Method and reactor for simultaneous removal of refractory organics by coupling manganese cycle with denitrification

Abstract

The application discloses a method and a reactor for removing recalcitrant organics by manganese cycle coupling denitrification, and comprises enrichment culture of sludge, preparation of biological inoculants, pretreatment of immobilized materials, preparation of immobilized materials, biofilm formation of the biological inoculants and operation of the reactor. The application connects manganese oxidation and manganese reduction in series, uses modified corncobs loaded with MnO2 as a manganese oxide source, constructs a manganese (II) and manganese (IV) cycle system, drives manganese oxidation-reduction cycle coupling denitrification by microorganisms, and efficiently removes nitrate and recalcitrant organics in water. The application can be continuously operated, and has the characteristics of being novel, efficient, green and free of secondary pollution.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of water treatment, and particularly relates to a method and a reactor for removing refractory organic matter by manganese cycle coupled with denitrification. BACKGROUND

[0002] Generally speaking, the contaminated water body contains heavy metals, inorganic salts such as nitrate, and a large amount of refractory organic matter. These toxic substances continuously migrate and transform with the water flow, and further penetrate into the soil and even the groundwater.

[0003] Among numerous water treatment technologies, the bioremediation technology using the metabolic action of microorganisms to degrade pollutants is widely used. However, up to now, the microorganisms are easily limited by the growth environment, and the cost is relatively high due to the large amount of carbon sources such as methanol and acetic acid. In addition, the existing water treatment technology cannot simultaneously remove nitrate and refractory organic matter, and the treatment process has high operating cost and large occupied area, which is easy to cause secondary pollution.

[0004] The biological denitrification technology mediated by manganese oxides has attracted widespread attention. By coupling manganese redox cycle with denitrification, the reaction speed of the biological pathway can be improved, and the demand for organic carbon by microorganisms can be significantly reduced. This method has potential application value when the existing traditional denitrification process is limited by low carbon-nitrogen ratio, and can provide a new idea for current water treatment methods. SUMMARY

[0005] To solve the above-mentioned defects in the prior art, the purpose of the present application is to provide a method and a reactor for removing nitrate and refractory organic matter pollution in water body by manganese redox cycle coupled with denitrification. The method connects manganese oxidation and manganese reduction in series, uses modified corncob loaded with MnO2 as a source of manganese oxide, constructs a cycle system of Mn(II) and Mn(IV), and drives manganese redox cycle coupled with denitrification by microorganisms to efficiently remove nitrate and refractory organic matter in water body.

[0006] The present application is realized by the following technical solutions.

[0007] In one aspect of the present application, a method for removing refractory organic matter by manganese cycle coupled with denitrification is provided, comprising:

[0008] Step (a), under anaerobic conditions, mix the reservoir sediment, MM culture solution and MnO2 in a mass ratio of (30-60):(160-200):(1-5), introduce nitrogen and seal, and carry out sludge enrichment culture;

[0009] Step (b), the sludge enriched in culture is mixed with MM culture solution in a mass ratio of (3-5):1, MnO2 powder and Mn(II) stock solution are added, and nitrogen is continuously introduced for incubation; when it is detected that the supernatant of the sludge to which MnO2 powder is added has increased Mn 2+ , and the supernatant of the sludge to which Mn(II) stock solution is added has reduced Mn 2+ , the two kinds of sludge are mixed in a volume ratio of 1:1 to obtain a composite biological inoculant;

[0010] Step (c), the dry corncob is pretreated, the pretreated dry corncob is added into a polypyrrole modification solution, is shaken, is left to soak, is washed, and is dried to obtain polypyrrole modified corncob;

[0011] Step (d), the polypyrrole modified corncob is added into a manganese chloride solution, and then KMnO4 solution is slowly added, the mass ratio of the manganese chloride solution to the KMnO4 solution is (20-30):(16-20); the pH value is adjusted, and the mixture is washed, diluted, and left to dry to obtain MnO2 loaded corncob immobilized material;

[0012] Step (e), the MnO2 loaded corncob immobilized material is soaked in a mixture of the composite biological inoculant in a volume ratio of 1:2 to obtain a biological inoculant filler, and MM culture solution is added for biofilm formation at room temperature;

[0013] Step (f), the MnO2 loaded corncob immobilized material after biofilm formation is put into a reactor for removal of nitrate and refractory organic matter in influent.

[0014] In step (a), the enrichment culture comprises: introducing 5-10 L / min of nitrogen gas for 5 min each time; 7 days is one culture cycle, the supernatant is replaced with MM culture solution continuously in each cycle, a shaking table with a rotation speed of 70-150 r / min is used, and the enrichment culture is carried out for 2-3 weeks; and the enrichment culture is ended when the nitrate removal rate is above 70%.

[0015] In step (a), the MM culture solution comprises: in terms of mass concentration, CH3COONa 0.1-0.2 g / L, NaHCO3 0.5-0.8 g / L, NaNO3 0.1-0.3 g / L, C6H 12 O6·H2O 0.05-0.08 g / L, KH2PO4 0.05-0.08 g / L, K2HPO4 0.15-0.20 g / L, MgCl2 0.05-0.08 g / L, CaCl2·7H2O 0.07-0.10 g / L, trace element solution I 1 mL, and distilled water 1000 mL, and the pH value is 7.0.

[0016] Trace element solution I includes: 0.5-0.8 g / L MgSO4·7H2O, 1.0-1.2 g / L EDTA, 0.2-0.5 g / L ZnSO4, 0.1-0.2 g / L MnCl2·4H2O, 0.5-0.8 g / L FeSO4·7H2O, 0.5-0.8 g / L CuSO4·5H2O, 0.2-0.5 g / L CoCl2·6H2O in terms of mass concentration.

[0017] In step (b), the Mn(II) stock solution is 0.05-0.08 g / L MnCl2·4H2O in terms of mass concentration;

[0018] Mn in the supernatant of sludge with MnO2 powder added 2+ Increased by 15-20 mg / L, Mn in the supernatant of sludge with Mn(II) stock solution added 2+ Reduced by 15-20 mg / L;

[0019] Incubation includes continuously passing nitrogen for 20-30 min, sealing, and incubating at 25-30℃ for 48-72 h.

