Enzyme reaction-based sewage treatment plant front-end organic matter high-value recovery technology

Abstract

The invention belongs to the technical field of sewage resource recovery, and discloses a sewage treatment plant front-end organic matter high-value recovery technology based on enzyme reaction, which comprises the following steps: adding a flocculating agent into sewage behind a grit chamber to promote a large amount of organic matters and colloids in water to precipitate, and then carrying out enzyme hydrolysis reaction on the precipitated flocculated sludge to obtain the high-value recovery of the front-end organic matters in the sewage. The flocculated sludge is promoted to be converted into small molecular acid composite high-value carbon sources such as acetic acid, propionic acid and butyric acid and is used for subsequent denitrification treatment; according to the invention, the consumption of an external carbon source in the denitrification process and resource waste and greenhouse gas emission caused by conversion of COD into carbon dioxide in the sewage treatment process can be reduced; the method is suitable for urban or industrial sewage treatment.

Description

Technical Field

[0001] The invention relates to the technical field of sewage resource recovery, and in particular to a high-value recovery technology of organic matter at the front end of a sewage treatment plant based on enzyme reaction. Background Art

[0002] At present, the sewage treatment process mainly relies on biological oxidation to remove organic matter and convert it into carbon dioxide and water, while producing a large amount of biological sludge. As the country's requirements for governance increase, the requirements for sludge treatment also increase. For modern sewage treatment plants, sludge treatment and disposal have become the most complex and expensive part of the operation of sewage treatment systems. However, conventional sludge reduction and disposal mostly use aerobic digestion, anaerobic digestion and other means. These treatment methods are time-consuming, occupy a large area and require a certain amount of energy consumption. Controlling sludge reduction from the source and sludge resource utilization are the main means to solve sludge pollution at this stage.

[0003] On the other hand, the sewage denitrification process requires the addition of carbon sources to the system due to its low carbon-nitrogen ratio, which also increases the operating costs of sewage treatment. Therefore, it is very necessary to seek a technology that can convert sludge into an efficient carbon source and supply it for denitrification to effectively reduce pollution and generate added value. Summary of the invention

[0004] The present invention aims to provide a high-value recovery technology for organic matter at the front end of a sewage treatment plant based on enzyme reaction. By constructing a front-end capture-subsequent enzyme hydrolysis-efficient carbon source denitrification utilization process for sewage treatment carbon sources, the carbon source in the water is used for subsequent denitrification and denitrification reactions, thereby reducing the amount of external carbon sources used in the denitrification process and reducing carbon dioxide emissions.

[0005] In order to achieve the above purpose, the following technical solutions are provided:

[0006] A high-value recovery technology for organic matter at the front end of a sewage treatment plant based on enzyme reaction, characterized in that it comprises the following steps:

[0007] S1. Urban and industrial sewage first undergoes sewage pretreatment processes, which include grit settling, oil removal and other processes and their combination;

[0008] S2, the pretreated sewage is flocculated and precipitated using a chemical flocculant, and the carbon source in the water is captured in this way, and carbon-rich sludge and supernatant are obtained after precipitation;

[0009] S3, the supernatant normally enters the conventional sewage treatment nitrification process, removes the residual COD in the water through aeration, and converts the ammonia nitrogen in the water into nitrate nitrogen;

[0010] S4, the carbon-rich sludge enters the enzymatic hydrolysis reaction section, and a composite enzyme preparation is added to carry out enzymatic hydrolysis reaction. The supernatant after the enzymatic hydrolysis reaction is the high-value carbon source;

[0011] S5. The supernatant in step S3 enters the denitrification process after nitrification reaction. The carbon source of the denitrification reaction is the high-value carbon source produced in step S4, and finally the effluent meets the discharge standards;

[0012] S6. Regularly discharge the hard precipitates in the enzyme reaction container and add the complex enzyme preparation once.

[0013] Furthermore, in step S2, the chemical flocculant includes one or more of ferric sulfate, ferric chloride, polyferric sulfate, polyferric chloride, aluminum sulfate, aluminum chloride, polyaluminum sulfate, and polyaluminum chloride. The flocculant concentration is configured to be 5-10% (m / m%), and the flocculant dosage is 15-25 ppm per 100 mg / L COD.

[0014] Furthermore, the enzyme involved in the enzymatic hydrolysis in step S4 includes one or more of hydrolases, proteases, and laccases.

[0015] Furthermore, in step S4, the enzyme involved in the enzymatic hydrolysis reaction needs to be adsorbed on the surface of silica gel or activated carbon to prepare an enzyme carrier.

[0016] Furthermore, step S4 occurs in an enzyme hydrolysis reactor, which is filled with 30-40% enzyme carriers and equipped with a water distributor and a micro-aeration system, and the reaction temperature is controlled to be 35-45° C. and the reaction time is 8-12 hours.

