JP6000651B2 - Method for treating wastewater containing sulfur and selenium - Google Patents

Description

  The present invention relates to a method for treating wastewater containing sulfur and selenium, and particularly obtained by extracting a part of combustion gas from a kiln exhaust gas passage from a kiln bottom of a cement kiln to a lowermost cyclone. The present invention relates to a method for separating and removing sulfur and selenium from wastewater generated when chlorine bypass dust or the like is washed with water.

Conventionally, for removing selenium contained in waste water, for example, a method of performing a coagulation precipitation process using ferrous chloride (FeCl ₂ ) as a reducing agent is known.

  Further, Patent Document 1 discloses a method in which an adsorbent containing a rare earth compound and wastewater containing selenium are brought into contact without performing pretreatment such as pH adjustment, and selenium in the wastewater is adsorbed and removed by a simple process. Proposed.

JP 2007-326077 A

  However, in the method of coagulating and precipitating using ferrous chloride as the reducing agent, a large amount of ferrous chloride as the reducing agent is consumed to remove the selenium concentration in the wastewater to a safe level. There was a problem that the operating cost would rise.

  On the other hand, the method for treating selenium-containing water described in Patent Document 1 has the advantage that pretreatment such as pH adjustment is unnecessary and can be treated in a simple process, but there is room for improvement in terms of the selenium removal rate. . Moreover, the removal of the sulfur content was not considered.

  Therefore, the present invention has been made in view of the problems in the above-described conventional technology, and an object thereof is to efficiently separate and remove sulfur and selenium from wastewater containing sulfur and selenium at low cost. And

In order to achieve the above object, the present invention is a method for treating waste water containing sulfur and selenium, comprising adding a pH adjuster to waste water containing sulfur and selenium, and adjusting the pH of the waste water to 1.0. above a first pH adjustment step of adjusting to less than 7.0, the contacting the effluent with sulfur content adsorbent pH adjustment in the first pH adjustment step, the sulfur adsorbing sulfur of the exhaust water a sulfur adsorption step Ru adsorbed on agents and adding a pH adjusting agent to the wastewater after the sulfur component adsorbed, and the second pH adjustment step of adjusting the pH of the drainage below 1.0 to 4.5, contacting the waste water with selenium adsorbent pH adjusted with the second pH adjustment step, characterized in that the selenium exhaust water and a selenium adsorption step of Ru adsorbed on the selenium adsorbent.

  And according to this invention, since wastewater can be processed by two-stage pH adjustment and a sulfur content and selenium adsorption | suction process, a sulfur content and selenium can be isolate | separated and removed at low cost.

  In the wastewater treatment method, the slurry obtained in the sulfur content adsorption step is subjected to solid-liquid separation to obtain a solid content containing sulfur and a liquid content containing selenium, and a liquid containing the selenium. A pH adjusting step of adding a pH adjusting agent to the minute and adjusting the pH to 1.0 or more and less than 4.5, and a selenium adsorption step of bringing the pH adjusted liquid component into contact with the selenium adsorbent.

  In the wastewater treatment method, the wastewater containing sulfur and selenium may contain chlorine, and the chlorine may be included in the wastewater after selenium adsorption. For example, it is attached to a cement firing device. The present invention can also be applied to wastewater containing chlorine, such as wastewater generated when washed chlorine bypass dust, etc., and the treated wastewater contains chlorine. Thus, it is possible to avoid chlorine returning to the cement manufacturing process.

  In the wastewater treatment method, the sulfur adsorbent is selected from the group consisting of allophane, imogolite, kaolinite, bentonite, hydrotalcite, halloysite, smectite, vermiculite, sepiolite, palygorskite, mica, chlorite, zeolite and humus. One or more inorganic adsorbents can be included.

  The inorganic adsorbent can be supported on a porous inorganic material or organic material and used as the sulfur adsorbent.

  The selenium adsorbent may contain one or more materials selected from the group consisting of oxides of yttrium, lanthanum, cerium or ytterbium, hydroxides, and materials having a methylglucamine group. it can.

  Further, the material can be supported on a porous inorganic material or organic material and used as the selenium adsorbent.

  As described above, according to the present invention, sulfur and selenium can be separated and removed efficiently from wastewater containing sulfur and selenium at low cost.

BRIEF DESCRIPTION OF THE DRAWINGS It is a whole block diagram which shows an example of the system which implements the processing method of the waste_water | drain containing the sulfur content and selenium concerning this invention. It is a whole block diagram which shows the other example of the system which enforces the processing method of the waste_water | drain containing the sulfur content and selenium concerning this invention.

