WO2013147396A1

WO2013147396A1 - Soil composition for water treatment and use thereof

Info

Publication number: WO2013147396A1
Application number: PCT/KR2012/011481
Authority: WO
Inventors: Sung-Hee JOO
Original assignee: Coway Co., Ltd.
Priority date: 2012-03-28
Filing date: 2012-12-26
Publication date: 2013-10-03

Abstract

A soil composition for water treatment and a use thereof are disclosed. More particularly, a soil composition for biological, chemical and physical treatment of wastewater which includes a soil, a radical generator, and an adsorbent and a use thereof are disclosed. The soil composition may have microbiological, chemical and physical treatment effects. In addition, the soil composition is relatively inexpensive and does not require separate equipment investment and thus is economical. Furthermore, the soil composition may be applied to various treatment processes according to objects to be treated.

Description

SOIL COMPOSITION FOR WATER TREATMENT AND USE THEREOF

The present invention relates to a soil composition for water treatment having both a biological treatment effect and chemical and physical treatment effects and a use thereof.

An increase in wastewater according to high levels of industrialization is the biggest obstacle to water treatment research and business and is a task that needs to be dealt with. Accordingly, various water treatment technologies are used, and, to improve these technologies, various studies have been conducted and various treatment methods have been proposed.

A general treatment process using a separator is performed by pre-treatment of wastewater and a biological treatment process or a separator treatment process, followed by post-treatment using an ultrafiltration membrane or a nanofiltration membrane and a discharging process.

The pre-treatment process is performed using soil containing various kinds of microorganisms having the ability to degrade organic materials.

Soil microorganisms include bacteria, actinobacteria, fungi, and protozoa, but types of microorganisms in soil vary according to environmental conditions, measurement methods, and the like. For example, bacteria such as Bacillus, Clostridium, Pseudomonas, Vibrio, and Micrococcus, actinobacteria such as Streptomyces, and fungi such as Penicillium, Aspergillus, and Fusarium decompose organic materials.

That is, contaminated wastewater to be treated passes through a soil layer in a pre-treatment process to induce biological degradation by the microorganisms, thereby decomposing organic materials or removing bad odors from the contaminated wastewater.

Korean Patent Application Publication No. 2002-0031916 discloses a method for treating organic wastewater using soil microorganisms and a device manufactured using the same, the method comprising: aerating the organic wastewater; precipitating the aerated organic wastewater; and treating the organic wastewater with a soil microorganism in the presence of activated silicate to obtain purified water, wherein the treatment process is performed by continuously contacting the organic wastewater with phenolic metabolites of the soil microorganism in an activated state in which a highly-concentrated corrosive precursor is filled.

Korean Patent Application Registration No. 10-1047507 discloses a method for treating wastewater using soil microorganisms, the method comprising placing cultured soil microorganisms in a bioreactor and passing sewage containing excrement therethrough.

Also, Korean Patent Application Registration No. 10-0386426 discloses that eutrophication and red-tide of coastal seas may be prevented using a yellow clay composition including yellow clay powder, alumina, iron oxide, and a soil microorganism such as Geobacter.

As described above, soil containing soil microorganisms may be widely used in various applications, such as treatment of various wastewaters, wastewater containing a large amount of organic contaminants, industrial wastewater contaminated with heavy metals (e.g., As, Cd, Pb, Cr, and the like), livestock wastewater, underground water containing a large amount of chlorine compounds and aromatic compounds, and soil. Also, soil containing soil microorganisms is widely used for pre-treatment of a membrane process, which is generally performed in wastewater treatment.

Furthermore, soil microorganism-containing soil is applied to a process for removal of exhaust gas or an organic compound, in addition to treatment of contaminated wastewater.

Korean Patent Application Registration No. 10-080222 discloses a method for purifying a gas containing bad odors and volatile organic compounds by passing the gas through a medium in which a soil microorganism is cultured or a contact oxidation packed tower filled with a filler to remove the bad odors and the volatile organic compounds therefrom.

As described above, environmental treatment processes using soil may be used in various applications. Accordingly, to improve treatment effects obtained using soil microorganisms, various methods have been introduced. As an example, a method for increasing treatment efficiency by additionally using chemicals having an adsorptive effect or an additional process may be implemented.

However, such a method is not economical with respect to treatment efficiency due to costs of electricity and equipment investment according to the costs of chemicals and the additional process.

[Patent Documents]

1. Korean Patent Application Publication No. 2002-0031916

2. Korean Patent Application Registration No. 10-1047507

3. Korean Patent Application Registration No. 10-080222

[Non-patent Documents]

1. Cao, H.; Huang, G.; Xuan, S.; Wu, Q.; Gu, F.; Li, C. (2008) Synthesis and Characterization of Carbon-Coated Iron Core/Shell Nanostructures. Journal of Alloys and Compounds, vol. 448, issues 1-2, pp. 272-276.

2. Godini, H.; Khorramabady, G.S.; Mirhosseini, S.H. (2011) The Application of Iron-Coated Activated Carbon in Humic Acid Removal From Water. 2011 2nd International Conference on Environmental Science and Technology, IPCBEE vol. 6 pp 32-36.

