CN107324594B - Wastewater treatment system and method - Google Patents
Wastewater treatment system and method Download PDFInfo
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- CN107324594B CN107324594B CN201710623569.7A CN201710623569A CN107324594B CN 107324594 B CN107324594 B CN 107324594B CN 201710623569 A CN201710623569 A CN 201710623569A CN 107324594 B CN107324594 B CN 107324594B
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F9/00—Multistage treatment of water, waste water or sewage
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/24—Treatment of water, waste water, or sewage by flotation
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/38—Treatment of water, waste water, or sewage by centrifugal separation
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F3/00—Biological treatment of water, waste water, or sewage
- C02F3/30—Aerobic and anaerobic processes
Abstract
The invention provides a wastewater treatment system which sequentially comprises a dissolved air tank, a primary cyclone group, a secondary cyclone group, a primary anoxic tank, a primary aerobic tank, a secondary anoxic tank and a secondary aerobic tank, wherein the dissolved air tank is connected with an air compressor, biological membrane components are arranged in the primary aerobic tank and the secondary aerobic tank to maintain the biomass of activated sludge, wastewater enters the primary cyclone group and the secondary cyclone group to remove heavy SS (suspended substances), light SS (suspended substances) and penetrating organic substances which have high specific gravity and mainly comprise inorganic SS (suspended substances), and test results show that COD (chemical oxygen demand) of effluent of the wastewater treatment system is less than 40mg/L, TN and less than 12mg/L, heavy SS (suspended substances) and light SS (suspended substances) are less than 50 mg/L.
Description
Technical Field
The invention relates to the technical field of sewage treatment, in particular to a wastewater treatment system and a wastewater treatment method.
Background
The sewage of municipal sewage plant is gone into aquatic toxicity, the organic matter content of difficult degradation is high, with regard to traditional grit chamber and primary sedimentation tank serial systems, area is big, only focus on the processing to silt, and it is poor to get rid of the effect to Suspended Solid (SS), especially light SS, in addition, when the raw water contains toxicity, the organic matter of difficult degradation (penetrating organic matter promptly), this type of organic matter can be attached to on some light or the SS of organic partially, traditional grit chamber and primary sedimentation tank serial systems do not play certain removal effect to the organic matter of difficult degradation of toxicity this moment. Simultaneously, biochemical treatment of urban sewage in northern severe cold regions faces two problems to be solved urgently: firstly, the limitation of the shortage of raw water organic carbon source on the deep denitrification of organisms; and secondly, in northern severe cold areas, the water temperature is low in winter, so that the nitrification process is seriously inhibited, and the biological denitrification effect is poor.
At present, people do not pay enough attention to the removal of light SS in sewage, permeable organic matters are also pretreated by using an advanced oxidation method such as ozone and the like before entering a secondary treatment stage to enhance the biodegradability of a subsequent treatment unit, but the equipment investment cost is high and the operation cost is high. In addition, the enhancement of the biochemical efficiency only focuses on engineering measures for adjusting the sludge age and the biological load, namely, the active sludge is kept to be high in sludge age and low in biological load, so that the complex organic matters difficult to degrade are effectively removed. However, the characteristics of the sludge are ensured by the overall optimization of environmental conditions, the change of individual working condition parameters is difficult to maintain the ideal sludge properties for a long time, if the load is reduced independently, the higher activity and high sludge concentration of the sludge are difficult to maintain, and finally the overall efficiency of the anoxic-aerobic system is difficult to maintain stably. In the prior engineering application, the mixing and shearing effects in the aerobic tank are enhanced by enhancing the aeration strength in the aerobic tank, but the energy consumption is wasted and the obtained effect is not obvious.
Disclosure of Invention
In view of the above, the present invention provides a wastewater treatment system, which uses an air flotation cyclone unit in series with an AO treatment system to achieve wastewater treatment of refractory organic industrial wastewater containing a significant proportion, significantly remove suspended matters in wastewater, assist in removing penetrating organic matters, effectively improve effluent quality, and reduce energy consumption.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a wastewater treatment system which sequentially comprises a dissolved air tank, a primary cyclone unit, a secondary cyclone unit, a first-stage anoxic tank, a first-stage aerobic tank, a second-stage anoxic tank and a second-stage aerobic tank, wherein the dissolved air tank is connected with an air compressor, and biological membrane components are arranged in the first-stage aerobic tank and the second-stage aerobic tank to maintain the biomass of activated sludge.
Preferably, the primary cyclone of the primary cyclone group is independently a conical barrel, the cone angle of the conical barrel is 12-16 degrees, and the length-diameter ratio of the primary cyclone is 4.5-5: 1, the classification particle size of the primary cyclone is 50-150 μm, and the vertical distance between a tangent water inlet and an overflow port of the primary cyclone is 250-300 mm; the swirler of second grade swirler group independently is conical barrel, the cone angle of conical barrel is 8 ~ 12, the draw ratio of second grade swirler is 6 ~ 6.5: 1, the classification particle size of the secondary cyclone is 40-100 mu m, and the vertical distance between a tangent water inlet of the secondary cyclone and an overflow port is 150-200 mm; the single maximum treatment capacity of the primary cyclone and the secondary cyclone is independently 30m3And h, the number of the swirl pipes at each stage is superposed in parallel according to the actual treated water amount.
