Method for denitrifying organic carbon source by anaerobic fermentation product of mixed wastewater containing sugar and formic acid

Abstract

The invention discloses a method for denitrifying an organic carbon source by anaerobic fermentation of mixed wastewater containing sugar and formic acid. The method comprises the following steps: mixing sugar-containing wastewater and formic acid-containing wastewater, inoculating a fermentation inoculant, and carrying out anaerobic fermentation; wherein the fermentation inoculant is one or more of ruminant animal manure or rumen, and the mixing ratio of the sugar-containing wastewater to the formic acid-containing wastewater is that the COD concentration ratio of the sugar-containing wastewater to the formic acid-containing wastewater is not higher than 8: 1. According to the present invention, the sugar-containing wastewater and the formic acid-containing and / or formate-containing wastewater are mixed and inoculated with one or more of ruminant animal manure or rumen for anaerobic fermentation, such that the content of the nitrogen removal organic carbon source of the sugar-containing wastewater product can be effectively improved, and the carbon dioxide emission is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of wastewater treatment, and more specifically, relates to a method for anaerobic fermentation biological denitrification organic carbon source of sugar- and formic acid-containing mixed wastewater. Background Art

[0002] Food processing industries such as molasses, sugar production, jujube, sugarcane, and fruit juice usually generate a large amount of sugar-containing wastewater. Formic acid is widely used in textile printing and dyeing, leather processing, rubber processing, silage, and medicine production.

[0003] The treatment methods of sugar-containing wastewater mainly include physical treatment, chemical treatment, biological treatment, etc. For example, the prior art CN102160596A proposes a method for producing feed using high-concentration waste sugar water of citric acid. This method mainly conducts comprehensive treatment and reuse of high-concentration waste sugar water in the citric acid industry through primary concentration, separation, secondary concentration, drying, etc. of the waste sugar water. Chinese invention patent CN104073521A proposes a method for continuously producing hydrogen by anaerobic fermentation of sugar-containing wastewater. This method selects an anaerobic sequencing batch reactor containing a high concentration of microorganisms for high-temperature anaerobic fermentation to produce hydrogen. By optimizing the sludge concentration and pH value settings, and using inoculated sludge from a wide range of sources, problems during the startup process are avoided and the hydrogen production rate is increased; CN105494320A proposes a method for straw preservation and biogas preparation. This method is to perform lactic acid fermentation on sugar-containing wastewater and then mix it with straw to achieve the preservation of straw. It not only effectively utilizes the sugar-containing wastewater but also improves the biogas fermentation efficiency of straw, providing a guarantee for the large-scale utilization of straw.

[0004] For the treatment of formic acid-containing organic wastewater, treatment methods that decompose formic acid are mostly used, such as oxidation method, catalytic decomposition method, biochemical treatment method, adsorption method, and electrolysis method, etc. Although these methods have relatively good treatment effects, they have high costs and small treatment volumes and are not suitable for industrial applications.

[0005] In the prior art, sugar-containing wastewater and formic acid-containing wastewater usually need to be treated separately, which not only causes waste of resources but also leads to carbon emissions. The simultaneous treatment of sugar- and formic acid-containing mixed wastewater is not involved, and even less is there any consideration of how to anaerobically ferment to produce a biological denitrification carbon source. Anaerobic biological treatment is an important means to realize the harmlessness, stabilization, and resource utilization of organic wastewater. How to maximize the conversion of waste organic matter into organic acids and prepare a biological denitrification organic carbon source is the key to the harmlessness, stabilization, and resource utilization of organic wastewater. Summary of the Invention

[0006] The object of the present invention is to overcome the deficiencies or defects in the above-mentioned prior art, and to provide a method for anaerobic fermentation of a sugar- and formic acid-containing mixed wastewater to produce a biological denitrification organic carbon source. By mixing the sugar-containing wastewater with the formic acid- and / or formate-containing wastewater and inoculating one or more of ruminant feces or rumen contents for anaerobic fermentation, the content of the biological denitrification organic carbon source produced from the sugar-containing wastewater can be effectively increased, and the carbon dioxide emission can be reduced.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for anaerobic fermentation of a sugar- and formic acid-containing mixed wastewater to produce a biological denitrification organic carbon source, comprising the following steps:

