Method and treatment device for realizing consumption reduction and emission reduction by optimizing carbon source circulation in sewage plant

Abstract

The application provides a method and a treatment device for realizing consumption reduction and emission reduction by optimizing carbon source circulation in a sewage plant, and the treatment method comprises the following steps: mixing residual sludge with biological surfactant, stirring and treating, and then performing low-temperature thermal hydrolysis treatment, and then performing stripping and separation of extracellular polymers through hydraulic cyclone; wherein the residual sludge is a mixture of biochemical sludge and physical-chemical sludge, and the temperature of the low-temperature thermal hydrolysis is not more than 90 DEG C; performing short-path fermentation on the treated sludge to obtain carbon source rich in volatile fatty acids; recycling sludge conversion carbon source; and putting the recycled carbon source into a biochemical denitrification treatment device to supplement biological denitrification carbon source. By adopting the technical scheme of the application, the extracellular polymers of the residual sludge can be converted into volatile fatty acids as the main fermentation substrate, and the volatile fatty acids can be used for in-situ denitrification, so that the carbon source in the sewage plant can be recycled, the sludge amount can be reduced, the cost can be saved, and the carbon emission can be reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of sewage treatment and resource utilization, and particularly relates to a method and a treatment device for realizing consumption reduction and emission reduction by optimizing carbon source circulation in a sewage plant. BACKGROUND

[0002] Activated sludge process is a main method for sewage treatment, which makes excess sludge become a main residue and byproduct in the treatment process. Today, excess sludge has become a problem that cannot be ignored, and its treatment cost even accounts for 50-60% of the total cost of sewage treatment plant operation. In addition to microbial communities, the excess sludge also contains endogenous metabolism and self-oxidation residues, and refractory organic and inorganic substances contained in raw sewage, which are rich in protein and carbohydrates, and have the potential for resource utilization. At present, the main treatment and utilization ways of excess sludge include recovery of biological energy and production of biological chemicals. However, the efficiency of hydrogen and methane production by anaerobic fermentation of excess sludge is low, and the production of high-value-added biological chemicals from excess sludge will become a new direction of sludge resource utilization. In the anaerobic fermentation process, macromolecular organic matter will produce soluble small-molecule organic matter such as volatile short-chain fatty acids (VFAs) through hydrolysis and acidification stages, which has high economic value and can be used as an external carbon source to input into a biochemical tank, replacing the input of glucose or sodium acetate, to provide growth and metabolism carbon source for heterotrophic denitrifying microorganisms, thereby reducing the carbon source backfill cost and achieving the removal of pollutants. Extracellular polymeric substance (EPS) is the main component of excess sludge, and its content accounts for more than half of the solid mass of excess sludge. These substances are mainly produced by microbial secretion and have the property of mutual adhesion, which is an important substrate for sludge skeleton and has an important influence on the physical and chemical properties and biological performance of sludge. The main organic matter of extracellular polymeric substance includes protein, polysaccharide, nucleic acid and lipid, etc. Therefore, how to fully release the carbon source in the extracellular polymeric substance of excess sludge has become a key problem for realizing carbon source resource utilization of sludge. The conventional anaerobic fermentation efficiency is low, and only half of the organic matter can be degraded in a month of treatment, so it is necessary to take appropriate pretreatment means to fully release the carbon source contained in the excess sludge and improve its efficiency. SUMMARY

[0003] In view of the above technical problems, the present application discloses a method and a treatment device for realizing consumption reduction and emission reduction by optimizing carbon source circulation in a sewage plant, which realizes overall sludge reduction and achieves the goal of carbon emission reduction by separating and in-situ utilizing the organic matter (polysaccharide, protein, etc.) in the sludge extracellular polymeric substance.

[0004] To this end, the technical scheme adopted by the present application is as follows:

[0005] A method for realizing consumption reduction and emission reduction by optimizing carbon source circulation in a sewage plant, comprising the following steps:

[0006] Step S1, mixing the residual sludge with biosurfactants, stirring treatment, and then low-temperature thermal hydrolysis treatment, and then realizing the stripping and separation of extracellular polymers through hydrocyclone; wherein the residual sludge is a mixture of biochemical sludge and materialized sludge, and the temperature of the low-temperature thermal hydrolysis is not more than 90℃;

[0007] Step S2, short-cut fermentation of the sludge treated in step S1 to obtain a carbon source rich in volatile fatty acids (VFAs);

[0008] Step S3, recycling the sludge conversion carbon source;

[0009] Step S4, putting the recycled carbon source into the biochemical denitrification treatment device to supplement the biological denitrification carbon source.