Preferably, when the wastewater treatment capacity in the wastewater treatment system is less than 1000m3When the water is dissolved in the air, the water is added into the air tank; when the wastewater treatment capacity is more than 1000m3And when the water is dissolved, adopting a partial water inlet pressurized dissolved air floatation method, and introducing 10-30% of inlet water into a dissolved air tank to be used as water for dissolving air.
Preferably, part of the effluent from the bottom flow port of the secondary cyclone unit flows back into the dissolved air tank, and when all the influent dissolved air is adopted in the dissolved air tank, the reflux ratio is 25-35%; when the dissolved air tank adopts partial water inlet dissolved air, the reflux ratio is 15-25%.
The invention also provides a method for treating wastewater by using the wastewater treatment system in the technical scheme, wherein the water temperature of the wastewater is less than or equal to 10 ℃, the content of suspended matters is 300-450 mg/L, the content of light suspended matters is 120-150 mg/L, the COD value is 200-300 mg/L, the content of ammonia nitrogen is 25-35 mg/L, and the total nitrogen content is 50-75 mg/L.
Preferably, the working pressure of the dissolved air tank is 0.36-0.4 MPa.
Preferably, the gas-liquid ratio in the gas dissolving tank is 5-10%.
Preferably, the pressure drop of the first-stage cyclone group is 0.06-0.1 MPa; and the pressure drop of the secondary cyclone group is 0.06-0.1 MPa.
Preferably, the underflow fraction of the first-stage cyclone group is 5-10%, and the underflow fraction of the second-stage cyclone group is 5-10%.
Preferably, the water inflow split ratio of the first-stage anoxic tank to the second-stage anoxic tank is 5:5 or 7: 3;
when the COD/TN of the raw sewage is lower than or equal to 3, the inflow split-flow ratio of the first-stage anoxic tank and the second-stage anoxic tank is 5: 5;
when the COD/TN of the raw sewage is more than 3, the water inlet flow dividing ratio of the first-stage anoxic tank to the second-stage anoxic tank is 7: 3.
Preferably, the reflux ratio of the mixed liquid in the second-stage aerobic tank is 2-4;
the ratio of the internal reflux quantity of the first-stage anoxic tank to the second-stage anoxic tank is the same as the ratio of the raw sewage water inflow quantity of the first-stage anoxic tank to the second-stage anoxic tank.
The invention provides a wastewater treatment system which sequentially comprises a dissolved air tank, a primary cyclone unit, a secondary cyclone unit, a first-stage anoxic tank, a first-stage aerobic tank, a second-stage anoxic tank and a second-stage aerobic tank, wherein the dissolved air tank is connected with an air compressor; when the wastewater treatment capacity is large, part of wastewater directly enters the first-stage cyclone group, and the rest wastewater enters the dissolved air tank. Meanwhile, the air compressor pumps air into the dissolved air tank, the inlet water is fully mixed with the air in the dissolved air tank and then enters the first-stage cyclone group to rotate and centrifuge at a high speed, because the bubbles released by the dissolved air water are insufficient, the first-stage cyclone group mainly completes the action of gravity hydraulic cyclone and auxiliary air flotation cyclone, the heavy SS which is higher than water and mainly comprises inorganic SS is discharged from the bottom of the cyclone, the light SS with lower specific gravity and the attached penetrability organic matters thereof flow into the second-stage cyclone group along with the water from an overflow port pipeline at the top of the cyclone through a pressure reducing valve, the air dissolved in the water is gradually and fully released, and the light SS with lower specific gravity and the attached penetrability organic matters thereof are carried to rotate and centrifuge at a high speed in the second-stage cyclone group to strengthen the adhesion of the light SS and the bubbles, so as to cause obvious air flotation cyclone effect, and part, the remaining part of the effluent is returned to the dissolved air tank by a pump. Meanwhile, the wastewater containing high-concentration light SS and the attached penetrating organic matters is discharged from the top overflow port.
Compared with the prior art, the invention has the following advantages and beneficial technical effects:
(1) the front end of the biochemical treatment section is provided with a first-stage cyclone group and a second-stage cyclone group, wastewater is subjected to cyclone desanding and floatation cyclone light SS and penetrable organic matter treatment, flow field distribution can be optimized by regulating and controlling pressure of a dissolved air tank, inlet-outlet pressure difference of the cyclones and the like, SS and microbubble adhesion are enhanced, centrifugal separation of SS and shearing stripping of light SS surface organic matters are achieved, the purpose of efficiently removing SS at the biochemical front section, reducing biochemical water inlet inorganic SS proportion and improving sludge floc organic component proportion is achieved. Meanwhile, the operation energy consumption is reduced by partially dissolving the gas in the wastewater, and the blockage of the dissolved gas tank can be effectively prevented by the effluent backflow of the secondary cyclone unit. Under the optimal operation condition, the removal rate of SS can reach 60% at most, which is higher than that of a common grit chamber (about 30-40%), the removal rate of light SS can reach 50% at most, which is 30-40% higher than that of the grit chamber, and compared with the 1-2 hours of sedimentation time of a primary sedimentation chamber, the air flotation cyclone treatment time is greatly shortened, which only needs 5-10 min approximately, so that the occupied area is greatly reduced. According to the running cost accounting, when the processing scale is 2000t/d, the running cost is 0.045 yuan/t, and when the processing scale is 10000t/d, the running cost is 0.03 yuan/t. Therefore, the air flotation rotational flow has a remarkable removal effect on SS, and the operation cost is reduced more remarkably when the operation scale is increased.
