JPH0760266A - Method for purification of sea water - Google Patents

Abstract

PURPOSE:To purify efficiently sea water by a method wherein a water-permeable case wherein a water-contg. polymer gel prepd. by immobilizing wholly microorganisms living in a water with a specified concn. of sodium ion is placed, is immersed in water and aeration is performed therein. CONSTITUTION:Purification of sea water is performed by a method wherein a water-permeable case 2 wherein a water-contg. polymer gel prepd. by immobilizing wholly microorganisms living in a water with a sodium ion concn. of at least 0.01g/l or microorganisms acclimated in a water with a sodium ion concn. of at least 0.01g/l, is placed, is immersed in water and aeration is performed therein. As these microorganisms, a bacterium contg. a nitrification bacterium which decomposes and nitrifies a nitrogen-contg. compd. such as COD ingredient and ammonia in the sea water and has oxidative ability, e.g. a petroleum decomposing bacterium is used and as a wholly immobilized carrier, a water-contg. polymer gel such as polyvinyl alcohol is used. The water permeable case 2 is provided by piling up continuously the cases as a closing channel and a divider (a fence) for a pond.

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 having a sodium ion concentration in a range from a brackish water area into which a closed inner bay, an inner bay contaminated by aquaculture or the like, and a basin river flow into seawater.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for purification of water in closed sea areas, and not only reduction of COD but also advanced treatment of pollutants such as oil components represented by nitrogen, phosphorus and n-hexane extracts. Is starting to appear. In particular, accumulation of eutrophication sources from inflowing rivers in closed system bays, residual feed in fish farms, fish excrement and seawater pollution due to feed additives are severe, which adversely affects fish growth. In addition, due to the balance between eutrophication and anoxic conditions due to sediment accumulation, red tides and blue tides occur, and pollution of seawater is only deepening. Regarding such a method for purifying the sea area, JP-A-4-62213 and JP-A-4-62213
62214, JP-A-4-62215, and JP-A-4-62215.
The mainstream is a method based on the gravel contact method shown in -62216, and these methods perform filtration or purification by a biofilm in which organisms are attached to a solid. Further, JP-A-4-90892 discloses a method of decomposing organic substances, harmful substances such as ammonia and nitrous acid, in seawater by ozone oxidation of seawater and removing residual oxidant with an activated carbon column. In addition, Japanese Patent Laid-Open No. 3-
No. 229692 discloses a device for purifying seawater in a harbor by arranging a microbial growth filler in a water-permeable case. Further, JP-A-5-68991 and JP-A-5-68992 disclose the use of a microbial carrier-filled mesh bag and a microbial carrier storage device for wastewater treatment. The characteristic of these conventional techniques is that the microbial carrier waits for the microorganisms to naturally adhere to the natural product such as pumice stone, oyster shell, gravel, coral or expanded polystyrene, sponge, non-woven fabric, Raschig ring, etc. is there. By waiting for the microorganisms to naturally attach to the surface of these carriers, it is not possible to identify the pollutants to be treated, it takes a long time to attach to the surface of the carrier, and there are changes in water temperature and season. Due to the change, the adhered microorganisms may fall off and there is a problem in stable treatment. Furthermore, when the specific gravity of the microbial carrier is greater than 1.0, various problems occur because the microbial carrier sinks, so the overall specific gravity of the microbial carrier-filled mesh bag is adjusted to 0.95 to 0.98. Therefore, there is a problem that it is difficult for the bag to contact the entire drainage. Furthermore, the volume of the carrier-filled mesh bag is 500 to 2000.
Since a large-capacity container such as a liter is filled with the microorganism carrier, there is a problem that it is difficult to contact the entire drainage. As described above, the conventional technique relating to seawater purification is merely known as the biofilm method, which utilizes the power of nature and waits for the natural growth of microorganisms on the surface of gravel, sand, stone, and the like.

