Apparatus and method for autotrophic denitrification and detoxification of coking wastewater by two-stage low-oxygen short-cut nitrification-sulfur autotrophic denitrification-anaerobic ammonia oxidation

Abstract

Two-stage low-oxygen short-cut nitrification-sulfur autotrophic denitrification-anaerobic ammonia oxidation treatment of coking wastewater autotrophic denitrification and detoxification device and method belong to the field of wastewater treatment. The device comprises a water inlet tank, a sequencing batch reactor, an intermediate water tank and an upflow anaerobic sludge blanket reactor. The method is that the coking wastewater containing ammonia nitrogen and thiocyanate which has been subjected to carbon capture is introduced into the sequencing batch reactor, ammonia nitrogen is oxidized into nitrite under limited oxygen condition, and at the same time, thiocyanate and nitrite are converted into nitrogen, sulfate and ammonia nitrogen by autotrophic denitrifying bacteria; the effluent of the reaction is mixed with coking wastewater and introduced into the upflow anaerobic sludge blanket, anaerobic ammonia oxidation bacteria convert ammonia nitrogen and nitrite into nitrogen, and a small amount of nitrate is produced; the residual nitrate, nitrite and thiocyanate are completely removed through sulfur autotrophic denitrification. The method provides a new idea for economical and efficient autotrophic denitrification and detoxification of coking wastewater containing thiocyanate and ammonia nitrogen.

Description

Technical Field

[0001] This invention discloses a two-stage low-oxygen short-cut nitrification-sulfur autotrophic denitrification-anaerobic ammonia oxidation device and method for autotrophic denitrification and detoxification of coking wastewater, belonging to the field of wastewater treatment. Background Technology

[0002] Coking wastewater is a typical industrial wastewater with a low C / N ratio, containing large amounts of ammonia nitrogen, recalcitrant organic matter, and toxic substances. The ammonia nitrogen concentration in the coking wastewater entering the biological treatment tank is 100–1000 mg / L, COD is 1500–3000 mg / L, and total nitrogen concentration is 200–1000 mg / L. The traditional anoxic / aerobic (A / O) process is currently the mainstream biological treatment process, but the lack of available carbon sources in the wastewater limits denitrification. Adding external carbon sources to enhance denitrification significantly increases the cost. Therefore, traditional biological treatment processes face bottlenecks such as substandard treatment and high costs.

[0003] Anaerobic ammonia oxidation (AAO) is a promising, economical, energy-saving, and sustainable biological nitrogen removal technology. The AAO process involves anaerobic bacteria using nitrite as an electron acceptor to oxidize ammonia nitrogen into nitrogen gas under anaerobic conditions, while simultaneously producing a small amount of nitrate. Compared to traditional nitrification-denitrification processes, AAO can save 60% of aeration energy, 100% of organic carbon sources, and reduce sludge production by 90%. Therefore, applying AAO to coking wastewater treatment can achieve efficient nitrogen removal while significantly reducing investment and operating costs. However, toxic substances in coking wastewater may have a certain impact on and inhibit AAO bacteria, thus limiting the application of AAO in coking wastewater treatment.

[0004] Thiocyanate is a major toxic substance in coking wastewater, with concentrations as high as 200–1000 mg / L, significantly impacting the activity of anaerobic ammonia-oxidizing bacteria. Simultaneously, thiocyanate contains nitrogen and has strong reducing properties, contributing to the total nitrogen and COD of the wastewater. Recent studies have shown that under anoxic conditions, specific autotrophic denitrifying bacteria utilize thiocyanate as an electron donor and nitrate and nitrite as electron acceptors. Through a series of redox reactions, nitrate and nitrite are reduced to nitrogen gas, while the toxic thiocyanate is oxidized to non-toxic sulfate and ammonia nitrogen, thus achieving simultaneous removal of thiocyanate and nitrogen.

