Mixed nutrient denitrification electron donor and construction method

Abstract

This application provides a mixed-nutrient denitrification electron donor and its construction method, relating to the field of biological nitrogen removal. The method includes: culturing denitrifying bacteria in a simulated wastewater anoxic tank using a liquid sulfur source as the electron donor, thus acclimatizing the sulfur-autotrophic denitrifying bacteria; using the influent from the wastewater treatment plant's anoxic tank as the water source, controlling the hydraulic retention time to match that of the anoxic tank, and adjusting the denitrification load and pH value to a preset range by adding a carbon source or an alkaline buffer; determining the reagent ratio based on the added liquid sulfur source, carbon source, or alkaline buffer, the ratio being used to prepare the mixed-nutrient denitrification electron donor, which is used as the denitrification electron donor in the wastewater treatment anoxic tank denitrification system. This application can obtain a mixed-nutrient denitrification electron donor tailored to wastewater quality, reducing organic carbon source consumption.

Description

Technical Field

[0001] This application relates to the field of biological denitrification, and more particularly to a mixed-nutrient denitrification electron donor and its construction method. Background Technology

[0002] Denitrification is a microbial-mediated biochemical process that primarily occurs in anaerobic environments and involves the conversion of nitrates (NO3-) into nitrogenous substances. - ) and nitrite (NO2) - Nitrogen is reduced to gaseous nitrogen compounds (such as N2 and N2O), ultimately releasing reactive nitrogen from water or soil into the atmosphere as nitrogen gas. In wastewater treatment, by designing and operating anaerobic or anoxic treatment units, the growth of denitrifying bacteria and the denitrification reaction are promoted, achieving effective removal of nitrogen from wastewater to meet discharge standards or resource recovery requirements. The denitrification process is of great value for the nitrogen balance of ecosystems, wastewater treatment, and environmental protection.

[0003] Traditional heterotrophic denitrification processes rely on organic carbon sources. For wastewater treatment plants with insufficient influent carbon sources, it is necessary to add organic carbon sources such as glucose and sodium acetate, which results in high operating costs and may pose a risk of carbon source breakthrough.

[0004] To address the aforementioned shortcomings, there is an urgent need for a hybrid nutrient-based denitrification electron donor and its construction method, which can obtain a hybrid denitrification electron donor tailored to wastewater quality and reduce the consumption of organic carbon sources. Summary of the Invention

[0005] This application provides a mixed nutrient-type denitrification electron donor and a method for constructing it, which can obtain a mixed denitrification electron donor for wastewater quality and reduce the consumption of organic carbon sources.

[0006] In a first aspect, this application provides a method for constructing a mixed-nutrient denitrification electron donor, comprising:

[0007] A simulated reactor was used to simulate anoxic wastewater tanks, with liquid sulfur source as electron donor to cultivate denitrifying bacteria, thus completing the domestication of sulfur autotrophic denitrifying bacteria;

[0008] Using the influent from the anoxic tank of the wastewater treatment plant as the water source, the hydraulic retention time is controlled to be consistent with that of the anoxic tank. The denitrification load and pH value are adjusted to the preset range by adding carbon source or alkaline buffer.

[0009] The proportion of reagents is determined based on the liquid sulfur source, the carbon source, or the alkaline buffer added. This proportion is used to prepare a mixed nutrient denitrification electron donor, which is used as the denitrification electron donor for the anoxic tank denitrification system in the wastewater treatment plant.

[0010] In one possible design, adjusting the denitrification load and pH value to a preset range by adding a carbon source or alkaline buffer includes:

[0011] The denitrification load in the denitrification process is obtained based on the nitrate concentration.

[0012] Determine whether the denitrification load is less than the preset load value;

[0013] If the load is less than the preset load value, a carbon source is added to the simulated reactor until the denitrification load is not less than the preset load value.

[0014] Determine whether the pH value is not less than a preset pH value; if it is less than the preset pH value, add an alkaline buffer until the pH value is not less than the preset pH value.

