A sewage low-carbon treatment system based on sludge carbon enhancement and a method thereof

Abstract

The application discloses a sewage low-carbon treatment system based on sludge carbon reinforcement and a method thereof, and belongs to the technical field of sewage treatment. The system comprises an adsorption tank, a reaction tank, a sedimentation tank and an aeration tank. The adsorption tank is communicated with a sewage inlet pipeline, and an outlet pipeline thereof is communicated with the sedimentation tank through the reaction tank. The upper part of the sedimentation tank is provided with a supernatant discharge pipe, and the bottom part is provided with a sludge discharge pipe and a sludge return pipe. The sludge return pipe is communicated with the reaction tank through the aeration tank, the sludge discharge pipe is communicated with a sludge treatment and sludge carbon preparation module, and the generated sludge carbon is used for being put into the adsorption tank. The application utilizes sludge carbon to adsorb ammonia nitrogen in sewage, improves the carbon-nitrogen ratio of sewage, reduces the energy consumption required by aeration, and reduces the carbon source required by denitrification. Through pre-aeration activation of sludge, sludge carbon is used to assist in sludge-water separation. Compared with a common activated sludge process, the application provides an activated sludge with a resource utilization path, reduces the carbon source required for denitrification, and saves energy and reduces consumption.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of sewage treatment, and particularly relates to a sewage low-carbon treatment system based on sludge carbon reinforcement and a method thereof. BACKGROUND

[0002] More than 80% of China's urban sewage treatment plants use biochemical treatment processes based on activated sludge method, such as A 2 O, etc., to remove nitrogen pollutants through nitrification-denitrification reaction. Due to the characteristics of low carbon-nitrogen ratio (C / N < 3) of urban sewage, there are problems such as insufficient available carbon source during biochemical denitrification, which leads to difficulty in meeting the TN standard. Most sewage treatment plants use additional carbon source (such as sodium acetate) as electron donor to make the denitrification process proceed smoothly and ensure that the TN standard is met. This not only greatly increases the operating cost, but also increases the greenhouse gas (CO2) emissions. Under the policy background of energy saving and emission reduction and green development, in order to meet the increasingly stringent discharge standards of sewage plants, it is urgent to develop new low-carbon sewage treatment processes.

[0003] At the same time, the increasing scale of urban sewage treatment in China has led to a significant increase in sludge production. According to statistics, the sludge production in China in 2019 exceeded 600 million tons (based on 80% moisture content). Due to the high moisture content of sludge, excessive heavy metals and other toxic and harmful substances, the commonly used treatment and disposal methods (land use, incineration, sanitary landfill, etc.) have encountered different degrees of obstacles. Sludge carbon, as a carbonaceous material produced by sludge pyrolysis, has the advantages of large specific surface area and strong adsorption capacity. Existing research shows that sludge carbon has strong adsorption capacity for a variety of pollutants, and the metals in sludge carbon can act as catalytic sites to make it act as a catalyst. The excellent properties of sludge carbon make it have broad application prospects in sludge treatment and disposal and resource utilization. Chinese invention patent CN115709052A discloses a carbon nanotube modified sludge carbon material, which is obtained by catalytic pyrolysis of a mixture of sludge-based activated carbon, iron-based catalyst and polypropylene plastic, and used as an adsorbent to remove various organic pollutants in biogas liquid. Chinese invention patent CN115108705A prepares a modified magnetic sludge carbon, which is obtained by pyrolysis of iron-containing sludge cake, and then immersed in potassium hydroxide solution to obtain modified magnetic sludge carbon, which is used to catalyze persulfate to generate sulfate radicals, hydroxyl radicals and superoxide radicals to degrade tetracycline. The above methods still have problems such as complex preparation process and limited use scenarios, which makes it difficult to promote the further resource utilization of sludge carbon.

[0004] To address the problems of low carbon-nitrogen ratio of urban sewage and promote sludge resource utilization, the present application develops a sewage low-carbon treatment system based on sludge carbon reinforcement and a method thereof. SUMMARY

[0005] The present application aims to overcome the defects existing in the current activated sludge process, reduce the addition of additional carbon source for enhanced denitrification, and promote the resource utilization of sludge, and provide a sewage low-carbon treatment system based on sludge carbon enhancement and a method thereof.

[0006] The specific technical solutions adopted by the present application are as follows:

[0007] In a first aspect, the present application provides a sewage low-carbon treatment system based on sludge carbon enhancement, comprising an adsorption tank, a reaction tank, a sedimentation tank and an aeration tank.

