JP2022125959A - Water bottom purifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water bottom purifier for efficiently reducing a thickness of an organic matter sedimented in a water bottom.

SOLUTION: A water bottom purifier includes a biological reaction apparatus 100 to be used in water treatment and upward flow generation means 600 to send water to be treated to the biological reaction apparatus. The biological reaction apparatus is assembled with a filter medium 200, a purification microorganism growing in the filter medium, a lead passage to lead water to be treated to the filter medium, a drainage water passage to drain water to be treated having been contacted with the filter medium, and aeration means 500 to supply oxygen to water to be treated to be lead to the filter medium. The purification microorganism comprises a hay bacillus which is an aerobic microorganism decomposing a dissolved organic matter, a nitrifying bacteria which is an aerobic microorganism conducting nitrification reaction, and a denitrification bacteria which is an anaerobic microorganism conducting denitrification reaction. The hay bacillus, the nitrifying bacteria, and the denitrification bacteria growth in the same filter medium, and nitrification and denitrification of a nitrogen compound involved in the water to be treated are performed simultaneously.

SELECTED DRAWING: Figure 9

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to a bioreactor that can be used for treating sewage, tap water, or various other water treatments. The invention also relates to a water bottom cleaning apparatus using the bioreactor for cleaning a water bottom on which organic matter is deposited.

Advanced water purification combines physical purification with bioreactor purification by microorganisms such as bacteria. In purification using a biological reactor, removal of organic substances and removal of nitrogen compounds such as ammonia and nitric acid are mainly performed.

Removal of ammonium nitrogen is particularly important in sewage treatment. In most common sewage treatment, the bioreactor consists of two filtration tanks, an aerobic tank with high dissolved oxygen concentration and an anaerobic tank with low dissolved oxygen concentration.
For example, there has been proposed a wastewater treatment apparatus composed of an anaerobic filter bed tank 1 (anaerobic tank) that decomposes organic matter with anaerobic bacteria and a contact aeration tank 2 (aerobic tank) that decomposes organic matter with aerobic bacteria. (For example, Patent Document 1).

In addition, for the purpose of downsizing the equipment and simplifying the treatment, a single-layer septic tank has been developed that serves both as an aerobic tank and an anaerobic tank.
For example, by controlling the operation of the blower 7 and changing the concentration of dissolved oxygen over time to alternately create aerobic and anaerobic conditions, aerobic and anaerobic bacteria can be treated in a single tank. (for example, Patent Document 2 and Patent Document 3).

Aerobic bacteria and anaerobic bacteria are propagated on different floating filter media, the filter media for anaerobic bacteria with heavy specific gravity are suspended in the lower part of the tank, the filter media for aerobic bacteria with heavy specific gravity are suspended in the upper part, and the aeration means is in the middle. (Aeration means) is provided to make the water to be treated rise, creating an aerobic state and an anaerobic state in one tank, realizing treatment with aerobic and anaerobic bacteria (for example, Patent Document 4).

Japanese Patent Laid-Open No. 4-298290 Japanese Patent Laid-Open No. 11-165190 Japanese Patent Laid-Open No. 6-328099 JP 2001-269688

The bioreactor described in Patent Document 1 requires two filtration tanks, an aerobic tank and an anoxic tank, and also requires complicated return control of activated sludge amount and sludge treatment. Therefore, there are various problems such as a complicated device configuration, an increased size of the device, and a longer processing time.

In the method of changing the dissolved oxygen concentration with time by so-called intermittent aeration described in Patent Document 2 and Patent Document 3, the aeration amount is adjusted with high accuracy so that aerobic bacteria and anaerobic bacteria are sufficiently activated. need to adjust. An advanced control system is required because the optimal amount of aeration varies depending on the degree of contamination of the water to be treated, the temperature of the water, and other factors. In addition, the treatment with aerobic bacteria and the treatment with anaerobic bacteria are alternately performed, so the purification efficiency is not high.

