JPH03181391A - Water treating device for decomposition ammoniacal nitrogen - Google Patents

Abstract

PURPOSE:To prevent accumulation of a nitrate ion and a nitrite ion and lowering of pH by constituting a water treating device for decomposing ammoniacal nitrogen so that water for breeding is circulated in series between an ozone treating device and an activated carbon device. CONSTITUTION:Water for breeding is introduced into a reaction tank 8 of ozone by a circulation pump 2 and brought into contact with ozone generated in an ozone generator 6. Oxidative substance is produced by reaction of ozone and a previously added bromine ion. Ammoniacal nitrogen in the water for breeding is allowed to react with the oxidative substance to form gaseous nitrogen and is treated. Ammoniacal nitrogen is directly removed without being accumulated as nitrite nitrogen and nitrate nitrogen. Further nitric acid is not produced and therefore lowering of pH of water can be prevented. Then the oxidative substance remaining in the water for breeding is decomposed in an activated carbon treating device 10. The water for breeding is returned to a water tank 1 for breeding and reutilized.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a technology for chemically treating ammonia nitrogen contained in water of fish and shellfish seedling production and aquaculture, or ornamental aquatic animal rearing tanks. be.

[Prior art] Breeding aquariums are used for the production and cultivation of fish and shellfish seeds, or for raising ornamental aquatic animals such as in aquariums. , water quality gradually deteriorates due to feed residue, etc. When water quality deteriorates, pathogenic bacteria can proliferate, making aquatic animals sick and dying, and inhibiting their healthy growth. To prevent this, - When fishing on a boat, new purified water is introduced into the aquarium to prevent the quality of the aquarium water from deteriorating.

There are two ways to do this: the flush method, in which a fixed amount of clean water is constantly flowing into the aquarium to replace the aquarium water, or the flush method, in which a fixed amount of aquarium water is drained at regular intervals and refilled with the same amount of clean water. There are other methods.

For this purpose, a large amount of clean water is required, and the energy cost required for heating or cooling this supplementary water to adjust it to the optimal rearing and production temperature for aquatic animals is disadvantageous.

As a method to solve these drawbacks, a circulating water reuse method with a purification function using microorganisms has been developed and is now in use in some areas.

Figure 5 shows, for example, the conventional technology shown in "Aquaculture and Water from Effective Utilization Technology of Secondary Water Collection to Improvement of Coastal Environment", Kazuo Sano, Scientist Publishing, pp. 111-112. It is a configuration diagram showing the flow of a circulating water regeneration treatment device, in which (1) is a breeding aquarium, (2) is a breeding water tank;
is the circulation pump, (3) is the filtration device, and (4) is the blower 1.
(5) is an air diffuser.

Next, the operation will be explained.

The water in the aquarium (1) that is contaminated by the metabolism and excrement of aquatic animals, food residue, etc. is sent to the filtration device (3) by the circulation pump (2), where suspended solids are removed and filter sand is removed. Some of the organic matter and ammonia nitrogen are oxidized by the microorganisms attached to it. The treated water returns to the breeding tank (1). On the other hand, the blower (4) is used to supply oxygen necessary for the growth of aquatic animals, and the blown air is passed through the diffuser a (5) into the breeding aquarium using the conventional circulation method for water regeneration. The processing device is configured as described above and has a certain level of purification performance. However, the decomposition of ammonia nitrogen is nitrification that adheres to filter sand! Since it is left to bacteria III, if these bacteria do not grow sufficiently, ammonia nitrogen will not be decomposed and will accumulate. Increased concentrations of ammonia nitrogen and nitrite ions may inhibit the growth or kill aquatic animals. In addition, if properly processed, it will become nitrate ions and its toxicity will decrease, but
Accumulation of nitrate ions causes a decrease in pH, and is therefore generally undesirable as water for breeding.

This invention was made to solve the above-mentioned problems, and aims to completely remove ammonia nitrogen produced by breeding aquatic animals, prevent the accumulation of nitrate ions and nitrite ions, and It is an object of the present invention to provide a water treatment device that decomposes ammonia nitrogen and can prevent a decrease in pH.

[Means for Solving the Problems] A water treatment device for decomposing ammonia nitrogen according to the present invention is composed of a breeding aquarium, an ozone treatment device, an activated carbon device, and a breeding water circulation device, and uses fresh water added with bromide ions. Breeding water consisting of these is circulated in series between them, and the ozone treatment device is installed upstream of the activated carbon device with respect to the flow direction of the breeding water.

