Sewage treatment method for enhancing nitrogen removal and phosphorus recovery by coupling biological chain with micro-electrolysis filler

Abstract

The invention relates to a sewage treatment method for enhancing nitrogen removal and phosphorus recovery by coupling a biological chain with a micro-electrolysis filler, which comprises the following steps: sewage sequentially enters an anaerobic zone, an anoxic zone, an aerobic zone and a metazoan growth zone, the treated effluent enters a turntable filter tank, and activated sludge in the effluent is filtered out; the filtered water enters a phosphorus recovery system provided with a micro-electrolysis filler; sewage passes through a phosphorus recovery system, then effluent enters a high-density sedimentation tank, a coagulation reaction is performed firstly, then a flocculation reaction is performed, and SS and most dissolved matters in water are removed through a sedimentation zone; and discharging the discharged water reaching the quasi-fourth class, and simultaneously discharging the sludge after the sludge is concentrated. According to the sewage treatment method provided by the invention, the yield of residual sludge is reduced from the source, the sludge pollution is reduced, the sewage treatment effect is enhanced, the phosphorus resource in the sewage is recycled, and the operation energy consumption and the power consumption are reduced; the required equipment is simple in structure, can operate automatically, does not increase the occupied area, and is small in maintenance amount; the method has the advantages of low investment and operation cost, low cost and the like.

Description

Technical Field

[0001] The invention relates to a sewage treatment method for strengthening nitrogen removal and phosphorus recovery by coupling a biological chain with a micro-electrolysis filler, and belongs to the technical field of sewage treatment. Background Art

[0002] With the continuous improvement of environmental protection laws and regulations and the continuous enhancement of public environmental awareness, on the one hand, the discharge standards of urban sewage treatment plants are becoming increasingly stringent, and urban sewage treatment is facing increasing pressure, requiring the effluent quality of sewage treatment plants to be better and more in line with environmental protection requirements; on the other hand, urban sewage treatment plants themselves also pay more attention to technological innovation based on traditional processes, and improve the treatment efficiency and treatment level of sewage treatment plants by introducing new technologies, new processes and new equipment, while reducing operating costs and energy consumption, in order to solve some problems existing in traditional sewage treatment processes, such as the need for a large amount of investment and operating costs, unstable effects, inability to effectively remove nitrogen and phosphorus, and low resource recovery and utilization rates. Therefore, it is urgent to develop a sewage treatment technology that is efficient, environmentally friendly and low-cost.

[0003] Phosphorus is an important scarce resource. Natural phosphate ore is decreasing year by year due to mining. It is estimated that the phosphorus discharged by urban sewage treatment plants can meet about 15-20% of human phosphorus demand. Therefore, it is necessary to recover phosphorus from sewage. At present, the phosphorus resource recovery of urban sewage treatment plants at home and abroad mainly focuses on the residual sludge of the biological phosphorus removal (BPR) process. High-concentration phosphate is obtained from sludge concentration, anaerobic fermentation supernatant and sludge filtrate, and then phosphorus products such as struvite and calcium phosphate are recovered by physical and chemical methods such as chemical precipitation and crystallization. Phosphorus recovery in this way relies on the BPR process to bio-enrich low-concentration phosphate in urban sewage in activated sludge, and obtain a phosphorus-rich solution that meets the recovery requirements by releasing or extracting phosphorus in the sludge. However, the BPR process is essentially still a process technology that focuses on the conversion and removal of organic matter, in which sewage organic matter is converted into microbial cells in large quantities, while consuming a large amount of oxygen. If, in the urban sewage treatment process whose main goal is resource utilization, the low-carbon and low-phosphorus sewage after organic matter recovery will be unable to meet the growth and metabolic needs of activated sludge in the traditional BPR process, the way to obtain high-concentration phosphate through this side stream mode will no longer exist, and new process technologies are needed to achieve the enrichment of phosphate in low-carbon and low-phosphorus sewage.

[0004] At present, the main methods for treating and disposing the residual sludge are incineration after dehydration, landfill disposal and agricultural utilization. Among them, the cost of sludge incineration is too high, and heavy metals affect the safety of agricultural utilization, so most of the residual sludge is disposed of by landfill. Landfill disposal has difficult-to-solve problems such as Pi and heavy metals, toxic organic matter, etc. polluting land and groundwater, producing toxic and harmful gases, and occupying a large amount of land. It has become a huge problem that plagues urban development and affects the living environment. Therefore, how to reduce sludge production from the source is also a technical problem that needs to be solved urgently. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] In order to solve the above problems in the prior art, the present invention provides a wastewater treatment method for enhancing nitrogen removal and phosphorus recovery by coupling a bio-chain with a micro-electrolysis filler.