[0015] In one possible design, the use of a simulated reactor to model anoxic wastewater ponds and the cultivation of denitrifying bacteria using a liquid sulfur source as an electron donor to complete the acclimatization of sulfur-autotrophic denitrifying bacteria includes:

[0016] Sludge from the anoxic tank of a wastewater treatment plant was inoculated into a simulated reactor, using the influent from the anoxic tank as the water source; the amount of liquid sulfur source added was determined based on the nitrate concentration in the simulated reactor.

[0017] The liquid sulfur source is added to the simulated reactor according to the specified addition amount; the nitrate concentration in the simulated reactor is monitored, and the denitrification rate is obtained based on the nitrate concentration. If the denitrification rate tends to stabilize, it is determined that the sulfur autotrophic denitrifying bacteria have been successfully domesticated.

[0018] In one possible design, determining the amount of liquid sulfur source added based on the nitrate concentration includes:

[0019] The required amount of sulfur is determined based on a nitrogen-to-sulfur ratio of 1:1.1.

[0020] The amount of liquid sulfur source to be added is determined based on the amount of sulfur and the ratio of sulfur to the amount of liquid sulfur source.

[0021] In one possible design, obtaining the denitrification load in the denitrification process based on the nitrate concentration includes:

[0022] Obtain the nitrate concentration before and after a preset period, and obtain the denitrification rate of that period based on the ratio of the change in nitrate concentration to the corresponding time interval.

[0023] The denitrification load is obtained based on the denitrification rate.

[0024] In one possible design, the liquid sulfur source is sodium sulfide or liquid sodium thiosulfate.

[0025] In one possible design, the preset pH value is set in the range of 6.5 to 8.0.

[0026] In one possible design, the alkaline buffer is sodium carbonate or sodium bicarbonate.

[0027] Secondly, this application provides a mixed nutrient type denitrification electron donor, comprising a mixture of one or more of a liquid sulfur source, a carbon source and an alkaline buffer in a preset ratio, wherein the preset ratio is the ratio obtained according to the above-mentioned method for constructing a mixed nutrient type denitrification electron donor.

[0028] Thirdly, this application provides an anoxic pond denitrification system, including the aforementioned mixed nutrient type denitrification nitrogen removal electron donor.

[0029] This application provides a mixed-nutrient denitrification electron donor and its construction method, comprising: culturing denitrifying bacteria in a simulated wastewater anoxic tank using a liquid sulfur source as the electron donor to complete the acclimatization of sulfur-autotrophic denitrifying bacteria; using the influent of the wastewater treatment plant's anoxic tank as the water source, controlling the hydraulic retention time to be consistent with the anoxic tank, and adjusting the denitrification load and pH value to a preset range by adding a carbon source or an alkaline buffer; determining the reagent ratio based on the added liquid sulfur source, carbon source, or alkaline buffer, the ratio being used to prepare the mixed-nutrient denitrification electron donor, which is used as the denitrification electron donor in the wastewater treatment anoxic tank denitrification system. The following technical effects are achieved:

[0030] The method provided in this application can simulate the water quality of the anoxic tank of a wastewater treatment plant and obtain a certain proportion of mixed nutrient denitrification electron donors. These electron donors have extremely high compatibility with the wastewater treatment plant, high electron utilization rate, and fast reaction rate. They can reduce the consumption of carbon sources in the anoxic tank and avoid the risk of system instability caused by pH changes in the denitrification system. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 A flowchart illustrating a method for constructing a mixed-nutrient denitrification electron donor provided in this application embodiment. Figure 1 ;

[0033] Figure 2 A flowchart illustrating a method for constructing a mixed-nutrient denitrification electron donor provided in this application embodiment. Figure 2 .

[0034] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0035] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of devices and methods consistent with some aspects of this application as detailed in the appended claims, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0036] It should be noted that, in the embodiments of this application, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design scheme described as "exemplary" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or design schemes. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0037] It should be noted that "at the time of..." in the embodiments of this application can be either at the instant when a certain situation occurs, or for a period of time after the occurrence of a certain situation. The embodiments of this application do not make specific limitations on this.

