JPH10230297A - Treatment of bottom sludge and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extract a nutrient material from a sludge to culture algae and to return a slurry to the sea bottom to recover natural purifying capacity by exposing a bottom sludge to ozone to reform before solid-liquid separating, introducing a separated liquid into other process and introducing the separated residue into the bottom of the water area. SOLUTION: The sludge deposited on the sea bottom is transported to an ozone mixing tank 3 by utilizing an ascending force of a gaseous mixture of ozone with air by a drawing up device 1 while being mixed and stirred in a sludge drawing pipe line 2. And a waste gas discharged from the upper part of the ozone mixing tank 3 is sucked by a blower 17, mixed and stirred in the ozone mixing tank 3 by the blower 17 to oxidize and stabilize a sulfide contained in the sludge and the nutrient material effective for the culture of an aquatic fodder is dissolved and extracted. After that, the sludge is solid-liquid separated for 30-120min in a primary sedimentation tank 4, the supernatant liquid flows out to a culture tank 7 and the sedimented slurry is scattered on the sea bottom through a slurry discharge control valve 5 and a slurry discharge pipe line 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for improving sediment and sediment, and more particularly to a method and an apparatus for effectively utilizing fish sludge on lake bottoms, estuaries, and sea bottoms for fishery feed and improving fishing grounds. About.

[0002]

2. Description of the Related Art In recent years, due to the influx of nutrients from rivers and the like and the overfeeding of remaining feed and feed in a cultivation farm, sludge sediment containing a large amount of organic matter (hereinafter referred to simply as sludge or sediment) is present on the seabed. ), Causing red tides, blue tides, and anoxic water masses, causing severe damage to fishing grounds.
As countermeasures against this, civil engineering techniques such as dredging method for dewatering sludge pumped from the sea floor and landfill disposal, sand covering method of spraying sand on the bottom sludge, backing method of blowing air into anoxic water area, bottom part Although mechanical measures have been implemented to generate water flow in the oxygen-deficient water area and introduce oxygen-containing water, the disposal of sediment generated by the dredging method, the securing of sand used for the sand covering method and the construction There are many problems, such as the impact on the surrounding environment and the small effect on energy consumption by mechanical measures.

Recently, there have been attempts to solidify sludge and use it effectively for fish reefs and seaweed beds. However, at present, it is still in the research stage. By forming tidal flats using members, a strong seawall is created (Japanese Patent Publication No. 7-65304) or an underwater structure is constructed (Japanese Patent Publication No. 7-4125). Due to problems such as lack of nutrients, it takes time to grow eelgrass and the like on the structure.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides not only the improvement of bottom mud, but also a resource recycling process that separates effective nutrients and contributes to the production of marine bait, etc. In particular, it proposes a technology that simultaneously achieves environmental protection and productivity improvement in the water area where aquaculture is carried out. That is, the present invention extracts nutrients that are effective as marine feeds from sludge, cultures algae, which are excellent feeds for shellfish and shrimps, and returns slurries that have been modified to prevent anaerobics to the seabed. The purpose is to restore the purification ability.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies to solve a series of problems, such as the above-mentioned sediment reforming, resource utilization, environmental conservation of water areas, and the like.
The inventors have found that the use of ozone is effective, and based on this finding, the above-mentioned object has been achieved, and the present invention has been made.

That is, the present invention has the following configuration. (1) After the bottom mud is exposed to ozone and reformed, the reformed bottom mud is separated into solid and liquid, and the separated liquid is led to another step, and the separation residue is led to the sediment of the water area. Bottom mud treatment method. (2) The method for treating bottom mud according to (1), wherein the bottom mud is sucked up on the water surface or land and exposed to ozone in an ozone mixing tank. (3) The method for treating bottom mud according to the above (1) or (2), wherein the separated liquid is led to an algal culture step. The produced algae is supplied to a cultivation center for aquatic products or an existing water area. (4) The method for treating bottom mud according to (3), wherein at least a part of the algae grown in the algae culturing step is supplied to an existing water area as a food product. (5) The method for treating bottom mud as described in (2) above, wherein ozone is injected into a pipeline for guiding the bottom mud to the surface of the water or land, so that ozone is absorbed efficiently.

