Municipal sewage short-process treatment system and operation method thereof

Abstract

The invention provides an urban sewage short-process treatment system and an operation method thereof, the urban sewage short-process treatment system mainly comprises two core units: (1) a carbon-phosphorus co-steering unit: a chemical enhanced pretreatment (CEPT) process is adopted, selective separation of particulate organic matters, suspended matters and phosphate is realized by adding a ferric salt coagulant, and meanwhile, a high-quality soluble carbon source is reserved; and support is provided for subsequent biological treatment. And (2) an enhanced synchronous nitrification and denitrification unit: combining a membrane aeration bio-membrane reactor (MABR) with a moving bed bio-membrane reactor (MBBR), introducing an elemental sulfur pulverization microcarrier as an electron donor, and coupling a sulfur autotrophic denitrification process to further improve the denitrification efficiency. According to the invention, efficient denitrification of urban sewage can be realized in a short process, meanwhile, the sludge yield and the operation energy consumption are reduced, and the effluent quality is stable and reaches the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant.

Description

Technical Field

[0001] The present invention relates to the field of sewage treatment and resource recovery, and in particular to a short-process urban sewage treatment system and an operation method thereof, which is suitable for synergistically improving the pollution reduction and carbon reduction of municipal sewage. Background Art

[0002] The existing municipal sewage treatment process has the following problems: ① the process is lengthy (the hydraulic retention time of the biochemical stage is as long as 20 hours); ② the carbon source distribution is inconsistent, requiring a large amount of external carbon source; ③ the aeration energy consumption required for the oxidation of organic matter is high; ④ the treatment process is energy-consuming, and the degree of energy and resource recovery is low. As a result, the carbon emissions of sewage treatment plants are high and there is a large room for emission reduction, which deviates from the green and low-carbon development goals. It is urgent to develop new green, low-carbon, short-process sewage treatment processes.

[0003] The change of material flow based on carbon diversion technology is an important way to transform sewage treatment plants into sewage resource plants. Among them, chemically enhanced primary treatment (CEPT) as a mature process that can achieve synchronous diversion of carbon and phosphorus has received more and more attention and research. The membrane aerated biofilm reactor (MABR) is a sewage treatment technology that uses membrane bubble-free aeration to achieve efficient biodegradation of pollutants. It has the dual functions of efficient oxygen supply and biofilm carrier, and can achieve simultaneous nitrification and denitrification. However, the MABR process alone is limited by the membrane area, and the amount of biofilm is small. The combination of MABR and moving bed biofilm reactor (MBBR) can further improve the carbon source utilization efficiency and enhance denitrification, and improve the process's ability to resist shock effects. A typical example is CN 221254219U, which discloses a combined MABR and MBBR device, and the TN removal rate is increased to <10 mg / L, saving 40% of the external carbon source. Therefore, the combination of carbon diversion technology and simultaneous nitrification and denitrification technology is expected to build a new low-carbon short-process process. Typical examples include CN116177823 A and CN 116143292 B, which combine carbon diversion technology with simultaneous nitrification and denitrification technology based on MABR to achieve synergistic effects in pollution reduction and carbon reduction. However, the above patents all ignore the mutual connection between process units and lack a sophisticated control method; and although MABR improves the utilization rate of influent carbon sources, in low carbon-nitrogen ratio municipal sewage treatment, the severe lack of electron donors after carbon diversion is still the key bottleneck limiting the TN standard of effluent.

[0004] In view of the actual needs of low-carbon short-process sewage treatment technology and the shortcomings of existing background technology, the present invention aims to propose a new short-process sewage treatment process that can achieve fine regulation of carbon shift and stable denitrification under carbon source limitation, so as to fill the deficiencies in this field. Summary of the invention

[0005] The object of the present invention is to provide a short - process treatment system for urban sewage and its operation method. Through the carbon - phosphorus diversion control method based on component analysis, selective separation of particulate organic matter, suspended solids and phosphate in the influent is achieved, and high - quality dissolved carbon sources are retained and enter the simultaneous nitrification and denitrification unit to realize the efficient utilization of influent carbon sources. Aiming at the problem of insufficient electron donors, the organic combination of MABR and MBBR is used to further improve the utilization rate of influent carbon sources. And by adding elemental sulfur - fluidized micro - carriers, sulfur autotrophic denitrification is introduced to further strengthen nitrogen removal, shorten the process flow, and achieve the synergistic effect of reducing pollution and carbon emissions.

[0006] The technical solution adopted by the present invention: A short - process treatment system for urban sewage includes a carbon - phosphorus co - diversion unit and an enhanced simultaneous nitrification and denitrification unit connected in sequence.

