A biocage wastewater treatment process based on glycogen-accumulating bacteria

Abstract

The present invention provides a sewage treatment process based on glycogen-aggregating bacteria. The sewage treatment process of the present invention utilizes a biocage reactor and an ammonia nitrogen adsorption functional filler. The sewage to be treated stays in the biocage for 2-12 hours for sewage treatment. The sewage in the biocage alternates between an anaerobic and an aerobic environment at a frequency of every 10 minutes to every 3 hours. During the sewage's stay in the reactor, the pollutants in the sewage are effectively degraded by the biofilm, and finally meet the discharge standards. The sewage treatment process has low energy consumption and high efficiency in biological denitrification. Under the action of this method, a high-abundance glycogen-aggregating bacteria biofilm can be domesticated. Under the action of the high-abundance glycogen-aggregating bacteria biofilm, the ammonia nitrogen adsorption filler can repeatedly adsorb ammonia nitrogen pollutants in the sewage. Based on the high-abundance glycogen-aggregating bacteria biofilm, the BOD in the sewage can be used to the maximum extent for denitrification, thereby obtaining a higher total nitrogen removal rate in the treatment of low carbon-nitrogen ratio sewage. The treatment equipment required for the sewage treatment process of the present invention has a small footprint, low energy consumption, low operating cost, and simple later maintenance.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and in particular relates to a high-efficiency and low-energy consumption bio-cage sewage treatment process based on polysaccharide bacteria. Background Art

[0002] Wastewater denitrification is a priority strategy for controlling eutrophication of water bodies. From the perspective of denitrification technology, biological denitrification technology is currently the most economical and effective technology for wastewater denitrification treatment.

[0003] According to the traditional biological denitrification principle, the biological denitrification process alternately forms anoxic zones and aerobic zones in space or time sequence, and realizes biological denitrification through nitrification and denitrification throughout the process.

[0004] The activated sludge denitrification technology is based on the anoxic-aerobic process. This technology has low denitrification efficiency, high energy consumption, and easy sludge expansion. The biofilm method is a type of wastewater treatment process in which microorganisms attach and grow in a system, including biofilters, biorotating discs, etc. The biofilm method has the characteristics of impact resistance, strong load capacity, convenient operation and management, and small amount of residual sludge. In recent years, the denitrification process based on the biofilm method has gradually attracted people's attention.

[0005] Compared with other processes, the bio-disc method has the advantages of high solid-liquid separation efficiency, small footprint, and compact structure. The traditional bio-disc is mainly composed of a disc, a contact reaction tank, a rotating shaft, and a drive device. The disc is the main component of the bio-disc, which is directly related to the treatment efficiency of the bio-disc. The larger the specific surface area of ​​the disc material, the more microorganisms grow on it; the rougher the surface of the disc material, the easier it is to attach biofilms, and the thicker the biofilms are; the lighter the disc material, the less energy consumption and the lower the operating costs.

[0006] The cage of the bio-cage reactor is an improvement on the disc material. It is based on the biological rotary disc, but it is replaced by biological fillers to increase the roughness of the disc, making the biofilm thicker, the biomass higher, and the biofilm not easy to fall off. The biofilm on the filler in the cage completes the alternation of aerobic and anaerobic during the rotation process, so that the sewage is purified. A single biological rotary disc is usually difficult to meet the demand for total nitrogen removal while removing COD from sewage. Therefore, it is necessary to combine other processes (such as adding pre-denitrification, etc.) and increase internal reflow facilities. This has increased excessive capital investment to a certain extent, causing inconvenience to the long-term operation and management of small-scale decentralized sewage treatment.

