CN110862186A - Method for treating high-concentration nitrate radical wastewater - Google Patents
Method for treating high-concentration nitrate radical wastewater Download PDFInfo
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Abstract
The invention discloses a method for treating high-concentration nitrate radical wastewater, which comprises the following steps: step S1, adding a carbon source and nitrogen and phosphorus nutrient salts into nitrate radical wastewater, and then adjusting the pH of the wastewater to 2-4 to obtain pretreated wastewater; step S2, mixing the pretreated wastewater with circulating water, introducing the obtained mixed water into an anoxic expanded bed reactor to enable the mixed water to be in contact with biological fillers for denitrification reaction, and obtaining denitrification-treated wastewater; wherein, the circulating water is a product obtained by carrying out denitrification reaction on the pretreated wastewater and the biological filler. The method for treating the nitrate radical wastewater has low cost, can continuously treat the wastewater with high concentration of nitrate radical (3000-35000mg/L), and has high treatment efficiency.
Description
Technical Field
The invention relates to a method for treating high-concentration nitrate radical wastewater.
Background
Nitrogen and phosphorus are one of the main factors causing water eutrophication, and particularly, the discharge amount of nitrate in industrial sewage is increased day by day, so that the natural circulation of nitrogen is seriously damaged. Nitrate can be reduced to nitrite, which causes methemoglobinemia. When the normal hemoglobin content in the human body is lower than 90%, the suffocation and even death of the human body can be caused. In order to maintain ecological environment and guarantee the health of people, the national sewage discharge standard is gradually strict, for example, the effluent standard TN (total nitrogen content) of the countries such as the United states and Canada is less than 3mg/L and TP (total phosphorus content) is less than 0.18mg/L, so the problem of treating and solving nitrate in wastewater is not slow.
Different methods can be adopted for treating high-concentration nitrate wastewater. The graphite electrode is reported to be adopted for electro-adsorption treatment of the nitrate salt water, the removal rate of nitrate nitrogen can reach 52.2 percent, but the method has the defects of high cost and poor nitrate removal capability. CN 103964550A discloses that nitrate in water is removed by adsorption with graphene-loaded nano-iron, the removal rate of nitrate nitrogen can reach 85%, but the preparation of graphene-loaded nano-iron needs to be carried out under the protection of inert atmosphere or nitrogen atmosphere, the operation is complex and large-scale wastewater cannot be treated, and the process is difficult to be practically applied. In another method, nitrate nitrogen wastewater is treated by a new ion exchange technology and treated by D890 resin, so that nitrate nitrogen in the wastewater can be completely removed, but the industrial production has large amount of nitrate nitrogen wastewater, and the D890 resin is expensive, so that the cost for treating a large amount of wastewater is too high, and the requirement of actual production is difficult to meet. CN106219716A discloses aThe method for treating the high-concentration nitrate radical wastewater is characterized in that zinc powder and sulfamic acid are added into the high-concentration nitrate radical wastewater for reaction at normal temperature and normal pressure, NO additional waste water treatment equipment is not needed to be purchased, and NO is treated after the waste water treatment3 -The concentration is less than or equal to 15mg/L, but the defect is secondary pollution caused by introducing zinc powder and the like.
Biological denitrification processes are widely concerned due to low treatment cost, denitrification bacteria convert nitrate into nitrogen gas and remove the nitrogen gas by taking a carbon source or an external carbon source in wastewater as an electron donor, but the activity of the denitrification bacteria is usually inhibited under the condition of high-concentration nitrate by the traditional denitrification technology. Therefore, in view of the current process situation of nitrate removal in water treatment, it is urgently needed to develop a novel enhanced biological denitrification technology, which can improve the treatment load and effectively reduce the operation and maintenance costs while ensuring the removal effect of nitrate and total nitrogen.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a method for treating high-concentration nitrate wastewater, which has low cost for treating the nitrate wastewater and can continuously treat the nitrate wastewater with high concentration (3000-.
According to a first aspect of the present invention, there is provided a method for treating high-concentration nitrate nitrogen wastewater, comprising:
step S1, adding a carbon source and nitrogen and phosphorus nutrient salts into the nitrate radical wastewater, and adjusting the pH of the wastewater to 2-4 to obtain pretreated wastewater;
step S2, mixing the pretreated wastewater with circulating water, introducing the obtained mixed water into an anoxic expanded bed reactor to enable the mixed water to be in contact with biological fillers for denitrification reaction, and obtaining denitrification-treated wastewater;
wherein, the circulating water is a product obtained by carrying out denitrification reaction on the pretreated wastewater and the biological filler.
