JP2005058934A - Treatment method for biologically treated water-containing water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a treatment method for biologically treated water-containing water for preventing a fall in the permeation flux of a reverse osmosis membrane when subjecting biologically treated water-containing water to separation treatment by using the reverse osmosis membrane to purify the same to perform a stable treatment. <P>SOLUTION: In this treatment method for biologically treated water-containing water, biologically treated water-containing water is filtered by using an ultrafiltration membrane with a fractional molecular weight of 10,000-250,000 while the filtered water is passed through an activated carbon column and the activated carbon-treated water is subjected to separation treatment using the reverse osmosis membrane. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for treating biologically treated water-containing water. More specifically, in the present invention, when water containing biologically treated water is separated and purified by a reverse osmosis membrane, a reduction in permeation flux of the reverse osmosis membrane can be prevented and a stable treatment can be performed. The present invention relates to a method for treating biologically treated water-containing water.

In recent years, environmental standards and water quality standards tend to be stricter, and it is desired that effluent water be highly purified. On the other hand, for the purpose of eliminating water shortage, advanced water treatment is desired in order to collect and reuse various wastewater.
Under such circumstances, the reverse osmosis membrane separation treatment can effectively remove impurities such as ions, organic matter, and fine particles in water, and thus has recently been used for secondary treatment of wastewater. It is getting more. For example, when recovering and recycling wastewater containing organic carbon (TOC) components such as acetone and isopropyl alcohol discharged from the semiconductor manufacturing process, the wastewater is first biologically treated to remove the organic carbon components, A method of purifying biologically treated water by reverse osmosis membrane separation treatment has been adopted.
Conventionally, as a reverse osmosis membrane used for the reverse osmosis membrane separation treatment, a wholly aromatic crosslinked polyamide composite membrane (PA membrane), a cellulose acetate membrane (CA membrane) and the like have been provided. Moreover, in reverse osmosis membrane separation processing, in order to prevent a decrease in permeation flux (flux) and perform stable treatment, a standard is provided for the water to be treated supplied to the reverse osmosis membrane device, and JIS K It is desired that the fouling index (FI) defined in 3802 is 4 or less. The smaller the fouling index, the less the load on the reverse osmosis membrane and the lower the permeation flux.
Among conventional reverse osmosis membranes, PA membranes are contaminated by a small amount of fouling substances such as surfactants, glycolipids and proteins contained in the water to be treated, and the permeation flux rapidly decreases. Therefore, there is a disadvantage that stable reverse osmosis membrane separation treatment cannot be continued. The CA membrane has better contamination resistance than the PA membrane, but has a problem that the desalination rate is low and the operation pressure is high.
In recent years, uncharged membranes have been developed as reverse osmosis membranes that have made membranes less susceptible to contamination by eliminating the charge on the membrane surface and improving hydrophilicity. In addition, when water containing components with relatively high tackiness, such as glycolipids and proteins, is treated, there is a problem that the stain resistance effect is low, and the permeation flux decreases with time.
As for human waste sewage, human waste sewage is used as a sewage treatment device that can improve the quality of treated water with less clogging of the membrane, without significantly reducing the amount of permeate, and can significantly extend the operating life of the membrane. Solid-liquid separation of the flocculation treatment liquid from the flocculation treatment means, means for biological nitrification denitrification of the separated water from the dehydration means, means for flocculation treatment of the biological treatment liquid from the nitrification denitrification means An apparatus for treating sewage sewage comprising means for separating membranes as it is has been proposed (Patent Document 1). In addition, when water containing a small amount of organic substances is treated by biological treatment with oligotrophic bacteria and membrane separation treatment, the permeation flux of the membrane is prevented from decreasing and stable and efficient treatment is achieved over a long period of time. As a method to perform, a method of maintaining the dissolved oxygen concentration in the biological reaction tank at 2 ppm or more has been proposed (Patent Document 2).
In reverse osmosis membrane separation treatment of biologically treated water-containing water, it is conceivable to remove fouling substances with relatively high tackiness such as proteins in advance by filtration, but these fouling substances are very small, Gravity filters, pressure filters and the like are not trapped and flow into the reverse osmosis membrane device, causing membrane clogging. In addition, even when membrane filtration is performed with a microfiltration membrane device having a pore size of 0.45 μm or less, the fouling index is 4 or less, and although the water supply condition to the reverse osmosis membrane is satisfied, the decrease in permeation flux cannot be suppressed. This has become clear in recent years.
Japanese Patent Publication No. 7-55318 (first page, second page) JP 2000-288578 A (2nd page)

  In the present invention, when water containing biologically treated water is separated and purified by a reverse osmosis membrane, the degradation of the permeation flux of the reverse osmosis membrane is prevented and stable treatment can be performed. The object is to provide a water treatment method.