  Next, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows an example of a wastewater treatment system for carrying out a method for treating wastewater containing sulfur and selenium according to the present invention. This wastewater treatment system 1 is a pH adjuster for wastewater W1 containing sulfur and selenium. A first pH adjusting tank 2 for adjusting pH by adding A1, and a sulfur adsorbent such as clay mineral C added to the waste water W2 discharged from the first pH adjusting tank 2 to be contained in the waste water W2. Sulfur content adsorption tank 3 that adsorbs sulfur content (sulfate radical), solid-liquid separator 4 that solid-liquid separates slurry S discharged from sulfur content adsorption tank 3, heavy metal contained in separated liquid content L1, etc. From the first resin 5 that adsorbs the liquid, the second pH adjusting tank 6 that adjusts the pH by adding the pH adjusting agent A2 to the liquid L2 from the first resin 5, and the second pH adjusting tank 6 And the second resin 7 that adsorbs selenium contained in the liquid component L3.

  The first resin 5 is provided to remove heavy metals such as lead, zinc, cadmium and the like contained in the liquid L1, and a chelate resin, an amphoteric ion exchange resin, or the like can be used. In the previous stage of the first resin 5, a pH adjusting tank for setting the liquid content L <b> 1 to a pH suitable for adsorption of heavy metals or the like by the first resin 5 can be provided.

  The second resin 7 carries a rare earth compound, in particular, one or more rare earth compounds selected from oxides or hydroxides of yttrium, lanthanum, cerium, or ytterbium, and the like. Tetravalent and hexavalent selenium can be effectively adsorbed and removed, and even when tetravalent selenium and hexavalent selenium coexist in the wastewater, the pH of the wastewater is only adjusted to 1 or more and less than 4.5 This makes it possible to remove selenium. The rare earth compounds used as the selenium adsorbent are preferably those listed above, but are not limited thereto.

  Next, a wastewater treatment method according to the present invention using the wastewater treatment system 1 will be described with reference to FIG.

  First, the wastewater W1 containing sulfur and selenium and the pH adjuster A1 are added to the first pH adjusting tank 2 and mixed to adjust the pH to 1.0 or more and less than 7.0. This pH adjustment is performed to lower the surface charge of clay mineral C, which will be described later, and to easily adsorb anions by lowering the pH.

  Next, clay mineral C is added as a sulfur content adsorbent to the wastewater W2 discharged from the first pH adjustment tank 2 to adsorb the sulfur content contained in the wastewater W2. Here, as the clay mineral C, allophane, imogolite, kaolinite, bentonite, hydrotalcite, halloysite, smectite, vermiculite, sepiolite, palygorskite, etc. can be used, and besides the clay mineral C, mica, chlorite Zeolite, humus, etc. can also be used. These 1 type may be used independently and 2 or more types may be used simultaneously.

  Next, the slurry S discharged from the sulfur content adsorption tank 3 is solid-liquid separated by the solid-liquid separator 4 to remove the cake CA containing the sulfur content, and the heavy metals contained in the separated liquid L1 are first removed. 1 is removed by adsorption.

  In the second pH adjusting tank 6, the pH adjusting agent A2 is added to the liquid L2 from the first resin 5 to adjust the pH to 1.0 or more and less than 4.5. This pH adjustment is performed so that the liquid content L1 becomes a pH suitable for the adsorption of selenium by the second resin 7.

  Next, selenium contained in the liquid L3 from the second pH adjustment tank 6 is adsorbed and removed by the second resin 7, and the L4 discharged from the second resin 7 is discharged to the ocean or the like.

  Next, another example of the wastewater treatment system for carrying out the method for treating wastewater containing sulfur and selenium according to the present invention will be described with reference to FIG.

  This waste water treatment system 11 includes a first pH adjustment tank 12 for adjusting pH by adding a pH adjuster A1 to waste water W1 containing sulfur and selenium, and waste water discharged from the first pH adjustment tank 12. A sulfur adsorption column 13 that adsorbs sulfur contained in the waste water W2 by adding clay mineral C or the like to W2, and a first resin that adsorbs heavy metals contained in the waste water W3 discharged from the sulfur adsorption column 13 15, selenium contained in the second pH adjustment tank 16 that adjusts the pH by adding the pH adjuster A2 to the wastewater W4 from the first resin 15, and the drainage W5 from the second pH adjustment tank 16 It is comprised with the 2nd resin 17 to adsorb | suck.

  The present system 11 is characterized in that a sulfur content adsorption column 13 is used in place of the sulfur content adsorption tank 3 and the solid-liquid separator 4 of the system 1 shown in FIG. It is common in.

  The sulfur content adsorption column 13 is a column in which clay mineral C or the like is packed as a sulfur content adsorbent, and the same mineral as the sulfur content adsorption tank 3 can be used.

  In the waste water treatment system 11, since the sulfur content contained in the waste water W2 is adsorbed by the sulfur content adsorption column 13 and remains in the sulfur content adsorption column 13, the waste water W3 discharged from the sulfur content adsorption column 13 is solid-liquid separated. Without being supplied to the first resin 15 as it is. Subsequent processes are the same as those of the system 1. When the amount of sulfur adsorbed on the sulfur content adsorption column 13 exceeds a predetermined value, the sulfur content is discharged from the sulfur content adsorption column 13 together with the clay mineral C or the like, and newly replenished with the clay mineral C or the like. .

