CN105293855A - Method of synchronously degrading excess sludge and treating hexavalent chromium wastewater - Google Patents

Abstract

A method for synchronously degrading excess sludge and treating hexavalent chromium wastewater, the invention relates to a method for recycling excess sludge and treating chromium-containing wastewater. The present invention aims to solve the problem of high treatment cost of the existing microbial fuel cell treatment of residual pollutants. This method: 1. Build a double-pool structure reactor; 2. Add excess sludge and nutrient solution to the anode chamber of the reactor, and add potassium ferricyanide catholyte to the cathode chamber for cultivation. When the voltage output is greater than 0.6V, The startup is successful; 3. Add the remaining sludge and nutrient solution to be treated into the anode chamber, and add the hexavalent chromium wastewater to be treated into the cathode chamber for treatment. The treatment cycle of the remaining sludge is 40-50 days, and the remaining sludge The degradation rate can reach 38% to 62%, the reduction period of hexavalent chromium wastewater is 2 to 10 days, and the reduction rate of hexavalent chromium can reach 66.4% to 93.2%, achieving the purpose of synchronously degrading excess sludge and treating hexavalent chromium wastewater .

Description

A method for synchronously degrading excess sludge and treating hexavalent chromium wastewater

technical field

The invention belongs to the technical field of microbial fuel cells, and in particular relates to a method for realizing resource utilization of surplus sludge, reduction of chromium-containing wastewater and synchronous power generation.

Background technique

Biomass energy is the only renewable energy that can fix carbon. Its high-efficiency conversion and clean utilization have attracted increasing attention from all over the world. Many countries have identified biomass energy as the goal of future energy development. Aiming at the problems of global energy shortage, high energy consumption and long hydraulic retention time in the traditional sewage/sludge treatment and disposal process, by introducing microbial fuel cell technology, the chemical energy in the pollutants can be converted into electrical energy while treating the remaining pollutants Recycling to realize the resource utilization and energy utilization of pollutants. Microbial fuel cells can directly convert the chemical energy in organic waste into clean electrical energy under normal temperature and pressure conditions. Mild conditions and other advantages.

The existing method of using microbial fuel cells to treat residual pollutants is to use residual pollutants as an anode substrate, and add potassium ferricyanide, potassium permanganate, etc. to the cathode area to carry out microbial chemical reactions. For example, the article "Microbial Fuel Cell Treatment of Excess Sludge and Synchronous Power Generation Performance" published in the Journal of Harbin Engineering University, Volume 31, Issue 6, June 2010 discloses a method for treating excess sludge using microbial fuel cell technology. Potassium ferricyanide is used as the cathode electron acceptor to directly convert the chemical energy in the sludge into electrical energy. However, this method needs to add an additional cathode electron acceptor, which increases the processing cost.

Contents of the invention

The invention aims to solve the technical problem of high treatment cost in the existing method of using microbial fuel cells to treat residual pollutants, and provides a method for synchronously degrading excess sludge and treating hexavalent chromium wastewater.

A method of synchronously degrading excess sludge and treating hexavalent chromium wastewater of the present invention is carried out in the following steps:

1. Build a double-cell structure reactor: the double-cell structure reactor is composed of a shell, a cation exchange membrane, a carbon fiber brush, a reference electrode and a stirrer. The cation exchange membrane is set in the shell, and the shell is divided into an anode chamber and an anode chamber. In the cathode chamber, the carbon fiber brush arranged in the anode chamber is used as the anode, and the carbon fiber brush arranged in the cathode chamber is used as the cathode, and sampling tubes are respectively arranged at the bottom of the anode chamber and the cathode chamber, and a gas collector is arranged on the top of the anode chamber; the anode and the cathode are passed through The external circuit is connected; the reference electrode penetrates into the anode chamber; the stirrer is set in the anode chamber;

2. Start-up: add excess sludge and nutrient solution to the anode chamber of the double-pool structure reactor, wherein the volume ratio of the nutrient solution under the excess sludge is (20-30):1, and add potassium ferricyanide catholyte to the cathode chamber , Nitrogen gas is introduced into the anode chamber to ensure its anaerobic environment. During the cultivation process, the agitator in the anode chamber stirs for 3 to 5 minutes every 1 hour, and the substrate in the anode chamber and cathode chamber is replaced every 2 to 3 days; After the structural reactor voltage output is greater than 0.6V, the startup is successful;