Furthermore, in the above device, the circulating water flowing out from the aquarium is divided into two parts, one of which passes through the ozone treatment device and the other bypasses the ozone treatment device, and is then mixed with the ozonated circulating water and sent to the activated carbon device. The amount of circulating water that flows in and is divided into the ozone treatment device is 5 x ammonia nitrogen concentration (mg/l) x circulating water amount (1/min) ≦ ozone absorption amount (mg/l) x circulating water amount (1 /min).

[Effect] As a result of intensive research into the fundamental problem of the method for removing ammonia nitrogen, the present inventors discovered that ammonia nitrogen can be completely removed by using ozone in the presence of bromine ions. This invention was made based on this knowledge. Ozone injected into circulating water from a breeding tank reacts with bromide ions pre-added to freshwater breeding water to produce oxidizing substances. chemical substances decompose ammonia nitrogen. The latter activated carbon treatment prevents injected ozone or oxidizing substances produced by the reaction between ozone and bromide ions from flowing into the aquarium containing the aquatic animals.

[Example] In discovering this invention, a fish tank, a circulation pump,
Closed circulation water treatment was performed in the following process order: sand filter tank, ozone treatment tank, activated carbon treatment tank, and fish culture tank, and the effectiveness of removing ammonia nitrogen in seawater was investigated.

As a result, ammonia nitrogen decreased sequentially through each treatment process. The decrease in ammonia nitrogen in the sand filter tank and activated carbon tank was thought to be due to the nitrification effect of nitrite bacteria living attached to the filter sand and activated carbon surface.

On the other hand, the nitrite nitrogen measured at the same time increased or remained unchanged with sand filtration and activated carbon treatment, that is, in this experiment, nitrite M!, which oxidizes nitrite to nitric acid! The activity of bacteria III was lower than that of nitrite bacteria. Nitrite nitrogen was significantly reduced by ozone treatment, and in the process flow used in the experiment, the removal effect of nitrite nitrogen by ozone was large.

Among the above experimental results, the nitrification effect by adherent microorganisms and the oxidative decomposition of nitrite nitrogen by ozone are phenomena that have been known for a long time.

In this experiment, the inventor noticed that ammonia nitrogen was reduced by ozone treatment. Ammonia nitrogen exists as ammonium ions near neutrality, but since ammonium ions do not react with ozone, it was thought that ozone treatment could hardly decompose it near neutrality ("Aquatic Growth and Water Volume 1 Water Quality "Evaluation and Technical Response", Kazuo Sano, Scientist Publishing, p. 157).

Based on these results, the present inventors inferred the decomposition mechanism of ammonia nitrogen in seawater by ozone as follows. When ozone is injected into seawater, bromine ions, which are present at about 60 mg/l in seawater, are oxidized to produce oxidizing substances, and the oxidizing substances produced here decompose ammonia nitrogen. Therefore, by using ozone to generate the oxidizing substances necessary to decompose ammonia nitrogen present in seawater, ammonia nitrogen can be efficiently decomposed by ozone. Furthermore, even when decomposing ammonia nitrogen present in freshwater systems, if bromine ions are intentionally added to water, ammonia nitrogen may be decomposed by ozone.

Based on this assumption, we conducted an experiment to investigate the relationship between the amount of ozone injection and the decomposition of ammonia nitrogen.

Phosphate buffer)α(p)17.3) 1mM potassium bromide (approximately 80mg/l as bromide ion) and ammonium chloride (2mg/l as ammonia nitrogen) were added to ion-exchanged water containing 1mM. After the addition, the amount of ozone injected was varied to examine the decrease in ammonia nitrogen concentration.

The results are shown in FIG. As is clear from the figure, the amount of ozone required to completely decompose 2 mg/l of ammonia nitrogen was found to be approximately 10.6 mg/l or more (point a). That is, if about 5.3 times or more ozone is absorbed into water per 1 mg of ammonia nitrogen, the ammonia nitrogen is completely decomposed.

Therefore, we detected the ammonia nitrogen concentration in the ozonated Ha artificial water, and found that the ozone consumption was approximately 5.3% of the ammonia nitrogen concentration.
By controlling the amount to double, feedforward control that can effectively decompose ammonia nitrogen is possible.

In addition, feedback control is also possible to correct excess or deficiency in the amount of ozone injection by measuring the concentration of oxidizing substances as well as ammonia nitrogen as the water quality after ozone treatment.

In this way, ammonia nitrogen is decomposed by ozone, and by adding feedback control and the like, ozone treatment is properly performed.

