Wastewater treatment device and method capable of adaptively adding nano-iron

Abstract

The invention discloses a wastewater treatment device and method capable of adaptively adding nano-iron, in the device, water in a wastewater adjusting tank is respectively connected with the bottom of an anaerobic reactor and a pulse water distributor through pipelines, and a circulating water pump is arranged in the anaerobic reactor to realize circulation of wastewater at the upper layer and the lower layer; a distributing device is also arranged in the anaerobic reactor and is connected with the nano-iron mixing tank through a pipeline so as to realize addition of nano-iron. According to the method, the concentration of nano zero-valent iron in an anaerobic reactor is determined according to the biodegradability of inlet water, so that the defects that the utilization rate is low, microbial inhibition is caused and the like due to the fact that the nano zero-valent iron is easy to agglomerate and strong in stimulation during actual use in the wastewater biological treatment process are overcome; the actual utilization efficiency is improved, the use cost is reduced, and the activity of a microbial system is enhanced.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to a wastewater treatment device and method for adaptively adding nano-iron. Background Art

[0002] At present, high-concentration organic wastewater generated by industrial activities is mainly treated by biochemical methods, among which anaerobic digestion is one of the widely used technologies, which has the advantages of good cost-effectiveness and the ability to recover biogas. However, with the rapid rise of large-scale comprehensive industrial parks, the efficiency of organic wastewater treatment has been greatly challenged. From the root cause analysis, there are two reasons for the poor treatment effect:

[0003] 1. In general comprehensive parks, wastewater generated by various enterprises is collected and treated in a centralized manner, which makes the composition of organic wastewater complex and fluctuates frequently. After pretreatment, it enters the anaerobic digestion system, which still has a great impact on the microbial community, causing the inhibition of microbial metabolic activity or even death, and ultimately leading to the deterioration of the reactor operation condition.

[0004] 2. The organic wastewater of some enterprises has poor biodegradability or a low carbon-nitrogen ratio. The microorganisms lack the necessary nutrients to maintain their own metabolic activities, so the expected treatment efficiency cannot be achieved.

[0005] Nowadays, the solution to this problem is mainly from two perspectives: improving the sludge stability in the anaerobic system and tapping the metabolic potential of microorganisms. There are two main methods:

[0006] (1) Regulate the operating conditions and screen the microbial flora with strong adaptability to improve the adaptability to high-concentration organic wastewater. However, this method has the disadvantages of slow response and insufficient stability in practical applications.

[0007] (2) Introduce exogenous enhancement measures to enhance sludge by stimulating microbial metabolism or improving sludge stability.

[0008] Nano zero-valent iron, as a cheap and readily available environmentally friendly nanomaterial, is used in the fields of groundwater and soil remediation. Due to its high reactivity and the advantages of being an excellent electron donor, it shows great potential in the field of wastewater treatment. Chinese patent CN117486363B discloses a method for strengthening the anaerobic digestion of sulfonamide wastewater with nano zero-valent iron, which greatly shortens the degradation time of sulfonamide wastewater. Chinese invention patent CN115583773A discloses a method for increasing the methane production during the anaerobic digestion of sludge with nano zero-valent iron. Nano zero-valent iron can flocculate and adsorb on the extracellular polymers around anaerobic microorganisms, thereby protecting most active microbial cell membranes from contact damage, maintaining the stability of the anaerobic digestion system, and improving the efficiency of anaerobic digestion.

[0009] The above-mentioned prior arts show that the existing application method of nano zero-valent iron is mainly direct addition, which will cause two problems:

[0010] 1) After entering the water, nano-zero-valent iron will quickly aggregate and reduce its reactivity;

[0011] 2) Due to the high density of nano zero-valent iron, it will sink to the bottom after direct addition.

[0012] The above two points will significantly reduce the actual contact amount with the sludge, resulting in material waste. Usually the dosage is increased to ensure the effect, but the cost of use is significantly increased.

