JP2000301160A - Method for treating oil-containing wastewater containing surfactant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To treat alkaline oil-containing wastewater containing a surfactant and acidic wastewater by one facility by mixing both in the detoxification of the alkaline wastewater containing. SOLUTION: For example, in metal surface treatment in a metal product factory, alkaline oil-containing wastewater containing a surfactant is added with pickling wastewater containing iron ions to become weakly acidic (preferably pH 4-6). The oil components, by being made weakly acidic, destroy emulsion to be separated. At the same time, the iron ions in the acidic wastewater are converted into iron hydroxide which adsorbs the separated oil components to remove them. In this way, the alkaline wastewater can be treated simultaneously with the acidic wastewater by an existing flocculation/precipitation facility so that the costs of water treating agents such as a neutralizing agent and an organic flocculant are reduced, and the installation of a floating treatment facility is obviated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a treatment method for detoxifying oil-containing wastewater containing a surfactant among surface-treated wastewater such as steel plates.

[0002]

2. Description of the Related Art Conventionally, in a metal product factory, before surface treatment of metal such as steel, deoiling is performed using an alkali such as caustic soda, and then derusting is performed using an acid such as hydrochloric acid and sulfuric acid. I have. The waste liquid after deoiling becomes a concentrated alkaline waste liquid containing oil, and after deoiling, the steel material is washed with water, so that an alkaline wastewater containing emulsified oil called oil-containing rinse wastewater is generated. In order to improve the cleaning effect, a surfactant is usually added to the cleaning water. Similarly, the waste liquid after derusting becomes a concentrated waste liquid containing chlorides and sulfates. Further, after the derusting, the steel material is washed with water, so that acidic drainage containing heavy metals called acid rinse drainage is generated.

[0003] As a treatment method for detoxifying the alkaline oil-containing wastewater containing a surfactant generated from the surface treatment step of the above-mentioned metal product factory, generally, the addition of dilute sulfuric acid adds p
Emulsified oil is separated by an acid break method of lowering H to 3 or an emulsion break method by addition of an organic coagulant, adsorbed on an inorganic flocculant, neutralized to pH 7 to 8, floated and separated, and detoxified. ing. Similarly, as a treatment method for detoxifying acidic concentrated waste liquid and acidic wastewater containing heavy metals, generally, an alkaline agent such as slaked lime or caustic soda is added to the wastewater to neutralize it and oxidize divalent iron by air aeration. Then, it precipitates and separates as hydroxide of trivalent iron, and performs detoxification treatment.

[0004] That is, Fig. 4 shows a treatment system diagram showing a floatation treatment system of an alkali oil-containing wastewater and a sedimentation treatment system of an acidic wastewater by the above-mentioned conventional method. As shown in this figure,
For the treatment of alkaline oil-containing wastewater generated from the surface treatment process of steel sheets, etc., the wastewater conveyed by piping is received in a regulating tank, quantitatively transferred to a reaction tank, neutralized to pH 7 with dilute sulfuric acid, and an organic coagulant is added to form an emulsion. After destruction, it was adsorbed by the addition of an inorganic coagulant, and then the floc was grown by the addition of a polymer coagulant in a coagulation tank, floated and separated in a pressurized flotation tank, and discharged as harmless treated water. The sludge separated by flotation was concentrated by a centrifuge and then incinerated.

On the other hand, in the treatment of acid rinse wastewater containing iron ions, wastewater transferred to a pipe is received in a regulating tank, neutralization is performed by adding slaked lime in a reaction tank, and oxidation of divalent iron is performed by aeration with air. The hydroxide was produced, and floc was grown by adding a polymer flocculant in a flocculation tank, and then detoxification treatment was performed by precipitation separation. The coagulated sludge is separately dehydrated and recycled as a raw material for the blast furnace.

[0006]

As described above, in metal product factories that manufacture welding can materials and steel plates for automobiles, surface treatments of metal plates such as steel plates are performed according to each application. Wastewater and wastewater generated from the surface treatment step are treated to neutralize the alkaline oil-containing wastewater by neutralization coagulation flotation separation treatment, and the acid rinse wastewater by neutralization coagulation sedimentation separation treatment. As described above, the alkaline oil-containing wastewater and the acid rinse wastewater cannot be treated simultaneously, and at present, wastewater treatment is performed by providing separate treatment facilities.

