Urban sewage treatment device and technology based on resource and energy recovery

Abstract

The invention discloses an urban sewage treatment device and process based on resource and energy recovery. The device comprises a coagulating sedimentation unit, a nitrogen and phosphorus adsorption unit, a biological filter unit, a sludge anaerobic digestion unit, a sewage source heat pump unit, a sludge concentration unit, a digested sludge resource recycling unit, a flocculant dosing tank, a first sewage adjusting tank and a second sewage adjusting tank. The coagulating sedimentation unit captures organic matters and changes the carbon flow direction, the sludge anaerobic digestion unit recovers chemical energy in sewage, and the nitrogen and phosphorus adsorption unit efficiently recovers nitrogen and phosphorus resources in the sewage. The synergistic effect that the digested sludge resource recycling unit recycles iron and phosphorus resources in digested sludge and the sewage source heat pump unit recycles tail water waste heat is achieved, and efficient removal of pollutants and efficient recycling of nitrogen, phosphorus and iron resources and energy are achieved. Therefore, the problems of high energy consumption, high material consumption and waste caused by the fact that resources and energy in sewage and sludge are not effectively recycled in the traditional town sewage treatment process at present are solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of urban domestic sewage treatment, and particularly relates to a device and process for treating urban sewage based on resource and energy recovery. BACKGROUND

[0002] Urban sewage treatment is an important part of environmental protection, and its goal is to effectively remove pollutants in water bodies and protect water environmental quality. Currently, traditional activated sludge methods such as A 2 O process and oxidation ditch process are mainly used to remove organic matter and nitrogen and phosphorus in urban domestic sewage treatment. That is, through the assimilation and dissimilation of microorganisms, pollutants are converted into byproducts such as carbon dioxide, nitrogen and sludge.

[0003] However, the traditional urban sewage treatment process usually consumes a large amount of external energy and chemicals, and the overall energy demand for sewage treatment reaches 0.3-0.6 kWh / m 3 , especially in the aeration process of biological oxidation of organic matter and nitrogen-containing compounds, the energy consumption accounts for as high as 50%. This method actually realizes the transfer of pollution form by high energy consumption and high material consumption, i.e. converting water pollution into air pollution and sludge pollution, which is equivalent to "energy consumption" and "pollution transfer", which is contrary to the concept of sustainable development advocated today.

[0004] At the same time, the domestic sewage contains huge resource and energy potential which has not been effectively utilized. For example, the chemical energy contained in the organic matter in sewage is 9-10 times the energy consumed in sewage treatment. More importantly, sewage is also rich in valuable nitrogen and phosphorus resources. If these resources can be recovered, it will not only help to prevent water eutrophication, delay the speed of phosphorus resource shortage, and reduce carbon emissions caused by phosphorus mining, but also effectively reduce the aeration energy consumption and carbon source dosage required in the denitrification process, thereby reducing the treatment cost and carbon emissions. In addition, sewage has stable flow, sufficient water quantity and residual heat, which contains considerable heat and has great energy-saving potential.

[0005] Therefore, in the existing urban sewage treatment process, high energy consumption and high material consumption will increase the treatment cost and carbon emissions, and the recovery efficiency of organic energy and inorganic resources in sewage is low, and a large amount of unrecovered resources is lost with sludge or effluent, which cannot fully utilize the resource and energy value in sewage. SUMMARY

[0006] In view of the problems in the prior art, the present application provides a municipal wastewater treatment device and process based on resource and energy recovery, aiming to realize efficient removal of pollutants and efficient recovery and utilization of nitrogen, phosphorus and iron resources and energy through the synergistic effect of the coagulation and sedimentation unit for capturing organic matter and changing the carbon flow, the sludge anaerobic digestion unit for realizing chemical energy recovery in wastewater, the nitrogen and phosphorus adsorption unit for efficiently recovering nitrogen and phosphorus resources, the digested sludge resource recovery and utilization unit for realizing recovery and resource utilization of phosphorus and iron resources in the digested sludge, and the wastewater source heat pump unit for recovering waste heat of tail water.

[0007] To achieve the above object, the present application adopts the following technical solutions:

[0008] In a first aspect, the present application provides a municipal wastewater treatment device based on resource and energy recovery.

[0009] A municipal wastewater treatment device based on resource and energy recovery comprises a coagulation and sedimentation unit, a nitrogen and phosphorus adsorption unit, a biological filter unit, a sludge anaerobic digestion unit, a digested sludge resource recovery and utilization unit, a wastewater source heat pump unit, a sludge concentration unit, a flocculant dosing tank, a first wastewater conditioning tank and a second wastewater conditioning tank, wherein:

[0010] The coagulation and sedimentation unit is provided with a water inlet, a supernatant outlet and a sludge outlet, the water inlet is connected with the first wastewater conditioning tank and the flocculant dosing tank, the supernatant outlet is connected with the inlet of the second wastewater conditioning tank, and the sludge outlet is connected with the inlet of the sludge concentration unit;

[0011] The outlet of the sludge concentration unit is connected with the inlet of the sludge anaerobic digestion unit;

[0012] The sludge anaerobic digestion unit is provided with a biogas slurry outlet and a sludge outlet, the biogas slurry outlet is connected with the inlet of the second wastewater conditioning tank, and the sludge outlet is connected with the inlet of the digested sludge resource recovery and utilization unit;

[0013] The digested sludge resource recovery and utilization unit comprises an acidification reaction tank, a blue vitriol generation reaction tank, a magnetic separation unit and a micro-aeration oxidation reaction tank;

[0014] The outlet of the nitrogen and phosphorus adsorption unit is connected with the inlet of the biological filter unit;

[0015] The outlet of the nitrogen and phosphorus adsorption unit is connected with the inlet of the biological filter unit;

[0016] The outlet of the biological filter unit is connected with the wastewater source heat pump unit.

