CN103872368B - Interactive three Room biological fuel cell devices and the method being applied to denitrogenation of waste water thereof - Google Patents

Abstract

The invention discloses a kind of interactive three Room biological fuel cell devices and the method being applied to denitrogenation of waste water thereof, belong to saprobia and repair field, particularly relate to for the denitrification denitrogenation processing method containing nitrate nitrogen waste water。The present invention is on the basis of traditional dual chamber biological fuel cell, and negative electrode uses nitrate to replace oxygen as electron acceptor, and constructs three Room biological fuel cells of grading electrode room, both sides cathode chamber。Simultaneously by Interactive control switch Interactive control grading electrode and the Guan Bi of both sides negative electrode, off-state so that the electrode denitrification of negative electrode and non-electrode denitrification process reasonable coordination carry out。The method produces electric current sustainably and effectively removes nitrate nitrogen, saves the organic carbon source needed for denitrification simultaneously, is a kind of based on energy-saving and cost-reducing Novel sewage treatment method, has good application prospect。

Description

Interactive three-chamber biofuel cell device and its application to wastewater denitrification

technical field

The invention relates to the field of water treatment and resource utilization, in particular to an interactive three-chamber biofuel cell that efficiently treats waste water containing nitrate nitrogen and simultaneously realizes electric energy recovery and its application to waste water denitrification.

Background technique

Excessive discharge of nitrogen can lead to eutrophication of water bodies and bring great harm to human beings. Since the "Twelfth Five-Year Plan", my country still insists on thoroughly implementing the basic national policy of resource conservation and environmental protection, and develops a circular economy. The issue of "energy saving and emission reduction" has always been a research hotspot. Therefore, in the face of the ever-increasing pressure to reduce nitrogen in sewage, it is urgent to develop a new technology for denitrification of sewage with "energy saving and emission reduction".

Microbial fuel cell (MFC, also referred to as biofuel cell) is a high-tech in the field of water treatment in the 21st century. It is a new type of sewage bioremediation technology, which has the advantages of simultaneously removing organic pollutants and obtaining energy output. field has also received increasing attention. According to the existing research results, MFC is expected to be applied to practical wastewater denitrification projects and become a new energy-saving and efficient wastewater denitrification technology.

In the traditional biological denitrification process, the organic carbon source is an important limiting factor. However, municipal sewage treatment plants in my country generally lack organic carbon sources in the influent, resulting in low nitrogen removal efficiency. If the carbon-to-nitrogen ratio is too high, the remaining organic matter needs further treatment; if the carbon-to-nitrogen ratio is low, the denitrification efficiency will be low and nitrite will accumulate.

In the MFC cathode denitrification process, due to the introduction of the reduction effect of the electrode, part of the required electrons can come from the electrons generated by the organic carbon source in the microbial metabolism process, and the other part (under biological catalysis) can be obtained directly from the cathode electrode. , so MFC can use a wider range of electron donors in the actual wastewater denitrification process, and its denitrification process is the result of the joint action of non-electrode denitrification and electrode denitrification. Therefore, the use of MFC for denitrification and denitrification of sewage can effectively reduce the carbon-to-nitrogen ratio and can make up for the shortage of organic carbon sources required for denitrification of sewage.

At present, scholars at home and abroad have carried out a lot of research on the denitrification of microbial fuel cells. Clauwaert et al. confirmed for the first time that the biocathode MFC can be used for denitrification, and realized the simultaneous denitrification, carbon removal and electricity generation functions in the MFC, and obtained a removal rate of 0.146kg/m ³ nitrate per day. Virdis et al. combined the traditional denitrification A/O process with MFC in series through an external aerobic nitrification reactor, and simultaneously denitrified and decarbonized, achieving removal of 2kg/m ³ COD and 0.41kg/m ³ nitrate per day Rate. Subsequently, Virdis et al. removed the additional nitrification reactor, and carried out simultaneous biological nitrification and denitrification reactions in the cathode chamber, and obtained a nitrogen removal rate of 94.1%. Xie et al. constructed an aerobic biocathode MFC and anaerobic biocathode MFC coupling system, and the removal rates of COD, ammonia nitrogen and total nitrogen can reach 98.8%, 97.4% and 97.3%, respectively. Huang Xia et al. disclose a biocathode type microbial fuel cell, which is composed of an anode chamber, an aerobic cathode chamber and an anoxic cathode chamber, and denitrification is carried out while removing organic matter and generating electricity. Yu Changping and others disclosed a microbial fuel cell wastewater treatment system to improve the denitrification effect, inoculate the cathode chamber with nitrification sludge and add embedded aerobic denitrification bacteria particles, so that nitrification and denitrification can be synergistically exerted in one reaction zone function, make full use of the DO and the remaining carbon source of the cathode to achieve the purpose of denitrification and further removal of COD.

