JPS63178890A - Method for biological cleaning of pollution in closed type water area - Google Patents

Abstract

PURPOSE:To efficiently clean the eutrophication pollution in a closed type water area by dispersing the deposits of bottom material forcibly into the water so that the polluting components are taken by living matters. CONSTITUTION:An aerator 2 and/or mechanical stirrer 3 is installed to a movable raft-like structural body 1 and a double pipe type contact device having inside cylinders 4, 4' and outside cylinders 5, 5' is provided toward the inside of the water. The bottom material deposits are forcibly dispersed and returned by such aerator 2 or stirrer 3 into the water to additionally dig out the deposits as needed. While the deposits are fluidized together with the living matters in the bottom material and water and are circulated by the double pipe type contact device, a high degree of contact is attained and the polluting components such as org. materials, phosphorus-contg. materials, nitrogen-contg. materials and metal salts in the deposits are taken by the living matters as the nutrition sources. The eutrophication pollution in the closed type water area is thus effectively cleaned.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention enables dispersion and return of eutrophic bottom sediments containing organic and inorganic sediments into water by forcibly aerating and/or mechanically stirring the sediments. The aim is to remove contaminant components from the sediment extremely efficiently while maintaining a fluidized state together with living organisms, thereby simultaneously purifying not only the sediment but also the water quality. More specifically, in a multi-phase system of two or more phases including at least a liquid phase out of three gas-solid-liquid phases, efficient contact with living organisms is achieved by a contact method preferably using a double-pipe contact device. , chemical oxygen demand (COD), phosphorus, etc., whose total amount is strictly regulated by laws and regulations such as the Water Pollution Prevention Act, the Seto Inland Sea Environmental Conservation Special Measures Act, and the Lake Water Quality Conservation Special Measures Act.
This invention relates to a method for extremely effectively removing and purifying pollutants such as nitrogen from bottom sediments.

In addition, by using the polluted components as a nutrient source, green algae (Ch Iorophyceae), heterochaetes (Xanthophyceae, or 1let
rocontae), Chrysoph
yceae), diatoms (Bacillarioph
yceae).

Cryptophyceae, dinoflagellates or Dinophyceae,
or Peridiniae).

green flagella (Chloromonadineae),
Eugleniae, brown algae, rhodophyte
phyceae), cyanobacteria (Myxophycea
When algae such as E. or Cyanophyceae are brought into contact in a fluidized state, the double-tube contact device can be used as a bioreactor uniform culture device that can grow the algae extremely efficiently. At the same time, it removes bottom sediments containing causative substances such as organic substances, phosphorus-containing substances, nitrogen-containing substances, and metal salts in closed waters where eutrophication and pollution have progressed due to the proliferation of algae. The present invention provides a method for removing pollutants from water bodies and purifying the pollutants in water bodies in an extremely high level and effectively.

Traditionally, as a method for purifying closed water bodies with advanced eutrophication, the method of purifying closed water bodies with advanced eutrophication has been to use Eichhornia crassi.
Methods for removing phosphorus, nitrogen, etc. by multiplying pes) have been studied from various viewpoints, and it is known to be effective to some extent in small-scale water bodies and in specific situations. However, since these methods are based on the use of natural phenomena as they are, when attempting to achieve large-scale water purification or systematic pollution purification that is subject to the above laws and regulations, it is important to consider temperature changes and systems. It was considered difficult to put it into practical use as it could not be adapted to modernization.

On the other hand, among algae, especially Asakusanori (Po
In the cultivation of Rphyra tenera), fertilization has long been carried out mainly by supplementing nitrogen sources in order to prevent discoloration in the nori fishing grounds in oligotrophic waters.

Although aquaculture technology has made significant progress in recent years, a certain amount of fertilizers such as nitrogen and phosphorus are still necessary to improve and stabilize productivity, but recently there has also been a phenomenon of eutrophication of water quality. In fact, it is almost no longer done. Here, it has been revealed that cultivation of this type of algae can purify coastal sea areas, albeit on a small scale, but it takes time to achieve effective purification of pollutants in closed water areas. However, there were major drawbacks in terms of cost and labor, and fixed aquaculture equipment alone had an incomplete purification effect, making it impractical in terms of efficiency.

The present invention can be easily achieved by simply forcibly dispersing and returning sediment to water by aeration or mechanical stirring, and bringing it into efficient contact with living organisms such as algae while maintaining a fluidized state. The present invention has been made in order to provide a new method for effectively purifying eutrophic pollution in closed water bodies.

