JP2011189278A - Apparatus and method for wastewater treatment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and method for wastewater treatment capable of decomposing an organic material at a high speed by preventing the inhibition of a sulfate-reducing bacterium by a sulfide in an anaerobic treatment environment and favorably growing the sulfate-reducing bacterium. <P>SOLUTION: The apparatus for wastewater treatment includes: an organic material concentration measuring device 3 which measures the concentration of the organic material of discharged water to be treated; an infusion pump 5b which adds a sulfate 5a to the discharged water to be treated so that the concentration of a sulfate ion is higher than one-third of the concentration of the organic material; a reaction vessel 2 which decomposes the organic material holding the anaerobic bacteria and taking in the discharged water to be treated; a sulfide concentration measuring device 6 which measures the concentration of the sulfide of the treated water subjected to the decomposing process of the organic material thereof in the reaction vessel 2; and a blower 8b which blows a nitrogen gas from a nitrogen gas cylinder 8a to the reaction vessel 2 when the measured sulfide concentration is higher than a predetermined threshold, and when it is lower than the threshold, stops blowing the nitrogen gas. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wastewater treatment apparatus and a wastewater treatment method for removing organic substances from wastewater such as industrial wastewater and sewage.

  Conventionally, there is a wastewater treatment technology for removing organic matter by biologically treating wastewater such as industrial wastewater and sewage, and there are aerobic treatment and anaerobic treatment as wastewater treatment methods by this biological treatment.

  In the aerobic treatment, microorganisms that require oxygen decompose organic substances into carbon dioxide and water, and in anaerobic treatment, microorganisms that do not require oxygen decompose organic substances into methane and carbon dioxide.

  In general, the water quality after treatment is excellent in aerobic treatment, but the aerobic treatment requires power for supplying oxygen and the cost is high, so that relatively low concentration of organic matter such as sewage is low. It is used for wastewater treatment. On the other hand, in anaerobic treatment, organic matter discharged from livestock and food industry facilities is used for wastewater treatment of high concentration, and the treated water is post-treated by aerobic treatment etc. according to the required discharged water quality. Many.

  In the anaerobic treatment, a methanogenic process is performed in which lower fatty acids such as acetic acid are decomposed by methane producing bacteria to produce methane, and when sulfate ions are contained in the waste water, the sulfate ions are A hydrogen sulfide generation process in which lower fatty acids such as acetic acid are decomposed and hydrogen sulfide is generated by reduction is performed.

  Therefore, the methane production process and the hydrogen sulfide production process are in a competitive relationship over a substrate such as acetic acid. Moreover, the hydrogen sulfide produced | generated by the reduction | restoration by a sulfate reduction bacterium inhibits the activity of a sulfate reduction bacterium and a methanogen, and causes the processing efficiency of organic substance decomposition | disassembly to fall.

  Then, there exists an anaerobic water treatment apparatus of patent document 1 as a technique which processes appropriately the waste_water | drain containing a large amount of sulfate ion by anaerobic treatment.

  The anaerobic water treatment apparatus described in Patent Document 1 purifies the wastewater in a reaction tank using anaerobic bacteria, and absorbs and removes hydrogen sulfide gas released to the gas phase part above the reaction tank. The hydrogen sulfide concentration in the liquid phase is reduced. Thus, by reducing the hydrogen sulfide concentration in the liquid phase, it is possible to reduce the inhibitory action on the methane-producing bacteria and perform good wastewater treatment.

Japanese Patent Laid-Open No. 3-278892

By the way, in sulfate-reducing bacteria, in addition to lower fatty acids such as hydrogen, alcohols, acetic acid and propionic acid, a substrate such as higher fatty acids up to _C18 , aromatics, glucose and fructose can be used to proceed with the sulfate reduction treatment. Since there are bacterial species, it is more resistant to inhibition than methanogenic bacteria and can be expected to decompose organic substances at high speed.

  Therefore, by adding sulfate to wastewater in anaerobic treatment, hydrogen sulfide generation treatment is activated, which suggests that sulfate-reducing bacteria grow and work as dominant species, and the organic matter decomposition rate increases. Is done.

  However, as described above, hydrogen sulfide produced by reduction by sulfate-reducing bacteria also inhibits the activity of sulfate-reducing bacteria, so that the addition of sulfate alone is not sufficient to sufficiently propagate the sulfate-reducing bacteria.

  The present invention has been made in view of the above circumstances, and it is possible to decompose organic substances at high speed by preventing inhibition of sulfate-reducing bacteria by sulfides in an anaerobic treatment environment and suitably growing the sulfate-reducing bacteria. It is an object of the present invention to provide a possible waste water treatment apparatus and waste water treatment method.

