Device for promoting multi-path efficient phosphorus removal by bioelectrochemistry and application thereof

Abstract

The application discloses a device for promoting multi-path efficient phosphorus removal by bioelectrochemistry and application thereof, wherein the device is provided with an iron oxide-iron-carbon felt composite anode in an anode chamber and a carbon brush cathode in a cathode chamber. The anode electrode of the application adopts the iron oxide-iron-carbon felt composite anode, which has the characteristics of corrosion resistance, more Fe(II) dissolution, improved Fe(II) bio-release efficiency of iron oxide, and high enrichment efficiency of electrogenic bacteria compared with the single iron anode and iron oxide anode, greatly prolongs the service life of the anode electrode, and reduces the operation cost of the system; and the carbon felt as the carrier of iron oxide can better enrich microorganisms and improve the phosphorus removal effect of the system; the application can be applied to phosphorus resourceization and efficient removal of phosphorus-containing waste water such as urban sewage, rural domestic sewage and industrial waste water, is environmentally friendly and safe, has low cost, is easy to maintain, and has the characteristics of fast removal rate and low cost.

Description

TECHNICAL FIELD

[0001] The application relates to a device for promoting multi-path efficient phosphorus removal by using bioelectrochemistry and an application thereof, and belongs to the field of biological electrochemical treatment of wastewater. BACKGROUND

[0002] At present, China's water ecological environment is facing severe challenges, and the problem of blue-green algae bloom and water ecological imbalance caused by the continuous accumulation of phosphorus still exists. The ecological problems such as water environment deterioration and biodiversity reduction and the economic and safety losses caused thereby have attracted more and more attention to the phosphorus pollution problem in water bodies. According to the Ecological Environment Statistical Yearbook released by the Ministry of Ecological Environment of China in 2022, the total phosphorus discharge in wastewater in China reached 346,000 tons. At the same time, phosphorus is also a nutrient element that is essential for the continuation of human life and the sustainable development of the ecological system. However, with the continuous development of economy, the exploitation of phosphorus ore by human beings has increased sharply, resulting in the depletion crisis of phosphorus ore, a non-renewable resource. The resource recycling of phosphorus is an effective measure to alleviate the phosphorus resource crisis. Therefore, the strengthened removal and resource recycling of phosphorus in wastewater have become important problems to be solved.

[0003] The phosphorus removal process used in traditional wastewater treatment plants mainly includes physical and chemical methods and biological methods. The physical and chemical methods include chemical precipitation, adsorption, and electrocoagulation. The chemical precipitation method has the defects of high cost of chemicals and operation, easy secondary pollution, and the like due to the addition of chemicals. The physical adsorption has the advantages of good instant effect and the need for additional cost for adsorption regeneration. The electrocoagulation has the problems of electrode passivation and high power consumption. The traditional biological phosphorus removal process based on anaerobic / aerobic alternation has a total phosphorus removal rate of generally 75-85%, and is easily affected by the fluctuation of influent water quality, so that the effluent is often difficult to meet the increasingly stringent phosphorus discharge standard. The traditional phosphorus removal process under the existing technology usually only transfers phosphorus from wastewater to other phases, and has a low recycling rate, and does not truly realize the recycling of phosphorus. Therefore, it is particularly important to develop a new type of technology for recycling and utilizing phosphorus elements in wastewater.

[0004] At the same time, the discharge standard of phosphorus in wastewater is continuously improved, and a single process has the problems of high energy consumption cost or unstable treatment that cannot meet the standard. Therefore, multiple processes often need to be cooperated to improve the removal and recovery of phosphorus in wastewater. The microbial fuel cell (MFC) can utilize the metabolic degradation of microorganisms to organic matters in wastewater to produce electrons, generate electricity from wastewater, and separate and recover nutrients, and is a sustainable, green and environmentally friendly bioelectrochemical system.

[0005] The current MFC system usually adopts carbon felt electrode, mainly relies on phosphorus absorption of polyphosphorus bacteria and addition of magnesium ions to form struvite precipitation for phosphorus removal, but there are still problems of long reaction time, limited phosphorus removal efficiency, high cost of external magnesium, harsh recovery conditions and low utilization rate. Low-cost iron or iron oxide is used as anode, which provides a new idea for multi-path high-efficiency phosphorus removal of MFC system. In the anode of MFC system, a large amount of Fe(II) is generated under the driving of iron sheet corrosion, which provides electrons for the system and generates precipitate chemical phosphorus removal with phosphate, and easy to produce blue vitriol as phosphorus recovery product; The dissolution of Fe2O3 is beneficial to the enrichment of iron-reducing bacteria, which can reduce Fe(III) to Fe(II) to release electrons to maintain its own metabolic activity, enhance power generation of the system, stimulate polyphosphorus bacteria and further strengthen biological phosphorus removal. Fe(II) dissolved by corrosion of iron sheet enters the cathode chamber through overflow and cation exchange membrane, and can be oxidized to Fe(III) as a flocculating agent to produce flocculation and precipitation with PO4 3- 、OH - in the cathode chamber, and further complete phosphorus element recovery. Under the support of power generation of MFC itself, dissolved oxygen generated by cathode aeration can be reduced to H2O2 on the surface of the electrode, which further reacts with Fe(II) permeated through the cation exchange membrane to produce hydroxyl radicals, and the electro-Fenton reaction provides a new way for removal of organic phosphorus in wastewater. However, due to the small amount of Fe2O3 dissolution, the fast corrosion speed of iron sheet and the lack of a stable carrier, if iron or iron oxide is used alone as anode, the problems of unstable phosphorus removal effect, short electrode service life and high cost often occur. SUMMARY

[0006] The technical problem solved by the present application is to provide a device for promoting multi-path high-efficiency phosphorus removal by bioelectrochemistry and application thereof.

