KR100783785B1 - Carbon source preparing method for advanced biological treatment of sewage and wastewater - Google Patents

Abstract

The present invention provides a method for producing a carbon source for advanced treatment of sewage and wastewater using sewage sludge, comprising: 1) introducing the sewage sludge into a mesophilic fermentation tank for hydrolysis and acid fermentation; 2) introducing the effluent of the mesophilic fermentation tank into the settling tank to separate the solids and the acid fermentation broth; 3) introducing the separated solids into a hot acid fermentation tank for further hydrolysis and acid fermentation; 4) returning the effluent produced in step 3) to the mesophilic fermentation tank; 5) The present invention relates to a method for producing a highly treated carbon source for sewage and wastewater, characterized by producing an acid fermentation solution that can be utilized as a highly treated carbon source from the sedimentation tank. Accordingly, the present invention can significantly reduce the amount of sewage sludge by the medium temperature high temperature acid fermentation process and at the same time efficiently obtain a carbon source for advanced treatment.

Carbon source, wastewater, high temperature acid fermentation tank, low temperature acid fermentation tank

Description

Carbon source for advanced treatment of sewage and wastewater {CARBON SOURCE PREPARING METHOD FOR ADVANCED BIOLOGICAL TREATMENT OF SEWAGE AND WASTEWATER}

1 is a process diagram schematically showing a manufacturing system for performing a method for producing a carbon source for advanced treatment of sewage and wastewater according to the present invention.

Explanation of symbols for the main parts of the drawings

1: settling tank

2: pH adjusting tank

3: chemical tank

4: Medium temperature fermentation tank

5: high temperature acid fermentation tank

6: settling tank

7: Acid Fermentation Liquid Storage Tank

8: anaerobic tank

9: drain tank

10: flow adjustment tank

The present invention relates to a method for producing a carbon source for advanced treatment of sewage and wastewater, and more particularly, to obtain a carbon source used to reduce sludge production and remove nutrients by a middle temperature and high temperature anaerobic fermentation process. It relates to a method for producing a carbon source for advanced treatment of wastewater.

The sewage flowing into Korea's sewage treatment plant has a BOD (biochemical oxygen demand) value of 80-100 mg / L on average, and the inflow water quality is not much lower than the design water quality. There are several difficulties in introducing advanced treatment processes for removal. Generally, the ratio of BOD / T-N required for efficient nitrogen removal is presented above 5, but most of domestic sewage is facing a serious carbon shortage problem because the ratio of BOD / T-N is only 2-3. In general, methanol is recommended as an external carbon source when there is a shortage of influent carbon sources in the advanced treatment process to remove nitrogen and phosphorus from sewage water. However, expensive methanol purchase costs put a considerable burden on the operation cost of the advanced treatment process. It becomes a more difficult factor.

In general, sewage sludge generates as much as 1-2% of the total treated sewage. Sewage sludge is solubilized when acid fermented under anaerobic conditions so that the particulate organics in the sewage sludge are converted to soluble organics, and some of the organic acids and soluble organics produced can be used as an efficient external carbon source in the denitrification process of advanced treatment systems. Therefore, a method for efficiently producing an advanced carbon source using sewage sludge generated during sewage treatment is very important.

Looking at activated sludge processes in domestic sewage treatment plants, research on sequencing bath reactors (SBRs), which are highly adaptable to load fluctuations, is being actively conducted. SBR has a small number of sites and simple facilities and operation. Recently, the number of application cases is increasing. However, SBR is rarely applied to domestic sewage treatment plants because it is difficult to apply to large-scale treatment facilities. Recently, modified SBR such as Cyclic Activated Sludge System (CAS) or Intermittent Cycle Extended Aeration System (ICEAS), which continuously injects some raw water, has been developed to overcome the disadvantage of batch type, but it is still difficult for large scale processing.

The existing Biological Nutrient Removal Processes (BNRs) currently being studied are mostly developed in foreign countries. In view of domestic characteristics such as sewage concentration, treatment plant facilities, technology level, economic environment, etc. Changes to the system and accumulation of operating techniques must be preceded.

Recently, we have started to develop a process suitable for our sewage. In Korea, A2 / 0 was installed, followed by methanol injection to maximize the removal of nitrogen and phosphorus, the DeN & P process, the MLE (Modified Ludzak-Ettinger) process combined with the Phostrip process, and the existing aeration tank. The intermittent aeration process, which operates by dividing with, has been studied. In addition, Bio-SAC BNR method and sponge media method are being studied.

