Liquid treatment method

Abstract

To provide a liquid treatment method that can efficiently recover phosphorus from a liquid containing ammonia and phosphorus.SOLUTION: A liquid treatment method includes the steps of: subjecting a liquid material containing ammonia and phosphorus to ultrasonic treatment to strip ammonia from the liquid material; adding an inorganic flocculant to the liquid material after the ultrasonic treatment; adding a polymer flocculant to the liquid material after the addition of the inorganic flocculant; and filtering the liquid material after the addition of the polymer flocculant to separate it into a phosphorus-containing precipitate and a filtrate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for treating a liquid containing ammonia and phosphorus, and more particularly to a method for removing ammonia from a liquid containing ammonia and phosphorus to recover phosphorus. [Background technology]

[0002] Various methods have been proposed for treating liquid materials such as livestock waste and digestive fluids. For example, a method has been proposed in which ammonia is stripped from a liquid material such as livestock manure (containing ammonia and phosphorus) and then phosphorus is recovered by crystallization (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-154343 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in conventional treatment methods, no method has been proposed for improving the efficiency of recovering phosphorus contained in liquid materials as precipitates (phosphorus coagulation effect), i.e., for efficiently recovering phosphorus from liquid materials such as livestock manure and digestive fluids.

[0005] The present invention has been made in view of the above-mentioned problems, and aims to provide a method for treating liquids that can efficiently recover phosphorus from liquids such as livestock manure and digestive fluids (liquids containing ammonia and phosphorus). [Means for solving the problem]

[0006] The method for treating a liquid material of the present invention is a method for treating a liquid material containing ammonia and phosphorus, and includes the steps of: subjecting the liquid material containing ammonia and phosphorus to ultrasonic treatment to strip ammonia from the liquid material; adding an inorganic flocculant to the liquid material after the ultrasonic treatment; adding a polymer flocculant to the liquid material after the inorganic flocculant has been added; and filtering the liquid material after the polymer flocculant has been added to separate it into a phosphorus-containing precipitate and a filtrate.

[0007] According to this method, a liquid containing ammonia and phosphorus is subjected to ultrasonic treatment to first strip the ammonia from the liquid, and then an inorganic flocculant and then a polymer flocculant are added to the ammonia-stripped liquid, thereby improving the efficiency of recovering phosphorus contained in the liquid as a precipitate (phosphorus flocculation effect). This makes it possible to efficiently recover phosphorus from a liquid containing ammonia and phosphorus. In addition, because the turbidity of the filtrate can be reduced (the filtrate can be made clear), if the filtrate's components can be made to comply with wastewater standards, it can be discharged (wastewater) into rivers, etc.

[0008] In the method for treating a liquid material of the present invention, in the step of stripping ammonia from the liquid material, a treatment of bringing the liquid material into contact with a gas may be carried out in parallel with the ultrasonic treatment.

[0009] According to this method, when ultrasonic treatment is performed on a liquid material containing ammonia and phosphorus, a process of bringing the liquid material into contact with a gas (aeration process) is performed in parallel with the ultrasonic treatment. This improves the phosphorus coagulation effect compared to when only ultrasonic treatment is performed on a liquid material containing ammonia and phosphorus, and enables phosphorus to be recovered efficiently.

[0010] In the method for treating a liquid material of the present invention, the liquid material containing ammonia and phosphorus may be digested liquid after methane fermentation or livestock manure before methane fermentation.

[0011] According to this method, it is possible to efficiently recover phosphorus from the digested liquid after methane fermentation or from livestock manure before methane fermentation.

[0012] In the method for treating a liquid material of the present invention, the inorganic flocculant may be ferric chloride, aluminum sulfate, polyferric sulfate, or polyaluminum chloride.

[0013] According to this method, by adding any one of ferric chloride, aluminum sulfate, polyferric sulfate, or polyaluminum chloride to the liquid material obtained by stripping ammonia, the phosphorus coagulation effect can be improved, and phosphorus contained in the liquid material can be efficiently recovered.

