KR100321681B1 - Wastewater purification method - Google Patents

Abstract

PURPOSE: A method is provided to increase removal efficiency for nitrogen and phosphorus by using the organic material in the intermittent aeration reactor and to enable the treated water to be reuses as reclamation. CONSTITUTION: The method comprises a water reservoir(2) which contains waste water for some time; a flow passage controller(1) by which wastewater is introduced into an anaerobic fermentation tank(3) from the water reservoir; an anaerobic fermentation tank in which the suspend solids of the wastewater are fermented; a secondary intermittent aeration reactor(6) from which the wastewater and microorganism are supplied to a secondary aeration reactor(7); a secondary aeration reactor which removes residual organics by supplying dissolved oxygen and increases the precipitation characteristics of microorganism by endogenous respiration.

Description

Wastewater Purification Method

The present invention can effectively treat organic matters and nutrients contained in organic wastewater, which is the main cause of pollution and eutrophication of lakes and streams, and can clean up effluent with water quality of water and small facilities compared to existing treatment methods. The present invention relates to a method for purifying wastewater that can be operated on a scale.

Conventional treatment of manure and high concentration organic wastewater is carried out by anaerobic digestion or aerobic digestion, and uses about 10-fold dilution water. This method is economical to use tap water when dilution water is used, so it is difficult to implement it in the absence of water sources such as lakes and rivers, and even when developing groundwater, problems such as ground subsidence may occur. Dilution with a large amount of water can lead to the misconception that only dilution is carried out rather than the concept of treatment.

In the case of integrated treatment of wastewater, the activated sludge method or the long-term aeration method, which is a modified form, is commonly used. The long-term aeration method has the advantage that the amount of excess sludge is generated, while the removal rate of nutrients is very low because nitrogen and phosphorus can be removed to the minimum required for microbial cell synthesis. have.

The method for removing nitrogen takes advantage of a long known phenomenon that the natural nitrogen cycle is converted to nitrogen gas by aerobic nitrifiers and anoxic denitrifiers. Phosphorus removal is carried out by the release of phosphorus which releases phosphorus in microbial cells to the body in anoxic state and the ingestion of phosphorus in aerobic state. At this time, microorganisms during non-aeration for denitrification and dephosphorization require organic matter (= electron donor) in metabolism. Therefore, the case where the ratio of organic matter / nitrogen in the inflow wastewater is high is preferable, and when the ratio of organic matter / nitrogen is low, it is necessary to inject external organic matter in order to treat nitrogen and phosphorus.

Therefore, in order to remove nitrogen and phosphorus, the process must be operated in aerobic and anaerobic (or anoxic) state, and more preferably, the organic / nitrogen ratio of the influent wastewater has a high and low supply of organic matter. These processes include A / O, A ² / O (Ref .; Hong, S., Kisenbauer, Ksand Fox, VG, (1981), Aninnovative biological nutrient removal system), Bardenpho (US Pat. No. 3964988), UCT, VIP And the like, and the intermittent aeration activated sludge process devised by the present invention (see Korean Patent Publication No. 97-20986), a flow path changing intermittent aeration activated sludge process (Korean Patent Publication Nos. 97-20987 and 97-20988) Etc.).

Intermittent Aeration and Flow Change Except for the intermittent aeration activated sludge process, the above processes are operated in a steady-state to pass through a reactor of aerobic and anaerobic conditions by arranging the reactor separately according to the presence or absence of oxygen. These processes operate stably if they are kept constant without significant changes in the flow rate and concentration of wastewater, such as in large-scale treatment plants.However, when the flow rate and concentration change is severe, such as in domestic small and medium-sized complexes, the process is less stable. Water quality often deteriorates.

In addition, the present inventors have applied for the intermittent aeration and flow path changing intermittent aeration sludge process can maintain the aeration and non-aeration in a single reaction tank to some extent to cope with changes in flow rate and concentration and organic matter, nitrogen and phosphorus The advantage is that it can be removed at the same time. However, in the small wastewater treatment, the fluctuation of the flow rate is so severe that a separate flow rate adjustment is required. In addition, the size of the treatment facility is reduced, the amount of excess sludge generated, the maximum use of organic matter in the wastewater during denitrification or dephosphorization, and the release of organic fine solids. Should be minimized. This requires additional supplementation to existing methods.

The present invention has been made to solve the conventional problems as described above, the object of the present invention is to effectively remove the organic matter, nitrogen and phosphorus in domestic wastewater, and technically easy to cope with changes in flow rate and concentration The present invention provides a method for the purification of wastewater that can guarantee stable runoff water quality.