[0008] The adsorption tank is in communication with a sewage inlet pipeline, and its outlet pipeline is in communication with the sedimentation tank through the reaction tank; the upper part of the sedimentation tank is provided with a supernatant discharge pipe, and the bottom part is provided with a sludge discharge pipe and a sludge return pipe; the sludge return pipe is in communication with the reaction tank through the aeration tank, and the sludge discharge pipe is in communication with a sludge treatment and sludge carbon preparation module, and the generated sludge carbon is used for input into the adsorption tank.

[0009] In a second aspect, the present application provides a sewage treatment method using the sewage low-carbon treatment system based on sludge carbon enhancement of the first aspect, which is specifically as follows:

[0010] S1: After the removal of large particle impurities through primary treatment, domestic sewage enters the adsorption tank together with sludge carbon, and is mixed and reacted; in this process, a large amount of ammonia nitrogen can be adsorbed onto the surface and pore structure of the sludge carbon, improving the carbon-nitrogen ratio of the sewage;

[0011] S2: The effluent of the adsorption tank and the activated sludge after pre-aeration in the aeration tank enter the reaction tank together, are mixed and reacted, and the activated sludge is used to capture sludge carbon, other organic matters and part of ammonia nitrogen;

[0012] S3: The effluent of the reaction tank enters the sedimentation tank for sludge-water separation, and the supernatant generated enters a tertiary treatment process; part of the sludge generated returns to the reaction tank after being activated by oxygen in the aeration tank through the sludge return pipe, and the other part is discharged through the sludge discharge pipe to prepare sludge carbon as a reinforcing agent for input into the adsorption tank.

[0013] As a preferred, in the step S1, the addition ratio of sludge carbon to sewage is 1.5-3g / L, the residence time of sewage in the adsorption tank is 0.5-1h, and the stirring power of the stirrer in the adsorption tank is not less than 1.0W / m 3 .

[0014] Preferably, in the step S2, the sludge concentration in the reaction tank is 3-4 g / L, the sludge load is 0.5-2 kgBOD / (kgMLSS·d), the residence time of the sewage in the reaction tank is 0.5-1 h, and the stirring intensity of the stirrer in the reaction tank is not more than 1.5 W / m 3 .

[0015] Preferably, in the step S3, the sludge settling time of the sedimentation tank is controlled to be 0.5-1.5 h.

[0016] Preferably, in the step S3, the sludge reflux ratio is 0.4-0.8, the dissolved oxygen of the sludge after aeration in the aeration tank is controlled to be more than 2 mg / L, and the residence time of the sludge in the aeration tank is 0.5-1 h.

[0017] Preferably, in the step S3, the sludge discharged through the sludge discharge pipe is first subjected to concentration, anaerobic digestion and deep dewatering treatment in sequence to make the water content of the sludge ≤40%, and then the sludge is added into a reaction kettle for hydrothermal carbonization treatment to obtain hydrothermal carbon with rich oxygen-containing functional groups; the hydrothermal carbon is collected by vacuum filtration and then dried, and then pyrolyzed under anoxic conditions to obtain sludge carbon.

[0018] Further, in the hydrothermal carbonization treatment, the addition ratio of the sludge to water is 1 g:(5-8) L, the temperature is controlled to be 180-200℃, and the reaction time is 2 h.

[0019] Further, the drying temperature is 105℃, and the drying time is 2 h.

[0020] Further, the pyrolysis temperature is 350-500℃, and the pyrolysis time is 2 h.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] 1) The sludge carbon has high adsorption capacity for ammonia nitrogen, which is trapped on the surface and pore structure of the sludge carbon, reducing the microbial uptake and nitrification of ammonia nitrogen, improving the carbon-nitrogen ratio of the sewage, saving the carbon source required for aeration and denitrification, and improving the activity of the functional enzymes related to denitrification, thereby facilitating the smooth progress of the denitrification process and reducing the generation of greenhouse gas N2O;

[0023] 2) The adsorption and biological flocculation capacity of the activated sludge is improved by pre-aeration of the sludge, and the activated sludge is used to capture the sludge carbon to separate the sludge carbon from the sewage;

[0024] 3) By shortening the residence time of the reaction tank and reducing the dissolved oxygen content, most of the organic matter in the sewage is adsorbed and intracellularly stored by the sludge, reducing the consumption of organic matter by endogenous respiration and reducing the emission of CO2;

