A method for treating low-carbon and high-nitrogen sewage

Abstract

The invention discloses a low-carbon and high-nitrogen sewage treatment method, belonging to the technical field of sewage treatment. The method places sewage in several special treatment pools and specifically controls the dissolved oxygen and filler filling rate of each treatment pool, so that the entire sewage treatment process does not need to introduce an additional carbon source, and nitrogen degradation is achieved with the carbon source in the sewage itself, and the sludge return process required by the traditional process is omitted. The water quality of the treated water body meets the standard, and the stability of the treatment effect can be achieved when the sewage C / N ratio is in the range of 0.5-5.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a method for treating low-carbon and high-nitrogen sewage. Background Art

[0002] Domestic sewage at the town level has the following characteristics: the water quality is low in carbon and high in nitrogen, and there is a certain fluctuation in water quality. The former will lead to low efficiency of sewage during traditional nitrification / denitrification treatment, requiring the introduction of additional carbon sources, and high difficulty in removing ammonia nitrogen, while the latter increases the difficulty of parameter regulation of the sewage treatment system and stability control of sewage treatment; in addition, traditional low-carbon and high-nitrogen sewage needs to be treated through sludge return equipment to control sludge return in real time to ensure the sewage treatment effect, which consumes a lot of energy. Summary of the invention

[0003] Based on the defects of the prior art, the purpose of the present invention is to provide a low-carbon and high-nitrogen sewage treatment method. This method places the sewage in several special treatment tanks and specifically controls the dissolved oxygen and filler filling rate of each treatment tank, so that the entire sewage treatment process does not need to introduce an additional carbon source, and nitrogen degradation is achieved with the carbon source in the sewage itself, and the sludge return process required by the traditional process is omitted. The water quality of the treated water meets the standard, and the stability of the treatment effect can be achieved when the sewage C / N ratio is in the range of 0.5~5.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A method for treating low-carbon and high-nitrogen sewage comprises the following steps:

[0006] (1) Conduct COD testing on the wastewater to be treated;

[0007] (2) If the COD of the sewage to be treated is determined to be ≤120 mg / L, the sewage to be treated is sent to the first aeration tank for the first aeration treatment, then transferred to the second aeration tank for the second aeration treatment, then transferred to the third aeration tank for the third aeration treatment, and finally sent to the filtration tank for filtration treatment, thus completing the sewage treatment;

[0008] (3) If the COD of the wastewater to be treated is determined to be greater than 120 mg / L, the wastewater to be treated is sent to an anoxic tank for degradation treatment, and then the same treatment is performed as in step (2);

[0009] The first to third aeration tanks and the anoxic tank are provided with suspended sludge, the concentration of the suspended sludge is 2000-2500 mg / L, the first to third aeration tanks and the filtration tank are provided with fillers, the fillers include polyurethane fillers and bamboo charcoal; the bamboo charcoal is subjected to pore formation / hardening treatment; and a biofilm is provided on the filler;

[0010] The third aeration tank is provided with a stirring device to perform stirring treatment synchronously during the third aeration treatment;

[0011] The dissolved oxygen content of the first aeration tank is 0.5-1.2 mg / L, and the filler filling rate is 28-32 vt%;

[0012] The dissolved oxygen content of the second aeration tank is 2-3 mg / L, and the filler filling rate is 58-62 vt%;

[0013] The dissolved oxygen content of the third aeration tank is 0.5-1.2 mg / L, and the filler filling rate is 22-26 vt;

[0014] The anoxic pool is provided with a portion of the water returned from the third aeration pool after the third aeration treatment, and is also provided with a stirring device to perform stirring treatment synchronously during the degradation treatment.

[0015] Compared with other types of sewage such as industrial sewage, town-level domestic sewage has two major characteristics. The first is that the COD value and ammonia nitrogen content of this type of sewage fluctuate greatly at different stages (such as weekdays and holidays), and the C / N ratio also varies greatly. It is often necessary to control the corresponding sewage treatment system in real time at different stages to meet the Class A water quality standard, which is difficult to operate. Generally, it is also necessary to control the sludge return in real time through sludge return equipment to ensure the sewage treatment effect, and the energy consumption is relatively high. The second is that the C / N of the sewage is relatively low, with a minimum of only about 1, and the total COD content is also low, with a minimum of 30 mg / L and a maximum of generally no more than 250 mg / L. The efficiency is low when using traditional nitrification / denitrification equipment for treatment, and additional carbon sources need to be introduced to ensure complete reaction, and the actual consumption is relatively high. To this end, in the technical solution of the present invention, for town-level domestic sewage with a low C / N ratio and a low total COD content, COD content detection is used to distinguish and treat the water differently: (1) When the COD content of the water body is less than 120 mg / L, the carbon source content of the water body is extremely low and cannot support the carbon source consumption demand of the nitrification-denitrification process of the traditional process. Therefore, the water body is directly introduced into three special gradient aeration treatment tanks for aeration treatment. Based on the specially designed dissolved oxygen, sludge concentration and filler filling rate, the water body begins to undergo denitrification reaction after contacting the sludge and filler in the first aeration tank. Subsequently, in the second aeration tank, the high dissolved oxygen content and biofilm concentration in a specific range can cause the water body to undergo a relatively concentrated oxygen-consuming nitrification reaction. (2) When the COD content of the water is high, the ammonia nitrogen content will also increase based on the characteristics of town-level domestic sewage. The carbon source in the water returned from the third aeration tank can be pre-degraded in the anoxic tank to reduce the total nitrogen content. Then, the water quality can be met after the same step-by-step aeration treatment as above. There is no need to set up sludge return or introduce additional compensatory carbon sources during the two treatment processes. Based on the carbon source of town-level domestic sewage itself, the water body can undergo a staged denitrification-nitrification-denitrification reaction on its own under a specific gradient aeration treatment (simultaneous nitrification / denitrification reaction hardly occurs in this process). There is no need for real-time regulation or operation, which is easy to implement and consumes less energy and materials.