[0017] As a further improvement, a pretreatment unit is also included, which includes a screen and a grit chamber arranged in sequence, with the outlet of the grit chamber connected to the inlet of the first wastewater equalization tank.

[0018] As a further improvement, an aeration device is installed in the first sewage equalization tank.

[0019] As a further improvement, the sludge anaerobic digestion unit is equipped with an anaerobic digester, which has an agitator inside, an insulation layer on its surface, and a stainless steel heating coil inside.

[0020] As a further improvement, the wastewater source heat pump unit is connected to a stainless steel heating coil for heating and insulation of the sludge anaerobic digestion unit.

[0021] As a further improvement, the nitrogen and phosphorus adsorption unit is formed by connecting two tanks of the same volume in series. Furthermore, each tank is divided into multiple compartments, and a water distribution method of alternating top and bottom water inlet is adopted.

[0022] Secondly, the present invention provides an urban wastewater treatment process based on resource and energy recovery.

[0023] A municipal wastewater treatment process based on resource and energy recovery includes the following steps:

[0024] Redox state adjustment before coagulation and sedimentation: The sewage in the first sewage equalization tank is aerated and adjusted to regulate the dissolved oxygen concentration of the water, so as to create an oxidation environment conducive to the coagulation and sedimentation reaction, thereby inhibiting the conversion of ferric iron to ferrous iron during coagulation and sedimentation.

[0025] Coagulation and sedimentation: The wastewater that has been treated by aeration in the first wastewater equalization tank is mixed with the iron-based covalent composite flocculant in the flocculant dosing tank and then enters the coagulation and sedimentation unit for coagulation and sedimentation. The suspended solids, particulate organic matter and phosphorus in the wastewater form flocs and settle. The supernatant of the coagulation and sedimentation unit enters the second wastewater equalization tank and the captured sludge enters the sludge thickening unit.

[0026] Sludge thickening and anaerobic digestion: The sludge thickening unit performs gravity thickening and sedimentation on the captured sludge, which is then sent to the sludge anaerobic digestion unit for mesophilic anaerobic digestion to produce biogas with high methane content; the biogas slurry produced by the sludge anaerobic digestion unit enters the second wastewater equalization tank.

[0027] Sludge Resource Recovery and Recycling: The iron- and phosphorus-rich sludge after anaerobic digestion enters the sludge resource recovery and recycling unit. In the acidification reaction tank, the iron and phosphorus in the sludge are released into the liquid phase through acidification. After solid-liquid separation, the pH value of the acidified supernatant is adjusted, and the dissolved ferrous iron reacts with phosphorus in the lapis lazuli formation reaction tank to form lapis lazuli precipitate. The lapis lazuli is then recovered in the magnetic separation unit using magnetic separation technology. The supernatant after magnetic separation is treated with micro-aeration in the micro-aeration oxidation reaction tank to convert the ferrous iron in it into ferric iron, and then formulated into an iron-based covalent composite flocculant, which is reused in the coagulation and sedimentation step.

[0028] Nitrogen and phosphorus adsorption: The mixed liquor in the second wastewater equalization tank flows into the nitrogen and phosphorus adsorption unit, where the adsorption filter media selectively adsorbs and recovers nitrogen and phosphorus from the wastewater mixed liquor; the effluent from the nitrogen and phosphorus adsorption unit enters the biological filter unit.

[0029] Advanced treatment via biological filter: The biological filter unit further removes residual organic matter and phosphorus through the biochemical action of microorganisms, ensuring that the effluent meets discharge standards;

[0030] Wastewater heat recovery: The effluent from the biological filter unit enters the wastewater source heat pump unit to recover the residual heat energy in the wastewater. The recovered heat energy is used to compensate for the heat consumption of the process system.

[0031] Preferably, in the step of adjusting the redox state before coagulation and sedimentation treatment, the wastewater is first treated by passing it through a screen and a grit chamber, and then enters the first wastewater equalization tank. The first wastewater equalization tank is used for aeration and equalization treatment to control the dissolved oxygen concentration in the wastewater to 0.5-1 mg / L.

[0032] Preferably, in the coagulation and sedimentation step, the dosage of the iron-based covalent composite flocculant in the coagulation and sedimentation unit is 20±2 mg / L (calculated as Fe). The iron-based covalent composite flocculant is a covalent hybrid flocculant prepared by hydrolysis copolymerization using APTES as the silicon source and FeCl3 as the inorganic metal salt, with alkaline solution slowly added at room temperature.