[0014] In the method for treating a liquid material of the present invention, the polymer flocculant may be a cationic polymer flocculant, an anionic polymer flocculant, or a nonionic polymer flocculant.

[0015] According to this method, by adding either a cationic polymer flocculant, an anionic polymer flocculant, or a nonionic polymer flocculant to the liquid after adding the inorganic flocculant, the flocculation effect of phosphorus can be improved, and the phosphorus contained in the liquid can be efficiently recovered. [Effects of the Invention]

[0016] According to the present invention, phosphorus can be efficiently recovered from a liquid material containing ammonia and phosphorus. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is an explanatory diagram of a method for treating a liquid material according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, a method for treating liquid materials according to an embodiment of the present invention will be described with reference to the drawings. In this embodiment, a method for treating liquid materials used for treating digestive fluids, livestock manure, etc. will be described as an example.

[0019] (Embodiment) A liquid treatment method according to an embodiment of the present invention will be described with reference to the drawings. The liquid in this embodiment is digested liquid after methane fermentation or livestock manure before methane fermentation, and contains ammonia and phosphorus. FIG. 1 is an explanatory diagram of the liquid treatment method according to this embodiment. As shown in FIG. 1, in this treatment method, first, the liquid containing ammonia and phosphorus is subjected to ultrasonic treatment to strip ammonia from the liquid. The ultrasonic treatment is performed using an ultrasonic generator U such as a vibrator. The ultrasonic frequency is low, preferably 20 kHz to 50 kHz. The ultrasonic may be generated continuously or intermittently. In this case, it is desirable to perform a treatment (aeration treatment) in which the liquid is brought into contact with a gas in parallel with the ultrasonic treatment. The gas used in this aeration treatment may be of any type, but air is usually sufficient, and air with reduced carbon dioxide content is particularly desirable. The ammonia stripped from the liquid may be recovered by an ammonia recovery device (not shown).

[0020] After ultrasonic treatment (and aeration treatment), an inorganic flocculant is added to the liquid. Ferric chloride, aluminum sulfate, polyferric sulfate, or polyaluminum chloride is used as the inorganic flocculant. The concentration of the inorganic flocculant is preferably 0.5 to 4%. When adding the inorganic flocculant, the liquid is preferably stirred using a stirring device S. In this case, when the volume of the liquid is in the range of 100 mL to 1 L, the stirring speed is preferably 120 rpm, and the stirring time is preferably 1 minute. Note that the stirring speed and stirring time can be adjusted depending on the volume of the liquid so that the stirring power and stirring state are constant.

[0021] After the inorganic flocculant is added, a polymer flocculant is added to the liquid. A cationic polymer flocculant, an anionic polymer flocculant, or a nonionic polymer flocculant is used as the polymer flocculant. The concentration of the polymer flocculant is preferably 0.001 to 0.003%. When adding the polymer flocculant, the liquid is preferably stirred using a stirring device S. In this case, when the volume of the liquid is in the range of 100 mL to 1 L, the stirring speed is preferably 45 rpm, and the stirring time is preferably 3 minutes. The polymer flocculant may be added simultaneously with the inorganic flocculant. Depending on the volume of the liquid, the stirring speed and stirring time can be adjusted to maintain a constant stirring power and stirring state.

[0022] After the polymer flocculant is added, stirring of the liquid is stopped. The stopping time is preferably 90 minutes. The liquid is then filtered through a filter (not shown) to separate the precipitate (containing phosphorus) and the filtrate. In this case, the filter pore size used for filtration is preferably 0.007 mm.

[0023] According to the liquid treatment method of this embodiment, a liquid containing ammonia and phosphorus is subjected to ultrasonic treatment to first strip ammonia from the liquid, and then an inorganic flocculant and then a polymer flocculant are added to the ammonia-stripped liquid, thereby improving the efficiency of recovering phosphorus contained in the liquid as a precipitate (phosphorus flocculation effect). This makes it possible to efficiently recover phosphorus from a liquid containing ammonia and phosphorus. Furthermore, in this case, the turbidity of the filtrate can be reduced (the filtrate can be made clear), and if the filtrate components can be made to comply with wastewater standards, the filtrate can be discharged (wastewater) into rivers, etc.