3. Add the remaining sludge and nutrient solution to be treated into the anode chamber, feed nitrogen into the anode chamber to ensure its anaerobic environment, add the hexavalent chromium wastewater to be treated into the cathode chamber, and stirrer 5 in the anode chamber every 1h Stir for 3 to 5 minutes, the remaining sludge in the anode chamber will be treated after 40 to 50 days, and the remaining sludge to be treated will be replaced; the hexavalent chromium wastewater in the cathode chamber will be treated in 2 to 10 days, and the new hexavalent chromium wastewater to be treated will be replaced , to complete the operation of synchronously degrading excess sludge and treating hexavalent chromium wastewater

Chromium and chromium salts are indispensable raw materials in industrial production, and are widely used in industries such as electroplating, printing and dyeing, and tanning. These industries can produce a large amount of chromium-containing wastewater and pollute the environment. Chromium in the environment can directly or indirectly enter the human body and cause harm to human health. Therefore, timely and effective methods should be adopted to treat chromium-containing wastewater and prevent chromium pollution. Chromium is a heavy metal element with divalent, trivalent and hexavalent valence states, among which trivalent and hexavalent compounds are more common. Among the chromium compounds, hexavalent chromium has the strongest biological toxicity, followed by trivalent chromium and the least toxic bivalent chromium. The toxicity of hexavalent chromium is about 100 times that of trivalent chromium. Hexavalent chromium is also recognized as one of the environmental carcinogens. Therefore, the conversion of hexavalent chromium to trivalent chromium is not only an effective detoxification method, but also a key step in the ultimate removal of chromium from the aquatic environment. The present invention utilizes the characteristic that the theoretical oxidation-reduction potential of the process of converting hexavalent chromium into trivalent chromium has reached a relatively high 1.33V, and uses hexavalent chromium as the cathode electron acceptor of the microbial fuel cell, thus achieving the removal of hexavalent chromium Effect, can also get a certain energy output, improve the cathode potential compared with the typical potassium ferricyanide cathode, and promote the operation of the whole battery to a certain extent, and at the same time, the reaction mode of the two-way removal of anode and cathode pollutants It also has certain positive significance for the research and development of new environmental engineering equipment. The principle of action is: the sludge in the anode chamber of the microbial fuel cell is in an anaerobic environment, so the sludge itself is in a slow anaerobic fermentation process under the action of anaerobic bacteria, that is, the organic matter is slowly degraded. After the start-up stage of the battery, electrochemically active bacteria (Geobacter, Clostridium, etc.) are gradually domesticated inside the sludge in the anode chamber. These bacteria use the soluble small molecule organic matter produced by the anaerobic fermentation process of the anode sludge to metabolize and export continuous electrons. At the same time, it will accelerate the anaerobic fermentation process in the anode chamber, thereby accelerating the degradation of sludge, which is the reaction principle of microbial fuel cells with sludge as the anode substrate. Compared with other sludge fuel cells, the use of hexavalent chromium wastewater in the catholyte can increase the cathode potential, thereby accelerating the output rate of electrons in the anode chamber, improving the electricity production efficiency and activity of electrochemically active bacteria, thereby improving the sludge degradation effect and power generation efficiency. Therefore, this process can not only realize the stabilization of excess sludge and the reduction of hexavalent chromium wastewater, but also improve the sludge degradation effect and electricity production effect. The treatment cycle of the remaining sludge in the anode chamber is 40-50 days, and the degradation rate of the remaining sludge can reach 38%-62%. %~93.2%. Using the method to simultaneously treat excess sludge and hexavalent chromium wastewater has low investment cost, low energy consumption and no pollution. The invention simultaneously realizes resource utilization of excess sludge, reduction of chromium-containing waste water and synchronous power generation.

Description of drawings

Fig. 1 is a structural schematic diagram of a double-cell structure reactor of the present invention. Among them, 1 is the shell, 2 is the cation exchange membrane, 3 is the carbon fiber brush, 4 is the reference electrode, 5 is the stirrer, 1-1 is the anode chamber, 1-2 is the cathode chamber, 1-3 is the sampling tube, 1- 4 is the air collecting pipe.

detailed description

Specific embodiments: a method for synchronously degrading excess sludge and treating hexavalent chromium wastewater according to the present embodiment is carried out in the following steps:

1. Build a double-cell structure reactor: the double-cell structure reactor is composed of a shell 1, a cation exchange membrane 2, a carbon fiber brush 3, a reference electrode 4 and a stirrer 5, and the cation exchange membrane 2 is set in the shell 1, Housing 1 is divided into anode chamber 1-1 and cathode chamber 1-2, the carbon fiber brush 3 that is arranged in the anode chamber 1-1 is an anode, the carbon fiber brush 3 that is arranged in the cathode chamber 1-2 is a cathode, in the anode chamber 1-1 and the bottom of the cathode chamber 1-2 are respectively provided with a sampling tube 1-3, and the top of the anode chamber is provided with a gas collector 1-4; the anode and the cathode are connected through an external circuit; the reference electrode 4 penetrates into the anode chamber; stirring Device 5 is arranged in the anode chamber;

2. Start-up: Add excess sludge and nutrient solution to the anode chamber 1-1 of the double-pool structure reactor. Potassium ferricyanide catholyte is added inside, and nitrogen is passed into the anode chamber to ensure its anaerobic environment. During the cultivation process, the agitator 5 in the anode chamber stirs for 3 to 5 minutes every 1 hour, and the anode chamber and the anode chamber are replaced every 2 to 3 days. The substrate in the cathode chamber; when the voltage output of the double-cell structure reactor is greater than 0.6V, the startup is successful;

3. Add the remaining sludge and nutrient solution to be treated into the anode chamber 1-1, feed nitrogen into the anode chamber to ensure its anaerobic environment, add the hexavalent chromium wastewater to be treated into the cathode chamber 1-2, and anode The stirrer 5 in the room stirs for 3 to 5 minutes every 1 hour. After 40 to 50 days, the remaining sludge in the anode chamber is treated and replaced with new remaining sludge to be treated; the hexavalent chromium wastewater in the cathode chamber is treated in 2 to 10 days. The new hexavalent chromium wastewater to be treated has completed the simultaneous degradation of excess sludge and the treatment of hexavalent chromium wastewater.

Specific embodiment two: the difference between this embodiment and specific embodiment one is that the composition and proportioning ratio of the nutrient solution in step two are as shown in Table 1:

The composition and proportioning ratio of table 1 nutrient solution

Others are the same as the first embodiment.

Specific embodiment three: what this embodiment is different from specific embodiment one or two is that in step two, potassium ferricyanide catholyte is according to the concentration of potassium ferricyanide (K ₃ [Fe(CN) ₆ ] is 30～35g/L 1. Potassium dihydrogen phosphate (KH ₂ PO ₄ ) with a concentration of 25-30 g/L, prepared by adding potassium ferricyanide and potassium dihydrogen phosphate into water; other aspects are the same as those in Embodiment 1 or 2.

Embodiment 4: The difference between this embodiment and one of Embodiments 1 to 3 is the treatment method of the two electrodes, the cathode and the anode, described in step 1 before use: wash the electrodes with water first, and then use 1mol/ L of HCl and 1mol/L NaOH solution were soaked for 2 hours each to remove impurities on the surface of the electrode material, and finally soaked in deionized water for 5 hours for later use; the others were the same as those of Embodiments 1 to 3.

Embodiment 5: The difference between this embodiment and Embodiment 1 to 4 is the treatment method of the proton exchange membrane described in step ₁ before use: the cation exchange membrane is first boiled with 30% H ₂ O 30min, Then soak in 1mol/L HCl and 1mol/L NaOH solutions for 2 hours in order to remove pollutants and impurities on the membrane surface, and finally soak in deionized water for 5 hours and set aside. Others are the same as one of the specific embodiments 1 to 4.

Embodiment 6: The difference between this embodiment and one of Embodiments 1 to 5 is that the volume ratio of the remaining sludge to the nutrient solution in step 2 is 25:1, and the others are the same as Embodiments 1 to 5.

Verify beneficial effect of the present invention with following test:

Test 1: A method for synchronously degrading excess sludge and treating hexavalent chromium wastewater in this test is carried out according to the following steps:

1. Build a double-cell structure reactor: the double-cell structure reactor is composed of a shell 1, a cation exchange membrane 2, a carbon fiber brush 3, a reference electrode 4 and a stirrer 5, and the cation exchange membrane 2 is set in the shell 1, The casing 1 is divided into an anode chamber 1-1 and a cathode chamber 1-2, the carbon fiber brush 3 arranged in the anode chamber 1-1 is an anode, the carbon fiber brush 3 arranged in the cathode chamber 1-2 is a cathode, and the anode chamber 1-1 and the bottom of the cathode chamber 1-2 are respectively provided with a sampling tube 1-3, and the top of the anode chamber is provided with a gas collector 1-4; the anode and the cathode are connected through an external circuit; the reference electrode 4 penetrates into the anode chamber; stirring The device 5 is set in the anode chamber; the treatment method of the two electrodes, the cathode and the anode, before use: rinse the electrodes with water first, and then soak them in 1mol/L HCl and 1mol/L NaOH solutions for 2 hours respectively to remove electrode materials Impurities on the surface should be soaked in deionized water for 5 hours at last; the treatment method of the proton exchange membrane before use: the cation exchange membrane is boiled with 30% H ₂ O ₂ for 30 minutes, and then successively with 1mol/L HCl and 1mol/L NaOH solution Soak for 2 hours each to remove pollutants and impurities on the membrane surface, and finally soak in deionized water for 5 hours;