Another object of the present invention is to maximize the removal of nutrients by using the organic acid produced in the anaerobic fermenter as an organic material (= electron donor) required for denitrification and dephosphorization during non-aeration, and to reduce the size of the facility by installing the precipitation tank in the aerobic reactor To provide a method for the purification of waste water.

1 is a schematic diagram showing a process for purifying wastewater according to a first preferred embodiment of the present invention, and

2 is a schematic view showing the configuration of the continuous sand filter paper shown in FIG.

<Explanation of symbols for the main parts of the drawings>

1: Flow control device 2: Flow storage tank

3: anaerobic fermenter 4a, 4b: sedimentation plate

5: 1st intermittent aeration reactor 6: 2nd intermittent aeration reactor

7: after-aeration reactor 8: continuous sand filtration tank

9: disinfection tank 10, 10a, 10b: pump

11: time control device 12: blower or compressor

In order to achieve the above object, the present invention,

The flow regulating device, the flow storage tank, the anaerobic fermentation tank, the first intermittent aeration reactor, the second intermittent aeration reactor and the post-aeration reactor are used in this order. As much as the inflow wastewater flows into the anaerobic fermentation tank from the flow storage tank, solid components in the inflow wastewater are fermented in the anaerobic fermentation tank, and in the first intermittent aeration reactor and the second intermittent aeration reactor, aeration and non-exposure. The groups are alternately operated alternately, and the purified wastewater and microorganisms discharged from the second intermittent aeration reactor are supplied to the post aeration reactor, and the end aeration reactor finally removes residual organic substances by supplying dissolved oxygen, and endogenously. Characterized by increasing the settling of microorganisms by respiration Provide a method for the purification of waste water.

Preferably, a disinfection tank is further disposed after the post-aeration reactor, the disinfection tank sterilizes the microorganisms that flow out, and a continuous sand filtration tank is further disposed between the post-aeration reactor and the disinfection tank, and the continuous sand In the filtration tank, the fine solids flowing out of the upper aeration reactor and the microorganisms not precipitated in the post-aeration reactor are removed.

Preferably, a first precipitation plate and a second precipitation plate are disposed at an inner upper portion of the anaerobic fermentation tank and the post-aeration reactor, and the liquid organic material treated in the anaerobic fermentation tank is disposed on the first precipitation plate. It is transferred to an intermittent aeration reactor, the organic acid dissolved in the fermentation in the anaerobic fermentation tank is provided into the first intermittent aeration reactor and the second intermittent aeration reactor and supplied to the organic material for denitrification and dephosphorization during non-aeration, the continuous The fine solids and microorganisms detached from the media of the filtration sand filter are returned to the anaerobic fermentation tank.

In general, domestic waste water has a high flow rate of 7-9, 12-15, and 17-20 hours, and relatively little other time. In addition, summer is the most seasonal (see Mettalf & eddy, Wastewater engineering, McGraw-Hill, Inc., 1991). Therefore, it should be a process that can minimize changes in flow rate and concentration during wastewater treatment.

In the present invention, the flow rate adjusting device 1 and the flow rate storage tank 2 to be described below are considered in consideration of this, thereby allowing the flow rate and the concentration to be introduced more consistently. In addition, in order to minimize the size of the facility, a precipitation plate tank was installed in the reaction tank to reduce the volume as much as possible, and the organic acid produced by fermenting the solid organic matter contained in the wastewater was used as an organic material necessary for the removal of nitrogen and phosphorus. Maximized the processing. In addition, the treated effluent was allowed to pass through a continuous sand filtration tank 8 to be described below to avoid the outflow of fine solids and microorganisms, and to disinfect the effluent for reuse of the treated water.

Hereinafter, the wastewater purification process of the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic diagram showing a process for purifying wastewater according to a first preferred embodiment of the present invention.

Referring to Figure 1, the apparatus for performing the waste water purification process according to a first embodiment of the present invention is a flow control device (1), flow storage tank (2), Imhoff type anaerobic fermentation tank (3), the first intermittent aeration A reactor 5, a second intermittent aeration reactor 6, a post aeration reactor 7, a continuous sand filter paper 8 and a disinfection tank 9 are included. Precipitation plates 4a and 4b are disposed in the anaerobic fermentation tank 3 and the post-aeration reactor 7, respectively.

Organics, nitrogen and phosphorus in wastewater can be removed by reacting with microorganisms under appropriate conditions. Therefore, the reaction time is longer than the time the microorganisms can remove contaminants. The reaction time of the microorganisms and contaminants is the residence time of the waste water in the reaction tank, which corresponds to the value obtained by dividing the reaction vessel volume by the flow rate of the waste water. In other words, wastewater flows into the reactor at a constant flow rate for effective treatment of wastewater.