[0033] Preferably, the mesophilic anaerobic digestion treatment is carried out in the anaerobic digester of the sludge anaerobic digestion unit, and the temperature inside the tank is controlled at 35±1℃, pH at 6.9-7.2, oxidation-reduction potential (ORP) at -240mv~-210mv, and solids residence time at 5-6 days.

[0034] Preferably, in the step of resource recovery and utilization of digested sludge, an acidic regulator is added to the digested sludge to adjust the pH to 2, and the mixture is stirred for 60 minutes to dissolve and release the iron and phosphorus in the sludge into the liquid phase.

[0035] Preferably, in the step of resource recovery and utilization of digested sludge, under the condition that the dissolved oxygen concentration is not higher than 0.2 mg / L, the reaction conditions of the obtained acidified supernatant are adjusted. By controlling the pH value to 6.5-7.5, the reactivity of ferrous iron in the system is maintained, so that dissolved phosphorus reacts with ferrous iron to form lapis lazuli precipitate. Utilizing the magnetic characteristics of lapis lazuli, phosphorus-rich lapis lazuli product is obtained by magnetic separation.

[0036] Preferably, in the nitrogen and phosphorus adsorption step, the adsorption filter material in the nitrogen and phosphorus adsorption unit is modified biochar based on sludge. The modified biochar based on sludge is used to selectively adsorb ammonia nitrogen and phosphate. The adsorption filter material after adsorption saturation is used as a soil conditioner or slow-release fertilizer.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] 1. The coagulation and sedimentation unit of this invention effectively alters the flow of carbon, capturing organic matter into the sludge, achieving an average COD capture rate of up to 62.57% in the influent. The sludge then enters the anaerobic digestion unit for mesophilic digestion, producing high-quality biogas with approximately 80% methane content. This biogas can be used for combined heat and power generation, effectively compensating for the electricity and heat consumption of the wastewater treatment process, fundamentally reducing the wastewater treatment plant's reliance on external energy, and achieving efficient recovery of chemical energy from wastewater and energy self-sufficiency.

[0039] 2. The nitrogen and phosphorus adsorption unit of this invention utilizes modified biochar based on biogas residue as the adsorption filter media, which can efficiently and selectively adsorb and recover nitrogen and phosphorus resources from wastewater. Examples show that the cumulative adsorption of TN and TP in the influent reaches 52% and 28.5%, respectively. The saturated filter media can be used as a soil conditioner or slow-release fertilizer, effectively alleviating the pressure of phosphorus resource scarcity and reducing carbon emissions from phosphate mining. It also avoids the aeration energy consumption and carbon source addition required by traditional denitrification processes, significantly reducing material and energy consumption.

[0040] 3. The sludge resource recycling unit of this invention achieves effective release of iron and phosphorus from the sludge through acidification treatment; generates blue iron ore by adjusting controlled conditions, and achieves efficient solid-liquid separation and recovery of phosphorus by magnetic separation; converts the remaining iron into ferric iron through micro-aeration and reuses it in the preparation of composite flocculants, realizing closed-loop recycling of iron salts.

[0041] 4. The wastewater source heat pump unit of this invention can efficiently recover residual heat energy from the effluent after biological filter treatment, with a recovery rate of over 75%. The recovered heat energy can be preferentially used to meet the heat consumption requirements of the process itself, especially the heating and insulation of the anaerobic digestion unit, thereby further reducing operating costs. In addition, the waste heat can also be used as an "energy plant" to output energy to the outside, improving the efficiency of waste heat energy recovery and comprehensive utilization.

[0042] In summary, this invention provides a municipal wastewater treatment solution that combines efficient pollutant removal, efficient resource and energy recovery, low energy consumption, low material consumption, and low carbon emissions through the synergistic effect of multiple units, including carbon flow optimization, anaerobic digestion for methanogenesis, nitrogen and phosphorus resource recovery, effluent waste heat recovery, and resource recycling of digested sludge. This reduces the external energy and reagent consumption required for pollutant transformation at the source. (Based on a 20,000 m³...) 3 Taking a scale of / d as an example, the electricity consumption per ton of water can be as low as approximately 0.21 kWh / m². 3 It is far lower than that of traditional processes. Attached Figure Description

[0043] Figure 1 This is a plan view of an urban wastewater treatment process based on resource and energy recovery according to the present invention.

[0044] Figure 2 This is a flowchart of an urban wastewater treatment process based on resource and energy recovery according to the present invention.