[0009] Mix the sugar-containing wastewater with the formic acid- and / or formate-containing wastewater and inoculate a fermentation bacterium agent for anaerobic fermentation;

[0010] Wherein, the fermentation bacterium agent is one or more of ruminant feces or rumen contents, and the mixing ratio of the sugar-containing wastewater to the formic acid- and / or formate-containing wastewater is that the COD concentration ratio of the sugar-containing wastewater to the formic acid- and / or formate-containing wastewater is not higher than 8:1.

[0011] In the above solution, by mixing the sugar-containing wastewater with the formic acid- and / or formate-containing wastewater for anaerobic fermentation, and using one or more of ruminant feces or rumen contents as the anaerobic fermentation bacteria, wastewater treatment can be synchronously achieved, and the addition of the formic acid- and / or formate-containing wastewater effectively increases the content of the biological denitrification organic carbon source generated by the anaerobic fermentation of the sugar-containing wastewater, and reduces the carbon dioxide emission.

[0012] It should be noted that in the present invention, the mixing ratio of the sugar-containing wastewater to the formic acid- and / or formate-containing wastewater is that the ratio of the two CODs is not higher than 8:1. For example, but not limited to, not higher than 8:1, 7:1, 6:1, 5:1 or 4:1, etc. can all achieve the present invention.

[0013] In some preferred specific embodiments, the mixing ratio of the sugar-containing wastewater to the formic acid- and / or formate-containing wastewater is that the COD concentration ratio of the two is 7:1 to 5:1.

[0014] Furthermore, the mixing ratio of the sugar-containing wastewater to the formic acid- and / or formate-containing wastewater is that the COD concentration ratio of the two is 6:1.

[0015] In some preferred embodiments, the COD concentration of the sugar-containing wastewater is 2 to 15 g / L, and the COD concentration of the formic acid- and / or formate-containing wastewater is 0.3 to 2 g / L.

[0016] Further, the COD concentration of the sugar-containing wastewater is 6 - 10 g / L, and the COD concentration of the formic acid-containing and / or formate-containing wastewater is 1 - 1.8 g / L.

[0017] Specifically, the method for measuring the COD concentration is Hach analysis.

[0018] In some preferred embodiments, the inoculation amount of the fermentation inoculant is 20 - 100 g of the fermentation inoculant added per liter of the mixed wastewater.

[0019] Further, the anaerobic fermentation is carried out by filling the headspace gas with CO2.

[0020] In some preferred specific embodiments, the CO2 concentration of the anaerobic fermentation is 1 - 10 mmol / L.

[0021] Further, the sugar-containing wastewater includes one or more of molasses wastewater, sugar-making wastewater, or wastewater from the food processing industry such as jujube, sugarcane, and fruit juice.

[0022] Further, the formic acid-containing and / or formate-containing wastewater includes one or more of printing and dyeing wastewater, leather processing wastewater, and rubber processing wastewater.

[0023] Specifically, the formate in the formate-containing wastewater includes, for example but not limited to, sodium formate and / or potassium formate.

[0024] In some preferred embodiments, the temperature of the anaerobic fermentation is 25 - 40 °C.

[0025] In some preferred embodiments, the initial pH of the anaerobic fermentation is 6.5 - 10.0.

[0026] Further, the initial pH of the anaerobic fermentation is 7.0.

[0027] In some preferred embodiments, the hydraulic retention time of the anaerobic fermentation is 3 - 7 days.

[0028] In some preferred embodiments, the ruminants include cows and / or sheep.