[0010] Biosurfactants are a kind of microbial source surfactants with strong biodegradability, which can separate the agglomerated organic matter in the residual sludge, disassemble large agglomerates into small pieces, and improve the solubility of organic matter. However, its separation effect on tightly bound EPS, i.e. TB-EPS, is limited, and a high concentration of 0.2 g / g TSS is required for treatment, so it cannot achieve sufficient stripping and further dissolution of EPS into the fermentation liquid phase. The hydrocyclone can realize the partial stripping of extracellular polymers through the self-rotation and revolution of sludge inside the machine, but due to the limited physical separation effect on biological and chemical combined organic matter, the effect is not significant. Our research group has used biosurfactants and hydrocyclone to pretreat sludge for VFAs production, which has achieved a certain degree of EPS stripping and dissolution, but in terms of application effect, a large amount of chemicals is used, and due to insufficient EPS stripping and high microbial activity, the sludge re-aggregation in the later fermentation period has worsened the dewatering property of the fermentation sludge, which is not conducive to the recovery of the fermentation carbon source. Thermal hydrolysis has also been widely used in sludge pretreatment to promote cell disruption and release of organic matter, but the application of low-temperature thermal hydrolysis, especially at temperatures of 60-80℃, is not in-depth and extensive, ignoring its role in preserving microbial cell integrity but loosening extracellular polymers. Therefore, low-temperature thermal hydrolysis is introduced in this technology to build a complete EPS high-efficiency stripping and in-situ resource reduction carbon process.

[0011] Therefore, the combination of biosurfactants and hydrocyclone can achieve the stripping and separation of carbon sources in extracellular polymers, and on this basis, short-cut fermentation can limit organic matter to the stage of producing small-molecule organic matter in hydrolysis and acidification, and suppress the further conversion of organic matter into hydrogen and methane. Moreover, the carbon source produced by short-cut fermentation can be recycled to the anoxic stage of the biochemical process and utilized by heterotrophic denitrifying bacteria, thereby reducing the additional carbon source addition cost, achieving sludge reduction, carbon source recycling, and carbon emission reduction.

[0012] In view of the large amount of residual sludge in the sewage treatment plant and the characteristics that the main component of the residual sludge, extracellular polymeric substance (EPS), is rich in organic matter (protein, polysaccharide, lipid and humic acid, etc.), the above technical solution can be used for sludge reduction treatment, and effectively realize efficient stripping and separation of EPS in the sludge, and convert high-biodegradability carbon source, thereby reducing the cost of external carbon source addition in the conventional sewage treatment process, achieving the purpose of internal carbon source circulation of the sewage treatment plant, and realizing the overall sludge reduction and carbon emission reduction of the sewage plant.

[0013] Further, the biosurfactant includes but is not limited to alcohol ether glycoside, rhamnolipid, sophorolipid, etc.

[0014] As a further improvement of the present application, in step S1, the concentration of the biosurfactant is 0.02-0.1 g / g TSS. Further, the stirring treatment time is 20-60 min. Further preferably, the stirring treatment time is 30 min.

[0015] As a further improvement of the present application, in step S1, the treatment temperature of the low-temperature thermal hydrolysis treatment is 75-85℃; further preferably, the treatment temperature of the low-temperature thermal hydrolysis treatment is 80℃.

[0016] As a further improvement of the present application, in step S1, the number of cycles of the hydrocyclone is 10-15 times. Further, the rated power of the hydrocyclone is 1-2 kW, and the nozzle injection flow rate is 15-25 L / min. Further preferably, the rated power of the hydrocyclone is 1.5 kW, and the nozzle injection flow rate is 20 L / min.

[0017] As a further improvement of the present application, in step S2, the sludge treated in step S1 is added to a fermentation vessel for anaerobic fermentation, the fermentation time is 3-5 d, the fermentation temperature is 25-45℃, and the initial pH is 8.0-9.0. Further preferably, the initial pH is 8.0, and the subsequent process does not control the pH.

[0018] As a further improvement of the present application, in step S3, an organic flocculant is used for coagulation and sedimentation of the fermented sludge, and then dewatering is performed to recover the fermentation liquor rich in volatile fatty acids.

[0019] As a further improvement of the present application, in step S3, the recovered fermentation liquor rich in VFAs is stored in a carbon source storage tank configured with a circulating water cooling and heat preservation assembly.

[0020] As a further improvement of the present application, the organic flocculant is cationic polyacrylamide (CPAM) with a molecular weight of 10-20 million, a dewatering pressure of 0.05-0.08 MPa, and a temperature of the carbon source storage tank of 4-15℃. Further preferably, the temperature of the carbon source storage tank is 10℃.

[0021] As a further improvement of the present application, in step S4, a small-scale denitrification potential test is performed on the carbon source recovered in step S3 to determine the denitrification utilization rate of the carbon source in the application environment, and then the carbon source is continuously fed into the biochemical denitrification treatment device.

[0022] Further, the denitrification utilization rate of the carbon source in the application environment, i.e., ΔC / ΔN, is determined after the small-scale denitrification test of the converted carbon source, and the fermentation broth is continuously fed back to the biochemical anoxic section. or nitrate The theoretical required carbon source content COD is and According to the actual loss and demand, the feeding amount can be expanded by multiplying a coefficient of 1.5-2.