[0045] In the diagram: 1. Coagulation and sedimentation unit; 2. Nitrogen and phosphorus adsorption unit; 3. Biological filter unit; 4. Anaerobic sludge digestion unit; 5. Digested sludge resource recycling unit; 6. Wastewater source heat pump unit; 7. Sludge thickening unit; 8. Flocculant dosing tank; 9. First wastewater equalization tank; 10. Second wastewater equalization tank. Detailed Implementation

[0046] To better understand the content of this invention, specific embodiments will be used to further illustrate the invention below. The following embodiments are based on the technology of this invention and provide detailed implementation methods and operating steps. However, the scope of protection of this invention is not limited to the following embodiments; that is, all other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0047] The present invention provides an urban sewage treatment device based on resource and energy recovery, comprising a coagulation and sedimentation unit 1, a nitrogen and phosphorus adsorption unit 2, a biological filter unit 3, an anaerobic sludge digestion unit 4, a digested sludge resource recovery and utilization unit 5, a sewage source heat pump unit 6, a sludge thickening unit 7, a flocculant dosing tank 8, a first sewage equalization tank 9, and a second sewage equalization tank 10. The coagulation and sedimentation unit 1 is equipped with an inlet, a supernatant outlet, and a sludge outlet. The inlet is connected to the first wastewater equalization tank 9 and the flocculant dosing tank 8. The supernatant outlet is connected to the inlet of the second wastewater equalization tank 10. The sludge outlet is connected to the inlet of the sludge thickening unit 7. The outlet of the sludge thickening unit 7 is connected to the inlet of the sludge anaerobic digestion unit 4. The sludge anaerobic digestion unit 4 is equipped with a biogas slurry outlet and a sludge outlet. The biogas slurry outlet is connected to the inlet of the second wastewater equalization tank 10. The sludge outlet is connected to the inlet of the digested sludge resource recovery and utilization unit 5. The digested sludge resource recovery and utilization unit 5 includes an acidification reaction tank, a blue iron ore generation reaction tank, a magnetic separation unit, and a micro-aeration oxidation reaction tank. The outlet of the second wastewater equalization tank 10 is connected to the inlet of the nitrogen and phosphorus adsorption unit 2. The outlet of the nitrogen and phosphorus adsorption unit 2 is connected to the inlet of the biological filter unit 3. The outlet of the biological filter unit 3 is connected to the wastewater source heat pump unit 6.

[0048] The system includes a coagulation and sedimentation unit 1 for efficiently capturing suspended solids, particulate organic matter, and phosphorus in wastewater; an anaerobic sludge digestion unit 4 for mesophilic digestion of the captured sludge to produce biogas with high methane content, thereby recovering chemical energy from wastewater and reducing sludge production; a sludge resource recovery and recycling unit 5 for efficiently recovering phosphorus and iron resources from the digested sludge and realizing closed-loop recycling of iron salts; a nitrogen and phosphorus adsorption unit 2 for efficiently recovering nitrogen and phosphorus resources using modified biochar based on biogas residue; a biofilter unit 3 for deep treatment of the effluent from the nitrogen and phosphorus adsorption unit 2 to ensure compliance with discharge standards; and finally, a wastewater source heat pump unit 6 for recovering residual heat energy from the biofilter effluent for process heating or external energy supply.

[0049] In some preferred embodiments of the present invention, the device further includes a pretreatment unit, which includes a screen and a grit chamber arranged in sequence, with the outlet of the grit chamber connected to the inlet of the first sewage equalization tank 9.

[0050] In some preferred embodiments of the present invention, an aeration device is provided inside the first sewage equalization tank for aeration and equalization treatment of sewage.

[0051] In some preferred embodiments of the present invention, the sludge anaerobic digestion unit 4 is equipped with an anaerobic digester, an agitator inside the anaerobic digester, an insulation layer on the surface of the anaerobic digester, and a stainless steel heating coil inside the anaerobic digester. A wastewater source heat pump unit 6 is connected to the stainless steel heating coil for heating and insulation of the sludge anaerobic digestion unit 4.

[0052] In some preferred embodiments of the present invention, the nitrogen and phosphorus adsorption unit 2 is formed by two tanks of the same volume connected in series, each tank is divided into multiple compartments, and water is distributed by alternating water intake from the top and bottom.

[0053] Unit 5, a resource recovery and utilization unit for digested sludge, effectively releases iron and phosphorus from the digested sludge through acidification treatment; generates blue iron ore by adjusting controlled conditions, and achieves efficient solid-liquid separation and recovery of phosphorus through magnetic separation; and converts the remaining iron in the supernatant after magnetic separation into ferric iron through micro-aeration and reuses it in the preparation of composite flocculants, thus realizing closed-loop recycling of iron salts.

[0054] This invention achieves efficient removal of pollutants through the synergistic effect of multiple units, and maximizes the recovery of chemical energy, nitrogen and phosphorus resources and waste heat from sewage and sludge. At the same time, it realizes closed-loop recycling of iron salts, significantly reducing energy consumption, material consumption and carbon emissions in the sewage treatment process. It has good environmental, economic and social benefits and is a sustainable low-carbon sewage treatment solution.

[0055] The present invention provides a municipal wastewater treatment process based on resource and energy recovery as follows:

[0056] (1) Pretreatment stage: Urban sewage is first pretreated by a screen and a grit chamber to remove large suspended solids and impurities such as sand and gravel from the water body; the effluent after pretreatment flows into the first sewage equalization tank 9 for equalization of water quantity and quality. At the same time, the sewage in the first sewage equalization tank 9 is aerated to adjust the dissolved oxygen concentration of the water body to 0.5-1 mg / L, so that the water treatment is conducive to the oxidation environment of coagulation and sedimentation reaction.

