JP3091299B2 - Water purification method for natural waters - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying water in a natural water system, and more particularly to a method for purifying water in a natural water system such as a pond, a lake, a beach, a river, or the like using an ecological food chain.

[0002]

2. Description of the Related Art Conventionally, there has been known a water purification method in which an object, such as gravel, a PVC corrugated sheet, a string-like material, or the like, to which microorganisms are liable to adhere is installed in a water channel and water is passed by utilizing a difference in water level. ,
For example, it is used for water purification of small rivers. Also,
Filling the water tank through which the polluted water circulates, rotating the packing for the purpose of attaching organisms on the water surface, or moving the water surface to be treated in the water tank up and down to expose the packing material on the water surface, There is known a water purification method in which oxygen is supplied to microorganisms attached to the packing by being buried below.

[0003] In such a water purification method, the microbial layer adhering to the packing is composed of an aerobic microbial layer, a microaerobic microbial layer,
Changes such as anaerobic microorganism layer and attachment surface are observed. In addition, from the entrance of the polluted water toward the exit, changes in the amount of living organisms and species due to the difference in the pollutant concentration of the polluted water are observed. Although there are changes in the species, the conventional water purification method is mainly intended to decompose BOD (biochemical oxygen demand) and oxidize NH ₃ (ammonia) by aerobic microorganisms.

In the treatment method using only aerobic microorganisms, the decomposition of nitric acid or nitrous acid, that is, denitrification occurs only incidentally, and there is a problem that a sufficient denitrifying effect cannot be obtained. . In addition, the food chain system of the organisms used in the above-mentioned conventional technology is up to protozoa, and the microorganisms that have multiplied must be separated and treated separately as excess sludge, and the management of biofilms and the like is complicated. was there.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention, in view of the above prior art, to not only decompose or nitrify BOD and NH ₃ , but also to decompose nitrate nitrogen, nitrite nitrogen and the like effectively. It is an object of the present invention to provide a method for purifying water quality of a natural water system using an ecological food chain, which can be performed and the generation of suspended solids is extremely small.

[0006]

In order to achieve the above object, the present invention provides a method for purifying water in a natural water system using the water purifying action of fish and shellfish, phytoplankton, aerobic microorganisms and anaerobic microorganisms. Forming a circulating flow from the top to the bottom through a filter bed provided in the natural water system and capable of inhabiting or infiltrating living organisms, and controlling the flow rate of the circulating flow to the dissolved oxygen concentration at the outlet of the filter bed. Is 1.5pp
m or less, oxygen is taken in by phytoplankton photosynthesis at the surface of the filter bed, and some phytoplankton are eaten by fish and shellfish,
Next, nitrification of ammonia nitrogen by an aerobic microorganism and decomposition of organic matter are performed by using oxygen obtained by photosynthesis of the phytoplankton in the middle layer of the filter bed, and thereafter, by anaerobic microorganisms in the lower layer of the filter bed. It is characterized by neutralization and denitrification.

[0007]

According to the present invention, a circulating flow is formed to circulate from the top to the bottom through a filter bed provided in a natural water system, and the circulating flow is maintained so that the dissolved oxygen concentration at the outlet of the lower part of the filter bed is maintained at 1.5 ppm or less. By controlling the flow rate, oxygen is generated by the photosynthetic reaction of phytoplankton in the surface layer of the filter bed, and predation of some phytoplankton occurs by fish and shellfish, and the surface layer in the middle layer of the filter bed Aerobic bacteria and nitrifying bacteria decompose organic matter and decompose ammonia nitrogen using oxygen generated by photosynthesis, and neutralization and denitrification by anaerobic bacteria and denitrifying bacteria due to lack of oxygen in the lower layer. Each of these causes the use of ecological food chains in multiple stages to slowly and reliably decompose pollutants in natural water systems and purify their water quality. That.

[0008] In the present invention, the filter bed provided in the natural water system may be any one that can be inhabited by organisms attached or penetrated, and examples of the filter medium include sand, gravel, crushed stone, zeolite, coral, and soft ceramic. Is used, and the particle size thereof is, for example, 0.2 mmφ to 2.0 mmφ.
It is. Since it is not microfiltration, it is preferable to use a filter medium having a relatively coarse particle size. The lower part of such a filter medium layer is supported by, for example, a crushed stone layer of 0.5 cmφ to 5.0 cmφ. The filter bed is preferably a deep filter bed as a whole including the crushed stone support layer. For example, the filter medium on the crushed stone support layer is laminated in a coarse, dense, coarse order, or a filter bed other than the crushed stone support layer. May be formed using a filter medium of 0.2 mmφ or more.