[0005] Theoretically, coupling anaerobic ammonia oxidation (ANAO) and thiocyanate autotrophic denitrification (THD) technologies can achieve simultaneous removal of ammonia nitrogen and thiocyanate, thus denitrifying and detoxifying coking wastewater. The coupling principle involves simultaneously performing short-cut nitrification and thiocyanate denitrification on coking wastewater containing ammonia nitrogen and thiocyanate, which has already undergone carbon capture, in a low-oxygen aeration reactor. The final effluent contains ammonia nitrogen, nitrite, and sulfate. This effluent from the low-oxygen aeration reactor is mixed with the coking wastewater and then enters the ANAO reactor. By adjusting the ratio of the mixed wastewater, simultaneous ANAO and thiocyanate denitrification are achieved. Therefore, how to construct the process and control the operating strategy to achieve the coupling of these two technologies is crucial for the application of anaerobic ammonia oxidizing bacteria in coking wastewater treatment. Summary of the Invention

[0006] This invention discloses a two-stage low-oxygen short-cut nitrification-sulfur autotrophic denitrification-anaerobic ammonia oxidation device and method for autotrophic denitrification and detoxification of coking wastewater. The method involves feeding coking wastewater containing ammonia nitrogen and thiocyanate, which has already undergone carbon capture, into a low-oxygen aeration sequencing batch reactor (SBR). Under limited oxygen conditions, the ammonia nitrogen in the influent is oxidized to nitrite by ammonia-oxidizing bacteria and accumulates. Simultaneously, the thiocyanate and nitrite in the influent are utilized by autotrophic denitrifying bacteria to generate nitrogen, sulfate, and ammonia nitrogen. The SBR effluent containing ammonia nitrogen and nitrite, mixed with the coking wastewater containing ammonia nitrogen and thiocyanate, enters an upflow anaerobic sludge blanket (UASB). In the UASB, ammonia nitrogen and nitrite are utilized by anaerobic ammonia-oxidizing bacteria to generate nitrogen and nitrate. The remaining nitrate, nitrite, and thiocyanate are utilized by autotrophic denitrifying bacteria to generate nitrogen. The two-stage process ultimately achieves simultaneous removal of ammonia nitrogen and thiocyanate from the wastewater.

[0007] The objective of this invention is achieved through the following technical solution: a two-stage low-oxygen short-cut nitrification-sulfur autotrophic denitrification-anaerobic ammonia oxidation device for autotrophic denitrification and detoxification of coking wastewater, characterized in that:

[0008] The equipment used includes: an inlet tank (1), a sequencing batch reactor (2), an intermediate tank (3), and an upflow anaerobic sludge bed reactor (4).

[0009] The inlet tank (1) includes a heating rod (1.1) and a third peristaltic pump (1.2); the sequencing batch reactor (2) includes a first peristaltic pump (2.1), a first inlet (2.2), a pH / DO meter (2.3), a stirrer (2.4), an aeration disc (2.5), a gas flow meter (2.6), an air pump (2.7), and a first outlet (2.8); the intermediate tank (3) includes a heating rod (3.1); the upflow anaerobic sludge bed reactor (4) includes a second peristaltic pump (4.1), a second inlet (4.2), a heating belt (4.3), a second outlet (4.4), and a pH / DO meter (4.5).

[0010] The coking wastewater containing ammonia nitrogen and thiocyanate in the inlet tank (1) is artificially mixed with NH4+. + -N concentration is 100-120 mg / L, SCN - The influent (with a concentration of 100-350 mg / L) is pumped into the sequencing batch reactor (2) through the first inlet (2.2) by the first peristaltic pump (2.1) to initiate short-cut nitrification and thiocyanate denitrification. The effluent is discharged into the intermediate tank (3) through the first outlet (2.8). The SBR effluent containing ammonia nitrogen and nitrite nitrogen is mixed with coking wastewater containing ammonia nitrogen and thiocyanate through the second inlet (4.2) by the second peristaltic pump (4.1) and the third peristaltic pump (1.2). When the liquid level in the reactor reaches the effective volume of the UASB, the effluent is discharged through the outlet (4.4).

[0011] This invention has the following advantages:

[0012] 1) The simultaneous short-path nitrification coupled with thiocyanate denitrification process is beneficial to ammonia oxidation, improves denitrification efficiency, achieves simultaneous removal of ammonia nitrogen and thiocyanate, and enables the accumulation of nitrite.

[0013] 2) Compared with the bottleneck problems of substandard treatment and high treatment cost faced by traditional biological treatment processes, the two-stage low-oxygen short-cut nitrification-anaerobic ammonia oxidation denitrification process has the advantages of low energy consumption, less residual sludge, no need to add organic carbon, and high denitrification efficiency.