According to a preferred embodiment of the present invention, in step S1, a carbon source is added to the nitrate wastewater, then nitrogen and phosphorus nutrient salts are added, and then the pH of the wastewater is adjusted.
According to the preferred embodiment of the invention, the concentration of nitrate in the nitrate wastewater is 3000-30000 mg/L.
After the wastewater is treated for a period of time, a biofilm grows on the filler, but an excessively thick biofilm can cause adhesion or agglomeration of filler particles, so that local water flow short circuit can be generated.
According to a preferred embodiment of the present invention, the method further comprises step S3 of performing an intermittent gas wash on the biological filler; preferably, the time interval of the air washing is 3-90min, and/or the intensity of the air washing is 8-15L/m2S, and/or the time of a single gas wash is 0.5-3 min. The invention can realize the quantitative control of the thickness of the biological membrane by controlling reasonable gas cleaning conditions, can prevent the long recovery time of biochemical treatment caused by excessive stripping, and can also prevent the problems of unfavorable mass transfer, aging of the biological membrane and the like caused by excessive thickness of the biological membrane.
According to a preferred embodiment of the present invention, the diameter of the bio-filler is 2.5-3.0mm, and preferably the bio-filler is a polished and degreased bio-filler.
According to a preferred embodiment of the present invention, the carbon source is added in step S1 so that the ratio of the mass concentration of COD to the mass concentration of nitrate nitrogen is (3.0-5.0):1, preferably (3.1-4.7):1, more preferably (3.4-4.5):1, and preferably the carbon source is methanol.
According to a preferred embodiment of the present invention, the step S1 of adding nitrogen and phosphorus nutritive salt is performed after the carbon source, preferably, the step S1 of adding nitrogen and phosphorus nutritive salt makes the COD, N: P, be (200) -400, 5:1 and N, P, respectively, be calculated by N, P element, preferably, the nitrogen nutritive salt is selected from ammonia and/or urea; and/or, the phosphorus nutrient salt is selected from KH2PO4And/or Na3PO4。
According to a preferred embodiment of the present invention, the anoxic expanded bed device comprises a feed tank, an anoxic expanded bed reactor and a nitrogen purge system,
the anoxic expanded bed reactor comprises a supporting layer, a filling zone, a transition section and a water outlet zone which are sequentially arranged from bottom to top, wherein a three-phase separator is arranged in the water outlet zone; the bottom end of the anoxic expanded bed reactor is provided with a water inlet/gas port, the upper part of the water outlet area is provided with a water outlet, preferably the water outlet is arranged on the side wall of the upper part of the water outlet area, and the water inlet end of the water outlet is provided with a water outlet filter screen;
the feeding tank is connected with a water inlet/gas outlet of the anoxic expansion bed reactor through a feeding pipe, a feeding pump is arranged on the feeding pipe, and the wastewater in the feeding tank is conveyed into the anoxic expansion bed reactor through the feeding pump; the water outlet of the anoxic expanded bed reactor is connected with a feeding pipe through a circulating water pipe, and a circulating pump is arranged on the circulating water pipe;
the nitrogen cleaning system comprises a nitrogen automatic control device, a nitrogen making machine system and a gas flowmeter, the nitrogen making machine system comprises a nitrogen making machine and a nitrogen storage tank, the nitrogen making machine is connected with the nitrogen storage tank, the nitrogen automatic control device regulates and controls the nitrogen making machine system through a time and flow control system to realize automatic control on the gas output quantity of nitrogen, the gas output time interval and the single gas output time, the nitrogen storage tank is connected with a water inlet/gas outlet through a gas inlet pipe, and the gas flowmeter is arranged on the gas inlet pipe;
the device also comprises a pH meter, a thermometer and an ORP meter, wherein the pH meter, the thermometer and the ORP meter are arranged at the upper part of the water outlet zone.
According to a preferred embodiment of the invention, the anoxic expanded bed device further comprises an ultrasonic cleaning device, the ultrasonic cleaning device comprises an ultrasonic probe, an ultrasonic transducer and an ultrasonic controller, the ultrasonic probe, the ultrasonic transducer and the ultrasonic controller are sequentially connected, the ultrasonic probe is arranged near a water outlet of the anoxic expanded bed reactor, and preferably the ultrasonic probe is arranged on the outer side of the water outlet filter screen. The water outlet filter screen is connected with the water outlet pipe, the water outlet filter screen is connected with the water outlet pipe.
