KR20200068814A - Porous sulfur media for removing nitrogen - Google Patents

Abstract

The present invention relates to a sulfur carrier for removing nitrate nitrogen in sewage and wastewater, a manufacturing method thereof, a denitrification reactor comprising the same, and a method for treating sewage or wastewater using the same. More specifically, the present invention relates to a sulfur denitrification carrier having a new structure capable of removing nitrate nitrogen present in sewage and wastewater with high efficiency by using the same in an existing biological treatment process or a post-treatment process, to a manufacturing method thereof, and to an application thereof.

Description

Sulfur support for removing nitrogen {Porous sulfur media for removing nitrogen}

The present invention relates to a sulfur carrier for removing nitrate nitrogen in sewage and waste water, a method for manufacturing the same, a denitrification reactor including the same, and a method for treating sewage or wastewater using the same.

More specifically, the present invention relates to a sulfur denitrification carrier having a new structure capable of removing nitrate nitrogen present in sewage and wastewater with high efficiency by using it in an existing biological treatment process or a post-treatment process, a method for manufacturing the same, and a use thereof will be.

Recently, due to the increase of the population and rapid development of the industry, environmental pollution is rapidly progressing, and the damage to the water environment is intensifying. Moreover, nutrients such as nitrogen and phosphorus are introduced into water resources such as rivers and lakes, causing eutrophication. Due to eutrophication, destruction of aquatic ecosystems, such as the death of fish and shellfish, or an increase in water treatment costs are caused. In particular, when nitrogen nitrate is present in drinking water at a high concentration, cyanosis may occur in infants.

As a countermeasure against this, the government revised its environmental policy to control the source of nitrogen pollution in water. In order to prevent water pollution in public waters such as rivers and lakes and to promote water conservation, in 1994, total nitrogen and total phosphorus were added to the effluent water quality standards in 2013. After that, the standard of nitrogen was strengthened to 20 mg/L.

In general, various advanced treatment methods for removing nitrogen contained in sewage/wastewater have been developed. Typical methods include biological advanced treatment methods such as Modified Ludzack-Ettinger (MLE), A2O, University of Cape Town (UCT), Modified University of Cape Town (MUCT), or Virgin Initiative Plant (VIP).

The above methods include an anaerobic tank, anoxic tank, and aerobic tank by circulating/nitrogen denitrification method using activated sludge, circulating sewage, and denitrification in anoxic tank, nitrification in aerobic tank to remove nitrogen. Since these methods require each reaction tank, a large site area is required, and a large-capacity aerobic tank is required.

On the other hand, there is a method of filling the carrier with immobilized activated sludge or nitrifying or denitrifying bacteria in order to obtain stable treatment water while having a small reaction tank volume, but this method has a disadvantage of high carrier cost.

In any of the methods described above, when the nitrogen concentration is high and the concentration of organic matter is low, that is, the sewage with a low C/N ratio requires a lot of energy to supply oxygen necessary for nitrification, and an electron donor must be added for denitrification. There was a problem such as excessive cost. In addition, the sulfur carrier used in the existing sulfur denitrification technology has a disadvantage that it is easily lost when used for a long time due to low mechanical properties.

Korean Registered Patent Announcement No. 10-0924681

An object of the present invention is to provide a sulfur carrier which has high denitrification efficiency and has excellent mechanical properties, so that it can be used for a long period of time, and particularly can be used in a fixed bed reactor as well as a fluidized bed reactor.

In order to achieve the above object, the present invention provides a sulfur carrier containing sulfur and activated carbon and having a weight reduction rate of 10% or less represented by the following general formula 1.

[Formula 1]

(Wi-Wf)/Wi X 100

In the above formula, Wi represents the dry weight of the sulfur carrier measured before the reaction, and Wf represents the dry weight of the sulfur carrier measured after reacting the sulfur carrier with water at 25° C. for 24 hours.

The content of the activated carbon is preferably 1 to 30 parts by weight based on 100 parts by weight of the total composition.