As a result of intensive studies to solve the above problems, the present inventor treated biologically treated water-containing water with an ultrafiltration membrane having a fractional molecular weight of 10,000 to 200,000, and then passed water through the activated carbon tower. In addition, by subjecting the obtained activated carbon treated water to reverse osmosis membrane separation treatment, it is possible to stably purify biologically treated water-containing water with a reverse osmosis membrane without causing a decrease in the permeation flux of the reverse osmosis membrane. As a result, the present invention has been completed based on this finding.
That is, the present invention
(1) Water containing biologically treated water is filtered through an ultrafiltration membrane having a molecular weight cut off of 10,000 to 250,000 and then passed through an activated carbon tower. The obtained activated carbon treated water is subjected to reverse osmosis membrane separation treatment. A method for treating the water containing biologically treated water,
Is to provide.
Furthermore, as a preferred embodiment of the present invention,
(2) The method for treating biologically treated water-containing water according to item 1, wherein a chlorinating agent is added to the biologically treated water-containing water and filtered through an ultrafiltration membrane.
(3) The method for treating biologically treated water-containing water according to item 1, wherein the membrane material of the ultrafiltration membrane is cellulose acetate,
(4) The method for treating biologically treated water-containing water according to item 1, wherein a scale inhibitor is added to the activated carbon treated water obtained by passing water through the activated carbon tower, and reverse osmosis membrane separation treatment is performed, and
(5) The method for treating biologically treated water-containing water according to item 1, wherein a reverse osmosis membrane separation treatment is performed by adding a slime control agent to activated carbon treated water obtained by passing water through an activated carbon tower;
Can be mentioned.

  According to the method for treating biologically treated water-containing water of the present invention, water containing biologically treated water containing glycolipids, proteins, etc. can be stabilized over a long period of time without causing a decrease in the permeation flux of the reverse osmosis membrane. And can be purified by reverse osmosis membrane separation treatment.

In the method for treating biologically treated water-containing water of the present invention, water containing biologically treated water is filtered through an ultrafiltration membrane having a molecular weight cut off of 10,000 to 250,000, and then passed through an activated carbon tower to obtain water. The obtained activated carbon treated water is subjected to reverse osmosis membrane separation treatment.
The biologically treated water-containing water to which the method of the present invention is applied includes standard activated sludge method, anaerobic aerobic method, circulating nitrification denitrification method, oxidation ditch, batch activated sludge method, etc. Biologically treated water obtained by anaerobic treatment such as fixed bed type such as filter bed, rotating disk method, contact oxidation method, biological filtration method and biological deodorization method, and anaerobic treatment such as anaerobic digestion method, and the organism Examples thereof include waste water containing treated water. The method of the present invention can be suitably applied to biologically treated water-containing water such as organic carbon-containing water discharged from a semiconductor manufacturing process and general waste water into which such biologically treated water flows. Although there is no restriction | limiting in particular in the quality of the biological treatment water containing water to which this invention method is applied, It is preferable that organic carbon concentration is 0.5-20 mg / L.

  In the method of the present invention, the biologically treated water-containing water is filtered through an ultrafiltration membrane having a fractional molecular weight of 10,000 to 250,000, more preferably a fractional molecular weight of 50,000 to 200,000. The fractional molecular weight of the ultrafiltration membrane is a molecular weight at which the blocking rate is 90% in the molecular weight fraction curve obtained by plotting the molecular weight and the blocking rate. If the molecular weight cut off of the ultrafiltration membrane is less than 10,000, the pressure loss in the ultrafiltration membrane may be excessive. If the molecular weight cut-off of the ultrafiltration membrane exceeds 250,000, glycolipids and proteins may pass through the ultrafiltration membrane and the permeation flux may decrease in the reverse osmosis membrane. By using an ultrafiltration membrane with a molecular weight cut off of 10,000 to 250,000, it is effective for biological metabolites such as glycolipids and proteins that cause a decrease in the permeation flux of reverse osmosis membranes contained in biologically treated water. Can be removed, and the decrease in the permeation flux of the reverse osmosis membrane can be suppressed.