[0029] In some preferred embodiments, the fermentation inoculant is cow manure and / or yellow cattle rumen content.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention uses a sugar-containing wastewater and a formic acid-containing and / or formate-containing wastewater to be mixed and inoculated with anaerobic fermentation bacteria for anaerobic fermentation, which can simultaneously achieve the comprehensive treatment of the sugar-containing wastewater and the formic acid-containing and / or formate-containing wastewater. Compared with the anaerobic fermentation using only the sugar-containing wastewater, the content of the organic carbon source for biological denitrification is increased by at least 10%, and the carbon dioxide release amount is reduced. Detailed Embodiments

[0032] The following further elaborates the present invention in detail with reference to specific embodiments. The embodiments are only used to explain the present invention and are not intended to limit the scope of the present invention. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the technical field.

[0033] Fermentation Bacterial Agent: Cow dung, taken from the Mashan Dairy Farm in Wuxi City, Jiangsu Province;

[0034] Fermentation Bacterial Agent: Bovine rumen content (yellow cattle), taken from the Xinlian Livestock and Poultry Slaughtering and Processing Factory in Wuxi City;

[0035] Fermentation Bacterial Agent: Clostridium butyricum, numbered CCAM 949, purchased from the Chengdu Institute of Biogas Science, Ministry of Agriculture and Rural Affairs;

[0036] The sugar-containing wastewater was simulated with self-made glucose solutions of 11.5, 23, and 46 mM, and the corresponding COD concentrations were 2208, 4417, and 8835 mg / L, respectively.

[0037] The formic acid-containing wastewater was simulated with self-made formate solutions of 23, 46, and 92 mM, and the corresponding COD concentrations were 380, 740, and 1480 mg / L, respectively.

[0038] Example 1

[0039] A method for anaerobic fermentation of a sugar- and formic acid-containing mixed wastewater to produce an organic carbon source for biological denitrification, comprising the following steps:

[0040] After mixing the sugar-containing wastewater with a COD concentration of 2208 mg / L and the formic acid-containing wastewater with a COD concentration of 380 mg / L, inoculate cow dung at an inoculation amount of 10% (i.e., the mass-volume ratio of cow dung to the mixed wastewater is 10 g:100 mL) for anaerobic fermentation. The headspace of the anaerobic reactor is filled with 5 mmol / L CO2, the initial pH is 7, and anaerobic fermentation is carried out at 30°C for 3 days.

[0041] Example 2

[0042] A method for anaerobic fermentation of a sugar- and formic acid-containing mixed wastewater to produce an organic carbon source for biological denitrification, comprising the following steps:

[0043] The sugar-containing wastewater with a COD concentration of 4417 mg / L and the formic acid-containing wastewater with a COD concentration of 740 mg / L were mixed, and then inoculated with bovine rumen contents at an inoculation amount of 6% (i.e., the mass-volume ratio of bovine rumen contents to the mixed wastewater was 6 g:100 mL) for anaerobic fermentation. The headspace of the anaerobic reactor was filled with 2 mmol / L CO2, the initial pH was 7, and anaerobic fermentation was carried out at 30 °C for 3 days.

[0044] Example 3

[0045] A method for anaerobic fermentation of a sugar- and formic acid-containing mixed wastewater to produce a biological denitrification organic carbon source, comprising the following steps:

[0046] The sugar-containing wastewater with a COD concentration of 8835 mg / L and the formic acid-containing wastewater with a COD concentration of 1480 mg / L were mixed, and then inoculated with cow dung at an inoculation amount of 2% (i.e., the mass-volume ratio of cow dung to the mixed wastewater was 2 g:100 mL) for anaerobic fermentation. The headspace of the anaerobic reactor was filled with 7 mmol / L CO2, the initial pH was 7, and anaerobic fermentation was carried out at 30 °C for 3 days.