[0013] Therefore, the purpose of the present invention is to provide an industrial organic wastewater biochemical treatment device and treatment method to overcome the defects of high cost and low utilization rate in the prior art. The present invention inputs a low dose of nano zero-valent iron to induce reaction with sludge, and further sorts the sludge by pulse mixing method, thereby strengthening the selective combination of nano zero-valent iron and sludge and improving the utilization rate of nano zero-valent iron. Summary of the invention

[0014] In view of the above-mentioned defects, the present invention aims to provide a wastewater treatment device and method with adaptive addition of nano-iron. First, the agglomeration problem of nano-zero-valent iron is solved by improving the device. Second, how to optimally control the lowest cost and efficient biochemical treatment problem is considered to improve the utilization rate of nano-zero-valent iron.

[0015] Technical solution: A wastewater treatment device with adaptive addition of nano-iron, the device includes a wastewater regulating tank, the water in the wastewater regulating tank is connected to the bottom of the anaerobic reactor through pipelines to control the water inlet, and a circulating water pump is arranged in the anaerobic reactor to realize the circulation of upper and lower wastewater; the device also includes a pulse water distributor arranged at the bottom of the anaerobic reactor, the pulse water distributor takes water from the wastewater regulating tank through a pipeline; the anaerobic reactor is also provided with a distributor, which is connected to the nano-iron mixing tank through a pipeline to realize the addition of nano-iron.

[0016] Furthermore, the device includes a pulse water distributor to achieve mixing of wastewater entering the pipeline with the bottom connecting pipeline of the anaerobic reactor, and then combining the amount of nano-iron added by the distributor to achieve zoning of the wastewater mixture in the anaerobic reactor, which is divided into a pulse mixing zone, a sludge sorting zone and a contact reaction zone.

[0017] Furthermore, the wastewater regulating tank is used to adjust the pH value of the wastewater, and a pulse ejector is provided on the connecting pipeline between the wastewater regulating tank and the bottom of the anaerobic reactor;

[0018] The water distributor adopts a semi-spherical reflector structure and is provided with a multi-hole water distribution pipe, which can improve the wastewater mixing effect and realize the stratification of particles in the wastewater.

[0019] Furthermore, the anaerobic reactor is an upflow anaerobic reactor, to which anaerobic digestion granular sludge is added.

[0020] The nano-iron mixing tank is provided with a stirrer, and a flow regulating control mechanism is provided on the pipeline between the stirrer and the anaerobic reactor.

[0021] The present invention also provides a method for biochemical treatment of organic wastewater by adaptively adding nano-iron, based on the above-mentioned industrial organic wastewater biochemical treatment device, performing the following operations:

[0022] S1. Adjust the pH of the wastewater in the inlet pool to 7-7.5, and pump the wastewater into the bottom of the anaerobic reactor through the inlet pipeline. The hydraulic retention time is 12-24h;

[0023] S2, control the pulse ejector to periodically infuse water, including a pulse interval of 2-6 hours, setting the pulse period to 1-10 minutes, the pulse frequency to 3-10 times / minute, and the pulse water inflow during the entire period to 0.5%-5% of the effective volume of the anaerobic reactor;

[0024] S3, adding nano zero-valent iron into a closed mixing tank, setting the stirring speed to 60-80 rpm to mix evenly, and the concentration of nano zero-valent iron added is 2.5-5.0 g / L;

[0025] S4, using a water pump to lift the nano zero-valent iron dispersion obtained in step S3 into a distributor, and controlling the inflow rate so that the nano zero-valent iron concentration in the reactor reaches 20-150 mg / L;

[0026] S5. During the operation of the anaerobic reactor, the upper liquid is continuously refluxed to the lower part through a circulation pump, and the reflux ratio is set to 6-20:1;

[0027] The concentration of nano zero-valent iron in the anaerobic reactor is determined according to the biodegradability of the influent. If the BOD5 / COD ratio is ≤0.3, the concentration of nano zero-valent iron in the anaerobic reactor is increased to 150 mg / L; if the BOD5 / COD ratio is between 0.3-0.5, the concentration in the anaerobic reactor is adjusted to 60-120 mg / L; if the BOD5 / COD ratio is ≥0.5, the concentration in the anaerobic reactor is controlled at 20-60 mg / L.

