JP2005081269A - Method and apparatus for treating wastewater containing organic matter - Google Patents

Abstract

[PROBLEMS] To prevent a decrease in flux and biofouling due to adhesion of organic matter in the RO membrane separator when treating and collecting wastewater containing organic matter using a reverse osmosis (RO) membrane separator for a long period of time. Perform stable processing.
After adjusting the pH of the organic substance-containing wastewater to 9.5 or more and passing it through the RO membrane separation device 2, the pH is adjusted to 4 to 8 by adding an acid, and then a chlorine-based disinfectant and After adding the slime control agent, water is passed through the activated carbon device 3. By setting the pH of the RO water supply to 9.5 or higher, biofouling in the RO membrane separation device is prevented, and the non-ionic surfactant is prevented from adhering to the membrane surface to prevent the flux from being lowered. The TOC value is further reduced by treating the RO permeate with activated carbon (AC). By adjusting the AC feed water to pH 4-8, an increase in the differential pressure in the activated carbon tower is prevented. By adding a chlorine-based disinfectant and / or slime control agent, an increase in differential pressure due to slime in the activated carbon tower is prevented.
[Selection] Figure 1

Description

  In the present invention, when wastewater containing high or low concentration organic matter (TOC) discharged from an electronic device manufacturing factory or the like is treated and recovered using a reverse osmosis (RO) membrane separator, organic matter in the RO membrane separator Of organic wastewater containing high-quality treated water by efficiently reducing the TOC concentration in water while simultaneously performing stable treatment over a long period of time by preventing flux reduction and bio-fouling due to film surface adhesion And a processing apparatus.

  In recent years, environmental standards and water quality standards tend to be stricter, and it is desired to purify discharged water to a high degree. On the other hand, for the purpose of eliminating water shortage, development of advanced water treatment technology is also desired in order to collect and reuse various wastewater.

  Under such circumstances, RO membrane separation treatment can effectively remove impurities (ions, organic substances, fine particles, etc.) in water, and has recently been used in many fields. It was. For example, when recovering and recycling wastewater containing high-concentration TOC or low-concentration TOC containing acetone, isopropyl alcohol, etc. discharged from the semiconductor manufacturing process, this is first biologically treated to remove the TOC component, A method of purifying by RO membrane treatment is widely adopted (for example, JP-A-2002-336886).

  However, in recent years, when biological treatment wastewater is passed through an RO membrane separation device, the problem that the membrane surface of the RO membrane is clogged and the flux is reduced due to biological metabolites generated by the decomposition of organic matter by microorganisms begins to become apparent. It has become like this.

  On the other hand, when these TOC-containing wastewater is directly passed through the RO membrane separator without using biological treatment, the TOC concentration flowing into the RO membrane separator is high, so that microorganisms propagate in the RO membrane separator. Easy environment. Therefore, for the purpose of suppressing biofouling in the RO membrane separation apparatus, a large amount of slime control agent is usually added to TOC-containing wastewater. However, since the slime control agent is expensive, it is cheaper. There is a need for a new biofouling suppression method.

In addition, the wastewater discharged from the electronic device manufacturing factory may be mixed with a nonionic surfactant that may adhere to the membrane surface of the RO membrane separator and reduce the flux. RO membrane separation treatment could not be applied to such nonionic surfactant-containing wastewater.
JP 2002-336886 A

  The present invention solves the above-mentioned conventional problems, and when processing / recovering wastewater containing high or low concentration organic matter discharged from an electronic device manufacturing factory and other various fields using an RO membrane separator, Organic matter that obtains high-quality treated water by efficiently reducing the TOC concentration in water while simultaneously performing stable treatment over a long period of time by preventing flux reduction and biofouling due to the membrane surface adhesion of organic matter in the separator It aims at providing the processing method and processing apparatus of contained wastewater.

  The method for treating organic matter-containing wastewater of the present invention includes a first pH adjustment step of adjusting the pH to 9.5 or more by adding alkali to the organic matter-containing wastewater, and a pH adjustment obtained in the first pH adjustment step. A membrane separation treatment step for subjecting water to reverse osmosis membrane separation, a second pH adjustment step for adjusting the pH to 4 to 8 by adding an acid to the permeated water of the membrane separation treatment, and the second pH adjustment step Characterized in that it comprises an antibacterial treatment step of adding a chlorine-based disinfectant and / or slime control agent to the pH-adjusted water obtained in step 1, and an activated carbon treatment step of treating the antibacterial treatment water with activated carbon.