The same applies to the method of changing the dissolved oxygen concentration depending on the location described in Patent Document 4, which requires advanced management of the amount of aeration. In addition, treatment with anaerobic bacteria is performed on the upstream side of the flow of the water to be treated, and treatment with aerobic bacteria is performed on the downstream side. The treatment with anaerobic bacteria is a treatment that reduces and denitrifies the nitrous acid and nitric acid produced by the treatment with aerobic bacteria. Therefore, since the direction of treatment is opposite to the progress of the reaction, the treatment efficiency as a whole is lowered.

Therefore, in each of the methods described in Patent Documents 2 to 4, treatment with aerobic bacteria and treatment with anaerobic bacteria are performed separately.
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and simultaneously performs treatment with aerobic bacteria and treatment with anaerobic bacteria, which has not been possible in the past. This makes it possible to purify water at an incomparably high speed.

The bottom water purification device according to the present invention is
a bioreactor for water treatment;
and an upward flow generating means for sending the water to be treated to the biological reactor,
The bioreactor is
a filter medium;
purifying microorganisms growing on the filter medium;
an introduction path for guiding the water to be treated to the filter medium;
a drainage path for draining the water to be treated that has come into contact with the filter medium;
and an aeration means for supplying oxygen to the water to be treated that is led to the filter medium,
The purifying microorganisms are Bacillus subtilis, which is an aerobic microorganism that decomposes dissolved organic matter, Nitrifying bacteria, which is an aerobic microorganism that performs nitrification, and Denitrifying bacteria, which is an anaerobic microorganism that performs denitrification,
The Bacillus subtilis, the nitrifying bacteria, and the denitrifying bacteria grow in the same filter medium,
Nitrification and denitrification of the nitrogen compounds contained in the water to be treated are performed simultaneously.

Since the bioreactor used for water treatment of the present invention is configured as described above, nitrification and denitrification of nitrogen compounds can be performed simultaneously. This makes it possible to perform nitrification and denitrification at extremely high speeds compared to conventional bioreactors.
Therefore, it is possible to increase the speed and efficiency of water treatment.
Furthermore, since the device configuration is simple, the size of the device can be reduced.
In addition, little excess activated sludge is generated, and excess sludge treatment costs can be reduced. Furthermore, since nitrification and denitrification progress at the same time, the water to be treated is not biased toward the acidic side. Therefore, the addition of alkali for neutralization is unnecessary, and the cost and trouble of pH adjustment are unnecessary.

By further providing an upward flow generating means for sending the water to be treated to the biological reaction device, it is possible to obtain a water bottom purification device that efficiently purifies the water bottom.
In estuaries, coastal areas, bays, lakes, ponds, etc., organic matter accumulates thickly on the bottom of water, which is a major factor in deteriorating water quality.
Dredging is also used to remove deposited organic matter, but it is not a fundamental countermeasure because the organic matter accumulates again after dredging, despite the enormous cost of removal.

On the other hand, the method of lifting up the deposited organic matter using a pump, screw, or the like can be performed at a relatively low cost, but there is a risk that the contaminated area will expand because the organic matter that has been lifted up diffuses into the surroundings.
However, in the present invention, by introducing the water to be treated containing the organic matter that has been swirled up into the bioreactor used for water treatment, biological purification can be performed before the organic matter diffuses into the surroundings. Since the bioreactor used for water treatment of the present invention has a high purification efficiency, even water to be treated containing high concentrations of organic substances and inorganic nitrogen can be treated to a good quality.

1 is an internal transparent side view of a bioreactor used for water treatment of the present invention; FIG. FIG. 2 is a see-through side view of the bioreactor used for water treatment of the present invention, showing the case where the aeration means is arranged on the downstream side. It is an experimental result showing the dissolved oxygen dependence of the quality of water treated with the bioreactor used for water treatment of the present invention, and is the case where the aeration means is arranged on the upstream side. It is an experimental result showing the dissolved oxygen dependence of the quality of water treated with the bioreactor used for water treatment of the present invention, and is the case where the aeration means is arranged downstream. It is an experimental result which shows the particle size dependence of the filter medium of the water quality processed with the bioreactor used for the water treatment of this invention. Fig. 2 shows the acclimation period dependence of water quality treated with the bioreactor used for water treatment of the present invention. It is a reference diagram showing the acclimation period dependence of water quality when Bacillus subtilis is not propagated. FIG. 2 is an internal transparent side view of a bioreactor used for water treatment according to Embodiment 2 of the present invention. It is a side view of the water bottom purification apparatus of Embodiment 3 of this invention. It is a side view of an aquaponics device according to Embodiment 4 of the present invention.