For this reason, there are the following problems. (A) An acid agent such as dilute sulfuric acid is required as an alkaline oil-containing wastewater, and an alkali agent such as slaked lime is required as a neutralizer as an acid wastewater. (B) The oil treatment of the alkaline oil-containing wastewater requires an excess acid agent in the acid break system or an organic coagulant in the emulsion break system and an inorganic coagulant such as polyaluminum chloride. (C) Due to the difference in the specific gravity of the generated floc, separate treatment equipment is required to adopt the floatation separation method for alkaline oil-containing wastewater and the sedimentation separation method for acid rinse wastewater.

As described above, at present, it is not economical to treat alkaline oil-containing wastewater and acid rinse wastewater, because separate treatment facilities and water treatment chemicals such as neutralizing agents and organic coagulants are required. . Therefore, in the present invention, such problems are solved, and all of the alkaline oil-containing wastewater and the acidic wastewater generated from the surface treatment step using the acid rinse wastewater treatment equipment,
The purpose of the present invention is to provide a method of processing with one facility.

[0009]

The gist of the invention is as follows: (1) In a method for detoxifying an alkaline oil-containing wastewater containing a surfactant, the wastewater is mixed with an acidic wastewater containing iron ions. A method for treating oil-containing wastewater containing a surfactant, comprising separating oil, adsorbing it to a hydroxide, and causing coagulation and precipitation. (2) The method for treating oil-containing wastewater containing a surfactant according to the above (1), wherein the alkaline oil-containing wastewater and the acidic wastewater are adjusted to a weak acid in a regulating tank.

(3) The method for treating oil-containing wastewater containing a surfactant according to the above (2), wherein the weak acid has a pH of 4 to 6. (4) The surface activity according to the above (1) to (3), wherein neutralization is performed to pH 7 with an alkali agent such as slaked lime in a reaction tank, oxidation is performed by air aeration, and coagulation precipitation is performed. In a method for treating oil-containing wastewater containing an agent.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The present inventors have conducted various studies, and as a result, by adding an acid rinse containing iron ions to an alkaline oil-containing wastewater containing a surfactant to make it a weak acid (preferably pH 4 to 6), the oil-containing wastewater can be obtained. It has been found that the oil contained therein is separated and adsorbed by the hydroxide of iron, and it is possible to simultaneously perform the solid-liquid separation treatment (coagulation sedimentation treatment) on the alkaline oil-containing wastewater and the acidic wastewater, which were difficult in the past.

That is, conventionally, in the case of the acid break system,
Separation of emulsified oil by lowering the pH to a strong acid of pH 3 and removal by adsorption with an inorganic flocculant (mainly polyaluminum chloride) resulted in acid rinse drainage as a result of research conducted by the present inventors. It has been found that hydrogen ions and iron ions contained therein can be removed. The oil in the alkaline oil-containing wastewater is mixed with an acidic wastewater to make a weak acid (preferably pH 4 to 6), whereby the emulsion is broken and separated. At the same time, iron ions in the acidic wastewater generate hydroxides, and the oil separated into the hydroxides is adsorbed and removed. Next, it is neutralized to pH 7 with an alkali agent such as slaked lime, the efficiency of use of iron ions is increased by oxidation by air aeration, and floc is grown by adding a polymer flocculant.

[0013]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. FIG. 1 is a view showing a processing mode of a mixing treatment of an alkaline oil-containing wastewater containing a surfactant and an acid rinse wastewater treatment according to the present invention. As shown in this figure, pH after mixing of alkaline oil-containing wastewater and acid rinse wastewater
Varies depending on the mixing ratio, and the relationship between the pH and the oil concentration of the treated water is shown in FIG. Figure 2 shows the pH after mixing on the horizontal axis.
And the vertical axis represents the oil concentration (mg / l) in the treated water. As can be seen from FIG. 2, the oil concentration in the treated water is clear from the drainage standard (less than 5 mg / l) from the acid region to the neutralized region. Has been proved to be possible.

In order to adsorb oil with iron hydroxide,
There is a possibility that the floc sedimentation speed may decrease and carry over to the treated water. The relationship between the sedimentation speed and the mixing pH can be found in FIG. That is, FIG.
H, and the vertical axis represents the sedimentation velocity (m / H). As can be seen from FIG. 3, the sedimentation velocity is affected by the mixed pH. This is because if the pH is low, the amount of slaked lime used for re-neutralization increases and the SS load increases, so that the sedimentation velocity increases. There was found. However, in general, the surface load of the coagulation and sedimentation equipment is about 1 m / H, and there is a sufficient margin, so there is no particular problem in the treatment.

