addition, organic substances such as proteins and lipids may be generated by being decomposed in an acid generation tank. Examples of these acidic organic substances include acetic acid, lactic acid, formic acid, butyric acid, and propionic acid.

  Moreover, if the scale component contained in the wastewater used as the object of anaerobic treatment is a scale component which precipitates in an alkaline region, there is no limitation. Examples of scales that deposit in the alkaline region include calcium carbonate, calcium phosphate, and magnesium ammonium phosphate (MAP), and these constituent components are examples of scale components.

As described above, in the anaerobic treatment in which the wastewater containing the scale component precipitated in the acidic organic substance and the alkaline region is treated water, the present invention sets the target pH in the pH adjusting means to pH 5.8 to scale deposition described later. Two or more points are set within the limit pH range, and the pH is adjusted so that the pH of the effluent from the methane fermenter falls within the range of 5.8 to the scale detection limit pH.
If the pH falls below 5.8, the activity of the methane fermentation bacteria decreases, so the pH in the methane fermentation tank is 5.8 or more, that is, the pH of the effluent from the pH adjusting means and the methane fermentation tank is 5.8 or more. There is a need to.
On the other hand, in the methane fermenter, the pH increases with the decomposition of the acidic organic matter, and when it exceeds a certain value, a scale starts to be generated in the methane fermenter, and the pH increases beyond this certain value. The amount of scale generation increases. In the present invention, it is necessary to maintain the pH of the effluent from the methane fermentation tank so that the ratio of the bacterial cells in the sludge retained in the methane fermentation tank (VSS / SS ratio) is 60% or more, The upper limit of this pH is defined as “scale deposition limit pH”. Here, VSS is an ignition loss of SS (suspension substance concentration), and is an amount of a substance that volatilizes in a solid part (suspension substance) by ignition (600 ° C.). It is an indicator of the amount (bacterial cell amount). That is, when VSS / SS ratio becomes small, the ratio of the inorganic substance (scale) in the sludge hold | maintained in a methane fermenter will become high, and this means that a microbial cell retention amount becomes small. Therefore, if the VSS / SS ratio is less than 60%, problems such as a decrease in organic substance removal performance and a deterioration in treated water quality occur.

The scale deposition limit pH varies depending on the type of scale and the concentration of the scale component, but if the pH in the methane fermentation tank exceeds 8.5, the activity of the methane fermentation bacteria decreases. Therefore, the pH of the effluent from the methane fermenter needs to be 8.5 or less. The present invention is often applied when the scale precipitation limit pH is lower than 8.5 (scale concentration). The scale deposition limit pH can be obtained by actually operating the apparatus according to the present invention, changing the pH, and actually measuring VSS / SS for each pH. In the present invention, pH _a1 , pH _a2 , pH _t1 , and pH _t2 are set within the range of 5.8 to the scale precipitation limit pH. Here, pH _a1 and pH _a2 are preferably set between 5.8 and 6.8, and the pH of the effluent from the methane fermenter is preferably in the range of 6.0 to 7.0. Adjusted to By adjusting the pH to such a range, the influence of concentration fluctuations of acidic organic substances and scale components in the raw water can be reduced, and stable control can be performed.

Specifically, pH _a1 , pH _a2 , pH _t1 , and pH _t2 are determined by testing as follows.
For example, using the test apparatus shown in FIG. 1 (lab scale apparatus smaller than the actual apparatus), simulated wastewater having the same organic substance concentration and inorganic (scale component) concentration as the wastewater to be treated or the assumed wastewater. Conduct a continuous water flow test. First, by changing the pH of the pH adjustment tank under conditions where raw water (treated wastewater and simulated wastewater) flows, the relationship between the pH of the pH adjustment tank and the pH of the effluent from the methane fermentation tank is clarified. At the same time, by measuring the VSS / SS ratio at the pH of the effluent, the scale precipitation limit pH of the effluent from the methane fermentation tank and the pH of the pH adjustment tank at that time can be obtained. The pH range of the effluent water is a range in which the activity of the methane fermentation bacteria does not decrease, that is, a pH value ranging from pH 5.8 to 8.5 and not more than the scale deposition limit pH value, for example, Set in the range of about pH 6.0-7.0. Next, the raw water is operated so that the pH of the effluent water is within the range of about pH 6.0 to 7.0 when the raw water is passed, and the pH of the pH adjusting tank at this time is set to pH _a1 . Next, stop the inflow of raw water into the methane fermenter and operate so that the pH of the effluent water from the methane fermenter is approximately 6.0 to 7.0 when only circulating operation is carried out, The pH of the pH adjusting tank at this time is set to pH _a2 . Here, if the inflow of the raw water is stopped and the circulation operation is continued, the acidic organic matter in the raw water supplied to the methane fermentation tank decreases and the pH in the methane fermentation tank does not increase, so the effluent from the methane fermentation tank Will gradually approach the pH of the pH adjusting tank.