[0014] 3) The autotrophic denitrification coupled with anaerobic ammonia oxidation process using thiocyanate is adopted. Thiocyanate acts as an electron donor in the anoxic system to reduce nitrate and nitrite to nitrogen gas, thereby achieving the simultaneous removal of ammonia nitrogen and thiocyanate and realizing the denitrification and detoxification of coking wastewater.

[0015] In summary, the present invention offers advantages such as saving aeration energy consumption, eliminating the need for adding organic carbon sources, and simultaneously and efficiently detoxifying and denitrifying coking wastewater containing thiocyanate and ammonia nitrogen. Attached Figure Description

[0016] Figure 1 Yes: A device and method for autotrophic denitrification and detoxification of coking wastewater using a two-stage low-oxygen short-cut nitrification-sulfur autotrophic denitrification-anaerobic ammonia oxidation process.

[0017] Figure 1In the middle section: 1—Inlet tank, 2—Sequencing batch reactor, 3—Intermediate tank, 4—Upflow anaerobic sludge blanket reactor; 1.1—Heating rod, 1.2—Third peristaltic pump, 2.1—First peristaltic pump, 2.2—First inlet, 2.3—pH / DO meter, 2.4—Agitator, 2.5—Aeration disc, 2.6—Gas flow meter, 2.7—Air pump, 2.8—First outlet; 3.1—Heating rod; 4.1—Second peristaltic pump, 4.2—Second inlet, 4.3—Heating belt, 4.4—Second outlet, 4.5—pH / DO meter Detailed Implementation

[0018] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples:

[0019] like Figure 1 As shown, the device for autotrophic denitrification and detoxification of coking wastewater by two-stage low-oxygen short-cut nitrification-sulfur autotrophic denitrification-anaerobic ammonia oxidation includes an inlet tank (1), a sequencing batch reactor (2), an intermediate tank (3), and an upflow anaerobic sludge bed reactor (4).

[0020] A two-stage low-oxygen short-cut nitrification-sulfur autotrophic denitrification-anaerobic ammonia oxidation method for autotrophic denitrification and detoxification of coking wastewater is characterized by the following steps:

[0021] Step I: Inoculate with ordinary activated sludge. The coking wastewater containing ammonia nitrogen and thiocyanate in the influent tank (1) is artificially mixed with NH4+. + -N concentration is 100-120 mg / L, SCN - Water is fed into the reactor in the form of a concentration of 100-350 mg / L and pumped into the sequencing batch reactor (2) through the first inlet (2.2) by the first peristaltic pump (2.1) to start short-cut nitrification and thiocyanate denitrification. The effluent is discharged into the intermediate water tank (3) through the first outlet (2.8).

[0022] Step II: The SBR effluent containing ammonia nitrogen and nitrite nitrogen, mixed with coking wastewater containing ammonia nitrogen and thiocyanate, enters the upflow anaerobic sludge blanket (4) through the second inlet (4.2) via the second peristaltic pump (4.1) and the third peristaltic pump (1.2). When the liquid level in the reactor reaches the effective volume of the UASB, the effluent is discharged through the outlet (4.4).

[0023] Test system such as Figure 1 As shown, both the short-cut nitrification and anaerobic ammonium oxidation reactors are made of plexiglass. The effective volume of the SBR is 10L, and the effective volume of the UASB is 4L.

[0024] During the experiment, simulated wastewater was used, with ammonium bicarbonate and sodium thiocyanate as the substrate. The specific water quality was as follows: NH4+ -N is 100-120 mg / L, SCN - The concentration is 100-350 mg / L, and an appropriate amount of sodium bicarbonate is added to adjust the pH to 7-8.