The bioreactor used for water treatment of the present invention can be used for various water treatments such as sewage treatment, clean water treatment, agricultural wastewater treatment and livestock wastewater treatment, that is, water purification.
It should be noted that, like the conventional bioreactor, it is assumed to be used together with physical filtration, chemical treatment, and the like. Of course, depending on the application, it can also purify water alone.

Several preferred embodiments are described below, but the present invention is not limited to these embodiments, but broadly includes similar inventive concepts.
First, in Embodiment 1, the basic requirements of the bioreactor used for water treatment of the present invention will be described, centering on the configuration of a fixed filter medium. Next, in Embodiment 2, the configuration of the fluid filter medium will be mainly described. In Embodiment 3, as an application of the bioreactor used for water treatment of the present invention, a method for removing organic matter deposited on the bottom of water will be described.

Embodiment 1.
<Configuration>
FIG. 1 is an internal transparent side view of a bioreactor used for water treatment of the present invention.
As shown in FIG. 1, a bioreactor 1 used for water treatment according to the present invention includes a filter medium 2, purifying microorganisms growing on the filter medium 2, an introduction path 3 for guiding water to be treated to the filter medium 2, and the filter medium 2. and an aeration means 5 for supplying oxygen to the water to be treated led to the filter medium 2 . The water to be treated is introduced into the bioreactor 1 through the introduction path 3 , flows through the filtering medium 2 , and is discharged through the drainage path 4 .

The filter medium 2 may be of any type as long as it allows microorganisms to propagate. For example, gravel, gravel, resin, ceramic, etc. are suitable. The filter medium 2 is immersed in the water to be treated. Alternatively, even if the filter medium 2 is not completely immersed in the water to be treated, the water to be treated may drip onto the filter medium 2 like a shower.

The purifying microorganisms are Bacillus subtilis, nitrifying bacteria, and denitrifying bacteria, and grow within the same filter medium 2 .
Here, Bacillus subtilis is an aerobic bacterium and is Bacillus subtilis or Bacillus subtilis var. natto.
Nitrifiers are aerobic bacteria, nitrites (ammonia-oxidizing bacteria) and nitrites (nitrite-oxidizing bacteria). Nitrite bacteria are bacteria that oxidize ammonia in soil to nitrite (ammonia oxidizing bacteria) or archaea (ammonia oxidizing archaea). Nitrate bacteria are bacteria that oxidize nitrite to nitrate.

In addition, denitrifying bacteria are facultative anaerobic bacteria that reduce nitrate HNO3 or nitrite HNO2, convert it to nitrogen gas, and release it into the air, and are also called denitrifying bacteria.

A major point of the present invention is that the growth (propagation) of Bacillus subtilis, nitrifying bacteria, and denitrifying bacteria in the same filter medium 2 creates a cooperative relationship among them. Grown within the same filter medium 2, these purifying microorganisms are believed to thrive in optimal locations within the filter medium 2 so that each can work most efficiently. Therefore, each can work cooperatively with each other. That is, synergistic highly efficient purification reactions may occur. In particular, the simultaneous occurrence of nitrification and denitrification may enable conversion of nitrogen compounds to nitrogen gas with very high efficiency. Furthermore, at this time, the oxidation reaction of organic substances by Bacillus subtilis may accelerate the nitrification and denitrification reactions.

The aeration means 5 introduces oxygen into the water to be treated using a pump, an air diffuser, or the like. Pure oxygen may be introduced, or air may be introduced. Alternatively, fine bubbles of air or oxygen may be used. In FIG. 1, the aeration means 5 is shown in the bioreactor 1, but before introducing the water to be treated into the bioreactor 1, for example, another water tank is provided, and the water to be treated is Oxygen may be dissolved. Therefore, the aeration means 5 does not necessarily have to be inside the bioreactor 1 .

<Verification experiment>
Several experiments were conducted to verify the performance of the bioreactor used for water treatment of the present invention. These experimental conditions and experimental results are detailed below.