In the present invention, since the filter bed is provided in a water environment of a natural water system, a means for generating a gentle flow of water passing through the filter bed is not required, especially a means for supplying the water to be treated. It is. In the present invention, the DO (dissolved oxygen concentration) of the circulating water flowing out from the lower part of the filter bed is 1.5 p.
pm or less. This will allow us to take advantage of multi-stage ecosystem food chains. If the amount of circulating water is too large (the amount of filtered water is too large), the oxygen taken in from the filter bed surface passes through the filter bed without being sufficiently consumed, so that the DO in the filtered water rises.
The denitrification effect becomes insufficient and the nitrogen removal rate as a whole decreases. On the other hand, when the amount of circulating water is small (the amount of filtered water is small), both the oxygen supply amount to the filter bed and the sludge load amount decrease,
Not only does the amount of denitrification decrease, but also sulfuric acid reduction and methane fermentation occur, reducing the overall purification capacity.

In the present invention, if the water quality of the water system to be purified is extremely poor, it is preferable to reduce the amount of circulating water or stop the circulating flow to prevent clogging, or wait for the clogging to recover, In the case of a high BOD load, it is preferable to use a filter medium having a large porosity. In the present invention, by inclining the filter bed surface to about 30 degrees,
A wider range of organisms can be inhabited and the ecosystem food chain available for water purification can be expanded. Even if the filter bed is inclined, there is no fear that the filter medium flows out as long as a downward flow passing through the filter bed is generated.

The present invention is also suitable as a eutrophication measure for natural water systems having relatively low organic pollution, and can be used for water purification of all water systems in the natural water environment such as ponds, lakes, marshes, beaches, and rivers.

[0012]

Next, the present invention will be described in more detail with reference to examples. FIG. 1 is an explanatory view of an apparatus used in the method for purifying water of a natural water system according to the present invention, and FIG. 2 is a sectional view of a main part of FIG. This device is provided in a lake, for example, to purify the water quality of the lake, for example, 0.2 mmφ ~
A filter bed 1 made of 2.0 mmφ sand or gravel;
A crushed stone layer 2 supporting the crushed stone below, a water collecting pipe 3 arranged in the supporting crushed stone layer 2, a water collecting pit 4 into which purified water collected by the water collecting pipe 3 flows, It mainly comprises a drain pipe 5 and a drain pump 6 arranged in the pit 4. The water collecting pipe 3 is made of a ceramic pipe, a steel pipe, or a PVC pipe having a diameter that does not cause a hydraulic gradient. For example, a large number of water collecting holes 9 are provided at a position 45 degrees downward from the center of the cross section. . The water collecting pit 4 is made of, for example, the same material as that of the water collecting pipe 3, and has a dissolved oxygen measuring unit (not shown). Also, the discharge pump 6
The amount of discharged water can be varied. Note that 7
Is a partition wall for preventing the filter bed 1 from collapsing, 8 is a revetment of a pond in which the device is installed, and 10 is an air diffuser plate for aerating air into a lake water system.

In such a configuration, when a predetermined amount of water is discharged from the discharge pipe 5 by operating the drainage pump 6 in the water collecting pit 4, water from the lake and marsh is conveyed to the filter bed 1 from the surface layer thereof. A circulating flow is formed that flows into the water collecting pit 4 through the filter bed 1, the supporting crushed stone layer 2, and the water collecting pipe 3. This circulation flow is controlled so that the dissolved oxygen concentration in the circulation flow flowing out from the lower part of the filter bed 1 is 1.5 ppm or less. In this way, a circulating flow under predetermined conditions is formed, and after a predetermined period of time, microorganisms suitable for the environment come into existence in the surface layer, the middle layer, and the lower layer of the filter bed 1 respectively. Filter bed 1
The phytoplankton generated on the surface portion of the plant grows by receiving sunlight passing through the water surface and releasing oxygen by a photosynthetic reaction to proliferate, and a part of the phytoplankton is eaten by fish and shellfish living on the filter bed surface portion. Oxygen produced by the photosynthesis of phytoplankton and oxygen taken in by the air diffuser plate enter the middle layer of the filter bed 1 as dissolved oxygen along with the circulating flow, and nitrifying bacteria and aerobic bacteria in the middle layer of the filter bed. Ingested. By the action of the nitrifying bacteria and the aerobic bacteria, the ammonia nitrogen in the water is nitrified, and organic substances are decomposed. Next, the circulating stream treated with ammonia nitrogen and organic matter reaches the lower part of the filter bed, where it is denitrified and neutralized by the action of denitrifying bacteria and anaerobic bacteria due to lack of oxygen. In this way, the treated water which is purified by the action of microorganisms and flows out from the lower part of the filter bed 1 flows into the water collecting pit 4 through the water collecting pipe 3 and flows to the surface of the lake through the discharge pump 6 and the discharge pipe 5. Circulated.

