Wastewater treatment device and method with adaptive addition of nano-iron

Abstract

The present invention discloses a wastewater treatment device and method for adaptively adding nano-iron. In this device, water in a wastewater regulating tank is connected to the bottom of an anaerobic reactor and a pulse water distributor via pipelines. The anaerobic reactor is provided with a circulating water pump to circulate the wastewater from the upper and lower layers. The anaerobic reactor is also provided with a distributor, which is connected to a nano-iron mixing tank via a pipeline to enable the addition of nano-iron. In this method, the concentration of nano-zero-valent iron in the anaerobic reactor is determined based on the biodegradability of the influent. This method addresses the shortcomings of nano-zero-valent iron in the wastewater biological treatment process, such as its low utilization rate and microbial inhibition caused by its easy aggregation and strong irritation when actually used. By designing a continuous, low-dose dynamic input device and method, the actual utilization efficiency is improved, the use cost is reduced, and the activity of the microbial system is enhanced.

Description

Technical Field

[0001] The present 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] Currently, high-concentration organic wastewater generated by industrial activities is primarily treated by biochemical methods, with anaerobic digestion being a widely used technology due to its cost-effectiveness and ability to recover biogas. However, with the rapid rise of large-scale, integrated industrial parks, the efficiency of organic wastewater treatment is facing significant challenges. Analyzing the root causes, there are two main reasons for the poor treatment results:

[0003] 1. In general integrated parks, the 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. Microorganisms lack the necessary nutrients to maintain their own metabolic activities, so the expected treatment efficiency cannot be achieved.

[0005] The current approach to solving this problem is to improve sludge stability in anaerobic systems and tap into the metabolic potential of microorganisms. There are two main approaches:

[0006] (1) Regulating operating conditions and screening highly adaptable microbial flora to improve 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 an inexpensive and readily available environmentally friendly nanomaterial, has been applied in fields such as groundwater and soil remediation. Due to its high reactivity and its ability to serve as an excellent electron donor, it has shown great potential in the field of wastewater treatment. Chinese patent CN117486363B discloses a method for using nano-zero-valent iron to enhance the anaerobic digestion of sulfonamide wastewater, significantly shortening the degradation time of sulfonamide wastewater. Chinese invention patent CN115583773A discloses a method for using nano-zero-valent iron to increase methane production during anaerobic digestion of sludge. Nano-zero-valent iron can flocculate and adsorb on extracellular polymers surrounding anaerobic microorganisms, thereby protecting the cell membranes of most active microorganisms 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 based on direct addition, which will cause two problems:

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

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

[0012] Both of the above 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 present invention aims to provide a biochemical treatment device and method for industrial organic wastewater to overcome the drawbacks of existing technologies, such as high cost and low utilization. This method utilizes a low-dose of nano-zero-valent iron to induce a reaction with sludge, and further separates the sludge using a pulsed mixing method. This enhances the selective binding of the nano-zero-valent iron with the sludge, thereby increasing its utilization rate. Summary of the Invention

[0014] In response to 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, 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 inlet, and a circulating water pump is provided in the anaerobic reactor to realize circulation of wastewater between the upper and lower layers; the device also comprises a pulse water distributor provided at the bottom of the anaerobic reactor, wherein the pulse water distributor draws water from the wastewater regulating tank through a pipeline; and a distributor is further provided in the anaerobic reactor, wherein the distributor is connected to a nano-iron mixing tank through a pipeline to realize the addition of nano-iron.

[0016] Furthermore, the device includes a pulse water distributor to mix the wastewater entering the pipeline with the wastewater connected to the bottom of the anaerobic reactor, and then combines the amount of nano-iron added by the distributor to realize the 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 jet is provided on the connecting pipe 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, and anaerobic digestion granular sludge is added.

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

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

[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 pipe. The hydraulic retention time is 12-24 hours;

[0023] S2. Control the periodic water inlet of the pulse ejector, including a pulse interval of 2-6 hours, a pulse period of 1-10 minutes, a pulse frequency of 3-10 times / minute, and a pulse water inlet volume of 0.5%-5% of the effective volume of the anaerobic reactor during the entire cycle;

[0024] S3. Add nano-zero-valent iron into a sealed mixing tank and set the stirring speed to 60-80 rpm to mix evenly. The concentration of nano-zero-valent iron added is 2.5-5.0 g / L.