3. Joo, S.H.; Mitch, W.A. (2007) Nitrile, Aldehyde, and Halonitroalkane Formation during Chlorination/Chloramination of Primary Amines. Environmental Science and Technology, vol. 41, pp. 1288-1296.

4. Nadagouda, M.N.; Lytle, D.A. (2011) Microwave-Assisted Combustion Synthesis of Nano Iron Oxide/Iron-Coated Activated Carbon, Anthracite, Cellulose Fiber, and Silica, with Arsenic Adsorption Studies. Journal of Nanotechnology, vol. 2011, 8 pages. doi: 10.1155/2011/972486.

5. Schwickard, M.; Olejnik, S.; Salabas, E.-L.; Schmidt, W.; Schuth, F. (2006) Scalable Synthesis of Activated Carbon with Superparamagnetic Properties. Chemical Communications, issue 38, pp. 3987-3989. doi: 10.1039/B608231A.

Therefore, the inventor of the present invention diversely studied a composition having improved treatment efficiency using a material that is relatively inexpensive and easily obtainable. As a result, the inventor invented a soil composition for performing biological, chemical and physical treatment processes at low costs using a composite of a soil having a biological treatment effect, a material that can be chemically treated, and a material that can be physically treated and a use thereof.

Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a novel soil composition having biological, chemical and physical treatment effects.

It is another object of the present invention to provide a use of the soil composition.

In accordance with the present invention, the above and other objects can be accomplished by the provision of a soil composition for biologically, physically and chemically treating wastewater, the soil composition comprising: a soil selected from the group consisting of sand, culture soil, clay sand, humus soil, and combinations thereof; a radical generator selected from the group consisting of zero-valent iron, iron oxide, ferric chloride, iron nitride, graphene, titania, and combinations thereof; and an adsorbent selected from the group consisting of iron oxide, zeolite, activated carbon, perlite, silica, montmorillonite, bentonite, illite, Maifan stone, clinoptilolite, and combinations thereof.

In accordance with an aspect of the present invention, the above and other objects can be accomplished by the provision of a water treatment apparatus for water treatment performed by passing a raw water to be treated through a reactor filled with a filter material to be in contact with the filter material, wherein the filter material is the soil composition described above.

According to the embodiments of the present invention, as compared to a case in which conventional soil is used alone, both a microbiological treatment effect and chemical and physical treatment effects may be obtained due to the adsorbent and the radical generator. Consequently, organic coloring components, bad odors, bad smells, volatile organic compounds, radionuclides, ammonia, sulfur, phosphorus, or various heavy metals may be effectively removed.

Furthermore, the adsorbent and the radical generator used in the present invention are relatively inexpensive and do not require separate equipment investment and thus are economical.

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a view illustrating application of a soil composition to a separator water treatment process, according to a first embodiment;

FIG. 2 is a view illustrating application of a soil composition as a filter material of a filter cell, according to a second embodiment;

FIG. 3 is a view illustrating application of a soil composition as a filter material of a column, according to a third embodiment;

FIG. 4 is a view illustrating use of a soil composition as a filter material in a UV-equipped filter cell, according to a fourth embodiment;

FIG. 5 is a view illustrating a water treatment apparatus used in Experimental Examples;

FIG. 6 is a graph showing a removal rate of an organic material according to time when continuously introduced water was treated using a soil composition of Experimental Example 1;

FIG. 7 is a graph showing a removal rate of total phosphorus according to time when continuously introduced water was treated using the soil composition of Experimental Example 1;

FIG. 8 is a graph showing a removal rate of total nitrogen according to time when continuously introduced water was treated using the soil composition of Experimental Example 1;

FIG. 9 is a graph showing a removal rate of an organic material according to time when continuously introduced water was treated using a soil composition of Experimental Example 2;

FIG. 10 is a graph showing a removal rate of total phosphorus according to time when continuously introduced water was treated using the soil composition of Experimental Example 2;

FIG. 11 is a graph showing a removal rate of total nitrogen according to time when continuously introduced water was treated using the soil composition of Experimental Example 2;

FIG. 12 is a graph showing a removal rate of an organic material according to time when continuously introduced water was treated using a soil composition of Experimental Example 3;

FIG. 13 is a graph showing a removal rate of total phosphorus according to time when continuously introduced water was treated using the soil composition of Experimental Example 3;

FIG. 14 is a graph showing a removal rate of total nitrogen according to time when continuously introduced water was treated using the soil composition of Experimental Example 3;

FIG. 15 is a graph showing removal rates of an organic material, total phosphorus, and total nitrogen according to time when continuously introduced water was treated using a soil composition of Experimental Example 4;

FIG. 16 is a graph showing removal rates of an organic material, total phosphorus, and total nitrogen according to time when continuously introduced water was treated using waste iron powder alone as a control of Experimental Example 4;

FIG. 17 is a graph showing a removal rate of an organic material according to time when continuously introduced water was treated using a soil composition of Experimental Example 5;

FIG. 18 is a graph showing a removal rate of total phosphorus according to time when continuously introduced water was treated using the soil composition of Experimental Example 5; and

FIG. 19 is a graph showing a removal rate of total nitrogen according to time when continuously introduced water was treated using the soil composition of Experimental Example 5.