[0020] In step (c), the natural corncob pretreatment includes soaking with 0.5-0.8 mol / L NaOH solution for 8-24 h, washing with water until neutral, and drying at 50-70℃ for 24-36 h.

[0021] In step (c), the polypyrrole modification solution is 1.5-4.0 mL pyrrole and 15-17 g FeCl3 solution per 100 mL deionized water; the pretreated dry corncob is placed in the polypyrrole modification solution, shaken for 5-10 min, soaked for 4 h, washed 2-3 times, and dried at 50-70℃ for 12-24 h.

[0022] In step (d), the MnO2-loaded corncob immobilized material includes adjusting the pH value to 5.5±0.1 with 1 g / L NaOH, shaking for 1-3 min, washing with diluted ethanol 3-5 times, and placing at 60-80℃ for 36-48 h.

[0023] In step (e), the biofilm is formed at room temperature for 7-10 days, and the process is ended when the nitrate removal rate is above 70% and the organic matter removal rate is above 90%.

[0024] The reactor operation includes controlling the influent pH value to be 5.5-7.5, the nitrate concentration to be 1-30 mg / L, and the concentration of refractory organic matter to be 1-3 mg / L; the operation is performed for 6-12 h at a temperature of 25-35℃.

[0025] In another aspect of the present application, a reactor used in the method is provided, which comprises a water inlet tank, a reactor body, a clean water tank, a supporting layer, a filler layer, an online pH meter, a temperature control probe, an online automatic water quality detector and a computer terminal.

[0026] The present application has the following beneficial effects due to the above technical solutions:

[0027] 1. The present application provides a filler layer in the reactor body, which is MnO2-loaded modified corncob with manganese-oxidizing bacteria and manganese-reducing bacteria. The MnO2-loaded modified corncob not only provides a source of manganese oxide and releases soluble organic matter as a carbon source, but also provides a carrier for microbial attachment sites. In addition, the MnO2 can adsorb and oxidize refractory organic matter in wastewater. Biomass corncob is a crop waste, and its main components are cellulose, hemicellulose and lignin. It has an ideal micro-nano structure composed of layer-by-layer stacked pores, and has the characteristics of low cost, light weight, large specific surface area, easy recovery, etc. The poly-pyrrole modified corncob has high electron transfer capacity and adsorption performance, which can fully exert the adsorption capacity of microorganisms.

[0028] 2. The present application realizes the simultaneous removal of nitrate and refractory organic matter in wastewater by coupling denitrification with manganese oxidation-reduction cycles driven by microorganisms. The reaction process does not cause secondary pollution, does not overflow Mn(II), and does not contain nitrite in the effluent.

[0029] 3. The reactor in the present application can be continuously and stably operated for 270 days without frequent replacement of immobilized materials. It is easy to operate and has low maintenance and management costs. The reactor does not require aeration or additional high-cost carbon source during operation. The removal rate of nitrate can reach more than 70%, and the removal rate of refractory organic matter can reach more than 90%. It has a significant ability to remove pollutants efficiently, greatly reducing capital investment and energy consumption.

[0030] 4. The present application enriches and domesticates a biological agent, which contains indigenous bacteria and does not require external bacterial sources. In addition, it has strong sludge retention capacity.

[0031] 5. The reactor in the present application is a closed device equipped with a temperature control probe in the reactor body, which can be used to maintain a constant temperature of the container. In addition, online water quality detectors are provided in the water inlet tank and the clean water tank, which can monitor the water quality and pollutant treatment efficiency in real time. The technical personnel can perform visual debugging, and the operation and management are convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of this application, and do not constitute an improper limitation of the present invention. In the drawings:

[0033] Figure 1 Schematic diagram of the reactor structure of the present invention;

[0034] FIG2( a ) is a schematic diagram of the nitrate removal effect of Example 1;

[0035] Figure 2(b) is a schematic diagram of the estradiol removal effect of Example 1;

[0036] FIG3( a ) is a schematic diagram of the nitrate removal effect of Example 2;

[0037] Figure 3(b) is a schematic diagram of the tetracycline removal effect of Example 2;

[0038] FIG4( a ) is a schematic diagram of the nitrate removal effect of Example 3;

[0039] FIG4( b ) is a schematic diagram of the phenol removal effect in Example 3. DETAILED DESCRIPTION

[0040] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The exemplary embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0041] like Figure 1 As shown, the present invention provides a reactor for removing nitrates and refractory organic matter by manganese redox denitrification. The reactor is an immobilized bioreactor and includes an inlet tank 1, a reactor body 4, a clear water tank 6, a support layer 7, a packing layer 8, an online pH meter 9, a temperature control probe 10, an online automatic water quality detector 13, and a computer terminal 14. The reactor body 4 includes, from bottom to top, an inlet layer, a support layer 7, a packing layer 8, and a reaction layer. The inlet layer is connected to the inlet tank 1, and the reaction layer is connected to the clear water tank 6. The online pH meter 9 and the temperature control probe 10 extend into the reaction layer and are connected to the online automatic water quality detector 13. The online automatic water quality detector 13 extends into the inlet tank 1 through an inlet water quality meter 11 to detect the inlet water quality, and extends into the clear water tank 6 through an outlet water quality meter 12 to detect the outlet water quality. The online automatic water quality detector 13 is connected to the computer terminal 14.

[0042] The water inlet tank 1 is connected to the water inlet tank 1 through a peristaltic pump 2 and a water inlet valve 3 communicating pipe, and a water outlet valve 5 is provided on the pipe communicating with the clean water tank 6.

[0043] In the embodiment, the reactor is cylindrical, made of organic glass or acrylic material, with a diameter of 0.4-0.5 m, a reactor shell thickness of 10-20 mm, and a total height of 2 m; a support layer 7 is arranged in the reactor main body, which is made of quartz sand with a particle size of 0.5-1.0 cm, and is laid with a thickness of 0.4-0.6 m, and the support layer plays a role of fixing the biomass carrier and uniformly distributing water.

