Wastewater treatment system based on a combined process of biofilm

Abstract

The application relates to a sewage treatment system based on a biological membrane combined process, and belongs to the technical field of sewage treatment. In the system, a biological treatment unit comprises a biological contact oxidation tank, a biological rotating disc device and a mixed liquid reflux tank which are sequentially connected; the biological contact oxidation tank is provided with an aeration equipment and fillers are added in the tank; a reflux pipe is further arranged between the biological contact oxidation tank and the mixed liquid reflux tank; the mixed liquid reflux tank is connected with a rotating disc tank of the biological rotating disc device; a water level adjusting equipment for adjusting the immersion rate of disc blades of the biological rotating disc device is arranged in the mixed liquid reflux tank; and the water outlet of the water level adjusting equipment is discharged into a post-stage treatment unit; the biological contact oxidation tank and the biological rotating disc device are respectively connected with a pre-stage treatment unit, and a unit water inlet for connecting pre-stage effluent to realize a preset distribution ratio. The system can meet the domestic sewage treatment demand of rural areas and similar areas with large changes in water quality and quantity.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sewage treatment, and particularly relates to a sewage treatment system based on a combined process of biofilm. BACKGROUND

[0002] Both the biofilm method and the activated sludge method belong to the main process technologies of sewage biological treatment. The biofilm method has many characteristics that the activated sludge method does not have. One of the technical implementation manners of the biofilm method is a biological rotating disc. The biological rotating disc has the characteristics of simple structure, easy maintenance, many types of microorganisms, long sludge age, low sludge yield, good sludge settling property, low suspended solids (SS) in effluent, no need for aeration and sludge return, etc. The biological rotating disc can treat low-concentration water and is suitable for centralized treatment of rural domestic sewage with small water quantity.

[0003] However, it is found through actual engineering practice that, generally speaking, the domestic sewage in rural areas indeed has the characteristic of low organic matter concentration. However, in some rural areas, the domestic sewage has the characteristics of large fluctuation of water quantity and water quality and obvious seasonal change. In the related technology, the sewage treatment system based on the biological rotating disc device has remarkable effects on removal of organic matter and ammonia nitrogen, but the denitrification is insufficient. When the concentration of NH3 or total nitrogen (TN) in the influent is high, the TN in the effluent is difficult to stably reach the relevant standard (such as the first-level A standard). In addition, there is a lack of effective control means for the case of large change of water quality and water quantity, which leads to the fact that the system cannot be well applied to the rural areas and other areas with similar sewage discharge conditions.

[0004] Therefore, how to improve the sewage treatment system using the biological rotating disc to meet the specific scene requirements has become a technical problem to be solved.

[0005] The above content is only used to assist in understanding the technical solutions of the application and does not mean that the above content is prior art. SUMMARY

[0006] In order to at least overcome the problems in the related technology, the application provides a sewage treatment system based on a combined biofilm process. In view of the domestic sewage conditions mentioned in the background technology, the technical problem of how to meet the sewage treatment requirements in the scene is solved based on the combination of the biological rotating disc and other biofilm process devices.

[0007] To achieve the above object, the application adopts the following technical solutions:

[0008] The application provides a sewage treatment system based on a combined process of biofilm. The sewage treatment system comprises a biological treatment unit. The biological treatment unit comprises a biological contact oxidation tank, a biological rotating disc device and a mixed liquid return tank which are sequentially connected.

[0009] The biological contact oxidation tank is provided with an aeration device and fillers, and a reflux pipe is arranged between the biological contact oxidation tank and the mixed liquid reflux tank to realize reflux of the mixed liquid with a preset reflux ratio;

[0010] The mixed liquid reflux tank is connected with the rotating disc tank of the biological rotating disc device, and a water level adjusting device for adjusting the disc immersion rate of the biological rotating disc device is arranged in the mixed liquid reflux tank, and the water outlet of the water level adjusting device is discharged into a post-treatment unit;

[0011] The biological contact oxidation tank and the biological rotating disc device are respectively connected with a pre-treatment unit to realize unit water inlet of the pre-treatment effluent with a preset distribution ratio;

[0012] The sewage treatment system is configured to dynamically adjust the disc immersion rate, the preset reflux ratio, the preset distribution ratio, and the aeration state of the biological contact oxidation tank based on the ammonia nitrogen detection value and the inflow of the system water.

[0013] Optionally, the rotating disc tank and the mixed liquid reflux tank are arranged adjacent to each other and share a tank wall, and the two tanks are connected through a through hole arranged in the shared tank wall.

[0014] Optionally, the fillers are suspended fillers.

[0015] The aeration device includes a tubular aeration pipe arranged at the bottom of the biological contact oxidation tank, and the air inlet end of the tubular aeration pipe is connected with a fan to realize intermittent air stirring or micro-aeration of the biological contact oxidation tank.

[0016] The water level adjusting device is a water level decanter.

[0017] Optionally, the pre-treatment unit is further provided.