[0023] As a further improvement of the present application, in the residual sludge, the mass ratio of biochemical sludge is 1 / 4-1 / 2. Preferably, in the residual sludge, the mass ratio of biochemical sludge is 1 / 3.

[0024] The present application discloses a treatment device for realizing consumption reduction and emission reduction by optimizing carbon source circulation in a sewage plant, which uses the method for realizing consumption reduction and emission reduction by optimizing carbon source circulation in a sewage plant as described above to treat residual sludge, and comprises a dosing premixing container, a hydrocyclone, a sludge fermentation container and a carbon source storage tank connected in sequence.

[0025] Compared with the prior art, the present application has the following advantages:

[0026] First, the technical scheme of the present application introduces low-temperature hydrolysis between biological surfactant treatment and hydrocyclone, and realizes more efficient cracking and separation of EPS by combining the three; this technical scheme converts the resources of extracellular polymeric substances (EPS) of residual sludge into VFA for in-situ use in wastewater treatment denitrification, improves the carbon source conversion rate, realizes the recycling of carbon sources in the plant, reduces sludge, saves costs, achieves carbon emission reduction through the reuse of carbon sources, can achieve 100% carbon source replacement, and at the same time realizes a total sludge reduction of 13.84%; the comprehensive operation cost of the wastewater treatment plant is reduced by 12.99%, about 826.76 ￥ / d, and the carbon emission reduction potential is about 746.21 kg CO 2e / d, about 4.95%.

[0027] Second, the technical scheme of the present application has a carbon source conversion rate of about 440 mg / (L·d), which is about 2300 mg / L higher than that of direct fermentation, the total VFAs yield is increased by 194.12%, the acetic acid content in the volatile acid composition is increased by 2.5-2.7 times, and the short-term fermentation mainly using EPS significantly improves the total yield of various acids and promotes the conversion of butyric acid and propionic acid to acetic acid. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a technical roadmap of a method for optimizing and recycling carbon sources in a wastewater treatment plant to achieve consumption reduction and emission reduction according to an embodiment of the present application.

[0029] Figure 2 is a specific flowchart of a method for optimizing and recycling carbon sources in a wastewater treatment plant to achieve consumption reduction and emission reduction according to an embodiment of the present application.

[0030] Figure 3 is a schematic diagram of a device for optimizing and recycling carbon sources in a wastewater treatment plant to achieve consumption reduction and emission reduction according to an embodiment of the present application.

[0031] Figure 4 is the total volatile acid (Total VFAs) production and release of different types and proportions of residual sludge during the pretreatment anaerobic conversion process according to an embodiment of the present application. Raw sludge is direct fermentation, pretreated sludge is pretreated short-term fermentation, AFS is physical sludge, WAS is biochemical sludge, DWS is dewatered sludge, MixS1 / 2 is residual sludge, and the mass ratio of biochemical sludge / physical sludge is 1 / 2; MixS1 / 3 is residual sludge, and the mass ratio of biochemical sludge / physical sludge is 1 / 3.

[0032] Figure 5Figure 1 is a comparison chart of the residual sludge extracellular polymeric substance (EPS) disintegration results of Examples 1-3 and Comparative Examples 1-3 of the present application; wherein RL-LTH(80)&HSH is Example 1, RL-LTH(90)&HSH is Example 2, RL-LTH(60)&HSH is Example 3, RL&HSHC is Comparative Example 1, LTH(80) is Comparative Example 2, and raw is Comparative Example 3.

[0033] Figure 6 Figure 2 is a comparison chart of the VFA yield and the carbon-nitrogen ratio (C / N) of the fermentation liquor after fermentation of Examples 1-3 and Comparative Examples 1-3 of the present application. Wherein RL-LTH(80)&HSH is Example 1, RL-LTH(90)&HSH is Example 2, RL-LTH(60)&HSH is Example 3, RL&HSHC is Comparative Example 1, LTH(80) is Comparative Example 2, and raw is Comparative Example 3.

[0034] Figure 7 Figure 3 is a comparison chart of the retention degree of short-chain fermentation organic components after fermentation of Example 1 and Comparative Examples 4-5 of the present application. Wherein PAM is Example 1 treated with organic cationic polyacrylamide (CPAM), PFS is Comparative Example 4, PAC is Comparative Example 5, and ori is the supernatant of the fermented sludge before coagulation dewatering recovery, i.e. Comparative Example 6.

[0035] Figure 8 Figure 4 is a comparison chart of the carbon-nitrogen ratio (C / N) of the recovered filtrate and the filtrate recovery amount under different dewatering pressure conditions of Example 4 of the present application.

[0036] Figure 9 Figure 5 is a comparison chart of the dewatering properties of the residual sludge of Example 1 and Comparative Examples 1 and 7 of the present application. Wherein RL-LTH(80)&HSH is Example 1, RL&HSH is Comparative Example 1, and Na(OH) (pH=10) is Comparative Example 7.