[0024] In this embodiment, when ultrasonic treatment is performed on a liquid material containing ammonia and phosphorus, a process of bringing the liquid material into contact with a gas (aeration process) is performed in parallel with the ultrasonic treatment. This improves the phosphorus coagulation effect compared to when only ultrasonic treatment is performed on a liquid material containing ammonia and phosphorus, and enables phosphorus to be recovered efficiently.

[0025] Furthermore, in this embodiment, it becomes possible to efficiently recover phosphorus from the digested liquid after methane fermentation or from livestock manure before methane fermentation.

[0026] Furthermore, in this embodiment, by adding any one of ferric chloride, aluminum sulfate, polyferric sulfate, or polyaluminum chloride to the liquid material obtained by stripping ammonia, the phosphorus coagulation effect can be improved, and phosphorus contained in the liquid material can be efficiently recovered.

[0027] Furthermore, in this embodiment, by adding either a cationic polymer flocculant, an anionic polymer flocculant, or a nonionic polymer flocculant to the liquid after adding the inorganic flocculant, the flocculation effect of phosphorus can be improved, and the phosphorus contained in the liquid can be efficiently recovered.

[0028] (Example) Specific examples of the present invention will be described below, but the scope of the present invention is not limited to any of the following examples.

[0029] [Method for measuring phosphate] The phosphate concentration (mg / L) was measured for a sample of digested liquor after methane fermentation that had been subjected to ultrasonic treatment and aeration in parallel, followed by the addition of an inorganic flocculant and a polymer flocculant (Example), and a sample of digested liquor after methane fermentation that had been subjected to ultrasonic treatment and aeration in parallel, followed by the addition of neither an inorganic flocculant nor a polymer flocculant (Comparative Example). The phosphate concentration was measured by diluting the sample 100 times and measuring the phosphate (PO4 3-The phosphoric acid concentration was measured as a concentration (mg / L) of the precipitate. In the examples, the precipitate and the filtrate could be separated, so the filtrate was diluted 100 times to measure the phosphoric acid concentration. In the comparative examples, the precipitate and the filtrate could not be separated, so the stock solution was diluted 100 times to measure the phosphoric acid concentration.

[0030] [Method of measuring turbidity] The turbidity was measured using a FUSO digital turbidity meter for a sample of digested liquor after methane fermentation, which was subjected to ultrasonic treatment and aeration treatment in parallel, followed by the addition of an inorganic flocculant and a polymer flocculant (Example), and a sample of digested liquor after methane fermentation, to which an inorganic flocculant and a polymer flocculant were added without ultrasonic treatment or aeration treatment (Comparative Example). For the Example, separation into sediment and filtrate was possible, so the turbidity of the filtrate was measured. For the Comparative Example, if separation into sediment and filtrate was possible, the turbidity of the filtrate was measured; if separation into sediment and filtrate was not possible, the turbidity of the raw liquid was measured as is.

[0031] [Example 1] Ferric chloride (concentration 1%) was used as the inorganic flocculant, and a cationic polymer flocculant (concentration 0.001%) was used as the polymer flocculant. Regarding phosphorus, the phosphorus concentration in Comparative Example 1 (no inorganic flocculant or polymer flocculant added; stock solution before flocculation) was 5.8 mg / L, while the phosphorus concentration in Example 1 (addition of inorganic flocculant and polymer flocculant; filtrate after flocculation) was 0.2 mg / L. In Example 1, the precipitate after flocculation contained 5.6 mg / L (= 5.8 - 0.2) of phosphorus in solution equivalent, and 96.6% (= (5.6 / 5.8) × 100) of the phosphorus was recovered as the precipitate. Regarding turbidity, the turbidity in Example 1 (ultrasonication and aeration treatment; filtrate after flocculation) was 5.97, while the turbidity in Comparative Example 1 (no ultrasonication or aeration treatment; filtrate after flocculation) was 47.17 (see Table 1).