As described above, domestic small-scale wastewater has a great change in flow rate and concentration depending on the place or time. In the present invention, in order to solve this problem, a flow rate storage tank 2 is installed to maintain the wastewater for a predetermined time, and the wastewater is injected into the anaerobic fermentation tank 3 at a constant rate using the pump 10 to be treated.

In the present invention, in order to reduce the size of the facility, instead of introducing all of the wastewater into the flow storage tank 2, only a predetermined flow rate is introduced into the anaerobic fermentation tank 3 by the flow control device 1. When the flow rate of the waste water is large, the amount of water corresponding to a predetermined flow rate or more is introduced into the flow storage tank 1, and when the flow rate is lower than the required flow rate, the waste water introduced into the flow storage tank 2 is pumped using the pump 10. Inflow into an anaerobic fermenter (3). Thereby, the advantage that the volume of the flow volume storage tank 2 can be made small is acquired.

Subsequent imhoff type anaerobic fermenter 3 is provided with a precipitation plate 4a and a pump 10a downstream. Solid components in the wastewater in the anaerobic fermentation tank (3) is fermented at the bottom of the anaerobic fermentation tank (3), the liquid organic matter is the first intermittent aeration reactor (5) in the upper part of the precipitation plate (4a) of the anaerobic fermentation tank (3) Is transferred to. Wastewater is divided into solid components and dissolved components. If the solid components are dissolved by fermentation, it will be more preferable for the subsequent treatment using microorganisms. During fermentation, in order to contact the microorganisms and the solid components intermittently by using the pump 10a (mechanical or air lift method) to enable stirring.

The organically oxidized dissolved and fermented in the anaerobic fermentation tank 3 is supplied to the organic material for denitrification and dephosphorization during non-aeration of the first and second intermittent aeration reactors 5 and 6 by the pump 10a. In order to increase the denitrification and dephosphorization efficiency, the first and second intermittent aeration reactors 5 and 6 are operated by injecting an external organic carbon source, which is an external electron donor. As the external organic carbon source to be injected, organic acids produced by fermentation of organic acids, foods or organic living wastes of acetic acid, methanol, propionic acid, livestock wastewater and municipal sewage sedimentation solids can be used.

The first and second intermittent aeration reactors 5 and 6 allow the aeration and non-aeration to alternately operate in one reactor. During aeration (aerobic state), the ammonia nitrogen (NH ₄ ⁺ -N) is introduced into the nitrate (NO ₃ ^-- N) during the aeration, and during the aeration (nitrogen state) nitrate produced by the nitrification reaction (NO ₃ ^-- N) is converted to gaseous nitrogen (N ₂ ) to allow denitrification to proceed to the atmosphere.

The organic material (= electron donor) required for the denitrification reaction makes it possible to use the organic material in the waste water, and can also use the liquid organic material (= organic acid) generated in the anaerobic fermentation tank (3). The period of aeration and non-aeration time can be changed to 1 hour / 1 hour, 2 hours / 2 hours, 2 hours / 1 hour, etc. according to the time required for nitrification and denitrification according to the waste water properties. . This is because the operation of the dynamic (state) rather than steady-state (dynamic-state) has the advantage that it is easy to cope with changes in the concentration and flow rate of the waste water, and the expectation of a more stable treatment water can be.

In the continuously operating aeration reactor 7 is equipped with a precipitation plate 4b at the top to utilize the upper water surface as a precipitation tank. The purified wastewater and microorganisms flowing out of the second intermittent aeration reactor 6 finally removed residual organic matter by the supply of dissolved oxygen in the post aeration reactor 7, and induced endogenous respiration to increase the settling of microorganisms. . The microorganisms are settled in the upper part of the precipitation plate 4b of the post-aeration reactor 7, and the purified wastewater separated from the microorganisms is discharged. The precipitated microorganisms are returned or discarded to the Imhoff fermentation tank 3 by a pump 10b (mechanical or air lift type).

In the continuous sand filtration tank (8) (upflow or downflow) is installed for the removal of micro-solids and microorganisms that could not be separated by sedimentation from the top of the precipitation plate (4b) in the post-aeration reactor (7).

On the other hand, in the continuous sand filtration tank (8), sand is used as a filter medium, but alternatively, sand, such as activated carbon, diatomaceous earth, anthracite coal, etc. may be employed as a filter medium to operate as a continuous filter tank.

