KR960002271B1 - Dyeing water treatment method - Google Patents

Abstract

The treatment of waste water from dyeing is conducted by (A) adjusting the pH of waste water at weak alkali or neutral value, (B) treating waste water biologically, and (C) treating it chemically with ferrous chloride and equivalent alkali to effectively remove BOD, COD and color sources. The amount of ferrous chloride used is 0.1-0.2 vol% with respect to waste water, whereas ferrous chloride being a mixture of 2-3wt% FeCl2 and 15-18wt% HCl. As alkali is used sodium hydroxide or calcium hydroxide.

Description

Treatment method of dye wastewater

The present invention relates to a method for treating dyed wastewater.

In particular, the present invention relates to a method for treating dyed wastewater, which is particularly efficient in removing BOD, COD sources, as well as chromatic sources by subjecting the dyeing wastewater to a biological treatment first followed by chemical treatment with ferrous chloride solution and an equivalent alkali.

Dyeing wastewater is usually very high BOD, COD and chromaticity, the treatment is emerging as a big problem. The dyeing wastewater treatment process and the chemicals used vary depending on the conditions of each discharger. However, in the general treatment process, primary chemical treatment and secondary biological treatment (active sludge treatment) are usually performed. The conventional treatment method is as follows.

1) Process Chart:

2) How to Treat:

The first treatment is usually neutralized with acid and alkali chemicals, and artificially formed scum using various organic and muco flocculants to remove BOD, COD, and other heavy metals from wastewater. Removed by adsorption precipitation (injury). At this time, sulfuric acid is mainly used as an acid, and caustic soda and slaked lime are used as an alkaline agent.

Inorganic coagulants include ferric salts such as ferric chloride (FeCl ₃ ), ferric sulfate (Fe ₂ (SO ₄ ) ₃ ), and ferric polysulfate (Poly-Fe ₂ (SO ₄ ) ₃ ) and liquid lactose peninsula (LAS). : 1-Al ₂ (SO ₄ ) ₃ ), PAC (Poly-Aluminium Chloride: [Al ₂ (OH) _n Cl _6-n ] m, PAS (Poly-Aluminium Sulfate: [Al ₂ (OH) _n (SO ₄₎ ) Various types such as aluminum themes such as _{3-n / 2} ] m are selected and used in industrial sites.

Generally, the removal efficiency of BOD, COD and chromaticity is about 30% in the primary chemical treatment, and the biological treatment (active sludge treatment), which is the next process, is treated to the emission limit standard of the Water Conservation Act.

Various biological treatment techniques have been developed, and the description thereof is omitted in the present invention by conventional methods. However, in the event that it is difficult to comply with the emission limit even after biological treatment, the biological treatment process must be repeated or secondary chemical treatment must be performed. However, even in the case of the above treatment method, if the pollution level of raw waste water is severe, BOD (50-150ppm), COD (50-150ppm) and SS (50-150ppm) (allowable wastewater) are the allowable emission standards without major facility investment. Very dependent on emissions and discharges).

The inventors of the present invention treated the mixed wastewater, such as cotton textile dyeing wastewater, polyester fiber dyeing wastewater, and printing wastewater by the conventional method as in the following process chart for many years are shown in Table 1 below.

TABLE 1

Average value of actual field operation results

As can be seen from the field operation results as described above, it is very difficult to comply with the emission allowance standard, and in particular, the color removal is very difficult as a conventional treatment method.

The present inventors have long studied the removal of such BOD, COD and chromatic source, especially in dyeing wastewater treatment. As a result, the raw wastewater is neutralized with acid, preferably sulfuric acid, the pH is adjusted from weak alkali to neutral, followed by biological treatment, followed by chemical treatment with ferrous chloride (FeCl ₂ ) solution and equivalent alkali. The present invention was completed by discovering the surprising fact that the color decreases below the reference value and the color is greatly reduced.