[0025] The specific operation steps are as follows:

[0026] (1) System startup:

[0027] (1.1) Start-up of low-oxygen aerated SBR: First, inoculate with ordinary activated sludge, maintaining the sludge concentration at 3000-4000 mg / L. The wastewater contains 100-120 mg / L of ammonia nitrogen. Then, under low thiocyanate concentration of 100-120 mg / L and high dissolved oxygen conditions, control the dissolved oxygen concentration at 2-5 mg / L to acclimate SCN. - Degrading bacteria and stable ammonia oxidation performance, when SCN - With a removal rate exceeding 90%, the influent SCN was increased. - Concentrations up to 100–200 mg / L, SCN - Once the removal rate stabilizes at over 90%, the concentration is increased to 200–300 mg / L. Simultaneously, the aeration rate is adjusted to create an oxygen-limited environment, maintaining the dissolved oxygen concentration at 0.1–0.3 mg / L to acclimate the thiocyanate denitrifying bacteria. When the thiocyanate removal rate reaches over 95%, the low-oxygen aeration SBR is considered to have started successfully.

[0028] (1.2) Start-up of UASB: First, inoculate with anaerobic ammonia oxidation granular sludge, maintaining the sludge concentration at 20000±500 mg / L. Start-up is carried out in wastewater containing 50-75 mg / L ammonia nitrogen and 60-100 mg / L nitrite. Subsequently, the thiocyanate concentration in the reactor is set at 75-150 mg / L to acclimate the coupling of anaerobic ammonia oxidation and thiocyanate autotrophic denitrification. A nitrogen removal efficiency of UASB of 72% or higher is considered a successful start-up.

[0029] (2) System operation:

[0030] (2.1) Operation of low-oxygen aeration SBR: Influent NH4 + -N concentration is 100-120 mg / L, SCN -Wastewater containing ammonia nitrogen and thiocyanate with a concentration of 300-350 mg / L is pumped into the short-cut nitrification SBR reactor (2) via a first peristaltic pump (2.1). A heater is placed in the reactor to control the operating temperature at 25-30℃. Aeration is carried out in the reactor by blower aeration, and the dissolved oxygen concentration is controlled at 0.1-0.3 mg / L by a gas flow meter. The reactor is stirred continuously during aeration. During the reaction, ammonia nitrogen is oxidized into nitrite by ammonia-oxidizing bacteria. At the same time, the thiocyanate and nitrite in the influent are utilized by autotrophic denitrifying bacteria to generate nitrogen, sulfate and ammonia nitrogen. The low-oxygen short-cut nitrification effluent containing ammonia nitrogen and nitrite enters the intermediate water tank (3).

[0031] (2.2) Operation of UASB: This step involves continuous water intake, with the reactor operating in a dark, anaerobic, and constant-temperature environment. Raw water from the intake tank (1) is pumped into the UASB reactor (4) via a third peristaltic pump (1.2); simultaneously, effluent from the sequencing batch reactor in the intermediate tank (3) enters the UASB reactor (4) via a second peristaltic pump (4.1), with a volume ratio of 1:1 between the two types of water. The device is externally wrapped with heating tape (4.3) to maintain the reactor temperature at 30-35°C. Ammonia nitrogen and nitrite in the intake water are utilized by anaerobic ammonia-oxidizing bacteria to generate nitrogen and nitrate. The generated nitrate, along with nitrite and thiocyanate in the intake water, are utilized by autotrophic denitrifying bacteria to generate nitrogen. The effluent is discharged through the outlet (4.4).

[0032] The experimental results show that after the system is running stably, thiocyanate-degrading bacteria have been successfully domesticated to achieve thiocyanate autotrophic denitrification. The coupling of short-cut nitrification and anaerobic ammonia oxidation processes has achieved efficient detoxification and denitrification of coking wastewater containing ammonia nitrogen and thiocyanate, and the effluent quality meets the treatment requirements.

[0033] The above are specific embodiments of the present invention, which enable those skilled in the art to better understand and apply the present invention. However, the implementation of the present invention is not limited thereto. Therefore, any simple improvements made to the present invention by those skilled in the art are within the protection scope of the present invention.