[0038] First, let's explain the terms used in this application:

[0039] Denitrification process: Denitrification is a series of reduction reactions carried out by specific microorganisms under anaerobic conditions, which convert nitrates and nitrites into gaseous nitrogen compounds. It can be used in denitrification systems in anoxic ponds and has important value for the nitrogen balance of ecosystems, wastewater treatment and environmental protection.

[0040] Carbon source: refers to substances that provide carbon. These substances typically contain abundant carbon compounds that can be absorbed by organisms and converted into organic matter they need. In the denitrification process of wastewater treatment, organic carbon sources are needed as electron donors to remove nitrogen from wastewater. Organic carbon sources include methanol, sodium acetate, and glucose. In practical applications, the selection of a carbon source needs to consider factors such as its bioavailability, economics, environmental impact, and ease of application to ensure the efficiency, stability, and economy of the wastewater treatment process.

[0041] Sulfate-autotrophic denitrifying bacteria are a type of microorganism capable of using sulfur compounds as electron donors to carry out denitrification (reducing nitrates to nitrogen gas) under anaerobic or microaerobic conditions. Sulfate-autotrophic denitrification deep nitrogen removal processes are often considered part of a tertiary biological treatment unit because they primarily target nitrates (NOx) remaining after primary and secondary biological treatment. 3- Further denitrification treatment is carried out to meet stricter nitrogen emission standards or water reuse requirements.

[0042] Secondary biological treatment unit: The secondary biological treatment unit is a core component of the wastewater treatment process. Its main objective is to further remove organic matter, suspended solids, and some nutrients such as nitrogen and phosphorus that remain in the wastewater after primary treatment (such as screens, grit chambers, and primary sedimentation tanks). Secondary biological treatment mainly relies on the biochemical action of microorganisms, which degrade organic pollutants through their metabolism, transforming them into harmless or low-toxic substances such as carbon dioxide, water, and nitrogen.

[0043] Tertiary biological treatment units, also known as advanced biological treatment or deep biological treatment, are biological treatment stages that follow primary and secondary biological treatment. They further remove low concentrations of organic matter, nitrogen, phosphorus, and other specific pollutants remaining in the wastewater after the first two stages of treatment. The goal of tertiary biological treatment is to meet stricter discharge standards, improve the quality of reclaimed water, or achieve highly efficient removal of specific pollutants.

[0044] In existing technologies, denitrification processes include autotrophic denitrification and heterotrophic denitrification. Heterotrophic denitrification is part of a secondary biological treatment unit. Sulfate autotrophic denitrification is currently commonly used in tertiary biological treatment units to further remove nitrogen from nitrates remaining after secondary biological treatment. Traditional heterotrophic denitrification processes rely on organic carbon sources. For wastewater treatment plants with insufficient influent carbon sources, external organic carbon sources such as glucose and sodium acetate are required, resulting in high operating costs and potential carbon source breakthrough risks.

[0045] To address the above-mentioned technical problems, this application provides a method for constructing a mixed-nutrient denitrification electron donor, used to obtain a mixed-nutrient denitrification electron donor, which is used for...

[0046] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0047] Figure 1 A flowchart illustrating a method for constructing a mixed-nutrient denitrification electron donor provided in this application embodiment. Figure 1 ;like Figure 1 As shown, the method includes:

[0048] S101. A simulated reactor is used to simulate anoxic wastewater tanks and liquid sulfur source is used as electron donor to cultivate denitrifying bacteria, thereby completing the domestication of sulfur autotrophic denitrifying bacteria.

[0049] Specifically, the domestication of sulfur-autotrophic denitrifying bacteria refers to the process of promoting the proliferation of these naturally occurring strains in the environment and adapting them to specific environmental conditions, thereby improving their denitrification activity and treatment efficiency.

[0050] Specifically, the simulated reactor generally uses a reaction vessel, which can realize functions such as inlet and outlet flow rate control, environmental parameter monitoring and control, and material output during the reaction process. It is used to simulate the denitrification process in anoxic wastewater ponds and meets the requirements for controllability and safety of the simulated process.

