A method for improving the sedimentation and separation effect of mud and water after biological capture of carbon and phosphorus

Abstract

This invention discloses a method for improving the sedimentation and separation effect of sludge and water after biological capture of carbon and phosphorus. The method includes: first, obtaining the settling properties of the sludge-water mixture entering the sedimentation separation zone; second, obtaining the concentrations of carbon and phosphorus and their dissolved components, sludge concentration, sludge discharge flow rate, and effluent flow rate in the settled sludge and effluent; third, using the ratio of captured to transferred carbon and phosphorus as the accounting value to obtain the carbon and phosphorus separation effect; fourth, determining that if the ratio is lower than the target value, further improvement of the sedimentation and separation effect after capture is needed; and fifth, determining whether to sequentially employ three methods—adjusting dissolved oxygen concentration, adjusting hydraulic retention time and sludge age, and adding auxiliary agents—to improve the sedimentation and separation effect after carbon and phosphorus capture, based on whether the target value can be met. This method improves the technical level of sludge-water separation after capturing carbon and phosphorus in wastewater, enhances the separation effect, and is environmentally friendly and low-carbon.

Description

Technical Field

[0001] This invention relates to a wastewater treatment method, and more particularly to a method for improving the sedimentation and separation effect of sludge and water after biological capture of carbon and phosphorus. Background Technology

[0002] The recovery and utilization of high-value resources such as organic carbon and phosphorus in wastewater is a major development direction for low-carbon wastewater treatment. Transferring carbon and phosphorus resources from the "aqueous phase" to the "sludge phase" in wastewater is fundamental to their recovery and utilization. Because biological systems for capturing carbon and phosphorus in wastewater have different objectives and significantly different operating parameters than traditional biological systems for phosphorus and nitrogen removal, the sludge quality of biological sludge from carbon and phosphorus capture systems differs significantly from that of traditional biological sludge. The sludge from carbon and phosphorus capture systems contains a higher proportion of active components and polysaccharides, has lower viscosity, and exhibits less stable sludge-water separation in the post-capture separation zone.

[0003] Improving the separation efficiency of sludge and water after carbon and phosphorus capture facilitates the enrichment of carbon and phosphorus resources in the sludge. Sedimentation, as a method for achieving sludge-water separation and sludge thickening after carbon and phosphorus capture, is usually implemented after the carbon and phosphorus biological capture unit. It separates the sludge from the water in the sludge-water mixture after carbon and phosphorus capture, thereby obtaining biological sludge with high carbon and phosphorus concentrations. Compared with membrane retention and electrochemical technologies, sedimentation technology has lower economic costs and is more suitable for large-scale engineering applications. Although directly adding chemical agents to assist sedimentation and reduce sludge flocs in the effluent can improve the sludge-water separation efficiency, adding large amounts of chemical agents not only generates indirect carbon emissions, which contradicts the concept of green and low-carbon wastewater treatment, but also affects the efficiency of subsequent anaerobic digestion reactions for methane production to recover carbon resources.

[0004] Biological methods for capturing and enriching carbon and phosphorus resources in wastewater are a new technology for wastewater resource and energy conversion. However, there is currently a lack of methods to systematically evaluate the sludge-water separation effect with the goal of obtaining sludge with high carbon and phosphorus enrichment, and to first optimize the sludge-water separation effect after capturing carbon and phosphorus based on the parameters of the capture and separation system. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a wastewater treatment method that improves the sedimentation and separation effect of sludge after biological capture of carbon and phosphorus. This method can reduce the dosage of chemical reagents and is more conducive to the efficient enrichment of carbon and phosphorus resources in wastewater into sludge for resource and energy utilization.

[0006] The present invention provides a method for improving the sedimentation and separation effect of mud and water after biological capture of carbon and phosphorus, comprising the following steps:

[0007] The first step is to determine the sludge concentration (MLSS) and sludge settling ratio (SV) of the anaerobic-aerobic sludge mixture after carbon and phosphorus capture in the sedimentation and separation zone. 30 Calculate the sludge volume index (SVI);

[0008] The second step is to measure the COD, total phosphorus (TP), and MLSS of the sludge in the sedimentation separation zone, and the COD, dissolved chemical oxygen demand (SCOD), and dissolved total phosphorus (STP) of the effluent. The concentrations of carbon, phosphorus, and dissolved components in the sedimentation sludge and effluent in the sedimentation separation zone, the sludge concentration of the sedimentation sludge, the sludge discharge flow rate, and the effluent flow rate are obtained respectively.

[0009] The third step is to calculate the ratio A of carbon capture to transfer and the ratio B of phosphorus capture to transfer, respectively.