Hereinafter, exemplary embodiments of the prevent invention will be described in detail with reference to the accompanying drawings.

The present invention provides a soil composition that enables wastewater to be biologically, physically and chemically treated.

In particular, the soil composition includes a radical generator that can be chemically treated together with soil and an adsorbent that can be physically treated.

The soil is not particularly limited as long as it is generally used in a water treatment process. For example, the soil includes one selected from the group consisting of sand, culture soil, clay sand, humus soil, and combinations thereof. The soil contains a microorganism and thus degrades an organic material in wastewater in a water treatment process.

The radical generator degrades toxic and harmful contaminants in wastewater by a powerful oxidation reaction, and also degrades organic coloring components and materials having odors and bad smells. The radical generator may be a commercially available and economical material. For example, the radical generator may include one selected from the group consisting of zero-valent iron, iron oxide, ferric chloride, iron nitride, graphene, titania and combinations thereof. Preferably, the radical generator may be iron oxide, zero-valent iron, or graphene mixed with iron.

The adsorbent may be various porous materials, for example, minerals. The mineral may adsorb cations or anions onto a surface thereof or may physically adsorb compounds contained in wastewater, for example, volatile organic compounds such as benzene, toluene, xylene, and the like, radionuclides, ammonia, sulfur, phosphorus, and various heavy, due to its ion-exchange functional group. In addition, the mineral may have a high porosity and thus may increase an adsorption rate. For example, such an absorbing mineral may include one selected from the group consisting of iron oxide, zeolite, activated carbon, perlite, silica, montmorillonite, bentonite, illite, Maifan stone, clinoptilolite, and combinations thereof. Preferably, the mineral may be iron oxide, activated carbon, or zeolite. The iron oxide may be used as an adsorbent since it can physically adsorb heavy metals and the like, as well as used as a radical generator.

The types of materials to be adsorbed may vary according to the types of minerals. The minerals may be appropriately selected according to the properties of the materials to be adsorbed and used in combination of one or more minerals or in the form of a coating.

For example, zeolites are basically comprised of porous aluminosilicate crystals with tetrahedral frameworks made of SiO₄ and AlO₄, have excellent ion exchange properties, and have a high absorption rate of radionuclides and heavy metals. By contrast, activated carbon consists of carbon, and has a functional group such as -COOH, -OH, -C=O, -NH₂, or the like on a surface thereof through activation and thus more preferably adsorbs an organic material such as a volatile organic compound and ammonia because the functional group acts as an adsorbing site. The functional group of the activated carbon may vary according to manufacturing conditions and thus may be appropriately selected according to materials to be treated.

A soil composition having such a composition may be used in a water treatment process in the form of a simple mixture or a composite. For example, the soil composition may be one of the following (1) to (5) types:

(1) A mixture of the soil, the radical generator, and the adsorbent;

(2) A mixture of the soil and a composite of the radical generator and the adsorbent;

(3) A mixture consisting of a mixture of the soil and the radical generator and a mixture of the soil and the adsorbent;

(4) A molded product formed by molding the soil, the radical generator, and the adsorbent;

(5) A mixture of a mixed molded product of the soil and the radical generator and a mixed molded product of the soil and the adsorbent.

Soil composition type (1)

A soil, a radical generator, and an adsorbent may be mixed at a constant ratio and the resulting mixture may then be filled into a reactor, e.g., a packing tower, a filter cell, or a column. Here, the amounts of the radical generator and the adsorbent may vary according to the kind of wastewater to be treated. Preferably, the amount of the radical generator may be 0.001 g to 1 kg based on 1 g of the adsorbent.

Soil composition type (2)

The mixture of a composite of a radical generator and an adsorbent and soil may be formed by coating or immersing the radical generator on a surface of or inside pores existing in the adsorbent such as activated carbon or zeolite.

Here, the amount of the radical generator to be coated or supported may be restricted according to porosity of the adsorbent. That is, even though the radical generator is used in a much larger amount than is sufficient to be coated in or on a surface of the pores of the adsorbent, the radical generator is no longer coated or supported due to supersaturation. Thus, the amount of the radical generator coated or supported is preferably 0.001 g to 0.01 g based on 1 g of an adsorbent used in a general water treatment process.

The coating or immersion method is not particularly limited. For example, various wet or dry methods may be used, and a wet method is preferably used in terms of cost reduction.

For example, zeolite is uniformly mixed in an aqueous solution containing zero-valent iron to prepare a slurry and the slurry is then dried. Through the drying process, the zero-valent iron may be coated on a surface of the zeolite. Also, a dry method, for example, deposition such as sputtering may be used.

Soil composition type (3)

Soil and a radical generator, and soil and an adsorbent are separately mixed and then the resulting mixtures are mixed at a constant ratio.

As an example, a mixture of a soil and an adsorbent is placed in a region which wastewater first contacts to induce physical and biological degradation, and the treated wastewater is passed through a mixture of soil and a radical generator to induce chemical and biological treatment reaction.

