Improved A2 / O + MBBR process for treating rural domestic sewage

Abstract

The invention discloses a process for treating rural domestic sewage by using an improved A2 / O + MBBR (Moving Bed Biofilm Reactor), and relates to the technical field of sewage treatment. The method comprises the steps of S1, initial-stage treatment, S2, reflux treatment and S3, tail-stage treatment. The rural domestic sewage is treated by an improved A2 / O + MBBR nitrogen and phosphorus removal process, and the rural domestic sewage is distributed into each tank by adopting a sectional water inlet technology, so that an alternate multi-stage facultative / aerobic environment is formed, and the biological nitrogen and phosphorus removal effect is enhanced; the improved A2 / O + MBBR process has the advantages of high nitrogen and phosphorus removal effect, low investment and operation cost, convenience in operation and management and the like; all returned sludge enters the pre-denitration tank and enters the front-section anaerobic tank and the front-section anoxic tank, a sludge concentration gradient from high to low is formed in each tank, and the average sludge concentration in each tank is increased and the hydraulic load of the sedimentation tank is not changed under the condition that the effluent sludge concentration is not increased, so that the proliferation speed of phosphorus-accumulating bacteria and nitrifying bacteria is accelerated; the proportion in the total amount of the activated sludge is increased, so that the nitrogen and phosphorus removal effect is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and is particularly concerned with an improved A 2 / O+MBBR process for treating rural domestic sewage. Background Art

[0002] Rural domestic sewage is to remove harmful substances and environmental pollution components in domestic sewage, degrade them and treat them harmlessly. Rural domestic sewage treatment should focus on the selection of mature and reliable technologies suitable for rural characteristics and actual sewage treatment. Rural sewage treatment can neutralize water quality and agricultural products according to actual conditions, so as to achieve reuse and environmentally friendly degradation and discharge;

[0003] However, the existing technology still has some defects in treating rural domestic sewage:

[0004] 1. There are two main methods for rural domestic sewage treatment: anaerobic method and aerobic method. During the treatment process, it is inconvenient to treat domestic sewage in sections. At the same time, the proliferation rate of polyphosphate bacteria and nitrifying bacteria decreases, and the range of filamentous bacteria cannot be controlled, resulting in poor nitrogen and phosphorus removal effects and a high probability of filamentous sludge bulking.

[0005] 2. When rural domestic sewage is treated by existing processes, the effluent quality after anaerobic treatment is poor and usually requires further treatment to meet higher discharge standards. It is not suitable for the treatment of rural sewage with large changes in water quality and quantity;

[0006] 3. At the same time, the existing technology requires three-level treatment before use, which results in lower water quality safety.

[0007] In view of the above problems, the inventor proposes an improved A 2 / O+MBBR process for treating rural domestic sewage is used to solve the above problems. Summary of the invention

[0008] In order to solve the above problems, the present invention aims to provide an improved A 2 / O+MBBR process for treating rural domestic sewage.

[0009] In order to solve the above technical problems, the present invention adopts the following technical solutions: an improved A 2 / O+MBBR process for treating rural domestic sewage includes the following steps:

[0010] S1. Initial processing

[0011] First, rural domestic sewage is introduced into the clear water tank, which regulates the incoming rural domestic sewage. The pre-denitrification tank receives sewage from the clear water tank. The sewage in the pre-denitrification tank enters the sedimentation tank after the action of the anaerobic tank, the anoxic tank and the aerobic tank. Phosphorus is released in the anaerobic tank, some organic matter is ammonified, denitrification is carried out in the anoxic tank, BOD is removed in the aerobic tank, nitrification and phosphorus are absorbed, and suspended fillers are added in the aerobic tank. Biofilm grows on the fillers. The fillers move freely with the water flow in the reactor. At the same time, aeration drives the fillers to move, so that the biofilm on the fillers and the sewage are fully in contact. After treatment, the sewage enters the sedimentation tank for precipitation;

[0012] S2. Reflux Processing

[0013] The pre-denitrification tank receives the return sludge from the sedimentation tank, and the return sludge is mixed with sewage and enters the subsequent A 2 / O system, so that the sludge concentration gradient from high to low is formed in the anaerobic tank, anoxic tank and aerobic tank. Without increasing the effluent sludge concentration, the average sludge concentration in each tank increases, and the hydraulic load of the sedimentation tank does not change, which accelerates the proliferation of polyphosphate bacteria and nitrifying bacteria and increases their proportion in the total amount of activated sludge, thereby improving the nitrogen and phosphorus removal effect;

[0014] S3, final processing

[0015] The rural domestic sewage in the sedimentation tank enters the filtration tank and the disinfection tank for treatment in turn. The filtration tank filters the purified rural domestic sewage, and the disinfection tank disinfects the rural domestic sewage before discharging it.