[0010] The formula for the ratio of carbon capture to carbon transfer is as follows:

[0011] Formula for the ratio of phosphorus capture to translocation:

[0012] Q in the formula 沉淀污泥 Q is the sludge discharge flow rate of the sedimentation and separation zone. 出水 The effluent flow rate of the sedimentation separation zone, COD 沉淀污泥 The COD and TP values ​​of the sludge in the sedimentation and separation zone are... 沉淀污泥 The TP value (COD-SCOD) of the sludge in the sedimentation and separation zone. 出水 The COD-SCOD value (TP–STP) in the effluent from the sedimentation separation zone is given. 出水 The TP–STP value in the effluent from the sedimentation separation zone;

[0013] The fourth step is to determine that if either value A or B is lower than the set target value, it is necessary to further improve the sedimentation and separation effect of the captured mud and water.

[0014] The fifth step involves taking the following steps in sequence to improve the mud-water separation effect after capturing carbon and phosphorus in the separation zone, as follows:

[0015] Step 501: If the SVI value is ≥150mL / g, increase the dissolved oxygen concentration in the mixed liquor at intervals of 0.3mg / L, with an upper limit of 1.5mg / L, until the ratio of the MLSS of the precipitated sludge in the separation zone to the MLSS of the sludge-water mixture entering the separation zone is ≥2.0. Then, operate the carbon and phosphorus biological capture and separation system with the adjusted dissolved oxygen concentration. If the SVI value is <150mL / g, proceed to step 502.

[0016] Step 502: Calculate the hydraulic retention time (HRT) and sludge age (SRT) of the biological capture carbon and phosphorus unit before entering the separation zone, and control the HRT and SRT to 2.5-3h and 2-3d, respectively; and determine whether A and B are greater than the target values. If so, maintain operation using the dissolved oxygen concentration in step 501 and the adjusted HRT and SRT; otherwise, proceed to the next step.

[0017] Step 503: Add a low dose of coagulant ferric chloride to the mixed liquid entering the separation zone to assist sedimentation. The dosage of ferric chloride is controlled with the target value of effluent SCOD / COD≥0.8 and the upper limit of total Fe dosage≤20mg / L until both A and B are greater than the target values.

[0018] The beneficial effects of this invention are:

[0019] 1. This invention addresses the problems of unstable sludge-water separation after biological capture of carbon and phosphorus in wastewater, large dosage of chemical coagulants when directly adding them to assist sedimentation, and reduced methanogenic efficiency in subsequent anaerobic digestion for carbon resource recovery. It improves the sludge-water separation technology by establishing a method that includes evaluating sedimentation separation performance, adjusting dissolved oxygen in the mixed liquor based on SVI value, adjusting the HRT and SRT operating values ​​of the biological capture system, and finally adding a low dose of coagulant. This invention overcomes the shortcomings of the new biological capture and enrichment technology for carbon and phosphorus resources in wastewater in obtaining high-concentration sludge.

[0020] 2. The method of the present invention optimizes the method of directly adding auxiliary precipitation chemical agents instead of the method of optimizing the parameters, which is beneficial to improving the efficiency of subsequent carbon and phosphorus recovery and the technology is more green and low-carbon.

[0021] 3. The method of this invention improves the separation effect. The parameters in the method are simple and easy to operate, and it can be used for engineering practice and promotion of biological capture of carbon and phosphorus resources and efficient separation technology. Attached Figure Description

[0022] Figure 1 This is a process flow diagram of a method for improving the sedimentation and separation effect of mud and water after biological capture of carbon and phosphorus according to the present invention. Detailed Implementation

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0024] As shown in the attached figure, a method of the present invention for improving the sedimentation and separation effect of mud and water after biological capture of carbon and phosphorus includes the following steps:

[0025] The first step is to determine the sludge concentration (MLSS) and sludge settling ratio (SV) of the anaerobic-aerobic sludge mixture after carbon and phosphorus capture in the sedimentation and separation zone. 30 The sludge volume index (SVI) is calculated (see page 89 of Volume II (Third Edition) of Drainage Engineering, published by China Building Industry Press in June 1996 for the method of calculating the sludge volume index). The SVI is used to determine the settling performance of the sludge-water mixture and to use the SVI value as a reference value for whether the dissolved oxygen concentration of the sludge-water mixture entering the sedimentation separation zone needs to be adjusted.

[0026] The second step is to measure the COD, total phosphorus (TP), and MLSS of the sludge in the sedimentation separation zone, and the COD, dissolved chemical oxygen demand (SCOD), and dissolved total phosphorus (STP) of the effluent. The concentrations of carbon, phosphorus, and dissolved components in the sedimentation sludge and effluent in the sedimentation separation zone, the sludge concentration of the sedimentation sludge, the sludge discharge flow rate, and the effluent flow rate are obtained respectively.

[0027] The third step is to calculate the ratio A of carbon capture to transfer and the ratio B of phosphorus capture to transfer, respectively, and use these ratios as the calculation values ​​to obtain the precipitation separation effect.