According to the preferred embodiment of the invention, the anoxic expansion bed device further comprises a heating device, wherein the heating device comprises a reactor jacket, a heater and a heating pump, the reactor jacket is sleeved outside the bearing layer and the filler area, the bottom end of the reactor jacket is provided with a hot water inlet, and the upper end of the reactor jacket is provided with a hot water outlet; the hot water inlet is connected with one end of the heater through the heating pump, and the hot water outlet is connected with the other end of the heater.
According to a preferred embodiment of the invention, the three-phase separator comprises a central tube and a cover body, the cover body comprises an upper cover body and a lower cover body, and the upper cover body and the lower cover body are connected through a connecting piece and form an overflowing channel; the upper cover body and the lower cover body are in an inverted funnel shape, and the necking end of the upper cover body is connected with the central pipe.
According to the preferred embodiment of the invention, the upper side wall of the filling area is provided with a sludge discharge port.
According to a preferred embodiment of the present invention, the cross-sectional area of the packing section is smaller than the cross-sectional area of the effluent section, and preferably the cross-section of the anoxic expanded bed reactor is circular, and the transition section gradually increases in diameter from bottom to top.
The pretreated wastewater is stored in a feeding tank, when the wastewater is treated, the wastewater in the feeding tank is conveyed to a feeding pipe through a feeding pump and is mixed with circulating water flowing out from a water outlet of an anoxic expansion bed reactor, the concentration of nitrate radical in mixed water obtained by mixing the wastewater in the feeding tank with the circulating water flowing out from the anoxic expansion bed reactor is reduced to a proper range in a denitrification process, the mixed water enters the anoxic expansion bed reactor through a water inlet/air port at the bottom of the anoxic expansion bed reactor, a graded large-particle-size gravel layer filled in a supporting layer is distributed with water and then enters a filler area, under the action of upward flowing water flow, the particle filler in the expansion bed floats along with the water flow, the flow velocity of the water flow is controlled to enable the filler in the filler area to be in an expansion state, and the expansion rate of the filler area is. The gravel particles in the gas-water distribution area do not float with the water flow due to large particle size. Because the water flow contains the biochemically degraded matrix, a microbial film can grow on the filler in the filler area, the denitrification reaction can be realized in the process that the water flow passes through the filler area, nitrogen is generated, and nitrate radicals in the water flow can be removed. The water flow enters the water outlet zone after passing through the filler zone and the transition section, the cross-sectional area of the water outlet zone is larger than that of the filler zone, the rising flow rate of the water flow in the water outlet zone is reduced relative to that in the filler zone, filler particles carried by the water flow in the filler zone are settled in the filler zone after the flow rate of the water flow is reduced, the filler is prevented from being carried out of the expansion bed, the water flow enters the water outlet zone and then enters the circulating pump through the water outlet, and the rest of the effluent water enters the drain pipe discharge system through liquid level difference overflow.
The anoxic expansion bed device can realize real-time continuous on-line monitoring of the denitrification process, the ORP meter can monitor the oxidation/reduction potential of the water outlet area of the reactor, the nitrate concentration is associated with the oxidation/reduction environment in the reaction process, the oxidation-reduction potential can reflect the change of the nitrate concentration of water in time, the pH meter monitors the pH of the water outlet area, the thermometer monitors the temperature of the water outlet area, and the conditions of the reactor can be adjusted in real time through the feedback results of the pH meter, the thermometer and the ORP meter, so that the continuous operation is ensured, and the working efficiency is improved.
The water outlet filter screen is connected with the water outlet pipe, the water outlet filter screen is connected with the water outlet pipe.
After a period of wastewater treatment, a biofilm grows on the filler, an excessively thick biofilm can cause adhesion or agglomeration of filler particles, and further local water flow short circuit can be generated. The nitrogen cleaning system can clean the biological membrane in time, regulate and control the thickness of the biological membrane in time, maintain high-efficiency matrix mass transfer rate and wastewater treatment efficiency, and prevent the adhesion or agglomeration of filler particles and the formation of local water flow short circuit.
Parameters manipulated during gas stripping include: (1) gas parameters: the air-wash frequency, the air-wash intensity, the air-wash time and the position of the gas distributor; (2) liquid parameters: increasing the flow rate and washing strength; (3) matrix loading: feed concentration and feed loading.
