JP2008188498A - Treatment method and treatment equipment for water to be treated - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a treatment method for water to be treated and treatment equipment for the water to be treated which can suppress precipitation of phosphate in a membrane surface or the like in membrane separation of the water to be treated after denitrification treatment. <P>SOLUTION: The treatment method for the water to be treated is provided for denitrifying the water to be treated containing phosphate, phosphoric ions produced from phosphate and metal ions, and a nitrogen compound or ions corresponding thereto in a denitrification tank thereby obtaining denitrified water, then subjecting the denitrified water to membrane separation while air-diffusing the denitrified water in a membrane separation tank, wherein the membrane separation is performed under the conditions where the solubility of the phosphate to a liquid phase including the denitrified water in the separation tank reaches the solubility of the phosphate to the liquid phase including the water to be treated in the denitrification tank or above. The treatment equipment 1 for the water to be treated uses the method and comprises: the denitrification tank 5; the membrane separation tank 6 where, while the denitrified water is air-diffused, it is subjected to solid-liquid separation by a membrane; and a regulation means 101a where the solubility of phosphate to the liquid phase including the denitrified water in the membrane separation tank 6 is regulated so that the solubility of the phosphate to the liquid phase in the membrane separation tank 6 becomes the solubility of the phosphate in the denitrification tank or above. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a treatment method and treatment equipment for water to be treated.

  Conventionally, organic waste liquids and organic solids containing nitrogen compounds and their ions are subjected to anaerobic treatment in the presence of sludge containing anaerobic microorganisms, biological nitrification and biological denitrification, A treatment for removing a nitrogen compound is performed (for example, Patent Document 1). In addition, when the treatment method described in Patent Document 1 is performed, the treated water containing sludge obtained after removing the nitrogen compound is separated into solid and liquid by a precipitation method or a membrane separation method (for example, Patent Document 2). Is applied to make the treated water clearer. Among these, the membrane separation method is frequently used in solid-liquid separation because it can stably and rapidly obtain treated water with higher clarity than the precipitation method.

However, in the case of performing solid-liquid separation by a membrane separation method as in the method described in Patent Document 2, depending on the composition of the nitrogen compound-containing waste liquid, if membrane separation is performed while being diffused in the membrane separation tank, Since carbon dioxide dissolved in the liquid in the separation tank is transferred to the atmosphere, the pH of the liquid in the membrane separation tank rises and the solubility of salts decreases, resulting in a scale on the membrane surface, etc. There is a drawback that the efficiency may be significantly reduced. Further, in the treatment method described in Patent Document 1, as described above, when scale is generated on the film surface or the like, the frequency of chemical cleaning on the film surface increases and the cost required for the treatment increases. There is. Furthermore, due to scaling to the membrane surface and increasing chemical cleaning frequency, there is a disadvantage that the lifetime of the membrane is shortened and the replacement cost of the membrane is also increased.
JP 2003-71497 A JP 2005-118719 A

  The present invention provides, for example, membrane separation after denitrification treatment even in the case where the treated water contains phosphates, phosphate ions and metal ions that can be generated from the phosphates, and nitrogen compounds or corresponding ions. At this time, an object is to provide a method for treating water to be treated, which can suppress precipitation of phosphate on the film surface and the like. Moreover, even if this invention contains the phosphate ion and metal ion which can arise from a phosphate or this phosphate in a to-be-processed water, and a nitrogen compound or the ion corresponding to it, the said to-be-processed water is included, for example Another object is to provide a treatment facility for water to be treated that can reduce the frequency of chemical cleaning of the membrane associated with the use of the treatment facility.

The present invention relates to a denitrification obtained by treating a treated water containing a phosphate or a phosphate ion and a metal ion that can be generated from the phosphate and a nitrogen compound or a corresponding ion in a denitrification tank. When treating the treated water while aeration in the membrane separation tank,
Membrane separation under conditions where the solubility of the phosphate in the liquid phase containing denitrified water in the membrane separation tank is equal to or higher than the solubility of the phosphate in the liquid phase containing water to be treated in the denitrification tank It is related with the processing method of to-be-processed water characterized by performing. Further, the present invention provides a denitrification tank for denitrifying a water to be treated containing phosphate or a phosphate ion, a metal ion, and a nitrogen compound or the ion that can be generated from the phosphate,
A membrane separation tank for solid-liquid separation by a membrane while aerating the denitrification water obtained by treatment in the denitrification tank;
In order to adjust the solubility of the phosphate in the liquid phase containing denitrified water in the membrane separation tank to be equal to or higher than the solubility of the phosphate in the liquid phase containing water to be treated in the denitrification tank Adjusting means,
The present invention relates to a treatment facility for water to be treated.

