KR101273265B1 - Bio gas recovery and the separated organic carbon from the raw sewage - Google Patents

Abstract

The present invention reduces the generation of organic matter (BOD ₅ ), nitrogen, phosphorus and solid carbon emissions in the sewage and wastewater of sewage treatment plants with significant changes in the inflow and water quality, and at the same time produces a low energy alternative carbon. The present invention relates to an advanced sewage and wastewater treatment system for the recovery and recycling of low-energy valuable resources, and utilizes bio-floculation and polymer organic / inorganic flocculant, and maximizes sewage sludge separation. Disclosed is a sewage and wastewater treatment apparatus and treatment method for recovering methane gas (Bio-energy) through a high temperature and medium temperature anaerobic digestion process and satisfying enhanced effluent water quality standards.

Description

Biogas recovery and the separated organic carbon from the raw sewage}

The present invention reduces the generation of organic matter (BOD ₅ ), nitrogen, phosphorus and solid carbon emissions in the sewage and wastewater of sewage treatment plants with significant changes in the inflow and water quality, and at the same time produces a low energy alternative carbon. The present invention relates to an advanced sewage and wastewater treatment system for the recovery and recycling of low energy valuable resources, and more specifically, the removal of colloidal and floating organic substances (VSS, SSCOD), nitrogen and phosphorus in sewage by physical, chemical and biological methods. The present invention relates to a new concept of advanced sewage and wastewater treatment system and method for reducing carbon dioxide and recovering methane gas (Bio-energy) through the high and medium temperature anaerobic digestion process.

In general, sewage and wastewater includes urban sewage, livestock waste, agricultural wastewater, and industrial wastewater, and the wastewater contains various nutrients such as nitrogen, phosphorus, and organic substances called BOD. have.

Therefore, it is the most essential nutrient element for microorganisms that metabolize and metabolize energy using these nutrients. For example, organic matter is decomposed and microbial cell synthesis is progressed by catabolism and assimilation of microorganisms as follows.

Catabolism: C _X H _Y O _Z + (X + Y / 4-Z / 2) O ₂ → XCO ₂ + (Y / 2) H ₂ O

-Assimilation: C _X H _Y NH ₃ + O ₂ → cellular material + CO ₂ + H ₂ O

In addition, nitrogen and phosphorus are the main components of the nucleic acid (nucleic acid), the organic structural component of the cell, the most basic unit of life. The nucleic acid is based on a single nucleotide consisting of a nitrogen-containing base (purine base, pyrimidine base), an pentose sugar (pentose) and phosphoric acid, and the phosphate between the 3'- and 5'-positions of the pentose of each nucleotide. Long chain polynucleotides polymerized by diester bonds, present in the nucleus of a cell. From these, nitrogen and phosphorus are the most essential elements for microorganisms that break down organic matter.

Therefore, organic nitrogen compounds contained in domestic wastewater include proteins, peptide bonds, amino acids, urine, and the like, while inorganic nitrogen compounds contain ammonium ions and small amounts of ammonia. Nitrogen oxides in the form of nitrates in wastewater are from industrial or agricultural wastewater. Most of the nitrate and ammonium compounds used in fertilizers are soluble. Or it is washed by the lake and flows in.

The use of phosphate fertilizer in fertilizer is only about half of nitrogen compound fertilizer and phosphate is insoluble, so the amount of phosphorus in agricultural wastewater is very small. Rather, the main source of phosphorus is synthetic detergent, which accounts for about 30% to 40% of the phosphorus flowing into the water ecosystem. Phosphates are used as builders for synthetic detergents, which, together with surfactants, contribute to the cleaning effect and make up a large part of synthetic detergents. Therefore, as the amount of synthetic detergent used increases, the share of phosphate in sewage is gradually increasing.

Eventually, when such nitrogen or phosphorus accumulates in reservoirs, eutrophication occurs. In addition, eutrophication occurs when nitrogen or phosphorus is introduced into a reservoir or the like and microorganisms such as algae that feed nitrogen or phosphorus are overgrown. Therefore, in order to fundamentally prevent eutrophication, nutrient components in sewage and wastewater must be removed before they can be introduced into water bodies such as lakes or rivers.

