Denitrification method of kitchen waste anaerobic biogas slurry

Abstract

The invention relates to a denitrification method of kitchen waste anaerobic biogas slurry, which comprises the following steps: carrying out first micro-aeration on the pretreated kitchen waste anaerobic biogas slurry, carrying out first mixing on the obtained primary effluent and the pretreated kitchen waste anaerobic biogas slurry, and then carrying out second micro-aeration, performing secondary mixing on the obtained secondary effluent and a carbon source, and performing aeration and third mixing in sequence to obtain denitrified effluent; the pH value, the temperature and the salinity of inlet water are respectively detected and controlled before the first micro-aeration, the second micro-aeration and the aeration. The denitrification method is relatively good in denitrification effect and stable in treatment effect, meanwhile, the treatment cost is reduced, and the energy consumption of an aeration fan is saved.

Description

Technical Field

[0001] The invention relates to the technical field of food waste biogas slurry treatment, and in particular to a method for denitrifying anaerobic biogas slurry from food waste. Background Art

[0002] Anaerobic digestate from food waste is a liquid waste produced from food waste through the anaerobic fermentation process. Specifically, in the process of treating food waste, organic matter is converted into methane, carbon dioxide and other gases through the action of microorganisms in an anaerobic environment, and anaerobic digestate is produced. Anaerobic digestate from food waste is characterized by high concentrations of ammonia nitrogen and total nitrogen, low concentration of organic matter, and serious C / N imbalance. Therefore, the treatment of digestate from food waste is somewhat difficult.

[0003] Conventional anaerobic biogas slurry denitrification treatment processes for food waste either use air stripping or conventional biological denitrification processes of nitrification and denitrification. For example, CN219031933U discloses a food waste biogas slurry denitrification and dephosphorization device, the device includes a reactor, the reactor includes an inner cylinder and an outer cylinder, the bottom of the inner cylinder is open, the feed pipe and the dispensing pipe pass through the wall of the reactor and extend to the primary reaction zone, the feed pipe is connected to a water distribution pipe located in the primary reaction zone, the air intake pipe passes through the wall of the reactor and extends to the sludge precipitation zone, the air intake pipe is connected to an aeration plate, and a capture net located at the bottom of the overflow zone is evenly laid between the inner cylinder and the outer cylinder. The utility model uses both air stripping and crystallization precipitation methods to treat sewage, improving the removal effect of nitrogen and phosphorus pollutants. CN106277452A discloses a method for denitrifying biogas slurry from pig breeding wastewater, which includes adding three reagents in order: CaO inorganic matter, organic alcohols such as a mixture of polyethylene glycol-200 and polyethylene glycol-400, and anionic polyacrylamide polymer organic flocculant. The above device or method can achieve denitrification effect, but the stripping process has high operating costs, unstable treatment effect, and secondary pollution problems.

[0004] CN108178475A discloses a highly efficient in-situ biogas denitrification method for anaerobic digestion of sludge, comprising the following steps: dewatered sludge is mixed and diluted with biogas after nitrosation to obtain a sludge mixed solution with a solid content of 10% to 15%; the sludge mixed solution is transported to the nitrite oxidation cell disruption hydrolysis phase for cell disruption pretreatment to complete the denitrification and denitrification of nitrite; the pretreated liquid is transported to the anaerobic digestion gas production phase to complete organic matter degradation and biogas preparation; after digestion, it is transported to a dehydrator for dehydration, and the stabilized biogas residue enters the post-treatment link, and the biogas containing high concentration of ammonia nitrogen is nitrosated and then returned to the mixing tank for mixing and dilution with dewatered sludge. However, the residence time of denitrification is long, the floor space is large, and it has certain limitations in industrial production. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for denitrifying anaerobic biogas slurry from food waste, which has good denitrification effect and stable treatment effect, while reducing treatment costs and saving energy consumption of aeration fans.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for denitrifying anaerobic biogas slurry from kitchen waste, the denitrification method comprising the following steps:

[0008] The pretreated anaerobic digestate from food waste is subjected to a first micro-aeration, the obtained primary effluent is first mixed with the pretreated anaerobic digestate from food waste and then subjected to a second micro-aeration, the obtained secondary effluent is second mixed with a carbon source and then subjected to aeration and a third mixing in sequence to obtain denitrified effluent;

[0009] The first micro-aeration, the second micro-aeration and before aeration respectively detect and control the pH value, temperature and salinity of the influent water.

