High-load thiocyanate-driven autotrophic denitrification low-carbon nitrogen removal method

Abstract

The invention discloses a high-load thiocyanate-driven autotrophic denitrification low-carbon denitrification method, and belongs to the field of biological sewage treatment. The invention aims to solve the technical problems of low treatment efficiency and unstable system caused by microorganism toxicity inhibition when the high-concentration thiocyanide-containing wastewater is treated by the existing biological method. According to the invention, through low-concentration induction, medium-concentration adaptation and high-concentration enhanced refined regulation and control, controllable environmental pressure screening is applied to microbial communities in a long period, microbial community succession is actively induced, and specific functional bacteria with efficient SCN-degradation pathway and high-toxicity tolerance are screened out. And in combination with compact granular sludge formed in the EGSB reactor, physical shielding is provided for internal microorganisms, and a microenvironment buffer layer for resisting impact of external high-concentration toxic substances is formed, so that macroscopic high-load tolerance of the whole system is realized. The invention is capable of tolerating and efficiently treating biological systems up to 1000 mg / L SCN-.

Description

Technical Field

[0001] This invention discloses a high-load thiocyanate-driven autotrophic denitrification low-carbon nitrogen removal method, belonging to the field of biological wastewater treatment. Background Technology

[0002] Industries such as coking, metallurgy, and mining generate industrial wastewater containing large amounts of toxic and harmful substances during their production processes. Among these, thiocyanate (SCN) is a significant toxic component. - SCN is a persistent and highly toxic pollutant, and its concentration in wastewater can reach 200-1000 mg / L, or even higher. - Not only does it exhibit significant biotoxicity, inhibiting cytochrome oxidase activity and interfering with hemoglobin oxygenation, but it also imposes a substantial burden on total nitrogen (TN) and chemical oxygen demand (COD) in water bodies. Due to its chemical stability, traditional physicochemical treatment technologies (such as adsorption, oxidation, and micro-electrolysis) often face challenges such as high costs, complex operations, or the potential for secondary pollution. Therefore, economical and environmentally friendly biological methods have become the preferred approach for treating SCN-containing water bodies. - Research hotspots in wastewater.

[0003] Currently, aerobic biodegradation of SCN - While the technology for anaerobic denitrification is relatively mature, its high energy consumption for aeration contradicts the current national energy conservation and emission reduction goals under the "dual carbon" policy. In contrast, anaerobic autotrophic denitrification technology shows great potential. Anaerobic autotrophic denitrification technology utilizes SCN... - The reducing sulfur produced by hydrolysis (such as S) 2- (etc.) as electron donors, using nitrates (NO3) in wastewater - ) or nitrite (NO2) - ( ) acts as an electron acceptor, converting nitrogen-containing pollutants into nitrogen gas (N2) under anaerobic conditions, thereby removing SCN. - Simultaneously achieving denitrification, this process requires no external organic carbon source, produces low sludge yield, and truly achieves the dual goals of "treating pollution with waste" and low-carbon emission reduction. Its theoretical reaction formula is as follows:

[0004]

[0005]

[0006] However, anaerobic autotrophic denitrification technology faces a key technical challenge in engineering applications: high concentrations of SCN. - It exhibits strong biotoxicity inhibition. Existing studies primarily focus on low to medium concentrations (typically below 200 mg / L) of SCN. - Wastewater treatment, when SCN - When the concentration increases sharply or remains at a high level for a prolonged period (e.g., > 400 mg / L), SCN...- It itself and its degradation intermediates (such as free cyanide CN) - Sulfides S 2- The combined toxic effects of SCN (such as sine and nitric acid) are prominent, leading to a strong inhibition of functional microbial activity and a sharp deterioration or even collapse of system treatment performance. When the influent contains SCN... - When the concentration is high, conventional biological treatment systems are often difficult to start, or the microbial activity may drop sharply, the treatment efficiency may be low, or the system may even collapse due to load shocks during operation.

