JP7053271B2 - Muddy water treatment method - Google Patents

Description

The present invention relates to a turbid water treatment method using a chitosan-based flocculant and an auxiliary agent that enhances the effect of the chitosan-based flocculant.

Muddy water generated in civil engineering work, etc. is discharged to rivers, etc. after being treated with muddy water so as to meet predetermined drainage standards. In the turbid water treatment, it is common to put various coagulants into the turbid water, aggregate and precipitate SS (suspended solids), and separate them into clear water and sludge (Patent Document 1).
Chitosan-based flocculants are known as coagulants used in turbid water treatment (Patent Documents 2 and 3, Non-Patent Document 1). Since chitosan is a natural material that is mainly refined from crab shells, chitosan-based flocculants are expected to reduce waste (crab shells, etc.) in the fishery industry and reduce the burden on the environment due to wastewater. It is a material of.

Polymer-based flocculants such as chitosan-based flocculants generally change from SS flocculation action to dispersion action as the addition concentration increases. Further, the chitosan-based flocculant has a problem that the applicable concentration range is narrower than that of an inorganic flocculant such as polyaluminum chloride (PAC), aluminum sulfate, and ferric chloride.
Since the SS concentration of the turbid water generated at the realization site fluctuates, the chitosan-based flocculant may be excessively added when the SS concentration decreases, and the SS may be dispersed without agglomeration. Therefore, when a chitosan-based flocculant is used, it is necessary to adjust the amount of the chitosan-based flocculant added according to the SS concentration of the turbid water, and the management work is complicated. When the chitosan-based flocculant is excessively added, it is necessary to add turbid water before the treatment, sludge after the treatment, etc. to increase the SS concentration and consume the excess amount of the chitosan-based flocculant. However, the work of adding the source of turbid water to clarify the turbid water is difficult to understand intuitively, so on-site workers use a chitosan-based flocculant to clarify the turbid water. Is often added, and mistakes often occur in dealing with problems that occur in the field.

Japanese Unexamined Patent Publication No. 2011-78893 Japanese Unexamined Patent Publication No. 11-60607 Japanese Unexamined Patent Publication No. 2007-119533

Mayiko Akatsuka, Eiji Ohwaki, Mutsumi Kawamata, Go Ohno, Yasushi Fujiwara: Effect of Inorganic Salt Addition in Turbid Water Treatment with Chitosan Aggregating Agent, JSCE Annual Academic Lecture Proceedings (CD-ROM), 66th, VII- 040, August 5, 2011

An object of the present invention is to provide a turbid water treatment method having a wide range of applicable concentrations of a chitosan-based flocculant.

The means for solving the problems of the present invention are as follows.
1. 1. A turbid water treatment method comprising adding an auxiliary agent containing at least one of an anionic dispersant, a nonionic dispersant, and an amphoteric ionic dispersant after a coagulation treatment with a chitosan-based flocculant.
2. 2. A turbid water treatment method characterized by simultaneously adding a chitosan-based flocculant and an auxiliary agent containing any of an anionic dispersant, a nonionic dispersant, and a zwitterionic dispersant.
3. 3. 1. The concentration of the chitosan-based flocculant added is 0.1 ppm or more and 100 ppm or less. Or 2. The turbid water treatment method described in.
4. 1. The auxiliary agent is added by 0.1 part by weight or more and 100 parts by weight or less (dry weight) with respect to 100 parts by weight (dry weight) of the chitosan-based flocculant. ~ 3. The turbid water treatment method according to any one of.
5. 1. The auxiliary agent is an environment-friendly material. ~ 4. The turbid water treatment method according to any one of.
6. A turbid water treatment agent comprising a chitosan-based flocculant and an auxiliary agent containing any of an anionic dispersant, a nonionic dispersant, and a zwitterionic dispersant.
7. 6. The auxiliary agent is an environment-friendly material. The turbid water treatment agent described in.

According to the turbid water treatment method of the present invention, the applicable concentration range of the chitosan-based flocculant can be widened, and the coagulant management during the turbid water treatment can be simplified. In the turbid water treatment method of the present invention, the turbidity is reduced by adding and stirring an auxiliary agent, so that the worker can easily understand the connection between the work and the result, and the work error can be reduced. By using the auxiliary agent, the turbidity is reduced even with a short stirring time, so that the treatment time can be shortened. Further, by using the auxiliary agent, the amount of the expensive chitosan-based flocculant used can be reduced, so that the cost can be reduced.