Alternatively, when a water treatment process including irradiating sunlight or UV or performing ozone treatment, a mixture of soil and a radical generator is placed in a region in direct contact with sunlight to activate the radical generator, and a mixture of a soil and an adsorbent is then placed thereon to more effectively implement chemical treatment.

When the radical generator and the adsorbent are separately mixed with soil, as described above, the resulting mixtures may be sequentially filled into a packing tower or may be subjected to the above-described molding process to form a molded product such as a filter cell. Here, the molded product may be formed by separately molding the mixture of soil and a radical generator and the mixture of soil and an adsorbent or molding the mixtures into a double-layered structure.

Soil composition type (4)

A soil composition may be used in the form of a molded product formed by molding soil, a radical generator, and an adsorbent.

This form of soil composition is advantageous in terms of convenience of use and treatment efficiency.

The molded product may be formed by mixing each component together, optionally adding a binder thereto, and drying or calcining the resulting mixture. To be suitable for use in a filling process, the molded product may be a small-sized molded product in the form of a granule, a pellet, a mat, or a flake, or a molded product that has pores and is of a plate type having a mesh, wave or honeycomb cell structure. The molding process may be performed using a known method, such as press molding, mold molding, or the like, and the drying or calcining may be performed within known temperature ranges.

These molded products having various structures may be appropriately selected by those skilled in the art according to a water treatment apparatus or an object to be treated. In addition, when an appropriate molded product is used, frequency and area of contact with an object to be treated are larger than those in a case in which soil alone is used, resulting in increased treatment efficiency.

Soil composition type (5)

The soil composition may be in the form of a mixture of a mixed molded product of soil and a radical generator and a mixed molded product of soil and an adsorbent.

The molded product may be in the various forms as described above in connection with the soil composition type (4), and the radical generator and the adsorbent may be separately used without being mixed together.

The soil composition according to the aforementioned embodiment may be in various other forms, in addition to the soil composition types (1) through (5) above, i.e., variously prepared by those skilled in the art using an appropriate method, such as mixing or molding. In addition, the soil composition may be applied to various treatment processes.

In this case, as compared to a case in which conventional soil is used alone, both a microbiological treatment effect and chemical and physical treatment effects may be obtained due to the adsorbent and the radical generator. Consequently, organic coloring components, bad odors, bad smells, volatile organic compounds, radionuclides, ammonia, sulfur, phosphorus, or various heavy metals may be effectively removed.

FIG. 1 is a view illustrating application of a soil composition according to a first embodiment. The soil composition may be sand used in a separator water treatment process or soil of a soil tower.

Referring to FIG. 1, wastewater is screened and then passed sequentially through a soil packing tower and a strainer, and discharged through a separator. In this configuration, a soil composition according to an embodiment of the present invention is used as a filling material of the soil packing tower which is used in the pre-treatment process.

Here, the soil packing tower may further include a device for performing sunlight irradiation, UV irradiation, or ozone treatment so as to increase activity of the radical generator inside the soil packing tower, resulting in increased chemical treatment by high level of oxidation. In this case, to facilitate increase in the activity of the radical generator by light irradiation, the radical generator or a mixture including the radical generator is disposed in the soil packing tower so as to be in direct contact with sunlight, UV, or ozone.

FIG. 2 is a view illustrating application of a soil composition according to a second embodiment. The soil composition may be used as a filter material of a filter cell filled therewith.

Here, the filter cell includes a housing having a space for accommodating the filter material inside thereof and opened first and second ends and a porous film disposed at each opened end of the housing. The porous film may be a non-woven fabric or polymer layer with excellent ventilation.

Referring to FIG. 2, in a device configuration in which wastewater is treated by being passed through the filter cell, the housing of the filter cell is filled with the soil composition according to the present embodiment. Here, the filter cell may further include a device for performing sunlight irradiation, UV irradiation, or ozone treatment so as to increase activity of the radical generator inside the filter cell, resulting in increased chemical treatment by high level of oxidation. In this case, to facilitate the increase in activity of the radical generator by light irradiation, the radical generator or a mixture including the radical generator is disposed in the filter cell so as to be in direct contact with sunlight, UV, or ozone.

FIG. 3 is a view illustrating application of a soil composition as a filter material of a column, according to a third embodiment.

Referring to FIG. 3, in a water treatment process including irradiation of light such as sunlight or the like, a mixture of an adsorbent and soil is stacked on a lower portion of the column and a mixture of soil and a radical generator is then stacked thereon. Here, the column with a filter or a glass filter attached thereto may be manufactured using a known technology. In the embodiment illustrated in FIG. 3, introduction of wastewater starts from the bottom of the column, and the introduced wastewater is treated with the adsorbent, the soil, and the radical generator included in the column and then discharged. In this regard, catalytic activity of the radical generator in the column may be increased by irradiation of light, and accordingly, chemical treatment by high level of oxidation may be increased.

Here, the filling methods of FIGS. 1 to 3 are not particularly limited. For example, a molded product including a soil composition prepared by uniformly mixing a soil, a radical generator, and an adsorbent may be packed, or a soil, a radical generator, and an adsorbent may be sequentially filled in a stacked form.