[0016] In this process, in order to ensure the stability and suspension dispersion effect of the early biofilm, as well as the sufficiency of the subsequent surface biofilm during the reaction, the filler needs to be matched with polyurethane filler and bamboo charcoal in the filler. Bamboo charcoal is a natural porous material of biological origin, which has better morphological strength than plastic materials. After pore-making and hardening treatment, it can ensure that the overall filler maintains a relatively stable structural morphology during water filtration. At the same time, compared with inorganic porous fillers such as ceramsite, bamboo charcoal can achieve a certain active adsorption at a larger size (using the unique biological hierarchical porous structure of biochar to physically adsorb the substance to be treated), which is more conducive to fixing the biofilm and will not cause particle separation after continuous water filtration. The domestication and working efficiency of the biofilm are higher. If pure polyurethane filler is used as filler or other inorganic fillers are used instead, it is impossible to achieve water treatment compliance requirements under such process conditions without carbon source and sludge return. If pore-making / hardening treatment is not performed, bamboo charcoal will not be able to effectively fix the biofilm, and will gradually granulate under the flow of water.

[0017] At the same time, in the process of the present invention, the settings of dissolved oxygen content, filler filling rate and suspended sludge concentration at different stages are critical. Once they are improperly controlled, the expected effect cannot be achieved.

[0018] Preferably, a variable frequency fan and a water dissolved oxygen content detection instrument are provided in the aeration tank, and the dissolved oxygen content in the aeration tank is adjusted by the variable frequency fan.

[0019] Preferably, the COD content of the sewage to be treated is 25-250 mg / L, the ammonia nitrogen content is 20-50 mg / L, and the C / N ratio is 0.5-5.

[0020] More preferably, when the COD content of the sewage to be treated is ≤120 mg / L, the ammonia nitrogen content is 20-45 mg / L; when the COD content of the sewage to be treated is >120 mg / L, the ammonia nitrogen content is 30-50 mg / L.

[0021] More preferably, the total phosphorus content of the wastewater to be treated is 2-4 mg / L.

[0022] The sewage treatment method of the present invention is specifically aimed at town-level domestic sewage, which has a low carbon source content (the C / N ratio of the water body during normal conditions may be ≤1) and a large component variation range (the C / N ratio variation range reaches 1-2). Without introducing sludge return and carbon source supplementation, based on a special gradient aeration treatment design, it can work continuously for a long time after adjustment and domestication is completed (including periods with holidays and periods when the water quality composition has obvious fluctuations), without the need for additional real-time operations during the period.

[0023] Preferably, the suspended sludge is municipal / domestic sludge derived from a municipal sewage plant, and the SV30 is 10-30%.

[0024] In the scheme described in the present invention, based on the special gradient dissolved oxygen content and filler ratio setting, municipal / domestic sludge with a low sedimentation ratio is required to achieve a good mud film reaction without additional reflux and supplementary carbon source, and effectively remove the neutral nitrogen in the water.

[0025] Preferably, the polyurethane filler in the filler has a specific surface area of ​​2000-2500m 2 / m 3 The porosity is 85-95%; the specific surface area of ​​the bamboo charcoal is 50-60m 2 / g, and an average pore size of 20-50nm; the filler is arranged in a hollow sphere, the average diameter of the hollow sphere is 8-12cm, and the number of the hollow spheres in the aeration tank is 3-5.

[0026] Preferably, the pore-forming / hardening treatment step of the bamboo charcoal is: mixing the bamboo charcoal with sodium hydroxide and zinc chloride in a mass ratio of 1: (0.08-0.15): (0.04-0.06) and dispersing and immersing the mixture in a dispersion liquid in a mass ratio of 1 g: 20-80 mL, then protecting and keeping warm in a nitrogen atmosphere at 300-400° C. for 0.5-1.5 h, and washing.

[0027] More preferably, the volume ratio of the polyurethane filling and the bamboo charcoal in the filler is (95-85):(5-15).

