An energy-saving AAO process for pre-pollutant enrichment sludge discharge

Abstract

The invention belongs to the field of sewage treatment technology; specifically discloses an energy-saving AAO process for pre-pollutant enriched sludge discharge, comprising the following steps: step one: sewage filtering treatment; step two: pre-treated sewage enters an anaerobic tank, and a stirrer is arranged in the anaerobic tank for stirring; step three, sewage above the side discharge tank enters an anoxic tank, and a stirrer is arranged in the anoxic tank for stirring; step four: sewage treated in step three enters a sedimentation tank, and the sedimentation tank settles the sludge to the bottom, and the treated clean water on the upper layer is discharged; all the sludge in the sedimentation tank is returned to the anaerobic tank, and part of the sludge after adsorption and absorption of carbon source organic matter enters the side discharge tank, and the side discharge tank discharges the sludge regularly; the process is simple to operate and has low cost, better economic benefits, and can also reduce the incoming water load of the biochemical unit, and can also alleviate the impact on the biochemical system caused by large fluctuations in incoming water concentration.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and in particular relates to an energy-saving AAO process for pre-pollutant enriched sludge discharge. Background Art

[0002] In sewage treatment, the AAO process is a commonly used biological denitrification and phosphorus removal process. However, when the carbon-nitrogen ratio (C / N) of sewage is high, the traditional AAO process faces some challenges. For example, in the anaerobic stage, excessive carbon sources may lead to intensified competition between polyphosphate bacteria and other microorganisms for carbon sources, affecting the phosphorus release effect of polyphosphate bacteria; in the anoxic stage, a high carbon-nitrogen ratio may make it difficult to accurately control the denitrification process, which may easily cause carbon source waste and insufficient carbon source in the subsequent aerobic stage, thereby affecting the removal efficiency of nitrogen and phosphorus in the entire process and the stability of the system.

[0003] The degradation (removal) process of organic matter by activated sludge can be divided into two stages: adsorption stage and stabilization stage. In the adsorption stage, the organic matter in the sewage is mainly transferred to the activated sludge, which is due to the large surface area of ​​the activated sludge and the presence of polysaccharide sticky substances on the surface. In the stabilization stage, the organic matter transferred to the activated sludge is mainly used by microorganisms. In the short time (5-10 min) after the sewage and activated sludge are in contact and mixed, the organic pollutants in the sewage, especially the suspended and colloidal organic matter, show a high removal rate. This initial high-speed removal phenomenon is the result of the combined effects of physical adsorption and biological adsorption. In this process, the organic substrate in the mixed liquid decreases rapidly and the COD decreases rapidly. This is because the surface area of ​​the activated sludge is large, and a large number of microorganisms are enriched on the surface, and the outside is covered with a mucous layer of polysaccharides. When the suspended and colloidal organic substrates in the sewage come into contact with the activated sludge flocs, they are quickly condensed and adsorbed and removed.

[0004] The current AAO process generally involves the following steps: after the sludge in the secondary sedimentation tank has been precipitated, the aerobic microorganisms in the aerobic tank degrade organic matter and nitrify ammonia nitrogen, consuming the organic carbon source, so that the sludge entering the sedimentation tank is in a clean state. Only a portion of the sludge precipitated in the secondary sedimentation tank is returned to the anaerobic tank to continue entering the system for adsorption and absorption of the organic carbon source. The remaining sludge is directly discharged for treatment to maintain the activity of the sludge in the entire system. The remaining clean sludge discharged does not completely adsorb organic matter and is directly discharged, resulting in a certain amount of waste of activated sludge resources. In addition, when treating sewage of the same magnitude, the traditional AAO process requires larger volumes of anaerobic tanks, anoxic tanks, and aerobic tanks. A larger amount of oxygen is required in the aerobic tank to ensure that the COD content of the system discharge water is qualified, resulting in high energy consumption for the entire system, high process complexity, and the need to add flocculants during sewage pretreatment, which is costly. Summary of the invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a pre-pollutant enrichment sludge discharge energy-saving AAO process. A side discharge pool is added between the anaerobic pool and the anoxic pool. The sludge refluxed from the secondary sedimentation tank passes through the anaerobic pool, enabling the sludge in the unsaturated adsorption state to re-adsorb and remove the suspended and colloidal organic substrates in the sewage. The rapid adsorption of the sludge is used to achieve the efficient and rapid concentration of the organic matter in the sewage, thereby avoiding the oxidation and degradation of the organic matter into CO2 during the aeration process. The effective recovery of the organic matter in the sewage can be realized, and the volume of each pool in the entire system can be effectively saved, the aeration volume in the aerobic pool can be reduced, the air volume injection can be reduced, and the energy efficiency can be saved, at least solving one of the problems in the background technology.

[0006] The present invention provides the following technical solutions:

[0007] A pre-pollutant enrichment sludge discharge energy-saving AAO process, comprising the following steps:

[0008] Step 1: Sewage filtration treatment. The sewage passes through a set grille to remove large floating objects, and the sewage after passing through the grille is sent to a grit chamber to precipitate and remove the sand and inorganic particles in the sewage.