[0007] Technical scheme: In order to solve the above technical problems, the present application provides a device for promoting multi-path high-efficiency phosphorus removal by bioelectrochemistry, which comprises an anode chamber, a cathode chamber and a cation exchange membrane arranged between the anode chamber and the cathode chamber, a water overflow pipe is arranged between the anode chamber and the cathode chamber, a carbon brush cathode is arranged in the cathode chamber, an iron oxide-iron-carbon felt composite anode is arranged in the anode chamber, the iron oxide-iron-carbon felt composite anode and the carbon brush cathode are connected by titanium wire, and a variable resistor is further connected to the titanium wire.

[0008] The iron oxide-iron-carbon felt composite anode is composed of carbon felt coated with iron oxide and iron sheet; the mass ratio of iron content in the iron sheet to the iron oxide is 1.5-2.5:1; if the proportion difference between the two metal materials of the anode is large, the electrode is more likely to be worn, which is not conducive to phosphorus treatment and recovery.

[0009] The preparation method of the iron oxide-iron-carbon felt composite anode comprises the following steps:

[0010] (1) Carbon felt treatment: after soaking the carbon felt, wash it with distilled water, ethanol and HCl respectively, and dry it;

[0011] (2) Preparation of iron oxide mixed solution: add Fe2O3, carbon black and polyvinylidene fluoride in N-methylpyrrolidone, and mix and ultrasonic;

[0012] (3) Anode preparation: take the iron oxide mixed solution in step (2) and smear it on the front and back of the treated carbon felt, dry it, combine it with the iron sheet, and fix it to obtain the iron oxide-iron-carbon felt composite anode.

[0013] In step (2), the mass ratio of N-methylpyrrolidone, Fe2O3, carbon black and polyvinylidene fluoride is 10:1:0.2-0.3:0.1-0.15.

[0014] The water outlet is arranged on the cathode chamber, and the aeration stone is arranged at the bottom of the cathode chamber, and the other end of the aeration stone is connected with the aeration pump.

[0015] The anaerobic sludge is put into the anode chamber, and the aerobic sludge is put into the cathode chamber.

[0016] The water inlet is arranged on the anode chamber, and the peristaltic pump is connected to the water inlet.

[0017] The application also provides a method for removing and / or recycling phosphorus in sewage by using the device, which comprises the following steps: starting the peristaltic pump to make the sewage enter the anode chamber from the water inlet, and setting the resistance value of the variable resistor to 5000Ω; the sewage treated by the anode chamber flows to the cathode chamber through the overflow pipe, the treated sewage flows out from the water outlet, and the next cycle of treatment is carried out; the total phosphorus and total iron content of the sewage are monitored once every two cycles; the dissolved oxygen (DO) in the cathode chamber is controlled to 3-4 mg / L by controlling the intermittent aeration of the aeration pump; when the TFe content in the anode water sample is lower than 6 mg / L for the first time, and the total phosphorus (TP) concentration of the system effluent exceeds 0.5 mg / L, the resistance value of the variable resistor is adjusted to 1000Ω; when the TFe content in the anode water sample is lower than 6 mg / L again, the resistance value of the variable resistor is adjusted to 200Ω, and the phosphorus element in the filtration recovery system is recovered after another cycle of treatment.

[0018] One cycle corresponds to a system hydraulic retention time of 8-12 h.

[0019] The molar ratio of iron in the iron oxide-iron-carbon felt composite anode to phosphorus in the sewage is 1.5-2.5:1.

[0020] The present application adopts iron oxide-iron-carbon felt composite anode, instead of traditional iron anode, combines iron and iron oxide with carbon felt in a reasonable proportion, on the one hand, the weak acidic environment of MFC anode can promote the corrosion of iron sheet, the electrode obtains a large amount of electrons, and the growth and reproduction of iron-reducing bacteria are enhanced, the electric bacteria are enriched on the surface of iron oxide, and then the electric bacteria are promoted, which is beneficial to stimulate the enhanced biological phosphorus removal of polyphosphorus bacteria; on the other hand, the dissolved Fe(II) of the iron sheet can efficiently combine with phosphate in the acidic environment of the MFC anode, generate blue vitriol precipitate, and perform chemical phosphorus removal to complete the recycling of phosphorus, and part of the unused Fe(II) enters the cathode chamber through overflow and cation exchange membrane, can be oxidized to Fe(III), as a flocculating agent, generates flocculation and precipitation with PO4 3- , OH- in the cathode chamber, further completes the recycling of phosphorus elements; in addition, the MFC cathode is aerated, H2O2 is generated under the oxidation condition, reacts with Fe(II) permeating into the cathode from the anode to generate hydroxyl radicals, the radicals oxidize organic phosphorus to form PO4 3- , and flocculation and precipitation are generated with the oxidized Fe(III), and the organic phosphorus is deeply removed and recycled.