  According to the method for treating water to be treated according to the present invention, the solubility of phosphate in the liquid phase containing denitrified water in the membrane separation tank is determined by the phosphate solubility in the liquid phase containing water to be treated in the denitrification tank. Since membrane separation is performed under conditions that result in solubility or higher, for example, phosphate or metal ions that can be generated from phosphate or the phosphate and nitrogen compounds or corresponding ions are contained in the water to be treated Even in this case, there is an excellent effect that the precipitation of phosphate on the membrane surface or the like can be suppressed during membrane separation after the denitrification treatment. In addition, the treatment facility of the water to be treated according to the present invention has a phosphate solubility in the liquid phase containing the denitrification water in the membrane separation tank, and the phosphate in the liquid phase containing the water to be treated in the denitrification tank. Therefore, according to the treated water treatment facility of the present invention, for example, phosphate in the treated water or phosphorus that can be generated from the phosphate is provided. Even when it contains an acid ion and a metal ion, and a nitrogen compound or a corresponding ion, an excellent effect of reducing the frequency of chemical cleaning of the membrane associated with the use of the treatment facility for the water to be treated can be obtained.

As described above, the method for treating water to be treated of the present invention comprises treating water containing a phosphate or a metal ion and a phosphate ion that can be generated from the phosphate, and a nitrogen compound or a corresponding ion. In the treatment with the denitrification water obtained by treatment in the denitrification tank being diffused in the membrane separation tank,
Membrane separation under conditions where the solubility of the phosphate in the liquid phase containing denitrified water in the membrane separation tank is equal to or higher than the solubility of the phosphate in the liquid phase containing water to be treated in the denitrification tank It is the method characterized by performing.

  The treated water is not particularly limited. For example, organic waste water (sewage, factory effluent, etc.) and organic waste such as sludge, human waste, manure, garbage, shochu lees, etc. generated by this biological treatment Waste water containing water, decomposition treated water obtained by decomposing the raw waste water through methane fermentation, etc., elution water (landfill leachate) generated from a landfill site, and the like. According to the method for treating water to be treated of the present invention, the water to be treated contains a phosphate, a phosphate ion and a metal ion that can be generated from the phosphate, and a nitrogen compound or a corresponding ion. In the case of water, scale separation in the membrane can be suppressed during membrane separation after the denitrification treatment.

  According to the method for treating water to be treated according to the present invention, when treating the water to be treated while denitrifying water obtained by treating in the denitrification tank is diffused in the membrane separation tank, the membrane separation tank Since membrane separation is performed under the condition that the solubility of phosphate in the liquid phase containing denitrified water in the inside is higher than the solubility of phosphate in the liquid phase containing treated water in the denitrification tank, In the membrane separation after the nitriding treatment, an excellent effect that scale generation in the membrane can be suppressed is exhibited. Furthermore, the chemical cleaning frequency of the film surface can be reduced (the cost required for cleaning can be reduced), and the film life can be maintained (the replacement cost of the film can be suppressed).

  The phosphate is not particularly limited, and examples thereof include magnesium phosphate, magnesium ammonium phosphate, calcium phosphate, and sodium phosphate. Such phosphate is a salt that can be precipitated in the denitrification water obtained after the denitrification reaction. Especially, the processing method of the to-be-processed water of this invention is advantageous at the point that solubility adjustment of a wide range is possible by adjustment of pH of a low frequency, when a phosphate is magnesium phosphate.

  In the present specification, “phosphate ions and metal ions that can be generated from phosphate” intends phosphate ions and metal ions that are generated when the phosphate is dissolved in a solution, for example, water. Examples of the metal ions include magnesium ions, calcium ions, sodium ions, and potassium ions.

  Although it does not specifically limit as said nitrogen compound, For example, ammonia, nitrous acid, nitric acid, etc. are mentioned.

  Although it does not specifically limit as an ion corresponding to the said nitrogen compound, For example, ammonium ion, nitrite ion, nitrate ion etc. are mentioned.

  In the present specification, the “solubility” refers to a value represented by the mass (g) of a solute dissolved in 100 g of a solvent at a constant temperature. The solubility of phosphate in the liquid phase containing denitrified water in the membrane separation tank is determined by changing the pH and temperature conditions and measuring the concentration of dissolved phosphate in the solution under each condition. Moreover, the solubility of the phosphate with respect to the liquid phase containing the to-be-processed water in the said denitrification tank is calculated | required by changing the pH and temperature conditions, and measuring the dissolved phosphate concentration in the solution in each condition.

  In the method for treating water to be treated according to the present invention, the adjustment of the conditions in the membrane separation is performed so that the pH of the liquid phase in the membrane separation tank is at least the same as the pH of the liquid phase in the denitrification tank. (Hereinafter also referred to as “method 1”), or adjusting the temperature of the liquid phase in the membrane separation tank to be different from the temperature of the liquid phase in the denitrification tank (hereinafter referred to as “method”). 2 ”).