[0009] Step 2: The sewage after pretreatment enters the anaerobic pool. A stirrer is provided in the anaerobic pool for stirring. The sewage stays in the anaerobic pool for 3 to 4 hours. Then, part of the mixed sewage enters the anoxic pool. 10% to 20% of the sludge is pumped from the anaerobic pool into the side discharge pool. The sludge precipitates in the side discharge pool, and the remaining sludge is regularly discharged through the sewage outlet provided in the side discharge pool.

[0010] Step 3: The sewage above the side discharge pool enters the anoxic pool. A stirrer is provided in the anoxic pool for stirring. The sewage stays in the anoxic pool for 3 to 4 hours. After the sewage passes through the anoxic pool, it enters multiple aerobic pools. An aerator is connected to the aerobic pool, and the aerator inputs air into the aerobic pool. The sewage stays in the aerobic pool for 15 to 24 hours.

[0011] Step 4: The sewage after being treated in Step 3 enters the sedimentation tank. The sedimentation tank precipitates the sludge to the bottom, and the treated water in the upper layer of the sedimentation tank is discharged from the drainage outlet. All the sludge in the sedimentation tank is refluxed into the anaerobic pool. The sludge adsorbs and absorbs the carbon source organic matter in the subsequent incoming sewage. Part of the sludge after adsorbing and absorbing the carbon source organic matter is pumped into the side discharge pool. The sludge pumped from the anaerobic pool into the side discharge pool is the excess sludge, which precipitates at the bottom of the side discharge pool, and the excess sludge is regularly discharged. The supernatant of the side discharge pool enters the anoxic pool.

[0012] Preferably, in step 2, in an anaerobic environment, polyphosphate bacteria in the sludge will release phosphorus, decompose the polyphosphate in the body, release the phosphate into the sewage, and at the same time generate energy for absorbing organic matter in the sewage and storing it in the cells; complex organic matter will also be fermented and decomposed into volatile fatty acids.

[0013] Preferably, in step three, the effluent from the anaerobic tank flows by gravity into the anoxic tank; a portion of the nitrification liquid at the end of the aerobic tank flows back to the anoxic tank, and the ratio of the nitrification liquid return flow to the inlet flow satisfies 100%-400%; under anoxic conditions, denitrifying bacteria use organic matter in the sewage as a carbon source to reduce nitrate nitrogen and nitrite nitrogen in the returned nitrification liquid to nitrogen gas.

[0014] Preferably, in step 4, the effluent from the anoxic tank flows into the aerobic tank; air is introduced into the sewage through an aeration device in the aerobic tank to provide sufficient dissolved oxygen, so that aerobic microorganisms can degrade organic matter and nitrify ammonia nitrogen; aerobic microorganisms oxidize ammonia nitrogen in the sewage into nitrate nitrogen, and the dissolved oxygen concentration in the aerobic tank meets 2mg-4mg / L.

[0015] Preferably, in step 4, the return rate of the sludge from the sedimentation tank to the anaerobic tank is 100%, and the ratio of COD to total nitrogen in the treated wastewater is greater than 50.

[0016] Preferably, the implementation device of the energy-saving AAO process includes an anaerobic tank, a side discharge tank, an anoxic tank, multiple aerobic tanks and a sedimentation tank; the anaerobic tank, the anoxic tank, the multiple aerobic tanks and the sedimentation tank are connected in sequence, a side discharge tank is provided between the anaerobic tank and the anoxic tank, the side discharge tank is connected to the anaerobic tank upstream, and the side discharge tank is connected to the anoxic tank downstream, the sludge outlet of the sedimentation tank is connected to the front end of the anaerobic tank through a sludge return pipe, and the end of the aerobic tank is connected to the anoxic tank by setting a sewage return pipe; flow meters and control valves are provided on the sludge outlet, the sludge return pipe and the sewage return pipe; a water outlet is provided at the top of the side discharge tank near the tank wall, and the water outlet is connected to the water inlet end of the anoxic tank.

[0017] Preferably, the side discharge pool includes a pool wall, and the bottom of the pool wall is a conical structure. A feed pipe is provided at the bottom of the pool wall, and the feed pipe is connected to the water outlet end of the anaerobic pool; an arc-shaped baffle is provided on the inner side of the pool wall near the top, and the arc-shaped baffle is arranged around the inner side of the pool wall. The feed pipe extends from the bottom of the side discharge pool to the inside of the pool wall, and a curved plate is provided on the circumferential side near the end of the feed pipe located on the inner side of the pool wall. The curved plate is bent toward the top of the side discharge pool, and a plurality of arc-shaped guide plates are provided on the upper surface of the curved plate; a plurality of sewage pipes are connected to the outer side wall of one end of the feed pipe located inside the pool wall, and the plurality of sewage pipes are evenly distributed on the outer side wall of the feed pipe, and the outlet end of the sewage pipe faces the curved plate.

[0018] Preferably, a sewage pipe is provided inside the feed pipe, one end of which is located outside the bottom of the pool wall 1, and the sewage pipe is connected to a sewage outlet, and the other end of the sewage pipe passes through the top of the feed pipe, and the sewage pipe and the feed pipe are sealed and connected to each other; one end of the feed pipe close to the top is evenly connected to a plurality of sewage extraction pipes along the circumference, and the other end of the sewage extraction pipe is located at the bottom of the side discharge pool.