However, the nitrogen removal rate of most of these processes is difficult to obtain a high removal rate of more than 90% unless an organic carbon source is injected in the denitrification process, such as the DeN & P process, and these external carbon sources are mostly expensive such as methanol, acetate, etc. have.

Accordingly, it is an object of the present invention to provide a method for producing a highly treated carbon source for sewage and wastewater to reduce the sludge production by the middle temperature-high temperature anaerobic acid fermentation process and to obtain a carbon source used to remove nutrients.

    The present invention provides a method for producing a carbon source for advanced treatment of sewage and wastewater using sewage sludge, comprising the steps of: 1) introducing the sewage sludge into a mesophilic fermentation tank for hydrolysis and acid fermentation; 2) introducing the effluent of the mesophilic fermentation tank into the settling tank to separate the solids and the acid fermentation broth; 3) introducing the separated solids into a hot acid fermentation tank for further hydrolysis and acid fermentation; 4) returning the effluent produced in step 3) to the mesophilic fermentation tank; 5) The present invention relates to a method for producing a highly treated carbon source for sewage and wastewater, characterized by producing an acid fermentation solution that can be utilized as a highly treated carbon source from the sedimentation tank.

  The internal temperature of the mesophilic acid fermentation tank is maintained between 20 ° C and 45 ° C and the hydraulic retention time of the mesophilic acid fermentation tank is 0.1 to 10 days.

  In addition, the internal temperature of the high temperature acid fermentation tank is maintained between 45 ° C and 75 ° C. The hydraulic residence time of the high temperature acid fermentation tank is characterized in that 0.1 to 5 days. In addition, the proper operating pH of the mesophilic acid fermentation tank and the high temperature acid fermentation tank is characterized in that the range of more than 5.5 and less than 7.

The step 1) further includes the step of introducing the sewage sludge into the pH adjustment tank, characterized in that the sulfuric acid injecting sulfuric acid fermentation tank and the hot acid fermentation tank to maintain the proper pH It relates to a method for producing a carbon source for advanced treatment of wastewater.

 Hereinafter, the present invention will be described in detail with reference to a flowchart illustrated in the accompanying drawings.

1 is a process diagram schematically showing a manufacturing system for performing a method for producing a carbon source for advanced treatment of sewage and wastewater according to the present invention.

The MLSS generated in the sewage treatment plant biological treatment process is solid-liquid separated in the sedimentation tank (1), and the sewage sludge separated therefrom is introduced into the subsequent pH adjusting tank (2). Sulfuric acid stored in the chemical tank 3 is injected into the pH adjusting tank 2 to adjust the pH of the sludge to 2-3. Sulfuric acid is an important factor in maintaining the proper holding pH of the mesophilic acid fermentation tank 4 and the high temperature acid fermentation tank 5 to be described later. The pH of the acid fermentation tank is determined by alkalinity. As acid fermentation proceeds, the alkalinity increases and affects the pH of the acid fermentation tank. That is, the pH of the mesophilic acid fermentation tank 4 is determined by the combination of the alkalinity generated by itself, the alkalinity introduced from the high temperature acid fermentation tank 5, and the acidity introduced from the pH adjusting tank 2. Therefore, if there is no inflow of sulfuric acid in the pH adjustment tank pH of the mesophilic acid fermentation tank (4) or high temperature acid fermentation tank (5) will rise without maintaining the proper pH.

The sludge introduced into the pH adjustment tank (2) is introduced into the completely mixed mesophilic acid fermentation tank (4) by the raw water transfer pump (not shown), and the organic material contained in the sludge is hydrolyzed and acid fermented. Hydrolyzed organics are converted to organic acids by acid fermentation bacteria.

The internal titration temperature of the mesophilic acid fermentation tank 4 is maintained at 20 ° C to 45 ° C, preferably 30 ° C to 40 ° C, and most preferably at about 35 ° C where the activity of the mesophilic bacteria is most active. The proper maintenance pH of the mesophilic acid fermentation tank (4) is operated in the range of 6.0 to 6.5, whereby the activity of methane bacteria is suppressed and some of the generated organic acid is used as an electron donor for sulfate reducing bacteria to reduce the organic matter contained in the sludge. This happens.

For example, when the pH of the mesophilic fermentation tank 4 increases to 7 or more, methane gas is generated in a large amount due to the rapid growth of the methane bacteria, and eventually the pH is further increased to lose the function of the acid fermentation tank. On the other hand, when the pH decreases below 5.5, the activity of acid fermentation bacteria gradually decreases, eventually losing the function of the acid fermentation tank. Therefore, in order to induce the reduction of organic matter contained in the sludge by continuous hydrolysis and acid fermentation, it is important to maintain a range of 6.5 to 6.5 pH.

