A MBR sewage treatment system and process with pre-phosphorus removal and post-endogenous denitrification coupling

Abstract

The present invention provides a pre-phosphorus removal and post-endogenous denitrification coupled MBR sewage treatment system and process. The system mainly includes a pre-phosphorus removal unit, a post-endogenous denitrification unit and a sludge return unit. The effluent from the grit chamber enters a flocculation sedimentation phosphorus removal tank for phosphorus removal; then the supernatant enters a post-endogenous denitrification unit, and denitrifying bacteria absorb carbon sources in the anaerobic tank. In the dynamic aerobic tank, dynamic and precise nitrification is carried out in conjunction with detection instruments and control equipment, and then post-endogenous denitrification is carried out in the anoxic tank, thereby achieving deep denitrification; the effluent and sludge from the anoxic tank enter the MBR membrane tank and the sludge return unit, and a double return system is adopted to maximize the function of the anaerobic zone, or a pre-anaerobic zone is set up to divert the influent and reduce the impact of high dissolved oxygen in the MBR membrane tank on the denitrifying bacteria. The system and process solve the problems of low denitrification efficiency of traditional pre-denitrification, the sludge age contradiction between post-biological phosphorus removal and denitrification, high suspended solids in biochemical effluent, and the inability to selectively increase sludge concentration in winter.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, in particular to a pre-phosphorus removal and post-endogenous denitrification coupled MBR sewage treatment system and process. Background Art

[0002] The current mainstream sewage treatment process is to use microorganisms for pre-denitrification denitrification and biological phosphorus removal combined with post-chemical enhanced phosphorus removal. That is, denitrification (mainly thorough denitrification) is completed in the first half of the process, and the subsequent aerobic stage is responsible for nitrification. A portion of the total phosphorus in the sewage is removed by discharging phosphorus-rich sludge. At the same time, phosphorus removal is enhanced by adding phosphorus removal agents to the biochemical effluent to ensure that the total phosphorus meets the standard and remove some suspended solids.

[0003] The main disadvantages of the above process are: (1) low total nitrogen removal rate. Pre-denitrification controls the denitrification efficiency by controlling the reflow ratio, but the reflow ratio is generally less than 300%. Therefore, the total nitrogen removal rate of the pre-denitrification process is generally less than 80%. (2) Biochemical denitrification and phosphorus removal are carried out simultaneously, resulting in a contradiction in sludge age. More sludge discharge is beneficial to phosphorus removal, but not to nitrogen removal. Less sludge discharge is beneficial to nitrogen removal but not to phosphorus removal. For some wastewaters with high total phosphorus, it is difficult to reconcile the contradiction between denitrification and phosphorus removal. (3) After chemical enhanced phosphorus removal, in order to ensure that the suspended solids meet the standards, it is generally necessary to add a filtration device, resulting in complex treatment processes, increased investment, and cumbersome operations. (4) It is difficult to increase the sludge concentration in the traditional secondary sedimentation tank. When the water temperature is low in winter, it is impossible to ensure the effluent quality by increasing the sludge concentration. (5) If MBR effluent and traditional post-phosphorus removal are used, since the MBR effluent SS is very low, it is not conducive to the phosphorus removal effect of the phosphorus removal agent.

[0004] Therefore, it is necessary to develop a deep denitrification and phosphorus removal wastewater treatment system and process that can solve the problems of low efficiency of traditional pre-denitrification denitrification, contradiction between sludge age of post-biological phosphorus removal and denitrification, high suspended solids in biochemical effluent, and inability to arbitrarily increase sludge concentration in winter. Summary of the invention

[0005] In order to solve the deficiencies in the prior art, the present invention provides a pre-phosphorus removal and post-endogenous denitrification coupled MBR sewage treatment system and process, which can solve the problems of low efficiency of traditional pre-denitrification denitrification, contradiction between sludge age of post-biological phosphorus removal and denitrification, high suspended solids in biochemical effluent, and inability to arbitrarily increase sludge concentration in winter. The specific technical scheme is as follows:

[0006] The present invention first provides a pre-phosphorus removal and post-endogenous denitrification sewage treatment system, comprising a sand settling tank, a flocculation sedimentation phosphorus removal tank, an anaerobic tank, a plurality of dynamic aerobic tanks, a plurality of anoxic tanks, an MBR membrane tank and a sludge concentration tank;

[0007] The grit chamber, the flocculation sedimentation phosphorus removal tank, the anaerobic tank, a plurality of dynamic aerobic tanks, a plurality of anoxic tanks, the MBR membrane tank and the sludge concentration tank are connected in sequence through pipelines;

[0008] The flocculation sedimentation phosphorus removal tank is connected to the sludge concentration tank through a pipeline, and a sludge pump is arranged in the pipeline.