[0007] The carbon - phosphorus co - diversion unit adopts the CEPT process to achieve chemical enhanced pretreatment and carbon - phosphorus directional separation, including a mixing tank and an enhanced primary sedimentation tank connected in sequence.

[0008] The mixing tank is provided with an influent port and a coagulant dosing module. The ferric salt coagulant is continuously injected by a diaphragm pump through the coagulant dosing module. The mixing tank takes in water from the top and discharges water from the bottom.

[0009] The bottom of the enhanced primary sedimentation tank is provided with an enhanced primary sedimentation tank sludge discharge pipe. The enhanced primary sedimentation tank takes in water in the middle, overflows and discharges water from the upper part, and the effluent enters the enhanced simultaneous nitrification and denitrification unit. The high - organic - matter and high - iron phosphate sludge generated by the enhanced primary sedimentation tank is discharged through the bottom enhanced primary sedimentation tank sludge discharge pipe and connected to the anaerobic digestion unit of the sewage treatment plant for co - generation of heat and power. The iron phosphate in its biogas slurry is used as a battery raw material for resource recovery, or transported outside the factory for other recoveries.

[0010] The enhanced simultaneous nitrification and denitrification unit aims to achieve stable and efficient nitrogen removal under carbon source limitation, including an MABR tank, an MBBR tank and an inclined tube sedimentation tank connected in sequence.

[0011] The MABR tank is internally provided with an MABR aeration membrane module, and a gas supply device is provided at the top of the MABR tank. The MABR tank is also provided with a reflux pipe. The MABR tank takes in water in the middle, enters the MBBR tank through the perforations in the tank body, and discharges water from above the MBBR tank. The MABR tank and the MBBR tank are separated by a pool wall.

[0012] A sulfur powder / sodium bicarbonate dosing module is provided above the MBBR tank. The MBBR tank is internally provided with sulfur powder and MBBR fillers, and a microporous aeration disk is provided at the lower part of the MBBR tank.

[0013] The inclined tube sedimentation tank is provided with a water outlet and a residual sludge discharge pipe. The inclined tube sedimentation tank is fed with water from the bottom and discharges water through the upper overflow weir into the advanced treatment unit of the sewage treatment plant. The sedimented muddy water in the inclined tube sedimentation tank is connected to the inlet end of the MABR tank through a bottom return port by a return pump; a sludge discharge regulating valve is provided on the residual sludge discharge pipe, and a small amount of residual sludge generated in the inclined tube sedimentation tank is discharged from the sludge discharge port and connected to the anaerobic digestion unit of the sewage treatment plant together with the primary sedimentation sludge, or transported out of the plant for other recycling.

[0014] Preferably, the effective volume ratio of the MABR tank to the MBBR tank is 1:4 to 1:1.

[0015] Preferably, stainless steel meshes with pore sizes ≤2 cm are installed at both the inlet and outlet of the MBBR tank to prevent the loss of fillers.

[0016] Preferably, the MABR tank and the MBBR tank also include an air circuit system, including an air inlet pipe and an air outlet pipe. The MABR aeration membrane module includes an air inlet and an air outlet. The air inlet pipe and the air outlet pipe of the air circuit system are respectively connected to the air inlet and the air outlet of the MABR aeration membrane module; the accessories include an aeration blower, an aeration flowmeter and an aeration regulating valve; the air circuit system also includes an aerator placed at the bottom of the MABR aeration membrane module, which functions to mix the activated sludge, the suspended fillers and make the aged biofilm fall off; the MABR aeration membrane module is any one of a hollow fiber membrane, a plate membrane, a spiral wound membrane and a tubular membrane, and the packing density is 100 - 200 m 2 / m 3 , and the MABR aeration membrane modules are arranged in parallel to ensure that the sewage flows through the membrane modules and the pollutants are effectively removed.

[0017] Preferably, the packing filling rate of the MBBR tank is 15% - 30%, and any one with an effective specific surface area SV ≥ 500 m 2 / m 3 can be selected; the MBBR tank adopts any one of "stirring + micro - pore aeration" or "micro - pore aeration + swirl aeration" to achieve the fluidization of the fillers and the control of dissolved oxygen with low energy consumption.