  In order to achieve the above object, the waste water treatment apparatus of the present invention includes an organic substance concentration measuring apparatus for measuring the organic substance concentration of waste water to be treated, and a sulfate ion concentration of 1/3 of the organic substance concentration measured by the organic substance concentration measuring apparatus A sulfate addition device for adding sulfate to the waste water to be treated, a reaction tank for holding anaerobic bacteria, taking the waste water for treatment and decomposing organic matter, and the reaction tank And a sulfide concentration measuring device for measuring the sulfide concentration of treated water subjected to the decomposition treatment of organic matter, and when the sulfide concentration measured by the sulfide concentration measuring device is higher than a preset threshold value And a gas supply device that blows an inert gas into the reaction tank and stops the blowing of the inert gas when lower than the threshold value.

  The waste water treatment apparatus further includes a sulfur concentration measurement device that measures the sulfur concentration of the waste water to be treated, and the sulfate addition device includes the sulfur concentration measured by the sulfur concentration measurement device and the sulfate to be added. Thus, sulfate may be added so that the sulfate ion concentration is higher than 1/3 of the organic concentration measured by the organic concentration measuring device.

  In addition, the waste water treatment apparatus includes a separation membrane installed in the reaction tank, an air diffuser installed in a lower portion of the separation membrane, and treated water that has been subjected to organic substance decomposition treatment from the reaction tank. A pump that causes the gas to flow out through the separation membrane, and the gas supply device operates when the sulfide concentration measured by the sulfide concentration measuring device is higher than a preset threshold value. Sometimes, the inert gas may be diffused from the diffuser to blow into the reaction vessel.

  In the wastewater treatment method of the present invention, the wastewater treatment device measures the organic matter concentration of the wastewater to be treated, and the sulfate ion concentration is higher than 1/3 of the organic matter concentration measured by the organic matter concentration measurement device. The treated water in which sulfate is added to the wastewater to be treated, the organic matter is decomposed by taking the wastewater to be treated into the reaction vessel holding the anaerobic bacteria, and the organic matter is decomposed in the reaction vessel. When the measured sulfide concentration is higher than a preset threshold value, an inert gas is blown into the reaction vessel, and when the measured sulfide concentration is lower than the threshold value, the blowing of the inert gas is stopped. It is characterized by that.

  Moreover, this waste water treatment method measures the sulfur concentration of the waste water to be treated, and when adding the sulfate, by combining the measured sulfur concentration with the sulfate to be added, the sulfate ion concentration is You may make it add so that it may become a value higher than 1/3 of the measured organic substance density | concentration.

  Further, this wastewater treatment method is performed when an inert gas is blown into the reaction tank, when the measured sulfide concentration is higher than a preset threshold value, and via a separation membrane installed in the reaction tank. When the pump that discharges the treated water is operated, the inert gas may be blown into the reaction tank by being diffused from the diffuser installed at the lower part of the separation membrane.

  According to the wastewater treatment apparatus and the wastewater treatment method of the present invention, it is possible to prevent the sulfate-reducing bacteria from being inhibited by sulfides in an anaerobic treatment environment and to allow the sulfate-reducing bacteria to grow appropriately, thereby decomposing organic matter at high speed. it can.

It is explanatory drawing which shows the structure of the waste water treatment equipment by 1st Embodiment of this invention. It is explanatory drawing which shows the structure of the apparatus which formed the waste water treatment apparatus by 1st Embodiment of this invention in simulation. It is a table | surface which shows various analysis results when drainage processing is performed with the apparatus which formed the wastewater treatment apparatus by 1st Embodiment of this invention in simulation. It is explanatory drawing which shows the structure of the gas measurement apparatus which measures the gas generation amount when drainage treatment is performed with the apparatus which formed the wastewater treatment apparatus by 1st Embodiment of this invention in simulation. It is a graph which shows the measurement result which measured the gas generation amount when the waste_water | drain process of artificial waste_water | drain is performed with the apparatus which formed the waste water treatment apparatus by 1st Embodiment of this invention in simulation. It is a graph which shows the measurement result which measured the gas generation amount when the waste water treatment of factory waste water was performed with the apparatus which formed the waste water treatment apparatus by 1st Embodiment of this invention in simulation. It is explanatory drawing which shows the structure of the waste water treatment equipment by 2nd Embodiment of this invention. It is explanatory drawing which shows the structure of the waste water treatment equipment by 3rd Embodiment of this invention.

<< First Embodiment >>
As a first embodiment of the present invention, a wastewater treatment apparatus 1A that treats wastewater that does not contain sulfur, is in a very small amount, or has a known sulfur concentration or can be estimated empirically will be described.

  The configuration of the wastewater treatment apparatus 1A according to the first embodiment of the present invention will be described with reference to FIG.

