JPS6232993B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an effective method for recovering red tide generated in a certain sea area.

In recent years, industrial wastewater has increased due to the development of industrial activities.
As urban sewage increases due to urban development, nitrogen compounds, phosphorus compounds, and other nutrients flow into inner bays and seas, creating favorable conditions for the occurrence of red tide. The Seto Inland Sea, Ise Bay, and other inland seas,
The inner bay has improved through years of efforts to improve aquaculture technology.
Aquaculture fisheries for yellowtail, pearl oysters, abalone, seaweed, etc. have made rapid progress, and their weight in the overall fishing industry has increased, but due to the occurrence of red tide, the aquaculture fisheries have suffered huge losses and are in danger. It is a well-known fact that they are doing so.

Red tide occurs when a certain type of plankton breeds explosively in a limited area of water, causing the seawater to change color, become cloudy and viscous, and sometimes emit an odor that lasts for several days or even tens of days. Although it is a persistent phenomenon, there is currently no way to prevent it from occurring, and even after it occurs, there is no effective way to deal with it, and once it occurs, we simply wait for it to disappear naturally. Ta.

The types of plankton that cause red tides vary depending on location and time of year; they include red bacteria, cyanobacteria, diatoms, algae, ciliates, and crustaceans, but algae are the most common. . Goniaurusk, gymnodenium, glenodeinium, kerateium, peridainium, etc. are famous as the main components of red tide. These plankton, which are mainly tens of microns in size, are dispersed in seawater or freshwater in the numbers of thousands to tens of thousands per c.c., causing the water to turn red during red tide. One possible measure against red tide is to collect red tide once it occurs before it causes damage to fisheries. The purpose of red tide collection is to collect suspended solids as effectively as possible from seawater where the concentration of suspended solids is low. Therefore, technically there are many points in common with water treatment technologies for general turbid water. A possible treatment method is to collect the red tide after coagulating and concentrating it with a polymer flocculant.
However, treating red tide is extremely difficult compared to treating general turbid water. The reason for this is that the concentration of suspended solids in red tide is lower than that in general turbid water.
Furthermore, due to the high salt concentration, the flocculation reaction cannot occur smoothly with common flocculants for turbid water treatment, and even if flocculation occurs, the floc strength is weak and breaks easily, making it impossible to concentrate and recover effectively. be.

Red tide is made up of microorganisms, so cationic polymers are effective in coagulating it, but conventional cationic polymers lose their cohesive power when the salt concentration is as high as seawater. It could not be put to practical use. Although the establishment of a red tide recovery system and its commercialization have been strongly desired by fisheries officials, one of the reasons why this has not been possible is that suspended solids in red tide can be effectively and powerfully coagulated and concentrated in seawater. One of the reasons is that there was no polymer flocculant.

The present inventor synthesized various polymers and conducted tests in order to find a cationic polymer that can strongly coagulate red tide without decreasing its cohesive force even in the presence of highly concentrated salts such as seawater. As a result of repeated studies, it was discovered that a polymer having a quaternary ammonium salt represented by the general formula [] is superior. This quaternary ammonium salt is generally obtained by quaternizing dialkylaminoalkyl (meth)acrylate with benzyl halide,
One of the cationic polymers currently commonly used as a flocculant has a quaternary ammonium salt quaternized with methyl halide instead of benzyl halide, and as is clear from the comparative example, this has a strong effect on red tide. Cohesion is extremely poor. In this way, even polymers with similar structures have large differences in red tide cohesive strength due to differences in the functional groups bonded to the quaternary ammonium nitrogen, and only the benzyl group-containing polymer of the present invention exhibits very specific and good cohesive performance. We have discovered the surprising fact that it is possible to demonstrate this, and have completed the present invention.

That is, in the present invention, a cationic polymer having a quaternary ammonium salt represented by the general formula [] as one constituent unit is added to red tide generated due to abnormal proliferation of plankton, and the plankton is aggregated. This method of collecting red tide is characterized by collecting it later.

The cationic polymer used in the present invention will be explained in more detail.