[0018] The operation method of the above - mentioned short - process urban sewage treatment system is as follows:

[0019] S1. Sewage enters the mixing tank, and an iron salt coagulant is added while stirring with a stirrer to obtain a mixed liquid;

[0020] S2. The mixed liquid prepared in step S1 is transported into the enhanced primary sedimentation tank for sedimentation to obtain supernatant with an extremely low carbon - nitrogen ratio (COD / TN ≤ 2.5) and low phosphorus content, and sedimented sludge with high organic matter and high ferric phosphate content;

[0021] S3. Transfer the supernatant with an extremely low carbon-nitrogen ratio and low phosphorus content obtained in step S2 into the MABR pool and the MBBR pool, add elemental sulfur powder and alkalinity supplement agents to form fluidized elemental sulfur microcarriers in the sludge mixture. At the same time, form a hierarchical biofilm with decreasing dissolved oxygen from the inside to the outside on the surface of the aeration membrane module in the MABR pool. The inner layer is the aerobic layer, enriching nitrifying functional bacteria, and the outer layer is the anoxic layer, enriching heterotrophic denitrifying functional bacteria and sulfur autotrophic denitrifying functional bacteria. Finally, under the combined action of suspended activated sludge, fluidized elemental sulfur as a carrier, the biofilm on the MABR membrane surface, and the biofilm on the surface of the suspended fillers in the MBBR pool, enhanced denitrification is achieved, and a mud-water mixture doped with sulfur powder is obtained.

[0022] S4. Transfer the mud-water mixture containing sulfur powder obtained in step S3 into an inclined tube sedimentation tank for further sedimentation to obtain a high-concentration mud-water mixture containing sulfur powder deposited at the bottom and an effluent that can meet the discharge standards.

[0023] Preferably, the sewage in step S1 is municipal sewage, and other sewage such as rural sewage and industrial wastewater without biological toxicity that requires enhanced denitrification is also applicable.

[0024] Preferably, the ferric salt coagulant added in step S1 includes one or a combination of ferric chloride, ferric sulfate, polyferric chloride, and polyaluminum ferric chloride. To obtain the best effect, the dosage of the agent needs to be confirmed through a coagulation beaker test, with most particulate organic matter being redirected for recovery (particle COD redirection rate ≥ 90%), a small amount of TP remaining in the effluent (0.2 - 0.5 mg / L), and an extremely small amount of ferric salt (≤ 0.2 mg / L) remaining in the effluent being the best. In some specific embodiments, the dosage of FeCl3 is 10 - 20 mg Fe / L.

[0025] Preferably, the reaction time of the mixing pool in step S1 is 20 - 40 min, and the stirring rate is 20 - 40 r / min.

[0026] Preferably, the surface load of the enhanced primary sedimentation tank in step S2 is 1 - 2 m 3 / (m 2 ·h), and the sedimentation time is 0.5 - 2 h.

[0027] Preferably, the enhanced primary sedimentation tank in step S2 uses intermittent sludge discharge, with a cycle of 4 - 8 h. The sludge discharge volume is theoretically determined according to the inlet particulate matter concentration and the inlet water volume. In some specific embodiments, it can be determined according to the sludge level in the primary sedimentation tank.

[0028] Preferably, in step S3, the MABR tank and the MBBR tank operate in a combined sludge and biofilm mode, with the sludge concentration set at 2000 - 4000 mg MLSS / L. Since the influent organic matter concentration is relatively low, most of it is used for biofilm attachment and heterotrophic denitrification processes, and the growth rate of the suspended sludge concentration is slow. To maximize the sludge age and promote the proliferation of autotrophic functional bacteria, the process can operate continuously without sludge discharge. In some specific implementation cases, when the sludge concentration exceeds 1.5 times the set sludge concentration, sludge discharge is carried out, and the sludge discharge volume is determined to restore the set sludge concentration.

[0029] Preferably, in step S3, a sulfur powder mixture is added to the MABR tank. The sulfur powder particle size is selected to be 50 - 500 μm. The sulfur powder mixture can be added continuously or intermittently. In some specific implementation manners, it is added daily, and the addition amount is set to be 2 - 5 times the daily designed nitrate nitrogen removal amount. Alkalinity is simultaneously supplemented in the MABR tank. The alkalinity agent can be selected from sodium carbonate, sodium bicarbonate, calcium carbonate, sodium hydroxide, and a combination of one or more substances containing the corresponding components. Whether external supplementation is required is judged based on the influent alkalinity content. When the raw water alkalinity (calculated as CaCO3) reaches 5 times or more of the average nitrate nitrogen concentration, no addition is required. When the raw water alkalinity is insufficient, alkalinity needs to be supplemented. The total addition amount (calculated as CaCO3) can be set to be 5 times the nitrate nitrogen removal amount of the day. Optionally, feedback adjustment is carried out by monitoring the pH value. When the pH value is lower than 6.8, alkalinity is continuously added for supplementation.