[0044] Correspondingly, the application provides a method for removing recalcitrant organics by manganese cycle coupled denitrification, comprising the following steps:

[0045] Step 1, enrichment culture of sludge

[0046] Under the condition of closed anaerobic conditions, 30-60 g of collected reservoir sediment samples are mixed with 160-200 g of MM culture solution and 1-5 g / L of MnO2, and then added into a 250 mL narrow-mouth bottle, 5-10 L / min of nitrogen is introduced for 5 minutes each time, and then sealed and placed in a constant-temperature incubator (25-30 °C) for enrichment culture; in the enrichment culture process, 7 days are taken as one culture period, the supernatant is replaced with MM culture solution every period, a shaker with a rotating speed of 70-150 r / min is used, and after 2-3 weeks of enrichment, when the nitrate removal rate is above 70%, it is indicated that the enrichment culture is completed.

[0047] The MM culture solution comprises, in terms of mass concentration, CH3COONa 0.1-0.2 g / L, NaHCO3 0.5-0.8 g / L, NaNO3 0.1-0.3 g / L, C6H 12 O6·H2O 0.05-0.08 g / L, KH2PO4 0.05-0.08 g / L, K2HPO4 0.15-0.20 g / L, MgCl2 0.05-0.08 g / L, CaCl2·7H2O 0.07-0.10 g / L, trace element solution I 1 mL, and distilled water 1000 mL, and the pH value is 7.0.

[0048] The trace element solution I comprises, in terms of mass concentration, 0.5-0.8 g / L of MgSO4·7H2O, 1.0-1.2 g / L of EDTA, 0.2-0.5 g / L of ZnSO4, 0.1-0.2 g / L of MnCl2·4H2O, 0.5-0.8 g / L of FeSO4·7H2O, 0.5-0.8 g / L of CuSO4·5H2O, and 0.2-0.5 g / L of CoCl2·6H2O.

[0049] Step 2, preparation of biological bacterial agent:

[0050] Take two anaerobic bottles, add 1 g / L of MnO2 powder to bottle ①, and add 20 mg / L of Mn(II) stock solution to bottle ②. The Mn(II) stock solution is 0.05-0.08 g / L of MnCl2·4H2O. Take the sludge obtained in step 1 and add it to two 300 mL anaerobic bottles in a mass ratio of 3-5:1 MM culture medium. Continuously pass nitrogen gas for 20-30 minutes, and finally seal with a butyl rubber plug. Incubate at 25-30°C for 48-72 hours. When the upper clear liquid in bottle ① is detected to increase to 15-20 mg / L, and the upper clear liquid in bottle ② is detected to decrease to 15-20 mg / L, mix the two cultured sludges in a volume ratio of 1:1 to obtain a composite biological inoculant. 2+ 2+ Take two anaerobic bottles, add 1 g / L of MnO2 powder to bottle ①, and add 20 mg / L of Mn(II) stock solution to bottle ②. The Mn(II) stock solution is 0.05-0.08 g / L of MnCl2·4H2O. Take the sludge obtained in step 1 and add it to two 300 mL anaerobic bottles in a mass ratio of 3-5:1 MM culture medium. Continuously pass nitrogen gas for 20-30 minutes, and finally seal with a butyl rubber plug. Incubate at 25-30°C for 48-72 hours. When the upper clear liquid in bottle ① is detected to increase to 15-20 mg / L, and the upper clear liquid in bottle ② is detected to decrease to 15-20 mg / L, mix the two cultured sludges in a volume ratio of 1:1 to obtain a composite biological inoculant.

[0051] Step 3, pretreatment of immobilization material:

[0052] Take 20 g of natural corn cob and cut it into blocks with a width of 1.0-1.5 cm. After wetting, soak it in a 0.5-0.8 mol / L sodium hydroxide solution for 8-24 hours. Then wash the corn cob with water until it is neutral, and then dry it at 50-70°C for 24-36 hours.

[0053] In a 500 mL flask, add 1.5-4.0 mL of pyrrole and 15-17 g of iron chloride per 100 mL of deionized water, and use a magnetic stirrer to stir for 4-6 hours to ensure complete mixing.

[0054] Add the pretreated dry corn cob to the shaker for 5-10 minutes, soak for 4 hours, then wash it with deionized water and anhydrous ethanol for 2-3 times, and dry it at 50-70°C for 12-24 hours to obtain the polypyrrole modified corn cob.

[0055] Step 4, preparation of immobilization material:

[0056] Add 20 g of modified corn cob to a solution of 20-30 g / L MnCl2·4H2O, then slowly add 16-20 g / L KMnO4 solution, and continuously stir with a magnetic stirrer for 15-25 minutes. Adjust the pH value to 5.5±0.1 using 1 g / L NaOH, and shake for 1-3 minutes. Finally, wash the obtained material with diluted ethanol for 3-5 times, and place it at 60-80°C for 36-48 hours until it is dry to obtain the MnO2 loaded corn cob immobilization material.

[0057] Step 5, bio-inoculant biofilm formation:

[0058] ​The biofilm carrier is obtained by immersing the immobilized material of step 4 in a mixture of MM culture solution and compound biological inoculant at a volume ratio of 1:2. In a closed reactor, the carrier is added to 30-40% of the volume of the reactor, and 2-3 L of MM culture solution is added. The biofilm is cultured for 7-10 days at room temperature. When the removal rate of nitrate is above 70% and the removal rate of organic matter is above 90%, the biofilm culture is completed.

[0059] Step 6, reactor operation:

[0060] The biofilm-cultured MnO2-loaded corncob immobilized material is placed on the support layer of the reactor, and the direct current power supply is turned on. The concentration of nitrate and refractory organic matter in the influent is measured by the influent water quality detector. The HRT is set to 6-12 hours according to the water quality of the wastewater to be treated, and the temperature is 25-35℃. At the same time, the influent valve is opened, and the wastewater to be treated is pumped into the reactor by the peristaltic pump. The concentration of nitrate is 15-30 mg / L, the concentration of refractory organic matter is 1-3 mg / L, and the pH value of the influent is controlled to be 5.5-7.5.