[0019] Preferably, a plurality of bottom vertical plates are evenly arranged on the inner side wall of the conical bottom of the side discharge pool, a bottom pipe is arranged between any two bottom vertical plates, the bottom pipe is connected to the side wall, and a plurality of suction holes are arranged on the bottom pipe.

[0020] Preferably, the sewage extraction pipe is connected to the bottom pipe, and a drain outlet 13 is provided on the pool wall near the top.

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

[0022] The present invention discloses an energy-saving AAO process for pre-pollutant enrichment sludge discharge, wherein a side discharge tank is added between the anaerobic tank and the anoxic tank, and the sludge returned from the secondary sedimentation tank passes through the anaerobic tank, so that the sludge in the unadsorbed saturated state can re-adsorb and remove the suspended and colloidal organic matter in the sewage, and the rapid adsorption of the sludge can achieve efficient and rapid concentration of organic matter in the sewage, thereby avoiding the oxidation and degradation of organic matter into CO2 during the aeration process, and can achieve effective recovery of organic matter in the sewage, and effectively save the volume of each tank of the entire system, reduce the aeration volume in the aerobic tank, reduce the air volume injection, and save energy efficiency; the rapid adsorption characteristics of the activated sludge on organic pollutants can be used to adsorb 30% to 60% of organic pollutants, thereby further achieving simple operation and low cost, better economic benefits, and reducing the overall process cost. It can also reduce the water load of the biochemical unit, and can also alleviate the impact on the biochemical system caused by the large fluctuation of the water concentration. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0024] Figure 1 It is a process flow chart of the present invention.

[0025] Figure 2 It is a schematic diagram of the overall structure of the side discharge pool of the present invention.

[0026] Figure 3 It is a schematic diagram of the longitudinal cross-section structure of the side discharge pool of the present invention.

[0027] Figure 4 It is a cross-sectional view of the internal structure of the side discharge pool of the present invention.

[0028] Figure 5 It is a schematic diagram of the internal structure of the side discharge pool of the present invention.

[0029] Figure 6 It is a schematic diagram of the curved panel structure of the present invention.

[0030] Figure 7 It is a schematic diagram of the cross-sectional structure of the side discharge pool of the present invention. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] In addition, in the present invention, descriptions such as "first" and "second" are only used for descriptive purposes, and do not specifically refer to the order or sequence, nor are they used to limit the present invention. They are only used to distinguish components or operations described with the same technical terms, and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions and technical features between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0034] Embodiment 1:

[0035] refer to Figure 1 , a pre-pollutant enrichment sludge discharge energy-saving AAO process, comprising the following steps:

[0036] Step 1: Sewage filtration treatment, the sewage is passed through a screen to remove large floating particles, and the sewage after passing through the screen is sent to a grit chamber to precipitate and remove sand and inorganic particles in the sewage;

[0037] Step 2: The pre-treated sewage enters the anaerobic tank, which is equipped with a stirrer for stirring. The sewage stays in the anaerobic tank for 3 to 4 hours, after which part of the mixed sewage enters the anoxic tank. 10% to 20% of the sludge is pumped from the anaerobic tank into the side discharge tank. The sludge is precipitated in the side discharge tank, and the remaining sludge is regularly discharged through the sewage outlet set in the side discharge tank;

[0038] Step 3: The sewage above the side discharge tank enters the anoxic tank, which is equipped with a stirrer for stirring. The sewage stays in the anoxic tank for 3 to 4 hours. After passing through the anoxic tank, the sewage enters multiple aerobic tanks. The aerobic tank is connected to an aerator, which inputs air into the aerobic tank. The sewage stays in the aerobic tank for 15 to 24 hours.

[0039] Step 4: The sewage treated in step 3 enters the sedimentation tank, which settles the sludge to the bottom. The treated water on the upper layer of the sedimentation tank is discharged from the drain outlet; all the sludge in the sedimentation tank flows back to the anaerobic tank, and the sludge adsorbs and absorbs the carbon source organic matter that enters the sewage later. After adsorbing and absorbing the carbon source organic matter, part of the sludge is pumped into the side discharge tank. The sludge pumped from the anaerobic tank into the side discharge tank is the residual sludge, which settles at the bottom of the side discharge tank. The residual sludge is discharged regularly, and the supernatant of the side discharge tank enters the anoxic tank. 80% to 90% of the sludge in the anaerobic tank is mixed with sewage and sent to the anoxic tank through the sewage pump. The anaerobic tank pumps 10% to 20% of the sludge to the side discharge tank through the sludge pump. This part of the sludge is the excess sludge in the system. As the microorganisms in the sludge continuously metabolize and decompose the organic matter in the sewage, and perform nitrogen and phosphorus removal reactions, the microorganisms will gradually age and die over time. If the sludge formed by these aged microorganisms is not discharged in time, they will accumulate in the system, occupy space and consume resources such as oxygen. At the same time, they may also release harmful substances, affecting the normal metabolism and growth of active microorganisms. Therefore, a side discharge tank is set to precipitate the sludge and discharge the excess sludge to maintain a virtuous cycle of the number of microorganisms in the entire process.

[0040] In step two, in an anaerobic environment, the polyphosphate bacteria in the sludge will release phosphorus. The polyphosphate bacteria will decompose the polyphosphate in the body and release the phosphate into the sewage. At the same time, they will generate energy to absorb the organic matter in the sewage and store it in the cells. Complex organic matter will also be fermented and decomposed into volatile fatty acids.

