JP7226731B2 - Processing method of the object to be processed - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for treating an object to be treated, and more particularly to a method for treating an object to be treated containing organic substances and soluble salts.

Materials to be treated, such as leachate from final waste disposal sites, leachate from landfill sites for industrial waste, etc., contain various organic matter and salt content. It is important from the point of view, and various proposals have been made for the processing method. For example, Patent Document 1 proposes methane fermentation treatment of organic wastewater, aerobic biological treatment of the resulting methane fermentation treated water, and solid-liquid separation of the mixed liquid after the aerobic biological treatment. Solid-liquid separation is carried out, for example, by means of settling tanks carrying out aerobic biological treatment (solid components settle). Further, Patent Document 2 discloses that organic wastewater containing ammoniacal nitrogen (which is strictly regulated by environmental standards) and soluble salts is treated using a nitrification reaction, and the resulting nitrified water is evaporated. I suggest concentrating.

JP 2012-061435 A JP 2006-239578 A

The present inventors have investigated the components of various materials to be treated (waste, wastewater, etc.) and found that the materials to be treated sometimes contain a large amount of organic substances and salts (soluble salts). I found out. Here, environmental standards are stipulated for organic substances such as BOD, and salt content may cause salt damage at the discharge destination if it is treated and discharged as wastewater without sufficiently removing it.

However, Patent Document 1 does not describe the salt content (for example, halogen elements such as chlorine and fluorine) contained in the organic wastewater. Specifically, as a specific example of aerobic biological treatment, the batch-type activated sludge method (which may be referred to as the "SBR method" in this specification) is cited, but the composition of the organic wastewater, which is the raw water for treatment, , only examples of BOD, COD, ammonia, phosphorus, etc. are disclosed, and there is no description of salinity, and it is considered that attention is not paid to salinity. Since the method described in Patent Document 1 is a biological treatment using microorganisms, when a large amount of salt is contained in the object to be treated, it cannot be sufficiently removed.

On the other hand, US Pat. No. 6,200,000 describes the treatment of organic wastewaters containing ammoniacal nitrogen and soluble salts. Specifically, the organic wastewater undergoes a nitrification reaction by aerobic biological treatment to obtain nitrification-treated water, and the pH value of the obtained nitrification-treated water is adjusted to 4 to 6 to suppress the generation of calcium carbonate scale. It is proposed to carry out evaporative concentration while avoiding. However, if the material to be treated contains a large amount of organic matter, it must be subjected to aerobic biological treatment, which increases the load on the microorganisms used in the treatment, and requires the replenishment and replacement of microorganisms. process may be required. This is a problem in the actual operation of processing the material to be processed.

The present invention has been made under such circumstances, and the problem to be solved is to appropriately treat even an object to be treated that contains a large amount of organic matter, ammonia, and soluble salts. To provide a method for treating an object to be treated, which can be operated at a low operating cost.

According to the research of the present inventors, in the treatment method described in Patent Document 2, the nitrification-treated water adjusted to pH 4 to 6 is evaporated and concentrated, and nitrification containing a conjugate base of a strong acid such as chloride ions is performed. The treated water will be kept in the evaporator in an acidic state and at a high temperature, in which case the conjugate base becomes corrosive. This necessitates the use of high-cost materials with excellent corrosion resistance such as Hastelloy (registered trademark) in the evaporative concentration apparatus, leading to an increase in facility costs. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method for treating an object to be treated, which is desirably capable of constructing a treatment apparatus without using high-cost materials even when the object to be treated contains a conjugate base of a strong acid. and

In order to solve the above-mentioned problems, the present inventors conducted further research.
Then, by changing the conventional technical concept, the digestion process (methane fermentation treatment by anaerobic organisms), the nitrification process (aerobic biological treatment), and the evaporative concentration process are sequentially performed on the material to be treated that contains organic matter, ammonia, and soluble salts. The present inventors have found that the above problems can be solved by performing

