JPH0938414A - Flocculating precipitant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a flocculating precipitant having a high sedimentation velocity when added to waste water, forming large flocks and facilitating the treatment of sludge. SOLUTION: This flocculating precipitant contains coarse particles of calcium carbonate having 50-500μm average particle diameter and fine particles of calcium carbonate having 1-30μm average particle diameter.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a flocculating precipitant,
More specifically, it can be easily used in the treatment of suspended solids (Suspended Solid, hereinafter abbreviated as SS) of industrial wastewater including civil engineering and construction wastewater, and the sludge after treatment has a high sedimentation speed of aggregates. The present invention relates to an aggregating and precipitating agent capable of easily separating the above.

[0002]

2. Description of the Related Art A large amount of organic and inorganic SS is generated in civil engineering and construction wastewater in the field of civil engineering and construction, and in chemical industry wastewater in the fields of paper, pulp, food and dyeing. Generally, wastewater treatment is to remove organic substances,
A method of performing biological treatment in an activated sludge tank, etc., and separating the precipitate in the precipitation tank by adding various coagulants to the precipitate,
In addition, a method is adopted in which a floating material that cannot be collected as a precipitate is removed by filtration. Therefore, a large-scale treatment facility is required for wastewater treatment, and the wastewater treatment cost becomes high.

As a simple method, a coagulant and gypsum,
It has been proposed to blend lime, calcium carbonate, cements, etc. (JP-A-2-71805). This method uses gypsum, lime, calcium carbonate, cements, etc. as a sequestering agent, but because the particle size cannot be controlled, not only the effect of the coagulant is not exhibited, but also the sedimentation rate is satisfactory. Was not.

[0004]

SUMMARY OF THE INVENTION In view of such circumstances, the present invention provides a coagulating sedimentation agent which reduces wastewater treatment cost, is simple, has a high sedimentation rate, and can efficiently perform wastewater treatment. It is intended.

[0005]

The present inventors have conducted various studies to develop the above-mentioned simple and fast flocculating precipitant, and as a result, the particle size and the amount of calcium carbonate in the flocculating agent are mixed. It was found that the object can be achieved by adjusting the above, and the present invention has been completed based on this finding. That is, the present invention has an average particle size of 50 to 5
The present invention is directed to a flocculating precipitant containing two kinds of calcium carbonate having different particle sizes, each of which consists of coarse particles of 00 μm and fine particles having an average particle diameter of 1 to 30 μm.

The present invention is characterized by using two types of ground calcium carbonate having different particle sizes in order to accelerate the sedimentation rate of the flocculant. The coarse particles of calcium carbonate used in the present invention have an average particle diameter of 50 to 500 μm, preferably 100 to 200 μm, and heavy calcium carbonate is usually used. If the average particle diameter of the coarse particles is smaller than 50 μm, the sedimentation speed becomes slow and the bulk density of the sludge becomes large. Further, if the average particle size of the coarse particles is larger than 500 μm, it is difficult to uniformly mix the coagulating / precipitating agent, and
The ability to capture is reduced.

The fine particles of calcium carbonate used in the present invention have an average particle size of 1 to 30 μm, preferably 5 to 20 μm.
m. Either heavy calcium carbonate or light calcium carbonate may be used, but heavy calcium carbonate is preferable from the viewpoint of particle size control and cost. The fine particles easily react with the acidic substance in the flocculant-precipitating agent, and the pH can be kept neutral. If the average particle size of the fine particles is smaller than 1 μm, the effect of the coagulant is reduced and the sedimentation rate is reduced. Further, if the average particle size of the fine particles is larger than 30 μm, the dissolution rate decreases and the reaction with the acidic substance in the flocculating and precipitating agent becomes slow, so that the pH control becomes difficult.

The content of calcium carbonate in the present invention is preferably 60% by weight or more, more preferably 70% or more. If the blending amount is less than 60% by weight, the sedimentation rate becomes slow and the object of the present invention cannot be sufficiently achieved. The upper limit is preferably 99% by weight.

The ratio of coarse particles to fine particles of calcium carbonate is preferably 2: 1 to 40: 1. Coarse particles are 2:
If it is less than 1, the effect is not exerted so much and the sedimentation speed becomes slow. If the coarse particles are more than 40: 1, pH control becomes difficult.

The coagulant of the present invention includes soluble aluminum salts, soluble iron salts, organic polymer coagulants, etc. in addition to calcium carbonate having different particle sizes, depending on the types of substances contained in the waste water and reacting with each other. Depending on the case, they may be used alone or in combination of two or more.