[0007] Research has found that glycogen-accumulating bacteria (GAOs) can absorb organic matter in the solution under anaerobic conditions and in the presence of organic carbon sources, and then synthesize intracellular carbon source polyhydroxyalkanoates (PHAs) and store them in the body. Among them, denitrifying glycogen-accumulating bacteria can use intracellular carbon source PHAs for denitrification, thereby achieving COD removal under anaerobic conditions, but its sewage treatment effect is single, and it requires a cyclic process of anaerobic-aerobic and water inlet-drainage. The process is complex, the investment is high, and it cannot effectively remove other pollutants such as ammonia nitrogen in the water at the same time.

[0008] Other studies have found that the combined action of saccharolytic bacteria and zeolite achieves the joint removal of COD and total nitrogen under anaerobic conditions, greatly improving the total nitrogen removal rate. The sewage treatment process in which saccharolytic bacteria and zeolite work together is named the passive aeration simultaneous nitrification and denitrification (PASND) process. Compared with the traditional activated sludge process, the aeration energy demand of the biofilm reactor based on the PASND process can theoretically be reduced by about 50%. Although the PASND process has a high COD removal and denitrification capacity, the zeolite powder adhering to the biofilm is easily lost as the biofilm falls off during long-term operation, resulting in a decrease in the efficiency of ammonia nitrogen removal. At the same time, the PASND process requires the anaerobic-aerobic process to be realized through water inlet-drainage. Therefore, it is difficult to perform multi-cycle anaerobic-aerobic treatment for high-concentration sewage in actual engineering applications to achieve the desired treatment results. Summary of the invention

[0009] In order to solve the problem that COD and ammonia nitrogen in the existing saccharolytic bacteria wastewater treatment process cannot be treated stably and efficiently with low energy consumption over multiple cycles, the present invention provides a bio-cage wastewater treatment process based on saccharolytic bacteria.

[0010] The sewage treatment process based on polysaccharide bacteria utilizes a biocage reactor and ammonia nitrogen adsorption functional fillers placed therein. The sewage to be treated stays in the biocage for 2-12 hours for sewage treatment. During sewage treatment, the sewage in the biocage alternates between an anaerobic and an aerobic environment at a frequency of every 10 minutes to every 3 hours. During the sewage's stay in the reactor, pollutants in the sewage are effectively degraded by the biofilm and are finally discharged in compliance with standards.

[0011] In order to achieve an alternating anaerobic-aerobic environment of sewage in the biological cage at a frequency of every 10 minutes to every 3 hours, the cage body of the biological cage can be arranged so that each part is alternately immersed in water and exposed to air every 10 minutes to every 4 hours.

[0012] The sewage treatment process based on glycogen-accumulating bacteria comprises the following steps:

[0013] 1) A biocage reactor and a water tank are provided. The biocage reactor comprises a water tank, a cage body and ammonia nitrogen adsorption functional filler. The ammonia nitrogen adsorption functional filler is fixed in the cage body, and the cage body is suspended above the water tank. ½ to ⅔ of the volume of the cage body is immersed in the water of the water tank, and the rest is exposed to the air; each part of the cage body is alternately immersed in water and exposed to the air every 10 minutes to every 4 hours, so as to achieve an alternating anaerobic-aerobic environment at a frequency of every 10 minutes to every 3 hours.

[0014] 2) The activated sludge is placed in the ammonia nitrogen adsorption functional filler of the cage of the biological cage reactor, and the cage of the biological cage reactor is passed through the sewage to be treated, and the sewage to be treated stays in the biological cage for 2-12 hours.

[0015] 3) During the sewage treatment process, the biocage rotates at the frequency described in step (1), so that the biofilm is in an alternating aerobic-anaerobic environment, while also providing a hunger feast environment for the biofilm, which is conducive to the cultivation of a high-abundance glycogen-accumulating bacterial biofilm.

[0016] 4) During the sewage’s stay in the reactor, pollutants in the sewage are effectively degraded by the biofilm and eventually meet discharge standards.

[0017] The water inlet mode of the sewage to be treated adopts a sequencing batch mode or a continuous mode. The hydraulic retention time of the sequencing batch mode is 2-12 hours. After the inlet water is biologically treated for a period of time, that is, the hydraulic retention time, the reactor is emptied every 2-12 hours and new sewage is introduced.