That is, the first invention for solving the above problems is
A method for treating an object to be treated containing organic matter, ammonia, and soluble salts,
a methane fermentation step of decomposing organic matter in the material to be treated to obtain methane fermentation-treated water by a methane fermentation method;
an aerobic biological treatment step of oxidizing ammonia in the methane fermentation-treated water into nitric acid by the action of aerobic organisms and decomposing organic matter to obtain nitrification-treated water;
and an evaporative concentration step for obtaining concentrated water and condensed water by evaporatively concentrating the nitrification treated water.
The second invention is
The method for treating an object to be treated according to the first invention, characterized in that the aerobic biological treatment step is carried out by a batch activated sludge method.
The third invention is
The method for treating an object to be treated according to the first or second invention, characterized in that the pH value of the nitrification-treated water to be subjected to the evaporative concentration step is adjusted to 8.5 or higher.
The fourth invention is
The ammonia concentration in the methane fermentation treated water is 10 to 10000 ppm in terms of nitrogen, the Cl ⁻ concentration is 1 to 50000 ppm, the COD is 10 to 100000 ppm, and the BOD is 10 to 10000 ppm. A method for processing an object to be processed according to any one of the above.
The fifth invention is
The method for treating an object to be treated according to any one of the first to fourth inventions, characterized in that the aerobic biological treatment step provides nitrified water having an ammonia concentration of 10 ppm or less in terms of nitrogen.
The sixth invention is
The method for treating an object to be treated according to any one of the third to fifth inventions, wherein the pH value of the nitrified water is adjusted to 8.5 or higher by adding an alkaline substance to the nitrified water. is.
The seventh invention is
A method for treating water to be treated having an ammonia concentration of 10 to 10,000 ppm in terms of nitrogen, a Cl ⁻ concentration of 1 to 50,000 ppm, a COD of 10 to 100,000 ppm, and a BOD of 10 to 10,000 ppm,
an aerobic biological treatment step of oxidizing ammonia in the water to be treated into nitric acid by the action of aerobic organisms and decomposing organic matter to obtain nitrified water;
an evaporative concentration step of evaporatively concentrating the nitrification-treated water to obtain concentrated water and condensed water;
The method for treating water to be treated is characterized in that the pH value of the nitrification-treated water to be subjected to the evaporative concentration step is adjusted to 8.5 or higher.

According to the present invention, even an object to be treated containing a large amount of organic substances, ammonia, and soluble salts can be treated appropriately, and can be operated at a low operating cost.

FIG. 2 is an operation flow diagram of a processing method according to the present invention; It is an appearance photograph of a nitrification-treated water sample, a concentrated water sample, and a condensed water sample. The schematic diagram of the processing apparatus used for the Example.

As described above, the present invention makes it possible to appropriately treat even an object to be treated containing a large amount of organic matter, ammonia, and soluble salts, and to operate at a low operating cost. Disclosed is a processing method for a processed material. Accordingly, the present invention will be described with reference to FIG. 1 showing the operation flow of the processing method according to the present invention.

As shown in FIG. 1, the present invention performs a methane fermentation step (20), an aerobic biological treatment step (30), and an evaporative concentration step (40) on an object to be treated (10) to produce condensation that can be discharged water. Water (41) and contaminant concentrated water (42) are obtained. In the present invention, the pH of the nitrified water (31) obtained in the aerobic biological treatment step (30) may be adjusted (32) as necessary.

Below, 1. object to be processed;2. 3. methane fermentation process; 4. aerobic biological treatment process; 4. Evaporative concentration step; 6. different embodiments; In the following order, the present invention will be described in detail.

1. Object to be treated The object to be treated containing organic matter, ammonia, and soluble salts to be treated by the present invention includes, for example, organic matter such as proteins, amino acids, nucleic acids, sugars, and fatty acids, ammonia, and soluble salts. . Specific examples include solid materials such as various wastes, and liquid materials such as leachate from waste landfill sites. These materials to be treated cause pollution of the environment when released into the environment.

2. Methane Fermentation Process In the present invention, a methane fermentation process using a methane fermentation method utilizing the action of methanogenic bacteria is carried out. Methane fermentation decomposes organic matter in the material to be treated. This organic matter includes organic matter that is difficult to decompose by aerobic organisms in the next aerobic biological treatment process, but it is decomposed by methane fermentation and becomes a substance that can be decomposed even by aerobic organisms. It is sent to the aerobic biological treatment process.

