JP2007319792A - Waste water treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a treatment method of high-concentration oil-containing waste water. <P>SOLUTION: The waste water treatment method of carrying out flocculation treatment and membrane filtration treatment of oil-containing waste water comprises loading the waste water with a flocculant containing an adsorbent, an aggregation agent and an organic polymer flocculant in a lump or in turn in response to a COD value of waste water and the amount of n-hexane extract, and carrying out membrane treatment of treated water subjected to the flocculation treatment. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wastewater treatment method. More specifically, the present invention relates to a method for treating wastewater containing a high concentration of water-soluble oil.

  Water-related environments such as saving water resources and water pollution are becoming harsher year by year, and effective use of water has become widespread in response to rising prices for water and sewage and drought in summer. On the other hand, most of the wastewater from offices and factories contains mineral oil, miscellaneous oil, wax, surfactant, suspension and the like. Such drainage is usually discharged into sewage or the like, but if the drainage load is high and exceeds the discharge regulation value, it is necessary to treat the wastewater by some means. Moreover, if the treated wastewater can be reused for other purposes, it will lead to cost reduction of water and sewage costs.

Particularly for oil-containing wastewater, several methods are known as treatment methods when the concentration of the contained oil is low. However, at high concentrations, the above method cannot be used for sufficient treatment.
JP2003-093807 JP2003-170007 JP-A-8-323350

  An object of this invention is to provide the processing method of high concentration oil-containing wastewater.

  The first invention is a wastewater treatment method for agglomeration treatment and membrane filtration treatment of water-soluble oil-containing wastewater having several tens to several thousand mg / l and n-hexane extract amount of 5 to several thousand mg / l, This is a wastewater treatment method in which treated water that has been coagulated by adding a coagulant containing an adsorbent, a coagulant, and an organic polymer flocculant to the wastewater is treated with a film.

  The second invention is a wastewater treatment method for agglomeration treatment and membrane filtration treatment of water-soluble oil-containing wastewater having a COD value of several tens to several tens of thousands mg / l and an n-hexane extract amount of 5 to several hundred thousand mg / l. Then, a wastewater treatment method in which an absorptive agent, a coagulant, and an organic polymer flocculant are respectively added to the wastewater in this order to perform a membrane treatment on treated water.

  In the present invention, as described above, different treatment methods are used depending on the concentration of oil contained therein.

  A third invention is the waste water treatment method according to the above invention, wherein the adsorbent is diatomaceous earth. 4th invention is a waste-water-treatment method whose coagulant is aluminum sulfate in said invention. 5th invention is said waste water treatment method including the process of adjusting pH of treated water to the alkali side after adding a coagulant | flocculant.

  According to the method of the present invention, even high-concentration oil-containing wastewater can be efficiently treated to reduce the COD and n-hexane extract concentration, and to achieve good water quality below the reference value.

The wastewater that is the target of the treatment method of the present invention has a very low oil concentration in the car wash wastewater, but the target wastewater of the present invention includes diecast mold release agent-containing wastewater, rolling oil-containing wastewater, and cutting oil-containing wastewater. , Etc., and the oil content is of a fairly high concentration.
1) Die-cast mold release agent-containing wastewater

  It is wastewater generated during the production of die-cast products, and has a COD value of 10 to 5000 mg / l and n-hexane extract of 5 to several thousand mg / l.

  The flocculant includes an adsorbent, a coagulant, and a polymer flocculant. As the adsorbent, oil adsorbents such as diatomaceous earth, montmorillonite and activated clay can be used. An inorganic compound such as aluminum sulfate can be used as the coagulant. As the polymer flocculant, for example, anionic and cationic polymer flocculants can be used.

  When the die cast mold release agent-containing wastewater is treated, it is preferable to collectively charge an adsorbent, aluminum sulfate, and a flocculant including anionic and cationic polymer flocculants. After the generated flocs are sufficiently settled, membrane treatment is performed, so that water to be treated can be obtained in which the oil content is reduced and the amount of COD and n-hexane extract is reduced.

  Further, depending on the concentration of oil in the raw water and the type of the flocculant to be used, the raw water can be diluted with an appropriate concentration or concentrated and then treated with the flocculant.