[0041] In step three, the effluent from the anaerobic tank flows by gravity into the anoxic tank; a portion of the nitrification liquid at the end of the aerobic tank flows back to the anoxic tank, and the ratio of the nitrification liquid return flow to the inlet flow meets 100%-400%; under anoxic conditions, denitrifying bacteria use organic matter in the sewage as a carbon source to reduce nitrate nitrogen and nitrite nitrogen in the return nitrification liquid to nitrogen gas.

[0042] In step 4, the effluent from the anoxic tank flows into the aerobic tank; air is introduced into the sewage through an aeration device in the aerobic tank to provide sufficient dissolved oxygen, so that aerobic microorganisms can degrade organic matter and nitrify ammonia nitrogen; aerobic microorganisms oxidize ammonia nitrogen in the sewage into nitrate nitrogen, and the dissolved oxygen concentration in the aerobic tank meets 2mg-4mg / L.

[0043] In step 4, the return rate of the sludge from the sedimentation tank to the anaerobic tank is 100%, and the ratio of COD to total nitrogen in the treated wastewater is greater than 50.

[0044] The activated sludge in the process contains microorganisms such as bell worms, branch worms, shield ciliates, cover ciliates, polycondensate worms and various metazoans and sippy worms, etc., which are fixed or crawling organisms. The number of microorganisms reaches more than 1000 / mL.

[0045] Embodiment 2:

[0046] Please refer to Figure 2-7The implementation device of the energy-saving AAO process includes an anaerobic tank, a side discharge tank, an anoxic tank, multiple aerobic tanks and a sedimentation tank; the anaerobic tank, the anoxic tank, multiple aerobic tanks and the sedimentation tank are connected in sequence, a side discharge tank is arranged between the anaerobic tank and the anoxic tank, the upstream of the side discharge tank is connected to the anaerobic tank, the downstream of the side discharge tank is connected to the anoxic tank, the sludge outlet of the sedimentation tank is connected to the front end of the anaerobic tank through a sludge return pipe, and the end of the aerobic tank is connected to the anoxic tank by setting a sewage return pipe; flow meters and control valves are arranged on the sludge outlet, the sludge return pipe and the sewage return pipe; a water outlet is arranged at the top of the side discharge tank near the tank wall, and the water outlet is connected to the water inlet end of the anoxic tank. The side discharge tank includes a tank wall 1, and the bottom of the tank wall 1 is a conical structure. A feed pipe 3 is provided at the bottom of the tank wall 1, and the feed pipe 3 is connected to the water outlet end of the anaerobic tank; an arc-shaped baffle plate 2 is provided on the inner side of the tank wall 1 near the top, and the arc-shaped baffle plate 2 is arranged around the inner side of the tank wall 1. The feed pipe 3 extends from the bottom of the side discharge tank to the inside of the tank wall 1. A curved plate 4 is provided on the circumferential side near the end of the feed pipe 3 located on the inner side of the tank wall 1. The curved plate 4 is bent toward the top of the side discharge tank, and a plurality of arc-shaped guide plates 5 are provided on the upper surface of the curved plate 4; a plurality of sewage pipes 6 are connected to the outer side wall of one end of the feed pipe 3 located inside the tank wall 1, and the plurality of sewage pipes 6 are evenly distributed on the outer side wall of the feed pipe 3, and the outlet end of the sewage pipe 6 faces the curved plate 4. A sewage pipe 8 is provided inside the feed pipe 3, one end of which is located outside the bottom of the pool wall 1, and the sewage pipe 8 is connected to a sewage outlet 7, and the other end of the sewage pipe 8 passes through the top of the feed pipe 3, and the sewage pipe 8 and the feed pipe 3 are sealed and connected to each other; one end of the feed pipe 3 near the top is evenly connected to a plurality of sewage extraction pipes 9 along the circumference, and the other end of the sewage extraction pipe 9 is located at the bottom of the side discharge pool. A plurality of bottom vertical plates 12 are evenly provided on the inner side wall of the conical bottom of the side discharge pool, and a bottom pipe 10 is provided between any two bottom vertical plates 12, and the bottom pipe 10 is connected to the side wall, and a plurality of suction holes 11 are provided on the bottom pipe 10. The sewage extraction pipe 9 is connected to the bottom pipe 10; a drainage outlet 13 is provided near the top of the pool wall.

