KR101775010B1 - Anaerobic treatment system of wastewater combinined pressure retarded osmosis system and bio-electrochemical system - Google Patents

Abstract

The present invention relates to an anaerobic wastewater treatment system, and more particularly, to a method of anaerobic wastewater treatment by combining a pressure delay osmosis system and a bio-electrochemical system before and after the anaerobic digestion process to pre-concentrate wastewater spontaneously upon generation of electricity through pressure delay osmosis, Which is capable of producing high-quality biogas by using electricity generated by pressure delay osmosis in the reduction of carbon dioxide in the biogas after supplying the biogas produced in the anaerobic digestion process to the process, To an anaerobic wastewater treatment system combining delayed osmosis and bio-electrochemical systems.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an anaerobic wastewater treatment system combined with pressure delayed osmosis and bio-electrochemical systems,

The present invention relates to an anaerobic wastewater treatment system, and more particularly, to a method and system for anaerobic wastewater treatment, which comprises combining pressure delay osmosis and bio-electrochemical systems before and after an anaerobic digestion process to eliminate high- cost aerobic processes and capture high- To an anaerobic wastewater treatment system that combines pressure-delayed osmosis and bio-electrochemical systems, which is an environmentally friendly self-sustaining wastewater treatment technology capable of maximizing the energy recovery rate with high efficiency.

Most of the technologies currently used in wastewater treatment, especially the treatment of domestic wastewater, require a vast amount of energy for aeration (more than 50% of the total operating cost of the wastewater treatment plant) For example, an activated sludge process). In addition, this exhalation process produces a significant amount of waste sludge, which is very costly to manage. Demand for wastewater purification continues to increase globally and continues to grow, especially in developing countries, with rapid industrialization and urbanization. In China, more than 600 wastewater treatment plants have been built in ten years to meet the needs of the population in 2007, and waste sludge production in China has increased to 5% per year. Wastewater treatment is inevitable because it is a sensitive issue directly related to environmental problems and health hygiene. However, the development of technologies that are economically, efficiently and environmentally friendly to the wastewater in the face of today's severe environmental crisis and energy crisis is the most difficult task.

Wastewater, in the form of biodegradable organic pollutants, contains much more energy than the energy required for aerobic treatment. In an energy balance study of an overall wastewater treatment plant (municipal WWTP, capacity of 35,700 m ³ / day), the potential energy content of untreated domestic wastewater (431 ± 8 mg / L COD) is needed to operate the entire plant It has been reported that it exceeds about 9.3 times of energy. If such energy can be recovered to a large extent, a domestic wastewater treatment plant may be capable of producing energy-neutral or net-energy. To this end, a conceivable approach is to first recover energy from untreated wastewater to minimize or eliminate the use of aerobic treatment prior to treatment of the wastewater with the exhalation process.

Anaerobic digestion (AD) has been studied for a long time to treat waste and wastewater containing sewage sludge and livestock manure, and to stabilize contaminated loads due to its ability to produce energy. Recently, the application of AD to low-effluent wastewater treatment is of interest, as the economic benefits of large AD over aerobic treatment have become more apparent recently due to rising energy prices. However, the most difficult problem in the direct AD of raw wastewater is the low organic matter concentration of the feedstrip (i.e. low chemical oxygen demand) and the low calorific value of the produced biogas (i.e. low methane content). Therefore, in order to produce high-quality biogas with high efficiency through AD, it is necessary to pre-concentrate wastewater and increase methane content of biogas produced in AD.

Increasing the methane content in the biogas can be achieved by converting the carbon dioxide present in the biogas into methane. International Patent Publication No. WO2009 / 155587, a biological process technology for capturing carbon dioxide and producing methane, discloses an electrical methanogenic reactor and process for methane production, which converts carbon dioxide to methane using a bio-cathode containing a methanogenic microorganism have. The International Patent Publication discloses a technique capable of producing methane gas by reducing carbon dioxide without using hydrogen and / or an organic carbon source. However, the electrochemical conversion of CO ₂ into CH ₄ is not thermodynamically favorable, Therefore, in order to maximize the methane production, it is necessary to supply the external electric power continuously and continuously for a long period of time in the case of increasing the organic matter content and the external voltage magnitude of the wastewater supplied to the electrical methane production reactor or the quality of the low- quality (low organic matter). That is, the technique disclosed in the above-mentioned international patent has a limitation in improving methane generation efficiency due to dependence on external voltage.