When a biosurfactant is used as an auxiliary agent, the chitosan-based flocculant is also of biological origin, so that the burden on the environment associated with the turbid water treatment can be reduced, and the turbid water treatment can be performed in an environmentally friendly manner.
In the turbid water treatment method of the present invention, the order of addition of the flocculant and the auxiliary agent is important, but by using a turbid water treatment agent in which the flocculant and the auxiliary agent are mixed in advance, it is possible to prevent an error in the order of addition. ..

The figure which shows the measurement result of the turbidity in Experiment 1. The figure which shows the measurement result of the turbidity in Experiment 2. The figure which shows the measurement result of the turbidity in Experiment 3. The figure which shows the measurement result of the turbidity in Experiment 4. The figure which shows the measurement result of the turbidity in Experiment 5.

The present invention relates to a turbid water treatment method using a chitosan-based flocculant and any of an anionic dispersant, a nonionic dispersant, and a zwitterionic dispersant as an auxiliary agent for enhancing the effect of the chitosan-based flocculant.

"Chitosan-based flocculant"
The chitosan-based flocculant used in the present invention can be used without particular limitation as long as it is soluble in water and exhibits an agglutinating ability with respect to suspended solids. For example, chitosan having a degree of deacetylation of 40 to 90 mol% can be used. If the degree of deacetylation is less than 40 mol%, the solubility in water is inferior, and if the degree of deacetylation is larger than 90 mol%, it is expensive because it takes time to produce from chitin, and it is expensive during the deacetylation reaction. Since the main chain is cleaved, the weight average molecular weight becomes low.

The weight average molecular weight of the chitosan-based flocculant is preferably 1,000 to 3,000,000, more preferably 3,000 to 2,000,000, and 10,000 to 1,500,000. Is even more preferable. The higher the weight average molecular weight, the more amino groups per molecule, so the ability to aggregate particles in turbid water is excellent, and suspended solids can be aggregated and precipitated in a small amount. However, when the weight average molecular weight becomes large, the solubility in water is lowered and the handleability is lowered.

Chitosan may have a part of a hydroxyl group or an amino group substituted with a polyoxyalkylene group, an acyl group, a sugar side chain or the like as long as it can be used as a flocculant. By substituting with these, the solubility in water can be improved. Examples of the polyoxyalkylene group include a polyethylene glycol group, and examples of the acyl group include an acetyl group and a propionyl group. Further, chitosan may be used alone or in combination of two or more having different molecular weights and deacetylation degrees.

"Auxiliary agent"
The present invention uses any of an anionic dispersant, a nonionic dispersant, and an amphoteric ionic dispersant as an auxiliary agent for enhancing the effect of the chitosan-based flocculant. Here, the dispersant means a compound having an effect of uniformly dispersing fine particles in water, and most of the surfactants act as dispersants.
Various anionic dispersants can be used, and for example, alkyl sulfate, alkylbenzene sulfonate, dialkylsulfosuccinate, alkyldiphenyletherdisulfonate, polyoxyethylenealkylsulfate, polyoxyethylenealkyllin. Examples thereof include acid salts.
Examples of the nonionic dispersant include polyoxyethylene alkyl ether, polyoxyethylene alkyl aryl ether, polyoxyethylene fatty acid ester, silicone type and the like.
As the zwitterionic dispersant, lecithin and the like can be mentioned. The zwitterionic dispersant is a dispersant that exhibits the properties of an anionic dispersant in the alkaline region and the properties of a cationic dispersant in the acidic region. Here, the pH range of the chitosan-based flocculant is preferably in the pH range of 5.6 to 8.6, and the turbid water generated at the construction site is mainly alkaline due to the influence of concrete and the like. Therefore, the turbid water treatment is often performed in a weak alkaline region after the neutralization step. The zwitterionic dispersant has the same effect as the anionic dispersant in the weak alkaline region.