Also, from July 2003, the landfill of sewage sludge will be banned due to the entry into force of the London Convention and the enactment of the Waste Management Act, and in the near future, regulations on marine discharges will be tightened. There is a growing interest in the long-term policy direction for the efficient and economical and efficient sewage sludge treatment.

In the United States and Europe, the recycling of sewage sludge has been progressing steadily. On the other hand, in Korea, sewage sludge has not been actively recycled due to various systems and technical issues. In addition, according to the Fertilizer Process Standard of the Ministry of Agriculture and Forestry, composting of sewage sludge in urban areas as a fertilizer is, in principle, a major obstacle to recycling.

Therefore, as a method of reducing such sewage sludge, economical and low-secondary biological methods such as anaerobic digestion, sludge intake by predator, and aerobic oxidation are emerging. However, the conventional sewage and wastewater treatment methods are designed to remove organic substances, and at the same time, there are insufficient points to remove sewage sludge generated by nitrogen, phosphorus and sewage altitude treatment. In particular, there are many problems to be applied to small-sized seedling sewage and wastewater treatment plants with fluctuating flow rate and water quality. Specifically, the nitrogen removal rate of urban sewage is only 10-40% by the existing treatment method, and physical and chemical treatments, which have a high treatment cost, are easier than sludge removal and biological treatment with less secondary pollution.

In such a conventional sewage and wastewater treatment device, the inflowing raw water first flows into the primary sedimentation basin after being settled. Suspended Solids (SS) having good sedimentability are sedimented and removed from primary sediment into primary sludge (Sludge) from the sewage, and the sedimented primary sludge is transferred to the sludge treatment facility through the transfer pipe. Transferred and processed. In addition, sewage that has not precipitated in the primary sedimentation basin is introduced into the bioreactor through the primary sedimentation basin and used for microbial cell synthesis and microbial growth to synthesize secondary sludge. This secondary sludge contains about 90% organic matter and this secondary sludge is usually called activated sludge. In addition, such activated sludge mixed liquid is also referred to as mixed liquid suspended solids (MLVSS). The activated sludge is solid-liquid separated from the secondary sedimentation basin, and the supernatant is discharged and a portion of the sedimented secondary sludge is returned to the aeration tank through the return pipe, and the remaining sediment sludge is transferred to the sludge treatment facility through the transfer pipe and processed. As the above process is repeated continuously, contaminants in the sewage and wastewater are purified and sewage sludge generated therefrom is treated.

The conventional sewage and wastewater treatment device is designed to focus on the removal of various nutrients such as organic matter, nitrogen, and phosphorus, which are simply contained in the sewage. Have And especially in the 21st century, climate change is focused on reducing carbon emissions and developing alternative energy sources in all areas. Thus, sewage is no longer a target for energy removal but must be transformed into a recovery target for a variety of valuable resources.

The prior art for the treatment of sewage and wastewater is Patent No. 10-814743 registered under the name of the present applicant, but the patent is a device for treating small sewage and wastewater, which is a small scale with severe changes in inflow flow and water quality. Its main characteristics are to reduce the amount of organic matter, nitrogen, phosphorus and solids flowing from sewage and wastewater in sewage treatment plants to reach the appropriate level.

In another prior art, Korean Patent Publication No. 10-2001-25729 discloses a method for simultaneously removing nitrogen and phosphorus from sewage / wastewater using a nitrification tank equipped with a rotating disc. In order to remove heavy nitrogen and phosphorus at the same time, a rotary disk for high-efficiency nitrification is used, and phosphorus is only a method of being absorbed and removed from the microorganism body.

Another Patent Publication No. 10-2005-99811 discloses a high sewage and wastewater treatment system using the electrolysis of the sludge and the return water, this is a suspended material removal tank, bioreactor, In addition to the solid-liquid separation tank, the sludge treatment tank and the bioreaction tank, it is shown that the electrolysis tank is further configured, and it is considered that the invention is completely different from the pursuit of the present invention.