[0016] Preferably, in S1, ammonia nitrogen in sewage is converted into nitrate nitrogen through nitrification reaction. This process is carried out in an aerobic tank. Subsequently, the nitrification liquid reflux system in the aerobic tank returns the nitrate nitrogen to the anoxic tank through a reflux pipeline to provide chemical oxygen for the denitrification reaction, carry out denitrification reaction, convert nitrate nitrogen into nitrogen gas and release it into the atmosphere, thereby achieving a denitrification effect.

[0017] Preferably, the exterior of the pre-denitrification tank, anaerobic tank, anoxic tank, aerobic tank, sedimentation tank, filtration tank and disinfection tank is insulated with rock wool boards.

[0018] Preferably, in S1, the residence time of the rural domestic sewage in the pre-denitrification tank is 1 hour, and the rural domestic sewage is intermittently aerated and stirred;

[0019] The residence time of the rural domestic sewage in the anaerobic tank is 1.5 hours, the filler filling rate in the anaerobic tank is 30%, and the rural domestic sewage is intermittently aerated and stirred;

[0020] The residence time of the rural domestic sewage in the anoxic tank is 2 hours, the filler filling rate in the anoxic tank is 30%, and the rural domestic sewage is aerated and stirred by perforation at the same time, and the dissolved oxygen concentration is ≤0.5mg / L;

[0021] The residence time of rural domestic sewage in the aerobic tank is 5.5h, the air-water ratio is 10-20:1, the dissolved oxygen concentration is 4.0mg / L, the sludge concentration is 4000mg / L, and the suspended filler is used with a specific surface area of ​​1000m 2 / m 3 , filler filling rate ≥ 20%;

[0022] The surface load in the sedimentation tank is 0.6-0.75m 3 / m 2 ·h;

[0023] The filtration speed of the filter pool is 6-9 m / h. The filter pool adopts a single-layer quartz sand filter material. The particle size of the single-layer quartz sand filter material is 0.55 mm, the thickness is 700 mm, and the backwash intensity is 12-15 L / m 2 .s, expansion rate is 45%, flushing time is 7 to 5 minutes, and flushing cycle is 12 to 24 hours;

[0024] The volume of the clear water tank is 8m 3 , to provide water for backwashing of the filter pool;

[0025] The disinfection pool adopts ultraviolet disinfection.

[0026] Preferably, the filler in the aerobic pool is modified hydrophilic polyurethane.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. In the present invention, by improving A 2 / O denitrification and phosphorus removal process is used to treat rural domestic sewage. This process uses segmented water inlet technology to distribute rural domestic sewage to various pools to form an alternating multi-stage facultative aerobic / aerobic environment, which strengthens the biological denitrification and phosphorus removal effect and improves A 2 The / O process has the advantages of high nitrogen and phosphorus removal effect, low investment and operating costs, and convenient operation and management;

[0029] 2. In the present invention, by improving A 2 / O denitrification and phosphorus removal process, all the return sludge enters the pre-denitrification tank, and then enters the front anaerobic tank and anoxic tank, forming a sludge concentration gradient from high to low in each tank. Without increasing the effluent sludge concentration, the average sludge concentration in each tank increases, and the hydraulic load of the sedimentation tank does not change, which accelerates the proliferation of polyphosphate bacteria and nitrifying bacteria and increases their proportion in the total amount of activated sludge, thereby improving the denitrification and phosphorus removal effect;

[0030] 3. In the present invention, by improving A 2 / O denitrification and phosphorus removal process, the pollutants at all levels in each pool are evenly distributed and in a relatively low concentration state, and at the same time, they are operated under a high sludge concentration, thereby improving the adaptability of each pool to the impact load of changes in water quality and water quantity, making the effluent effect stable, and thus making this process particularly suitable for the treatment of rural sewage with large changes in water quality and water quantity;

[0031] 4. In the present invention, by improving A 2 / O denitrification and phosphorus removal process, the alternating existence of anoxic and aerobic environments makes its ecological environment conducive to the growth of floc bacteria, and the mechanism of biological competition is used to inhibit the excessive growth and reproduction of filamentous bacteria, so that the filamentous bacteria are controlled within a reasonable range, thereby reducing the occurrence of filamentous sludge bulking;

[0032] 5. In the present invention, by adopting the MBBR process, the effluent water quality is excellent and stable, and the suspended matter, colloidal matter, and microbial flora lost from the biological unit in the wastewater are separated from the purified water by efficient solid-liquid separation, and the water can be directly reused without tertiary treatment, and has high water quality safety;