According to this embodiment, a filter bed is provided below the water surface of a lake, a circulating flow slowly passing from the top to the bottom of the filter bed is generated, and DO of circulating water flowing out from the lower part of the filter bed is generated. By controlling the circulation flow rate to 1.5 ppm or less, oxygen is taken in by the photosynthesis of phytoplankton in the surface layer of the filter bed, and decomposition of organic substances and ammonia by the action of aerobic bacteria and nitrifying bacteria in the middle layer. Nitrogenation of nitrogen is carried out, and denitrification and neutralization by anaerobic bacteria and denitrifying bacteria are sequentially and continuously performed in the lower part, respectively. Therefore, BOD, suspended solids (SS), NH ₃ , NOx, etc. in the water system Can be effectively decomposed. Further, according to the present embodiment, since slow water purification using the food chain of the ecosystem is performed, for example, it is also possible to reproduce underflow water of a river and infiltration water of a seaside, which is effective in all natural waters. Can purify the water quality.

According to this embodiment, most of the filter bed, the water collecting pipe, the water collecting pit and the like can be installed under the surface of the natural water system, so that the landscape is not spoiled, and the filter bed is suitable for living organisms. Or spawning ground. Further, according to this embodiment, the circulating flow passes through the filter bed as a downward flow, so that oxygen generated by photosynthesis on the filter bed surface can be effectively used in the filter bed. Further, by providing the diffuser plate in the water system to be treated, it is possible to eliminate shortage of DO due to insufficient sunshine time or insufficient growth of phytoplankton.

In this embodiment, the thickness of the filter bed is 30 to 10
It is preferably about 0 cm. In addition, the water collection pipe 3 should be as uniform as possible from the filter bed surface to the water collection pipe.
Is preferably arranged. In this embodiment, the removal efficiency of P (phosphorus) can be improved by mixing a calcium compound that reacts with an acid and a mineral that easily forms an insoluble matter with phosphoric acid in the lower part of the filter bed. .

In this embodiment, a diffuser plate is not particularly necessary, but when used together, it may be arranged at a position where the distance to each part of the filter bed becomes uniform as shown in FIG. 3, for example. preferable. As the partition 7 of the filter bed 1, for example, an orchid pile, a gabion, a masonry, or the like can be used, but the partition may not be provided. In addition, in a place where a sandy beach exists, the water quality can be effectively purified only by using the sandy beach as a filter bed and burying a water collecting pipe and a water collecting pit.

In this embodiment, it is preferable that the discharge pump can adjust the filtration speed of the filter bed by 1 to 5 m / day. The drainage pump 6 can be directly connected to the water collecting pipe 3 to omit the water collecting pit 4, but in this case, it is necessary to take measures for detecting dissolved oxygen in the water collecting. In addition, by using an air lift instead of the submersible pump as the discharge pump, more efficient automatic operation can be performed.

[0019]

According to the present invention, a filter bed is provided in a water system in the natural world to form a circulating flow that circulates slowly through the filter bed from above to below, and dissolves the outlet water at the lower part of the filter bed. By controlling the amount of circulating water so that the oxygen is 1.5 ppm or less, effective water purification using the food chain of the ecosystem can be performed, and the function of natural waters such as rivers, lakes, and beaches can be improved. Can be reproduced.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a water purification device used in one embodiment of the present invention.

FIG. 2 is a sectional view of a main part of FIG.

FIG. 3 is an explanatory diagram illustrating an example of the arrangement of a diffuser plate;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Filter bed, 2 ... Support crushed stone layer, 3 ... Water collecting pipe, 4 ... Water collecting pit, 5 ... Discharge pipe, 6 ... Discharge pump, 7 ... Partition wall, 8 ... Revetment, 9 ... Water collecting hole, 10 ... CFL diffuser plate, 11 ... discharge water.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI C02F 3/34 101 C02F 3/34 101D (72) Inventor Satoshi Ogura 5-6-4 Tsukiji, Chuo-ku, Tokyo Mitsui Engineering & Shipbuilding Co., Ltd. (56) References JP-A-3-147726 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C02F 3/30 C02F 3/06 C02F 3/10 C02F 3/32 C02F 3/34 C02F 3/34 101

Claims (1)

(57) [Claims] 1. A method for purifying water in a natural water system using a water purification effect of fish and shellfish, phytoplankton, aerobic microorganisms and anaerobic microorganisms, wherein organisms attached or infiltrated provided in the natural water system. To form a circulating flow that circulates from the upper side to the lower side through the filter bed capable of inhabiting, and the flow rate of the circulating flow is set to 1.5 pp.
m or less, oxygen is taken in by phytoplankton photosynthesis at the surface of the filter bed, and some phytoplankton are eaten by fish and shellfish,
Next, nitrification of ammonia nitrogen and decomposition of organic matter by aerobic microorganisms using oxygen obtained by photosynthesis of the phytoplankton are performed in the middle layer of the filter bed, and thereafter, by anaerobic microorganisms in the lower layer of the filter bed. A water purification method for natural waters, comprising performing neutralization and denitrification.