(6) An ozone mixing tank containing the bottom mud and exposing it to ozone, an ozone generator, a solid-liquid separation tank for solid-liquid separation of the modified bottom sediment derived from the ozone mixing tank, A separation liquid lead-out line for guiding the separated liquid led out from the liquid separation tank to another step, and a reforming slurry lead-out line for leading the separation residue led out from the solid-liquid separation tank to the sediment of the water area. An apparatus for treating sediment, characterized in that: (7) The apparatus for treating bottom sediment according to the above (6), wherein the separation liquid outlet pipe is communicated with the algae culture tank.

(8) The apparatus for treating bottom mud according to the above (6) or (7), wherein the separated liquid outlet pipe is connected to the algal culture tank via a filter. (9) The bottom mud according to (6), wherein the ozone mixing tank is installed on water or on land, and a bottom mud supply pump and a bottom mud supply pipe for introducing bottom mud into the ozone mixing tank are provided. Processing equipment. (10) The apparatus for treating bottom mud according to (9), further comprising an ozone supply pump and an ozone supply pipe for supplying ozone into the bottom mud supply pipe.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows one embodiment of ozone treatment of sludge, solid-liquid separation of the treated modified sludge, and reuse of the solid-liquid separated mud section and supernatant water section. Using the rising power of the mixed gas of ozone and air, the mixture is transferred to the ozone mixing tank 3 while mixing and stirring in the sludge pumping line 2. Ozone mixing tank 3
Can be installed underwater, but as in this example, it is preferably installed on water (that is, on a ship or a structure) or on land, and the transfer water depth is suitably from 0 to about 30 to 50 m. In this example, the supply means is shown by an air lift, but it may be transferred by a positive displacement pump.

First, a mixed gas of ozone and air is injected into the seabed marine sludge from the primary ozone supply pipe 19 into the discharge port of the sludge pumping apparatus 1, and a large amount of sludge contained in the sludge is drawn in the sludge pumping pipe 2. It is preferable to mix efficiently by utilizing the settling force of sand or silt and the rising force of the mixed gas. Further, as a second stage, in the ozone mixing tank 3 installed on the sea or land, a diffuser 21 for injecting a mixed gas of ozone and air is installed at the bottom, and the sludge and the mixed gas are brought into contact. Further, since the exhaust gas discharged from the upper part of the tank contains residual ozone, this exhaust gas is no. 2 blowers 1
It sucks in 7 and uses it instead of air of the mixed gas. As described above, the system is characterized in that the reforming of sludge is made more effective by injecting ozone gas in two stages, and the exhaust gas is reused, so that the absolute amount of the mixed gas required for injection can be reduced.

[0011] In the ozone mixing tank 3, the No. 3 is further installed on the sea or land. The mixture is mixed and stirred for 10 to 30 minutes with the 2 blower 17 to stabilize the sulfide contained in the sludge by oxidation and to dissolve and extract a nutrient substance effective for cultivation of the marine feed. At the same time, it is expected that damage caused by harmful microorganisms and viruses in sludge will be suppressed. Then 30-120
The liquid is separated into solid and liquid in the primary sedimentation separation tank 4 for one minute, the supernatant water flows out to the culture tank 7, and the sedimented slurry is sprayed to the seabed through the slurry discharge control valve 5 and the slurry discharge line 6.