[0032] [Table 1]

[0033] [Example 2] Ferric chloride (concentration 2%) was used as the inorganic flocculant, and an anionic polymer flocculant (concentration 0.001%) was used as the polymer flocculant. Regarding phosphorus, the phosphorus concentration in Comparative Example 2 (no inorganic flocculant or polymer flocculant added; stock solution before flocculation) was 7.2 mg / L, while the phosphorus concentration in Example 2 (addition of inorganic flocculant and polymer flocculant; filtrate after flocculation) was 0.1 mg / L. In Example 2, the precipitate after flocculation contained 7.1 mg / L (= 7.2 - 0.1) of phosphorus in solution equivalent, and 98.6% (= (7.1 / 7.2) × 100) of the phosphorus was recovered as the precipitate. Regarding turbidity, the turbidity in Example 2 (ultrasonication and aeration treatment; filtrate after flocculation) was 2.23, while the turbidity in Comparative Example 2 (no ultrasonication or aeration treatment; stock solution before flocculation) was 341 (see Table 2).

[0034] [Table 2]

[0035] [Example 3] Ferric chloride (concentration 1%) was used as the inorganic flocculant, and a cationic polymer flocculant (concentration 0.001%) was used as the polymer flocculant. Regarding phosphorus, the phosphorus concentration in Comparative Example 3 (no inorganic flocculant or polymer flocculant added; stock solution before flocculation) was 7.2 mg / L, while the phosphorus concentration in Example 3 (addition of inorganic flocculant and polymer flocculant; filtrate after flocculation) was 0.1 mg / L. In Example 3, the precipitate after flocculation contained 7.1 mg / L (= 7.2 - 0.1) of phosphorus in solution equivalent, and 98.6% (= (7.1 / 7.2) × 100) of the phosphorus was recovered as the precipitate. Regarding turbidity, the turbidity in Example 3 (ultrasonication and aeration treatment; filtrate after flocculation) was 0.0, while the turbidity in Comparative Example 3 (no ultrasonication or aeration treatment; filtrate after flocculation) was 118 (see Table 3).

[0036] [Table 3]

[0037] [Example 4] The inorganic flocculant was polyferric sulfate (concentration 1%), and the polymer flocculant was a cationic polymer flocculant (concentration 0.001%). Regarding phosphorus, the phosphorus concentration in Comparative Example 4 (no inorganic flocculant or polymer flocculant added; stock solution before flocculation) was 7.2 mg / L, while the phosphorus concentration in Example 4 (addition of inorganic flocculant and polymer flocculant; filtrate after flocculation) was 0.0 mg / L. In Example 4, the precipitate after flocculation contained 7.2 mg / L (= 7.2 - 0.0) of phosphorus in solution equivalent, and nearly 100% (= (7.2 / 7.2) × 100) of the phosphorus was recovered as precipitate. Regarding turbidity, the turbidity in Example 4 (ultrasonication and aeration treatment; filtrate after flocculation) was 11.49, while the turbidity in Comparative Example 4 (no ultrasonication or aeration treatment; stock solution before flocculation) was < 1000 (see Table 4).

[0038] [Table 4]

[0039] [Example 5] Aluminum sulfate (concentration 3%) was used as the inorganic flocculant, and an anionic polymer flocculant (concentration 0.001%) was used as the polymer flocculant. Regarding phosphorus, the phosphoric acid concentration in Comparative Example 5 (no inorganic flocculant or polymer flocculant added; stock solution before flocculation) was 7.2 mg / L, while the phosphoric acid concentration in Example 5 (addition of inorganic flocculant and polymer flocculant; filtrate after flocculation) was 0.0 mg / L. In Example 5, the precipitate after flocculation contained 7.2 mg / L (= 7.2 - 0.0) of phosphoric acid in solution equivalent, and nearly 100% (= (7.2 / 7.2) × 100) of the phosphorus was recovered as precipitate. Regarding turbidity, the turbidity in Example 5 (ultrasonication and aeration treatment; filtrate after flocculation) was 4.96, while the turbidity in Comparative Example 5 (no ultrasonication or aeration treatment; filtrate after flocculation) was 45.77 (see Table 5).