(2) The biochemical treatment stage adopts a two-stage novel anoxic and aerobic treatment system with an embedded biological membrane. The main optimization means comprises multi-point water inflow, multi-stage backflow and application of a biological membrane component in a tail end O tank. Aiming at the problems that the COD of the inlet water is low and the denitrification is influenced by the shortage of the organic carbon source, the working condition parameters are optimized, and the specific optimization results are as follows: the inlet water and the mixed liquid reflux respectively enter a first-stage anoxic tank and a second-stage inlet water according to the proportion of 7:3, and the reflux ratio of the outlet water of the terminal aerobic tank is 2-4; test results show that the effluent can respectively reach 12mg/L and 0.5mg/L, and the COD of the effluent is less than 40mg/L, TN and less than 12mg/L, NH3-N＜0.5mg/L。
Drawings
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Fig. 1 is a schematic view of a wastewater treatment system provided in example 1 of the present invention, in which 1: gas dissolving tank, 2: first-stage swirler group, 3: second-stage swirler group, 4: first-stage anoxic tank, 5: a first-stage aerobic tank, 6: second-stage anoxic tank, 7: a second-stage aerobic tank, 8: a biofilm assembly;
FIG. 2 is a schematic view of a wastewater treatment system provided in example 2 of the present invention, wherein 1: gas dissolving tank, 2: first-stage swirler group, 3: second-stage swirler group, 4: first-stage anoxic tank, 5: a first-stage aerobic tank, 6: second-stage anoxic tank, 7: a second-stage aerobic tank, 8: a biological membrane component.
Detailed Description
The invention provides a wastewater treatment system which sequentially comprises a dissolved air tank, a primary cyclone unit, a secondary cyclone unit, a first-stage anoxic tank, a first-stage aerobic tank, a second-stage anoxic tank and a second-stage aerobic tank, wherein the dissolved air tank is connected with an air compressor, and biological membrane components are arranged in the first-stage aerobic tank and the second-stage aerobic tank to maintain the biomass of activated sludge.
The waste water treatment system provided by the invention comprises a dissolved air tank; the top of the dissolved air tank is preferably connected with the water outlet of the fine grid. The source of the dissolved air tank is not limited in any way, and the dissolved air tank can be obtained from commercial products well known to those skilled in the art;
the wastewater treatment system provided by the invention comprises a primary cyclone group; the single root maximum treatment capacity of the primary cyclone is preferably 30m3And h, the number of the swirl pipes at each stage is superposed in parallel according to the actual treated water amount.
In the invention, the primary cyclone is independently a conical barrel, and the cone angle of the conical barrel is preferably 12-16 degrees and more preferably 15 degrees; the length-diameter ratio of the primary cyclone is preferably 4.5-5: 1, more preferably 4.75: 1.
in the invention, the classification particle size of the primary cyclone is preferably 50-150 μm independently, and more preferably 80-120 μm; the vertical distance between a tangent water inlet of the primary cyclone and the overflow port is preferably 250-300 mm independently, and more preferably 260-280 mm.
In the invention, the overflow caliber of the primary cyclone is independently preferred to be 150-180 mm, more preferably 160mm, the underflow caliber of the primary cyclone is independently preferred to be 80-100 mm, more preferably 90mm, and the water inlet caliber of the primary cyclone is independently preferred to be 150-180 mm, more preferably 160 mm.
The wastewater treatment system provided by the invention comprises a secondary cyclone group; the maximum treatment capacity of a single secondary cyclone is preferably 30m3And h, the number of the swirl pipes at each stage is superposed in parallel according to the actual treated water amount.
In the invention, the secondary cyclone is independently a conical barrel, and the cone angle of the conical barrel is preferably 8-12 degrees and more preferably 10 degrees; the length-diameter ratio of the secondary cyclone is preferably 6-6.5: 1, more preferably 6.25: 1.
in the invention, the classification particle size of the secondary cyclone is 40-100 μm independently, and more preferably 50-80 μm; the vertical distance between the tangent water inlet of the secondary cyclone and the overflow port is preferably 150-200 mm independently, and more preferably 160-180 mm.
In the invention, the overflow caliber of the secondary cyclone is preferably 80-100 mm independently, more preferably 90mm, the underflow caliber of the secondary cyclone is preferably 150-180 mm independently, more preferably 160mm independently, and the inlet caliber of the secondary cyclone is preferably 150-180 mm independently, more preferably 160 mm.
The wastewater treatment system provided by the invention comprises a first-stage anoxic tank, a first-stage aerobic tank, a second-stage anoxic tank and a second-stage aerobic tank. The sources of the first-stage anoxic tank, the first-stage aerobic tank, the second-stage anoxic tank and the second-stage aerobic tank are not limited in any way, and commercially available products well known to those skilled in the art can be adopted.