[0007] (II) Technical solution

[0008] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0009] The wastewater treatment method for enhancing nitrogen removal and phosphorus recovery by coupling the biochain with micro-electrolysis filler comprises the following steps:

[0010] S1. Sewage enters the biological chain system and first enters the anaerobic zone, where the organic matter in the sewage is decomposed into small molecular hydrolysis products by bacterial flocs, and some organic matter is ammonified, releasing phosphorus at the same time; then the sewage is denitrified by anoxic microorganisms to reduce the total nitrogen concentration in the sewage, and then the ammonia nitrogen in the sewage is nitrified by aerobic microorganisms, and then passes through the protozoan and metazoan growth zone, where protozoans and metazoans eat excess sludge. At the same time, protozoans eat some pollutants to further improve the effluent quality and reduce the effluent turbidity;

[0011] S2, the effluent from the protozoan growth area enters the rotary filter tank to filter out the activated sludge in the effluent, and the filtered water enters the phosphorus recovery system equipped with micro-electrolysis filler;

[0012] S3. After the sewage passes through the phosphorus recovery system, the effluent enters the high-density sedimentation tank, where it first undergoes coagulation reaction and then flocculation reaction to remove dissolved matter and SS in the water. The treated sewage enters the sedimentation tank to obtain clarified water and concentrated sludge.

[0013] In the sewage treatment method as described above, preferably, the food chain system includes an anaerobic zone, an anoxic zone, an aerobic zone, and a protozoan growth zone which are connected in sequence; an aeration plate is arranged at the bottom of the aerobic zone and the metazoan growth zone, and the organisms in the protozoan growth zone include protozoa, rotifers, nematodes, earthworms, etc.

[0014] Furthermore, two anaerobic zones are provided, 2 to 4 anoxic zones are provided, 3 to 4 aerobic zones are provided, 1 to 2 protozoan growth zones are provided, and the anaerobic to protozoan growth zones are divided into 8 to 12 zones in total; fixed fillers A are provided in the anaerobic zone, the fillers are arranged in parallel, and the intervals are 8 to 12 cm. After a period of sludge cultivation, biofilm A is formed on the fixed fillers A; fixed fillers B are provided in the anoxic zone, the fillers are arranged in parallel, and the intervals are 8 to 12 cm. After a period of sludge cultivation, biofilm B is formed on the fixed fillers B; fixed fillers C are provided in the aerobic zone, the fillers are arranged in parallel, and the intervals are 8 to 10 cm. After a period of sludge cultivation, biofilm C is formed on the fixed fillers C, wherein the fixed fillers A, B, and C are made of carbon fiber fillers.

[0015] In the sewage treatment method as described above, preferably, in step S2, the concentrated activated sludge after filtration is returned to the anaerobic tank in the biochain system through a sludge return pump, and is returned to the anaerobic tank together with the return sludge from the sludge return pump at the bottom of the aerobic zone, thereby increasing the sludge concentration in the anaerobic tank.

[0016] Further preferably, the bottom outlet of the aerobic zone in the biological chain system is provided with a sludge return pump to return the sludge to the anaerobic zone, and the return flow rate is controlled at 100% to 300%;

[0017] The sludge at the bottom of the rotary filter is returned to the anaerobic zone through a pipe, and the return volume is controlled at 50% to 100%. The sludge is discharged from the anaerobic zone intermittently, once every 10 to 15 days.

[0018] In the sewage treatment method as described above, preferably, in step S2, the phosphorus recovery system includes an iron-carbon micro-electrolysis tank, an iron phosphate separator, and an iron phosphate storage tank. When the sewage enters the iron-carbon micro-electrolysis tank provided with an iron-carbon filler, the phosphorus in the sewage undergoes a micro-electrolysis reaction with the surface of the spherical iron-carbon filler, and a dense iron phosphate is generated on the surface of the iron-carbon filler and attached to the surface of the iron-carbon filler. When the coverage rate of the surface reaches more than 50%, air-water backwashing is used to achieve the shedding of the dense iron phosphate from the surface of the iron-carbon filler. The detached iron phosphate is deposited at the bottom of the iron-carbon micro-electrolysis tank and enters the iron phosphate separator with gravity and water flow. After separation by the iron phosphate separator, the iron phosphate is separated from the water and enters the iron phosphate storage tank.

[0019] In the sewage treatment method as described above, further preferably, the order of air-water backwashing is: 1) air washing for 5 minutes; 2) air-water mixed washing for 5 minutes; the backwashing time is determined by the phosphorus removal rate, and backwashing is performed when the removal rate is less than 50%.

[0020] In the sewage treatment method as described above, preferably, in step S3, the coagulation reaction is carried out in a coagulation tank, PAC is added and the coagulation reaction is carried out under the action of a stirring paddle, and the water flow of the inlet and outlet of the coagulation tank is controlled at the surface.

[0021] In the sewage treatment method as described above, preferably, in step S3, the flocculation reaction is carried out in a flocculation tank, an anionic polymer coagulant is added into the flocculation tank and the flocculation reaction is carried out under the action of a stirring paddle.

[0022] In the sewage treatment method as described above, preferably, the sedimentation tank portion includes an inlet area and an extended sedimentation area, a sludge recovery area and an inclined tube clarification area; sludge collectors arranged along the entire width of the tank in the inlet area and the extended sedimentation area separate the sludge from the water and discharge it; the sludge is directly deposited on the inclined plate below the sludge recovery area, and then slowly settles to the bottom of the sedimentation tank. After the sludge is concentrated by gravity at the bottom of the tank, the sludge is continuously scraped into the central sludge collection pit by a scraper, and then intermittently discharged to the sludge treatment system by a sludge discharge screw pump; the clean water after the sewage is treated in the inclined plate clarification area meets the external discharge standard.