[0009] The MBR membrane tank is connected to a sludge return system;

[0010] The anaerobic tank and the anoxic tank are both equipped with a stirrer, and the dynamic aerobic tank is both equipped with an aeration device and a stirrer.

[0011] In some specific embodiments of the present invention, the sludge return system includes a pipeline connecting the MBR membrane tank and the front end of the dynamic aerobic tank and a sludge pump.

[0012] In some specific embodiments of the present invention, the end of the anoxic tank is connected to the front end of the anaerobic tank through a pipeline, and a sludge return pump is provided in the pipeline.

[0013] In some specific embodiments of the present invention, the sludge return system includes a pre-anaerobic tank, which is connected to the MBR membrane tank and the flocculation sedimentation phosphorus removal tank through pipelines, and the pipelines are all equipped with sludge return pumps; the pre-anaerobic tank is connected to the water inlet of the anaerobic tank through a pipeline.

[0014] In some specific embodiments of the present invention, the dynamic aerobic pool and the anoxic pool are both provided with a pH detector and a DO detector.

[0015] In some specific embodiments of the present invention, a PLC controller is further included, and the PLC controller is communicatively connected with the pH detector, the DO detector, the aeration equipment and the agitator respectively.

[0016] The present invention also provides a wastewater treatment process with pre-phosphorus removal and post-endogenous denitrification, comprising the following process steps:

[0017] S1: After being treated in the primary sedimentation tank, the sewage enters the flocculation sedimentation phosphorus removal tank, where it is mixed with the flocculation phosphorus removal agent added to the flocculation sedimentation phosphorus removal tank. The sludge and water are then separated, and the supernatant enters the anaerobic tank, while the precipitated sludge enters the sludge thickening tank.

[0018] S2: After the sewage enters the anaerobic tank for mixing, the anaerobic tank is stirred, and the denitrifying bacteria absorb the carbon source, and the retention time is T1 hours;

[0019] S3: The effluent from the anaerobic tank enters several dynamic aerobic tanks. The retention time of each dynamic aerobic tank is T2 hours. Nitrification is carried out under the action of stirring and aeration to degrade ammonia nitrogen and remaining organic matter in the sewage. When it is detected that the dissolved oxygen in the last dynamic aerobic tank is still higher than 4 mg / L when the aeration volume is lower than 30% of the normal aeration volume, and the pH value rises at this time, the aeration of this dynamic aerobic tank and the subsequent dynamic aerobic tanks are automatically turned off and become anoxic tanks. Only the agitator is turned on in the anoxic tank.

[0020] S4: sewage entering the anoxic tank, the total residence time in the anoxic tank is T3 hours, and denitrification is achieved through endogenous denitrification by denitrifying bacteria;

[0021] S5: The sewage in the anoxic tank enters the MBR membrane tank after discharge to achieve mud-water separation. The sludge is returned to the front end of the anaerobic tank or dynamic aerobic tank through the sludge return system. The remaining sludge is discharged into the sludge thickening tank and the supernatant is discharged.

[0022] In some specific embodiments of the present invention, in step S5, the sludge from the MBR membrane pool is returned to the front end of the dynamic aerobic pool, with a return ratio of 50%; the sludge from the end of the anoxic pool is returned to the front end of the anaerobic pool, with a return ratio of 100%.

[0023] In some specific embodiments of the present invention, 10% of the effluent from the flocculation sedimentation phosphorus removal tank enters the pre-anaerobic tank, and the rest enters the anaerobic tank; in step S5, the sludge from the MBR membrane tank is returned to the pre-anaerobic tank, and the return ratio is 100%; the effluent from the pre-anaerobic tank enters the anaerobic tank.

[0024] In some specific embodiments of the present invention, the flocculating phosphorus removal agent is PAC or PFC, and the dosage of PAC or PFC is 50 mg / L to 200 mg / L.

[0025] In some specific embodiments of the present invention, the T1 is 0.5-2, the T2 is 2-3, and the T3 is 8-12;

[0026] In some specific embodiments of the present invention, the dissolved oxygen concentration during aeration of the dynamic aerobic tank is controlled at 2 mg / L-4 mg / L.

[0027] In some specific embodiments of the present invention, when the carbon-nitrogen ratio of the influent of the anaerobic tank is less than 3, a carbon source is added to the anaerobic tank.

[0028] The beneficial effects of the present invention are:

[0029] ①Put phosphorus removal at the front end of the biochemical process. Through chemical phosphorus removal, the competition for carbon sources by subsequent phosphorus removal bacteria is reduced, while the growth of non-functional bacteria and sludge growth is reduced, maximizing the enrichment of denitrification bacteria;

[0030] ② The AOA mode can achieve deep removal of total nitrogen. Combined with the MBR process, it can not only flexibly control the sludge concentration, but also ensure that the suspended solids in the effluent meet the standards, eliminating the need for subsequent deep treatment systems;

[0031] ③ By adopting a double recirculation system, the function of the anaerobic zone can be maximized, or a pre-anaerobic zone can be set up to divert the influent and reduce the impact of high dissolved oxygen in the MBR membrane pool on denitrifying bacteria.