[0028] More preferably, the water inlets of the first aeration tank, the second aeration tank and the third aeration tank are arranged at the bottom of the aeration tank, the water outlets are arranged at the top of the aeration tank, the height of the aeration tank is 4-5m, and the hollow sphere is arranged at a height of 0.3-0.6m from the bottom of the aeration tank.

[0029] In order to ensure that the reaction type between the biofilm and the sludge in each aeration tank is single, thereby maintaining a segmented denitrification-nitrification-denitrification treatment process, the filler provided with the biofilm needs to be set close to the water inlet of the aeration tank and be equivalent to the aeration tank being suspended in the air, so as to achieve a rapid reaction at a shorter distance. If the conventional suspended filler setting method is adopted, or it is directly set parallel to the water inlet, it is difficult to achieve the same treatment effect.

[0030] Preferably, the biofilm disposed on the filler in the first aeration tank has a thickness of 0.5 to 1 mm;

[0031] Preferably, the biofilm disposed on the filler in the second aeration tank has a thickness of 0.5 to 1 mm;

[0032] Preferably, the biofilm disposed on the filler in the third aeration tank has a thickness of 0.5-1 mm.

[0033] If the conventional nitrification and denitrification tank processes are used, the biofilm cannot achieve the specific staged treatment of the present invention, and the water quality target cannot be achieved without the introduction of carbon sources and sludge return.

[0034] Preferably, the setting temperature of the first aeration tank, the second aeration tank and the third aeration tank is 15-30°C;

[0035] Preferably, the inlet flow rate and outlet flow rate of the first aeration tank are 0.5-0.6 m / s; the inlet flow rate and outlet flow rate of the second aeration tank are 0.6-0.7 m / s; and the inlet flow rate and outlet flow rate of the third aeration tank are 0.5-0.6 m / s.

[0036] Preferably, the treatment time of at least one of the first aeration treatment, the second aeration treatment, and the third aeration treatment is 2.5 to 3.5 hours.

[0037] Preferably, the stirring rate of the stirring device in the third aeration tank is 300-400 rpm.

[0038] Preferably, a reflux device is provided in the third aeration tank to return the water obtained after aeration treatment to the anoxic tank under stirring, and the ORP (oxidation-reduction potential) of the third aeration tank is maintained at -100~50mV by adjusting the water reflux ratio.

[0039] More preferably, the water reflux ratio is 40-80%.

[0040] Returning the water after denitrification in the third aeration tank to the anoxic tank for degassing can effectively ensure that when the COD content of the sewage to be treated is high, after degradation treatment in the anoxic zone, the expected denitrification treatment can still be carried out in the first aeration tank, thereby avoiding excessive consumption of carbon sources in the water in the first aeration tank, making it impossible to implement subsequent treatment without carbon source supplementation and sludge return.

[0041] Preferably, the water inlet of the anoxic pool is arranged at the bottom, the water outlet is arranged at the top, and the height of the anoxic pool is 4-5m.

[0042] More preferably, the water inlet rate and outlet rate of the anoxic pool are 0.5-0.6 m / s.

[0043] More preferably, the dissolved oxygen content of the anoxic tank is less than 0.5 mg / L, and the degradation treatment time of the wastewater to be treated in the anoxic tank is 2.5 to 3.5 hours.

[0044] More preferably, the ORP of the anoxic tank is -100~50mV.

[0045] When the COD content of the sewage to be treated is high, before the first aeration treatment, part of the return water from the third aeration zone needs to be introduced for degradation treatment under anoxic conditions to ensure that the water body has sufficient carbon source during subsequent aeration treatment and that the final ammonia nitrogen content can be treated to the standard range. If the treatment process under low COD conditions is directly used, it will be difficult to achieve the expected treatment effect.

[0046] Preferably, the filter tank is provided with filler, and the filling rate of the filler is 65~75vt%.

[0047] More preferably, the water inlet of the filter pool is arranged at the bottom, the water outlet is arranged at the top, the height of the filter pool is 4-5m, and the rising filtration rate of the water body from bottom to top during the filtration treatment is set to 4.5-5.5m / h.

[0048] After the denitrification-nitrification-denitrification treatment specially arranged in the present invention, the water body can reach the water quality standard after conventional filtration treatment, without the need for backwashing treatment, and the operation is simple.

[0049] Preferably, the low-carbon and high-nitrogen sewage treatment method is carried out in a sewage treatment system, and the sewage treatment system comprises an anoxic tank, a first aeration tank, a second aeration tank, a third aeration tank and a filtration tank;

[0050] The first aeration tank, the second aeration tank, and the third aeration tank are provided with a variable frequency fan and a water body dissolved oxygen detection device;

[0051] The anoxic tank and the first aeration tank are provided with a sewage inlet pipe, and the sewage inlet pipe is provided with an intelligent switching valve and a COD detection device, and the intelligent switching valve is used to allow the sewage to be treated to enter the anoxic tank or the first aeration tank according to the COD content of the sewage to be treated;

[0052] The third aeration tank is provided with a reflux device and a stirring device;

[0053] The anoxic tank is provided with a stirring device.