[0051] S102. Using the influent from the anoxic tank of the wastewater treatment plant as the water source, the hydraulic retention time is controlled to be consistent with that of the anoxic tank. The denitrification load and pH value are adjusted to the preset range by adding carbon source or alkaline buffer.

[0052] Specifically, the hydraulic retention time (HRT) in the anoxic tank of a wastewater treatment plant refers to the average residence time of influent in the anoxic tank. Calculated based on the ratio of effective volume to influent flow rate, it is an important parameter for measuring the contact time between the fluid and the media (such as activated sludge, packing material, soil, etc.) within the treatment unit. Maintaining the hydraulic retention time consistent with that in the anoxic tank allows for better simulation of the denitrification process within the anoxic tank of the wastewater treatment plant.

[0053] Specifically, the addition of carbon source is used to adjust the denitrification load to reach the design value. The consumption of carbon source is an alkali-producing reaction, and the consumption of autotrophic denitrifying bacteria is an acid-producing reaction. Therefore, an alkaline buffer is used to adjust the pH value in the reactor to ensure that the pH value in the system is balanced and stable.

[0054] S103. Determine the reagent ratio based on the liquid sulfur source, carbon source, or alkaline buffer added. The ratio is used to prepare a mixed nutrient denitrification electron donor. The mixed nutrient denitrification electron donor is used as the denitrification electron donor for the anoxic tank denitrification system in wastewater treatment.

[0055] Specifically, the ratio of the liquid sulfur source added in step S101, the carbon source that may be added in step S102, and the alkaline buffer is the reagent ratio in the anoxic tank of the wastewater treatment plant, and the reagent mixture with the same ratio is the reagent in the dosing system of the anoxic tank of the wastewater treatment plant.

[0056] This application provides a method for constructing a mixed-nutrient denitrification electron donor. This method involves acclimating sulfur-autotrophic denitrifying bacteria in a simulated reactor, simulating the denitrification process in an anoxic tank of a wastewater treatment plant, and adjusting the denitrification load and pH value to a preset range by adding a carbon source or alkaline buffer. This determines the reagent ratio, and the denitrification reagent is then configured according to this ratio to serve as the denitrification electron donor in the anoxic tank of the wastewater treatment plant. This method achieves the following technical effects:

[0057] The method provided in this embodiment can simulate the water quality of the anoxic tank of a wastewater treatment plant and obtain a certain proportion of mixed nutrient denitrification electron donors. These electron donors have extremely high compatibility with the wastewater treatment plant, high electron utilization rate, and fast reaction rate, which can reduce the consumption of carbon sources in the anoxic tank.

[0058] Figure 2 A flowchart illustrating a method for constructing a mixed-nutrient denitrification electron donor provided in this application embodiment. Figure 2 ;like Figure 2 As shown, the method includes:

[0059] S201. Inoculate the anoxic tank sludge from the wastewater treatment plant into the simulated reactor, using the influent from the anoxic tank as the water source; determine the amount of liquid sulfur source to be added based on the nitrogen concentration in the simulated reactor.

[0060] Specifically, the liquid sulfur source is a sulfate compound, including liquid sodium thiosulfate and sodium sulfide, which can be one or more of these.

[0061] Specifically, the required amount of sulfur is determined based on a nitrogen-to-sulfur ratio of 1:1 to 1:2; the amount of liquid sulfur source to be added is determined based on the amount of sulfur and the ratio of sulfur to the amount of liquid sulfur source.

[0062] Specifically, the reaction formula for nitrogen (N) and sulfur (S) elements in wastewater is as follows:

[0063] NO3-+1.10S+0.40CO2+0.76H2O+0.08NH4+→0.5N2+1.10SO4 2- +1.28H + +0.08C5H7O2N

[0064] According to the above formula, the nitrogen-sulfur ratio is 1:1.11, where 1:1.1 is the molar ratio of nitrogen and sulfur, in moles; converted to a nitrogen-sulfur mass ratio of 14:35, that is, if 14mg of nitrogen is required to react, 35mg of sulfur needs to be added.

[0065] Specifically, since different substances can be selected as liquid sulfur sources, after obtaining the amount of sulfur, the amount of liquid sulfur source to be added is determined based on the proportion of sulfur in the liquid sulfur source.