[0032] ④ Equipped with pH and DO detectors, combined with PLC and aeration equipment that can automatically adjust the aeration volume, it can realize automatic switching and variable frequency operation of the equipment, further reduce labor costs, save energy consumption, and support the dual carbon policy. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] 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.

[0034] Figure 1 Schematic diagram of the MBR sewage treatment system with pre-phosphorus removal and post-endogenous denitrification coupling provided by the present invention;

[0035] Figure 2 Schematic diagram of the MBR sewage treatment system with pre-phosphorus removal and post-endogenous denitrification coupling provided by the present invention;

[0036] Figure 3 This is a schematic diagram of a MBR sewage treatment system with pre-phosphorus removal and post-endogenous denitrification coupling in the control group of Example 5 of the present invention;

[0037] Figure 4 The data of the removal effect of COD in sewage by the sewage treatment system with three different sludge return modes in Example 5 of the present invention;

[0038] Figure 5 The data of the removal effect of total nitrogen in sewage by sewage treatment systems with three different sludge return modes in Example 5 of the present invention; DETAILED DESCRIPTION

[0039] 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 and should not be used to limit the protection scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0040] Example 1: A MBR sewage treatment system with pre-phosphorus removal and post-endogenous denitrification

[0041] like Figure 1 As shown, a pre-phosphorus removal and post-endogenous denitrification coupled MBR sewage treatment system includes a grit chamber, a flocculation sedimentation phosphorus removal chamber, an anaerobic chamber, a plurality of dynamic aerobic chambers, a plurality of anoxic chambers, an MBR membrane chamber and a sludge thickening chamber; the grit chamber, the flocculation sedimentation phosphorus removal chamber, the anaerobic chamber, a plurality of dynamic aerobic chambers, a plurality of anoxic chambers, an MBR membrane chamber and a sludge thickening chamber are connected through a pipeline; the flocculation sedimentation phosphorus removal chamber is connected to the sludge thickening chamber through a pipeline, and a sludge pump is arranged on the pipeline; the MBR membrane chamber is connected to a sludge return flow The sludge return system includes a pipeline connecting the MBR membrane tank and the front end of the dynamic aerobic tank and a sludge pump; the end of the anoxic tank is connected to the front end of the anaerobic tank through a pipeline, and a sludge return pump is arranged in the pipeline; the anaerobic tank and the anoxic tank are equipped with a stirrer, the dynamic aerobic tank is equipped with a stirrer and aeration equipment, the dynamic aerobic tank and the anoxic tank are equipped with a PH detector and a DO detector, and the PLC controller is respectively communicated with the PH detector, the DO detector, the aeration equipment and the stirrer.

[0042] The pre-phosphorus removal and post-endogenous denitrification sewage treatment system of the present invention mainly comprises three main parts: a pre-phosphorus removal part, a post-endogenous denitrification part, and an MBR membrane tank and sludge return part. The sewage treatment processes of these three parts are as follows:

[0043] ① Pre-phosphorus removal

[0044] Pre-phosphorus removal makes full use of the high suspended solids content in the influent of the primary sedimentation tank by adding efficient phosphorus removal agents, maximizes physical and chemical phosphorus removal, reduces the total phosphorus content in the influent of the biochemical stage, and thus ensures the subsequent denitrification effect.

[0045] Through the treatment of this process section, the total phosphorus in the sewage can basically meet the discharge standards, and the subsequent biochemical section only needs to treat the COD and total nitrogen in the sewage.

[0046] ②Post-endogenous denitrification

[0047] The theoretical basis of post-endogenous denitrification is that denitrifying bacteria have the characteristic of storing carbon sources. The endogenous denitrification potential of denitrifying bacteria is huge. The main factors affecting the endogenous denitrification effect are the anaerobic stirring time after water inflow, the dissolved oxygen concentration during aeration, and the nitrification time. The time of anaerobic stirring is generally controlled at about 1 hour, and generally does not need to exceed 2 hours. At this stage, denitrifying bacteria can complete the adsorption and absorption of organic matter in sewage.