(Verification experiment 1)
The water tank of the bioreactor 1 was 1 m long and 1 m20 cm high, and about 1 ton of water to be treated was placed therein. Then, the water to be treated was introduced and discharged at a flow rate of 150 L/min.
Relatively dirty river water was used as the water to be treated introduced into the bioreactor 1 and mixed with ammonium sulfate so that the ammonia nitrogen concentration was 10 mg/L.

Sand having an average particle size of 3 mm was used as the filter medium 2 . The total volume of sand is 300L. Bacillus subtilis, nitrifying bacteria, and denitrifying bacteria were propagated and acclimatized in the filter medium 2 by continuously flowing the water to be treated for one month.

Nitrogen gas is introduced in advance into the water to be treated to make the dissolved oxygen concentration (DO) almost zero, and by changing the aeration amount of the aeration means 5, the dissolved oxygen concentration of the water to be treated in the bioreactor 1 changed. The dissolved oxygen concentration was measured in the vicinity of the aeration means 5. That is, the dissolved oxygen concentration of the water was measured before the oxygen was consumed by the purifying microorganisms.
As shown in FIG. 1, the aeration means 5 was arranged on the upstream side of the flow of the water to be treated (introduction path 3 side) with respect to the filter medium 2, and the dissolved oxygen concentration was measured at the point indicated by A.
For comparison, a similar experiment was also conducted by changing the position of the aeration means. As shown in FIG. 2, the aeration means 5a was arranged downstream of the flow of the water to be treated (on the side of the drainage path 4) with respect to the filter medium 2, and the dissolved oxygen concentration was measured at the point indicated by B.

The water quality was judged by the rate of removal of nitrogen compounds from the water discharged from the water discharge means 4 to be treated. That is, evaluation was made by measuring the concentrations of ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen.
The water temperature of the water to be treated is 25°C.

3 shows the water quality evaluation results when the aeration means is arranged upstream of the flow of the water to be treated with respect to the filter medium 2 (in the case of FIG. 1), and FIG. It is a water quality evaluation result when it arrange|positions at the downstream of a flow (in the case of FIG. 2). The horizontal axis is the concentration of dissolved oxygen, and the vertical axis is the concentrations of ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen in waste water (water after purification).

Whether the aeration means is arranged upstream or downstream, the concentrations of ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen show similar trends with respect to the dissolved oxygen concentration, and are 5 mg/L. to the saturated dissolved oxygen concentration. That is, good water quality improvement was achieved at high dissolved oxygen concentrations.

However, it was found that the concentrations of ammonium nitrogen, nitrite nitrogen, and nitrate nitrogen became lower when the aeration means was arranged upstream, and the effect of improving water quality was greater. When the aeration means is arranged upstream and the dissolved oxygen concentration is increased from 5 mg/L to the saturated dissolved oxygen concentration, almost no ammonium nitrogen and nitrite nitrogen are detected, and the concentration of nitrate nitrogen is also extremely low. rice field.

This result also indicates that nitrification and denitrification of nitrogen compounds occur simultaneously. If only nitrification was carried out, nitrous acid and nitric acid would remain in high concentrations. However, the low concentration of nitrous acid and nitric acid in one-pass treatment without circulating the water to be treated indicates that nitrification and denitrification are progressing simultaneously. An important result was obtained that when nitrification and denitrification proceeded simultaneously, the higher the dissolved oxygen concentration, the more efficient the nitrification and denitrification.

(Verification experiment 2)
Next, the dissolved oxygen concentration was fixed at 7 mg/L, and the average particle size of the filter medium 2 was varied from 0.2 mm to 18 mm to investigate how the average particle size of the filter medium 2 affects water quality improvement. . The arrangement of the aeration means 5 is on the upstream side.
Other conditions are the same as in Verification Experiment 1.

FIG. 5 shows the experimental results.
Good results were obtained with an average particle size of 1 mm to 10 mm. Regarding the average particle size of the filter medium 2, it was confirmed that a good water quality improvement effect was obtained in such a wide range.

