JPH0412164B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD This invention relates to a flocculant having a deodorizing function and used in sludge treatment and coagulation and sedimentation treatment in sewage treatment plants, human waste treatment plants, food factories, chemical factories, etc. Conventional technology Conventionally, sludge treatment and coagulation sedimentation treatment at sewage treatment plants, human waste treatment plants, food factories, chemical factories, and slaughterhouses use sulfides such as hydrogen sulfide and methyl mercaptan,
Bad odors such as ammonia and amines have become a problem, and the methods for removing them include using oxidizing agents such as hydrogen peroxide and sodium hypochlorite, or using sulfuric acid
There is a method using iron salts such as iron, ferric chloride, ferric sulfate, and polyferrous sulfate. On the other hand, organic polymers such as sodium polyacrylate and polyacrylamide are used as flocculants. Recently, however, the toxicity of the above-mentioned organic polymer flocculants has become a problem, and chitosan, a naturally occurring organic polymer flocculant, is used in some sludge dewatering treatments that require relatively large amounts of additives. has been done. Problems to be solved by the invention Hydrogen sulfide, methyl mercaptan, ammonia,
Methods of treating malodorous substances such as amines with oxidizing agents such as hydrogen peroxide and sodium hypochlorite are expensive and cause significant equipment corrosion, as the oxidizing agents are consumed in decomposing other organic substances. There are drawbacks such as the need for 3 to 4 equivalents. Also, ferrous sulfate,
Methods using iron salts such as ferric chloride, ferric sulfate, and polyferrous sulfate have the advantage of being long-lasting and acting effectively as flocculants, but the pH during use decreases and the iron Hydrogen sulfide that reacts with components and fixes the PH
Since it becomes liberated again due to fluctuations in the amount, it is necessary to use it in combination with an organic polymer flocculant. There are also disadvantages such as coloring of the treated sludge and wastewater, and inconvenience in handling when used in combination with an organic polymer flocculant. On the other hand, chitosan, a natural organic polymer flocculant, dissolves in acetic acid and the like, but it is difficult to produce an aqueous solution. Means for Solving the Problems The present inventor conducted various studies to solve the above problems, and found that 1. Zinc compounds react more easily with malodorous substances than iron salts, and 2. Zinc compounds react with iron salts. 3. Chitosan is soluble in an acidic solution with a pH of about 3. 4. Zinc compounds are easily soluble in an acidic solution of chitosan. 5.
We found that chitosan easily forms chelates with metal ions. The present invention is based on these findings and is a flocculant having a deodorizing function, which is characterized in that chitosan contains one or more zinc compounds consisting of zinc acetate, zinc sulfate, zinc nitrate, and zinc chloride. The zinc compound used in the present invention may be any of the compounds mentioned above, but zinc acetate is most preferred in view of uniformity and ease of handling. In addition, the proportion of zinc component and chitosan in the zinc compound is expressed as a weight ratio.
0.01 to 5.0 is preferred. If the weight ratio of the zinc component to chitosan is less than 0.01, there will be no deodorizing effect, and if it is more than 5.0, the coagulation effect will be poor, and unreacted zinc may remain in the treated water, which may exceed the water quality standards for wastewater. The flocculant having a deodorizing function of the present invention may be either solid or liquid, but in consideration of uniformity during use, addition method, etc., liquid is preferable. In the case of a solid, chitosan and a zinc compound may be mixed at a certain ratio. In the case of a liquid, it is prepared by mixing chitosan dissolved in a dilute acid and the solution of the zinc compound at a constant ratio. Example (1) Chitosan is dissolved in a 1% acetic acid solution to prepare a 2% solution of chitosan. A flocculant according to the present invention is prepared by adding a zinc acetate solution to the solution so that the weight ratio of the zinc component to chitosan becomes a predetermined value. Next, the PH is 6.0 and the total sulfur concentration is 2.9.
%, the concentration of _H2S is 160ppm, the concentration of _CH3SH is
Table 1 shows the H ₂ S, etc. in the sludge that was dehydrated using a belt press tester after adding the above-mentioned flocculant to 80 ppm sewage sludge in a proportion equivalent to 0.5% of the dry solid content in the sludge. Shown below.

[Table] As shown in Table 1, it can be seen that a weight ratio of zinc component to chitosan of 0.01 to 5.0 is favorable. (2) Prepare a flocculant according to the present invention in which the weight ratio of zinc component to chitosan is 1.0 and the concentration of chitosan is 2.0%. Next, the pH is 5.9, the total sulfur content is 2.7%, the VTS (organic content) is 73.8%, and the _H2S concentration is
The same as that obtained by adding the above-mentioned flocculant to sewage sludge with a CH ₃ SH concentration of 900 ppm and 86 ppm in a proportion equivalent to 0.5% of the dry solid content in the sludge, and then dewatering it using a belt press tester. In sludge treated by adding only chitosan to sludge,
H ₂ S etc. are shown in Table 2.

[Table] Effects of the Invention According to the present invention, malodorous components such as hydrogen sulfide can be removed by adding a small amount to sludge, so it is of great practical value.

Claims (1)

[Claims] 1. A flocculant having a deodorizing function, characterized in that chitosan contains one or more zinc compounds consisting of zinc acetate, zinc sulfate, zinc nitrate, and zinc chloride.