KR20200081001A - Sewage disposal system having hydrogen generation ability - Google Patents

Abstract

Provided is a sewage treatment system for producing hydrogen to produce hydrogen in real time at low costs. According to the present invention, the sewage treatment system for producing hydrogen comprises: a grit chamber removing sand and foreign matters from inflow sewage; a first settling basin removing fine organic particles from the sewage supplied through the sand basin; a microorganism electrolysis cell reactor including an anode degrading an organic material included in an organic solution supplied through the first settling basin by microorganisms attached to a surface thereof to generate an electron and a free proton, a power supply unit transferring the electron generated from the anode, and a cathode receiving the electron through the power supply unit and reacting the free proton and the electron to generate hydrogen; and a second settling basin treating outflow water transferred from the microorganism electrolysis cell reactor to discharge final treatment water.

Description

Hydrogen production sewage treatment system {SEWAGE DISPOSAL SYSTEM HAVING HYDROGEN GENERATION ABILITY}

The present description relates to a sewage treatment system capable of hydrogen production.

Sewage discharged from homes or factories contains suspending, colloidal, and soluble substances, and if released into natural waters in that state, it can destroy ecosystems or spread waterborne infectious diseases. To prevent this, sewage treatment is required to purify the sewage by physicochemical or biological methods.

According to the most widely used biological method for sewage treatment, contaminants consisting of carbon-based organic materials, nitrogen-containing compounds, phosphorus-containing compounds, etc. are biologically treated in a reaction tank including an anaerobic tank, anoxic tank, and aerobic tank. However, the conventional reaction tank is equipped with an aeration device for aeration of the mixed solution. By aerating the mixed liquid, the dissolved oxygen concentration in the mixed liquid required for the activity of the activated sludge microorganisms can be improved or the mixed liquid can be stirred. When the amount of air supplied to the mixed liquid of the aerobic tank by the aeration device (hereinafter referred to as "aeration air volume") is insufficient, the water quality of the treated water deteriorates. Thus, conventionally, a dissolved oxygen concentration meter is installed in the exhalation tank, and the aeration air volume of the exhalation tank is controlled so that the measured value of the dissolved oxygen concentration meter becomes a set dissolved oxygen concentration target value. However, because it is based on an indirect indicator called dissolved oxygen concentration, in order to maintain the water quality of the treated water within a regulated value, a high dissolved oxygen concentration target value must be set, and the aeration air volume of the exhalation tank is always excessive. Therefore, the aeration device that requires energy for operation has hindered the reduction of the operating cost and energy saving of the recycled water production system.

The present disclosure seeks to provide a hydrogen-producing sewage treatment system capable of producing hydrogen and enabling energy self-sufficiency while saving energy by not requiring aeration.

The hydrogen production sewage treatment system according to the embodiments includes a sedimentation basin to remove sediment and contaminants from the inflowing sewage, a primary sedimentation basin to remove fine organic particles of the sewage flowing through the sedimentation basin, and an inflow through the primary sedimentation basin The organic substance contained in the organic solution to be decomposed by microorganisms attached to the surface to generate electrons and glass protons, a power supply unit that transfers electrons generated from the anode, and receives electrons through the power supply unit and receives glass protons It includes a microbial electrolysis cell reactor comprising a cathode that generates hydrogen by reacting the electrons, and a secondary sedimentation basin to treat the effluent delivered from the microbial electrolysis cell reactor to discharge the final treated water.

The hydrogen production sewage treatment system according to the embodiments does not include a bioreactor that requires aeration. Therefore, it is possible to save operating cost and energy used in the aeration device. In addition, hydrogen can be produced in real time and at low cost through a microbial electrolysis device installed in place of the bioreactor and an additionally installed water electrolysis device.

1 is a schematic diagram of a hydrogen-producing sewage treatment system according to the first embodiment.
2 and 3 are schematic diagrams showing modifications of the microbial electrolysis cell reactor applied to the hydrogen-producing sewage treatment system.
4 is a schematic view showing a case in which a plurality of microbial electrolysis cells are installed in a reactor.
5 is a schematic diagram of a hydrogen-producing sewage treatment system according to a second embodiment.
6 is a schematic diagram of a water electrolysis device applied to a hydrogen production sewage treatment system according to a second embodiment.

Hereinafter, the embodiments will be described in detail so that those skilled in the art can easily implement them. Embodiments may be implemented in many different forms, and are not limited to the specific embodiments described herein.

1 is a schematic diagram of a hydrogen-producing sewage treatment system according to the first embodiment.

Referring to Figure 1, the hydrogen production sewage treatment system includes a sedimentation basin, a primary sedimentation basin, a microbial electrolysis cell reactor, and a secondary sedimentation basin.

