Treatment apparatus for ammonia-containing water

Abstract

To provide a treatment apparatus for ammonia-containing water capable of efficiently and reliably removing ammonia from the ammonia-containing water, while also facilitating easy maintenance of the diaphragm and the apparatus.SOLUTION: A treatment apparatus includes an electrolyzer 12 for electrolytic treatment of ammonia-containing water, and a diaphragm 14 within the electrolyzer 12. The electrolyzer 12 comprises an anode chamber 18 connected to the positive side of a DC power source and a cathode chamber 22 adjacent to the anode chamber 18 via the diaphragm 14. The anode chamber 18 includes an anode 16, and the cathode chamber 22 includes a cathode 20. The diaphragm 14 includes numerous minute water-permeable slits. The slits are sized to allow water flow in a laminar state without causing diffusion due to turbulence, and are sized to permit passage of treated water Wb from which ammonia has been removed from the ammonia-containing water.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Conventional methods for decomposing ammonia in seawater have used microorganisms. Microbial treatment involves oxidation to nitrate ions followed by denitrification. Because both nitrification and denitrification utilize biological reactions, they have the drawbacks of being slow and requiring large facilities. Furthermore, because biological denitrification requires organic matter, the addition of acetic acid or alcohol is often necessary. Therefore, while microbial methods are effective for treating human waste and sewage, when using microorganisms to treat ammonia in seawater or saltwater, they are unable to achieve high ammonia purification capabilities due to the low ammonia decomposition capacity of microorganisms in saltwater. Therefore, electrolytic treatment devices have been proposed as a treatment method for efficiently removing ammonia from seawater, using electrolysis to remove ammonia-containing water.

[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 an adverse effect on fish in the water. Therefore, Patent Document 1 describes a method in which seawater containing active chlorine after electrolysis is supplied to a bed packed with activated carbon, and the active chlorine is removed by the catalytic action of the activated carbon.

[0004] Furthermore, the seawater circulation device for aquaculture disclosed in Patent Document 2 is a seawater circulation device for aquaculture that circulates and utilizes seawater in aquaculture tanks where fish and shellfish are cultivated, and is equipped with an electrolysis means in the circulation path for circulating the seawater to perform processes such as decomposing ammonia in the seawater. This seawater circulation device for aquaculture also does not use microorganisms for the ammonia decomposition process, but instead uses electrolysis to decompose the ammonia.

[0005] Furthermore, as disclosed in Patent Document 3, a closed circulation aquaculture system has been proposed in which seawater from a breeding tank is purified and circulated to breed fish and shellfish in the breeding tank, and the system includes an anode chamber and a cathode chamber separated by a diaphragm. This closed circulation aquaculture system includes 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 whose space above the water surface is connected to the space above the water surface in the aeration tank and in which water is stored or passed, 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 with 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 above-mentioned background art patent documents 1 and 2, the treatment equipment is large-scale, and ammonia decomposition is carried out by hypochlorous acid generated on the anode side, so the efficiency of ammonia decomposition and removal relative to the total capacity of the treatment tank is not high. 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 ammonia decomposition in the anode chamber is high, but because an ion exchange membrane is used as the diaphragm, performance deteriorates due to diaphragm fouling over long-term use, and maintenance of the diaphragm is troublesome and costly. Furthermore, 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 ammonia treatment efficiency is not high.

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

[0009] The present invention provides an apparatus for treating ammonia-containing water, comprising an electrolytic cell for electrolyzing ammonia-containing water introduced therein, a diaphragm disposed within the electrolytic cell, the electrolytic cell being partitioned via the diaphragm 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 and having a cathode connected to the negative side of the DC power supply, the diaphragm having a large number of minute water-passing holes formed therein, the water-passing holes being of a size that allows water to pass through in a laminar flow state without causing diffusion due to turbulence, and being of a size that allows treated water from the ammonia-containing water 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 in a laminar flow state and does not diffuse due to turbulence.

[0011] The diaphragm is an insulating plate, and the slit width is 0.3 to 0.7 mm. Furthermore, the diaphragm is a synthetic resin plate, 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 provided with a predetermined distance from the other side edge, and the slit width is preferably 0.4 to 0.6 mm.

