Ammonia-containing water treatment device

Abstract

Provided is a treatment device for ammonia-containing water that can efficiently and reliably remove ammonia from the ammonia-containing water and that facilitates maintenance of the diaphragm and the device. [Solution] The electrolytic cell 12 is provided with ammonia-containing water for electrolysis, and has a diaphragm 14 inside the electrolytic cell 12. The electrolytic cell 12 has an anode chamber 18 connected to the positive side of a DC power supply, and a cathode chamber 22 adjacent to the anode chamber 18 via the diaphragm 14. The anode chamber 18 has an anode 16, and the cathode chamber 22 has a cathode 20. The diaphragm 14 has a large number of slits which are minute water-passing holes. The slits are of a size that allows water to pass through in a laminar flow state and does not cause diffusion due to turbulence, and are of a size that allows treated water Wb from ammonia-containing water from which ammonia has been removed to pass through.

Description

[Technical field]

[0001] The present invention relates to a treatment device for removing ammonia from saltwater, such as seawater, that contains ammonia. [Background technology]

[0002] Conventionally, there have been methods using microorganisms to decompose ammonia in seawater. Treatment using microorganisms involves oxidation to nitrate ions followed by denitrification. Both nitrification and denitrification utilize biological reactions, and therefore have the disadvantages of being slow and requiring large facilities. In addition, because biological denitrification requires organic matter, it is often necessary to add acetic acid or alcohol. Therefore, although methods using microorganisms are effective for night soil treatment and sewage treatment, when treating ammonia using microorganisms in seawater or salt water, the decomposition ability of microorganisms in salt water is low, and therefore they cannot demonstrate a high purification ability for ammonia. Therefore, an electrolytic treatment device has been proposed as a treatment device that efficiently removes ammonia from seawater, which electrolyzes ammonia-containing water to remove ammonia.

[0003] For example, the method disclosed in Patent Document 1 involves electrolyzing seawater to generate active chlorine, which is then used to decompose and remove NH3. This method has the problem that unreacted active chlorine that is not used to decompose NH3 remains in the water and has a detrimental effect on fish in the water. Therefore, in Patent Document 1, seawater containing active chlorine after electrolysis is supplied to an activated carbon packed bed, and the active chlorine is removed by the catalytic action of the activated carbon.

[0004] Furthermore, the seawater circulating device for aquaculture disclosed in Patent Document 2 is a seawater circulating device for aquaculture that circulates seawater in aquaculture tanks in which fish and shellfish are cultivated, and is equipped with an electrolysis means for decomposing ammonia in the seawater in the circulation path for circulating the seawater. This seawater circulating device for aquaculture also does not use microorganisms for ammonia decomposition, but decomposes ammonia by electrolysis.

[0005] Also, as disclosed in Patent Document 3, a closed circulation type aquaculture system has been proposed in which seawater in a breeding tank is purified and circulated to breed fish and shellfish in the breeding tank, the closed circulation type aquaculture system being provided with an anode chamber and a cathode chamber separated by a diaphragm. This closed circulation type aquaculture system is provided with an electrolytic cell that electrolyzes seawater supplied from the breeding tank, an aeration tank to which seawater is supplied from the anode chamber, a chlorine dissolution tank in which water is stored or passed and whose space above the water surface is connected to the space above the water surface of the aeration tank, an aeration device that sprays air from the space in the chlorine dissolution tank into the seawater in the aeration tank and into the water in the chlorine dissolution tank for aeration, a neutralization tank that neutralizes active chlorine remaining in the seawater supplied from the aeration tank with a carbonizing agent, and a mixing tank that mixes seawater supplied from the cathode chamber and seawater supplied from the neutralization tank and returns the mixture to the breeding tank. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Publication No. 2002-10724 [Patent Document 2] Publication No. 2002-335811 [Patent Document 3] Publication No. 2006-204235 Summary of the Invention [Problem to be solved by the invention]

[0007] In the cases of Patent Documents 1 and 2 of the background art, the treatment equipment is large-scale, and ammonia is decomposed by hypochlorous acid generated on the anode side, so the efficiency of decomposition and removal of ammonia is not high relative to the total capacity of the treatment tank. In contrast, in the case of Patent Document 3, an anode chamber and a cathode chamber separated by a diaphragm are provided, so the efficiency of decomposition of ammonia in the anode chamber is high, but since an ion exchange membrane is used as the diaphragm, performance is reduced due to contamination of the diaphragm over long-term use, and maintenance of the diaphragm is troublesome and costly. In addition, in the device disclosed in Patent Document 3, seawater is introduced into the cathode chamber side and the anode chamber side, and the treated water flowing out from both chambers is mixed again and circulated, so the efficiency of ammonia treatment is not high.