[0007] The patent "A method for autotrophic denitrification of wastewater using desulfurization wastewater as an electron donor (CN 116081813 A)" discloses a method for autotrophic denitrification of nitrogen using desulfurization wastewater containing thiosulfate and thiocyanate. However, this method explicitly controls the thiocyanate concentration in the reactor to below 2.5 mM (approximately 145 mg / L) to avoid the toxic inhibitory effect of high concentrations of thiocyanate. Therefore, it is mainly suitable for medium- and low-load thiocyanate-containing wastewater and is difficult to cope with high SCN. - The patents "Device and Method for Autotrophic Denitrification and Detoxification of Coking Wastewater by Two-Stage Low-Oxygen Short-Cut Nitrification-Sulfur Autotrophic Denitrification-Anaerobic Ammonia Oxidation (CN 120058119 A)" and "Dual-Type DEAMOX Process for Efficient Simultaneous Treatment of Acrylic Fiber Wastewater and Nitrate Wastewater (CN 115432808 B)" disclose the use of two-stage or dual-type reactors to couple thiocyanate autotrophic denitrification with short-cut nitrification, anaerobic ammonia oxidation, or heterotrophic denitrification processes to achieve simultaneous denitrification and detoxification. However, these two patents involve multiple process couplings, resulting in complex system flows and significant control difficulties. Furthermore, their thiocyanate load capacity is limited, with a treatment concentration of 300-350 mg / L. The core issue lies in the integration of multiple technologies, but they do not fundamentally solve the problems of toxicity inhibition and performance stability of a single autotrophic denitrification system under high-concentration thiocyanate shocks. Therefore, how to overcome high-concentration SCN... - The biological toxicity of this technology and the construction and maintenance of an autotrophic denitrification system that can operate stably and efficiently for a long time are key bottlenecks that limit the technology from laboratory to engineering application and urgently need to be overcome. Summary of the Invention

[0008] To address the technical challenges of low treatment efficiency and system instability caused by microbial toxicity inhibition in the treatment of high-concentration thiocyanate-containing wastewater, this invention proposes a high-load thiocyanate-driven autotrophic denitrification low-carbon nitrogen removal method.

[0009] The high-load thiocyanate-driven autotrophic denitrification low-carbon nitrogen removal method of the present invention is carried out according to the following steps:

[0010] I. Initiation and Induction Period:

[0011] Activated sludge was inoculated into the industrial wastewater in the EGSB reactor from days 1 to 90; the substrate concentration was adjusted in two stages from days 1 to 45, and SCN was added. - The concentration of NO3 was adjusted to 49-51 mg / L. - Adjust the -N concentration to 19-21 mg / L and the TP concentration to 1 mg / L; add SCN on days 46-90. - The concentration of NO3 was adjusted to 99-101 mg / L. - The concentration of -N was adjusted to 49-51 mg / L, and the concentration of TP was adjusted to 1 mg / L; this achieved preliminary domestication and functional screening of the microbial community, promoting the formation of a biological community to degrade SCN. - Specific metabolic functions at the core;

[0012] II. Adaptation and Selection Period:

[0013] SCN is gradually implemented in multiple stages. - and NO3 - The concentration of -N is increased to the target concentration, SCN - The concentration gradient is 100-200 mg / L, NO3 - The concentration gradient of -N is 50-100 mg / L, and the running time of each stage is 30 days;

[0014] III. Strengthening and Stabilization Period:

[0015] When SCN - After reaching the target concentration, maintain system operation for 30 days to achieve enrichment of dominant bacterial species and obtain sludge with a high-density granular structure.