The process of the anoxic expanded bed air-washing and membrane-removing method of the invention is as follows: when the biomembrane growing on the filler is too thick and influences the matrix mass transfer rate and the treatment effect of the reactor, the nitrogen automatic control device controls the nitrogen storage tank to be started to generate nitrogen, the nitrogen flows through the gas flowmeter, enters the anoxic expansion bed reactor through the gas inlet pipe and the water/gas inlet, bubbles upwards rub the biomembrane on the filler, after a period of time, the biomembrane on the filler particles is removed, and the nitrogen automatic control device stops supplying gas.
The automatic control of the nitrogen gas output quantity, the gas output time interval and the single gas output time is realized through the regulation and control of the time and flow control system. The time interval of air washing is set to be 3-90min, and/or the intensity of the air washing is 8-15L/m2S, and/or the time of each air-wash is 0.5-3 min. The parameter conditions set by the invention can realize the quantitative control of the thickness of the biological membrane, not only can prevent the long recovery time of biochemical treatment caused by excessive membrane removal, but also can prevent the problems of unfavorable mass transfer, aging of the biological membrane and the like caused by excessive thickness of the biological membrane.
In the invention, the wastewater is mixed with the mixed water and then is introduced into the anoxic expansion bed, because the denitrification reaction is an alkali-producing reaction, and the pH value of the mixed circulating water and the pretreated wastewater can reach the proper range in the denitrification process, the consumption of neutralizing alkali can be reduced in the pretreatment process.
The invention treats the high-concentration nitrate radical wastewater, reduces the economic investment, saves the occupied land and has high treatment load; the packed bed is in an expansion state during normal operation, the flow state of solid and liquid phases is favorable for the contact and mass transfer of microorganisms and sewage, the biological reaction efficiency is improved, and the stability and the impact resistance of the biological reaction process are improved by adopting forced water flow circulation to treat high-concentration nitrate radical wastewater; the nitrogen automatic control device realizes effective regulation and control of the thickness of the biological membrane by regulating the gas washing condition; the ultrasonic cleaning system can clean the water outlet filter screen in time, so that the device can continuously discharge mud, and the problem of filler blockage is solved; the ORP meter is adopted to monitor the oxidation/reduction potential in the reactor, so that the actual concentration change of nitrate radicals in the reactor can be effectively tracked, and the method is more rapid and accurate.
Drawings
FIG. 1 is a schematic diagram of an anoxic expanded bed apparatus;
FIG. 2 is a schematic diagram of a three-phase separator configuration;
FIG. 3 is a schematic diagram of a nitrogen generator system;
the device comprises a feeding tank 1, a feeding pump 2, a feeding pump 3, a water inlet/gas outlet 4, a supporting layer 5, a packing area 6, a water outlet area 7, a water collecting tank 8, a water outlet weir 9, a water outlet 10, a three-phase separator 11, a sludge discharge port 12, a hot water inlet 13, a hot water outlet 14, a heater 15, a heating pump 16, a circulating pump 17, an ultrasonic probe 18, an ultrasonic transducer 19, an ultrasonic controller 20, a water outlet filter screen 21, an ORP meter 22, a pH meter 23, a thermometer 24, a gas flowmeter 25, a nitrogen automatic control device 26, a nitrogen generator system 27, a transition section 10-a, a central pipe 10-b, an upper cover 10-c, a lower cover 10-d, a connecting piece 26-a, a nitrogen generator 26-b and a nitrogen storage tank.
Detailed Description
The present invention will be described in detail with reference to examples, but the present invention is not limited to the examples.
The invention provides a method for treating high-concentration nitrate wastewater, and the structure of a device used in the embodiment of the invention for treating the high-concentration nitrate wastewater is as follows: as shown in fig. 1 to 3, the anoxic expanded bed apparatus for treating nitrate wastewater according to the present invention includes a feed tank 1, an anoxic expanded bed reactor, a nitrogen cleaning system, an ultrasonic cleaning system, and a heating apparatus.