[0023] (III) Beneficial effects

[0024] The beneficial effects of the present invention are:

[0025] (1) The wastewater treatment method provided by the present invention uses a biochain coupled micro-electrolysis filler to enhance denitrification and phosphorus recovery, uses protozoa to reduce the production of excess sludge from the source, enhances the denitrification effect of wastewater, recovers phosphorus resources, and reduces operating energy and electricity consumption, thereby reducing sludge pollution.

[0026] (2) The wastewater treatment method provided by the present invention uses a bio-chain coupled micro-electrolysis filler to enhance denitrification and phosphorus recovery. The phosphorus recovery system can be used to recover phosphorus resources in wastewater. The recovered iron phosphate has high purity, few impurities, and good prospects for resource utilization. The phosphorus recovery system is used to recover phosphorus at a lower cost than directly adding PAC and PAM, and has a high degree of automation, which can reduce the operating cost of phosphorus recovery.

[0027] The present invention not only improves the sewage treatment effect, reduces the sludge output, but also recovers the phosphorus resources through the coupling of biofilm, activated sludge method, phosphorus recovery and high-density sedimentation tank;

[0028] Through biofilm and regular addition of protozoa, the sludge production rate is reduced by 50% to 90% compared with the activated sludge method.

[0029] (3) The wastewater treatment method provided by the present invention, which uses a biological chain coupled with micro-electrolysis fillers to enhance nitrogen removal and phosphorus recovery, requires a simple equipment structure, and mainly adds fillers to the original biochemical pool. The modification is convenient, the operation is automated, the land occupation is not increased, and the maintenance is small;

[0030] The investment and operation costs are low and the management is convenient. Compared with the activated sludge method which requires sludge treatment, it has cost advantages.

[0031] (4) The wastewater treatment method provided by the present invention uses a bio-chain coupled micro-electrolysis filler to enhance denitrification and phosphorus recovery. The method can simultaneously remove nitrogen and phosphorus from wastewater, and has high treatment effect, low cost, simple operation and good stability. It is particularly suitable for cost reduction and efficiency improvement of existing projects, and can also be used to reduce organic sludge production and phosphorus recovery in newly built wastewater treatment projects. It is of great significance to the development and promotion of wastewater treatment technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the structure of the food chain system provided by the present invention.

[0033] Figure 2 A schematic diagram of the structure of the phosphorus recovery system provided by the present invention;

[0034] Figure 3 This is a schematic structural diagram of the high-density sedimentation tank provided by the present invention.

[0035] [Description of Reference Numerals]

[0036] 1: Anaerobic tank;

[0037] 2: Anoxic pool;

[0038] 3: Aerobic pool;

[0039] 4: First proto-metazoan growth pool;

[0040] 5: Second proto-metazoan growth pool;

[0041] 6: Blower;

[0042] 7: flow hole;

[0043] 8: DC (integrated online monitoring instrument);

[0044] 9: Water inlet pump;

[0045] 10: Water inlet electric valve;

[0046] 11: Flow meter;

[0047] 12: External discharge pump;

[0048] 13: Rotating disc filter;

[0049] 14: The first sludge return pump;

[0050] 15: Second sludge return pump;

[0051] 16: Protozoan dosing device;

[0052] 17: First intermediate pool;

[0053] 18: Iron-carbon micro-electrolysis tank;

[0054] 19: Iron-carbon filler;

[0055] 20: valve;

[0056] 21: Backwash air pipe;

[0057] 22: Iron phosphate separator;

[0058] 23: Iron phosphate storage tank;

[0059] 24: Second intermediate pool;

[0060] 25: Electric valve. DETAILED DESCRIPTION

[0061] The present invention uses bio-chain technology to enhance sewage denitrification and reduce sludge production, and simultaneously couples micro-electrolysis to recover phosphorus, so as to achieve the purpose of sewage quality improvement, sewage resource utilization and sludge reduction.

[0062] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation modes in conjunction with the accompanying drawings. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0063] Example 1

[0064] The wastewater treatment method that uses biochain coupling micro-electrolysis fillers to enhance nitrogen removal and phosphorus recovery can be divided into three small systems according to the process: biochain system, phosphorus recovery system, and high-density sedimentation tank system.

[0065] The biological chain system is sequentially provided with anaerobic zone, anoxic zone, aerobic zone, protozoan growth zone, and protozoan feeding tank, and the supporting equipment includes: water inlet pump, valve, flow meter, pipeline and instrument, etc. Generally, 2 grids are set in the anaerobic zone, 2-4 grids in the anoxic zone, 3-4 grids in the aerobic zone, 1-2 grids in the protozoan growth zone, and a total of 8-12 grids are divided from the anaerobic to the protozoan growth zone. Fixed carbon fiber filler A is set in the anaerobic zone, and the fillers are arranged in parallel with an interval of 8-12 cm. After a period of sludge cultivation, biofilm A is formed on the fixed filler A. Fixed carbon fiber filler B is set in the anoxic zone, and the fillers are arranged in parallel with an interval of 8-12 cm. After a period of sludge cultivation, biofilm B is formed on the fixed filler B. Fixed carbon fiber filler C is set in the first aerobic zone, and the fillers are arranged in parallel with an interval of 8-10 cm. After a period of sludge cultivation, biofilm C is formed on the fixed filler C.