[0057] (2) Coagulation and sedimentation stage: The sewage in the first sewage equalization tank 9 and the iron-based covalent composite flocculant in the flocculant dosing tank 8 are rapidly mixed through a pipeline mixer. The iron-based covalent composite flocculant is a covalent bond hybrid flocculant prepared by hydrolysis copolymerization with APTES as silicon source and FeCl3 as inorganic metal salt by slowly adding alkaline solution at room temperature. The dosage of the compound flocculant is 20±2 mg / L based on Fe. Subsequently, the sewage mixture is pumped into the flocculation zone of the coagulation and sedimentation unit 1 for flocculation reaction. It enters the sedimentation zone through the lower left inlet of the sedimentation tank. After sedimentation by inclined plate and inclined tube, the supernatant is discharged by overflow and enters the second sewage equalization tank 10. The bottom sludge enters the sludge thickening unit 7 through the sludge discharge port. The coagulation and sedimentation unit 1 mainly captures suspended solids, particulate organic matter and phosphorus in the sewage, capturing organic matter into the sludge, thereby changing the direction of carbon flow.

[0058] In some preferred embodiments of the present invention, the flocculation zone of the coagulation sedimentation unit 1 has a length, width, and height of 0.24m, 0.4m, and 0.54m, respectively; the sedimentation zone has a length, width, and height of 0.6m, 0.4m, and 0.21m, respectively, and the lower part is shaped like a mud bucket with a volume of 0.023m³. 3 Sludge removal is carried out every two hours.

[0059] In some preferred embodiments of the present invention, the preparation method of the compound flocculant specifically includes: adding 5L of 0.5mol / L FeCl3 solution, 1L of 0.5mol / L APTES and 1L of ultrapure water to a 15L water tank, mixing them evenly with a stirrer, and then adding 3L of 1.25mol / L NaOH solution to the water tank at a certain rate to prepare the compound flocculant. It can be seen that the molar ratio of Si to Fe in the compound flocculant is 0.5mol(Si):2.5mol(Fe) = 1:5; excessive Si will lead to Si-O-Si self-aggregation, and excessive Fe will cause Fe(OH)3 to easily precipitate separately, both of which will reduce the hybridization effect.

[0060] (3) Sludge thickening and anaerobic digestion stage: The sludge captured by the coagulation and sedimentation unit 1 is discharged into the sludge thickening unit 7 through the sludge discharge port for gravity thickening and sedimentation for about 24 hours; the thickened sludge is pumped into the sludge anaerobic digestion unit 4 for mesophilic anaerobic digestion treatment. The temperature inside the digester is 35±1℃, the pH is 6.9-7.2, the ORP is -240mv~-210mv, and the solids retention time is 5-6 days; through anaerobic digestion, chemical energy in wastewater is recovered, biogas with high methane content is produced, and sludge production is effectively reduced. The anaerobic digester of the sludge anaerobic digestion unit 4 is equipped with an insulation layer on the surface and a 35m long 304 stainless steel heating coil inside, which is used to heat the sludge and maintain the temperature of the digester.

[0061] In some preferred embodiments of the present invention, the volume of the sludge thickening unit 7 is 0.5 m³. 3 The anaerobic digestion unit 4 for sludge is fed once a day, with a feed volume of 80±5L. The anaerobic digester is cylindrical, with a diameter of 0.75m and a total height of 1.5m. The bottom is shaped like a sludge hopper, and an agitator is installed inside to stir the sludge. Sludge is fed in and discharged from the bottom. An exhaust port is located at the top of the tank for releasing biogas, and a biogas slurry outlet and four sampling valves are also provided.

[0062] (4) Sludge Resource Recovery and Utilization Stage: The iron- and phosphorus-rich sludge after digestion in anaerobic digestion unit 4 enters the acidification reaction tank of sludge resource recovery and utilization unit 5. Hydrochloric acid is added to adjust the pH of the system to 2, and the reaction is carried out for 60 minutes under stirring conditions. Through acidification, the iron and phosphorus in the sludge are released into the liquid phase. After the reaction, solid-liquid separation is carried out. The dissolved oxygen concentration of the acidified supernatant is adjusted to no more than 0.2 mg / L, and an alkaline regulator is slowly added to adjust the pH of the system to 6.5-7.5. In the lapis lazuli formation reaction tank, the dissolved ferrous iron reacts with phosphate to generate lapis lazuli, and then magnetic separation is carried out in the magnetic separation unit to recover lapis lazuli. The supernatant after magnetic separation still contains a certain concentration of dissolved iron. It is oxidized by micro-aeration to gradually convert the ferrous iron in it into ferric iron, and then formulated into an iron-based covalent composite flocculant, which is reused in the coagulation and sedimentation step to realize the closed-loop recycling of iron salts.

[0063] (5) Nitrogen and phosphorus adsorption stage: The wastewater mixture in the second wastewater equalization tank 10 (i.e., the supernatant of the coagulation sedimentation unit 1 and the biogas slurry after digestion by the sludge anaerobic digestion unit 4) flows into the nitrogen and phosphorus adsorption unit 2; this unit is formed by two tanks of the same volume connected in series, and uses adsorption filter media to selectively adsorb and recover nitrogen and phosphorus in the wastewater mixture; specifically, the wastewater is first treated by nitrogen adsorption filter media and then enters the phosphorus adsorption unit for treatment; the empty bed retention time of a single tank in the nitrogen and phosphorus adsorption unit is 13-15h.

