KR100497797B1 - Nutrient removal of wastewater using media - Google Patents

Abstract

The present invention relates to a process for effectively treating organic matter, nitrogen, and phosphorus in wastewater, and in order to maximize denitrification and dephosphorization (phosphorus removal) by using organic matter in wastewater as an organic carbon source for denitrification reaction of nitrogen removal during wastewater treatment. to be. The composition of the present invention is composed of an anaerobic reactor (1), nitrification reactor (2), anoxic reactor (3), post-aeration reactor (4), and precipitation tank (5), and each reactor has a floating media such as Linpor (media). It is an advanced treatment system that removes nutrients from wastewater by attaching microorganisms to wastewater by injecting it into the reactor.

According to this configuration, the organic matter in the wastewater during the wastewater treatment is adsorbed by the microorganisms attached to the media and can be used for denitrification. In addition, as the microorganisms are attached and grown, there is an advantage that can reduce the amount of sludge generated compared to the biological treatment process using the floating growth microorganisms.

The wastewater treatment process devised in the present invention is applicable to municipal sewage and livestock wastewater having a low C / N (organic / nitrogen) ratio of inflow wastewater.

Description

Nutrient removal of wastewater using media

The present invention is a method for purifying wastewater for effectively removing nitrogen and phosphorus from wastewater known as a causative agent of eutrophication using microorganisms attached to and growing on media. In general, nitrogen and phosphorus contained in wastewater or sewage act as toxic to aquatic colors in addition to eutrophication of rivers, causing odor and closure of filtration membranes during water treatment. It also generates red tide when entering the ocean.

As a representative physicochemical treatment technique for removing nutrients, a method of precipitation removal using chemicals such as Alum (coagulant) may be used, but disadvantages such as excessive chemical costs and increased treatment cost of precipitated waste sludge There is this. Biological treatment, on the other hand, combines the process for removing organic matter from wastewater with nutrients, and removes organic matter, nitrogen and phosphorus to treat wastewater economically, and it is widely used due to its high stability of treated water quality. . Such nutrient treatment processes include A / O, A ² / O, UCT, VIP, Bardenpho, etc., which have already been developed in developed countries, and include microorganisms such as Patent No. 0243565 and Patent Application 0026824 developed by the present inventors. It is possible to operate the changed treatment process by using the reaction characteristic of. This is because even if the same wastewater is treated, the treatment efficiency of organic matter, nitrogen and phosphorus of the microorganism is different according to different treatment processes and operating conditions.

Biological treatments for treating nutrients can be divided into pre-denitrification and post-denitrification. First, the mechanism for removing nitrogen requires nitrification and denitrification. Nitrification takes longer than denitrification. This is because the reaction proceeds by autotrophic microorganisms (Autotrophics). The ammonia nitrogen present in the wastewater is oxidized to nitric acid (NO ₃ ⁻ ) under aerobic conditions by nitrifying bacteria, and then reduced to nitrogen gas by denitrifying bacteria under anoxic conditions and released into the atmosphere. . The method for removing the phosphorus compound requires release of phosphorus by Phosphate Accumulate Organisms (PAO) under anoxic conditions and overingestion into microbial cells again under aerobic conditions. Therefore, in order to remove nitrogen and phosphorus from waste water, the appropriate environmental conditions listed above are required, namely, aerobic reaction for nitrification and phosphorus intake, anoxic conditions for denitrification and phosphorus release, and anaerobic conditions. The state is more advantageous for phosphorus removal. In the denitrification reaction, it is preferable to use the organic material contained in the waste water as the electron donor (organic substance) required in the denitrification reaction. Treatment processes for removing nutrients vary in efficiency depending on the configuration and operation of the system. However, the problems to be solved are to increase the efficiency of nitrogen and phosphorus removal by reducing the organic matter of the influent wastewater to denitrification and dephosphorization, and also to reduce the sludge volume generated is a way to reduce the wastewater treatment costs.

The present invention has the advantage of reducing the amount of sludge generated during wastewater treatment by using the organic matter in the wastewater as denitrification and dephosphorization as possible, by treating the microorganisms attached to the media using the media. In order to make the best use of organic matters in wastewater, the microorganisms that separate microorganisms and wastewater after adsorption of microorganisms and wastewater in anaerobic reactor are transferred to denitrification tank, and the wastewater from which organic matter is removed is transferred to nitrification tank. . In the prior art DEPHANOX process (Ref. G. Bortone et al. (1997), Water Science and Technology, Vol 35, No10, pp.87-94), an intermediate sedimentation tank is used to separate microorganisms and wastewater, but the denitrification efficiency is increased. However, the sedimentation tank located in the middle of the system is uneconomical because it is not a structure in which the reaction proceeds. The intermediate sedimentation tank, which is applied to separate microorganisms and wastewater in the middle of the treatment process, is required for floating microorganisms, but in the case of adherent microorganisms such as media, it can be separated by a screening device without a sedimentation tank. In addition, microorganisms that grow and adhere to the media have the advantage of less sludge generation compared to systems operated as floating microorganisms.