  In the method 1, the pH of the liquid phase in the membrane separation tank is adjusted by adding a pH adjusting agent such as sulfuric acid or hydrochloric acid to the membrane separation tank; the denitrification treated water obtained in the denitrification tank is This may be performed by adding the pH adjuster to denitrification water before being introduced into the membrane separation tank. When the phosphate is, for example, magnesium phosphate, sulfuric acid may be added to the denitrification water to adjust the pH to be equal to or lower than that of the denitrification tank.

  In the method 2, the temperature of the liquid phase in the membrane separation tank is adjusted so that the temperature of the liquid phase in the membrane separation tank is different from the temperature of the liquid phase in the denitrification tank. The temperature adjusting means is used. For example, the temperature adjusting means may include a jacket for circulating a cooling medium in the membrane separation tank, a pipe for circulating the cooling medium in the membrane separation tank, or heat exchange of the liquid in the membrane separation tank. For example, a heat exchanger may be installed outside the membrane separation tank. When the phosphate is, for example, magnesium phosphate, the temperature of the liquid phase in the membrane separation tank may be adjusted to be lower than the temperature of the liquid phase in the denitrification tank.

The treatment method of the water to be treated of the present invention includes, for example, anaerobic biological treatment such as methane fermentation; biological denitrification treatment such as nitrification and denitrification; aerobic biological treatment of organic matter by activated sludge method; It may further include a process such as dephosphorization treatment. As a method for treating the water to be treated of the present invention, specifically, for example,
Denitrifying biologically (by denitrifying bacteria) the water to be treated containing phosphates and phosphate ions and metal ions that can be generated from the phosphates, and nitrogen compounds or their corresponding ions. A step of obtaining denitrification treated water (hereinafter also referred to as “denitrification step”), and the denitrification treatment water obtained in the denitrification step in the membrane separation tank while being diffused, The solubility of the phosphate in the liquid phase containing denitrified water in the membrane separation tank is greater than the solubility of the phosphate in the liquid phase containing water to be treated in the denitrification tank. Step for solid-liquid separation (hereinafter also referred to as “membrane separation step”)
A method comprising:
An anaerobic organism such as methane fermentation is carried out in an anaerobic biological treatment tank containing treated water containing a phosphate or a phosphate ion and a metal ion that can be generated from the phosphate, and a nitrogen compound or a corresponding ion. A step of decomposing by treatment to obtain anaerobic biological treatment water (hereinafter also referred to as “anaerobic biological treatment step”),
The anaerobic biological treatment water obtained in the anaerobic biological treatment step and a part of the nitrification water described later are introduced into the first denitrification tank, and nitrate nitrogen in the nitrification water is removed in the first denitrification tank. , A step of biologically denitrifying using a hydrogen donor in the anaerobic biological treated water to obtain a first denitrified treated water (hereinafter referred to as “first denitrifying step”),
The first denitrification treated water obtained in the first denitrification step is biologically nitrified in a nitrification tank to obtain nitrification treated water (hereinafter referred to as “nitrification step”),
The step of biologically denitrifying the nitrification water obtained in the nitrification step in a denitrification tank to obtain denitrification water (hereinafter also referred to as “denitrification step”),
When the denitrification water obtained in the denitrification step is treated in the membrane separation tank while being diffused, the solubility of the phosphate in the liquid phase containing the denitrification water in the membrane separation tank is determined. , A step of performing solid-liquid separation with a membrane under conditions that are higher than the solubility of the phosphate in the liquid phase containing water to be treated in the denitrification tank (hereinafter also referred to as “membrane separation step”), and the membrane separation The step of dephosphorizing the membrane separation treated water obtained in the step in the dephosphorization tank (hereinafter also referred to as “dephosphorization step”)
And the like.

A treatment facility for treated water according to the present invention includes a denitrification tank for denitrifying treated water containing a phosphate or a phosphate ion that can be generated from the phosphate, a metal ion, and a nitrogen compound or the ion. ,
A membrane separation tank for solid-liquid separation by a membrane while aerating the denitrification water obtained by treatment in the denitrification tank;
In order to adjust the solubility of the phosphate in the liquid phase containing denitrified water in the membrane separation tank to be equal to or higher than the solubility of the phosphate in the liquid phase containing water to be treated in the denitrification tank Adjusting means,
Is a processing facility.

  The treatment facility of the water to be treated according to the present invention has a phosphate solubility in a liquid phase containing denitrified water in a membrane separation tank that is equal to or higher than a phosphate solubility in a liquid phase containing water to be treated in a denitrification tank. For example, a phosphate in the water to be treated or a phosphate ion and a metal ion that can be generated from the phosphate, and a nitrogen compound or a corresponding ion are included in the water to be treated. Even if it contains, the outstanding effect that the frequency of the chemical | medical agent washing | cleaning of the film | membrane accompanying use of the said treated water treatment facility can be reduced is exhibited. Furthermore, the treated water treatment facility of the present invention exhibits an excellent effect that the life of the membrane can be maintained (the membrane replacement cost can also be suppressed).