As a result of intensive research to achieve the above object, the present inventor has developed a gas-solid-liquid system using a double-pipe contact device, which is constructed by the present inventor and can be used for a wide range of eutrophic waters. A purification system that significantly increases the contact efficiency while circulating between the inner cylinder and the outer cylinder by fluidizing at least two, preferably three, of the three phases including the liquid phase is suitable for this purpose. They discovered this and arrived at the present invention.

The purification method of the present invention includes installing an aeration device and/or a mechanical stirring device in a movable raft-like structure, and equipping a double-pipe contact device facing the water. The device forcibly disperses the bottom sediment back into the water, excavates additional sediment as required, and fluidizes the sediment together with organisms in the bottom sediment and water, and circulates it through the contact device. However, a high degree of contact is achieved, and the contaminant components such as organic substances, phosphorus-containing substances, nitrogen-containing substances, and metal salts in the sediment are ingested as nutritional sources by the organisms.

To explain a specific example of the purification method of the present invention with reference to the drawings, in FIG. A double pipe contact device having an inner cylinder of 4.4 degrees and an outer cylinder of 5 degrees is provided, an aeration part 2' is provided outside the outer cylinder, and a stirring part 3 degrees is provided inside the cylinder. In order to create a circulation flow between the outer cylinder and the inner cylinder, a flexible rubber conical introduction part 6.6' is installed at the bottom of the outer cylinder of the contact device, and a baffle plate 7.7° is installed at the top. . Inside the contact device, at least two phases including the liquid phase among the gas-solid-liquid three phases, preferably three phases, are kept in a fluidized state, while the internal liquid phase is circulated from the inner tube to the outer tube and from the outer tube to the inner tube.・Fluidize. At this time, although it is possible to generate a circulating flow and fluidize using only an aeration device, circulation and fluidization can be carried out more effectively by using an auxiliary mechanical stirring device. Note that it is possible to cause a certain degree of circulation and fluidization by mechanical stirring alone, and an aeration device can also be used as an auxiliary aid. The small windows 8 and 8 degrees provided in the -1 part of the double-tube contact device and the removal devices 9 and 9 degrees attached to them are provided to remove and take out the solid phase containing the proliferated organisms. be. The positional relationship between the water surface 10, the bottom surface 11, and the apparatus is as shown in FIG. 1. In the figure, the rings are bubbles, and the dots are solid particles. Since the fluidized bed circulates between the inner cylinder and the outer cylinder according to the arrow, high-order contact is achieved through fluidization between living organisms and pollutant components including nutrients, and as a result, the pollutant components in the bottom sediment are mixed with living organisms. They are extremely efficiently taken up and removed by the species, and purify the bottom of closed water bodies.

The fluidized state required in the purification method of the present invention is such that the bottom sediment and/or living organisms of the closed water area are used as a solid phase;
In a three-phase system in which the liquid phase is water obtained by dispersing and returning sediment, and the gas phase is air supplied by an aeration device (or strong rotation of a stirring device), two or more, preferably three phases including at least a liquid phase are used. This is achieved by fluidizing the phase at a flow rate that is higher than the minimum fluidization velocity of a fluidized bed in chemical engineering. However, even at a flow rate higher than the minimum fluidization velocity, complete fluidization may not occur due to uneven particle size distribution of the solid phase, or complete fluidization may not occur because a sufficient minimum fluidization velocity cannot be obtained. Even in such a case, the main objective of the purification method of the present invention can be fully achieved, and the method has characteristics that allow the purification of sediment to be realized without detracting from the significance of the present invention.

The raft-like structure used in the present invention is made of metals such as iron, aluminum, and stainless steel, wood, plastics such as vinyl chloride resin, polyethylene resin, polyacrylic resin, Teflon resin, and synthetic rubber, and ceramics such as glass and ceramics. Products etc. can be used, and it is preferably practically suitable to use metal or wood, plastic, ceramic products, etc. as a base and reinforced with metal.

The double pipe contact device used in the present invention can be made of the same material as the above-mentioned raft-like structure, but it is particularly preferable to use one made of metal or plastic. The structure and shape of the double tube is preferably one in which a cylindrical outer tube and an inner tube are doubled, and the diameter ratio of the outer tube and the inner tube is 1.2:1 to 10:1. You can choose up to 1st place, and you should choose based on a 2:1 ratio. In any case, the diameter and length of the double pipe are closely related to the fluidization conditions, so after careful consideration, choose the combination of diameter and length that will most easily fluidize and provide a circulating flow. You need to choose. The pipe length of the double pipe can be selected according to the water depth of the closed water area to be purified, and is usually 0.5 to 0.5 to 0.5 m below the average water depth.
It is preferable to make it about 1m shorter, and generally the average water depth is 9.
It is sufficient to make the length of the tube about a certain amount. The water areas targeted by the present invention are generally up to about 10 meters deep, and the fluctuations in water depth are not very large. The use of a tube and a flexible conical introduction tube made of rubber can also be used to make the present invention extremely efficient.