[0028] The formula for the ratio of carbon capture to carbon transfer is as follows:

[0029] Formula for the ratio of phosphorus capture to translocation:

[0030] Q in the formula 沉淀污泥 Q is the sludge discharge flow rate of the sedimentation and separation zone. 出水 The effluent flow rate of the sedimentation separation zone, COD 沉淀污泥 The COD and TP values ​​of the sludge in the sedimentation and separation zone are... 沉淀污泥 The TP value (COD-SCOD) of the sludge in the sedimentation and separation zone. 出水 The COD-SCOD value (TP–STP) in the effluent from the sedimentation separation zone is given. 出水 The TP–STP value in the effluent from the sedimentation separation zone;

[0031] The fourth step is to determine that if either value A or B is lower than the set target value, it is necessary to further improve the sedimentation and separation effect of the captured mud and water. The target value is usually flexibly set based on the separation rate desired by the designers or operators.

[0032] The fifth step involves taking the following steps in sequence to improve the mud-water separation effect after capturing carbon and phosphorus in the separation zone, as follows:

[0033] Step 501: Based on the SVI value of the sludge-water mixture entering the sedimentation separation zone, determine whether to adjust the dissolved oxygen concentration of the mixture to improve the sedimentation performance of the sludge-water mixture, reduce the particulate carbon and phosphorus concentration in the effluent, and improve the sludge-water separation effect: If the SVI value is ≥150mL / g, increase the dissolved oxygen concentration in the mixture at intervals of 0.3mg / L with an upper limit of 1.5mg / L (the dissolved oxygen concentration in the mixture can be increased by the existing method of increasing the aeration rate of the aerobic section) until the ratio of the MLSS of the sludge settled in the separation zone to the MLSS of the sludge-water mixture entering the separation zone is ≥2.0. Then, operate the carbon and phosphorus biological capture and separation system with the adjusted dissolved oxygen concentration, and maintain the original parameters for the rest.

[0034] If the SVI value is <150mL / g, then maintain the original dissolved oxygen concentration of the mud-water mixture entering the separation zone and proceed directly to step 502;

[0035] Step 502: If the capture-to-transfer ratio is still lower than the target value after executing step 501, continue to calculate the hydraulic retention time (HRT) and sludge age (SRT) of the biological carbon and phosphorus capture unit before entering the separation zone. Control the HRT and SRT to 2.5–3 h and 2–3 d, respectively. Increase the A and B values ​​by increasing the carbon and phosphorus capture amount, i.e., increase the capture-to-transfer ratio. Determine whether A and B are greater than the target values. If so, maintain operation using the dissolved oxygen concentration in step 501 and the adjusted HRT and SRT; otherwise, proceed to the next step.

[0036] Hydraulic retention time (HRT) is calculated by dividing the volume of the biocapture carbon and phosphorus unit by its influent volumetric flow rate; sludge age (SRT) is calculated by dividing the sludge mass of the biocapture carbon and phosphorus unit by the sludge mass discharged from the sedimentation zone.

[0037] Step 503: If the ratio of captured amount to transferred amount is still lower than the target value after step 502, a low dose of coagulant ferric chloride is added to the mixed liquid entering the separation zone to assist sedimentation. The dosage of ferric chloride is controlled with the target value of effluent SCOD / COD≥0.8 and the upper limit of total Fe dosage≤20mg / L until both A and B are greater than the target values.

[0038] Example 1

[0039] In a wastewater treatment plant in a northern city, an anaerobic-aerobic biological capture-sedimentation separation system was in operation. The method of this invention was used to improve the sludge-water sedimentation separation effect.

[0040] The first step was to determine the MLSS and SV of the mud-water mixture after capturing carbon and phosphorus in the sedimentation separation zone. 30 The SVI value was calculated to obtain the sludge settling performance of the sludge-water mixture, and the SVI value was used as a reference value for whether the dissolved oxygen concentration of the mixture needed to be adjusted; the specific measured values ​​were: MLSS 2344 mg / L, SV 30 The SVI was 61%, and the calculated SVI was 260 mL / g.

[0041] The second step involves measuring the COD, TP, and MLSS of the sludge in the sedimentation separation zone, and the COD, SCOD, TP, and STP of the effluent. This also includes obtaining the concentrations of carbon, phosphorus, and dissolved components in the sedimented sludge and effluent, as well as the sludge concentration, sludge discharge flow rate, and effluent flow rate. Specific measured values ​​are: COD of the sedimented sludge is 3304 mg / L, TP is 39.80 mg / L, and MLSS is 2744 mg / L.

[0042] The effluent COD was 160 mg / L, SCOD was 44 mg / L, TP was 2.70 mg / L, and STP was 1.83 mg / L;

[0043] The sludge discharge flow rate is 3.0 L / h, and the effluent flow rate is 153.6 L / h.