[0066] Aeration pipes are set in the anaerobic zone and the anoxic zone. The aeration plates connected to the aeration pipes are set at the bottom of the aerobic zone and the metazoan growth zone. The aeration pipes and the aeration plates are connected to the blower through the air pipe, and the blower supplies aeration. This system requires precise control of the aeration volume. Therefore, valves and flow meters are set on the connecting pipelines to adjust the opening of the aeration valve according to the dissolved oxygen content in the water to determine the aeration flow.

[0067] The protozoan growth area is mainly for cultivating protozoans, using them to eat excess sludge, and at the same time, further improving the effluent water quality and reducing the effluent turbidity. In order to improve the efficiency of the protozoan growth area eating sludge and reduce the slow growth period of protozoans, a protozoan addition tank is set up to maintain the sludge reduction effect by directly adding protozoans. Finally, the effluent of the biochain system reaches the Class A or Quasi-Class IV standards except for phosphorus. When the Class A standard is met except for phosphorus, the system residence time is shorter, and when the Quasi-Class IV standard is met except for phosphorus, the residence time is longer. If the total nitrogen is high, a part of the carbon source needs to be added.

[0068] The process flow of the biological chain system is as follows: the sewage is lifted to the anaerobic zone by a lifting pump, and the water flow is accurately controlled by valves and flow meters in the middle. At the same time, the sludge returned from the sludge return pump of the post-biological zone is fully mixed with the returned sludge under the stirring of the submersible mixer. In the anaerobic zone, the oxygen concentration is very low. At this time, the organic matter is decomposed into small molecular hydrolysis products by the bacterial flocs, and some of the organic matter is ammonified, and at the same time, phosphorus is released.

[0069] The effluent from the anaerobic zone enters the anoxic zone, and the return sludge that flows back from the bottom of the proto-metazoan growth zone through the internal return pump also enters simultaneously. The main function of the anoxic zone is to use anoxic microorganisms to reduce nitrates in sewage into nitrogen gas in the absence of oxygen, thereby achieving the purpose of denitrification. The implementation path is to use the anoxic microorganisms in the return sludge at the bottom of the biofilm and metazoan growth zone, and use the nitrate nitrogen carried in the return sludge as an electron acceptor to carry out rapid denitrification, while preparing for the full release of anaerobic phosphorus removal and reducing the total nitrogen concentration in the sewage;

[0070] The effluent from the anoxic zone enters the aerobic zone, and air is aerated into the water through the blower and aeration system. Aerobic microorganisms absorb oxygen from the air in the sewage, and the microorganisms use organic pollutants and oxygen to grow. Under aerobic conditions, the microorganisms can nitrify the ammonia nitrogen in the domestic sewage to generate nitrates. During the growth process, the microorganisms further degrade organic matter, which is conducive to the aerobic microorganisms using the ammonia nitrogen in the wastewater to generate nitrates and nitrites, thereby strengthening the nitrification effect.

[0071] The effluent from the aerobic zone enters the metazoan growth zone. There are many protozoans in this zone, and the growth of protozoans consumes a lot of oxygen and bacteria. Therefore, a blower and an aeration system are needed to fill air. The oxygen in the air is absorbed by the metazoans in the sewage. The protozoan growth zone is mainly composed of protozoa, rotifers, nematodes, earthworms and other organisms, which feed on tiny microorganisms and organic particles. The microorganisms in the sewage as food include various bacterial flocs such as nitrifying bacteria and denitrifying bacteria. Through the food chain, the sludge production is greatly reduced, achieving the purpose of sludge reduction; Return ratio: 1) Internal sludge return: The sludge is refluxed from the bottom outlet of the aerobic zone to the anaerobic zone through the sludge reflux pump 1, and the reflux volume is controlled at 100% to 300%; 2) Sludge reflux from the rotary filter: The sludge at the bottom of the rotary filter is refluxed to the anaerobic zone through the pipeline, and the reflux volume is controlled at 50% to 100%; the sludge is discharged in the second anaerobic zone, intermittently, generally once every 10 to 15 days. When the SS content is high, the sludge discharge interval is shorter, and when the SS content is low, the sludge discharge interval is longer, generally not exceeding 15 days. Because the biofilm shedding cycle is about one month, in order to ensure the timely discharge of the shedding sludge, it is generally not more than 15 days;

[0072] At this time, the effluent of the biological chain system reaches Class A or quasi-Class IV standards except for phosphorus. Its SS, COD, ammonia nitrogen and total nitrogen are low. The effluent is relatively clear and contains a small amount of activated sludge. The concentration is generally 10-50 mg / L, with an average of about 30 mg / L. In order to reduce the activated sludge in the effluent and reduce the effluent SS, a rotary filter is set at the end of the biological chain system to filter out the activated sludge in the effluent. The filtered water is dephosphorized and recycled. The concentrated activated sludge after filtration is returned to the anaerobic tank through the sludge return pump 2, and returned to the anaerobic tank together with the return sludge of the sludge return pump 1 at the bottom of the aerobic zone, thereby increasing the sludge concentration in the anaerobic tank.

