JP5928070B2 - Method for removing ammonia from wastewater containing ammonia - Google Patents

Description

  The present invention relates to a method for removing ammonia from ammonia-containing wastewater.

  Ammonia is a basic nitrogen source in the chemical industry and is used in many fields as an extremely important substance. The factory wastewater containing ammonia is regulated by laws and regulations such as the Water Pollution Control Law because it may lead to environmental pollution if it is discharged outside the factory as general wastewater. For this reason, development of a new treatment technique for removing ammonia nitrogen from wastewater containing ammonia is demanded.

  Conventionally, as a method for removing ammonia from wastewater containing ammonia, an ammonia stripping method for physically removing ammonia (for example, see Patent Document 1) and a biological treatment method using cultured organisms (for example, for example, Patent Document 2) has been used.

  However, in the ammonia stripping method, ammonia is removed while the wastewater falls down the packing material in the deammonification tower. Therefore, in order to increase the stripping efficiency, the tower height of the deammonification tower is increased. The device becomes extremely large. Further, there is a problem that a separate means for absorbing and decomposing ammonia gas that has become a gas is required.

  In addition, it is difficult for the biological treatment method to cope with changes in the concentration of wastewater, and it requires facilities such as a vast pond as a living culture environment, which complicates operations.

Japanese Patent Laid-Open No. 08-197039 JP 09-290297 A

  Therefore, the present invention has been proposed in view of such circumstances, and ammonia such as factory effluent can be efficiently and effectively added without complicating the equipment and processing environment as in the prior art. It aims at providing the ammonia removal method which can remove ammonia from the waste_water | drain containing.

That is, the ammonia removal method according to the present invention is a method of removing ammonia from wastewater containing ammonia, and the pH of the ammonia-containing wastewater is adjusted to 10 or more and the temperature is adjusted to 50 ° C or more, and then the hydrophobic hollow The liquid is fed to a degassing membrane apparatus in which a yarn is incorporated, and is brought into contact with a reduced-pressure gas as a fluid in a countercurrent contact manner for a time of 500 seconds to 1000 seconds.

  According to the ammonia removal method of the present invention, ammonia can be efficiently and effectively removed from wastewater containing ammonia such as factory wastewater without complicating the equipment and processing environment as in the prior art. Can do.

It is a system flow figure showing an example of the flow of the removal method of ammonia concerning a 1st embodiment. It is a graph which shows the relationship between the contact time about the ammonia containing waste_water | drain which changed pH between 8-13, and the ammonia nitrogen density | concentration in waste_water | drain. It is a graph which shows the relationship between the contact time about the ammonia containing waste_water | drain which changed liquid temperature between 10 degreeC-50 degreeC, and the ammoniacal nitrogen density | concentration in waste_water | drain. It is a system flow figure showing an example of the flow of the removal method of ammonia concerning a 2nd embodiment. It is a graph which shows the relationship of the ammonia nitrogen density | concentration in waste_water | drain with respect to the contact time of ammonia containing waste_water | drain at the time of carrying out countercurrent contact using the sulfuric acid solution as a fluid.

  Hereinafter, a specific embodiment (hereinafter referred to as this embodiment) of an ammonia removal method according to the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to the following embodiment, A change is possible in the range which does not change a summary to this invention.

<First Embodiment>
The method for removing ammonia according to the present embodiment is a method for removing ammonia from wastewater containing ammonia such as factory wastewater (hereinafter also referred to as “ammonia-containing wastewater” or simply “drainage”), Ammonia can be removed efficiently and effectively.

  Specifically, in this ammonia removal method, after adjusting the pH of the ammonia-containing wastewater to 10 or higher, the pH-adjusted ammonia-containing wastewater is sent to a degassing membrane device incorporating a hydrophobic hollow fiber, It is characterized by making countercurrent contact with a decompressed gas (air) as a fluid.