In the ozone mixing tank 3, as a separation device suitable for solid-liquid separation of sludge sufficiently mixed with the mixed gas, known devices such as a device using a membrane and a device using centrifugal force are used. Although the apparatus using the above method can be applied, the sedimentation tank is preferable in view of sludge characteristics. Further, at the time of solid-liquid separation, improvements such as adding a flocculant, and providing a settling plate or a settling tube in the primary settling / separation tank 4 are optional. Therefore, the separation time also varies depending on these situations. Further, as a sedimentation separation method, a continuous type in which inflow and discharge are continuously performed and an intermittent type in which intermittent flow is performed intermittently can be selectively adopted according to the scale of the system.

[0013] Since the modified slurry has reduced organic matter and sterilized microorganisms, it is close to a state of sand covering by spraying on sludge on the seabed. In the primary settling tank, depending on the particle size distribution of the reformed slurry,
It is also possible to adopt a structure in which fine sand or a solidifying agent can be added (injected). The properties of bottom mud, especially underwater sludge, vary greatly depending on the type of cultured fish and shellfish, the surrounding environment, topography and geology. It is advisable to use an ozone injection controller or the like that incorporates the previously investigated properties, the amount of sludge pumped from the sea floor, and the automatic measurement of residual oxidant to prevent secondary damage due to excessive ozone injection.

In the culture tank 7, a filter filled with a filter material having a fine particle diameter is used for efficiently cultivating excellent microalgae as a feed for fish and shellfish and for eliminating impurities and living algae as much as possible. Is installed at the subsequent stage of the primary sedimentation separation tank 4, and a culture is performed by adding excellent microalgae seeds to the filtrate. As a filter, a floating filtration type filter capable of efficiently removing finer SS and having a small amount of washing wastewater is preferable. In addition, as for the flotation filtration type, a filter that can be treated in accordance with the quality of the separated water is selected by selecting an appropriate filter medium. In addition, although various types of algae inhabit the sludge, the types of the algae decrease due to the injection of ozone, which makes it easier to culture the target algae. As unsuitable algae and damage to the cultivation of good algae to be cultured, it is necessary to remove ozone, and it is preferable to remove impurities and harmful algae as much as possible. The machine is also effective as a deozonizer due to its structure.

In the cultivation tank 7, seawater obtained by mixing ozone and air with local plankton sludge and sedimenting and separating minerals contains a large amount of nutrients necessary for culturing marine feed eluted from the sludge. Therefore, the culture solution of diatoms, haptoalgae, prasinoalgae, nannochloropsis and chlorella (originally transported from another facility) is added to the supernatant water containing nutrients of the marine feed extracted by ozone. It is characterized by injecting the seeds through the seed return pipe 13 by the seed return pump 9 and contacting with sunlight under air stirring for about 5 to 10 days for culture.

In the culture tank 7, these nutrients are mixed with an excellent algae seed strain as a marine feed and cultured. A diffuser is provided at the bottom of the culture tank 7 for spraying air into fine bubbles, and the top is opened so that sunlight can be taken in. The structure is such that algae are efficiently brought into contact with sunlight by air stirring. Further, a secondary sedimentation separation tank 8 for separating slurry in the culture solution and a seed return pump 9 are installed at the latter stage of the culture tank 7 so that the concentrated algae are brought into contact with newly-introduced separated water to culture the algae. It is characterized by performing. In this device, the circulating volume is adjusted until a specified cell concentration is reached. Any known photoreactor can be used as the algal culture tank. Further, in the present invention, the object to be cultured is algae, that is, phytoplankton, but since a large light-receiving area of the sea surface can be effectively used, adherent algae, seaweeds, and photosynthetic bacteria may be used. Suitable for culturing microorganisms that require light.

The cultured algae and the like are placed in a secondary sedimentation separation tank 8.
And the supernatant is led to the feed transfer pump tank 10,
A tidal flat through a feed transfer line 12 with a feed transfer pump 11,
Transport to aquaculture facilities such as seaweed beds and cultivation centers. Note that, of course, the present position is not limited to the above and may be the current position. Also,
The solid-liquid separated algae may be used for cultivation of zooplankton and other feed organisms, and may be used as foods and preparations, and all known uses can be applied.