[0066] S202. Add liquid sulfur source to the simulated reactor according to the addition amount; monitor the nitrate concentration in the simulated reactor, obtain the denitrification rate based on the nitrate concentration, and if the denitrification rate tends to stabilize, it is determined that the sulfur autotrophic denitrifying bacteria have been successfully domesticated.

[0067] Specifically, liquid sulfur source is used as the electron donor for sulfur autotrophic denitrification. The amount added is determined, and once the denitrification rate stabilizes, the sulfur autotrophic denitrifying bacteria are considered successfully domesticated.

[0068] In one embodiment, the nitrate concentration in the simulated reactor is monitored every preset period, and the denitrification rate within a preset period is obtained based on the nitrate concentration; if the difference between the denitrification rates within 2 to 3 consecutive preset periods is less than a preset difference, the denitrification rate is determined to be stable.

[0069] As one example, for the nitrate concentration before and after a preset period, the denitrification rate can be obtained based on the ratio of the change in nitrate concentration to the corresponding time interval.

[0070] S203. Using the influent from the anoxic tank of the wastewater treatment plant as the water source, the hydraulic retention time is controlled to be consistent with that of the anoxic tank, and the denitrification load in the denitrification process is obtained based on the nitrate concentration.

[0071] Specifically, the method for calculating the new denitrification load based on nitrate concentration includes: obtaining the nitrate concentration before and after a preset period; obtaining the denitrification rate of that period based on the ratio of the change in nitrate concentration to the corresponding time interval; and obtaining the denitrification load based on the denitrification rate.

[0072] Specifically, the denitrification rate is the amount of nitrate nitrogen removed divided by the reaction time; denitrification nitrogen removal load: the nitrogen removal load refers to the mass of nitrate that microorganisms can consume per unit time and per unit volume, and the unit is kgN / m³. 3 ·d.

[0073] In one embodiment, the denitrification load can be obtained by unit conversion based on the denitrification rate.

[0074] In another embodiment, the denitrification load can be obtained based on the mass of nitrate consumed, i.e., denitrification load = mass of nitrate consumed (kg) / reaction volume (m3) / reaction time (d).

[0075] S204. Determine if the denitrification load is less than the preset load value; if it is less than the preset load value, add a carbon source to the simulated reactor until the denitrification load is not less than the preset load value; proceed to S205; if it is not less than the preset load value; proceed to S205.

[0076] As one embodiment, when the denitrification load is less than the preset load value, one unit of carbon source is added to the simulated reactor. After a preset time period, the nitrate concentration is re-acquired to calculate the new denitrification load. The denitrification load is then re-determined to see if it is less than the preset load value. If it is less, the operation of adding one unit of carbon source to the simulated reactor is repeated until it is determined that the denitrification load is not less than the preset load value. The total amount of carbon source added is recorded, and step S205 is executed.

[0077] As one example, the preset load value is generally taken as 300-1200 gNO3-N / m 3 ·d, this unit represents the mass of nitrate nitrogen removed per cubic meter per day;

[0078] Specifically, a preset time period is used to wait for the drug to be added and to ensure a full reaction.

[0079] S205. Determine if the pH value is not less than the preset pH value; if it is less than the preset pH value, add alkaline buffer until the pH value is not less than the preset pH value, then proceed to S206; if it is not less than the preset pH value, proceed to S206.

[0080] Specifically, this method couples the acid production process of sulfur-consuming autotrophic denitrifying bacteria with the alkali production process of carbon-consuming bacteria. In order to ensure the acid-base stability of the entire system, the pH value needs to be adjusted to neutral.

[0081] Specifically, similar to S204, the pH value is gradually adjusted by adding small doses multiple times until it is not less than the preset pH value.

[0082] In some embodiments, sodium carbonate or sodium bicarbonate is used as the alkaline buffer in this application;

[0083] Furthermore, the preset pH value is determined to be within the range of 6.5-8.0;

[0084] Preferably, the preset pH value is 7.5.