However, in reality, it is not always possible to add a system to control the amount of ozone injection, so it is necessary to take measures to deal with excesses and deficiencies in the amount of ozone injection. If the amount of ozone injected is too large relative to ammonia nitrogen, oxidizing agents such as ozone and bromine oxide remain in the treated water. Oxidizing substances have strong oxidizing power and are generally considered to be toxic to aquatic animals.

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a configuration diagram showing a water treatment device for decomposing ammonia nitrogen according to an embodiment of the present invention. In the same figure, (
6) is an ozone generator for removing ammonia nitrogen from breeding water, (7) is an aeration device, and (8) is water containing ammonia nitrogen and ozone generated by the ozone generator (6). (9) is an exhaust ozone treatment device, and (10) is an activated carbon treatment device for removing oxidizing substances such as ozone remaining in the treated water after decomposing nitrogen components.

Next, the operation will be explained. The breeding water polluted by the metabolism and excretion of aquatic animals in the breeding aquarium (1) is removed using the circulation pump (2).
) into the ozone reaction tank (8), where it is brought into contact with the ozone generated by the ozone generator (6). here,
Oxidizing substances generated by the reaction between ozone and bromine ions added in advance react with ammonia nitrogen in the rearing water, and the ammonia nitrogen is converted into nitrogen gas and treated. Unreacted ozone gas is treated in the exhaust ozone treatment device (9) and then released into the atmosphere.

Oxidizing substances remaining in the rearing water after ammonia nitrogen has been decomposed in the ozone reaction tank (8) are then decomposed in an activated carbon treatment device (1O). The breeding water is returned to the breeding tank (1
) and reused for breeding and production of aquatic animals.
), and the breeding aquarium (1), it is convenient if the breeding water is moved by a water level difference.

By installing an ozone treatment device and an activated carbon treatment device in a rearing water circulation system to which bromide ions have been added in advance, ammonia nitrogen in the rearing water can be prevented from accumulating as nitrite nitrogen or nitrate nitrogen. removed directly. In addition, since nitric acid is not produced, it is possible to prevent a drop in the pH of the water, making it almost unnecessary to replace the water with clean water.

Furthermore, since oxidizing substances are decomposed by activated carbon treatment, oxidizing substances will not flow into the aquarium and have a negative impact on aquatic animals.

By the way, in this invention, by adding a suspended solids removal device such as a sand filter tank between the circulation pump (2) and the ozone reaction tank (8), suspended solids in the water to be treated can be removed from the ozone. It is also possible to adopt a configuration in which the ozone is removed before the treatment and the ozone is injected to efficiently decompose the ammonia nitrogen.

Next, other embodiments of the invention will be described.

In the above example, in addition to decomposing ammonia nitrogen using ozone, by taking a means to remove unreacted oxidizing substances, ammonia nitrogen can be removed in a circulating water treatment reprint system without having any adverse effects on farmed animals. nitrogen can be decomposed. However, the experiment conducted earlier suggested that the substance presumed to be bromamine, a compound of ammonia nitrogen and bromine oxide, reverts back to ammonium ions in the activated carbon treatment equipment.

Therefore, there is no problem when there is an amount of ozone sufficient to decompose ammonia nitrogen, but a problem occurs when the amount of ozone required for decomposition exceeds the capacity of the ozone generator. In other words, when the amount of ozone is insufficient, ammonia nitrogen is not completely decomposed to V gas, but is thought to change to bromamine, a bound bromine compound, but bromamine is converted back to ammonium ions in an activated carbon device. This reduces the effectiveness of ozone treatment.

On the other hand, it is assumed that the circulating liquid to be treated is divided into two halves, one of which is subjected to ozone treatment, and the other of which is not. In this way, the absolute amount of ammonia nitrogen flowing into the ozonation system is halved. For example, in FIG. 2, the ozone treatment corresponds to point 6 in full treatment, and the ozone treatment corresponds to point a in half treatment, and most of the ammonia nitrogen is decomposed into nitrogen gas. Although ammonia nitrogen is not decomposed in one of the systems in which ozone treatment is not performed, approximately half of the total amount is decomposed, resulting in better results than the system for the batch treatment of all water according to the embodiment shown in FIG. FIG. 3 is a block diagram showing the system flow of such a water treatment device. In the figure, (11) is a flow divider that branches ozonated water and untreated water at an arbitrary ratio, and (I2) is a It is a water confluencer for the system.

Next, the operation will be explained. Breeding water contaminated by fish metabolism, excretion, etc. in the breeding tank (1) is divided by a flow divider (11), and some water flows into the ozone reaction tank (8), where it is treated with an ozone generator (6). When brought into contact with the generated ozone, the oxidizing substances produced by the reaction between ozone and water react with the ammonia nitrogen in the breeding water, and the ammonia nitrogen is converted into nitrogen gas and treated.