[0048] Entering the dynamic aerobic pool, the dissolved oxygen concentration during aeration is controlled at 2mg / L-4mg / L. At the same time, in order to shorten the nitrification time as much as possible, the over-aeration time needs to be reduced. In order to achieve accurate aeration of sewage, several relatively independent dynamic aerobic pools are set up (each dynamic aerobic pool is connected by a pipe and is almost completely mixed). DO detectors and pH detectors are set in the dynamic aerobic pools. The changes in pH and DO in the dynamic aerobic pools can be observed to determine whether the system has completed nitrification (at the end of nitrification, the dissolved oxygen (DO) of the sewage will increase relatively due to the decrease in the activity of nitrifying bacteria and the reduction in oxygen consumption; and since nitrification consumes the alkalinity in the sewage, the pH value of the dynamic aerobic pool will gradually decrease. After the nitrification is completed, the pH value will gradually increase). When it is detected that the dissolved oxygen in one of the dynamic aerobic pools is still higher than 4 mg / L when the aeration volume is lower than 30% of the normal aeration volume, and the pH value rises at this time, it can be determined that the system has completed nitrification, and this dynamic aerobic pool and subsequent dynamic aerobic pools can stop aeration, which saves energy and ensures complete nitrification in the shortest possible time.

[0049] Entering the anoxic pool, deep denitrification is achieved through endogenous denitrification by denitrifying bacteria.

[0050] ③MBR membrane pool and sludge return part

[0051] In order to solve the problem of excessive suspended solids in effluent and unadjustable sludge concentration, MBR membrane tanks are used instead of traditional secondary sedimentation tanks, which can not only achieve the suspended solids standard and save the subsequent filtration process, but also extend the sludge age of the sewage treatment system and improve the denitrification effect of the sewage treatment system. In order to ensure the effect of absorbing carbon sources in the anaerobic section, the main sludge return is carried out from the end of the anoxic tank. In order to maintain the sludge concentration of the MBR membrane tank and not destroy the function of the anaerobic tank, the sludge of the MBR membrane tank is returned to the front end of the dynamic aerobic tank.

[0052] The COD, ammonia nitrogen, total nitrogen, total phosphorus and suspended solids of the effluent treated by the sewage treatment system of the present invention all meet the standards.

[0053] Example 2: A MBR sewage treatment process with pre-phosphorus removal and post-endogenous denitrification

[0054] The process in this embodiment is based on the system in Example 1, and is mainly used for the treatment of municipal sewage. The main water inlet indicators are COD 2000mg / L~2200mg / L, ammonia nitrogen 360mg / L~450mg / L, and total phosphorus 10mg / L~20mg / L. After the sewage is treated in the grit chamber, it enters the flocculation sedimentation phosphorus removal tank, mixes with the flocculation phosphorus removal agent added to the tank, and then realizes mud and water separation. The supernatant enters the anaerobic section of the biochemical stage, and the precipitated sludge enters the sludge concentration tank. The flocculation phosphorus removal agent can use PAC or PFC. The amount of PAC or PFC is selected according to the water quality. 50mg / L~200mg / L, the total phosphorus removal rate of this process section is above 90%, and the total phosphorus of the effluent is controlled at 0.3mg / L~1mg / L. After the sewage enters the anaerobic tank, the activated sludge absorbs the internal carbon source, and only needs to be stirred, and the residence time is 6 hours. The aerobic pool is composed of several dynamic aerobic pools, each of which is connected by a pipeline. The HRT of each dynamic aerobic pool is 3 hours. They are equipped with aeration equipment, stirring equipment, pH detector and dissolved oxygen detector. The pH and DO detectors are connected to the PLC, and the aeration equipment is finally controlled by a computer. The dissolved oxygen in the dynamic aerobic pool is controlled at 2-4 mg / L. When it is detected that the dissolved oxygen in one of the dynamic aerobic pools is still higher than 4 mg / L when the aeration volume is lower than 30% of the normal aeration volume, and the pH value rises at this time, it indicates that the system nitrification is completed, and this dynamic aerobic pool and subsequent dynamic aerobic pools automatically shut down aeration. The HRT of all dynamic aerobic pools is 12 hours in total, with a total of 4 dynamic aerobic pools, and the retention time can be controlled to 9-12 hours as needed. The anoxic pool is connected to the back of the dynamic aerobic pool, which is mainly used to complete endogenous denitrification for deep denitrification. The retention time of the anoxic pool is 12 hours in total, and only stirring is required. The sludge at the end of the anoxic tank is returned to the anaerobic tank, and the sludge return ratio is 100%; the hydraulic retention time of the entire biochemical stage is 30 hours, and the sewage finally enters the MBR membrane tank for mud-water separation, the supernatant is discharged, and the sludge is pumped back to the front end of the dynamic aerobic tank through the sludge pump, the sludge return ratio is 50%, and the remaining sludge is discharged into the sludge thickening tank.