In particular, in FIG. 3, to increase an effect of the radical generator by irradiation of light, the radical generator may be disposed on a layer onto which sunlight is directly irradiated so as to be in direct contact with sunlight. As described above, the molded product may be a small-sized molded product in the form of a granule, a pellet, a mat, or a flake to be suitable for use in a filling process.

The soil compositions according to the aforementioned embodiments are preferably applied to treatment of wastewater generated from domestic water, agricultural water, or industrial water through water treatment apparatuses illustrated in FIGS. 1 through 3. A packing tower, a filter cell, or a column may be filled with these soil compositions. Here, the size or shape of a water treatment apparatus including the packing tower, the filter cell, or the column may be variously modified.

As an example, a column including the soil composition according to the present invention may be applied to a package-type portable treatment apparatus so that various organic contaminants can be simultaneously treated.

Water used in a swimming pool or a spa is essentially involved in sterilization by a chemical such as chlorine. In this regard, harmful byproducts such as trihalomethanes (THMs) are produced by chlorination, and bladder cancer may be caused by long-term exposure to the harmful byproducts. A recent study has discovered that when water is treated by chloramination, a new kind of carcinogen is produced (Joo and Mitch (2007), Environ. Sci. Technol., Vol.41, pp.1288-1296).

Thus, instead of chlorination, water used in a swimming pool or a spa may be treated through a filter cell filled with the soil composition according to the present invention and be reused.

FIG. 4 is a view illustrating use of a soil composition as a filter material in a UV-equipped filter cell, according to a fourth embodiment.

Referring to FIG. 4, water used in a swimming pool or a spa is introduced into the UV-equipped filter cell via a pump, and the treated water returns to the swimming pool or the spa via the pump.

Here, a circulating pump is used as the pump and is continuously operated for 6 to 8 hours per day, as necessary. To increase lifespan of the filter cell (replacement about every two to five years), reverse washing for 5 to 10 minutes and rinsing for 1 to 2 minutes may be performed. The treatment time may be adjusted according to an amount of wastewater to be treated.

The UV-equipped filter cell is filled with a soil and an adsorbent (e.g., zeolite or clinoptilolite) and a radical generator such as graphene is filled thereon, and thus, a harmful contaminant can be chemically treated. Furthermore, by UV irradiation, as a chemical oxidation catalyst, production of byproducts of the harmful contaminant may be prevented and the contaminant may be clearly removed, thereby obtaining good water quality. In an apparatus including the UV-equipped filter cell, removal of contaminants includes photodegradation and photoadsorption, i.e., a “heterogeneous process” according to a UV catalyst as an adsorbent.

After water treatment, the UV-equipped filter cell reversely introduces purified water via the circulating pump to remove contaminants attached to the filter cell.

An apparatus having the above-described configuration does not include a chemical such as chlorine and may provide good water quality. In addition, the apparatus may be commercialized as a portable treatment apparatus and thus may be used on a work site. Moreover, there is no need for further maintenance because the reverse washing process is periodically performed.

The soil compositions according to the exemplary embodiments have been described, but may be applied to various other fields, in addition to the above-described embodiments.

[Examples]

A.

Comparison

1 between water treatment effects of soil compositions

A soil composition including a soil, an adsorbent, and a radical generator was prepared, and a column of an experimental apparatus illustrated in FIG. 5 was filled with the soil composition. Water treatment effects of the soil composition were evaluated.

Experimental apparatus and conditions

Wastewater used in this experiment was collected from a K sewage treatment plant. The experiment was implemented using reverse osmosis (RO) concentrated water obtained through pilot operating procedures for reuse of sewage (i.e., pressured microfiltration (MF) and RO) as a raw water. An initial concentration (mg/L) of the RO concentrated water had the following ranges: DOC: 18.4～22.9 ppm, T-N: 24.6～29.8 ppm, and T-P: 4.9～5.1 ppm.

An outer shape of a glass column (1.1cm I.D. X 10cm L) and an experimental setting were the same as illustrated in FIG. 1, and opposite end portions of the glass column were equipped with a glass filter. The glass column had an empty bed volume of 9.5cm3, a bed porosity of 0.32, and an empty bed contact time (EBCT) of 9.5 minutes at a flow rate of 1 ml/min. Sampling time was set to 0 (before passing the concentrated water through the column), 15, 30, 45, 60, 90, 120, and 150 minutes, and the number of pore volume (=Q.t/pore volume) according to sampling time was 0, 4.9, 9.9, 14.8, 19.7, and 29.6. The flow rate was 1.0 ml/min, all tubing was made of silicone, and the concentrated water was continuously injected using a peristaltic pump.

Sand used in this experiment was purchased from Sigma-Aldrich (Quartz Silicon Dioxide, SiO₂, 50-70 mesh, CAS # 14808-60-7). Culture soil was dried at 105℃ for 30 minutes and then sieved through a 20 mesh sieve (850 mm) and a 40 mesh sieve (425 mm), and the finally obtained soil was used in this experiment.