[0018] The pre-treatment unit includes a grid and a conditioning tank, and the water inlet end of the grid and the conditioning tank is connected with a system water inlet pipe to receive system water.

[0019] The pre-treatment unit further includes a cyclone pre-treater.

[0020] The water inlet of the cyclone pre-treater is connected with a sewage lifting pump arranged in the grid and the conditioning tank through a first water inlet pipe.

[0021] The top opening of the cyclone pre-treater is connected with a first water outlet pipe and a second water outlet pipe, and the water outlet of the top opening is respectively discharged into the biological contact oxidation tank and the biological rotating disc device through the first water outlet pipe and the second water outlet pipe.

[0022] Optionally, the bottom opening of the cyclone pre-treater is connected with an external discharge pipe, and an external discharge electric valve is arranged on the external discharge pipe.

[0023] The external discharge pipe section between the external discharge electric valve and the bottom opening is further connected in communication with the first water inlet pipe through a backflush pipe, and a backflush electric valve is arranged on the backflush pipe.

[0024] The external discharge electric valve and the backflush electric valve are configured to be closed and opened respectively when the water pressure at the water inlet of the cyclone pre-treater is greater than a preset pressure or the continuous operation time of the cyclone pre-treater reaches a first preset time length.

[0025] Optionally, the system further comprises a sludge-water separation treatment unit as the post-stage treatment unit.

[0026] Optionally, the system further comprises a deep treatment unit for deep treatment of clean water discharged from the sludge-water separation treatment unit.

[0027] Optionally, the system further comprises a system terminal device for disinfection and metering of water discharged from the deep treatment unit.

[0028] Optionally, the sludge-water separation treatment unit is a secondary sedimentation tank, the deep treatment unit comprises a filter device, and the system terminal device comprises an ultraviolet disinfection channel and a pasteurization metering tank.

[0029] The above technical scheme has at least the following beneficial effects:

[0030] In the wastewater treatment system of this application, the biological treatment unit includes a biological contact oxidation tank, a biological rotating disc device, and a mixed liquor return tank connected in sequence. The biological contact oxidation tank is equipped with aeration equipment and packing material. A return pipe is also installed between the biological contact oxidation tank and the mixed liquor return tank to achieve a preset return ratio for the mixed liquor return. The mixed liquor return tank is connected to the rotating disc tank of the biological rotating disc device. A water level regulating device is installed in the mixed liquor return tank to adjust the disc immersion rate of the biological rotating disc device. The effluent from the water level regulating device is discharged into the subsequent treatment unit. The biological contact oxidation tank and the biological rotating disc device are respectively connected to the upstream treatment unit to receive the upstream effluent to achieve a preset distribution ratio for the unit influent. The wastewater treatment system is configured to dynamically adjust the disc immersion rate, preset return ratio, preset distribution ratio, and aeration status of the biological contact oxidation tank based on the ammonia nitrogen detection value and influent flow rate of the system influent. The technical solution of this application adopts a biofilm combination process that combines a biological contact oxidation tank and a biological rotating disc in the biological treatment unit. With multiple water inlets, simultaneous nitrification and denitrification can occur in each biological stage, resulting in high nitrogen removal efficiency and strong resistance to shock loads. Furthermore, the system can dynamically switch between different operating modes according to changes in wastewater volume and quality, such as using different operation and maintenance modes during the rainy season and dry season. This ensures that the treated wastewater meets the discharge standards under the corresponding conditions, thus meeting the domestic wastewater treatment needs of rural areas and similar areas where the influent water quality and volume vary greatly.

[0031] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from an examination of the following, or may be learned from the practice of the invention. Attached Figure Description

[0032] The accompanying drawings are used to provide a further understanding of the technical solutions of this application or the prior art, and constitute a part of the specification. The drawings illustrating embodiments of this application, together with the embodiments of this application, are used to explain the technical solutions of this application, but do not constitute a limitation on the technical solutions of this application.

[0033] Figure 1 This is a schematic diagram illustrating the structure of the biological treatment unit in a wastewater treatment system based on a biofilm combined process in one embodiment of this application.

[0034] Figure 2 This is a schematic diagram illustrating the structure of a wastewater treatment system based on a biofilm combined process in one embodiment of this application.