[0010] The denitrification method of anaerobic digestive slurry from kitchen waste provided by the present invention firstly performs micro-aeration on the pretreated anaerobic digestive slurry from kitchen waste according to the NH3-N concentration and ORP of the influent, and nitrification reaction occurs. After precipitation, the primary effluent is mixed with the pretreated anaerobic digestive slurry from kitchen waste and then micro-aerated, and ammonia is used as an electron donor, and nitrite produced by the nitrification reaction is used as an electron acceptor to perform denitrification reaction, and finally N2 is produced; the secondary effluent after the reaction is aerated, mixed, precipitated, and finally the effluent meets the discharge standards under the condition of adding a small amount of carbon source. The denitrification method has a stable treatment effect, can reduce treatment costs, and save energy consumption of aeration fans.

[0011] Preferably, the pretreatment includes flotation and high-load aeration.

[0012] In the high-load aeration, the DO concentration in the anaerobic digestate of the food waste is maintained at 1-2 mg / L by controlling the aeration volume, and the biological adsorption process is mainly adopted, and the sludge age is controlled within 3 days.

[0013] Preferably, the pH value of the anaerobic digestate of food waste before the first micro-aeration is controlled to be 7-8.6, for example, 7, 7.2, 7.5, 7.8, 8, 8.3 or 8.6, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0014] Preferably, the temperature of the anaerobic digestate of food waste is controlled to be 30-35°C before the first micro-aeration, for example, 30°C, 31°C, 32°C, 33°C or 35°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0015] The pH value and temperature described in the present invention are not within the specified range and need to be adjusted specifically to ensure that they are within the control limits.

[0016] Preferably, before the first micro-aeration, the salinity of the anaerobic digestate of food waste is controlled to be ≤1%, for example, it can be 1%, 0.8%, 0.5%, 0.3% or 0.1%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0017] If the salinity in the present invention exceeds the control limit, water intake is stopped and the water is discharged to the original biogas slurry regulating tank after sedimentation.

[0018] Preferably, the DO concentration of the anaerobic digestate of food waste in the first micro-aeration is controlled to be 0.3-0.5 mg / L, for example, it can be 0.3 mg / L, 0.35 mg / L, 0.4 mg / L, 0.45 mg / L or 0.5 mg / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0019] The first micro-aeration, the second micro-aeration and the aeration in the present invention are all performed by automatically controlling the fan through the DO detector.

[0020] Preferably, the endpoint of the first micro-aeration is to make the NH3-N concentration of the first-stage effluent ≤280 mg / L and the TN concentration ≤400 mg / L.

[0021] The NH3-N concentration of the primary effluent is ≤280 mg / L, for example, it can be 280 mg / L, 250 mg / L, 220 mg / L, 200 mg / L or 180 mg / L, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0022] The TN concentration of the primary effluent is ≤400 mg / L, for example, it can be 400 mg / L, 380 mg / L, 350 mg / L, 320 mg / L or 300 mg / L, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0023] Preferably, the first micro-aeration, the second micro-aeration and the third mixing are respectively left to stand.

[0024] Preferably, the first-stage effluent part flows back to the first micro-aeration system, and the second-stage effluent part flows back to the second micro-aeration system.

[0025] The first micro-aeration and the second micro-aeration reactions increase the return flow from the outlet water to the inlet water, and can realize the dynamic adjustment of the inlet water.

[0026] Preferably, the NH3-N concentration in the influent of the first micro-aeration is ≤1000 mg / L, and the NH3-N concentration in the influent of the second micro-aeration is ≤500 mg / L.

[0027] “The first micro-aerated influent” refers to the influent obtained by mixing the pretreated anaerobic digestate from food waste with part of the returned primary effluent; “the second micro-aerated influent” refers to the influent obtained by mixing the primary effluent, the pretreated anaerobic digestate from food waste and part of the returned secondary effluent.