However, the use of denitrifying microbial fuel cells for wastewater denitrification still has many difficulties in the prior art. Among them, the competition between electrode denitrification and non-electrode denitrification in the cathodic chamber system is the main contradiction. Existing studies have shown that in the process of biological denitrification, nitrate nitrogen will preferentially use organic carbon sources (rather than electrode electrons) as electron donors for the denitrification process. That is, higher concentrations of organic carbon sources have an inhibitory effect on electrode denitrification. In the cathode chamber, when two kinds of electron donors (organic carbon source and cathode electrons) coexist, the non-electrode denitrification effect is stronger, and the electrode denitrification effect is weaker, which will make the battery's power generation capacity low and waste the organic carbon source. ; But on the other hand, if no organic carbon source is added, only rely on electrode denitrification, the denitrification rate is very low, affecting the denitrification efficiency. This contradiction makes the application prospect of denitrifying microbial fuel cells questioned.

Contents of the invention

Purpose of the invention: the purpose of the present invention is to construct a new type of combined biofuel cell and adopt a reasonable method to realize its high-efficiency biological denitrification function, while overcoming the deficiencies of the prior art, and solving the problem of electrode denitrification and non-electrode denitrification in the cathode chamber of the prior art. The contradiction between the two processes of nitrification enables the device to make full use of electron donors and save the consumption of denitrification organic carbon sources on the basis of efficient power generation and denitrification.

1. An interactive three-chamber biofuel cell device, comprising: middle anode chamber (5), both sides cathode chamber (1), external circuit and resistance (10), interactive control switch (11), described middle anode The chamber (6) includes an electrode chamber, a water inlet and outlet, and a sample injection port, in which anaerobic sludge is inoculated to control the anaerobic state, and an anode (6) of carbon felt material is placed;

It is characterized by:

Described cathode chamber (1), comprises water inlet and outlet (4), (3), sample inlet ( ⁹ ), inoculates through domesticated anoxic sludge, and places the carbon felt material that surface area is 28cm as cathode ( 2);

The cathode chambers (1) on both sides include two mirror-symmetrical ones (1A, 1B), each with a volume of 350 cm ² , separated from the anode chamber by a proton exchange membrane (7) with a diameter of 20 cm;

The external circuit and the resistor (10) connect the anode to the two cathodes (2A, 2B) respectively, the external resistor is fixed at 800 ohms, and two mirror-symmetric biofuel cells are formed by three electrode chambers;

The interactive control switch (11) is connected to the anode (6), and is used to control the selection of the cathode connected to the anode, and alternately forms a closed circuit with the two cathodes, and the anode is always in an operating state.

2. A method based on the above-mentioned interactive three-chamber biofuel cell device applied to wastewater denitrification, comprising the steps of:

Step 1: Inoculate the anode chamber (5) with anaerobic sludge, and inoculate the two cathode chambers (1) with acclimated anoxic denitrification sludge;

Step 2: The waste water containing nitrate nitrogen that needs to be treated enters the cathode chambers (1A, 1B) on both sides of the three-chamber biofuel cell alternately in batches. First, the cathode (2A) on the A side is disconnected from the anode, and the cathode chamber on the A side (1A) Inlet, carry out non-electrode denitrification utilizing organic carbon source;

Step 3: After 24 hours, the B-side cathode (2B) is disconnected from the anode, and the B-side cathode chamber (1B) is filled with water for non-electrode denitrification using an organic carbon source. At this time, the A-side cathode chamber (1A) organic carbon When it is exhausted, the interactive control switch controls the anode to communicate with the A-side cathode (2A), and the A-side cathode chamber conducts electrode denitrification using cathode electrons, and simultaneously generates electrical energy;

Step 4: After another 24 hours, the B-side cathode chamber (1B) enters the low-carbon source state, the interactive control switch controls the anode to communicate with the B-side cathode (2B), and the B-side cathode chamber conducts electrode denitrification and generates electric energy at the same time. The cathode chamber on side A drains water and enters new waste water;

Step 5: Repeat the above steps 2, 3, and 4, the two cathode chambers alternately enter and drain water, and are alternately in the state of "low carbon source" and "high carbon source" (the organic matter required for denitrification of one side of the cathode chamber When the carbon source is exhausted, the so-called "low carbon source" state) and with the interactive control switch (11), the control anode (6) is always connected to the cathode of the "low carbon source", so that the two batteries operate alternately, That is, when the A-side cathode (2A) is in the off-circuit state for non-electrode denitrification and enters the "low-carbon source" state (at this time, there is still nitrate nitrogen in the sewage that has not been removed), through the interactive control switch (11) and The cathode (2A) on side A is connected to further denitrify the electrode and then discharge water. At the same time, the cathode chamber (1B) on side B is in an open circuit state, and the organic carbon source is used for non-electrode denitrification.