  The treatment apparatus for organic matter-containing wastewater of the present invention includes a first pH adjusting means for adjusting the pH to 9.5 or more by adding alkali to the organic matter-containing wastewater, and a pH adjustment obtained by the first pH adjusting means. A reverse osmosis membrane separation device into which water is introduced, a second pH adjustment means for adjusting the pH to 4 to 8 by adding an acid to the permeated water of the reverse osmosis membrane separation device, and the second pH adjustment means A chemical injection means for adding a chlorine-based disinfectant and / or a slime control agent to the pH-adjusted water obtained in the above, and an activated carbon device into which water added with the chemical by the chemical injection means is introduced. Features.

  In the present invention, after adjusting the pH of the water to be treated introduced into the RO membrane separator (hereinafter sometimes referred to as “RO water supply”) to 9.5 or higher and passing the water through the RO membrane separator, Is added to adjust the pH to 4 to 8, and then a chlorine-based disinfectant and / or slime control agent is added, followed by activated carbon treatment.

  The reason for adjusting the pH of the RO water supply to 9.5 or higher is as follows.

  That is, microorganisms cannot live in the alkaline region. Therefore, by adjusting the pH of the RO feed water to 9.5 or more, it becomes possible to create an environment where there are nutrient sources but microorganisms cannot live in the RO membrane separation device. Biofouling in the RO membrane separator can be suppressed without the need for addition.

  In addition, nonionic surfactants that may lower the flux are known to be desorbed from the membrane surface in the alkaline region. By increasing the pH of the RO water supply to 9.5 or higher, these are applied to the RO membrane surface. It becomes possible to suppress adhesion of these components.

  The reason why the activated carbon treatment is performed after the RO membrane separation treatment is as follows.

  That is, the higher the TOC concentration of the RO feed water, the worse the TOC value of the permeated water of the RO membrane separation device (hereinafter sometimes referred to as “RO permeated water”), and this permeated water is recovered and reused. In this case, the TOC value is not negligible, but the activated carbon treatment can adsorb and remove the residual TOC in the permeated water leaking from the RO membrane separation device, so that the TOC value of the final treated water can be reduced.

  The chlorine-based disinfectant and / or slime control agent added to the RO permeated water to be subjected to the activated carbon treatment is added for the purpose of suppressing the propagation of slime in the activated carbon tower and the increase in the differential pressure in the tower.

  Moreover, the reason for adjusting the pH of water used for the activated carbon treatment (hereinafter sometimes referred to as “AC feed water”) to 4 to 8 is as follows.

  That is, if the pH of the AC feed water is less than 4, inorganic ions such as Fe may leak from the activated carbon and contaminate the subsequent apparatus. In particular, when a chlorine-based disinfectant is used, harmful chlorine gas may be generated at a pH lower than 4. When the pH of the AC feed water exceeds 8, there is a problem in durability (alkali resistance) of the activated carbon itself, and self-decomposition occurs in the chlorine-based disinfectant and / or slime control agent, which may reduce the effect. There is. For this reason, activated carbon treatment is performed in the range of pH 4-8.

  According to the method and apparatus for treating organic matter-containing wastewater of the present invention, wastewater containing high-concentration or low-concentration organic matter discharged from an electronic device manufacturing factory and other various fields, particularly wastewater containing a nonionic surfactant. When processing / recovering using RO membrane separators, the TOC concentration in the water is reduced at the same time as performing stable treatment over a long period of time by preventing flux reduction and biofouling due to organic membrane adhesion in the RO membrane separator. Can be efficiently reduced to obtain high-quality treated water.

  DESCRIPTION OF EMBODIMENTS Embodiments of a method and apparatus for treating organic matter-containing wastewater according to the present invention will be described in detail below with reference to the drawings.

  FIG. 1 is a system diagram showing an embodiment of the method and apparatus for treating wastewater containing organic matter according to the present invention.

  First, an alkaline agent is added to the raw water (organic matter-containing wastewater) introduced through the tank 1 to adjust the pH to 9.5 or more, preferably 10 or more, more preferably 10.5 or more, for example, pH 10.5 to 11. Introduced into the RO membrane separator 2. The alkaline agent used here is not particularly limited as long as it is an inorganic alkaline agent that can adjust the pH of raw water to 9.5 or higher, such as sodium hydroxide and potassium hydroxide.

  As the RO membrane of the RO membrane separation device, those having alkali resistance, for example, a polyetheramide composite membrane, a polyvinyl alcohol composite membrane, an aromatic polyamide membrane, etc. are preferably used. This RO membrane may be of any type such as a spiral type, a hollow fiber type, and a tubular type.