[0073] The structural diagram of the food chain system is as follows Figure 1As shown, the anaerobic zone is provided with two anaerobic pools 1, the anoxic zone is provided with two anoxic pools 2, the aerobic zone is provided with six aerobic pools 3, the protozoan growth zone is provided with two protozoan growth pools, the first protozoan growth pool 4 and the second protozoan growth pool 5, and the partition plate between the two adjacent pools is provided with an upper flow hole and a lower flow hole 7 in sequence. The aeration plate is provided at the bottom of the aerobic pool 3, and the aeration pipe and the aeration plate are connected to the blower 6 through the air pipe, and valves and flow meters are provided on the connecting pipeline. The first pool in each zone is equipped with a DC (integrated online monitoring instrument) 8 for measuring dissolved oxygen, pH, etc. The front end of the anaerobic pool 1 is provided with a water inlet pipe, and the water inlet pipe is provided with a water inlet pump 9, a water inlet electric valve 10 and a flow meter 11 in sequence. The second anaerobic tank 1 is also provided with an external discharge pump 12. The last tank, i.e., the second protometazoan growth tank 5, is connected to a rotary filter 13. The bottom of the rotary filter 13 is connected to a first sludge return pump 14. The bottom of the last aerobic tank 3 is connected to a second sludge return pump 15. The first sludge return pump 14 and the second sludge return pump 15 are connected to the first anaerobic tank 1 through pipelines. A protometazoan dosing device 16 is also provided above the first protometazoan growth tank 4 and the second protometazoan growth tank 5.

[0074] When the effluent from the rotary filter tank enters the phosphorus recovery system, the purpose of the phosphorus recovery system is to recover phosphorus in the sewage, thereby realizing phosphorus recovery. The phosphorus recovery system includes an iron-carbon micro-electrolysis tank, an iron phosphate separator, and an iron phosphate storage tank. When the sewage enters the iron-carbon micro-electrolysis tank, the phosphorus in the sewage reacts with the surface of the spherical iron-carbon filler through micro-electrolysis, and dense iron phosphate is generated on the surface of the iron-carbon filler, which is attached to the surface of the iron-carbon filler. When the surface coverage rate reaches more than 50%, air-water backwashing is required to achieve the detachment of the dense iron phosphate from the surface of the iron-carbon filler. The detached iron phosphate is deposited at the bottom of the iron-carbon micro-electrolysis tank, and enters the iron phosphate separator with gravity and water flow. After separation by the iron phosphate separator, the iron phosphate is separated from the water and enters the iron phosphate storage tank. After being stored to a certain amount, it is sent to a fertilizer plant, etc., to be used as a phosphorus fertilizer. The order of air-water backwashing is: 1) air washing for 5 minutes; 2) air-water mixed washing for 5 minutes; the backwashing time is determined by the removal rate of phosphorus, and when the removal rate is less than 50%, backwashing is performed.

[0075] like Figure 2As shown, the water outlet of the rotary filter tank is connected to the water inlet of the first intermediate water tank 17 through a pipeline, and the upper end of the first intermediate water tank 17 is provided with an air-water backwash pipeline connected to the water inlet of the upper end of the iron-carbon micro-electrolysis tank 18. The iron-carbon micro-electrolysis tank 18 is provided with an iron-carbon filler 19, and the lower end of the iron-carbon micro-electrolysis tank 18 is provided with a pipeline connected to the lower end of the first intermediate water tank 17, and a valve 20 is provided on the pipeline. The iron-carbon micro-electrolysis tank 18 is also connected to a backwash air pipe 21. The lower end of the iron-carbon micro-electrolysis tank 18 is connected to the iron phosphate separator 22 through a pipeline, and the lower end of the iron phosphate separator 22 is connected to the iron phosphate storage tank 23 through a pipeline. The upper end of the iron-carbon micro-electrolysis tank 18 is also provided with a pipeline connected to the second intermediate water tank 24, and an electric valve 25 is also provided on the pipeline between the two.

[0076] After the sewage passes through the phosphorus recovery system, the phosphorus removal rate is 50% to 70%, and the effluent TP is about 0.5 mg / L. If the quasi-Class IV standard is required at this time, a high-density sedimentation tank is also needed to further reduce the phosphorus content in the effluent. At this time, polyaluminum chloride (PAC) and polyacrylamide (PAM) are added to the high-density sedimentation tank to further remove dissolved matter and suspended solids (SS) in the water. The high-density sedimentation tank includes a coagulation and flocculation tank equipped with a stirrer, as well as an efficient inclined plate sedimentation tank and a sludge concentration area.