Accordingly, an object of the present invention, in the treatment of dye wastewater, the pH of the raw wastewater is adjusted to weak alkali to neutral with acid and then subjected to biological treatment first, and then precipitated in the precipitation tank and then chemical treatment with ferrous chloride and alkali It is to provide a method of significantly lowering the BOD, COD and chromaticity by flocculation sedimentation with a polymer coagulant.

The present invention is represented by a process diagram as follows.

Next, the present invention will be described in detail by way of examples.

EXAMPLE

Dye wastewater (pH 11.5-12.0; BOD 900-1000; COD 850-950; chromaticity 1,000) is used.

A) Adjust the dyeing wastewater to pH 7.2-7.5 with sulfuric acid so that it does not interfere with the biological treatment, which is a post-process.

B) The first biological treatment is aerated for 24 hours, and after precipitation, it is put into the post-process.

C) Secondary biological treatment is treated after precipitation as a 12-hour aeration.

D) Waste hydrochloric acid containing ferrous chloride which is prepared by using ferric chloride and hydrochloric acid to contain 2-3% by weight of ferrous chloride and hydrochloric acid (15-18% by weight) or as a by-product from iron and steel making processes. To adjust the concentration to prepare a ferric chloride solution.

E) Add 0.1% to 0.2% (capacity) of ferrous chloride to raw water and caustic soda at the same time.

F) A proper amount of polymer coagulant is added and coagulated and settled.

The pH, BOD, COD and chromaticity of the treated effluent are shown in Table 2 below.

TABLE 2

On-site actual operation result

As in the contrast of Table 2 and Table 1, it can be seen that the effluent of the dyeing wastewater treated by the method of the present invention is significantly improved in the degree of purification in BOD, COD and chromaticity.

When ferric chloride reacts with an alkali such as caustic soda or calcium hydroxide, ferrous hydroxide is produced according to the following reaction formula. (Example of using caustic soda)

The ferrous hydroxide thus produced is a highly soluble material and is naturally oxidized in air to be oxidized to ferric hydroxide (Fe (OH) ₂ ), which is reddish yellow and therefore, it is expected that there will be a problem in coloration. It has not been used directly until now.

However, the present inventors have found a surprising fact that the use of ferrous chloride does not exhibit such a problem, but rather almost completely eliminates the chromaticity.

As described in detail above, in the treatment of the dye wastewater, unlike the conventional method of performing the chemical treatment and then the biological treatment, first biological treatment and then using the ferric chloride and the equivalent alkali By chemical treatment, the processing efficiency can be greatly increased.

In the present invention, ferrous chloride may be used, or waste hydrochloric acid as a by-product from iron and steel mills may be used as it is or may be used by adjusting the concentration.

The effects of the present invention are as follows.

First, it is possible to effectively remove the chromatic source, which is the biggest challenge of dyeing water treatment, which can greatly improve the quality of discharged water.

Secondly, it is very effective for removing BOD and COD sources.

Third: By using ferrous chloride, a by-product of the steel mill, without using expensive chemicals (inorganic coagulants, colorants), the atom can be greatly reduced.

Claims (5)

In the treatment of dye wastewater, the wastewater is adjusted to pH alkaline or neutral and then subjected to biological treatment first and then chemically treated with ferrous chloride solution and equivalent alkali to effectively remove BOD, COD and chromatic source. The method according to claim 1, wherein the ferrous chloride solution is used in an amount of 0.1-0.2% (volume) relative to the wastewater. The method according to claim 1, wherein a mixed solution of 2-3% by weight of FeCL ₂ and 15-18% by weight of hydrochloric acid is used as the ferric chloride solution. The method of claim 1 wherein sodium hydroxide or calcium hydroxide is used as the alkali. The method according to claim 1, wherein the hydrochloric acid waste liquid discharged from the steelmaking and steel mills is used as ferrous chloride solution or the concentration is adjusted.