[0030] Preferably, in step S3, the aeration pressure of the aeration membrane module in the MABR tank is generally set at 10 - 50 kPa. Optionally, due to significant differences in the oxygen mass transfer rate caused by differences in the membrane module material, feedback adjustment of the aeration pressure can be carried out by monitoring the dissolved oxygen concentration. The dissolved oxygen concentration in the MABR tank is controlled at 0.2 - 1.0 mg / L.

[0031] Preferably, in step S3, the dissolved oxygen concentration in the MBBR tank is controlled at 1.5 - 2.5 mg / L. Through enhanced nitrification, the limit removal of ammonia nitrogen is achieved. At the same time, through the biofilm on the surface of the packing and the biofilm on the surface of the suspended elemental sulfur microcarriers, synchronous nitrification and denitrification with sulfur autotrophic enhancement are carried out to achieve the standard treatment of TN.

[0032] Preferably, in step S3, the hydraulic retention time of the MABR tank and the MBBR tank is set at 6 - 12 h.

[0033] Preferably, the surface loading of the inclined tube sedimentation tank in step S4 is 10 - 25 m 3 / (m 2 ·h), and the sedimentation time is 0.5 - 2 h.

[0034] Preferably, the high-concentration muddy water mixture containing sulfur powder in step S4 is refluxed to the MABR tank through a reflux pump, and the reflux ratio is set to 50% - 100% to circulate the sulfur powder and activated sludge in the biochemical treatment system.

[0035] Preferably, the effluent in step S4 meets the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB18918 - 2002).

[0036] A short-process treatment system for urban sewage and its operation method provided by the present invention can be applied in the field of simultaneous pollution reduction and carbon emission reduction of urban sewage.

[0037] Beneficial effects of the present invention:

[0038] (1) Achieve efficient resource recovery and optimized utilization of carbon sources: Through the chemically enhanced primary treatment (CEPT) unit based on iron salt regulation, this patent can accurately separate phosphorus (TP conversion rate > 85%) and most particulate organic matter (particulate COD conversion rate ≥ 90%) in the influent into the sludge. These high-organic matter and high-ferric phosphate sludge can be used for anaerobic digestion to produce methane (improve energy recovery) or recover phosphorus resources. At the same time, this regulation method can selectively retain most of the high-quality dissolved COD (about 89%) and enter the subsequent biochemical treatment unit, effectively solving the problem of carbon source distribution contradiction in traditional processes and providing a valuable internal carbon source for subsequent denitrification.

[0039] (2) Overcome carbon source limitations and achieve short-process, efficient and stable denitrification: Aiming at the bottleneck of difficult denitrification caused by severe shortage of carbon sources (electron donors) after carbon conversion, this patent innovatively combines MABR and MBBR and introduces elemental sulfur as an electron donor for sulfur autotrophic denitrification. This "heterotrophic + autotrophic" synergistic denitrification mode, combined with the high-efficiency nitrification and simultaneous nitrification and denitrification capabilities of MABR / MBBR itself, can achieve stable and efficient total nitrogen removal (TN removal rate > 90%, effluent TN < 10 mg / L) even under extremely low carbon-nitrogen ratios (COD / TN ≤ 2.5), significantly shortening the traditional denitrification process flow (the hydraulic retention time of the biochemical section is shortened to 6 - 12 hours), and improving the impact load resistance of the system.

[0040] (3) Significantly reduce energy consumption and sludge production, and achieve synergistic effects of pollution reduction and carbon emission reduction: The core of this patent adopts the MABR technology. Its unique bubble-free aeration method enables the oxygen mass transfer efficiency to be over 85%, and the energy consumption can be reduced by 40 - 60% compared with traditional aeration. At the same time, the process characteristics based on biofilm result in a significant reduction in sludge yield (50 - 70% less than the activated sludge process). Combined with the energy / resource recovery achieved by the front-end CEPT, the entire process flow not only efficiently removes pollutants (pollution reduction) but also significantly reduces the operating energy consumption and sludge disposal volume, thereby reducing the overall carbon emissions of the sewage treatment plant (carbon emission reduction), achieving a win-win situation for environmental and economic benefits. Description of the Drawings

[0041] Figure 1 It is an analysis diagram of the turning of different C\N\P\Fe components under the regulation of different ferric salt dosages;

[0042] Figure 2 It is a schematic diagram of a short-process urban sewage treatment system of the present invention;

[0043] Figure 3 It is a flowchart of the operation method of a short-process urban sewage treatment system of the present invention. Detailed Embodiments

[0044] The following will describe the implementation schemes of the present invention in detail in combination with embodiments. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer are followed. The reagents or instruments not specified in the manufacturer are all conventional products that can be obtained through commercial purchase.