  FIG. 1 is a system flow diagram showing an example of a flow of an ammonia removal method according to the present embodiment. In FIG. 1 and the system flow diagram of FIG. 4 to be described later, as “deaeration membrane devices 13 and 14”, a configuration including two deaeration membrane devices for removing ammonia in waste water is shown. In the treatment, basically, both of the degassing membrane devices are operated to perform ammonia removal treatment. When the degassing membrane constituting the degassing membrane device is clogged, one of the clogged ones is removed. The clogging of the deaeration film can be removed by stopping and performing a process such as cleaning.

  The system is not limited to an embodiment having two degassing membrane devices as shown in FIG. 1, and may be provided with three or more, depending on the amount of ammonia-containing wastewater to be treated, etc. Thus, the number of deaeration devices can be changed.

  As shown in FIG. 1, first, a stock solution of ammonia-containing wastewater such as factory wastewater is temporarily stored in a wastewater supply tank 11, and the liquid introduction ports 13 a and 13 a of the degassing membrane devices 13 and 14 are driven by the liquid feed pump 12. 14a. On the other hand, air (gas) recovered from the atmosphere is evacuated by the vacuum pump 15 and introduced into the fluid inlets 13b and 14b of the degassing membrane devices 13 and 14 as a decompressed gas.

  Deaeration membranes 13 and 14 incorporate a deaeration membrane made of a hydrophobic hollow fiber. In the degassing membrane devices 13 and 14, when ammonia-containing wastewater is introduced from the liquid introduction ports 13a and 14a, the degassing membrane devices 13 and 14 come into countercurrent contact with the decompressed gas introduced from the fluid introduction ports 13b and 14b. Then, based on Henry's law, the ammonia concentration in the ammonia-containing wastewater decreases. That is, non-dissociable dissolved ammonia is degassed (moved into the air) and removed.

  The deaeration membrane comprising hydrophobic hollow fibers incorporated in the deaeration membrane devices 13 and 14 is not particularly limited. For example, the hollow fiber has a diameter of about 300 μm and a pore size of about 0.03 μm (average) ) Porosity is about 40-50%. Thus, in the deaeration membrane devices 13 and 14, since the pore size of the deaeration membrane as a constituent member is small, for example, components having a large molecular diameter such as organic substances do not escape from the pores in the ammonia-containing wastewater. In this case, only the ammonia that remains and is to be removed is reliably removed.

  In the ammonia removal method according to the present embodiment, it is important to adjust the pH of the ammonia-containing wastewater and introduce it into the degassing membrane devices 13 and 14 at this time. Specifically, the ammonia-containing wastewater is introduced after adjusting to pH 10 or more, preferably 11 or more, more preferably pH 13 or more. As described above, by adjusting the pH of the ammonia-containing wastewater in advance to pH 10 or higher, preferably 11 or higher, more preferably pH 13 or higher and introducing it into the degassing membrane devices 13 and 14, the ammonia removal efficiency is effectively improved. Can be increased.

  Here, in FIG. 2, each sample of ammonia-containing wastewater (ammonia nitrogen concentration: 7 to 8 g / L, liquid temperature 25 ° C.) whose pH was changed between 8 and 13 was reduced using a degassing membrane device. The relationship of the ammonia nitrogen density | concentration which remained in the ammonia containing waste_water | drain with respect to the time made to contact countercurrent with gas is shown. In this test, a degassing membrane apparatus incorporating a degassing membrane having a hollow fiber diameter of about 300 μm, a pore size of about 0.03 μm, and an (average) porosity of about 40 to 50% was used, and the drainage flow rate was 5 L / min. , And processed under reduced pressure gas pressure -0.05 MPaG.