  In the treatment water treatment facility of the present invention, as the adjusting means, specifically, the pH of the liquid phase in the membrane separation tank is adjusted to be the same as the pH of the liquid phase in the denitrification tank. And a temperature adjusting means for adjusting the temperature of the liquid phase in the membrane separation tank to be different from the temperature of the liquid phase in the denitrification tank.

  When the adjustment means is a pH adjustment means, the pH adjustment means is arranged to adjust the pH of the denitrification treated water introduced from the denitrification tank into the membrane separation tank. May be.

  The pH adjusting means is provided with a pH measurement electrode in each of the preceding denitrification tank and the subsequent membrane separation tank, and the pH of the liquid phase in the membrane separation tank is equal to or more than the pH of the liquid phase in the denitrification tank. By means of injecting the acid of the pH adjusting agent so as to be a low value. In addition, injection | pouring of a pH adjuster is performed by automatically inject | pouring to a preset pH value, for example from a metering pump (diaphragm pump etc.) etc.

  When the adjusting means is a temperature adjusting means, the temperature adjusting means can be provided, for example, in a membrane separation tank.

  The temperature adjusting means is a means capable of adjusting the temperature so that the temperature of the liquid in the membrane separation tank is different from the temperature of the liquid in the denitrification tank by installing a temperature measuring device in each of the preceding denitrification tank and the subsequent membrane separation tank. I just need it. Examples of the temperature adjusting means include a mantle that circulates a cooling medium, piping that circulates the cooling medium, and a membrane separation tank as a heat exchanger for heat exchange of the liquid in the membrane separation tank. The outer jacket through which the cooling medium is circulated can be provided, for example, in a membrane separation tank. Moreover, the piping which distribute | circulates the said cooling-heat medium can be installed in a membrane separation tank, for example. Furthermore, a heat exchanger for exchanging heat in the liquid in the membrane separation tank can be installed outside the membrane separation tank. When the temperature adjusting means is a heat exchanger, for example, when the temperature of the liquid in the membrane separation tank is lowered, heat exchange between the cooling water and the liquid in the membrane separation tank is performed by the heat exchanger, thereby The temperature of the liquid in the separation tank is automatically lowered to the set temperature.

  As an example of the embodiment of the to-be-treated water treatment facility of the present invention, for example, the to-be-treated water treatment facility schematically shown in FIGS. Hereinafter, although the treatment facility of the to-be-treated water of the embodiments shown in FIGS. 1 to 3 will be described as an example, the present invention is not limited to such embodiments.

A treatment facility 1 shown in FIG. 1 treats treated water containing phosphates or phosphate ions and metal ions that can be generated from the phosphates, and nitrogen compounds or ions corresponding thereto with methane fermentation. Methane fermentation tank 2 for processing by
Biologically denitrifying a portion of nitrate nitrogen in the nitrification water obtained in the nitrification tank 4 described later using the organic matter in the methane fermentation treatment water obtained in the methane fermentation tank 2 as a hydrogen donor. A first denitrification tank 3 for
A nitrification tank 4 for biologically nitrifying the denitrification water obtained in the first denitrification tank 3,
A second denitrification tank 5 for biologically denitrifying the nitrification water obtained in the nitrification tank 4,
A membrane separation tank 6 for performing solid-liquid separation with a membrane while aeration of the denitrification water obtained in the second denitrification tank 5;
A dephosphorization tank 7 for removing phosphorus from the membrane separation treated water separated in the membrane separation tank 6 is provided. Further, in the membrane separation tank, a membrane separation device 103 for performing solid-liquid separation and an air diffusion device 102 for cleaning the membrane surface by aerating bubbles on the membrane surface of the membrane separation device 103 are installed. Further, outside the membrane separation tank, the phosphate solubility in the liquid phase containing the denitrification water in the membrane separation tank 6 is set to the phosphorus solubility in the liquid phase containing the nitrification water in the second denitrification tank 5. PH adjusting means 101a for adjusting so as to be higher than the solubility of the acid salt is attached.

In the treatment facility 1 shown in FIG. 1, the treatment water containing phosphate or a phosphate ion and a metal ion that can be generated from the phosphate, and a nitrogen compound or a corresponding ion is methane. Introduced into the fermenter 2, the treated water is treated by methane fermentation,
The methane fermentation treated water discharged from the methane fermentation tank 2 is introduced into the first denitrification tank 3 after removing impurities as necessary, and a part of the nitrification treated water obtained in the nitrification tank 4 is first. 1 Introduced into the denitrification tank 3, the nitrate nitrogen in the nitrification water is biologically denitrified using the organic matter in the methane fermentation treatment water as a hydrogen donor,
The denitrification water discharged from the first denitrification tank 3 is introduced into the nitrification tank 4, and the denitrification water is biologically nitrified,
The nitrification water discharged from the nitrification tank 4 is introduced into the second denitrification tank 5, and the nitrification water is biologically denitrified,
The denitrification treated water discharged from the second denitrification tank 5 is introduced into the membrane separation tank 6, and the solubility of the phosphate in the liquid phase containing the denitrification treated water in the membrane separation tank 6 is changed to the second denitrification tank 6. The pH of the liquid phase in the membrane separation tank 6 is adjusted by the pH adjusting means 101a so as to be equal to or higher than the solubility of phosphate in the liquid phase containing the nitrifying water in the nitrogen tank 5, and a diffuser for cleaning the membrane surface. The solid-liquid separation is performed by the membrane of the membrane separation device 103 while being diffused by 102,
The membrane separation treated water obtained in the membrane separation tank is introduced into the dephosphorization tank 7 and arranged so as to be dephosphorized, for example, by adding a chemical that reacts with phosphate ions to form a solid salt. It has the structure made. Therefore, according to the treatment facility 1 of the water to be treated shown in FIG. 1, generation of scale in the membrane of the membrane separation apparatus in the membrane separation tank can be suppressed.

