KR100471963B1 - Method for Manufacturing Anaerobic Fermentation Broth from Organic Wastes for Using in Nutrient Removal - Google Patents

Abstract

The present invention relates to an anaerobic fermentation method of organic waste for obtaining an anaerobic fermentation broth that can be used as an external carbon source when nitrogen and phosphorus are removed from wastewater. According to the anaerobic fermentation method through the semi-continuous cultivation of the present invention, the ratio of organic acid to dissolved COD is more than 85%, acetic acid is about 50% of the total organic acid, butyric acid is about 21% with high nitrogen and phosphorus removal efficiency It is possible to obtain a fermentation broth with a high ratio of two organic acids and a yield of 0.35 or more, which is expressed as the total amount of organic acids in the fermentable portion of the food waste. These results show that organic wastes are not only bioavailable because of the high yield of acetic acid and butyric acid, which are known to be highly efficient in biological denitrification and dephosphorization, as well as the yield and the ratio of organic acid in dissolved COD. By providing an anaerobic fermentation method that can be efficiently recycled to denitrification and dephosphorization, it is possible to establish a clear plan for organic waste, which is a social problem, by securing organic waste treatment technology and economic effects in terms of recycling it. have.

Description

Method for Manufacturing Anaerobic Fermentation Broth from Organic Wastes for Using in Nutrient Removal

The present invention relates to a method for producing an external carbon source for effectively removing nitrogen and phosphorus from wastewater, sewage and sewage (hereinafter referred to as 'wastewater') from organic waste. More specifically, the present invention relates to a process for anaerobic fermentation of organic waste to obtain a low cost carbon source that can be effectively used for biological nitrogen, phosphorus removal.

As industries become more advanced and population concentration grows, the amount of nitrogen and phosphorus entering the waters is increasing. The influx of nutrients is recognized as a major cause of eutrophication by adversely affecting the river's self-cleaning action. At present, the discharged water quality standards of our country shows that the sewage treatment plant has 60 ppm of total nitrogen and 8 ppm of total nitrogen. In the manure and wastewater treatment plants, the total nitrogen is 120 ppm and the total phosphorus is 16 ppm or less, which is too high compared to the fact that nitrogen and phosphorus may cause eutrophication even at concentrations of 0.2 to 0.3 ppm and 0.01 to 0.02 ppm, respectively. It is true. However, since most terminal plants are designed with a focus on the removal of organics, expansion of facilities for the removal of nitrogen and phosphorus is required.

Biological nitrogen removal is achieved by oxidation of ammonia nitrogen and reduction of oxidized nitrogen with nitrogen gas. Organic denitration, which reduces nitrogen oxides to nitrogen gas, requires an organic carbon source as an electron donor. In order to use organic materials, the process is complicated by complicated combination or circulation of the reaction tank, and even in this case, when the treatment rate is low, in most cases, an organic carbon source must be supplied from the outside. Many studies have been conducted on denitrification using methanol, glucose, and acetic acid as organic carbon sources. Among these, denitrification by acetic acid is known to be the highest (Tam NFY, Wong YS and Leung G., Wat). Res., 26 (9): 1229-1236 (1992). Currently, when commercialized organic material is used as an electron donor, methanol is widely used because it is the most economical, but it is very urgent to find a substitute for methanol to reduce the operating cost of the wastewater treatment plant.

On the other hand, in the case of phosphorus, the release of phosphorus starts simultaneously with the storage of organic matter in the anaerobic state, and is removed by overingesting and storing phosphorus in the form of polyphosphate in aerobic state (Levin G, V and Shapiro J. , J. WPCF., 37: 800 (1965). By repeatedly forming anaerobic and aerobic conditions, phosphorus is removed by consuming more phosphorus than microorganisms release phosphorus. The cells involved in phosphorus removal are short-chain fatty acids such as acetic acid as carbon sources. The composition of organics present in the influent source has been recognized as a very important factor because it requires (Fuhs GW and Chen M., Microbiol. Ecol., 2: 119-138 (1975)).