  The wastewater treatment apparatus 1A according to the present embodiment holds anaerobic bacteria such as methanogens and sulfate-reducing bacteria, measures a reaction tank 2 that takes in wastewater to be treated and decomposes organic matter, and measures the concentration of organic matter in the wastewater. An organic substance concentration measuring device 3, a sulfate addition control device 4 that calculates the addition amount of sulfate based on the organic substance concentration measured by the organic substance concentration measurement device 3, and controls to add the addition amount of sulfate, sulfuric acid A sulfate addition device 5 for adding sulfate to waste water under the control of the salt addition control device 4, a sulfide concentration measurement device 6 for measuring the sulfide concentration of treated water treated in the reaction tank 2, and a sulfide concentration measurement device 6 determines whether or not nitrogen gas needs to be supplied based on the sulfide concentration measured in Step 6, and the gas supply control device 7 controls the supply ON / OFF of the nitrogen gas based on the determination result, and the reaction is controlled by the gas supply control device 7. Nitrogen gas in tank 2 And a gas supply device 8 supplies. Among these, the sulfate addition device 5 is constituted by a sulfate 5a and an injection pump 5b, and the gas supply device 8 is constituted by a nitrogen gas cylinder 8a and a blower 8b.

  When the wastewater treatment is started in the wastewater treatment apparatus 1A, the organic matter concentration of the wastewater to be treated is measured in the organic matter concentration measurement device 3.

  Next, in the sulfate addition control device 4, the sulfate addition amount is calculated so that the sulfate ion concentration becomes higher than １ ／ of the organic substance concentration measured by the organic substance concentration measurement device 3. At this time, in the present embodiment, the sulfur is not contained in the waste water, is a very small amount, or the sulfur concentration is known in advance or can be inferred. The sulfate addition amount is calculated based on the above.

  Then, the sulfate addition control device 4 controls the sulfate addition device 5 so that the calculated addition amount of sulfate is added to the waste water.

  Thus, by adding sulfate to the waste water so that the sulfate ion concentration is higher than 1/3 of the organic matter concentration, the waste water flows into the reaction tank 2 and the organic matter is decomposed by anaerobic bacteria. When the purification treatment is performed, methanogenic bacteria decrease due to competition with sulfate-reducing bacteria, while sulfate-reducing bacteria grow and the reaction rate for decomposing organic matter is increased.

  The sulfide concentration measuring device 6 measures the sulfide concentration of the treated water treated in the reaction tank 2.

  Next, in the gas supply control device 7, the measured sulfide concentration is compared with a preset threshold value. When the measured sulfide concentration is higher than the threshold value, supply of nitrogen gas is necessary and measured. When the sulfide concentration is lower than this threshold, it is determined that the supply of nitrogen gas is unnecessary.

  Then, when it is determined from the determination result in the gas supply control device 7 that the supply of nitrogen gas is necessary, the gas supply device 8 is controlled to supply the nitrogen gas to the reaction tank 2, and the supply of nitrogen gas Is determined to be unnecessary, the supply of nitrogen gas is controlled to be stopped.

  By supplying nitrogen gas when the sulfide concentration is high in this way, dissociated sulfide ions produced by sulfate-reducing bacteria are released as non-dissociated hydrogen sulfide gas, and sulfuric acid is added. Inhibition by hydrogen sulfide is prevented.

Example 1
As Example 1, a test for purifying the simulated wastewater prepared with the reagents as follows was performed by the wastewater treatment device 20 shown in FIG. 2, which simulatedly formed the wastewater treatment device 1A according to the first embodiment described above. .

  In this example, the digested sludge collected from the existing anaerobic treatment facility was used as seed sludge, the liquid prepared with the reagent was used as simulated waste water, and the continuous waste water treatment operation was performed by the waste water treatment device 20. In this example, the test period is about one month, and five patterns of RUN1 (comparative example), RUN2 (comparative example), RUN3 (comparative example), RUN4 (corresponding to the present invention), and RUN5 (corresponding to the present invention) A wastewater treatment test was conducted under the conditions.

  In FIG. 2, digested sludge 21 as seed sludge was prepared so as to have an organic suspended solid concentration of 10000 mg / l and stored in a reaction tank 22.

  The reaction tank 22 is held in a constant temperature water tank 23, and a thermometer 24 for measuring the temperature of the constant temperature water and a temperature controller 25 for controlling the temperature of the constant temperature water are connected to the constant temperature water tank 23. A heater 27 that is operated under the control of the temperature controller 25 is installed. In the present embodiment, the heater 27 was controlled by the temperature controller 25 while monitoring the measured value of the thermometer 26 that measures the temperature in the constant temperature water tank 23 so that the temperature in the constant temperature water tank 23 becomes 37 ° C.

Moreover, the simulated waste water 29 was put in the raw | natural water tank 28 provided separately from the reaction tank 22, and the stirrer 31 was rotated with the stirrer 30, and it stirred so that water quality might become fixed. This simulated wastewater 29 is prepared by adding glucose as a carbon source, ammonium chloride as a nitrogen source, and potassium dihydrogen phosphate as a phosphorus source, RUN1 is 0 mg ^SO4 / L (no addition), RUN2 is 250 mg ^SO4 / L RUN3 and RUN4 were added with 1000 mg ^SO4 / L, and RUN5 was added with 4500 mg ^SO4 / L sulfuric acid. The amount of organic matter in the simulated waste water 29 relative to the amount of digested sludge 21 was supplied to be 0.2 kg / day.

