Method of using biologically treated water

Abstract

To provide a method of using biologically treated water capable of enlarging an application range of biologically treated water of various kinds of industrial waste, sewage water, and the like for farmland spraying.SOLUTION: A method of using biologically treated water includes adjusting a pH of ammonia-containing biologically treated water, bringing the liquid into contact with an adsorbent, adjusting the fertilizer component concentration of the liquid, and using the liquid as a liquid fertilizer. The fertilizer component includes ammonia, potassium, phosphorus, or the like, and the adsorbent includes zeolite or the like. The adsorbent after adsorbing the fertilizer component is used as a fertilizer or a soil improving material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for utilizing biologically treated water, and more particularly to a method for treating biologically treated water and utilizing it as liquid fertilizer. [Background technology]

[0002] Ammonia is present at concentrations of 100 mg / L or more in biologically treated water from various industries, including the food industry, chemical industry, and agriculture, as well as in sewage. Anaerobic biologically treated water, particularly in biogas power plants, often contains ammonia at concentrations of 1000 mg / L or more. In addition to ammonia, biologically treated water also contains potassium, phosphorus, and other components that can be effectively used as fertilizer. Therefore, biologically treated water is often sprayed on agricultural land and used as fertilizer (Patent Document 1, paragraph 0007). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2022-34249 Summary of the Invention [Problem to be solved by the invention]

[0004] When biologically treated water is sprayed on farmland, if the soil to be sprayed contains a high content of a certain fertilizer component (e.g., ammonia or potassium), the spraying may result in an excess of that component in the soil, making the farmland unsuitable for spraying the biologically treated water. As such, the spraying of biologically treated water on farmland is restricted by the soil properties of the farmland, and therefore, the spraying of biologically treated water on farmland is not widely practiced.

[0005] An object of the present invention is to provide a method for utilizing biologically treated water, such as various types of industrial wastewater and sewage, which can expand the scope of application to agricultural land spraying. [Means for solving the problem]

[0006] The present invention has the following gist.

[0007] [1] A method of using biologically treated water containing ammonia, in which the pH is adjusted, the water is brought into contact with an adsorbent, the concentration of fertilizer components in the liquid is adjusted, and the water is then used as liquid fertilizer.

[0008] [2] The method for utilizing the biologically treated water according to [1], wherein the fertilizer components are ammonia, potassium, and phosphorus, and the adsorbent is zeolite.

[0009] [3] The method for utilizing biologically treated water according to [1], wherein the biologically treated water is anaerobically treated water.

[0010] [4] The method for utilizing biologically treated water according to [3], wherein the anaerobic treatment is methane fermentation treatment.

[0011] [5] The method for utilizing the biologically treated water according to any one of [1] to [4], wherein the adsorbent after adsorbing the fertilizer components is used as a fertilizer or a soil improvement material. [Effects of the Invention]

[0012] The present invention uses an adsorbent to recover valuables such as ammonia from biologically treated water, such as various industrial wastewater and sewage, in order to promote the effective utilization of valuables such as ammonia, potassium, and phosphorus. The adsorbent after adsorption is used as a fertilizer or soil conditioner. By changing the pH conditions during this adsorption treatment, the ratio of ammonia to potassium or the ratio of ammonia to phosphorus in the biologically treated water can be changed. This allows the biologically treated water to be adjusted to properties suitable for spraying on agricultural land, depending on the soil components of the target agricultural land.

[0013] In one embodiment of the present invention, a treatment solution with a low ammonia ratio is prepared and sprayed on soil with a high ammonia ratio, and a treatment solution with a high ammonia ratio is prepared and sprayed on soil with a low ammonia ratio.

[0014] Thus, according to the present invention, by adjusting the properties of the biologically treated water, the area of ​​agricultural land that can be sprayed is increased. Also, the amount of biologically treated water that is not used for spraying is reduced. As a result, the effective use of the amount of fertilizer components (resources) in the biologically treated water that is sprayed is promoted.

[0015] In one embodiment of the present invention, zeolite is used for adsorption treatment. The zeolite that has adsorbed ammonia, potassium, etc. is then utilized as a fertilizer or soil conditioner in agriculture. When zeolite is used to recover ammonia, etc. from biologically treated water, regeneration treatment is generally required. However, by utilizing the zeolite with adsorbed ammonia as a fertilizer or soil conditioner in agriculture, regeneration treatment becomes unnecessary.

