JP2008126168A - Coagulating sedimentation method of waste water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the amount of an added natural material and cost while ensuring safety in coagulating sedimentation treatment of waste water. <P>SOLUTION: In a coagulating sedimentation method of waste water, a coagulant containing chitosan derived from a natural material and a coagulant containing sodium alginate derived from a natural material are added to the waste water at a ratio of 1:1 to perform the coagulating sedimentation treatment. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for coagulating and precipitating wastewater that aggregates and precipitates various fine suspended matters such as sludge, filth, and heavy metals contained in various types of wastewater such as civil engineering and construction work wastewater, factory wastewater, and dredging wastewater.

Conventionally, coagulants used for coagulating and precipitating wastewater that coagulates and precipitates various fine suspended matters such as sludge, sewage, and heavy metals contained in various types of wastewater such as civil engineering construction wastewater, factory wastewater, and dredging wastewater include the following: As described in Patent Documents 1 to 4, inorganic flocculants using PAC (polyaluminum chloride), sulfuric acid bands, etc., and synthetic polymer flocculants that further increase the size of flocs to promote precipitation are known. It is.
In addition, the inorganic flocculants and synthetic polymer flocculants are also used in the treatment of waterworks, but there are still questions about the safety of chemical substances in recent years, and there is a movement to regulate their use in terms of safety measures. is there.
JP-A-10-76279 JP 11-285603 A JP 11-347593 A JP 2004-174305 A

  An object of the present invention is to perform efficient coagulation sedimentation treatment while ensuring safety in coagulation sedimentation treatment of wastewater, and an object of the present invention is to provide a coagulation sedimentation treatment method for wastewater that solves this problem.

  In order to achieve the above-mentioned object, the technical means adopted by the present invention is a method for coagulating and precipitating wastewater with a flocculant containing chitosan derived from natural substances and sodium alginate derived from natural substances. The coagulation-precipitation treatment method of waste water is characterized in that the agent is added at a ratio of 1: 1 for coagulation-precipitation treatment.

  Also, in the method of coagulating and precipitating wastewater, coagulating and precipitating the wastewater by adding a coagulant containing natural substance-derived chitosan and natural substance-derived sodium alginate in a ratio of 1: 1. This is a method of coagulating and precipitating wastewater.

The chitosan referred to in the present invention may be derived from natural substances, and for example, those extracted and purified from the shells of crustacean organisms such as crabs and shrimps are known.
Further, the sodium alginate referred to in the present invention may be derived from natural substances, and for example, those extracted and purified from seaweeds such as kombu and seaweed are known.

  According to the present invention, it is possible to reduce the cost by reducing the amount of the natural substance added while ensuring the safety in the coagulation sedimentation treatment of the wastewater.

Hereinafter, the best mode for carrying out the coagulation sedimentation treatment method of wastewater according to the present invention will be described.
In the following examples, experiments in which various wastewaters are coagulated and precipitated using the coagulant according to the present invention and results obtained in the experiments are shown.

(Example 1)
This example shows the coagulation sedimentation treatment of clay wastewater having a raw water turbidity of 554 degrees and a pH of 7.09.
Specifically, the addition amount of chitosan solution (hereinafter referred to as flocculant B) is equal to the addition amount of 25 ppm (mg / l) of sodium alginate solution (hereinafter referred to as flocculant A) in which the waste water is added to 500 ml. Table 2 shows the results of measuring the sedimentation rate of flocs aggregated with each wastewater added at the addition ratio, 2 times, 3 times, and 4 times, and the supernatant water turbidity, pH, and floc particle size after standing for 5 minutes. It is shown in 1.
Further, in this example, the flocculant B was added to the waste water and stirred and mixed, and then the flocculant A was added and stirred and mixed for aggregation.
Further, the flocculant A of this example is a 0.2% solution of sodium alginate using wakame as a raw material, and the flocculant B is chitosan and acetic acid using crab shell as a raw material in a ratio of 1: 1. It is a mixed 0.2% solution.
In addition, the floc particle diameter shown in the table is a symbol indicating the diameter, D-1 is 0.3 mm to 0.5 mm, D-2 is 0.5 mm to 0.75 mm, and D-3 is 0.75 mm. -1.0 mm, D-4 means 1.0 mm to 1.5 mm, and D-5 means 1.5 mm to 2.25 mm, respectively.

According to this example, when flocculant A and flocculant B were added to wastewater at a ratio of 1: 1, floc particle size and pH were almost the same as when added to wastewater at other ratios. Although the sedimentation rate was high, the supernatant turbidity was low.
In addition, when the addition amount of the flocculant B was increased with respect to the addition amount of the flocculant A, a floc that was string-like and easily floated was generated, and the result was that the supernatant water turbidity was extremely high.
From this result, it was proved that the coagulation-precipitation processing ability when the ratio of the coagulant A and the coagulant B was 1: 1 and added to the wastewater was high.