(Verification experiment 3) (Experiment to show the effect of coexisting Bacillus subtilis in the same filter medium)
Nitrogen compounds are generally removed by nitrifying bacteria and denitrifying bacteria, but in order to confirm whether Bacillus subtilis plays a supplementary role, whether or not the presence or absence of Bacillus subtilis breeding causes a difference in water quality. Verification experiments were also conducted for

Aeration was performed on the upstream side, and the dissolved oxygen concentration was adjusted to 7 mg/L. Moreover, the average particle size of the filter medium was set to 3 mm. Changes in water quality from the start of propagation of purifying microorganisms were examined when Bacillus subtilis was propagated on the filter medium 2 and when only nitrifying bacteria and denitrifying bacteria were propagated without Bacillus subtilis. That is, we investigated how the water quality changed during and after the acclimatization period of the purifying microorganisms.

FIG. 6 shows water quality data when Bacillus subtilis, nitrifying bacteria, and denitrifying bacteria are propagated on the filter medium 2, and the horizontal axis indicates the period from the start of propagation. Four weeks after the start of breeding, ammonium nitrogen and nitrite nitrogen almost disappeared, and nitrate nitrogen also became low. The water quality was good even after 4 weeks from the start of breeding.

FIG. 7 shows water quality data when only nitrifying bacteria and denitrifying bacteria are propagated in the filter medium 2 . Ammonia nitrogen was detected until the 8th week, and became low after the 10th week. In addition, although the concentration of nitrous acid became low at the 10th week, it did not disappear completely, and about 0.2 mg/L was still detected after the 10th week.

As described above, it was found that the presence or absence of Bacillus subtilis caused a clear difference in both the acclimation period and water quality. It was confirmed that a cooperative relationship was obtained, the acclimatization period could be shortened, and the water quality was improved.

<Summary of this embodiment>
As described above, it was confirmed that the bioreactor used for water treatment of the present invention can purify water, particularly remove nitrogen compounds, at an extremely high speed.

A characteristic configuration of the present invention is to grow three kinds of purifying microorganisms in one filter medium. This is thought to be due to the fact that each microorganism breeds in a place and under conditions where it can work most efficiently, so that the three types of purifying microorganisms cooperate with each other to perform water treatment.

Although the details of the cooperative relationship are unknown, for example, regarding the relationship between Bacillus subtilis and nitrifying bacteria, as Bacillus subtilis decomposes dissolved organic matter, the concentration of dissolved organic matter, which is an inhibitor of the nitrification reaction performed by nitrifying bacteria, becomes low. It is thought that nitrification occurs with high efficiency. In addition, when Bacillus subtilis decomposes dissolved organic matter, carbon dioxide is generated. Nitrifying bacteria can utilize this carbon dioxide to synthesize proteins and promote their propagation.
As for the relationship between Bacillus subtilis and denitrifying bacteria, the dissolution of suspended organic matter by Bacillus subtilis provides sufficient hydrogen donors necessary for the denitrifying reaction of the denitrifying bacteria.

It can be imagined that the cooperative relationship as described above actually progresses more complicatedly among the three kinds of purifying microorganisms, and extremely high-speed water treatment is performed. Such a cooperative relationship is made possible because three kinds of purifying microorganisms coexist in one filter medium.

Another characteristic of the present invention is that not only nitrification but also denitrification is carried out at high speed at a high dissolved oxygen concentration of 5 mg/L or more. In conventional water treatment systems, nitrification must be performed under high oxygen concentration and denitrification must be performed under oxygen-free or extremely low oxygen concentration. It is considered that this is because nitrification and denitrification do not occur separately, but proceed simultaneously, that is, as a continuous reaction.

Due to such a characteristic configuration of the present invention, a water treatment apparatus having many features described below has been embodied.
First of all, high-speed nitrification and denitrification, which had been unthinkable in the past, could be realized simultaneously. As a result, the device can be made smaller, and the cost of the water treatment facility can be greatly reduced. It can also be used as a water purification system for households and small groups.
Furthermore, since nitrification and denitrification progress at the same time, the water to be treated is not biased toward the acidic side. Therefore, no alkali is required for neutralization.

Second, no sophisticated control of the amount of aeration is required. Since denitrification can be performed under the same high dissolved oxygen concentration as nitrification, detailed control is not required. If sufficient oxygen can be supplied to the water to be treated, both nitrification and denitrification can proceed at high speed.