[0016] In one embodiment of the present invention, potassium is adsorbed onto zeolite in addition to ammonia. The zeolite with adsorbed ammonia and potassium is suitable for use as a fertilizer or soil conditioner in agriculture. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a flow chart showing an example of the method of the present invention. [Figure 2] 10 is a graph showing the results of an experimental example. [Figure 3] 10 is a graph showing the results of an experimental example. DETAILED DESCRIPTION OF THE INVENTION

[0018] In the present invention, at least a portion of valuable materials such as ammonia and potassium in biologically treated water obtained by biologically treating various industrial wastewaters such as food industry wastewater and chemical industry wastewater, agricultural wastewater, sewage, etc., is adsorbed and removed by an adsorbent, preferably zeolite, and the concentrations of ammonia, potassium, etc. in the biologically treated water are adjusted to prepare liquid fertilizer for application to agricultural land. Zeolite with adsorbed ammonia, potassium, etc. can be effectively used as a fertilizer or soil conditioner in agriculture.

[0019] As the biological treatment, anaerobic treatment, particularly methane fermentation treatment, is preferred.

[0020] Mordenite is suitable as the zeolite used for ammonia adsorption. In particular, zeolite with a Si / Al ratio of SiO2 / Al2O3 of 100 or less, preferably 5 to 50, is desirable.

[0021] The method for utilizing biologically treated water in the present invention is carried out, for example, according to the flow shown in FIG.

[0022] In Fig. 1, the biologically treated water is subjected to solid-liquid separation, the pH is adjusted, and then adsorption treatment is performed using zeolite. Suitable solid-liquid separation methods include, but are not limited to, screening, coagulation sedimentation, filtration, and membrane treatment.

[0023] The adsorption treatment after solid-liquid separation is carried out by passing the solid-liquid separated water through a packed tower packed with zeolite. In the case of biologically treated water with an ammonia nitrogen concentration of about 100 to 1000 mg / L, the water passing SV through the packed tower is 2 hours. -1 The following is preferred:

[0024] The liquid may be passed through the adsorption tower in either an upward or downward direction. The adsorption treatment can also be carried out as a batch treatment in which an adsorbent is added to the solid-liquid separated water.

[0025] The water after adsorption treatment (adsorption-treated water) is used to spread on agricultural land as adjusted liquid fertilizer. If the amount of this adsorption-treated water is excessive, part of it is treated by nitrification and denitrification in a small-scale wastewater treatment facility using the nitrification and denitrification method before being released. If the amount of solid-liquid separation-treated water is excessive, part of it is also treated by nitrification and denitrification in a small-scale wastewater treatment facility before being released.

[0026] In Figure 1, a portion of the solid-liquid separation water is not subjected to adsorption treatment and is used as unadjusted liquid fertilizer. This unadjusted liquid fertilizer has higher concentrations of ammonia and potassium than adjusted liquid fertilizer.

[0027] In the present invention, a liquid fertilizer having a desired ammonia or potassium concentration can be prepared by mixing an adjusted liquid fertilizer with an unadjusted liquid fertilizer.

[0028] If the solid concentration in the biologically treated water is low, the solid-liquid separation may not be performed. Alternatively, only a portion of the biologically treated water may be subjected to solid-liquid separation, with the remainder not being subjected to solid-liquid separation. [Example]

[0029] [Experimental Example 1] The following sample solutions were subjected to ammonia, potassium and phosphorus adsorption tests.

[0030] <Sample solution> The liquid with the following properties was obtained by filtering biologically treated digested liquid (methane fermentation treated liquid) from livestock wastewater through filter paper 5A. <Sample liquid properties> pH:8 Ammonia nitrogen (NH4-N) concentration: 800 mg / L Potassium concentration: 1000mg / L Phosphorus concentration: 5mg / L

[0031] <Experimental Method> A column was packed with zeolite as an adsorbent, and the sample solution was passed upward through the column either directly (condition 1) or after pH adjustment (conditions 2 and 3). Column test conditions Column inner diameter: 27 mm Adsorbent: Zeolite (Tokachi Zeolite, Kyosei Renthem) Adsorbent filling amount: 50mL Liquid passing rate: 50mL / h (SV=1 / h) Temperature: room temperature

[0032] In condition 1, a sample solution (pH=8) without pH adjustment was passed through.

[0033] In conditions 2 and 3, an aqueous solution of sodium hydroxide was added to the sample solution, and the solution was adjusted to pH 9.5 before being passed through.