[0077] The sewage undergoes coagulation reaction in the coagulation tank in front of the high-density sedimentation tank. PAC is added to the water as a coagulant to destabilize the suspended colloids in the water and remove part of the soluble phosphates through chemical precipitation reaction. The whole coagulation process adopts the principle of dynamic coagulation. The water flow of the inlet and outlet of the coagulation tank is controlled at the surface of the tank. The sewage then flows into the flocculation tank. The flocculation reaction is also a physical and mechanical process. In this process, the floccules increase due to physical stirring and intermolecular forces to facilitate precipitation. Anionic polymer coagulant (PAM) is added to the flocculation tank to play an adsorption and bridging role to improve the flocculation effect. After coagulation and flocculation, the sewage enters the sedimentation tank. The sedimentation area mainly includes three parts: the inlet area and the extended sedimentation area, the sludge recovery area and the inclined tube clarification area. a) Inlet area and extended sedimentation area: The scum collector arranged along the entire width of the sedimentation tank in the inlet area separates the scum from the water and discharges it. The sedimentation area can separate the alum flocs with a larger specific gravity (about 80% of the total SS content) and directly precipitate them in the sludge recovery area, reducing the amount of sludge passing through the inclined plate and reducing the risk of sludge accumulation and clogging of the inclined plate. b) Sludge recovery area: The precipitated sludge will slide down the inclined plate and then fall to the bottom of the pool. The precipitated sludge can form a sludge layer of floccules (flocculent contact layer) to a certain extent, which will have the following effects: increase crystallization nuclei; reduce the consumption of coagulants; increase the density of floccules and thus increase the sedimentation rate. After the sludge is concentrated at the bottom of the pool, a slow-rotating scraper continuously scrapes the sludge into the central sludge collection pit. The bars on the scraper can further improve the sludge concentration effect. The concentrated sludge is controlled by a certain set program or a mud level meter to achieve an optimized sludge concentration, and is intermittently discharged to the sludge treatment system through a mud discharge screw pump. c) Inclined plate clarification area: inclined plate and matching support system. Clarified water collection system: The inclined plate has a large gap (80mm) and an inclination angle (60°), which allows the sludge to slide down the inclined plate under the action of gravity. At the same time, the lower Reynolds coefficient (close to laminar flow) and the structure of the inclined plate (increased wet perimeter and sedimentation area) also ensure the separation efficiency of mud and water. The clarified water on the upper layer of the inclined plate is collected by the water collection tank. In order to facilitate the distribution of water flow when the water volume is small, the water outlet weir on the water collection tank can be triangular or rectangular. The clear water treated in the inclined plate clarification area reaches the quasi-fourth-class effluent water quality, meeting the requirements of the "Special Emission Limit" of the "Pollutant Emission Standard for Urban Wastewater Treatment Plants" (Draft for Comments).

[0078] The structural diagram of the high-density sedimentation tank is as follows: Figure 3As shown, a pipeline is provided at the lower end of the second intermediate water tank 24, which is connected to the central barrel 28 set between the coagulation tank 26 and the flocculation tank 27 through a lifting pump 25. A sedimentation tank 28 is provided adjacent to the flocculation tank 27. The sedimentation tank is provided with a water inlet area and an extended sedimentation area, a sludge recovery area and an inclined tube clarification area. The sedimentation tank is provided with a partition to divide the sedimentation tank into a water inlet area and a sludge recovery area. A scraper 29 is provided below the sludge recovery area. A water collection channel 30 and a water collection weir 31 are provided above the sludge recovery area. The inclined plate is provided about 1m below the water of the sedimentation tank. Multiple rows of inclined tubes 32 are provided below the water collection weir 31, and a water outlet pipe 33 is provided on one side of the water collection weir 31. A sludge return pipe 34 and a sludge discharge pipe 35 are provided below the scraper 29 at the bottom of the sedimentation tank 28.

[0079] The biochain provided by the present invention utilizes the interaction and synergy of microorganisms and is processed together with metazoans, utilizes the metabolic process of microorganisms themselves to realize material energy conversion to complete the degradation of pollutants in water, promotes the degradation and reduction of organic matter through the ecological environment of the microbial community, reduces the addition of external energy and agents, thereby reducing secondary pollution and realizing the removal of nitrogen and phosphorus in sewage, with high treatment effect, and greatly reduces the sludge output through metazoans, thereby achieving the purpose of sludge reduction; and the equipment cost, energy consumption and operation and maintenance cost of the bioreactor are low; the biochain purification technology can achieve a high purification effect on pollutants within a controllable time and has high efficiency; at the same time, because the biochain water treatment technology is designed based on the principle of natural ecosystem, its treatment process meets the requirements of environmental protection and can reduce pollution to the environment; in addition, the biochain treatment forms a relatively stable microbial community, has good operation stability and resistance to water quality shock, can domesticate adaptive biochains under different water quality conditions, is more suitable for diverse, complex and changeable treatment environments, and is a green, low-carbon and sustainable water treatment technology.

[0080] The micro-electrolysis filler adopted in the present invention adopts iron-carbon micro-electrolysis, which can efficiently degrade organic matter in sewage and remove pollutants, has obvious treatment effect, stable effluent water quality, can remove nitrogen and phosphorus in sewage in a short time, and has a high removal rate of more than 90%; it can achieve efficient treatment at a relatively low voltage, is easy to operate and maintain, and can reduce energy consumption and operating costs; chemical agents need to be added during its operation, and no agent residues and secondary pollution will be generated, which meets environmental protection requirements.