[0008] The present invention has been made in consideration of the problems in the background art described above, and has an object to provide an apparatus for treating ammonia-containing water, which can efficiently and reliably remove ammonia from ammonia-containing water and can easily maintain the diaphragm and the apparatus. [Means for solving the problem]

[0009] The present invention provides an electrolytic cell for electrolyzing ammonia-containing water, the electrolytic cell being provided with a diaphragm, the electrolytic cell being partitioned into an anode chamber having an anode connected to the positive side of a DC power supply and a cathode chamber adjacent to the anode chamber via the diaphragm and having a cathode connected to the negative side of the DC power supply, the diaphragm having a large number of minute water passage holes, With respect to the flow rate of the ammonia-containing water passing through the water passage hole, The water passage hole is of a size that allows water to pass through in a laminar flow state without causing diffusion due to turbulence, and is of a size that allows treated water from the ammonia-containing water from which ammonia has been removed to pass through.

[0010] The water passage holes are a plurality of slits, and the width of the water passage holes is such that water passes through them in a laminar flow state and does not cause diffusion due to turbulence.

[0011] The diaphragm is an insulating plate, and the width of the slit is 0.3 to 0.7 mm.Furthermore, it is preferable that the diaphragm is a synthetic resin plate, the slits are formed parallel to each other from one side edge of the synthetic resin plate toward the other side edge, and are provided at a predetermined interval from the other side edge, and the width of the slits is 0.4 to 0.6 mm.

[0012] In addition, the synthetic resin plate has a thickness of 5 to 6 mm, and the slits are formed parallel to each other from one side edge of the synthetic resin plate to the other side edge, and are of a width that allows water to pass through in a laminar flow state and does not cause diffusion due to turbulence. Effect of the Invention

[0013] The treatment apparatus for ammonia-containing water of the present invention can efficiently and reliably remove ammonia from ammonia-containing water, and can easily clean the diaphragm and perform other maintenance of the apparatus, thereby enabling efficient removal of ammonia at low cost. [Brief description of the drawings]

[0014] [Figure 1] 1 is a conceptual diagram of an ammonia-containing water treatment device according to an embodiment of the present invention. [Diagram 2] 3A is a plan view, FIG. 3B is a front view, and FIG. 3C is a bottom view of a diaphragm of the device for treating ammonia-containing water according to this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 and Fig. 2 show one embodiment of the present invention, and an ammonia-containing water treatment device 10 of this embodiment is provided with an electrolytic cell 12 that electrolyzes water to be treated Wa, which is ammonia-containing water. The water to be treated Wa, which is ammonia-containing water, is salt water such as seawater used for land-based aquaculture of saltwater fish. In particular, it is discharged seawater or circulating water for land-based aquaculture that circulates seawater.

[0016] First, the treatment of ammonia will be described using wastewater treatment related to land-based aquaculture of saltwater fish as an example. In fish farming, if ammonia discharged from farmed fish accumulates in the farm tank, it will have a negative effect on the habitat of the fish, so the treatment of ammonia is important in land-based aquaculture that uses recycled seawater. The mechanism of ammonia removal in the present invention utilizes the reaction between hypochlorite ions and ammonium ions generated by electrolysis of seawater using an electrolytic cell. The reaction at the anode in the electrolytic cell of the present invention is as shown in the following formula (1). Cl - +H2O → ClO - + 2H + + 2e - (1) The ammonia removal reaction is shown in the following formula (2). 2NH4 + +3ClO - → N2↑+3Cl - +3H2O+2H + (2) These reactions have the advantages of being fast, requiring small equipment, and allowing the amount of ammonia removed to be easily controlled by the amount of electricity.