[0034] In condition 3, hydrochloric acid was added to the sample solution, and the solution was adjusted to pH 6.5 and then passed through.

[0035] <Result> Figures 2 and 3 show the change in the ammonia and potassium concentrations in the adsorption-treated liquid versus the amount of liquid passed through the column. Table 1 also shows the ammonia and potassium concentrations in the total amount of liquid passed through the column up to 12 BV. BV stands for the amount of liquid passed through, and is expressed as a multiple of the adsorbent loading volume. Table 1 also lists the properties of the sample liquid.

[0036] [Table 1]

[0037] Under conditions 1, 2, and 3, the ammonia and potassium concentrations in the adsorption treatment liquid were low at the beginning of the water flow, and after 3 BV or more, the concentrations increased. As the water flow continued, the zeolite reached a saturated adsorption state, and the ammonia and potassium concentrations rose to the same levels as in the raw water.

[0038] Under condition 1, saturation does not occur until about 12 BV, and a treated solution with lower concentrations of ammonia and potassium than the original sample solution can be obtained. The adsorbent after adsorption can be used separately as a soil improvement material, etc.

[0039] As shown in Figures 2 and 3, when comparing conditions 1 and 2, the increase in ammonia nitrogen concentration in the adsorption treatment solution was greater under condition 2, while the increase in potassium concentration was smaller under condition 2. The reason for this is thought to be that under condition 2 (pH = 9.5), the ammonia component is in the form of free ammonia rather than ammonium ions, making it difficult for the adsorbent to adsorb. As a result, it was found that treatment under condition 2 yielded a treatment solution with a higher ratio of ammonia nitrogen compared to the ratio of ammonia nitrogen to potassium obtained under condition 1.

[0040] Comparing conditions 1 and 3, the increase in the ammonia nitrogen concentration in the adsorption treatment liquid was slightly lower under condition 3, while the increase in the potassium concentration was slightly higher under condition 3. This is thought to be because, under condition 3 (pH = 6.5), the dissociation rate of ammonia in the liquid (ammonium ion ratio) was higher, making it easier for the ammonia to be adsorbed by the adsorbent. As a result, it was found that treatment under condition 3 yielded a treatment liquid with a slightly higher ratio of potassium compared to the ratio of ammonia nitrogen to potassium obtained under condition 1.

[0041] These results are also reflected in the ratio of ammonia nitrogen to potassium (nitrogen-potassium ratio (=amount of ammonia nitrogen / amount of potassium)) contained in the total amount of treated liquid obtained after passing a specified amount of liquid. That is, as shown in Table 1, the nitrogen-potassium ratio was 0.8 under condition 1, which was the same as that of the sample, but under condition 2, where the liquid was passed under alkaline conditions, the nitrogen-potassium ratio increased to 1.46, and under condition 3, where the liquid was passed under acidic conditions, the nitrogen-potassium ratio slightly decreased to 0.79.

[0042] Based on these results, it is possible to adjust the fertilizer component ratio of the liquid fertilizer depending on the soil where it is to be sprayed. For example, if you want to spray more potassium than nitrogen on soil, you can spray an alkaline adsorbed treatment liquid, and if you want to spray more potassium on soil, you can spray a neutral or acidic treatment liquid.

[0043] As phosphorus was only present in low concentrations in this sample solution, the change in concentration due to adsorption treatment was small, but it was confirmed that the nitrogen-phosphorus ratio in the adsorption-treated water changes depending on the water flow pH, just like the nitrogen-potassium ratio. Therefore, if the phosphorus concentration is high and there are restrictions on the soil to which it is applied, it is possible to adjust the liquid fertilizer to be applied by making similar adjustments.

Claims

1. A method for utilizing biologically treated water containing ammonia, in which the pH of the biologically treated water is adjusted, the water is brought into contact with an adsorbent, the concentration of fertilizer components in the liquid is adjusted, and the water is then used as liquid fertilizer.

2. 2. The method for utilizing biologically treated water according to claim 1, wherein the fertilizer components are ammonia, potassium, and phosphorus, and the adsorbent is zeolite.

3. The method for utilizing biologically treated water according to claim 1, wherein the biologically treated water is anaerobically treated water.

4. 4. The method for utilizing biologically treated water according to claim 3, wherein the anaerobic treatment is a methane fermentation treatment.

5. 5. The method for utilizing the biologically treated water according to claim 1, wherein the adsorbent after adsorbing the fertilizer components is used as a fertilizer or a soil improvement material.

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