[0003]

In the water having a sodium ion concentration of 0.1 g / liter or more, especially seawater, since the growth of halophilic microorganisms is extremely slow, the surface of gravel, sand, stones, etc. is naturally affected by microorganisms. In the biofilm method that waits for growth, the ability to purify water is slow, the ability to purify water is low considering the area of attachment, and the biofilm is peeled off due to seasonal changes and changes in water temperature. There is a problem that it is impossible to selectively retain the bacteria to be purified in the sea area such as the harbor, and it was a very unstable method for purifying seawater. An object of the present invention is to provide a method for efficiently purifying water having a sodium ion concentration of 0.1 g / liter or more, particularly seawater, which does not have the above problems.

[0004]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have found that the microorganisms inhabiting water having a sodium ion concentration of 0.01 g / liter or more or the sodium ion concentration of 0.1 g / liter or more. Immersing a water-permeable case containing a high-molecular water-containing gel in which microorganisms, which have been acclimatized in water of 01 g / l or more, are immobilized in water and aerated, and having a sodium ion concentration of 0.1 g / l or more. The inventors have found a method for purifying water and completed the present invention. The microorganism in the present invention is a petroleum-degrading bacterium that decomposes and nitrifies COD components in seawater and nitrogen-containing compounds such as ammonia, and contains nitrifying bacteria having oxidizing ability, and oxidizes organic carbon compounds in seawater. Etc. As the entrapping immobilization carrier,
It is a polymer hydrogel such as polyvinyl alcohol, and its shape may be a dice shape with a maximum of 1 cm square, a particle shape, a fibrous shape, or the like. Examples of the water-permeable case include a tubular or plate-shaped material having a mesh-like water-permeable property, and the material thereof is stainless steel, a resin net, or the like.
The carrier has a mesh of cm or less, and the carrier entrapping and immobilizing microorganisms does not flow out and has water permeability.

As a method of installing the water-permeable case in a closed port or a fish farm, it is installed as a fence at the height from the sea bottom to the tide level at high tide and connected to piles or floats as a partition of the dead bay or pond. According to this installation method, when the contaminated seawater passes through the water-permeable case containing the hydrous polymer gel in which microorganisms are entrapped and immobilized, the stored oxygen in seawater (hereinafter , DO) or contact with oxygen when exposed to air, which promotes the oxidation reaction. Further, a method may be used in which air is introduced from the outside into the sea or the sea floor using an air compressor and aerated through an air diffuser. According to the present invention, a flow of seawater occurs due to the flow of air, and this flow passes through a water-permeable case containing a high-molecular hydrogel in which microorganisms are entrapped and immobilized, whereby oxygen and seawater are actively entrapped and immobilized. By bringing into contact with the polymerized hydrogel, an oxidation reaction occurs and seawater is purified. This method may be used to clean a closed bay or pond (see Figure 1 (a), Figure 2), or a non-closed but light-flowing port (Figure 1 (b), (See FIG. 2) and the like. 3 (a) and 4 (a) are reference views of the entire apparatus used in the purification method of the present invention, and FIG. 3 (b) and FIG.
A sectional view thereof is shown in FIG.

The microorganism of the present invention has a sodium ion concentration of 0.01 g / liter or more (preferably 0.0
1 to 20 g / liter, more preferably 0.1 to 15 g
The concentration of microorganisms or sodium ions inhabiting water of 0.01 g / liter or more (preferably 0.01 to 20 g / liter, more preferably 0.1 to 20 g / liter).
(15 g / l) of water, and is a microorganism that exhibits living activities such as nitrification ability and respiration ability in the range of salt concentration of seawater and salt concentration of a chiller for mixing seawater and river water. The composition of seawater has been analyzed for a long time, and specific examples (ionic species and their concentrations: g
/ Kg solution) is shown below. C1 ^-, 18.98; So _{4
^{2-, 2.65; HCO 3 -,}} 0.14; Br -, 0.0
6; F ⁻ , 0.001; H ₃ BO ₃ ⁻ , 0.02; total anions, 21.86; Na ⁺ , 10.56; Mg ²⁺ , 1.2
7; Ca ²⁺ , 0.40; K ⁺ , 0.38; Sr ²⁺ , 0.
01; total cation, 12.62; total 34.48 ionic species and the kind and concentration (g / kg solution) of the salt compound calculated from the concentration thereof are as follows. CaSo ₄ ,
1.38; MgSO ₄ , 2.10; MgBr ₂ , 0.0
8; MgCl ₂ , 3.28; KCl, 0.72; NaC
1, 26.69; 34.25 in total, ranging from seawater to air-water with the above composition (preferably sodium ion concentration of 0.1 to 140 g / liter, more preferably 1 to 15).
Since it is necessary to exhibit activity at (g / l), the activity is low in water having a sodium ion concentration of 0.1 g / l or less. Examples of the material for the polymer hydrogel include natural polymer hydrogels such as agar, alginate and carrageenan, and synthetic polymer hydrogels such as polyethylene glycol, polyvinyl alcohol, acrylamide and epoxy. Among these, polyvinyl alcohol hydrogel having high habitability of microorganisms and excellent strength and durability is preferable.