The sedimentation site 100 removes sediments and contaminants from the sewage.

The primary sedimentation tank 200 removes fine organic particles with respect to the inflow sewage from which the sediment and debris have been removed through the sedimentation tank 100 to reduce the filtration load of pollutants in subsequent processes. The primary sedimentation basin 200 may be a gravity sedimentation basin.

The microbial electrolysis cell (MEC) reactor 300 decomposes organic substances introduced from the primary sedimentation tank 200 into carbon dioxide and simultaneously generates hydrogen. 1 illustrates a case where the microbial electrolysis cell reactor 300 is composed of a single chamber type MEC.

The organic matter (substrate, (CHO)n) contained in the organic solution flowing through the primary sedimentation tank 200 is decomposed by microorganisms 315 having electrochemical activity attached to the anode 310 and carbon dioxide (CO2) and Generate electrons. Therefore, the reaction as in Formula 1 or 2 below proceeds at the anode 310. Formula 1 is described using glucose as an example, and Formula 2 is illustrated using sodium acetate as an example.

[Formula 1]

_{C 6 H 12 O 6 + 6H} 2 O → 6CO 2 + 24H + + 24e -

[Formula 2]

^{_{CH 3 COO - + 4H 2 O}} → 2HCO 3 - + 9H + + 8e -

The pH around the anode 310 is about 4 to about 6, and the temperature can be about 20°C to about 100°C. Under these circumstances, an efficient organic material decomposition reaction may occur, and more electrons may be generated.

The electrons generated at the anode 310 are transferred to the cathode 320 through the anode 310 and the power supply 340, and the glass proton generated at the anode 310 and delivered to the cathode 320 ( It is combined with free proton, H ⁺ ) to produce hydrogen as shown in Chemical Formula 3.

[Formula 3]

2H ⁺ + 2e- → H ₂ ↑

In addition, by the DC power supplied from the power supply unit 340, a water decomposition reaction as shown in Chemical Formula 4 is performed at the cathode 320, and hydrogen (H ₂ ) may be additionally generated.

[Formula 4]

^{_{2H 2 O + 2e - → 2H}} 2 ↑ + 2OH -

When a direct-current power supply of 0.3 to 2.0 V, preferably 0.9 to 1.2 V, is applied from the power supply 150, the water decomposition reaction of Chemical Formula 4 may proceed smoothly.

For energy independence, the power supplied to the power supply unit 150 may be supplied through external sustainable energy. 1, sustainable energy may be supplied by the solar power generator 600.

The generated hydrogen (H ₂ ) may be discharged to an external hydrogen gas storage tank 500 through a hydrogen collection unit 350 formed in the microbial electrolysis cell reactor 300, and the hydrogen thus stored is compressed, compressed, cooled, etc. It may be supplied to the hydrogen filling tank 700 through and be supplied to a hydrogen gas vehicle or the like. Also, although not shown in the drawings, the hydrogen gas stored in the hydrogen gas storage tank 500 may be used as a raw material for other power generation devices, such as a fuel cell, to produce new power.

Microbial Electrolysis Cell (Microbial Electrolysis Cell, MEC) Reactor (reactor) (300) constituting the electrochemical activity of the microorganism (315) is an anaerobic microorganism, and thus does not require an aeration device unlike the conventional sewage treatment system.

The secondary sedimentation tank 400 collects the sludge precipitated from the effluent delivered from the microbial electrolysis cell centrally, or highly filters the pollutants including untreated organic substances, suspended solids, and phosphorus in the effluent to maintain river water or other The final treated water is discharged after filtration and disinfection to be reused for the purpose.

2 and 3 are schematic cross-sectional views showing various modifications of a microbial electrolysis cell (MEC) reactor 300 that can be applied to a sewage treatment system according to one embodiment.

2 is a vertical structure in which the anode 310 is installed in the main chamber 315 and the cathode 320 is installed in the cover 325 thereon to show a structure in which hydrogen gas is more easily captured.

3 shows an MEC reactor consisting of two chambers, an anode chamber 312 on which the anode 310 is placed by a separation exchange membrane 330 and a cathode chamber 322 on which the cathode 320 is placed.

The separation and exchange membrane not only prevents microorganisms in the anode chamber 312 from moving, but also allows free proton (H ⁺ ) generated in the anode chamber 312 to move to the cathode chamber 322 or the cathode chamber 322. It may be composed of a proton exchange membrane, or an anion exchange membrane, a bipolar membrane or a charge mosaic membrane to maintain the purity of the hydrogen gas generated in the.