[0061] When the concentration of nitrate in the influent is 16 mg / L or the concentration of refractory organic matter is 1 mg / L, the HRT is set to 6-8 hours; when the concentration of nitrate in the influent is 25 mg / L or the concentration of refractory organic matter is 2 mg / L, the HRT is set to 10-12 hours.

[0062] After the wastewater flows through the successfully biofilm-cultured and started biological reactor, the effluent is discharged to the clean water tank, and the water quality of the effluent is measured by the effluent water quality detector.

[0063] The reactor operation includes the following steps:

[0064] (1) Open the influent valve 3, and the wastewater flows out of the influent tank 1, passes through the peristaltic pump 2 and the influent valve 3, and flows into the reactor body 4;

[0065] (2) After the wastewater flows through the support layer 7, it enters the filler layer 8. In the filler layer 8, the microorganisms in the sludge cooperate with the MnO2-loaded corncob immobilized material to drive the manganese oxidation-reduction cycle coupled denitrification, and simultaneously remove the nitrate and refractory organic matter in the wastewater. The removal rate of nitrate can be above 70%, and the removal rate of refractory organic matter can be above 90%;

[0066] (3) Open the effluent valve 5, and the wastewater flows through the effluent valve 5 into the clean water tank 6. The water in the clean water tank is detected by the effluent water quality detector 12, analyzed by the online automatic water quality detector 13, and finally fed back to the computer terminal 14. The computer terminal 14 calculates the water quality detection results and the removal rate of pollutants.

[0067] The removal of nitrate and refractory organic matter is further illustrated by different examples.

[0068] Example 1

[0069] Example 1 The sewage to be treated is from the effluent of a secondary sedimentation tank of a sewage treatment plant in Xi'an City, and a trace amount of estradiol is added to the water.

[0070] Specifically includes the following steps:

[0071] Step 1, enrichment culture of sludge:

[0072] Into a 250 mL narrow-mouth bottle, 5 L / min of nitrogen gas is introduced for 5 minutes each time to ensure airtight anaerobic conditions. 30 g of the collected reservoir sediment sample is mixed with 180 g of MM culture solution and 3 g / L of MnO2, and then added to the 250 mL narrow-mouth bottle. Nitrogen gas is introduced and sealed, and the enrichment culture is placed in a constant-temperature incubator (30°C) for enrichment culture. 7 days is one culture period, and the supernatant is replaced with MM culture solution. A shaker with a rotation speed of 100 r / min is used. After 2 weeks of enrichment, when the nitrate removal rate is above 70%, it indicates that the enrichment culture is complete.

[0073] The MM culture solution includes, in terms of mass concentration, CH3COONa 0.1 g / L, NaHCO3 0.6 g / L, NaNO3 0.2 g / L, C6H 12 O6·H2O 0.05 g / L, KH2PO4 0.07 g / L, K2HPO4 0.18 g / L, MgCl2 0.06 g / L, CaCl2·7H2O 0.07 g / L, trace element solution I 1 mL, and distilled water 1000 mL, with a pH value of 7.0.

[0074] The addition of trace element solution I to the MM culture solution includes, in terms of mass concentration, 0.6 g / L of MgSO4·7H2O, 1.0 g / L of EDTA, 0.5 g / L of ZnSO4, 0.2 g / L of MnCl2·4H2O, 0.7 g / L of FeSO4·7H2O, 0.5 g / L of CuSO4·5H2O, and 0.4 g / L of CoCl2·6H2O.

[0075] Step 2, preparation of biological inoculant:

[0076] Take two anaerobic bottles. Add 1 g / L of MnO2 powder to the No. 1 anaerobic bottle, and add 20 mg / L of Mn(II) stock solution to the No. 2 anaerobic bottle. The Mn(II) stock solution is 0.05 g / L of MnCl2·4H2O. Take the sludge obtained in Step 1 and add MM culture solution in a mass ratio of 4:1 to two 300 mL anaerobic bottles. Continuously introduce nitrogen gas for 20 minutes, and finally seal with a butyl rubber plug. Incubate at 30°C for 48 hours. When the upper clear liquid in the No. 1 bottle is detected to have increased by 20 mg / L, and the upper clear liquid in the No. 2 bottle is detected to have increased by 20 mg / L, it indicates that the enrichment culture is complete. 2+ ​2+ The two sludges cultivated were mixed in a volume ratio of 1:1 to obtain a composite biological inoculant, with a reduction of 18 mg / L.

[0077] Step 3, immobilization material pretreatment:

[0078] 20 g of natural corn cob was divided into 1.5 cm solid blocks, moistened, soaked in 0.5 mol / L sodium hydroxide solution for 10 hours, then washed with water until neutral, and then dried at 60°C for 24 hours.

[0079] In a 500 mL flask, 250 mL of deionized water, 4.0 mL of pyrrole, and 40 g of iron chloride were added, and a magnetic stirrer was used to stir for 5 hours to ensure complete mixing.

[0080] The pretreated dry corn cob was added to the shaker for 10 minutes, soaked for 4 hours, then washed with deionized water and anhydrous ethanol for 3 times, dried at 60°C for 24 hours, and finally obtained the polypyrrole modified corn cob.

[0081] Step 4, immobilization material preparation:

[0082] 20 g of modified corn cob was added to a solution of 20 g / L MnCl2·4H2O, then 100 mL of a solution containing 18 g / L KMnO4 was added, and a magnetic stirrer was used to continuously stir for 20 minutes. The pH value was adjusted to 5.5±0.1 using 1 g / L NaOH, and shaken for 3 minutes. Finally, the resulting material was washed with diluted ethanol for 3 times, and placed at 80°C for 40 hours until dry, to obtain the MnO2 loaded corn cob immobilization material.