  As shown in FIG. 2, when the pH of the ammonia-containing wastewater is around 8 to 9, the ammonia is hardly removed even if the contact time is increased, but when the pH is adjusted to 10 or more, the contact time It can be seen that the ammonia nitrogen concentration in the waste water is effectively reduced and the ammonia is removed as the length is increased. This is presumably because non-dissociable ammonia in the waste water increases by adjusting the pH to 10 or more in advance. In particular, when the pH is adjusted to 13 or more, it can be seen that about 70% or more of ammonia is removed in a short time of about 500 seconds and can be removed more efficiently.

  The pH adjustment of the ammonia-containing waste water can be performed, for example, in the waste water supply tank 11 shown in FIG. The pH can be adjusted by adding an alkali such as sodium hydroxide or potassium hydroxide.

  Moreover, in the ammonia removal method according to the present embodiment, it is preferable to adjust the temperature (liquid temperature) of the ammonia-containing wastewater as described above as well as the pH of the ammonia-containing wastewater. Specifically, it is preferable to introduce the ammonia-containing wastewater into the degassing membrane devices 13 and 14 after the temperature of the ammonia-containing wastewater is raised to 50 ° C. or higher in advance. Thus, by adjusting the pH of the ammonia-containing wastewater and adjusting the temperature to 50 ° C. or higher and introducing it into the degassing membrane devices 13 and 14, the ammonia removal efficiency can be further enhanced. The ammonia in the ammonia-containing waste water can be removed almost certainly.

  Here, in FIG. 3, each sample of ammonia-containing wastewater (ammonia nitrogen concentration: 7-8 g / L, pH 10) whose liquid temperature was changed between 10 ° C. and 50 ° C. was depressurized using a degassing membrane device. The relationship of the ammonia nitrogen density | concentration which remained in the ammonia containing waste_water | drain with respect to the time made to contact countercurrent with gas is shown. In addition, the deaeration process conditions including a deaeration membrane apparatus are the same as the conditions in the above-mentioned pH examination.

  As shown in FIG. 3, it can be seen that as the temperature of the ammonia-containing wastewater is increased, the ammoniacal nitrogen concentration in the wastewater is effectively reduced as the contact time elapses, and ammonia is removed. In particular, it can be seen that when the temperature of the waste water was adjusted to 50 ° C. or higher, most of the ammonia was removed in a short time of about 500 seconds and completely removed in a short time of about 1000 seconds. This is thought to be because the Henry's constant increases by adjusting the liquid temperature to 50 ° C. or higher in advance.

  Thus, when removing ammonia in the ammonia-containing wastewater by the degassing membrane devices 13 and 14, the pH of the wastewater is adjusted to 10 or higher in advance as described above, and the temperature is adjusted to 50 ° C or higher. Thus, ammonia can be removed more efficiently and effectively.

  The temperature adjustment of the ammonia-containing wastewater can be performed, for example, by controlling the temperature of the wastewater supply tank 11 shown in FIG. In addition, a heater or the like may be provided around the waste water supply tank 11 to heat the contained ammonia-containing waste water and adjust the temperature to 50 ° C. or higher.

  The waste water 10 introduced into the degassing membrane devices 13 and 14 and from which ammonia has been removed as described above is sent to the discharge tank 16 as shown in FIG. 1 and transferred to waste water treatment via the liquid feed pump 17. To do. The waste water 10 may be circulated so as to be returned to the waste water supply tank 11 and repeatedly introduced into the deaeration membrane devices 13 and 14.

  On the other hand, the air evacuated by the vacuum pump 15 is recovered by the recovered ammonium scrubber 18 together with the ammonia gas contained in the ammonia-containing wastewater after passing through the degassing membrane devices 13 and 14. The recovered ammonium sulfate scrubber 18 contains the supplied sulfuric acid solution, and recovers ammonia gas to produce ammonium sulfate. The produced ammonium sulfate is reused via the liquid feed pump 19.