The sulfur carrier further comprises an alkali source selected from CaCO ₃ or shell, and the content of the alkalinity source is preferably 10 to 50 parts by weight based on 100 parts by weight of sulfur.

The sulfur carrier also further includes a binder selected from liquid sodium silicate or potassium silicate, and the content of the binder is preferably 40 to 80 parts by weight based on 100 parts by weight of the total composition.

The present invention also comprises the steps of mixing the sulfur and activated carbon to form a mixture;

Heating the mixture; And

It provides a method for producing a sulfur carrier according to the present invention comprising the step of drying the heated mixture.

The forming of the mixture may include mixing sulfur, activated carbon and an alkali source to form a first mixture; And mixing the first mixture with a binder to form a second mixture.

The step of heating the mixture may be performed at a temperature of 80 to 110 °C, and the step of drying the heated mixture may be performed at room temperature for 20 hours or more.

The present invention also provides a denitrification reactor comprising the sulfur carrier of the present invention and a sulfur oxidative autotrophic denitrifying microorganism.

The sulfur oxidative autotrophic denitrifying microorganism may include Thiobacillus denitrificans or Thiomicrospira denitrificans , and the reactor is preferably a fluidized bed.

The present invention also provides a method for treating sewage or wastewater comprising contacting the sulfur carrier of the present invention with sewage or wastewater.

The sulfur carrier according to the present invention includes activated carbon, has excellent denitrification efficiency, and has excellent strength, thereby increasing the use time of the carrier to consume sulfur as much as possible. Therefore, the carrier of the present invention can be used in an existing biological fluidized bed reactor without additional equipment, thereby significantly improving water treatment efficiency.

1 is a cross-sectional view showing a cross-section of a solar cell including an adhesive sheet according to an embodiment of the present invention.
2 is an image of a scanning electron microscope (Scanning Electron Microscope) of the carrier surface according to the amount of PAC in an embodiment of the present invention.
Figure 3 shows a photo before / after the introduction of the sulfur carrier in an oxygen-free tank according to an embodiment and a comparative example of the present invention.

The present invention can be applied to various modifications and may have various embodiments, and specific embodiments will be illustrated in the drawings and described in detail in the detailed description.

However, this is not intended to limit the present invention to specific embodiments, and it should be understood that all modifications, equivalents, and substitutes included in the spirit and scope of the present invention are included.

In the present invention, terms such as "comprises" or "have" are intended to indicate that there are features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and one or more other features. It should be understood that the existence or addition possibilities of fields or numbers, steps, operations, components, parts or combinations thereof are not excluded in advance.

The present invention relates to a sulfur carrier containing sulfur and activated carbon and having a weight reduction rate of 20% or less represented by the following general formula (1).

[Formula 1]

(Wi-Wf)/Wi X 100 (%)

In the above formula, Wi represents the dry weight of the sulfur carrier measured before the reaction, and Wf represents the dry weight of the sulfur carrier measured after reacting the sulfur carrier with water at 25° C. for 24 hours. In a specific example, Wf is introduced into a carrier (about 3 carriers) of about 10 to 20 g in 500 mL of DI (ultra pure water), and a stainless stirrer having a cross section of 20 cm ² at 25° C. is stirred at a rate of 40 rpm for 24 hours. It shows the measured weight. In the general formula 1, the dry weight means a weight measured after drying for 5 hours or more at 60° C. using an oven.

Among the components of the sulfur carrier, sulfur serves as a substrate for the denitrification reaction of sulfated microorganisms, and in the present invention, sulfur may use powdered sulfur.

In addition, the activated carbon may be used as a component for increasing denitrification efficiency and strength, and powdered activated carbon may be used.