In industrial waste disposal sites and landfill sites where waste food, etc., is buried as buried matter, methane bacteria may exist in the buried matter, and organic matter in the buried matter may be decomposed by methane fermentation. be. In the present invention, such spontaneous methane fermentation may be considered as a methane fermentation process that produces digestive juice as methane fermentation treated water (21).

The properties and composition of the methane fermentation-treated water are as follows from the viewpoint that the effects of the present invention are favorably exhibited.

That is, from the viewpoint of suitably exhibiting the effects of the present invention, the pH value of the methane fermentation-treated water is preferably 4 to 11, more preferably 4.2 to 10.8, and still more preferably 4.5 to 10.5. is.
From a similar point of view, the amount of total soluble solids in the methane fermentation-treated water (which may be referred to as "TDS" in this specification) is preferably 10 to 100,000 ppm, more preferably 500 to 100,000 ppm, and still more preferably 8,000 ppm. ~80000ppm.
From a similar point of view, the concentration of ammonia in the methane fermentation-treated water is preferably 10 to 10,000 ppm, more preferably 100 to 10,000 ppm, and still more preferably 300 ppm in terms of nitrogen (that is, the concentration of ammonia nitrogen (NH ₃ —N)). ~9000ppm.
From a similar point of view, the chemical oxygen demand (COD) of methane fermentation treated water is preferably 10 to 100000 ppm, more preferably 1000 to 100000 ppm, still more preferably 5000 to 80000 ppm.
From the same point of view, the biological oxygen demand (BOD) of methane fermentation treated water is preferably 10 to 10000 ppm, more preferably 500 to 10000 ppm, still more preferably 1000 to 9000 ppm.
From a similar point of view, the concentration of hydrogen sulfide (H ₂ S) in the methane fermentation-treated water is preferably 1-100 ppm, more preferably 2-95 ppm, and still more preferably 3-90 ppm.
From the same point of view, the concentration of sulfate ions (SO ₄ ²⁻ ) in the methane fermentation-treated water is preferably 10-10000 ppm, more preferably 300-10000 ppm, still more preferably 1000-8000 ppm.
From the same point of view, the chloride ion (Cl ⁻ ) concentration in the methane fermentation-treated water is preferably 1 to 50000 ppm, more preferably 500 to 50000 ppm, still more preferably 6000 to 45000 ppm.
From the same point of view, the concentration of calcium ions (Ca ²⁺ ) in the methane fermentation-treated water is preferably 1 to 10000 ppm, more preferably 2 to 9000 ppm, still more preferably 3 to 8000 ppm.
From the same point of view, the sodium ion (Na ⁺ ) concentration in the methane fermentation-treated water is preferably 1 to 10000 ppm, more preferably 2 to 9500 ppm, and still more preferably 3 to 9000 ppm.

3. Aerobic biological treatment step and pH adjustment In the aerobic biological treatment step (30), ammonia in the methane fermentation-treated water (digestive juice) (21) obtained in the methane fermentation step (20) is converted to nitrite by the action of microorganisms. It is a step of oxidizing to nitric acid (nitrification) through the process and decomposing organic matter in the treated water to obtain nitrified water (31). Various methods such as a continuous method and a circulation method are known as methods for carrying out such a reaction, and the SBR method is known as a highly efficient treatment method. Therefore, the aerobic biological treatment step (30) will be described below with reference to the SBR method as an example of the nitrification treatment method.

The SBR method is an aerobic treatment that integrates the functions of an aeration tank and a final sedimentation tank into a single reaction tank. Specifically, in a reaction tank containing activated sludge, <<1>> introduction of methane fermentation treated water to be treated, <<2>> aeration treatment, <<3>> sedimentation separation, <<4>> nitrification treated water as supernatant wastewater, and each treatment is performed sequentially.