[0021] On the other hand, the present application adjusts the ratio of iron and iron oxide in the anode electrode, and adjusts the resistance value of the external resistance, so as to regulate the electric production of the system and the yield of Fe(II), realizes the dynamic balance of the residual concentrations of iron and phosphorus, avoids excessive iron addition, keeps the colority of the effluent stable, and effectively reduces the energy consumption. The method and device improve the phosphorus removal efficiency of the MFC system through the organic integration of biology, electricity and chemistry, prolong the service life of the anode electrode, reduce the phosphorus removal cost, and realize the recycling of phosphorus resources.

[0022] The anaerobic sludge is added in the anode chamber, the volume ratio of the anaerobic sludge added in the anode chamber is 20%, the aerobic sludge is added in the cathode chamber, and the volume ratio of the aerobic sludge added in the cathode chamber is 20%.

[0023] Further, after the device is started, in the running process, the variable resistance is adjusted according to the water quality of the sewage, the TFe content in the anode, and the TP concentration of the system effluent, so as to ensure the phosphorus removal effect of the MFC system and recycle the phosphorus elements.

[0024] The present application adopts iron oxide-iron-carbon felt composite anode, and adjusts the relative content of iron oxide and iron sheet in the anode and the resistance value of the external resistance, so as to regulate the balance between the yield of Fe(II) and the conversion amount of PO4 3- , and solve the problems of high effluent colority and energy consumption loss caused by excessive iron addition, strengthen the electric production of the MFC system, reduce the electrochemical phosphorus removal cost, improve the phosphorus removal efficiency, and improve the resource utilization rate of phosphorus.

[0025] Working principle: as Figure 2As shown, the prepared iron oxide-iron-carbon felt composite anode 4 is connected with the carbon brush cathode 5 on the same variable resistor 7 using titanium wire 6, and the iron oxide-iron-carbon felt composite anode 4 and the carbon brush cathode 5 are respectively placed in the anode chamber 1 and the cathode chamber 2, and the anaerobic sludge domesticated in the anode chamber 1 is easy to adhere to the iron oxide-iron-carbon felt composite anode 4 and reduce the iron oxide to enrich the electricity-producing bacteria, before sewage treatment, the sewage is pumped into the anode chamber 1 from the water inlet 8 by starting the peristaltic pump 11, then the phosphorus in the sewage combines with the dissolved iron in the iron oxide-iron-carbon felt composite anode 4 to generate iron phosphorus precipitate to chemically remove phosphorus, the residual Fe(II) and Fe(III) flow into the cathode chamber 2 through the overflow pipe 10 with the effluent in the anode chamber 1, and part of them also migrate to the cathode chamber 2 through the cation exchange membrane 3, during the sewage treatment process, the cathode chamber 2 is intermittently aerated by the aeration pump 12, the sewage entering the cathode chamber 2 is first kept in an anaerobic state, the sludge in the cathode chamber 2 releases phosphorus first, and then is converted into an aerobic state by aeration, the sludge absorbs phosphorus in excess under the action of electric stimulation, at the same time, the Fe(II) in the cathode chamber 2 reacts with the oxidized H2O2 to generate hydroxyl radicals, oxidize organic phosphorus, and Fe(III) adsorbs phosphorus by forming Fe(OH)3 flocculation, and the phosphorus removal process is completed through biological and chemical actions, and the effluent is discharged from the water outlet 9 of the cathode chamber 2. During the sewage treatment process, the resistance of the variable resistor 7 is adjusted, the variable resistor is adjusted according to the water quality of the sewage, the TFe content in the anode and the TP concentration of the effluent of the system, to ensure the phosphorus removal effect of the MFC system and recover the phosphorus element.

[0026] Advantages: Compared with the prior art, the present application has the following obvious advantages:

[0027] 1. The anode electrode of the present application adopts an iron oxide-iron-carbon felt composite anode, in a 30-day test period, compared with the reactor adopting a traditional iron anode, the MFC reactor adopting the composite anode has more days of up to standard effluent phosphorus by 8 days, the average effluent phosphorus concentration is lower by 11.89%, and the total iron concentration in the anode chamber is higher by 28.92%; the average output voltage of the MFC system adopting the composite electrode anode is 0.216V, which is only slightly lower than that of the traditional iron electrode and is much higher than that of the carbon felt anode and the pure iron oxide anode. Therefore, compared with the single iron electrode, the composite electrode has the characteristics of corrosion resistance, more dissolved Fe(II), improved biological slow-release Fe(II) efficiency of iron oxide, and high enrichment efficiency of electricity-producing bacteria. The traditional iron anode can only produce electricity for 22 days, while the iron oxide-iron-carbon felt composite electrode can work for 30 days in the test period, greatly prolonging the service life of the anode electrode and reducing the operation cost of the system; and the carbon felt as the carrier of iron oxide can better enrich the microorganisms and improve the phosphorus removal effect of the system;