[0044] The third step involves calculating the carbon, phosphorus, and dissolved carbon and phosphorus concentrations in the settled sludge and effluent, along with the sludge discharge flow rate and effluent flow rate, using the following formula: and

[0045] In the formula Q 沉淀污泥 Q represents the sludge discharge flow rate. 出水 For effluent flow rate, COD 沉淀污泥 The COD and TP values ​​of the sludge in the sedimentation and separation zone are... 沉淀污泥 The total phosphorus value (COD-SCOD) of the sludge in the sedimentation and separation zone. 出水 The COD-SCOD value (TP–STP) in the effluent from the sedimentation separation zone is given. 出水 The TP–STP value is the effluent from the sedimentation separation zone.

[0046] Calculate the ratio of COD and TP capture amount to transfer amount, and use this ratio as the accounting value to obtain the precipitation separation effect. The calculated values ​​are A (i.e., COD separation rate) = 35.7% and B (i.e., TP separation rate) = 47.2%.

[0047] The fourth step was to set the target values ​​for the sedimentation separation rate of COD and TP to 65%. It was found that the separation rates of both COD and TP were lower than the target values, indicating that the sedimentation separation effect of the captured mud and water needs to be further improved.

[0048] The fifth step involves using the following methods to improve the sedimentation and separation effect of mud and water after carbon and phosphorus capture in the separation zone, as detailed below:

[0049] Method 1: Based on the SVI value of the sludge-water mixture entering the sedimentation separation zone, determine whether adjusting the dissolved oxygen concentration of the mixture can improve the sedimentation performance of the sludge-water mixture, reduce the concentration of particulate carbon and phosphorus in the effluent, and improve the sludge-water separation effect. The measured SVI of the sludge-water mixture was 260 mL / g, which is higher than 150 mL / g. The method of increasing the dissolved oxygen concentration of the mixture can be used to improve the sedimentation performance of the sludge-water mixture entering the sedimentation zone. The dissolved oxygen concentration of the sludge-water mixture was further measured to be 0.8 mg / L. The dissolved oxygen concentration was increased in increments of 0.3 mg / L, namely 1.1 mg / L and 1.4 mg / L. When the dissolved oxygen concentration was increased to 1.4 mg / L, the ratio of the MLSS of the settled sludge (5860 mg / L) to the MLSS of the sludge-water mixture entering the sedimentation separation zone (2930 mg / L) was 2.0. The dissolved oxygen concentration was not increased further.

[0050] After implementing Method 1 to increase the dissolved oxygen concentration of the mixed liquor to 1.4 mg / L, the COD of the settled sludge was measured to be 5403 mg / L and TP to be 116.78 mg / L, the COD of the effluent was 87 mg / L and SCOD to be 45 mg / L, TP to be 1.24 mg / L and STP to be 0.94 mg / L. The calculated separation rates of COD and TP were increased to 71.0% and 88.4% respectively, which met the target values.

[0051] Method 1 was determined to be the method to adjust the dissolved oxygen concentration to 1.4 mg / L, and the carbon and phosphorus capture and separation system was to be run with the original parameters.

[0052] Example 2

[0053] The first step was to determine the MLSS and SV of the mud-water mixture after capturing carbon and phosphorus in the sedimentation separation zone. 30 The SVI value was calculated to obtain the sludge settling performance of the sludge-water mixture, and the SVI value was used as a reference value for whether the dissolved oxygen concentration of the mixture needed to be adjusted; the specific measured values ​​were: MLSS 1062 mg / L, SV 30 The SVI is 35%, and the calculated SVI is 330 mL / g;

[0054] The second step involves measuring the COD, TP, and MLSS of the sludge in the sedimentation separation zone, and the COD, SCOD, TP, and STP of the effluent. This process also yields the concentrations of carbon, phosphorus, and dissolved components in the sedimented sludge and effluent, as well as the sludge concentration, sludge discharge flow rate, and effluent flow rate. Specific measured values ​​are: sedimented sludge COD 1286 mg / L, TP 33.5 mg / L, MLSS 1380 mg / L; effluent COD 230 mg / L, SCOD 88 mg / L, TP 2.35 mg / L, STP 1.03 mg / L; sludge discharge flow rate 1.8 L / h; and effluent flow rate 153.6 L / h.

[0055] The third step involves calculating the carbon, phosphorus, and dissolved carbon and phosphorus concentrations in the settled sludge and effluent, along with the sludge discharge flow rate and effluent flow rate, using the following formula: and The ratios of COD and TP capture amounts to transfer amounts were calculated, and these ratios were used as accounting values ​​to obtain the precipitation separation effect. The calculated values ​​were 9.5% for COD and 22.9% for TP.

[0056] The fourth step was to set the target values ​​for the sedimentation separation rate of COD and TP to 65%. It was found that the separation rates of both COD and TP were lower than the target values, indicating that the sedimentation separation effect of the captured mud and water needs to be further improved.