The present invention is to solve the problems of the prior art as described above, and to provide a sewage and wastewater treatment apparatus of a new concept, utilizing bio-floculation and polymer organic / inorganic flocculant and sewage organic material Maximize the separation and subsequently treat the sewage and wastewater treatment system and treatment method that recovers methane gas (Bio-energy) through the high temperature and medium temperature anaerobic digestion process for sewage sludge linkage treatment and meets the enhanced effluent water quality standards. The purpose is to provide.

The present invention to achieve the above object of the present invention;

An agitation tank for receiving a digestive liquid that has undergone inflow, wastewater and sludge anaerobic digestion;

UST (Up-flow Septic Tank) reactor for introducing the raw water through the outlet of the upper part of the stirring tank and separating the solid-liquid separation of the colloidal and floating organic substances contained in the inflow source and the digestive liquid and the nitrate transported from the next tank. Wow;

AF (Aerated Filter) reaction tank for nitrifying the supernatant after the solid-liquid separation in the UST reaction tank to nitric acid inhabiting the media in the tank;

An acid production tank for hydrolyzing the sludge sedimented by solid-liquid separation of the UST reaction tank;

A storage tank for solid-liquid separation of the hydrolyzed influent in the acid production tank;

And a methane generating tank for generating methane by introducing the effluent separated from the storage tank into a solid solution; And

It provides a sewage and wastewater organic material separation and biogas recovery apparatus including a sedimentation tank for discharging the sludge and discharged treated water from the AF reaction tank.

In the stirring tank, the UST reaction tank, the acid generating tank, the storage tank, and the methane generating tank, it is preferable that a stirring motor for stirring the inflow water therein is installed at the top.

In addition, the lower side of the UST reaction tank is connected to the acid production tank transport pipe for transporting the sludge sedimented by solid-liquid separation to the acid production tank, which is operated by the transfer pump.

Also in the lower part of the AF reactor, a transfer pipe for transferring a portion of the treated water for the denitrification reaction of nitrate nitrate to the stirring tank is connected to the stirring tank, which is operated by a transfer pump. Of course, the transfer pipe may be directly connected to the UST reactor.

In addition, it is preferable that an aeration device is installed at one side of the AF reactor to supply oxygen for nitrification in the reactor.

In addition, one side of the methane generation tank may be connected to the transfer pipe for transferring the remaining raw water to the stirring tank after the discharge of the gas, the methane production tank is preferably provided with a gas discharge port and sludge discharge port.

In addition, a coagulant injector for adding a polymer organic / inorganic coagulant may be connected to the stirring vessel.

In addition, the storage tank may be provided with a settling sludge discharge port and the gas discharge portion by the solid-liquid separation.

According to the present invention, as well as the removal of organic substances, nitrogen, phosphorus, as well as various nutrients such as ammonia nitrogen is effectively made, easy to operate and unlike the existing MBR by using a short SRT to increase the amount of high-quality sludge (VSS) generation Reduction of power consumption through methane gas recovery through internal anaerobic digestion process, internal purifying, improvement of nutrients removal by utilizing limited organic materials to the maximum, operation cost reduction, aeration device by supplying minimum oxygen demand for nitrification by filling media in aerobic tank The energy cost savings and the adsorption of organic matter by the microorganisms by bio-aggregation in the UST reactor do not require separate stirring energy. Therefore, the recovery of alternative energy by anaerobic digestion is expected to create new economic added value in economic terms.

1 is a process diagram shown for explaining the apparatus and method of the present invention.

Hereinafter, with reference to the accompanying drawings and embodiments will be described the present invention in more detail. The following examples and the like are intended to assist in the practice of the present invention and are not intended to limit the present invention thereto.

The present invention satisfies the technology for separating organic matter from sewage by bio-floculation and polymer organic / inorganic flocculant, recovering valuable resources (methane gas) through high and medium temperature anaerobic digestion process, and strengthened effluent water quality standards. The anaerobic / aerobic combination sewage treatment process was completed.