[0047] The effluent at the tail end of the anaerobic tank enters from the bottom of the feed pipe 3 and is ejected from a plurality of sewage pipes 6 connected to the upper end of the feed pipe 3. The outlet of the sewage pipe 6 is vertically arranged with the curved plate 4. Since the curved plate 4 is bent upward, the curved arc side of the curved plate 4 faces the outlet end of the sewage pipe 6. When the sewage ejected downward from the sewage pipe 6 hits the curved plate 4, the flow direction and speed of the sewage change. It should be understood that the curved plate 4 is a hemispherical structure, the length of the curved surface between any two points on the edge of the curved plate 4 is ra, and the radius of the sphere formed by the curved plate 4 is R, then In order to ensure that the water sprayed onto the curved panel 4 can quickly overflow from the edge of the curved panel 4, change the flow direction of the water, and the water flow velocity after the redirection is not greatly attenuated, ra satisfies: 0.5R≤ra≤1.8R; when ra is less than 0.5R, the curvature of the curved panel 4 is too small to redirect the water flow to flow upward, and the water flow will flow downward along the edge of the curved surface. When ra≥1.8R, the curvature of the panel is too large, and the water flow is subject to a greater gravity when flowing upward along the curved panel 4, which will reduce the water flow velocity and is not conducive to subsequent sludge precipitation. The water outlet of the feed pipe 3 sprays water downward. After the water contacts the curved plate 4, the water flows upward along the curved plate 4. At the same time, a plurality of arc-shaped guide plates 5 are arranged on the upper surface of the curved plate 4. The arc-shaped guide plates 5 are arranged around the center of the curved plate 4. An arc-shaped guide groove is formed between any two guide plates 5. The arc-shaped guide groove forms an arc-shaped spiral outward from the center of the curved plate 4. When the water on the curved plate 4 flows upward along the inside of the curved plate 4, it is guided by the plurality of guide plates 5 to form a vortex in the pool. Due to the effect of the vortex, it is beneficial for the heavier sludge to settle at the bottom of the side discharge pool, which is convenient for the subsequent discharge of residual sludge. It can also fully contact the suspended matter and large-particle organic matter in the sewage with the sludge and be adsorbed by the sludge, so as to achieve a better decontamination effect. At the same time, the curved plate 4 is arranged to block the downward water flow to prevent the water flow from impacting the sludge at the bottom, which is not conducive to the precipitation of the sludge. In order to better form a vortex, the height of the guide plate 5 is h, the circumference between the guide plates 5 at the edge of the curved panel 4 is C, and the central angle θ formed by the intersection of the two guide plates 5 on the edge of the curved panel 4 and the center of the curved panel 4 satisfies the range of 5°-15°; then 2 / 3C≥h≥2 / 5C; it should be understood that when the water flows through the guide plate 5 to form a vortex, the water flow will be affected by the distance between the two guide plates 5 and the water outlet direction of the guide plate 5, resulting in changes in the direction and speed of the water flow, thereby forming a vortex of water. Therefore, when θ is less than 5°, the guide plates 5 are too dense and the water flow is too dispersed, which is not conducive to the formation of a vortex. When θ is greater than 15°, the guide plates 5 are not enough to form a good guiding effect on the water flow, and the vortex speed of the formed water is low, and the sludge sedimentation effect is not good. If h is greater than 2 / 3C, the height of the guide plate 5 will be too high, affecting the vortex; if h is less than 2 / 5C, the height of the guide plate 5 will be too low, which is not enough to form a guide, and it is difficult to form a vortex, affecting the stability of the vortex.

[0048] In the process of the water flowing upward after being guided by the curved plate 4, the flowing water touches the arc baffle 2. The side of the arc baffle 2 away from the pool wall 1 is tilted downward, and the water near the edge of the pool wall 1 is blocked by the arc baffle 2 and flows in the opposite direction. The water at the center position continues to flow upward, and the water flow that is blocked and changed direction by the arc baffle 2 is opposite to the subsequent upward water flow, forming an up and down flowing vortex near the lower position of the arc plate. In the process of the continuously formed vortex, the sludge returned from the sedimentation tank in the side discharge tank is fully mixed with the organic pollutants in the sewage and contacts the sludge, further adsorbs the polluted organic matter, further reduces the organic pollutants in the sewage, and makes the remaining sludge in a state of fully adsorbing the polluted organic matter when discharged, thereby improving the sludge utilization rate.

[0049] The side discharge tank is provided with a conical bottom, and a plurality of bottom vertical plates 12 are provided at the bottom of the side discharge tank, a sludge storage tank is formed between the plurality of vertical plates, a bottom pipe 10 is provided in the sludge storage tank, and a plurality of suction holes 11 are arranged in an array near the bottom and the top of the bottom pipe 10, and the bottom pipe 10 is connected with a sewage extraction pipe 9, and the sewage extraction pipe 9 penetrates and is sealed inside the feed pipe 3. By means of top sewage extraction, it is possible to avoid water flow turbulence in the side discharge tank during sewage discharge compared to direct sewage discharge from the bottom, and the sludge after discharge has a high water content, making subsequent treatment of the sludge difficult. By means of the bottom pipe 10 connected to the top sewage extraction pipe 9, the sludge is directly extracted by suction, which can avoid causing turbulence to the water vortex in the side discharge tank and affecting the normal adsorption of polluted organic matter by the sludge.

[0050] Embodiment three:

[0051] An experiment was set up to verify the effect of returning sludge from the secondary sedimentation tank to the anaerobic tank to treat sewage; the experiment is as follows:

[0052] Experimental water: Raw water volume of cooked food production wastewater: 500ml; Stirring speed: Coagulant: 800r / min; Coagulant aid: 400r / min; Stirring time: 3min Sludge pretreatment method: Take 1000ml of return sludge and let it stand for 30min, remove the supernatant, and take the activated sludge after precipitation.

[0053] How to do it:

[0054] (1) 500ml of raw water was used for flocculation and sedimentation experiments to determine the optimal dosage and removal rate. PAC: 0.5ml, 1ml, 1.5ml, 2ml, 2.5ml, 3ml, 3.5ml, 4ml.