  The concentrated water of the RO membrane separation device 2 is discharged to the outside of the system after adjusting to pH neutrality by adding an acid as necessary. Next, the permeated water of the RO membrane separation device 2 is adjusted to pH 4 to 8 by adding an acid, and further added with a chlorine-based disinfectant and / or slime control agent, and then passed through the activated carbon device 3 to be treated with activated carbon. There is no restriction | limiting in particular as an acid used here, Mineral acids, such as hydrochloric acid and a sulfuric acid, are mentioned.

  Moreover, the kind of chlorine type disinfectant is not particularly limited, and examples thereof include sodium hypochlorite and potassium hypochlorite. The addition concentration of the chlorine-based disinfectant is preferably 0.1 to 10 mg / L, more preferably 0.3 to 2 mg / L in terms of residual chlorine concentration. 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.

  Moreover, when using a slime control agent, the kind is not particularly limited, and examples thereof include isothiazoline-based slime control agents such as 2-methyl-4-isothiazolin-3-one and benzoisothiazolin-3-one. The addition concentration of the slime control agent is preferably 0.5 to 10 mg / L, and more preferably 1 to 5 mg / L.

  The activated carbon device 3 may be either a powdered activated carbon agitation tank or an activated carbon packed tower, but an activated carbon packed tower is preferred in terms of treatment efficiency and treated water quality.

  The activated carbon type to be charged in the activated carbon tower may be any of coal-based, coconut shell-based, etc., and there are no particular restrictions on the shape, type, etc. of crushed coal, granulated coal, formed coal, cloth, fiber, etc. The activated carbon filling system for the activated carbon tower may be any of a fluidized bed, an expanded bed, a fixed bed, etc., but a fixed bed is preferred because the outflow of activated carbon is small. The water flow system of the activated carbon tower may be upward circulating water or downward circulating water.

  As shown in FIG. 1, the raw water is adjusted to pH 9.5 or higher and then subjected to RO membrane separation treatment, then the pH is adjusted to 4 to 8, and the activated carbon treatment is performed by adding a chlorine-based disinfectant and / or a slime control agent. By doing this, it is possible to obtain a high-quality treated water from which TOC is highly removed by performing a stable treatment over a long period of time without causing a decrease in flux in the RO membrane separation device and an increase in differential pressure in the activated carbon tower. .

  FIG. 1 shows an example of an embodiment of the present invention, and the present invention is not limited to the illustrated one as long as the gist of the present invention is not exceeded. For example, the process by the RO membrane separation apparatus is not limited to a single stage process, and may be a multistage process with two or more stages. Moreover, in TOC-containing wastewater discharged from electronic device manufacturing factories, there are few cases where calcium ions, etc., which cause scales are basically mixed, but when raw materials contain calcium ions, RO membranes You may install a softening apparatus in the front | former stage of a separation apparatus. Moreover, you may provide the mixing tank for addition of pH adjustment, a chlorine-type disinfectant, and / or a slime control agent.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

Example 1
After adding NaOH as a raw water from an electronic device manufacturing factory wastewater (pH 7.2, TOC 10 mg) containing a nonionic surfactant to make the pH 10.5, RO membrane separator (low pressure aromatic polyamide RO membrane manufactured by Nitto Denko) RO membrane separation treatment was performed under the conditions of “NTR-759”) with a recovery rate of 90%. Adjust the pH to 7 by adding HCl to the RO permeate, then NaClO
After adding 5 mg / L, water was passed through the activated carbon device (activated carbon “KW-10-32” packed column manufactured by Kuraray Chemical Co., Ltd.) at SV10 hr ⁻¹ .

  The changes over time in the flux of the RO membrane separator and the number of viable bacteria in the RO concentrated water at this time were examined, and the results are shown in FIGS. Moreover, the time-dependent change of the differential pressure of the activated carbon tower was examined, and the result is shown in FIG.

  The TOC value at each point is as shown in Table 1.

Comparative Example 1
The treatment was carried out under the same conditions as in Example 1 except that the pH of the RO water supply was set to 7, and changes over time in the membrane flux of the RO membrane separator and the number of viable bacteria in the RO concentrated water are shown in FIGS.

Comparative Example 2
The treatment was performed under the same conditions as in Example 1 except that the pH of the RO water supply was set to 7, and 5 mg / L of the isothiazoline slime control agent ("Kuriverta EC-503" manufactured by Kurita Kogyo Co., Ltd.) was added to the RO water supply. Changes in the membrane flux and viable cell count over time of the RO membrane separator are shown in FIGS.