In the first sewage and wastewater advanced treatment method of the present invention, the effluent after the anaerobic digestion process of the influent sewage and sewage sludge is introduced into an up-flow eptic tank (UST) pre-anoxic filter. Therefore, the following mechanism occurs in the UST anaerobic filter. For example, sedimentation and separation of organic substances and solids contained in anaerobic digestion of influent sewage and sewage sludge, followed by nitrified treated water by well-developed bacteria inhabited by aerated filters installed, Happens. Filtration, adsorption, and denitrification occur simultaneously in the anaerobic filter, whereby more than 90% of organic matter in the influent is removed. From the subsequent aerobic filter, heterotrophic bacteria and autotrophic bacteria Nitrogen reaction by nitrifying bacteria, an independent nutrient, can be efficiently performed by minimizing competition with the nutrient, and sludge accumulated in the lower portion of the UST reactor is oxidized and methanated into an anaerobic digester, and the effluent is again used as a UST reactor. The sludge is reduced as much as VS in the sludge removed due to the digestion, which can be used as a carbon source for denitrification, thereby reducing the amount of solids generated during sewage treatment. In addition, through the anaerobic digestion, recovery of methane gas (Bio-energy) is performed.

Here, the second sewage and wastewater advanced treatment method of the present invention was introduced as an alternative for further maximizing the improvement of the solid sedimentation separation efficiency of the UST.

The second sewage and wastewater treatment method of the present invention further maximizes the separation of solids in the UST reactor by additionally installing an agglomeration tank at the front end of the first sewage and wastewater treatment method.

The present invention as described above will be described with reference to the accompanying drawings.

1 is a process diagram for explaining the apparatus of the present invention and a method of using the same, first, the digestion liquid which has undergone the anaerobic digestion process of the inflow sewage and wastewater sludge is introduced into the stirring tank 100 by the transfer pumps 10 and 20. . In order to equalize the raw water introduced into the stirring tank 100 and the digestive liquid that has undergone the anaerobic digestion process, the motor 101 installed on the stirring tank 100 performs stirring at a speed of about 150 rpm. The complete mixed liquid equalized by the stirring is introduced into the Up-flow Septic Tank (UST) reactor 200 through an outlet installed at the upper end of the stirring vessel 100.

In the UST reactor 200, the solid-liquid separation of colloidal and floating organic substances (VSS, SSCOD) contained in the digestive liquid that has undergone the anaerobic digestion process of raw water and sewage sludge mainly introduced from the stirring tank 100 and subsequent Denitrification of the nitrate transferred from the AF (Aerated Filter) reactor 300 is performed. Therefore, for smooth denitrification of the UST reactor 200, the upper motor 201 is stirred at low stirring strength (about 10 rpm). In addition, the supernatant that has undergone the solid-liquid separation of the UST reactor 200 is introduced into the AF (Aerated Filter) reactor 300 through an outlet installed at the upper end of the UST reactor 200, and the sludge settled by the solid-liquid separation is the sludge discharge port 202. And slowly flows into the acid production tank 400 from the inlet installed at the bottom of the acid production tank 400 through the transfer pump (40).

In addition, the first treatment water introduced into the AF reactor 300 is induced nitrification by the nitride bacteria in the media (media) filled in the AF reactor 300, where the oxygen for induction of nitrification The supply is regulated and supplied to the flow controller 302 through the air amplifier 301. Accordingly, a part of the final treated water in the AF reactor 300 is transferred to the settling tank 700 through an outflow passage installed at the lower portion of the AF reactor 300, and the other portion is transferred to the UST reactor 200 through the transfer pump 30. Returned to induce denitrification. Therefore, the nitrate contained in the final treated water induces bio-flocculation in the UST reactor 200 to further facilitate solid-liquid separation.

The final treated water transferred to the settling tank 700 is separated into solids in the settling tank 700 so that the supernatant is discharged through an outlet installed at the top of the settling tank 700, and the sludge settled by the solid-liquid separation is discharged through the sludge discharge port 701. Drain out of the system.

In addition, in the acid production tank 400, the motor 401 installed at the top for smooth hydrolysis of proteins to amino acids, polysaccharides in carbohydrates to monosaccharides, and glycerin to fatty acids, at low stirring strength (about 10 rpm). After stirring, the hydrolyzed water is introduced into the storage tank 500 through an outlet installed at the upper end of the acid production tank 400.