Thirdly, purification microorganisms are of the fixed filter medium type, and surplus sludge is hardly generated compared to the floating type activated sludge method. Therefore, the cost of treating excess sludge, which occupies a large cost in conventional water treatment, is greatly reduced. In addition, since the configuration of returned sludge and the like becomes unnecessary, it is possible to reduce the cost of the apparatus and simplify the management.

As described above, the present invention has various advantages necessary for a water treatment apparatus, such as speeding up of water treatment, downsizing of the apparatus, reduction of apparatus cost and running cost, and simplification of management.

Embodiment 2.
A bioreactor used for water treatment according to Embodiment 2 will be described with reference to FIG. FIG. 8 is an internal see-through side view of bioreactor 10 .
In the first embodiment, purifying microorganisms are propagated on the fixed filter medium, but in this embodiment, purifying microorganisms are propagated on the filter medium 20 flowing in the water to be treated.

The filter medium has micropores such as polyethylene glycol, polyvinyl formal, ethylene foam, urethane, and volcanic debris such as pumice, and any material with a specific gravity equal to or slightly higher than that of water can be used. Good material.
The size of the filter medium ranges from several millimeters to several centimeters.
It is desirable that the fine holes have a diameter of about 0.5 mm to 2 mm. In order to propagate Bacillus subtilis, nitrifying bacteria, and denitrifying bacteria, micropores of this size are suitable.

A filter medium 20 propagated with Bacillus subtilis, nitrifying bacteria, and denitrifying bacteria is allowed to flow in the water to be treated. The water to be treated is introduced into the bioreactor 10 through the introduction route 30 and discharged through the discharge route 40 . An aeration means 50 is provided at the bottom of the bioreactor 10 . The aeration means 50 is, for example, an air diffuser, and air and oxygen are released in the form of bubbles. The buoyancy of the bubbles causes the filter medium 20 to flow. That is, the means for fluidizing the filter medium 20 is an air lift using an aeration means.

The flow of the filter medium 20 in the water to be treated increases the chances of contact between the water to be treated and the purifying microorganisms that propagate in the filter medium 20, and purification of the water to be treated is efficiently performed.

Further, when the water to be treated is seawater, the foam separating means 80 provided on the upper part of the bioreactor 10 removes the foam attached to the surface of the organic matter, thereby efficiently removing the suspended organic matter. is also possible.

Furthermore, the addition of Bacillus subtilis var. natto to the bioreactor 10 accelerates the removal of organic matter. This is because Bacillus subtilis natto releases γ-polyglutamic acid, which aggregates suspended organic matter by taking a fibrous structure. If the aeration means 50 is stopped, the flocculated Bacillus subtilis natto settles in the sediment accumulation part 70 provided at the bottom of the bioreactor 10, and can be discharged by opening the valve V3.

(Verification experiment 4)
4m3 of water collected from a pond where domestic wastewater accumulated was stored in a tank and purified. The main water qualities before purification were as follows.

COD (Chemical Oxygen Demand): 50mg/L
SS (suspended organic matter): 55mg/L
Ammonia nitrogen: 20mg/L
Nitrite nitrogen: 0.5mg/L
Nitrate nitrogen: 2mg/L

Hyugaite with an average diameter of 1 cm was used as a filter medium, and nitrifying bacteria, denitrifying bacteria and Bacillus subtilis were propagated in advance. Then, about 1.5 m3 of filtering material was placed in the tank for purification. The amount of aeration is 50 L/min, and the flow rate of treated water is 50 L/min.

The water quality after purification is as follows.

COD (Chemical Oxygen Demand): 20mg/L
SS (suspended organic matter): 26mg/L
Ammonia nitrogen: 1mg/L
Nitrite nitrogen: 2.8mg/L
Nitrate nitrogen: 4mg/L

As described above, the water quality was improved, and it was found that even when the filter medium was made to flow, there was an effect of improving water quality in the same way as with the fixed filter medium.

(Verification experiment 5)
A purification experiment was conducted by flowing the filter medium in the same manner as in Verification Experiment 4. The difference from Verification Case 4 is that 10 cc/min of Bacillus subtilis natto was introduced from the upper part 80 of the tank.