The anoxic expanded bed reactor comprises a supporting layer 4, a filling zone 5, a transition section 27 and a water outlet zone 6 which are sequentially arranged from bottom to top, wherein a three-phase separator 10 is arranged at the central position of the water outlet zone 6; the bottom end of the anoxic expanded bed reactor is provided with a water inlet/gas outlet 3, the side wall of the upper part of the water outlet zone 6 is provided with a water outlet 9, and the water inlet end of the water outlet is provided with a water outlet filter screen 20;
the feeding tank 1 is connected with a water inlet/gas outlet 3 of the anoxic expansion bed reactor through a feeding pipe, a feeding pump 2 is arranged on the feeding pipe, and the wastewater in the feeding tank 1 is conveyed into the anoxic expansion bed reactor through the feeding pump 2; a water outlet 9 of the anoxic expanded bed reactor is connected with a feeding pipe through a circulating water pipe, and a circulating pump 16 is arranged on the circulating water pipe;
the nitrogen cleaning system comprises a nitrogen automatic control device 25, a nitrogen making machine system 26 and a gas flowmeter 24, the nitrogen making machine system comprises a nitrogen making machine 26-a and a nitrogen storage tank 26-b, the nitrogen making machine 26-a is connected with the nitrogen storage tank 26-b, the nitrogen automatic control device 25 comprises a time control system and a flow control system, the nitrogen making machine system 26 is regulated and controlled by the time and flow control system to realize automatic control of the gas output quantity of nitrogen, the gas output time interval and the single gas output time, the nitrogen storage tank is connected with a water inlet/gas outlet through a gas inlet pipe, the gas inlet pipe is provided with the gas flowmeter, and gas generated by the nitrogen making machine system flows through the gas flowmeter and enters the reactor through the water inlet/gas outlet.
A pH meter 22, a thermometer 23 and an ORP meter 21 are arranged at the upper part of the water outlet zone and are respectively used for monitoring the pH, the temperature and the oxidation/reduction potential of the water outlet zone;
ultrasonic cleaning device includes ultrasonic probe 17, ultrasonic transducer 18 and ultrasonic controller 19, and ultrasonic probe 17, ultrasonic transducer 18 and ultrasonic controller 19 link to each other in proper order, ultrasonic probe 17 sets up near oxygen deficiency expanded bed reactor's delivery port 9, prefers ultrasonic probe sets up the outside of play water filter screen 20.
The heating device comprises a reactor jacket, a heater 14 and a heating pump 15, the reactor jacket is sleeved outside the supporting layer 4 and the filler zone 5, the bottom end of the reactor jacket is provided with a hot water inlet 12, and the upper end of the reactor jacket is provided with a hot water outlet 13; the hot water inlet 12 is connected with one end of a heater 14 through a heating pump 15, and the hot water outlet 13 is connected with the other end of the heater 14;
the three-phase separator comprises a central tube 10-a and a cover body, the cover body comprises an upper cover body 10-b and a lower cover body 10-c, and the upper cover body 10-b and the lower cover body 10-c are connected through a connecting piece 10-d and form an overflowing channel; the upper cover body 10-b and the lower cover body 10-c are inverted funnel-shaped, and the necking end of the upper cover body 10-b is connected with the central tube 10-a.
And a sludge discharge port 11 is arranged on the side wall of the upper part of the filler zone, the cross section area of the filler zone 5 is smaller than that of the water outlet zone 6, preferably, the cross section of the anoxic expanded bed reactor is circular, and the diameter of the transition section is gradually increased from bottom to top. The anoxic expanded bed reactor is vertically arranged, namely the cross section of the anoxic expanded bed is parallel to the arrangement surface.
The method for treating the wastewater comprises the following steps of firstly pretreating the wastewater, wherein the pretreatment of the wastewater comprises the steps of adding a carbon source and nitrogen and phosphorus nutrient salts into the wastewater containing nitrate radicals, adjusting the pH value of the wastewater to 2-4 to obtain pretreated wastewater, then storing the pretreated wastewater in a feeding tank, introducing the pretreated wastewater into an anoxic expanded bed reactor when the denitrification reaction is started, and after water flows pass through a graded large-particle-size gravel layer filled in a supporting layer for water distribution, the water flows through a filler region and a transition section and then enters a water outlet region and flows out of a water outlet region to enter a circulating pipeline, so that the anoxic expanded bed reactor is started. The method comprises the steps that water obtained by contact reaction of pretreated wastewater and fillers flows out from a water outlet to form circulating water, the circulating water is mixed with the wastewater from a feeding tank, the concentration of nitrate radicals in the mixed water obtained by mixing the wastewater in the feeding tank and the circulating water flowing out of an anoxic expansion bed is reduced to a proper range in a denitrification process, the mixed water enters the anoxic expansion bed reactor through a water inlet/air port at the bottom of the anoxic expansion bed reactor, a graded large-particle-size gravel layer filled in a supporting layer is distributed with water and then enters a filler area, under the action of upward flowing water flow, particle fillers in the expansion bed float along with the water flow, the flow rate of the water flow is controlled to enable the fillers in the filler area to be in an expansion state, and the expansion rate of the filler area is. The gravel particles in the gas-water distribution area do not float with the water flow due to large particle size. Because the water flow contains the biochemically degraded matrix, a microbial film can grow on the filler in the filler area, the denitrification reaction can be realized in the process that the water flow passes through the filler area, nitrogen is generated, and nitrate radicals in the water flow can be removed. And water flow enters the water outlet zone after passing through the filler zone and the transition section, the cross sectional area of the water outlet zone is larger than that of the filler zone, the rising flow rate of the water flow in the water outlet zone is reduced relative to that in the filler zone, filler particles carried by the water flow in the filler zone are settled in the filler zone after the flow rate of the water flow is reduced, the filler is prevented from being carried out of the expansion bed, part of the water flow enters the circulating pump through the water outlet to form circulating water, and the rest part of the water flow overflows through the liquid level difference and enters the drain pipe discharge.