In order to operate safely and stably, pH _t2 is desirably set within a range lower than the scale precipitation limit pH by 2.5, for example, when the scale precipitation limit pH is 7.5, pH _t2 is set in the range of 5-7.5. Further, it is desirable that pH _t1 and pH _t2 are separated by 0.2 or more.
In the above method, the target pH in the pH adjustment tank is 2 points and the set pH of the effluent water from the methane fermentation tank is 2 points, but between pH _a1 and pH _a2 set in this way, pH _a3 and pH Set _a4 (pH _a1 <pH _a3 <pH _a4 <pH _a2 ) etc., and set pH _t3 or pH _t4 (pH _t1 <pH _t3 <pH _t4 <pH _t2 ) etc. between pH _t1 and pH _t2 When operating with the target pH set to pH _a3 , the target pH is set to pH _a4 when the pH of the effluent falls below pH _t3, and the target pH is set to pH _a4 when the pH of the effluent falls below pH _{t1. It} may be _a2 . On the other hand, if the concentration of acidic organic substances in the raw water decreases, the pH increase in the methane fermenter is suppressed, and the pH of the effluent exceeds pH _t4 when operating at the set pH of pHa ₄ , the target If the pH is _adjusted to pH _a3 and further the increase in pH in the methane fermenter is suppressed and the pH of the effluent water exceeds pH _t2 , the target pH may be set to pH _a1 . Thus, it is possible to operate by setting the target pH in the pH adjustment tank to 3 points or more and the set pH of the effluent water from the methane fermentation tank to 3 points or more.

  Since the concentration of acidic organic substances contained in the water to be treated is high and the pH increase in the methane fermentation tank is large, or because the concentration of the scale component precipitated in the alkaline region is high, the pH of the influent water is 5.8. If the pH of the effluent water exceeds the scale precipitation limit pH value even if the target is controlled, the water to be treated is mixed with the dilution water and then flowed into the methane fermentation tank. The target pH value in the pH adjusting means is set to 5.8, and the dilution water may be added and mixed in an amount equal to or higher than the dilution rate so that the effluent water pH is not more than the scale precipitation limit pH value. As dilution water, water having lower organic matter concentration and scale component concentration than treated water such as city water, industrial water, well water, river water, treated water of other treatment systems, and the like is used. Moreover, you may utilize some treated water which isolate | separated and removed the scale component after the anaerobic process.

  Dilution with dilution water reduces the concentration of acidic organic substances and scale components contained in the water to be treated, and the effects of reducing the pH increase range in the methane fermentation tank and reducing the precipitation limit pH value of the scale, respectively. The

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.
<Example 1>

FIG. 1 shows a processing flow in the first embodiment.
The water quality wastewater shown in Table 1 below was treated as treated water. If the target pH in the pH adjusting means (pH adjusting tank) is set to two points, pH 5.8 and pH 6.3, and the pH of the effluent from the methane fermentation tank is 6.3 or less, the target of the pH adjusting tank When the pH reached 6.3 and the pH of the effluent water exceeded 6.5, the system was operated under the condition that the target pH of the pH adjustment tank was switched to 5.8.

In FIG. 2, transition of pH (measured value) of a pH adjustment tank, pH (measured value) of the outflow water from a methane fermentation tank, and the flow volume of to-be-processed water is shown.
FIG. 3 is a graph showing the transition of COD _Cr removal rate in anaerobic treatment.
FIG. 4 is a graph showing transition of Mg concentration in anaerobic treated water.