Although not shown in the drawings, the reactor 300 may be configured in a cylindrical shape, the details of which are described in detail in KR2016-0153426 filed by the applicant, the contents of which are incorporated herein.

4 is a schematic diagram showing a case in which multiple MECs are installed in the reactor 300 to improve the efficiency of hydrogen production.

A number of MECs are installed in one reactor 300, and in this case, the MECs may be MECs disclosed in FIGS. 1 to 3, but are implemented as MECs having a cylindrical shape disclosed in KR2016-0153426. It can be advantageous.

5 is a schematic diagram of a sewage treatment system according to a second embodiment.

Referring to FIG. 5, the sewage treatment system is different from the first embodiment in that it further includes a water decomposition device 500 at the rear end of the secondary sedimentation tank 400 unlike the first embodiment of FIG. 1.

The water decomposition device 500 receives the treated water and decomposes it to generate hydrogen. Therefore, the hydrogen production efficiency of the hydrogen production sewage treatment can be increased. As the water decomposition device 500, a large capacity reverse electrodialysis device (RED) may be used.

6 is a large-capacity RED applied to the water decomposition apparatus 500 of the hydrogen-producing sewage treatment system according to the second embodiment is composed of a membrane stack 810, a cathode chamber 830, and an anode chamber 840.

When the batch type first RED 100 illustrated in FIG. 2 is compared with the conventional RED 1000 illustrated in FIG. 3, in the case of the batch type first RED 100, the cathode chamber 830 and the anode chamber 840 ), a neutral pH water is used as an electrode solution (catholyte, anolyte). As a neutral pH water, a neutral pH NaCl or Na 2 SO 4 aqueous solution may be used. Also, the electrolytes of the cathode chamber 830 and the anode chamber 840 are non-circulated and exist only in each chamber 830 or 840. Therefore, it is easy to collect the hydrogen obtained as a result of the water decomposition reaction to the outside through the collection column 870 connected to the upper portion of the chamber.

The minimum number of unit cells constituting the membrane stack 810 may vary according to a concentration difference between the brine (HC) and the fresh water (LC) treated water flowing into the membrane stack 810. When using normal seawater with a concentration of 35,000 mg/L as brine (HC) and passing through the secondary sedimentation tank 400, it is provided after treatment with a concentration of 0 to 1,000 mg/L as fresh water (LC), i.e. When the concentration difference between the brine and the treated water (fresh water) is about 30, if more than 50 cells, a sufficient membrane voltage (6V) capable of causing an electrolysis of water can be formed.

When the concentration difference between brine and fresh water is 30 or more and the number of unit cells is 50 cells or more, it is possible to form a sufficient membrane voltage that can cause an electrolysis reaction of water. Even when neutral pH water or fresh water is used, the amount of power reduction and the amount of hydrogen production due to electrode solution resistance become negligible. Furthermore, due to the nature of large-capacity RED, as the number of cells increases, the minimum overpotential for electrode reaction and the electrode solution The electrode resistance due to resistance becomes relatively small. Therefore, it is not necessary to use strong corrosive acids and strong bases as electrode solutions to reduce overpotential. In other words, in reverse electrodialysis salt-differentiated power generation consisting of hundreds of cells and even more than 1,000 cells, it is possible to produce hydrogen at the same time while producing electricity with pure water, so it has various advantages over hydrogen production by conventional water electrolysis. have. In conventional water electrolysis, pure water cannot be used as an electrolyte because the effect of solution resistance is large, so pure water is not used as an electrolyte. In the high-capacity RED illustrated in FIG. 6, hydrogen can be produced by supplying only pure water without using an existing redox species to the cathode chamber 830, thereby producing more pure hydrogen gas. Accordingly, it is possible to directly connect to the hydrogen filling station 700 or the fuel cell without additional separation devices such as a hydrogen separation membrane. In addition, since it does not use strong acids or strong bases, it is free from structural instability and handling precautions due to corrosion reactions.

Of course, in order to lower the solution resistance of the cathode chamber 830 and the anode chamber 840, an aqueous solution in which a salt is dissolved may be used as necessary. For example, NaCl or Na ₂ SO ₄ end An aqueous solution dissolved at 2.92 g/L to 5.8 g/L may also be used. When the salt is dissolved, the effect of reducing the resistance of the electrode solution can be seen. However, as described above, if the number of cells increases, the effect of the resistance of the electrode solution is minimal, so pure water or fresh water can be used as the electrode solution.

That is, as shown in Chemical Formula 5, oxygen and electrons may be generated by the oxidation reaction of water at the anode 842. When sodium chloride is dissolved in the solution of the anode chamber 840, chloride ions are oxidized to generate chlorine gas as shown in Chemical Formula 6.