Food waste accounts for 28-31% of all household wastes, and it is the most abundant of household wastes. Excluding cans and papers being recycled, the share of household waste is 50-60%. Our country wastes about 8 trillion won of food every year as garbage, which causes serious environmental pollution. Food waste is almost organic, and when it is landfilled, it causes odor and leachate problems, and incineration generates air pollutants. Therefore, it is urgent to provide effective technical management measures for food waste. As a conventional technique prepared for recycling such food waste, there have been attempts to obtain a fermentation broth containing organic acid by anaerobic fermentation, and then add it as an external carbon source for the removal of nitrogen and phosphorus, but the anaerobic fermentation conditions are optimized. In addition to acetic acid and butyric acid, which are highly efficient in the removal of nitrogen and phosphorus, valerian and caproic acid, which are known to be inefficient, are also produced. In this low aspect, the efficiency of recycling food waste is inevitably deteriorated. All.

Therefore, there is a rapid need for an anaerobic fermentation method of organic wastes in order to solve the problems of the prior art.

Therefore, the present inventors have made diligent research to develop a method for obtaining anaerobic fermentation broth of organic waste, which is highly efficient in removing nitrogen and phosphorus from wastewater, compared to the conventional research results. As a result, organic matters such as food waste, grass, sawdust and rice straw, etc. In the anaerobic fermentation of waste, various conditions have been established to complete the present invention.

After all, the main object of the present invention is to provide an anaerobic fermentation method of organic waste to obtain an external carbon source used to remove nitrogen and phosphorus in the wastewater.

The anaerobic fermentation method of the organic waste of the present invention uses anaerobic sludge as a cell for the anaerobic fermentation in anaerobic fermentation in a semi-continuous reactor in which one or more organic waste selected from the group consisting of food waste, grass, sawdust, rice straw and waste paper is used. , Fermentation broth with high proportion of acetic acid and butyric acid, which are highly efficient for removing nitrogen and phosphorus, and high proportion of organic acid in dissolved COD.

At this time, the semi-continuous reactor used in the present invention is an anaerobic reactor containing no air, and includes a temperature control device, a pH control device, and a stirring device. Quasi After adding the anaerobic sludge obtained from the anaerobic digester of the sewage treatment plant to the continuous reactor as a microbial inoculum, one or more organic wastes selected from the group consisting of food waste, grass, sawdust, rice straw and waste paper are supplied once a day. do. In order to maintain a constant volume in the reactor, a portion of the fermentation broth is discharged just before feeding the organic waste at a predetermined hydraulic residence time. The discharged fermentation broth becomes the desired product. In this anaerobic fermentation process, the pH is maintained in the range of 5.3 to 6.5 in order to suppress the growth of methane bacteria, the temperature is 30 to 45 ℃, the hydraulic retention time is 6 to 12 days, the organic input rate based on dry weight In the range of 7 to 13 g / L · d, the organic acid concentration of the fermentation broth is 20 to 35 g / L, 30,000 to 50,000 ppm of dissolved COD, 70 to 95% of organic acid in dissolved COD, A fermentation broth is obtained in which the ratio of acetic acid is 20 to 55% and the ratio of butyric acid is 10 to 25%. Such fermentation broth has a high ratio of acetic acid and butyric acid in organic COD and high efficiency in nitrogen and phosphorus removal of dissolved COD, while the concentration of ammonia and phosphoric acid is very low. It can be used as an economical and efficient external carbon source.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are intended to illustrate the present invention in more detail, and it will be apparent to those skilled in the art that the scope of the present invention is not limited to these examples.