In addition, the hydraulic retention time in the mesophilic acid fermentation tank (4) has a range of 0.1 day to 10 days, preferably 2-3 days. If the hydraulic retention time is less than 0.1, the function of acid fermentation is significantly reduced. If it is more than 10 days, it is difficult to preserve organic acid due to the growth of methane.

After completion of the hydrolysis and acid fermentation under the above conditions, the effluent of the mesophilic acid fermentation tank 4 flows into the subsequent settling tank 6. The settling tank 6 separates the effluent into solid sludge and an acid fermentation solution. The settling tank 6 may be used a variety of commercialized methods including a gravity settling tank, a centrifuge, and the like.

The acid fermentation liquor, which is the supernatant liquid separated from the settling tank 6, is introduced into the acid fermentation liquor storage tank 7 in order to be utilized as a carbon source of the advanced treatment process.

On the other hand, the residual solid separated in the settling tank (6) is introduced into the fully mixed high temperature acid fermentation tank (5) which is operated in a high temperature anaerobic condition by a sludge transfer pump (not shown). The internal temperature of the high temperature acid fermentation tank 5 is operated at 45 ° C to 75 ° C, preferably at 50 ° C to 60 ° C, and most preferably at about 55 ° C with the best activity of the high temperature bacteria. Hydraulic residence time of the high temperature acid fermentation tank (5) has a range of 0.1 to 5 days, preferably 2-3 days. The proper pH of the high temperature acid fermentation tank 5 is the same as the proper pH range of the intermediate temperature fermentation tank 4.

Residual solid sludge introduced into the high temperature acid fermentation tank (5) undergoes further hydrolysis and acid fermentation under high temperature and sulfate reduction conditions. Some of the low organic acid produced in the high temperature acid fermentation tank 5 is used as an electron donor for sulfate reducing bacteria during the high temperature acid fermentation as in the middle temperature acid fermentation tank 4 to reduce the organic matter of the sludge.

After the hydrolysis and acid fermentation process in the high temperature acid fermentation tank (5) proceeds, the resulting effluent is transferred to the intermediate temperature fermentation tank (4) for further acid fermentation of the residual solids of the high temperature acid fermentation tank (5).

The effluent transferred to the mesophilic fermentation tank 4 is hydrolyzed and acid fermented, and then flows into the precipitation tank 6, which is the next step. The effluent flowing into the settling tank 6 is separated and the acid fermentation liquor, which is a supernatant, is transferred to the acid fermenting liquor storage tank 7 for use as a carbon source for advanced processing.

Then, the returned acid fermentation liquid is transferred to an anaerobic tank 8 of the sewage treatment process connected to the acid fermentation liquid storage tank 7 by a treated water pump (not shown). The oxygen-free tank (8) is a reaction tank used to remove nitrogen in the advanced treatment process serves to convert the ammonia nitrogen to nitrite nitrogen and nitrate nitrogen, the microorganism uses organic matter (carbon source) Nitrogen removal efficiency can be improved by injecting organic materials produced in the fermenter.

Drain tank (9) is an emergency concept for discharging wastewater in the reactor in case of problems in the reactor equipment used for acid fermentation production.

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples of the present invention.

<Example>

Example of the present invention is a result obtained by operating a model plant (Pilot Plant) of a capacity of 96 m ³ / d using the living sewage in the copper environmental establishment for 12 months.

The model facility of the present invention is composed of an advanced sewage treatment process for nitrogen phosphorus treatment in domestic sewage and a medium temperature high temperature acid fermentation process for supplying a carbon source. The sewage advanced treatment process consists of anaerobic tank, anaerobic tank, aerobic tank and sedimentation tank. The sludge used in the medium temperature high temperature fermentation process consisted of the sludge generated in the sedimentation tank of the sewage treatment process. The pH of the sludge inflow was 5.2 to 5.8. The sludge was first introduced into the pH adjustment tank to reduce the pH to 2-3 and introduced into the mesophilic fermentation tank by the raw water transfer pump.

The mesophilic acid fermentation tank was operated at a pH of 6.0 to 6.5, and the organic sludge was reduced by hydrolysis and acid decomposition. The effluent of the mesophilic acid fermentation tank was introduced into a subsequent settling tank and separated into solid sludge and acid fermentation broth.

The supernatant separated from the settling tank was transferred to the acid fermentation liquor storage tank, and the residual solids were returned to the high temperature acid fermentation tank by the sludge transfer pump.