[0047] Example 4

[0048] A method for anaerobic fermentation of a sugar- and formic acid-containing mixed wastewater to produce a biological denitrification organic carbon source, comprising the following steps:

[0049] The sugar-containing wastewater with a COD concentration of 2208 mg / L and the formic acid-containing wastewater with a COD concentration of 380 mg / L were mixed, and then inoculated with cow dung at an inoculation amount of 2% (i.e., the mass-volume ratio of cow dung to the mixed wastewater was 2 g:100 mL) for anaerobic fermentation. The headspace of the anaerobic reactor was filled with 2 mmol / L CO2, the initial pH was 7, and anaerobic fermentation was carried out at 30 °C for 5 days.

[0050] Example 5

[0051] A method for anaerobic fermentation of a sugar- and formic acid-containing mixed wastewater to produce a biological denitrification organic carbon source, comprising the following steps:

[0052] The sugar-containing wastewater with a COD concentration of 4417 mg / L and the formic acid-containing wastewater with a COD concentration of 740 mg / L were mixed, and then inoculated with cow dung at an inoculation amount of 2% (i.e., the mass-volume ratio of cow dung to the mixed wastewater was 2 g:100 mL) for anaerobic fermentation. The headspace of the anaerobic reactor was filled with 2 mmol / L CO2, the initial pH was 7, and anaerobic fermentation was carried out at 30 °C for 5 days.

[0053] Example 6

[0054] A method for anaerobic fermentation of a sugar- and formic acid-containing mixed wastewater to produce a biological denitrification organic carbon source, comprising the following steps:

[0055] Mix the sugar-containing wastewater with a COD concentration of 8835 mg / L and the formic acid-containing wastewater with a COD concentration of 1480 mg / L, and then inoculate cow dung for anaerobic fermentation at an inoculation amount of 2% (i.e., the mass-volume ratio of cow dung to the mixed wastewater is 2 g:100 mL). Charge 2 mmol / L CO2 into the headspace of the anaerobic reactor, with an initial pH of 7, and carry out anaerobic fermentation at 30 °C for 5 days.

[0056] Comparative Example 1

[0057] A method for anaerobic fermentation of a sugar- and formic acid-containing mixed wastewater to produce a biological denitrification organic carbon source, comprising the following steps:

[0058] Carry out anaerobic fermentation on the sugar-containing wastewater with a COD concentration of 2208 mg / L by inoculating cow dung at an inoculation amount of 2% (i.e., the mass-volume ratio of cow dung to the mixed wastewater is 2 g:100 mL). Charge 2 mmol / L CO2 into the headspace of the anaerobic reactor, with an initial pH of 7, and carry out anaerobic fermentation at 30 °C for 5 days.

[0059] Comparative Example 2

[0060] A method for anaerobic fermentation of a sugar- and formic acid-containing mixed wastewater to produce a biological denitrification organic carbon source, comprising the following steps:

[0061] Carry out anaerobic fermentation on the sugar-containing wastewater with a COD concentration of 4417 mg / L by inoculating cow dung at an inoculation amount of 2% (i.e., the mass-volume ratio of cow dung to the mixed wastewater is 2 g:100 mL). Charge 2 mmol / L CO2 into the headspace of the anaerobic reactor, with an initial pH of 7, and carry out anaerobic fermentation at 30 °C for 5 days.

[0062] Comparative Example 3

[0063] A method for anaerobic fermentation of a sugar- and formic acid-containing mixed wastewater to produce a biological denitrification organic carbon source, comprising the following steps:

[0064] Carry out anaerobic fermentation on the sugar-containing wastewater with a COD concentration of 8835 mg / L by inoculating cow dung at an inoculation amount of 2% (i.e., the mass-volume ratio of cow dung to the mixed wastewater is 2 g:100 mL). Charge 7 mmol / L CO2 into the headspace of the anaerobic reactor, with an initial pH of 7, and carry out anaerobic fermentation at 30 °C for 5 days.