[0055] Example 3: A MBR sewage treatment system with pre-phosphorus removal and post-endogenous denitrification

[0056] like Figure 1As shown, a pre-phosphorus removal and post-endogenous denitrification coupled MBR sewage treatment system includes a grit chamber, a flocculation sedimentation phosphorus removal chamber, an anaerobic chamber, a plurality of dynamic aerobic chambers, a plurality of anoxic chambers, an MBR membrane chamber and a sludge thickening chamber; the grit chamber, the flocculation sedimentation phosphorus removal chamber, the anaerobic chamber, a plurality of dynamic aerobic chambers, a plurality of anoxic chambers, an MBR membrane chamber and a sludge thickening chamber are connected through a pipeline; the flocculation sedimentation phosphorus removal chamber is connected to the sludge thickening chamber through a pipeline, and a sludge pump is arranged on the pipeline; the MBR membrane chamber is connected to a sludge return system, and the sludge The reflow system includes a pre-anaerobic tank, which is connected to the MBR membrane tank and the flocculation sedimentation phosphorus removal tank through pipes respectively. The pipes are equipped with sludge return pumps. The pre-anaerobic tank is also connected to the water inlet of the anaerobic tank through a pipe. The anaerobic tank and the anoxic tank are equipped with a stirrer, and the dynamic aerobic tank is equipped with a stirrer and aeration equipment. The dynamic aerobic tank and the anoxic tank are equipped with a PH detector and a DO detector. The PLC controller is communicated with the PH detector, DO detector, aeration equipment and stirrer respectively.

[0057] The pre-phosphorus removal and post-endogenous denitrification sewage treatment system of the present invention mainly comprises three main parts: a pre-phosphorus removal part, a post-endogenous denitrification part, and an MBR membrane tank and sludge return part. The sewage treatment processes of these three parts are as follows:

[0058] ① Pre-phosphorus removal

[0059] Pre-phosphorus removal makes full use of the high suspended solids content in the influent of the primary sedimentation tank by adding efficient phosphorus removal agents, maximizes physical and chemical phosphorus removal, reduces the total phosphorus content in the influent of the biochemical stage, and thus ensures the subsequent denitrification effect.

[0060] Through the treatment of this process section, the total phosphorus in the sewage can basically meet the discharge standards, and the subsequent biochemical section only needs to treat the COD and total nitrogen in the sewage.

[0061] ②Post-endogenous denitrification

[0062] The theoretical basis of post-endogenous denitrification is that denitrifying bacteria have the characteristic of storing carbon sources. The endogenous denitrification potential of denitrifying bacteria is huge. The main factors affecting the endogenous denitrification effect are the anaerobic stirring time after water inflow, the dissolved oxygen concentration during aeration, and the nitrification time. The time of anaerobic stirring is generally controlled at about 1 hour, and generally does not need to exceed 2 hours. At this stage, denitrifying bacteria can complete the adsorption and absorption of organic matter in sewage.

[0063] Entering the dynamic aerobic pool, the dissolved oxygen concentration during aeration is controlled at 2mg / L-4mg / L. At the same time, in order to shorten the nitrification time as much as possible, the over-aeration time needs to be reduced. In order to achieve accurate aeration of sewage, several relatively independent dynamic aerobic pools are set up (each dynamic aerobic pool is connected by a pipe and is almost completely mixed). DO detectors and pH detectors are set in the dynamic aerobic pools. The changes in pH and DO in the dynamic aerobic pools can be observed to determine whether the system has completed nitrification (at the end of nitrification, the dissolved oxygen (DO) of the sewage will increase relatively due to the decrease in the activity of nitrifying bacteria and the reduction in oxygen consumption; and since nitrification consumes the alkalinity in the sewage, the pH value of the dynamic aerobic pool will gradually decrease. After the nitrification is completed, the pH value will gradually increase). When it is detected that the dissolved oxygen in one of the dynamic aerobic pools is still higher than 4 mg / L when the aeration volume is lower than 30% of the normal aeration volume, and the pH value rises at this time, it can be determined that the system has completed nitrification, and this dynamic aerobic pool and subsequent dynamic aerobic pools can stop aeration, which saves energy and ensures complete nitrification in the shortest possible time.

[0064] Entering the anoxic pool, deep denitrification is achieved through endogenous denitrification by denitrifying bacteria.

[0065] ③MBR membrane pool and sludge return part

[0066] In order to solve the problem of excessive suspended solids in effluent and unadjustable sludge concentration, MBR membrane tanks are used instead of traditional secondary sedimentation tanks, which can not only achieve the suspended solids standard and save the subsequent filtration process, but also extend the sludge age of the sewage treatment system and improve the denitrification effect of the sewage treatment system. In order to ensure the effect of anaerobic section absorbing carbon source, maintain the sludge concentration of MBR membrane tank, and do not destroy the function of anaerobic tank, the sludge of MBR membrane tank is returned to the pre-anaerobic tank, and the inlet water of pre-anaerobic tank is 10% of the total water volume, in order to consume the dissolved oxygen in the return sludge of MBR tank, and then the effluent of pre-anaerobic tank enters the anaerobic tank.