[0057] The fifth step is to improve the sedimentation and separation effect of mud and water after capturing carbon and phosphorus in the separation zone using the following methods:

[0058] Method 1: Based on the SVI value of the sludge-water mixture entering the sedimentation separation zone, determine whether adjusting the dissolved oxygen concentration of the mixture can improve the sedimentation performance of the sludge-water mixture, reduce the concentration of particulate carbon and phosphorus in the effluent, and improve the sludge-water separation effect. The measured SVI of the sludge-water mixture is 330 mL / g, which is higher than 150 mL / g. The method of increasing the dissolved oxygen concentration of the mixture can be used to improve the sedimentation performance of the sludge-water mixture. Further, the dissolved oxygen concentration of the sludge-water mixture is measured to be 0.7 mg / L. The dissolved oxygen concentration is increased at intervals of 0.3 mg / L. When it reaches the upper limit of 1.5 mg / L, the ratio of the MLSS of the settled sludge (2839 mg / L) to the MLSS of the sludge-water mixture (1670 mg / L) is 1.70. Since the dissolved oxygen has reached the upper limit, even though the ratio of the MLSS of the settled sludge to the MLSS of the entering sludge-water mixture is less than 2.0, the system is still operated with a dissolved oxygen concentration of 1.5 mg / L.

[0059] After implementing Method 1 to increase the dissolved oxygen concentration of the mixed liquor to 1.5 mg / L, the COD of the settled sludge was measured to be 5158 mg / L and TP to be 73.47 mg / L, the COD of the effluent was 108 mg / L and SCOD to be 59 mg / L, TP to be 1.77 mg / L and STP to be 1.19 mg / L. The calculated separation rates of COD and TP were increased to 55.2% and 59.7% respectively. It was determined that the separation rates of the two indicators were still lower than the target values.

[0060] Method 2: After adjusting the dissolved oxygen concentration to 1.5 mg / L in Method 1, the ratios of COD and TP capture to transfer were still lower than the target values. The hydraulic retention time (HRT) and sludge age (SRT) of the biological carbon and phosphorus capture system were recalculated by dividing the volume of the capture system by its influent volume flow rate and the mass of the capture system sludge by the mass of the sludge discharged from the sedimentation zone. The calculated values ​​were 2.5 h and 5 d, respectively. The HRT was maintained at 2.5 h and the SRT was adjusted to 3 d. The ratio of capture to transfer was increased by increasing the capture amount.

[0061] After implementing Method 2, the COD of the settled sludge was measured to be 4763 mg / L and TP to be 144.8 mg / L, the COD of the effluent was 67 mg / L and SCOD to be 23 mg / L, TP to be 0.89 mg / L and STP to be 0.54 mg / L, and the separation rates of COD and TP were calculated to be 67.8% and 86.1% respectively, which was determined to meet the target values.

[0062] The dissolved oxygen concentration was adjusted to 1.5 mg / L in Method 1, the HRT and SRT were controlled to 2.5 h and 3 d in Method 2, and the carbon and phosphorus capture and separation system was operated under the original conditions for the rest.

[0063] Example 3

[0064] The first step was to determine the MLSS and SV of the mud-water mixture after capturing carbon and phosphorus in the sedimentation separation zone. 30 The SVI value was calculated to obtain the sludge settling performance of the sludge-water mixture, and the SVI value was used as a reference value for whether the dissolved oxygen concentration of the mixture needed to be adjusted; the specific measured values ​​were: MLSS 1253 mg / L, SV 30 The SVI was 40%, and the calculated SVI was 319 mL / g.

[0065] The second step involves determining the COD, TP, and MLSS of the sludge in the sedimentation separation zone, and the COD, SCOD, TP, and STP of the effluent. This process also yields the concentrations of carbon, phosphorus, and dissolved components in the sedimented sludge and effluent, as well as the sludge concentration, sludge discharge flow rate, and effluent flow rate. Specific measured values ​​are as follows: sedimented sludge COD 1567 mg / L, TP 38.4 mg / L, MLSS 1479 mg / L; effluent COD 221 mg / L, SCOD 91 mg / L, TP 2.13 mg / L, STP 0.94 mg / L; sludge discharge flow rate 1.8 L / h; and effluent flow rate 153.6 L / h.

[0066] The third step involves calculating the carbon, phosphorus, and dissolved carbon and phosphorus concentrations in the settled sludge and effluent, along with the sludge discharge flow rate and effluent flow rate, using the following formula: and The ratios of COD and TP capture amounts to transfer amounts were calculated, and these ratios were used as accounting values ​​to obtain the precipitation separation effect. The calculated values ​​were 12.3% for COD and 27.4% for TP.

[0067] The fourth step was to set the target values ​​for the sedimentation separation rate of COD and TP to 90%. It was found that the separation rates of both COD and TP were lower than the target values, indicating that it was necessary to further improve the sedimentation separation effect of the captured mud and water.