[0025] 4) Sludge is made into sludge charcoal and used as a wastewater treatment enhancer. It is then separated from wastewater in a secondary sedimentation tank and further treated together with sludge. Sludge charcoal can act as an electron shuttle to enhance the anaerobic digestion performance of sludge, promote the resource utilization and energy conversion of organic matter captured by sludge, and the digested and dewatered sludge can continue to be used as raw material to prepare sludge charcoal. This invention provides a way for the long-term utilization and resource utilization of sludge. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the processing system of the present invention;

[0027] Figure 2 R during the operation of the reaction system in the embodiment BC and Control group MLVSS(a) and SVI 50 (b) change;

[0028] Figure 3 In the embodiment R BC (a) and Control(b) groups for NH4 + and TN removal performance;

[0029] Figure 4 In the embodiment R BC Comparison of the activities of key denitrification functional enzymes in activated sludge of the Control group. Detailed Implementation

[0030] The present invention will be further described and illustrated below with reference to the accompanying drawings and specific embodiments. The technical features of each embodiment of the present invention can be combined accordingly, provided that there is no mutual conflict.

[0031] In view of the problems of high energy consumption and high carbon emissions in urban domestic sewage treatment, this invention provides a low-carbon sewage treatment system based on sludge carbon enhancement, such as... Figure 1 As shown in the diagram, the treatment system mainly includes an adsorption tank, a reaction tank, a sedimentation tank, and an aeration tank. Specifically, the adsorption tank is connected to the wastewater inlet pipe, its outlet pipe is connected to the reaction tank, and the reaction tank's outlet pipe is connected to the sedimentation tank. The sedimentation tank has a supernatant discharge pipe at the top and a sludge discharge pipe and a sludge return pipe at the bottom. The sludge return pipe is connected to the aeration tank, and the aeration tank is connected to the reaction tank. The sludge discharge pipe is connected to the sludge treatment and sludge carbon preparation module, which processes the sludge to prepare sludge carbon, which is then fed into the adsorption tank.

[0032] The wastewater treatment method utilizing the above-described sludge-char-enhanced low-carbon wastewater treatment system of the present invention mainly includes sludge char preparation, sludge char pretreatment, mixing reaction, sedimentation separation, and aeration activation, as detailed below:

[0033] S1: The primary treated domestic sewage and sludge carbon are mixed in the adsorption tank to fully react.

[0034] In the process, the sludge carbon with strong adsorption capacity and good biocompatibility is prepared by hydrothermal and anoxic pyrolysis of the residual sludge, and is mixed with the domestic sewage to be treated in the adsorption tank. Since the adsorption capacity of the sludge carbon for ammonia nitrogen is significantly higher than that of the carbon-containing organic matter, a large amount of ammonia nitrogen can be adsorbed to the surface and pore structure of the sludge carbon, thereby improving the carbon-nitrogen ratio of the sewage.

[0035] In actual application, the primary treatment mainly refers to the treatment of coarse and fine screens to remove large-particle impurities in the wastewater.

[0036] As a preferred treatment mode in actual application, the addition ratio of the sludge carbon to the sewage is 1.5-3 g / L, the residence time of the sewage in the adsorption tank is 0.5-1 h, and the stirring power of the stirrer in the adsorption tank is not less than 1.0 W / m 3 .

[0037] S2: The effluent from the adsorption tank and the activated sludge pre-aerated in the aeration tank are mixed in the reaction tank to fully react.

[0038] In the process, the activated sludge is pre-aerated to be in a "starvation" state, which can significantly improve the adsorption and biological flocculation capacity of the sludge; the activated sludge after aeration is mixed with the sewage with sludge carbon to capture the sludge carbon and other organic matter and part of the ammonia nitrogen.

[0039] As a preferred treatment mode in actual application, the sludge concentration in the reaction tank is 3-4 g / L, the sludge loading is 0.5-2 kgBOD / (kgMLSS·d), the residence time of the sewage in the reaction tank is 0.5-1 h, and the stirring intensity of the stirrer in the reaction tank is not more than 1.5 W / m 3 .

[0040] S3: The effluent from the reaction tank is subjected to sludge-water separation in the sedimentation tank.

[0041] As a preferred treatment mode in actual application, the sludge settling time of the sedimentation tank is controlled to be 0.5-1.5 h to separate the sludge mixed with the sludge carbon and the sewage.

[0042] S31: The supernatant generated is subjected to the tertiary treatment process.

[0043] In actual application, the tertiary treatment process can be selected according to the actual water quality of the supernatant, for example, to perform denitrification and phosphorus removal treatment.