[0045] Taking the domestic sewage after the fine grille of the sewage treatment plant as the raw water, the water quality characteristics are: ammonia nitrogen 30 - 40 mg / L, carbon-nitrogen ratio 1.8 - 2.5. The operating conditions of CEPT are: the dosage of polyferric chloride is 0, 10, 20, 30, 40, 50, 60 mg Fe / L, the stirring rate of the mechanical mixing tank is 50 r / min, the reaction time of the mixing tank is 20 min, and the sedimentation time of the enhanced sedimentation tank is 0.6 h. The detection results of the water quality characteristics of the effluent from the chemical enhanced pretreatment tank are as Figure 1 .

[0046] The optimal dosage of FeCl3 is 5-20 mg Fe / L to achieve a relatively good diversion efficiency, and the optimal dosage is 10 mg Fe / L. Specifically, at this dosage, the diversion efficiencies of colloidal and particulate organic matters and TP basically reach the inflection point, while most of the BOD (≥200 mg / L) and an appropriate amount of TP (~1 mg / L) are retained in the downstream ecosystem to achieve the synergy between processes. After the dosage exceeds 20 mg Fe / L, the marginal benefit decreases, and Fe gradually enters the downstream biochemical system from the effluent, which may have an adverse impact on the downstream biochemical system. Generally speaking, the Fe dosing method proposed in the present invention is more economical, which can maximize energy and resource recovery while retaining high-quality carbon sources and necessary phosphorus elements to ensure the effectiveness of the downstream biochemical system operation and achieve the synergy and mutual consideration between processes.

[0047] As Figure 2 shown, an urban sewage short-process treatment system includes a carbon and phosphorus co-diversion unit and an enhanced simultaneous nitrification and denitrification unit connected in sequence.

[0048] The carbon and phosphorus co-diversion unit adopts the CEPT process to achieve chemical enhanced pretreatment and carbon and phosphorus directional separation, and includes a mixing tank 3 and an enhanced primary sedimentation tank 5 connected in sequence.

[0049] The mixing tank 3 is provided with a water inlet 1 and a coagulant dosing module 2, and the ferric salt coagulant is continuously injected into the mixing tank 3 through the coagulant dosing module 2 by a diaphragm pump. The mixing tank 3 takes in water from the top and discharges water from the bottom.

[0050] The enhanced primary sedimentation tank 5 is provided with an enhanced primary sedimentation tank sludge discharge pipe 4 at the bottom. The enhanced primary sedimentation tank 5 takes in water from the middle and overflows and discharges water from the upper part, and the effluent enters the enhanced simultaneous nitrification and denitrification unit. The high-organic-matter and high-ferric phosphate sludge generated by the enhanced primary sedimentation tank 5 is discharged from the bottom enhanced primary sedimentation tank sludge discharge pipe 4 and connected to the anaerobic digestion unit of the sewage treatment plant for co-generation of heat and power. The ferric phosphate in its biogas slurry is used as a battery raw material for resource recovery, or transported outside the plant for other recovery.

[0051] The enhanced simultaneous nitrification and denitrification unit aims to achieve stable and efficient nitrogen removal under carbon source limitation, and includes an MABR tank 9, an MBBR tank 11 and an inclined tube sedimentation tank connected in sequence.

[0052] The MABR pool 9 is internally provided with an MABR aeration membrane module 7, and an air supply device 6 is arranged at the top of the MABR pool 9. The MABR pool 9 is also provided with a reflux pipe 8. The middle part of the MABR pool 9 intakes water, and the water enters the MBBR pool 11 through the perforations in the pool body and exits from above the MBBR pool 11. The MABR pool 9 and the MBBR pool 11 are separated by a pool wall. A sulfur powder / sodium bicarbonate dosing module 10 is arranged above the MBBR pool 11. Sulfur powder 12 and MBBR fillers 14 are arranged inside the MBBR pool 11, and a microporous aeration disk 13 is arranged at the lower part of the MBBR pool 11. The effective volume ratio of the MABR pool 9 to the MBBR pool 11 is 1:4 to 1:1. Stainless steel meshes with a pore diameter ≤ 2 cm are installed at the inlet and outlet of the MBBR pool 11 to prevent the loss of fillers. The MABR pool 9 and the MBBR pool 11 also include an air path system, including an inlet pipe and an outlet pipe. The MABR aeration membrane module 7 includes an air inlet and an air outlet. The inlet pipe and the outlet pipe of the air path system are respectively connected to the air inlet and the air outlet of the MABR aeration membrane module 7. The accessories include an aeration fan, an aeration flowmeter, and an aeration regulating valve. The air path system also includes an aerator placed at the bottom of the MABR aeration membrane module 7, which functions to mix the activated sludge, suspend the fillers, and make the aged biofilm fall off. The MABR aeration membrane module 7 is any one of a hollow fiber membrane, a plate membrane, a spiral wound membrane, and a tubular membrane, and the packing density is 100 - 200 m 2 / m 3 , and the MABR aeration membrane modules 7 are arranged in parallel to ensure that the sewage flows through the membrane modules and the pollutants are effectively removed. The packing filling rate of the MBBR pool 11 is 15% - 30%, and any one with an effective specific surface area SV ≥ 500 m 2 / m 3 can be selected. The MBBR pool 11 adopts any one of "stirring + microporous aeration" or "microporous aeration + swirl aeration" to achieve the fluidization of the fillers and the control of dissolved oxygen with low energy consumption.