[0068] The fifth step is to improve the sedimentation and separation effect of mud and water after capturing carbon and phosphorus in the separation zone using the following methods:

[0069] Method 1: Based on the SVI value of the sludge-water mixture entering the sedimentation separation zone, determine whether adjusting the dissolved oxygen concentration of the mixture can improve the sedimentation performance of the sludge-water mixture, reduce the concentration of particulate carbon and phosphorus in the effluent, and improve the sludge-water separation effect. The measured SVI of the sludge-water mixture was 319 mL / g, which is higher than 150 mL / g. The method of increasing the dissolved oxygen concentration of the mixture can be used to improve the sedimentation performance of the sludge-water mixture. The dissolved oxygen concentration of the sludge-water mixture was further measured to be 0.8 mg / L. The dissolved oxygen concentration was increased at intervals of 0.3 mg / L. When it reached the upper limit of 1.5 mg / L, the ratio of the MLSS of the settled sludge (2678 mg / L) to the MLSS of the sludge-water mixture (1532 mg / L) was measured to be 1.75. Since the dissolved oxygen has reached the upper limit, even though the ratio of the MLSS of the settled sludge to the MLSS of the entering sludge-water mixture is less than 2.0, the system is still operated with a dissolved oxygen concentration of 1.5 mg / L.

[0070] After implementing Method 1 to increase the dissolved oxygen concentration of the mixed liquor to 1.5 mg / L, the COD of the settled sludge was measured to be 5265 mg / L and TP to be 77.76 mg / L, the COD of the effluent was 98 mg / L and SCOD to be 50 mg / L, TP to be 1.54 mg / L and STP to be 0.78 mg / L. The calculated separation rates of COD and TP were increased to 56.2% and 54.5% respectively. It was determined that the separation rates of the two indicators were still lower than the target values.

[0071] Method 2: After adjusting the dissolved oxygen concentration to 1.5 mg / L in Method 1, the COD and TP capture-to-transfer ratios were still lower than the target values. The hydraulic retention time (HRT) and sludge age (SRT) of the biological carbon and phosphorus capture system were calculated to be 2.5 h and 5 d, respectively. The HRT and SRT were adjusted to 3 h and 3 d, respectively. The capture-to-transfer ratio was increased by increasing the capture amount.

[0072] After implementing method 2, the COD of the settled sludge was measured to be 5578 mg / L and TP to be 156.7 mg / L, the COD of the effluent was 56 mg / L and SCOD to be 25 mg / L, TP to be 0.87 mg / L and STP to be 0.48 mg / L. The calculated separation rates of COD and TP increased to 74.8% and 90.9% respectively, but the COD separation rate was still lower than the target value.

[0073] Method 3: If the COD capture to transfer ratio is still lower than the target value after implementing Method 2, a low dose of ferric chloride coagulant is added to the mixed liquor entering the separation zone to assist precipitation. The ferric chloride dosage is controlled with the target value of effluent SCOD / COD ≥ 0.8 and the upper limit of total Fe dosage ≤ 20 mg / L. When the ferric chloride dosage is 15 mg / L, the effluent COD is 27.3 mg / L, SCOD is 24.0 mg / L, TP is 0.66 mg / L, STP is 0.46 mg / L, the SCOD / COD ratio is 0.88, and the calculated COD and TP separation rates are increased to 97.5% and 95.3%, respectively, meeting the target values.

[0074] The following steps were taken: Method 1 was performed with the dissolved oxygen concentration adjusted to 1.5 mg / L; Method 2 was performed with the HRT and SRT controlled to 3 h and 3 d respectively; Method 3 was performed with the addition of 15 mg / L ferric chloride to assist precipitation; and the carbon and phosphorus capture and separation system was operated under the original conditions.

[0075] Example 4

[0076] The first step was to determine the MLSS and SV of the mud-water mixture after capturing carbon and phosphorus in the sedimentation separation zone. 30 The SVI value was calculated to obtain the sludge settling performance of the sludge-water mixture, and the SVI value was used as a reference value for whether the dissolved oxygen concentration of the mixture needed to be adjusted; the specific measured values ​​were: MLSS 1356 mg / L, SV 30 The SVI was 9.6%, and the calculated SVI was 71 mL / g;

[0077] The second step involves determining the COD, TP, and MLSS of the sludge in the sedimentation separation zone, and the COD, SCOD, TP, and STP of the effluent. This process also yields the concentrations of carbon, phosphorus, and dissolved components in the sedimented sludge and effluent, as well as the sludge concentration, sludge discharge flow rate, and effluent flow rate. Specific measured values ​​are: sedimented sludge COD 3178 mg / L, TP 109.9 mg / L, MLSS 2710 mg / L; effluent COD 94 mg / L, SCOD 50 mg / L, TP 2.84 mg / L, STP 1.13 mg / L; sludge discharge flow rate is 6.0 L / h, and effluent flow rate is 256 L / h.

[0078] The third step involves calculating the carbon, phosphorus, and dissolved carbon and phosphorus concentrations in the settled sludge and effluent, along with the sludge discharge flow rate and effluent flow rate, using the following formula: and The ratios of COD and TP capture amounts to transfer amounts were calculated, and these ratios were used as accounting values ​​to obtain the precipitation separation effect. The calculated values ​​were 63.8% for COD and 61.1% for TP.

