KR100430382B1 - Treatment method for livestock waste water including highly concentrated organoc, nitrogen and phosphate and treatment system used therein - Google Patents

Abstract

The present invention relates to a livestock wastewater treatment method and treatment system capable of simultaneously treating organic matter, nitrogen and phosphorus contained in the livestock wastewater.

Livestock wastewater treatment method of the present invention is based on the high anaerobic digestion tank and aeration tank of the absolute anaerobic condition using the absolute anaerobic microorganism in the denitrification step, and pretreatment (solid-liquid separation) and post-treatment (coagulation sedimentation, ozone oxidation, Electrolysis, filtration), etc., ie solid waste separator-high rate anaerobic digestion tank-aeration tank-aggregation, such as livestock wastewater with BOD 10,000ppm, suspended solids concentration (SS) 7,000ppm, total nitrogen concentration 3,500ppm. The present invention relates to an economical treatment method capable of satisfying the final effluent water quality below the regulation level by efficiently treating the high concentration organic matter, nitrogen, and phosphorus contained in the livestock wastewater.

Description

Process for treating livestock wastes containing high concentrations of organic matter, nitrogen and phosphorus and treatment system used therein {TREATMENT METHOD FOR LIVESTOCK WASTE WATER INCLUDING HIGHLY CONCENTRATED ORGANOC, NITROGEN AND PHOSPHATE AND TREATMENT SYSTEM USED THEREIN}

The present invention relates to a livestock wastewater treatment method and a livestock wastewater treatment system capable of simultaneously treating organic matter, nitrogen and phosphorus contained in the livestock wastewater.

Livestock wastewater degrades water quality primarily by contaminating rivers and lakes with high concentrations of organic matter, and secondly, nitrogen and phosphorus cause eutrophication and destroy water systems. In particular, since most livestock farms are adjacent to water sources and streams, they are increasing water pollution. Therefore, in order to secure a clean water source, nitrogen and phosphorus must be treated stably and reliably.

On the other hand, domestic livestock wastewater is B5,000 25,000 ~ 35,000ppm, total nitrogen 2,500 ~ 7,000ppm, total phosphorus 150 ~ 2,000ppm, the characteristics of the source is very different, and the concentration of nitrogen and phosphorus is very high. In Korea, aerobic biological treatment such as liquid corrosion and long-term aeration and anaerobic biological treatment using anaerobic microorganisms have been used to treat high concentration livestock wastewater. However, such a treatment method has a problem in that nitrogen and phosphorus cannot be treated simultaneously as a treatment method for organic matter treatment.

Anaerobic-aerobic repetition processes are used as electrochemical and biological treatments to treat organic matter, nitrogen and phosphorus in wastewater at the same time. However, in the case of electrolysis, the treatment efficiency is high, but the facility cost and maintenance cost cannot be used universally.

The anaerobic-aerobic repetition process with biological nitrogen and phosphorus treatment uses the principle that microorganism nitrifies ammonia nitrogen in aerobic conditions, phosphorus accumulates in the microorganism, denitrifies nitrogen in anaerobic condition and phosphorus is released into the microorganism in vitro. will be. During the anaerobic-aerobic repetition process, nitrogen is gradually oxidized to ammonia nitrogen and nitrite nitrogen by a nitrifying bacteria under aerobic conditions.Nitrate nitrogen is again passed through nitrite nitrogen under anoxic conditions. Reduced to and removed. Phosphorus accumulated in the microorganisms under aerobic conditions is removed when the excess microorganisms are removed.

However, most biological treatment technologies capable of simultaneously treating organic matter, nitrogen, and phosphorus target low-density wastewater such as sewage (Korean Patent Publication No. 96-014012, Korean Patent No. 153211). It is still insignificant [Advanced Environmental Technology 3 (1) 1995, Wastewater Treatment Engineering 1993].

Microorganisms used for biological treatment utilize random microorganisms in activated sludge. However, activated sludge has a limitation in treating high concentration wastewater, so it is difficult to treat high concentration wastewater such as livestock wastewater. Therefore, dilution up to the concentration that can be treated with activated sludge or the processing time becomes long, and as a result, the treatment facility should be large in capacity.