[0053] The inclined tube sedimentation tank 16 is provided with an outlet 17 and a residual sludge discharge pipe 18. The inclined tube sedimentation tank 16 intakes water from the bottom and exits water through the upper overflow weir into the advanced treatment unit of the sewage treatment plant. The sedimented muddy water in the inclined tube sedimentation tank 16 is connected to the inlet end of the MABR pool 9 through a bottom return port by a return pump 15. A sludge discharge regulating valve is arranged on the residual sludge discharge pipe 18. A small amount of residual sludge generated in the inclined tube sedimentation tank 16 is discharged from the sludge discharge port and is connected to the anaerobic digestion unit of the sewage treatment plant together with the primary sedimentation sludge, or is transported outside the plant for other recycling.

[0054] As Figure 3 shown, adopting the above system, a method for operating a low-carbon short-process treatment process for urban sewage is as follows:

[0055] (1) Using the sewage filtered by the fine grid in the urban sewage treatment plant as the raw water, the water quality characteristics are: the influent flow rate is 30000 m3 , the COD concentration is 386 mg / L, the NH4 + -N concentration is 32 mg / L, the TN concentration is 49.9 mg / L, the TP concentration is 4.9 mg / L, the average water temperature of the sewage is 24.7 °C, and the pH value is 7.6. Using the above sewage as the influent, the water quality of the influent and the content of each component are shown in the following table. Enter the mixing tank, the stirring rate of the mixing tank is 40 r / min, and the dosage of polyferric chloride is 10 mg Fe / L. React in the mechanical mixing tank for 20 min to obtain a mixed solution;

[0056] (2) Transport the mixed solution prepared in step (1) to the vertical flow enhanced primary sedimentation tank and precipitate for 1 h;

[0057] (3) The effluent from the enhanced primary sedimentation tank enters the MABR-MBBR tank, which is divided into 2 compartments: the MABR tank and the MBBR tank. Both of them operate in a sludge-film hybrid mode, and the sludge concentration is 2500 mg MLSS / L. The aeration pressure of the MABR tank is 40 kPa, and the membrane module is arranged by hollow fiber membranes; the dissolved oxygen in the MBBR tank is controlled at 2 mg / L, the particle size of the sulfur powder added is 50 μm, and the mass of the sulfur powder and sodium bicarbonate added are both 5 times the target nitrate nitrogen removal equivalent. The hydraulic retention time of the MABR-MBBR tank is 10 h.

[0058] (4) The effluent from the MABR-MBBR tank enters the inclined tube sedimentation tank, and its surface load is 15 m 3 / (m 2 ·h), and the sedimentation time is 1 h. Part of the high-concentration muddy water mixture containing sulfur powder is returned to the MABR tank through a reflux pump, and the reflux ratio is 50%;

[0059] Table 1 Treatment conditions of the short-process sewage treatment system

[0060]

[0061] The effluent of each stage of the equipment is detected, as shown in Table 1. Among them, for the effluent of the enhanced primary sedimentation tank in step (2), after detection, the COD concentration in the effluent is reduced to 224.7 mg / L, a decrease of 41.8% compared with the influent of the mechanical mixing tank, the TP concentration is reduced to 1.1 mg / L, a decrease of 77.5% compared with the influent of the mechanical mixing tank, the TN concentration is reduced to 41.4 mg / L, and the COD / TN decreases from 7.7 to 5.4. In addition, the pH value decreases from 7.5 to 7.2.

[0062] For the effluent of the MABR-MBBR tank in step (3), it is found that the COD concentration is reduced to 19.6 mg / L, a decrease of 94.9% compared with the raw water influent, the TP concentration is reduced to 0.4 mg / L, a decrease of 91.8% compared with the raw water influent, the TN concentration is reduced to 11 mg / L, and in addition, the pH value is reduced to 7.0.

