JP4203576B2 - Treatment method for boron-containing wastewater - Google Patents

Description

  The present invention relates to a wastewater treatment method, and more particularly to a method for treating wastewater containing boron.

  For example, wastewater discharged from various facilities such as sewage effluent from garbage incineration plants, semiconductor manufacturing factories, pharmaceutical manufacturing factories, etc., contains boron compounds such as boric acid and nitrogen compounds such as ammonia. Yes. For this reason, various treatments have been applied to such wastewater in order to satisfy environmental standards.

  In order to treat such wastewater containing boron, Japanese Patent Application Laid-Open No. 10-225682 discloses a method for removing boron as an insoluble precipitate with slaked lime or aluminum sulfate. Japanese Patent Application Laid-Open No. 2003-112917 discloses a method of adsorbing and removing a boron compound with a boron adsorption resin.

JP-A-10-225682 JP 2003-1112917 A

  However, when slaked lime or aluminum sulfate is added, it is considered that a large amount of chemicals must be used to treat high-concentration boron-containing wastewater. Similarly, when a high concentration boron-containing wastewater is treated using a boron adsorbing resin, a large amount of adsorbing resin is required, and there is a concern about an increase in processing cost.

  Accordingly, an object of the present invention is to treat boron-containing wastewater by a low-cost and simple method.

According to the present invention, it is any one of incineration ash generated when incineration of industrial waste or general waste in an incinerator, combustion debris, soot that has been made harmless, sludge discharged from wastewater treatment, and press cake. In a state where boron-containing wastewater is mixed with the landfill, and boron-containing wastewater is mixed with the landfill, it is maintained alkaline, and at least one of boron content, BOD, COD, or nitrogen content of the boron-containing wastewater is obtained. Provided is a method for treating boron-containing wastewater, characterized in that it is reduced.

  By mixing boron-containing wastewater into landfills such as incineration ash generated in incinerators and sludge generated in wastewater treatment, the landfill plays the same role as ion-adsorbing resin, and boric acid contained in the wastewater. It is possible to improve the water quality by adsorbing and removing boron compounds and nitrogen compounds such as ammonia and lowering BOD and COD in water.

  In the present invention, the landfill is exemplified by incineration ash generated when incineration of industrial waste or general waste in an incinerator, dust, debris that has been detoxified (insolubilized), and the like. In addition, sludge discharged from wastewater treatment, press cake, etc. are also included in the landfill. Landfill means an object that can be landfilled at the final disposal site. That is, in the present invention, the landfill is an industrial waste or general waste that is incinerated, etc., so that it can be landfilled as it is at the first disposal as it is, and no heavy metals are required. Etc.) are detoxified. The components of the landfill are miscellaneous and cannot be specified, but the landfill includes ferrous and non-ferrous metals, their oxides, and those with other components attached to the surface of the oxide. The landfill is usually composed mainly of Ca, Al, Fe, and Si. The landfill includes carbides other than metals.

  Boron-containing wastewater is wastewater containing boric acid, other boron compounds, and boron ions. Boron-containing wastewater includes wastewater discharged from various facilities such as smoke-washing wastewater from garbage incineration plants, semiconductor manufacturing plants, pharmaceutical manufacturing plants, and the like. Boron-containing wastewater also includes wastewater at the disposal site that is generated when rainwater is supplied to various wastes stored at the disposal site.

  When mixing boron-containing wastewater into landfills, for example, by adding landfills into pits that were enforced so that water does not leak out, adding boron-containing wastewater, and mixing them, the added boron-containing wastewater However, it should be ensured that it does not flow out of the landfill storage system. Boron-containing wastewater may be added by sprinkling boron-containing wastewater from above the landfill, or by supplying a feed pipe or the like inside the landfill and supplying boron-containing wastewater into the landfill.

  The amount of boron-containing wastewater added to the landfill is determined by the boron concentration of the boron-containing wastewater and the boron adsorption capacity of the landfill. Since these are not constant, it is preferable that the amount of boron-containing wastewater added to the landfill is appropriately set according to the boron concentration of the boron-containing wastewater used and the boron adsorption capacity of the landfill used.

  In this way, the amount of boron-containing wastewater added to landfills should be determined individually by the boron concentration of the boron-containing wastewater used and the boron adsorption capacity of the landfill used. It is preferable to add about 0.1 to 50 wt% of boron-containing wastewater with respect to the weight. This is because if the amount of boron-containing wastewater exceeds 50 wt%, the landfill will be slurried and the landfill will easily flow out.