[0067] The COD, ammonia nitrogen, total nitrogen, total phosphorus and suspended solids of the effluent treated by the sewage treatment system of the present invention all meet the standards.

[0068] Example 4: A MBR sewage treatment process with pre-phosphorus removal and post-endogenous denitrification

[0069] The process in this embodiment is based on the system in Example 3, and is mainly used for the treatment of municipal sewage. The main water inlet indicators are COD2000mg / L~2200mg / L, ammonia nitrogen 360mg / L~450mg / L, and total phosphorus 10mg / L~20mg / L. After the sewage is treated in the grit chamber, it enters the flocculation sedimentation phosphorus removal tank, mixes with the flocculation phosphorus removal agent added to the tank, and then realizes mud and water separation. 90% of the supernatant enters the anaerobic section of the biochemical stage, 10% of the supernatant enters the pre-anaerobic tank, and the precipitated sludge enters the sludge concentration tank. The flocculation phosphorus removal agent can use PAC or PFC. The amount of PAC or PFC is selected according to the water quality. 50mg / L~200mg / L, the total phosphorus removal rate of this process section is above 90%, and the total phosphorus of the effluent is controlled at 0.3mg / L~1mg / L. After the sewage enters the anaerobic tank, the activated sludge absorbs the internal carbon source, and only needs to be stirred, and the residence time is 6 hours. The aerobic pool is composed of several dynamic aerobic pools, each of which is connected by a pipeline. The HRT of each dynamic aerobic pool is 3 hours. They are equipped with aeration equipment, stirring equipment, pH detector and dissolved oxygen detector. The pH and DO detectors are connected to the PLC, and the aeration equipment is finally controlled by a computer. The dissolved oxygen in the dynamic aerobic pool is controlled at 2-4 mg / L. When it is detected that the dissolved oxygen in one of the dynamic aerobic pools is still higher than 4 mg / L when the aeration volume is lower than 30% of the normal aeration volume, and the pH value rises at this time, it indicates that the system nitrification is completed, and this dynamic aerobic pool and subsequent dynamic aerobic pools automatically shut down aeration. The HRT of all dynamic aerobic pools is 12 hours in total, with a total of 4 dynamic aerobic pools, and the retention time can be controlled to 9-12 hours as needed. The anoxic pool is connected to the back of the dynamic aerobic pool, which is mainly used to complete endogenous denitrification for deep denitrification. The retention time of the anoxic pool is 12 hours in total, and only stirring is required. The hydraulic retention time of the entire biochemical stage is 30 hours. The sewage finally enters the MBR membrane tank for mud-water separation, the supernatant is discharged, and the sludge is pumped back to the pre-anaerobic tank through the sludge pump. The sludge return ratio is 100%, and the remaining sludge is discharged into the sludge thickening tank.

[0070] Example 5: Industrial wastewater treatment based on pre-phosphorus removal and post-endogenous denitrification coupled MBR wastewater treatment system with different sludge reflow modes

[0071] This embodiment sets up a control group, and the sewage treatment system of the control group is as follows: Figure 3As shown, it specifically includes a grit chamber, a flocculation sedimentation phosphorus removal chamber, an anaerobic chamber, several dynamic aerobic chambers, several anoxic chambers, an MBR membrane chamber and a sludge thickening chamber which are connected in sequence through pipelines; the flocculation sedimentation phosphorus removal chamber is connected to the sludge thickening chamber through a pipeline, and a sludge pump is arranged in the pipeline; the MBR membrane chamber is connected to the front end of the anaerobic chamber through a pipeline and a sludge return pump; the anaerobic chamber and the anoxic chamber are both equipped with a stirrer, the dynamic aerobic chamber is both equipped with a stirrer and an aeration device, the dynamic aerobic chamber and the anoxic chamber are both equipped with a PH detector and a DO detector, and the PLC controller is respectively communicated with the PH detector, the DO detector, the aeration device and the stirrer.

[0072] In order to verify the technical effect of the sewage treatment system and process of the present invention, the sewage treatment effect was tested based on the control sewage treatment system and the sewage treatment systems of Examples 1 and 3, respectively, using the sewage treatment process of the present invention.

