JP4336863B2 - Removal method of adhering substances for cultured seaweed - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for removing diatoms and the like adhering to a laver during cultivation and a laver net.
[0002]
[Prior art]
The seaweeds and laver nets that are being cultivated are attached to the algae that grow in the seawater, mainly diatoms, leading to a deterioration in the quality of the seaweeds, as well as an operational management problem at the time of noriculture and collection. Therefore, an acid treatment agent is used to remove such diatoms. Currently, organic acids are frequently used as acid treating agents, and a solution obtained by mixing a dilute solution of malic acid, citric acid, acetic acid, etc., or a solution in which fertilizer is dissolved, into an acidic solution is used.
[0003]
[Problems to be solved by the invention]
The above-described cleaning with an organic acid has the following problems.
In general, analysis of diatoms adhering to aquaculture laver and laver net gives, for example, the following results.
[0004]
Table 1 (Analytical value with Ca as 100)
Ca 100
Cl 54.4
Fe 30.0
Si 14.7
K 11.9
Na 11.6
S 9.6
P 6.2
Al 5.6
Mg 4.5
Note: Na and Cl are due to NaCl in seawater.
[0005]
In other words, diatoms have a very high calcium content, followed by iron and silicon, according to their analytical values. Organic acids are difficult to remove deposits on the surface of nori such as calcium salts. Moreover, although the permeability is good, it is difficult to remove the permeated organic acid. In acid treatment, it is important to adjust the acidity of the liquid (for example, pH = 0.6 to 2.0). However, in the measurement with a pH meter, water repellency occurs at the interface of the measurement electrode and the indication becomes unstable. Therefore, it is difficult to obtain stable measurement values, and it is difficult to automatically control pH. Furthermore, COD and BOD are greatly affected compared to inorganic acids, and when laver or laver nets are washed, a large amount of organic acid may flow into the sea as waste liquid and cause red tide. Incidentally, when malic acid and citric acid are used as the organic acid and hydrochloric acid (35% by weight) is used as the inorganic acid, and when these are each diluted 100 times, the organic acid is about 3,000. In contrast, the inorganic acid is about 40.
[0006]
In view of the above-mentioned problems, this invention uses an inorganic acid as an acid treatment agent, and by adding sodium alginate, it is possible to efficiently remove calcium contained in the cleaning liquid. .
[0007]
[Means for Solving the Problems]
That is, the present invention is characterized in that laver and laver net with adhering diatoms and other algae are washed with a dilute solution of inorganic acid containing sodium alginate, and calcium components and heavy metals eluted in the washing solution are precipitated and separated. It is the removal method of the cultured laver adhesion substance. Examples of the inorganic acid to be used include hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid and the like, but hydrochloric acid is particularly preferable, and nitric acid is preferable in other cases. In addition, the washing liquid from which calcium and the like are precipitated and separated by sodium alginate can be recycled and reused by supplementing with an inorganic acid and sodium alginate if necessary. The last waste liquid only needs to be neutralized with alkali.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
In order to carry out the present invention, the laver and the laver net with diatoms and other mixed algae attached are lifted, and the hull is passed under the laver, and the laver is cut to a certain length by a cutter on the ship. After that, it is guided to a washing tank provided in the hull. In the washing tank, the laver net after washing is wound up by power to advance the laver and the laver net while being immersed in the washing liquid. According to another method, instead of the washing tank, a mixing tank containing the washing liquid is provided on the ship, and the laver net after cutting the laver is passed over the mixing tank, and the washing liquid in the mixing tank is pumped up by the pump. It can also be sprayed on the top and washed, and the washed liquid can be returned to the mixing tank and circulated. The laver net after washing can be reused because it is stretched on the sea surface and then cultured for laver.
[0009]
As a cleaning liquid, a dilute solution of an inorganic acid to which sodium alginate is added and mixed is previously filled in a cleaning tank or a mixing tank. As an example of the composition, 40 ml of 35% by weight hydrochloric acid and 60 ml of a 1 g / l aqueous solution of sodium alginate are mixed and diluted 100 to 150 times. The pH required for washing is about 1.7 to 2.0, preferably about 1.7 to 1.8 for washing with a washing tank, and about 0.6 to 1.5, preferably 0 for spray washing. About 8 to 1.5. The calcium content in the washing solution reacts with sodium alginate to form an insoluble alginate and settles in the tank. Heavy metals such as iron also form poorly soluble alginate and coprecipitate. The washing solution after use can be recycled after separating the precipitate by filtration.