[0012] 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. [Effects of the Invention]

[0013] The apparatus for treating ammonia-containing water of the present invention can efficiently and reliably remove ammonia from ammonia-containing water, and cleaning of the diaphragm and other maintenance of the apparatus are easy, enabling efficient removal of ammonia at low cost. [Brief explanation 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. [Figure 2] 1A is a plan view, FIG. 1B is a front view, and FIG. 1C is a bottom view of a diaphragm of an apparatus for treating ammonia-containing water according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Figures 1 and 2 show one embodiment of the present invention, in which an apparatus 10 for treating ammonia-containing water in this embodiment is provided with an electrolytic cell 12 for electrolyzing water Wa, which is ammonia-containing water. The water Wa, which is ammonia-containing water, is saltwater 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 uses recycled seawater.

[0016] First, we will explain the treatment of ammonia 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 tanks, it will have a negative impact on the fish habitat, so treating ammonia is important in land-based aquaculture that uses recycled seawater. The mechanism of ammonia removal in this 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 this invention is shown in the following formula (1). Cl - +HO → 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 placed and electrolyzed, and a diaphragm 14 is provided inside 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 connected to the negative side of a DC power supply (not shown) and adjacent to the anode chamber 18 via the diaphragm 14 is provided. A drain outlet 26 for 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 without causing diffusion due to turbulence, and are large enough to allow treated water Wb, from which ammonia has been removed, to pass through in a laminar flow state.

[0019] Specifically, the anode chamber 18 and the cathode chamber 22 each have a capacity of 300 mL, for example. The electrodes used are a platinum-plated titanium plate for the anode 16 and a stainless steel wire for the cathode 20. As shown in FIG. 2, a synthetic resin plate such as an acrylic plate with slits 24 formed therein is used for the diaphragm 14. The synthetic resin plate has a 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 aquaculture ponds 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 in the diaphragm 14 and moves to the cathode chamber 22. Here, since the electrolytic cell 12 is divided into the anode chamber 18 and the cathode chamber 22 by the diaphragm 14, ClO generated at the anode 16 is - The slits 24 allow the ammonium ions to efficiently come into contact with the ammonium ions in the raw water, i.e., the water to be treated Wa. Furthermore, the water to be treated Wa that passes through the slits 24 thereafter can only pass in a laminar flow state, and 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 water to be treated 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 porous diaphragms such as ceramic plates, the slits have a width of 0.5 mm, so 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. Furthermore, 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, which suppresses turbulent diffusion and prevents the liquids in the anode chamber 18 and the cathode chamber 22 from mixing, so that the diaphragm can function as a diaphragm.

[0022] The ammonia-containing water treatment device 10 of this embodiment can efficiently and reliably remove ammonia from the ammonia-containing water to be treated Wa, and the cleaning of the diaphragm 14 and other maintenance of the device are easy. The diaphragm can also be made highly durable, enabling efficient ammonia removal at low cost. This allows ammonia to be efficiently and continuously removed from seawater or saltwater in a circulating aquaculture tank, making the device effective for aquaculture of fish and shellfish. Furthermore, the diaphragm 14 having the slits 24 can be easily and efficiently manufactured by, for example, laser processing a synthetic resin plate.

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

[0024] Next, an experimental example using the treatment method using 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 conducted 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: 0.80 mg-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: 1.0 mg / -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: 0.02 mg-N / L Voltage 3.3 V (power consumption 99 mW)

[0027] From the above Experiment 1, it was confirmed that the presence of a diaphragm can significantly reduce the ammonium ion concentration in the treated water. Therefore, when the current value was increased from 20 mA in Experiment 1 to 30 mA, a similar experiment was conducted, and it was confirmed that the ammonium ion concentration could be significantly reduced. However, if the current value is increased and electrolysis proceeds too much, excess ClO - This will leave a residue 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. 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 a 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 a negative side of the DC power supply; The diaphragm is formed with a large number of minute water-passing holes, the water-passing holes are of a size that allows water to pass through in a laminar flow state without causing diffusion due to turbulence, and the water-passing holes are 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 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, and 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 through in a laminar flow state and does not cause diffusion due to turbulence.

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