Since ammonia cannot be removed in the evaporative concentration step (40) following the aerobic biological treatment step (30), it is preferable to sufficiently treat ammonia by the SBR method. Specifically, it is preferable to perform a sufficient aeration treatment so that the ammonia concentration in the nitrified water (31) obtained in this step is 10 ppm or less in terms of nitrogen. From the viewpoint of achieving such a low ammonia concentration and reducing the treatment cost, as a guideline, the residence time in the aeration treatment by the SBR method is preferably 6 to 30 days.

By performing the SBR process, the numerical values such as BOD, COD, and TDS in the methane fermentation treated water (21) and the ammonia concentration are reduced. In addition, if the ammonia concentration is sufficiently reduced in this step, it is preferable in that it becomes unnecessary to perform expensive processes such as stripping and reverse osmosis membrane treatment in order to remove ammonia thereafter.

According to the studies of the present inventors, when the pH value of the nitrification treated water (31) is less than 8.5, the pH value is adjusted to 8.5 or higher by adjusting the pH value (32) by adding an appropriate alkaline substance or the like. preferably. In addition, the methane fermentation-treated water (21) obtained in the methane fermentation step (20) or the You may add an alkaline substance in the middle of receiving a process by. This is from the viewpoint of avoiding corrosion of the inside of the evaporative concentration apparatus by the strong acid conjugate base such as Cl ^{2 -} contained in the nitrification treated water (31) in "4. Evaporative concentration step" described later. As the alkaline substance, sodium hydroxide is preferable because it is inexpensive and highly versatile.

Although the embodiment has been described by exemplifying the SBR method as the aerobic biological treatment process (30), it is also possible to adopt a continuous activated sludge method or the like for part or all of the aerobic biological treatment process (30). be.

4. Evaporative Concentration Step In the evaporative concentration step (40), the nitrification treated water (31) is thermally distilled in a closed vessel (evaporator) under reduced pressure to concentrate, for example, 2 times or more and 40 times or less by volume. (42) and a step of obtaining condensed water (41) after evaporation.

The evaporative concentration apparatus used in the process is not particularly limited. For example, the steam compression brine distiller described in JP-A-59-26184 (a steam compression brine distiller equipped with a horizontal heat transfer tube and a steam compressor), the self described in JP-A-10-57702 An evaporative compression type concentrator (a concentrator capable of two-stage compression by two compression means), a vacuum evaporator described in JP 2011-185192 A (a vacuum evaporator equipped with a roots blower), etc. are used in the process. Can be used as an evaporator.

Regarding the evaporation conditions in the evaporative concentration step (40), it is preferable to set the liquid temperature in the evaporator to 60 to 70° C. and the pressure in the evaporator to 5 to 50 kPaabs from the viewpoint of reducing the operating cost. The concentration ratio of the concentrated water (42) obtained in this step is preferably 2 to 20 times by volume from the viewpoint of reducing operating costs.

In order to remove coloring components (e.g., azo compounds) from the nitrified water (31), a decolorization process using an inorganic flocculant and a polymer flocculant may be carried out. Not only can TDS and COD be reduced, but also coloring components can be removed at the same time, and the operating cost can be reduced. In addition, since the soluble salts contained in the nitrification treated water (31) do not evaporate, they remain in the concentrated water (42) without being transferred to the condensed water (41).

From the above, the values of BOD, TDS, and COD are reduced from the object to be treated containing organic matter, ammonia, and soluble salts, and the condensed water ( 41) and a concentrated water (42) to be disposed of appropriately could be obtained at low equipment and operating costs.

Here, as explained in the above "pH adjustment", in the present invention, preferably the pH of the nitrification treated water (31) is adjusted to alkaline, preferably to 8.5 or higher (32), and then the evaporative concentration step (40). , the pH value of the generated concentrated water (42) becomes 9 or more and 13 or less inside the evaporative concentration device. As a result, in the concentrated water (42), the conjugate bases of strong acids such as ^Cl.sup.- do not exhibit corrosiveness, so there is no need to use expensive materials with excellent corrosion resistance for the evaporative concentration device, and the cost of the device can be reduced. This is preferable because it leads to cost reduction.