[0037] The reference signs include:

[0038] 1-physicochemical sludge storage tank, 2-biochemical sludge storage tank, 3-medicine storage tank, 4-medicine pre-mixing tank, 5-hydrocyclone, 6-sludge fermentation tank, 7-carbon source storage tank, 8-biochemical section;

[0039] 1.2, 2.2, 4.5, 5.3 are sludge feeding pumps, 3.2 is a medicine feeding pump, 6.6 and 7.3 are carbon source pumps, 4.1 and 6.1 are stirring paddles, 6.2 is a pH probe, 6.3 is a DO probe, and 5.4 is a sludge return pump.

[0040] 1.1, 2.1, 3.1, 4.2, 4.3, 4.4, 4.5, 5.1, 5.2, 5.5, 6.4, 6.5, 7.1, 7.2 are valves. DETAILED DESCRIPTION

[0041] The preferred embodiments of the present invention will be described in further detail below.

[0042] Example 1

[0043] like Figures 1-2 As shown, a method based on the in-situ utilization of extracellular polymer resources to achieve overall sludge reduction and carbon emission reduction in wastewater treatment plants is proposed.

[0044] It mainly includes three stages: the pretreatment stage of excess sludge, the short-range fermentation stage of sludge, and the carbon source replenishment stage, in order to realize the in-situ resource utilization of extracellular polymers and reduce energy consumption and emissions in wastewater treatment plants.

[0045] The specific phased operation is as follows (taking sludge generated from wastewater treatment in an actual wool textile industrial park as an example):

[0046] (1) Sludge Pretreatment Stage: Excess sludge is pretreated in a chemical premixing tank and a hydrocyclone. In the chemical premixing tank, physicochemical and biological sludge are mixed, and biosurfactants are added and thoroughly homogenized. The ratio of physicochemical to biological sludge is 3:1. The added biosurfactant is 25% rhamnolipin at a concentration of 0.04 g / g TSS. After thorough mixing, the sludge is hydrolyzed at 80℃ for 30 minutes and then pumped at high speed into a hydrocyclone for 12.5 cycles to achieve complete separation of EPS and microorganisms.

[0047] (2) Short-cut fermentation stage of sludge: This stage is carried out in a sludge fermenter. EPS is stripped and separated from the sludge and enters the fermentation liquid phase, improving EPS utilization. By restricting the fermentation conditions, the fermentation process is limited to the hydrolysis and acidification stage, which decomposes large organic molecules into small carbon sources and slows down methanogenesis. The short-cut fermentation time is 5 days. The fermentation temperature is controlled at 35℃, the initial pH is set to 8.0, and the pH is not adjusted during the fermentation process.

[0048] (3) Carbon source recovery and storage stage: After the fermentation sludge is coagulated and settled by 0.5 mg / g TSS CPAM with a molecular weight of 12 million, it is dewatered by belt filter, the pressure is adjusted to 0.08 MPa, the fermentation liquid is recovered by pressure filtration, and the filtrate is collected and stored in a carbon source storage tank with a temperature control of about 10℃.

[0049] (4) Carbon source replenishment and utilization stage: After conducting a small-scale test on the denitrification potential of the recovered carbon source, the nitrogen removal utilization rate of the activated sludge system for the carbon source, i.e., ΔC / ΔN, is determined. Then, the carbon source is continuously replenished to the denitrification section for nitrogen removal. (Basic reference: Removal of nitrite nitrogen) or nitrate Theoretically, the required COD input is 1.71g COD / g and 2.59g The dosage can be expanded according to actual loss and demand, and multiplied by a coefficient of 1.5-2.

[0050] (5) Finally, according to the actual treatment efficiency, the environmental and economic benefits of the process are evaluated in combination with the accounting method provided by the method.

[0051] According to the above steps, different types and different proportions of residual sludge are pretreated and subjected to anaerobic conversion, and direct fermentation is used as a comparison. Among them, different types and different proportions of residual sludge mainly include: AFS, WAS, DWS, MixS1 / 2, and MixS1 / 3. The comparison results of the VFAs yield of different types and different proportions of residual sludge pretreated or not subjected to anaerobic conversion are shown in Figure 4 As shown in the figure, when the mixed mass ratio of the AFS and the WAS retained by the air floatation tank in the influent is 3:1, the effect is the best. The main reference index is the VFAs yield of anaerobic conversion, and the acid yield of the mixed sludge is nearly 2 times that of the biochemical sludge.

[0052] Example 2

[0053] In this example, the temperature of the low-temperature thermal hydrolysis is 90°C, and the other conditions are the same as those in Example 1.

[0054] Example 3

[0055] In this example, the temperature of the low-temperature thermal hydrolysis is 60°C, and the other conditions are the same as those in Example 1.

[0056] Comparative Example 1

[0057] In this comparative example, the low-temperature thermal hydrolysis step is cancelled, that is, the biological surfactant and the hydrocyclone are used for pretreatment in the sludge pretreatment stage.

[0058] Comparative Example 2

[0059] In this example, the biological surfactant and the hydrocyclone are not added, that is, only the low-temperature thermal hydrolysis at 80°C is used for pretreatment in the sludge pretreatment stage.