[0035] In the picture,

[0036] 100 Bar screen and equalization tank; 101 System inlet pipe; 102 Bar screen; 103 Agitator; 104 First inlet pipe; 105 Sewage lift pump;

[0037] 200 - cyclone pretreatment device; 201 - water inlet; 202 - top port; 203a - first water outlet pipe; 203b - second water outlet pipe; 204 - bottom port; 205 - external discharge pipe; 206 - external discharge electric valve; 207 - backwash pipe; 208 - backwash electric valve; 209 - pressure gauge;

[0038] 300 - biological contact oxidation tank; 301 - filler; 302a - tubular aeration pipe; 302b - fan; 303 - reflux pipe;

[0039] 400 - biological rotating disc device; 401 - biological rotating disc; 402 - rotating disc tank;

[0040] 500 - mixed liquor reflux tank; 501 - mixed liquor reflux pump; 502 - water level decanter; 503 - PAC agent;

[0041] 600 - secondary sedimentation tank; 601 - sludge discharge pipe; 700 - filter; 701 - backwash drain pipe; 800 - ultraviolet disinfection channel and pasteurization metering tank; 801 - system water outlet pipe. DETAILED DESCRIPTION

[0042] In order to make the objectives, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be described in detail below. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0043] Based on the background art, the traditional activated sludge method is prone to problems such as poor sludge settling property, sludge loss, and reduced biomass. The biofilm method has many characteristics that the activated sludge method does not have. The biological rotating disc technology belongs to the biofilm method, and the related process device has the characteristics of simple structure, easy maintenance, many types of microorganisms, long sludge age, low sludge yield, good sludge settling property, low effluent SS, no need for aeration and sludge reflux, and the ability to treat low-concentration water, and is suitable for centralized treatment of rural domestic sewage with small water quantity.

[0044] However, the water quantity and quality of domestic sewage in some rural areas fluctuate greatly and change significantly with the seasons, and the organic matter concentration of the domestic sewage in these areas is also relatively low. In the related art, the sewage treatment system based on the biological rotating disc device has a significant effect on the removal of organic matter and ammonia nitrogen, but the denitrification effect is insufficient. When the concentration of NH3 or total nitrogen TN in the influent is high, it is difficult for the effluent TN to stably meet the relevant standards (such as the first-level A standard), and there is a lack of effective control means for large changes in water quality and quantity, which leads to the fact that this type of system cannot be well applied to such rural areas and other areas with similar sewage discharge conditions.

[0045] In response to this, this application proposes a wastewater treatment system based on a combined biofilm process, which combines a biological rotating disc with other biofilm process devices to specifically address the technical problem of how to meet the wastewater treatment needs in such scenarios.

[0046] In one embodiment, the wastewater treatment system based on combined biofilm technology proposed in this application includes a biological treatment unit, such as... Figure 1 As shown, the biological treatment unit in this embodiment includes a biological contact oxidation tank 300, a biological rotating disc device 400 (which includes a biological rotating disc 401 and a rotating disc pool 402 for containing the rotating disc) and a mixed liquor reflux tank 500 connected in sequence.

[0047] As a specific implementation method, the mixed liquor reflux tank 500 is generally small in practice. For the sake of engineering cost, the rotary tank 402 and the mixed liquor reflux tank 500 can be set up adjacent to each other and share a tank wall. The two tanks can be connected by a through hole set in the shared tank wall, so that the mixed liquor reflux tank and the rotary tank can be set up in separate compartments.

[0048] In this embodiment, an aeration device is installed at the biological contact oxidation tank 300 and packing material 301 is added to the tank;

[0049] For example, in this embodiment, the aeration equipment is a tubular aeration equipment, which includes a tubular aeration pipe 302a installed at the bottom of the biological contact oxidation tank, and a blower 302b. The air inlet end of the tubular aeration pipe 302a is connected to the blower 302b. In practice, based on the control of the blower 302b, intermittent gas stirring or micro-aeration of the biological contact oxidation tank can be achieved. For example, the packing material 301 here can be a suspended packing material, so that the packing material is fixed at the top and bottom, which helps to prevent the packing material from accumulating.

[0050] like Figure 1 As shown, a return pipe 303 is also provided between the biological contact oxidation tank 300 and the mixed liquor return tank 500 to realize the return of the mixed liquor at a preset return ratio (for example, a mixed liquor return pump 501 is provided in the mixed liquor return tank 500, and the return pipe 303 is connected to it, so that the preset return ratio can be realized based on the control of the mixed liquor return pump 501).

[0051] The biological contact oxidation tank 300 is mainly used to improve the denitrification capacity of the system and further reduce the SS concentration. At the same time, the internal return nitrified liquid also enters the anoxic contact oxidation tank 300, which facilitates the control of the total nitrogen removal rate in the wastewater.

[0052] In this embodiment, such as Figure 1As shown, the mixed liquid reflux pool 500 is connected to the rotating disc pool 402 of the biological rotating disc device 400, and a water level adjusting device (for example, a water level decanter 502) is arranged in the mixed liquid reflux pool 500 to adjust the disc immersion rate of the biological rotating disc device 400. The water outlet of the water level adjusting device (corresponding to the OUT icon) is connected to the subsequent treatment unit. Figure 1 In the actual implementation, the water level adjusting device is arranged in the mixed liquid reflux pool, and the sewage in the reflux pool flows into the water level adjusting device and is discharged through the adjusting device. Since the reflux pool is connected to the rotating disc pool, the disc immersion rate is finally adjusted based on the principle of a communicating vessel.