[0018] When the water inlet mode is continuous, in this mode, sewage continuously enters the reactor and is discharged from the reactor at a constant flow rate at the same time. The hydraulic retention time of sewage in the reactor is 2-12 hours.

[0019] Furthermore, the structure of the biological cage reactor also includes a driving device and an automatic control component, wherein the automatic control component is composed of a time-controlled switch and a solenoid valve; the automatic control component controls the rotation of the cage body and the water inlet and outlet of the system respectively.

[0020] The ammonia nitrogen adsorption functional filler is composited by an ammonia nitrogen adsorption material and a hydrophilic porous material, wherein the ammonia nitrogen adsorption material includes: zeolite, activated carbon, biochar, fly ash, bentonite, etc.; the hydrophilic porous material includes: polyurethane foam, urea-formaldehyde foam, melamine foam, etc.

[0021] The cage body rotation speed of the biological cage reactor is 0.125~3 revolutions per hour. The speed is achieved by controlling the rotation of the motor through a time switch, and the instantaneous speed should not be too fast. For example, if the speed is set to 0.5 revolutions per hour, the implementation method is that the time switch controls the motor and then controls the cage body of the biological cage reactor to work at 0.25 revolutions per minute for 2 minutes, and then stops for 58 minutes, thereby achieving the purpose of 0.5 revolutions per hour.

[0022] The rotation of the biological cage makes the biofilm in the water in an anaerobic environment, and the biofilm in the air in an aerobic environment, further making the biofilm in the rotating cage alternately experience anaerobic and aerobic conditions in time.

[0023] Compared with the cage of a conventional bio-cage reactor, the cage of the bio-cage reactor of the present invention is controlled by a time-controlled switch to rotate the cage. The rotation speed of 0.5 to 1 revolutions per hour, that is, the cage only rotates half a circle or one circle per hour, is the key to domesticating high-abundance saccharide-accumulating bacteria and achieving high sewage treatment efficiency and low energy consumption.

[0024] The short time of the water inlet and outlet process controlled by the solenoid valve of the present invention is conducive to the normal operation of the device, and it is preferably completed within 30 minutes. If the pump flow and power are not considered, the shorter the water inlet time, the better. Too long time will result in a shorter time for the reactor to be full of water, shorten the anaerobic time, thereby reducing the denitrification effect and hindering the removal of TN.

[0025] The water tank of the biocage reactor of the present invention is also provided with a water outlet, which can discharge aged and fallen biofilms while emptying water.

[0026] The dissolved oxygen in the water tank is less than 0.2 mg / L. The rotating cage runs at an ultra-low speed, so that the dissolved oxygen in the water tank is continuously maintained at a low level (less than 0.2 mg / L), thereby meeting the requirements of the two processes of denitrification and anaerobic synthesis of PHA by polysaccharide bacteria for dissolved oxygen.

[0027] The cage of the biological cage reactor of the present invention is divided into aerobic and anaerobic zones in the vertical space and alternating aerobic and anaerobic zones in time when working, so as to realize synchronous nitrification and denitrification: the aerobic zone is the part exposed to the air, the biofilm in the aerobic zone undergoes nitrification reaction to regenerate the biological filler saturated with ammonia nitrogen adsorption, and denitrification reaction occurs inside the biofilm, and at the same time, the biofilm in the aerobic zone metabolizes and stores PHAs; the polysaccharide bacteria in the biofilm in the anaerobic zone absorb BOD and store it in the form of PHAs, and at the same time, the biological filler in the anaerobic zone absorbs ammonia nitrogen pollutants in the sewage.