[0060] Comparative Example 3

[0061] The residual sludge with a ratio of 3:1 of the AFS and the WAS is directly fermented without pretreatment.

[0062] The EPS cracking effects of the sludge treated in Examples 1-3 and Comparative Examples 1-3 are compared, and the results are as follows:Figure 5 As shown in the figure. A comparison of soluble EPS (S-EPS) reveals that the soluble EPS (S-EPS) of Examples 1-3 is higher than that of Comparative Examples 1-3. Furthermore, Example 1, employing a combined action of biosurfactant-low-temperature hot water hydrolysis-hydrocyclone, can increase S-EPS by 38.60 mg COD / gVSS. Comparative Example 2, directly using 80℃ low-temperature hot water hydrolysis pretreatment, can increase S-EPS by 4.59 mg COD / gVSS; Comparative Example 1, using biosurfactant and hydrocyclone pretreatment, can increase S-EPS by 16.47 mg COD / gVSS; the combined increase in S-EPS of Comparative Examples 1 and 2 is 21.05 mg COD / gVSS. This demonstrates that the use of biosurfactant-low-temperature hot water hydrolysis-hydrocyclone pretreatment for residual sludge in this example produces a synergistic effect, with the biosurfactant treatment, low-temperature hot water hydrolysis treatment, and hydrocyclone treatment all contributing to the overall effect. The comparison shows that the introduction of low-temperature hot water hydrolysis significantly improves the overall effect, more efficiently breaking down and stripping EPS.

[0063] The comparison chart of VFA yield and C / N ratio of fermentation broth after fermentation of Examples 1-3 and Comparative Examples 1-3 is shown in the figure below. Figure 6 As shown, the VFA yield and C / N ratio of the fermentation broth in Examples 1-3 are higher than those in Comparative Examples 1-3. Furthermore, the 90°C low-temperature hot hydrolysis in Example 3 caused cell disruption of the microorganisms, releasing a large amount of nitrogen, resulting in a lower biochemical property (C / N) of the fermentation product. Figure 5 Therefore, the optimal temperature for low-temperature hot water hydrolysis is 80℃.

[0064] Comparative Example 4

[0065] Based on Example 1, the difference in this comparative example is that in step (3) the carbon source recovery and storage stage, polyferric sulfate (PFS) is used for coagulation and sedimentation of fermented sludge.

[0066] Comparative Example 5

[0067] Based on Example 1, the difference in this comparative example is that in step (3) the carbon source recovery and storage stage, polyaluminum chloride (PAC) is used for coagulation and sedimentation of fermented sludge.

[0068] Comparative Example 6

[0069] Based on Example 1, this comparative example differs in that no coagulant is used to coagulate and settle the fermented sludge in step (3) carbon source recovery and storage stage (i.e., ori).

[0070] The retention results of organic components after short-range fermentation in Examples 1 and Comparative Examples 4-5 are as follows: Figure 7As shown, it is found that the embodiment 1 adopts the organic flocculant cationic polyacrylamide (CPAM) to have the highest retention of carbon source, which is basically maintained above 89%.

[0071] Embodiment 4

[0072] On the basis of the embodiment 1, the difference of the present embodiment lies in the dewatering pressure in the recovery and storage stage of the carbon source in step (3). The present embodiment selects different dewatering pressures, and the comparative results of the carbon-nitrogen ratio (C / N) of the recovered filtrate and the filtrate recovery amount are as follows Figure 8 As shown, it can be seen that when the dewatering pressure is kept in the low pressure range of 0.05-0.08 MPa, the filtrate recovery amount and the biochemical property are both higher.

[0073] Comparative Example 7

[0074] On the basis of the embodiment 1, the difference of the present comparative example lies in that in step (1) the sludge pretreatment stage, NaOH is used to adjust the sludge pH to 10, and the pretreated sludge is fully treated for 30-60 min. The pH of the sludge after the short-term fermentation stage is 10.

[0075] The comparative results of the dewatering property of the residual sludge of the embodiment 1 and the comparative examples 1 and 7 are as follows Figure 9 As shown, it can be seen that due to the full stripping of EPS and the fact that the microorganisms are basically killed except for the inoculated sludge, the phenomenon of re-aggregation and re-release of a large amount of EPS combined water between the living cells in the fermentation system, especially in the later stage, is inhibited to a certain extent, so the dewatering property is partially improved. Among them, the embodiment 1 has a low-temperature hydrolysis pretreatment at 80°C, compared with the comparative example 2, the CST (sludge capillary water absorption time) is reduced by 1.6 s / gTSS.

