KR800000190B1 - Treating method for waste plating-water - Google Patents

Abstract

A waste rinse water from metal surface treatment was adjusted to an appropriate pH and oxidized by aeration to form metallic hydroxides and the metallic oxides were sepd. by flocculation, pptn. or flotation in the presence of a high-mol. wt. flocculent. The supernatant liq. was filtered and the filtrate was treated with activated carbon and then by O3 oxidn. The treated water was passed through as series of ion-exchange towers.

Description

Metal Surface Treatment Wastewater Treatment Method

The accompanying drawings are process drawings showing the processing method of the present invention.

The present invention relates to a method for cleaning wastewater containing hydrophilic organic matter, which is always discharged from the surface treatment process of metals, which continuously comprises air oxidation, flocculation sedimentation or flotation flotation, rapid filtration, activated carbon adsorption, ozone oxidation and ion exchange. It consists of a combined treatment method, the purpose is to circulate the waste water discharged from the metal surface treatment process to the extent that can be reused, and to operate the non-drained metal surface treatment process It is to let.

The wastewater discharged from the surface treatment process of metals contains organic substances such as various organic solvents (glycol, aromatic, aliphatic, etc.), organic acids, various surfactants, coloring dyes, oil-soluble fluorescent dyes, in addition to heavy metals and other inorganic salts. In general, it is difficult to separate the inorganic salts and organic substances from the drainage system, and in treating the metal surface treatment wastewater, it is necessary to treat the wastewater mixed with these. The conventional treatment method of this wastewater is as follows.

Oxidation (Fe ⁺² etc.) or reduction (Cr ⁺⁶ etc.) with pH adjustment of the wastewater is carried out to precipitate the heavy metal ions in the wastewater with hydroxide precipitation, and then the coagulant sedimentation separation or flocculation flotation separation To remove it. At this time, a part of the organic matter contained in the waste water is removed by flocculation sedimentation separation or flocculation flotation separation with heavy metal hydroxide precipitation by the adsorption and flocculation effect of the heavy metal hydroxide precipitation. Organic matter that is not removed by such treatment is, if necessary, removed through SS (Suspended solid: suspended matter = suspended or suspended matter, separated by filtration or centrifugation) and then activated carbon, etc. It is treated by adsorbent treatment.

According to the conventional treatment method described above, the heavy metal ions in the wastewater are almost sufficiently removed, but the removal of organic matter is insufficient, so that the BOD (biochemical oxygen demand) and COD (chemical oxygen demand) are not sufficiently lowered to below the discharge threshold. It is often not processed. Therefore, in the end, metal surface treatment wastewater contains a large amount of organic substances (for example, hydrophilic organic substances such as ethylene glycol) that are hardly adsorbed to activated carbon. In addition, the conventional treatment method does not consider at all the removal of inorganic salts other than heavy metal ions such as sodium ions, potassium ions, or sulfate ions and chlorine ions. At the same time, the treated water cannot be circulated as washing water or the like.

In the treatment method of the present invention, the washing wastewater is treated by a treatment method that combines air oxidation method, flocculation sedimentation method or flocculation flotation method, rapid filtration method, activated carbon adsorption method, ozone oxidation method, and ion exchange method. According to the treatment method of the present invention, it is possible to completely remove organic substances and inorganic salts which were impossible with the conventional method. In addition, since the treated water obtained by the treatment method of the present invention is pure water, it can be recycled and reused, thereby eliminating the need to discharge the treated water out of the factory, thereby enabling operation of a non-drained metal surface treatment process. will be. Such a processing method of the present invention will be described in detail below with reference to a process diagram shown in the accompanying drawings.

The washing waste water 1 is transferred to the storage tank 2 and again to the aeration tank 8 by the pump 3. In the aeration tank 8, air is blown into the wastewater by the blower 18, and air oxidation treatment is performed. This air oxidation treatment is performed to oxidize divalent iron ions (Fe ⁺⁺ ) into trivalent iron ions (Fe ⁺⁺⁺ ) contained in a large amount in the waste water, and pumps from the caustic soda aqueous solution 4 simultaneously with aeration. The pH value of the wastewater is adjusted to 7 to 8 by adding caustic soda solution according to (5) to produce ferric hydroxide and other heavy metal hydroxide precipitates, whereby oxidized organic matter in the wastewater is oxidized by air oxidation treatment. When the polymer coagulant is added by the pump 7 from the coagulation preparation 6 to the wastewater containing the heavy metal hydroxide precipitate in the coagulation tank 9, the hydroxide precipitate coagulates and flocks. It is removed by the sedimentation separation method in (10), in which case the floating separation method may be used instead of the sedimentation separation method. By sedimentation or flocculation separation, heavy metal ions contained in the wastewater are almost completely removed (a small amount of residual heavy metal ions are removed by the ion exchange method described below), and also a part of the organic matter contained in the wastewater (especially coloring dyes) Etc.) are removed by flocculation sedimentation or flocculation flotation by the adsorption and flocculation effect of hydroxide precipitation.