[0083] Step 5, bio-inoculant biofilm formation:

[0084] The biofilm formation filler was obtained by soaking the immobilization material of step four above in a mixture of MM culture solution and composite biological inoculant in a volume ratio of 1:2. In a closed reactor, 30% of the filler was added to the container, 3 L of MM culture solution was added, and the biofilm was formed at room temperature for 8 days. When the nitrate removal rate was above 70% and the removal rate of refractory organic matter was above 90%, the biofilm formation was considered complete.

[0085] Step 6, reactor operation:

[0086] The MnO2 loaded corncob immobilized material after biofilm formation is placed on the support layer of the reactor, the direct current power supply is turned on, and the influent water quality tester is used to measure the concentration of nitrate and refractory organic matter in the influent water. The support layer uses quartz sand with a particle size of 1.0 cm, and the laying thickness is 0.5 m. At the same time, the influent valve is opened, and the wastewater to be treated is pumped into the reactor by the peristaltic pump. Since the influent nitrate concentration is about 25 mg / L, and the estradiol concentration is about 1 mg / L, the influent pH value is controlled to be maintained at 5.5-7.5, the main operating parameter HRT of the system is set to 10 hours, and the temperature is about 35°C. After the wastewater flows through the successfully started biological reactor, the effluent is discharged to the clean water tank, and the effluent water quality is measured by the effluent water quality tester.

[0087] The reactor operation steps are as follows:

[0088] (1) Open the influent valve 3, and the wastewater flows out of the influent tank 1, passes through the peristaltic pump 2 and the influent valve 3, and flows into the reactor body 4;

[0089] (2) After the wastewater flows through the support layer 7, it enters the filler layer 8. In the filler layer, the microorganisms in the sludge cooperate with the MnO2 loaded corncob immobilized material to drive the manganese oxidation-reduction cycle coupled denitrification, and simultaneously remove nitrate and refractory organic matter in the wastewater;

[0090] (3) Open the effluent valve 5, and the wastewater flows through the effluent valve into the clean water tank 6. The water in the clean water tank is detected by the effluent water quality detector 12, analyzed by the online automatic water quality detector 13, and finally fed back to the computer terminal 14. The computer terminal calculates the water quality detection results and the pollutant removal rate.

[0091] As can be seen from FIGS. 2(a) and 2(b), the removal rates of nitrate and estradiol are low at the initial stage of device operation, which may be due to the fact that the activity of the bacteria therein has not reached the highest, and indirectly indicates that it is necessary to set the residence time. With the extension of time, the removal rates of the reactor for nitrate and estradiol gradually increase, and the removal rate of the reactor for nitrate can reach 89%, and the removal rate of the reactor for estradiol can reach 92% in the stable period of the reactor, which shows good ability to simultaneously remove nitrate and refractory organic matter.

[0092] Example 2

[0093] In this example, the water body to be treated comes from a certain farmer's self-use groundwater in Xianyang City, Shaanxi Province, and a trace amount of tetracycline is added to the water. This example provides a method and a reactor for removing nitrate and tetracycline in groundwater by manganese oxidation-reduction coupled denitrification, which comprises the following steps:

[0094] Step 1, enrichment culture of sludge:

[0095] Into a 250ml flask, 8L / min nitrogen was introduced for 5 minutes each time to ensure anaerobic conditions. 50g of the collected sediment sample was mixed with 200g of MM culture solution and 5g / L of MnO2 and added to the 250ml flask, which was then sealed and placed in a constant temperature incubator (25℃) for enrichment culture. The culture period was 7 days, and the supernatant was replaced with MM culture solution. The enrichment culture was carried out for 3 weeks using a shaker with a rotation speed of 70r / min. When the nitrate removal rate was more than 70%, the enrichment culture was considered complete.

[0096] The MM culture solution includes: CH3COONa 0.2g / L, NaHCO3 0.5g / L, NaNO3 0.3g / L, C6H 12 O6·H2O 0.08g / L, KH2PO4 0.05g / L, K2HPO4 0.15g / L, MgCl20.05g / L, CaCl2·7H2O 0.10g / L, trace element solution I 1mL, distilled water 1000mL, pH = 7.0;

[0097] The addition of trace element solution I to the MM culture solution includes: 0.5g / L MgSO4·7H2O, 1.1g / L EDTA, 0.2g / L ZnSO4, 0.1g / L MnCl2·4H2O, 0.8g / L FeSO4·7H2O, 0.7g / L CuSO4·5H2O, 0.5g / L CoCl2·6H2O.

[0098] Step 2, preparation of biological inoculant:

[0099] Two anaerobic bottles were taken. In the ① anaerobic bottle, 1g / L of MnO2 powder was added, and in the ② anaerobic bottle, 20mg / L of Mn(Ⅱ) stock solution was added. The Mn(Ⅱ) stock solution was 0.06g / L of MnCl2·4H2O. The sludge obtained in step 1 was added to two 300ml anaerobic bottles according to the mass ratio of 5:1 MM culture solution. Nitrogen was continuously introduced for 30 minutes, and finally sealed with a butyl rubber plug. Incubation was carried out at 25℃ for 72 hours. When the upper clear liquid in the ① bottle was detected to increase by 15mg / L, and the upper clear liquid in the ② bottle was detected to decrease by 20mg / L, the two types of sludge were mixed in a volume ratio of 1:1 to obtain a composite biological inoculant. 2+ 2+ Step 2, preparation of biological inoculant:

[0100] Step 3, pretreatment of immobilized material:

[0101] ​Take 20 g of natural corncob and cut into 1.0 cm solid blocks, wet it and soak in 0.7 mol / L alkali solution for 8 hours, then wash the corncob with water until it is neutral, and then dry it at 70°C for 30 hours.

[0102] In a 500 mL flask, add 200 mL of deionized water, 3.0 mL of pyrrole, 34 g of iron chloride, and stir with a magnetic stirrer for 4 hours to ensure complete mixing.