Depending on the required quality of the water to be treated, the treated water after the membrane filtration treatment can be further treated with activated carbon.
2) Rolling oil-containing drainage

This is drainage generated when cleaning and removing rolling oil that has deteriorated due to long-term use in a metal rolling mill, COD value is several tens to several tens of thousands mg / l, n hexane extract is several tens to several tens of thousands mg / l ones.
3) Wastewater containing cutting oil

  Wastewater that is generated when lubricating oil and cooling coolant are turned into waste liquid in parts cutting processes at parts processing plants for automobiles, etc. From hundreds to hundreds of thousands of mg / l.

  Since these rolling oil-containing wastewater and cutting oil-containing wastewater contain a higher concentration of water-soluble oil than the above-mentioned die-cast wastewater, unlike the above, the following treatment method is used.

  First, an oil adsorbent such as diatomaceous earth, montmorillonite or activated clay is added to adsorb the oil to the adsorbent. Next, a coagulant such as aluminum sulfate is added and the liquid is stirred. At this time, the pH of the liquid to be treated becomes the acid side, and micro flocs are formed. When a cationic or anionic polymer flocculant is added to this and then the pH of the liquid to be treated is adjusted to around 8 using an alkaline aqueous solution such as caustic soda, a sufficiently large floc is formed.

  After sufficiently allowing the flocs to settle, membrane treatment is performed to obtain water to be treated in which the oil content is reduced and the amount of COD or n-hexane extract is reduced.

  Further, depending on the concentration of oil in the raw water and the type of the flocculant to be used, the raw water can be diluted with an appropriate concentration or concentrated and then treated with the flocculant.

  Depending on the required quality of the water to be treated, the treated water after the membrane filtration treatment can be further treated with activated carbon.

  Next, FIG. 1 shows an example of an apparatus used in the processing method of the present invention.

  In the figure, 1 is a raw water storage tank, 2 is an agitation tank, 5 is a sedimentation tank, 7 is a dehydration processing section, 10 is a membrane raw water storage tank, 12 is a membrane processing section, 13 is a treated water storage tank, and 14 is an activated carbon processing section. , 15 is a chemical tank.

  The raw water is stored in the raw water storage tank 1 and then transferred to the agitation tank 2 by a pump. In the agitation tank 2, a predetermined amount of the flocculant is charged from the chemical tank 4 into the water to be treated. During this time, the water to be treated is stirred by the stirrer 3 to cause agglomeration reaction. After the agglomeration reaction, the water to be treated moves downward in a cylindrical portion 9 provided in the center of the precipitation tank 5 and is then left in the precipitation tank 5. After standing for a predetermined time, when the floc is sufficiently precipitated, the supernatant liquid of the precipitation tank 5 is transferred to the membrane raw water storage tank 10.

  On the other hand, the floc accumulated at the bottom of the settling tank 5 is pulled out from the bottom 6 by a pump 8 at a predetermined interval, dehydrated by the dehydration processing unit 7 and then disposed of as industrial waste.

  The raw membrane water drawn from the bottom of the raw membrane water storage tank 10 is pumped to the membrane treatment unit 12 and subjected to membrane filtration treatment, and the treated water that has permeated the membrane is stored in the water storage tank 13.

  If necessary, the water to be treated in the water storage tank 13 is treated by the activated carbon treatment unit 14 and then reused as irrigation water in the factory. The recycled water is then treated again by the method of the present invention and recycled.

  Further, if the membrane filtration in the membrane treatment unit 12 is continued, dirt adheres to the raw water side of the membrane and the filtration performance deteriorates. Therefore, it is preferable to periodically perform back pressure cleaning. In that case, the chemical solution from the chemical solution tank 15, for example, sodium hypochlorite aqueous solution, is pumped to the permeation side of the membrane for cleaning. The interval of back pressure washing is preferably 15-60 minutes, and the flow rate during back pressure washing is preferably 1-20 m / d, more preferably 2-15 m / d.