[0028] 2. The trivalent iron oxide of the anode can efficiently enrich iron-reducing bacteria, and the corrosion and dissolution of the iron sheet under the weak acidic conditions of the MFC anode release Fe(II), which is also conducive to the enrichment of iron-reducing bacteria, thereby enhancing the electricity generation of the microbial fuel cell, stimulating the activity of phosphorus-accumulating bacteria, and strengthening the biological phosphorus removal effect in the system; on the other hand, the dissolved Fe(II) of the iron oxide-iron-carbon felt composite anode 4 is easily combined with PO4 3- in the system in an acidic environment to generate blue vitriol precipitation, realize chemical phosphorus removal, and recover part of the phosphorus element; the unused Fe(II) in the anode chamber 1 enters the cathode through overflow and a cation exchange membrane 3, and is oxidized to Fe(III) in the MFC cathode chamber 2, which can be used as a flocculant to combine with phosphorus-containing pollutants and OH- in the cathode chamber 2 to produce flocculation precipitation, and further complete the recovery of phosphorus elements;

[0029] 3. The present application adjusts the resistance value or the proportion of iron and iron oxide on the electrode load, changes the electrochemical conditions, flexibly controls the Fe(II) release rate of the iron sheet and the reduction conditions of Fe(III) by iron-reducing bacteria, regulates the MFC phosphorus removal effect, balances the Fe(II) yield and PO4 3- conversion amount, and avoids the problem of excessive residual iron color in the effluent caused by excessive addition of conventional chemical phosphorus removal agents; in practical application, when the Fe / P molar ratio is 2:1, blue vitriol can be formed in the anaerobic digestion (AD) process of sewage sludge; in addition, the conditions of the MFC itself are also conducive to the efficient formation of blue vitriol precipitation, the pH of the MFC anode is between 4.5 and 7, under which condition the blue vitriol crystal is more concentrated, the ORP of the MFC is between -300 and -400 mV, which can provide the required reduction environment, and the Ksp of the blue vitriol itself is small, which is easy to precipitate in the system, thereby strengthening the phosphorus removal efficiency, realizing phosphorus recovery, and avoiding the problems of high effluent color and energy loss caused by excessive iron addition; in the present application, the MFC system and the adjustment of the electrode material and resistance can be used to promote the formation of blue vitriol;

[0030] 4. In the system, part of the Fe(II) dissolved from the anode electrode enters the cathode chamber through overflow and a cation exchange membrane, and can be oxidized to Fe(III) as a flocculant to combine with phosphorus-containing pollutants and OH- in the cathode chamber to produce flocculation precipitation;

[0031] 5. Through cathode aeration pump 12 aeration, oxygen is reduced to H2O2 in the cathode, reacts with Fe(II) from the anode to produce hydroxyl radicals, forms an electro-Fenton reaction, and can deeply remove refractory organic phosphorus in wastewater, and the generated PO4 3- and the oxidized Fe(III) form flocculation precipitation to deeply remove organic phosphorus and recover;

[0032] 6. This invention can be applied to the resource recovery and efficient removal of phosphorus from phosphorus-containing wastewater such as urban sewage, rural domestic sewage, and industrial wastewater. It is environmentally friendly, safe, low-cost, and easy to maintain, and features fast removal rate and low cost. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of the present invention;

[0034] Figure 2 A schematic diagram of the phosphorus removal principle provided by the present invention;

[0035] In the diagram: 1. Anode chamber; 2. Cathode chamber; 3. Cation exchange membrane; 4. Iron oxide-iron-carbon felt composite anode; 5. Carbon brush cathode; 6. Titanium wire; 7. Variable resistor; 8. Inlet; 9. Outlet; 10. Overflow pipe; 11. Peristaltic pump; 12. Aeration pump; 13. Aeration stone. Detailed Implementation

[0036] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0037] Example 1

[0038] like Figure 1 As shown, a bioelectrochemically promoted high-efficiency multi-pathway phosphorus removal device includes an anode chamber 1, a cathode chamber 2, and a cation exchange membrane 3. The anode chamber 1 and the cathode chamber 2 are separated by the cation exchange membrane 3. An iron oxide-iron-carbon felt composite anode 4 is installed inside the anode chamber 1, and a carbon brush cathode 5 (Shanghai Leton Industrial Co., Ltd.) is installed inside the cathode chamber 2. The iron oxide-iron-carbon felt composite anode 4 and cathode 5 are connected by a titanium wire 6, and a variable resistor 7 with a resistance of 100Ω to 5000Ω is connected to the titanium wire 6. An overflow pipe 10 is installed between the anode chamber 1 and the cathode chamber 2. The two ends of the overflow pipe 10 are connected to the top of the anode chamber 1 and the top of the cathode chamber 2, respectively. An inlet 8 is opened at the top of the anode chamber 1, and a peristaltic pump 11 is connected to the inlet 8. An outlet 9 is opened on the side of the cathode chamber 2. An aeration stone 13 is installed at the bottom of the cathode chamber 2, and an aeration pump 12 is connected to the aeration stone 13. Anaerobic sludge is placed at the bottom of the anode chamber 1, which can float up with the sewage and attach to the iron oxide-iron-carbon felt composite anode 4; aerobic sludge is placed inside the cathode chamber 2, and when the aeration pump 12 is turned on, the aerobic sludge can be blown up by the aeration stone 13.