The shape of the gel of the present invention may be appropriately selected from plate-like, dice-like, spherical, fibrous, film-like and the like. When the gel is used by flowing it, it is water-permeable. In order to prevent the polymer hydrogel contained in the case from flowing out and to maximize the oxidation reaction by contacting with seawater, a dice shape or a spherical shape is preferable, and its diameter is preferably 1 to 10 mm, and 2 to 7 mm is more preferable.
The filling rate of the polymer water-containing gel depends on the fact that the polymer water-containing gel in which microorganisms are entrapped and immobilized in the water-permeable case container needs to flow in the water-permeable case container in order to make good contact with air and water. It is preferable to fill the aqueous case container with a filling rate of 50% or less. If the filling rate exceeds 50%, the fluidity of the polymer hydrogel in the water-permeable case container will decrease, and the polymer hydrogel on which the microorganisms have been immobilized will not contact the air and water well. It is not preferable because it is anaerobic.

As the kind of the microorganism used in the present invention, a bacterium that oxidizes or hydrolyzes the BOD component, the COD component and the nitrogen-containing component ammonia protein in seawater is preferable. Particularly, a salt-tolerant microorganism that exerts an oxidizing and hydrolyzing ability in seawater is preferable, and salt concentration of seawater (about 2 to
It is salt-tolerant and can oxidize, nitrify, and even denitrify ammonia, BOD, and COD by using activated sludge bacteria, Pseudomonas, and commonly used nitrifying sludge at 3.5 wt%). is there. For example, nitrifying bacteria consist of nitrite bacteria that oxidize ammoniacal nitrogen to nitrite nitrogen and nitrate bacteria that oxidize nitrite nitrogen to nitrate nitrogen. For nitric acid bacteria, Nitrobacte
r, Nitrocystis, Nitrosomon
as, Nitrosococcus, Nitrosop
rira, Nitrosociatis, Nitrog
loea, etc. Denitrifying bacteria are generically referred to as bacteria that perform so-called nitric respiration, which reduces nitrite nitrogen or nitrate nitrogen to a gas such as nitrogen gas or nitrous oxide. Is Pse
udomonas, Bacillus, Achromo
Genus such as Bacter and Micrococcus are used. Among them, Pseudomonas is particularly used.
Denitricans has high denitrification activity. Also, these bacteria can live aerobically by using oxygen, and can live anaerobically if NO ₃ ⁻ exists, but when both coexist, oxygen is preferentially used. Then, denitrification is not performed, and denitrification is not effectively performed. Therefore, in order to effectively perform denitrification, it is necessary to make the dissolved oxygen concentration in the habitat of denitrification bacteria as low as possible. In order to promote the degradability of animal and vegetable oils, it is preferable to use activated sludge that is used at a seawater concentration containing animal and vegetable oils. In order to accelerate the decomposition of petroleum-based oil components, by culturing petroleum-degrading bacteria that have been separated and extracted from seawater containing oil-based oil components or in the soil of oil fields, etc. It oxidizes and is oxidized or hydrolyzed to carbon dioxide, compounds such as calcium carbonate, low molecular weight substances, and even water.