In the denitrification process, nitrate nitrogen is denitrated by denitrification microorganisms with nitrogen gas. At this time, the denitrification microorganisms denitrify while consuming at least four times the organic carbon (organic matter) in relation to the concentration of nitrate nitrogen contained in the waste water. However, in the case of livestock waste water, the nitrogen concentration is high, so the ratio of organic matter concentration / nitrogen nitrogen concentration is 4 or less, so it is very difficult to denitrate and additional organic carbon source must be added. In addition, organic matter in livestock wastewater is difficult to decompose because it is hardly decomposable, and consequently denitrification is more difficult.

An object of the present invention is to provide an economical treatment method that can efficiently treat the high concentration of organic matter, nitrogen, phosphorus contained in the livestock wastewater to satisfy the final quality of the discharged water below the regulatory value. In the present invention

First, absolute anaerobic microorganisms are used in the denitrification stage.

In the conventional method, an anaerobic or anaerobic condition was imparted using an optional microorganism, that is, activated sludge in the denitrification step, and an aerobic microorganism was used in the nitrification step. In the present invention, an absolute anaerobic microorganism was used in the denitrification step. A high rate anaerobic digester with anaerobic conditions was used. In the nitrification step, the same aerobic microorganism was used. Absolute anaerobes in high rate anaerobic digesters have the advantage of treating high concentration organic wastewater with high efficiency without dilution. In addition, the process of anaerobic decomposition of organic matter is the process of acid fermentation of organic matter with organic acid and then methane fermentation of organic acid again. It is an easy form. Therefore, denitrification occurs easily by using an organic acid that is easily decomposed as an organic carbon source in the denitrification process.

Second, the raw wastewater is introduced through the bottom distributor and the wastewater returned from the settling tank is introduced between the bottom of the carrier bed and the top of the sludge bed.In conventional methods, nitrified wastewater and raw wastewater in anaerobic or anaerobic tanks where denitrification occurs, and As the microbes were mixed, phosphorus release and denitrification occurred simultaneously. However, in the presence of nitrate nitrogen or nitrite nitrogen, the release of phosphorus is suppressed and phosphorus cannot be effectively removed. In the present invention, the nitrified wastewater is introduced between the lower layer of the carrier and the lower sludge layer of the digester when the nitrified wastewater is returned to the high rate anaerobic digester in order to effectively release phosphorus together with the denitrification reaction. Therefore, denitrification and phosphorus release of microorganisms can occur effectively without interfering with each other.

Third, the supernatant and precipitated sludge in the settling tank is returned to the anaerobic digester.

The conventional method uses random activated sludge and in the case of the anaerobic (or anoxic) → aerobic repetition process, the wastewater and sludge (microorganism) treated in the anaerobic tank are introduced into the aerobic tank together. In addition, the wastewater and sludge treated in the aerobic tank are precipitated in the settling tank so that the supernatant is discharged and the sludge is returned for maintaining the concentration of microorganisms in the anaerobic and aeration tanks. In the present invention, the absolute anaerobic microorganism is used to reduce the aerobic sludge returned from the aerobic tank. This reduces the amount of excess sludge generated in the whole process. Phosphorus is removed along with the excess sludge removed from the settling tank, and the aerobic treated water returned to the high rate anaerobic tank is denitrated by absolute anaerobes.

1: process chart of livestock wastewater treatment method of the present invention

Figure 2: Cross section of high rate anaerobic digester

Livestock wastewater treatment method and treatment system of the present invention is based on the high anaerobic digestion tank and aeration tank of the absolute anaerobic condition, and according to the characteristics of the wastewater pretreatment (solid-liquid separation) and post-treatment (coagulation sedimentation, ozone oxidation, electrolysis, filtration), etc. You can add In other words, in case of livestock wastewater with BOD 10,000ppm, suspended solids concentration (SS) 7,000ppm, and total nitrogen concentration 3,500ppm, the process of solid-liquid separator, high rate anaerobic digestion tank, aeration tank, and coagulation sedimentation can be configured. The role of each process is as follows.

Solid-liquid Separation:

Before the wastewater is introduced into the high-rate anaerobic digester, solid-liquid separation is used to minimize the concentration variation and reduce the concentration to the maximum to reduce the load on the next process. As the solid-liquid separation, a centrifugal separation method and a filter method are used according to the concentration and flow rate of the waste water.