As described above, the supernatant liquid of the clarifier 10 from which heavy metal ions and some organic substances have been removed is transferred to the rapid filtration tower 11, and rapid filtration is performed. This rapid filtration treatment is carried out to remove SS, which causes clogging in activated carbon adsorption treatment, ion exchange treatment, and the like described later, and the organic matter is also slightly removed by this treatment. After the rapid filtration treatment, the waste water is activated carbon adsorption treatment in the activated carbon adsorption tower (12). The activated carbon used for the activated carbon adsorption treatment is preferably a granular product that is easy to handle and has good regeneration efficiency. This activated carbon treatment is mainly intended to remove organic matter from the wastewater. The metal surface treated wastewater contains a large amount of organic matter which is hardly adsorbed to activated carbon, for example, hydrophilic organic substances such as glycols, and is contained by the activated carbon adsorption treatment. It is difficult to sufficiently remove organic matter. Although BOD and COD after activated carbon adsorption treatment are somewhat lower than BOD and COD of raw wastewater, they are not lowered to a sufficient degree and often exceed the discharge standard. This is also a hindrance when recycled water is recycled as washing water or the like.

In the treatment method of the present invention, residual organic substances that could not be treated by the above-mentioned activated carbon adsorption treatment method are treated by the ozone oxidation method. In other words, the wastewater that has passed through the activated carbon adsorption tower 12 is oxidized and decomposed by ozone from the ozone generator 23 blown in by the compressor 24 in the ozone oxidation tank 13. Residual organics that could not be sufficiently removed by the ozone oxidation treatment, for example, glycol, aromatic or high molecular weight aliphatic organic solvents, surfactants having a polar group, and the like are hexacyclic rings. V), double bonds, triple bonds and the like are decomposed to lower molecular weight fatty acids such as acetic acid and ureic acid. This fatty acid is removed by the ion exchange treatment following the ozone oxidation treatment. After the ozone oxidation treatment, the wastewater is transferred to an ion exchange column to undergo ion exchange treatment. The ion exchange tower is composed of a strong acid cation exchange tower 14, a weakly basic anion exchange tower 15, a strong basic anion exchange tower 16, and a mixed phase pure water device 17. The ion exchange treatment removes inorganic salts other than heavy metal ions such as sodium ions and potassium ions or sulfate ions and chlorine ions in the wastewater, residual metal ions, and low molecular weight fatty acids produced by the ozone oxidation treatment. Wastewater is treated as pure. That is, the wastewater subjected to ozone oxidation is first transferred to the strong acid cation exchange tower 14. In this strongly acidic cation exchange column 14, by air oxidation treatment with pH adjustment described above other than heavy metal ions such as sodium ions, potassium ions, magnesium ions, etc. in the wastewater, and subsequent flocculation sedimentation separation or flocculation flotation separation. The cations not removed are adsorbed and removed, and residual heavy metal ions are also adsorbed and removed at the same time. Next, the waste liquid is transferred to the weakly basic anion exchange tower 15 and the strong basic anion exchange tower 16, and anion exchange treatment is performed. In the weakly basic anion exchange column 15, anions having strong adsorption powers, such as sulfate ions and chlorine ions, are adsorbed and removed. In the strongly basic anion exchange tower 16, anions having relatively weak adsorption powers, such as organic acids, are adsorbed and removed. At this time, the treatment with the weakly basic anion exchange column and the treatment with the strong basic anion exchange column must be performed first with the weakly basic anion exchange column. This is because, when the treatment with the strong basic anion exchange column is performed first, it is difficult to elute the anion retained by the strong basic anion exchange column. In addition, chromium is contained in the metal surface treatment wastewater as chromate ions (CrO ₄ -2). In the treatment method of the present invention, the chromic acid ions are completely removed by anion exchange treatment. After treatment by the strongly acidic cation exchange tower 14, the weakly basic anion exchange tower 15, and the strong basic anion exchange tower 16, the wastewater is transferred to the mixed-phase pure water device 17. The mixed phase pure water device is usually composed of a strong acid anion exchange resin and a strong base anion exchange resin, which adsorbs and removes a small amount of impurity ions remaining in the waste water to make the treatment more sure and simultaneously adjusts the pH. Thus, the treated water 27 discharged from the mixed-phase pure water device 17 is pure water, its conductivity is 1.0, μV / cm or less, and BOD and COD are remarkably low. Thus, cleaning in the metal surface treatment process is performed. The recycled material can be used as water. The easy liquid discharged during the regeneration of the strongly acidic cation exchange tower 15, the strong basic anion exchange tower 16, and the mixed-phase pure water device 17 is temporarily stored in the water tank 26 and then pumped to the pump 25. It is transferred to the combustion evaporation furnace 22 and processed according to the combustion evaporation method.