The invention provides a wastewater treatment system which comprises a biological membrane component. In the embodiment of the invention, the biological membrane component is covered on the top of the first-stage aerobic tank and the second-stage aerobic tank, or on the tail end of the second-stage aerobic tank. In the invention, the filling material of the biological membrane component is preferably shale ceramsite or light porous particles which are not easy to block; the particle size of the filling material is preferably 10-20 mm, and the volume weight is preferably 0.36-0.8 g/cm3The porosity is preferably not less than 45% and the inner diameter of the micropores is preferably not less than 5 μm.
The wastewater treatment system provided by the invention comprises an air compressor, wherein the air compressor is connected with the dissolved air tank.
In the present invention, the wastewater treatment system is used for a method of wastewater treatment, preferably comprising the steps of:
when the wastewater is lifted by the pump, selecting a water inlet mode according to the treatment capacity, and when the wastewater treatment capacity is small, lifting the wastewater by the pump and then completely introducing the wastewater into the dissolved air tank; when the wastewater treatment capacity is large, part of wastewater directly enters the first-stage cyclone group, and the rest wastewater enters the dissolved air tank. Meanwhile, the air compressor pumps air into the dissolved air tank, the inlet water is fully mixed with the air in the dissolved air tank and then enters the first-stage cyclone group to rotate and centrifuge at a high speed, because the bubbles released by the dissolved air water are insufficient, the first-stage cyclone group mainly completes the action of gravity hydraulic cyclone and auxiliary air flotation cyclone, the heavy SS which is higher than water and mainly comprises inorganic SS is discharged from the bottom of the cyclone, the light SS with lower specific gravity and the attached penetrability organic matters thereof flow into the second-stage cyclone group along with the water from an overflow port pipeline at the top of the cyclone through a pressure reducing valve, the air dissolved in the water is gradually and fully released, and the light SS with lower specific gravity and the attached penetrability organic matters thereof are carried to rotate and centrifuge at a high speed in the second-stage cyclone group to strengthen the adhesion of the light SS and the bubbles, so as to cause obvious air flotation cyclone effect, and part, the remaining part of the effluent is returned to the dissolved air tank by a pump. Meanwhile, the wastewater containing high-concentration light SS and the attached penetrating organic matters is discharged from the top overflow port.
When the wastewater treatment capacity in the wastewater treatment system is less than 1000m3When the water is dissolved in the air, the water is added into the air tank; when the wastewater treatment capacity is more than 1000m3When the pressure is higher than the pressure, the gas-dissolved air floatation method is adopted，10-30% of inlet water is introduced into the dissolved air tank to be used as water for dissolving air, and more preferably 20%.
In the invention, the working pressure of the dissolved air tank is preferably 0.36-0.4 MPa, more preferably 0.38MPa, the gas-liquid ratio of the dissolved air tank is preferably 5-10%, more preferably 8%, and the hydraulic retention time of the wastewater in the dissolved air tank is preferably 1-3 min, more preferably 1 min.
In the invention, the wastewater enters the primary cyclone group from the water outlet at the lower end of the dissolved air tank. In the invention, the pressure drop of the first-stage cyclone group is preferably 0.06-0.1 MPa, and more preferably 0.08 MPa.
In the present invention, the underflow fraction of the first-stage cyclone group is preferably 5% to 10%, more preferably 6% to 8%.
In the invention, the hydraulic retention time of the wastewater in the primary cyclone group is preferably 5-8 s, and more preferably 6 s.
According to the invention, after wastewater enters the primary cyclone group, heavy SS in the wastewater is discharged from the underflow port of the primary cyclone group, and light SS and permeable organic matters in the wastewater flow into the secondary cyclone group along with the wastewater from the overflow port of the primary cyclone group through the pressure reducing valve.
The pressure of the effluent of the first-stage cyclone group after being decompressed by the pressure reducing valve is preferably not less than 0.12MPa, and more preferably 0.12 MPa.
In the invention, the pressure drop of the secondary cyclone group is preferably 0.06-0.1 MPa, and more preferably 0.08 MPa.
In the present invention, the underflow fraction of the second-stage cyclone group is preferably 5% to 10%, more preferably 6% to 8%.
In the present invention, the hydraulic retention time of the wastewater in the secondary cyclone group is preferably 5s to 8s, more preferably 6 s.
In the invention, part of the effluent from the bottom flow port of the secondary cyclone group flows back into the dissolved air tank, and when the dissolved air tank adopts all the inflow dissolved air, the reflux ratio is 25-35%, and more preferably 30%; when the dissolved air tank adopts partial water inflow dissolved air, the reflux ratio is 15-25%, and more preferably 20%.
In the invention, after passing through the secondary cyclone group, the wastewater sequentially enters a first-stage anoxic tank, a first-stage aerobic tank, a second-stage anoxic tank and a second-stage aerobic tank from the underflow port of the secondary cyclone group for treatment.
In the invention, the water inlet flow-dividing ratio of the first-stage anoxic tank to the second-stage anoxic tank is preferably 5:5 or 7: 3;
when the COD/TN of the raw sewage is lower than or equal to 3, the inflow split-flow ratio of the first-stage anoxic tank and the second-stage anoxic tank is preferably 5: 5;
when the COD/TN of the raw sewage is more than 3, the inflow split-flow ratio of the first-stage anoxic tank and the second-stage anoxic tank is preferably 7: 3.
