KR100996283B1 - A porous sulfur-calcium carbonate foam including polymer and method for eliminating nitrate through sulfur-oxidation denitrification using the same - Google Patents

Abstract

The present invention relates to a porous sulfur-calcium carbonate composite carrier using a polymer and a method for removing nitrogen nitrate during sulfur oxidation independent nutrient denitrification using the same, and a porous sulfur-calcium carbonate prepared by mixing a polymer of sulfur, calcium carbonate and a polymer. The composite carrier has many surface pores, a large surface area, and roughness, which facilitates the attachment of microorganisms and has an excellent effect of dissolving sulfur easily without dissolving sulfur at high temperatures. In addition, the porous sulfur-calcium carbonate composite carrier of the present invention has an excellent effect of the removal efficiency of nitrogen nitrate compared to conventional sulfur-calcium carbonate pellets in the autotrophic denitrification process using sulfur.

Porous sulfur-calcium carbonate composite carrier using polymer, autotrophic denitrification, sulfated denitrification, nitrate nitrogen

Description

A porous sulfur-calcium carbonate foam including polymer and method for eliminating nitrate through sulfur-oxidation denitrification using the same}

1 is a photograph taken by scanning electron microscopy (SEM) of the surface of the porous sulfur-CaCO ₃ composite carrier used for the sulfur oxidation autotrophic denitrification reaction, A and B are photographs of the actual matrix, C and D are 100 The SEM photograph is shown magnified 500 times.

Figure 2 shows the removal efficiency of nitrogen nitrate in three kinds of reactors.

Figure 3 shows the change in pH with time of each reactor.

Figure 4 is a sulfur-lime (S + lime granule, 1), sulfur-CaCO ₃ composite carrier (SC foam, 2), sulfur-CaCO ₃ pellets (SC-pellet, 3) of the nitrogen nitrate according to the pH of each The removal efficiency is shown.

The present invention relates to a porous sulfur-calcium carbonate composite carrier using a polymer and a method for removing nitrogen nitrate in a sulfur oxidation independent nutrient denitrification process using the same. More specifically, the present invention is to prepare a porous sulfur-CaCO ₃ composite carrier by adding the high polymer 3000 pre-polymer of the polymer to the sulfur-CaCO ₃ mixture, sulfur oxide independent nutrition using the sulfur-CaCO ₃ composite carrier The present invention relates to a method for removing nitrogen nitrate in the denitrification process.

Recently, as part of tightening regulations on pollutants discharged to public waters, there is a movement to tighten the TN regulation of wastewater discharge limits. TN, when discharged into the water, leads to eutrophication, which not only reduces the availability of river water, but also causes aesthetic problems. However, the regulation of industrial wastewater with various characteristics and flow rates according to industry, product size, and operating conditions of the plant in a batch means that new treatment technology with the regulation value is considered. It is emerging as a deterrent to the effective implementation of policies. The metal plating wastewater discharge industry in industrial wastewater is mostly small, and due to the nature of the chemicals used in the process, the concentration of organic matter is very low, but the concentration of NO ₃ -N is high.

In the heterotrophic denitrification process, which is currently used, in order to treat NO ₃ -N, the carbon source in raw water must be present at 5: 1 (C / N ratio). Since the same organic material must be injected to induce denitrification, there is a disadvantage in that the treatment cost is increased.

On the other hand, a method using autotrophic microorganisms using nitrate nitrogen (NO ₃ -N) as an electron donor while oxidizing sulfur, hydrogen, iron, etc. has recently been highly evaluated for its practicality. Ongoing research on sulfur oxide autotrophic denitrification is being actively conducted. Autotrophic denitrification using sulfur is characterized by the fact that sulfur oxidative denitrification microorganisms oxidize various sulfur compounds into sulfate ions (SO ₄ ^2- ; sulfate) while simultaneously converting nitric acid (NO ₃ -N) to N _{2 (g)} . Use the principle. In other words, Thiobacillus Dinatripicans , a sulfur oxidative denitrifying microorganism denitrificans ) and Thiomicrospira ( Thiomicrospira) denitrificans) different types of sulfur compounds by using a denitrifying bacteria, such as ^{_{(S 0, S 2 O 3}} 2 -, S 4 O 6 2 -, SO 3 2 -) , while the denitration oxidized to a sulfate ion (SO ₄ ^2-) Proceed with the reaction. Since sulfur oxidative denitrification microorganisms are independent nutrient microorganisms, they do not require external carbon sources and can induce denitrification economically and stably without administering methanol to waste water having a low C / N ratio.