In the present invention, the auxiliary agent may contain two or more kinds of anionic dispersant, nonionic dispersant, and zwitterionic dispersant as long as the effects of the present invention are not impaired. When two or more kinds of dispersants are contained, two or more kinds of dispersants having the same performance and two or more kinds of dispersants having different performances can be used. For example, one or more of two or more anionic dispersants, anionic dispersants and nonionic dispersants can be contained.

Further, as an auxiliary agent, it is preferable to use an environment-friendly material that is naturally derived and biodegradable. In the turbid water treatment method of the present invention, the clear water after the turbid water treatment is discharged to a river or the like, but a flocculant (chitosan) and an auxiliary agent may remain in the clear water. The turbid water treatment method of the present invention using an environment-friendly material as an auxiliary agent shall be an environment-friendly treatment method having a small environmental load because both the flocculant and the auxiliary agent are naturally derived and biodegradable. Can be done.

Examples of the environment-friendly material include lecithin and biosurfactant, which are the above-mentioned plant-derived dispersants. Biosurfactants are surfactant-like substances secreted by microorganisms to take up highly hydrophobic substances into cells.
The biosurfactant can be used without particular limitation on amino acid type, sugar type, polymer type and the like. For example, amino acid type surfactin, viscocin, sugar type ramnolipid, sophorolipid, mannosylerythritol lipid, trehalose lipid, high Among the molecular types of emalzan and the like, anionic, nonionic and zwitterionic ones having a dispersive ability can be used.

"Muddy water treatment method"
The turbid water treatment method of the present invention is characterized in that an auxiliary agent is added after the aggregation treatment with a chitosan-based flocculant or at the same time as the chitosan-based flocculant. If the chitosan-based flocculant is added after the auxiliary agent is added, the effect of the present invention may not be obtained. The turbid water treatment method of the present invention is based on conventionally known devices and methods, except that an auxiliary agent containing at least one of an anionic dispersant, a nonionic dispersant, and an amphoteric ionic dispersant is used. It can be carried out.

Although the detailed mechanism by which the aggregating action is enhanced by the combined use of the chitosan-based flocculant and the auxiliary agent is unknown, the present inventor speculates as follows.
Suspended solids in water are usually negatively charged. Since chitosan has a positive charge, it acts to aggregate these suspended solids. However, when the amount of chitosan is excessive, the chitosans having positive charges repel each other, resulting in a dispersion effect. The auxiliaries interact with the positively charged and uncharged parts of chitosan, respectively, to weaken the repulsive force between the chitosans. As a result, the concentration range in which the dispersal action of chitosan works is narrowed, and the applicable concentration of the chitosan-based flocculant is widened.

It can also be added as a turbid water treatment agent in which a chitosan-based flocculant and an auxiliary agent are mixed in advance. The turbid water treatment agent can be in the form of a solid or a liquid. By using a turbid water treatment agent in which a chitosan-based flocculant and an auxiliary agent are mixed in advance, there is an advantage that the order of adding the flocculant and the auxiliary agent during the turbid water treatment is not mistaken.

The concentration of the chitosan-based flocculant added is preferably 0.1 ppm or more and 100 ppm or less, more preferably 0.5 ppm or more and 50 ppm or less, and further preferably 1 ppm or more and 30 ppm or less. The amount of the auxiliary agent added (dry weight) is preferably 0.1 part by weight or more and 100 parts by weight or less, preferably 0.5 part by weight, based on 100 parts by weight (dry weight) of the chitosan-based flocculant. It is more preferably 50 parts by weight or less, and further preferably 1 part by weight or more and 30 parts by weight or less.

"Experiment 1"
Kaolin powder prepared to have a particle size of 75 μm or less was added to distilled water and stirred to prepare simulated turbid water 1 (500 ppm). When the initial turbidity of the simulated turbid water 1 was measured with a turbidity meter (device name: portable turbidity meter, manufactured by HANNA instruments, measuring range 0.00 to 1000 FTU), the initial turbidity was 368 FTU. The pH of the simulated turbid water 1 was 7.8.
200 ml of this simulated muddy water 1 was dispensed into a beaker. Add a chitosan-based flocculant (Fujiclean, manufactured by Fuji Engineering Co., Ltd.) to each beaker so that the amount is 5 ppm, and further, 3 types of anionic dispersants, 5 types of nonionic dispersants, and amphoteric ionic dispersants shown below. One kind and one kind of cationic dispersant are added so as to be 1 ppm each, and after a stirring cycle of rapid stirring (120 rpm) for 1 minute, slow stirring (30 rpm) for 3 minutes, and standing for 5 minutes, from the water surface. 10 ml was collected from a place of 1 cm and the turbidity was measured with a turbidity meter. Then, 1 ppm of the dispersant was further added, the stirring cycle was performed again, and the turbidity was measured for the second time in the same manner. The same operation was performed except that the dispersant was not added as a control. The turbidity of each sample is shown in FIG.