In the high temperature acid fermentation tank, further hydrolysis and acid fermentation were carried out to reduce organic matter, and the effluent from the high temperature acid fermentation tank was transferred to the intermediate temperature fermentation tank.

The supernatant separated from the settling tank by this process was transferred to the acid fermentation liquor storage tank and introduced into the anoxic tank by the treated water pump.

As a result, all the sludge generated in the sewage altitude treatment process during the operation of the middle temperature-high temperature two-stage acid fermentation process of the present invention was used in the acid fermentation process, so that there was almost no sludge waste and the carbon source required in the sewage altitude treatment process was efficiently Could.

Comparative Example

The single-phase mesophilic fermentation process used as a comparative example of the present invention was tested under the same conditions as the mesophilic high temperature fermentation process except that the target sludge was used as the primary sludge and the high temperature acid fermentation tank was not used.

According to the above Examples and Comparative Examples, the experimental data is summarized as shown in Table 1 below.

TABLE 1

Item Medium temperature high temperature two stage acid fermentation process Single Phase Mid Temperature Acid Fermentation Process inflow Emissions (carbon source) inflow Emissions (carbon source) Target sludge Primary and Secondary Mixed Sludge Primary sludge pH 5.2-5.8 6.3-6.5 6.5-7.0 6.0-7.0 Alkaline (mg / L CaCO3) 500- 1,000 2,000-2,500 1,500- 2,000 2,000- 3,000 Soluble Chemical Oxygen Demand (mg / L) 3,200- 5,000 8,000-12,000 2,000- 3,000 3,500- 4,000 Volatile Fatty Acids (mg HAc / L) 1,200- 2,000 3,000- 4,000 1,000 1,600- 2,000 Hydraulic stay (days) 2.5 2.5 Middle temperature fermentation tank: High temperature acid fermentation tank volume ratio  5: 1  -

The ratio of the mesophilic acid fermentation tank and the high temperature acid fermentation tank is determined by the flow rate returned to the HRT and the high temperature bath of each fermentation tank. Typically, when the HRT of the mesophilic fermentation tank and the high temperature acid fermentation tank is 2 days and 1 day, respectively, the range that can be returned from the mesophilic acid fermentation tank to the high temperature acid fermentation tank is in the range of 10% to 60% of the raw sludge flow rate flowing into the mesophilic fermentation tank. . Therefore, the volume ratio of the high temperature acid fermentation tank to the preferred mesophilic acid fermentation tank is preferably in the range of 20: 1 to 1.67: 1, but the optimum range is 5: 1.

 As can be seen from Table 1, the results of the comparative example by the single-phase mesophilic acid fermentation process showed that the soluble chemical oxygen demand and the concentration of the organic acid of the carbon source were only 3500 to 4000 mg / L and 1600 to 2000 mg HAc / L, respectively.

However, according to the embodiment of the present invention, it was found that the soluble chemical oxygen demand of the carbon source and the concentration of volatile fatty acids were 8000 to 12000 mg / L and 3000 to 4000 mg HAc / L, respectively. Can be.

Therefore, the present invention can significantly reduce the amount of sewage sludge by the medium temperature high temperature acid fermentation process and at the same time efficiently obtain a carbon source for advanced treatment.

Claims (8)

1) introducing the sewage sludge into a mesophilic fermentation tank for hydrolysis and acid fermentation, 2) introducing the effluent of the mesophilic fermentation tank into a settling tank to separate the solids and the acid fermentation liquor, and 3) the separated solids. Additionally inflowing into a high temperature acid fermentation tank for hydrolysis and acid fermentation, 4) transferring the effluent generated in step 3) to the mesophilic fermentation tank , 5) introducing the acid fermentation liquid separated from the precipitation tank into a storage tank In the method of producing a carbon source for advanced treatment of sewage and wastewater, Prior to the step 1), further comprising the step of introducing the sewage sludge into the pH adjustment tank , And the sulfuric acid fermentation tank and the high temperature acid fermentation tank are operated by adjusting sulfuric acid to the pH adjustment tank so as to be operated in a range of more than pH 5.5 to less than pH 7. The method of claim 1, wherein the internal temperature of the mesophilic fermentation tank is maintained between 20 ° C and 45 ° C. The method of claim 1, wherein the hydraulic retention time of the mesophilic fermentation tank is 0.1 to 10 days. The method of claim 1, wherein the internal temperature of the high temperature acid fermentation tank is maintained between 45 ° C and 75 ° C. The method of claim 1, wherein the hydraulic residence time of the high temperature acid fermentation tank is 0.1 to 5 days. delete delete delete

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