Nano-particles of zero-valent iron were synthesized. In particular, to prepare 0.1 g/L of iron nano-particles, first, 100 ml of deionized (DI) water was put in a 250 ml flask and N₂ gas was injected thereto. Then, 0.06 g/10 ml of FeSO₄·7H₂O was added to the flask and 0.0192 g/10 ml of NaBH4 was added dropwise thereto via a buret to prepare zero-valent iron particles. Iron oxide having an average particle size of 20 to 30 nm and a specific surface area of 40 to 60 m²/g was purchased, and graphene having an average particle size of 15 μm, a thickness of 6 to 8 nm, and a specific surface area of 120 to 150 m²/g was purchased. In addition, activated carbon purchased, which was used in coating of iron, had an average particle size of 100 nm or less and a specific surface area of 1300 m²/g.

Analysis method

Amount of organic material (dissolved organic carbon (DOC)): A sample was filtered through a 0.45 μm PVDF filter, and 30 ml of the obtained filtrate was added to a 40 ml vial and then analyzed using a TOC analyzer (TOC-VCPH/CPN, Shimadzu). An automatic sampler of the analyzer performed an injection process needed for analysis and automatically analyzed total carbon (TC) and inorganic carbon (IC). The DOC was calculated as a concentration value obtained by subtracting the IC from the TC (DOC=TC-IC). A calibration concentration of each of the TC and the IC was set to 0, 0.2, 1, 2, and 10 mg/l, a calibration curve was regularly drawn and checked, and amounts of the TC and IC injected for analysis were 50 μl and 65 μl, respectively.

Content of total phosphorus (T-P): A DRB200 reactor was turned on and heated to 150℃. 5 ml of a sample was added to a total and acid hydrolysable test vial and shaken. The vial was placed in the DRB200 reactor, maintained at 150℃ for 30 minutes, taken out of the vial, and then cooled down to room temperature. 2 ml of 1N NaOH was added to the vial and shaken to mix the contents of the vial together. The reactor was set to zero, a PhosVer 3 powder pillow was added to the vial, and the vial was shaken for 10 to 15 seconds to mix the contents thereof together. The resulting sample was maintained for 2 minutes to induce a reaction therebetween and measured at 880 nm within two to eight minutes.

Content of total nitrogen (T-N): A DRB200 reactor was turned on and heated to 105℃ and a total nitrogen persulfate reagent powder pillow was added to two vials. Thereafter, 2 ml of a sample was added to one of the vials, 2 ml of DI water was added to the other vial, and each vial was shaken for 30 minutes to mix contents thereof together. Then, each vial was put in the preheated reactor and heated for 30 minutes. The vial was taken out of the reactor and cooled down to room temperature, and a total nitrogen reagent A powder pillow was added to each vial. After shaking each vial for 15 minutes, each vial was maintained for 3 minutes, and a total nitrogen reagent B powder pillow was added to each vial. Afterwards, each vial was shaken for 15 minutes and then maintained for 2 minutes. Then, two new vials were opened, 2 ml of the digested sample was added to one thereof, and the digested blank was added to the other thereof. After shaking each vial for 10 minutes, each vial was maintained for 5 minutes and then measured at 410 nm.

Preparation and analysis of soil compositions

Mixtures or soil compositions having the compositions shown in Table 1 were prepared. The mixtures or soil compositions were packed using a wet packing method in which the mixture or soil composition was added to a glass column together with DI water and then maintained until the DI water was completely removed.

Table 1

(1) Analysis results of soil composition of Experimental Example 1

FIG. 6 is a graph showing a removal rate of an organic material according to time when continuously introduced water (i.e., concentrated water) was treated using the soil composition of Experimental Example 1. FIG. 7 is a graph showing a removal rate of total phosphorus according to time when continuously introduced water was treated using the soil composition of Experimental Example 1. FIG. 8 is a graph showing a removal rate of total nitrogen according to time when continuously introduced water was treated using the soil composition of Experimental Example 1. Referring to FIGS. 6 through 8, it is confirmed that the soil composition of Experimental Example 1 effectively removes an organic material, phosphorus, and nitrogen less than 20 minutes after the treatment process was performed using the soil composition.

Each removal rate measured based on a breakthrough of the control when the concentrated water was continuously introduced, shown in FIGS. 6 through 8, is shown in Table 2 below.

Table 2

From the results shown in Table 2, it is confirmed that a mixture of sand, iron oxide, and graphene may effectively remove an organic material, phosphorus, and nitrogen contained in wastewater when the wastewater is treated.

(2) Analysis results of soil composition of Experimental Example 2

FIG. 9 is a graph showing a removal rate of an organic material according to time when continuously introduced water (i.e., concentrated water) was treated using the soil composition of Experimental Example 2. FIG. 10 is a graph showing a removal rate of total phosphorus according to time when continuously introduced water was treated using the soil composition of Experimental Example 2. FIG. 11 is a graph showing a removal rate of total nitrogen according to time when continuously introduced water was treated using the soil composition of Experimental Example 2. Referring to FIGS. 9 through 11, it is confirmed that the soil composition of Experimental Example 2 may effectively remove an organic material, phosphorus, and nitrogen for the first 15 minutes after the treatment process was performed using the soil composition. In particular, as shown in FIG. 10, it is confirmed that the soil composition may exhibit a high removal rate of phosphorus.