  By the way, as described above, the pore size of the degassing membranes constituting the degassing membrane devices 13 and 14 is small, so that liquid components having a large molecular diameter such as organic substances do not pass through the degassing membrane and contain ammonia-containing wastewater. Remains in. However, when used continuously for a long period of time in wastewater treatment, clogging of the membrane may occur due to the organic matter and salts in the wastewater. When such clogging occurs, the ammonia removal efficiency is significantly reduced.

  Therefore, in this ammonia removal method, it is preferable to wash the deaeration membranes constituting the deaeration membrane devices 13 and 14 after feeding the ammonia-containing waste water with an acid solution such as sulfuric acid. Specifically, as shown in FIG. 1, for example, a sulfuric acid solution is supplied to and stored in the membrane regeneration liquid storage tank 21, and the deaeration membrane device 13 is supplied by the liquid feed pump 22 through the liquid inlets 13 a and 14 a. , 14 is washed with a degassing membrane in which clogging has occurred. For example, when the degassing membrane in which clogging has occurred is configured in the degassing membrane device 13, the degassing membrane device 13 is stopped and the processing capability of the other degassing membrane device 14 is increased. Supplement the ammonia removal process.

  When acid cleaning is performed with the sulfuric acid solution introduced from the membrane regeneration acid storage tank 21 in this way, the sulfuric acid solution circulates and causes clogging of the degassing membrane in the membrane regeneration acid storage tank 21. The compounds such as organic substances that have been transferred will be transferred. This sulfuric acid solution is sent to the discharge tank 16 via the liquid feed pump 22 and is subjected to waste water treatment together with the waste water from which ammonia has been removed.

  This acid cleaning of the degassing membrane may be performed periodically at regular intervals, but the effect of clogging on the degassing membrane differs depending on the type of wastewater 10 to be treated. It is preferable to perform the treatment before the removal efficiency is lowered. Specifically, as the method, for example, the pressure of the ammonia-containing wastewater before being sent to the degassing membrane devices 13 and 14 and the pressure of the wastewater after being sent to the degassing membrane devices 13 and 14 and removing ammonia. Each is measured, and clogging of the deaeration film is detected according to the pressure difference between the pressures to perform acid cleaning.

  More specifically, as shown in FIG. 1, for example, a pressure gauge 23 is provided in a pipe between the drainage supply tank 11 and the degassing membrane devices 13, 14, and is sent from the drainage supply tank 11 to be removed. The pressure of the ammonia-containing waste water before being introduced into the gas membrane devices 13 and 14 is measured. Moreover, the pressure gauge 24 is provided in the piping between the deaeration membrane apparatuses 13 and 14 and the discharge tank 16, and the pressure of the waste water after sending ammonia to the deaeration membrane apparatuses 13 and 14 and removing ammonia is measured. To do. Then, the pressure difference between these measured pressures is measured and monitored, and when the pressure difference exceeds a predetermined value, it is determined that clogging has occurred, and the deaeration membrane device 13 (or 14) including the deaeration membrane is determined. ) And stop the degassing membrane by acid cleaning.

  When clogging occurs in the degassing membrane, the contact between the ammonia-containing waste water and the reduced pressure gas decreases, and the ammonia removal efficiency decreases. Therefore, paying attention to the pressure difference between the drainage before and after the liquid feeding to the degassing membrane devices 13 and 14, when the pressure difference exceeds a predetermined value, it is determined that the degassing membrane is clogged, and the ammonia removal efficiency In order to recover the problem, the deaeration membrane is subjected to an acid cleaning treatment to remove clogging of the deaeration membrane. Thereby, it becomes possible to perform an efficient process, without reducing the ammonia removal efficiency of the deaeration membrane apparatuses 13 and 14 excessively. Further, by efficiently performing the acid cleaning, the degassing membrane can be repeatedly used.

  This acid cleaning treatment is performed when, for example, the degassing membrane devices 13 and 14 receive pressure values measured by the pressure gauges 23 and 24 to calculate a pressure difference, and when the pressure difference exceeds a predetermined value. A configuration may be adopted in which a degassing membrane apparatus including a degassing membrane in which clogging has occurred is automatically stopped, and a cleaning control unit is provided to control the degassing membrane so as to perform acid cleaning, thereby performing automatic control.