[0028] The NH3-N concentration in the influent of the first micro-aeration is ≤1000 mg / L, for example, it can be 1000 mg / L, 950 mg / L, 900 mg / L, 850 mg / L or 800 mg / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0029] The NH3-N concentration in the influent of the second micro-aeration is ≤500 mg / L, for example, it can be 500 mg / L, 450 mg / L, 400 mg / L, 350 mg / L or 300 mg / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0030] Preferably, in the first mixture, the ratio of NH3-N concentration to NO2-N concentration is (1-1.32):1, for example, it can be 1:1, 1.1:1, 1.2:1, 1.3:1 or 1.32:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] The ratio of NH3-N concentration to NO2-N concentration is regulated by controlling the reflux at the outlet and the degree of nitrification of the pretreated ammonia nitrogen. The reaction is a dynamic equilibrium. NO2-N is an intermediate product, which is produced in the previous step reaction in the reactor and utilized in the next step reaction. The theoretical reaction ratio is (1-1.32):1.

[0032] Preferably, the pH value of the influent is controlled to be 6.5-8.8 after the first mixing and before the second micro-aeration, for example, 6.5, 7, 7.5, 8, 8.5 or 8.8, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0033] Preferably, the inlet water temperature after the first mixing and before the second micro-aeration is controlled to be 30-35°C, for example, 30°C, 31°C, 32°C, 33°C or 35°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0034] Preferably, the salinity of the influent is controlled to be ≤1% after the first mixing and before the second micro-aeration, for example, 1%, 0.8%, 0.5%, 0.3% or 0.1%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0035] Preferably, the ORP value of the influent is controlled to be -300 to -400 mV after the first mixing and before the second micro-aeration, for example, -300 mV, -320 mV, -350 mV, -380 mV or -400 mV, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0036] Preferably, the DO concentration of the influent controlled in the second micro-aeration is 0.3-0.5 mg / L, for example, 0.3 mg / L, 0.35 mg / L, 0.4 mg / L, 0.45 mg / L or 0.5 mg / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0037] Preferably, the endpoint of the second micro-aeration is to make the NH3-N concentration of the secondary effluent 74-76 mg / L and the TN concentration 128-132 mg / L.

[0038] The NH3-N concentration of the secondary effluent is 74-76 mg / L, for example, it can be 74 mg / L, 74.5 mg / L, 75 mg / L, 75.5 mg / L or 76 mg / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0039] The TN concentration of the secondary effluent is 128-132 mg / L, for example, it can be 128 mg / L, 129 mg / L, 130 mg / L, 131 mg / L or 132 mg / L, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] The carbon source of the present invention is mainly a substance that is easily biodegradable, including methanol, sodium acetate, composite carbon source, etc. The amount of the carbon source is such that BOD / TN is ≥4. Taking methanol as an example, the amount is 0.45-0.67 g / L.

[0041] Preferably, in the second mixing, the ratio of COD concentration to TN concentration is controlled to be (4-5):1, for example, it can be 4:1, 4.2:1, 4.5:1, 4.8:1 or 5:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0042] Preferably, the pH value of the influent after the second mixing and before aeration is controlled to be 7-8.5, for example, 7, 7.5, 8 or 8.5, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0043] Preferably, the temperature of the inlet water after the second mixing and before aeration is controlled to be 28-32°C, for example, 28°C, 29°C, 30°C, 31°C or 32°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] Preferably, the salinity of the influent is controlled to be ≤1% after the second mixing and before aeration, for example, 1%, 0.8%, 0.5%, 0.3% or 0.1%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0045] Preferably, the ORP value of the inlet water after the second mixing and before aeration is controlled to be -300 to -400 mV, for example, -300 mV, -320 mV, -350 mV, -380 mV or -400 mV, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0046] Preferably, the DO concentration of the influent controlled during aeration is 1.7-2 mg / L, for example, 1.7 mg / L, 1.8 mg / L, 1.9 mg / L, 1.95 mg / L or 2 mg / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0047] Preferably, the endpoint of aeration is to make the NH3-N concentration of the effluent ≤ 5 mg / L, for example, it can be 5 mg / L, 4 mg / L, 3 mg / L, 2 mg / L or 1 mg / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0048] Preferably, the power of the third mixing is 8-12 W / m 3 , for example, it can be 8W / m 3 , 9W / m 3 、10W / m 3 , 11W / m 3 or 12W / m 3 , but not limited to the listed values, other unlisted values ​​within the numerical range are also applicable.