On the other hand, when the pH of the liquid to be subjected to evaporative concentration is made acidic as in Patent Document 2 to prevent calcium carbonate scale, water containing a conjugate base of a strong acid such as Cl ^- ) will be retained in the evaporative concentration apparatus, and Cl ^{2 −} and the like will exhibit strong corrosiveness. As a result, it is necessary to use an expensive material such as Hastelloy for the evaporative concentration apparatus, which is highly resistant to corrosion, which leads to an increase in the cost of the apparatus.

In the present invention, the pH of the nitrification-treated water (31) is preferably 8.5 or higher in view of the increase in equipment cost. In order to carry out the evaporative concentration step (40), scale is generated inside the evaporative concentration apparatus. The scale is considered to be mainly composed of calcium carbonate. Accumulation of the scale lowers the heat transfer coefficient of the evaporative concentration apparatus, requiring maintenance to remove the scale.

According to the studies of the present inventors, it was found that the scale generated inside the evaporative concentration apparatus in the present invention can be easily dissolved with chemicals, maintenance is easy, and it hardly leads to an increase in operating costs.

The reason why the scale generated inside the evaporative concentration apparatus can be easily dissolved in the present invention is presumed as follows.

That is, in the present invention, the pH of the nitrified water (31) is preferably adjusted (32) to an alkalinity of 8.5 or higher, so CO ₃ ²⁻ in the nitrified water (31) is converted to CO ₂ It stays without volatilizing. Therefore, Ca ²⁺ which is a scale component reacts with CO ₃ ^2- to produce calcium carbonate. The produced calcium carbonate then combines and reacts with CO ₃ ²⁻ in the nitrification treated water (31) [CaCO ₃ →Ca(HCO ₃ ) ₂ ] to become calcium bicarbonate, and the produced scale is easily dissolved.・I think it will be removed.

When the object to be treated (10) contains SO ₄ ^2- , the nitrification treated water (31) contains SO ₄ ^2- , and when Ca ²⁺ forms scale, the gypsum becomes a strong scale. (CaSO ₄ ) can occur. However, as described above, the nitrified water (31) having a pH value of 8.5 or more contains abundant CO ₃ ²⁻ , and Ca ²⁺ preferentially reacts with this, thus suppressing the formation of gypsum. From the viewpoint of easily removing the scale in this way, the amount of CO ₃ ^2- in the nitrification treated water (31) is preferably 180 to 900 ppm, more preferably 200 to 800 ppm, as total inorganic carbon (TIC). .

When the concentration of soluble salts contained in the material to be treated (10) or the methane fermentation treated water (21) is high (as a result, the concentration of soluble salts in the nitrification treated water (31) is also high), Easy descaling is achievable.

On the other hand, it is also preferable to previously add fine crystals of calcium carbonate as seed crystals to the nitrification-treated water (31). This is because the amount of calcium carbonate deposited on the inner wall of the evaporative concentration apparatus can be reduced by preliminarily adding the seed crystals so that the generated calcium carbonate is deposited around the seed crystals.

5. Different Embodiments As described above, the methane fermentation step (20), the aerobic biological treatment step (30), and the evaporative concentration step (40) are performed on the material to be treated (10) (suitable for the pH of the nitrification treated water (31). The method for treating the object (10) has been described, in which the pH adjustment (32) is performed), purified treated water (condensed water (41)) and concentrated water (42) are obtained.

The technical idea of the present invention is also applicable to, for example, wastewater (23) generated through methane fermentation, shown as biogas power generation, etc. (22) in FIG. In this case, the waste water (23) or the like may be subjected to an aerobic biological treatment process (30) and an evaporative concentration process (40).

Further, a still different embodiment of the present invention focusing on preferably setting the pH value of the nitrification-treated water to 8.5 or more is as follows.