[0073] This embodiment combines the sewage treatment system of the control group and the sewage treatment systems of Examples 1 and 3 into one sewage treatment system, and realizes the sewage treatment functions of the sewage treatment system of the control group and the sewage treatment systems of Examples 1 and 3 by selecting different reflow modes. That is, the sewage treatment system of the embodiment specifically includes a grit chamber, a flocculation sedimentation phosphorus removal tank, an anaerobic tank, a plurality of dynamic aerobic tanks, a plurality of anoxic tanks, an MBR membrane tank and a sludge thickening tank; a grit chamber, a flocculation sedimentation phosphorus removal tank, an anaerobic tank, a plurality of dynamic aerobic tanks, a plurality of anoxic tanks, an MBR membrane tank and a sludge thickening tank; the MBR membrane tank is connected to the front end of the anaerobic tank through a pipeline and a sludge return pump; the MBR membrane tank is also connected to the front end of the dynamic aerobic tank through a pipeline and a sludge return pump, and at the same time, the end of the anoxic tank is connected to the front end of the anaerobic tank through a pipeline, and the pipe A sludge return pump is set in the pipeline; a pre-anaerobic tank is also set, and the pre-anaerobic tank is connected with the MBR membrane tank and the flocculation sedimentation phosphorus removal tank through pipelines, and the pipelines are all equipped with sludge return pumps. The pre-anaerobic tank is also connected with the water inlet of the anaerobic tank through a pipeline; the anaerobic tank and the anoxic tank are equipped with a stirrer, and the dynamic aerobic tank is equipped with a stirrer and aeration equipment. The dynamic aerobic tank and the anoxic tank are equipped with a PH detector and a DO detector, and the PLC controller is respectively communicated with the PH detector, DO detector, aeration equipment and stirrer. This embodiment realizes the operation of the sewage treatment system in three sludge return modes by closing and opening different pipelines and sludge return pumps, including the direct return of sludge from the MBR membrane tank to the anaerobic tank (the sewage treatment system of the control group, such as Figure 3 As shown), the sludge from the MBR membrane pool flows back to the aerobic pool and the sludge from the anoxic pool flows back to the anaerobic section (the sewage return system in Example 1, as shown Figure 1 As shown) and the MBR membrane pool sludge is returned to the pre-anaerobic tank ((Example 3 sewage return system, such as Figure 2 shown))

[0074] The above-mentioned sewage treatment system and the sewage treatment process of the present invention are used to treat certain industrial sewage, and the industrial sewage indicators are COD2000mg / L~2200mg / L, ammonia nitrogen 360mg / L~450mg / L, and total phosphorus 10mg / L~20mg / L. The hydraulic retention time of the anaerobic + aerobic + anoxic sections of the three sewage treatment processes is the same, which is 45 hours. Among them, the group using the pre-anoxic tank has a pre-anoxic retention time of 2 hours. After the sewage passes through the phosphorus removal sedimentation tank, the total phosphorus concentration of the sewage is stabilized at less than 1mg / L, and the removal rate reaches more than 95%. The phosphorus removal effect is very stable. The three operating modes are basically the same for the removal of ammonia nitrogen in sewage. The effluent ammonia nitrogen concentration is less than 1mg / L, and the removal rate reaches more than 99%. The removal rates of COD and total nitrogen are as follows Figure 4 and Figure 5 As shown. Figure 4 It can be seen that the three systems have very similar COD removal rates, with the effluent concentration maintained at around 300 mg / L and the removal rate stable at more than 85%, with no significant differences among the three groups. Figure 5 It can be seen that in the first mode, due to the high dissolved oxygen in the sludge return liquid, the absorption effect of denitrifying bacteria on carbon sources decreased, the total nitrogen concentration of the final effluent of the system was high, maintained at about 90 mg / L, and the total nitrogen removal rate was 72% to 80%. From the 16th day, the return mode was changed, the sludge in the MBR membrane pool was returned to the aerobic zone, and the sludge at the end of the anoxic zone was returned to the front end of the anaerobic tank. Through the change of return flow, the denitrifying bacteria in the sludge can fully absorb the organic matter in the sewage, the simultaneous nitrification and denitrification effects of the system and the endogenous denitrification effects have been strengthened, the total nitrogen concentration of the effluent gradually decreased, and the final total nitrogen concentration of the effluent stabilized to about 30 mg / L, and the total nitrogen removal rate stabilized at about 92%. From the 31st day, the sludge return mode was switched to return only from the MBR membrane pool, and all the sludge was returned to the pre-anaerobic tank, 10% of the influent entered the pre-anaerobic tank, and 90% entered the normal anaerobic tank. From the data, we can see that after the operation mode is switched, the total nitrogen concentration in the effluent has not changed significantly, and it is stable at about 30 mg / L, and the total nitrogen removal rate is greater than 92%. It can be seen that among the three sludge return modes, the sewage treatment system in which the sludge of the control group MBR membrane pool is directly returned to the anaerobic tank has the worst denitrification effect, and the total nitrogen removal rate of the effluent is less than 80%. The main reason is that after the direct return, a large amount of dissolved oxygen destroys the anaerobic state of the system's anaerobic grid and affects the absorption of carbon sources by denitrifying bacteria. Based on the pre-phosphorus removal and post-endogenous denitrification sewage treatment system, the denitrification efficiency of the system can be effectively guaranteed by changing the sludge return method or the water inlet method.