[0039] The preparation method of the iron oxide-iron-carbon felt composite anode 4 is as follows:

[0040] (1) Carbon felt treatment: The carbon felt is soaked with tap water, then ultrasonic cleaned with distilled water for 10 min, followed by ultrasonic cleaning with analytical pure ethanol for 10 min, then ultrasonic cleaning with distilled water for 10 min, followed by cleaning with (1+3) HCl solution for 10 min, then rinsing with flowing distilled water for 2-3 min, then ultrasonic cleaning with distilled water for 10 min, and finally drying the carbon felt in an oven, with the drying temperature controlled at 150°C and the drying time controlled at 1 h, and the carbon felt treatment completed after drying;

[0041] (2) Anode preparation: 3 mL of the iron oxide mixed solution is evenly applied to the front and back of the treated carbon felt, and the carbon felt after applying the solution is dried in a drying oven, with the drying temperature controlled at 150°C and the drying time controlled at 1 h, and the iron oxide-carbon felt composite anode is obtained after drying, an iron sheet (the mass ratio of the iron sheet (pure iron) to iron in the iron oxide is 1.5-2.5:1) is placed between the prepared iron oxide-carbon felt composite anode and a 14-mesh 304 stainless steel mesh, and the iron oxide-iron-carbon felt composite anode 4 is fixed by the titanium wire 6.

[0042] The preparation method of the iron oxide mixed solution is as follows: Fe2O3, carbon black and polyvinylidene fluoride are added to 10 mL of N-methyl pyrrolidone, and the mixture is ultrasonically mixed for 20 min to obtain a mixed solution, and the weight ratio of N-methyl pyrrolidone, Fe2O3, carbon black and polyvinylidene fluoride in the mixed solution is 10:1:0.2-0.3:0.1-0.15.

[0043] The molar ratio of iron in the prepared anode to phosphorus in the wastewater is 1.5-2.5:1, the anode replacement cycle is 30-60 days, the influent is fed in a sequencing batch mode, and the effluent quality of the cathode chamber 2 is detected every two cycles during the wastewater treatment process, wherein the hydraulic retention time of one cycle corresponds to 12 h, and the aeration frequency is set to stop aeration for 4 h after aeration for 2 h during the intermittent aeration of the cathode chamber 2; the dissolved oxygen (DO) in the cathode chamber 2 is controlled at 3-4 mg / L by controlling the intermittent aeration of the aeration pump 12, which can be adjusted according to specific conditions. During the wastewater treatment process, the resistance value of the variable resistor 7 is adjusted according to the wastewater quality, the TFe content in the anode, and the TP concentration of the system effluent to ensure the phosphorus removal effect of the MFC system and recover phosphorus elements.

[0044] Example 2

[0045] A method for promoting multi-path efficient phosphorus removal by bioelectrochemistry, applied in the above-mentioned device for promoting multi-path efficient phosphorus removal by bioelectrochemistry, comprising the following steps:

[0046] 1. Sludge sampling: mature aerobic sludge and anaerobic sludge were sampled from the anaerobic tank and the aerobic tank of the Nanjing Municipal Wastewater Treatment Plant, respectively;

[0047] 2. Equipment treatment: sludge was put into the anode chamber 1 and the cathode chamber 2, respectively; the anaerobic sludge was put into the anode chamber 1, and the volume ratio of the anaerobic sludge in the anode chamber 1 was 20%; the aerobic sludge was put into the cathode chamber 2, and the volume ratio of the aerobic sludge in the cathode chamber 2 was 20%.

[0048] 3. Anode connection: the prepared iron oxide-iron-carbon felt composite anode 4 and the carbon brush cathode 5 were connected to the same variable resistor 7 using titanium wire 6, and the iron oxide-iron-carbon felt composite anode 4 and the carbon brush cathode 5 were placed in the anode chamber 1 and the cathode chamber 2, respectively;

[0049] 3.1 Carbon felt treatment: the carbon felt was soaked in tap water, then ultrasonic cleaned with distilled water for 10 min, then ultrasonic cleaned with analytical pure ethanol for 10 min, then ultrasonic cleaned with distilled water for 10 min, then cleaned with (1+3) HCl solution for 10 min, then rinsed with flowing distilled water for 3 min, then ultrasonic cleaned with distilled water for 10 min, and finally dried in an oven at a temperature of 150℃ for 1 h to complete the carbon felt treatment;

[0050] 3.2 Anode preparation: 3 mL of iron oxide mixed solution was evenly applied to the front and back of the treated carbon felt, and the carbon felt after applying the solution was dried in a drying oven at a temperature of 150℃ for 1 h to obtain an iron oxide-carbon felt composite anode. A 14-mesh 304 stainless steel mesh was used to combine and fix the iron sheet and the prepared iron oxide-carbon felt composite anode according to the method of Example 1 (the mass ratio of iron content in the iron sheet to iron oxide was 1.5:1), and an iron oxide-iron-carbon felt composite anode 4 was prepared.