[0025] S4. Using a water pump, lift the nano-zero-valent iron dispersion obtained in step S3 into a distributor, and control 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 jet are adjusted according to the concentration of nano-zero-valent iron in the anaerobic reactor:

[0034] If the nano-zero-valent iron concentration 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 ≥60 mg / L and <120 mg / L, adjust the pulse interval to 3-4 hours and the cycle to 3-7 minutes;

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

[0037] Furthermore, the pulse intensity of the pulse jet 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, adjust the pulse frequency to 6-10 times / minute, and the pulse water inflow during the entire cycle should be 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 existing technology, the present invention induces the reaction of nano-zero-valent iron with sludge by inputting low doses, and further sorts the sludge by using a 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 structural schematic diagram 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 is shown below:

[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, objectives and beneficial effects of the present invention, the technical solutions of the present invention are described in detail below in conjunction with the following specific embodiments, but they should not be construed as limiting the scope of implementation 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 and strong stimulation, resulting in low utilization rate and microbial inhibition when actually put into use, 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 of the present invention consists of a water inlet section, a biochemical section, and a feeding section. The water inlet section consists of a wastewater regulating tank 1 and a water inlet pump 2; the biochemical section 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; and the feeding section consists of a nano-iron mixing tank 9, an agitator 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 both 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. A water inlet pipe is set above it, and two water outlet pipes are set below it, which serve as the water inlet at the bottom of the upflow anaerobic reactor 5 and the water inlet pipe of the pulse water distributor 4 respectively. In the upflow anaerobic reactor 5, considering that it is impossible to use a stirrer or the like to mix the 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 wastewater, sludge and other particles can be realized. A pulse mixing zone, a sludge sorting zone and a contact reaction zone can be formed in the upflow anaerobic reactor 5, including the gradient distribution control of solid particles. The distributor 6 used in the present invention uses a porous water distribution pipe with a pore size 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 significant 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 effects of the prior art:

[0053] Patent document CN118812017A discloses a combined anaerobic and contact suspended filler device for treating high-difficulty wastewater. The device incorporates a stirring device inside the body to promote the reaction and contact between the feed and microorganisms. However, this existing device is not suitable for anaerobic digestion equipment for the following reasons: (1) If stirring is used to achieve sufficient contact between the granular sludge and the nano-zero-valent iron, a high stirring speed is required, which will generate large water flow shear forces 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 in large anaerobic digestion reactors, and the structural complexity increases, making maintenance more difficult. In addition, the anaerobic digestion reactor has a three-phase separation device at the top, which is difficult to accommodate 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 feed port and directly mixed before entering the granular sludge generator; the sludge is agglomerated 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 an anaerobic system. However, the following problems still exist: (1) Due to the need for three-phase separation, the anaerobic digestion reactor configuration is mainly upflow, so the nano-zero-valent iron mixed with the influent will directly sink to the bottom and cannot fully contact the granular sludge. In particular, the invention patent mentions that the directional enhancement of granular sludge with small specific gravity and small particle size cannot be achieved; (2) If the powder state is used, the dispersion is still insufficient, and the organic wastewater often fluctuates greatly and the water quality is complex. If the powder is drawn by the influent, it cannot be dynamically adjusted according to the water quality.

[0055] Example 2

[0056] The first test of the comprehensive wastewater from a nitrocellulose production enterprise revealed the following basic pollutant concentrations: CODCr (dichromate index) 421.5 mg / L, BOD5 (biochemical oxygen demand) 243 mg / L, TN (total nitrogen) 715 mg / L, and NO3--N (nitrate nitrogen) 610 mg / L. This represents a typical low C / N ratio wastewater with good biodegradability and high total nitrogen content. The wastewater was treated using the apparatus described in Example 1. The effective reaction volume of the upflow anaerobic reactor 5 was 10 L, and the treatment steps were 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 pulse ejector to inject 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 pulse water inflow during the entire cycle being 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 operation of the device, the reactor outlet water 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 CODCr removal rate reached 84.49%, a 46.10% increase compared to the blank control group without nano-zero-valent iron. The effluent quality was also more stable, demonstrating that the system has improved its adaptability to organic wastewater inflow. This example demonstrates that the device and method described herein can achieve excellent treatment results when treating typical low-C / N ratio organic wastewater.

[0063] Example 3

[0064] The first test of the comprehensive wastewater from a surface treatment industrial park revealed the following pollutant concentrations: CODCr 834 mg / L, BOD 5215 mg / L, TN 120 mg / L, and NO₃--N 64 mg / L, representing typical low-biodegradability wastewater. The wastewater was treated using the apparatus described in Example 1. The effective reaction volume of the upflow anaerobic reactor 5 was 10 L, and the treatment steps were 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 pulse ejector to inject 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 pulse water inflow during the entire cycle being 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 CODCr concentration of the reactor outlet water was measured at regular intervals, 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 reached 77.25%, and the effluent water quality was stable. This embodiment shows that the device and method of the present invention can achieve good treatment effects when treating typical low-biodegradable organic wastewater.