[0064] In some preferred embodiments of the present invention, modified biochar based on sludge is used as the adsorption filter media for selective adsorption of ammonia nitrogen and phosphate, achieving efficient recovery of nitrogen and phosphorus resources from wastewater; the adsorption filter media after adsorption saturation can be used as a soil conditioner or slow-release fertilizer. Calcium-magnesium bimetallic modified biochar based on sludge, as a highly efficient phosphate adsorption material, exhibits a maximum adsorption capacity of 156.82 mg•g for phosphate at 298 K. -1 Electrically assisted magnesium-aluminum supported biochar based on sludge was used as a highly efficient ammonia nitrogen adsorbent, exhibiting a maximum adsorption capacity of 65.19 mg•g at 298 K. -1 .

[0065] In some preferred embodiments of the present invention, the length, width and height of each tank of the nitrogen and phosphorus adsorption unit 2 are 2m, 0.85m and 1.5m respectively, the support plate of the adsorption filter material is 0.35m from the bottom of the tank, each tank is divided into 4 compartments, and water is introduced alternately from the top and bottom.

[0066] (6) Deep treatment stage of biological filter: The effluent from nitrogen and phosphorus adsorption unit 2 is lifted to the top of biological filter unit 3 by a booster pump for drip filtration; through the biochemical action of microorganisms, the remaining organic matter and phosphorus in the sewage are further removed to ensure that the final effluent meets the discharge standards. The treated effluent from biological filter unit 3 enters sewage source heat pump unit 6.

[0067] In some preferred embodiments of the present invention, the height of the packing zone in the biological filter is 1.4m, and the length and width are both 1m. The main packing materials are pebbles and biological ceramic particles.

[0068] (7) Wastewater heat recovery stage: Wastewater source heat pump unit 6 utilizes the treated wastewater through water source heat pump to efficiently recover the residual heat energy in the wastewater; the recovered heat energy is mainly used for heating and heat preservation of sludge anaerobic digestion unit 4 to reduce its operating energy consumption, and can also be used as an "energy plant" to output energy to the outside of the plant to achieve comprehensive energy utilization.

[0069] Through the synergistic effect of the above units, this invention achieves efficient removal and resource recovery of organic matter, nitrogen, and phosphorus pollutants in urban sewage, effectively recovers chemical energy and residual heat energy in sewage, and realizes closed-loop recycling of iron salts. It significantly reduces chemical and energy consumption in sewage treatment and has significant advantages such as good effluent quality, high resource recovery rate, and low operating cost.

[0070] The present invention can be further understood through the following embodiments and comparative examples.

[0071] Comparative Example 1

[0072] The wastewater treatment plant where the pilot plant is located has a daily treatment capacity of 40,000 tons in its third phase. The pretreatment unit includes coarse and fine screens, wastewater lifting pump station, grit chamber, etc. The biological treatment unit adopts a double-ditch oxidation ditch and a radial flow secondary sedimentation tank. The deep treatment unit includes a denitrification deep bed filter and ultraviolet disinfection treatment.

[0073] The characteristics of the wastewater influent to the wastewater treatment plant are as follows: COD is 257.73±24.09 mg / L. The concentration was 30.33±2.8 mg / L, the TN concentration was 34.59±3.31 mg / L, and the TP concentration was 4.2±0.75 mg / L.

[0074] The effluent quality characteristics of the wastewater treatment plant are as follows: COD is 15.6 ± 1.23 mg / L. The concentration was 0.59±0.34 mg / L, TN concentration was 8.42±0.69 mg / L, and TP concentration was 0.07±0.02 mg / L; the power consumption per ton of wastewater treated was 0.36 kWh / m³. 3 As shown in Table 1.

[0075] Table 1. Influent and Effluent Indicators for Comparative Example 1

[0076]

[0077] Example 1

[0078] The test site for this embodiment is located in Nanjing, Jiangsu Province, and the experimental water is the effluent from the grit chamber of a sewage treatment plant in Nanjing.

[0079] Among them, the influent flow rate is 4m 3 / d, its water quality characteristics are as follows: COD is 182.18±47.29mg / L, NH4+ + The concentrations of -N were 25.75±4.08 mg / L, TN was 30.49±4.38 mg / L, and TP was 3.38±0.55 mg / L.

[0080] After the system has been operating stably, the effluent indicators have consistently met the standards of "Urban Wastewater Reuse - Water Quality for Urban Miscellaneous Uses" (GB / T 18920-2020).