[0079] The fourth step was to set the target values ​​for the sedimentation separation rate of COD and TP to 65%. It was found that the separation rates of both COD and TP were lower than the target values, indicating that the sedimentation separation effect of the captured mud and water needs to be further improved.

[0080] The fifth step is to improve the sedimentation and separation effect of mud and water after capturing carbon and phosphorus in the separation zone using the following methods:

[0081] Method 1: Based on the SVI value of the mud-water mixture entering the sedimentation separation zone, determine whether to adjust the dissolved oxygen concentration of the mixture to improve the sedimentation performance of the mud-water mixture, reduce the concentration of particulate carbon and phosphorus in the effluent, and improve the mud-water separation effect: the measured SVI of the mud-water mixture is 71 mL / g, which is lower than 150 mL / g. Maintain the original dissolved oxygen concentration of the mud-water mixture entering the separation zone, and determine that the ratio of carbon and phosphorus capture to transfer after implementing Method 1 is lower than the target value.

[0082] Method 2: If the ratio of COD and TP capture to transfer is lower than the target value after maintaining the original dissolved oxygen concentration in Method 1, continue to calculate the hydraulic retention time (HRT) and sludge age (SRT) of the biological carbon and phosphorus capture system. The calculated values ​​are 1.5 h and 1.5 d, respectively. Adjust HRT and SRT to 2.7 h and 2 d, respectively, and increase the capture amount to improve the ratio of capture to transfer.

[0083] After implementing method 2, the COD of the settled sludge was measured to be 5914 mg / L and TP to be 124.4 mg / L, the COD of the effluent was 72 mg / L and SCOD to be 43 mg / L, TP to be 1.31 mg / L and STP to be 0.85 mg / L, and the separation rates of COD and TP were calculated to be 86.5% and 89.5% respectively, which was determined to meet the target values.

[0084] The carbon and phosphorus capture and separation system was operated under the following conditions: Method 1 was performed to maintain the original dissolved oxygen concentration; Method 2 was performed to adjust the HRT and SRT to 2.7 h and 2 d, respectively; and the rest of the system was operated under the original conditions.

[0085] Example 5

[0086] The first step was to determine the MLSS and SV of the mud-water mixture after capturing carbon and phosphorus in the sedimentation separation zone. 30 The SVI value was calculated to obtain the sludge settling performance of the sludge-water mixture, and the SVI value was used as a reference value for whether the dissolved oxygen concentration of the mixture needed to be adjusted; the specific measured values ​​were: MLSS 1275 mg / L, SV 30 The SVI was 10.4%, and the calculated SVI was 81 mL / g.

[0087] The second step involves measuring the COD, TP, and MLSS of the sludge in the sedimentation separation zone, and the COD, SCOD, TP, and STP of the effluent. This process also yields the concentrations of carbon, phosphorus, and dissolved components in the sedimented sludge and effluent, as well as the sludge concentration, sludge discharge flow rate, and effluent flow rate. Specific measured values ​​are: sedimented sludge COD 3654 mg / L, TP 112.6 mg / L, MLSS 2679 mg / L; effluent COD 89 mg / L, SCOD 54 mg / L, TP 2.76 mg / L, STP 1.34 mg / L; sludge discharge flow rate 5.0 L / h; and effluent flow rate 256 L / h.

[0088] The third step involves calculating the carbon, phosphorus, and dissolved carbon and phosphorus concentrations in the settled sludge and effluent, along with the sludge discharge flow rate and effluent flow rate, using the following formula: and The ratios of COD and TP capture amounts to transfer amounts were calculated, and these ratios were used as accounting values ​​to obtain the precipitation separation effect. The calculated values ​​were 68.1% for COD and 61.8% for TP.

[0089] The fourth step was to set the target values ​​for the sedimentation separation rate of COD and TP to 90%. It was determined that the separation rates of both COD and TP were lower than the target values, and it was decided that the sedimentation separation effect of the captured mud and water needed to be further improved.

[0090] The fifth step is to improve the sedimentation and separation effect of mud and water after capturing carbon and phosphorus in the separation zone using the following methods:

[0091] Method 1: Based on the SVI value of the mud-water mixture entering the sedimentation separation zone, determine whether to adjust the dissolved oxygen concentration of the mixture to improve the sedimentation performance of the mud-water mixture, reduce the concentration of particulate carbon and phosphorus in the effluent, and improve the mud-water separation effect: the measured SVI of the mud-water mixture is 81 mL / g, which is lower than 150 mL / g. Maintain the original dissolved oxygen concentration of the mud-water mixture entering the separation zone, and determine that the ratio of carbon and phosphorus capture to transfer after implementing Method 1 is lower than the target value.

[0092] Method 2: If the ratio of COD and TP capture to transfer is lower than the target value after maintaining the original dissolved oxygen concentration in Method 1, the hydraulic retention time (HRT) and sludge age (SRT) of the biological carbon and phosphorus capture system are calculated to be 1.8 h and 1.5 d, respectively. The HRT and SRT are then adjusted to be controlled at 2.5 h and 2.5 d, respectively. The ratio of capture to transfer is increased by increasing the capture amount.