[0065] Comparative Example 4

[0066] A method for anaerobic fermentation of a sugar- and formic acid-containing mixed wastewater to produce a biological denitrification organic carbon source, comprising the following steps:

[0067] The sugar-containing wastewater with a COD concentration of 8835 mg / L and the formic acid-containing wastewater with a COD concentration of 740 mg / L were mixed, inoculated with cow dung at an inoculation amount of 2% (i.e., the mass-volume ratio of cow dung to the mixed wastewater was 2 g:100 mL) for anaerobic fermentation. The headspace of the anaerobic reactor was filled with 2 mmol / L CO2, the initial pH was 7, and anaerobic fermentation was carried out at 30 °C for 5 days.

[0068] Comparative Example 5

[0069] A method for anaerobic fermentation of a sugar- and formic acid-containing mixed wastewater to produce a biological denitrification organic carbon source, comprising the following steps:

[0070] The sugar-containing wastewater with a COD concentration of 2208 mg / L and the formic acid-containing wastewater with a COD concentration of 380 mg / L were mixed, inoculated with Clostridium butyricum at an inoculation amount of 2% (i.e., the volume ratio of the bacterial solution with OD 600 = 0.2 to the mixed wastewater was 2:100) for anaerobic fermentation. The headspace of the anaerobic reactor was filled with 7 mmol / L CO2, the initial pH was 7, and anaerobic fermentation was carried out at 30 °C for 5 days.

[0071] Experimental Example 1

[0072] (1) Detection method for biological denitrification organic carbon source: The concentration of biological denitrification organic carbon source (including acetic acid, propionic acid, butyric acid, and ethanol) was determined by gas chromatography. The samples obtained under various conditions were filtered through a 0.22 μm aqueous filter membrane and mixed with phosphoric acid (acidifying agent) with a concentration of 3 mmol / L (volume ratio 1:1), and then added into the sample vial. The VFAs concentration in the sample was determined using a gas chromatograph. The gas chromatograph parameters were: automatic sampler (AOC-20i), capillary column (PEG-20M, 30 m × 0.32 mm × 0.5 μm), hydrogen flame ionization detector (FID) with a detection limit of 3 pgC / s, high-purity N2 as the carrier gas, column oven temperature of 210 °C, and injection port and detector temperatures both set at 250 °C.

[0073] (2) Determination of CO2 emission: The CO2 concentration was determined using a gas chromatograph. The carrier gas was high-purity argon, and the other gas chromatograph parameters were: thermal conductivity detector (TCD) and stainless steel packed column (AE.TDX-01, 2 m × 3 mm). The analysis conditions were: column temperature of 100 °C, detector temperature and injection port temperature both set at 150 °C. Using a CO2 standard gas as the standard sample, the detector current was adjusted to 80 mA, and 2.5 mL of gas was collected and analyzed using a manual injector.

[0074] (3) Determination of the reduction of glucose and formic acid: The glucose concentration was determined by the phenol-sulfuric acid method. Respectively, 0, 10, 20, 40, 80, 120, and 160 μL of glucose standard solution with a concentration of 1 g / L were taken into test tubes and made up to 2 mL. Then, 1 mL of phenol solution (5%) and 5 mL of concentrated sulfuric acid solution were added to the above test tubes in sequence. After thoroughly mixing with a vortex mixer, they were left at room temperature for 30 min. Finally, with the blank solution as the reference, the absorbance values corresponding to each glucose standard solution were measured at a wavelength of 490 nm, and a glucose standard curve was plotted. The sample was centrifuged at 8000 rpm for 10 min, and the supernatant was taken. Then, 1 mL of phenol solution (5%) and 5 mL of concentrated sulfuric acid solution were added to the test tube in sequence. After thoroughly mixing with a vortex mixer, they were left at room temperature for 30 min, and then the absorbance values of each sample were measured at a wavelength of 490 nm. According to the obtained glucose standard curve, the corresponding glucose concentration was calculated by comparing the measured absorbance value. The formic acid concentration was determined by high-performance liquid chromatography. Respectively, 1 mL of formic acid standard solutions with concentrations of 0, 100, 200, 400, 600, 800, and 1000 mg / L were injected into chromatographic injection vials, and the peak emergence time and peak area at each formic acid concentration were measured using a high-performance liquid chromatograph. 20 μL of the sample was separated on a Thermo Scientific C18 column (4.6 mm × 250 mm), and the mobile phase was a mixed solution of KH2PO4 with a concentration of 0.01 mol / L and methanol (volume ratio 95:5). The analysis conditions of the liquid chromatograph were: detection wavelength 206 nm, temperature 30 °C, and flow rate 1.00 mL / min. A standard curve was plotted based on the peak area and formic acid standard solution concentration. The samples obtained under each condition were filtered through a 0.22 μm aqueous filter membrane to remove the precipitate. The diluted filtrate was injected into a chromatographic injection vial, and the analysis conditions were the same. According to the obtained formic acid standard curve, the formic acid concentration in the corresponding sample was calculated by comparing the peak area.