In the invention, the first-stage anoxic tank, the first-stage aerobic tank, the second-stage anoxic tank and the second-stage aerobic tank adopt multi-point internal reflux, thereby solving the problem of uneven distribution of nitrate nitrogen in the multi-stage anoxic-aerobic reaction tank caused by single-point internal reflux and strengthening the denitrification effect.
In the invention, the reflux ratio of the mixed liquid in the second-stage aerobic tank is preferably 2-4;
the ratio of the internal reflux amount of the first-stage anoxic tank to the second-stage anoxic tank is preferably the same as the ratio of the raw sewage water inflow amount of the first-stage anoxic tank to the second-stage anoxic tank.
In the invention, air aeration is preferably carried out in the first-stage aerobic tank and the second-stage aerobic tank, granular medium biological membrane components with the thickness of 0.3-0.6 m are immersed and hung at the position 0.2-0.5 m below the liquid level in a filter screen with the mesh aperture smaller than 0.8cm, and are integrally arranged in a framework constructed by a non-corrodible high-strength material and then fixed on the inner walls of the first-stage aerobic tank and the second-stage aerobic tank.
In the invention, the operation conditions in the first stage anoxic tank and the second stage anoxic tank are independently as follows: the dissolved oxygen is not more than 0.5mg/L, the hydraulic retention time is 3-5 h, and more preferably, the hydraulic retention time is 4 h.
In the invention, the operation conditions in the first-stage aerobic tank and the second-stage aerobic tank are independently as follows: the dissolved oxygen is 2-4 mg/L, the hydraulic retention time is 10-15 h, and more preferably, the hydraulic retention time is 12 h.
In the invention, the wastewater treatment method also comprises the step of enabling the second-stage aerobic tankAnd the effluent enters a secondary precipitation section for precipitation treatment. The specific operation of the secondary precipitation section can be referred to the book of Water pollution control engineering (Water pollution control engineering, Main code of Wang Yu, auxiliary code of forest and Kei, chemical industry Press, 2008), and preferably, the conditions of the secondary precipitation section include a surface load rate of 1-1.5 m3/(m2·h)。
The invention provides a wastewater treatment system, which sequentially comprises a dissolved air tank, a primary cyclone group, a secondary cyclone group, a primary anoxic tank, a primary aerobic tank, a secondary anoxic tank and a secondary aerobic tank, wherein the dissolved air tank and an air compressor are arranged in the primary aerobic tank and the secondary aerobic tank, biological membrane components are arranged in the primary aerobic tank and the secondary aerobic tank to maintain the biomass of activated sludge, when wastewater is lifted by a pump, a water inlet mode is selected according to the treatment capacity, and when the treatment capacity of the wastewater is smaller, the wastewater is lifted by the pump and then is completely introduced into the dissolved air tank; when the wastewater treatment capacity is large, part of wastewater directly enters the first-stage cyclone group, and the rest wastewater enters the dissolved air tank. Meanwhile, the air compressor pumps air into the dissolved air tank, the inlet water is fully mixed with the air in the dissolved air tank and then enters the first-stage cyclone group to rotate and centrifuge at a high speed, because the bubbles released by the dissolved air water are insufficient, the first-stage cyclone group mainly completes the action of gravity hydraulic cyclone and auxiliary air flotation cyclone, the heavy SS which is higher than water and mainly comprises inorganic SS is discharged from the bottom of the cyclone, the light SS with lower specific gravity and the attached penetrability organic matters thereof flow into the second-stage cyclone group along with the water from an overflow port pipeline at the top of the cyclone through a pressure reducing valve, the air dissolved in the water is gradually and fully released, and the light SS with lower specific gravity and the attached penetrability organic matters thereof are carried to rotate and centrifuge at a high speed in the second-stage cyclone group to strengthen the adhesion of the light SS and the bubbles, so as to cause obvious air flotation cyclone effect, and part, the remaining part of the effluent is returned to the dissolved air tank by a pump. Meanwhile, the wastewater containing high-concentration light SS and the attached penetrating organic matters is discharged from the top overflow port.
Compared with the prior art, the invention has the following advantages and beneficial technical effects:
1) the front end of the biochemical treatment section is provided with a first-stage cyclone group and a second-stage cyclone group, wastewater is subjected to cyclone desanding and second-stage cyclone light SS and penetrable organic matter treatment, flow field distribution can be optimized by regulating and controlling pressure of a dissolved air tank, inlet-outlet pressure difference of the cyclones and the like, SS and microbubble adhesion are enhanced, centrifugal separation of SS and shearing stripping of light SS surface organic matters are achieved, the purpose of efficiently removing SS at the biochemical front section is achieved, biochemical water inflow inorganic SS proportion is reduced, and sludge floc organic component proportion is improved. Meanwhile, the operation energy consumption is reduced by partially dissolving the gas in the wastewater, and the blockage of the dissolved gas tank can be effectively prevented by the effluent backflow of the secondary cyclone unit. Under the optimal operation condition, the removal rate of SS can reach 60% at most, which is higher than that of a common grit chamber (about 30-40%), the removal rate of light SS can reach 50% at most, which is 30-40% higher than that of the grit chamber, and compared with the 1-2 hours of sedimentation time of a primary sedimentation chamber, the air flotation cyclone treatment time is greatly shortened, which only needs 5-10 min approximately, so that the occupied area is greatly reduced. According to the running cost accounting, when the processing scale is 2000t/d, the running cost is 0.045 yuan/t, and when the processing scale is 10000t/d, the running cost is 0.03 yuan/t. Therefore, the air flotation rotational flow has a remarkable removal effect on SS, and the operation cost is reduced more remarkably when the operation scale is increased.