[0028] The beneficial technical effects of the present invention are as follows: the present invention provides a low-energy consumption and high-efficiency biological denitrification sewage treatment method; under the action of the method, a high-abundance glycogen-accumulating bacteria biofilm is domesticated, and under the action of the high-abundance glycogen-accumulating bacteria biofilm, the ammonia nitrogen adsorption filler can repeatedly adsorb the ammonia nitrogen pollutants in the sewage; based on the high-abundance glycogen-accumulating bacteria biofilm, the BOD in the sewage can be used to the maximum extent for denitrification, thereby obtaining a higher total nitrogen removal rate in the treatment of low carbon-nitrogen ratio sewage. The sewage treatment process of the present invention requires a small footprint, low energy consumption, low operating cost, and simple later maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 : A schematic structural diagram of the biocage reactor.

[0030] Figure 2 : Changes in pollutant concentration during the sewage treatment cycle of Example 1.

[0031] Figure 3 : Changes in pollutant removal rate during the sewage treatment cycle of Example 1.

[0032] Figure 4 : The biofilm of Example 1 was subjected to microbial community structure analysis.

[0033] Figure 5 : Changes in pollutant removal rate during the sewage treatment cycle of Example 2.

[0034] Figure 6 : Changes in pollutant removal rate during the sewage treatment cycle of Example 3

[0035] Figure 7 : Changes in pollutant concentration during the sewage treatment cycle of Comparative Example 1.

[0036] Figure 8 : Change in dissolved oxygen concentration of Comparative Example 1.

[0037] Fig. 9 : Change in pollutant removal rate during the sewage treatment cycle of Comparative Example 1.

[0038] Figure 1 Middle: 1-motor, 2-drive shaft, 3-water trough, 4-feed port, 5-cage grid, 6-cage partition, 7-overflow pipe, 8-water inlet pipe, 9-water outlet pipe, 10-water inlet solenoid valve, 11-water outlet solenoid valve, 12-time switch 1, 13-time switch 2, 14-time switch 3. DETAILED DESCRIPTION

[0039] In the embodiments of the present invention, the devices used are as follows Figure 1The dimensions of the biocage device are shown as follows: a semi-cylindrical water tank of φ24 cm×25 cm, an effective volume of the water tank of 4 L, a rotating cage of φ20 cm×20 cm, a grid plate and a filter mesh aperture of φ1.3 cm, a grid is used to divide the interior of the rotating cage into 4 cavities, the size of the filler in the rotating cage is 1.5 cm×1.5 cm×1.5 cm, and the filler filling volume is 4 L. The immersion ratio of all running biocages is 40%.

[0040] The activated sludge used was taken from the aeration biochemical tank of the municipal sewage plant. The laboratory simulated the quality of domestic sewage, and the water quality of the configured influent was as shown in Table 1. Sodium acetate was used as the carbon source to reflect the COD index of the sewage.

[0041] Table 1 Influent water quality

[0042] Removal rate calculation method:

[0043] Removal rate q = inlet water concentration / outlet water concentration × 100%

[0044] Total nitrogen expression method:

[0045] Total nitrogen = ammonia nitrogen + nitrate nitrogen + nitrite nitrogen Example

[0046] (1) In this embodiment, the ammonia nitrogen adsorption material used is polyurethane foam (pore size 25 ppi) loaded with zeolite powder (200 mesh). This material has a high biofilm loading capacity and also has the ability to adsorb ammonia nitrogen.

[0047] (2) In this embodiment, the rotating cage speed is 0.5 rpm, and the hydraulic retention time is 6 hours. Intermittent water inlet and outlet operation, that is, the pump is controlled to have a flow rate of 0.8 liters / minute, and the water inlet is completed in 5 minutes; after running at the current speed for 5 hours and 50 minutes, the water outlet electromagnetic valve is controlled to open to discharge water, and the water outlet is completed after 5 minutes, and then this operation cycle is taken as the operation cycle and the next cycle of operation is immediately entered.