  The simulated waste water 29 in the raw water tank 28 was injected into the reaction tank 22 by the raw water pump 32. The injection amount and injection cycle of the simulated waste water 29 into the reaction tank 22 were controlled by a timer 33 that controls the flow rate setting of the raw water pump 32 and the operation ON / OFF of the raw water pump 32.

  The simulated waste water 29 injected into the reaction tank 22 was brought into contact with the digested sludge 21 in the reaction tank 22 by operating a stirrer 34 installed to stir the reaction tank 22. At this time, the rotational speed of the stirrer 34 was set to 25 rpm while visually confirming that the simulated waste water 29 and the digested sludge 21 were uniformly mixed.

  The operation ON / OFF of the stirrer 34 is controlled by a timer 35, and after the simulated waste water 29 and the digested sludge 21 are sufficiently brought into contact with the waste water treatment, the stirrer 34 is stopped for at least two hours. Digested sludge 21 was precipitated.

  Then, the supernatant of the solution in the reaction tank 22 on which the digested sludge 21 was precipitated was drawn out as the treated water 36 by the treated water pump 37. The amount and period of withdrawal from the reaction tank 22 were controlled by a timer 38 that controls the flow rate setting of the treated water pump 37 and the operation ON / OFF of the treated water pump 37. The treated water 36 withdrawn from the reaction tank 22 was injected into the treated water tank 39.

  Further, a pH meter 40 for measuring the pH of the reaction solution in the reaction tank 22 is installed, and an alkali injection mechanism in which an alkali solution 42 is injected by an alkali injection pump 41 is used, so that the pH in the reaction tank 22 is reduced. It was controlled by the pH controller 43 so as to be in the sex range.

  In addition, the biogas 44 generated in the reaction tank 22 by bringing the simulated waste water 29 and the digested sludge 21 into contact with each other is removed by the trap 45 and then sulfidized by the desulfurizer 46 equipped with a dry desulfurizing agent. Hydrogen was removed and the gas flow rate was measured with a gas meter 47.

  Further, a gas sampling port 48 for collecting an analytical sample is separately provided in the gas line, and this gas sampling port 48 is closed with a pinch cock 49 except during gas sampling.

  In addition, for the purpose of removing dissolved sulfide from the treated water in the reaction tank 22, a mechanism for blowing nitrogen gas into the solution in the reaction tank 22 is provided. RUN1 to RUN3 do not blow nitrogen gas, and RUN4 and RUN5 Nitrogen gas was blown in about several to 100 ml / min depending on the test conditions.

  As a mechanism for blowing nitrogen gas into the reaction tank 22, nitrogen gas supplied from the nitrogen gas cylinder 50 is diffused into the solution by a bubbler 51, and is installed on a pipe connecting the nitrogen gas cylinder 50 and the bubbler 51. The amount of nitrogen gas supplied by the flow meter 52 was adjusted by visual confirmation so that the bubble of the diffused gas would shake the liquid level.

  The air diffused by the bubbler 51 is set to operate periodically by a timer 53 connected to the flow meter 52, and the position of the bubbler 51 is such that the digested sludge 21 does not roll up even when the digested sludge 21 is settled. Set to the height of.

  In the treatment carried out as described above, the simulated waste water 29 is collected from the raw water tank 28 and analyzed for COD (chemical oxygen demand) and sulfate ion concentration, and the treated water 36 after the treatment is collected from the treated water tank 39. The COD, sulfate ion concentration, and sulfide ion concentration were analyzed. In addition, biogas was sampled from the gas sampling port 48 and analyzed for hydrogen sulfide concentration, methane content rate, and carbon dioxide content rate.

  The execution conditions and analysis results for each RUN are shown in FIG.

[RUN1 (comparative example)]
RUN1 is a result when the test is performed on the simulated waste water 29 under a condition where sulfuric acid is not added and nitrogen gas is not supplied, that is, under a normal anaerobic condition.

  In RUN1, the COD of the treated wastewater before treatment was 3000 mg / L, while the COD of the treated water after treatment was 490 mg / L, so the COD removal rate exceeded 80%, and the wastewater was discharged appropriately. It can be seen that has been purified.

  At this time, since the methane content in the collected biogas is as high as 69%, it is understood that the methane producing bacteria acted as dominant species and the wastewater treatment was performed.

[RUN2 (comparative example)]
RUN2 is a result of adding 250 mg ^SO4 / L of sulfuric acid at a sulfate ion concentration to the simulated waste water 29 having a COD of 3000 mg / L.