High rate anaerobic digester:

The high concentration of organic matter contained in the wastewater flowing into the solid-liquid separation is removed first. In the step of removing the organics, the denitrified wastewater is denitrated using organic acids and acetates produced as intermediate products. At the same time, phosphorus is released.

Aeration tank:

In the high-rate anaerobic digester, residual organic matter present in the first treated wastewater is removed and nitrified ammonia nitrogen contained in the wastewater. Phosphorus is ingested in the body of the microorganism and is removed together when removing excess sludge.

In order to increase the efficiency of the aeration tank, the number of aeration tanks may be two or more.

Sedimentation tank:

Gravity separates microorganisms from wastewater with biological treatment. Precipitated sludge contains excess phosphorus and the supernatant is nitrified wastewater, part of which is discharged, and part of which is returned to a high-rate anaerobic digester, the primary biological treatment step, to complete denitrification. The surplus sludge is also returned to the high rate anaerobic digester with supernatant.

Post-treatment: flocculation, sedimentation, ozone oxidation, filtration

As a final step of satisfying the discharge standard of treated water, the intrinsic chromaticity of the livestock wastewater is removed simultaneously. The post-treatment method is selected from coagulation sedimentation, ozone oxidation, electrolysis, and filtration (sand filtration + activated charcoal filtration) according to the characteristics of the wastewater after biological treatment.

Hereinafter, the present invention will be described in detail.

The high rate anaerobic digester used the high rate anaerobic digester developed by the present inventors (Korean Patent Application No. 97-75848), and other types of high rate anaerobic digester having absolute anaerobic conditions may be used. The upper part of the anaerobic digester is filled with a porous ceramic carrier developed by the present inventors (Korean Patent Nos. 123019 and 153156), and denitrification microorganisms are immobilized on the carrier to further enhance the denitrification efficiency of the high rate anaerobic tank. In this anaerobic digester, the decomposition of high concentration organic matter proceeds actively.

At this time, an organic acid is produced as an intermediate product, which is very easy to use as an energy source of denitrification microorganisms. In general, when the ratio of organic matter and nitrogen in the denitrification step is too low (4.0 or less), the organic carbon source is introduced from the outside, and the most frequently used substance is methanol. This is because the microorganism in the form of a single molecule is very easy to use. Therefore, organic acids (mainly composed of 3-4 carbon molecules) are more suitable as carbon sources in the denitrification step than other forms of organic materials, so that the utilization efficiency of microorganisms can be maximized, thus minimizing the amount of external carbon sources, which may be unnecessary in some cases. It may be. In particular, since microorganisms are easily used as substrates than raw wastewater as a carbon source, it is possible to maintain a fast denitrification rate, and as a result, it is possible to reduce the volume of the anaerobic digester to increase competitiveness.

Phosphorus is released under anaerobic conditions, where phosphorus release is suppressed if nitrate or nitrite nitrogen coexists in the wastewater returned from the aeration tank. Therefore, in the present invention, the position where the nitrified wastewater (the form of nitrogen is mostly in the form of nitrate nitrogen as the wastewater conveyed in the aeration tank) is higher than the position of the inflowing raw wastewater to facilitate the use of organic acids. This ensures that phosphorus release and denitrification occur smoothly without interfering with each other. Figure 2 shows this in a cross-sectional view of a high rate anaerobic digester.

In the aeration tank, a second biological treatment of the effluent from the high-rate anaerobic digester is used to decompose the residual organic matter contained in the livestock wastewater and nitrify the ammonia nitrogen. The aeration tank may have two or more water quantities to further increase efficiency. In other words, most of the nitrogen contained in the wastewater flowing into the aeration tank maintains the form of ammonia nitrogen. This ammonia nitrogen should be changed in form from ammonia nitrogen to nitrite nitrogen to nitrate nitrogen under aerobic conditions by nitrifying bacteria. However, when untreated organics are present in the wastewater and the BOD ₅ / TKN is 3 to 5 or more, the activity of the microorganisms for removing the organics becomes active, whereas the nitrifying microorganisms decrease in number and weaken their activity. Therefore, residual organic matter should be removed for smooth nitrification. For this purpose, the number of aeration tanks is two, so that some nitrification reactions occur in the first aeration tank, but the main reaction is to remove residual organic matter, and the second aeration tank can complete nitrification and excess intake of phosphorus.