In addition, in the metal surface treatment, the waste water which is thick at the time of surface treatment liquid update sometimes discharges. Others are as small as 1/100 to 1/200 compared to the rinsing wastewater and the concentration of impurities is very high. Such rich wastewater is treated, for example, by combustion evaporation. That is, the rich wastewater 19 is temporarily stored in the water tank 20 and then transferred to the combustion evaporation furnace 22 by the pump 21, where the combustion evaporation is performed by heating. Inorganic salts in the wastewater solidify as oxides or other salts, and organic matter is oxidatively decomposed to carbon dioxide and water and released into the atmosphere.

According to the treatment method of the present invention, the ions in the heavy metals in the rinsing wastewater are mainly removed by air oxidation, flocculation sedimentation or flotation separation and ion exchange methods involving pH adjustment, and the organic matter is air oxidation, flocculation sedimentation, or flocculation. The treated water is removed by continuous treatment by flotation separation method, rapid filtration method, activated carbon adsorption method, ozone oxidation method and ion exchange method, and inorganic salts other than heavy metal ions are mainly sufficiently removed by ion exchange method. Significantly lower BOD and COD also allow the use of circulating materials, furthermore enabling the operation of a non-drained metal surface treatment process.

As described above, the industrial value of the present invention is large.

Next, an Example demonstrates this invention.

EXAMPLE

The washing wastewater drained from the metal surface treatment process (containing the impurity components and amounts thereof) is fed to the aeration tank (capacity 15.6 L) at a flow rate of 200 cc / min. Hydrogen precipitate was formed when pH value was adjusted to 8.0 by adding 2% caustic soda aqueous solution while air was fed into the aeration tank at a flow rate of 4 to 6 l / min to perform air oxidation. Next, the wastewater containing the hydroxide precipitate was transferred to a flocculation tank (capacity 7.8 l), and 10 ppm of 0.1% aqueous solution of anionic polymer flocculant was added to flocculate the hydroxide precipitate. It precipitated and solid-liquid separation was performed.

The supernatant was passed through a rapid filtration tower (100 mmø 1000 mmH) filled with anthracite to remove SS and then passed through an activated carbon adsorption tower (1000 mm 3000 mmH) filled with granular activated carbon.

Wastewater is introduced into an ozone oxidizer (capacity 12.5ℓ), and 0.5 g / hr of ozone is fed into the ozoneizer to perform ozone oxidation, followed by strong acid cation exchange towers, weakly basic anion exchange towers, and steel. A basic ion exchange column and a mixed column (250 mm x 1000 mmH, respectively) were passed through.

Impurities in the rinsing wastewater raw water used in the present embodiment, and types, amounts, pH values, and conductivity of impurities in the treated water obtained after the above-described treatment are as shown in the following table. It can be seen that the heavy metals and other inorganic salts are sufficiently removed, and the BOD and COD are also significantly reduced, which is below the standard value.

The treated water obtained by the present example could be reused as the washing water of the metal surface treatment step. In addition, about 3 liter of the eluent obtained when the ion exchange tower of this Example was saturated was put into a combustion evaporation furnace with rich wastewater, and the combustion evaporation process was carried out at about 1000 degreeC.

Claims (1)

The cleaning wastewater containing hydrophilic organic matter, which is always discharged from the metal surface treatment process, is subjected to air oxidation treatment with pH value adjustment to precipitate the metal hydroxide from the washing wastewater, and coagulation sedimentation separation or flocculation by addition of a polymer flocculant. The purified water obtained by flotation separation is subjected to rapid filtration, followed by activated carbon adsorption treatment, followed by ozone oxidation treatment, followed by ion conversion into a strongly acidic cation exchange tower, a weakly basic anion exchange tower, a strong basic anion exchange tower, and a mixed pure water device. A method for treating metal surface treatment wastewater, characterized in that the ion exchange treatment is carried out in an exchange column.

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