Dispersant (trade name)
・ Anionic 1. Master Pozoris No. 70 (manufactured by BASF)
2. 2. Master Grenium SP8 (manufactured by BASF)
3. 3. Kaneka SF (Kaneka, environmentally friendly material)
・ Nonionic 4. Tween20 (manufactured by Kanto Chemical Co., Inc.)
5. Tween80 (manufactured by Kanto Chemical Co., Inc.)
6. Triton (manufactured by Wako Pure Chemical Industries, Ltd.)
7. Defoamer SI (manufactured by Wako Pure Chemical Industries, Ltd.)
8. KM-72 (manufactured by Shinetsu Silicone)
・ Zwitterionic 9. Lecithin (manufactured by Wako Pure Chemical Industries, Ltd., environmentally friendly material)
・ Cationic 10. Trimethylstearylammonium chloride (manufactured by Wako Pure Chemical Industries, Ltd.)

By using the flocculant in combination with an auxiliary agent consisting of an anionic dispersant, a nonionic dispersant, or a zwitterionic dispersant, the turbidity is reduced as compared with the case where the flocculant alone is used. It was confirmed that it would be done.
With the cationic dispersant, the turbidity was deteriorated, and the effect of the flocculant could not be enhanced.
Compared to the first time when the flocculant and the auxiliary agent were added at the same time, the turbidity was further reduced in the second time when the auxiliary agent was added, and it was confirmed that the turbidity could be lowered by adding the auxiliary agent. ..

"Experiment 2"
Simulated turbid water 2 was prepared in the same manner as in Experiment 1 above, except that the kaolin concentration was set to 5000 ppm. The initial turbidity of the simulated turbid water 2 exceeded the measurement limit of the turbidity meter and was 1000 FTU or more.
200 ml of this simulated muddy water 2 was dispensed into a beaker. A chitosan-based flocculant was added to each beaker at 3 ppm, 5 ppm and 10 ppm, respectively, and the mixture was stirred in the same stirring cycle as in Experiment 1 above. The turbidity was measured at the 1st, 3rd, and 10th stirrings. The turbidity of each sample is shown in FIG. When the same operation was performed except that the chitosan-based flocculant was not added as a control, the turbidity of each was 1000 FTU or more.

The turbidity was the lowest when the concentration of the chitosan-based flocculant was 5 ppm, and the turbidity increased when the concentration was 10 ppm. That is, it was confirmed that the applicable concentration range of the chitosan-based flocculant was narrow.
At any concentration of chitosan added, the turbidity was reduced by increasing the number of stirrings. From this, it was confirmed that the dispersion of the chitosan-based flocculant is important in the turbid water treatment using the chitosan-based flocculant.

"Experiment 3"
Except for the addition of the anionic dispersant 1 or the nonionic dispersant 4 as an auxiliary agent at the same time as the chitosan-based flocculant (3 ppm), the stirring cycle was performed once in the same manner as in the above experiment 2, and then the turbidity was observed. The degree was measured. The measurement results are shown in FIG. 3 together with the results of the chitosan-based flocculant (3 ppm) in Experiment 2.

By adding the chitosan-based flocculant and the auxiliary agent at the same time, the turbidity was lowered by only one stirring cycle as compared with the case where only the chitosan-based additive was added and the stirring cycle was repeated three times. From this, it was confirmed that the time required for the turbid water treatment can be shortened by using the auxiliary agent. It was also confirmed that the amount of expensive chitosan-based flocculant used can be reduced and the cost of turbid water treatment can be reduced.