[0017] Next, an apparatus 10 for treating ammonia-containing water will be described with reference to Figures 1 and 2. The treatment apparatus 10 includes an electrolytic cell 12 in which water to be treated Wa, which is ammonia-containing water, is charged and electrolyzed, and a diaphragm 14 is provided in the electrolytic cell 12. The electrolytic cell 12 is partitioned into an anode chamber 18 in which an anode 16 connected to the positive side of a DC power supply (not shown) is provided, and a cathode chamber 22 in which a cathode 20 is provided that is adjacent to the anode chamber 18 via the diaphragm 14 and connected to the negative side of a DC power supply (not shown). A drain outlet 26 for the treated water Wb from which ammonia has been removed is formed above the cathode chamber 22.

[0018] A large number of slits 24, which are minute water passage holes, are formed in the diaphragm 14. The slits 24 have a width that allows water to pass through in a laminar flow state and does not cause diffusion due to turbulence, and are large enough to allow treated water Wb, from ammonia-containing water to be treated Wa, from which ammonia has been removed, to pass through in a laminar flow state.

[0019] Specifically, the capacity of each of the anode chamber 18 and the cathode chamber 22 is, for example, 300 mL. The electrodes used for the anode 16 are platinum-plated titanium plates, and for the cathode 20 are stainless steel wires. As shown in FIG. 2, the diaphragm 14 is a synthetic resin plate such as an acrylic plate in which slits 24 are formed. The synthetic resin plate has a plate thickness of 5 to 6 mm, for example 5 mm, and the width of the slits 24 is 0.3 to 0.7 mm, preferably 0.4 to 0.6 mm, for example 0.5 mm. The interval between the slits 24 is 4 to 6 mm, for example 5 mm.

[0020] Next, the function of the ammonia-containing water treatment device 10 of this embodiment will be described below. Water to be treated Wa, which is ammonia-containing water from an aquaculture pond or the like, flows into the anode chamber 18 of the electrolytic cell 12. The water to be treated Wa passes through the slit 24 of the diaphragm 14 and moves to the cathode chamber 22. Since the electrolytic cell 12 is divided into the anode chamber 18 and the cathode chamber 22 by the diaphragm 14, ClO generated in the anode 16 is removed. - The slit 24 can efficiently contact with the ammonium ions in the raw water (the water to be treated Wa). For example, in the case of 75 mL / min in the example described below, The water in the anode chamber 18 and the water in the cathode chamber 22 do not mix due to turbulent diffusion. As a result, the treated water Wa, from which ammonia has been effectively removed by the above reaction in the anode chamber 18, passes through the slits 24 in the diaphragm 14 as treated water Wb and is discharged from the outlet 26 of the cathode chamber 22.

[0021] The reason for using a plate having slits 24 as the diaphragm 14 is that, unlike a porous diaphragm such as a ceramic plate, the slits have a width of 0.5 mm and therefore the diaphragm 14 does not block the space between the anode chamber 18 and the cathode chamber 22, the diaphragm 14 is easy to clean, and further electrolysis is possible while the treated water Wb passes through the slits 14. In addition, even if the diaphragm 14 is not a porous plate or other plate having fine holes, the plate having the slits 24 formed therein has a thickness, so that turbulent diffusion is suppressed and the liquids in the anode chamber 18 and the cathode chamber 22 do not mix, and the diaphragm 14 can function as a diaphragm.

[0022] According to the ammonia-containing water treatment device 10 of this embodiment, ammonia can be efficiently and reliably removed from the ammonia-containing water to be treated Wa, cleaning of the diaphragm 14 and other maintenance of the device are easy, the durability of the diaphragm can be made high, and efficient ammonia removal is possible at low cost. As a result, ammonia can be efficiently and continuously removed from seawater or salt water in a circulating aquaculture tank, and the device can be effectively used for aquaculture of fish and shellfish. In addition, the diaphragm 14 having the slits 24 can be easily and efficiently manufactured by, for example, laser processing of a synthetic resin plate.