"A method for treating water to be treated containing organic matter, ammonia, and soluble salts,
an aerobic biological treatment step of oxidizing ammonia in the water to be treated into nitric acid by the action of aerobic organisms and decomposing organic matter to obtain nitrified water;
a pH adjustment step of setting the pH value of the nitrification-treated water to 8.5 or higher;
A method for treating water to be treated, characterized by comprising an evaporative concentration step of evaporatively concentrating the nitrification-treated water whose pH value has been adjusted to obtain concentrated water and condensed water. "

In the configuration of this embodiment, predetermined water to be treated (wastewater) is subjected to nitrification treatment (aerobic biological treatment process), and the obtained nitrification treated water has a pH value of 8.5 or higher. Even in this configuration, the calcium carbonate scale generated in the evaporative concentration apparatus can be easily removed by an appropriate method, and it hardly leads to an increase in operating costs. Moreover, this can be achieved even when the concentration of soluble salts contained in the water to be treated is high.

As described above, the TDS and COD values are reduced from the object to be treated (10) containing ammonia and soluble salts, or the wastewater (23) generated from the process using methane fermentation, and the solubility is reduced. It is possible to obtain condensed water (41) that does not contain salts and has a colorless and transparent appearance and that can be released to the environment and concentrated water (42) that should be properly disposed of at low equipment and operating costs. rice field.

Different embodiments of the invention focusing on the above effects are as follows.

"Ammonia concentration is 10 to 10000 ppm in terms of nitrogen, Cl ⁻ concentration is 1 to 50000 ppm, COD is 10 to 100000 ppm, BOD is 10 to 10000 ppm.
an aerobic biological treatment step of oxidizing ammonia in the water to be treated into nitric acid by the action of aerobic organisms and decomposing organic matter to obtain nitrified water;
an evaporative concentration step of evaporatively concentrating the nitrification-treated water to obtain concentrated water and condensed water;
A method for treating water to be treated, wherein the pH value of the nitrified water to be subjected to the evaporative concentration step is adjusted to 8.5 or higher. "

Note that the configurations described in the embodiments of the present invention may be appropriately combined with each of the configurations of the different embodiments of the invention described above.

6. Summary As described in detail above, according to the present invention, it is possible to treat an object containing organic substances, ammonia and soluble salts at low equipment and operating costs.

The present invention will be specifically described below with reference to examples.

(Example 1)
Landfill leachate was obtained as an example sample. The presence of methanobacteria has been confirmed in the landfill site, and the leachate is digestive fluid that has undergone methane fermentation. The properties and composition of the digestive juice sample are shown in Table 1, "Column of Example Digestive Juice".

The digested liquid sample was processed by a series of apparatuses having an SBR tank 50, a clarification pond 60 for an evaporative concentration facility, and an evaporative concentration facility 70, the schematic diagram of which is shown in FIG. The first embodiment will be described below with reference to the apparatus shown in FIG.

A digested liquid sample 51 of 80 m ³ was supplied to an SBR tank 50 having a volume of 1000 m ³ (sludge volume 40%). The dissolved oxygen concentration in the liquid in the SBR tank 50 immediately after the supply was 0 ppm.

Air 53 was blown into the SBR tank 50 using a blower (pump) 52 to start the aeration treatment. The end point of the aeration was controlled by dissolved oxygen concentration. The dissolved oxygen concentration at the completion of treatment was 5 ppm.

After the aeration treatment was completed, the aeration was stopped to allow the activated sludge 55 containing the nitrification treated water to settle, and then the supernatant (nitrification treated water sample 61) was obtained. The nitrification-treated water sample 61 was sent by the pump 54 to the clear pond 60 for evaporative concentration equipment. When the pH value of the nitrified water sample 61 was measured, it was 8.5. The pH value is measured using a HORIBA pH meter F-16. If the temperature at the time of measurement is 25°C, the actual measured value is used. The pH value at 25°C was determined.

Since ammonia is converted to nitric acid by the aeration treatment, the pH value of the nitrification-treated water sample 61 is considered to decrease from the original 8.3, but on the contrary, it increased. This pH increase may be caused by some component in the aerated digestive fluid sample 51 or by the influence of microorganisms in the SBR tank 50 (conversion from nitric acid to nitrogen).

The properties of the nitrified water sample 61 are shown in Table 1, "Nitrified water column". The appearance of the nitrified water sample 61 is shown in FIG. In addition, each characteristic regarding the properties of the nitrification-treated water, etc. in Tables 1 and 2 was measured as follows.