[0063] For the inclined tube sedimentation effluent of step (4), after detection, the COD concentration in the effluent is reduced to 31.9 mg / L, a decrease of 91.7% compared with the raw water inlet; the TP concentration is reduced to 0.32 mg / L, a decrease of 93.5% compared with the raw water inlet; the TN concentration is reduced to 9.7 mg / L, and all indicators meet the effluent limit standards.

[0064] It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as within the protection scope of the present invention.

Claims

1. A short-process treatment system for urban sewage, characterized in that: It includes a carbon-phosphorus co-rotation unit and an enhanced simultaneous nitrification and denitrification unit connected in sequence; The carbon-phosphorus co-rotation unit includes a mixing tank and an enhanced primary sedimentation tank connected in sequence; the mixing tank is provided with a water inlet and a coagulant dosing module, and the ferric salt coagulant is continuously injected by a diaphragm pump through the coagulant dosing module. The mixing tank takes in water at the top and discharges water at the bottom; the enhanced primary sedimentation tank is provided with an enhanced primary sedimentation tank sludge discharge pipe at the bottom, takes in water in the middle, overflows and discharges water at the upper part, and the discharged water enters the enhanced simultaneous nitrification and denitrification unit; the sludge generated by the enhanced primary sedimentation tank is discharged through the enhanced primary sedimentation tank sludge discharge pipe at the bottom, and is connected to the anaerobic digestion unit of the sewage treatment plant or transported outside the plant for other recycling; The enhanced simultaneous nitrification and denitrification unit includes an MABR tank, an MBBR tank and an inclined tube sedimentation tank connected in sequence; the MABR tank is internally provided with an MABR aeration membrane module, and a gas supply device is provided at the top of the MABR tank. The MABR tank is also provided with a reflux pipe; the MABR tank takes in water in the middle, enters the MBBR tank through the perforations in the tank body, and discharges water above the MBBR tank. The MABR tank and the MBBR tank are separated by a pool wall; a sulfur powder / sodium bicarbonate dosing module is provided above the MBBR tank, sulfur powder and MBBR fillers are provided inside the MBBR tank, and microporous aeration discs are provided at the lower part of the MBBR tank; the inclined tube sedimentation tank is provided with a water outlet and a surplus sludge discharge pipe. The inclined tube sedimentation tank takes in water from the bottom, overflows through the upper overflow weir and discharges water into the advanced treatment unit of the sewage treatment plant. The sedimented muddy water of the inclined tube sedimentation tank is connected to a reflux pump through the bottom reflux port and refluxed to the water inlet end of the MABR tank; a sludge discharge regulating valve is provided on the surplus sludge discharge pipe, and a small amount of surplus sludge generated by the inclined tube sedimentation tank is discharged from the sludge discharge port and connected to the anaerobic digestion unit of the sewage treatment plant together with the primary sedimentation sludge, or transported outside the plant for other recycling.

2. The short - process treatment system for urban sewage according to claim 1, wherein: The effective volume ratio of the MABR tank to the MBBR tank is 1:4 to 1:1, and stainless steel meshes with a pore diameter ≤ 2 cm are installed at both the inlet and outlet of the MBBR tank.

3. The short-process treatment system for urban sewage according to claim 2, wherein: The MABR tank and the MBBR tank also include an air path system, which includes an inlet pipe and an outlet pipe. The MABR aeration membrane module includes an air inlet and an air outlet. The inlet pipe and the outlet pipe of the air path system are respectively connected to the air inlet and the air outlet of the MABR aeration membrane module; the accessories include an aeration blower, an aeration flowmeter, and an aeration regulating valve; the air path system also includes an aerator placed at the bottom of the MABR aeration membrane module; the MABR aeration membrane module is any one of a hollow fiber membrane, a plate membrane, a spiral wound membrane, and a tubular membrane, and the packing density is 100 - 200m 2 / m 3 , and the MABR aeration membrane modules are arranged in parallel.

4. A short-process urban sewage treatment system according to claim 3, characterized in that: The filling rate of the packing in the MBBR tank is 15% - 30%, and any one with an effective specific surface area SV≥500m 2 / m 3 is selected; the MBBR tank adopts any one of "stirring + micro-pore aeration" or "micro-pore aeration + swirl aeration".