[0076] Extracellular polymeric substance (EPS) is the third largest component of excess sludge besides cells and water, accounting for about 70% of total organic matter in excess sludge, mainly composed of protein and polysaccharide, humus and other substances, and approximately distributed around microorganisms in a layered package distribution, and the microorganisms are connected together to form sludge flocs. In the technical scheme of the above embodiment, the biological surfactant is used to treat the excess sludge, and combined with low-temperature thermal hydrolysis pretreatment and hydrocyclone, the EPS can be effectively broken and peeled off, so as to be used as the main organic substrate for subsequent short-term fermentation. A small amount of biological surfactant is used to reduce the adhesion force inside the excess sludge, loosen the EPS, and break the large sludge flocs into small pieces, which is manifested as a significant reduction in sludge particle size; the low-temperature thermal hydrolysis can maximize the solubilization of the organic matter in the EPS under the condition of ensuring the weak cell breaking of the sludge, further reduce the combination of EPS and microorganisms, the linking effect of EPS on the sludge flocs, and increase the dissolved organic matter in the sludge liquid; finally, the high-efficiency peeling of the EPS is realized through the centrifugal force of the hydrocyclone and the public spinning and shearing action of the sludge particles in the hydrocyclone.

[0077] The combination of biological surfactant, low-temperature thermal hydrolysis and hydrocyclone can maximize the peeling and solubilization of EPS, so as to utilize and preserve the integrity of the microbial cells. The main purposes are as follows: one is to improve the quality of the converted carbon source, because the release of nitrogen and phosphorus into the fermentation substrate can be minimized, the content of ammonia nitrogen and phosphate in the product can be reduced, the C / N of the converted carbon source can be improved, the availability of the carbon source for denitrification and phosphorus removal can be increased, and the secondary pressure on the system after recycling can be reduced; the other is to improve the dewatering property of the fermentation sludge, because the low-temperature thermal hydrolysis (not higher than 90°C) kills most of the microorganisms to reduce the rapid re-aggregation of the flocs in the fermentation system, and at the same time, the cell integrity is preserved as much as possible to avoid the continuous binding of the combined water by the large cell fragments and EPS flocs after cell breaking, and a large part of the combined water is tightly combined with the large molecular protein in the EPS and difficult to remove.

[0078] Example 5

[0079] The method of example 1 was used to resourceize and utilize in-situ the EPS of sludge from a wool textile industrial wastewater treatment plant in Heze, Shandong Province.

[0080] The wastewater treatment plant adopts a two-stage A / O (A / O-A / O) treatment method, and the influent quantity is Q influent = 2000 m 3COD content in the influent of biochemical section is relatively low (1200-1300 mg / L) compared with high sludge concentration (≈20 g / L), ammonia nitrogen content is high (140-180 mg N / L), and there is a large amount of COD (about 500 mg / L) that is difficult to be biochemically utilized, resulting in insufficient carbon source for denitrification in the biochemical section. In order to remove ammonia and maintain high concentration of biochemical sludge, the water plant needs to add a large amount of glucose as denitrification carbon source and sludge biochemical carbon source.

[0081] The above facts result in a large amount of residual sludge and the input of exogenous carbon source. In view of the problems of large sludge production and insufficient carbon source for denitrification in the treatment process, a suitable fermentation sludge ratio (materialization:biochemistry=3:1) of sludge in the wool textile industry sewage plant is selected, and EPS is stripped and separated by biological surfactant coupling hydrocyclone, and then short-term fermentation treatment (fermentation time 5d) is carried out to release and convert carbon source to meet the utilization of heterotrophic denitrifying bacteria in the biochemical anoxic section, instead of the original glucose addition in the sewage treatment plant. The sludge reduction, operation cost and carbon emission reduction potential are calculated.

[0082] The device used in the embodiment is shown in Figure 3 It includes a dosing premix tank 4, a hydrocyclone 5, a sludge fermentation tank 6 and a carbon source storage tank 7 connected in sequence, the inlet of the dosing premix tank 4 is connected with the materialization sludge storage tank 1, the biochemical sludge storage tank 2 and the storage tank 3, the storage tank 3 contains biological surfactant, and the outlet of the carbon source storage tank 7 is connected with the biochemical section 8 (anoxic tank). The sludge fermentation tank 6 is provided with a stirring paddle 6.1, a pH probe 6.2 and a DO probe 6.3.

[0083] As shown in Figure 3 The specific operation process and operation effect are as follows:

[0084] (1) Open the relevant valves 1.1, 2.1, 3.1, 4.2, 4.3 and 4.4 of the materialization sludge storage tank 1, the biochemical sludge storage tank 2, the storage tank 3 and the dosing premix tank 4. Open the sludge inlet pumps 1.2 and 2.2 and the dosing pump 3.2, and enter the dosing premix tank 4 according to the mass ratio of materialization sludge and biochemical sludge 3:1, at the same time, the amount of biological surfactant added is 0.005-0.1 g / g TSS. Open the stirrer 4.1 to make the three fully mixed in it.

[0085] (2) Close the valves and pumps in step (1) above, open the hydrocyclone 5 related valves 4.5 and 5.1, and pass the fully mixed sludge into the hydrocyclone 5 at high speed. Open the sludge return pump 5.4 and the valves 5.2 and 5.5 to make the sludge continuously cyclone between the dosing premix tank 4 and the hydrocyclone 5 for multiple cycles, and the duration is 0.5-20 min.