The present invention is to provide a method for separating the microorganisms and wastewater adsorbed organic matter without separate intermediate sedimentation tank to be used for denitrification and dephosphorization reaction in the wastewater as much as possible and to reduce the amount of sludge generated during system operation.

In order to achieve the above object, the present invention is in the order of anaerobic reaction tank, nitrification reaction tank, anoxic reaction tank, post-aeration reaction tank and precipitation tank, injecting the media (eg, Linpor, etc.) to each reaction tank to grow microorganisms attached to the media Do it. The media is allowed to flow in complete mixture as the waste water is stirred in the reactor. The microorganisms attached to the median in the anaerobic tank adsorb organic substances in the wastewater, and the phosphorus is released. At this time, the media and the waste water are transferred to the nitrification tank by the separation device in the anaerobic reactor outlet pipe, and the nitrification reaction proceeds. The microorganisms adsorbing the organic matter enter the anoxic tank and the adsorbed organic matter is used for the denitrification reaction. Since anaerobic tank wastewater is introduced into the nitrification tank after the organic matter is removed, the autotrophics in the nitrification tank can be advantageously competed with the heterotrophic microorganism (Heterotrophics), so that the nitrification can easily proceed. In addition, since the microorganisms that adsorb organic matter in the anaerobic reactor are transferred to the oxygen-free reactor, the adsorbed organic matter can be used as an electron donor in the denitrification reaction. In the post-aeration reactor, as the aeration progresses, complete removal of organic matter and excessive intake of phosphorus proceed. In addition, if the concentration of microorganisms in the media is high due to aeration, partly desorption proceeds and partly becomes suspended. Suspended microorganisms are precipitated in sedimentation tanks, some are returned and some are discarded. As the microorganisms are discarded, phosphorus is removed in the whole process. The present invention maximizes the removal of organic matter, nitrogen and phosphorus in the wastewater by operating the anaerobic reactor, nitrification reactor, anoxic reactor and the post aeration reactor described above, and because the media is used, the water content of the sludge generated during the wastewater treatment is low. It is characterized by a very small volume compared to the flotation process. This is a very desirable process in Korea, where dumping of waste sludge has been banned since 2005.

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

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

As shown in FIG. 1, in the first embodiment, the anaerobic reactor 1, the nitrification reactor 2, the oxygen-free reactor 3, the post-aeration reactor 4 and the precipitation tank 5 are discharged from the anaerobic reactor. A separator 6 and a screen 7 for separating the waste water and the media. Each reactor except the settling tank is equipped with stirring facilities, and the sludge precipitated in the settling tank is partially disposed of and returned to the anaerobic reactor 1. Screens are installed at the outlets of the nitrification reactor 2 and the post-aeration tank 4 to prevent the media from flowing out into the anoxic reactor 3 and the precipitation tank 5, which are subsequent processes. The media in the after-aeration tank 4 is returned to the anaerobic reaction tank 1 without being transferred to the settling tank 5.

The organic matter in the wastewater is adsorbed by the microorganisms attached to the media in the anaerobic reactor 1. Thereafter, the wastewater from which the organic matter is removed and the microorganisms of the media which adsorb the organic matter are separated from the separator 6, and the wastewater is transferred to the nitrification tank 2. In the nitrification tank, microorganisms adhere to the media under aerobic conditions, and since the organic matter in the waste water is removed from the anaerobic reactor (1), the microorganisms attached to the media in the nitrification tank (2) do not maintain the nitrifying bacteria in large part. It is possible. Therefore, in the nitrification reaction tank without inflow and outflow of media, the nitrifying bacteria are concentrated under the preferable conditions for the growth of nitrifying bacteria which require a long residence time. This can accelerate the nitrification reaction and require less residence time. That is, there is an advantage that can reduce the size of the reactor. Wastewater from which nitrification is completed in the nitrification tank 2 is transferred to the anoxic reactor 3 through the screen of the outlet. At this time, the microorganisms attached to the media are not transferred to the anoxic reaction tank 3 by the screen and are involved in the continuous nitrification reaction in the nitrification reaction tank 2. In the oxygen-free reaction tank (3) is operated in a non-aerated form, the inflow of waste water is nitrified and the microorganisms adsorbed organic matter in the anaerobic reaction tank (1) is attached to the media. The organic material adsorbed to the microorganism is used as an electron donor during the denitrification reaction, and the denitrification reaction proceeds to remove nitrogen. In the post-aeration reactor 4, the final treatment of organic matter and the adsorption of phosphorus proceed in an aerobic state. The microorganisms grown in the media are returned to the anaerobic reactor 1 for some continuous reaction, and partly detached and converted to floating during the aeration. The purified wastewater and the floating microorganisms are separated in the settling tank 5. The suspended microorganisms precipitated in the settling tank 5 are partially discarded and returned to the anaerobic reaction tank 1 again.