[0044] S3: A part of the generated sludge is returned to the aeration tank through a sludge return pipe for oxygenation and activation, and then returned to the reaction tank. That is, a part of the sludge is returned to the aeration tank for normal growth and reproduction.

[0045] As a preferred processing mode in actual application, the sludge return ratio is 0.4-0.8, the dissolved oxygen of the sludge after aeration in the aeration tank is controlled to be greater than or equal to 2 mg / L, and the residence time of the sludge in the aeration tank is 0.5-1 h.

[0046] S33: Another part of the generated sludge is discharged through a sludge discharge pipe, and then prepared into sludge carbon as a reinforcing agent and fed into the adsorption tank.

[0047] As a preferred processing mode in actual application, the sludge discharged through the sludge discharge pipe is first sequentially subjected to concentration, anaerobic digestion and deep dewatering treatment to make the water content of the sludge be less than or equal to 40%, and then the sludge is added into a reaction kettle for hydrothermal carbonization treatment to obtain hydrothermal carbon with rich oxygen-containing functional groups; the hydrothermal carbon is collected by vacuum filtration and then dried, and then pyrolyzed under anoxic conditions to obtain sludge carbon.

[0048] Further, the preferred parameters of the above steps are: in the hydrothermal carbonization treatment, the addition ratio of the sludge to water is 1 g:(5-8) L, the temperature is controlled to be 180-200°C, and the reaction time is 2 h; the drying temperature is 105°C, the drying time is 2 h; the pyrolysis temperature is 350-500°C, and the pyrolysis time is 2 h.

[0049] EMBODIMENT

[0050] In this embodiment, the residual sludge of a sewage treatment plant (a certain town sewage treatment plant in Hangzhou) is used as the inoculated sludge of the reaction tank and the raw material for preparing sludge carbon, the inoculated MLSS is 4000±100 mg / L, the MLVSS is 2000±60 mg / L, and the SVI30 is 48 mL / g. The artificial simulated wastewater with sodium acetate and ammonium chloride as the only carbon source and nitrogen source is treated, the influent COD is 300±40 mg / L, and the C / N ratio is maintained at 5:1. The specific surface area of the sludge carbon prepared by hydrothermal-anoxic pyrolysis is 66.16 m 2 / g, the pore volume is 0.08010 cm 3 / g; the effective volume of the adsorption tank and the reaction tank is 4.0 L; the sludge carbon addition ratio in the pretreatment link (i.e. the adsorption tank) is 3.0 g / L, the residence time is 1.0 h, and the stirring intensity is 2.0 W / m 3 ; then the sludge is fed into the reaction tank, the sludge concentration is controlled to be 3500 mg / L, the residence time is 1.0 h, and the stirring intensity is 1.0 W / m 3 ; after the reaction is completed, the sludge is fed into the sedimentation tank, the sedimentation time is 1.0 h; the sludge return ratio is controlled to be 0.5, the aeration intensity is 5.0 L / min, and the aeration residence time is 0.5 h; and the average treatment capacity is 1.14 L / h.

[0051] like Figure 2 As shown, during the operating cycle, the sludge MLVSS gradually increased from 2000 mg / L to 6125 mg / L (R). BC The concentration of sludge in the control group (Rc) was 5148 mg / L (Control), which is better than that in the experimental group (Control). This indicates that the sludge settling performance is improving, which helps to assist in the addition of sludge-charred material for sludge-water separation. The control group was a normal activated sludge SBR process without the addition of sludge-charred material, and the treatment steps were the same as those in the experimental group (Rc). BC Consistent.

[0052] like Figure 3 As shown, under conditions of a low carbon-to-nitrogen ratio (C / N = 5), R BC NH4 + The removal efficiencies of -N and TN increased to 98.2±1.2% and 84.6±1.4%, respectively, after 15 days, and then remained stable. In contrast, the pollutant removal rates of the control group did not stabilize until 25 days later, with NH4... + -N removal rate was 99.1±1.5%, compared with R BC No difference, but R C The TN removal rate was 70.2 ± 0.3%, significantly lower than that of R. BC The results showed that the addition of sludge-based biochar enabled the reactor to quickly reach a stable ammonia nitrogen removal level, while also improving the denitrification performance of microorganisms, thus increasing the total nitrogen removal rate by 14.4 ± 1.2%.