  In addition, the treated water dephosphorized by adding a chemical | medical agent (for example, slaked lime) in the dephosphorization tank 7 will be discharged | emitted out of the system, after adjusting pH by adding an acid. In the said to-be-processed water processing equipment 1, since the acid of a pH adjuster is added in a membrane separation tank, the outstanding effect that the addition amount of the pH adjuster after a dephosphorization process can be reduced by that much is exhibited.

  In the treatment facility 1 shown in FIG. 1, the pH adjustment unit 101 a is introduced with denitrification water from the second denitrification tank 5, and the solubility of phosphate in the liquid phase in the membrane separation tank 6 is What is necessary is just to adjust so that it may become the pH which becomes more than the solubility of the phosphate with respect to the liquid phase containing the nitrification water in the 2nd denitrification tank 5. FIG. Thereby, according to the to-be-processed water processing equipment 1 shown in FIG. 1, the outstanding effect that generation | occurrence | production of the scale in the membrane surface of the membrane separation apparatus 103 in the membrane separation tank 6 can be suppressed is exhibited. . The pH adjusting means 101a includes a second denitrification tank pH meter 201 that measures the pH of the liquid phase in the second denitrification tank 5, a membrane separation tank pH meter 202 that measures the pH of the liquid phase in the membrane separation tank 6, A pH adjuster tank 203a and a pH adjuster adding means 204a (pump in this embodiment) for adding a pH adjuster to the liquid phase in the membrane separation tank 6, a second denitrification tank pH meter 201, and a membrane separation tank pH A control device 205 for controlling the pH adjusting agent adding means 204a based on the measured value of the total 202 is provided.

In the treated water treatment facility 1 shown in FIG. 2, a pH adjustment tank 8 is disposed between the second denitrification tank 5 and the membrane separation tank 6,
The denitrification water discharged from the second denitrification tank 5 is introduced into the pH adjustment tank 8, and the solubility of phosphate in the liquid phase containing the denitrification water in the membrane separation tank 6 is the first. 2 The pH of the liquid phase in the membrane separation tank 6 is adjusted so as to be equal to or higher than the solubility of phosphate in the liquid phase containing the nitrification water in the denitrification tank 5, and the obtained pH adjusted water is used as the membrane separation tank. 1, and the water to be treated shown in FIG. 1 is arranged so that solid-liquid separation is performed by the membrane of the membrane separation device 103 while being diffused by the air diffusion device 102. This is different from the processing facility 1.

  The pH adjusting means 101b includes a second denitrification tank pH meter 201 for measuring the pH of the liquid phase in the second denitrification tank 5, a membrane separation tank pH meter 202 for measuring the pH of the liquid phase in the membrane separation tank 6, A pH adjuster tank 203b and a pH adjuster adding means 204b (pump in this embodiment) for adding a pH adjuster to the liquid phase in the pH adjuster tank 8, a second denitrification tank pH meter 201, and a membrane separation tank pH A control device 204b for controlling the pH adjusting agent adding means 204b based on the measured value of the total 202 is provided.

The treatment facility 1 shown in FIG. 3 uses methane fermentation of treated water containing phosphate or phosphate ions and metal ions that can be generated from the phosphate, and nitrogen compounds or ions corresponding thereto. Methane fermentation tank 2 for processing by
Biologically denitrifying a portion of nitrate nitrogen in the nitrification water obtained in the nitrification tank 4 described later using the organic matter in the methane fermentation treatment water obtained in the methane fermentation tank 2 as a hydrogen donor. A first denitrification tank 3 for
A nitrification tank 4 for biologically nitrifying the denitrification water obtained in the first denitrification tank 3,
A second denitrification tank 5 for biologically denitrifying the nitrification water obtained in the nitrification tank 4,
A membrane separation tank 6 for performing solid-liquid separation with a membrane while aeration of the denitrification water obtained in the second denitrification tank 5;
A dephosphorization tank 7 for removing phosphorus from the membrane separation treated water separated in the membrane separation tank 6 is provided.