[Formula 5]

^{_{H 2 O → 2H + + 2e}} - + 1 / 2O 2 (Anode)

[Formula 6]

_{^{2Cl - → Cl 2 + 2e -}} ( anode)

In addition, hydrogen and hydroxide ions may be generated by a reduction reaction of water at the cathode 32 as shown in Chemical Formula 7.

[Formula 7]

_{2H 2 O + 2e- → H 2} ↑ + 2OH - ( cathode)

The cathode 832 and the anode 842 may be formed of noble metals such as Pt. For example, non-precious metals such as carbon, titanium, nickel, manganese, and copper can be used as electrodes.

The electrode solution of the cathode chamber 830 of the large-capacity RED and the electrode solution of the anode chamber 840 are configured as a non-circulating type, so that the cathode chamber 830 and the anode chamber 840 may be independently configured. When the cathode chamber 830 and the anode chamber 840 are independently configured, hydrogen generated in the cathode chamber 830 and oxygen or chlorine gas generated in the anode chamber 840 are not mixed with each other, and then collected again. No separation process is necessary.

Therefore, hydrogen is transferred to the hydrogen gas storage tank 500 through the collection column 870 of the cathode chamber 830, and to the oxygen or chlorine gas storage tank 550 through the collection column 870 of the anode chamber 840. Oxygen or chlorine is delivered.

In the case of treated water, most of the organic pollutants or polyvalent ions are filtered through the sedimentation tank 100, the primary sedimentation 200, the microbial electrolysis cell reactor 300, and the secondary sedimentation 400 of the shearing stage. Due to the introduction of water, fouling problems and the like can be significantly reduced.

The film stack 810 is stacked in a structure in which a cathode 832 and an anode 842 are disposed at both ends. The cathode 832 and the anode 842 each undergo a reduction and oxidation reaction to generate a flow of electrons (e ⁻ ). The cathode 832 and the anode 842 are formed in a mesh shape having a constant open area. The cathode 832 and the anode 842 are configured in a mesh shape, thereby preventing the membrane stack 810 from expanding and allowing the membrane stack 810 to directly contact the solution in the cathode chamber 830 or the anode chamber 840. . The cathode 832 and the anode 842 may be formed of a metal mesh, and in the case of the metal mesh, a titanium mesh or the like may be used.

The details of the above-described water decomposition apparatus are described in detail in KR2018-0033943 filed by the applicant, the contents of which are incorporated herein.

Various embodiments have been described above, but the scope of the rights is not limited thereto. The embodied form can be implemented in various ways within the scope of the detailed description of the invention and the accompanying drawings, and it is natural that this also belongs to the scope of rights.

Claims (5)

A sedimentary basin to remove influent sewage deposits and debris;
A primary sedimentation basin to remove fine organic particles of the sewage flowing through the sedimentation basin;
An anode that generates electrons and free protons by decomposing organic substances contained in the organic solution flowing through the primary sedimentation tank by microorganisms attached to the surface, and a power supply unit that delivers electrons generated from the anode, through the power supply unit A microbial electrolysis cell reactor comprising a cathode that receives electrons and reacts free protons with the electrons to generate hydrogen; And
Hydrogen-producing sewage treatment system including a secondary sedimentation basin to discharge the final treated water by treating the effluent delivered from the microbial electrolysis cell reactor. According to claim 1,
The power supply unit is a hydrogen production lower processing system to apply a DC power of 0.9V or more to the cathode to cause a water decomposition reaction in the cathode. The method according to claim 1 or 2,
The microbial electrolysis cell reactor further includes a hydrogen collection unit for collecting the generated hydrogen,
The hydrogen production lower processing system in which the hydrogen is delivered to an external hydrogen gas storage tank through the hydrogen collection unit. The method according to claim 1 or 2,
Hydrogen production bottom processing system further comprising a water decomposition device for generating hydrogen by water decomposition at the rear end of the secondary settling tank. According to claim 4,
The water decomposition device
A membrane stack composed of a cation exchange membrane and an anion exchange membrane alternately forming a brine channel and the final treated water channel, and a plurality of unit cells are stacked to provide a membrane voltage required for the water decomposition reaction;
A cathode chamber and an anode chamber which are installed at both ends of the membrane stack and each of which contains water as an electrode solution;
A cathode installed in the cathode chamber to generate the hydrogen by a reduction reaction of the water; And
The anode installed in the anode chamber includes an anode that generates oxygen and electrons by the oxidation reaction of the water in the anode chamber,
A hydrogen production bottom processing system, which is a reverse electrodialysis device that produces electricity while the electrons generated in the anode chamber are supplied to the cathode through a load.

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