International Publication No. WO2009 / 155587 (International Publication Date: December 23, 2009)

Accordingly, it is an object of the present invention to combine PRO (pressure-retarded osmosis) and BES (bio-electrochemical system) before and after the AD process, When the electricity is generated through PRO using seawater as an inducing solution as a feed solution, the wastewater is voluntarily pre-concentrated and supplied to the AD process. The biogas produced in the AD process is supplied to an electrometanogenesis cell PRO, and BES, which are environmentally friendly self-supporting wastewater treatment technologies that can convert high-quality biogas into high-quality biogas by converting carbon dioxide into methane in electric furnace biogas generated from PRO.

In order to achieve the object of the present invention, the present invention provides a PRO system including a PRO system using a salinity difference between wastewater and seawater, an anaerobic digestion tank, and an anode chamber for removing organic matter and a cathode chamber for generating biogas. And an anaerobic wastewater treatment system combining BES.

In one embodiment of the present invention, as the water moves from the wastewater to the seawater in the PRO system, the concentrated wastewater may be supplied to the anaerobic digester.

In one embodiment of the present invention, electricity generated in accordance with the water flow from wastewater to seawater in the PRO system may be to propel the BES.

In one embodiment of the present invention, the anaerobic digester may comprise an anaerobic microorganism.

In one embodiment of the present invention, the release water discharged from the anaerobic digestion tank may be supplied to the anode chamber of the BES and the biogas produced by the anaerobic digestion tank may be supplied to the cathode chamber of the BES.

In one embodiment of the present invention, the BES may be an electromethanogenesis cell (electro-methane generating cell).

In one embodiment of the present invention, the cathode of the ENC may be coated with an electroactive anaerobic microorganism on its surface.

In one embodiment of the present invention, the electroactive anaerobic microorganism may be a methanogenic microorganism.

In one embodiment of the present invention, the biogas produced in the BES may be recovered.

In one embodiment of the present invention, the biogas may comprise at least about 85% by volume of methane relative to the total volume.

According to the present invention, it is possible to generate high-quality biogas of pipeline natural gas level from wastewater, thereby maximizing the energy recovery rate due to wastewater treatment.

In particular, the PRO and BES-combined anaerobic wastewater treatment systems of the present invention combine PRO, AD, and BES (particularly EMC) with intensive, self-sustained wastewater treatment technology to naturally pre- It is an energy-efficient, environmentally friendly technology that can increase the content of methane in the biogas generated in wastewater treatment process and remove the carbon dioxide that causes environmental problems. In addition, the anaerobic wastewater treatment system combined with PRO and BES according to an embodiment of the present invention can be used in an energy-neutral or net-energy production system by receiving concentrated wastewater and / The implementation effect can be expected.

1 is a block diagram of an anaerobic wastewater treatment system combining PRO and BES according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

It is to be understood that the terms or words used in the specification and claims are not to be construed in a conventional or dictionary sense and that the inventor may properly define the concept of a term in order to best describe its invention And should be construed in accordance with the principles and meanings and concepts consistent with the technical idea of the present invention.

In the specification of the present invention, when a component is referred to as "comprising ", it means that it can include other components as well as other components, .

In the specification of the present invention, "A and / or B" means A or B, or A and B.

Hereinafter, the present invention has been specifically described with reference to the accompanying drawings, but the present invention is not limited thereto.

1 is a block diagram of an anaerobic wastewater treatment system combining PRO and BES according to an embodiment of the present invention.

Referring to FIG. 1, an anaerobic wastewater treatment system combining PRO and BES according to an embodiment of the present invention includes a PRO system, anaerobic digestion tank, and BES.

In one embodiment of the present invention, the PRO system utilizes wastewater as a feed solution and seawater as a draw solution to generate power through the pressure-delayed osmosis membrane module and the electricity generating turbine, . In the case of using the wastewater as the feed solution and the seawater as the induction solution in separating the feed solution and the induction solution with the semi-permeable membrane which is permeable to water but not the solute through the PRO system, The water in the wastewater is moved to the seawater through the semi-permeable membrane. At this time, the pressure applied to the seawater causes the electricity generating turbine to rotate to generate electricity.