[0040] [Table 5]

[0041] [Example 6] Polyaluminum chloride (concentration 4%) was used as the inorganic flocculant, and a cationic polymer flocculant (concentration 0.001%) was used as the polymer flocculant. Regarding phosphorus, the phosphorus concentration in Comparative Example 6 (no inorganic flocculant or polymer flocculant added; stock solution before flocculation) was 1.7 mg / L, while the phosphorus concentration in Example 6 (addition of inorganic flocculant and polymer flocculant; filtrate after flocculation) was 0.1 mg / L. In Example 6, the precipitate after flocculation contained 1.6 mg / L (= 1.7 - 0.1) of phosphorus in solution equivalent, and 94.1% (= (1.6 / 1.7) × 100) of the phosphorus was recovered as the precipitate. Regarding turbidity, the turbidity in Example 6 (ultrasonication and aeration treatment; filtrate after flocculation) was 0.20, while the turbidity in Comparative Example 6 (no ultrasonication or aeration treatment; filtrate after flocculation) was 436 (see Table 6).

[0042] [Table 6]

[0043] [Example 7] The inorganic flocculant used was polyferric sulfate (concentration 2%), and the polymer flocculant used was a nonionic polymer flocculant (concentration 0.001%). Regarding phosphorus, the phosphorus concentration in Comparative Example 7 (no inorganic flocculant or polymer flocculant added; stock solution before flocculation) was 7.2 mg / L, while the phosphorus concentration in Example 7 (addition of inorganic flocculant and polymer flocculant; filtrate after flocculation) was 0.0 mg / L. In Example 7, the precipitate after flocculation contained 7.2 mg / L (= 7.2 - 0.0) of phosphorus in solution equivalent, and nearly 100% (= (7.2 / 7.2) × 100) of phosphorus was recovered as precipitate. Regarding turbidity, the turbidity in Example 7 (ultrasonication and aeration treatment; filtrate after flocculation) was 0.00, while the turbidity in Comparative Example 7 (no ultrasonication and aeration treatment; filtrate after flocculation) was 47.18 (see Table 7).

[0044] [Table 7]

[0045] Although the embodiments of the present invention have been described above by way of example, the scope of the present invention is not limited to these, and can be modified and changed according to the purpose within the scope of the claims. [Industrial Applicability]

[0046] As described above, the method for treating a liquid material according to the present invention has the effect of enabling efficient recovery of phosphorus from a liquid material containing ammonia and phosphorus, and is useful for application to treatment systems for digestive fluids and livestock manure, etc. [Explanation of symbols]

[0047] U Ultrasonic generator S Stirring device

Claims

1. A method for treating a liquid containing ammonia and phosphorus, comprising: The processing method comprises: subjecting the liquid material containing ammonia and phosphorus to ultrasonic treatment to strip ammonia from the liquid material; adding an inorganic flocculant to the liquid after the ultrasonic treatment; adding a polymer flocculant to the liquid after adding the inorganic flocculant; a step of filtering the liquid after adding the polymer flocculant to separate it into a phosphorus-containing precipitate and a filtrate; A method for treating a liquid, comprising:

2. In the step of stripping ammonia from the liquid, The method for treating a liquid material according to claim 1 , further comprising the step of contacting the liquid material with a gas in parallel with the ultrasonic treatment.

3. 2. The method for treating a liquid material according to claim 1, wherein the liquid material containing ammonia and phosphorus is a digested liquid after methane fermentation or livestock manure before methane fermentation.

4. 2. The method for treating a liquid substance according to claim 1, wherein the inorganic flocculant is ferric chloride, aluminum sulfate, polyferric sulfate, or polyaluminum chloride.

5. 2. The method for treating a liquid material according to claim 1, wherein the polymer flocculant is a cationic polymer flocculant, an anionic polymer flocculant, or a nonionic polymer flocculant.

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