[0017] Furthermore, in the denitrification reaction in step S4, according to the total nitrogen concentration, 15-25 mg of high-value carbon source needs to be added for 10 mg of total nitrogen.

[0018] Principle and beneficial effects of the technical solution: The technical solution of the present invention adds flocculants to the sewage after the sewage pretreatment process. The flocculants cause a large amount of organic matter and colloids in the water to precipitate, and then the precipitated flocculated sludge, i.e., the carbon source capture, is subjected to an enzymatic hydrolysis reaction to promote the directional conversion of the flocculated sludge, and the sludge is directionally converted into a composite high-value carbon source of small molecule acids such as acetic acid, propionic acid, butyric acid, and these composite high-value carbon sources are used in subsequent denitrification and denitrification treatment, thereby effectively reducing the waste of resources and greenhouse gas emissions caused by the conversion of COD into carbon dioxide in the sewage treatment plant process; the reaction conditions using biological enzymes are mild, and compared with conventional sludge treatment processes, it not only saves chemicals and energy, but also shortens the reaction time; the enzymatic reaction can more accurately convert COD into small molecule acids, which are much more valuable than sludge supernatant, and its application scenarios are also more extensive. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a process diagram of the present invention;

[0020] Figure 2Carbon source concentration of supernatant after enzymatic hydrolysis reaction with different amounts of enzyme preparations added;

[0021] Figure 3 VFA concentration in the supernatant after enzymatic hydrolysis with different amounts of enzyme preparations added. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments:

[0023] Embodiment 1:

[0024] A high-value recovery technology for organic matter at the front end of a sewage treatment plant based on enzyme reaction. The treatment process is as follows: Figure 1 As shown, the specific processing process is:

[0025] After the pretreatment process of the screen and grit chamber, the sewage of a certain city enters the flocculation tank, where 5% concentration of ferric chloride and polyferric chloride are added, with the dosage of 50ppm.

[0026] During the flocculation process, stirring was performed by an adjustable stirring paddle, the reaction time was 5 min, the stirring speed was set to 100 rad / min in the first 2 min, and the stirring speed was set to 60 rad / min in the later period.

[0027] After the coagulation reaction, the sludge enters the sedimentation tank. The sedimentation tank adopts a high-density sedimentation tank with a hydraulic retention time of 20 minutes. After sedimentation, the sludge enters enzyme hydrolysis and the supernatant enters the subsequent sewage treatment process.

[0028] After carbon capture, the sludge enters the enzyme hydrolysis reactor. The enzymes involved in the enzymatic hydrolysis reaction include hydrolases, proteases, and laccases, which are adsorbed on silica gel to prepare enzyme carriers. The enzyme dosage is 6x10 8 u / m 3 , the reaction temperature was controlled at 37°C, the reaction time was controlled at 10h, and after the reaction was completed, 70% of the supernatant was discharged as a high-value carbon source for subsequent denitrification and denitrification treatment.

[0029] In the denitrification process, add 30g / m 3 Carbon source.

[0030] In the subsequent treatment, the hard sediment (mostly gravel) at the bottom of the reactor is discharged from the reactor regularly (1-3 months) and the complex enzyme preparation is added once.

[0031] The carbon source concentration and VFA concentration after sludge enzymatic hydrolysis reaction were measured after adding 6000U enzyme preparation and 8000U enzyme preparation. The results are as follows Figure 2 , Figure 3As shown. COD concentration is the chemical amount required for the oxidation and decomposition of organic matter in water. The higher the COD concentration, the more organic matter there is in the water, and the more carbon sources there are. VFA, or volatile fatty acids (common ones are acetic acid, propionic acid, and butyric acid), can serve as electron donors for denitrification, thereby promoting the removal of nitrogen in sewage.

[0032] Embodiment 2:

[0033] After a certain industrial wastewater pretreatment process including grit chamber and oil removal, carbon source is captured by flocculation and sedimentation.

[0034] The chemical flocculants include ferric sulfate, ferric chloride, polyferric sulfate and polyferric chloride, and are configured to a concentration of 8% (m / m%), and are added at a rate of 20 ppm per 100 mg / L COD.

[0035] During the flocculation process, mixing was performed by an adjustable stirring paddle, the reaction time was set at 5 min, the stirring speed was set at 120 rad / min in the first 2 min, and the stirring speed was set at 70 rad / min in the later period.

[0036] After the coagulation reaction, the sludge enters the sedimentation tank. The sedimentation tank adopts a vertical flow sedimentation tank or a high-density sedimentation tank. The hydraulic retention time is set to 20 minutes. After sedimentation, the sludge enters the enzyme hydrolysis stage, and the supernatant enters the subsequent sewage treatment process.