[0049] Preferably, the endpoint of the third mixing is to make the TN concentration of the denitrification effluent ≤45 mg / L, for example, it can be 45 mg / L, 40 mg / L, 35 mg / L, 30 mg / L or 25 mg / L, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0050] Preferably, the denitrification method is carried out by a denitrification device system for anaerobic digestate from food waste, the denitrification device system comprises a primary SBR reactor, a secondary SBR reactor and a tertiary SBR reactor which are sequentially connected along the material flow direction, the secondary SBR reactor is also provided with an anaerobic digestate inlet for food waste, the primary effluent portion of the primary SBR reactor flows back to the primary SBR reactor, the secondary effluent portion of the secondary SBR reactor flows back to the secondary SBR reactor, and a carbon source delivery device is provided between the secondary SBR reactor and the tertiary SBR reactor.

[0051] Preferably, the primary SBR reactor is provided with a first pH detector, a first DO detector, a first ORP detector, a first NH3-N detector, a first NO2-N detector and a first salinity detector.

[0052] Preferably, the secondary SBR reactor is provided with a second pH detector, a second DO detector, a second ORP detector, a second NH3-N detector, a second NO2-N detector and a second salinity detector.

[0053] Preferably, the three-stage SBR reactor is provided with a third pH detector, a third DO detector, a COD detector, a third NH3-N detector, a TN detector and a third salinity detector.

[0054] Preferably, temperature sensors are provided inside the primary SBR reactor, the secondary SBR reactor and the tertiary SBR reactor.

[0055] Preferably, the carbon source dosing device comprises a carbon source dosing pump, and the carbon source dosing pump is connected to a carbon source storage device.

[0056] Preferably, the carbon source storage device comprises a carbon source storage tank.

[0057] The present invention collects various parameters through sensors in SBR reactors at various levels, automatically analyzes various control indicators of the denitrification device system at any time, such as pH, DO, ORP, NH3-N, NO2-N, COD, TN, salinity, etc., and compares them with the control limits set by the system. Through corresponding measures, various indicators are targetedly regulated, and precise control of aeration volume, aeration time, stirring intensity and stirring time can be achieved, which effectively reduces the processing cost and saves the energy consumption of the aeration fan.

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] The method for denitrification of anaerobic digestate from kitchen waste provided by the present invention effectively solves the problem of denitrification of anaerobic digestate from kitchen waste, has a high degree of automation, and the aeration volume, aeration time, and mixing degree can be precisely controlled. Most of the total nitrogen can be removed with only a small amount of carbon source added, which can effectively reduce the treatment cost, save the energy consumption of the aeration fan, have a stable treatment effect, and are easy to manage and maintain. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 It is a schematic diagram of the structure of the denitrification device system for anaerobic biogas slurry from food waste provided in Example 1 of the present invention.

[0061] Among them: 1, the first-stage SBR reactor; 2, the second-stage SBR reactor; 3, the third-stage SBR reactor; 4, the carbon source dosing pump; 5, the carbon source storage tank; 6, the first pH detector; 7, the first DO detector; 8, the first ORP detector; 9, the first NH3-N detector 10, the first NO2-N detector; 11, the first salinity detector; 12, the second pH detector; 13, the second DO detector; 14, the second ORP detector; 15, the second NH3-N detector; 16, the second NO2-N detector; 17, the second salinity detector; 18, the third pH detector; 19, the third DO detector; 20, the COD detector; 21, the third NH3-N detector; 22, the TN detector; 23, the third salinity detector. DETAILED DESCRIPTION

[0062] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0063] Example 1

[0064] This embodiment provides a method for denitrifying anaerobic biogas slurry from food waste, and the denitrification method comprises the following steps:

[0065] The first micro-aeration is performed on the anaerobic digestate of the food waste that has undergone flotation and high-load aeration. Before the first micro-aeration, the pH value of the anaerobic digestate of the food waste is controlled to be 8, the temperature is 32°C, and the salinity is 0.5%. During the first micro-aeration, the DO concentration of the anaerobic digestate of the food waste is controlled to be 0.4 mg / L. The end point of the first micro-aeration is to make the NH3-N concentration of the first-level effluent 180 mg / L and the TN concentration 300 mg / L. After standing, the first-level effluent obtained is first mixed with the anaerobic digestate of the food waste that has undergone flotation and high-load aeration, and then subjected to the second micro-aeration. During the first mixing, the ratio of the NH3-N concentration to the NO2-N concentration is controlled to be 1.2:1. After the first mixing and before the second micro-aeration, the pH value of the influent is controlled to be 7.5, the temperature is 32°C, the salinity is 0.5%, and the ORP value is -300 mV. During the second micro-aeration, the DO concentration of the influent is controlled to be 0.4 mg / L. The end point of the second micro-aeration is to make the NH3-N concentration of the secondary effluent 75mg / L and the TN concentration 130mg / L; the first effluent part is returned to the first micro-aeration, and the second effluent part is returned to the second micro-aeration; the NH3-N concentration in the inlet water of the first micro-aeration is 900mg / L, and the NH3-N concentration in the inlet water of the second micro-aeration is 400mg / L; the secondary effluent obtained after standing is mixed with 0.45g / L of methanol for the second time and then aerated, in the second mixing, the ratio of COD concentration to TN concentration is controlled to be 4.5:1, after the second mixing and before aeration, the pH value of the inlet water is controlled to be 8, the temperature is 30℃, the salinity is 0.5%, the ORP value is -300mV, the DO concentration of the inlet water is controlled to be 1.8mg / L during aeration, and the end point of aeration is to make the NH3-N concentration of the effluent 2mg / L; then at a power of 10W / m 3 The third mixing is carried out under the condition of standing to obtain the denitrified effluent.

[0066] The denitrification method is carried out by using a denitrification device system for anaerobic digestion liquid from food waste, and the structural schematic diagram is shown in FIG. Figure 1 As shown, the denitrification device system includes a primary SBR reactor 1, a secondary SBR reactor 2 and a tertiary SBR reactor 3 which are sequentially connected along the material flow direction. The secondary SBR reactor 2 is also provided with an anaerobic digestate inlet for food waste. The primary effluent portion of the primary SBR reactor 1 flows back into the primary SBR reactor 1, and the secondary effluent portion of the secondary SBR reactor 2 flows back into the secondary SBR reactor 2. A carbon source delivery device is provided between the secondary SBR reactor 2 and the tertiary SBR reactor 3, and the carbon source delivery device includes a carbon source delivery pump 4, and the carbon source delivery pump 4 is connected to a carbon source storage tank 5.

[0067] The first-stage SBR reactor 1 is provided with a first pH detector 6, a first DO detector 7, a first ORP detector 8, a first NH3-N detector 9, a first NO2-N detector 10 and a first salinity detector 11; the second-stage SBR reactor 2 is provided with a second pH detector 12, a second DO detector 13, a second ORP detector 14, a second NH3-N detector 15, a second NO2-N detector 16 and a second salinity detector 17; the tertiary SBR reactor 3 is provided with a third pH detector 18, a third DO detector 19, a COD detector 20, a third NH3-N detector 21, a TN detector 22 and a third salinity detector 23.

[0068] The TN concentration of the denitrification effluent in this embodiment is 45 mg / L, indicating that the denitrification method provided in this embodiment can remove most of the total nitrogen with only a small amount of carbon source added, effectively reducing the treatment cost, saving the energy consumption of the aeration fan, and the treatment effect is relatively stable.

[0069] Example 2

[0070] This embodiment provides a method for denitrifying anaerobic biogas slurry from food waste, and the denitrification method comprises the following steps:

[0071] The first micro-aeration is performed on the anaerobic digestate of the food waste that has undergone flotation and high-load aeration. Before the first micro-aeration, the pH value of the anaerobic digestate of the food waste is controlled to be 7, the temperature is 30°C, and the salinity is 1%. During the first micro-aeration, the DO concentration of the anaerobic digestate of the food waste is controlled to be 0.3 mg / L. The endpoint of the first micro-aeration is to make the NH3-N concentration of the first-level effluent 220 mg / L and the TN concentration 350 mg / L. After standing, the first-level effluent obtained is first mixed with the anaerobic digestate of the food waste that has undergone flotation and high-load aeration, and then subjected to the second micro-aeration. During the first mixing, the ratio of the NH3-N concentration to the NO2-N concentration is controlled to be 1:1. After the first mixing and before the second micro-aeration, the pH value of the influent is controlled to be 6.5, the temperature is 30°C, the salinity is 1%, and the ORP value is -350 mV. During the second micro-aeration, the DO concentration of the influent is controlled to be 0.3 mg / L. The endpoint of the second micro-aeration is to make the NH3-N concentration of the secondary effluent 74mg / L and the TN concentration 128mg / L; the primary effluent part is returned to the first micro-aeration, and the secondary effluent part is returned to the second micro-aeration; the NH3-N concentration of the influent of the first micro-aeration is 950mg / L, and the NH3-N concentration of the influent of the second micro-aeration is 450mg / L; the secondary effluent obtained after standing is mixed with 0.45g / L of methanol for the second time and then aerated, in the second mixing, the ratio of COD concentration to TN concentration is controlled to be 4:1, after the second mixing and before aeration, the pH value of the influent is controlled to be 7, the temperature is 28°C, the salinity is 1%, the ORP value is -350mV, the DO concentration of the influent is controlled to be 1.7mg / L during aeration, and the endpoint of aeration is to make the NH3-N concentration of the effluent 4mg / L; then at a power of 12W / m 3 The third mixing is carried out under the condition of standing to obtain the denitrified effluent.

[0072] The denitrification method is carried out by a denitrification device system for anaerobic digestate of food waste, and the denitrification device system is the same as that in Example 1.

[0073] The TN concentration of the denitrification effluent in this embodiment is 80 mg / L, indicating that the denitrification method provided in this embodiment can remove most of the total nitrogen with only a small amount of carbon source added, effectively reducing the treatment cost, saving the energy consumption of the aeration fan, and the treatment effect is relatively stable.

[0074] Example 3

[0075] This embodiment provides a method for denitrifying anaerobic biogas slurry from food waste, and the denitrification method comprises the following steps:

[0076] The first micro-aeration is performed on the anaerobic digestate of the food waste that has undergone flotation and high-load aeration. Before the first micro-aeration, the pH value of the anaerobic digestate of the food waste is controlled to be 8.6, the temperature is 35°C, and the salinity is 1%. During the first micro-aeration, the DO concentration of the anaerobic digestate of the food waste is controlled to be 0.5 mg / L. The endpoint of the first micro-aeration is to make the NH3-N concentration of the first-level effluent 280 mg / L and the TN concentration 400 mg / L. After standing, the first-level effluent obtained is first mixed with the anaerobic digestate of the food waste that has undergone flotation and high-load aeration, and then subjected to the second micro-aeration. During the first mixing, the ratio of the NH3-N concentration to the NO2-N concentration is controlled to be 1.32:1. After the first mixing and before the second micro-aeration, the pH value of the influent is controlled to be 8.8, the temperature is 35°C, the salinity is 1%, the ORP value is -400 mV, and the DO concentration of the influent is controlled to be 0.5 mg / L during the second micro-aeration. L, the end point of the second micro-aeration is to make the NH3-N concentration of the secondary effluent 76mg / L and the TN concentration 132mg / L; the first effluent part is returned to the first micro-aeration, and the second effluent part is returned to the second micro-aeration; the NH3-N concentration in the influent of the first micro-aeration is 1000mg / L, and the NH3-N concentration in the influent of the second micro-aeration is 500mg / L; the secondary effluent obtained after standing is mixed with 0.67g / L of methanol for the second time and then aerated, in the second mixing, the ratio of COD concentration to TN concentration is controlled to be 5:1, after the second mixing and before aeration, the pH value of the influent is controlled to be 8.5, the temperature is 32℃, the salinity is 1%, the ORP value is -400mV, the DO concentration of the influent is controlled to be 2mg / L during aeration, and the end point of aeration is to make the NH3-N concentration of the effluent 5mg / L; then at a power of 8W / m 3 The third mixing is carried out under the condition of standing to obtain the denitrified effluent.

[0077] The denitrification method is carried out by a denitrification device system for anaerobic digestate of food waste, and the denitrification device system is the same as that in Example 1.

[0078] The TN concentration of the denitrification effluent in this embodiment is 85 mg / L, indicating that the denitrification method provided in this embodiment can remove most of the total nitrogen with only a small amount of carbon source added, effectively reducing the treatment cost, saving the energy consumption of the aeration fan, and the treatment effect is relatively stable.