[0053] like Figure 4 As shown, the activities of key denitrification enzymes (AMO, NXR, NAP, NIR) in the activated sludge of the experimental group increased by 18.9%, 32.7%, 72.6%, and 35.4% respectively compared with the control group. This indicates that the addition of sludge carbon significantly improved the activity of key denitrification enzymes, which is conducive to the smooth progress of the denitrification process and reduces the generation of N2O.

[0054] This invention utilizes sludge activated carbon to adsorb ammonia nitrogen in wastewater, improving the carbon-to-nitrogen ratio of wastewater, reducing the energy consumption required for aeration, and lowering the carbon source addition required for denitrification. By pre-aeration and activation of sludge, sludge activated carbon is assisted in achieving sludge-water separation. Compared with ordinary activated sludge processes, this invention provides a resource utilization path for activated sludge, reduces the carbon source addition required for denitrification, and saves energy and reduces consumption.

[0055] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained through equivalent substitution or transformation fall within the protection scope of the present invention.

Claims

1. A wastewater treatment method utilizing a sludge-char-enhanced low-carbon wastewater treatment system, characterized in that, The wastewater low-carbon treatment system based on sludge carbon enhancement includes an adsorption tank, a reaction tank, a sedimentation tank, and an aeration tank. The adsorption tank is connected to the wastewater inlet pipeline, and its outlet pipeline is connected to the sedimentation tank after passing through the reaction tank. The sedimentation tank is equipped with a supernatant discharge pipe at the top and a sludge discharge pipe and a sludge return pipe at the bottom. The sludge return pipe is connected to the reaction tank after passing through the aeration tank, and the sludge discharge pipe is connected to the sludge treatment and sludge carbon preparation module, and the generated sludge carbon is fed into the adsorption tank. The wastewater treatment method is as follows: S1: Domestic sewage, after primary treatment to remove large particulate impurities, enters the adsorption tank together with sludge and carbon and is mixed to ensure a full reaction. During this process, sludge and carbon can adsorb a large amount of ammonia nitrogen onto the surface and pore structure of the sludge and carbon, thereby improving the carbon-nitrogen ratio of the sewage. S2: The effluent from the adsorption tank and the activated sludge that has been pre-aerated in the aeration tank are brought into the reaction tank together and mixed to ensure a full reaction. The activated sludge is used to capture sludge carbon and other organic matter and some ammonia nitrogen. S3: The effluent from the reaction tank enters the sedimentation tank for mud-water separation, and the resulting supernatant enters the tertiary treatment process. Part of the generated sludge is returned to the aeration tank through the sludge return pipe for oxygenation and activation, and then returned to the reaction tank. The other part is discharged through the sludge discharge pipe and then used to prepare sludge carbon as an adsorption agent. In step S2, the sludge concentration in the reaction tank is 3-4 g / L, the sludge load is 0.5-2 kg BOD / (kg MLSS·d), the wastewater retention time in the reaction tank is 0.5-1 h, and the stirring intensity of the agitator in the reaction tank does not exceed 1.5 W / m. 3 ; In step S3, the sludge return ratio is 0.4-0.8, the dissolved oxygen of the sludge after aeration in the aeration tank is controlled above 2 mg / L, and the sludge residence time in the aeration tank is 0.5-1 h. In step S3, the sludge discharged through the sludge discharge pipe is first subjected to concentration, anaerobic digestion and deep dewatering treatment in sequence to make the sludge moisture content ≤40%. Then, the sludge is added to the reactor for hydrothermal carbonization treatment to obtain hydrothermal carbon rich in oxygen functional groups. The hydrothermal carbon is collected by vacuum filtration and dried. Then, it is pyrolyzed under anaerobic conditions to obtain sludge carbon.

2. The wastewater treatment method according to claim 1, characterized in that, In step S1, the dosage ratio of sludge-char to wastewater is 1.5-3 g / L, the retention time of wastewater in the adsorption tank is 0.5-1 h, and the stirring power of the agitator in the adsorption tank is not less than 1.0 W / m³. 3 .

3. The wastewater treatment method according to claim 1, characterized in that, In step S3, the sludge settling time in the sedimentation tank is controlled at 0.5-1.5h.

4. The wastewater treatment method according to claim 3, characterized in that, In the hydrothermal carbonization treatment, the ratio of sludge to water is 1g:(5-8)L, the temperature is controlled at 180-200℃, and the reaction time is 2h.

5. The wastewater treatment method according to claim 3, characterized in that, The drying temperature is 105℃ and the drying time is 2 hours.

6. The wastewater treatment method according to claim 3, characterized in that, The pyrolysis temperature is 350-500℃, and the pyrolysis time is 2 hours.

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