  Also in this RUN2, since the COD of the treated water after treatment is 490 mg / L, the COD removal rate exceeds 80%, and it can be seen that the waste water was appropriately purified.

At this time, the concentration of hydrogen sulfide in the collected biogas is 19000 ppm and the concentration of sulfide ions in the treated water is 20 mg ^S2- / L, so the sulfate ions of sulfuric acid added to the wastewater are reduced and sulfided. It turns out that it becomes hydrogen and undissociated hydrogen sulfide is contained in biogas, and dissociated hydrogen sulfide exists as sulfide ions.

  Moreover, since the content rate in the collected biogas was 51%, which was lower than that of RUN1, it can be seen that wastewater treatment was carried out by coexistence of methane-producing bacteria and sulfate-reducing bacteria.

Moreover, since the sulfate ion concentration of treated water is 40 mg ^SO4 / L and the sulfate ion removal rate exceeds 80%, it can be seen that the added sulfuric acid was appropriately removed.

[RUN3 (comparative example)]
RUN3 is the result of adding sulfuric acid to 1000 mg ^SO4 / L of sulfuric acid ion concentration to the simulated wastewater 29 with COD of 3000 mg / L, that is, the sulfuric acid ion concentration to 1/3 of the organic matter concentration of the simulated wastewater. It is.

In this RUN3, the amount of sulfuric acid added increased, so the hydrogen sulfide concentration in the collected biogas increased to 25000 ppm compared to RUN2, and the sulfide ion concentration also increased in the treated water, 180 mg ^S2- / L. Therefore, the sulfate ion of sulfuric acid added to the wastewater is reduced to hydrogen sulfide, undissociated hydrogen sulfide is contained in the biogas, and more dissociated hydrogen sulfide exists as sulfide ions. I understand.

  In addition, as described above, the hydrogen sulfide concentration in biogas and the sulfide ion concentration in treated water are higher than RUN2, and the methane content in the collected biogas is 31%, which is lower than in RUN1 and RUN2. This suggests that methanogens were inhibited by hydrogen sulfide produced by sulfate-reducing bacteria, and methanogens were reduced.

On the other hand, the sulfate concentration in the treated water is 201 mg ^SO4 / L and the sulfate ion removal rate is 80%, so the added sulfuric acid is properly removed and the sulfate-reducing bacteria are not inhibited by hydrogen sulfide. Is suggested.

  However, in this RUN3, since the COD of treated water after treatment is 960 mg / L and the COD removal rate is reduced to 68%, sulfate-reducing bacteria can decompose undegraded organic matter due to the reduction of methanogenic bacteria This suggests that it has not proliferated as much. In other words, in the case of RUN3, methanogenic bacteria were inhibited and decreased by the generated hydrogen sulfide, but the growth of sulfate-reducing bacteria was not large, so the organic substance decomposition treatment load on sulfate-reducing bacteria increased relatively, and COD removal The rate is thought to have declined.

[RUN4 (present invention)]
RUN4 adds sulfuric acid to the simulated wastewater 29 with a COD of 3000 mg / L so that the sulfuric acid ion concentration is 1000 mg ^SO4 / L, that is, the sulfuric acid ion concentration relative to the organic matter concentration of the simulated wastewater is 1/3. It is a result at the time of blowing in gas.

In this RUN4, the hydrogen sulfide concentration in the collected biogas further increased to 38000 ppm, whereas the sulfide ion concentration in the treated water was 0 mg ^S2- / L, which is nitrogen that does not contain hydrogen sulfide. It is suggested that sulfide ions in the treated water were released as non-dissociated hydrogen sulfide gas into the gas by blowing the gas.

  Therefore, in RUN4, the methane content in the biogas has decreased, but this is not due to the inhibition of the methanogen by hydrogen sulfide. It is thought that it decreased.

In addition, the sulfate ion concentration in the treated water is 160 mg ^SO4 / L and the sulfate ion removal rate exceeds 80%, so the added sulfuric acid is properly removed and the sulfate-reducing bacteria are working properly. It is suggested.

  In this RUN4, the COD of treated water after treatment was reduced to 506 mg / L, the same level as in RUN1 and RUN2, and the COD removal rate exceeded 80%. It is suggested that it grew to such an extent that undegraded organic matter can be decomposed due to the reduction of the produced bacteria.

  That is, in the case of RUN4, it is considered that the influence of inhibition of hydrogen sulfide due to an increase in the amount of sulfuric acid added was removed by blowing nitrogen gas into the treated water, and sulfate-reducing bacteria were grown.

[RUN5 (present invention)]
RUN5 adds sulfuric acid to the simulated wastewater 29 with a COD of 3000 mg / L so that the sulfate ion concentration is 4500 mg ^SO4 / L, that is, the sulfate ion concentration is 1.5 times the organic matter concentration of the simulated wastewater. It is a result at the time of blowing in nitrogen gas.