[0018]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. Example 1 Using sludge deposited under a shellfish farm, sludge modification and elution experiments of nutrients were performed. The sludge used in the experiment was a seawater-diluted sludge that was diluted 3 to 5 times with seawater, and 0.5 l of the sludge was packed in a glass column having a diameter of 5 cm and a length of 72 cm. The column filled with the diluted sludge was aerated with ozone gas at a flow rate of 1 liter / min under the conditions shown in Table 1.

[0019]

[Table 1]

The sludge treated under the conditions shown in Table 1 was subjected to solid-liquid separation using filter paper, and the sulfide in the separated treated mud was measured, and this was used as an index of the degree of sludge modification. Table 2 shows the results of the amount of sulfide in the treated mud.

[0021]

[Table 2]

The amount of sulfide was untreated (ozone concentration: 0 mg /
(Ml, processing time: 0 minutes) 0.2 mg / g of mud
On the other hand, the amount of sulfide in the ozone-treated mud was all 0.1 mg / g or less. Further, the concentrations of TOC, total nitrogen and total phosphorus, which are nutrients for algae culture in the treated water, which were separated by treatment under the conditions shown in Table 1, were measured. The results are shown in FIGS. 2, 3 and 4, respectively.
Shown in In each case, it was confirmed that the elution concentration increased as the treatment time increased, and the elution amount increased as the ozone treatment concentration increased.

The properties of the untreated, air-treated and ozone-treated sludge were observed under a microscope. The untreated one was confirmed to have a unique sludge structure in which algae such as small gravel and diatoms were mixed. In the case where air was ventilated under the conditions of a processing time of 30 minutes and a flow rate of 1 liter / min, there was almost no change from the case of untreated sludge. On the other hand, it was confirmed that the sludge particles were finely changed in the case where aeration was performed under the conditions of an ozone concentration of 30 mg / liter, a processing time of 30 minutes, and a flow rate of 1 liter / minute.

Example 2 The separated seawater treated in Example 1 was used as a feed for high-grade invertebrates such as bivalves and sea urchins.
A cultivation experiment of Ruteri (Pavlova lutheri) was performed. Pavlova is a species that is highly valued as a feed because it contains a large amount of higher unsaturated fatty acids such as EPA and DHA, but it is difficult to cultivate it outdoors in large quantities. Guillard's F with adjusted vitamins and trace metals
Medium (1963) and f / 2 Provasoli whose concentration is 1/2
Improved medium (1957) and the like are used. In FIGS.
The time-dependent change of the growth of Pavlova by the treated water when the ozone treatment time was changed was shown by the cell density. The culture method is 20
100 ml of the treated water was dispensed into a 0 ml Erlenmeyer flask, and after planting Pavlova, about 30 μEm ² · s ⁻¹
Under light conditions.

FIG. 5 shows the case where the ozone treatment concentration is 10 mg / l, FIG. 6 shows the case where the ozone treatment concentration is 20 mg / l, and FIG. 7 shows the case where the ozone treatment concentration is 30 mg / l. In FIGS. 5 to 7, ○ indicates separated water without ozone treatment. After culturing for 20 days, the cell density was 1.6 to 2.3 times higher than that of the ozone-untreated separated water at 10 days from the start of the culture. Showed expenses required for f / 2 medium composition and culture 1 m ³ prepared in Table 3.

[0026]

[Table 3]

Various chemicals (materials) are used for preparing the f / 2 medium.
, The cost of 404 yen is required to prepare 1 m ³ , while the use of sludge ozone-treated separated water requires 0 yen, and the above results As a result, pavlova, which is considered difficult to culture, could be sufficiently cultured, so that sludge could be effectively used.