In the present invention, (l O
) Describe the aeration equipment and/or mechanical stirring equipment used. A wide variety of aeration systems are available, including those using ordinary compressed air. As the mechanical stirring device, an electric type is preferable, and a propeller of various shapes can be arbitrarily selected while taking into account the structure and compatibility of the double pipe contact device. A type that uses turbulence to cause the liquid to flow by rotation can be suitably used. It should be reiterated that the present invention is not limited to any aeration device and/or mechanical stirring device or other fluidization method other than those described above, as long as the method can effectively achieve the present invention. Needless to say.

The pollutant components to be purified in the present invention are components that can be ingested by living organisms, and include organic substances including carbohydrates, organic and inorganic phosphorus-containing substances, organic and inorganic nitrogen-containing substances, and metal salts. It can be given as follows. Organic substances include pollutant components in household wastewater, human waste, and pollutant components in industrial wastewater; phosphorus-containing substances include orthophosphates, polyphosphates, and organic phosphorus compounds; and nitrogen-containing substances include ammonia, nitrates, and nitrates. Metal salts such as nitrates, urea, and organic nitrogen compounds include sodium salts, potassium salts, magnesium salts, calcium salts, and iron salts.

However, for substances that are harmful or toxic to living organisms used in the present invention, in principle, it is effective only when the concentration is such that the living organisms are not adversely affected. It is also possible to use the method for removing and purifying the substance by acclimatizing the organism.

As organisms that can be used in the present invention, various fungi and aerobic/anaerobic microorganisms can be suitably used, including the 11 types of algae mentioned above. Examples of fungi include algae, ascomycetes, and basidiomycetes, and as aerobic microorganisms, ordinary activated sludge containing various aerobic bacteria including microorganisms in water is most suitable for the present invention. Anaerobic microorganisms contained in sediments also work effectively in the present invention. As for the size of living organisms, a size of several cm or less is suitable for maintaining the fluidized state as referred to in the present invention, and more specifically, a size of several mm or less is preferable for maintaining a stable fluidized state.

However, in the present invention, all kinds of freshwater, seawater, and brackish water organisms, including the above-mentioned organisms, can be used, and the size thereof is not particularly specified. It can be said that it is applicable. However, when considering favorable conditions for maintaining an appropriate fluidized state, it is necessary to limit the types of organisms and their sizes to some extent as described above.

In addition, taking as an example the case where the algae Porphyra tenera is used as the organism, in the seaweed fishing grounds in oligotrophic waters, nitrogen sources, phosphorus sources, metal salts, etc. have traditionally been used to prevent discoloration. Although fertilization has been carried out mainly through replenishment, the purification method of the present invention is highly evaluated as a method for efficiently carrying out fertilization. That is, in the case of artificial fertilization, the effect did not last long even if it was applied, and the color of the algae obtained could only be improved for several hours or a few days after fertilization, which was not satisfactory. In addition, this eutrophication phenomenon may actually be advantageous in seaweed cultivation, which is currently seen in the Seto Inland Sea, where water quality is becoming extremely eutrophic. However, the optimal water surface is relatively small, and the effects of underwater nutrients alone are not sustainable, so it has not been possible to achieve sufficient results over a long period of time.

According to the method of the present invention, it is possible to suppress the proliferation of harmful algae such as Aonori laver, Hibimidoguchi, Ulva algae, etc., to some extent during cultivation of Asakusa nori, so it is possible to prevent not only contamination due to fertilization but also the proliferation of harmful plants. . The algae cultivation method of the present invention is superior to the method of the present invention, compared to the fact that in artificial cultivation fisheries, the growth of algae actually stops if there is an excessive amount of phosphorus, which is a fertilizer component of algae. Since it is possible to constantly supply a nutrient source in a form similar to that of algae at a constant rate suitable for the growth of algae, there is no need to control the amount added, and it is extremely practical. As described above, a further object of the present invention is to provide an improved method for cultivating algae that does not require fertilization, and at the same time, the bottom mud is dispersed and returned to the water so that it can be ingested by living organisms and the bottom sediment can be removed. It lies in being able to achieve purification.