(2) The biochemical treatment stage adopts a two-stage novel anoxic and aerobic treatment system with an embedded biological membrane. The main optimization means comprises multi-point water inflow, multi-stage backflow and application of a biological membrane component in a tail end O tank. Aiming at the problems that the COD of the inlet water is low and the denitrification is influenced by the shortage of the organic carbon source, the working condition parameters are optimized, and the specific optimization results are as follows: the inlet water and the mixed liquid reflux respectively enter a first-stage anoxic tank and a second-stage inlet water according to the proportion of 7:3, and the reflux ratio of the outlet water of the terminal aerobic tank is 2-4; test results show that the effluent can respectively reach 12mg/L and 0.5mg/L, and the COD of the effluent is less than 40mg/L, TN and less than 12mg/L, NH3-N＜0.5mg/L。
The wastewater treatment system and method provided by the present invention will be described in detail with reference to the following examples,
they are not to be construed as limiting the scope of the invention.
In the following examples, the sludge loads of the activated sludge used were all 0.3kgCOD/(kg sludge d); the COD value is determined by dichromate method (GB 11914-89); content of Ammonia Nitrogen (NH)3-N) is naesli reagent spectrophotometry (HJ 535-2009); the nitrate nitrogen content (NO3- -N) is determined by ultraviolet spectrophotometry (HJ 535-2009); the method for measuring the total nitrogen level (TN) is alkaline potassium persulfate digestion ultraviolet spectrophotometry (HJ 636-2012); the measuring method of the SS content is a gravimetric method (GB 11901-89); the determination method of the light SS content comprises standing the sample for 30min, discarding the precipitate, collecting the supernatant, and measuring by gravimetric method (GB 11901-89); the content of di (2-ethylhexyl) phthalate and pyridine is determined by GC-MS method.
Example 1
The treatment capacity of a modification project of a sewage plant in the north is 2000t/d, and the problem of overproof total nitrogen of effluent in winter mainly exists before modification. The water quality of the inlet water is as follows: the COD is 145-250mg/L, the ammonia nitrogen content is 27-45mg/L, the total nitrogen content is 40-60mg/L, the SS content is 488-545mg/L, and the pH value is 6.0-8.0. The permeable refractory organic pollutants are represented by di (2-ethylhexyl) phthalate and pyridine, and the removal effect of the permeable refractory organic pollutants in an air flotation rotational flow-AO system is inspected.
The present embodiment will be described with reference to fig. 1.
In this embodiment, 80% waste water after the waste water is promoted through the pump directly gets into one-level swirler group (2) in, remaining 20% waste water gets into dissolves in gas pitcher (1), the air compressor machine is squeezed into the air with the air simultaneously and is dissolved gas pitcher (1), the intaking gets into high-speed rotation in one-level swirler group (2) after dissolving gas pitcher (1) and air intensive mixing, the centrifugation, because it is not abundant to dissolve gas water release bubble, this moment one-level swirler group (2) mainly accomplishes gravity hydraulic cyclone and supplementary air supporting whirl effect, great heavy SS of using inorganic SS as the main than the proportion of water is discharged from the swirler bottom, light SS and the penetrating organic matter that adheres to that the proportion is less flows into second stage swirler group (3) along with water from swirler top overflow mouth pipeline through the relief pressure-reducing valve, the air that dissolves in the aquatic at this moment is abundant release gradually, and carry light SS and the penetrating organic matter that the proportion is less and adheres, Centrifuging to strengthen the adhesion of the light SS and bubbles to cause a remarkable air flotation cyclone effect, wherein a part of the water discharged from the second-stage cyclone group (3) sequentially enters the first-stage anoxic tank (4) from a underflow port, then sequentially flows into the first-stage aerobic tank (5), the second-stage anoxic tank (6) and the second-stage aerobic tank (7) to perform biological denitrification treatment, wherein the second-stage aerobic tank (7) contains a biological membrane component (8), and finally performs secondary precipitation; the remaining part of the effluent is returned into the dissolved air tank (1) by a pump. Meanwhile, the wastewater containing high-concentration light SS and the attached penetrating organic matters is discharged from the top overflow port.