At the start of operation, the pH of the effluent from the methane fermentation tank was around 6.7 relative to the target pH 5.8 of the pH adjustment tank. However, as shown in FIG. 1, since a part of the effluent from the methane fermentation tank is circulated and the inflow of the treated water (raw water) is stopped, only the circulation is continued. If the target pH of the adjustment tank was maintained at 5.8, the pH of the effluent water from the methane fermentation tank gradually decreased and approached the target pH of the pH adjustment tank of 5.8. When the pH of the effluent from the methane fermenter became 6.3 or lower, the pH of the effluent from the methane fermenter was changed as a result of switching the target pH of the pH adjustment tank from 5.8 to 6.3. It was stable at 6.3, the same as the target pH of the pH adjustment tank.
Then, when inflow of to-be-processed water was restarted and the anaerobic reaction began to progress, the pH of the effluent from the methane fermentation tank began to rise again. And when pH of the outflow water from a methane fermentation tank exceeded 6.5, the target pH in a pH adjustment tank was switched from 6.3 to 5.8, and the driving | operation was continued. As a result, the pH of the effluent from the methane fermenter again stabilized at around 6.7. The removal rate of COD _Cr remained almost unchanged before and after the stoppage of the inflow of treated water, and was stably maintained at 90% or more.
During the operation period, the Mg concentration in the effluent water was almost the same as the concentration of the water to be treated, and scales such as MAP were hardly precipitated.

<Comparative Example 1>
In FIG. 5, the flow of the anaerobic processing apparatus of the comparative example 1 is shown.
In the same manner as in Example 1, the water quality waste water shown in Table 1 was used as the water to be treated. Operation was performed with the target pH in the pH adjustment tank set at 5.8.
FIG. 6 is a graph showing changes in pH (measured value) of the pH adjusting tank, pH of the effluent water from the methane fermentation tank (measured value), and the flow rate of the water to be treated.
FIG. 7 is a graph showing the transition of COD _Cr removal rate in anaerobic treatment.
FIG. 8 is a graph showing transition of Mg concentration in anaerobic treated water.

From the start of operation, the pH of the effluent from the methane fermentation tank was around 6.7 relative to the target pH 5.8 of the pH adjustment tank when the water to be treated was introduced. However, due to the stoppage of the water to be treated, the pH of the effluent from the methane fermentation tank dropped to 5.8, the same as the target pH of the pH adjustment tank, in about one day.
After the supply of water to be treated was stopped for 6 days, the inflow of water to be treated was resumed. The COD _Cr removal rate was about 90% before the stop, but after the stop, it was 90% before the stop. The COD _Cr removal rate was about 75% at the treated water flow rate, and the treatment capacity was reduced.
On the other hand, the scales of MAP and the like were hardly precipitated during the above operation period, in which the Mg concentration in the effluent water was almost the same as the concentration of the water to be treated.

<Example 2>
FIG. 9 shows a processing flow in the second embodiment.
The water quality treated water shown in Table 2 below was diluted 2 times and treated.

If the target pH in the pH adjustment tank is set to two points, pH 5.8 and pH 6.3, and the pH of the effluent from the methane fermentation tank is 6.3 or less, the target pH of the pH adjustment tank is set to 6.3. In addition, if the pH of the effluent water from the methane fermentation tank exceeded 6.5, it was operated under the condition of switching the target pH of the pH adjustment tank to 5.8.
FIG. 10 is a graph showing the transition of the pH (measured value) of the pH adjusting tank, the pH of the effluent water from the methane fermenter (measured value), and the VSS / SS ratio of the sludge retained in the methane fermenter. is there.
At the time of inflow of the water to be treated, the pH of the effluent from the methane fermentation tank was around 6.5 with respect to the target pH 5.8 of the pH adjustment tank. Moreover, when the inflow of treated water was stopped, the pH of the effluent from the methane fermentation tank was lowered, but the target pH in the pH adjustment tank was switched to 6.3, and the pH of the effluent from the methane fermentation tank was lowered. Could be prevented.
During this operation period, the VSS / SS ratio of the granular sludge retained in the methane fermentation tank is stable at 80 to 90% without precipitation of scale, and can be stably treated without precipitation of scale. It was.

