JPH0459039B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field The present invention is applicable to wastewater containing malodorous substances such as hydrogen sulfide, methyl mercaptan, and ammonia as stipulated in the Offensive Odor Prevention Law, such as wastewater from paper mills, wastewater from human waste treatment plants, and wastewater from iron manufacturing plants. The present invention relates to a deodorizing method for treating ammonium water, wastewater from food factories, etc. with a coagulant and oxidizing agent whose main component is trivalent iron. BACKGROUND TECHNOLOGY AND PROBLEMS There are various conventional methods for deodorizing this type of waste liquid. A widely used method is adsorption using activated carbon. Although this method is simple, it has drawbacks such as slow reaction, high processing cost, and the need to reprocess adsorbed bad odors because it uses physical adsorption. Further, as a method using chemical reactions, there is a method of decomposing the above-mentioned malodorous substances with hydrogen peroxide, sodium hypochlorite, etc. In this method, the added drug is 5-10% of the theoretical value.
twice as necessary. Moreover, if the drug remains unresponsive,
The COD value becomes high or sediment floats to the surface. Apart from this, ferrous sulfate has been used as a deodorizing agent for toilets and the like for a long time.
Recently, a deodorizer Aniko (trade name), which is produced by adding ascorbic acid to a ferrous sulfate solution, has been put into practical use. This deodorizer is effective in removing odors (gas), but when used to deodorize wastewater,
Disadvantages include that if the pH after treatment is not raised to 9 or higher, there will be a large amount of residual iron, and the COD value will also be high, much higher than the regulatory value. For this reason, it is rarely applied to wastewater treatment. The present inventors previously proposed a polyferric sulfate solution as an iron-based inorganic polymer flocculant, studied its physical properties, functions, etc., and reported that it has deodorizing performance. As a result of further research, the present inventors found that iron salts have the effect of removing bad odors by reacting with malodorous substances such as hydrogen sulfide, methyl mercaptan, ammonia, and amic acids, and that divalent iron is present in wastewater. Therefore, trivalent iron does not become dissolved iron in the wastewater, but becomes iron hydroxide, which coprecipitates the product that reacts with the malodorous substance. Iron salt alone completely eliminates the malodor. trivalent iron is partially reduced by hydrogen sulfide, which is a malodorous substance; oxidizing agents decompose malodorous substances, but a large amount (5 to 10 times the theoretical value) is required; Malodorous substances are
When iron is present when oxidized by an oxidizing agent, it acts as a catalyst and improves efficiency.When an oxidizing agent, especially hydrogen peroxide, acts on divalent iron, oxidation occurs strongly through the Fuenton reaction and decomposes malodorous substances. I found out that. Means for Solving the Problems and Their Effects The present invention is based on the above-mentioned findings. This is a deodorizing method in which an iron-based flocculant whose main component is added and an oxidizing agent is added subsequently or simultaneously to perform flocculation treatment and efficiently remove malodorous substances. In the present invention, the coagulant is mainly composed of trivalent iron. Even if it contains some divalent iron, it is acceptable as long as the amount of residual iron in the wastewater after treatment is within the regulated value. It is from. The content of divalent iron varies depending on the processing pH, but it is preferably 30% or less of the total iron content.
Less than 15%. Trivalent iron is partially reduced to divalent iron in wastewater containing malodorous substances, especially sulfides (which are often anaerobic), but this reacts with sulfides. Promotes this, and when combined with trivalent iron, it produces even better effects. Furthermore, this divalent iron reacts with an oxidizing agent and acts as a catalyst to decompose malodorous substances. The flocculant whose main component is trivalent iron may be any iron salt such as polyferric sulfate solution, ferric sulfate, or ferric chloride, but ammonia,
Considering the reaction with amines, acidic salts are preferred, and sulfates are particularly preferred. The oxidizing agent may be hydrogen peroxide, sodium hypochlorite, or the like, but it is preferable to use one that does not contain sulfur. Regarding the order of addition of the flocculant containing trivalent iron as a main component and the oxidizing agent, it is necessary to add the flocculant containing trivalent iron as a main component either first or at the same time. Example Table 1 shows the results immediately after treatment of pulp wastewater from the paper industry by adding polyferric sulfate solution and hydrogen peroxide.

[Table] Based on the present invention, in the case of treatment examples No. 7 to 10 in which both a coagulant mainly composed of trivalent iron (polyferrous sulfate) and hydrogen peroxide were added, the settled sludge remained even after 3 days.
However, as shown in examples Nos. ₄ to 6, the conventional treatment with aluminum sulfate and hydrogen peroxide produced about H ₂ S after one day.
40ppm was generated. Also, the moisture content of dehydrated cake is 2~
It decreased by 5%. Effects of the Invention According to the present invention, it is possible to reduce the COD value and malodorous components of the treatment liquid, so it is of great practical value.

Claims (1)

[Scope of Claims] 1. A first method of subjecting wastewater containing malodorous substances mainly consisting of hydrogen sulfide, methyl mercaptan, and ammonia to coagulation-sedimentation treatment with a flocculant containing trivalent iron as a main component and removing the malodor. 1. A method for deodorizing a waste liquid, characterized in that the step is combined with a second step of decomposing malodorous substances remaining in the waste liquid treated in the first step using an oxidizing agent. 2. A flocculant and an oxidizing agent mainly composed of trivalent iron are simultaneously added to the wastewater containing malodorous substances mainly composed of hydrogen sulfide, methyl mercaptan, and ammonia to perform coagulation-sedimentation treatment and decomposition of malodorous substances. A method for deodorizing wastewater characterized by the following.