  Further, in the membrane separation tank, a membrane separation device 103 for performing solid-liquid separation and an air diffusion device 102 for aerating bubbles and cleaning the membrane surface on the membrane surface of the membrane separation device 103 are installed. Further, the solubility of the phosphate in the liquid phase containing the denitrification treated water in the membrane separation tank 6 is set in the membrane separation tank, and the solubility of the phosphate in the liquid phase containing the nitrification treated water in the second denitrification tank 5. A mantle (jacket) that is a part of the temperature adjusting means 101c for adjusting so as to be as described above and that is supplied with a cooling medium is provided. In addition to the jacket (jacket), the temperature adjusting unit 101c includes a thermometer 301 that measures the temperature of the liquid phase inside the second denitrification tank 5, and a temperature that measures the temperature of the liquid phase inside the membrane separation tank 6. There are provided a total 302, a cooling medium supply means 303 for supplying a cooling medium to a jacket (jacket), and a control device 304 for controlling the operation of the cooling medium supply means. Further, the supply amount and temperature of the cooling medium from the cooling medium supply means 303 to the jacket (jacket) are controlled by the control device 304 based on the temperatures measured by the thermometer 301 and the thermometer 302.

In the treated water treatment facility 1 shown in FIG.
Water to be treated, which may contain a phosphate or a phosphate ion and a metal ion that can be generated from the phosphate, and a nitrogen compound or a corresponding ion, is introduced into the methane fermenter 2 and the treated water Water is treated by methane fermentation,
The methane fermentation treated water discharged from the methane fermentation tank 2 is introduced into the first denitrification tank 3 after removing impurities as necessary, and a part of the nitrification treated water obtained in the nitrification tank 4 is first. 1 Introduced into the denitrification tank 3, the nitrate nitrogen in the nitrification water is biologically denitrified using the organic matter in the methane fermentation treatment water as a hydrogen donor,
The denitrification water discharged from the first denitrification tank 3 is introduced into the nitrification tank 4, and the denitrification water is biologically nitrified,
The nitrification water discharged from the nitrification tank 4 is introduced into the second denitrification tank 5, and the nitrification water is biologically denitrified,
The temperature adjusting means 101c allows the denitrification treated water discharged from the second denitrification tank 5 to be equal to or higher than the solubility of phosphate in the liquid phase containing the nitrification treated water in the second denitrification tank 5. Solid-liquid separation is performed by the membrane of the membrane separation device 103 while being introduced into the membrane separation tank 6 in which the temperature of the liquid phase is adjusted and diffused by the air diffusion device 102,
The membrane separation treated water obtained in the membrane separation tank 6 is introduced into the dephosphorization tank 7 so that it is dephosphorized by adding a chemical that reacts with phosphate ions to form a solid salt, for example. It has an arranged configuration. Therefore, according to the treatment facility 1 of the water to be treated shown in FIG. 3, it is possible to suppress the generation of scale in the membrane of the membrane separation device in the membrane separation tank.

  In the treatment water treatment facility 1 shown in FIG. 3, the temperature adjusting means 101 c is arranged so that the temperature of the liquid phase inside the membrane separation tank 6 is relative to the liquid phase containing the nitrification water in the second denitrification tank 5. Any arrangement may be used as long as the temperature is adjusted to be equal to or higher than the solubility of phosphate. Thereby, according to the to-be-processed water processing equipment 1 shown in FIG. 3, the outstanding effect that generation | occurrence | production of the scale in the membrane surface of the membrane separation apparatus 103 in the membrane separation tank 6 can be suppressed is exhibited. .

  In the membrane separation apparatus 103 applied to the present invention, the type of membrane is an ultrafiltration (UF) membrane, a microfiltration (MF) membrane, etc., and the form is a hollow fiber membrane, a flat membrane, etc. Examples of the material of the film include, but are not particularly limited to, a fluororesin (for example, PVDF), polypropylene, polyethylene, and the like.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to these Examples.

(Example 1)
In the treatment facility 1 shown in FIG. 4, the treated water (raw water), the first denitrification tank 3, the nitrification tank 4 (4a to 4c), the second denitrification tank 5 (denitrification tank in the present invention), and the membrane The pH of the liquid phase of each separation tank 6, the calcium ion concentration, the magnesium ion concentration, the sulfate ion concentration, and the phosphate ion concentration in the liquid phase were measured. The calcium ion concentration was measured by flame atomic absorption spectrometry (JIS K0102 50.2). Magnesium ion concentration was measured by flame atomic absorption spectrometry (JIS K0102 51.2). The sulfate ion concentration was measured by an ion chromatographic analysis method (JIS K0102 41.3). The phosphate ion concentration was measured by molybdenum blue (ascorbic acid reduction) absorptiometry (JIS K0102 46.1.1). The raw water was methane fermentation treated water that was a mixture of raw garbage, manure and sewage sludge, and scale was generated on the membrane surface of the membrane separation device 103 of the membrane separation tank 6. The membrane separator 103 was an MF membrane (PVDF hollow fiber membrane). The results are shown in FIG. 5 and FIG. 5 and 6, DN 1 indicates the first denitrification tank 3, N 1 indicates the nitrification tank 4 a, N 2 indicates the nitrification tank 4 b, N 3 indicates the nitrification tank 4 c, and DN 2 indicates the second denitrification tank 5.

