JP3345670B2 - Flocculant for wastewater treatment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flocculant effective for both organic wastewater and inorganic wastewater discharged from civil engineering works or various factories.

[0002]

2. Description of the Related Art Conventional flocculants are classified into organic type and inorganic type. Organic flocculants are based on organic polymers and have large and strong flocs formed by flocculation.
Since the treated water and the treated sludge are viscous, there is a problem in the subsequent dehydration treatment operation, and the organic components remaining in the treated water may adversely affect the microbial environment. In addition, the organic coagulant greatly changes the pH of the treated water with respect to the pH of the raw water, and thus requires a neutralization step with a chemical later,
It is not suitable for treatment of continuously discharged polluted water and the like because it requires a neutralization tank and a residence time until discharge.
On the other hand, inorganic coagulants mainly use the cohesive force of aluminum ions and have good separability of treated water, but have low cohesive force compared to organic coagulants and generally lower the PH value. Therefore, a neutralization step is required before release.

[0003]

The desired flocculant is capable of forming a floc having the same size and strength as an organic flocculant with a small addition amount without being affected by organic and inorganic components in raw water. The floc has good sedimentation properties and does not require a neutralization treatment when discharged.

[0004]

The present invention provides a flocculant comprising a mixture of aluminum sulfate, calcium sulfate, alkali metal carbonate and cement powder as a main component, to which zeolite powder and / or a cationic flocculant are added. is there. In the present invention, the coagulation main agent itself is known, and aluminum sulfate 20
４０40 parts by weight, calcium sulfate 30 カ ル シ ウ ム 60 parts by weight, alkali metal carbonates such as sodium carbonate for adjusting the pH reduction of the water to be treated within the range of 5９9 at a weight ratio of about 3: 2 to aluminum sulfate. The cement powder further contains 5 to 15 parts by weight of a cement powder which is added and further improves cohesive floc and improves sedimentation. If the amount of aluminum sulfate is less than 20 parts by weight, the cohesive force is lost, and if the amount exceeds 40 parts by weight, it becomes cloudy. 30 for calcium sulfate
If the amount is less than 10 parts by weight, the floc is too small, and the cloudiness increases as the amount approaches 60 parts by weight. When the above-mentioned flocculant is used alone, the generated floc is generally fine and fine particles float in the supernatant, so that the clarity of the treated water is not good.

However, when the zeolite powder is added at the same time, the growth of the floc is promoted because the zeolite powder itself forms the core of the floc, a larger strong floc is formed, and the water separation property in the dehydration step is increased. Also improve. In addition, zeolite has the effect of reducing sulfate ions and calcium ions in the treated water, which increase with the agglutination reaction, due to its ion exchange capacity. That is, the supernatant water becomes cloudy as the blending amount of aluminum sulfate and calcium sulfate approaches the upper limit,
Even with the same amount of blend, the flocculant mixed with zeolite does not have white turbidity and shows a remarkable difference in clarity. The amount of the zeolite powder is in the range of 5 to 20 parts by weight,
The preferred range is 8 to 15 parts by weight. In addition, by adding a cationic polymer flocculant to the main agent, it effectively acts on water to be treated containing organic substances,
A good coagulation effect is also observed on both organic and mixed water qualities. This prevents aluminum ions in the solution from becoming negatively charged due to a rise in pH (pH 9 or more), maintains the optimum pH range for a long time, more effectively exerts the cohesive force of aluminum sulfate, and an organic coagulant. It is considered that the cohesive force is enhanced in combination with the function as the above.
Further, in this case, it is presumed that the presence of zeolite can prevent an excessive decrease in pH of the water to be treated, which is lowered by the cationic coagulant, and as a result, a larger amount of cationic polymer can be mixed. However, the cationic polymer is effective even at 1 part by weight, but the separation of water is extremely reduced up to about 30 parts by weight. Therefore, the addition of a large amount of the cationic flocculant is limited to a special use.

[0006]

EXAMPLE A mixture of 30 parts by weight of aluminum sulfate, 50 parts by weight of calcium sulfate, and 20 parts by weight of sodium carbonate was defined as 100, and 10 parts by weight of Portland cement, 10 parts by weight of zeolite powder and 10 parts by weight of a cationic organic polymer flocculant were used. A part by weight was added and blended to form a flocculant.