In general, bottom mud is used as a nutrient source for living things, and scales (l
4) This has been known to some extent for fish, crustaceans, shellfish, etc., but as in the present invention, by forcibly dispersing and returning the bottom mud to the water, the fluidized state can be achieved with the above configuration. It can be said that it is extremely significant that the action and effect on small organisms, especially algae, has been significantly enhanced by maintaining the

It is generally known that algae require large amounts of nutrients such as nitrogen and phosphorus, and in particular, in Asakusanori cultivation, the amount of nitrogen is less than 0.2 mg/I, and the amount of phosphorus is less than 0.02 mg/I.
It is said that if the concentration is less than 0.1 mg/l of nitrogen, it becomes a limiting factor for the growth of nori, but on the other hand, according to the Fisheries Environmental Standards, the conditions for red tide to occur are nitrogen 0.1 mg/l or more, phosphorus 0.015
o+g/1 or more, and sufficient consideration must be given to the risk of red tide occurring due to nori cultivation. However, the amount of nutrients in seawater near the coast is about 0.1 mg/I as nitrogen and about 0.015 mg/I as phosphorus, so in the case of nori cultivation, the amount of nutrients in seawater is considerably larger than the amount present. is required. In addition, it is known that the amount of nutritional salts present decreases to one-tenth after about one month after the start of aquaculture, and to one-twentieth after about three months, making it extremely effective. You can imagine that nitrogen, phosphorus, etc. are ingested. In addition, the absolute required amount, minimum required amount, and normal required amount for the nitrogen content of seaweed are 1.2 to 1.3%, 4.0 to 5.0%, and 4.0 to 5.0%, respectively, based on the dry weight of seaweed.
Nitrogen is essential for seaweed, as it is said to be 5.5 to 7.0%. Furthermore, nitrogen is closely related to the quality of seaweed, as it is said that the higher the total nitrogen content in seaweed, the better the quality, and the same can be said for phosphorus.

The method of the present invention satisfies all of these conditions and can be applied to a wide range of algae cultivation methods other than seaweed. Furthermore, since the algae cultivation method according to the present invention can be carried out in any bottom sediment or water quality such as seawater, river water, lake water, pond water, etc., inland seas such as the Seto Inland Sea, Tokyo Bay, Ise Bay, Nakaumi, etc. It is also extremely effective as a treatment method that can effectively and inexpensively purify eutrophic bottom sludge in closed water bodies such as ports and lakes such as Lake Biwa, Lake Kasumigaura, and Lake Kojima. Both elemental technologies, which combine biomass and algae cultivation, are expected to have a promising future as they can be easily implemented industrially.

The examples described below serve to better explain the invention and are not intended to limit the scope of the invention. It should be noted that all percentages and parts shown in the Examples are based on a double fluorescent standard unless otherwise specified. Further, the analysis and measurement of nitrogen and phosphorus in the examples were conducted in accordance with the factory wastewater test method JIS K0102 (1971) published by the Japanese Standards Association. Nitrogen was determined by calculating nitrate nitrogen and ammonia nitrogen using a colorimetric method.

Total phosphorus was determined by colorimetric method.

Example 1 Nitrogen 0.08 mg/I, phosphorus 0.01 mg in tank 101
1 part of seabed sludge is added to 10 parts of seawater containing /I, and Porphyra sludge is added to this tank.
When 20 g of Nera) was added and cultured for 20 days while stirring the sludge with air, the yield of grown Asakusa nori was 76 g, and a normal black-purple nori was obtained. Similarly, the yield without stirring is 65 g.
It was dark green in color and rather frail.

When agitated with a propeller under the same conditions, the yield of grown Asakusa nori was 72 g, and a normal black-purple nori was obtained. In this case, the nitrogen content in seawater is 0.
The phosphorus content was 22 mg/l, and the phosphorus content was Q,03 mg/l, which exceeded the nitrogen and phosphorus concentrations initially added, and the elution of nitrogen and phosphorus from the sludge was confirmed.

Example 2 When cultivating Asakusa nori in seawater in the Seto Inland Sea, if a sand pump was used to stir up the seabed sediment and the bottom mud was dispersed and returned to the seawater, the proliferation and growth of nori was promoted. On average, 4,500 sheets of nori were harvested per day. A normal black-purple color was obtained over 4 months with almost no discoloration. 1 if no stirring operation is performed
An average of 3,000 sheets of nori were harvested per day, but after about three months, the color faded and it became impossible to harvest.