In the embodiment, 20% of water at the underflow outlet of the second-stage cyclone group (3) flows back to the dissolved air tank through the pump, the rest water enters the first-stage anoxic tank and the second-stage anoxic tank at different points according to the proportion of 7:3, and the whole sewage sequentially enters the following working condition working sections:
(1) dissolving a gas tank: inlet air pressure is 0.38MPa, hydraulic retention time is 1min, and gas-liquid ratio is 8%;
(2) a first-stage swirler group: the cyclone tube has three openings and two spare openings, the pressure drop is 0.08MPa, the hydraulic retention time is 6s, and the effluent water pressure after passing through the pressure reducing valve is 0.12 MPa;
(3) (3) a secondary cyclone group: the cyclone tube has three openings and two spare openings, the pressure drop is 0.08MPa, and the hydraulic retention time is 6 s;
(4) a first-stage anoxic tank: the dissolved oxygen is 0.5mg/L, the temperature is 11 ℃, and the hydraulic retention time is 4 h;
(5) a first-stage aerobic tank: the dissolved oxygen is 2mg/L, the temperature is 11 ℃, and the hydraulic retention time is 12 h;
(6) a second-stage anoxic tank: the dissolved oxygen is 0.5mg/L, the temperature is 10 ℃, and the hydraulic retention time is 4 h;
(7) a second-stage aerobic tank: the dissolved oxygen is 2mg/L, the temperature is 10 ℃, the hydraulic retention time is 12h, a biological membrane component with the thickness of 0.6m is arranged at the top, the coverage range is 1/3 of the total length of the tank body, 9/10 of the total width is positioned at the tail end of the tank body, and the distance between the upper surface of the component and the sewage liquid level is 0.3 m. And (3) refluxing the sludge-water mixed liquor led out from the second-stage aerobic tank to the first-stage anoxic tank and the second-stage anoxic tank in a point-to-point manner, wherein the total reflux ratio is 4, and the point-to-point reflux ratio is consistent with the water inlet ratio of raw water, and the ratio is 7: 3. After a period of stable operation, effluent data are obtained as shown in table 1:
TABLE 1 detection results of various indexes at different detection stages
As can be seen from the above examples, the method of the present invention effectively improves effluent quality, particularly effluent SS and total nitrogen concentration, to a relatively low level; meanwhile, the permeable organic matters in the first-stage cyclone group and the second-stage cyclone group are removed to a certain extent, so that the biodegradability of subsequent anoxic and aerobic treatment is enhanced.
Example 2
The treatment capacity of a modification project of a sewage plant in the north is 1000t/d, and the problem of overproof total nitrogen of effluent in winter mainly exists before modification. The water quality of the inlet water is as follows: COD is 120-200mg/L, ammonia nitrogen content is 35-52mg/L, total nitrogen content is 55-72mg/L, SS content is 320-500mg/L, and pH value is 6.0-8.0. The permeable refractory organic pollutants are represented by di (2-ethylhexyl) phthalate and pyridine, and the removal effect of the permeable refractory organic pollutants in an air flotation rotational flow-AO system is inspected.
The present embodiment will be described with reference to fig. 2.
In the embodiment, the waste water is lifted by a pump and then completely enters the dissolved air tank (1), meanwhile, the air compressor pumps air into the dissolved air tank (1), the inlet water is fully mixed with the air in the dissolved air tank (1) and then enters the first-stage cyclone group (2) to rotate and centrifuge at a high speed, the air is not fully released by the dissolved air water, at the moment, the first-stage cyclone group (2) mainly completes the action of gravity hydraulic cyclone and auxiliary air floatation cyclone, the heavy SS which has larger specific gravity and is mainly inorganic SS is discharged from the bottom of the cyclone, the light SS and the organic matters with smaller specific gravity flow into the second-stage cyclone group (3) along with the water from an overflow port pipeline at the top of the cyclone through a pressure reducing valve, at the moment, the air dissolved in the water is gradually and fully released, and the light SS and the organic matters with smaller specific gravity are carried to rotate and centrifuge at a high speed in, a significant air flotation cyclone effect is caused, part of the water discharged from the second-stage cyclone group (3) sequentially enters the first-stage anoxic tank (4) from the underflow port, then sequentially flows into the first-stage aerobic tank (5), the second-stage anoxic tank (6) and the second-stage aerobic tank (7) for biological denitrification treatment, wherein the second-stage aerobic tank (7) contains a biological membrane component (8), and finally secondary sedimentation is carried out; the remaining part of the effluent is returned into the dissolved air tank (1) by a pump. Meanwhile, the wastewater containing high-concentration light SS and the attached penetrating organic matters is discharged from the top overflow port.