  In this RUN5, compared with RUN4, the sulfate ion concentration and sulfide ion concentration in the treated water increased, and the hydrogen sulfide concentration in biogas increased and the methane content decreased. Although the COD removal rate is reduced, it is 80% and the sulfide ion removal rate is high at 91%. In the case of RUN5, the amount of sulfuric acid added by blowing nitrogen gas into the treated water as in the case of RUN4. It is suggested that the effect of the inhibition of hydrogen sulfide due to the increase in the amount of sulfate was removed, and sulfate-reducing bacteria were proliferated, and the sulfate-reducing bacteria became the dominant species and the organic matter was decomposed.

  In addition, in the experimental results of FIG. 3, the sulfate ion concentration, the sulfide ion concentration, and the sulfur concentration of hydrogen sulfide in the biogas are less than the sulfur amount of sulfate ion based on the added amount of sulfuric acid in the wastewater. However, during the operation of the wastewater treatment apparatus 20, since the adhesion and deposition of a short yellow solid substance was observed inside the reaction tank 22, it was precipitated as elemental sulfur during the reduction of sulfate ions to hydrogen sulfide, It is suggested that the amount of sulfur in biogas has decreased.

  By adding the sulfuric acid so that the sulfate ion concentration becomes 1/3 or more with respect to the COD of the waste water by the above Example 1, and blowing nitrogen gas not containing hydrogen sulfide into the solution in the reaction tank 22, This suggests that sulfate-reducing bacteria can be proliferated to become preferred species, and that the generated sulfide ions can prevent the activity of methanogenic bacteria and sulfate-reducing bacteria from being inhibited.

  In this embodiment, the case where sulfuric acid is added to the simulated waste water has been described. However, the present invention is not limited to this, and any sulfate solution such as sodium sulfate can be used as long as sulfate ions can be added. The effect is obtained.

  In this embodiment, the case where nitrogen gas is blown into the simulated waste water has been described. However, the present invention is not limited to this, and sulfide ions existing in a dissociated state in the simulated waste water are gas as non-dissociated hydrogen sulfide gas. Any gas can be used as long as it is an inert gas that does not contain hydrogen sulfide, rather than a gas that inhibits digested sludge of anaerobic bacteria such as oxygen.

  In the present embodiment, it is not economically preferable to constantly blow nitrogen gas into the waste water. Therefore, only when the sulfate ion concentration and the sulfide ion concentration of the treated water are increased, the nitrogen gas is blown until they are reduced. Thus, the cost can be reduced. At that time, according to Example 1 described above, when the results of RUN3 and RUN4 are compared depending on whether nitrogen gas is blown or not, there is a clear difference in the sulfide ion concentration of the treated water. The gas supply control device 7 determines whether or not the supply of nitrogen gas is necessary using the sulfide ion concentration measured by the above as an index, and the gas supply device 8 supplies the nitrogen gas when it is determined that the supply of nitrogen gas is necessary. By doing so, the cost can be reduced and inhibition by hydrogen sulfide can be prevented.

(Example 2)
Next, as Example 2, the organic matter decomposition rate in the case where the methanogen works as the dominant species and the case where the sulfate-reducing bacteria work as the dominant species for the easily degradable wastewater and the wastewater with a slow decomposition rate are compared. A test was conducted.

  In this example, the RUN1 and RUN4 of Example 1 were used for the easy-decomposable simulated wastewater that is an artificial wastewater mainly composed of glucose and polypeptone, and the A factory wastewater having a slow decomposition speed. A comparison test of the decomposition rate of the organic matter was performed by the gas measurement device 60 of FIG. 4 and the amount of gas generated by the decomposition of the organic matter in the waste water under the treatment conditions of two patterns. Here, in the case of RUN1, it is assumed that the methanogen acts as the dominant species, and in the case of RUN4, the sulfate-reducing bacteria act as the dominant species.

  In this example, the digested sludge was previously taken in a bottle (not shown) from the test apparatus shown in FIG. 2, purged with nitrogen, sealed and stored.

  Next, simulated waste water and factory waste water, which are waste water 61 to be treated, were placed in sealable bottles 62, added with phosphate buffer, and then purged with nitrogen once to close the lid.

  Thereafter, the digested sludge was put in the bottle 62, and nitrogen was purged to close the lid. These nitrogen purges were performed to prevent anaerobic microorganisms contained in the digested sludge used in this example from coming into contact with air (oxygen).

  Next, the waste water 61 and the digested sludge amount were adjusted so that the organic matter amount of each waste water 61 with respect to the digested sludge was 0.2 kg / kg. Moreover, sulfuric acid was added to the bottle 62 implemented on the condition of RUN4 about each waste_water | drain 61 so that the sulfate ion density | concentration with respect to COD of a waste_water | drain might become 1/3.