In the method of the present invention, treatments such as pressure filtration, gravity filtration, microfiltration, pressurized flotation, and precipitation can be performed before the ultrafiltration membrane to reduce the load on the ultrafiltration membrane.
In the method of the present invention, it is preferable to add a chlorine agent to the biologically treated water-containing water supplied to the ultrafiltration membrane. By adding a chlorine agent to the biologically treated water-containing water so that residual chlorine is present, generation of slime in the ultrafiltration membrane device can be prevented and an increase in the differential pressure can be suppressed. There is no restriction | limiting in particular in the chlorine agent to add, For example, sodium hypochlorite, potassium hypochlorite, etc. can be mentioned. Although there is no restriction | limiting in particular in the addition amount of a chlorine agent, It is preferable that the residual chlorine density | concentration in biological treatment water containing water is 0.1-10 mg / L, and it is more preferable that it is 0.3-2 mg / L. If the residual chlorine concentration is less than 0.1 mg / L, the slime prevention effect may not be sufficiently exhibited. If the residual chlorine concentration exceeds 10 mg / L, the apparatus may be corroded.

  In the method of the present invention, the membrane material of the ultrafiltration membrane is not particularly limited. For example, polymer materials such as polysulfone, polyethersulfone, polyacrylonitrile, polyvinylidene fluoride, polyolefin, cellulose acetate, alumina, zirconia, titania, etc. Inorganic materials and the like can be mentioned. Among these, a cellulose acetate membrane can be suitably used because it has little adhesion of biological metabolites. The ultrafiltration membrane module used in the method of the present invention is not particularly limited, and examples thereof include a flat membrane module, a tube type module, a spiral module, a capillary module, a monolith type module, a tank immersion type module, and a rotating disk membrane module. it can.

In the method of the present invention, filtered water obtained by filtering biologically treated water-containing water through an ultrafiltration membrane is passed through an activated carbon tower. By passing the filtered water obtained from the ultrafiltration membrane through the activated carbon tower, the non-biodegradable nonionic surfactant is adsorbed and removed, and the oxidizing substances such as residual chlorine are adsorbed and removed. The inflow of the oxidizing substance to the reverse osmosis membrane device can be prevented. There is no restriction | limiting in particular in the activated carbon with which an activated carbon tower is filled, For example, wood type granular activated carbon, coal type granular activated carbon, peat charcoal type granular activated carbon, etc. can be mentioned. Among these, peat charcoal-based granular activated carbon can be suitably used because of its excellent adsorption capacity for surfactants.
In the process of the present invention is not particularly limited to the water flow rate to the activated carbon column, it is preferable that SV (space velocity) is 1～20Hr ^-1, and more preferably 5~15hr ^-1. If the SV is less than ¹ hr ⁻¹ , the activated carbon tower may have an excessive volume. When SV exceeds 20 hr ⁻¹ , the adsorption and removal of the nonionic surfactant and the oxidizing substance may be insufficient. The permeation flux of the reverse osmosis membrane can be prevented from decreasing by passing the filtered water of the ultrafiltration membrane through the activated carbon tower to adsorb and remove the nonionic surfactant.

  In the method of the present invention, activated carbon treated water obtained by passing water through an activated carbon tower is subjected to reverse osmosis membrane separation treatment. By treating the activated carbon treated water with reverse osmosis membrane separation, biological metabolites generated by organic matter decomposition of microbes remaining in the activated carbon treated water are removed, preventing a decrease in the permeation flux of the reverse osmosis membrane and purity. Highly treated water can be obtained efficiently. There is no restriction | limiting in particular in the reverse osmosis membrane used for this invention method, For example, a fully aromatic bridge | crosslinking polyamide membrane (PA membrane), a cellulose acetate membrane (CA membrane), an uncharged membrane etc. can be mentioned. After filtration through an ultrafiltration membrane with a molecular weight cut off of 10,000 to 250,000, the permeation flux of the reverse osmosis membrane is prevented from being lowered by subjecting the treated water passed through the activated carbon tower to reverse osmosis membrane separation. Thus, the biologically treated water-containing water can be efficiently treated to obtain highly purified final treated water.