[Example 1]
The size of the apparatus shown in FIG. 1 (however, the size of the stirring tank, the precipitation tank, and the membrane raw water storage tank is 0.14 m3, 0.7 m3, and 0.25 m3, respectively, and the membrane area of the membrane treatment unit is 16 m2. The material of the membrane was cellulose acetate or polyethersulfone), and the diecast mold release agent-containing wastewater discharged from the diecast production process was treated by the above-described treatment operation. The water quality before treatment of this wastewater was COD 420 mg / l, n-hexane extract amount 580 mg / l.

  Memfloc U002 (manufactured by Daisen Membrane Systems Co., Ltd.) was added to the waste water so as to have a concentration of 500 mg / l, and agitation was performed for 15 minutes with stirring. After precipitating the liquid to be treated in a sedimentation tank, membrane treatment was performed in the membrane treatment section. Furthermore, when it processed through the activated carbon processing part, the water quality of the to-be-processed water after a process was COD 4 mg / l and n-hexane extract amount was less than 2 mg / l.

[Example 2]
Using the apparatus shown in FIG. 1 (however, the size of the stirring tank, the sedimentation tank, and the membrane raw water storage tank is 0.8 m3, 0.8 m3, and 0.5 m3, respectively, and the membrane area of the membrane treatment unit is 5 m2. In addition, the membrane oil was polyethersulfone), and the rolling oil-containing wastewater discharged from the rolling process was treated by the above-described treatment operation. The water quality of this waste water before treatment was COD 960 mg / l, n-hexane extract amount 2400 mg / l.

  The waste water was put into a stirring tank of the apparatus, diatomaceous earth was charged so as to have a concentration of 1000 mg / l, and stirred for 5 minutes. After that, when aluminum sulfate was charged to a concentration of 1000 mg / l and stirred for 5 minutes, micro flocs were formed. Further, Memfloc U002 (manufactured by Daisen Membrane Systems Co., Ltd.) was added so as to have a concentration of 2000 mg / l, and then the aqueous solution of caustic soda was added to adjust the pH of the liquid to be treated to 8. When the aggregation reaction treatment was performed for 3 minutes with stirring, a large floc was formed.

  After precipitating the liquid to be treated in a sedimentation tank, membrane treatment was performed in the membrane treatment section. Furthermore, when it processed through the activated carbon process part, the quality of the to-be-processed water after a process was COD 4.3 mg / l, and the amount of n-hexane extracts was less than 2 mg / l.

[Example 3]
Wastewater containing cutting oil discharged from the parts processing process (water quality is COD 10540 mg / l, n-hexane extract amount 2000 mg / l), and the concentrations of diatomaceous earth, aluminum sulfate, and Memflock U002 used are The same operation as in Example 2 was performed, except that they were 4000 mg / l, 1000 mg / l, and 1000 mg / l, respectively.

  As a result, the water quality of the treated water after the treatment was COD 558 mg / l and n-hexane extract amount was less than 1 mg / l.

The flowchart which shows an example of the processing apparatus used for the processing method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Raw water storage tank 2 Agitation tank 5 Settling tank 7 Dehydration processing part 10 Membrane raw water storage tank 12 Membrane processing part 13 Water to be treated water storage tank 14 Activated carbon processing part 15 Chemical solution tank

Claims (5)

A wastewater treatment method for coagulation treatment and membrane filtration treatment of water-soluble oil-containing wastewater having a COD value of several tens to several thousand mg / l and an amount of n-hexane extract of 5 to several thousand mg / l, A wastewater treatment method in which a coagulation treatment is performed by adding a coagulant including an adsorbent, a coagulant, and an organic polymer flocculant to perform a film treatment. A wastewater treatment method for coagulation treatment and membrane filtration treatment of water-soluble oil-containing wastewater having a COD value of tens to tens of thousands mg / l and n-hexane extract amount of 5 to hundreds of thousands mg / l, , An adsorbent, a coagulant, and an organic polymer flocculant are added in this order, and the treated water is subjected to a flocculant treatment to form a membrane. The wastewater treatment method according to claim 1 or 2, wherein the adsorbent is diatomaceous earth. The wastewater treatment method according to claim 1 or 2, wherein the coagulant is aluminum sulfate. The wastewater treatment method according to claim 2, comprising a step of adjusting the pH of the treated water to the alkali side after adding the coagulant.

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