2 is a schematic view showing the configuration of the continuous sand filter paper shown in FIG. As shown in Fig. 2, the continuous sand filtration tank 8 enables continuous back washing by the air lift method. The media is regenerated continuously, and the fine solids and microorganisms detached from the media are returned to the anaerobic fermenter. Finally, the sterilization tank 9 is operated to sterilize the microorganisms flowing out to reuse the outflow water as heavy water.

On the other hand, all the reaction tank is maintained in the aerobic state to ensure that dissolved oxygen is supplied by the air supply. In addition, all reactors can be treated with an attachment carrier or medium in order to increase the amount of microorganisms.

Operation of the process is more advantageous for domestic wastewater treatment, which has a large change in flow rate and concentration, and it is a process that can not only reduce the size of facilities but also minimize the amount of excess sludge and high treatment efficiency of organic matter, nitrogen and phosphorus. .

According to the purification process of the wastewater according to the present invention as described above, it is possible to maximize the treatment of nitrogen and phosphorus, which is the main cause of eutrophication, it is possible to re-use the treated water as a heavy water. In addition, it is not significantly affected by the flow rate and concentration change of the influent wastewater, and there is an advantage that the cost of energy supply can be reduced because the facility size is small and the air is intermittently injected. In addition, since the liquid organic matter (= organic acid) produced in the anaerobic fermentation tank 3 is used as an organic material required for denitrification and dephosphorization reaction during the non-aeration of the intermittent aeration reactor, the treatment efficiency of nitrogen and phosphorus can be increased. It is a very valuable process.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below. I can understand that you can.

Claims (8)

The flow rate adjusting device, the flow storage tank, the anaerobic fermentation tank, the first intermittent aeration reactor, the second intermittent aeration reactor and the post-aeration reactor are used in this order. As much as the inflow wastewater flows into the anaerobic fermentation tank from the flow storage tank, solid components in the inflow wastewater are fermented in the anaerobic fermentation tank, and the purified wastewater and microorganisms flowing out from the second intermittent aeration reactor are Supplied to the aeration reactor, and the post-aeration clarified wastewater and microorganisms are supplied to the post-aeration reactor. The post-aeration reactor is a wastewater purification method characterized in that the residual organic matter is finally removed by the supply of dissolved oxygen and at the same time to increase the settling of microorganisms by endogenous respiration. The method of claim 1, wherein a disinfection tank is further disposed after the post-aeration reactor, and the sterilization tank sterilizes the microorganisms flowing out. The method of claim 2, wherein a continuous filtration tank is further disposed between the post-aeration reactor and the disinfection tank, and the continuous filtration tank is not sedimented and separated from the fine solids flowing out of the upper aeration reactor and the post-aeration reactor. Method for purification of waste water, characterized in that the microorganisms are removed. According to claim 3, wherein the first and second sedimentation plate is disposed in the inner upper portion of the anaerobic fermentation tank and the post-aeration reactor, respectively, the first pump, downstream of the flow rate storage tank, the anaerobic fermentation tank and the post-aeration reactor; A second pump and a third pump are disposed, respectively, and the inflow wastewater remaining in the flow reservoir for a predetermined time is injected into the anaerobic fermenter at a constant speed by the first pump, and the liquid organic matter treated in the anaerobic fermenter. Is transferred from the upper part of the first precipitation plate to the first intermittent aeration reactor, and the organic oxidized dissolved in the anaerobic fermentation tank is introduced into the first intermittent aeration reactor and the second intermittent aeration reactor by the second pump. Fine which is provided and supplied as an organic material for denitrification and dephosphorization during non-aeration, and desorbed from the media of the continuous filtration tank. Solids and microorganisms are returned to the anaerobic fermentation tank by the third pump. The method of claim 4, wherein the filter medium of the continuous filtration tank is a particle selected from the group consisting of sand, activated carbon, diatomaceous earth, and anthracite coal. The method according to any one of claims 1 to 5, wherein the first intermittent aeration reactor and the second intermittent aeration reactor are operated by injecting an external organic carbon source, which is an external electron donor, to increase the denitrification and dephosphorization efficiency. Wastewater purification method 7. The method of claim 6, wherein the external organic carbon source is selected from the group consisting of acetic acid, methanol, propionic acid, livestock wastewater and organic acid from municipal sewage sediment solid, organic acid produced by food fermentation, and organic acid produced by fermentation of organic living waste. Method for purification of waste water, characterized in that the selected material. The method of claim 1, wherein the first intermittent aeration reactor, the second intermittent aeration reactor, and the post-aeration reactor are provided with an attachment carrier or a medium.