[0075] The experimental data measured for each example and comparative example are shown in Table 1.

[0076] Table 1 Experimental data of each example and comparative example

[0077]

[0078]

[0079] As can be seen from 1, when anaerobic fermentation is carried out by mixing sugar-containing wastewater with formic acid-containing and / or formate-containing wastewater using one or more of ruminant feces or rumen contents, the production amount of denitrifying organic carbon source increases, and the carbon dioxide release amount is lower than that of wastewater with the same COD concentration.

[0080] Comparing Examples 4 to 6 with Comparative Examples 1 to 5, it can be seen that, compared with anaerobic fermentation of single glucose wastewater, anaerobic fermentation of the mixed wastewater of sugar-containing wastewater and formic acid- and / or formate-containing wastewater can increase the production of denitrifying organic carbon source by at least 10%, and significantly reduce the carbon dioxide release. When the COD concentrations of the sugar-containing wastewater and the formic acid- and / or formate-containing wastewater in the mixed wastewater are too high, the production of denitrifying organic carbon source will be inhibited; when using other fermentation agents (commonly fermentation bacteria from intestinal sources), although the contents of glucose and formic acid decrease, the production amount of denitrifying organic carbon source does not increase.

[0081] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limiting the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all implementation manners here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A method for anaerobic fermentation of a mixed wastewater containing sugar and formic acid to produce a biological denitrification organic carbon source, characterized in that, It includes the following steps: Mixing the sugar-containing wastewater with the formic acid-containing and / or formate-containing wastewater and inoculating a fermentation inoculum for anaerobic fermentation; Wherein, the fermentation inoculum is one or more of ruminant feces or rumen contents, and the mixing ratio of the sugar-containing wastewater to the formic acid-containing and / or formate-containing wastewater is that the COD concentration ratio of the sugar-containing wastewater to the formic acid-containing and / or formate-containing wastewater is not higher than 8:

1.

2. The method according to claim 1, wherein The COD concentration of the sugar-containing wastewater is 2-15 g / L, and the COD concentration of the formic acid-containing and / or formate-containing wastewater is 0.3-2 g / L.

3. The method according to claim 1, wherein The inoculation amount of the fermentation inoculum is 20-100 g of the fermentation inoculum added per liter of the mixed wastewater.

4. The method according to claim 1, wherein The anaerobic fermentation is carried out by charging CO2 into the headspace gas.

5. The method according to claim 4, wherein The CO2 concentration of the anaerobic fermentation is 1-10 mmol / L.

6. The method according to claim 1, characterized in that The sugar-containing wastewater includes one or several of molasses wastewater, sugar-making wastewater, or wastewater from the processing of Chinese dates, sugarcane, or fruit juice.

7. The method according to claim 1, characterized in that, The formic acid-containing and / or formate-containing wastewater includes one or several of printing and dyeing wastewater, leather processing wastewater, or rubber processing wastewater.

8. The method according to claim 1, characterized in that, The temperature of the anaerobic fermentation is 25-40 °C.

9. The method according to claim 1, characterized in that The initial pH of the anaerobic fermentation is 6.5-10.

0.

10. The method according to claim 1, wherein The ruminants include cattle and / or sheep.

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