[0079] Example 4

[0080] This embodiment provides a method for denitrifying anaerobic digestate from food waste, which differs from Embodiment 1 in that the pH value of the anaerobic digestate from food waste is controlled to be 6.8 before the first micro-aeration, the pH value of the influent is controlled to be 6.2 after the first mixing and before the second micro-aeration, and the pH value of the influent is controlled to be 6.8 after the second mixing and before aeration, and the rest is the same as Embodiment 1.

[0081] In this embodiment, since the pH value of the biogas slurry is controlled too low before each level of aeration, the rate of nitrite reaction will be greatly reduced, resulting in the failure of NO2-N accumulation, while the denitrification reaction requires NO2 - As a substrate for the reaction, it causes the reaction to fail normally, microorganisms to die, and the system to collapse.

[0082] Example 5

[0083] This embodiment provides a method for denitrifying anaerobic digestate from food waste, which differs from Embodiment 1 in that the pH value of the anaerobic digestate from food waste is controlled to be 9 before the first micro-aeration, the pH value of the influent is controlled to be 9 after the first mixing and before the second micro-aeration, and the pH value of the influent is controlled to be 9 after the second mixing and before aeration, and the rest is the same as Embodiment 1.

[0084] In this embodiment, since the pH value of the biogas slurry is controlled too high before each level of aeration, the nitrite reaction rate will also be greatly reduced, and the reaction cannot be normal, the microorganisms die, and the system collapses.

[0085] Example 6

[0086] This embodiment provides a method for denitrifying anaerobic digestate from food waste. The difference from Embodiment 1 is that in the first mixing, the ratio of NH3-N concentration to NO2-N concentration is adjusted to 0.8:1, and the rest is the same as Embodiment 1.

[0087] In this embodiment, since the concentration of ammonia nitrogen in the first mixture is too low and the concentration of nitrite nitrogen is too high, there will be excess unreacted NO2 - It produces biological toxicity to denitrification reaction microorganisms, thereby reducing their activity and significantly decreasing the denitrification efficiency. If it continues for a long time, it will cause the system to collapse.

[0088] Example 7

[0089] This embodiment provides a method for denitrifying anaerobic digestate from food waste. The difference from Embodiment 1 is that in the first mixing, the ratio of NH3-N concentration to NO2-N concentration is adjusted to 1.5:1, and the rest is the same as Embodiment 1.

[0090] Denitrification reaction microorganisms are very sensitive to substrate concentrations. Too high or too low a substrate concentration will affect their activity. In this embodiment, since the ammonia nitrogen concentration in the first mixture is too high and the nitrite nitrogen ratio is too low, the unreacted ammonia nitrogen will also produce biological toxicity to the microorganisms, reduce their activity, and reduce the denitrification efficiency. Long-term continuation will cause the system to collapse.

[0091] Comparative Example 1

[0092] This comparative example provides a method for denitrifying anaerobic biogas slurry from food waste, which differs from Example 1 in that there is no second micro-aeration step, and the rest is the same as Example 1.

[0093] In this comparative example, since the second micro-aeration step is not set, the nitrite reaction cannot occur and the substrate NO2 required for the denitrification reaction will not be formed. - Therefore, denitrification is impossible, TN will not change, and only a small amount of organic nitrogen will be converted into ammonia nitrogen.

[0094] In summary, the method for denitrification of anaerobic digestate from food waste provided by the present invention effectively solves the problem of denitrification of anaerobic digestate from food waste, has a high degree of automation, and the aeration volume, aeration time, and mixing degree can be precisely controlled. Most of the total nitrogen can be removed by adding only a small amount of carbon source, which can effectively reduce the treatment cost, save the energy consumption of the aeration fan, have a stable treatment effect, and are easy to manage and maintain.

[0095] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for denitrification of anaerobic biogas slurry from kitchen waste, characterized in that: The denitrification method comprises the following steps: The pretreated anaerobic digestate from food waste is subjected to a first micro-aeration, the obtained primary effluent is first mixed with the pretreated anaerobic digestate from food waste and then subjected to a second micro-aeration, the obtained secondary effluent is second mixed with a carbon source and then subjected to aeration and a third mixing in sequence to obtain denitrified effluent; The first micro-aeration, the second micro-aeration and before aeration respectively detect and control the pH value, temperature and salinity of the influent water.