[0054] The sewage treatment system corresponding to the sewage treatment method of the present invention is not provided with a carbon source supplement device and a sludge return device. When it comes to town-level domestic sewage, the carbon source of the sewage itself can be used to directly complete the nitrogen purification of the water body through a special treatment tank structure and treatment step setting. At the same time, there is no need to perform real-time parameter adjustment and control at different time stages (such as switching between weekdays and holidays). It is only necessary to switch the intelligent regulating valve according to the water quality changes of the water body during the treatment of the water body so that the water body flows into the anoxic tank or the third aeration tank for treatment, thereby ensuring that the water body treatment meets the standards, the operation is convenient, and the manpower and material resources are low. In addition, the system has a simple structure, occupies a small area, and can be constructed in a variety of terrains.

[0055] The beneficial effect of the present invention is that the present invention provides a low-carbon and high-nitrogen sewage treatment method. The method places the sewage in several special treatment tanks and specifically controls the dissolved oxygen and filler filling rate of each treatment tank, so that the entire sewage treatment process does not need to introduce an additional carbon source, and nitrogen degradation is achieved with the carbon source in the sewage itself, and the sludge return process required by the traditional process is omitted. The water quality of the treated water body meets the standard, and the stability of the treatment effect can be achieved when the sewage C / N ratio is in the range of 0.5~5. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 It is a schematic diagram of the sewage treatment system of the present invention, wherein A is the sewage inlet, B is the COD detection intelligent water inlet switching valve, C is the anoxic tank, D is the first aeration tank, E is the second aeration tank, F is the third aeration tank, and G is the filtration tank.

[0057] Figure 2 It is a schematic diagram of the filler arranged in the hollow sphere according to the present invention. DETAILED DESCRIPTION

[0058] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments and comparative examples, the purpose of which is to understand the content of the present invention in detail, rather than to limit the present invention. All other embodiments obtained by those of ordinary skill in the art without making creative work premise belong to the protection scope of the present invention. The experimental reagents and instruments involved in the implementation of the present invention, unless otherwise specified, are all commonly used common reagents and instruments.

[0059] Example 1

[0060] The present invention provides a method for treating low-carbon and high-nitrogen sewage, which comprises: Figure 1The sewage treatment system shown in the figure is implemented. The system is set up in a town in southern China. After 7 days of debugging and acclimatization, the sewage samples during the normal period of the local area are used for a 28-day trial operation (the period includes 20 normal days and 5 holidays, of which the COD of the treated sewage on the 20 normal days is 30-40 mg / L, the ammonia nitrogen content is 30-45 mg / L, the C / N ratio is 0.9-1.2, and the total phosphorus is 2.5 mg / L; the COD of the treated sewage on the 5 holidays is 150-200 mg / L, the ammonia nitrogen content is 40-50 mg / L, the C / N ratio is 3.5-4, and the total phosphorus is 3 mg / L). The specific treatment process includes the following steps:

[0061] (1) Conduct COD testing on the wastewater to be treated;

[0062] (2) If the COD of the sewage to be treated is determined to be ≤120 mg / L, the sewage to be treated is sent to the first aeration tank for the first aeration treatment for 3 hours, then transferred to the second aeration tank for the second aeration treatment for 3 hours, then transferred to the third aeration tank for the third aeration treatment for 3 hours, and finally sent to the filtration tank for filtration treatment, thus completing the sewage treatment;

[0063] (3) If the COD of the sewage to be treated is determined to be greater than 120 mg / L, the sewage to be treated is sent to the anoxic tank for degradation treatment for 3 hours, and then the treated water is sent to the first aeration tank for the first aeration treatment for 3 hours, and then transferred to the second aeration tank for the second aeration treatment for 3 hours, and then transferred to the third aeration tank for the third aeration treatment for 3 hours, and finally sent to the filtration tank for filtration treatment, thus completing the sewage treatment;

[0064] The first to third aeration tanks are all provided with suspended sludge and fillers, the water inlets are all arranged at the bottom, the water outlets are arranged at the top, the height of the aeration tank is 4.5m, and the fillers are arranged in hollow spheres, such as Figure 2 As shown, the diameter of the hollow sphere is 10 cm, and each aeration tank has 3 to 5 spheres, and they are fixed at a height of 0.5 m at the bottom of the aeration tank by a fixing plate;

[0065] The filler is a mixture of commercially available polyurethane filler and commercially available bitter bamboo charcoal in a volume ratio of 9:1, wherein the specific surface area of ​​the polyurethane filler is 2400m 2 / m 3 The shape is 20*20*30mm block, the porosity is 90%, while the shape and size of bamboo charcoal are similar to polyurethane filler, and the specific surface area is about 53m 2 / g, with an average pore size of 32nm; the bamboo charcoal is a commercially available product with an original specific surface area of ​​25m 2 / g, with an average pore size of 16nm, was pre-mixed with sodium hydroxide and zinc chloride at a mass ratio of 1:0.1:0.05, and the mixture was dispersed and impregnated in a water / ethanol (V90:10) mixture at a mass ratio of 1g:50mL, then protected and kept warm at 350℃ for 1h in a nitrogen atmosphere, and finally washed to complete the pore formation and hardening treatment;