TDS was measured on total dissolved solids with an Orion ^™ Versa Star Pro ^™ pH/Conductivity desktop multi-parameter meter.
The concentration of ammonium nitrogen (NH ₃ —N) was measured by an ion electrode method (Orion ^TM Versa Star Pro ^TM , manufactured by Thermo Fisher).
COD was measured by the Nichromic acid method (COD _Cr ).
Total inorganic carbon (TIC) was obtained by measuring total carbon and total organic carbon with a TOC meter (TOC-L, manufactured by Shimadzu Corporation) and taking the difference between them.
BOD was measured according to the method defined in JIS K 0102.
Hydrogen sulfide was measured by the cadmium acetate method.
Sulfate and chloride ions were determined by ion chromatography.
Metal elements (calcium ions and sodium ions) were measured by an inductively coupled plasma emission spectrometer (ICP-AES, ICAP-7000 manufactured by Thermo fisher).

In this example, VVCC-90 manufactured by Sasakura Co., Ltd. was used as the evaporative concentration equipment 70 . The heat transfer tube 71 of this device is made of titanium, and the evaporator 72 is made of SUS316L. In addition, the device is equipped with a heat pump 73 to compress the evaporated vapor and recover latent heat. The recovered heat is reused for heating the supernatant again or as evaporation heat.

Regarding the operating conditions of this apparatus, the degree of vacuum in the evaporator 72 was set to 20 kPa abs, and the temperature of the retained liquid 74 was set to 65°C to 70°C. The increase in boiling point due to the concentration of the components of the retained liquid 74 was controlled within 8°C. The extraction of the concentrated water sample 75 was controlled by the specific gravity of the retained liquid 74, and when the specific gravity reached 1.1 kg/L, the concentrated liquid was discharged and treated continuously.
The composition of the condensed water sample 76 obtained by this apparatus is shown in Table 1, "Condensed water column".

The average concentration ratio of the condensed water sample 76 was 12 times by volume. The TDS of the condensed water sample 76 was then reduced to 233 ppm and the COD to less than 100 ppm. Also, the pH value of the condensed water sample 76 was 7.3, and the condensed water sample 76 was purified to a water quality capable of being discharged without additional post-treatment. The appearance of the condensed water sample 76 is shown in FIG. The colored components of the nitrified water sample 61 were fixed on the concentrated water sample 75 side, and the condensed water sample 76 was colorless and transparent.

On the other hand, the TDS, ammonia, and COD components purified by this device were fixed in the concentrated water sample 75 . The composition of the concentrated water sample 75 obtained by this apparatus is shown in the "concentrated water column" in Table 1.

From the results shown in Table 1, the pH value of the concentrated water sample 75 increased to 9.6. As a result of maintaining the pH of the concentrated water sample 75 at a neutral level or higher, particularly at 9.0 or higher, no corrosion in the apparatus due to Cl ^- ions contained in the concentrated water sample 75 was confirmed.

The appearance of the concentrated water sample 75 is shown in FIG.

It was confirmed that scale deposition on the surface of the heat transfer tube 71 and reduction in the overall heat transfer coefficient were observed when the concentration operation described above was continuously performed using this apparatus. However, the component of the scale was calcium carbonate, which could be easily removed by washing with a 10% by weight sulfamic acid aqueous solution.

(Comparative example 1)
Landfill leachate was obtained as a comparative sample. The presence of methanobacteria has been confirmed in the landfill site, and the leachate is digestive fluid that has undergone methane fermentation. The properties and composition of the digestive juice sample are shown in Table 2, "Comparative Digestive Juice Column".

The digestive fluid sample of Comparative Example 1 was directly supplied to the evaporative concentration apparatus described in Example 1 without being supplied to the SBR sludge tank.

The operating conditions of this device were the same as in Example 1.

The composition of the obtained condensed water sample is shown in Table 2, "Condensed water column". The average concentration ratio was 13 times by volume.