(Example 2)
In this example, based on the experimental results of Example 1, the settling rate was 5 minutes when the addition amounts of flocculant A and flocculant B in a ratio of 1: 1 were 20 ppm, 30 ppm, and 40 ppm. Table 2 shows the results of measuring the supernatant water turbidity, pH, and floc particle size after placement.
The flocculant A and the flocculant B in the present example are the same as those used in the above example.

According to the present example, as the addition amount of the flocculant A and the flocculant B increased, the sedimentation rate, floc particle diameter, and pH did not change so much, but the supernatant water turbidity decreased.
From this result, it was proved that the aggregating ability can be increased by increasing the addition amount of the aggregating agent A and the aggregating agent B.

(Example 3)
In this example, when the flocculant A and the flocculant B are added to the waste water, the coagulation sedimentation treatment capacity of (A) is compared with the coagulation precipitation treatment capacity of the case where only the flocculant B is added (B), The results are shown in Table 3.
Further, in this example, the addition amount of the flocculant B was 10 ppm for both (A) and (B), and in the case of (A), the addition amount of the flocculant A was 2.0 ppm, and each added at the addition ratio. Table 3 shows the results of measuring the sedimentation rate of flocs aggregated with wastewater and the supernatant water turbidity, pH, and floc particle size after standing for 5 minutes.
Further, the flocculant A and the flocculant B in this example are the same as those used in the above example.
The waste water used in this example is a clay waste water having a raw water turbidity of 3800 degrees, a pH of 6.95, and an SS concentration of 1150 mg / l.

According to the present Example, the result that the supernatant water turbidity became low by adding only 2.0 ppm of flocculant A compared with the case where only flocculant B was added was obtained.
From this result, it was proved that the coagulation ability was higher when both coagulant A and coagulant B were added than when coagulant B was added alone.

Example 4
In this example, the flocculant A and flocculant B of the present invention and the conventional flocculant C are obtained as waste water at a ratio of 1: 1 in order to obtain the same coagulation sedimentation treatment result. Tables 4 and 5 show the results of measuring the addition amount (Table 4) to be added and the addition amount (Table 5) in which the conventionally used flocculant C (PAC and synthetic polymer) is added to the wastewater.
The waste water used in this example is a raw water having a turbidity of 655 degrees and adjusted to pH 7.3 from pH 9.7 with a neutralizing agent.

According to this example, when the flocculant C is added to the wastewater, the supernatant water turbidity is lowered when 2 ppm to 5 ppm of the flocculant A and the flocculant B are added to the wastewater. As shown in Table 5, at least an addition amount of PAC of more than 75 ppm is required, and in this example, 100 ppm, and in the case of adding flocculant A and flocculant B from 2 ppm to 5 ppm, The result was lower than the degree.
From this result, it was proved that the addition amounts of the flocculant A and the flocculant B can be greatly reduced as compared with the conventional addition amount of the flocculant C in order to obtain the same result of the coagulation precipitation treatment.

In the method for coagulating and precipitating wastewater of this embodiment, when coagulant A and coagulant B are used in combination, the coagulant and precipitating ability is superior to adding coagulant B alone. When added at a ratio of: 1, a higher coagulation sedimentation throughput can be obtained.
In addition, when the flocculant A and the flocculant B are added at a ratio of 1: 1, even if the amount of the flocculant C is greatly reduced as compared with the amount of the conventional flocculant C added, at least equal to or greater than the amount of the flocculent precipitation treatment. Ability can be gained.
Furthermore, since the raw material of the flocculant A is sodium alginate using seaweed, and the raw material of the flocculant B is chitosan using crab shell, the flocculant C It is superior in terms of ensuring safety compared to.
Therefore, it is possible to reduce the cost by reducing the amount of the natural substance added while ensuring the safety in the coagulation sedimentation treatment of the wastewater.

It should be noted that the present invention is not limited to the illustrated embodiments, and can be implemented with configurations within a range that does not deviate from the contents described in the respective claims.
In the method for coagulating and precipitating wastewater exemplified in the above embodiment, the coagulating and precipitating treatment is performed by adding a coagulant containing chitosan derived from a natural substance and a coagulant containing sodium alginate derived from a natural substance at a ratio of 1: 1. However, even if the coagulant is added by adding a flocculant containing chitosan derived from a natural substance and sodium alginate derived from a natural substance in a ratio of 1: 1, The same effect can be expected.

Claims (2)

In the coagulation sedimentation treatment method of wastewater,
Coagulation of waste water characterized by adding coagulant containing chitosan derived from natural substance and coagulant containing sodium alginate derived from natural substance at a ratio of 1: 1 to waste water. Precipitation method. In the coagulation sedimentation treatment method of wastewater,
Coagulation and sedimentation treatment of wastewater, characterized by adding coagulant containing 1: 1 ratio of chitosan derived from natural substance and sodium alginate derived from natural substance to wastewater Method.