[0066] The filler surface is provided with a biofilm;

[0067] The biofilm thickness of the filler in the first aeration tank is 0.8 mm;

[0068] The biofilm thickness of the filler in the second aeration tank is 1 mm;

[0069] The biofilm thickness of the filler in the third aeration tank is 0.6 mm;

[0070] The filling rate of the first aeration tank is 30vt%;

[0071] The filling rate of the second aeration tank is 60vt%;

[0072] The filling rate of the third aeration tank is 25vt%;

[0073] The set temperature of the first aeration tank, the second aeration tank, and the third aeration tank is 23~28℃;

[0074] The inlet and outlet flow rates of the first aeration tank are 0.5 and 0.55 m / s; the inlet and outlet flow rates of the second aeration tank are 0.6 and 0.65 m / s; the inlet and outlet flow rates of the third aeration tank are 0.5 and 0.55 m / s;

[0075] The concentration of the suspended sludge is 2200-2400 mg / L, the sludge comes from a local municipal sewage plant, is municipal / domestic sludge, and the SV30 is 20-25%;

[0076] The third aeration tank is provided with a stirring device to perform stirring at 300 rpm during the third aeration treatment; at the same time, part of the water will be refluxed to the anoxic tank after the water is treated again, and the aeration tank is provided with an ORP detection device to control the water reflux ratio according to the ORP being stable in the range of -100~50mV, and the reflux ratio is in the range of 40~80%;

[0077] The first to third aeration tanks are provided with variable frequency fans, and the dissolved oxygen content is controlled by the variable frequency fans, wherein the dissolved oxygen content of the first aeration tank is 0.5-1.2 mg / L;

[0078] The dissolved oxygen content of the second aeration tank is 2~3mg / L;

[0079] The dissolved oxygen content in the third aeration tank is 0.5~1.2 mg / L.

[0080] The height, the position of the water inlet and outlet and the sludge setting of the anoxic tank are the same as those of the first to third aeration tanks, but no variable frequency fan is provided, the dissolved oxygen content is less than 0.5 mg / L, no filler is provided, and an ORP meter is provided to ensure that the ORP in the tank is stable in the range of -100~50mV. A stirring device is also provided to control the speed at 300 to perform stirring treatment synchronously during the degradation treatment;

[0081] The inlet and outlet flow rates of the anoxic pool are 0.5 and 0.55 m / s.

[0082] The height and the position of the water inlet and outlet of the filter tank are the same as those of the first to third aeration tanks. There is no variable frequency fan, the dissolved oxygen content is less than 0.5 mg / L, there is no sludge, the filler filling rate is 60vt%, the filler type is the same as the aeration tank, the biofilm thickness on the filler is 0.5 mm, and the water body's climbing filtration rate from bottom to top is set to 5 m / h.

[0083] The results showed that during the trial operation, the water after treatment met the national Class A water quality effluent standards, COD ≤ 50 mg / L, total nitrogen content ≤ 15 mg / L, and ammonia nitrogen content ≤ 5 mg / L.

[0084] Example 2

[0085] The present invention provides a method for treating low-carbon and high-nitrogen sewage, which comprises: Figure 1 The sewage treatment system shown in the embodiment is implemented, and the system is set in another town in southern China that is different from Example 1. The sewage sample of the normal period is used for 7 days of debugging and acclimation and then a 20-day trial operation is carried out (the period includes 17 normal days and 3 holidays, wherein the COD of the treated sewage on the 17 normal days is 40-60 mg / L, the ammonia nitrogen content is 25-40 mg / L, the C / N ratio is 1-1.6, and the total phosphorus is 2.6 mg / L; the COD of the treated sewage on the 3 holidays is 130-160 mg / L, the ammonia nitrogen content is 35-45 mg / L, the C / N ratio is 3.2-3.8, and the total phosphorus is 3.2 mg / L). The specific treatment process includes the following steps:

[0086] (1) to (3) are the same as in Example 1;

[0087] The configuration of the first to third aeration tanks is the same as that of Example 1;

[0088] The setting of the filler and the thickness of the biofilm are similar to those in Example 1, and will not be shown one by one again;

[0089] The concentration of the suspended sludge is 2000-2300 mg / L, the sludge comes from a local municipal sewage plant, is municipal / domestic sludge, and the SV30 is 15-20%;

[0090] The anoxic pool and the filter pool are arranged in the same manner as in Example 1;

[0091] The results showed that during the trial operation, the water after treatment met the national Class A water quality effluent standards, COD ≤ 50 mg / L, total nitrogen content ≤ 15 mg / L, and ammonia nitrogen content ≤ 5 mg / L.