The PRO system is an osmotic-centric membrane process. When the solution with different osmotic pressure ( Π ) is separated by a dense membrane (semi-permeable membrane) in which water permeability is water-permeable but solute permeation is limited, the salt concentration difference between the inductive solution and the feed solution Therefore, the osmotic pressure is generated in the low-Π The water spontaneously flows from the solution (feed solution) to the high Π solution (induction solution). Typical seawater has an osmotic pressure of about 2.5 MPa, while the osmotic pressure of typical wastewater (e.g., domestic wastewater) is only about 0.05 to 0.1 MPa. Due to this, low Π wastewater can be effectively enriched through the PRO 'osmotic pump action' using spontaneously available seawater as an inducing solution. At this time, there is no need to apply artificial pressure. On the other hand, seawater has a higher pressure than atmospheric pressure due to the elevated water level due to water movement, and this pressure can turn the electricity generating turbine. Essentially, the PRO system converts the chemical potential energy (i.e., osmotic energy) between the inductive solution and the feed solution into mechanical energy (the pressure of water that can later be used to turn the turbine for generating electricity). PRO power density is given by? P J _v , where? Is the turbine efficiency factor, P is the seawater pressure (which can be set during operation), and J _v is the permeate flux through the PRO transflective membrane.

As described above, the PRO system has the ability to concentrate the feed solution and the power production capability. When wastewater is used as the feed solution as in the present invention, when electricity is generated due to sufficient water movement, the wastewater loses a considerable amount of water and remains in a concentrated state. At this time, the concentration of the concentrated wastewater can be increased about 5 times to about 20 times, or about 10 times to about 15 times, or about 10 times that of the untreated concentration, but the present invention is not limited thereto.

In one embodiment of the present invention, the seawater may be seawater, or may be synthetic seawater, i.e., saline.

In one embodiment of the present invention, the wastewater may be a domestic wastewater containing at least one selected from the group consisting of food processing wastes, milk wastes, sewage slurry, domestic animal excrement, carbohydrate processing wastes, and fish processing wastes.

In general, wastewater can be regarded as a low-concentration organic wastewater with a low organic content, with a COD of about 300 mg / L to about 800 mg / L and an average of 431 ± 8 mg / L without any treatment. Since such low-concentration organic wastewater is high in volume and large in volume, it is possible to reduce the energy efficiency of the low-concentration organic wastewater, which is high in volume, in accordance with the operation temperature of the anaerobic microorganism, even if the wastewater is purified using anaerobic treatment, , It is advantageous from the viewpoint of energy to produce high concentration organic wastewater through pre-concentration.

In the present invention, pre-concentration of wastewater can be performed naturally when electricity is generated via PRO using seawater as an inductive solution. It is important to improve the output of the PRO power density and improve the pre-concentration efficiency by preventing film fouling and concentration polarization (CP) in the PRO transflective film for subsequent optimization of the AD processing.

Factors limiting the PRO power density include (1) the role of the interaction between the hydrodynamic force and the contaminant-odorous / contaminant-membrane interactions, (2) reverse solute diffusion in PRO, and (3) PRO fouling, such as the interaction between back-diffusing solute and contaminant in the feed solution and its effect on PRO fouling.

In order to minimize film fouling and concentration polarization in the PRO transflective film, a double skin osmotic membrane filled with a porous support may be used in the present invention, but the present invention is not limited thereto.

The porous support may be a porous polymer-based fiber. The porous polymer may be, but is not limited to, polyester, polysulfone, polyethersulfone, polyamide, polypropylene, polyvinyladene fluoride, or copolymers thereof.

In addition, the porous support may further include alumina, silica, or a combination thereof.

According to one embodiment of the present invention, the use of the semi-permeable membrane for controlling film fouling and concentration polarization results in at least about 2 W / m ² per membrane area, for example, at least about 3 W / m ^2, may implement a significantly enhanced PRO power density in W / m ² or at least about 5 W / m ² to about 20 W / m ² or from about 5 W / m ² to about 10 W / m ² (as a reference, the realization to date The maximum value of the PRO power density is about 1 W / m < ² >). The PRO system may be, but is not limited to, a computer-based fluid dynamics (CFD) model for optimization.

Electricity generated through the PRO system can be used in an anaerobic wastewater treatment system combining PRO and BES of the present invention, and in particular, can be used to propel EMC, a BES. Some of the electricity generated through the PRO system may be used during construction of the present invention and the remainder may be stored.

In one embodiment of the present invention, the AD process is a process of removing organic matter from the high concentration organic wastewater and producing biogas, and the wastewater concentrated in the PRO system is supplied to the anaerobic digester for AD. At this time, the high concentration organic wastewater means wastewater concentrated through the above PRO system.

The anaerobic digester may comprise an anaerobic microorganism. In the anaerobic digestion tank, hydrolysis, acid fermentation, nitrate formation and methane production are carried out by the action of the anaerobic microorganism. The anaerobic microorganisms used in the anaerobic digestion tank may be, but not limited to, fermentative bacteria.