2. Start-up: add 500mL of residual sludge from the secondary settling tank with a water content of 92% and TCOD of 48435mg/L in the anode chamber 1-1 of the double-cell structure reactor as the anode substrate, and then add 15mL of the nutrient solution (see Table 1), add 350mL potassium ferricyanide catholyte in cathode compartment 1-2, during cultivating, the stirrer 5 in anode compartment stirs 3 minutes every 1h, replaces the bottom of anode compartment and cathode compartment every 2 days After 5 days, when the voltage output of the double-cell structure reactor was stable at 0.6V, the start-up was successful, wherein the potassium ferricyanide catholyte was 32.9g according to the concentration of potassium ferricyanide (K ₃ [Fe(CN) ₆ ]) /L, the concentration of potassium dihydrogen phosphate (KH ₂ PO ₄ ) is 27.2g/L, which is prepared by adding potassium ferricyanide and potassium dihydrogen phosphate into water; after successful startup, electrochemically active bacteria ( Geobacter, Clostridium, etc.);

3. Add 500mL of residual sludge from the secondary settling tank with a moisture content of 92% and TCOD of 48435mg/L to be treated as an anode substrate into the anode chamber 1-1, and then add 15mL of nutrient solution (see Table 1 for composition) In the anode chamber 1-1, feed nitrogen into the anode chamber to ensure its anaerobic environment, and add 350 mL of hexavalent chromium wastewater to be treated with a hexavalent chromium ion concentration of 9 mg/L into the cathode chamber 1-2. Stirrer 5 stirred for 3 minutes every 1 hour to reduce the mass transfer internal resistance of the battery and promote the rapid degradation of organic matter. The treatment results were tested every 6 hours. After 2 days, the total chromium removal rate was 83.20%, and the hexavalent chromium removal rate was 83.20%. The rate is 93.2%, after that every 2 days, that is, the cathode hexavalent chromium wastewater is replaced at the end of each cathode reaction cycle, the TCOD degradation rate of the remaining sludge after 50 days is 38.03%, and the remaining sludge is replaced every 50 days thereafter, realizing Simultaneously degrade excess sludge and treat hexavalent chromium wastewater.

Test 2: The difference between this test and Test 1 is that step 3 is replaced by the following operation: 500mL of secondary sedimentation tank residual sludge with a water content of 92% and a TCOD of 48435 mg/L to be treated is added to the anode chamber 1- 1, then add 15mL of nutrient solution (see Table 1 for the composition) into the anode chamber 1-1, and add 350mL of hexavalent chromium waste water with a hexavalent chromium concentration of 18mg/L into the cathode chamber 1-2, The stirrer 5 in the anode chamber stirs for 3 minutes every 1h, to reduce the mass transfer internal resistance of the battery and promote the rapid degradation of organic matter, take a sample every 8 hours to test the treatment results, after 4 days, the total chromium removal rate is about 83.01%, The removal rate of hexavalent chromium is 85.03%, and the TCOD degradation rate of excess sludge is 40.15%, which can realize simultaneous degradation of excess sludge and treatment of hexavalent chromium wastewater.

Test 3: The difference between this test and Test 1 is that step 3 is replaced by the following operation: 500mL of secondary sedimentation tank residual sludge with a water content of 92% and a TCOD of 48435 mg/L to be treated is added to the anode chamber 1- 1, then add 15mL of nutrient solution (see Table 1 for the composition) in the anode chamber 1-1, and the hexavalent chromium concentration to be treated is 27mg/L hexavalent chromium wastewater is added in the cathode chamber 1-2, and the anode chamber Stirrer 5 stirs for 3 minutes every 1 hour to reduce the mass transfer internal resistance of the battery and promote the rapid degradation of organic matter. The treatment results are tested every 8 hours. After 4 days, the total chromium removal rate is about 68.95%, and the hexavalent chromium The removal rate is 80.3%, and the TCOD degradation rate of excess sludge is 53.86%, which can realize simultaneous degradation of excess sludge and treatment of hexavalent chromium wastewater.