[0007]

Test Example 1 20 ppm of the above coagulant was added to 1 liter of a 1,000 ppm solution of red clay in Okinawa (inorganic muddy water containing mainly iron oxide and some iron sulfide). Table 1 shows the results of observing the floc and supernatant clarity.

[0008]

[Table 1] Agent A is the one obtained by removing the zeolite powder and the cationic coagulant from the coagulant of the example, Agent B is the one obtained by removing the cationic coagulant, and Agent C is the one obtained by removing the zeolite It is. As indicated, there was no suspended fine particles in the supernatant, the clarity was the highest, and the floc generated by aggregation was 2-3 mm.

[0009]

Test Example 2 Each flocculant was added to 1 liter of a 1000 ppm solution of horticultural black soil mixed with corroded soil and organic fertilizer until the formation of flocs was visible. Table 2 shows the aggregation results.
It was like.

[0010]

[Table 2]

[0011]

[Test Example 3] 1 A of the civil engineering waste mud containing bentonite and CMC (collected from the "Dashibashi Bridge Replacement Lower Construction Site" of the Civil Affairs Bureau of Kawasaki City) until the floc formation was visually confirmed with the agent A and the example flocculant, respectively. Was added. The results were as shown in Table 3.

[0012]

[Table 3] In addition, even if the rate of addition of the solution to the example product was 80, 40
The results were the same as in the case of (1), and when the value was further set to 100, the amount was the same as the appropriate addition amount, but the filtrate became slightly cloudy.

The agent A has a wide range from about 75% to 200% with respect to the appropriate addition rate according to the jar test and can be used for continuous treatment of wastewater. Not practical. On the other hand, the reactivity of the product of the present invention is recognized in a much wider range of 75 to 250%, and it is clear that it can be economically used for continuous treatment of waste mud whose concentration constantly changes. However, if it exceeds 200% of the appropriate addition rate, a slight cloudiness remains.

The change in water quality before and after treatment of the water to be treated in Test Example 3 is as shown in Table 4. The BOD removal rate is 95%, the COD removal rate is 96.3%, and the SS removal rate is 99.9%.

[0015]

[Table 4]

[0016]

The coagulant of the present invention can effectively use organic wastewater, inorganic wastewater, and wastewater mixed with both as wastewater to be treated, and is economical because the amount used is small. In addition, the floc diameter generated by the addition of the present agent is large, which is advantageous for dehydration, and the range of the appropriate addition rate is 40 to 8
It can be used in a wide range up to 0 mg / l. The pH value of the treated water is small, and the PH value of the treated water can always be kept in a neutral range by adjusting the mixing ratio of aluminum sulfate and sodium carbonate. Further, the amount of the organic agent in the flocculant of the present invention is small, and unlike the conventional treatment using only an organic agent, the amount of residual organic matter in the treated water is small, so that the quality of the treated water is good and the influence on the microbial environment can be reduced. effective.

Claims (4)

(57) [Claims] 1. 20 to 40 parts by weight of aluminum sulfate, 30 to 60 parts by weight of calcium sulfate, an alkali metal carbonate as a pH adjuster in a weight ratio of about 3: 2 with respect to the aluminum sulfate, and flocculent flocculation. An aggregating agent comprising 5 to 20 parts by weight of a zeolite powder uniformly mixed with 5 to 15 parts by weight of a cement powder as an agent. 2. 20 to 40 parts by weight of aluminum sulfate, 30 to 60 parts by weight of calcium sulfate, an alkali metal carbonate as a pH adjuster in a weight ratio of about 3: 2 with respect to the aluminum sulfate, and flocculent flocculation. A coagulant comprising 1 to 20 parts by weight of a cationic coagulant uniformly mixed with 5 to 15 parts by weight of a cement powder as an agent. 3. An aluminum sulfate (20 to 40 parts by weight), calcium sulfate (30 to 60 parts by weight), an alkali metal carbonate in a weight ratio of about 3: 2 with respect to the aluminum sulfate as a pH adjuster, and flocculated floc sedimentation. 5 to 20 parts by weight of zeolite powder and cationic coagulant 1 to 5 to 15 parts by weight of cement powder as an agent
A coagulant in which 30 parts by weight are uniformly blended. 4. A mixture of 30 parts by weight of aluminum sulfate, 50 parts by weight of calcium sulfate, 20 parts by weight of sodium carbonate, 10 parts by weight of cement, 10 parts by weight of zeolite powder and 10 parts by weight of a cationic coagulant. Flocculant.