  As is clear from FIG. 2, in Example 1, no decrease in flux was observed even after the start of water flow for 500 hours, whereas in Comparative Example 1, it was already about half of the initial flux after the start of water flow for 300 hours. Diminished. Moreover, also in the comparative example 2 which added the slime control agent, it fell to about 60% of the initial flux by 300 hours of water flow start.

  From FIG. 3, in Example 1 and Comparative Example 2, no increase in the number of viable bacteria was observed, whereas in Comparative Example 1, the number of viable bacteria increased with an increase in water passage time.

  From the above results, in Comparative Example 1, the flux decreased due to the synergistic effect of the propagation of microorganisms in the RO membrane and the adhesion of the nonionic surfactant to the membrane surface, and in Comparative Example 2, the addition of the slime control agent caused the microbial activity. Even though the propagation can be suppressed, the flux decreases due to the adhesion of the nonionic surfactant to the membrane surface. However, in Example 1 according to the present invention, the propagation of microorganisms in the RO membrane separation apparatus and the nonionic surfactant It is clear that both film surface adhesion can be suppressed simultaneously.

Moreover, as apparent from Table 1, the TOC value that was 0.5 mg / L in the RO permeated water was reduced to about 0.1 mg / L by the activated carbon treatment, and the activated carbon treatment was performed after the RO membrane separation treatment. It can be seen that the TOC value can be further reduced by carrying out the above process.
Examples 2 and 3, Comparative Example 3
The activated carbon tower was treated under the same conditions as in Example 1 except that the pH of the AC feed water was 4 (Example 2), 8 (Example 3), or 8.5 (Comparative Example 3) using HCl. The change over time in the differential pressure was examined, and the results are shown in FIG.

  From FIG. 4, it is clear that the increase in the differential pressure in the activated carbon tower can be suppressed by adjusting the pH of the AC feed water to 4 to 8 and then adding a chlorine-based disinfectant.

  INDUSTRIAL APPLICABILITY The present invention is effectively applied to water treatment for discharging, collecting or reusing wastewater containing high or low concentration TOC discharged in the electronic device manufacturing field, semiconductor manufacturing field, and other various industrial fields.

It is a systematic diagram which shows embodiment of the processing method and processing apparatus of the organic substance containing waste_water | drain of this invention. It is a graph which shows the time-dependent change of the flux of the RO membrane separator in Example 1 and Comparative Examples 1 and 2. It is a graph which shows the time-dependent change of the viable cell count of the RO membrane separation apparatus in Example 1 and Comparative Examples 1 and 2. It is a graph which shows a time-dependent change of the differential pressure | voltage of the activated carbon tower in Examples 1-3 and Comparative Example 3.

Explanation of symbols

1 Tank 2 RO membrane separator 3 Activated carbon device

Claims (6)

A first pH adjusting step of adjusting the pH to 9.5 or higher by adding alkali to the organic matter-containing wastewater;
A membrane separation treatment step of performing reverse osmosis membrane separation treatment on the pH adjusted water obtained in the first pH adjustment step;
A second pH adjusting step of adjusting the pH to 4 to 8 by adding an acid to the permeated water of the membrane separation treatment;
An antibacterial treatment step of adding a chlorine-based disinfectant and / or a slime control agent to the pH-adjusted water obtained in the second pH adjustment step;
A method for treating wastewater containing organic matter, comprising an activated carbon treatment step of treating the antibacterial treated water with activated carbon.   In Claim 1, pH is adjusted to 10-12 in this 1st pH adjustment process, The processing method of the organic substance containing waste_water | drain characterized by the above-mentioned.   3. The method for treating organic matter-containing wastewater according to claim 1, wherein in the sterilization treatment step, 0.1 to 10 mg / L of a chlorine-based disinfectant is added at a residual chlorine concentration.   3. The method for treating organic matter-containing wastewater according to claim 1, wherein 0.5 to 10 mg / L of a slime control agent is added in the sterilization treatment step. First pH adjusting means for adjusting pH to 9.5 or higher by adding alkali to organic matter-containing wastewater;
A reverse osmosis membrane separation apparatus into which the pH adjusted water obtained by the first pH adjusting means is introduced;
A second pH adjusting means for adjusting the pH to 4 to 8 by adding an acid to the permeated water of the reverse osmosis membrane separation device;
Chemical injection means for adding a chlorine-based disinfectant and / or slime control agent to the pH-adjusted water obtained by the second pH adjusting means;
An organic matter-containing wastewater treatment apparatus comprising: an activated carbon apparatus into which water to which a chemical is added by the chemical injection means is introduced.   6. The apparatus for treating organic matter-containing wastewater according to claim 5, wherein the activated carbon apparatus includes an activated carbon packed tower.

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