Unreacted ozone gas is treated in the exhaust ozone treatment device (9) and then released into the atmosphere.

- On the other hand, water that has not passed through the ozone reaction tank (8) in the flow divider (11) is mixed with ozonated water in the confluencer (12) and sent to the activated carbon treatment device (10). The breeding water that has passed through the activated carbon treatment device (10) is returned to the breeding aquarium (1) and reused for breeding and production of aquatic animals.

By setting the flow rate diverted to the ozone treatment tank (8) by the flow divider (+1) to be equal to or higher than the amount of ozone that generates the oxidizing substances necessary to decompose ammonia nitrogen, at least ozone treatment can be performed. In this system, most of the ammonia nitrogen can be decomposed.

Specifically, from the results shown in Figure 2, 5 of ammonia nitrogen
It is good to have an amount of water that absorbs more than double the amount of ozone. That is, 5x ammonia nitrogen concentration (mg/) x circulating water amount (
1/min)≦Ozone absorption amount (mg/l)
/minute>. In this way, by diverting some of the water to the ozone treatment tank through the branch pipe, it is possible to prevent the production of large amounts of bromamine, which is an intermediate decomposition product of ammonia nitrogen, and to convert ammonia nitrogen into nitrogen gas. Decomposition is carried out efficiently.

FIG. 4 shows an embodiment in which the positions of the flow divider (11) and the merger (12) are reversed, and (13) is a pump that sends water to the ozone treatment tank (8). In FIG. 4, a confluencer (12) is installed upstream of a flow divider (11), thereby improving the mixing of water in both systems until it flows into the activated carbon device (10). Furthermore, by increasing the contact time with oxidizing substances, etc., the decomposition reaction is made to proceed more easily.

[Effects of the Invention] As described above, according to the present invention, a water treatment device for decomposing ammonia nitrogen is configured by a breeding aquarium, an ozone treatment device, an activated carbon device, and a water circulation device for breeding, and bromine ions are not added. Breeding water consisting of fresh water circulates between them in series, and the ozone treatment device is installed upstream of the activated carbon device with respect to the flow direction of the breeding water, so that breeding of aquatic animals, etc. This has the effect of completely removing the ammonia nitrogen generated by the process, preventing the accumulation of nitrate ions and nitrite ions, and preventing a decrease in pH.

Furthermore, in the above device, the circulating water flowing out from the aquarium is divided into two parts, one of which passes through the ozone treatment device and the other bypasses the ozone treatment device, and is then mixed with the ozonated circulating water and sent to the activated carbon device. The amount of circulating water that flows in and is divided into the ozone treatment device is 5 x ammonia nitrogen concentration (m3/l) x circulating water ff1 (1/min) ≦ ozone absorption amount (mg/l) x circulating water 11 (1/min), ammonia nitrogen can be reliably decomposed.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a water treatment apparatus according to an embodiment of the present invention, FIG. 2 is a characteristic diagram showing the relationship between ozone absorption amount and ammonia nitrogen concentration, and FIGS. 3 and 4 are each according to the present invention. FIG. 5 is a block diagram showing a water treatment apparatus according to another embodiment, and FIG. 5 is a block diagram showing a conventional water treatment apparatus. In the figure, (+) is a breeding tank, (2) is a circulation pump,
(F3) is an ozone generator, (8) is an ozone reaction tank, (
9) is an exhaust ozone treatment device, (10) is an activated carbon treatment device,
(11) is a flow divider, and (12) is a merger. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] (1) Consisting of a breeding aquarium, an ozone treatment device, an activated carbon device, and a breeding water circulation device, breeding water consisting of fresh water to which bromide ions have been added circulates in series between these, and the flow of the breeding water. A water treatment device for decomposing ammonia nitrogen, wherein the ozone treatment device is installed upstream of the activated carbon device with respect to the direction. (2) The circulating water flowing out from the breeding aquarium is divided into two parts, one passes through the ozone treatment device, and the other bypasses the ozone treatment device, then mixes with the ozonated circulating water and flows into the activated carbon device, And the amount of circulating water divided into the ozone treatment equipment is 5 x ammonia nitrogen concentration (mg/l).
) × Circulating water amount (l/min) ≦ Ozone absorption amount (mg/l) ×
The water treatment device for decomposing ammonia nitrogen according to claim 1, wherein the amount of circulating water is controlled to be (l/min).