  Here, in this ammonia removal method, the degassing membranes constituting the degassing membrane devices 13 and 14 on the side through which the decompressed gas as the fluid is passed are passed through the gas. Clogging is unlikely to occur. However, if clogging occurs even in a degassing membrane through which reduced pressure gas has been passed, the ammonia removal efficiency will be reduced. Accordingly, in this case as well, it is preferable that clogging of the deaeration membranes constituting the deaeration membrane devices 13 and 14 can be accurately detected.

  In this way, by accurately detecting clogging of the degassing membrane that has passed through the decompression gas, the degassing membrane device including the degassing membrane can be quickly stopped, and there is no problem due to a decrease in ammonia removal efficiency. It is possible to prevent the occurrence of sufficient processing, and the operation efficiency can be increased. In addition, since clogging can be accurately detected in this manner, appropriate processing such as cleaning according to the cause of the clogging can be quickly performed on the deaeration membrane apparatus whose operation has been stopped.

  Specifically, as a method for detecting the clogging, as shown in FIG. 1, for example, the pressure of the decompressed gas before being introduced into the degassing membrane devices 13 and 14 is measured with a pressure gauge 25, and the degassing membrane is measured. The pressure of the decompressed gas after passing through the devices 13 and 14, that is, the decompressed gas containing the removed ammonia, is measured by the pressure gauge 26, and is detected according to the pressure difference between the measured pressures.

  More specifically, when clogging of the degassing membrane occurs and ammonia removal efficiency is reduced, the pressure of the decompressed gas before being introduced into the degassing membrane devices 13 and 14 and the degassing membrane device 13, The difference from the pressure of the decompressed gas after 14 passes increases. Therefore, when the pressure difference between the pressures measured by the above-described pressure gauges 25 and 26 exceeds a predetermined value, it is determined that the degassing membranes constituting the degassing membrane devices 13 and 14 are clogged. Can do.

  When clogging occurs in the degassing membrane, the contact between the ammonia-containing waste water and the reduced pressure gas decreases, and the ammonia removal efficiency decreases. Therefore, paying attention to the pressure difference of the drainage before and after feeding to the degassing membrane devices 13 and 14, when the pressure difference exceeds a predetermined value, it is determined that the degassing membrane is clogged. When clogging is detected, the operation of the deaeration membrane device is stopped. Thereby, for example, when clogging occurs in the degassing membrane of the degassing membrane device 13, the ammonia removal efficiency is excessively increased by quickly supplementing the processing capability of the other degassing membrane device 14. Efficient processing can be performed without excessive reduction.

  For detecting the clogging of the degassing membrane on the decompression gas side, for example, in the degassing membrane devices 13 and 14, the pressure values measured by the pressure gauges 25 and 26 are received and the pressure difference is calculated, It may be configured to automatically control by providing a control unit that automatically issues a warning or the like to stop the operation of the deaeration membrane device when the pressure difference exceeds a predetermined value.

  As described above, according to the ammonia removal method according to the present embodiment, ammonia-containing wastewater whose pH is adjusted to 10 or higher in advance, and more preferably adjusted to 50 ° C. or higher, is used as a degassing membrane device. By sending the solution, ammonia can be removed from the waste water with a high removal rate.

  Moreover, as described above, it can be performed by a simple facility with a small number of facilities using at least a degassing membrane device, a liquid feed pump, and a vacuum pump, and the facility configuration and processing environment are not complicated as in the past. Ammonia can be removed efficiently and effectively.

<Second Embodiment>
In the first embodiment described above, the example in which the ammonia-containing wastewater is brought into countercurrent contact with the decompressed gas as a fluid in the degassing membrane devices 13 and 14 has been described. Alternatively, the sulfuric acid solution may be used as a fluid to make countercurrent contact. In the following description, the same components as those in the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.

