Method for treating wastewater containing cyanogen and ammonia

Abstract

Provided is a method for treating water containing cyanogen and ammonia with which cyanogen and ammonia are sufficiently decomposed even in cases where the concentration of soluble iron is high. This method for treating wastewater containing cyanogen and ammonia involves a step for oxidizing and decomposing cyanogen and ammonia by adding a chemical solution including hypobromous acid and / or hypochlorous acid to wastewater containing cyanogen and ammonia. A solution in which hypobromous acid and / or a hypobromite have / has been produced by mixing a bromide aqueous solution and a hypochlorite aqueous solution is added to wastewater containing cyanogen and ammonia. A sodium bromide aqueous solution and a sodium hypochlorite aqueous solution are mixed and added at an equimolar ratio or such that sodium hypochlorite is excessive.

Description

technical field

[0001] The invention relates to a treatment method for waste water containing cyanide and ammonia, in particular to a method for treating waste water containing cyanide and ammonia containing soluble iron by using an improved method of the alkali chlorine method. Background technique

[0002] As a treatment method for cyanide-containing wastewater discharged from industrial facilities such as electroplating plants, steel plants, metallurgical plants, power plants, and coke manufacturing plants, the most widely used method is the alkali chlorine method. In this method, a chlorine source, such as sodium hypochlorite, is added to wastewater containing cyanide under alkalinity to oxidize cyanogen in the wastewater (Patent Documents 1 and 2).

[0003] In the alkaline chlorine method of Patent Document 1, cyanide compounds are oxidatively decomposed by a two-step reaction of pH and ORP (oxidation-reduction potential) control values ​​as shown below.

[0004] The f...

Examples

Embodiment 1

[0049] [Example 1 (treatment with liquid containing sodium hypobromite)]

[0050] As test water, steel mill wastewater of the following water quality was used.

[0051] pH: 8.3,

[0052] Total cyanide concentration: 0.8mg / L,

[0053] Ammonium ion concentration: 532mg / L,

[0054] TOC: 22mg / L,

[0055] Soluble iron: 1.3mg / L

[0056] ORP: 90mV

[0057] For a liquid containing sodium hypobromite as a chemical solution, use a sodium bromide solution with a concentration of 40wt% and a sodium hypochlorite solution with a concentration of 12wt% in NaBr:NaOCl=1:1 (molar ratio) to generate hypobromous acid Sodium hypobromite and sodium hypochlorite in water.

[0058] 1000 mL of test water was stored in a glass container, the temperature of the water was kept at 50° C., and the pH was adjusted to 12 with NaOH, then the chemical solution (sodium hypobromite and sodium hypochlorite aqueous solution) was added under the conditions in Table 1. The reaction time of the cyanide decompo...

Embodiment 2

[0061] As test water, steel mill wastewater of the following water quality was used.

[0062] pH: 8.15,

[0063] Total cyanide concentration: 0.7mg / L,

[0064] Ammonium ion concentration: 354mg / L,

[0065] TOC: 17mg / L,

[0066] Soluble iron: 1.4mg / L

[0067] ORP: 230mV

[0068] For the sodium hypobromite-containing liquid as the chemical solution, the same liquid as in Example 1 was used. And it processed similarly to Example 1 except having made pH into 9 with NaOH. Table 1 shows the amount of chemical reagents added, free residual chlorine concentration after the aforementioned reaction time, ORP, total cyanide concentration, total cyanide decomposition rate, ammonium ion concentration, and ammonium ion decomposition rate.

Embodiment 3

[0070] As test water, steel mill wastewater of the following water quality was used.

[0071] pH: 8.6,

[0072] Total cyanide concentration: 1.2mg / L,

[0073] Ammonium ion concentration: 410mg / L,

[0074] TOC: 18mg / L,

[0075] Soluble iron: 1.0mg / L

[0076] ORP: 264mV

[0077] Except having added NaOH so that pH might become 9.6, it processed similarly to Example 2, and tested water. The results are shown in Table 1.

technical field

[0001] The invention relates to a treatment method for waste water containing cyanide and ammonia, in particular to a method for treating waste water containing cyanide and ammonia containing soluble iron by using an improved method of the alkali chlorine method. Background technique

[0002] As a treatment method for cyanide-containing wastewater discharged from industrial facilities such as electroplating plants, steel plants, metallurgical plants, power plants, and coke manufacturing plants, the most widely used method is the alkali chlorine method. In this method, a chlorine source, such as sodium hypochlorite, is added to wastewater containing cyanide under alkalinity to oxidize cyanogen in the wastewater (Patent Documents 1 and 2).

[0003] In the alkaline chlorine method of Patent Document 1, cyanide compounds are oxidatively decomposed by a two-step reaction of pH and ORP (oxidation-reduction potential) control values ​​as shown below.

[0004] The f...

Examples

Embodiment 1

[0049] [Example 1 (treatment with liquid containing sodium hypobromite)]

[0050] As test water, steel mill wastewater of the following water quality was used.

[0051] pH: 8.3,

[0052] Total cyanide concentration: 0.8mg / L,

[0053] Ammonium ion concentration: 532mg / L,

[0054] TOC: 22mg / L,

[0055] Soluble iron: 1.3mg / L

[0056] ORP: 90mV

[0057] For a liquid containing sodium hypobromite as a chemical solution, use a sodium bromide solution with a concentration of 40wt% and a sodium hypochlorite solution with a concentration of 12wt% in NaBr:NaOCl=1:1 (molar ratio) to generate hypobromous acid Sodium hypobromite and sodium hypochlorite in water.

[0058] 1000 mL of test water was stored in a glass container, the temperature of the water was kept at 50° C., and the pH was adjusted to 12 with NaOH, then the chemical solution (sodium hypobromite and sodium hypochlorite aqueous solution) was added under the conditions in Table 1. The reaction time of the cyanide decompo...

Embodiment 2

[0061] As test water, steel mill wastewater of the following water quality was used.

[0062] pH: 8.15,

[0063] Total cyanide concentration: 0.7mg / L,

[0064] Ammonium ion concentration: 354mg / L,

[0065] TOC: 17mg / L,

[0066] Soluble iron: 1.4mg / L

[0067] ORP: 230mV

[0068] For the sodium hypobromite-containing liquid as the chemical solution, the same liquid as in Example 1 was used. And it processed similarly to Example 1 except having made pH into 9 with NaOH. Table 1 shows the amount of chemical reagents added, free residual chlorine concentration after the aforementioned reaction time, ORP, total cyanide concentration, total cyanide decomposition rate, ammonium ion concentration, and ammonium ion decomposition rate.

Embodiment 3

[0070] As test water, steel mill wastewater of the following water quality was used.

[0071] pH: 8.6,

[0072] Total cyanide concentration: 1.2mg / L,

[0073] Ammonium ion concentration: 410mg / L,

[0074] TOC: 18mg / L,

[0075] Soluble iron: 1.0mg / L

[0076] ORP: 264mV

[0077] Except having added NaOH so that pH might become 9.6, it processed similarly to Example 2, and tested water. The results are shown in Table 1.

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