However, it is pointed out that in the early stage of operation, it is difficult to dominate and retain autotrophic denitrification bacteria, and when denitrification consumes alkalinity, the pH is lowered, and high concentration denitrification is difficult. In order to solve this problem, a case of using sulfur particles as a carrier was mixed with limestone to supply alkalinity by calcium carbonate contained in limestone and to solve a problem of lowering pH.

The independent nutrient denitrification process using sulfur oxidizing microorganisms can be explained by the following reaction.

_{^{1.06NO 3 - + 1.11S 0 + 0.3HCO}} 3 - + 0.485H 2 O → 0.5N 2 + 1.11SO 4 2 - + 0.86H + + 0.06C 5 H 7 O 2 N (1)

Equation (1) shows that when 1.06 mole of NO ₃ ^- is denitrified to N _{2 (g)} , 0.86 mole of H ⁺ is produced and when 1 g of NO ₃ ^-- N is denitrified, 3.91 g of alkalinity is consumed. . Therefore, if sufficient alkalinity is not supplied, the pH continues to decrease during the autotrophic denitrification process, which affects the sulfur oxidation autotrophic denitrification microorganisms and thus denitrification efficiency.

Koenig et al. Reported that the autotrophic denitrification ability using particulate sulfur and particulate CaCO ₃ as a medium using the above principle prevented the pH drop by limestone (CaCO ₃ ). However, with the particles of CaCO ₃ in the reactor for a long time clogging phenomena and backwash when large amounts of particulate sulfur and limestone (CaCO ₃₎ is a loss resulting in the operation cost increase. Due to the consumption of sulfur, the particle size of sulfur and limestone and CaCO ₃ charged in the reactor dissociate and confine the pores due to the reduction of the particle size. In addition, Ca ₂ ⁺ and SO ₄ ^{2 -} is a bond and the resulting CaSO ₄ is caused to clog the reactor. The blockage causes nitrogen gas from the denitrification process to fill the voids and block the flow of influent.

Therefore, an object of the present invention is to prepare a porous composite sulfur carrier using a polymer to reduce the clogging phenomenon by the particle size reduction of the existing particulate sulfur and increase the adhesion of microorganisms for autotrophic denitrification using sulfur without injection of a separate carbon source. do.

Another object of the present invention is to remove nitrogen nitrate effectively in the sulfur oxidation independent nutrient denitrification process using the porous composite sulfur carrier.

The object of the present invention is to prepare a porous composite carrier using sulfur, calcium carbonate and polymer polymer, and to investigate the removal rate of nitrate nitrogen compared with the conventional carrier, and denitrification in the sulfur oxide autotrophic denitrification process This was achieved by examining the pH change during this time.

The present invention comprises a step of producing a porous composite carrier using sulfur, calcium carbonate and a polymer polymer and the step of examining the removal ability of the nitrate nitrogen of the composite carrier.

One feature of the present invention is to mix sulfur and calcium carbonate in a weight ratio of 5: 4 (w / w), and to the mixture is a 2: 1 (w / w) Hypol 3000 pre-polymer It is characterized by providing a method for producing a porous sulfur-calcium carbonate composite carrier, characterized in that by mixing in a weight ratio of.

The porous sulfur-calcium carbonate composite carrier has the following excellent effects in removing nitrogen nitrate in the sulfur oxidation independent nutrient denitrification process:

First, when the porous sulfur-calcium carbonate composite carrier is filled in the autotrophic denitrification process using sulfur, the denitrification efficiency is high. This is because the porous sulfur-calcium carbonate composite carrier prepared using the polymer has a large surface porosity, so that the surface area is wide and the roughness facilitates the attachment of microorganisms and the sulfur is easily dissolved.