[0016] The principle and beneficial effects of this invention are as follows:

[0017] (1) This invention employs a refined regulation process of "low-concentration induction - medium-concentration adaptation - high-concentration enhancement" to apply a controllable environmental pressure to the microbial community over a long period. This is not merely a simple concentration increase, but rather an active induction of microbial community succession and screening for microorganisms with highly efficient SCNs. - The method utilizes specific functional bacterial genera (such as Thiobacillus) with specific degradation pathways and high toxicity tolerance. Simultaneously, the dense granular sludge formed within the EGSB reactor provides a physical shield for the internal microorganisms, forming a "microenvironment buffer layer" to resist the impact of high concentrations of external toxic substances, thus achieving high macroscopic load tolerance of the entire system. A system capable of tolerating and efficiently treating up to 1000 mg / LSCN was successfully constructed. - This biological system breaks through the technical bottleneck of traditional biological methods that struggle to treat high-concentration thiocyanate-containing wastewater.

[0018] The formation mechanism of high-density granular sludge is as follows: the high upward flow velocity within the EGSB reactor provides the key hydraulic selective pressure, preferentially eliminating flocculent biomass with poor settling performance, while selectively enriching high-density, high-mechanical-strength microbial aggregates; on the other hand, under high concentrations of SCN... - Under continuous toxic stress, the dominant functional bacterial community secretes a large amount of extracellular polymeric substances (EPS) as a physiological protection mechanism. EPS, as a biological adhesive, greatly enhances the adhesion between cells, promotes the self-aggregation process of microorganisms, and ultimately forms dense particles.

[0019] The principle of physical shielding in dense granular sludge is based primarily on mass transfer limitation. When high concentrations of SCN... - When pollutants and their toxic intermediates diffuse from the bulk liquid phase of the reactor into the granular sludge, a significant concentration gradient is formed due to the dense structure of the particles and the obstruction of the EPS matrix. Microorganisms on the particle surface first degrade most of the pollutants, thereby significantly reducing the concentration of toxins transferred into the particle, creating a stable and low-toxicity "microenvironment buffer layer" for the core microbial community. This synergistic effect of physical shielding and biodegradation enables the entire biological system to macroscopically resist the impact of high concentrations of external toxic substances, thus achieving long-term stable operation under high loads.

[0020] (2) The present invention can achieve efficient and stable SCN. - and NO3 - -N synchronous removal performance, under high load conditions, SCN - and NO3 - The synchronous removal rate of -N can be kept stable at over 90% for a long time, the system has strong shock resistance and the effluent water quality is excellent.

[0021] (3) The method of the present invention utilizes SCN in wastewater - As an endogenous electron donor, it eliminates the need for expensive external organic carbon sources, significantly reducing treatment costs and avoiding the risk of secondary pollution from residual external carbon sources. Simultaneously, it produces low sludge, meeting the "dual carbon" target requirements, and boasts low operating costs and environmental friendliness.

[0022] (4) This invention removes the highly toxic pollutant SCN - High-efficiency resource utilization, SCN - As an endogenous electron donor and a driving force for high-load denitrification processes, it provides a novel and feasible engineering solution for treating similar highly toxic industrial wastewater, realizing high-value "waste treatment". Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the EGSB reactor used in Example 1;

[0024] Figure 2 In Example 1, SCN is involved in the high-load thiocyanate-driven autotrophic denitrification low-carbon denitrification process. - Concentration and SCN - Removal rate change graph;

[0025] Figure 3 In Example 1, SO4 is generated during the high-load thiocyanate-driven autotrophic denitrification low-carbon nitrogen removal process. 2- -S concentration variation graph;

[0026] Figure 4 In Example 1, NO3 is generated during the high-load thiocyanate-driven autotrophic denitrification low-carbon nitrogen removal process. - -N concentration, NO2 - -N concentration, NH4 + -N concentration, NO3 - -N removal rate variation graph;

[0027] Figure 5 This is a graph showing the changes in TN concentration and TN removal rate during the high-load thiocyanate-driven autotrophic denitrification low-carbon nitrogen removal process in Example 1. Detailed Implementation

[0028] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any reasonable combination of the specific embodiments.