Example 1 Anaerobic Fermentation Results for Hydrodynamic Retention Time Variation

In order to secure acid-producing microorganism sludge, anaerobic digester sludge of Daejeon Sewage Treatment Plant was acquired and adapted for concentration of acid-producing microorganism. The average composition of the used food waste was 80% water content and 95% volatile solids. Elemental analysis showed that the proportion of nitrogen was significantly lower than that of carbon at 47% of carbon, 39% of oxygen, 7% of hydrogen, and 3% of nitrogen. The reactor for anaerobic fermentation was made of transparent acrylic, the total volume was 2L, a pH control device was attached for pH control, and a motor and an impeller were mounted to allow mixing. The temperature was adjusted to 35 ° C. using a thermostat and the pH was adjusted to 5.5. The feeding amount was 5 g / L · d on the basis of dry weight, and the hydraulic residence time was 4, 8, and 12 days, and the fermentation was performed semi-continuously with discharge and inflow once daily. After 4-5 times the hydraulic residence time after the start of fermentation, it was possible to observe the steady state, and all the results are the steady state. The composition of the organic waste fermentation broth was analyzed using HPLC (L-6000, Hitachi, Japan) equipped with a refractive index detector and Aminex HPX-87H (Richmond, BioRad Co., USA) column, COD Was measured using the potassium dichromate method, and the concentrations of nitrogen and phosphorus were measured according to the standard method (7th edition, APHA-AWWA-WDCF). The results of the anaerobic fermentation according to the hydraulic residence time change are shown in Table 1 below.

Normal after 4-5 times the hydraulic residence time after the start of fermentation Attainment of the fetus was observed, and the longer the hydraulic residence time, the higher the total amount of organic acid produced. The concentration of organic acid produced at the hydraulic retention time of 12 days was around 22 g / l. However, it was observed that the concentrations of ammonia and phosphorus were continuously diluted and maintained at about 0 and 10-18 ppm after reaching the steady state, respectively. Yield was also increased as the hydraulic residence time increases. However, since there is little difference between 8 and 12 days, the hydraulic residence time for organic acid fermentation at 5 g / L 8 days was enough.

Example 2 Anaerobic Fermentation Results for Changes in Organic Feed Rate

In order to secure acid-producing microorganism sludge, anaerobic digester sludge of Daejeon Sewage Treatment Plant was acquired and adapted for concentration of acid-producing microorganism. The average composition of the used food waste was 80% water content and 95% volatile solids. Elemental analysis showed that 47% of carbon, 39% of oxygen, 7% of hydrogen, and 3% of nitrogen were compared to that of carbon. It was confirmed that the ratio is quite low. The reactor for anaerobic fermentation was made of transparent acrylic, the total volume was 2L, a pH control device was attached for pH control, and a motor and an impeller were mounted to allow mixing. The temperature was adjusted to 35 ° C. using a thermostat and the pH was adjusted to 5.5. The hydraulic residence time was 8 days, and the anaerobic fermentation was carried out in a semi-continuous manner with the discharge and inflow of food once a day. The organic loading rate was 5 g / l · d, 9 g / l · d, 13 g / l · d on the basis of dry weight was observed the results. After 4-5 times the hydraulic residence time after the start of fermentation, it was possible to observe the steady state, and all the results are the steady state. The composition of the organic waste fermentation broth was analyzed using HPLC (L-6000, Hitachi, Japan) equipped with a refractive index detector and Aminex HPX-87H (Richmond, BioRad Co., USA) column, COD Was measured using the potassium dichromate method and the concentrations of nitrogen and phosphorus were measured according to the standard method (7th edition, APHA-AWWA-WDCF). The results of the anaerobic fermentation according to the change of the organic input rate are shown in Table 2 below.

As shown in Table 2, it was confirmed that the dissolved COD increased with increasing organic input rate. However, the comparison of yields showed a tendency to decrease as the rate of organic matter input increased, which may be due to the input of food waste at an excess of the fermentation rate of microorganisms. This reduced yield means the accumulation of unfermented food waste. Therefore, it is important to find the optimal point considering both the production side of organic acid for nitrogen and phosphorus removal and the side of disposal of food waste. In the case of operating the hydraulic residence time of 8 days, it was determined that about 9 g / L · d would be appropriate. The composition of the organic acid was confirmed that the ratio of acetic acid increases as the organic input rate increases. On the other hand, caproic acid having a large number of carbons was produced as the organic input rate increased, and when succinic acid was 13g / l · d at 9g / l · d, succinic acid and lactic acid were observed. It was also observed that the concentrations of ammonia and phosphorus in fermentation products increased as the rate of organic matter input increased, but it was significantly lower than the dissolved COD. It seems to be no problem to use it.