5. The operating method of an urban sewage short - process treatment system according to claim 1, 2, 3 or 4, characterized in that, The steps are as follows: S1. Sewage enters the mixing tank, ferric salt coagulant is added, and at the same time, it is stirred by a stirrer to obtain a mixed solution; S2. The mixed solution prepared in step S1 is transported into the enhanced primary sedimentation tank for sedimentation to obtain supernatant with an extremely low carbon-nitrogen ratio and low phosphorus content and sediment sludge with high organic matter and high ferric phosphate content; S3. The supernatant with an extremely low carbon-nitrogen ratio and low phosphorus content obtained in step S2 is transported into the MABR tank and the MBBR tank, elemental sulfur powder and alkalinity supplementing agent are added, a fluidized elemental sulfur microcarrier is formed in the sludge mixed solution, and at the same time, a stratified biofilm with decreasing dissolved oxygen from inside to outside is formed on the surface of the MABR tank aeration membrane module. The inner layer is an aerobic layer, enriching nitrifying functional bacteria, and the outer layer is an anoxic layer, enriching heterotrophic denitrifying functional bacteria and sulfur autotrophic denitrifying functional bacteria. Finally, under the combined action of suspended activated sludge, fluidized elemental sulfur as a carrier, the biofilm on the MABR membrane surface and the biofilm on the surface of the suspended fillers in the MBBR tank in the MABR tank and the MBBR tank, enhanced nitrogen removal is achieved, and a muddy water mixture doped with sulfur powder is obtained; S4. Transfer the muddy water mixture containing sulfur powder obtained in step S3 into an inclined tube sedimentation tank for further sedimentation to obtain a high-concentration muddy water mixture containing sulfur powder deposited at the bottom and effluent that can meet the discharge standards.

6. The operation method of an urban sewage short - process treatment system according to claim 5, characterized in that, In step S1, the sewage is municipal sewage; the iron salt coagulant added in step S1 includes one or a combination of more of ferric chloride, ferric sulfate, polyferric chloride, and polyaluminum ferric chloride. The reaction time of the mixing tank in step S1 is 20 to 40 min, and the stirring rate is 20 to 40 r / min.

7. The operation method of an urban sewage short - process treatment system according to claim 6, characterized in that, The surface load of the enhanced primary sedimentation tank in step S2 is 1-2 m 3 / (m 2 ·h), and the sedimentation time is 0.5-2 h; the enhanced primary sedimentation tank in step S2 adopts intermittent sludge discharge with a cycle of 4-8 h.

8. The operation method of an urban sewage short - process treatment system according to claim 7, characterized in that, In step S3, the MABR tank and the MBBR tank operate in a combined sludge and membrane mode, and the sludge concentration is set to 2000 to 4000 mg MLSS / L; in step S3, a sulfur powder mixture is added to the MABR tank, and the sulfur powder particle size is selected to be 50 to 500 μm. The sulfur powder mixture can be added continuously or intermittently; alkalinity is supplemented in the MABR tank at the same time. The alkalinity agent is selected from one or a combination of more of sodium carbonate, sodium bicarbonate, calcium carbonate, and sodium hydroxide. Whether external supplementation is required is judged by the alkalinity content in the influent. When the raw water alkalinity reaches 5 times or more of the average nitrate nitrogen concentration, no addition is required. When the raw water alkalinity is insufficient, alkalinity needs to be supplemented, and the total addition amount is set to 5 times the daily nitrate nitrogen removal amount; feedback regulation is carried out by monitoring the pH value. When the pH value is lower than 6.8, alkalinity is continuously added for supplementation.

9. The operating method of an urban sewage short - process treatment system according to claim 8, characterized in that, In step S3, the aeration pressure of the aeration membrane module in the MABR tank is set to 10 to 50 kPa. Due to the large difference in oxygen mass transfer rate caused by the difference in membrane module materials, feedback regulation of the aeration pressure is carried out by monitoring the dissolved oxygen concentration. The dissolved oxygen concentration in the MABR tank is controlled at 0.2 to 1.0 mg / L; in step S3, the dissolved oxygen concentration in the MBBR tank is controlled at 1.5 to 2.5 mg / L. The ultimate removal of ammonia nitrogen is achieved through enhanced nitrification. At the same time, the synchronous nitrification and denitrification of sulfur autotrophic enhancement are achieved through the biofilm on the surface of the filler and the biofilm on the surface of the suspended elemental sulfur microcarrier to achieve the standard treatment of TN; in step S3, the hydraulic retention time of the MABR tank and the MBBR tank is set to 6 to 12 h.

10. The operating method of an urban sewage short - process treatment system according to claim 9, characterized in that, The surface loading of the inclined tube sedimentation tank in step S4 is 10-25 m 3 / (m 2 ·h), and the sedimentation time is 0.5-2 h; the high-concentration muddy water mixture containing sulfur powder in step S4 is refluxed to the MABR tank through a reflux pump, and the reflux ratio is set to 50%-100% to circulate sulfur powder and activated sludge in the biochemical treatment system; the effluent in step S4 meets the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants".

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