  FIG. 4 is a system flow diagram illustrating an example of a flow of an ammonia removal method according to the second embodiment. As shown in FIG. 4, first, a stock solution of ammonia-containing wastewater such as factory wastewater is temporarily stored in the wastewater supply tank 11, and the liquid introduction ports 13 a of the degassing membrane devices 13 and 14 are driven by the liquid feed pump 12. 14a. On the other hand, a sulfuric acid solution used as a fluid is supplied to and stored in the sulfuric acid / ammonium sulfate tank 31, and is introduced into the fluid inlets 13 b and 14 b of the degassing membrane devices 13 and 14 by driving the liquid feed pump 32.

  At this time, similarly to the first embodiment described above, the pH of the ammonia-containing wastewater is adjusted to 10 or more, for example, in the wastewater supply tank 11 before the ammonia is removed by the degassing membrane devices 13 and 14. Preferably, the pH is adjusted to 10 or higher, and the liquid temperature is adjusted to 50 ° C. or higher.

  In the degassing membrane devices 13 and 14, the ammonia-containing wastewater introduced and the sulfuric acid solution as a fluid are brought into countercurrent contact with each other, whereby the non-dissociable dissolved ammonia contained in the ammonia-containing wastewater is deaerated. As a result, ammonia in the ammonia-containing waste water is removed.

  Here, in FIG. 5, when ammonia-containing wastewater (pH 10, liquid temperature 50 ° C.) is brought into countercurrent contact with a sulfuric acid solution as a fluid as described above, the ammoniacality remaining in the ammonia-containing wastewater with respect to the contact time. The relationship of nitrogen concentration is shown. The graph of FIG. 5 also shows the transition of the ammoniacal nitrogen concentration when the countercurrent contact is performed using the decompressed gas as the fluid (first embodiment).

  In addition, the ammonia containing waste_water | drain used as the process target used the thing of the low concentration whose ammoniacal nitrogen density | concentration is 2.6-2.9 g / L. In this test, a degassing membrane apparatus incorporating a degassing membrane having a hollow fiber diameter of about 300 μm, a pore size of about 0.03 μm, and an (average) porosity of about 40 to 50% was used, and the drainage flow rate was 5 L / min. The sulfuric acid flow rate was 2.5 L / min. In the treatment with the reduced pressure gas as the reference example, the reduced pressure gas pressure was set to -0.05 MPaG.

  As shown in FIG. 5, when a sulfuric acid solution is used as the fluid, even in a low concentration ammonia-containing wastewater, the ammonia nitrogen concentration can be reduced to 1 g / L or less in a short time of less than 200 seconds. It can be seen that ammonia can be efficiently removed. Moreover, it can be seen that the removal efficiency is improved as compared with the case of using the decompressed gas as the fluid. Furthermore, it can be seen that when the sulfuric acid solution is used, the ammonia nitrogen concentration reduction rate is higher than when the reduced pressure gas is used, and ammonia can be removed more effectively.

  In this way, by using a sulfuric acid solution as a fluid and making countercurrent contact with ammonia-containing wastewater, ammonia can be efficiently and effectively removed even with low-concentration ammonia-containing wastewater.

  The waste water 10 introduced into the degassing membrane devices 13 and 14 and from which ammonia has been removed as described above is sent to the discharge tank 16 as shown in FIG. 1 and transferred to waste water treatment via the liquid feed pump 17. To do. On the other hand, the sulfuric acid solution is recovered again in the sulfuric acid / ammonium sulfate tank 31 together with the ammonia contained in the ammonia-containing waste water after passing through the degassing membrane devices 13 and 14.