Second, the porous sulfur-calcium carbonate composite carrier in the autotrophic denitrification process has better removal efficiency of nitrate nitrogen than conventional SC pellets.

Third, the porous sulfur-calcium carbonate composite carrier showed almost 100% nitrogen nitrate removal rate at 24h HRT and 18h HRT, and the removal rate was more than 98% after system stabilization at 12h HRT.

Fourth, the porous sulfur-calcium carbonate composite carrier is less economical in manufacturing, and does not need to dissolve sulfur at high temperatures, it is economical.

Fifth, pH correction and alkalinity supply are effectively performed by calcium carbonate contained in the porous sulfur-calcium carbonate composite carrier.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are only for illustrating the present invention in more detail, it will be apparent to those skilled in the art that the scope of the present invention is not limited to these examples.

[Example]

Example  1: sulfur-calcium carbonate Complex  Produce

Sulfur (99.9% purity) and calcium carbonate powder used to prepare the porous sulfur-calcium carbonate composite carrier (SC-foam) were made from Midas Company and Enbiomax Company, and the Hypol 3000 pre-polymer ( Hypol 3000 pre-polymer) used the product of Dow Chemical Company.

First, sulfur and calcium carbonate (CaCO ₃ ) were mixed at a weight ratio of 5: 4 (W / W), and the high-poly 3000 pre-polymer, which was a polymer melted at 55 ° C. for 2 hours or more, with a weight ratio of 2: 1. After mixing and drying at a ratio of (W / W), the carrier was cut to 3 ~ 5mm. In the present SC-pellet manufacturing process, sulfur must be melted at a high temperature of 120 ° C. or higher in order to mix sulfur and calcium carbonate. However, in the present embodiment, sulfur and powdered sulfur are mixed in a high-pol 3000 pre-polymer preheated at 55 ° C. The calcium carbonate was sufficiently mixed and dried to prepare a porous sulfur-CaCO ₃ composite carrier.

In order to remove the unreacted polymer during the preparation of the carrier, the dried porous sulfur-CaCO ₃ carrier was immersed in tap water for about 15 minutes and this process was repeated three times. Since then porous sulfur-CaCO ₃ The carrier was placed in a dry oven at 60 ° C. and dried for about 3 days.

Porous composite sulfur-CaCO ₃ prepared using sulfur, calcium carbonate and polymer Sulfur in the carrier acts as a substrate for denitrification of sulfated microorganisms as shown in Scheme (1) above, and calcium carbonate adheres to the porous carrier by supplementing the alkalinity which decreases as denitrification proceeds, as shown in Scheme (2) below. It was used as a substance to be added to create a condition of pH 6-8 where microorganisms could be denitrified smoothly.

_{^{CaCO 3 + H + → Ca 2}} + + HCO 3 - (2)

Figure 1 shows a photograph of the surface of the porous sulfur-CaCO ₃ composite carrier used in the sulfur oxidation autotrophic denitrification by SEM (Scanning Electron Microscophy). Sulfur and SC-pellets have a smooth surface and few voids. However, in the case of the sulfur-calcium carbonate composite carrier (SC-foam), there were many voids and the surface was rough. In other words, the polymer used in the preparation of the composite carrier broadened the surface area and the roughness was also found to be converted to a good condition for the attachment of microorganisms.

Example  2: porous sulfur-calcium carbonate Complex carrier  Sulfur Oxidation Independent Nutritional Denitrification Removability  Research

In order to investigate the denitrification ability of the porous sulfur-calcium carbonate composite carrier prepared in Example 1, the removal rate of nitrogen nitrate according to the type of carrier and the pH change according to the reaction time were examined.