[0029] Specific Implementation Method 1: This implementation method, a high-load thiocyanate-driven autotrophic denitrification low-carbon nitrogen removal method, is carried out according to the following steps:

[0030] I. Initiation and Induction Period:

[0031] Activated sludge was inoculated into the industrial wastewater in the EGSB reactor from days 1 to 90; the substrate concentration was adjusted in two stages from days 1 to 45, and SCN was added. - The concentration of NO3 was adjusted to 49-51 mg / L. - Adjust the -N concentration to 19-21 mg / L and the TP concentration to 1 mg / L; add SCN on days 46-90. - The concentration of NO3 was adjusted to 99-101 mg / L. - The concentration of -N was adjusted to 49-51 mg / L, and the concentration of TP was adjusted to 1 mg / L; this achieved preliminary domestication and functional screening of the microbial community, promoting the formation of a biological community to degrade SCN. - Specific metabolic functions at the core;

[0032] II. Adaptation and Selection Period:

[0033] SCN is gradually implemented in multiple stages. - and NO3 - The concentration of -N is increased to the target concentration, SCN - The concentration gradient is 100-200 mg / L, NO3 - The concentration gradient of -N is 50-100 mg / L, and the running time of each stage is 30 days;

[0034] III. Strengthening and Stabilization Period:

[0035] When SCN - After reaching the target concentration, maintain system operation for 30 days to achieve enrichment of dominant bacterial species and obtain sludge with a high-density granular structure.

[0036] The principle and beneficial effects of this implementation method are as follows:

[0037] (1) This implementation method applies a controlled environmental pressure to the microbial community over a long period through a refined regulation of "low concentration induction - medium concentration adaptation - high concentration enhancement". This is not just a simple concentration increase, but an active induction of microbial community succession and screening for microorganisms with highly efficient SCN. - The method utilizes specific functional bacterial genera (such as Thiobacillus) with specific degradation pathways and high toxicity tolerance. Simultaneously, the dense granular sludge formed within the EGSB reactor provides a physical shield for the internal microorganisms, forming a "microenvironment buffer layer" to resist the impact of high concentrations of external toxic substances, thus achieving high macroscopic load tolerance of the entire system. A system capable of tolerating and efficiently treating up to 1000 mg / L SCN was successfully constructed. - This biological system breaks through the technical bottleneck of traditional biological methods that struggle to treat high-concentration thiocyanate-containing wastewater.

[0038] The formation mechanism of high-density granular sludge is as follows: the high upward flow velocity within the EGSB reactor provides the key hydraulic selective pressure, preferentially eliminating flocculent biomass with poor settling performance, while selectively enriching high-density, high-mechanical-strength microbial aggregates; on the other hand, under high concentrations of SCN... - Under continuous toxic stress, the dominant functional bacterial community secretes a large amount of extracellular polymeric substances (EPS) as a physiological protection mechanism. EPS, as a biological adhesive, greatly enhances the adhesion between cells, promotes the self-aggregation process of microorganisms, and ultimately forms dense particles.

[0039] The principle of physical shielding in dense granular sludge is based primarily on mass transfer limitation. When high concentrations of SCN... - When pollutants and their toxic intermediates diffuse from the bulk liquid phase of the reactor into the granular sludge, a significant concentration gradient is formed due to the dense structure of the particles and the obstruction of the EPS matrix. Microorganisms on the particle surface first degrade most of the pollutants, thereby significantly reducing the concentration of toxins transferred into the particle, creating a stable and low-toxicity "microenvironment buffer layer" for the core microbial community. This synergistic effect of physical shielding and biodegradation enables the entire biological system to macroscopically resist the impact of high concentrations of external toxic substances, thus achieving long-term stable operation under high loads.

[0040] (2) This implementation method can achieve efficient and stable SCN. - and NO3 - -N synchronous removal performance, under high load conditions, SCN - and NO3 - The synchronous removal rate of -N can be kept stable at over 90% for a long time, the system has strong shock resistance and the effluent water quality is excellent.

[0041] (3) The method of this embodiment utilizes SCN in wastewater - As an endogenous electron donor, it eliminates the need for expensive external organic carbon sources, significantly reducing treatment costs and avoiding the risk of secondary pollution from residual external carbon sources. At the same time, it produces low sludge, meeting the "dual carbon" target requirements, and has low operating costs and is environmentally friendly.