[0103] Add the pretreated dry corncob to the shaker for 8 minutes, soak for 4 hours, then wash with deionized water and anhydrous ethanol for 2 times, and dry at 70°C for 12 hours to obtain the polypyrrole modified corncob.

[0104] Step 4, immobilized material preparation:

[0105] Add 30 g of modified corncob to a solution of 20 g / L MnCl2·4H2O, then add a solution of 16 g / L KMnO4, and continuously stir with a magnetic stirrer for 15 minutes. Adjust the pH to 5.5±0.1 using 1M NaOH, and shake for 1 minute. Finally, wash the resulting material with diluted ethanol 5 times, and place it at 60°C for 48 hours until dry to obtain the MnO2 loaded corncob immobilized material.

[0106] Step 5, bio-agent film formation:

[0107] The film formation filler is obtained by soaking the immobilized material from Step 4 above in a mixture of MM culture medium and composite bio-agent at a volume ratio of 1:2. In a closed reactor, add 40% of the filler by volume, and add 2L of MM culture medium, and allow it to film for 7 days at room temperature. When the nitrate removal rate is above 70% and the tetracycline removal rate is above 90%, the film formation is complete.

[0108] Step 6, reactor operation:

[0109] Place the film-formed MnO2 loaded corncob immobilized material on the support layer of the reactor, turn on the direct current power supply, and use the influent water quality tester to measure the concentration of nitrate and refractory organic matter in the influent water. The support layer uses quartz sand with a particle size of 0.5 cm, and the thickness is 0.6 m. At the same time, open the influent valve, and let the treated groundwater enter the reactor through the peristaltic pump. Since the influent nitrate concentration is about 15 mg / L and the tetracycline concentration is about 1.6 mg / L, the pH of the influent water is controlled to be between 5.5 and 7.5, and the main operating parameter HRT is set to 6 hours, and the temperature is about 25°C. After the groundwater flows through the successfully film-formed and started biological reactor, the effluent is discharged to the clean water pool, and the effluent water quality is measured by the effluent water quality tester.

[0110] The reactor operation steps are as follows:

[0111] (1) Open the water inlet valve 3, the groundwater flows out from the water inlet tank 1, through the peristaltic pump 2, the water inlet valve 3 into the reactor main body 4;

[0112] (2) After the groundwater flows through the supporting layer 7, it enters the filler layer 8, in which the microorganisms in the sludge cooperate with the MnO2 loaded corncob immobilized material to drive the manganese oxidation-reduction cycle coupled denitrification, and simultaneously remove the nitrate and refractory organic matter in the sewage;

[0113] (3) Open the water outlet valve 5, the groundwater flows through the water outlet valve into the clean water tank 6, the water in the clean water tank is detected by the water quality detector 12 and analyzed by the online automatic water quality detector 13, and finally fed back to the computer terminal 14, which calculates the water quality detection results and the pollutant removal rate.

[0114] As can be seen from FIGS. 3(a) and 3(b), the device operates well, and the removal rate of nitrate in the stable period of the reactor can reach 92%, and the removal rate of tetracycline can reach 91%, which shows good ability to simultaneously remove nitrate and refractory organic matter.

[0115] Example 3

[0116] The sewage to be treated in Example 3 comes from the effluent of the secondary sedimentation tank of a sewage treatment plant in Xi'an City, and a small amount of phenol is added to the water.

[0117] Specifically, the following steps are included:

[0118] Step 1, enrichment culture of sludge:

[0119] A 250 mL narrow-mouth bottle is filled with 10 L / min nitrogen gas for 5 minutes each time to ensure airtight anaerobic conditions, 60 g of collected reservoir sediment sample is mixed with 180 g of MM culture solution and 1 g / L of MnO2 and added to the 250 mL narrow-mouth bottle, a 150 mL narrow-mouth bottle is filled with 10 L / min nitrogen gas for 5 minutes each time to ensure airtight anaerobic conditions, 30 g of collected reservoir sediment sample is mixed with MM culture solution and 1 g / L of MnO2 and added to the 150 mL narrow-mouth bottle, nitrogen gas is filled and sealed, and placed in a constant temperature incubator (30°C) for enrichment culture, 7 days for one culture period, the supernatant is replaced with MM culture solution, a shaking table with a rotation speed of 150 r / min is used, after 2 weeks of enrichment, when the nitrate removal rate is above 70%, it indicates that the enrichment culture is completed.

[0120] The MM culture solution includes, in terms of mass concentration, CH3COONa 0.15 g / L, NaHCO3 0.8 g / L, NaNO3 0.1 g / L, C6H 12O6-H2O 0.08 g / L, KH2PO4 0.08 g / L, K2HPO4 0.20 g / L, MgCl2 0.08 g / L, CaCl2-7H2O 0.09 g / L, trace element solution I 1 mL, distilled water 1000 mL, pH = 7.0;

[0121] The trace element solution I added in the MM culture solution includes, in terms of mass concentration, 0.8 g / L MgSO4-7H2O, 1.2 g / L EDTA, 0.3 g / L ZnSO4, 0.15 g / L MnCl2-4H2O, 0.5 g / L FeSO4-7H2O, 0.8 g / L CuSO4-5H2O, and 0.2 g / L CoCl2-6H2O.

[0122] Step 2, preparation of the biological agent:

[0123] Two anaerobic bottles were taken, 1 g / L of MnO2 powder was added to the No. 1 anaerobic bottle, and 20 mg / L of Mn(II) stock solution was added to the No. 2 anaerobic bottle, the Mn(II) stock solution was 0.08 g / L of MnCl2-4H2O in terms of mass concentration. The sludge obtained in Step 1 was added to the two 300 mL anaerobic bottles in a mass ratio of 3:1 MM culture solution, nitrogen was continuously introduced for 25 minutes, and finally it was sealed with a butyl rubber plug and incubated at 30°C for 60 hours. When the upper clear liquid in the No. 1 bottle was detected to increase by 18 mg / L, and the upper clear liquid in the No. 2 bottle was detected to decrease by 15 mg / L, the two cultured sludges were mixed in a volume ratio of 1:1 to obtain a composite biological agent. 2+ 2+ Step 2, preparation of the biological agent:

[0124] Step 3, pretreatment of the immobilization material:

[0125] 20 g of natural corn cob was cut into 1.0 cm solid blocks, soaked in 0.6 mol / L sodium hydroxide solution for 24 hours, then washed with water until neutral, and then dried at 50°C for 36 hours.