  As a result, as shown in FIG. 5 and FIG. 6, the magnesium ion concentration (legend of FIG. 5: black square) and phosphate ion concentration with a slight change in pH from the second denitrification tank 5 to the membrane separation tank 6. (Legend in FIG. 6: black triangles) is reduced, so it is considered that magnesium phosphate is precipitated in the membrane separation tank 6. Therefore, it is suggested that generation of scale on the membrane surface of the membrane separation apparatus 103 in the membrane separation tank 6 can be suppressed by maintaining the solubility of magnesium phosphate in the membrane separation tank 6 high.

(Example 2)
The membrane surface of the membrane separation device 103 in the membrane separation tank 6 in the treatment water treatment facility 1 shown in FIG. 4 is subjected to an energy dispersive X-ray fluorescence analyzer (trade name: EMAX-5770W, manufactured by Horiba, Ltd.). The sample was analyzed under the conditions of acceleration voltage: 15 kV, analysis method: point analysis, measurement time: 100 seconds. The result is shown in FIG.

  As a result, as shown in FIG. 7, magnesium, phosphorus, and oxygen are present on the film surface, and carbon and fluorine, which are components of the film, are not detected and are other components contained in the water to be treated. It can be seen that calcium, sulfur and nitrogen are also not detected. Thus, it is suggested that the scale component is magnesium phosphate.

(Test Example 1)
The pH and temperature of the liquid phase of each of the second denitrification tank 5 and the membrane separation tank 6 of the treatment water treatment facility 1 shown in FIG. 4 were measured. The pH of the liquid phase of the second denitrification tank 5 is 7.8, the temperature is 40 ° C., the pH of the liquid phase of the membrane separation tank 6 is 8.1, and the temperature is 40 ° C. It was.

  Moreover, the solubility of the magnesium phosphate in each liquid phase of the 2nd denitrification tank 5 and the membrane separation tank 6 at this time was measured. As a result, the solubility of magnesium phosphate in the liquid phase of the second denitrification tank 5 was 281 mg / l, and the solubility of magnesium phosphate in the liquid phase of the membrane separation tank 6 was 252 mg / l.

  Next, sulfuric acid (concentration: 10% by weight) was added to the liquid phase of the membrane separation tank 6 without changing the temperature of the liquid phase of the membrane separation tank 6 of the treatment facility 1 (liquid temperature 40 ° C.) 2 It adjusted so that it might become the same pH (pH 7.8) as the pH of the liquid phase of the denitrification tank 5. Thereafter, the solubility of magnesium phosphate and the amount of precipitated magnesium phosphate were measured. Table 1 shows these results (the solubility of magnesium phosphate in the liquid phase of the membrane separation tank 6 and the amount of precipitated magnesium phosphate), and the temperature and pH of the liquid phase of the membrane separation tank 6.

(Test Example 2)
As in Test Example 1, first, the pH and temperature of the liquid phase of each of the second denitrification tank 5 and the membrane separation tank 6 of the treatment facility 1 shown in FIG. 4 were measured. The pH of the liquid phase of the second denitrification tank 5 was 7.8, and the temperature was 40 ° C. Moreover, pH of the liquid phase of the membrane separation tank 6 was 8.1, and temperature was 40 degreeC. Moreover, the solubility of the magnesium phosphate in each liquid phase of the 2nd denitrification tank 5 and the membrane separation tank 6 at this time was measured. The solubility of magnesium phosphate in the liquid phase of the second denitrification tank 5 was 281 mg / l, and the solubility of magnesium phosphate in the liquid phase of the membrane separation tank 6 was 252 mg / l.

  Next, the pH of the liquid phase in the membrane separation tank 6 of the treatment facility 1 is not changed (pH 8.1), the temperature of the liquid phase in the membrane separation tank 6 is passed through the heat exchanger. After cooling, the cooled liquid was returned to the membrane separation tank to adjust to a temperature (30 ° C.) lower by 10 ° C. than the liquid phase temperature of the second denitrification tank 5. Thereafter, the solubility of magnesium phosphate was measured. Table 2 shows these results (the solubility of magnesium phosphate in the liquid phase of the membrane separation tank 6 and the amount of precipitated magnesium phosphate), and the temperature and pH of the liquid phase of the membrane separation tank 6.