[0048] (3) In this embodiment, two stages of operation are performed, namely, the rotation speed of the tumbler in stage I is 0.5 rpm and the rotation speed of the tumbler in stage II is 1 rpm.

[0049] Depend on Figure 2It is known that this embodiment operates at a low speed, and the pollutant concentration gradually decreases during the operation cycle. In sewage with extremely low dissolved oxygen (anaerobic zone), the ammonia nitrogen concentration is still decreasing, reflecting the adsorption capacity of biological fillers for ammonia nitrogen; and the ammonia nitrogen is decreasing every hour / every 0.5 hour during the cycle, indicating that the nitrification reaction of the biofilm in the aerobic zone in the first 1 hour / first 0.5 hour has regenerated the ability of zeolite to adsorb ammonia nitrogen. The reduction of COD in the anaerobic zone is mainly caused by anaerobic absorption of saccharolytic bacteria (GAOs), and at the same time provides the carbon source required for denitrification inside the membrane for the subsequent aerobic zone biofilm.

[0050] Table 2 Average processing capacity of Example 1 at different speeds

[0051] From Table 2 and Figure 3 It is known that the COD and total nitrogen removal rates of the two stages can be stabilized at more than 80% and 70% in the later stage, and the COD removal rate of stage II reaches 95%, and the total nitrogen removal rate reaches 90%, which reflects the high COD and high total nitrogen removal capacity of the biological cage running at a low speed of the present invention, and the treatment cost is relatively low.

[0052] (6) Changes in microbial abundance after biocage operation stabilizes

[0053] like Figure 4 It is shown that after the biocage runs stably at a low speed, the biofilm is taken for microbial community structure analysis, and compared with the microbial community of the initial activated sludge, the abundance of saccharifying bacteria represented by Candidatus Competibacter bacteria is significantly improved. The abundance of saccharifying bacteria in the biofilm increases by 45 times after the operation of stage I, and increases by 35 times after the operation of stage II. This shows that the high COD and high total nitrogen removal capacity of the low-speed biocage operated in the present invention is related to the high abundance of saccharifying bacteria in the biofilm. Example

[0054] The operating speed was 0.5 rpm, and other operating parameters were the same as those in Example 1. Stage experiments were conducted at different hydraulic retention times. Stage 1 was operated at a hydraulic retention time of 4 hours, and stage 2 was operated at a hydraulic retention time of 2 hours.

[0055] (1) The ability of biocages to remove pollutants at different hydraulic retention times

[0056] Table 3 Average treatment capacity of Example 2 at different hydraulic retention times

[0057] Depend on Figure 5As shown in Table 3, reducing the hydraulic retention time reduces the pollutant removal capacity, but has little effect on the COD removal capacity. This is the embodiment of the pollutant degradation capacity of the biocage based on the polysaccharide bacteria of the present invention. The biocage running at an ultra-low speed can have a high efficiency in removing COD. The total nitrogen in the effluent exists in the form of ammonia nitrogen, which can reduce the effluent ammonia nitrogen concentration by increasing the anaerobic-aerobic alternation frequency of the biofilm, thereby improving the total nitrogen removal rate. Example

[0058] This example is based on the operation of Example 1, and is operated at 1 rpm, with a hydraulic retention time of 6 hours and a continuous water inlet and outlet mode (ie, for a reactor with an effective volume of 4 L, the water inlet flow rate is 11.1 mL / min).

[0059] Table 4 Average treatment capacity of biocages in continuous water inlet and outlet mode

[0060] Figure 6 Table 4 shows the pollutant removal capacity of the present invention in the continuous water inlet and outlet mode. Compared with Example 1, it can be seen that under the same operating conditions, the treatment capacity of the present invention in the intermittent water inlet and outlet mode is relatively better than that in the continuous water inlet and outlet mode. The biocage process based on polysaccharide bacteria operating in the continuous water inlet and outlet mode also belongs to the scope of the present invention.