The content of the powdered activated carbon is preferably 1 to 30 parts by weight, for example, 2 to 25 parts by weight, or 3 to 20 parts by weight based on 100 parts by weight of the total composition. If the content of activated carbon is too low or high, nitrogen removal efficiency may decrease. Without being limited by theory, it is believed that activated carbon facilitates the attachment of sulfur oxidized denitrifying bacteria to the sulfur carrier, and nitrogen can be removed from the initial reaction time. However, if the content of activated carbon is too large, the sulfur content on the surface may be relatively reduced, thereby reducing the overall nitrogen removal rate.

The sulfur carrier of the present invention may further include an alkali source. The source of alkalinity is a material added to make up the condition of pH 6~8, which allows microorganisms to smoothly denitrify by replenishing the alkalinity that decreases as the denitrification reaction progresses.

The alkalinity source may be a material such as CaCO ₃ or shell. The content of the alkalinity source is preferably 10 to 50 parts by weight, for example, 15 to 45 parts by weight, or 20 to 40 parts by weight based on 100 parts by weight of sulfur. It is possible to maintain a pH range optimized for denitrification within the above content range.

The sulfur carrier may further include a binder for uniformly mixing the sulfur, activated carbon, and alkalinity sources. The binder can be selected from liquid sodium silicate or liquid potassium silicate when considering the mechanical strength of the final sulfur carrier. The content of the binder is preferably 40 to 80 parts by weight, for example, 50 to 70 parts by weight based on 100 parts by weight of the total composition. Within this range, the sulfur carrier may have excellent mechanical strength.

Meanwhile, the sulfur carrier of the present invention preferably has a density of 0.8 g/cm 3 or more or 0.9 g/cm 3 or more. The upper limit of density is not particularly limited, but is 1.3 g/cm 3 or less. If the density is too low, there is a fear that the mechanical strength is deteriorated, and if the density is too high, the nitrogen efficiency may be deteriorated.

The sulfur carrier of the present invention also preferably has an open cell (open cell) volume (%) of 52.5% or less, or 50% or less. In general, porosity decreases as density increases. Among them, open pores are pores that communicate with outside air. Microorganisms that need to grow by attaching to the carrier require anoxic conditions, so open pores through the outside air are not desirable for microbial growth. Of course, the reactor itself forms anoxic conditions, but it is good to minimize the effect of some dissociated oxygen.

The present invention also comprises the steps of mixing the sulfur and activated carbon to form a mixture; Heating the mixture; And it provides a method for producing a sulfur carrier according to the present invention comprising the step of drying the heated mixture.

The forming of the mixture may include mixing sulfur, activated carbon and an alkali source to form a first mixture; And mixing the first mixture with a binder to form a second mixture.

The mixing ratio of each component in the step of forming the first mixture is as described above. The mixing step can stir the mixture for a sufficient time for uniform mixing. Stirring can be carried out through known means.

The mixing ratio of the binder and the first mixture in the step of forming the second mixture is as described above. The second mixture may be stirred for a sufficient time as in the step of forming the first mixture.

The step of heating the mixture may be performed at a temperature of 80 to 120 °C, for example, 90 to 110 °C. The time of the heating step is not particularly limited, but may be performed for 24 hours. Also, the step of drying the heated mixture may be performed at room temperature for 20 hours or more, for example, 20 to 30 hours. The temperature and time conditions of the heating step and the time of the drying step can affect the strength of the final carrier.

The present invention also provides a denitrification reactor comprising the sulfur carrier of the present invention and a sulfur oxidative autotrophic denitrifying microorganism.

The sulfur oxide autotrophic denitrifying microorganism, but may include thio Bacillus Denny pecan tree's (Thiobacillus denitrificans) or thio micro Spirra Denny pecan tree's (Thiomicrospira denitrificans), but is not limited thereto.

The reactor includes both a fixed bed reactor and a fluidized bed reactor, but is preferably a fluidized bed reactor. Conventional sulfur carriers are not excellent in strength and can only be used in a fixed bed reactor. However, the sulfur carrier of the present invention has excellent strength and can be used in a fluidized bed reactor.