[0037] After carbon capture, the sludge enters the enzyme hydrolysis reactor. The enzymes involved in the enzymatic hydrolysis reaction include hydrolases, proteases, and laccases. The enzymes are adsorbed on the surface of activated carbon to prepare enzyme carriers. The enzyme dosage is 6x10 8 u / m 3 , the reaction temperature was controlled at 45°C, the reaction time was controlled at 10h, and after the reaction was completed, 70% of the supernatant was discharged as a high-value carbon source for subsequent denitrification and denitrification treatment.

[0038] When the total COD and soluble COD of the influent are 750 mg / L and 420 mg / L respectively, the corresponding values ​​of the effluent are 150 mg / L and 105 mg / L, and the corresponding removal rates are 80% and 25% respectively, and the COD capture rate is 80%.

[0039] Comparative Example 1: Ordinary precipitation method

[0040] The total COD and soluble COD of the sewage were 833 mg / L and 255 mg / L respectively. After 50 minutes of static sedimentation, the effluent values ​​were 617 mg / L and 252 mg / L. The corresponding removal rates were 25.9% and 1.2% respectively. The COD capture rate was 25.9%, and there was no oxidation.

[0041] Comparative Example 2: Chemically enhanced primary treatment technology

[0042] Polyferric sulfate was used as coagulant, with mixing time of 1 min, reaction time of 15 min, and sedimentation time of 45 min. The total COD and soluble COD of sewage were 857 mg / L and 244 mg / L respectively. When the dosage of polyferric sulfate reached 375 mg / L, the corresponding values ​​of effluent were 280 mg / L and 240 mg / L respectively, and the corresponding removal rates were 68.5% and 5.5% respectively. The COD capture rate was 39.5%, and there was no oxidation.

[0043] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the technical solution of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A high-value recovery technology for organic matter at the front end of a sewage treatment plant based on enzyme reaction, characterized in that: The following steps are involved: S1. Urban and industrial sewage first undergoes sewage pretreatment processes, which include grit settling, oil removal and other processes and their combination; S2, the pretreated sewage is flocculated and precipitated using a chemical flocculant, and the carbon source in the water is captured in this way, and carbon-rich sludge and supernatant are obtained after precipitation; S3, the supernatant normally enters the conventional sewage treatment nitrification process, removes the residual COD in the water through aeration, and converts the ammonia nitrogen in the water into nitrate nitrogen; S4, the carbon-rich sludge enters the enzymatic hydrolysis reaction section, and a composite enzyme preparation is added to carry out enzymatic hydrolysis reaction. The supernatant after the enzymatic hydrolysis reaction is the high-value carbon source; S5. The supernatant in step S3 enters the denitrification process after nitrification reaction. The carbon source of the denitrification reaction is the high-value carbon source produced in step S4, and finally the effluent meets the discharge standards; S6. Regularly discharge the hard precipitates in the enzyme reaction container and add the complex enzyme preparation once.

2. The high-value recovery technology of organic matter at the front end of a sewage treatment plant based on enzyme reaction according to claim 1 is characterized by: The chemical flocculant in step S2 includes one or more of ferric sulfate, ferric chloride, polyferric sulfate, polyferric chloride, aluminum sulfate, aluminum chloride, polyaluminum sulfate, and polyaluminum chloride. The concentration of the flocculant is 5-10%, and the dosage of the flocculant is 15-25 ppm per 100 mg / L COD.

3. The high-value recovery technology of organic matter at the front end of a sewage treatment plant based on enzyme reaction according to claim 1 is characterized by: The enzyme involved in the enzymatic hydrolysis in step S4 includes one or more of hydrolases, proteases, and laccases.

4. The high-value recovery technology of organic matter at the front end of a sewage treatment plant based on enzyme reaction according to claim 1 is characterized by: In step S4, the enzyme involved in the enzymatic hydrolysis reaction needs to be adsorbed on the surface of silica gel or activated carbon to prepare an enzyme carrier.

5. The high-value recovery technology of organic matter at the front end of a sewage treatment plant based on enzyme reaction according to claim 1 is characterized by: The enzymatic hydrolysis reaction in step S4 takes place in an enzymatic hydrolysis reactor, which is filled with 30-40% enzyme carriers and equipped with a water distributor and a micro-aeration system. The reaction temperature is controlled at 35-45° C. and the reaction time is 8-12 hours.

6. The high-value recovery technology of organic matter at the front end of a sewage treatment plant based on enzyme reaction according to claim 1 is characterized by: In the denitrification reaction in step S5, according to the total nitrogen concentration, 15-25 mg of high-value carbon source needs to be added for 10 mg of total nitrogen.

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