  In the method of the present invention, it is preferable to add a scale inhibitor to the activated carbon-treated water subjected to reverse osmosis membrane separation treatment. By adding a scale inhibitor to the activated carbon treated water, it is possible to prevent the scale from being deposited in the reverse osmosis membrane device and increase the recovery rate of the final treated water. There is no particular limitation on the scale inhibitor to be added. Monomers having a carboxyl group such as phosphonic acid, acrylic acid, methacrylic acid, maleic acid, itaconic acid, vinyl sulfonic acid, styrene sulfonic acid, 2-hydroxyethyl methacrylate, acrylamide, 2-hydroxy-3-allyloxy-1 And low molecular weight copolymers with monomers such as propanesulfonic acid. The addition amount of the scale inhibitor is preferably 1 to 20 mg / L and more preferably 5 to 15 mg / L with respect to the activated carbon-treated water.

In the method of the present invention, it is preferable to add a slime control agent to the activated carbon-treated water. By adding a slime control agent to the activated carbon treated water, generation of slime in the reverse osmosis membrane device can be prevented and the recovery rate of the final treated water can be increased. The slime control agent to be added is preferably a non-oxidizing slime control agent. For example, isothiazoline-based slime control agents such as 2-methyl-4-isothiazolin-3-one and benzisothiazolin-3-one are preferably used. be able to. The addition amount of the slime control agent is preferably 0.5 to 10 mg / L, more preferably 1 to 5 mg / L with respect to the activated carbon-treated water.
In the method of the present invention, the activated carbon treated water supplied to the reverse osmosis membrane device is preferably adjusted to pH 6 or less. By adjusting the pH to 6 or less, precipitation of calcium-based scales such as calcium carbonate and calcium phosphate in the reverse osmosis membrane device can be prevented.

FIG. 1 is a process flow diagram of one embodiment of the method for treating biologically treated water-containing water of the present invention. After the chlorinating agent is added to the biologically treated water-containing water, it is sent to an ultrafiltration membrane with a molecular weight cut off of 10,000 to 250,000, filtered, and glycolipids, proteins, etc. contained in the biologically treated water-containing water Is removed. The filtered water of the ultrafiltration membrane is passed through an activated carbon tower, and the remaining hardly biodegradable nonionic surfactant is adsorbed and removed. A scale inhibitor and a slime control agent are added to the activated carbon treated water flowing out from the activated carbon tower, and final treated water is obtained by reverse osmosis membrane separation treatment.
The method of the present invention is not limited to the process flow diagram shown in FIG. 1, but, for example, it is also possible to perform advanced processing by multi-stage reverse osmosis membrane treatment by arranging reverse osmosis membrane devices in two or more stages in series. In that case, means such as adjusting the pH of the feed water of the reverse osmosis membrane apparatus in the second and subsequent stages to be alkaline to enhance the removal effect of the carbonic acid component can also be adopted.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
Example 1
As biologically treated water-containing water, treated water obtained by treating wastewater from a semiconductor manufacturing factory with a biological filtration device was used. The organic carbon (TOC) concentration of this biologically treated water-containing water was 10 mg / L, and it contained 5 mg / L of nonionic surfactant.
To this biological treatment-containing water, an aqueous sodium hypochlorite solution was added so that the residual chlorine concentration was 0.5 mg / L, followed by filtration through a cellulose acetate ultrafiltration membrane having a fractional molecular weight of 200,000. The obtained filtered water was passed through an activated carbon tower packed with peat charcoal activated carbon at SV 10 hr ⁻¹ .
To the obtained activated carbon-treated water, a phosphonic acid scale inhibitor [Kurita Kogyo Co., Ltd., Clifloat D-170] 10 mg / L and an isothiazoline slime control agent [Kurita Kogyo Co., Ltd., Krivata EC-503] 3 mg / L In addition to adding L, hydrochloric acid was added to adjust the pH to 5, and reverse osmosis membrane separation treatment was performed using a reverse osmosis membrane device [Nitto Denko Corporation, NTR-759] at a recovery rate of 60%. The change with time in the permeation flux of the device was examined.
Comparative Example 1
A test was performed under the same conditions as in Example 1 except that water was passed through a microfiltration membrane having a pore size of 0.1 μm instead of an ultrafiltration membrane with a molecular weight cut off of 200,000. The change with time was examined.
Comparative Example 2
The filtered water obtained by filtering through a cellulose acetate ultrafiltration membrane having a molecular weight cut off of 200,000 was passed through an activated carbon tower, and the phosphonic acid scale inhibitor [Kurita Kogyo Co., Ltd., Cliflot D- 170] 10 mg / L and an isothiazoline-based slime control agent [Kurita Kogyo Co., Ltd., Krivata EC-503] 3 mg / L were added and recovered using a reverse osmosis membrane device [Nitto Denko Corporation, NTR-759]. Reverse osmosis membrane separation treatment was performed at a rate of 60%, and changes with time in the permeation flux of the reverse osmosis membrane device were examined.
The results of Example 1 and Comparative Examples 1 and 2 are shown in Table 1 and FIG.