The present invention also provides a method for treating sewage or wastewater comprising contacting the sulfur carrier of the present invention with sewage or wastewater. Sewage or waste water may contain nitrate nitrogen. The specific steps and methods for contacting the sulfur carrier of the present invention with sewage or wastewater can be used without any major modifications to the method of treating wastewater using a conventional sulfur carrier, and thus detailed description is omitted.

Hereinafter, the present invention will be described in more detail by examples and experimental examples.

However, the following examples and experimental examples are merely illustrative of the present invention, and the contents of the present invention are not limited to the following examples and experimental examples.

Example One

A mixture of 5 g of sulfur powder (SAMCHUN Chemical, purity 98%), 1.7 g of calcium carbonate (SHOWA, purity 98%) weight, and 0.6 g of powdered activated carbon weight (3% by mass of sulfur mixture) was uniformly mixed at room temperature using a mixer. Mixing to form a first mixture. In the case of powdered activated carbon, the mixture was stirred in deionized water (DI) for 24 hours, dried at 105° C., and used. The second mixture was formed by mixing 7.3 g of the first mixture with 13.4 g of liquid sodium silicate (zero anisotropy) for 1 hour at room temperature using a mixer. The second mixture was heated at 105° C. for 24 hours. The heated molded body was dried at room temperature for 24 hours, and the dried molded body was ground to a size of 3-5 mm.

Comparative example 1 and Example 2 to 5

A sulfur carrier was prepared in the same manner as in Example 1, except that the contents of each component were changed to those shown in Table 1 below.

Comparative example 2

A sulfur carrier was prepared in the same manner as in Example 1, except that the heating body of the second mixture was dried at room temperature for 16 hours.

Comparative example 3

A sulfur carrier was prepared in the same manner as in Example 1, except that twilight mixture (sulfur 5g, calcium carbonate 1.7g) was mixed and mixed with 6.7g (1:1 weight ratio) of sodium alginate.

Experimental Example .

The following experiment was performed to evaluate the performance of the sulfur carrier according to the present invention.

A) Denitrification test

In a fixed bed reaction tank (inner diameter 100 mm, height 240 mm, height of the filled carrier was 150 mm, the total carrier volume 1126 cm ³ , acrylic), the change of TN according to PAC concentration was observed for 20 days. At this time, the residence time was fixed to 10 hr, and the TN concentration in the influent proceeded to a high concentration of 206.3 mg/L on average, and changes were observed, which is illustrated in FIG. 1.

The concentration of T-N in the effluent was observed to be an average of 36.13 mg/L for the PAC 5% carrier, and 169 mg/L for the PAC 0% carrier, and the T-N removal rate increased by 63.14% when 5% PAC was added. This is thought to be because the addition of PAC during the production of the carrier provided an advantageous environment in which sulfur denitrifying bacteria could be attached. However, the average effluent T-N of the PAC 15% carrier was 52 mg/L, and the average effluent T-N concentration of the PAC 20% carrier was 91.25 mg/L, and the removal rate was reduced by 16.75% and 24.1%, respectively, compared to the PAC 5%.

As shown in FIG. 1, as the PAC content increased, the removal rate of T-N decreased, but the initial adaptation period of the sulfur oxidized denitrifying bacteria tended to decrease. Specifically, the adaptation period of denitrifying bacteria of the PAC 5% carrier was 13 days, the PAC 15% carrier was 11 days, and the case of the PAC 20% carrier was 5 days. It was observed that the nitrogen removal stabilization period became shorter as the concentration of the PAC increased. . Therefore, it was confirmed that the addition of PAC to the carrier facilitates the attachment of the sulfur oxidized denitrifying bacteria, thereby shortening the initial adaptation period of the carrier of the sulfur oxidizing denitrifying bacteria and preventing the phenomenon of excessive consumption of sulfur.

B) Evaluation of surface properties

Surface analysis of the carrier was measured using a scanning electron microscope (Scanning Electron Microscope) and is shown in FIG. 2. Referring to Figure 2, it can be seen that the larger the pores on the surface, the more PAC is added. In this case, it can be seen that the proportion of sulfur present on the surface is lowered. When PAC is added in excess, the overall removal rate decreases because the proportion of sulfur on the surface of the carrier decreases.