[0086] (3) Close valves 4.5, 5.1, and 5.5, close the sludge return pump 5.4, and open the sludge inlet pump 5.3 and valve 6.4 to allow the sludge to enter the sludge fermentation tank 6. After the sludge is full, close the sludge inlet pump 5.3 and valve 6.4, and open the agitator 6.1 to allow the sludge to ferment in the sludge fermentation tank 6 for 5 days. At the same time, open the pH probe 6.2 and DO probe 6.3 to monitor the pH, temperature, and DO in the sludge fermentation tank 6 in real time, and keep the temperature between 25-45℃.

[0087] (4) Open valves 6.5, 7.1 and pump 6.6 so that the carbon source produced by fermentation enters the carbon source storage tank 7 after the sludge is intercepted by coagulation and microfiltration.

[0088] (5) Calculate the required COD content based on the denitrification needs of the biochemical anoxic section, open valve 7.2 and pump 7.3, and add carbon source to biochemical section 8.

[0089] (6) The sludge residue retained by coagulation and microfiltration after sludge fermentation is used for sludge brick making.

[0090] Based on the above specific processes and operating methods, the potential for carbon source substitution, overall sludge reduction, economic savings, and carbon emission reduction at the wastewater treatment plant are calculated through the following process. The specific calculation steps are as follows:

[0091] (1) Carbon source substitution and cost

[0092] Based on the daily sludge production (V) of the sewage treatment plant sludge m 3 / d) and sludge concentration (C sludge Calculate the total amount of sludge generated daily (TSS) using g / L. total (g / d):

[0093] TSS total =1000×V sludge ×Cs ludge

[0094] The daily carbon source production (T) of wastewater treatment plant sludge was calculated by measuring the carbon source yield per unit sludge unit (SCOD, SCOD g / g TSS) during short-path fermentation. SCOD (g / d):

[0095] T SCOD =TSS total ×SCOD

[0096] Without adding glucose as a carbon source, the concentration of nitrogen that cannot be removed (C) N Calculate the nitrogen load (ΔN, g / d) required to meet the standard:

[0097] △N=Q influent ×CN

[0098] Assuming that this part of nitrogen is all nitrate nitrogen That is, according to the maximum required SCOD amount (2.59 g COD / gN) calculation, while according to the actual loss and demand can expand the amount of adding, multiplied by the coefficient k (1.5-2), the theoretical need to add carbon source (T need , g / d) is:

[0099] T need = 2.59 x k x ΔN

[0100] The ratio of carbon source produced by fermentation to the theoretical need to add carbon source η is:

[0101]

[0102] That is, the sludge produced by fermentation can meet the demand for carbon source η, compared with the actual amount of glucose added (Q glucose ), the amount of glucose that can be reduced daily (△Q glucose , g / d) is:

[0103]

[0104] Through the cost of unit mass of glucose (p), the daily savings of carbon source addition cost (△P) is calculated:

[0105] △P = △Q glucose x p

[0106] (2) Sludge reduction

[0107] The total suspended solid particle concentration (TSS) before and after sludge short-term fermentation is evaluated.

[0108] The sludge reduction ratio is defined as follows:

[0109]

[0110] Where: TSS original — original sludge concentration, g / L;

[0111] TSS fermentation — sludge concentration after fermentation, g / L.

[0112] (3) Carbon emission reduction potential accounting

[0113] The carbon emission sources of the water plant can be divided into direct emission sources and indirect emission sources. Direct emission is the direct emission of greenhouse gases such as CO2, CH4, N2O to the atmosphere by microbial proliferation and metabolism activities in the biochemical process. Indirect emission refers to the carbon emissions generated by the power, chemicals and sludge further transported and disposed by the water plant operation.

[0114] The selection principle of the emission factor of the sewage treatment plant gives priority to the similar process conditions of the sewage treatment plant in the adjacent geographical position as the reference. It should be noted that, limited by the current research results, even if the same treatment process, the obtained greenhouse gas emission intensity also has a large range of variation.

[0115] Here, the direct emission of three main greenhouse gases (CH4, N2O and CO2 of fossil origin) of the sewage treatment plant is mainly considered. For convenience of comparison, different greenhouse gases are converted into carbon dioxide equivalent (CO 2e 2) for comparison: one ton of CH4 and one ton of N2O are equivalent to 28 tons and 265 tons of CO2 in terms of warming capacity.