The water outlet filter screen is connected with the water outlet pipe, the water outlet filter screen is connected with the water outlet pipe.
After a period of wastewater treatment, a biofilm grows on the filler, an excessively thick biofilm can cause adhesion or agglomeration of filler particles, and further local water flow short circuit can be generated. The nitrogen cleaning system can clean the biological membrane in time, regulate and control the thickness of the biological membrane in time, maintain high-efficiency matrix mass transfer rate and wastewater treatment efficiency, and prevent the adhesion or agglomeration of filler particles and the formation of local water flow short circuit.
Parameters manipulated during gas stripping include: (1) gas parameters: the air-wash frequency, the air-wash intensity, the air-wash time and the position of the gas distributor; (2) liquid parameters: increasing the flow rate and washing strength; (3) matrix loading: feed concentration and feed loading.
The process of the anoxic expanded bed air-washing and membrane-removing method of the invention is as follows: when the biomembrane growing on the filler is too thick and influences the matrix mass transfer rate and the treatment effect of the reactor, the nitrogen automatic control device controls the nitrogen storage tank to be opened to generate nitrogen, the nitrogen flows through the gas flowmeter, enters the nitrogen outlet distributor through the gas inlet pipe, enters the anoxic expansion bed, bubbles upwards rub the biomembrane on the filler, after a period of time, the biomembrane with the excessive thickness on the filler particles is removed, and the nitrogen automatic control device stops supplying gas.
The time interval of air washing is set to be 3-90min, and/or the intensity of the air washing is 8-15L/m2S, and/or the time of each air-wash is 0.5-3 min. Can realize the quantitative control of the thickness of the biological membrane, not only can prevent the long recovery time of biochemical treatment caused by excessive demoulding, but also can prevent the problems of unfavorable mass transfer, aging of the biological membrane and the like caused by excessive thickness of the biological membrane.
Example 1
The industrial wastewater treated in this example had a nitrate concentration of 13766mg/L (NO)3 -The N concentration is 3108mg/L), the COD concentration is 2430mg/L, and the pH is 0.5.
Firstly, the industrial wastewater is pretreated, comprising the following steps:
(1) supplementing carbon source (methanol) into industrial wastewater to make COD 11344mg/L and COD NO3-the ratio of mass concentration of N is 3.65;
(2) adding nitrogen nutrient salt (ammonia water or urea) and phosphorus nutrient salt (KH) into the wastewater obtained in the step (1)2PO4Or Na3PO4) Respectively, the concentration of N is 142mg/L calculated by N element, the concentration of P is 28mg/L calculated by P element, and the mass concentration ratio of COD to N to P is 400:5: 1;
(3) and (3) adding alkali (NaOH) into the wastewater obtained in the step (2) to adjust the pH of the wastewater to 2, so as to obtain pretreated wastewater.
Introducing the pretreated wastewater into an anoxic expanded bed reactor at a certain flow rate, distributing the water through a graded large-particle-size gravel layer filled in a supporting layer, flowing through a filler region, performing contact reaction with the filler in the filler region, then flowing through a transition section and a water outlet region, flowing out from a water outlet, mixing with the pretreated wastewater from a feed pipe after flowing through a circulating pump, feeding the mixed water into the anoxic expanded bed reactor from a water inlet/gas port, distributing the water through the graded large-particle-size gravel layer filled in the supporting layer, and then feeding the mixed water into the filler region, the transition section and the water outlet region. Because the water flow contains the biochemically degraded matrix, a microbial film can grow on the filler in the filler area, the denitrification reaction can be realized in the process that the water flow passes through the filler area, nitrogen is generated, and nitrate radicals in the water flow can be removed. The water flow part enters the circulating pump through the water outlet, and the rest part overflows into the drain pipe discharge system through the liquid level difference.