  Next, a test example of the wastewater treatment method according to the present invention will be described.

  First, examples will be described. As Example 1, water 3 was added to the chlorine bypass dust 1 discharged from the cement manufacturing process, mixed and filtered, and a chlorine bypass dust washing waste water was obtained.

  After adding HCl to a beaker containing 200 g of chlorine bypass dust washing waste water and adjusting the pH to 4, 66.6 g of soil containing allophane as a sulfur adsorbent is added, and HCl is appropriately added to adjust the pH. The mixture was stirred for 30 minutes while maintaining 4 and the slurry was filtered.

  Further, 100 g of the above liquid was taken into another beaker, and HCl was added to adjust the pH to 4. A resin carrying 0.76 g of a cerium hydroxide reagent as a selenium adsorbent was added thereto and stirred for 30 minutes. .

  As Example 2, Example 1 except that the pH before and after the addition of allophane-containing soil is maintained at 3 and that the pH is adjusted to 4 by adding NaOH to the liquid when adsorbing selenium. The same method was used.

  As a comparative example, chlorine bypass dust washed waste water was obtained in the same manner as in Example 1, 100 g of this waste water was taken into a beaker, and HCl was added to adjust the pH to 4. A resin carrying 0.76 g of cerium hydroxide reagent was added thereto and stirred for 30 minutes.

  The test results are shown in Table 1. As shown in the table, it can be seen that in the example, sulfur and selenium can be separated and removed with higher efficiency than in the comparative example.

  In the above description of the embodiment and examples, the case where the present invention is applied to a cement manufacturing process has been described. However, the present invention contains sulfur and selenium even in processes other than the cement manufacturing process. It can be applied to drainage.

DESCRIPTION OF SYMBOLS 1 Waste water treatment system 2 1st pH adjustment tank 3 Sulfur content adsorption tank 4 Solid-liquid separator 5 1st resin 6 2nd pH adjustment tank 7 2nd resin 11 Waste water treatment system 12 1st pH adjustment tank 13 Sulfur content adsorption column 15 1st resin 16 2nd pH adjustment tank 17 2nd resin

Claims (7)

Adding a pH adjusting agent to the wastewater containing sulfur and selenium, and the first pH-adjusting step of adjusting the pH of the drainage below 1.0 to 7.0,
A sulfur adsorption process is brought into contact with the waste water and sulfur content adsorbent pH adjustment, Ru adsorbed sulfur of the exhaust water in the sulfur sorbent in said first pH adjustment step,
A second pH adjusting step of adding a pH adjuster to the waste water after adsorption of sulfur, and adjusting the pH of the waste water to 1.0 or more and less than 4.5;
Contacting the waste water with selenium adsorbent pH adjusted with the second pH adjustment step, sulfur and characterized in that it comprises a selenium adsorption step of Ru adsorbed selenium exhaust water to the selenium adsorbent A method for treating wastewater containing selenium. Solid-liquid separation of the slurry obtained in the sulfur content adsorption step, to obtain a solid content containing sulfur content and a liquid content containing selenium,
A pH adjusting step of adding a pH adjusting agent to the liquid containing selenium and adjusting the pH to 1.0 or more and less than 4.5;
The method for treating wastewater containing sulfur and selenium according to claim 1, further comprising a selenium adsorption step in which the pH-adjusted liquid is brought into contact with a selenium adsorbent.   The treatment of wastewater containing sulfur and selenium according to claim 1 or 2, wherein the wastewater containing sulfur and selenium contains chlorine, and the chlorine is contained in the wastewater after adsorption of selenium. Method.   The sulfur adsorbent is one or two selected from the group consisting of allophane, imogolite, kaolinite, bentonite, hydrotalcite, halloysite, smectite, vermiculite, sepiolite, palygorskite, mica, chlorite, zeolite and humus. The processing method of the waste_water | drain containing the sulfur content and selenium of Claim 1, 2, or 3 characterized by including the above inorganic adsorption agent.   The method for treating waste water containing sulfur and selenium according to claim 4, wherein the inorganic adsorbent is supported on a porous inorganic material or organic material and used as the sulfur adsorbent. The selenium adsorbent includes one or more materials selected from the group consisting of oxides of yttrium, lanthanum, cerium or ytterbium, hydroxides, and materials having a methylglucamine group. The processing method of the waste_water | drain containing the sulfur content and selenium in any one of Claim 1 thru | or 4.   The method for treating wastewater containing sulfur and selenium according to claim 6, wherein the raw material is supported on a porous inorganic material or organic material and used as the selenium adsorbent.

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