  Thereafter, the bottle 62 is held in a constant temperature water bath 63 at 37 ° C., the biogas 64 generated in the bottle 62 is introduced into a water-sealed volumetric flask 65, the amount of biogas is measured at predetermined time intervals, and the biogas generation rate Was calculated as the organic matter decomposition rate to be evaluated.

  FIG. 5 shows the calculation result of the organic matter decomposition rate when the artificial drainage is treated under the conditions of RUN1 and RUN4.

  As shown in FIG. 5, in the treatment of artificial waste water, the organic matter decomposition rates were almost the same for both the RUN1 and RUN4 conditions. This is considered to be because the artificial wastewater is easily decomposed, and it is difficult to make a difference between the case where the methanogen acts as the dominant species and the case where the sulfate-reducing bacteria act as the dominant species.

  Moreover, the calculation result of the organic matter decomposition speed at the time of processing a factory waste water on the conditions of RUN1 and RUN4 is shown in FIG.

  As shown in FIG. 6, in the treatment of factory waste water, the organic matter decomposition rate under the RUN4 condition was about twice as fast as the organic matter decomposition rate under the RUN1 condition.

  By using the digested sludge with sulfate-reducing bacteria that can use a lot of temperament as the dominant species, the organic matter decomposition rate is improved for low-decomposable wastewater that is difficult to decompose. Was suggested.

<< Second Embodiment >>
As a second embodiment of the present invention, a wastewater treatment apparatus 1B that treats wastewater whose sulfur content is unknown or that may change will be described.

  The configuration of the wastewater treatment apparatus 1B according to the second embodiment of the present invention will be described with reference to FIG.

  The wastewater treatment apparatus 1B according to the present embodiment has a configuration in which a sulfur concentration measurement device 9 that measures the sulfur concentration in the wastewater is added to the wastewater treatment apparatus 1A of the first embodiment. The sulfur concentration measuring device 9 measures the total sulfur or sulfate ion concentration.

  The sulfate addition control device 4 of the wastewater treatment apparatus 1B according to the present embodiment is configured such that the sulfate ion concentration is based on the organic matter concentration measured by the organic matter concentration measuring device 3 and the sulfur concentration measured by the sulfur concentration measuring device 9. The amount of sulfate added is calculated so as to be a value higher than 1/3 of the organic substance concentration measured by the measuring device 3. That is, by combining the sulfur concentration measured by the sulfur concentration measuring device 9 and the sulfate to be added, the sulfate ion concentration is higher than 1/3 of the organic concentration measured by the organic concentration measuring device 3. To do.

  Then, the sulfate addition control device 4 controls the calculated addition amount of the sulfate 5a to be added to the wastewater by the injection pump 5b functioning as the sulfate addition device.

  Thus, by adding sulfate 5a to the waste water so that the sulfate ion concentration is higher than 1/3 of the organic matter concentration, methanogenic bacteria are reduced by competition with sulfate-reducing bacteria, while sulfate-reducing bacteria. And the reaction rate for decomposing organic matter is increased.

  Similarly to the wastewater treatment apparatus 1A in the first embodiment, the sulfide concentration is measured by the sulfide concentration measuring device 6, and if necessary, the nitrogen gas in the nitrogen gas cylinder 8a functions as a gas supply device based on this measured value. The dissociated sulfide ions produced by the sulfate reducing bacteria are released as non-dissociated hydrogen sulfide gas by being supplied to the reaction tank 2 by the blower 8b, and the hydrogen sulfide is inhibited by adding sulfuric acid. Is prevented.

  In this embodiment, when the sulfide concentration measuring device 6 measures the sulfide concentration in the reaction tank 2, the reaction tank 2 is considered to have a substantially uniform concentration in the reaction tank 2 due to the shape of the reaction tank 2. It may be measured with the solution inside, or when it is considered that the concentration is uneven in the reaction tank 2, it may be measured near the outlet of the reaction tank 2 or outside the outlet.

<< Third Embodiment >>
A wastewater treatment apparatus 1C as a third embodiment of the present invention will be described. The wastewater treatment apparatus 1C according to the present embodiment adds a separation membrane 10 and an air diffuser 11 to the reaction tank 2 of the wastewater treatment apparatus 1A of the first embodiment or the wastewater treatment apparatus 1B of the second embodiment, and is further processed. The pump 12 for flowing the treated water out of the reaction tank 2 through the separation membrane 10 is added. The air diffuser 11 is installed so as to diffuse from the lower part of the separation membrane 10.

  In this embodiment, when supplying nitrogen gas from the nitrogen gas cylinder 8 a to the reaction tank 2, the gas is supplied by being diffused from the air diffuser 11, and the gas supply control device 7 supplies the nitrogen gas. Nitrogen gas is diffused from the diffuser 11 when it is determined that it is necessary or when the treated water is discharged from the reaction tank 2 through the separation membrane 10 when the pump 12 is operated. To be blown in.