[0092] Example 3

[0093] The present invention provides a method for treating low-carbon and high-nitrogen sewage, which comprises: Figure 1 The sewage treatment system shown in the figure is implemented, and the system is set in another town in southern China that is different from Examples 1 and 2. The sewage sample of the normal period is used for 7 days of debugging and acclimation and then a 15-day trial operation is carried out (the period includes 10 normal days and 5 holidays, wherein the COD of the treated sewage on the 15 normal days is 30-45 mg / L, the ammonia nitrogen content is 30-40 mg / L, the C / N ratio is 0.8-1.3, and the total phosphorus is 2.5 mg / L; the COD of the treated sewage on the 5 holidays is 150-230 mg / L, the ammonia nitrogen content is 30-50 mg / L, the C / N ratio is 3.5-4.5, and the total phosphorus is 3.5 mg / L). The specific treatment process includes the following steps:

[0094] (1) to (3) are the same as in Example 1;

[0095] The configuration of the first to third aeration tanks is the same as that of Example 1;

[0096] The setting of the filler and the thickness of the biofilm are similar to those in Example 1, and will not be shown one by one again;

[0097] The concentration of the suspended sludge is 2200-2500 mg / L, the sludge comes from a local municipal sewage plant, is municipal / domestic sludge, and the SV30 is 20-30%;

[0098] The anoxic pool and the filter pool are arranged in the same manner as in Example 1;

[0099] The results showed that during the trial operation, the water after treatment met the national Class A water quality effluent standards, COD ≤ 50 mg / L, total nitrogen content ≤ 15 mg / L, and ammonia nitrogen content ≤ 5 mg / L.

[0100] Comparative Example 1

[0101] A method for treating low-carbon and high-nitrogen sewage is implemented simultaneously at the location and water body described in Example 1, and the difference from Example 1 is that:

[0102] The dissolved oxygen content of the first aeration tank is 2~3mg / L, and the filler filling rate is 60vt%

[0103] The dissolved oxygen content of the second aeration tank is 0.5~1.2mg / L, and the filler filling rate is 30vt%

[0104] The dissolved oxygen content of the third aeration tank is 0.5~1.2mg / L, and the filler filling rate is 25vt%.

[0105] It was found that the water quality requirements could not be achieved during the commissioning process and the trial operation was not carried out.

[0106] Comparative Example 2

[0107] A method for treating low-carbon and high-nitrogen sewage is implemented simultaneously at the location and water body described in Example 1, and the difference from Example 1 is that:

[0108] There is no design for water return in the third aeration tank, and no return water is introduced into the anoxic tank.

[0109] It was found that the water quality requirements could not be achieved during the commissioning process and the trial operation was not carried out.

[0110] Comparative Example 3

[0111] A method for treating low-carbon and high-nitrogen sewage is implemented simultaneously at the location and water body described in Example 1, and the difference from Example 1 is that:

[0112] The dissolved oxygen content of the first aeration tank is 0.5~1.2mg / L, and the filler filling rate is 35vt%

[0113] The dissolved oxygen content of the second aeration tank is 3~4mg / L, and the filler filling rate is 40vt%

[0114] The dissolved oxygen content of the third aeration tank is 0.5~1.2mg / L, and the filler filling rate is 30vt%.

[0115] It was found that the water quality requirements could not be achieved during the commissioning process and the trial operation was not carried out.

[0116] Comparative Example 4

[0117] A method for treating low-carbon and high-nitrogen sewage is implemented simultaneously at the location and water body described in Example 1, and the difference from Example 1 is that:

[0118] The dissolved oxygen content of the first aeration tank is 0.5~1.2mg / L, and the filler filling rate is 30vt%

[0119] The dissolved oxygen content of the second aeration tank is 1.5~2mg / L, and the filler filling rate is 60vt%

[0120] The dissolved oxygen content of the third aeration tank is 0.5~1.2mg / L, and the filler filling rate is 25vt%.

[0121] It was found that the water quality requirements could not be achieved during the commissioning process and the trial operation was not carried out.

[0122] Comparative Example 5

[0123] A method for treating low-carbon and high-nitrogen sewage is implemented simultaneously at the location and water body described in Example 1, and the difference from Example 1 is that:

[0124] The filler is replaced with a pure polyurethane filler.

[0125] It was found that the water quality requirements could not be achieved during the commissioning process and the trial operation was not carried out.

[0126] Comparative Example 6

[0127] A method for treating low-carbon and high-nitrogen sewage is implemented simultaneously at the location and water body described in Example 2, and the difference from Example 2 is that:

[0128] The fillers in the first to third aeration tanks are freely suspended.

[0129] It was found that the water quality requirements could not be achieved during the commissioning process and the trial operation was not carried out.

[0130] Comparative Example 7

[0131] A method for treating low-carbon and high-nitrogen sewage is implemented simultaneously at the location and water body described in Example 2, and the difference from Example 2 is that:

[0132] The dissolved oxygen content of the first aeration tank is 0.5~1.2mg / L, and the filler filling rate is 50vt%

[0133] The dissolved oxygen content of the second aeration tank is 2~3mg / L, and the filler filling rate is 50vt%

[0134] The dissolved oxygen content of the third aeration tank is 0.5~1.2mg / L, and the filler filling rate is 50vt%.