Here, the storage tank 500 leads the solid-liquid separation role for the selection of useful substrates required for methane production in the acid production tank 400 and the methane production tank 600 that follows. The stirring in the storage tank 500 is operated at a low stirring strength of about 10rpm. Therefore, the supernatant after the solid-liquid separation is introduced into the methane production tank 600 through the inlet installed at the bottom of the methane production tank 600 through the outlet of the storage tank 500, the sludge sedimented by the solid-liquid separation discharged sludge Ejected through port 503. In addition, the gas discharge unit 502 was installed in consideration of the possibility of generating some CO ₂ or gas such as methane in the storage tank.

In the methane production tank 600, in order to induce smooth methanation of methane producing bacteria, the methane was stirred at a low stirring strength (about 10 rpm) through the upper motor 601. Accordingly, the methane capture was performed using the gas discharge ports 602 and 603. The gas was collected by using, and the sludge generated through the sludge discharge port 604 is discharged. Here, the residual raw water is transferred to the stirring tank 100 through the transfer pipe.

In addition, the flocculant injection pump 50 may be further installed on one side of the agitation tank 100 to add a polymer organic / inorganic flocculant to the agitation tank 100 to further solidify liquid separation in the UST reaction tank 200.

Table 2 and Table 3 show the results of carrying out the present invention as described above in the operating conditions shown in Table 1. As can be seen from the table below, according to the present invention, the organic matter is 95.37%, the total nitrogen is 76.23%, and the total phosphorus is 77.51%, and the removal efficiency of the sludge generated in the present invention is as follows. The biodegradability (UST sludge 42.2%) was higher than the dehydration cake (6.0%) or the return sludge (29.1%) generated in the sewage treatment plant. Therefore, methane production rate can be increased.

10, 20, 30, 40, 50: pump 100: stirring tank
200: UST reactor 202: sludge discharge port
300: AF reactor 301: air amplifier
302: flow controller 400: acid production tank
500: storage tank 502: gas discharge unit
503: sludge discharge port 600: methane gas generating tank
602, 603: gas discharge port 604: sludge discharge port
700: sedimentation tank 701: sludge discharge port

Claims (7)

An agitation tank receiving digestion liquid after inflow, wastewater and sludge anaerobic digestion process; UST (Up-flow Septic Tank) reactor for introducing the raw water through the outlet of the upper part of the stirring tank and separating the solid-liquid separation of the colloidal and floating organic substances contained in the inflowing source and the digestive liquid and the nitrate transferred from the next tank. ; AF (Aerated Filter) reaction tank for nitrifying the supernatant after the solid-liquid separation in the UST reaction tank to nitric acid inhabiting the media in the tank; An acid production tank for hydrolyzing the sludge sedimented by solid-liquid separation of the UST reaction tank; A storage tank for solid-liquid separation of the hydrolyzed influent in the acid production tank; And a methane generating tank for generating methane by introducing the effluent separated from the storage tank into a solid solution; And a sedimentation tank for discharging the treated water from the AF reaction tank and discharging the sludge.
The lower side of the UST reaction tank is connected to the acid production tank transfer pipe for transporting the sludge sedimented by the solid-liquid separation to the lower acid production tank,
The lower part of the AF reaction tank is separated from the organic matter and biogas recovery of sewage and wastewater, characterized in that the transfer pipe for transferring a portion of the treated water for the denitrification reaction of nitrified nitrate to the stirring tank is connected to the stirring tank Device. According to claim 1, wherein the stirring tank, UST reaction tank, acid production tank, storage tank and methane generation tank is characterized in that the organic material separation and biogas separation of sewage and waste water, characterized in that the stirring motor for stirring the inflow of the inside is installed on the top Recovery device. delete delete The apparatus of claim 1, wherein an aeration device is installed at one side of the AF reactor for supplying oxygen for nitrification in the reactor. According to claim 1, wherein one side of the methane generating tank is a transfer pipe for transferring the remaining raw water to the stirring tank after the discharge of the gas is connected to the stirring tank, the methane production tank is characterized in that the gas discharge port and the sludge discharge port is provided Separation and organic gas recovery apparatus of sewage and wastewater. According to claim 1, wherein the stirring tank is a flocculant injection device for adding a polymer organic / inorganic flocculant is connected to the organic material separation and biogas recovery apparatus of sewage.

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