[0055] (2) Take raw water and add it to the sludge. After stirring for 30 minutes, let the sample stand and settle for 30 minutes before sampling and testing.

[0056] (3) Take the raw water and add the drug for flocculation. Then mix the flocculated raw water with the remaining activated sludge after return. Stir for 30 minutes and let it stand for 30 minutes before sampling and testing.

[0057] (4) Take raw water and add it to the sludge. Add flocculant according to the optimal dosage. After stirring for 30 minutes, let the sample stand and settle for 30 minutes before sampling and testing.

[0058] Selection of optimal raw water removal rate and dosage, raw water flocculation removal rate and dosage data:

[0059]

[0060] According to the above data, when the flocculant PAC dosage ratio is 0.5‰, the removal rate is high and the removal effect is good. Compared with a larger dosage, the removal effect is not significantly reduced. Therefore, the optimal dosage ratio is 0.5‰ when adding flocculants. The raw water pretreatment method is to add PAC flocculants for precipitation treatment.

[0061] Compare the removal effects of organic pollutants by residual activated sludge without and with pretreatment.

[0062] Experimental data without preprocessing:

[0063]

[0064] There are preprocessed experimental data:

[0065]

[0066] According to the above experimental data, it can be found that the removal rate of the pre-treated and mixed return sludge is almost the same as that of the non-pre-treated experimental samples. The removal effect of the pre-treated samples is slightly better than that of the non-pre-treated samples.

[0067] The removal rate of the sample without pretreatment is slightly lower than that of the sample with pretreatment. Combined with specific data analysis, for example, the comparison of the experiment with and without pretreatment for 30 minutes: the COD value without pretreatment is 284.4mg / L, and the COD value with pretreatment is 240.8mg / L. In actual operation, the sample without pretreatment has been able to meet the requirements of pretreatment removal rate. Therefore, the organic pollutants at the front end can be directly adsorbed and degraded by the residual sludge returned, so that the raw water does not need to be treated. The sludge returned from the secondary sedimentation tank is completely sent to the anaerobic tank to replace the raw water with flocculant pretreatment. The rapid adsorption characteristics of activated sludge on organic pollutants can adsorb 30% to 60% of organic pollutants, thereby further achieving simple operation and low cost, without the need to add flocculants to pretreat the raw water, better economic benefits, and reduced overall process costs. Reducing the inflow load of the biochemical unit can also alleviate the impact on the biochemical system caused by large fluctuations in the concentration of the inflow.

[0068] Embodiment 4:

[0069] Control group: 1# system, which does not use the AAO process system with side discharge pool to discharge sludge for sewage treatment.

[0070] Experimental group 1: 2# system; The water quality indicators of the sewage system actually treated by this process are as follows: COD (chemical oxygen demand) is 3988 / L, ammonia nitrogen is 43.8 / L, total nitrogen is 30.7mg / L, and carbon-nitrogen ratio is 91;

[0071] Step 1: Sewage pretreatment, the screen gap is 8mm, the sewage passes through the screen to remove large floating particles, and the sewage after passing through the screen is sent to the grit chamber to precipitate and remove sand and inorganic particles in the sewage;

[0072] Step 2: The pretreated sewage enters the anaerobic tank. The stirring speed of the anaerobic tank is 20 rpm. The anaerobic tank is equipped with a stirrer for stirring. The sewage stays in the anaerobic tank for 3 hours. After that, the sewage is sent to the side discharge tank. The sludge is precipitated in the side discharge tank, and the remaining sludge is discharged through the sewage outlet set in the side discharge tank.

[0073] Step 3: The sewage above the side discharge tank enters the anoxic tank, which is equipped with a stirrer for stirring. The sewage stays in the anoxic tank for 3 hours. After passing through the anoxic tank, the sewage enters multiple aerobic tanks. The aerobic tank is connected to an aerator, which inputs air into the aerobic tank to maintain the dissolved oxygen concentration at 3 mg / L. The sewage stays in the aerobic tank for 20 hours.

[0074] Step 4: The sewage treated in step 3 enters the sedimentation tank with a surface load of 1m³ / (m²・h); the sedimentation tank settles the sludge to the bottom, and the treated clean water on the upper layer is discharged; all the sludge in the sedimentation tank is returned to the anaerobic tank, and the sludge adsorbs and absorbs the carbon source organic matter that subsequently enters the sewage. After adsorbing and absorbing the carbon source organic matter, the sludge enters the side discharge tank with the water flow, and part of the sludge enters the anoxic tank with the sewage, and the other part of the sludge is the residual sludge, which is precipitated at the bottom of the side discharge tank, and the residual sludge is discharged regularly.

[0075] The results are shown in the table.

[0076]

[0077] As can be seen from the above table, the 2# system with side discharge tank is used for sludge discharge, and the COD, BOD, SS, NH3-N, TN, and TP emissions of the discharged water all meet the safe discharge standards. However, a side discharge tank is added between the anaerobic tank and the anoxic tank. The sludge returned from the secondary sedimentation tank passes through the anaerobic tank, so that the sludge in the unadsorbed saturated state can re-adsorb and remove the suspended and colloidal organic matter in the sewage. The rapid adsorption of sludge can achieve efficient and rapid concentration of organic matter in the sewage, thereby avoiding the oxidation and degradation of organic matter into CO2 during the aeration process, which can achieve effective recovery of organic matter in sewage and effectively save the volume of each tank in the entire system; reduce the aeration volume in the aerobic tank, reduce the air volume injection, save energy efficiency, and reduce the volume of the reaction vessels at each stage by 10%.