[0081] The above method removes nitrogen and phosphorus from sewage at the same time, and has high treatment effect, low cost, simple operation and good stability, and can be widely used in domestic sewage and industrial sewage treatment.

[0082] The method of the present invention combines the biological chain with the iron-carbon micro-electrolysis technology and can be used for sewage treatment with different water qualities and types of pollutants. It can be applied to sewage treatment plants of different sizes and has good application prospects.

[0083] Example 2

[0084] On the basis of Example 1, when there are 4 anoxic zones, 6 aerobic zones, 2 protozoan growth zones, and a total of 12 zones from anaerobic to protozoan growth zones, 1) sludge internal reflow: from the bottom outlet of the aerobic zone, the sludge is recirculated to the anaerobic zone through the second sludge reflow pump, and the reflow rate is controlled at 200%; 2) filter tank sludge reflow: the sludge at the bottom of the filter tank is recirculated to the anaerobic zone through the pipeline, and the reflow rate is controlled at 5%, the sewage treatment results are based on the urban sewage treatment plant The pollutant discharge standard GB18918-2002 was used for testing. The inlet water quality was chemical oxygen demand (CODCr): 180mg / L, five-day biochemical oxygen demand (BOD5) 78mg / L, ammonia nitrogen: 32mg / L, TN: 43mg / L, TP: 3.8mg / L, and the effluent water quality was CODcr: 28mg / L, ammonia nitrogen: 0.9mg / L, TN: 13mg / L, TP: 0.28mg / L. The sludge reduction effect reached 88%. The phosphorus recovery rate reached 50% (the phosphorus recovery rate is calculated by dividing the recovered phosphorus by the phosphorus content in the effluent of the biochemical pool).

[0085] Example 3

[0086] On the basis of Example 1, when there are 5 anoxic zones, 6 aerobic zones, and 1 protozoan growth zone, there are 12 zones from anaerobic to protozoan growth zones, 1) sludge internal reflow: from the bottom outlet of the aerobic zone, the second sludge reflow pump is used to reflow to the anaerobic zone, and the reflow rate is controlled at 250%; 2) sludge reflow from the rotary filter: the sludge at the bottom of the rotary filter is reflowed to the anaerobic zone through a pipeline, and the reflow rate is controlled at 5%, the sewage treatment results are as follows: the influent water quality is CODcr: 216mg / L, ammonia nitrogen: 58mg / L, TN: 68mg / L, TP: 5.1mg / L, and the effluent water quality is CODcr: 26mg / L, ammonia nitrogen: 1.6mg / L, TN: 14mg / L, TP: 0.26mg / L. The sludge reduction effect reaches 82%. The phosphorus recovery rate reaches 60% (the phosphorus recovery rate is calculated by dividing the recovered phosphorus amount by the phosphorus content in the effluent of the biochain system).

[0087] Comparative Example 1

[0088] This comparative example is based on Example 1. When the conventional A2O process + deep treatment is used, that is, no carbon fiber filler and phosphorus recovery are set to treat the sewage. When the inlet water quality is CODcr: 216mg / L, ammonia nitrogen: 32mg / L, TN: 40mg / L, TP: 3.2mg / L, the final effect obtained is that the effluent water quality is CODcr: 46mg / L, ammonia nitrogen: 0.6mg / L, TN: 14mg / L, TP: 0.4mg / L. The sludge output is large, and the carbon source and phosphorus removal agent are consumed at the same time, and no phosphorus is recovered. According to calculations, the use of the technology of the present invention, relative to the conventional A2O process + deep treatment process, reduces the sludge by 80%, reduces the addition of carbon source by 50%, reduces the addition of phosphorus removal agent by 60%, and harvests phosphates at the same time, and the phosphorus resources are recycled.

[0089] Comparative Example 2

[0090] This comparative example is based on Example 1, without phosphorus recovery and sewage treatment. When the influent water quality is CODcr: 216mg / L, ammonia nitrogen: 32mg / L, TN: 40mg / L, TP: 3.2mg / L, the final effect obtained is that the effluent water quality is CODcr: 30mg / L, ammonia nitrogen: 1.3mg / L, TN: 14mg / L, TP: 0.9mg / L. The sludge reduction effect reaches 80%.

[0091] Comparative Example 3

[0092] This comparative example is based on Example 1, which is different from the present invention. It does not use carbon fiber fillers to treat sewage. It uses conventional A / O process. When the influent water quality is CODcr: 216mg / L, ammonia nitrogen: 32mg / L, TN: 40mg / L, TP: 3.2mg / L, the final effect is that the effluent water quality is CODcr: 46mg / L, ammonia nitrogen: 0.9mg / L, TN: 14mg / L, TP: 0.46mg / L. The phosphorus recovery effect is about 30%. There is no sludge reduction effect, more reagents are added, and the operating cost is high.