"Experiment 4"
Distilled water is added to the soil collected from the reservoir at the construction site, and after stirring, it is allowed to stand for 10 minutes to precipitate solid content with a large particle size, and then the liquid phase is collected and simulated turbid water 3 (10000 ppm) is added. Created. The initial concentration of the simulated turbid water 3 was above the measurement limit, but when diluted and measured, it was calculated to be about 2000 FTU.
200 ml of this simulated muddy water 3 was dispensed into a beaker. A chitosan-based flocculant was added to each beaker at 2.5 ppm, 12.5 ppm, and 30 ppm, respectively, and the mixture was stirred in the same stirring cycle as in Experiment 1 to measure turbidity. In addition, a chitosan-based flocculant was added little by little, the stirring cycle was repeated, and the turbidity was measured for each stirring cycle. The results are shown in FIG.

The simulated turbid water 3 had a turbidity of 11 FTU with the addition of 12.5 ppm of a chitosan-based flocculant and a turbidity of 235 FTU with the addition of 30 ppm. Further, when the chitosan-based flocculant was added little by little, the turbidity did not deteriorate even if the chitosan-based flocculant was excessive. From this, it was confirmed that the dispersion of the chitosan-based flocculant is involved in the aggregation.

"Experiment 5"
In Experiment 4, 1 ppm of the anionic dispersant 3, which is a biosurfactant, was added to the turbid water having a turbidity of 235 FTU to which 30 ppm of a chitosan-based flocculant was added, and the turbidity measurement after the stirring cycle was repeated three times. The results are shown in FIG.

It was confirmed that the turbidity was reduced by adding an auxiliary agent to the turbid water in which the chitosan-based flocculant was excessively added.

"Experiment 6"
Using the simulated turbid water 3 prepared in Experiment 4 and the simulated turbid water 4 (5000 ppm) prepared by adding distilled water to the bentonite powder prepared to have a particle size of 75 μm or less and stirring the mixture, a chitosan-based flocculant and an anion which is a biosurfactant are used. The order of addition of the ionic dispersant 3 was examined. The simulated turbid water 4 was prepared so as to have the same turbidity as the simulated turbid water 3, diluted and measured, and was calculated to be about 2000 FTU.

The coagulant or auxiliary agent was added in the order shown in Table 1 below, and after the addition of each agent, one stirring cycle was performed, and the turbidity was measured after the stirring cycle.

By using an auxiliary agent, the amount of chitosan-based flocculant added could be reduced. When the coagulant was added after the adjunct was added, the effect of the coagulant was not sufficiently exhibited, but it was confirmed that the coagulation proceeded by further adding the coagulant.

Claims (6)

For turbid water containing fine particles derived from earth and sand floating in negatively charged water
After the aggregation treatment with a chitosan-based flocculant, an auxiliary agent containing at least one of an anionic dispersant, a nonionic dispersant, and an amphoteric dispersant is added .
A turbid water treatment method characterized in that the addition concentration of the chitosan-based flocculant is higher than the addition concentration at which the aggregation action changes to the dispersion action when used only with the chitosan-based flocculant . For turbid water containing fine particles derived from earth and sand floating in negatively charged water
A chitosan-based flocculant and an auxiliary agent containing at least one of an anionic dispersant, a nonionic dispersant, and a zwitterionic dispersant are simultaneously added .
A turbid water treatment method characterized in that the addition concentration of the chitosan-based flocculant is higher than the addition concentration at which the aggregation action changes to the dispersion action when used only with the chitosan-based flocculant . The turbid water treatment method according to claim 1 or 2, wherein the addition concentration of the chitosan-based flocculant is 0.1 ppm or more and 100 ppm or less. The invention according to any one of claims 1 to 3, wherein the auxiliary agent is added by 0.1 part by weight or more and 100 parts by weight or less (dry weight) with respect to 100 parts by weight (dry weight) of the chitosan-based flocculant. The turbid water treatment method described. The turbid water treatment method according to any one of claims 1 to 4, wherein the auxiliary agent is an environment-friendly material. Claim 1 is characterized in that the auxiliary agent is a biosurfactin selected from the group consisting of amino acid type surfactin, viscocin, sugar type ramnolipid, sophorolipid, mannosylerythritol lipid, trehalose lipid, and high molecular weight type emalzan. The turbid water treatment method according to any one of 5 to 5.

Images