In the embodiment, 30% of water at the underflow outlet of the second-stage cyclone group (3) flows back to the dissolved air tank through the pump, the rest water enters the first-stage anoxic tank and the second-stage anoxic tank at different points according to the proportion of 5:5, and the whole sewage sequentially enters the following working condition working sections:
(1) dissolving a gas tank: inlet air pressure is 0.38MPa, hydraulic retention time is 1min, and gas-liquid ratio is 8%;
(2) a first-stage swirler group: the cyclone tube has three openings and two spare openings, the pressure drop is 0.08MPa, the hydraulic retention time is 6s, and the effluent water pressure after passing through the pressure reducing valve is 0.12 MPa;
(3) a second-stage swirler group: the cyclone tube has three openings and two spare openings, the pressure drop is 0.08MPa, and the hydraulic retention time is 6 s;
(4) a first-stage anoxic tank: the dissolved oxygen is 0.5mg/L, the temperature is 8 ℃, and the hydraulic retention time is 4 h;
(5) a first-stage aerobic tank: the dissolved oxygen is 2mg/L, the temperature is 8 ℃, and the hydraulic retention time is 12 h;
(6) a second-stage anoxic tank: the dissolved oxygen is 0.5mg/L, the temperature is 8 ℃, and the hydraulic retention time is 4 h;
(7) a second-stage aerobic tank: the dissolved oxygen is 2mg/L, the temperature is 8 ℃, and the hydraulic retention time is 12 h. A biofilm assembly with the thickness of 0.6m is arranged at the top, the coverage range is 1/3 of the total length of the tank body, 9/10 of the total width is positioned at the tail end of the tank body, and the distance between the upper surface of the assembly and the sewage level is 0.3 m. And (3) refluxing the sludge-water mixed liquor led out from the second-stage aerobic tank to the first-stage anoxic tank and the second-stage anoxic tank in a point-by-point manner, wherein the total reflux ratio is 2, and the point-by-point reflux ratio is consistent with the raw water inlet ratio, and the ratio of the partial reflux ratio to the raw water inlet ratio is 5: 5. After a period of stable operation, effluent data are obtained as shown in table 2:
TABLE 2 detection results of various indexes in different detection stages
As can be seen from the above examples, the method of the present invention effectively improves effluent quality, particularly effluent SS and total nitrogen concentration, to a relatively low level; meanwhile, the permeable organic matters in the first-stage cyclone group and the second-stage cyclone group are removed to a certain extent, so that the biodegradability of subsequent anoxic and aerobic treatment is enhanced.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (9)
1. A wastewater treatment system is characterized by sequentially comprising a dissolved air tank, a primary cyclone unit, a secondary cyclone unit, a first-stage anoxic tank, a first-stage aerobic tank, a second-stage anoxic tank and a second-stage aerobic tank, wherein the dissolved air tank is connected with an air compressor, and biological membrane components are arranged in the first-stage aerobic tank and the second-stage aerobic tank to maintain the biomass of activated sludge; the one-level swirler in the one-level swirler group independently is conical barrel, the cone angle of conical barrel is 12 ~ 16, the draw ratio of one-level swirler is 4.5 ~ 5: 1, the classification particle size of the primary cyclone is 50-150 μm, and the vertical distance between a tangent water inlet and an overflow port of the primary cyclone is 250-300 mm; the secondary cyclone in the secondary cyclone group is independently a conical barrel, the cone angle of the conical barrel is 8-12 degrees, and the length-diameter ratio of the secondary cyclone is 6-6.5: 1, the classification particle size of the secondary cyclone is 40-100 mu m, and the vertical distance between a tangent water inlet of the secondary cyclone and an overflow port is 150-200 mm;
the single maximum treatment capacity of the primary cyclone and the secondary cyclone is independently 30m3Use of primary and secondary cyclonesThe amount is superposed in parallel according to the actual treated water amount.
2. The treatment system of claim 1, wherein the wastewater treatment system is configured to treat less than 1000m of wastewater3When the water is dissolved in the air, the water is added into the air tank; when the wastewater treatment capacity is more than 1000m3And when the water is dissolved, adopting a partial water inlet pressurized dissolved air floatation method, and introducing 10-30% of inlet water into a dissolved air tank to be used as water for dissolving air.
3. The treatment system of claim 1, wherein a part of effluent from the bottom flow port of the secondary cyclone group flows back into the dissolved air tank, and when the dissolved air tank adopts all the influent dissolved air, the reflux ratio is 25-35%; when the dissolved air tank adopts partial water inlet dissolved air, the reflux ratio is 15-25%.
4. The method for treating wastewater by using the wastewater treatment system as claimed in claim 1, wherein the temperature of the wastewater is less than or equal to 10 ℃, the content of suspended matters is 300-450 mg/L, the content of light suspended matters is 120-150 mg/L, the COD value is 200-300 mg/L, the content of ammonia nitrogen is 25-35 mg/L, and the total nitrogen content is 50-75 mg/L; the light suspended substance is a suspended substance with a specific gravity smaller than that of water.
5. The method of claim 4, wherein the gas-liquid ratio in the gas dissolving tank is 5% to 10%; the working pressure of the dissolved air tank is 0.36-0.4 MPa.
6. The method according to claim 4, wherein the pressure drop of the primary cyclone group is 0.06-0.1 MPa; and the pressure drop of the secondary cyclone group is 0.06-0.1 MPa.
7. The method of claim 4, wherein the underflow fraction of the first stage cyclone group is 5% to 10% and the underflow fraction of the second stage cyclone group is 5% to 10%.
8. The method of claim 4, wherein the split ratio of the influent to the first stage anoxic tank is 5:5 or 7: 3;
when the COD/TN of the raw sewage is lower than or equal to 3, the inflow split-flow ratio of the first-stage anoxic tank and the second-stage anoxic tank is 5: 5;
when the COD/TN of the raw sewage is more than 3, the water inlet flow dividing ratio of the first-stage anoxic tank to the second-stage anoxic tank is 7: 3.
9. The method as claimed in claim 4, wherein the reflux ratio of the mixed liquor in the second-stage aerobic tank is 2-4;
the ratio of the internal reflux quantity of the first-stage anoxic tank to the second-stage anoxic tank is the same as the ratio of the raw sewage water inflow quantity of the first-stage anoxic tank to the second-stage anoxic tank.
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| CN104609560A (en) * | 2015-02-15 | 2015-05-13 | 华东理工大学 | Method for performing nitrogen biological removal on low-temperature low-carbon nitrogen ratio sewage |
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| CN104609560A (en) * | 2015-02-15 | 2015-05-13 | 华东理工大学 | Method for performing nitrogen biological removal on low-temperature low-carbon nitrogen ratio sewage |
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