[0116] The CO2 emission of the relevant section involved in the transformation is calculated, mainly from the CO2 generated by power consumption and the CO2 caused by sludge reduction. If the treatment section is not transformed, the CO2 emission does not change. Then the total carbon emission reduction change (ΔG) is:

[0117] G =∑G i ΔG =∑ΔG i

[0118]

[0119]

[0120] G i is the carbon emission of each section before transformation;

[0121] ΔG i is the difference in carbon emission of each transformed section before and after transformation;

[0122] G is the total carbon emission of the section before transformation;

[0123] ΔG is the difference in carbon emission of the total section before and after transformation;

[0124] EF i CH4 is the CH4 emission factor caused by COD load of each process section, g CH4 / kg COD;

[0125] EF i CO2 is the CO2 emission factor caused by COD load of each process section, g CO2 / kg COD;

[0126] EF i N2ON2O emission factor caused by TN load of each process section, g N2O / kg TN;

[0127] R i COD COD amount of each process section, kg COD / d;

[0128] R i TN TN amount of each process section, kg TN / d;

[0129] ΔR i COD COD reduction amount of each process section, kg COD / d;

[0130] ΔR i TN TN reduction amount of each process section, kg TN / d;

[0131] 28, 256 are the ratios of unit mass CH4, N2O converted into carbon dioxide equivalent;

[0132] According to the original carbon emission amount (Q, kg CO2 / d), the emission reduction ratio (γ) is calculated as:

[0133] Based on the in-situ utilization of extracellular polymer resources, the sludge generated by the sewage treatment plant is pretreated and subjected to short-term fermentation, and the carbon source generated is used to replace the carbon source of the biological treatment denitrification stage. The carbon source replacement potential, total sludge reduction potential, economic saving potential, and carbon emission reduction potential of the sewage plant are calculated. The results are shown in Tables 1-3:

[0134] Table 1 Change in sludge concentration before and after treatment and sludge reduction ratio

[0135]

[0136] Table 2 Economic accounting results before and after modification

[0137]

[0138] Table 3 Carbon emission amount and total carbon emission amount change of each unit of the treatment process before and after modification

[0139]

[0140] As can be seen from the above, the in-situ utilization of extracellular polymer resources based on the technical scheme of the present application can achieve 100% carbon source replacement, save carbon source cost by about 1000 ￥ / d, and the remaining sludge pretreatment short-term fermentation can produce carbon source to supplement the denitrification process, which can achieve a total sludge reduction of 13.84%, and at the same time, can achieve a carbon emission reduction of 4.95% in the water plant. Therefore, it is proved that the method of in-situ utilization of extracellular polymer resources to achieve total sludge reduction and carbon emission reduction in the sewage plant is feasible and effective.

[0141] The above description is further detailed in connection with specific preferred embodiments of the present application, and it is not to be construed that the specific implementation of the present application is limited to these descriptions. For those skilled in the art to which the present application belongs, without departing from the concept of the present application, a number of simple deductions or substitutions can be made, and all of them should be considered as falling within the protection scope of the present application.

Claims

1. A method for realizing consumption reduction and emission reduction by optimizing carbon source circulation in a sewage plant, characterized in that, It comprises the following steps: Step S1, mixing the residual sludge with biological surfactant, stirring treatment, then low-temperature thermal hydrolysis treatment, and then through hydrocyclone to realize the stripping and separation of extracellular polymer; wherein the residual sludge is a mixture of biochemical sludge and materialized sludge, the treatment temperature of the low-temperature thermal hydrolysis treatment is 75-85℃, and the cycle number of the hydrocyclone is 10-15 times; Step S2, short-term fermentation of the sludge treated in step S1 to obtain carbon source rich in volatile fatty acids; Step S3, recycling sludge conversion carbon source; Step S4, putting the recycled carbon source into the biochemical denitrification treatment device to supplement the biological denitrification carbon source; In step S3, organic flocculants are used for coagulation and sedimentation of the fermented sludge, and then dewatering is performed to recover the fermentation broth rich in volatile fatty acids; The organic flocculants are cationic polyacrylamide, the molecular weight of the cationic polyacrylamide is 1000±200 million, the dewatering pressure is 0.05-0.08MPa, and the temperature of the carbon source storage tank is 4-15℃.

2. The method for realizing consumption reduction and emission reduction by optimizing carbon source circulation in sewage plants according to claim 1, characterized in that: In step S1, the concentration of the biological surfactant is 0.02-0.1g / gTSS, and the stirring treatment time is 20-60min.

3. The method for realizing consumption reduction and emission reduction by optimizing carbon source circulation in sewage plants according to claim 1, characterized in that: In step S2, the sludge treated in step S1 is added to the fermentation container for anaerobic fermentation, the fermentation time is 3-5d, the fermentation temperature is 25-45℃, and the initial pH is 8.0-9.

0.

4. The method for realizing consumption reduction and emission reduction by optimizing carbon source circulation in sewage plants according to claim 3, characterized in that: In step S3, the recycled fermentation broth rich in volatile fatty acids is stored in a carbon source storage tank equipped with a circulating water cooling and heat preservation assembly.

5. The method for realizing consumption reduction and emission reduction by optimizing carbon source circulation in sewage plants according to claim 4, characterized in that: In step S4, the denitrification potential of the recycled carbon source in step S3 is determined by a small-scale test, and then the denitrification utilization rate of the carbon source in the application environment is determined, and then the continuous flow is input into the biochemical denitrification treatment device.

Images