[0053] The biological rotating disc device is mainly used for removing organic matter, ammonia nitrogen, SS and the like in sewage. The disc and the large amount of biofilm attached to the surface of the biological rotating disc continuously and alternately contact air and sewage, and the microorganisms continuously maintain the process of oxygen absorption, adsorption and oxidative decomposition, so that the sewage is purified. The disc performs nitrification reaction, and as the film thickens, the inner layer of the microorganisms contacts a reduced oxygen concentration, so that the biological rotating disc has a certain degree of simultaneous nitrification and denitrification function. Figure 1 As shown, the PAC agent 503 can also be added into the mixed liquid reflux pool 500, mixed with the sewage, and then introduced into the subsequent treatment unit, so as to chemically assist in removing phosphorus and SS.

[0054] In this embodiment, as shown, the biological contact oxidation pool 300 and the biological rotating disc device 400 are respectively connected to the front-stage treatment unit to introduce the front-stage effluent (corresponding to the IN icon) into the unit to achieve a preset distribution ratio. Figure 1 As shown, the biological contact oxidation pool 300 and the biological rotating disc device 400 are respectively connected to the front-stage treatment unit to introduce the front-stage effluent (corresponding to the IN icon) into the unit to achieve a preset distribution ratio. Figure 1 As shown, the biological contact oxidation pool 300 and the biological rotating disc device 400 are respectively connected to the front-stage treatment unit to introduce the front-stage effluent (corresponding to the IN icon) into the unit to achieve a preset distribution ratio. Figure 1 As shown, the biological contact oxidation pool 300 and the biological rotating disc device 400 are respectively connected to the front-stage treatment unit to introduce the front-stage effluent (corresponding to the IN icon) into the unit to achieve a preset distribution ratio.

[0055] In this embodiment, the sewage treatment system is configured to dynamically adjust the disc immersion rate, the preset reflux ratio, the preset distribution ratio, and the aeration state of the biological contact oxidation pool based on the ammonia nitrogen detection value of the system influent and the inflow.

[0056] As can be easily understood, in the actual implementation and operation of the sewage treatment system, a plurality of online detection instruments are arranged, and the system related state data can be obtained based on these instruments, such as the inflow Q i of the system influent, the ammonia nitrogen detection value NH 3i of the influent, the dissolved oxygen detection value DO1 in the biological contact oxidation pool 300, the ammonia nitrogen detection value NH 3S in the rotating disc pool 402, the flow rate Q1 of the front-stage effluent into the biological contact oxidation pool, the flow rate Q2 of the front-stage effluent into the rotating disc pool 402, and the like.

[0057] Further, the ammonia nitrogen detection value NH of the system influent can be used as a basis 3i and the water inflow Q i , by regulating the water level adjusting device, the reflux pump, the influent valve, the fan, the disc speed regulating device, etc., to dynamically adjust the disc immersion rate, the preset reflux ratio, the preset distribution ratio, and the aeration state of the biological contact oxidation tank, to achieve the standard discharge of the system in different situations (such as using different operation modes in the rainy season and the dry season), which can effectively meet the domestic sewage treatment needs of rural areas and similar areas with large changes in water quality and quantity.

[0058] Moreover, the biological treatment unit in the system adopts a combined biofilm process, combined with multi-point influent, and each biological section can have simultaneous nitrification and denitrification, so that the system has high nitrogen removal efficiency and strong impact load bearing capacity.

[0059] To facilitate understanding of the technical solutions of the present application, the technical solutions of the present application are described below with another embodiment.

[0060] In this embodiment, the sewage treatment system based on a combined biofilm process proposed by the present application includes a biological treatment unit (as described in the previous embodiment), and further includes a pretreatment unit as a front-stage treatment unit of the biological treatment unit.

[0061] As shown in Figure 2 , the pretreatment unit in this embodiment includes a grid and adjusting tank 100, and the influent end of the grid and adjusting tank 100 is connected with a system influent pipe 101 for connecting the system influent. For example, in practice, the grid and adjusting tank can adopt a steel-concrete structure or a modular finished equipment, the gap of the grid 102 is set to 10-15 mm, mainly used to intercept larger floating objects in the sewage; and the adjusting tank is used to homogenize the water quantity and quality of the raw water, and to degrade part of the organic matter in the sewage, and a stirrer 103 is arranged in the adjusting tank.

[0062] To avoid the adverse effects of solid particles and SS with high density in the sewage on the downstream biological treatment, in this embodiment, the pretreatment unit further includes a cyclone pretreater 200; the influent port 201 of the cyclone pretreater 200 is connected with a sewage lifting pump 105 arranged in the grid and adjusting tank through a first influent pipe 104, as shown in Figure 2 , the sewage lifting pump 105 is arranged at the side of the adjusting tank in the grid and adjusting tank.

[0063] The top port 202 of the cyclone pretreater is connected with a first water outlet pipe 203a and a second water outlet pipe 203b, and the water outlets of the top port 202 correspondingly enter a biological contact oxidation tank 300 and a biological rotating disc device 400 through the first water outlet pipe 203a and the second water outlet pipe 203b.