The performance of an anaerobic digester is greatly influenced by small changes in the microbial community. Conversely, if the performance of a digester is changed, the anaerobic microbial population included in the anaerobic digester may be changed.

The anaerobic digester may comprise a temperature controller for measuring and controlling the internal temperature of the anaerobic digester, the internal temperature of the anaerobic digester being selected from the group consisting of a temperature between about 30 ° C and about 40 ° C (mesophilic) and a temperature between about 50 ° C and about 60 ° C Thermal stability). The two temperature conditions may be sequential and may be maintained at a high temperature of about 50 ° C to about 60 ° C by heating and maintained at a temperature of about 30 ° C to about 40 ° C lower than the waste heat, To maintain a low temperature of 30 占 폚 to about 40 占 폚, and then to maintain the high temperature of about 50 占 폚 to about 60 占 폚 for the first time. This temperature regulation can be repeated alternately over a period of time and is intended to match the appropriate operating temperature of the microorganism in the anaerobic digester. Regardless of the sequence, organic matter removal proceeds by mesophilic microorganisms having activity at temperatures in this region at about 30 ° C to about 40 ° C, and at about 50 ° C to about 60 ° C, Organic matter removal proceeds by microorganisms.

Alternatively, the anaerobic digester may be a plurality of serially connected anaerobic digesters. At this time, the preceding one anaerobic digester may be maintained at a temperature of about 50 캜 to about 60 캜, and the other anaerobic digester may be maintained at a temperature of about 30 캜 to about 40 캜.

The biogas produced in the AD process includes methane, carbon dioxide, hydrogen sulfide, and ammonia. The methane content is about 55 vol% to about 80 vol% with respect to the total volume of the biogas, the carbon dioxide content is about 20 Vol.% To about 45 vol.%, And the remaining gas content is trace. However, biogas, which is considered as an alternative energy, has an average methane content of only about 60%, and the calorific value of the biogas produced in the AD process is higher than 95% by volume of pipeline natural gas ), Which is about 60% of the calorific value of 23 MJ / m ³ . Generally, the biogas produced in the AD process is low in quality and low in value as an alternative energy. Therefore, it is important to improve the quality of the biogas through subsequent BES, particularly EMC.

In one embodiment of the invention, the BES is carried out by an electro-methanogenic cell (EMC) which converts the current and CO ₂ directly to CH ₄ with the aid of an electroactive methanogenic bacterium. The EMC may include, but is not limited to, a cathode surface coated with electroactive methanogenic bacteria.

In the preceding PRO system, electricity generated by the water flow from the wastewater to seawater drives the EMC, and the effluent discharged from the anaerobic digester is supplied to the anode chamber of the BES, for example, the EMC, Biogas is supplied to the cathode chamber of the BES, for example, EMC.

The inside of the anode chamber is filled with biodegradable organic matter, which is discharged water from the anaerobic digestion tank, while the inside of the cathode chamber may be filled with a minimal nutrient microorganism liquid excluding pure water, an electrolyte aqueous solution, or an oxygen source.

The biodegradable organic substances discharged from the anaerobic digestion tank and supplied to the anode chamber are converted into CO ₂ , H ⁺ and electrons by the organic active bacteria. The electrons flow to the cathode through an electric circuit connecting the anode and the cathode outside the chamber, while the cation (H ⁺ ) physically moves to the cathode chamber through the cation exchange membrane separating the two chambers. At the cathode, under anaerobic conditions, electrons and cations react with CO ₂ to produce CH ₄ . In the cathode chamber, the carbon dioxide in the biogas is converted into methane with the aid of an electroactive methanogenic bacterium coated on the surface of the cathode, and the chemical formula of the methanation reaction is as follows:

CO ₂ + 8H ⁺ + 8e ^- ? CH ₄ + 2H ₂ O.

As shown in the above formula, the direct conversion of CO ₂ to CH ₄ not only improves the biogas quality, but also increases the methane content.