Example 3 A prototype device as shown in Figure 1 was installed at Lake Kojima in Okayama Prefecture and operated with sewage sludge injected into the inner cylinder of the double-pipe contact device. The chemical oxygen demand (COD), nitrogen, and phosphorus concentrations in the initial IO+ag/I, l mg/I, and 0.1 mg/I, respectively.
3 mg/], (l) in a double tube 48 hours after
8) Decrease to 0.1mg/L Q, QLmg/I.

Similarly, when the prototype device is operated under conditions that cause the bottom sediment to disperse and return to the lake water, C'O
D, nitrogen, and phosphorus concentration decreases are constantly replenished from pollutant components in the bottom mud, so the initial concentration of each is 11 m
g/I, 0.9 mg/], O, I2+ng/], but after 48 hours it was 8 B/l, 0.7 mg/l,
The amount was only 0.09 mg/]. however,
It was confirmed by a comparative analysis of the bottom mud and bottom sediments that had remained in the double pipe that a considerable amount of the pollutant components in the bottom mud had been purified by this method.

Example 4 The prototype device of Example 3 was installed on the coast of the Seto Inland Sea in winter, and it was operated continuously for one week with 98% water content of Asakusanori fed into the inner cylinder of the double-pipe contact device. From the first day of operation, a large amount of black-purple snails began to accumulate on the baffle plate at the top of the contact device, so they were removed using a removal device. It was confirmed that the quality of the obtained Asakusanori was very good, so we conducted a gas-solid-liquid three-phase circulation-fluidization (I
9) Compared to the conventional large-scale stationary cultivation method, the method of cultivating Asakusanori allows for easier movement of the raft-like structure, and is not only effective for cultivation but also effective in purifying pollutant components in the bottom sediment. It has been found that it can be extremely effective against

Example 5 In the same manner as in Example 2, when seaweed (Undaria pinnatifida) was cultivated on the coast of a remote island in the Seto Inland Sea, the proliferation and growth of seaweed was significantly promoted when the bottom mud was stirred with a sand pump. ,
Normal black-brown wakame seaweed was harvested for 6 months. It is interesting that the effect of the present invention was clearly observed even in algae that are rooted on the seabed, and that some of the algae's color faded from blackish brown to yellowish brown when no agitation was performed. It was observed.

The seawater quality at this time was 0.18 mg/l of nitrogen and 0.03 B/l of phosphorus when stirring was performed, and 0.09 mg/l of nitrogen and 0.03 B/l of phosphorus when stirring was not performed. Phosphorus 0
．． It was 01 mg/l.

Example 6 Nitrogen 0.15B/] in the 101 water tank used in Example 1,
Add 1 part of pond bottom sludge to 10 parts of fresh water containing 0.02 mg/I of phosphorus, and add water hyacinth (
P, 1 chhornia crassipes) 50
When the sludge was cultured for 30 days with stirring, the water hyacinth grew to 68 g. Similarly, if stirring is not performed, 54 g
Met. In addition, the water quality when stirred is nitrogen 0.26
mg/I, phosphorus 0.05 mg/].

Example 7 Fresh water 5 containing almost no nitrogen and phosphorus in the same <101 aquarium
I, and 50g of lake bottom sludge (solid content 25%) containing 4.5% nitrogen by Kercoeur method was added.
While stirring the sludge by blowing air, add 50 g of duckweed (Spirodela polyrhiza).
After culturing for 3 months, the duckweed grew to 82 g.

After completing this experiment, the nitrogen content in the sludge was analyzed by the Kerkuhl method, and the nitrogen content was 2.6%.

A similar analysis was conducted for COD, phosphorus, metal salts, etc., and it was found that the three elements of fertilizer, nitrogen, phosphorus, and potassium, behaved in the same way.

Claims (5)

[Claims] (1) A biological purification method for a closed water area, which is characterized by forcibly dispersing bottom sediment into water and ingesting pollutant components into living organisms. (2) When dispersing bottom sediments in water, maintain the water in a gas-liquid and/or solid-liquid fluidized state by aeration and/or mechanical stirring to make contact with living organisms highly efficient. The method according to claim 1, characterized in that the ingestion of contaminant components is promoted. (3) In fluidizing bottom sediments and/or organisms,
The method according to claim 1 or 2, characterized in that a double tube contact device is used. (4) The pollutant components to be purified are organic substances, phosphorus-containing substances,
The method according to claim 1, 2, or 3, characterized in that the nitrogen-containing substance and a metal salt are used. (5) Claims 1, 2, 3, or 4, characterized in that algae and/or fungi and/or aerobic/anaerobic microorganisms are used as living organisms. Method.