[0064] It should be noted that in wastewater treatment technologies, grit chambers and primary sedimentation tanks are generally used to deal with denser solid particles and suspended solids (SS) in wastewater. However, due to practical engineering considerations, grit chambers and primary sedimentation tanks (mostly reinforced concrete structures) are rarely used in rural domestic wastewater treatment processes. The cyclone pre-processor 200 installed here has the functions of both a grit chamber and a primary sedimentation tank. Moreover, this device can be a prefabricated unit, has a very small footprint, high treatment efficiency, low investment cost, and is easy to install.

[0065] In practical engineering, for example, a cyclone pre-processor of a certain finished product device is made of stainless steel, and the single-unit processing capacity is 10-100m³. 3 With a flow rate of 1.0–10 seconds per hour, the retention time is significantly lower than that of traditional grit chambers. The effluent ratio at the bottom port 204 of this vortex pre-processor is ≤6%, which can be adjusted according to the wastewater volume and quality. Taking the above vortex pre-processor as an example, the influent to the vortex pre-processor is transported by the corresponding wastewater lift pump 105. The effluent from the wastewater lift pump 105 enters the inlet 201 of the vortex pre-processor through the first inlet pipe 104. Under certain pressure (0.10–0.18 MPa) and flow rate conditions, through the enhanced centrifugal force, the denser solids in the wastewater are discharged from the bottom port 204 of the vortex pre-processor for further external treatment. The clarified water is discharged from the top port 202 of the vortex pre-processor and enters the biological treatment unit.

[0066] In practice, when the cyclone preprocessor runs for a long time or the equipment is restarted, the operating resistance of the cyclone preprocessor increases, which will lead to a reduction in the processing capacity and a decrease or even no discharge of sediment from the bottom outlet.

[0067] In view of this, as a specific implementation method, such as Figure 2 As shown, the bottom port 204 of the vortex preprocessor is connected to an external discharge pipe 205, and an external discharge electric valve 206 is installed on the external discharge pipe 205; the external discharge pipe section between the external discharge electric valve 206 and the bottom port 205 is also connected to the first water inlet pipe 104 through a backflushing pipe 207, and a backflushing electric valve 208 is installed on the backflushing pipe 207.

[0068] The external discharge electric valve 206 and the backwash electric valve 208 are configured to, at the inlet water pressure of the vortex pre-processor (based on...) Figure 2 When the pressure gauge 209 set in front of the inlet 201 (to obtain the inlet pressure) is greater than the preset pressure or when the continuous running time of the vortex preprocessor reaches the first preset time, the discharge electric valve 206 closes and the backwash electric valve 208 opens and remains for the second preset time.

[0069] For example, when the pressure gauge reading P ≥ P o (P o To run the set value, Po > 0.1 MPa), or the continuous running time reaches t o (t o is set, wherein t o ≥ 24 h), the electric discharge valve 206 is closed, the backwash electric valve 208 is opened, the pressure flow of the sewage lifting pump 105 is used to backwash the cyclone pretreater through the bottom opening 204 for 10-30 min, the backwash water volume can reach 200%-500% of the discharge volume, then the backwash electric valve 208 is closed, the discharge electric valve 206 is opened, and the equipment is normally pretreated; in this implementation, a separate backwash tank and backwash pump are not needed, and the ideal washing effect can be achieved without stopping production.

[0070] In this embodiment, as Figure 2 shown, the biological treatment unit is also realized based on the combination of the biological rotating disc and other biological membrane process devices, and the related structure has been described in the previous embodiments.

[0071] Based on the above description, the biological treatment unit includes a biological contact oxidation tank 300, a biological rotating disc device 400, and a mixed liquid reflux tank 500; as Figure 2 shown, the clarified water discharged from the top opening 202 of the cyclone pretreater enters the biological contact oxidation tank 300 and the biological rotating disc device 400 respectively to realize multi-point water inlet.

[0072] The main function of the biological contact oxidation tank 300 is to improve the nitrogen removal capacity of the system and further reduce the SS concentration, and the internal reflux nitrification liquid also enters the biological contact oxidation tank 300 to facilitate the control of the total nitrogen removal rate in the wastewater; for example, the hydraulic retention time of the biological contact oxidation tank 300 is 2-6 h, the filling rate of the filler 301 in the tank is not less than 30%, and the specific surface area of the filler 301 is 4000-6000 m 2 / m 3 , such as biomimetic water grass; the biological contact oxidation tank 300 is provided with a tubular aeration pipe 302a, which is in communication with a fan 302b to realize intermittent air stirring or micro-aeration of the biological contact oxidation tank 300.