[0126] In a 500 mL flask, 200 mL of deionized water, 4.0 mL of pyrrole, and 30 g of iron chloride were added, and a magnetic stirrer was used to stir for 6 hours to ensure complete mixing.

[0127] The pretreated dry corn cob was added, shaken on a shaker for 5 minutes, soaked for 4 hours, then washed twice with deionized water and anhydrous ethanol, and dried at 50°C for 18 hours to obtain polypyrrole modified corn cob.

[0128] Step 4, preparation of the immobilization material:

[0129] ​The 20 g modified corncob was added into a solution of 25 g / L MnCl2-4H2O, and then added into a solution containing 16 g / L KMnO4, and continuously stirred using a magnetic stirrer for 25 minutes. The pH value was adjusted to 5.5±0.1 using 1 g / L NaOH, and shaken for 2 minutes. Finally, the obtained material was washed 4 times with diluted ethanol, and placed at 70°C for 36 hours until dried to obtain the MnO2-loaded corncob immobilized material.

[0130] Step 5, bio-agent film formation:

[0131] The film formation filler was obtained by soaking the immobilized material of step 4 above in a mixture of MM culture solution and composite bio-agent at a volume ratio of 1:2. In a closed reactor, 30% of the volume of the container was filled with the filler, and 2.5 L of MM culture solution was added, and the film was formed at room temperature for 10 days. When the removal rate of nitrate was above 70%, and the removal rate of refractory organic matter was above 90%, it was indicated that the film formation was completed.

[0132] Step 6, reactor operation:

[0133] The film-formed MnO2-loaded corncob immobilized material was placed on the support layer of the reactor, and the direct current power supply was turned on. The influent nitrate and refractory organic matter concentrations were measured using an influent water quality detector. The support layer used quartz sand with a particle size of 1.0 cm, and the thickness of the layer was 0.4 m. At the same time, the influent valve was opened, and the wastewater to be treated was fed into the reactor through a peristaltic pump. Since the influent nitrate concentration was about 30 mg / L, and the phenol concentration was about 3 mg / L, the influent pH value was controlled to be maintained at 5.5-7.5, and the main system operating parameter HRT was set to be 12 hours, and the temperature was about 25°C. After the wastewater flowed through the successfully film-formed and started biological reactor, the effluent was discharged to the clean water tank, and the effluent water quality was measured using an effluent water quality detector.

[0134] The reactor operation steps are as follows:

[0135] (1) The influent valve 3 was opened, and the wastewater flowed out of the influent tank 1, and flowed into the reactor body 4 through the peristaltic pump 2 and the influent valve 3;

[0136] (2) After the wastewater flowed through the support layer 7, it entered the filler layer 8, and in the filler layer, the microorganisms in the sludge cooperated with the MnO2-loaded corncob immobilized material to drive the manganese oxidation-reduction cycle coupled denitrification, and simultaneously removed the nitrate and refractory organic matter in the wastewater;

[0137] (3) The effluent valve 5 was opened, and the wastewater flowed through the effluent valve into the clean water tank 6. The water in the clean water tank was detected by the effluent water quality detector 12, and then analyzed by the online automatic water quality detector 13, and finally fed back to the computer terminal 14. The computer terminal calculated the water quality detection results and the pollutant removal rate.

[0138] As can be seen from FIG. 4(a) and FIG. 4(b), the removal rates of nitrate and phenol are low at the initial stage of the operation of the device, which may be due to that the activity of the bacteria therein has not reached the highest, and indirectly indicates that it is necessary to set the residence time. With the extension of time, the removal rates of the reactor for nitrate and phenol gradually increase, and the removal rate of the reactor for nitrate can reach 90% and the removal rate for phenol can reach 92% in the stable period of the reactor, which shows a good ability of simultaneous removal of nitrate and refractory organic matter.

[0139] The process for removing nitrate and refractory organic matter by the manganese redox cycle coupled denitrification in the application is as follows:

[0140] When the wastewater to be treated passes through the reactor in which the biofilm has been successfully formed, under anaerobic conditions, the MnO2 loaded by the modified corncob immobilized material is used to enrich manganese-reducing bacteria, the bacteria use organic carbon source as electron donor to reduce MnO2 to dissolve to form a large amount of Mn(III) and Mn(II). Mn(II) enriches manganese-oxidizing bacteria, the bacteria use Mn(II) and organic carbon source as electron donor to oxidize NO3 - as electron acceptor, metabolize by using the energy released by the redox reaction and organic carbon, and achieve the effect of denitrification. In addition, Mn(III) as electron donor can be re-oxidized to Mn(IV) through active oxygen on the surface of MnO2, and the reaction promotes the denitrification process to achieve the removal of nitrate in the system. On the other hand, the biological manganese oxides (MnO2 and Mn3O4) produced by manganese-oxidizing bacteria in the oxidation process have the characteristics of large specific surface area and strong surface activity, and the surface will produce active oxygen and catalytically active Mn(III) intermediates, which can adsorb and catalytically oxidize refractory organic matter, thereby achieving the degradation and removal of refractory organic matter. The application combines manganese-oxidizing bacteria and manganese-reducing bacteria, uses the MnO2 loaded by the modified corncob as the source of manganese oxide, and constructs the large cycle between Mn(II) and Mn(IV) and the small cycle between Mn(III) and Mn(IV). By driving the manganese redox cycle coupled denitrification through microorganisms, nitrate and refractory organic matter in water can be efficiently removed. As can be seen from the examples, the removal rate of nitrate in the water by the method of the application can reach 90%, and the removal rate of refractory organic matter can reach 91%.