In the sedimentation tank, where solid-liquid separation occurs by gravity, activated sludge is precipitated to form flocs and the wastewater remains as supernatant. At this time, the precipitated activated sludge (sludge) is excessively ingested with phosphorus and is removed when the excess microorganism is removed. Some of the activated sludge is returned to the aeration tank to maintain a constant concentration of microorganisms in the aeration tank. In the present invention, the return rate to the aeration tank was set to 20 to 150% (value of the flow rate of the raw waste water) based on the appropriate microbial concentration.

The activated sludge returned to the anaerobic digester is reduced by absolute anaerobic microorganisms, thereby reducing the amount of surplus microorganisms (waste sludge) produced in the overall process. At this time, the settling supernatant is also returned and denitrified by the anaerobic microorganisms. In the present invention, the rate of return to the high-rate anaerobic digester according to the flow rate and concentration of the livestock wastewater was adjusted to 200 to 600% (value compared to the flow rate of the original wastewater).

The post-treatment step is to finally adjust the organic matter, phosphorus and chromaticity to meet the discharge criteria for the wastewater after biological treatment. Coagulation and sedimentation methods, ozone oxidation, and electrolysis are selected according to the characteristics of the wastewater. In the case of the coagulation sedimentation method, an inorganic coagulant and a polymer coagulant are used. In this step, an alumina coagulant and iron salt are used as the inorganic coagulant, and an anionic polymer coagulant is used as the coagulant.

First, high-density anaerobic digester using absolute anaerobic microorganisms can be used to treat high concentration wastewater without dilution, and denitrification efficiency and microbial carbon source by using biodegradable organic acid generated in organic decomposition step as carbon source needed in denitrification step. Increase the efficiency At this time, the inflow of the raw wastewater is processed by using the lowest distributor to treat organic matter.The wastewater and sludge returned from the settling tank after the aerobic treatment flows into the middle height of the digester and denitrification using the organic acid produced in the organic matter decomposition step in the digester. Let's do it. As a result, high concentration wastewater can be treated in a short time without dilution, and the denitrification efficiency can be improved, thereby reducing the equipment cost. In addition, it is possible to minimize the input amount of organic carbon source required in the denitrification process, thereby reducing operating costs and easy operation.

1. In the anaerobic digestion tank, the waste water returned after aerobic treatment is higher than the position where the raw water is introduced, so it is easy to remove phosphorus as well as effective denitrification in one reactor.

2. The existing method of using activated sludge is divided into roles in each tank (for example, nitrification tank, denitrification tank, anaerobic tank, etc.), and thus requires a plurality of reaction tanks. In a high rate anaerobic digester, efficient denitrification, phosphorus release, and organic matter removal reactions occur, making it possible to miniaturize the equipment.

3. After sludge treatment, the sludge and the supernatant are simultaneously returned to the high-rate anaerobic digester to perform denitrification, which minimizes the amount of excess sludge in the overall process.

Hereinafter, the present invention will be described in detail with reference to Examples.

Example 1

The treatment process of the present invention was applied to the livestock wastewater generated in C farm in Nonsan, Chungnam. The livestock wastewater used was 10,000 ppm of BOD, 7,000 ppm of suspended solids, 3,500 ppm of total nitrogen, and 200 ppm of total nitrogen.

The capacity of the high rate anaerobic digester was 10 liters and the top was filled with 50% porous ceramic carrier. Anaerobic digested sludge from the sewage treatment plant was precipitated for 1 day and then added. The residence time was 16 hours. The first aeration tank had a capacity of 40 liters with a residence time of 1.3 days and a microbial concentration of 5,000 ppm. The second aeration tank had a retention time of 2 days and a microbial concentration of 5,000 ppm with a capacity of 40 liters. The return sludge of the sewage terminal treatment plant was used for the first aeration tank and the second aeration tank. The settling tank had a residence time of 1 hour at a capacity of 1 liter. The return rate to the aeration tank 1 was 100% of the raw water inflow, and the return rate to the high-rate anaerobic digester was 200%, but the settling sludge and the supernatant of the settling tank were returned at the same ratio. In the flocculation tank, 1,000 ppm of alumina sulfate was added and stirred at 100 rpm for 15 minutes, followed by 10 ppm of anionic polymer flocculant, followed by stirring at 30 rpm for 40 minutes. Thereafter, it was precipitated for 90 minutes. After filtration (sand + activated carbon) step was discharged.