[0073] The rotating disc pool 402 of the biological rotating disc device 400 is communicated with the biological contact oxidation pool 300, and the clarified water discharged from the cyclone pretreater top port 202 also enters the biological rotating disc device; the biological rotating disc device 400 mainly removes the organic matter, ammonia nitrogen, SS and the like in the sewage; the disc piece of the biological rotating disc device 400 and the large amount of biological membrane attached to the surface continuously and alternately contact the air and the sewage, the microorganisms continuously maintain the oxygen absorption, adsorption and oxidation decomposition process, so as to realize the purification of the sewage, the disc piece performs nitrification reaction, and with the thickening of the membrane, the reduction of the inner layer microorganism contact oxygen concentration, the biological rotating disc has the function of a certain degree of simultaneous nitrification and denitrification and nitrogen removal;

[0074] For example, the disc piece can be made of high-strength high-molecular material, the disc piece has a diameter of 1.5-3.0 m, and a corrugated disc surface structure is adopted, so that the effective area per unit volume can be greatly increased, and the treatment efficiency is improved; similar to the prior art, the disc piece can be specially treated to make it more easily attach microorganisms, and the sludge-water separation effect is good; even in the case of low water quantity and low pollutant concentration, the biological membrane amount and the treatment capacity can also be maintained; the design surface organic load of the biological rotating disc 401 is 2-10 gBOD5 / (m 2 ·d), the rotating speed is 2-4 r / min, and the residence time is 2.0-4.0 h; the rotating speed of the biological rotating disc 401 can be controlled by a variable frequency motor, so as to realize the control of the dissolved oxygen concentration and the ammonia nitrogen concentration.

[0075] The mixed liquid reflux pump 501 is arranged in the mixed liquid reflux pool 500 and can be controlled by frequency conversion; generally, the reflux ratio is controlled to be 50%-150%, and the reflux ratio is adjusted according to different operation modes; the oxygen content of the biological membrane in the biological rotating disc 401 should be higher than that of the water body, so that even if the dissolved oxygen content in the water body is low, the biological rotating disc 401 can still maintain good nitrification reaction; the liquid level height in the rotating disc pool 402 can be controlled by the water level decanter 502; generally, the disc piece immersion rate is adjusted to be in the range of 40%-60% to adapt to the water quantity and water quality changes; the low liquid level can improve the decarburization and nitrification capacity, and the high liquid level can strengthen the denitrification capacity.

[0076] The single biological rotating disc has remarkable effect on organic matter and ammonia nitrogen removal, but the denitrification is insufficient. When the concentration of NH3 or TN in the influent is high, it is difficult for the effluent TN to reach the first level A standard stably, and there is no effective control means for the change of water quality and quantity. Herein, the biological rotating disc is combined with the biological contact oxidation tank, and the intermittent air agitation or micro-aeration is conducted by the pipe aeration pipe, the mixed liquid reflux control is increased, the multi-point water inlet is adopted, and the operation mode of the biological membrane combined process is adjusted according to the change of water quantity and quality by controlling the immersion rate of the biological rotating disc, so that the water quantity is increased and the operation cost is reduced under the guarantee of TN removal effect. The combined process has no sludge reflux, and the microorganisms in the biological contact oxidation tank and the biological rotating disc are basically cultured independently. The biological contact oxidation tank is beneficial to the enrichment of denitrifying bacteria to realize low-carbon denitrification, and is suitable for the treatment of sewage with low carbon-nitrogen ratio.

[0077] The operation mode of the system is illustrated as follows:

[0078] Based on the foregoing description, the related online detection instruments can be set in the system application to obtain the related monitoring data, such as the water quantity Q i of the influent, the detection value NH 3i of the ammonia nitrogen of the influent, the detection value DO1 of the dissolved oxygen in the biological contact oxidation tank 300, the detection value NH 3S of the ammonia nitrogen in the rotating disc tank 402, the flow rate Q1 of the pre-stage effluent into the biological contact oxidation tank, the flow rate Q2 of the pre-stage effluent into the rotating disc tank 402, and the like.

[0079] The biological rotating disc mainly enriches oxygen in the water body by the disc with biological membrane. The rotation speed is the main factor affecting the concentration of dissolved oxygen, and then affects the nitrification effect. The automatic operation of the equipment is realized by the online ammonia nitrogen instrument controlling the frequency reducer. When the effluent NH3 value increases, the system will automatically increase the rotation speed to strengthen the nitrification reaction, and vice versa.

[0080] Regarding the operation mode, for example, when the concentration of sewage is low and the water quantity is large, such as Q O <Q i ≤150%Q O (Q O is the design scale) and NH 3i ≤20mg / L, the biological treatment unit distributes the influent Q1:Q2=2:1, the mixed liquid reflux pump can be not started, the air blower is started to continuously aerate the biological contact oxidation tank for oxygen supply, DO1 is controlled at 0.5-1.5mg / L, the disc immersion rate of the biological rotating disc is adjusted at 40%-50% by the water level decanter, the biological contact oxidation tank and the biological rotating disc device are operated in this mode, the nitrification reaction and the denitrification reaction occur, and the simultaneous nitrification and denitrification effect can occur, so that the low-concentration sewage can be discharged stably under the overload water quantity.