The water quality after purification is as follows.

COD (Chemical Oxygen Demand): 3mg/L
SS (suspended organic matter): 2mg/L
Ammonia nitrogen: Below detection limit Nitrite nitrogen: 0.3mg/L
Nitrate nitrogen: 4mg/L

Thus, by adding Bacillus subtilis natto, the water quality was significantly improved, and both organic matter and inorganic nitrogen were significantly reduced.

<Summary of this embodiment>
As can be seen from the above results, the use of the fluidized filter bed (fluidized carrier) also enables highly efficient purification as with the fixed filter bed shown in the first embodiment. In particular, it was confirmed that adding Bacillus natto not only removed organic matter but also improved the efficiency of nitrification and denitrification.

Embodiment 3.
A water bottom cleaning apparatus according to Embodiment 3 will be described with reference to FIG. It is a device that performs particularly effective purification in a water area where organic matter has accumulated on the bottom of the water, and is intended to reduce the thickness of the deposited organic matter and improve the purification environment of the water bottom.

The upward flow generating means 600 is used to lift up the sedimentary organic matter 700 and lead the water to be treated to the bioreactor 100 used for water treatment. The aeration means 500 is desirably provided near the bottom of the water, but the dissolved oxygen near the surface of the water may be supplied to the vicinity of the bottom of the water by downward flow from the water surface.

The upward flow generation means 600 is, for example, a pump or a screw, and any mechanism can be used as long as it can gradually lift up the deposited organic matter by creating a negative pressure in the vicinity of the surface of the deposited organic matter. good.

As shown in FIG. 9, the bioreactor 100 used for water treatment has a filter medium 200 that can be fixed or can flow inside. Nitrifying bacteria, denitrifying bacteria and Bacillus subtilis are propagated in the filter medium 200 .

By using the apparatus having such a configuration, the deposited organic matter on the bottom of the water can be gradually reduced in thickness. Furthermore, by introducing the wound up organic matter into the bioreactor 100 used for water treatment, suspended organic matter, dissolved organic matter, and inorganic nitrogen can be greatly reduced.

<Summary of this embodiment>
In estuaries, coastal areas, bays, lakes, ponds, etc., organic matter accumulates thickly on the bottom of water, which is a major factor in deteriorating water quality.
Dredging is also used to remove deposited organic matter, but it is not a fundamental countermeasure because the organic matter accumulates again after dredging, despite the enormous cost of removal.

On the other hand, the method of lifting up the deposited organic matter using a pump, screw, or the like can be performed at a relatively low cost, but there is a risk that the contaminated area will expand because the organic matter that has been lifted up diffuses into the surroundings.

In the present embodiment, by guiding the water to be treated containing the organic matter that has been swirled up to the bioreactor used for water treatment shown in the first and second embodiments, biological purification is performed before the organic matter diffuses to the surroundings. be able to. Since the bioreactor used for water treatment of the present invention has a high purification efficiency, even water to be treated containing high concentrations of organic substances and inorganic nitrogen can be treated to a good quality.

Embodiment 4.
Recently, research on aquaponics, which combines aquaculture and hydroponics, is progressing. In aquaponics, the breeding water for aquatic organisms is used as the nutrient solution for the plants, and the nutrient solution used for the plants is recycled as the breeding water again.
Ammonia, which is a deadly poison contained in the excreta of aquatic organisms, is oxidized by nitrifying bacteria to become weakly toxic nitrous acid and nitric acid. Although nitrites and nitrates are weakly toxic, they can adversely affect the health of aquatic organisms when accumulated in breeding waters to high concentrations. However, breeding water containing nitrous acid and nitric acid becomes a nutrient solution for plants, and the nitrous acid and nitric acid are absorbed by the roots of the plants and used for photosynthesis. This avoids accumulation of nitrous and nitric acids. In this way, the basic concept of aquaponics is that nitrous and nitric acids, which are toxic to aquatic organisms, are consumed by photosynthesis in plants, thereby facilitating good circulation of water.