As seen in Table 1 and FIG. 2, in Example 1 in which biologically treated water-containing water was filtered through an ultrafiltration membrane having a molecular weight cut off of 200,000, the permeation flux decreased even after 500 hours from the start of water flow. Hardly occurs. In contrast, in Comparative Example 1 in which the biologically treated water-containing water was filtered through a microfiltration membrane having a pore size of 0.1 μm, the permeation flux was already reduced by about 25% with respect to the initial permeation flux after 300 hours from the start of water flow. . Further, in Comparative Example 2 in which the filtered water obtained by filtering biologically treated water-containing water through an ultrafiltration membrane having a fractional molecular weight of 200,000 was subjected to reverse osmosis membrane separation treatment without passing through an activated carbon tower, After 400 hours from the start of water, the permeation flux decreases by about 15% with respect to the initial permeation flux.
Example 2
A test was conducted under the same conditions as in Example 1 except that water was passed through an ultrafiltration membrane having a molecular weight cut off of 50,000 instead of an ultrafiltration membrane having a molecular weight cut off of 200,000. The change with time of the flux was examined.
Comparative Example 3
A test was performed under the same conditions as in Example 1 except that water was passed through an ultrafiltration membrane with a molecular weight cut off of 300,000 instead of an ultrafiltration membrane with a molecular weight cut off of 200,000. The change with time of the flux was examined.
Comparative Example 4
A test was conducted under the same conditions as in Example 1 except that water was passed through a microfiltration membrane having a pore size of 0.45 μm instead of an ultrafiltration membrane having a molecular weight cut off of 200,000. The change with time was examined.
Comparative Example 5
A test was conducted under the same conditions as in Example 1 except that water was passed through a No. 5A filter paper instead of an ultrafiltration membrane with a molecular weight cut off of 200,000, and the change over time in the permeation flux of the reverse osmosis membrane device was examined. It was.
The results of Example 2 and Comparative Examples 3 to 5 are shown in Table 2 and FIG.

  As seen in Table 2 and FIG. 3, in Example 2 in which biologically treated water-containing water was filtered through an ultrafiltration membrane having a molecular weight cut off of 50,000, the permeation flux was almost constant until the water passage time was 30 hours. ing. On the other hand, Comparative Example 3 filtered through an ultrafiltration membrane having a molecular weight cut off of 300,000, Comparative Example 4 filtered through a microfiltration membrane having a pore size of 0.45 μm, and Comparative Example 5 filtered through a No. 5A filter paper. As the pore diameter of the filter medium increases, the degree of decrease in the permeation flux increases.

  According to the method for treating biologically treated water-containing water of the present invention, the wastewater discharged from the electronic device manufacturing process can be efficiently recovered and reused. If there is a biological treatment before the reverse osmosis membrane separation treatment, a biological metabolite produced by the decomposition of organic matter of microorganisms causes clogging of the reverse osmosis membrane. Furthermore, wastewater from the electronic device manufacturing process often contains a nonionic surfactant that reduces the permeation flux of the reverse osmosis membrane, and the nonionic surfactant is hardly biodegradable. According to the method of the present invention, the nonionic surfactant remaining in the biologically treated water-containing water is removed by passing water through the activated carbon tower, thereby reducing the load on the reverse osmosis membrane and increasing the large permeation flux over a long period of time. Can be maintained.

It is a process flow diagram of one mode of implementation of a processing method of biological treatment water content water of the present invention. It is a graph which shows the relationship between the water flow time and permeation | transmission flux in an Example and a comparative example. It is a graph which shows the relationship between the water flow time and permeation | transmission flux in an Example and a comparative example.

Claims (1)

Water containing biologically treated water is filtered through an ultrafiltration membrane with a molecular weight cut off of 10,000 to 250,000, then passed through an activated carbon tower, and the obtained activated carbon treated water is subjected to reverse osmosis membrane separation treatment. A method for treating water containing biological treated water as a feature.

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