[0075] In summary, the two combined treatment processes designed by the present invention are used to treat an industrial sewage with COD of 2000mg / L-2200mg / L, ammonia nitrogen of 360mg / L-450mg / L, and total phosphorus of 10mg / L-20mg / L. The effluent COD, total nitrogen and total phosphorus are about 300m / L, 30mg / L and 1mg / L, respectively, and the removal rates are 82%, 92% and more than 95%, respectively.

[0076] The above-mentioned specific implementations are only specific cases of the present invention. The patent protection scope of the present invention includes but is not limited to the product form and style of the above-mentioned specific implementations. Any appropriate changes or modifications made to them by ordinary technicians in the technical field that conform to the claims of the present invention shall fall within the patent protection scope of the present invention.

Claims

1. A pre-phosphorus removal and post-endogenous denitrification coupled MBR sewage treatment system, characterized in that: Including grit chamber, flocculation sedimentation phosphorus removal tank, anaerobic tank, several dynamic aerobic tanks, several anoxic tanks, MBR membrane tank and sludge thickening tank; The grit chamber, the flocculation sedimentation phosphorus removal tank, the anaerobic tank, a plurality of dynamic aerobic tanks, a plurality of anoxic tanks, the MBR membrane tank and the sludge concentration tank are connected in sequence through pipelines; The flocculation sedimentation phosphorus removal tank is connected to the sludge concentration tank through a pipeline, and a sludge pump is provided in the pipeline; The MBR membrane tank is connected to a sludge return system; The anaerobic tank and the anoxic tank are both equipped with a stirrer, and the dynamic aerobic tank is both equipped with an aeration device and a stirrer; The sludge return system comprises a pre-anaerobic tank, which is connected to the MBR membrane tank and the flocculation sedimentation phosphorus removal tank through pipelines, and the pipelines are all provided with sludge return pumps; The pre-anaerobic tank is connected with the water inlet of the anaerobic tank through a pipeline.

2. The pre-phosphorus removal and post-endogenous denitrification coupled MBR sewage treatment system according to claim 1, characterized in that: The dynamic aerobic pool and the anoxic pool are both provided with a pH detector and a DO detector; The sewage treatment system also includes a PLC controller, which is respectively connected to the pH detector, the DO detector, the aeration equipment and the agitator for communication.

3. A pre-phosphorus removal and post-endogenous denitrification coupled MBR sewage treatment process, characterized in that: S1: After being treated in the primary sedimentation tank, the sewage enters the flocculation sedimentation phosphorus removal tank, where it is mixed with the flocculation phosphorus removal agent added to the flocculation sedimentation phosphorus removal tank, and then the mud and water are separated. 10% of the effluent from the flocculation sedimentation phosphorus removal tank enters the pre-anaerobic tank, and the rest enters the anaerobic tank. The precipitated sludge enters the sludge thickening tank; S2: After the sewage enters the anaerobic tank for mixing, the anaerobic tank is stirred, and the denitrifying bacteria absorb the carbon source, and the retention time is T1 hours; S3: The effluent from the anaerobic tank enters several dynamic aerobic tanks. The retention time of each dynamic aerobic tank is T2 hours. Nitrification is carried out under the action of stirring and aeration to degrade ammonia nitrogen and remaining organic matter in the sewage. When it is detected that the dissolved oxygen in the last dynamic aerobic tank is 30% lower than the normal aeration volume, the dissolved oxygen is still higher than 4 mg / L, and the pH value rises at this time, the aeration of this dynamic aerobic tank and the subsequent dynamic aerobic tanks are automatically turned off and become anoxic tanks. Only the agitator is turned on in the anoxic tank; S4: sewage entering the anoxic tank, the total residence time in the anoxic tank is T3 hours, and denitrification is achieved through endogenous denitrification by denitrifying bacteria; S5: The sewage in the anoxic tank enters the MBR membrane tank after effluent to achieve mud-water separation. The sludge in the MBR membrane tank is returned to the pre-anaerobic tank with a return ratio of 100%. The effluent from the pre-anaerobic tank enters the front end of the anaerobic tank, and the remaining sludge is discharged into the sludge thickening tank, and the supernatant is discharged.

4. The MBR sewage treatment process with pre-phosphorus removal and post-endogenous denitrification coupling as claimed in claim 3 is characterized by: The flocculating phosphorus removal agent is PAC or PFC, and the dosage of PAC or PFC is 50mg / L-200mg / L; the T1 is 0.5-2, the T2 is 2-3, and the T3 is 8-12; the dissolved oxygen concentration during aeration of the dynamic aerobic pool is controlled at 2mg / L-4mg / L.

5. The MBR sewage treatment process with pre-phosphorus removal and post-endogenous denitrification coupling as claimed in claim 4 is characterized by: When the carbon-nitrogen ratio of the influent of the anaerobic tank is less than 3, a carbon source is added to the anaerobic tank.

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