  In the ammonia removal method according to the second embodiment, the pressure of the ammonia-containing wastewater before being introduced from the wastewater supply tank 11 and introduced into the degassing membrane devices 13 and 14 is measured with the pressure gauge 23. Then, the pressure of the waste water after being sent to the degassing membrane devices 13 and 14 to remove ammonia and measured with a pressure gauge 24, clogging occurs when the pressure difference between these measured pressures exceeds a predetermined value. The deaeration device 13 (or 14) including the deaeration membrane in which clogging has occurred is stopped, and an acid such as a sulfuric acid solution is used for the deaeration membrane in which clogging has occurred. Acid cleaning can be performed. At this time, the ammonia removal process is supplemented by increasing the processing capacity of the other degassing membrane device 14 (or 13) with respect to the stopped degassing membrane device 13 (or 14).

  Specifically, as shown in FIG. 4, for example, sulfuric acid is supplied from the liquid introduction ports 13 a and 14 a of the degassing membrane devices 13 and 14 from the sulfuric acid / ammonium sulfate tank 31 supplied with the sulfuric acid solution via the liquid feed pump 32. By introducing the solution, the deaeration membrane on the side where the ammonia-containing waste water is introduced is washed.

  When acid cleaning is performed with the sulfuric acid solution introduced from the sulfuric acid / ammonium sulfate tank 31 in this way, the sulfuric acid solution circulates and the organic matter that has caused clogging of the deaeration film in the sulfuric acid / ammonium sulfate tank 31. Etc. will be transferred. This sulfuric acid solution is sent to the discharge tank 16 via the liquid feed pump 32 and is subjected to waste water treatment together with the waste water from which ammonia has been removed.

  In the ammonia removal method according to the second embodiment, a sulfuric acid solution is used as the fluid. For this reason, the degassing membrane on the side where the sulfuric acid solution as the fluid is introduced is likely to be clogged, and therefore it is preferable to perform an appropriate cleaning treatment.

  As for the cleaning process of the degassing membrane on the side where the sulfuric acid solution as the fluid is introduced, the pressure of the sulfuric acid solution before being introduced into the degassing membrane devices 13 and 14 is measured with a pressure gauge 33 as shown in FIG. In addition to the measurement, the pressure of the sulfuric acid solution containing the removed ammonia after passing through the degassing membrane devices 13 and 14 is measured by the pressure gauge 34, and the cleaning process is performed according to the pressure difference between the measured pressures.

  When clogging of the degassing membrane occurs and the ammonia removal efficiency is reduced, the pressure of the sulfuric acid solution before being introduced into the degassing membrane devices 13 and 14 and the sulfuric acid solution after passing through the degassing membrane devices 13 and 14 Therefore, the clogging can be accurately detected by the pressure difference.

  Specifically, it is determined that the deaeration membrane constituting the deaeration membrane device 13 (or 14) is clogged when the pressure difference between the pressures exceeds a predetermined value, and the deaeration membrane device 13 (or 14) is stopped and the deaeration film is subjected to a cleaning process. This makes it possible to perform an efficient process without excessively reducing the ammonia removal efficiency.

  The degassing membrane on the side of introducing the sulfuric acid solution as a fluid can be washed using water or an organic acid solution. Specifically, as shown in FIG. 4, for example, water or an organic acid solution is supplied to and stored in the membrane regeneration liquid storage tank 21, and the liquid of the deaeration membrane apparatuses 13 and 14 is supplied via the liquid feed pump 22. Water or an organic acid solution is introduced from the inlets 13b and 14b to clean the deaeration membrane.

  When the acid cleaning is performed with the water or the organic acid solution introduced from the membrane regeneration liquid storage tank 21 in this way, the water or the organic acid solution is circulated and degassed into the membrane regeneration liquid storage tank 21. A compound containing a salt or the like that causes clogging of the film is transferred. The solution containing the compound containing salt or the like is sent to the discharge tank 16 via the liquid feed pump 22 and subjected to waste water treatment together with the waste water from which ammonia has been removed.