[0033] 6. In the present invention, by adopting the MBBR process, the process flow is short, the operation control is flexible and stable, and due to the efficient separation effect of the membrane, there is no need to set up separate solid-liquid separation tanks such as sedimentation and filtration. At the same time, the volume load is high and the floor space is small. The biomass in the treatment unit can be maintained at a high concentration, which greatly improves the volume load. At the same time, the high efficiency of membrane separation greatly shortens the hydraulic retention time of the treatment unit;

[0034] 7. In the present invention, by adopting the MBBR process, the sludge age is long, the sludge discharge is small, the secondary pollution is small, the biological sludge in the membrane bioreactor can reach a dynamic balance during operation, and the residual sludge discharge is very small. At the same time, the biological denitrification effect is good, and the SRT and HRT are completely separated, which is conducive to the retention, growth and reproduction of slowly proliferating nitrifying bacteria and the nitrification efficiency of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 This is an improved A 2 / O+MBBR process flow chart for treating rural domestic sewage.

[0037] Figure 2 This is a diagram of the rural domestic sewage treatment steps of the present invention. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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.

[0039] Example: Figure 1-2 As shown, the present invention provides an improved A 2 / O+MBBR process for treating rural domestic sewage; including the following steps:

[0040] S1. Initial processing

[0041] First, rural domestic sewage is introduced into the clean water tank, the volume of which is 8m 3 , supply water for backwashing of the filter tank, the clear water tank regulates the incoming rural domestic sewage, the pre-denitrification tank receives sewage from the clear water tank, the sewage stays in the pre-denitrification tank for 1 hour, and the rural domestic sewage is intermittently aerated and stirred, the sewage in the pre-denitrification tank enters the sedimentation tank after the action of the anaerobic tank, the anoxic tank and the aerobic tank, and releases phosphorus in the anaerobic tank, the sewage stays in the anaerobic tank for 1.5 hours, and the filler filling rate in the anaerobic tank is 30%, at the same time, the sewage is intermittently aerated and stirred, part of the organic matter is ammonified, and denitrification is carried out in the anoxic tank, the sewage stays in the anoxic tank for 2 hours, and the filler filling rate in the anoxic tank is 3 0%, and at the same time, the rural domestic sewage is perforated and aerated, with a dissolved oxygen concentration of ≤0.5mg / L. BOD is removed in the aerobic pool, nitrification and phosphorus absorption are carried out, and modified hydrophilic polyurethane is added to the aerobic pool to grow the biofilm on the filler. The modified hydrophilic polyurethane moves freely with the water flow in the reactor, and the modified hydrophilic polyurethane is pushed to move by aeration, so that the biofilm on the filler and the sewage are fully in contact. The residence time of the sewage in the aerobic pool is 5.5h, the air-water ratio is 10-20:1, the dissolved oxygen concentration is 4.0mg / L, the sludge concentration is 4000mg / L, and the modified hydrophilic polyurethane is used with a specific surface area of ​​1000m 2 / m 3 , the filling rate of modified hydrophilic polyurethane is ≥20%. After treatment, the sewage enters the sedimentation tank for sedimentation. The surface load in the sedimentation tank is 0.6-0.75m 3 / m 2 ·h;

[0042] S2. Reflux Processing

[0043] The pre-denitrification tank receives the return sludge from the sedimentation tank, and the return sludge is mixed with sewage and enters the subsequent A 2 / O system, so that the sludge concentration gradient from high to low is formed in the anaerobic tank, anoxic tank and aerobic tank. Without increasing the effluent sludge concentration, the average sludge concentration in each tank increases, and the hydraulic load of the sedimentation tank does not change, which accelerates the proliferation of polyphosphate bacteria and nitrifying bacteria and increases their proportion in the total amount of activated sludge, thereby improving the nitrogen and phosphorus removal effect;

[0044] S3, final processing

[0045] The rural domestic sewage in the sedimentation tank enters the filtration tank and the disinfection tank for treatment in turn. The purified rural domestic sewage is filtered by the filtration tank. The filtration speed of the filtration tank is 6-9 m / h. The filtration tank adopts a single-layer quartz sand filter material. The particle size of the single-layer quartz sand filter material is 0.55 mm, the thickness is 700 mm, and the backwash intensity is 12-15 L / m 2 .s, expansion rate is 45%, flushing time is 7-5min, flushing cycle is 12-24h, rural domestic sewage is disinfected by ultraviolet rays in the disinfection pool and then discharged;

[0046] In S1, ammonia nitrogen in sewage is converted into nitrate nitrogen through nitrification reaction. This process is carried out in an aerobic tank. Subsequently, the nitrification liquid reflux system in the aerobic tank returns the nitrate nitrogen to the anoxic tank through a reflux pipeline, providing oxygen in a chemical state for the denitrification reaction. The denitrification reaction is carried out to convert the nitrate nitrogen into nitrogen gas and release it into the atmosphere, thus achieving a denitrification effect.