2 is a schematic diagram showing a purification process of wastewater according to a second preferred embodiment of the present invention. The wastewater purification process shown in FIG. 2 is a wastewater purification process according to the first embodiment of the present invention shown in FIG. 1 except that the anoxic reactor 3 shown in FIG. 1 operates in the form of intermittent aeration. Is the same as

Referring to FIG. 2, the aeration and non-aeration reaction times of the intermittent aeration reactor 9 may be operated for 1 hour / 1 hour, 2 hours / 1 hour, 2 hours / 2 hours, and the like according to an operation method. This is because the denitrification reaction time required by the wastewater properties acts as an influence factor. During the non-aeration period, the denitrification reaction proceeds, and during the aeration, phosphorus intake and residual organic matter are removed.

3 is a schematic view showing a wastewater purification process according to a third preferred embodiment of the present invention. The present invention shown in FIG. 3 is the same as the wastewater purification process according to the second embodiment of the present invention shown in FIG. 2 except that the intermittent aeration reactor shown in FIG. 2 is operated in two. This wastewater purification process can improve the treatment stability of wastewater treatment by using two intermittent aeration reactors. This may be particularly advantageous when operating high concentration wastewater such as livestock wastewater.

4A and 4B are schematic diagrams showing examples of the separation device installed in FIGS. 1, 2 and 3. In the first, second and third preferred embodiments of the present invention, an example of a device for separating media from wastewater flowing out of the anaerobic reactor 1 is shown. The media mixed with the waste water are separated in the separator. The waste water is liquid and can pass through the screen, and the media cannot pass through the screen depending on the size (eg Linpor media, 12 × 12 × 15mm). It is possible. Such a separation device is not possible to separate the floating microorganisms, but in the adhesive treatment process in which microorganisms grow on the media, the media can be separated by a screen using the microorganism and the wastewater. Separation of microorganisms and wastewater after the reaction in the anaerobic reactor (1) can effectively improve the denitrification efficiency by using organic matter in the wastewater because the microorganisms are transferred to the denitrification reactor, and the wastewater separated from the microorganisms nitrification because there is less organic matter In the reactor, there is an advantage that the growth and nitrification of nitrifying bacteria can be enhanced. In addition, the use of media in the overall process can reduce sludge production.

The wastewater purification method according to the present invention is capable of treating nitrogen and phosphorus, which is the cause of eutrophication, and has the advantage of maximizing the removal efficiency of nitrogen and phosphorus by using the organic matter of the influent wastewater as much as possible by adsorbing it to microorganisms. . In addition, the sludge volume generated due to the use of media in the treatment process in the form of adherent growth can be reduced, which can greatly reduce the cost of sludge treatment.

1 is a schematic view showing a wastewater purification process according to a first preferred embodiment of the present invention;

2 is a schematic view showing a wastewater purification process according to a second preferred embodiment of the present invention.

3 is a schematic view showing a wastewater purification process according to a third preferred embodiment of the present invention.

Figures 4a and 4b is a schematic diagram of a separator for separation of media and wastewater in Figures 1, 2 and 3

<Description of the code | symbol about the principal part of drawing>

1: anaerobic reactor 2: nitrification reactor

3: oxygen-free reactor 4: post-aeration reactor

5: settling tank 6: separator

7: Screen 8: Mediah

9: intermittent aeration reactor

Claims (3)

In the waste water purification method, anaerobic reactor, nitrification reactor, anoxic reactor, post-aeration tank and precipitation tank are injected and operated by injecting media in the reaction tank. Waste water treatment method characterized in that by operating. The wastewater treatment method according to claim 1, wherein the anoxic reactor is operated in the form of an intermittent aeration. The method of claim 1, wherein the anaerobic reactor is divided into two reactors and operated in the form of intermittent aeration.