2. The denitrification method according to claim 1, characterized in that: The pretreatment includes air flotation and high-load aeration; Preferably, the pH value of the anaerobic digestate of the food waste is controlled to be 7-8.6 before the first micro-aeration; Preferably, the temperature of the anaerobic digestate of the food waste is controlled to be 30-35°C before the first micro-aeration; Preferably, before the first micro-aeration, the salinity of the anaerobic digestate from the food waste is controlled to be ≤1%.

3. The denitrification method according to claim 1 or 2, characterized in that: The DO concentration of the anaerobic digestate of the kitchen waste is controlled to be 0.3-0.5 mg / L in the first micro-aeration; Preferably, the endpoint of the first micro-aeration is to make the NH3-N concentration of the first-stage effluent ≤280 mg / L and the TN concentration ≤400 mg / L; Preferably, the first micro-aeration, the second micro-aeration and the third mixing are respectively left to stand.

4. The denitrification method according to any one of claims 1 to 3, characterized in that: The first-stage effluent part is returned to the first micro-aeration system, and the second-stage effluent part is returned to the second micro-aeration system; Preferably, the NH3-N concentration in the influent of the first micro-aeration is ≤1000 mg / L, and the NH3-N concentration in the influent of the second micro-aeration is ≤500 mg / L; Preferably, in the first mixture, the ratio of NH3-N concentration to NO2-N concentration is (1-1.32):1; Preferably, after the first mixing and before the second micro-aeration, the pH value of the influent is controlled to be 6.5-8.8; Preferably, the temperature of the inlet water is controlled to be 30-35°C after the first mixing and before the second micro-aeration; Preferably, the salinity of the influent is controlled to be ≤1% after the first mixing and before the second micro-aeration.

5. The denitrification method according to any one of claims 1 to 4, characterized in that: The DO concentration of the influent is controlled to be 0.3-0.5 mg / L in the second micro-aeration; Preferably, the endpoint of the second micro-aeration is to make the NH3-N concentration of the secondary effluent 74-76 mg / L and the TN concentration 128-132 mg / L.

6. The denitrification method according to any one of claims 1 to 5, characterized in that: The amount of the carbon source is such that BOD / TN ≥ 4; Preferably, in the second mixing, the ratio of COD concentration to TN concentration is controlled to be (4-5):1; Preferably, the pH value of the influent is controlled to be 7-8.5 after the second mixing and before aeration; Preferably, the temperature of the inlet water is controlled to be 28-32°C after the second mixing and before aeration; Preferably, the salinity of the influent is controlled to be ≤1% after the second mixing and before aeration.

7. The denitrification method according to any one of claims 1 to 6, characterized in that: The DO concentration of the influent is controlled to be 1.7-2 mg / L during aeration; Preferably, the end point of aeration is to make the NH3-N concentration of the effluent ≤ 5 mg / L.

8. The denitrification method according to any one of claims 1 to 7, characterized in that: The power of the third mixture is 8-12W / m 3 ; Preferably, the endpoint of the third mixing is to make the TN concentration of the denitrification effluent ≤45 mg / L.

9. The denitrification method according to any one of claims 1 to 8, characterized in that: The denitrification method is carried out by a denitrification device system for anaerobic digestate of food waste, wherein the denitrification device system comprises a primary SBR reactor, a secondary SBR reactor and a tertiary SBR reactor which are sequentially connected along a material flow direction, wherein the secondary SBR reactor is further provided with an anaerobic digestate inlet for food waste, wherein the primary effluent portion of the primary SBR reactor flows back to the primary SBR reactor, and the secondary effluent portion of the secondary SBR reactor flows back to the secondary SBR reactor, and a carbon source delivery device is provided between the secondary SBR reactor and the tertiary SBR reactor.

10. The denitrification method according to claim 9, characterized in that: The primary SBR reactor is provided with a first pH detector, a first DO detector, a first ORP detector, a first NH3-N detector, a first NO2-N detector and a first salinity detector; Preferably, the secondary SBR reactor is provided with a second pH detector, a second DO detector, a second ORP detector, a second NH3-N detector, a second NO2-N detector and a second salinity detector; Preferably, the three-stage SBR reactor is provided with a third pH detector, a third DO detector, a COD detector, a third NH3-N detector, a TN detector and a third salinity detector; Preferably, the carbon source dosing device comprises a carbon source dosing pump, and the carbon source dosing pump is connected to a carbon source storage device.

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