Water quality analysis was performed while operating the process of the present invention, and after the steady state was reached, the effluents of major biological processes were analyzed according to the number of operating days. The water quality analysis items were BOD, total nitrogen, total phosphorus, and excess sludge generation. The results are shown in Table 1.

Comparative Example 1)

In carrying out the denitrification of the nitrified wastewater, it was carried out in the same manner as in Example 1 by using an arbitrary microorganism in the general activated sludge instead of using an absolute anaerobic microorganism. For this purpose, an open digester was used rather than a sealed reactor, such as a high rate anaerobic digester. The carbon source required in the denitrification step was an organic substance contained in the raw wastewater. During the operation, after reaching the steady state, water quality analysis was performed according to the operation days. Water quality analysis items were the same as in Example 1 and are shown in Table 2.

Comparative Example 2)

In carrying out the denitrification reaction by returning the nitrified wastewater stored in the settling tank, only the supernatant was returned to the high-rate anaerobic digester in the same manner as in Example 1. During the operation, after reaching the steady state, water quality analysis was performed according to the operation days. Water quality analysis items were the same as in Example 1 and are shown in Table 3.

Claims (8)

In the wastewater treatment system consisting of anaerobic digestion tank, aeration tank and sedimentation tank, the method for treating wastewater containing high concentration of organic matter, nitrogen and phosphorus, Livestock wastewater treatment method comprising the step of returning the supernatant and precipitated sludge precipitated in the settling tank to the anaerobic digester in order to denitrate the nitrified wastewater in the aeration tank. The method of claim 1, The anaerobic digester uses an absolute anaerobic microorganism and uses organic acid as a carbon source. The method of claim 1, The anaerobic digester comprises a bottom distributor, through which raw wastewater flows, a bottom sludge layer on top of the bottom distributor, and a carrier layer on top of the bottom sludge layer. The supernatant and sludge to be returned is introduced between the uppermost layer of the lower sludge layer and the lowermost layer of the carrier layer. delete In the method for treating livestock wastewater containing high concentrations of organic matter, nitrogen and phosphorus using a wastewater treatment system consisting of anaerobic digestion tank and aeration tank, Discharging the wastewater introduced into the anaerobic digester by the microorganisms in the anaerobic digester; Nitrifying the ammonia nitrogen contained in the wastewater in the aeration tank and accumulating the released phosphorus in the microorganism; Returning a portion of the nitrified wastewater to the anaerobic digester; And Livestock wastewater treatment method comprising the step of denitrifying the wastewater returned from the anaerobic digester. In a livestock wastewater treatment system for treating livestock wastewater containing high concentrations of organic matter, nitrogen and phosphorus, An anaerobic digestion tank that primarily decomposes the organic matter contained in the incoming wastewater, denitrates the nitrate and nitrite nitrogen contained in the aerobic treated wastewater, and releases phosphorus into the microorganism in vitro; An aerobic aeration tank for nitrifying ammonia nitrogen contained in wastewater flowing out through the anaerobic digester and accumulating phosphorus in microorganisms; And And a conveying apparatus for conveying a portion of sludge and supernatant water generated by sedimenting the treated water flowing out of the aerobic aeration tank for denitrification to the anaerobic digester. The method of claim 6, The anaerobic digester includes a bottom distributor for the inflow of raw wastewater, and a carrier layer formed on the bottom distributor. The anaerobic digester has an inlet for the inflow of the supernatant and sludge returned between the bottom distributor and the carrier layer. The method of claim 5, The anaerobic digester uses an absolute anaerobic microorganism to denitrate nitric acid and nitrite nitrogen, and uses an organic acid as a carbon source of the absolute anaerobic microorganism.