Beneficial effect:

In traditional biofuel cells used for denitrification, due to the competition of two electron donors (organic carbon source and cathode electrons exist at the same time), the higher concentration of organic carbon source in the cathode chamber will inhibit the electrode denitrification process, and cause The power generation capacity of the system and the ability to obtain electric energy are reduced; and if the electrode denitrification is solely relied on, the reaction rate is relatively slow.

In the present invention, by improving the structure of the microbial fuel cell and the sewage treatment method interleaved in time and space, the denitrification process of the electrode is always kept in the state of "low carbon source", which weakens the competitiveness of the two types of electron donors, and is effective from the perspective of time and space. Solve the contradiction between electrode denitrification and non-electrode denitrification effectively. This enables the system to make full use of electron donors while ensuring high power production capacity and efficient denitrification effects, saving the consumption of organic carbon sources required for denitrification, and reducing sludge production. The average output power of the device in one reaction cycle of the present invention is 27.0mW/cm ² , the comprehensive denitrification rate is 2.62mg/(L·h), the organic carbon source COD/NO ₃ ^- consumed by denitrification is less than 4, and the overall performance is excellent Compared with ordinary double-chamber denitrifying microbial fuel cells, and under the premise of little increase in manufacturing costs (attached), the sewage treatment efficiency (water volume) is doubled. It is a new sewage treatment method based on energy saving and consumption reduction. It is suitable for the treatment of nitrate nitrogen wastewater with insufficient organic carbon source, and has good environmental and economic benefits.

Description of drawings

Fig. 1 is a structural diagram of an interactive three-chamber microbial fuel cell of the present invention. In the picture:

1. Cathode chamber (there are two symmetrical chambers 1A and 1B), 2. Cathode, 3. Cathode chamber water outlet, 4. Cathode chamber water inlet, 5. Anode chamber, 6. Anode, 7. Proton exchange membrane, 8. Wire port, 9. Cathode sampling port, 10. External circuit and resistance, 11. Interactive control switch,

detailed description

An interactive three-chamber biofuel cell device, comprising: a middle anode chamber (5), two-side cathode chambers (1), an external circuit and resistance (10), and an interactive control switch (11).

The intermediate anode chamber (5) includes an electrode chamber, a water inlet and an outlet, and a sample inlet, in which anaerobic sludge is inoculated to control the anaerobic state, and an anode (6) of carbon felt material is placed;

Described cathode chamber (1), comprises water inlet and outlet (4), (3), sample inlet ( ⁹ ), inoculates through domesticated anoxic sludge, and places the carbon felt material that surface area is 28cm as cathode ( 2);

The cathode chambers (1) on both sides include two mirror-symmetrical ones (1A, 1B), each with a volume of 350 cm ² , separated from the anode chamber by a proton exchange membrane (7) with a diameter of 20 cm;

The external circuit and the resistance (10) connect the anode to the two cathodes respectively, the external resistance is fixed at 800 ohms, and two mirror-symmetric biofuel cells are formed by three electrode chambers;

The interactive control switch (11) is connected to the anode (6), and is used to control the selection of the cathode connected to the anode, and alternately forms a closed circuit with the two cathodes (2A, 2B).

Implementation case 1:

The above-mentioned interactive three-chamber biofuel cell device was used to carry out the denitrification experiment of wastewater containing nitrate nitrogen.