Example 3 Anaerobic Fermentation Results for Temperature Changes

Anaerobic Digester Sludge at Daejeon Sewage Treatment Plant to Secure Acid-producing Microorganism Sludge Paper was obtained and adapted for the enrichment of acid producing microorganisms. The average composition of the used food waste was 80% water content and 95% volatile solids. Elemental analysis showed that the proportion of nitrogen was significantly lower than that of carbon at 47% of carbon, 39% of oxygen, 7% of hydrogen, and 3% of nitrogen. The reactor for anaerobic fermentation was made of transparent acrylic, the total volume was 2L, a pH control device was attached for pH control, and a motor and an impeller were mounted to allow mixing. The pH was 5.5, the food input was 9 g / ℓ · d on the basis of dry weight, the hydraulic residence time was 8 days, and the anaerobic fermentation was carried out in a semi-continuous manner with discharge and inflow once a day. The temperature was changed to 25 ° C., 35 ° C. and 45 ° C. using a thermostat, and the results were observed. After 4-5 times the hydraulic residence time after the start of fermentation, it was possible to observe the steady state, and all the results are the steady state. The composition of the organic waste fermentation broth was analyzed using HPLC (L-6000, Hitachi, Japan) equipped with a refractive index detector and Aminex HPX-87H (Richmond, BioRad Co., USA) column, COD Was measured using the potassium dichromate method, and the concentrations of nitrogen and phosphorus were measured according to the standard method (7th edition, APHA-AWWA-WDCF). The results of anaerobic fermentation with temperature change are shown in Table 3 below.

As shown in Table 3, the concentration and yield of organic acids were the highest at 35 ° C, and the inhibition of hydrolysis due to the low concentration was observed at 25 ° C. Acetic acid was the highest at 45 ℃, but the concentration of capronic acid was also high. As a carbon source, 35 degreeC was considered to be advantageous.

Example 4 Anaerobic Fermentation Results for pH Change

In order to secure acid-producing microorganism sludge, anaerobic digester sludge of Daejeon Sewage Treatment Plant was acquired and adapted for concentration of acid-producing microorganism. The average composition of the used food waste was 80% water content and 95% volatile solids. Elemental analysis showed that the proportion of nitrogen was significantly lower than that of carbon at 47% of carbon, 39% of oxygen, 7% of hydrogen, and 3% of nitrogen. The reactor for anaerobic fermentation was made of transparent acrylic, the total volume was 2L, a pH control device was attached for pH control, and a motor and an impeller were mounted to allow mixing. The feeding amount was 9 g / l · d on the basis of dry weight, the hydraulic residence time was 8 days, and the anaerobic fermentation was carried out in a semi-continuous manner with discharge and inflow once a day. The temperature was adjusted to 35 ° C. using a thermostat and the pH was changed to 5.0, 5.5, and 6.0, and the results were observed. After 4-5 times the hydraulic residence time after the start of fermentation, it was possible to observe the steady state, and all the results are the steady state. The composition of the organic waste fermentation broth was analyzed using HPLC (L-6000, Hitachi, Japan) equipped with a refractive index detector and Aminex HPX-87H (Richmond, BioRad Co., USA) column, COD Was measured using the potassium dichromate method, and the concentrations of nitrogen and phosphorus were measured according to the standard method (7th edition, APHA-AWWA-WDCF). The results of the anaerobic fermentation according to the pH change are shown in Table 4 below.