Experimental Example  One: carrier  By type Nitrate  Removal rate

Sulfur oxidation autotrophic denitrification microorganisms used to investigate the removal rate of nitrate nitrogen according to the carrier type were Thiobacillus denitrificans ) was cultured as follows using a culture medium. Activated Sludge and Thiobacillus Dinatripicans in Y Sewage Treatment Plant denitrificans ) A medium for the culture _{(2g / L Na 2 S 2} O 3 .5H 2 O, 2g / L KNO 3, 2g / LK 2 HPO 4, 0.5g / L NH 4 Cl, 0.5g MgCL 2 · 6H 2 O, 0.01 FESO ₄ 7H ₂ O, 1 g / L NaHCO ₃ And 40 ml of mineral solution (0.5 g / L EDTA, 0.0554 g / L CaCl ₂ , 0.0157 g / L CuSO ₄ · 5H ₂ O, 0.0161 g / L CoCl ₂ · 6H ₂ O, g / L 0.0506 MnCL ₂ · 4H ₂ O, consisting of 0.22 g / L ZnSO ₄ · 7H ₂ O and 0.0499 g / L FeSO ₄ · 7H ₂ O), were mixed in a 20 L tank and incubated at 28 ° C. by adding 277 mg / L of nitrate nitrogen. After that, when the concentration of NO ₃ -N was less than 10 mg / L, the supernatant was discarded and a new Thiobacillus denitrificans ) Culture medium and nitrate nitrogen concentration 500mg / L was added. When the nitrate nitrogen concentration was less than 10mg / L, the sludge was put in a column and incubated at room temperature and used for continuous experiments.

For continuous experiments, three columns having a bed volume of 2.1 L each contained a porous sulfur-CaCO ₃ carrier, particulate sulfur and limestone, and a carrier of SC-pellet, respectively. At this time, the bulk solution (bulk solution) in consideration of the expansion when the carrier was absorbed in the net mesh (net mesh) at the top of the column was allowed about 1 inch. Each column was infused with 1 L of sludge cultured with sulfur oxidative autotrophic denitrification microorganisms and artificial wastewater purged with nitrogen gas for 1 hour (Table 1). The carrier constituents of each reactor are shown in Table 2.

The temperature during the experiment was set to 20-25 ° C., and the water quality was analyzed by collecting samples 100 ml at intervals of 24 hours while maintaining the same conditions. HRT (Hydraulic retention time) experiments were gradually reduced from 24 hours to 18 hours and 12 hours while monitoring the denitrification performance.

Water quality analysis items were pH, alkalinity, NO ₃ -N, NO ₂ -N, and ammonia. NO ₃ -N, NO ₂ -N, and ammonia were used by Bran + Luebbe Automatic Analyzer 3, and pH was measured using Thermo Orion pH meter. Used. The alkalinity was analyzed according to the Standard Methods for the Examination of Water and Wastewater (APHA, 1995). The removal rate of NO ₃ -N over time is shown in FIG. 2.

Composition of Artificial Wastewater Artificial wastewater Mineral solution KNO ₃ 0.721-1.26 g EDTA 0.5 g K ₂ HPO ₄ 0.2 g CaCl ₂ 0.0554 g NH ₄ Cl 0.06 ml CuSO ₄ .5H ₂ O 0.0157 g MgCl. ₆ H ₂ O 2.5 ml CoCl ₂ .6H ₂ O 0.0161 g FeSO ₄ .7H ₂ O 2.5 ml MnCl ₂ .4H ₂ O 0.0506 g NaHCO ₃ 10 ml ZnSO ₄ .7H ₂ O 0.22 g Mineral solution 10 ml FeSO ₄ .7H ₂ O 0.0499g DI 974.94 ml DI 1000 ml Adjust pH to 7.5 with 1N HCl. Adjust pH to 6.0 with 1M KOH.