[0047] The exterior of the pre-denitrification tank, anaerobic tank, anoxic tank, aerobic tank, sedimentation tank, filtration tank and disinfection tank are insulated with rock wool boards.

[0048] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. An improved A 2 / O+MBBR process for treating rural domestic sewage, characterized in that: The following steps are involved: S1. Initial processing First, rural domestic sewage is introduced into the clear water tank, which regulates the incoming rural domestic sewage. The pre-denitrification tank receives sewage from the clear water tank. The sewage in the pre-denitrification tank enters the sedimentation tank after the action of the anaerobic tank, the anoxic tank and the aerobic tank. Phosphorus is released in the anaerobic tank, some organic matter is ammonified, denitrification is carried out in the anoxic tank, BOD is removed in the aerobic tank, nitrification and phosphorus are absorbed, and suspended fillers are added in the aerobic tank. Biofilm grows on the fillers. The fillers move freely with the water flow in the reactor. At the same time, aeration drives the fillers to move, so that the biofilm on the fillers and the sewage are fully in contact. After treatment, the sewage enters the sedimentation tank for precipitation; S2. Reflux Processing The pre-denitrification tank receives the return sludge from the sedimentation tank, and the return sludge is mixed with sewage and enters the subsequent A 2 / O system, so that the sludge concentration gradient from high to low is formed in the anaerobic tank, anoxic tank and aerobic tank. Without increasing the effluent sludge concentration, the average sludge concentration in each tank increases, and the hydraulic load of the sedimentation tank does not change, which accelerates the proliferation of polyphosphate bacteria and nitrifying bacteria and increases their proportion in the total amount of activated sludge, thereby improving the nitrogen and phosphorus removal effect; S3, final processing The rural domestic sewage in the sedimentation tank enters the filtration tank and the disinfection tank for treatment in turn. The filtration tank filters the purified rural domestic sewage, and the disinfection tank disinfects the rural domestic sewage before discharging it.

2. An improved A as claimed in claim 1 2 / O+MBBR process for treating rural domestic sewage, characterized in that: In S1, ammonia nitrogen in sewage is converted into nitrate nitrogen through nitrification reaction. This process is carried out in an aerobic tank. Subsequently, the nitrification liquid reflux system in the aerobic tank returns the nitrate nitrogen to the anoxic tank through a reflux pipeline, providing chemical oxygen for the denitrification reaction, and carrying out the denitrification reaction to convert the nitrate nitrogen into nitrogen gas and release it into the atmosphere, thereby achieving a denitrification effect.

3. An improved A as claimed in claim 1 2 / O+MBBR process for treating rural domestic sewage, characterized in that: The exteriors of the pre-denitrification tank, the anaerobic tank, the anoxic tank, the aerobic tank, the sedimentation tank, the filtration tank and the disinfection tank are insulated with rock wool boards.

4. An improved A as claimed in claim 1 2 / O+MBBR process for treating rural domestic sewage, characterized in that: In S1, the residence time of the rural domestic sewage in the pre-denitrification tank is 1 hour, and the rural domestic sewage is intermittently aerated and stirred; The residence time of the rural domestic sewage in the anaerobic tank is 1.5 hours, the filler filling rate in the anaerobic tank is 30%, and the rural domestic sewage is intermittently aerated and stirred; The residence time of the rural domestic sewage in the anoxic tank is 2 hours, the filler filling rate in the anoxic tank is 30%, and the rural domestic sewage is aerated and stirred by perforation at the same time, and the dissolved oxygen concentration is ≤0.5mg / L; The residence time of rural domestic sewage in the aerobic tank is 5.5h, the air-water ratio is 10-20:1, the dissolved oxygen concentration is 4.0mg / L, the sludge concentration is 4000mg / L, and the suspended filler is used with a specific surface area of ​​1000m 2 / m 3 , filler filling rate ≥ 20%; The surface load in the sedimentation tank is 0.6-0.75m 3 / m 2 ·h; The filtration speed of the filter pool is 6-9 m / h. The filter pool adopts a single-layer quartz sand filter material. The particle size of the single-layer quartz sand filter material is 0.55 mm, the thickness is 700 mm, and the backwash intensity is 12-15 L / m 2 .s, expansion rate is 45%, flushing time is 7 to 5 minutes, and flushing cycle is 12 to 24 hours; The volume of the clear water tank is 8m 3 , to provide water for backwashing of the filter pool; The disinfection pool adopts ultraviolet disinfection.

5. An improved A as claimed in claim 4 2 / O+MBBR process for treating rural domestic sewage, characterized in that: The filler in the aerobic pool is modified hydrophilic polyurethane.

Images