[0081] As shown in Tables 2 and 3;

[0082] Table 2 Influent and Effluent Indicators for Example 1

[0083]

[0084] Table 3. Phased Indicators of Resource and Energy Recovery in Example 1

[0085]

[0086] As can be seen, in this embodiment, the average capture rates of COD and phosphorus by the coagulation and sedimentation unit reached 62.57% and 55.29%, respectively, effectively capturing pollutants into the sludge; the nitrogen and phosphorus adsorption unit achieved an average cumulative adsorption of 52% and 28.5% of TN and TP in the process influent, respectively, realizing the resource utilization of nitrogen and phosphorus; the anaerobic digestion unit produces approximately 15L of biogas daily, with a methane content as high as 80%, effectively recovering the chemical energy from the wastewater; the sludge resource utilization unit releases approximately 75% of iron and 85% of phosphorus into the supernatant through acidification and digestion of sludge. By adjusting the pH of the acidified supernatant, lapis lazuli is generated, and magnetic separation is used to recover lapis lazuli, achieving a total phosphorus recovery rate of up to 60% in the digested sludge. The supernatant after magnetic separation is micro-aerated to convert ferrous iron to ferric iron, which can be reused in the preparation of coagulation and sedimentation composite flocculants, realizing the closed-loop recycling of iron salts; at the same time, based on the operating data of this case, it is estimated that with a capacity of 20,000 m³, 3 Based on the inflow rate, the electricity consumption per ton of water is approximately 0.21 kWh / m³. 3 The efficiency is significantly lower than that of traditional processes; the wastewater source heat pump unit achieves a waste heat recovery rate of over 75% for the effluent; the nitrogen resource recovery rate of the entire process system is approximately 52%, and the phosphorus resource recovery rate is approximately 62%, which fully demonstrates the significant advantages of this process in resource and energy recovery and energy consumption reduction.

[0087] Example 2

[0088] This embodiment was also conducted in Nanjing, Jiangsu Province, and the experimental water was the effluent from the grit chamber of a sewage treatment plant in Nanjing.

[0089] Among them, the influent flow rate is 5m 3 / d, its water quality characteristics are as follows: COD is 169.26±31.89mg / L, NH4+ + The concentrations of -N were 23.81±4.85 mg / L, TN was 26.62±4.62 mg / L, and TP was 3.07±0.42 mg / L.

[0090] After the system has been operating stably, the effluent indicators have consistently met the standards of "Urban Wastewater Reuse - Water Quality for Urban Miscellaneous Uses" (GB / T 18920-2020).

[0091] As shown in Tables 4 and 5;

[0092] Table 4 Inlet and outlet water indicators for Example 2

[0093]

[0094] Table 5. Phased Indicators of Resource and Energy Recovery in Example 2

[0095]

[0096] This invention can have other embodiments based on the above preparation method, which will not be listed one by one. Therefore, any simple modifications, equivalent changes and alterations made by any person skilled in the art to the above embodiments without departing from the scope of the technical solution of this invention shall still fall within the scope of the technical solution of this invention.

Claims

1. A municipal wastewater treatment device based on resource and energy recovery, characterized in that: The device comprises a coagulation and sedimentation unit (1), a nitrogen and phosphorus adsorption unit (2), a biological filter unit (3), a sludge anaerobic digestion unit (4), a sludge resource recycling unit (5), a sewage source heat pump unit (6), a sludge concentration unit (7), a flocculant dosing tank (8), a first sewage adjusting tank (9) and a second sewage adjusting tank (10); wherein: The coagulation and sedimentation unit (1) is provided with a water inlet, a supernatant outlet and a sludge outlet, the water inlet is connected with the first sewage adjusting tank (9) and the flocculant dosing tank (8), the supernatant outlet is connected with the inlet of the second sewage adjusting tank (10), and the sludge outlet is connected with the inlet of the sludge concentration unit (7); The outlet of the sludge concentration unit (7) is connected with the inlet of the sludge anaerobic digestion unit (4); The sludge anaerobic digestion unit (4) is provided with a biogas slurry outlet and a sludge outlet, the biogas slurry outlet is connected with the inlet of the second sewage adjusting tank (10), and the sludge outlet is connected with the inlet of the sludge resource recycling unit (5); The sludge resource recycling unit (5) comprises an acidification reaction tank, a blue vitriol generation reaction tank, a magnetic separation unit and a micro-aeration oxidation reaction tank; The outlet of the second sewage adjusting tank (10) is connected with the inlet of the nitrogen and phosphorus adsorption unit (2); The outlet of the nitrogen and phosphorus adsorption unit (2) is connected with the inlet of the biological filter unit (3); The outlet of the biological filter unit (3) is connected with the sewage source heat pump unit (6).

2. The apparatus of claim 1, wherein: Further comprising a pretreatment unit, the pretreatment unit comprises a grid and a grit chamber arranged in sequence, the outlet of the grit chamber is connected with the inlet of the first sewage adjusting tank (9); and the first sewage adjusting tank (9) is provided with an aeration device.

3. The device of claim 1, wherein: The sludge anaerobic digestion unit (4) is provided with an anaerobic digestion tank, the inside of the anaerobic digestion tank is provided with a stirrer, the surface of the anaerobic digestion tank is provided with a heat preservation layer, and the inside of the anaerobic digestion tank is provided with a stainless steel heating coil; The sewage source heat pump unit (6) is connected with the stainless steel heating coil and is used for heating and heat preservation of the sludge anaerobic digestion unit (4); The nitrogen and phosphorus adsorption unit (2) is formed by two same-volume tank bodies connected in series, each tank body is divided into multiple grids, and an up-down water inlet alternating water distribution mode is adopted.