  If the anaerobic treatment method and apparatus of the present invention are used, in the anaerobic treatment of organic wastewater containing acidic organic substances and scale components that precipitate in the alkaline region, the generation of the scale is suppressed, and it is stable and efficient. Since the treatment becomes possible, the present invention can be suitably used for the treatment of such waste water.

Claims (10)

In the method of performing anaerobic wastewater treatment by introducing wastewater containing acidic organic components and scale components precipitated in the alkaline region into the methane fermentation tank via the pH adjusting means as treated water,
At least two points of pH _a1 and pH _a2 (where pH _a1 <pH _a2 ) are set as target pHs in the pH adjusting means, and pH _{t1 is} set as the set pH of the effluent from the methane fermenter. And pH _t2 (however, pH _t1 ≤ pH _t2 ), and when the pH of the effluent from the methane fermentation tank is below pH _t1 , the target pH in the pH adjusting means is set to pH _a2. On the other hand, when the pH of the effluent from the methane fermenter exceeds pH _t2 , acid and / or alkali is added to the pH adjusting means so that the target pH in the pH adjusting means becomes pH _a1. And adjusting the pH of the inflow water to the methane fermenter,
The anaerobic wastewater treatment method characterized by the above. The pH _a1 , pH _a2 , pH _t1 , and pH _t2 are pH 5.8 or higher, and the cell ratio (VSS / SS ratio) in the sludge retained in the methane fermentation tank is 60% or higher. The anaerobic wastewater treatment method according to claim 1, which is defined within a range of an upper limit value of pH of effluent water from the tank.   The anaerobic wastewater treatment method according to claim 1 or 2, wherein the treated water contains an organic component that generates ammonia by biodegradation.   The anaerobic wastewater treatment method according to claim 3, wherein the water to be treated is an organic wastewater containing a distillation residual liquid discharged from a whiskey distillation process. The organic waste water includes a whiskey distillation residue having a magnesium concentration of 150 mg / L or more and a total phosphorus (TP) of 500 mg / L or more, and a total chemical oxygen demand (T-COD _Cr ). The anaerobic wastewater treatment method according to claim 4, wherein waste alcohol having a (mg / L) of 200,000 or more and general wastewater are mixed and diluted 2 to 4 times with the general wastewater. .   The anaerobic wastewater treatment method according to any one of claims 1 to 5, wherein the scale component is magnesium ammonium phosphate (MAP). The pH _a1 and pH _a2 are set within the range of pH 5.8 to 6.8, and the pH of the effluent from the methane fermentation tank is 6.0 to 7.0. The anaerobic wastewater treatment method according to any one of claims 2 to 6, wherein the pH of the inflow water in the tank is adjusted.   The anaerobic wastewater treatment method according to claim 7, wherein the treated water is diluted with dilution water so that a precipitation limit pH value of a scale component generated in the methane fermentation tank is 7.0 or less.   The anaerobic wastewater treatment method according to claim 8, wherein a part of the treated water separated and removed is used as the dilution water by adjusting the effluent from the methane fermentation tank to pH 7.0 or more to precipitate a scale. . In order to use wastewater containing acidic organic components and scale components precipitated in the alkaline region as treated water, into a methane fermentation tank via pH adjusting means, and to use in a method of anaerobic wastewater treatment, An anaerobic wastewater treatment apparatus including a pH adjusting means and a methane fermentation tank, wherein in the pH adjusting means, pH _a1 and pH _a2 (where pH _a1 <pH _a2 ) are set as target pH values in the pH adjusting means. ) And at least two pH _t1 and pH _t2 (however, pH _t1 ≦ pH _t2 ) are set as the pH of the effluent from the methane fermenter. When the pH of the effluent water is below pH _t1 , the target pH in the pH adjusting means is pH _a2 , while when the pH of the effluent water from the methane fermenter exceeds pH _t2 , the pH adjustment The pH adjusting means so that the target pH at the means is pH _a1. An anaerobic wastewater treatment apparatus comprising a pH setting control device for controlling the pH of water flowing into the methane fermentation tank by adding acid and / or alkali to the methane fermentation tank.

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