[0042] (4) This embodiment uses the highly toxic pollutant SCN - High-efficiency resource utilization, SCN - As an endogenous electron donor and a driving force for high-load denitrification processes, it provides a novel and feasible engineering solution for treating similar highly toxic industrial wastewater, realizing high-value "waste treatment".

[0043] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that: the SCN described in step two... - The target concentration is ≥1000 mg / L, for the NO3... - The target concentration of -N is ≥250 mg / L.

[0044] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that: the EGSB reactor consists of an inlet water tank (1), a peristaltic pump (2), a reaction zone (4), and a three-phase separation zone (7). The three-phase separation zone (7) is located at the top of the reaction zone (4). The three-phase separation zone (7) is provided with a reflux port (3) and an outlet (6). The reaction zone (4) is provided with a sampling port (5). The bottom of the reaction zone (4) is provided with an inlet water port, which is connected to an inlet water pipe. The inlet water pipe is connected to the outlet of the inlet water tank (1). The reflux port (3) is connected to a reflux pipe, which is connected to the inlet water pipe. The inlet water pipe and the reflux pipe are respectively provided with peristaltic pumps (2).

[0045] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: Step One involves adjusting the substrate concentration in two stages, from day 1 to day 45, using SCN... - The concentration of NO3 was adjusted to 50 mg / L. - Adjust the -N concentration to 19-21 mg / L and the TP concentration to 1 mg / L; from day 46 to 90, add SCN. - The concentration of NO3 was adjusted to 99-101 mg / L. - The concentration of -N was adjusted to 49-51 mg / L, and the concentration of TP was adjusted to 1 mg / L.

[0046] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One through Four in that: Step One involves adjusting the substrate concentration in two stages, from day 1 to day 45, using SCN... - The concentration of NO3 was adjusted to 49-51 mg / L. - The concentration of -N was adjusted to 20 mg / L, and the concentration of TP was adjusted to 1 mg / L; SCN was added between days 46 and 90. - The concentration of NO3 was adjusted to 99-101 mg / L. - The concentration of -N was adjusted to 49-51 mg / L, and the concentration of TP was adjusted to 1 mg / L.

[0047] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One through Five in that: Step One involves adjusting the substrate concentration in two stages, from day 1 to day 45, using SCN... - The concentration of NO3 was adjusted to 49-51 mg / L. - Adjust the -N concentration to 19-21 mg / L and the TP concentration to 1 mg / L; add SCN on days 46-90. - The concentration of NO3 was adjusted to 100 mg / L. - The concentration of -N was adjusted to 49-51 mg / L, and the concentration of TP was adjusted to 1 mg / L.

[0048] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One through Six in that: Step One involves adjusting the substrate concentration in two stages, from day 1 to day 45, using SCN... - The concentration of NO3 was adjusted to 49-51 mg / L. - Adjust the -N concentration to 19-21 mg / L and the TP concentration to 1 mg / L; add SCN on days 46-90. - The concentration of NO3 was adjusted to 99-101 mg / L. - The concentration of -N was adjusted to 50 mg / L, and the concentration of TP was adjusted to 1 mg / L.

[0049] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One through Seven in that step two employs multiple stages to gradually introduce the SCN. - and NO3 - The concentration of -N is increased to the target concentration, SCN - The concentration gradient is 200 mg / L, NO3 - The concentration gradient of -N was 50-100 mg / L, and each stage lasted for 30 days.

[0050] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One through Eight in that step two employs multiple stages to gradually transfer the SCN. - and NO3 - The concentration of -N is increased to the target concentration, SCN - The concentration gradient is 100-200 mg / L, NO3 - The concentration gradient of -N was 50 mg / L, and each stage lasted for 30 days.