[0028]

According to the present invention, marine sediment deposited on the seabed, lake bottom or estuary bottom, which has been difficult to treat without any effective disposal means in the past, is treated with ozone. The content and sulfide content, which is a pollution index, is reduced to 0.1 mg / g or less, and the sulphide content is reduced to 0.1 mg / g. Since the content is also reduced by 10 to 30%, by returning this to the seabed or the like as a sand covering agent, restoration of the natural purification ability including sterilization of microorganisms is brought about, and the separated water is excellent as a marine feed. Since it contains nitrogen and phosphorus necessary for cultivation of various algae, it is possible to reuse these algae as a culture solution. The method for treating bottom mud including such reuse can greatly contribute to improving the treatment of difficult-to-treat bottom mud.

[Brief description of the drawings]

FIG. 1 shows an example of an embodiment of the present invention.

FIG. 2 shows the relationship between ozone treatment time and TOC in treated water.

FIG. 3 shows the relationship between ozone treatment time and total nitrogen content in treated water.

FIG. 4 shows the relationship between ozone treatment time and total phosphorus content in treated water.

FIG. 5 shows the change over time in the growth of P. lutheri using treated water that had been agitated at an ozone concentration of 10 mg / l.

FIG. 6 shows the change over time of the growth of P. lutheri using treated water that had been agitated at an ozone concentration of 20 mg / liter.

FIG. 7 shows the time course of the growth of P. lutheri using treated water which was aerobically conditioned at an ozone concentration of 30 mg / liter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sludge pumping device 2 Sludge pumping line 3 Ozone mixing tank 4 Primary sedimentation separation tank 5 Slurry discharge control valve 6 Slurry discharge line 7 Culture tank 8 Secondary sedimentation separation tank 9 Seed return pump 10 Feed transfer pump tank 11 Feed transfer pump 12 Feed transfer line 13 Seed return line 14 No. 1 Ozone injector 15 No. 2 Ozone injection machine 16 No. 1 blower 17 No. 2 blower 18 No. 3 Blower 19 Primary ozone supply line 20 Secondary ozone supply line 21 Diffuser 22 Exhaust gas line 23 Light 30 Sludge layer 40 Sand layer

Claims (10)

[Claims] 1. After the bottom mud is exposed to ozone and reformed, the reformed bottom mud is separated into solid and liquid, and the separated liquid is led to another step.
A method for treating sediment, wherein the separation residue is led to the sediment of a water area. 2. The method for treating bottom mud according to claim 1, wherein the bottom mud is sucked up on the water surface or land and exposed to ozone. 3. The method for treating bottom mud according to claim 1, wherein the separated liquid is led to an algal culture step. 4. The method for treating bottom mud according to claim 3, wherein at least a part of the algae grown in the algae culturing step is supplied to an existing water area as a food product. 5. The method for treating bottom sediment according to claim 2, wherein ozone is injected into a conduit for guiding the bottom sediment on the water surface or on land. 6. An ozone mixing tank containing bottom sediment and exposing ozone thereto, an ozone generator, a solid-liquid separation tank for solid-liquid separation of modified bottom sediment derived from the ozone mixing tank, and the solid-liquid separation tank A separation liquid lead-out line for leading the separated liquid led out of the separation tank to another step, and a reforming slurry lead-out line for leading the separation residue led out of the solid-liquid separation tank to the sediment of the water area. A treatment apparatus for bottom mud, characterized by: 7. The apparatus for treating bottom mud according to claim 6, wherein the separation liquid outlet pipe is connected to an algal culture tank. 8. The algae culture tank according to claim 6, wherein the separation liquid outlet pipe is connected to an algal culture tank via a filter.
Bottom mud processing apparatus according to the above. 9. The system according to claim 6, wherein the ozone mixing tank is installed on water or on land, and a bottom mud supply pump and a bottom mud supply pipe for introducing bottom mud into the ozone mixing tank are provided. Sediment treatment equipment. 10. An apparatus for treating bottom mud according to claim 9, further comprising an ozone supply pump and an ozone supply pipe for supplying ozone into said bottom mud supply pipe.