[0078] Embodiment five:

[0079] Control group: 1# system, which does not use the AAO process system to discharge sludge from the side discharge pool for sewage treatment.

[0080] Experimental group 2, 2# system, the water quality indicators of sewage system 2 actually treated by this process are as follows: COD (chemical oxygen demand) is 4304 / L, ammonia nitrogen is 33.3 / L, total nitrogen is 20.22mg / L, and carbon-nitrogen ratio is 129;

[0081] Step 1: Sewage pretreatment, the screen gap is 6mm, the sewage passes through the screen to remove large floating particles, and the sewage after passing through the screen is sent to the grit chamber to precipitate and remove sand and inorganic particles in the sewage;

[0082] Step 2: The pretreated sewage enters the anaerobic tank. The stirring speed of the anaerobic tank is 18 rpm. The anaerobic tank is equipped with a stirrer for stirring. The sewage stays in the anaerobic tank for 4 hours. After that, the sewage is sent to the side discharge tank. The sludge is precipitated in the side discharge tank and the remaining sludge is discharged through the sewage outlet set in the side discharge tank.

[0083] Step 3: The sewage above the side discharge tank enters the anoxic tank, which is equipped with a stirrer for stirring. The sewage stays in the anoxic tank for 4 hours. After passing through the anoxic tank, the sewage enters multiple aerobic tanks. The aerobic tank is connected to an aerator, which inputs air into the aerobic tank to maintain the dissolved oxygen concentration at 2.5 mg / L. The sewage stays in the aerobic tank for 21 hours.

[0084] Step 4: The sewage treated in step 3 enters the sedimentation tank with a surface load of 0.9m³ / (m²・h); the sedimentation tank settles the sludge to the bottom, and the treated clean water on the upper layer is discharged; all the sludge in the sedimentation tank is returned to the anaerobic tank, and the sludge adsorbs and absorbs the carbon source organic matter that subsequently enters the sewage. After adsorbing and absorbing the carbon source organic matter, the sludge enters the side discharge tank with the water flow, and part of the sludge enters the anoxic tank with the sewage, and the other part of the sludge is the residual sludge, which is precipitated at the bottom of the side discharge tank, and the residual sludge is discharged regularly.

[0085] The results are shown in the table:

[0086]

[0087] As can be seen from the above table, the 2# system with side discharge tank is used for sludge discharge, and the COD, BOD, SS, NH3-N, TN, and TP emissions of the discharged water all meet the safe discharge standards. However, a side discharge tank is added between the anaerobic tank and the anoxic tank. The sludge returned from the secondary sedimentation tank passes through the anaerobic tank, so that the sludge in the unadsorbed saturated state can re-adsorb and remove the suspended and colloidal organic matter in the sewage. The rapid adsorption of sludge can achieve efficient and rapid concentration of organic matter in the sewage, thereby avoiding the oxidation and degradation of organic matter into CO2 during the aeration process, which can achieve effective recovery of organic matter in sewage and effectively save the volume of each tank in the entire system; reduce the aeration volume in the aerobic tank, reduce the air volume injection, save energy efficiency, and reduce the volume of the reaction vessels at each stage by 10%.

[0088] Other technical solutions not described in detail in the present invention are all existing technologies in the field and will not be described in detail here.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various changes and modifications. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A pre-pollutant enrichment sludge discharge energy-saving AAO process, characterized in that: The following steps are involved: Step 1: Sewage filtration treatment, the sewage is passed through a screen to remove large floating particles, and the sewage after passing through the screen is sent to a grit chamber to precipitate and remove sand and inorganic particles in the sewage; Step 2: The pretreated sewage enters the anaerobic tank, which is equipped with a stirrer for stirring. The sewage stays in the anaerobic tank for 3 to 4 hours. 80% to 90% of the sludge in the anaerobic tank is mixed with sewage and sent to the anoxic tank through a sewage pump. 10% to 20% of the sludge is pumped from the anaerobic tank into the side discharge tank. The sludge is precipitated in the side discharge tank, and the remaining sludge is regularly discharged through the sewage outlet set in the side discharge tank. Step 3: The sewage above the side discharge tank enters the anoxic tank, which is equipped with a stirrer for stirring. The sewage stays in the anoxic tank for 3 to 4 hours. After passing through the anoxic tank, the sewage enters multiple aerobic tanks. The aerobic tank is connected to an aerator, which inputs air into the aerobic tank. The sewage stays in the aerobic tank for 15 to 24 hours. A portion of the nitrification liquid at the end of the aerobic tank flows back to the anoxic tank, and the ratio of the nitrification liquid return flow to the water inlet flow meets 100% -400%; the dissolved oxygen concentration in the aerobic tank meets 2 to 4 mg / L. Step 4: The sewage treated in step 3 enters the sedimentation tank, where the sludge is settled to the bottom, and the treated water on the upper layer of the sedimentation tank is discharged from the drain outlet; All the sludge from the sedimentation tank is returned to the anaerobic tank. The sludge adsorbs and absorbs the carbon source organic matter that enters the sewage later. The sludge after adsorbing and absorbing the carbon source organic matter is partially pumped into the side discharge tank. The sludge pumped from the anaerobic tank into the side discharge tank is the residual sludge, which settles at the bottom of the side discharge tank. The residual sludge is discharged regularly, and the supernatant of the side discharge tank enters the anoxic tank. The ratio of COD to total nitrogen in the treated sewage is greater than 50.