[0051] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One through Nine in that step two employs multiple stages to gradually apply the SCN. - and NO3 - The concentration of -N is increased to the target concentration, SCN - The concentration gradient is 200 mg / L, NO3 - The concentration gradient of -N was 50 mg / L, and each stage lasted for 30 days.

[0052] Example 1:

[0053] The high-load thiocyanate-driven autotrophic denitrification low-carbon nitrogen removal method in this embodiment is carried out according to the following steps:

[0054] I. Initiation and Induction Period:

[0055] Activated sludge was inoculated into the industrial wastewater in the EGSB reactor from days 1 to 90; the substrate concentration was adjusted in two stages from days 1 to 45, and SCN was added. - The concentration of NO3 was adjusted to 50 mg / L. - The concentration of -N was adjusted to 20 mg / L, and the concentration of TP was adjusted to 1 mg / L; SCN was added between days 46 and 90. - The concentration of NO3 was adjusted to 100 mg / L. - The concentration of -N was adjusted to 50 mg / L, and the concentration of TP was adjusted to 1 mg / L; this achieved preliminary acclimatization and functional screening of the microbial community, promoting the formation of a biological community to degrade SCN. - Specific metabolic functions at the core;

[0056] II. Adaptation and Selection Period:

[0057] SCN is gradually implemented in multiple stages. - and NO3 - The concentration of -N is increased to the target concentration, SCN - The concentration gradient is 200 mg / L, NO3 - The concentration gradient of -N was 50 mg / L, and the running time for each stage was 30 days;

[0058] The SCN - The target concentration is 1000 mg / L, and the NO3... - The target concentration of -N is 250 mg / L;

[0059] III. Strengthening and Stabilization Period:

[0060] When SCN - After reaching the target concentration, maintain system operation for 30 days to achieve enrichment of dominant bacterial species and obtain sludge with a high-density granular structure.

[0061] Figure 1 This is a schematic diagram of the EGSB reactor used in Example 1. The EGSB reactor in this example consists of an inlet water tank (1), a peristaltic pump (2), a reaction zone (4), and a three-phase separation zone (7). The three-phase separation zone (7) is located at the top of the reaction zone (4). The three-phase separation zone (7) is provided with a reflux port (3) and an outlet (6). The reaction zone (4) is provided with a sampling port (5). The bottom of the reaction zone (4) is provided with an inlet water port, which is connected to an inlet pipe. The inlet pipe is connected to the outlet of the inlet water tank (1). The reflux port (3) is connected to a reflux pipe, which is connected to the inlet pipe. The peristaltic pump (2) is provided on the inlet pipe and the reflux pipe, respectively.

[0062] Figure 2In Example 1, SCN is involved in the high-load thiocyanate-driven autotrophic denitrification and low-carbon nitrogen removal process. - Concentration and SCN - Removal rate change graph; SCN in the graph - inf SCN for reactor inlet - Concentration, SCN - eff SCN for reactor effluent - concentration;

[0063] Figure 3 In Example 1, SO4 is generated during the high-load thiocyanate-driven autotrophic denitrification and low-carbon nitrogen removal process. 2- -S concentration variation graph; SO4 in the graph 2- -S eff SO4 in the reactor effluent 2- -S concentration, theoretical SO4 2- -S eff For water-based SCN - Theoretical effluent SO4 calculated from complete oxidation 2- -S concentration;

[0064] Figure 4 In Example 1, NO3 is generated during the high-load thiocyanate-driven autotrophic denitrification and low-carbon nitrogen removal process. - -N concentration, NO2 - -N concentration, NH4 + -N concentration, NO3 - -N removal rate variation graph; NO3 - -N inf NO3 in reactor influent - -N concentration, NO3 - -N eff NO3 in reactor effluent - -N concentration, NO2 - -N eff NO2 in reactor effluent - -N concentration, NH4 + -N eff NH4 in the reactor effluent + -N concentration;

[0065] Figure 5 This is a graph showing the changes in TN concentration and TN removal rate during the high-load thiocyanate-driven autotrophic denitrification and low-carbon nitrogen removal process in Example 1; TN inf TN concentration in reactor influent eff This represents the TN concentration in the reactor effluent.