Each removal rate measured based on a breakthrough of the control when the concentrated water was continuously introduced, shown in FIGS. 9 through 11, is shown in Table 3 below.

Table 3

From the results shown in Table 3, it is confirmed that a mixture of culture soil, iron oxide, and graphene may effectively remove an organic material, phosphorus, and nitrogen contained in wastewater when the wastewater is treated.

(3) Analysis results of soil composition of Experimental Example 3

FIG. 12 is a graph showing a removal rate of an organic material according to time when continuously introduced water (i.e., concentrated water) was treated using the soil composition of Experimental Example 3. FIG. 13 is a graph showing a removal rate of total phosphorus according to time when continuously introduced water was treated using the soil composition of Experimental Example 3. FIG. 14 is a graph showing a removal rate of total nitrogen according to time when continuously introduced water was treated using the soil composition of Experimental Example 3. Referring to FIGS. 12 through 14, as the same is the case for Experimental Examples 1 and 2, it is confirmed that the soil composition of Experimental Example 3 may effectively remove an organic material, phosphorus, and nitrogen at the early stage after the treatment process was performed using the soil composition.

Each removal rate measured based on a breakthrough of the control when the concentrated water was continuously introduced, shown in FIGS. 12 through 14, is shown in Table 4 below.

Table 4

From the results shown in Table 4, it is confirmed that a mixture of culture soil, iron oxide, and zero-valuent iron may effectively remove an organic material, phosphorus, and nitrogen, in particular, phosphorus and nitrogen, contained in wastewater when the wastewater is treated.

(4) Soil composition prepared in the form of a composite

An adsorbent (e.g., activated carbon) and a radical generator (e.g., iron/iron oxide) were made composite using the following method and the composite of the adsorbent and the radical generator was mixed with soil. The resultant mixture may be used as a soil composition.

4.1. Soil composition prepared using iron-coated activated carbon

Activated carbon and an Fe(III) solution were mixed at various ratios using pestle and mortar, and the resultant mixture was put in an alumina crucible and heat treated by microwave irradiation for 3 minutes (Nadagouda and Lytle, 2011).

The iron-coated activated carbon was mixed with a soil to prepare a soil composition. As the same is the case for the soil compositions of Experimental Examples 1 to 3, the soil composition effectively removed the organic material, phosphorus and nitrogen contained in wastewater.

4.2. Soil composition prepared using activated carbon-coated iron nanoparticles

Activated carbon-coated iron nanoparticles may be prepared by chemical vapor deposition. As an example, activated carbon was immersed into an Fe(III) solution and impregnated therewith, followed by drying and calcination. In the calcination process, iron particles were formed in pores of the activated carbon, and the resultant activated carbon was subjected to a coating process using benzene by chemical vapor deposition to form an activated carbon layer (Cao et al. 2008; Schwickard et al. 2006).

The activated carbon-coated iron nanoparticles were mixed with a soil to prepare a soil composition. As the same is the case for the soil compositions of Experimental Examples 1 to 3, the soil composition effectively removed the organic material, phosphorus and nitrogen contained in wastewater, in particular, phosphorus and nitrogen.

B.

Comparison

2 between water treatment effects of soil compositions

Soil compositions were prepared in the form of a composite, not in the form of a simple mixture, and water treatment effects thereof were compared with each other using the same method as described in A above. The soil compositions had the compositions as shown in Table 5 below.

Table 5

As the waste iron powder used in Experimental Example 4, a commercially available waste iron powder was used after being sieved through a sieve having a 20 mesh (850 mm) without pretreatment. The waste iron powder consisted of zero-valent iron at an inner portion thereof and iron oxide at an outer portion thereof by oxidation. The iron-coated activated carbon used in Experimental Example 5 was prepared using a method proposed by Godini et al (2011 2nd International Conference on Environmental Science and Technology, 2011) and was in the form of a composite in which pores of the activated carbon were coated with iron.

(1). Analysis results of soil composition of Experimental Example 4

FIG. 15 is a graph showing removal rates of an organic material, total phosphorus, and total nitrogen according to time when continuously introduced water was treated using the soil composition of Experimental Example 4. FIG. 16 is a graph showing removal rates of an organic material, total phosphorus, and total nitrogen according to time when continuously introduced water was treated using waste iron powder alone as a control.

Referring to FIG. 15, the soil composition according to the present invention effectively removed the organic material, phosphorus and nitrogen at the early stage after the treatment process was performed. By contrast, referring to FIG. 16, the waste iron powder used alone exhibited high removal rates of phosphorus and nitrogen, while it did not remove the organic material at all.

Each removal rate measured 15 minutes after treatment based on the control when the concentrated water was continuously introduced, shown in FIGS. 15 and 16, is shown in Table 6 below.