[0081] When the sewage inflow Q i ≤ Q O and 20mg / L < NH 3i ≤ 30mg / L, the biological treatment unit allocates the inflow Q1:Q2 = 1:1, starts the mixed liquor reflux pump, controls the reflux ratio to be 50% to 100%, and the fan intermittently operates, for example, set the program to open for 30 to 60s and stop for 5 to 15min, to intermittently air-agitate the biological contact oxidation tank, mainly to perform the denitrification reaction in the tank, and the disc immersion ratio of the biological rotating disc is controlled to be 40% to 50%, mainly to perform the nitrification reaction, so as to realize the sewage discharge standard in this case;

[0082] When the sewage inflow Q i ≤ Q O and NH 3i > 30mg / L, the biological treatment unit allocates the inflow Q1:Q2 = 1.5:1, controls the reflux ratio of the mixed liquor reflux pump to be 100% to 150%, strengthens the nitrification liquid reflux, and the fan intermittently operates, for example, set the program to open for 30 to 60s and stop for 5 to 15min, to intermittently air-agitate the biological contact oxidation tank, to enhance the denitrification effect of the biological contact oxidation tank, the disc immersion ratio of the biological rotating disc is controlled to be 50% to 60% through the water level decanter, the hydraulic retention time can be increased through the high liquid level, the biological rotating disc mainly performs the nitrification reaction, but can strengthen the simultaneous nitrification and denitrification capacity, so as to realize the sewage discharge standard in this case.

[0083] In this embodiment, the sewage treatment system based on the combined biofilm process further comprises a sludge-water separation treatment unit as a post-treatment unit of the biological treatment unit, specifically as shown in Figure 2 , the sludge-water separation treatment unit here is a secondary sedimentation tank 600;

[0084] Further comprising a depth treatment unit for depth treatment of the clear water discharged from the sludge-water separation treatment unit (the secondary sedimentation tank 600), specifically as shown in Figure 2 , the depth treatment unit here comprises a filter device 700;

[0085] Further comprising a system terminal device for disinfection and metering of the effluent of the depth treatment unit, as shown in Figure 2 , the system terminal device here comprises an ultraviolet disinfection channel and a Pasteur metering tank 800.

[0086] In actual engineering practice, the secondary sedimentation tank 600 can adopt a vertical flow type or other forms, which mainly plays a role of sludge-water separation; the effluent of the water level decanter 502 enters the secondary sedimentation tank 600 for sludge-water separation, the clear water flows into the filter 700 for depth treatment, and the remaining sludge is discharged by the sludge discharge pipe 601, the sludge produced by the biofilm method has good sedimentation, and is easy to separate solid and liquid;

[0087] The filter 700 is a complete set of equipment here for specific scene needs, and is designed with a water flux of 3-5 m 3 / (m 2 ·h) and a filtering precision of 10 μm; under the condition that the SS concentration of the water entering the equipment is less than 50 mg / L, the water can reach the national standard of level A; the filter cloth with a filtering precision of 10 μm has high filtering precision, automatic control operation, low backwash water volume (backwash drainage is performed through the reverse drainage pipe 701), continuous operation without water stop during backwash, low operation cost, and simple and convenient maintenance.

[0088] The ultraviolet disinfection channel and the Pasteur metering tank 800 are an integrated complete set of equipment here for specific scene needs, are made of stainless steel, disinfect and meter the end water, and discharge the final system water from the system water outlet pipe 801.

[0089] The technical scheme of the present application can be applied to the treatment of rural domestic sewage, and has at least the following advantages compared with the existing rural domestic sewage treatment system:

[0090] (1) The cyclone pretreater is applied to the treatment of rural domestic sewage, has the functions of a sand trap and a primary sedimentation tank, and can enhance the pretreatment effect; the cyclone pretreater performs online backwashing using the water pressure, does not need a separate backwashing system, and has high automation; the cyclone pretreater can also be used in medium and large sewage treatment plants to replace a sand trap or a primary sedimentation tank with a steel and concrete structure, and has the same advantages;

[0091] (2) The cyclone pretreater is a finished product, can be applied to large, medium and small sewage treatment plants, has extremely small land occupation, high treatment efficiency, low investment cost, and convenient installation and operation and maintenance;

[0092] (3) The biological membrane combined process is adopted, combined with multi-point water inlet, and the simultaneous nitrification and denitrification effect can occur in each biological section, so that the denitrification efficiency is high and the impact load capacity is strong;

[0093] (4) The biological membrane combined process can switch different operation modes according to the changes of the water quantity and quality of the sewage, for example, different operation modes are adopted in the rainy season and the dry season, so as to ensure that the sewage treatment meets the discharge standard;

[0094] (5) The biological rotating disc tank realizes the speed optimization of the biological rotating disc through the numerical control of the frequency reducer by the online ammonia nitrogen instrument, which is beneficial to improve the automatic operation of the equipment.