[0135] It was found that the water quality requirements could not be achieved during the commissioning process and the trial operation was not carried out.

[0136] Comparative Example 8

[0137] A method for treating low-carbon and high-nitrogen sewage is implemented simultaneously at the location and water body described in Example 2, and the difference from Example 2 is that:

[0138] The bamboo charcoal in the filler is replaced with an equal volume of commercially available hollow ceramsite with an average particle size of 15 mm, and the gap between the hollow spheres is adjusted accordingly so that the ceramsite will not leak out.

[0139] It was found that the water quality requirements could not be achieved during the commissioning process and the trial operation was not carried out.

[0140] Comparative Example 9

[0141] A method for treating low-carbon and high-nitrogen sewage is implemented simultaneously at the location and water body described in Example 2, and the difference from Example 2 is that:

[0142] The dissolved oxygen content of the first aeration tank is ≤0.5mg / L, and the filler filling rate is 30vt%

[0143] The dissolved oxygen content of the second aeration tank is 2~3mg / L, and the filler filling rate is 60vt%

[0144] The dissolved oxygen content of the third aeration tank is 0.5~1.2mg / L, and the filler filling rate is 60vt%.

[0145] It was found that the water quality requirements could not be achieved during the commissioning process and the trial operation was not carried out.

[0146] Comparative Example 10

[0147] A method for treating low-carbon and high-nitrogen sewage is implemented simultaneously at the location and water body described in Example 2, and the difference from Example 2 is that:

[0148] The concentration of the suspended sludge is 2800-3000 mg / L, and the filler filling rate of the third aeration tank is 30 vt%.

[0149] It was found that the water quality requirements could not be achieved during the commissioning process and the trial operation was not carried out.

[0150] According to the comparison of the results of each embodiment and the comparative example, it is found that the traditional sewage treatment process cannot achieve a lasting water purification effect for town-level domestic sewage without introducing a carbon source and without sludge return. In particular, when the water quality composition undergoes staged changes over time, it is difficult to achieve the expected goal without real-time operation. The process of the present invention can perform staged denitrification-nitrification-denitrification treatment based on the carbon source of this type of water quality itself, and only needs to perform diversion treatment according to the change of COD content in the water quality to complete the task of meeting the water quality standards. It is easy to operate and has high economic cost performance.

[0151] Comparative Example 11

[0152] A method for treating low-carbon and high-nitrogen sewage is implemented simultaneously at the location and water body described in Example 2, and the difference from Example 2 is that:

[0153] The bamboo charcoal is not subjected to pore-forming and hardening treatments.

[0154] It was found that the water quality requirements could not be met during the commissioning process, and the bamboo charcoal became granulated and flowed out of the aeration tank with the sewage, so the trial operation was not carried out.

[0155] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the present invention.

Claims

1. A method for treating low-carbon and high-nitrogen sewage, characterized in that: The following steps are involved: (1) Conduct COD testing on the wastewater to be treated; (2) If the COD of the sewage to be treated is determined to be ≤120 mg / L, the sewage to be treated is sent to the first aeration tank for the first aeration treatment, then transferred to the second aeration tank for the second aeration treatment, then transferred to the third aeration tank for the third aeration treatment, and finally sent to the filtration tank for filtration treatment, thus completing the sewage treatment; (3) If the COD of the wastewater to be treated is determined to be greater than 120 mg / L, the wastewater to be treated is sent to an anoxic tank for degradation treatment, and then the same treatment is performed as in step (2); The first to third aeration tanks and the anoxic tank are provided with suspended sludge, the concentration of the suspended sludge is 2000-2500 mg / L, the first to third aeration tanks and the filtration tank are provided with fillers, the fillers include polyurethane fillers and bamboo charcoal; the bamboo charcoal is subjected to pore formation / hardening treatment; and a biofilm is provided on the filler; The third aeration tank is provided with a stirring device to perform stirring treatment synchronously during the third aeration treatment; The dissolved oxygen content of the first aeration tank is 0.5-1.2 mg / L, and the filler filling rate is 28-32 vt%; The dissolved oxygen content of the second aeration tank is 2-3 mg / L, and the filler filling rate is 58-62 vt%; The dissolved oxygen content of the third aeration tank is 0.5-1.2 mg / L, and the filler filling rate is 22-26 vt; The anoxic tank is provided with a portion of the water returned from the third aeration tank after the third aeration treatment, and a stirring device is provided to perform stirring treatment simultaneously during the degradation treatment; The low-carbon and high-nitrogen sewage treatment method is carried out in a sewage treatment system, which includes an anoxic tank, a first aeration tank, a second aeration tank, a third aeration tank and a filtration tank; the first aeration tank, the second aeration tank and the third aeration tank are provided with a variable frequency fan and a water dissolved oxygen detection device; the anoxic tank and the first aeration tank are provided with a sewage inlet pipe, and the sewage inlet pipe is provided with an intelligent switching valve and a COD detection device, and the intelligent switching valve is used to allow the sewage to be treated to enter the anoxic tank or the first aeration tank according to the COD content of the sewage to be treated; the third aeration tank is provided with a reflux device and a stirring device; the anoxic tank is provided with a stirring device.