Claims

1. A two-stage low-oxygen short-cut nitrification-sulfur autotrophic denitrification-anaerobic ammonia oxidation method for treating coking wastewater for autotrophic denitrification and detoxification, wherein the apparatus used in this method includes an inlet tank (1), a sequencing batch reactor (2), an intermediate tank (3), and an upflow anaerobic sludge bed reactor (4). The inlet tank (1) includes a heating rod (1.1) and a third peristaltic pump (1.2); the sequencing batch reactor (2) includes a first peristaltic pump (2.1), a first inlet (2.2), a pH / DO meter (2.3), a stirrer (2.4), an aeration disc (2.5), a gas flow meter (2.6), an air pump (2.7), and a first outlet (2.8); the intermediate tank (3) includes a heating rod (3.1); the upflow anaerobic sludge bed reactor (4) includes a second peristaltic pump (4.1), a second inlet (4.2), a heating belt (4.3), a second outlet (4.4), and a pH / DO meter (4.5); The coking wastewater containing ammonia nitrogen and thiocyanate in the inlet tank (1) is fed in by artificial water distribution and pumped into the sequencing batch reactor (2) through the first inlet (2.2) by the first peristaltic pump (2.1) to start short-cut nitrification and thiocyanate denitrification. The effluent is discharged into the intermediate tank (3) through the first outlet (2.8). The SBR effluent containing ammonia nitrogen and nitrite nitrogen is mixed with the coking wastewater containing ammonia nitrogen and thiocyanate and enters the upflow anaerobic sludge bed (4) through the second inlet (4.2) by the second peristaltic pump (4.1) and the third peristaltic pump (1.2). The effluent after the reaction is discharged through the outlet (4.4). Its features Includes the following steps: (1) System startup: (1.1) Start-up of low-oxygen aerated SBR: First, inoculate with ordinary activated sludge, maintaining the sludge concentration at 3000-4000 mg / L. The wastewater contains 100-120 mg / L of ammonia nitrogen. Then, under low thiocyanate concentration of 100-120 mg / L and high dissolved oxygen conditions, control the dissolved oxygen concentration at 2-5 mg / L to acclimate SCN. - Degrading bacteria and stable ammonia oxidation performance, when SCN - With a removal rate exceeding 90%, the influent SCN was increased. - Concentrations up to 100–200 mg / L, SCN - Once the removal rate stabilizes at over 90%, the concentration is increased to 200–300 mg / L, while maintaining the dissolved oxygen concentration at 0.1–0.3 mg / L to acclimate the thiocyanate denitrifying bacteria. When the thiocyanate removal rate reaches over 95%, the low-oxygen aeration SBR is considered to have started successfully. (1.2) Start-up of UASB: First, inoculate anammox granular sludge and maintain the sludge concentration at 20000±500 mg / L; start-up is carried out in wastewater containing 50-75 mg / L ammonia nitrogen and 60-100 mg / L nitrite. Then, set the thiocyanate concentration in the reactor to 75-150 mg / L to acclimate the coupling of anammox and thiocyanate autotrophic denitrification. The start-up is considered successful when the UASB nitrogen removal efficiency reaches 72% or more. (2) System operation: (2.1) Operation of low-oxygen aeration SBR: Influent NH4 + -N concentration is 100-120 mg / L, SCN - Wastewater containing ammonia nitrogen and thiocyanate with a concentration of 300-350 mg / L is pumped into the short-cut nitrification SBR reactor (2) through the first peristaltic pump (2.1), and the operating temperature inside the reactor is controlled at 25-30℃. Aeration is carried out in the reactor, and the dissolved oxygen concentration is controlled at 0.1-0.3 mg / L through a gas flow meter. The reactor is stirred continuously during the aeration process. During the reaction, ammonia nitrogen is oxidized into nitrite by ammonia-oxidizing bacteria. At the same time, the thiocyanate and nitrite in the influent are utilized by autotrophic denitrifying bacteria to generate nitrogen, sulfate and ammonia nitrogen. The low-oxygen short-cut nitrification effluent containing ammonia nitrogen and nitrite enters the intermediate water tank (3). (2.2) Operation of UASB: This step involves continuous water intake, and the reactor is in a light-proof, anaerobic, and constant-temperature environment; the raw water in the water inlet tank (1) is pumped into the UASB reactor (4) through the third peristaltic pump (1.2); at the same time, the effluent from the sequencing batch reactor in the intermediate water tank (3) enters the UASB reactor (4) through the second peristaltic pump (4.1), and the volume ratio of the two types of water intake is 1:1; the outside is wrapped with heating tape (4.3) to maintain the reactor temperature at 30-35℃, and the effluent is discharged through the outlet (4.4).

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