Test 4: The difference between this test and Test 1 is that step 3 is replaced by the following operation: 500mL of secondary sedimentation tank residual sludge with a water content of 92% and a TCOD of 48435 mg/L to be treated is added to the anode chamber 1- 1, then add 15mL nutrient solution (see Table 1 for composition) in the anode chamber 1-1, the hexavalent chromium wastewater to be treated is 35mg/L of hexavalent chromium is added in the cathode chamber 1-2, the anode The stirrer 5 in the room stirred for 3 minutes every 1 hour to reduce the mass transfer internal resistance of the battery and promote the rapid degradation of organic matter. The treatment results were tested every 8 hours. After 4 days, the total chromium removal rate was about 64.93%, and the hexavalent The chromium removal rate is 66.38%, and the TCOD degradation rate of the excess sludge is 62.18%, which can simultaneously degrade excess sludge and treat hexavalent chromium wastewater.

Claims (5)

1. a method for synchronously degrading excess sludge and processing hexavalent chromium waste water, characterized in that the method is carried out in the following steps: 1. Build a double-cell structure reactor: the double-cell structure reactor consists of a shell (1), a cation exchange membrane (2), a carbon fiber brush (3), a reference electrode (4) and a stirrer (5). The exchange membrane (2) is arranged in the casing (1), and the casing (1) is divided into an anode chamber (1-1) and a cathode chamber (1-2), and the carbon fiber brush arranged in the anode chamber (1-1) (3) is an anode, and the carbon fiber brush (3) that is arranged in the cathode chamber (1-2) is a cathode, and sampling tube (1- 3), the top of the anode chamber is provided with a gas collector (1-4); the anode and the cathode are connected through an external circuit; the reference electrode (4) penetrates into the anode chamber; the stirrer (5) is arranged in the anode chamber; 2. Start-up: Add excess sludge and nutrient solution to the anode chamber (1-1) of the double-pool structure reactor, wherein the volume ratio of the nutrient solution under the excess sludge is (20-30): 1, and feed it to the cathode chamber ( 1-2) Potassium ferricyanide catholyte was added, and nitrogen gas was introduced into the anode chamber to ensure its anaerobic environment. Replace the substrate in the anode chamber and cathode chamber once a day; when the voltage output of the double-cell structure reactor is greater than 0.6V, the start-up is successful; 3. Add the remaining sludge and nutrient solution to be treated in the anode chamber (1-1), feed nitrogen into the anode chamber to ensure its anaerobic environment, and add the hexavalent chromium wastewater to be treated into the cathode chamber (1-2 ), the agitator (5) in the anode chamber stirs for 3 to 5 minutes every 1 hour, and the remaining sludge in the anode chamber is treated after 40 to 50 days, and new remaining sludge to be treated is replaced; the hexavalent chromium wastewater in the cathode chamber is 2 to 50 days. After 10 days of treatment, replace with new hexavalent chromium wastewater to be treated, and complete the simultaneous degradation of remaining sludge and treatment of hexavalent chromium wastewater. 2. a kind of method for synchronously degrading excess sludge and processing hexavalent chromium waste water according to claim 1, is characterized in that in step 2, potassium ferricyanide catholyte is 30～35g/L by the concentration of potassium ferricyanide , The concentration of potassium dihydrogen phosphate is 25-30g/L, which is prepared by adding potassium ferricyanide and potassium dihydrogen phosphate into water. 3. according to claim 1 or 2 described a kind of method of synchronously degrading excess sludge and processing hexavalent chromium wastewater, it is characterized in that the treatment method of these two electrodes of cathode and anode described in step 1 before use: Rinse the electrode with water first, then soak it in 1mol/L HCl and 1mol/L NaOH solution for 2 hours to remove impurities on the surface of the electrode material, and finally soak it in deionized water for 5 hours, and set it aside. 4. A method for synchronously degrading excess sludge and treating hexavalent chromium wastewater according to claim 1 or 2, characterized in that the treatment method of the proton exchange membrane described in step 1 before use: the cation exchange membrane first Boil in 30% H ₂ O ₂ for 30 minutes, then soak in 1mol/L HCl and 1mol/L NaOH solutions for 2 hours respectively to remove membrane surface pollutants and impurities, and finally soak in deionized water for 5 hours and set aside. 5. A method for synchronously degrading excess sludge and treating hexavalent chromium wastewater according to claim 1 or 2, characterized in that the volume ratio of excess sludge to nutrient solution in step 2 is 25:1.