[0061] Comparative Example 1:

[0062] In order to better reflect the technical advantages of the present invention, a comparative experiment was conducted. In this comparative example, the influent water quality, hydraulic retention time, immersion ratio, and filler are the same as those in Example 1, except that the operating speed is 3 rpm (the general speed of the biological rotary disc process in the prior art is 2-4 rpm).

[0063] Depend on Figure 7 It can be seen that when the biological cage is running at a high speed, the dissolved oxygen in the sewage is high, so that COD is consumed quickly, and COD basically drops to the minimum value 1 hour after the water enters. COD degradation and ammonia nitrogen nitrification both require oxygen consumption. During the operation cycle, COD and ammonia nitrogen increase instantly after the water enters, and then the concentration gradually decreases, and the dissolved oxygen concentration also decreases and gradually increases. The concentration change of dissolved oxygen is as follows Figure 8 shown.

[0064] Table 5 Average water quality before and after treatment of general high speed operation of Comparative Example 1

[0065] like Fig. 9 As shown in Table 5, the biocage running at high speed has better COD removal capacity, but the total nitrogen removal capacity is only 62.1%, and the total nitrogen in the effluent exists in the form of nitrate nitrogen with a higher concentration.

Claims

1. A sewage treatment process based on glycogen-accumulating bacteria, characterized in that: The sewage treatment process based on glycogen-accumulating bacteria comprises the following steps: 1) Setting up a biocage reactor and a water tank, wherein the biocage reactor comprises a water tank, a cage body and ammonia nitrogen adsorption functional filler, wherein the ammonia nitrogen adsorption functional filler is fixed in the cage body, and the cage body is suspended above the water tank; ½ to ⅔ of the volume of the cage body is immersed in the water of the water tank, and the rest is exposed to the air; 2) The activated sludge is placed in the ammonia nitrogen adsorption functional filler of the cage of the biological cage reactor, and the cage of the biological cage reactor is passed through the sewage to be treated; The sewage to be treated adopts a batch mode or a continuous mode for inlet; The sequencing batch mode is adopted, and the hydraulic retention time of the sequencing batch mode is 2-12 hours. After the influent is biologically treated for a period of time, that is, the hydraulic retention time, the reactor is emptied every 2-12 hours and new sewage is introduced; Among them, the continuous mode, in which sewage continuously enters the reactor and is discharged from the reactor at the same flow rate, and the hydraulic retention time of sewage in the reactor is 2-12 hours; 3) The sewage to be treated stays in the biocage for 2-12 hours for sewage treatment; 4) During the stay of sewage in the reactor, pollutants in the sewage are effectively degraded by the biofilm and finally meet the discharge standards; The cage body rotation speed of the biological cage reactor is 0.5 revolutions per hour; the implementation method is that the time-controlled switch controls the motor and then controls the cage body of the biological cage reactor to work at 0.25 revolutions per minute for 2 minutes, and then stop for 58 minutes, thereby reaching 0.5 revolutions per hour; The ammonia nitrogen adsorption functional filler is composited by an ammonia nitrogen adsorption material and a hydrophilic porous material, wherein the ammonia nitrogen adsorption material is selected from any one of zeolite, activated carbon, biochar, fly ash or bentonite; and the hydrophilic porous material is selected from any one of polyurethane foam or melamine foam; The dissolved oxygen in the water tank of the biocage reactor is less than 0.2 mg / L.

2. The sewage treatment process based on saccharide-accumulating bacteria according to claim 1, characterized in that: The structure of the biological cage reactor also includes a driving device and an automatic control component, wherein the automatic control component is composed of a time-controlled switch and a solenoid valve; the automatic control component controls the rotation of the cage body and the water inlet and outlet of the system respectively.

3. The sewage treatment process based on saccharide-accumulating bacteria according to claim 1, characterized in that: The water tank of the biocage reactor is also provided with a water outlet, which can discharge the aged and fallen biofilm while draining the water.

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