Step 1: Inoculate the anode chamber (5) with anaerobic sludge, add NaAc (COD: 1000 mg/L) into the anode solution as an electron donor, inoculate the two cathode chambers (1) with anoxic denitrification sludge, and feed water into the cathode (Simulated wastewater) contains sodium acetate (COD concentration is 200mg/L) and NaNO ₃ (NO ₃ –N is 70mg/L), and 2g/L Na ₂ CO ₃ is added as the inorganic material required for the growth of cathode denitrifying bacteria carbon source;

Step 2: The catholyte enters the cathode chambers (1A, 1B) on both sides of the three-chamber biofuel cell alternately in batches, first the cathode (2A) on the side A is disconnected from the anode, and the cathode chamber (1A) on the side A enters water, and the Non-electrode denitrification using organic carbon sources;

Step 3: After 24 hours, the B-side cathode (2B) is disconnected from the anode and the B-side cathode chamber (1B) is fed with water to perform non-electrode denitrification using an organic carbon source. At this time, the organic carbon in the A-side cathode chamber is exhausted ( At this point, it enters the low-carbon source state), the interactive control switch controls the anode to communicate with the A-side cathode (2A), and the A-side cathode chamber performs electrode denitrification using cathode electrons, and simultaneously generates electric energy;

Step 4: After another 24 hours, the organic carbon source in the B-side cathode chamber (1B) is exhausted, the interactive control switch controls the anode to communicate with the B-side cathode, and the B-side cathode chamber conducts electrode denitrification and generates electric energy at the same time, while the A-side cathode Chamber drains and enters new waste water;

Step 5: Repeat the above steps 2, 3 and 4, the two cathode chambers alternately enter and drain water, and are alternately in the state of "low carbon source" and "high carbon source", and cooperate with the interactive control switch (13) to control the anode (6) It is always connected to the cathode of the "low carbon source", so that the two batteries A and B operate alternately, that is, when the A side cathode (2A) is in the open circuit state, it will enter the "low carbon source" state after non-electrode denitrification for 24 hours (At this time, there is still nitrate nitrogen in the sewage that has not been removed), and the interactive control switch (11) is connected to the negative electrode (2A) on the A side, and the water is discharged after further denitrification of the electrode. At the same time, the cathode chamber on the B side ( 1B) is in an open circuit state, using organic carbon sources for non-electrode denitrification.

Taking the A side cathode as the object of investigation (the B side is the same), the experimental results are as follows (two processes):

(1) Non-electrode denitrification process on side A (at this time, electrode denitrification on side B) process: disconnect the anode and cathode on side A, after 24 hours of reaction, the cathode NO ₃ -N35.5mg/L, COD31.2mg/L , the denitrification rate in this process is 4.11mg/(L·h), which is non-electrode denitrification, and the A-side battery does not generate electricity at this time.

(2) The denitrification process of the electrode on the A side (at this time, the non-electrode denitrification process on the B side): connect the anode and the cathode of the A side, continue to react for 24 hours, the cathode NO ₃ -N26.0mg/L, COD28.2mg/L, The denitrification rate in this process is 0.56 mg/(L·h), mainly electrode denitrification (low COD consumption, less non-electrode denitrification). At this time, battery A generates electric energy, with an average voltage of 246mV and an average output power of 27.0mW/cm ² within 24 hours.

Overall process: The comprehensive denitrification rate of the overall process of battery A is 2.62 mg/(L··h), the organic carbon source COD/NO ₃ ^-ratio of denitrification consumed is 3.9, and the electric energy generated is 6.54W. 13.08W.

Implementation case 2:

A traditional double-chamber denitrification biofuel cell is used, and other experimental conditions are the same as in Example 1, but the negative and positive electrodes are always connected, as a comparison with Case 1. After 48 hours of reaction, the cathode effluent NO ₃ -N 28.7mg/L, COD 22.4mg/L at this time, at this time, the average voltage within 48 hours is 203.1mV, and the average output power is 18.4mW/cm ² . The comprehensive denitrification rate is 2.46mg/(L·h), the ratio ^of organic carbon source COD/NO ₃ -consumed by denitrification is 4.3, and the electric energy generated is 4.46W. Various performance indicators such as organic carbon source consumption are lower than the device of the present invention (case 1), and the amount of treated water is also reduced by half.

Implementation case 3:

Other operating conditions are the same as in Example 1, and no interactive control switch is used for the three-chamber battery, so that the two batteries are opened and closed at the same time, compared with Example 1. There are two processes:

(1) The non-electrode denitrification process is carried out at the same time on A and B sides: disconnect the anode and the two cathodes, after 24 hours of reaction, the cathode NO ₃ -N35.5mg/L, COD31.2mg/L, the denitrification rate of this process is 4.11 mg/(L h) (the result is the same as the process 1 in the implementation case 1), at this time, the batteries A and B do not produce electric energy.