Carrier Components of Each Reactor Reactor Badge type SC ratio Powder: Polymer Ratio Matrix size R1 Sulfur + Limestone (Particulate) 3: 1 - 3-5mm R2 SC-composite 5: 4 2: 1 3-5mm R3 SC-pellets - - 3-10mm

As shown in Figure 2, at 24 hours and 18 hours of HRT, nitric nitrate (50-175 mg / L) was removed almost 100% in all three columns. After the reduction of HRT to 12 hours, the removal rate of 175 mg / L of nitrogenous nitrate was unstable during the initial acclimation period of about 20 days, but the removal rate of nitrogenous nitrogen of porous sulfur-CaCO ₃ composite carrier was almost 98%. This is almost the same as the column with particulate sulfur and limestone. On the other hand, in the case of SC-pellets, the removal rate of nitrogen nitrate was 85% or less after 20 days, which was about 15-25% lower than that of the porous sulfur-CaCO ₃ composite carrier.

Therefore, the denitrification performance was almost similar to that of sulfur-limestone, which was already used, and showed higher denitrification performance than SC-pellets.

Experimental Example  2: depending on the reaction time pH Change

In sulfur-independent nutrient denitrification, H ³ is generated as NO ₃ ⁻ becomes N _{2 (g)} during denitrification. The production of H ⁺ decreases the pH and lowers the denitrification ability. The optimum pH of sulfur oxidizing microorganisms in autotrophic denitrification using sulfur is 6.8-8.2, and the denitrification limit pH of sulfur oxidizing microorganisms is generally known as 6.2. Therefore, the change of pH with time of each reactor was investigated.

As shown in FIG. 3, the pH of each reactor during the experiment was considered to have no effect on the denitrification efficiency in the range of 6.3 to 8.5. This is generated as a fill CaCO ₃ haeri HCO ₃ ^- can be combined with the generated from denitrification by H ⁺ seen as a correction because pH ^-, CO ₃ ^2. In particular, when the pH was 7 or more, a high removal rate of nitric nitrate (NO ₃ -N) was observed.

In addition, as shown in Figure 4, it can be seen that the SC-pellets exhibit a higher frequency at pH7 or less than in the case of porous sulfur-CaCO ₃ composite carrier or particulate sulfur + limestone. This confirmed that the SC-pellets have a lower denitrification rate than the other reactors. In the case of SC-pellets, the amount of calcium carbonate mixed with sulfur is eluted in a short time.

As described in the above Examples and Experimental Examples, the present invention relates to a porous sulfur-calcium carbonate composite carrier using a polymer and a method for removing nitrogen nitrate in a sulfur oxidation independent nutrient denitrification process using the same. Porous sulfur-calcium carbonate composite carriers prepared by mixing polymers have excellent surface pores, a large surface area, and roughness to facilitate the attachment of microorganisms and to easily dissolve sulfur without having to dissolve sulfur at high temperatures. In addition, the porous sulfur-calcium carbonate composite carrier of the present invention has an excellent effect of the removal efficiency of nitrogen nitrate compared to conventional sulfur-calcium carbonate pellets in the autotrophic denitrification process using sulfur. Therefore, the present invention is a very useful invention in the wastewater treatment industry.

Claims (3)

In preparing a composite carrier of sulfur and calcium carbonate, Preparing a mixture of sulfur and calcium carbonate (CaCO ₃ ) by mixing sulfur and calcium carbonate (CaCO ₃ ) in a weight ratio of 5: 4 (W / W); Dissolving the Hypol 3000 pre-polymer at 55 ° C. for at least 2 hours; Preparing a porous sulfur-calcium carbonate composite carrier by mixing the sulfur and calcium carbonate (CaCO ₃ ) mixture with a Hypo 3000 pre-polymer in a weight ratio of 2: 1 (W / W); Immersing the dried porous sulfur-carbonate composite carrier in running water to remove unreacted polymer; And Drying the porous sulfur-calcium carbonate composite carrier from which unreacted polymer is removed in a dry oven Method for producing a porous sulfur-calcium carbonate composite carrier, characterized in that carried out continuously. A porous sulfur-calcium carbonate composite carrier prepared by the method of claim 1. The method of removing nitrogen nitrate in the sulfur oxidation independent nutrient denitrification process using the porous sulfur-calcium carbonate composite carrier according to claim 2.

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