2. The energy-saving AAO process for pre-pollutant enrichment sludge discharge according to claim 1 is characterized in that: In step two, in an anaerobic environment, the polyphosphate bacteria in the sludge will release phosphorus. The polyphosphate bacteria will decompose the polyphosphate in the body and release the phosphate into the sewage. At the same time, they will generate energy to absorb the organic matter in the sewage and store it in the cells. Complex organic matter will also be fermented and decomposed into volatile fatty acids.

3. The energy-saving AAO process for pre-pollutant enrichment sludge discharge according to claim 1 is characterized in that: In step three, the effluent from the anaerobic tank flows by gravity into the anoxic tank; under anoxic conditions, denitrifying bacteria use organic matter in the sewage as a carbon source to reduce nitrate nitrogen and nitrite nitrogen in the reflowing nitrification solution into nitrogen gas.

4. The energy-saving AAO process for pre-pollutant enrichment sludge discharge according to claim 1 is characterized in that: In step 4, the effluent from the anoxic tank flows into the aerobic tank; air is introduced into the sewage through an aeration device in the aerobic tank to provide sufficient dissolved oxygen, so that aerobic microorganisms can degrade organic matter and nitrify ammonia nitrogen; aerobic microorganisms oxidize ammonia nitrogen in the sewage into nitrate nitrogen.

5. The energy-saving AAO process for pre-pollutant enrichment sludge discharge according to claim 1 is characterized in that: In step 4, the return rate of sludge from the sedimentation tank to the anaerobic tank is 100%.

6. The energy-saving AAO process for pre-pollutant enrichment sludge discharge according to claim 1 is characterized in that: The implementation device of the energy-saving AAO process includes an anaerobic tank, a side discharge tank, an anoxic tank, multiple aerobic tanks and a sedimentation tank; the anaerobic tank, the anoxic tank, multiple aerobic tanks and the sedimentation tank are connected in sequence, a side discharge tank is arranged between the anaerobic tank and the anoxic tank, the upstream of the side discharge tank is connected to the anaerobic tank, the downstream of the side discharge tank is connected to the anoxic tank, the sludge outlet of the sedimentation tank is connected to the front end of the anaerobic tank through a sludge return pipe, and the end of the aerobic tank is connected to the anoxic tank by setting a sewage return pipe; flow meters and control valves are arranged on the sludge outlet, the sludge return pipe and the sewage return pipe; a water outlet is arranged at the top of the side discharge tank near the tank wall, and the water outlet is connected to the water inlet end of the anoxic tank.

7. The energy-saving AAO process for pre-pollutant enrichment sludge discharge according to claim 6 is characterized in that: The side discharge tank comprises a tank wall (1), the bottom of the tank wall (1) is a conical structure, a feed pipe (3) is provided at the bottom of the tank wall (1), and the feed pipe (3) is connected to the water outlet of the anaerobic tank; a curved baffle (2) is provided at a position near the top of the inner side of the tank wall (1), the curved baffle (2) is arranged around the inner side of the tank wall (1), the feed pipe (3) extends from the bottom of the side discharge tank to the inside of the tank wall (1), a curved plate (4) is provided near the end of the feed pipe (3) located on the inner side of the tank wall (1), the curved plate (4) is bent toward the top of the side discharge tank, and a plurality of curved guide plates (5) are provided on the upper surface of the curved plate (4); a plurality of sewage pipes (6) are connected to the outer side wall of one end of the feed pipe (3) located inside the tank wall (1), the plurality of sewage pipes (6) are evenly distributed on the outer side wall of the feed pipe (3), and the outlet end of the sewage pipe (6) faces the curved plate (4).

8. The energy-saving AAO process for pre-pollutant enrichment sludge discharge according to claim 7 is characterized in that: A sewage guide pipe (8) is provided inside the feed pipe (3), one end of the sewage guide pipe (8) is located outside the bottom of the pool wall (1), and the sewage guide pipe (8) is connected to a sewage outlet (7), the other end of the sewage guide pipe (8) passes through the top of the feed pipe (3), and the sewage guide pipe (8) and the feed pipe (3) are sealed and connected to each other; one end of the feed pipe (3) close to the top is evenly connected to a plurality of sewage extraction pipes (9) along the circumference, and the other end of the sewage extraction pipe (9) is located at the bottom of the side discharge pool.

9. The energy-saving AAO process for pre-pollutant enrichment sludge discharge according to claim 8 is characterized in that: A plurality of bottom upright plates (12) are evenly arranged on the inner side wall of the conical bottom of the side discharge pool, a bottom pipe (10) is arranged between any two bottom upright plates (12), the bottom pipe (10) is connected to the side wall, and a plurality of suction holes (11) are arranged on the bottom pipe (10).

10. The energy-saving AAO process for pre-pollutant enrichment sludge discharge according to claim 9, characterized in that: The sewage extraction pipe (9) is connected to the bottom pipe (10); a drainage outlet (13) is provided at a position near the top of the pool wall.

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