[0093] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any person skilled in the art can use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A wastewater treatment method for enhancing nitrogen removal and phosphorus recovery by coupling a biological chain with a micro-electrolysis filler, characterized in that: It includes the following steps: S1. Sewage enters the biological chain system and first enters the anaerobic zone, where the organic matter in the sewage is decomposed into small molecular hydrolysis products by bacterial flocs, and some organic matter is ammonified, releasing phosphorus at the same time; then the sewage is denitrified by anoxic microorganisms to reduce the total nitrogen concentration in the sewage, and then the ammonia nitrogen in the sewage is nitrified by aerobic microorganisms, and then passes through the protozoan and metazoan growth zone, where protozoans and metazoans eat excess sludge. At the same time, protozoans and metazoans eat some pollutants, further improving the effluent quality and reducing the effluent turbidity; S2, the effluent from the protozoan growth area enters the rotary filter tank to filter out the activated sludge in the effluent, and the filtered water enters the phosphorus recovery system equipped with micro-electrolysis filler; S3. After the sewage passes through the phosphorus recovery system, the effluent enters the high-density sedimentation tank, where it undergoes coagulation reaction first, then flocculation reaction, and the SS and most of the dissolved matter in the water are removed through the sedimentation area; the effluent meets the quasi-Class IV standard for discharge, and the sludge is concentrated and discharged.

2. The sewage treatment method according to claim 1, characterized in that: The biological chain system comprises an anaerobic zone, an anoxic zone, an aerobic zone and a protozoan growth zone which are connected in sequence; an aeration plate is arranged at the bottom of the aerobic zone and the metazoan growth zone, and the organisms in the protozoan growth zone include protozoa, rotifers, nematodes and earthworms.

3. The sewage treatment method according to claim 2, characterized in that: There are two anaerobic zones, 2 to 4 anoxic zones, 3 to 4 aerobic zones, and 1 to 2 protozoan growth zones. There are a total of 8 to 12 zones from anaerobic to protozoan growth zones.

4. The sewage treatment method according to claim 1, characterized in that: In step S2, the concentrated activated sludge after filtration is returned to the anaerobic tank in the biological chain system through the sludge return pump, and is returned to the anaerobic tank together with the return sludge from the sludge return pump at the bottom of the aerobic zone, thereby increasing the sludge concentration in the anaerobic tank.

5. The sewage treatment method according to claim 4, characterized in that: The bottom outlet of the aerobic zone in the biological chain system is equipped with a sludge return pump to return the sludge to the anaerobic zone, and the return volume is controlled at 100% to 300%; The sludge at the bottom of the rotary filter is returned to the anaerobic zone through a pipe, and the return volume is controlled at 50% to 100%. The sludge is discharged from the anaerobic zone intermittently, once every 10 to 15 days.

6. The sewage treatment method according to claim 1, characterized in that: In step S2, the phosphorus recovery system includes an iron-carbon micro-electrolysis tank, an iron phosphate separator, and an iron phosphate storage tank. When sewage enters the iron-carbon micro-electrolysis tank provided with an iron-carbon filler, the phosphorus in the sewage undergoes a micro-electrolysis reaction with the surface of the spherical iron-carbon filler, and a dense iron phosphate is generated on the surface of the iron-carbon filler and attached to the surface of the iron-carbon filler. When the coverage rate of the surface reaches more than 50%, air-water backwashing is used to achieve the shedding of the dense iron phosphate from the surface of the iron-carbon filler. The detached iron phosphate is deposited at the bottom of the iron-carbon micro-electrolysis tank and enters the iron phosphate separator with gravity and water flow. After separation by the iron phosphate separator, the iron phosphate is separated from the water and enters the iron phosphate storage tank.

7. The sewage treatment method according to claim 6, characterized in that: The order of air-water backwashing is: 1) air washing for 5 minutes; 2) air-water mixed washing for 5 minutes; the backwashing time is determined by the removal rate of phosphorus. When the removal rate is less than 50%, backwashing is performed.

8. The sewage treatment method according to claim 1, characterized in that: In step S3, the coagulation reaction is carried out in a coagulation tank, PAC is added and the coagulation reaction is carried out under the action of a stirring paddle, and the flow rate and flow state of the inlet and outlet water flows of the coagulation tank need to be controlled to improve the mixing effect.

9. The sewage treatment method according to claim 1, characterized in that: In step S3, the flocculation reaction is carried out in a flocculation tank, an anionic polymer coagulant is added into the flocculation tank and the flocculation reaction is carried out under the action of a stirring paddle.

10. The sewage treatment method according to claim 1, characterized in that: The sedimentation tank part includes a water inlet area and an extended sedimentation area; a sludge recovery area; an inclined tube clarification area; scum collectors arranged along the entire width of the tank in the water inlet area and the extended sedimentation area separate the scum from the water and discharge it; The sludge settles directly on the inclined plate below the sludge recovery area, and then slowly settles to the bottom of the sedimentation tank. After being concentrated by gravity at the bottom of the tank, the sludge is continuously scraped into the central sludge collection pit by a sludge scraper, and then intermittently discharged to the sludge treatment system by a sludge discharge screw pump; The clean water after sewage treatment in the inclined plate clarification area meets the discharge standards.

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