[0023] The ammonia-containing water treatment device of the present invention is not limited to the above-mentioned embodiment, and the size of the water tank of the electrolytic cell and the diaphragm, the size and material of the electrodes, etc. can be changed as appropriate. The water passage hole of the diaphragm may be a through hole other than a slit, and the diameter and width can be set as appropriate, so long as the size and thickness of the diaphragm do not allow the water to be treated to pass or diffuse in a turbulent state. EXAMPLES

[0024] Next, an experimental example using the treatment method of the treatment device 10 for ammonia-containing water will be described. [Experimental result 1] Ammonia nitrogen (ammonium ion) concentration in seawater: 1.0 mg-N / L Flow rate 75mL / min (residence time: 4 minutes for each tank) Current 20mA (constant current operation) When an experiment was carried out using the same electrolytic cell under the above conditions, the following results were obtained. [When the diaphragm of the present invention is present in the electrolytic cell] Treated water ammonium ion concentration: 0.50mg-N / L Voltage 2.8V (power consumption 56 mW) [If the electrolytic cell does not have a diaphragm] Treated water ammonium ion concentration: 0.80mg-N / L Voltage 2.6V (power consumption 52mW)

[0025] From the above Experimental Result 1, it was confirmed that in the case of the treatment device provided with the diaphragm of the present invention, the ammonium ion concentration in the seawater to be treated was 1.0 mg / L, while the ammonium ion concentration in the treated water was 0.50 mg / L, which was a significant reduction in ammonium ions compared to the ammonium ion concentration of 0.80 mg / L in the treated water without the diaphragm.

[0026] [Experimental result 2] Ammonium ion concentration in seawater: 1.0mg / -NL Flow rate 75 mL / min (residence time: 4 minutes for each tank) Current 30 mA (constant current operation) [When the diaphragm of the present invention is present in the electrolytic cell] Treated water ammonium ion concentration: 0.02mg-N / L Voltage 3.3 V (power consumption 99 mW)

[0027] From the above Experiment 1, it was confirmed that the ammonium ion concentration in the treated water can be significantly reduced when a diaphragm is used. Therefore, when the current value was increased from 20 mA in Experiment 1 to 30 mA, a similar experiment was performed, and it was confirmed that the ammonium ion concentration can be significantly reduced further. However, if the current value is increased and electrolysis proceeds too much, the excess ClO - This will remain and have a negative effect on farmed fish, so it is preferable to reduce the ammonium ion concentration to the level shown in Experiment Result 2 above. [Explanation of symbols]

[0028] 10. Ammonia-containing water treatment device 12 Electrolytic cell 14 Diaphragm 16 Anode 18 Anode chamber 20 cathode 22 Cathode Chamber 24 Slit 26 Drain Wa Treated water Wb Treated water

Claims

1. The electrolytic cell is provided with an electrolytic cell in which ammonia-containing water is charged and subjected to electrolysis, a diaphragm is provided in the electrolytic cell, and the electrolytic cell is partitioned into an anode chamber in which an anode connected to a positive side of a DC power supply is provided, and a cathode chamber adjacent to the anode chamber via the diaphragm and in which a cathode connected to the negative side of the DC power supply is provided, The diaphragm is formed with a large number of minute water passage holes, the water passage holes are of a size that allows water to pass through in a laminar flow state and does not cause diffusion due to turbulence with respect to the flow rate of the ammonia-containing water passing through the water passage holes, and is of a size that allows treated water from the ammonia-containing water from which ammonia has been removed to pass through.

2. 2. The apparatus for treating ammonia-containing water according to claim 1, wherein the water passage holes are a plurality of slits, and the width of the water passage holes is such that water passes through the water in a laminar flow state and does not diffuse due to turbulence.

3. 3. The apparatus for treating ammonia-containing water according to claim 2, wherein the diaphragm is an insulating plate, and the width of the slit is 0.3 to 0.7 mm.

4. The diaphragm is a synthetic resin plate, the slits are formed from one side edge of the synthetic resin plate toward the other side edge in parallel with each other, and are provided at a predetermined interval from the other side edge, and the width of the slits is 0.4 to 0.6 mm.

5. The synthetic resin plate has a thickness of 5 to 6 mm, the slits are formed parallel to each other from one side edge of the synthetic resin plate toward the other side edge, and have a width that allows water to pass in a laminar flow state and does not cause diffusion due to turbulence.

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