[0051] The preparation method of the iron oxide mixed solution is as follows: 10 mL of N-methyl pyrrolidone is added with Fe2O3, carbon black and polyvinylidene fluoride, and the mixture is ultrasonically mixed for 20 min to obtain a mixed solution. The weight ratio of N-methyl pyrrolidone, Fe2O3, carbon black and polyvinylidene fluoride in the mixed solution is 10:1:0.3:0.15, and the mass ratio of iron content in the iron sheet to iron oxide is 1.5:1;

[0052] The molar ratio of iron in the prepared iron oxide-iron-carbon felt composite anode 4 to phosphorus in the wastewater is 2.5:1, and the anode replacement cycle is 30 days;

[0053] 4. Sewage treatment: when the device is started, connect the variable resistor 7 with resistance of 5000 Ω to the titanium wire 6. Start the peristaltic pump 11 to pump the simulated sewage with COD concentration of 300 mg / L, ammonia nitrogen concentration of 40 mg / L, total nitrogen concentration of 40 mg / L, and total phosphorus concentration of 8 mg / L from the water inlet 8 into the anode chamber 1, for 15 min, at a flow rate of 12 mL / min. After the simulated sewage is treated in the anode chamber 1 for 6 hours, continue to pump the simulated sewage into the anode chamber 1 through the peristaltic pump 11, and the sewage treated in the anode chamber before is discharged into the cathode chamber 2 through the overflow pipe 10, and continue to be treated in the cathode chamber 2 for 6 hours, to complete one cycle of treatment (one cycle corresponds to a hydraulic retention time of 12 h). Thereafter, continue to use the peristaltic pump 11 to feed water into the anode chamber 1, and perform the second cycle of treatment. Since the water feeding rate is slow, the disturbance to the solution in the system is small, and therefore untreated sewage will not directly enter the cathode chamber.

[0054] During the sewage treatment process, the cathode chamber 2 is intermittently aerated by the aeration pump 12, and the aeration frequency is set to stop aeration for 4 h after aeration for 2 h, and the dissolved oxygen DO in the cathode chamber 2 is controlled at 3-4 mg / L by controlling the intermittent aeration of the aeration pump 12. During the sewage treatment process, the treated sewage is sampled at the water outlet 9 and water quality detection is performed, and during the period when the device is not feeding and discharging water, the overflow pipe 10 is removed, the water sample in the anode chamber is extracted, and the total soluble iron TFe content is monitored, and the detection is performed once every two cycles. Since the carbon felt serves as a carrier for oxidized iron, it can better enrich the microorganisms in the sewage, thereby reducing the total phosphorus in the sewage. When the TFe content in the anode water sample is less than 6 mg / L for the first time, and the total phosphorus TP concentration of the system effluent exceeds 0.5 mg / L, the resistance of the variable resistor is adjusted to 1000 Ω, the treated sewage is sampled at the water outlet 9 and water quality detection is performed, the anode TFe content is monitored, and the anode chroma (concentration of reaction ferrous ions) is observed. When the TFe content in the anode water sample is less than 6 mg / L again, the resistance of the variable resistor is adjusted to 200 Ω, the treated sewage is sampled at the water outlet 9 and water quality detection is performed, and the anode TFe content is monitored. After the experiment is performed for 30 days, the phosphorus element in the filtration recovery system is recovered.

[0055] Example 3

[0056] The iron content of the iron oxide in the iron oxide-iron-carbon felt composite anode 4 is set to be 1:2 by mass ratio of iron sheet, and a mixed solution is obtained by mixing Fe2O3, carbon black and polyvinylidene fluoride in 10 mL of N-methyl pyrrolidone after ultrasonic mixing for 20 min, wherein the weight ratio of N-methyl pyrrolidone, Fe2O3, carbon black and polyvinylidene fluoride in the mixed solution is 10:1:0.2:0.1, the molar ratio of iron in the prepared iron oxide-iron-carbon felt composite anode 4 to phosphorus in the sewage is 1.5:1, and other conditions are the same as those in Example 2. The variable resistor 7 is adjusted according to the running condition and the effluent soluble total iron during operation.

[0057] The iron oxide-iron-carbon felt composite anode 4 is arranged in the anode chamber 1, the iron content of the iron oxide is 1:2 by mass ratio of iron sheet, the prepared iron oxide-iron-carbon felt composite anode 4 is connected with the carbon brush cathode 5 on the same variable resistor 7 by using titanium wire 6, and the iron oxide-iron-carbon felt composite anode 4 and the carbon brush cathode 5 are respectively arranged in the anode chamber 1 and the cathode chamber 2. The variable resistor 7 is adjusted according to the running condition and the effluent soluble total iron during operation.

[0058] The resistance value of the variable resistor is adjusted to 5000Ω, the peristaltic pump 11 is started to pump the simulated sewage with COD concentration of 300 mg / L, ammonia nitrogen concentration of 40 mg / L, total nitrogen concentration of 40 mg / L and total phosphorus concentration of 8 mg / L from the water inlet 8 into the anode chamber 1, the effluent in the anode chamber 1 flows into the cathode chamber 2 through the overflow pipe 10, and the cathode chamber 2 discharges the effluent from the water outlet 9. The cathode chamber 2 is intermittently aerated by the aeration pump 12 during the sewage treatment process, the aeration frequency is set to stop aeration for 4 h after aeration for 2 h, and the dissolved oxygen DO in the cathode chamber 2 is controlled to be 3-4 mg / L by controlling the intermittent aeration of the aeration pump 12.

[0059] The treated sewage is sampled at the water outlet 9 and water quality detection is performed, the overflow pipe is removed during the non-inlet and outlet water period of the device, the anode water sample is extracted to monitor the TFe content, and the TFe content is detected once every two periods. When the TFe content in the anode of the device is less than 6 mg / L for the first time and the TP concentration of the system effluent exceeds 0.5 mg / L, the resistance value of the variable resistor is adjusted to 1000Ω, the treated sewage is sampled at the water outlet 9 and water quality detection is performed, the anode TFe content is monitored, and the anode chroma is observed.