[0085] S206. Determine the reagent ratio based on the liquid sulfur source, carbon source, or alkaline buffer added. The ratio is used to prepare a mixed nutrient denitrification electron donor. The mixed nutrient denitrification electron donor is used as the denitrification electron donor for the anoxic tank denitrification system in wastewater treatment.

[0086] Specifically, the proportions of the liquid sulfur source, carbon source, and alkaline buffer added in the method of this application are fixed proportions.

[0087] Specifically, liquid sulfur source, carbon source and alkaline buffer of the same substance are mixed in a certain proportion to obtain a mixture as a mixed nutrient denitrification electron donor. This electron donor is used as a dosing agent in the denitrification system of the anoxic tank of the wastewater treatment plant.

[0088] Specifically, depending on the characteristics of the water source, the above method may be used in situations where it is not necessary to add a carbon source or alkaline buffer. The mixed nutrient denitrification electron donor may include one or more of the following: liquid sulfur source, carbon source, and alkaline buffer.

[0089] In one embodiment, a mixed-nutrient denitrification electron donor obtained according to this application is delivered to the anoxic tank via a dosing system. During the initial startup phase of the mixed-nutrient denitrification system in the anoxic tank of a wastewater treatment plant, the abundance of sulfur-autotrophic denitrifying bacteria in the anoxic tank may be low. During the initial commissioning of the mixed-nutrient denitrification process in the wastewater treatment plant, the total nitrogen concentration in the effluent should be monitored continuously via an online monitoring system. If the total nitrogen concentration increases, timely replenishment of organic carbon sources should be initiated. As the startup time of the mixed-nutrient denitrification system extends, the abundance of sulfur-autotrophic denitrifying bacteria gradually increases, and the contribution of sulfur-autotrophic denitrification increases, allowing for a gradual reduction or even elimination of additional carbon source replenishment.

[0090] The method provided in this application embodiment uses a simulated reactor to simulate anoxic wastewater tanks, cultivating denitrifying bacteria with a liquid sulfur source as an electron donor to complete the acclimatization of sulfur-autotrophic denitrifying bacteria; using the influent of the wastewater treatment plant's anoxic tank as the water source, controlling the hydraulic retention time to be consistent with the anoxic tank, and adjusting the denitrification load and pH value to a preset range by adding a carbon source or alkaline buffer; determining the reagent ratio based on the added liquid sulfur source, carbon source, or alkaline buffer, and using this ratio to prepare a mixed nutrient denitrification electron donor, which is used as the denitrification electron donor in the wastewater treatment anoxic tank denitrification system. This achieves the following technical effects:

[0091] The electron donor obtained through the embodiments of this application serves as the denitrification electron donor in the anoxic tank. The denitrification system constructed by it gradually increases the abundance of sulfur autotrophic denitrifying bacteria as the system is used for longer periods, thus increasing the contribution of sulfur autotrophic denitrification to nitrogen removal. This can gradually reduce or even eliminate the need for additional carbon source replenishment. It can replace the traditional anoxic denitrification system in wastewater treatment plants with insufficient carbon sources, greatly reducing the carbon source addition cost of wastewater treatment plants.

[0092] The embodiments of this application can advance the sulfur autotrophic denitrification deep denitrification process of the secondary biological treatment unit to the anoxic tank of the secondary biological treatment unit for denitrification, thereby shortening the wastewater treatment process and achieving low-cost deep denitrification.

[0093] The embodiments of this application couple the autotrophic denitrification process that produces acid and the heterotrophic denitrification process that produces alkali, thereby avoiding the risk of system instability caused by pH changes in the denitrification system.

[0094] The embodiments of this application employ a composite electron donor composed of a liquid sulfur source and a traditional carbon source, which has the advantages of high electron utilization rate and fast reaction rate, and the formulation can be flexibly adjusted without the risk of penetration.

[0095] This application provides a mixed-nutrient denitrification electron donor, comprising a mixture of one or more of a liquid sulfur source, a carbon source, and an alkaline buffer in a preset ratio, wherein the preset ratio is obtained according to the above-described method for constructing a mixed-nutrient denitrification electron donor.