Typical examples of quaternary ammonium salts represented by the general formula [] include dimethylaminoethyl acrylate or methacrylate, diethylaminoethyl acrylate or methacrylate, dimethylaminopropyl acrylate or methacrylate, etc., which are quaternized with benzyl halide. 4 ammonium salts can be mentioned. The flocculant of the present invention can be obtained by copolymerizing this quaternary ammonium salt alone or with other monomers in a conventional manner.

In this case, the most preferred copolymerizable monomer is acrylamide, and other materials such as N-vinylpyrrolidone can also be used. The copolymerization ratio with such monomers can be arbitrarily adjusted depending on economic efficiency and the target red tide, but in order to exhibit sufficient performance, the quaternary ammonium salt must be approximately 10 mol% or more. It is desirable that there be.

The polymer of the present invention is added to red tide, agglomerated, concentrated and recovered, and the amount of the polymer of the present invention added is preferably 5 to 1000 ppm relative to red tide. General turbid water treatment methods such as natural sedimentation followed by recovery, centrifugation, and flotation separation methods can be used for concentration and recovery, but suspended solids in red tide have a specific gravity different from that of seawater. Because there is not much and it is easy to float,
It is desirable to adopt flotation separation method. Furthermore, according to the present invention, it is possible to recover 90% or more of suspended solids in red tide.

Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

However, the red tide targeted in each of the following examples is
It is an abnormal occurrence in Ise Bay, and according to microscopic observation, it is mainly composed of Gymnodenium, a type of flagellate, and it is about 45,000 per c.c. of seawater.
There were several. The liquid was slightly viscous, red and cloudy in color. In addition, the concentration of suspended solids in red tide was 13 ppm.

Example 1 500 ml of red tide was collected in a beaker. This is combined with the polymer of the present invention, a copolymer of methacryloyloxyethyldimethylbenzylammonium chloride and acrylamide (cation density
After adding 5 ml of a 0.1% aqueous solution of 2.8 meq/g polymer and 0.5% Bruckfield viscosity (BV) 590 cps), the mixture was stirred at 100 rpm for 60 seconds using a jar tester. The red tide components quickly aggregated to form a floc, which settled to the bottom of the beaker when stirring was stopped. This was further rapidly stirred at 250 rpm for 2 minutes to perform a floc destruction test, but the flocs were hardly broken and could be easily separated, and the filtrate was clear and colorless with no red remaining.

Comparative Example 1 A test similar to Example 1 was conducted using a conventional cationic polymer, a copolymer of methacryloyloxyethyltrimethylammonium chloride and acrylamide (cation density 3.0 meq/g polymer, 0.5% BV 650 cps). The aggregation of the red tide components was slower than in Example 1, and although flocs were formed, they were fluffy and weak. Furthermore, when rapid stirring was performed at 250 rpm for 2 minutes, the flocs were almost destroyed and the entire liquid returned to its red color, making it impossible to separate and recover the suspended solids in the red tide.

Example 2 A pressure flotation separation test was conducted using an experimental floatation tester. The flotation tank has an inner diameter of 100
Made of transparent acrylic resin with a height of 500 mm. After adding 3000 ml of red tide to this, 20 ppm of the polymer of the present invention of Example 1 was added. 800 ml of seawater pressurized to 3 kg/cm ³ was injected from the bottom of the tank to carry out pressure flotation concentration, and the red tide scum that floated to the surface was collected and analyzed, and the recovery rate was 96%.

Comparative Example 2 When the same experiment was conducted in Example 2 using the conventional polymer of Comparative Example 1, the recovery rate was 30%. When tested without adding polymer, the recovery rate was 12%.

Claims (1)

[Claims] 1. General formula for red tide generated due to abnormal proliferation of plankton species (However, R is hydrogen or a methyl group, R ₁ and R ₂ are alkyl groups having 1 to 4 carbon atoms, A is a chain or branched aliphatic group having 2 to 4 carbon atoms, × ^(-) is ammonium A method for treating red tide characterized by adding a cationic polymer having a quaternary ammonium salt (a negative group that forms nitrogen and a salt) as one constituent unit and collecting the plankton after agglomerating them. Collection method.