[0060] When the TFe content in the anode of the device is less than 6 mg / L again, the resistance value of the variable resistor is adjusted to 200Ω, the treated sewage is sampled at the water outlet 9 and water quality detection is performed, the anode TFe content is monitored, and the phosphorus element in the recovery system is filtered and recovered.

[0061] Comparative Example 1

[0062] The anode is a conventional carbon felt anode, and the resistance value of the variable resistor 7 is kept constant at 1000 Ω. The other conditions are the same as in Example 2.

[0063] The anode is a conventional carbon felt anode, and the resistance value of the variable resistor 7 is kept constant at 1000 Ω. The other conditions are the same as in Example 2.

[0064] The peristaltic pump 11 is started to pump simulated wastewater with a COD concentration of 300 mg / L, an ammonia nitrogen concentration of 40 mg / L, a total nitrogen concentration of 40 mg / L, and a total phosphorus concentration of 8 mg / L from the water inlet 8 into the anode chamber 1. The effluent in the anode chamber 1 flows into the cathode chamber 2 through the overflow pipe 10, and the cathode chamber 2 discharges the effluent through the water outlet 9. During the wastewater treatment process, the cathode chamber 2 is intermittently aerated by the aeration pump 12, and the aeration frequency is set to stop aeration for 4 h after aeration for 2 h. The dissolved oxygen DO in the cathode chamber 2 is controlled at 3-4 mg / L by controlling the aeration pump 12 to intermittently aerate. After the experiment is conducted for 30 days, the treated wastewater is sampled at the water outlet 9 and subjected to water quality detection.

[0065] Comparative Example 2

[0066] The mass ratio of iron content in the iron oxide to the iron sheet in the iron oxide-iron-carbon felt composite anode 4 is 1:2, and the TFe content and Fe(II) content in the monitoring device are monitored. The resistance value of the variable resistor 7 is kept constant at 1000 Ω. The other conditions are the same as in Example 2.

[0067] The anode is an iron oxide-iron-carbon felt composite anode 4, and the mass ratio of iron oxide to iron is 1:2. The titanium wire 6 is used to connect the prepared iron oxide-iron-carbon felt composite anode 4 and the carbon brush cathode 5 to the same variable resistor 7. The iron oxide-iron-carbon felt composite anode 4 and the carbon brush cathode 5 are respectively placed in the anode chamber 1 and the cathode chamber 2, and the resistance value of the variable resistor 7 is kept constant at 1000 Ω.

[0068] The peristaltic pump 11 is started to pump simulated wastewater from the water inlet 8 into the anode chamber 1. The effluent in the anode chamber 1 flows into the cathode chamber 2 through the overflow pipe 10, and the cathode chamber 2 discharges the effluent through the water outlet 9. During the wastewater treatment process, the cathode chamber 2 is intermittently aerated by the aeration pump 12, and the aeration frequency is set to stop aeration for 4 h after aeration for 2 h. The dissolved oxygen DO in the cathode chamber 2 is controlled at 3-4 mg / L by controlling the aeration pump 12 to intermittently aerate.

[0069] After the experiment is conducted for 30 days, the treated wastewater is sampled at the water outlet 9 and subjected to water quality detection.

[0070] Comparative Example 3

[0071] The iron content of the iron oxide-iron-carbon felt composite anode 4 is set to 1:1 of the mass ratio of iron oxide to iron sheet, the TFe content and Fe(II) content in the monitoring device are monitored, and the resistance value of the variable resistor 7 is kept constant at 1000Ω. The other conditions are the same as in Example 2.

[0072] The iron oxide-iron-carbon felt composite anode 4 is set in the anode chamber 1, the mass ratio of iron oxide to iron is 1:1, the titanium wire 6 is used to connect the prepared iron oxide-iron-carbon felt composite anode 4 and the carbon brush cathode 5 on the same variable resistor 7, and the iron oxide-iron-carbon felt composite anode 4 and the carbon brush cathode 5 are respectively placed in the anode chamber 1 and the cathode chamber 2, and the resistance value 7 of the variable resistor is kept constant at 1000Ω.

[0073] The peristaltic pump 11 is started to pump the simulated sewage from the water inlet 8 into the anode chamber 1, the water outlet of the anode chamber 1 flows into the cathode chamber 2 through the overflow pipe 10, the cathode chamber 2 discharges water through the water outlet 9, and the cathode chamber 2 is intermittently aerated by the aeration pump 12 during the sewage treatment process, the aeration frequency is set to stop aeration for 4h after aeration for 2h, and the dissolved oxygen DO in the cathode chamber 2 is controlled at 3-4mg / L by controlling the intermittent aeration of the aeration pump 12.

[0074] After the test is conducted for 30 days, the treated sewage is sampled at the water outlet 9 and water quality detection is performed.