[0095] The above merely describes preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A wastewater treatment system based on a combined process of biofilm, comprising a biological treatment unit, characterized in that, The biological treatment unit comprises a biological contact oxidation tank, a biological rotating disc device and a mixed liquor reflux tank connected in sequence. The biological contact oxidation tank is provided with an aeration device and fillers, and a reflux pipe is arranged between the biological contact oxidation tank and the mixed liquor reflux tank to realize mixed liquor reflux with a preset reflux ratio. The mixed liquor reflux tank is connected with the rotating disc tank of the biological rotating disc device, and a water level adjusting device for adjusting the disc immersion rate of the biological rotating disc device is arranged in the mixed liquor reflux tank. The biological contact oxidation tank and the biological rotating disc device are respectively connected with a front-stage treatment unit to realize water inlet with a preset distribution ratio. The sewage treatment system is configured to dynamically adjust the disc immersion rate, the preset reflux ratio, the preset distribution ratio, and the aeration state of the biological contact oxidation tank based on the ammonia nitrogen detection value NH3-N and the water inflow Q of system inflow i , When Q O < Q i ≤ 150% Q O and NH3-N≤20 mg / L, the preset distribution ratio is 2:1, the preset reflux ratio is 0, the biological contact oxidation tank is continuously supplied with micro-aeration oxygen, the dissolved oxygen is controlled at 0.5-1.5 mg / L, the disc immersion rate is controlled at 40%-50%, the biological contact oxidation tank and the biological rotating disc device both undergo nitrification and denitrification, When Q i ≤ Q O and 20 mg / L < NH3-N < 30 mg / L, the preset distribution ratio is 1:1, the preset reflux ratio is 50%~100%, the biological contact oxidation tank is intermittently gas-agitated, the biological contact oxidation tank mainly performs denitrification reaction, and the disc immersion rate is controlled at 40%~50%. When Q i ≤ Q O and NH3-N > 30 mg / L, the preset distribution ratio is 1.5:1, the preset reflux ratio is 100%~150%, the biological contact oxidation tank is intermittently gas-agitated, the denitrification of the biological contact oxidation tank is enhanced, and the disc immersion rate is controlled at 50%~60%, where Q O represents the throughput of the design size.

2. The sewage treatment system of claim 1, wherein, The rotating disc tank and the mixed liquor reflux tank are arranged adjacent to each other and share a tank wall, and the two tanks are connected through a through hole arranged in the shared tank wall.

3. The sewage treatment system according to claim 1, wherein The fillers are suspended fillers. The aeration device comprises a tubular aeration pipe arranged at the bottom of the biological contact oxidation tank, and the air inlet end of the tubular aeration pipe is connected with a fan to realize intermittent air agitation or micro-aeration of the biological contact oxidation tank. The water level adjusting device is a water level decanter.

4. The sewage treatment system of claim 1, wherein, Further comprising a pretreatment unit as the front-stage treatment unit. The pretreatment unit comprises a grid and a conditioning tank, and the water inlet end of the grid and the conditioning tank is connected with a system water inlet pipe to receive system water inlet. The pretreatment unit further comprises a cyclone pretreater. The water inlet of the cyclone pretreater is connected with a sewage lifting pump arranged in the grid and the conditioning tank through a first water inlet pipe. The top opening of the cyclone pretreater is connected with a first water outlet pipe and a second water outlet pipe, and the water outlet of the top opening enters the biological contact oxidation tank and the biological rotating disc device through the first water outlet pipe and the second water outlet pipe respectively.

5. The sewage treatment system of claim 4, wherein, The bottom opening of the cyclone pretreater is connected with a discharge pipe, and a discharge electric valve is arranged on the discharge pipe. The discharge pipe segment between the discharge electric valve and the bottom opening is further connected with the first water inlet pipe through a backflush pipe, and a backflush electric valve is arranged on the backflush pipe. The discharge electric valve and the backflush electric valve are configured to be closed and opened respectively when the water inlet pressure at the water inlet of the cyclone pretreater is greater than a preset pressure or the continuous running time of the cyclone pretreater reaches a first preset time, and the backflush electric valve is kept open for a second preset time.

6. The sewage treatment system of claim 1, wherein, Further comprising a sludge-water separation treatment unit as the rear-stage treatment unit.

7. The sewage treatment system of claim 6, wherein, Further comprising a deep treatment unit for deep treatment of the clear water discharged from the sludge-water separation treatment unit.

8. The sewage treatment system of claim 7, wherein, Further comprising a system terminal device for disinfection and metering of the water outlet of the deep treatment unit.

9. The sewage treatment system of claim 8, wherein, The sludge-water separation treatment unit is a secondary sedimentation tank, the deep treatment unit comprises a filter device, and the system terminal device comprises an ultraviolet disinfection channel and a pasteurization metering tank.

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