Table 6

From the results shown in Table 6, it is confirmed that when culture soil, iron oxide, and zero-valent iron are used together in water treatment, an organic material, phosphorus and nitrogen contained in wastewater, in particular, phosphorus and nitrogen, may be effectively removed.

(2) Analysis results of soil composition of Experimental Example 5

FIG. 17 is a graph showing a removal rate of an organic material according to time when continuously introduced water (i.e., concentrated water) was treated using the soil composition of Experimental Example 5. FIG. 18 is a graph showing a removal rate of total phosphorus according to time when continuously introduced water was treated using the soil composition of Experimental Example 5. FIG. 19 is a graph showing a removal rate of total nitrogen according to time when continuously introduced water was treated using the soil composition of Experimental Example 5. Referring to FIG. 17, it is confirmed that in spite of continuous introduction of wastewater, the soil composition according to the present invention exhibits a high treatment rate, i.e., 100% degradation of the organic material 60 minutes after water treatment and also effectively removes total phosphorus and total nitrogen.

Each removal rate measured based on a breakthrough of the control when the concentrated water was continuously introduced, shown in FIGS. 17 and 19, is shown in Table 7 below.

Table 7

From the results shown in Table 7, it is confirmed that when sand is used together with iron-coated activated carbon in water treatment, an organic material, phosphorus and nitrogen contained in wastewater may be effectively removed.

As is apparent from the above description, the present invention provides a soil composition having biological, physical and chemical treatment effects due to use of an adsorbent and a radical generator, as compared to a case in which a soil is used alone. Accordingly, the soil composition may effectively remove organic coloring components, bad odors, bad smells, volatile organic compounds, radionuclides, ammonia, sulfur, phosphorus, or various heavy metals.

In addition, both the adsorbent and the radical generator are relatively inexpensive and do not require separate equipment investment and thus are economical. Furthermore, the soil composition may be applied to various treatment processes according to objects to be treated.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

A soil composition for biological, physical and chemical treatment of wastewater, the soil composition comprising:

a soil selected from the group consisting of sand, culture soil, clay sand, humus soil, and combinations thereof;

a radical generator selected from the group consisting of zero-valent iron, iron oxide, ferric chloride, iron nitride, graphene, titania and combinations thereof; and

an adsorbent selected from the group consisting of iron oxide, zeolite, activated carbon, perlite, silica, montmorillonite, bentonite, illite, Maifan stone, clinoptilolite, and combinations thereof
The soil composition according to claim 1, wherein the soil composition has (1) to (5) types below:

(1) A mixture of the soil, the radical generator, and the adsorbent;

(2) A mixture of the soil and a composite of the radical generator and the adsorbent;

(3) A mixture obtained by mixing a mixture of the soil and the radical generator and a mixture of the soil and the adsorbent;

(4) A molded product formed by molding the soil, the radical generator, and the adsorbent; and

(5) A mixture of a mixed molded product of the soil and the radical generator and a mixed molded product of the soil and the adsorbent.
The soil composition according to claim 2, wherein the composite has a structure in which the radical generator is coated or supported on a surface of or in the adsorbent.
The soil composition according to claim 2, wherein the molded product is in the form of a granule, a pellet, a mat, or a flake.
A water treatment apparatus for water treatment preformed by passing a raw water to be treated through a reactor filled with a filter material to be in contact with the filter material, wherein the filter material is the soil composition according to claim 1.
The water treatment apparatus according to claim 5, wherein the soil composition has (1) to (5) types below:

(1) A mixture of the soil, the radical generator, and the adsorbent;

(2) A mixture of the soil and a composite of the radical generator and the adsorbent;

(3) A mixture obtained by mixing a mixture of the soil and the radical generator and a mixture of the soil and the adsorbent;

(4) A molded product formed by molding the soil, the radical generator, and the adsorbent; and

(5) A mixture of a mixed molded product of the soil and the radical generator and a mixed molded product of the soil and the adsorbent.
The water treatment apparatus according to claim 6, wherein the composite has a structure in which the radical generator is coated or supported on a surface of or in the adsorbent.
The water treatment apparatus according to claim 6, wherein the molded product is in the form of a granule, a pellet, a mat, or a flake.
The water treatment apparatus according to claim 5, wherein the reactor is a tower, a filter cell, or a column.
The water treatment apparatus according to claim 9, wherein the filter cell comprises: a housing having a space for accommodating a filter material inside thereof and opened first and second ends; and a porous film disposed at each opened end of the housing.
The water treatment apparatus according to claim 5, wherein the reactor is irradiated by sunlight or UV or treated with ozone.
The water treatment apparatus according to claim 11, wherein the radical generator or a mixture comprising the radical generator is disposed in the reactor so as to be in direct contact with the sunlight, UV or ozone.
The water treatment apparatus according to claim 5, wherein the water treatment apparatus is used for the reuse of water used in a swimming pool or a spa,

wherein the water passes through a filter cell via a circulating pump and the filtered water returns to the swimming pool or the spa.
The water treatment apparatus according to claim 13, wherein the water treatment apparatus comprises an UV irradiation device above the reactor.
The water treatment apparatus according to claim 13, wherein the filter cell is subjected to reverse washing using a circulating pump connected thereto.