[0028] In this method, before adding nano zero-valent iron into a closed mixing tank, clean water is added and nitrogen is introduced for 20 minutes to ensure that the tank is in an oxygen-free state.

[0029] Furthermore, the reflux ratio of the circulating water pump on the anaerobic reactor is adjusted according to the concentration of nano zero-valent iron:

[0030] If the nano zero-valent iron concentration is ≥120 mg / L, adjust the reflux ratio to 20:1;

[0031] If the nano zero-valent iron concentration is ≥60 mg / L and <120 mg / L, adjust the reflux ratio to 10:1;

[0032] If the concentration of nano zero-valent iron is less than 60 mg / L, adjust to 6:1.

[0033] Furthermore, the pulse interval and period of the pulse ejector are adjusted according to the concentration of nano zero-valent iron in the anaerobic reactor:

[0034] If the concentration of nano zero-valent iron is ≥120 mg / L, adjust the pulse interval to 2-3 hours and the cycle to 5-10 minutes;

[0035] If the nano zero-valent iron concentration is ≥60mg / L and <120mg / L, adjust the pulse interval to 3-4h and the cycle to 3-7 minutes;

[0036] If the concentration of nano zero-valent iron is less than 60 mg / L, the pulse interval is adjusted to 4-6 hours and the cycle is 1-3 minutes.

[0037] Furthermore, the pulse intensity of the pulse ejector is adjusted according to the height-to-diameter ratio of the anaerobic reactor:

[0038] If the height-to-diameter ratio of the anaerobic reactor is greater than 4, the pulse frequency is adjusted to 6-10 times / minute, and the pulse water inflow during the entire cycle is 2%-5% of the effective volume of the anaerobic reactor;

[0039] If the height-to-diameter ratio of the anaerobic reactor is greater than 2 and less than or equal to 4, the pulse frequency is adjusted to 3-6 times / minute, and the pulse water inflow during the entire cycle is 0.5%-2% of the effective volume of the anaerobic reactor.

[0040] Beneficial effects: Compared with the prior art, the present invention induces the reaction between nano-zero-valent iron and sludge by inputting low-dose nano-zero-valent iron, and further sorts the sludge by pulse mixing method, thereby strengthening the selective combination of nano-zero-valent iron and sludge and improving the utilization rate of nano-zero-valent iron. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram of the structure of the device of the present invention;

[0042] Figure 2 The relationship between CODCr removal rate and time in Example 2 of the present invention;

[0043] Figure 3 The relationship between CODCr removal rate and time in Example 3 of the present invention;

[0044] Figure 4The relationship between CODCr removal rate and time in Example 4 of the present invention;

[0045] Figure 5 The relationship between CODCr removal rate and time in Comparative Example 1 of the present invention;

[0046] Figure 6 This is the relationship between CODCr removal rate and time in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0047] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical scheme of the present invention is now described in detail in conjunction with the following specific embodiments, but it should not be understood as limiting the applicable scope of the present invention.

[0048] Combined with the application of existing technologies, we know that the role of nano zero-valent iron in wastewater treatment mainly includes reduction, adsorption and precipitation. However, in the process of wastewater biological treatment, nano zero-valent iron encounters the disadvantages of easy agglomeration, strong stimulation resulting in low utilization rate and microbial inhibition when actually used, resulting in low efficiency and quality of wastewater biological treatment, and thus high cost of use.

[0049] Example 1

[0050] This embodiment is to introduce the device structure of the present invention. Figure 1 As shown, the device described in the present invention is composed of a water inlet part, a biochemical part and a feeding part. The water inlet part is composed of a wastewater regulating tank 1 and a water inlet pump 2; the biochemical part includes a pulse ejector 3, a pulse water distributor 4, an upflow anaerobic reactor 5, a distributor 6, a reflux circulation pump 7, a three-phase separator 8, a water outlet 13, and an air outlet 14; the feeding part is composed of a nano iron mixing tank 9, a stirrer 10, a feeding port 11 and a water inlet pump 12.