[0010]
[Action]
Sodium alginate used in the present invention is a high-viscosity high-molecular substance, and is a substance that forms a cell membrane of algae such as kelp, kajime and arame. In other words, it is a familiar substance because it is similar to laver, and has the effect of relaxing the non-affinity of inorganic acids, which are completely different from laver, and making it easier to become familiar with laver. Accordingly, the inorganic acid can easily come into contact with the details of the laver form, and the adhered substances can be efficiently eluted. Further, since it forms a hardly soluble salt with calcium and heavy metals, it can be easily separated into solid and liquid. Furthermore, sodium alginate has a function of forming a film on the surface of the laver and protecting it.
[0011]
【Example】
Example 1
5 kg of sodium alginate was added to 1 m ³ of water and dissolved by stirring for 1 hour. 35 wt% hydrochloric acid 3401 was added to this solution 6601 to make a stock solution. This stock solution 101 was diluted to 1 m ³ with water to prepare a cleaning solution of 0.0033 wt% sodium alginate. Nori culture began on November 1, 1997, and 20 pieces of laver nets (hereinafter simply referred to as nets) having a net size of 1 m × 20 m were installed in the sea. From mid-December, we began to remove diatoms and slime attached to laver and nets. In this operation, a mixing tank containing cleaning liquid is installed at the top of the hull, the net is lifted, the hull is moved under it, and the cleaning liquid in the mixing tank is sprayed on the net while circulating with a pump. Then, it was continuously washed by spraying. Prior to washing, the laver is cut to a certain length by a cutter provided on the ship. The cleaning time for one net was within about 1 minute, and the pH of the cleaning liquid was raised by the net cleaning. Therefore, the pH was automatically adjusted using the above-mentioned stock solution and kept at pH = 1.4. The washed net was returned to the sea again to start aquaculture. Such washing operation was performed 5 times at 10-day intervals. The end date of the washing was February 10, 1998. After that, the cultivation was continued and the laver was harvested twelve times until March 16, 1998. The last harvest date was April 7, 1998. The seaweed obtained in this way had a yield 1.5 times that of the case where no lavage was performed. Moreover, the yield per one time was 25,000-30,000, and the quality was evaluated as a special product.
[0012]
Comparative Example In parallel with Example 1, laver culture and laver and net washing operations were performed in the same manner as in Example 1 except that the washing solution was changed to an organic acid aqueous solution such as citric acid. The seaweed obtained in this way had a yield of 1.2 times that of the case where no washing was performed. The quality was evaluated as a special product. When washing was not performed, the number of harvests during this period was about 4 times, and the quality of the harvested laver was evaluated as a normal product.
[0013]
Example 2
In Example 1, diatoms and other miscellaneous algae adhering to laver and nets were almost completely dissolved in the cleaning solution, and precipitates of calcium and the like were generated and deposited on the bottom of the mixing tank. The washing solution was filtered and the precipitate was collected as a filter cake and analyzed. As a result, Ca was about 100 g / kg, Fe was about 10 g / kg, calcium in the filtrate was about 100 mg / l, Fe was about 1 mg / l. Migration was observed during precipitation. This filtrate could be reused as part of the next wash.
[0014]
【The invention's effect】
According to this invention, diatoms and other miscellaneous algae adhering to laver and laver nets during laver culture can be separated and removed efficiently as precipitates. Moreover, since a protective film is formed on the surface of nori with sodium alginate, it is effective in preventing deterioration of the quality of nori. The used cleaning liquid can be filtered and recycled. In addition, since an inorganic acid is used in the present invention, there is little influence of seawater COD and BOD, and there is no possibility of causing trouble in terms of environmental protection.

Claims (3)

Adhesion of cultured seaweed, characterized by washing laver and laver nets with diatoms and other mixed algae with a dilute solution of inorganic acid containing sodium alginate, and precipitating and separating calcium and elution of heavy metals in the washing solution How to remove material. The method for removing a cultured laver adhesion substance according to claim 1, wherein the inorganic acid is hydrochloric acid and / or nitric acid. The method for removing a cultured laver adhering substance according to claim 1 or 2, characterized in that a cleaning liquid obtained by precipitating and separating calcium and heavy metals is circulated and used.