[0075] Table 1 is a quality evaluation table of the sewage samples obtained from the control groups 1-3 and the examples 2-3

[0076]

[0077]

[0078] As shown in Table 1, after the sewage treated by the device and method for promoting multi-path efficient phosphorus removal by bioelectrochemistry provided by the application, such as the sewage sample treated in Example 2, the pollutant concentration in the water body is greatly reduced, the TFe concentration meets the standard (<0.3 mg / L), the precipitate in the MFC anode chamber is recovered, and after drying, the weight is measured, and analysis shows that 43.84% of phosphorus resources are recovered; in Example 3, the sewage is treated by the device, and the variable resistor is adjusted according to the actual operation, but the ratio of iron and ferrous iron in the metal composite anode is not optimal, and the optimal device operation effect is not achieved, the TFe concentration does not meet the standard, and only 20.61% of phosphorus elements are recovered. The sewage not treated by the device and method, such as the sewage sample treated in Comparative Example 1, has the worst removal effect of pollutants in the water body, no phosphorus-containing precipitates such as electric flocculation and struvite are generated in the system, and phosphorus elements cannot be recovered; although the sewage in Comparative Example 2 is treated by the device, the composite electrode contains iron and iron oxide, but the ratio of the two is not optimal, and the resistance value of the variable resistor is constant, after the iron in the anode is consumed, the phosphorus removal effect in the system rapidly decreases, and the TP removal rate is only 49.20% at the end of the 30-day test period, no phosphorus-containing precipitate is generated; the composite electrode in Comparative Example 3 combines the characteristics of rapid release of iron and slow release of iron oxide, and can achieve good phosphorus removal effect in the early stage, but the resistance is not adjusted, there is a problem of large iron residual amount in the early stage and insufficient iron content in the later stage, the total phosphorus removal rate of the effluent is low, the standard meeting days are short, about 26.39% of phosphorus elements can be recovered from the generated precipitate.

Claims

1. A device for promoting multi-path efficient phosphorus removal by bioelectrochemistry, comprising an anode chamber (1), a cathode chamber (2) and a cation exchange membrane (3) arranged between the anode chamber (1) and the cathode chamber (2), a water overflow pipe (10) is arranged between the anode chamber (1) and the cathode chamber (2), and a carbon brush cathode (5) is arranged in the cathode chamber (2), characterized in that, The anode chamber (1) is internally provided with an iron oxide-iron-carbon felt composite anode (4), the iron oxide-iron-carbon felt composite anode (4) is connected with a carbon brush cathode (5) through a titanium wire (6), and the titanium wire (6) is further connected with a variable resistor (7); anaerobic sludge is put into the anode chamber (1), and aerobic sludge is put into the cathode chamber (2).

2. The apparatus of claim 1, wherein, The iron oxide-iron-carbon felt composite anode (4) is composed of carbon felt coated with iron oxide and iron sheets; the mass ratio of iron content in the iron sheets to iron oxide is 1.5-2.5:

1.

3. The apparatus of claim 1, wherein The preparation method of the iron oxide-iron-carbon felt composite anode (4) comprises the following steps: (1) carbon felt treatment: after soaking the carbon felt, wash it with distilled water, ethanol and HCl respectively, and dry it; (2) preparation of iron oxide mixed solution: add Fe2O3, carbon black and polyvinylidene fluoride into N-methyl pyrrolidone, and mix and ultrasonic; (3) anode preparation: take the iron oxide mixed solution in step (2) and smear it on the front and back of the treated carbon felt, dry it, combine it with iron sheets, and fix it to obtain the iron oxide-iron-carbon felt composite anode.

4. The apparatus of claim 3, wherein The mass ratio of N-methyl pyrrolidone, Fe2O3, carbon black and polyvinylidene fluoride in step (2) is 10:1:0.2-0.3:0.1-0.

15.

5. The apparatus of claim 1, wherein The cathode chamber (2) is provided with a water outlet (9), and the bottom of the cathode chamber (2) is provided with an aeration stone (13), and the other end of the aeration stone (13) is connected with an aeration pump (12).

6. The apparatus of claim 1, wherein The anode chamber (1) is provided with a water inlet (8), and the water inlet (8) is connected with a peristaltic pump (11).

7. A method for removing and / or recovering phosphorus from sewage using the device according to any one of claims 1 to 6, characterized in that, The method comprises the following steps: Start the peristaltic pump (11) to make the sewage enter the anode chamber (1) from the water inlet (8), and set the resistance value of the variable resistor (7) to 5000Ω; the treated sewage in the anode chamber (1) flows to the cathode chamber (2) through the overflow pipe (10), the treated sewage flows out through the water outlet (9), and the next cycle of treatment is carried out; the total phosphorus and total iron content of the sewage are monitored once every two cycles; wherein, the dissolved oxygen (DO) in the cathode chamber (2) is controlled at 3-4 mg / L by controlling the intermittent aeration of the aeration pump (12); when the total iron content in the anode water sample is less than 6 mg / L for the first time, and the total phosphorus (TP) concentration of the system effluent exceeds 0.5 mg / L, the resistance value of the variable resistor is adjusted to 1000Ω; when the total iron content in the anode water sample is less than 6 mg / L again, the resistance value of the variable resistor is adjusted to 200Ω, and the phosphorus element in the system is recovered after another cycle of treatment.

8. The method of claim 7, wherein, One cycle corresponds to a system hydraulic retention time of 8-12 h.

9. The method of claim 7, wherein, The molar ratio of iron in the iron oxide-iron-carbon felt composite anode (4) to phosphorus in the sewage is 1.5-2.5:1.

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