[0051] The wastewater regulating tank 1 and the nano-iron mixing tank 9 are connected to the upflow anaerobic reactor 5 through pipelines. The wastewater regulating tank 1 is used for pH value regulation, with water inlet at the upper end and water outlet at the lower end. An inlet pipe is arranged above it, and two outlet pipes are arranged below it, which are respectively used as the water inlet at the bottom of the upflow anaerobic reactor 5 and the water inlet pipe of the pulse water distributor 4. In the upflow anaerobic reactor 5, considering that it is impossible to use a stirrer or the like to mix wastewater, the present invention proposes to use a pulse water distributor 4, and set a pulse ejector 3 on its pipeline for control. The pulse water distributor 4 adopts a semi-spherical reflector structure. The combination of the two can realize the liquid stirring work in the pulse mixing zone of the lower layer of the anaerobic reactor 5. Based on the control of the mixing process, the stratification of other particles such as wastewater and sludge can be realized. In the upflow anaerobic reactor 5, a pulse mixing zone, a sludge sorting zone, and a contact reaction zone can be formed, including the gradient distribution control of solid particles. The distributor 6 used in the present invention uses a porous water distribution pipe with an aperture of 3-5mm. The nano-iron mixing tank 9 is a cylindrical sealed tank, wherein the agitator 10 is made of non-magnetic material, which can be polytetrafluoroethylene or austenitic stainless steel. Anaerobic digestion granular sludge is added to the upflow anaerobic reactor 5 .

[0052] It is further pointed out that the remarkable effect of the device of the present invention on the stirring mechanism (pulse water distributor 4) inside the anaerobic reactor can be analyzed in combination with the disclosure and use effect of the prior art:

[0053] Patent document CN118812017A discloses an anaerobic and contact type suspended filler combined equipment for high-difficulty wastewater treatment. A stirring device is designed inside the body to promote the reaction contact between the feed and the microorganisms. However, this existing device is not suitable for anaerobic digestion devices for the following reasons: (1) If stirring is used to achieve full contact between the granular sludge and the nano zero-valent iron, a higher stirring speed is required, which will bring about a large water flow shear force and cause the granular sludge to break up. If the speed is reduced, the nano zero-valent iron will sink to the bottom due to insufficient stirring force. (2) The built-in stirring device is not practical enough in large anaerobic digestion reactors, the structural complexity is increased, and the maintenance is difficult. In addition, the anaerobic digestion reactor has a three-phase separation device at the top, which is difficult to be compatible with the stirring device.

[0054] Chinese invention patent CN116924567A discloses a sewage treatment system and sewage treatment method based on granular sludge, wherein activated carbon particles are drawn into the water inlet pipe through the feeding port and directly mixed and then enter the granular sludge generator; the sludge is condensed and screened by forming a vortex in the granular sludge generator. From the design concept, this technology realizes the mixing of powdered activated carbon materials with granular sludge in the anaerobic system. However, the following problems still exist: (1) Due to the need for three-phase separation, the configuration of the anaerobic digestion reactor is mainly upflow, so the nano zero-valent iron mixed with the influent will sink directly to the bottom and cannot fully contact with the granular sludge. In particular, the invention patent mentions that directional strengthening of granular sludge with small specific gravity and small particle size cannot be achieved; (2) If the powder state is used, the dispersibility is still not sufficient, and the organic wastewater often fluctuates greatly and the water quality is complex. It is impossible to dynamically adjust according to the water quality of the incoming water by relying on the influent to suck the powder.

[0055] Example 2

[0056] The comprehensive wastewater of a nitrocellulose production enterprise was tested for the first time. The basic conditions of the water pollutant concentrations were: CODCr (dichromate index) 421.5 mg / L, BOD5 (biochemical oxygen demand) 243 mg / L, TN (total nitrogen) 715 mg / L, NO3--N (nitrate nitrogen) 610 mg / L. It is a typical low C / N ratio wastewater with good biodegradability and high total nitrogen. We used the device described in Example 1 to treat the wastewater. The effective reaction volume of the upflow anaerobic reactor 5 is 10L, and the treatment steps are as follows:

[0057] (1) Adjust the pH of the wastewater in the inlet pool to between 7 and 7.5, and pump the wastewater into the bottom of the anaerobic reactor through a circulation pump with a hydraulic retention time of 16 hours.