2. The low-carbon and high-nitrogen sewage treatment method according to claim 1, characterized in that: The COD content of the sewage to be treated is 25-250 mg / L, the ammonia nitrogen content is 20-50 mg / L, and the C / N ratio is 0.5-5.

3. The low-carbon and high-nitrogen sewage treatment method according to claim 2, characterized in that: When the COD content of the sewage to be treated is ≤120 mg / L, the ammonia nitrogen content is 20-45 mg / L; when the COD content of the sewage to be treated is >120 mg / L, the ammonia nitrogen content is 30-50 mg / L.

4. The low-carbon and high-nitrogen sewage treatment method according to claim 1, characterized in that: The suspended sludge is municipal / domestic sludge, which comes from a municipal sewage plant and has an SV30 of 10-30%.

5. The low-carbon and high-nitrogen sewage treatment method according to claim 1, characterized in that: The polyurethane filler in the filler has a specific surface area of ​​2000~2500m 2 / m 3 , the porosity is 85~95%.

6. The low-carbon, high-nitrogen sewage treatment method according to claim 1, characterized in that: The specific surface area of ​​the bamboo charcoal is 50-60 m 2 / g, and the average pore size is 20~50nm.

7. The low-carbon, high-nitrogen sewage treatment method according to claim 1, characterized in that: The filler is arranged in a hollow sphere, the average diameter of the hollow sphere is 8-12 cm, and the number of the hollow spheres in the aeration tank is 3-5.

8. The low-carbon, high-nitrogen sewage treatment method according to claim 1, characterized in that: The volume ratio of polyurethane filling and bamboo charcoal in the filler is (95-85): (5-15).

9. The low-carbon, high-nitrogen sewage treatment method according to claim 7, characterized in that: The water inlets of the first aeration tank, the second aeration tank and the third aeration tank are arranged at the bottom of the aeration tank, and the water outlets are arranged at the top of the aeration tank. The height of the aeration tank is 4-5m, and the hollow sphere is arranged at a height of 0.3-0.6m from the bottom of the aeration tank.

10. The low-carbon, high-nitrogen sewage treatment method according to claim 1, characterized in that: The thickness of the biofilm set on the filler in the first aeration tank is 0.5-1 mm; the thickness of the biofilm set on the filler in the second aeration tank is 0.5-1 mm; the thickness of the biofilm set on the filler in the third aeration tank is 0.5-1 mm.

11. The low-carbon, high-nitrogen sewage treatment method according to claim 1, characterized in that: The set temperature of the first aeration tank, the second aeration tank and the third aeration tank is 15~30℃.

12. The low-carbon, high-nitrogen sewage treatment method according to claim 1, characterized in that: The inlet flow rate and outlet flow rate of the first aeration tank are 0.5-0.6 m / s; the inlet flow rate and outlet flow rate of the second aeration tank are 0.6-0.7 m / s; the inlet flow rate and outlet flow rate of the third aeration tank are 0.5-0.6 m / s.

13. The low-carbon, high-nitrogen sewage treatment method according to claim 1, characterized in that: The treatment time of at least one of the first aeration treatment, the second aeration treatment, and the third aeration treatment is 2.5 to 3.5 hours.

14. The low-carbon, high-nitrogen sewage treatment method according to claim 1, characterized in that: A reflux device is provided in the third aeration tank to return the water obtained after aeration treatment to the anoxic tank under stirring, and the ORP of the third aeration tank is maintained at -100~50mV by adjusting the water reflux ratio; the water reflux ratio is 40~80%.

15. The low-carbon, high-nitrogen sewage treatment method according to claim 14, characterized in that: The dissolved oxygen content of the anoxic tank is less than 0.5 mg / L, and the degradation treatment time of the sewage to be treated in the anoxic tank is 2.5 to 3.5 hours.

16. The low-carbon, high-nitrogen sewage treatment method according to claim 15, characterized in that: The water inlet of the anoxic pool is arranged at the bottom, the water outlet is arranged at the top, and the height of the anoxic pool is 4-5m; the water inlet rate and the water outlet rate of the anoxic pool are 0.5-0.6m / s.

17. The low-carbon, high-nitrogen sewage treatment method according to claim 1, characterized in that: The filter tank is provided with a filler, and the filling rate of the filler is 65-75vt%.

18. The low-carbon, high-nitrogen sewage treatment method according to claim 1, characterized in that: The water inlet of the filter pool is arranged at the bottom, the water outlet is arranged at the top, and the height of the filter pool is 4-5m.

19. The low-carbon, high-nitrogen sewage treatment method according to claim 18, characterized in that: During the filtering process, the water body's upward filtration rate is set to 4.5-5.5 m / h.

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