However, in reality, such ideal water circulation is difficult, and there are almost no examples of aquaponics being realized on a commercial basis.
One of the major problems is that the nitrous acid and nitric acid generated in breeding tanks are not sufficiently absorbed by the plants, and thus accumulate in the long term and harm the health of aquatic organisms. In commercial aquaculture, aquatic organisms are kept at fairly high densities. Therefore, the amount of excretion by aquatic organisms is also large, and the amount of nitrous acid and nitric acid generated is also considerable. In order for the plants to absorb this large amount of nitrous acid and nitric acid, a much larger plant cultivation area is required compared to the breeding tanks for aquatic organisms. become difficult.
In addition, many of the aquatic organisms with high commercial added value are marine fish. Therefore, breeding water becomes salt water, which is not suitable as a nutrient solution for plants.
The above two problems are major obstacles in realizing aquaponics on a commercial basis.

FIG. 10 shows an example of aquaponics using the bioreactor shown in the first or second embodiment. Water in a breeding tank 3000 in which fish grow is pumped up to a bioreactor 1000 by a pump P. The pumped water is purified by purification microorganisms growing on the filter medium 2000 and flowed to the planter 4000 where plants grow. The water used as a nutrient solution for plants in the planter 4000 returns to the breeding tank 3000 .
The point of the present embodiment is that water containing a large amount of fish excrement is highly efficiently purified in the bioreactor 1000 . As shown in Embodiments 1 and 2, since nitrification and denitrification occur with high efficiency, the concentrations of nitrous acid and nitric acid are low. Therefore, even in a planter having an area similar to that of the breeding tank, the remaining nitrous acid and nitric acid are sufficiently consumed by the plants.
In addition, since the nitrite concentration of the circulating water is maintained at a very low concentration, it becomes possible to reduce the salinity of the water to a low concentration of brackish water. For marine fish, the brackish water level reduces the load of osmotic pressure regulation and grows faster. However, since nitrous acid and chloride ions are competing substances when absorbed from the gills, if the salinity is low, the amount of nitrous acid absorbed increases, and respiratory disorders are likely to occur. However, in the bioreactor 1000, since highly efficient purification is performed and the nitrite concentration is always kept low, even brackish salt water does not cause such a problem.

As described above, by using the bioreactor shown in Embodiments 1 and 2, the two problems of conventional aquaponics can be solved or mitigated, so commercial aquaponics can be realized. become easier.

Reference Signs List 1 biological reaction device 2 filter medium 3 to-be-treated water introduction means 4 to-be-treated water drainage means 5 aeration means

10 bioreactor 20 filter medium (fluidized filter medium)
30 to-be-treated water introduction means 40 to-be-treated water drainage means 50 aeration means

100 biological reaction device 200 filter medium 500 aeration means 600 upward flow generating means

Claims (5)

a bioreactor for water treatment;
and an upward flow generating means for sending the water to be treated to the biological reaction device,
The bioreactor is
a filter medium;
purifying microorganisms growing on the filter medium;
an introduction path for guiding the water to be treated to the filter medium;
a drainage path for draining the water to be treated that has come into contact with the filter medium;
and an aeration means for supplying oxygen to the water to be treated that is led to the filter medium,
The purifying microorganisms are Bacillus subtilis, which is an aerobic microorganism that decomposes dissolved organic matter, Nitrifying bacteria, which is an aerobic microorganism that performs nitrification, and Denitrifying bacteria, which is an anaerobic microorganism that performs denitrification,
The Bacillus subtilis, the nitrifying bacteria, and the denitrifying bacteria grow in the same filter medium,
A water bottom cleaning apparatus characterized by simultaneously performing nitrification and denitrification of nitrogen compounds contained in the water to be treated. The filter medium is a fixed bed,
The water bottom cleaning apparatus according to claim 1, wherein the dissolved oxygen concentration of the water to be treated on the introduction path side of the filter medium is 5 ppm or more and the saturated dissolved oxygen concentration or less. The filter medium flows in the water to be treated,
The water bottom cleaning apparatus according to claim 1, wherein the dissolved oxygen concentration of the water to be treated is 5 ppm or more and the saturated dissolved oxygen concentration or less. The bottom water purification apparatus according to claim 3, further comprising a natto bacteria introduction means for introducing natto bacteria. 5. The water bottom cleaning apparatus according to any one of claims 1 to 4, further comprising a moving means.

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