[0058] (2) Use a pulsed ejector to feed water at fixed intervals, with the pulse interval set to 5 h, the pulse period set to 2 min, the pulse frequency set to 5 times / min, and the pulsed water volume during the entire cycle set to 1% of the effective volume of the anaerobic reactor;

[0059] (3) Add nano-zero-valent iron into a closed mixing tank and set the stirring speed to 80 rpm to mix evenly. The concentration of nano-zero-valent iron added is 2.5 g / L.

[0060] (4) The nano-zero-valent iron dispersion obtained in step (3) is lifted into the distributor using a circulation pump, and the inflow rate is controlled so that the nano-zero-valent iron concentration in the reactor reaches 50 mg / L.

[0061] (5) During the process, a circulating pump is used to continuously reflux the upper liquid to the lower part, and the reflux ratio is set to 6:1.

[0062] During the 30 days of the device operation, the reactor effluent was taken at regular intervals to measure CODCr. The relationship between the CODCr concentration of the inlet and outlet water and time is as follows: Figure 2 As shown, the average removal rate of CODCr reached 84.49%. Compared with the blank group without adding nano zero-valent iron, the average removal rate of CODCr increased by 46.10%, and the effluent water quality was more stable, indicating that the system has improved its adaptability to organic wastewater inflow. This embodiment shows that when using the device and method described in the present invention to treat typical low C / N ratio organic wastewater, good treatment effect can be achieved.

[0063] Example 3

[0064] The comprehensive wastewater of a surface treatment industrial park was tested for the first time. The basic conditions of the water pollutant concentrations were: CODCr834mg / L, BOD5215 mg / L, TN 120mg / L, NO3--N 64mg / L, which is a typical low biodegradable wastewater. The device described in Example 1 was used to treat the wastewater. The effective reaction volume of the upflow anaerobic reactor 5 is 10L, and the treatment steps are as follows:

[0065] (1) Adjust the pH of the wastewater in the inlet pool to between 7 and 7.5, and pump the wastewater into the bottom of the anaerobic reactor through a circulation pump with a hydraulic retention time of 24 hours.

[0066] (2) Use a pulsed ejector to feed water at fixed intervals, with the pulse interval set to 2 h, the pulse period set to 10 min, the pulse frequency set to 6 times / min, and the pulsed water volume during the entire cycle set to 2% of the effective volume of the anaerobic reactor;

[0067] (3) Add nano-zero-valent iron into a closed mixing tank and set the stirring speed to 80 rpm to mix evenly. The concentration of nano-zero-valent iron added is 5 g / L.

[0068] (4) The nano-zero-valent iron dispersion obtained in step (3) is lifted into the distributor using a circulation pump, and the inflow rate is controlled so that the nano-zero-valent iron concentration in the reactor reaches 150 mg / L.

[0069] (5) During the process, a circulating pump is used to continuously reflux the upper liquid to the lower part, and the reflux ratio is set to 20:1.

[0070] During the 30 days of operation of the device of the present invention, the effluent from the reactor was taken at regular intervals to measure the CODCr concentration, wherein the relationship between the CODCr concentration of the inlet and outlet water and time is as follows: Figure 3 As shown, the average removal rate of CODCr reaches 77.25%, and the effluent quality is stable. This embodiment shows that when using the device and method of the present invention to treat typical low-biodegradable organic wastewater, good treatment effect can be achieved.

[0071] Example 4

[0072] The comprehensive wastewater of a biopharmaceutical enterprise was tested for the first time. The basic conditions of its water quality pollutant concentrations were: CODCr203mg / L, BOD590 mg / L, TN 52mg / L, NO3--N 21mg / L. It is a typical organic wastewater with good biodegradability but low COD. The device described in Example 1 was used to treat the wastewater. The effective reaction volume was 10L, and the treatment steps were as follows:

[0073] (1) Adjust the pH of the wastewater in the inlet pool to between 7 and 7.5, and pump the wastewater into the bottom of the anaerobic reactor through a circulation pump with a hydraulic retention time of 12 hours.