Specific examples of the inorganic type include aluminum sulfate, polyaluminum chloride, ferrous sulfate, ferric sulfate and the like, and these may be used alone or in combination of two or more. These acidic substances are calcium carbonate and
It easily reacts with calcium hydroxide, which is a pH adjuster, and SS
To adsorb. Examples of the organic type include polymer aggregating agents such as polyacrylamide, sodium polyacrylate and polymethacrylic acid ester, which may be used alone or in combination of two or more kinds. The organic flocculant granulates the particles adsorbed by the calcium carbonate and the inorganic flocculant to form large flocs.

In the flocculating and precipitating agent of the present invention, the inorganic flocculating agent is acidic and calcium carbonate is alkaline, but calcium hydroxide and sodium hydroxide are used as pH adjusters in order to neutralize the flocculating and precipitating agent. , Sodium carbonate and the like can be used. The coagulant-precipitating agent of the present invention may further contain additives such as commonly used cement, fly ash and bentonite.

[0013]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Examples 1, 2, 3 Coarse particles of heavy calcium carbonate (average particle size 100 μm
m), fine particles of heavy calcium carbonate (average particle size 3.
1 μm), a sulfuric acid band (aluminum sulfate), calcium hydroxide and a polymer flocculant polyacrylamide were added in amounts shown in Table 1 and mixed with a mixer for 5 minutes to obtain a flocculating precipitant. Using the obtained coagulant-precipitating agent, the coagulant was added to mud generated at a civil engineering site so that the concentration of the coagulant was constant, and a sedimentation test was conducted. The evaluation was performed on the degree of aggregation (size of flocs), sedimentation speed, transparency, pH, and sludge filterability, and the evaluation results are also shown in Table 1.

The evaluation criteria for the degree of aggregation, sedimentation speed, transparency and sludge filterability are as follows. Aggregation degree: ◯: Good. Sedimentation rate: ◯: Fast △: Slightly slow Transparency: 〇: Transparent Δ: Slightly opaque ×: Opaque Sludge filterability: ◯: Good Δ: Slightly bad ×: Bad

Comparative Examples 1, 2, 3 Without mixing coarse particles and fine particles of heavy calcium carbonate,
Aggregating and precipitating agents were obtained in the formulations and amounts shown in Table 1. The sedimentation test was evaluated in the same manner as in Example 1, and the evaluation results are also shown in Table 1.

As is apparent from Table 1, Examples 1 to 3
Has a higher sedimentation rate and better transparency than Comparative Examples 1 to 3. In Comparative Example 1, since fine particles of heavy calcium carbonate were not included, the reaction with the acidic substance in the flocculating and precipitating agent was slow, the transparency was poor, and the pH was acidic. Further, in Comparative Example 2, since coarse particles of heavy calcium carbonate are not included, the sedimentation speed is slow and the transparency is poor, and the sludge is poor in filterability when it is subjected to a filtering process, and there is a problem in sludge disposal. Recognize. Further, in Comparative Example 3, the amount of heavy calcium carbonate is small and the sedimentation rate is slow.

Comparative Example 4 Cement was blended in place of the ground calcium carbonate to obtain a coagulating sedimentation agent. A sedimentation test was conducted in the same manner, and the evaluation results are also shown in Table 1. Both the sedimentation rate and the transparency were inferior, and the pH became alkaline.

[0019]

[Table 1]

[0020]

As described above, the flocculating and precipitating agent of the present invention is
When added to wastewater, the sedimentation speed is high and large flocs are formed, and sludge can be easily treated. The flocculating and precipitating agent of the present invention is in the form of powder and is easy to handle.

Claims (4)

[Claims] 1. An aggregating and precipitating agent comprising two kinds of calcium carbonate having different particle sizes, which comprises coarse particles having an average particle size of 50 to 500 μm and fine particles having an average particle size of 1 to 30 μm. 2. The flocculating and precipitating agent according to claim 1, wherein the mixing ratio of the coarse particles and the fine particles is 2: 1 to 40: 1 by weight. 3. The flocculating precipitant according to claim 1, wherein the content of calcium carbonate is 60% by weight or more. 4. The flocculating precipitant according to claim 1, further comprising at least one selected from the group consisting of a soluble aluminum salt, a soluble iron salt, and an organic polymer flocculant.