  By operating the air diffuser 11 and the pump 12 in this way, the solid matter is removed by the separation membrane 10 when the treated water flows out of the reaction tank 2, and the quality of the treated water is improved. The clogging of the separation membrane 10 can be prevented by the air diffusion. Moreover, the outflow of bacteria from the reaction tank 2 can be prevented, and the growth rate of sulfate-reducing bacteria can be increased.

DESCRIPTION OF SYMBOLS 1A, 1B, 1C ... Waste water treatment device 2 ... Reaction tank 3 ... Organic substance concentration measuring device 4 ... Sulfate addition control device 5 ... Sulfate addition device 5a ... Sulfate 5b ... Injection pump 6 ... Sulfide concentration measuring device 7 ... Gas Supply control device 8 ... Gas supply device 8a ... Nitrogen gas cylinder 8b ... Blower 9 ... Sulfur concentration measuring device 10 ... Separation membrane 11 ... Aeration device 12 ... Pump 20 ... Waste water treatment device 21 ... Digested sludge 22 ... Reaction tank 23 ... Constant temperature water tank 24 ... Thermometer 25 ... Temperature controller 26 ... Thermometer 27 ... Heater 28 ... Raw water tank 29 ... Simulated drainage 30 ... Stirrer 31 ... Stirrer 32 ... Raw water pump 33 ... Timer 34 ... Stirrer 35 ... Timer 36 ... Treated water 37 ... Treated water pump 38 ... Timer 39 ... Treated water tank 40 ... pH meter 41 ... Alkaline injection pump 42 ... Alkaline solution 43 ... pH controller 44 ... Ogas 45 ... Trap 46 ... Desulfurization device 47 ... Gas meter 48 ... Gas sampling port 49 ... Pinch cock 50 ... Nitrogen gas cylinder 51 ... Bubbler 52 ... Flow meter 53 ... Timer 60 ... Gas measurement device 61 ... Waste water 62 ... Bottle 63 ... Constant temperature water bath 64 ... biogas 65 ... volumetric flask

Claims (6)

An organic matter concentration measuring device that measures the organic matter concentration of the wastewater to be treated;
A sulfate addition device for adding sulfate to the wastewater to be treated so that the sulfate ion concentration is higher than 1/3 of the organic concentration measured by the organic concentration measurement device;
A reaction tank that holds anaerobic bacteria and takes in the wastewater to be treated to decompose organic matter,
A sulfide concentration measuring device for measuring the sulfide concentration of treated water in which organic matter decomposition treatment is performed in the reaction vessel;
Gas supply that blows inert gas into the reaction vessel when the sulfide concentration measured by the sulfide concentration measuring device is higher than a preset threshold value, and stops blowing inert gas when the sulfide concentration is lower than the threshold value Equipment,
A wastewater treatment apparatus comprising: A sulfur concentration measuring device for measuring the sulfur concentration of the waste water to be treated;
The sulfate addition device combines the sulfur concentration measured by the sulfur concentration measurement device with the sulfate to be added, so that the sulfate ion concentration is more than 1/3 of the organic matter concentration measured by the organic concentration measurement device. The waste water treatment apparatus according to claim 1, wherein sulfate is added so as to have a high value. A separation membrane installed in the reaction tank, an air diffuser installed in the lower part of the separation membrane, and treated water from which the organic substance has been decomposed outflowed from the reaction tank via the separation membrane. And a pump
The gas supply device diffuses an inert gas from the air diffuser when the sulfide concentration measured by the sulfide concentration measuring device is higher than a preset threshold value or when the pump is operated. The waste water treatment apparatus according to claim 1, wherein the waste water treatment apparatus is blown into the reaction tank. Wastewater treatment equipment
Measure the organic matter concentration in the wastewater to be treated,
Sulfate is added to the wastewater to be treated so that the sulfate ion concentration is higher than 1/3 of the organic matter concentration measured by the organic matter concentration measuring device,
Into the reaction tank holding anaerobic bacteria, the wastewater to be treated is taken to decompose organic matter,
Measure the sulfide concentration of treated water in which organic matter decomposition treatment was performed in the reaction vessel,
When the measured sulfide concentration is higher than a preset threshold value, an inert gas is blown into the reaction tank, and when the measured sulfide concentration is lower than the threshold value, the blowing of the inert gas is stopped.
A wastewater treatment method characterized by that. Measure the sulfur concentration of the wastewater to be treated,
When adding the sulfate, by adding the measured sulfur concentration to the added sulfate, the sulfate ion concentration is added to a value higher than 1/3 of the measured organic concentration. The wastewater treatment method according to claim 4. When the inert gas is blown into the reaction tank, the pump for causing the treated water to flow out when the measured sulfide concentration is higher than a preset threshold or through a separation membrane installed in the reaction tank The wastewater treatment method according to claim 4 or 5, wherein when the is operated, an inert gas is diffused from a diffuser installed at a lower portion of the separation membrane to blow into the reaction tank.

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