  As a result, by adjusting the pH of the liquid phase of the membrane separation tank 6 to be equal to or lower than that of the second denitrification tank 5, it is possible to prevent the generation of scale on the membrane surface of the membrane separation apparatus 103 in the membrane separation tank 6. Recognize. Further, if the temperature of the liquid phase in the second denitrification tank 5 is in the range of 20 to 40 ° C., that is, the temperature range in which biological denitrification treatment is performed, the temperature of the liquid phase in the membrane separation tank 6 is changed to the second denitrification tank 6. It can be seen that the generation of scale on the membrane surface of the membrane separation apparatus 103 in the membrane separation tank 6 can be prevented by adjusting the temperature lower than the nitrogen tank 5 by 10 ° C. or more.

  The present invention can be used for water treatment of waste liquid that may contain, for example, phosphates or phosphate ions and metal ions that can be generated from the phosphates, and nitrogen compounds or corresponding ions. it can.

FIG. 1 is a schematic view showing an embodiment of the treatment facility for water to be treated according to the present invention. FIG. 2 is a schematic view showing an embodiment of the treatment facility for water to be treated according to the present invention. FIG. 3 is a schematic view showing one embodiment of the treatment facility for water to be treated according to the present invention. FIG. 4 is a schematic diagram illustrating an example of the treatment facility of water to be treated. 5 shows the water to be treated (raw water), the first denitrification tank 3, the nitrification tank 4 (4a to 4c), the second denitrification tank 5 and the membrane separation tank 6 of the treatment equipment 1 shown in FIG. FIG. 6 is a graph showing fluctuations in pH of each liquid phase (legend: black circle), calcium ion concentration (legend: black triangle), and magnesium ion concentration (legend: black square) in the liquid phase. In the figure, DN1 indicates a first denitrification tank 3, N1 indicates a nitrification tank 4a, N2 indicates a nitrification tank 4b, N3 indicates a nitrification tank 4c, and DN2 indicates a second denitrification tank 5. 6 shows the water to be treated (raw water), the first denitrification tank 3, the nitrification tank 4 (4a to 4c), the second denitrification tank 5, and the membrane separation tank 6 of the treatment equipment 1 shown in FIG. FIG. 6 is a graph showing fluctuations in pH of the liquid phase (legend: black circle), sulfate ion concentration (legend: black triangle) and phosphate ion concentration (legend: black square) in the liquid phase. In the figure, DN1 indicates a first denitrification tank 3, N1 indicates a nitrification tank 4a, N2 indicates a nitrification tank 4b, N3 indicates a nitrification tank 4c, and DN2 indicates a second denitrification tank 5. FIG. 7 is a diagram showing an energy dispersive X-ray fluorescence analysis result of the membrane surface of the membrane separation device 103 in the membrane separation tank 6 of the treatment facility 1 of the water to be treated shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Processing equipment of treated water 2 Methane fermentation tank 3 1st denitrification tank 4 Nitrification tank 5 2nd denitrification tank 6 Membrane separation tank 101 Adjustment means 102 Aeration apparatus 103 Membrane separation apparatus

Claims (8)

Denitrification treated water obtained by treating in a denitrification tank membranes treated water containing phosphate ions and metal ions that can be generated from the phosphates, and nitrogen compounds or corresponding ions. When processing with aeration in the separation tank,
Membrane separation under conditions where the solubility of the phosphate in the liquid phase containing denitrified water in the membrane separation tank is equal to or higher than the solubility of the phosphate in the liquid phase containing water to be treated in the denitrification tank A method for treating water to be treated, characterized in that:   The method for treating water to be treated according to claim 1, wherein the pH of the liquid phase in the membrane separation tank is adjusted to be at least the same as the pH of the liquid phase in the denitrification tank.   The processing method of the to-be-processed water of Claim 1 which adjusts the temperature of the liquid phase in this membrane separation tank so that it may differ with respect to the temperature of the liquid phase in this denitrification tank. A denitrification tank for denitrifying water to be treated containing phosphate ions, metal ions and nitrogen compounds or ions thereof, which can be generated from the phosphates;
A membrane separation tank for solid-liquid separation by a membrane while aerating the denitrification water obtained by treatment in the denitrification tank;
In order to adjust the solubility of the phosphate in the liquid phase containing denitrified water in the membrane separation tank to be equal to or higher than the solubility of the phosphate in the liquid phase containing water to be treated in the denitrification tank Adjusting means,
A facility for treating water to be treated.   The treated water according to claim 4, wherein the adjusting means is a pH adjusting means for adjusting the pH of the liquid phase in the membrane separation tank to be the same as the pH of the liquid phase in the denitrification tank. Processing equipment.   The treatment of water to be treated according to claim 5, wherein the pH adjusting means is arranged so as to adjust the pH of the denitrification treated water introduced from the denitrification tank into the membrane separation tank. Facility.   The to-be-processed object of Claim 4 which is a temperature adjustment means for this adjustment means to adjust the temperature of the liquid phase in this membrane separation tank so that it may differ with respect to the temperature of the liquid phase in this denitrification tank. Water treatment facility.   The processing equipment according to claim 4, wherein the temperature adjusting means is provided around the membrane separation tank.

Images