[0074] (2) Use a pulsed ejector to feed water at fixed intervals, with the pulse interval set to 4 h, the pulse period set to 1 min, the pulse frequency set to 3 times / min, and the pulsed water volume during the entire cycle set to 0.5% of the effective volume of the anaerobic reactor;

[0075] (3) Add nano-zero-valent iron into a closed mixing tank and set the stirring speed to 80 rpm to mix evenly. The concentration of nano-zero-valent iron added is 5 g / L.

[0076] (4) The nano-zero-valent iron dispersion obtained in step (3) is lifted into the distributor using a circulation pump, and the inflow rate is controlled so that the nano-zero-valent iron concentration in the reactor reaches 20 mg / L.

[0077] (5) During the process, a circulating pump is used to continuously reflux the upper liquid to the lower part, and the reflux ratio is set to 6:1.

[0078] During the 30 days of the operation of the device, the reactor effluent was taken at regular intervals to measure the CODCr concentration. The relationship between the CODCr concentration of the inlet and outlet water and time is as follows: Figure 4 As shown, it can be seen that the average removal rate of CODCr reaches 87.10%, and the effluent quality is stable. This embodiment shows that when using the device and method described in the present invention to treat typical low-biodegradable organic wastewater, good treatment effects can be achieved.

[0079] Comparative Example 1

[0080] The wastewater treatment was carried out using the device described in Example 1. The effective reaction volume of the upflow anaerobic reactor 5 was 10 L, and the treatment steps were as follows:

[0081] 1) Adjust the pH of the wastewater in the inlet pool to between 7 and 7.5, and pump the wastewater into the bottom of the anaerobic reactor through a circulation pump with a hydraulic retention time of 16 hours.

[0082] 2) Add nano zero-valent iron into a closed mixing tank, and set the stirring speed to 80 rpm to mix evenly. The added concentration of nano zero-valent iron is 2.5 g / L.

[0083] 3) The nano zero-valent iron dispersion obtained in step 2) is lifted into the distributor using a circulation pump, and the inflow rate is controlled so that the nano zero-valent iron concentration in the reactor reaches 50 mg / L.

[0084] 4) During the process, a circulating pump is used to continuously reflux the upper liquid to the lower part, and the reflux ratio is set to 6:1.

[0085] The difference between Comparative Example 1 and the above-mentioned Example 2 is that step (2) in Example 2 is removed, that is, the pulse ejector 3 is not fed with water. The performance test is the same as that of Example 2. The relationship between the CODCr concentration and removal rate of the inlet and outlet water and time is as follows: Figure 5 As shown, the average removal rate of CODCr reached 75.54%, and the water quality stability did not change significantly compared with Example 2. Therefore, the treatment steps of Example 2 can achieve better treatment effects.

[0086] Comparative Example 2

[0087] The wastewater treatment was carried out using the device described in Example 1. The effective reaction volume of the upflow anaerobic reactor 5 was 10 L, and the treatment steps were as follows:

[0088] 1) Adjust the pH of the wastewater in the inlet pool to between 7 and 7.5, and pump the wastewater into the bottom of the anaerobic reactor through a circulation pump with a hydraulic retention time of 16 hours.

[0089] 2) Use a pulse ejector to inject water at fixed intervals, with the pulse interval set to 5 hours, the pulse period set to 2 minutes, the pulse frequency set to 5 times / minute, and the pulse water inflow during the entire cycle being 1% of the effective volume of the anaerobic reactor;

[0090] 3) 1 g of nano zero-valent iron powder was directly added into the reactor, and the nano zero-valent iron powder was replenished once a day, with each replenishment amount being 1 g.

[0091] 4) During the process, a circulating pump is used to continuously reflux the upper liquid to the lower part, and the reflux ratio is set to 6:1.