At the heart of this methane generation (carbon dioxide reduction) reaction is a "bio-cathode" coated with a specific methanogenic bacterium capable of directly capturing and using electrons to reduce CO ₂ to CH ₄ . The catalyst of the reaction is a microorganism. In the present invention, it is not necessary to use a noble metal such as platinum as a cathode coated with microorganisms. When a stable cathodic biofilm is developed, due to its use as a bio-cathode, EMC is attractive because it can operate with a minimum maintenance ratio, especially at a voltage of 1V. This means not only an improvement in the biogas quality but also an increase in the production of CH ₄ , which is significantly different from the conventional physico-chemical biogas purification method. For reference, physico-chemical means can be used to purify biogas by removing contaminants / impurities including CO ₂ and improve the quality of biogas to the level of natural gas quality. However, It is easy to generate. More importantly, the physico-chemical post-purification process can increase the CH ₄ content in the final produced unit biogas, but not the total amount of CH ₄ produced, and the difference in total energy recovery with or without purification steps none.

The cathode may be one selected from the group consisting of graphite felts, graphite rods, carbon fibers, and carbon rods.

The bio-cathode used in the present invention is a unique feature of EMC and is not shared with a microbial fuel cell (MFC) or a microbial electrolysis cell (MEC) that generates hydrogen by microbial activity.

In one embodiment of the present invention, the biogas produced in the BES may be recovered and utilized as energy. The biogas may be of improved quality by containing at least about 85% by volume, such as from about 85% by volume to about 99% by volume of methane, based on the total volume. At this time, the bio-gas quality is improved with the EMC, pipeline natural gas levels: it is possible to achieve a high quality (95 vol.% Or more CH ₄ containing the heating value of 36-40 MJ / m ^3). The biogas may have a methane content of at least about 85 vol%, at least about 90 vol%, or at least about 95 vol%, based on the total volume, and may range from about 85 vol% to about 99 vol%, about 85 vol% , From about 85 vol% to about 90 vol%, from about 90 vol% to about 99 vol%, from about 95 vol% to about 99 vol%, or from about 90 vol% to about 95 vol% .

According to one embodiment of the present invention, it is possible to combine AD and BES (particularly, EMC) in the process of producing biogas from organic wastewater to improve the methane content of the energy gas in the biogas, Can be removed. As a result, it is possible to improve the quality of the biogas to achieve the high quality of the pipeline natural gas level (with a CH ₄ content of more than 95% by volume: 36-40 MJ / m ³ ), and the energy recovery rate Can be maximized.

In addition, the effect of the energy-neutral or net-energy production system can be expected by naturally supplying the concentrated wastewater and / or electric power required in the AD and BES processes from the PRO.

Therefore, the anaerobic wastewater treatment system combining PRO and BES according to the present invention is expected to solve environmental pollution and energy crisis problems.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention. You will understand. It is therefore to be understood that the embodiments described above are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

Claims (10)

A pressure retarded osmosis system utilizing the salinity difference between wastewater and seawater;
Anaerobic digester; And
An anode chamber for removing organic matter, and a cathode chamber for generating biogas,
In the pressure delay osmosis system, concentrated wastewater is supplied to the anaerobic digester as the water moves from the wastewater to the seawater.
An anaerobic wastewater treatment system combining pressure-delayed osmosis and bio-electrochemical systems.
delete The method according to claim 1,
Wherein the electricity generated in accordance with the water flow from the wastewater to the seawater in the pressure delay osmosis system propels the bio-electrochemical system.
The method according to claim 1,
Wherein the anaerobic digester comprises an anaerobic microorganism. ≪ RTI ID = 0.0 > 11. < / RTI >
The method according to claim 1,
Wherein the discharged water discharged from the anaerobic digestion tank is supplied to the anode chamber of the bioelectrochemical system and the biogas produced in the anaerobic digestion tank is supplied to the cathode chamber of the bioelectrochemical system. To the anaerobic wastewater treatment system.
The method according to claim 1,
Wherein the bio-electrochemical system is an electromethanogenesis cell. ≪ RTI ID = 0.0 > 11. < / RTI >
The method according to claim 6,
Wherein the cathode of the electro-methane generating cell is coated with an electro-active anaerobic microorganism on its surface.
8. The method of claim 7,
Wherein the electroactive anaerobic microorganism is a methanogenic microorganism, wherein the anaerobic wastewater treatment system incorporates a pressure delay osmosis and bio electrochemical system.
The method according to claim 1,
Wherein the biogas produced in the bio-electrochemical system is recovered. ≪ Desc / Clms Page number 24 > 21. An anaerobic wastewater treatment system incorporating a pressure delay osmosis and bio-electrochemical system.
10. The method of claim 9,
Wherein the biogas comprises at least 90 vol.% Methane, based on the total volume, of an anaerobic wastewater treatment system incorporating a pressure delay osmosis and bio electrochemical system.

Images