[0066] pass Figures 2-5 It can be seen that in the influent SCN -Under extreme load conditions with a phased gradient increase in concentration to 1000 mg / L, the reactor exhibited extremely strong shock resistance. During the initial stage of load increase, the effluent SCN... - Concentration may fluctuate briefly, but the microbial community can quickly adapt and restore its efficient degradation activity. In the influent SCN... - At extreme loading levels with concentrations as high as 1000 mg / L, SCN - The removal rate remained stable at over 93%, with no inhibition failure observed. This demonstrates that the microenvironment buffer layer and dominant bacterial groups (such as Thiobacillus) constructed in this invention successfully overcame the biotoxic inhibition of high concentrations of thiocyanate, achieving stable operation under high loads. Figure 3 Data shows that the measured SO4 content in the water 2- -S concentration curve and based on influent SCN - The calculated values ​​from complete oxidation show a high degree of agreement with the theoretical values, proving that SCN... - The sulfur element in the solution follows a complete oxidation pathway and is completely converted into stable sulfate. No elemental sulfur or other intermediate products accumulate during the reaction, thus achieving the complete and harmless degradation of high-concentration thiocyanate.

[0067] Throughout the entire operating cycle, NO3 acts as an electron acceptor. - -N removal rate remained above 97%, and no nitrite (NO2) was detected in the effluent. - The accumulation of SCN indicates that the autotrophic denitrification process is very thorough. - NH4 produced by hydrolysis + -N does not participate in denitrification electron transfer, and the total nitrogen (TN) removal rate of the system remains at around 70%; however, the measured NH4 in the effluent... + The -N concentration was significantly lower than the theoretical hydrolysis production, indicating that under high-load screening pressure, microorganisms converted some nitrogen into cellular material through strong assimilation. This reduced the nitrogen load in the effluent and also promoted the maintenance and renewal of high-density granular sludge in the reactor.

Claims

1. A high-load thiocyanate-driven autotrophic denitrification low-carbon nitrogen removal method, characterized by: The high-load thiocyanate-driven autotrophic denitrification low-carbon nitrogen removal method is performed according to the following steps: I. Start-up and induction period: The industrial wastewater in the EGSB reactor was inoculated with activated sludge from day 1 to day 90; the substrate concentration was adjusted in two stages, the concentration of SCN - was adjusted to 49-51 mg / L, the concentration of NO3 - -N was adjusted to 19-21 mg / L, and the concentration of TP was adjusted to 1 mg / L from day 1 to day 45; the concentration of SCN - was adjusted to 99-101 mg / L, the concentration of NO3 - -N was adjusted to 49-51 mg / L, and the concentration of TP was adjusted to 1 mg / L from day 46 to day 90; preliminary domestication and functional screening of the microbial community were achieved, and the biological community was formed to degrade the specific metabolic function with SCN - as the core; II. Adaptation and screening period: The concentration of SCN - and NO3 - -N is gradually increased to the target concentration in multiple stages - The concentration of SCN - is increased by 100-200 mg / L, and the concentration of NO3 - N is increased by 50-100 mg / L, and each stage is run for 30 days III. Strengthening and stabilization period: When the SCN - After the increase to the target concentration, the system was maintained for 30 days, achieving the enrichment of the dominant species and obtaining a high-density granular sludge.

2. The high-loaded thiocyanate-driven autotrophic denitrification low carbon nitrogen removal process according to claim 1, characterized in that: The SCN of step two - a target concentration of > 1000 mg / L of NO3 - a target concentration of > 250 mg / L of -N.