[0092] The difference between Comparative Example 2 and the above-mentioned Example 2 is that the nano zero-valent iron powder is added once during the treatment process, that is, steps (3) and (4) in Example 2 are adjusted. The performance test is the same as that in Example 2. The relationship between CODCr removal rate and time is as follows Figure 6As shown, it can be seen that the average removal rate of CODCr reached 59.35%. In addition, the initial effluent CODCr concentration was abnormal and the effluent water quality was unstable, which should be caused by the inhibitory effect of high-dose nano-zero-valent iron on the system. As the reaction proceeded, the microbial community evolved adaptively and gradually adapted to the high-dose nano-zero-valent iron impact.

[0093] In summary, embodiments 1-4 above can achieve the following significant technical effects.

[0094] 1. In the present invention, nano zero-valent iron is first dispersed evenly in water before being put into use. Compared with the method of adding powder in solid state, the dispersion effect is good, the waste caused by material agglomeration is reduced, and the utilization rate of nano zero-valent iron is improved.

[0095] 2. Use a circulating pump to input the nano zero-valent iron mixed liquid into the reactor. The real-time dosage of nano zero-valent iron in the reactor can be adjusted by controlling the flow rate, which can flexibly adapt to the fluctuation of organic wastewater and save the cost of use. When the incoming water quality deteriorates and the anaerobic digestion system has poor treatment effect, the input of nano zero-valent iron can be increased immediately to maintain the activity of microorganisms and improve the effluent quality; when the incoming water quality is highly biodegradable, the input of nano zero-valent iron can be reduced to reduce costs.

[0096] 3. Nano-zero-valent iron is continuously fed into the reactor at low doses, avoiding instantaneous high-dose stimulation after conventional direct addition, thereby reducing oxidative stress and microbial damage. At the same time, it ensures moderate stimulation to improve microbial activity.

[0097] 4. The pulsed sludge mixing structure not only ensures efficient and thorough mixing of nano zero-valent iron and sludge, but also realizes sludge sorting according to the difference in sedimentation velocity, strengthens the contact with the upper layer of granular sludge with small specific gravity and small particle size, and improves the utilization efficiency of nano zero-valent iron.

Claims

1. A wastewater treatment device with adaptive addition of nano-iron, comprising a wastewater regulating tank, wherein the water in the wastewater regulating tank is connected to the bottom of an anaerobic reactor through pipelines to control water inflow, and a circulating water pump is provided in the anaerobic reactor to realize the circulation of wastewater in upper and lower layers; characterized in that: The device also includes a pulse water distributor at the bottom of the anaerobic reactor, and the pulse water distributor takes water from the wastewater regulating tank through a pipeline; the anaerobic reactor is also provided with a distributor, and the distributor is connected to the nano-iron mixing tank through a pipeline to achieve the addition of nano-iron, and the addition of nano-iron is determined according to the biodegradability of the influent water; The device includes a pulse water distributor to achieve mixing of wastewater entering the pipeline with the bottom connection pipeline of the anaerobic reactor, and then combining the amount of nano iron added by the distributor to achieve zoning of the wastewater mixture in the anaerobic reactor, which is divided into a pulse mixing zone, a sludge sorting zone and a contact reaction zone.

2. The wastewater treatment device with adaptive addition of nano-iron according to claim 1, characterized in that: The wastewater regulating tank is used to adjust the pH value of the wastewater, and a pulse ejector is provided on the connecting pipeline between the wastewater regulating tank and the bottom of the anaerobic reactor; The water distributor adopts a semi-spherical reflector structure and is provided with a multi-hole water distribution pipe, which can improve the wastewater mixing effect and realize the stratification of particles in the wastewater.

3. The wastewater treatment device with adaptive addition of nano-iron according to claim 1, characterized in that: The anaerobic reactor is an upflow anaerobic reactor, which is added with anaerobic digestion granular sludge.

4. The wastewater treatment device with adaptive addition of nano-iron according to claim 1, characterized in that: The nano-iron mixing tank is provided with a stirrer, and a flow regulating control mechanism is provided on the pipeline between the stirrer and the anaerobic reactor.