  In a state where boron-containing wastewater is mixed with the landfill, it is preferably maintained alkaline. If it is acidic, there is a risk of dissolving the metal contained in the landfill. In order to adsorb boron to the landfill, it is preferably alkaline.

Example 1
Three types of boron-containing wastewater with boron concentrations of 13 mg / liter, 23 mg / liter, and 63 mg / liter were prepared. 500 ml of each boron-containing wastewater was added to 50 g of landfill obtained by incineration of industrial waste and stirred. The stirring time was 10, 30, and 60 minutes. After stirring, the mixture was filtered and separated into a filtrate and a residue. The boron content in this filtrate was measured, and the boron adsorption capacity of the landfill was confirmed by the reduction.

  The results are shown in Table 1. Even if the initial boron concentration was 63 (mg / liter), the removal rate was as high as 79%, and the time was sufficiently effective from 10 minutes. The removal rate is 58% even when the boron concentration is 13 (mg / liter), which is relatively low, and it can be seen that there is sufficient adsorption capacity even at a low concentration. Boron removal rate (%) = (initial boron concentration (mg / liter) −boron concentration after stirring (mg / liter)) / (initial boron concentration (mg / liter)) is expressed in percentage. Further, boron adsorption amount = initial boron concentration (mg / liter) −value obtained by the boron concentration after stirring (mg / liter).

(Example 2)
As shown in FIG. 1, 500 g of landfill 2 obtained by incineration of industrial waste was packed in a water flow column 1. Boron-containing waste water pumped out from the tank 3 was fed by a pump 4 and sprayed onto the landfill 2 from above the water flow column 1. Further, the boron-containing wastewater that flows out below the water flow column 1 is received by the container 5, and sprayed onto the landfill 2 again from above the water flow column 1 together with the boron-containing wastewater in the tank 3. . Thus, the boron-containing waste water was continuously passed through the landfill 2 obtained in the water flow column 1 at a flow rate of 20 ml / min. The water passing time was 30 minutes and the adsorption capacity was confirmed. The water flow was adjusted to two levels of pH 7 and 10. Boron-containing wastewater was tested using three types of liquids.

  The results are shown in Tables 2 and 3. In both cases of pH 7 and 10, boron could be removed by the landfill. However, when compared at the same initial boron concentration, it was found that the removal rate of boron was higher at pH 10 and the boron removal ability was improved at higher pH. It was also found that the boron removal ability improved with higher pH for ammoniacal nitrogen. However, with regard to COD and BOD, the lower the pH, the higher the removal rate.

(Example 3)
The sustainability of boron removal ability by landfill was confirmed. In the same manner as in Example 2, 500 g of a landfill was prepared, and this was put into a water flow column having a volume of about 500 ml, and the boron-containing wastewater was continuously passed through the landfill at a flow rate of 20 ml / min. Water was passed through the column. The passage time (number of days) was set to 6 days, and changes in boron removal ability were examined every day. The initial boron concentration of the boron-containing wastewater is 13 (mg / liter), and the initial COD is 52 (mg / liter). The boron-containing wastewater was extracted after passing water, and new boron-containing wastewater was continuously passed through the same landfill. This operation was performed for a total of 6 days (total 144 hours).

  The results are shown in Table 4. From this result, it was found that boron adsorption lasts for a long time in landfills. On the other hand, the removal rate on the first day was the largest for COD.

  The present invention is not limited to the treatment of smoke effluent from incinerators, incinerator ash and debris generated when incinerators are used to incinerate various effluents containing boron, such as flue gas desulfurization effluent from coal-fired power plants. It can be applied to the detoxification process using landfills such as dedusted (insolubilized) soot, sludge discharged from wastewater, and press cake.

It is explanatory drawing of Example 2, 3. FIG.

Claims (1)

Boron-containing wastewater in landfills that are either incineration ash, incinerators, debris that has been detoxified, sludge discharged by wastewater treatment, or press cake generated when incineration of industrial or general waste in an incinerator In a state where boron-containing wastewater is mixed with the landfill, the alkali is maintained and at least one of boron content, BOD, COD, or nitrogen content of the boron-containing wastewater is reduced. A method for treating wastewater containing boron.

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