[0093] After implementing method 2, the COD of the settled sludge was measured to be 5811 mg / L and TP to be 132.9 mg / L, the COD of the effluent was 88 mg / L and SCOD to be 63 mg / L, TP to be 1.25 mg / L and STP to be 0.81 mg / L. The calculated separation rates of COD and TP increased to 84.5% and 87.6% respectively. It was determined that the separation rates of COD and TP were still lower than the target values.

[0094] Method 3: If the ratio of COD and TP capture to transfer is still lower than the target value after implementing Method 2, a low dose of coagulant ferric chloride is added to the mixed liquor entering the separation zone to assist precipitation. The ferric chloride dosage is controlled with the target value of effluent SCOD / COD ≥ 0.8 and the upper limit of total Fe dosage ≤ 20 mg / L. When the ferric chloride dosage is 10 mg / L, the effluent COD is 37.8 mg / L, SCOD is 31.7 mg / L, TP is 0.57 mg / L, STP is 0.49 mg / L, and the SCOD / COD ratio is 0.84. The calculated COD and TP separation rates are increased to 96.8% and 97.9%, respectively, meeting the target values.

[0095] The following steps were taken: Method 1 was performed to maintain the original dissolved oxygen concentration; Method 2 was performed to adjust the HRT and SRT to 2.5 h and 2.5 d, respectively; Method 3 was performed to add 10 mg / L of ferric chloride to assist precipitation; and the carbon and phosphorus capture and separation system was operated under the original conditions for the rest of the steps.

[0096] It is worth noting that although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to the specific embodiments described above. The embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other modifications without departing from the spirit and scope of the claims, and these modifications all fall within the scope of the present invention.

Claims

1. A method for improving the sedimentation and separation effect of mud and water after biological capture of carbon and phosphorus, characterized in that... Includes the following steps: The first step is to determine the sludge concentration (MLSS) and sludge settling ratio (SV) of the anaerobic-aerobic sludge mixture after carbon and phosphorus capture in the sedimentation and separation zone. 30 Calculate the sludge volume index (SVI); The second step is to measure the COD, total phosphorus (TP), and MLSS of the sludge in the sedimentation separation zone, and the COD, dissolved chemical oxygen demand (SCOD), and dissolved total phosphorus (STP) of the effluent. The concentrations of carbon, phosphorus, and dissolved components in the sedimentation sludge and effluent in the sedimentation separation zone, the sludge concentration of the sedimentation sludge, the sludge discharge flow rate, and the effluent flow rate are obtained respectively. The third step is to calculate the ratio A of carbon capture to transfer and the ratio B of phosphorus capture to transfer, respectively. The formula for the ratio of carbon capture to carbon transfer is as follows: Formula for the ratio of phosphorus capture to translocation: Q in the formula 沉淀污泥 Q is the sludge discharge flow rate of the sedimentation and separation zone. 出水 The effluent flow rate of the sedimentation separation zone, COD 沉淀污泥 The COD and TP values ​​of the sludge in the sedimentation and separation zone are... 沉淀污泥 The TP value (COD-SCOD) of the sludge in the sedimentation and separation zone. 出水 The COD-SCOD value (TP–STP) in the effluent from the sedimentation separation zone is given. 出水 The TP–STP value in the effluent from the sedimentation separation zone; The fourth step is to determine that if either value A or B is lower than the set target value, it is necessary to further improve the sedimentation and separation effect of the captured mud and water. The fifth step involves taking the following steps in sequence to improve the mud-water separation effect after capturing carbon and phosphorus in the separation zone, as follows: Step 501: If the SVI value is ≥150mL / g, increase the dissolved oxygen concentration in the mixed liquor at intervals of 0.3mg / L, with an upper limit of 1.5mg / L, until the ratio of the MLSS of the precipitated sludge in the separation zone to the MLSS of the sludge-water mixture entering the separation zone is ≥2.

0. Then, operate the carbon and phosphorus biological capture and separation system with the adjusted dissolved oxygen concentration. If the SVI value is <150mL / g, proceed to step 502. Step 502: Calculate the hydraulic retention time (HRT) and sludge age (SRT) of the biological capture carbon and phosphorus unit before entering the separation zone, and control the HRT and SRT to 2.5-3h and 2-3d, respectively; and determine whether A and B are greater than the target values. If so, maintain operation using the dissolved oxygen concentration in step 501 and the adjusted HRT and SRT; otherwise, proceed to the next step. Step 503: Add a low dose of coagulant ferric chloride to the mixed liquid entering the separation zone to assist sedimentation. The dosage of ferric chloride is controlled with the target value of effluent SCOD / COD≥0.8 and the upper limit of total Fe dosage≤20mg / L until both A and B are greater than the target values.

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