(2) The electrode denitrification process is carried out at the same time on the A and B sides: the anode and the two cathodes are connected, and after 24 hours of continuous reaction, the single-side cathode NO ₃ -N32.9mg/L, COD30.4mg/L, the denitrification rate of this process It is 0.15mg/(L·h), and at this time, the (average) power generation capacity of one side of the battery is 2.86W, a total of 5.72W.

Since a single anode is connected to two cathodes at the same time, the current density dispersion (and instability) leads to a decrease in the denitrification rate of the electrodes on both sides, that is, the operation mode of the three-chamber battery switching at the same time, the denitrification rate and power generation capacity of the electrodes are not as good as The interactive control switch controls the mode of operation.

Implementation case 4:

Other operating conditions are the same as in Example 1, changing the alternate operation time to 12h, 24h, 36h, 48h, etc., and comparing the influence of the alternate time.

In the experiment, when the cathode COD is lower than 30mg/L, the non-electrode denitrification rate is greatly reduced to about 0.08mg/(L·h), even lower than the electrode denitrification rate of 0.1-0.6mg/(L·h). As for the influent sodium acetate (COD concentration about 200mg/L) and NaNO ₃ (NO ₃ -N about 70mg/L), under the experimental conditions, when the process I reacted for 24 hours, the COD just dropped to about 30mg/L. If the non-electrode denitrification time is too long, such as 36h, the COD is too low, resulting in a very low non-electrode denitrification rate; if the time is too short, a large amount of remaining organic carbon sources will affect the rate and production capacity of the electrode denitrification process. Therefore, for this water inflow condition, the optimal time control point is 24h.

If the conditions such as influent COD and nitrate nitrogen change, the optimal interaction time control point can be found for optimal operation by adjusting the reaction time.

Claims (2)

1. An interactive three-chamber biofuel cell device, comprising: middle anode chamber (5), both sides cathode chamber (1), external circuit and resistance (10), interactive control switch (11), described middle anode The chamber (5) includes an electrode chamber, a water inlet and outlet, and a sample injection port, in which anaerobic sludge is inoculated to control the anaerobic state, and an anode (6) of carbon felt material is placed; It is characterized by: Described cathode chamber (1), comprises water inlet and outlet (4), (3), sample inlet ( ⁹ ), inoculates through domesticated anoxic sludge, and places the carbon felt material that surface area is 28cm as cathode ( 2); The cathode chambers (1) on both sides include two mirror-symmetrical chambers (1A, 1B) with a volume of 350 cm ² , separated from the anode chamber by a proton exchange membrane (7) with a diameter of 20 cm; The external circuit and the resistor (10) connect the anode to the two cathodes (2A, 2B) respectively, the external resistor is fixed at 800 ohms, and two mirror-symmetric biofuel cells are formed by three electrode chambers; The interactive control switch (11) is connected with the anode (6), and alternately controls the closing and disconnection of the anode and the two cathodes. 2. A method based on the interactive three-chamber biofuel cell device as claimed in claim 1 being applied to wastewater denitrification, comprising the steps of: Step 1: Inoculate the anode chamber (5) with anaerobic sludge, and inoculate the two cathode chambers (1A and 1B) with acclimated anoxic denitrification sludge; It is characterized in that it also includes the following steps: Step 2: The waste water containing nitrate nitrogen that needs to be treated enters the cathode chambers (1A, 1B) on both sides of the three-chamber biofuel cell alternately in batches. First, the cathode (2A) on the A side is disconnected from the anode, and the cathode chamber on the A side (1A) Inlet, carry out non-electrode denitrification utilizing organic carbon source; Step 3: After 24 hours, the B-side cathode (2B) is disconnected from the anode, and the B-side cathode chamber (1B) is filled with water for non-electrode denitrification using an organic carbon source. At this time, the A-side cathode chamber (1A) organic carbon When it is exhausted, the interactive control switch controls the connection between the anode and the cathode on side A, and the cathode chamber on side A conducts denitrification of the electrode using cathode electrons, and simultaneously generates electric energy; Step 4: After another 24 hours, the organic carbon in the B-side cathode chamber (1B) is exhausted, the interactive control switch controls the anode to communicate with the B-side cathode, and the B-side cathode chamber conducts electrode denitrification and generates electric energy at the same time, while the A-side cathode Chamber drains and enters new waste water; Step 5: Repeat the above steps 2, 3 and 4, the two cathode chambers are alternately fed and drained, and with the interactive control switch (11), the control anode (6) is always connected to the cathode of "the organic carbon source is exhausted" , making the two batteries run alternately.