5. A biochemical treatment method for organic wastewater by adaptively adding nano-iron, characterized in that: The method is based on the wastewater treatment device with adaptive addition of nano-iron as claimed in claim 1 and performs the following operations: S1. Adjust the pH of the wastewater in the inlet pool to 7-7.5, and inject the wastewater into the bottom of the anaerobic reactor through the inlet pipeline. The hydraulic retention time is 12-24h; S2, control the pulse ejector to periodically inlet water, with a pulse interval of 2-6 hours, set the pulse period to 1-10 minutes, the pulse frequency to 3-10 times / minute, and the pulse water inflow during the entire period to be 0.5%-5% of the effective volume of the anaerobic reactor; S3, adding nano zero-valent iron into a closed mixing tank, setting the stirring speed to 60-80 rpm to mix evenly, and the concentration of nano zero-valent iron added is 2.5-5.0 g / L; S4, using a water pump to lift the nano zero-valent iron dispersion obtained in step S3 into a distributor, and controlling the inflow rate so that the nano zero-valent iron concentration in the reactor reaches 20-150 mg / L; S5. During the operation of the anaerobic reactor, the upper liquid is continuously refluxed to the lower part through a circulating pump, the reflux outlet is located lower than the height of the distributor, and the reflux ratio is set to 6-20:1; The concentration of nano zero-valent iron in the anaerobic reactor is determined according to the biodegradability of the influent. If the BOD5 / COD ratio is ≤0.3, the concentration of nano zero-valent iron in the anaerobic reactor is increased to 150 mg / L; if the BOD5 / COD ratio is between 0.3-0.5, the concentration in the anaerobic reactor is adjusted to 60-120 mg / L; if the BOD5 / COD ratio is ≥0.5, the concentration in the anaerobic reactor is controlled at 20-60 mg / L.

6. The method for biochemical treatment of organic wastewater according to claim 5, characterized in that: The method comprises the following steps: before adding nano zero-valent iron into a closed mixing tank, adding clean water and introducing nitrogen for 20 minutes to ensure that the tank is in an oxygen-free state.

7. The method for biochemical treatment of organic wastewater according to claim 5, characterized in that: The reflux ratio of the circulating water pump on the anaerobic reactor is adjusted according to the concentration of nano zero-valent iron: If the nano zero-valent iron concentration is ≥120 mg / L, adjust the reflux ratio to 20:1; If the nano zero-valent iron concentration is ≥60 mg / L and <120 mg / L, adjust the reflux ratio to 10:1; If the concentration of nano zero-valent iron is less than 60 mg / L, adjust to 6:

1.

8. The method for biochemical treatment of organic wastewater according to claim 5, characterized in that: The pulse interval and period of the pulse ejector are adjusted according to the concentration of nano zero-valent iron in the anaerobic reactor: If the concentration of nano zero-valent iron is ≥120 mg / L, adjust the pulse interval to 2-3 hours and the cycle to 5-10 minutes; If the nano zero-valent iron concentration is ≥60mg / L and <120mg / L, adjust the pulse interval to 3-4h and the cycle to 3-7 minutes; If the concentration of nano zero-valent iron is less than 60 mg / L, the pulse interval is adjusted to 4-6 hours and the cycle is 1-3 minutes.

9. The method for biochemical treatment of organic wastewater according to claim 5, characterized in that: The pulse intensity of the pulse ejector is adjusted according to the height-to-diameter ratio of the anaerobic reactor: If the height-to-diameter ratio of the anaerobic reactor is greater than 4, the pulse frequency is adjusted to 6-10 times / minute, and the pulse water inflow during the entire cycle is 2%-5% of the effective volume of the anaerobic reactor; If the height-to-diameter ratio of the anaerobic reactor is greater than 2 and less than or equal to 4, the pulse frequency is adjusted to 3-6 times / minute, and the pulse water inflow during the entire cycle is 0.5%-2% of the effective volume of the anaerobic reactor.

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