[0096] Its principle and technical effect are similar to the construction method of a mixed nutrient type denitrification electron donor mentioned above, and will not be repeated here.

[0097] This application also provides an anoxic tank denitrification system, which uses the above-mentioned mixed nutrient type denitrification electron donor as the denitrification electron donor.

[0098] Its principle and technical effect are similar to the construction method of a mixed nutrient type denitrification electron donor mentioned above, and will not be repeated here.

[0099] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to this application. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are all optional embodiments, and the actions and modules involved are not necessarily essential to this application.

[0100] It should be further noted that although the steps in the flowchart are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowchart may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the sub-steps or stages of other steps.

Claims

1. A method for constructing a mixed-nutrient denitrification electron donor, characterized in that, include: A simulated reactor was used to simulate anoxic wastewater tanks, with liquid sulfur source as electron donor to cultivate denitrifying bacteria, thus completing the domestication of sulfur autotrophic denitrifying bacteria; Using the influent from the anoxic tank of the wastewater treatment plant as the water source, the hydraulic retention time is controlled to be consistent with that of the anoxic tank. Heterotrophic denitrifying bacteria are cultivated by adding carbon source to adjust the denitrification load until it is determined that the denitrification load is not less than a preset load value, and the total amount of carbon source added is recorded. The pH value is adjusted to a preset range using an alkaline buffer. The heterotrophic denitrifying bacteria and the sulfur autotrophic denitrifying bacteria are in the same simulated reactor. The reagent ratio is determined based on the added liquid sulfur source, carbon source, and alkaline buffer. This ratio is used to prepare a mixed nutrient denitrification electron donor, which serves as the denitrification electron donor for the denitrification system in the anoxic tank of the wastewater treatment plant. The process of acclimatizing denitrifying bacteria using a simulated reactor to simulate anoxic wastewater and culturing denitrifying bacteria with liquid sulfur as an electron donor, thereby completing the domestication of sulfur-autotrophic denitrifying bacteria, includes: Sludge from an anoxic tank of a wastewater treatment plant is inoculated into a simulated reactor, using the influent from the anoxic tank as the water source. The amount of liquid sulfur source added is determined based on the concentration of nitrate in the simulated reactor. The amount of liquid sulfur source added is determined based on the amount of sulfur and the ratio of sulfur to the amount of liquid sulfur source. The amount of sulfur is determined based on a nitrogen-sulfur ratio of 1:1 to 1:

2. The liquid sulfur source is added to the simulated reactor according to the specified addition amount; the nitrate concentration in the simulated reactor is monitored, and the denitrification rate is obtained based on the nitrate concentration. If the denitrification rate tends to stabilize, it is determined that the sulfur autotrophic denitrifying bacteria have been successfully domesticated.

2. The method according to claim 1, characterized in that, The step of adjusting the denitrification load by adding a carbon source to cultivate heterotrophic denitrifying bacteria, and the step of adjusting the pH value to a preset range by using an alkaline buffer, include: The denitrification load in the denitrification process is obtained based on the nitrate concentration. Determine whether the denitrification load is less than the preset load value; If the load is less than the preset load value, a carbon source is added to the simulated reactor until the denitrification load is not less than the preset load value. Determine whether the pH value is not less than a preset pH value; if it is less than the preset pH value, add an alkaline buffer until the pH value is not less than the preset pH value.

3. The method according to claim 1, characterized in that, The amount of sulfur is determined based on a nitrogen-to-sulfur ratio of 1:1.

1.

4. The method according to claim 2, characterized in that, The step of obtaining the denitrification load in the denitrification process based on the nitrate concentration includes: Obtain the nitrate concentration before and after a preset period, and obtain the denitrification rate of that period based on the ratio of the change in nitrate concentration to the corresponding time interval. The denitrification load is obtained based on the denitrification rate.

5. The method according to claim 1, characterized in that, The liquid sulfur source is sodium sulfide or liquid sodium thiosulfate.

6. The method according to claim 2, characterized in that, The preset pH value is set in the range of 6.5 to 8.

0.

7. The method according to claim 2, characterized in that, The alkaline buffer is sodium carbonate or sodium bicarbonate.

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