The present invention will be described in more detail with reference to the case where polyvinyl alcohol is used as a material for the high-molecular hydrogel. The average degree of polymerization of polyvinyl alcohol (PVA) used for the polyvinyl alcohol-based hydrogel is 1
000 or more, preferably 1700 or more, more preferably 1700 to 25000 and having a saponification degree of 98.5 mol% or more, preferably 99.8 mol% or more from the viewpoint of forming a PVA hydrogel. preferable. The PVA of the present invention includes various known modified PVA and syndiotactic PV within a range that does not impair the effects of the present invention.
A etc. can also be used. The concentration of the PVA aqueous solution is PV
From the viewpoint of A water-containing gel formability, 0.1 to 40 wt% is possible, and the higher the PVA concentration, the stronger the gel is formed, but if the required gel strength is obtained, the lower the PVA concentration is. It is advantageous in terms of raw material cost. In order to form the PVA hydrogel into a spherical shape, a water-soluble polymer polysaccharide, such as sodium alginate, may be used. Further, to the aqueous solution of PVA, a microbial medium, a reinforcing agent for increasing the strength of the immobilized carrier, a filler for adjusting the specific gravity of the produced gel, and the like may be added within a range that does not inhibit the gelation of PVA. .

Various methods are known as PVA gelation methods, and the following two methods are preferably used. Freeze the PVA aqueous solution at −5 ° C. or lower, preferably −10 ° C. or lower, and hold it for at least 1 hour or longer, preferably 10 hours or longer, and then thaw-freeze-thaw at least once, preferably twice or more. . The PVA aqueous solution is brought into contact with an aqueous solution containing a substance having a synergic action of PVA, for example, an aqueous sodium sulfate solution. The concentration of the sodium sulfate aqueous solution is preferably 100 mg / liter or more, and a saturated aqueous solution is particularly preferable. Immersion time is 1
0 minutes or more is preferable and 30 minutes or more is more preferable. Further, the methods of and may be used in combination, or a drying operation and a crosslinking operation with formaldehyde or glutaraldehyde may be performed.

[0011]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The material and shape of the polymer hydrogel are not limited, but a spherical PVA hydrogel, which is particularly excellent in durability and habitability of microorganisms, will be described as an example.

Example 1 Polyvinyl alcohol (PVA) manufactured by Kuraray Co., Ltd. (average polymerization degree: 4000, saponification degree: 99.9 mol%) was added at 40 ° C.
After washing with warm water for about 1 hour, PVA was adjusted to pH 7 by adding water to PVA so as to have a concentration of 10 wt% to make the total amount 4 kg. This is treated at 110 ℃ for 120 minutes, PVA
Was dissolved and then left to cool to room temperature. To this PVA aqueous solution, 2 kg of a 4 wt% sodium alginate aqueous solution was added and mixed, and the sodium ion concentration was 0.01 to 0.
Wastewater treatment of 02 g / l wastewater Activated sludge obtained from the aeration tank and concentrated (MLSS 8000
2 mg (0 mg / liter) was added and sufficiently stirred. These mixed solutions were fed at a rate of 1 ml / min per nozzle by a roller pump using a stainless steel pipe having an inner diameter of 2 mmφ with a nozzle having an inner diameter of 1 mm attached to the tip, and stirred with a stirrer to give 0.1 mol / liter calcium chloride. (Ca
It was added dropwise to the cl ₂ ) aqueous solution from a height of 15 cm on the liquid surface. The dropped liquid droplets immediately became spherical and settled in the aqueous solution of Cacl ₂ . These spheronized PVA mixture molded product separated from the whole amount CaCl ₂ aqueous solution, washed briefly with distilled water and frozen in a freezer of -20 ° C. ± ° C.. After freezing for 20 hours and thawing, an opaque brown flexible PVA hydrogel having a diameter of about 5 mm and having a high flexibility was obtained.
The above freeze-thawing operation was repeated twice more in order to increase the strength of the water-containing gel A. This was used as a microorganism-immobilized PVA hydrogel. As a water-permeable case, mesh size is 5m
m Polyvinyl chloride coated nylon mesh net was used as a material to make a cylinder with a diameter of 40 cm and a height of 2 m (volume: 250 liters), in which 50 liters of microorganism-immobilized P
A VA hydrogel was added (filling rate 20%). This is 10
Frames framed by steel frames were sunk in the sea at 400 m intervals, and 400 frames were arranged at 50 cm intervals. At high tide, the tip of the water-permeable case was exposed to the surface of the sea, and a weight was attached to suspend it in the seawater. A blower was installed on the land so that air could be sent, and it was introduced to the seabed by piping, and the tip of the blower was aerated for 1 week from a ceramic diffuser (Fig. 4 (a) and Fig. 4 (b)).
checking). As a result, Table 1 shows the water quality near the test area. As a comprehensive judgment, COD decreased and ammonia was removed.