3. The high-loaded thiocyanate-driven autotrophic denitrification low carbon nitrogen removal process according to claim 1, characterized in that: The EGSB reactor is composed of a water inlet tank (1), a peristaltic pump (2), a reaction zone (4) and a three-phase separation zone (7), the three-phase separation zone (7) is arranged at the upper part of the reaction zone (4), the three-phase separation zone (7) is provided with a reflux port (3) and a water outlet (6), the reaction zone (4) is provided with a sampling port (5), the bottom of the reaction zone (4) is provided with a water inlet, the water inlet is connected with a water inlet pipe, the water inlet pipe is connected with the water outlet of the water inlet tank (1), the reflux port (3) is connected with a reflux pipe, the reflux pipe is connected with the water inlet pipe, and the peristaltic pump (2) is arranged on the water inlet pipe and the reflux pipe respectively.

4. The high-loaded thiocyanate-driven autotrophic denitrification low carbon nitrogen removal process according to claim 1, characterized in that: Step one adjusts the substrate concentrations in two stages. From day 1-45, the concentration of SCN - is adjusted to 50 mg / L, the concentration of NO3 - -N is adjusted to 19-21 mg / L, and the concentration of TP is adjusted to 1 mg / L. From day 46-90, the concentration of SCN - is adjusted to 99-101 mg / L, the concentration of NO3 - -N is adjusted to 49-51 mg / L, and the concentration of TP is adjusted to 1 mg / L.

5. The high-loaded thiocyanate-driven autotrophic denitrification low carbon nitrogen removal process according to claim 1, characterized in that: Step one adjusts the substrate concentration in two stages, from day 1-45 the concentration of SCN - is adjusted to 49-51 mg / L, the concentration of NO3 - -N is adjusted to 20 mg / L and the concentration of TP is adjusted to 1 mg / L; from day 46-90 the concentration of SCN - is adjusted to 99-101 mg / L, the concentration of NO3 - -N is adjusted to 49-51 mg / L and the concentration of TP is adjusted to 1 mg / L.

6. The high-loaded thiocyanate-driven autotrophic denitrification low carbon nitrogen removal process according to claim 1, characterized in that: Step one adjusts the substrate concentration in two stages. From day 1-45, the concentration of SCN - is adjusted to 49-51 mg / L, the concentration of NO3 - -N is adjusted to 19-21 mg / L, and the concentration of TP is adjusted to 1 mg / L. From day 46-90, the concentration of SCN - is adjusted to 100 mg / L, the concentration of NO3 - -N is adjusted to 49-51 mg / L, and the concentration of TP is adjusted to 1 mg / L.

7. The high-loaded thiocyanate-driven autotrophic denitrification low carbon nitrogen removal process according to claim 1, characterized in that: Step one adjusts the substrate concentration in two stages. From day 1-45, the concentration of SCN - is adjusted to 49-51 mg / L, the concentration of NO3 - -N is adjusted to 19-21 mg / L, and the concentration of TP is adjusted to 1 mg / L. From day 46-90, the concentration of SCN - is adjusted to 99-101 mg / L, the concentration of NO3 - -N is adjusted to 50 mg / L, and the concentration of TP is adjusted to 1 mg / L.

8. The high-loaded thiocyanate-driven autotrophic denitrification low carbon nitrogen removal process according to claim 1, characterized in that: Step two gradually increases the concentration of SCN - and NO3 - to the target concentration in multiple stages - The concentration of SCN - is increased by 200 mg / L and the concentration of NO3 - N is increased by 50-100 mg / L in each stage, with a 30-day run time.

9. The high-loaded thiocyanate-driven autotrophic denitrification low carbon nitrogen removal process according to claim 1, characterized in that: Step two gradually increases the concentration of SCN - and NO3 - to the target concentration in multiple stages - The concentration of SCN - is increased by 100-200 mg / L, and the concentration of NO3 - N is increased by 50 mg / L, with each stage running for 30 days.

10. The high-loaded thiocyanate-driven autotrophic denitrification low carbon nitrogen removal process according to claim 1, characterized in that: Step two involves using multiple stages to gradually introduce SCN. - and NO3 - The concentration of -N is increased to the target concentration, SCN - The concentration gradient is 200 mg / L, NO3 - The concentration gradient of -N was 50 mg / L, and each stage lasted for 30 days.

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