4. A municipal wastewater treatment process based on resource energy recovery, using the device according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: Redox state adjustment before coagulation and sedimentation treatment: the wastewater in the first sewage adjusting tank (9) is subjected to aeration adjustment treatment to adjust the dissolved oxygen concentration of the water body, so that the water body treatment is conducive to the oxidation environment of the coagulation and sedimentation reaction, thereby inhibiting the transformation of trivalent iron into divalent iron during coagulation and sedimentation; Coagulation and sedimentation: after the wastewater in the first sewage adjusting tank (9) is subjected to aeration adjustment treatment, the wastewater is mixed with the iron-based covalent composite flocculant in the flocculant dosing tank (8) and then enters the coagulation and sedimentation unit (1) for coagulation and sedimentation, so that the suspended solids, particulate organic matter and phosphorus in the wastewater form flocs and are precipitated, the supernatant of the coagulation and sedimentation unit (1) enters the second sewage adjusting tank (10), and the captured sludge enters the sludge concentration unit (7); Sludge concentration and anaerobic digestion: The sludge concentration unit (7) carries out gravity concentration sedimentation on the captured sludge, and then sends the sludge into a sludge anaerobic digestion unit (4) for mesophilic anaerobic digestion treatment to produce biogas with high methane content; The biogas produced by the sludge anaerobic digestion unit (4) enters a second sewage adjusting tank (10); Digestion sludge resource recycling: The iron-rich and phosphorus-rich sludge after digestion in the sludge anaerobic digestion unit (4) enters a digestion sludge resource recycling unit (5), and the iron and phosphorus in the sludge are released into the liquid phase through acidification in the acidification reaction tank; After solid-liquid separation, the supernatant of acidification is adjusted to a certain pH value, and the dissolved divalent iron and phosphorus are reacted to form a blue vitriol precipitate in the blue vitriol formation reaction tank. The blue vitriol is recovered by magnetic separation technology in the magnetic separation unit; The supernatant after magnetic separation is treated by micro-aeration in the micro-aeration oxidation reaction tank, so that the divalent iron is converted into trivalent iron, and an iron-based covalent composite flocculant is prepared and used in the coagulation and sedimentation step. Nitrogen and phosphorus adsorption: The mixed liquid in the second sewage adjusting tank (10) flows into a nitrogen and phosphorus adsorption unit (2), which selectively adsorbs and recovers nitrogen and phosphorus in the mixed liquid of sewage by using adsorption filter material; The effluent of the nitrogen and phosphorus adsorption unit (2) enters a biological filter unit (3); Biological filter advanced treatment: The biological filter unit (3) further removes residual organic matter and phosphorus through biochemical action of microorganisms to ensure that the effluent meets discharge standards; Tail water waste heat recovery: The effluent of the biological filter unit (3) enters a sewage source heat pump unit (6) to recover waste heat energy in the sewage, and the recovered heat energy is used to compensate for process system heat consumption.

5. The process of claim 4, wherein: In the step of adjusting the redox state before coagulation and sedimentation treatment, the sewage is first treated by a grid and a sand trap, and then enters a first sewage adjusting tank (9). The first sewage adjusting tank (9) is subjected to aeration adjustment treatment to control the dissolved oxygen concentration in the sewage to be 0.5-1 mg / L.

6. The process of claim 4, wherein: In the coagulation and sedimentation step, the dosage of the iron-based covalent composite flocculant in the coagulation and sedimentation unit (1) is 20±2 mg / L in terms of Fe. The iron-based covalent composite flocculant is a covalent bond type hybrid flocculant prepared by hydrolysis copolymerization using APTES as a silicon source and FeCl3 as an inorganic metal salt, and slowly adding alkali solution at room temperature.

7. The process of claim 4, wherein: The mesophilic anaerobic digestion treatment is carried out in the anaerobic digestion tank of the sludge anaerobic digestion unit (4), and the temperature, pH, oxidation-reduction potential and solid retention time in the tank are controlled to be 35±1℃, 6.9-7.2, -240 mv~-210 mv and 5-6 d, respectively.

8. The process of claim 4, wherein: In the digestion sludge resource recycling step, an acid regulator is added to the sludge after digestion to adjust the pH to 2, and the sludge is stirred for 60 min to dissolve and release the iron and phosphorus in the sludge into the liquid phase.

9. The process of claim 4, wherein: In the step of recycling and utilizing the sewage sludge, the obtained acidified supernatant is adjusted in reaction conditions under the condition that the dissolved oxygen concentration is not higher than 0.2 mg / L, the reaction activity of divalent iron in the system is maintained by controlling the pH value to be 6.5-7.5, the dissolved phosphorus reacts with the divalent iron to generate a blue vitriol precipitate, the phosphorus-rich blue vitriol product is obtained by magnetic separation through the magnetic characteristics of the blue vitriol.

10. The process of claim 4, wherein: In the step of nitrogen and phosphorus adsorption, the adsorption filter material in the nitrogen and phosphorus adsorption unit (2) is modified biogas residue-based biochar, the modified biogas residue-based biochar is used for selectively adsorbing ammonia nitrogen and phosphate, and the adsorption filter material after saturation is used as a soil conditioner or slow-release fertilizer.

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