[0013]

[Table 1]

Example 2 Using a stainless steel plate material having an opening of 5 mm, a width of 10 c
m, depth 2m, length 2m water-permeable case (0.4m ³ )
And the microorganism-immobilized P prepared in Example 1 therein.
129 liters of VA hydrous gel was added (filling rate 30
%). Such a water-permeable case panel was installed so as to close into the bay and left for one month so that seawater could flow in and out due to the natural sea level of the seawater (see FIGS. 1 (a), 1 (b) and 2). See). As a result, the water quality of seawater is shown in Table 2.

[0015]

[Table 2]

Example 3 55 liters of seawater from the Seto Inland Sea (Kojima Bay) was placed in a glass tank having a width of 60 cm, a height of 35.8 cm, and a depth of 29.4 cm, and 11 chinu were introduced. As a water-permeable case, an onion bag made of polyethylene having a fiber thickness of 300 μm was sewn into a bag shape of 30 cm in height and 10 cm in width, and the microorganism-immobilized PVA hydrogel 200 prepared in Example 1 was sewn into the bag.
g was put and laid flat on a filter provided in the upper part of the water tank, and immersed so that the circulating seawater was applied. Seawater in the water tank was flown into the filter at 1 liter / hr, and seawater overflowing from the filter tank was returned to the water tank. Aeration was continued and 10 g of food was added every day. The seawater in the aquarium was not replaced. After 30 days, the seawater in the aquarium remained transparent, algae did not reproduce, and no abnormalities were observed in the fish.
The TOC and ammonia nitrogen concentration in the water tank were measured. The results are shown in Table 3, and it was found that the excellent water quality was maintained.

[0017]

[Table 3]

[0018]

According to the present invention, BOD and CO in seawater
It became possible to purify D and ammonia components. In addition, it will be possible to purify the inside of the harbor, closed sea areas and aquaculture areas, and it will be useful for environmental conservation such as prevention of eutrophication and red tide measures.

[Brief description of drawings]

1 (a) shows the entrance to a closed bay, FIG.
(B) is a plan view in which a water-permeable case is arranged in a closed bay.

FIG. 2 is a schematic cross-sectional view of FIGS. 1 (a) and 1 (b).

FIG. 3 (a) and FIG. 3 (b) are a plan view and a cross-sectional view in which a plate-shaped water permeable case is arranged in a closed bay.

FIG. 4 (a) and FIG. 4 (b) are a plan view and a cross-sectional view in which a tubular water-permeable case is arranged in a closed bay.

[Explanation of symbols]

 1: Land 2: Water-permeable case 3: Fixed pile or float of water-permeable case 4: Sea 5: Sea bottom 6: Tidal level at high tide 7: Tidal level at low tide 8: Basis of water-permeable case 9: Air blower 10 : Air supply pipe 11: Air diffuser 12: Support column for fixing 2 2 13: Brace

Claims (1)

[Claims] 1. A high-molecular hydrogel containing a polymer immobilizing and entrapping microorganisms inhabiting water having a sodium ion concentration of 0.01 g / liter or more or microorganisms acclimatized in water having a sodium ion concentration of 0.01 g / liter or more. A method for purifying water having a sodium ion concentration of 0.1 g / liter or more, which comprises immersing the water-permeable case in water and aerating.