[0071] Example 4

[0072] The first test of the wastewater from a biopharmaceutical company revealed the following pollutant concentrations: CODCr 203 mg / L, BOD 590 mg / L, TN 52 mg / L, and NO₃--N 21 mg / L. This represents a typical organic wastewater with good biodegradability and low COD. The wastewater was treated using the apparatus described in Example 1. The effective reaction volume was 10 L, 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) Water was introduced using a pulsed ejector at fixed intervals, with the pulse interval set to 4 h, the pulse period set to 1 min, and the pulse frequency set to 3 times / min. The pulsed water volume during the entire cycle was 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 CODCr concentration of the reactor outlet water was measured at regular intervals. 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 water quality is stable. This embodiment shows that the device and method of the present invention can achieve good treatment effects when treating typical low-biodegradable organic wastewater.

[0079] Comparative Example 1

[0080] Wastewater treatment was performed using the apparatus 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 sealed 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.

[0083] 3) The nano-zero-valent iron dispersion obtained in step 2) was pumped into the distributor using a circulation pump, and the inflow rate was controlled so that the nano-zero-valent iron concentration in the reactor reached 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 only difference between Comparative Example 1 and Example 2 is that step (2) in Example 2 is omitted, i.e., water is not fed into the pulse jet 3. 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 over time is shown in the figure. 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] Wastewater treatment was performed using the apparatus 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 to 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 only difference between Comparative Example 2 and Example 2 is that 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, the average CODCr removal rate reached 59.35%. Furthermore, the initial effluent CODCr concentration was abnormal and the effluent quality was unstable. This was likely due to the inhibitory effect of the high-dose nano-zero-valent iron on the system. As the reaction progressed, the microbial community evolved adaptively, gradually adapting 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. A circulating pump feeds the nano-zero-valent iron mixture into the reactor. By controlling the flow rate, the real-time dosage of nano-zero-valent iron in the reactor can be adjusted, flexibly adapting to fluctuations in organic wastewater and saving costs. When the incoming water quality deteriorates and the anaerobic digestion system is ineffective, the nano-zero-valent iron input can be increased immediately to maintain microbial activity and improve effluent quality. When the incoming water quality is highly biodegradable, the nano-zero-valent iron input can be reduced to reduce costs.

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

[0097] 4. The pulsed sludge mixing structure ensures efficient and thorough mixing of nano-zero-valent iron and sludge, while also achieving sludge sorting based on the difference in sedimentation velocity, strengthening contact with the upper layer of granular sludge with small specific gravity and small particle size, and improving the utilization efficiency of nano-zero-valent iron.

Claims

1. A biochemical treatment method for organic wastewater with adaptive addition of nano-iron, characterized in that: The method is used to control the adaptive addition of nano-iron to a wastewater treatment device. The wastewater treatment device includes a wastewater regulating tank. Water in the wastewater regulating tank is connected to the bottom of an anaerobic reactor through pipelines to control water inflow. A circulating water pump is provided in the anaerobic reactor to achieve circulation of wastewater in upper and lower layers. The method is characterized in that the device also includes a pulse water distributor provided at the bottom of the anaerobic reactor, the pulse water distributor draws water from the wastewater regulating tank through a pipeline. The anaerobic reactor is also provided with a distributor, which is connected to a nano-iron mixing tank through a pipeline to achieve the addition of nano-iron. The addition of nano-iron is determined according to the biodegradability of the influent. The device includes a pulse water distributor to achieve mixing of wastewater entering the pipeline and the bottom connection pipeline of the anaerobic reactor, and then combined with the amount of nano-iron added by the distributor to achieve the partitioning 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; The method performs the following operations based on the above-mentioned wastewater treatment device: 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 pipe. The hydraulic retention time is 12-24 hours; S2. Control the pulse ejector to periodically feed water, with a pulse interval of 2-6 hours, a pulse period of 1-10 minutes, a pulse frequency of 3-10 times / minute, and a pulse water volume of 0.5% - 5% of the effective volume of the anaerobic reactor during the entire cycle; S3. Add nano-zero-valent iron to a sealed mixing tank and set the stirring speed to 60-80 rpm to mix evenly. The concentration of nano-zero-valent iron added is 2.5-5.0 g / L. S4. Using a water pump, lift the nano-zero-valent iron dispersion obtained in step S3 into a distributor, and control 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 below 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. The reflux ratio of the circulating water pump on the anaerobic reactor is adjusted as follows 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; The pulse interval and period of the pulse jet are adjusted as follows according to the concentration of nano-zero-valent iron in the anaerobic reactor: If the nano-zero-valent iron concentration 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 ≥60 mg / L and <120 mg / L, adjust the pulse interval to 3-4 hours and the cycle to 3-7 minutes; If the nano-zero-valent iron concentration is less than 60 mg / L, adjust the pulse interval to 4-6 hours and the cycle to 1-3 minutes; The pulse intensity of the pulse jet 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, adjust the pulse frequency to 6-10 times / minute, and the pulse water inflow during the entire cycle should be 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.

2. The method for biochemical treatment of organic wastewater according to claim 1, characterized in that: The method includes adding clean water and introducing nitrogen for 20 minutes before adding nano zero-valent iron into a closed mixing tank to ensure that the tank is in an oxygen-free state.

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