C) Use Before and after Carrier Size comparison

MBR reaction tank made of acrylic is composed of anaerobic tank, anaerobic tank, and aerobic tank. The aerobic tank and the anaerobic tank were equipped with a stirrer, and the membrane separation tank was installed with an air pipe to perform air cleaning. The daily treatment efficiency of the reactor was about 0.01 m ³ , and the membrane filtration rate was maintained at 0.4 m ³ /m ³ /day. MBR operation was stopped for 1 minute after 9 minutes of operation by intermittent filtration operation. The prepared sulfur carrier (1:2 ratio of liquid silicate of sulfur mixture, PAC 15%) was introduced into the anoxic tank (10% relative to the volume of the anoxic tank) to conduct the experiment, and the results are shown in FIG. 3. As shown in FIG. 3, in Example 1 (drying time 24h) and Comparative Example 2 (drying time 16h) having different drying times, it was confirmed that the volume of the carrier was reduced more after use.

D) Weight reduction rate

Three carriers (Comparative Example 1 and Examples 2, 3, 4, and 5) were added to 500 mL of DI (ultra pure water), and the stainless stirrer having a cross section of 20 cm ² was stirred at 25 rpm for 24 hours at 25° C. The weight was measured, and the dry weight was dried at 60°C using an oven. This is shown in Table 2. As shown in Table 2, it was confirmed that the weight loss rate of the sulfur carrier of the present invention was clearly reduced compared to the prior art.

E) Density and open pore volume measurement

Density and volume of open pores were determined by measuring dry weight, catcher weight and suspension weight according to known methods and are shown in Table 3.

Claims (14)

Contains sulfur and activated carbon,
A sulfur carrier having a weight reduction rate of 20% or less represented by the following general formula 1.
[Formula 1]
(Wi-Wf)/Wi X 100
In the above formula, Wi represents the dry weight of the sulfur carrier measured before the reaction, and Wf represents the dry weight of the sulfur carrier measured after reacting the sulfur carrier with water at 25° C. for 24 hours.
According to claim 1,
The content of activated carbon is 1 to 30 parts by weight of a sulfur carrier with respect to 100 parts by weight of the total composition.
According to claim 1,
A sulfur carrier further comprising an alkali source selected from CaCO ₃ or shell.
According to claim 3,
The content of the alkalinity source is 10 to 50 parts by weight of sulfur carrier relative to 100 parts by weight of sulfur.
According to claim 1,
A sulfur carrier further comprising a binder selected from liquid sodium silicate or liquid potassium silicate.
The method of claim 5,
The content of the binder is a sulfur carrier that is 40 to 80 parts by weight based on 100 parts by weight of the total composition.
Mixing sulfur and activated carbon to form a mixture;
Heating the mixture; And
Method for producing a sulfur carrier according to claim 1 comprising the step of drying the heated mixture.
The method of claim 7,
The step of forming the mixture,
Mixing sulfur, activated carbon and an alkali source to form a first mixture; And
A method of manufacturing a sulfur carrier comprising the step of forming a second mixture by mixing the first mixture with a binder.
The method of claim 7,
The method of heating the mixture is carried out at a temperature of 80 to 120 ℃ sulfur carrier manufacturing method.
The method of claim 7,
The step of drying the heated mixture is performed at room temperature for 20 hours or more.
Denitrification reactor comprising the sulfur carrier of claim 1 to claim 6 and a sulfur oxidative autotrophic denitrifying microorganism.
The method of claim 11,
Sulfur-oxidized autotrophic denitrifying microorganisms are thiobacillus denitrificans or thiomicrospira denitrificans .
The method of claim 11,
The reactor is a denitrification reactor which is a fluidized bed.
A method for treating sewage or wastewater, comprising contacting the sulfur carrier of claim 1 with sewage or wastewater.

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