The nitrogen automatic control device controls the cleaning to be carried out once at intervals of 20min, and the strength of the gas washing is 10L/m2S, the time of single air washing is 0.5-1.5min,
the volume load (calculated according to the inflow water) of the nitrate radical in the wastewater can be up to 10.6 kg/(m)3D) the maximum nitrate volume load in the wastewater can be 10.1 kg/(m) calculated according to the inlet water and the outlet water3D), the nitrate nitrogen in the treated water can be reduced to below 10mg/L from 3108mg/L, the removal rate of nitrate nitrogen reaches above 99%, and the removal rate of methanol reaches 95%.
Example 2
The nitrate content of the industrial wastewater treated in the example is 29178mg/L (NO)3 -The N concentration is 6588 mg/L), the COD concentration is 4300mg/L, and the pH is 0.3.
Firstly, the industrial wastewater is pretreated, comprising the following steps:
(1) supplementing carbon source (methanol) into the industrial wastewater to make COD 26020mg/L and COD: NO3-the ratio of mass concentration of N is 3.9;
(2) adding nitrogen nutrient salt (ammonia water or urea) and phosphorus nutrient salt (KH) into the wastewater obtained in the step (1)2PO4Or Na3PO4) Respectively, the concentration of N is 435mg/L calculated by N element, the concentration of P is 87mg/L calculated by P element, and the mass concentration ratio of COD to N to P is 299 to 5 to 1;
(3) and (3) adding alkali (NaOH) into the wastewater obtained in the step (2) to adjust the pH of the inlet water to 2.2, so as to obtain pretreated wastewater.
Introducing the pretreated wastewater into an anoxic expanded bed reactor at a certain flow rate, distributing the water through a graded large-particle-size gravel layer filled in a supporting layer, flowing through a filler region, performing contact reaction with the filler in the filler region, then flowing through a transition section and a water outlet region, flowing out from a water outlet, mixing with the pretreated wastewater from a feed pipe after flowing through a circulating pump, feeding the mixed water into the anoxic expanded bed reactor from a water inlet/gas port, distributing the water through the graded large-particle-size gravel layer filled in the supporting layer, and then feeding the mixed water into the filler region, the transition section and the water outlet region. Because the water flow contains the biochemically degraded matrix, a microbial film can grow on the filler in the filler area, the denitrification reaction can be realized in the process that the water flow passes through the filler area, nitrogen is generated, and nitrate radicals in the water flow can be removed. The water flow part enters the circulating pump through the water outlet, and the rest part overflows into the drain pipe discharge system through the liquid level difference.
The nitrogen automatic control device controls the cleaning to be carried out once every 15min, and the strength of the gas washing is 10L/m2S, the time of a single air wash is 1-2.5 min.
The volume load (calculated by the inflow water) of the nitrate radical in the wastewater can be up to 11.58 kg/(m)3D) the highest capacity load of treating nitrate radical in the wastewater can reach 11.13 kg/(m) calculated according to inlet and outlet water3D), the nitrate nitrogen in the treated water can be reduced to 35mg/L from 6588mg/L, the removal rate of nitrate nitrogen reaches more than 98%, and the removal rate of methanol reaches 96%.
It should be noted that the above-mentioned embodiments are only for explaining the present invention, and do not constitute any limitation to the present invention. The present invention has been described with reference to exemplary embodiments, but the words which have been used herein are words of description and illustration, rather than words of limitation. The invention can be modified, as prescribed, within the scope of the claims and without departing from the scope and spirit of the invention. Although the invention has been described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein, but rather extends to all other methods and applications having the same functionality.
Claims (10)
1. A method of treating high-concentration nitrate-nitrogen wastewater, comprising:
step S1, adding a carbon source and nitrogen and phosphorus nutrient salts into nitrate radical wastewater, and then adjusting the pH of the wastewater to 2-4 to obtain pretreated wastewater;
step S2, mixing the pretreated wastewater with circulating water, introducing the obtained mixed water into an anoxic expansion bed device to enable the mixed water to be in contact with biological fillers for denitrification reaction, and obtaining denitrification-treated wastewater;
wherein, the circulating water is a product obtained by carrying out denitrification reaction on the pretreated wastewater and the biological filler.
2. The method as claimed in claim 1, wherein the concentration of nitrate in the nitrate wastewater is 3000-30000 mg/L.
3. The method according to claim 1 or 2, further comprising step S3, performing an intermittent gas wash on the biological filler; preferably, the time interval of the air washing is 3-90min, and/or the intensity of the air washing is 8-15L/m2S, and/or the time of a single gas wash is 0.5-3 min.