This device reduced the TDS of the condensed water by 95% and the COD by 96%. However, about 300 ppm of ammonia remained in the condensed water, and the removal rate of ammonia was 42%. The pH value of the condensed water was 9.4.

From the above, it was found that the condensed water sample was not purified to a water quality that could be discharged. On the other hand, the composition of the concentrated water sample is shown in the "concentrated water column" in Table 2.

From the results shown in Table 2, the pH value of the concentrated water sample decreased to 6.0. When the pH of the concentrated water sample is in such an acidic range, corrosiveness develops, so it was found that the material of the evaporative concentration device must be a corrosion-resistant material.

10: Material to be treated 20: Methane fermentation process 21: Methane fermentation treated water 22: Biogas power generation, etc. 23: Waste water 30: Aerobic biological treatment process 31: Nitrified water 32: pH adjustment 40: Evaporative concentration process 41: Condensation Water 42: Concentrated water 50: SBR tank 51: Digestive liquid 52: Blower 53: Air 54: Pump 55: Activated sludge 60: Evaporative concentration facility clarifier 61: Nitrified water 70: Evaporative concentration facility 71: Heat transfer tube 72: Evaporator 73: Heat pump 74: Retained liquid 75: Concentrated water 76: Condensed water P: Pump pH: pH measurement DO: Dissolved oxygen measurement

Claims (9)

A method for treating an object to be treated containing organic matter, ammonia, and soluble salts,
a methane fermentation step of decomposing organic matter in the material to be treated by a methane fermentation method to obtain methane fermentation-treated water having a Cl ⁻ concentration of 6000 to 50000 ppm;
an aerobic biological treatment step of oxidizing ammonia in the methane fermentation-treated water into nitric acid by the action of aerobic organisms and decomposing organic matter to obtain nitrification-treated water;
an evaporative concentration step of evaporatively concentrating the nitrification-treated water to obtain concentrated water and condensed water;
A processing method for an object to be processed, comprising: The sulfate ion concentration in the methane fermentation treated water is 300 to 10000 ppm,
CO in the nitrified water ₃ ^2- The method for treating an object to be treated according to claim 1, wherein the amount of is 180 to 900 ppm as total inorganic carbonic acid (TIC). 3. The method for treating an object to be treated according to claim 1, wherein the aerobic biological treatment step is performed by a batch activated sludge method. 4. The method for treating an object to be treated according to any one of claims 1 to 3, wherein the pH value of said nitrification treated water to be subjected to said evaporative concentration step is adjusted to 8.5 or higher. 5. The methane fermentation treated water has an ammonia concentration of 10 to 10,000 ppm in terms of nitrogen, a Cl ^- concentration of 6,000 to 50,000 ppm, a COD of 10 to 100,000 ppm, and a BOD of 10 to 10,000 ppm. 3. The method for processing the object to be processed according to . 6. The method for treating an object to be treated according to any one of claims 1 to 5, wherein the aerobic biological treatment step obtains nitrified water having an ammonia concentration of 10 ppm or less in terms of nitrogen. 7. The method for treating an object to be treated according to any one of claims 4 to 6, wherein the pH value of the nitrified water is adjusted to 8.5 or higher by adding an alkaline substance to the nitrified water. A method for treating water to be treated having an ammonia concentration of 10 to 10,000 ppm in terms of nitrogen, a Cl ^- concentration of 6,000 to 50,000 ppm, a COD of 10 to 100,000 ppm, and a BOD of 10 to 10,000 ppm,
an aerobic biological treatment step of oxidizing ammonia in the water to be treated into nitric acid by the action of aerobic organisms and decomposing organic matter to obtain nitrified water;
an evaporative concentration step of evaporatively concentrating the nitrification-treated water to obtain concentrated water and condensed water;
A method for treating water to be treated, wherein the pH value of the nitrification-treated water to be subjected to the evaporative concentration step is adjusted to 8.5 or higher. The sulfate ion concentration in the water to be treated is 300 to 10000 ppm,
CO in the nitrified water ₃ ^2- The method for treating water to be treated according to claim 8, wherein the amount of is 180 to 900 ppm as total inorganic carbonic acid (TIC).

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