  This degassing membrane cleaning may be performed periodically at regular intervals, but the effect of clogging on the degassing membrane differs depending on the type of wastewater 10 to be treated. It is preferable to process before efficiency falls. Therefore, as described above, the degassing membrane on the side of introducing the ammonia-containing wastewater detects clogging according to the pressure difference of the ammonia-containing wastewater before and after the passage of the degassing membrane devices 13 and 14, and serves as a fluid. For the degassing membrane on the side where the sulfuric acid solution is introduced, clogging is detected according to the pressure difference of the sulfuric acid solution before and after passing through the degassing membrane devices 13 and 14, and the degassing membrane is washed. This makes it possible to perform an efficient process without reducing the ammonia removal efficiency.

  As described above, as shown in the second embodiment, the sulfuric acid solution is used instead of the decompression gas for the ammonia-containing wastewater whose pH is adjusted to 10 or more, and preferably the temperature is adjusted to 50 ° C. or more. If the countercurrent contact is made, ammonia can be efficiently removed at a higher removal rate even with wastewater having a low ammonia concentration.

  DESCRIPTION OF SYMBOLS 11 Wastewater supply tank, 12 Liquid feed pump, 13, 14 Deaeration membrane apparatus, 13a, 14a Liquid inlet, 13b, 14b Fluid inlet, 15 Vacuum pump, 16 Discharge tank, 17 Liquid pump, 18 Recovery ammonium sulfate scrubber, 19 Liquid feed pump, 21 Membrane regeneration liquid reservoir, 22 Liquid feed pump, 23, 24, 25, 26 Pressure gauge, 31 Sulfuric acid / ammonium sulfate tank, 32 Liquid feed pump

Claims (10)

A method for removing ammonia from wastewater containing ammonia,
The pH of the ammonia-containing waste water was fed to the degassing membrane device hydrophobic hollow fibers is incorporated after adjusting the temperature to more than 50 ° C. at 10 or higher, as a fluid vacuum gas and 1000 seconds or less than 500 seconds A method for removing ammonia, characterized by contacting in countercurrent over time.   The ammonia removal method according to claim 1, wherein the pH of the ammonia-containing waste water is adjusted to 13 or more.   The ammonia removal method according to claim 1 or 2, wherein the degassing membrane device after feeding the ammonia-containing wastewater is washed with an acid solution.   The pressure difference between the pressure of the ammonia-containing wastewater before being sent to the degassing membrane device and the pressure of the wastewater after being sent to the degassing membrane device and removing the ammonia is measured. 4. The ammonia removing method according to claim 3, wherein the degassing membrane device is washed with the acid solution when the above is reached.   The ammonia removal method according to claim 1 or 2, wherein a sulfuric acid solution is used as a fluid instead of the reduced-pressure gas, and the sulfuric acid solution and the ammonia-containing waste water are brought into countercurrent contact.   6. The ammonia removing method according to claim 5, wherein the deaeration membrane device after feeding the ammonia-containing waste water is washed with an acid solution.   The pressure difference between the pressure of the ammonia-containing wastewater before being sent to the degassing membrane device and the pressure of the wastewater after being sent to the degassing membrane device and removing the ammonia is measured. 7. The ammonia removing method according to claim 6, wherein the degassing membrane device is washed with the acid solution when the above is reached.   The ammonia removal method according to any one of claims 5 to 7, wherein the degassing membrane device after the sulfuric acid solution as the fluid is fed is washed with water or an organic acid solution.   When the pressure difference between the pressure of the sulfuric acid solution before being introduced into the degassing membrane device and the sulfuric acid solution containing ammonia that has been removed by passing through the degassing membrane device is measured, and the pressure difference exceeds a predetermined value 9. The method for removing ammonia according to claim 8, wherein the degassing membrane device is washed with the water or organic acid solution.   The ammonia removal method according to any one of claims 1 to 9, wherein a plurality of the degassing membrane devices are used.

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