As a result of this mixing treatment, the organic coagulant and the inorganic coagulant conventionally used for the alkaline oil-containing wastewater treatment become unnecessary, and the mutual neutralization reduces the amount of the dilute sulfuric acid and slaked lime used as the neutralizing agent. . In addition, since the use of an inorganic coagulant is not required, the amount of sludge generated by the inorganic coagulant is reduced, and recycling from conventional incineration to raw material for a blast furnace becomes possible. In addition, since the floating processing equipment can be stopped, the maintenance cost of the equipment is not required. FIG.
Table 1 shows the treatment aqueous properties as a result of the treatment shown in Table 1.

[0016]

[Table 1]

As shown in Table 1, according to the method of the present invention, the alkaline oil-containing wastewater can be mixed with the acidic wastewater, and the treated water quality can sufficiently satisfy the wastewater standards. Table 2 shows the results of comparison between the conventional processing method and the method of the present invention in terms of processing performance. As can be seen from the results in Table 2, according to the method of the present invention, an organic coagulant and an inorganic coagulant for treating an alkaline oil-containing wastewater are not required, and the amount of the neutralizing agent is reduced. And contribute to the reduction of the amount of generated sludge (dewatered cake) and cost reduction.

[0018]

[Table 2]

[0019]

As described above, according to the method of the present invention, it is possible to simultaneously treat an alkaline oil-containing wastewater containing a surfactant with an acidic wastewater containing iron ions by an existing coagulation-sedimentation treatment facility. It goes without saying that the cost reduction of water treatment chemicals such as a neutralizing agent and an organic coagulant and the necessity of newly installing a flotation treatment facility are eliminated, so that the economic effect is improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a treatment form of a mixing treatment of an alkaline oil-containing wastewater containing a surfactant and an acid rinse wastewater treatment according to the present invention;

FIG. 2 is a diagram showing the relationship between the pH of mixed wastewater and the concentration of treated water oil,

FIG. 3 is a diagram showing the relationship between the pH of mixed wastewater and the settling rate of coagulated sludge,

FIG. 4 is a treatment system diagram showing an alkali oil-containing wastewater floating separation treatment system and an acidic wastewater sedimentation separation treatment system according to a conventional method.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C02F 1/66 540 C02F 1/66 540H (72) Inventor Kenji Mizurai 2-3-3 Tokaicho, Tokai City, Aichi Prefecture No. 14 Inside Tehara original Nagoya branch (72) Inventor Kenji Hashimoto 5-3 Tokai-cho, Tokai-shi, Aichi Prefecture Inside Nippon Steel Corporation Nagoya Works (72) Inventor Hiroshi Koga 5 Tokai-cho, Tokai-shi, Aichi prefecture -3 Inside Nippon Steel Corporation Nagoya Works (72) Inventor Takashi Suzuki 5-3 Tokaicho, Tokai City, Aichi Prefecture F-term in Nagoya Works Nippon Steel Corporation 4D062 BA19 BA21 BA21 BB12 CA06 CA07 DA12 DA39 DC02 DC06 EA04 EA06 EA13 EA17 EA32 FA01 FA25 FA28

Claims (4)

[Claims] In a method for detoxifying an alkaline oil-containing wastewater containing a surfactant, the wastewater is mixed with an acidic wastewater containing iron ions to separate an oil component, adsorb it to a hydroxide, and cause coagulation and sedimentation. A method for treating oil-containing wastewater containing a surfactant. 2. The method for treating oil-containing wastewater containing a surfactant according to claim 1, wherein the alkaline oil-containing wastewater and the acidic wastewater are adjusted to a weak acid in a regulating tank. 3. The method for treating oil-containing wastewater containing a surfactant according to claim 2, wherein the weak acid has a pH of 4 to 6. 4. In a reaction tank, p is added with an alkaline agent such as slaked lime.
The method for treating oil-containing wastewater containing a surfactant according to any one of claims 1 to 3, wherein the mixture is neutralized to H7 and oxidized by air aeration, and then coagulated and precipitated.