4. A method according to any one of claims 1-3, characterized in that the diameter of the biological filler is 2.5-3.0mm, preferably the biological filler is a polished and degreased biological filler.
5. The method according to any one of claims 1 to 4, wherein the carbon source is added in step S1 so that the mass concentration ratio of COD to nitrate nitrogen is (3.0-5.0):1, preferably (3.1-4.7):1, more preferably (3.4-4.5):1, and preferably the carbon source is methanol.
6. The method of any one of claims 1-5The method is characterized in that the nitrogen and phosphorus nutritive salt is added in the step S1 after the carbon source, preferably, the nitrogen and phosphorus nutritive salt is added in the step S1 to ensure that the COD, the N: P, is (200) -400, the mass concentration of 5:1 and N, P is N, P elements respectively, and preferably, the nitrogen nutritive salt is selected from ammonia water and/or urea; and/or, the phosphorus nutrient salt is selected from KH2PO4And/or Na3PO4。
7. The method of any one of claims 1 to 6, wherein the anoxic expanded bed arrangement comprises a feed tank, an anoxic expanded bed reactor and a nitrogen purge system,
the anoxic expanded bed reactor comprises a supporting layer, a filling zone, a transition section and a water outlet zone which are sequentially arranged from bottom to top, wherein a three-phase separator is arranged in the water outlet zone; the bottom end of the anoxic expanded bed reactor is provided with a water inlet/gas port, the upper part of the water outlet area is provided with a water outlet, preferably the water outlet is arranged on the side wall of the upper part of the water outlet area, and the water inlet end of the water outlet is provided with a water outlet filter screen;
the feeding tank is connected with a water inlet/gas outlet of the anoxic expansion bed reactor through a feeding pipe, a feeding pump is arranged on the feeding pipe, and the wastewater in the feeding tank is conveyed into the anoxic expansion bed reactor through the feeding pump; the water outlet of the anoxic expanded bed reactor is connected with a feeding pipe through a circulating water pipe, and a circulating pump is arranged on the circulating water pipe;
the nitrogen cleaning system comprises a nitrogen automatic control device, a nitrogen making machine system and a gas flowmeter, the nitrogen making machine system comprises a nitrogen making machine and a nitrogen storage tank, the nitrogen making machine is connected with the nitrogen storage tank, the nitrogen automatic control device regulates and controls the nitrogen making machine system through a time and flow control system to realize automatic control on the gas output quantity of nitrogen, the gas output time interval and the single gas output time, the nitrogen storage tank is connected with a water inlet/gas outlet through a gas inlet pipe, and the gas flowmeter is arranged on the gas inlet pipe;
the device also comprises a pH meter, a thermometer and an ORP meter, wherein the pH meter, the thermometer and the ORP meter are arranged at the upper part of the water outlet zone.
8. The method according to claim 7, wherein the anoxic expanded bed device further comprises an ultrasonic cleaning device, the ultrasonic cleaning device comprises an ultrasonic probe, an ultrasonic transducer and an ultrasonic controller, the ultrasonic probe, the ultrasonic transducer and the ultrasonic controller are sequentially connected, the ultrasonic probe is arranged near the water outlet of the anoxic expanded bed reactor, and preferably the ultrasonic probe is arranged outside the water outlet filter screen.
9. The method as claimed in claim 7 or 8, wherein the anoxic expanded bed device further comprises a heating device, the heating device comprises a reactor jacket, a heater and a heating pump, the reactor jacket is sleeved outside the supporting layer and the filler region, the bottom end of the reactor jacket is provided with a hot water inlet, and the upper end of the reactor jacket is provided with a hot water outlet; the hot water inlet is connected with one end of the heater through the heating pump, and the hot water outlet is connected with the other end of the heater;
and/or the three-phase separator comprises a central pipe and a cover body, wherein the cover body comprises an upper cover body and a lower cover body, and the upper cover body and the lower cover body are connected through a connecting piece and form an overflowing channel; the upper cover body and the lower cover body are in an inverted funnel shape, and the necking end of the upper cover body is connected with the central pipe.
10. The process according to any one of claims 7 to 9, wherein the cross-sectional area of the packing section is smaller than the cross-sectional area of the effluent section, preferably the cross-section of the anoxic expanded bed reactor is circular, and the transition section gradually increases in diameter from bottom to top.
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