According to Table 4, as the pH was increased, the concentration and yield of the organic acid increased, showing the best results at 6.0, and in the case of pH 5.0, it was observed that the efficiency of acid fermentation was decreased due to the decrease of microbial activity according to the low pH. At pH 6.0, the concentration of acetic acid was about 12 g / l, which was the highest concentration of the conditions examined so far, and no capric acid or succinic acid was observed. Therefore, it was proved that the fermentation conditions considered were the most effective for anaerobic fermentation of food waste for nitrogen and phosphorus removal at 8 days of hydraulic residence time, 9 g / L · d of organic matter, temperature of 35 ° C., and pH 6.0. Under these conditions, the dissolved COD of the anaerobic fermentation broth was about 40,000 ppm, of which the organic acid accounted for 88-90%. In addition, in the concentration of 24.4-25.5 g / l of total organic acid, acetic acid was about 50% and butyric acid was about 21%, and the ratio of two kinds of organic acids having high efficiency of nitrogen and phosphorus removal was very high. About 6% and no capronic acid was detected. Since the ammonia concentration was 35-50 ppm and the total phosphorus concentration was 65-80 ppm, which is more than 500 times lower than the 39,000-40,000 ppm dissolved COD, the nitrogen and phosphorus loadings of the fermentation broth were negligible. The yield of the total organic acid in the fermentable portion of the food waste was 0.36-0.37, which was considerably higher than the conventional methods.

As described above in detail specific parts of the present invention, it is apparent to those skilled in the art that such specific descriptions are merely preferred embodiments, and thus the scope of the present invention is not limited thereto. something to do. Thus, the substantial scope of the present invention will be defined by the claims and their equivalents.

As described and demonstrated in detail above, the present invention provides an anaerobic fermentation method of organic waste to obtain an anaerobic fermentation broth that can be used as an external carbon source when nitrogen and phosphorus are removed from wastewater. According to the anaerobic fermentation method using the semi-continuous cultivation of the present invention, the dissolved COD is 39,000 ppm or more under the conditions of a hydraulic retention time of 8 days, an organic feed rate of 9 g / L · d, 35 ° C., pH 6.0, Among these, fermentation broth with an organic acid ratio of 88% or more can be obtained. In addition, in the concentration of 24.4-25.5 g / l of total organic acid, acetic acid is about 50% and butyric acid is about 21%. A fermentation broth with a yield of 0.36 or greater, expressed in terms of total organic acid, can be obtained. These results indicate that organic wastes are not only high in yield, but also high in organic COD in dissolved COD and high in acetic acid and butyric acid, which are known to be highly efficient in biological denitrification and dephosphorization. By suggesting anaerobic fermentation methods that can be efficiently recycled for biological denitrification and dephosphorization, we can establish a clear plan for organic waste, which is a social problem, and secure economical effects in terms of recycling it by securing organic waste treatment technology. Can be. By adding the organic acid solution obtained from acid fermentation of organic waste as an external carbon source, nitrogen and phosphorus can be effectively removed even in a system using a single reactor such as a continuous batch reactor. Significantly simplified nitrogen, phosphorus compared to process It is contemplated that operation of the removal process will be possible. In addition, securing external carbon sources from waste is expected to enable the development of various processes that can further improve the quality of effluents within the limits of economic feasibility.

1 is a diagram schematically showing the configuration of a fermenter for semi-continuous fermentation of organic waste.

Claims (4)

The method for producing an organic acid having 2 to 6 carbon atoms from organic wastes by semi-continuous anaerobic fermentation using anaerobic sludge as a cell in a reactor including a thermostat, a stirrer and a pH regulator, wherein the fermentation is pH 5.3 ˜6.5, temperature 30-45 ° C., hydraulic residence time 6-12 days and organic feed rate 7-13 g / l · d, and the dissolved COD of the organic acid obtained by the fermentation is 30,000-50,000 ppm, wherein the proportion of organic acid in the dissolved COD is 70-95%, and the proportion of acetic acid and butyric acid in the organic acid is 20-55% and 10-25%, respectively. delete delete The method of claim 1, Organic wastes are found in groups consisting of food waste, grass, sawdust and rice straw. Anaerobic fermentation method of organic waste, characterized in that at least one selected.