[0141] The method of the application has the characteristics of green, high efficiency, no secondary pollution, and no need to add a large amount of carbon source, and provides a new way for the existing water treatment process technology.

[0142] The application is not limited to the above examples, and based on the technical solutions disclosed in the application, those skilled in the art can make some substitutions and modifications to some technical features according to the disclosed technical content without creative labor, and the substitutions and modifications are all within the protection scope of the application.

Claims

1. A method for simultaneous removal of recalcitrant organics by manganese cycling coupled denitrification, characterized in that, The method comprises the following steps: Step (a), under anaerobic conditions, mixing the reservoir sediment, MM culture solution and MnO2 powder according to the mass ratio of (30-60):(160-200):(1-5), introducing nitrogen and sealing, and carrying out sludge enrichment culture; Step (b), the sludge enriched culture is mixed with MM culture solution according to mass ratio (3-5):1, MnO2 powder and Mn(II) stock solution are added, and nitrogen is continuously introduced for incubation; when it is detected that the supernatant of the sludge added with MnO2 powder has increased Mn 2+ , and the supernatant of the sludge added with Mn(II) stock solution has reduced Mn 2+ , the two kinds of sludge are mixed according to volume ratio 1:1 to obtain a composite biological inoculant; Step (c), pretreating the dry corncob, adding the pretreated dry corncob into a polypyrrole modification solution, oscillating and shaking, standing and soaking, washing, and drying to obtain the polypyrrole modified corncob; Step (d), adding the polypyrrole modified corncob into a manganese chloride solution, slowly adding a KMnO4 solution, adjusting the pH value, diluting and washing, and placing to dryness to obtain the MnO2 loaded corncob immobilized material; Step (e), soaking the MnO2 loaded corncob immobilized material and the mixed solution of the composite biological agent according to the volume ratio of 1:2 to obtain a biological agent filler, and adding the MM culture solution to carry out biofilm formation at room temperature; Step (f), placing the MnO2 loaded corncob immobilized material after biofilm formation into a reactor to remove nitrate and refractory organic matter in the influent.

2. The method of claim 1, wherein, The enrichment culture comprises the following steps: introducing 5-10 L / min of nitrogen gas, each time for 5 min; 7 days as one culture cycle, continuously replacing the supernatant with the MM culture solution in each cycle, using a shaker with a rotating speed of 70-150 r / min, and enriching for 2-3 weeks; and when the nitrate removal rate is above 70%, the enrichment culture is ended.

3. The method of claim 1, wherein, The MM culture solution comprises, in terms of mass concentration, CH3COONa 0.1-0.2 g / L, NaHCO3 0.5-0.8 g / L, NaNO3 0.1-0.3 g / L, C6H 12 O6·H2O 0.05-0.08 g / L, KH2PO4 0.05-0.08 g / L, K2HPO4 0.15-0.20 g / L, MgCl2 0.05-0.08 g / L, CaCl2·7H2O 0.07-0.10 g / L, trace element solution I 1 mL, distilled water 1000 mL, and pH value = 7.

0. The trace element solution I comprises, in terms of mass concentration, 0.5-0.8 g / L of MgSO4·7H2O, 1.0-1.2 g / L of EDTA, 0.2-0.5 g / L of ZnSO4, 0.1-0.2 g / L of MnCl2·4H2O, 0.5-0.8 g / L of FeSO4·7H2O, 0.5-0.8 g / L of CuSO4·5H2O and 0.2-0.5 g / L of CoCl2·6H2O.

4. The method of claim 1, wherein, The Mn(II) stock solution is MnCl2·4H2O with a mass concentration of 0.05-0.08 g / L. Mn in supernatant of sludge with MnO2 powder 2+ Increased by 15-20 mg / L, Mn in supernatant of sludge with Mn(II) stock solution 2+ Reduced by 15-20 mg / L; The incubation comprises the following steps: continuously introducing nitrogen gas for 20-30 min, sealing, and incubating at 25-30 °C for 48-72 h.

5. The method of claim 1, wherein, The pretreatment of the natural corncob comprises the following steps: soaking the corncob in a NaOH solution with a concentration of 0.5-0.8 mol / L for 8-24 h, washing the corncob with water until neutral, and drying the corncob at 50-70 °C for 24-36 h.

6. The method of claim 1, wherein, The polypyrrole modification solution comprises 1.5-4.0 mL of pyrrole and 15-17 g of FeCl3 solution per 100 mL of deionized water. The pretreated dry corncob is placed into the polypyrrole modification solution, oscillated and shaken for 5-10 min, soaked for 4 h, washed for 2-3 times, and dried at 50-70 °C for 12-24 h.

7. The method of claim 1, wherein, The MnO2 loaded corncob immobilized material comprises the following steps: adjusting the pH value to 5.5±0.1 by using 1 g / L of NaOH, oscillating for 1-3 min, washing 3-5 times with diluted ethanol, and placing at 60-80 °C for 36-48 h.

8. The method of claim 1, wherein, The biofilm formation is ended when the nitrate removal rate is above 70% and the organic matter removal rate is above 90% after 7-10 days of biofilm formation at room temperature.

9. The method of claim 1, wherein, The reactor is operated, including controlling the pH value of the influent to be 5.5-7.5, the nitrate concentration to be 1-30 mg / L, and the concentration of the refractory organic matter to be 1-3 mg / L; the operation is performed for 6-12 h, and the temperature is 25-35 ℃.

10. A reactor for use in the process according to any one of claims 1 to 9, characterised in that, The reactor comprises an influent tank, a reactor main body, a clean water tank, a supporting layer, a filler layer, an online pH meter, a temperature control probe, an online automatic water quality detector, and a computer terminal. The reactor main body comprises an influent layer, a supporting layer, a filler layer, and a reaction layer. The influent layer is connected to the influent tank. The reaction layer is connected to the clean water tank. The online pH meter and the temperature control probe are inserted into the reaction layer and connected to the online automatic water quality detector. The online automatic water quality detector is connected to the influent tank and the clean water tank for water quality detection. The online automatic water quality detector is connected to the computer terminal.

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